JP2000218415A - Electric chucking device and its operating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric chucking device for a machine tool, capable of improving machining quality with safety and increasing productivity, and its control method. SOLUTION: A scroll chuck 1 is rotary-driven by a main spindle motor 2 via the outer shaft 28 of a double structure shaft, and a claw is driven by a chuck driving device 3 disposed coaxially to and via the middle shaft of the double structure shaft. The chuck driving device 3 is provided with a rotation transformer 4, a servo motor 5, a brake 6 and a rotational position detector 7, and power is supplied to the servo motor 5 and the brake 6 in non-contact. The servo motor 5 is controlled for its rotational position and torque, and the gripping force of the claw is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric chuck device for a machine tool in which a claw provided on a chuck for gripping a workpiece is driven by a motor.

[0002]

2. Description of the Related Art Lathes have a simple structure and are capable of precision machining among machine tools, and have been widely used since ancient times. When the work is processed by the lathe, the work is gripped and rotated by claws provided on a chuck, and is cut by applying a fixed tool. The chuck is generally provided with a scroll in which spiral teeth are formed and a plurality of claws which can move in the radial direction by meshing with the teeth, but are not limited to such a mechanism. It can be moved by other mechanisms. When using this, the operator manually turns the scroll to move the claws to grip or release the work. Since the work of gripping and releasing the work is simple and may take some time, an electric chuck with a built-in motor has been developed. Has become. The technology is disclosed in, for example, JP-A-8-19903 and JP-A-8-1903.
As disclosed in Japanese Patent Laid-Open No. 50531, a motor is provided so that a claw can be moved by electric power.

[0003]

However, according to these prior arts, since the electric chuck and the chuck are mechanically connected, maintenance such as replacement of parts is not easy and requires time and effort. There was a problem. In addition, since the axis of the motor that moves the pawl and the axis of rotation of the chuck are parallel at a distant position, power is transmitted through gears, and the physical size in the radial direction increases and There has been a problem that the installation places restrictions on the space. In addition, since power is transmitted via gears, when a workpiece is gripped by the chuck, a radial force is applied to the chuck in addition to torque, and a slight bending occurs in the radial direction, so that the workpiece is accurately gripped at the center of the chuck. There was a problem that it was not easy. In addition, since power is transmitted through gears, wear is inevitable, and maintenance is required, thereby increasing maintenance costs. Further, when the motor is driven to grip the work with the claws, the gripping force is not controlled, so that when the thin work is gripped, there is a problem that deformation tends to occur and it is not easy to increase the processing quality. In addition, when performing a cutting process while gripping a workpiece, it is easy for the nails to loosen and the workpiece to shift, which makes it difficult not only to improve the processing quality but also from the viewpoint of safety. There was a problem. Accordingly, the present invention has been made in view of these problems, and provides an electric chuck device for a machine tool, which is safe, can improve processing quality, and can improve productivity, and a control method therefor. The purpose is to:

[0004]

SUMMARY OF THE INVENTION Accordingly, an electric chuck device according to the present invention is a machine tool comprising a chuck having claws for gripping a work, a spindle motor for rotating the chuck, and a chuck driving device for driving the claws. In the electric chuck device for use, the outer shaft and the center shaft connected to the chuck, each of which is capable of moving the claw by relative rotation, and a double structure shaft, and via the double structure shaft A spindle motor that drives the chuck, a frame is fixed to the outer shaft of the double structure shaft, a brake, a servo motor, a rotary transformer, and a chuck driving device that incorporates a rotary position detector, and The brake integrates a brake stator with a built-in coil and the outer shaft and the center shaft depending on whether the brake stator is excited or not. And a mechanism that can rotate freely with respect to each other, the servo motor comprises a stator fixed to a frame of the chuck driving device, and a rotor fixed to the center shaft, When the stator is excited, the rotor rotates to rotate the center shaft relatively to the outer shaft, and the rotary transformer is fixed to a frame of the chuck driving device to perform secondary winding. A rotor consisting of a wire and an iron core, and a rotor fixed to a fixed shaft disposed coaxially with the center shaft.
And a stator composed of a secondary winding and an iron core.
When the secondary winding is excited, power is transmitted to the secondary winding via an air gap to supply power to the servo motor and the brake, and the rotational position detector includes:
The servo motor comprises: a detection surface provided on the center shaft; and a detection element provided on the fixed shaft of the rotary transformer, and capable of detecting a rotation position of the center shaft. A reducer is provided between the rotor and the center shaft, and when the rotor rotates, the rotation is reduced and the claw of the chuck can be moved via the center shaft. The rotor is concentric with the double structure shaft and fixed to an outer shaft of the double structure shaft. Further, according to the operation method of the electric chuck device of the present invention, when the workpiece is gripped by moving the claw, (1) power is supplied to the rotary transformer. (2) Power is supplied to the brake via the rotary transformer, and the brake is released. (3) Supplying electric power to the servomotor via the rotary transformer based on the signal of the rotational position detector, controlling the rotational position of the center shaft while controlling the torque of the servomotor, and setting the claw to Move. (4) When the torque of the servo motor reaches a predetermined value, the excitation of the servo motor is stopped. (5) Stop excitation of the brake. It is characterized by operating according to the following procedure. As described above, the work can be grasped accurately while minimizing the bending of the work, and the work can be quickly and automatically replaced.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a configuration of an electric chuck device of the present invention, in which a lower half shows an external appearance and an upper half shows an internal structure. In the drawing, reference numeral 1 denotes a scroll chuck having spiral teeth (not shown) and a plurality of not-shown pawls which mesh with the teeth and are movable in the radial direction. The spindle motor 3 for rotating is a chuck driving device for rotating the scroll to move the pawl. Reference numeral 11 denotes a center shaft whose right end is connected to the scroll of the scroll chuck 1;
Reference numeral 8 denotes an outer shaft whose right end is connected to the scroll chuck 1. The outer shaft 28 is concentric with the center shaft 11 provided in the outer shaft 28. The outer shaft 28 and the middle shaft 11 form a double structural shaft. In the scroll chuck 1, the outer shaft 28 and the center shaft 1
1, a bearing (not shown) is provided, and is supported so as to be capable of relative rotation.

The spindle motor 2 includes a frame 21, brackets 22 and 23 fixed to both ends thereof, and a frame 21.
Stator 26 consisting of windings and iron core fixed inside
And a rotor 27 fixed to the outer shaft 28. The frame 21, the brackets 22, 23, and the stator 26 are fixed to a fixed side (not shown), and the outer shaft 2 is supported by bearings 24, 25 inserted in the brackets 22, 23.
8 is rotatably supported. When the stator 26 is excited, torque is generated between the stator 26 and the rotor 27, and the outer shaft 28 can be rotated. The chuck driving device 3 mainly includes a rotary transformer 4, a servomotor 5, a brake 6, and a rotational position detector 7, which are arranged in an internal space surrounded by a frame 31 and brackets 32 and 33. I have. The bracket 32 is fixed to the left end of the outer shaft 28 and rotatably supports the center shaft 11 via the bearing 15. The bracket 32 and the frame 31, and the frame 31 and the bracket 33 are fixed, and the bracket 33 is rotatably supported by a fixed shaft 41 via a bearing. The center of the fixed shaft 41 coincides with the center of the center shaft 11 and the outer shaft 28, and is arranged concentrically.

The rotary transformer 4 is fixed inside the frame 31 and includes a rotor 41 composed of a winding and an iron core, and a fixed shaft 41.
And a stator 42 composed of a winding and an iron core, so that electric power can be supplied from the stator 42 to the rotor 41 in a non-contact manner. The servo motor 5 is composed of a stator 51 fixed to the inside of the frame 31 and composed of a winding and an iron core, and a rotor 52 fixed to the center shaft 11. The rotor 52 rotates when the stator 51 is excited. Is available. The brake 6 includes a brake stator and a rotating disk. The brake stator is provided with a coil 61 incorporated in a bracket 32, a stator core formed by a part of the bracket 32, and a gap between the stator core and the stator core. And a fixed disk fixed to the frame 31. A rotating disk provided on the center shaft 11 is disposed between the stator core and the fixed disk, and the rotating disk is movable only in the axial direction with respect to the center shaft 11. The rotating disk is preloaded by a spring and pressed against the fixed disk.
If 1 is not excited, the fixed disk and the rotating disk do not rotate integrally with each other, and the outer shaft 28 and the center shaft 11 can rotate integrally without relative rotation. When the coil 61 is excited, the rotating disk is pulled toward the stator core against the preload of the spring, and a gap is created between the fixed disk and the rotating disk, so that the rotating disk can rotate relatively freely. Therefore, the outer shaft 28 and the center shaft 11 can rotate relatively.

The rotational position detector 7 comprises a detection surface provided at the left end of the center shaft 11 and a detection element provided at the right end of the fixed shaft 41, and a plurality of circumferentially formed marks formed on the detection surface. Thereby, the rotational position of the center shaft 11 can be detected. The detection element and the surface to be detected may be anything as long as the relative rotation position can be detected, such as a combination of a magnetic sensor and a gear or a combination of an optical sensor and a slit, and the means does not matter. The lead wire 42 of the detecting element is guided to the outside via a conductive path (not shown) formed on the fixed shaft 41, and is connected to an amplifier (not shown) built in a chuck drive control device (not shown) to detect the rotational position of the central shaft 11. Function as a rotating position detector. The wiring of the chuck driving device 3 is as follows. At the rotary transformer 4, the lead wire 42 of the stator 41 is led to a chuck drive control device (not shown) via a conduction path (not shown) formed on the fixed shaft 41,
Part of the lead wire 35 of the rotor 41 is connected to the stator 51 of the servomotor 5 and part of the lead wire 35 of the brake 6
It is connected to the. The chuck drive control device (not shown) functions to excite the servomotor 5 and the brake 6 in response to the signal from the rotational position detector 7. When exciting the servomotor, position control for controlling the rotational position of the center shaft 11 and torque control for controlling the torque of the servomotor 5 function.

In the above embodiment, the case where the rotor is fixed to the outer shaft so that the main shaft motor can be directly driven at the double structure shaft has been described. However, the main shaft motor is separately arranged, and the main shaft motor is connected via the belt. The torque may be transmitted to the outer shaft, or may be conventionally transmitted to the outer shaft via a gear, and if the torque can be transmitted to the double-structure shaft, the means may be used. Regardless, it does not impose any structural restrictions. In addition, the rotation of the rotor 52 of the servo motor 5 is directly transmitted to the scroll chuck 1 through the center shaft 11.
However, as a modification of the above-described embodiment, a speed reducer may be provided between the servo motor 5 and the brake 6 and the scroll chuck 1. If a speed reducer is provided, the torque of the rotor 52 is amplified and transmitted to the scroll, so that the servo motor 5, the rotary transformer 4, and the brake 6 can be downsized, and the chuck driving device 3 can be downsized and installed on a lathe. The space to be used can be reduced. Further, in the above-described embodiment, a lathe in which the axis of the rotating part is horizontal has been described. However, according to the gist of the present invention, the lathe is not limited to the lathe if it can have the same components, and the axis of the rotating part becomes vertical. It doesn't matter what machine tool you have.

Further, the brake of the above-mentioned embodiment is
A case has been described in which the rotating disk provided on the shaft is moved in the axial direction to integrate the center shaft 11 and the outer shaft 28. However, another stator that can move in the axial direction and faces the brake stator, 1 between shaft and brake stator
1 may be provided, and when the brake stator is excited, another movable stator may move and come into close contact with the rotating disk to rotate the center shaft 11 and the outer shaft 28 integrally. . As described above, the means is not limited to the above-described embodiment as long as the means enables the mutual rotation of the center shaft 11 and the outer shaft 28 to be free or integrated, and other means may be used. Further, as a modified example of the above embodiment,
The center shaft 11 may be a hollow shaft. In this case, since the work can be passed through the scroll chuck 1 and the center shaft 11, a long work can be gripped by the scroll chuck 1, and the restriction imposed on the work is reduced, and the practicality can be improved.

Next, the operation when the electric chuck device thus configured is used will be described. When grasping the work by moving the claw of the scroll chuck 1, first,
The chuck drive controller supplies (1) power to the rotary transformer 4. Then, (2) electric power is supplied to the coil 61 of the brake 6 via the rotary transformer 4, the rotary disk is separated from the fixed disk, and the brake 6 is released. by this,
The center shaft 11 and the outer shaft 28 can rotate relatively.
Next, (3) the chuck drive control device operates based on the signal of the rotational position detector 7 to supply electric power to the servomotor 5 via the rotary transformer 4 and control the torque thereof while controlling the center shaft 11.
The claw of the scroll chuck 1 is moved by controlling the rotation position of the scroll chuck 1. (4) When the torque of the servo motor 5 reaches a predetermined value, the excitation of the servo motor 5 is stopped and the movement of the nail is stopped. The torque of the servomotor 5 is converted from a current supplied by a known technique and its frequency. When the claws grip the work with a predetermined torque, (5) the excitation of the brake 6 is stopped. The work is automatically grasped by such a procedure. When the excitation of the brake 6 is stopped in (5), the brake 6 functions by the spring,
Since the center shaft 11 can rotate integrally with the outer shaft 28, when the main shaft motor 2 is excited, the scroll chuck 1 rotates while holding the work. Scroll chuck 1
When the work is removed from, the procedure (1) to (5) is different from the procedure (3) only in that the nail is moved in the loosening direction. Good.

[0012]

As described above, according to the present invention, electric power is supplied to the servo motor 5 and the brake 6 of the chuck driving device 3 in a non-contact manner, and the rotational position and the torque of the servo motor 5 are controlled. The chuck drive device can be made compact, and at the same time, there is no abnormal force applied to the work, so that the work can be gripped without giving any deformation, and the work can be easily attached and detached without bothering you. You can do it. Therefore, the work can be automatically attached and detached, the operability is good, the work time can be shortened, the maintenance can be greatly reduced, the chuck driving device and the spindle motor can be downsized, the processing accuracy can be increased, and dust is hardly generated. Significant advantages such as cleanliness and safety can be obtained, and the practicality of the machine tool can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an electric chuck device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scroll chuck 2 Spindle motor 3 Chuck drive device 4 Rotary transformer 5 Servo motor 6 Brake 7 Position detector 11 Center shaft 15, 24, 25, 34 Bearing 21, 31 Frame 22, 23, 32, 33 Bracket 26, 42, 51 Stator 27, 41, 52 Rotor 28 Outer shaft 35, 42 Lead 41 Fixed shaft 61 Coil

Claims (4)

[Claims] 1. An electric chuck device for a machine tool, comprising: a chuck having claws for gripping a work; a spindle motor for rotating the chuck; and a chuck driving device for driving the claws. A double-structured shaft composed of an outer shaft and a central shaft, each of which can move the claw by rotating relative to each other, a spindle motor that drives the chuck via the double-structured shaft, and the double-structured shaft A frame is fixed to an outer shaft of the brake, a brake, a servo motor, a rotary transformer, and a chuck driving device having a built-in rotation position detector, and the brake, a brake stator having a built-in coil, the Depending on whether the brake stator is excited or not, the outer shaft and the middle shaft can be integrally rotated or freely rotated with each other. The servo motor is comprised of a stator fixed to the frame of the chuck driving device, and a rotor fixed to the center shaft, when the stator is excited, the rotor rotates, The center shaft can be relatively rotated with respect to the outer shaft, and the rotary transformer is fixed to a frame of the chuck driving device, and a rotor including a secondary winding and an iron core is disposed coaxially with the center shaft. A primary winding fixed to a fixed shaft and a stator made of an iron core. When the primary winding is excited, electric power is transmitted to the secondary winding via an air gap, and the servo is driven. An electric power can be supplied to a motor and the brake, and the rotational position detector is formed by a detection surface provided on the center shaft and a detection element provided on the fixed shaft of the rotary transformer. Electric chuck device, wherein a can be made is by detecting the rotational position of the middle axle. 2. A speed reducer is provided between a rotor of the servomotor and the center shaft, and when the rotor rotates, the rotation is reduced and the claw of the chuck can be moved via the center shaft. The electric chuck device according to claim 1. 3. The electric chuck device according to claim 1, wherein a rotor of the spindle motor is concentric with the double structure shaft and fixed to an outer shaft of the double structure shaft. 4. A method of operating an electric chuck device, wherein the operation is performed in the following procedure when the workpiece is gripped by moving the claw. (1) Supply power to the rotary transformer. (2) Power is supplied to the brake via the rotary transformer, and the brake is released. (3) Supplying electric power to the servomotor via the rotary transformer based on the signal of the rotational position detector, controlling the rotational position of the center shaft while controlling the torque of the servomotor, and setting the claw to Move. (4) When the torque of the servo motor reaches a predetermined value, the excitation of the servo motor is stopped. (5) Stop excitation of the brake.