JPH11239902A - Spindle supporting device for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a size of a preload applied to a bearing to be adapted to the number of revolutions of a main spindle without a supply source of pressure fluid and an auxiliary equipment of a controller or the like. SOLUTION: A main spindle supporting device is provided with spacers 4, 5 and a plurality of pieces 6, and grooves of the same number as the pieces 6 and having the width fitted to the pieces 6 are formed circumferentially and equally ta the axial edges of the spacers 4, 5, wherein the bottom surfaces 7 are inclined in the direction close to one another from the internal diameter side to the external diameter side as well as the spacers 4, 5 are integrally formed by keys 9 with the main spindle 1 in the rotational direction. The sum of length in the axial direction of the spacers 4, 5 fitting the pieces 6 in the grooves is constructed so as to substantially correspond to the spacing in the axial direction of inner rings 2a of angular contact bearings 2 when a preload is applied in accordance with the low speed rotation of the main spindle. The centrifugal force acted on the pieces 6 moves the spaces 4, 5 in the axial direction against disc springs 11. The centrifugal force applied to the pieces 6 is increased as the number of revolutions is increased, and the preload is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle support device for a machine tool, which is suitable for use in a machine tool, particularly a machining center, and can be used from low speed rotation to high speed rotation.

[0002]

2. Description of the Related Art In general, when machining a workpiece made of iron, the efficiency can be improved by performing so-called medium- and low-speed heavy-load cutting in which the number of revolutions of the spindle is increased to several thousand to deepen the depth of cut. . Therefore, in machining centers that mainly use iron-based work, the rigidity of the bearing is increased by applying a relatively large preload to the bearing that supports the main shaft, so that medium / low speed heavy load cutting can be performed. On the other hand, in recent years, the number of aluminum products has increased, and
It has become necessary to perform so-called high-speed light-load cutting in which the depth of cut is made shallow by setting it to 00 rpm or more.

If the main shaft is rotated at a high speed while the preload of the bearing is adjusted to a medium / low speed heavy load cutting (that is, increased), the bearing generates heat and seizure occurs. On the other hand, if the preload is reduced for light-load cutting, machining efficiency is reduced because medium / low-speed heavy-load cutting cannot be performed. Therefore, as shown in JP-A-5-209614, an inner ring of a pair of bearings for supporting a main shaft is fixed in an axial direction, and a spacer that can be extended and contracted in an axial direction by fluid pressure between two outer rings. And controlling the preload to an optimum value by adjusting the fluid pressure according to the rotation speed of the main shaft.

[0004]

However, in the above-mentioned prior art, an auxiliary device such as a supply source of the pressure fluid and a control device is required, and the structure of the bearing is complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and eliminate the need for a device such as a pressure fluid supply source and a control device, and to set the magnitude of the preload applied to the bearing to a value suitable for the rotational speed of the main shaft. An object of the present invention is to provide a spindle support device of a machine tool that can be used.

[0006]

In order to achieve the above object, the present invention provides an outer ring (2) of a pair of bearings (2, 2).
c) is fixed in the axial direction, the main shaft (1) is supported on the inner ring (2a), and the inner rings are biased in the direction approaching each other in the axial direction to apply a preload to the pair of bearings. A spindle support device for a machine tool, wherein at least two spacers (4) and (5) externally fitted in series on the spindle (1) so as to be axially movable and relatively non-rotatable, and between opposed end faces of these spacers. A plurality of pieces (6) interposed therebetween, and the bottom surface (7) is inclined in a direction approaching from at least one of the axial ends of the spacer toward the outer diameter side from the inner diameter side toward the outer diameter side. Then, a plurality of grooves (8) whose circumferential width is slightly larger than the width of the piece (6) are equally formed in the circumferential direction, and the pieces (6) are formed in the grooves (8).
Sum of the axial lengths of the spacers fitted with (p)
Is set to be substantially equal to or less than the axial distance between the pair of inner rings in a state where a preload is applied in accordance with the low-speed rotation of the main shaft.

[Operation] Based on the above structure, the inner ring (2a) of the pair of bearings (2) and (2) based on the biasing force of the disc spring (11) set by the nut (12), for example.
A preload corresponding to the low rotation of the main shaft (1) acts on (2a). The main shaft (1) is pressurized to press iron-based workpieces.
When rotating at a low speed, the spacers (4) (5) and the plurality of pieces (6) fitted in the grooves (8) also rotate integrally with the main shaft (1), but since these rotations are relatively low, The centrifugal force acting on the piece (6) is small. In this state,
Based on the centrifugal force, the spacer (4)
The axial force acting on (5) is small, so that
The main shaft (1) is supported by the bearings (2) and (2) in a state where a preload suitable for low-speed rotation is applied.

On the other hand, when the main shaft (1) is rotated at a high speed in order to process an aluminum-based work or the like, a large centrifugal force acts on the piece (6) that rotates integrally with the main shaft, and the piece due to the centrifugal force is applied. The force to move in the outer diameter direction of (6) acts as an axial force in a direction away from the spacers (4) and (5) due to the wedge effect due to the inclination at the bottom surface (7) of the groove (8). The axial force is applied to the disc spring (1).
The preload acting on the inner rings (2a) and (2a) of the pair of bearings (2) and (2) is reduced by acting against the urging force of 1) and the like. Thus, the main shaft (1) is supported by the bearings (2) and (2) in a preload state suitable for the high-speed rotation of the main shaft (1).

Note that the reference numerals in parentheses are for comparison with the drawings, but do not limit the configuration of the present invention.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is a sectional view of a spindle head of a machine tool according to an embodiment of the present invention, FIG. 2 is an AA view of FIG. 1, and FIG. 3 is an enlarged sectional view showing a dimensional relationship of main parts. In the figure, reference numeral 1 denotes a main shaft, which is rotatably supported by a bearing housing 3 through a pair of angular contact ball bearings 2 combined on the back. These angular bearings 2 include an inner ring 2a in contact with the main shaft 1, an outer ring 2c fitted in the bearing housing 3, and a ball 2b inscribed in the inner ring 2a and the outer ring 2c. Reference numerals 4 and 5 denote spacers having an axial length of k. Reference numeral 6 denotes an iron piece, which is a cylindrical column having a radius r formed on the outer diameter side into a spherical surface having a radius r. As shown in FIG. 3, the opposite ends of the spacers 4 and 5 have axial bottom surfaces inclined at an angle θ in a direction approaching each other from the inner diameter side to the outer diameter side, as shown in FIG. The number of pieces 6 whose circumferential width is slightly larger than the width (2r) of the piece 6 (6 in the figure)
) Grooves 8 are formed equally in the circumferential direction. 9 is a key, and the spacers 4 and 5 are integrated with the main shaft 1 in the circumferential direction.
They are connected movably in the axial direction. 10 is color, 11
Is a disc spring, and 12 is a nut. The collar 10 abuts on the inner ring 2a of one of the bearings, and the nut 12 is screwed onto the main shaft 2, whereby the disc spring 11 urges the inner ring 2a in the axial direction. ing. A bearing 13 rotatably supports the rear end of the main shaft 1. A collar 14 and a retaining ring 15 fix the inner ring of the bearing 13 in the axial direction.
The bearing 13 is movable in the axial direction with respect to the bearing housing 3. Reference numeral 16 denotes a spacer, which is disposed between the outer rings 2c of the pair of angular contact ball bearings 2 and has a length L. A cover 17 is fixed to the bearing housing 3 by bolts (not shown), and positions and fixes the outer ring 2c and the spacer 16 between the cover and the flange 3a provided on the bearing housing 3.

The dimensions of the above components are determined as follows. FIG. 3 is a diagram showing the dimensional relationship of each component. In the figure, the distance p is determined by adjusting the position of the nut 12 for stopping the main shaft 1 and urging the disc spring 11 to a value suitable for medium / low speed heavy load cutting (for example, when the main shaft is 5 This is the distance between the pair of inner races 2c when set to about 60 kgf when rotating at 2,000 rpm). Then, the piece 6 is connected to the spindle 1
And the distance between the spacer 4 and the spacer 5 when circumscribing the outer periphery of the groove and the bottom surface 7 of the two grooves 8 is represented by g, 2k + g ≦
p.

Next, the operation of this embodiment will be described.

Assume that the number of revolutions of the spindle 1 is set to, for example, 20,000 rpm in order to process an aluminum-based work. The spacers 4, 5 rotate integrally with the main shaft 1,
The piece 6 in the groove 8 also rotates integrally with the main shaft 1. Then, the centrifugal force applied to the piece 6 presses the bottom surface 7 and presses the spacers 4 and 5 in a direction against the disc spring 11. As a result, the preload based on the disc spring 11 acting on the pair of angular contact bearings 2 and 2 is reduced, the distance between the inner rings 2c becomes larger than the distance p, and the preload becomes small (about 10 kgf). . Therefore, the calorific value of the angular bearing 2 is small, and no seizure occurs. When the number of revolutions decreases and the centrifugal force of the piece 6 decreases, the piece 6 returns to the original position by the urging force of the disc spring 11.

On the other hand, when an iron-based workpiece is machined at 5,000 rpm, as described above, the preload on the pair of angular contact bearings 2 and 2 by the urging force of the disc spring 11 based on the position of the nut 12 is a low-speed load. Since the value is suitable for load cutting, it is possible to perform processing with excellent accuracy. Note that the centrifugal force applied to the piece 6 is
Is applied in the axial direction, but since the centrifugal force is proportional to the square of the angular velocity, the change in the preload is small at about 5,000 rpm. Since the grooves 8 into which the pieces 6 are fitted are formed at equal intervals in the circumferential direction, the balance at the time of high-speed rotation is excellent, and vibration does not occur.

It is more effective if the distance p is determined in consideration of the centrifugal force applied to the piece 6 when the main shaft 1 is rotated at 5,000 rpm. Also, the angle θ
The magnitude of the centrifugal force can be arbitrarily designed by appropriately selecting any one or all of the values of the size, the number or the mass of the pieces 6. If it is desired to further increase the centrifugal force, the spacers 4 and 5 may be divided and grooves 8 may be formed on the divided surfaces to increase the number of pieces 6. Further, the piece 6 may have another shape (for example, a spherical shape).

Although the groove 8 is provided in the spacers 4 and 5 in the above description, it may be provided in only one of them.

[0018]

As described above, according to the present invention,
Based on the centrifugal force acting on the piece when the spindle rotates, the spacer is pressed in the direction opposite to the preload direction, and the centrifugal force applied to the piece increases as the spindle speed increases. The bearings are automatically reduced and the bearings are not seized even if the spindle is rotated at high speed.Therefore, use the spindle with a simple configuration that does not use pressure fluid, etc., and use the spindle at a wide range of rotation speed from low speed to high speed. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle head of a machine tool according to an embodiment of the present invention.

FIG. 2 is an AA view of FIG.

FIG. 3 is a diagram showing a dimensional relationship between components.

[Explanation of symbols]

 2 (Angular contact) bearing 2a Inner ring 2c Outer ring 4, 5 Spacer 6 Piece 7 Bottom 8 Groove 9 Key 11 Disc spring 16 Spacer

Claims (1)

[Claims] An outer ring of a pair of bearings is axially fixed, a main shaft is supported by an inner ring, and the inner rings are biased in a direction approaching each other in an axial direction to apply a preload to the pair of bearings. A spindle support device for a machine tool, wherein at least two spacers are fitted in series on the spindle so as to be axially movable and relatively unrotatable, and a plurality of spacers interposed between opposed end faces of the spacers. At least one of the axial ends of the spacer facing each other, the bottom surface is inclined in a direction approaching from the inner diameter side to the outer diameter side, and the circumferential width is greater than the width of the piece. A plurality of grooves slightly wider in the circumferential direction are equally formed in the circumferential direction, and the sum of the axial lengths of the spacers in which the pieces are fitted in the grooves is pre-loaded in accordance with the low-speed rotation of the main shaft. 1 Inner ring in the axial direction of the spacing was set to approximately equal to or less that a machine tool spindle supporting device comprising a.