JPH03111103A - Spindle stock with hybrid bearing - Google Patents

Abstract

PURPOSE:To obtain a spindle stock with a hybrid bearing, which enables us to carry out high precision machining in addition to high-speed and heavy load machining by using only one spindle stock, by giving a main bearing double structures, e.g. rolling bearing and static pressure bearing, and providing a switching means switching from the static pressure bearing to the rolling bearing. CONSTITUTION:When a main spindle 7 rotates at a low speed in accordance with a command from a controller 10, since frinctional resistance of a pre-loaded rolling bearing 5 greater than that of a static pressure bearing, an intermediate housing 4 rotates together with the spindle 7. When the spindle 7 rotates at this time, the rolling bearing 5 serves as a static pressure bearing. Next, when the rotating speed of the spindle 7 becomes a medium one according to a change of a command value from a controller 10, rotation is initiated between the housing 4 and the spindle 7, and a mixed bearing condition, or a combination of the rolling bearing 5 and static pressure bearing, appears. However, since a rotational difference between the housing 4 and the main spindle 7 is small, the rotation of the main spindle 7 is maintained basically under the action of the static pressure bearing. Next, when an electromagnetic disc brake 21 is applied by a programmed command in order to restrict the rotation of the housing 4, the spindle 7 is rotated on the rolling bearing 5. At this time, the temperature-regulated, pressure oil supplied static pressure pads 12a to 12c gives the bearing 5 a cooling effect, while it gives the spindle 7 a damping capacity against the vibration through the static pressure plane.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improved headstock for G bearings.

Conventional technology Conventionally, bearing number 51 for the main spindle used in the 8-fold spindle of -L machine tools, static pressure bearings were used for relatively high precision machining: J:
Rolling bearings are generally used for high-speed single-layer cutting.

Problems to be Solved by the InventionL7 The rolling bearings described in the conventional technology have low damping properties against vibrations, so they tend to cause chatter during cutting, which has a negative effect on the roughness of the finished surface. However, hydrostatic bearings have good vibration damping properties and are suitable for high-precision machining that requires good surface roughness, but they are not suitable for high-speed rotation or high-speed rotation. The problem is that it is not suitable for heavy cutting.

The present invention was made in view of the above-mentioned problems of the conventional technology, and its purpose is to provide a hybrid chisel bearing headstock that can perform high-precision machining and high-speed single-cutting with a single headstock. It is something that is intended to be done.

Means for Solving the Problems In order to achieve the above object, the hybrid bearing of the present invention has a spindle having a two-F bearing having a double structure of a rolling bearing and a hydrostatic bearing, and a means for switching to the rolling bearing. It has been established.

When the main shaft is rotated by a main bearing with a knee-heavy structure in the low to medium speed range, a double-rolled bearing with less preload has a higher kinetic frictional resistance than a hydrostatic bearing, so a hydrostatic bearing The spindle is rotated and becomes a high-precision headstock. When the static pressure bearing portion is fixed by the switching means and the main shaft is rotated by the rolling bearing, a high-speed single-cutting type headstock is obtained.

Example An embodiment will be described with reference to FIG.

In a well-known machine tool headstock, a rear housing 2 is fitted into a small diameter hole 1a of a stepped hole drilled in a headstock body 1, and a front housing 2 is fitted on the front end surface of the main body 1 concentrically with the stepped hole. Housing 3 is fixed.

An intermediate housing 4 having flanges at both ends is rotatably supported in the center hole of the front housing 3, and a plurality of bearings 5 are fitted in the center hole of the intermediate housing 4 and the center hole of the rear housing 2. A main shaft 7 is rotatably supported by a bearing 6 fitted in the main shaft 7 . A motor housing 8 having heat radiation fins on the outer periphery is fitted into a large diameter hole 1b on the rear side of the stepped hole of the headstock body 1, and the rotation speed is controlled by a control device 10 in the center hole of the motor housing 8. A stator 9A of the built-in motor 9 is fitted, and a rotor 9B is fitted at a corresponding position on the main shaft 7. A center hole 3a of the front housing 3 and both sides 3b of the center hole.

3C, static pressure pads 12a, 12b12c are respectively carved, and pressure oil is supplied to the static pressure pads 12a, 12b, 12c through throttles 13a, 13b, 13c, and the outer housing 3 A hydrostatic bearing in the journal direction and the thrust direction is constructed between the intermediate housing 4 and the intermediate housing 4. The pressure oil supplied to this hydrostatic bearing is oil whose temperature is controlled by an oil temperature controller 15, which is supplied by a hydraulic pump 16 through a pipe line 17, and then through a pipe line 18 that branches from the middle of the pipe line 17 to the motor housing. The oil is also supplied to an oil jacket having eight outer radiating fins to cool the built-in motor 9. Furthermore, a brake disc 20 is fixed concentrically to the right end of the intermediate housing 4, and an electromagnetic brake 21 is attached to the headstock main body 1 at a corresponding position. In this electromagnetic disc brake, a solenoid is actuated by a command from a program of a control device 10 to apply brakes on both ends of the outer circumference of the brake disc 2o to restrict rotation of the intermediate housing 4.

Next, the operation of this embodiment will be explained.

Pressure oil whose temperature is controlled by the oil temperature controller 15 is now supplied to the static pressure pads 12a to 12C of the front housing 3 through the throttles 1.3a to 13c, and static pressure is created between the front housing 3 and the intermediate housing 4. A pressure bearing is configured, the solenoid of the electromagnetic brake 21 is de-energized, and the intermediate housing is allowed to rotate.

The main shaft 7 is activated by the built-in motor 9 according to the command from the control device IO.
When the is rotated at a low speed, the rolling bearing 5 to which a preload is applied has greater kinetic frictional resistance than the static pressure bearing, so the intermediate housing 4 rotates together with the main shaft 7, and the front bearing side becomes a static pressure bearing. The main shaft 7 is rotated.

Next, when the rotational speed command value of the control device 10 changes and the main shaft 7 is rotated at a medium speed, rotation also occurs between the intermediate housing 4 and the main shaft 7, resulting in a bearing state in which a rolling bearing and a hydrostatic bearing are mixed. However, the difference in rotation between the intermediate housing and the main shaft is small, and basically the main shaft rotation is maintained by the hydrostatic bearing.

Next, when the solenoid is energized by a program command and the electromagnetic disc brake is activated to restrict the rotation of the intermediate housing 4, the main shaft 7 is rotated by the rolling bearing 5, and the static pressure pads 12a to 12c are The temperature-controlled pressure oil sent has a cooling effect on the rolling bearing and a static pressure surface that provides vibration damping properties to the spindle, eliminating the risk of seizing accidents and chatter during cutting due to high-speed rotation of the spindle 7. However, the main spindle 7 is rotated at high speed according to the high speed rotation command of the program, and heavy cutting work is performed.

Effects of the Invention Since the present invention is configured as described above, it produces the following effects.

The main bearing has a dual structure of a rolling bearing and a hydrostatic bearing.
Since it can be switched according to the application, high-precision machining using a static pressure bearing and high-speed single-layer cutting using a rolling bearing + two can be achieved with a single headstock.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the high cylinder bearing headstock of this embodiment, including a partial block diagram. 5...Rolling bearing +2a, 12b, 12cm-static pressure vanod 13a, 13)
), ], 33cm ・Aperture 20・・Brake disc 21・・Electromagnetic brake

Claims (1)

[Claims] (1) The main bearing is a rolling bearing (5) and a hydrostatic bearing (12a).
~12c, 13a~13c) A hybrid bearing headstock characterized in that it has a double structure and is provided with switching means (20, 21) for switching to the rolling bearing.