JPH0632245Y2 - Bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an improvement in a bearing device used in, for example, a machine tool for cutting or drilling, and particularly to high rigidity at low speed rotation and low heat generation at high speed rotation. Bearing device.

[Conventional technology]

As a conventional bearing device, for example, Japanese Utility Model Laid-Open No. 56-72927 (name is bearing lid) previously proposed by the present applicant.
There is one described in.

This conventional bearing device is a device in which a shaft in a housing is rotatably supported by three bearings, and a radial load is loaded by three bearings, and an axial load is loaded by two bearings including a central bearing. Bearing is loaded.

Also, if a preload is applied to the bearing used in the bearing device,
Since there are various advantages such as smaller displacement of the shaft due to load and higher rigidity of the bearing (the higher the preload is, the higher the rigidity is), the bearing of the bearing device as described above is in a preloaded state. Was generally used in.

[Problems to be solved by the device]

However, the bearing preload increases due to centrifugal force applied to the bearing as the shaft rotates at high speed, thermal expansion due to the frictional resistance of the bearing, and the frictional resistance of the bearing that causes heat generation is It grows in proportion to the size. That is, since the temperature of the bearing to which the preload is applied tends to rise during high-speed rotation, there is a high risk of seizure, but such a problem can be solved by reducing the preload applied to the bearing. .

However, if the preload applied to the bearing is reduced, high rigidity cannot be obtained even at low speed rotation when heavy cutting is performed, so that there arises a problem that sufficient cutting force cannot be exerted in a machine tool or the like.

In other words, in the conventional bearing device, when a high preload is applied to the bearing, heat generation at high speed is promoted, and when the preload is reduced, sufficient rigidity is achieved during heavy cutting (low speed rotation). There was an unsolved problem that was not obtained.

Therefore, the present invention has been made by paying attention to the unsolved problem in such a conventional bearing device. A bearing device having high rigidity during low speed rotation (during heavy cutting) and low heat generation during high speed rotation is provided. The purpose is to provide.

[Means for Solving the Problems]

In order to achieve the above object, the device of claim (1) is
A housing, a shaft, and first, second, and third bearings that rotatably support the shaft in the housing, and the first, second, and third bearings are arranged in this order in the axial direction. In the bearing device described above, the first and second bearings are preloaded, and are configured by angular contact ball bearings in a combination of back surfaces, and the outer ring of the second bearing has a ring having a larger linear expansion coefficient than that of the outer ring. The member was externally fitted at room temperature with a predetermined interference, and a gap was provided between the outer peripheral surface of the ring member and the inner surface of the housing.

The invention according to claim (2) is the device according to claim (1), in which the predetermined interference is caused by the ring member and the second member when the bearing device is rotated at the maximum speed in normal use. It was set to approximately zero by thermal expansion with the outer ring of the bearing.

[Action]

In the bearing device of the present invention, since the first and second bearings are used in a preloaded state, rigidity proportional to the magnitude of the applied preload can be obtained at low speed rotation.

On the other hand, when the shaft rotates at high speed, the preload increases due to the centrifugal force applied to the bearing, and the bearing generates heat due to frictional resistance.

However, the ring member, which is fitted on the outer ring of the second bearing at room temperature with a predetermined interference, has a larger linear expansion coefficient than that of the outer ring. Then, the interference is reduced and the outer ring raceway diameter is increased.

That is, since the increase in preload due to the centrifugal force or the like is offset by the decrease in preload due to the increase in the outer ring raceway diameter of the second bearing, the increase in preload of the first and second bearings is suppressed.

Further, since the bearing provided with the ring member is the second bearing located at the center, even if a gap is provided between the ring member and the housing, the radial load is applied by the first and third bearings. Since it is possible, the shaft does not swing due to the provision of the gap.

Further, in the invention of claim (2), since the interference between the outer ring and the ring member of the second bearing becomes substantially zero at the maximum rotation speed of the bearing device in normal use, the interference can be reduced by the interference. The applied preload becomes almost zero. In other words, since the preload applied by the interference gradually decreases as the bearing device is normally used, the preload is always obtained, and therefore, the action of the device according to claim (1) is always obtained.

〔Example〕

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

1 and 2 show an embodiment of the present invention. FIG. 1 is an overall sectional view of the bearing device 1, and FIG. 2 is an enlarged sectional view of a main part of FIG.

First, the configuration will be described.

The bearing device 1 is used, for example, to rotate a tool bit of a machine tool, and has a shaft 3, a first bearing 4, a second bearing 5, and a third bearing 3 inside a housing 2.
It is rotatably supported by the bearing 6.

The housing 2 has a cylindrical insertion hole 7 into which the shaft 3 is inserted.
The sealing lids 8a and 8b forming a labyrinth with the shaft 3 are fixed near both openings of the insertion hole 7. Further, the bearing device 1 is provided on the outer surface of the housing 2.
An oil groove 2a for passing oil for cooling the oil is formed.

Then, in the insertion hole 7, the inner diameter of the central portion 7a is smaller than the inner diameters of the both end portions 7b and 7c, and
A groove 7d that is continuous in the circumferential direction is provided on the side of the central portion 7a of the end portion 7b.
Is provided, and the first bearing 4 is provided on the opening side of the end 7b.
Is arranged, the second bearing 5 is arranged in the groove 7d, and the end 7
The third bearing 6 is arranged at c.

The first bearing 4 and the second bearing 5 are angular contact ball bearings, and both of them are in a combination of back surfaces and are in a pre-loaded state due to the following arrangement structure.

That is, the outer ring 4a of the first bearing 4 is sandwiched between the pressing body 9 pressed by the sealing lid 8 and the outer ring spacer 10a, and the inner ring 4b of the first bearing 4 and the projection 3a of the shaft 3 and the inner ring 4a. Spacer 10b
The outer ring 4a and the end portion 7b, and the inner ring 4b and the shaft 3 are tightly fitted to each other.

Further, the second bearing 5 is, as shown in the enlarged view of FIG.
The outer ring 5a is sandwiched between the housing 2 and the outer ring spacer 10a, and the inner ring 5b is sandwiched between the inner ring spacer 10b and the end surface of the sleeve 11a fixed to the shaft 3. Thus, the inner ring 5b and the shaft 3 are fitted tightly together. In addition, 5c in FIG. 2 is a ball 5
It is a holder that holds d.

The ring member 12 is fitted on the outer ring 5a of the second bearing 5.

The ring member 12 is formed of a material having a linear expansion coefficient larger than that of the outer ring 5a, and a predetermined interference is provided between the inner peripheral surface of the ring member 12 and the outer peripheral surface of the outer ring 5a. That is, the outer ring 5a is tightened by the ring member 12 and has a reduced diameter at normal temperature. A gap 13 is formed between the outer peripheral surface of the ring member 12 and the inner peripheral surface of the groove 7d.
Is provided.

Therefore, the ring member 1 is attached to the first bearing 4a and the outer ring 5a in advance.
By appropriately selecting the width dimensions of the outer ring spacer 10a and the inner ring spacer 10b that are mounted between the second bearing 5 and the second bearing 5 to which 2 is fitted, the first and second bearings 4 and 5 can be formed. An appropriate preload can be given in advance.

Further, the third bearing 6 is a double-row cylindrical roller bearing having a structure in which a load in the axial direction is not applied, and its outer ring 6a.
Is sandwiched between the stepped portion between the central portion 7a and the end portion 7c and the sealing lid 8b, and the inner ring 6b thereof is aligned with the end surface of the sleeve 11b fixed to the shaft 3 and the sealing lid 8b to form a labyrinth. And is sandwiched between the end surface of the sleeve 11c and the end surface of the sleeve 11c.

Therefore, in the bearing device 1 according to the present embodiment, the radial load is applied to the first and third bearings 4 and 6, and the axial load is applied to the first and second bearings 4 and 5. You can

The shaft 3 penetrates in the axial direction of the through hole 15, and a taper hole 15a for fixing a bite or the like is formed on the left side of the through hole 15 in FIG.

Then, the bite for cutting or the like has a through hole 15 in a state in which the opposite side of the cutting is brought into contact with the tapered surface of the tapered hole 15a.
It is fixed to the shaft 3 by pulling it from the opposite side with a suitable fixing tool.

Further, a pulley 16 connected to an output shaft of a motor (not shown) via an endless belt or the like is fixed to the outer peripheral surface of the shaft 3 exposed from the housing 2 on the right side in FIG. The shaft 3 can be rotated at any speed.

Next, the operation of the above embodiment will be described.

Assuming that the shaft 3 is rotated at a relatively low speed in order to perform heavy cutting, the temperature of the bearing device 1 does not rise so much in this state, and the bearing device 1 maintains substantially the same state as at room temperature.

Therefore, since the first and second bearings 4 and 5 maintain the pre-loaded state, high rigidity suitable for heavy cutting can be obtained.

Then, when the shaft 3 is rotated at a high speed, the first force is generated by centrifugal force applied to the bearing, thermal expansion due to frictional resistance heat of the bearing, and the like.
And the preload of the second bearings 4, 5 generally increases.

However, in this embodiment, since the ring member 12 fitted on the outer ring 5a of the second bearing 5 has a larger coefficient of linear expansion than the outer ring 5a, the interference between the inner peripheral surface of the ring member 12 and the outer peripheral surface of the outer ring 5a is controlled by the temperature. Decreases with increasing.

When the interference amount decreases, the race diameter of the outer ring 6a increases, so that the tightening force of the second bearing 5 in the radial direction decreases and the preload of the first and second bearings 4 and 5 decreases.

That is, an increase in preload due to centrifugal force or the like during high-speed rotation is offset by a decrease in preload due to an increase in the raceway diameter of the outer ring 5a, so that an increase in preload on the first and second bearings 4 and 5 is suppressed. . As a result, the heat generation of these bearings 4 and 5 is reduced, and the risk of seizure and the like is reduced.

As described above, with the bearing device 1 having the configuration as in the above-described embodiment, it is possible to obtain the ideal characteristics of high rigidity during low speed rotation (during heavy cutting) and low heat generation during high speed rotation.

Here, the function and effect of the above-described embodiment will be described in detail with specific numerical values.

For example, the second bearing 5 (material bearing steel SUS), the inner diameter 6
Angular contact ball bearing with 5mm, outer diameter 100mm, width 18mm, contact angle α = 15 degrees, with outer ring 5a having inner diameter 100mm, outer diameter 120mm, width 18mm stainless steel (SU
The ring member 12 made of S304) at room temperature of 20 ° C. for 1
If the outer ring 5a is fitted with the interference of 0 μm, the race diameter of the outer ring 5a is reduced by 7 μm.

Therefore, it is assumed that such a second bearing 5 is used in the bearing device 1 of the above-mentioned embodiment and a preload of 20 kgf is applied at room temperature (20 ° C.). The interference between the inner ring 5b and the shaft 3 is 2 μm.

Then, the shaft 3 is rotated at the maximum rotation speed of the bearing device 1 for normal use (for example, 10000 rpm), and the temperature becomes 41
Assuming that the temperature rises to ℃, the linear expansion coefficient of bearing steel used for ordinary bearings is 12.5 × 10 ^−6.
Since the linear expansion coefficient of S304 is 17.3 × 10 ⁻⁶ ,
Since the interference between the outer peripheral surface of the outer ring 5a and the inner peripheral surface of the ring member 12 is 0 μm, the race diameter of the outer ring 5a is increased by 7 μm as compared with the interference. The expansion of a minute increases by 7 μm by the amount by which the interference amount is decreased due to the expansion of the inner ring 5b and the ball 5d and hardly affects the preload amount, and the preload given by the interference amount becomes zero. The change in the orbital diameter is
The preload gap in the axial direction is changed by 12 μm.

That is, the increase in preload due to the influence of centrifugal force or the like is due to the outer ring 5a.
Since it is offset by the increase in the orbit diameter, the preload at 41 ° C is only 28 kgf. In the case of the conventional bearing device, the preload increases to 44 kgf under the same conditions, which causes seizure of the bearing.

Further, as described above, when the interference between the outer peripheral surface of the outer ring 5a and the inner peripheral surface of the ring member 12 becomes zero at the maximum rotation speed of the bearing device 1 during normal use, the preload increase as described above is performed. The suppression effect of is always obtained.

Then, the ring member 12 is externally fitted and the gap 13 is formed.
Since the second bearing 5 provided with is disposed in the center between the other bearings 4 and 6, the shaft 3 is not shaken by the gap 13.

In addition, in the above-described embodiment, the gap 13 is formed between the ring member 12 and the housing 2 by providing the groove 7d. However, the gap 13 may be formed by, for example, the second gap even if the groove 7d is not provided. The bearing 5 can also be formed by using a bearing that is thinner than the first bearing 4.

Further, although not particularly shown, by providing a heating device such as a heater or a temperature sensor in the vicinity of the ring member 12,
If the ring member 12 can be positively changed in temperature, the preload can be freely adjusted.

[Effect of device]

As described above, according to the bearing device of the present invention, in the bearing device having the first, second, and third bearings, the first and second bearings are in a preloaded state and the angular contact balls of the rear combination are used. A ring member having a linear expansion coefficient larger than that of the outer ring is externally fitted to the outer ring of the second bearing, which is formed of a bearing and is arranged at the center in the axial direction, with a predetermined interference at room temperature. Since a gap is provided between the outer peripheral surface of the ring member and the inner surface of the housing, high rigidity is obtained by maintaining a preload state at low speed rotation where heavy cutting is performed, and preload increases at high speed rotation. It is suppressed and the heat value of the bearing is reduced, and as a result,
It is effective in preventing seizure of the bearing.

Further, as in the invention as set forth in claim (2), when the bearing device is rotated at the maximum speed during normal use, the predetermined interference is caused by thermal expansion between the ring member and the outer ring of the second bearing. When it is set to substantially zero, there is an effect that an effect of suppressing an increase in preload due to high speed rotation can always be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing the overall construction of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the main part of FIG. 1 ... Bearing device, 2 ... Housing, 3 ... Shaft, 4 ...
First bearing, 4a ... Outer ring of first bearing, 4b ... First
Inner ring of bearing 5 ... second bearing, 5a ... outer ring of second bearing, 5b ... inner ring of second bearing, 6 ... third bearing, 6a ... outer ring of third bearing , 6b ... Inner ring of the third bearing, 12 ... Ring member, 13 ... Gap.

Claims (2)

[Scope of utility model registration request] 1. A housing, a shaft, and first, second, and third bearings for rotatably supporting the shaft in the housing, wherein the first, second, and third bearings are provided. In the bearing device sequentially arranged in the axial direction, the first and second
Of the second bearing is a ring member having a linear expansion coefficient larger than that of the outer ring of the second bearing and having a predetermined interference at room temperature. And a gap is provided between the outer peripheral surface of the ring member and the inner surface of the housing. 2. The predetermined interference is substantially zero due to thermal expansion between the ring member and the outer ring of the second bearing when the bearing device rotates at the highest speed in normal use.
The bearing device according to (1).