JP7185546B2 - Cooling structure of bearing unit and spindle unit of machine tool - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure for a bearing device and, for example, to a cooling structure for a main shaft of a machine tool and a bearing incorporated in the main shaft.

In the spindle device of a machine tool, it is necessary to keep the temperature rise of the device small in order to ensure machining accuracy. However, recent machine tools tend to operate at higher speeds in order to improve machining efficiency, and the heat generated from the bearings that support the spindles has also increased along with the higher speeds. In addition, so-called motor built-in types, in which a driving motor is built into the device, are becoming more common, and this is becoming a factor in generating heat in the device.
An increase in temperature of the bearing due to heat generation results in an increase in the preload of the bearing, which should be suppressed as much as possible in consideration of higher spindle speeds and higher machining accuracy.

As one of the means for suppressing the temperature rise of the spindle device, as shown in FIG. Patent Document 1 and the like propose a cooling method in which compressed air is discharged through the air.

Japanese Patent No. 6144024

In the case of the configuration of Patent Document 1, since the spacer width W is equivalent to the bearing width X, even if the nozzle 110 for discharging compressed air is provided at the center of the outer ring spacer 104 in the axial direction, the distance between the discharge port and the bearing is short, a sufficient cooling effect can be obtained.

However, when the spacer width W is large, for example, when the spacer width W is 2.5 times or more the bearing width X as shown in FIG. Even if the nozzle 110 is provided and the inner ring spacer 105 is cooled by the effect of compressed air, the cooling effect is reduced because the distance from the positively cooled portion S to the bearing 1 is long.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cooling structure for an air-cooled bearing device and a spindle device for a machine tool, which can ensure a cooling effect for the bearings even when the width of the spacer is large.

A cooling structure for a bearing device of the present invention includes an outer ring spacer and an inner ring spacer adjacent to an outer ring and an inner ring of a bearing, respectively, and a nozzle for discharging compressed air to the outer ring spacer toward the outer peripheral surface of the inner ring spacer. A cooling structure for a bearing device provided with
The nozzle is inclined forward in the direction of rotation of the inner ring spacer and is offset from an arbitrary radial line in a cross section perpendicular to the axial center of the outer ring spacer in a direction perpendicular to the straight line,
The width of the outer ring spacer and the inner ring spacer is 2.5 times or more the bearing width, and the distance from the center of the nozzle to the side surface of the bearing is equal to or less than the bearing width and 1 of the bearing width. /2 or more.

According to this configuration, since the nozzle is inclined forward in the rotational direction, compressed air for cooling is sprayed from the nozzle onto the outer peripheral surface of the inner ring spacer. As a result, the compressed air turns into a swirling flow in the annular gap between the outer peripheral surface of the inner ring spacer and the inner peripheral surface of the outer ring spacer to cool the inner ring spacer. As a result, the bearing inner ring fixed in contact with the end surface of the inner ring spacer is cooled by heat conduction.

If the nozzle is placed at a position far from the bearing, the cooling effect is reduced as described in the subject. On the other hand, if it is arranged at a position close to the bearing, the compressed air will not swirl in the direction of rotation of the inner ring, and will quickly diffuse in the axial direction. Therefore, it cannot stay on the surface of the inner ring spacer for a long time, and the cooling effect is lowered. In the case of grease lubrication, there is a problem that the grease enclosed in the bearing is discharged out of the bearing, lowering lubrication reliability.
Therefore, as shown in FIG. 8, an obstacle wall 105a is provided on the end surface of the inner ring spacer to reduce the inflow of compressed air. Furthermore, the distance Y from the center of the nozzle to the side surface of the bearing is set to be equal to or less than the bearing width X and equal to or more than 1/2 of the bearing width X. Within this range, the distance from the position where the inner ring spacer is cooled by the compressed air discharged from the nozzle to the bearing is not too far, and the nozzle position is too close, causing the compressed air to spread without swirling. It was confirmed that the cooling effect of the bearing can be ensured even when the width of the spacer is large. When the width of the spacer is narrow, the nozzle position is too far away and the cooling effect is reduced. The effect of restricting the distance Y to the side surface is exhibited.

In the cooling structure of the bearing device of the present invention, the outer ring spacer has an exhaust path for exhausting air from the space between the outer ring spacer and the inner ring spacer to the bearing side and the opposite side of the nozzle. may be provided.

When a nozzle for discharging compressed air is provided near the bearing, the compressed air flowing toward the bearing is discharged through an exhaust passage provided between the outer ring spacer and the bearing and through the inside of the bearing. On the other hand, if there is no place to exhaust the compressed air flowing toward the opposite side of the bearing, the compressed air tends to stay in the space between the inner ring spacer and the outer ring spacer after taking heat from the inner ring spacer, thereby reducing the cooling effect. For this reason, it is necessary to provide exhaust air on the side opposite to the bearing as well.

When each of the exhaust passages is provided, the exhaust passage on the side opposite to the bearing may be inclined so that the exhaust port faces forward in the rotational direction of the inner ring spacer.
Although the exhaust passage may be provided in the radial direction, the exhaust performance is improved by providing the exhaust passage so as to be inclined forward in the direction of rotation of the inner ring spacer.

Further, when each of the exhaust passages is provided, the difference between the volume of the exhaust passage on the bearing side and the volume of the exhaust passage on the side opposite to the bearing is preferably within 10% of the volume of the exhaust passage on the bearing side. .
By making the volume of the exhaust groove provided on the side opposite to the bearing equal to that of the exhaust groove provided on the bearing side, it is possible to prevent the compressed air from flowing biasedly toward either the bearing side or the opposite side.

In the bearing device cooling structure of the present invention, the outer ring spacer and the inner ring spacer are interposed between two adjacent bearings, and the nozzles are provided on both sides of the center position of the spacer width of the outer ring spacer. may be
When the outer ring spacer and the inner ring spacer are arranged between the bearings in this way, and the nozzles are provided for the bearings on both sides, the cooling caused by restricting the distance between the nozzles and the bearings and the spacer width Securing of the effect is exhibited more effectively.

A spindle device for a machine tool of the present invention may include the cooling structure for a bearing device having any one of the above configurations of the present invention.
In the spindle device of a machine tool, it is necessary to keep the temperature rise of the device small in order to ensure machining accuracy.

A cooling structure for a bearing device of the present invention includes an outer ring spacer and an inner ring spacer adjacent to an outer ring and an inner ring of a bearing, respectively, and a nozzle for discharging compressed air to the outer ring spacer toward the outer peripheral surface of the inner ring spacer. , wherein the nozzle is inclined forward in the rotational direction of the inner ring spacer, and from an arbitrary radial straight line in a cross section perpendicular to the axis of the outer ring spacer, At a position offset in a direction orthogonal to this straight line, the width of the outer ring spacer and the inner ring spacer is 2.5 times or more the bearing width, and the distance from the center of the nozzle to the side surface of the bearing is Since it is equal to or less than the bearing width and equal to or more than 1/2 of the bearing width, the cooling effect of the bearing can be ensured even when the width dimension of the spacer is large.

Since the spindle device of the machine tool of the present invention includes the cooling structure for the bearing device of any one of the configurations of the present invention, it is possible to ensure the cooling effect of the bearings even when the width dimension of the spacer is large.

1 is a cross-sectional view of a cooling structure for a bearing device according to a first embodiment of the present invention; FIG. It is explanatory drawing of the dimensional relationship of the bearing and spacer. FIG. 4 is a cross-sectional view of the outer ring spacer and the inner ring spacer in the cooling structure of the bearing device taken at the nozzle position; FIG. 5 is a cross-sectional view of a cooling structure for a bearing device according to another embodiment of the present invention; FIG. 4 is a cross-sectional view of an outer ring spacer showing an example of an exhaust passage on the side opposite to the bearing in the cooling structure of the bearing device; FIG. 5 is a cross-sectional view of an outer ring spacer showing another example of an exhaust passage on the side opposite to the bearing in the cooling structure of the bearing device; FIG. 2 is a cross-sectional view of a spindle device of a machine tool provided with a cooling structure for the bearing device; FIG. 11 is a cross-sectional view of a conventional example; FIG. 4 is a cross-sectional view of a cooling structure for a bearing device according to a proposed example;

A cooling structure for a bearing device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. The cooling structure of the bearing device of this example is applied to, for example, a spindle device of a machine tool, which will be described later with reference to FIG. However, it is not limited to the spindle device of the machine tool.
As shown in FIG. 1, in this bearing device, outer ring spacers 4 and inner ring spacers 5 are interposed between outer rings 2, 2 and inner rings 3, 3 of a plurality of bearings 1, 1 arranged axially. there is The outer ring 2 and the outer ring spacer 4 are installed on the inner peripheral surface of the housing 6 , and the inner ring 3 and the inner ring spacer 5 are fitted on the outer peripheral surface of the rotating shaft 7 . The rotating shaft 7 is, for example, a main shaft of a machine tool. A rolling bearing, specifically an angular contact ball bearing is used for each bearing 1, and the bearings 1, 1 on both sides are installed in a back-to-back arrangement. Both bearings 1, 1 are provided with counter bores on the opposite side of the contact angle on the outer diameter surface of the inner ring 2 and the inner diameter surface of the outer ring 3, respectively. A plurality of rolling elements 8 are interposed between the raceway surfaces of the inner and outer rings 3 and 2, and these rolling elements 8 are held by a retainer 9 at regular intervals in the circumferential direction. The retainer 9 has a ring shape and is of an outer ring guide type.

A cooling structure will be described. Near both ends of the outer ring spacer 4, one or a plurality of (three in this example) nozzles 10 for discharging compressed air toward the outer peripheral surface of the inner ring spacer 5 are provided side by side in the circumferential direction. . The nozzle 10 has a stepped round hole that is thicker on the inflow side and narrower on the discharge side.

On the bearing side of the nozzle 10, the outer ring spacer 4 is provided with an exhaust passage 15 for exhausting air from the space between the outer ring spacer 4 and the inner ring spacer 5 to the outside at one or more locations in the circumferential direction. there is The exhaust path 15 is configured as a radial through hole formed by a radial groove formed in the end surface of the outer ring spacer 4 and the side surface of the outer ring 2 of the bearing 1 .

The inner peripheral surface portion of the outer ring spacer 4 at the axial position where the nozzle 10 is provided is close to the outer peripheral surface of the inner ring spacer 5 with an annular convex portion 4a formed thereon. Annular obstacle walls 5 a are provided on the outer peripheral surface of both ends of the inner ring spacer 5 , the projecting ends of which approach the outer peripheral surface of the outer ring spacer 4 . The obstruction wall 5 a prevents the compressed air discharged from the nozzle 10 between the outer ring spacer 4 and the inner ring spacer 5 from flowing toward the rolling bearing 1 and guides the compressed air to the exhaust path 14 .

The inner ring spacer 5 is assembled with the inner ring spacer 5 and the outer ring spacer 4 by interference between the obstacle walls 5a at both ends of the inner ring spacer 5 and the protrusions 4a at both ends of the outer ring spacer 4. is divided into two axially aligned inner ring spacer divisions 5A, 5A. Although the division position is the center in the axial direction, it may be shifted to any position. In this specification, the width W of the inner ring spacer 5 refers to the combined width of the two inner ring spacer segments 5A, 5A.

The axial position of the nozzle 10 is regulated as follows. That is, the distance Y (FIG. 2) from the center of the nozzle 10 to the side surface of the bearing is set to be equal to or less than the bearing width X and equal to or more than 1/2 of the bearing width X. Expressed as a formula,
(1/2)X≧Y≧X.
However, the restriction on the distance Y is applied when the width W of the outer ring spacer 4 and the inner ring spacer 5 is 2.5 times the bearing width X or more.

As shown in FIG. 3, the plurality of nozzles 10 are arranged equidistantly around the circumference. The air discharge direction of each nozzle 10 is inclined forward in the rotational direction A of the main shaft 7 . Each nozzle 10 has a linear shape and is offset from an arbitrary radial straight line L in a cross section perpendicular to the axial center of the outer ring spacer 4 in a direction perpendicular to the straight line L by an offset amount OFF. . The reason for offsetting the nozzles 10 is to make the discharged air act as a swirling flow in the rotation direction of the main shaft 7 to improve the cooling effect. The offset amount OFF of the nozzle 10 is set within the range of 0.8D/2 or more and D/2 or less with respect to the outer diameter dimension (D) of the inner ring spacer 5 . This range is the result of testing and provides the greatest cooling effect.

An introduction groove 11 for introducing compressed air, which is cooling air, is provided on the outer peripheral surface of the outer ring spacer 4 . A cooling air supply hole 13 (FIG. 1) is provided in the housing 6 so as to communicate with the introduction groove 11. The cooling air supply hole 13 is connected to a compressed air supply source such as a blower outside the housing 6 (see FIG. 1). not shown).

Actions and effects will be described.
Using the inner ring spacer 5 and the outer ring spacer 4, the bearing 1 is indirectly cooled by discharging compressed air from a nozzle 10 provided on the outer ring spacer 4 to the outer peripheral surface of the inner ring spacer 5. It can be carried out. Since the compressed air nozzle 10 of the outer ring spacer 4 is inclined forward in the rotational direction A, the compressed air for cooling is supplied from the cooling air supply hole 13 provided in the housing 6 through the nozzle 10 between the inner rings. The outer peripheral surface of the seat 5 is sprayed. As a result, the compressed air turns into a swirling flow in the annular gap between the outer peripheral surface of the inner ring spacer 5 and the inner peripheral surface of the outer ring spacer 4 to cool the inner ring spacer 5 . As a result, the bearing inner ring 3 fixed in contact with the end surface of the inner ring spacer 5 is cooled by heat conduction.

In this case, if the nozzle 10 is too far from the bearing 1, the cooling effect is lowered. On the other hand, even if it is too close to the bearing 1, the compressed air will not swirl in the direction of rotation of the inner ring, and will soon diffuse in the axial direction. Therefore, since it cannot stay on the surface of the inner ring spacer 5 for a long time, the cooling effect is lowered. In the case of grease lubrication, the grease enclosed in the bearing 1 is discharged outside the bearing, lowering lubrication reliability.
Therefore, the distance Y from the center of the nozzle 10 to the side surface of the bearing 1 is set to be equal to or less than the bearing width X and equal to or more than 1/2 of the bearing width X. Within this range, the distance from the position where the inner ring spacer 5 is cooled by the compressed air discharged from the nozzle 10 to the bearing 1 is not too far, and the nozzle position is too close so that the compressed air is diffused without swirling. The cooling effect of the bearing 1 can be ensured even when the width W of the spacers 4 and 5 is large. When the spacer width W is narrow, there is no problem that the nozzle position is too far and the cooling effect is lowered. to the side surface of the bearing is effective.

FIG. 4 shows another embodiment of the invention. In this embodiment, in the first embodiment described with FIGS. An exhaust passage 16 is provided on the side opposite to the bearing.
The exhaust path 16 on the side opposite to the bearing is a hole that penetrates between the inner and outer peripheral surfaces of the outer ring spacer 4, is positioned in the center of the outer ring spacer 4 in the axial direction, and is provided at one or more locations in the circumferential direction. is provided. Further, in this example, the exhaust passage 16 on the side opposite to the bearing extends in the radial direction of the outer ring spacer 4 .
The volume difference between the exhaust path 15 on the bearing side and the exhaust path 16 on the side opposite to the bearing is within 10% of the volume of the exhaust path 15 on the bearing side.
Other configurations in this embodiment are the same as those in the first embodiment.

The reason why the exhaust path 16 is provided on the side opposite to the bearing is as follows. When a nozzle 10 for discharging compressed air is provided near the bearing, the compressed air flowing toward the bearing is discharged through an exhaust passage 15 provided between the outer ring spacer 4 and the bearing 1 and the inside of the bearing 1. . On the other hand, if there is no place to exhaust the compressed air flowing toward the opposite side of the bearing, after taking heat from the inner ring spacer 5, it tends to stay in the space between the inner ring spacer 10 and the outer ring spacer 4, resulting in a cooling effect. goes down. By providing the exhaust path 16 on the side opposite to the bearing, the air that has taken heat from the inner ring spacer 10 is discharged to the outside, enhancing the cooling effect.

When providing the exhaust passage 16 on the side opposite to the bearing, the difference between the volume of the exhaust passage 15 on the bearing side and the volume of the exhaust passage 16 on the side opposite to the bearing should be within 10% of the volume of the exhaust passage 15 on the bearing side. is preferred.
By making the volume of the exhaust path 16 provided on the opposite side to the same as that of the exhaust path 15 provided on the bearing side, it is possible to prevent the compressed air from flowing biasedly toward either the bearing side or the anti-bearing side. can.

The exhaust passage 16 on the side opposite to the bearing of the outer ring spacer 4 may be inclined so that the exhaust port 16a faces forward in the rotational direction A of the inner ring spacer 5, as shown in FIG.
Although the exhaust passage 16 may be provided in the radial direction as shown in FIG. 5, the exhaust capacity can be further improved by providing the exhaust passage 16 so as to be inclined forward in the rotational direction A of the inner ring spacer 5 .

FIG. 7 shows an example of a spindle device of a machine tool, to which the bearing device cooling structure of the embodiment described with FIG. 1 or FIG. 4 is applied.
A main shaft 7A, which is the rotating shaft 7 in FIG. The main shaft 7A is provided with a chuck 17 for gripping a tool or a work at its tip, and is connected to a drive motor 18 at its rear end. Although the drive motor 18 is provided outside the housing 6 in this example, it may be of the built-in type provided inside the housing 6 . Between the bearings 1, 1, the above-mentioned structure, for example, the outer ring spacer 4 and the inner ring spacer 5 in the example of FIG. 4 are provided. The housing 6 is provided with cooling air supply holes 13 that communicate with the nozzles 10 of the outer ring spacer 4 through the introduction grooves 11, and an in-housing exhaust path 20 that communicates with the exhaust paths 15 and 16. there is Further, the housing 6 is provided with a coolant flow path 21 for circulating the coolant.

According to the main spindle device of the machine tool having this configuration, the cooling effect obtained by applying the cooling structure of the bearing device is exhibited, and high speed rotation of the main spindle 7A and high precision machining can be obtained.

In each of the above-described embodiments, the case where the bearings 1 are provided in two rows and the nozzle 10 is provided in the outer ring spacer 4 disposed between them has been described. or one row. Further, the outer ring spacer 4 on which the nozzle 10 is provided may not be provided between the bearings. Furthermore, lubrication can be applied with either oil (air oil, oil mist) or grease, and is not limited by lubrication specifications.

As mentioned above, although the form for implementing this invention was demonstrated based on embodiment, embodiment disclosed here is an illustration and is not restrictive at all points. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

DESCRIPTION OF SYMBOLS 1... Bearing 2... Outer ring 3... Inner ring 4... Outer ring spacer 5... Inner ring spacer 6... Housing 7... Rotating shaft 10... Nozzle 15... Exhaust path on bearing side 16... Exhaust path on opposite side of bearing

Claims (6)

A cooling structure for a bearing device comprising an outer ring spacer and an inner ring spacer adjacent to an outer ring and an inner ring of a bearing, respectively, wherein the outer ring spacer is provided with a nozzle for discharging compressed air toward the outer peripheral surface of the inner ring spacer. There is
The nozzle is inclined forward in the direction of rotation of the inner ring spacer and is offset from an arbitrary radial line in a cross section perpendicular to the axial center of the outer ring spacer in a direction perpendicular to the straight line,
The width of the outer ring spacer and the inner ring spacer is 2.5 times or more the bearing width, and the distance from the center of the nozzle to the side surface of the bearing is equal to or less than the bearing width and 1 of the bearing width. /2 or more ,
An exhaust path is provided in the outer ring spacer on the bearing side with respect to the nozzle for exhausting air from a space between the outer ring spacer and the inner ring spacer to the outside.
Cooling structure of the bearing device. 2. The cooling structure for a bearing device according to claim 1, wherein the outer ring spacer is provided with an exhaust passage for exhausting air from a space between the outer ring spacer and the inner ring spacer to the outside with respect to the nozzle on the side opposite to the bearing. Cooling structure of the mounted bearing device. 3. The cooling structure for a bearing device according to claim 2, wherein the exhaust passage on the side opposite to the bearing is inclined such that the exhaust port faces forward in the rotational direction of the inner ring spacer. 4. The bearing device cooling structure according to claim 2, wherein the difference between the volume of the exhaust passage on the bearing side and the volume of the exhaust passage on the side opposite to the bearing is 10 times the volume of the exhaust passage on the bearing side. Cooling structure of the bearing device within %. 5. The cooling structure for a bearing device according to any one of claims 1 to 4, wherein the outer ring spacer and the inner ring spacer are interposed between two adjacent bearings, and the outer ring spacer A cooling structure for a bearing device in which the nozzles are provided on both sides of the center position of the width. A spindle device of a machine tool comprising the bearing device cooling structure according to any one of claims 1 to 5.

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