JP2007177900A - Tapered roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust a preload by a simple structure during operation without lowering the rigidity of a bearing in the rotating range between low-speed rotation and high-speed rotation. <P>SOLUTION: The large flange part of an inner ring 2 on the raceway surface 2a side is formed of a separate flange ring 6. A tapered surface 6a diverting to the end face of the tapered roller 4 on the opposite side of the large end surface 4a of a tapered roller 4 is formed on the inner diameter side of the flange ring 6. A fixed tapered ring 7 having, on the outer diameter side, a tapered surface 7a fitted to the tapered surface 6a of the flange ring 6 is secured to a bearing box 12. The flange ring 6 is axially moved along the tapered surface 7a of the fixed tapered ring 7 due to a difference in thermal expansion amount between the flange ring 6 and the fixed tapered ring 7 caused by the rotation of a bearing. Consequently, the preload can be adjusted during the operation by axially moving the flange ring 6 not receiving a tightening force by a simple structure without lowering the rigidity of the bearing in the rotating range between the low-speed rotation and the high-speed rotation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tapered roller bearing, and more particularly to a tapered roller bearing suitable for supporting a main shaft of a machine tool.

  In machine tools, the spindle has become more rigid and faster in order to improve machining accuracy, machined surface quality, and machining efficiency. Rolling bearings that support the spindle have radial and axial loads. In many cases, tapered roller bearings capable of supporting the shaft with high rigidity have been used. The tapered roller bearing that supports the main shaft of a machine tool is attached to the main shaft on which the inner ring rotates, and the outer ring is fixed to the bearing housing.When the main shaft rotates at a high speed, the temperature rise of the inner ring becomes larger than that of the outer ring, and the heat The bearing gap decreases due to the difference in expansion amount. For this reason, the preload of the bearing becomes excessive during the operation of the machine tool, and problems such as heat generation and seizure may occur.

  As a means to suppress excessive preload of the tapered roller bearing during machine tool operation, a constant pressure preload method that presses the outer ring in the axial direction with a spring or the like, and adjustment of the bearing clearance during assembly to ensure proper preload during high-speed rotation There is a fixed position preload method. There is also a hydraulic cylinder device that presses and moves the outer ring in the axial direction so as to adjust the preload during operation (for example, see Patent Document 1).

Japanese Utility Model Publication No. 5-32828

  The constant pressure preloading method in which the outer ring is pressed in the axial direction with a spring or the like as described above may cause problems in the machining accuracy of the machine tool and the quality of the machined surface because the bearing rigidity is lowered. Further, the fixed position preloading method for adjusting the bearing clearance so as to obtain an appropriate preload during high-speed rotation increases the bearing clearance during low-speed rotation and decreases the bearing rigidity, which also decreases the processing accuracy and the quality of the processed surface.

  On the other hand, the method of adjusting the preload during operation by pressing and moving the outer ring in the axial direction with the hydraulic cylinder device described in Patent Document 1 causes the outer ring to thermally expand during operation of the machine tool. There is a problem that the tightening force of the outer ring becomes large and it is difficult to smoothly move the outer ring in the axial direction. Further, since a bearing load such as a radial load or an axial load is also applied to the outer ring during operation, a hydraulic cylinder device with a large output is required to move the outer ring in the axial direction.

  Accordingly, an object of the present invention is to make it possible to adjust the preload during operation with a simple configuration without reducing the bearing rigidity from low speed rotation to high speed rotation.

  In order to solve the above-described problems, the present invention provides a plurality of tapered rollers arranged between a raceway surface of an inner ring attached to a rotating shaft and a raceway surface of an outer ring fixed to a bearing housing, and these tapered rollers. In the tapered roller bearing in which the large collar portion that restricts the axial movement of the inner ring toward the large end surface side is provided on the raceway surface side of the inner ring, the large collar portion is formed as a separate collar ring, and the inner diameter of the collar ring A tapered surface having a tapered surface on the outer diameter side is provided on the bearing housing side so that a tapered surface that expands toward the end surface on the side opposite to the large end surface of the tapered roller is provided. A configuration is adopted in which the saddle wheel is moved in the axial direction along the tapered surface of the fixed taper ring due to a difference in thermal expansion between the saddle wheel and the fixed taper ring due to a temperature rise during rotation of the bearing.

  That is, a large collar portion on the raceway surface side of the inner ring is formed by a separate collar, and a tapered surface is provided on the inner diameter side of the collar to expand to the end surface side opposite to the large end surface of the tapered roller. A fixed taper ring having a tapered surface on the outer diameter side that fits with the tapered surface of the saddle wheel is fixed to the bearing box side, and due to a difference in thermal expansion between the saddle wheel and the fixed tapered ring due to a temperature rise during bearing rotation, By moving the saddle wheel in the axial direction along the taper surface of the fixed taper ring, the rigid ring that does not act on the tightening force can be moved in the axial direction with a simple configuration to reduce the bearing rigidity from low speed rotation to high speed rotation. The preload can be adjusted during operation.

  Since the roller ring is in sliding contact with the large end surface of the tapered roller, the temperature rise increases as the bearing rotates at a higher speed, and the thermal expansion amount becomes larger than that of the fixed tapered ring. As a result, the saddle wheel moves axially in a direction to escape from the large end face of the tapered roller. Further, as described above, as the bearing rotates at a higher speed, the temperature increase of the inner ring becomes larger than that of the outer ring, and the bearing gap decreases due to the difference in the amount of thermal expansion. Therefore, when the bearing clearance is reduced due to high-speed rotation, the preload can be adjusted during operation by letting the tapered rollers escape to the side of the saddle wheel.

  By forming the saddle ring with a material having a larger linear expansion coefficient than the fixed tapered ring, the difference in thermal expansion from the fixed tapered ring is further increased, and the saddle ring is moved in a direction to escape from the large end surface of the tapered roller. The direction can be moved.

  By providing a gap between the inner diameter surface of the saddle ring and the outer diameter surface of the inner ring, and providing a oil discharge hole for discharging lubricating oil toward the gap in the fixed tapered ring, a large tapered roller that comes into sliding contact is provided. Good lubrication can be achieved between the end face and the collar.

  Each of the tapered roller bearings described above is suitable for supporting a spindle of a machine tool.

  In the tapered roller bearing of the present invention, the large collar portion on the raceway surface side of the inner ring is formed by a separate collar, and the diameter of the inner ring is expanded to the end surface side opposite to the large end surface of the tapered roller. A taper surface is provided, and a fixed taper wheel having a taper surface on the outer diameter side to be fitted with the taper surface of the saddle wheel is fixed to the bearing box side. Due to the difference in thermal expansion, the saddle wheel is moved in the axial direction along the taper surface of the fixed taper ring. The preload can be adjusted during operation without reducing the bearing stiffness until high speed rotation.

  By forming the saddle wheel with a material having a larger linear expansion coefficient than the fixed taper ring, the difference in thermal expansion with the fixed taper ring is made larger, so that the saddle ring escapes from the large end surface of the tapered roller in the axial direction. Can be moved.

  By providing a gap between the inner diameter surface of the saddle wheel and the outer diameter surface of the inner ring, and providing a fixed tapered ring with oil discharge holes for discharging lubricating oil toward the gap, the large end surface of the tapered roller in sliding contact with It is possible to lubricate well between the heel rings.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a spindle 11 of a machine tool supported by a tapered roller bearing 1 according to the present invention. The main shaft 11 is supported by a pair of tapered roller bearings 1 arranged with the back side facing the bearing box 12. The bearing box 12 is fitted into the outer cylinder 13 and is externally cooled by cooling oil circulating from the cooling oil supply path 14 provided in the outer cylinder 13 through the cooling groove 15 to the oil discharge path 16. The bearing box 12 is sealed on both sides with lids 17 and 18 so that the inside is air-oil lubricated. The oil supply holes 19 provided on the lids 17 and 18 are used to supply oil to the bearing box 12. Air oil is supplied to the front side and the back side of each tapered roller bearing 1 through the path 20, and used air oil is provided to the lids 17 and 18 through oil drain paths 21 provided in the bearing box 12. The oil is discharged from the oil drain hole 22 to the outside.

  Each inner ring 2 of the pair of tapered roller bearings 1 is attached to the main shaft 11 with an inner ring spacer 23 spaced apart on the back side, and the inner ring 2 on the left side in FIG. 1 is axially fixed to the step portion 11 a of the main shaft 11. The inner ring 2 on the right side of FIG. 1 is positioned by an inner ring spacer 24 and is fastened and fixed by a nut 25. Each outer ring 3 is positioned and fixed to the stepped portion 12a of the bearing housing 12 via the outer ring spacer 26, and the front side is pressed by the lids 17 and 18 via the outer ring spacer 27.

  FIG. 2 shows an enlarged view of the tapered roller bearing 1 on the left side of FIG. The tapered roller bearing 1 has a plurality of tapered rollers 4 held in a cage 5 between a raceway surface 2 a of an inner ring 2 and a raceway surface 3 a of an outer ring 3, and the raceway surface 2 a of the inner ring 2. A separate collar 6 and a fixed taper ring 7 that form a large collar are disposed on the front side.

The fixed tapered ring 7 is formed of amber having a small linear expansion coefficient α (2 × 10 ⁻⁶ / ° C.), and the saddle ring 6 has a larger linear expansion coefficient α (12.5 × 10 ⁻⁶ / ° C.). It is made of high carbon chromium bearing steel SUJ2. The fixed taper ring 7 may be formed of Kovar having a small linear expansion coefficient α (5 × 10 ⁻⁶ / ° C.). Alternatively, the fixed taper ring 7 can be made of SUJ2, and the eaves ring 6 can be made of copper, aluminum, or an alloy thereof having a larger linear expansion coefficient α.

  The saddle ring 6 is in sliding contact with the large end surface 4a of the tapered roller 4 at the inner end surface, and a tapered surface 6a is provided on the inner diameter side thereof and is expanded toward the outer end surface side. Further, the fixed taper ring 7 is coupled to an outer ring spacer 27 fixed to the bearing housing 12 with a bolt 8, and an inward taper surface 7 a that fits the taper surface 6 a of the flange ring 6 is provided on the outer diameter side thereof. It has been. Therefore, as the bearing rotates at a higher speed, the temperature increase of the flange 6 in sliding contact with the large end surface 4a of the tapered roller 4 increases, and the difference in thermal expansion from the fixed tapered ring 7 increases. It moves along the taper surface 7a in the axial direction to escape from the end surface 4a, and when the bearing clearance is reduced due to high-speed rotation, the tapered roller 4 is released to the side of the flange 6 and the preload is adjusted during operation. .

  The outer ring spacer 27 on the front side of the bearing is provided with an oil supply path 27 a that communicates with the oil supply path 20 of the bearing housing 12, and the fixed taper ring 7 communicates with the oil supply path 27 a and An oil discharge hole 7b is provided in the gap between the inner ring 2 and the outer diameter surface of the inner ring 2. Therefore, the space between the large end surface 4a of the tapered roller 4 that is in sliding contact with the flange 6 is favorably lubricated by the air oil discharged from the oil discharge hole 7b. Further, the outer ring spacer 26 on the back side of the bearing is provided with an oil discharge hole 26a communicating with the oil supply passage 20 of the bearing housing 12, and air oil is discharged from the oil discharge hole 26a on the back side.

  Although the enlarged illustration is omitted, the tapered roller bearing 1 on the right side of FIG. 1 has the same configuration, and a separate collar 6 disposed on the front side is accompanied by a difference in thermal expansion from the fixed tapered ring 7. Thus, it moves in the axial direction along the tapered surface 7a, and the preload is adjusted during operation.

FIG. 3 shows the axial clearance ε between the tapered surfaces 6a, 7a, that is, the axial movement amount of the saddle wheel 6 in accordance with the difference in thermal expansion δ (for the radius) between the saddle wheel 6 and the fixed tapered ring 7. Indicates the size. When the inclination angle of each taper surface 6a, 7a is θ, the axial gap ε is expressed by equation (1).
ε = δ / tan θ (1)

  Therefore, if the amount of thermal expansion difference δ when the bearing reaches the maximum rotational speed and the axial movement amount of the saddle wheel 6 necessary for preload adjustment, that is, the axial clearance ε, are obtained by experiment or analysis, the equation (1) is obtained. Based on this, it is possible to appropriately determine the inclination angle θ of each tapered surface 6a, 7a. When the determined inclination angle θ is smaller than the friction angle, the friction coefficient between the tapered surfaces 6a and 7a is reduced to reduce the friction angle, or the heat between the saddle wheel 6 and the fixed tapered ring 7 is reduced. If the inclination angle θ is increased by changing the expansion amount difference δ, the shrinking saddle wheel 6 is lowered along the tapered surface 7a of the fixed taper ring 7 when the temperature is lowered when the bearing is stopped or rotated at a low speed. It moves and adjusts so that a preload does not fall.

  In the above-described embodiment, the tapered roller bearing supports the main shaft of the machine tool. However, the tapered roller bearing according to the present invention is applied to a bearing that supports another rotating shaft whose preload changes at high speed. Also good.

  In the embodiment described above, the saddle wheel is formed of a material having a larger linear expansion coefficient α than that of the fixed taper wheel. However, since the temperature of the saddle wheel is larger than that of the fixed taper wheel, It can also be formed of a material having the same expansion coefficient α.

The longitudinal cross-sectional view which shows the main axis | shaft of the machine tool supported with the tapered roller bearing which concerns on this invention 1 is an enlarged longitudinal sectional view showing a portion of the tapered roller bearing on the left side of FIG. Sectional drawing which shows the magnitude | size of the axial clearance gap (epsilon) between each taper surface accompanying the thermal expansion amount difference (delta) of the saddle wheel and fixed taper ring of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tapered roller bearing 2 Inner ring 2a Raceway surface 3 Outer ring 3a Raceway surface 4 Tapered roller 4a Large end surface 5 Cage 6 Collar ring 6a Tapered surface 7 Fixed taper ring 7a Tapered surface 7b Oil discharge hole 8 Bolt 11 Main shaft 11a Stepped part 12 Bearing box 12a Stepped portion 13 Outer cylinder 14 Oil supply path 15 Cooling groove 16 Oil discharge path 17, 18 Lid 19 Oil supply hole 20 Oil supply path 21 Oil discharge path 22 Oil discharge holes 23, 24 Inner ring spacer 25 Nut 26, 27 Outer ring spacer 26a Discharge Oil hole 27a Oil supply passage

Claims (4)

  A plurality of tapered rollers are arranged between the raceway surface of the inner ring that is attached to the rotating shaft and the raceway surface of the outer ring that is fixed to the bearing housing, and the axial movement of these tapered rollers to the large end face side is restricted. In the tapered roller bearing in which the flange portion is provided on the raceway surface side of the inner ring, the large flange portion is formed by a separate flange ring, and the end surface opposite to the large end surface of the tapered roller is formed on the inner diameter side of the flange ring. A fixed taper ring having a tapered surface on the outer diameter side is provided on the outer diameter side to provide a tapered surface that expands to the side, and the flange is caused by a temperature rise during rotation of the bearing. A tapered roller bearing characterized in that the saddle wheel is moved in the axial direction along the taper surface of the fixed taper ring due to a difference in thermal expansion between the ring and the fixed taper ring.   The tapered roller bearing according to claim 1, wherein the saddle ring is formed of a material having a larger linear expansion coefficient than the fixed tapered ring.   The gap according to claim 1 or 2 which provided a crevice between the inner diameter surface of the above-mentioned collar ring, and the outer diameter surface of the above-mentioned inner ring, and provided the oil discharge hole which discharges lubricating oil towards this gap in the above-mentioned fixed taper ring. Tapered roller bearing.   The tapered roller bearing according to any one of claims 1 to 3, wherein the tapered roller bearing supports a spindle of a machine tool.

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