Vehicle drive device

Abstract

Provided is a vehicle drive device comprising a parallel-shaft reducer and a motor connected to the input shaft of said parallel-shaft reducer. The parallel-shaft reducer comprises multiple pairs of intermeshing helical gears. In at least one of the multiple pairs, a first disc-shaped member is provided on both sides of a first gear out of the pair of helical gears and has a circumferential edge part that slides against a lateral surface of the second gear. The surface of the circumferential edge part that slides against the second gear is a convex surface that protrudes in the direction of the second gear and has an apical part having a circular shape centered on the gear axis.

Description

Vehicle drive system

[0001] The present invention relates to a vehicle drive device equipped with a parallel shaft reducer.

[0002] In electric vehicles, the prime mover that generates the vehicle's driving force has been replaced by a motor, which reduces the noise of the prime mover and increases the noise of the reducer that transmits the driving force. Therefore, helical gears are used in the reducers used in vehicle drive systems for electric vehicles to improve the meshing ratio and reduce meshing vibration. The improvement in the meshing ratio achieved by helical gears increases as the helical gear's helical angle increases. Therefore, to improve noise reduction, helical gears for vehicle drive systems are often designed with a larger helical angle than helical gears used in general industrial applications.

[0003] In helical gears, a thrust load acts in the gear axial direction due to the helix angle. This thrust load increases as the helix angle increases. Therefore, in vehicle drive systems where helical gears are set to a large helix angle, it is necessary to select bearings that can support the thrust load, which results in larger bearing sizes. In recent years, there has been a demand for smaller reducers to improve mountability, and the use of high-strength materials has been particularly promoted for gear materials. However, even if the gears are made smaller and the center distance between the gears is reduced, the large bearing sizes still create the problem of interference between bearings arranged on the same plane.

[0004] A known structure supports the thrust load of a helical gear with a flange provided on the side of the gear (see Patent Document 1). In the technology described in Patent Document 1, a flange with a diameter larger than the outer diameter of the driven gear is fixed coaxially with the driven gear, and one surface of the flange extending from the outer periphery of the driven gear is in sliding contact with the side of the drive gear. In this configuration, the flange can support the thrust load generated by the helical gear.

[0005] Japanese Patent Application Publication No. 2006-163198

[0006] However, in the technology of Patent Document 1, the flange portion and the gear side surface are in surface contact, resulting in large friction loss due to rotation. Meanwhile, vehicle drive systems are strongly required to achieve high efficiency in order to extend cruising distances, and large friction loss is a problem. Furthermore, in vehicle drive systems, the input shaft of the reducer is rotated in both forward and reverse directions, so thrust load acts on the gear shaft not only in one axial direction but also in the reverse direction. Therefore, the problem of increasing bearing size remains.

[0007] A vehicle drive device according to one aspect of the present invention is a vehicle drive device comprising a parallel shaft reducer and a motor connected to the input shaft of the parallel shaft reducer, wherein the parallel shaft reducer comprises a plurality of pairs of helical gears that mesh with each other, and at least one of the plurality of pairs has a first disk-shaped member on both side surfaces of a first gear of the pair of helical gears, the first disk-shaped member having a peripheral portion that slides against the side surface of a second gear, and the surface of the peripheral portion that slides against the second gear is a convex curved surface that protrudes toward the second gear and has an apex that forms a circle centered on the gear axis.

[0008] According to the present invention, it is possible to reduce friction loss and downsize bearings in a reduction gear of a vehicle drive device.

[0009] FIG. 1 is a diagram showing a schematic configuration of a vehicle drive device of a first embodiment. FIG. 2 is a perspective view showing the configuration of a reducer provided in the vehicle drive device. FIG. 3 is a cross-sectional view of a collar provided on the upper side of the input shaft drive gear in the drawing. FIG. 4 is a perspective view of an intermediate shaft driven gear composed of a helical gear. FIG. 5 is a diagram explaining forces acting on each rotating gear. FIG. 6 is a diagram showing an example of a collar when the driven gear is thicker. FIG. 7 is a diagram showing a vehicle drive device when a collar is provided on the intermediate shaft driven gear. FIG. 8 is a diagram showing a schematic configuration of a vehicle drive device of a second embodiment. FIG. 9 is a cross-sectional view of a collar provided on the side of a gear. FIG. 10 is a diagram showing a collar when the driven gear is thicker. FIG. 11 is a diagram showing a vehicle drive device when collars are applied to gears on all axes. FIG. 12 is a diagram showing a schematic configuration of a vehicle drive device of a third embodiment. FIG. 13 is a diagram showing a cross section taken along line A-A in FIG. 12.

[0010] Hereinafter, an embodiment of a semiconductor device according to the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. Furthermore, in the following description, identical or similar elements and processes are given the same reference numerals, and duplicate explanations may be omitted. Note that the content described below merely shows one example of an embodiment of the present invention, and the present invention is not limited to the following embodiment, and can be implemented in various other forms.

[0011] 1 and 2 are diagrams showing an example of a first embodiment of a vehicle drive device according to the present invention. FIG. 1 is a diagram showing a schematic configuration of a vehicle drive device 100. FIG. 2 is a perspective view showing the axial configuration of a reducer provided in the vehicle drive device 100. The vehicle drive device 100 includes a rotationally driven motor 200 and a reducer 300. The reducer 300 is a parallel-axis reducer with a three-axis structure that is widely used in vehicle drive devices for electric vehicles.

[0012] The reducer 300 is composed of three shafts: an input shaft 1, an intermediate shaft 2, and an output shaft 3. The input shaft 1 is supported by an input shaft bearing 8, the intermediate shaft 2 is supported by an intermediate shaft bearing 9, and the output shaft 3 is supported by an output shaft bearing 10. When the input shaft 1 is driven to rotate by the motor 200, an input shaft drive gear 4 provided on the input shaft 1 meshes with an intermediate shaft driven gear 5 provided on the intermediate shaft 2, thereby transmitting rotational torque to the intermediate shaft 2. Two gears, an intermediate shaft driven gear 5 and an intermediate shaft drive gear 6, are installed on the intermediate shaft 2. The intermediate shaft drive gear 6 meshes with an output shaft driven gear 7 provided on the output shaft 3, thereby finally transmitting torque to the output shaft 3. Note that in the various embodiments described below, a parallel-shaft reducer with a three-shaft structure will be described as an example of the reducer 300, but the present invention is also applicable to parallel-shaft reducers with two shafts or four or more shafts.

[0013] Disk-shaped collars 11 are provided on both side surfaces of the input shaft drive gear 4. Note that in Fig. 1, the collar 11 provided on the upper side surface of the input shaft drive gear 4 is shown in cross section. The pair of collars 11 are arranged so that the peripheral edges of each collar 11 sandwich the intermediate shaft driven gear 5 from above and below in the figure, and each collar 11 is in contact with the side surface of the intermediate shaft driven gear 5.

[0014] Figure 3 is a cross-sectional view of the collar 11 provided on the upper side surface of the input shaft drive gear 4 shown in Figure 2. The collar 11 provided on the lower side surface of the input shaft drive gear 4 has the same shape as the upper collar 11, and is disposed upside down relative to the upper collar 11. The shape of the upper collar 11 will be described below as an example. In Figure 3, the input shaft 1, input shaft drive gear 4, and intermediate shaft driven gear 5 are indicated by imaginary lines (two-dot chain lines). The dash-dotted line J1 is the axis of both the input shaft 1 and the input shaft drive gear 4.

[0015] The collar 11 has a thick fixed portion 11a in the central region that is fixed to the side of the input shaft drive gear 4. A convex curved surface 110 is formed on the peripheral edge of the disc-shaped collar 11, facing the input shaft drive gear 4. The convex curved surface 110 is formed in a ring shape centered on the gear axis. The convex curved surface 110 has a crowning shape with an apex 111 at its tip. The apex 111 of the convex curved surface 110 forms a circle with a diameter D and centered on the gear axis. The position of the apex 111 of the convex curved surface 110 is set to be located on or near the pitch circle 41 of the input shaft drive gear 4. In the example shown in FIG. 3 , the diameter D is set to be the same as the diameter of the pitch circle 41 of the input shaft drive gear 4. That is, at the meshing position, the apex 111 of the convex curved surface 110 contacts the pitch circle 41 on the side of the meshed gears 4, 5.

[0016] Figure 4 is a perspective view of the intermediate shaft driven gear 5, which is a helical gear. The dashed line labeled 51 represents the pitch circle of the intermediate shaft driven gear 5, which is tangent to the pitch circle 41 of the input shaft drive gear 4 at the position where the gears 4, 5 mesh. As explained in Figure 3, the diameter D of the apex 111 is the same as the diameter of the pitch circle 41, so in Figure 4, the circle representing the apex 111 is superimposed on the pitch circle 41.

[0017] When the gears 4 and 5 rotate, the apex 111 enters the side surface area of ​​the intermediate shaft driven gear 5 from the tooth tip side, approaches the pitch circle 51 while sliding on the side surface, and then moves from the pitch circle 51 toward the tooth tip side and leaves the side surface area of ​​the intermediate shaft driven gear 5. Because the peripheral speeds of the meshing gears 4 and 5 are the same on the pitch circle, the sliding speed (relative speed) of the apex 111 sliding on the side surface near the pitch circle with respect to the side surface of the intermediate shaft driven gear 5 is relatively small. Therefore, friction loss due to sliding can be kept small.

[0018] However, as shown in Figure 4, the pitch circle 41 passes through the area between the pitch circle 51 and the tip circle (not shown) of the intermediate shaft driven gear 5. When the gear is rotating, the tooth space area and the tooth area alternately pass over the crest 111 between the pitch circle 51 and the tip circle. As a result, the ratio of the tooth space area and the tooth area that are in contact with the crest 111 changes periodically, which could increase gear noise depending on conditions such as the rotational speed and load.

[0019] Therefore, by setting the diameter D of the apex 111 larger like the circle indicated by reference symbol 111a, the apex 111 may be brought into contact with the region on the inner periphery side of the root circle of the intermediate shaft driven gear 5, i.e., the region where the surface is continuous. With this configuration, there is a possibility that friction loss will increase, but noise can be reduced.

[0020] Figure 5 is a diagram illustrating the forces acting on the rotating gears 4 to 7. In Figure 5, the collar 11 is shown with an imaginary line (two-dot chain line). As mentioned above, helical gears are used for the gears 4 to 7 provided in the reducer 300. Helical gears have twisted tooth traces, and when the helical gears rotate, radial loads and thrust loads are generated due to the meshing of the gears. To improve noise reduction performance, the helix angle is made larger to increase the meshing ratio.

[0021] However, the larger the torsion angle, the larger the thrust load. If collar 11 is not provided, the radial load and thrust load generated on each of shafts 1 to 3 will be borne by the bearings 8 to 10 supporting both ends of each of shafts 1 to 3. For example, when input shaft 1 rotates in the R direction, radial loads Fr1 to Fr4 and thrust loads Fs1 to Fs4 act on each of shafts 1 to 3, as indicated by the arrows. For this reason, it is necessary to select bearings 8 to 10 that can support both radial loads Fr1 to Fr4 and thrust loads Fs1 to Fs4.

[0022] In the first embodiment, a collar 11 is provided on the drive-side gear, and the collar 11 bears the thrust load. For example, in the example shown in Figures 1 and 2, collars 11 are provided on both side surfaces of the input shaft drive gear 4. When the rotation direction of the input shaft 1 is direction R shown in Figure 5, the thrust load Fs2 acting on the intermediate shaft driven gear 5 is borne by the collar 11 provided on the lower side surface of the input shaft drive gear 4.

[0023] Because an upward thrust load Fs1 acts on the input shaft drive gear 4 provided with the collar 11, a downward thrust load Fs2 acting on the collar 11 cancels out the thrust load Fs1. As a result, the thrust force acting on the input shaft bearing 8 supporting the input shaft 1 can be reduced, broadening the range of options for bearing selection and enabling the selection of smaller bearings. Regarding the intermediate shaft 2, the thrust load Fs2 acting on the intermediate shaft driven gear 5 is received by the collar 11 provided on the side surface of the input shaft drive gear 4 on the lower side in the figure, eliminating the effect of the thrust load Fs2 on the intermediate shaft bearing 9 supporting the intermediate shaft 2. Furthermore, by making the convex curved surface 110 crowned, only the apex 111 makes linear contact with the side surface of the intermediate shaft driven gear 5, thereby reducing the contact area compared to the configuration described in Patent Document 1 and reducing friction loss.

[0024] On the other hand, if the collar 11 is not provided, a thrust load Fs1 acts on the input shaft bearing 8, so a larger bearing must be selected than when the collar 11 is applied, which increases the loss of oil agitation inside the bearing.

[0025] Note that FIG. 5 shows the thrust load and radial load generated when the input shaft 1 is driven to rotate in the R direction. In the vehicle drive device 100, the motor 200 is driven to rotate in both forward and reverse directions. Therefore, when the input shaft 1 is driven to rotate in the direction opposite to the R direction (-R direction), the thrust loads Fs1 to Fs4 act in the opposite direction to those shown in FIG. 5. That is, the arrows of the thrust loads Fs1 and Fs3 point downward, and the arrows of the thrust loads Fs2 and Fs4 point upward. In this case, the thrust load Fs2 is received by the upper collar 11, and cancels out the downward thrust load Fs1 acting on the input shaft drive gear 4. In this way, the collars 11 are provided on both sides of the input shaft drive gear 4 to accommodate both forward and reverse rotation of the motor 200.

[0026] 5, thrust loads Fs3 and Fs4 are also generated when the intermediate shaft drive gear 6 and the output shaft driven gear 7 mesh together. Therefore, by applying a collar 11 to the intermediate shaft drive gear 6 as well, the influence of the thrust loads Fs3 and Fs4 on the bearings 9 and 10 can be eliminated, and the thrust force acting on the bearings 9 and 10 can be reduced.

[0027] 1 and 2, etc., show a case where the thicknesses of the drive-side and driven-side gears are equal. FIG. 6, which corresponds to FIG. 3, shows an example of the collar 11 when the driven-side gear is thicker. The thickness t1 of the input shaft drive gear 4 and the thickness t2 of the intermediate shaft driven gear 5 are set so that t2 > t1. In this case, the thickness of the fixing portion 11a of the collar 11 is set thicker than in the case shown in FIG. 3, so that the apex 111 of the convex curved surface 110 contacts the side surface of the intermediate shaft driven gear 5. As a result, a gap is formed between the apex 111 and the side surface of the input shaft drive gear 4.

[0028] In the example shown in Figures 1 and 2, a collar 11 is provided on the drive gear of a pair of meshing gears, just as the input shaft drive gear 4 is provided with a collar 11. However, the collar 11 may be provided on either the drive gear or the driven gear. For example, as shown in Figure 7, collars 11 may be provided on both sides of the intermediate shaft driven gear 5 instead of the input shaft drive gear 4. For example, if the drive gear is smaller than the driven gear and it is difficult to provide a collar 11, the configuration shown in Figure 7 may be used. The same effect can be achieved whether the collar 11 is provided on the drive gear or the driven gear. Note that in Figure 7, the collar 11 provided on the upper side of the intermediate shaft driven gear 5 is shown in cross section.

[0029] That is, when applying the collar 11, it may be applied to any gear of a pair of meshing gears, provided that the collar 11 is applied to any gear provided on any shaft, and it may be applied to any pair of meshing gears. Furthermore, when there are multiple pairs of meshing gears, the collar 11 may be applied to all pairs.

[0030] Since gears are subjected to surface treatments and heat treatments after machining, it is desirable to form the collar 11 separately from the gear on which it is to be mounted. By forming the collar 11 separately, it is possible to use a material different from that of the gear, for example, a material with high wear resistance different from that of the gear, and it is also easy to apply shot peening or low-friction resin coating. The collar 11 may also be formed from a resin material such as a high-strength resin.

[0031] Second Embodiment Figure 8 is a diagram showing the schematic configuration of a vehicle drive device 100 according to a second embodiment of the present invention. As in Figure 2, Figure 8 also shows a cross-sectional view of the collar 11 provided on the upper side of the gear. As described above, if the diameter D of the apex 111 of the ring-shaped convex surface 110 is set to be the same as the diameter of the pitch circle 41 of the input shaft drive gear 4, a portion of the apex 111 will face the tooth groove side surface, resulting in reduced noise reduction. Therefore, in the second embodiment, disk-shaped collars 12 are provided on both side surfaces of the intermediate shaft driven gear 5, and the apex 111 of the convex surface 110 of the collar 11 comes into contact with the side surface of the collar 12.

[0032] FIG. 9 is an enlarged cross-sectional view of the collars 11, 12 provided on the upper side surfaces of the gears 4, 5. As in FIG. 3 , the gears 4, 5 are shown in phantom lines (two-dot chain lines), and only a portion of the collar 12 is shown. The disk-shaped collar 12 is slightly thinner at its periphery, forming a step on the surface facing the gear side. This step creates a gap between the collar 12 and the side surface of the input shaft drive gear 4, preventing the collar 12 from contacting the input shaft drive gear 4. At the meshing position in the cross section shown in FIG. 9 , the apex 111 of the convex curved surface 110 of the collar 11 contacts the upper surface of the collar 12 on the pitch circle 41. The outer diameter of the collar 12 is set larger than the diameter of the pitch circle 51 of the intermediate shaft driven gear 5.

[0033] For example, when the input shaft 1 is rotationally driven in the -R direction (the opposite direction to the R direction shown in FIG. 5), the thrust load Fs2 acting on the intermediate shaft driven gear 5 becomes an upward force in the figure. Therefore, the upward thrust load Fs2 is received by the collar 11. Since a downward thrust load Fs1 acts on the input shaft driving gear 4, the thrust loads Fs1 and Fs2 cancel each other out. As a result, the thrust force acting on the bearings 8 and 9 supporting the shafts 1 and 2 can be reduced, and the bearings 8 and 9 can be made smaller.

[0034] Furthermore, in the second embodiment, as shown in Fig. 9, the apex 111 of the convex curved surface 110 slides on the side surface of the collar 12, which is made up of a flat surface without any irregularities. Therefore, noise can be reduced compared to when the apex 111 slides on the side surface region including the tooth groove region of the intermediate shaft driven gear 5, as shown in Figs. 3 and 4.

[0035] If the thickness of the intermediate shaft driven gear 5 is thicker than the thickness of the input shaft drive gear 4, as in the case of the gears 4 and 5 shown in Fig. 6, the collar 12 can be made into a disk shape without any steps, as shown in Fig. 10. In the disk-shaped collar 12, the peripheral area where the apex 111 contacts comes into contact with the side surface of the intermediate shaft driven gear 5. Therefore, even if the thrust loads Fs1 and Fs2 shown in Fig. 9 are generated and the apex 111 presses the collar 12 downward, deformation of the collar 12 can be prevented.

[0036] 8 and 9, the collar 11 having the convex curved surface 110 is provided on the input shaft drive gear 4, and the disk-shaped collar 12 is provided on the intermediate shaft driven gear 5, but it is also possible to provide the collar 12 on the input shaft drive gear 4 and the collar 11 on the intermediate shaft driven gear 5. In that case, when the input shaft 1 rotates in the −R direction as shown in FIG. 9, the downward thrust load Fs1 acting on the input shaft drive gear 4 is received by the collar 12 on the lower side of the intermediate shaft driven gear 5.

[0037] Furthermore, when applying the collars 11 and 12, they may be applied to gears mounted on any shaft as long as they are a pair of meshing gears. Figure 11 shows a case in which, in addition to gears 4 and 5, a collar 11 is provided on the intermediate shaft driving gear 6, and a collar 12 is provided on the output shaft driven gear 7. Note that the collars 11 and 12 mounted on the upper side of gears 6 and 7 are shown in cross section. This configuration makes it possible to reduce thrust loads on all bearings, allowing for the selection of smaller bearings.

[0038] (Third Embodiment) FIG. 12 is a diagram showing the schematic configuration of a vehicle drive system 100 according to a third embodiment of the present invention. In the third embodiment, a sliding bearing 15 is used as an input shaft bearing supporting the input shaft 1. In recent years, as motors have become smaller and faster, input shafts have become faster to rotate and have lower torque. Furthermore, by using the collars 11 and 12 described above, it is possible to reduce the thrust load acting on the bearing to zero. In the vehicle drive system 100, the input shaft 1 rotates at high speed. Under these conditions, pressure is likely to be generated by an oil film on the sliding surface of the sliding bearing, making it possible to use a sliding bearing that is even smaller than a rolling bearing.

[0039] Incidentally, sliding bearings have a large friction loss due to shearing of the oil film. Furthermore, because they are in surface contact at startup, they also have a larger starting torque than rolling bearings. Figure 13 is a cross-section taken along the line A-A in Figure 12. The imaginary circle indicates the intermediate shaft 2. As shown in Figure 12, a radial load Fr1 acts on the input shaft drive gear 4 in the left direction in the figure. The radial load Fr1 generated by the meshing of the gears 4 and 5 is constant in direction, and the sliding bearing 15 is constantly subjected to a force F in the left direction in the figure, as shown in Figure 13.

[0040] The sliding bearing 15 has a notch cut out on the sliding surface opposite the bearing land portion 150, so that the area that slides against the input shaft 1 remains as a bearing land portion 150. The area indicated by the symbol B indicates the range of the notch region 151. In other words, the sliding surface on the anti-load side with respect to the axis J15 of the sliding bearing 15, i.e., the sliding surface in the direction of the intermediate shaft 2 on which the intermediate shaft driven gear 5 is provided (sliding surface in range B), is cut out. By employing this structure, it is possible to reduce friction loss in the notch region 151, i.e., friction loss of the sliding bearing 15.

[0041] The clearance in sliding bearing 15 depends on the design, but for example, if the clearance on the left side of the figure is about 10 μm, the largest clearance on the right side of the figure will be about five times that on the left. Furthermore, because loss reduction is proportional to the area of ​​the cutout region, it is preferable to cut out most of the sliding surface on the anti-load side.

[0042] According to the embodiment described above, the following advantageous effects are achieved.

[0043] (1) As shown in FIGS. 1 to 7 , the vehicle drive device 100 includes a reducer 300, which is a parallel-axis reducer, and a motor 200 connected to an input shaft 1 of the reducer 300. The reducer 300 includes a plurality of pairs of helical gears that mesh with each other. At least one of the plurality of pairs of helical gears includes an input shaft drive gear (first gear) 4 of the pair of meshing helical gears. A collar (first disk-shaped member) 11, whose peripheral portion is in sliding contact with a side surface of an intermediate shaft driven gear (second gear) 5, is provided on each side surface of the input shaft drive gear (first gear). The peripheral surface that is in sliding contact with the intermediate shaft driven gear 5 is a convex curved surface 110 that protrudes toward the intermediate shaft driven gear 5 and has an apex 111 that forms a circle centered on the gear axis J1.

[0044] As described above, since the collars 11 are provided on both sides of the input shaft drive gear 4, when the input shaft 1 rotates in the R direction as shown in Fig. 5, for example, the thrust load Fs2 of the intermediate shaft driven gear 5 is received by one of the collars 11 (the lower one in the figure), and the thrust loads Fs1 and Fs2 cancel each other out. When the input shaft 1 rotates in the direction opposite to the R direction, the thrust load Fs2 is received by the other collar 11 (the upper one in the figure), and similarly the thrust loads Fs1 and Fs2 cancel each other out. As a result, compared to when the collars 11 are not provided, the thrust force acting on the input shaft bearing 8 that supports the input shaft 1 is reduced, and the input shaft bearing 8 can be made smaller in size.

[0045] Furthermore, since the apex 111 of the convex curved surface 110 is configured to come into contact with the side surface of the intermediate shaft driven gear 5, it is possible to reduce the contact area between the collar 11 and the side surface of the intermediate shaft driven gear 5 compared to the configuration described in Patent Document 1. As a result, it is possible to reduce friction loss.

[0046] (2) In the above (1), as shown in Figures 8 to 11, the intermediate shaft driven gear (second gear) 5 has collars (second disk-shaped members) 12 on both sides of the intermediate shaft driven gear 5, and the convex curved surface 110 of the collar (first disk-shaped member) 11 slides against the side of the collar 12 instead of the side of the intermediate shaft driven gear 5. With this configuration, the apex 111 of the convex curved surface 110 slides against the side of the collar 12, which is formed as a flat surface without any irregularities. Therefore, in addition to the effect of the above (1), noise caused by gear rotation can be reduced.

[0047] (3) In the above (1) or (2), as shown in Fig. 3 etc., the diameter D of the apex 111 of the convex curved surface 110 is set to the diameter of the pitch circle 41 of the input shaft drive gear (first gear) 4. Since the peripheral speeds of the gears 4 and 5 are the same on the pitch circle 41, the sliding speed (relative speed) of the apex 111 with respect to the side surface of the intermediate shaft driven gear 5 is kept relatively small. Therefore, friction loss due to sliding can be kept small.

[0048] (4) In (1) above, as shown in Figures 12 and 13, the input shaft bearing that supports the input shaft (gear shaft) 1 of the input shaft drive gear (drive-side gear) 4 of the pair of gears 4, 5 that mesh with each other is a plain bearing 15. By providing the collar 11, the thrust force acting on the input shaft bearing that supports the input shaft 1 can be reduced to almost zero, making it possible to use the plain bearing 15 as the input shaft bearing. This allows the input shaft bearing to be further downsized.

[0049] (5) In (4) above, as shown in Figure 13, the sliding surface of the plain bearing 15 is cut out in the direction of the intermediate shaft (gear shaft) 2, on which the intermediate shaft driven gear (driven gear) 5 meshing with the input shaft drive gear (drive gear) 4 is provided, relative to the axis J15 of the plain bearing 15 (the sliding surface in range B). As a result, friction loss in the cut-out region is reduced, and it is possible to reduce friction loss in the plain bearing 15.

[0050] The above-described embodiments are merely examples, and the present invention is not limited to these embodiments as long as the features of the invention are not impaired. Other embodiments that are conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0051] DESCRIPTION OF SYMBOLS 1...input shaft, 2...intermediate shaft, 3...output shaft, 4...input shaft drive gear, 5...intermediate shaft driven gear, 6...intermediate shaft drive gear, 7...output shaft driven gear, 8...input shaft bearing, 9...intermediate shaft bearing, 10...output shaft bearing, 11, 12...collar, 15...plain bearing, 100...vehicle drive device, 110...convex curved surface, 111...top, 150...bearing land portion, 151...cutout area, 200...motor, 300...reduction gear

Claims

1. A vehicle drive device comprising a parallel shaft reducer and a motor connected to the input shaft of the parallel shaft reducer, wherein the parallel shaft reducer comprises a plurality of pairs of helical gears that mesh with each other, and at least one of the plurality of pairs of helical gears has a first disk-shaped member on each side of a first gear of the pair of helical gears, the peripheral portion of which is in sliding contact with the side surface of a second gear, and the surface of the peripheral portion that is in sliding contact with the second gear is a convex curved surface that protrudes toward the second gear and has an apex that forms a circle centered on the gear axis.

2. A vehicle drive device according to claim 1, wherein the second gear has second disk-shaped members on both side surfaces of the second gear, and the convex curved surface of the first disk-shaped member slides against the side surface of the second disk-shaped member instead of the side surface of the second gear.

3. A vehicle drive device according to claim 1 or claim 2, wherein the diameter of the apex of the convex curved surface is set to the diameter of the pitch circle of the first gear.

4. A vehicle drive device according to claim 1, wherein the bearing supporting the gear shaft of the drive gear of the pair of gears that mesh with each other is a sliding bearing.

5. A vehicle drive device according to claim 4, wherein the sliding surface of the plain bearing is notched in the direction of the gear shaft on which the driven gear meshing with the drive gear is mounted relative to the axis of the plain bearing.

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