Thermostat device and method for manufacturing a thermostat device

Abstract

In a fuel cell cooling device, sliding damage to a piston and the deterioration of sealing performance are prevented despite using a simple structure in which a portion sliding with the piston is made of a brass bush and a simple and inexpensive method of setting the assembly of the brass bush to a press-fitted state by light press-fitting and ball burnishing.　Provided is a stainless steel cylindrical guide member (32) slidably holding a stainless steel piston (11a) provided at the open end of a bottomed cylindrical case (31) containing a thermal expansion body and moving forward and backward according to the expansion and contraction of the thermal expansion body. A brass bush (33) is fitted into the inner peripheral portion of the cylindrical guide member (32) by light press-fitting and subjected to precise finishing on the inner peripheral surface, for example, by ball burnishing, to be expanded radially by the pressure from the inside and press-fitted.

Description

Technical Field

[0001] The present invention relates to a thermostat device suitable for use in a cooling device of a fuel cell and a method for manufacturing the thermostat device in a fuel cell power generation system such as a fuel cell vehicle or a stationary type.

Background Art

[0002] For example, a water-cooling system using a radiator is used to cool an automotive engine (internal combustion engine). Conventionally, in this type of cooling system, a thermostat using a thermal expansion body that adjusts the amount of cooling water circulated to the radiator side or a valve unit by electric control is used to control the temperature of the cooling water introduced into the engine.

[0003] In the thermostat device using the above thermal expansion body, a control valve is provided by being interposed in a part of the cooling water passage, for example, on the inlet side or the outlet side of the engine. When the cooling water temperature is low, the control valve is closed and the cooling water is circulated through the bypass passage without passing through the radiator. When the cooling water temperature rises, the control valve is opened and the cooling water is circulated through the radiator. Thereby, the temperature of the cooling water is controlled to a required state.

[0004] Conventionally, as a thermostat device used for a cooling device of this type of automotive engine, there is, for example, one disclosed in Patent Document 1. That is, a thermo element is disclosed in which a piston made of stainless steel (SUS) that moves forward and backward according to the expansion and contraction of a thermal expansion body is slidably held by a cylindrical guide member made of brass such as a brass material enclosing the thermal expansion body at an open end portion of a bottomed cylindrical case made of brass or the like.

[0005] Furthermore, in the thermo-element described in Patent Document 1, a stainless steel bush, which improves the sliding properties of the piston and does not undergo chemical reactions with the antifreeze or rust inhibitor in the cooling water, is placed on the inner circumference of a brass cylindrical guide member made of brass or the like. This configuration ensures that the piston moves in the required state.

[0006] While the thermostat device with the above configuration presents few problems for use as an engine cooling system, it presents problems for use as a fuel cell cooling system in fuel cell vehicles and stationary fuel cell power generation systems, which are being actively developed in recent years.

[0007] To elaborate, in the case of a thermostat device for a fuel cell vehicle, unlike in typical gasoline vehicles, there is a risk of electrical leakage if ions dissolve into the coolant circuit. Therefore, to reduce ion dissolution by brass, it is preferable to manufacture the guide member from stainless steel, in addition to the stainless steel piston.

[0008] In other words, the coolant used to cool a fuel cell needs to have a low conductivity to prevent electrical leakage. Furthermore, since brass is a material that easily releases ions, there is a possibility that the released ions may increase the conductivity of the coolant, and there are concerns about loss of function due to stress corrosion cracking of brass components caused by ion release, etc. Therefore, in thermostat devices for fuel cell vehicles, etc., guide members that slidably hold stainless steel pistons are made of stainless steel, or bottomed cylindrical cases are made of stainless steel, in order to reduce ion release. (See, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Utility Model Publication No. 57-25114 [Patent Document 2] Japanese Patent Publication No. 2005-285398 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, as mentioned above, when a stainless steel piston is held in place by a stainless steel guide member and slid, or when a stainless steel piston is slid in place by a stainless steel bush positioned on the inner circumference of a cylindrical guide member, there is a problem that the piston gets scratched during sliding, resulting in poor sealing performance.

[0011] To prevent this, surface treatment (plating or heat treatment) of the piston could be considered, but this would increase costs. Furthermore, stainless steel guide components are more difficult to process than brass ones for the piston sliding surface, making it unavoidable that they would be more expensive.

[0012] In other words, since the stainless steel guide member is formed by machining the piston sliding portion, it is difficult to control the inner diameter dimensions. Also, when pressing the bush into the inner circumference of the guide member, the outer diameter of the bush was made tighter than the inner diameter of the guide member to prevent the bush from coming loose. Furthermore, there were various processing problems, such as the difficulty of the work being increased because it is necessary to press it in firmly using appropriate machine tools, and the roughness of the inner surface of the bush sometimes resulting in scratches on the piston.

[0013] This invention has been made in view of these circumstances, and aims to provide a thermostat device and a method for manufacturing the same that can prevent deterioration of sealing performance at the piston sliding portion, eliminate the need for surface treatment to prevent damage to the piston, and reduce costs. [Means for solving the problem]

[0014] According to the first means to achieve this objective, the thermostat device is provided with a stainless steel cylindrical guide member that slidably holds a stainless steel piston, which moves back and forth in accordance with the expansion and contraction of the thermal expansion body, located at the open end of a stainless steel bottomed cylindrical case containing a thermal expansion body, and a brass bush is press-fitted into the piston sliding portion on the inner circumference of the cylindrical guide member.

[0015] With the above configuration, by using a brass bush for the sliding part with the piston, friction scratches on the piston can be prevented, thus preventing deterioration of sealing performance. This eliminates the need for surface treatment to prevent scratches on the piston, thereby reducing costs.

[0016] Furthermore, the thermostat device Manufacturing method teeth, A method for manufacturing a thermostat device comprising a stainless steel cylindrical guide member that slidably holds a stainless steel piston, which moves back and forth in accordance with the expansion and contraction of a thermal expansion body, provided at the open end portion of a stainless steel cylindrical case with a bottom containing a thermal expansion body, wherein a brass bush is press-fitted into the piston sliding portion on the inner circumference of the cylindrical guide member, The brass bush may be fitted into the inner circumference of the cylindrical guide member in a light press-fit state, and the inner surface may be precisely finished so that it expands in diameter under internal pressure and becomes press-fitted. In this way, even if the cylindrical guide member is made of stainless steel, it is only necessary to process its inner circumference to the extent that the brass bush can be lightly press-fitted, and furthermore, the difficulty of processing is reduced compared to the piston sliding part, thus reducing costs.

[0017] Furthermore, the thermostat device Manufacturing method teeth, A method for manufacturing a thermostat device comprising a stainless steel cylindrical guide member that slidably holds a stainless steel piston, which moves back and forth in accordance with the expansion and contraction of a thermal expansion body, provided at the open end portion of a stainless steel cylindrical case with a bottom containing a thermal expansion body, wherein a brass bush is press-fitted into the piston sliding portion on the inner circumference of the cylindrical guide member, The brass bush may be fitted into the inner circumference of the cylindrical guide member in a light press-fit state, and the inner surface of the brass bush may be finished with ball burnishing, thereby expanding the diameter of the brass bush by applying pressure from the inside and thus providing a press-fit state. In this way, by applying ball burnishing as a finishing process to the sliding part with the piston, the diameter of the brass bush is expanded and it is prevented from coming loose, so only light press-fitting is required when assembling the bush, which not only improves ease of assembly but also simplifies the assembly equipment compared to conventional methods. Furthermore, since the inner diameter of the brass bush can be precisely finished, there is also the advantage that the piston is less likely to be scratched.

[0018] Further, in the thermostat device Manufacturing method an annular step may be provided at a portion of the inner peripheral surface of the cylindrical guide member corresponding to the tip portion on the press-fitting side in the axial direction of the brass bush. By doing so, when the inner peripheral surface of the brass bush is finished and the bush is expanded in diameter by the pressing force from the inside, the deformed portion extruded escapes into the annular groove portion. Thereby, it is possible to prevent the deformed portion from protruding and contacting the component side of components such as an O-ring which is an adjacent component, and prevent problems such as adversely affecting the sealing state.

[0019] Further, in the thermostat device Manufacturing method a tapered portion that gradually reduces in diameter from the tip side may be provided on the inner peripheral surface of the tip portion on the press-fitting side in the axial direction of the brass bush press-fitted into the inner peripheral portion of the cylindrical guide member. By doing so, when the inner peripheral surface of the brass bush is finished and the bush is expanded in diameter by the pressing force from the inside, the deformed portion extruded escapes between the tapered portion and the piston. Thereby, it is possible to prevent the deformed portion from protruding and contacting the component side of components such as an O-ring which is an adjacent component, and prevent problems such as adversely affecting the sealing state.

[0020] Further, the thermostat device may be used in a fuel cell cooling device in a fuel cell power generation system. By doing so, by using the brass bush only for the piston sliding portion of the cylindrical guide member, it is possible to reduce ion elution, so it is suitable to use the thermostat device in a fuel cell cooling device in a fuel cell vehicle or a fuel cell power generation system.

[0021] According to a second means for achieving the above object, there is provided a method for manufacturing a thermostat device including a cylindrical guide member made of stainless steel that slidably holds a stainless steel piston provided at an open end portion of a bottomed cylindrical case made of stainless steel and enclosing a thermal expansion body, the piston advancing and retreating due to expansion and contraction of the thermal expansion body. In the method, a brass bush for slidably holding the piston is press-fitted into an inner peripheral portion of the cylindrical guide member in a lightly press-fitted state, and a finishing process for precisely finishing an inner peripheral surface of the brass bush is performed to expand a diameter of the brass bush by a pressing force from the inside and provide the brass bush in a press-fitted state in the inner peripheral portion of the cylindrical guide member.

[0022] According to the above configuration, by using a brass bush for a sliding portion with the piston, sliding damage to the piston can be prevented, so that deterioration of sealing performance can be prevented, and surface treatment for preventing damage to the piston becomes unnecessary, thereby reducing costs. Further, even if the cylindrical guide member is made of stainless steel, it may be processed to such an extent that the brass bush can be lightly press-fitted into its inner peripheral portion, and further, the processing difficulty can be suppressed as compared with the piston sliding portion, so that cost reduction can be achieved.

[0023] Further, in the method for manufacturing the thermostat device, the brass bush may be press-fitted into the inner peripheral portion of the cylindrical guide member in a lightly press-fitted state, and a ball burnishing process may be performed as a finishing process for the inner peripheral surface of the brass bush, and the diameter of the brass bush may be expanded by a pressing force from the inside to provide the brass bush in a press-fitted state. By doing so, by performing a ball burnishing process as a finishing process on the sliding portion with the piston, the diameter of the brass bush is expanded and retained, so that it is only necessary to lightly press-fit during assembly of the bush. Not only does the assembly property improve, but simplification of the assembly equipment can be achieved as compared with the conventional case. Further, since the inner diameter portion of the brass bush can be precisely finished, there is also an advantage that the piston is less likely to be damaged.

[0024] Furthermore, in the manufacturing method of the thermostat device, an annular step forming an annular groove may be provided on the inner circumferential surface of the cylindrical guide member, in the portion corresponding to the press-fit end portion in the axial direction of the brass bush. In this case, when the inner circumferential surface of the brass bush is finished and the bush is expanded in diameter by internal pressure, the deformed portion that is pushed out escapes into the annular groove. This prevents the deformed portion from protruding and coming into contact with adjacent parts such as O-rings, thus preventing problems such as adverse effects on the sealing state.

[0025] Furthermore, in the manufacturing method of the thermostat device, a tapered portion that gradually decreases in diameter from the tip side may be provided on the inner circumferential surface of the press-fitting end of the brass bush, which is press-fitted into the inner circumference of the cylindrical guide member, in the axial direction. In this case, when the inner circumferential surface of the brass bush is finished and the bush is expanded by an internal pressure, the deformed portion that is pushed out escapes between the tapered portion and the piston. This prevents the deformed portion from protruding and coming into contact with adjacent parts such as O-rings, thus preventing problems such as adverse effects on the sealing state.

[0026] Furthermore, in the method for manufacturing the thermostat device, the thermostat device may be used as a fuel cell cooling device in a fuel cell power generation system. In this case, by making only the piston sliding portion of the cylindrical guide member a brass bush, ion elution can be reduced, making the thermostat device suitable for use as a fuel cell cooling device in fuel cell vehicles and fuel cell power generation systems. [Effects of the Invention]

[0027] According to the thermostat device and the method for manufacturing the thermostat device of the present invention, deterioration of sealing performance can be prevented, and surface treatment to prevent damage to the piston becomes unnecessary, thereby reducing costs. [Brief explanation of the drawing]

[0028] [Figure 1](a), (b), (c), and (d) are explanatory diagrams showing a first embodiment of the method for manufacturing a thermostat device according to the present invention. [Figure 2] (a) and (b) are schematic side views of the entire device and enlarged cross-sectional views of its main parts, showing a first embodiment of the thermostat device according to the present invention. [Figure 3] (a), (b), and (c) are enlarged cross-sectional views of the main parts showing a second embodiment of the thermostat device and its manufacturing method according to the present invention, and (d) is an enlarged cross-sectional view of part A of (b). [Figure 4] (a), (b), and (c) are enlarged cross-sectional views of key parts showing modified examples of the thermostat device and its manufacturing method shown in Figure 3. [Modes for carrying out the invention]

[0029] Figures 1 and 2 show a first embodiment of the thermostat device and its manufacturing method according to the present invention. In this embodiment, the case in which the thermostat device is used as a fuel cell cooling device in fuel cell vehicles and stationary fuel cell power generation systems is described.

[0030] In these figures, the component shown as a whole, denoted by reference numeral 10, is a thermostat device, which is a temperature-sensing automatic valve. This thermostat device 10 is installed, for example, in a fuel cell cooling system (not shown) in a fuel cell power generation system such as a fuel cell vehicle, at the intersection of the cooling water passage on the radiator side and the bypass passage from the outlet side of the fuel cell cooling water passage. The thermostat device 10 is used to control the cooling water temperature leading to the inlet of the fuel cell cooling water passage by selectively switching the flow of cooling water in the fluid passage formed by these passages. In Figure 2(a), the flow of cooling water in an inlet-controlled thermostat device is illustrated, but it goes without saying that in an outlet-controlled type, the flow will be the opposite of what is shown.

[0031] As shown in Figures 2(a) and (b), the thermostat device 10 includes a thermoelement 11, which is an actuator that operates in response to changes in the temperature of the fluid. One end of the thermoelement 11 (upper side in the figure) is provided with a first valve body 12 that is roughly umbrella-shaped, and the other end (lower side in the figure) is provided with a second valve body 13 that is roughly plate-shaped at the tip (lower end in the figure) of a valve shaft (described later). In addition, a coil spring 14, which is a biasing means for biasing the first valve body 12 to the valve closed position, and a frame 15, which also serves as a spring retainer, are fitted into the axial central portion of the thermoelement 11. The frame 15 is locked to a support leg on the valve housing side, which is a fixed part described later, thereby biasing the first valve body 12 in the valve closed direction via the coil spring 14, and is a member that slidably holds the thermoelement 11.

[0032] The thermoelement 11 includes a temperature sensing section containing a thermally expanding material such as wax that expands and contracts in response to the temperature of the fluid, and a piston rod (hereinafter referred to as piston) 11a protrudes from the tip (upper end in the figure) of the temperature sensing section so as to be able to move back and forth.

[0033] In the figure, 20 is a housing that houses the thermostat device 10 and contains a passage through which cooling water from the radiator, which is the fluid inlet and outlet, flows in and communicates with the inlet of the fuel cell cooling passage. Inside the housing 20, a valve chamber 21 is formed in which the thermostat device 10 is located. In the upper part of the figure, there is a cooling water passage from the radiator (first passage) 21A, in the right part of the figure, there is a cooling water passage toward the fuel cell (second passage) 21B, and in the lower part of the figure, there is a fluid passage 25 from the bypass passage (third passage). Note that the housing 20 is shown here as having a structure divided into upper and lower halves.

[0034] Furthermore, a valve seat 22 is formed on the inside of a flange-like portion located in the middle of the longitudinal direction of the thermostat device 10, and is opposed to the first valve body 12 so that it can be seated. The thermoelement 11 and the frame 15 that slidably holds it are incorporated into the thermoelement 11 and the valve seat 22 so that the first valve body 12 can be seated on it.

[0035] Furthermore, 23 in the figure is a locking part that locks and holds the tip of the piston 11a. In the state shown in Figure 2(a), when the piston 11a protrudes upward in the figure due to the thermal expansion of the thermal expansion body, the thermo element 11 and the first valve body 12 move relatively downward in the figure, and the first valve body 12 opens to an appropriate valve position, allowing coolant from the radiator to flow to the engine side.

[0036] On the other hand, the second valve body 13, which is substantially plate-shaped, is fitted and assembled to the lower end of the rod portion 18, which serves as a valve stem and extends downward from the thermoelement 11, and is secured with an E-ring or the like, and is elastically supported by being biased by a coil spring 19. Furthermore, a fluid passage (communication passage) 25, which is opened and closed by the second valve body 13, opens below the housing 20, and a valve seat portion 26 is formed around the periphery of the opening.

[0037] Here, the second valve body 13 is structured to seat on the valve seat portion 26 and is configured to function as a relief valve that opens and closes in accordance with the cooling water pressure on the bypass flow path side.

[0038] The present invention is characterized in that the thermo-element 11 in the thermostat device 10 with the above-described configuration is configured as shown in Figure 2(b). Specifically, it is provided with a stainless steel cylindrical guide member 32 that slidably holds the stainless steel piston 11a, which moves back and forth in accordance with the expansion and contraction of the thermal expansion body, and is located at the open end portion of a stainless steel bottomed cylindrical case 31 containing a thermal expansion body (not shown). A brass bush 33 is press-fitted into the piston sliding portion on the inner circumference of the cylindrical guide member 32.

[0039] Here, the brass bush 33 is formed with a flange that can restrain its axial movement. In the figure, 33a is the flange. The brass bush 33 has a tip at the end that is press-fitted into the inner circumference of the cylindrical guide member 32, and a rear end at the flange 33a side. Furthermore, the open end of the bottomed cylindrical case 31 of the thermo element 11 is crimped with the cylindrical guide member 32 fitted inside, which slidably holds the piston 11a, and is locked in a non-detachable state. In addition, 35 and 36 in Figure 2(b) are O-rings that seal the bottomed cylindrical case 31 and the cylindrical guide member 32, and the space between the cylindrical guide member 32 and the piston 11a.

[0040] In the above configuration, the brass bush 33 can be incorporated into the cylindrical guide member 32 as follows. That is, as shown in Figure 1(a), the brass bush 33 is fitted into the inner circumference of the cylindrical guide member 32 from the tip side in a light press-fit state. Here, the press-fit allowance setting value due to the difference in inner and outer diameters between the cylindrical guide member 32 and the brass bush 33 should be, for example, 0.06 to 0.10 mm. This design eliminates the need for high machining precision at the assembly point between the cylindrical guide member 32 and the brass bush 33, offering advantages in terms of machinability. Furthermore, the assembly process can be performed easily and reliably without the need for special machining jigs, thus reducing costs.

[0041] Then, in the light press-fit state described above, as shown in Figure 1(b), the inner circumferential surface 33b of the brass bush 33 is subjected to a precision finishing process, such as ball burnishing, while the brass bush 33 is expanded in diameter by internal pressure, and the inner circumferential surface 33b is precisely finished. Here, the design setting value for the change in the inner diameter of the brass bush 33 before and after ball burnishing should be, for example, about 0.01 mm. In addition to ball burnishing, other precision finishing processes such as roller burnishing can be used, and any other process that can similarly perform precision finishing on the inner circumferential surface 33b of the brass bush 33 is also acceptable.

[0042] As a result, the brass bush 33 is press-fitted into the inner circumference of the cylindrical guide member 32. The cylindrical guide member 32 with the brass bush 33 assembled in this way is fitted into the open end portion of the closed-bottom cylindrical case 31 while slidably holding the piston 11a, and the thermo element 11 is completed by fixing it in place by crimping the open end of the closed-bottom cylindrical case 31.

[0043] Here, ball burnishing is a process that is also performed on the piston sliding portion of conventional brass guide members. After machining the piston sliding portion of the guide member, a slightly larger diameter ball (ball burnishing jig) 40 is passed through it to adjust the inner diameter dimension of the piston sliding portion and reduce the roughness of the inner circumferential surface.

[0044] According to the thermostat device 10 and the method for manufacturing the thermostat device 10 according to the present invention, which have the above configuration, by making the sliding portion with the piston 11a the brass bush 33, sliding scratches on the piston 11a can be prevented, thus preventing deterioration of sealing performance, eliminating the need for surface treatment to prevent scratches on the piston 11a, and thereby reducing costs.

[0045] Furthermore, with the above-described configuration, even if the cylindrical guide member 32 is made of stainless steel, it only needs to be machined to the extent that the brass bush 33 can be lightly press-fitted into its inner circumference. Moreover, the difficulty of machining can be reduced compared to the piston sliding portion, thus reducing costs.

[0046] Furthermore, according to the above-described configuration and manufacturing method, by applying a ball burnishing process as a finishing step to the sliding portion with the piston 11a, the brass bush 33 is enlarged and prevented from coming loose. Therefore, when assembling the brass bush 33, only a light press-fit is required, improving ease of assembly. In addition, since the inner diameter portion of the brass bush 33 can be precisely finished, there is also the advantage that the piston 11a is less likely to be scratched.

[0047] Here, as described above, when the brass bush 33, which is lightly press-fitted into the inner circumference of the stainless steel cylindrical guide member 32, is subjected to a ball burnishing process as a finishing step, thereby expanding the inner diameter of the brass bush 33, there is a risk that the material that is squeezed and brought together will cause the brass bush 33 to stretch in the axial direction, resulting in a convex shape that protrudes into the space 32a where the adjacent O-ring 36 is fitted.

[0048] To solve this problem, the axial length of the brass bush 33, which is fitted into the inner circumference of the cylindrical guide member 32, may be made shorter in advance. In this way, the problem of protrusion caused by ball burnishing as a finishing process on the inner circumference of the brass bush 33 can be eliminated.

[0049] Figure 3 shows a second embodiment for solving the problem of protrusion caused by ball burnishing as a finishing process on the brass bush 33 described above. In these figures, parts that are the same as or corresponding to those in the previously described embodiments are given the same numbers, and detailed descriptions thereof are omitted. In this embodiment, an annular step 51 is provided on the inner circumferential surface of the cylindrical guide member 32, in the portion corresponding to the press-fit end portion in the axial direction of the brass bush 33, forming an annular groove 50.

[0050] To elaborate, the end of the cylindrical guide member 32 facing the space 32a for loading the O-ring 36 has an opening for pressing in the brass bush 33. An annular step 51, which constitutes the annular groove 50, is recessed in the peripheral edge of the shaft hole as an axial recess relative to the seat surface 32a of the O-ring 36.

[0051] When the annular groove 50 is provided by the annular step 51, the brass bush 33 is fitted into the inner circumference of the cylindrical guide member 32 by light press-fitting. Then, as shown in Figure 3, when the inner surface of the brass bush 33 is subjected to a ball burnishing process using the ball 40 as a finishing process, the brass bush 33 is expanded in diameter by the pressure applied from the inside, and the deformed portion 33c that is pushed out at that time escapes into the annular groove 50 provided by the annular step 51 on the inner surface of the cylindrical guide member 32.

[0052] The deformed portion 33c of the brass bush 33, which is compressed by the ball burnishing process, escapes into the annular groove 50, preventing it from protruding in a convex shape into the adjacent space 32a for loading the O-ring 36 (above the seat surface 32b in Figure 3). This prevents the deformed portion 33c of the brass bush 33 from coming into contact with the adjacent O-ring 36 during assembly of the thermostat device 10, thus completely and safely preventing problems such as adverse effects on the sealing state of the O-ring 36.

[0053] In the embodiment shown in Figure 3 above, the annular groove 50 is provided by an annular step 51 in the portion of the cylindrical guide member 32 corresponding to the press-fit end portion in the axial direction of the brass bush 33, but the present invention is not limited thereto. For example, as shown in Figure 4, the brass bush 33 may be configured to have a frustoconical tapered portion 52 that gradually decreases in diameter from the tip side, along the entire circumference of the inner surface of the tip portion on the press-fitting side in the axial direction into the inner circumference of the cylindrical guide member 32.

[0054] The tapered portion 52 allows the deformed portion 33c, which is pushed out when the brass bush 33 is expanded in diameter by internal pressure through ball burnishing, to escape into the annular space formed by the tapered portion 52. This prevents the deformed portion 33c of the brass bush 33, caused by ball burnishing, from protruding in a convex shape into the adjacent space 32a for loading the O-ring 36 (above the seat surface 32b in Figure 4).

[0055] This completely and safely prevents the deformed portion 33c of the brass bush 33 from coming into contact with the O-ring 36 during the assembly of the thermostat device 10, thereby preventing any adverse effects on the sealing state of the O-ring 36.

[0056] Of course, the tapered portion 52 is not limited to the inner circumferential surface of the tip side of the brass bush 33 as described above. For example, a frustoconical tapered portion may be formed along the entire circumference of the outer circumferential surface of the tip side of the brass bush 33 on the press-fit side in the axial direction, with the outer diameter gradually increasing. It is easy to understand that equivalent effects can be obtained in such a case.

[0057] It goes without saying that the present invention is not limited to the structure described in the above-described embodiments, and the shape, structure, etc. of each part constituting the thermostat device 10 and the manufacturing method of the thermostat device 10 can be appropriately modified or changed. For example, it goes without saying that various modifications can be considered for structures other than the assembly consisting of the cylindrical guide member 32 fitted into the open end portion of the bottomed cylindrical case 31 and the brass bush 33 attached to its inner circumference in a press-fit state.

[0058] Furthermore, the present invention is characterized in part by the thermo-element 11 in an inlet-controlled, outlet-controlled thermostat device 10 used in fuel cell cooling devices in fuel cell power generation systems such as fuel cell vehicles and stationary fuel cell power generation systems. The thermo-element 10 can be applied and effective in various applications, such as cooling devices for automobile engines (internal combustion engines), and even in hot and cold water mixing faucets for controlling water temperature. [Explanation of Symbols]

[0059] 10 Thermostat device 11a Piston rod (piston) 31. Cylindrical case with bottom 32 Cylindrical guide member 33 Brass bushings 40 Ball (Ball burnishing jig) 50 Annular groove section 51 Ring-shaped step 52 Tapered section

Claims

1. The device comprises a stainless steel cylindrical guide member that slidably holds a stainless steel piston, which moves back and forth in accordance with the expansion and contraction of the thermal expansion material, located at the open end of a stainless steel cylindrical case with a bottom that encloses a thermal expansion material. A thermostat device characterized by having a brass bush pressed into the piston sliding portion on the inner circumference of the cylindrical guide member.

2. A method for manufacturing a thermostat device comprising a stainless steel cylindrical guide member that slidably holds a stainless steel piston, which moves forward and backward in accordance with the expansion and contraction of a stainless steel piston, provided at the open end portion of a stainless steel cylindrical case with a bottom containing a thermal expansion body, When a brass bush is press-fitted into the piston sliding portion on the inner circumference of the cylindrical guide member, A method for manufacturing a thermostat device, characterized by providing a brass bush that is fitted into the inner circumference of the cylindrical guide member in a light press-fit state and whose inner surface is precisely finished, thereby expanding in diameter due to internal pressure and becoming press-fitted.

3. A method for manufacturing a thermostat device comprising a stainless steel cylindrical guide member that slidably holds a stainless steel piston, which moves forward and backward in accordance with the expansion and contraction of a stainless steel piston, provided at the open end portion of a stainless steel cylindrical case with a bottom containing a thermal expansion body, When a brass bush is press-fitted into the piston sliding portion on the inner circumference of the cylindrical guide member, A method for manufacturing a thermostat device, characterized by fitting the brass bush into the inner circumference of the cylindrical guide member in a light press-fit state, applying a ball burnishing process to the inner surface of the brass bush as a finishing process, and expanding the diameter of the brass bush by applying pressure from the inside, thereby providing it in a press-fit state.

4. A method for manufacturing a thermostat device according to claim 2 or claim 3, A method for manufacturing a thermostat device, characterized in that an annular step is provided on the inner circumferential surface of the cylindrical guide member, in a portion corresponding to the press-fit end portion in the axial direction of the brass bush, to form an annular groove.

5. A method for manufacturing a thermostat device according to claim 2 or claim 3, A method for manufacturing a thermostat device, characterized in that a tapered portion is provided on the inner circumferential surface of the tip of the brass bush, which is press-fitted into the inner circumference of the cylindrical guide member, on the press-fitting side in the axial direction, gradually decreasing in diameter from the tip side.

6. A thermostat device according to claim 1, The thermostat device is characterized in that it is used in a fuel cell cooling device in a fuel cell power generation system.

7. A method for manufacturing a thermostat device comprising a stainless steel cylindrical guide member that slidably holds a stainless steel piston, which moves back and forth due to the expansion and contraction of the thermal expansion body, provided at the open end portion of a stainless steel cylindrical case with a bottom containing a thermal expansion body, A method for manufacturing a thermostat device, characterized by fitting a brass bush that slidably holds the piston into the inner circumference of the cylindrical guide member in a light press-fit state, and by performing a precision finishing process on the inner surface of the brass bush, thereby expanding the diameter of the brass bush by an internal pressure and providing it in a press-fit state to the inner circumference of the cylindrical guide member.

8. A method for manufacturing a thermostat device according to claim 7, A method for manufacturing a thermostat device, characterized by fitting the brass bush into the inner circumference of the cylindrical guide member in a light press-fit state, applying a ball burnishing process to the inner surface of the brass bush as a finishing process, and expanding the diameter of the brass bush by applying pressure from the inside, thereby providing it in a press-fit state.

9. A method for manufacturing a thermostat device according to claim 7 or claim 8, A method for manufacturing a thermostat device, characterized in that when the inner circumferential surface of the brass bush is finished, the deformed portion that is pushed out when the brass bush is expanded in diameter by an internal pressure is released into an annular groove formed by a step on the inner circumferential surface of the cylindrical guide member, in a portion corresponding to the press-fit end portion in the axial direction of the brass bush.

10. A method for manufacturing a thermostat device according to claim 7 or claim 8, A method for manufacturing a thermostat device, characterized by applying a finishing process to the inner circumferential surface of the brass bush, and releasing the deformed portion that is pushed out when the brass bush is expanded by an internal pressure into a space provided on the inner circumferential surface of the tip of the brass bush on the press-fitting side in the axial direction, which is press-fitted into the inner circumferential portion of the cylindrical guide member, by a tapered portion that gradually decreases in diameter from the tip side.

11. A method for manufacturing a thermostat device according to claim 7, A method for manufacturing a thermostat device, characterized in that the thermostat device is used in a fuel cell cooling device in a fuel cell power generation system.

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