JP2525071Y2 - Rotary headstock for machine tools - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary headstock that supports a rotary shaft of a machine tool such as a main spindle for high-speed internal grinding.

2. Description of the Related Art Conventionally, a built-in motor is provided in a housing as a rotating headstock of a machine tool as described above, and the center of the rotating shaft is fitted and fixed to the rotor of the motor, and the rotating shaft projects from the rotor. In some cases, the two end portions are supported on the housing by ball bearings. Further, as the ball bearing, there has been one using a light ceramic ball in order to prevent heat generation of the bearing caused by centrifugal force acting on the ball.

In a rotating headstock of a conventional machine tool, when both ends of a rotating shaft are supported on a housing by bearings using ceramic balls as described above, the vibration of the ceramic is attenuated as compared with steel. Has a problem that the vibration of the rotating shaft increases. This invention solves the above-mentioned problems, reduces the vibration of the rotating shaft, and even if the rotating shaft rotates at high speed, can prevent problems such as seizure due to heat generation of the bearing part. It is an object of the present invention to provide a rotary headstock for a machine tool such as the above.

According to the present invention, in the above-mentioned rotary headstock of a machine tool, one of the two ends of the rotary shaft has a small diameter, the other has a large diameter, and the large-diameter end has a ceramic ball. The bearing is supported on the housing by a bearing, and the end on the small diameter side is supported on the housing by a steel ball bearing.

In the rotary headstock of the machine tool according to the present invention, the large-diameter end of the rotary shaft is supported by the housing by the ceramic ball bearing. Therefore, even if the rotary shaft rotates at high speed, the large-diameter end is maintained. Heat is less likely to be generated in the supporting bearing portion. Further, since the steel (SUJ) ball bearing has the same vibration damping ratio as that of the ceramic ball bearing by about 20 to 30% in the same model number, the end of the small diameter side of the rotating shaft is formed by the steel ball bearing. By supporting the rotary shaft on the housing, vibration of the rotary shaft can be reduced as compared with a conventional rotary headstock in which both ends of the rotary shaft are supported on the housing by ceramic ball bearings. In the steel ball bearing, only the small-diameter end of the rotating shaft is supported by the housing. The inner diameter of the steel ball bearing is smaller than the large-diameter end of the rotating shaft, and the rotating shaft rotates at high speed. However, since the centrifugal force acting on the steel ball bearing is small, the steel ball bearing portion is hardly seized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a high-speed internal grinding machine will be described below with reference to FIG. In FIG. 1, reference numeral 1 denotes a housing for a rotary headstock. The housing 1 includes a substantially cylindrical housing main body 2, a front cover 3 fixed to a front side 2a of the main body 2, and a rear side of the housing main body 2. The rear cover 4 fixed to the housing 2b and closing the rear end face of the housing 1 is configured as a main member. The stator 5a of the built-in motor 5 is fitted and fixed in the axial center portion 2c of the housing body 2 via the bush 7, and the center portion of the rotating shaft 6 is fitted to the rotor 5b rotatably fitted to the stator 5a. 6a is fitted and fixed. The rotating shaft 6 has a large diameter front end 6b protruding forward of the rotor 5b, and a holder 9 of a grindstone 8 is detachably supported on the front end 6b. Note that the grindstone 8 is disposed axially forward of the front cover 3 of the housing 1. The front cover 3 has a cylindrical portion 3a fitted and fixed in a small-diameter front side portion 2a of the housing body 2, and a large-diameter front end portion 6b of the rotary shaft 6 is fixed to the cylindrical portion by angular ceramic ball bearings 10,10. Part 3a
I support it. The ceramic ball bearing 1
Positions 0 and 10 are spaced from each other in the axial direction. Also, the front end of the front cover 3 and the front end 6b of the rotary shaft 6
And a non-contact type sealing mechanism 11 is interposed between them. In order to receive the grinding resistance applied to the grinding wheel 8, the rotating shaft 6
The diameter of the front end 6b and the ceramic balls 10, 10 is increased to increase the bearing rigidity. The housing body 2
The holding cylinder 12 is fitted and fixed to the inner peripheral surface of the rear side 2b, and the front end of the holding cylinder 12 is supported on the step 2d at the rear end of the small-diameter front side 2a of the housing body 2 via the bush 7, and the holding cylinder 12 The rear end is supported by the front end of the rear cover 4, and the presser cylinder 12 is positioned in the axial direction. A clamping cylinder 14 is supported in the holding cylinder 12 via a number of steel balls 13 so as to be movable in the axial direction of the rotating shaft 6. The rotary shaft 6 has a rear end 6c on the small diameter side in order to reduce the centrifugal force behind the rotor 5b of the built-in motor 5, and the rear end 6c is provided with an angular steel type (SUJ) ball bearing 15, 1
5, the holding cylinder 12, the steel ball 13 and the tightening cylinder 1
4 is supported on the rear side 2b of the housing main body 2. The steel ball bearings 15, 15 are provided with an interval between each other in the axial direction, and the inner ring is connected to the rear end 6c of the rotating shaft 6.
In addition, the outer ring is axially positioned on the tightening cylinder 14 respectively. Holes 12a are provided at a plurality of positions in the circumferential direction at the rear end of the holding cylinder 12, and a spring 16 fitted into these holes 12a is brought into contact with a flange 14a protruding toward the outer peripheral side of the rear end of the tightening cylinder 14. As a result, the tightening cylinder 14 is urged rearward in the axial direction of the holding cylinder 12. The preload is applied to the steel ball bearings 15 by this bias. In addition, an inlet 17a and an outlet 17b are formed in the housing 1 so that the fluid passage 17 is opened at the rear end of the rear cover 4.
The cooling liquid is supplied from the inlet 17a, and is injected through a cooling portion 17c between a spiral groove provided on the outer peripheral surface of the bush 7 and the inner peripheral surface of the central portion 2c of the housing body 2, and is discharged from the outlet 17b. It is configured to discharge. The rotating headstock according to the above-described embodiment includes ceramic ball bearings 10 and 1.
In a state where the preload is applied to the steel ball bearings 15 and 15, the built-in motor 5 is driven to rotate the rotating shaft 6, and the grinding wheel 8 rotates together with the rotating shaft 6.
The inner surface of a concave portion such as a hole of a workpiece is ground by using this method. In addition, this invention is not limited to the rotating headstock of the spindle for high-speed internal grinding, but can be widely applied to the rotating headstock of other machine tools.

As described above, the present invention is directed to a rotating shaft stand of a machine tool in which both ends of a rotating shaft are rotatably supported by a housing via ball bearings. , One with a small diameter, the other with a large diameter,
The large-diameter end is supported by the housing by the ceramic ball bearing, and the small-diameter end is supported by the housing by the steel ball bearing. The following effects are obtained. That is, in the rotary headstock of the machine tool according to the present invention, the large diameter end of the rotary shaft is supported by the housing by the ceramic ball bearing. Therefore, even if the rotary shaft rotates at a high speed, the ceramic ball is light. Heat generation is less likely to occur in the bearing portion supporting the radial end. In addition, steel (SUJ) ball bearings
Since the vibration damping ratio of the same model number is larger than that of the ceramic ball bearing by about 20 to 30%, both ends of the rotating shaft are supported by supporting the small diameter end of the rotating shaft to the housing by the steel ball bearing. The vibration of the rotary shaft can be reduced as compared with a conventional rotary headstock whose part is supported by a housing by a ceramic ball bearing. The steel ball bearing supports only the small-diameter end of the rotating shaft in the housing. The inner diameter of the steel ball bearing is smaller than the large-diameter end of the rotating shaft, and the rotating shaft rotates at high speed. However, since the centrifugal force acting on the steel ball bearing is small, the steel ball bearing is hardly seized. Therefore, according to the present invention, the vibration of the rotating shaft can be reduced, and even if the rotating shaft rotates at high speed, problems such as seizure due to heat generation of the bearing portion can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially cutaway longitudinal sectional view showing a rotary headstock of a machine tool according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 5 Built-in motor 6 Rotation shaft 6a Central part 6b Large diameter front end 6c Small diameter rear end 10 Ceramic ball bearing 15 Steel ball bearing

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho 62-138505 (JP, U) Japanese Utility Model Sho 60-103725 (JP, U) Japanese Patent Publication No. 52-38280 (JP, B2)

Claims (1)

(57) [Scope of request for utility model registration] 1. A rotating shaft base of a machine tool having both ends of a rotating shaft rotatably supported by a housing via ball bearings, wherein one of both ends of the rotating shaft has a small diameter and the other has a large diameter. A rotary headstock for a machine tool, wherein a large-diameter end is supported by the housing by a ceramic ball bearing and a small-diameter end is supported by the housing by a steel ball bearing.