JPH0876847A - Mechanism and method for backlash correction in drive device - Google Patents

Abstract

PURPOSE: To effectively and precisely correct the backlash that is caused when a drive device is started. CONSTITUTION: The feeding directions of ball screws 1A-1C and the moved amount of these screws equivalent at least to the backlash width which are set when a drive device is started,y are previously stored in memories 9A-9C and 10A-10C respectively. When the drive device is started, the screws 1A-1C are moved by servo controllers 8A-8C by initial moved amount M1 in the feeding directions stored in the memories 9A-9C and 10A-10C and then moved in the opposite direction also by M1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlash compensating mechanism and a compensating method for compensating a backlash when a device such as a machine tool is started up when the power is turned on or the emergency stop is released. .

[0002]

2. Description of the Related Art As a technique of this kind, Japanese Patent Laid-Open No. 62-92 is known.
A backlash correction method as disclosed in Japanese Patent Publication No. 002 has been proposed. In this conventional method, as shown in FIG. 4A, for example, in a table drive device of an NC machine tool, a ball screw 21 moved by a drive source and a table 22 fed and moved by the ball screw 21 are provided. ing. In this device, the value of the backlash width B1 between the table 22 and the ball screw 21 is set and stored in advance, and the reference movement direction D of the table 22 is set.
2 has been decided.

Further, the ball screw 21 moves in the reference movement direction D2, the ball screw 21 and the table 22 contact each other, and the relative positional relationship between them is determined as the reference position P3. In this state, ball screw 2
1 or a detection position from an absolute position detector (not shown) provided in the drive source and an actual position of the table 22 are set to coincide with each other.

When the apparatus is activated, the feed direction of the ball screw 21 based on the feed command is compared with the preset reference movement direction D2. As a result, FIG. 4 (b)
As shown in, when the actual movement direction is the same as the reference movement direction D2, the ball screw 21 moves the movement amount M2 based on the command.
Only moved. On the other hand, as shown in FIG. 4 (c), when the movement direction is opposite to the reference movement direction D2, the ball screw 21 is moved more than the movement amount M2 based on the command by the backlash width B1. It This makes it possible to match the actual position of the table 22 after movement with the detection position from the absolute position detector.

[0005]

However, in this conventional backlash correction method, the method shown in FIGS.
As shown in (b), the table 22 may move from the reference position P3 due to external force or the like when the power is off or in an emergency stop state. When the table 22 moves in this way, a positional deviation occurs between the actual position of the table 22 and the detection position from the absolute position detector. Then, in this state, when the device is started up with the power being turned on or the emergency stop being released, the feeding operation is performed with the positional deviation error generated, and the table 22 accompanying the subsequent movement command is issued.
Position control continues. Therefore, there is a problem in that accurate position control cannot be performed and accurate processing cannot be performed.

As another backlash correction method, a method of temporarily moving a moving part such as a table to the origin position at the time of starting the apparatus is implemented. When the home-return operation is performed in this way, backlash is absorbed, the relative positional relationship between the transmission mechanism and the moving unit is inevitably determined, and backlash correction is performed at the time of starting the apparatus. On the other hand, this method has a drawback in that work efficiency is reduced because time is wasted that the moving unit returns to the origin and moves from the origin to a required position for machining.

The present invention has been made by paying attention to such problems existing in the prior art. It is an object of the present invention to provide a backlash correction mechanism and a correction method that can surely perform backlash correction at the time of starting the apparatus and can eliminate the need for the home-return operation.

[0008]

In order to achieve the above object, in the invention of the backlash correction mechanism in the drive device according to claim 1, the drive side in the transmission mechanism is at least the drive side and the driven side. The first setting means for setting the movement amount data for moving in the feed direction by the backlash width between the first and second sides, the second setting means for setting the movement direction data on the driving side, and First,
Based on the data set in the second setting means, the drive source in the transmission mechanism is moved in the predetermined feed direction by at least the backlash width, and is also moved in the opposite direction by the same amount so as to be returned and moved. And a control means for controlling the operation of.

According to a second aspect of the invention, in the first aspect of the invention, the movement amount data set in the first setting means is less than twice the backlash width. According to a third aspect of the present invention, in the first or second aspect of the present invention, there is provided a changing unit for changing the movement amount data set in the first setting unit.

According to the invention described in claim 4,
In any one of the above aspects, a plurality of sets of drive sources, transmission mechanisms and moving parts are provided, and the first and second setting means are provided corresponding to at least one of them.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the drive source includes an absolute position detector for detecting the amount of movement thereof, and the control means detects from the absolute position detector. The position of the moving unit is determined based on the data.

According to the invention of the backlash correction method in the drive device described in claim 6, in the drive device in which the moving part reciprocates through the transmission mechanism by the drive source, the drive in the transmission mechanism is started at the time of starting the device. After the side is moved in the predetermined feeding direction by at least the backlash width between the driving side and the driven side, the driving side is moved in the reverse direction by the same amount.

According to the invention of claim 7, in the invention of claim 6, the amount of movement on the drive side is not more than twice the backlash width.

[0014]

According to the inventions of claims 1 and 6, when the drive device is started, the drive side in the feed mechanism is moved by a predetermined movement amount in one of the feed directions and then returned by the same amount in the opposite direction. Be moved. As a result, even if the moving unit is moving due to an external force or the like when the device is stopped, the driving side and the driven side in the transmission mechanism are determined to have a predetermined positional relationship.

In the inventions of claims 2 and 7, in the inventions of claims 1 and 6, the movement on the drive side in the backlash correction is less than twice the backlash width. The amount of movement on the drive side for backlash correction is extremely small, and backlash correction can be performed in a short time.

According to a third aspect of the present invention, in the first or second aspect of the invention, when the backlash width changes, the movement data can be corrected by the changing means so as to correspond thereto. .

According to the invention described in claim 4, in any one of the inventions of claims 1 to 3, the backlash correction is performed only for a necessary portion. According to a fifth aspect of the invention, in any one of the first to fourth aspects of the invention, the position of the moving portion can be accurately determined at the same time as the device is activated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drive device embodying the present invention will be described in detail below with reference to FIGS.

As shown in FIG. 1, this driving apparatus is provided with three moving bodies 2A, 2B, 2C as moving parts, the moving bodies 2A, 2B being on a table not shown, and the moving body 2C being a saddle not shown. It is fixed to. A work is supported on the table, and a tool is attached to the saddle. The three ball screws 1A, 1B, 1C are arranged so as to thread through the screw holes 2a, 2b, 2c of the respective moving bodies 2A, 2B, 2C. 2A and 2B are moved in the X-axis and Y-axis directions to move the table in the same direction, and the moving body 2C is moved in the Z-axis direction to move the saddle in the same direction. The ball screw 1A, 1B, 1C and the screw holes 2a, 2b, 2c constitute a transmission mechanism.

Ball screw 1 on the drive side in the transmission mechanism
A, 1B, 1C and screw holes 2a, 2b on the driven side,
The backlash width between 2c and 2c is represented by B1 in FIGS. In addition, in FIG. 2 and FIG.
In order to facilitate understanding, each mobile unit 2A, 2B, 2C,
Screw holes 2a, 2b, 2c and ball screws 1A, 1B, 1
C is simplified and schematically drawn. 2 and 3, 1a, 1b, 1c are the screw holes 2a, 2b, 2c.
The thread of ball screw 1A, 1B, 1C screwed with is shown.

Three servo motors 3A as drive sources,
3B and 3C are connected to the respective ball screws 1A, 1B and 1C via couplings 4A, 4B and 4C, and the motors 3A, 3B and 3C allow the ball screws 1A, 1B and 1C to be connected.
Is rotated in both forward and reverse directions. Therefore, in this embodiment, the drive source, the transmission mechanism, and the moving part are three in number.
It is provided in pairs. The three absolute position detectors 5A, 5B and 5C, each of which is an encoder, are connected to each servo motor 3
A detection signal indicating an absolute position corresponding to the operation amount of the servo motors 3A, 3B, 3C is output by being connected to the rotary shafts (not shown) of the A, 3B, 3C.

The controller 6 includes an NC controller 7 and servo controllers 8A, 8B and 8C for controlling the servo motors 3A, 3B and 3C, respectively. Each servo controller 8A, 8B, 8C constitutes a control means, and inside thereof, initial movement amount memories 9A, 9B, 9C as first setting means, and initial movement direction memories 10A, 10B as second setting means, 10C, backlash amount memory 11A, 11B, 11C.

The initial movement amount memories 9A, 9B and 9C are
The data of the initial movement amount of each ball screw 1A, 1B, 1C at the time of starting the device upon turning on the power, releasing the emergency stop, etc. is stored and set. In this example,
As shown in FIGS. 2 and 3, the initial movement amount M1 is set to a value obtained by adding a predetermined additional distance α to the backlash width B1. The additional distance α is smaller than the backlash width B1.
Therefore, the initial movement amount M1 is less than twice the backlash width.

The ball screws 1A, 1B and 1C only perform rotational movement and do not actually move in the feed direction, but their threads 1a, 1b and 1c apparently move in the feed direction and feed. Since it operates, it is used for ball screw 1A,
The feed movement is 1B and 1C. Initial movement direction memory 10
Data of the initial moving direction D1 which is the feed moving direction of the ball screws 1A, 1B and 1C at the time of starting the apparatus is stored and set in A, 10B and 10C. Data of the backlash width B1 is stored and set in the backlash amount memories 11A, 11B and 11C. In addition,
The initial movement direction D1 and the backlash width B1 are values set for each axis and are not the same numerical value.

Further, each of the servo controllers 8A, 8
Absolute position detectors 5A, 5B and 5C are connected to B and 8C, respectively. Each servo motor 3A, 3B, 3C is connected to the servo controller 8A, 8B, 8C via a servo amplifier 14A, 14B, 14C. When operating the device, NC controller 7 is servo controller 8
A command signal is output to A, 8B, and 8C, and the servo controllers 3A, 3B, and 3 are output from the servo controllers 8A, 8B, and 8C.
A drive signal based on the command is output to C.

A keyboard 15 as a changing means is connected to the control device 6, and data of the initial movement amount, the initial movement direction and the backlash width are keyed in by the keyboard 15, and the initial movement amount memories 9A, 9B, 9
The data in C, the initial movement direction memories 10A, 10B and 10C and the backlash amount memories 11A, 11B and 11C are rewritten.

The backup power source 16 is connected to each servo controller 8A, 8B, 8C. Then, when the power of the device is turned off, each of the memories 9
A, 9B, 9C, 10A, 10B, 10C and 11A,
The required power of 11B and 11C is secured by this backup power supply 16.

Next, the operation of the backlash correcting mechanism constructed as described above will be described. Now, in this drive device, each of the memories 9A, 9B, 9C, 1
Data of initial movement amount M1, initial movement direction D1, and backlash width B1 are set in 0A, 10B, 10C, 11A, 11B, and 11C, respectively.

Then, when the drive unit is started up when the power is turned on or the emergency stop is released, the memories 9A, 9B,
The data of each initial movement amount M1 and initial movement direction D1 stored in 9C, 10A, 10B and 10C are read out, and as shown in FIG. 2B, the ball screws 1A, 1B and 1C are respectively rotated by the rotation. In the initial movement direction D1, the initial movement amount M1 is passed over the backlash width B1. Thereby, the backlash located on the feed direction side between the ball screws 1A, 1B, 1C and the moving bodies 2A, 2B, 2C is absorbed, and at the same time, the ball screws 1A, 1C.
B, 1C and the moving bodies 2A, 2B, 2C are arranged in the positional relationship P2.

Thereafter, as shown in FIG. 2 (c), the ball screws 1A, 1B, 1C reversely rotate, and the ball screws 1A, 1B, 1C move in the direction opposite to the initial moving direction D1 and the initial moving amount M1. The same amount is moved back. As a result, the moving bodies 2A, 2B, 2C are returned from the position of the positional relationship P2 of FIG. 2 (b) to the direction opposite to the moving direction D1 and moved to the position of the predetermined positional relationship P1 shown in FIG. 2 (a). Will be placed. In this state, the backlash on the side opposite to the feeding direction is absorbed.

On the other hand, the moving bodies 2A, 2B, 2C are movable with respect to the ball screws 1A, 1B, 1C within the range of the backlash width B1. For this reason, the moving bodies 2A, 2B, 2C are moved by an external force or the like in the apparatus stopped state, and when the power is turned on or the emergency stop is released, as shown in FIGS. , 2
B and 2C may deviate from the position of the positional relationship P1 where B and 2C contact the ball screws 1A, 1B and 1C.

However, when the moving bodies 2A, 2B, 2C are moved to any position in the feed direction, the ball screws 1A, 1B, 1C are moved in the initial movement direction D1.
By moving by the initial movement amount M1 over the backlash width B1, the moving bodies 2A, 2B, 2C are moved to the position of the positional relationship P2. Then, the ball screws 1A, 1B, 1C are moved in the direction opposite to the initial movement direction D1 by the same amount as the initial movement amount M1, so that the moving bodies 2A, 2B, 2C are moved from the position of the positional relation P2 to the positional relation P1. Moved to the position of.

Then, as shown in FIG. 2C, the absolute position detectors 5A, 5A, 2A, 2B, 2C are initially set to the positional relationship P1 in which the moving bodies 2A, 2B, 2C are in contact with the ball screws 1A, 1B, 1C. The position data of the moving bodies 2A, 2B, 2C are fetched from 5B, 5C, and the actual positions of the table and saddle are detected. Therefore, even if the table and the ball screws 1A, 1B, 1C are misaligned when the apparatus is stopped, the misalignment can be surely corrected by the backlash correction operation at the start, and the moving body 2A, Two
B, 2C, that is, the actual positions of the table and saddle and the detection positions from the absolute position detectors 5A, 5B, 5C can be accurately matched. Therefore, the subsequent work processing can be performed accurately.

That is, after the backlash correction is completed, the NC controller 7 to the servo controller 8
The servomotors 3A, 3B, 3C are rotationally controlled based on the movement command sent to the A, 8B, 8C, and the moving body 2 is moved.
A, 2B and 2C are moved to required positions. When the moving directions of the moving bodies 2A, 2B, 2C are changed, the ball screws 1A, 1B, 1B, 1B, A normal backlash correction operation of adding a feed movement amount of 1C is performed.

As described above, in this embodiment, the backlash correction is performed at the time of starting the device when the power is turned on, the emergency stop is released, etc., and the ball screws 1A, 1B and 1C whose absolute positions have been detected are detected. On the other hand, moving bodies 2A, 2
B, 2C, i.e. the table and saddle, are correctly positioned. Therefore, the subsequent work processing can be performed accurately. Further, in this embodiment, since the origin returning operation is not necessary, the origin returning operation or the operation of moving the origin to a desired machining position is not necessary, so that waste of time is prevented and efficient machining is achieved. Can contribute.
Moreover, the ball screw 1A for backlash correction,
Since the amount of movement of 1B and 1C in the feed direction is less than twice the backlash width, the actual amount of rotation of the ball screws 1A, 1B and 1C is very small. Therefore, the operation itself for backlash correction can be performed in an extremely short time.

Further, when the backlash width B1 changes due to wear of the ball screws 1A, 1B, 1C, etc. during the operation of this apparatus, the backlash width B1 is measured. And this measured backlash width B1
The data in the backlash amount memories 11A, 11B and 11C is rewritten by the keyboard 15 based on the above. Therefore, accurate backlash correction is always possible.

The present invention is not limited to the configuration of the above embodiment, but can be embodied in the following modes. (1) Set the initial movement amount M1 to be the same as the backlash width B1. (2) In the above embodiment, the drive source, the transmission mechanism, and the driven portion are embodied in a device having three sets, and the backlash correction is performed for each of the three sets. Omit backlash compensation. For example, in FIG. 1, since the ball screw 1C corresponding to the Z axis actually extends in the vertical direction, a downward load is always applied to the moving body 2C. Therefore, when the device is stopped, the backlash between the driving side and the driven side is always located on the one direction side, and the moving body 2C is less likely to move when the device is stopped. Therefore, in such a case, backlash correction is not always necessary. (3) Embodying the present invention in a drive device having another configuration, for example, a drive device using a rack and a pinion. (4) Applying the backlash correction mechanism and correction method of the present invention to an apparatus involving rotation. That is, FIG.
As shown in (a) and (b), the drive-side gear 25 is rotated by a motor 26 as a drive source. The rotary table 27 as a moving part has a tooth portion that meshes with a tooth portion of the gear 25 on the outer peripheral edge thereof, and is rotated in a predetermined direction by the rotation of the gear 25. The transmission mechanism is composed of the teeth of the gear 25 and the teeth of the rotary table 27. Instead of the rotary table 27, a rotary head or another rotating object may be used.

By the way, technical ideas other than the claims understood from the above embodiment will be described below together with their effects. (A) The backlash correction method according to claim 6, wherein a plurality of sets of drive sources, transmission mechanisms, and moving parts are provided, and at least one set among them is reciprocated. With this configuration, only the desired driving side can be driven, and power can be saved. (B) In claim 6, the drive source is provided with an absolute position detector for detecting the amount of movement, and after the drive side is returned and moved in the opposite direction, the absolute position detector detects the absolute position of the moving portion. Backlash Compensation Method in a Driving Device for Driving.
With this configuration, the position of the moving unit can be accurately detected.

[0039]

Since the present invention is constructed as described above, it has the following effects.

According to the first and sixth aspects of the present invention, the backlash at the time of starting the apparatus can be surely corrected, and the origin returning operation can be eliminated, and the backlash can be corrected quickly.

According to the second and seventh aspects of the present invention, it is possible to minimize the feed movement amount on the drive side for the backlash correction and to perform the correction operation in an extremely short time. According to the third aspect of the invention, even if the backlash width changes, the correction amount can be corrected according to the backlash width, and accurate backlash correction can always be performed.

According to the fourth aspect of the present invention, the backlash correction configuration of the portion that does not require backlash compensation can be omitted, and the configuration is simplified. In the invention according to claim 5, the position of the moving part is accurately detected, and the work can be accurately processed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a backlash correction mechanism embodying the present invention.

FIG. 2 is a schematic diagram sequentially showing a backlash correction operation at startup in the backlash correction mechanism.

FIG. 3 is a schematic diagram showing a backlash correction operation at the time of startup when the position of a moving body as a moving unit changes during a stop.

FIG. 4 is a schematic diagram showing a backlash correction operation at startup in a conventional backlash correction device.

FIG. 5 is a schematic diagram showing a state in which the position of a moving body changes during stoppage in the conventional backlash correction device.

6A is a front view of a backlash correction mechanism showing another example of the present invention, and FIG. 6B is a plan view thereof.

[Explanation of symbols]

1A, 1B, 1C ... Ball screw as transmission mechanism, 2
A, 2B, 2C ... Moving body as moving section, 3A, 3B,
3C: Servo motor as drive source, 5A, 5B, 5C
... Absolute position detector, 6 ... Control device, 8A, 8B, 8C ...
Servo controller as control means, 9A, 9B, 9
C ... Initial movement amount memory as first setting means, 10A,
10B, 10C ... Initial movement direction memory as second setting means, 15 ... Keyboard as changing means, M1 ... Initial movement amount, B1 ... Backlash width, D1 ... Initial movement direction.

Claims (7)

[Claims] 1. A drive device in which a moving part is moved by a drive source via a transmission mechanism, wherein a drive side in the transmission mechanism is at least a backlash width between the drive side and the driven side. First setting means for setting movement amount data for moving only in the feed direction, second setting means for setting the movement direction data on the driving side, and setting for the first and second setting means at the time of starting the apparatus. A control for controlling the operation of the drive source so that the drive side in the transmission mechanism is moved in the predetermined feed direction by at least the backlash width and is returned and moved in the opposite direction by the same amount based on the obtained data. And a backlash correction mechanism in a drive device including a means. 2. The backlash correction mechanism according to claim 1, wherein the movement amount data set in the first setting means is equal to or less than twice the backlash width. 3. The backlash correction mechanism in a drive device according to claim 1, further comprising a changing unit for changing the movement amount data set in the first setting unit. 4. The drive source, the transmission mechanism, and the moving part are provided in plural sets according to claim 1, and
The backlash correction mechanism in the drive device, wherein the setting means is provided corresponding to at least one of them. 5. The drive source according to any one of claims 1 to 4, wherein the drive source includes an absolute position detector for detecting an operation amount of the drive source, and the control means controls the moving unit based on detection data from the absolute position detector. Backlash correction mechanism in the drive device that determines the position. 6. A drive device in which a moving part is moved by a drive source via a transmission mechanism, wherein the drive side of the transmission mechanism is backlashed at least between the drive side and the driven side when the device is started. A backlash correction method in a drive device in which a drive side is moved in the predetermined feed direction by the width and then the drive side is returned and moved in the opposite direction by the same amount. 7. The moving amount on the driving side according to claim 6,
A backlash correction method for a drive device having a backlash width of twice or less.