JP2003089040A - Combined grinding device using free abrasive grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent clogging of a grinding wheel by activating the repeat of leaving and adsorption of silica abrasive grain adsorbed at the grinding wheel. SOLUTION: A workpiece is loaded on a rotary member and the member is rotation driven. A conductive grinding wheel and an electrode are immersed in an alkaline working liquid with ultrafine silica abrasive grains dispersed, the conductive grinding wheel and the electrode are connected to a positive electrode and a negative electrode, respectively and pulse voltage is applied. The ultrafine silica abrasive grains, thus, are adsorbed to the conductive grinding wheel by electrophoretic phenomenon to perform grinding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite grinding apparatus using free abrasive grains for highly accurately grinding a workpiece formed of a brittle material such as silicon by preventing chipping.

[0002]

2. Description of the Related Art An electrically conductive grindstone that is rotationally driven is relatively moved with respect to a brittle material workpiece that is rotationally driven, and the workpiece is roughly ground by the electrically conductive grindstone to produce ultrafine silica abrasive grains. With the conductive grindstone and the electrode facing each other immersed in the dispersed alkaline machining liquid, the conductive grindstone is connected to the anode of the DC power supply, the electrode is connected to the cathode, and the conductive grindstone is coated with ultrafine silica abrasive grains. BACKGROUND ART Finishing grinding of a work made of a brittle material by adsorbing it by an electrophoretic phenomenon is performed.

[0003]

In the conventional method for grinding a work made of a brittle material, the work is roughly ground with abrasive grains of a conductive grindstone, and a constant DC voltage is applied between the conductive grindstone and the electrode. When applied, the ultrafine silica abrasive grains are adsorbed to the conductive grindstone by an electrophoretic phenomenon to finish-grind the workpiece. In the case of ultra-precision grinding of workpieces, the conductive grindstone uses fine abrasive grains, and the silica abrasive grains dispersed in the working fluid use finer particles, so a constant voltage is applied and free grinding is performed on the grindstone grinding surface. If a cut is made in the state where the grains are adsorbed, the silica abrasive grains that are adsorbed are less likely to fall off, the clogging of the grindstone becomes severe, and there is a problem that the grinding surface is burned.

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to prevent clogging of the grindstone by actively repeating the removal and adsorption of silica abrasive grains adsorbed on the grindstone. is there.

[0005]

In order to solve the above-mentioned problems, the structural feature of the invention according to claim 1 is that a rotating member and a conductive grindstone on which a workpiece is detachably mounted and driven to rotate are provided. In a grinding device including a grindstone shaft that is attached and rotationally driven, an electrode disposed so as to face the conductive grindstone and an alkaline machining liquid in which ultrafine silica abrasive grains are dispersed are retained and the conductivity is maintained. A working fluid retention device for immersing a grindstone and an electrode in the working fluid, and a pulse in which the conductive grindstone is connected to an anode and the electrode is connected to a cathode to adsorb ultrafine silica abrasive grains to the conductive grindstone. And a pulse voltage applying device for applying a voltage.

According to a second aspect of the present invention, in the composite grinding apparatus using the loose abrasive grains according to the first aspect, an average current value flowing between the conductive grindstone and the electrode is detected. Is provided, and the pulse voltage applying device shortens the on-time in one cycle of the pulse voltage as the average current value decreases based on the output of the average current value monitor.

According to a third aspect of the present invention, in the composite grinding apparatus using the loose abrasive grains according to the first aspect, an average current value flowing between the conductive grindstone and the electrode is detected. Is provided, and the pulse voltage applying device lowers the voltage of the pulse voltage as the average current value decreases based on the output of the average current value monitor.

According to a fourth aspect of the present invention, in the composite grinding apparatus using the loose abrasive grains according to the first aspect, the average current value flowing between the conductive grindstone and the electrode is detected. And an inter-electrode gap changing device that changes the gap between the conductive grindstone and the electrode by moving the electrode, and the inter-electrode gap changing device is based on the output of the average current value monitor. That is, the gap is increased as the average current value decreases.

[0009]

In the invention according to claim 1 configured as described above, the workpiece is mounted on the rotary member and driven to rotate, and the conductive grindstone and the electrode are dispersed with ultrafine silica abrasive grains. Immerse in an alkaline processing liquid, connect the conductive grindstone to the anode, connect the electrode to the cathode and apply a pulse voltage, so that the ultrafine silica abrasive grains are adsorbed to the conductive grindstone by the electrophoretic phenomenon to perform grinding processing. Therefore, the silica abrasive grains are partly removed by the grinding resistance during the turning off of the pulse voltage, the clogging of the grindstone is prevented, and the grinding surface can be ground with high precision without burning.

In the invention according to claim 2 configured as described above, the average current value flowing between the conductive grindstone and the electrode becomes high when the silica abrasive grains are not adsorbed to the grinding surface of the grindstone so much. Since the on-time during one cycle of the pulse voltage is shortened as the average current value becomes smaller, the amount of silica abrasive particles adsorbed on the grinding surface of the grindstone should be adjusted appropriately. It is possible to control and grind the workpiece with high precision without causing burn on the grinding surface.

In the invention according to claim 3 configured as described above, the voltage of the pulse voltage is lowered as the average current value flowing between the conductive grindstone and the electrode becomes smaller. It is possible to prevent burning of the grinding surface due to excessive silica abrasive particles adsorbed on the.

In the invention according to claim 4 configured as described above, since the gap between the conductive grindstone and the electrode is increased as the average current value decreases, an appropriate amount of silica grind on the grindstone grinding surface. By adsorbing the particles, it is possible to grind the work piece with high precision without causing burn on the grinding surface.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the column 1 is on the bed 10.
1 is mounted so as to be movable in the Y-axis direction, and is moved in the front-rear direction by a servo motor via a ball screw mechanism (not shown).
A grindstone base 12 is mounted on the column 11 so as to be movable in the Z-axis direction, and is vertically moved by a servomotor 14 via a ball screw mechanism 13. Whetstone stand 1
A grindstone shaft 15 is rotatably supported by 2 on a vertical axis, and is rotationally driven by a motor 16 via a pulley and a belt. A cup-shaped grindstone 17 is fixed to the lower end of the grindstone shaft 15. The cup-shaped grindstone 17 is a conductive one in which a conductive tip formed by metal-bonding abrasive grains such as diamond or cubic boron nitride is fixed to the end face of a cup-shaped base made of a lightweight metal such as aluminum, or a cup-shaped metal. A conductive one is used in which a conductive chip having abrasive grains such as diamond or cubic boron nitride bonded to a resin mixed with a metal filler is fixed to the end face of the substrate.

A table 18 is mounted on the bed 10 so as to be movable in the X-axis direction, and is moved in the left-right direction by a servomotor 20 via a ball screw mechanism 19 to move the table 18
A rotary table 21 as a rotary member is provided above the grindstone 12
The motor 22 is rotatably supported around the vertical axis, and is rotationally driven by the motor 22 via a speed reduction mechanism. A workpiece W made of a brittle material such as silicon is removably mounted on the upper surface of the rotary table 21 with a vacuum chuck or the like. In FIG. 2, a liquid tank 26 storing an alkaline machining liquid 25 in which ultrafine silica abrasive particles are dispersed is liquid-tightly fixed on the outer periphery of the rotary table 21, and is attached to the machining liquid 25 on the rotary table 21. Workpiece W
And, the end surface tip portion of the cup-shaped grindstone 17 lowered to the processing position is immersed. The ultrafine silica abrasive grains (SiO ₂ ) have a particle size of 10 to 100 nm and have the property of being negatively charged in an alkaline solution. The tip end surface of the cup-shaped grindstone 17 faces and grinds the workpiece W in the machining angle range, and the electrode 27 and the machining liquid 25 mounted in the liquid tank 26 in an angle range that does not overlap the machining angle range. For example, the distance between electrodes is 3
It is designed to face each other in mm. The liquid tank 26 constitutes a machining liquid retention device for retaining the alkaline machining liquid 25 in which ultrafine silica abrasive particles are dispersed and for immersing the grindstone and the electrode in the machining liquid.

Reference numeral 30 denotes a pulse voltage applying device having a voltage of 30 V, in which a conductive cup-shaped grindstone 17 is connected to an anode via a brush 28 and a grindstone shaft 15 which are in sliding contact with the rear end surface of the grindstone shaft 15 and an electrode 27 is provided. Connected to the cathode, a pulse voltage is applied between the end surface, which is the ground surface of the conductive cup-shaped grindstone 17, and the electrode 27. An average current value monitor 29 that detects the average current value flowing between the conductive cup-shaped grindstone 17 and the electrode 27 is connected in the circuit, and the detection output of the average current value monitor 29 is input to the pulse voltage application device 30. ing.

The average current value flowing between the cup-shaped grindstone 17 and the electrode 27 increases when the adsorption amount of the silica abrasive grains 32 on the grinding surface of the cup-shaped grindstone 17 is small, and decreases when the adsorption amount is large. As shown in FIG. 3, when the average current value is between the lower limit value A1 and the upper limit value A2, the amount of silica abrasive particles adsorbed on the grinding surface of the cup-shaped grindstone 17 is appropriate and the workpiece is ground. Grinding can be performed with high precision without causing burning on the surface. If the average current is less than the lower limit value A1,
The amount of silica abrasive particles 32 adsorbed on the grinding surface is excessive, burns occur on the grinding surface, and when the upper limit value A2 is more than, the amount of silica abrasive particles 32 adsorbed on the grinding surface is insufficient. It was found that the surface accuracy of the ground surface deteriorates. Therefore, the pulse voltage application device 30 uses the average current value monitor 29.
So that the average current value falls between the lower limit value A1 and the upper limit value A2 based on the output of
By changing the ratio of ON time and OFF time in one cycle of the pulse voltage which is the ON / OFF rate of the pulse voltage applied between and, the amount of silica abrasive grains adsorbed on the grinding surface is controlled. There is. That is, when the average current value is between the lower limit value A1 and the upper limit value A2, the pulse voltage applying device is
As shown in (a), when a pulse voltage having the same length of on time and off time is applied and the average current value is less than the lower limit value A1, the on time as shown in FIG. When a shorter pulse voltage is applied and the average current value is larger than the upper limit value A2, a pulse voltage whose on-time is longer as shown in FIG. 4C is applied.

Next, the operation of the compound grinding machine using loose abrasive grains according to the present invention will be described. The wheel spindle 15 is rotated, for example, 300 min ^-1 by the motor 16, by mounting the workpiece W on the rotating table 21 is rotated by the motor 22, for example 20min ^-1, the wheel head 12 Sa - lowered by Bomota 14 Then, the cup-shaped grindstone 17 is cut into the workpiece W, the column 11 and the table 18 are moved in the X and Y-axis directions by the respective servo motors, and the workpiece W is roughly ground by the tip of the cup-shaped grindstone 17.

Next, the pulse voltage applying device 30 is activated,
A pulse voltage is applied between the cup-shaped grindstone 17 connected to the anode and the electrode 27 connected to the cathode to adsorb the negatively charged ultrafine silica abrasive grains 32 on the ground surface of the cup-shaped grindstone 17. In this state, the grindstone base 12 is moved in the Z-axis direction to cut the cup-shaped grindstone 17 in a minute amount with respect to the workpiece W, and the column 11 and the table 18 are moved in the X-axis and Y-axis directions so that the workpiece W is cupped. Finish grinding is performed by the ultrafine silica abrasive grains 32 formed on the tip end surface of the die grindstone 17 without causing chipping. The silica abrasive grains 32 adsorbed on the grinding surface of the cup-shaped grindstone 17 are partly dropped by the grinding resistance during the pulse voltage is turned off, and the clogging of the grindstone is prevented.
Is ground with extremely high precision without causing burns on the ground surface. When the finish grinding is completed, the grindstone 12 is retracted to the upper end, the rotation of the rotary table 21 is stopped, and the workpiece W
Is removed from the work table 21.

During finish grinding, a pulse voltage application device 30
Is 1 of the pulse voltage applied between the ground surface of the cup-shaped grindstone 17 and the electrode 27 so that the average current value falls between the lower limit value A1 and the upper limit value A2 based on the output of the average current value monitor 29. The ratio of the on time and the off time in the cycle is changed to control the amount of silica abrasive particles adsorbed on the ground surface.

In the above-described embodiment, the cup type grindstone is mounted on the grindstone shaft of the vertical axis surface grinder, and the rotary table on which the workpiece is removably mounted is mounted.
In a cylindrical grinder, an electrically conductive flat grindstone is attached to a grindstone shaft that is rotatably supported on a grindstone around a horizontal axis, and a work piece made of brittle material is mounted on a spindle that is rotatably supported around a horizontal axis. , A liquid tank containing the machining fluid 25 is attached to the grindstone base so that the lower part of the flat grindstone is immersed, the outer peripheral surface of the lower part of the flat grindstone faces the electrode, and a pulse voltage is applied to the conductive flat grindstone. An electrode may be connected to the cathode of the apparatus 30, and the ultrafine silica abrasive grains 32 may be adsorbed to the outer peripheral surface of the rotating conductive plain grindstone by an electrophoretic phenomenon to finish-ground the workpiece.

Further, in the above embodiment, when the average current value of the current flowing between the conductive grindstone and the electrode is less than the lower limit value A1, a pulse voltage having a shorter on-time is applied to obtain the average current value. Is larger than the upper limit value A2, a pulse voltage with a longer on-time is applied, but without setting a threshold, the on-time of the pulse voltage can be shortened continuously as the average current value decreases. You may

In the above embodiment, the on / off rate of the pulse voltage is changed according to the average current value of the current flowing between the conductive grindstone and the electrode, but the magnitude of the pulse voltage may be changed. Good.

Further, the electrodes can be moved by a servomotor, and the gap between the conductive grindstone and the electrode or the facing area where the ground surface of the conductive grindstone and the electrode face each other is changed according to the average current value. You may

Further, the working fluid or the liquid tank may be vibrated by ultrasonic waves or the like, and the frequency or amplitude of the vibration may be changed according to the average current value. Alternatively, air may be sent between the grindstone grinding surface and the electrode, and the amount of air may be changed according to the average current value.

[Brief description of drawings]

FIG. 1 is a diagram showing a compound grinding apparatus using loose abrasive grains according to the present invention.

FIG. 2 is a diagram showing a relationship between a cup-shaped grindstone, a workpiece, electrodes, and the like.

FIG. 3 is a diagram showing a change in average current value and a state in which silica abrasive grains are adsorbed on a grindstone grinding surface.

FIG. 4 is a diagram showing pulse voltages having different on / off rates.

[Explanation of symbols]

10 ... Bed, 11 ... Column, 12 ... Grindstone base, 15 ... Grindstone axis, 17 ... Cup grindstone, 18
... table, 21 ... rotary table (rotating member), 25 ... machining liquid, 26 ... liquid tank, 27 ...
Electrodes, 29 ... Average current value monitor, 30 ... Pulse voltage applying device, 32 ... Ultra fine silica particles, W ... Workpiece.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Suzuki             3 Okuyama, Myodaiji Town, Okazaki City, Aichi Prefecture (72) Inventor Toshio Murakami             1-1 Asahi-cho, Kariya city, Aichi             Machine Co., Ltd. (72) Inventor Mamoru Abe             1-1 Asahi-cho, Kariya city, Aichi             Machine Co., Ltd. F term (reference) 3C047 AA01 AA24 FF01 FF02 FF03                 3C049 AA02 AC01 AC04 BB02 BC02                       CA04 CB01 CB03

Claims (4)

[Claims] 1. A grinding apparatus including a rotating member, on which a workpiece is detachably mounted and driven to rotate, and a grindstone shaft, on which a conductive grindstone is attached and which is driven to rotate, and which is arranged facing the conductive grindstone. Electrode, a machining fluid retention device for retaining an alkaline machining fluid in which ultrafine silica abrasive particles are dispersed to immerse the conductive grindstone and the electrode in the machining fluid, and the electromechanical grindstone Composite grinding using loose abrasive grains, characterized in that the electroconductive grindstone is used as an anode to adsorb silica abrasive grains, and a pulse voltage applying device is connected to the cathode to apply a pulse voltage to the electrode. apparatus. 2. The composite grinding apparatus using loose abrasive grains according to claim 1, further comprising an average current value monitor for detecting an average current value flowing between the conductive grindstone and the electrode,
The above-mentioned pulse voltage applying device shortens the on-time during one cycle of the pulse voltage as the average current value decreases based on the output of the average current value monitor. apparatus. 3. The composite grinding apparatus using loose abrasive grains according to claim 1, further comprising an average current value monitor for detecting an average current value flowing between the conductive grindstone and the electrode,
The composite grinding device using loose abrasive grains, wherein the pulse voltage application device lowers the voltage of the pulse voltage as the average current value decreases based on the output of the average current value monitor. 4. The composite grinding apparatus using loose abrasive grains according to claim 1, wherein an average current value monitor for detecting an average current value flowing between the conductive grindstone and the electrode, and moving the electrode. Then, an inter-electrode gap changing device that changes the gap between the conductive grindstone and the electrode is provided, and the inter-electrode gap changing device is configured to reduce the gap as the average current value decreases based on the output of the average current value monitor. The compound grinding device using loose abrasive grains is characterized in that