JP2019035419A - Drive device for vehicle and design method of drive device for vehicle - Google Patents

Abstract

To provide a drive device for vehicle capable of suppressing groan auditory sense of human recognizes as fluctuation noise.SOLUTION: A drive device 1 for vehicle comprises: a first rotary electrical machine 30A connected to a left front wheel; a second rotary electrical machine 30B connected to a right front wheel; a first speed reducer 40A configured to reduce rotation of the first rotary electrical machine 30A; and a second speed reducer 40B configured to reduce rotation of the second rotary electrical machine 30B, and whose speed reduction ratio is set so as to differ from a speed reduction ratio of the first speed reducer 40A.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vehicle drive device and a method for designing a vehicle drive device.

  In recent years, as a drive device mounted on a vehicle such as a hybrid vehicle or an electric vehicle, a device including a pair of rotating electric machines has been devised (see, for example, Patent Document 1). As one type of such a drive device, there is one in which a pair of rotating electrical machines are provided coaxially on the left and right, and a left wheel and a right wheel are connected to a rotor of each rotating electrical machine. In this type of driving device, the left wheel is rotated by the left rotating electric machine, and the right wheel is rotated by the right rotating electric machine, thereby driving the vehicle.

JP 2013-38937 A

  By the way, for example, when the left and right wheels are rotating at the same peripheral speed, such as when the vehicle is going straight, due to the outer diameter tolerance of the tire, there is a difference between the rotation speed of the left wheel and the rotation speed of the right wheel. There is. In this case, there is also a difference between the rotational speed of the left rotating electrical machine and the rotational speed of the right rotating electrical machine. There is a possibility that a beat will be recognized.

  Therefore, the present invention provides a vehicle drive device and a vehicle drive device design method capable of suppressing beats that are recognized as fluctuating sounds by human hearing.

  The vehicle drive device of the present invention (for example, the vehicle drive device 1 in the embodiment) is a first rotating electrical machine (for example, the first in the embodiment) connected to the first wheel (for example, the left front wheel LWf in the embodiment). The rotating electric machine 30A), the second rotating electric machine (for example, the second rotating electric machine 30B in the embodiment) connected to the second wheel (for example, the right front wheel RWf in the embodiment), and the drive rotation of the first rotating electric machine. The first reduction gear (for example, the first reduction gear 40A in the embodiment) that decelerates and the drive rotation of the second rotating electrical machine are decelerated, and a reduction ratio that is different from the reduction ratio of the first reduction gear is set. 2 reduction gears (for example, 2nd reduction gear 40B in an embodiment).

  When a pair of rotating electrical machines rotate with a slight difference in rotational speed, the rotational order components in the operating sound of each rotating electrical machine combine to produce a fluctuation in the amplitude of the combined waveform, which varies in human hearing. A beat that is recognized as sound occurs. According to the present invention, for example, when the first wheel and the second wheel are rotated at the same peripheral speed, it is possible to make a difference in the rotational speeds of the first rotating electrical machine and the second rotating electrical machine. For this reason, even if a slight difference occurs in the rotation speed of the first wheel and the second wheel due to the difference in the outer diameter of the tires of the first wheel and the second wheel, the difference in the rotation speed between the pair of rotating electric machines is beaten. It can be made larger than the difference in the number of rotations that occurs. Therefore, it is possible to suppress a beat that is recognized as a fluctuating sound by human hearing.

  In the above vehicle drive device, the difference between the reduction ratio of the first reduction gear and the reduction ratio of the second reduction gear is that the first wheel and the second wheel are rotating at the same peripheral speed. Thus, the frequency difference of each rotation order component of the operating sound generated in each of the first rotating electrical machine and the second rotating electrical machine is set to be equal to or greater than a value recognized as a fluctuating sound within a predetermined frequency band. It is desirable that

  If there is a difference in outer diameter between the tires of the first wheel and the second wheel, the rotational speeds of the first wheel and the second wheel will be different even if the first wheel and the second wheel are rotating at the same peripheral speed. Differences occur. According to the present invention, in the state where the first wheel and the second wheel are rotating at the same peripheral speed, the frequency of each rotation order component of the operating sound generated in each of the first rotating electrical machine and the second rotating electrical machine is obtained. Since the difference is greater than or equal to a value recognized as a fluctuating sound within a predetermined frequency band, it is possible to suppress beats that occur when the frequency difference is less than the value recognized as a fluctuating sound.

  In the above vehicle drive device, the value recognized as the fluctuating sound is preferably 20 Hz.

  According to the present invention, the difference in frequency of each rotational order component of the operating sound generated in each of the first rotating electrical machine and the second rotating electrical machine is 20 Hz or more, which is the upper limit of the frequency generally recognized as a beat, It is possible to suppress beats that are recognized by human hearing as fluctuating sounds.

  The vehicle drive device design method of the present invention includes a first rotating electrical machine (for example, the first rotating electrical machine 30A in the embodiment) coupled to a first wheel (for example, the left front wheel LWf in the embodiment), and a second wheel. (E.g., the second rotating electrical machine (e.g., the second rotating electrical machine 30 </ b> B in the embodiment) coupled to the right front wheel RWf in the embodiment) and a first speed reducer (e.g., decelerating the drive rotation of the first rotating electrical machine) A vehicle drive device design method comprising: a first speed reducer 40A) in the embodiment; and a second speed reducer (for example, the second speed reducer 40B in the embodiment) that decelerates the drive rotation of the second rotating electrical machine. And the difference between the reduction ratio of the first reduction gear and the reduction ratio of the second reduction gear is determined so that the first wheel and the second wheel rotate at the same peripheral speed. Rotating electric machine and the second rotation The difference between the frequencies of the rotational order component of the operation sound generated by the respective machine is set to be less than the value that is recognized as a variation sound within a predetermined frequency band, characterized in that.

  According to the present invention, even if a slight difference occurs in the rotational speeds of the first wheel and the second wheel due to the difference in the outer diameters of the tires of the first wheel and the second wheel, the first rotating electric machine and the second rotating electric machine It is possible to suppress beats that occur when the difference in the frequency of each rotation order component of the operating sound generated is less than the value recognized as a fluctuating sound. Therefore, it is possible to suppress a beat that is recognized as a fluctuating sound by human hearing.

  According to the present invention, it is possible to suppress beats that are recognized as fluctuation sounds by human hearing.

It is a block diagram which shows schematic structure of the vehicle carrying the vehicle drive device of embodiment. It is a longitudinal section showing the whole vehicle drive device of an embodiment. It is explanatory drawing explaining the beat frequency of a wheel drive device. It is a characteristic view which shows the relationship between a frequency and acoustic sensitivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the front / rear, up / down / left / right directions are the same as the front / rear, up / down, left / right directions in the vehicle unless otherwise specified, and in the drawings, arrow UP indicates upward, arrow FR indicates front, and arrow LH indicates left. Yes. The left-right direction in the vehicle is the same as the vehicle width direction.

FIG. 1 is a block diagram illustrating a schematic configuration of a vehicle on which the vehicle drive device of the embodiment is mounted.
The vehicle drive device 1 of the present embodiment uses a pair of rotating electrical machines 30A and 30B as a drive source for driving the front wheels, and is used in, for example, a vehicle 100 having a drive system as shown in FIG. In the following description, a case where the vehicle drive device 1 is used for front wheel drive will be described as an example, but the vehicle drive device 1 may be used for rear wheel drive.

  As shown in FIG. 1, a vehicle 100 is a hybrid vehicle having a drive unit 101 in which an internal combustion engine 102 and a rotating electrical machine 103 are connected in series. In the vehicle 100, for example, the power of the drive unit 101 disposed behind the vehicle 100 is transmitted to the rear wheels (the left rear wheel LWr and the right rear wheel RWr) via the transmission 104. On the other hand, the power of the vehicle drive device 1 provided, for example, in front of the vehicle 100 separately from the drive unit 101 is transmitted to the front wheels (the left front wheel LWf (first wheel) and the right front wheel RWf (second wheel)). The rotating electrical machine 103 of the drive unit 101 and the rotating electrical machines 30A and 30B of the vehicle drive device 1 are connected to the battery 106 via the PDU 105 (power drive unit), and the power supply from the battery 106 and the rotating electrical machines 103 and 30A are connected. , 30B to the battery 106, energy regeneration is performed via the PDU 105.

FIG. 2 is a longitudinal sectional view showing the entire vehicle drive device of the embodiment.
As shown in FIG. 2, the vehicle drive device 1 mainly includes a pair of axles 10A and 10B, a housing 20, a pair of rotating electrical machines 30A and 30B, and a pair of speed reducers 40A and 40B. . The pair of axles 10 </ b> A and 10 </ b> B are left and right axles connected to front wheels LWf and RWf (see FIG. 1) of the vehicle 100. Specifically, the pair of axles 10A is a left axle 10A connected to the left front wheel LWf of the vehicle 100 and a right axle 10B connected to the right front wheel RWf of the vehicle 100. The pair of axles 10A and 10B each extend along the left-right direction. The pair of axles 10A and 10B are arranged in a state in which the ends on the same axis and in the left-right direction are opposed to each other. In the following description of the vehicle drive device 1, the direction along the central axis of the axles 10A and 10B is referred to as “axial direction”, and the circumferential direction around the axles 10A and 10B is simply referred to as “circumferential direction”. A direction extending radially from the axles 10A and 10B perpendicularly to the axle is referred to as a “radial direction”.

  The housing 20 includes a central case 21 disposed in the central portion in the axial direction, and a left side case 23A and a right side case 23B disposed on the left and right sides of the central case 21 so as to sandwich the central case 21, respectively. Yes. The housing 20 is formed in a cylindrical shape as a whole, and is disposed coaxially with the pair of axles 10A and 10B. A partition wall 25 extending inward in the radial direction is provided at the end of each side case 23A, 23B on the central case 21 side. In addition, a left and right dividing wall 27 extending inward in the radial direction is provided at the central portion of the central case 21 in the axial direction. The housing 20 houses a pair of rotating electrical machines 30A and 30B and a pair of speed reducers 40A and 40B. The housing 20 is supported by a vehicle frame (not shown).

  The pair of rotating electrical machines 30A and 30B are connected to the left front wheel LWf via the left axle 10A and drive the left front wheel LWf, and to the right front wheel RWf via the right axle 10B and connected to the right front wheel RWf. The second rotating electrical machine 30B to be driven. The pair of rotating electrical machines 30 </ b> A and 30 </ b> B are coaxial with the pair of axles 10 </ b> A and 10 </ b> B and are disposed symmetrically within the housing 20. The number of pole pairs of the pair of rotating electrical machines 30A and 30B is set to be the same. In the present embodiment, the pair of rotating electrical machines 30A and 30B is set to a 4-pole pair.

  The first rotating electrical machine 30A includes a stator 31A, a rotor 33A, and a shaft 35A. The stator 31 </ b> A is formed in a cylindrical shape and is fixed inside the left side case 23 </ b> A of the housing 20. The rotor 33A is formed in a cylindrical shape, and is disposed on the radially inner side of the stator 31A. Inside the rotor 33A, a shaft 35A is inserted and fixed by press-fitting or the like. The shaft 35A is formed in a cylindrical shape and is extrapolated to the left axle 10A. The shaft 35A protrudes from both sides of the rotor 33A in the axial direction. The shaft 35 </ b> A is supported by the left side case 23 </ b> A of the housing 20 through a bearing 61 in a state of being rotatable with respect to the left axle 10 </ b> A and is supported by the partition wall 25 of the housing 20 through a bearing 62. . Thus, the rotor 33A is provided integrally with the shaft 35A so as to be rotatable with respect to the housing 20. A resolver 37 </ b> A that detects rotational position information of the rotor 33 </ b> A is provided at an end portion on the axially outer side (left side) of the shaft 35 </ b> A.

  The second rotating electrical machine 30B has the same structure as the first rotating electrical machine 30A. That is, the second rotating electrical machine 30B includes a stator 31B, a rotor 33B, and a shaft 35B. Further, a resolver 37B that detects rotational position information of the rotor 33B is provided at an end portion on the axially outer side (right side) of the shaft 35B.

  The pair of reducers 40A and 40B are a first reducer 40A that decelerates the drive rotation of the first rotating electrical machine 30A, and a second reducer 40B that decelerates the drive rotation of the second rotating electrical machine 30B. The pair of reduction gears 40A and 40B are planetary gear type reduction gears. The pair of speed reducers 40 </ b> A and 40 </ b> B are disposed symmetrically within the housing 20.

  The first speed reducer 40 </ b> A is disposed between the partition wall 25 extending from the left side case 23 </ b> A and the left and right dividing walls 27. The first reduction gear 40A includes a sun gear 41A, a planetary gear 43A, a planetary carrier 47A, and a ring gear 50A. The sun gear 41A is formed on the outer peripheral surface of the axially inner end of the shaft 35A of the first rotating electrical machine 30A. The planetary gear 43 </ b> A is a double pinion having a first pinion 44 having a large diameter that meshes with the sun gear 41 </ b> A and a second pinion 45 having a smaller diameter than the first pinion 44. The first pinion 44 and the second pinion 45 are integrally formed with the same axis and the second pinion 45 being offset inward in the axial direction with respect to the first pinion 44. The planetary gear 43A is rotatably supported by the planetary carrier 47A. The planetary carrier 47A has an axially inner end that extends radially inward and is spline-fitted to the left axle 10A, and is supported so as to be integrally rotatable with the left axle 10A. The planetary carrier 47A is supported on the partition wall 25 of the housing 20 through the bearing 63 at the end on the outer side in the axial direction.

  The ring gear 50 </ b> A includes a gear portion 51 that meshes with the second pinion 45 of the planetary gear 43 </ b> A, a small diameter portion 52 that is smaller in diameter than the gear portion 51 and disposed inward of the gear portion 51, and an axially inner end of the gear portion 51. And a connecting portion 53 that connects the end of the small-diameter portion 52 and the end portion on the axially outer side in the radial direction.

  The second reduction gear 40B is disposed between the partition wall 25 extending from the right side case 23B and the left and right dividing walls 27. The second speed reducer 40B has the same structure as the first speed reducer 40A except that the speed reduction ratio described later is different. That is, the second reduction gear 40B includes a sun gear 41B, a planetary gear 43B, a planetary carrier 47B, and a ring gear 50B. The small diameter portion 52 of the ring gear 50B is opposed to the small diameter portion 52 of the ring gear 50A of the first reduction gear 40A in the axial direction.

  A one-way clutch 55 is disposed between the connecting portions 53 of the pair of ring gears 50A and 50B. The one-way clutch 55 is, for example, a sprag type, and transmits only power in one direction to the ring gears 50A and 50B and cuts off power in the other direction. Small diameter portions 52 of the ring gears 50A and 50B are spline-fitted to the inner race 56 of the one-way clutch 55. As a result, the ring gears 50 </ b> A and 50 </ b> B are coupled to each other and rotate integrally with the inner race 56. The outer race 57 of the one-way clutch 55 is fixed to the left and right dividing walls 27 of the housing 20.

  A hydraulic brake 59 is disposed between the gear portion 51 of the ring gear 50A of the first reduction gear 40A and the housing 20. The hydraulic brake 59 is formed so that a braking force can be applied to the ring gear 50A. The hydraulic brake 59 fixes the ring gear 50 </ b> A to the housing 20 by applying a braking force to the ring gear 50 </ b> A. Further, the hydraulic brake 59 allows the ring gear 50A to freely rotate with respect to the housing 20 by releasing the braking force applied to the ring gear 50A. As described above, since the pair of ring gears 50A and 50B are coupled to each other, the ring gear 50A of the first reduction gear 40A is fixed to the housing 20 so that the ring gear 50B of the second reduction gear 40B is also fixed. Fixed to the housing 20. Further, the ring gear 50A of the first reduction gear 40A is allowed to freely rotate with respect to the housing 20, and the ring gear 50B of the second reduction gear 40B is also allowed to freely rotate with respect to the housing 20.

  The reduction ratios of the first reduction gear 40A and the second reduction gear 40B are different. As a result, when the left front wheel LWf and the right front wheel RWf are rotating at the same peripheral speed, such as when the vehicle 100 is traveling straight, there is a difference between the rotational speed of the first rotating electrical machine 30A and the rotational speed of the second rotating electrical machine 30B. To suppress the occurrence of beats described later. The peripheral speed is a distance that a point on the ground contact surface of the tire moves per unit time.

Next, an example will be described in which a beat that is recognized as a fluctuating sound occurs in human hearing.
FIG. 3 is an explanatory diagram for explaining the beat frequency of the vehicle drive device, (a) is a schematic diagram of a vehicle on which the vehicle drive device of the comparative example is mounted, and (b) is a diagram of the first rotating electrical machine. It is a figure which shows the waveform of the operating sound which arises, (c) is a figure which shows the waveform of the operating sound which arises in a 2nd rotary electric machine, (d) is a synthesis | combination of the operational noise which arises in a 1st rotary electric machine and a 2nd rotary electric machine. It is a figure which shows a waveform.

  As shown in FIG. 3A, the vehicle drive device 201 of the comparative example includes a first rotating electrical machine 230A coupled to the left wheel LW, a second rotating electrical machine 230B coupled to the right wheel RW, The first reduction device 240A that decelerates the drive rotation of the rotary electric machine 230A and the second reduction device 240B that decelerates the drive rotation of the second rotary electric machine 230B are provided. The number of pole pairs of each of the first rotating electrical machine 230A and the second rotating electrical machine 230B is set to be the same. The reduction ratios of the first reduction gear 240A and the second reduction gear 240B are set to be the same.

  Here, for example, when the left wheel LW and the right wheel RW are rotating at the same peripheral speed, such as when the vehicle is traveling straight, due to the outer diameter tolerance of the tire, the rotation speed of the left wheel LW and the rotation speed of the right wheel RW If there is a difference, a difference occurs between the rotation speed of the rotor of the first rotating electrical machine 230A and the rotation speed of the rotor of the second rotating electrical machine 230B. Then, as shown in FIGS. 3B and 3C, there is a difference between the frequency of the operating sound G1 of the first rotating electrical machine 230A and the frequency of the operating sound G2 of the second rotating electrical machine 230B. When operating sounds having different frequencies are synthesized, as shown in FIG. 3 (d), periodic fluctuation occurs in the synthesized waveform G3, and the intensity of the sound is heard at a period corresponding to the frequency of the fluctuation. That is, a beat is generated. The beat frequency is equal to the absolute value of the frequency difference between the operating sounds G1 and G2 before synthesis. In general, human hearing recognizes beats of less than 20 Hz as fluctuating sounds.

Next, as a method for designing the vehicle drive device 1 of the embodiment, a method for setting the reduction ratios of the first reduction gear 40A and the second reduction gear 40B will be described.
FIG. 4 is a characteristic diagram showing the relationship between frequency and acoustic sensitivity. In FIG. 4, the vertical axis indicates acoustic sensitivity, and the horizontal axis indicates frequency. FIG. 4 shows the result of measuring the sound generated in the vicinity of the vehicle drive device 1 a plurality of times in the passenger compartment in the vehicle of the example to which the configuration of the vehicle 100 of the present embodiment is applied. As shown in FIG. 4, the frequency band from 700 Hz to less than 2400 Hz is a band in which sound (vibration) is easily transmitted from the vehicle drive device 1 to the vehicle interior. That is, it is possible to suppress the beat from being transmitted to the vehicle interior by suppressing the beat in the frequency band of 700 Hz to less than 2400 Hz. Therefore, in the following description, it is assumed that the frequency band of the operating sound of a rotating electrical machine that can be a problem as a beat is 700 Hz or more and less than 2400 Hz.

Table 1 shows the relationship between the rotation speed of the rotating electrical machine and the frequency of the operating sound for each rotation order. The data shown in Table 1 is data for a four-pole pair of rotating electrical machines, and is intended for the first rotating electrical machine 30A and the second rotating electrical machine 30B of the embodiment.
A case where the rotation order is 8th will be described. As shown in Table 1, when the rotational speed of the rotating electrical machine is 5250 rpm or more and less than 18000 rpm, the operating sound of the rotating electrical machine is 700 Hz or more and less than 2400 Hz. The condition for generating a beat of less than 20 Hz in the range of the rotational speed of the rotating electrical machine is when the difference in rotational speed between the pair of rotating electrical machines is greater than 0 rpm and less than 150 rpm. The ratio of 150 rpm to 5250 rpm is about 2.9%. The ratio of 150 rpm to 18000 rpm is about 0.8%. That is, if the difference in the rotational speeds of the pair of rotating electrical machines is 2.9% or more of the average value of the rotational speeds of the pair of rotating electrical machines, no beat is recognized by human hearing.

  A case where the rotation order is 16th will be described. As shown in Table 1, when the rotational speed of the rotating electrical machine is 2625 rpm or more and less than 9000 rpm, the operating sound of the rotating electrical machine is 700 Hz or more and less than 2400 Hz. The condition for generating a beat of less than 20 Hz in the range of the rotational speed of the rotating electrical machine is when the difference in rotational speed between the pair of rotating electrical machines is greater than 0 rpm and less than 75 rpm. The ratio of 75 rpm to 2625 rpm is about 2.9%. The ratio of 75 rpm to 9000 rpm is about 0.8%. That is, if the difference in the rotational speeds of the pair of rotating electrical machines is 2.9% or more of the average value of the rotational speeds of the pair of rotating electrical machines, no beat is recognized by human hearing.

  A case where the rotation order is 24th will be described. As shown in Table 1, when the rotational speed of the rotating electrical machine is 1750 rpm or more and less than 6000 rpm, the operating sound of the rotating electrical machine is 700 Hz or more and less than 2400 Hz. The condition for generating a beat of less than 20 Hz in the rotational speed range of the rotating electrical machine is when the difference in rotational speed between the pair of rotating electrical machines is greater than 0 rpm and less than 50 rpm. The ratio of 50 rpm to 1750 rpm is about 2.9%. The ratio of 50 rpm to 6000 rpm is about 0.8%. That is, if the difference in the rotational speeds of the pair of rotating electrical machines is 2.9% or more of the average value of the rotational speeds of the pair of rotating electrical machines, no beat is recognized by human hearing.

  As described above, the pair of rotating electrical machines 30A and 30B has a difference in rotational speed of 2.9% or more of the average value of the rotational speeds of the pair of rotating electrical machines 30A and 30B regardless of the rotational order. Generation of beats of less than 20 Hz can be suppressed in a frequency band of less than 20.

Here, if the tire outer diameter tolerances of the left and right front wheels LWf and RWf are + a% and −b%, the maximum difference between the tire outer diameters of the left and right front wheels LWf and RWf is (a + b)%. Therefore, when the vehicle 100 is traveling straight, the difference in rotational speed between the left and right front wheels LWf and RWf due to the difference in tire outer diameter between the left and right front wheels LWf and RWf is (a + b)% at the maximum. Therefore, by setting the reduction ratio of the first reduction gear 40A and the reduction ratio of the second reduction gear 40B to be ± {(2.9 + a + b) / 2}% with respect to the reference reduction ratio, Regardless of the outer diameter difference between the tires of the front wheels LWf and RWf, the difference in the rotational speeds of the pair of rotating electrical machines 30A and 30B should be 2.9% or more of the average rotational speed of the pair of rotating electrical machines 30A and 30B. Can do. Specifically, if the reduction ratio of one of the first reduction gear 40A and the second reduction gear 40B is R1, the other reduction ratio is R2, and the reference reduction ratio is Rr, a pair of reduction gears 40A, The reduction ratio R1, R2 of 40B is calculated by the following formulas (1) and (2).
R1 = Rr + Rr × {(2.9 + a + b) / 2} / 100 (1)
R2 = Rr−Rr × {(2.9 + a + b) / 2} / 100 (2)
The reference reduction ratio is, for example, a reduction ratio applied when the reduction ratios of the reduction gears are the same.

  Therefore, in the state where the left wheel LW and the right wheel RW are rotating at the same peripheral speed, such as when the vehicle 100 is traveling straight, the frequency of each rotational order component of the operating sound generated by each of the pair of rotating electrical machines 30A and 30B. Is 20 Hz or more in a frequency band of 700 Hz or more and less than 2400 Hz.

  Thus, the vehicle drive device 1 according to the present embodiment drives the first rotating electrical machine 30A coupled to the left front wheel LWf, the second rotating electrical machine 30B coupled to the right front wheel RWf, and the driving of the first rotating electrical machine 30A. The first reduction device 40A that reduces the rotation and the second reduction device 40B that reduces the drive rotation of the second rotating electrical machine 30B and has a reduction ratio different from the reduction ratio of the first reduction device 40A are provided. According to this configuration, for example, when rotating the left and right front wheels LWf and RWf at the same peripheral speed, it is possible to make a difference in the rotational speeds of the first rotating electrical machine 30A and the second rotating electrical machine 30B. For this reason, even if a slight difference occurs in the rotational speed of the left and right front wheels LWf and RWf due to the difference in the outer diameter of the tires of the left and right front wheels LWf and RWf, a beat occurs due to the difference in the rotational speed between the pair of rotating electrical machines 30A and 30B It can be made larger than the difference in the number of rotations. Therefore, it is possible to suppress a beat that is recognized as a fluctuating sound by human hearing.

  Here, if there is a difference in outer diameter between the tires of the left and right front wheels LWf and RWf, even if the left and right front wheels LWf and RWf rotate at the same peripheral speed, a difference occurs in the rotational speeds of the left and right front wheels LWf and RWf. In the present embodiment, the difference between the reduction ratio of the first reduction gear 40A and the reduction ratio of the second reduction gear 40B is such that the left and right front wheels LWf and RWf are rotating at the same peripheral speed, The frequency difference of each rotation order component of the operating sound generated at 30B is set to be 20 Hz or more within a frequency band of 700 Hz or more and less than 2400 Hz. For this reason, the beat which arises when the difference in frequency is less than 20 Hz can be suppressed.

The present invention is not limited to the above-described embodiment described with reference to the drawings, and various modifications can be considered within the technical scope thereof.
For example, in the above-described embodiment, a case where a beat of less than 20 Hz is recognized as a fluctuating sound is described as an example. .

  Moreover, in the said embodiment, although the case where the frequency band of the sound which is easy to be transmitted from the vehicle drive device 1 to the vehicle interior of the vehicle 100 is 700 Hz or more and less than 2400 Hz is described as an example, it is not limited to this. The frequency band may be set as appropriate.

  In addition, it is possible to appropriately replace the components in the above-described embodiments with known components without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle drive device 30A ... 1st rotary electric machine 30B ... 2nd rotary electric machine 40A ... 1st reduction gear 40B ... 2nd reduction gear LWf ... Left front wheel (1st wheel) RWf ... Right front wheel (2nd wheel)

Claims (4)

A first rotating electrical machine coupled to the first wheel;
A second rotating electrical machine coupled to the second wheel;
A first speed reducer that decelerates drive rotation of the first rotating electrical machine;
A second reduction device that decelerates the drive rotation of the second rotating electrical machine and that has a reduction ratio different from the reduction ratio of the first reduction device;
A vehicle drive device comprising: The difference between the speed reduction ratio of the first speed reducer and the speed reduction ratio of the second speed reducer is such that the first rotating electrical machine and the second wheel are rotating at the same peripheral speed. The frequency difference of each rotation order component of the operating sound generated in each of the second rotating electrical machines is set to be equal to or greater than a value recognized as a fluctuating sound within a predetermined frequency band.
The vehicle drive device according to claim 1. The value recognized as the fluctuating sound is 20 Hz.
The vehicle drive device according to claim 2. A first rotating electrical machine coupled to the first wheel;
A second rotating electrical machine coupled to the second wheel;
A first speed reducer that decelerates drive rotation of the first rotating electrical machine;
A second speed reducer that decelerates the drive rotation of the second rotating electrical machine;
A vehicle drive device design method comprising:
The difference between the speed reduction ratio of the first speed reducer and the speed reduction ratio of the second speed reducer is determined so that the first rotating electrical machine and the first rotating electrical machine and the second wheel are rotating at the same peripheral speed. The frequency difference of each rotational order component of the operating sound generated in each of the second rotating electrical machines is set to be equal to or greater than a value recognized as a fluctuating sound within a predetermined frequency band.
A method for designing a vehicle drive device.

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