JPH01171739A - Driving device for table - Google Patents

Abstract

PURPOSE:To get rid of backlash and obtain high rigidity in the axial direction by providing a plurality of driving devices consisting of servo motors and ball screws and a driver for controlling the driving devices in the same axial direction as a linear guide table. CONSTITUTION:Two sets of table driving devices consisting of servo motors 4a, 4b and ball screws 3a, 3b are provided while providing a control portion having a position signal input for moving them in the same direction and a pre-load signal input for moving them in the mutually opposite directions in the captioned device. Thereby, at the time of moving a table 2, a pre-load signal in a degree of offsetting backlash is given to effect stable feeding, while giving a pre-load signal several times the quantity of backlash at the time of stopping. Thereupon, stress is applied to the ball screw 3a, 3b portions, coupling 7a, 7b portions, and bearing 8a, 8b portions preventing lopsided contact while improving the rigidity of table including a table driving system.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a table drive device used in machine tools such as grinding machines, automatic machines such as robots, and the like.

BACKGROUND OF THE INVENTION In recent years, table drive devices are required to have high positioning accuracy as the mechanical equipment they are mounted on has become more accurate.

An example of a conventional table driving device will be described below with reference to the drawings.

FIG. 3 shows the configuration of a conventional table driving device. In FIG. 3, 21 is a table bed, and 22 is a table, which slides on the table bed in the direction of arrow X. A ball screw shaft 23 is rotationally driven by a servo motor 24, and drives the table 22 at a ball screw nut portion 26. 26 is the motor bracket,
Fix the servo motor 24. 27 is a coupling,
The servo motor 24 and ball screw shaft 23 are connected. 28 is an angular bearing that regulates the ball screw shaft 23.

Problems to be Solved by the Invention However, in the above configuration, even if the servo motors are interlocked, backlash exists in drive parts such as the angular bearing and the ball screw nut, so the backlash of the table as a whole is reduced. There was a problem in that a rush occurred.

The present invention addresses the above problems and provides a table drive device that is completely free of backlash and has high rigidity in the axial direction.

Means for Solving the Problems In order to solve the above problems, the table drive mounting of the present invention includes two or more sets of ball screws and servo motors, which are attached to the table part in pairs. Furthermore, the servo motor is operated by a signal from a motor driver, and the motor driver also has the function of slightly moving the servo motor.

Effect The present invention has the above-described configuration, so that when the table is moved, -
One set of ball screws has a planu offset equivalent to the backlash, and the other set of ball screws has a minus offset equivalent to the backlash. By performing such processing, backlash can be eliminated. When the table is stopped, it is offset in the same way as when moving, but by making the displacement larger than the backlash,
This has the effect of applying preload in the axial direction of the table, and as a result, it is possible to increase the table rigidity.

Embodiments Hereinafter, table driving devices according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a table driving device in an embodiment of the present invention. In FIG. 1, 1 is a table bed, and 2 is a table, which slides on the table bed in the direction of arrow X. 32L.

3b is a ball screw shaft and a servo motor 42L.

4b, and the ball screw nut part sa
, sb to drive table 2 06a.

6b is a motor bracket that fixes the servo motor. Couplings 7a and 7b connect the servo motor and ball screw. sa and ab are angular bearings that regulate the shaft of the ball screw.

FIG. 2 shows a servo motor control system diagram.

9 is the input of the position signal to the servo system, and the information on the table position .

112L is an adder that performs the calculation of X+ΔX. 11b is a subtracter that performs the calculation of X-ΔX. 12ab is a counter that measures the output pulses of the encoder attached to the servo motor to measure the actual position.013a, 13b
is a comparator that compares the output signal of the counter and the output of the adder/subtractor, and uses the difference as an error signal to drive the servo motor 41.
In addition to L and 4b, drive the motor so that the difference is reduced,
Apply servo lock.

Regarding the table driving device configured as described above, the first
A control method for moving the table position shown in the figure from 0 to P will be explained. First, the preload signal 10 in FIG. 2 is set to O or equivalent to PACKRASONY so as to be suitable for movement, and then the position signal 9 is changed from 0 to P. Then, the comparators 132L and 1 pass through the adders and subtracters 112L and 11b.
This causes a difference between the signal input to counter 3b and the signal input from counters 122L and 12b. Next, comparator 13a
, 13b outputs an error signal to drive the servo motors 4a, 4b. Then ball screw 32L
.

3b rotates and moves the table 2 from 0 to P position. After this movement step is completed, the preload signal 1oΔX is increased to an amount suitable for when the table is stationary, and the table is fixed at the P position.

As described above, according to the present embodiment, two sets of table drive devices each consisting of a servo motor and a ball screw are provided, and a position signal input for moving each device in the same direction and a preload signal input for moving each device in the opposite direction are provided. By providing a control unit, a preload signal sufficient to offset backlash is applied when the table moves, achieving stable feeding, and a preload signal several times the pack la sonille amount is applied when the table is stopped. Then,
Stress is applied to the ball screws, couplings, and bearings, which prevents uneven contact and increases the rigidity of the table including the table drive system.

In this embodiment, two sets of drive systems each using a ball screw and a servo motor are provided, but a plurality of sets such as three or four sets may be provided.

Effects of the Invention As described above, the present invention provides a mechanism for separately controlling multiple stages of drive devices using servo motors and ball screws, moving each stage slightly in opposite directions, and providing a mechanism for applying preload. It is possible to realize a table drive device with high rigidity.

[Brief explanation of the drawing]

FIG. 1 is a main mechanism diagram of a table driving device according to an embodiment of the present invention, FIG. 2 is a control system diagram thereof, and FIG. 3 is a configuration diagram of a conventional table driving device. 1...Table bed, 2...Table, 3a. 3b...Ball screw, 4&, 4b...
Servo motor 0 Name of agent Patent attorney Toshi Nakao Male and 1 other person? −
Table 7a, b-11 Cutting ring 8a, b--Ichikasu Figure 1

Claims (1)

[Claims] A table driving device that has a driving device consisting of a plurality of servo motors and a ball screw in the same axial direction as a linear guide table, and a driver that controls the driving device.