Thermally responsive element and its manufacturing method

Abstract

Provided is a thermally-actuated element having a high degree of freedom for setting a differential across a wide temperature band, and with which it is also possible to set a comparatively low differential. This plate-shaped thermally-actuated element 100, which has a shape that changes in conjunction with a change in temperature, has a cross-section at a room temperature that is a composite curve formed by combining a plurality of curves, the cross-section being at different curves at a center portion 121 of the thermally-actuated element and an outer peripheral portion 122 surrounding the center portion. The shape of the thermally-actuated element changes at a prescribed temperature outside the range of room temperature, the cross-section of the thermally-actuated element after the shape change is a composite curve formed by combining a plurality of curves, and the cross-section is at different curves at the center portion of the thermally-actuated element and the outer peripheral portion surrounding the center portion. A boundary 123 between the center portion and the outer peripheral portion is the same before and after the shape change of the thermally-actuated element.

Description

[Technical Field]

[0001] The present invention relates to a thermally responsive element used in a temperature switch such as a thermostat, and a method for manufacturing the same. [Background technology]

[0002] Temperature switches such as thermostats are used to prevent overheating and control temperature in defrosting heaters installed in refrigerators and equipment used in cold climates, and in anti-freeze heaters installed in water pipes and manufacturing equipment in chemical plants. To prevent water pipes from freezing, for example, a temperature switch is used that turns on the heater at 3°C ​​and turns it off at 10°C. In addition, for industrial and commercial applications, there is a demand for temperature switches that can control the temperature of freezers between -30°C and -20°C, and temperature switches that can control the temperature of heaters between 90°C and 100°C.

[0003] When a bimetal is used as the thermally responsive element of such a temperature switch, it is necessary that the differential be relatively small.

[0004] Patent Document 1 describes that the reversal temperature and return temperature can be adjusted arbitrarily, and that it is possible to manufacture a bimetal with a temperature range of approximately -30°C to 200°C. Furthermore, Patent Document 2 describes a bimetal disc with a small temperature difference (differential) between reversal and reversal. This bimetal disc is formed by bending a flat bimetal disc all around at a fixed distance from the center, so that the cross section is straight at both the center and the periphery, forming a rimmed dish shape. It is said that by bending it toward the low expansion side, it can also operate at temperatures lower than room temperature. Furthermore, Patent Document 3 describes a disk-shaped bimetal in which at least one surface of the protruding region is provided with irregularities to increase the surface area. This disk-shaped bimetal is said to have a low reversal and recovery temperature and a small temperature difference therebetween. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 63-16285 [Patent Document 2] Japanese Patent Application Laid-Open No. 198788-1988 [Patent Document 3] Special Publication No. 48-10429 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, when a bimetal is used as a thermally responsive element, it is known that its operating temperature and recovery temperature are strongly related to the shape of the bimetal. However, Patent Document 1 only describes a spherical shape and does not disclose a specific method for setting an arbitrary temperature within a variety of temperature ranges. Patent Document 2 states that a bimetal can be made to operate at temperatures lower than room temperature, but does not disclose a detailed method or specific operating temperature. Furthermore, the processing of the uneven surface in Patent Document 3 is considered to be complicated.

[0007] Therefore, an object of the present invention is to provide a thermally responsive element that allows a high degree of freedom in setting the differential over a wide temperature range, from a low temperature range below room temperature to a high temperature range above 100°C, and also allows the setting of a relatively small differential. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a plate-shaped thermally responsive element whose shape changes with temperature, the cross section of the thermally responsive element at room temperature being a compound curve formed by combining a plurality of curves, and the cross sections at the center of the thermally responsive element and the outer periphery surrounding the center being different curves. When the temperature reaches a predetermined temperature outside the room temperature range, the shape of the thermally responsive element changes, and the cross section of the thermally responsive element after the shape change is a compound curve formed by combining a plurality of curves, the cross sections at the center of the thermally responsive element and the outer periphery surrounding the center being different curves, and the boundary between the center and the outer periphery is the same before and after the shape change of the thermally responsive element. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a thermally responsive element that allows a high degree of freedom in setting the differential over a wide temperature range from a low temperature range below room temperature to a high temperature range above 100°C, and also allows the setting of a relatively small differential. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of a thermally responsive element according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA' in FIG. [Figure 3] FIG. 10 is a cross-sectional view of the thermally responsive element after inversion. [Figure 4A] FIG. 3 is an explanatory view showing a first step of the method for manufacturing the thermally responsive element. [Figure 4B] FIG. 10 is an explanatory view showing a second step in the manufacturing process of the thermally responsive element. [Figure 5A] FIG. 10 is an explanatory view showing a first step of another method for manufacturing a thermally responsive element. [Figure 5B] FIG. 10 is an explanatory view showing a second step of another method for manufacturing a thermally responsive element. [Figure 6] FIG. 10 is a perspective view of a punch used in the second step. [Figure 7] FIG. 3 is a cross-sectional view in a second step. [Figure 8] FIG. 10 is a plan view of a thermally responsive element according to a second embodiment. [Figure 9] FIG. 9 is a cross-sectional view taken along line BB′ in FIG. 8. [Figure 10] FIG. 10 is a cross-sectional view of the thermally responsive element after inversion. [Figure 11A] FIG. 3 is an explanatory view showing a first step of the method for manufacturing the thermally responsive element. [Figure 11B] FIG. 10 is an explanatory view showing a second step in the manufacturing process of the thermally responsive element. [Figure 12A] FIG. 10 is an explanatory view showing a first step of another method for manufacturing a thermally responsive element. [Figure 12B] FIG. 10 is an explanatory view showing a second step of another method for manufacturing a thermally responsive element. [Figure 13A] FIG. 10 is a plan view of a thermally responsive element according to a third embodiment. [Figure 13B] FIG. 10 is another plan view of the thermally responsive element according to the third embodiment. [Figure 13C] FIG. 10 is a still further plan view of the thermally responsive element according to the third embodiment. [Figure 14A] FIG. 10 is a plan view of a thermally responsive element according to a fourth embodiment. [Figure 14B] FIG. 10 is another plan view of the thermally responsive element according to the fourth embodiment. [Figure 14C] FIG. 10 is a plan view of still another thermally responsive element according to the fourth embodiment. [Figure 15] FIG. 10 is a plan view of a thermally responsive element according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on the illustrated embodiments. However, the present invention is not limited to the embodiments described below. Furthermore, the dimensional ratios of shapes shown in the drawings may not be the actual dimensional ratios. The dimensional ratios may be changed to make the shapes easier to understand.

[0012] In this specification, "room temperature" (or "normal temperature") means a temperature of 18°C ​​or higher and 38°C or lower.

[0013] [First embodiment] [composition] Fig. 1 is a plan view of a bimetal 100, which is a thermally responsive element according to this embodiment. Fig. 2 is a cross-sectional view taken along line A-A' in Fig. 1. Both figures show the shape of the bimetal 100 at room temperature, which has been formed by multiple-stage pressing using a punch and a die.

[0014] 1 and 2, the bimetal 100 is a plate-shaped member having a low expansion layer 111 and a high expansion layer 112 located below the low expansion layer. The material of the high expansion layer 112 has a higher thermal expansion coefficient than the material of the low expansion layer 111.

[0015] The bimetal 100 also has a center 121, an outer periphery 122 surrounding the center, and a boundary 123 between the center 121 and the outer periphery 122. When viewed from above, the center 121 has a concave shape, and when viewed from below, the center 121 has a convex shape. The bimetal 100 can also be said to be shaped like a rimmed dish. The angle α1 between the center 121 and the outer periphery 122 is an obtuse angle. The cross-sectional structure of the bimetal 100 is a compound curve formed by combining multiple curves. Specifically, the cross-sectional structure of the center 121 is an upwardly convex curve, and the cross-sectional structures of the outer peripheries 122 on either side of the center 121 are also upwardly convex curves. The radius of curvature of the curves in the center 121 and the outer peripheries 122 may be the same or different.

[0016] In plan view, the central portion 121 is circular, and the outer peripheral portion 122 is a rectangle with rounded corners.

[0017] The boundary 123 is on the circumference of a concentric circle having a diameter L12 that is 1% to 50% of the diameter L11 of a circumscribing circle 131 that circumscribes the outer periphery 122. However, the diameter L12 of this concentric circle is smaller than the width of the rounded rectangle.

[0018] The bimetal 100 may be made of, for example, a Ni-Fe alloy for the low expansion layer 111 and a Cu-Ni-Mn alloy for the high expansion layer 112. The length, width, corner shape, and thickness of the rounded rectangle may be set arbitrarily depending on the desired reversal temperature.

[0019] When the temperature of the bimetal drops and reaches a predetermined temperature (reset temperature) that is lower than room temperature, the bimetal flips over with a snap action, changing from the shape shown in Figure 2 to the shape shown in Figure 3. After flipping, the bimetal 100 has a convex shape with a protruding center 121 when viewed from above, and a concave shape with a recessed center 121 when viewed from below.

[0020] The shape after inversion is a compound curve made up of a combination of multiple curves. The boundary 123 between the center 121 and the outer periphery 122 remains unchanged before and after inversion. 3, the cross-sectional structure of the central portion 121 is an upwardly convex curve, and the cross-sectional structures of both outer peripheral portions 122 on either side of the central portion 121 are also upwardly convex curves. The curvature radii of the respective curves may be the same or different. In FIG. 3, the angle β1 formed between the central portion 121 and the outer peripheral portion 122 is an obtuse angle larger than the angle α1. Angle β1 is larger than angle α1, and the fact that the central portion 121 and both outer peripheral portions 122 each have an upwardly convex curved shape remains unchanged before and after reversal makes it possible to set a relatively small differential of around 10 degrees. Furthermore, as shown in Figure 2, because the central portion 121 and both outer peripheral portions 122 are curved (upwardly convex curved) in the same direction (inward), it is also possible to set an extremely low return temperature. Then, when the temperature of the bimetal rises and reaches a predetermined temperature (operating temperature) that is lower than room temperature, the bimetal reverses with a snap action and returns from the shape shown in Figure 3 to the shape shown in Figure 2. This operating temperature is higher than the above-mentioned return temperature. In a compound curve, the boundary between one curve and another may be rounded or sharp. Although the above cross section has been described as being characteristic of a cross section taken along a line parallel to the longitudinal direction of the bimetal and passing through the center of the circumscribing circle, the same characteristics apply to a cross section taken along any line passing through the center. Also, while Figure 2 shows the shape at room temperature after being formed by multiple pressing processes using a punch and die, bimetals that are heat-treated after being formed by pressing also have similar characteristics regarding their shape at room temperature.

[0021] [Manufacturing method] The method for manufacturing the bimetal 100 includes the steps of cutting a bimetal material composed of two metal layers with different thermal expansion coefficients into a desired shape, and forming the cut bimetal material into the bimetal 100 through a multi-stage pressing process using a press machine. The multi-stage pressing process is performed while the bimetal material and a mold including a punch and a die are maintained at a temperature similar to room temperature (18°C to 38°C). However, the multi-stage pressing process may also be performed after cooling or heating. The punch is made of metal, such as alloy tool steel, and the die is made of an elastic material.

[0022] Figure 4A shows the first step of pressing the bimetal material 100a after cutting. The bimetal material 100a after cutting is placed on a die D having a flat surface. At this time, the bimetal material 100a is placed so that the low expansion layer 111 faces the metal punch P1 and the high expansion layer 112 faces the die D. Then, the punch P1, which has a convex curved end face, is lowered to press the bimetal material 100a. This first step results in the bimetal material 100b (Figure 4B). FIG. 4B shows the second step (final pressing step) in which the bimetal material 100b formed in the first step is further pressed. The bimetal material 100b obtained in the first step is placed on a die D having a flat surface. At this time, the bimetal material 100b is placed so that the low expansion layer 111 faces the metal punch P2 and the high expansion layer 112 faces the die D. Then, the punch P2, which has a protrusion formed on its end face, is lowered to press the bimetal material 100b. This second step produces the bimetal 100 shown in FIGS. 1 and 2.

[0023] As shown in Figure 5A, in the first step, when the bimetal material 100a after cutting is placed on the die D, the high expansion layer 112 may be placed on the punch P1 side and the low expansion layer 111 on the die D side. In this way, the arrangement of the bimetal material 100a shown in Figure 4A can be reversed. By this first step, a bimetal material 100c (Figure 5B) is obtained. In the second step shown in FIG. 5B, similarly to FIG. 4B, the bimetal material 100c is placed so that the low expansion layer 111 faces the punch P2 and the high expansion layer 112 faces the die D, and then pressing is performed.

[0024] As shown in Fig. 6, a substantially cylindrical protrusion X is formed at the approximate center of the end face Y of the substantially cylindrical punch P2. The diameter L13 of the protrusion X is 1% to 50% of the diameter L11 of a circumscribing circle 131 that circumscribes the rounded rectangle. The protrusion amount H of the protrusion X from the end face Y is 0.05 to 1 mm. The end face of the protrusion X and the surrounding end face Y may be flat or dish-shaped (concave). However, it is preferable that the diameter L14 of the end face Y be equal to or greater than the diameter L11 of the circumscribing circle 131. The end face Y is not limited to a circular shape, but may also be an ellipse or a rectangle (not shown).

[0025] Referring to FIG. 7, the effect of the second process (final pressing process) using punch P2 and die D made of an elastic material will be described. The bimetal blank 100b (or bimetal blank 100c) that has undergone the first process is placed on die D, and when punch P2 is lowered, the central portion 121b and the outer peripheral portion 122b of bimetal blank 100b are sandwiched and fixed between punch P2 and die D. As punch P2 presses, the die D, made of an elastic material, pushes back, resulting in the compound curved cross-sectional shape described above. Unlike conventional technology, a high degree of processing is achieved around the boundary 123, which cannot be achieved by simply pressing with a punch with a curved surface. This allows for extremely low or extremely high operating temperature recovery temperatures and a relatively small differential of around 10°. 7 shows a manufacturing method using a metal punch and a die made of elastic material, but this is not limiting. After processing the outer shape of the bimetal material, the bimetal material may be clamped between upper and lower metal dies having a curved shape that matches the desired curved shape of the bimetal and pressed. After pressing, the bimetal material is subjected to heat treatment at a temperature of 50°C to 300°C for, for example, one hour.

[0026] [Actions and Effects] In the above manufacturing method, the bimetal material (composition, thickness, temperature), the shape after cutting, the pressing forces (force, time, temperature) in the first and second steps, the end face shapes of punch P1 and punch P2 (diameter lengths L13 and L14, protrusion amount H), and the die material are all selected appropriately. This allows the operating temperature to be set lower than room temperature, and the return temperature can be freely set. It is also possible to set a relatively small differential of around 10 degrees. The operating temperature, return temperature, and differential can also be adjusted by changing the end face shape of punch P1 in the first step. If the diameter L12 of the center portion 121 is less than 1% of the diameter L11 of the circumscribed circle 131, the differential adjustment effect is small, and if it exceeds 50% of the diameter L11, the bimetal will not easily flip with a snap action, and even if it does flip, the height after flipping will be low. In other words, it is considered undesirable for use in a temperature switch, etc. (it cannot be effectively used to open and close electrical contacts).

[0027] [Second embodiment] [composition] Fig. 8 is a plan view of a bimetal 200, which is a thermally responsive element according to this embodiment. Fig. 9 is a cross-sectional view taken along line BB' in Fig. 8. Both figures show the shape of the bimetal 200 at room temperature, which has been formed by multiple-stage pressing using a punch and a die.

[0028] 8 and 9, the bimetal 200 is a plate-shaped member having a low expansion layer 211 and a high expansion layer 212 located below the low expansion layer. The material of the high expansion layer 212 has a higher thermal expansion coefficient than the material of the low expansion layer 211.

[0029] The bimetal 200 has a center 221, an outer periphery 222 surrounding the center, and a boundary 223 between the center 221 and the outer periphery 222. When viewed from above, the center 221 has a protruding convex shape, and when viewed from below, the center 221 has a concave shape. The bimetal 200 can also be said to be shaped like a rimmed dish. The angle α2 between the center 221 and the outer periphery 222 is an obtuse angle. The cross-sectional structure of the bimetal 200 is a compound curve formed by combining multiple curves. Specifically, the cross-sectional structure of the center 221 is a downwardly convex curve, and the cross-sectional structures of the outer peripheries 222 on either side of the center 221 are also downwardly convex curves. The radius of curvature of the curves in the center 221 and the outer peripheries 222 may be the same or different.

[0030] In plan view, the central portion 221 is circular, and the outer peripheral portion 222 is a rectangle with rounded corners.

[0031] The boundary 223 is on the circumference of a concentric circle having a diameter L22 that is 1% to 50% of the diameter L21 of a circumscribing circle 231 that circumscribes the outer periphery 222. However, the diameter L22 of this concentric circle is smaller than the width of the rounded rectangle.

[0032] The bimetal 200 may be made of, for example, a Ni-Fe alloy for the low expansion layer 211 and a Cu-Ni-Mn alloy for the high expansion layer 212. The length, width, corner shape, and thickness of the rounded rectangle may be set arbitrarily depending on the desired reversal temperature.

[0033] When the temperature of the bimetal rises and reaches a predetermined temperature (operating temperature) that is higher than room temperature, the bimetal flips over with a snap action, changing from the shape shown in Figure 9 to the shape shown in Figure 10. After flipping, bimetal 200 has a concave shape with a recessed center 221 when viewed from above, and a convex shape with the center 221 protruding when viewed from below.

[0034] The shape after inversion is a compound curve made up of a combination of multiple curves. The boundary 223 between the center portion 221 and the outer periphery 222 remains unchanged before and after inversion. 10, the cross-sectional structure of the central portion 221 is a downwardly convex curve, and the cross-sectional structures of both outer peripheral portions 222 on either side of the central portion 221 are also downwardly convex curves. The curvature radii of the respective curves may be the same or different. In FIG. 10, the angle β2 formed between the central portion 221 and the outer peripheral portion 222 is an obtuse angle larger than the angle α2. Because angle β2 is larger than angle α2 and the central portion 221 and both outer peripheral portions 222 each have a downward convex curved shape that remains unchanged before and after inversion, it is possible to set a relatively small differential of around 10°. Furthermore, as shown in Figure 9, because the central portion 221 and both outer peripheral portions 222 are curved (downward convex curved) in the same direction (inward), it is also possible to set an extremely high operating temperature. Then, when the temperature of the bimetal drops below a predetermined temperature (return temperature), the bimetal reverses with a snap action and returns from the shape shown in Figure 10 to the shape shown in Figure 9. This return temperature is lower than the operating temperature. In a compound curve, the boundary between one curve and another may be rounded or sharp. Although the above cross section has been described as being characteristic of a cross section taken along a line parallel to the longitudinal direction of the bimetal and passing through the center of the circumscribing circle, the same characteristics apply to a cross section taken along any line passing through the center. 9 shows the shape at room temperature after being formed by multiple pressing processes using a punch and die. However, bimetals that are formed by pressing and then heat-treated also have similar characteristics regarding their shape at room temperature.

[0035] [Manufacturing method] The manufacturing method of the thermally responsive element 200 according to this embodiment is almost the same as the manufacturing method of the thermally responsive element 100 according to the first embodiment. However, in the second step of the manufacturing method of the thermally responsive element 100, the bimetal material is pressed from the low expansion layer side, whereas in the second step of the manufacturing method of the thermally responsive element 200, the bimetal material is pressed from the high expansion layer side. 11A shows the first step of press-forming the bimetal material 200a after cutting. The bimetal material 200a after cutting is placed on a die D having a flat surface. At this time, the bimetal material 200a is placed so that the high expansion layer 212 faces the punch P1 and the low expansion layer 211 faces the die D. Then, a punch P1 with a convex curved end face is lowered to press the bimetal material 200a. By this first step, the bimetal material 200b (FIG. 11B) is obtained. FIG. 11B shows the second step (final pressing step) of further pressing the bimetal blank 200b obtained in the first step. The bimetal blank 200b obtained in the first step is placed on a die D having a flat surface. At this time, the bimetal blank 200b is placed so that the high expansion layer 212 faces the punch P2 and the low expansion layer 211 faces the die D. Then, the punch P2, which has a protrusion formed on its end face, is lowered to press the bimetal blank 200b. By this second step, the bimetal 200 shown in FIGS. 8 and 9 is obtained.

[0036] As shown in Fig. 12A, in the first step, when the bimetal material 200a after cutting is placed on the die D, the low expansion layer 211 may be placed on the punch P1 side and the high expansion layer 212 on the die D side. In this way, the arrangement of the bimetal material 200a shown in Fig. 11A can be reversed. By this first step, the bimetal material 200c (Fig. 11B) is obtained. 12B, similarly to FIG. 11B, the bimetal material 100c is placed so that the high expansion layer 212 faces the punch P2 and the low expansion layer 211 faces the die D, and then pressing is performed.

[0037] The punches P1 and P2 are made of metal, such as alloy tool steel, and the die D is made of an elastic material. The processed bimetal is subjected to heat treatment at a temperature of 100°C to 500°C for, for example, one hour.

[0038] [Actions and Effects] In the above manufacturing method, the bimetal material (composition, thickness, temperature), the shape after cutting, the pressing forces (force, time, temperature) in the first and second steps, the end face shapes of punch P1 and punch P2 (diameter lengths L13 and L14, protrusion amount H), and the die material are all selected appropriately. This allows the operating temperature to be set higher than room temperature, and the return temperature can be freely set. It is also possible to set a relatively small differential of around 10 degrees. The operating temperature, return temperature, and differential can also be adjusted by changing the end face shape of punch P1 in the first step. If the diameter L22 of the center portion 221 is less than 1% of the diameter L21 of the circumscribed circle 231, the differential adjustment effect is small, and if it exceeds 50% of the diameter L21, the bimetal will not easily reverse with a snap action, and even if it does reverse, the height after reversal is thought to be low. In other words, it is thought to be undesirable for use in a temperature switch, etc. (it cannot be effectively used to open and close electrical contacts).

[0039] [Third embodiment] 13A to 13C are plan views of a bimetal having an outer shape different from that of the bimetal according to the first and second embodiments. 13A, bimetal 300 has a circular shape in a plan view, and has circular center portion 321 and outer periphery 322. Diameter L2 of center portion 321 is 1% to 50% of diameter L1 of bimetal 300. 13B, bimetal 400 has an elliptical shape in a plan view, and has circular center portion 421 and outer periphery 422. Diameter L2 of center portion 421 is 1% to 50% of diameter L1 of circumscribing circle 431 that circumscribes the outer periphery of bimetal 400. 13C, bimetal 500 has a diamond shape in plan view, and has circular center portion 521 and outer periphery 522. Diameter L2 of center portion 521 is 1% to 50% of diameter L1 of circumscribed circle 531 that circumscribes the outer periphery of bimetal 500. The cross-sectional shapes of the bimetals 300, 400 and 500 are the same as the cross-sectional shapes of the bimetals 100 and 200. The bimetals 300, 400 and 500 can also provide the same functions and effects as those described above.

[0040] [Fourth embodiment] 14A to 14C are plan views of a bimetal having a central part with a different shape from the bimetals according to the first and second embodiments. 14A, bimetal 600 has a rectangular shape in plan view, and has elliptical central portion 621 and outer peripheral portion 622. The major axis of central portion 621 extends in the width direction of bimetal 600. The length L2 of the major axis is 1% to 50% of the diameter L1 of circumscribing circle 631 that circumscribes the outer peripheral portion of bimetal 600. The center of central portion 621 is at the center of circumscribing circle 631. 14B, bimetal 700 has a rectangular shape in plan view, and has elliptical central portion 721 and outer peripheral portion 722. The major axis of central portion 721 extends in the length direction of bimetal 700. The length L2 of the major axis is 1% to 50% of the diameter L1 of circumscribing circle 731 that circumscribes the outer peripheral portion of bimetal 700. The center of central portion 721 is at the center of circumscribing circle 731. 14C, bimetal 800 has a rectangular shape in a plan view, and has a central portion 821 and an outer periphery 822. Central portion 821 is peanut-shaped (having a narrowed middle and bulging sides), and the longitudinal direction of central portion 821 is parallel to the length direction of bimetal 800. Length L2 of central portion 821 is 1% to 50% of diameter L1 of circumscribing circle 831 that circumscribes the outer periphery of bimetal 800. The center of central portion 821 is at the center of circumscribing circle 831. When manufacturing the bimetals 600, 700, and 800, the shape of the protrusion X of the punch P2 can be elliptical or peanut-shaped. The cross-sectional shapes of the bimetals 600, 700, and 800 are the same as those of the bimetals 100 and 200. Such bimetals 600, 700, and 800 also provide the same functions and effects as those described above. By orienting the major axis of the central ellipse or peanut shape in the length or width direction of the bimetal's outer shape, it is possible to adjust the differential and change the reversal height when the bimetal reverses. By orienting the major axis of the central ellipse or peanut shape in the width direction of the bimetal's outer shape, the height of the bimetal after reversal is greater than when the major axis is in the length direction of the bimetal's outer shape. By increasing the height of the bimetal after reversal, for example, when used in a temperature switch, the bimetal can increase the height to which the movable plate on which the movable contact is provided is pushed up, thereby increasing the breaking current capacity. In this way, by making the central shape non-circular, it is possible to create a variety of bimetal reversal characteristics.

[0041] [Fifth embodiment] 15 shows a bimetal 150. This bimetal 150 is obtained by providing a hole 151 in the center 121 of the bimetal 100 according to the first embodiment. Note that a hole may also be provided in the center 221 of the bimetal 200 according to the second embodiment. The hole can be used to position and fix the bimetal when incorporating it into a temperature switch or the like. The hole is not limited to a circle, but may be an ellipse (not shown). However, it is preferable that the hole be located inside the boundary 123 between the central portion 121 and the outer periphery 122, and that the center of the hole be the same as the center of the circumscribed circle 131. The holes may be formed before the pressing step, in the middle of the pressing step (between the first step and the second step), or after the final step. Such a bimetal also provides the same effects as those described above.

[0042] The first and second embodiments may be modified as appropriate by combining the outer shape, central part shape, and hole of the bimetal described in the third to fifth embodiments. The pressing process has been described as a two-step process, the first and second steps, but it may also be three or more steps. However, in the final pressing step, the bimetal is formed using a punch with a protruding portion and a die with a flat portion. This allows the above-described actions and effects to be obtained. In the first and second embodiments, the first step is carried out after the bimetal material is cut, but the pressing process of the first step may be carried out simultaneously with cutting the bimetal. Also, a progressive press may be used to carry out the steps of drilling holes in the bimetal, punching the outer shape, pressing, and cutting. The operating temperature and reset temperature can be adjusted by the temperature and time of heat treatment of the bimetal after pressing. By increasing the temperature and time of heat treatment, the operating temperature and reset temperature can be increased.

[0043] [Example] Next, with reference to Table 1, experiments conducted to confirm the effects of the first to third and fifth embodiments and their results will be described. In all experiments, a press machine was used, and alloy tool steel was used for the punch and urethane, an elastic material, was used for the die. The pressing force in the first and second steps was measured using a load cell (load transducer). The operating temperature and return temperature were measured by changing the temperature in the chamber using an air-circulating bimetal temperature testing device to detect the impact of the bimetal reversal. As mentioned above, the operating temperature is the temperature at which the shape of Fig. 3 changes from that of Fig. 2 or from that of Fig. 9 to that of Fig. 10 as the temperature increases, and the return temperature is the temperature at which the shape of Fig. 2 changes from that of Fig. 3 or from that of Fig. 10 to that of Fig. 9 as the temperature decreases. In the experiments, the operating temperature was measured by increasing the temperature in the chamber at a rate of 1°C / min, and the return temperature was measured by decreasing the temperature at a rate of 1°C / min. [Table 1]

[0044] [Example 1 (corresponding to the first embodiment)] A bimetal (low expansion layer made of Ni-Fe alloy, high expansion layer made of Cu-Ni-Mn alloy) with a thickness of 0.15 mm was cut into the rounded rectangle shown in Figure 1. The outer dimensions were 14 mm x 10 mm, and the four corners were curved with a radius of curvature of 3 mm. The diameter of the circumscribed circle of this bimetal was 14.9 mm. The bimetal and the mold containing the punch and die were maintained at a temperature similar to room temperature. In the first step, this bimetal was placed on a flat die, and a punch with a tip having a curvature radius of 24 mm was lowered to press the bimetal with a force of approximately 100 kgf for approximately 1 second, with the low-expansion layer of the bimetal facing the punch and the high-expansion layer facing the die, or the high-expansion layer facing the punch and the low-expansion layer facing the die. Next, in the second step (final pressing step), the bimetal formed in the first step was placed on a die with a flat surface, and a punch with a convex portion was lowered to press the bimetal. The low-expansion layer of the bimetal faced the punch, and the high-expansion layer faced the die. The shape of the convex portion was the same as that shown in Figure 6. The end faces of protrusion X and end face Y were flat. The diameter L13 of the end face of protrusion X was 5 mm, the protrusion amount H was 0.3 mm, and the diameter L14 of face Y was 15 mm. The diameter L13 (5 mm) was approximately 34% of the circumscribed circle diameter of 14.9 mm. Pressing was performed for approximately 1 second, and the bimetal was then heat-treated at 200°C for 1 hour after pressing. Table 1 shows the results of experiments conducted by varying the pressing force in the second step as Examples 1-1 to 1-5. As shown in Table 1, the operating temperature and return temperature were below room temperature, and as shown in Examples 1-1 to 1-4, the operating temperature and return temperature decreased with increasing pressing force, reaching a minimum operating temperature of -21.4°C and a minimum return temperature of -32.3°C. Under all conditions, the differential was narrowed to the 10° range.

[0045] [Example 2 (corresponding to the first embodiment)] The same conditions as in Example 1 were used, except that the diameter L13 of the convex portion of the punch used in the second step was 1.2 mm, 3 mm, or 6.4 mm, and the pressing force was varied. The diameter L13 of 1.2 mm, 3 mm, and 6.4 mm are approximately 8%, 20%, and 43% of the circumscribed circle diameter of 14.9 mm, respectively. Table 1 shows the results for Examples 2-1 to 2-5. The temperature characteristics can be varied by varying the pressing force of the punch and the diameter L13 of the convex portion in the second step. Thus, by using a punch with a convex diameter of 1.2 mm, 3 mm, or 6.4 mm, a differential of less than 10 degrees can be achieved.

[0046] [Example 3 (corresponding to the fifth embodiment)] A bimetal material with a hole of 2 mm diameter was prepared, and an experiment similar to that of Example 1 was carried out. The results are also shown in Table 1 as Example 3. Even when using a bimetal with a hole, it was possible to produce a bimetal with extremely low temperature characteristics and a narrow differential of the 10° range.

[0047] [Example 4 (corresponding to the third embodiment)] The bimetal had a circular outer shape as shown in Figure 13A, with a diameter of 13 mm. The results of an experiment conducted under the same conditions as in Example 1 except for the outer shape of the bimetal are also shown in Table 1 (Example 4). Even with a circular outer shape, a bimetal was produced that had cryogenic temperature characteristics and a differential of less than 10 degrees. In the second process, the diameter L13 of the end face of the protruding portion X of the punch was 5 mm, which is approximately 38% of the 13 mm diameter of the bimetal.

[0048] [Example 5 (corresponding to the second embodiment)] A bimetal material (low expansion layer made of Ni-Fe alloy, high expansion layer made of Cu-Ni-Mn alloy) with a thickness of 0.15 mm was cut into the rounded rectangle shown in Figure 8. The outer dimensions were 14 mm x 10 mm, and the four corners were curved with a radius of curvature of 3 mm. The diameter of the circumscribed circle of this bimetal was 14.9 mm. The mold containing the bimetal, punch, and die was maintained at a temperature similar to room temperature. In the first step, the bimetal material was placed on a flat die, and a punch with a tip surface having a curvature radius of 24 mm was lowered to press the bimetal material with a force of approximately 100 kgf for approximately 1 second, with the high-expansion layer of the bimetal facing the punch and the low-expansion layer facing the die. Next, in the second step (final pressing step), the bimetal formed in the first step was placed on a flat die, and a punch with a protruding portion was lowered to press the bimetal. The high-expansion layer of the bimetal faced the punch, and the low-expansion layer faced the die. The shape of the protruding portion was the same as that shown in Figure 6. The end faces of protruding portion X and end face Y were flat. The diameter L13 of the end face of protruding portion X was 5 mm, the protrusion amount H was 0.3 mm, and the diameter L14 of face Y was 15 mm. The diameter L13 (5 mm) was approximately 34% of the circumscribed circle diameter of 14.9 mm. Pressing was performed for approximately 1 second, and the bimetal was then heat-treated at 200°C for 1 hour after pressing. The results of experiments in which the pressing force in the second step was changed are shown as Examples 5-1 to 5-3 in Table 1. As shown in the results, the operating temperature and return temperature were above room temperature, and as the punch pressure in the second step increased, the operating temperature and return temperature increased, and a differential of less than 10 degrees was also obtained.

[0049] [Comparative Example 1] The same conditions as in Example 1 were used, except that the diameter L13 of the convex portion of the punch used in the second step was set to 7.6 mm and the pressing force was changed. The diameter L13 (7.6 mm) was approximately 51% of the circumscribed circle diameter of 14.9 mm. Table 1 shows the results as Comparative Example 1. The bimetal manufactured under these conditions did not reverse by snap action, and the reversal temperature could not be measured using a bimetal temperature inspection device. This shows that if the convex portion of the punch (i.e., the bimetal boundary 123) exceeds 50% of the circumscribed circle diameter, the bimetal will not reverse by snap action.

[0050] [Comparative Examples 2 and 3] The punch used in the second step was the same as the punch used in the first step, with a tip having a radius of curvature of 24 mm. In Comparative Example 2, the first step was performed so that the low-expansion layer of the bimetal was on the punch side and the high-expansion layer was on the die side, and in the second step, the high-expansion layer of the bimetal was on the punch side and the low-expansion layer was on the die side. In Comparative Example 3, the first step was performed so that the high-expansion layer of the bimetal was on the punch side and the low-expansion layer was on the die side, and in the second step, the low-expansion layer of the bimetal was on the punch side and the high-expansion layer was on the die side. The results of experiments conducted under the same conditions as in Example 1, except for changing the pressing force in the second step, are also shown in Table 1 (Comparative Examples 2 and 3). Even when the direction of pressure on the bimetal was changed, the operating temperature and release temperature did not change much, and the differential exceeded 35°. The cross-sectional structure at room temperature when these bimetals reverse below the release temperature is similar to Figure 3 in that the low expansion layer has an upward convex curve, but it is a single curve (not shown), not a compound curve. Furthermore, the cross-sectional structure reversed above the operating temperature is also a single curve (not shown), not a compound curve. Bimetals with a cross-sectional structure consisting of such a single curve have no freedom in setting the operating temperature, release temperature, and differential, and it is not possible to set a relatively narrow differential of around 10°.

[0051] As described above, according to the embodiments of the present invention, it is possible to provide a thermally responsive element that can freely set the differential over a wide temperature range, has a relatively small differential of around 10 degrees, and has an operating temperature and a recovery temperature that are extremely low, below room temperature.

[0052] The embodiments described so far can also be applied to thermally responsive elements other than bimetals, such as shape memory alloys (100° C. or less) and trimetals.

[0053] The following notes are provided regarding the embodiments described above. [Appendix 1] A plate-shaped thermally responsive element whose shape changes with temperature change, The cross section of the thermally responsive element at room temperature is a compound curved shape formed by combining a plurality of curves, and the cross sections of the central part of the thermally responsive element and the outer peripheral part surrounding the central part are each different curved shapes, When the temperature reaches a predetermined temperature outside the range of room temperature, the shape of the thermally responsive element changes, The cross section of the thermally responsive element after the shape change is a compound curved shape formed by combining a plurality of curves, and the cross section at the center of the thermally responsive element and the cross section at the outer periphery surrounding the center are different curved shapes, The boundary between the central portion and the outer periphery is the same before and after the shape of the thermally responsive element is changed. Thermal response element. [Appendix 2] the thermally responsive element is a bimetal including a first metal layer and a second metal layer located below the first metal layer and having a thermal expansion coefficient greater than that of the first metal layer; the predetermined temperature is a temperature lower than the room temperature, At room temperature, the thermally responsive element has a downwardly convex shape as a whole, with the central portion protruding downward, After the shape change, the thermally responsive element has an upwardly convex shape as a whole, with the central portion protruding upward. 2. The thermally responsive element according to claim 1. [Appendix 3] the thermally responsive element is a bimetal including a first metal layer and a second metal layer located below the first metal layer and having a thermal expansion coefficient greater than that of the first metal layer; the predetermined temperature is a temperature higher than the room temperature, At room temperature, the thermally responsive element has an upwardly convex shape as a whole, with the central portion protruding upward, After the shape change, the thermally responsive element has a downwardly convex shape as a whole, with the central portion protruding downward. 2. The thermally responsive element according to claim 1. [Appendix 4] The thermally responsive element has a rounded rectangular shape in a plan view, A thermally responsive element according to any one of appendixes 1 to 3, wherein the boundary is on the circumference of a concentric circle having a diameter that is 1% to 50% of the diameter of a circumscribing circle that circumscribes the rounded rectangle. [Appendix 5] The thermally responsive element is circular in plan view, 4. The thermally responsive element according to any one of claims 1 to 3, wherein the boundary is on the circumference of a concentric circle having a diameter that is 1% to 50% of the diameter of the circle. [Appendix 6] A method for producing the thermally responsive element according to any one of Supplementary Notes 1 to 5, a step of molding the material of the thermally responsive element by a multi-stage pressing process using a press machine; In the final stage of the pressing process in the multiple stages, a metal punch having a protruding central portion and a die made of an elastic material are used. method. [Appendix 7] A method for producing the thermally responsive element according to any one of Supplementary Notes 1 to 5, The method includes a step of sandwiching the material of the thermally responsive element between upper and lower metal molds and pressing the material.

[0054] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical concept of the present invention. [Explanation of symbols]

[0055] 100, 150, 200, 300, 400, 500, 600, 700, 800 Bimetal 111, 211 Low expansion layer 112, 212 High expansion layer 121, 221 Center 122, 222 outer periphery 123, 223 boundaries 131, 231 circumscribed circle 151 Hole L1, L11, L21 lengths L2, L12, L22 lengths P1, P2 punch D die

Claims

1. A plate-shaped thermally responsive element whose shape changes with temperature change, The cross section of the thermally responsive element at room temperature is a compound curved shape formed by combining a plurality of curves, and the cross sections of the central part of the thermally responsive element and the outer peripheral part surrounding the central part are each different curved shapes, When the temperature reaches a predetermined temperature outside the range of room temperature, the shape of the thermally responsive element changes, The cross section of the thermally responsive element after the shape change is a compound curved shape formed by combining a plurality of curves, and the cross section at the center of the thermally responsive element and the cross section at the outer periphery surrounding the center are different curved shapes, The boundary between the central portion and the outer periphery is the same before and after the shape of the thermally responsive element is changed. Thermal response element.

2. the thermally responsive element is a bimetal including a first metal layer and a second metal layer located below the first metal layer and having a thermal expansion coefficient greater than that of the first metal layer; the predetermined temperature is a temperature lower than the room temperature, At room temperature, the thermally responsive element has a downwardly convex shape as a whole, with the central portion protruding downward, After the shape change, the thermally responsive element has an upwardly convex shape as a whole, with the central portion protruding upward. The thermally responsive element according to claim 1 .

3. the thermally responsive element is a bimetal including a first metal layer and a second metal layer located below the first metal layer and having a thermal expansion coefficient greater than that of the first metal layer; the predetermined temperature is a temperature higher than the room temperature, At room temperature, the thermally responsive element has an upwardly convex shape as a whole, with the central portion protruding upward, After the shape change, the thermally responsive element has a downwardly convex shape as a whole, with the central portion protruding downward. The thermally responsive element according to claim 1 .

4. The thermally responsive element has a rounded rectangular shape in a plan view, The thermally responsive element according to any one of claims 1 to 3, wherein the boundary is on the circumference of a concentric circle having a diameter that is 1% to 50% of the diameter of a circumscribing circle that circumscribes the rounded rectangle.

5. The thermally responsive element is circular in plan view, 4. The thermally responsive element according to claim 1, wherein the boundary is on the circumference of a concentric circle having a diameter that is 1% to 50% of the diameter of the circle.

6. A method for manufacturing the thermally responsive element according to any one of claims 1 to 3, comprising the steps of: a step of molding the material of the thermally responsive element by a multi-stage pressing process using a press machine; In the final stage of the pressing process in the multiple stages, a metal punch having a protruding central portion and a die made of an elastic material are used. method.

7. A method for manufacturing the thermally responsive element according to any one of claims 1 to 3, comprising the steps of: The method includes a step of sandwiching the material of the thermally responsive element between upper and lower metal molds and pressing the material.

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