JPH03318A - Bearing support device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a bearing support device for a high-speed rotating shaft used in an internal grinder of a machine tool or the like.

[Conventional technology]

High-frequency motor spindles and the like used in internal grinders of machine tools are required to have high precision, high rigidity, and high-speed rotation. For this purpose, an angular contact bearing or the like is used as the bearing that supports the spindle, and a preload is applied to the bearing in the axial direction by a coil spring or the like. In such a bearing structure, when the spindle is rotating at high speed, the centrifugal force of the bearing rolling elements increases, causing a significant increase in the surface pressure on the outer rolling surface of the bearing rolling elements, causing heat generation in the bearing. The amount may become large enough to cause thermal deformation of the entire spindle. Furthermore, when the spindle is heated and thermally expanded, the bearing is compressed, causing a further increase in the amount of heat generated, and the bearing may seize.

Therefore, conventionally, a bearing support device as shown in FIG. 3 has been proposed. In this device, the spindle shaft 1
is supported at both ends within the housing 2 by a front (output shaft) side angular contact ball bearing 3 and a rear side angular contact ball bearing 4, and the inside of the motor stator 5 fixed to the housing 2 is fixed to the spindle shaft 1. The motor rotor 6 rotates. The angular contact ball bearing 4 on the rear side is press-fitted into a cylindrical sleeve 7, and between the outer circumferential surface 8 of this sleeve 7 and the inner circumferential surface 9 of the housing 2,
A ball bush 10 is provided to allow the sleeve 7 to move in the axial direction.

Further, a coil spring 13 is interposed between the rear end 11 of the sleeve 7 and the housing inner surface 12 facing the end 11, and applies preload to the sleeve 7 toward the left in the figure. There is. As a result, even if the spindle shaft 1 is deformed due to thermal expansion, the sleeve 7 together with the spindle shaft 1 can freely move in the axial direction inside the housing 2 via the ball bushing 10, while the preload in the axial direction is applied from the coil spring 13. A constant value is added to the bearing 4 and spindle shaft 1 via the sleeve 7.

FIG. 4 is a diagram showing another conventional bearing support device, in which the rear angular contact ball bearing 4 is press-fitted into a sleeve 21 that is movable in the axial direction within the housing 2; An O-ring 22 is placed between the inner peripheral surface of the housing 2
A coil spring 23 is interposed between the housing 2 and the sleeve 21 to apply an axial preload to the sleeve 21. Therefore, even if the spindle shaft 1 is deformed due to thermal expansion or the like, the sleeve 21, to which a certain preload is applied by the coil spring 23, slides in the housing 2 in the axial direction via the O-ring 22, and this causes the spindle shaft to deform. A constant preload is always applied to the shaft 1.

[Problem to be solved by the invention]

However, in the conventional device shown in FIG. 3, by reducing the gap between the ball bush 10 and the housing 2 and the gap between the ball bush 10 and the sleeve 7, the accuracy in the radial direction is improved and the rigidity is improved. Although this is possible, there is a problem in that the rolling resistance of the ball bush 10 becomes large and it becomes difficult to apply a minute preload to the spindle shaft 1.

Further, in the conventional device shown in FIG. 4, there was a problem that the rigidity was reduced due to the elasticity of the O-ring 22.The present invention was made to solve the above problem, and the It is an object of the present invention to provide a bearing support device that has high precision and high rigidity by applying an appropriate preload, and is capable of high-speed rotation.

[Means to solve the problem]

In order to achieve the above object, a bearing support device according to the present invention includes a fixed side bearing that supports a front portion of a rotating shaft within a housing, and a fixed side bearing that is disposed within an inner circumferential wall of the housing with a gap therebetween, a cylindrical sleeve to which a preload is applied so as to be movable in the axial direction; an outer ring mounted within the sleeve; a free side bearing supporting the rear part of the rotating shaft; It is equipped with a flow path for supplying.

[Effect]

According to the present invention having the above configuration, by supplying pressure fluid to the gap between the cylindrical sleeve and the inner circumferential wall of the housing, the frictional resistance between the sleeve and the housing becomes extremely small, and the sleeve smoothly moves in the axial direction. It becomes possible to move.

〔Example〕

An embodiment embodying the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a bearing support device according to the present invention, and as shown in the figure, the housing 3° includes a front housing 31 and a rear housing 32 fitted and fixed thereto.
and a journal bushing 38 (described later) fixed to this rear housing 32.
A drive motor stator 33 is incorporated in the inner central portion of the motor. A spindle shaft 34 as a rotating shaft is disposed within the housing 30, and the front portion (output shaft side) and rear portion of this shaft 34 are supported by rolling bearings. That is, the front part of the spindle shaft 34 is
The rear part of the spindle shaft 34 is supported in the front housing 31 by a fixed side angular contact ball bearing 35 as a fixed side bearing press-fitted into the shaft 34, and a free side angular contact ball bearing 36 as a free side bearing press-fitted into the shaft 34. It is supported within the rear nozzle housing 32. A motor rotor 37, which is disposed opposite to the motor stator 33, is press-fitted into the center of the spindle shaft 34 by shrink fitting, and the motor stator 33 and motor rotor 37 rotate the spindle shaft 34.
drive the rotation.

A journal bushing 38 having a cylindrical inner surface (cylindrical in this embodiment) is press-fitted into the rear housing 32 and fixed thereto.
A cylindrical (cylindrical in this embodiment) sleeve 39 is disposed within the inner circumferential wall of this journal bushing 38 with a gap 40 in between. Preload is added. The outer ring 41 of the free side angular contact ball bearing 36 is press-fitted and fixed into the sleeve 39.

A flow path 42 is formed within the housing 30 for supplying compressed air as a pressure fluid to the gap 40 . This flow path 42 is formed inside the rear housing 32,
A compressed air supply passage 43 for introducing compressed air supplied from the outside into the bearing, and a plurality of compressed air supply passages 43 formed in the journal bushing 38 and communicating with the passage 43 and for jetting compressed air into the gap 40. It is composed of a diaphragm 44. Therefore, when compressed air is supplied to the compressed air supply passage 43, this compressed air is passed from the throttle 44 to the sleeve 39.
The sleeve 39 is ejected into the gap 40 between the journal bushing 38 and the air bearing, and the sleeve 39 becomes a shaft constituting an air bearing and is held floating in the center of the journal bushing 38. This allows the sleeve 39 to move smoothly in the axial direction with extremely low friction.

A hydrostatic thrust air bearing is configured between the rear end surface 45 of the sleeve 39 and the journal bushing inner surface 46 opposite to this end surface 45, and the sleeve 3 is
By pressing 9 forward (to the left in the figure), a preload is applied to the angular contact ball bearings 35 and 36. That is, a passage 47 for supplying compressed air is formed in the rear housing 32, and a passage 47 is formed in the journal bushing 38.
A plurality of apertures 48 are arranged in an annular manner to communicate with the journal bushing and to blow out compressed air from the inner surface 46 of the journal bushing. Also, the four detents are engaged with the sleeve 39 and the journal bushing 38, so that the sleeve 39
is prevented from rotating.

Therefore, in the bearing support device configured as described above, compressed air passes through the passage 47 and is ejected from the throttle 48, so that the sleeve 39 is pressed forward and preloaded. By jetting into the gap 40 through the passage 43 and the restriction 44,
The three sleeves are held without contact with the journal bushing 38.

Therefore, even if the change in the preload applied to the sleeve 39 is minute, the sleeve 39 will move smoothly in the axial direction due to the hydrostatic air bearing in response to the change in preload.
Even when the spindle shaft 34 is rotating at high speed, an appropriate preload can be applied to the bearings 35, 36 through the three sleeves.

Further, by pressurizing the three sleeves with air pressure or a coil spring, a small preload can be applied to the bearing.

Furthermore, by setting the air bearing area of the sleeve 39 to be larger than the outer ring surface of the bearing 36, the sleeve 39 is precisely and highly rigidly held at the center of the inner diameter, resulting in high precision and
A highly rigid bearing support device can be constructed.

FIG. 2 is a partial sectional view showing another embodiment of the present invention,
In this embodiment, as a means for pressing the sleeve 39 forward, a pressure ring 62 is screwed into the inside of the journal bushing 61 instead of the thrust air bearing, and the annular groove 63 on the end surface of the pressure ring 62 and the sleeve end surface 45 An O-ring 64 as an elastic body is interposed between the two. Therefore, if the pressure ring 62 is rotated and slightly moved in the axial direction, the
The ring 64 is deformed and a preload is applied to the sleeve 39, causing the sleeve 39 to move smoothly in the axial direction.

By the way, the O-ring 64 also acts as a damper in the axial and radial directions, and may be made of other than the O-ring as long as it is an elastic body.

Incidentally, the present invention can also be used in a driving part of a centrifugal separator.

Although compressed air is used as the pressure fluid in each of the above embodiments, other fluids such as pressure surfaces may be used. Further, the outer peripheral shape of the sleeve 39 only needs to be cylindrical, and may be a polygonal cylindrical shape other than a cylindrical shape.

〔Effect of the invention〕

As is clear from the detailed description above, according to the present invention, the sleeve can move in the axial direction with extremely low friction.
It becomes possible to apply an appropriate preload to the bearing regardless of the rotation speed of the rotating shaft, and there are effects of high precision and high rigidity, and high speed rotation.

35... Fixed side bearing (fixed side angular contact ball bearing), 3
6... Free side bearing (free side angular contact ball bearing), 40
... Gap, 41... Outer ring, 42... Channel.

Claims (1)

[Claims] A fixed side bearing that supports the front part of the rotating shaft within the housing, a cylindrical sleeve disposed with a gap within the inner circumferential wall of the housing and preloaded to be movable in the axial direction, and an outer ring. A bearing support device comprising: a free-side bearing mounted in the sleeve to support a rear part of the rotating shaft; and a flow path formed in the housing to supply pressurized fluid to the gap. .