Power device

Abstract

To provide a power device that outputs power from an electric motor to left and right driving shafts, which is configured so that the electric motor and a differential gear are prevented from being enlarged in size to improve performance in mounting the power device on a vehicle.SOLUTION: A power device 10A comprises: a motor 20 (an electric motor) as a power source mounted on a vehicle 1A; a differential gear 30 arranged coaxially with the motor 20, outside the motor 20; and a pair of deceleration mechanisms 40 arranged among the differential gear 30 and left and right driving shafts 4R and 4L. The motor 20 includes a hollow rotor 22 in which a through-hole 22a extending along an axial direction X is formed at a center part. The differential gear 30 includes: a differential ring gear 31 (an input member) that is connected to the rotor 22, to which power is inputted; a first output shaft 36 connected to one (a deceleration mechanism 40R) of the pair of deceleration mechanisms 40; and a second output shaft 37 extended through the through-hole 22a of the rotor 22 and connected to the other (a deceleration mechanism 40L) of the pair of deceleration mechanisms 40.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power unit that is mounted on a vehicle and outputs power from an electric motor to left and right drive shafts. [Background technology]

[0002] Conventionally, there are known technologies relating to power units that are mounted on vehicles and output power from an electric motor to left and right drive shafts. For example, Patent Document 1 describes a powertrain assembly that incorporates a differential gear assembly (differential device) inside the hollow rotor shaft of an electric motor. In this powertrain assembly, a planetary assembly, a differential gear assembly, and a planetary assembly are coaxially arranged inside the rotor shaft, thereby shortening the axial width. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6966035 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the structure described in the above Patent Document 1, although the axial width of the power plant can be shortened, the differential device and the planetary gear mechanism as a reduction mechanism are inserted into the rotor of the electric motor, so that the outer diameter of the electric motor becomes large. Also, as shown in FIG. 1 of the above Patent Document 1, for example, in the power plant of a commonly used electric vehicle, the differential device is connected to the rotor of the electric motor via multiple reduction gears, and the torque input to the differential device is increased by the amount of torque amplified by the reduction gears. Therefore, the differential device is likely to be enlarged in size in order to ensure durability, which may result in an increase in the size of the power plant.

[0005] The present invention has been made in consideration of these problems, and its purpose is to suppress the increase in size of the electric motor and differential device in a power unit that outputs power from an electric motor to left and right drive axles, and to improve the mountability of the power unit on a vehicle. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the power unit of the present invention comprises an electric motor mounted on a vehicle as a power source, a differential gear arranged coaxially with the electric motor outside the electric motor, and a pair of reduction gear mechanisms arranged between the differential gear and left and right drive shafts, the electric motor including a hollow rotor having a through hole formed in its center extending along the axial direction of the left and right drive shafts, and the differential gear including an input member connected to the rotor to input power, a first output shaft connected to one of the pair of reduction gear mechanisms, and a second output shaft extending through the through hole of the rotor and connected to the other of the pair of reduction gear mechanisms.

[0007] With this configuration, the differential gear is arranged coaxially outside the electric motor, and only the second output shaft of the differential gear components is passed through the rotor, so that the diameter of the electric motor can be made smaller than when the differential gear is housed inside the rotor. In addition, by connecting the input member of the differential gear to the rotor of the electric motor and providing a pair of reduction mechanisms between the differential gear and the left and right drive shafts, the torque from the electric motor is input to the differential gear, and the amplified torque after reduction is not input. As a result, the size of the differential gear can be suppressed. Therefore, according to the present invention, in a power unit that outputs power from the electric motor to the left and right drive shafts, it is possible to suppress the size of the electric motor and the differential gear and improve the mountability of the power unit on a vehicle.

[0008] Preferably, the power plant further includes a power supply device that supplies electricity to the electric motor, the electric motor and the differential gear are disposed offset from the left and right drive shafts in the radial direction of the left and right drive shafts, and the power supply device is disposed in a space formed between the electric motor and the differential gear, the pair of reduction mechanisms, and the left and right drive shafts. With this configuration, it is possible to secure a space for disposing the power supply device and improve the mountability of the power plant on a vehicle, while disposing the power supply device close to the electric motor.

[0009] In addition, it is preferable that the input member of the differential device constitutes a parking gear of the vehicle. With this configuration, it is possible to reduce the number of parts of the vehicle on which the power unit is mounted.

[0010] In addition, the pair of reduction mechanisms is preferably composed of a plurality of external gears that mesh with each other or are connected to each other. With this configuration, it is easier to set a large reduction ratio compared to a case where a planetary gear mechanism is used as the reduction mechanism. Also, by rearranging the plurality of external gears, it is easy to accommodate changes in the arrangement positions of the electric motor and the differential device. Effect of the Invention

[0011] According to the present invention, in a power plant that outputs power from an electric motor to left and right drive shafts, it is possible to suppress an increase in size of the electric motor and the differential device, and to improve the mountability of the power plant on a vehicle. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing a main part of a vehicle equipped with a power unit according to an embodiment; [Diagram 2] FIG. 11 is a schematic diagram showing a main part of a vehicle equipped with a power unit according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the main parts of a vehicle equipped with a power unit according to the embodiment. In FIG. 1, the up-down direction in the drawing indicates the vertical direction, and the left-right direction indicates the vehicle width direction of the vehicle 1A. The vehicle 1A is an electric vehicle that travels by transmitting power from a motor 20 (electric motor) as a power source to left and right front wheels 2R, 2L as drive wheels via left and right drive shafts 4R, 4L. The drive shafts 4R, 4L are arranged coaxially. The vehicle 1A is equipped with a power unit 10A including the motor 20, a differential gear 30, a pair of reduction mechanisms 40, and a power supply device 50.

[0014] The motor 20 is disposed at a position offset from the drive shafts 4R and 4L in the radial direction Y of the drive shafts 4R and 4L. The motor 20 includes a rotor 22 as a rotor including a permanent magnet (not shown). The rotor 22 is rotatable around an axis parallel to the axial direction X of the drive shafts 4R and 4L. The rotor 22 is configured as a hollow member having a through hole 22a formed in its center and extending along the axial direction X. In addition, a stator (not shown) is provided on the outer periphery of the rotor 22 as a fixed part. In the motor 20, AC power is supplied from a power supply device 50 to a plurality of coils (not shown) attached to the stator, and the rotor 22 including a permanent magnet is rotated by a magnetic field generated by the plurality of coils.

[0015] The differential device 30 is a bevel gear type differential device including a differential ring gear 31 (input member), a differential case 32, a pair of pinion gears 33, a first side gear 34, and a second side gear 35. The differential device 30 is disposed coaxially with the motor 20, and is disposed offset from the drive shafts 4R, 4L together with the motor 20 in the radial direction Y.

[0016] The differential ring gear 31 is connected to the rotor 22 of the motor 20 and rotates together with the rotor 22. The differential case 32 is connected to the differential ring gear 31 and accommodates therein a pair of pinion gears 33, a first side gear 34, and a second side gear 35. The pair of pinion gears 33 are bevel gears supported by the differential case 32 and rotate around the rotor 22 together with the differential case 32. The first side gear 34 and the second side gear 35 are accommodated in the differential case 32 and mesh with the pair of pinion gears 33, and are supported rotatably around the axis of the rotor 22.

[0017] Also, a first output shaft 36 extends from the first side gear 34 coaxially with the rotor 22. The first output shaft 36 extends along the axial direction X, penetrates the differential case 32, and is connected to the front wheel 2R via one of a pair of reduction mechanisms 40 (a reduction mechanism 40R described later). On the other hand, a second output shaft 37 extends from the second side gear 35 coaxially with the rotor 22. The second output shaft 37 extends along the axial direction X, passes through a through hole 22a of the rotor 22 formed in a hollow shape, and extends to the front wheel 2L side beyond the rotor 22. The second output shaft 37 is connected to the front wheel 2L via the other of the pair of reduction mechanisms 40 (a reduction mechanism 40L described later).

[0018] As a result, when the vehicle 1A travels straight, the differential device 30 rotates about the axis of the rotor 22 without relative rotation between the pair of pinion gears 33 and the first and second side gears 34 and 35, and transmits the power of the motor 20 to the front wheels 2R and 2L. On the other hand, when the vehicle 1A turns, the differential device 30 rotates about the axis of the rotor 22 while absorbing the difference in rotation speed between the front wheels 2R and 2L by relative rotation between the pair of pinion gears 33 and the first and second side gears 34 and 35, and transmits the power of the motor 20 to the front wheels 2R and 2L.

[0019] In this embodiment, the differential ring gear 31 of the differential device 30 constitutes a part of a parking lock device for locking the rotation of the drive shafts 4R, 4L when the shift range of the vehicle 1A is set to the P range (parking range). Specifically, the differential ring gear 31 is formed with a plurality of external teeth (not shown), and when the P range is selected by the driver, a claw portion formed on a parking sprag (not shown) engages with the external teeth, thereby fixing the differential ring gear 31 so as to be unable to rotate.

[0020] The pair of reduction mechanisms 40 include a reduction mechanism 40R connected to the front wheel 2R and a reduction mechanism 40L connected to the front wheel 2L. The reduction mechanism 40R is disposed closer to the drive shaft 4R (front wheel 2R) than the motor 20 and the differential gear 30 in the axial direction X. The reduction mechanism 40L is disposed closer to the drive shaft 4L (front wheel 2L) than the motor 20 and the differential gear 30 in the axial direction X. Therefore, a space V (see the range indicated by the dashed line) is formed between the motor 20 and the differential gear 30, the pair of reduction mechanisms 40, and the drive shafts 4R and 4L.

[0021] Each of the reduction mechanisms 40R and 40L is composed of a plurality of external gears that mesh with each other or are connected to each other. Specifically, the reduction mechanisms 40R and 40L include a first reduction gear 41, a second reduction gear 42, a third reduction gear 43, and a fourth reduction gear 44. The first reduction gear 41 is an external gear arranged coaxially with the rotor 22 and is connected to the differential device 30. Specifically, the first reduction gear 41 of the reduction mechanism 40R is connected to a first output shaft 36 extending from a first side gear 34 of the differential device 30. On the other hand, the first reduction gear 41 of the reduction mechanism 40L is connected to a second output shaft 37 extending from a second side gear 35 of the differential device 30. The second reduction gear 42 is an external gear that meshes with the first reduction gear 41 and is arranged below the first reduction gear 41. The third reduction gear 43 is disposed coaxially with the second reduction gear 42 and is connected to the second reduction gear 42. The fourth reduction gear 44 is an external gear disposed below the third reduction gear 43 and meshes with the third reduction gear, and is disposed coaxially with the drive shafts 4R and 4L. The fourth reduction gear 44 of the reduction mechanism 40R is connected to the drive shaft 4R, and the fourth reduction gear 44 of the reduction mechanism 40L is connected to the drive shaft 4L. As a result, the pair of reduction mechanisms 40 reduce the rotation from the motor 20 at a predetermined reduction ratio while amplifying the torque and outputting it to each of the drive shafts 4R and 4L.

[0022] The power supply device 50 includes an inverter 52 and an oil tank 54. The inverter 52 is a power conversion device that converts DC power from a power source (not shown), such as a battery mounted on a vehicle, into AC power and supplies the AC power to a plurality of coils (not shown) of the motor 20. The inverter 52 is an oil-cooled inverter and is cooled by oil stored in an oil tank 54. The oil tank 54 may be disposed at a location other than the power supply device 50. The inverter 52 may be water-cooled or air-cooled. When the inverter 52 is water-cooled, the oil tank 54 may be a tank that stores cooling water. When the inverter 52 is air-cooled, the oil tank 54 may be omitted. Furthermore, the power supply device 50 may include other devices for supplying power to the motor 20, such as a converter as a boost circuit, and a battery as a power source. The power supply device 50 is disposed in the space V formed between the motor 20, the differential device 30, the pair of reduction mechanisms 40, and the drive shafts 4R and 4L. The power supply device 50 may be disposed in sufficient proximity to the motor 20 so as to satisfy the minimum ground clearance required for the vehicle 1A.

[0023] As described above, the power unit 10A of the embodiment includes a motor 20 (electric motor) as a power source mounted on the vehicle 1A, a differential gear 30 arranged coaxially with the motor 20 outside the motor 20, and a pair of reduction gears 40 arranged between the differential gear 30 and the left and right drive shafts 4R, 4L, and the motor 20 includes a hollow rotor 22 having a through hole 22a formed in its center and extending along the axial direction X, and the differential gear 30 includes a differential ring gear 31 (input member) connected to the rotor 22 to input power, a first output shaft 36 connected to one of the pair of reduction gears 40 (reduction gear 40R), and a second output shaft 37 extending through the through hole 22a of the rotor 22 and connected to the other of the pair of reduction gears 40 (reduction gear 40L).

[0024] With this configuration, the differential device 30 is arranged coaxially outside the motor 20, and only the second output shaft 37 of the components of the differential device 30 is passed through the rotor 22, so that the diameter of the motor 20 (rotor 22) can be made smaller than when the differential device 30 is housed inside the rotor 22. In addition, by connecting the differential ring gear 31 of the differential device 30 to the rotor 22 of the motor 20 and providing a pair of reduction mechanisms 40 between the differential device 30 and the left and right drive shafts 4R and 4L, the torque from the motor 20 is input to the differential device 30, and the amplified torque after reduction is not input. As a result, the size of the differential device 30 can be suppressed. Therefore, in the power unit 10A that outputs the power from the motor 20 to the left and right drive shafts 4R and 4L, it is possible to suppress the size of the motor 20 and the differential device 30 from being increased, and improve the mountability of the power unit 10A on a vehicle.

[0025] Furthermore, being able to reduce the diameter of the rotor 22 as described above means, in other words, that the outer diameter (volume) of the rotor 22 can be made larger when the outer diameter of the rotor 22 is the same as when the differential gear 30 is housed inside the rotor 22. Therefore, by appropriately adjusting the outer diameter of the rotor 22, it is possible to achieve both the magnitude of the output required of the motor 20 and the improvement of the mountability of the power unit 10A on the vehicle 1A by making the motor 20 smaller.

[0026] Furthermore, in the power unit 10A, it is not necessary to arrange the motor 20 and the differential gear 30 coaxially with the drive shafts 4R, 4L. Therefore, even if the motor 20 and the differential gear 30 are formed with a relatively large diameter, it is easy to ensure the minimum ground clearance required for the vehicle 1A. This makes it possible to further improve the mountability of the power unit 10A on the vehicle 1A.

[0027] In addition, because the differential gear 30 is disposed outside the motor 20, the structure and size of the differential gear 30 are not restricted by the size of the rotor 22, as compared to a case in which the differential gear 30 is housed inside the rotor 22. Furthermore, it becomes easier to provide a supply path and mechanism for lubricating the differential gear 30.

[0028] The power unit 10A further includes a power supply unit 50 that supplies power to the motor 20, the motor 20 and the differential unit 30 being disposed offset from the left and right drive shafts 4R, 4L in the radial direction Y of the left and right drive shafts 4R, 4L, and the power supply unit 50 being disposed in a space V formed between the motor 20 and the differential unit 30, the pair of reduction mechanisms 40, and the left and right drive shafts 4R, 4L. This configuration allows the power supply unit 50 to be disposed close to the motor 20 while ensuring a space for disposing the power supply unit 50 and improving the mountability of the power unit 10A on the vehicle 1A.

[0029] Moreover, the differential ring gear 31 of the differential device 30 constitutes a parking gear of the vehicle 1A. With this configuration, it is possible to reduce the number of parts of the vehicle 1A on which the power unit 10A is mounted.

[0030] Further, the pair of reduction mechanisms 40 are composed of a plurality of external gears (first reduction gear 41, second reduction gear 42, third reduction gear 43, and fourth reduction gear 44) that mesh with each other or are connected to each other. In the power plant 10A, not only the differential gear 30 but also the pair of reduction mechanisms 40 are disposed outside the motor 20, so that the pair of reduction mechanisms 40 are not restricted by the size of the rotor 22. This makes it possible to employ a reduction mechanism using a plurality of external gears (first reduction gear 41, second reduction gear 42, third reduction gear 43, and fourth reduction gear 44). This configuration makes it easier to set a large reduction ratio compared to a case in which a planetary gear mechanism is used as the pair of reduction mechanisms 40.

[0031] FIG. 2 is a schematic diagram showing the main parts of a vehicle 1B to which a power unit 10B of another example is applied. In the power unit 10B, the motor 20 and the differential gear 30 are disposed at a position close to the drive shafts 4R and 4L at the bottom of the vehicle 1B. The motor 20 and the differential gear 30 only need to be disposed so as to satisfy the minimum ground clearance required for the vehicle 1B, and are disposed here offset slightly above the drive shafts 4R and 4L. On the other hand, the power supply device 50 is provided close to the motor 20 in the space above the motor 20 and the differential gear 30. As described above, in the power unit 10B, it is not necessary to dispose the motor 20 coaxially with the drive shafts 4R and 4L, and the diameter of the motor 20 can be suppressed from being increased. Therefore, even if the motor 20 and the differential gear 30 are disposed at the bottom of the vehicle 1B, it is possible to easily ensure the minimum ground clearance required for the vehicle 1B.

[0032] Furthermore, in the power plant 10B, the external gears of the pair of reduction gear mechanisms 40 are rearranged in accordance with the positions of the motor 20 and the differential gear 30. Specifically, the second reduction gear 42 is arranged above the first reduction gear 41, and the fourth reduction gear 44 is arranged below the third reduction gear 43, resulting in a configuration in which the entire system is folded up and down. In this way, by rearranging, for example, the positions of the multiple external gears (the first reduction gear 41, the second reduction gear 42, the third reduction gear 43, and the fourth reduction gear 44), it is possible to easily accommodate changes in the positions of the motor 20, the differential gear 30, and the power supply device 50.

[0033] Although the description of the embodiment is finished above, the aspect of the present invention is not limited to this embodiment. For example, the differential device 30 is not limited to the bevel gear type differential device shown in the embodiment as long as it includes the above-mentioned input member, the first output shaft, and the second output shaft. The differential device 30 may be, for example, a planetary gear mechanism type differential device or an LSD (Limited Slip Differential Gear). As described above, in the power plants 10A and 10B of the embodiment, the size and structure of the differential device 30 are not restricted by the size of the rotor 22, so that various configurations can be easily adopted. In addition, the input member of the differential device 30 does not have to constitute the parking gear of the vehicles 1A and 1B.

[0034] In addition, the pair of speed reduction mechanisms 40 may be speed reduction mechanisms using a planetary gear mechanism. In addition, the power supply device 50 is not limited to being mounted at the position shown in Figs. 1 and 2, and may be mounted at any position on the vehicles 1A and 1B. [Explanation of symbols]

[0035] Cars 1A and 1B 2R, 2L front wheel 4R, 4L drive shaft 10A, 10B power unit 20 Motor (electric motor) 22 Rotor 22a Through hole 30 differential gear 31 Differential ring gear (input member) 36 First output shaft 37 Second output shaft 40 Pair of reduction mechanisms 50 Power supply equipment V space X-axis direction Y radial direction

Claims

1. An electric motor as a power source mounted on the vehicle; a differential device arranged coaxially with the electric motor outside the electric motor; a pair of reduction mechanisms disposed between the differential device and the left and right drive shafts; Equipped with The electric motor includes a hollow rotor having a through hole formed in a center thereof and extending along the axial direction of the left and right drive shafts, The differential device includes an input member connected to the rotor to receive power, a first output shaft connected to one of the pair of reduction mechanisms, and a second output shaft extending through the through hole of the rotor and connected to the other of the pair of reduction mechanisms. Power plant.

2. A power supply device for supplying power to the electric motor is further provided, the electric motor and the differential gear are disposed offset from the left and right drive shafts in a radial direction of the left and right drive shafts, 2. The power plant according to claim 1, wherein the power supply device is disposed in a space defined between the electric motor, the differential device, the pair of reduction mechanisms, and the left and right drive shafts.

3. 2. The power plant of claim 1, wherein the input member of the differential comprises a parking gear for the vehicle.

4. 4. The power plant according to claim 1, wherein the pair of reduction mechanisms are formed of a plurality of external gears that mesh with each other or are connected to each other.

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