Cooling structure for bearing device and bearing device with cooling structure

Abstract

To provide a cooling structure for a bearing device capable of obtaining a cooling effect while maintaining a bearing function in a bearing device of grease lubrication, and the bearing device with the cooling structure.SOLUTION: A bearing device J comprises: a plurality of rolling bearings 1 and 1 disposed side by side in an axial direction; and an inter-outer-ring seat 4 and an inter-inner-ring seat 5 which are interposed between outer rings and inner rings 3 of the rolling bearings 1 and 1. The rolling bearing 1 is lubricated by grease encapsulated in a bearing internal space S1 between the inner and outer rings. In both ends of the inter-inner-ring seat 5 in the axial direction, provided is an obstacle wall 33 which is expanded to an outer diameter side and blocks a flow of compressed air A supplied from a supply port into the beating internal space S1. An outer diameter end of the obstacle wall 33 is opposed to an inner peripheral face of the inter-outer-ring seat 4 via a radial gap δ2. A step Δt is provided between an abutment face 5a of the inter-inner-ring seat 5 with the inner ring and an outer side face 33a of the obstacle wall 33 in the axial direction, and the step Δt is recessed axially inside of the inter-inner-ring seat 5 with respect to the abutment face 5a.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a cooling structure of a bearing device and a bearing device provided with the cooling structure, and mainly relates to a technology applicable to a grease-lubricated angular ball bearing used for a main shaft of a machine tool and the like.

Background Art

[0002] In a main shaft device of a machine tool, in order to ensure machining accuracy, it is necessary to suppress a temperature rise of the device as small as possible. However, recent machine tools tend to be high-speed in order to improve machining efficiency, and heat generation from the bearings that support the main shaft is also increasing with the increase in speed. As a method for suppressing the temperature rise of the bearing accompanying the high speed of the main shaft device, there is a method of sending compressed air for cooling to the bearing to cool the shaft and the bearing. Particularly in grease lubrication, a structure has been proposed in which obstacle walls projecting outward on the outer diameter side are provided at both ends of the inner ring spacer in order to prevent the grease inside the bearing from scattering by the compressed air (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When cooling the shaft and the bearing with compressed air, it is essential to apply a member such as a seal to the bearing to prevent grease scattering. The seal is preferably arranged as close as possible to both ends of the bearing in order to secure the internal space of the bearing that affects the amount of grease enclosed in the bearing. However, the seal is arranged from the end faces of the inner and outer rings of the bearing to the inside of the bearing in order to prevent interference (contact) with the peripheral structure of the bearing. On one side, obstacle walls protruding outward on the outer diameter side are provided at both ends of the inner ring spacer disposed between the bearings. In order to prevent interference between the seal and the obstacle wall of the inner ring spacer, it is necessary to ensure a clear gap between the seal and the obstacle wall.

[0005] As methods for applying preload to the bearings, there are fixed-position preload and constant-pressure preload. Also, as basic combinations of bearings, there are face combination, back combination, and parallel combination. In the main shaft device of a machine tool, most of them are used in the back combination DB in Fig. 15 or the parallel combination DT in Fig. 16. When the main shaft device is used with fixed-position preload, since the axial positions of the bearings and the spacer are fixed, the gap between the seal and the obstacle wall of the inner ring spacer is maintained at the initial gap.

[0006] When the main shaft device is used with constant-pressure preload and parallel combination, as shown in Fig. 17, in the initial state, a gap a is set between the seal 31 and the inner ring spacer 5Z. As shown in Fig. 18, when the bearing 1 generates heat and mainly the inner ring 3 thermally expands, the outer ring 2 and the outer ring spacer 4 move in one axial direction, which is the left direction in Fig. 18, in order to ensure a predetermined preload amount. At this time, since the seal 31 is fitted to the outer ring 2, the seal 31 also moves together with the outer ring 2. As a result, the gap between the seal 31 and the obstacle wall 33B of the inner ring spacer 5Z decreases, and there is a risk of interference.

[0007] As shown in Fig. 19, even when the main shaft device is used with constant-pressure preload and back combination, the outer ring 2 and the outer ring spacer 4 move axially in the same way as in the case of parallel combination. Therefore, the gap between the seal 31 and the obstacle wall of the inner ring spacer 5Z decreases, and there is a risk of interference.

[0008] An object of the present invention is to provide a cooling structure for a bearing device that can obtain a cooling effect while maintaining the bearing function in a grease-lubricated bearing device, and a bearing device equipped with the cooling structure.

Means for Solving the Problems

[0009] The cooling structure of the bearing device of the present invention includes a plurality of rolling bearings arranged in the axial direction, and an outer-race spacer and an inner-race spacer respectively interposed between the outer races and between the inner races of these rolling bearings. The rolling bearings are bearings lubricated by grease enclosed in the bearing internal space between the inner and outer races. A supply port for supplying compressed air for cooling is provided on the inner peripheral surface of the outer-race spacer toward the outer peripheral surface of the inner-race spacer, and a discharge port for discharging the compressed air supplied from the supply port is provided in the outer-race spacer. At both axial ends of the inner-race spacer, there are provided barrier walls that project outward in the outer diameter direction to prevent the compressed air supplied from the supply port from flowing into the bearing internal space. The outer diameter end of this barrier wall faces the inner peripheral surface of the outer-race spacer with a radial clearance. This is the cooling structure of the bearing device. A step Δt is provided between the mating surface of the inner-race spacer with the inner race and the outer axial surface of the barrier wall, and this step Δt is recessed axially inward of the inner-race spacer relative to the mating surface. When seal members are provided at both axial ends of the outer race, the "bearing internal space" is, in the axial direction, the space located between the inner axial surfaces of both seal members. When no seal member is provided, the "bearing internal space" is, in the axial direction, the space located between the axial ends of the inner and outer races. When a seal member is provided only at one axial end of the outer race, the "bearing internal space" is, in the axial direction, the space located between the inner axial surface of the seal member and the axial end of the inner and outer races that does not have the seal member.

[0010] According to this configuration, compressed air for cooling is supplied from the supply port provided in the outer-race spacer toward the outer peripheral surface of the inner-race spacer, so that the compressed air colliding with the inner-race spacer takes away the heat of the bearing device and the shaft supported by this bearing device. Thereby, the bearing device and the shaft are efficiently cooled. Barrier walls are provided at both axial ends of the inner-race spacer, and since the compressed air is prevented from flowing into the bearing internal space, the grease enclosed in the bearing internal space is prevented from being displaced by the compressed air. Therefore, a good lubrication state can be maintained.

[0011] A step Δt is provided between the mating surface of the inner ring spacer with the inner ring and the outer axial surface of the obstacle wall. This step Δt is recessed axially inward of the inner ring spacer with respect to the mating surface. Therefore, even when the outer ring and the outer ring spacer move axially due to the thermal expansion of the inner ring during bearing operation, a clearance can be ensured between the fixed components such as the seal fixed to the outer ring and the obstacle wall of the inner ring spacer. This prevents the fixed components from interfering with the obstacle wall of the inner ring spacer

[0012] The step Δt may satisfy the relationship of 0.1 mm < Δt < 0.5 mm. In this case, the dimensional accuracy of the step Δt can be easily ensured, and the manufacturing cost can be reduced. If the step Δt is 0.1 mm or less, it may be difficult to ensure the dimensional accuracy in the machining of the inner ring spacer. If the step Δt is 0.5 mm or more, the amount of material removed from the inner ring spacer is large, the machining man-hours increase, and the manufacturing cost rises.

[0013] The inner ring spacer has two inner ring spacer split bodies with the axial middle part divided, and when the outer diameter D on the mating side in each inner ring spacer split body that mates these inner ring spacer split bodies with each other and the outer diameter D' of the mating surface in the inner ring spacer are considered, the relationship D ≦ D', preferably D = D', may be satisfied. In this case, the load from one inner ring in the axial direction can be reliably transmitted to the other inner ring in the axial direction through the inner ring spacer. Both end faces of the spacer are ground simultaneously. When D ≠ D', the areas of the grinding surfaces on the left and right of the spacer are different. The larger the area, the smaller the amount that can be removed by grinding. Therefore, since the amount removed by grinding is different on the left and right, it is difficult to finely adjust the width dimension. When D = D', the grinding ranges of both end faces of the inner ring spacer split body can be made the same, and the amount removed by grinding can be made the same on the left and right, so that the width dimension can be easily finely adjusted. For this reason, the machining man-hours can be reduced compared to the case of D < D'.

[0014] The outer diameter surface of the obstacle wall may be in a tapered shape in which the amount of overhang to the outer diameter side is larger on the side closer to the rolling bearing in the axial direction, and the discharge port of the outer ring spacer may be a notch provided on the axial end face of the outer ring spacer.

[0015] In this case, the compressed air supplied from the supply port flows axially outward in the space between the inner raceway seat and the outer raceway seat along the outer peripheral surface of the inner raceway seat, which is the internal space of the raceway, and is further guided radially outward along the tapered outer diameter surface of the obstacle wall of the inner raceway seat, and is discharged from the notch provided in the axial end surface of the outer raceway seat. As a result, the flow of the compressed air in the internal space of the raceway and the discharge of the compressed air from the internal space of the raceway become smooth. Further, since a smooth flow of the compressed air occurs in the internal space of the raceway, the internal pressure of the internal space of the raceway becomes lower than the internal pressure of the internal space of the bearing, and the inflow of the compressed air into the internal space of the bearing is suppressed.

[0016] The circumferential positions of the supply port and the notch may be shifted from each other. In this case, when the compressed air supplied from the supply port to the internal space of the raceway flows to the notch along the outer peripheral surface of the inner raceway seat, in addition to the axial outward movement, it involves a circumferential movement. Therefore, the time for the compressed air to contact the inner raceway seat becomes longer, and the effect of cooling the bearing device and the shaft is enhanced.

[0017] The rolling bearing has a seal member for sealing the internal space of the bearing at the axial end of the outer ring. The outer diameter end of the obstacle wall is located on the outer diameter side of the outer diameter side end of the end surface of the inner ring and on the inner diameter side of the inner diameter side end of the end surface of the outer ring. The axial outer surface of the obstacle wall is in a shape facing the seal member with an axial clearance therebetween, and the seal member and the obstacle wall may have a labyrinth seal effect. Thereby, the inflow of the compressed air into the internal space of the bearing can be further prevented. The "labyrinth seal effect" is to enhance the sealing performance of the seal member by creating a curved passage between the obstacle wall, which is a rotating part, and the seal member, which is a fixed part.

[0018] When the inner diameter D1 of the seal member and the outer diameter D' of the mating surface in the inner raceway seat are considered, the relationship D1 > D' may be satisfied. The inner diameter D1 refers to the radial dimension of the inner diameter edge on the outer surface of the seal member. According to this configuration, it is possible to more reliably prevent interference between the seal member and the obstacle wall of the inner raceway seat.

[0019] The cooling structure of the bearing device of the present invention can be suitably used for supporting the main shaft of a machine tool. In that case, since the cooling effect of the main shaft is high, operation in a higher speed range becomes possible. The bearing device of the present invention includes any one of the above-described cooling structures.

Effect of the Invention

[0020] The cooling structure of the bearing device of the present invention includes a plurality of rolling bearings arranged in the axial direction, and an outer-race spacer and an inner-race spacer respectively interposed between the outer races and between the inner races of these rolling bearings. The rolling bearings are bearings lubricated by grease enclosed in the bearing internal space between the inner and outer races. A supply port for supplying compressed air for cooling is provided on the inner peripheral surface of the outer-race spacer toward the outer peripheral surface of the inner-race spacer. The outer-race spacer is provided with a discharge port for discharging the compressed air supplied from the supply port. Obstacle walls are provided at both axial ends of the inner-race spacer, protruding outward in the outer diameter direction to prevent the compressed air supplied from the supply port from flowing into the bearing internal space. The outer diameter end of this obstacle wall is a cooling structure of a bearing device facing the inner peripheral surface of the outer-race spacer with a radial clearance. A step Δt is provided between the mating surface of the inner-race spacer with the inner race and the outer axial surface of the obstacle wall, and this step Δt is recessed axially inward of the inner-race spacer compared to the mating surface. Therefore, in a grease-lubricated bearing device, a cooling effect can be obtained while maintaining the bearing function.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

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Figure 10

Figure 11

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Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

[0022] [First Embodiment] The cooling structure of the bearing device according to the embodiment of the present invention will be described with reference to FIGS. 1 to 9. The bearing device is used, for example, for supporting the main shaft of a machine tool described later. As shown in FIG. 1, the bearing device J includes a plurality of rolling bearings 1, 1 arranged in the axial direction, and an outer-ring spacer 4 and an inner-ring spacer 5 interposed between the outer rings 2, 2 and between the inner rings 3, 3 of these rolling bearings 1, 1, respectively. In a housing 6 shown in FIG. 3, a main shaft 7 (FIG. 3), which is a rotating body, is rotatably supported via the rolling bearings 1, 1, the outer-ring spacer 4, the inner-ring spacer 5, etc. of FIG. 1.

[0023] In the following description, the direction of the bearing center axis AX is referred to as the "axial direction", the direction perpendicular to the bearing center axis AX is referred to as the "radial direction", and the circumferential direction around the bearing center axis AX is referred to as the "circumferential direction". Also, the side facing the bearing center axis AX is referred to as the "inner diameter side", and the side away from the bearing center axis AX is referred to as the "outer diameter side".

[0024] <Rolling bearing> Each rolling bearing 1 is an angular contact ball bearing. These angular contact ball bearings are installed, for example, in a parallel combination and used with a constant pressure preload. In this specification, the rolling bearing 1 may sometimes be simply referred to as a "bearing". The rolling bearing 1 includes an inner ring 3, an outer ring 2, a plurality of rolling elements 8, a cage 9, and seal members 31, 31. The plurality of rolling elements 8 are interposed between the raceway surfaces of the inner and outer rings 3, 2. The plurality of rolling elements 8 are held in a circumferentially equidistant manner by the cage 9. The rolling bearing 1 is lubricated by grease sealed in the bearing internal space S1 between the inner and outer rings 3, 2. The outer ring 2 of each rolling bearing 1 is fixed in the housing 6, and the inner ring 3 is fitted and fixed to the outer peripheral surface of the main shaft 7.

[0025] The inner and outer rings 3, 2 are made of bearing steel or the like. Each rolling element 8 is a steel ball made of bearing steel or the like or a ceramic ball made of ceramics. The inner peripheral surfaces on both axial sides of the outer ring 2 are guide surfaces along which the outer peripheral surface of the cage 9 is guided. Both axial ends of the inner and outer rings 3, 2 are sealed by seal members 31, 31 which are non-contact seals. Each seal member 31 includes a core metal and an elastic body covering the core metal. The non-contact seals are adopted to cope with high-speed operation.

[0026] Outer ring seal grooves are respectively formed at both axial ends on the inner peripheral surface of the outer ring, and seal members 31 are respectively fitted and fixed in each outer ring seal groove. The seal member 31 on the side of the contact angle bias has its inner diameter side tip arranged so as to be separated from the inner ring counterbore by a defined radial clearance. The seal member 31 on the side opposite to the contact angle bias has its inner diameter side tip arranged so as to be separated from the inner ring seal groove on the outer peripheral surface of the inner ring by a predetermined lubrication clearance. The defined radial clearance and the predetermined lubrication clearance are clearances arbitrarily determined by design or the like, and are determined, for example, by obtaining an appropriate clearance through either one or both of tests and simulations.

[0027] <Regarding the cooling structure> As shown in FIG. 2, a radial clearance δ1 is provided between the inner peripheral surface of the outer ring spacer 4 and the outer peripheral surface of the inner ring spacer 5. A supply port 10 for supplying compressed air for cooling is provided on the inner peripheral surface of the outer ring spacer 4 facing the outer peripheral surface of the inner ring spacer 5. In this example, as shown in FIG. 3, the number of supply ports 10 is, for example, three, and each supply port 10 is equally distributed in the circumferential direction.

[0028] As shown in FIGS. 2 and 3, an annular introduction groove 11 for introducing compressed air A is provided on the outer peripheral surface of the outer ring spacer 4. The introduction groove 11 is provided at the axial intermediate portion on the outer peripheral surface of the outer ring spacer 4 and communicates with each supply port 10 through a connection hole 11a. Compressed air A is supplied to the introduction groove 11 through a compressed air introduction hole 46 provided in the housing 6 from an external compressed air supply device (not shown) provided outside the bearing device J.

[0029] <Regarding the obstacle wall, etc.> As shown in FIG. 1, both axial ends of the inner ring spacer 5 are obstacle walls 33 that project outward in the outer diameter direction. The obstacle wall 33 prevents the compressed air A supplied from the supply port 10 from flowing into the bearing internal space S1. The obstacle wall 33 has a tapered shape in which the amount of projection to the outer diameter side is larger on the side closer to the axial rolling bearing 1. A notch 34 serving as an outlet for the compressed air A supplied from the supply port 10 is provided on the axial end surface of the outer ring spacer 4.

[0030] The notch 34 has, for example, a rectangular cross-sectional shape as shown in FIG. 4, and the outer ring 2 of the rolling bearing 1 is arranged adjacent to the outer ring spacer 4 in FIG. 2. As a result, the notch 34 has an opening shape that communicates the inner space S2 between the outer ring spacer 4 and the inner ring spacer 5 with the outside of the bearing device J. The circumferential positions of the supply port 10 and the notch 34 are provided identically as shown in FIG. 4. However, it is not limited to such a circumferential position. In this configuration, as shown in FIG. 2, in order to enable the assembly of the outer ring spacer 4 (to prevent interference between the inner circumference of the outer ring spacer 4 and the obstacle wall 33), the inner ring spacer 5 has, for example, two inner ring spacer divided bodies 5A, 5A whose axial intermediate portions are divided.

[0031] The outer diameter end of the obstacle wall 33 faces through a radial clearance δ2 defined on the inner circumferential surface of the outer ring spacer 4. As shown in FIG. 5, a step Δt is provided between the mating surface 5a of the inner ring spacer 5 with the inner ring 3 and the axially outer surface 33a of the obstacle wall 33. The step Δt is recessed toward the axially inner side A1 of the inner ring spacer 5 from the mating surface 5a. In other words, the position of the obstacle wall 33 on the mating side with the inner ring 3 of the inner ring spacer 5 (the portion on the outer diameter side from the outer diameter of the inner ring that does not abut against the inner ring 3) is formed into a stepped shape shifted toward the axially inner side A1 of the inner ring spacer 5.

[0032] By forming the inner ring spacer 5 into such a stepped shape, a large axial clearance b in the initial state between the seal member 31 and the obstacle wall 33 of the inner ring spacer 5 is ensured. The axial clearance b in the initial state is a value (a + Δt) obtained by adding the step Δt to the axial length a between the axially outer surface 33a of the seal member 31 and the inner ring end face in the initial state of the bearing device J (the state before bearing operation).

[0033] The outer diameter end 33D of the obstacle wall 33 is located on the outer diameter side from the outer diameter side end of the end face of the inner ring 3 and on the inner diameter side from the inner diameter side end of the end face of the outer ring 2, and the axially outer surface 33a of the obstacle wall 33 faces the seal member 31 with an axial clearance b therebetween. As a result, a labyrinth seal portion 35 having a labyrinth seal effect is constructed by the seal member 31 and the obstacle wall 33, and the bearing inner space S1 and the spacer inner space S2 are separated by this labyrinth seal portion 35.

[0034] In the preload adjustment state due to heat generation shown in Fig. 6, when the outer ring movement amount associated with the preload adjustment is Δa, the axial clearance b´ between the seal member 31 and the inner raceway seat 5 becomes a value obtained by subtracting the outer ring movement amount Δa from the axial clearance b (Fig. 5) in the initial state. Therefore, in the bearing used with constant pressure preload, even if the outer ring 2 and the seal member 31 fitted to the outer ring 2 move axially for preload adjustment, the axial clearance b´ between the seal member 31 and the barrier wall 33 of the inner raceway seat 5 can be ensured, preventing interference between the seal member 31 and the barrier wall 33 of the inner raceway seat 5.

[0035] On the other hand, in the manufacturing process of the inner raceway seat 5, generally, the process of "turning → heat treatment → grinding" is adopted. In particular, the "grinding process" that determines the width dimension of the inner raceway seat 5 is important. In this inner raceway seat 5, it is assumed that a large warp occurs in the barrier wall 33 protruding to the outer diameter side in the "heat treatment process". In the conventional shape shown in Figs. 7(a) and (b), since the grinding range Ga and the grinding amount Gb (Fig. 7(b)) in the "grinding process" become large, it is difficult to adjust the width dimension W5 of the inner raceway seat. The solid line in Fig. 7(a) shows the state where the barrier wall 33B is warped, and the two-dot chain line in the same figure shows the original state of the barrier wall 33B.

[0036] As shown in Figs. 8(a) and (b), when the above-described barrier wall 33 has a stepped shape, the grinding range Ga and the grinding amount in the "grinding process" can be suppressed to be smaller than those in the conventional shape, and the adjustment of the width dimension W5 of the inner raceway seat 5 becomes easy.

[0037] <Parameter> As shown in Fig. 9, the step Δt satisfies the relationship of 0.1 mm < Δt < 0.5 mm. In this case, the dimensional accuracy of the step Δt can be easily ensured, and the manufacturing cost can be reduced. When the step Δt is 0.1 mm or less, it may be difficult to ensure the dimensional accuracy in the processing of the inner raceway seat 5. When the step Δt is 0.5 mm or more, the cutting amount of the inner raceway seat 5 is large, the processing man-hours increase, and the manufacturing cost increases.

[0038] When the outer diameter D on the mating side of each of the inner raceway split bodies 5A, 5A (Fig. 1) that are mated with each other and the outer diameter D' of the mating surface 5a of the inner raceway 5 with the inner race 3 are considered, the relationship D ≤ D', preferably D = D', may be satisfied. In this case, the load from one of the inner races 3 in the axial direction in Fig. 1 can be reliably transmitted to the other inner race 3 in the axial direction via the inner raceway 5. Both end faces of the spacer are ground simultaneously. When D ≠ D', the areas of the grinding surfaces on the left and right of the spacer are different. The larger the area, the smaller the amount that can be ground off. Therefore, since the amount that can be ground off is different between the left and right, it is difficult to finely adjust the width dimension. When D = D' as shown in Fig. 9, the grinding ranges of both end faces of the inner raceway split body 5A can be made the same, and the amount that can be ground off can be made the same between the left and right, so it is easy to finely adjust the width dimension. For this reason, the number of processing steps can be reduced compared to the case where D < D'.

[0039] When the inner diameter D1 on the outer surface of the seal member 31 and the outer diameter D' of the mating surface 5a of the inner raceway 5 with the inner race 3 are considered, the relationship D1 > D' may be satisfied. In this case, it is possible to more reliably prevent the seal member 31 and the barrier wall 33 of the inner raceway 5 from interfering with each other.

[0040] <Function and Effect> In the bearing device J of Fig. 1, during operation or the like, the cooling compressed air A sent from a compressed air supply device provided outside the bearing device J is supplied from the supply port 10 of the outer raceway spacer 4 toward the outer peripheral surface of the inner raceway 5. This compressed air A, after colliding with the inner raceway 5, flows axially on both sides along the outer peripheral surface of the inner raceway 5, and is further guided to the outer diameter side along the tapered outer diameter surface of the barrier wall 33 of the inner raceway 5, and is discharged from the notch 34 of the outer raceway spacer 5. By guiding the compressed air A to the outer diameter side by the barrier wall 33, the flow of the compressed air A in the spacer internal space S2 and the discharge of the compressed air A from the spacer internal space S2 become smooth. While the compressed air A passes through the spacer internal space S2, it takes away the heat of the bearing device J and the main shaft 7 supported by this bearing device J. Thereby, the bearing device J and the main shaft 7 are efficiently cooled.

[0041] Since the obstacle walls 33 are provided at both axial ends of the inner race spacer 5, the inflow of the compressed air A into the bearing inner space S1 is blocked. Further, since the bearing inner space S1 and the spacer inner space S2 are separated by the labyrinth seal portion 35 (FIG. 5), the inflow of the compressed air A into the bearing inner space S1 is more effectively blocked. Furthermore, since the compressed air A flows smoothly in the spacer inner space S2, the internal pressure of the spacer inner space S2 is lower than the internal pressure of the bearing inner space S1, and it is difficult for the compressed air A to flow into the bearing inner space S1. From these facts, the inflow of the compressed air A into the bearing inner space S1 can be suppressed as much as possible, and the grease enclosed in the bearing inner space S1 is prevented from being displaced by the compressed air A. Therefore, a good lubrication state can be maintained.

[0042] As shown in FIG. 5, a step Δt is provided between the mating surface 5a of the inner race spacer 5 with the inner race 3 and the axially outer surface 33a of the obstacle wall 33. This step Δt is recessed axially inward A1 of the inner race spacer 5 from the mating surface 5a. Therefore, as shown in FIG. 6, even when the outer race 2 and the outer race spacer 4 move axially due to the thermal expansion of the inner race 3 during bearing operation, the clearance b´ in the axial direction between the seal member 31 fixed to the outer race 2 and the obstacle wall 33 of the inner race spacer 5 can be ensured. Thereby, interference between the seal member 31 and the obstacle wall of the inner race spacer 5 can be prevented in advance, and the bearing function can be maintained.

[0043] <Regarding other embodiments> In the following description, the same reference numerals are given to the parts corresponding to the matters described in advance in each embodiment, and the overlapping descriptions are omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those in the embodiments described in advance unless otherwise specified. The same configuration exhibits the same operational effects. Not only the combinations specifically described in each embodiment, but also the embodiments can be partially combined with each other as long as there is no problem with the combination.

[0044] [Second Embodiment: Phase of Supply Port and Notch] As shown in FIGS. 10 and 11, the supply port 10 and the notch 34 may be arranged with their circumferential positions shifted from each other. When the circumferential positions of the supply port 10 and the notch 34 are shifted from each other, as shown in FIG. 10, when the compressed air A supplied from the supply port 10 to the inner ring spacer internal space S2 flows to the notch 34 along the outer peripheral surface of the inner ring spacer 5, in addition to the axial outward movement, it involves a circumferential movement. Therefore, the time during which the compressed air A contacts the inner ring spacer 5 becomes longer, and the effect of cooling the bearing device J and the main shaft 7 is enhanced.

[0045] [Third Embodiment: Supply Port Inclination] When the shaft supported by the bearing device J rotates in a fixed direction like the main shaft 7 of the machine tool, as shown in FIG. 12, the air discharge direction of each supply port 10 may be inclined forward in the rotation direction L1 of the inner ring 3 (FIG. 1) and the main shaft 7. Each supply port 10 is linear, and is located at a position offset (offset amount OS) in a direction orthogonal to this straight line L2 from an arbitrary radial straight line L2 in a cross section perpendicular to the axis of the outer ring spacer 4. In this way, when the air discharge direction of each supply port 10 is inclined, the discharged compressed air A hits the outer peripheral surface of the inner ring spacer 5 and, when flowing along the outer peripheral surface to the notch 34, promotes circumferential movement in addition to axial outward movement. Therefore, the time during which the compressed air A contacts the inner ring spacer 5 becomes longer, and the effect of cooling the bearing device J and the main shaft 7 is enhanced.

[0046] [Fourth Embodiment: Back-to-Back Assembly] As shown in FIG. 13, the angular contact ball bearings 1, 1 may be installed in a back-to-back assembly and used with a preload in a fixed position. The rolling bearings can also be installed in a parallel assembly or a back-to-back assembly and used with a preload in a fixed position.

[0047] [Application Example to the Main Shaft Device of a Machine Tool] As shown in Fig. 14, in the bearing device J, the outer rings 2, 2 of the rolling bearings 1, 1 and the intermediate housing 4 between the outer rings are fitted to the inner peripheral surface of the housing 6, and the inner rings 3, 3 of the rolling bearings 1, 1 and the intermediate housing 5 between the inner rings are fitted to the outer peripheral surface of the main shaft 7 of the machine tool. For example, the outer ring 2 and the intermediate housing 4 between the outer rings are clearance-fitted to the housing 6, and the inner ring 3 and the intermediate housing 5 between the inner rings are interference-fitted to the shaft 7. The outer ring 3 of the rolling bearing 1 on one side (the right side in the figure) is axially positioned by the stepped portion 6a of the housing 6, and the inner ring 3 of the rolling bearing 1 is axially positioned by the positioning spacer 41. Then, the bearing device J is fixed to the housing 6 by pressing the outer ring retainer 43 and the inner ring retainer 42 against the outer ring 2 and the inner ring 3 of the rolling bearing 1 on the other side (the left side in the figure), respectively.

[0048] The housing 6 and the outer ring retainer 43 are provided with a compressed air introduction hole 46 for introducing the cooling compressed air A sent from the compressed air supply device 45 to the bearing device J. The compressed air introduction hole 46 communicates with the introduction groove 11 provided on the outer peripheral surface of the intermediate housing 4 between the outer rings. The housing 6 and the outer ring retainer 43 are provided with exhaust holes 47, and the exhaust holes 47 communicate with the notch 34 of the intermediate housing 4 between the outer rings through the connection holes 48.

[0049] Since the cooling structure of this bearing device J has a high cooling effect on the bearing device J and the main shaft 7 as described above, it is possible to operate the main shaft device in a high-speed region. Therefore, this bearing device J can be suitably used for supporting the main shaft of a machine tool. The bearing device J may be used for applications other than supporting the main shaft of a machine tool. As each rolling bearing, a tapered roller bearing may be applied.

[0050] As described above, the embodiments for carrying out the present invention have been described based on the embodiments, but the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Description of Reference Numerals

[0051] 1... rolling bearing, 2... outer ring, 3... inner ring, 4... spacer between outer rings, 5... spacer between inner rings, 5a... mating surface with inner ring, 6... housing, 7... main shaft, 10... supply port, 31... seal member, 33... obstacle wall, 33a... axially outer surface, 34... notch, J... bearing device, S1... internal space of bearing S2... internal space of spacer

Claims

1. A bearing device comprising a plurality of rolling bearings arranged in the axial direction, and an outer-race spacer and an inner-race spacer interposed between the outer races and the inner races of these rolling bearings, respectively, wherein the rolling bearings are lubricated by grease enclosed in a bearing internal space between the inner and outer races, a supply port for supplying compressed air for cooling is provided on the inner peripheral surface of the outer-race spacer toward the outer peripheral surface of the inner-race spacer, and a discharge port for discharging the compressed air supplied from the supply port is provided in the outer-race spacer, barrier walls that project outward in the outer diameter direction are provided at both axial ends of the inner-race spacer to prevent the compressed air supplied from the supply port from flowing into the bearing internal space, and the outer diameter ends of these barrier walls face the inner peripheral surface of the outer-race spacer with a radial clearance therebetween, which is a cooling structure of the bearing device, a step Δt is provided between the mating surface of the inner-race spacer with the inner race and the outer side surface in the axial direction of the barrier wall, and this step Δt is a cooling structure of the bearing device that is recessed inward in the axial direction of the inner-race spacer from the mating surface.

2. In the cooling structure of the bearing device according to Claim 1, the step Δt satisfies the relationship 0.1 mm < Δt < 0.5 mm, which is a cooling structure of the bearing device.

3. In the cooling structure of the bearing device according to Claim 2, the inner-race spacer has two inner-race spacer divided bodies whose intermediate portions in the axial direction are divided, and when the outer diameter D on the mating side in each inner-race spacer divided body that mates these inner-race spacer divided bodies with each other and the outer diameter D' of the mating surface in the inner-race spacer are defined, it satisfies the relationship D ≤ D', which is a cooling structure of the bearing device.

4. In the cooling structure of the bearing device according to Claim 3, the outer diameter surface of the barrier wall has a tapered shape in which the amount of projection to the outer diameter side is larger on the side closer to the rolling bearing in the axial direction, and the discharge port of the outer-race spacer is a notch provided in the axial end surface of the outer-race spacer, which is a cooling structure of the bearing device.

5. In the cooling structure of the bearing device according to Claim 4, the circumferential positions of the supply port and the notch are offset from each other, which is a cooling structure of the bearing device.

6. In the cooling structure of the bearing device according to claim 1 or claim 2, the rolling bearing has a seal member that seals the bearing internal space at the axial end of the outer ring, the outer diameter end of the obstacle wall is located on the outer diameter side of the outer diameter side end of the end face of the inner ring and on the inner diameter side of the inner diameter side end of the end face of the outer ring, the axial outer surface of the obstacle wall is in a shape facing the seal member with an axial clearance therebetween, and a cooling structure of a bearing device having a labyrinth seal effect between the seal member and the obstacle wall.

7. In the cooling structure of the bearing device according to claim 6, a cooling structure of a bearing device that satisfies the relationship D1 > D', where D1 is the inner diameter of the seal member and D' is the outer diameter of the butting surface in the inner ring seat.

8. The cooling structure of the bearing device according to claim 1 or claim 2, which is used for supporting the main shaft of a machine tool.

9. A bearing device provided with the cooling structure of the bearing device according to any one of claims 1 to 5.

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