JP2011226551A - Tapered roller bearing set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tapered roller bearing set capable of preventing release of preload caused by thermal expansion during operating the bearing, preventing decrease in rigidity of the bearing and decrease in bearing life, and enhancing flexibility of designing, without providing additional components to it.SOLUTION: The tapered roller bearing set comprises a pair of tapered roller bearings abutted on the rear faces to each other and fitted to a common shaft Sh. The bearing set is configured in such a manner that the contact length between a rolling surface 3a and an outer ring raceway surface 2a is made larger than the contact length between the rolling surface 3a and an inner ring raceway surface 1a, under the condition of r<Ltanθ, where θ represents an angle of the outer ring raceway surface 2a with respect to the bearing axis C in each tapered roller bearing, L represents an axial distance between centers of contact portions of the outer ring raceway surface 2a and a roller 3 in both tapered roller bearings, and r represents a radial distance between the center of the contact portion and the bearing axis.

Description

  The present invention relates to a tapered roller bearing set used with a preload applied.

Hubs of large automobiles, rear-wheel-side final reduction gears for rear-wheel drive or four-wheel-drive automobiles, pinion shafts, railcar journals, spindles of machine tools for heavy cutting, etc. must be supported by back-to-back tapered roller bearings. There are many. The “back-to-back alignment” is a radial bearing in which the back surfaces of the bearings are combined to face each other. This back-to-back tapered roller bearing is usually used with a preload applied. Further, a shaft or a final reduction gear of an automobile transmission is used with a preload applied in front of the bearing. The “front alignment” is a radial bearing in which the front surfaces of the bearings are combined to face each other.
The preload is applied to ensure the rigidity and life of the bearing, but if the temperature around the bearing changes during use of the bearing, the preload may be released due to thermal expansion.

2. Description of the Related Art Conventionally, in a tapered roller bearing for an automobile transmission used for front-to-face alignment, a technique for preventing preload loss by pressing an outer ring in the axial direction with a leaf spring has been proposed (Patent Document 1).
Shifting the apex of the conical angle between the inner ring unit including the inner ring and rollers and the outer ring, and eliminating the so-called edge contact between the roller small end and the outer ring raceway surface even if the preload is lost, thereby extending the bearing life. A technique has been proposed (Patent Document 2).

A technology has been proposed that offsets preload loss due to axial elongation and temperature increase due to radial elongation by designing the contact angle of the tapered roller bearing and the distance between the bearings to a certain ratio (patent) Reference 3).
A technique has been proposed in which a shim made of a material having a linear expansion coefficient different from steel is brought into contact with the end surface of the outer ring, and the outer ring is moved in the axial direction by thermal expansion of the shim to prevent preload loss (Patent Document 4). , 5).

Japanese Utility Model Publication No. 6-35642, FIGS. 1 and 3 JP 2006-234087 A JP 2008-110426 A JP 2008-249019 A JP 2009-79696 A

In the case of using the leaf spring or shim to prevent preload loss, additional parts are required, which complicates the structure and increases the manufacturing cost.
Shifting the apex of the conical angle between the inner ring unit and the outer ring is effective in reducing the service life due to preload loss, but the rigidity of the bearing cannot be ensured.
In the case where the contact angle of the tapered roller bearing and the distance between the bearings are designed at a constant ratio, there is a problem that the dimensions are restricted and the degree of freedom in design is reduced.

  The object of the present invention is to prevent preload loss due to thermal expansion during operation of the bearing without providing additional parts, etc., and to prevent a decrease in bearing rigidity and a decrease in bearing life. The present invention is to provide a tapered roller bearing set capable of enhancing the above.

A tapered roller bearing set according to a first aspect of the present invention is a tapered roller bearing set comprising a pair of tapered roller bearings fitted to a common shaft in back-to-back alignment, and each outer ring raceway bearing in each tapered roller bearing. When the angle with respect to the shaft center is θ, the axial distance between the contact center of the tapered roller bearing and the outer ring raceway surface is L, and the radial distance between the contact center and the bearing shaft is r, Under the condition of r <Ltanθ, the contact length between the roller rolling surface and the outer ring raceway surface is made larger than the contact length between the roller rolling surface and the inner ring raceway surface.
The “contact length” refers to the length of the so-called axial plane where the roller rolling contact surface and the raceway contact each other in a state where a constant radial load and / or axial load is applied to the bearing. Say. However, when the load is not strictly acting, it becomes a point in the ideal state.

In a pair of tapered roller bearings used for back-to-back alignment, if the temperature difference of the cone assembly with respect to the outer ring (subunit consisting of the inner ring and the cage) is Δt and the linear expansion coefficient is α, the amount of interference between the rollers and the outer ring The change Δδ is simply expressed as follows.
That is, as the change Δδ in the amount of interference between the roller and the outer ring is negative and the absolute value thereof is larger, it means that the preload loss is larger. Accordingly, if r> Ltanθ, Δδ (> 0) can be increased by increasing Δt, and if r <Ltanθ, Δδ (< 0) can be made large.

  Under normal driving conditions, the temperature on the inner ring side is higher than that on the outer ring, and in order to reduce Δt, it is necessary to increase the heat generation on the outer ring side. When the contact length of the contact portion between the roller rolling surface and the outer ring raceway surface is larger than the contact length of the contact portion between the roller rolling surface and the inner ring raceway surface, when the same load is applied to the bearing, The shorter the contact portion, the smaller the friction loss, so that a large amount of heat is generated on the outer ring side and the heat generation on the inner ring side is relatively small. Conversely, in order to increase Δt, it is necessary to reduce the heat generation on the outer ring side. That is, when the heat generation on the inner ring side is not sufficient under normal operating conditions, the contact length of the contact portion between the roller rolling surface and the inner ring raceway surface is determined from the contact length of the contact portion between the roller rolling surface and the outer ring raceway surface. Also make it big.

  According to this configuration, the contact length between the roller rolling surface and the outer ring raceway surface is made larger than the contact length between the roller rolling surface and the inner ring raceway surface under the condition of r <Ltanθ. The heat generation on the side can be increased, and the heat generation on the inner ring side can be relatively reduced. For this reason, compared with the case where the contact length of the contact part of an outer ring | wheel side and an inner ring | wheel side is comparable, the thermal expansion on an outer ring side becomes large and the thermal expansion on an inner ring side becomes small. Therefore, the change Δδ in the amount of interference between the roller and the outer ring is negative, and the absolute value thereof can be increased. As a result, it is possible to prevent preload loss due to thermal expansion during operation of the bearing, thereby preventing a decrease in bearing rigidity and a decrease in bearing life. Compared with conventional ones, preload loss can be prevented without providing additional parts such as leaf springs and shims. Since the number of parts can be reduced and the structure can be simplified in this way, the manufacturing cost can be reduced.

In the first invention, the inner ring raceway surface in a section viewed by cutting the inner ring in a plane including the bearing axis of each tapered roller bearing is a single arc crowning having an arc shape having a single curvature, The outer ring raceway surface in a cross section viewed by cutting the outer ring along a plane including the bearing axis may be formed by a straight line.
In this case, the contact length between the roller rolling surface and the outer ring raceway surface can be reliably and easily made larger than the contact length between the roller rolling surface and the inner ring raceway surface. Since the single arc crowning of the inner ring raceway surface is easy to process, the manufacturing cost can be reduced.

1st invention WHEREIN: The said inner ring raceway surface in the cross section seen by cut | disconnecting the inner ring | wheel by the plane containing a bearing axial center among each tapered roller bearing is made into the partial circular arc crowning containing a partial circular arc shape, and an outer ring | wheel is a bearing shaft. The outer ring raceway surface in a cross section viewed by cutting along a plane including the center may be formed by a straight line.
In this case, the contact length between the roller rolling surface and the outer ring raceway surface can be reliably made larger than the contact length between the roller rolling surface and the inner ring raceway surface. Moreover, since the said partial arc crowning can be measured with high precision on the basis of a straight part, highly accurate processing is possible.

  In any one of the inventions described above, the outer ring may be provided with a flange in contact with the roller large end face. In this case, since a part of the heat source can be changed from the inner ring side to the outer ring side, the temperature on the outer ring side is more likely to rise. Therefore, the change Δδ in the amount of interference between the rollers and the outer ring is negative, and the absolute value thereof can be further increased. As a result, it is possible to prevent preload loss due to thermal expansion during operation of the bearing, thereby preventing a decrease in bearing rigidity and a decrease in bearing life.

  A tapered roller bearing set according to a second aspect of the present invention is a tapered roller bearing set comprising a pair of tapered roller bearings fitted on a common shaft in back-to-back alignment. When the angle with respect to the shaft center is θ, the axial distance between the contact center of the tapered roller bearing and the outer ring raceway surface is L, and the radial distance between the contact center and the bearing shaft is r, Under the condition of r> Ltan θ, the contact length between the roller rolling surface and the inner ring raceway surface is made larger than the contact length between the roller rolling surface and the outer ring raceway surface.

  According to this configuration, under the condition of r> Ltanθ, the contact length between the roller rolling surface and the inner ring raceway surface is made larger than the contact length between the roller rolling surface and the outer ring raceway surface. Small and Δt can be large. Therefore, the change Δδ in the amount of interference between the rollers and the outer ring is negative, and the absolute value thereof can be further increased. As a result, it is possible to prevent preload loss due to thermal expansion during operation of the bearing, thereby preventing a decrease in bearing rigidity and a decrease in bearing life.

A tapered roller bearing set according to a third aspect of the present invention is a tapered roller bearing set comprising a pair of tapered roller bearings fitted on a common shaft in face-to-face alignment, and the roller rolling surface in each tapered roller bearing. The contact length between the roller rolling surface and the inner ring raceway surface is larger than the contact length between the outer ring raceway surface and the outer ring raceway surface.
In the case of face-to-face alignment, if preload loss is a problem, the amount of expansion on the housing side is larger, so the amount of heat generated on the inner ring side needs to be larger than that on the outer ring side. In the face-to-face tapered roller bearing set, the contact length between the roller rolling surface and the inner ring raceway surface is larger than the contact length between the roller rolling surface and the outer ring raceway surface. Can be increased to prevent a reduction in bearing rigidity and bearing life.

  2nd or 3rd invention WHEREIN: The outer ring raceway surface in the cross section seen by cut | disconnecting an outer ring in the plane containing a bearing axial center among each tapered roller bearing WHEREIN: The single circular arc which consists of circular arc shape which has a single curvature The inner ring raceway surface in a section viewed by cutting the inner ring along a plane including the bearing axis may be formed by a straight line. Since the single arc crowning of the outer raceway surface is easy to process, the manufacturing cost can be reduced.

  In any one of the inventions described above, the roller rolling surface in a cross section obtained by cutting the roller along a plane including the bearing axis may have a logarithmic crowning shape represented by a logarithmic curve. The roller rolling surface is desirably a crowning shape expressed by a logarithmic curve, so-called logarithmic crowning, in order to secure a substantial contact length with the raceway. With an optimally designed logarithmic crowning, it is possible to reduce the surface pressure as much as possible compared to other crownings, that is, to increase the contact length of the contact portion while preventing edge loading. be able to.

The rotating machine according to the present invention may be used by applying a preload to the tapered roller bearing set according to any one of the above inventions.
The machine tool spindle of the present invention may be one using the tapered roller bearing set of any of the above inventions.
The automobile transmission according to the present invention may be one in which the tapered roller bearing set according to any one of the above inventions is fitted into a housing made of an aluminum alloy.

  A tapered roller bearing set according to a first aspect of the present invention is a tapered roller bearing set comprising a pair of tapered roller bearings fitted on a common shaft in back-to-back alignment. When the angle with respect to the shaft center is θ, the axial distance between the contact center of the tapered roller bearing and the outer ring raceway surface is L, and the radial distance between the contact center and the bearing shaft is r, Under the condition of r <Ltanθ, the contact length between the roller rolling surface and the outer ring raceway surface is made larger than the contact length between the roller rolling surface and the inner ring raceway surface. It is possible to prevent preload loss due to thermal expansion during operation, prevent a decrease in bearing rigidity and a decrease in bearing life, and further increase the degree of freedom in design.

  A tapered roller bearing set according to a second aspect of the present invention is a tapered roller bearing set comprising a pair of tapered roller bearings fitted on a common shaft in back-to-back alignment. When the angle with respect to the shaft center is θ, the axial distance between the contact center of the tapered roller bearing and the outer ring raceway surface is L, and the radial distance between the contact center and the bearing shaft is r, Under the condition of r> Ltanθ, the contact length between the roller rolling surface and the inner ring raceway surface is made larger than the contact length between the roller rolling surface and the outer ring raceway surface. It is possible to prevent preload loss due to thermal expansion during operation, prevent a decrease in bearing rigidity and a decrease in bearing life, and further increase the degree of freedom in design.

  A tapered roller bearing set according to a third aspect of the present invention is a tapered roller bearing set comprising a pair of tapered roller bearings fitted on a common shaft in face-to-face alignment, and the roller rolling surface in each tapered roller bearing The contact length between the roller rolling surface and the inner ring raceway surface is larger than the contact length between the outer ring raceway surface and the outer ring raceway surface, so that preload loss due to thermal expansion during bearing operation is prevented without providing additional parts. Further, it is possible to prevent a decrease in bearing rigidity and a decrease in bearing life, and further increase the degree of freedom in design.

It is sectional drawing of the tapered roller bearing group which concerns on one Embodiment of this invention. It is principal part sectional drawing of each tapered roller bearing in the same tapered roller bearing group. It is a figure which expands and shows the crowning shape of the inner ring | wheel of the same tapered roller bearing. It is a figure which shows the crowning shape of the roller of the same tapered roller bearing. It is a figure explaining the relationship between the presence or absence of crowning of the inner and outer rings and the amount of heat generation. It is a figure which shows the crowning shape of the inner ring | wheel of the tapered roller bearing set which concerns on other embodiment of this invention. It is sectional drawing of each tapered roller bearing in the tapered roller bearing group which concerns on further another embodiment of this invention. It is sectional drawing of the tapered roller bearing set which concerns on other embodiment of this invention. It is sectional drawing of the tapered roller bearing set which concerns on other embodiment of this invention. It is sectional drawing which shows the example which used the tapered roller bearing set which concerns on embodiment of this invention for the support of a machine tool spindle. It is sectional drawing which shows the example which incorporated the tapered roller bearing set which concerns on embodiment of this invention in the transmission for motor vehicles.

  An embodiment of the present invention will be described with reference to FIGS. The following description also includes an explanation of a method for designing a tapered roller bearing assembly. As shown in FIG. 1, the tapered roller bearing assembly according to this embodiment includes a pair of tapered roller bearings fitted on a common shaft in back-to-back alignment. As shown in FIGS. 1 and 2, each tapered roller bearing includes an inner ring 1, an outer ring 2, and a plurality of tapered rollers 3 interposed between the inner and outer rings 1 and 2. The tapered roller 3 may be simply referred to as “roller 3”. An inner ring raceway surface 1a is formed on the outer periphery of the inner ring 1, and a large brim 4 and a small brim 5 are provided on the large diameter side and the small diameter side of the inner ring raceway surface 1a, respectively. The outer ring 2 is formed with an outer ring raceway surface 2a opposite to the inner ring raceway surface 1a on the inner periphery, and has no collar.

  The outer periphery of the roller 3 is formed as a rolling surface 3a, and the roller 3 can freely roll between the inner ring raceway surface 1a and the outer ring raceway surface 2a. As shown in FIG. 2, each roller 3 is accommodated in a pocket of the cage Rt and is held at a predetermined interval in the circumferential direction. In FIG. 1, the cage Rt is omitted. The front surface of the bearing ring represents a bearing ring side surface (also referred to as “end face”) that does not support the axial load, and the rear surface of the bearing ring represents the bearing ring side surface that supports the axial load. In the entire bearing, the front and back surfaces are defined with the direction of the outer ring.

As shown in FIG. 1, in the pair of tapered roller bearings used for back-to-back alignment, the angle of the outer ring raceway surface 2a in each tapered roller bearing with respect to the bearing axis C is θ, and the outer ring raceway surface 2a of both tapered roller bearings. However, let L be the axial distance between the center of the contact portion with 3 and r be the radial distance between the center of the contact portion and the bearing axis C. The “contact portion center” is an intermediate length of a portion where the roller rolling surface 3a and the outer ring raceway surface 2a are in contact with each other on the axial plane of the tapered roller bearing in a state where a constant radial load is applied to the bearing. Point to a point. If the temperature difference of the cone assembly with respect to the outer ring 2 (subunit consisting of the inner ring 1 and 3 and the cage Rt) is Δt and the linear expansion coefficient is α, the change Δδ in the amount of interference between the roller 3 and the outer ring 2 is simply as follows: It is expressed as the following formula (1).

That is, as the change Δd in the amount of interference between the roller 3 and the outer ring 2 is negative and the absolute value thereof is large, the preload loss is large. Accordingly, if r> Ltanθ, Δδ (> 0) can be increased by increasing Δt, and if r <Ltanθ, Δδ (< 0) can be made large.

  Under normal operating conditions, the temperature on the inner ring 1 side is higher than that on the outer ring 2, and in order to reduce Δt, it is necessary to increase the heat generation on the outer ring 2 side. If the contact length of the contact portion between the roller rolling surface 3a and the outer ring raceway surface 2a is larger than the contact length of the contact portion between the roller rolling surface 3a and the inner ring raceway surface 1a, the same load acts on the bearing. In general, the shorter the contact portion, the smaller the friction loss, so that a large amount of heat is generated on the outer ring side and the heat generation on the inner ring side is relatively small. Conversely, in order to increase Δt, it is necessary to reduce the heat generation on the outer ring side. That is, when heat generation on the inner ring side is not sufficient under normal operating conditions, the contact length of the contact portion between the roller rolling surface 3a and the inner ring raceway surface 1a is set to the contact portion between the roller rolling surface 3a and the outer ring raceway surface 2a. Greater than the contact length.

  In this embodiment, the contact length between the roller rolling surface 3a and the outer ring raceway surface 2a is determined from the contact length between the roller rolling surface 3a and the inner ring raceway surface 1a in each tapered roller bearing under the condition of r <Ltanθ. Is big. That is, each tapered roller bearing has a roller length from the contact length between the roller rolling surface 3a and the inner ring raceway surface 1a in a cross section obtained by cutting the tapered roller bearing along a plane including the bearing axis C (axial plane). The contact length between the rolling surface 3a and the outer ring raceway surface 2a is increased. The “contact length” is a length of a portion of the axial plane where the roller rolling surface 3a and the inner ring raceway surface 1a or the outer ring raceway surface 2a are in contact with each other in a state where a certain radial load is applied to the bearing. Say. Specifically, the inner ring raceway surface 1a in a cross section viewed by cutting the inner ring 1 along the axial plane is a single arc crowning having an arc shape having a single curvature R1 (FIG. 3). Further, the outer ring raceway surface 2a in a cross section viewed by cutting the outer ring 2 along the axial plane is formed by a straight line. Further, as shown in FIGS. 2 and 4, the roller rolling surface 3a in a cross section obtained by cutting the roller 3 along the axial plane has a crowning shape expressed by a logarithmic curve.

  When the bearing ring is crowned as described above, when a certain radial load is applied to the bearing, for example, the contact of the contact portion between the roller rolling surface 3a and the raceway surface is greater than that when the bearing ring is not crowned. The length is shortened. In addition, if the cross-sectional shape of the raceway surface is an arc shape with a single curvature, the contact portion with the raceway surface and the rolling surface 3a is a point contact, but a constant radial load and / or an axial load is applied to the bearing. When the composite load is applied, the raceway 3 is elastically deformed within a minute range including the contact portion. By this elastic deformation, the contact portion between the raceway surface and the rolling surface 3a becomes a line contact. Therefore, the contact length of a contact part can be compared.

  When crowning is applied to the race, the contact length of the contact portion is shorter than that without crowning. Table 1 compares the presence / absence of crowning of the inner and outer rings 1 and 2 and the calculation result of the generated frictional heat. In Table 1, the ratio of frictional heat generated in the outer ring 2 when the amount of heat generated in the inner ring 1 is “1” is shown.

According to Table 1, it can be seen that when the outer ring 2 is crowned, the heat generation ratio of the outer ring 2 is reduced, and the heat generation amount in the inner ring 1 is relatively increased. Therefore, the temperature of the inner ring 1 and the shaft Sh fitted to the inner peripheral surface of the inner ring is increased, and the expansion of the shaft Sh is promoted.
On the other hand, when the inner ring 1 is crowned, the heat generation amount of the outer ring 2 is relatively increased, and the expansion of the housing Hs fitted to the outer peripheral surface of the outer ring is promoted.
In this embodiment, the pair of tapered roller bearings are back-to-back and r <Ltan θ. In this case, in order to make Δt small, as shown in FIG. 5C, the above-mentioned crowning is applied to the inner ring raceway surface 1a, and the outer ring raceway surface 2a is formed in a straight line.

  According to the tapered roller bearing set described above, the contact length between the roller rolling surface 3a and the outer ring raceway surface 2a is determined from the contact length between the roller rolling surface 3a and the inner ring raceway surface 1a under the condition of r <Ltanθ. Therefore, during the bearing operation, heat generation on the outer ring side can be increased and heat generation on the inner ring side can be relatively reduced. For this reason, compared with the case where the contact length of the contact part of an outer ring | wheel side and an inner ring | wheel side is comparable, the thermal expansion on an outer ring side becomes large and the thermal expansion on an inner ring side becomes small. Therefore, the change Δδ in the amount of interference between the roller 3 and the outer ring 2 is negative and the absolute value thereof can be increased. As a result, it is possible to prevent preload loss due to thermal expansion during operation of the bearing, thereby preventing a decrease in bearing rigidity and a decrease in bearing life. Compared with conventional ones, preload loss can be prevented without providing additional parts such as leaf springs and shims. Since the number of parts can be reduced and the structure can be simplified in this way, the manufacturing cost can be reduced.

  Of the tapered roller bearings, the inner ring raceway surface 1a in a cross section viewed by cutting the inner ring 1 along a plane including the bearing axis C is a single arc crowning having an arc shape having a single curvature, and the outer ring 2 is When the outer ring raceway surface 2a in a cross section viewed along a plane including the bearing axis C is formed in a straight line, the roller rolling surface 3a is longer than the contact length between the roller rolling surface 3a and the inner ring raceway surface 1a. And the outer ring raceway surface 2a can be reliably and easily increased in length. Since the single arc crowning of the inner ring raceway surface 1a is easy to process, the manufacturing cost can be reduced.

  The roller rolling surface 3a has a crowning shape represented by a logarithmic curve, so-called logarithmic crowning, in order to ensure a substantial contact length with the outer ring 2, so that the logarithmic crowning that is optimally designed It is possible to reduce the surface pressure as much as possible as compared with the crowning of. That is, the contact length of the contact portion can be increased while preventing edge loading.

  As another embodiment of the present invention, as shown in FIG. 6, the inner ring raceway surface 1a in a cross section obtained by cutting the inner ring 1 along the axial plane is a partial arc crowning including partial arc shapes R2 and R3. The outer ring raceway surface 2a in a cross section viewed by cutting the outer ring 2 along an axial plane may be formed by a straight line (FIG. 2). The partial arc crowning includes a straight portion 6 at the center of the raceway surface, and crowning portions 7 and 8 at both ends of the raceway surface on the large diameter side and the small diameter side that smoothly follow the straight portion 6. Also in this case, the contact length between the roller rolling surface 3a and the outer ring raceway surface 2a can be reliably made larger than the contact length between the roller rolling surface 3a and the inner ring raceway surface 1a. Moreover, since the said partial arc crowning can be measured with high precision on the basis of the straight part 6, high-precision processing is possible as a whole. Therefore, it is possible to obtain a tapered roller bearing that can further reduce the thermal expansion on the inner ring side.

As shown in FIG. 7, the outer ring 2 may be provided with a flange 9 in contact with the roller large end surface 3b. An outer ring raceway surface 2a in a cross section obtained by cutting the outer ring 2 along an axial plane is formed by a straight line. The inner ring raceway surface 1a is formed with a single arc crowning similar to FIG. 3 or a partial arc crowning similar to FIG. However, the inner ring 1 is not formed with a large brim or a small brim.
According to this configuration, since a part of the heat source that generates heat between the large collar and the large end surface 3b of the inner ring 1 can be changed from the inner ring side to the outer ring side, the temperature on the outer ring side is more likely to rise. Therefore, the change Δδ in the amount of interference between the roller 3 and the outer ring 2 is negative, and the absolute value thereof can be further increased. As a result, it is possible to prevent preload loss due to thermal expansion during operation of the bearing, thereby preventing a decrease in bearing rigidity and a decrease in bearing life.

As shown in FIG. 8, in a tapered roller bearing set including a pair of tapered roller bearings fitted to a common shaft for back-to-back alignment, under the condition of r> Ltan θ, the roller rolling surface 3 a and the outer ring raceway surface 2 a The contact length between the roller rolling surface 3a and the inner ring raceway surface 1a may be made longer than the contact length.
In this case, the heat generation on the outer ring side can be reduced and Δt can be increased. Therefore, the change Δδ in the amount of interference between the roller 3 and the outer ring 2 is negative, and the absolute value thereof can be further increased. As a result, it is possible to prevent preload loss due to thermal expansion during operation of the bearing, thereby preventing a decrease in bearing rigidity and a decrease in bearing life.

  As shown in FIG. 9, a tapered roller bearing set including a pair of tapered roller bearings fitted to a common shaft Sh in front-to-face alignment is used, and a roller rolling surface 3a and an outer ring raceway surface 2a in each tapered roller bearing are formed. The contact length between the roller rolling surface 3a and the inner ring raceway surface 1a may be made larger than the contact length. Also in this case, similarly to the configuration of FIG. 8, the heat generation on the outer ring side can be reduced and Δt can be increased. Therefore, the change Δδ in the amount of interference between the roller 3 and the outer ring 2 is negative, and the absolute value thereof can be further increased. As a result, it is possible to prevent preload loss due to thermal expansion during operation of the bearing, thereby preventing a decrease in bearing rigidity and a decrease in bearing life.

  FIG. 10 shows an example in which a tapered roller bearing set including a pair of tapered roller bearings that are back-to-back in the embodiment is incorporated in a machine tool spindle. In machine tool spindle bearings, it is extremely important to ensure rigidity in order to increase machining accuracy. Although it is possible to apply a constant pressure preload to the bearing using a spring or the like, a fixed position preload is often used to simplify the structure. In this example, the width dimensions of the inner and outer rings 1 and 2 and the spacer 10 are adjusted, and the nut 11 is screwed into the female screw of the shaft Sh, thereby giving a fixed position preload in the axial direction to the tapered roller bearing set. Is done. In the case of this fixed position preload, it is important to optimize the temperature distribution and prevent the preload from decreasing during the bearing operation. When the tapered roller bearing set according to any of the embodiments of the present invention is incorporated in the machine tool main shaft Sh, preload loss due to thermal expansion during operation of the bearing is prevented at a fixed position preload, and the rigidity of the bearing is reduced. It is possible to prevent a decrease in life. In this case, the entire structure can be simplified as compared with the constant pressure preload, and the manufacturing cost can be reduced. A tapered roller bearing set composed of a pair of tapered roller bearings that face each other may be incorporated in the machine tool spindle.

FIG. 11 is a cross-sectional view illustrating an example in which the tapered roller bearing set including a pair of tapered roller bearings facing each other according to the embodiment is incorporated in an automobile transmission. In this example, the housing Hs is made of an aluminum alloy to reduce the weight, and a pair of tapered roller bearings that face each other are incorporated in the housing Hs. A gear (not shown) is attached to the outer periphery of the shaft Sh.
The linear expansion coefficient of the aluminum alloy is about twice as large as the linear expansion coefficient of steel. Therefore, when the shaft Sh and the housing Hs are at the same temperature, the housing Hs made of an aluminum alloy having a large linear expansion coefficient. Has a large thermal expansion. For this reason, it acts on the bearing in the direction in which the preload is released. Even in such a case, since the tapered roller bearing assembly comprising the pair of front-facing tapered roller bearings of the above-described embodiment is incorporated in an automobile transmission, preload loss due to thermal expansion during bearing operation is prevented. Thus, it is possible to prevent a decrease in bearing rigidity and a decrease in bearing life.

  A tapered roller bearing set including a pair of tapered roller bearings according to any one of the above embodiments is used for a hub of a large automobile, a rear wheel side final reduction device pinion shaft of a rear wheel drive or a four wheel drive vehicle, and a main shaft of a railway vehicle journal. It may be provided by being fitted to.

DESCRIPTION OF SYMBOLS 1 ... Inner ring 1a ... Inner ring raceway surface 2 ... Outer ring 2a ... Outer ring raceway surface 3 ... Roller 3a ... Roller rolling surface Sh ... Shaft HS ... Housing

Claims (13)

Tapered roller bearing assembly comprising a pair of tapered roller bearings fitted on a common shaft for back-to-back alignment, wherein the angle of the outer ring raceway surface of each tapered roller bearing with respect to the bearing axis is θ, and the outer ring of both tapered roller bearings When the axial distance between the contact portion centers with the raceway surface is L, and the radial distance between the contact portion center and the bearing axis is r,
A tapered roller bearing assembly characterized in that the contact length between the roller rolling surface and the outer ring raceway surface is made larger than the contact length between the roller rolling surface and the inner ring raceway surface under the condition of r <Ltanθ.   The outer ring according to claim 1, wherein the inner ring raceway surface in a cross section obtained by cutting the inner ring along a plane including the bearing axis of each tapered roller bearing is a single arc crowned having an arc shape having a single curvature. A tapered roller bearing assembly in which the outer ring raceway surface in a cross section viewed by cutting along a plane including the bearing axis is formed by a straight line.   2. The inner ring raceway surface in a cross section obtained by cutting an inner ring of each tapered roller bearing along a plane including a bearing axis is a partial arc crowning including a partial arc shape, and the outer ring is a bearing axis. A tapered roller bearing assembly in which the outer ring raceway surface in a cross section viewed by cutting a plane including a straight line is formed by a straight line.   The tapered roller bearing set according to any one of claims 1 to 3, wherein the outer ring is provided with a flange in contact with the large end surface of the roller. Tapered roller bearing assembly comprising a pair of tapered roller bearings fitted on a common shaft for back-to-back alignment, wherein the angle of the outer ring raceway surface of each tapered roller bearing with respect to the bearing axis is θ, and the outer ring of both tapered roller bearings When the axial distance between the contact portion centers with the raceway surface is L, and the radial distance between the contact portion center and the bearing axis is r,
A tapered roller bearing set characterized in that the contact length between the roller rolling surface and the inner ring raceway surface is made larger than the contact length between the roller rolling surface and the outer ring raceway surface under the condition of r> Ltanθ.   Tapered roller bearing assembly consisting of a pair of tapered roller bearings fitted on a common shaft for face-to-face alignment. Tapered roller bearing assembly characterized by having a large contact length between the inner ring raceway surface and the inner ring raceway surface.   7. A single circular arc having a single curvature in the outer ring raceway surface of the tapered roller bearing according to claim 5, wherein the outer ring raceway surface in a cross section obtained by cutting the outer ring along a plane including the bearing axis is shown. A tapered roller bearing assembly in which the inner ring raceway surface is formed by a straight line in a cross section when the inner ring is cut along a plane including a bearing axis center.   The inner ring according to claim 5 or 6, wherein the outer ring raceway surface in a cross section obtained by cutting an outer ring of each tapered roller bearing along a plane including a bearing axis is a partial arc crowning including a partial arc shape. A tapered roller bearing assembly in which the inner ring raceway surface in a cross section viewed by cutting along a plane including the bearing axis is formed by a straight line.   The tapered roller according to any one of claims 1 to 8, wherein the roller rolling surface in a cross section obtained by cutting the roller along a plane including a bearing axis is a logarithmic crowning shape represented by a logarithmic curve. Bearing assembly.   A rotating machine that uses a tapered roller bearing set according to any one of claims 1 to 9 with a preload applied thereto.   A machine tool spindle using the tapered roller bearing set according to any one of claims 1 to 9.   An automotive transmission in which the tapered roller bearing set according to any one of claims 1 to 9 is fitted in a housing made of an aluminum alloy.   A final reduction gear for an automobile, wherein the tapered roller bearing set according to any one of claims 1 to 9 is fitted in a housing made of an aluminum alloy.