JPS6250242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that corrects the position of a tailstock by displacing the center of the tailstock in response to the displacement of the main shaft.

Conventionally, displacement occurs due to thermal deformation of the headstock due to heat generated from bearings, gears, etc., and the rotation axis of the workpiece connects the center of rotation of the chuck attached to the main spindle and the center of the tailstock. It is not parallel to the direction of movement, and as a result, the workpiece becomes tapered, resulting in a workpiece with poor cylindricity. As a countermeasure against this problem, various measures have been taken to lubricate and cool the bearings of the headstock in order to suppress thermal displacement of the spindle. However, these methods are methods for preventing thermal displacement, but do not completely eliminate displacement, and are not methods for proactively improving cylindricity accuracy when thermal displacement occurs.

The present invention was made in view of the above problems, and detects the amount of displacement in the radial direction of the spindle, applies a displacement equal to this amount of displacement to the center of the tailstock, and positions the rotation center of the workpiece. The purpose is to provide a machine tool that makes corrections and produces highly accurate workpieces.

Embodiments of the present invention will be described below with reference to the drawings. In Figure 1, 1 is the drive motor and the headstock 2
The rotational force is transmitted to the main shaft 3 via the inner gear train. 7
is a center, which is supported by a tailstock 8 fixed to a bed 11 (the bearing structure will be described later), and the center of the center 7 coincides with the axis position of the main shaft 3 when it is not displaced. Reference numeral 4 denotes a workpiece, one end of which is chucked by a chuck 9 attached to the main shaft 3, and the other end supported by a center hole 7 inserted into the workpiece after a center hole is formed. A turret 6 has a cutting tool 5 fixed on the side of the workpiece 4, and a mechanism for moving the tool in a direction parallel to the axis of the workpiece 4 and a mechanism for moving it towards and away from the workpiece 4 are not shown but are well known. This is the feeding mechanism. 1
0a, 10b, and 10c are displacement detectors, and although not shown, one equivalent to the displacement detector 10d is disposed opposite the displacement detector 10c via the main shaft 3. These four displacement detectors are provided at 90° intervals, and the displacement detector 10a and the displacement detector 10
b is the detector on the Y-axis side, and the others are called the detectors on the X-axis side. Note that this displacement detector group is preferably a non-contact type displacement meter.

Next, the bearing structure of the center 7 will be explained with reference to FIGS. 2 and 3. The static pressure bearing member 19 with the center 7 inserted and the lid 12 fixed is inserted into the through hole 8a of the tailstock 8.
and secure it with the screw ring 18. 13,1
4, 15, 16 (Fig. 3) and 17 (Fig. 3) are static pressure pads, and the conduction holes for supplying hydraulic oil to each are static pressure pads so that they coincide with the conduction holes of the tailstock 8. The pressure bearing member 19 is attached. For example, the conduction hole 8b and the conduction hole 14 of the static pressure pad 14
It seems that the conduction hole 8c and the conduction hole 15a of the static pressure pad 15 coincide with each other. Also, to explain the arrangement of the static pressure pad group, there are four static pressure pads 14, 1 at 90° intervals corresponding to the outer circumference of the center 7.
5, 16, 17 are arranged, and the end 7a of the center 7
A static pressure pad 13 is arranged correspondingly.

FIG. 4 is a block diagram showing an embodiment of the control device.

Since the displacement system is the same for both the X and Y directions, the Y direction will be explained.

Detection signals Y _A ,
Y _B is input to the comparator 21, and if the detection signals Y _A , Y
If there is a difference in _B , a signal corresponding to the difference is output from the comparator 21, amplified by the servo amplifier 22, and sent to the servo valve 23. The servo motor of the servo valve 23 is actuated by the input signal and is driven to create a pressure difference at the output ports 23a, 23b so as to apply a pressure difference corresponding to the difference to the static pressure pads 14,15.
Then, the center 7 (FIG. 2) moves in the direction of decreasing supply pressure. Note that the same applies to the X direction, and members having the same function are indicated with a symbol "'".

The operation of the embodiment of the present invention will be explained with the above configuration. One end of the workpiece 4 is chucked to a chuck 9, and the other end is supported by a center 7 after drilling a center hole. At this time, static pressure pads 14, 15, 16, 1
7 is supplied with hydraulic oil with zero differential pressure. In addition, hydraulic oil is supplied to the static pressure pad 13 at a constant supply pressure so that the center 7 supports the workpiece 4 and pushes the axial thrust with a force as if both were one body. has been done. Next, the workpiece 4 is rotated and cutting is performed. At this time,
The spindle 3 is thermally deformed due to processing heat, for example,
Assuming that the axis of the main shaft 3 is displaced downward in the Y-axis direction by l, the displacement detector 10a detects +l, and the displacement detector 10b detects -l. So comparator 2
1 is the value of (Y _A - Y _B )/2, that is, a signal corresponding to l, and the static pressure pad 1 on the side where the value of +l was detected
4, a command signal is given to the servo valve 23 via the servo amplifier 22 to increase the supply pressure, and to the static pressure pad 15 on the side where -l is detected, to decrease the supply pressure. The servo valve 23 that receives this signal operates, applies a pressure difference between the output port 23a and the output port 23b, and supplies hydraulic oil with increased supply pressure to the conduction hole 14a directly connected to the output port 23a, and outputs Hydraulic oil with a reduced supply pressure is supplied to the guide hole 15a directly connected to the port 23b. Therefore, the center 7 is forcibly displaced downward on the Y-axis in the same manner as the displacement l of the main shaft 3. The above is a description of the Y-axis downward displacement, but it goes without saying that the center 7 can also be positioned in the X-axis direction or in the combined direction of the X and Y axes.

As described above, according to the center correction device for a machine tool of the present invention, the spindle displacement is automatically measured, the center position is corrected equal to the amount of displacement, and the axis of the workpiece and the moving direction of the cutter are kept parallel to each other. This has the effect of maintaining the cylindricity of the workpiece with high precision.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the outline of the machine of the present invention, Fig. 2 is a sectional view showing details of the tailstock, and Fig. 3 is an explanatory diagram showing the outline of the machine of the present invention.
FIG. 4 is a block diagram showing the control device of the present invention. 2... Headstock, 3... Main spindle, 8... Tailstock, 7... Center, 13, 14, 15, 16, 17... Static pressure pad, 10a, 10b, 10c, 10d... Displacement detector, 21, 21'... Comparator, 22, 22'... Servo amplifier, 23, 23'... Servo valve.

Claims (1)

[Claims] 1 A main spindle rotatably supported on a headstock provided at one end of the bed, a tailstock provided at the other end of the bed opposite to the headstock, and a radial displacement of the main spindle. four displacement detectors provided on the headstock in pairs passing through the axis of the main spindle to be detected; a hydrostatic bearing disposed inside the tailstock for bearing the center; A center correction device for a machine tool, comprising a control device comprising at least a comparator and a servo valve, which controls working fluid supplied to the hydrostatic bearing based on a signal from a displacement detector.