JP2001129741A - High resolving power positioning feeder and machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the resolving power even at a low feeding speed. SOLUTION: This positioning feeder comprises transmitting mechanisms 14, 19 mounted between an object 3 to be controlled driven by a motor 8 of which a rotation angular position is numerically controlled and the motor 8. A reduction gear 9 is mounted between the transmission mechanisms 14, 19 and the motor 8. The reduction gear 9 is substantially free from the backlash. As the backlash is not found and a reduction gear ration is high, the stick slip at a high speed generated caused by the rigidity of the part can be prevented, and the desired resolving power (corresponding to a command value) can be obtained. A friction-type power transmitting mechanism is used as the reduction gear 9 substantially free from the backlash. The friction-type power transmitting mechanism has a planetary roller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-resolution positioning feeder and a machine tool, and more particularly to a high-resolution positioning feeder and a machine tool suitable for ultra-precision machining of glass and semiconductor crystals by grinding stones.

[0002]

2. Description of the Related Art A machine tool is provided with a positioning feed device. Grinding of a brittle material such as a crystal for a glass or a semiconductor requires continuous feed of a minute unit in order to position a grindstone in a cutting direction. The known positioning feeder shown in FIG. 7 includes a servomotor 101,
It is provided as a feedback system including a feed screw 102 and a displacement sensor 103. The table 104 to be feed-controlled is connected to the feed screw 102 via a nut 105. The nut 105 is fixed to the table 104. A servo system is established in which position data detected by the displacement sensor 103 is sent to the servo motor 101 via the computer 106.

The positioning control of the feed device of the servo system forms a closed loop control system as shown in FIG. 8, and the minimum unit of the resolution is the minimum unit of the servo motor which is the minimum unit of the feedback scale. It does not become smaller than the larger stick-slip amount determined from the relationship between the servo error determined by the feed unit and the relationship between the frictional force of the sliding surface and the rigidity (spring coefficient) of the drive system. Regarding stick-slip, refer to Fig. 2.26 in "Illustration Precision Positioning Mechanism Design" (by Jiro Otsuka, published by the Industrial Research Institute, first edition on June 1, 1996).
"Stick-slip occurs when the coefficient of static friction is greater than the coefficient of dynamic friction.", But this is incorrect in the sense that the relative speed between the table and the slide guide sliding surface is v, When the friction coefficient is μ, the relationship of v−μ is..., And μ has a negative gradient, and stick-slip occurs when the rigidity (spring constant) between the table and the nut is small. ” ing.

[0004] Even if the servo gain is increased by using a scale having a small resolution in the servo system shown in FIG. 8, there is a limit to the resolution determined by the load inertia and the attenuation of the servomotor. It is difficult to obtain the positioning resolution. Further, a scale having a small resolution easily picks up spatial noise (vibration, change in molecular density of air) in the vicinity thereof, and it is difficult to obtain a stable position signal.

Another known positioning feeder shown in FIG. 9 includes a servomotor 201 and a feed slider 202.
And a displacement sensor 203 are provided as a feedback system. The table 204 to be fed is connected to the feed slider 202 via a connecting shaft 205. The connection shaft 205 is fixed to the table 204. A servo system is established in which position data detected by the displacement sensor 203 is sent to the servo motor 201 via the controller 206. In this positioning feed device, a servo motor 201 and a feed slider 202
Are interlocked through. The mechanical connection between the driving wheel 207 and the feed slider 202 is based on frictional force. The principle of the servo system is the same as that of the apparatus of FIG. 7 shown in FIG. The reason why the resolution of this device is limited is the same as the reason described above.

[0006] When the feed speed is low, the feed servo system has a problem that it is difficult to increase the resolution, as shown in the above-mentioned relationship of v-μ. Positioning that can increase the resolution even when the feed speed is low is required.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-resolution positioning feed device and a machine tool capable of increasing the resolution even when the feed speed is low.

[0008]

Means for solving the problem are described as follows. The technical items appearing in the expression are appended with numbers, symbols, and the like in parentheses (). The numbers, symbols, and the like are technical items that constitute at least one embodiment or a plurality of the embodiments of the present invention, in particular, the embodiments or the examples. Corresponds to the reference numerals, reference symbols, and the like assigned to the technical matters expressed in the drawings corresponding to the above. Such reference numbers and reference symbols clarify the correspondence and bridging between the technical matters described in the claims and the technical matters of the embodiments or examples. Such correspondence / bridge does not mean that the technical matters described in the claims are interpreted as being limited to the technical matters of the embodiments or the examples.

A high-resolution positioning feeder according to the present invention comprises a motor (8) whose rotational angle position is numerically controlled, a control object (3) driven by the motor (8), and a control object (3). A transmission mechanism (14, 19) interposed between the motors (8) and a speed reducer (9) interposed between the transmission mechanisms (14, 19) and the motor (8); (9) has substantially no backlash. Since there is no backlash and the reduction ratio is large, there is no stick-slip at high speed caused by the rigidity of the portion, and the resolution can be obtained as expected (according to the command value).

The speed reducer (9) having substantially no backlash can be easily realized by a conventional means which is a friction type power transmission mechanism. Such a friction type power transmission mechanism can be formed from a plurality of rollers that transmit friction. More specifically, such a friction-type power transmission mechanism includes an input shaft (1).
2), an output shaft (16), and a planetary roller mechanism interposed between the input shaft (12) and the output shaft (16),
The planetary roller mechanism includes a first roller (27) axially coupled to the input shaft (12), a rotating body (29) axially coupled to the output shaft (16), and a planetary roller frictionally coupled to the first roller (27). (32) and a second roller (34) having an inner peripheral surface frictionally coupled to the planetary roller (32). Unlike such a gear type power transmission mechanism, such a friction type power transmission mechanism has no backlash and is hardly affected by the rigidity described above.

Accordingly, the control scales (103 and 203 in the known drawings) for detecting the position of the control target (3) are unnecessary and need not be present. The reduction ratio of the reduction gear (9) is 1
This effect is particularly effective when N is greater than 100.

[0012] The machine tool according to the present invention can be used particularly effectively when such a high-resolution positioning feed device is recessed and a brittle material is ground by a grindstone.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Corresponding to the drawings, an embodiment of a high-resolution positioning feeder according to the present invention is provided with a machine tool together with a feed mechanism. The machine tool 1
As shown in FIG. 1, a slide base 2 is provided. A slide unit 3 is mounted on a slide base 2. The slide unit 3 is guided by the slide base 2 and is supported thereon so as to be capable of linear movement. A spindle head 4 is mounted on the slide unit 3. A tool spindle 5 is rotatably attached to the spindle head 4. The tool spindle 5 approaches the workpiece 6 which is the object to be processed while rotating, and processes it.

FIG. 2 shows a drive mechanism for driving the slide unit 3. The slide base 2 is firmly supported by the main body bed 7. A servo motor 8 is fixedly supported on the main body bed 7. On the main body bed 7,
Further, a friction drive speed reducer 9 is fixedly supported.
The output shaft 11 of the servomotor 8 and the speed reducer input shaft 12 of the friction drive speed reducer 9 are axially connected via a coupling 13 in the rotational direction.

A feed screw 14 is further rotatably supported on the main body bed 7 via a bearing 15. The reduction gear output shaft 16 of the friction drive reduction gear 9 and the input end 17 of the feed screw 14 are axially coupled in the rotational direction by a coupling 18. A nut 19 is firmly fixed to the lower end surface side of the slide unit 3. The feed screw 14 is rotatably screwed to the nut 19.

As shown in FIG. 3, the slide unit 3 is fitted in a groove on the upper surface of the slide base 2 and slides linearly with respect to the slide base 2 in the axial direction. The groove fitting is performed by two guide grooves 22,22. Nut 1
9 is firmly fixed to the slide unit 3 by bolts 23.

FIG. 4 shows the details of the friction drive speed reducer 9. A first bearing 26 is attached to an end face 25 of a main body casing 24 of the friction drive reduction gear 9. The reduction gear input shaft 12 described above is rotatably supported by the first bearing 26. A friction roller 27 extends in the axial direction and is coaxially connected to the front end of the speed reducer input shaft 12. A second bearing 28 is attached to a front portion of the friction drive reducer 9. The reduction gear output shaft 16 described above is supported by a second bearing 28.
The output shaft 16 of the reduction gear is provided with a flange 29 at its end as an output shaft.

Three planet arms 31 are attached to the collar 29. The three planetary arms 31 are arranged at equal angular intervals on one circumference, and their axial directions are parallel to the axis L shared by the reduction gear input shaft 12 and the reduction gear output shaft 16. Three planetary rollers 32 are respectively connected to the three planetary arms 31 coaxially with the planetary arms 31. A planet bearing 33 is interposed between one planetary roller 32 and one planetary arm 31.

Each of the three planetary rollers 32 is in frictional contact with one friction roller 27. The three planetary rollers 32 roll in contact with the inner peripheral surface of the guide roller 34 disposed on the outer peripheral side. The three planetary rollers 32 are integrally connected to the speed reducer output shaft 16 in the rotational direction via the planetary arms 31 and the flange 29.

When the servo motor 8 is started, the output shaft 11 rotates, and the reduction gear input shaft 12 is rotationally driven via the coupling 13. The friction roller 27 which is the same as the reduction gear input shaft 12 rotates. The three planetary rollers 32 in frictional contact with the rotating friction roller 27 rotate around the planetary bearing 33 in synchronization.

The planetary roller 32 which rotates in contact with and comes into contact with the guide roller 34 is brought into frictional contact with the inner peripheral surface of the planetary roller 32 and rolls on that surface to revolve around the axis.
The planetary arm 31 which is the axis of the planetary roller 32 has a collar 29
To rotate. The speed is reduced between the speed reducer input shaft 12 and the planetary roller 32, the speed is also reduced between the rotation period of the planetary roller 32 and its revolution period, and the rotation speed of the flange 29 is reduced by the rotation of the speed reducer input shaft 12. An extremely low speed is performed compared to the speed.

Since no reduction gear is provided between the reduction gear input shaft 12 and the flange 29, the reduction gear input shaft 12 and the collar 29 are not provided.
There is no backlash between them. The rotation of the friction drive reduction gear 9 is directly transmitted to the feed screw 14 via the reduction gear output shaft 16 and the input side end 17 as it is.
Power transmission between the feed screw 14 and the slide unit 3 is performed via a nut 19. A ball screw or the like is used as the feed screw 14, and the backlash between the feed screw 14 and the slide unit 3 can accommodate the size of the backlash generated between them within a range of desired accuracy. High speed rotating reducer input shaft 12
, Ie, the drive system from the servo motor 8 to the speed reducer input shaft 12 is a high-speed rotation system.
No stick-slip occurs between the servomotor 8 and the servomotor 8 or between the servomotor 8 and the speed reducer input shaft 12.

Even when the slide unit 3 is caused to perform a linear motion with a feed unit (resolution) of 0.1 mm or less at a feed speed of 1 mm / min or less, such a driving force transmission system has the following problems. Has been resolved. (1) Due to the extremely low speed feed, the rotation of the servo motor 8 becomes low speed, stable rotation cannot be obtained, and speed fluctuation occurs. (2) When direct feedback is performed using a fine position detection scale, a detection signal becomes unstable due to disturbance (e.g., air flow, density change, and vibration) around the scale. (3) The frictional force and machining force of the linear motion are transmitted to the feed screw via the nut, and finally become the load torque of the servomotor, and the rigidity (hardness) from the point where the frictional force and machining force is generated to the servomotor ) And elastic deformation is generated which is inversely proportional to the above. (4) Regarding the frictional force, when the friction coefficient in the stationary state is larger than the friction coefficient during the movement, the energy storage due to the elastic deformation and the energy release due to the start of the movement occur alternately, and an intermittent movement called stick-slip occurs. .

The high-resolution positioning feeder according to the present invention which solves such a problem has a friction reduction gear having a large reduction ratio (1/100 level) and a zero backlash (substantially zero) and a servo motor and a feed screw. The above-mentioned problem is solved by inserting the coupling into the gap between them and having no backlash in the rotation direction, and has the following physical effects.

(1) Even at extremely low-speed feed, the rotation of the servomotor can be greatly increased, the rate of change with the feed speed is reduced, and stable continuous feed is possible (rotation at the reciprocal of the reduction ratio). Several speeds). (2) Continuous extremely low-speed feed is possible without direct feedback by the position detection scale, thereby realizing a control system positioning device that is resistant to disturbance. (3) Since the frictional force and the working force are controlled by the rigidity between the feed screw and the nut across the speed reducer having the large reduction ratio, the amount of elastic deformation is significantly reduced. (4) If the amount of elastic deformation is small, the amount of stick-slip is small, and it is possible to make the positioning resolution fine.

FIG. 5 shows the position error and the resolution when there is no stick-slip, and FIG. 6 shows the position error and the resolution when there is no stick-slip. 5 and 6
The vertical axis indicates the moving amount of the table, and the horizontal axis indicates the command value of the moving position by the computer or the controller. In FIG. 5, a thin line indicates an expected movement amount corresponding to the command value, and a thick line indicates an actual movement amount for the command value.

According to the known device, as shown in FIG. 5, the resolution is actually three to four times the expected resolution. On the other hand, according to the embodiment of the present invention, a resolution which is completely responsive to the command value and which is as expected is obtained.

[0028]

The high-resolution positioning feeder and machine tool according to the present invention can perform positioning without backlash even at a low speed, and can achieve the designed resolution. This is achieved by a very simple mechanism.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a high-resolution positioning / feeding device according to the present invention.

FIG. 2 is a front sectional view of a part of FIG. 1;

FIG. 3 is a side sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view of a part of the speed reducer of FIG. 2;

FIG. 5 is a graph showing resolution data of a known device.

FIG. 6 is a graph showing resolution data according to the present invention.

FIG. 7 is a front view showing a known device.

FIG. 8 is a circuit block diagram showing a control system of the known device.

FIG. 9 is an axial projection view showing another known device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 ... Control object 8 ... Motor 9 ... Reduction gear 12 ... Input shaft 14, 19 ... Transmission mechanism 14 ... Feed screw 16 ... Output shaft 19 ... Nut 27 ... 1st roller 29 ... Rotating body 32 ... Planetary roller 34 ... 2nd roller

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihito Fujita 130 Rokujizo, Ritsuto-cho, Kurita-gun, Shiga Prefecture Inside the Kyoto Seiki Seisakusho, Mitsubishi Heavy Industries, Ltd. Kyoto Seiki Manufacturing Co., Ltd.

Claims (8)

[Claims] A motor whose rotation angle position is numerically controlled; a control object driven by the motor; a transmission mechanism interposed between the control object and the motor; And a speed reducer interposed between the motors, wherein the speed reducer has substantially no backlash. 2. The high-resolution positioning feeder according to claim 1, wherein the speed reducer having substantially no backlash is a friction type power transmission mechanism. 3. The high-resolution positioning feeder according to claim 2, wherein the friction type power transmission mechanism is formed by a plurality of rollers that transmit friction. 4. The planetary roller according to claim 2, wherein the friction type power transmission mechanism includes an input shaft, an output shaft, and a planetary roller mechanism interposed between the input shaft and the output shaft. The mechanism has a first roller axially coupled to the input shaft, a rotating body axially coupled to the output shaft, a planetary roller frictionally coupled to the first roller, and an inner peripheral surface frictionally coupled to the planetary roller. A high-resolution positioning feeder including a second roller. 5. The high-resolution positioning / feeding device according to claim 4, wherein a control scale for detecting the position of the control object does not exist. 6. The high-resolution positioning / feeding device according to claim 5, wherein the speed reduction ratio of the speed reducer is 1: N, where N is greater than 100. 7. A machine tool into which the high-resolution positioning feeder according to claim 1, which is selected from claims 1, 2, 3, 4, 5, and 6, is incorporated. 8. The machine tool according to claim 7, wherein the brittle material is ground by a grindstone.