JPH0737811B2 - Spindle device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle device for machine tools.

[0002]

2. Description of the Related Art In a spindle device of a machine tool axially supported by a front bearing and a rear bearing, a preload is applied to the front bearing and the rear bearing in order to improve the spindle rigidity and the accuracy of shaft runout. There is. The front bearing supports the tip end side of the main shaft on which the tool is mounted, and the rear bearing supports the rear end side of the main shaft. This preload is applied by constantly applying a constant amount of preload to the bearing with a coil spring, etc., even if the dimension between the bearings expands due to thermal displacement of the main shaft, etc. In general, it is responded by sliding in the direction through the sliding portion.

To further explain, as shown in FIG. 2, in the conventional method, a main shaft 5 is rotatably supported by a front bearing 3 and a rear bearing 4 in a housing 2 of a main spindle head 1. Front bearing 3 is
As shown, two are used in combination, either
Can withstand both axial and radial loads
Configured as a front bearing unit
It By the way, heat generation and conduction from the built-in motor 9,
Alternatively, since the main shaft 5 is heated and expands / deforms due to heat generation of the bearing due to rotation, etc.
In order to cope with the thermal deformation of the housing, the bearing case 6 that supports the outer race of the rear bearing 4 is
Is supported on the inner wall of the housing by fitting, and elastic force is applied in the rear direction by the coil spring 7 provided between the rear bearing 4 and the housing 2 even if the main shaft 5 is thermally deformed. Since the main shaft is displaced in the direction, and the front side of the main shaft is supported by the housing 2 via the front bearing 3, it is configured so as to be hardly displaced.
The reason why the rear bearing case 6 is displaced without displacing the front side is that the machining accuracy is not adversely affected.

In the figure, reference numeral 8 is a front bearing retainer, 9 is a built-in motor, and it is composed of a rotor 5a attached to the main shaft 5 side and a stator 9b provided on the inner wall of the housing, and 10 is an outer wall of the rear bearing case 6 and a housing. The sliding surface with the inner wall 2 and the coil spring 7 are provided between the upper edge portion 2a of the housing 2 and the upper end flange 6a of the rear bearing case.

[0005]

By the way, in the configuration shown in FIG. 2, the rear bearing case 6 is provided in the housing 2.
In contrast, since it is moved by sliding, the stability of the thermal displacement at the tip of the main shaft 5 (variation at the start of rotation, ripple at constant rotation) is impaired if required in the order of microns. There are the following factors. The rear bearing position varies in the radial direction by the amount of clearance required for the fitting of the housing 2 and the rear bearing case 6. A stick-slip phenomenon occurs due to sliding friction between the housing 2 and the rear bearing case 6. The vibration is transmitted to the sliding surface 10 between the rear bearing case 6 and the housing 2, and if it is for a long period of time, a fretting phenomenon occurs in which the sliding surface 10 is roughened.

Incidentally, FIG. 3 shows the relationship between the time as the unstable element of the thermal displacement of the spindle when a constant rotation is applied and the thermal displacement of the tip of the spindle. As described above, the thermal displacement of the tip of the main spindle not only has large fluctuations at the start of rotation, but also ripple fluctuations appear at constant rotations.

Therefore, according to the present invention, by supporting the rear bearing case in a form having no sliding portion, the followability of the casing to the variation of the dimension between the bearings is enhanced, the inconvenience in the above-mentioned conventional system is eliminated, and the tip of the main spindle is eliminated. The purpose is to improve the stability of thermal displacement.

[0008]

[Means for Solving the Problems] The present invention is configured as follows to achieve the above object. The spindle was rotatably supported by bearings in the housing of the spindle head .
In the spindle device, the front bearing unit
The front part of the spindle against the housing.
Support so that it does not move in the
Install the rear bearing and attach the outer
-Axial rear bearing case that supports the race
Provided with freely move in a direction, the radial direction of the gap between the outer peripheral surface and the inner wall surface of the housing of the rear bearing case provided, at least two spaced a gap axial direction on an outer peripheral portion of the rear bearing case of the thin plate member is fixed parallel to the, the outer peripheral portion of the thin plate member also fixed to the housing, Shinano maintaining said spindle and concentricity of the rear bearing case can be moved with a small force in the Raa Kisharu direction A spindle device, which is configured to be provided with a predetermined rigidity in a radial direction, and provided with elastic means for applying a predetermined elastic force in an axial direction between the housing and the rear bearing case.

[0009]

According to the present invention, since the rear bearing case is supported by at least two thin plate members (diaphragms), the rear bearing case is easily elastically displaced in the axial direction and is supported with high rigidity in the radial direction. It will be. The case can be made to cope with thermal displacement in the axial direction while maintaining the coaxiality with the main shaft, and the tip of the main shaft fluctuates due to stick-slip phenomenon caused by sliding friction with the housing and fretting phenomenon caused by vibration. A spindle device without

[0010]

1 is a sectional view of a machine tool spindle device according to the present invention taken in the spindle direction, and FIG. 2 is a sectional view of a conventional device.
FIG. 3 is an explanatory diagram showing fluctuations due to thermal displacement of the spindle by a conventional device.

FIG. 1 shows a cross section of a spindle device according to the present invention. However, in the present invention, a mutual relationship between a rear bearing case 10 and a spindle head 1 is different from that in FIG. 2 showing a conventional device. Therefore, the same reference numerals are used for the other parts, and the description thereof will be omitted.

As shown in FIG. 1, the rear bearing case
The outer peripheral surface of 11 faces the inner wall of the housing 2 with a gap 12 therebetween, and the outer peripheral surface of the rear bearing case 11 has two thin plate members (diaphragms) 13 spaced apart in the longitudinal axis direction, 14 is mounted perpendicular to the axis,
The outer peripheral edges of the two diaphragms 13 and 14 are fitted into an annular recess 15 formed on the inner wall of the housing 2 of the spindle head 1, and the annular collar 16 is provided between the two diaphragms 13 and 14.
In the inserted state, it is fixed by the diaphragm retainer 17 from the rear end side of the housing 2.

The rear bearing case 11 is held at that position by the front bearing 3 by inserting the coil spring 7 between the flange 11a of the rear bearing case 11 and the diaphragm retainer 17 as in the conventional example. An elastic force in the rear direction is applied to the rear portion of the main shaft 5, which allows the position variation due to the thermal displacement of the main shaft to be dealt with by the elastic deflection of the two diaphragms 13 and 14 in the axial direction, and with a space therebetween. Two diaphragms provided 1
The support of Nos. 3 and 14 prevents the central axis of the main shaft from falling. In addition, three or more diaphragms may be provided as needed. The front bearing 3 is shown in the figure.
It is used by combining two as shown in
Can withstand both char load and radial load
It is configured as a front bearing unit.

[0014]

According to the present invention, the positional variation due to the thermal displacement of the main shaft is caused by the two thin plate members 13 and 14 which are provided in parallel between the bearing case 11 and the housing 2 with a gap in the axial direction. Since the structure is adapted by holding the main shaft, the following effects can be obtained.

By utilizing the directional characteristics of the thin plate member, it is possible to easily bend in the axial direction but to secure a predetermined rigidity in the radial direction. Further, by utilizing the elastic displacement of the thin plate member, backlash and hysteresis are eliminated, and the followability is good. Since the rear bearing case is supported by the two thin plate members, the outer wall of the bearing case faces the inner wall of the spindle head housing with the gap 12 therebetween, so that sliding friction between the housing and the bearing case does not occur.
Stick-slip due to the same friction does not occur. Further, in the conventional device, the above-mentioned slip fit is a gap of about 5 μm in actual combination, and the hardness difference is prevented against fretting, but such consideration is unnecessary. Since the bearing case is supported by arranging the two thin plate members at a distance, the central axis of the main shaft does not fall and the coaxiality between the main shaft and the rear bearing case is maintained.

[Brief description of drawings]

FIG. 1 is a sectional view of a machine tool spindle device according to the present invention taken in the spindle direction.

FIG. 2 is a sectional view of a conventional device similar to FIG.

FIG. 3 is an explanatory diagram showing fluctuations due to thermal displacement of a spindle in a conventional device.

[Explanation of symbols]

 1 spindle head 2 housing 3 front bearing 4 rear bearing 5 spindle 6 rear bearing case 7 coil spring 8 front bearing retainer 9 built-in motor 10 sliding surface 11 rear bearing case 12 gap 13 diaphragm 14 diaphragm 15 annular recess 16 annular collar 17 diaphragm retainer

Claims (1)

[Claims] 1. A bearing is provided in the housing of the spindle head .
Ri in the spindle apparatus rotatably supported main shaft, Freon
The front part of the main shaft is
Do not displace in the axial direction with respect to the housing
Support, install a rear bearing on the rear part of the main shaft,
A rear base that supports the outer race of the rear bearing.
If the mounting case is provided so as to be movable in the axial direction,
Further , a radial gap is provided between the outer peripheral surface of the rear bearing case and the inner wall surface of the housing, and at least two thin plate members are arranged in parallel with each other in the outer peripheral portion of the rear bearing case with an axial gap. Fixed,
The outer peripheral portion of the thin plate member also fixed to the housing, the <br/> the rear bearing cases to maintain the main shaft and concentricity can move with a small force in the Raa Kisharu direction, the radial direction A spindle device, which is configured to be provided with elastic means for supporting it with a predetermined rigidity and for applying a predetermined elastic force in the axial direction between the housing and the rear bearing case.