JP7483364B2 - Method and apparatus for heat treatment of workpiece - Google Patents

Description

The present invention relates to a method for heat treating a workpiece and a heat treatment device.

For example, in the manufacturing process of an annular member made of steel such as SUJ2, such as the raceway of a rolling bearing, a quenching process is carried out to impart the mechanical strength required for the annular member. This heat treatment includes a heating process in which a heat treatment is carried out to heat the base material of the annular member (annular workpiece) to a target temperature, and a cooling process in which a cooling process is carried out to cool and quench the heated workpiece. The heating process can be carried out using an atmospheric heating furnace such as a mesh belt type continuous furnace, or an induction heating device. The cooling process can be carried out by immersing the workpiece in a cooling liquid such as water.

When quenching is performed on an annular workpiece as described above, the decrease in roundness may become a problem. The decrease in roundness may be caused by, for example, temperature unevenness during heating or cooling, uneven distribution of the metal structure, residual stress in the previous process, or expansion during martensitic transformation. For this reason, when performing finish processing after quenching, for example, a method of setting the finishing allowance in anticipation of the decrease in roundness is common. In addition, from the viewpoint of near-net shape and shortening the processing time, a method of correcting the shape of the workpiece by applying mechanical force after quenching has been proposed (see, for example, Patent Document 1), or a method of performing quenching while the workpiece is restrained by a mold has been proposed (see, for example, Patent Document 2). In particular, if the workpiece is restrained by a mold during quenching, the dimensional accuracy of the workpiece immediately after quenching is improved and heat treatment distortion is reduced, so that the subsequent heat treatment (tempering treatment, etc.) and finish processing can be simplified or omitted.

Japanese Patent Application Laid-Open No. 11-1721 JP 2010-248556 A

When the material, shape, or size (external diameter, thickness, etc.) of the workpiece to be quenched changes, it is necessary to set the quenching conditions appropriately according to the type of workpiece in order to minimize the distortion (heat treatment distortion) that occurs during quenching and to stably obtain a good metal structure. Here, as a result of the inventors' investigation, it was found that when cooling while restraining the workpiece with a mold, it is particularly necessary to appropriately adjust (1) the timing of cooling the workpiece, (2) the timing of restraining the workpiece with the mold, and (3) the restraining force of the mold according to the material, shape, size, etc. of the workpiece. This is because the cooling curve differs depending on the shape of the workpiece, and the volume of the part to be quenched changes if the thickness or height dimension differs, so it is necessary to match the timing of cooling, the timing of restraint, and the force (restraint force) at that time to the type of workpiece described above.

However, in conventional equipment, hydraulic lifting devices and presses are commonly used, making it difficult to set the above conditions (1) to (3) in detail for each workpiece. In particular, when using a method in which multiple molds are used depending on the temperature of the workpiece, as described in Patent Document 2, it becomes necessary to set the above conditions (2) and (3) as many times as the number of molds, which makes the above-mentioned problems more pronounced.

In view of the above, the technical problem to be solved in this specification is to provide a heat treatment method or heat treatment device that can obtain good heat treatment quality while simplifying adjustments when changing workpieces and reducing heat treatment distortion.

The above-mentioned problems are solved by the method for heat treating a workpiece according to the present invention. That is, this heat treatment method includes a heating step for heating the workpiece, and a cooling step for supplying a coolant to the workpiece heated in the heating step to cool the workpiece and perform a predetermined heat treatment. In at least the cooling step, the method for heat treating a workpiece cools the workpiece while it is restrained by a restraining mold, and is characterized in that the timing for moving the workpiece to the coolant supply area, the timing for restraining the workpiece by the restraining mold, and the restraining force of the workpiece by the restraining mold are all electrically controlled. Note that "controlling the timing" here means controlling the above-mentioned predetermined operation to be performed at a predetermined time.

In this way, in the heat treatment method according to the present invention, among the heat treatment conditions for the workpiece, the timing of moving the workpiece to the cooling liquid supply area, the timing of restraining the workpiece with the restraining mold, and the restraining force of the workpiece by the restraining mold are controlled, and all of these controls are performed electrically. By electrically controlling the movement timing and restraining timing of the workpiece, as well as the restraining force, the responsiveness of the corresponding drive device can be improved compared to, for example, a hydraulic drive type, and the cooling and restraining of the workpiece can be started at an appropriate timing. In addition, a restraining force of an appropriate magnitude can be applied to the workpiece. Therefore, it is possible to cool each workpiece while restraining it with the mold under appropriate temperature history and restraining conditions, which makes it possible to obtain a high-quality heat-treated product while reducing heat treatment distortion. In addition, by controlling electrically, adjustments when changing the workpiece can be made by simply changing the content of the control command, so that it is possible to significantly shorten the work time compared to mechanical adjustments on the drive side, such as replacing the restraining mold, and to improve production efficiency.

In addition, in the heat treatment method for a workpiece according to the present invention, the workpiece may be moved to the cooling liquid supply area by a servo actuator.

A servo actuator not only responds quickly to commands from the control unit, but also has excellent positioning accuracy, making it possible to improve not only the timing at which the workpiece begins to cool, but also the positioning accuracy of the cooling liquid supply area. This makes it possible to further improve cooling accuracy.

In addition, in the heat treatment method for a workpiece according to the present invention, the workpiece restraint operation using the restraint mold may be performed by a servo actuator.

A servo actuator can respond not only to commands from the control unit, but also to pressure control with high precision. Therefore, by driving the constraint mold with a servo actuator, it is possible to control not only the timing at which the constraint of the workpiece begins but also the constraint force within a more suitable range. This makes it possible to individually optimize the constraint conditions according to the type of workpiece.

In addition, in the heat treatment method for a workpiece according to the present invention, the workpiece may be rotated by a motor in the area where the cooling liquid is supplied.

By rotating the workpiece in this manner in the coolant supply area, the workpiece can be cooled evenly. In particular, if the workpiece is annular, the workpiece can be cooled evenly in the circumferential direction, which makes it possible to more effectively reduce heat treatment distortion. Furthermore, in this case, if the workpiece is rotated by a motor, the timing at which the workpiece starts to rotate and the rotation speed can be controlled with high precision, making it possible to precisely adjust the cooling efficiency and therefore the cooling speed according to the workpiece.

In addition, in the heat treatment method for a workpiece according to the present invention, the cooling liquid may be sprayed from a nozzle toward the workpiece in the cooling liquid supply area, and a valve provided on the nozzle may be electrically controllable.

By spraying the cooling liquid from the nozzle in this way, the cooling efficiency can be easily increased, and the cooling rate can be adjusted more flexibly (over a larger range). In addition, by spraying the cooling liquid while rotating the workpiece, the workpiece can be cooled evenly without bias even with fewer nozzles. In addition, by making it possible to electrically control the valve installed in the nozzle, the amount of cooling liquid supplied to the workpiece can be easily and precisely adjusted, making it easier to control the cooling rate for each workpiece.

In addition, in the workpiece heat treatment method according to the present invention, the movement timing, restraint timing, and restraint force may all be electrically controlled by a PLC.

As devices for electrically controlling the drive equipment, in addition to PLCs, there are control devices and microcomputers that combine electromagnetic relays and electronic timers. However, when the movement timing, restraint timing, and restraint force described above need to be changed for each workpiece, as in the present application, with a PLC, adjustments can be made in a very short time and with little effort, since it is only necessary to change the control program according to the workpiece. This is therefore very advantageous in terms of production efficiency. In addition, with a PLC, for example, detection signals from various sensors can be easily received, so that, for example, it is relatively easy to detect an identification information display section provided on the surface of a workpiece with a sensor to identify the type of workpiece, and then to carry out appropriate control according to the type of workpiece identified.

In this case, in the workpiece heat treatment method according to the present invention, the PLC may select a control program related to the movement timing, restraint timing, and restraint force that is preset for each workpiece according to the workpiece to be heat treated, and electrically control the movement timing, restraint timing, and restraint force.

As described above, when electrical control is performed using a PLC, multiple control programs related to the movement timing, restraint timing, and restraint force are linked in advance to the corresponding type of workpiece, and an appropriate control program is selected according to the workpiece that is actually to be heat treated, making it possible to complete adjustments for each workpiece in an extremely short time and easily. The program may be stored in an internal memory in advance, for example, or may be loaded from an external memory. Alternatively, it may be loaded from an electrically connectable storage area such as a server, or may be obtained via a network such as the cloud.

In addition, in the heat treatment method for a workpiece according to the present invention, the workpiece may be induction heated to a target temperature in the heating process, and the heated workpiece may be cooled in the cooling process to perform a predetermined heat treatment.

By using induction heating to heat the workpiece to the target temperature in this way, it is possible to directly heat only the workpiece, achieving high energy efficiency and making the entire heat treatment equipment, including the heating space, compact. Making the entire equipment compact is also advantageous in terms of energy efficiency and running costs.

The workpiece heat treatment method described above simplifies adjustments when changing workpieces and reduces heat treatment distortion while still achieving good heat treatment quality, making it suitable as a method for heat treating mass-produced parts with shapes (e.g., annular) where heat treatment distortion is likely to be a problem, such as the raceways of rolling bearings.

The above-mentioned problems are also solved by the heat treatment device for workpieces according to the present invention. That is, this heat treatment device is a heat treatment device for workpieces that includes a heating device for heating the workpiece, a cooling device for supplying a cooling liquid to the workpiece heated by the heating device to cool the workpiece and perform a predetermined heat treatment, and a restraining mold capable of restraining the workpiece when cooling the workpiece with the cooling device, and is characterized in that it further includes a moving device for moving the workpiece to a coolant supply area, a restraining drive device for performing the workpiece restraining operation with the restraining mold, and a control device capable of electrically controlling the moving device and the restraining drive device.

In the heat treatment apparatus having the above configuration, as in the heat treatment method according to the present invention described above, the timing at which the moving device moves the workpiece to the cooling liquid supply area, the timing at which the restraining drive device restrains the workpiece with the restraining mold, and the restraining force of the workpiece by the restraining mold can all be electrically controlled by the control device. Therefore, the responsiveness of the corresponding drive device can be improved, and the cooling and restraining of the workpiece can be started at an appropriate timing, and an appropriate amount of restraining force can be applied to the workpiece. Therefore, each workpiece can be cooled while restraining it with the mold under appropriate temperature history and restraining conditions, which makes it possible to obtain a high-quality heat-treated product while reducing heat treatment distortion. In addition, by controlling electrically, adjustments when changing the workpiece can be made by simply changing the content of the control command, which makes it possible to significantly shorten the work time and improve production efficiency compared to mechanical adjustments on the drive device side.

As described above, the workpiece heat treatment method and heat treatment device of the present invention simplify adjustments when changing workpieces, and make it possible to obtain good heat treatment quality while reducing heat treatment distortion.

1 is a front view showing an overview of a heat treatment apparatus according to an embodiment of the present invention; FIG. 2 is a vertical cross-sectional view of the heating device shown in FIG. FIG. 2 is a vertical cross-sectional view of the cooling device shown in FIG. FIG. 4 is a vertical cross-sectional view of the cooling device shown in FIG. 3 in a state where a workpiece is restrained by a restraining type, for explaining an example of a mode of use of the cooling device shown in FIG. FIG. 4 is a vertical cross-sectional view for explaining an example of a mode of use of the cooling device shown in FIG. 3, showing a state in which the restraint mold and the workpiece are immersed together in a cooling liquid tank.

One embodiment of the present invention will be described below with reference to the drawings. Note that in this embodiment, the case of performing hardening treatment on a workpiece will be described as an example.

1 is a front view showing an outline of a heat treatment apparatus 10 according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a heating apparatus 20 constituting the heat treatment apparatus 10, and FIG. 3 is a vertical cross-sectional view of a cooling apparatus 30 constituting the heat treatment apparatus 10. The heat treatment apparatus 10 shown in FIG. 1 is configured to perform a quench hardening treatment on an annular workpiece W (e.g., a base material of an outer or inner ring of a rolling bearing) made of a steel material such as SUJ2 while feeding the workpiece W along a conveying path 11 shown in FIG. 1. Therefore, the heat treatment apparatus 10 includes a heating apparatus 20 on the upstream side of the feed direction of the workpiece W, in which a heating step S1 is performed to heat the workpiece W to a target temperature (quenching temperature), and a cooling apparatus 30 in which a cooling step S2 is performed to cool the workpiece W heated in the heating step S1 by the cooling apparatus 30 and perform a quenching treatment. Therefore, the workpiece W can be transported from the heating apparatus 20 to the cooling apparatus 30 via the conveying path 11. Hereinafter, the configuration of the heat treatment apparatus 10 will be described first, and then an example of a heat treatment method using the heat treatment apparatus 10 will be described.

The heating device 20 is for induction heating the workpiece W to a target temperature, and in this embodiment, as shown in FIG. 2, includes a heating area 21 located above the transport path 11, a roughly annular outer heating coil 22 arranged radially outward of the workpiece W transported to the heating area 21, a roughly annular inner heating coil 23 arranged radially inward of the workpiece W, and a workpiece supply device 24 that supplies the workpiece W on the transport path 11 toward the heating area 21.

The outer heating coil 22 and the inner heating coil 23 are so-called multi-turn coils formed by spirally winding a tubular body made of a conductive metal such as a copper pipe, and are arranged coaxially with the workpiece W located in the heating area 21. Note that in this embodiment, an example is shown in which heating coils (outer heating coil 22, inner heating coil 23) are arranged on both the outside and inside of the workpiece W located in the heating area 21, but depending on the shape, size, etc. of the workpiece W, a heating coil may be arranged only on the outside or inside (for example, only the outer heating coil 22).

The work supply device 24 is, for example, a cylinder (hydraulic cylinder, air cylinder, or electric cylinder) having an extendable cylinder rod 25b with a flange portion 25a on which the work W can be placed at the end of the line.

The heating device 20 also has a transport device (not shown) for transporting the workpiece W along the transport path 11. For example, a transport conveyor constituting part of the transport path 11, or a cylinder (hydraulic cylinder, air cylinder, electric cylinder) capable of reciprocating along the longitudinal direction of the transport path 11, can be used as this transport device. Although not shown in FIG. 2, the heating area 21 and the outer and inner heating coils 22, 23 may be covered with a wall. In addition, if covered with a wall, the atmosphere (temperature, humidity, oxygen concentration, etc.) of the space inside the wall may be controlled by an atmosphere control device (not shown).

The cooling device 30 is a device for cooling the workpiece W heated to a target temperature by the heating device 20 and performing a quenching process, and is configured to be able to cool (quench) the workpiece W while it is restrained by the restraining mold 33. As shown in FIG. 3, the cooling device 30 includes a cooling liquid supply device 31, a moving device 32 that moves the workpiece W to a supply area of the cooling liquid 46 (here, in the cooling liquid 47 stored in a storage tank 47 described later), a restraining drive device 34 that performs the restraining operation of the workpiece W by the restraining mold 33, and a control device 35 that electrically controls the moving device 32 and the restraining drive device 34.

The moving device 32 has a support section 36 that supports the workpiece W, and a servo cylinder (first servo cylinder 37) as a ball actuator that moves the support section 36 in the vertical direction. The first servo cylinder 37 is fixed to a base section 38 of the cooling device 30. In this embodiment, the support section 36 is provided with a rotating table 39 that supports the workpiece W, and a rotation drive device 40 that drives the rotating table 39 to rotate around a predetermined central axis (a central axis that extends in the vertical direction in this illustrated example).

The rotation drive device 40 also includes a first spindle 41 that is located, for example, below the rotating table 39 and is connected coaxially to the rotating table 39, a second spindle 43 that is connected to the first spindle 41 so as to be capable of transmitting power, for example, via a pair of meshing gears 42a and 42b, and a motor 44 that drives the second spindle 43 to rotate around its longitudinal axis. Any type of motor can be used for the motor 44, and a suitable example is a servo motor.

When the moving device 32 is configured as described above, the transport path 11 is configured to pass over the upper surface of the turntable 39 in the state shown in FIG. 3, in other words, before the workpiece W is moved to the cooling liquid supply area. In this case, the transport path 11 extends along the front-to-back direction of the paper surface of FIG. 3.

The restraint drive device 34 is for driving the restraint mold 33, and in this embodiment, is composed of a servo cylinder (second servo cylinder 45) as a servo actuator that drives the restraint mold 33 in the vertical direction. Here, the second servo cylinder 45 is fixed to the support part 36, and the support part 36, the rotating table 39, and the rotation drive device 40 are capable of moving vertically together. Therefore, the second servo cylinder 45 fixed to the support part 36 is also capable of moving vertically together with the rotating table 39 and the workpiece W placed on the rotating table 39.

In this embodiment, the cooling liquid supply device 31 mainly includes a storage tank 47 in which the cooling liquid 46 is stored, and a nozzle 48 that sprays the cooling liquid 46 toward the workpiece W. In this embodiment, the nozzle 48 is disposed at a position where the cooling liquid 46 can be sprayed onto the workpiece W while the workpiece W is immersed in the cooling liquid 46 stored in the storage tank 47 (see FIG. 5 described later).

A pump 49 is connected to the nozzle 48, and as shown in FIG. 3, for example, the cooling liquid 46 in the storage tank 47 can be sucked in by driving the pump 49, and sprayed from the nozzle 48 onto the workpiece W. In this embodiment, a valve 50 is provided between the nozzle 48 and the pump 49. This valve 50 is preferably configured to be capable of adjusting the flow rate of the cooling liquid 46 sprayed from the nozzle 48, and an electrically controllable type of valve, such as a solenoid type, is preferably used.

The control device 35 is configured to be able to control the driving of the moving device 32 and the restraint drive device 34. In this embodiment, in addition to the moving device 32 and the restraint drive device 34, the control device 35 is configured to be able to control the driving of the valve 50. In detail, the control device 35 is electrically connected to the first servo cylinder 37 that is the drive unit of the moving device 32, and is also electrically connected to the second servo cylinder 45 that constitutes the restraint drive device 34. In this embodiment, the motor 44 that is the drive unit of the rotation drive device 40 is electrically connected to the control device 35, and the valve 50 of the nozzle 48 is electrically connected to the control device 35. As a result, the first servo cylinder 37, the second servo cylinder 45, the motor 44, and the valve 50 can all be electrically controlled by the control device 35. In addition, for example, the first servo cylinder 37, the second servo cylinder 45, the motor 44, and the valve 50 can also be electrically controlled based on the same time axis.

The control device 35 can have any configuration as long as it can be electrically controlled. For example, a PLC is preferable from the viewpoint of ease of changing the control content according to the type of workpiece W, as described below.

In this case, the PLC can electrically control the movement timing, restraint timing, and restraint force by selecting a control program related to the movement timing of the moving device 32 to the cooling liquid supply area (here, the cooling liquid 46 in the storage tank 47) by the moving device 32, the restraint timing of the workpiece W by the restraint drive device 34, and the restraint force applied to the workpiece W, which are set in advance for each workpiece W, according to the workpiece W to be subjected to the actual heat treatment (hardening treatment). In this case, specifically, a control program related to the drive timing of the first servo cylinder 37, the drive timing of the second servo cylinder 45, and the pressure force of the second servo cylinder 45 on the workpiece W (the reaction force received by the second servo cylinder 45 when the workpiece W is pressurized by the restraint mold 33) is set in advance for each number of types of workpieces W that can be processed. Then, by selecting a predetermined program from among these multiple programs in a predetermined manner, it is possible to control the PLC (control device 35) according to the program. In this embodiment, the drive timing means that the first servo cylinder 37 and the second servo cylinder 45 start to be driven at a specific time on a common time axis. For example, time control can be performed based on a specific moment during the heat treatment period of the workpiece W, such as when the heat treatment by the heating device 20 starts, when the workpiece W is removed from the heating device 20, or when the workpiece W is brought into the cooling device 30.

In addition, when the heating device 20 is configured with a heating coil for induction heating (at least one of the outer heating coil 22 and the inner heating coil 23) as in this embodiment, the heating coil may be electrically connected to the control device 35, and the heating coil may be controlled based on a time axis common to the control of each servo cylinder 37, 45 by the control device 35.

Next, an example of a method for heat treating a workpiece W using the heat treatment device 10 configured as described above will be described.

The heat treatment method for the workpiece W according to this embodiment includes a heating step S1 and a cooling step S2. Each step will be described in detail below with reference to Figures 2 to 5.

(S1) Heating step First, the workpiece W is carried into the heating device 20 shown in Fig. 1 and Fig. 2, and then the workpiece W is subjected to a heating process. Specifically, as shown in Fig. 2, when the workpiece W reaches the flange portion 25a located on the conveying path 11, the cylinder rod 25b is extended to raise the workpiece W to the heating area 21. At this time, since the heating area 21 is located at the same height as the outer heating coil 22 and the inner heating coil 23, by moving the workpiece W to the heating area 21, the workpiece W becomes in a state where it can be heated by each of the heating coils 22, 23. Then, the outer heating coil 22 and the inner heating coil 23 are energized, respectively, to inductively heat the workpiece W so as to have a predetermined temperature history. In this embodiment, the workpiece W is inductively heated until it reaches a predetermined target temperature. Then, the workpiece W is lowered to the conveying path 11, taken out of the heating device 20, and conveyed toward the cooling device 30.

(S3) Cooling Step In this step, as described above, the workpiece W heated to a target temperature by the heating device 20 (heating step) is cooled so as to follow a predetermined temperature history. Specifically, as shown in FIG. 3, first, the workpiece W transferred on the conveying path 11 is stopped at a position where the center of rotation of the turntable 39 and the central axis of the workpiece W coincide with each other. Next, the control device 35 selects a control program preset according to the type of workpiece W on the turntable 39, and controls the drive start timing of the second servo cylinder 45 according to the selected program. As a result, a predetermined control signal is sent from the control device 35 to the second servo cylinder 45, and the second servo cylinder 45 starts driving at a predetermined time. As a result, the restraining mold 33 connected to the tip of the second servo cylinder 45 starts to descend, and as shown in FIG. 4, the workpiece W placed on the turntable 39 is restrained. In addition, the magnitude of the restraining force (downward pressure force in this embodiment) on the workpiece W at this time is controlled to a predetermined magnitude (or a predetermined restraining force history) by the control device 35 according to a preselected control program.

After the workpiece W is restrained by the restraining mold 33 in the above manner, as shown in FIG. 5, the workpiece W, the restraining mold 33, the support 36, the rotating table 39, the rotary drive device 40, and the second servo cylinder 45 are lowered together and immersed in the cooling liquid 46 stored in the storage tank 47. In this embodiment, the control device 35 controls the timing of starting the drive of the first servo cylinder 37 in accordance with the control program selected as described above. As a result, a predetermined control signal is sent from the control device 35 to the first servo cylinder 37, and the first servo cylinder 37 starts driving at a predetermined time. As a result, the workpiece W starts to be immersed in the cooling liquid 46 together with the support 36, etc., and the first servo cylinder 37 is stopped when the workpiece W has descended to a predetermined height position.

In addition, in this embodiment, the control device 35 controls the timing at which the motor 44 starts to drive in accordance with the control program selected as described above. This causes the control device 35 to send a predetermined control signal to the motor 44, which starts to drive at a predetermined time. As a result, the immersed workpiece W starts to rotate around its central axis, and continues to rotate around the axis at a predetermined rotation speed (number of rotations).

At this time, the control device 35 controls the operation of the valve 50 in accordance with the control program selected as described above. Specifically, the opening of the valve 50 is electrically controlled to control the timing at which the nozzle 48 starts spraying the cooling liquid 46 toward the workpiece W. The flow rate of the cooling liquid 46 discharged toward the workpiece W is also controlled. As a result, a predetermined flow rate of the cooling liquid 46 is sprayed toward a predetermined position in the circumferential direction while the immersed workpiece W rotates around its central axis. Therefore, even when a nozzle 48 that sprays the cooling liquid 46 in one direction is used, it is possible to spray the cooling liquid 46 evenly in the circumferential direction of the workpiece W.

By cooling the workpiece W in the above manner, the workpiece W is rapidly cooled with a temperature history according to its type. After a predetermined time of immersion, the control device 35 drives the first servo cylinder 37 to raise the workpiece W together with the restraining mold 33 and the support portion 36, etc., and returns the workpiece W to the conveying path 11. Thereafter, the control device 35 drives the second servo cylinder 45 to further raise only the restraining mold 33, thereby releasing the restrained state of the workpiece W. Finally, the workpiece W is conveyed downstream of the conveying path 11 by a conveying device (not shown), thereby completing the quenching hardening process for the workpiece W. The subsequent workpiece W is also subjected to the quenching process by following the same path, and is discharged outside the heat treatment device 10. In this manner, quenching is performed continuously and automatically on multiple workpieces W.

As described above, according to the heat treatment method and heat treatment device 10 of the present invention, among the heat treatment conditions for the workpiece W, the timing at which the workpiece W starts moving into the cooling liquid 46 (i.e., immersion), the timing at which the workpiece W starts being restrained by the restraining mold 33, and the restraining force applied to the workpiece W by the restraining mold 33 are controlled, and all of these controls are performed electrically. By electrically controlling the immersion start timing and restraining start timing of the workpiece W, as well as the restraining force, the responsiveness of the corresponding drive device can be improved compared to, for example, a hydraulic drive type, and the cooling and restraining of the workpiece W can be started at an appropriate timing. In addition, a restraining force of an appropriate magnitude can be applied to the workpiece W. Therefore, it is possible to cool each workpiece W while restraining it with a mold under appropriate temperature history and restraining conditions, which makes it possible to obtain a high-quality hardened product while reducing heat treatment distortion. In addition, by controlling electrically, adjustments when changing the type of workpiece W can be made by simply changing the command content from the control device 35, so that it is possible to significantly shorten the work time and improve production efficiency compared to when mechanical adjustments are made on the drive side, such as replacing the restraining mold 33.

In addition, in this embodiment, the drive unit of the moving device 32 for moving the above-mentioned workpiece W is configured with a first servo cylinder 37 as a servo actuator, and the drive unit of the restraint drive device 34 for restraining the workpiece W is configured with a second servo cylinder 45 as a servo actuator, and these servo cylinders 37 and 45 are both electrically controlled by the control device 35. A servo actuator is excellent not only in responsiveness to commands from the control unit, but also in accuracy during position control and pressure control, so that it is possible to improve not only the timing at which the workpiece W starts to be cooled, but also the positioning accuracy in the cooling liquid 46. In addition, it is possible to control not only the timing at which the workpiece W starts to be restrained, but also the restraining force at that time to a more suitable range. Therefore, it is possible to further improve the cooling accuracy and individually optimize the restraint conditions according to the type of workpiece W. In particular, in this embodiment, in addition to the first and second servo cylinders 37 and 45, the motor 44 and the valve 50 are also electrically controlled, so it is possible to set optimal cooling conditions for each workpiece W and further improve the cooling accuracy. In addition, it is possible to further reduce heat treatment distortion and further improve the hardening quality.

In addition, in this embodiment, the first and second servo cylinders 37, 45, the motor 44, and the valve 50 are all electrically controlled collectively by the PLC as the control device 35, which can improve the accuracy of the drive start timing in particular. Furthermore, with a PLC, the adjustment required is only to change the control program in accordance with the workpiece W, so that it is possible to adjust the equipment in a very short time with little effort. This is therefore very advantageous in terms of production efficiency. Of course, when increasing, decreasing, or changing the types of workpiece W, it is also highly versatile, since the adjustment required is only to increase, decrease, or change the control program for each workpiece W.

The above describes a heat treatment method and heat treatment apparatus 10 according to one embodiment of the present invention, but these heat treatment methods and heat treatment apparatus 10 can be modified as appropriate without departing from the spirit and scope of the present invention.

For example, in the above embodiment, a servo cylinder (first servo cylinder 37) is used as a servo actuator in the drive section of the moving device 32 for the workpiece W, but of course other configurations are also possible. That is, a servo actuator other than a servo cylinder can also be used, and an electrically controllable drive device other than a servo type can also be used. Similarly, a servo actuator other than a servo cylinder can also be used for the drive section (second servo cylinder 45) of the restraint drive device 34, and an electrically controllable drive device other than a servo type can also be used.

In the above embodiment, a single-hole type nozzle 48 is arranged so that the cooling liquid 46 can be sprayed toward a predetermined position in the circumferential direction of the workpiece W, but of course other types of nozzles (cooling liquid spraying devices) can also be used. For example, although not shown, an annular nozzle having a substantially circular shape with multiple openings on its inner circumference may be arranged on the radial outside of the workpiece W. Alternatively, an annular nozzle having a substantially circular shape with multiple openings on its outer circumference may be arranged on the radial inside of the workpiece W. In this case, too, an electrically controllable flow rate adjustment valve (not shown) can be arranged upstream of the nozzle.

In addition, in the above embodiment, a rotating table 39 and a nozzle 48 are arranged to spray the coolant 46 while rotating the workpiece W around its central axis, but some or all of these may be omitted. That is, depending on the type of workpiece W, the spraying of the coolant 46 may be omitted, and the axial rotation of the workpiece W in the coolant 46 may be omitted. Alternatively, both the spraying of the coolant 46 and the axial rotation of the workpiece W may be omitted.

In the above embodiment, after the workpiece W is restrained by the restraining mold 33, the workpiece W, the restraining mold 33, the support 36, the rotating table 39, the rotation drive device 40, and the second servo cylinder 45 are lowered together to be immersed in the cooling liquid 46 stored in the storage tank 47. However, this order is not limited to the above. For example, the workpiece W separated from the restraining mold 33 may be lowered together with the support 36, etc., to start the immersion operation in the cooling liquid 46 in the storage tank 47, and then the second servo cylinder 45 may be driven to start the restraint of the workpiece W by the restraining mold 33. In short, the overlapping form of the restraint period and the immersion period is arbitrary. Also, the restraint period and the immersion period may overlap partially or entirely.

In the above explanation, the workpiece W is heated to the target temperature by induction heating in the heating step S1, but of course this is not limited to this. If there is no particular problem in terms of the heating speed, other heating methods such as atmospheric heating may be used to heat the workpiece W to the target temperature.

In addition, in the above explanation, the heat treatment method and heat treatment device 10 of the present invention are applied to hardening the raceway (outer or inner ring) of a rolling bearing. However, the heat treatment method and heat treatment device 10 of the present invention can also be preferably applied to hardening other annular workpieces, such as plain bearings, outer joint members and inner joint members that constitute constant velocity universal joints, (base materials of) cages incorporated into rolling bearings and constant velocity universal joints, and even workpieces having shapes other than annular.

In addition, the above explanation has been given of an example in which the workpiece W is quenched by carrying out a specified heating process and cooling process, but the present invention can of course be applied to heat treatments other than quenching.

The present invention is not limited to the above-described embodiment, and may be implemented in various other forms without departing from the spirit of the present invention. In other words, the scope of the present invention is defined by the claims, and includes the equivalent meanings set forth in the claims, as well as all modifications within the scope of the claims.

1 Heat treatment device 2 Patent document 2 Heating section 10 Heat treatment device 11 Transport path 20 Heating device 21 Heating area 22 Outer heating coil 23 Inner heating coil 24 Work supply device 25a Flange section 25b Cylinder rod 30 Cooling device 31 Cooling liquid supply device 32 Moving device 33 Constraint type 34 Constraint drive device 35 Control device 36 Support section 37, 45 Servo cylinder 38 Base section 39 Rotating table 40 Rotation drive device 41 First spindle 42a, 42b Gear 43 Second spindle 44 Motor 46 Cooling liquid 47 Reservoir 48 Nozzle 49 Pump 50 Valve W Work

Claims (8)

A method for heat treating a workpiece, comprising a heating step of heating a workpiece, and a cooling step of supplying a cooling liquid to the workpiece heated in the heating step to cool the workpiece and perform a predetermined heat treatment, wherein the workpiece is cooled in a state of being restrained by a restraining mold at least in the cooling step,
a control program for electrically controlling the movement timing, the restraint timing, and the restraint force of the workpiece by the restraint mold, which are preset for each workpiece, selected from control programs relating to the movement timing, the restraint timing, and the restraint force, according to the workpiece to be subjected to the specified heat treatment , to electrically control the movement timing, the restraint timing, and the restraint force. The method for heat treating a workpiece according to claim 1, in which the workpiece is moved to the cooling liquid supply area by a servo actuator. The method for heat treating a workpiece according to claim 1 or 2, in which the workpiece is restrained by the restraining mold using a servo actuator. The method for heat treating a workpiece according to any one of claims 1 to 3, in which the workpiece is rotated by a motor in the area where the cooling liquid is supplied. A method for heat treating a workpiece according to any one of claims 1 to 4, in which the cooling liquid is sprayed from a nozzle toward the workpiece in the cooling liquid supply area, and a valve provided on the nozzle is electrically controllable. The method for heat treating a workpiece according to any one of claims 1 to 5, in which the workpiece is induction heated to a target temperature in the heating step, and the heated workpiece is cooled in the cooling step to perform the specified heat treatment. The heat treatment method for a workpiece according to any one of claims 1 to 6, wherein the workpiece is an annular ring of a rolling bearing. A heat treatment apparatus for a workpiece, the heat treatment apparatus comprising: a heating apparatus for heating a workpiece; a cooling apparatus for cooling the workpiece by supplying a cooling liquid to the workpiece heated by the heating apparatus, and a restraining mold for restraining the workpiece when the workpiece is cooled by the cooling apparatus,
The present invention further includes a moving device that moves the workpiece to a supply area of the cooling liquid, a constraint drive device that performs a constraint operation of the workpiece using the constraint mold, and a PLC control device that is capable of electrically controlling the moving device and the constraint drive device,
The PLC is configured to electrically control the movement timing, the restraint timing, and the restraint force by selecting a control program related to the movement timing, the restraint timing, and the restraint force that is previously set for each workpiece in accordance with the workpiece to be subjected to the specified heat treatment .

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