Heat treatment device and method for controlling the temperature of a cooling liquid in the heat treatment device

Abstract

To provide a heat treatment apparatus for cooling a heated object, such as quenching, with excellent energy saving performance and reduced operation costs.SOLUTION: A heat treatment apparatus 1 has: a cooling tank 6 in which a coolant C for cooling a heated object 100 is stored; a thermometer 7 for measuring a temperature of the coolant C; a temperature adjustment mechanism 25 including a cooling section 27 for cooling the coolant C and a heating section 28 for heating the coolant C; and a control section 8 for controlling the temperature adjustment mechanism 25. The control unit 8 is configured to execute an induction cooling mode. In the induction cooling mode, the control section 8 sets a target temperature Tt of the coolant C to change over time, and drives the temperature adjustment mechanism 25 so that a measured temperature Tm of the coolant C becomes the target temperature Tt.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat treatment apparatus and a method for controlling the temperature of a coolant in the heat treatment apparatus. [Background technology]

[0002] As an apparatus for quenching a metal workpiece, an oil quenching apparatus is known which includes a heating chamber for heating the workpiece and an oil quenching chamber for cooling the workpiece heated in the heating chamber with quenching oil (see, for example, Patent Document 1).

[0003] The oil quenching chamber stores quenching oil for cooling the workpiece. The workpiece is cooled by immersing it in the quenching oil in the oil quenching chamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-309314 Summary of the Invention [Problem to be solved by the invention]

[0005] When a workpiece is cooled in an oil quenching device, the temperature of the quenching oil rises. While the quenching oil is used repeatedly for multiple quenching processes, the temperature of the quenching oil immediately before quenching must be at a set temperature (predetermined temperature) to perform the desired heat treatment. Therefore, after quenching of the workpiece is complete, the quenching oil must be cooled to the above-mentioned predetermined temperature in preparation for the next cooling process. For this reason, a heat exchanger is used to cool the quenching oil.

[0006] Conventionally, heat exchangers begin cooling the quenching oil immediately after the workpiece is quenched, rapidly cooling the oil, and then stop operating once the oil temperature has dropped to the predetermined temperature. However, after the oil has cooled to the predetermined temperature, it can take a long time before the next quenching operation. In this case, a heating unit is operated at regular intervals to keep the oil warm and maintain the oil temperature at the predetermined temperature. Because the heating unit consumes a large amount of energy, excessive operation of the heating unit is undesirable from the standpoint of energy conservation and results in high energy costs.

[0007] The present invention has been made in view of the above background, and aims to provide a heat treatment apparatus that performs a process of cooling a heated workpiece, such as quenching, that is energy-efficient and has reduced operating costs. [Means for solving the problem]

[0008] (1) A heat treatment apparatus according to an aspect of the present invention, which was made based on the above findings, includes a cooling tank for storing a cooling liquid for cooling a heated workpiece, a temperature sensor for measuring the temperature of the cooling liquid, a temperature adjustment mechanism including a cooling unit for cooling the cooling liquid and a heating unit for heating the cooling liquid, and a control unit for controlling the temperature adjustment mechanism, wherein the control unit is configured to be able to execute an induction cooling mode, and in the induction cooling mode, the control unit adjusts a target temperature of the cooling liquid over time. Linearly decreasing to the final target temperature The temperature adjusting mechanism is driven so that the actually measured temperature of the cooling liquid becomes the target temperature.

[0009] With this configuration, the cooling liquid, whose temperature has risen due to the introduction of a heated workpiece into the cooling tank, can be cooled before the next heated workpiece is introduced into the cooling tank. During this cooling, the control unit, in induction cooling mode, sets the target temperature of the cooling liquid to change over time and drives the temperature adjustment mechanism so that the measured temperature of the cooling liquid reaches the target temperature. This configuration prevents the cooling unit from rapidly cooling the cooling liquid. This allows the control unit to gradually lower the temperature of the cooling liquid. As a result, the heating operation of the cooling liquid to maintain the required temperature after it reaches the required temperature at the start of cooling the workpiece can be reduced to zero or to the minimum necessary. In other words, the energy required to heat the cooling liquid can be reduced, resulting in a heat treatment device that performs processes such as quenching to cool heated workpieces, which has an excellent energy-saving configuration and reduces operating costs such as energy costs. Furthermore, the target temperature per unit time required when the induction cooling mode is executed can be set by simple calculation.

[0010] (2) The control unit determines a period from the start to the end of the induction cooling mode, and the actual measured temperature at the start of the induction cooling mode and the actual measured temperature at the end of the induction cooling mode. final The target temperature may be set based on the temperature difference from the target temperature.

[0011] According to this configuration, the target temperature per unit time required when the induction cooling mode is executed is set for the period from the start to the end of the induction cooling mode, and the actual measured temperature at the start of the induction cooling mode and the actual measured temperature at the end of the induction cooling mode. final The temperature can be set based on the temperature difference from the target temperature. This allows the target temperature to be set for each unit time with simple calculations and with a high degree of freedom.

[0014] ( 3) The target temperature has a predetermined temperature range, and within the temperature range, a target central temperature, a target upper limit temperature higher than the target central temperature, and a target lower limit temperature lower than the target central temperature are set, and the control unit may drive the temperature adjustment mechanism so that the actually measured temperature falls between the target upper limit temperature and the target lower limit temperature.

[0015] According to this configuration, since a temperature range is set for the target temperature, it is not necessary to strictly control the coolant temperature, and the coolant temperature control can be achieved with a simpler configuration.

[0016] ( 4 ) The difference between the target upper limit temperature and the target lower limit temperature in the later stage of the induction cooling mode may be smaller than the difference between the target upper limit temperature and the target lower limit temperature in the early stage of the induction cooling mode.

[0017] With this configuration, after cooling the workpiece, the temperature of the cooling liquid into which the heated workpiece is then added can be more accurately brought closer to the required temperature at the time the workpiece is added.

[0018] ( 5 The control unit may drive the cooling unit to cool the cooling liquid when the measured temperature is higher than the target core temperature.

[0019] According to this configuration, the trigger for starting the drive of the cooling unit can be configured simply.

[0020] ( 6 ) When the actual measured temperature is the target upper limit temperature, the control unit may start driving the cooling unit to cool the cooling liquid, and may stop driving the cooling unit when the actual measured temperature drops to the target core temperature.

[0021] This configuration can prevent the cooling unit from cooling the coolant excessively, thereby reducing the need for the heating unit to reheat the coolant, which requires a lot of energy, due to the coolant temperature dropping too low.

[0022] ( 7 The control unit may drive the heating unit to heat the coolant when the measured temperature is lower than the target core temperature.

[0023] With this configuration, the temperature of the coolant can be maintained so that it does not become too low from the target core temperature.

[0024] ( 8 ) The control unit may start driving the heating unit to heat the cooling liquid when the actual measured temperature is the target lower limit temperature, and may stop driving the heating unit when the actual measured temperature rises to the target core temperature.

[0025] This configuration can prevent the cooling liquid from being excessively heated by the heating unit, thereby allowing the temperature of the cooling liquid to be maintained with minimal heating.

[0026] ( 9 ) The heat treatment device is a carburizing treatment device that carburizes the workpiece, and is configured to heat the workpiece to a predetermined carburizing temperature and then lower the temperature to a predetermined soaking temperature, then maintain the workpiece at the soaking temperature for a predetermined time, and then charge the workpiece into the cooling tank, and the control unit may be configured to predict a temperature drop time required for the temperature of the workpiece to drop from the carburizing temperature to the soaking temperature, terminate the induction cooling mode during the temperature drop time, and then execute a constant temperature mode that controls the temperature adjustment mechanism to maintain the target temperature constant.

[0027] This configuration allows the control unit to operate in induction cooling mode for a longer period of time, thereby shortening the time spent in constant temperature mode. In constant temperature mode, the target temperature must be maintained constant, so the heating unit must frequently heat the coolant. However, shortening the time spent in constant temperature mode reduces the energy consumption associated with the heating operation.

[0028] (10 In order to solve the above-mentioned problems, a method for controlling the temperature of a coolant in a heat treatment apparatus according to one aspect of the present invention is provided, in a heat treatment apparatus having a temperature adjustment mechanism including a cooling tank in which a coolant for cooling a heated workpiece is stored, a cooling unit for cooling the coolant, and a heating unit for heating the coolant, the method comprising: adjusting a target temperature of the coolant over time; Linearly decreasing to the final target temperature The temperature adjusting mechanism is driven so that the actually measured temperature of the cooling liquid becomes the target temperature.

[0029] According to this configuration, a heat treatment apparatus that cools a heated object to be treated can be configured to be highly energy-efficient, and operating costs such as electricity charges can be reduced. Furthermore, the target temperature per unit time required to lower the measured temperature of the coolant can be set by a simple calculation. [Effects of the Invention]

[0030] According to the present invention, a heat treatment apparatus for cooling a heated workpiece can be configured to be highly energy-efficient and can reduce operating costs. Furthermore, the target temperature per unit time required to lower the measured temperature of the coolant can be set by a simple calculation. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a schematic cross-sectional view of a heat treatment apparatus according to one embodiment of the present invention, showing the heat treatment apparatus as viewed from the side. [Figure 2] FIG. 2 is a block diagram for explaining the main parts of the electrical configuration of the heat treatment apparatus. [Figure 3] FIG. 3 is a diagram for explaining the relationship between the processing pattern of the workpiece and the coolant temperature. [Figure 4] FIG. 4 is a diagram showing an example of the history of the actually measured temperature of the coolant in the "forced cooling control example." [Figure 5] FIG. 5 is a diagram showing an example of the history of the measured temperature of the coolant in the "heating control example." [Figure 6]FIG. 6 is a diagram for explaining the relationship between the treatment pattern of the workpiece and the coolant temperature in a modified example in which the heat treatment device performs a treatment different from that of the carburizing treatment device. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0033] Fig. 1 is a schematic cross-sectional view of a heat treatment apparatus 1 according to one embodiment of the present invention, showing the state of the heat treatment apparatus 1 as viewed from the side. Fig. 2 is a block diagram for explaining the main parts of the electrical configuration of the heat treatment apparatus 1.

[0034] 1 and 2, in this embodiment, the heat treatment apparatus 1 is a carburizing furnace. The heat treatment apparatus 1 is configured to introduce a heat treatment gas into a heating chamber 3 to perform a carburizing treatment on a workpiece 100 placed in the heating chamber 3. The material of the workpiece 100 may be any material that can be carburized on its surface. An example of the workpiece 100 is a metal part such as a steel part. Carburizing is a heat treatment method in which carbon penetrates and diffuses into the surface of steel. After carburizing heating, the steel is quenched in a cooling tank 6 in a cooling chamber 4 to obtain high surface hardness.

[0035] The heat treatment device 1 has a heat treatment mechanism 2 including a heating chamber 3 and a cooling chamber 4, a heating chamber thermometer 5 that measures the ambient temperature in the heating chamber 3, a liquid thermometer 7 that measures the temperature of the cooling liquid C in the cooling tank 6 of the cooling chamber 4, a control unit 8, and an operation / display unit 9.

[0036] In this embodiment, the heating chamber 3 and cooling chamber 4 of the heat treatment mechanism 2 form a heat treatment space for carburizing the workpiece 100. The heating chamber 3 and cooling chamber 4 may be used for other heat treatments, such as nitriding, carbonitriding, quenching, gas nitrocarburizing, and aluminumization, in addition to carburizing. The heat treatment mechanism 2 may be a batch furnace that replaces the workpiece 100 in the heat treatment mechanism 2 after each heat treatment cycle (carburizing), or a continuous furnace that transports the workpiece 100 in one direction while sequentially and continuously heat-treating multiple workpieces 100. In this embodiment, the heat treatment mechanism 2 is described as a batch furnace. The path of the workpiece 100 in the heat treatment mechanism 2 of this embodiment is indicated by a dashed line.

[0037] In this embodiment, the heat treatment mechanism 2 has a heating chamber 3, a cooling chamber 4, a first door 11 for opening and closing the entrance / exit 4a of the cooling chamber 4, a first door opening / closing mechanism 12, a second door 14 for opening and closing the passage 13 between the heating chamber 3 and the cooling chamber 4, a second door opening / closing mechanism 15, and a transport mechanism 16 for transporting the workpiece 100 between the heating chamber 3 and the cooling chamber 4.

[0038] The heating chamber 3 is provided for heating, carburizing, and soaking the workpiece 100. The heating chamber 3 is formed in a hollow shape and can accommodate the workpiece 100. In this embodiment, the workpiece 100 is loaded into the heating chamber 3 through the cooling chamber 4.

[0039] The heating chamber 3 is provided with a heating chamber thermometer 5, a gas supply pipe 18 for introducing a heat treatment gas into the heating chamber 3, a fan 21, and a heating chamber heater 22.

[0040] The fan 21 is provided to agitate the gas (heat treatment gas) in the heating chamber 3. The fan 21 has an electric motor and agitating blades, and is driven to rotate during the heat treatment of the workpiece 100. This allows the gas to be distributed more evenly in the heating chamber 3.

[0041] The heating chamber heater 22 is provided to heat the gas in the heating chamber 3 and the workpiece 100. Examples of the heating chamber heater 22 include a gas burner and a resistance heater. The heating chamber heater 22 is configured to be able to change the temperature of the heating chamber 3.

[0042] The heating chamber thermometer 5 (temperature sensor) is provided to measure the ambient temperature inside the heating chamber 3. The heating chamber thermometer 5 includes, for example, a thermocouple, and a temperature measurement portion is disposed inside the heating chamber 3. The heating chamber thermometer 5 detects the ambient temperature inside the heating chamber 3 and outputs a detection signal obtained therefrom to the control unit 8.

[0043] The cooling chamber 4 is provided to quench the workpiece 100 heated in the heating chamber 3 by cooling (rapid cooling). The cooling chamber 4 is formed in a hollow shape and is capable of accommodating the workpiece 100. An entrance / exit 4a is formed in the cooling chamber 4, and the workpiece 100 is taken in and out of the cooling chamber 4 through this entrance / exit 4a.

[0044] The first door 11 opens the entrance 4a when the object to be treated 100 is loaded through the entrance 4a, but is closed except when the object to be treated 100 is passing through the entrance 4a. The first door opening / closing mechanism 12 includes a power source such as a pneumatic cylinder, and is configured to open and close the first door 11 when a predetermined command signal is given to it.

[0045] The space within the cooling chamber 4 is continuous with the space within the heating chamber 3 via a passage 13. The cooling chamber 4 includes a cooling tank 6 that stores a coolant C that cools the heated workpiece 100. The cooling tank 6 is disposed, for example, below the cooling chamber 4, and the workpiece 100 is quenched by being immersed in the coolant C in the cooling tank 6. In this embodiment, the coolant C is quenching oil, but it may be other cooling media such as cooling water.

[0046] The cooling chamber 4 is provided with a liquid thermometer 7, a temperature adjustment mechanism 25 for adjusting the temperature of the cooling liquid C, and an agitator .

[0047] The temperature adjustment mechanism 25 includes a cooling unit 27 for cooling the coolant C and a heating unit 28 for heating the coolant C.

[0048] The cooling unit 27 includes, for example, a heat exchanger 27a that is provided in a pipe 27c that is installed so that the coolant C in the cooling tank 6 circulates and that comes into contact with the coolant C, and a pump 27b that pumps the coolant C so that the coolant C circulates between the cooling tank 6 and the pipe 27c. The cooling unit 27 starts operation of the pump 27b in response to a predetermined command signal (operation start signal) from the control unit 8, causing the coolant C to pass through the heat exchanger 27a, thereby continuing the cooling operation of the coolant C, and stops operation of the pump 27b in response to a predetermined command signal (operation stop signal) from the control unit 8, thereby stopping the cooling operation of the coolant C. In this embodiment, "driving the cooling unit 27" refers to driving the pump 27b. Note that the specific configuration of the cooling unit 27 is not limited as long as it is capable of lowering the temperature of the coolant C and is configured to perform the cooling operation in response to the command signal from the control unit 8.

[0049] Heating unit 28 is disposed, for example, so as to come into contact with coolant C in cooling tank 6. Heating unit 28 continues the heating operation of coolant C when a predetermined command signal (operation start signal) is given from control unit 8, and stops the heating operation of coolant C when a predetermined command signal (operation stop signal) is given from control unit 8. Note that heating unit 28 may have any configuration as long as it is capable of increasing the temperature of coolant C and performs the heating operation when given the command signal from control unit 8, and the specific configuration is not limited. Another example of heating unit 28 is a heat pump heater.

[0050] The agitator 26 is provided to agitate the coolant C. The agitator 26 has an agitating blade disposed in the coolant C and an electric motor that rotates the agitating blade. For example, the agitator 26 may be constantly rotated to agitate the coolant C while the workpiece 100 is carried into the heat treatment mechanism 2, thereby operating to make the temperature of the coolant C in the cooling tank 6 as uniform as possible.

[0051] The thermometer 7 is an example of the "temperature sensor" of the present invention. The thermometer 7 is provided to measure the temperature of the coolant C. The thermometer 7 includes, for example, a thermocouple, and a temperature measurement portion is disposed in the cooling tank 6. The thermometer 7 detects the temperature of the coolant C and outputs a detection signal obtained therefrom to the control unit 8.

[0052] The second door 14 opens the passage 13 when the workpiece 100 is transported between the heating chamber 3 and the cooling chamber 4, but is closed while the workpiece 100 is being heated in the heating chamber 3. The second door opening / closing mechanism 15 includes a power source such as a pneumatic cylinder, and is configured to open and close the second door 14 in response to a predetermined command signal. The timing at which the second door 14 is opened and closed is set appropriately.

[0053] The transport mechanism 16 has a table on which the workpiece 100 is placed and a movement mechanism for moving the table. The movement mechanism has, for example, an electric motor and a motion conversion mechanism that converts the output of the electric motor into a force for moving the table. The transport mechanism 16 is configured to move the workpiece 100 between a position within the heating chamber 3, a position above the cooling tank 6 in the cooling chamber 4, and a position where the entire workpiece 100 is immersed in the coolant C.

[0054] The control unit 8 is provided to control various devices of the heat treatment apparatus 1, including the temperature adjustment mechanism 25. The control unit 8 is formed using a PLC (Programmable Logic Controller) or the like. The control unit 8 may be formed using a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory), may have a configuration including an FPGA (Field Programmable Gate Array), or may be formed using a sequence circuit or the like.

[0055] When the control unit 8 has a configuration including a calculation device, a program for the control unit 8 to perform the processes described in this embodiment is stored in the control unit 8 or is provided from an external source. For example, the operation of the control unit 8 in this embodiment can be realized by loading this program into the memory of the calculation device and executing it.

[0056] The control unit 8 is electrically connected to the heating chamber thermometer 5, the fan 21, the heating chamber heater 22, the liquid thermometer 7, the first door opening / closing mechanism 12, the second door opening / closing mechanism 15, the conveying mechanism 16, the agitator 26, the cooling unit 27, the heating unit 28, and the operation / display unit 9.

[0057] The control unit 8 receives the detection result of the heating chamber temperature by the heating chamber thermometer 5. The control unit 8 outputs a command signal to the fan 21 to control the rotation operation of the fan 21. The control unit 8 outputs a command signal to the heating chamber heater 22 to control the heating operation inside the heating chamber 3 by the heating chamber heater 22 and the heating chamber temperature.

[0058] The control unit 8 receives the detection result of the coolant temperature by the liquid thermometer 7. The control unit 8 controls the opening and closing operation of the first door 11 by outputting a command signal to the first door opening / closing mechanism 12. The control unit 8 controls the opening and closing operation of the second door 14 by outputting a command signal to the second door opening / closing mechanism 15. The control unit 8 controls the transport operation of the workpiece 100 by the transport mechanism 16 by outputting a command signal to the agitator 26. The control unit 8 drives the agitator 26, for example, while the heating operation of the coolant C is being performed by the heating unit 28 and while the cooling operation of the coolant C is being performed by the cooling unit 27. The control unit 8 controls the cooling operation of the coolant C by the cooling unit 27 by outputting a command signal to the heating unit 28. The control unit 8 controls the heating operation of the coolant C by the heating unit 28 by outputting a command signal to the heating unit 28.

[0059] The operation and display unit 9 is, for example, a touch panel, and is configured to display various operation keys and information. The operation and display unit 9 is configured to communicate with the control unit 8. A command signal generated by an operator operating the operation and display unit 9 is output from the operation and display unit 9 to the control unit 8. In addition, the control unit 8 outputs data specifying predetermined display content to the operation and display unit 9.

[0060] FIG. 3 is a diagram for explaining the relationship between the processing pattern of the workpiece 100 and the temperature of the coolant C. The upper diagram of FIG. 3 is a diagram for explaining the processing pattern of the workpiece 100, with the horizontal axis representing time and the vertical axis representing the actual measured value of the heating chamber temperature (ambient temperature inside the heating chamber). In this embodiment, the heating chamber temperature is substantially the same as the design temperature of the heating chamber 3. The lower diagram of FIG. 3 is a diagram for explaining the temperature of the coolant C, with the horizontal axis representing time and the vertical axis representing the temperature of the coolant C.

[0061] The processing pattern for the workpiece 100 is carburization, in which the heating chamber 3 is heated to a predetermined preheating temperature (e.g., approximately 900°C to 950°C) for preheating (timings A3 to A4). Next, carburization is performed while introducing heat treatment gas at a carburization temperature equal to the preheating temperature (timings A4 to A5). Further, diffusion is performed at a diffusion temperature equal to the preheating temperature and the carburization temperature (timings A5 to A6). Next, the heating chamber temperature is lowered by ΔF°C (e.g., approximately 50°C to 100°C) to the soaking temperature (timings A6 to A7), and the workpiece 100 is soaked for a certain period of time (timings A7 to A1). Next, the workpiece 100 is transferred to the cooling chamber 4 and immersed in the coolant C for quenching (timings A1 to A2'). During the initial period of the quenching period P1, purging is performed to replace the gas in the cooling chamber 4 with the heat treatment gas (timings A1 to A2). After purging is complete, the workpiece 100 is loaded into the heating chamber 3 through the cooling chamber 4 via the entrance / exit 4a. When the workpiece 100 is loaded into the heating chamber 3, the ambient temperature of the heating chamber 3 drops, and the heating chamber heater 22 returns the temperature of the heating chamber 3 to the preheating temperature (reheating) (timings A2 to A3). After reheating, the preheating (timings A3 to A4) and subsequent processes are repeated. For example, the workpiece 100 is immersed in the coolant C in the cooling chamber 4 during quenching, and is otherwise placed in the gas atmosphere of the heating chamber 3 or the cooling chamber 4. When the workpiece 100 is transported between the heating chamber 3 and the cooling chamber 4, the second door 14 is opened.

[0062] As described above, in this embodiment, the heat treatment device 1 is a carburizing treatment device that carburizes the workpiece 100, and after heating the workpiece 100 to a predetermined carburizing temperature, the temperature is lowered to a predetermined soaking temperature, the workpiece 100 is then maintained at the soaking temperature for a predetermined time, and the workpiece 100 is then placed in a cooling tank 6 to perform quenching.

[0063] In the above-mentioned treatment patterns, the treatment pattern in the heating chamber 3 includes "reheating", "preheating", "carburizing", "diffusion", "temperature reduction" and "soaking" as one cycle.

[0064] While the above processing pattern is being carried out in the heating chamber 3, in the cooling chamber 4, "quenching," "coolant temperature reduction," and "coolant temperature maintenance" are carried out.

[0065] 3, during the quenching period P1, purging, the workpiece 100 is loaded, and reheating begins (timings A1 to A2'). In this embodiment, the temperature of the coolant C is lowered (periods P2 to P4) after quenching is completed and continues until the later stage of temperature lowering in the heating chamber 3. In this embodiment, the coolant is kept at a constant temperature (constant temperature period P5) after the temperature of the coolant C is lowered until timing A1, when quenching begins.

[0066] In this embodiment, the temperature drop and constant temperature periods of the coolant C are performed for the above-mentioned periods, but this is not necessarily the case. The temperature drop period of the coolant C may be shorter or longer than the above-mentioned periods, and the constant temperature period of the coolant C may be omitted.

[0067] In this embodiment, the quenching period P1 is, for example, a period of about 20 minutes (timings A1 to A2'). The period from the end of the quenching period P1 to the completion of reheating is defined as a natural cooling period P2 (timings A2' to A3). The period from the start of preheating to the completion of diffusion is defined as a first slow-cooling period P3 (timings A3 to A6). The period from the end of the first slow-cooling period P3 to the middle of the temperature drop is defined as a second slow-cooling period P4 (timings A6 to A6'). The period from the end of the second slow-cooling period P4 to the completion of soaking is defined as a constant-temperature period P5 (timings A6' to A1). In the lower diagram of FIG. 3, periods P1 and P2 indicate an example of the measured temperature Tm of the coolant C, and periods P3 to P5 indicate an example of the target temperature Tt of the coolant C.

[0068] During the quenching period P1, the workpiece 100 is immersed in the coolant C, and the measured temperature Tm of the coolant C increases sharply, for example, by about 20°C, and then gradually decreases. In this embodiment, during the quenching period P1, the control unit 8 does not perform either a heating operation by the heating unit 28 or a cooling operation by the cooling unit 27, and instead allows the coolant C to cool naturally. The length of the quenching period P1 may be set by an operator operating the operation and display unit 9, or may be set by the operator selecting a processing pattern displayed on the operation and display unit 9. During the quenching period P1, the control unit 8 may also perform a cooling operation of the coolant C by the cooling unit 27.

[0069] During periods P2 to P5, the workpiece 100 is removed from the cooling tank 6. In this embodiment, during the natural cooling period P2, the control unit 8 executes the natural cooling mode, thereby not performing either the heating operation by the heating unit 28 or the cooling operation by the cooling unit 27. The control unit 8 determines that the natural cooling period P2 has ended when the measured temperature of the heating chamber 3 reaches the preheating temperature.

[0070] During the first slow-cooling period P3 and the second slow-cooling period P4, the control unit 8 is configured to execute an induction cooling mode. The induction cooling mode is a mode in which a target temperature Tt of the coolant C is set to change over time, and the temperature adjustment mechanism 25 is driven so that the measured temperature Tm of the coolant C becomes the target temperature Tt. Particularly in this embodiment, the induction cooling mode is a mode in which the temperature adjustment mechanism 25 is driven so that the measured temperature Tm of the coolant C falls within the target temperature Tt.

[0071] The control unit 8 sets the target temperature Tt for each unit time based on the period (P3, P4) from the start to the end of the induction cooling mode and the temperature difference ΔT1 (Tm1-Ttf) between the measured temperature Tm1 of the coolant C at the start of the induction cooling mode and the target temperature Ttf at the end of the induction cooling mode.

[0072] Specifically, the control unit 8 first refers to the first annealing period P3. When determining the first annealing period P3, the control unit 8 refers to the times required for preheating, carburizing, and diffusion. The times required for preheating, carburizing, and diffusion may be set, for example, by an operator operating the operation and display unit 9, or may be set by the operator selecting a processing pattern displayed on the operation and display unit 9. The control unit 8 then sets the total time required for preheating, carburizing, and diffusion (timings A3 to A6) as the first annealing period P3. The temperature of the heating chamber 3 during preheating, carburizing, and soaking may be set by the operator operating the operation and display unit 9, or may be set by the control unit 8 based on the operator selecting a processing pattern displayed on the operation and display unit 9.

[0073] Furthermore, the control unit 8 calculates a second slow-cooling period P4. When calculating the second slow-cooling period P4, the control unit 8 refers to the temperature drop time (the time between timings A6 and A7). The temperature drop time is the time it takes for the temperature of the workpiece 100 to drop from the diffusion temperature to the soaking temperature, and in this embodiment, it is the time it takes for the measured temperature of the heating chamber 3 to drop from the diffusion temperature to the soaking temperature. The control unit 8 calculates this temperature drop period based on the known characteristics of the heat treatment device 1, the treatment pattern of the workpiece 100, etc.

[0074] The control unit 8 calculates the temperature drop time (the time between timings A6 and A7) using the following formula (1). Cooling time = ΔF / Vm(min)…(1) Here, ΔF is (carburizing temperature−soaking temperature) in the heating chamber 3. Furthermore, Vm is the temperature drop rate (° C. / min) of the heating chamber 3 in the heat treatment mechanism 2, and is, for example, a constant.

[0075] In this embodiment, the time when the measured temperature Tm of the heating chamber 3 reaches the soaking temperature plus a predetermined temperature f (for example, 10°C), that is, the time when (ΔF-f) / Vm (min) is reached, is set as the second slow-cooling period P4. Expressed as a formula, the second slow-cooling period P4 is given by the following formula (2). Second slow cooling period P4=(ΔF-f) / Vm(min)...(2)

[0076] The control unit 8 may calculate the second slow-cooling period P4=(ΔF-f) / Vm(min) without calculating the temperature-dropping time=ΔF / Vm(min). The control unit 8 may also set the temperature-dropping time (the period from timing A6 to A7) to be the second slow-cooling period P4. That is, the second slow-cooling period P4 may end at the start of soaking (timing A7). The second slow-cooling period P4 may also end immediately before the start of quenching (timing A1). In this case, the control unit 8 may set the second slow-cooling period P4 to the total period (timing A6 to A1) of the temperature-dropping time (the period from timing A6 to A7) and the soaking period (the period from timing A7 to A1).

[0077] The control unit 8 sets the above-mentioned first slow-cooling period P3+second slow-cooling period P4 as the induction cooling mode execution period.

[0078] Next, the control unit 8 calculates the temperature difference ΔT1 between the measured temperature Tm1 of the coolant C at timing A3 when the reheating is completed (when the heating chamber temperature reaches the preheating temperature) and the target temperature Ttf of the coolant C during soaking, i.e., immediately before the next quenching. This target temperature Ttf is the final target temperature of the coolant C, and is set in advance based on the processing pattern of the workpiece 100, etc. The final target temperature Ttf of the coolant C may be set by an operator operating the operation and display unit 9, or may be set by the control unit 8 based on the operator setting the processing pattern displayed on the operation and display unit 9.

[0079] In this embodiment, in the induction cooling mode, the control unit 8 sets the target temperature Tt of the coolant C so that it decreases linearly over time. Furthermore, in this embodiment, the target temperature Tt has a predetermined temperature range (Tt1-Tt2). Within the temperature range (Tt1-Tt2), a target core temperature Tt0, a target upper limit temperature Tt1 that is higher than the target core temperature Tt0, and a target lower limit temperature Tt2 that is lower than the target core temperature Tt0 are set. The control unit 8 drives the temperature adjustment mechanism 25 so that the measured temperature Tm falls between the target upper limit temperature Tt1 and the target lower limit temperature Tt2.

[0080] More specifically, the control unit 8 sets the target core temperature Tt0 for each time Px in the induction cooling mode at the start of the first slow-cooling period T3. In this embodiment, the target core temperature Tt0 is set so that the rate of decrease of the target core temperature Tt0 is constant during the induction cooling mode execution period (periods P3+P4). In other words, the control unit 8 sets the target core temperature Tt0 = Tm1 - {Px / (P3+P4)} × ΔT1, the measured temperature of the coolant C at the start of the induction cooling mode. In the lower diagram of FIG. 3, this target core temperature Tt0 is shown as a linear graph.

[0081] In this embodiment, in the first slow-cooling period P3, the target upper limit temperature Tt1 is set as the target core temperature Tt0 + α1°C (in this embodiment, α1°C = 3°C), and the target lower limit temperature Tt2 is set as the target core temperature Tt0 - α2°C (in this embodiment, α2°C = 3°C). Note that α1 and α2 may be less than 3 or greater than or equal to 3. Furthermore, α1 and α2 may be the same value or different values.

[0082] In this embodiment, in the second slow-cooling period P4, the target upper limit temperature Tt1 is set as the target core temperature Tt0 + α3°C (in this embodiment, α3°C = 1°C), and the target lower limit temperature Tt2 is set as the target core temperature Tt0 - α4°C (in this embodiment, α4°C = 1°C). Note that α3 and α4 may be less than 1 or greater than 1. Furthermore, α3 and α4 may be the same value or different values.

[0083] In this embodiment, the difference (Tt1-Tt2) between the target upper limit temperature Tt1 and the target lower limit temperature Tt2 in the second slow cooling period P4, i.e., in the latter part of the induction cooling mode (2°C in this embodiment), is smaller than the difference (Tt1-Tt2) between the target upper limit temperature Tt1 and the target lower limit temperature Tt2 in the first slow cooling period P3, i.e., in the early part of the induction cooling mode (6°C in this embodiment).

[0084] In this embodiment, when switching from the first slow-cooling period P3 to the second slow-cooling period P4, the control unit 8 is configured to reset the target temperature Tt for each unit time (e.g., each time it takes to decrease the temperature of the coolant C by 1°C). Specifically, the control unit 8 calculates the temperature difference ΔT2 between the measured temperature Tm2 of the coolant C at the end of the first slow-cooling period P3 (timing A6 set by the control unit 8) and the target temperature Ttf of the coolant C during soaking, i.e., immediately before the next quenching. Next, the control unit 8 sets the target core temperature Tt0 for each time Px (e.g., each time it takes to decrease the temperature of the coolant C by 1°C) during the second slow-cooling period P4. At this time, the target core temperature Tt0 is again set so that the rate of decrease of the target core temperature Tt0 is constant during the second slow-cooling period P4.

[0085] That is, the target core temperature Tt0 = the measured temperature of the coolant C at the start of the second slow-cooling period P4 Tm2 - (Px / P4) × ΔT2 is set by the control unit 8. In the lower diagram of Fig. 3, for convenience, the target core temperature Tt0 after resetting is set to the same as the graph of the target core temperature Tt0 before resetting.

[0086] It should be noted that the control unit 8 does not need to reset the target temperature Tt at the start of the second slow-cooling period P4.

[0087] During the induction cooling mode execution period, which includes the first slow-cooling period P3 and the second slow-cooling period P4, the control unit 8 drives the temperature adjustment mechanism 25 so that the measured temperature Tm of the coolant C becomes the target temperature Tt. As described above, in this embodiment, the control unit 8 predicts the temperature drop time (the time from timing A6 to A7) required for the temperature of the workpiece 100 to drop from the carburizing temperature to the soaking temperature, and ends the induction cooling mode midway through the temperature drop time (timing A6'). Next, during the constant temperature period P5, the control unit 8 executes the constant temperature mode, controlling the temperature adjustment mechanism 25 to maintain the target temperature constant.

[0088] During the constant temperature period P5, the control unit 8 operates in the constant temperature mode, thereby driving the temperature adjustment mechanism 25 so that the measured temperature Tm of the coolant C becomes the constant target temperature Ttf. Specifically, the control unit 8 sets the time from the end of the second slow-cooling period P4 to the end of soaking (timing A6' to A1) as the constant temperature period P5. The soaking period may be set by an operator operating the operation and display unit 9, or may be set by the control unit 8 based on the operator selecting a processing pattern displayed on the operation and display unit 9.

[0089] Next, the control unit 8 sets a target core temperature Tt0, a target upper limit temperature Tt1, and a target lower limit temperature Tt2 as the target temperatures Tt of the coolant C. During the constant temperature period P5, the target core temperature Tt0 is the final target temperature Ttf of the coolant C (Tt0 = Ttf). The target upper limit temperature Tt1 is a temperature that is higher than the target core temperature Tt0 by, for example, 0 to 2°C. The target lower limit temperature Tt2 is a temperature that is lower than the target core temperature Tt0 by, for example, 0 to 2°C. When the actual measured temperature Tm of the coolant C is equal to or higher than the target upper limit temperature Tt1, the control unit 8 drives the cooling unit 27 to lower the temperature of the coolant C, and when the actual measured temperature Tm of the coolant C is equal to or lower than the target lower limit temperature Tt2, the control unit 8 drives the heating unit 28 to raise the temperature of the coolant C.

[0090] As described above, during the quenching period P1 and the natural cooling period P2, the control unit 8 executes the natural cooling mode, thereby not driving either the heating unit 28 or the cooling unit 27, and naturally cools the coolant C, particularly during the natural cooling period P2. During the first slow cooling period P3 and the second slow cooling period P4, the control unit 8 executes the induction cooling mode, thereby driving the temperature adjustment mechanism 25 so that the measured temperature Tm of the coolant C gradually decreases. Furthermore, during the constant temperature period P5, the control unit 8 drives the temperature adjustment mechanism 25 so that the measured temperature Tm of the coolant C becomes a constant target core temperature Tt0.

[0091] In this embodiment, the control unit 8 is configured to minimize the time during which the heating unit 28 performs the heating operation on the coolant C. The history of the measured temperature Tm of the coolant C obtained by the temperature control of the coolant C by the control unit 8 will be described in more detail with reference to two examples shown in FIGS.

[0092] In this embodiment, the control unit 8 can execute temperature control of the coolant C according to the "forced cooling control example" shown in Fig. 4 and temperature control of the coolant C according to the "heating control example" shown in Fig. 5. The temperature control of the coolant C according to the "forced cooling control example" shown in Fig. 4 is performed when the natural cooling rate of the coolant C is slower than the target cooling rate (amount of decrease in the target temperature Tt per unit time) determined by setting the target temperature Tt for each time Px. On the other hand, the temperature control of the coolant C according to the "heating control example" shown in Fig. 5 is performed when the natural cooling rate of the coolant C is faster than the target cooling rate.

[0093] 4 is a diagram showing an example of the history of the measured temperature Tm of the coolant C in the "forced cooling control example." The measured temperature Tm is indicated by a solid line.

[0094] 1 and 4, as described above, during the quenching period P1 and the natural cooling period P2, the control unit 8 executes the natural cooling mode, thereby not driving either the heating unit 28 or the cooling unit 27. When the workpiece 100 is immersed in the coolant C and quenched under these conditions, the measured temperature Tm of the coolant C rises sharply in the first half of the quenching period P1 and then falls gradually.

[0095] Then, when the natural cooling period P2 ends and the first slow-cooling period P3 begins, the control unit 8 executes the induction cooling mode. In the induction cooling mode, the control unit 8 drives the temperature adjustment mechanism 25 so that the measured temperature Tm falls within the target temperature Tt set per unit time (the time required to reduce the temperature of the coolant C by 1°C). In the "forced cooling control example" of Fig. 4, the control unit 8 drives the cooling unit 27 to cool the coolant C when the measured temperature Tm is higher than the target core temperature Tt0.

[0096] When the measured temperature Tm of the coolant C is equal to the target upper limit temperature Tt1, the control unit 8 starts driving the cooling unit 27 to cool the coolant C. For example, during the first slow-cooling period P3, the control unit 8 naturally cools the coolant C until a certain timing D1. Then, at timing D1, the control unit 8 determines that the measured temperature Tm of the coolant C has reached the target upper limit temperature Tt1, and drives the cooling unit 27 to cool the coolant C. Then, at timing D2 after timing D1, the control unit 8 determines that the measured temperature Tm of the coolant C has dropped to the target core temperature Tt0, and stops driving the cooling unit 27.

[0097] In this manner, when the measured temperature Tm of the coolant C reaches the target upper limit temperature Tt1, the cooling unit 27 starts cooling the coolant C. Then, when the measured temperature Tm reaches the target core temperature Tt0, the operation of the cooling unit 27 is stopped. This operation is repeated, so that the measured temperature Tm gradually drops in a stepwise manner during the first slow-cooling period P3. Note that in the forced cooling control example, the heating unit 28 does not perform a heating operation whether the cooling unit 27 is operating or not. Also, in the forced cooling control example, the operation of the cooling unit 27 may be stopped when the measured temperature Tm reaches any temperature between the target upper limit temperature Tt1 and the target lower limit core temperature Tt2.

[0098] When the first slow-cooling period P3 ends and the second slow-cooling period P4 begins, the control unit 8 resets the target temperature Tt as described above. The control unit 8 then continues to drive the temperature adjustment mechanism 25 so that the measured temperature Tm falls within the set target temperature Tt. In the second slow-cooling period P4, the temperature adjustment mechanism 25 is driven in the same manner as in the first slow-cooling period P3, except that the temperature width of the target temperature Tt is different, so that the measured temperature Tm gradually decreases in a stepwise manner.

[0099] When the second slow-cooling period P4 ends and the constant temperature period P5 begins, the control unit 8 sets the target core temperature Tt0 to a constant final target temperature Ttf and controls the temperature adjustment mechanism 25 so that the measured temperature Tm becomes the final target temperature Ttf. During the constant temperature period P5, the control unit 8 heats the coolant C by the heating unit 28 when the measured temperature Tm reaches the target lower limit temperature Tt2.

[0100] Fig. 5 is a diagram showing an example of the history of the measured temperature Tm of the coolant C in the "heating control example." With reference to Figs. 1 and 5, the "heating control example" shown in Fig. 5 differs from the "forced cooling control example" shown in Fig. 4 in the control content in the induction cooling mode in the first slow-cooling period P3 and the second slow-cooling period P4. The control of the temperature adjustment mechanism 25 by the control unit 8 in periods P1, P2, and P5 is the same as in the example shown in Fig. 4, so a description thereof will be omitted.

[0101] In the "heating control example" of FIG. 5, the control unit 8 drives the heating unit 28 to heat the coolant C when the measured temperature Tm is lower than the target core temperature Tt0.

[0102] When the measured temperature Tm of the coolant C is equal to the target lower-limit temperature Tt2, the control unit 8 starts driving the heating unit 28 to heat the coolant C. For example, during the first slow-cooling period P3, the control unit 8 naturally cools the coolant C until a certain timing E1. Then, at timing E1, the control unit 8 determines that the measured temperature Tm has reached the target lower-limit temperature Tt2, and drives the heating unit 28 to heat the coolant C. Then, at timing E2 after timing E1, the control unit 8 determines that the measured temperature Tm has risen to the target core temperature Tt0, and stops driving the heating unit 28.

[0103] In this manner, when the measured temperature Tm of the coolant C reaches the target lower-limit temperature Tt2, the heating unit 28 starts heating the coolant C. Then, when the measured temperature Tm reaches the target core temperature Tt0, the driving of the heating unit 28 is stopped. This operation is repeated, so that the measured temperature Tm gradually drops in a stepwise manner during the first slow-cooling period P3. Note that in the heating control example, the cooling operation by the cooling unit 27 is not performed whether the heating unit 28 is operating or not. Also, in the heating control example, the driving of the heating unit 28 may be stopped when the measured temperature Tm reaches any temperature between the target upper-limit temperature Tt1 and the target lower-limit core temperature Tt2.

[0104] When the first slow-cooling period P3 ends and the second slow-cooling period P4 begins, the control unit 8 resets the target temperature Tt as described above. The control unit 8 then continues to drive the temperature adjustment mechanism 25 so that the measured temperature Tm falls within the set target temperature Tt. In the second slow-cooling period P4, the temperature adjustment mechanism 25 is driven in the same manner as in the first slow-cooling period P3, except that the temperature range (Tt1-Tt2) of the target temperature Tt is different, so that the measured temperature Tm gradually decreases in a stepwise manner.

[0105] As described above, in this embodiment, in the induction cooling mode, the control unit 8 sets the target temperature Tt of the coolant C to change over time and drives the temperature adjustment mechanism 25 so that the measured temperature Tm of the coolant C becomes the target temperature Tt. This configuration allows the coolant C, whose temperature has risen when the heated workpiece 100 is placed in the cooling tank 6, to be cooled during the time until the next heated workpiece 100 is placed in the cooling tank 6. During this cooling, the control unit 8 sets the target temperature Tt of the coolant C to change over time in the induction cooling mode (slow cooling periods P3 and P4) and drives the temperature adjustment mechanism 25 so that the measured temperature Tm of the coolant C becomes the target temperature Tt. This configuration prevents the coolant C from being rapidly cooled by the cooling unit 27. This allows the control unit 8 to gradually lower the temperature of the coolant C. As a result, once the temperature of the coolant C reaches the temperature (final target temperature Ttf) required at the start of quenching the workpiece 100, the heating operation of the coolant C for maintaining this temperature can be reduced to zero or to a minimum. In other words, as a result of being able to reduce the energy required to heat the coolant C, the heat treatment device 1 that performs a process of cooling the heated workpiece 100, such as quenching, can be configured to be highly energy-efficient, and operating costs such as energy costs can be reduced.

[0106] Furthermore, according to this embodiment, the target temperature Tt per unit time required when the induction cooling mode is executed can be set based on the period from the start to the end of the induction cooling mode (slow cooling periods P3 and P4) and the temperature difference ΔT1 between the measured temperature Tm1 at the start of the induction cooling mode and the target temperature Ttf at the end of the induction cooling mode. This allows the target temperature per unit time to be set with simple calculations and with a high degree of freedom.

[0107] Furthermore, in this embodiment, in the induction cooling mode, the control unit 8 linearly lowers the target temperature Tt of the coolant C over time. With this configuration, the target temperature Tt per unit time required when executing the induction cooling mode can be set by simple calculation.

[0108] Furthermore, according to this embodiment, since the target temperature Tt is set within a temperature range (Tt1-Tt2), the coolant temperature does not need to be controlled strictly, and the coolant temperature control can be achieved with a simpler configuration.

[0109] Furthermore, in this embodiment, the difference (Tt1-Tt2) between the target upper limit temperature Tt1 and the target lower limit temperature Tt2 in the later period (period P4) of the induction cooling mode is smaller than the difference (Tt1-Tt2) between the target upper limit temperature Tt1 and the target lower limit temperature Tt2 in the early period (period P3) of the induction cooling mode. With this configuration, after cooling the workpiece 100, the temperature of the coolant C into which the heated workpiece 100 is then introduced can be more accurately brought closer to the required temperature (final target temperature Ttf).

[0110] Furthermore, according to this embodiment, when the measured temperature Tm is higher than the target core temperature Tt0, the control unit 8 can drive the cooling unit 27 to cool the coolant C. With this configuration, the trigger for starting to drive the cooling unit 27 can be configured simply.

[0111] Furthermore, according to this embodiment, the control unit 8 can start driving the cooling unit 27 to cool the coolant C when the measured temperature Tm is at the target upper limit temperature Tt1, and can stop driving the cooling unit 27 when the measured temperature Tm drops to the target core temperature Tt0. This configuration can prevent the cooling unit 27 from excessively cooling the coolant C. This can reduce the need for a large amount of energy-intensive operation, such as reheating the coolant C by the heating unit 28 due to an excessive drop in the coolant temperature.

[0112] Furthermore, according to this embodiment, when the measured temperature Tm is lower than the target core temperature Tt0, the control unit 8 can drive the heating unit 28 to heat the coolant C. With this configuration, the temperature of the coolant C can be maintained so that it does not become too low below the target core temperature Tt0.

[0113] Furthermore, according to this embodiment, the control unit 8 can start driving the heating unit 28 to heat the coolant C when the measured temperature Tm is at the target lower limit temperature Tt2, and can stop driving the heating unit 28 when the measured temperature Tm rises to the target core temperature Tt0. This configuration can prevent the heating unit 28 from excessively heating the coolant C. As a result, the temperature of the coolant C can be maintained with minimal heating.

[0114] Furthermore, in this embodiment, the control unit 8 predicts the temperature drop time (the time from timing A6 to A7) required for the temperature of the workpiece 100 to drop from the carburizing temperature to the soaking temperature, terminates the induction cooling mode midway through this temperature drop time (timing A6', the end of period P4), and then executes the constant temperature mode (constant temperature period P5). With this configuration, the control unit 8 can execute the induction cooling mode for a longer period of time. Accordingly, the time for executing the constant temperature mode can be shortened accordingly. In the constant temperature mode (constant temperature period P5), the target temperature Tt must be maintained constant, so the heating unit 28 must frequently heat the coolant C. However, by shortening the execution time of this constant temperature mode, the energy consumption associated with the heating operation can be reduced.

[0115] Although the embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims.

[0116] (1) In the above-described embodiment, in the induction cooling mode (slow cooling periods P3 and P4) of the "heating control example" shown in FIG. 5, the heating unit 28 repeatedly heats the coolant C, gradually lowering the measured temperature Tm of the coolant C. However, this does not have to be the case. For example, when the measured temperature Tm of the coolant C is lower than the target core temperature Tt0, the heating unit 28 may temporarily heat the coolant C so that the measured temperature Tm of the coolant C reaches a temperature between the target core temperature Tt0 and the target upper limit temperature Tt1. Thereafter, as shown in the "forced cooling control example" of FIG. 4, the cooling unit 27 may intermittently cool the coolant C. In this case, the time over which the heating unit 28 heats the coolant C in the induction cooling mode can be shortened.

[0117] (2) In the above embodiment, the target temperature Tt is continuously (linearly) decreased over time in the induction cooling mode (first slow cooling period P3 and second slow cooling period P4). 。

[0118] (3) In the above embodiment, an example has been described in which the cooling operation of the coolant C by the cooling unit 27 is not performed during the quenching period P1 and the natural cooling period P2. However, this does not have to be the case. For example, the control unit 8 may perform the cooling operation of the coolant C by the cooling unit 27 during the quenching period P1. Furthermore, the control unit 8 may perform the cooling operation of the coolant C by the cooling unit 27 during the natural cooling period P2. An operator may operate the operation and display unit 9 to select whether natural cooling or the cooling operation of the coolant C by the cooling unit 27 is to be performed during the quenching period P1 and the natural cooling period P2.

[0119] (4) In the above embodiment, the end of the natural cooling period P2 was the point at which the measured temperature Tm of the heating chamber 3 returned to the preheating temperature. However, this does not have to be the case. The end of the natural cooling period P2 may be a point after the start of preheating. Furthermore, the natural cooling period P2 may be omitted, and the first slow cooling period P3 may start immediately after the quenching period P1.

[0120] (5) The end of the second slow-cooling period T4 may also be the end of the soaking period (time A1), in which case the constant temperature mode can be omitted.

[0121] (6) In the above-described embodiment, the heat treatment device 1 is a carburizing treatment device. However, this is not necessarily the case. For example, the present invention may be applied to other heat treatment devices, such as nitriding treatment devices, carbonitriding treatment devices, quenching devices, gas soft-nitriding treatment devices, and aluminum solution treatment devices. Even when the present invention is applied to the above-described other heat treatment devices, the control unit can execute the induction cooling mode, for example, between the completion of quenching with a coolant and the next quenching.

[0122] Next, an example of control when the heat treatment device 1 performs a process other than carburizing will be described. Note that the following mainly describes differences from the embodiment, and the same components as those in the embodiment will be denoted by the same reference numerals or explanations in the drawings, and detailed description will be omitted.

[0123] FIG. 6 is a diagram illustrating the relationship between the treatment pattern of the workpiece and the coolant temperature in a modified example in which the heat treatment device 1 performs a treatment different from that of a carburizing treatment device. In the modified example shown in FIG. 6, the heat treatment device 1 heats the workpiece 100 at a heat treatment temperature instead of the preheating, carburizing, and diffusion temperatures used in the embodiment. Also, in the modified example shown in FIG. 6, soaking at a temperature lower than the heat treatment temperature is not performed. The upper diagram in FIG. 6 is a diagram illustrating the treatment pattern of the workpiece 100, with the horizontal axis representing time and the vertical axis representing the measured temperature of the heating chamber (ambient temperature within the heating chamber). The lower diagram in FIG. 6 is a diagram illustrating the temperature of the coolant C, with the horizontal axis representing time and the vertical axis representing the temperature of the coolant C.

[0124] The processing pattern for the workpiece 100 in the modified example shown in FIG. 6 will be described. Heating processing is performed by heating the heating chamber 3 to a predetermined heat processing temperature and heating the workpiece 100 (timings A3 to A1). Next, the workpiece 100 is transported to the cooling chamber 4 and immersed in the coolant C for quenching (timings A1 to A2'). During the initial period of the quenching period P1, purging is performed to replace the gas in the cooling chamber 4 with a heat treatment gas (timings A1 to A2). After purging is complete, the workpiece 100 is loaded into the heating chamber 3 through the cooling chamber 4 via the inlet / outlet 4a. When the workpiece 100 is loaded into the heating chamber 3, the ambient temperature of the heating chamber 3 drops, and the heating chamber heater 22 returns the temperature of the heating chamber 3 to the heating chamber temperature (reheating) (timings A2 to A3). After reheating, the processing from timing A3 onwards is repeated.

[0125] In the above-mentioned processing pattern, the processing pattern in the heating chamber 3 includes "reheating" and "heating" as one cycle.

[0126] While the above processing pattern is being carried out in the heating chamber 3, in the cooling chamber 4, "quenching," "coolant temperature reduction," and "coolant temperature maintenance" are carried out.

[0127] As shown in FIG. 6, during the quenching period P1, purging, the workpiece 100 is loaded, and reheating begins (timings A1 to A2'). In this modified example, the temperature of the coolant C is lowered (periods P2 to P4) for a predetermined period after quenching is completed (timings A2' to A3''). In this modified example, the constant temperature of the coolant (constant temperature period P5) is maintained until the timing when quenching begins after the temperature of the coolant C is lowered (timings A3'' to A1).

[0128] In this modification, the period from the end of the quenching period P1 to the completion of reheating is defined as a natural cooling period P2 (timing A2' to A3). Furthermore, the period from the start to the middle of the period during which the heating chamber temperature is at the heat treatment temperature is defined as a first slow cooling period P3 (timing A3 to A3'). Furthermore, a predetermined period from the end of the first slow cooling period P3 is defined as a second slow cooling period P4 (timing A3' to A3''). Furthermore, the period from the end of the second slow cooling period P4 to just before the start of quenching is defined as a constant temperature period P5 (timing A3'' to A1). In the lower diagram of FIG. 6, periods P1 and P2 show an example of the measured temperature Tm of the coolant C, and periods P3 to P5 show an example of the target temperature Tt of the coolant C.

[0129] In this embodiment, the temperature drop and constant temperature periods of the coolant C are performed for the above-mentioned periods, but this is not necessarily the case. The temperature drop period of the coolant C may be shorter or longer than the above-mentioned periods, and the constant temperature period of the coolant C may be omitted.

[0130] In this modified example, the timings A1, A2, A2', A3, A3', and A3'' may be set by an operator operating the operation and display unit 9, or may be set in response to the operator selecting a processing pattern displayed on the operation and display unit 9. The timings A2 and A3 may be left to chance. Similarly, the quenching period P1, the natural cooling period P2, the first slow cooling period P3, the second slow cooling period P4, and the constant temperature period P5 may be set by an operator operating the operation and display unit 9, or may be set in response to the operator selecting a processing pattern displayed on the operation and display unit 9. The natural cooling period P2 may be left to chance.

[0131] During periods P2 to P5, the workpiece 100 is removed from the cooling tank 6. In this modification, the control unit 8 executes the natural cooling mode during the quenching period P1 and the natural cooling period P2. The control unit 8 determines that the natural cooling period P2 has ended when the measured temperature in the heating chamber 3 reaches the heat treatment temperature (timing A3).

[0132] In the first slow-cooling period P3 and the second slow-cooling period P4, the control unit 8 is configured to execute the induction cooling mode.

[0133] The control unit 8 sets the target temperature Tt for each unit time based on the period from the start to the end of the induction cooling mode (periods P3, P4) and the temperature difference ΔT1 (Tm1-Ttf) between the measured temperature Tm1 of the coolant C at the start of the induction cooling mode and the target temperature Ttf at the end of the induction cooling mode.

[0134] Specifically, the control unit 8 first calculates the first slow-cooling period P3 and the second slow-cooling period P4. Then, the control unit 8 sets the above-mentioned first slow-cooling period P3+second slow-cooling period P4 as the induction cooling mode execution period.

[0135] Next, the control unit 8 calculates the temperature difference ΔT1 between the measured temperature Tm1 of the coolant C at time A3 (when the heating chamber temperature reaches the heat treatment temperature) and the target temperature Ttf of the coolant C at the end of the induction cooling mode (time A3'').

[0136] In this modification, similar to the embodiment, the control unit 8 sets the target temperature Tt of the coolant C in the induction cooling mode so as to decrease linearly with the passage of time.

[0137] In this modified example, when switching from the first slow-cooling period P3 to the second slow-cooling period P4, the control unit 8 is configured to reset the target temperature Tt for each unit time (for example, for each time it takes to lower the temperature of the cooling liquid C by 1°C).

[0138] The control unit 8 does not need to reset the target temperature Tt at the start of the second slow-cooling period P4. The control unit 8 may continue the same temperature control as in the first slow-cooling period P3 in the second slow-cooling period P4, in addition to the first slow-cooling period P3.

[0139] In this modification, the control unit 8 executes the constant temperature mode during the constant temperature period P5.

[0140] In this modified example, the control unit 8 can also perform temperature control of the cooling liquid C using the ``forced cooling control example'' shown in Figure 4 and temperature control of the cooling liquid C using the ``heating control example'' shown in Figure 5 during the first and second slow cooling periods P3 and P4.

[0141] (7) The present invention is not limited to any other configuration as long as the control unit 8 can at least execute the induction cooling mode. In other words, the present invention is not limited to any other configuration as long as the target temperature Tt of the coolant C is set to change over time and the temperature adjustment mechanism 25 is driven so that the measured temperature Tm of the coolant C becomes the target temperature Tt. [Industrial Applicability]

[0142] The present invention can be applied to a heat treatment device and a method for controlling the temperature of a coolant in the heat treatment device. [Explanation of symbols]

[0143] 1. Heat treatment equipment 6 Cooling tank 7 Liquid thermometer (temperature sensor) 8 Control Unit 25 Temperature adjustment mechanism 27 Cooling section 28 Heating section 100 Processing object C Coolant Tm Actual coolant temperature Tm1: Actual temperature at the start of induction cooling mode Tt Coolant target temperature Tt0 Target center temperature Tt1 Target upper limit temperature Tt2 Target lower limit temperature Ttf Target temperature at the end of induction cooling mode Tt1-Tt2 temperature range ΔT1 temperature difference

Claims

1. a cooling tank in which a cooling liquid for cooling the heated object to be treated is stored; a temperature sensor for measuring the temperature of the cooling liquid; a temperature adjustment mechanism including a cooling unit for cooling the cooling liquid and a heating unit for heating the cooling liquid; a control unit that controls the temperature adjustment mechanism, The control unit is configured to be able to execute an induction cooling mode, In the induction cooling mode, the control unit sets the target temperature of the cooling liquid to be linearly lowered over time to a final target temperature, and drives the temperature adjustment mechanism so that the actual measured temperature of the cooling liquid becomes the target temperature.

2. The heat treatment device according to claim 1, The control unit sets the target temperature based on a period from the start to the end of the induction cooling mode and a temperature difference between the actual measured temperature at the start of the induction cooling mode and the final target temperature at the end of the induction cooling mode.

3. The heat treatment apparatus according to claim 1 or 2, the target temperature has a predetermined temperature range, Within the temperature range, a target center temperature, a target upper limit temperature higher than the target center temperature, and a target lower limit temperature lower than the target center temperature are set, The control unit drives the temperature adjustment mechanism so that the actually measured temperature falls between the target upper limit temperature and the target lower limit temperature.

4. The heat treatment apparatus according to claim 3, a difference between the target upper limit temperature and the target lower limit temperature in a later stage of the induction cooling mode is smaller than a difference between the target upper limit temperature and the target lower limit temperature in an early stage of the induction cooling mode.

5. The heat treatment apparatus according to claim 3 or 4, The control unit drives the cooling unit to cool the cooling liquid when the measured temperature is higher than the target core temperature.

6. The heat treatment apparatus according to claim 5, the control unit starts driving the cooling unit to cool the cooling liquid when the actual measured temperature is the target upper limit temperature, and stops driving the cooling unit when the actual measured temperature drops to the target core temperature.

7. The heat treatment apparatus according to any one of claims 3 to 6, The control unit drives the heating unit to heat the cooling liquid when the measured temperature is lower than the target core temperature.

8. The heat treatment apparatus according to claim 7, the control unit starts driving the heating unit to heat the cooling liquid when the actual measured temperature is the target lower limit temperature, and stops driving the heating unit when the actual measured temperature rises to the target core temperature.

9. The heat treatment apparatus according to any one of claims 1 to 8, the heat treatment device is a carburizing treatment device that carburizes the workpiece, and is configured to heat the workpiece to a predetermined carburizing temperature, then lower the temperature to a predetermined soaking temperature, then maintain the workpiece at the soaking temperature for a predetermined time, and then introduce the workpiece into the cooling tank; the control unit is configured to predict a temperature drop time required for the temperature of the workpiece to drop from the carburizing temperature to the soaking temperature, terminate the induction cooling mode during the temperature drop time, and then execute a constant temperature mode in which the temperature adjustment mechanism is controlled to maintain the target temperature constant.

10. a cooling tank in which a cooling liquid for cooling the heated object to be treated is stored; a temperature adjustment mechanism including a cooling unit for cooling the cooling liquid and a heating unit for heating the cooling liquid; In a heat treatment apparatus comprising: A method for controlling the temperature of a cooling liquid in a heat treatment apparatus, comprising: setting a target temperature of the cooling liquid to be linearly lowered over time to a final target temperature; and driving the temperature adjustment mechanism so that the actual measured temperature of the cooling liquid becomes the target temperature.

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