JP7110955B2 - in-wheel motor - Google Patents

Description

The present invention relates to an in-wheel motor.

Patent Literature 1 discloses an in-wheel motor in which a plurality of electric motors are provided inside one wheel as drive sources for driving the wheel.

WO2012/131953

In the in-wheel motor, a plurality of gears are arranged between the electric motor and the drive shaft of the wheel. However, in the configuration described in Patent Document 1, a plurality of electric motors are provided inside the wheel, and the output gear of the second electric motor is structured to mesh with external teeth provided on the outer peripheral surface of the ring gear. There is a risk that the physique will increase in size. Furthermore, since a plurality of electric motors are arranged inside the wheel, it is difficult to secure a sufficient installation space for the gear mechanism inside the wheel, and it is difficult to set the reduction ratio of the gear mechanism to a large value.

The present invention has been made in view of the above circumstances, and in a configuration having a plurality of electric motors, it is possible to reduce the size and increase the reduction ratio of the gear mechanism installed inside the wheel. The object is to provide a wheel motor.

The present invention provides an in-wheel motor including, inside a wheel, a plurality of electric motors for driving the wheel, and a gear mechanism for transmitting power output from the plurality of electric motors to a drive shaft of the wheel, The gear mechanism has a drive gear that is an external gear provided on the output shaft of each electric motor, and a driven gear that is configured by an internal gear that meshes with each drive gear, and each output shaft is different from the drive shaft of the wheel. The plurality of electric motors, which are arranged on different axes, are arranged along the circumferential direction of the driven gear at positions overlapping each other in the axial direction of the wheel.

According to the present invention, since the driven gear is an internal gear, it is possible to increase the number of teeth of the driven gear and set the reduction ratio of the gear mechanism to a large value. In addition, it becomes possible to mesh a plurality of drive gears with the internal gear at different positions in the circumferential direction. Therefore, a plurality of electric motors can be arranged along the circumferential direction of the driven gear at positions overlapping each other in the axial direction, and the axial length can be shortened.

FIG. 1 is a diagram schematically showing an in-wheel motor of an embodiment. FIG. 2 is a diagram for explaining the internal structure of the in-wheel motor. FIG. 3 is a diagram schematically showing a motor case and a gear case. FIG. 4 is a diagram showing a vibration canceling image of the motor case. FIG. 5 is a diagram for explaining the reduction ratio of a gear pair including an internal gear. FIG. 6 is a diagram schematically showing a modified in-wheel motor. FIG. 7 is a diagram for explaining the internal structure of the in-wheel motor of the modification. FIG. 8 is a diagram for explaining the schematic configuration of the motor drive system.

Hereinafter, in-wheel motors according to embodiments of the present invention will be specifically described with reference to the drawings. In addition, this invention is not limited to embodiment described below.

FIG. 1 is a diagram schematically showing an in-wheel motor of an embodiment. FIG. 2 is a diagram for explaining the internal structure of the in-wheel motor. Note that FIG. 2 schematically shows a cross section taken along the line AA of FIG.

The in-wheel motor 1 includes four motors 10, 20, 30, and 40 functioning as power sources for driving the wheels 2 inside the wheels 3 of the wheels 2, and outputs from the respective motors 10, 20, 30, and 40. and a gear mechanism 50 that transmits power to the drive shaft 5 of the wheel 2 . This in-wheel motor 1 has a plurality of motors 10, 20, 30, 40 for one wheel 2, and has a structure in which a gear mechanism 50 and a plurality of motors 10, 20, 30, 40 are unitized. have. The wheel 2 includes a wheel 3 and a tire 4. As shown in FIG.

As shown in FIG. 1 , four motors 10 , 20 , 30 , 40 are arranged along the circumferential direction of the wheel 2 . The first motor 10, the second motor 20, the third motor 30, and the fourth motor 40 are all composed of small motor generators. In the in-wheel motor 1, a plurality of small motors are arranged in tandem. In the example shown in FIG. 1 , the first motor 10 , the second motor 20 , the third motor 30 and the fourth motor 40 are arranged in this order clockwise in the circumferential direction of the wheel 2 . A first motor 10 and a third motor 30 are arranged at symmetrical positions with respect to the rotation center O of the wheel 2 . Similarly, the second motor 20 and the fourth motor 40 are arranged at symmetrical positions with respect to the rotation center of the wheel 2 . The first motor 10, the second motor 20, the third motor 30, and the fourth motor 40 are arranged so that the centers of rotation of the motors 10, 20, 30, and 40 are equidistantly positioned in the circumferential direction of the wheel 2. It is Motors 10 , 20 , 30 , 40 are arranged on axes different from the rotation center axis of wheel 2 .

The first motor 10 has a rotor 11 and a stator 12 . The rotor 11 and stator 12 are housed inside a motor case 13 . As shown in FIG. 2, stator 12 is fixed to motor case 13 . The output shaft 14 of the first motor 10 is a rotating shaft that rotates integrally with the rotor 11 and is rotatably supported with respect to the motor case 13 via bearings. The output shaft 14 is arranged parallel to the drive shaft 5 of the wheel 2 and rotates on a rotation center axis different from that of the drive shaft 5 . A first drive gear 51 is provided on one end of the output shaft 14 . The first drive gear 51 is an external gear serving as an output gear of the first motor 10 , and rotates integrally with the output shaft 14 while being arranged inside the gear case 56 . The first drive gear 51 meshes with an internal driven gear 55 having teeth on its inner periphery. The power output from the first motor 10 is transmitted to the wheels 2 via a gear pair in which the first drive gear 51 and the driven gear 55 mesh.

The second motor 20 , the third motor 30 , and the fourth motor 40 also include rotors 21 , 31 , 41 and stators 22 , 32 , 42 like the first motor 10 . As shown in FIG. 1, the second motor 20 includes a rotor 21 and a stator 22 housed inside a motor case 23, and a second drive gear 52 provided on an output shaft that rotates integrally with the rotor 21 to drive a wheel. Output power toward 2. The second drive gear 52 is an external gear serving as an output gear of the second motor 20 and meshes with an internal driven gear 55 . The third motor 30 has a rotor 31 and a stator 32 housed inside a motor case 33 , and supplies power to the wheels 2 from a third drive gear 53 provided on an output shaft 34 that rotates integrally with the rotor 31 . Output. The third drive gear 53 is an external gear serving as an output gear of the third motor 30 and meshes with an internal driven gear 55 . Further, as shown in FIG. 2, the third motor 30 is arranged at a position overlapping the first motor 10 in the axial direction. The fourth motor 40 has a rotor 41 and a stator 42 housed inside a motor case 43, and outputs power to the wheels 2 from a fourth drive gear 54 provided on an output shaft that rotates integrally with the rotor 41. do. The fourth drive gear 54 is an external gear serving as an output gear of the fourth motor 40 and meshes with an internal driven gear 55 . The in-wheel motor 1 does not include a motor arranged on the same axis as the drive shaft 5, and the output shafts of the motors 10, 20, 30, 40 are arranged on axes different from the drive shaft 5. ing.

In this way, the drive gears 51, 52, 53, 54 attached to the output shafts of the motors 10, 20, 30, 40 mesh with the driven gear 55, which is an internal gear. Power output from each motor 10 , 20 , 30 , 40 is transmitted to the drive shaft 5 of the wheel 2 via the gear mechanism 50 . The gear mechanism 50 is a reduction gear mechanism that reduces the rotation speed of the motor and transmits the power of the motor to the wheels 2 .

The gear mechanism 50 has four drive gears 51 , 52 , 53 , 54 and a driven gear 55 and is housed inside a gear case 56 . As shown in FIG. 1, four drive gears 51, 52, 53, and 54 mesh with a driven gear 55, which is an internal gear, at equal intervals in the circumferential direction. As shown in FIG. 2 , the driven gear 55 is provided on the drive shaft 5 connected to the wheel 2 and rotates integrally with the drive shaft 5 . The drive shaft 5 is a rotating shaft functioning as an output shaft of the gear mechanism 50 and a wheel shaft connected to the wheel 3 . The drive shaft 5 is arranged on the rotation center axis of the wheel 2 and rotates integrally with the wheel 2 .

Further, as shown in FIG. 3, the motor cases 13, 23, 33, 43 are arranged independently along the circumferential direction and provided at positions overlapping each other in the axial direction. The first motor 10 is housed inside the motor case 13 . The second motor 20 is housed inside the motor case 23 . The third motor 30 is housed inside the motor case 33 . The fourth motor 40 is housed inside the motor case 43 . That is, the motors 10, 20, 30, 40 are arranged at positions overlapping each other in the axial direction. Each motor case 13 , 23 , 33 , 43 is integrated with the gear case 56 . In the in-wheel motor 1, a plurality of motors 10, 20, 30, 40 housed inside respective motor cases 13, 23, 33, 43 and a gear mechanism 50 are unitized.

As shown in FIGS. 3 and 1, the gear case 56 is provided with a suspension connecting surface 56a on the side on which the motor cases 13, 23, 33, 43 are provided. A suspension arm (not shown) is connected to the gear case 56 via an elastic body (mount) at a suspension mounting portion 60 (shown in FIG. 1).

Further, inside the gear case 56, a band brake 61 (shown in FIG. 2) arranged on the outer circumference of the driven gear 55 is accommodated. Further, the gear case 56 and the motor cases 13, 23, 33, 43 are separated by partition walls. The inside of the gear case 56 is filled with oil having excellent braking characteristics. The inside of each motor case 13, 23, 33, 43 is filled with oil having excellent heat transfer and insulation properties. Note that the oil need only be stored in the case, and the case does not necessarily have to be filled.

Here, the NV reduction effect of the in-wheel motor 1 will be described with reference to FIG. 4 . FIG. 4 is a diagram showing a vibration canceling image of the motor case.

As shown in FIG. 4, deformation of each motor case 13, 23, 33, 43 caused by the generation of the rotating magnetic field causes vibration for each motor case. In the in-wheel motor 1, the magnetic field rotation period is shifted by a half phase so that the vibration of each motor case is offset by the vibration generated in the opposite or adjacent motor case. As for the relationship between adjacent motors, for example, the first motor 10 and the second motor 20 are arranged so that their magnetic field rotation periods are in opposite phases. As for the relationship of the opposed motors, for example, the first motor 10 and the third motor 30 are arranged so that the magnetic field rotation periods have the same phase. As a unit of the in-wheel motor 1 , vertical vibration, horizontal vibration, and torsional vibration can thus be canceled on the suspension connection surface 56 a of the gear case 56 .

As described above, according to the embodiment, by arranging a plurality of small motors inside one wheel 2, both high rotation and high output of the in-wheel motor 1 can be achieved. One wheel 2 can be driven by a combined force of the power output from each motor 10 , 20 , 30 , 40 . Therefore, the output of the in-wheel motor 1 can be increased. In addition, since the required power can be distributed among the plurality of motors 10, 20, 30, 40, it is possible to reduce the size of each motor in the radial direction, thereby improving durability against centrifugal force during high rotation. be able to. Therefore, the rotation of the in-wheel motor 1 can be increased.

In addition, since the motors 10, 20, 30 and 40 are arranged along the circumferential direction of the wheel 2 at positions overlapping each other in the axial direction, the mountability is improved. As a result, the in-wheel motor 1 has a configuration capable of outputting the necessary power, and the size in the axial direction can be reduced. Therefore, according to the in-wheel motor 1, it is possible to achieve both high rotation, high output, and mountability.

Further, in a gear pair using internal gears, meshing efficiency is improved and loss can be reduced, so torque density is improved. Therefore, by using the driven gear 55 as an internal gear, the speed reduction ratio of the gear mechanism 50 can be set large, and the meshing efficiency can be improved. For example, as shown in FIG. 5, two parallel rotating shafts are connected by a gear pair in which the external gears mesh with each other so that power can be transmitted (the gear pair on the left side of FIG. 5), and the external gear and the internal gear are connected by a pair of meshing gears so as to be able to transmit power (a pair of gears on the right side of FIG. 5). When the distance L between the input-side rotary shaft (drive shaft) and the output-side rotary shaft (driven shaft) is the same, and the number of teeth of the drive-side external gear is the same, the drive-side The reduction ratio of the gear pair in which the external gear meshes with the internal gear on the driven side is larger than the reduction ratio of the gear pair in which the external gear on the drive side meshes with the external gear on the driven side. This is because even under the constraint that the distance between the parallel shafts is the same, the diameter of the internal gear can be set larger in the case of the internal gear than in the case of the external gear, and the number of teeth of the internal gear is This is because many can be set. As described above, in the in-wheel motor 1, it is possible to increase the speed reduction ratio of the gear mechanism 50 in the limited installation space inside the wheel 3, thereby suppressing an increase in size in the radial direction. can.

Furthermore, by arranging a plurality of small motors evenly in the circumferential direction of the wheel 2, NV (noise, vibration) caused by the motors can be reduced. In addition, since the suspension arm is connected to the gear case 56 via an elastic body, the vibration caused by the motor can be damped, making it difficult to transmit the vibration to the vehicle body.

In addition, since the motor cases 13, 23, 33, and 43 contain oil with excellent heat conductivity, the heat generated by the motors can be radiated to the motor cases via the oil. Thereby, the heat dissipation of each motor 10, 20, 30, 40 is improved.

Further, since the band brake 61 is arranged on the outer peripheral side of the driven gear 55 of the internal gear, the length in the axial direction (axial length) can be shortened. As a result, the in-wheel motor 1 can be downsized in the axial direction. If a brake device using a brake disc and a caliper were to be used, the axial length of the unit would be longer than that of the band brake 61 .

Modifications of the above embodiment will now be described with reference to FIGS. 6 to 8. FIG. FIG. 6 is a diagram schematically showing an in-wheel motor 1 of a modified example. FIG. 7 is a diagram for explaining the internal structure of the in-wheel motor 1 of the modification. FIG. 8 is a diagram for explaining the schematic configuration of the motor drive system.

As shown in FIGS. 6 and 7 , the in-wheel motor 1 of the modification has a structure in which an inverter 70 is provided in the gear case 56 . The inverter 70 is arranged at a central position surrounded by the motor cases 13, 23, 33, and 43, and is fixed to the surface of the gear case 56 on the inner side of the vehicle (suspension connecting surface 56a side). That is, one inverter 70 electrically connected to a plurality of motors 10 , 20 , 30 , 40 is arranged inside the wheel 3 of one wheel 2 .

As shown in FIG. 8 , in motor drive system 100 , motors 10 , 20 , 30 and 40 are electrically connected to battery 80 via one inverter 70 . Each motor 10 , 20 , 30 , 40 is driven by electric power stored in the battery 80 . The inverter 70 and the battery 80 are electrically connected by two wires. Also, the inverter 70 and the four motors 10, 20, 30, 40 are electrically connected by three wires. These three wires are the wires connected to the U-phase coils of the motors 10, 20, 30, and 40, the wires connected to the V-phase coils of the motors 10, 20, 30, and 40, and the V-phase coils of the motors 10, 20, 30, and 40. and wires connected to the W-phase coils of the motors 10 , 20 , 30 , 40 .

According to this modification, one inverter 70 can simultaneously drive a plurality of motors 10 , 20 , 30 , 40 . Also, the number of parts can be reduced, and motor wiring can be reduced. Furthermore, it is possible to suppress transmission of the vibration of each motor case 13, 23, 33, 43 to the inverter case.

1 in-wheel motor 2 wheel 3 wheel 4 tire 5 drive shaft 10 first motor 11 rotor 12 stator 13 motor case 14 output shaft 20 second motor 21 rotor 22 stator 23 motor case 30 third motor 31 rotor 32 stator 33 motor case 40 Fourth Motor 41 Rotor 42 Stator 43 Motor Case 50 Gear Mechanism 51 First Drive Gear 52 Second Drive Gear 53 Third Drive Gear 54 Fourth Drive Gear 55 Driven Gear 56 Gear Case 60 Suspension Mounting Portion 61 Band Brake 70 Inverter 80 Battery 100 Motor drive system

Claims (1)

An in-wheel motor comprising, inside a wheel, a plurality of electric motors for driving the wheel, and a gear mechanism for transmitting power output by the plurality of electric motors to a drive shaft of the wheel,
a plurality of electric motor cases each accommodating an electric motor;
a gear case that houses the gear mechanism;
prepared,
The gear mechanism is
A drive gear of an external gear provided on the output shaft of each electric motor;
and a driven gear configured by an internal gear meshing with each drive gear,
each output shaft is arranged on a different axis than the drive shaft of the wheel,
The plurality of electric motors are arranged along the circumferential direction of the driven gear at positions overlapping each other in the axial direction of the wheel ,
The plurality of electric motor cases are arranged independently along the circumferential direction, are provided at positions overlapping each other in the axial direction, and are integrated with the gear case,
The gear case and each electric motor case are partitioned by partition walls,
Insulating oil is contained inside each motor case
An in-wheel motor characterized by:

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