Drive device

Abstract

To efficiently operate both a counter gear and a hypoid gear in a drive device.SOLUTION: A drive unit mounted on a vehicle, comprises: an electric motor housed in a motor chamber; a first shaft arranged parallel or coaxially with a rotor shaft of the electric motor; a counter gear that transmits the rotation of the rotor shaft to the first shaft; a second shaft that rotates wheels of the vehicle; a hypoid gear that transmits the rotation of the first shaft to the second shaft; an oil seal that seals a gap between the first shaft and a case; a first lubricant housed in the motor chamber and a counter gear chamber; and a second lubricant housed in a hypoid gear chamber.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a drive device.

[0002] The drive unit disclosed in Patent Document 1 has an electric motor, a pinion shaft, a wheel axle, a counter gear, and a hypoid gear. The pinion shaft is arranged parallel to the rotor shaft of the electric motor. The counter gear transmits the rotation of the rotor shaft to the pinion shaft. The wheel axle extends in a different direction from the rotor shaft. The hypoid gear transmits the rotation of the pinion shaft to the wheel axle. The electric motor is housed in an electric motor chamber. The counter gear and the hypoid gear are housed in a common gear chamber. Lubricating oil is stored in the gear chamber. The gear chamber and the electric motor chamber are isolated from each other by a sealant or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-050886 A Summary of the Invention [Problem to be solved by the invention]

[0004] The type of lubricant suitable for the counter gear is different from the type of lubricant suitable for the hypoid gear. In Patent Document 1, the same lubricant is used for the counter gear and the hypoid gear, so the performance of either the counter gear or the hypoid gear cannot be fully utilized. This specification proposes a technology for appropriately operating both the counter gear and the hypoid gear. [Means for solving the problem]

[0005] The drive unit disclosed in this specification is mounted on a vehicle and includes a case having a motor chamber, a counter gear chamber, and a hypoid gear chamber, a motor housed in the motor chamber, a first shaft arranged parallel or coaxially with a rotor shaft of the motor and extending from the counter gear chamber to the hypoid gear chamber, a counter gear housed in the counter gear chamber and transmitting the rotation of the rotor shaft to the first shaft, a second shaft extending from the hypoid gear chamber to the outside of the case and rotating wheels of the vehicle, a hypoid gear housed in the hypoid gear chamber and transmitting the rotation of the first shaft to the second shaft, an oil seal that seals a gap between the first shaft and the case, a first lubricating oil housed in the motor chamber and the counter gear chamber, and a second lubricating oil housed in the hypoid gear chamber.

[0006] In this drive unit, the counter gear chamber is isolated from the hypoid gear chamber by an oil seal. Therefore, different lubricants can be used in the counter gear chamber and the hypoid gear chamber. Therefore, both the counter gear and the hypoid gear can be operated efficiently. In addition, a common first lubricant is used in the electric motor chamber and the counter gear chamber. Even if a common lubricant is used for the electric motor and the counter gear, they can still operate efficiently. In addition, by using a common lubricant for the electric motor chamber and the counter gear chamber, the increase in the types of lubricant used in the drive unit can be suppressed. [Brief description of the drawings]

[0007] [Figure 1] FIG. [Diagram 2] FIG. 4 is a cross-sectional view of the left drive system 90 taken along the left-right direction. [Diagram 3] FIG. 4 is a cross-sectional view of the left drive system 90 along the front-rear direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The following are additional features of the drive device disclosed in this specification:

[0009] The viscosity of the first lubricant may be lower than the viscosity of the second lubricant.

[0010] According to this configuration, the high viscosity second lubricating oil can prevent oil film shortage on the tooth surface of the hypoid gear, and the low viscosity first lubricating oil can rotate the rotor and counter gear with low loss.

[0011] The drive device may further include an oil pump that circulates the first lubricating oil between the motor chamber and the counter gear chamber.

[0012] With this configuration, the electric motor and the counter gear can be cooled. EXAMPLES

[0013] A drive unit 10 of the embodiment shown in Fig. 1 is mounted on an electric vehicle. In Fig. 1, an arrow FR indicates the front direction of the vehicle, and an arrow RH indicates the right direction of the vehicle. The drive unit 10 has a case 12. A left drive system 90 and a right drive system 91 are provided inside the case 12. The left drive system 90 drives a left rear wheel 92 of the electric vehicle. The right drive system 91 drives a right rear wheel 93 of the electric vehicle. The left drive system 90 and the right drive system 91 are symmetrical, so the left drive system 90 will be described below.

[0014] Inside the case 12, there are a left motor chamber 13, a left terminal block chamber 14, a left counter gear chamber 15, and a left hypoid gear chamber 16. The left terminal block chamber 14 is disposed rearward of the left motor chamber 13. The left counter gear chamber 15 is disposed rearward of the left terminal block chamber 14. The left hypoid gear chamber 16 is disposed rearward of the left counter gear chamber 15. The left motor chamber 13 houses an electric motor 20. The left terminal block chamber 14 houses a terminal block 20e. The terminal block 20e is provided with a terminal for supplying power to the electric motor 20. The left counter gear chamber 15 houses a gear set constituting a counter gear. The left hypoid gear chamber 16 houses a gear set constituting a hypoid gear. A left drive system 90 is constituted by the electric motor 20, the gear set in the left counter gear chamber 15, and the gear set in the left hypoid gear chamber 16, etc.

[0015] As shown in FIG. 2, the electric motor 20 has a rotor 20a and a stator 20b. The rotor 20a has a rotor shaft 20c. The rotor shaft 20c has a shaft 20c-1 and a shaft 20c-2. The shafts 20c-1 and 20c-2 each have a cylindrical shape. One end of the shaft 20c-1 is inserted into the shaft 20c-2. The shaft 20c-1 is fixed to the shaft 20c-2 by a spline engagement. The rotor 20a is housed in the left motor chamber 13 with the rotor shaft 20c extending along the front-rear direction of the electric vehicle. The rotor shaft 20c penetrates the partition wall of the case 12 and extends from the left motor chamber 13 to the left counter gear chamber 15. More specifically, the shaft 20c-1 extends from the left motor chamber 13 to the left terminal block chamber 14, and the shaft 20c-2 extends from the left terminal block chamber 14 to the left counter gear chamber 15. The rotor 20a is rotatably supported by a bearing provided in the case 12. The stator 20b is disposed around the rotor 20a. The stator 20b is electrically connected to the terminal block 20e. When a current is supplied to the stator 20b via the terminal block 20e, the rotor 20a rotates.

[0016] A countershaft 23 and an output shaft 24 are disposed in the left counter gear chamber 15. The countershaft 23 is disposed parallel to the rotor shaft 20c. More specifically, the central axis of the countershaft 23 is parallel to the central axis of the rotor shaft 20c. The countershaft 23 is rotatably supported by a bearing provided in the case 12. The output shaft 24 is disposed behind the rotor shaft 20c. The output shaft 24 extends coaxially with the rotor shaft 20c. More specifically, the central axis of the output shaft 24 coincides with an extension line of the central axis of the rotor shaft 20c. A through hole 18 is provided in the partition wall between the left counter gear chamber 15 and the left hypoid gear chamber 16. The output shaft 24 extends from the left counter gear chamber 15 to the left hypoid gear chamber 16 through the through hole 18. A gap between the outer circumferential surface of the output shaft 24 and the inner circumferential surface of the through hole 18 is sealed by an oil seal 25. The front end of the output shaft 24 is inserted into the central hole of the rotor shaft 20c from the rear end of the rotor shaft 20c. The gap between the inner peripheral surface of the rotor shaft 20c and the outer peripheral surface of the output shaft 24 is sealed by an oil seal 26. The output shaft 24 is rotatably supported by a bearing provided in the case 12.

[0017] The gear set provided in the left counter gear chamber 15 has gears 21a, 21b, 22a, and 22b. The gear 21a is a cylindrical gear and is fixed to the rotor shaft 20c. The gear 21b is a cylindrical gear and is fixed to the counter shaft 23. The gear 21a is engaged with the gear 21b. The gears 21a and 21b form a first counter gear 21. The gear 22a is a cylindrical gear and is fixed to the counter shaft 23. The gear 22b is a cylindrical gear and is fixed to the output shaft 24. The gear 22a is engaged with the gear 22b. The gears 22a and 22b form a second counter gear 22.

[0018] When the rotor shaft 20c rotates, the gear 21a rotates, and the driving force is transmitted from the gear 21a to the gear 21b. Therefore, the gear 21b, the countershaft 23, and the gear 22a rotate. When the gear 22a rotates, the driving force is transmitted from the gear 22a to the gear 22b. Therefore, the gear 22b and the output shaft 24 rotate. The gear ratio of the first counter gear 21 is set so that the rotation speed of the countershaft 23 is slower than the rotation speed of the rotor shaft 20c. In addition, the gear ratio of the second counter gear 22 is set so that the rotation speed of the output shaft 24 is slower than the rotation speed of the countershaft 23. Therefore, the output shaft 24 rotates at a slower speed than the rotor shaft 20c. In this way, a reducer is configured by the drive system in the left counter gear chamber 15.

[0019] A drive shaft 27 is disposed in the left hypoid gear chamber 16. The drive shaft 27 extends in the left-right direction of the electric vehicle. The drive shaft 27 extends from the left hypoid gear chamber 16 through the left wall of the case 12 to the outside of the case 12. As shown in FIG. 1, a left rear wheel 92 is connected to the left end of the drive shaft 27. The drive shaft 27 is rotatably supported by a bearing provided in the case 12.

[0020] As shown in Fig. 2, the gear set provided in the left hypoid gear chamber 16 has gears 28a and 28b. Gear 28a is a truncated cone gear and is fixed to the output shaft 24. Gear 28b is a truncated cone gear and is fixed to the drive shaft 27. Gear 28a is engaged with gear 28b. Gears 28a and 28b form a hypoid gear 28.

[0021] When the electric motor 20 is driven, the rotor shaft 20c rotates. As described above, when the rotor shaft 20c rotates, the output shaft 24 rotates. When the output shaft 24 rotates, the gear 28a rotates, and the driving force is transmitted from the gear 28a to the gear 28b. As a result, the gear 28b and the drive shaft 27 rotate. When the drive shaft 27 rotates, the left rear wheel 92 rotates. In this way, the left drive system 90 rotates the left rear wheel 92 by the driving force of the electric motor 20.

[0022] As shown in FIG. 3, a first lubricating oil 80 is stored at the bottom of the left counter gear chamber 15. A second lubricating oil 82 is stored at the bottom of the left hypoid gear chamber 16. The first lubricating oil 80 is a different type of lubricating oil from the second lubricating oil 82. The viscosity of the first lubricating oil 80 is lower than the viscosity of the second lubricating oil 82. The left counter gear chamber 15 and the left hypoid gear chamber 16 are separated by a partition wall except for the through hole 18. The through hole 18 is sealed by an oil seal 25. The oil seal 25 prevents the lubricating oil from leaking between the left counter gear chamber 15 and the left hypoid gear chamber 16. In this way, the left counter gear chamber 15 and the left hypoid gear chamber 16 are separated so that the lubricating oils do not mix.

[0023] The lower part of the gear 28b is immersed in the second lubricating oil 82. Therefore, when the gear 28b rotates, the hypoid gear 28 is lubricated by the second lubricating oil 82. In general, a higher pressure is likely to be applied to the tooth surface of a hypoid gear than to the tooth surface of a counter gear (i.e., a helical gear, a spur gear, etc.). For this reason, the oil film is likely to break on the tooth surface of the hypoid gear. In this embodiment, the pressure applied to the tooth surface of the hypoid gear 28 is higher than the pressure applied to the tooth surfaces of the first counter gear 21 and the second counter gear 22. However, in this embodiment, the hypoid gear 28 is lubricated by the second lubricating oil 82, which has a high viscosity, so that the oil film break on the tooth surface of the hypoid gear 28 is prevented.

[0024] An oil suction port 34 is provided at the bottom of the left counter gear chamber 15. As shown in FIG. 2, the drive unit 10 has an oil circulation passage 35. The upstream end of the oil circulation passage 35 is connected to the oil suction port 34. As described above, the rotor shaft 20c has a cylindrical shape. A shaft passage 36 is formed by the central hole of the rotor shaft 20c. The downstream end of the oil circulation passage 35 is connected to the front end of the shaft passage 36. An oil pump 30 is provided in the oil circulation passage 35. The oil pump 30 sends out the first lubricating oil 80 in the oil circulation passage 35 from the oil suction port 34 toward the shaft passage 36. The rotor shaft 20c (i.e., the shaft 20c-1) in the left motor chamber 13 is provided with a plurality of oil discharge ports 40 extending from the shaft passage 36 to the outer circumferential surface of the rotor shaft 20c. The rotor shaft 20c (i.e., shaft 20c-2) in the left counter gear chamber 15 is provided with a plurality of oil discharge ports 42 extending from the shaft passage 36 to the outer circumferential surface of the rotor shaft 20c. A shaft passage 38 extending along the central axis of the output shaft 24 is provided inside the output shaft 24. The front end of the shaft passage 38 is connected to the shaft passage 36. The output shaft 24 is provided with a plurality of oil discharge ports 44 extending from the shaft passage 38 to the outer circumferential surface of the output shaft 24.

[0025] During the operation of the electric motor 20, the oil pump 30 operates. When the oil pump 30 operates, the first lubricating oil 80 stored in the left counter gear chamber 15 is supplied to the shaft flow passage 36 in the rotor shaft 20c through the oil suction port 34 and the oil circulation flow passage 35. The first lubricating oil flows rearward through the shaft flow passage 36. The electric motor 20 is cooled by the first lubricating oil flowing through the shaft flow passage 36. A part of the first lubricating oil in the shaft flow passage 36 is discharged from the oil discharge port 40 into the left electric motor chamber 13. The electric motor 20 is lubricated by the first lubricating oil discharged into the left electric motor chamber 13. The first lubricating oil discharged into the left electric motor chamber 13 flows to the left counter gear chamber 15 through an oil flow passage (not shown) and the left terminal block chamber 14. A part of the first lubricating oil in the shaft flow passage 36 is discharged from the oil discharge port 42 into the left counter gear chamber 15. The first counter gear 21 is lubricated and cooled by the first lubricating oil discharged from the oil discharge port 42. The first lubricating oil that has flowed through the shaft passage 36 to the rear end flows into the shaft passage 38 in the output shaft 24. The first lubricating oil in the shaft passage 38 is discharged from the oil discharge port 44 into the left counter gear chamber 15. The second counter gear 22 is lubricated and cooled by the first lubricating oil discharged from the oil discharge port 44.

[0026] As described above, the first lubricating oil circulates between the left motor chamber 13 and the left counter gear chamber 15, thereby cooling and lubricating the electric motor 20, the first counter gear 21, and the second counter gear 22. Since the pressure applied to the tooth surfaces of the first counter gear 21 and the second counter gear 22 is low, the oil film on the tooth surfaces of the first counter gear 21 and the second counter gear 22 can be prevented from breaking even if the viscosity of the first lubricating oil is low. Furthermore, since the viscosity of the first lubricating oil is low, the rotor 20a, the first counter gear 21, and the second counter gear 22 can rotate with low loss. Furthermore, since the viscosity of the first lubricating oil is low, the first lubricating oil can be efficiently circulated by the oil pump 30. In this way, the loss is suppressed by using the first lubricating oil having a low viscosity for the electric motor 20 and the counter gear.

[0027] In the above-described embodiment, the first counter gear 21 and the second counter gear 22 are provided in the left counter gear chamber 15. However, one set of counter gears may be provided in the left counter gear chamber 15. In this case, a counter shaft may be arranged to extend from the left counter gear chamber 15 to the left hypoid gear chamber 16, and each shaft and gear may be arranged so that driving force is transmitted from the counter shaft to the drive shaft via the hypoid gear.

[0028] In the above-described embodiment, the left counter gear chamber 15 functions as a storage tank for storing the first lubricating oil. However, a storage tank for storing the first lubricating oil may be provided separately from the left counter gear chamber 15. In this case, the left counter gear chamber 15 does not need to store the first lubricating oil.

[0029] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0030] 10: Drive unit 12: Case 13:Left motor room 15: Left counter gear room 16: Left hypoid gear chamber 20: Electric motor 20c: rotor shaft 21: 1st counter gear 22: 2nd counter gear 23: Countershaft 24: Output shaft 25: Oil seal 27: Drive shaft 28: Hypoid gear 80:1st lubricant 82:Second lubricant

Claims

1. A drive device mounted on a vehicle, a case having a motor chamber, a counter gear chamber, and a hypoid gear chamber; an electric motor accommodated in the electric motor chamber; a first shaft disposed parallel to or coaxial with a rotor shaft of the electric motor and extending from the counter gear chamber to the hypoid gear chamber; a counter gear housed in the counter gear chamber and configured to transmit rotation of the rotor shaft to the first shaft; A second shaft extending from the hypoid gear chamber to the outside of the case and rotating wheels of the vehicle; a hypoid gear housed in the hypoid gear chamber and configured to transmit rotation of the first shaft to the second shaft; an oil seal that seals a gap between the first shaft and the case; A first lubricating oil is contained in the electric motor chamber and the counter gear chamber; A second lubricating oil contained in the hypoid gear chamber; A drive unit having the same.

2. The drive device according to claim 1 , wherein the first lubricant has a lower viscosity than the second lubricant.

3. 3. The drive device according to claim 1, further comprising an oil pump for circulating the first lubricating oil between the electric motor chamber and the counter gear chamber.

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