JPH04223815A - Eccentric amount-variable chuck - Google Patents

Abstract

PURPOSE:To process efficiently a workpiece eccentric in one direction on an NC lathe. CONSTITUTION:An eccentric chuck 20 movable in the diameter direction is provided on a chuck base 17 provided on a main shaft shaft-end, an eccentric amount regulating shaft 28 to regulate a projection 25 at the rear side of the eccentric chuck 20 by a sloped hole 27 to be a cam surface is inserted rotatably and movably in the axial direction to the center of the main shaft, a connecting shaft 36 is provided movably in the axial direction by a ball screw 35 driven by a servo motor 32, and the connecting shaft 36 is connected to the eccentric amount regulating shaft 28 through a rotary coupling 40. The rotation of the ball screw 35 by the servo motor 32 moves the sloped hole 27 in the axial direction to make the eccentric chuck 20 eccentric through the projection 25.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable eccentricity chuck suitable for machining a workpiece having an eccentric outer shape with respect to the center of a spindle in a machine tool, particularly a lathe.

0002

[Prior Art] The first method for machining a workpiece with an eccentric outer shape with respect to the center using a conventional lathe is to move the eccentric chuck 3 diametrically to the chuck base 2 at the end of the main spindle 1, as shown in Fig. 6. The adjustment bolt 4, which is screwed onto the chuck base 2 so that it can move forward and backward toward the center, is manually adjusted so that the chuck base 2 can be installed and eccentric by a predetermined amount. As a second method, machining is performed by NC control using reciprocating movement of the X-axis of the tool rest in synchronization with the rotation of the main shaft (C-axis) or by copy turning using a cam. Alternatively, as a third method, machining is performed using a special processing machine in which a cutting tool rotates around the workpiece to control its position in the radial direction.

0003

Problems to be Solved by the Invention The first method requires the troublesome operation of changing the grip of the workpiece, which does not improve work efficiency and tends to cause variations in accuracy. The second method has a problem in that it is difficult to increase the speed due to inertia caused by the weight of the turret since the position of the turret is controlled. Furthermore, the third method lacks versatility because it uses a special-purpose machine, and has the problem of high costs for workpieces that are not mass-produced. The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to provide a variable eccentricity chuck that can perform machining with high turning efficiency.

0004

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention includes a chuck base attached to a main shaft, and an eccentric chuck having workpiece gripping claws fitted into the chuck base so as to be movable in the diametrical direction. an eccentricity adjusting means that is rotatably and axially movably supported at the center of the main shaft and changes the eccentricity of the eccentric chuck by moving in the axial direction; and a drive that moves the eccentricity adjusting means in the axial direction. means.

[0005]

[Operation] The eccentric amount adjusting means is moved in the axial direction by the action of the driving means that is controlled in accordance with the Z-axis direction position of the cutting tool of the workpiece gripped by the jaws of the eccentric chuck, and the eccentricity adjustment means is moved in the axial direction according to the amount of movement. The eccentric chuck is eccentric and the workpiece is machined into a predetermined eccentric shape.

[0006]

[Embodiment] A description will be given below based on FIGS. 1, 2, and 3. Known tool rest X-axis and Z-axis position control (not shown) NC
In a lathe, a hollow main shaft 12 is rotatably supported on a headstock 11 by front and rear bearings 13, a rotor 14 is fixed to the main shaft 12 between the front and rear bearings 13, and a stator 15 corresponding to the rotor 14 is fixed to the main shaft 12 between the front and rear bearings 13. is fixed to the main shaft 12
is driven by a built-in motor. A chuck base 17, in which a center boss is fitted into a center hole of the spindle, is fitted to the tip of the main shaft 12, and parallel dovetails 18 are cut into the front end surface of the chuck base at symmetrical positions across the diameter. . An eccentric chuck 20 having a workpiece gripping claw 19 on this dovetail 18
are slidably fitted in the dovetail groove 21.

A protrusion 25 having an inclined cylindrical tip is provided at the center of the back side of the eccentric chuck 20 and is inserted into a center hole 26 of the chuck base 17. An eccentricity adjustment shaft is provided in the center hole 26 of the chuck base 17, and a hole 27 is bored in the head thereof to form a cylindrical cam surface that is inclined at the same angle as the inclination angle of the inclined cylinder of the projection 25 from the shaft end to the axis center. 28 is rotatably and axially movably supported by front and rear bearings 29. The inclined cylinder of the protrusion 25 is slidably fitted into the hole 27 without a gap, and the distance from the central axis at the center point of contact between the inclined hole surface and the protrusion 25 is the eccentricity of the eccentric chuck 20. As the eccentric chuck, a scroll or independent type manual chuck or a front drive type power chuck is used.

A servo motor 32 with a detector 33 is attached to the rear bracket 31 of the headstock 11, and a ball screw 35, which is provided so as to be rotatable only by a bearing 34 of the bracket 31 concentrically with the center of the spindle, rotates. controlled. A ball screw nut 37 integrated with a connecting shaft 36 is screwed onto this ball screw 35, and the spline portion fits into a female spline shaft 38 fixed to the bracket 31, so that the connecting shaft 36, which is prevented from rotating, moves only in the axial direction. It is possible. The connecting shaft 36 and the eccentricity adjusting shaft 28 are connected by a rotary joint 40 to allow rotation of the eccentricity adjusting shaft 28, so that the movement in the axial direction is faithfully transmitted. Note that the amount of movement of the eccentric chuck with respect to the rotation angle of the ball screw 35 is detected in advance.

The operation of the present invention configured as described above will be explained. Assume that a workpiece whose eccentric direction is constant as shown in FIG. 4 is to be machined, and the NC device stores the shape of the workpiece, that is, the amount of eccentricity at the axial center position (Z-axis). A workpiece is gripped by the jaws 19 of the eccentric chuck 20.

The tool is positioned at the cutting start point by controlling the X-axis and Z-axis of the tool post, and the servo motor 32 is driven simultaneously with cutting by commands from the NC device. As the ball screw 35 rotates, the ball screw nut 37 and the connecting shaft 36 are moved in the axial direction, and the eccentricity adjustment shaft 28 is moved in the axial direction via the rotary joint 40, and the protrusion 25 and the eccentric chuck 20 are moved by the inclined hole 27. is moved in the diametrical direction to be eccentric, and by detecting the current angle of the detector 33, the eccentricity is controlled to an accurate amount corresponding to the axial position,
The outer diameter of the workpiece is machined into the shape shown in FIG.

By simultaneously controlling the amount of eccentricity and the X-axis and Z-axis of the tool rest, it is possible to machine the workpiece shown in Fig. 5. In this case, there is no need to synchronize the X-axis feed with the rotation angle of the C-axis, so accuracy Perfect circular cutting is possible. Furthermore, by adding known C-axis control, it is possible to provide a Y-axis function excluding the direction perpendicular to the eccentric axis by three-axis synthesis of the C-axis, X-axis, and eccentric axis.

0012

[Effects of the Invention] Since the present invention is configured as described above, the following effects can be achieved. Eccentricity control can be performed by NC, and it is possible to efficiently process workpieces with a perfect circular cross section that is eccentric in one direction. In addition, since eccentricity, Z-axis, and X-axis three-axis synchronization control is easy, it is extremely effective for turning various cams.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a chuck portion of the present invention.

FIG. 2 is a partial vertical cross-sectional view of the eccentric drive section of the chuck of the present invention.

FIG. 3 is a longitudinal sectional view of the chuck portion of FIG. 1 at a position shifted by 90 degrees.

FIG. 4 is a diagram showing an example of the shape of a workpiece.

FIG. 5 is a diagram showing another example of the shape.

FIG. 6 is a diagram of a conventional eccentric chuck.

[Explanation of symbols]

11 Headstock 12 Main shaft 17 Chuck base 20 Eccentric chuck 25 Tsuko 27 Slanted hole 28 Eccentricity adjustment shaft 32 Servo motor 40 Rotating joint 35 Ball screw 37 Ball screw nut

Claims (1)

[Claims] 1. A chuck base attached to a main shaft, an eccentric chuck fitted to the chuck base so as to be movable in the diametrical direction and having workpiece gripping claws, and supported at the center of the main shaft so as to be rotatable and movable in the axial direction. A variable eccentricity chuck comprising: an eccentricity adjusting means for changing the eccentricity of the eccentric chuck by moving in the axial direction; and a driving means for moving the eccentricity adjusting means in the axial direction.