JP2018020415A - Driving device for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device for a machine tool capable of accurately detecting a movement quantity of a movement part of the machine tool, and capable of high-speed position control.SOLUTION: A driving device comprises a ball screw 14 and a ball nut 16, and controls a position of a movement part 12 by moving the ball nut 16 by rotation of the ball screw 14. Output shafts 26 and 27 of servo-motors 24 and 25 are respectively rotatably connected to both ends of the ball screw 14, and a motor control device 28 is provided for synchronously operating the respective servo-motors 24 and 25, and is provided with a movement quantity detection device 30 composed of a linear feedback scale 34 having the length of a movement distance or more of the movement part 12 and formed in a straight line shape and a detection head 32 for detecting a movement quantity by the relative movement with the linear feedback scale 34. The linear feedback scale 34 is installed in the movement part 12, and the detection head 32 is installed in a fixing member. The movement quantity of the movement part 12 is directly detected by the movement quantity detection device 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a machine tool drive device that moves a moving part such as a table of a machine tool using a ball screw and a ball nut.

  Conventionally, a drive device used for an NC machine tool has a servo motor connected to an end of a ball screw, and the ball screw is driven by the servo motor to move a ball nut provided with a moving portion. In particular, in an NC machine tool, in order to increase the feed speed of the moving part, rapid start and rapid stop are required, and the absolute value of acceleration during acceleration and deceleration must be increased. Therefore, as disclosed in Patent Documents 1 to 3, for example, servo motors are attached to both ends of a ball screw that moves the moving part of the machine tool, both servo motors are operated synchronously, and the ball screw is rotated at high speed. There is provided a machine tool drive device in which a ball nut is moved to dispose a moving portion at a predetermined position.

Japanese Patent Application Laid-Open No. 11-114762 JP-A-9-42406 Japanese Patent Laid-Open No. 9-76139

  In the drive device for NC machine tools, the distance between the ball nut on the ball screw and each motor during operation frequently changes due to processing or the like. Therefore, the torsional rigidity of the ball screw portion from each motor at both ends to the ball nut is different, and this causes the amount of twist to be different for each motor at both ends, and there is a problem that the position control of the ball nut cannot be accurately performed.

  The present invention has been made in view of the above background art, and provides a machine tool drive device that can accurately detect the amount of movement of a moving part of a machine tool and enables high-speed position control. With the goal.

  The present invention is a machine tool drive device having a ball screw and a ball nut, wherein the ball nut is moved by the rotation of the ball screw to control the position of the moving part, and the output of each servo motor is provided at each end of the ball screw. A linear feedback scale having a length that can detect the moving distance of the moving unit, and a linear feedback scale that is provided with a motor control device that is rotatably connected to a shaft and that synchronously operates the servo motors; A movement amount detection device comprising a detection head for detecting the movement distance by relative movement with respect to the linear feedback scale, wherein one of the linear feedback scale and the detection head is attached to the moving unit, and the other is the other Attached to a fixed member, the amount of movement of the moving part can be detected directly by the amount of movement detection device It is a machine tool drive unit provided.

  The linear feedback scale of the movement amount detection device is fixed to the moving unit, and the detection head is attached to another fixing member.

  The machine tool drive device of the present invention can detect the position of the moving portion and perform accurate position control regardless of the amount of twist of the ball screw during driving. Therefore, when the position of the ball nut is controlled at high speed by a pair of servo motors, even if the twist amount and torsional rigidity of the ball screw are different on both sides of the ball nut, the position of the moving part is accurately detected and moved. Positioning can be performed, and higher-speed position control can be performed in the moving part of the machine tool.

It is a front view of the drive device for machine tools of one Embodiment of this invention.

  A machine tool drive device according to an embodiment of the present invention will be described below with reference to FIG. The machine tool drive device 10 of this embodiment is attached to an NC machine tool (not shown). As shown in FIG. 1, the table 12 is a moving part of the NC machine tool and the movement direction of the table 12 is parallel. And a ball nut 16 screwed into the ball screw 14. The ball nut 16 is moved by the rotation of the ball screw 14 so that the table 12 can be moved to a predetermined position.

  The table 12 is a part to which a predetermined processing machine or workpiece (not shown) of the NC machine tool is attached, and is slidably supported by a guide rail or the like (not shown). A nut mounting portion 12a is provided on the lower surface of the table 12, and a ball nut 16 is fixed thereto. The ball nut 16 is fixed by, for example, a double nut method, and is attached so as to reduce the backlash by applying a preload and improve the feeding accuracy.

  The ball screw 14 into which the ball nut 16 is screwed is provided with a male screw formed on the peripheral surface thereof so that the table 12 can be moved to a desired position with a length longer than the moving range of the table 12 and can be stopped. The vicinity of both end portions 14a of the ball screw 14 is rotatably supported by a bearing 20 fixed to a support portion 18 extended from a fixing member of a machine tool (not shown). Both end portions 14 a of the ball screw 14 are directly connected to output shafts 26 and 27 of a pair of servomotors 24 and 25 via joints 22, respectively.

  The pair of servo motors 24 and 25 are connected to the motor control device 28 and are driven and controlled by the motor control device 28. The motor control device 28 is connected to the output of the detection head 32 of the movement amount detection device 30.

  The movement amount detection device 30 includes a detection head 32 and a linear feedback scale 34. The detection head 32 of the movement amount detection device 30 is composed of, for example, an optical element and a lens (not shown), and the linear feedback scale 34 is provided with a grid scale on a straight line so that the position can be detected on the order of several μm to several tens of μm. Is formed. The detection head 32 is fixed to a fixing member such as a base (not shown), and is disposed to face the grid scale of the linear feedback scale 34. The linear feedback scale 34 is fixed in parallel to the moving direction of the table 12 on the side surface or the bottom surface of the table 12 that is a moving unit.

  Next, the operation of the machine tool drive device 10 having the above structure will be described below. When the table 12 is moved from a predetermined retraction position, the motor control device 28 sends a drive signal to the pair of servo motors 24 and 25 so that the output shafts 26 and 27 rotate at the same speed in the same direction. Output. At this time, the detection head 32 reads the grid scale of the linear feedback scale 34 and outputs the actual movement amount of the table 12 to the motor control device 28. The movement of the table 12 output from the detection head 32 is calculated by the motor control device 28 and compared with a desired movement amount. When the table 12 reaches a desired position, the movement of the pair of servo motors 24 and 25 is performed. The rotation is stopped. Since the operations of the ball screw 14 and the ball nut 16 at this time are well known, description thereof will be omitted.

  The pair of servo motors 24, 25 drive both ends of the ball screw 14 synchronously by the motor control device 28. As a result, the torsional rigidity of the ball screw 14 can be reduced to almost half as compared with driving by one end with only one servo motor.

  According to the machine tool drive device 10 of this embodiment, since the ball screw 14 is driven by the pair of servo motors 24 and 25, the ball screw 14 can be driven at a high speed, and the table 12 can be driven regardless of the twist amount of the ball screw 14. The position can be detected and accurate position control becomes possible. Accordingly, the position of the ball nut 16 is controlled at a high speed by the pair of servo motors 24 and 25, and the position of the table 12 is accurately adjusted even when the twist amount and the twist rigidity of the ball screw 14 are different on both sides of the ball nut 16. It can be detected and moved and positioned, and the position control of the table 12 can be performed more quickly and accurately.

  Furthermore, in the machine tool drive device 10 of this embodiment, since the linear feedback scale 34 is attached to the table 12 and the detection head 32 with wiring is provided on the fixed member, wiring processing is easy and detection with a small volume is possible. The head 32 can be easily arranged on the lower side or the side of the table 12 of the machine tool. On the other hand, the table 12 has a wide flat surface, and a relatively long near feedback scale 34 can be easily arranged.

  In addition, in the machine tool drive device 10 of this embodiment, since both ends 14a of the ball screw 14 are respectively fixed to the pair of servo motors 24 and 25, the ball screw 14 can be made thinner. It can be rotated at high speed. Further, by using the two servo motors 24 and 25, it is possible to use a servo motor with a small rotor inertia. From this point, it is possible to increase the acceleration and speed during movement.

  The machine tool drive device 10 of the present invention is not limited to the above embodiment, and the linear feedback scale 34 may be fixed to a fixed member by providing the detection head 32 in the moving part. In addition to the optical detection head 32, the movement amount detection device 30 may use an electromagnetic position detection method, and the detection method is not limited. Further, the machine tool to be applied may be other than the NC machine tool, and can be applied to detection of moving parts of various machine tools.

DESCRIPTION OF SYMBOLS 10 Machine tool drive device 12 Table 12a Nut attaching part 14 Ball screw 14a End part 16 Ball nut 18 Support part 20 Bearing 22 Joint 24, 25 Servo motor 26, 27 Output shaft 28 Motor control apparatus 30 Movement amount detection apparatus 32 Detection head 34 Linear feedback scale

Claims (2)

A machine tool drive device (10) having a ball screw (14) and a ball nut (16), and controlling the position of the moving portion (12) by moving the ball nut (16) by rotation of the ball screw (14). Because
Output shafts (26, 27) of servo motors (24, 25) are rotatably connected to both ends of the ball screw (14), respectively, and a motor control device (28) for synchronously operating the servo motors (24, 25). )
A linear feedback scale (34) having a length capable of detecting the moving distance of the moving unit (12) and formed linearly, and the moving distance is detected by relative movement with respect to the linear feedback scale (34). A movement amount detection device (30) comprising a detection head (32) for
One of the linear feedback scale (34) and the detection head (32) is attached to the moving part (12), the other is attached to another fixed member, and the amount of movement of the moving part (12) is the amount of movement. A machine tool drive device characterized in that it can be directly detected by a detection device (30).   The machine tool according to claim 1, wherein the linear feedback scale (34) of the movement amount detection device (30) is fixed to the moving portion (12), and the detection head (32) is attached to another fixed member. Drive device.

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