JP2014047725A - Thermostat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a cooling water temperature drop tendency in an engine, regarding a thermostat.SOLUTION: A thermostat includes: housings 2 and 4 including a first opening section and a second opening section circulating cooling water; a valve 5 stored in the housings 2 and 4; springs 6 energizing the valve 5 in a valve closing direction; a temperature sensing section 10 including a case 10b fixed to the valve 5 and wax 10a stored in the case 10b on the second opening section side; a rod 3 moving the valve 5 in a valve opening direction during melting and expansion of the wax 10a; a shield member 20 which is fixed to an outer peripheral surface of the valve 5 or the case 10b and partitions the inside of the housing between the valve 5 and the case 10b storing the wax 10a.

Description

  The present invention relates to a thermostat, and in particular, a thermostat provided at a junction between an engine inlet-side flow path for supplying cooling water from a radiator to a water jacket and a bypass flow path for bypassing cooling water supplied from the water jacket from the radiator. About.

  Generally, a thermostat provided in an engine cooling water circuit is provided at a branch portion between an engine outlet side channel for supplying cooling water from a water jacket to a radiator and a bypass channel for bypassing cooling water from the radiator. (Hereinafter also referred to as an outlet-side thermostat) is known.

  A thermostat is also provided at the junction of the engine inlet-side flow path that supplies cooling water from the radiator to the water jacket and the bypass flow path that bypasses the radiator (hereinafter also referred to as the inlet-side thermostat). It has been. A cooling water circuit including such an inlet-side thermostat is disclosed in Patent Document 1, for example.

JP-A-2005-90726

  By the way, in the case of the inlet side thermostat, when the valve is opened, both the low-temperature cooling water from the radiator and the high-temperature cooling water from the bypass channel (engine) flow into the temperature sensing part of the thermostat. As a result, there is a possibility that the thermostat does not operate properly because the low-temperature cooling water flows into the thermosensitive part of the thermostat even though the cooling water from the bypass channel is high temperature. Therefore, in order to avoid overheating, it is necessary to set the thermostat set temperature low.

  As a result, the inlet side thermostat tends to lower the cooling water temperature inside the engine, and the friction loss also increases due to the viscosity hardening of the engine oil, which may worsen the fuel consumption.

  The present invention has been made in view of these points, and an object of the present invention is to effectively prevent deterioration in fuel consumption by suppressing a decrease in cooling water temperature inside the engine and reducing engine friction loss. To provide a thermostat.

  In order to achieve the above-described object, the thermostat of the present invention has a first opening, a second opening, and a third opening for circulating cooling water, and the first opening and the first opening. A housing formed opposite to the second opening, and accommodated in the housing, and prevents the coolant from flowing through the first opening when the valve is closed, while the first opening when the valve is opened. A valve that allows the coolant to flow through the part, a spring that urges the valve in the valve closing direction, a case that is fixed to the valve, and at least a part of the case is positioned on the second opening side, and A temperature sensing part which is contained in the case on the second opening side and has a wax which solidifies, shrinks and melts and expands according to the cooling water temperature, and one end is fixed to the housing on the first opening side. And accommodate the other end in the case And a rod that moves the valve in the valve opening direction when the wax is melted and expanded, and is fixed to the outer peripheral surface of the valve or the case, and the inside of the housing between the valve and the case containing the wax. And a shielding member for partitioning.

  The shielding member may have a skirt portion that extends conically from the outer peripheral surface of the valve or the case toward the second opening.

  The housing may slidably accommodate the valve, and the third opening may be formed on a side portion where the valve slides.

  The thermostat of the present invention has a first opening, a second opening, and a third opening through which cooling water flows, and the first opening and the second opening are A housing formed oppositely and housed in the housing, and prevents cooling water flow through the first opening when the valve is closed, while allowing cooling water flow through the first opening when the valve is opened. A valve to be allowed, a spring that urges the valve in a valve closing direction, a case fixed to the valve and at least a part of which is positioned on the second opening side, and the second opening A temperature-sensitive part which is contained in the case on the part side and has a wax which solidifies, shrinks and expands according to the cooling water temperature, and one end is fixed to the housing on the first opening part side and the other end is Of the wax contained in the case A rod that moves the valve in the valve opening direction during melt expansion, and the housing slidably accommodates the valve, and the third opening is formed on a side portion on which the valve slides. It is characterized by that.

  The portion of the case containing the wax may be formed with a diameter smaller than the inner diameter of the cooling water circuit facing the second opening, and at least a part of the portion may be positioned in the cooling water circuit.

  The thermostat of the present invention has a first opening, a second opening, and a third opening through which cooling water flows, and the first opening and the second opening are A housing formed oppositely and housed in the housing, and prevents cooling water flow through the first opening when the valve is closed, while allowing cooling water flow through the first opening when the valve is opened. A valve to be allowed, a spring that urges the valve in a valve closing direction, a case fixed to the valve and at least a part of which is positioned on the second opening side, and the second opening A temperature-sensitive part which is contained in the case on the part side and has a wax which solidifies, shrinks and expands according to the cooling water temperature, and one end is fixed to the housing on the first opening part side and the other end is Of the wax contained in the case A rod that moves the valve in the valve opening direction during melt expansion, and the portion of the case that contains the wax is formed with a diameter smaller than the inner diameter of the cooling water circuit that the second opening faces. It is characterized in that at least a part thereof is located in the cooling water circuit.

  The cooling water circuit includes an engine inlet-side flow path for supplying cooling water from a radiator to a water jacket, and a bypass flow path for bypassing cooling water supplied from the water jacket from the radiator. A first opening facing the radiator; a second opening facing the bypass flow path; and a third opening facing the water jacket. You may arrange | position in the junction part of an entrance side flow path and the said bypass flow path.

  According to the thermostat of the present invention, it is possible to effectively prevent the deterioration of fuel consumption by suppressing the cooling water temperature drop inside the engine and reducing the friction loss of the engine.

It is a typical fragmentary sectional view showing the whole cooling water circuit composition to which the thermostat concerning a first embodiment of the present invention is applied. It is a typical fragmentary sectional view showing the whole thermostat composition concerning a first embodiment of the present invention. It is a typical fragmentary sectional view showing the state where the thermostat concerning a first embodiment of the present invention opened. It is a typical fragmentary sectional view showing the whole thermostat composition concerning a second embodiment of the present invention. It is a typical fragmentary sectional view showing the whole thermostat composition concerning a third embodiment of the present invention. It is a typical fragmentary sectional view showing the whole thermostat composition concerning other embodiments.

  Hereinafter, each embodiment of the thermostat according to the present invention will be described with reference to the accompanying drawings.

[First embodiment]
A thermostat 1A according to the first embodiment of the present invention will be described based on FIGS. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  First, the cooling water circuit 30 of the engine E to which the thermostat 1A according to the first embodiment of the present invention is applied will be described with reference to FIG. The cooling water circuit 30 includes a water jacket 31 formed in the cylinder block of the engine E, a radiator 32 that performs heat exchange between the cooling water and the outside air, and an engine outlet side that supplies the cooling water from the water jacket 31 to the radiator 32. A flow path 33, an engine inlet-side flow path 34 for supplying cooling water from the radiator 32 to the water jacket 31, and a bypass flow path 35 for bypassing the cooling water from the radiator 32 are provided. In addition, a water pump P that is driven by the power of the engine E and pumps cooling water is interposed in the engine inlet-side flow path 34 adjacent to the inlet portion of the water jacket 31.

  In the present embodiment, the bypass flow path 35 is connected to a portion where the engine inlet-side flow passage 34 is bent (in this embodiment, approximately 90 degrees), and this bent portion is the cooling water flowing through the engine inlet-side flow passage 34. A junction M with the cooling water flowing in from the bypass channel 35 is formed. And the thermostat 1A of this embodiment is provided in this junction M.

  Next, a detailed configuration of the thermostat 1A of the present embodiment will be described based on FIG. The thermostat 1A includes a main housing 2, a main rod 3, a sub housing 4, a main valve 5, a main spring 6, a bypass valve 7, a bypass rod 8, a bypass spring 9, a temperature sensing unit 10, And a shielding member 20. For convenience of explanation, the radiator side in FIG. 2 is defined as the upper side and the engine outlet side as the lower side as necessary.

  The main housing 2 includes a fixed flange 2a formed in an annular shape having a larger diameter than the inner diameter of the engine inlet-side flow path 34, and a main frame 2b having a substantially arcuate longitudinal section extending from the fixed flange 2a. It is formed in a shape that does not hinder the flow of cooling water from the radiator 32. The fixed flange 2 a has an outer edge portion fixed to the engine inlet side flow path 34 closer to the radiator 32 than the junction M. The central opening of the fixed flange 2a corresponds to the first opening of the present invention. The upper end of the main rod 3 is fixed at the center of the arc of the main frame 2b.

  The sub-housing 4 is formed in a substantially cylindrical shape, and includes an annular fixed flange 4a that protrudes outward from the upper end and an annular support flange 4b that protrudes inward from the lower end. A plurality of opening holes are provided in the side portion of the sub-housing 4 and are formed in a shape that does not hinder the flow of the cooling water from the radiator 32 as in the main housing 2. A main valve 5 is accommodated in the cylinder of the sub housing 4 so as to be relatively movable. Further, the fixed flange 4 a is fixed to the fixed flange 2 a of the main housing 2, and the flange surface of the support flange 4 b supports the lower end of the main spring 6. In the present embodiment, the central opening of the support flange 4b corresponds to the second opening of the present invention, and the plurality of opening holes formed in the side portion of the sub-housing 4 are formed in the third opening of the present invention. Equivalent to.

  The temperature sensing unit 10 includes a known wax 10a that solidifies and shrinks and melts and expands according to the cooling water temperature, and a bottomed cylindrical wax case 10b that accommodates the wax 10a. Further, a through hole through which the main rod 3 is slidably inserted is formed in the upper surface portion of the wax case 10b, and the lower end portion of the main rod 3 is accommodated in the case.

  The main valve 5 is formed in a flat plate circular shape having a diameter larger than that of the opening hole of the fixed flange 2a, and a through hole having substantially the same diameter as the wax case 10b is formed at the center thereof. A cylindrical flange 5a that fits with the outer peripheral surface of the wax case 10b (the outer peripheral surface above the wax 10a) is formed at the peripheral edge of the through hole. Further, an annular seal member 5 b is provided on the upper plane of the main valve 5. Further, a main spring 6 for biasing the main valve 5 toward the fixed flange 2a is interposed between the main valve 5 and the support flange 4b.

  That is, when the cooling water temperature is low and the wax 10a is solidified and contracted, the main valve 5 is configured to be seated (ie, closed) on the fixed flange 2a via the seal member 5a by the urging force of the main spring 6. Yes. On the other hand, when the cooling water temperature is high and the wax 10a melts and expands, the main valve 5 is configured to move away from the fixed flange 2a (that is, to open the valve) against the urging force of the main spring 6 together with the temperature sensing unit 10. ing.

  The bypass valve 7 is formed in a flat plate shape having a diameter larger than the inner diameter of the bypass flow path 35, and a through hole through which a bypass rod 8 fixed to the wax case 10b is slidably inserted is formed at the center. Is formed. Further, a bypass spring 9 that urges the bypass valve 7 toward the bypass flow path 35 is interposed between the bypass valve 7 and the lower surface portion of the wax case 10b.

  The shielding member 20 includes a substantially conical skirt portion 20a and a cylindrical top portion 20b provided on the top portion of the skirt portion 20a. The cylindrical top portion 20b is formed with substantially the same diameter as the cylindrical flange 5a of the main valve 5, and the outer peripheral surface of the cylindrical flange 5a is fitted into the cylinder. The cylindrical top portion 20b may be fitted to the outer peripheral surface of the wax case 10b above the wax 10a.

  The outer diameter of the skirt portion 20a (the outer diameter of the outer periphery of the lower end of the skirt) is formed slightly smaller than the inner diameter of the merging portion M so that the shielding member 20 can slide in the merging portion M. That is, only a minute clearance that allows a slight flow of cooling water is provided between the lower edge of the skirt portion 20a and the inner peripheral surface of the merging portion M. Thereby, the area of the merging portion M is divided into the main valve 5 side and the bypass flow path 35 side by the shielding member 20, and an annular cooling water flow path is formed between the main valve 5 and the shielding member 20. .

  Next, the effect by the thermostat 1A which concerns on this embodiment is demonstrated.

  When the temperature of the cooling water flowing into the junction M from the bypass channel 35 rises to a predetermined temperature (for example, about 70 ° C.), the wax 10a starts to melt and expand. Accordingly, the main valve 5 fixed to the outer peripheral surface of the wax case 10b via the cylindrical flange 5a moves toward the bypass flow path 35 against the urging force of the main spring 6 and is opened (FIG. 3). That is, the low-temperature cooling water that passes through the main housing 2 and reaches the main valve 5 from the radiator 32 flows into the junction M between the main valve 5 and the shielding member 20.

  Here, in the thermostat 1A of the present embodiment, the shielding member 20 having the conical skirt portion 20a is provided on the annular flange 5a of the main valve 5. With this shielding member 20, as shown in FIG. 3, the joining portion M is a bypass where the annular portion is formed between the main valve 5 and the shielding member 20, and the temperature sensing portion 10 is disposed. It is divided into two regions, the region β on the channel 35 side.

  That is, the low-temperature cooling water flowing from the radiator 32 when the main valve 5 is opened flows through the annular flow path formed by the main valve 5 and the shielding member 20 and is drawn into the water pump P. Inflow to the merging portion M (region β) closer to the bypass flow path 35 than the shielding member 20 in which the temperature sensing unit 10 is disposed is prevented. As a result, only the cooling water flowing from the engine E via the bypass flow path 35 reaches the temperature sensing unit 10, and the influence of the low-temperature cooling water from the radiator 32 is effectively suppressed.

  Therefore, according to the thermostat 1A of the present embodiment, it is not necessary to set the set temperature of the thermostat 1A low, and it is possible to suppress the tendency of the cooling water temperature in the engine to decrease. As a result, it is possible to prevent viscosity hardening of the engine oil and increase in friction loss, and to effectively improve fuel efficiency.

[Second Embodiment]
Hereinafter, based on FIG. 4, the thermostat 1B which concerns on 2nd embodiment of this invention is demonstrated.

  As shown in FIG. 4, the thermostat 1 </ b> B of the second embodiment is the one in which the shielding member 20 is omitted and the shape of the sub-housing 4 and the shape of the junction M are changed as shown in FIG. 4. is there. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  The sub-housing 4 has an annular fixed flange 4a fixed to the annular flange 2a of the main housing 2, an upper cylindrical outer peripheral portion 4b extending downward substantially perpendicularly from the fixed flange 4a, and a substantially vertical position from the lower end of the upper cylindrical outer peripheral portion 4b. An annular outer peripheral portion 4c extending inwardly, a lower cylindrical outer peripheral portion 4d extending substantially vertically downward from an inner end of the annular outer peripheral portion 4c, and an inner portion extending substantially vertically inward from the lower end of the lower cylindrical outer peripheral portion 4d. An annular support flange 4e that supports the lower end of the main spring 6 is provided.

  The upper cylindrical outer peripheral portion 4 b is formed so that its inner diameter is slightly larger than the outer diameter of the main valve 5 so as to slidably accommodate the main valve 5. That is, the clearance between the inner side surface of the upper cylindrical outer peripheral portion 4b and the outer peripheral edge portion of the main valve 5 is formed as a minute clearance that allows only the sliding movement of the main valve 5 and prevents the flow of cooling water. ing. In addition, the upper cylindrical outer peripheral portion 4b facing the engine inlet side is allowed to flow into the engine inlet side of the cooling water flowing from the radiator side into the merging portion M and the cooling water flowing from the bypass channel 35 into the merging portion M. An opening 4f is formed.

  The inner diameter of the lower cylindrical outer peripheral portion 4 d is smaller than the outer diameter of the main valve 5 and larger than the outer diameter of the main spring 6. That is, the cylinder inside the lower cylindrical outer peripheral portion 4d is formed in a size that accommodates the temperature sensing portion 10 and a part (lower end portion) of the main spring 6 but does not allow the main valve 5 to enter.

  The merge portion M of the engine inlet side flow path 34 is continuous from an upper bent portion 34a having an L-shaped vertical section, an intermediate bent portion 34b having an L-shaped vertical section continuing from the upper bent portion 34a, and an intermediate bent portion 34b. And a lower bent portion 34c.

  An annular flange 2a of the main housing 2 is fixed to the upper end of the upper bent portion 34a. The inner side surface of the upper bent portion 34a forms an annular flow path between the annular flange 2a of the main housing 2 and the valve plane of the main valve 5 when the main valve 5 is opened.

  The intermediate bent portion 34b is formed to be bent at a substantially right angle in accordance with the shapes of the upper cylindrical outer peripheral portion 4b and the annular outer peripheral portion 4c. That is, in a state where the thermostat 1B is disposed in the merge portion M, the outer surfaces of the upper cylindrical outer peripheral portion 4b and the annular outer peripheral portion 4c are in close contact with the inner side surface of the intermediate bent portion 34b.

  The lower bent portion 34c is formed to have an inner diameter larger than the outer diameter of the lower cylindrical outer peripheral portion 4d and to be longer in the vertical direction than the lower cylindrical outer peripheral portion 4d. That is, in a state where the thermostat 1B is disposed in the merge portion M, the outer surface of the lower cylindrical outer peripheral portion 40d is in close contact with the inner surface of the lower bent portion 34c. Further, the lower cylindrical outer peripheral portion 4d, the bypass valve 7, the bypass rod 8, and the bypass spring 9 are accommodated inside the lower bent portion 34c.

  Next, the effect by the thermostat 1B which concerns on this embodiment is demonstrated.

  In the thermostat 1B of the present embodiment, when the main valve 5 is opened, an annular flow path is formed by the inner surface of the upper bent portion 34a, the annular flange 2a of the main housing 2, and the valve plane of the main valve 5. Further, the interval between the inner side surface of the upper cylindrical outer peripheral portion 4b and the outer edge portion of the main valve 5 is formed with a minute clearance that allows only the sliding movement of the main valve 5 and prevents the flow of cooling water. And the opening part 4f which accept | permits the distribution | circulation of the cooling water which flows in into the confluence | merging part M from the radiator side is formed in the upper cylindrical outer peripheral part 4b which faces an engine inlet side.

  That is, when the main valve 5 is opened, the cooling water in the low temperature state flowing from the radiator side passes through the annular passage formed by the main valve 5 and the shielding member 20 through the opening 4f to the water pump P. And is prevented from flowing into the merging portion M on the bypass flow path 35 side than the main valve 5 in which the temperature sensing unit 10 is disposed. As a result, only the cooling water that flows from the engine E via the bypass flow path 35 reaches the temperature sensing unit 10, and the influence of the low-temperature cooling water from the radiator 32 is effectively suppressed.

  Therefore, according to the thermostat 1B of the present embodiment, it is not necessary to set the set temperature of the thermostat 1B low, and it is possible to suppress the cooling water temperature drop inside the engine. As a result, it is possible to prevent viscosity hardening of the engine oil and increase in friction loss, and to effectively improve fuel efficiency.

[Third embodiment]
Hereinafter, based on FIG. 5, the thermostat 1C which concerns on 3rd embodiment of this invention is demonstrated.

  As shown in FIG. 5, the thermostat 1 </ b> C of the third embodiment is obtained by omitting the shielding member 20 and the bypass rod 8 and changing the arrangement position of the temperature sensing unit 10 in the thermostat 1 </ b> A of the first embodiment. is there. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  The temperature sensing unit 10 includes a wax 10a, a bottomed cylindrical wax case 10b that accommodates the wax 10a, and a case extension 10c provided on the top of the wax case 10b.

  The case extension 10c is formed in a cylindrical shape having the same diameter as the wax case 10b, and a cylindrical flange 5a of the main valve 5 is fitted to the upper outer peripheral surface thereof. An annular support flange 10d that supports the upper end of the bypass spring 9 is provided on the intermediate outer peripheral surface of the case extension 10c. Furthermore, a through hole through which the main rod 3 is slidably inserted is formed in the upper surface portion and the lower surface portion of the case extension 10c.

  The wax case 10 b has an outer diameter that is smaller than the inner diameter of the bypass channel 35, and most of the wax case 10 b (particularly, the portion that contains the wax 10 a) is positioned in the bypass channel 35. Further, a through hole through which the main rod 3 is slidably inserted is formed in the upper surface portion of the wax case 10b, and the lower end portion of the main rod 3 is accommodated in the case. Further, a support flange 10e for supporting the bypass valve 7 from below is provided on the outer peripheral surface above the wax 10a of the wax case 10b.

  The bypass valve 7 is formed in a flat plate circular shape having a diameter larger than the inner diameter of the bypass flow path 35, and a through hole is formed in the center thereof so as to be slidably inserted through the wax case 10b and the case extension 10c. ing. Further, a bypass spring 9 that urges the bypass valve 7 toward the bypass flow path 35 is interposed between the bypass valve 7 and the support flange 10d.

  Next, the effect by the thermostat 1C which concerns on this embodiment is demonstrated.

  In the thermostat 1C of the present embodiment, the outer diameter of the wax case 10b that accommodates the wax 10a is formed to be smaller than the inner diameter of the bypass channel 35, and the majority (particularly, the portion that accommodates the wax 10a) is the bypass channel. 35.

  That is, the low-temperature cooling water flowing from the radiator 32 when the main valve 5 is opened flows through the junction M to the water pump P without reaching the wax case 10b located in the bypass flow path 35. Be drawn. As a result, only the high-temperature cooling water flowing from the engine E via the bypass channel 35 reaches the wax case 10b containing the wax 10a, and the influence of the low-temperature cooling water from the radiator 32 is effectively suppressed. .

  Therefore, according to the thermostat 1C of the present embodiment, it is not necessary to set the set temperature of the thermostat 1C low, and it is possible to suppress the cooling water temperature drop inside the engine. As a result, it is possible to prevent viscosity hardening of the engine oil and increase in friction loss, and to effectively improve fuel efficiency.

  The present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented without departing from the spirit of the present invention.

  For example, as shown in FIG. 6, you may combine the shielding member 20 of 1st embodiment, and the shape of the subhousing 4 and the junction part M of 2nd embodiment. Moreover, although detailed illustration is abbreviate | omitted, you may further apply 3rd embodiment to 1st embodiment, 2nd embodiment, or the combination of these 1st and 2nd embodiment. In any of these cases, the same effects as those of the above-described embodiments can be obtained.

  Further, the place where the thermostats 1A to C of each embodiment are arranged is not limited to the junction M between the engine inlet side flow path 34 and the bypass flow path 35. For example, the engine outlet side flow path 33 and the bypass flow path 35 are arranged. And may be provided at a branch portion.

  In each of the above-described embodiments, the bypass valve 7, the bypass rod 8, and the bypass spring 9 can be omitted.

1A, 1B, 1C Thermostat 2 Main housing (housing)
3 Main rod (rod)
4 Sub housing (housing)
5 Main valve (valve)
6 Main spring (spring)
7 Bypass valve 8 Bypass rod 9 Bypass spring 10 Temperature sensing part 10a Wax 10b Wax case (case)

Claims (7)

A housing having a first opening, a second opening, and a third opening for circulating cooling water, wherein the first opening and the second opening are opposed to each other; ,
A valve that is housed in the housing and prevents the cooling water flow in the first opening when the valve is closed, while allowing the cooling water flow in the first opening when the valve is opened;
A spring for urging the valve in the valve closing direction;
The case is fixed to the valve and at least part of the case is located on the second opening side, and the case is accommodated in the case on the second opening side. A temperature sensitive part having a wax that melts and expands;
One end is fixed to the housing on the first opening side, the other end is accommodated in the case, and the rod moves the valve in the valve opening direction when the wax is melted and expanded.
A thermostat, comprising: a shielding member that is fixed to an outer peripheral surface of the valve or the case and partitions the housing between the valve and the case containing the wax.   2. The thermostat according to claim 1, wherein the shielding member has a skirt portion that expands in a conical shape from an outer peripheral surface of the valve or the case toward the second opening.   The thermostat according to claim 1 or 2, wherein the housing slidably accommodates the valve, and the third opening is formed on a side portion on which the valve slides. A housing having a first opening, a second opening, and a third opening for circulating cooling water, wherein the first opening and the second opening are opposed to each other; ,
A valve that is housed in the housing and prevents the cooling water flow in the first opening when the valve is closed, while allowing the cooling water flow in the first opening when the valve is opened;
A spring for urging the valve in the valve closing direction;
The case is fixed to the valve and at least part of the case is located on the second opening side, and the case is accommodated in the case on the second opening side. A temperature sensitive part having a wax that melts and expands;
A rod having one end fixed to the housing on the first opening side and the other end housed in the case to move the valve in a valve opening direction when the wax is melted and expanded,
A thermostat characterized in that the housing slidably accommodates the valve and the third opening is formed on a side portion on which the valve slides.   The portion of the case containing the wax is formed to have a diameter smaller than the inner diameter of the cooling water circuit facing the second opening, and at least a part thereof is positioned in the cooling water circuit. To 4. The thermostat according to any one of 4 to 4. A housing having a first opening, a second opening, and a third opening for circulating cooling water, wherein the first opening and the second opening are opposed to each other; ,
A valve that is housed in the housing and prevents the cooling water flow in the first opening when the valve is closed, while allowing the cooling water flow in the first opening when the valve is opened;
A spring for urging the valve in the valve closing direction;
The case is fixed to the valve and at least part of the case is located on the second opening side, and the case is accommodated in the case on the second opening side. A temperature sensitive part having a wax that melts and expands;
A rod having one end fixed to the housing on the first opening side and the other end housed in the case to move the valve in a valve opening direction when the wax is melted and expanded,
The portion of the case containing the wax is formed to have a smaller diameter than the inner diameter of the cooling water circuit facing the second opening, and at least a part thereof is positioned in the cooling water circuit. A thermostat. The cooling water circuit includes an engine inlet side flow path for supplying cooling water from a radiator to a water jacket, and a bypass flow path for bypassing the cooling water supplied from the water jacket from the radiator,
The housing has the first opening facing the radiator, the second opening faces the bypass flow path, and the third opening faces the water jacket. The thermostat according to any one of claims 1 to 6, wherein the thermostat is disposed at a junction of the engine inlet side flow path and the bypass flow path.