Pressure control system

Abstract

To provide a pressure control system for a heat treatment device allowing maintainability of a vacuum pump unit evacuating a carburization chamber to be improved in low running cost.SOLUTION: A pressure control system is provided with: a first passage 11 one end of which is connected to carburization chambers 2, 3 into which carburization gas is introduced in a state where steel members W are loaded; a first vacuum pump unit 12 to which the other end of the first passage 11 is connected to vacuum the carburization chambers 2, 3; a second passage 13 different from the first passage 11 one end of which is connected to the carburization chambers 2, 3; a second pump unit 14 to which the other end of the second passage 13 is connected; and a control device 21 vacuuming the carburization chambers 2, 3 using the first vacuum pump unit 12 for a first period set within a period before timing when the carburization gas is introduced into the carburization chambers 2, 3 and vacuuming the carburization chambers 2, 3 using the second vacuum pump 14 for a second period set within a period including the timing but not overlapped with the first period in the state where the steel members W are loaded in the carburization chamber 2, 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure control system provided in a heat treatment device for steel members. [Background technology]

[0002] One method involves using a heat treatment device to carburize steel members using a carburizing gas in a carburizing chamber, and then holding the steel members at a high temperature in a temperature-reducing and soaking chamber. For example, this is disclosed in Patent Document 1 below. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 7,267,793 Summary of the Invention [Problem to be solved by the invention]

[0004] When the carburizing gas is introduced into the carburizing chamber, the vacuum pump unit that performs the evacuation becomes contaminated with tar, soot, and other contaminants from the carburizing gas. For this reason, for example, Patent Document 1 discloses a method in which hydrogen is injected into the pressure vessel of the carburizing chamber to suppress the generation of soot.

[0005] However, although the method disclosed in the above Patent Document 1 improves maintainability, there is a problem in that the running costs are high because hydrogen gas must be used periodically.

[0006] In view of the above problems, an object of the present invention is to provide a pressure control system that improves the maintainability of a vacuum pump unit that evacuates a carburizing chamber in a heat treatment apparatus at low running costs. [Means for solving the problem]

[0007] In order to achieve the above object, a control device is provided which includes a first flow path having one end connected to a carburizing chamber into which carburizing gas is introduced with a steel member installed therein, a first vacuum pump unit to which the other end of the first flow path is connected and which reduces the pressure in the carburizing chamber, a second flow path which is different from the first flow path and has one end connected to the carburizing chamber, and a second vacuum pump unit to which the other end of the second flow path is connected, and which reduces the pressure in the carburizing chamber by the first vacuum pump unit during a first period which is set within a period before the timing at which the carburizing gas is introduced into the carburizing chamber with the steel member installed in the carburizing chamber, and which reduces the pressure in the carburizing chamber by the second vacuum pump unit during a second period which is set within a period which includes the timing and does not overlap with the first period.

[0008] Furthermore, the control device reduces the pressure in the carburizing chamber by the first vacuum pump unit during a third period that is set within a period after the second period ends and the steel member is extracted from the carburizing chamber.

[0009] In addition, there are multiple carburizing chambers, the one end side of the first flow path branches into a plurality of first flow path pieces connected to each of the carburizing chambers, the one end side of the second flow path branches into a plurality of second flow path pieces connected to each of the carburizing chambers, and the system further includes a first valve provided in each of the first flow path pieces and a second valve provided in each of the second flow path pieces.

[0010] In addition, the control device controls the opening and closing of each first valve so that the timings at which the first vacuum pump unit depressurizes each carburizing chamber do not overlap with each other, and controls the opening and closing of each second valve so that the timings at which the second vacuum pump unit depressurizes each carburizing chamber do not overlap with each other.

[0011] In addition, the control device controls the opening and closing of the first valve and the second valve so that a timing at which the second vacuum pump unit depressurizes one of the plurality of carburizing chambers in the second period overlaps a timing at which the first vacuum pump unit depressurizes another of the plurality of carburizing chambers in the first period, and a timing at which the second vacuum pump unit depressurizes the other carburizing chambers in the second period overlaps a timing at which the first vacuum pump unit depressurizes the one carburizing chamber in the first period.

[0012] The system further includes a temperature-reducing and -soaking chamber for heating and holding the steel member extracted from the carburizing chamber, a third flow path having one end connected to the temperature-reducing and -soaking chamber and the other end connected to the first flow path, a third valve provided in the third flow path, a fourth flow path different from the third flow path, having one end connected to the temperature-reducing and -soaking chamber and the other end connected to the second flow path, and a fourth valve provided in the fourth flow path.

[0013] In addition, the control device controls the opening and closing of the first valve, the second valve, the third valve, and the fourth valve so that the first vacuum pump unit reduces the pressure in the temperature-reducing and soaking chamber as well as in any one of the plurality of carburizing chambers. Effect of the Invention

[0014] According to the pressure control system of the present invention, it is possible to improve the maintainability of the vacuum pump unit that evacuates the carburizing chamber in the heat treatment apparatus with low running costs. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram illustrating a pressure control system according to an embodiment of the present invention. [Diagram 2] 2 is a block diagram illustrating a schematic functional configuration of a control device illustrated in FIG. 1. [Diagram 3] 2 is a timing chart showing an example of the operation of the pressure control system shown in FIG. 1 in a carburizing treatment. [Figure 4]4 is a timing chart showing an example of the timing at which the first vacuum pump unit and the second vacuum pump unit shown in FIG. 1 operate with respect to the first carburizing chamber, the second carburizing chamber, and the temperature-reducing / soaking chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same reference numerals are used to designate the same components in each drawing, and duplicated description will be omitted as appropriate.

[0017] === Implementation form === <Overall composition> FIG. 1 is a block diagram illustrating a pressure control system 1 according to an embodiment of the present invention (hereinafter referred to as “the present embodiment”), together with a first carburizing chamber 2, a second carburizing chamber 3, a temperature-reducing and soaking chamber 4, and a transfer chamber 5.

[0018] The first carburizing chamber 2 and the second carburizing chamber 3 shown in Fig. 1 are chambers into which carburizing gas is introduced with a steel member W placed therein. Specifically, these are chambers in which the steel member W is heated by a heater (not shown) provided inside and carburizing gas is introduced inside to perform a thermal carburizing treatment. The steel member W is heated in the first carburizing chamber 2 or the second carburizing chamber 3, for example, to about 930°C.

[0019] The temperature-reducing and soaking chamber 4 is a chamber in which the steel member W after the carburizing treatment is heated and held at, for example, about 850°C and subjected to a soaking treatment (temperature-reducing and soaking treatment). In FIG. 1, as an example, the temperature-reducing and soaking chamber 4 is shown provided between the first carburizing chamber 2 and the second carburizing chamber 3.

[0020] The transfer chamber 5 is provided extending in the direction in which the first carburizing chamber 2, the second carburizing chamber 3, and the temperature-reducing and soaking chamber 4 are arranged, and is adjacent to each of the first carburizing chamber 2, the second carburizing chamber 3, and the temperature-reducing and soaking chamber 4. Note that, a plurality of oil tanks (not shown) are provided on the opposite side of the transfer chamber 5. Note that, the oil tanks are chambers in which the steel material W after the temperature-reducing and soaking treatment is immersed in heat treatment oil and rapidly cooled to about 120°C to perform quenching treatment.

[0021] A transfer device (not shown) is provided inside the transfer chamber 5. This transfer device transfers the steel member W to each of the above-mentioned chambers (the first carburizing chamber 2, the second carburizing chamber 3, the temperature-reducing and soaking chamber 4, and each oil tank).

[0022] As shown in FIG. 1 , the pressure control system 1 according to this embodiment includes, as its main components, a first flow path 11, a first vacuum pump unit 12, a second flow path 13, a second vacuum pump unit 14, a first vacuum exhaust valve 15A (first valve), a second vacuum exhaust valve 15B (first valve), a fifth vacuum exhaust valve 15C (third valve), a third vacuum exhaust valve 16A (second valve), a fourth vacuum exhaust valve 16B (second valve), a sixth vacuum exhaust valve 16C (fourth valve), a first furnace pressure adjustment valve 17A (second valve), a second furnace pressure adjustment valve 17B (second valve), a third furnace pressure adjustment valve 17C (fourth valve), a third flow path 18, a fourth flow path 19, and a control device 21.

[0023] The first flow passage 11 is a flow passage having one end connected to the first carburizing chamber 2 and the second carburizing chamber 3. Specifically, one end side of the first flow passage 11 branches into a first flow passage piece 11A and a first flow passage piece 11B which are connected to the first carburizing chamber 2 and the second carburizing chamber 3, respectively.

[0024] The first vacuum pump unit 12 includes an oil rotary vacuum pump 12A and a vacuum exhaust main valve 12B connected thereto. Hereinafter, the on state of the first vacuum pump unit 12 refers to the oil rotary vacuum pump 12A being on and the vacuum exhaust main valve 12B being open. In addition, the off state of the first vacuum pump unit 12 refers to the oil rotary vacuum pump 12A being on and the vacuum exhaust main valve 12B being closed.

[0025] With the other end of the first flow path 11 connected (to the vacuum exhaust main valve 12B) and the steel member W placed in the first carburizing chamber 2, the first vacuum pump unit 12 reduces the pressure (evacuates) the first carburizing chamber 2 during a period T2 (a first period; described in detail later) which is set within a period before the timing when the carburizing gas is introduced into the first carburizing chamber 2. Furthermore, the first vacuum pump unit 12 also reduces the pressure in the first carburizing chamber 2 during a period T5 (a third period; described in detail later) which is set within a period after the steel member W is extracted from the first carburizing chamber 2.

[0026] Even when the steel member W is placed in the second carburizing chamber 3, the first vacuum pump unit 12 reduces the pressure in the second carburizing chamber 3 in the same manner as in the case of the first carburizing chamber 2 described above.

[0027] The second flow passage 13 is a flow passage different from the first flow passage 11, and one end of the second flow passage 13 is connected to the first carburizing chamber 2 and the second carburizing chamber 3. Specifically, one end of the second flow passage 13 branches into second flow passage pieces 13A and 13B which are connected to the first carburizing chamber 2 and the second carburizing chamber 3, respectively.

[0028] The second vacuum pump unit 14 includes an oil rotary vacuum pump 14A, a mechanical booster pump 14C connected thereto, and a vacuum exhaust main valve 14B connected thereto. Hereinafter, the second vacuum pump unit 14 is in an on state, which means that the oil rotary vacuum pump 14A and the mechanical booster pump 14C are in an on state, and the vacuum exhaust main valve 14B is in an open state. In addition, the second vacuum pump unit 14 is in an off state, which means that the oil rotary vacuum pump 14A and the mechanical booster pump 14C are in an on state, and the vacuum exhaust main valve 14B is in a closed state.

[0029] With the other end of the second flow path 13 connected (to the vacuum exhaust main valve 14B) and a steel member W placed in the first carburizing chamber 2, the second vacuum pump unit 14 reduces the pressure in the first carburizing chamber 2 during period T3 (second period, described in detail later) which includes the timing when the carburizing gas is introduced into the first carburizing chamber 2 and is set within a period not overlapping with period T2.

[0030] Even when the steel member W is placed in the second carburizing chamber 3, the second vacuum pump unit 14 reduces the pressure in the second carburizing chamber 3 in the same manner as in the first carburizing chamber 2 described above.

[0031] The first vacuum exhaust valve 15A (first valve) is an on-off valve (a valve that is either fully open or fully closed) provided in one of the first flow path pieces 11A, and the second vacuum exhaust valve 15B (first valve) is an on-off valve provided in the other of the first flow path pieces 11B.

[0032] With the first vacuum pump unit 12 in an ON state, the first vacuum exhaust valve 15A is opened to reduce the pressure (evacuate) in the first carburizing chamber 2. With the first vacuum pump unit 12 in an ON state, the second vacuum exhaust valve 15B is opened to reduce the pressure (evacuate) in the second carburizing chamber 3.

[0033] The third vacuum exhaust valve 16A (second valve) is an on-off valve provided in one of the second flow passage pieces 13A. The fourth vacuum exhaust valve 16B (second valve) is an on-off valve provided in the other of the second flow passage pieces 13B. The first furnace pressure regulating valve 17A (second valve) is an regulating valve provided on the first carburizing chamber 2 side of the third vacuum exhaust valve 16A in one of the second flow passage pieces 13A. The second furnace pressure regulating valve 17B (second valve) is an regulating valve provided on the first carburizing chamber 2 side of the fourth vacuum exhaust valve 16B in the other of the second flow passage pieces 13B.

[0034] With the second vacuum pump unit 14 in an ON state, the third vacuum exhaust valve 16A and the first furnace pressure regulating valve 17A are opened to reduce the pressure (evacuate) in the first carburizing chamber 2. In addition, the pressure in the first carburizing chamber 2 is adjusted by adjusting the valve opening of the first furnace pressure regulating valve 17A.

[0035] With the second vacuum pump unit 14 in an ON state, the fourth vacuum exhaust valve 16B and the second furnace pressure regulating valve 17B are opened to reduce the pressure (evacuate) in the second carburizing chamber 3. The pressure in the second carburizing chamber 3 is adjusted by adjusting the valve opening of the second furnace pressure regulating valve 17B.

[0036] The pump capacity is such that the first vacuum pump unit 12 is smaller than the second vacuum pump unit 14. When carburizing treatment is performed in the first carburizing chamber 2 or the second carburizing chamber 3, first, during period T2, the first vacuum pump unit 12 reduces the pressure inside the first carburizing chamber 2 or the second carburizing chamber 3 to about 0.1 to 1 kPa (from atmospheric pressure), and then, during period T3, the second vacuum pump unit 14 reduces the pressure inside the first carburizing chamber 2 or the second carburizing chamber 3 to about 0.01 kPa.

[0037] One end of the third flow path is connected to the temperature-reducing and soaking chamber 4, and the other end is connected to the first flow path 11. The fifth vacuum exhaust valve 15C (third valve) is an on-off valve provided in the third flow path .

[0038] When the first vacuum pump unit 12 is in an ON state, the fifth vacuum exhaust valve 15C is in an open state, whereby the temperature-reducing and soaking chamber 4 is depressurized (evacuated).

[0039] The fourth flow path 19 is a flow path different from the third flow path 18, and has one end connected to the temperature-reducing and soaking chamber 4 and the other end connected to the second flow path 13. The sixth vacuum exhaust valve 16C (fourth valve) is a valve provided in the fourth flow path 19. Furthermore, the third furnace pressure regulating valve 17C (fourth valve) is an regulating valve provided in the fourth flow path 19 on the side of the sixth vacuum exhaust valve 16C that is closer to the temperature-reducing and soaking chamber 4.

[0040] With the second vacuum pump unit 14 in an ON state, the sixth vacuum exhaust valve 16C and the third furnace pressure regulating valve 17C are opened to reduce the pressure (evacuate) in the temperature-reducing and soaking chamber 4. In addition, the pressure in the temperature-reducing and soaking chamber 4 is adjusted by adjusting the valve opening of the third furnace pressure regulating valve 17C.

[0041] In addition, valves 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B, and 17C are angle valves (valves whose inlet and outlet directions are perpendicular to each other), and the outlets on the side of the first vacuum pump unit 12 or the second vacuum pump unit 14 face vertically downward.

[0042] The third vacuum exhaust valve 16A, the fourth vacuum exhaust valve 16B, the first furnace pressure regulating valve 17A and the second furnace pressure regulating valve 17B are provided with traps 16AA, 16BA, 17AA and 17BA vertically below the outlets, respectively.

[0043] The traps 16AA, 16BA, 17AA, and 17BA are containers that collect dirt derived from the carburizing gas when the first vacuum pump unit 12 evacuates the first carburizing chamber 2 or the second carburizing chamber 3 while the carburizing gas is being introduced therein.

[0044] That is, the inner diameter of the flow passage expands suddenly at the outlet of the valves 16A, 16B, 17A, and 17B, so the carburizing gas turns into mist due to a condensation reaction caused by adiabatic expansion. The mist turns into droplets and falls into the traps 16AA, 16BA, 17AA, and 17BA located vertically below the valves 16A, 16B, 17A, and 17B.

[0045] In FIG. 1, a sixth vacuum exhaust valve 16C and a third furnace pressure regulating valve 17C provided in a fourth flow path 19 connected to the temperature-reducing / soaking chamber 4 are also provided with traps 16CA and 17CA, respectively.

[0046] The first pressure gauge 2A is a pressure gauge that measures the pressure in the first carburizing chamber 2. The second pressure gauge 3A is a pressure gauge that measures the pressure in the second carburizing chamber 3. The third pressure gauge 4A is a pressure gauge that measures the pressure in the temperature-reducing and soaking chamber 4.

[0047] The control device 21 includes a processor 21A and a memory 21B (main storage device) as main hardware components, and controls the vacuum pump units 12 and 14 and the valves 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B, and 17C.

[0048] <Functional configuration of the control device> FIG. 2 is a block diagram illustrating an example of a functional configuration of the control device 21 shown in FIG. 1 together with the pressure gauges 2A, 3A, and 4A and the valves 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B, and 17C.

[0049] As shown in FIG. 2, functionally, the control device 21 mainly includes an acquisition unit 22, a control unit 23, and a storage unit 24.

[0050] The acquisition unit 22 acquires the measurement results of the first pressure gauge 2A, the second pressure gauge 3A, and the third pressure gauge 4A. Further, the storage unit 24 stores the first predetermined pressure value P1, the second predetermined pressure value P2, and the like.

[0051] In a state where the steel member W is installed in the first carburizing chamber 2 or the second carburizing chamber 3, the control unit 23 reduces the pressure of the first carburizing chamber 2 or the second carburizing chamber 3 to the first predetermined pressure value P1 by the first vacuum pump unit 12 during the period T2.

[0052] Also, in a state where the steel member W is installed in the first carburizing chamber 2 or the second carburizing chamber 3, the control unit 23 reduces the pressure of the first carburizing chamber 2 or the second carburizing chamber 3 to the second predetermined pressure value P2 (P2 < P1) by the second vacuum pump unit 14 during the period T3.

[0053] Furthermore, the control unit 23 controls the opening and closing of each valve 16A, 16B, 17A, 17B so that the timing of the first vacuum pump unit 12 reducing the pressure of the first carburizing chamber 2 does not overlap with the timing of reducing the pressure of the second carburizing chamber 3.

[0054] Furthermore, the control unit 23 controls the opening and closing of each valve 16A, 16B, 17A, 17B so that the timing of the second vacuum pump unit 14 reducing the pressure of the first carburizing chamber 2 does not overlap with the timing of reducing the pressure of the second carburizing chamber 3.

[0055] Furthermore, the control unit 23 controls the opening and closing of the valves 15A, 15B, 16A, 16B, 17A, 17B so that the timing of the second vacuum pump unit 14 reducing the pressure of the first carburizing chamber 2 during the period T3 overlaps with the timing of the first vacuum pump unit 12 reducing the pressure of the second carburizing chamber 3 during the period T2.

[0056] Furthermore, the control unit 23 controls the opening and closing of the valves 15A, 15B, 16A, 16B, 17A, and 17B so that the timing when the second vacuum pump unit 14 depressurizes the second carburizing chamber 3 during period T3 and the timing when the first vacuum pump unit 12 depressurizes the first carburizing chamber 2 during period T2 overlap.

[0057] Furthermore, the control unit 23 controls the opening and closing of the valves 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B, and 17C so that the first vacuum pump unit 12 or the second vacuum pump unit 14 reduces the pressure in the temperature-reducing and soaking chamber 4 as well as the first carburizing chamber 2 or the second carburizing chamber 3.

[0058] <Motion Control> FIG. 3 is a timing chart showing an example of the operation of the pressure control system 1 shown in FIG.

[0059] The changes in temperature and pressure in the first carburizing chamber 2 (or the second carburizing chamber 3) and the operation of each component (each actuator) will be explained in chronological order (in the order of period T1 → period T2 → period T3 → period T4 → period T5) with reference to Fig. 3. Note that although the carburizing process in the first carburizing chamber 2 is explained below, the carburizing process in the second carburizing chamber 3 is similar.

[0060] [Period T1] When the carburizing treatment is performed in the first carburizing chamber 2, first, the door (not shown in FIG. 1) of the first carburizing chamber 2, which has been heated to a high temperature by a heater (not shown in FIG. 1) provided in the first carburizing chamber 2, is opened, and the steel member W is loaded and placed by the transfer device (not shown in FIG. 1) in the transfer chamber 5. After that, the door of the first carburizing chamber 2 is closed.

[0061] [Period T2 (first period)] By the operation control of the control device 21, the first vacuum pump unit 12 is turned on and the first vacuum exhaust valve 15A is opened. The second vacuum pump unit 14 is turned off, and the third vacuum exhaust valve 16A and the first furnace pressure regulating valve 17A are closed. As a result, the first vacuum pump unit 12 reduces the pressure in the first carburizing chamber 2 to a first predetermined pressure value P1 (approximately 1 kPa). Thereafter, under the control of the control device 21, the first vacuum pump unit 12 is turned off and the first vacuum exhaust valve 15A is closed. During the period T2, the heater is turned on and the room temperature in the first carburizing chamber 2 rises to about 930°C.

[0062] [Period T3 (second period)] By the operation control of the controller 21, the second vacuum pump unit 14 is turned on, and the third vacuum exhaust valve 16A and the first furnace pressure regulating valve 17A are opened. As a result, the second vacuum pump unit 14 reduces the pressure in the first carburizing chamber 2 to a second predetermined pressure value P2 (approximately 0.01 kPa). In this state, carburizing gas is introduced into the first carburizing chamber 2 . Thereafter, the second vacuum pump unit 14 is turned off, and the third vacuum exhaust valve 16A and the first furnace pressure regulating valve 17A are closed under the control of the control device 21. Also, the heater is turned off.

[0063] [Period T4] Nitrogen gas is introduced from a nitrogen gas tank (not shown) into the first carburizing chamber 2, thereby restoring pressure inside the first carburizing chamber 2. Thereafter, the door is opened, and the steel member W is extracted from the first carburizing chamber 2 by a transfer device.

[0064] [Period T5] By the operational control of the controller 21, the first vacuum pump unit 12 is turned on and the first vacuum exhaust valve 15A is opened. As a result, the first vacuum pump unit 12 reduces the pressure in the first carburizing chamber 2 to a first predetermined pressure value P1 (approximately 0.1 to 1 kPa). During the period T5, the heater is turned on and the room temperature in the first carburizing chamber 2 rises to about 850°C. The above is an example of the operation of the pressure control system 1 in the carburizing treatment of the steel member W.

[0065] FIG. 4 is a timing chart roughly showing an example of the timing when the first vacuum pump unit 12 and the second vacuum pump unit 14 shown in FIG. 1 are used for the first carburizing chamber 2, the second carburizing chamber 3, and the temperature-reducing / soaking chamber 4 (on / off switching is omitted).

[0066] In addition, (1) to (6) in FIG. 4 show the order in which multiple steel members W are processed, and the bar graphs of the first vacuum pump unit and the second vacuum pump unit indicate the period during which they are used, and the bar graphs of each carburizing chamber indicate the period during which each steel member is processed.

[0067] The first vacuum pump unit 12 is used to evacuate the first carburizing chamber 2, the second carburizing chamber 3, and the temperature-reducing and soaking chamber 4 as shown in Fig. 4 by controlling the opening and closing of each valve. Of these, the operation when used for the carburizing treatment in the first carburizing chamber 2 is as explained in Fig. 3, and the operation when used for the carburizing treatment in the second carburizing chamber 3 is similar.

[0068] 4, the first vacuum pump unit 12 is first used for carburizing the first steel member W ((1) in FIG. 4) in the first carburizing chamber 2 (first carburizing chamber-(1) in FIG. 4). During this period, the second vacuum exhaust valve 15B and the fifth vacuum exhaust valve 15C are closed, and the first vacuum exhaust valve 15A is open as in period T2 in FIG. 3.

[0069] The second vacuum pump unit 14 is first used for carburizing the first steel member W ((1) in FIG. 4) in the first carburizing chamber 2 (first carburizing chamber-(1) in FIG. 4). During this period, under the control of the control device 21, the fourth vacuum exhaust valve 16B, the second furnace pressure adjustment valve 17B, the sixth vacuum exhaust valve 16C and the third furnace pressure adjustment valve 17C are closed, and the third vacuum exhaust valve 16A and the first furnace pressure adjustment valve 17A are open as shown in period T3 in FIG.

[0070] Also, while the third vacuum exhaust valve 16A and the first furnace pressure regulating valve 17A are open and the second vacuum pump unit 14 is evacuating the first carburizing chamber 2, that is, during the period T3 in Fig. 3, the control device 21 closes the first vacuum exhaust valve 15A and opens the second vacuum exhaust valve 15B and the fifth vacuum exhaust valve 15C, and the first vacuum pump unit 12 evacuates the second carburizing chamber 3 and the temperature-reducing and soaking chamber 4. Of these, the evacuation of the second carburizing chamber 3 corresponds to the period T2 in Fig. 3.

[0071] Then, halfway through the carburizing treatment of the first steel member W in the first carburizing chamber 2, the carburizing treatment of the second steel member W ((2) in Figure 4) in the second carburizing chamber 3 begins (the carburizing treatment in the second carburizing chamber 3 is the same as in Figure 3).

[0072] When the carburizing treatment in the first carburizing chamber 2 is completed, the second vacuum pump unit 14 is used for the carburizing treatment of the second steel member W in the second carburizing chamber 3, which has already started (second carburizing chamber-(2) in FIG. 4). During this period, under the control of the control device 21, the third vacuum exhaust valve 16A, the first furnace pressure regulating valve 17A, the sixth vacuum exhaust valve 16C and the third furnace pressure regulating valve 17C are in a closed state, and the fourth vacuum exhaust valve 16B and the second furnace pressure regulating valve 17B are in an open state, similar to the third vacuum exhaust valve 16A and the first furnace pressure regulating valve 17A during period T3 in FIG. 3.

[0073] Thereafter, the first vacuum pump unit 12 and the second vacuum pump unit 14 perform operations related to the carburization treatment of a plurality of steel members W (six in FIG. 4) in a similar cycle.

[0074] <Action and effect> In the pressure control system 1 according to the present embodiment described above, the second vacuum pump unit 14 reduces the pressure in the first carburizing chamber 2 or the second carburizing chamber 3 during periods other than when the carburizing gas is being introduced. Therefore, the carburizing gas does not get mixed into the second vacuum pump unit 14. Therefore, the removal of dirt derived from the carburizing gas is only required in the first vacuum pump unit 12. Therefore, in this embodiment, the ease of maintenance is improved.

[0075] Furthermore, in the pressure control system 1 according to this embodiment, the first vacuum pump unit 12 reduces the pressure in the first carburizing chamber 2 or the second carburizing chamber 3 after the carburizing treatment is completed and the steel member W is extracted. This makes it possible to adjust the pressure in the first carburizing chamber 2 or the second carburizing chamber 3 after the carburizing treatment.

[0076] Furthermore, in the pressure control system 1 according to this embodiment, when the multiple carburizing chambers 2, 3 are used to process multiple steel members W in parallel, the reduction in pressure in each of the carburizing chambers 2, 3 by the first vacuum pump unit 12 and the second vacuum pump unit 14 can be controlled by the opening and closing of each of the valves 15A, 15B, 16A, 16B, 17A, 17B, respectively, thereby improving convenience.

[0077] Furthermore, in the pressure control system 1 according to this embodiment, the control device 21 controls the timing of the depressurization of the first carburizing chamber 2 by the first vacuum pump unit 12 to be different from the timing of the depressurization of the second carburizing chamber 3. Also, the timing of the depressurization of the first carburizing chamber 2 by the second vacuum pump unit 14 to be different from the timing of the depressurization of the second carburizing chamber 3 is different from the timing of the depressurization of the first carburizing chamber 2 by the second vacuum pump unit 14. This allows the carburizing treatments in the carburizing chambers 2, 3 to be carried out independently. This improves the quality of the steel member W.

[0078] Furthermore, in the pressure control system 1 according to this embodiment, the timing at which the first carburizing chamber 2 is depressurized by the second vacuum pump unit 14 overlaps with the timing at which the second carburizing chamber 3 is depressurized by the first vacuum pump unit 12. Conversely, the timing at which the first carburizing chamber 2 is depressurized by the first vacuum pump unit 12 overlaps with the timing at which the second carburizing chamber 3 is depressurized by the second vacuum pump unit 14. This improves production efficiency.

[0079] Furthermore, in the pressure control system 1 according to this embodiment, pressure control during heating and holding of the steel member W in the temperature-reducing and soaking chamber 4 can also be performed by the first vacuum pump unit 12 and the second vacuum pump unit 14. This improves convenience.

[0080] Moreover, in the pressure control system 1 according to this embodiment, the pressure reduction in the temperature-reducing and soaking chamber 4 is performed simultaneously with the pressure reduction in the first carburizing chamber 2 or the second carburizing chamber 3. This improves production efficiency.

[0081] === Variations === The present invention is not limited to the above-described embodiment. In other words, the above-described specific example may be modified by a person skilled in the art as appropriate, and the modifications may be included in the scope of the present invention as long as they include the features of the present invention. In addition, the elements of the above-described embodiment and the following modifications may be combined to the extent technically possible, and the combinations of these may be included in the scope of the present invention as long as they include the features of the present invention.

[0082] For example, in the above embodiment, there are two carburizing chambers, the first carburizing chamber 2 and the second carburizing chamber 3, but the number of carburizing chambers may be any number. However, having multiple carburizing chambers is preferable to having one, since it allows multiple steel members W to be carburized in parallel. Furthermore, the number of flow path pieces connected to each carburizing chamber at one end of the first flow path 11 and one end of the second flow path 13 will naturally correspond to the number of carburizing chambers (however, if there is only one carburizing chamber, there is no need for one end of the first flow path 11 and one end of the second flow path 13 to branch off, so no flow path pieces are formed). [Explanation of symbols]

[0083] 1: pressure control system, 2: first carburizing chamber, 3: second carburizing chamber, 4: temperature drop and soaking chamber, 5: transfer chamber, 11: first flow path, 11A, 11B: first flow path piece (first flow path), 12: first vacuum pump unit, 13: second flow path, 13A, 13B: second flow path piece (second flow path), 14: second vacuum pump unit, 15A: first vacuum exhaust valve (first valve), 15B: second vacuum exhaust valve (first valve), 15C: fifth vacuum exhaust valve (third valve), 16A: third vacuum exhaust valve (second valve), 16B: fourth vacuum exhaust valve (second valve), 16C: sixth vacuum exhaust valve (fourth valve), 17A: first furnace pressure adjustment valve (second valve), 17B: second furnace pressure adjustment valve (second valve), 17C: second furnace pressure adjustment valve (fourth valve), 18: third flow path, 19: fourth flow path, 21: control device

Claims

1. a first flow passage having one end connected to a carburizing chamber into which a carburizing gas is introduced with the steel member placed therein; a first vacuum pump unit connected to the other end of the first flow path and configured to reduce the pressure in the carburizing chamber; a second flow passage different from the first flow passage, the second flow passage having one end connected to the carburizing chamber; a second vacuum pump unit connected to the other end of the second flow path; a control device which, with the steel member placed in the carburizing chamber, reduces the pressure in the carburizing chamber by the first vacuum pump unit during a first period which is set within a period prior to the timing at which the carburizing gas is introduced into the carburizing chamber, and which reduces the pressure in the carburizing chamber by the second vacuum pump unit during a second period which is set within a period which includes the timing and does not overlap with the first period; A pressure control system comprising:

2. 2. The pressure control system according to claim 1, wherein the control device reduces the pressure in the carburizing chamber by the first vacuum pump unit during a third period that is set within a period after the second period ends and the steel member is extracted from the carburizing chamber.

3. The carburizing chamber is a plurality of chambers; the one end side of the first flow passage is branched into a plurality of first flow passage pieces each connected to one of the carburizing chambers, the one end side of the second flow passage is branched into a plurality of second flow passage pieces each connected to one of the carburizing chambers, A first valve provided in each of the first flow passage pieces; A second valve provided in each of the second flow passage pieces; 3. The pressure control system according to claim 1, further comprising:

4. 4. The pressure control system according to claim 3, wherein the control device controls the opening and closing of each of the first valves so that timings at which the first vacuum pump unit depressurizes each of the carburizing chambers do not overlap with each other, and controls the opening and closing of each of the second valves so that timings at which the second vacuum pump unit depressurizes each of the carburizing chambers do not overlap with each other.

5. 5. The pressure control system according to claim 4, wherein the control device controls the opening and closing of the first valve and the second valve so that a timing at which the second vacuum pump unit depressurizes one of the plurality of carburizing chambers in the second period overlaps a timing at which the first vacuum pump unit depressurizes another of the plurality of carburizing chambers in the first period, and a timing at which the second vacuum pump unit depressurizes the other carburizing chambers in the second period overlaps a timing at which the first vacuum pump unit depressurizes the one carburizing chamber in the first period.

6. a temperature-reducing and soaking chamber in which the steel member removed from the carburizing chamber is heated and held; a third flow path, one end of which is connected to the temperature-reducing and soaking chamber and the other end of which is connected to the first flow path; A third valve provided in the third flow path; a fourth flow path which is different from the third flow path and has one end connected to the temperature-reducing and soaking chamber and the other end connected to the second flow path; a fourth valve provided in the fourth flow path; The pressure control system of claim 3 further comprising:

7. 7. The pressure control system according to claim 6, wherein the control device controls opening and closing of the first valve, the second valve, the third valve, and the fourth valve so that the first vacuum pump unit reduces the pressure in the temperature-reducing and soaking chamber as well as in any one of the plurality of carburizing chambers.

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