Exhaust structure of vacuum heat treatment device

Abstract

To provide an exhaust structure of a vacuum heat treatment device which can inhibit a valve body of a pressure regulation valve from adhering to a valve seat due to liquefaction of a gas.SOLUTION: A pressure regulation valve 22 forming a part of an exhaust structure 14 includes: a valve seat 50 provided with a circulation hole 54 which allows a primary chamber R1 and a secondary chamber R1 of a body 40 to communicate with each other in a vertical direction and having a seating surface 52 extending in a direction substantially orthogonal to the vertical direction; a valve body 60 which is provided within the primary chamber R1 and separates from or is seated on the seating surface 52 through vertical movement to open or close the circulation hole 54; and a contraction part 80 which extends downward or obliquely downward and is formed within the secondary chamber R2 so as to narrow a cross sectional area of a gas passage.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an exhaust structure of a vacuum heat treatment apparatus that sucks and exhausts gas in a heat treatment chamber.

Background Art

[0002] Conventionally, a vacuum heat treatment apparatus that heat-treats the surface of an object to be treated under reduced pressure has been known. Prior to this heat treatment, "vacuum exhaust" is performed to reduce the pressure in the heat treatment chamber by sucking the gas in the heat treatment chamber with a vacuum pump.

[0003] Patent Document 1 discloses an exhaust device that provides a pressure regulating valve at the atmospheric opening side end of an exhaust pipe and maintains the pressure in the exhaust pipe on the downstream side of the vacuum pump higher than atmospheric pressure. In this exhaust device, a trap for collecting evaporation oil is provided in the exhaust pipe.

[0004] Patent Document 2 discloses a vacuum exhaust device in which the lower side of a vacuum carburizing furnace is connected to a vacuum pump via a vertical pipe section, a gas cooler, a horizontal pipe section, and a control valve. In this vacuum exhaust device, a dust or tar collection container is detachably provided at the lower part of the vertical pipe section.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] FIG. 4 is a diagram schematically showing the structure of the pressure regulating valve 1 in the conventional example. A gas flow hole 3 is provided in the internal space of the body 2 of the pressure regulating valve 1. The valve body 4 is provided above the flow hole 3 and is configured to open and close the flow hole 3 by moving in the vertical direction. In the structural example of FIG. 4, the gas flows from the primary chamber above the valve seat 5, through the flow hole 3, to the secondary chamber below the valve seat 5.

[0007] By the way, according to the structure shown in FIG. 4, when the valve body 4 is in the open state, the cross-sectional area of the flow path formed by being surrounded by the lower surface of the valve body 4 and the seating surface 6 of the valve seat 5 is narrow, and the cross-sectional area of the flow path suddenly expands at the position where the flow hole 3 is reached. Then, due to the aggregation reaction caused by adiabatic expansion, the gas becomes misty, and the sticky substance M is likely to be generated. For example, when the sticky substance M adheres to the inner wall 7 of the body 2, this sticky substance M falls along the inner wall 7. However, when the sticky substance M adheres to the seating surface 6 of the valve seat 5, this sticky substance M stays on the seating surface 6 without moving. As a result, there is a problem that the valve body 4 is fixed to the valve seat 5 due to the presence of the sticky substance M, and the pressure regulating valve 1 fails to function.

[0008] The present invention has been made in view of such problems, and an object thereof is to provide an exhaust structure of a vacuum heat treatment apparatus capable of suppressing the fixing of a valve body to a valve seat due to liquefaction of a gas with respect to a pressure regulating valve.

Means for Solving the Problems

[0009] The exhaust structure of the vacuum heat treatment apparatus in the present invention includes a vacuum pump that sucks and exhausts the gas in the heat treatment chamber, and a pressure regulating valve provided in an exhaust pipe connecting the heat treatment chamber and the vacuum pump for adjusting the pressure in the heat treatment chamber. The pressure regulating valve includes a body in which a primary chamber is provided on the upper side in the vertical direction in the internal space, and a secondary chamber is provided on the lower side in the vertical direction in the internal space than the primary chamber; a valve seat provided with a flow hole for communicating the primary chamber and the secondary chamber in the vertical direction and having a seating surface extending in a direction substantially orthogonal to the vertical direction; a valve body provided in the primary chamber and opening and closing the flow hole by moving away from or seating on the seating surface through the vertical movement; and a throttle portion formed in the secondary chamber and extending downward or obliquely downward so that the cross-sectional area of the gas flow path becomes narrower.

[0010] Further, the valve body includes a main body portion having a flat surface facing the flow hole, and a protruding portion protruding downward from the flat surface, and the throttle portion is surrounded by the inner wall of the secondary chamber and the protruding portion.

[0011] Further, the pressure regulating valve further includes a guide member provided in the secondary chamber for separating the adhesive substance generated by the liquefaction of the gas from the throttle portion and guiding it downward.

[0012] Further, the guide member has a hollow truncated cone shape and has a tapered curved surface whose distance from the central axis becomes shorter as it goes from the upper side to the lower side.

Advantages of the Invention

[0013] According to the present invention, with respect to the pressure regulating valve, it is possible to suppress the valve body from sticking to the valve seat due to the liquefaction of the gas.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. For ease of understanding of the description, the same components in each drawing are given the same reference numerals as much as possible, and duplicate descriptions are omitted.

[0016] [Configuration of Exhaust Structure 14] FIG. 1 is a diagram showing the overall configuration of a heat treatment system 10 incorporating an exhaust structure 14 of a vacuum heat treatment apparatus 12 in an embodiment of the present invention. The heat treatment system 10 performs heat treatment on the surface of a workpiece (not shown). The workpiece is, for example, a work made of steel material. Specifically, the heat treatment system 10 includes a vacuum heat treatment apparatus 12 and an exhaust structure 14.

[0017] The vacuum heat treatment apparatus 12 is an apparatus for heat-treating the surface of a workpiece under reduced pressure, for example, a vacuum carburizing apparatus. In the case of an in-line system, the vacuum heat treatment apparatus 12 includes a heat treatment chamber 16, a cooling and soaking chamber 17, and a transfer mechanism 18.

[0018] The heat treatment chamber 16 is provided for performing heat treatment (for example, vacuum carburizing treatment) on the workpiece. The cooling and soaking chamber 17 is provided for performing a process of heating and holding the heat-treated workpiece for soaking (that is, cooling and soaking heat treatment). The transfer mechanism 18 is configured to be able to transfer the workpiece to each chamber (for example, the heat treatment chamber 16 and the cooling and soaking chamber 17) of the vacuum heat treatment apparatus 12.

[0019] The exhaust structure 14 is connected to the vacuum heat treatment apparatus 12 and is provided for exhausting the gas in the heat treatment chamber 16. Specifically, this exhaust structure 14 includes a first exhaust system 20 and a second exhaust system 30. The first exhaust system 20 is configured to exhaust a gas (e.g., a hydrocarbon-based gas) to which dirt easily adheres. The second exhaust system 30 is configured to exhaust a gas (e.g., nitrogen gas or air) to which dirt hardly adheres.

[0020] The first exhaust system 20 is configured to include, in order from the upstream side to the downstream side of the gas, a pressure regulating valve 22, a vacuum exhaust valve 23, a vacuum pump 24, and traps 26 and 27. The second exhaust system 30 is configured to include, in order from the upstream side to the downstream side of the gas, a vacuum exhaust valve 32 and a vacuum pump 34.

[0021] The pressure regulating valve 22 is an on-off valve for regulating the pressure in the heat treatment chamber 16. The vacuum exhaust valves 23 and 32 are on-off valves for opening or blocking the flow path from the heat treatment chamber 16 to the vacuum pumps 24 and 34. The vacuum pumps 24 and 34 are devices for sucking and exhausting the gas in the heat treatment chamber 16. Examples of the types of the vacuum pumps 24 and 34 include a mechanical booster pump, an oil rotary vacuum pump, or a screw type dry vacuum pump.

[0022] The traps 26 and 27 are containers for collecting sticky substances (e.g., tar) derived from the gas. In the example of FIG. 1, the trap 26 is installed immediately below the pressure regulating valve 22, and the trap 27 is installed immediately below the vacuum exhaust valve 23.

[0023] FIG. 2 is a cross-sectional view showing an example of the structure of the pressure regulating valve 22 in FIG. 1. The "vertical direction" shown in FIG. 2 is equal to the vertical direction, which is the direction of the action of gravity, or is equal within an allowable range (e.g., within ±10°). Also, the "horizontal direction" is a direction substantially orthogonal to the vertical direction. This vertical direction and horizontal direction are similarly defined in FIG. 3 described later.

[0024] The pressure regulating valve 22 is mainly composed of a metal material. The pressure regulating valve 22 is substantially cylindrical and has a body 40 extending in the vertical direction. An upper primary chamber R1 is provided above the internal space of the body 40, and a secondary chamber R2 is provided below the primary chamber R1 in the vertical direction.

[0025] The body 40 has, in order from the upper side to the lower side, a large-diameter portion 42 with a relatively large cross-sectional diameter and a small-diameter portion 44 with a relatively small cross-sectional diameter. An inlet 46, which is a port for introducing gas from the exhaust pipe P1 into the primary chamber R1, is provided in the large-diameter portion 42. An outlet 48, which is a port for discharging the gas in the secondary chamber R2 to the exhaust pipe P2, is provided in the small-diameter portion 44. The inlet 46 is arranged at a position higher than the outlet 48.

[0026] The stepped portion between the large-diameter portion 42 and the small-diameter portion 44 constitutes a valve seat 50 on which a valve body 60 described later seats. The valve seat 50 has a seating surface 52 extending in the horizontal direction. A circular cross-sectional flow hole 54 for communicating the primary chamber R1 and the secondary chamber R2 is provided at approximately the center of the seating surface 52.

[0027] In the primary chamber R1 of the body 40, a valve body 60, a stem 62, a spring seat 64a, an adjusting spring 66, a spring seat 64b, and a handle portion 68 are accommodated in order from the lower side to the upper side.

[0028] The valve body 60 is connected to the lower end of the stem 62, and the spring seat 64a is connected to the upper end of the stem 62. The spring seat 64a is fixed to the lower end of the adjusting spring 66, and the spring seat 64b is fixed to the upper end of the adjusting spring 66. The handle portion 68 can move forward and backward in the vertical direction integrally with the spring seat 64b by rotating clockwise or counterclockwise. The spring seat 64a is supported by a diaphragm 70 that is displaced according to the action of pressure. The diaphragm 70 is fixed to the body 40 at a position above the inlet 46.

[0029] The valve body 60 opens and closes the flow hole 54 by moving up and down to separate from or seat on the seating surface 52. In the example of Fig. 2, since the valve body 60 is seated on the seating surface 52, the pressure regulating valve 22 is in the "closed" state. Specifically, the valve body 60 includes a main body portion 72, a seal ring 74, and a protrusion 76.

[0030] The main body portion 72 has a substantially disc shape and has a flat surface facing the flow hole 54. The main body portion 72 is provided so as to include the range of the flow hole 54 when viewed from above.

[0031] The seal ring 74 is made of an elastic member including rubber, synthetic rubber, or resin, and is fixed to the lower surface along the outer periphery of the main body portion 72. In the seated state of the valve body 60, the seal ring 74 and the valve seat 50 are in close contact with each other on the seating surface 52.

[0032] The protrusion 76 is provided so as to protrude downward from the flat surface of the main body portion 72. A throttle portion 80 is formed in the secondary chamber R2 by being surrounded by the inner wall 78 of the body 40 and the protrusion 76. The annular throttle portion 80 extends downward and is provided so that the cross-sectional area of the gas flow path becomes narrower.

[0033] A guide member 82 for guiding the adhesive substance M derived from the hydrocarbon-based gas downward is fixed at a position below the flow hole 54 in the secondary chamber R2. The guide member 82 has a hollow truncated cone shape and has a tapered curved surface whose distance from the central axis decreases from the upper side to the lower side. A trap 26 (see Fig. 1) for collecting the adhesive substance M is disposed below the secondary chamber R2.

[0034] [Operation of the Exhaust Structure 14] The exhaust structure 14 in this embodiment is configured as described above. Subsequently, the operation of this exhaust structure 14 (particularly, the pressure regulating valve 22) will be described with reference to Figs. 1 to 3.

[0035] As shown in Fig. 1, assume a case where a hydrocarbon gas in the heat treatment chamber 16 of the vacuum heat treatment apparatus 12 is evacuated. In the initial state, the vacuum pumps 24 and 34 are stopped, and all of the pressure regulating valves 22, the vacuum exhaust valves 23 and 32 are in the "closed" state. When evacuating with the first exhaust system 20, the operation of the vacuum pump 24 is started, and when both the pressure regulating valve 22 and the vacuum exhaust valve 23 are in the "open" state, the hydrocarbon gas is sucked and exhausted.

[0036] As shown in Fig. 2, the hydrocarbon gas is introduced into the primary chamber R1 of the body 40 through the exhaust pipe P1 and the inlet 46. By introducing the hydrocarbon gas, pressure acts on the diaphragm 70, causing the diaphragm 70 to generate an elastic force. When the elastic force of the diaphragm 70 exceeds the elastic force of the adjusting spring 66, the valve body 60 moves upward integrally with the spring seat 64a and the stem 62. As a result, the pressure regulating valve 22 shifts from the "closed" state to the "open" state.

[0037] Fig. 3 is a diagram schematically showing the effect of the pressure regulating valve 22 in Fig. 2. More specifically, Fig. 3 corresponds to a partially enlarged view showing the peripheral portions of the valve seat 50 and the valve body 60 when the valve body 60 is in the fully open state. The solid arrows indicate the flow of the hydrocarbon gas. Let the cross-sectional area of the flow path 84 between the seal ring 74 and the valve seat 50 be S1, and the cross-sectional area of the throttle portion 80 be S2. For example, the magnitude relationship of 0.25·S1 ≤ S2 ≤ S1 is satisfied.

[0038] The cross-sectional areas of the flow path 84 and the throttle portion 80 are narrow, and the cross-sectional area of the flow path rapidly expands at the outlet position of the throttle portion 80. That is, while inducing the aggregation reaction of the hydrocarbon gas at the peripheral position of the throttle portion 80 downstream of the position of the flow path 84, the aggregation reaction of the hydrocarbon gas at the position of the flow path 84 is suppressed. Also, when the adhesive substance M adheres to the inner wall 78 of the body 40, this adhesive substance M falls along the inner wall 78 and the guide member 82 and is then collected by the trap 26 directly below the guide member 82.

[0039] [Function and Effect] As described above, in the exhaust structure 14 of the vacuum heat treatment apparatus 12 in this embodiment, since the throttle portion 80 extends downward or obliquely downward and is formed such that the cross-sectional area of the gas flow path becomes narrower, an aggregation reaction of the gas is induced at a peripheral position of the throttle portion 80, while an aggregation reaction on the seating surface 52, that is, generation of the adhesive substance M can be suppressed. Thereby, with respect to the pressure regulating valve 22 including the valve seat 50 having the horizontally extending seating surface 52 and the valve body 60 that opens and closes the flow hole 54 of the valve seat 50 by moving in the vertical direction, fixation of the valve body 60 to the valve seat 50 due to liquefaction of the gas is suppressed.

[0040] Further, when the valve body 60 includes the main body portion 72 having a flat surface facing the flow hole 54 and the protruding portion 76 protruding downward from the flat surface, the throttle portion 80 may be configured to be surrounded by the inner wall of the secondary chamber R2 and the protruding portion 76. Thereby, the throttle portion 80 can be formed while having a relatively simple device configuration.

[0041] Further, the pressure regulating valve 22 may be provided in the secondary chamber R2 and may further include a guide member 82 that separates the adhesive substance M generated by liquefaction of the gas from the throttle portion 80 and guides it downward. Thereby, adhesion of the adhesive substance M to the throttle portion 80 is suppressed.

[0042] Further, the guide member 82 may have a hollow truncated cone shape and have a tapered curved surface whose distance from the central axis becomes shorter as it goes from the upper side to the lower side. Thereby, the falling position of the adhesive substance M can be concentrated around the central axis. In particular, by disposing the trap 26 immediately below the guide member 82, the adhesive substance M can be efficiently collected.

[0043] [Modification Example] As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings. Needless to say, the present invention is not limited to the above-described examples. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention.

Description of Symbols

[0044] 10… Heat treatment system, 12… Vacuum heat treatment apparatus, 16… Heat treatment chamber, 22… Pressure regulating valve, 24… Vacuum pump, 40… Body, 50… Valve seat, 52… Seating surface, 54… Flow hole, 60… Valve body, 70… Main body portion, 72… Seal ring, 76… Protrusion, 80… Throttle portion, 82… Guide member, M… Adhesive substance, R1… Primary chamber, R2… Secondary chamber

Claims

1. A vacuum pump that sucks and exhausts the gas in the heat treatment chamber, A pressure regulating valve provided in an exhaust pipe connecting the heat treatment chamber and the vacuum pump and for regulating the pressure in the heat treatment chamber, Comprising, The pressure regulating valve, A body in which a primary chamber is provided on the upper side in the vertical direction in the internal space, and a secondary chamber is provided on the lower side in the vertical direction than the primary chamber in the internal space, A valve seat provided with a flow hole for communicating the primary chamber and the secondary chamber in the vertical direction and having a seating surface extending in a direction substantially orthogonal to the vertical direction, A valve body provided in the primary chamber and opening and closing the flow hole by separating from or seating on the seating surface through the vertical movement, A throttle portion formed in the secondary chamber and extending downward or obliquely downward so that the cross-sectional area of the gas flow path becomes narrower, An exhaust structure of a vacuum heat treatment apparatus, characterized by comprising.

2. The valve body is configured to include a main body portion having a flat surface facing the flow hole and a protruding portion protruding downward from the flat surface, The throttle portion is surrounded by an inner wall of the secondary chamber and the protruding portion. The exhaust structure of the vacuum heat treatment apparatus according to claim 1.

3. The pressure regulating valve further includes a guide member provided in the secondary chamber for separating the adhesive substance generated by the liquefaction of the gas from the throttle portion and guiding it downward. The exhaust structure of the vacuum heat treatment apparatus according to claim 2.

4. The guide member has a hollow truncated cone shape and has a tapered curved surface in which the distance from the central axis becomes shorter from the upper side to the lower side. The exhaust structure of the vacuum heat treatment apparatus according to claim 3.

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