JP2004042174A - Surface grinding process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve grinding precision in a grinding process using a planar grinder, through a simple structure of the grinder. <P>SOLUTION: The surface surface grinding process is a method to grind work W to obtain a specific machining allowance by revolving a grinding stone through a stone rotational electric motor 8 and moving the stone in the direction of stone core. While the rotating stone 3 is being moved toward the work in the direction of the rotational axis core of the stone after the current from the electric motor 8 is detected through a current detector, when a fixed current increase is detected from the non-load electric current value, the grinding is started, and grinding the specified machining allowance D6 is implemented with the grinding start location P3 as the basis. The fixed current increase value for determining the grinding start position is preferably set to 0.5 ampere. As a result, it is not necessary to attach any special measuring instrument or sensor, and maintenance or adjustment activities are not needed, either. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of the present application is a so-called in-feed type surface grinding method for grinding a work by rotating a grindstone by an electric motor for rotating a grindstone and moving the grindstone in the axis direction of the grindstone rotation. The present invention relates to a surface grinding method applicable to various surface grinding machines such as a surface grinding machine or a double-sided surface grinding machine.
[0002]
[Prior art]
Conventionally, in the infeed type surface grinding method, various in-process methods such as dial gauges are used so that the workpiece can be ground with a constant allowance for variations in workpiece dimensions in the pre-processing and variations in the mounting height of the workpiece during grinding. The actual grinding amount is measured for each work using a measuring device, and the allowance is adjusted.
[0003]
[Problems to be solved by the invention]
In the method of actually measuring the amount of grinding using an in-process measuring device as described above, a measuring member such as a sensor must be separately attached to the grinding machine, so that maintenance and adjustment are complicated, and the measuring operation is troublesome.
[0004]
[Object of the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a surface grinding method which can always be ground with a fixed allowance without newly providing a measuring member such as a sensor in the surface grinding method and has a high grinding accuracy.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, an invention according to claim 1 of the present application is directed to a surface grinding method for performing surface grinding of a work by rotating a grinding wheel by an electric motor for rotating a grinding wheel and moving the grinding wheel in a direction of a grinding wheel rotation axis. When the current of the electric motor for grinding wheel is moved to the work side from the standby position away from the work to the work side in the direction of the grinding wheel rotation axis, the current of the electric motor for grinding wheel rotation increases by a predetermined amount from the value in the no-load state. A surface grinding method characterized in that a grinding wheel position is set as a grinding start position and grinding is performed with a predetermined allowance based on the grinding start position.
[0006]
According to a second aspect of the present invention, in the surface grinding method according to the first aspect, the position of the grinding wheel when the current of the electric motor for rotating the grinding wheel increases by 0.5 amperes from a value in a no-load state is set as a grinding start position. It is characterized by.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 4 show a vertical plane (one-sided) grinding machine for performing an in-feed type surface grinding method according to the present invention. FIG. 1 is a side view showing a partial cross section. In FIG. 1, an annular rotary grindstone 3 is detachably fixed to a lower end head 2 of a vertical grindstone shaft 1, and the grindstone shaft 1 is a vertical slide cylinder. 5 and is rotatably supported by the grindstone rotating electric motor 8 via a power transmission mechanism described later, and is rotated at a desired rotation speed by the grindstone rotating electric motor 8. It has become. The vertical slide cylinder 5 is supported by the grinding machine main body 7 so as to be movable in the vertical direction, and is linked to an elevation AC servomotor 10 via an elevation mechanism described later, and is driven at a desired speed by the elevation AC servomotor 10. It can be moved up and down.
[0008]
A circular index table 11 is disposed in front of and below the grindstone 3 in a horizontal posture. The index table 11 is supported by a table support case 12 so as to be rotatable around a vertical rotation axis O1 and a table driving electric motor (not shown). It is linked to a motor and is controlled by 180 ° index rotation. On the index table 11, a pair of work holding jigs 15 are arranged with a phase difference of 180 ° around the table rotation axis O1, and each of them rotates around the rotation axis O2 in a cylindrical jig support case 16. The work holding jig 15 can be changed between a grinding position A1 on the grinding wheel side and a detachable position A2 on the opposite side by rotating the index table 11 half a turn.
[0009]
A work attachment / detachment device 17 is disposed in front of the table support case 12, and the work attachment / detachment device 17 supports a left-right slide 21 movably in the left-right direction on the front surface of a mounting frame 20 fixed to the grinding machine body 7. The left and right sliders 21 are provided with a work gripping claw 23 of an internal expansion type via a cylinder 22 so as to be able to move up and down.
[0010]
FIG. 2 is an enlarged cross-sectional view taken along the line II-II in FIG. 1. The cylinder 22 and the work gripping claw 23 are provided in a pair at right and left intervals, and the work gripping claw 23 is inserted into the center hole of the work W. The work W can be grasped by expanding the work W. The left work gripping claw 23 is for loading, and the left and right sliders 21 move in the left and right directions to move the unworked work loading mechanism 18 disposed on the left side of the mounting frame 20 and the work holding jig 15 at the attachment / detachment position A2. The right work gripping claw 23 is for unloading, and the right and left sliders 21 move in the left-right direction to move the processed work unloading mechanism 19 disposed on the right side of the mounting frame 20 and the attachment / detachment position. It reciprocates between the work holding jigs 15 of A2.
[0011]
FIG. 3 is a schematic side view showing an example of a grindstone raising / lowering mechanism, a grindstone rotating mechanism, and a control mechanism thereof. The upper and lower slide cylinder 5 is fixed to a travel nut 26 of a ball screw mechanism 25. The feed screw 27 is movably screwed to a vertical feed screw 27 via a worm gear mechanism 29. In other words, the rotation of the lifting AC servomotor 10 raises and lowers the grinding wheel shaft 1 and the grinding wheel 3 together with the vertical slide cylinder 5 via the worm gear mechanism 29 and the ball screw mechanism 25.
[0012]
A rotary encoder 31 is connected to the lifting / lowering AC servomotor 10, and by detecting the rotation angle of the lifting / lowering AC servomotor 10 with the rotary encoder 31, the vertical position of the grinding wheel 3 and the vertical movement amount ( (Elevation). For example, the rotary encoder 31 has a performance of detecting a vertical movement amount of 0.5 μm with one pulse of the rotary encoder 31.
[0013]
A spline portion 1a is formed at an upper end portion of the grinding wheel shaft 1. The spline portion 1a is spline-fitted to a sprocket 30 having an inner peripheral spline so as to be vertically slidable. And is linked to the electric motor 8 for rotating the grindstone through the shaft. That is, the rotation of the electric motor 8 for rotating the grinding wheel rotates the grinding wheel shaft 1 and the grinding wheel 3 via the belt transmission mechanism 28, the sprocket 30, and the spline fitting portion, and moves the grinding wheel shaft 1 and the grinding wheel 3 in the vertical direction. Is forgiving. The electric motor 8 for rotating the grindstone is provided with a current detector 32 for measuring a current value flowing in the electric motor 8 for rotating the grindstone in order to detect a grinding start position (contact position) of the grindstone 3 with respect to the workpiece W. ing.
[0014]
In order to control the on / off and rotation speed of the electric motor 8 for rotating the grinding wheel and the AC servomotor 10 for lifting and lowering the grinding wheel, the two motors 8 and 10 are connected to a controller 33 having a built-in microcomputer. The current detector 32 and the rotary encoder 31 are connected, and the current value of the grinding wheel rotating electric motor 8 detected by the current detector 32 and the rotation angle detection signal of the feed screw 27 detected by the rotary encoder 31 are input. It has become so.
[0015]
The controller 33 calculates the vertical position and the vertical movement of the grindstone 3 based on the rotation angle and the number of rotations of the feed screw 27 detected by the rotary encoder 31, and inputs from the current detector 32. When the measured current value increases by 0.5 amperes with respect to the value at the time of the no-load rotation (for example, 7 amps), it is determined that the grindstone 3 has reached the grinding start position, and the amount of decrease from the grinding start position is determined by the grinding amount. Is set to be measured by the rotary encoder 31.
[0016]
FIG. 4 is an enlarged longitudinal sectional view of the work W and the work holding jig 15 at the grinding position A1. The work W is a bearing member of the compressor, and has a boss portion 40 and a flange portion 41 integrally. The surface of the flange portion 41 is a surface to be ground by the grinding method of the present invention.
[0017]
A vertical work rotation shaft 34 is supported by the jig support case 16 so as to be rotatable around the rotation axis O2. A cylindrical jig body 35 is fixed to the upper end surface of the work rotation shaft 34 in a coaxial manner. An annular positioning piece 36 is fixed to the upper surface of the jig main body 35 in a coaxial manner, and the jig main body 35 and the work rotating shaft 34 are coaxial with each other by a cylindrical member 37 which fits into the both 35 and 34. Are aligned. The inner diameter of the positioning piece 36 is set to a size to which the boss 41 of the work W fits, and a detent and positioning pin 38 that projects upward is fixed at a position eccentric from the rotation axis O2. A center rod 39 protruding upward is fixed to the center of the cylindrical member 37 by a bolt 44, and the center rod 39 is set to a size that fits into the center hole 42 of the workpiece W.
[0018]
The positional relationship between the grindstone 3 and the workpiece holding jig 15 at the grinding position A1 in the front-rear direction is set so that the rotation axis O2 passes through the center line of the grinding surface width E of the grindstone 3.
[0019]
FIG. 5 shows the descending speed and descending amount (feed amount and grinding amount) of the grindstone 3 controlled by the controller 33 based on the vertical position and the amount of elevation of the grindstone 3 detected by the rotary encoder 31 of FIG. FIG. 4 is an operation explanatory diagram showing only the vertical dimension in an enlarged manner for easy understanding.
[0020]
In FIG. 5, a position P1 is a standby position where the grindstone 3 is located at the uppermost position, and a high feed speed V1 (for example, 2000 μm / s) from the standby position P1 to the workpiece W rotating at the grinding position A1. Is set so that the grinding wheel 3 starts to descend.
[0021]
The position P2 is a position where the high-speed feed speed V1 is switched from the high-speed feed speed V1 to the medium-speed feed speed V2 (for example, 200 μm / s), and is set below the standby position P1 by a distance D1 (for example, 320 μm).
[0022]
The position P3 is a grinding start position at which the grindstone 3 comes into contact with the surface of the work W, and the current value detected by the current detector 32 in FIG. 3 increases by 0.5 amp from the value at no load (7 amp). It is the position when you did. At the grinding start position P3, the setting is made so that the medium feed speed V2 can be switched to a low cutting speed V3 (for example, 70 μm / s). The distance D5 from the standby position P1 to the expected grinding start position P3 is approximately 400 μm, and the distance D2 from the position P2 to the expected grinding start position P3 is approximately 80 μm.
[0023]
The position P4 is a position that is switched from the low grinding speed V3 to a very low finishing speed V4 (for example, 12 μm) during grinding, and the distance D3 from the grinding start position P3 is set to 70 μm.
[0024]
The position P5 is a grinding end position, and a distance D4 from the grinding start position P3 to the grinding end position P5 is set to a predetermined allowance of 100 μm.
[0025]
Further, at the grinding end position P5, the timer is set to spark out for, for example, 2 seconds, and thereafter, the grindstone 3 is set to return to the upper standby position P1.
[0026]
In FIG. 5, the change of the descending speed V1 → V2 → V3 → V4 is shown in such a manner that the change is performed sharply at each of the positions P2, P3, and P4. It is set to change through the deceleration distance of
[0027]
FIG. 6 shows a temporal change of the current value of the electric motor 8 for rotating the grinding wheel. When no load is applied, the current value is 7 amps as described above, and the current value rises sharply when the grinding wheel comes into contact with the workpiece. .
[0028]
At the initial stage of this ascent process, the time Ts at which the increase from 7 amps to 0.5 amps is detected is defined as the grinding start position P3.
[0029]
The current value has increased even after the grinding start position P3, and after switching from the grinding speed V3 to the finishing speed V4, the current value decreases, and the spark-out period S.P. It temporarily stabilizes at the stage of moving to O, and then decreases to the current value at no load.
[0030]
In FIG. 6, as in FIG. 5, a change GA of the descending speed V1 → V2 → V3 → V4 → 0 is rapidly performed, but this is also a convenient expression. It changes after a certain deceleration distance. Therefore, it is around T3 that is slightly later than the grinding start position P3 (Ts) until the grinding speed V3 is actually reduced from the medium feed speed V2 to the grinding speed V3.
[0031]
[Grinding method]
[Work supply]
In FIG. 2, the left and right sliders 21 of the work attaching / detaching device 17 are moved to the left, the work grasping claws 23 are lowered, inserted into the center holes 42 of the work W, and expanded, so that the work is not processed by the left work grasping claws 23. At the same time as the workpiece W is gripped, the processed workpiece W on the attaching / detaching position A2 is gripped by the right workpiece gripping claw 23.
[0032]
The unprocessed work W is placed on the work holding jig 15 at the attachment / detachment position A2 by raising the both work gripping claws 23 to move rightward and moving down to reduce the diameter, and unloading the processed work W. Put on the mechanism 19.
[0033]
Subsequently, the index table 11 is rotated by 180 °, and the work holding jig 15 on which the unprocessed work W is placed is positioned at the grinding position A1.
[0034]
At the grinding position A1, the surface of the work W is ground by a predetermined allowance by the lowering of the grindstone 3, and after finishing the grinding, the index table 11 is again rotated by 180 ° to return the processed work W to the attaching / detaching position A2 for unloading. Is transferred onto the work unloading mechanism 19 by the work gripping claw 23.
[0035]
[Grinding work]
FIG. 7 is a flowchart showing the flow of the grinding operation. The grinding operation will be described with reference to FIG.
[0036]
In step 1, the grindstone 3 is lowered at a high feed rate V1 from the standby position P1 with respect to the workpiece W rotating at the grinding position A1, and at the same time, the rotor encoder 31 lowers the grindstone 3 from the vertical position and the standby position P1. In addition to measuring the distance, the current detector 31 measures the current value (at no load) of the electric motor 8 for rotating the grinding wheel.
[0037]
In step 2, it is determined whether or not the descending distance has reached D1 set in advance. If YES, the process proceeds to step 3 where the descending speed is reduced from V1 to V2, and if NO, the process returns to step 1.
[0038]
In step 4, the medium feed speed V2 is maintained, and the process proceeds to step 5, in which it is determined whether the current value of the electric motor 8 for rotating the grinding wheel has increased by 0.5 amperes from the value at no load (7 amps). . In the case of NO, the process returns to Step 4, and in the case of YES, it is determined that the grindstone 3 has been lowered to the grinding start position P3 where it comes into contact with the workpiece W, and the process proceeds to Step 6, where the descent speed is reduced from the medium feed speed V2 to the low At the same time as the grinding speed V3, the measurement of the grinding amount (falling amount) from the grinding start position P3 is started.
[0039]
In step 7, the descending speed V3 is maintained, and the process proceeds to step 8, where it is determined whether or not the grinding amount from the grinding start position P3 has reached D3. If NO, the process returns to step 7, and if YES, the process proceeds to step 9. Then, the descending speed is switched from the low grinding speed V3 to the very low finishing speed V4, and the grinding at the finishing speed V4 is continued in step 10.
[0040]
In step 11, during grinding at the speed V4, it is determined whether or not the grinding amount from the grinding start position P3 has reached D6 (predetermined allowance). If NO, return to step 10, and if YES, return to step 12. Then, spark-out is started by stopping the grindstone 3 at the grinding end position P5, and at the same time, counting by a timer is started.
[0041]
In step 13, the spark-out is continued while counting the timer, the process proceeds to step 14, and it is determined whether or not the timer counting is completed. If NO, the process returns to step 13, and if YES, the spark-out is completed. In step 15, the grindstone 3 is raised to the standby position P1.
[0042]
In the above-mentioned grinding operation, the surface of the unprocessed work W attached to the work holding jig 15 has a change due to a variation in the accuracy of the pre-processing. The grinding start position (contact position) is detected, and a predetermined amount of allowance is ground, so that stable grinding accuracy can be obtained.
[0043]
The work W in the above embodiment is a bearing portion of a compressor, and in order to secure gas tightness during assembly, the grinding surface of the grindstone 3 is positioned on the rotation axis O2 of the work and slightly inclined. By doing so, the work surface is ground to a concave shape in which the center portion is slightly recessed by 1.5 μm from the peripheral edge, as shown by a virtual line in FIG. Such grinding requires higher straightness than grinding a normal perfect plane, but the grinding method according to the present invention provides stable grinding accuracy.
[0044]
[Other embodiments]
(1) The grinding method of the present invention can be applied to a horizontal axis type surface grinding machine in which a grinding wheel shaft is arranged horizontally or a double-sided surface grinding machine having a pair of opposed rotating grinding wheels.
[0045]
(2) The amount of increase in the current value, which is a reference for setting the grinding start position, is set to 0.5 amps in the above-described embodiment. It is possible to set appropriate various values.
[0046]
【The invention's effect】
As described above, according to the present invention, (1) in the method of performing surface grinding by infeed grinding, a grinding start position at which the grinding wheel contacts the workpiece by detecting an increase in the current value of the electric motor for rotating the grinding wheel. , And a predetermined allowance is ground based on the grinding start position, so even if there is a variation in accuracy during pre-processing of the work, the grinding start position can be easily detected for each work, Grinding accuracy is improved.
[0047]
(2) Since the grinding start position is detected by detecting a change in the current value of the electric motor for rotating the grinding wheel, a measuring tool such as a sensor is used as compared with a conventional case where the grinding amount is actually measured by an in-process measuring device. It does not need to be attached, so that maintenance and adjustment can be omitted and the structure is not complicated.
[0048]
(3) If the amount of current increase for recognizing the grinding start position is set to 0.5 amperes, a portion that is not included in the actual allowance, such as a black scale portion on the work surface, is removed. , And the actual meat portion of the work is not excessively ground, and can be efficiently ground without waste.
[Brief description of the drawings]
FIG. 1 is a side view of a single-side grinding machine to which a grinding method according to the present invention is applied.
FIG. 2 is an enlarged cross-sectional view taken along the line II-II of FIG.
FIG. 3 is a view showing a mechanism for raising and lowering and rotating the grindstone.
FIG. 4 is an enlarged longitudinal sectional view of a work holding jig and a work.
FIG. 5 is an operation explanatory diagram showing a descending speed and a feed amount of a grindstone.
FIG. 6 is a diagram showing a change over time of a current value of an electric motor for rotating a grindstone.
FIG. 7 is a flowchart showing an example of a grinding method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Whetstone axis 3 Whetstone 8 Electric motor for rotation of whetstone 10 AC servomotor for raising and lowering whetstone 11 Index table 15 Work holding jig 17 Work attaching / detaching device 25 Ball screw mechanism (elevation mechanism)
31 rotary encoder 32 current detector 33 controller

Claims (2)

In a surface grinding method for performing surface grinding of a work by rotating a grinding wheel by a grinding wheel rotating electric motor and moving the grinding wheel in the axial direction of the grinding wheel,
Detects the current of the electric motor for grinding wheel rotation,
While moving the grindstone from the standby position away from the work to the work side in the direction of the grindstone rotation axis, the position of the grindstone when the current of the electric motor for rotating the grindstone increases by a predetermined amount from a value in a no-load state is set as a grinding start position, A surface grinding method characterized in that grinding is performed with a predetermined allowance based on the grinding start position. 2. The surface grinding method according to claim 1, wherein a position of the grinding wheel when a current of the electric motor for rotating the grinding wheel increases by 0.5 amperes from a value in a no-load state is set as a grinding start position.

Images