JP2010091066A - Bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device having simple construction preventing an unnecessary slip at starting rotation, suppressing a rise of a preload during high-speed rotation, and securing high spindle rigidity. <P>SOLUTION: A spindle 3 of a machine tool is installed on a housing 2 via a load-side bearing 5A and a counter-load-side bearing 5B as angular ball bearings arranged back to back. The load-side bearing 5A has an outer ring 11A which is positioned and fixed onto the housing 2 in the axial direction, and the counter-load-side bearing 5B has an outer ring 11B which is not positioned and fixed to the housing 2 in the axial direction. The axial positions of inner rings 12A, 12B of both bearings 5A, 5B are restricted. The size of an axial internal clearance δ of the bearing 5B is positive in a room-temperature operation stopped condition and negative in an operated condition resulting from a temperature difference between the inner and outer rings and the operation of centrifugal force to produce the fixed-position preload. Between the back face of the outer ring 11B of the bearing 5B and the housing 2, an elastic body 10 is laid for energizing the outer ring 11B of the bearing 5B to the front-face side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bearing device including a multi-row angular ball bearing used for supporting a machine tool spindle.

  Among machine tools, a device that rotates a tool and scrapes a workpiece, such as a spindle device of a machining center, is often used at a high speed. In this main shaft device, in the fixed position preload combination angular contact ball bearing that supports the main shaft, the internal preload of the bearing rises during high-speed rotation, so selection of the initial preload amount is important.

  FIG. 16 shows the concept of fixed position preload. When preload is applied to the two angular ball bearings 25A and 25B arranged back to back as shown in the figure, an axial internal clearance δ1 is provided between the inner rings 32A and 32B as shown in FIG. A preload is applied by tightening 32A and 32B in the axial direction. As shown in FIG. 5B, when the axial internal gap δ2 is provided between the outer rings 31A and 31B on both sides, no preload is applied. This will be specifically described.

  FIG. 9 shows an example in which two angular ball bearings 25A and 25B are arranged on the load side and the anti-load side so as to face each other as the bearing device 24 that supports the main shaft 23 of the main shaft device on the front side. The load side in this case refers to the spindle front end side to which an axial load is applied during machining. In the bearing device 24 of this example, as shown in FIG. 10, an axial internal clearance δ1 is provided between the back surface of the inner ring 32B of the bearing 25B on the anti-load side and the inner ring spacer 26, and the main shaft until the axial internal clearance δ1 is blocked. The bearings 25A and 25B are preloaded by tightening the inner rings 32A and 32B of the bearings 25A and 25B between the shoulders 23a of the main shaft 23 and the spacers 28 with the nuts 29 screwed into the bearings 23. The outer rings 31A and 31B of the two bearings 25A and 25B are on the inner diameter side of the bearing fitting surface where the outer ring holding lid 27 provided at the front end of the housing 22 and the outer rings 31A and 31B of the two bearings 25A and 25B of the housing 22 are fitted. The position is fixed in the axial direction by being sandwiched by the inner diameter side protruding portion 22a protruding in the axial direction.

  Thus, in the bearing device 24 in which the preload is in the initial state, when the main shaft 23 is rotated, the increase in the preload of the bearings 25A and 25B is as shown in the graph of FIG. In this case, if the calculated limit preload of the bearings 25A and 25B is 200 kgf, the bearings 25A and 25B may be overheated due to the excessive preload when the main shaft 23 is rotated to 10000 rpm.

FIG. 12 shows the bearing device 24 of FIG. 9 with the inner ring 32A, 32B of both bearings 25A, 25B tightened with a nut 29, and the rear surface of the outer ring 31B of the bearing 25B on the anti-load side and the protruding portion on the inner diameter side of the housing 22 An example in which an axial gap δ2 is provided between 22a and 22a is shown. In this case, since there is an initial gap in the outer ring 31B, no preload is applied even if the inner ring 32B is tightened. In this example, the outer ring spacer 30 in the case of FIG. 9 is replaced with an inner diameter side protruding portion 22b that protrudes more on the inner diameter side than the fitting surface of the both bearing outer rings 31A and 31B of the housing 22.
In this bearing device, when the outer ring 31B of the bearing 25B on the anti-load side is tightened in the axial direction as shown in FIG. 13B from the initial state shown in FIG. 13A, there is a gap between the inner ring 32B and the ball 33B. It turns out that occurs.

  As described above, in the bearing device 24 having the initial gap δ2 in the outer ring 31B, the change in the preload of the bearings 25A and 25B is as shown in the graph of FIG. Will remain. The use of the bearing in such a state with the gap δ2 is not appropriate, and an oil film is not well formed between the raceway surface and the ball due to unnecessary slip, and adverse effects such as metal contact are caused.

In order to avoid excessive preload during high speed rotation, a preload switching mechanism has been proposed in which the amount of preload is switched between low speed rotation and high speed rotation (Patent Document 1). The increase in preload in this case is as shown by a graph in FIG.
Japanese Patent No. 2602325

However, when machining is limited to high-speed rotation, preload at low-speed rotation is not important, and using the preload switching mechanism disclosed in Patent Document 1 has a problem that the structure is expensive and complicated.
Therefore, it is possible to suppress an increase in preload by starting operation with the gap δ2 as shown in FIG. However, in this case, as described above, rattling of the main shaft 23 occurs in the stopped state. This rattling can also cause flaws and indentations in the bearing 25B during transportation and conveyance of the machine. Further, at the start of rotation, no preload is applied to the bearings 25A and 25B, and an oil film is not formed well between the raceway surface of the bearing 25B and the ball due to unnecessary slip, which causes adverse effects such as metal contact.

  An object of the present invention is to provide a bearing device that can eliminate unnecessary slip at the start of rotation, suppress an increase in preload during high-speed rotation, and ensure high spindle rigidity with a simple configuration.

The bearing device according to the present invention includes a housing in which a main shaft of a machine tool is disposed on a load side which is an end side where a load acts on the main shaft, and a bearing disposed on an anti-load side with respect to the load side bearing. The load-side and anti-load-side bearings are angular contact ball bearings, facing each other, and the load-side bearing has the outer ring fixed in the axial direction with respect to the housing. The side bearing is a bearing device in which the outer ring is fixed in a non-positional position relative to the housing in the axial direction, and provided with inner ring position restricting means for restricting the axial position of the inner ring of the bearings on both sides by the housing and the inner ring position restricting means. The axial internal clearance of the bearing to be regulated becomes positive when the bearing is stopped at room temperature, and becomes negative when the bearing is operating due to the temperature difference between the inner and outer rings and the centrifugal force. The preload is generated when the bearing operation is stopped by urging the outer ring of the anti-load side bearing to the front side between the rear surface of the outer ring of the anti-load side bearing and the housing. It is characterized by interposing an elastic body.
According to this configuration, the fixed position preload does not occur at the time of stopping or at the start of operation because the axial internal gap is generated. However, since a certain axial load acts as a constant pressure preload on the outer ring of the non-load bearing due to the spring force of the elastic body, it acts as a constant pressure preload, so the main shaft caused by the axial internal clearance is increased to a certain rotational speed. It eliminates rattling and eliminates unnecessary slipping at the start of rotation. When the rotational speed exceeds a certain level, there is no axial internal clearance due to the difference in thermal expansion due to the temperature difference between the inner and outer rings due to the temperature rise of the bearing and the effect of the inner ring diameter expansion due to centrifugal force, resulting in a fixed position preload state. That is, the constant pressure preload is set at the start of the operation, and is switched to the fixed position preload as the operation proceeds. Thereafter, the preload gradually increases. In addition, since operation with constant position preload during high speed rotation is possible, the rigidity of the main shaft is increased compared to the main shaft of constant pressure preload and the main shaft of a mechanism that switches to constant pressure preload, which is advantageous for increasing the preload at normal speed. Can do. In addition, the size of the initial axial internal clearance that determines the temperature at which the fixed position preload is generated and the spindle rotation speed, that is, the temperature and the spindle rotation speed at which the fixed position preload is generated, is determined by this bearing device. What is necessary is just to set suitably according to the machine tool to which this is applied, the processing purpose, etc.
Thus, according to this bearing device, with a simple configuration, unnecessary slip at the start of rotation can be eliminated, an increase in preload during high-speed rotation can be suppressed, and high spindle rigidity can be ensured.

  In this invention, the elastic body may be an O-ring concentric with the bearing. If an O-ring is used, the configuration can be further simplified.

  In the present invention, the elastic body may be a plurality of coil springs distributed in the circumferential direction. Use of a coil spring makes it easy to obtain an appropriate pressing force with high accuracy.

  In this invention, the elastic body may be a disc spring concentric with the bearing. When a disc spring is used, it is easy to give a strong preload by an elastic body.

  In this invention, between the outer ring of the bearing on the load side and the outer ring of the bearing on the anti-load side, an annular inner diameter protruding to the inner diameter side from the bearing fitting surface on which the outer rings of the bearings on both sides of the housing are fitted A side protrusion may be interposed, and the elastic body may be provided on the end face of the inner diameter side protrusion. By providing the elastic body on the housing side in this way, it is not necessary to perform processing for arranging the elastic body on the bearing outer ring, and a bearing having a normal configuration can be used as it is.

  In this invention, you may provide the said elastic body in the outer ring | wheel of the bearing of the said anti-load side. When the outer ring of the bearing is provided with an elastic body, the bearing can be manufactured and prepared with an elastic body, and the housing does not require processing for the arrangement of the elastic body. The configuration can be simplified.

  In this invention, between the outer ring of the bearing on the load side and the outer ring of the bearing on the anti-load side, an annular inner diameter protruding to the inner diameter side from the bearing fitting surface on which the outer rings of the bearings on both sides of the housing are fitted A side protrusion may be interposed, and an outer ring spacer may be disposed between the inner diameter side protrusion and the outer ring of the bearing on the anti-load side, and the elastic body may be provided in the outer ring spacer. When an elastic body is provided in the outer ring spacer, the elastic body is provided in the outer ring spacer, which is smaller than the housing and the like and is a simpler part than the bearing outer ring. Thus, the configuration can be further simplified.

  In the present invention, either one or both of the load side and the anti-load side may be a combination of a plurality of rows of bearings. Even in such a combination of a plurality of rows of bearings, an appropriate preload from the start of operation to high-speed operation can be obtained.

The machine tool spindle device of the present invention is such that the spindle of the machine tool is supported by the bearing device of any one of the above inventions.
According to this configuration, the unnecessary slip at the start of rotation in the bearing device can be eliminated, the increase in the preload at the time of high speed rotation can be suppressed, and high spindle rigidity can be ensured, so that the spindle rotation accuracy can be ensured.

  The bearing device according to the present invention includes a housing in which a main shaft of a machine tool is disposed on a load side which is an end side where a load acts on the main shaft, and a bearing disposed on an anti-load side with respect to the load side bearing. The load-side and anti-load-side bearings are angular contact ball bearings, facing each other, and the load-side bearing has the outer ring fixed in the axial direction with respect to the housing. The side bearing is a bearing device in which the outer ring is fixed in a non-positional position relative to the housing in the axial direction, and provided with inner ring position restricting means for restricting the axial position of the inner ring of the bearings on both sides by the housing and the inner ring position restricting means. The axial internal clearance of the bearing to be regulated becomes positive when the bearing is stopped at room temperature, and becomes negative when the bearing is operating due to the temperature difference between the inner and outer rings and the centrifugal force. The preload is generated when the bearing operation is stopped by biasing the outer ring of the anti-load side bearing to the front side between the housing and the rear surface of the outer ring of the anti-load side bearing. Since an elastic body is interposed, an unnecessary slip at the start of rotation can be eliminated with a simple configuration, and an increase in preload during high-speed rotation can be suppressed, and high spindle rigidity can be ensured.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1A is a sectional view of a spindle device of a machine tool in which the bearing device of this embodiment is used. The main shaft device 1 is a housing 2 in which a main shaft 3 is rotatably supported by a bearing device 4. The bearing device 4 is a multi-row angular contact ball bearing.

  The bearing device 4 includes a bearing 5A disposed on the load side, which is an end side where a load acts on the main shaft 3, and a bearing 5B disposed on the side opposite to the load side bearing 5A. A front portion and a rear portion, which are load side portions on the tool mounting end 3 a side of the main shaft 3, are supported by the housing 2 via both the bearings 5 </ b> A and 5 </ b> B. The load-side and anti-load-side bearings 5A and 5B are composed of angular contact ball bearings having outer rings 11A and 11B, inner rings 12A and 12B, balls 13A and 13B, and cages 14A and 14B for holding the balls 13A and 13B, respectively. They are facing each other. Between the outer ring 11A of the bearing 5A on the load side and the outer ring 11B of the bearing 5B on the anti-load side, the inner diameter side of the bearing fitting surface where the outer rings 11A and 11B of the bearings 5A and 5B on both sides of the housing 2 are fitted. An annular inner-side protruding portion 2a protruding is interposed. An inner ring spacer 6 is interposed between the inner rings 12A and 12B of both bearings 5A and 5B.

  The load-side bearing 5 </ b> A has its outer ring 11 </ b> A fixed in the axial direction with respect to the housing 2. Specifically, the outer ring 11A of the bearing 5A on the load side is fixed in the axial direction by being sandwiched between the outer ring holding lid 7 fixed to the front end of the housing 2 and the end surface of the inner diameter side protruding portion 2a of the housing 2. Has been. The bearing 5B on the non-load side has its outer ring 11B fixed to the housing 2 in the axial direction. Specifically, the outer ring 11 </ b> B of the bearing 5 </ b> B on the anti-load side is a loose fit on the bearing fitting surface of the housing 2.

  The axial positions of the inner rings 12A and 12B of both bearings 5A and 5B are restricted by the inner ring position restricting means 20. Specifically, one end surface of the inner ring 12A of the bearing 5A on the load side is engaged with the end surface of the shoulder portion 3b having a large diameter following the tool mounting end 3a of the main shaft 3, and the bearing 5B on the anti-load side One end surface of the inner ring 12B is tightened with a nut 9 via a spacer 8 which is a cylindrical member. Thereby, the axial direction positions of the inner rings 12A and 12B of both bearings 5A and 5B are restricted. That is, the inner ring position restricting means 20 includes the main shaft 3, its shoulder 3a, the inner ring spacer 6, the spacer 8, the nut 9, and the like.

Between the rear surface of the outer ring 11B of the bearing 5B on the opposite load side and the housing 2, a predetermined amount of gap δ is provided in an initial state regulated by the inner ring position regulating means 20. This gap δ becomes an axial internal gap of the bearing 5B on the anti-load side. The size of the axial internal gap δ is positive when the bearings 5A and 5B are stopped at room temperature (ie, room temperature), and the diameter of the inner ring 12B is increased by the temperature difference between the inner and outer rings and centrifugal force when the bearings 5A and 5B are in operation. The magnitude is negative due to the action and generates a fixed position preload. It should be noted that the axial axial clearance δ is negative and the temperature and the spindle speed at which the fixed position preload is generated, that is, the initial axial that determines the temperature and the spindle speed at which the fixed position preload is generated. The size of the internal gap δ may be set as appropriate according to the machine tool to which the bearing device 1 is applied, the processing purpose, and the like. For example, the main shaft rotational speed is 4000 rpm (the temperature difference between the inner and outer rings is about 2 ° C.). The size is such that it becomes zero.
As a specific example, several tens of μm is set as the axial internal gap δ.

  Between the back surface of the outer ring 11B of the bearing 5B on the anti-load side and the housing 2, an elastic body 10 that urges the outer ring 11B of the bearing 5B on the anti-load side to the front side is interposed. Specifically, as shown in FIG. 1 (B), which is an enlarged view of portion A in FIG. 1 (A), an annular circumferential groove 15 concentric with the bearings 5A and 5B on the end face of the inner diameter side protruding portion 2a of the housing 2. And an O-ring is accommodated as the elastic body 10 in the circumferential groove 15. In a state where both bearings 5A and 5B are assembled (that is, in a state where the axial internal gap δ is an initial value), the elastic body 10 made of an O-ring is compressed, and the outer ring of the bearing 5B on the anti-load side is compressed by the restoring force. 11A is urged to the front side.

  The operation of the above configuration will be described. When the operation of the bearing device 4 is stopped or started, there is a gap δ between the outer ring 11B of the bearing 5B on the anti-load side and the end face of the inner diameter side protruding portion 2a of the housing 2, and this gap δ is on the anti-load side. This is an axial internal clearance of the bearing 5B, and no fixed position preload occurs. However, since the elastic body 10 is interposed in a compressed state between the end face of the inner diameter side protruding portion 2a of the housing 2 and the outer ring 11B, a preload is applied to the bearing 5B on the anti-load side by the elastic restoring force of the elastic body 10. It is done. In other words, until the axial gap δ between the end surface of the inner diameter side protruding portion 2a of the housing 2 and the back surface of the outer ring 11B is blocked, the bearing 5B is preloaded by the constant pressure preload by the elastic restoring force. As a result, it is possible to eliminate shakiness of the main shaft 3 caused by the axial internal gap δ until the rotational speed is increased to some extent, and to eliminate unnecessary slip at the start of rotation.

  In the bearing 5B on the non-load side, the axial internal clearance δ becomes smaller due to the expansion of the inner ring 12B due to centrifugal force and the temperature difference between the inner and outer rings 12B and 11B (normally the inner ring 12B has a higher temperature). Become. When the rotational speed increases and the axial internal gap δ becomes a negative value, a fixed position preload occurs. That is, the constant pressure preload is switched to the fixed position preload.

FIG. 2 is a graph showing changes in the amount of preload in the bearing device. When the rotational speed exceeds a certain level, the axial internal gap δ disappears and the amount of preload increases. In the graph of FIG. 2, when the rotational speed exceeds 4000 rpm, the internal gap becomes smaller due to the action of centrifugal force, etc., and the axial interior between the end surface of the inner diameter side protruding portion 2a of the housing 2 and the rear surface of the outer ring 11B. The gap δ is clogged and a fixed position preload is reached, and thereafter the preload gradually increases. The increase in the preload in this case is suppressed because the axial internal gap δ is given at the time of assembly, and the limit preload does not exceed 200 kgf even at 10,000 rpm. By adjusting the set amount of the axial internal gap δ set at the time of assembly, the axial internal gap δ can be blocked at the target rotational speed. A preload state is established.
In the example shown in the figure, the axial internal clearance δ becomes zero when the rotational speed exceeds 4000 rpm, but the axial internal clearance δ is within the range of 2000 to 6000 rpm (for example, about 2000 rpm, 3000 rpm, 5000 rpm, or 6000 rpm). The axial internal gap δ at the initial stage (when operation is stopped) may be set so that becomes zero. In this case, an increase in the rotational speed is accompanied by an increase in the bearing temperature, but the initial axial internal gap δ may be set by paying attention only to the rotational speed regardless of the temperature change.

FIG. 3 is a graph showing the rigidity of a φ90 mm angular ball bearing in a 200 kgf preload state in comparison with a fixed position preload and a fixed pressure preload, and the fixed position preload is superior in rigidity. Represents that. Since the bearing device 4 of this embodiment can be operated by the fixed position preload at the time of high speed rotation as described above, as is clear from the graph of FIG. Compared with the main shaft of the mechanism that switches to the constant pressure preload which is advantageous for increasing the preload, the main shaft rigidity can be increased.
Thus, in this bearing device 4, with a simple configuration, unnecessary slip at the start of rotation can be eliminated, an increase in preload during high-speed rotation can be suppressed, and high spindle rigidity can be ensured.

  Further, the spindle device 1 of the machine tool provided with the bearing device 4 eliminates unnecessary slip at the start of rotation in the bearing device 4 and can suppress an increase in preload during high-speed rotation, thereby improving the spindle rotation accuracy. Can do.

  FIG. 4 shows another embodiment of the present invention. In this embodiment, in the bearing device 4 shown in FIGS. 1 to 3, a plurality of (6 to 10 in the illustrated example) coils are provided between the back surface of the outer ring 11 </ b> B of the bearing 5 </ b> B on the anti-load side and the housing 2. An elastic body 10A made of a spring is interposed. Specifically, a plurality of concave portions 16 are provided in the circumferential direction on the end surface of the annular inner shape protruding portion 2a protruding toward the inner diameter side of the housing 2, and a coil spring is provided as an elastic body 10A in these concave portions 16. Each is housed. The elastic body 10A made of a coil spring is compressed in a state where the fixed position preload is applied to both the bearings 5A and 5B, and the outer ring 11A of the anti-load side bearing 5B is urged to the front side by the restoring force. Yes. Other configurations and operational effects are the same as those of the embodiment of FIGS.

  FIG. 5 shows still another embodiment of the present invention. In this embodiment, in the bearing device 4 shown in FIGS. 1 to 3, an elastic body made of a disc spring concentric with the bearings 5 </ b> A and 5 </ b> B between the rear surface of the outer ring 11 </ b> B of the bearing 5 </ b> B on the opposite load side and the housing 2. 10B is interposed. Specifically, an elastic body 10B made of a disc spring is interposed between the end face of the annular inner protrusion 2a that protrudes toward the inner diameter side of the housing 2 and the back surface of the outer ring 11B of the bearing 5B that faces this. I am letting. Other configurations and operational effects are the same as those of the embodiment of FIGS.

  FIG. 6 shows still another embodiment of the present invention. In this embodiment, in the bearing device 4 shown in FIGS. 1 to 3, an annular circumferential groove 17 concentric with the bearings 5 </ b> A and 5 </ b> B is provided on the back surface of the outer ring 11 </ b> B of the bearing 5 </ b> B on the opposite load side. An O-ring is accommodated as the elastic body 10C. Other configurations and operational effects are the same as those of the embodiment of FIGS.

  FIG. 7 shows still another embodiment of the present invention. In this embodiment, in the bearing device 4 shown in FIGS. 1 to 3, an outer ring spacer 18 is disposed between the inner diameter side protruding portion 2a of the housing 2 and the outer ring 11B of the bearing 5B on the opposite load side. An elastic body 10D is interposed between the spacer 18 and the inner diameter side protruding portion 2a. Specifically, an annular circumferential groove 19 concentric with the bearings 5A and 5B is provided on an end face of the outer ring spacer 18 facing the inner diameter side protruding portion 2a, and an O-ring is accommodated in the circumferential groove 19 as an elastic body 10D. is doing. Other configurations and operational effects are the same as those of the embodiment of FIGS.

  FIG. 8 shows still another embodiment of the present invention. In this embodiment, in the bearing device 4 shown in FIGS. 1 to 3, the load-side bearing 5A and the anti-load-side bearing 5B are each a combination of two rows of bearings. Specifically, as the load-side bearing 5A, two angular ball bearings with the front side facing the front side of the main shaft 3 are arranged in the axial direction, and as the anti-load side bearing 5B, the front side is the rear of the main shaft 3. Angular ball bearings facing the side are arranged in two rows in the axial direction. Of the two rows of bearings 5B and 5B on the opposite load side, the elastic body 10 is interposed between the back surface of the outer ring 11B of the bearing 5B near the inner diameter side protruding portion 2a of the housing 2 and the inner diameter side protruding portion 2a. . Other configurations and operational effects are the same as those of the embodiment of FIGS.

  In the embodiment shown in the figure, the type of elastic body and the installation structure of the elastic body in each embodiment shown in FIGS. 4 to 7 may be adopted. Further, the number of bearing arrangements of the load-side bearing 5A and the anti-load-side bearing 5B is not limited to two, but may be three or more, and only one of the bearings 5A and 5B is a plurality of rows. Also good.

  In each of the above embodiments, the front side bearing of the housing 1 is the load side bearing 5A and the rear side bearing is the anti-load side bearing 5B. However, the front side bearing is a bearing device comprising an array of a plurality of angular ball bearings. The rear side bearing may be configured by a bearing device having an arrangement of cylindrical roller bearings, and the present invention may be applied to the front side bearing.

(A) is sectional drawing of the front side of the main axis | shaft apparatus of the machine tool which mounts the bearing apparatus concerning 1st Embodiment of this invention, (B) is an enlarged view of the A section in (A). It is a graph which shows the preload rise of the bearing apparatus. It is a graph which compares and shows the case where a fixed position preload is given to an angular ball bearing, and the case where a constant pressure preload is given. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing of the bearing apparatus in which the preload is contained in the initial state. It is an expanded sectional view of the important section of the bearing device. It is a graph which shows the preload rise of the bearing apparatus. It is a graph which shows the preload rise of the bearing apparatus using a preload switching mechanism. Sectional drawing of the bearing apparatus which provided the axial clearance gap in the initial state is shown. (A) is principal part sectional drawing which shows the state before giving preload to the bearing apparatus, (B) is principal part sectional drawing which shows the state after preload provision. It is a graph which shows the preload rise of the bearing apparatus. It is explanatory drawing which shows the state at the time of the fixed position preload of a general bearing apparatus, and the time of axial gap provision.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main shaft apparatus 2 ... Housing 2a ... Inner diameter side protrusion part 3 ... Main shaft 4 ... Side bearing apparatus 5A, 5B ... Bearing 10, 10A, 10B, 10C, 10D ... Elastic body 11A, 11B ... Outer ring 12A, 12B ... Inner ring 18 ... Outer ring spacer 20 ... Inner ring position restricting means

Claims (9)

The main axis of the machine tool is installed in the housing via a bearing arranged on the load side, which is an end side where a load acts on the main spindle, and a bearing arranged on the side opposite to the load side bearing. The bearings on the anti-load side are angular contact ball bearings, facing each other, the bearings on the load side fix the outer ring in the axial direction with respect to the housing, and the bearing on the anti-load side has the outer ring attached to the housing. In a bearing device provided with inner ring position restricting means that is non-position fixed in the axial direction and restricts the axial position of the inner ring of the bearings on both sides.
The axial internal clearance of the bearing, which is regulated by the housing and the inner ring position regulating means, is positive when the bearing is stopped at normal temperature, and is negative due to the temperature difference between the inner and outer rings and the centrifugal force. The size is such that a preload at a fixed position is generated, and the outer ring of the anti-load side bearing is urged to the front side between the rear surface of the outer ring of the anti-load side bearing and the housing to generate pre-load when the bearing operation is stopped. A bearing device comprising an elastic body to be interposed.   The bearing device according to claim 1, wherein the elastic body is an O-ring concentric with the bearing.   The bearing device according to claim 1, wherein the elastic body is a plurality of coil springs distributed in the circumferential direction.   The bearing device according to claim 1, wherein the elastic body is a disc spring concentric with the bearing.   5. The bearing fitting surface according to claim 1, wherein the outer rings of the bearings on both sides of the housing are fitted between the outer ring of the bearing on the load side and the outer ring of the bearing on the anti-load side. A bearing device in which an annular inner diameter side protruding portion that protrudes further toward the inner diameter side is interposed, and the elastic body is provided on an end surface of the inner diameter side protruding portion.   The bearing device according to claim 1, wherein the elastic body is provided on an outer ring of the bearing on the anti-load side.   5. The bearing fitting surface according to claim 1, wherein the outer rings of the bearings on both sides of the housing are fitted between the outer ring of the bearing on the load side and the outer ring of the bearing on the anti-load side. An annular inner diameter protruding portion that protrudes further toward the inner diameter side is interposed, and an outer ring spacer is disposed between the inner diameter side protruding portion and the outer ring of the bearing on the anti-load side, and the elastic body is disposed on the outer ring spacer. Bearing device provided with.   5. The bearing device according to claim 1, wherein one or both of the load side and the anti-load side bearings are a combination of a plurality of rows of bearings. 6.   A machine tool spindle device in which a spindle of a machine tool is supported by the bearing device according to any one of claims 1 to 8.

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