JPH1163266A - Thermostat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously prevent leakage of cooling water generating at the time when a valve is closed even if operation of an engine is repeated by providing a solid lubrication film on one of a valve surface and a valve seat surface. SOLUTION: A solid lublication film 9 composed of solid lubication material and binder is provided on at least one of a valve 1 surface including a lip 8 and a metal-made valve seat 3 surface. Accordingly, the valve 1 surface is indirectly brought into contact with the valve seat 3 surface through the film 9, thereby preventing generation of wear. The contact surfaces of the valve 1 and the valve seat 3 have a reduced frictional resistance and a reduced stress by the lubricating action of the solid lublicant retained by the binder, thereby improving the service life against fatigue. With the constitution, the purpose is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thermostat.

[0002]

2. Description of the Related Art A thermostat closes a valve during warm-up of an engine, recirculates the cooling water in the engine without flowing the cooling water to the radiator, opens the valve when the temperature of the cooling water rises, flows the cooling water into the radiator, and cools the cooling water. Adjusting the water temperature. If the cooling water leaks to the radiator while the engine is warming up, the temperature of the cooling water hardly rises and it takes time to warm up the engine. Therefore, conventionally, as disclosed in Japanese Utility Model Publication No. 48-37303, Or
As shown in FIG. 5, a rubber lip 18 is provided at the contact portion of the valve 11 with the valve seat 13 to enhance the sealing property and prevent leakage of cooling water when the valve 11 is closed.

[0003]

However, when the valve is closed, the valve 11 is closed by a rubber lip 18 as shown in FIG.
Is excessively stressed due to large deformation, and is worn due to contact with the metal valve seat 13. Then, when the operation of the engine is repeated, the lip 1
In No. 8, contact / sliding with the valve seat 13 is repeated, fatigue cracks are generated due to repeated stress, and the amount of wear is increased. As a result, the sealing performance with the valve seat 13 is reduced and cooling water leaks. . An object of the present invention is to provide a thermostat capable of continuously preventing leakage of cooling water when a valve is closed by imparting lubricity to a contact surface between a valve and a valve seat even when engine operation is repeated. It is in.

[0004]

The present invention to achieve the above object is as follows. (1) A thermostat having a solid lubricating film on at least one of a valve surface and a valve seat surface. (2) The thermostat according to (1), wherein the solid lubricant comprises a solid lubricant and a binder, and the solid lubricant is selected from at least one of molybdenum disulfide, polytetrafluoroethylene, graphite, and boron nitride. (3) The thermostat according to (1) or (2), wherein the solid lubricating film comprises a solid lubricant and a binder, and the binder comprises a thermosetting resin.

In the thermostats (1), (2) and (3), since the solid lubricating film is provided on at least one of the valve surface and the valve seat surface, the valve does not directly contact the valve seat when the valve is closed. Therefore, wear is prevented, and the contact portion between the valve and the valve seat is lubricated, whereby the deformation of the valve is eased and the fatigue life is improved. As a result, even if the operation of the engine is repeated and the valve repeatedly contacts the valve seat, wear and fatigue cracks are less likely to occur, and leakage of cooling water (engine cooling water) when the valve is closed is prevented for a long time. In the thermostat of the above (2), the solid lubricating film is cooled by forming a solid lubricating film from a binder and a solid lubricant selected from at least one of molybdenum disulfide, polytetrafluoroethylene, graphite, and boron nitride. Has high lubricity even in water. In the thermostat of (3), the thermostat of (1) or (2) uses a thermosetting resin for the binder constituting the solid lubricating film, and thus the solid lubricating film has heat resistance and wear resistance.

[0006]

1 shows a thermostat according to an embodiment of the present invention, FIG. 2 shows details of a portion A shown in FIG. 1 (when the valve is opened), and FIG. 3 shows details of a portion A shown in FIG. (When the valve is closed), and FIG. 4 shows the measurement results of the friction coefficient of the solid lubricating film in the first embodiment of the present invention.

First, an outline of a thermostat according to an embodiment of the present invention will be described with reference to FIG. The thermostat includes a disc-shaped rubber valve 1 and a spring 2 provided on the valve 1 for urging the valve 1 against a metal valve seat 3.
A wax element 4 having a hollow portion connected to the valve 1, a wax 5 arranged in the hollow portion of the wax element 4 and expanding and contracting according to a temperature, and a cooling water inserted through the hollow portion of the wax element 4. A shaft 6 coupled to a horizontal plate 7 having a hole for flowing (engine cooling water) to the radiator side. The thermostat is provided at a cooling water outlet of a cylinder head of the engine. When the temperature of the cooling water is low, the valve 1 is urged to the valve seat 3 by the spring 2 to cut off the flow path of the cooling water and circulate the cooling water in the engine. When the temperature of the cooling water rises, the wax 5 in the wax element 4 expands and tries to push up the shaft 6, but since the shaft 6 is connected to the horizontal plate 7, the wax element 4 and the wax The valve 1 connected to the element 4 compresses the spring 2 and descends downward. As a result, a gap is formed between the valve 1 and the valve seat 3, a flow path of the cooling water is secured, and the engine side to the radiator. Cooling water flows.

The valve 1 is made of EPDM, H-NBR, NB
A rubber lip 8 protruding radially outward is provided integrally or separately on the circumference of the valve 1 in order to enhance the sealing performance with the valve seat 3 when the valve is closed. Have been. The valve seat 3 is made of stainless steel, a rustproof steel plate, or the like.

A solid lubricating film 9 is provided on at least one of the valve 1 and the valve seat 3. FIG.
Shows a case where the solid lubricating film 9 is provided on both the valve 1 surface and the valve seat 3 surface. However, the solid lubricating film 9 may be provided only on the valve 1 surface or only the valve seat 3 surface. When the valve seat 3 has irregularities on the surface as it is machined, and when the irregularities are exposed, the solid lubricating film provided on the valve 1 surface is shaved when the valve seat 3 comes into contact with or slides on the valve 1 surface. Therefore, it is desirable to provide the solid lubricating film 9 on at least the surface of the valve seat 3.

The solid lubricating film 9 comprises a solid lubricant and a binder. The solid lubricant used has lubricity even in engine cooling water, and is selected from at least one of molybdenum disulfide, polytetrafluoroethylene, graphite, and boron nitride. In particular, molybdenum disulfide has excellent wear resistance in a liquid, and polytetrafluoroethylene has excellent lubricity.

As the binder, a thermosetting resin having heat resistance and wear resistance is used. For example, there are polyamide imide resin, epoxy resin, polyimide resin and the like.
In particular, polyamideimide resin has excellent abrasion resistance, sealability, and liquid resistance, and is suitable for use as a binder. However, since the firing temperature is high, it is more preferable to provide the resin in the valve seat 1 than in the valve 3 made of rubber. . An epoxy resin having a low firing temperature is suitable for the valve 3.

The solid lubricating film desirably comprises 20 to 70% by weight of a solid lubricating material and the remainder is a binder from the viewpoints of lubricity and film strength.

It is desirable that the thickness of the solid lubricating film is 5 to 20 μm. The solid lubricating film preferably has a thickness of 5 μm or more in order to maintain the lubricating property for a long time, and preferably has a thickness of 20 μm or less in order not to deteriorate the sealing property when partially peeled off.

The method for forming a solid lubricating film comprises a step of applying a mixture of a solid lubricant and a binder to at least one of a valve surface and a valve seat surface by spraying, dipping, printing, or the like, and then firing.

Next, the operation will be described. At least one of the valve 1 surface (including the lip portion 8) and the valve seat 3 surface is provided with a solid lubricating film 9 made of a solid lubricant and a binder. Is not in direct contact with the surface of the valve seat 3 made of stainless steel, but indirectly through the solid lubricating film 9 to prevent wear. Further, the contact surface (also a sliding surface) between the valve 1 surface and the valve seat 3 surface has a reduced frictional resistance due to the lubricating action of the solid lubricant held by the binder. And slide smoothly,
The deformation of the valve 1 is reduced as compared with the conventional one (see FIG. 3), and the stress is reduced, so that the fatigue life is improved.
Therefore, even if the thermostat is repeatedly subjected to the cooling / heating cycle, and the contact and sliding between the valve 1 surface and the valve seat 3 surface are repeated, the sealing performance between the valve 1 surface and the valve seat 3 surface is maintained, and the cooling water leaks. Can be prevented for a long time. In addition, various metal compounds easily accumulate on the valve seat surface, and in a conventional thermostat without a solid lubricating film on either the valve surface or the valve seat surface, the metal compound adheres to the metal valve seat surface. Although the valve may be worn, in the embodiment of the present invention,
Since the solid lubricating film 9, which is a resin film, is provided on the surface of the valve seat 3, the metal compound hardly adheres,
It is also possible to prevent the valve 1 from being worn due to biting of the metal compound.

Next, embodiments of the present invention will be described. In the first example of the present invention, in order to examine a desirable blending amount of the solid lubricant in the solid lubricant film, test pieces having different blending amounts of the solid lubricant were prepared, and respective friction coefficients were measured. Six types of test pieces (a) to (f) were prepared. The base material of each test piece is EPDM. The test piece (a) has no film on the surface for comparison, and the test piece (b)
(F) has a solid lubricating film composed of molybdenum disulfide as a solid lubricant and an epoxy resin as a binder on the surface of the base material, and the compounding amount of molybdenum disulfide is 0, 20, 5 or less.
0, 70, 80% by weight. The friction coefficient was measured by applying a stainless steel ball to each of the test pieces (a) to (f) under a load of 2.
The resistance value obtained when the object was slid left and right at a sliding speed of 0.1 m / s while pressing with kgf was converted into a coefficient of friction (Bauden test). FIG. 4 shows the measurement results of the coefficient of friction of each of the test pieces (a) to (f). According to FIG. 4, since the test piece (a) without the solid lubricating film has the highest friction coefficient, when the sliding surface between the valve surface and the valve seat surface has no solid lubricating film (corresponding to a conventional thermostat), It can be seen that the sliding resistance is large when sliding, and the valve surface is easily deformed. In the test piece (f) having a solid lubricating film containing 80% by weight of molybdenum disulfide, the solid lubricating film was worn during the test. It is understood that the film has low strength and is not suitable for the sliding surface between the valve surface and the valve seat surface. Further, since the test pieces (c), (d), and (e) each having a solid lubricating film containing 20 to 70% by weight of molybdenum disulfide have a low coefficient of friction, the solid lubricating film has high lubricity, and the It can be seen that, when the coating is provided on at least one of the valve seat surfaces, the sliding resistance is reduced, so that the deformation of the valve surface is suppressed. In particular, molybdenum disulfide should be 50 ~
Test piece with solid lubricating film containing 70% by weight (d)
(E) is highly effective.

In a second embodiment of the present invention, a durability test example of a thermostat will be described. The thermostat used for the test was
A mixture prepared by mixing molybdenum disulfide and an epoxy resin in a ratio of 1: 1 is applied to each sliding surface of a valve 1 made of EPDM and a valve seat 3 made of stainless steel by spraying, and then at 140 ° C. It has a solid lubricating film obtained by firing for 30 minutes. The thermostat was subjected to a thermal cycle to test the durability of the valve surface and the valve seat surface. As a result, there is almost no wear on the valve surface and the valve seat surface, and the life of the fatigue crack is about 1.10 compared with the conventional thermostat in which a solid lubricating film is not formed on the sliding surface between the valve surface and the valve seat surface. 5 times improvement.

[0018]

According to the first, second and third aspects of the thermostat, since the solid lubricating film is provided on at least one of the valve surface and the valve seat surface, wear of the valve surface is prevented. In addition, since the sliding with the valve seat surface is lubricated and the deformation is suppressed, the stress applied to the valve is reduced and the fatigue life is improved. Therefore, even if the engine is repeatedly used, the sealing properties of the thermostat valve and the valve seat are maintained, and leakage of the cooling water can be prevented for a long period of time. According to the thermostat of claim 2, the solid lubricant forming the solid lubricant film is molybdenum disulfide,
Since it is selected from at least one of polytetrafluoroethylene, graphite, and boron nitride, the solid lubricating film has high lubricity even in cooling water. Claim 3
According to the thermostat, the binder forming the solid lubricating film is a thermosetting resin, and imparts heat resistance and wear resistance to the solid lubricating film.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a thermostat according to an embodiment of the present invention.

FIG. 2 is a view showing details (when a valve is opened) of a portion A in FIG. 1;

FIG. 3 is a diagram showing details of a portion A in FIG. 1 (when a valve is closed).

FIG. 4 is a view showing a friction coefficient of each test piece of the first embodiment of the present invention.

FIG. 5 is a view showing a valve and a valve seat (when the valve is opened) of a conventional thermostat.

FIG. 6 is a diagram showing a valve and a valve seat (when the valve is closed) of a conventional thermostat.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve 3 Valve seat 8 Lip 9 Solid lubricating film

Claims (3)

[Claims] 1. A thermostat having a solid lubricating film on at least one of a valve surface and a valve seat surface. 2. The solid lubricant according to claim 1, wherein the solid lubricant comprises a solid lubricant and a binder, and the solid lubricant is selected from at least one of molybdenum disulfide, polytetrafluoroethylene, graphite, and boron nitride. thermostat. 3. The thermostat according to claim 1, wherein the solid lubricating film comprises a solid lubricant and a binder, and the binder comprises a thermosetting resin.