JPH01274943A - Driving device for movable table - Google Patents

Abstract

PURPOSE:To vary quantity of pre-load on bearing devices and nut member part so as to enable the pre-load on the both end parts to vary according to the moving condition of a movable table by varying the thickness of adjusting washers with current supply to piezoelectric elements. CONSTITUTION:When a movable table 1 is quickly traversed, pre-loads on bearing devices 6, 6 and nut member 9 are almost removed, by supplying current respectively to adjusting washers 17, 17 inserted in the bearing devices 6, 6 on the both ends of a ball screw 5 and an adjusting washer 19 inserted in the nut member 9, so as to make these washers thin. Hereby the movable table 1 can be moved with a light load. On the other hand, at completion of positioning of the movable table 1 and at movement for precise interpolation, respective washers 17, 17, 19 are made to be thick so as to be given pre-loads to the bearing devices 6, 6 and the nut member 9. Hereby backlash in the driving system is eliminated, its rigidity becomes high, precise locus and positioning can be obtained, and adjusting thickness of respective adjusting washers can be performed at will even during movement of the movable table.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a drive device for a moving table that can be moved at high speed and with high precision, and the moving table is used in precision processing machines and feeding devices of measuring instruments. used as.

[Conventional technology]

A conventional movable table driving device is shown in FIG. 5, in which a movable table 1 is movably mounted on a rail 4 on a base 3 via a block 2. A ball screw 5 is provided on the base 3 in parallel with the rail 4, and both ends of the ball screw 5 are supported by brackets 7 via bearing devices 6.6.
A nut member 9 attached via a fixing member 8 is screwed together, and as the ball screw 5 rotates, the movable table 1 reciprocates along the rail 4.

A motor 11 is connected to one end of the ball screw 5 via a coupling 1o, and by controlling the rotation of the motor 11, the movable table 1 is moved by the ball screw 5 and stopped at a predetermined position. ing.

In such a movable table drive device, when high precision is required to control the movement unit and stop position of the movable table,
A spacer 12a is interposed between the fixed member 8 side and the nut member 9, and a preload is applied to the nut member 9 with respect to the ball screw 5 by means of a device 7, and a shim 12b is also provided for the bearing device 6.6 that supports the ball screw 5. (2) to remove axial play by interposing and applying preload to this.

[Problem to be solved by the invention]

However, when preload is applied in the axial direction of the ball screw 5 by the above-mentioned means, the nut member 9 and the bearing devices 6, 6 are always under preload, so the nut member and the bearing 6,
The friction torque of No. 6 is large, which puts a heavy burden on the motor, especially during rapid traverse, etc., which requires large torque. This also caused increased wear and heat generation of the ball screw, which is important for positioning accuracy.

The present invention has been made in view of the above, and the thickness of the spacer can be arbitrarily changed even while the moving table is moving.
Driving a moving table in which the preload on the nut member or bearing can be changed, and the preload on the spacer can be changed depending on the operation status of the moving table, thereby reducing the friction torque on the bearing or nut member. The aim is to provide equipment.

[Means to solve the problem]

In order to solve the two-legged object, the movable table driving device according to the present invention includes a ball screw whose both ends are supported by bearing devices, and a movable table that is movable in the axial direction of the ball screw. In a movable table drive device in which a movable table is moved by screwing together a nut member and driving a ball screw with a motor, between a bearing device that supports the ball screw and a housing that fits the bearing device, Adjustment spacers each made of a piezoelectric element are interposed between the nut part (1) and the nut part (2) which is screwed into the ball screw and the member supporting it.

[For production]

By changing the thickness of the piezoelectric element by energizing it, the amount of preload on the bearing device and the nut member changes, and the preload on both ends can be changed arbitrarily depending on the operating status of the movable table.

〔Example〕

Embodiments of the present invention will be described based on FIGS. 1 to 4. In this embodiment, the same members as those in the conventional example shown in FIG. 5 are designated by the same reference numerals, and the explanation thereof will be omitted.

The bearing devices 6 6 that support both ends of the ball screw 5 have the same configuration as shown in FIG. Ball bearings (angular contact type) 13.13 are arranged back to back with washers 14 in between, their inner rings 13a, 13a are fixed to the ball screw 5, and their outer rings 13b, 13b are fitted into the bearing housing 15. It is a combination. The outer rings 13b, 13b have a support member 16 screwed onto the bearing housing 15 on the - end side.
The other end side is in contact with a fixed plate 18 via an adjustment spacer 17.

Further, an adjustment spacer 19 is interposed between the nut member 9 screwed onto the ball screw 5.

The readjustment spacers 17 and 19 are cylindrical piezoelectric elements 20a and 2.
0b and electrodes 21a and 21a' located on both sides of this
, 21b, 21b' and an insulator 22a covering them,
The piezoelectric element 20a is formed by applying a DC voltage to the wirings 23a and 23b connected to the electrodes.

20b expands and contracts, so that the thickness of the adjustment spacer 1-7.19 changes.

In the above configuration, when the movable table 1 is moved rapidly, the adjustment spacers 17.17 inserted into the bearing devices 6.6 at both ends of the ball screw 5 and the adjustment spacers 19 inserted into the nut member 9, respectively. The spacers 17, 17, 19 are electrically energized in the direction in which they become thinner to reduce their thickness, and the bearing device 6.6 and the nut member 90 are brought into a state where there is almost no preload.

As a result, the moving table 1 is moved with a light load.

- When the positioning of the blade moving table 1 is completed (when stopped) and during precision interpolation movement, the thickness of each adjusting spacer 17, 17° 19 is increased to apply preload to the bearing device 6.6 and the nut member 9.

This eliminates play in the drive system, making it highly rigid and allowing precise locus and positioning. The thickness adjustment of each adjustment spacer 17, 17, 19 can be performed arbitrarily even while the moving table is moving.

Fig. 4 shows another embodiment, in which the single-axis type movable table device shown in Fig. 1 is stacked one on top of the other with the XY force directions shifted, and the lower movable table The upper moving table base 2 of device B is attached to the moving body of device A.
3 is fixed, and by driving the motor 11 to the lower movable table device, the upper movable table device B moves in the X direction via the ball screw 5, and the motor 11' of the upper movable table B moves. By driving , the movable table 1' of the upper movable table device B is moved in the Y direction via the ball screw 5', and eventually the movable table 1' of the upper movable table device B is moved in the XY force directions.

〔Effect of the invention〕

According to the present invention, the thickness of each adjustment spacer 17, 17.19 can be changed arbitrarily even during movement of the moving table, so that the operating conditions of the moving table 1.1', that is, the moving table 1. Adjustable spacer 17 according to 1' rapid movement or precise movement and positioning movement.
The preload due to ゜17.19 can be changed, and during rapid traverse operations that do not require much preload, the preload is reduced to reduce the friction torque of the bearings 6, 6 and nut member 9, thereby reducing the burden on the motor 11 during rapid traverse operations. In addition to improving the durability of the drive system and reducing changes over time, the load on the ball screw 5 is also reduced and the elongation of the ball screw 5 due to heat generation is reduced, improving positioning accuracy. You can improve your performance.

[Brief explanation of the drawing]

Figures 1 to 4 show embodiments of the present invention.
The figure is a sectional view, FIGS. 2 and 3 are sectional views showing the configuration of essential parts, FIG. 4 is a perspective view showing a different configuration example, and FIG. 5 is a sectional view showing a conventional example. Applicant Komatsu Manufacturing Co., Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Claims] A ball screw 5 whose both ends are supported by bearing devices 6, 6,
A nut member 9 provided on a movable table 1 that is movable in the axial direction of the ball screw 5 is screwed together, and the movable table 1 is moved by driving the ball screw 5 with a motor 11. In the drive device, between the bearing devices 6, 6 that support the ball screw 5 and the housing that fits this, and between the nut member 9 that screws into the ball screw 5 and the member that supports it, A driving device for a movable table, characterized in that adjustment spacers 17 and 19 made of piezoelectric elements 20a and 20b are interposed.