JPS5866641A - Fine feed device of spindle in machine tool - Google Patents

Abstract

PURPOSE:To finely feed a spindle in the direction of an axial line and perform its accurate feed, by supporting the spindle through a static pressure bearing in a freely rotating further floating state and finely changing pressure in a bearing part. CONSTITUTION:Pressure of oil is increased to a prescribed level by an oil hydraulic pump 8 and relief valve 16, on the one hand, the oil is reduced with its pressure to a certain level Ps by a pressure regulating valve 10 and fed into a lower thrust feed oil pocket 7A and journal feed oil pocket 5A. On the other hand, the pressure oil is controlled to pressure P2 by a variable pressure control valve 11 and fed into an upper thrust feed oil pocket 6A. A work table 19 can be finely moved to the axial direction by controlling the variable pressure control valve 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a micro-feeding device for a tool spindle or a workpiece spindle of a machine tool.

Traditionally, mechanical feed devices such as ball screws have been commonly used as feed devices for machine tool spindles, but there are deflection errors in the mechanical feed system, lead errors in the feed screws, and backlash errors in gears, etc., which are around 1 μm. It was very difficult to accurately transmit V.

The present invention aims to solve these problems,
The spindle is rotatably and floatingly supported by a hydrostatic bearing, and the fluid pressure supplied to the thrust bearing is slightly changed by a variable pressure control valve, and the spindle shaft is moved in the axial direction to achieve ultra-precision minute feed. This invention relates to a micro-feeding device for the spindle of a machine tool that makes it possible to do this.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. There is a radial clearance (5) between 3) and the bearing part (4).
Upper thrust clearance 1 (6) and lower thrust clearance (7
) is now formed. For this purpose, the bearing part (4) has a journal lubrication pocket (5A), an upper thrust lubrication pocket, and a lower thrust lubrication pocket (7A).
A plurality of each are provided. A rotary table 4 is attached to the upper end of the shaft portion (2) of the rotary hydrostatic spindle (2), and a pulley (1) for rotating the detail (3) of the rotary hydrostatic spindle is attached to the lower end. The journal oil supply socket (5A) is connected to the pressure regulating valve αO through the throttle C1:lk, and the lower thrust oil supply socket (7A) is connected to the same pressure regulation valve (1 (1) through the throttle (12).
is familiar with Upper thrust lubrication pocket (6A)
is connected to the variable pressure theory strain valve (11) VC through the restrictor (restriction).The pressure regulating valve (10) and nJ variable pressure regulating valve 01 are connected to the hydraulic pump (8) via the check valve (9). In addition, (IQ is IJ IJ-FHALF, 0η is the pump drive motor, (old hazard filter, Ql
) How Work Table (]!J) The workpiece is placed on the VC, and the arrow (A) shows the direction of the cutting feed.

The pressure oil, which has been raised to a predetermined pressure by the hydraulic pump (8) and the IJ-F valve OQ, is on the one hand passed through the pressure regulating valve (10).
The pressure is reduced to a predetermined constant pressure ps, and it passes through the throttle α2 to the lower thrust oil supply pocket (7A) and the throttle 0].
Through the journal oil supply pocket (5A) K feed 9 included'
: f 扛る. On the other hand, pressure oil controlled to a pressure kP2 by the flexible pressure control valve (11) is sent through the throttle (14) to the upper thrust oil supply socket (6A).

The current variable pressure adjustment valve θvV is set to the same pressure P2 as the E force adjustment valve (101, which is the same pressure ps.
The shaft part (3) has a soil Ft15 j with respect to the Tsukuda I receiving part (4).
- Suppose that the lower clearance (7) is at the position of θ2 at Kishi (6) or 01. Here, when the pressure P2 is increased by ΔP1 8E'f by the variable pressure regulating valve αη, the pressure supplied to the upper thrust oil supply socket (6A) increases, so the shaft part (3) is pushed up. and moves by a slight amount in the direction of the arrow (4) with respect to the bearing part (4). Furthermore, the pressure P2
If the pressure is increased by ΔP2, the shaft portion (3) further moves by i/rCδ2 in the direction of arrow ■a. At this time, the upper thrust clearance (6) becomes 01-δ1-δ2, and the lower thrust clearance (7) becomes e2+δ1+δ2.

Generally, f@1 of a hydrostatic bearing is e, +82=50
~60 μm, and the amount of movement is p S = 2
5 If Ky/al is used, P2 is 20s/d to 50'9
/lyJ, the overall reduction is about 10μ.
It is possible to move by m8 degrees. Further increase the pressure by 2 to 3 to 1/-
By changing the pressure by 0.5"F/cJ, it is possible to feed by about 0.2 μm.

Figure 2 shows the calculation results of the upper thrust supply pressure P2 adjusted by the variable pressure regulating valve in the rotary static pressure spindle and the amount of movement of the shaft of the hydrostatic bearing, which was performed on an actually manufactured rotary table. ·be.

In addition, since the 1911 part (3) is floating without making any contact with the bearing part (4), the movement of the shaft part (3) requires resistance on the contact surface that occurs with mechanical feeding. Moves smoothly without causing any errors. Furthermore, even if the shaft part (3) moves a small amount by sliding into the bearing part (4), the journal bearing is also under static pressure, so as a rotary static pressure spindle, it will not change l as a bearing in any way. do not have.

As described above, according to the present invention, the spindle is supported by a hydrostatic bearing, and the pressure supplied to the plow 1 is adjusted little by little by the pressure of the variable pressure regulating valve.
On the other hand, it is not only easy to make feeds in μm units, and even fine feeds in subμm units, but also enables precision feeds with little variation, so it is widely applicable to machine tools such as precision face lathes and low-pressure surface grinders. It can produce excellent effects.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a static pressure spindle as an example of a rotary table in which the present invention is implemented, and a hydraulic circuit diagram of a rotary table that uses all hydraulic circuits for static pressure. It is a graph showing the relationship between pressure P2 and the amount of movement of the shaft portion of the hydrostatic bearing. (2)...Rotary static pressure spindle (3)...Shaft part (4)...Bearing part (5
)...Journal groove (6) (7)...Thrust clearance (6AX7A)...Thrust feed r mountain pocket (8)...Pressure source (10)...Pressure control valve agent patent attorney Jun Kawauchi

Claims (1)

[Claims] A spindle of a machine tool is floatingly and rotatably supported by a pair of thrust bearings and journal bearings of a hydrostatic bearing, and at least one thrust oil supply pocket is connected to a pressure source via a variable pressure regulating valve. A minute feed device for a spindle of a machine tool, which is characterized by: