JP2020044618A - Grinding machine and grinding method - Google Patents

Abstract

To provide a grinding machine and a grinding method which can improve cycle time while maintaining accuracy of processing for a work-piece.SOLUTION: The grinding machine comprises: a work-piece support device that rotates a work-piece around a shaft line; a grinding wheel for grinding the work-piece; a feeding/driving device that feeds at least either one of the grinding wheel and the work-piece support device in a direction in which the grinding wheel and the work-piece support device relatively approach or separate from each other; a feeding control part that controls the feeding/driving device so that feed speed of at least either of the grinding wheel and the machine tool supporting device is reduced depending on a progress situation of grinding by the grinding wheel; and a chuck control part that controls clamping force on the work-piece by a chuck and reduces the clamping force from first pressure P1 to second pressure p2 when reducing the feed speed or after reducing the feed speed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a grinding machine and a grinding method.

  During the grinding by the grinder, the workpiece is supported on both sides in the axial direction. In this regard, Patent Document 1 discloses a technique in which one end of a workpiece is supported by a headstock center and the other end of the workpiece is supported by a tailstock center. Patent Document 1 discloses that the center pressing force of the tailstock at the time of finish grinding is made smaller than the center pressing force of the tailstock at the time of rough grinding, so that the bending of the workpiece caused by the center pressing force is reduced. A suppression technique is disclosed.

JP 2018-24026 A

  Here, when the surface of the workpiece is ground, the stress remaining inside the workpiece is released. On the other hand, when the edge of the workpiece is clamped by the chuck in the grinding machine, bending caused by stress release of the workpiece is suppressed, and the workpiece is bent by unclamping the chuck.

  In this regard, in the conventional grinding, the grinder once performs unclamping of the chuck after the roughing is completed, thereby causing bending of the workpiece due to stress release of the workpiece. Then, the grinding machine re-clamps the workpiece with a chuck with a smaller pressure than during roughing, and performs finishing processing so that the workpiece is supported in the state where bending has occurred in the workpiece, after finishing The aim is to improve the machining accuracy of the workpiece. However, in this case, it is necessary to stop the grinding process during unclamping and re-clamping of the chuck, so that the cycle time is reduced.

  An object of the present invention is to provide a grinding machine and a grinding method that can improve the cycle time while maintaining the processing accuracy for a workpiece.

  A grinding machine according to the present invention has a chuck that clamps one end of a workpiece and a support that supports the other end of the workpiece, and a workpiece support device that rotates the workpiece about an axis. A grinding wheel for grinding the workpiece, and at least one of the grinding wheel and the workpiece support device, a feed driving device that sends the grinding wheel and the workpiece support device in a direction to relatively approach or separate, A feed control unit that controls the feed drive device and reduces the feed speed of at least one of the grinding wheel and the workpiece support device according to the progress of grinding by the grinding wheel, and A chuck control for controlling a clamping force and reducing the clamping force from a first pressure to a second pressure smaller than the first pressure when the feeding speed is reduced or after the feeding speed is reduced. Provided with a door.

  In addition, a grinding method according to the present invention has a chuck that clamps one end of a workpiece and a support that supports the other end of the workpiece, and a workpiece support device that rotates the workpiece about an axis. A grinding wheel for grinding the workpiece, and a feed drive device for sending at least one of the grinding wheel and the workpiece support device in a direction in which the grinding wheel and the workpiece support device are relatively approached or separated from each other. Is used. In the grinding method, a rough processing step of performing rough grinding on the workpiece by the grinding wheel, and the feed speed of the at least one of the grinding wheel and the workpiece support device is set lower than the rough processing step. In the state, on the workpiece on which the rough grinding has been performed, a finishing processing step of performing finishing processing by the grinding wheel, and at the end of the rough processing step, or in the finishing processing step, the machining by the chuck A first clamping force decreasing step of decreasing a clamping force of the object from the first pressure to a second pressure smaller than the first pressure.

  According to the grinding machine and the grinding method of the present invention, the chuck control unit reduces the clamping force when the feed speed is reduced or after the feed speed is reduced. As a result, the workpiece supported by the workpiece support device bends due to stress release. The grinding machine can improve the processing accuracy of the processed workpiece by grinding the workpiece supported by the workpiece support device in a state where the bending has occurred.

  In other words, the grinding machine and the grinding method avoid the need to perform unclamping and re-clamping of a workpiece by a chuck, and apply a method to a workpiece supported by a workpiece support device in a state in which bending due to stress release occurs. On the other hand, grinding can be performed. Therefore, the grinding machine and the grinding method can improve the cycle time while maintaining the processing accuracy for the workpiece.

It is a top view of a grinding machine in one embodiment of the present invention. It is a block diagram of a control device. It is a flowchart which shows the grinding process performed by a control apparatus. 4 is a graph showing the relationship between the timing of the decrease in the feed speed of the grinding wheel and the timing of the decrease in the clamping force of the workpiece by the chuck. It is a graph which shows the relationship between the timing of the fall of the feed speed of the grinding wheel and the timing of the fall of the clamping force of the workpiece by the chuck in the first modification. It is a graph which shows the relationship between the timing of the fall of the feed speed of the grinding wheel and the timing of the fall of the clamping force of the workpiece by the chuck in the second modification. It is a graph which shows the relationship between the timing of the fall of the grinding load in the third modification, and the timing of the fall of the clamping force of the workpiece by the chuck.

  Hereinafter, embodiments to which a grinding machine and a grinding method according to the present invention are applied will be described with reference to the drawings. First, an outline of a grinding machine 1 according to an embodiment of the present invention will be described with reference to FIG.

(1. Configuration of grinding machine 1)
As shown in FIG. 1, the grinding machine 1 is a grindstone traverse grinding machine that performs grinding while rotating a cylindrical workpiece W. The grinding machine 1 includes a bed 2, a workpiece support device 10, a grinding wheel 20, a grinding wheel base 30, a table 40, a table driving device 50, a feed driving device 60, a coolant supply device 70, It mainly includes a device 80 and a control device 100 (see FIG. 2).

  The bed 2 is a portion serving as a base of the grinding machine 1. The bed 2 is provided with an operation panel 3 for inputting various parameters relating to grinding conditions and the like, and the operation panel 3 is operated by an operator. The workpiece support device 10 rotates the workpiece W around the axis while supporting both ends of the long workpiece W formed in a cylindrical shape in the axial direction (left-right direction in FIG. 1). The workpiece support device 10 mainly includes a headstock 11 and a tailstock 12.

  The headstock 11 rotatably supports one end (the right end in FIG. 1) of the workpiece W in the axial direction. The headstock 11 is a headstock body 13 as a housing, a master spindle 14 rotatably supported by the headstock body 13 and movably in the Z-axis direction, and moves the master spindle 14 in the Z-axis direction. And a master moving device 15. The headstock 11 is provided with a master motor 11a that drives the master spindle 14 to rotate. In addition, the master spindle 14 is provided with a spindle center 14a as a support portion for supporting an end face at one axial end of the workpiece W and a chuck 14b for clamping an outer peripheral face at one axial end of the workpiece W. . The chuck 14b includes a chuck main body attached to the master spindle 14, a plurality of claws rotatably or slidably provided on the chuck main body, and a cylinder device for opening and closing the plurality of claws. The chuck 14b clamps or unclamps the workpiece W by moving the tips of the plurality of claws in the radial direction.

  The master moving device 15 includes a slider 15a, a slider driving device 15b, and a floating joint 15c. The slider 15a is provided movably in the Z-axis direction with respect to the bed 2. A guide 15d extending in the Z-axis direction is provided on the upper surface of the bed 2, and the slider 15a moves in the Z-axis direction while being guided by the guide 15d. The slider driving device 15b is a screw feed device that feeds the slider 15a in the Z-axis direction. The floating joint 15c connects the slider 15a and the master spindle 14, and the master spindle 14 moves in the Z-axis direction with the movement of the slider 15a in the Z-axis direction, and allows the rotation of the master spindle 14 with respect to the joint 15c. I do.

  The tailstock 12 includes a tailstock body 16 as a housing, a slave spindle 17 rotatably supported by the tailstock body 16 and movably in the Z-axis direction, and a slave spindle 17 in the Z-axis direction. And a slave moving device 18 for moving to the main position. The tailstock 12 is provided with a slave motor 12 a for rotating the slave spindle 17. Further, the slave main shaft 17 is provided with a tailstock center 17a as a supporting portion for supporting an end surface of the workpiece W at the other end in the axial direction (the left end in FIG. 1).

  The slave moving device 18 includes a slider 18a, a slider driving device 18b, and a spring 18c. The slider 18a is provided on the bed 2 so as to be movable in the Z-axis direction. A guide 18d extending in the Z-axis direction is provided on the upper surface of the bed 2, and the slider 18a moves in the Z-axis direction while being guided by the guide 18d. The slider driving device 18b is a screw feed device that sends the slider 18a to the bed 2 in the Z-axis direction.

  The spring 18c is provided between the slider 18a and the joint 18e. When moving the slider 18a in the direction approaching the workpiece W, the slave moving device 18 moves the slave spindle 17 in the direction approaching the workpiece W while compressing the spring 18c. The slave moving device 18 is provided with a stopper rod 18f for connecting the slider 18a and the joint 18e. When the slider 18a moves away from the workpiece W, the joint 18e allows the slave main shaft 17 to rotate. While moving along the slider 18a, it moves with the slave spindle 17 in a direction away from the workpiece W (Z-axis direction).

  The workpiece support device 10 adjusts the center support force of the spindle center 14a and the tailstock center 17a by using the master moving device 15 and the slave moving device 18, so that the bending of the workpiece W caused by the center supporting force is achieved. Can be suppressed.

  The grinding wheel 20 grinds the workpiece W supported by the workpiece support device 10. The grindstone stand 30 is provided with a grindstone shaft member 31 and a grindstone motor 32. The grindstone shaft member 31 is rotatably supported on the grindstone table 30 around a rotation axis parallel to the Z axis. The grinding wheel 20 is rotatable integrally with the grindstone shaft member 31 with respect to one end of the grindstone shaft member 31. Provided. The grinding wheel motor 32 rotationally drives the grinding wheel shaft member 31 via the belt pulley mechanism 33 to rotate the grinding wheel 20.

  Further, a grinding wheel cover 34 that covers the grinding wheel 20 is provided on the upper surface of the grinding wheel stand 30. The grindstone cover 34 prevents the coolant supplied from the coolant supply device 70 toward the grinding wheel 20 from scattering. The grinding machine 1 is provided with a grinding load detector 35 for detecting a current value of the grinding wheel motor 32. That is, the grinding machine 1 detects the current value of the grinding wheel motor 32 as a grinding load and detects the grinding load generated during the grinding of the workpiece W by the grinding wheel 20.

  The table 40 supports the grinding wheel head 30. The table driving device 50 is a screw feed device that sends the table 40 to the bed 2 in the Z-axis direction. The feed drive device 60 is a screw feed device that feeds the grindstone table 30 in the X-axis direction with respect to the table 40. The grinder 1 sends the grindstone table 30 in the X-axis direction with respect to the table 40, so that the workpiece W supported by the workpiece support device 10 and the grinding wheel 20 can be relatively approached or separated from each other. . In addition, the feed driving device 60 is provided with an encoder 61 (see FIG. 2) for detecting the position of the grindstone head 30 in the X-axis direction.

  The coolant supply device 70 includes a coolant storage tank 71, a pump 72, and a coolant nozzle 73. The coolant storage tank 71 and the pump 72 are installed on the bed 2, and the coolant nozzle 73 is attached to the grindstone cover 34. The coolant supply device 70 pumps out the coolant stored in the coolant storage tank 71 with a pump 72 and sends the coolant to a coolant nozzle 73 connected to the pump 72 with a pipe. The sizing device 80 is provided on the upper surface of the bed 2. The sizing device 80 is used when measuring the outer diameter of the workpiece W.

  The control device 100 includes a workpiece rotation control unit 110, a grinding wheel rotation control unit 120, a traverse control unit 130, a feed control unit 140, a chuck control unit 150, and a center support control unit 160.

  The workpiece rotation control unit 110 controls the driving of the master motor 11a and the slave motor 12a to rotate and stop the rotation of the workpiece W supported by the workpiece support device 10. The grinding wheel rotation control unit 120 controls the drive of the grinding wheel motor 32 to rotate and stop the rotation of the grinding wheel 20. The traverse control unit 130 controls the driving of the table motor 51 provided in the table driving device 50, and moves the table 40 in the Z-axis direction.

  The feed control unit 140 drives and controls the feed motor 62 provided in the feed drive device 60, and sends the grinding wheel base 30 and the grinding wheel 20 in the X-axis direction. In addition, the feed control unit 140 includes a speed command unit 141 and a speed calculation unit 142. In the speed command unit 141, a target feed speed of the grinding wheel head 30 (hereinafter, referred to as “target feed speed”) is set. Further, the speed calculating unit 142 calculates the distance traveled by the grindstone head 30 within a predetermined time by differentiating the position signal output from the encoder 61, and calculates the feed speed of the grindstone head 30. Then, the feed control unit 140 controls the speed of the feed motor 62 while performing feedback control of the feed speed so that the feed speed matches the target feed speed.

  The chuck controller 150 controls the clamping force of the workpiece W by the chuck 14b. Specifically, the chuck 14b includes a pump that discharges pressure oil, a switching valve that selectively supplies the pressure oil to the clamp chamber or the amplifier lamp chamber of the cylinder device, and a pressure reducing valve that controls the pressure of the pressure oil. The chuck control unit 150 is provided, and controls the clamping force by controlling the pressure of the pressure reducing valve. Then, as described later, the chuck controller 150 changes the clamping force by the chuck 14b according to the feed speed of the grindstone table 30. The center support controller 160 drives and controls the slider driving device 15b of the master moving device 15 and the slider driving device 18b of the slave moving device 18, and controls the center supporting force of the spindle center 14a and the tailstock center 17a.

(2. Grinding process)
Next, a grinding process performed by the control device 100 will be described with reference to FIG. The grinding process is a process executed when the workpiece W is ground by the grinding machine 1. The feed control unit 140 controls the grinding wheel 20 (the wheel head) in accordance with the progress of the grinding by the grinding wheel 20. 30) Decrease the feed speed.

  As shown in FIG. 3, the grinding machine 1 executes a rough processing step (S1) for performing rough grinding on a workpiece W that has been subjected to quenching processing as an initial processing in the grinding processing. The grinding machine 1 performs the grinding while measuring the outer diameter of the workpiece W by the sizing device 80. In the roughing step (S1), the outer diameter of the workpiece W is reduced to a fine grinding diameter set in advance. It runs until it reaches.

  When the outer diameter of the workpiece W reaches the fine grinding diameter, the grinding machine 1 shifts to a first finishing step (S2) for performing fine grinding on the workpiece W. In the first finishing process (S2), the feed control unit 140 lowers the target feed speed of the grindstone head 30 from the target feed speed in the roughing process (S1). As a result, in the first finishing processing step (S2), the feed speed of the grindstone table 30 is lower than in the rough processing step (S1), and the cutting depth is smaller than in the rough processing step (S1). Subsequently, the grinding machine 1 executes the first finishing processing step (S2) until the outer diameter of the workpiece W reaches a preset fine grinding diameter.

  Then, when the outer diameter of the workpiece W reaches the fine grinding diameter, the grinding machine 1 proceeds to a second finishing processing step (S3) for performing fine grinding on the workpiece W. In the second finishing process (S3), the feed control unit 140 lowers the target feed speed of the grindstone head 30 from the target feeding speed in the first finishing process (S2). As a result, in the second finishing step (S3), the feed speed of the grindstone table 30 is lower than in the first finishing step (S2), and the cutting depth is smaller than in the first finishing step (S2). Become. Then, the grinding machine 1 executes the second finishing process (S3) until the outer diameter of the workpiece W reaches a preset finishing diameter.

  When the outer diameter of the workpiece W reaches the finish diameter, the grinding machine 1 proceeds to a spark-out step (S4) for performing spark-out on the workpiece W. In the spark-out step (S4), the grinding machine 1 rotates the grinding wheel 20 in a state where the feed of the grinding wheel stand 30 is stopped.

  Here, the workpiece support device 10 supports the outer peripheral surface at one axial end of the workpiece W with the chuck 14b while supporting the end faces on both axial sides of the workpiece W with the spindle center 14a and the tailstock center 17a. . In this regard, since the spindle center 14a and the tailstock center 17a simply support both end faces of the workpiece W, when performing grinding while pressing the grinding wheel 20 against the workpiece W, the workpiece W Cannot be sufficiently suppressed.

  In contrast, the chuck 14b has a larger contact area with the workpiece W than the spindle center 14a and the tailstock center 17a, and supports the workpiece W fixedly from the outer peripheral surface. Therefore, the displacement of the workpiece W is suppressed at least in a range where the outer peripheral surface is supported by the chuck 14b. The chuck 14b firmly supports the workpiece W, so that the workpiece W can be suppressed from bending. As a result, the grinding machine 1 can suppress bending of the workpiece W when performing grinding while strongly pressing the grinding wheel 20 against the workpiece W. Therefore, it is possible to improve the processing accuracy of the workpiece W. it can.

  In the case where the workpiece W that has been subjected to the quenching process is subjected to grinding, the stress remaining inside the workpiece W is released by grinding the surface of the workpiece W. In this regard, the workpiece W is likely to bend when the internal stress is released, while the workpiece W caused by the stress release is held in a state where the workpiece W is firmly supported by the chuck 14b. Is suppressed. Therefore, it is necessary for the grinding machine 1 to perform the grinding process in a state where the bending due to the release of the stress has occurred, and to maintain the processing accuracy for the workpiece W after the processing.

  On the other hand, the chuck control unit 150 reduces the clamping force of the workpiece W by the chuck 14b when the feed speed of the grinding wheel 20 (the grinding wheel base 30) is reduced. As a result, the workpiece W supported by the workpiece support device 10 bends due to the internal stress released by the rough grinding. Then, the grinding machine 1 grinds the workpiece W supported on the workpiece support device 10 in a state where the bending has occurred. Thus, the grinding machine 1 can improve the processing accuracy of the workpiece W after the grinding.

(3. Relationship between the feed speed of the grinding wheel base 30 and the clamping force of the workpiece W by the chuck 14b)
Here, the relationship between the feed speed of the grinding wheel 20 (grinding wheel base 30) and the clamping force of the chuck 14b will be described with reference to FIG. In the graph shown in FIG. 4, the time at which the rough processing step (S1) is completed is t1, the time at which the first finishing processing step (S2) is completed is t2, and the time at which the second finishing processing step (S3) is completed is time. At t3, the clamping force of the chuck 14b in the roughing step (S1) is set to the first pressure P1.

  As shown in FIG. 4, in the roughing step (S1), when the outer diameter of the workpiece W reaches the fine grinding diameter, the feed control unit 140 controls the grinding wheel to shift from the roughing step to the first finishing step. The feed speed of the wheel 20 (the wheel head 30) is reduced. Accordingly, the chuck controller 150 reduces the clamping force of the workpiece W by the chuck 14b from the first pressure P1 to the second pressure P2 (P1> P2) as the feed speed of the grindstone table 30 decreases. First clamping force lowering step).

  Here, the workpiece W subjected to the rough grinding is bent due to the release of the internal stress. In other words, the workpiece W that has been subjected to the quenching process as a pre-process of the grinding process releases the residual stress inside the workpiece W by performing the grinding process. However, in a state where the workpiece W is clamped on the chuck 14b with a certain or more clamping force, bending of the workpiece W due to release of internal stress is suppressed.

  Further, in the grinding machine 1, it is necessary to increase the clamping force of the workpiece W by the chuck 14b by the amount of cutting in the roughing process. On the other hand, the cutting amount in the first finishing step (S2) is smaller than the cutting amount in the rough processing step (S1), and the grinding load applied to the workpiece W is reduced. Therefore, in the first finishing step, the chuck control unit 150 maintains the clamping force required in the first finishing step (S2), and holds the workpiece W by the chuck 14b more than in the roughing step (S1). Decrease the clamping force. Then, the grinding machine 1 performs fine grinding on the workpiece W supported by the workpiece support device 10 in a state where the bending has occurred.

  In the first finishing step (S2), when the outer diameter of the workpiece W reaches the fine grinding diameter, the feed control unit 140 shifts from the first finishing step (S2) to the second finishing step (S3). To shift, the feed speed of the grinding wheel 20 (grinding wheel base 30) is reduced from the second pressure P2 to the third pressure P3 (P2> P3) (second clamping force reduction step). Then, the chuck controller 150 reduces the clamping force of the workpiece W by the chuck 14b as the feed speed of the grinding wheel 20 decreases. In addition, when the outer diameter of the workpiece W reaches the finish diameter, the feed control unit 140 stops the feed of the grindstone table 30 to shift to the spark-out step (S4). Along with this, the chuck control unit 150 further reduces the clamping force of the workpiece W by the chuck 14b as the feed speed of the grindstone table 30 decreases.

  Thus, the grinding machine 1 reduces the clamping force by the chuck 14b in a plurality of steps in a step-like manner. Thus, the grinding machine 1 can reduce the amount of decrease in the clamping force per operation, so that it is possible to suppress adverse effects on the grinding process (such as occurrence of grinding burn) due to the decrease in the clamping force.

  As described above, the chuck controller 150 reduces the clamping force of the workpiece W by the chuck 14b when the feed speed of the grinding wheel 20 (the grinding wheel base 30) is reduced. Thereby, the grinding machine 1 can generate a bending caused by the stress release in the workpiece W supported by the workpiece supporting device 10. The grinding machine 1 can improve the processing accuracy of the processed workpiece W by grinding the workpiece W supported by the workpiece support device 10 in a state where the bending has occurred.

  That is, the grinding machine 1 avoids unclamping and re-clamping of the workpiece W by the chuck 14b, and the workpiece supported by the workpiece support device 10 in a state in which bending due to stress release occurs. Grinding can be performed on W. Therefore, the grinding machine 1 can improve the cycle time while maintaining the processing accuracy for the workpiece W.

  In the present embodiment, the grinding machine 1 performs a grinding process on the workpiece W that has been subjected to the quenching process. The workpiece W that has been subjected to the quenching process has a large internal stress remaining therein, and may bend the workpiece W when the stress is released. On the other hand, when the feed speed of the grinding wheel 20 (the grinding wheel base 30) is reduced, the grinding machine 1 reduces the clamping force of the workpiece W by the chuck 14b. Therefore, the grinding machine 1 can improve the processing accuracy for the workpiece W. In addition, even in the workpiece W formed by forging, since the stress remaining inside is large, the grinder 1 is used even when the workpiece W formed by forging is ground. Can be improved in processing accuracy.

<4. Modification>
Next, a modified example of the timing at which the clamping force by the chuck 14b is reduced will be described. First, a first modification will be described with reference to FIG.

  As shown in FIG. 5, in the first modification, the chuck control unit 150 reduces the clamping force of the workpiece W by the chuck 14b after a predetermined time has elapsed since the feed speed of the grindstone table 30 was reduced. That is, the grinding load applied to the workpiece W supported by the workpiece support device 10 may increase immediately after the feed speed of the grindstone table 30 is reduced.

  On the other hand, after a lapse of a predetermined time from the end of the roughing step (S1), that is, in the first finishing step (S2), the grinding machine 1 applies the clamping force of the workpiece W by the chuck 14b to the first pressure. The pressure is reduced from P1 to the second pressure P2. Similarly, the grinding machine 1 applies the clamping force of the workpiece W by the chuck 14b to the second finishing processing step (S3) after a lapse of a predetermined time after the completion of the first finishing processing step (S2). The pressure is reduced from the pressure P2 to the third pressure P3.

  In this way, the grinding machine 1 reduces the feed speed of the grinding wheel 20 (the grinding wheel base 30), and then reduces the clamping force of the workpiece W after waiting for the grinding load to surely decrease. The workpiece W can be stably held. As a result, the grinding machine 1 can suppress an adverse effect on the grinding process due to a decrease in the clamping force.

  Subsequently, a second modification will be described with reference to FIG. As shown in FIG. 6, when the roughing step (S1) is completed and the feed speed of the grinding wheel 20 (the grinding wheel base 30) is reduced, the grinding machine 1 increases the clamping force by the chuck 14b from the first pressure P1. The pressure is gradually decreased to the second pressure P2. Specifically, the chuck control unit 150 gradually lowers the workpiece W by the chuck 14b from the start of the first finishing step (S2) to the end of the second finishing step (S3). In this case, the grinding machine 1 can suppress the adverse effect on the grinding process due to the decrease in the clamping force, so that the processing accuracy for the workpiece W can be improved.

  In the second modified example, the chuck control unit 150 reduces the clamping force by the chuck 14b at a constant rate, but is not limited to this, and changes the decreasing rate of the clamping force with time. May be.

  Next, a third modification will be described with reference to FIG. In the third modified example, the grinding machine 1 detects a grinding load generated during the grinding process, and performs the machining by the chuck 14b when the grinding load decreases with a decrease in the feed speed of the grinding wheel 20 (the grinding wheel base 30). The clamping force of the object W is reduced. Here, as a method of detecting the grinding load, in the third modification, the current value of the grinding wheel motor 32 detected by the grinding load detector 35 (see FIG. 2) is regarded as the grinding load, and the chuck control unit 150 When the value (current value) of the grinding load detected by the load detector 35 decreases, the clamping force of the workpiece W by the chuck 14b is reduced. In addition, as another method of detecting the grinding load, a method of detecting the current value of the master motor 11a or the feed motor 62 and regarding the detected value as the grinding load is exemplified.

  Specifically, in the roughing process (S1), when the outer diameter of the workpiece W reaches the fine grinding diameter in the roughing process (S1), the feed control unit 140 shifts the grinding wheel 20 (from the roughing process to the first finishing process). The feed speed of the wheel head 30) is reduced. Accordingly, when the grinding load decreases with a decrease in the feed speed of the grindstone table 30, the chuck control unit 150 reduces the clamping force of the workpiece W by the chuck 14b from the first pressure P1 to the second pressure P2. .

  In the first finishing step (S2), when the outer diameter of the workpiece W reaches the fine grinding diameter, the feed control unit 140 shifts from the first finishing step (S2) to the second finishing step (S3). To shift, the feed speed of the grinding wheel 20 (grinding wheel base 30) is reduced from the second pressure P2 to the third pressure P3. Then, when the grinding load decreases as the feed speed of the grinding wheel 20 decreases, the chuck controller 150 decreases the clamping force of the workpiece W by the chuck 14b. In addition, when the outer diameter of the workpiece W reaches the finish diameter, the feed control unit 140 stops the feed of the grindstone table 30 to shift to the spark-out step (S4). Accordingly, when the grinding load decreases with a decrease in the feed speed of the grindstone table 30, the chuck controller 150 further reduces the clamping force of the workpiece W by the chuck 14b.

  As described above, the grinding machine 1 reduces the clamping force by the chuck 14b in a plurality of steps in a stepwise manner as the grinding load decreases. Thus, the grinding machine 1 can reduce the amount of decrease in the clamping force per operation, so that it is possible to suppress adverse effects on the grinding process (such as occurrence of grinding burn) due to the decrease in the clamping force.

  Further, since the grinding machine 1 reduces the clamping force by the chuck 14b as the grinding load decreases, it is possible to suppress the adverse effect on the grinding process due to the decrease in the clamping force by the chuck 14b. Therefore, the grinding machine 1 can improve the processing accuracy of the workpiece W.

  In the third modification, the case where the chuck control unit 150 reduces the clamping force when the grinding load decreases has been described. However, the chuck control unit 150 determines that a predetermined time has elapsed since the grinding load decreased. Later, the clamping force may be reduced. In this case, the grinding machine 1 can stably hold the workpiece W by reducing the clamping force of the workpiece W after waiting for the grinding load to surely decrease. As a result, the grinding machine 1 can suppress an adverse effect on the grinding process due to a decrease in the clamping force.

  Further, in the third modification described above, the case where the chuck control unit 150 reduces the clamping force in a stepwise manner when the grinding load is reduced has been described. The clamping force by the chuck 14b may be gradually reduced from the first pressure P1 to the second pressure P2. In this case, the grinding machine 1 can suppress the adverse effect on the grinding process due to the decrease in the clamping force, so that the processing accuracy for the workpiece W can be improved.

  The grinding load generated during the grinding process changes not only according to the change in the feed speed of the grinding wheel 20 (the grinding wheel base 30), but also according to the flow rate of the coolant from the coolant nozzle 73. Therefore, the grinding machine 1 may reduce the clamping force by the chuck 14b when the coolant supply device 70 reduces the supply amount of the coolant.

<5. Others>
As described above, the present invention has been described based on the above-described embodiment and each modified example. However, the present invention is not limited to the above-described embodiment and each modified example, and various modifications may be made without departing from the spirit of the present invention. It is easy to guess that improvements are possible. For example, in the above embodiment, the case where the chuck 14b is provided only on the headstock 11 has been described as an example, but the chuck 14b may be provided on both the headstock 11 and the tailstock 12.

  In the above embodiment, the grinding process is performed while measuring the outer diameter of the workpiece W with the sizing device 80, and when the outer diameter of the workpiece W reaches a predetermined value, the feed speed of the grindstone table 30 is reduced. However, the present invention is not limited to this. For example, the grinding machine 1 performs the grinding while detecting the relative position of the grinding wheel 20 (grinding wheel base 30) with respect to the workpiece supporting device 10 by the encoder 61, and the relative position of the grinding wheel 20 with respect to the workpiece supporting device 10 is determined. When reaching the position (the position where the outer diameter of the workpiece W becomes the fine grinding diameter, the fine grinding diameter or the finishing diameter), the feed speed of the grinding wheel head 30 may be reduced.

  In this modification, the case where the grinding machine 1 regards the current value of the feed driving device 60 as the grinding resistance has been described, but the present invention is not limited to this. For example, if the power of the feed driving device 60 varies according to the grinding resistance, the grinding machine 1 regards a power value other than the current value as the grinding resistance, and controls the drive of the feed driving device 60 based on the power value. May go. The power value other than the current value is exemplified by a voltage value, electric power, and the like.

  In the above-described embodiment, the case where the workpiece support device 10 moves only in the X-axis direction with respect to the bed 2 has been described, but the grinding machine 1 moves the workpiece support device 10 in the X-axis direction with respect to the bed 2. A guide device for guiding the workpiece may be provided, and the workpiece support device 10 may be configured to be movable in a direction relatively approaching and separating from the grinding wheel 20.

  Further, in the above embodiment, the case where the table driving device 50 and the feed driving device are screw feeding devices has been described, but a shaft motor may be used instead of the screw feeding device. Further, in the above embodiment, the case where the grinding machine 1 is a grindstone traverse grinder is described as an example, but the present invention can be applied to a table traverse grinder.

  In the present embodiment, the case where the chuck 14b clamps one end of the workpiece W from the outer peripheral surface has been described, but the chuck 14b clamps one end of the cylindrical workpiece W from the inner peripheral surface. It may be something. Also in this case, since the workpiece W is fixedly supported in the range clamped by the chuck 14b, even if the internal stress of the workpiece W is released during the roughing, the workpiece W is bent. Can be suppressed.

  1: grinding machine, 10: workpiece support device, 14a: spindle center (support portion), 14b: chuck, 17a: tailstock center, 20: grinding wheel, 60: feed drive unit, 140: feed control unit, 150: Chuck control unit, P1: first pressure, P2: second pressure, P3: third pressure, W: workpiece

The feed control unit 140 drives and controls the feed motor 62 provided in the feed drive device 60, and sends the grinding wheel base 30 and the grinding wheel 20 in the X-axis direction. In addition, the feed control unit 140 includes a speed command unit 141 and a speed calculation unit 142. In the speed command unit 141, a target feed speed of the grinding wheel head 30 (hereinafter, referred to as “target feed speed”) is set. Also, the speed calculation unit 142, by differentiating the position signal output from the encoder 61, and calculates the feed rate of the abrasive stone table 30. Then, the feed control unit 140 controls the speed of the feed motor 62 while performing feedback control of the feed speed so that the feed speed matches the target feed speed.

Claims (16)

A workpiece support device having a chuck for clamping one end of the workpiece and a support for supporting the other end of the workpiece, and rotating the workpiece about an axis;
A grinding wheel for grinding the workpiece,
A feed drive device that sends at least one of the grinding wheel and the workpiece support device in a direction in which the grinding wheel and the workpiece support device are relatively approached or separated,
A feed control unit that controls the feed drive device, and reduces the feed speed of the at least one of the grinding wheel and the workpiece support device according to the progress of grinding by the grinding wheel,
Controlling the clamping force of the workpiece by the chuck, when reducing the feed speed or after reducing the feed speed, the clamp force from the first pressure to a second pressure smaller than the first pressure A chuck control unit for lowering;
Grinder equipped with.   The chuck controller, when the outer diameter of the workpiece reaches a predetermined value, or when the relative position of the grinding wheel with respect to the workpiece support device has reached a predetermined position, the clamping force the first pressure. The grinding machine according to claim 1, wherein the grinding pressure is changed stepwise from the pressure to the second pressure.   2. The grinding machine according to claim 1, wherein the chuck controller changes the clamping force from the first pressure to the second pressure in a step-like manner after a lapse of a predetermined time since the feed speed is reduced.   The chuck controller, when the outer diameter of the workpiece reaches a predetermined value, or when the relative position of the grinding wheel with respect to the workpiece support device has reached a predetermined position, the clamping force the first pressure. The grinding machine according to claim 1, wherein the grinding pressure is gradually changed from the pressure to the second pressure.   2. The grinding machine according to claim 1, wherein the chuck control unit gradually changes the clamping force from the first pressure to the second pressure after a lapse of a predetermined time after reducing the feed speed. 3. The grinding machine includes a grinding load detector that detects a grinding load generated by grinding the workpiece by the grinding wheel,
The chuck control unit, when the grinding load is reduced with a decrease in the feed speed, or after the grinding load is reduced, reduces the clamping force from the first pressure to the second pressure, Item 2. The grinding machine according to Item 1.   The grinding machine according to claim 6, wherein the chuck controller changes the clamping force in a step-like manner from the first pressure to the second pressure when the grinding load decreases.   After changing the clamping force from the first pressure to the second pressure, the chuck control unit further changes the clamping force from the second pressure to a third pressure smaller than the second pressure in a stepwise manner. The grinding machine according to claim 2, wherein the grinding machine is operated.   The grinding machine according to claim 7, wherein the chuck controller changes the clamping force from the first pressure to the second pressure in a step-like manner after a lapse of a predetermined time after the reduction of the grinding load.   The grinding machine according to claim 7, wherein the chuck controller gradually changes the clamping force from the first pressure to the second pressure when the grinding load decreases.   The grinding machine according to claim 7, wherein the chuck control unit gradually changes the clamping force from the first pressure to the second pressure after a lapse of a predetermined time after the grinding load decreases.   The grinding machine according to any one of claims 1 to 11, wherein the grinding machine performs a grinding process on the workpiece that has been subjected to a quenching process.   The grinding machine according to claim 1, wherein the grinding machine performs a grinding process on the workpiece formed by forging. A workpiece support device having a chuck for clamping one end of the workpiece and a support for supporting the other end of the workpiece, and rotating the workpiece about an axis;
A grinding wheel for grinding the workpiece,
A feed drive device that sends at least one of the grinding wheel and the workpiece support device in a direction in which the grinding wheel and the workpiece support device are relatively approached or separated,
Grinding method using a grinding machine provided with,
Rough processing step of performing rough grinding on the workpiece by the grinding wheel,
In a state where the feed speed of the at least one of the grinding wheel and the workpiece support device is set to be lower than that of the rough machining step, the workpiece subjected to the rough grinding is subjected to finishing by the grinding wheel. Finishing process,
At the end of the roughing step, or in the finishing step, a first clamping force lowering step of reducing a clamping force of the workpiece by the chuck from a first pressure to a second pressure smaller than the first pressure. ,
A grinding method comprising: The finish processing step,
A first finish processing step of performing fine grinding in a state where the feed speed is lower than the rough processing step,
A second finish processing step of performing fine grinding in a state where the feed speed is lower than the first finish processing step,
With
The grinding method, at the end of the first finishing processing step, or, in the second finishing processing step, a second clamping force lowering step of reducing the clamping force by the chuck,
The grinding method according to claim 14, comprising: The grinding machine includes a grinding load detector that detects a grinding load generated by grinding the workpiece by the grinding wheel,
In the first clamping force lowering step, when the grinding load is reduced with a decrease in the feed speed, or after the grinding load is reduced, the clamping force is reduced from the first pressure to the second pressure. The grinding method according to claim 14, wherein the grinding is performed.

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