JP2001179621A - Displacement measurement device and grinding attachment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately remove an error generated by the expansion and contraction of a linear scale measuring equipment with a temperature change. SOLUTION: A displacement obtained by the linear scale measuring equipment 19 with the movement of a grinding tool support 8 is compared with a signal indicating the predetermined rotating angle of a feed screw 10 obtained by a position detector 11 to calculate a correction coefficient for a controlled displacement of the grinding tool support 8. The correction coefficient is multiplied by positional command data and the movement of the grinding tool support 8 is controlled in accordance therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding device suitable for rotating and grinding a work.

[0002]

2. Description of the Related Art A conventional grinding device is provided with a usual positioning control device. The rotation of the servomotor is controlled by the positioning control device, and the rotational driving force of the servomotor is transmitted to the grinding wheel support via a feed mechanism constituted by a feed screw or the like, thereby positioning the grinding wheel.

For example, as a control device for performing high-speed and high-accuracy positioning, a positioning control device disclosed in Japanese Patent Application Laid-Open No. H10-337352 is known. This positioning control device uses a linear scale as measuring means for measuring the position of the grinding wheel support with high accuracy. And
By correcting the transfer function used for the drive control of the servomotor based on the actual measurement result of the position of the grinding wheel support obtained from the linear scale, positioning control of the grinding wheel support moving at high speed is realized with high accuracy.

[0004]

By the way, a machine tool in a machining environment is exposed to a change in air temperature over time from the start of operation, a change in processing heat or a cooling water temperature or an oil temperature that absorbs the processing heat, and a machine tool. It may take several hours for the temperature to stabilize. During that time, the machine temperature may change by several tens of degrees in some cases. That is, in the machine tool, the temperature of the entire apparatus gradually increases from the start of operation, and accordingly, the constituent members of each part expand accordingly.

[0005] For example, a 1-meter-long iron is accompanied by a linear expansion change of about 1 μm when the temperature changes by 1 degree. Similarly, the linear scale of the above-described positioning control device has a linear expansion coefficient that is about one digit smaller than that of iron, but expands to a considerable extent. For this reason, the position control of the grindstone support table using the linear scale becomes inaccurate and the machining accuracy becomes inaccurate. In particular, the machining accuracy of the work machined within about 30 minutes from the start of operation is not stable, and Is reduced.

On the other hand, a rotation detector mounted on a rotation shaft of a feed motor of a grinding wheel support, which detects a rotation angle of the motor, detects the rotation angle of the motor. Not affected. For this reason, the rotation detector always performs accurate detection per rotation without causing a detection error.

However, the rotation detector is inferior in resolution to a precision linear scale and cannot be expected to have precise detection accuracy. The present invention has been made to solve such a problem existing in the related art. The aim is to remove the effects of temperature changes,
An object of the present invention is to make it possible to always accurately grasp the position of a grindstone support table and perform highly accurate grinding.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a linear scale portion along a moving direction of a grindstone support table which is linearly moved by rotation of a feed screw is provided. A linear scale measuring device that measures the amount of movement of the grinding wheel support in the linear scale portion, a rotation detector that detects a rotation angle due to the rotation of the feed screw, and a rotation angle corresponding to a predetermined rotation angle in the rotation detector. A movement error calculating means for calculating an error between the movement amount of the grinding wheel support and the movement amount of the grinding wheel support from the measured value of the linear scale measuring device.

According to the second aspect of the present invention, there is provided a linear scale portion along the moving direction of the grinding wheel support that is linearly moved by the rotation of the feed screw, and the movement amount of the grinding wheel support is measured at the linear scale portion. A linear scale measuring device, a rotation detector that measures the amount of movement of the grindstone support base from the rotation angle of the feed screw, a comparing unit that compares each measured amount with the linear scale measuring device and the rotation detector, Calculate their error ratio from the comparison result by means,
Calculating means for calculating an actual movement amount of the grinding wheel support corresponding to a measured value of the rotation detector due to rotation of the feed screw based on the error ratio.

According to the third aspect of the present invention, the work support mechanism rotatably supports the work, and the work support mechanism can linearly approach and separate in a direction perpendicular to the rotation axis of the work supported by the work support mechanism. A grinding wheel support that rotatably supports the grinding wheel, in a grinding device such that the grinding wheel is rotated by the movement of the grinding wheel support to perform a grinding process on the work, is attached to the grinding wheel support, A linear scale measuring device that measures the linear movement amount of the grinding wheel support in the linear scale section, and a rotation detection that is connected to a motor that drives the movement of the grinding wheel support by rotating the feed screw and detects the rotation angle with the rotation of the motor And a linear scale measuring device that measures the amount of movement of the grinding wheel support corresponding to a predetermined rotation angle of the rotation detector. Calculation means for calculating a movement error of the support base, and control means for controlling the operation of the motor so that the movement amount of the grindstone support base corresponding to the rotation angle of the feed screw is corrected based on the movement error. It is.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a cam grinder will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the work support table 1 is supported on the upper surface of one side of the base 2 so as to be movable in the horizontal direction indicated by the arrow Z in the figure. The headstock 3 is provided on the upper surface of the work support 1, and includes a spindle 4 for detachably supporting one end of the camshaft W and a spindle motor 5 composed of a servomotor for rotating the spindle 4. Have. The tailstock 6 is disposed on the upper surface of the work support 1 so that the distance between the tailstock 6 and the main shaft 4 can be adjusted.

A camshaft W as a work rotating shaft is supported between the main shaft 4 and the tailstock 6 so as to extend in the Z direction. 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. A work support mechanism is constituted by the work support 1, the headstock 3, the tailstock 6, and the like.

A position detector 7 serving as a rotation detector is attached to the spindle motor 5, and a rotation detection pulse generated by the position detector 7, that is, a rotation angle signal is output from the position detector 7 in FIG.
Is supplied to the control device 18 shown in FIG. This position detector 7
Detects the rotation angle of the spindle motor 5. The rotation of the spindle motor 5 detected by the position detector 7 is
Positioning is controlled by a closed loop via the control device 18.

The grindstone support 8 is supported on the base 2 so as to be movable in a horizontal direction (indicated by an arrow X in the figure) orthogonal to the axial direction of the camshaft W. The moving motor 9 composed of a servomotor is attached to the base 2, and the feed screw 10 is rotated by the moving motor 9, and the arrow X at which the grinding wheel support 8 approaches or separates from the camshaft W.
In the direction perpendicular to the direction in which the camshaft W extends.

The grinding wheel 12 is rotatably supported by a support shaft 13 at one end of the grinding wheel support 8 so as to face the camshaft W. The grinding wheel 12 is used to rotate the grinding surface W of the cam Wa.
b is ground. The grindstone rotation motor 14 is disposed on the grindstone support base 8, and the grindstone wheel 12 is rotated in one direction via the pulleys 15, 16 and the belt 17 by the grindstone rotation motor 14. The grindstone support 8 is provided with a working fluid supply mechanism (not shown).
The grinding fluid is supplied to the ground surface Wb and the grinding surface of the grinding wheel 12.

On the other hand, a position detector 11 as a rotation detector for detecting the movement position of the grinding wheel support 8 is attached to the movement motor 9, and the movement motor 9 generated at the position detector 11 A rotation detection pulse signal indicating the rotation angle of the screw 10 is supplied to the control device 18. Further, a linear scale measuring device 19 for measuring a moving position of the grinding wheel support 8 by a linear scale 19a is attached to the grinding wheel support 8. The linear scale measuring device 19 has a linear scale portion 19a extending in the moving direction of the grinding wheel support 8, that is, in the X arrow direction. The linear actual movement amount of the grindstone support 8 measured in the direction of the arrow X measured by the linear scale 19a, that is, the actual movement amount of approaching / separating from the camshaft W, is directly measured, and position detection information indicating the value is generated. I do. The position detection information generated by the linear scale measuring device 19 is also supplied to the control device 18.

The rotation of the moving motor 9 is controlled by a loop formed by a control device 18, a position detector 11 for detecting the rotation angle of the moving motor 9, and a linear scale measuring device 19 for detecting the position of the grinding wheel support. Is controlled by the positioning.

FIG. 3A shows an electrical configuration of the embodiment. 1 and 2 are denoted by the same reference numerals. The control device 18 serving as a control unit, a calculation unit and a comparison unit includes a control unit 23 mainly composed of a microcomputer and a memory 23a shown in FIG. 3B, a spindle motor 5, a movement motor 9, and a grindstone rotation. 3 provided corresponding to each of the
Drive circuits 24, 25, and 26.

The memory 23a of the control unit 23 stores speed control data defining the relationship between the rotation angle and the rotation speed of the main shaft 4 according to the shape of the cam Wa of the camshaft W, and the rotation angle of the main shaft 4 and the grinding wheel support. Position control data defining the relationship with the feed amount of No. 8 is stored. The control unit 23 stores position detection information from the linear scale measuring device 19, rotation detection information from the two position detectors 7 and 11, and a memory 23a.
, And outputs control signals to the three drive circuits 24, 25, and 26 based on the control data stored in. Based on this control signal, each of the drive circuits 24, 25,
26 operates the motors 5, 9, and 14.

Accordingly, the operation of the entire cam grinding machine is centrally managed by the control unit 23. As a result, the main shaft 4 is rotated, and accordingly, the camshaft W is rotated in one direction. At the same time, the grindstone support 8 is moved forward and backward in accordance with the rotation angle of the main shaft 4, and the cam Wa of the camshaft W mounted on the main shaft 4 is ground into a predetermined shape.

FIG. 4 is a diagram equivalently showing a control system formed by the above-described position detector 11, linear scale measuring device 19, control unit 23, drive circuit 25, moving motor 9, and the like. In FIG. 4, the position information of the grinding wheel support 8 generated by the control unit 23 is supplied to the positive input terminal of the first subtractor 33. This position information is stored in the whetstone support 8
Indicates the movement position of. The measurement output from the linear scale measuring device 19 is supplied to the negative input terminal of the first subtractor 33. The output of the first subtractor 33 is supplied to the positive input terminal of another second subtractor 35 via the converter 34.
The converter 34 converts the position signal into a velocity signal by adding a time element.

The output signal of the position detector 11 corresponding to the rotation angle of the moving motor 9 and the feed screw 10 is supplied to the minus input terminal of the second subtractor 35. The output of the second subtractor 35 is supplied as a position signal via the converter 36 to the movement motor 9 via the amplifier 38, and the rotation amount of the movement motor 9 is controlled. Controlled.

The amplifier 38 adjusts the rotation speed of the moving motor 9. In the control unit 23, profile data of the cam Wa is selected from a predetermined storage area, and based on the profile data, target position data for moving the grinding wheel support 8 corresponding to the rotation angle of the cam Wa is calculated. Is done. The movement motor 9 is controlled via the drive circuit 25 based on the target position data.

Next, the data of the position detection information of the linear scale measuring device 19 is sampled for the actual movement amount of the grinding wheel support 8 in the process of working the camshaft W. Then, the detected position information is stored in the memory 23a in the control unit 23.

As described above, when the control unit 23 operates, the moving position of the grinding wheel support 8 to be subjected to the positioning control is detected by the position detector 11 as the rotation angle of the moving motor 9. Then, the position control of the moving position and the moving speed of the grinding wheel support 8 is performed, and the moving position data corresponding to the rotation angle of the moving motor 9 and the feed screw 10 is detected by the linear scale measuring device 19.

Then, the control section 23 corrects an error with respect to the measurement result of the linear scale measuring device 19 in a predetermined procedure based on the position information stored in the memory. Specifically, prior to the start of processing, the grindstone support 8 is moved from the origin position to a predetermined position, and the movement amount at that time is obtained as a rotation angle signal of the position detector 11. At the same time, it is obtained from the position detection information from the linear scale measuring device 19 corresponding to the rotation angle signal from the position detector 11. The count value obtained from the position detector 11 is represented by Lr, and the movement amount obtained from the linear scale measuring device 19 is represented by Lr.
Assuming that l, these are compared in the comparison unit 23b of the control unit 23, and the correction coefficient indicating the movement error of the grinding wheel support 8 is calculated as Ll / Lr.

The correction coefficient is multiplied by a position command from the control unit 23 and supplied to the first subtractor 33. That is, when the linear scale portion 19a of the linear scale measuring device 19 is expanded and contracted due to a temperature change, an error occurs in the measurement result of the linear scale measuring device 19 with respect to the distance actually moved. In such a case, the position detector 1 at the processing point
Assuming that the moving amount including the error obtained from 1 is Lo and the actual moving amount is Ln, the actual moving amount Ln is expressed by the following (1).
The corrected position command obtained by the equation is used as control position data of the wheel head moving motor 9 as the next grinding position control.

Ln = Lo · (L1 / Lr) (1) In this case, regardless of the temperature of the apparatus, the position detector 11
Is constant.
Therefore, when the linear scale measuring device 19 expands or contracts due to heat, the correction coefficient changes accordingly. Therefore, if this correction coefficient is used, the positioning of the grinding wheel support 8 can be accurately performed even if the linear scale measuring instrument 19 is deformed.

In the actual operation, the positioning movement of the grinding wheel support 8 in the X direction for calculating the correction coefficient is performed in order to shorten the cycle time of the grinding process.
The correction coefficient is calculated in parallel with the positioning of the grindstone support 8 during the actual machining. Specifically, in the positioning from the cycle start original position during processing to the intermediate position with respect to the cam Wa, the movement amount Lr obtained from the position detector 11 and the movement amount Ll obtained from the linear scale measuring device 19 Thus, the correction coefficient (L1 / Lr) is calculated.
Then, using the obtained correction coefficient, the position information associated with all the position controls of the grindstone support 8 is corrected and reflected on the grinding position coordinates from the machining start position. The calculation of the correction coefficient is sequentially performed for each processing of one cam Wa to be ground of the camshaft W, and the correction coefficient is updated. As a result, an error correction process is performed using the new correction coefficient, and an error caused by expansion and contraction of the linear scale caused by a temperature change is removed.

As described above, this embodiment has the following effects. A rotation angle signal due to the rotation of the feed screw 10 for moving the grinding wheel support 8 is secured by the position detector 11, and the control unit 23 measures the linear scale measuring device 19 corresponding to a predetermined rotation angle of the position detector 11. The movement error of the grinding wheel support 8 is calculated from the value. That is,
Since the measured value of the position detector 11 is constant irrespective of the expansion and contraction of the linear scale measuring device 19, a correction coefficient was calculated from the value and the measured value of the linear scale measuring device 19 changed by the expansion and contraction. Then, the correction value was multiplied by the count value of the linear scale measuring device 19 to obtain the moving amount of the grinding wheel support 8. For this reason, the count value of the linear scale measuring device 19 can be corrected according to the degree of expansion and contraction, and the movement of the grinding wheel support 8 can be accurately controlled using the measured value of the linear scale measuring device 19 having excellent resolution. can do. Therefore, high-precision cutting can be realized.

As described above, since error correction is performed in accordance with the amount of temperature change of the linear scale measuring device 19, separate detection means such as a temperature sensor is not required. In addition, the configuration that takes measures against the influence of the temperature change of the linear scale is simple.

The present invention can be embodied in the following modes. -In the above-described embodiment, the case where the present invention is applied to the cam grinder has been described. However, the present invention is applied to other crankpin grinders and processing machines having a positioning control device. In this case, the same effect as in the above embodiment can be obtained.

Every time one grinding is completed, the position information used for controlling the grinding, that is, the position information of the position detector 11 and the linear scale measuring device 19 stored in the memory of the control unit 23 is read. Newly rewrite the position information obtained as a result of grinding. Then, at the next grinding, a correction coefficient (L
1 / Lr), generating new position information of the grinding wheel support 8 based on the corrected data, and performing position control of the grinding wheel support 8 based on the new information.

[0035]

The present invention is configured as described above, and has the following effects. According to the first to third aspects of the present invention, the rotation angle signal from the rotation detector corresponding to the predetermined rotation angle of the feed screw is corrected based on the measurement value obtained from the linear scale measuring device. Even if the measuring device expands and contracts, the movement of the grindstone support can be controlled based on the measurement value from the linear scale measuring device. For this reason, the positioning of the grindstone support base can be performed with high precision, high-precision processing can be realized, and the yield rate can be improved.

[Brief description of the drawings]

FIG. 1 is a partially broken side view showing a configuration of an embodiment.

FIG. 2 is a plan view showing the configuration of one embodiment.

FIG. 3A is a block diagram illustrating an electrical configuration of an embodiment, and FIG. 3B is a block diagram illustrating a memory in a control unit.

FIG. 4 is a circuit diagram showing a control system according to one embodiment.

[Explanation of symbols]

5: Spindle motor, 8: Grinding wheel support, 9: Moving motor, 11: Position detector as rotation detector, 12: Grinding wheel, 14: Grinding wheel rotation motor, 19: Linear scale measuring device, 23 ... A control unit as a calculation unit, a comparison unit, and a control unit.

Claims (3)

[Claims] 1. A linear scale measuring device having a linear scale portion along a moving direction of a grinding wheel support that is linearly moved by rotation of a feed screw, and measuring a movement amount of the grinding wheel support in the linear scale portion; A rotation detector that detects a rotation angle due to the rotation of the feed screw, and a movement error of the grinding wheel support from a movement amount of the grinding wheel support corresponding to a predetermined rotation angle in the rotation detector and a measurement value of the linear scale measuring device. And a movement error calculation means for calculating the movement amount. 2. A linear scale measuring device having a linear scale portion along a moving direction of a grindstone support base that is linearly moved by rotation of a feed screw, and measuring a moving amount of the grindstone support base in the linear scale section; A rotation detector that measures the amount of movement of the grindstone support base from the rotation angle of the feed screw, and a comparison unit that compares each measurement amount with the linear scale measurement unit and the rotation detector, Calculation means for calculating an error ratio, and calculating an actual movement amount of the grinding wheel support corresponding to a measured value of the rotation detector due to rotation of the feed screw based on the error ratio. Table movement amount measuring device. 3. A work supporting mechanism for rotatably supporting a work, and a grinding wheel rotatably supporting a grinding wheel capable of linearly approaching and separating in a direction orthogonal to a rotation axis of the work supported by the work supporting mechanism. A grinding wheel support, wherein the grinding wheel is rotated by the movement of the grinding wheel support to perform a grinding process on a workpiece. The grinding device is provided with the grinding wheel support, and the linear movement amount of the grinding wheel support is provided. A linear scale measuring device that measures the scale provided in the bed portion, and a rotation detector that is connected to a motor that drives the movement of the grindstone support base by rotating the feed screw and detects a rotation angle signal with the rotation of the motor. From the measured value of the linear scale measuring device that measures the amount of movement of the grinding wheel support corresponding to the predetermined rotation angle of the rotation detector, the movement of the grinding wheel support with respect to the rotation angle of the feed screw Calculating means for calculating an error, and control means for controlling the operation of the motor so that the amount of movement of the grindstone support base corresponding to the rotation angle of the feed screw is corrected based on the movement error. Grinding equipment.