JPH0976139A - Machine tool feeder - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To reduce twisting of a ball screw to cope with high speed and high accuracy, and also to avoid a large motor to reduce an installation space and improve servo performance. To provide a feeder. A feed device for a machine tool in which a ball screw 6 is screwed into a nut 5 of a movable table 3 arranged on a fixed table 2 and the ball screw 6 is rotationally driven to reciprocate the movable table 3. 1, the left and right end portions 6a and 6b of the ball screw 6 have drive motors 9 and 1 respectively.
0 is connected to detect the rotation angle of the left and right end portions 6a and 6b of the ball screw 6, and the above-mentioned driving in accordance with the detection values from the rotation angle detection means 11 and 12. Driving force control means 1 for controlling the driving force of the motors 9 and 10
And 3 are provided. In this case, the rotation angles or angular velocities of the drive motors 9 and 10 are matched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed device for a machine tool in which a ball screw is rotationally driven by a drive motor to reciprocate a moving table, for example.

[0002]

2. Description of the Related Art For example, in an NC machine tool, a rod-shaped ball screw is screwed into a nut portion of a moving table on which a work is placed, and one end of the ball screw is rotationally driven by a drive motor to reciprocate the moving table. A moving feeder is adopted.

On the other hand, in this type of machine tool, it is required to increase the feed rate of the moving table and increase the accuracy of positioning. To increase the speed, the rotation speed of the drive motor must be increased, but there are problems such as a limit on DmN, an increase in vibration and noise, a limit on a critical speed, and an increase in temperature and thermal expansion. However, there is a limit to the high rotation speed.

Therefore, since the feed rate of the ball screw is determined by the product of the lead (screw pitch) and the number of revolutions, a method of increasing the feed rate without increasing the number of revolutions by increasing the lead is adopted. There is. However, if the lead is made large, the torsional load on the ball screw increases, and as a result, problems such as torsional vibration and positioning error occur.

In order to solve the problems of the torsional vibration and the positioning error, it is necessary to increase the torsional rigidity of the ball screw. This torsional rigidity (Kt) is, as shown in the following equation,
Since it increases in proportion to the fourth power of the root diameter d of the screw shaft,
By increasing the root diameter, the positioning error can be reduced to a negligible level. Kt = πGd ⁴ / 32L L: distance between points of action, d: root diameter of screw shaft, G: lateral elastic modulus

However, in the method of increasing the valley diameter of the screw shaft to increase the torsional rigidity, the inertia of the ball screw increases as the valley diameter increases, so that a drive motor with a large output is required, which is not preferable in terms of servo performance. .

Further, since the load (Tf) of the drive motor increases in proportion to the lead L of the screw as shown in the following formula, the output torque of the motor must be increased to obtain the same thrust. Moreover, a motor with a large output not only requires a large mounting space, but also has a large rotor inertia, which is not preferable in terms of servo performance. Tf = FL / 2πη F: driven load, L: ball screw lead, η: ball screw efficiency

By the way, as a means for correcting the error due to the twist of the ball screw described above, conventionally, one end of the ball screw is driven by a servomotor and the rotation angles of both ends of the ball screw are detected, and both detected values are detected. Has been proposed in which the drive force of the drive motor is controlled with the average value of (1) as the target (see Japanese Patent Laid-Open No. 62-39161). That is, in this conventional apparatus, for example, when the rotation angle on the motor side is θ and the rotation angle on the tip side is θ−ε, the driving force is controlled so that the rotation angle on the motor side is θ + ε / 2.

[0009]

However, in the method of controlling the driving force of the motor by the average value of the rotation angles at both ends of the ball screw as in the above-mentioned prior art publication, although the positioning error can be reduced, the twist itself can be reduced. Therefore, the problem of torsional vibration cannot be solved.

Further, since one end of the ball screw is driven, a drive motor having a large output is required to achieve the above-mentioned high speed operation, which causes a problem that the rotor inertia becomes large and the mounting space becomes large. Not resolved.

The present invention has been made in view of the above-mentioned conventional circumstances, and particularly when the lead is made large, it is possible to eliminate the positioning error and the torsional vibration due to the twisting of the ball screw, and to cope with the high speed and the high accuracy. Furthermore, it is an object of the present invention to provide a machine tool feed device capable of solving problems in arrangement space and servo performance.

[0012]

According to a first aspect of the invention, a ball screw is screwed into a nut portion of a moving member movably arranged on a fixed portion, and the ball screw is rotationally driven to move the ball screw. In a machine tool feeding device configured to reciprocally move a member, a drive motor is connected to both ends of the ball screw, and a rotation angle detecting means for detecting a rotation angle of each end of the ball screw, and the rotation angle. And a driving force control means for controlling the driving force of each of the drive motors according to the detection value from the detection means.

According to a second aspect of the present invention, the driving force control means is configured to control the driving force so that the rotation angles or angular velocities of the respective drive motors match.

Here, movably disposing the movable member on the fixed portion in the present invention means, for example, disposing the movable table on the fixed table, disposing the headstock on the bed,
Various modes such as disposing the spindle head on the column are included. The present invention includes not only the case of directly detecting the rotation angle of each end of the ball screw but also the case of detecting the rotation angle of the output shaft of the drive motor or the intermediate shaft from the output shaft to the ball screw.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram for explaining a machine tool feeding apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a machine tool feed device of the present embodiment. In the machine feed device 1, a movable table 3 is mounted on the upper surface of a fixed table 2 so as to be reciprocally movable in the direction of the arrow shown in the figure. A long rod-shaped ball screw 6 is screwed into a nut 5 fixed to an arm 3 via an arm member 4. The ball screw 6 is arranged parallel to the moving direction of the moving table 3 and is pivotally supported by the fixed table 2 via a bearing (not shown).

The left and right end portions 6 of the ball screw 6 are
Independent drive motors 9 and 10 are connected to a and 6b via couplings 7 and 8, respectively, and the drive motors 9 and 10 serve as rotation angle detection means for detecting the rotation angle. The pulse coders 11 and 12 are connected. Detected values from the palcoders 11 and 12 are input to a controller 13 as a driving force control unit that controls the driving force of the drive motors 9 and 10.

The controller 13 reads the rotation angles of the drive motors 9 and 10 output from the pulse coders 11 and 12, and the driving forces of the drive motors 9 and 10 so that the rotation angles match (synchronize). Is configured to control.

According to the feeding device 1 of this embodiment, the drive motors 9 and 10 are connected to the left and right ends 6a and 6b of the ball screw 6, respectively, so that the rotation angles of the motors 9 and 10 are the same. Since the drive control is performed, the positioning error, the torsional vibration, and the noise due to the twisting phenomenon can be reduced, the positioning accuracy of the moving table 3 can be improved, and the above-described request for higher accuracy can be met.

Further, since both ends of the ball screw 6 are simultaneously driven to be rotated by the drive motors 9 and 10, the ball screw 6 having a small diameter and a large lead can be employed, and the screw inertia and the rotor inertia can be reduced and the servo can be reduced. The performance can be improved and the feed speed can be increased. Further, in this case, a small motor can be adopted as each of the drive motors 9 and 10, and the arrangement space and cost can be reduced as compared with the case where a large motor is arranged on one side of the related art.

In the above embodiment, an example in which the drive motors 9 and 10 are directly connected to both ends 6a and 6b of the ball screw 6 has been described, but the present invention is not limited to this, and the gears and timings are not limited thereto. It may be driven via a belt / pulley or the like. In the above embodiment, the rotation angles of the drive motors are detected and matched, but the rotation angles of the ball screw may be detected and matched, or the angular velocities of the drive motor and the ball screw are matched. You may allow it.

FIG. 2 shows a feeder according to another embodiment. This fixes the driven gear 15 to the left and right end portions 6a and 6b of the ball screw 6, fixes the drive gear 16 to the drive motors 9 and 10, and meshes the gears 15 and 16 to rotate the ball screw 6. Is configured to drive. The pulse coders 11, 1 are provided at both ends of the ball screw 6.
2 are connected, and the controller 13 controls the driving force of the drive motors 9 and 10 so that the rotation angles of both ends of the ball screw 6 match or the angular velocities of both ends match. Also in this embodiment, the same effect as that of the above embodiment can be obtained.

[0023]

As described above, according to the machine tool feeding apparatus of the first aspect of the invention, drive motors are connected to both ends of the ball screw, and for example, the ball screw of the second aspect of the invention is used. Since the drive motors are controlled so that the rotation angles of the respective ends of the ball screw are the same, or the angular velocities of the respective ends are the same, the twisting of the ball screw can be suppressed, and the positioning error and twisting can be suppressed. This has the effect of reducing vibration and improving positioning accuracy.

Since both ends of the ball screw are driven to rotate by the drive motor, it is possible to employ a ball screw having a small diameter and a large lead, which has the effect of increasing the feed speed, and further employs a small motor. It is possible to reduce the arrangement space and improve the servo performance.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram for explaining a machine tool feeding apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a feeding device according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Feeding device 2 Fixed table (fixed part) 3 Moving table (moving member) 6 Ball screw 9,10 Drive motor 11,12 Pulse coder (rotation angle detection means) 13 Controller (driving force control means)

Claims (2)

[Claims] 1. A machine tool in which a ball screw is screwed into a nut portion of a moving member movably arranged on a fixed portion and the ball screw is rotationally driven to reciprocate the moving member. In the feeding device, drive motors are connected to both ends of the ball screw, respectively, and rotation angle detecting means for detecting a rotation angle of each end portion of the ball screw; A feed device for a machine tool, comprising: a drive force control means for controlling a drive force of a drive motor. 2. The machine tool according to claim 1, wherein the driving force control means is configured to control the driving force so that the rotation angles or angular velocities of the respective drive motors match. Feeder.