Pressure relief valve

Abstract

To provide a pressure relief valve which can maintain an open-valve state when an inner pressure of a fluid passage reaches an abnormal high pressure, and is prevented from complication in valve mechanism.SOLUTION: A pressure relief valve includes: a valve mechanism having a valve body, a valve seat, a valve shaft, and a spring for urging the valve body in an open-valve direction; a casing for storing the valve mechanism; a manual valve-open lever swingably connected to one end of the valve shaft extending outside of the casing via a pin; a first lever movement restriction mechanism which maintains the manual valve-open lever at a first position in a predefined direction by hindering a movement of the manual valve-open lever in the predefined direction which is different from a valve open / close direction when a projection amount of the one end of the valve shat outward from the casing is less than a predefined value, and permits a movement of the manual valve-open lever in the predefined direction when the projection amount is the predefined value or more; an elastic body that urges the manual valve-open lever in the predefined direction; and a second lever movement restriction mechanism which hinders a movement in a close-valve direction of the valve shaft connected to the manual valve-open lever by being engaged with the manual valve-open lever at a second position with respect to the predefined direction by moving in the predefined direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pressure relief valve.

Background Art

[0002] The applicant of the present application proposed in Patent Document 1 a pressure relief valve that opens when the internal pressure of a fluid path reaches or exceeds a predetermined value, discharges the fluid in the fluid path to the external environment, and reduces the internal pressure of the fluid path. The above pressure relief valve is configured such that a conventional pressure relief valve closes when it opens and the internal pressure of the fluid path drops below a predetermined value. Even when the internal pressure of the fluid path becomes abnormally high due to a malfunction of equipment connected to the fluid path, etc., it opens and closes when the internal pressure of the fluid path drops. Therefore, there is a possibility that the internal pressure of the fluid path may become abnormally high again before the cause is eliminated. It was made in view of the problems of conventional pressure relief valves, and it can maintain an open state when the internal pressure of the fluid path becomes abnormally high.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The pressure relief valve of Patent Document 1 has a problem that a mechanism for maintaining an open state when the internal pressure of the fluid path becomes abnormally high is arranged in the valve casing, and the valve mechanism is complicated. The present invention has been made in view of the above problems, and aims to provide a pressure relief valve that can maintain an open state when the internal pressure of the fluid path becomes abnormally high and that prevents complication of the valve mechanism.

Means for Solving the Problems

[0005] In order to solve the above problems, in the present invention, there is provided a pressure relief valve characterized by comprising: a valve mechanism having a valve body, a valve seat, a valve shaft, and a spring for biasing the valve body in the valve closing direction; a casing for housing the valve mechanism; a manual valve opening lever swingably connected via a pin to one end of the valve shaft extending outside the casing; a first lever movement restricting mechanism that blocks the movement of the manual valve opening lever in a predetermined direction different from the valve opening / closing direction and holds the manual valve opening lever in a first position when the protruding amount of the one end of the valve shaft outside the casing is less than a predetermined value, and allows the movement of the manual valve opening lever in the predetermined direction when the protruding amount is greater than or equal to the predetermined value; an elastic body for biasing the manual valve opening lever in the predetermined direction; and a second lever movement restricting mechanism that engages with the manual valve opening lever moving in the predetermined direction and being in a second position with respect to the predetermined direction, and blocks the movement of the valve shaft connected to the manual valve opening lever in the valve closing direction. A pressure relief valve in which a manual valve opening lever is disposed outside the valve casing is generally used. The manual valve opening lever is provided to wash away foreign matter adhering to the valve body and valve seat by using the liquid discharged to the external environment by manually forcing the valve to open. In the present invention, a mechanism for maintaining the valve open state when the internal pressure of the fluid path becomes abnormally high is configured by utilizing the manual valve opening lever. Even if the pressure relief valve opens when the internal pressure of the fluid path exceeds the opening pressure of the pressure relief valve, when the internal pressure of the fluid path is less than a predetermined value and the protruding amount of one end of the valve shaft outside the casing is less than a predetermined value, the first lever movement restricting mechanism operates to block the movement of the manual valve opening lever in a predetermined direction different from the valve opening / closing direction. Therefore, when the internal pressure of the fluid path decreases, the manual valve opening lever and the valve shaft also move in the valve closing direction, and the pressure relief valve closes. When the internal pressure of the fluid path becomes abnormally high and the protruding amount of one end of the valve shaft outside the casing becomes greater than or equal to a predetermined value, the movement restriction by the first lever movement restricting mechanism is released, and the manual valve opening lever biased by the elastic body moves in a predetermined direction different from the valve opening / closing direction and reaches a second position with respect to the predetermined direction. Then, the second lever movement restricting mechanism operates to restrict the movement of the valve shaft connected to the manual valve opening lever in the valve closing direction, and the valve open state is maintained. Since the movement mechanism and the movement restricting mechanism of the manual valve opening lever are disposed outside the casing, the valve mechanism does not become complicated. The valve opening state can be released by pushing the manual valve opening lever from the second position toward the first position.

[0006] In a preferred embodiment of the present invention, the first lever movement restricting mechanism includes a surface of the manual valve opening lever facing in the predetermined direction and a protrusion that stands up from the outer surface of the casing and can abut against the surface of the manual valve opening lever facing in the predetermined direction. The second lever movement restricting mechanism includes a surface of the manual valve opening lever facing in the valve closing direction and a protrusion that stands up from the outer surface of the casing and can abut against the surface of the manual valve opening lever facing in the valve closing direction. The first lever movement restricting mechanism can be formed by a surface of the manual valve opening lever facing in the predetermined direction and a protrusion that stands up from the outer surface of the casing and can abut against the surface of the manual valve opening lever facing in the predetermined direction. The second lever movement restricting mechanism can be formed by a surface of the manual valve opening lever facing in the valve closing direction and a protrusion that stands up from the outer surface of the casing and can abut against the surface of the manual valve opening lever facing in the valve closing direction. In a preferred embodiment of the present invention, the contact surface between the surface of the manual valve opening lever facing in the valve closing direction at the second position with respect to the predetermined direction and the protrusion on the outer surface of the casing forms an inclined surface that is inclined in the valve opening direction from the second position toward the first position. By making the contact surface between the surface of the manual valve opening lever facing in the valve closing direction at the second position with respect to the predetermined direction and the protrusion on the outer surface of the casing an inclined surface that is inclined in the valve opening direction from the second position toward the first position, the elastic force of the spring that biases the valve body in the valve closing direction is utilized as the resistance to the movement of the manual valve opening lever from the second position to the first position, and an unexpected return of the manual valve opening lever from the second position to the first position can be prevented. In a preferred embodiment of the present invention, the valve body has a bellows diaphragm. By increasing the pressure receiving area using the bellows diaphragm, it is possible to rapidly increase the valve opening speed and discharge flow rate of the pressure relief valve and to quickly reduce the internal pressure in the fluid path.

[0007] In a preferred embodiment of the present invention, the pressure relief valve is attached to a circulation path connecting a hot water storage unit and a heat source unit of a hot water supply heater including a hot water storage unit having a hot water storage tank and a heat source unit having a heat pump, or a circulation path connecting an indoor heat exchanger and a heat source unit of a heater including an indoor heat exchanger and a heat source unit having a heat pump. The abnormal internal pressure generated in the circulation path connecting the hot water storage unit and the heat source unit of the hot water supply heater including the hot water storage unit having a hot water storage tank and the heat source unit having a heat pump, or the circulation path connecting the indoor heat exchanger and the heat source unit of the heater including the indoor heat exchanger and the heat source unit having a heat pump, is often caused by the mixing of high-pressure refrigerant into the circulating water due to damage to the water-cooled refrigerant heat exchanger provided in the heat pump. Currently, in order to suppress global warming, hydrocarbons with a low warming coefficient and flammability, ammonia with toxicity, etc. are becoming the mainstream as refrigerants used in heat pumps. If any damage occurs in the part extending indoors in the circulation path of the above-mentioned hot water supply heater or heater, the refrigerant mixed into the circulating water will be released indoors, which is dangerous. By using the pressure relief valve according to the present invention, the refrigerant mixed into the circulating water can be released to the external environment to prevent the release of the refrigerant into the room.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 15

Modes for Carrying Out the Invention

[0009] The pressure relief valve according to the first embodiment of the present invention and an application example of the pressure relief valve to a hot water storage type water heater and heater will be described below. As shown in FIG. 1, the hot water storage type water heater and heater includes a heat pump type heat source unit 1 that generates high-temperature water and a hot water storage tank unit 2. The heat source unit 1 includes a water-cooled medium heat exchanger 11, a compressor 12, an evaporator 13, and an expansion valve 14 that are sequentially connected in a ring shape by refrigerant pipes. The hot water storage tank unit 2 includes a hot water storage tank 21, a water supply pipe 22 connected to the lower part of the hot water storage tank 21, a water cooling medium heat exchanger 11, a circulation pump 23, and a three-way valve 24 connected to the upper part of the hot water storage tank 21 and then connected to the lower part of the hot water storage tank 21 through them. Further, while forming a heat exchange pipe 25a, it extends upward in the hot water storage tank 21 to reach the upper part of the hot water storage tank, a first circulation path 25, a hot water outlet pipe 26 for taking out high-temperature water from the upper part of the hot water storage tank 21, a first pressure relief valve 27 for protecting the hot water storage tank connected to the hot water outlet pipe 26, a drain pipe 28 extending from the first pressure relief valve 27, and a hot and cold water mixing valve 29 connected to a branch pipe 22a extending from the hot water outlet pipe 26 and the water supply pipe 22. A faucet 30 is connected to the hot and cold water mixing valve 29 through a hot water supply pipe. The combined hot water supply and heating machine further includes a second pressure relief valve 3 for protecting the water cooling medium heat exchanger 11 and for dealing with damage, which is connected to a part extending in the heat source unit 1 of the first circulation path 25, more specifically, a part immediately downstream of the water cooling medium heat exchanger 11, and a drain part 30a of the second pressure relief valve 3. The combined hot water supply and heating machine further includes a heating unit 4. The heating unit 4 includes a second circulation path 41 whose upstream end is connected to a three-way valve 24 for flow path switching and whose downstream end is connected to a part downstream of the hot water storage tank 21 of the first circulation path 25, and an indoor heat exchanger 42 disposed on the way of the second circulation path 41. A part extending in the indoor heat exchanger 42 of the second circulation path 41 forms a heat exchange pipe 41a.

[0010] In the following description, the arrows I II, III, IV, V, VI in FIGS. 2 to 15 are called upward, downward, leftward, rightward, forward, and backward directions. As shown in FIGS. 2(a) to 2(c), the second pressure relief valve 3 includes a casing 31 of a cylinder body extending vertically. An opening 31a1 connected to the first circulation path 25 is formed at the lower end of the casing 31, and an opening 31a2 connected to the drainage part 30a is formed at the front part of the lower part of the circumferential side wall of the casing 31. A valve seat 31b is formed at a portion extending between the opening 31a1 and the opening 31a2 of the casing 31. A valve body 32 is disposed facing the valve seat 31b. The valve body 32 includes a valve main body 32a and a bellows diaphragm 32b attached to the valve main body 32a. A valve shaft 33 extending upward from the valve main body 32a is slidably inserted into a small-diameter cylinder body 31c at the upper part of the casing 31 and extends outward above the casing 31. A coil spring 34 is disposed to engage with the valve main body 32a and the upper end wall 31d of the casing around the small-diameter cylinder body 31c to urge the valve main body 32a and thus the valve body 32 downward, that is, in the closing valve direction.

[0011] A manual valve opening lever 36 is connected to the upper end portion 33a of the valve shaft 33 so as to be swingable about a horizontal axis X which is the central axis of the pin 35 through a pin 35 slidably penetrating the upper end portion 33a extending outside the casing 31 of the valve shaft 33 in the left-right direction. As shown in FIG. 3, the rear end portion of the manual valve opening lever 36 forms a cylinder body 36a extending vertically with a rectangular cross section. The pin 35 penetrates the left and right side walls of the cylinder body 36a, and the head portion 35a of the pin 35 is screwed into the right side wall of the cylinder body 36a. A coil spring 37 for urging the head portion 35a, and thus the manual valve opening lever 36, in the right direction is disposed between the head portion 35a of the pin 35 and the right side surface of the upper end portion 33a of the valve shaft. When the manual valve opening lever 36 is swung clockwise in FIG. 2(b), the front end wall of the cylinder body 36a abuts against the upper end wall 31d of the casing, and then swings about the abutting portion, and the valve shaft 33 is lifted to open the valve. As shown in FIGS. 2(a) and 2(d), a first protrusion 31e in the shape of a substantially rectangular cylinder stands upright upward from the upper end wall 31d of the casing. The first protrusion 31e includes a front end wall 31e1 that is curved in a top view and slidably contacts the upper end portion 33a of the valve shaft to guide the upper end portion 33a of the valve shaft, a central partition wall 31e2 in the front-rear direction, and a rear end wall 31e3. The front end wall 31e1 and the central partition wall 31e2 in the front-rear direction have the same height that is higher than the rear end wall 31e3. The first protrusion 31e further includes left and right side walls 31e4 that connect the left and right ends of the front end wall 31e1, the central partition wall 31e2 in the front-rear direction, and the rear end wall 31e3. A second protrusion 31f in the shape of a U in a top view that surrounds the first protrusion 31e stands upright upward from the upper end wall 31d of the casing outside the first protrusion 31e in a top view. The second protrusion 31f includes a rear end wall 31f1 and side walls 31f2 that extend downward and forward from the rear end wall 31f1. A step portion 31f3 is formed at the central portion in the front-rear direction on the upper surface of the side wall 31f2. As a result, the upper surface of the second protrusion 31f has an upper step portion formed by the upper surface of the rear end wall 31f1, a middle step portion that slopes downward, and a lower step portion 31f4 in front of the step portion 31f3. A curved concave portion 31f5 is formed in the lower step portion 31f4 on the upper surface of the right side wall 31f2. As shown in FIG. 2(d), the upper surface of the flat portion 31f6 at the front end of the middle step portion of the upper surface of the second protrusion 31f is flush with the upper surface of the portion extending between the front end wall 31e1 and the central partition wall 31e2 of the side wall 31e4 of the first protrusion. The rear end wall 31e3 of the first protrusion is integrated with the rear end wall 31f1 of the second protrusion.

[0012] The operation of the hot water storage type water heater and heater and the second pressure relief valve 3 will be described. Tap water is supplied to the lower part of the hot water storage tank 21 through the water supply pipe 22. The circulation pump 23 operates, and the high-temperature water heated by the water-cooled medium heat exchanger 11 of the heat source unit 1 flows into the heat exchange pipe 25a via the first circulation path 25 and the three-way valve 24. The low-temperature tap water flowing into the lower part of the hot water storage tank 21 exchanges heat with the high-temperature water flowing through the heat exchange pipe 25a and is heated to become high-temperature water, filling the upper part of the hot water storage tank 21 with high-temperature water and pressurizing the hot water storage tank 21 due to thermal expansion. The water in the heat exchange pipe 25a whose temperature has decreased due to heat exchange with the low-temperature tap water returns to the water-cooled medium heat exchanger 11 through the first circulation path 25, is reheated to become high-temperature water, and refluxes to the heat exchange pipe 25a in the hot water storage tank 21. The high-temperature water pressurized from the upper part of the hot water storage tank 21 discharges through the hot water discharge pipe 26, is mixed with the tap water supplied through the branch pipe 22a by the hot and cold water mixing valve 29 to become appropriate-temperature water, and discharges from the faucet 30. When the internal pressure of the hot water storage tank 21 reaches a predetermined value A, the first pressure relief valve 27 opens, and the high-pressure high-temperature water is discharged to the external environment through the drain pipe 28 to decompress the hot water storage tank 21. As a result, damage to the hot water storage tank 21 is prevented. After the hot water storage tank 21 is decompressed, the first pressure relief valve 27 closes. The high-temperature water heated by the water-cooled medium heat exchanger 11 of the heat source unit 1 flows into the heat exchange pipe 41a extending in the indoor heat exchanger 42 via the first circulation path 25, the three-way valve 24, and the second circulation path 41. The indoor cold air sucked into the indoor heat exchanger 42 exchanges heat with the high-temperature water flowing through the heat exchange pipe 41a and is heated to become warm air and refluxes into the room.

[0013] When the second pressure relief valve 3 shown in Fig. 2 is closed, as can be seen from Figs. 2 and 4, the rear end portion cylinder 36a of the manual valve opening lever 36 fits into the gap between the first protrusion 31e and the second protrusion 31f, and the right surface of the left side wall of the cylinder 36a abuts against the left surface of the left side wall 31e4 of the first protrusion, preventing the manual valve opening lever 36 from moving rightward, and the manual valve opening lever 36 is held at a first predetermined position with respect to the right direction. Also, the lower bottom surface of the corming 36a1 that protrudes rightward from the right surface of the right side wall of the cylinder 36a and houses the pin head 35a abuts against the curved concave portion 31f5 at the lower stage of the upper surface of the right side wall of the second protrusion 31f, preventing the manual valve opening lever 36 and thus the valve shaft 33 from moving in the valve closing direction.

[0014] When the internal pressure of the first circulation path 25 exceeds a predetermined value B due to some cause such as a malfunction of the heat source unit 1, as shown in Fig. 5, the second pressure relief valve 3 opens, and the high-pressure and high-temperature water in the first circulation path 25 is discharged to the external environment, reducing the internal pressure of the first circulation path 25 and preventing damage to the heat source unit 1. When the internal pressure of the first circulation path 25 reaches the predetermined value B, the amount of protrusion of the upper end portion 33a of the valve shaft outside the casing 31 is less than the predetermined value. As can be seen from Fig. 5, the contact between the right surface of the left side wall of the cylinder 36a and the left surface of the left side wall 31e4 of the first protrusion is maintained, the movement of the manual valve opening lever 36 rightward is blocked, and the manual valve opening lever 36 is held at the first position with respect to the right direction. Therefore, when the internal pressure of the first circulation path 25 decreases, the manual valve opening lever 36 and thus the valve shaft 33 descend and the second pressure relief valve 3 closes.

[0015] When the water-cooled medium heat exchanger 11 of the heat source unit 1 is damaged and high-pressure refrigerants such as ammonia and hydrocarbons in the heat pump refrigerant circuit mix into the circulating water in the first circulation path 25, and the internal pressure of the first circulation path 25 abnormally rises exceeding the predetermined value B, the valve body 32 rises further from the valve opening position shown in Fig. 5, abuts against the annular stepped portion 31g formed inside the casing 31 as shown in Fig. 6, and stops, and the second pressure relief valve 3 fully opens. Due to the presence of the bellows 32b, the pressure receiving area of the valve body 32 is increased, so the second pressure relief valve 3 quickly becomes fully open, the discharge flow rate of the circulating water rapidly increases, and the high-pressure water and high-pressure refrigerant in the first circulation path 25 are quickly discharged to the external environment. As a result, even if a part of the first circulation path 25, for example, the heat exchange pipe 25a, or a part of the second circulation path 41, for example, the heat exchange pipe 41a, is damaged, there is no risk of flammable or toxic refrigerant being released into the room. In the process of the second pressure relief valve 3 fully opening, the protruding amount of the upper end portion 33a of the valve shaft outside the casing 31 becomes equal to or more than the predetermined value, and in the fully open state of the second pressure relief valve 3 shown in Fig. 6, the contact between the right surface of the left side wall of the cylindrical body 36a and the left surface of the left side wall 31e4 of the first protrusion is released. As a result, as shown in Fig. 7, the manual valve opening lever 36 receiving the biasing force of the coil spring 37 moves rightward, the right surface of the left side wall of the cylindrical body 36a abuts against the left surface of the upper end portion 33a of the valve shaft and stops, and is held at the second position with respect to the right direction. When the internal pressure of the first circulation path 25 decreases, the valve body 32, and thus the valve shaft 33 and the manual valve opening lever 36, descend under the biasing force of the spring 34. However, as shown in Fig. 8, the lower surface of the left side wall of the cylindrical body 36a abuts against the upper surface of the portion extending between the front end wall 31e1 of the left side wall 31e4 of the first protrusion and the central partition wall 31e2, and the lower surface of the right side wall of the cylindrical body 36a abuts against the front flat portion 31f6 in the middle of the upper surface of the right side wall 31f2 of the second protrusion, preventing the descent of the manual valve opening lever 36 and thus the valve shaft 33. As a result, the valve opening state of the second pressure relief valve 3 is maintained. Therefore, the refrigerant is surely discharged to the external environment and the safety of the room is ensured. Also, a situation where the internal pressure of the first circulation path 25 becomes abnormally high again before the cause of the abnormal high pressure is eliminated does not occur. Since the movement mechanism and movement restricting mechanism of the manual valve opening lever 36 are arranged outside the casing 31, the valve mechanism of the second pressure relief valve 3 is not complicated. When releasing the maintenance of the open valve state, the head 35a of the pin may be biased leftward to return the manual opening lever 36 to the first position.

[0016] The second pressure relief valve 3 according to the second embodiment of the present invention will be described. As shown in FIG. 9, a notch 36a1 is formed in a part of the left side wall of the cylindrical body 36a, and a leaf spring 36b is integrally formed with the cylindrical body 36a in the notch 36a1 instead of the coil spring 37 of the first embodiment. In the no-load state, as shown in FIG. 9(c), the lower end protrusion 36b1 of the leaf spring 36b is formed so as to protrude leftward from the notch 36a1. Except for the above, the configuration of the second pressure relief valve 3 according to the second embodiment is the same as the configuration of the second pressure relief valve 3 according to the first embodiment. As shown in FIGS. 9(d) and (e), when the second pressure relief valve 3 is closed, the lower end protrusion 36b1 of the leaf spring 36b is sandwiched between the left side wall 31e4 of the first protrusion and the left side wall 31f2 of the second protrusion, and the leaf spring 36b is pushed into the notch 36a1. As a result, the rightward movement of the manual opening lever 36 is blocked. Even when the internal pressure in the circulation path reaches a predetermined value B and the second pressure relief valve 3 opens, the amount of protrusion of the upper end portion 33a of the valve shaft outside the casing 31 is less than the predetermined value, so the state is maintained as shown in FIG. 10. Therefore, when the internal pressure in the circulation path decreases, the second pressure relief valve 3 closes. When the internal pressure in the circulation path abnormally rises exceeding a predetermined value B, the second pressure relief valve 3 fully opens. In the process of the second pressure relief valve 3 fully opening, the amount of protrusion of the upper end portion 33a of the valve shaft outside the casing 31 becomes equal to or greater than the predetermined value. As shown in FIG. 11(a), the lower end protrusion 36b1 of the leaf spring is released from the state of being sandwiched between the left side wall 31e4 of the first protrusion and the left side wall 31f2 of the second protrusion. As shown in FIG. 11(b), the cylindrical body 36a and thus the manual valve opening lever 36 that receives the elastic force of the leaf spring 36b move rightward. The left side wall of the cylindrical body 36a abuts against the upper end portion 33a of the valve shaft, and the manual valve opening lever 36 is held at the second position with respect to the right direction. When the internal pressure in the circulation path decreases, the valve body 32 and thus the valve shaft 33 receive the biasing force of the spring 34 and descend. However, as shown in FIG. 11(c), the lower surface of the left side wall of the cylindrical body 36a abuts against the upper surface of the portion extending between the front end wall 31e1 of the left side wall 31e4 of the first protrusion and the central partition wall 31e2, and the lower surface of the right side wall of the cylindrical body 36a abuts against the front flat portion 31f6 in the middle section of the upper surface of the right side wall 31f2 of the second protrusion, thereby preventing the descent of the manual valve opening lever 36 and thus the valve shaft 33. As a result, the open state of the second pressure relief valve 3 is maintained. When releasing the maintenance of the open state, the right end portion of the pin 35 may be biased leftward to return the manual valve opening lever 36 to the first position.

[0017] The second force relief valve 3 according to the third embodiment of the present invention will be described. As shown in FIG. 12, instead of the leaf spring 36b integrally formed with the cylindrical body 36a in the second embodiment, a leaf spring 38 separate from the cylindrical body 36a is housed in a recess 36a2 formed in a part of the left surface of the left side wall of the cylindrical body 36a. The hook-shaped front end portion of the leaf spring 38 fits into the hook-shaped slit formed by the front end portion of the recess 36a2, and the rear end portion is elastically fitted to the claw portion formed at the rear end portion of the recess 36a2, whereby the leaf spring 38 is locked to the cylindrical body 36a. The leaf spring 38 is formed such that the lower cut-up protrusion 38a protrudes leftward from the recess 36a2 in the no-load state. The operation of the leaf spring 38 is the same as the operation of the leaf spring 36b. Therefore, the operation of the second force relief valve 3 according to the third embodiment is the same as the operation of the second pressure relief valve 3 according to the second embodiment.

[0018] The second pressure relief valve 3 according to the fourth embodiment of the present invention will be described. As shown in FIG. 13, a long recess 36a3 extending in the front-rear direction is formed on the right side surface of the left side wall of the cylindrical body 36a, and a long hole 36a4 extending in the front-rear direction is formed on the right side wall of the cylindrical body 36a facing the long recess 36a3. The pin 35 penetrates the upper end portion 33a of the valve shaft and is fixed to the upper end portion 33a of the valve shaft. The left and right end portions of the pin 35 are slidably engaged with the long recess 36a3 and the long hole 36a4. A coil spring 37 is disposed between the lid 39 screwed into the front end of the cylindrical body 36a and the front surface of the upper end portion 33a of the valve shaft. A portion 31e5 extending between the front end wall 31e1 of the left and right side walls 31e4 of the first protrusion and the central partition wall 31e2 extends above the front end wall 31e1 and the central partition wall 31e2, and a stepped portion 31h directed rearward and composed of an upper step portion 31h1 and a lower step portion 31h2 is formed on the upper surface of the left and right side walls 31e5. As shown in FIG. 13(b), the rear side surface of the lower step portion 31h2 is not flush with the rear side surface of the central partition wall 31e2 of the first protrusion but is slightly shifted forward. Thereby, when the manual opening lever 36 is swung clockwise in FIG. 13(b) to manually open the second pressure relief valve 3, interference between the lower part of the front surface of the rear side wall of the cylindrical body 36a and the rear end of the lower step portion 31h2 is prevented. The upper end of the rear side surface of the central partition wall 31e2 is chamfered. A third protrusion 31i is formed on the upper surface of the casing in front of the upper end portion 33a of the valve shaft. The configuration of the second pressure relief valve 3 according to the fourth embodiment is the same as that of the second pressure relief valve 3 according to the first embodiment, except for the above and the fact that the upper surface of the side wall 31f2 of the second protrusion 31f does not have a middle section inclined downward.

[0019] When the second pressure relief valve 3 is closed, as shown in FIGS. 13(a) and 13(b), the front surface of the rear side wall of the cylindrical body 36a abuts against the rear surface of the central partition wall 31e2 of the first protrusion, preventing the manual opening lever 36 from moving forward, and the manual opening lever 36 is held at the first position with respect to the front. Also, the lower surface of the front side wall of the cylindrical body 36a abuts against the upper surface of a fourth protrusion 31j formed on the upper surface of the casing in front of the upper end portion 33a of the valve shaft, thereby preventing the manual opening lever 36 and thus the valve shaft 33 from moving in the closing direction. The left and right end portions of the pin 35 abut against the front ends of the long recess 36a3 and the long hole 36a4. When the internal pressure of the first circulation path 25 exceeds a predetermined value B due to some cause such as a malfunction of the heat source unit 1, the second pressure relief valve 3 opens as shown in FIG. 14. However, the amount of protrusion of the upper end portion 33a of the valve shaft outside the casing 31 when the internal pressure of the first circulation path 25 reaches the predetermined value B is less than the predetermined value. As can be seen from FIG. 14(b), the front surface of the rear side wall of the cylindrical body 36a disengages from the contact with the rear surface of the first protrusion central partition wall 31e2, but abuts against the rear side surface of the lower portion 31h2 of the upper step portion of the first protrusion side wall. The manual valve opening lever 36 has stopped in a slightly forwardly moved state, and the manual valve opening lever 36 is held substantially in the first position with respect to the forward direction. Therefore, when the internal pressure of the first circulation path 25 decreases, the rear side surface of the cylindrical body 36a receiving the biasing force of the spring 34 descends along the chamfered portion at the upper end of the rear side surface of the first protrusion central partition wall 31e2, and as a result, the manual valve opening lever 36 and the valve shaft 33 descend, and the second pressure relief valve 3 closes.

[0020] When the water-cooled medium heat exchanger 11 of the heat source unit 1 is damaged and the high-pressure refrigerant in the refrigerant circuit mixes into the circulating water in the first circulation path 25 and the internal pressure of the first circulation path 25 abnormally rises beyond the predetermined value B, the valve body 32 rises further from the valve opening position shown in FIG. 14(b), abuts against the annular step 31g formed inside the casing, and stops. As shown in FIG. 15(b), the second pressure relief valve 3 fully opens. In the process of the second pressure relief valve 3 fully opening, the amount of protrusion of the upper end portion 33a of the valve shaft outside the casing 31 becomes equal to or more than the predetermined value. In the fully open state of the second pressure relief valve 3 shown in FIG. 15(b), the contact between the front surface of the rear side wall of the cylindrical body 36a and the rear side surface of the lower portion 31h2 of the upper step portion of the first protrusion side wall is released. As a result, as shown in FIGS. 15(a) and (c), the manual valve opening lever 36 receiving the biasing force of the coil spring 37 moves forward, and the lower front surface of the rear side wall of the cylindrical body 36a abuts against the rear side surface of the upper step portion 31h1 of the first protrusion side wall and stops, and is held in the second position with respect to the forward direction. When the internal pressure of the first circulation path 25 decreases, the valve body 32 and thus the valve shaft 33 descend under the biasing force of the spring 34. However, as shown in FIG. 15(c), the lower surface of the rear side wall of the cylindrical body 36a abuts against the lower portion 31h2 of the upper step portion of the first protrusion side wall, and the lower surface of the front side wall of the cylindrical body 36a abuts against the upper surface of the third protrusion 31i, preventing the descent of the manual valve opening lever 36 and thus the valve shaft 33. As a result, the open state of the second pressure relief valve 3 is maintained. When releasing the maintenance of the valve opening state, the front end of the manual valve opening lever 36 may be biased rearward to return the manual valve opening lever 36 to the first position.

[0021] In the above first to fourth embodiments, the contact surface between the lower surface of the cylinder body 36a for maintaining the valve opening state and the upper surfaces of the protrusions 31e, 31f, and 31i of the casing may be an inclined surface that slopes upward from the second position toward the first position. By making the contact surface between the lower surface of the cylinder body 36a and the upper surface of the protrusion an inclined surface that slopes upward, that is, in the valve opening direction, from the second position toward the first position, the elastic force of the spring 34 that biases the valve body in the valve closing direction is utilized as the resistance to the movement of the manual valve opening lever 36 from the second position to the first position, and an unexpected return of the manual valve opening lever 36 from the second position to the first position can be prevented.

Industrial Applicability

[0022] The present invention is widely applicable to a pressure relief valve, particularly a pressure relief valve attached to a circulation path connecting a hot water storage unit and a heat source unit of a hot water storage type water heater including a hot water storage unit and a heat source unit, or a pressure relief valve attached to a circulation path connecting an indoor heat exchanger and a heat source unit of a heater including an indoor heat exchanger and a heat source unit having a heat pump.

Explanation of Reference Numerals

[0023] 1 Heat source unit 2 Hot water storage tank unit 27 First pressure relief valve 3 Second pressure relief valve 4 Heating unit 31 Casing 31e First protrusion 31f Second protrusion 31i Third protrusion 31j Fourth protrusion 32 Valve body 33 Valve shaft 33a Upper end portion of the valve shaft 35 Pin 36 Manual valve opening lever 36a Cylinder body 36b leaf spring 37 coil spring 38 leaf spring

Claims

1. A valve mechanism having a valve body, a valve seat, a valve shaft, and a spring for biasing the valve body in the valve closing direction; a casing for housing the valve mechanism; a manual valve opening lever swingably connected via a pin to one end of the valve shaft extending outside the casing; a first lever movement restricting mechanism that blocks the movement of the manual valve opening lever in a predetermined direction different from the valve opening / closing direction and holds the manual valve opening lever in a first position with respect to the predetermined direction when the amount of protrusion of the one end of the valve shaft outside the casing is less than a predetermined value, and allows the movement of the manual valve opening lever in the predetermined direction when the protrusion amount is greater than or equal to the predetermined value; an elastic body for biasing the manual valve opening lever in the predetermined direction; and a second lever movement restricting mechanism that engages with the manual valve opening lever moving in the predetermined direction and being in a second position with respect to the predetermined direction and blocks the movement of the valve shaft connected to the manual valve opening lever in the valve closing direction. A pressure relief valve characterized by comprising these components.

2. The first lever movement restricting mechanism includes a surface of the manual valve opening lever facing the predetermined direction and a protrusion standing up from the outer surface of the casing and capable of abutting against the surface of the manual valve opening lever facing the predetermined direction. The second lever movement restricting mechanism includes a surface of the manual valve opening lever facing the valve closing direction and a protrusion standing up from the outer surface of the casing and capable of abutting against the surface of the manual valve opening lever facing the valve closing direction. The pressure relief valve according to Claim 1, characterized by comprising these components.

3. The contact surface between the surface of the manual valve opening lever facing the valve closing direction at the second position with respect to the predetermined direction and the protrusion on the outer surface of the casing forms an inclined surface inclined in the valve opening direction from the second position to the first position. The pressure relief valve according to Claim 2, characterized by this configuration.

4. The pressure relief valve according to any one of Claims 1 to 3, characterized in that the valve body has a bellows.

5. A hot water storage type water supply machine, characterized by comprising a hot water storage unit having a hot water storage tank, a heat source unit having a heat pump, and the pressure relief valve according to any one of Claims 1 to 4 attached to a circulation path connecting the hot water storage unit and the heat source unit.

6. A heater, characterized by comprising a heating unit having an indoor heat exchanger, a heat source unit having a heat pump, and the pressure relief valve according to any one of Claims 1 to 4 attached to a circulation path connecting the heating unit and the heat source unit.

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