Drive unit

Abstract

To provide a driving device capable of suppressing noise.SOLUTION: A driving device is equipped with: a first shaft connected to an electric motor; a second shaft rotating along with the first shaft; and a first bearing for supporting the first shaft and the second shaft. In the driving device, the first shaft and the second shaft are splined to be coupled and connected by a spigot.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a drive device. [Background technology]

[0002] In hybrid vehicles and the like that use an electric motor as a drive source, a drive device is formed by connecting a rotor shaft of the electric motor to an output shaft for outputting power (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-175261 Summary of the Invention [Problem to be solved by the invention]

[0004] By connecting two shafts with a spline, it is possible to transmit rotational force. However, for example, if there is a dimensional discrepancy between the two shafts, the shafts may whirl. This whirling of the shafts can generate noise. Therefore, the objective of this invention is to provide a drive unit that can suppress noise. [Means for solving the problem]

[0005] The above object is achieved by providing a rotating shaft drive system including a first shaft connected to an electric motor, a second shaft rotating together with the first shaft, and a first bearing supporting the first shaft and the second shaft, wherein the first shaft and the second shaft are spline-connected at a spline connection portion and are spigot-jointed at a spigot-joint connection portion, the spigot-joint connection portion being located closer to the tip of the first shaft than the spline connection portion, and the inner peripheral surface of the first shaft and the outer peripheral surface of the second shaft are in contact at the spigot-joint connection portion. The first bearing surrounds the spigot joint portion where the first shaft and the second shaft are spigot-jointed, and supports the first shaft and the second shaft. This can be achieved by the drive unit.

[0007] One of the two ends of the first shaft and one of the two ends of the second shaft may be splined and spigot-connected, and the bearing may include a second bearing that supports the other of the two ends of the first shaft, and a third bearing that supports the other of the two ends of the second shaft.

[0008] The second shaft may include a gear.

[0009] A fourth bearing may be provided to support the second shaft in a thrust direction. [Effects of the Invention]

[0010] A drive device capable of suppressing noise can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic view illustrating a drive device according to the first embodiment. [Figure 2] FIG. 2 is an enlarged view of a portion of the drive unit. [Figure 3] FIG. 3 is a diagram illustrating a drive device according to a comparative example. [Figure 4] 4(a) is a diagram illustrating an example of the load applied to the rotor shaft, and FIG. 4(b) is a diagram illustrating an example of the load applied to the gear shaft. [Figure 5] FIG. 5 is a diagram illustrating an example of a load in the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating a driving device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment The drive system of this embodiment will be described below with reference to the drawings. Fig. 1 is a schematic diagram illustrating a drive system 100 according to a first embodiment. The drive system 100 is a hybrid drive system used in a hybrid vehicle. The drive system 100 has an internal combustion engine 10 (engine), motor generators MG1 and MG2, a planetary gear mechanism 12, and a gear train 14, and drives drive wheels 18.

[0013] The internal combustion engine 10 generates power by burning fuel such as gasoline. The motor generators MG1 and MG2 are electric motors, each having a rotor and a stator. The motor generators MG1 and MG2 function as electric motors that rotate the rotors, and as generators that generate electric power by the rotation of the rotors.

[0014] A crankshaft (not shown) of the internal combustion engine 10 is connected to an input shaft 20. The input shaft 20 and a rotor shaft 22 of the motor generator MG1 are connected to the planetary gear mechanism 12.

[0015] The counter output shaft 21 is arranged concentrically with the input shaft 20. The counter drive gear 23 is arranged on the outer periphery of the counter output shaft 21 and meshes with the counter driven gear 25.

[0016] A counter driven gear 27 is connected to one end of the counter shaft 26, and a differential drive pinion gear 28 is connected to the other end of the counter shaft 26. The counter driven gear 27 and the differential drive pinion gear 28 can rotate integrally with the counter shaft 26.

[0017] The MG shaft 30 extends, for example, parallel to the input shaft 20 and the counter shaft 26. The counter drive gear 24 is formed integrally with the MG shaft 30 and meshes with a counter driven gear 27. The differential drive pinion gear 28 meshes with a differential ring gear 29. The differential ring gear 29 is connected to the differential case 19. The differential case 19 is connected to the drive wheels 18 via the drive shaft 17.

[0018] Torque output from the internal combustion engine 10 is transmitted to the drive wheels 18 via the input shaft 20, the planetary gear mechanism 12, the counter output shaft 21, the counter drive gear 23, the counter driven gear 25, the counter shaft 26, the differential drive pinion gear 28, and the differential case 19. The torque of the internal combustion engine 10 can also be transmitted to the motor generator MG1 via the planetary gear mechanism 12. The motor generator MG1 functions as a generator and generates electric power. A battery (not shown) can be charged with the electric power.

[0019] Motor generator MG2 is driven by the supply of electric power from the battery. The power generated by motor generator MG2 is transmitted to counter driven gear 27 via MG shaft 30 and counter drive gear 24. The power of motor generator MG2 is combined with the power of internal combustion engine 10 and transmitted to drive wheels 18. The transmission of power to drive wheels 18 causes the vehicle to move.

[0020] FIG. 2 is an enlarged view of a portion of the drive unit 100. The MG shaft 30 and bearings 44, 46, and 48 are housed inside a case 31. The MG shaft 30 has a rotor shaft 32 (first shaft) and a gear shaft 34 (second shaft). The rotor shaft 32 is the rotor shaft of the motor generator MG2 and protrudes outward from the motor generator MG2. The rotor shaft 32 and the gear shaft 34 are arranged parallel to each other, are connected, and rotate integrally on the same axis. The counter drive gear 24 is provided integrally with the gear shaft 34 on the outer circumferential surface of the gear shaft 34.

[0021] At least a portion of the rotor shaft 32 has a hollow structure. The gear shaft 34 is inserted into the hollow portion of the rotor shaft 32. The rotor shaft 32 and the gear shaft 34 are spline-connected and spigot-connected. That is, the drive unit 100 has a spline-connected portion 40 and a spigot-connected portion 42.

[0022] At the splined connection portion 40, the rotor shaft 32 has a plurality of internal teeth 32a. The internal teeth 32a protrude from the inner peripheral surface of the rotor shaft 32. At the splined connection portion 40, the gear shaft 34 has a plurality of external teeth 34a. The external teeth 34a protrude from the outer peripheral surface of the gear shaft 34. The internal teeth 32a and the external teeth 34a mesh with each other, and the rotor shaft 32 and the gear shaft 34 are splined together.

[0023] The spigot joint portion 42 is located closer to the tip end of the rotor shaft 32 than the spline joint portion 40. At the spigot joint portion 42, the inner peripheral surface of the rotor shaft 32 and the outer peripheral surface of the gear shaft 34 come into contact with each other.

[0024] Between the rotor shaft 32 and the gear shaft 34, a rotational force is transmitted by a spline connection portion 40. A radial force is transmitted by a spigot connection portion 42.

[0025] The rotor shaft 32 is supported by bearings 44 and 46. The gear shaft 34 is supported by bearings 44 and 48. The bearing 44 (first bearing) is shared by the rotor shaft 32 and the gear shaft 34. The bearing 44 is located closer to the tip of the rotor shaft 32 than the bearing 46 (second bearing) and closer to the tip of the gear shaft 34 than the bearing 48 (third bearing). The bearing 44 surrounds the spigot joint portion 42 and supports the rotor shaft 32 and the gear shaft 34 circumferentially at the spigot joint portion 42. The bearing 46 supports the other end of the rotor shaft 32 circumferentially. The bearing 48 supports the other end of the gear shaft 34 circumferentially. The bearings 44, 46, and 48 are, for example, ball bearings.

[0026] The driving force generated by motor generator MG2 is input to rotor shaft 32, causing rotor shaft 32 to rotate, and gear shaft 34 to also rotate. Counter drive gear 24 rotates integrally with gear shaft 34. Counter drive gear 24 meshes with counter driven gear 27 shown in FIG. 1. When counter drive gear 24 is rotated, a reaction force is applied to gear shaft 34.

[0027] The rotor shaft 32 and the gear shaft 34 are made of metal. During the manufacturing process, cutting and heat treatment are performed. Dimensional errors may occur due to distortion caused by the heat treatment. The central axes of the rotor shaft 32 and the gear shaft 34 may not coincide with each other and may become misaligned.

[0028] 3 is a diagram illustrating a driving device 100R according to a comparative example. The rotor shaft 32 and the gear shaft 34 are spline-connected but not spigot-connected. The rotor shaft 32 is supported by bearings 46 and 47. The gear shaft 34 is supported by bearings 48 and 49. The rotor shaft 32 and the gear shaft 34 do not share the bearing 44.

[0029] As described above, dimensional deviations may occur between the rotor shaft 32 and the gear shaft 34. For example, the central axes of the rotor shaft 32 and the gear shaft 34 may not coincide with each other and may become misaligned. In the comparative example, radial forces are transmitted along with rotational forces at the spline coupling 40. This causes whirling of the rotor shaft 32 and the gear shaft 34. The whirling changes the radial load.

[0030] Fig. 4(a) is a diagram illustrating the load applied to the rotor shaft 32. Fig. 4(b) is a diagram illustrating the load applied to the gear shaft 34. The horizontal axis represents time, and the vertical axis represents the load in the radial direction.

[0031] The load varies with time as shown in Figures 4(a) and 4(b). The load shown in Figure 4(a) is received by bearing 47. The load shown in Figure 4(b) is received by bearing 49. At times t1, t3, t5, and t7, the load in Figure 4(a) reaches a maximum value, and the load in Figure 4(b) reaches a minimum value. At times t2, t4, t6, and t8, the load in Figure 4(a) reaches a minimum value, and the load in Figure 4(b) reaches a maximum value. In other words, the load applied to rotor shaft 32 and the load applied to gear shaft 34 change over time in opposite phases to each other.

[0032] In the comparative example, the rotor shaft 32 and the gear shaft 34 whirl, resulting in a large radial displacement. At times t1, t3, t5, and t7, the radial displacement of the gear shaft 34 increases. The load is less likely to be applied to the bearing 49. Meanwhile, the bearing 47 is subjected to loads from both the rotor shaft 32 and the gear shaft 34. At times t2, t4, t6, and t8, the radial displacement of the rotor shaft 32 increases. The load is less likely to be applied to the bearing 47. Meanwhile, the bearing 49 is subjected to loads from both the rotor shaft 32 and the gear shaft 34. Since the load is transferred between the rotor shaft 32 and the gear shaft 34, the change in load over time increases. The rotor shaft 32 and the gear shaft 34 vibrate significantly in response to the change in load, generating noise.

[0033] FIG. 5 is a diagram illustrating an example of a load in the first embodiment. The bearing 44 receives the load shown in FIG. 5. The period of time change of the load in FIG. 5 is the same as that in the examples of FIGS. 4(a) and 4(b), for example. The magnitude (amplitude) of the load is smaller than that of the load shown in FIGS. 4(a) and 4(b).

[0034] In the first embodiment, the rotor shaft 32 and the gear shaft 34 are spigot-jointed, and radial force is transmitted through the spigot-joint portion 42. The spigot-jointed rotor shaft 32 and the gear shaft 34 rotate in contact with each other. This suppresses whirling and reduces load fluctuations. Furthermore, the bearing 44 supports both the rotor shaft 32 and the gear shaft 34. The bearing 44 receives a load from the rotor shaft 32 and a load from the gear shaft 34. Specifically, the bearing 44 receives a load as shown in FIG. 4(a) and a load as shown in FIG. 4(b), and these two loads are superimposed. Because the two loads change in opposite phases, they cancel each other out due to the superposition. This results in a load with a small amplitude, as shown in FIG. 5. The load fluctuations are reduced, displacement of the rotor shaft 32 and the gear shaft 34 is suppressed, and noise is reduced.

[0035] According to the first embodiment, the rotor shaft 32 and the gear shaft 34 are spline-connected and spigot-connected. The rotational force is transmitted by the spline-connected portion 40. The radial force is transmitted by the spigot-connected portion 42. The spigot-connected portion 42 is connected to the rotor shaft 32. Inner surface and gear shaft 34 Outer surface The rotor shaft 32 and the gear shaft 34 are in contact with each other and rotate as a unit, thereby suppressing whirling. This suppresses changes in load over time and displacement, and reduces noise.

[0036] The bearing 44 supports the rotor shaft 32 and the gear shaft 34. The bearing 44 receives the load of the rotor shaft 32 and the load of the gear shaft 34. By superimposing the two loads, the change in the load over time is smaller than in the comparative example, as shown in Figure 5. This suppresses displacement and reduces noise.

[0037] The bearing 44 is preferably provided at the spigot joint 42. Radial forces are transmitted at the spigot joint 42. By arranging the bearing 44 so as to surround the spigot joint 42, the bearing 44 receives the radial forces. This makes it possible to effectively suppress whirling.

[0038] The rotor shaft 32 is supported by bearings 44 and 46. Supported by two bearings, the rotor shaft 32 can rotate stably. The gear shaft 34 is supported by bearings 44 and 48. Supported by two bearings, the gear shaft 34 can rotate stably. Bearing 44 is shared by the rotor shaft 32 and the gear shaft 34, and bears the load from the two shafts. This reduces the change in load over time, and noise can be suppressed.

[0039] The gear shaft 34 is provided with the counter drive gear 24. The gear shaft 34 receives a radial reaction force from the counter drive gear 24. The reaction force is received by the spigot joint 42 and the bearing 44. This makes it possible to suppress whirling.

[0040] Second Embodiment 6 is a diagram illustrating a drive unit 200 according to a second embodiment, and is an enlarged view similar to FIG. 2. As in the first embodiment, in the second embodiment, the rotor shaft 32 and the gear shaft 34 are spline-connected and spigot-jointed. Bearings 44 support the rotor shaft 32 and the gear shaft 34.

[0041] As shown in Fig. 6, the drive unit 200 has a bearing 50 (fourth bearing). The bearing 50 is located between the spigot joint 42 and the counter drive gear 24 in the extension direction of the gear shaft 34, and supports the gear shaft 34 from the thrust direction. Specifically, the bearing 50 comes into contact with a surface 34b of the gear shaft 34 facing the rotor shaft 32. A thrust force (a force in the extension direction of the gear shaft 34) is generated from the gear shaft 34 to the counter drive gear 24. The bearing 50 absorbs the thrust force.

[0042] According to the second embodiment, the bearing 50 receives thrust force, stabilizing the gear shaft 34 and making it less likely to displace. The rotor shaft 32 and the gear shaft 34 are spline-connected and spigot-connected. A bearing 44 supports the rotor shaft 32 and the gear shaft 34. Suppressing whirling reduces noise.

[0043] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0044] 10 Internal combustion engine 12 Planetary gear mechanism 14 Gear train 17 Drive shaft 18 Drive wheels 19 Differential case 20 Input shaft 21 Counter output shaft 22, 32 Rotor shaft 23, 24 Counter drive gear 25, 27 Counter driven gear 26 Countershaft 28 Differential drive pinion gear 29 Differential ring gear 30 MG shaft 31 cases 32a Internal teeth 34 Gear shaft 34a external teeth 34b side 40 Spline joint 42 Spigot joint 44, 46, 47, 48, 49, 50 Bearings 100, 100R, 200 drive unit MG1, MG2 motor generators

Claims

1. a first shaft connected to the electric motor; a second shaft that rotates together with the first shaft; a first bearing supporting the first shaft and the second shaft; the first shaft and the second shaft are spline-connected at a spline connection portion and spigot-jointed at a spigot-joint connection portion, the spigot joint portion is located closer to the tip end of the first shaft than the spline joint portion, At the spigot joint portion, an inner peripheral surface of the first shaft and an outer peripheral surface of the second shaft are in contact with each other, The first bearing surrounds the spigot joint portion where the first shaft and the second shaft are spigot-jointed, and supports the first shaft and the second shaft.

2. one end of the two ends of the first shaft and one end of the two ends of the second shaft are spline-connected and spigot-jointed together, a second bearing supporting the other of the two ends of the first shaft; 2. The drive device according to claim 1, further comprising: a third bearing supporting the other end of the two ends of the second shaft.

3. 3. The drive device according to claim 1, further comprising a gear provided on the second shaft.

4. 4. The drive device according to claim 1, further comprising a fourth bearing that supports the second shaft in a thrust direction.

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