Gas Supply System

Abstract

A gas supply system is provided that can reduce mass production costs by increasing the total flow rate and reducing the consumption of oxygen gas by mixing air into oxygen gas and supplying it. [Solution] The gas supply system includes a furnace body having a heat treatment space therein for heat-treating the workpiece, a first MFC for controlling the flow rate of oxygen gas supplied into the heat treatment space, a second MFC for controlling the flow rate of air supplied into the heat treatment space, an oxygen concentration meter for detecting the oxygen concentration in the heat treatment space, an exhaust duct provided on the top of the furnace body for connecting the heat treatment space to the outside of the furnace body and configured to be able to discharge exhaust gas generated in the heat treatment space to the outside, a receiving unit for receiving inputs of the total flow rate of the oxygen gas flow rate and the air flow rate and the target oxygen concentration in the heat treatment space, and a control device for controlling the first MFC and the second MFC based on the total flow rate and target oxygen concentration received via the receiving unit and the detection value of the oxygen concentration meter.

Description

[Technical Field]

[0001] The present disclosure relates to a gas supply system for a heat treatment furnace. [Background technology]

[0002] Conventionally, in a firing process for manufacturing positive electrode materials for lithium ion batteries or ceramic honeycomb formed bodies, the oxygen concentration in the space inside a heat treatment furnace is increased to promote oxidation reactions (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-83400 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional configurations, high-purity oxygen gas is used to oxidize materials such as cathode materials for lithium-ion batteries or honeycomb ceramic bodies when they are fired. The flow rate of oxygen gas is then increased to expel carbon dioxide gas and other gases generated by the oxidation of the cathode materials from the exhaust duct. This results in an increased consumption of oxygen gas.

[0005] One aspect of the present disclosure aims to provide a gas supply system that can increase the total flow rate and reduce the consumption of oxygen gas by mixing air with oxygen gas and supplying it, thereby reducing mass production costs. [Means for solving the problem]

[0006] In order to solve the above problems, a gas supply system according to one embodiment of the present disclosure includes a furnace body having a heat treatment space therein for heat-treating a workpiece, a first mass flow controller for controlling the flow rate of oxygen gas supplied into the heat treatment space, a second mass flow controller for controlling the flow rate of air supplied into the heat treatment space, an oxygen concentration meter for detecting the oxygen concentration in the heat treatment space, an exhaust duct provided at an upper part of the furnace body for connecting the heat treatment space to the outside of the furnace body and configured to discharge exhaust gas generated in the heat treatment space to the outside, a receiving unit for receiving inputs of the total flow rate of the oxygen gas and the flow rate of the air and a target oxygen concentration for promoting oxidation of the workpiece in the heat treatment space, and a control device for controlling the first mass flow controller and the second mass flow controller based on the total flow rate and the target oxygen concentration received via the receiving unit and the detection value of the oxygen concentration meter. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, by mixing oxygen gas with air and supplying the mixture, the total flow rate can be increased, the amount of oxygen gas consumed can be reduced, and mass production costs can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a gas supply system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing an example of an electrical configuration of a control device. [Figure 3] 10 is a flowchart illustrating an example of an oxygen gas supply process executed by a control unit. [Figure 4] 10 is a flowchart illustrating an example of an oxygen gas supply process executed by a control unit. [Figure 5] 5 is a flowchart illustrating an example of a sub-process of the gas amount adjustment process of FIG. 4. [Figure 6] 10 is a flowchart illustrating an example of an oxygen gas supply process executed by a control unit. [Figure 7]FIG. 4 is a diagram showing an example of a gas flow rate table stored in a storage unit. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Outline of gas supply system] An embodiment of the present disclosure will be described in detail below with reference to Figures 1 to 5. In Figure 1, arrows indicate the top, bottom, front, and rear directions of the furnace body 10. In the following description, directions will be described based on these directions.

[0010] First, the schematic configuration of a gas supply system 1 according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing an example of the schematic configuration of the gas supply system 1 according to this embodiment. FIG. 2 is a block diagram showing an example of the electrical configuration of a control device 40. A furnace body 10, which is a heat treatment furnace constituting the gas supply system 1, is a furnace that sinters an object to be treated 5 housed in a sagger 3 or the like, such as a cathode material and an anode material for a lithium-ion battery, a ceramic product, or the like. The cathode material for a lithium-ion battery contains, for example, at least one of nickel, cobalt, manganese, and iron.

[0011] [Furnace body 10] 1, the gas supply system 1 includes a furnace body 10, which is a heat treatment furnace, a door 20 that closes an opening 10A of the furnace body 10, a gas supply unit 30 that supplies oxygen gas and air into a heat treatment space 10B within the furnace body 10, a control device 40, a display 51, and an operation unit 52. The furnace body 10 is configured so that an operator can open and close the door 20 while standing to load and unload a workpiece 5 into the furnace body 10. The furnace body 10 is roughly rectangular and open at the front, and is made of a metal plate (such as a stainless steel plate) of a predetermined thickness. The inner bottom, ceiling, and inner wall surfaces of the left, right, and rear side walls are covered with a heat insulating material 11.

[0012] The heat insulating material 11 is formed, for example, by stacking ceramic fiber boards formed into a predetermined shape. The ceramic fiber boards are formed into a plate shape by adding inorganic filler and inorganic / organic binder to so-called bulk fiber. The thickness and number of ceramic fiber boards are appropriately set depending on the heating temperature of the workpiece 5.

[0013] Within the furnace body 10, a table 12 on which the workpiece 5 contained in a sagger 3 or the like is placed is suspended between the left and right side walls. The table 12 is composed of multiple rollers arranged in the front-to-rear direction, allowing the workpiece 5 contained in the sagger 3 or the like to be easily moved in the front-to-rear direction. Additionally, multiple heaters 13 arranged in the front-to-rear direction are suspended above and below the table 12 between the left and right side walls. The heaters 13 are composed of ceramic heaters such as cylindrical SiC heaters, and the number of heaters 13 arranged in the front-to-rear direction is appropriately determined depending on the heating temperature of the workpiece 5. The heat treatment space 10B is heated by the heaters 13 to, for example, 600°C to 1100°C.

[0014] [Exhaust duct 15, oxygen concentration meter 16, thermocouple 17] Furnace body 10 also includes exhaust duct 15 protruding vertically upward from the top of furnace body 10, an oxygen concentration meter 16, and a thermocouple 17. Exhaust duct 15 connects heat treatment space 10B within furnace body 10 to the outside of furnace body 10, and is configured to be able to discharge exhaust gases such as carbon dioxide generated within heat treatment space 10B to the outside.

[0015] The oxygen concentration meter 16 is inserted into the furnace body 10 from the top thereof, detects the oxygen concentration in the heat treatment space 10B, and outputs a detection signal to the control device 40. As shown in Fig. 2, the oxygen concentration meter 16 is electrically connected to the control device 40. As shown in Fig. 1, the oxygen concentration meter 16 is attached to the center of the furnace body 10 in the front-to-rear direction.

[0016] Furthermore, the detection unit 16A (lower end in FIG. 1) of the oxygen concentration meter 16 is disposed in a position that does not interfere with the placement and removal of the sagger 3 containing the workpiece 5 onto the receiving stand 12. For example, the detection unit 16A of the oxygen concentration meter 16 is disposed in approximately the center of the furnace body 10 in the front-rear and left-right directions, approximately 30 mm to 50 mm above the sagger 3 containing the workpiece 5 placed on the receiving stand 12 (above the workpiece 5). This enables the oxygen concentration meter 16 to detect the oxygen concentration around the workpiece 5 and output a detection signal to the control device 40.

[0017] The thermocouple 17 is inserted into the furnace body 10 from the rear thereof, detects the temperature in the heat treatment space 10B, and outputs a detection signal to the control device 40. The thermocouple 17 is electrically connected to the control device 40. The thermocouple 17 is attached to the rear wall of the furnace body 10 at approximately the center in the vertical and horizontal directions. The detection part 17A (front end in FIG. 1 ) of the thermocouple 17 is positioned so as not to interfere with the placement and removal of the sagger 3 containing the workpiece 5 on the pedestal 12. For example, the detection part 17A of the thermocouple 17 is positioned approximately 30 mm to 50 mm behind the sagger 3 containing the workpiece 5 placed on the pedestal 12. This allows the thermocouple 17 to detect the temperature around the workpiece 5 and output a detection signal to the control device 40.

[0018] [Door 20] The door 20 has a rectangular shape when viewed from the front and closes the opening 10A of the furnace body 10. It has a door frame 21 made of a metal plate (such as a stainless steel plate) of a predetermined thickness. The door frame 21 covers almost the entire front side of the furnace body 10. The right edge of the door 20 is rotatably attached to the front edge of the right side of the furnace body 10 via multiple hinges, for example, three hinges, and is opened and closed using a handle 23. The inner surface of the door frame 21 is covered with a heat insulating material 22 that is fitted into the opening 10A of the furnace body 10.

[0019] The heat insulating material 22 is made of ceramic fiber boards formed into a predetermined shape and stacked in the left-right width direction of the door frame 21. Furthermore, the heat insulating material 22 provided on the inner surface of the door frame 21 is configured so that, when the door 20 is closed, both left-right and up-down edge portions thereof are close to or abut the front end portions of the heat insulating material 11 provided on the opposing inner wall of the furnace body 10. As a result, when the door 20 is closed, a heat treatment space 10B is formed in the furnace body 10 in which the workpiece 5 is heat-treated by each heater 13.

[0020] [Gas supply unit 30] 1, the gas supply unit 30 is a device that supplies oxygen gas and air into the heat treatment space 10B to adjust the oxygen concentration in the heat treatment space 10B, and further causes exhaust gases such as carbon dioxide generated by the oxidation reaction of the workpiece 5 to flow out of the furnace body 10 through the exhaust duct 15. The gas supply unit 30 includes a first mass flow controller (hereinafter referred to as "first MFC") 31 that supplies oxygen gas into the heat treatment space 10B, and an oxygen cylinder 32 that supplies oxygen gas to the first MFC 31.

[0021] The gas supply unit 30 also includes a second mass flow controller (hereinafter referred to as "second MFC") 33 that takes in air through an air filter 35 and supplies the air into the heat treatment space 10B. As shown in FIG. 2, the first MFC 31 and the second MFC 33 are electrically connected to the control device 40.

[0022] 1, the first MFC 31 adjusts the flow rate (mass flow rate) of oxygen gas supplied from the oxygen cylinder 32 to a flow rate (mass flow rate) instructed by the control device 40, and supplies the oxygen gas at a predetermined pressure into the furnace body 10 through an air supply pipe 18 provided at the bottom of the furnace body 10. The second MFC 33 adjusts the flow rate (mass flow rate) of external air supplied from an air pump (not shown) through an air filter 35 to a flow rate (mass flow rate) instructed by the control device 40, and supplies the air at a predetermined pressure into the furnace body 10 through the air supply pipe 18 provided at the bottom of the furnace body 10.

[0023] The oxygen gas that has passed through the first MFC 31 and the air that has passed through the second MFC 33 are mixed in advance in the piping before being sent to the air supply pipe 18. The air supply pipe 18 is not limited to being located at the bottom of the furnace body 10, and multiple air supply pipes may be provided, such as on the left and right side walls or the rear side wall of the furnace body 10.

[0024] As a result, the heat treatment space 10B within the furnace body 10 is maintained at a predetermined pressure, for example, 0 [PaG] to approximately 50 [PaG], and more preferably approximately 10 [PaG], by the mixed gas of oxygen gas supplied from the first MFC 31 and air supplied from the second MFC 33. Then, the mixed gas of oxygen gas supplied from the first MFC 31 and air supplied from the second MFC 33 forms a flow that causes exhaust gases such as carbon dioxide generated by the oxidation reaction of the workpiece 5 to flow out of the furnace body 10 through the exhaust duct 15.

[0025] [Electrical configuration] Next, the electrical configuration of the control device 40 will be described with reference to Fig. 2. As shown in Fig. 2, the control device 40 has a control unit 41, a storage unit 42, and an input / output interface 43. Note that the control device 40 may be realized by a PLC (Programmable Logic Controller) equipped with a control unit, a storage unit, an input / output interface, and the like.

[0026] The control unit 41 is configured, for example, by a CPU (Central Processing Unit). The control unit 41 may also be configured by a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an MPU (Micro Processing Unit), an FPU (Floating point number Processing Unit), a PPU (Physics Processing Unit), a microcontroller, or a combination thereof.

[0027] The storage unit 42 is configured with a semiconductor random access memory (RAM), a flash memory, a hard disk drive (HDD), a solid state drive (SSD), an optical disk drive (ODD), or a combination of these. The control unit 41 executes various arithmetic processes based on various programs and various parameters stored in the storage unit 42. The storage unit 42 also stores in advance a gas flow rate table 61 (see FIG. 5), which will be described later.

[0028] The input / output interface 43 electrically connects the first MFC 31, the second MFC 33, the operation unit 52, the display 51, the oxygen concentration meter 16, the thermocouple 17, and the heater 13. The input / output interface 43 outputs detection values detected from the respective detection signals input from the operation unit 52, the oxygen concentration meter 16, and the thermocouple 17 to the control unit 41. The control unit 41 stores the respective detection values of the operation unit 52, the oxygen concentration meter 16, and the thermocouple 17 input from the input / output interface 43 in the memory unit 42.

[0029] Furthermore, the control unit 41 outputs control signals to the first MFC 31 and the second MFC 33 via the input / output interface 43, and controls the flow rates (mass flow rates) of the first MFC 31 and the second MFC 33. The control unit 41 outputs control signals to the display 51 via the input / output interface 43, and displays various images on the display 51. The control unit 41 outputs control signals to the heater 13 via the input / output interface 43, and controls the on / off and heating temperature of the heater 13.

[0030] The display 51 is composed of a liquid crystal display, an organic EL display, or the like. The display 51 displays a screen for inputting, for example, the furnace set temperature [°C], the target oxygen concentration [%], the total flow rate [L / min], and the treatment time [min]. The furnace set temperature [°C] represents the set temperature inside the furnace body 10. The target oxygen concentration [%] represents the target oxygen concentration [%] in the heat treatment space 10B. The total flow rate [L / min] represents the total flow rate [L / min] of the oxygen gas supplied by the first MFC 31 and the air supplied by the second MFC 33. The treatment time [min] represents the treatment time [min] for firing the workpiece 5.

[0031] The operation unit 52 is a device that accepts operations by the user. The user can input various instructions to the control device 40 by operating the operation unit 52. The operation unit 52 may be configured as a touch panel that is integrally arranged on the screen of the display 51. The operation unit 52 functions as an example of a reception unit.

[0032] [Oxygen gas supply processing] Next, an example of an oxygen gas supply process executed by the control unit 41 of the control device 40, in which the first MFC 31 and the second MFC 33 are controlled to supply oxygen gas and air to the heat treatment space 10B in the furnace body 10, will be described with reference to FIGS. 3 to 7. In this embodiment, a case in which the gas supply process of supplying oxygen gas and air to the heat treatment space 10B and the heat treatment process of heating the inside of the furnace body 10 to the furnace set temperature [°C] are processed in parallel (independently at the same time) will be illustrated. In this case, the control unit 41 may be equipped with multiple hardware processors or may be equipped with a multi-core processor.

[0033] The workpiece 5 is contained in a sagger 3 or the like and placed on a receiving table 12 in the furnace body 10, with the door 20 closed. Figures 3, 4, and 6 are flowcharts illustrating an example of an oxygen gas supply process executed by the control unit 41. Figure 5 is a flowchart illustrating an example of a sub-process of the gas amount adjustment process of Figure 4. Figure 7 is a diagram showing an example of a gas flow rate table 61 stored in the memory unit 42.

[0034] 3, in step S11, the control unit 41 acquires various setting values for performing heat treatment on the workpiece 5 via the operation unit 52 and stores them in the storage unit 42. Specifically, the control unit 41 displays a screen on the display 51 for inputting various setting values, such as the furnace temperature setting [°C], the target oxygen concentration [%], the total flow rate [L / min], and the treatment time [min]. The control unit 41 then stores the furnace temperature setting [°C], the target oxygen concentration [%], the total flow rate [L / min], the treatment time [min], and the like input via the operation unit 52 in the storage unit 42, and then proceeds to the processing of step S12.

[0035] For example, the input target oxygen concentration [%] is 22 [%] to 99 [%]. The input total flow rate [L / min] is 50 [L / min], for example. The input furnace set temperature [°C] is 600 [°C] to 1100 [°C], for example. The input processing time [min] is 30 [min] to 240 [min], for example.

[0036] In step S12, the control unit 41 starts measuring the processing time for performing the heat treatment on the workpiece 5, and then proceeds to both step S13A and step S13B as parallel processing. Here, step S13A is a connector A connecting step S12 to step S21 in the flowchart shown in Fig. 4. Also, step S13B is a connector B connecting step S12 to step S41 in the flowchart shown in Fig. 6.

[0037] [Gas supply processing] Next, a gas supply process for supplying oxygen gas and air to the heat treatment space 10B will be described with reference to the flowchart of FIG. 4. In step S21, the control unit 41 reads the total flow rate [L / min] and target oxygen concentration [%] stored in the memory unit 42 in step S11. The control unit 41 then reads the oxygen gas flow rate [L / min] and air flow rate [L / min] corresponding to the combination of the read total flow rate [L / min] and target oxygen concentration [%] from the gas flow rate table 61 previously stored in the memory unit 42. The control unit 41 then stores the read oxygen gas flow rate [L / min] as the flow rate set value for the first MFC 31 and the read air flow rate [L / min] as the flow rate set value for the second MFC 33 in the memory unit 42, and then proceeds to step S22.

[0038] For example, when the total flow rate [L / min] is 50 [L / min] and the target oxygen concentration [%] is 70 [%], the control unit 41 reads out 31.11 [L / min] as the oxygen gas flow rate [L / min] from the gas flow rate table 61. The control unit 41 also reads out 18.89 [L / min] as the air flow rate [L / min]. The control unit 41 then sets the read-out 31.11 [L / min] as the flow rate set value for the first MFC 31 and stores 18.89 [L / min] as the flow rate set value for the second MFC 33 in the memory unit 42.

[0039] In step S22, the control unit 41 reads out the oxygen gas flow rate [L / min] stored in the memory unit 42 as the flow rate set value in step S21, and outputs it as the flow rate at which oxygen gas is to be supplied to the first MFC 31. As a result, the first MFC 31 supplies oxygen gas into the furnace body 10 via the air supply pipe 18 at the input oxygen gas flow rate [L / min]. The control unit 41 also reads out the air flow rate [L / min] stored in the memory unit 42 as the flow rate set value in step S21, and outputs it as the flow rate at which air is to be supplied to the second MFC 33. As a result, the second MFC 33 supplies air into the furnace body 10 via the air supply pipe 18 at the input air flow rate [L / min]. Thereafter, the control unit 41 proceeds to the processing of step S23.

[0040] For example, the first MFC 31 supplies oxygen gas through the air supply pipe 18 into the furnace body 10 at a flow rate of 31.11 [L / min]. The second MFC 33 supplies air through the air supply pipe 18 into the furnace body 10 at a flow rate of 18.89 [L / min]. This makes it possible to supply gas with an oxygen concentration of approximately 70 [%] at a total flow rate of oxygen gas and air of 50 [L / min] into the furnace body 10. The oxygen gas that has passed through the first MFC 31 and the air that has passed through the second MFC 33 are mixed in advance in the piping before being sent to the air supply pipe 18.

[0041] In step S23, the control unit 41 waits for a certain period of time, for example, about 5 to 10 minutes, to elapse, and then proceeds to the processing of step S24. That is, the control unit 41 waits for the oxygen concentration [%] in the furnace body 10 to reach the target oxygen concentration [%].

[0042] In step S24, the control unit 41 measures the oxygen concentration [%] in the heat treatment space 10B in the furnace body 10 via the oxygen concentration meter 16. The control unit 41 also reads out the target oxygen concentration [%] stored in step S11 from the memory unit 42. Next, the control unit 41 determines whether the measured oxygen concentration [%] is approximately equal to the target oxygen concentration [%], for example, whether it is within a range of ±1 [%] to ±5 [%] of the target oxygen concentration [%].

[0043] If the control unit 41 determines that the measured oxygen concentration [%] is substantially equal to the target oxygen concentration [%] (S24: YES), the control unit 41 proceeds to the processing of step S26, which will be described later.

[0044] On the other hand, if the control unit 41 determines that the measured oxygen concentration [%] is not substantially equal to the target oxygen concentration [%] (S24: NO), the control unit 41 proceeds to the sub-processing of "gas amount adjustment process" in step S25.

[0045] [Sub-processing of gas volume adjustment processing] Here, the sub-processing of the "gas amount adjustment process" will be described with reference to Fig. 5. As shown in Fig. 5, in step S31, the control unit 41 determines whether the oxygen concentration [%] measured in step S24 is lower than the target oxygen concentration [%].

[0046] If the control unit 41 determines that the oxygen concentration [%] measured in step S16 is lower than the target oxygen concentration [%] (S31: YES), the control unit 41 proceeds to the process of step S32.

[0047] In step S32, the control unit 41 reads out the oxygen gas flow rate [L / min] stored as the flow rate set value of the first MFC 31 from the memory unit 42. Then, the control unit 41 adds a predetermined gas flow rate [L / min], for example, about 2 [L / min] to 3 [L / min] to obtain an added oxygen gas flow rate [L / min], and stores this added oxygen gas flow rate [L / min] again in the memory unit 42 as the flow rate set value of the first MFC 31.

[0048] Next, the control unit 41 outputs this added oxygen gas flow rate [L / min] as the flow rate at which oxygen gas is to be supplied to the first MFC 31. Thereafter, the control unit 41 proceeds to the processing of step S33. As a result, the first MFC 31 supplies oxygen gas into the furnace body 10 through the gas supply pipe 18 at the input added oxygen gas flow rate [L / min], and the flow rate of the oxygen gas increases by the predetermined gas flow rate [L / min].

[0049] In step S33, the control unit 41 reads out the air flow rate [L / min] stored as the flow rate setting value of the second MFC 33 from the memory unit 42. Then, the control unit 41 subtracts a predetermined gas flow rate [L / min], for example, about 2 [L / min] to 3 [L / min], from this read air flow rate [L / min], and stores the resulting air flow rate [L / min] again in the memory unit 42 as the flow rate setting value of the second MFC 33.

[0050] Next, the control unit 41 outputs this subtracted air flow rate [L / min] as the flow rate at which air is supplied to the second MFC 33. Thereafter, the control unit 41 ends the sub-processing of the "gas amount adjustment process" and returns to the main flowchart, proceeding to the process of step S26. As a result, the second MFC 33 supplies air into the furnace body 10 through the air supply pipe 18 at the input subtracted air flow rate [L / min], and the air flow rate is reduced by the predetermined gas flow rate [L / min]. Therefore, the oxygen concentration [%] in the heat treatment space 10B in the furnace body 10 can be increased by the predetermined concentration.

[0051] On the other hand, in step S31, if the control unit 41 determines that the oxygen concentration [%] measured in step S24 is higher than the target oxygen concentration [%] (S31: NO), the process proceeds to step S34.

[0052] In step S34, the control unit 41 reads out the oxygen gas flow rate [L / min] stored as the flow rate set value of the first MFC 31 from the memory unit 42. Then, the control unit 41 subtracts a predetermined gas flow rate [L / min], for example, about 2 [L / min] to 3 [L / min], from the read oxygen gas flow rate [L / min], and stores the resulting subtracted oxygen gas flow rate [L / min] again in the memory unit 42 as the flow rate set value of the first MFC 31.

[0053] Next, the control unit 41 outputs this subtracted oxygen gas flow rate [L / min] as the flow rate at which oxygen gas is to be supplied to the first MFC 31. Thereafter, the control unit 41 proceeds to the processing of step S35. As a result, the first MFC 31 supplies oxygen gas into the furnace body 10 through the air supply pipe 18 at the input subtracted oxygen gas flow rate [L / min], and the flow rate of the oxygen gas is reduced by the predetermined gas flow rate [L / min].

[0054] In step S35, the control unit 41 reads out the air flow rate [L / min] stored as the flow rate setting value of the second MFC 33 from the memory unit 42. Then, the control unit 41 adds a predetermined gas flow rate [L / min], for example, about 2 [L / min] to 3 [L / min] to obtain an added air flow rate [L / min], and stores this added air flow rate [L / min] again in the memory unit 42 as the flow rate setting value of the second MFC 33.

[0055] Next, the control unit 41 outputs this added air flow rate [L / min] as the flow rate at which air is supplied to the second MFC 33. Thereafter, the control unit 41 ends the sub-processing of the "gas amount adjustment process" and returns to the main flowchart, proceeding to the process of step S26. As a result, the second MFC 33 supplies air into the furnace body 10 through the air supply pipe 18 at the input added air flow rate [L / min], and the air flow rate increases by the predetermined gas flow rate [L / min]. Therefore, the oxygen concentration [%] in the heat treatment space 10B in the furnace body 10 can be reduced by the predetermined concentration.

[0056] [Oxygen gas supply processing] Next, the processing from step S26 onwards shown in Fig. 4 will be described. As shown in Fig. 4, in step S26, the control unit 41 reads out from the storage unit 42 the heat treatment time [min] of the workpiece 5, the measurement of which was started in step S12, and the processing time [min] stored in step S11. Then, the control unit 41 determines whether the heat treatment time [min] of the workpiece 5 has reached the processing time [min]. If the control unit 41 determines that the heat treatment time [min] of the workpiece 5 has not reached the processing time [min] (S26: NO), it executes the processing from step S23 onwards again.

[0057] On the other hand, if the control unit 41 determines that the heat treatment time [min] of the workpiece 5 has reached the treatment time [min] (S26: YES), the control unit 41 proceeds to the process of step S27. In step S27, the control unit 41 outputs a stop instruction to the first MFC 31 to instruct it to stop the supply of oxygen gas. As a result, the first MFC 31 stops the supply of oxygen gas into the furnace body 10. Thereafter, the control unit 41 proceeds to the process of step S28.

[0058] The control unit 41 may continue to supply air into the furnace body 10 by the second MFC 33, and may cause the exhaust gas in the heat treatment space 10B in the furnace body 10 to flow outside via the exhaust duct 15. The control unit 41 may also set the air flow rate [L / min] of the second MFC 33 to the total flow rate [L / min] stored in step S11. This allows the exhaust gas in the heat treatment space 10B in the furnace body 10 to flow quickly outside via the exhaust duct 15.

[0059] In step S28, the control unit 41 notifies the user via the display 51 that the heat treatment of the workpiece 5 has been completed, and then terminates the gas supply process. This allows the user to know that the heat treatment of the workpiece 5 has been completed.

[0060] [Heat treatment] Next, a heating process for heating the inside of the furnace body 10 to the furnace set temperature [°C] will be described with reference to the flowchart of Fig. 6. In step S41, the control unit 41 reads out the furnace set temperature [°C] stored in the memory unit 42 in step S11. Then, the control unit 41 drives each heater 13 to heat the furnace while detecting the furnace temperature via the thermocouple 17 so that the temperature of the heat treatment space 10B in the furnace body 10 becomes the furnace set temperature [°C]. Thereafter, the control unit 41 proceeds to the process of step S42.

[0061] In step S42, the control unit 41 detects the temperature [°C] of the heat treatment space 10B in the furnace body 10 via the thermocouple 17. The control unit 41 also reads out the furnace set temperature [°C] stored in step S11 from the memory unit 42. Next, the control unit 41 determines whether the temperature [°C] of the heat treatment space 10B in the furnace body 10 detected via the thermocouple 17 has risen to the furnace set temperature [°C].

[0062] If the control unit 41 determines that the temperature [°C] of the heat treatment space 10B in the furnace body 10 detected via the thermocouple 17 has not risen to the furnace set temperature [°C] (S42: NO), it executes the processing from step S41 onwards again.

[0063] On the other hand, if the control unit 41 determines that the temperature [°C] of the heat treatment space 10B in the furnace body 10 detected via the thermocouple 17 has risen to the furnace set temperature [°C] (S42: YES), the control unit 41 proceeds to the processing of step S43. For example, if the temperature [°C] of the heat treatment space 10B in the furnace body 10 detected via the thermocouple 17 is within a range of ±5 [°C] of the furnace set temperature [°C] (S42: YES), the control unit 41 determines that the temperature has risen to the furnace set temperature [°C], and proceeds to the processing of step S43.

[0064] In step S43, when the temperature of the heat treatment space 10B in the furnace body 10 reaches the furnace set temperature [°C], the control unit 41 repeatedly controls the heater 13 to turn on and off so as to maintain the furnace set temperature [°C]. Then, the control unit 41 proceeds to the processing of step S45.

[0065] In step S45, the control unit 41 reads out from the memory unit 42 the heat treatment time [min] of the workpiece 5 whose measurement started in step S12 and the treatment time [min] stored in step S11. Then, the control unit 41 determines whether the heat treatment time [min] of the workpiece 5 has reached the treatment time [min]. If the control unit 41 determines that the heat treatment time [min] of the workpiece 5 has not reached the treatment time [min] (S45: NO), it executes the processes from step S43 onwards again.

[0066] On the other hand, if the control unit 41 determines that the heat treatment time [min] of the workpiece 5 has reached the treatment time [min] (S45: YES), the control unit 41 proceeds to the process of step S46. In step S46, the control unit 41 turns off each heater 13 to stop heating, and then ends the heat treatment.

[0067] As described above in detail, in the gas supply system 1 according to this embodiment, the control unit 41 controls the oxygen flow rate by the first MFC 31 and the air flow rate by the second MFC 33 based on the total flow rate [L / min] of the oxygen gas flow rate and the air flow rate, the target oxygen concentration [%], and the detection value of the oxygen concentration meter 16, all of which are input via the operation unit 52. As a result, the control unit 41 can control the oxygen concentration in the heat treatment space 10B in the furnace body 10 using the first MFC 31, while controlling the air flow rate by the second MFC 33, which generates a gas flow for discharging exhaust gases such as carbon dioxide generated in the heat treatment space 10B from the exhaust duct 15.

[0068] As a result, the control unit 41 can increase the air flow rate while controlling the total flow rate of the oxygen gas and the air flow rate required for the oxidation treatment of the workpiece 5 in the furnace body 10, thereby reducing the consumption of oxygen gas, thereby reducing mass production costs.

[0069] Furthermore, a gas flow rate table 61 that stores the total flow rate [L / min] of the oxygen gas flow rate and the air flow rate and the oxygen gas flow rate [L / min] and the air flow rate [L / min] corresponding to the target oxygen concentration [%] is stored in the memory unit 42. This allows the control unit 41 to quickly determine and control the oxygen gas flow rate [L / min] of the first MFC 31 and the air flow rate [L / min] of the second MFC 33 that correspond to the total flow rate [L / min] and the target oxygen concentration [%] input via the operation unit 52.

[0070] Furthermore, when the oxygen concentration [%] in the heat treatment space 10B detected by the oxygen concentration meter 16 is lower than the target oxygen concentration [%], the control unit 41 increases the flow rate of oxygen gas from the first MFC 31 by a predetermined amount and decreases the flow rate of air from the second MFC 33 by a predetermined amount. This allows the control unit 41 to quickly increase the oxygen concentration [%] in the heat treatment space 10B to the target oxygen concentration [%].

[0071] On the other hand, when the oxygen concentration [%] in the heat treatment space 10B detected by the oxygen concentration meter 16 is higher than the target oxygen concentration [%], the control unit 41 reduces the flow rate of oxygen gas from the first MFC 31 by a predetermined amount and increases the flow rate of air from the second MFC 33 by a predetermined amount. This allows the control unit 41 to quickly reduce the oxygen concentration [%] in the heat treatment space 10B to the target oxygen concentration [%].

[0072] Furthermore, the oxygen gas supplied from the first MFC 31 and the air supplied from the second MFC 33 are supplied into the furnace body 10 through an air supply pipe 18 provided at the bottom of the furnace body 10. This allows exhaust gases such as carbon dioxide generated by the oxidation of the workpiece 5 to be efficiently exhausted from an exhaust duct 15 provided at the top of the furnace body 10.

[0073] [Variations] A modification of the above embodiment will be described. In the following description, for the sake of convenience, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0074] [Variation 1] For example, the first MFC 31 may supply oxygen gas into the furnace body 10 via the air supply pipe 18, and the second MFC 33 may supply nitrogen gas, instead of air, supplied from a nitrogen gas cylinder into the furnace body 10 via the air supply pipe 18. This allows the control unit 41 to increase the flow rate of nitrogen gas while controlling the total flow rate of oxygen gas and nitrogen gas required for the oxidation treatment of the workpiece 5 in the furnace body 10, thereby reducing the consumption of oxygen gas. This allows for a reduction in mass production costs.

[0075] [Variation 2] Furthermore, for example, the furnace body 10, which is a heat treatment furnace, may be configured as a roller hearth kiln that performs heat treatment on the workpieces 5 while transporting saggers 3 or the like containing the workpieces 5. The roller hearth kiln may be configured so that oxygen gas is supplied by the first MFC 31 and air is supplied by the second MFC 33 in each of a plurality of zones with different heating temperatures provided along the transport direction of the roller hearth kiln. The first MFC 31 and second MFC 33 provided in each of the plurality of zones with different heating temperatures may be controlled by a single control device 40.

[0076] This allows the air flow rate to be increased while controlling the total flow rate of oxygen gas and air required for oxidation treatment of the workpiece 5 in each of the multiple regions of the roller hearth kiln, thereby reducing the consumption of oxygen gas. Therefore, mass production costs in the roller hearth kiln can be further reduced.

[0077] [Variation 3] 3, the control unit 41 may acquire various setting values for each of a plurality of heat treatment patterns to be sequentially performed on the workpiece 5 via the operation unit 52 and store them in the memory unit 42. The various setting values include the furnace temperature setting [°C], the target oxygen concentration [%], the total flow rate [L / min], the treatment time [min], etc.

[0078] Then, the control unit 41 reads out the various setting values of the first heat treatment pattern from the storage unit 42, and after executing the process of step S12, executes the processes of steps S21 to S26 shown in Fig. 4 and the processes of steps S41 to S45 shown in Fig. 6 in parallel. Then, in steps S26 and S45, when the heat treatment time [min] of the workpiece 5 reaches the treatment time [min] of the first heat treatment pattern, the control unit 41 reads out the various setting values of the second heat treatment pattern from the storage unit 42. Next, after executing the process of step S12, the control unit 41 executes the processes of steps S21 to S26 shown in Fig. 4 and the processes of steps S41 to S45 shown in Fig. 6 in parallel.

[0079] Next, in steps S26 and S45, when the heat treatment time [min] of the workpiece 5 reaches the treatment time [min] of the second heat treatment pattern, the control unit 41 repeatedly executes similar parallel processing for the third and subsequent heat treatment patterns in order. Then, for the last heat treatment pattern, when the heat treatment time [min] of the workpiece 5 reaches the treatment time [min] of the last heat treatment pattern in steps S26 and S45, the control unit 41 may execute parallel processing of steps S27 and subsequent steps and step S46, and then terminate the oxygen gas supply process.

[0080] This allows the control unit 41 to repeat a heat treatment pattern multiple times for the workpiece 5. By repeating a plurality of heat treatment patterns, the control unit 41 can execute a more complicated heating pattern.

[0081] [summary] A gas supply system of a first aspect includes a furnace body having a heat treatment space therein for heat-treating a workpiece, a first mass flow controller for controlling the flow rate of oxygen gas supplied into the heat treatment space, a second mass flow controller for controlling the flow rate of air supplied into the heat treatment space, an oxygen concentration meter for detecting the oxygen concentration in the heat treatment space, an exhaust duct provided at an upper part of the furnace body for connecting the heat treatment space to the outside of the furnace body and configured to be able to discharge exhaust gas generated in the heat treatment space to the outside, a receiving unit for receiving inputs of the total flow rate of the oxygen gas and the flow rate of the air and a target oxygen concentration for promoting oxidation of the workpiece in the heat treatment space, and a control device for controlling the first mass flow controller and the second mass flow controller based on the total flow rate and the target oxygen concentration received via the receiving unit and the detection value of the oxygen concentration meter.

[0082] A second aspect is the gas supply system of the first aspect, wherein the control device has a memory unit that stores the oxygen gas flow rate and the air flow rate corresponding to the total flow rate and the target oxygen concentration, and controls the first mass flow controller to set the oxygen gas flow rate to correspond to the total flow rate and the target oxygen concentration stored in the memory unit, and controls the second mass flow controller to set the air flow rate to correspond to the total flow rate and the target oxygen concentration stored in the memory unit.

[0083] A third aspect is the gas supply system of the second aspect, wherein the control device executes a concentration determination process to determine whether the oxygen concentration in the heat treatment space is higher or lower than the target oxygen concentration; and a gas amount adjustment process to control the first mass flow controller to increase the flow rate of the oxygen gas by a predetermined amount and the second mass flow controller to decrease the flow rate of the air by a predetermined amount if the concentration determination process determines that the oxygen concentration in the heat treatment space is lower than the target oxygen concentration; and a gas amount adjustment process to control the first mass flow controller to decrease the flow rate of the oxygen gas by a predetermined amount and the second mass flow controller to increase the flow rate of the air by a predetermined amount if the oxygen concentration in the heat treatment space is determined to be higher than the target oxygen concentration.

[0084] A fourth aspect is the gas supply system according to any one of the first to third aspects, wherein the oxygen gas and the air are supplied into the heat treatment space from a bottom of the furnace body.

[0085] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0086] 1: Gas supply system 5: Processing object 10: Furnace body 10B: Heat treatment space 15: Exhaust duct 16: Oxygen concentration meter 31: First mass flow controller (first MFC) 33: Second mass flow controller (second MFC) 40: Control device 41: Control unit 42: Storage part 52:Operation unit

Claims

1. a furnace body having a heat treatment space therein for heat-treating the object to be treated; a first mass flow controller for controlling the flow rate of oxygen gas supplied into the heat treatment space; a second mass flow controller for controlling the flow rate of air supplied into the heat treatment space; an oxygen concentration meter for detecting the oxygen concentration in the heat treatment space; an exhaust duct provided on an upper portion of the furnace body, connecting the heat treatment space with the outside of the furnace body, and configured to be able to discharge exhaust gas generated in the heat treatment space to the outside; a receiving unit that receives input of a total flow rate of the oxygen gas and the air, and a target oxygen concentration for promoting oxidation of the object to be treated in the heat treatment space; a control device that controls the first mass flow controller and the second mass flow controller based on the total flow rate and the target oxygen concentration received via the receiving unit and the detection value of the oxygen concentration meter; A gas supply system comprising:

2. The control device a memory unit that stores the total flow rate and the flow rate of the oxygen gas and the flow rate of the air corresponding to the target oxygen concentration, controlling the first mass flow controller so that the flow rate of the oxygen gas corresponds to the total flow rate and the target oxygen concentration stored in the storage unit; controlling the second mass flow controller so that the flow rate of the air corresponds to the total flow rate and the target oxygen concentration stored in the storage unit; The gas supply system of claim 1 .

3. The control device a concentration determination process for determining whether the oxygen concentration in the heat treatment space is higher or lower than the target oxygen concentration; When it is determined in the concentration determination process that the oxygen concentration in the heat treatment space is lower than the target oxygen concentration, the first mass flow controller is controlled so that the flow rate of the oxygen gas increases by a predetermined amount, and the second mass flow controller is controlled so that the flow rate of the air decreases by a predetermined amount; a gas amount adjustment process for controlling the first mass flow controller so as to decrease the flow rate of the oxygen gas by a predetermined amount and controlling the second mass flow controller so as to increase the flow rate of the air by a predetermined amount when it is determined that the oxygen concentration in the heat treatment space is higher than the target oxygen concentration; The gas supply system according to claim 2 , wherein the gas supply system performs the following steps:

4. The oxygen gas and the air are supplied into the heat treatment space from the bottom of the furnace body. The gas supply system according to any one of claims 1 to 3.

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