JPH08174306A - Variable pre-load bearing - Google Patents

Abstract

PURPOSE: To realize low speed high rigidity and high speed operation by applying pre-load uniformly in radial direction in a bearing supporting a spindle. CONSTITUTION: A pre-load adjusting ring 9 is disposed between an outer ring 5 of a cylindrical roller bearing 3 supporting a spindle 2 and a housing so as for it to freely contract/expand in radius. Positioning in radial expansion of the ring 9 is made with the housing 1, and positioning in radial contraction is made with a shoulder portion of a gap washier 8, 8. Groove is disposed on outer periphery of the pre-pressure adjusting ring 9, and oil pressure or air pressure is supplied to an discharged from the groove with a supply portion 11. And thus, in the cylindrical roller bearing 3, changeover between heavy pre-load and light pre-load at specific position becomes possible, so that oil. pressure or air pressure is exerted over whole periphery of groove and thus the pre-load adjusting ring and the outer ring 5 are uniformly contracted in radius.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preload variable bearing unit capable of adjusting the amount of preload in a radial direction of a rolling bearing that supports a rotating main shaft to obtain high rigidity and high speed of the main shaft. .

[0002]

2. Description of the Related Art Conventionally, a spindle of a machine tool is operated by applying a required preload to a bearing that supports the spindle in order to obtain the rotational accuracy and rigidity of the spindle.

In such a machine tool, when the main shaft is rotated at a high speed with a large initial preload, the bearing is overloaded and a large amount of heat is generated, which may cause a problem.

On the contrary, if the initial preload is set small so that the main shaft can rotate at high speed, the preload at low speed rotation becomes insufficient, and there is a problem that high rigidity cannot be obtained at low speed rotation.

In order to deal with the above problems, a cylindrical roller bearing or an angular contact ball bearing is used as the spindle bearing, and the amount of preload applied in the radial direction of this bearing is made variable so that heavy preload and high speed rotation are possible in the low speed rotation range. Then, the present applicant has proposed a bearing unit of variable preload type that can be switched to a light preload in Japanese Patent Application No. 5-174018.

3A and 3B show an example in which the cylindrical roller bearing of the above bearing unit is used. The cylindrical roller bearing 3 is housed in the housing 1 and rotatably supports the main shaft 2.
Has a structure in which the inner ring 5 supports the main shaft 2, and the outer ring 7 is fitted on the outer side of the inner ring 5 via a large number of rollers 6.

Spacers 8, 8 are provided on both sides of the cylindrical roller bearing 3 in the housing 1 for abutting against the side surface of the outer ring 7 for positioning and holding the bearing 3 in the thrust direction.
Further, a preload adjusting ring 9 capable of reducing the diameter is arranged between the outer peripheral surface of the outer ring 7 and the inner peripheral surface of the housing 1.

The preload adjusting ring 9 is wider than the outer ring 7 and is an O-ring 1 which is pressed against the housing 1 on both sides of the outer peripheral surface.
0 and 10 are provided, and the inner peripheral surface of the outer ring 7 is fitted so as to always come into contact with the outer ring 7, and the diameter can be reduced and expanded freely.
It is movable in the housing 1 in the radial direction.

Reference numeral 11 in the drawing is a supply portion for supplying a pressurized fluid such as hydraulic pressure, and 13 is a passage for air-oil lubrication provided in the spacer 8.

FIG. 3 (A) shows a state of heavy preload in which pressurized fluid is supplied to the pressurized fluid supply section 11. The preload adjusting ring 9 is reduced in diameter until the outer ring 7 contacts the shoulder 12 of the spacer 8. The bearing clearance is small in this state, and it is suitable for low speeds where spindle rigidity is required.

On the other hand, FIG. 3B shows a state in which the pressure fluid is off, and the outer peripheral surface of the preload adjusting ring 9 is in contact with the inner peripheral surface of the housing 1. In this state, the bearing clearance is large and the cylindrical roller bearing is large. A light preload is applied to No. 3 so that the spindle 2 can be operated at high speed.

As described above, by supplying / discharging the pressure fluid, it is possible to switch the two-stage fixed position preload in the radial direction, that is, heavy preload and light preload, and by switching the pressure fluid on and off during operation, A preload variable bearing unit having a clearance or preload characteristic as shown in FIG. 4 can be obtained.

By the way, in the above-mentioned preload variable bearing unit, the pressure of the pressure fluid is applied to the fitting portion of the housing 1 and the preload adjusting ring 9 to reduce the diameter of the preload adjusting ring 9 and the outer ring 7 to adjust the bearing clearance. It is necessary to reliably apply the pressure fluid to the entire circumference of the outer diameter surface of the preload adjusting ring 9.

[0014]

However, in the above-mentioned preload variable bearing unit, it is necessary to aim the clearance between the housing and the preload adjusting ring to zero by securing the rotation accuracy of the main shaft after the bearing is assembled. Therefore, the opening end of the pressure fluid supply unit facing the fitting portion is closed by the outer diameter surface of the preload adjusting ring, and when the pressure fluid is supplied from the supply unit when the heavy preload is introduced, the pressure fluid becomes It acts locally on the outer diameter surface of the preload adjusting ring that faces the supply portion, and becomes uneven over the entire circumference of the outer diameter surface.

Therefore, an object of the present invention is to provide a preload variable bearing unit in which the pressure fluid can be made to uniformly act on the entire outer peripheral surface of the preload adjusting ring and the heavy preload of the bearing can be surely introduced. To provide.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention makes the pressure fluid from the supply portion act uniformly on the fitting portion of the housing and the preload adjusting ring. It adopts a configuration in which the groove is provided.

[0017]

[Operation] When heavy preload is introduced into the rolling bearing, if pressure fluid is supplied from the supply part, the pressure fluid passes through the groove and acts on the entire circumference of the outer diameter surface of the preload adjusting ring. Can be uniformly reduced in diameter.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. The basic structure of the preload variable bearing unit is the same as that described in the section of the related art shown in FIGS. 3 (A) and 3 (B), and therefore the same parts are designated by the same reference numerals. Instead of.

In the first embodiment shown in FIGS. 1A and 1B, on the outer diameter surface of the preload adjusting ring 9 fitted in the housing 1, there are concentric circles located at both ends of this outer diameter surface. Groove 2
1, 21 and both grooves 21, 21 are located between both grooves 21,
A spiral groove 22 that communicates with 21 is provided, and the pressure fluid supply unit 11 communicates with one groove 21.

The first embodiment of the present invention has the above-described structure, and when the heavy preload is introduced, the pressure fluid from the supply portion 11 initially flows from one groove 21 to the spiral groove 22 and the other groove 21.
And acts on the entire grooves 21, 21 and the spiral groove 22 to slightly contract the preload adjusting ring 9. And
When the preload adjusting ring 9 contracts, a clearance is created between the inner peripheral surface of the housing 1 and the groove forming projection 23, and the pressure fluid acts on this clearance, so that the preload adjusting ring 9 has a uniform outer diameter surface. The outer ring 7 is uniformly contracted, and a heavy preload is applied to the cylindrical roller bearing 3.

When the supply of the pressure fluid is released, FIG.
As shown in (A), the groove forming projection 23 of the preload adjusting ring 9 comes into contact with the inner peripheral surface of the housing 1 so that the fitting clearance is substantially zero.

Next, in the second embodiment shown in FIGS. 2A and 2B, the shallow and wide groove 2 is formed on the outer peripheral surface of the preload adjusting ring 9.
4 is provided over the entire circumference, and groove forming projections 25 are formed on the outer peripheral surfaces of both ends.

The width of the groove 24 is larger than the width dimension of the outer ring 7 fitted to the inner peripheral surface in order to make the outer ring 7 contract uniformly.

Also in this second embodiment, the supplied pressure fluid acts on the entire circumference of the groove 24, and the outer ring 7 can be uniformly reduced in diameter.
As shown in (A), the groove forming protrusions 25, 25 on both sides contact the inner peripheral surface of the housing 1.

In both of the examples, the groove is provided on the outer diameter surface of the preload adjusting ring in the above example, but the inner peripheral surface of the housing 1 is shown in the first and second embodiments. You may provide the groove similar to that. Further, as the bearing, an angular ball bearing may be used instead of the cylindrical roller bearing.

[0026]

As described above, according to the present invention, since the groove is provided in the fitting portion of the housing and the preload adjusting ring,
The pressure fluid can be uniformly applied to the entire outer diameter surface of the preload adjusting ring, and the preload on the rolling bearing can be reliably performed.

[Brief description of drawings]

FIG. 1A is a longitudinal sectional view of a main part of a preload variable bearing unit according to a first embodiment of the present invention in a light preload state, and FIG.
Is a front view showing the preload adjusting ring of the above.

FIG. 2A is a longitudinal sectional view of a main part of a second embodiment in a light preload state, and FIG. 2B is a front view showing the preload adjusting ring of the same.

FIG. 3A is a vertical sectional view showing a heavy preload state of a conventional preload variable bearing unit, and FIG. 3B is a vertical sectional view showing the same light preload state.

[Fig. 4] Preload characteristic diagram for cylindrical roller bearings

[Explanation of symbols]

 1 Housing 2 Spindle 3 Cylindrical Roller Bearing 5 Inner Ring 6 Roller 7 Outer Ring 8 Spacer 9 Preload Adjusting Ring 11 Pressurized Wash Body Supply Port 21 Groove 22 Spiral Groove 23, 25 Groove Forming Protrusion 24 Groove

Claims (1)

[Claims] 1. A preload adjusting ring whose diameter can be changed is provided between an outer ring of a rolling bearing and a housing holding the bearing, and the preload adjusting ring is positioned in the radial direction in the housing to reduce the radial direction. A preload variable bearing unit in which spacers arranged on both sides of the outer ring are used for positioning, and a pressure fluid supply portion serving as a means for reducing the diameter of the preload adjustment ring is provided at a position corresponding to the outer diameter surface of the preload adjustment ring of the housing. The preload variable bearing unit according to claim 1, wherein a groove for allowing the pressure fluid from the supply section to act uniformly on the preload adjusting ring is provided in the fitting portion of the housing and the preload adjusting ring.