JP3159889B2 - Cam grinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cam grinder for grinding a cam used for a valve train of an internal combustion engine, and more particularly to a grindstone positioning control device for grinding a cam.

[0002]

2. Description of the Related Art Conventionally, as a device for rotating a main shaft on which a workpiece is mounted and relatively moving a grindstone in a direction orthogonal to the main shaft to grind the outer periphery of the workpiece into a non-circular shape, For example, a cam grinder for grinding a cam in a vehicle engine is known.

In this type of cam grinder, speed control data that sets the relationship between the rotation angle of the spindle and the rotation speed according to a predetermined cam profile, and the relationship between the rotation angle of the spindle and the feed amount of the grinding wheel head. Is previously stored in a numerical control device (hereinafter, referred to as an NC device). Then, based on the control data, N
The rotation of the spindle motor for rotating the spindle and the movement motor for moving the grinding wheel head are controlled by the C device. As a result, the spindle is rotated at a speed corresponding to the rotation angle, and the grindstone head is moved forward and backward according to the rotation angle of the spindle, so that the cam as the workpiece mounted on the spindle has a predetermined cam profile. It is ground to a corresponding non-round shape.

In the above-described grinding machine, when controlling the rotation speed of the spindle and the feed amount of the grinding wheel head, a tracking delay occurs individually in the spindle and the grinding wheel head due to an operation delay of each motor and the like. Due to the delay, there is a problem that the synchronous relationship between the rotation angle of the main spindle and the moving position of the grinding wheel head is shifted. Such a follow-up delay is particularly remarkable when the cut amount with respect to the cam is increased or the spindle rotation speed is increased in order to improve productivity, and the delay causes a reduction in machining accuracy. The problem had arisen.

As a countermeasure against such a problem, the control data is corrected in advance in anticipation of a follow-up delay. However, the follow-up delay depends on machining conditions such as a cutting depth and a spindle rotation speed at that time. And the characteristics of individual grinders vary, making it extremely difficult to set when the environment changes.

In order to solve the above-mentioned problem, a deviation between the feed amount of the grinding wheel head in the positioning control data and the actual position of the grinding wheel head has been conventionally determined, and based on the deviation, the next grinding wheel head in the positioning control data is determined. Correct the feed amount,
In the next processing, learning control such as controlling the moving motor based on the correction control data is performed. In the learning control for correcting such a deviation, the processing error is gradually learned by repeating the processing while correcting the deviation and is reflected in the control of the next processing, so that the processing error is reduced with the progress of the processing, Finally, a highly accurate cam with little error can be obtained.

[0007]

However, in the conventional learning control, an extremely large number of learning controls may be required to converge a machining error depending on the magnitude of the following delay described above. There was a possibility that processing could not be performed efficiently in a short time. In some cases, no matter how many times the learning control is performed, the machining error does not converge below a certain value, and today, when higher machining accuracy is required, the machining accuracy that can be satisfied with the conventional learning control is not sufficient. I can't get it.

Further, in the conventional learning control, the deviation for the learning control is stored as a reference time for each minute time as an address. That is, in the related art, the wheel head feed amount in the next machining is corrected based on the deviation of the wheel head feed amount from the positioning control data when the spindle reaches a certain rotation angle at a certain reference time. However, the spindle rotation angle at a certain reference time shown in the next processing may not match the spindle rotation angle at the same previous reference time due to the influence of disturbance such as vibration. In such a case, the correction data learned in the previous machining is not accurately reflected at the next machining position, and the machining error is kept constant regardless of the number of times of the learning control, as in the case described above. There has been a problem that it does not converge below.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to correct a machining error as quickly as possible so that the machining error can be converged to a minimum.
It is an object of the present invention to provide a cam grinder capable of performing high-precision machining with very little machining error at the time of finishing a workpiece.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a rotating means for rotating a spindle on which a workpiece is mounted, and a grindstone for grinding a cam surface of the workpiece are provided. Means for moving the grinding wheel head for relative movement in a direction perpendicular to the spindle, and movement based on control data in which a relative positional relationship between the rotation angle of the spindle and the feed amount of the grinding wheel head is set in advance according to a desired machining shape. And a control means for feedback controlling the means, by performing a plurality of grinding operations by rotating the workpiece, in a cam grinding machine for grinding the cam surface of the workpiece to a desired cam profile,
In accordance with the movement of the grindstone head in accordance with the rotation of the spindle, the control means controls the feed amount of the grindstone head in the control data and the actual A learning means for determining a deviation from the position of the grinding wheel head, and correcting the control data used in the next grinding operation based on the deviation. The learning means comprises a plurality of learning means respectively corresponding to each reference time for one rotation of the spindle. Storage means having a storage area of the following, based on the deviation found corresponding to the reference time at the current processing position, the storage means corresponding to the reference time before the reference time at the current processing position Rewriting and storing the storage values in the designated storage areas, and based on the storage values in the designated storage areas corresponding to the reference time after the reference time at the current machining position, Current Correction means for correcting the control data at the reference time at the machining position, and corresponding to the reference time at the current machining position of the storage area to be specified, according to the degree of delay of the grinding wheel head following the control command to the moving means. The amount of separation from the storage area to be changed is set, and the number of the storage areas to be designated is changed according to the degree of variation of the spindle rotation angle at each reference time indicated at each grinding operation for each spindle rotation. And setting means for performing the setting.

According to the invention of claim 2, in claim 1,
The storage means rewrites a storage value based on a value obtained by weighting the obtained deviation with a predetermined weighting coefficient, and the correction means weights each storage value in a plurality of storage areas with a predetermined weighting coefficient. The correction of the control data is performed based on the sum of the values obtained by the above.

[0012] In the invention according to claim 3, in claim 1 or 2, the setting means, as the follow-up delay of the grinding wheel head is larger,
The separation amount of the specified storage area is set to be large. According to a fourth aspect of the present invention, in any one of the first to third aspects, the setting means sets the number of designated storage areas to be smaller as the variation in the spindle rotation angle is smaller.

[0013]

[0014]

[0015]

[0016]

According to the first aspect of the present invention, in the process of rotating the workpiece and performing the grinding operation a plurality of times, the spindle 1
At each reference time for each predetermined time indicated during each grinding operation for each rotation, a deviation between the feed amount of the grinding wheel head and the actual grinding wheel position in the control data is obtained, and based on this deviation, in the next grinding operation. The control data to be used is corrected. Specifically, based on the deviation obtained corresponding to the reference time at the current processing position on the workpiece by the grindstone, a predetermined time corresponding to the reference time before the reference time at the current processing position is specified. The stored values in the plurality of storage areas are rewritten and stored. Further, the control data at the reference time at the current machining position is corrected based on the stored values in a plurality of storage areas designated in advance corresponding to the reference time after the reference time at the current machining position.

Here, the amount of separation from the storage area corresponding to the reference time at the current processing position of the specified storage area is:
The setting is changed in accordance with the degree of delay of the grinding wheel head following the control command to the moving means. That is, the correction is performed based on the stored value in the storage area corresponding to the processing position that is a predetermined distance away from the current processing position in accordance with the degree of the delay of the grinding wheel head following. The number of the storage areas to be specified is
It is changed and set according to the degree of variation in the spindle rotation angle at each reference time indicated during each grinding operation for each spindle rotation.

As a result, the optimum learning control can be executed in accordance with the following delay of the grinding wheel head and the variation of the spindle rotation angle, and the machining error can be converged with a minimum number of learning times. Can be reliably converged within an allowable range.

According to the second aspect of the present invention, the control data is appropriately corrected based on the sum of the values obtained by weighting the storage values in the plurality of storage areas with the predetermined weighting coefficient.
According to the third aspect of the present invention, the larger the following delay of the grinding wheel head is, the larger the amount of separation of the designated storage area is set, so that the control data at the reference time at the current processing position can be further separated. It is possible to predict and correct the tendency of the deviation in the position. For this reason, a large following delay can be quickly dealt with, and the convergence of the processing error is quickened.

According to the fourth aspect of the invention, the smaller the variation in the spindle rotation angle, the smaller the number of designated storage areas is set, so that more concentrated correction amounts are obtained, and the convergence of machining errors is accelerated. The number of learning controls can be reduced.

[0021]

[0022]

EXAMPLES hereinafter, an embodiment embodying the present invention, FIG. 1
It will be described with reference to-FIG 1 0.

As shown in FIGS. 1 and 2, the work support table 1 is provided on one upper surface of the base 2 by a moving mechanism (not shown).
Is supported so as to be movable in the left-right direction (Z direction). The headstock 3 is disposed on the upper surface of the work support 1, and has a spindle 4 for detachably supporting one end of the camshaft W, and a spindle motor composed of a servomotor as a rotating means for rotating the spindle 4. 5 is provided. Further, a plurality of cams Wa as workpieces are formed on the camshaft W at predetermined intervals in the axial direction, and the outer peripheral surfaces of these cams Wa are ground surfaces Wb.

The holder 6 is disposed on the upper surface of the work support 1 so that the distance between the holder 6 and the main shaft 4 can be adjusted. The cam shaft W is rotatable so that the camshaft W extends in the Z direction between the main shaft 4 and the holder 6. It is detachably supported. Then, in this supported state, the camshaft W is rotated in a predetermined direction as the main shaft motor 5 is driven. The encoder 7 is attached to the spindle motor 5, and a detection signal from the encoder 7 is input to an NC device 18 described later.

The grinding wheel head 8 is provided with a camshaft W on the base 2.
Are supported so as to be movable in a horizontal direction (X direction) orthogonal to the axis of. A moving motor 9 composed of a servomotor is attached to the side of the base 2, and the ball screw 10 is rotated by the moving motor 9 to move the grinding wheel base 8 in a direction to approach or separate from the camshaft W. . In this embodiment, a moving means is constituted by the moving motor 9 and the ball screw 10 and the like. The encoder 11 is attached to the moving motor 9, and a detection signal from the encoder 11 is input to an NC device 18 described later. The rotating grindstone 12 as a tool is rotatably supported on one end of the grindstone stand 8 by a support shaft 13 so as to face the camshaft W. The grinding wheel motor 14 is disposed on the grinding wheel stand 8,
The grinding wheel 12 is rotated in one direction by the grinding wheel motor 14 via the pulleys 15 and 16 and the belt 17.

The NC device 18 constituting the control means, the learning means and the setting means controls the operation of the whole apparatus. The NC device 18 has a CP for performing various arithmetic processes.
U (central processing unit) 19, ROM (read only memory) 20 storing a program for controlling the operation of the entire apparatus, and RAM (random access memory) 21 for temporarily storing various information. I have.

The RAM 21 stores spindle speed control data for controlling the rotation speed of the spindle 4 and wheel head position control data for controlling the position of the wheel head 8 in the X direction according to a predetermined cam profile. Is stored in advance. As illustrated in FIG. 3, the spindle speed control data indicates the relationship between the rotation angle and the rotation speed of the spindle 4, and the grinding wheel head position control data indicates the relationship between the rotation angle of the spindle 4 and the feed amount (moving position) of the grinding wheel head 8. The relationship is set, for example, for each main shaft angle of 1 degree.

At the time of grinding, the NC device 1
8 is a reference time generator 23 to be described later, as shown in FIG.
Based on the spindle speed control data and the wheel head position control data shown in FIG. 3, for example, corresponding to a reference time t _N indicated every 1 ms, an interpolation calculation (for example, a spline interpolation calculation) using a predetermined interpolation formula is performed. , The rotational speed command value of the spindle 4 corresponding to the current angle σ _N of the spindle 4 and the grinding wheel head 8
Calculating the moving command value B _N of. The NC device 18 detects the current angle σ _N of the main shaft 4 at that time by the encoder 7. FIG. 5 shows the obtained movement command value B _N of the grinding wheel head 8. Note that the rotation speed command value of the main shaft 4 is obtained in the same manner, but is not shown. As will be described later, the deviation data Z _N in FIG. 4 is obtained in correspondence with the reference time t _N in order to correct the movement command value B _N of the grinding wheel head 8 by a prediction error. It is stored in the storage area. Further, the NC device 18 detects the movement position of the grinding wheel head 8 in the X direction at that time by the encoder 11 corresponding to the reference time t _N.

The NC device 18 controls the rotation of the spindle motor 5 and the movement motor 9 while rotating the grindstone 12 based on the command values as shown in FIG. As a result, the cam Wa (that is, the main shaft 4) is rotated at a speed corresponding to the rotation angle, and the grinding wheel head 8 is moved forward and backward in the X direction according to the rotation angle of the main shaft 4. In the graph of FIG. 5, the main shaft rotation angle when the cam Wa is in the state of FIG. 6 is 0 degree. Further, the NC device 18 controls the movement of the work support base 1 in the Z direction, and arranges a predetermined cam Wa to face the grindstone 12. As a result, the predetermined cam Wa is ground into a non-circular shape corresponding to the predetermined cam profile.

FIG. 7 is a control block diagram relating to the control of the moving motor 9 executed by the NC unit 18. As shown in FIG. As shown in FIG.
The memory 22 constitutes a part of the AM 21.
Stores the wheel head position control data described above.
The reference time generator 23 indicates the reference time, for example, every 1 ms. Then, based on the wheel head position control data in the control data storage 22, the control data extractor 24 controls the wheel head 8 at each reference time as described above.
Is obtained at each reference time. As described above, this movement command value is set as a value corresponding to the rotation angle of the main shaft 4 at each reference time.

The obtained movement command value of the grinding wheel head 8 is:
This is provided to the adder 25. The adder 25 corrects the movement command value by adding an error prediction correction value described later to the given movement command value. Then, the corrected movement command value is output to the first subtractor 26. On the other hand, in the position counter 27, based on the detection signal from the encoder 11, the current value of the X-direction position of the grinding wheel head 8 is obtained and output to the first subtractor 26. Then, the first subtractor 26
Then, the deviation between the corrected movement command value from the adder 25 and the current value of the position of the grinding wheel head 8 in the X direction from the position counter 27 is determined. This deviation is determined by the deviation value judging means 35.
Is determined to be within a predetermined value set in advance.

Next, when the deviation is given to the speed command setting device 28, the speed command output to the moving motor 9 via the motor driver 29 is set by the speed command setting device 28. As described above, the rotational position of the moving motor 9, that is, the X-direction position of the grindstone table 8 is controlled.

Therefore, in the above control process, the adder 25
In, the error prediction correction value is added to the movement command value based on the wheel head position control data, so that each movement command value is subjected to error prediction correction.

On the other hand, the current value of the position of the grinding wheel head 8 in the X direction, which is the output of the position counter 27, is also given to the second subtractor 30. In the second subtractor 30, the grinding wheel head 8
The deviation between the current value of the X-direction position and the movement command value of the X-direction position of the grinding wheel head 8 given from the control data extractor 24 is obtained at each reference time, and the deviation is given to the correction means 31.

The correction means 31 is an error prediction correction means 32
And a deviation data storage 33 as storage means. In the error prediction correction means 32, the second subtractor 30
Is applied to the deviation between the current value of the X-direction position of the grinding wheel head 8 in the X direction and the movement command value to calculate the error prediction correction value by applying a calculation formula (1) shown below as an example. The error prediction correction value obtained by the error prediction correction means 32 is
The error prediction correction value extractor 34 supplies the value to the adder 25.

On the other hand, the deviation data storage 33 comprises a ring memory and means for rewriting the contents of the memory. FIG. 8 shows a conceptual layout of the ring memory.
Incidentally, the storage areas in the ring memory are provided corresponding to the respective reference times indicated by the reference time generator 23, and the number thereof is equal to the number of the reference times generated during one rotation of the cam Wa. Is equivalent. As shown in FIG. 8, each storage area in the ring memory has a one-to-one correspondence with a processing position corresponding to each reference time on a cam Wa as a workpiece.
Is set corresponding to. In other words, each storage area in the ring memory is set in one-to-one correspondence with the spindle rotation angle corresponding to each reference time. That is, assuming that the current processing position of the cam Wa is N, in the ring memory, the traveling direction of the processing position (the direction opposite to the rotation direction S of the cam Wa).
Along with the storage areas corresponding to the positions of N + 1, N + 2, N + 3, N + 4,..., And N-1, N-2, N-3, N along the direction opposite to the advancing direction of the machining position.
The storage areas corresponding to the positions of -4... Are set.

In this case, in the present embodiment, in the ring memory, in a storage area set along the traveling direction of the machining position and the opposite direction, a process of calculating an error prediction correction value, which will be described later, and rewriting the stored value. The configuration is such that the number n of storage areas designated for processing can be changed and set.

Next, an example of the processing in the error prediction correction means 32 will be described. The error prediction correction means 32 uses, for example, the following formula (1) to calculate the deviation
Based on the data on the deviation generated in the already-processed operation stored in the ring memory No. 3, what kind of deviation will occur at the unprocessed position where the processing proceeds after the current processing position, and the tendency of the deviation is predicted and added. Then, a correction value of the movement command value based on the wheel head position control data at the current processing position is set. In other words, the error prediction correction means 32 calculates a correction value for correcting the moving position of the grinding wheel head 8 in the X direction. Here, it is assumed that, for example, seven storage areas are specified in the ring memory along the traveling direction of the processing position including the current processing position of the cam Wa. _{F N = E N + (K} 11 × Z [N] + K 12 × Z [N + 1] + K 13 × Z [N + 2] + K 14 × Z [N + 3] + K 15 × Z [N + 4] + K 16 × Z [N + 5] + K ₁₇ × Z [N + 6]) × K ₂ (1) F _N : Error prediction correction value at N position E _N : Deviation at N position K ₂ : Depends on individual processing device, type of cam Wa and processing speed determined constant Z [N] ~Z [N + 6]: N~N + 6 stored value in the ring memory corresponding to the position (the previous processing time values based on the deviation data) K ₁₁ ~K _17: weighting coefficient (where, K ₁₁ + K ₁₂ + K ₁₃ +
K ₁₄ + K ₁₅ + K ₁₆ + K ₁₇ = 1) That is, the stored value is simultaneously output from a predetermined storage area of the ring memory of the deviation data storage 33, and the stored value corresponding to the unprocessed position, that is, the current processed position is set to N. Then, along the traveling direction, N, N + 1, N + 2, N + 3, N + 4,.
Stored values Z [N], Z [N + 1], Z corresponding to the positions
[N + 2], Z [N + 3], Z [N + 4],... Are weighted by a predetermined weighting factor (for example, Hanning window function) and added to the deviation E _N at the current machining position. error prediction correction value F _N is obtained in the. In other words, the error prediction correction value at each current machining position affects the deviation of the current machining position as the magnitude of the expected deviation of occurrence of a plurality of stored values corresponding to each unprocessed position and the tendency of the direction. Is determined, and error prediction correction is performed accordingly.

Further, as the machining progresses in the above-described process, a predetermined plurality of n storage areas of the ring memory of the deviation data storage 33 corresponding to the already machined machining positions on the cam Wa are stored in the following order. (2) is simultaneously performed. Here, it is assumed that, for example, seven storage areas are specified in the ring memory along the direction opposite to the advancing direction of the processing position including the current processing position of the cam Wa. Z [N] = Z [N ] + K 21 × E N × K 1 Z [N-1] = Z [N-1] + K 22 × E N × K 1 Z [N-2] = Z [N-2 _{] + K 23 × E N ×} K 1 Z [N-3] = Z [N-3] + K 24 × E N × K 1 Z [N-4] = Z [N-4] + K 25 × E N × K _{1 Z [N-5] =} Z [N-5] + K 26 × E N × K 1 Z [N-6] = Z [N-6] + K 27 × E N × K 1 ··· (2) Z [N] ~Z [N-6 ]: N~N + 6 stored value in the ring memory corresponding to the position E _N: deviation K ₁ in the N position: separate processing device, the constant K determined by the type and the processing speed of the cam Wa ₂₁ ~K _27: weighting coefficient _{(where, K 21 + K 22 + K} 23 +
K ₂₄ + K ₂₅ + K ₂₆ + K ₂₇ = 1) In addition, in the above-described calculation processing of the error prediction correction value and the rewriting processing of the stored value, as shown in FIG. The weight of each stored value within is set smaller as going from the central value to both sides. In this case, in this embodiment, the separation amount A from the storage area of the ring memory corresponding to the current machining position N to the central storage area having the largest weight can be changed and set. Note that the release amount A is A ≧
(N / 2) +1 is established, and is set to such an extent that the storage area corresponding to the current machining position N is not unnecessarily far from the storage area.

Next, the grinding operation performed on the cam Wa by the NC device 18 will be described with reference to the flowchart of FIG. First, before starting the machining operation,
In step S1, the number n of storage areas in the ring memory and the amount of separation A specified in the calculation processing of the error prediction correction value and the rewriting processing of the storage value are set to predetermined values, and a weighting coefficient is set accordingly. You.
Next, in step S2, the storage value in each storage area in the ring memory is initialized to “0”. When the machining operation is started in this state, first, in step S3, the spindle 4 starts rotating according to the spindle speed control data. At the same time, in step S4,
The wheel head 8 starts moving forward and backward in accordance with the wheel head position control data.

In this state, the error prediction correction means 32 calculates an error prediction correction value. That is, first, in step S5, for example, the current processing position (grinding point)
Are set to N = 1. Subsequently, in step S6, a deviation E _N between the movement command value of the grinding wheel head 8 determined based on the grinding wheel head position control data and the current position of the grinding wheel head 8 from the position counter 27 is determined. Next, step S7
, The obtained deviation E _N and the deviation data storage 33
The error prediction correction value F _N is calculated in accordance with the above equation (1) based on the stored value in a predetermined storage area in the ring memory.

[0042] Then, in step S8, movement motor 9 based on the calculated error predicted correction value F _N is controlled, the wheel head 8 is moved to a predetermined X-direction position. At the same time, in step S9, the stored value in a predetermined storage area in the ring memory of the deviation data storage 33 is rewritten according to the above equation (2).

Thereafter, in step S10, the cam W
It is determined whether or not a has been rotated once, and if it has not been rotated once, the process proceeds to step S11, and a new current grinding point associated with the movement of the grinding point is set to N = N + 1. Then, returning to step S6, the cam Wa becomes 1
Until the rotation is performed, the processing of steps S6 to S11 is repeated.

Thereafter, if the decision result in the step S10 is YES, the process shifts to a step S12, where the deviation value judging means 35 determines whether each deviation in one rotation of the cam Wa is within a predetermined value set in advance. Is determined. Here, when the deviation is within the predetermined value, the machining operation is terminated at that point in time, and when the deviation is not within the predetermined value, the process proceeds to step S13 and the cam W
It is determined whether the number of rotations of a (i.e., the number of times of learning) has reached a predetermined number of times set in advance. Here, if the predetermined number of times has not been reached, the process returns to step S5 to continue the grinding operation as it is, and the current grinding point is again set to N =
1 is set, and the processing of steps S5 to S13 is repeated. If the predetermined number has been reached, it is determined that the number n of storage areas, the separation amount A, and the weighting coefficient set in step S1 are not appropriate, and the process returns to step S1. Then, the number n of storage areas, the separation amount A, and the weighting coefficient are reset, and the processing of steps S1 to S13 is repeated.

FIG. 10 is a diagram for explaining the state of rewriting the stored value in the ring memory in step S9. In this figure, for ease of explanation,
One rotation of the cam is divided into 20. In the figure, as shown by hatching, rewriting of the stored value is performed, for example, in a ring memory for a total of seven storage areas corresponding to the current grinding point of the cam Wa and six previous grinding points before the cam Wa. Is being done. Incidentally, when calculating the error prediction correction value F _N in the step S7, in the ring memory is referenced values stored in each storage area corresponding to the current unground point of a predetermined number of grinding points after the cam Wa .

As described above, in the present embodiment, based on the stored value stored in the storage area corresponding to the processing position after the current processing position in the deviation data storage unit 33, the processing is not performed after the current processing position. What kind of deviation occurs at the processing position, the tendency of the deviation is predicted, and the movement command value based on the wheel head position control data at the current processing position is corrected to perform the processing. For this reason, it is possible to reduce the processing error as the processing proceeds, following the processing conditions that change every moment.

In the present embodiment, in order to calculate the error prediction correction value and rewrite the stored value, the ring memory is set to center on the storage area corresponding to the current processing position N in the ring memory. A predetermined number n of storage areas are designated in advance along the traveling direction and the reverse direction. In this case, in the present embodiment, the separation amount A from the storage area corresponding to the current machining position N to the center storage area having the largest weight among the specified predetermined number n of storage areas can be changed and set. It is configured. This is set in advance by an experiment or a trial process before performing the actual machining operation, in accordance with the degree of delay of the grinding wheel head 8 following the control command to the moving motor 9 when the movement of the grinding wheel head 8 is controlled. Things.

For example, when the following delay of the grinding wheel head 8 is large, the separation amount A of the storage area in the ring memory is set to be large, and the storage value to be referred to when rewriting and calculating the error prediction correction value is increased from the current machining position. Keep away. In this way, the movement command value based on the wheel head position control data at the current processing position can be corrected by predicting the tendency of the deviation at a farther unprocessed position. Therefore, it is possible to appropriately and quickly cope with a large following delay, and to quickly converge the machining error with a small number of learnings. Therefore, the machining can be performed efficiently in a short time, and a high-precision cam Wa with extremely few machining errors can be obtained in the finishing machining.

In this embodiment, the number n of the storage areas designated in the ring memory can be changed and set in the calculation of the error prediction correction value and the rewriting of the stored value. This is set in advance by an experiment or trial machining before performing the actual machining operation, according to the degree of variation in the spindle rotation angle at each reference time indicated at each grinding operation each time the spindle 4 makes one rotation. Things.
The variation in the spindle rotation angle is, for example, the spindle rotation angle at a certain reference time shown in the next processing,
This refers to the deviation from the spindle rotation angle at the same reference time shown during the previous machining.

For example, when the variation in the spindle rotation angle is large, the number n of storage areas designated in the ring memory is set to be large, so that the number of storage values that can be referred to when rewriting and calculating the error prediction correction value is increased. To In this way, it is possible to correct the movement command value based on the wheel head position control data at the current processing position by incorporating the deviation tendency at the unprocessed position over a wider range. As a result, even if the variation is large, in other words, even if the spindle rotation angle at a certain reference time shown in the next machining greatly deviates from the spindle rotation angle at the same reference time shown in the previous machining, The error can be reliably converged within an allowable range.

For example, when the variation of the spindle rotation angle is small, the number n of storage areas designated in the ring memory is set small, and the number of storage values that can be referred to when rewriting and calculating the error prediction correction value is small. To be. With this configuration, it is possible to correct the movement command value based on the wheel head position control data at the current processing position by incorporating the movement command value for a necessary range without taking the tendency of the deviation at the unprocessed position more than necessary. . As a result, machining errors can be converged as quickly as possible.

FIG. 8 shows an example of the setting of the separation amount A of the storage area designated in the ring memory and the number n of the designated storage areas. As illustrated in the drawing, it is assumed that the center storage area having the largest weight is set to the one corresponding to the processing positions N + 3 and N-3 by setting the specified separation amount A of the storage area. In this case, assuming that the number n of the designated storage areas is set to “7”, the storage areas corresponding to the machining positions N + 3 and N−3 for the process of calculating the error prediction correction value and the process of rewriting the storage values. , The storage areas respectively corresponding to the processing positions N to N + 6 and N to N-6 are designated. At this time, in the designated storage area range, the weights of the respective storage values and deviations are as shown by a solid line L1 in FIG. 8 according to, for example, a Hanning window function.

It is also assumed that, by setting the specified separation amount A of the storage area, the central storage area having the largest weight is set to the one corresponding to the processing positions N + 3 and N-3, as described above. In this case, assuming that the number n of the designated storage areas is set to “5”, the storage areas corresponding to the machining positions N + 3 and N−3 for the calculation processing of the error prediction correction value and the rewriting processing of the storage value. , The storage areas respectively corresponding to the processing positions N + 1 to N + 5 and N-1 to N-5 are designated. At this time, in the specified storage area range, the weights of the respective storage values and the deviations are indicated by a chain line L2 in FIG. 8 according to, for example, a Hanning window function.

That is, as is clear from the comparison between the solid line L1 and the chain line L2 in FIG. 8, the smaller the number n of storage areas to be designated is set, the larger the weight corresponding to the central storage area becomes. The difference from the weighting corresponding to the storage area is large. Therefore, when the variation of the spindle rotation angle described above is small, if the number n of the designated storage areas is set to be small, the influence of the storage value in the most necessary central storage area becomes large at the time of learning control. Since the influence of the stored values in the other storage areas is reduced, the convergence of the processing error is accelerated.

As described above, in the present embodiment, the optimum learning control can be executed in accordance with the following delay of the grinding wheel head 8 and the variation of the spindle rotation angle, and the machining error can be converged with the minimum number of learning times. In addition, the machining error can be surely converged within an allowable range.

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

The present invention is not limited to the above embodiment, but may be embodied by changing the configuration of each unit as follows, for example. (1) In the above-described embodiment, the error prediction correction is performed at the time of controlling the position of the grinding wheel head 8. However, the error prediction correction is also performed at the time of controlling the speed of the spindle 4.

[0064]

As described in detail above, according to the present invention, the following excellent effects can be obtained. According to the first aspect of the present invention, it is possible to execute the optimal learning control in accordance with the following delay of the grinding wheel head and the variation of the spindle rotation angle, and it is possible to converge the machining error with a minimum number of learning times. The processing error can be surely converged within an allowable range.

According to the second aspect of the present invention, control data is appropriately corrected based on the sum of values obtained by weighting each storage value in a plurality of storage areas with a predetermined weighting coefficient.
According to the third aspect of the invention, it is possible to correct the control data at the current machining position by predicting the tendency of the deviation at a more distant unprocessed position, and to quickly cope with a large following delay. Thus, the processing error can be quickly converged with a small number of times of learning.

According to the fourth aspect of the present invention, the control data at the current machining position can be corrected by taking in only a necessary range without taking the tendency of the deviation at the unmachined position more than necessary. The machining error can be quickly converged by the number of times of learning.

[0067]

[Brief description of the drawings]

FIG. 1 is a partially broken side view showing an embodiment in which the present invention is embodied in a grinding machine.

FIG. 2 is a plan view of a grinding machine.

FIG. 3 is an explanatory diagram showing spindle speed control data and grinding wheel head position control data.

FIG. 4 is an explanatory diagram showing each data obtained corresponding to a reference time.

FIG. 5 is a graph showing a movement command value of a grinding wheel head with respect to a spindle rotation angle.

FIG. 6 is a partial side view showing a cam and a grindstone on a spindle.

FIG. 7 is a control block diagram relating to control of a movement motor.

FIG. 8 is a conceptual diagram illustrating a ring memory in the deviation data storage;

FIG. 9 is a flowchart showing a grinding operation for a cam.

FIG. 10 is an explanatory diagram showing a state of rewriting a stored value in a ring memory.

[Explanation of symbols]

4 ... spindle, 5 ... spindle motor as rotating means, 7 ... encoder, 8 ... grinding wheel head, 9 ... moving motor constituting moving means, 10 ... ball screw constituting moving means,
11 ... encoder, 12 ... rotary grinding wheel, 18 ... control means,
NC device constituting learning means and setting means, 22: control data storage, 23: reference time generator, 31: correction means, 32: error prediction correction means, 33: deviation data storage as storage means, Wa ... Cam as workpiece, Wb
... the surface to be ground.

Continuation of the front page (56) References JP-A-4-201060 (JP, A) JP-A-4-201058 (JP, A) JP-A-3-65706 (JP, A) JP-A-7-195254 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B24B 19/12 G05B 19/404 G05B 19/4155

Claims (4)

(57) [Claims] 1. A rotating means for rotating a spindle on which a workpiece is mounted, a moving means for a grinding wheel base for relatively moving a grinding wheel for grinding a cam surface of the workpiece in a direction orthogonal to the spindle, and Control means for performing feedback control of moving means based on control data in which the relative positional relationship between the rotation angle of the spindle and the feed amount of the grindstone head is set in advance in accordance with the processing shape of the workpiece. In a cam grinder for grinding a cam surface of a workpiece to a desired cam profile by performing grinding operations a number of times, the control means rotates the grinding wheel base according to the rotation of the spindle, and rotates the spindle one revolution. At each reference time for each predetermined time indicated during each grinding operation, a deviation between the feed amount of the grinding wheel head and the actual grinding wheel position in the control data is obtained, and the next grinding operation is performed based on the deviation. Learning means for correcting the control data used in the storage means, the learning means includes a plurality of storage areas each corresponding to each reference time for one rotation of the spindle, and the storage means includes a current machining position. Based on the deviation obtained corresponding to the reference time in, based on the stored value in a plurality of storage areas specified in advance corresponding to the reference time before the reference time at the current machining position, and Based on each storage value in a plurality of storage areas specified in advance corresponding to the reference time after the reference time at the current processing position,
Correction means for correcting the control data at the reference time at the current processing position; and a reference time at the current processing position of the storage area to be specified, according to the degree of delay of the grinding wheel head following the control command to the moving means. The number of the storage areas to be designated is changed according to the degree of variation in the spindle rotation angle at each reference time indicated during each grinding operation for each spindle rotation, while changing the amount of separation from the storage area corresponding to A cam grinding machine provided with setting means for changing and setting. 2. The storage unit rewrites a storage value based on a value obtained by weighting the obtained deviation with a predetermined weighting coefficient, and the correction unit stores a predetermined value in each storage value in a plurality of storage areas. 2. The cam grinding machine according to claim 1, wherein the control data is corrected based on a sum of values weighted by the weighting coefficients. 3. The cam grinding machine according to claim 1, wherein the setting unit sets a larger amount of separation of the designated storage area as the following delay of the grinding wheel head is larger. 4. The cam grinding machine according to claim 1, wherein said setting means sets a smaller number of designated storage areas as the variation in the spindle rotation angle is smaller .