JPH07279955A - Preloading device for bearing - Google Patents

Abstract

PURPOSE:To insure preload adjustment by a cheap and simple configuration by preloading bearings by means of a belleville spring, making the velleville spring of a shape-memory alloy, and stepwise adjusting a preloading force by regulating the temperature of the belleville spring. CONSTITUTION:A large diameter belleville spring 26 is arranged between a first recessed part 24b and a second recessed part 15b, and the belleville spring 26 is made of a shape-memory alloy. The belleville spring 26 is formed from a plate-like spring material into a shape of bottomless tray, and since it is difficult to deform laterally, but it stably reflects in the direction of load, it can give a stable preload. By the aid of the shape-memorizing characteristic, the belleville spring 26 functions as a spring, for example, at temperatures of less than 40 deg.C but it does not function as the spring and is deformed to be idle at temperatures of 40 deg.C or more. As a result of the above mentioned characteristic, when the temperatures of first and second bearings 16, 17 rise and the temperature of the belleville spring 26 is also raised by heat conduction, the belleville spring 26 operates at temperatures of less than 40 deg.C to give a maximum preload, and the belleville spring 26 is idle at temperatures of 40 deg.C or more to give a minimum preload.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing preload device for a spindle of a machining center.

[0002]

2. Description of the Related Art In recent years, the demand for high-speed cutting in machine tools has increased. In the case of ultra-high speed cutting in which the spindle rotates at a high speed of 15,000 rpm or 20,000 rpm or more, the bearing becomes considerably hot. When the bearing becomes hot, seizure easily occurs. Further, at high temperatures, the bearing and its peripheral members expand and preload tends to become excessively large, resulting in frequent bearing damage.

On the other hand, in cutting at low speed, heavy cutting is required and a large preload is required.

Therefore, there has been devised a preloading device for adjusting the preload in multiple stages by low speed heavy cutting and high speed light cutting. In these preload devices, for example, a piezoelectric sensor and a hydraulic system are used to control the preload.

[0005]

[Problems to be Solved by the Invention] Hydraulic system and piezoelectric sensor
The preloading device for controlling the preloading by means of has a complicated structure and tends to be large in size. There were also problems in terms of manufacturing cost and maintenance.

In view of the above problems of the prior art, the present invention has a simple structure, can be manufactured at a relatively low cost, is easy to maintain, and is capable of reliably adjusting the preload. The purpose is to provide a preload device.

[0007]

In order to solve the above-mentioned problems, the first invention of the present application is to preload a bearing by using at least one disc spring, and to form part or all of the disc spring with a shape memory alloy. A gist of a bearing preloading device is characterized in that the preloading force is adjusted according to the temperature of the disc spring.

The second invention of the present application is characterized in that the bearing is preloaded by using one large diameter disc spring, the disc spring is made of a shape memory alloy, and the preload is adjusted by the temperature of the disc spring. The gist of this is the bearing preload device.

According to a third aspect of the present invention, the bearing is preloaded by using a plurality of small-diameter disc springs, part or all of the disc springs are made of a shape memory alloy, and the preload is adjusted by the temperature of the disc springs. A gist of the present invention is a bearing preloading device.

Further, according to the fourth invention of the present application, the bearing is preloaded by using a plurality of small-diameter disc springs, and some or all of the disc springs are made of a shape memory alloy and have different shape memory characteristics. A gist of a preload device for a bearing is a combination of a plurality of types of disc springs, and the preload is adjusted according to the temperature of the disc springs.

It is desirable to adjust the preload in multiple stages by using a combination of a plurality of disc springs having different shape memory characteristics (features regarding temperature showing shape memory effect).

As the shape memory alloy, Ti--Ni, Au
-Cd, Cu-Au-Zn, In-Tl, In-Cd,
Ti-Ni-Cu, Cu-Zn-Al, Cu-Al-N
i or the like can be used.

[0013]

In the bearing preload device of the present invention, the temperature of the bearing rises and is transmitted to the disc spring, and when the disc spring reaches or exceeds the predetermined temperature, the disc spring is deformed by the shape memory effect and the preload is reduced.

When several types of disc springs having different characteristics are used, the preload decreases in multiple steps as the temperature rises.

As described above, the bearing preload device of the present invention is inexpensive and has a simple structure, and the preload can be adjusted reliably.

[0016]

EXAMPLES Referring to the first embodiment FIGS. 1 to 3, illustrating a pressure unit for a bearing according to the first embodiment of the present invention. FIG. 3 shows a machine tool having a bearing preload device on its main shaft.

The machine tool has a bed 1, a table 2, a column 3, a spindle head 4, and motors 5, 6, 7, 11.

A work W is attached to the table 2, and the table 2 can be moved in the X direction by the motor 5. The column 3 can be moved in the Y1 and Y2 directions by the motor 6. The spindle head 4 can be moved in the Z1 and Z2 directions by a motor 7.

The tool holder 1 is attached to the spindle 12 of the spindle head 4.
0 is attached detachably. The tool holder 10 and its tool 13 can be rotated by a motor 11.

Next, referring to FIG. FIG. 1 shows a part of the spindle head 4. The main shaft 12 includes first to fourth bearings 16,
It is rotatably supported by the frame 15 via 17, 18 and 19.

The flange 22 of the first member 20 is a bolt 23.
It is fixed to the frame 15 by. A second member 21 is set at the lower end of the first member 20 via a bolt 21a. The third to fourth bearings 18 and 19 are provided between the first member 20 and the main shaft 12, and rotatably support the main shaft 12.

The flange portion 1 in the middle of the frame 15
The third member 25 is located inside 5a. The fourth member 24 is fixed to the upper side of the third member 25 with bolts 27. The 4th member 24 is provided with the 1st recessed part 24b for installing a disc spring. The flange 15a is also provided with a second recess 15b corresponding to the first recess 24b.

Between the first recess 24b and the second recess 15b,
One large diameter disc spring 26 is arranged (see FIG. 2).
The disc spring 26 is made of a shape memory alloy.

As is well known, the shape memory alloy remembers the shape memorized at a high temperature, and has the property of returning to its original shape when heated even if it is deformed at room temperature. The shape memory effect is found in alloys that undergo martensitic transformation, and examples of shape memory alloys include Ti-Ni, Cu-Zn-Al, and Cu-Al-.
Ni etc. can be mentioned.

First and second bearings 16 and 17 are arranged between the third member 25 and the main shaft 12 to rotatably support the main shaft 12. A tubular fifth member 28 is provided above the inner rings of the first and second bearings 16 and 17. Further, a pressing member 29 with a screw is provided above the fifth member 28.
Screwed into.

The disc spring 26 includes the fourth member 24 and the third member 2.
By pressurizing 5 upwards, the first and second bearings 16,
Preload is applied to 17. The preload is adjusted stepwise by the temperature of the disc spring 26.

The disc spring 26 is a plate-shaped spring material formed into a disc-like shape (a truncated cone) without a bottom. The disc spring 26 is less likely to be deformed in the lateral direction as compared with a coil-shaped spring, and is stably bent in the load direction. Therefore, a stable preload can be given.

The shape memory characteristic of the disc spring 26 is as follows, for example. That is, the disc spring 26 has a temperature of 40 ° C.
It has a shape memory characteristic that it functions as a spring at less than 40 ° C., and deforms to play without functioning as a spring at 40 ° C. or higher.

There is preferably heat conduction between the disc spring 26 and the first and second bearings 16 and 17. In this case, the preload can be adjusted so as to correspond to the temperatures of the first and second bearings 16 and 17.

When the temperatures of the first and second bearings 16 and 17 rise and the temperature of the disc spring 26 also rises due to heat conduction, the preload mechanism having the disc spring 26 made of a shape memory alloy is as follows. Acts like. Disc springs 2 at temperatures below 40 ° C
6 works to obtain the maximum preload, for example 132 kg.
Above 40 ° C, the disc spring 26 plays and provides a minimum preload, for example 20 kg.

The disc spring 26 is arranged concentrically with the main shaft 12.

[0032] With reference to the second embodiment FIGS. 3 to 5, illustrating a pressure unit for a bearing according to a second embodiment of the present invention. In the description of the second embodiment, FIG. 3 shows a machine tool having a bearing preload device according to the second embodiment. Components corresponding to those in the first embodiment described above are designated by the same reference numerals as those in the first embodiment.

The machine tool has a bed 1, a table 2, a column 3, a spindle head 4, and motors 5, 6, 7, 11.

A work W is attached to the table 2, and the table 2 can be moved in the X direction by the motor 5. The column 3 can be moved in the Y1 and Y2 directions by the motor 6. The spindle head 4 can be moved in the Z1 and Z2 directions by a motor 7.

The tool holder 1 is attached to the spindle 12 of the spindle head 4.
0 is attached detachably. The tool holder 10 and its tool 13 can be rotated by a motor 11.

Referring to FIG. FIG. 4 shows a part of the spindle head 4. The main shaft 12 includes first to fourth bearings 16 and 1
The frame 15 is rotatably supported via 7, 18, and 19.

The flange 22 of the first member 20 is a bolt 23.
It is fixed to the frame 15 by. A second member 21 is set at the lower end of the first member 20 via a bolt 21a. The third to fourth bearings 18 and 19 are provided between the first member 20 and the main shaft 12, and rotatably support the main shaft 12.

The flange portion 1 in the middle of the frame 15
The third member 25 is located inside 5a. The fourth member 24 is fixed to the upper side of the third member 25 with bolts 27. The fourth member 24 is provided with a large number of first recesses 4b for installing small-diameter disc springs 26a to 26d. Corresponding to the first recess 24b, the flange 15a is also provided with a large number of second recesses 15b. In the illustrated example, the numbers of the first recesses 24b and the second recesses 15b are 16 each.

Between the first recess 24b and the second recess 15b,
A large number of small-diameter first to fourth disc springs 26a to 26d are arranged (see FIG. 5). First to fourth disc springs 26a to 26d
Are arranged along a circumference concentric with the main shaft 12.

In the illustrated example, the first to fourth disc springs 26
The number of a to 26d is 4, and the total is 16.

The first to third disc springs 26a to 26c are made of shape memory alloy. The fourth disc spring 26d is a normal disc spring.

As is well known, the shape memory alloy remembers the shape memorized at a high temperature, and has the property of returning to its original shape when heated even if it is deformed at room temperature. The shape memory effect is found in alloys that undergo martensitic transformation, and examples of shape memory alloys include Ti-Ni, Cu-Zn-Al, and Cu-Al-.
Ni etc. can be mentioned.

First and second bearings 16 and 17 are arranged between the third member 25 and the main shaft 12, and rotatably support the main shaft 12. A tubular fifth member 28 is provided above the inner rings of the first and second bearings 16 and 17. Further, a pressing member 29 with a screw is provided above the fifth member 28.
Screwed into.

The first to fourth disc springs 26a to 26d press the fourth member 24 and the third member 25 upward,
Preload is applied to the first and second bearings 16 and 17. First to
The preload is adjusted stepwise by the temperature of the fourth disc springs 26a to 26d.

Each of the first to fourth disc springs 26a to 26d is a plate-shaped spring material having a bottomless disc shape (a truncated cone shape).
It is a spring molded into. The disc spring 26 is less likely to be deformed in the lateral direction as compared with a coil-shaped spring, and is stably bent in the load direction. Therefore, a stable preload can be given.

The shape memory characteristics of the first to fourth disc springs 26a to 26d are different from each other, and are as follows, for example. That is, the first to third disc springs 26a, 26
b and 26c are 25 ° C (normal temperature), 30 ° C and 40 ° C, respectively.
Acts as a spring at temperatures below ℃, 25 ℃ (normal temperature), 3
It has a shape memory characteristic that it deforms to play without functioning as a spring at temperatures of 0 ° C and 40 ° C or higher.

The first to fourth disc springs 26a to 26d and the first to fourth
There is preferably heat conduction between the second bearings 16 and 17. In this case, the preload can be adjusted so as to correspond to the temperatures of the first and second bearings 16 and 17.

When the temperatures of the first and second bearings 16 and 17 rise and the temperatures of the first to fourth disc springs 26a to 26d also rise due to heat conduction, the first to the first shape memory alloys The preload mechanism having the third disc springs 26a to 26c operates as follows. At temperatures below 25 ° C, the first to fourth disc springs 2
6a to 26d work to obtain the maximum preload, for example, 132 kg. When the temperature is 25 ° C or higher and lower than 30 ° C, the first disc spring 26a plays and the second to fourth disc springs 26b to 26d work to obtain an intermediate preload, for example, 84 kg. When the temperature is 30 ° C or higher and lower than 40 ° C, the first disc spring 26a and the second disc spring 26b play, and
Intermediate preload by the disc spring 26c and the fourth disc spring 26d,
For example, 50 kg is given. Above 40 ° C, the first to third disc springs 26a to 26c play, and only the fourth disc spring 26d gives a minimum preload, for example, 20 kg.

Since the preload is adjusted in multiple steps in this way, the preload can be adjusted appropriately with respect to the temperature change of the bearing.

The present invention is not limited to the above-mentioned first and second embodiments. For example, the number and arrangement of disc springs can be set arbitrarily.

As is well known, various types of bearings can be used in combination.

Although the disc spring is deformed so as to play at a predetermined temperature or higher, conversely, the disc spring is deformed so as to function as a spring at a predetermined temperature or higher to reduce the preload. You may arrange. In this case,
The disc spring is idle at low temperatures (below a certain temperature). Further, the bearing preload device of the present invention can be used for bearings other than the bearing that supports the spindle of the machine tool.

Further, the shape of the disc spring is not limited to the above-mentioned shape, and the same shape as the conventional disc spring can be adopted.

[0054]

According to the first to fourth inventions of the present application, the bearing is preloaded by using at least one disc spring, a part or all of the disc spring is formed of a shape memory alloy, and the temperature of the disc spring varies depending on the temperature of the disc spring. Since the preload is adjusted stepwise, it is possible to make the construction cheaper and simpler than the conventional preload device. Moreover, it is possible to reliably adjust the preload.

According to the fourth invention of the present application, a part or all of the disc spring is made of a shape memory alloy, which is a combination of a plurality of types of disc springs having different shape memory characteristics. Since the preload is adjusted according to the temperature of
When the temperature of the disc spring is made to correspond to the temperature of the bearing, the preload can be adjusted appropriately with respect to the temperature change of the bearing.

[Brief description of drawings]

FIG. 1 is a sectional view exemplifying a part of a spindle head in which a bearing preload device according to a first embodiment of the present invention is installed.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a side view of a machine tool including the spindle head shown in FIG.

FIG. 4 is a sectional view exemplifying a part of a spindle head in which a bearing preload device according to a second embodiment of the present invention is installed.

5 is a sectional view taken along line BB in FIG.

[Explanation of symbols]

16, 17, 18, 19 Bearing 12 Spindle 4 Spindle head 26, 26a, 26b, 26c Shape memory alloy disc spring 26d Normal disc spring

Claims (4)

[Claims] 1. A bearing is preloaded using at least one disc spring, a part or all of the disc spring is made of a shape memory alloy, and the preload is adjusted stepwise according to the temperature of the disc spring. Bearing preload device. 2. A bearing preload device characterized in that a bearing is preloaded using one large-diameter disc spring, the disc spring is made of a shape memory alloy, and the preload is adjusted by the temperature of the disc spring. 3. A bearing characterized in that a plurality of disc springs having a small diameter are used to preload the bearing, a part or all of the disc spring is made of a shape memory alloy, and the preload is adjusted according to the temperature of the disc spring. Preload device. 4. A combination of a plurality of types of disc springs in which a bearing is preloaded by using a plurality of disc springs having a small diameter, a part or all of the disc springs are made of a shape memory alloy, and have different shape memory characteristics. The bearing preloading device is characterized in that the preload is adjusted according to the temperature of the disc spring.