VARIABLE DISPLACEMENT OIL PUMP AND METHOD FOR PRODUCING VARIABLE DISPLACEMENT OIL PUMP

Description

TECHNICAL FIELD

The present invention relates to a variable displacement oil pump and a method for producing a variable displacement oil pump.

BACKGROUND ART

Patent Document 1 described below discloses a conventional variable displacement oil pump.

The conventional variable displacement oil pump disclosed in Patent Document 1 includes a cam ring that is swingably contained in a pump container of a housing. The cam ring includes an arm that is formed oppositely to a swing fulcrum across a center of the cam ring and is in elastic contact with a coil spring. The coil spring exerts bias force that biases the cam ring in a direction to increase an amount of eccentricity of the cam ring. This bias mechanism suppresses the coil spring from undergoing position shift, by forming a cylindrical projection projecting from a spring contact surface of the arm of the cam ring. The projection is fitted to an inner periphery of the coil spring, and supports the inner periphery of a first end (i.e., an end seated on the cam ring) of the coil spring.

PRIOR ART DOCUMENT(S)

Patent Document(s)

• • Patent Document 1: JP 2019-019716 A

SUMMARY OF THE INVENTION

Problem(s) to be Solved by the Invention

However, the above conventional variable displacement oil pump configured to fit the projection to the inner periphery of the coil spring has a room for improvement in view of a problem of difficulty in installation of the coil spring because of necessity for fitting the projection to the inner periphery of the coil spring while restoring the coil spring from a compressed state upon the installation.

In view of the foregoing technical problem of the conventional variable displacement oil pump, it is desirable to provide a variable displacement oil pump structured to suppress position shift of a coil spring while ensuring easiness in installation of the coil spring.

Means for Solving the Problem(s)

According to one aspect of the present invention, a projection is formed in a cam ring, extends in a longitudinal direction of a coil spring from a spring contact surface being in contact with the coil spring, and overlaps with a part of an outer periphery of the coil spring.

Effect(s) of the Invention

The present invention serves to suppress position shift of a coil spring while ensuring easiness in installation of the coil spring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded oblique view of a pump main body of a variable displacement oil pump according to the present invention.

FIG. 2 is a planar view of the pump main body when omitting a second housing shown in FIG. 1.

FIG. 3 is a longitudinal sectional view of a control valve of the variable displacement oil pump according to the present invention.

FIG. 4 is an enlargement view of a chief part in FIG. 1.

FIG. 5 is a sectional view along a line A-A in FIG. 3.

FIG. 6 are illustration views of a method for producing the variable displacement oil pump according to the present invention. FIG. 6(a) is a schematic view illustrating processes for displacing a coil spring. FIG. 6(b) is a sectional view along a line B-B in FIG. 6(a).

FIG. 7 is an illustration view of how the variable displacement oil pump according to the present invention operates, in a state of a cam ring at a maximum in amount of eccentricity.

FIG. 8 is an illustration view of how the variable displacement oil pump according to the present invention operates, in a state of the cam ring at a minimum in amount of eccentricity.

MODE(S) FOR CARRYING OUT THE INVENTION

The following details an embodiment of a variable displacement oil pump according to the present invention, with reference to the drawings. The embodiment below shows an example of employing the variable displacement oil pump as an oil pump for supplying lubrication oil to an internal combustion engine for a vehicle. For convenience, the following explanation refers to a direction of a rotational axis of a drive shaft 2 as “axial direction”, refers to a direction orthogonal to the rotational axis of drive shaft 2 as “radial direction”, and refers to a rotational direction of drive shaft 2 as “circumferential direction”.

(Configurations of Oil Pump)

FIG. 1 is an exploded oblique view of a pump main body PA of the variable displacement oil pump according to the present invention. FIG. 2 is a planar view of pump main body PA when detaching a second housing 12 shown in FIG. 1.

As shown in FIG. 1, the variable displacement oil pump includes the pump main body PA and a control valve SV (see FIG. 3) structured to control an amount of discharge (i.e., control a discharge pressure) from pump main body PA. Pump body PA includes a drive shaft 2, a pump element 3, a cam ring 4, and a coil spring SP. Drive shaft 2 drives and rotates pump element 3. Cam ring 4 is disposed around pump element 3 so as to be swingable. Coil spring SP biases cam ring 4. Drive shaft 2, pump element 3, cam ring 4, and coil spring SP are contained inside a housing 1. According to the present embodiment, pump main body PA is fastened to an engine not show (in detail, a side face of a cylinder block not shown) with bolts not shown.

As shown in FIGS. 1 and 2, housing 1 includes a first housing 11 and a second housing 12. First housing 11 has a shape of a cup, and serves as a pump shell. Second housing 12 is joined to first housing 11, and serves as a cover that closes an opening of first housing 11. First housing 11 and second housing 12 are fastened to each other with screws SW while positioned with positioning pin PN. First housing 11 and second housing 12 are both made of a metal such as an aluminum alloy, and are formed integrally with each other.

First housing 11 includes a bottom wall 111 and a peripheral wall 112. Peripheral wall 112 rises from an outer periphery of bottom wall 111, and is continuous along the outer periphery of bottom wall 111 in the circumferential direction. Thus, first housing 11 includes an axial first end being open and facing second housing 12 and an axial second end closed by bottom wall 111. In other words, bottom wall 111 and peripheral wall 112 define a cup-shaped pump container 110 inside the first housing 11.

First housing 11 further includes a join surface 113 in a rim of the opening of the axial first end of first housing 11, for join with second housing 12. Join surface 113 spreads outwardly in the radial direction of first housing 11, and are formed integrally with peripheral wall 112. Join surface 113 includes a plurality of (e.g., two in the present embodiment) internal screw holes 113a. Internal screw holes 113a are arranged at an interval in the circumferential direction, and respectively receive screws SW screwed therein to fasten second housing 12 to first housing 11. Join surface 113 further includes a plurality of (e.g., four in the present embodiment) first-housing-side mounting holes 113b. First-housing-side mounting holes 113b are arranged at intervals in the circumferential direction, and serve as pump mounting holes for mounting the variable displacement oil pump to the cylinder block not shown, together with second-housing-side mounting holes 121b formed in second housing 12.

Bottom wall 111 serving as a first end wall of pump container 110 includes at its substantially center a first bearing hole not shown extending through bottom wall 111 and supporting a first end of drive shaft 2 rotatably. Bottom wall 111 further includes a first suction port 114 in its inner side surface. First suction port 114 has a substantially arc shape, is formed around the first bearing hole, and is structured to open to a suction region that is a region in which pump chambers 30 described below increase in capacity, in response to pump action of pump element 3. On the other hand, bottom wall 111 includes a first discharge port 115 that has a substantially arc shape and, is formed oppositely to the suction region across a rotational center Z of drive shaft 2, and is structured to open to a discharge region that is a region in which pump chambers 30 described below decrease in capacity. The inner side surface of bottom wall 111 includes a first pin support groove 111b. First pin support groove 111b is positioned in an outer circumferential side with respect to discharge port 115, and swingably supports cam ring 4 via a pivot pin 40 having a substantially cylindrical shape. Pivot pin 40 includes an axial first end press-fitted in first pin support groove 111b.

In a rotational direction D of drive shaft 2, first suction port 114 is shaped to be narrowest in a starting end, be widest in a middle part, and gradually shrink as going from the middle part to a terminal end. First suction port 114 includes a suction port extension 114a extending outwardly in the radial direction continuously from the middle part of first suction port 114. Suction port extension 114a includes a suction inlet 114b (see FIG. 5) extending through bottom wall 111 to open to the outside. Via the suction inlet 114b, oil pooled in an oil pan not shown in introduced. Incidentally, suction inlet 114b may directly open to the oil pan via an oil strainer not shown, or may be connected to the oil pan via a suction passage not shown.

According to the above configurations, as shown in FIGS. 1 and 2, the variable displacement oil pump is structured such that oil pooled in the oil pan not shown is sucked into pump chambers 30 positioned in the suction region, via suction inlet 114b, first suction port 114, and a second suction port 124 described below, due to back pressure generated in response to pump action of pump element 3. Thus, the variable displacement oil pump according to the present embodiment includes a suction section composed of suction inlet 114b, first suction port 114, and second suction port 124 described below.

As shown in FIG. 2, first discharge port 115 is shaped to gradually expand from a starting end to a middle part and gradually shrink from the middle part to a terminal end, in rotational direction D of drive shaft 2. First discharge port 115 includes a discharge outlet not shown extending through bottom wall 111 to open to the outside.

According to this configuration, as shown in FIGS. 1 and 2, the variable displacement oil pump is structured such that oil is pressurized by pump action of pump element 3 and discharged to first discharge port 115 and a second discharge port 125 described below, and then is supplied to sliding contact parts (e.g., crank metals) of the engine not shown, an oil jet device not shown for cooling pistons of the engine, a valve timing control device not shown, etc., via the discharge outlet and a main gallery formed inside the cylinder block not shown. Thus, the variable displacement oil pump according to the present embodiment includes a discharge section composed of first discharge port 115, second discharge port 125 described below, and the discharge outlet not shown.

Bottom wall 111 of first housing 11 includes a communication groove not shown connecting the first discharge port 115 and the first bearing hole not shown. Via the communication groove, oil is supplied to the first bearing hole and to side parts of a rotor 31 and vanes 32 described below. This serves to ensure favorable lubrication of sliding contact parts. The communication groove is formed not to coincide with retraction directions of vanes 32. This suppresses vanes 32 from dropping into the communication groove.

Peripheral wall 112 serving as a side wall of pump container 110 includes in its inner surface a first seal slide surface 112a and a second seal slide surface 112b. First seal slide surface 112a and second seal slide surface 112b are respectively structured to be in sliding contact with a first seal member S1 and a second seal member S2 formed in an outer periphery of cam ring 4, and are positioned above a cam ring reference line M in FIG. 2. Cam ring reference line M is a straight line connecting a center Z of first bearing hole 111a being a rotational center of drive shaft 2 and a center Q of first pin support groove 111b being a center of swing of cam ring 4. First seal slide surface 112a is an arc-shaped surface having a curvature defined by a first radius R1 about center Q of first pin support groove 111b, and has a circumferential length that allows sliding contact with first seal member S1 within a swing region of cam ring 4. Similarly, second seal slide surface 112b is an arc-shaped surface having a curvature defined by a second radius R2 about center Q of first pin support groove 111b, and has a circumferential length that allows sliding contact with second seal member S2 within the swing region of cam ring 4.

Peripheral wall 112 further includes a third seal slide surface 112c below cam ring reference line M in FIG. 2. Third seal slide surface 112c is structured to be in sliding contact with a third seal member S3 formed in the outer periphery of cam ring 4. Third seal slide surface 112c is an arc-shaped surface having a curvature defined by a third radius R3 about center Q of first pin support groove 111b, and has a circumferential length that allows sliding contact with third seal member S3 within the swing region of cam ring 4.

As shown in FIG. 1, second housing 12 serves as a cover closing the opening of first housing 11 (in detail, pump container 110), and is joined to join surface 113 of first housing 11 with screws SW. Specifically, second housing 12 includes screw through holes 121a positioned in correspondence to internal screw holes 113a of first housing 11. Screws SW pierce screw through holes 121a and are screwed in internal screw holes 113a of first housing 11, and thereby fasten second housing 12 to first housing 11.

Second housing 12 includes a second bearing hole 122a positioned oppositely to first bearing hole 111a of first housing 11. Second bearing hole 122a supports a second end of drive shaft 2 rotatably. Second housing 12 further includes in its inner surface a second suction port 124 and a second discharge port 125. Second suction port 124 and second discharge port 125 respectively correspond to first suction port 114 and first discharge port 115, and are respectively positioned oppositely to first suction port 114 and first discharge port 115. Second housing 12 still further includes in its inner surface a second pin support groove 122b positioned oppositely to first pin support groove 111b. Second pin support groove 122b retains an axial second end of pivot pin 40 press-fitted therein, and supports pivot pin 40 in cooperation with first pin support groove 111b.

As shown in FIGS. 1 and 2, drive shaft 2 includes in its axial first end a drive shaft ordinary part 21 rotatably supported by first bearing hole 111a. On the other hand, drive shaft 2 includes in its axial second end a drive shaft large-diameter part 22 greater in outer diameter than drive shaft ordinary part 21. Drive shaft large-diameter part 22 is rotatably supported by second bearing hole 122a of second housing 12. Drive shaft 2 further includes a drive shaft end 23 closer to the axial second end than drive shaft large-diameter part 22. Drive shaft end 23 is less in diameter than drive shaft large-diameter part 22, faces the outside via first bearing hole 111a, and is linked to a crankshaft of the engine not shown via a transmission member such as a chain not shown. Thus, drive shaft 2 rotates pump element 3 in rotational direction D shown in FIG. 2, with rotational force transmitted from the crankshaft not shown. FIG. 2 shows a cam ring eccentricity direction line N that is a straight line passing through rotational center Z of drive shaft 2 and being orthogonal to cam ring reference line M, and is a boundary between the suction region and the discharge region.

As shown in FIGS. 1 and 2, pump element 3 includes rotor 31 and vanes 32. Rotor 31 has a substantially cylindrical shape, is contained in an inner circumferential side of cam ring 4, and is driven and rotated by drive shaft 2. Each of vanes 32 is contained in a corresponding one of slits 312 so as to be retractable, wherein slits 312 are open and are arranged radially in an outer periphery of rotor 31. Both axial ends of rotor 31 are provided with a pair of pair of rings 33, 33 each of which is less in diameter than rotor 31 and is contained in a radially inner side with respect to vanes 32.

Rotor 31 includes an axial through hole 311. Axial through hole 311 has a substantially circular shape, extends through a center of rotor 31 in the axial direction, and includes an interior through which drive shaft ordinary part 21 extends. Rotor 31 further includes slits 312. Slits 312 are radially formed by cutting, and extend outwardly in a direction from the center of shaft through hole 311 to the radially outer side. Each of slits 312 includes a bottom including a back pressure chamber 313 having a substantially circular cross section and serving for introduction of oil. Thus, vanes 32 are structured to be pushed outwardly (i.e., to the cam ring 4 side) by centrifugal force generated in response to rotation of rotor 31 and pressure force of oil introduced to back pressure chambers 313.

Each of vanes 32 contained in rotor 31 is made of a predetermined metal, has a shape of a rectangular plate, and includes a tip surface structured to come in sliding contact with an inner peripheral surface of cam ring 4 (i.e., a peripheral wall of a pump element container 41 described below) in response to rotation of rotor 31. This sliding contact between the tip surfaces of vanes 32 and the inner peripheral surface of cam ring 4 define pump chambers 30 in rotational direction D of rotor 31, wherein each of pump chambers 30 is defined by rotor 31, a circumferentially adjacent pair of vanes 32, 32, and cam ring 4. Each of vanes 32 includes a base end surface structured to come in sliding contact with an outer peripheries of the pair of rings 33, 33 in response to rotation of rotor 31. This causes the pair of rings 33, 33 to push vanes 32 outwardly in the radial direction, and thereby allows pump chambers 30 to be liquid-tightly separated from each other by sliding contact between the tip surfaces and the inner peripheral surface of cam ring 4, even in case of being low in centrifugal force due to rotation of rotor 31 and/or in oil pressure inside back pressure chambers 313.

Cam ring 4 has a annular shape, is made of a sintered material, and includes pump element container 41 that contains pump element 3 in an inner circumferential side thereof. The outer periphery of cam ring 4 includes a swing supporter 42. Swing supporter 42 is an arc-shaped groove extending in the axial direction, and is structured to be in sliding contact with an outer periphery of pivot pin 40 shaped cylindrical and supported by housing 1. Swing supporter 42 is pressed onto pivot pin 40 by a discharge pressure P exerted on the inner peripheral surface of cam ring 4 (in detail, pump element container 41) in the discharge region in response to pump action of pump element 3.

The outer periphery of cam ring 4 includes a first seal component 431, a second seal component 432, and a third seal component 433 that respectively face first seal slide surface 112a, second seal slide surface 112b, and third seal slide surface 112c. First seal component 431 includes a first seal surface 431a having an arc shape concentric with first seal slide surface 112a. Second seal component 432 includes a second seal surface 432a having an arc shape concentric with second seal slide surface 112b. Third seal component 433 includes a third seal surface 433a having an arc shape concentric with third seal slide surface 112c.

First seal surface 431a includes a first seal retention groove 431b extending in the axial direction and being open toward first seal slide surface 112a. Second seal surface 432a includes a second seal retention groove 432b extending in the axial direction and being open toward second seal slide surface 112b. Third seal surface 433a includes a third seal retention groove 433b extending in the axial direction and being open toward third seal slide surface 112c.

In first seal retention groove 431b, first seal member S1 structured to come in sliding contact with first seal slide surface 112a upon swing of cam ring 4 is contained. In second seal retention groove 432b, second seal member S2 structured to come in sliding contact with second seal slide surface 112b upon swing of cam ring 4 is contained. In third seal retention groove 433b, third seal member S3 structured to come in sliding contact with third seal slide surface 112c upon swing of cam ring 4 is contained.

As shown in FIGS. 1 and 4, each of first seal member S1, second seal member S2, and third seal member S3 is made of a material low in friction, such as a fluorine-based resin, and is shaped elongated to extend straight in the axial direction of cam ring 4. As shown in FIG. 4, each of first seal retention groove 431b, second seal retention groove 432b, and third seal retention groove 433b includes a bottom provided with an elastic member BR made of a rubber. Thus, first seal member S1, second seal member S2, and third seal member S3 respectively contact with first seal slide surface 112a, second seal slide surface 112b, and third seal slide surface 112c via elastic force of elastic members BR, and thereby respectively establish liquid-tight sealing between first seal surface 431a, second seal surface 432a, and third seal surface 433a and first seal slide surface 112a, second seal slide surface 112b, and third seal slide surface 112c.

According to the above configurations, the sliding contact between first seal member S1 and first seal slide surface 112a and the sliding contact between second seal member S2 and second seal slide surface 112b define a first control oil chamber PR1 around cam ring 4. First control oil chamber PR1 receives a first control oil pressure P1 introduced thereto via a first passage L1 that is a first one of two passages branching from a discharge pressure introduction passage Lb connected to the main gallery. First control oil pressure P1 introduced to first control oil chamber PR1 is substantially equal to discharge pressure P introduced to the main gallery. First passage L1 is connected to a first control pressure introduction hole 118 extending through bottom wall 111 of first housing 11. This allows first control oil pressure P1 to be directly introduced to first control oil chamber PR1 via first control pressure introduction hole 118. First control oil pressure P1 having been introduced to first control oil chamber PR1 is exerted on a first pressure-receiving surface 441 formed between first seal component 431 and second seal component 432 out of the outer peripheral surface of cam ring 4 facing first control oil chamber PR1. The oil pressure exerted on first pressure-receiving surface 441 provides cam ring 4 with movement force (i.e., swing force) in a direction for decrease in amount Δ of eccentricity of cam ring 4 (i.e., eccentricity amount of a center O of pump element container 41 with respect to rotational center Z of drive shaft 2). Hereinafter, this direction is referred to as “concentric direction”.

Similarly, the sliding contact between swing supporter 42 and pivot pin 40 and the sliding contact between second seal member S2 and second seal slide surface 112b define a second control oil chamber PR2 around cam ring 4. Second control oil chamber PR2 receives a second control oil pressure P2 introduced thereto via pressure reduction in control valve SV, from a second passage L2 that is a second one of the two passages branching from discharge pressure introduction passage Lb. In second passage L2, second control oil pressure P2 is introduced to second control oil chamber PR2 via a second control oil pressure introduction hole (not shown) extending through second housing 12. Second control oil pressure P2 having been introduced to second control oil chamber PR2 is exerted on a second pressure-receiving surface 442 formed between swing supporter 42 and third seal component 433 out of the outer peripheral surface of cam ring 4 facing second control oil chamber PR2. The oil pressure exerted on second pressure-receiving surface 442 provides cam ring 4 with movement force (i.e., swing force) in a direction for increase in amount Δ of eccentricity of cam ring 4 (i.e., eccentricity amount of center O of pump element container 41 with respect to rotational center Z of drive shaft 2). Hereinafter, this direction is referred to as “eccentric direction”.

Coil spring SP is contained in a spring container 119 positioned oppositely to pivot pin 40 across rotational center Z of drive shaft 2. Thus, coil spring SP compressed at a predetermined preload (i.e., a set load W1) is installed between a first end wall 119a of spring container 119 and an arm 45 extending from the outer periphery of cam ring 4. Spring container 119 is formed by depressing a part of peripheral wall 112 of pump container 110 outwardly in the radial direction, around first suction port 114 of first housing 11. While first end wall 119a of spring container 119 serves as a seat surface for coil spring SP, a second end wall 119b of spring container 119 serves as a stopper for restricting a movable range of cam ring 4 in the eccentric direction. Cam ring 4 is always biased in the eccentric direction by coil spring SP, and is structured to be maintained at a maximum eccentric state due to contact between arm 45 of cam ring 4 and second end wall 119b of spring container 119.

According to the above configurations, cam ring 4 moves in the eccentric direction due to set load W1 of coil spring SP so as to be set in the maximum eccentric state such as one shown in FIG. 2, in case that bias force due to internal pressure (i.e., first control oil pressure P1) in first control oil chamber PR1 is less than set load W1 of coil spring SP. On the other hand, in case that discharge pressure P rises and the bias force due to the internal pressure (i.e., first control oil pressure P1) in first control oil chamber PR1 becomes greater than set load W1 of coil spring SP, cam ring 4 moves in the concentric direction in response to discharge pressure P.

(Configurations of Control Valve)

FIG. 3 is a longitudinal sectional view of control valve SV structured to control a discharge amount (i.e., a discharge pressure) of the variable displacement oil pump (i.e., pump main body PA) according to the present embodiment.

As shown in FIG. 3, control valve SV is a solenoid valve controlled and driven by a controller not shown configured to control the engine. Specifically, control valve SV includes a valve 5 and a solenoid 6. Valve 5 serves for control on opening and closing of second passage L2. Solenoid 6 is disposed at a first end of valve 5, and serves for control on opening and closing of valve 5 depending on exciting current outputted from the controller not shown.

Valve 5 is a so-called three-way valve including a valve case 51, a spool valve body 52, a retainer 53, and a valve spring 54. Valve 5 may be integrated with the variable displacement oil pump as a built-in device in housing 1, or may be separated from the variable displacement oil pump as an independent device.

Valve case 51 is made of a metallic material such as an aluminum alloy, has a shape of a substantial cylinder open at both ends in a direction of a center axis Y, and internally includes a valve body container 510. Valve body container 510 includes a stepped through hole extending through valve case 51 in the direction of center axis Y of valve case 51. In detail, valve body container 510 includes a first valve body slide part 511 in a first end of valve body container 510 in the direction of center axis Y, and includes a second valve body slide part 512 in a second end of valve body container 510 in the direction of center axis Y, wherein second valve body slide part 512 is greater in diameter than first valve body slide part 511. The opening of valve body container 510 in the first valve body slide part 511 side is closed by solenoid 6. On the other hand, the opening of valve body container 510 in the second valve body slide part 512 side is open to a drain passage Ld, and serves as a drain port Pd for discharge of oil from a spring container chamber 55 described below. In another manner, drain port Pd may be not open to drain passage Ld but be open directly to the oil pan not shown serving as a low-pressure section. As long as being in communication with a low-pressure section, drain port Pd may be configured in still another manner rather than being in communication with the oil pan not shown having an atmospheric pressure. For example, drain port Pd may be in communication with a vicinity of suction inlet 114b having a negative pressure. For convenience, the following explanations refer to the end of valve 5 in the first valve body slide part 511 side (i.e., a right side in FIG. 3) as the first end, and refer to the end of valve 5 in the second valve body slide part 512 side (i.e., a left side in FIG. 3) as the second end.

Valve 5 includes a first annular groove 513 formed around first valve body slide part 511 by cutting an outer peripheral surface of valve case 51 in the circumferential direction. First annular groove 513 includes in its bottom a plurality of first valve holes 513a establishing communication between an inside and an outside of valve body container 510 in a radial direction of valve case 51 orthogonal to center axis Y. Each of first valve holes 513a is a round hole shaped substantially circular in planar view, and serves as a supply-discharge port Pc for supply/discharge of oil (having second control oil pressure P2) to/from second control oil chamber PR2 via second passage L2.

Similarly, valve 5 includes a second annular groove 514 formed around second valve body slide part 512 by cutting the outer peripheral surface of valve case 51 in the circumferential direction. Second annular groove 514 includes in its bottom a second valve hole 514a establishing communication between the inside and the outside of valve body container 510 in the radial direction of valve case 51 orthogonal to center axis Y. Second valve hole 514a is a round hole shaped substantially circular in planar view, and serves as an introduction port Pb for introduction of oil (having discharge pressure P) from discharge pressure introduction passage Lb.

Spool valve body 52 is contained in valve body container 510 of valve case 51 so as to be slidable, and has a stepped cylindrical shape that varies in outer diameter, in the direction of center axis Y being a moving direction of spool valve body 52. Specifically, spool valve body 52 includes a first land 521 in sliding contact with first valve body slide part 511 and a second land 522 in sliding contact with second valve body slide part 512. Second land 522 is greater in diameter than first land 521. Spool valve body 52 further includes an intermediate shaft 523 between first land 521 and second land 522. Intermediate shaft 523 is less in outer diameter than first land 521 and second land 522, and defines a relay chamber Rc between intermediate shaft 523 and valve body container 510 in the radial direction of valve case 51.

In relay chamber Rc, first land 521 and second land 522 face each other in the direction of center axis Y, and serve as a pair of pressure-receiving surfaces that receive oil pressure introduced via second valve hole 514a. First land 521 serves as a first pressure-receiving surface Pf1, while second land 522 serves as a second pressure-receiving surface Pf2. Second pressure-receiving surface Pf2 is wider than first pressure-receiving surface Pf1, because second land 522 is greater in outer diameter than first land 521. This difference in pressure-receiving area between first pressure-receiving surface Pf1 and second pressure-receiving surface Pf2 causes second pressure-receiving surface Pf2 to receive oil pressure introduced from second valve hole 514a to relay chamber Rc more than first pressure-receiving surface Pf1, and thereby causes spool valve body 52 to be pressed to the second end side.

Spool valve body 52 includes a shaft end 524 formed to be closer to the first end than first land 521 and less in outer diameter than first land 521. Shaft end 524 defines a back pressure chamber Rb between shaft end 524 and valve body container 510 in the radial direction of valve case 51. Back pressure chamber Rb is structured to collect oil that has leaked from relay chamber Rc via an outer periphery of first land 521 (i.e., via a minute gap between first land 521 and valve body container 510). Back pressure chamber Rb is in communication with spring container chamber 55 described below via a discharge hole 525 and an internal passage 526. Discharge hole 525 is formed in a peripheral wall of a first end of spool valve body 52 facing back pressure chamber Rb. Internal passage 526 connects discharge hole 525 to spring container chamber 55. The oil collected in back pressure chamber Rb is led to spring container chamber 55 via discharge hole 525 and internal passage 526, and is discharged to the oil pan not shown via drain port Pd and drain passage Ld.

Spool valve body 52 includes a spring supporter 527 formed in an end of spool valve body 52 in the second land 522 side facing retainer 53. Spring supporter 527 supports a first end of valve spring 54 facing spool valve body 52. Spring supporter 527 is formed by expanding stepwise an inner periphery of spool valve body 52 in diameter as going toward second land 522, and includes a spring envelopment 527a shaped tubular and a spring support surface 527b shaped flat. Thus-configured spring supporter 527 surrounds an outer periphery of the first end of valve spring 54 with spring envelopment 527a, while supporting the first end of valve spring 54 with spring support surface 527b.

Retainer 53 includes a spring seat 531 and a retainer opening 530. Spring seat 531 has an annular shape, and supports a second end of valve spring 54. Retainer opening 530 has a circular shape, and extends through a center of spring seat 531. Retainer 53 includes a rim fitted in an open end of valve case 51 in the second end side so as to support the second end of valve spring 54, while retainer opening 530 establishes communication between second valve hole 514a and drain port Pd.

Vale spring 54 is a known compression coil spring, and is installed with a predetermined preload (i.e., a set load W2) in spring container chamber 55 defined between spool valve body 52 and retainer 53. This causes valve spring 54 to always bias spool valve body 52 to the first end side by set load W2.

Solenoid 6 includes a casing 61 and a rod 62. Casing 61 has a cylindrical tubular shape, and contains a coil and an armature not shown. Rod 62 is fixed to the armature, and is structured retractable in the direction of center axis Y together with the armature. Solenoid 6 is energized by excitation current from a controller not shown, depending on operational conditions of the engine not shown measured or calculated from predetermined parameters such as an oil temperature and an water temperature in the engine and an engine speed of the engine. Solenoid 6 is structured to provide electromagnetic force Fm a magnitude of which is variable continuously. Solenoid 6 is controlled by pulse width modulation (PMW), a current value of which is given by a duty ratio.

(Restriction Structure of Coil Spring at Arm)

FIG. 4 is an enlargement view of a chief part in FIG. 1, which enlarges a vicinity of coil spring SP contained in spring container 119 of FIG. 1. FIG. 5 is a sectional view along a line A-A shown in FIG. 3.

As shown in FIGS. 4 and 5, spring container 119 is positioned in a region being in the outer periphery of pump container 110 and being in an outer periphery of first suction port 114, has a substantially rectangular shape extending in a direction tangent to an outer peripheral edge of pump container 110, and is open to join surface 113 of first housing 11. Arm 45 of cam ring 4 faces spring container 119, where coil spring SP biasing cam ring 4 in the eccentric direction is contained between arm 45 and spring container 119, in a compressed state by a predetermined amount with the predetermined preload (i.e., set load W1).

Spring container 119 is shaped substantially rectangular in planar view, and has a depth set such that a center X of coil spring SP is positioned at a substantial middle of an axial width (i.e., a width in a Z-axis direction) of cam ring 4. Thus, as shown in FIG. 5, the present embodiment is configured to have a predetermined gap C1 between coil spring SP and second housing 12 (i.e., coil spring SP and the join surface of first housing 11), when coil spring SP is contained in spring container 119.

Spring container 119 includes a first end wall 119a and a second end wall 119b. First end wall 119a is formed in a first end side of spring container 119 in an X-axis direction, and is in contact with arm 45 of cam ring 4. Second end wall 119b is formed in a second end side of spring container 119 in the X-axis direction oppositely to first end wall 119a, and is in contact with coil spring SP. The contact between first end wall 119a and arm 45 of cam ring 4 restricts a maximum amount of eccentricity of cam ring 4. The contact between second end wall 119b and coil spring SP supports coil spring SP.

Spring container 119 includes an outer restriction wall 119c serving as a first restriction wall structured to restrict radially-outward position shift of coil spring SP. Oppositely to outer restriction wall 119c across the X-axis being a center of an outer diameter of coil spring SP, spring container 119 includes an inner restriction wall 119d structured to restrict radially-inward position shift of coil spring SP: in detail, position shift of an end of coil spring SP in the second end wall 119b side. Furthermore, spring container 119 includes a bottom restriction wall 119e oppositely to projection 46 across the X-axis. Bottom restriction wall 119e is a part of a bottom wall of spring container 119, and serves as a third restriction wall structured to restrict position shift of coil spring SP toward an opposite side to projection 46 in the axial direction of coil spring SP.

Projection 46 is formed in an end of arm 45 facing join surface 113 of spring container 119, extends in a longitudinal direction of coil spring SP (i.e., the X-axis direction) from spring contact surface 451 being the contact surface between arm 45 and coil spring SP, and overlaps with a part of an outer periphery of coil spring SP. Projection 46 is formed integrally with arm 45, has a shape of a quadrangular pole with a substantially rectangular cross section, and overlaps only with a partial circumferential region of an end of coil spring SP facing arm 45. The shape of projection 46 is not an annular shape covering an entire circumference of the end of coil spring SP facing arm 45. In addition, projection 46 is apart from coil spring SP disposed in an inner side with respect to coil spring SP, and has a minute gap C2 with coil spring SP being in an upright state.

It is desirable to dispose projection 46 in a side to which coil spring SP is likely to incline due to a flow of oil: i.e., dispose projection 46 at a position downstream with respect to coil spring SP in view of a flow of oil led from suction inlet 114b. According to the present embodiment, projection 46 is desirably disposed at the end of arm 45 facing join surface 113 of first housing 11, wherein the said end is in the downstream side in view of the flow of oil led from suction inlet 114b (see an arrow F in FIG. 5). In other words, projection 46 may be disposed at an arbitrary position to allow projection 46 to restrict the inclination of coil spring SP, depending on occurrence circumstances of the inclination of coil spring SP. Furthermore, it is desirable to dispose projection 46 at a position to overlap with the center of the outer diameter of coil spring SP (i.e., the X-axis), in case of disposing projection 46 at the end of arm 45 facing join surface 113 first housing 11 as described above. While the present embodiment shows an example of disposing the single projection 46, it is allowed to dispose a plurality of projections 46 depending on occurrence circumstances of the inclination of coil spring SP.

Cam ring 4 includes in its outer periphery a cam ring restriction wall 47 corresponding to a second restriction wall. Cam ring restriction wall 47 is a flat surface being substantially parallel with outer restriction wall 119c of first housing 11 in the maximum eccentric state of cam ring 4 shown in FIG. 4, and is structured to support the outer periphery of coil spring SP and restrict radially-inward position shift of coil spring SP.

(Method for Installation of Coil Spring)

FIG. 6 are illustration views of a method for producing the variable displacement oil pump according to the present embodiment. FIG. 6(a) is a schematic view illustrating steps for displacing the coil spring. FIG. 6(b) is a sectional view along a line B-B shown in FIG. 6(a).

As shown in FIG. 6(a), the first step for installation of coil spring SP is compression of coil spring SP with use of a jig 7. Jig 7 includes a connection base 70 including a pair of spring retainers composed of a first retainer 71 and a second retainer 72 movable relatively with respect to each other. First retainer 71 has a shape bifurcated via cut-out part 710, i.e., a U-shape in planar view. Second retainer 72 has a flat plate shape parallel with first retainer 71 and opposite to first retainer 71. Coil spring SP is compressed by sandwiching coil spring SP with first retainer 71 and second retainer 72 and narrowing an interval Cx between first retainer 71 and second retainer 72 below a free length of coil spring SP.

The second step is insertion of coil spring SP, which has been compressed with jig 7, into a gap between arm 45 and second end wall 119b of spring container 119, in a state in which cam ring 4 is contained in pump container 110 of first housing 11 (see an upper tier of FIG. 6(a)). In detail, as shown in FIGS. 6(a) and 6(b), this is performed by inserting jig 7 between arm 45 and second end wall 119b of spring container 119 from the join surface 113 side of first housing 11, while maintaining coil spring SP in the compressed state between first retainer 71 and second retainer 72 and avoiding projection 46 of cam ring 4 via cut-out part 710 of jig 7.

The third step is pushing-out of coil spring SP, which is sandwiched and retained between first retainer 71 and second retainer 72 in the compressed state, in a direction of the arrow (see a middle tier of FIG. 6(a)) into the gap between arm 45 and second end wall 119b of spring container 119, with use of a push-out mechanism of jig 7 not shown. Coil spring SP having been pushed out is expanded by restoring force due to the compression, elastically contacts with spring contact surface 451 of arm 45 via the first end of coil spring SP, and elastically contacts with second end wall 119b of spring container 119 via the second end of coil spring SP. Then, the installation of coil spring SP is completed (see a lower tier of FIG. 6(a)).

(Explanation of Action of Oil Pump)

The following describes action of the variable displacement oil pump according to the present embodiment, with reference to FIGS. 7 and 8. FIG. 7 shows an operational state at a maximum in amount of eccentricity of cam ring 4, out of operational states of the variable displacement oil pump. FIG. 8 shows a state at a minimum in amount of eccentricity of cam ring 4, out of the operational states of the variable displacement oil pump.

As shown in FIGS. 7 and 8, the variable displacement oil pump according to the present embodiment is structured such that rotation of the crank shaft not shown is transmitted to drive shaft 2 via the chain not shown, and drives and rotates rotor 31 in rotational direction D via drive shaft 2. This rotation of rotor 31 causes oil to be sucked from the oil pan not shown via suction inlet 114b, first suction port 114, and second suction port 124. Simultaneously with this suction action, oil in pump chambers 30 positioned in the discharge region is discharged to a discharge passage not shown via first discharge port 115, second discharge port 125, and first discharge port 115a. The oil discharged to the discharge passage is sent with pressure to sliding contact parts (e.g., the crank metals) of the engine not shown, the oil jet device not shown, the valve timing control device not shown, etc., via the main gallery, while also being led to first passage L1 and second passage L2 via discharge pressure introduction passage Lb connected to the main gallery. The main gallery is provided with an oil pressure sensor not shown structured to measure discharge pressure P, and measurement results of the oil pressure sensor is fed back to the controller not shown.

Cam ring 4 swings about pivot pin 40 as a fulcrum. This changes eccentricity amount Δ (see FIG. 2) being a difference between rotational center Z of drive shaft 2 and center O of pump element container 41, and changes a volume change amount (i.e., a difference between a maximum volume and a minimum volume) of pump chambers 30. The volume change amount of pump chambers 30 increases with increase in eccentricity amount Δ, and decreases with decrease in eccentricity amount Δ. Eccentricity amount Δ varies depending on bias force in the concentric direction due to internal pressure in first control oil chamber PR1 (i.e., first control oil pressure P1) and bias force in the eccentric direction due to set load W1 of coil spring SP and internal pressure in second control oil chamber PR2 (i.e., second control oil pressure P2).

Specifically, in a period from engine start to a predetermined engine speed, first control oil pressure P1 is introduced to first control oil chamber PR1 via first passage L1 branching from discharge pressure introduction passage Lb. In control valve SV, bias force (i.e., an oil pressure force Fp2) generated due to exertion of discharge pressure P (which is introduced via second passage L2 branching from discharge pressure introduction passage Lb) on second pressure-receiving surface Pf2 of spool valve body 52 becomes less than set load W2 of valve spring 84. This maintains spool valve body 52 at a state of maximum displacement to the first end side as shown in FIG. 7, establishes communication between introduction port Pb and supply-discharge port Pc (i.e., a first state), and introduces second control oil pressure P2 into second control oil chamber PR2. This results in that a resultant force of set load W1 of coil spring SP and oil pressure force Fp2 generated due to exertion of second control oil pressure P2 of second control oil chamber PR2 onto second pressure-receiving surface 442 exceeds an oil pressure force Fp1 generated due to exertion of first control oil pressure P1 of first control oil chamber PR1 onto first pressure-receiving surface 441, and thereby cam ring 4 is maintained at the maximum eccentric state.

After the engine speed reaches the predetermined level and discharge pressure P reaches a predetermined engine requirement oil pressure, an oil pressure force Po of discharge pressure P becomes greater than set load W2 of valve spring 54, in a state of 0% in duty ratio of excitation current supplied to solenoid 6. As shown in FIG. 8, this causes spool valve body 52 to move to the second end side, blocks communication between introduction port Pb and supply-discharge port Pc, establish communication between supply-discharge port Pc and drain port Pd (i.e., a second state), discharges oil from second control oil chamber PR2, and causes discharge pressure P to be exerted only on first control oil chamber PR1. This results in that oil pressure force Fp1 generated due to exertion of first control oil pressure P1 onto first pressure-receiving surface 441 exceeds set load W1 of coil spring SP, eccentricity amount Δ of cam ring 4 decreases to the minimum eccentric state with increase in discharge pressure P, and discharge pressure P is maintained at the engine requirement oil pressure.

Thus, the variable displacement oil pump undergoes the following A and B alternately and continuously, where: A is movement of spool valve body 52 to the second end side due to the above-described increase in discharge pressure P; and B is movement of spool valve body 52 to the first end side due to movement of spool valve body 52 to the second end side and shift to the minimum eccentric state. In other words, the variable displacement oil pump is switched alternately and continuously between the state of established communication between supply-discharge port Pc and introduction port Pb and the state of established communication between supply-discharge port Pc and drain port Pd. This maintains discharge pressure P at the engine requirement oil pressure.

The present embodiment exemplifies the operational states of the variable displacement oil pump upon engine start and upon highness in discharge pressure P. However, even in case of oil pressure force Po of discharge pressure P being lower than set load W2 of valve spring 54, the variable displacement oil pump is structured to shift to the above-described second state at an arbitrary timing with use of electromagnetic force Fm of solenoid 6 of control valve SV by adjusting the duty ratio of the excitation current supplied to solenoid 6, and control discharge pressure P of the variable displacement oil pump to multi-stages.

Effects of Present Embodiment

As described above, the conventional variable displacement oil pump is configured to fit the coil spring to the outer periphery of the projection projecting from the spring contact surface of the arm of the cam ring. This has a room for improvement due to difficulty in installation of the coil spring, because of necessity for fitting the projection to the inner periphery of the coil spring while restoring the compressed coil spring during installation thereof.

To suppress position shift of the coil spring, another possible configuration is: forming a substantially tubular projection or depression surrounding the outer periphery of the coil spring, in the spring contact surface of the arm of the cam ring; fitting the coil spring to an inner periphery of the projection or depression; and supporting the outer periphery of the coil spring with the projection or depression. However, even this case requires fitting the compressed coil spring to the inner periphery of the projection or depression while restoring the coil spring during installation thereof, and has a room for improvement due to difficulty in installation of the coil spring similarly to the former case of fitting the coil spring to the outer periphery of the projection.

The following details the difficulty in installation of the coil spring. Each of the case of fitting the coil spring to the outer periphery of the projection and the case of fitting the coil spring to the inner periphery of the projection or depression uses a jig for installing the coil spring in a compressed state for providing the coil spring with a preload. The jig includes a pair of retainers opposite to each other, inserts the coil spring together with the pair of retainers into a gap between the housing (i.e., a spring container) and the arm of the cam ring while sandwiching and compressing the coil spring between the pair of retainers, and pushes and installs the coil spring into the gap between the housing and the arm.

In this occasion, the coil spring has to be compressed in surplus by an amount equivalent to thicknesses of the pair of retainers inserted between the housing (i.e., the spring container) and the arm of the cam ring together with the coil spring. This increases the coil spring in restoring force by the amount of surplus compression, causes the coil spring to be released with a greater restoring force when pushing out the coil spring from the jig, and thereby causes the coil spring to contact with the housing (i.e., the spring container) and the arm of the cam ring more strongly. Such contact of the coil spring may damage the housing and the arm.

Furthermore, the releasing of the coil spring by pushing out it from the jig increases difficulty in control on an attitude of the coil spring after pushed out from the jig. Thus, it is very difficult to fit the coil spring to the outer periphery or the inner periphery of the projection having a gap with the coil spring relatively narrow. This worsens workability in installation of the coil spring. Furthermore, the difficulty in attitude control of the coil spring after released from the jig may cause a failure in installation of the coil spring such as a case of the coil spring installed in an inclined attitude.

Instead of fitting the coil spring to the outer periphery of the projection, it is conceivable to form the projection as a so-called retainer member separate from the cam ring, and installing the coil spring with the retainer member fitted to the inner periphery of the coil spring beforehand. This serves to avoid worsening in workability for installation of the coil spring, but increases the variable displacement oil pump in number of components because of forming the projection as the separate retainer member. This results in increase in production cost of the retainer member, management man-hours, assembly man-hours, and then production cost of the variable displacement oil pump.

On the other hand, the variable displacement oil pump according to the present embodiment includes: housing 1 (i.e., first housing 11) including pump container 110; cam ring 4 movably contained in pump container 110; pump element 3 that is rotatably contained in the inner circumferential side of cam ring 4, and forms pump chambers 30 in cooperation with cam ring 4; coil spring SP that is disposed in pump container 110, and biases cam ring 4 in the direction to increase the eccentricity of cam ring 4 with respect to the rotational axis of pump element 3; and projection 46 that is formed in cam ring 4, extends in the longitudinal direction of coil spring SP from spring contact surface 451 being in contact with coil spring SP, and overlaps with a part of the outer periphery of coil spring SP.

Thus, the variable displacement oil pump according to the present embodiment includes projection 46 formed in spring contact surface 451 of cam ring 4 in order to partially overlap with the outer periphery of coil spring SP, and thereby restricts inclination of coil spring SP with projection 46. This serves to maintain coil spring SP at an upright attitude and provide cam ring 4 (i.e., arm 45) with appropriate bias force.

Moreover, the configuration of projection 46 partially overlapping with the outer periphery of coil spring SP allows coil spring SP to be installed merely by pushing coil spring SP into the inside with respect to projection 46. This eliminates necessity for fitting coil spring SP to a projection or depression unlike the conventional arts, and facilitates installation of coil spring SP.

Furthermore, the configuration of projection 46 partially overlapping with the outer periphery of coil spring SP also allows an installation state of coil spring SP to be visible from outside, in comparison with a case of shaping projection 46 annular to surround the outer periphery of coil spring SP as described above. This allows easy determination on quality of the installation state of coil spring SP by visual inspection, and serves for efficient quality assurance of the oil pump.

Instead of forming projection 46 in cam ring 4, projection 46 can be disposed in an inner peripheral surface of second housing 12 closing spring container 119. However, this may worsen productivity and increase production costs and is inappropriate, because the inner peripheral surface of second housing 12 is finished by machining, and the configuration of forming projection 46 in the inner peripheral surface of second housing 12 requires machining avoiding projection 46 during the machining of the inner peripheral surface of second housing 12.

In the variable displacement oil pump according to the present embodiment, housing 1 (first housing 11) includes the first restriction wall (i.e., outer restriction wall 119c) structured to restrict outward movement of coil spring SP in the radial direction orthogonal to rotational axis Z of pump element 3. Cam ring 4 includes the second restriction wall (i.e., cam ring restriction wall 47) structured to restrict inward movement of coil spring SP in the radial direction orthogonal to rotational axis Z of pump element 3.

Thus, the present embodiment is configured to restrict position shift of coil spring SP with use of outer restriction wall 119c being the first restriction wall formed in spring container 119 of housing 1 (first housing 11) and cam ring restriction wall 47 being the second restriction wall formed in cam ring 4. This serves to effectively suppress occurrence of inclination of coil spring SP in cooperation with projection 46.

In the variable displacement oil pump according to the present embodiment, projection 46 is one in number.

This configuration of the present embodiment forming the single projection 46 serves for installation of coil spring SP, which employs jig 7 including first retainer 71 bifurcated by cut-out part 710 and second retainer 72 shaped flat and thereby allows coil spring SP to be installed between cam ring 4 (i.e., spring contact surface 451 of arm 45) and housing 1 (i.e., second end wall 119b of spring container 119 of first housing 11) while retaining coil spring SP in a compressed state between first retainer 71 and second retainer 72 and while avoiding projection 46 with use of cut-out part 710. This serves to improve workability in installation of coil spring SP.

Furthermore, projection 46 is disposed at a middle in a flow of oil led from suction inlet 114b, and may disturb the flow of oil. In view of this, the configuration of forming the single projection 46 serves to reduce a resistance against the flow of oil in comparison with a case of forming a plurality of projections 46, and thereby reduce a pressure loss of the pump cause due to presence of projection(s) 46.

In the variable displacement oil pump according to the present embodiment, projection 46 is positioned to overlap with center X of the outer diameter of coil spring SP.

This configuration of the present embodiment positioning projection 46 to overlap with center X of the outer diameter of coil spring SP serves to perform restriction of inclination of coil spring SP with projection 46, appropriately in well balance. In other words, this configuration allows projection 46 to appropriately restrict movement of coil spring SP even upon swing of cam ring 4.

In the variable displacement oil pump according to the present embodiment, housing 1 (first housing 11) includes the third restriction wall (i.e., bottom restriction wall 119e) structured to restrict movement of coil spring SP to the side opposite to projection 46 in the radial direction of coil spring SP.

Thus, the present embodiment is configured to form bottom restriction wall 119e serving as the third restriction wall structured to restrict movement of coil spring SP, in the side opposite to projection 46 in the radial direction of coil spring SP. This causes coil spring SP to be sandwiched by projection 46 and housing 1 (i.e., bottom restriction wall 119e of spring container 119 of first housing 11), and further facilitates positioning of coil spring SP.

In the variable displacement oil pump according to the present embodiment, coil spring SP is disposed in an oil passage that is continuous from suction inlet 114b formed in housing 1, to pump chambers 30, wherein projection 46 is positioned downstream with respect to coil spring SP, in the oil passage.

Thus, the present embodiment is configured to dispose projection 46 downstream with respect to coil spring SP, in the oil passage continuous from suction inlet 114b to pump chambers 30. This serves to effectively suppress occurrence of inclination of coil spring SP due to a flow of oil flowing from suction inlet 114b into pump chambers 30.

A method for producing the variable displacement oil pump according to the present embodiment includes: a cam ring installation step for disposing cam ring 4 in pump container 110; and a coil spring installation step for disposing coil spring SP in pump container 110 after the cam ring installation step. The coil spring installation step includes: retaining coil spring SP in a compressed state with use of jig 7 including first retainer 71 and second retainer 72, wherein first retainer 71 has a bifurcated shape with cut-out part 710 at a middle thereof and is structured to retain the first end of coil spring SP, and second retainer 72 is structured to retain the second end of coil spring SP; and disposing coil spring SP in pump container 110 by inserting jig 7 between pump container 110 and cam ring 4 in order to avoid projection 46 with use of cut-out part 710 of first retainer 71.

Thus, the present embodiment is configured to installing coil spring SP by: retaining coil spring SP in the compressed state with use of jig 7 including first retainer 71 bifurcated with cut-out part 710 and second retainer 72; and inserting coil spring SP between pump container 110 (i.e., second end wall 119b of spring container 119) and cam ring 4 (i.e., spring contact surface 451 of arm 45) while avoiding projection 46 with use of cut-out part 710. In comparison with the conventional case of surrounding the entire circumference of coil spring SP with the projection or depression, the configuration of the present embodiment allowing avoidance of projection 46 via cut-out part 710 eliminates necessity for compressing coil spring SP in surplus for avoidance of projection 46 as in the conventional case. This serves to reduce a compression amount of coil spring SP by an amount equivalent to a height of projection 46 as shown in FIG. 6, and thereby reduce a repulsive force (i.e., a restoring force) of coil spring SP when released from jig 7. This suppresses a failure in installation of coil spring SP such as a case of coil spring SP installed in an inclined state due to a large repulsive force (restoring force) of coil spring SP, and thereby serves for appropriate installation of coil spring SP.

Furthermore, the reduction of the repulsive force (restoring force) of coil spring SP when released from jig 7 also serves to suppress coil spring SP from damaging seat surfaces (specifically, spring contact surface 451 of arm 45 and second end wall 119b of spring container 119) for coil spring SP upon installation of coil spring SP.

The present invention is not limited to the configurations disclosed in the above embodiment. For example, the configurations may be freely modified depending on specifications of an engine, a valve timing control device, etc. of a vehicle to which a variable displacement oil pump is mounted.

In particular, a variable displacement oil pump available as an application target of the present invention is not limited to the vane type variable displacement oil pump as exemplified in the above embodiment, but may be another type of variable displacement oil pump such as a trochoid type pump. In case of applying the present invention to a trochoid type pump, what corresponds to the above-described cam ring is an outer rotor forming a circumscribed gear.