WO2018181032A1

WO2018181032A1 - Cooling structure for bearing device

Info

Publication number: WO2018181032A1
Application number: PCT/JP2018/011808
Authority: WO
Inventors: 惠介那須; 真人吉野
Original assignee: Ntn株式会社
Priority date: 2017-03-29
Filing date: 2018-03-23
Publication date: 2018-10-04
Also published as: JP2018168886A

Abstract

An outer race (2) and an inner race (3), which face inward and outward in a roller bearing (1) of a bearing device (J), are respectively provided with an outer race spacer (4) and an inner race spacer (5) that are adjacent to each other. The outer race (2) and the outer race spacer (4) are installed in a housing (6), and the inner race (3) and the inner race spacer (5) are installed in a main shaft (7). An axial between-spacer space (13) is formed between the outer race spacer (4) and the inner race spacer (5). A nozzle hole (15) that discharges compressed air (A) into the between-spacer space (13) is formed in the outer race spacer (4). An outlet (15a) of the nozzle hole (15) opens in the inner peripheral surface of the outer race spacer (4) and discharges the compressed air (A) from the outlet (15a) toward the outer peripheral surface of the inner race spacer (5). The nozzle hole (15) is provided so that the axis of the compressed air (A) discharged from the outlet (15a) to the between-spacer space (13) is eccentric relative to the axial center of the outer race spacer (4).

Description

Cooling structure of bearing device

Related applications

This application claims the priority of Japanese Patent Application No. 2017-064941 filed on Mar. 29, 2017, which is incorporated herein by reference in its entirety.

The present invention relates to, for example, a spindle of a machine tool and a cooling structure for a bearing device incorporated in the spindle.

In the spindle device of a machine tool, it is necessary to keep the temperature rise of the device small to ensure machining accuracy. However, recent machine tools have a tendency to increase the speed in order to improve the machining efficiency. Heat generation from the bearing that supports the main shaft is also increasing as the speed increases. In addition, so-called motor built-in types in which a drive motor is incorporated in the apparatus are becoming more and more, and this is a cause of heat generation of the apparatus.

¡The temperature rise of the bearing due to heat generation results in an increase in preload, and we want to suppress it as much as possible from the viewpoint of speeding up the spindle and increasing accuracy. As a method for suppressing the temperature rise of the main shaft device, there is a method of cooling the shaft and the bearing by sending cooling air to the bearing (for example, Patent Documents 1 and 2). In

Patent Documents

1 and 2, cold air is injected into the space between the two bearings at an angle in the rotational direction. Thereby, the cooling of the shaft and the bearing is performed by the cool air becoming a swirling flow.

Further, in Patent Document 2, an annular recess is provided in a peripheral surface of the outer ring spacer facing the inner ring spacer, an outlet of the nozzle hole is opened in the recess, and compressed air for cooling is supplied from the nozzle hole to the inner ring. It is discharged toward the circumferential surface of the spacer. According to this cooling structure, the compressed air is adiabatically expanded by being discharged at once from the narrow nozzle hole into the space of the recess. Therefore, the flow rate of compressed air increases and the temperature decreases. When this low-temperature compressed air strikes the inner ring spacer, the inner ring spacer and the inner ring of the rolling bearing in contact therewith are more efficiently cooled.

JP 2000-161375 A Japanese Patent Laying-Open No. 2015-183738

In the cooling structure of Patent Document 2, the cooling effect increases as the amount of compressed air discharged from the nozzle hole increases. However, increasing the amount of compressed air increases the running cost. In addition, in order to increase the amount of compressed air, it is necessary to increase the capacity of the air compressor, which increases the equipment cost.

An object of the present invention is to provide a cooling structure for a bearing device that can efficiently cool the bearing device even if the amount of compressed air is relatively small.

A cooling structure for a bearing device according to the present invention includes a stationary spacer and a rotating spacer adjacent to a stationary bearing ring and a rotating bearing ring facing the inside and outside of a rolling bearing, respectively. The fixed side spacer is installed on a fixed member of a fixed member and a rotating member, and the rotating side race and the rotating side spacer are installed on a rotating member of the fixed member and the rotating member. It is a cooling structure of a bearing device.

In this cooling structure, a spacer space is formed between the fixed spacer and the rotating spacer. The spacer space is axisymmetric with respect to the axial center of the axial width of the fixed spacer. An opening extending in the axial direction from the spacer space is formed. The stationary spacer has a nozzle hole for discharging compressed air into the spacer space. The outlet of the nozzle hole opens to a surface where the spacers in the fixed side spacer face each other, and the nozzle hole compresses from the outlet toward the surface where the spacers in the rotating side spacer face each other. Air is discharged. The nozzle hole is provided so that the axis of the compressed air discharged from the outlet into the spacer space is biased with respect to the axial center. Here, “the axis of the compressed air is biased with respect to the center in the axial direction” means that the flow of the compressed air becomes uneven on both sides of the center in the axial direction of the spacer space. The fixed-side raceway is, for example, an outer ring, and the rotation-side raceway is, for example, an inner ring.

According to this configuration, the compressed air for cooling is discharged from the nozzle holes provided in the fixed spacer to the spacer space toward the rotating spacer. The compressed air is adiabatically expanded by being discharged from the narrow nozzle hole to the wide spacer space. This adiabatic expansion increases the flow rate of the compressed air and decreases the temperature. Therefore, the rotating side spacer is efficiently cooled, and the rotating side bearing ring of the rolling bearing in contact therewith is also cooled. Thereafter, the compressed air is discharged from the opening of the interstitial space to the outside of the interstitial space.

Since the axis of the compressed air discharged from the nozzle hole into the spacer space is biased with respect to the axial center, the flow of compressed air is uneven on both sides of the axial center and vortices are generated in the bearing width direction. Cheap. For this reason, it takes time for the compressed air to be discharged from the interstitial space, and the time for the compressed air to remain in the interstitial space becomes longer. Thereby, a rotation side spacer can be cooled much more efficiently. Therefore, the bearing device can be efficiently cooled even if the amount of compressed air is relatively small.

By offsetting the axial position of the outlet of the nozzle hole in the axial direction with respect to the axial center of the spacer space, the axis of the compressed air discharged from the outlet of the nozzle hole is pivoted in the spacer space. A bias can be given to the center in the direction.
The said structure WHEREIN: When the axial direction width | variety of the said fixed side spacer is set to HB, the offset amount of the said exit is good also as (HB / 2) x0.1 or more. According to this structure, the vortex which goes to the width direction of a bearing can be produced in the space between spacers, and the time for compressed air to stay in the space between spacers becomes long.

Further, the central axis of the outlet of the nozzle hole may be inclined in the axial direction. According to this configuration, the axis of the compressed air discharged from the outlet of the nozzle hole is biased with respect to the axial center in the spacer space. Thereby, the vortex which goes to the width direction of a bearing can be produced in the space between spacers, and time for compressed air to stay in the space between spacers becomes long.

Any combination of at least two configurations disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of each claim in the claims is included in the invention.

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description only and should not be used to define the scope of the present invention. The scope of the invention is defined by the appended claims. In the accompanying drawings, the same part numbers in a plurality of drawings indicate the same or corresponding parts.
It is sectional drawing of the machine tool spindle apparatus provided with the cooling structure of the bearing apparatus which concerns on 1st Embodiment of this invention. It is an expanded sectional view of the cooling structure of the bearing device. It is a figure which shows the spacer space between the cooling structures of the bearing device. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1. It is sectional drawing of the cooling structure of the bearing apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the spacer space between the cooling structures of the bearing device.

A cooling structure for a bearing device according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view of a machine tool spindle device provided with a cooling structure for the bearing device. In this example, the cooling structure of the present invention is applied to a spindle device of a machine tool, but is not limited to this.

The bearing device J includes two rolling

bearings

1 and 1 arranged in the axial direction. An outer ring spacer 4 is interposed between the

outer rings

2 and 2 of the two rolling

bearings

1 and 1, and an inner ring spacer 5 is interposed between the

inner rings

3 and 3. The outer ring 2 and the outer ring spacer 4 are installed in the housing 6, and the inner ring 3 and the inner ring spacer 5 are fitted to the main shaft 7. The rolling bearing 1 is an angular ball bearing, and a plurality of rolling elements 8 are interposed between the raceway surfaces of the outer ring 2 and the raceway surface of the inner ring 3. The rolling elements 8 are held by the cage 9 at equal intervals in the circumferential direction. The two rolling

bearings

1 and 1 are arranged in combination with each other on the back surface. Depending on the width dimension difference between the outer ring spacer 4 and the inner ring spacer 5, the initial preload of each rolling

bearing

1, 1 is set.

In this embodiment, the rolling bearing 1 is an inner ring rotating type. That is, the outer ring 2 constitutes a “fixed side raceway ring”, and the inner ring 3 constitutes a “rotation side raceway ring”. The outer ring spacer 4 constitutes a “fixed side spacer”, and the inner ring spacer 5 constitutes a “rotation side spacer”. Further, the main shaft 7 constitutes a “rotating member”, and the housing 6 constitutes a “fixing member”. The same applies to a second embodiment described later.

In this embodiment, the

outer rings

2 and 2 and the outer ring spacer 4 are fitted into the housing 6 with a clearance, and are positioned in the axial direction by the step portion 6a of the housing 6 and the end surface cover 40. Further, the

inner rings

3 and 3 and the inner ring spacer 5 are tightly fitted to the main shaft 7 and are positioned in the axial direction by the

positioning spacers

41 and 42 on both sides. The left positioning spacer 42 in FIG. 1 is fixed by a nut 43 screwed onto the main shaft 7. However, the installation method of the

outer rings

2, 2, the outer ring spacer 4, the

inner rings

3, 3, and the inner ring spacer 5 is not limited to this.

[Cooling structure]
The cooling structure will be described.
As shown in FIG. 2 which is a partially enlarged view of FIG. 1, the outer ring spacer 4 includes an outer ring spacer body 11 and a ring-shaped lubricating oil hole forming member 12 made of a member different from the outer ring spacer body 11. Twelve. The outer ring spacer main body 11 has a substantially T-shaped cross section. Lubricating oil

hole forming members

12 and 12 are fixed to both sides in the axial direction of the outer ring spacer body 11. The two lubricating oil

hole forming members

12 and 12 are axisymmetric with respect to the axial center line (line orthogonal to the axial direction) of the outer ring spacer 4. Note that FIG. 1 and FIG. 2 differ in the cut surface of one (right side) rolling bearing 1.

The inner diameter of the outer ring spacer body 11 is larger than the inner diameter of the lubricating oil

hole forming members

12 and 12. Thus, a recess 13 a is formed on the inner peripheral surface of the outer ring spacer 4 by the inner peripheral surface of the outer ring spacer main body 11 and the side surfaces of the lubricating oil

hole forming members

12, 12 following the inner peripheral surface. . The inner peripheral surface of the outer ring spacer main body 11 constitutes the bottom surface of the recessed portion 13a, and the side surfaces of the lubricating oil

hole forming members

12, 12 constitute the side wall surface of the recessed portion 13a. As shown in FIG. 3, the inner diameter end of the side surface of the lubricating oil hole forming member 12 is chamfered to form a chamfered portion 12a.

A spacer space 13 is formed between the outer ring spacer 4 and the inner ring spacer 5. The spacer space 13 is an annular space between the outer ring spacer 4 and the inner ring spacer 5. The spacer space 13 is line symmetric with respect to the center C1 in the axial direction of the outer ring spacer 4. The interstitial space 13 includes a recessed portion 13a and an inner space portion 13b located on the inner diameter side of the recessed portion 13a. The axial direction range of the inner space portion 13 b is a radial gap between the spacer space 13 and the inner ring spacer 5. The axial direction range of the inner space portion 13b is between the inner diameter ends P and P of the chamfered

portions

12a and 12a of the lubricating oil

hole forming members

12 and 12, respectively.

An annular gap 14 is formed between the lubricating oil hole forming member 12 and the inner ring spacer 5. The annular gap 14 constitutes an opening extending in the axial direction from the interstitial space 13. The interstitial space 13 is connected to the internal space of the rolling bearing 2 via an annular gap 14 and an annular gap 22 described later. That is, the interstitial space 13 has a shape in which a part of the closed space is opened.

As shown in FIG. 2, a nozzle hole 15 is provided in the outer ring spacer main body 11. The nozzle hole 15 discharges the compressed air A for cooling to the spacer space 13 toward the outer peripheral surface of the inner ring spacer 5. The outlet 15 a of the nozzle hole 15 opens at the bottom surface of the recessed portion 13 a of the outer ring spacer 4. In this example, a plurality of (for example, three) nozzle holes 15 are provided, and the nozzle holes 15 are arranged at equal intervals in the circumferential direction.

The axial position of the outlet 15a of the nozzle hole 15 is offset in the axial direction with respect to the axial center C1 of the spacer space 13 (the axial center of the outer ring spacer 4). In other words, the axis C2 of the compressed air A discharged from the outlet 15a of the nozzle hole 15 is set so as to be biased with respect to the axial center C1 in the spacer space 13. That is, the flow of the compressed air A discharged from the outlet 15a becomes uneven on both sides of the center C1 in the axial direction of the spacer space 13. A nozzle hole 100 in which the axis of the compressed air coincides with the axial center C1 of the interstitial space 13, that is, the nozzle hole 100 that is not biased with respect to the axial center C1 of the interstitial space 13 is shown in FIG. It is indicated by a dotted line.

The offset amount OS is set to (HB / 2) × 0.1 or more when the axial width of the outer ring spacer 4 is HB. By offsetting in this way, as will be described later, the compressed air A discharged from the nozzle hole 15 creates a vortex in the spacer space 13 in the bearing width direction.

As shown in FIG. 4, the axis C 2 of the outlet 15 a of each nozzle hole 15 is inclined forward in the rotational direction of the inner ring spacer 5. That is, in the cross section perpendicular to the axial center of the outer ring spacer 4, the axial center C 2 of the outlet 15 a is offset from an arbitrary radial straight line L in a direction perpendicular to the straight line L. By offsetting the nozzle holes 15, the compressed air A acts as a swirling flow in the rotation direction of the inner ring spacer 5 and the cooling effect is improved. In FIGS. 1 and 2, the outer ring spacer 4 is indicated by a cross section passing through the center line of the nozzle hole 15.

An introduction groove 16 for introducing the compressed air A into each nozzle hole 15 from the outside of the bearing is formed on the outer peripheral surface of the outer ring spacer body 11. As shown in FIG. 4, the introduction groove 16 is provided in an intermediate portion in the axial direction on the outer peripheral surface of the outer ring spacer 4, and is formed in an arc shape communicating with each nozzle hole 15. Specifically, the introduction groove 16 is provided over an angular range α that occupies most of the circumferential direction on the outer peripheral surface of the outer ring spacer body 11.

The portion where the introduction groove 16 is not formed on the outer peripheral surface of the outer ring spacer body 11 is a circumferential position where an air oil supply path (not shown) described later is provided. As shown in FIG. 1, a compressed air introduction path 45 is provided in the housing 6, and the introduction groove 16 communicates with the compressed air introduction path 45. An air supply device (not shown) is provided outside the housing 6, and the compressed air A is supplied to the compressed air introduction hole 45.

[Lubrication structure]
The lubrication structure will be described.
As shown in FIG. 1, the outer ring spacer 4 has lubricating oil

hole forming members

12 and 12 for supplying lubricating oil into the bearing. In this example, air oil is used as the lubricating oil. Each lubricating oil hole forming member 12 has a base portion 20 on the outer ring spacer main body 11 side, and a hook-shaped tip portion 21 that protrudes axially outward from the base portion 20. The inner peripheral surface of the base 20 faces the inner ring spacer 5 with a gap 14 therebetween.

The inner peripheral surface of the tip portion 21 faces the outer peripheral surface of the inner ring 3, and an annular gap 22 for passing air oil is formed between the inner peripheral surface of the tip portion 21 and the outer peripheral surface of the inner ring 3. In other words, the tip 21 of the lubricating oil hole forming member 12 is disposed so as to enter the bearing so as to cover the outer peripheral surface of the inner ring 3. Further, the distal end portion 21 of the lubricating oil hole forming member 12 is disposed radially inward from the inner peripheral surface of the cage 9.

As shown in FIG. 2, the lubricating oil hole forming member 12 is provided with a lubricating oil hole 23 for supplying air oil to the annular gap 22. The lubricating oil hole 23 is inclined toward the inner diameter side toward the bearing side. The outlet of the lubricating oil hole 23 opens to the inner peripheral side of the tip portion 21. Air oil is supplied to the lubricating oil hole 23 via a lubricating oil supply path (not shown) provided in the housing 6 and the outer ring spacer main body 11. An annular recess 24 is provided on the outer peripheral surface of the inner ring 3. The annular recess 24 is provided at a location facing the lubricating oil hole 23 on the outer peripheral surface of the inner ring 3.

The oil of air oil discharged from the lubricating oil hole forming member 12 accumulates in the annular recess 24. This oil is guided to the bearing center side along the outer peripheral surface of the inner ring 3, which is an inclined surface, by centrifugal force accompanying the rotation of the inner ring 3.

[Exhaust structure]
The exhaust structure will be described.
As shown in FIG. 1, the bearing device J is provided with an exhaust passage 46 for exhausting compressed air for cooling and air oil for lubrication. The exhaust path 46 includes an exhaust groove 47, a radial exhaust hole 48, and an axial exhaust hole 49. The exhaust groove 47 is provided in a part of the outer ring spacer body 11 in the circumferential direction. The radial exhaust hole 48 and the axial exhaust hole 49 are provided in the housing 6 and communicate with the exhaust groove 47. The exhaust groove 47 of the outer ring spacer body 11 is formed in a circumferential position diagonally different from the position where the lubricating oil supply path is provided (180 ° phase difference).

[Operation of cooling structure]
The effect | action of the cooling structure of the bearing apparatus which consists of the said structure is demonstrated.
From the nozzle hole 15 provided in the outer ring spacer 4, compressed air A for cooling is discharged into the spacer space 13 toward the outer peripheral surface of the inner ring spacer 5. The compressed air A is adiabatically expanded by being discharged from the narrow nozzle hole 15 to the wide spacer space 13. By this adiabatic expansion, the flow rate of the compressed air A increases and the temperature decreases. Therefore, the inner ring spacer 5 is efficiently cooled, and the inner ring 3 of the rolling bearing 1 in contact therewith is also cooled. Thereafter, the compressed air A flows into the bearing space through the gap 14 and the annular gap 22 which are openings of the spacer space 13, and is further discharged to the outside through the exhaust path 46.

The axis C2 of the compressed air A discharged from the nozzle hole 15 into the spacer space 13 is biased with respect to the axial center C1. Therefore, the flow of the compressed air A is uneven on both sides of the axial center C1, and vortices are easily generated in the bearing width direction. For this reason, it takes time for the compressed air A to be discharged from the spacer space 13, and the time for the compressed air to remain in the spacer space 13 becomes longer. Thereby, the inner ring spacer 5 can be cooled more efficiently. As a result, the bearing device can be efficiently cooled even if the amount of compressed air is relatively small. Therefore, running cost can be kept low. Moreover, since the capacity of the air compressor is small, the equipment cost can be reduced.

In this embodiment, the nozzle hole 15 is inclined forward in the rotational direction of the inner ring spacer 5. For this reason, the compressed air A discharged from the nozzle hole 15 flows in the axial direction while turning along the outer peripheral surface of the inner ring spacer 5, and is discharged to the outside of the bearing through the exhaust path 46. Since the compressed air A turns, the time during which the compressed air A is in contact with the outer peripheral surface of the inner ring spacer 5 is longer than when the compressed air A flows straight in the axial direction. Thereby, the inner ring spacer 5 can be cooled more efficiently. For this reason, the inner ring spacer 5 can be cooled more efficiently.

[Other Embodiments]
5 and 6 show a second embodiment. In the cooling structure of the bearing device of the second embodiment, the central axis C2 of the outlet 15a of the nozzle hole 15 is inclined with respect to the axial direction. The axial position of the outlet 15 a of the nozzle hole 15 may or may not be offset in the axial direction with respect to the axial center C 1 of the spacer space 13. In the example of FIGS. 5 and 6, the nozzle hole 15 is located in the center C 1 in the axial direction of the spacer space 13, and the outlet 15 a extends obliquely from the nozzle hole 15. The axial position of the outlet 15 a of the nozzle hole 15 is offset in the axial direction with respect to the axial center C 1 of the spacer space 13. Other configurations are the same as those of the first embodiment.

Also in the cooling structure of the bearing device J of the second embodiment, the axis C2 of the compressed air A discharged from the nozzle hole 15 to the spacer space 13 is biased with respect to the axial center C1. Therefore, similarly to the first embodiment, the flow of the compressed air A is uneven on both sides of the axial center C1, and a vortex in the spacer space 13 tends to occur in the bearing width direction. For this reason, the compressed air A stays in the spacer space 13 for a long time, and the inner ring spacer 5 can be efficiently cooled.

As described above, the preferred embodiments have been described with reference to the drawings. However, the present invention is not limited to the above embodiments, and various additions and modifications can be made without departing from the gist of the present invention. Or it can be deleted. Therefore, such a thing is also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Rolling bearing 2 ... Outer ring (fixed side ring)
3. Inner ring (rotating raceway)
4. Outer ring spacer (fixed side spacer)
5 ... Inner ring spacer (rotating side spacer)
6 ... Housing (fixing member)
7 ... Spindle (Rotating member)
13 ... Space between spacers 15 ... Nozzle hole 15a ... Outlet A ... Compressed air C2 ... Center axis of outlet (axis of compressed air)
J ... Bearing device

Claims

A stationary spacer and a rotating spacer are provided adjacent to the stationary bearing ring and the rotating bearing ring facing the inside and outside of the rolling bearing, respectively, and the stationary bearing ring and the stationary spacer are fixed and rotated. A cooling structure for a bearing device that is installed on a fixed member of the members, and wherein the rotating raceway and the rotating spacer are installed on the rotating member of the fixed member and the rotating member;
A spacer space is formed between the fixed spacer and the rotating spacer,
The spacer space is axisymmetric with respect to the axial center of the axial width of the fixed side spacer,
An opening extending in the axial direction from the space between the spacers is formed,
The fixed side spacer has a nozzle hole for discharging compressed air into the spacer space,
The outlet of the nozzle hole opens to the surface where the spacers in the fixed side spacer face each other,
The nozzle hole discharges the compressed air from the outlet toward a surface where the spacers in the rotating spacer are opposed to each other,
The bearing structure cooling structure in which the nozzle hole is provided so that an axis of the compressed air discharged from the outlet to the spacer space is biased with respect to the axial center.
2. The cooling structure for a bearing device according to claim 1, wherein an axial position of the outlet of the nozzle hole is offset in an axial direction with respect to an axial center of the space between the spacers.
The cooling structure of the bearing device according to claim 2, wherein when the axial width of the fixed spacer is HB, the offset amount of the outlet is (HB / 2) × 0.1 or more. Cooling structure.
2. The cooling structure for a bearing device according to claim 1, wherein a central axis of the outlet of the nozzle hole is inclined in the axial direction.