THERMOSTAT FOR ENGINE COOLING SYSTEM

Description

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0017300, filed on Feb. 14, 2019, the entire contents of which are incorporated herein by reference.

FIELD

Exemplary embodiments of the present disclosure relate to a thermostat constituted in an engine cooling system to perform valve opening or closing in response to temperature of coolant.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

As illustrated in FIG. 1, a thermostat may be applied to an engine cooling system such that valve opening or closing thereof is controlled in response to a preset temperature of coolant.

In other words, the thermostat controls a bypass flow rate of the coolant circulating into an engine and a flow rate of the coolant in a radiator.

A mechanical thermostat among such thermostats cannot perform variable control considering conditions of the engine and environmental factors whereas an electronic thermostat can control a flow rate of the coolant by controlling valve opening or closing in response to operating conditions of the engine and the environmental factors.

In other words, the electronic thermostat, under high load condition, controls temperature of the coolant such that no problem in durability of the engine occurs whereas, under low load condition, it controls temperature of the coolant to be high in consideration of fuel efficiency and performance of the engine.

Cooling modes in the engine cooling system may include an outlet controlled cooling mode as shown in FIG. 1 and an inlet controlled cooling mode as shown in FIG. 2 depending on position of the thermostat.

Differential characteristics of the outlet controlled cooling mode and the inlet controlled cooling method can be summarized as shown in the following Table 1.

TABLE 1
	Outlet	Inlet
	controlled	controlled
Item	cooling mode	cooling mode
1) Follow-up to abrupt	Disadvantage	Advantage
fluctuation in coolant	(Hunting is remarkable,	(Hunting is
temperature	Overshoot/Undershoot is	insignificant)
	remarkable)
2) Control of coolant	Disadvantage	Advantage
temperature depending
on engine load
3) Cavitation at high	Advantage	Disadvantage
coolant temperature
4) Flow rate of coolant	Not affected	Not affected
5) Layout of cooling	Simple	Complicated
system		(Being difficult to
		inject coolant)
6) Durability of	Disadvantage	Advantage
thermostat	(Being liable to be
	affected by fluctuation of
	coolant pressure and
	temperature)
7) Operability of	Not affected by	Affected by
thermostat	differential pressure of	differential
	coolant	pressure of coolant

As shown in Table 1, the outlet controlled cooling mode and the inlet controlled cooling mode each have advantages and disadvantages. Particularly, in the case of the outlet controlled cooling mode, there is a disadvantage in terms of abrupt fluctuation in coolant temperature.

Specifically, when coolant temperature rises in the engine, the thermostat is opened whereby the coolant circulates to the radiator. At this time, we have discovered that as the temperature of the coolant in the radiator is low, high temperature coolant in the engine and low temperature coolant in the radiator are mixed with each other when the thermostat is opened at the initial stage and, resulting in abrupt fluctuation in coolant temperature (i.e., overshoot/undershoot and hunting of the coolant) as shown in FIG. 3.

As a result, fluctuation in temperature of the coolant in an engine head and block, the radiator, a heater core, an oil cooler, an exhaust gas recirculation (EGR) cooler and the like becomes large, durability of both the engine and the radiator may be deteriorated due to thermal shock of the engine.

Such thermal shock due to abrupt fluctuation in coolant temperature, which may be caused by valve opening/closing actuation of the thermostat, occurs in both mechanical and electronic thermostats.

The above information disclosed in this Background section is only for assisting understanding of the background of the disclosure and it may therefore contain information that does not form the prior art that is already known to those who have ordinary skill in the art.

SUMMARY

The present disclosure provides a thermostat for an engine cooling system, which is capable of reducing or minimizing occurrence of thermal shock which may be caused by abrupt fluctuation in coolant temperature.

Other objects and advantages of the present disclosure can be understood by the following description and become apparent with reference to the embodiments of the present disclosure. Also, it is obvious to those skilled in the art to which the present disclosure pertains that the objects and advantages of the present disclosure can be realized by the means as claimed and combinations thereof.

In accordance with one aspect of the present disclosure, a thermostat for an engine cooling system which is arranged between an engine and a radiator comprises: a housing having a coolant inlet through which coolant flows in from the engine and an outlet leading the coolant to the radiator; and a main valve provided in the housing and coupled to one side of wax and configured to open or close the outlet as the volume of the wax is changed. In particular, the main valve is formed with at least one coolant hole.

Further, the thermostat may further comprise a bracket provided in the housing and configured to support the main valve. In one form, the bracket may comprise an upper plate capable of contacting or being separated from the main valve to open or close the outlet leading to the radiator, and a stepped portion formed in an inner diameter portion of the upper plate may be arranged so as to abut against a part of the main valve.

More specifically, the at least one coolant hole of the main valve may be arranged at a position to be abutted against the stepped portion.

Therefore, the at least one coolant hole is opened before the main valve opens the outlet leading to the radiator so that some of the coolant flows through the at least one coolant hole to the outlet leading to the radiator.

The at least one coolant hole may include a plurality of coolant holes formed through top and bottom surfaces of the main valve, and the plurality of coolant holes may be arranged along a peripheral portion of the main valve with predetermined intervals.

In one form, the thermostat may further comprise a bypass valve configured to open or close a bypass outlet formed in the housing, and the bypass outlet is configured to guide the coolant coming through the coolant inlet to the engine.

Further, the bypass valve may be configured to move in a direction of closing the bypass outlet when the at least one coolant hole is moved in a direction of being opened.

Further, the bypass valve may be configured to be connected to the wax by means of a shaft of the bypass valve to operate in conjunction with the main valve.

Further, with this configuration, a flow path to the radiator is closed when the main valve is in contact with both the upper plate and the stepped portion; the flow path to the radiator is opened partially when the main valve is in contact with the upper plate and spaced apart from the stepped portion; and the flow path to the radiator is opened when the main valve is spaced apart from both the upper plate and the stepped portion.

It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

FIG. 1 is a schematic view of an example of an engine cooling system of an outlet controlled cooling mode;

FIG. 2 is a schematic view of an example of an engine cooling system of an inlet controlled cooling mode;

FIG. 3 is a graph for showing problems in an outlet controlled cooling mode;

FIG. 4 is a schematic diagram of an engine cooling system according to an embodiment of the present disclosure;

FIG. 5 is a schematic view of a thermostat for an engine cooling system according to an embodiment of the present disclosure;

FIGS. 6A and 6B show examples of configuration of a thermostat according to an embodiment of the present disclosure respectively; and

FIGS. 7 and 8 illustrate operating states of a thermostat for an engine cooling system according to an embodiment of the present disclosure respectively.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

In order to fully understand the present disclosure, operational advantages of the present disclosure and objects achieved by implementing the present disclosure, the accompanying drawings exemplifying forms of the present disclosure and contents described in the accompanying drawings need to be referred to.

In describing the exemplary forms, detailed description of technology known in the art or iterative description may be made shortly or omitted to avoid obscuring the subject matter of the present disclosure.

FIG. 4 is a schematic diagram of an engine cooling system according to an embodiment of the present disclosure and FIG. 5 is a schematic view of a thermostat for an engine cooling system according to an embodiment of the present disclosure.

Hereinafter, the thermostat for an engine cooling system according to the embodiment of the present disclosure will be described with reference to FIGS. 4 and 5.

The thermostat according to the embodiment of the present disclosure is provided between an engine (head, block) and a radiator in an engine cooling system as shown in FIG. 4 to control valve opening or closing of bypass lines leading to a heater and an exhaust gas recirculation (EGR) cooler, to a radiator and to an oil cooler depending on coolant temperature and to control flow rate of coolant depending on opening degree of a valve.

By using such control of flow rate of coolant, flow rate of the coolant can be optimally controlled depending on characteristics, control strategy and operating conditions of the engine, so that engine performance, fuel efficiency and cooling and heating performance can be improved even by a simple configuration.

In addition, such control can be applied to an engine cooling system of an outlet controlled cooling mode in which a thermostat is provided at an outlet side of the engine, in order to prevent thermal shock due to abrupt fluctuation in temperature of the coolant, which may be caused because high temperature coolant passed through the engine and low temperature coolant from a radiator are mixed with each other.

To this end, the thermostat according to the embodiment of the present disclosure is arranged in a flow path between the engine (engine head and engine block) and the radiator and configured such that a valve supported by a bracket 170 is operated as the volume of wax 120 in a housing 110 is changed. The valve controls the path and flow rate of coolant.

The housing 110 is formed with a coolant inlet 111, a bypass outlet 112 and an outlet 113 leading to the radiator.

In addition, a main valve 130 and a bypass valve 140 are provided to control opening/closing and flow rate of the outlet 113 leading to the radiator and the bypass outlet 112, respectively.

The main valve 130 is arranged to be coupled to a piston 150 so as to open or close the outlet 113 leading to the radiator. This main valve is shifted at the top of the piston 150 by means of change in volume of the wax 120 in the bracket 170 and in turn open or close the outlet 113 guiding the coolant to the radiator. Then, after shifting the position, the main valve is returned elastically to its original position by means of a main valve spring 161 of which one side is coupled to the main valve 130 and the other side is supported in the bracket 170.

Further, a bypass valve 140 is coupled to the other side of the wax 120.

The bypass valve 140 is provided at the bypass outlet 112 side and coupled to the wax 120 by means of a shaft 141 of the bypass valve to open or close the bypass outlet 112.

Accordingly, the bypass valve is shifted by means of change in volume of the wax 120. Then, after shifting the position, the bypass valve is returned elastically to its original position by means of a bypass valve spring 162 of which one side is coupled to the bypass valve 140 and the other side is coupled to the wax 120.

In this way, the main valve 130 and the bypass valve 132 are operated to be opened or closed in conjunction with each other by means of change in volume of the wax 120.

Further, a sensor 180 for measuring temperature of the coolant may be provided at the coolant inlet 111 to control the coolant.

In this way, when the volume of the wax 120 is changed as shown in FIG. 7, the bypass valve 140 closes the bypass outlet 112 and the main valve 130 is operated to supply the coolant from the coolant inlet 111 to the outlet 113 leading to the radiator.

Furthermore, this embodiment of the present disclosure employs a means for preventing abrupt fluctuation in temperature due to mixing of high temperature coolant at the coolant inlet 111 side and low temperature coolant at the outlet 113 side leading to the radiator.

Specifically, an upper plate 171 of the bracket 170, which abuts against the main valve 130 to close the flow path or is separated from the main valve 130 to open the flow path, is provided at its inner diameter portion with a stepped portion 171-1 wherein the stepped portion 171-1 and the main valve 130 are to be arranged in such a manner that the stepped portion covers a part of a peripheral portion of the main valve 130.

Further, the main valve 130 is formed with a coolant hole 131. In one form the coolant hole 131 is formed through top and bottom surfaces of the main valve 130.

Accordingly, when the main valve 130 is shifted downward as shown in FIG. 7, side ends of the main valve 130 abut against the upper plate 171 so that the coolant cannot pass through the peripheral portion of the main valve 130, whereas the top face of the main valve is separated from the stepped portion 171-1 so that the outlet 113 leading to the radiator is partially opened and thus only a small amount of the coolant can pass through the coolant hole 131 formed in the main valve 130.

This embodiment of the present disclosure is configured such that the main valve 130 is not completely opened for a moment but the coolant hole 131 formed in the main valve 130 is first opened, thereby allowing only a small amount of flow rate of the coolant to flow through the outlet 113 leading to the radiator.

Accordingly, cold coolant is less circulated when the thermostat is opened at the initial stage. As a result, engine warm up is faster so that fuel efficiency is improved. In addition, there is no abrupt thermal shock (overshoot/undershoot and hunting) in temperature of the coolant of the engine and the radiator so that thermal durability of the engine is improved.

Moreover, when the main valve 130 is further shifted downward than that shown in FIG. 7, as shown in FIG. 8, the main valve 130 is separated from both the upper plate 171 and the stepped portion 171-1. As a result, the outlet 113 leading to the radiator is completely opened whereby the coolant is allowed to flow through the outlet 113 leading to the radiator via the coolant hole 131 formed in the main valve 130 and the flow path between the side face of the main valve 130 and the upper plate 171.

The coolant hole 131 is formed in a portion of the main valve 130 which is covered by the stepped portion of the upper plate 171. In addition, the coolant hole may be implemented in various ways.

As a way of example, the coolant hole 131 may be a plurality of coolant holes 131-1 having a circular shape in a plane section wherein the holes are spaced from each other at equal intervals or predetermined intervals and positioned at the same radial distance, as shown in FIG. 6A.

Alternatively, each hole may be formed in a shape of the hole 131-2 which is formed by perforating a partial section of the main valve irregularly, as shown in FIG. 6B.

According to the thermostat for the engine cooling system of the present disclosure, initial flow rate of the coolant in the thermostat is precisely controlled so that thermal shock by coolant, which may be caused by initial uncontrolled opening of the thermostat, can be prevented.

In addition, cold coolant less circulates when the thermostat is opened at the initial stage and as a result, engine warm up is faster so that fuel efficiency can be improved.

Therefore, abrupt thermal shock (overshoot/undershoot and hunting) by coolant is prevented from occurring in the head and block, etc. of the engine so that thermal durability of the engine and the radiator is improved.

Further, durability and reliability of the engine can be improved in that thermal shock by coolant, which may be caused by initial uncontrolled opening of the thermostat and ultimately affects the radiator, the heater core, the oil cooler, the EGR cooler and the like, is prevented and thus excessive fluctuation in temperature is prevented.

Although the present disclosure has been described in the foregoing with reference to the drawings illustrated by way of an example, the present disclosure is not limited to the disclosed embodiments and it is apparent to those of ordinary skill in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope of the disclosure.