INTERNAL COMBUSTION ENGINE AND INTERNAL COMBUSTION ENGINE SYSTEM

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2024-219752, filed December 16, 2024; the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to an internal combustion engine and an internal combustion engine system.

BACKGROUND

In an internal combustion engine, oil (engine oil) is supplied as a lubricant oil or the like to supply targets including an oil jet. In the internal combustion engine, such oil is discharged from a pump and supplied to the supply targets via a supply channel. Also, an internal combustion engine which includes a return channel for returning oil from a discharge side of a pump to a suction side of the pump and a relief valve arranged in the return channel is known (Jpn. Pat. Appln. KOKAI Publication No. 2012-31781). In such an internal combustion engine, opening the relief valve causes oil to flow through the return channel from the discharge side to the suction side of the pump so that the pressure of the oil is released on the discharge side of the pump.

SUMMARY

According to an aspect of the present invention, an internal combustion engine includes a pump, an oil filter, a supply channel, a return channel, a soot separation unit and a relief valve. The pump discharges oil and the oil filter filters the oil discharged from the pump. The supply channel extends from the pump through the oil filter, and the return channel branches off from the supply channel. The soot separation unit collects soot contained in the oil in the return channel. The relief valve is provided in the return channel, and causes, by opening itself, the oil that has entered the return channel as a split flow to flow through the soot separation unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of an internal combustion engine system according to an embodiment.

FIG. 2 is a schematic diagram for explaining an example of an oil system (lubricant oil system) for supplying oil to supply targets in an internal combustion engine according to the embodiment.

FIG. 3 is a flowchart schematically showing an example of operation control performed by a controller for the internal combustion engine in the embodiment.

FIG. 4 is a schematic diagram for explaining an example of an oil system (lubricant oil system) for supplying oil to supply targets in an internal combustion engine according to a modification.

FIG. 5 is a schematic diagram for explaining an example of an oil system (lubricant oil system) for supplying oil to supply targets in an internal combustion engine according to a modification different from FIG. 4.

DETAILED DESCRIPTION

Embodiments will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an example 1 of an internal combustion engine system 1 according to an embodiment. The internal combustion engine system 1 includes an internal combustion engine 2 and a controller 3. The internal combustion engine 2 and the controller 3 are mountable on an internal combustion engine-mounting device. Such an internal combustion engine-mounting device on which the internal combustion engine 2 and the controller 3 are mounted may be a vehicle, a stationary-type electric power generator, an industrial machine, a motive power source apparatus, or the like. The internal combustion engine 2 may be, for example, a diesel engine, or a gasoline engine. The internal combustion engine 2 generates motive power by burning fuel such as diesel oil or gasoline.

The controller 3 is constituted of a computer provided in the internal combustion engine-mounting device, such as a vehicle-mounted computer, and the computer that constitutes the controller 3 includes a processor or an integrated circuit, and a storage medium (non-transitory storage medium). In the controller 3, the processor or the integrated circuit includes any of an electronic control unit (ECU), a central processing unit (CPU), an application specific integrated circuit (ASIC), a microcomputer, a field programmable gate array (FPGA), and a digital signal processor (DSP). The controller 3 may include such a processor or the like as a single component, or may include a multiple of such processors or the like. Also, as the storage medium, the controller 3 includes either a main storage medium including a memory, or an auxiliary storage medium. The controller 3 controls operations of the internal combustion engine 2 by running a program or programs stored in the storage medium.

In the internal combustion engine 2, oil (engine oil) is supplied as a lubricant oil or the like to supply targets. FIG. 1 shows the flows of oil in the internal combustion engine 2 using arrows with solid lines. Also, FIG. 1 shows the operational control by the controller 3 using arrows with broken lines.

FIG. 2 is a schematic diagram for explaining an example of an oil system (lubricant oil system) for supplying oil to the supply targets in the internal combustion engine 2 according to the embodiment. As shown in FIGS. 1 and 2, the internal combustion engine 2 includes an oil pan 5, a pump 6, an oil filter 7, and an oil cooler 8. The oil pan 5 includes an oil reservoir 11 for storing oil. The internal combustion engine 2 also includes a suction channel 12 which extends from the reservoir 11 of the oil pan 5 to the pump 6. The pump 6 operates to draw up the oil stored in the oil reservoir 11 of the oil pan 5. The drawn oil flows into the pump 6 via the suction channel 12. The pump 6 then discharges the drawn oil. The oil discharged by the pump 6 is eventually stored in the oil pan 5.

The internal combustion engine 2 includes a supply channel (main supply channel) 13 and an oil gallery (main oil gallery) 15. The supply channel 13 extends from the pump 6 to the oil gallery 15 while passing through the oil filter 7 and the oil cooler 8 in this order. In the supply channel 13, the oil filter 7 is arranged on upstream side relative to the oil cooler 8. The pump 6 discharges the oil to the supply channel 13. In the internal combustion engine 2, the oil discharged from the pump 6 is supplied to the oil gallery 15 via the supply channel 13.

In the course of the supply channel 13, the oil filter 7 filters the oil discharged from the pump 6. The oil filter 7 includes a filter element 16 which is a filter material. Filtering at the oil filter 7 removes impurities such as abrasion powder and dirt from the oil. However, soot contained in the oil is microscopic. As such, soot is not removed or hardly removed by the filtering at the oil filter 7. The oil cooler 8 cools the oil. In the supply channel 13, therefore, the oil in the downstream side region relative to the oil cooler 8 has a lower temperature than the oil in the upstream side region relative to the oil cooler 8.

The internal combustion engine 2 includes a cylinder block 17 and a cylinder head 18. For the internal combustion engine 2, an exterior is formed by the oil pan 5, the cylinder block 17, the cylinder head 18, etc. The cylinder block 17 includes a cylinder and a crank case. The pump 6, etc. are arranged inside the cylinder block 17. In the internal combustion engine 2, also, the oil reservoir 11 of the oil pan 5 is formed inside the exterior part. The cylinder block 17 has an outer surface (outer wall surface) 21 exposed outside the internal combustion engine 2. The outer surface 21 of the cylinder block 17 forms a part of the exterior of the internal combustion engine 2. The oil filter 7 and the oil cooler 8 are arranged on the outer surface 21 of the cylinder block 17 and exposed outside the internal combustion engine 2. Note that, in FIG. 2, the wall portions that separate the inside and the outside of the internal combustion engine 2 from each other at the oil pan 5, the cylinder block 17, and the cylinder head 18 are schematically illustrated.

In the internal combustion engine 2, the oil supplied to the oil gallery 15 via the supply channel 13 is then supplied to each of the supply targets. The supply targets are each subjected to lubricating, etc. with the supplied oil. The oil that has been supplied to each of the supply targets is then returned to the oil reservoir 11 of the oil pan 5. The internal combustion engine 2 includes an oil jet 22 as one of the oil supply targets. The oil jet 22 is arranged inside the cylinder block 17. The internal combustion engine 2 includes a sub-supply channel 23 which extends from the oil gallery 15 to the oil jet 22. In the internal combustion engine 2, oil is supplied from the oil gallery 15 to the oil jet 22 via the sub-supply channel 23. Thus, the oil discharged from the pump 6 is supplied to the oil jet 22 by being routed through the supply channel 13, the oil gallery 15, and the sub-supply channel 23 in this order.

The internal combustion engine 2 includes a piston 25 and a crank shaft 26. The piston 25 and the crank shaft 26 are arranged inside the cylinder block 17. In the internal combustion engine 2, combustion, etc. of the fuel cause reciprocating movements of the piston 25 to rotate the crank shaft 26. The motive force generated by the rotation of the crank shaft 26 is transmitted from the internal combustion engine 2 to the driving unit of the internal combustion engine-mounting device. The oil jet 22 in the internal combustion engine 2 is adapted so that it can discharge the supplied oil toward the reciprocating piston 25. The piston 25 is cooled by the oil discharged from the oil jet 22. The internal combustion engine 2 also includes, as the oil supply targets other than the oil jet 22, a valve train mechanism (not shown in the figure) of the cylinder head 18, a journal unit (not shown in the figure) of the crank shaft 26, a turbo charger (not shown in the figure), and so on.

The internal combustion engine 2 includes an oil check valve 27. In the sub-supply channel 23, the oil check valve 27 is arranged between the oil gallery 15 and the oil jet 22. In an example, the oil check valve 27 is an on-off valve or a proportional valve. Also, the oil check valve 27 may be, for example, a solenoid valve which transitions between the opened and closed states in accordance with the electric power supply state. Opening of the oil check valve 27 causes the oil to be supplied to the oil jet 22 and enables the oil jet 22 to discharge the oil toward the piston 25. The closed state of the oil check valve 27 withholds the supply of oil to the oil jet 22. In an instance where the oil check valve 27 is a proportional valve, the amount of oil supplied to the oil jet 22 is changed in accordance with the opening degree of the oil check valve 27, which thus changes the amount of oil discharged by the oil jet 22.

The internal combustion engine 2 includes a return channel 31 which branches off from the supply channel 13. The return channel 31 branches off from the supply channel 13 on the upstream side relative to the oil cooler 8. In the internal combustion engine 2 as shown in FIGS. 1 and 2, the point where the return channel 31 branches off from the supply channel 13 is between the pump 6 and the oil filter 7. The internal combustion engine 2 also includes a soot separation unit 32 and a relief valve 33. The soot separation unit 32 and the relief valve 33 are provided in the return channel 31. The return channel 31 extends from the point of connection to the supply channel 13 (i.e., the branching point from the supply channel 13) and passes through the relief valve 33 and the soot separation unit 32 in this order. The relief valve 33 is thus arranged between the branching point of the return channel 31 and the soot separation unit 32.

The soot separation unit 32 in one example is constituted by a centrifugal separator. The soot separation unit 32 includes a centrifugal rotor 35 and a trapping member 36 which is a filter material. The soot separation unit 32 rotates the centrifugal rotor 35 to separate soot from the oil by centrifugation. The centrifugally separated soot is then collected by the trapping member 36. In the internal combustion engine 2, thus, the soot separation unit 32 collects the soot contained in the oil in the course of the return channel 31. In this manner, the soot contained in the oil is removed by the soot separation unit 32.

In the return channel 31, the relief valve 33 is arranged between the connection point to the supply channel 13 and the soot separation unit 32. In an example, the relief valve 33 is an on-off valve or a proportional valve. Also, the relief valve 33 may be, for example, a solenoid valve which transitions between the opened and closed states in accordance with the electric power supply state. Opening of the relief valve 33 causes the oil that has entered the return channel 31 as a split flow from the supply channel 13 to flow toward the soot separation unit 32 and be supplied to the soot separation unit 32. Also, opening of the relief valve 33 releases the pressure of the oil on the discharge side (at a discharge port) of the pump 6, and accordingly releases the pressure of the oil in the supply channel 13. The closed state of the relief valve 33 withholds the supply of oil to the soot separation unit 32. In an instance where the relief valve 33 is a proportional valve, the amount of oil supplied to the soot separation unit 32 is changed in accordance with the opening degree of the relief valve 33. As such, by opening the relief valve 33, the oil that has entered the return channel 31 as a split flow is caused to flow through the soot separation unit 32.

The internal combustion engine 2 arranges the soot separation unit 32 and the relief valve 33 on the outer surface (outer wall surface) 21 of the cylinder block 17. The soot separation unit 32 and the relief valve 33 are thus exposed outside the internal combustion engine 2. Also, the end of the return channel 31 that is on the side opposite to the connection point to the supply channel 13 (the branching point from the supply channel 13) is connected neither to the suction channel 12 nor to the suction side of the pump 6. The end of the return channel 31 that is on the side opposite to the connection point to the supply channel 13 is in communication with the oil reservoir 11 of the oil pan 5. Thus, the oil from which soot has been collected is discharged to the oil reservoir 11 of the oil pan 5 via the return channel 31 from the soot separation unit 32. For the above configuration, the return channel 31 differs from a return channel for sending back the oil from the discharge side of the pump 6 to the suction side of the pump 6. Further, the relief valve 33 is provided as a discrete component from the pump 6.

In the internal combustion engine system 1, the controller 3 controls operations of the oil check valve 27 and the relief valve 33. For example, assuming that the oil check valve 27 is a solenoid valve, the controller 3 controls the supply of electric power to the oil check valve 27 so as to control the excited state of the oil check valve 27 and thus control the opened and closed states of the oil check valve 27. Similarly, for example, assuming that the relief valve 33 is a solenoid valve, the controller 3 controls the supply of electric power to the relief valve 33 so as to control the excited state of the relief valve 33 and thus control the opened and closed states of the relief valve 33.

The controller 3 estimates the temperature of the piston 25 and controls the operations of the oil check valve 27 based on the estimation result for the temperature of the piston 25. The opened and closed states of the oil check valve 27 are thus controlled based on the estimation result for the temperature of the piston 25, and the supply of oil to the oil jet 22 is controlled. In the state where the internal combustion engine 2 is in operation, the controller 3 temporally repeats the estimation of the temperature of the piston 25. The controller 3 estimates the temperature of the piston 25 based on the rotational speed of the crank shaft 26 and the amount of oil sprayed out from the oil jet 22 for a predetermined time period.

The internal combustion engine 2 includes an angle sensor (not shown in the figure) for detecting a crank angle of the crank shaft 26. The controller 3 calculates the temporal change in the crank angle based on the detection result from the angle sensor and calculates the rotational speed of the crank shaft 26. Also, the controller 3 calculates the amount of oil sprayed out from the oil jet 22 for a predetermined time period based on the temporal change in the opened and closed states of the oil check valve 27. The storage medium, etc. of the controller 3 store relationship data indicative of the relationship of the temperature of the piston 25 relative to the rotational speed of the crank shaft 26, a fuel injection amount, and the amount of the sprayed oil from the oil jet 22. In one example, the relationship data takes the form of a data table in which the temperature of the piston 25 is associated with the rotational speed of the crank shaft 26, the fuel injection amount, and the amount of the sprayed oil from the oil jet 22. The controller 3 calculates the temperature of the piston 25 based on the calculation result for the rotational speed of the crank shaft 26, the calculation result for the amount of oil sprayed out from the oil jet 22 for a predetermined time period, and the relationship data.

In the internal combustion engine system 1, the controller 3 controls operations of the relief valve 33 in conjunction with the opened and closed states of the oil check valve 27. Thus, in the internal combustion engine 2, the control of the flow of oil to the soot separation unit 32 via the return channel 31 is realized by controlling the operations of the relief valve 33 in accordance with the state of oil supply to the oil jet 22. In other words, for the internal combustion engine 2, the operations of the relief valve 33 are controlled in accordance with the state of oil supply to the oil jet 22 so that the oil flowing through the soot separation unit 32 in the return channel 31 is controlled.

FIG. 3 is a flowchart schematically showing an example of the operation control performed by the controller 3 for the internal combustion engine 2 in the embodiment. The operation control shown in FIG. 3 is temporally repeated in the state where the internal combustion engine 2 is in operation. Upon starting of the process shown in FIG. 3, the controller 3 estimates the temperature of the piston 25 (S101). The temperature of the piston 25 is estimated in the manner described above. The controller 3 then determines whether or not the estimated temperature of the piston 25 is equal to or below a reference temperature (S102).

If the estimated temperature is higher than the reference temperature (S102: No), the controller 3 opens the oil check valve 27 or keeps the oil check valve 27 opened (S103). This causes the oil to be supplied to the oil jet 22 or maintains the state of supplying the oil to the oil jet 22. Also, the controller 3 closes the relief valve 33 or keeps the relief valve 33 closed (S104). This stops the supply of the oil to the soot separation unit 32 or maintains the state of withholding the supply of the oil to the soot separation unit 32.

On the other hand, if the estimated temperature is equal to or below the reference temperature (S102: Yes), the controller 3 closes the oil check valve 27 or keeps the oil check valve 27 closed (S105). This stops the supply of the oil to the oil jet 22 or maintains the state of withholding the supply of the oil to the oil jet 22. Also, the controller 3 opens the relief valve 33 or keeps the relief valve 33 opened (S106). This causes the oil to be supplied to the soot separation unit 32 or maintains the state of supplying the oil to the soot separation unit 32. Accordingly, the pressure of the oil in the supply channel 13 is released, or the supply channel 13 is maintained in the state where the pressure of the oil has been released.

According to the present embodiment, etc., as described above, the supply channel 13 extends from the pump 6 through the oil filter 7 and the return channel 31 branches off from the supply channel 13. Here, by opening the relief valve 33 which is arranged between the branching point of the return channel 31 and the soot separation unit 32, the oil that has entered the return channel 31 as a split flow from the supply channel 13 is caused to flow through the soot separation unit 32. Thus, even if a pressure increase occurs on the discharge side of the pump 6, the relief valve 33 is opened to release the pressure of the oil in the supply channel 13 (the discharge side of the pump 6). An increase in the oil pressure on the discharge side of the pump 6 can therefore be suppressed. Suppressing an increase in the oil pressure on the discharge side (at the discharge port) of the pump 6 allows for the reduction of the driving force of the pump 6. The reduced driving force of the pump 6 can consequently realize the reduced amount of fuel consumption in the internal combustion engine 2.

Moreover, the opening of the relief valve 33 causes the oil to flow through the soot separation unit 32, and accordingly, soot can be suitably removed from the oil by utilizing the soot separation unit 32 in the state where the internal combustion engine 2 is in operation. Such suitable removal of soot from the oil can keep the concentration of soot low in the oil to be supplied as a lubricant oil to sliding parts of the internal combustion engine 2. This can reduce the amount of wear at the sliding parts, and can consequently realize a longer operating life for the internal combustion engine 2.

In the internal combustion engine 2, the oil may be supplied to the oil jet 22 at a higher ratio than the ratio of oil supply to each of the other supply targets. The controller 3 according to the embodiment controls the operations of the relief valve 33 in accordance with the state of oil supply to the oil jet 22, and controls the flow of oil passing through the soot separation unit 32 in the return channel 31. With such control, the relief valve 33 is opened at the timing during the withholding of the oil supply to the oil jet 22, so as to release the oil pressure in the supply channel 13. Accordingly, an increase in the oil pressure on the discharge side (at the discharge port) of the pump 6 is suitably suppressed at timings where the oil supply to the oil jet 22 is withheld. This can further reduce the driving force of the pump 6.

Moreover, with the above described control, the oil is supplied to the soot separation unit 32 at the timing during withholding of the spray of oil from the oil jet 22. Accordingly, the soot removal from the oil is suitably conducted without interfering with the operations of the oil jet 22.

Also, according to the embodiments, etc., the controller 3 stops the supply of oil to the oil jet 22 and thus stops the spray of oil toward the piston 25, based on the estimation result for the temperature of the piston 25 indicating that the temperature is equal to or below the reference temperature. This can prevent the temperature of the piston 25 from being excessively decreased by the oil from the oil jet 22 so that the temperature fluctuation range of the piston 25 can be kept small. Consequently, a longer operating life for the piston 25 can be realized.

Moreover, since the excessive temperature decrease of the piston 25 is prevented, contraction of a piston ring attached to the piston 25 is suppressed, and accordingly, the end gap of the piston ring is prevented from becoming large. This can reduce the amount of a blow-by gas flowing toward the bottom side of the piston through the end gap of the piston ring. Further, the prevention of the excessive temperature decrease of the piston 25 also suppresses the drop in a temperature of the exhaust gas discharged from the internal combustion engine 2. This can increase the work efficiency in post-processing devices for the exhaust gases and a turbo charger.

Also, according to the embodiments, etc., the soot separation unit 32 and the relief valve 33 are arranged on the outer surface (outer wall surface) 21 of the cylinder block 17 and are exposed outside the internal combustion engine 2. Such an arrangement can realize a configuration where the soot separation unit 32 and the relief valve 33 are provided for the return channel 31, without entailing a large change in the configuration that does not include the soot separation unit 32. Moreover, by adopting a configuration where the relief valve 33 is exposed outside the internal combustion engine 2, the relief valve 33 can have an improved maintainability. For example, easy implementation of the connection of wiring or the like to the relief valve 33 for electric power supply, repair of the relief valve 33 at the occurrence of its malfunction, and so on can be realized. Also, since the location to arrange the soot separation unit 32 and the relief valve 33 is the cylinder block 17, a suitable strength can be secured at the part where the soot separation unit 32 and the relief valve 33 are arranged.

Also, the end of the return channel 31 that is on the opposite side to the connection point to the supply channel 13 is in communication with the oil reservoir 11 of the oil pan 5, so that the oil flows from the soot separation unit 32 via the return channel 31 and is discharged to the oil pan 5. As such, the return channel 31 is not connected to the suction side of the pump 6 (or the suction channel 12). According to this configuration, the return channel 31 extending through the soot separation unit 32 and the relief valve 33 can be formed with a simple structure even with the soot separation unit 32 and the relief valve 33 arranged on the outer surface 21 of the cylinder block 17.

Also, according to the embodiments, etc., the return channel 31 branches off from the supply channel 13 on the upstream side relative to the oil cooler 8. This suitably prevents the oil that has been cooled by the oil cooler 8 from flowing into the soot separation unit 32. As a result, this allows the oil of a relatively high temperature to be supplied to the soot separation unit 32, that is, the soot separation unit 32 receives a supply of a relatively less viscous oil. Accordingly, the soot separation at the soot separation unit 32 can further be facilitated and the soot collecting efficiency can be enhanced.

Moreover, according to an example shown in FIG. 2, the return channel 31 branches off from the supply channel 13 at a point between the pump 6 and the oil filter 7. With such a configuration, the pressure on the discharge side (at the discharge port) of the pump 6 decreases by at least an amount equivalent to the pressure loss at the oil filter 7, unlike in the configuration where the return channel 31 branches off on the downstream side relative to the oil filter 7. Therefore, the driving force of the pump 6 can further be reduced.

FIG. 4 is a schematic diagram for explaining an example of an oil system (lubricant oil system) for supplying oil to supply targets in the internal combustion engine 2 according to a modification. FIG. 4 schematically shows the wall portions that separate the inside and the outside of the internal combustion engine 2 from each other at the oil pan 5, the cylinder block 17, and the cylinder head 18. According to this modification as shown in FIG. 4, the return channel 31 branches off from the supply channel 13 on the downstream side relative to the oil filter 7. That is, the return channel 31 branches off from the supply channel 13 at a point between the oil filter 7 and the oil cooler 8.

The modification shown in FIG. 4 employs the same configuration for its oil system as that of the example shown in FIG. 2, etc., except that the branching point of the return channel 31 is different. As such, the present modification also provides the same effects and advantages as described in relation to the foregoing embodiments, etc. Also, according to this modification, the return channel 31 branches off from the supply channel 13 on the downstream side relative to the oil filter 7, and thus, the oil from which impurities have been removed by the oil filter 7 is supplied to the soot separation unit 32. Therefore, the soot separation at the soot separation unit 32 can further be facilitated and the soot collecting efficiency can be enhanced.

FIG. 5 is a schematic diagram for explaining an example of an oil system (lubricant oil system) for supplying oil to supply targets in the internal combustion engine 2 according to a modification different from FIG. 4. FIG. 5 schematically shows the wall portions that separate the inside and the outside of the internal combustion engine 2 from each other at the oil pan 5, the cylinder block 17, and the cylinder head 18. According to this modification as shown in FIG. 5, the internal combustion engine 2 includes a removal device 40 which is a combination of the oil filter 7 and the soot separation unit 32. The removal device 40 is arranged on the outer surface 21 of the cylinder block 17. Thus, this modification may also be interpreted as arranging the oil filter 7, the soot separation unit 32, and the relief valve 33 on the outer surface of the cylinder block 17.

In the removal device 40, a portion functioning as the oil filter 7 is partitioned from a portion functioning as the soot separation unit 32. Also, in the removal device 40, the supply channel 13 passes through the portion functioning as the oil filter 7 and the return channel 31 passes through the portion functioning as the soot separation unit 32. In the removal device 40, the portion where the supply channel 13 passes through is not communicated with the portion where the return channel 31 passes through. With this configuration of the removal device 40, in which the oil filter 7 and the soot separation unit 32 are combined with each other, the flow of oil from the supply channel 13 into the return channel 31 as well as the flow of oil from the return channel 31 into the supply channel 13 are prevented.

The modification shown in FIG. 5 employs the same configuration for its oil system as that of the example shown in FIG. 2, etc., except that the oil filter 7 and the soot separation unit 32 are combined. As such, the present modification also provides the same effects and advantages as described in relation to the foregoing embodiments, etc. Also, according to this modification, the oil filter 7 and the soot separation unit 32 are combined together, and therefore, an enhanced mountability of the oil filter 7 and the soot separation unit 32 is realized. Moreover, replacement of the filter element 16 and the trapping member 36 can be facilitated, and accordingly, an improved maintainability of the oil filter 7 and the soot separation unit 32 is realized.

According to another modification, the return channel 31 branches off from the supply channel 13 at a point between the oil filter 7 and the oil cooler 8 as in the configuration shown in FIG. 4. The internal combustion engine 2 here is provided with the removal device 40 which is a combination of the oil filter 7 and the soot separation unit 32 as in the configuration shown in FIG. 5. Such a modification can also provide the same effects and advantages as described in relation to the foregoing embodiments, etc.

The foregoing embodiments, etc. have assumed arrangements where the relief valve 33 is present between the branching point of the return channel 31 and the soot separation unit 32, but no limitations are intended by this. According to a modification, the relief valve 33 is arranged at a position of the return channel 31 that is between the soot separation unit 32 and the oil reservoir 11 of the oil pan 5. In this case, the soot separation unit 32 is arranged between the branching point of the return channel 31 and the relief valve 33. In such a modification, too, opening of the relief valve 33 provided in the return channel 31 causes the oil that has entered the return channel 31 as a split flow from the supply channel 13 to flow through the soot separation unit 32. As such, this modification also provides the same effects and advantages as described in relation to the foregoing embodiments, etc.

Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.