JP2013129027A - Method and device for monitoring grinding abnormality - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for monitoring a grinding abnormality capable of improving determination accuracy of grinding burn generated in grinding of a workpiece.SOLUTION: A threshold of grinding load of a grinding wheel 43 is set in relation to rotating speed of a workpiece W when the grinding burn of the workpiece W is generated on the basis of a relationship between the rotating speed of the workpiece W when grinding the workpiece W and the grinding load of the grinding wheel 43. When grinding the workpiece W, the grinding load of the grinding wheel 43 and the rotating speed of the workpiece W are detected. Accordingly, grinding burn of the workpiece W generated by heating due to large grinding load applied instantaneously and grinding burn of the workpiece W generated by heat conduction due to contact between the workpiece W and abrasive grain and chip over many hours can be monitored, thereby enabling improvement of determination accuracy of grinding burn generated in grinding of the workpiece W.

Description

  The present invention relates to a method for monitoring a grinding abnormality in grinding a workpiece and a device for monitoring a grinding abnormality.

  When the temperature of the workpiece rises during grinding of the workpiece, grinding burn is likely to occur as an abnormal grinding of the workpiece. The temperature rise of the workpiece is caused by heat generation due to a large grinding load applied instantaneously or heat conduction due to long-time contact between the workpiece and abrasive grains and chips.

  For example, Japanese Patent Application Laid-Open No. 4-348867 (Patent Document 1) discloses a method for minimizing the fluctuation within one rotation of the workpiece of the grinding load given by the rotation speed of the workpiece and the cutting speed of the grinding wheel. A grinding machine is disclosed that corrects the shape error of the workpiece over time. According to this grinding machine, since the fluctuation of the grinding load is controlled, it is possible to monitor the grinding burn of the workpiece caused by the heat generated by the large grinding load applied instantaneously.

JP-A-4-348867

  As described above, in the invention described in Patent Document 1, it is possible to monitor grinding burn of a workpiece generated by heat generated by a large grinding load that is instantaneously applied. However, since contact between the workpiece and the abrasive grains and chips for a long time does not show a great change in the grinding load, it is impossible to monitor grinding burn of the workpiece caused by heat conduction due to the contact.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a grinding abnormality monitoring method and a grinding abnormality monitoring apparatus capable of improving the accuracy of determination of grinding burn that occurs in grinding of a workpiece. And

(Grinding abnormality monitoring method)
(Claim 1) The grinding abnormality monitoring method of the present invention uses a grinding machine that rotates the workpiece and rotates the grinding wheel and grinds the workpiece by relatively moving the workpiece and the grinding wheel. In the grinding abnormality monitoring method for monitoring the grinding burn of the workpiece, a threshold setting step for setting a threshold value for the rotational speed of the workpiece and the grinding load of the grinding wheel when the grinding burn of the workpiece occurs, A grinding load detecting step for detecting a grinding load of the grinding wheel when grinding the workpiece, a rotational speed detecting step for detecting a rotational speed of the workpiece when grinding the workpiece, and the detected grinding wheel And a grinding burn determination step of determining occurrence of grinding burn of the workpiece based on a relationship between a grinding load of the vehicle and the detected rotation speed of the workpiece and the set threshold value.

  (Claim 2) The grinding abnormality monitoring method includes a threshold value determining step for determining the threshold value corresponding to the detected rotational speed of the workpiece, and the threshold value setting step is performed when the workpiece is ground. Based on the relationship between the rotational speed of the workpiece and the grinding load of the grinding wheel, a threshold is set for the grinding load of the grinding wheel with respect to the rotational speed of the workpiece when grinding burn of the workpiece occurs, In the grinding burn determination step, when the detected grinding load of the grinding wheel becomes equal to or more than the determined threshold value, it may be determined that grinding burn has occurred on the workpiece.

  (Claim 3). The threshold value setting step may set a plurality of threshold values corresponding to a plurality of types of workpieces.

  (Claim 4) The grinding abnormality monitoring method includes a condition changing step of changing the grinding condition of the grinding wheel so that the detected grinding load of the grinding wheel does not exceed the threshold and approaches the threshold. You may do it.

  (Claim 5) The threshold value setting step sets a grinding load threshold value for a grinding load of the grinding wheel and a rotational speed threshold value for a rotational speed of the workpiece when grinding burn of the workpiece occurs. In the grinding burn determination step, when the detected rotational speed of the workpiece is less than the rotational speed threshold, and at least one of the detected grinding load of the grinding wheel is greater than or equal to the grinding load threshold, You may make it determine with the grinding burn generation | occurrence | production of the said workpiece | work.

  (Claim 6) The present invention is applied to a grinding machine for simultaneously grinding a plurality of grinding parts of the workpiece, and detects a deflection displacement amount or a temperature of each of the grinding parts of the workpiece by a plurality of displacement sensors or temperature sensors. The respective grinding loads may be calculated based on the respective deflection displacement amounts or temperatures, and the grinding burns of the respective grinding sites may be determined based on the respective grinding loads.

(Grinding abnormality monitoring device)
(Claim 7) The grinding abnormality monitoring device of the present invention uses a grinding machine for rotating the workpiece and rotating the grinding wheel and grinding the workpiece by relatively moving the workpiece and the grinding wheel. In the grinding abnormality monitoring device for monitoring the grinding burn of the workpiece, the grinding burn of the workpiece is determined based on the relationship between the rotational speed of the workpiece when grinding the workpiece and the grinding load of the grinding wheel. Threshold setting means for setting a threshold for the grinding load of the grinding wheel with respect to the rotational speed of the workpiece when it is generated, and grinding load detection means for detecting the grinding load of the grinding wheel when grinding the workpiece. A rotational speed detecting means for detecting the rotational speed of the workpiece when grinding the workpiece; a threshold determining means for determining the threshold corresponding to the detected rotational speed of the workpiece; and the detected grinding wheel of Cutting load comprises a grinding burn occurs and determines grinding burn determination means of the workpiece when a determined the threshold or more, the.

  (Claim 1) The grinding speed at which the contact time between the workpiece and the abrasive grains and chips changes greatly in grinding is the rotational speed of the workpiece. When the rotational speed of the workpiece is lowered, the contact time between the workpiece and the abrasive grains and chips becomes longer, and the grinding burn of the workpiece is likely to occur. Therefore, as in the grinding abnormality monitoring method of the present invention, a threshold value is set for the rotational speed of the workpiece and the grinding load of the grinding wheel when grinding burn of the workpiece occurs, and the detected grinding load of the grinding wheel and Based on the relationship between the detected rotation speed of the workpiece and the set threshold, occurrence of grinding burn of the workpiece is determined. In this way, the grinding burn of the workpiece caused by heat generated by a large grinding load applied instantaneously and the grinding burn of the workpiece caused by heat conduction due to long-time contact between the workpiece and abrasive grains and chips are monitored. Can do. Therefore, it is possible to improve the determination accuracy of grinding burn that occurs in grinding of a workpiece. Each process is not described in time series, and can be executed in any order.

  (Claim 2) More specifically, based on the relationship between the rotational speed of the workpiece when grinding the workpiece and the grinding load of the grinding wheel, the workpiece when grinding burn of the workpiece occurs A threshold value for the grinding load of the grinding wheel with respect to the rotation speed is set. Then, a threshold value corresponding to the detected rotational speed of the workpiece is determined, and when the detected grinding load of the grinding wheel is equal to or greater than the determined threshold value, it is determined that the grinding burn of the workpiece has occurred. In this way, the grinding burn of the workpiece caused by heat generated by a large grinding load applied instantaneously and the grinding burn of the workpiece caused by heat conduction due to long-time contact between the workpiece and abrasive grains and chips are monitored. Can do. Therefore, it is possible to improve the determination accuracy of grinding burn that occurs in grinding of a workpiece.

  (Claim 3) When the shape, material, etc. of the workpiece are changed, the grinding load of the grinding wheel and the rotational speed of the workpiece, which cause grinding burn, may be different. Therefore, as in the grinding abnormality monitoring method of the present invention, a plurality of threshold values corresponding to a plurality of types of workpieces are set. Thereby, grinding burn of the workpiece when the shape or material of the workpiece is changed can be monitored with high accuracy.

  (Claim 4) When determining the grinding burn of the workpiece, if the grinding load of the grinding wheel does not exceed the threshold value, it is determined that the grinding burn of the workpiece has not occurred. That is, even if the grinding conditions are changed so that the grinding load of the grinding wheel does not exceed the threshold and approaches the threshold, it can be determined that grinding burn of the workpiece has not occurred. Therefore, the grinding load of the grinding wheel does not exceed the threshold value, and a target value for condition change that is close to the threshold value is set, and if this target value for condition change is exceeded, the grinding condition is changed so as to fall below the target value for condition change. Thus, the grinding time, that is, the grinding cycle time can be shortened.

  (Claim 5) As another method, more specifically, a grinding load threshold for the grinding load of the grinding wheel and a rotational speed threshold for the rotational speed of the workpiece when grinding burn of the workpiece occurs are set. . Then, when the detected grinding load of the grinding wheel is equal to or larger than the set grinding load threshold, it is determined that the grinding burn of the workpiece has occurred. This makes it possible to monitor the grinding burn of the workpiece caused by heat generated by a large grinding load that is instantaneously applied. Further, when the detected rotational speed of the workpiece is less than the set rotational speed threshold value, it is determined that grinding burn of the workpiece has occurred. As a result, it is possible to monitor the grinding burn of the workpiece caused by heat conduction due to contact between the workpiece and the abrasive grains and chips for a long time. Therefore, it is possible to improve the determination accuracy of grinding burn that occurs in grinding of a workpiece.

  (Claim 6) Thereby, when grinding several grinding parts of a workpiece simultaneously, the grinding abnormality of each grinding part can be determined.

  (Claim 7) According to the grinding abnormality monitoring device of the present invention, the same effects as those in the above-described grinding abnormality monitoring method can be obtained. Further, other characteristic portions in the grinding abnormality monitoring method can be similarly applied to the grinding abnormality monitoring apparatus of the present invention. And the same effect is produced.

It is a top view of a grinding machine. 1 is a functional block diagram of a grinding abnormality monitoring device. 1st embodiment: It is a flowchart of a burning monitoring program. It is a figure which shows the table data of the relationship with the threshold value as a grinding load of the grinding wheel with respect to the rotational speed of a workpiece. The history display state of the screen of the display device is shown. 2nd embodiment: It is a functional block diagram of the grinding abnormality monitoring apparatus. Second Embodiment: A flowchart of a burn monitoring program. It is a figure which shows the 1st example in 3rd embodiment. It is a figure which shows the 2nd example in 3rd embodiment. It is a figure which shows the 3rd example in 3rd embodiment.

(1. Machine configuration of grinding machine)
As an example of the grinding machine 1, a headstock traverse type internal grinding machine will be described as an example and described with reference to FIG. 1. A case where the workpiece W to be ground by the grinding machine 1 is used as an outer ring of a bearing and the inner peripheral raceway surface of the outer ring of the bearing is ground using the grinding machine 1 will be described as an example. Here, a case where a plurality of workpieces W of the same type are ground, that is, a case where a workpiece W as a mass-produced product is manufactured will be described.

  As shown in FIG. 1, the grinding machine 1 includes a bed 10, a table 20, a headstock 30, a grindstone support device 40, a proximity switch 50, a contact detection sensor 80, and a grinding wheel molding device (not shown). ) And the control device 60.

  The bed 10 has a substantially rectangular shape and is disposed on the floor. However, the shape of the bed 10 is not limited to a rectangular shape. A pair of Z-axis guide rails 11a and 11b are formed on the upper surface of the bed 10 so as to extend in the left-right direction (Z-axis direction) in FIG. The pair of Z-axis guide rails 11a and 11b are rails on which the table 20 can slide. Further, the bed 10 is provided with a Z-axis ball screw 11c for driving the table 20 in the left-right direction in FIG. 1 between the pair of Z-axis guide rails 11a and 11b. A Z-axis motor 11d that rotates is disposed.

  Further, on the upper surface of the bed 10, a pair of X-axis guide rails 12a and 12b on which the grindstone table 41 can slide are formed so as to extend in the vertical direction (X-axis direction) in FIG. Has been. Further, the bed 10 is provided with an X-axis ball screw 12c between the pair of X-axis guide rails 12a and 12b for driving the grinding wheel base 41 in the vertical direction in FIG. 1, and this X-axis ball screw 12c. An X-axis motor 12d that rotates the motor is disposed.

  The table 20 is formed in a long rectangular flat plate shape, and is slidably disposed on the pair of Z-axis guide rails 11 a and 11 b in the upper surface of the bed 10. The table 20 is connected to a nut member of the Z-axis ball screw 11c, and moves along the pair of Z-axis guide rails 11a and 11b by driving the Z-axis motor 11d. The Z-axis motor 11d has an encoder, and the encoder can detect the rotation angle of the Z-axis motor 11d.

  The headstock 30 is provided on the upper surface of the table 20 and supports the workpiece W in a rotatable manner. Specifically, the head stock 30 includes a head stock main body 31, a magnet chuck 32, a shoe 33, and a main shaft motor 34. The headstock body 31 is fixed to the left side of FIG. The headstock body 31 is provided with a magnet chuck 32 that can rotate about the Z-axis.

  The magnet chuck 32 attracts and holds a bearing, which is a workpiece W, by a magnetic force. The shoe 33 and the magnet chuck 32 are provided on the headstock 30, and the workpiece W is positioned by supporting the side surface of the workpiece W by the shoe 33. The magnet chuck 32 is rotationally driven with respect to the head stock body 31 by the main shaft motor 34. The main shaft motor 34 has an encoder, and the rotation angle of the main shaft motor 34 can be detected by the encoder.

  The grinding wheel support device 40 includes a grinding wheel base 41, a grinding wheel driving motor 42, and a grinding wheel 43. The grinding wheel base 41 is slidably disposed on the pair of X-axis guide rails 12a and 12b on the upper surface of the bed 10. The grindstone base 41 is connected to the nut member of the X-axis ball screw 12c, and moves along the pair of X-axis guide rails 12a and 12b by driving the X-axis motor 12d.

  A grinding wheel driving motor 42 is fixed to an end surface of the grinding wheel head 41 in the X-axis direction on the head stock 30 side. At the tip of the grinding wheel drive motor 42, a grinding wheel 43 for grinding the inner peripheral raceway surface of the bearing outer ring, which is the workpiece W, is provided. That is, the grinding wheel 43 is attached to the grinding wheel base 41 so as to be rotatable around the Z axis.

  The proximity switch 50 is a switch that is provided on the upper surface of the bed 10 and detects the start and end of the grinding cycle of the bearing outer ring that is the workpiece W by the grinding wheel 43. That is, the proximity switch 50 determines that the grinding cycle starts when the grinding wheel base 41 approaches the proximity switch 50 and the Z-axis direction separation distance between the proximity switch 50 and the grinding wheel base 41 becomes equal to or less than the set value. On the other hand, the proximity switch 50 determines that the grinding cycle is completed when the grinding wheel base 41 is moved away from the proximity switch 50 and the Z-axis direction separation distance between the proximity switch 50 and the grinding wheel base 41 exceeds a set value.

The contact detection sensor 80 is a sensor that is provided on the side surface of the headstock body 31 and detects the start of grinding of the bearing outer ring that is the workpiece W by the grinding wheel 43. That is, when the grinding wheel 43 contacts the workpiece W, the contact detection sensor 80 detects the contact and determines that grinding is started. For example, an AE sensor is used as the contact detection sensor 80.
In the present embodiment, the contact detection sensor 80 is used to determine the start and end of collection of grinding load data of the grinding wheel 43 and rotation speed data of the workpiece W. Instead of the contact detection sensor 80, the start and end of collection of grinding load data of the grinding wheel 43 and rotation speed data of the workpiece W are determined based on the X-axis position of the grinding wheel base 41 and the Z-axis position of the table 20. You can also.

  The grinding wheel molding device (not shown) is a dresser that is provided on the headstock 30 or the bed 10 and molds the outer peripheral surface of the grinding wheel 43, for example. The grinding wheel 43 dressed by this grinding wheel molding device is in a state of good sharpness and is formed in a desired shape.

  The control device 60 controls each motor to rotate the workpiece W around the Z axis, rotate the grinding wheel 43, and make the workpiece W and the grinding wheel 43 relative to each other in the Z axis direction and the X axis direction. By moving, adaptive control of grinding of the inner peripheral raceway surface of the bearing outer ring which is the workpiece W is performed. Details will be described later. In addition, the control device 60 includes a grinding abnormality monitoring device 70 that monitors grinding burn in grinding of the workpiece W. However, the grinding abnormality monitoring device 70 is not limited to the one provided inside the control device 60, and can also be applied as an external device.

(2. Explanation of grinding burn and threshold)
Next, the threshold value set in the grinding burn and grinding abnormality monitoring device 70 monitored by the grinding abnormality monitoring device 70 will be described. When the temperature of the workpiece W rises during grinding of the workpiece W, grinding burn of the workpiece W is likely to occur. The temperature rise of the workpiece W is caused by heat generation due to a large grinding load applied instantaneously or heat conduction due to long-time contact between the workpiece W and abrasive grains and chips.

  The rotation speed of the workpiece W is a grinding condition in which the contact time between the workpiece W and the abrasive grains and chips changes greatly in grinding. When the rotational speed of the workpiece W is reduced, the contact time between the workpiece W and the abrasive grains and chips becomes longer, and grinding burn of the workpiece W is likely to occur. Therefore, based on the relationship between the rotational speed of the workpiece W when grinding the workpiece W and the grinding load of the grinding wheel 43, as shown in FIG. A threshold value R (v) for the grinding load R of the grinding wheel 43 with respect to the rotational speed V of the workpiece W is set. This threshold value R (v) has a relationship that increases as the rotational speed V of the workpiece W increases.

  This threshold value R (v) is set, and the grinding load R of the grinding wheel 43 and the rotational speed V of the workpiece W when the workpiece W is ground are detected. Then, a threshold value R (v) corresponding to the detected rotational speed V of the workpiece W is determined, and the workpiece W is determined when the detected grinding load R of the grinding wheel 43 becomes equal to or greater than the determined threshold value R (v). It is determined that no grinding burn occurred. As a result, the grinding burn of the workpiece W generated by heat generated by the large grinding load R applied instantaneously, and the grinding burn of the workpiece W generated by heat conduction due to the contact between the workpiece W and the abrasive grains and chips for a long time. Can be monitored. Therefore, it is possible to improve the determination accuracy of grinding burn that occurs in the grinding of the workpiece W.

  In addition, when the shape, material, or the like of the workpiece W is changed, the grinding load R of the grinding wheel 43 that causes grinding burn and the rotational speed V of the workpiece W may be different. Therefore, as shown in FIG. 4, a plurality of threshold values R (v) (R (va) and R (vb) in FIG. 4) corresponding to a plurality of types (two types in FIG. 4) of workpieces W are set. Set. Thereby, grinding burn of the workpiece W when the shape, material, etc. of the workpiece W are changed can be monitored with high accuracy.

  Further, when the grinding burn of the workpiece W is determined, if the grinding load R of the grinding wheel 43 does not exceed the threshold value R (v), it is determined that the grinding burn of the workpiece W has not occurred. That is, even if the grinding condition is changed so that the grinding load R of the grinding wheel 43 does not exceed the threshold value R (v) and approaches the threshold value R (v), it is determined that the grinding burn of the workpiece W has not occurred. it can. Accordingly, a condition change target value is set so that the grinding load R of the grinding wheel 43 does not exceed the threshold value Rv and is close to the threshold value Rv, and when the condition change target value is exceeded, the grinding condition is set so as to fall below the condition change target value. The grinding time, that is, the grinding cycle time can be shortened by changing.

(3. Configuration of grinding abnormality monitoring device)
Next, the grinding abnormality monitoring device 70 will be described with reference to the functional block diagram of FIG. Here, in describing the grinding abnormality monitoring device 70, FIG. 2 also describes a partial configuration of the grinding machine 1 described above. Here, in FIG. 2, the same code | symbol is attached | subjected about the structure same as the structure of the grinding machine 1 of FIG. A motor rotation speed sensor 34 a that measures the rotation speed of the spindle motor 34 is attached to the spindle motor 34. Note that the rotational speed may be measured by an encoder of the spindle motor 34 instead of the motor rotational speed sensor 34a. Further, a motor wattmeter 42 a for measuring the driving power of the grinding wheel driving motor 42 is attached to the grinding wheel driving motor 42. Instead of the motor wattmeter 42a, the power value may be directly collected by a motor amplifier of the grinding wheel driving motor 42.

  The grinding abnormality monitoring device 70 includes a rotation speed calculation unit 71, a grinding load calculation unit 72, a data storage unit 73, a threshold value determination unit 74, a burn determination unit 75, an output unit 76, and a condition change unit 77. It is prepared for. The rotation speed calculation unit 71 calculates the rotation speed V of the workpiece W based on the rotation speed of the spindle motor 34 taken from the motor rotation speed sensor 34a. The rotational speed V of the workpiece W has a relationship that increases as the rotational speed of the spindle motor 34 increases.

  The grinding load calculation unit 72 calculates the grinding load R of the grinding wheel 43 generated by grinding the workpiece W by the grinding wheel 43 based on the driving power of the grinding wheel driving motor 42 taken in from the motor wattmeter 42a. To do. The grinding load R of the grinding wheel 43 has a relationship that increases as the driving power of the grinding wheel driving motor 42 increases. As a method for calculating the grinding load R of the grinding wheel 43, in this embodiment, the driving power of the grinding wheel driving motor 42 is used. However, the grinding load R of the grinding wheel 43 may be calculated in the following manner. it can. For example, the grinding load R of the grinding wheel 43 rotates the current value of the grinding wheel driving motor 42, the current value, power value, and power value of the X-axis motor 12d that moves the grinding wheel 43 and the workpiece W relative to each other. It can be calculated from the current value, power value of the spindle motor 34 that can be driven, the amount of deflection deformation of the grinding wheel 43 or the support portion of the workpiece W, and the like.

  Further, the grinding load R can be calculated based on the deformation amount of the grinding part in the workpiece W, that is, the deflection displacement amount of the workpiece W caused by being pressed against the grinding wheel 43. This is because the amount of deflection displacement depends on the grinding load R. The deflection displacement amount of the grinding part in the workpiece W is measured by, for example, a displacement sensor.

  Further, the grinding load R can be calculated from the temperature of the grinding part of the workpiece W. This is because the temperature depends on the grinding load. However, it is not easy to measure the temperature of the workpiece W in contact with the grinding wheel 43, that is, the temperature of the grinding point. Therefore, the temperature of the portion of the workpiece W having a phase shifted from the grinding point (contact point with the grinding wheel 43) in the grinding portion (inner peripheral surface or outer peripheral surface) is measured. The temperature of the grinding part of the workpiece W differs depending on the phase deviated from the grinding point and the phase deviated from the grinding point, but the phase temperature deviated from the grinding point is a value corresponding to the temperature of the grinding point. Therefore, even a phase shifted from the grinding point can be measured sufficiently. And the temperature of the phase shifted | deviated from the grinding point among the grinding | polishing parts of the workpiece W is measured with the contact-type temperature sensor made to contact the said site | part, or the non-contact-type temperature sensor made non-contact with the said site | part.

  The data storage unit 73 includes table data (see FIG. 4) of the threshold R (v) for the grinding load R of the grinding wheel 43 with respect to the rotational speed V of the workpiece W measured in advance by the operator, and the grinding load of the grinding wheel 43. The table data (see FIG. 4) of the condition change target value R (x) that R does not exceed the threshold value R (v) and is close to the threshold value R (v) is stored.

  The threshold value determination unit 74 is calculated by the rotation speed calculation unit 71 based on the table data of the threshold value R (v) for the grinding load R of the grinding wheel 43 with respect to the rotation speed V of the workpiece W stored in the data storage unit 73. A threshold value R (v) for the grinding load R of the grinding wheel 43 with respect to the rotational speed V of the workpiece W to be worked is determined.

  The burn determination unit 75 determines that grinding burn has occurred when the grinding load R of the grinding wheel 43 calculated by the grinding load calculation unit 72 is equal to or greater than a threshold value R (v).

  When it is determined that grinding burn has occurred, the output unit 76 displays information on grinding burn on the screen of the display device 81, print processing by the printing device 82, storage processing in the storage device 83, or communication device 84. To perform communication output to external devices. The output is selected by the operator. Thereby, the operator can surely grasp the grinding burn according to the output form selected by the worker for the information on the grinding burn.

  The condition changing unit 77 uses a threshold R based on the table data of the condition changing target value R (x) stored in the data storage unit 73 so that the grinding load R of the grinding wheel 43 calculated by the grinding load calculating unit 72 is calculated. The grinding condition of the grinding wheel 43 is changed so as not to exceed (v) and approach the threshold value R (v).

(4. Processing by grinding abnormality monitoring device)
Next, execution of the grinding abnormality monitoring program by the grinding abnormality monitoring device 70 will be described with reference to FIG. The grinding abnormality monitoring program determines whether grinding burn has occurred based on the threshold value R (v) for the grinding load R of the grinding wheel 43 with respect to the current rotational speed V of the workpiece W. This will be described in detail below.

  As shown in FIG. 3, the table data (see FIG. 4) of the threshold value R (v) for the grinding load R of the grinding wheel 43 with respect to the rotational speed V of the workpiece W and the grinding load R of the grinding wheel 43 as data relating to the threshold value. It is determined whether the table data (see FIG. 4) of the condition change target value R (x) that does not exceed the threshold value R (v) and is close to the threshold value R (v) has already been stored (step S1). If not stored yet, data relating to the threshold is read (step S2).

  If data relating to the threshold is stored, a grinding cycle is started (step S3). When the grinding cycle is started, as shown in FIG. 2, the control device 60 drives each motor and starts grinding the inner circumferential raceway surface of the bearing outer ring as the workpiece W by the grinding wheel 43. More specifically, after starting the grinding cycle, as shown in FIG. 1, the grinding wheel base 41 is moved to the reference position (see FIG. 1) toward the position where the grinding wheel 43 can enter the inside of the bearing outer ring, which is the workpiece W, in the radial direction. (Not shown) is moved in the X-axis direction. Then, the grinding wheel 43 enters the radial inner side of the bearing outer ring, which is the workpiece W, by moving the table 20 in the Z-axis direction. Then, the grinding wheel 43 moves in the X-axis direction toward the inner peripheral raceway surface of the bearing outer ring that is the workpiece W, and after detecting contact between the workpiece W and the grinding wheel 43, grinding is started. Grinding of the workpiece W is carried out continuously after grinding the black skin and then performing rough grinding. When the grinding is finished, the operation is performed in the reverse order from the start of grinding, the process returns to the reference position, and the grinding cycle is finished.

  When the proximity switch 50 is in the ON state, that is, when the grinding cycle is started, it is determined whether or not the contact detection sensor 80 has detected contact between the workpiece W and the grinding wheel 43 (step S4).

  When the contact detection sensor 80 detects the contact between the workpiece W and the grinding wheel 43 (step S4: Yes), the grinding load R and the rotational speed V of the workpiece W when the workpiece W is ground by the grinding wheel 34 are detected. Is measured (steps S5 and S6). Then, a threshold value R (v) for the rotational speed V of the workpiece W is determined from the threshold value determination data (step S7). Specifically, based on the table data of the threshold value R (v) for the grinding load R of the grinding wheel 43 with respect to the rotational speed V of the workpiece W stored in the data storage unit 73 shown in FIG. A threshold value R (v) for the rotational speed V of the workpiece W calculated by 71 is determined.

  Then, immediately after measurement of the grinding load R of the grinding wheel 34 and the rotational speed V of the workpiece W, grinding burn determination is performed (step S8). That is, the grinding conditions of the grinding wheel 43 such as grinding of the grinding wheel 43 so that the grinding load R of the grinding wheel 43 with respect to the rotational speed V of the workpiece W does not exceed the threshold value R (v) and approaches the threshold value R (v). Change the feed speed, rotation speed, etc., and judge grinding burn.

  Specifically, as shown in FIG. 4, a condition change target value R (x) that does not exceed the threshold R (v) and is close to the threshold R (v) is set, and the condition change target value R ( If x) is exceeded, the grinding conditions are changed so as to fall below the condition change target value R (x). If the grinding load R of the grinding wheel 43 does not exceed the threshold value R (v), it is determined that there is no grinding burn (step S9), and whether the proximity switch 50 is in an OFF state, that is, whether the grinding cycle is finished. Is determined (step S10). If the grinding cycle has not ended, the process returns to step S5 and the above-described processing is performed.

  On the other hand, when the grinding load R of the grinding wheel 43 exceeds the threshold value R (v) in step S8, it is determined that grinding burn has occurred, and the burn content is displayed on the display device 81 by the output unit 76 of FIG. Then, the burn contents are stored in the storage device 83 (step S11). Then, the grinding cycle is stopped (step S12).

  On the other hand, if the grinding cycle is completed in step S10, it is determined whether or not there is a next workpiece W (step S13). If there is a next workpiece W, the installation of the workpiece W is determined. Setup is performed (step S14), and the processing is repeated from step S3. On the other hand, if there is no next workpiece W, the grinding cycle is stopped (step S12).

(5. History display status of display device screen)
Next, the history display state of the screen of the display device 81 will be described with reference to FIG. When grinding burn occurs due to execution of the grinding abnormality monitoring program of FIG. 3 (step S11 of FIG. 3), the date and time of occurrence of grinding burn is stored in the storage device 83. When a large number of workpieces W are ground, the past burn history is stored in the storage device 83. Further, it can be seen that the workpiece W that is not stored as occurrence of grinding burn has no grinding burn. Thus, by storing the past history of information related to grinding burn, the tendency of grinding burn can be grasped. Thus, by using the tendency of grinding burn, a sign of occurrence of grinding burn can be predicted when performing future grinding. As a result, appropriate measures can be determined for future grinding.

<Second embodiment>
Next, the grinding abnormality monitoring device of the second embodiment will be described. The grinding abnormality monitoring device 70 described above sets a threshold value R (v) for the grinding load R of the grinding wheel 43 with respect to the rotational speed V of the workpiece W when grinding burn of the workpiece W occurs. In the present embodiment, the grinding load threshold Rt for the grinding load R of the grinding wheel 43 when the grinding burn of the workpiece W occurs, and the rotational speed threshold Vt for the rotational speed V of the workpiece W are respectively set. did. That is, the grinding load threshold Rt when the grinding burn of the workpiece W occurs at a predetermined rotational speed V for grinding the workpiece W is set. This makes it possible to monitor the grinding burn of the workpiece caused by heat generated by a large grinding load that is instantaneously applied. In addition, a rotation speed threshold value Vt when the grinding burn of the workpiece W occurs when the predetermined rotation speed V is set at a low rotation speed due to an operator's work mistake or the like is set. As a result, it is possible to monitor the grinding burn of the workpiece caused by heat conduction due to contact between the workpiece W and the abrasive grains and chips for a long time. Therefore, it is possible to improve the determination accuracy of grinding burn that occurs in grinding of a workpiece. This will be described in detail below.

(1. Configuration of grinding abnormality monitoring device)
The grinding abnormality monitoring device 170 in this embodiment will be described with reference to FIG. The grinding abnormality monitoring device 170 according to the present embodiment includes a rotation speed calculation unit 71 (similar to the first embodiment), a grinding load calculation unit 72 (similar to the first embodiment), a threshold data storage unit 173, and a burn determination. A unit 75 (similar to the first embodiment) and an output unit 76 (similar to the first embodiment) are provided.

  The threshold data storage unit 173 is data of the grinding load threshold Rt when the workpiece W is ground and burned at a predetermined rotational speed V for grinding the workpiece W measured in advance by the operator, an operator's operation error, and the like. Then, when the predetermined rotational speed V is set at a low rotational speed, the rotational speed threshold value Vt data when grinding burn of the workpiece W occurs is stored.

(2. Processing by grinding abnormality monitoring device)
Processing by the grinding abnormality monitoring device 170 will be described with reference to FIG. Data on the grinding load threshold value Rt for the grinding load R of the grinding wheel 43 and data on the rotational speed threshold value Vt for the rotational speed V of the workpiece W are already stored as threshold data. It is determined whether or not (step S21). If not stored yet, the threshold data is read (step S22).

  If threshold data is stored, a grinding cycle is started (step S23). When the grinding cycle is started, as shown in FIG. 6, the control device 60 drives each motor and starts grinding the inner circumferential raceway surface of the bearing outer ring as the workpiece W by the grinding wheel 43.

  When the proximity switch 50 is in the ON state, that is, when the grinding cycle is started, it is determined whether or not the contact detection sensor 80 has detected contact between the workpiece W and the grinding wheel 43 (step S24).

  And if the contact detection sensor 80 detects the contact with the workpiece W and the grinding wheel 43 (step S24: Yes), the grinding load R at the time of grinding the workpiece W with the grinding wheel 43 will be measured (step S25). Then, it is determined whether or not the measured grinding load R of the grinding wheel 43 is equal to or greater than the grinding load threshold value Rt stored in the threshold data storage unit 173 (step S26), and the grinding load R of the grinding wheel 43 is the grinding load. If it is equal to or greater than the threshold value Rt, it is determined that grinding burn has occurred, and the burn content is displayed on the display device 81 and the burn content is stored in the storage device 83 by the output unit 76 of FIG. 6 (step S27). Then, the grinding cycle is stopped (step S28).

  On the other hand, when the grinding load R of the grinding wheel 43 is less than the grinding load threshold value Rt in step S26, the rotational speed V of the workpiece W when grinding the workpiece W by the grinding wheel 43 is measured (step S29). . Then, it is determined whether or not the measured rotational speed V of the workpiece W is less than the rotational speed threshold Vt stored in the threshold data storage unit 173 (step S30), and the rotational speed V of the workpiece W is the rotational speed. When it is less than the threshold value Vt, it is determined that grinding burn has occurred, and the burn content is displayed on the display device 81 and the burn content is stored in the storage device 83 by the output unit 76 of FIG. 6 (step S27). Then, the grinding cycle is stopped (step S28).

  On the other hand, when the rotational speed V of the workpiece W is equal to or higher than the rotational speed threshold value Vt in step S30, it is determined that there is no grinding burn (step S31), and whether the proximity switch 50 is in the OFF state, that is, whether the grinding cycle has ended. Is determined (step S32). If the grinding cycle has not ended, the process returns to step S25 to perform the above-described processing. On the other hand, when the grinding cycle is completed in step S32, it is determined whether or not there is a next workpiece W (step S33). If there is a next workpiece W, the installation of the workpiece W is determined. Setup is performed (step S34), and the processing is repeated from step S23. On the other hand, if there is no next workpiece W, the grinding cycle is stopped (step S28).

  In addition, although the contact detection sensor 80 was used in the said embodiment for the determination of the collection start and collection completion | finish of grinding load data, without using this contact detection sensor 80, the grindstone base 41 and the table 20 were preset. It can also be performed by moving to the axial position and the Z-axis position.

<Third embodiment>
Next, when grinding a plurality of positions of the workpiece W at the same time, it can be performed as follows. That is, it is also possible to calculate the grinding load at each grinding site and monitor the grinding burn at each grinding site using each grinding load. A third embodiment will be described with reference to FIGS.

  A first example is shown in FIG. The workpiece W of the first example is formed in a shaft shape having a plurality of flange portions Wb, Wb, Wb. Then, the outer peripheral surfaces of the small-diameter shaft portions Wa and Wa located between the adjacent flange portions Wb, Wb and Wb of the workpiece W are ground by the grinding wheels 43 and 43, respectively. Then, a plurality of displacement sensors 100, 100 are used to shift the phase by 180 ° from the grinding points to be ground by the grinding wheels 43, 43 in the outer peripheral surfaces (grinding portions) of the small-diameter shaft portions Wa, Wa of the workpiece W. Detects the deflection displacement of the position.

  Each displacement sensor 100, 100 detects a local deflection displacement amount of each grinding part. Each of the displacement sensors 100 and 100 may be a sensor that contacts the workpiece W or a non-contact sensor. For example, an eddy current sensor can be applied as a non-contact type sensor. Here, the deflection displacement amount is a value corresponding to the local grinding load of each grinding part. Then, the grinding load calculation unit 72 (corresponding to the grinding load calculation unit 72 shown in FIGS. 2 and 6) determines the grinding load or the grinding load of each grinding part based on the deflection displacement detected by the displacement sensors 100 and 100. The corresponding value is calculated. And similarly to the said embodiment, it is determined whether each grinding site | part is a grinding burn in the burn determination part 75 shown in FIG. In this way, it is possible to determine whether grinding burn has occurred for each of the plurality of grinding sites.

  Further, the displacement sensors 100, 100 can be replaced with the temperature sensors 100, 100. Similar to the displacement sensors 100, 100, the temperature sensors 100, 100 may be sensors that contact the workpiece W or non-contact sensors. Each temperature sensor 100, 100 detects the temperature of each grinding part of the workpiece W. The temperature sensors 100 and 100 are positions shifted in phase from the grinding points to be ground by the grinding wheels 43 and 43 on the outer peripheral surfaces (grinding portions) of the small-diameter shaft portions Wa and Wa of the workpiece W, for example, 90 °. The temperature at a position of 180 ° is detected. Here, the higher the grinding load, the higher the temperature of the grinding part. That is, the temperature of the grinding part detected by each temperature sensor 100, 100 is a value corresponding to the grinding load of each grinding part. And the grinding load calculation part 72 calculates the value according to the grinding load or grinding load of each grinding part based on the temperature of each grinding part.

  Next, a second example will be described. As shown in FIG. 9, the workpiece W of the second example has a large-diameter shaft portion Wc and a small-diameter shaft portion Wd that are continuously provided in the axial direction. The grinding parts of the workpiece W are the outer peripheral surface of the large-diameter shaft portion Wc, the outer peripheral surface of the small-diameter shaft portion Wd, and the step end surface between the large-diameter shaft portion Wc and the small-diameter shaft portion Wd. These are simultaneously ground by the grinding wheel 43 of the total type.

  Then, the displacement sensors 200 and 300 detect the respective deflection amount in the radial direction of the outer peripheral surface of the large diameter shaft portion Wc and the small diameter shaft portion Wd. Then, the grinding load calculation unit 72 calculates a grinding load at each grinding site or a value corresponding to the grinding load based on the respective deflection displacement amounts detected by the displacement sensors 200 and 300. And similarly to the said embodiment, it is determined whether each grinding site | part is a grinding burn in the burn determination part 75 shown in FIG. In this example as well, the displacement sensors 200 and 300 can be replaced with temperature sensors.

  Next, a third example will be described. As shown in FIG. 10, the workpiece W of the third example has a shaft portion We and a flange portion Wf. The grinding part of the workpiece W is the outer peripheral surface of the shaft portion We and the end surface of the flange portion Wf. At the same time, angular grinding is performed on the outer peripheral surface of the grinding wheel 43 (angular grinding wheel). Here, the angular grinding refers to a method of grinding the outer peripheral surface and the end surface of the workpiece W in a state where the rotation center axis of the grinding wheel 43 is inclined with respect to the rotation center axis of the workpiece W.

  Then, the displacement sensor 400 detects the amount of radial deflection displacement of the outer peripheral surface of the shaft portion We which is a grinding site. On the other hand, the displacement sensor 500 detects the amount of axial deflection displacement of the end face of the flange portion Wf, which is another grinding part. Then, the grinding load calculation unit 72 calculates a grinding load at each grinding site or a value corresponding to the grinding load based on the respective deflection displacement amounts detected by the displacement sensors 400 and 500. And similarly to the said embodiment, it is determined whether each grinding site | part is abnormal in grinding in the burn determination part 75 shown in FIG. In this example as well, the displacement sensors 400 and 500 can be replaced with temperature sensors.

  Further, in the first to third examples, the grinding load of each grinding part was calculated using the detection values of the plurality of grinding parts by the displacement sensor or the temperature sensor. In addition, one displacement sensor or temperature sensor can be reduced by using together the driving power of the grinding wheel driving motor 42 as shown in the first embodiment. That is, the grinding load generated in the entire workpiece W is calculated based on the driving power of the grinding wheel driving motor 42, and the local grinding load of the grinding portion is calculated by the displacement sensor or the temperature sensor. And the grinding site | part which does not provide the displacement sensor and the temperature sensor can be calculated by subtracting the local grinding load from the grinding load of the whole workpiece W.

<Others>
In the above embodiment, when shifting from rough grinding to finish grinding, switching is performed according to the elapsed time from the start of grinding or the relative position of the grinding wheel 43 and the workpiece W in the X-axis direction. Here, the timing of the start of finish grinding may be when the grinding diameter of the workpiece W reaches a set value by the sizing device. In this case, the sizing device or the control device outputs a start signal when finishing grinding is started. Therefore, when monitoring the abnormality, the threshold for rough grinding can be applied until the signal is acquired, and the threshold for finish grinding can be applied after acquiring the signal. Thus, the switching timing between the rough grinding threshold and the finish grinding threshold can be determined using the output signal from the sizing device or the control device.

1: grinding machine 10: bed, 11a, 11b: Z-axis guide rail, 11c: Z-axis ball screw 11d: Z-axis motor, 12a, 12b: X-axis guide rail, 12c: X-axis ball screw 12d: X-axis motor 20 : Table 30: Headstock, 31: Main body, 32: Magnet chuck, 33: Shoe 34: Spindle motor 40: Wheel support device, 41: Wheel head, 42: Wheel driving motor 42a: Motor wattmeter, 43 : Grinding wheel 50: proximity switch, 60: control device, 80: contact detection sensor 70: grinding abnormality monitoring device, 71: rotation speed calculation unit, 72: grinding load calculation unit 73: data storage unit, 74: threshold value determination unit, 75: Burn determination unit 76: Output unit 77: Condition change unit 170: Grinding abnormality monitoring device 173: Threshold data storage unit 100, 200, 300, 400, 00: displacement sensor or temperature sensor

Claims (7)

In a grinding abnormality monitoring method for monitoring grinding burn of the workpiece by using a grinding machine for rotating the workpiece and rotating the grinding wheel and relatively moving the workpiece and the grinding wheel to grind the workpiece. ,
A threshold setting step for setting a threshold for the rotational speed of the workpiece when grinding burn of the workpiece and the grinding load of the grinding wheel;
A grinding load detection step of detecting a grinding load of the grinding wheel when grinding the workpiece;
A rotational speed detection step of detecting the rotational speed of the workpiece when grinding the workpiece;
Grinding burn determination step for determining occurrence of grinding burn of the workpiece based on the relationship between the detected grinding load of the grinding wheel and the detected rotation speed of the workpiece and the set threshold value;
Grinding abnormality monitoring method comprising: In claim 1,
The grinding abnormality monitoring method is:
A threshold value determining step for determining the threshold value corresponding to the detected rotational speed of the workpiece,
The threshold value setting step is based on the relationship between the rotational speed of the workpiece when grinding the workpiece and the grinding load of the grinding wheel, and the rotation of the workpiece when grinding burn of the workpiece occurs. Set a threshold for grinding load of the grinding wheel with respect to speed,
The grinding burn determination step is a grinding abnormality monitoring method in which when the detected grinding load of the grinding wheel is equal to or greater than the determined threshold value, occurrence of grinding burn of the workpiece is determined. In claim 1 or 2,
The threshold value setting step is a grinding abnormality monitoring method in which a plurality of the threshold values corresponding to a plurality of types of the workpieces are set. In any one of Claims 1-3,
The grinding abnormality monitoring method is:
A grinding abnormality monitoring method comprising: a condition changing step of changing a grinding condition of the grinding wheel so that the detected grinding load does not exceed the threshold and approaches the threshold. In claim 1,
The threshold setting step sets a grinding load threshold for a grinding load of the grinding wheel and a rotational speed threshold for a rotational speed of the workpiece when grinding burn of the workpiece occurs,
The grinding burn determination step is performed when the detected rotational speed of the workpiece is less than the rotational speed threshold and when the detected grinding load of the grinding wheel is greater than or equal to the grinding load threshold. , A grinding abnormality monitoring method for determining the occurrence of grinding burn of the workpiece. In any one of Claims 1-5,
Applied to a grinding machine for simultaneously grinding a plurality of grinding parts of the workpiece;
Detecting a deflection displacement amount or temperature of each of a plurality of grinding portions of the workpiece by a plurality of displacement sensors or temperature sensors, and calculating each grinding load based on each deflection displacement amount or temperature;
A grinding abnormality monitoring method for determining grinding burn of each grinding portion based on each grinding load. In a grinding abnormality monitoring device for monitoring grinding burn of the workpiece by using a grinding machine for rotating the workpiece and rotating the grinding wheel and relatively moving the workpiece and the grinding wheel to grind the workpiece. ,
Based on the relationship between the rotational speed of the workpiece when grinding the workpiece and the grinding load of the grinding wheel, the grinding wheel relative to the rotational speed of the workpiece when grinding burn of the workpiece occurs Threshold setting means for setting a threshold for the grinding load;
Grinding load detecting means for detecting a grinding load of the grinding wheel when grinding the workpiece;
Rotational speed detection means for detecting the rotational speed of the workpiece when grinding the workpiece;
Threshold determination means for determining the threshold corresponding to the detected rotational speed of the workpiece;
Grinding burn judgment means for judging that the grinding burn of the workpiece is generated when the detected grinding load of the grinding wheel is equal to or more than the determined threshold value;
Grinding abnormality monitoring device comprising:

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