Conical roller bearing

Abstract

To provide a conical roller bearing capable of achieving downsizing and weight saving, while realizing a high load capacity.SOLUTION: A conical roller bearing 10 is used with an outer ring 2 loosely fitted into a housing 15. The conical roller bearing 10 comprises: an inner ring 1 having a raceway surface 1a on an outer peripheral surface at an angle to an axial core AX, with a small rib 1b on one side and a large rib 1c on the other side; an outer ring 2 having a raceway surface 2a on an inner peripheral surface facing the inner ring raceway surface 1a; and a plurality of conical rollers 3 interposed between the inner and outer rings 1, 2. The shape of the outer ring raceway surface 2a viewed from an axial direction is an ellipse, and a dimension a of a major axis and a dimension b of a minor axis of an ellipse satisfy the relation: 1.00023≤(a / b)≤1.00027.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tapered roller bearing used in a hydraulic motor for a construction machine. [Background technology]

[0002] Tapered roller bearings are widely used in hydraulic motors for construction machinery. In such devices, the shaft may tilt or bend due to the load position, so the size of the bearing must be selected with attention paid to the maximum contact pressure and maximum edge stress (see, for example, Patent Document 1). Patent Documents 2 to 6 disclose techniques for making the raceway elliptical. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication number 08-005100 [Patent Document 2] International Publication No. 2015 / 136622 [Patent Document 3] Utility Model Registration No. 3196575 [Patent Document 4] JP 2016-148417 A [Patent Document 5] JP 2017-101692 A [Patent Document 6] JP 2019-163842 A Summary of the Invention [Problem to be solved by the invention]

[0004] For press machines used in electric vehicles, there is a particular demand for compact equipment and low noise, and the built-in bearings are required to have a high load capacity. In addition, there is a need for compactness and weight reduction in hydraulic motors, but when a bearing that satisfies the life and tolerances required for the load acting on the motor is selected, the bearing size tends to be large. In response to these issues, the devices in Patent Documents 1 to 6 have the following problems.

[0005] Patent Document 1 discloses a technique for applying preload to the outer ring of a tapered roller bearing in a hydraulic motor for construction machinery. However, the technique in Patent Document 1 relates to applying preload by tightening a nut, which increases the number of parts. In other words, the device is likely to become large and heavy.

[0006] Patent Document 2 discloses a technique for pressing a "roller" onto the outer ring raceway surface as a roller pressing member. In detail, Patent Document 2 discloses a technique for pressing a roller onto the outer ring raceway surface to prevent roller skew. This is a technique for bending into an elliptical shape using a rigid plug, but it is necessary to fix the inner diameter surface to an elliptical gear by interference fit, and in the case of inner ring rotating load / outer ring stationary load, if the outer ring / housing is a clearance fit, the elliptical deformation of the outer ring raceway surface may be impaired.

[0007] Patent Document 3 discloses a technology in which the outer ring elastically deforms into an ellipse. By forming the raceway surface into an elliptical shape in advance, it is not necessary to elastically deform the outer ring and install the bearing into the housing as in Patent Documents 1 and 2. However, there is a clearance fit between the outer ring and the housing, and the bearing cannot be used as the free side.

[0008] Patent Document 4 discloses a technique in which the cage guideway has an elliptical shape. This is a technique in which the cage and the outer ring raceway surface are actively pressed together by making the cage guideway elliptical, and the solid lubricant blended in the cage is transferred to contribute to lubrication. Thus, Patent Document 4 discloses a technique related to an elliptical shape, but does not disclose a technique for deforming the outer ring raceway surface into an ellipse.

[0009] Patent Document 5 discloses a technology for a bearing having an elliptical raceway surface with a major axis in the vertical direction. However, this technology is related to a rolling bearing used for a wheel support bearing, and is a technology for mitigating the impact load when a vehicle runs over a curb or step. Thus, the rolling bearing unit of Patent Document 5 is a wheel support bearing (ball bearing), and is not a tapered roller bearing used in hydraulic motors for construction machinery.

[0010] Patent Document 6 discloses a technology in which a substantially circular inner ring is fitted to a shaft having an elliptical cross section. In the device of Patent Document 6, a substantially circular bearing inner ring is fitted to a shaft having an elliptical cross section, and the inner diameter surface of the bearing inner ring is deformed into an elliptical shape when the interference fit is achieved. However, a shaft having an elliptical cross section has poor versatility, and in order to apply the structure of Patent Document 7 to an existing machine device and shaft, the existing machine device and shaft would need to be significantly modified, making it impractical.

[0011] An object of the present invention is to provide a tapered roller bearing that can achieve a high load capacity while also achieving size and weight reduction. [Means for solving the problem]

[0012] The tapered roller bearing of the present invention includes an inner ring having a raceway surface on its outer peripheral surface which is angled with respect to the axis and has a small rib on one side and a large rib on the other side, an outer ring having a raceway surface on its inner peripheral surface opposing the raceway surface of the inner ring, and a number of tapered rollers interposed between the inner ring and the outer ring, and the outer ring is used with loose fit in a housing, wherein the shape of the outer ring raceway surface when viewed from the axial direction is an ellipse, and the dimension a of the major axis and the dimension b of the minor axis of the ellipse satisfy the relationship 1.00023≦(a / b)≦1.00027. The tapered roller bearing of the present invention is used in, for example, a hydraulic motor or a pump for a forging machine.

[0013] According to this configuration, the outer ring raceway surface having an elliptical shape is fitted and fixed to the housing so that it has a vertical elliptical shape with its major axis existing in a radial plane including the axis of the bearing, thereby increasing the number of tapered rollers that receive the load of the bearing, and reducing the maximum contact surface pressure and maximum edge stress. As a result of being able to reduce the maximum contact surface pressure and maximum edge stress, the bearing can be made more compact, and when used in a hydraulic motor for a construction machine, the hydraulic motor can be made more compact. Furthermore, when used in a pump for a forging machine, the tapered roller bearing can be made to withstand high surface pressure and save space, and the load capacity can be increased and high rigidity can be achieved without increasing the size of the tapered roller bearing.

[0014] In the above configuration, the shape of the outer ring raceway surface as viewed from the axial direction of the tapered roller bearing is elliptical, and the length a of the major axis of the ellipse and the length b of the minor axis of the ellipse are set to satisfy the relationship 1.00023≦(a / b)≦1.00027. This allows the bearing to be attached to a machine so that it has a vertical elliptical shape for radial loads, dispersing the load rate of the rolling elements and making the contact pressure acting on the bearing uniform. As a result, the maximum contact pressure and maximum edge stress can be reduced. In addition, the number of tapered rollers present in the load area can be increased, reducing the contact stress per roller and suppressing flaking, etc.

[0015] In the present invention, the outer ring may be provided with an identification means that enables identification of the major axis position or the minor axis position of the elliptical outer ring raceway surface. This allows the elliptical raceway surface of the bearing outer ring to be assembled so that it becomes a vertical ellipse with respect to the radial load, thereby making the contact surface pressure uniform.

[0016] In the present invention, the outer ring raceway may be elliptical, and the gap between a reference circle having a diameter equal to the minor axis of the ellipse and the major axis of the ellipse may be set to 0.010 mm to 0.020 mm. The optimum value of the gap is, for example, 0.015 mm. With this configuration, it is possible to obtain a surface pressure reduction effect of approximately 6 to 9%.

[0017] In the present invention, the outer ring may be provided with a rotation prevention structure, which allows the elliptical shape of the outer ring raceway surface to be assembled so as to be a vertical ellipse, thereby making the contact surface pressure on each roller uniform. Effect of the Invention

[0018] According to the tapered roller bearing of the present invention, it is possible to achieve a high load capacity while achieving a reduction in size and weight. [Brief description of the drawings]

[0019] [Figure 1] 1 is a vertical sectional view showing a tapered roller bearing device equipped with a tapered roller bearing according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view showing the tapered roller bearing. [Diagram 3] 2 is an enlarged cross-sectional view showing a main portion of the tapered roller bearing. FIG. [Figure 4] 4 is an explanatory diagram of the shape and dimensions of an elliptical outer ring raceway surface of the tapered roller bearing. FIG. [Diagram 5] 6 is another explanatory view of the shape and dimensions of the elliptical outer ring raceway surface of the tapered roller bearing. FIG. [Figure 6A] 4 is a table showing the maximum contact pressure of each rolling element of the inner ring of the tapered roller bearing. [Figure 6B] FIG. 4 is a diagram showing the surface pressure distribution of the inner ring of the tapered roller bearing. [Figure 6C] FIG. 4 is another view showing the surface pressure distribution of the inner ring of the tapered roller bearing. [Figure 7A] 4 is a table showing the maximum contact pressure of each rolling element of the outer ring of the tapered roller bearing. [Figure 7B] FIG. 4 is a diagram showing the surface pressure distribution of the outer ring of the tapered roller bearing. [Figure 7C] FIG. 4 is another view showing the surface pressure distribution of the outer ring of the tapered roller bearing. [Figure 8] FIG. 2 is a diagram showing the arrangement of tapered rollers in the tapered roller bearing. [Figure 9A] FIG. 4 is a cross-sectional view showing a modified example of the tapered roller bearing. [Figure 9B]FIG. 4 is a cross-sectional view showing a modified example of the tapered roller bearing. [Figure 10A] FIG. 4 is a cross-sectional view showing another modified example of the tapered roller bearing. [Figure 10B] FIG. 4 is a cross-sectional view showing another modified example of the tapered roller bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the terms "axial direction", "radial direction" and "circumferential direction" refer to the "axial direction", "radial direction" and "circumferential direction" of a tapered roller bearing device, respectively.

[0021] Fig. 1 is a vertical cross-sectional view of a tapered roller bearing device BD equipped with a tapered roller bearing according to a first embodiment of the present invention. A tapered roller bearing device equipped with a tapered roller bearing of the present invention is used, for example, in a hydraulic motor or a pump of a forging machine. The tapered roller bearing device BD shown in Fig. 1 rotatably supports an input shaft 20 of an inclined-axis type axial piston pump P. However, the use of the tapered roller bearing device BD equipped with a tapered roller bearing of the present invention is not limited to this.

[0022] The tapered roller bearing device BD comprises a tapered roller bearing 10 that rotatably supports an input shaft 20 of a pump P, and a housing 15 to which the tapered roller bearing 10 is fixed. The tapered roller bearing 10 of this embodiment has a pair of tapered roller bearings 11, 12 arranged in a face-to-face combination. The tapered roller bearings 11, 12 are different in size but have the same structure.

[0023] Tapered roller bearing 10 comprises inner ring 1 which is a rotating ring, outer ring 2 which is a fixed ring, and a plurality of tapered rollers 3 interposed between inner ring 1 and outer ring 2. Housing 15 is loosely fitted, i.e., gap-fitted, onto the outer peripheral surface of outer ring 2 of tapered roller bearing 10. In other words, housing 15 is fitted with play onto the outer peripheral surface of outer ring 2 of tapered roller bearing 10, and outer ring 2 of tapered roller bearing 10 and housing 15 are configured to be able to move relative to one another.

[0024] The configuration of tapered roller bearing 10 of this embodiment will be described with reference to Figures 2 and 3. As shown in Figure 2, inner ring 1 has, on its outer circumferential surface, a conical raceway surface 1a (hereinafter referred to as "inner ring raceway surface 1a") that is angled with respect to axis center AX of tapered roller bearing 10. Inner ring 1 has small rib 1b on one axial side, or small diameter side, of its outer circumferential surface, and large rib 1c on the other axial side, or large diameter side. Small rib 1b and large rib 1c respectively form small rib surface 1ba and large rib surface 1ca.

[0025] The outer ring 2 has a conical raceway 2a (hereinafter referred to as "outer ring raceway 2a") on its inner peripheral surface. The outer ring raceway 2a faces the inner ring raceway 1a in the radial direction. A plurality of tapered rollers 3 are arranged between the inner ring raceway 1a and the outer ring raceway 2a.

[0026] In this tapered roller bearing 10, the inner ring raceway 1a and the outer ring raceway 2a of the tapered rollers 3 are in line contact, and the tapered rollers 3 are designed so that an extension line of the inner ring raceway 1a, the outer ring raceway 2a and the center O of the tapered rollers 3 coincides at a point P1 on the axis AX of the bearing 10. The angle θ is the contact angle of the tapered roller bearing 10.

[0027] In tapered roller bearing 10, the cone angle of inner ring raceway surface 1a and the cone angle of outer ring raceway surface 2a are different, so the resultant force of the load applied to tapered roller 3 from raceway surfaces 1a, 2a acts in a direction pushing tapered roller 3 toward the big end. As a result, tapered roller 3 is guided by having its large end face 3a pressed against large rib surface 1c of inner ring 1, where it comes into sliding contact.

[0028] The tapered roller bearing 10 further includes a cage 4 that positions the tapered rollers 3 at equal intervals in the circumferential direction. This cage 4 is formed, for example, by pressing a cold-rolled steel plate, a polished strip steel for bearings, or the like. However, the material and processing method of the cage 4 are not limited to these.

[0029] Next, the shape and dimensions of the outer ring raceway surface 2a of this embodiment will be described with reference to Fig. 4 and Fig. 5. Fig. 4 and Fig. 5 are views of the outer ring raceway surface 2a as viewed from the axial direction AX (Fig. 3) of the bearing 10. As is clear from these drawings, the shape of the outer ring raceway surface as viewed from the axial direction AX of the bearing 10 is an ellipse.

[0030] 4 and 5, the minor axis direction of the ellipse of the outer ring raceway surface 2a of the tapered roller bearing 10 is the X direction, and the major axis direction is the Y direction. Here, the major axis dimension of the outer ring raceway surface 2a shown in FIG. 4 is a, and the minor axis dimension is b, and the surface pressure distribution of the ratio (a / b) of the major axis a and the minor axis b of the ellipse of the basic vertical ellipse shape of the outer ring raceway surface 2a of any tapered roller bearing 10 was calculated. As a result, it was found that when the following formula (1) is satisfied, edge stress is not generated and the contact surface pressure of the tapered roller bearing 10 is substantially uniform. Here, the basic vertical ellipse shape refers to an ellipse shape whose major axis extends vertically and whose minor axis extends horizontally. 1.00023≦(a / b)≦1.00027 ···(1)

[0031] As shown in Fig. 4 and Fig. 9B and Fig. 10B described later, in this specification, the major axis is the length of the semi-major axis, and the minor axis is the length of the semi-minor axis. Since the formula (1) defines the ratio of the major axis a to the minor axis b, there is no problem in using the major axis and the minor axis instead of the length of the major axis (major axis) and the length of the minor axis (minor axis).

[0032] When verifying formula (1), we used a typical model number for tapered roller bearings, JIS (Japanese Industrial Standards) 30312J3 or equivalent. Specifically, the contact pressures on the inner ring side of each rolling element (tapered roller) for 30312J3 or equivalent are shown in Figures 6A to 6C, and the contact pressures on the outer ring side are shown in Figures 7A to 7C. The positions of the rolling elements (tapered rollers) are shown in Figure 8.

[0033] In this embodiment, 16 tapered rollers 3 are incorporated into the tapered roller bearing 10. That is, the numbers 1 to 16 shown in B in the tables of Figures 6A and 7A, the numbers 1 to 16 shown radially in Figures 6B and 7B, and the rolling element numbers 1 to 16 in Figures 6C and 7C indicate each tapered roller 3.

[0034] When tapered roller bearing 10 is arranged so that its minor axis (horizontal axis X) faces horizontally as shown in Fig. 8, the tapered roller 3 at the lowest point of bearing 10 is numbered 1, and the 16 tapered rollers 3 are numbered 2, 3, ... N in the counterclockwise direction. In this embodiment, 16 tapered rollers 3 are incorporated, so N = 16. In other words, tapered rollers 3 at positions 1 to 16 in Fig. 8 correspond to tapered rollers 3 at positions 1 to 16 in Figs. 6A to 6C and 7A to 7C.

[0035] 6B and 7B, the annular (hexagonal) lines indicate the contact pressure acting on each roller 3. The lines indicating the contact pressure are drawn at intervals of 200 MPa, with the center point indicating 0 MPa and the outermost line indicating 1800 MPa.

[0036] It can be seen from Figures 6A to 7C and Figures 7A to 7C that the contact pressure is substantially uniform in this embodiment. Here, the "c value" in Figures 6A to 7C and Figures 7A to 7C refers to the "gap c" between a reference circle Cr having a diameter equal to the minor axis of the ellipse shown in Figure 5 and the major axis a of the ellipse. From Figures 6A to 6C and Figures 7A to 7C, in order to uniform the contact pressure, it is preferable to set this gap c to 0.010 mm to 0.020 mm on the elliptical outer ring raceway surface 2a.

[0037] As shown in Figure 6A, when the c value (gap c) is zero on the inner ring side, the maximum contact pressure is 1735 MPa (first roller). This maximum contact pressure (=1735 MPa) is the reference value. When the c value (gap c) is 0.005 mm, the maximum contact pressure is 1662 MPa (first roller), which is about 4% smaller than the reference value.

[0038] When the c value (gap c) is 0.010 mm, the maximum contact pressure is 1601 MPa (between No. 2 and No. 16), which is about 8% lower than the standard value. When the c value (gap c) is 0.015 mm, the maximum contact pressure is 1590 MPa (between No. 3 and No. 15), which is about 8% lower than the standard value. When the c value (gap c) is 0.020 mm, the maximum contact pressure is 1590 MPa (between No. 3 and No. 15), which is about 8% lower than the standard value.

[0039] When the c value (gap c) is 0.025 mm, the maximum contact pressure is 1622 MPa (between No. 4 and No. 14), which is about 6% smaller than the standard value. Also, when the c value (gap c) is 0.030 mm, the maximum contact pressure is 1657 MPa (between No. 4 and No. 14), which is about 4% smaller than the standard value. Thus, when the c value (gap c) is 0.010 to 0.020 mm, the maximum contact pressure is particularly small.

[0040] As shown in Figure 7A, when the c value (gap c) on the outer ring side is zero, the maximum contact pressure is 1424 MPa (roller No. 1). This maximum contact pressure (= 1424 MPa) is the reference value. When the c value (gap c) is 0.005 mm, the maximum contact pressure is 1364 MPa (roller No. 1), which is approximately 4% smaller than the reference value.

[0041] When the c value (gap c) is 0.010 mm, the maximum contact pressure is 1314 MPa (between No. 2 and No. 16), which is about 8% smaller than the standard value. When the c value (gap c) is 0.015 mm, the maximum contact pressure is 1305 MPa (between No. 3 and No. 15), which is about 8% smaller than the standard value. When the c value (gap c) is 0.020 mm, the maximum contact pressure is 1305 MPa (between No. 3 and No. 15), which is about 8% smaller than the standard value.

[0042] When the c value (gap c) is 0.025 mm, the maximum contact pressure is 1331 MPa (between numbers 4 and 14), which is about 6% smaller than the standard value. Also, when the c value (gap c) is 0.030 mm, the maximum contact pressure is 1360 MPa (between numbers 4 and 14), which is about 4% smaller than the standard value. Thus, when the c value (gap c) is 0.010 to 0.020 mm, the maximum contact pressure is particularly small.

[0043] From the above, a preferable value of the gap c is 0.010 to 0.020 mm. When the gap c is 0.010 to 0.020 mm, the maximum contact pressure is particularly small. In this way, by setting the gap c between the elliptical outer ring raceway surface 2a and the apex of the reference circle Cr in the Y direction to 0.010 to 0.020 mm, the contact pressure can be further equalized.

[0044] When the ratio (a / b) of the major axis a to the minor axis b of the elliptical shape of the outer ring raceway surface 2a satisfies the relationship of the above-mentioned formula (1), the contact surface pressure acting on the tapered roller bearing 10 can be made approximately uniform, and flaking damage due to the application of excessive edge stress can be suppressed.

[0045] Here, it is advisable to attach the tapered roller bearing 10 to the machine so that the major axis of the ellipse of the outer ring raceway surface 2a is in the radial load direction and the minor axis of the ellipse is in the vertical direction. In this way, when the radial load on the bearing 10 is large, excessive edge stress can be suppressed by making the contact surface pressure approximately uniform without the need for special crowning, and as a result, damage to the bearing due to flaking can be suppressed.

[0046] To achieve this "approximate uniformity of contact pressure," it is necessary to maintain the elliptical shape of the outer ring raceway surface 2a as a vertical ellipse in the radial direction. Therefore, as shown in Figures 9A and 9B, it is advisable to provide the outer ring 2 with an identification means 30 that enables identification of the position of the major axis or the minor axis of the elliptical outer ring raceway surface 2a, and to incorporate the identification means into a machine device so that the ellipse becomes a vertical ellipse. This makes it possible to uniform the contact pressure when an equivalent radial load is applied.

[0047] 9A and 9B, as shown in Fig. 9A, a mark 30 such as a black dot is provided as the identification means 30 on the end face 2b of the outer ring 2 on the inner ring rib side. The circumferential position of the mark 30 is the position of the major axis of the elliptical outer ring raceway surface 2a, for example, as shown in Fig. 9B.

[0048] Furthermore, in order to maintain the vertical elliptical shape of the outer ring raceway surface 2a of the tapered roller bearing 10, the outer ring 2 may be provided with an anti-rotation structure 40. Furthermore, this anti-rotation structure 40 may also serve as the identification means 30 for grasping the position of the major axis or minor axis of the outer ring raceway surface 2a.

[0049] Since the vertical elliptical shape of the outer ring raceway surface 2a is on the order of microns, it is difficult to grasp the elliptical shape, i.e., the major and minor axes of the ellipse, but by providing the rotation prevention structure 40 to the outer ring 2, it is possible to assemble the elliptical shape of the outer ring raceway surface 2a so that it becomes a vertical ellipse. Furthermore, there is no risk of the vertical elliptical shape being damaged by creep or the like, and it is possible to grasp the position of the major or minor axis of the above-mentioned ellipse.

[0050] Figures 10A and 10B show an example of anti-rotation structure 40. In the example of Figures 10A and 10B, as shown in Figure 10A, a knock pin 40 that protrudes radially outward is provided on the outer circumferential surface of outer ring 2 as anti-rotation means 30. The circumferential position of knock pin 40 is, for example, the position of the major axis of elliptical outer ring raceway surface 2a as shown in Figure 10B.

[0051] The configuration of the anti-rotation structure 40 provided on the outer ring 2 is not particularly limited, but it is desirable that the anti-rotation structure 40 has a structure that can exert an anti-rotation effect even when the housing 15 is loosely fitted into the outer ring 2. Examples of such anti-rotation structure 40 include a structure in which a knock pin or a key groove is provided on the outer diameter surface of the outer ring 2 as shown in Fig. 10A, a structure in which the outer diameter surface of the outer ring 2 has a D-cut shape, a structure in which a step is provided on the outer diameter surface of the outer ring 2 and an annular body covered with rubber is fitted thereon, and the like. However, the anti-rotation structure 40 is not limited to these.

[0052] According to the above configuration, by fitting and fixing the elliptical outer ring raceway surface 2a to the housing so that it is a vertical ellipse in the radial direction, the number of tapered rollers 3 that receive the load of the bearing 10 can be increased, and the maximum contact surface pressure and maximum edge stress can be reduced. As a result of being able to reduce the maximum contact surface pressure and maximum edge stress, the bearing can be made more compact, and when used in a hydraulic motor for a construction machine, the hydraulic motor can be made more compact. Furthermore, when used in a pump for a forging machine, the tapered roller bearing 10 can be made to withstand high surface pressure and save space, and the load capacity can be increased and high rigidity can be achieved without increasing the size of the tapered roller bearing 10.

[0053] In the above configuration, the shape of the outer ring raceway 2a as viewed from the axial direction of the tapered roller bearing 10 is elliptical, the length a of the major axis of the ellipse and the length b of the minor axis of the ellipse are set to satisfy the relationship 1.00023≦(a / b)≦1.00027, and the outer ring 2 is provided with an identification means 30 for identifying the position of the major axis or minor axis of the ellipse. This allows the bearing 10 to be mounted in a machine so that it assumes a vertical elliptical shape in response to a radial load, dispersing the load rate of the rolling elements and making the contact pressure acting on the bearing uniform. As a result, the maximum contact pressure and maximum edge stress can be reduced.

[0054] In addition, the number of tapered rollers 3 in the load area can be increased, reducing the contact stress per roller and suppressing damage such as flaking. As a result, the maximum contact pressure and maximum edge stress can be reduced, realizing higher output in the case of the current size and a more compact hydraulic motor for construction machinery in the case of a size reduction. This technology has the advantage that the elliptical shape of the outer ring raceway surface 2a is not damaged by fitting the housing 15 and the outer ring 2 with a loose fit, i.e., a clearance fit.

[0055] In the example of Fig. 1, in an axial piston pump P, rotation of the input shaft 10 rotates a cylinder block 22 tilted relative to the input shaft 10 and multiple pistons 24, and the pistons 24 reciprocate with a phase difference to suck in and discharge oil. In this case, a large thrust load based on the reaction force of the pistons 24 acts on the bearings 11 and 12 of the input shaft 10. For this reason, there is a tendency for the bearings 11 and 12 to be front-to-back combination tapered roller bearings with a large contact angle θ (see Fig. 2).

[0056] Therefore, if the tapered roller bearing 10 of this embodiment is used to support the input shaft 10 of an axial piston pump P, flaking can be suppressed, thereby improving durability and achieving higher speeds. Note that in this pump P, if the piston 24 is hydraulically driven to reciprocate, it can also be used as a hydraulic motor with the input shaft 10 supported by the tapered roller bearing 10 as the output shaft.

[0057] The outer ring raceway surface 2a of the tapered roller bearing 10 may be made elliptical in radial cross section, and identification means 30 for identifying the major axis or minor axis of the ellipse of the outer ring raceway surface 2a may be provided on the outer ring end face or the outer diameter surface of the outer ring as shown in Fig. 9A. This allows the tapered roller bearing 10 to be assembled with respect to a mechanical device so that the outer ring raceway surface 2a forms a vertical ellipse when loosely fitted into the housing 15. As a result, the elliptical outer ring raceway surface 2a of the tapered roller bearing 10 can be easily fitted and fixed into the housing 15 so that it forms a vertical ellipse in the radial direction.

[0058] In this embodiment, the gap c between the reference circle Cr having the minor axis of the ellipse of the outer ring raceway surface 2a as its diameter and the major axis of the ellipse may be set to 0.010 mm to 0.020 mm. The optimum value of the gap c is, for example, 0.015 mm. This can provide a surface pressure reduction effect of approximately 6 to 9%.

[0059] In this embodiment, as shown in Fig. 10A, the outer ring 2 may be provided with an anti-rotation structure 40. This allows the outer ring raceway surface 2a to be assembled into a mechanical device so that the elliptical shape is a vertical ellipse, and the contact pressure on each roller can be made uniform.

[0060] The present invention can be used in a variety of applications for the purpose of suppressing flaking of tapered roller bearings 10, but is preferably used in tapered roller bearings 10 that support the main shaft of a hydraulic motor for construction machinery. By applying the tapered roller bearing 10 of the present invention to a tapered roller bearing that supports the main shaft of a hydraulic motor for construction machinery, the number of tapered rollers 3 present in the load area can be increased, reducing the contact stress per roller and suppressing flaking, etc.

[0061] The tapered roller bearing 10 of the present invention can also be applied to tapered roller bearings used in pumps of forging machines. By adopting the tapered roller bearing 10 of the present invention, it is possible to increase the high surface pressure resistance of the tapered roller bearing 10 and to reduce space required. As a result, it is possible to increase the load capacity without increasing the size of the tapered roller bearing 10, and it is also possible to achieve high rigidity.

[0062] The present invention is not limited to the above-described embodiment, and various additions, modifications, and deletions are possible without departing from the scope of the present invention. Therefore, such modifications are also included in the scope of the present invention. [Explanation of symbols]

[0063] 1. Inner Circle 1a Inner ring raceway surface 1b Kotsuba 1c large tsuba 2 Outer ring 2a Outer ring raceway 3 Tapered roller 4 Cage 10 Tapered roller bearings 15. Housing 30 Means of Identification 40 Anti-rotation structure a Dimension of the semi-major axis radius of the outer ring raceway b Dimension of the minor axis radius of the ellipse of the outer ring raceway

Claims

1. A tapered roller bearing comprising: an inner ring having a raceway surface on its outer peripheral surface which is angled with respect to an axis and which has a small rib on one side and a large rib on the other side; an outer ring having a raceway surface on its inner peripheral surface opposing the raceway surface of the inner ring; and a plurality of tapered rollers interposed between the inner ring and the outer ring, the outer ring being used with a clearance fitted in a housing, A tapered roller bearing in which the shape of an outer ring raceway surface when viewed from the axial direction is an ellipse, and a dimension a of the major axis of said ellipse and a dimension b of the minor axis thereof satisfy the relationship 1.00023≦(a / b)≦1.00027.

2. 2. The tapered roller bearing according to claim 1, further comprising an outer ring raceway surface having an elliptical shape, A tapered roller bearing in which the gap between a reference circle having a diameter equal to the minor axis of an ellipse and the major axis of the ellipse is set to 0.010 mm to 0.020 mm.

3. 3. The tapered roller bearing according to claim 1, wherein the outer ring is provided with an anti-rotation structure.

4. 3. The tapered roller bearing according to claim 1, which is used in a hydraulic motor.

5. 3. A tapered roller bearing according to claim 1, which is used in a pump of a forging machine.

6. 3. A tapered roller bearing according to claim 1, wherein said outer ring is provided with an identification means for identifying the position of the major axis or minor axis of said ellipse.

Images