JPH048474A - Infeed controller for grinder - Google Patents

Abstract

PURPOSE:To absorb the extent of variations in quality to be produced in a grinding wheel or dressing variations so sufficiently as well as to grind the cylindricity of a cylindrical workpiece without these variations by installing such a compensation value operating means that compensates the propertional gain of a control means on the basis of abrasion loss in the grinding wheel from an abrasion loss operation means. CONSTITUTION:A detecting means (b) takes out grinding force being imposed on a grinding wheel 10 electrically as a grinding force signal. Next, a control means (c) controls an infeed rate proportionally so as to make it become equal to the setting value preset with the specified proportional gain on the basis of the grinding force signal out of the detecting means (b). Afterward, an abrasion loss operating means (d), with the specified wheel diameter in the wheel 10 as a criterion, after grinding a work W into the specified size with this wheel 10 or from a difference between the wheel diameter and the reference wheel diameter in the midway of grinding, an abrasive loss P2 in the wheel 10 is operated. A compensation value operating means (e) compensates the proportional gain of the control means (c) on the basis of this abrasion loss P2 of the wheel 10 from the abrasion loss operating means (d).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a technique for controlling the cutting speed in a grinding machine using a proportional gain corrected according to the amount of wear of a grindstone.

(Prior art) In general, for example, an internal grinding machine rotates and holds a cylindrical workpiece on a cutting table that can be moved back and forth via a work holding mechanism, and this cylindrical workpiece is fed by cutting the cutting table. By doing so, the internal surface of the cylindrical workpiece is ground by a grindstone located at the grinding position, and the internal dimensions of the cylindrical workpiece are measured using an in-process gauge, and when the measured dimension becomes equal to a predetermined dimension, the The cutting table is configured to be moved backward.

In addition, in the above-mentioned internal grinding machine, the grinding force applied to the grinding wheel is output as a grinding force signal using, for example, the current value or power value of the motor of the grinding wheel shaft to which the grinding wheel is attached, and this grinding force is A grinding force deviation is obtained from the signal and a preset grinding force target value, and the grinding force deviation is multiplied by a predetermined proportional gain to proportionally control the feed rate of the cutting table.

However, when the inner surface of a cylindrical workpiece as described above is ground multiple times with a grindstone, as the number of workpieces to be ground increases, the grindstone wears and the diameter of the grindstone changes, and the grinding performance of the grindstone also changes. As a result, according to the proportional control as described above, the grinding force applied to the grindstone no longer reaches the grinding force target value depending on the rate at which the grinding performance of the grindstone changes.

Therefore, the rate at which the grinding performance of the grinding wheel used will change by performing the grinding process is predicted in advance, and the predicted rate is used as a constant to correct the proportional gain in the proportional control.

(Problem to be solved by the invention) However, in such conventional internal grinding machines, the rate at which the grinding performance of the grinding wheel predicted in advance by performing the grinding process is used as a constant is used as a constant. Since it is configured to correct the proportional gain in the control, its constant is fixed, but on the other hand, the grinding performance of each grinding wheel may vary depending on, for example, variations in the quality of the grinding wheel or variations in the dressing that occurs when dressing the grinding wheel. It is inevitable that things will be different.

However, in conventional internal grinding machines, the above proportional gain is simply corrected using a single fixed constant as described above, so it is not possible to make appropriate corrections that match the grinding performance of each grinding wheel. Therefore, it is impossible to sufficiently absorb the variation in quality or the variation in dress that occurs between grinding wheels, and as a result, there is a problem in that the cylindricity of the ground cylindrical workpiece varies.

(Means for Solving the Problems) This invention was made in view of the above-mentioned circumstances, and its purpose is to correct the proportional gain in proportional control according to the grinding performance that changes as the grindstone wears. In particular, in order to achieve the above object, the present invention is constructed as follows.

That is, according to the claim correspondence diagram in FIG. 1, the grinding means a causes the workpiece and the grinding wheel to approach each other relatively and feed the cut, and by this feeding, continuously grinds a plurality of the workpieces to the same size. .

The detection means electrically extracts the grinding force applied to the grinding wheel as a grinding force signal.

The control means C proportionally controls the cutting feed speed based on the grinding force signal F from the detection means so that it becomes equal to a preset value using a predetermined proportional gain Kp.

The wear amount calculation means d uses the predetermined diameter of the grindstone 10 as a reference, and calculates the difference between the diameter of the grindstone after grinding the workpiece W to the above-mentioned dimensions with the grindstone 10 or during the grinding process, and the diameter of the reference grindstone. The wear amount P2 of the grindstone 10 is calculated.

The correction value calculation means e uses the grinding wheel 1 from the wear amount calculation means d.
The proportional gain Kp of the control means C is corrected based on the wear iP2 of 0.

(Function) This invention makes it possible to control the grinding force at a constant level by using a proportional gain adapted to the amount of wear on the grindstone, as shown by the solid line in Figure 2. The calculation means d calculates the wear amount P2 of the grindstone 10, and the correction value calculation means e operates to correct the proportional gain KP in the control means C based on the wear amount P2.

(Description of an Embodiment) Hereinafter, an embodiment in which a grinding device according to the present invention is applied to an internal grinder will be described in detail with reference to FIGS. 3 and 4.

That is, as shown in FIG. 3, the internal grinding machine is equipped with a cutting table 1 that is movable back and forth in the X-axis direction and a grindstone head 2 that is movable back and forth in the Z-axis direction. The grindstone head 2 is driven via a motor 3 and a ball screw mechanism (not shown), while the grindstone head 2 is driven by a motor 4 and a ball screw mechanism 5.
is configured to be driven through the

Further, a cylindrical workpiece W which is rotatably held by a workpiece holding mechanism (not shown) is disposed on the upper surface side of the cutting table 1, and a general structure for measuring the inner surface dimensions of the workpiece W is installed. A process gauge 6 is provided,
The dimension measured via this in-process gauge 6 is output to a dimension detector 7, and according to this dimension detector 7, when the measured dimension becomes equal to a predetermined dimension, a dimension completion point signal S is set as a numerical value which will be described later. It is configured to output to the wear amount calculation section in the control section 12.

Furthermore, a grindstone spindle unit 9 having a grindstone shaft 8 is mounted on the upper surface side of the grindstone stand 2, and a grindstone 10 is attached to the tip of the grindstone shaft 8.
According to this method, the inner surface of the workpiece W is ground at a grinding position A to which the grindstone head 2 is moved.

Further, the grinding wheel shaft 8 of the grinding wheel spindle unit 9 is supported by a magnetic bearing having a general structure, which allows the grinding wheel 10 that performs internal grinding as described above to change the grinding force applied to the grinding wheel 10. , by utilizing the fact that the change in the excitation current that excites the electromagnet of the magnetic bearing is equal, the grinding force applied to the grinding wheel 10 is detected as an analog value grinding horn signal F, using the excitation current,
The grindstone spindle unit 9 is configured to output its grinding force signal F1 to an A/D converter 13 in a numerical control section 12, which will be described later.

The dresser 11 dresses the grindstone 10 at a dressing position B where one end surface of the grindstone 10 is moved.

Next, the configuration of the numerical control section 12 of the internal grinding machine will be explained. This consists of the digital grinding force signal F2 outputted via the A/D converter 13 and the grinding force target value Fo.
The comparator 13 calculates the grinding force deviation α from Multiply by the feedforward gain KF to obtain the cutting table speed V for the feedforward control system. seek.

Then, in the adder 14, the cutting table speed V related to the feedback control system and the cutting table speed ■o related to the feedforward control system are added to calculate the cutting table speed command value ■, and the cutting table speed command value ■ is calculated. The speed command value ■ is configured to be output to the axis controller 15.

Further, the axis controller 15 moves the cutting table 1 via the servo driver 16 and the servo motor 3 based on the cutting table speed command value V, and also controls the position of the cutting table 1 by the servo motor 3 and the servo driver 16. The position P of the cutting table at the grinding end point among the read positions.

is configured to be output to the wear amount calculation section 17.

The wear amount calculation unit 17 uses the grindstone diameter after internally grinding the first workpiece to a predetermined dimension using the grindstone 10 dressed with the dresser 11 as a reference, and uses the grindstone 10 to grind the second or more pieces. The wear amount P2 of the grindstone is calculated from the difference between the grindstone diameter after grinding the workpiece to the same predetermined dimensions as above and the reference grindstone diameter. After grinding the workpiece and the second or more workpieces, the amount of change in the position P1 of the cutting table outputted from the axis controller 15 is determined, and the amount of change is outputted to the correction value calculation section 18. There is.

The correction value calculation unit 18 is equipped with a proportionality constant kp set in advance and a wear constant kc shown in FIG. Multiply by to obtain 1 for the proportional gain correction value,
The proportional gain KP in the numerical control section 12 is calculated by adding the proportional constant kp to this proportional gain correction value. Therefore, the proportional gain Kp is configured to be corrected using a proportional gain correction value based on the amount of wear of the grindstone.

Next, regarding the operation of the internal grinding machine, using the flowchart shown in FIG. , the case will be explained starting from the case where the number of grinding completions N is 0.

According to the above flowchart, the grinding force signal value F2 is read (step 100), and then it is determined whether or not the workpiece W is being ground based on whether or not the grindstone head 2 is at the grinding position A (step 100). 101), if the judgment result is that grinding is not in progress (NO), the process returns to step 100 again and the grinding force signal value F2 is read. On the other hand, if the above judgment result indicates that grinding is in progress (YES), read the number N (=0) of finished grinding from the dress skip counter (step 102), and then read the number N (=0) of finished grinding and 1 from the dress skip counter (step 102). As a result of the comparison (step 103), the number N (=0) of completed grinding is smaller than 1 (YES), so 1 should be set to 0 in the proportional gain correction value (step 104), and the output from the dimension detector is read ( Step 105), it is determined whether or not the dimension completion point signal S is output (Step 106).
).

If it is determined that the dimension completion point signal S is not output in the above determination result (NO), the grinding force target value F
. step 107), and set its grinding force target value FC.
The above grinding force signal value F2 is subtracted from , and the subtraction result (F
As a result of comparing CF2) with 0 (step 108), if the comparison result is smaller than 0 (NO), that is, the above-mentioned grinding force target value F. is smaller than the grinding force signal value F2, the cutting table speed V1 in the feedback control system is set to 0 (step 109).

On the other hand, if the comparison result is greater than 0 (YES), that is, the grinding force target value F. is larger than the grinding force signal value F2, in order to calculate the cutting table speed V1 in the feedback control system, a proportionality constant kP is set (Step 110) This proportionality constant kp and the step 104
The proportional gain KP is obtained by adding the proportional gain correction value (k,=0) set in , and the cutting table speed V in the feedback control system is calculated using equation (1).

is set (step 111).

V+ −(FOF2)X (to kp+,) ・++ (
1) (kp+J = Kp) Next, the feedforward constant KF is multiplied by the grinding force target value Fo to determine the cutting table speed V in the feedforward control system. (step 112), and then step 109. Alternatively, the cutting table speed command value V is calculated by adding the cutting table speed V1 in the feedback control system set in step 110 and the cutting table speed Vo in the feedforward control system, and (step 1
13) The cutting table 1 is fed into the cutting based on the cutting table speed command value V (step 114), and the process returns to step 100 to perform the above-described series of processing operations again.

By the way, the above series of processing operations (step 10
0 to step 114), step 10
If it is determined that the dimension completion point signal S has been output as a result of the judgment in step 6 (YES), the cutting table position P1 is read (step 115), the speed command value for retracting the cutting table is set (step 116), and the Retract the cutting table. On the other hand, the number N of grinding completed on the dress skip counter
(=0) and set N=1 step 117)
Then, it is determined whether N=1 or not (step 118). Since N=1 as described above (YES), the cutting table position P1 is set as the cutting table reference position P. , and temporarily stores the cutting table reference position Po (step 119).
L The operation of grinding the first workpiece using the grindstone after finishing the dressing is completed.

Next, a case where a second workpiece is ground with the grindstone after finishing dressing, that is, a case where the number of workpieces finished grinding in the dressing skip counter is N=1 will be explained.

This is the same as above from step 100 to step 1.
In the middle of performing a series of processing operations in the order of 14, step 10
If it is determined that the judicial completion point signal S has been output as a result of the judgment in step 6 (YES), the cutting table position P1 is read (step 115), the speed command value for retracting the cutting table is set (step 116), and the Retract the cutting table.

On the other hand, the number N (=1) of finishing grinding of the dress skip counter
is counted to set N=2 (step 117), and then it is determined whether N=1 (step 118).
, as described above (N=2, so (No)) By subtracting the cutting table reference position Po from the cutting table position P, the amount of wear for the radius of the worn grindstone is calculated. After calculating the wear amount P2 of the grindstone by doubling the wear amount for the radius (step 120), the wear amount P2 of the grindstone is multiplied by the wear constant ko to obtain the proportional gain correction value (
In step 112), when a third workpiece is to be ground, the proportional gain correction value is added to the proportional constant kp in step 111 to form a proportional gain Kp.

Therefore, according to the present embodiment, the wear amount of the grindstone is determined as described above, and the proportional gain correction value obtained by multiplying the wear amount by the wear constant is added to the proportional constant, thereby calculating the proportional gain. , it is possible to perform an appropriate proportional gain correction that is suitable for the grinding performance of the grindstone, which changes depending on the amount of wear of the grindstone.

According to this embodiment, the grinding force is detected from the excitation current of the magnetic bearing that supports the grinding wheel shaft, but instead of this, the grinding wheel shaft is supported by a bearing, and a load cell or the like is installed on the outer ring of the bearing. Alternatively, the grinding force may be detected from the current value or C value in a motor for rotating the grindstone shaft.

Further, in this embodiment, the workpiece is fed by cutting into the grindstone and the feed speed is controlled, but instead of this, the grindstone may be fed into the cut by the workpiece, or the workpiece and the feed speed are controlled. Both of the grindstones may be fed into the cut.

Furthermore, according to this embodiment, the position of the cutting table at the grinding end point is detected, but instead of this grinding ending point, the position of the cutting table is detected at an arbitrarily determined grinding point in the middle of grinding. Good too.

Further, in this embodiment, an internal grinder has been described, but it goes without saying that the grinding device according to the present invention may be applied to a cylindrical grinder instead.

(Effects of the Invention) The grinding device according to the present invention is configured such that the wear amount calculation means calculates the wear amount of the grindstone and the correction value calculation means corrects the proportional gain in the control means based on the wear amount. Since the cutting feed speed can be controlled proportionally using a proportional gain that matches the grinding performance of the grinding wheel, which changes depending on the amount of wear, variations in quality or dress that occur in the grinding wheel can be fully absorbed, and the It is possible to grind without any variation in cylindricity.

[Brief explanation of drawings]

Figure 1 is a diagram corresponding to complaints, Figure 2 is an explanatory diagram explaining the relationship between grinding wheel wear amount and proportional gain, Figure 3 is a block diagram of an internal grinder to which the present invention is applied, and Figure 4 is Figure 3. 3 is a flowchart showing the operation of the internal grinding machine shown in FIG. 10... Grinding wheel 12... Numerical control section 17... Wear amount calculation section 18... Correction value calculation section F,, F2... Grinding force signal... 1 for proportional gain... Proportional gain correction value F2...Wear amount W...Workpiece

Claims (1)

[Scope of Claims] 1. Grinding means for moving a workpiece and a grinding wheel relatively close to each other and feeding the cutting process, and using this feeding to continuously grind a plurality of workpieces to the same size; a detecting means for electrically extracting the grinding force as a grinding force signal; and a detecting means for electrically extracting the grinding force as a grinding force signal; and based on the grinding force signal from the detecting means, adjusting the cutting feed so that it becomes equal to a preset value using a predetermined proportional gain. In a grinding machine comprising a control means for proportionally controlling speed, a predetermined diameter of the grinding wheel is used as a reference, and the diameter of the grinding wheel is adjusted to the diameter of the grinding wheel after or during grinding of the workpiece to the above dimensions using the grinding wheel. a wear amount calculating means for calculating the wear amount of the grinding wheel from the difference between the grinding wheel diameter and a correction value calculating means for correcting the proportional gain of the control means based on the wear amount of the grinding wheel from the wear amount calculating means; A cutting control device for a grinding machine, which is characterized by: