Transmission

Abstract

To improve performance of a transmission.SOLUTION: An input gear unit 10 provided in a speed reducer 1 comprises: an input shaft 11 having a first input shaft raceway surface K11 and a second input shaft raceway surface K12 on an outer peripheral surface; a plurality of balls 14 arranged around the first input shaft raceway surface K11; and a plurality of balls 17 arranged around the second input shaft raceway surface K12. A groove curvature radius ratio between the ball 14 and the first input shaft raceway surface K11 on a side with a large dynamic equivalent load is smaller than a groove curvature radius ratio between the ball 17 and the second input shaft raceway surface K12.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a transmission that changes the rotational speed of an input rotational force and outputs the changed rotational speed. [Background technology]

[0002] For example, as described in Patent Document 1, there is a transmission that reduces the rotational speed of a drive shaft of a drive unit before outputting it. Such a transmission has multiple rotating shafts with gears attached, and reduces the rotational speed by sequentially transmitting the rotation of the drive shaft to the multiple rotating shafts through engagement of the gears. For this reason, such a transmission is provided with multiple bearings that rotatably support the rotating shafts relative to the housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-3048 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-described transmission uses components such as a rotating shaft and bearings that support the rotating shaft. To ensure proper gear shifting, the transmission is required to improve the durability and other performance of these components. Therefore, an object of the present invention is to provide a transmission that can achieve improved performance. [Means for solving the problem]

[0005] A transmission according to a first aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, and at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on an outer circumferential surface thereof, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on an inner circumferential surface thereof, and a gear that is provided on the first shaft raceway surface and a first outer ring raceway surface, a second outer ring attached to a second support portion that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner peripheral surface, and a plurality of second balls arranged between the second shaft raceway surface and the second outer ring raceway surface, wherein the dynamic equivalent load at the first shaft raceway surface, the first balls, and the first outer ring is greater than the dynamic equivalent load at the second shaft raceway surface, the second balls, and the second outer ring, and the groove curvature radius ratio at the first balls and the first shaft raceway surface is smaller than the groove curvature radius ratio at the second balls and the second shaft raceway surface.

[0006] In this transmission, the groove curvature radius ratio between the first ball, which is on the side with the larger dynamic equivalent load, and the first shaft raceway surface is smaller than the groove curvature radius ratio on the side with the smaller dynamic equivalent load. Here, as the groove curvature radius ratio decreases, the contact ellipse (contact surface) between the ball and the raceway surface provided on the rotating shaft becomes larger, and the surface pressure between the ball and the raceway surface decreases. Therefore, in this transmission, the surface pressure between the first ball, which is on the side with the larger dynamic equivalent load, and the first shaft raceway surface is reduced, thereby improving their lifespan and reducing static surface pressure. In this way, this transmission can improve performance by setting the groove curvature radius ratio.

[0007] In the above-described transmission, the groove curvature radius ratio between the first ball and the first outer ring raceway surface may be smaller than the groove curvature radius ratio between the second ball and the second outer ring raceway surface. Here, as the groove curvature radius ratio decreases, the contact ellipse between the ball and the raceway surface on the outer ring increases, and the surface pressure between the ball and the raceway surface decreases. Therefore, in this transmission, the surface pressure between the first ball and the first outer ring raceway surface on the side with a larger dynamic equivalent load is reduced, thereby improving their lifespan and reducing static surface pressure. In this way, this transmission's performance can be further improved by adjusting the groove curvature radius ratio.

[0008] A transmission according to a second aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, and at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner circumferential surface, and a gear that is provided between the first shaft raceway surface and the first outer ring raceway surface. a second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner peripheral surface; and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface, wherein the dynamic equivalent load at the first shaft raceway surface, the first rolling elements, and the first outer ring is greater than the dynamic equivalent load at the second shaft raceway surface, the second rolling elements, and the second outer ring, the raceway diameter of the first shaft raceway surface is greater than the raceway diameter of the second shaft raceway surface, and the raceway diameter of the first outer ring raceway surface is greater than the raceway diameter of the second outer ring raceway surface.

[0009] In this transmission, the raceway diameter of the first shaft raceway surface and the raceway diameter of the first outer ring raceway surface, which are on the side with the larger dynamic equivalent load, are larger than the raceway diameter of the second shaft raceway surface and the raceway diameter of the second outer ring raceway surface, which are on the side with the smaller dynamic equivalent load. This increases the pitch circle diameter (PCD) on the side with the larger dynamic equivalent load, thereby increasing the number of first rolling elements and increasing the bearing capacity on the side with the larger dynamic equivalent load. In this way, in this transmission, the number of first rolling elements on the side with the larger dynamic equivalent load can be increased, thereby improving the life of the bearing on the side with the larger dynamic equivalent load. Therefore, in this transmission, performance can be improved by configuring the shaft raceway surface and the outer ring raceway surface.

[0010] A transmission according to a third aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, and at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, and a first outer ring raceway that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner circumferential surface. The bearing has a ring, a plurality of first balls arranged between the first shaft raceway surface and the first outer ring raceway surface, a second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner surface, and a plurality of second balls arranged between the second shaft raceway surface and the second outer ring raceway surface, wherein the axial load received by the first shaft raceway surface is greater than the axial load received by the second shaft raceway surface, and the groove curvature radius ratio between the first balls and the first shaft raceway surface is greater than the groove curvature radius ratio between the second balls and the second shaft raceway surface.

[0011] In this transmission, the groove curvature radius ratio between the first ball and the first shaft raceway, which is the side with the larger axial load, is larger than the groove curvature radius ratio between the second ball and the second shaft raceway, which is the side with the smaller dynamic equivalent load. Here, as the groove curvature radius ratio increases, the osculating ellipse between the ball and the raceway surface on the rotating shaft becomes smaller, making it more difficult for the ball to climb up the raceway surface on the rotating shaft. Note that "the ball climbing up the raceway surface" refers to the osculating ellipse (contact surface) between the ball and the raceway surface protruding from the groove (raceway surface). Therefore, in this transmission, the osculating ellipse between the first ball and the first shaft raceway surface on the side with the larger axial load can be reduced, thereby preventing the first ball from climbing up. In this way, this transmission's performance can be improved by adjusting the groove curvature radius ratio.

[0012] In the above transmission, the groove curvature radius ratio between the first ball and the first outer ring raceway surface may be greater than the groove curvature radius ratio between the second ball and the second outer ring raceway surface. As the groove curvature radius ratio increases, the osculating ellipse between the ball and the raceway surface of the outer ring becomes smaller, making it more difficult for the ball to climb up the raceway surface of the outer ring. Therefore, in this transmission, the osculating ellipse between the first ball on the side with a greater axial load and the first outer ring raceway surface can be made smaller, preventing the first ball from climbing up. In this way, in this transmission, performance can be further improved by adjusting the groove curvature radius ratio.

[0013] A transmission according to a fourth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, and at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner circumferential surface, and a gear that is provided between the first shaft raceway surface and the second shaft raceway surface. a second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner surface; and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface, wherein the dynamic equivalent load at the first shaft raceway surface, the first rolling elements, and the first outer ring is greater than the dynamic equivalent load at the second shaft raceway surface, the second rolling elements, and the second outer ring, the diameter of the first rolling elements is greater than the diameter of the second rolling elements, and the number of first rolling elements is greater than the number of second rolling elements.

[0014] In this transmission, the diameter of the first rolling elements, which are on the side with the larger dynamic equivalent load, is larger than the diameter of the second rolling elements, which are on the side with the smaller dynamic equivalent load, and the number of first rolling elements on the side with the larger dynamic equivalent load is greater than the number of second rolling elements on the side with the smaller dynamic equivalent load. Here, the bearing on the side with the higher load (the side with the larger dynamic equivalent load) is required to have a higher dynamic load rating. Therefore, by increasing the diameter of the first rolling elements on the side with the larger dynamic equivalent load and increasing the number of first rolling elements, the first rolling elements can appropriately support the rotating shaft so that it can rotate even under heavy loads. In this way, when the rotating shaft is supported at two locations around the first and second rolling elements, an appropriate design according to the load is possible. Therefore, in this transmission, performance can be improved by adjusting the diameter and number of the rolling elements.

[0015] In the above-described transmission, the raceway diameter of the first shaft raceway surface and the raceway diameter of the second shaft raceway surface may be different from each other. Here, the strength levels required for the portion of the rotating shaft supported by the first rolling elements may differ from those required for the portion of the rotating shaft supported by the second rolling elements. In such a case, by making the raceway diameter of the first shaft raceway surface and the raceway diameter of the second shaft raceway surface different from each other, a rotating shaft that meets the required strength levels can be obtained. For example, by setting the raceway diameter of the first shaft raceway surface and the raceway diameter of the second shaft raceway surface to sizes that meet the respective required strength levels, it is possible to prevent the rotating shaft from becoming excessively thick, thereby enabling the rotating shaft to be made smaller.

[0016] A transmission according to a fifth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, and at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, and a gear that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface. a first outer ring having a first outer ring raceway surface on its inner circumferential surface, and a plurality of first rolling elements arranged between the first shaft raceway surface and the first outer ring raceway surface; a second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner circumferential surface, and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface, and the gear is subjected to a load directed towards the first rolling elements, and the number of first rolling elements is greater than the number of second rolling elements.

[0017] In this transmission, the gear receives a load directed toward the first rolling element. In other words, the gear receives a load that is inclined toward the first rolling element. The number of first rolling elements on the side of the gear that receives the load is greater than the number of second rolling elements. This allows this transmission to improve radial rigidity on the side of the first rolling elements that receive the load when the first rolling elements support the rotating shaft. In this way, this transmission can achieve performance improvement by setting the number of rolling elements on the side that receives the load.

[0018] In the above transmission, the diameter of the first rolling element may be larger than the diameter of the second rolling element, which can further improve the radial rigidity of the transmission on the side of the first rolling element that receives the load when the first rolling element supports the rotating shaft.

[0019] A transmission according to a sixth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, and at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner circumferential surface, and a first The gear has a plurality of first balls arranged between the shaft raceway surface and the first outer ring raceway surface, a second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner surface, and a plurality of second balls arranged between the second shaft raceway surface and the second outer ring raceway surface, an input part into which rotational force is input is provided at the end of the rotating shaft on the side where the second shaft raceway surface is provided, and the gear outputs the rotational force input from the input part to the rotating shaft, and the groove curvature radius of the second shaft raceway surface is larger than the groove curvature radius of the first shaft raceway surface.

[0020] In this transmission, a second shaft raceway surface is provided on the rotating shaft between an input section to which rotational force is input and a gear that outputs the rotational force. The groove curvature radius of the second shaft raceway surface is larger than the groove curvature radius of the first shaft raceway surface. Here, a larger torsion (twisting force) is applied to the second shaft raceway surface provided between the input section and the gear than to the first shaft raceway surface. Therefore, by increasing the groove curvature radius of the second shaft raceway surface, stress concentration on the second shaft raceway surface can be suppressed. In this way, this transmission can improve performance by adjusting the groove curvature radius.

[0021] A seventh aspect of the present invention provides a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner circumferential surface, and a first The gear has a plurality of first rolling elements arranged between the shaft raceway surface and the first outer ring raceway surface, a second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner surface, and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface, and an input part into which rotational force is input is provided at the end of the rotating shaft on the side where the second shaft raceway surface is provided, and the gear outputs the rotational force input from the input part to the rotating shaft, and the raceway diameter of the second shaft raceway surface is larger than the raceway diameter of the first shaft raceway surface.

[0022] In this transmission, a second shaft raceway surface is provided on the rotating shaft between an input section to which rotational force is input and a gear that outputs the rotational force. The raceway diameter of the second shaft raceway surface is larger than the raceway diameter of the first shaft raceway surface. Here, a larger torsion (twisting force) is applied to the second shaft raceway surface provided between the input section and the gear than to the first shaft raceway surface. Therefore, by increasing the raceway diameter of the second shaft raceway surface, stress concentration on the second shaft raceway surface can be suppressed. In this way, in this transmission, performance can be improved by setting the raceway diameter of the shaft raceway surface.

[0023] A transmission according to an eighth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner circumferential surface, and a plurality of second outer rings that are arranged between the first shaft raceway surface and the first outer ring raceway surface. the second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner peripheral surface; and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface, wherein an input part into which rotational force is input is provided at the end of the rotating shaft on the side where the second shaft raceway surface is provided, and the gear outputs the rotational force input from the input part to the rotating shaft, and a large diameter part is provided on the rotating shaft between the second shaft raceway surface and the gear, and the large diameter part has an outer diameter larger than the part of the rotating shaft with the largest outer diameter between the first shaft raceway surface and the gear.

[0024] In this transmission, the rotating shaft is provided with a large-diameter portion between the second shaft raceway surface and the gear, the portion having a larger outer diameter than the largest outer-diameter portion of the rotating shaft between the first shaft raceway surface and the gear. Here, rotational force is input to the rotating shaft from the input portion. The input rotational force is then output from the gear on the rotating shaft. As a result, a larger torsion (twisting force) is applied to the portion of the rotating shaft between the second shaft raceway surface and the gear than to the portion between the gear and the first shaft raceway surface. Therefore, by providing a large-diameter portion between the second shaft raceway surface and the gear, stress concentration in the portion between the second shaft raceway surface and the gear can be suppressed. In this way, this transmission can improve performance by setting the outer diameter of the rotating shaft.

[0025] A transmission according to a ninth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units includes a rotating shaft having an axis raceway surface on its outer peripheral surface, a gear that rotates integrally with the rotating shaft, an outer ring that is attached to a support part that supports the rotating shaft and is arranged to surround the axis raceway surface and has an outer ring raceway surface on its inner peripheral surface, and a plurality of balls that are arranged between the axis raceway surface and the outer ring raceway surface, and the outer diameter of the rotating shaft from one end of the rotating shaft to the center position in the width direction of the axis raceway surface is the raceway diameter of the axis raceway surface.

[0026] In this transmission, the outer diameter of one end of the rotating shaft is the same as the raceway diameter of the shaft raceway surface. Therefore, with multiple balls arranged inside the outer ring, the outer ring and balls can be easily assembled to the rotating shaft by sliding them from one end of the rotating shaft to the position of the shaft raceway surface. In this way, this transmission improves the assembly of the rotating shaft unit.

[0027] A transmission according to a tenth aspect of the present invention is a transmission that has a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units has a rotating shaft having an axis raceway surface on its outer peripheral surface, a gear that rotates integrally with the rotating shaft, an outer ring that is attached to a support part that supports the rotating shaft and is arranged to surround the axis raceway surface and has an outer ring raceway surface on its inner peripheral surface, and a plurality of rolling elements arranged between the axis raceway surface and the outer ring raceway surface, wherein the plurality of rolling elements include a first group of rolling elements aligned along the circumferential direction of the rotating shaft, and a second group of rolling elements adjacent to the first group of rolling elements in the extension direction of the rotating shaft and aligned along the circumferential direction of the rotating shaft, and the outer ring raceway surface has a shape in which an intermediate portion between one end and the other end in the extension direction of the rotating shaft is curved in an arc shape radially outward.

[0028] In this transmission, a first group of rolling elements and a second group of rolling elements are arranged in two rows around the rotating shaft, and these rolling elements abut against an outer ring raceway surface that is curved in an arc. In other words, in this transmission, the first group of rolling elements and the second group of rolling elements abut against a common outer ring raceway surface that has a large groove curvature radius. As a result, this transmission can provide a self-aligning function for the rotating shaft even when the inner ring of the bearing and the rotating shaft are integrated, thereby improving robustness. In this way, this transmission can achieve improved performance.

[0029] A transmission according to an eleventh aspect of the present invention is a transmission that has a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, and at least one of the plurality of rotating shaft units has a rotating shaft having an axial raceway surface on its outer peripheral surface, a gear that rotates integrally with the rotating shaft, an outer ring that is attached to a support part that supports the rotating shaft and is arranged to surround the axial raceway surface and has an outer ring raceway surface on its inner peripheral surface, a plurality of balls arranged between the axial raceway surface and the outer ring raceway surface, and a sealing member that is fixed to one end of the outer ring in the extension direction of the rotating shaft and extends toward the outer peripheral surface of the rotating shaft.

[0030] In this transmission, the outer area of ​​the outer ring and the inner area of ​​the outer ring where the balls are arranged can be separated by a seal member around the rotating shaft. This can, for example, prevent lubricating oil from leaking out from the inside of the outer ring, improving lubrication performance. It can also, for example, prevent foreign matter from entering the inside of the outer ring from the outside, preventing a decrease in rotation performance. In this way, the provision of a seal member in this transmission can improve performance.

[0031] A transmission according to a twelfth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units includes a rotating shaft having an axis raceway surface on its outer peripheral surface, a gear that rotates integrally with the rotating shaft, an outer ring that is attached to a support part that supports the rotating shaft and is arranged so as to surround the axis raceway surface and has an outer ring raceway surface on its inner peripheral surface, and a plurality of rolling elements that are arranged between the axis raceway surface and the outer ring raceway surface, wherein the rotating shaft has a gear mounting part on which the gear is mounted, and a raceway surface forming part that is adjacent to the gear mounting part and on which the axis raceway surface is formed, wherein the outer diameter of the gear mounting part is larger than the outer diameter of the raceway surface forming part, and the corners of the step portion between the gear mounting part and the raceway surface forming part form an arc-shaped curved surface.

[0032] In this transmission, the corners of the step between the gear mounting portion and the raceway surface forming portion are formed into arc-shaped curved surfaces. This prevents stress from concentrating at the corners of the step between the gear mounting portion and the raceway surface forming portion under load, thereby improving the strength of the rotating shaft. In this way, by forming the corners of the step into arc-shaped curved surfaces, this transmission can achieve improved performance.

[0033] A transmission according to a thirteenth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner circumferential surface, and a gear that is provided between the first shaft raceway surface and the first outer ring raceway surface. The gear has a plurality of first rolling elements arranged between the first and second outer ring raceway surfaces, a second outer ring attached to a second support part that supports the rotating shaft and arranged to surround the second shaft raceway surface, and having a second outer ring raceway surface on its inner peripheral surface, and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface, and an input part into which rotational force is input is provided at the end of the rotating shaft on the side where the second shaft raceway surface is provided, and the gear outputs the rotational force input from the input part to the rotating shaft, and a groove part extending circumferentially is provided on the outer peripheral surface of the rotating shaft between the input part and the second shaft raceway surface.

[0034] In this transmission, a groove is provided on the rotating shaft between the input portion, to which rotational force is input, and the second shaft raceway surface. By providing the groove on the rotating shaft in this way, a weaker portion can be intentionally provided between the input portion and the second shaft raceway surface. This makes it possible to reduce stress on the second shaft raceway surface even when rotational force is input to the rotating shaft from the input portion, thereby improving the strength of the bearing around the second shaft raceway surface. In this way, providing the groove on the rotating shaft in this transmission can improve performance.

[0035] A transmission according to a fourteenth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on an outer circumferential surface thereof, a gear that is provided on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is provided so as to surround the first shaft raceway surface and has a first outer ring raceway surface on an inner circumferential surface thereof, a plurality of first rolling elements that are arranged between the first shaft raceway surface and the first outer ring raceway surface, and a second support part that supports the rotating shaft and is provided so as to surround the second shaft raceway surface and has an inner circumferential surface the second outer ring having a second outer ring raceway surface at the end of the rotating shaft on the side where the second shaft raceway surface is provided, and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface; an input section to which a rotational force is input is provided at the end of the rotating shaft on the side where the second shaft raceway surface is provided; the gear outputs the rotational force input from the input section to the rotating shaft; the rotating shaft has a shaft hole formed therein and extending along the extension direction of the rotating shaft, the shaft hole including a first shaft hole portion having a first hole diameter and a second shaft hole portion having a second hole diameter smaller than the first hole diameter; the first shaft hole portion and the second shaft hole portion are adjacent to each other, and the first shaft hole portion is located on the side closer to the input section; and a step portion between the first shaft hole portion and the second shaft hole portion is located between the second shaft raceway surface and the input section in the extension direction of the rotating shaft.

[0036] In this transmission, a large-diameter first shaft hole portion and a small-diameter second shaft hole portion are provided inside the rotating shaft. The step portion between the first shaft hole portion and the second shaft hole portion is located between the second shaft raceway surface and the input portion. In other words, the second shaft raceway surface is provided in the thick-walled portion of the rotating shaft (the portion where the small-diameter second shaft hole portion is provided). The input portion is provided in the thin-walled portion of the rotating shaft (the portion where the large-diameter first shaft hole portion is provided). This reduces stress on the second shaft raceway surface even when a rotational force is input to the rotating shaft from the input portion, improving the strength of the bearing around the second shaft raceway surface. In this way, this transmission can improve performance by providing shaft hole portions of different diameters inside the rotating shaft.

[0037] A transmission according to a fifteenth aspect of the present invention is a transmission that has a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, at least one of the plurality of rotating shaft units has a rotating shaft having an axial raceway surface on its outer peripheral surface, a gear that rotates integrally with the rotating shaft, an outer ring that is attached to a support part that supports the rotating shaft and is arranged to surround the axial raceway surface and has an outer ring raceway surface on its inner peripheral surface, and a plurality of balls arranged between the axial raceway surface and the outer ring raceway surface, and the axial width of the outer ring is approximately equal to or less than the diameter of the balls.

[0038] In this transmission, the narrow width of the outer ring ensures a large axial gap between the outer ring and the gear. Here, for example, when assembling the outer ring and balls to the rotating shaft, the outer ring is positioned eccentrically with respect to the rotating shaft, and the balls are positioned between the shaft raceway surface and the outer ring raceway surface. At this time, a jig is placed below the outer ring to support the balls, which are positioned between the outer ring (outer ring raceway surface) and the rotating shaft (shaft raceway surface), so that they do not fall out. In this transmission, because a large gap is ensured between the outer ring and the gear, a jig can be placed below the outer ring without interfering with the gear, and the jig can support the balls so that they do not fall out. This allows this transmission to achieve improved assembly performance.

[0039] A transmission according to a sixteenth aspect of the present invention is a transmission that includes a plurality of rotating shaft units and outputs the rotational speed of an input rotational force by changing the rotational speed between the rotating shaft units, wherein at least one of the plurality of rotating shaft units includes a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer peripheral surface, a gear that is arranged on the rotating shaft between the first shaft raceway surface and the second shaft raceway surface and rotates integrally with the rotating shaft, a first outer ring that is attached to a first support part that supports the rotating shaft and is arranged so as to surround the first shaft raceway surface and has a first outer ring raceway surface on its inner peripheral surface, and a plurality of first rolling elements that are arranged between the first shaft raceway surface and the first outer ring raceway surface, a second outer ring that is attached to a second support part that supports the rotating shaft and is arranged so as to surround the second shaft raceway surface and has a second outer ring raceway surface on its inner peripheral surface, and a plurality of second rolling elements that are arranged between the second shaft raceway surface and the second outer ring raceway surface, wherein the inner diameter of the first outer ring is larger than the outer diameter of the second outer ring.

[0040] Generally, the outer ring of a bearing is formed by forging. The inner diameter of the first outer ring of the present invention is larger than the outer diameter of the second outer ring. Therefore, by performing a single forging process on the raw material for the outer ring, it is possible to form the preform for the first outer ring and the preform for the second outer ring in one go. In this way, with the present invention, the number of forging processes for forming the first outer ring and the second outer ring can be reduced, and the productivity of the first outer ring and the second outer ring can be improved. As a result, this transmission can achieve improved productivity. [Effects of the Invention]

[0041] According to various aspects of the present invention, performance can be improved. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 1 is a cross-sectional view showing a main part of a reducer according to an embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the input gear unit and its surroundings in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the ball and the raceway surface for explaining the groove curvature radius ratio. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the counter gear unit and its surroundings shown in FIG. [Figure 5] FIG. 5 is an enlarged cross-sectional view of the differential gear unit and its surroundings shown in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view of the drive unit and its surroundings in FIG. [Figure 7] FIG. 7 is an enlarged cross-sectional view of an input gear unit according to a third modified example. [Figure 8] FIG. 8 is an enlarged cross-sectional view of a bearing according to a modified example. [Figure 9] FIG. 9 is an enlarged cross-sectional view of an input gear unit according to a fourth modified example. [Figure 10] FIG. 10 is a cross-sectional view showing how a first input shaft outer ring and balls are assembled to an input shaft of an input gear unit according to a fourth modified example. [Figure 11] FIG. 11 is an enlarged cross-sectional view of an input gear unit according to a fifth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0043] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and duplicated explanations will be omitted. In addition, the following description will be given using a reducer that reduces the rotational speed of a drive unit as the transmission according to the present invention.

[0044] As shown in FIG. 1, the reducer (transmission) 1 includes a plurality of rotating shaft units, and outputs the rotational speed of an input rotational force after changing the rotational speed between the rotating shaft units. Specifically, the reducer 1 includes an input gear unit 10 as a rotating shaft unit, a counter gear unit 20 as a rotating shaft unit, a differential gear unit 30, and a drive unit 40. The drive unit 40 includes an electric motor. As an example, the reducer 1 in this embodiment is configured as a three-shaft parallel reducer for an EV (Electric Vehicle) that includes the drive unit 40. Although not shown in FIG. 1, the reducer 1 includes a housing that houses each mechanism, such as the input gear unit 10.

[0045] [Input gear unit configuration] The input gear unit 10 is connected to the rotor shaft 42 of the drive unit 40. That is, the rotation of the rotor shaft 42 of the drive unit 40 is directly transmitted to the input gear unit 10. More specifically, as shown in Fig. 2, the input gear unit 10 includes an input shaft (rotating shaft) 11, an input shaft output gear (gear) 12, a first input shaft outer ring (first outer ring, outer ring) 13, a plurality of balls (first ball, balls, first rolling elements, rolling elements) 14, a first input shaft retainer 15, a second input shaft outer ring (second outer ring, outer ring) 16, a plurality of balls (second ball, balls, second rolling elements, rolling elements) 17, and a second input shaft retainer 18.

[0046] The input shaft 11 is connected to the rotor shaft 42 of the drive unit 40. Here, a spline (input portion) 11s is formed on the outer peripheral surface of the end of the input shaft 11 that is connected to the rotor shaft 42. The input shaft 11 is spline-coupled to the rotor shaft 42 by the spline 11s. The input shaft 11 also has a first input shaft raceway surface (first shaft raceway surface, shaft raceway surface) K11 and a second input shaft raceway surface (second shaft raceway surface, shaft raceway surface) K12 on its outer peripheral surface.

[0047] The first input shaft raceway surface K11 is provided on the outer peripheral surface of the input shaft 11 near the end opposite to the end where the spline 11s is formed. The second input shaft raceway surface K12 is provided on the outer peripheral surface of the input shaft 11 near the spline 11s. The first input shaft raceway surface K11 and the second input shaft raceway surface K12 are grooves extending circumferentially on the outer peripheral surface of the input shaft 11.

[0048] The input shaft output gear 12 is provided on the input shaft 11 and rotates integrally with the input shaft 11. The input shaft output gear 12 is provided at a position between the first input shaft raceway surface K11 and the second input shaft raceway surface K12. In this embodiment, the input shaft output gear 12 is provided integrally with the input shaft 11. The input shaft output gear 12 outputs the rotational force input to the input shaft 11 to the counter gear unit 20.

[0049] The first input shaft outer ring 13 is attached to an input shaft support portion (first support portion, support portion) C1a that supports the input shaft 11. The input shaft support portion C1a is, for example, a part of a housing that houses the input gear unit 10 and the like. The first input shaft outer ring 13 is provided so as to surround the first input shaft raceway surface K11. The first input shaft outer ring 13 has an outer peripheral surface 13a that is attached to the input shaft support portion C1a and an inner peripheral surface 13b that faces the outer peripheral surface of the input shaft 11 (first input shaft raceway surface K11).

[0050] First input shaft outer ring 13 has a first input shaft outer ring raceway surface (first outer ring raceway surface, outer ring raceway surface) L11 on its inner circumferential surface 13b. First input shaft outer ring raceway surface L11 is a groove extending circumferentially on inner circumferential surface 13b of first input shaft outer ring 13.

[0051] The plurality of balls 14 are arranged between a first input shaft raceway surface K11 of the input shaft 11 and a first input shaft outer ring raceway surface L11 of the first input shaft outer ring 13. The balls 14 are spherical. The first input shaft retainer 15 holds each of the plurality of balls 14 between the outer peripheral surface of the input shaft 11 and the inner peripheral surface 13b of the first input shaft outer ring 13 so that they can roll freely.

[0052] The second input shaft outer ring 16 is attached to an input shaft support portion (second support portion, support portion) C1b that supports the input shaft 11. The input shaft support portion C1b is, for example, a part of a housing that houses the input gear unit 10 and the like. The second input shaft outer ring 16 is provided so as to surround the second input shaft raceway surface K12. The second input shaft outer ring 16 has an outer peripheral surface 16a that is attached to the input shaft support portion C1b and an inner peripheral surface 16b that faces the outer peripheral surface of the input shaft 11 (the second input shaft raceway surface K12).

[0053] The second input shaft outer ring raceway surface (second outer ring raceway surface, outer ring raceway surface) L12 is a groove extending circumferentially on the inner peripheral surface 16b of the second input shaft outer ring 16.

[0054] The plurality of balls 17 are arranged between a second input shaft raceway surface K12 of the input shaft 11 and a second input shaft outer ring raceway surface L12 of the second input shaft outer ring 16. The balls 17 are spherical. The second input shaft retainer 18 holds each of the plurality of balls 17 between the outer peripheral surface of the input shaft 11 and the inner peripheral surface 16b of the second input shaft outer ring 16 so that they can roll freely.

[0055] In this way, the input shaft 11 is rotatably supported at two locations: the first input shaft raceway surface K11 and the second input shaft raceway surface K12. Furthermore, the input gear unit 10 of this embodiment does not have a component that functions only as the inner ring of the bearing. In the input gear unit 10 of this embodiment, the input shaft 11 also functions as the inner ring of the bearing.

[0056] Furthermore, in the input gear unit 10 of this embodiment, the first input shaft outer ring 13, the balls 14, and the first input shaft raceway surface K11 of the input shaft 11 form a bearing mechanism G1A, which is a deep groove ball bearing. Similarly, the second input shaft outer ring 16, the balls 17, and the second input shaft raceway surface K12 of the input shaft 11 form a bearing mechanism G1B, which is also a deep groove ball bearing. That is, in the input gear unit 10, the input shaft 11 is rotatably supported by the bearing mechanisms G1A and G1B.

[0057] The input shaft 11 in this embodiment has a first raceway surface forming portion (raceway surface forming portion) 11a, a gear mounting portion 11b, and a second raceway surface forming portion (raceway surface forming portion) 11c. The first raceway surface forming portion 11a is a portion of the input shaft 11 where the first input shaft raceway surface K11 is provided. The second raceway surface forming portion 11c is a portion of the input shaft 11 where the second input shaft raceway surface K12 is provided. The gear mounting portion 11b is located between the first raceway surface forming portion 11a and the second raceway surface forming portion 11c. In other words, the first raceway surface forming portion 11a is adjacent to the gear mounting portion 11b. Similarly, the second raceway surface forming portion 11c is adjacent to the gear mounting portion 11b. The input shaft output gear 12 is provided on the gear mounting portion 11b.

[0058] The outer diameter of the gear mounting portion 11b is larger than the outer diameter of the first raceway surface forming portion 11a. That is, the connection portion between the first raceway surface forming portion 11a and the gear mounting portion 11b forms a step portion. To suppress stress concentration at this step portion, a corner E1 of the step portion between the gear mounting portion 11b and the first raceway surface forming portion 11a forms an arc-shaped curved surface. That is, the end face of the gear mounting portion 11b on the first raceway surface forming portion 11a side and the outer peripheral surface of the first raceway surface forming portion 11a are connected to each other at the corner E1 so as to form an arc-shaped curved surface. The larger the radius of curvature (corner R) at the corner E1, the better.

[0059] Furthermore, the outer diameter of the gear mounting portion 11b is larger than the outer diameter of the second raceway surface forming portion 11c. That is, the connection portion between the second raceway surface forming portion 11c and the gear mounting portion 11b forms a step portion. To suppress stress concentration at the step portion, a corner E2 of the step portion between the gear mounting portion 11b and the second raceway surface forming portion 11c forms an arc-shaped curved surface. That is, the end face of the gear mounting portion 11b on the second raceway surface forming portion 11c side and the outer peripheral surface of the second raceway surface forming portion 11c are connected to each other at the corner E2 so as to form an arc-shaped curved surface. The larger the radius of curvature (corner R) at the corner E2, the better.

[0060] In the input gear unit 10 of this embodiment, for example, the dynamic equivalent load in the bearing mechanism G1A is higher than the dynamic equivalent load in the bearing mechanism G1B. The input gear unit 10 has a configuration for dealing with this dynamic equivalent load. Specifically, as a configuration for dealing with the dynamic equivalent load, the bearing mechanism G1A and the bearing mechanism G1B have different groove curvature radius ratios.

[0061] Here, the groove curvature radius ratio will be explained using Figure 3. As shown in Figure 3, a groove-shaped raceway surface K is formed on the outer peripheral surface of the shaft S. The shape of the groove of the raceway surface K in the axial direction of the shaft S is an arc along a raceway groove imaginary circle S1. The radius of the raceway groove imaginary circle S1 is taken as r1. Also, the radius of the spherical ball T is taken as r2. The groove curvature radius ratio between the raceway surface K of the shaft S and the ball T is expressed as r1 / r2.

[0062] In this embodiment, the groove curvature radius ratio between the balls 14 and the first input shaft raceway surface K11 is smaller than the groove curvature radius ratio between the balls 17 and the second input shaft raceway surface K12. As a result, the osculating ellipse (contact surface) between the balls 14 and the first input shaft raceway surface K11 is larger than the osculating ellipse between the balls 17 and the second input shaft raceway surface K12. Therefore, the surface pressure between the balls 14 and the first input shaft raceway surface K11 is smaller than the surface pressure between the balls 17 and the second input shaft raceway surface K12.

[0063] Furthermore, the groove curvature radius ratio between balls 14 and the first input shaft outer ring raceway surface L11 is smaller than the groove curvature radius ratio between balls 17 and the second input shaft outer ring raceway surface L12. As a result, the contact ellipse between balls 14 and the first input shaft outer ring raceway surface L11 is larger than the contact ellipse between balls 17 and the second input shaft outer ring raceway surface L12. Therefore, the surface pressure between balls 14 and the first input shaft outer ring raceway surface L11 is smaller than the surface pressure between balls 17 and the second input shaft outer ring raceway surface L12.

[0064] In this way, the input gear unit 10 can reduce the surface pressure on the bearing mechanism G1A side by reducing the groove curvature radius ratio of the bearing mechanism G1A, which is the side with the larger dynamic equivalent load.

[0065] To accommodate the dynamic equivalent load, the bearing mechanisms G1A and G1B have different raceway diameters for their shaft raceways. Specifically, the raceway diameter of the first input shaft raceway surface K11 of the bearing mechanism G1A, which has a larger dynamic equivalent load, is larger than the raceway diameter of the second input shaft raceway surface K12 of the bearing mechanism G1B. The raceway diameter of the first input shaft outer ring raceway surface L11 of the bearing mechanism G1A, which has a larger dynamic equivalent load, is larger than the raceway diameter of the second input shaft outer ring raceway surface L12 of the bearing mechanism G1B. Increasing the raceway diameters allows for an increase in the number of balls 14 disposed between the first input shaft raceway surface K11 and the first input shaft outer ring raceway surface L11. In this case, the diameters of the balls 14 and the balls 17 may be the same or different.

[0066] Furthermore, in order to accommodate the dynamic equivalent load, the ball configurations of bearing mechanism G1A and bearing mechanism G1B are different from each other. Specifically, the diameter of balls 14 of bearing mechanism G1A, which has a larger dynamic equivalent load, is larger than the diameter of balls 17 of bearing mechanism G1B. Furthermore, the number of balls 14 of bearing mechanism G1A, which has a larger dynamic equivalent load, is greater than the number of balls 17 of bearing mechanism G1B.

[0067] Although the case where the dynamic equivalent load on the bearing mechanism G1A side is high has been described as an example, the dynamic equivalent load of bearing mechanism G1B may be higher than that of bearing mechanism G1A. In this case, the configurations applied to the bearing mechanism G1A and bearing mechanism G1B described above can be reversed and applied.

[0068] Next, a description will be given of a configuration for improving the strength of each part of the input gear unit 10. The balls 14 and 17 may be subjected to a special heat treatment. In this case, surface roughness of the first input shaft raceway surface K11 and the second input shaft raceway surface K12 caused by the rotation of the input shaft 11 can be reduced, and the fatigue strength of the input shaft 11 can be improved.

[0069] Furthermore, to improve strength, the first input shaft raceway surface K11 and the second input shaft raceway surface K12 may be induction hardened. This improves the fatigue strength of the input shaft 11. It is recommended that induction hardening be performed from the first input shaft raceway surface K11 and the second input shaft raceway surface K12 to the inner diameter surface of the input shaft 11 (the inner peripheral surface of the second shaft hole portion M2). This improves the strength of the portion where stress is generated on the inner diameter surface of the input shaft 11 when the balls 14 roll on the first input shaft raceway surface K11. Similarly, it improves the strength of the portion where stress is generated on the inner diameter surface of the input shaft 11 when the balls 17 roll on the second input shaft outer ring raceway surface L12.

[0070] Next, a configuration for reducing stress on the shaft raceway surface will be described. Here, a rotational force is input to the input shaft 11 through the spline 11s, and the input rotational force is output from the input shaft output gear 12. Therefore, a particularly large torsional force is generated between the spline 11s of the input shaft 11 and the input shaft output gear 12. For this reason, a configuration for reducing stress on the second input shaft raceway surface K12 will be described.

[0071] A shaft hole M is provided inside the input shaft 11, extending along the axial direction of the input shaft 11 (the direction of the rotation axis A1). The shaft hole M may be used, for example, as an oil passage. The shaft hole M includes a first shaft hole portion M1 having a first diameter and a second shaft hole portion M2 having a second diameter smaller than the first diameter. The first shaft hole portion M1 and the second shaft hole portion M2 are adjacent to each other and communicate with each other, and the first shaft hole portion M1 is located on the side closer to the spline 11s. A step portion (connection portion) between the first shaft hole portion M1 and the second shaft hole portion M2 is located between the second input shaft raceway surface K12 and the spline 11s in the extension direction of the input shaft 11. In other words, the second input shaft raceway surface K12 is located in a thicker portion of the input shaft 11 than the portion where the spline 11s is provided. As a result, when a rotational force (torque) is input to the input shaft 11 from the spline 11s, the stress on the second input shaft raceway surface K12 is reduced.

[0072] Furthermore, as a configuration for reducing stress on the shaft raceway surface, a groove extending in the circumferential direction is provided on the outer peripheral surface of the input shaft 11. Specifically, a groove 11d extending in the circumferential direction is provided on the outer peripheral surface of the input shaft 11 between the spline 11s and the second input shaft raceway surface K12. The groove shape of the groove 11d may be arc-shaped or rectangular. In other words, by providing the groove 11d, the area of ​​the groove 11d becomes a weakened portion. As a result, when a rotational force (torque) is input to the input shaft 11 from the spline 11s, stress is concentrated on the groove 11d, and stress on the second input shaft raceway surface K12 is reduced.

[0073] Next, a configuration for improving the accuracy of the input shaft 11 during manufacturing will be described. The input shaft 11 is polished to finish the shapes of the first input shaft raceway surface K11 and the second input shaft raceway surface K12. Therefore, the input shaft 11 is configured to have sufficient machining allowances (cutting margins) on the first input shaft raceway surface K11 and the second input shaft raceway surface K12 before finish polishing. This makes it possible to suppress misalignment of the first input shaft raceway surface K11 and the second input shaft raceway surface K12 during finish polishing.

[0074] [Counter gear unit configuration] As shown in Fig. 1, rotational force is transmitted to the counter gear unit 20 from the input gear unit 10. More specifically, as shown in Fig. 4, the counter gear unit 20 includes a countershaft (rotating shaft) 21, a countershaft input gear 22, a countershaft output gear (gear) 23, a first countershaft outer ring (first outer ring, outer ring) 24, a plurality of balls (first ball, ball) 25, a first countershaft cage 26, a second countershaft outer ring (second outer ring, outer ring) 27, a plurality of balls (second ball, ball) 28, and a second countershaft cage 29.

[0075] Rotational force is transmitted to the countershaft 21 from the input gear unit 10 via a countershaft input gear 22. The rotation axis A2 of the countershaft 21 and the rotation axis A1 of the input shaft 11 are parallel to each other (see FIG. 1). The countershaft 21 has, on its outer circumferential surface, a first countershaft raceway surface (first shaft raceway surface, shaft raceway surface) K21 and a second countershaft raceway surface (second shaft raceway surface, shaft raceway surface) K22.

[0076] The first countershaft raceway surface K21 is provided on the outer peripheral surface near one end of the countershaft 21. The second countershaft raceway surface K22 is provided on the outer peripheral surface near the other end of the countershaft 21. The first countershaft raceway surface K21 and the second countershaft raceway surface K22 are grooves extending in the circumferential direction of the outer peripheral surface of the countershaft 21.

[0077] The countershaft input gear 22 is provided on the countershaft 21 and rotates integrally with the countershaft 21. The countershaft input gear 22 is provided at a position between the first countershaft raceway surface K21 and the second countershaft raceway surface K22. The countershaft input gear 22 meshes with the input shaft output gear 12 of the input gear unit 10. As a result, rotational force is transmitted to the countershaft 21 from the input gear unit 10 via the countershaft input gear 22.

[0078] In this embodiment, the countershaft input gear 22 is provided as a separate member from the countershaft 21. The countershaft 21 and the countershaft input gear 22 are connected, for example, by a spline. In this case, for example, the countershaft input gear 22 may be prevented from coming off the countershaft 21 by a nut 22a.

[0079] The number of teeth provided on the counter shaft input gear 22 is greater than the number of teeth provided on the input shaft output gear 12 of the input gear unit 10. Therefore, when the rotational force is transmitted from the input gear unit 10 to the counter gear unit 20, the rotational speed is reduced.

[0080] The countershaft output gear 23 is provided on the countershaft 21 and rotates integrally with the countershaft 21. The countershaft output gear 23 is provided at a position between the countershaft input gear 22 and the second countershaft raceway surface K22. In this embodiment, the countershaft output gear 23 is provided integrally with the countershaft 21. The countershaft output gear 23 outputs rotational force to the differential gear unit 30.

[0081] The first countershaft outer ring 24 is attached to a countershaft support portion (first support portion, support portion) C2a that supports the countershaft 21. The countershaft support portion C2a is, for example, a part of a housing that houses the input gear unit 10 and the like. The first countershaft outer ring 24 is provided so as to surround the first countershaft raceway surface K21. The first countershaft outer ring 24 has an outer peripheral surface 24a that is attached to the countershaft support portion C2a. The inner peripheral surface of the first countershaft outer ring 24 is provided with a first countershaft outer ring raceway surface (first outer ring raceway surface, outer ring raceway surface) L21 that faces the first countershaft raceway surface K21. The first countershaft outer ring raceway surface L21 is a groove that extends circumferentially on the inner peripheral surface 24b of the first countershaft outer ring 24.

[0082] The plurality of balls 25 are arranged between the first countershaft raceway surface K21 of the countershaft 21 and the first countershaft outer ring raceway surface L21 of the first countershaft outer ring 24. The balls 25 are spherical. The first countershaft cage 26 holds each of the plurality of balls 25 between the outer peripheral surface of the countershaft 21 and the inner peripheral surface 24b of the first countershaft outer ring 24 so that they can roll freely.

[0083] The second countershaft outer ring 27 is attached to a countershaft support portion (second support portion, support portion) C2b that supports the countershaft 21. The second countershaft outer ring 27 is provided so as to surround the second countershaft raceway surface K22. The second countershaft outer ring 27 has an outer peripheral surface 27a that is attached to the countershaft support portion C2b. The inner peripheral surface 27b of the second countershaft outer ring 27 is provided with a second countershaft outer ring raceway surface (second outer ring raceway surface, outer ring raceway surface) L22 that faces the second countershaft raceway surface K22. The second countershaft outer ring raceway surface L22 is a groove that extends circumferentially on the inner peripheral surface 27b of the second countershaft outer ring 27.

[0084] The plurality of balls 28 are arranged between the second countershaft raceway surface K22 of the countershaft 21 and the second countershaft outer ring raceway surface L22 of the second countershaft outer ring 27. The balls 28 are spherical. The second countershaft cage 29 holds each of the plurality of balls 28 between the outer peripheral surface of the countershaft 21 and the inner peripheral surface 27b of the second countershaft outer ring 27 so that they can roll freely.

[0085] In this way, the countershaft 21 is rotatably supported at two locations: the first countershaft raceway surface K21 and the second countershaft raceway surface K22. Furthermore, the counter gear unit 20 of this embodiment does not have a component that functions only as the inner ring of the bearing. In the counter gear unit 20 of this embodiment, the countershaft 21 also functions as the inner ring of the bearing.

[0086] Furthermore, in the counter gear unit 20 of this embodiment, the first countershaft outer ring 24, the balls 25, and the first countershaft raceway surface K21 of the countershaft 21 form a bearing mechanism G2A, which is a deep groove ball bearing. Similarly, the second countershaft outer ring 27, the balls 28, and the second countershaft raceway surface K22 of the countershaft 21 form a bearing mechanism G2B, which is also a deep groove ball bearing. That is, in the counter gear unit 20, the countershaft 21 is rotatably supported by the bearing mechanisms G2A and G2B.

[0087] The counter gear unit 20 can have at least one of the following features of the input gear unit 10 described above: "a configuration for suppressing stress concentration at the step portion," "a configuration for coping with dynamic equivalent loads," "a configuration for improving strength," "a configuration for reducing stress on the shaft raceway surface," and "a configuration for improving accuracy."

[0088] [Differential gear unit configuration] As shown in Fig. 1, rotational force is transmitted to the differential gear unit 30 from the counter gear unit 20. More specifically, as shown in Fig. 5, the differential gear unit 30 includes a differential case 31, a differential input gear 32, a differential mechanism 33, a first differential outer ring 34, a plurality of rolling elements 35, a first differential cage 36, a second differential outer ring 37, a plurality of rolling elements 38, and a second differential cage 39.

[0089] Rotational force is transmitted to the differential case 31 from the counter gear unit 20 via a differential input gear 32. The rotation axis A3 of the differential case 31 and the rotation axis A2 of the counter gear unit 20 are parallel to each other (see FIG. 1). The differential case 31 has an internal storage space for storing the differential mechanism 33. The differential case 31 has a first differential raceway surface K31 and a second differential raceway surface K32 on its outer circumferential surface.

[0090] The first differential raceway K31 is provided on the outer peripheral surface near one end of the differential case 31 in the direction of the rotation axis A3. The first differential raceway K31 has a truncated cone shape whose diameter decreases toward one end of the differential case 31. The second differential raceway K32 is provided on the outer peripheral surface near the other end of the differential case 31 in the direction of the rotation axis A3. The second differential raceway K32 has a truncated cone shape whose diameter decreases toward the other end of the differential case 31.

[0091] The differential input gear 32 is provided in the differential case 31 and rotates integrally with the differential case 31. The differential case 31 is provided at a position between the first differential raceway surface K31 and the second differential raceway surface K32. The differential input gear 32 meshes with the counter shaft output gear 23 of the counter gear unit 20. As a result, rotational force is transmitted from the counter gear unit 20 to the differential case 31 via the differential input gear 32. In this embodiment, the differential input gear 32 is provided integrally with the differential case 31.

[0092] The number of teeth provided on the differential input gear 32 is greater than the number of teeth provided on the counter shaft output gear 23 of the counter gear unit 20. Therefore, when the rotational force is transmitted from the counter gear unit 20 to the differential gear unit 30, the rotational speed is reduced.

[0093] The differential mechanism 33 is provided inside the differential case 31. The differential mechanism 33 is, for example, a differential mechanism of a vehicle differential gear unit equipped with pinion gears, side gears, etc. Various well-known mechanisms can be used as the differential mechanism 33. The differential case 31 is provided with a first insertion port h1 and a second insertion port h2 at both ends of the differential case 31 in the direction of the rotation axis A3. The differential mechanism 33 transmits rotational force to drive shafts and the like inserted through the first insertion port h1 and the second insertion port h2. The first insertion port h1 is located inside the first differential raceway surface K31 that extends annularly. The second insertion port h2 is located inside the second differential raceway surface K32 that extends annularly.

[0094] The first differential outer ring 34 is attached to a differential support portion C3a that supports the differential case 31. The differential support portion C3a is, for example, a part of a housing that houses the input gear unit 10 and the like. The first differential outer ring 34 is arranged to surround the first differential raceway K31. The first differential outer ring 34 has an outer peripheral surface 34a that is attached to the differential support portion C3a. The inner peripheral surface of the first differential outer ring 34 is provided with a first differential outer ring raceway L31 that faces the first differential raceway K31. The first differential outer ring raceway L31 has a truncated cone shape whose diameter decreases toward one end (outside) of the differential case 31.

[0095] The plurality of rolling elements 35 are arranged between the first differential raceway surface K31 of the differential case 31 and the first differential outer ring raceway surface L31 of the first differential outer ring 34. The rolling elements 35 are tapered rollers. The first differential cage 36 holds each of the plurality of rolling elements 35 between the outer peripheral surface of the differential case 31 and the inner peripheral surface of the first differential outer ring 34 so that they can roll freely.

[0096] The differential case 31 has a first differential small flange portion 31a provided adjacent to the small diameter side end of the first differential track surface K31, and a first differential large flange portion 31b provided adjacent to the large diameter side end of the first differential track surface K31.

[0097] The second differential outer ring 37 is attached to a differential support portion C3b that supports the differential case 31. The differential support portion C3b is, for example, a part of a housing that houses the input gear unit 10 and the like. The second differential outer ring 37 is provided so as to surround the second differential raceway K32. The second differential outer ring 37 has an outer peripheral surface 37a that is attached to the differential support portion C3b. The second differential outer ring 37 has an inner peripheral surface that is provided with a second differential outer ring raceway L32 that faces the second differential raceway K32. The second differential outer ring raceway L32 has a truncated cone shape whose diameter decreases toward the other end (outside) of the differential case 31.

[0098] The plurality of rolling elements 38 are arranged between the second differential raceway surface K32 of the differential case 31 and the second differential outer ring raceway surface L32 of the second differential outer ring 37. The rolling elements 38 are tapered rollers. The second differential cage 39 holds each of the plurality of rolling elements 38 between the second differential raceway surface K32 of the differential case 31 and the second differential outer ring raceway surface L32 of the second differential outer ring 37 so that they can roll freely.

[0099] In addition, the differential case 31 has a second differential small flange portion 31c provided adjacent to the small diameter side end of the second differential track surface K32, and a second differential large flange portion 31d provided adjacent to the large diameter side end of the second differential track surface K32.

[0100] In this way, the differential case 31 is rotatably supported at two locations: the location of the first differential raceway surface K31 and the location of the second differential raceway surface K32. Furthermore, the differential gear unit 30 of this embodiment does not have a component that functions only as an inner ring of a bearing. In the differential gear unit 30 of this embodiment, the differential case 31 also functions as an inner ring of a bearing.

[0101] In the differential gear unit 30 of this embodiment, the first differential outer ring 34, the rolling elements 35, and the first differential raceway surface K31 of the differential case 31 form a tapered roller bearing. Similarly, the second differential outer ring 37, the rolling elements 38, and the second differential raceway surface K32 of the differential case 31 form a tapered roller bearing.

[0102] [Drive unit configuration] As shown in Fig. 1, the drive unit 40 constitutes an electric motor unit that serves as a drive source for the vehicle. More specifically, as shown in Fig. 6, the drive unit 40 includes a motor rotor 41, a rotor shaft 42, a first rotor shaft outer ring 43, a plurality of balls 44, a first rotor shaft retainer 45, a second rotor shaft outer ring 46, a plurality of balls 47, and a second rotor shaft retainer 48.

[0103] The motor rotor 41 constitutes the rotor of an electric motor. Although not shown, the drive unit 40 includes components such as magnets that constitute the electric motor as a drive mechanism. The drive unit 40 may also include electronic components such as an inverter.

[0104] The rotor shaft 42 is provided at the center of the motor rotor 41. The rotor shaft 42 is driven to rotate by the motor rotor 41. The rotor shaft 42 serves as the output shaft of the rotational force (driving force) of the drive unit 40. The rotor shaft 42 is connected to the input shaft 11 of the input gear unit 10. The rotation axis A4 of the rotor shaft 42 and the rotation axis A1 of the input shaft 11 are coaxial.

[0105] Here, splines 42s are formed on the inner peripheral surface of the rotor shaft 42 at the end connected to the input shaft 11. The splines 42s of the rotor shaft 42 and the splines 11s of the input shaft 11 are spline-engaged to connect the rotor shaft 42 and the input shaft 11. The rotor shaft 42 also has a first rotor shaft raceway surface K41 and a second rotor shaft raceway surface K42 on its outer peripheral surface.

[0106] The first rotor shaft raceway surface K41 is provided on the outer peripheral surface of the rotor shaft 42 near the end thereof connected to the input shaft 11. The second rotor shaft raceway surface K42 is provided on the outer peripheral surface of the rotor shaft 42 near the end thereof opposite to the first rotor shaft raceway surface K41. The first rotor shaft raceway surface K41 and the second rotor shaft raceway surface K42 are grooves extending circumferentially on the outer peripheral surface of the rotor shaft 42.

[0107] The first rotor shaft outer ring 43 is attached to a rotor shaft support part C4a that supports the rotor shaft 42. The rotor shaft support part C4a is, for example, a part of a housing that houses the input gear unit 10 and the like. The first rotor shaft outer ring 43 is provided so as to surround the first rotor shaft raceway surface K41. The first rotor shaft outer ring 43 has an outer peripheral surface 43a that is attached to the rotor shaft support part C4a and an inner peripheral surface 43b that faces the outer peripheral surface of the rotor shaft 42 (the first rotor shaft raceway surface K41).

[0108] The first rotor shaft outer ring 43 has a first rotor shaft outer ring raceway L41 on its inner circumferential surface 43b. The first rotor shaft outer ring raceway L41 is a groove extending in the circumferential direction of the inner circumferential surface 43b of the first rotor shaft outer ring 43.

[0109] The plurality of balls 44 are arranged between a first rotor shaft raceway surface K41 of the rotor shaft 42 and a first rotor shaft outer ring raceway surface L41 of the first rotor shaft outer ring 43. The balls 44 are spherical. The first rotor shaft retainer 45 holds each of the plurality of balls 44 between the outer peripheral surface of the rotor shaft 42 and the inner peripheral surface 43b of the first rotor shaft outer ring 43 so that they can roll freely.

[0110] The second rotor shaft outer ring 46 is attached to the rotor shaft support part C4b that supports the rotor shaft 42. The second rotor shaft outer ring 46 is provided so as to surround the second rotor shaft raceway surface K42. The second rotor shaft outer ring 46 has an outer peripheral surface 46a that is attached to the rotor shaft support part C4b, and an inner peripheral surface 46b that faces the outer peripheral surface of the rotor shaft 42 (the second rotor shaft raceway surface K42).

[0111] The second rotor shaft outer ring 46 has a second rotor shaft outer ring raceway L42 on its inner circumferential surface 46b. The second rotor shaft outer ring raceway L42 is a groove extending in the circumferential direction of the inner circumferential surface 46b of the second rotor shaft outer ring 46.

[0112] The plurality of balls 47 are arranged between a second rotor shaft raceway surface K42 of the rotor shaft 42 and a second rotor shaft outer ring raceway surface L42 of the second rotor shaft outer ring 46. The balls 47 are spherical. The second rotor shaft retainer 48 holds each of the plurality of balls 47 between the outer peripheral surface of the rotor shaft 42 and the inner peripheral surface 46b of the second rotor shaft outer ring 46 so that they can roll freely.

[0113] In this way, the rotor shaft 42 is rotatably supported at two locations: the first rotor shaft raceway surface K41 and the second rotor shaft raceway surface K42. Furthermore, the drive unit 40 of this embodiment does not include a component that functions only as the inner ring of the bearing. In the drive unit 40 of this embodiment, the rotor shaft 42 also functions as the inner ring of the bearing.

[0114] In the drive unit 40 of this embodiment, a deep groove ball bearing is formed by the first rotor shaft outer ring 43, the plurality of balls 44, and the first rotor shaft raceway surface K41 of the rotor shaft 42. Similarly, a deep groove ball bearing is formed by the second rotor shaft outer ring 46, the balls 47, and the second rotor shaft raceway surface K42 of the rotor shaft 42.

[0115] As described above, in the input gear unit 10 of the reducer 1, the groove curvature radius ratio between the balls 14 on the bearing mechanism G1A side, which has a large dynamic equivalent load, and the first input shaft raceway surface K11 is smaller than the groove curvature radius ratio between the balls 17 on the bearing mechanism G1B side, which has a small dynamic equivalent load, and the second input shaft raceway surface K12. Here, as the groove curvature radius ratio decreases, the contact ellipse (contact surface) between the balls and the raceway surface on the rotating shaft increases, and the surface pressure between the balls and the raceway surface decreases. Therefore, in the input gear unit 10, the surface pressure between the balls 14 on the bearing mechanism G1A side, which has a large dynamic equivalent load, and the first input shaft raceway surface K11 is reduced, thereby improving their lifespan and reducing static surface pressure. In this way, the performance of the reducer 1 can be improved by adjusting the groove curvature radius ratio.

[0116] Furthermore, the groove curvature radius ratio between balls 14 on the bearing mechanism G1A side, which has a large dynamic equivalent load, and the first input shaft outer ring raceway surface L11 is smaller than the groove curvature radius ratio between balls 17 on the bearing mechanism G1B side, which has a small dynamic equivalent load, and the second input shaft outer ring raceway surface L12. Therefore, in this input gear unit 10, the surface pressure between balls 14 on the bearing mechanism G1A side, which has a large dynamic equivalent load, and the first input shaft outer ring raceway surface L11 is reduced, thereby improving their lifespan and reducing static surface pressure. In this way, in this reducer 1, the performance can be further improved by adjusting the groove curvature radius ratio.

[0117] In the input gear unit 10, the raceway diameters of the first input shaft raceway surface K11 and the first input shaft outer ring raceway surface L11 on the bearing mechanism G1A side, which has a large dynamic equivalent load, are larger than the raceway diameters of the second input shaft raceway surface K12 and the second input shaft outer ring raceway surface L12 on the bearing mechanism G1B side, which has a small dynamic equivalent load. This increases the pitch circle diameter (PCD) of the bearing mechanism G1A side, which has a large dynamic equivalent load, thereby increasing the number of balls 14 and increasing the bearing capacity of the bearing mechanism G1A side, which has a large dynamic equivalent load. In this way, the input gear unit 10 can increase the number of balls 14 on the side with a large dynamic equivalent load, thereby improving the life of the bearing mechanism G1A, which has a large dynamic equivalent load. Therefore, the performance of this reducer 1 can be improved by adjusting the shaft raceway surface and outer ring raceway surface.

[0118] In the input gear unit 10, the diameter of the balls 14 on the bearing mechanism G1A side, which has a larger dynamic equivalent load, is larger than the diameter of the balls 17 on the bearing mechanism G1B side, which has a smaller dynamic equivalent load. Furthermore, in the reducer 1, the number of balls 14 on the bearing mechanism G1A side, which has a larger dynamic equivalent load, is greater than the number of balls 17 on the bearing mechanism G1B side, which has a smaller dynamic equivalent load. Here, a higher dynamic load rating is required for the bearing on the side with a higher load (the side with a larger dynamic equivalent load). Therefore, by increasing the diameter and number of balls 14 on the bearing mechanism G1A side, which has a larger dynamic equivalent load, the balls 14 can appropriately support the input shaft 11 so that it can rotate even under heavy loads. In this way, when the input shaft 11 is supported at two points around the balls 14 and 17, an appropriate design according to the load is possible. Therefore, in this reducer, performance can be improved by adjusting the diameters and numbers of the balls 14 and 17.

[0119] In the input gear unit 10, the raceway diameter of the first input shaft raceway surface K11 and the raceway diameter of the second input shaft raceway surface K12 are different from each other. Here, in the input shaft 11, the strength levels required for the portion supported by the balls 14 and the portion supported by the balls 17 may differ from each other. In such a case, by making the raceway diameter of the first input shaft raceway surface K11 and the raceway diameter of the second input shaft raceway surface K12 different from each other, it is possible to obtain an input shaft 11 that meets the required strength level. For example, by setting the raceway diameter of the first input shaft raceway surface K11 and the raceway diameter of the second input shaft raceway surface K12 to sizes that meet the respective required strength levels, it is possible to prevent the input shaft 11 from becoming excessively thick, and to reduce the size of the input shaft 11.

[0120] In the input gear unit 10, corner E1 of the step between the gear mounting portion 11b and the first raceway surface forming portion 11a, and corner E2 of the step between the gear mounting portion 11b and the second raceway surface forming portion 11c, each have an arc-shaped curved surface. This makes it possible to prevent stress from concentrating on corners E1 and E2 of the step between the gear mounting portion 11b and the raceway surface forming portions 11a and 11c when a load is applied, thereby improving the strength of the input shaft 11. In this way, in this reducer 1, by making corners E1 and E2 of the step portions have an arc-shaped curved surface, it is possible to improve performance.

[0121] The input shaft 11 has a groove 11d between the spline 11s, to which rotational force is input, and the second input shaft raceway surface K12. By providing the groove 11d in the input shaft 11 in this way, a weak portion can be intentionally provided between the spline 11s and the second input shaft raceway surface K12. As a result, in the input gear unit 10, even when rotational force is input to the input shaft 11 from the spline 11s, stress on the second input shaft raceway surface K12 can be reduced, and the strength of the bearing around the second input shaft raceway surface K12 can be improved. In this way, by providing the groove 11d in the input shaft 11, the performance of the reducer 1 can be improved.

[0122] In the input gear unit 10, a large-diameter first shaft hole portion M1 and a small-diameter second shaft hole portion M2 are provided inside the input shaft 11. The step portion between the first shaft hole portion M1 and the second shaft hole portion M2 is located between the second input shaft raceway surface K12 and the spline 11s. In other words, the second input shaft raceway surface K12 is provided in a thick portion of the input shaft 11 (the portion where the small-diameter second shaft hole portion M2 is provided). The spline 11s is provided in a thin portion of the input shaft 11 (the portion where the large-diameter first shaft hole portion M1 is provided). As a result, in the input gear unit 10, even when a rotational force is input to the input shaft 11 from the spline 11s, stress on the second input shaft raceway surface K12 can be reduced, and the strength of the bearing around the second input shaft raceway surface K12 can be improved. In this way, in this reducer 1, by providing shaft hole portions (first shaft hole portion M1, second shaft hole portion M2) with different hole diameters inside the input shaft 11, it is possible to improve performance.

[0123] [Variations] Next, a modified example of the reducer 1 according to this embodiment will be described. The following description will focus on the differences from the above embodiment.

[0124] [First modified example of input gear unit] In the above embodiment, the input gear unit 10 is configured to accommodate a dynamic equivalent load by making the groove curvature radius ratio different between the bearing mechanism G1A and the bearing mechanism G1B. In the input gear unit 10 according to the first modification, the groove curvature radius ratio can be made different between the bearing mechanism G1A and the bearing mechanism G1B as a configuration to accommodate balls riding up from the raceway surface. Specifically, in the input gear unit 10 according to the first modification, the groove curvature radius ratio of the bearing mechanism G1A or the bearing mechanism G1B that receives the larger axial load is made larger.

[0125] For example, suppose the axial load received by the first input shaft raceway surface K11 on the bearing mechanism G1A side is greater than the axial load received by the second input shaft raceway surface K12 on the bearing mechanism G1B side. In this case, in the input gear unit 10, the groove curvature radius ratio between the balls 14 and the first input shaft raceway surface K11 is made greater than the groove curvature radius ratio between the balls 17 and the second input shaft raceway surface K12. Similarly, in the input gear unit 10, the groove curvature radius ratio between the balls 14 and the first input shaft outer ring raceway surface L11 is made greater than the groove curvature radius ratio between the balls 17 and the second input shaft outer ring raceway surface L12.

[0126] Here, as the groove curvature radius ratio increases, the contact ellipse between the ball and the raceway surface becomes smaller, making it more difficult for the ball to climb up the raceway surface. The ball climbing up the raceway surface refers to the contact ellipse (contact surface) between the ball and the raceway surface protruding from the groove (raceway surface). Therefore, in the input gear unit 10 according to the first modification, the contact ellipse between the ball 14 on the bearing mechanism G1A side, which is subject to a large axial load, and the first input shaft raceway surface K11 can be reduced, thereby preventing the ball 14 from climbing up. Furthermore, in the input gear unit 10 according to the first modification, the contact ellipse between the ball 14 on the bearing mechanism G1A side, which is subject to a large axial load, and the first input shaft outer ring raceway surface L11 can be reduced, thereby preventing the ball 14 from climbing up. In this way, the performance of the reducer 1 equipped with the input gear unit 10 according to the first modification can be further improved by adjusting the groove curvature radius ratio.

[0127] Although the axial load on the bearing mechanism G1A side is greater than that on the bearing mechanism G1B side, the axial load on the bearing mechanism G1B side may be greater than that on the bearing mechanism G1A side. In this case, the magnitude relationship of the groove curvature radius ratios described above can be reversed between the bearing mechanism G1A side and the bearing mechanism G1B side.

[0128] Moreover, the counter gear unit 20 can be provided with the "structure for dealing with balls riding up from the raceway surface" of the input gear unit 10 according to the first modified example.

[0129] [Second modified example of input gear unit] In the above embodiment, the input gear unit 10 is configured to accommodate a dynamic equivalent load by having different ball diameters and numbers between the bearing mechanism G1A and the bearing mechanism G1B. In the input gear unit 10 according to the second modification, the diameters and numbers of balls (rolling elements) can be made different between the bearing mechanism G1A and the bearing mechanism G1B to improve the radial rigidity on the side where the gear tilts. Specifically, in the input gear unit 10 according to the second modification, the number of balls on the side where the input shaft output gear 12 tilts, of the bearing mechanism G1A and the bearing mechanism G1B, is increased, and the diameter of the balls is also increased.

[0130] For example, suppose that the input shaft output gear 12 is subjected to a load directed toward the bearing mechanism G1A (balls 14). In other words, suppose that the input shaft output gear 12 is subjected to a load that is inclined toward the bearing mechanism G1A (balls 14). In this case, the number of balls 14 on the bearing mechanism G1A side is greater than the number of balls 17 on the bearing mechanism G1B side. Also, the diameter of the balls 14 on the bearing mechanism G1A side is larger than the diameter of the balls 17 on the bearing mechanism G1B side.

[0131] In the input gear unit 10 according to the second modification, the number of balls 14 on the bearing mechanism G1A side where the input shaft output gear 12 receives a load is greater than the number of balls 17. As a result, in the input gear unit 10 according to the second modification, the radial rigidity when the balls 14 support the input shaft 11 on the ball 14 side where the load is received can be improved. In this way, in the reducer 1 including the input gear unit 10 according to the second modification, performance can be improved by setting the number of balls on the load side. Furthermore, the diameter of the balls 14 on the bearing mechanism G1A side where the input shaft output gear 12 receives a load is larger than the diameter of the balls 17. As a result, in the reducer 1 including the input gear unit 10 according to the second modification, the radial rigidity when the balls 14 support the input shaft 11 on the ball 14 side where the input shaft output gear 12 receives a load can be further improved.

[0132] Although the example has been described in which input shaft output gear 12 is inclined toward bearing mechanism G1A, input shaft output gear 12 may be configured to be inclined toward bearing mechanism G1B. In this case, the above-mentioned relationship between the number of balls and the diameters of the balls may be reversed between bearing mechanism G1A and bearing mechanism G1B.

[0133] The counter gear unit 20 may also be provided with a "structure for improving the radial rigidity of the side on which the gear tilts" of the input gear unit 10 according to the second modified example. In this case, the "gear" may be the counter shaft input gear (gear) 22 of the counter gear unit 20 or the counter shaft output gear (gear) 23.

[0134] [Third modified example of input gear unit] Next, a third modified example of the input gear unit will be described. As shown in Fig. 7, a rotational force is input from a spline 11s to an input shaft (rotating shaft) 11A of an input gear unit (rotating shaft unit) 10A according to the third modified example, and the input rotational force is output from an input shaft output gear 12. As a result, a particularly large torsional force is generated between the spline 11s of the input shaft 11A and the input shaft output gear 12. First, a configuration for reducing stress on the second input shaft raceway surface (second outer ring raceway surface, outer ring raceway surface) K12A will be described.

[0135] The input gear unit 10A according to this modification differs from the input gear unit 10 according to the embodiment in that the raceway diameter on the bearing mechanism G1B side is larger than the raceway diameter on the bearing mechanism G1A side. Specifically, the bearing mechanism G1B, which is a deep groove ball bearing, is configured by the second input shaft outer ring (second outer ring, outer ring) 16A, balls 17, and the second input shaft raceway surface (second shaft raceway surface, shaft raceway surface) K12A of the input shaft 11A. The bearing mechanism G1B is provided between the spline 11s and the input shaft output gear 12. In other words, the spline 11s is provided at the end of the input shaft 11A on the side where the second input shaft raceway surface K12A is provided.

[0136] To reduce stress applied to the input shaft 11A, the raceway diameter of the second input shaft raceway surface K12A on the bearing mechanism G1B side is larger than the raceway diameter of the first input shaft raceway surface K11 on the bearing mechanism G1A side. The raceway diameter of the second input shaft outer ring raceway surface L12A on the bearing mechanism G1B side is larger than the raceway diameter of the first input shaft outer ring raceway surface L11 on the bearing mechanism G1A side. A larger torsion (twisting force) is applied to the second input shaft raceway surface K12A, which is provided between the spline 11s and the input shaft output gear 12, than to the first input shaft raceway surface K11. Therefore, by increasing the raceway diameter of the second input shaft raceway surface K12A, stress concentration on the second input shaft raceway surface K12A can be suppressed. In this way, in the reducer 1 equipped with the input gear unit 10A according to the third modified example, performance can be improved by setting the raceway diameter of the shaft raceway surface.

[0137] As a configuration for reducing stress applied to the input shaft 11A, the input shaft 11A has portions where the outer diameter differs between the bearing mechanism G1A side and the bearing mechanism G1B side. Specifically, the input shaft 11A is provided with a second shaft portion (large diameter portion) 11f between the second input shaft raceway surface K12A and the input shaft output gear 12. The second shaft portion 11f has an outer diameter larger than the largest outer diameter portion of the input shaft 11A between the first input shaft raceway surface K11 and the input shaft output gear 12. In this embodiment, the first shaft portion 11g has the same outer diameter throughout the entire region between the first input shaft raceway surface K11 and the input shaft output gear 12. In other words, the second shaft portion 11f has an outer diameter larger than that of the first shaft portion 11g.

[0138] Here, a rotational force is input to the input shaft 11A through the spline 11s. Then, the input rotational force of the input shaft 11A is output from the input shaft output gear 12. As a result, a larger torsion (twisting force) is applied to the portion of the input shaft 11A between the second input shaft raceway surface K12A and the input shaft output gear 12 than to the portion between the input shaft output gear 12 and the first input shaft raceway surface K11. Therefore, by providing the second shaft portion 11f, which has a larger outer diameter, between the second input shaft raceway surface K12A and the input shaft output gear 12, stress concentration in the portion between the second input shaft raceway surface K12A and the input shaft output gear 12 can be suppressed. In this way, in the reducer 1 including the input gear unit 10A according to the third modified example, performance can be improved by adjusting the outer diameter of the input shaft 11A.

[0139] Furthermore, as a configuration for reducing stress applied to the input shaft 11A, the groove curvature radius of the second input shaft raceway surface K12A is larger than the groove curvature radius of the first input shaft raceway surface K11. Here, a larger torsion (twisting force) is applied to the second input shaft raceway surface K12A provided between the spline 11s and the input shaft output gear 12 than to the first input shaft raceway surface K11. Therefore, by increasing the groove curvature radius of the second input shaft raceway surface K12A, stress concentration on the second input shaft raceway surface K12A can be suppressed. In this way, in the reducer 1 equipped with the input gear unit 10A according to this third modified example, performance can be improved by adjusting the groove curvature radius.

[0140] Furthermore, the input gear unit 10A has a configuration that improves assembly of the input gear unit 10A. Specifically, the outer diameter of the end 11e of the input shaft 11A on the side where the first input shaft raceway surface K11 is provided is the same as the raceway diameter of the first input shaft raceway surface K11. In other words, the outer diameter of the input shaft 11A from one end of the input shaft 11A to the center position of the first input shaft raceway surface K11 in the width direction is the same as the raceway diameter of the first input shaft raceway surface K11.

[0141] Therefore, with the plurality of balls 14 arranged inside the first input shaft outer ring 13, the first input shaft outer ring 13 and the balls 14 can be easily assembled to the input shaft 11A by sliding them from the end 11e of the input shaft 11A to the position of the first input shaft raceway surface K11. In this way, in the reducer 1 equipped with the input gear unit 10A according to the third modified example, the performance of the reducer 1 can be improved by improving the assembly ease of the input gear unit 10A.

[0142] The structure for improving the ease of assembly of the input gear unit 10A can be applied to the bearing mechanism G1B side. Also, this "structure for improving the ease of assembly" can be applied to the counter gear unit 20.

[0143] The input gear unit 10A also has a configuration that improves lubrication performance. Specifically, the bearing mechanism G1B further includes a seal member 19. The seal member 19 is annular. The outer peripheral edge of the seal member 19 is fixed to one end of the second input shaft outer ring 16A in the extension direction of the input shaft 11A. In this modification, a seal mounting portion 16c is provided at the end of the second input shaft outer ring 16A on the spline 11s side. The seal mounting portion 16c has a larger diameter than the inner peripheral surface 16b of the second input shaft outer ring 16A on which the second input shaft raceway surface K12A is formed.

[0144] Seal member 19 is fixed to second input shaft outer ring 16A by fitting the outer peripheral edge of seal member 19 into seal mounting portion 16c. The inner peripheral edge of seal member 19 extends toward the outer peripheral surface of input shaft 11A. In other words, seal member 19 covers the area between inner peripheral surface 16b of second input shaft outer ring 16A and the outer peripheral surface of input shaft 11A.

[0145] In this way, in the input gear unit 10A, the area outside the second input shaft outer ring 16A and the area inside the second input shaft outer ring 16A in which the balls 17 are arranged can be separated by the sealing member 19 around the bearing mechanism G1B of the input shaft 11A.

[0146] As a result, for example, the input gear unit 10A can prevent lubricating oil from leaking out from the inside of the second input shaft outer ring 16A to the outside, thereby improving the lubrication performance of the bearing mechanism G1B. Also, for example, the input gear unit 10A can prevent foreign matter from entering the inside of the second input shaft outer ring 16A from the outside (spline 11s side) of the second input shaft outer ring 16A, thereby preventing a decrease in rotation performance. In this way, the provision of the seal member 19 in the reducer 1 including the input gear unit 10A according to this third modified example can improve performance.

[0147] The structure for improving the lubrication performance of the input gear unit 10A can be applied to the bearing mechanism G1A side. Also, the "structure for improving the lubrication performance" can be applied to the counter gear unit 20.

[0148] In the above-described embodiment, the bearing mechanism G1A of the input gear unit 10 may be configured as a ball bearing having a self-aligning function (self-aligning ball bearing) as shown in FIG. 8. Specifically, the bearing mechanism G1A includes a first group of balls (rolling elements) 14A arranged along the circumferential direction of the outer circumferential surface of the input shaft 11, and a second group of balls (rolling elements) 14B adjacent to the first group of balls 14A in the extension direction of the input shaft 11 and arranged along the circumferential direction of the outer circumferential surface of the input shaft 11. A first input shaft outer ring raceway surface (outer ring raceway surface) L11B is provided on the inner circumferential surface of the first input shaft outer ring 13. The first input shaft outer ring raceway surface L11B has a shape in which an intermediate portion between one end and the other end in the extension direction of the input shaft 11 is curved in an arc shape radially outward.

[0149] Further, a first input shaft raceway surface (axial raceway surface) K11A on which the first group of balls 14A rolls and a first input shaft raceway surface (axial raceway surface) K11B on which the second group of balls 14B rolls are provided on the outer peripheral surface of the input shaft 11. The first input shaft raceway surfaces K11A and K11B are grooves extending in the circumferential direction of the input shaft 11.

[0150] In other words, in the input gear unit 10 equipped with this bearing mechanism G1A having a self-aligning function, the first group of balls 14A and the second group of balls 14B are arranged in two rows around the input shaft 11, and these balls 14A and 14B abut against the arc-shaped first input shaft outer ring raceway L11B. In other words, in this input gear unit 10, the first group of balls 14A and the second group of balls 14B abut against the common first input shaft outer ring raceway L11B, which has a large groove curvature radius. As a result, the input gear unit 10 equipped with this bearing mechanism G1A can provide the input shaft 11 with a self-aligning function and improve robustness, even when the bearing inner ring and the rotating shaft are integrated. In this way, a reducer equipped with this bearing mechanism G1A can achieve improved performance.

[0151] Like the bearing mechanism G1A, the bearing mechanism G1B may have the same bearing configuration with self-aligning function as shown in Fig. 8. In addition to the input gear unit 10 according to the above-described embodiment, the bearing configuration with self-aligning function may also be applied to the input gear units according to the various modifications. Similarly, the bearing configuration with self-aligning function may also be applied to the counter gear unit 20.

[0152] [Fourth modified input gear unit] Next, a fourth modified example of the input gear unit will be described. As shown in FIG. 9, an input gear unit (rotating shaft unit) 10B according to the fourth modified example has a configuration that can improve the assembly of the bearing portion. Specifically, the input gear unit 10B includes a first input shaft outer ring (outer ring) 13B and a second input shaft outer ring (outer ring) 16B instead of the first input shaft outer ring 13 and the second input shaft outer ring 16 in the embodiment. In this modified example, the axial width of the first input shaft outer ring 13B is approximately equal to or smaller than the diameter of the balls 14. Furthermore, the axial width of the second input shaft outer ring 16B is approximately equal to or smaller than the diameter of the balls 17.

[0153] Note that "substantially equal" here does not only mean that the diameter of the balls and the width of the outer ring are the same, but also includes cases where the width of the outer ring is slightly larger than the diameter of the balls. For example, "slightly larger" may mean that the outer ring is slightly larger to ensure its strength, or it may be slightly larger than the diameter of the balls for other reasons. Furthermore, "substantially equal" also includes cases where the width of the outer ring is slightly larger than the diameter of the balls, as long as the purpose of ensuring a large gap between input shaft output gear 12 and first input shaft outer ring 13B, etc., is not violated, as will be described later. For example, "slightly equal" includes cases where the width of the outer ring is up to approximately 110% of the diameter of the balls (ball diameter x 1.1), and in some cases, includes cases where the width of the outer ring is up to approximately 120% of the diameter of the balls (ball diameter x 1.2).

[0154] Here, as an example, a case will be described in which the first input shaft outer ring 13B and the balls 14 are assembled to the input shaft 11. When assembling, as shown in FIG. 10 , the first input shaft outer ring 13B is arranged in an eccentric state with respect to the input shaft 11. Then, the balls 14 are arranged between the first input shaft outer ring raceway surface L11 of the first input shaft outer ring 13B and the first input shaft raceway surface K11 of the input shaft 11. At this time, a jig 50 is placed below the first input shaft outer ring 13B. Then, the balls 14 arranged between the first input shaft outer ring 13B and the input shaft 11 are supported by the jig 50 to prevent them from falling.

[0155] For example, due to miniaturization of the input gear unit 10, the gap between the input shaft output gear 12 and the first input shaft outer ring 13B may be small, as shown in FIG. 10 . Even in this case, the axial width of the first input shaft outer ring 13B is approximately equal to or less than the diameter of the balls 14, so that a large gap can be secured between the first input shaft outer ring 13B and the input shaft output gear 12 in the axial direction. A jig 50 can then be placed in this gap. For example, if the width of the first input shaft outer ring 13B is large, as shown by the dashed line in FIG. 10 , the gap between the first input shaft outer ring 13B and the input shaft output gear 12 becomes small, making it difficult to place a jig 50 in this gap.

[0156] In this way, the input gear unit 10B can improve the assembly performance of the bearing mechanism G1A when assembling the bearing mechanism G1A using the jig 50. Therefore, the transmission including the input gear unit 10B can improve the assembly performance. Furthermore, the second input shaft outer ring 16B has the same configuration as the first input shaft outer ring 13B. Therefore, the input gear unit 10B can improve the assembly performance of the bearing mechanism G1B when assembling the bearing mechanism G1B using the jig 50.

[0157] In this modification, the widths of both the first input shaft outer ring 13B and the second input shaft outer ring 16B are set to be approximately equal to or less than the diameters of the balls 14 and 17, respectively. However, this is not limiting, and the width of only one of the outer rings may be set to be approximately equal to or less than the diameter of the balls. Furthermore, the configuration that improves the assemblability of the input gear unit 10B can be applied to the input gear units of the above-described embodiment and each modification. Furthermore, the configuration that improves the assemblability of the input gear unit 10B can also be applied to the counter gear unit 20, etc.

[0158] [Fifth modified input gear unit] Next, a fifth modified example of the input gear unit will be described. As shown in FIG. 11, an input gear unit (rotating shaft unit) 10C according to the fifth modified example has a configuration that improves the productivity of the outer ring. Specifically, the input gear unit 10C includes a first input shaft outer ring 13C having a larger diameter than the first input shaft outer ring 13, instead of the first input shaft outer ring 13 in the embodiment. In addition, in this modified example, the raceway diameter of the first input shaft raceway surface K11 provided on the input shaft 11 is larger than the raceway diameter of the first input shaft raceway surface K11 in the embodiment. The inner diameter (diameter of the inner peripheral surface 13b) of the first input shaft outer ring 13C is larger than the outer diameter (diameter of the outer peripheral surface 16a) of the second input shaft outer ring 16.

[0159] Generally, the first input shaft outer ring 13C and the second input shaft outer ring 16 are formed by forging. In this modification, as described above, the inner diameter of the first input shaft outer ring 13C is larger than the outer diameter of the second input shaft outer ring 16. Therefore, by performing a single forging process on the raw material for the outer rings, it is possible to form the raw material for the first input shaft outer ring 13C and the raw material for the second input shaft outer ring 16 in one go. Thereafter, the raw material for the first input shaft outer ring 13C and the raw material for the second input shaft outer ring 16 can be separated, and the first input shaft outer ring 13C and the second input shaft outer ring 16 can be formed, respectively.

[0160] In this way, with the outer ring configuration of this modified example, it is possible to reduce the number of forging processes for molding first input shaft outer ring 13C and second input shaft outer ring 16, thereby improving the productivity of first input shaft outer ring 13C and second input shaft outer ring 16. Therefore, a transmission equipped with this outer ring configuration can achieve improved productivity.

[0161] The configuration for improving the productivity of the two outer rings can be applied to the input gear units of the above-described embodiment and each modified example. Furthermore, the configuration for improving the productivity of the outer ring of the input gear unit 10C can also be applied to the outer rings of the counter gear unit 20, the differential gear unit 30, and the drive unit 40.

[0162] Although the embodiments and various modifications of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications, and various modifications are possible without departing from the spirit of the present invention. Furthermore, at least some of the embodiments and various modifications described above may be combined in any desired manner.

[0163] In the above embodiment and modified example, the bearing mechanism G1A is described as a deep groove ball bearing equipped with balls 14. However, this is not limiting, and the bearing mechanism G1A may be a tapered roller bearing equipped with tapered rollers (rolling elements, first rolling elements) instead of balls 14. In this case, the first input shaft raceway surface K11 and the first input shaft outer ring raceway surface L11 only need to have a tapered trapezoid shape rather than a groove. Similarly, the bearing mechanism G1B may be a tapered roller bearing equipped with tapered rollers (rolling elements, second rolling elements) instead of balls 17. Furthermore, the bearing mechanisms G2A and G2B may also be tapered roller bearings equipped with tapered rollers (rolling elements, first rolling elements, second rolling elements).

[0164] Even when the bearing mechanism G1A, etc., constitutes a tapered roller bearing, various configurations for improving performance as described above can be applied to the bearing mechanism G1A, etc. Here, among the configurations for improving various performances as described above, various configurations other than the configuration related to the groove curvature radius ratio, the configuration related to the groove curvature radius, the configuration for improving the ease of assembly of the input gear unit 10A described with reference to FIG. 7, and the configuration for improving lubrication performance can be applied to the bearing mechanism G1A, etc., which constitutes a tapered roller bearing. Note that the diameter of the tapered roller may be the diameter of the larger diameter side, the diameter of the smaller diameter side, or the average diameter. Furthermore, when the raceway surfaces (shaft raceway surface, outer ring raceway surface) have a conical trapezoidal shape, the raceway diameter may be the diameter of the larger diameter side, the diameter of the smaller diameter side, or the average diameter.

[0165] Furthermore, the case where the bearing mechanism G1A etc. constitutes a self-aligning ball bearing has been described using Figure 8. However, the present invention is not limited to this, and the bearing mechanism G1A etc. may constitute a self-aligning tapered roller bearing having two rows of tapered rollers (rolling elements) instead of having two rows of balls.

[0166] Furthermore, the reducer 1 may further include a rotating shaft unit having a rotating shaft in addition to the above-described input gear units 10, 10A, 10B, and 10C, counter gear unit 20, differential gear unit 30, and drive unit 40. This rotating shaft unit may have various configurations of the above-described input gear units 10, 10A, 10B, and 10C.

[0167] Furthermore, in the above description, a speed reducer is used as the transmission according to the present invention. However, the present invention is not limited to this, and the transmission according to the present invention may also be a speed increaser that increases the rotational speed of a drive unit. Even when the transmission according to the present invention is a speed increaser, the same configurations as those described for the speed reducer 1 can be employed, with the only difference being the rotational speed conversion ratio by gears between each unit. [Explanation of symbols]

[0168] 1... reducer (transmission), 10, 10A, 10B, 10C... input gear unit (rotating shaft unit), 11, 11A... input shaft (rotating shaft), 11a... first raceway surface forming portion (raceway surface forming portion), 11b... gear mounting portion, 11c... second raceway surface forming portion (raceway surface forming portion), 11d... groove portion, 11f... second shaft portion (large diameter portion), 11s... spline (input portion), 12... input shaft output gear (gear), 13, 13B, 13C... first input shaft input shaft outer ring (first outer ring, outer ring), 14, 25...balls (first balls, balls, first rolling elements, rolling elements), 14A...balls (first group of rolling elements), 14B...balls (second group of rolling elements), 16, 16A...second input shaft outer ring (second outer ring, outer ring), 17, 28...balls (second balls, balls, second rolling elements, rolling elements), 19...sealing member, 20...counter gear unit (rotating shaft unit), 21...counter shaft (rotating shaft), 22...counter shaft input gear (gear), 23... Outer shaft output gear (gear), 24...First countershaft outer ring (first outer ring, outer ring), 27...Second countershaft outer ring (second outer ring, outer ring), E1, E2...Corner, K11, K11A, K11B...First input shaft raceway surface (first shaft raceway surface, shaft raceway surface), K12, K12A...Second input shaft raceway surface (second shaft raceway surface, shaft raceway surface), K21...First countershaft raceway surface (first shaft raceway surface, shaft raceway surface), K22...Second counter - Shaft raceway surface (second shaft raceway surface, shaft raceway surface), L11, L11B... first input shaft outer ring raceway surface (first outer ring raceway surface, outer ring raceway surface), L12, L12A... second input shaft outer ring raceway surface (second outer ring raceway surface, outer ring raceway surface), L21... first countershaft outer ring raceway surface (first outer ring raceway surface, outer ring raceway surface), L22... second countershaft outer ring raceway surface (second outer ring raceway surface, outer ring raceway surface), M... shaft hole, M1... first shaft hole portion, M2... second shaft hole portion.

Claims

[Claim 1] A transmission having a plurality of rotating shaft units, which changes the rotational speed of an input rotational force between the rotating shaft units and outputs the rotational force, At least one of the plurality of rotating shaft units is a rotating shaft having a first shaft raceway surface and a second shaft raceway surface on its outer circumferential surface; a gear provided on the rotating shaft between the first shaft orbital surface and the second shaft orbital surface, the gear rotating integrally with the rotating shaft; a first outer ring attached to a first support portion that supports the rotating shaft, provided so as to surround the first shaft raceway surface, and having a first outer ring raceway surface on an inner circumferential surface; a plurality of first balls arranged between the first shaft raceway surface and the first outer ring raceway surface; a second outer ring attached to a second support portion that supports the rotating shaft, provided so as to surround the second shaft raceway surface, and having a second outer ring raceway surface on an inner circumferential surface; a plurality of second balls disposed between the second shaft raceway surface and the second outer ring raceway surface; and a dynamic equivalent load on the first shaft raceway surface, the first ball, and the first outer ring is greater than a dynamic equivalent load on the second shaft raceway surface, the second ball, and the second outer ring; a groove curvature radius ratio between the first ball and the first axial raceway surface is smaller than a groove curvature radius ratio between the second ball and the second axial raceway surface, a groove curvature radius ratio between the first ball and the first outer ring raceway surface is smaller than a groove curvature radius ratio between the second ball and the second outer ring raceway surface.

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