JP6789395B2 - Torque vectoring drive - Google Patents

Description

The following disclosure relates to a drive device using a motor prepared for each drive shaft, and particularly to a drive device capable of generating a torque difference between a pair of drive shafts by using a planetary gear set and a differential.

Devices that drive vehicles using motors prepared for each axle have been studied since the end of the 19th century, and some of them have been put into practical use. It is advantageous in terms of energy efficiency because the torque generated by the motor is transmitted to the axle with almost no loss. Furthermore, by generating different torque for each motor, there is an advantage that a torque difference can be generated between the axles and the vehicle can be directed (vectoring) independently of the direction of the wheels.

Torque vectoring itself can be realized without preparing a motor for each axle. For example, according to the related technology disclosed in Patent Document 1, torque is applied from the engine to the differential via the propeller shaft, and by combining a pair of clutches with the differential, the torque distributed from the differential is different. Is being generated.

Japanese Patent Publication No. 2007-132517

Even if the torque from one motor is reduced to, for example, 80% of the torque from the other motor, the torque ratio applied to both axles is only 10: 8 and the total output is reduced to 90%. In a torque vectoring system using a clutch, a non-negligible energy loss occurs in a long drive train or clutch from the engine to the differential.

The following devices were created in view of these problems.

According to the aspect, the drive device includes a pair of drive shafts that can rotate around an axis, and a pair of motors that are coaxial with the pair of drive shafts and generate torque around the shafts. A pair of side gears that are drivenly coupled to any one of the pair of drive shafts, a casing that is gear-coupled to the pair of side gears to allow differential between the pair of drive shafts, and a casing that can rotate around the shaft. And a pair of planetary gear sets, each of which is a first gear fixedly coupled to the casing and meshes with the first gear of the pair of motors. A second gear that is drivenly coupled to one of them to receive an input and a second gear that is drivenly coupled to one of the pair of drive shafts and meshes with the second gear to decelerate the input and the drive shaft. A pair of planetary gear sets including a third gear that outputs to.

FIG. 1 schematically shows a drive device according to an embodiment, and shows an example in which a differential casing is coupled to one outer gear of a mysterious planetary gear set. FIG. 2 schematically shows a drive device according to another embodiment. FIG. 3 schematically shows a drive device according to still another embodiment. FIG. 4A shows an example in which another type of planetary gear set is used, in which the differential casing is coupled to the sun gear of the planetary gear set. FIG. 4B shows an example in which another type of planetary gear set is used, in which the differential casing is coupled to the outer gear of the planetary gear set. FIG. 5 shows an example in which a radial gap type motor is used. FIG. 6 is a schematic diagram for explaining the principle of torque difference. FIG. 7 is a schematic view of a rear-wheel drive vehicle according to an example in which the drive device according to any of the embodiments is applied. FIG. 8 is a schematic view of a walking robot according to an example in which the driving device according to any of the embodiments is applied.

Some exemplary embodiments will be described below with reference to the accompanying drawings.

In the following description and claims, unless otherwise specified, the shaft means the center of rotation of a drive shaft such as an axle.

The following description primarily relates to an example in which the drive unit is applied to a pair of front or rear axles. In such an example, the left and right axles can be driven by only a pair of motors without an external power source, and a significant torque difference can be generated between the two axles. However, the following example is just an example for convenience of explanation, and of course the drive device can be applied to both the front and rear axles, and it can be applied to the propeller shaft connecting the front and rear axles to the front and rear wheels. It can be used for the purpose of dynamically adjusting the torque distribution. Further, the drive device according to the following embodiment can be combined with an auxiliary power source such as another motor or an internal combustion engine.

Mainly referring to FIG. 1, the drive device according to the present embodiment generally includes a pair of drive shafts 1A and 1B, a differential 3 that allows a differential between them, and a differential 3 and drive shafts 1A and 1B. It is provided with planetary gear sets 5A and 5B coupled with any of the above, and the whole thereof is supported by bearings 9A and 9B and can rotate about an axis. The motors 7A and 7B, which are the power sources of the drive device, are coaxial with the drive shafts 1A and 1B, and generate torque around the shafts, respectively, to the drive shafts 1A and 1B via any of the planetary gear sets 5A and 5B. Gives torque. The drive shafts 1A and 1B are, for example, right and left axles, and as shown in FIG. 6, wheels WA and WB are provided at their respective ends. As described above, the drive shafts are connected to a propeller shaft and other shafts. You may be.

Returning to FIG. 1, the drive shafts 1A and 1B are coupled to the side gears 11A and 11B of the differential 3, respectively, both of which mesh with a plurality of pinions 13 rotatably supported by the casing 15. Therefore, the differential between them is allowed. The differential 3 may be a bevel gear type as shown in FIG. 1, a face gear type as shown in FIG. 2, or a double pinion gear type as shown in FIG. Since the differential dimensions can be suppressed in the axial direction or the radial direction, respectively, the entire device can be configured extremely compactly. Alternatively, since the planetary gear sets 5A and 5B can be brought close to each other, it is advantageous to connect or link the planetary gear sets 5A and 5B in some structural, mechanical, electrical or other sense. Of course, any other form of differential can be used.

Although not shown, the differential 3 may include a differential limiting mechanism. This is useful not only as a countermeasure when one axle loses traction, but also as a safety measure when one motor fails.

The casing 15 is not drivenly connected to a power source other than the motors 7A and 7B connected via the planetary gear sets 5A and 5B, that is, the casing 15 can freely rotate about the axis. Since there is no ring gear protruding outward from the casing 15, the casing 15 can be made compact, and the casing 15 can be housed inside the pair of motors 7A and 7B. Of course, or the casing 15 may be provided with a ring gear to receive torque and may be connected to an external auxiliary power source.

The planetary gear sets 5A and 5B each have a first gear 21A and 21B fixedly coupled to the casing 15, a second gear 23A and 23B for receiving torque, and a third gear 25A for output, respectively. , 25B.

The second gears 23A and 23B are planetary gears, and the carriers 31A and 31B rotatably supporting the second gears 23A and 23B are connected to the motors 7A and 7B to receive torque and rotate about an axis. Further, one ends 33A and 33B mesh with the first gears 21A and 21B, and the other ends 35A and 35B mesh with the third gears 25A and 25B. Needless to say, the second gears 23A and 23B rotate around their own axes and also around the axes of the drive shafts 1A and 1B.

The first gears 21A and 21B and the third gears 25A and 25B can both be outer gears having internal teeth, in which case the second gears 23A and 23B mesh with each other inside them. If the first gears 21A and 21B are fixed, the planetary gear sets 5A and 5B match the so-called mysterious planetary gears, but in the present embodiment, both the first gears 21A and 21B are fixed to the casing 15. They are coupled and both rotate about an axis. Further, the third gears 25A and 25B are fixedly coupled to the drive shafts 1A and 1B, respectively, and both rotate around the shaft.

The number of teeth of the first gears 21A and 21B is slightly larger (or less) than the number of teeth of the third gears 25A and 25B, and the second gears 23A and 23B are replaced by the first gears 21A and 21B. On the other hand, when rotating, the third gears 25A and 25B rotate with a reduction ratio k corresponding to the difference in the number of teeth. In the present embodiment, the planetary gear sets 5A and 5B not only have the purpose of boosting according to the reduction ratio, but also the torque directly input from the motors 7A and 7B to the drive shafts 1A and 1B and via the differential 3. It is used for the purpose of distributing the torque to be generated according to the reduction ratio k. This will be described in more detail later.

Since a larger reduction ratio k can be obtained as the difference in the number of teeth is smaller, the above-described embodiment is advantageous for obtaining a large reduction ratio k. Of course, other configurations may be applied to the planetary gear sets 5A and 5B. In the examples shown in FIGS. 4A-4B, mechanisms corresponding to classical planetary gears are utilized. Hereinafter, only one planetary gear set 5A will be described, but the same applies to the other planetary gear set 5B.

According to the example shown in FIG. 4A, the first gear 21A is a sun gear, the second gear 23A is an outer gear having internal teeth, and the third gear 25A is a planetary gear. The third gear 25A meshes with both the first gear 21A and the second gear 23A, rotates about an axis, and also rotates around its own axis. When the second gear 23A rotates with respect to the first gear 21A, the third gear 25A rotates with the reduction ratio k.

The casing 15 of the differential 3 is fixedly coupled to the first gear 21A, both of which rotate about an axis. The second gear 23A is connected to the motor 7A to receive torque. The third gear 25A is rotatably supported by the carrier 31A, and the carrier 31A is fixedly coupled to the drive shaft 1A.

It is difficult to obtain a large reduction ratio as compared with the examples shown in FIGS. 1 to 3, but a simpler structure produces the same effect.

Alternatively, as shown in FIG. 4B, the first gear 21A is an outer gear fixedly coupled to the casing 15, the second gear 23A is a sun gear drivenly coupled to the motor 7A, and the third gear 25A is these. It may be a planetary gear that meshes with. The carrier 31A of the third gear 25A is fixedly coupled to the drive shaft 1A.

The motor must be coupled to the sun gear located on the inner circumference, and even in such an example, the same operation as in the examples of FIGS. 1 to 4A is obtained.

As the motors 7A and 7B, for example, as illustrated in each figure, an axial gap type motor can be used. The solenoids 43A and 43B have a gap in the axial direction, and the rotors 41A and 41B are interposed in the gap, which is drivenly coupled to the second gears 23A and 23B as described above. The magnetic flux flowing between the gaps causes the rotors 41A and 41B to generate torque around the shaft, which is transmitted to the second gears 23A and 23B.

Since the axial gap type generates torque in proportion to the cube of the diameter of the rotor, it is advantageous to generate a large torque. Further, since the axial dimension can be reduced, it is advantageous for the miniaturization of the entire device. Of course, as shown in FIG. 5, a radial gap type motor may be used. The radial gap type is advantageous in that a large torque can be maintained even at a relatively high rotation speed.

The bearings 9A and 9B may support the differential 3 as shown, or directly support the planetary gear sets 5A and 5B or the drive shafts 1A and 1B, and the other elements indirectly support them. There may be. Of course, the number of bearings is not limited to one pair.

The operation of the drive device according to each embodiment will be described with reference to FIG.

Part D of the torques Ia and Ib generated by the motors 7A and 7B is input to the differential 3 via the planetary gear sets 5A and 5B, and is further distributed to the drive shafts 1A and 1B via the differential 3. The portion (Ia-D) that does not pass through the differential 3 passes through the planetary gear sets 5A and 5B, is multiplied according to the reduction ratio k, and is transmitted to the drive shafts 1A and 1B. As a result, the torques applied to the drive shafts 1A and 1B are Oa = D + (Ia−D) × k and Ob = D + (Ib−D) × k, respectively.

When the torques Ia and Ib generated by the motors 7A and 7B are equal to each other, they are also equal to D, and as a result, Oa = Ob = Ia = Ib, and torque vectoring does not occur. However, if Ib = 8 with respect to Ia = 10, for example, the differential 3 divides D = (10 + 8) / 2 = 9 equally into the drive shafts 1A and 1B, so that the output torque Oa = 9 + (10-9). ) × k = 9 + k, Ob = 9 + (8-9) × k = 9-k. For example, if the reduction ratio k is 8, the output ratio Oa: Ob = 17: 1 with respect to the input ratio Ia: Ib = 10: 8, and the output torque difference is much larger than the motor torque difference. ..

That is, according to the present embodiment, a much larger torque vectoring effect can be obtained than when the motor directly drives the drive shaft. Alternatively, to obtain the same torque vectoring effect, it is only necessary to slightly reduce the output of the other motor with respect to one, so that the decrease in the total output is small. This offers enormous advantages in situations where total power needs to be maintained, such as when driving on rough or steep roads.

In a system in which a motor drives each drive shaft independently, even if the torque generated by the motor is equal, the vehicle cannot go straight unless the rotation speed is equal. In order to solve such a problem, for example, a mechanism such as a counter shaft that synchronizes both drive shafts is required. In the present embodiment, since the differential is interposed between the drive shafts and the planetary gear sets are connected via the casing, the drive shafts are autonomously synchronized and the straightness is guaranteed. That is, a mechanism such as a counter shaft can be omitted.

According to the present embodiment, a motor coaxial with the differential or the drive shaft can be used, and a structure protruding outward in the radial direction can be omitted. An extremely compact drive device is provided as compared with a device having an internal combustion engine or an electric motor externally. Needless to say, all structures for inputting torque from an external combustion engine or electric motor, such as propeller shafts and ring gears, can be omitted, so energy loss caused by these can be avoided and extremely simple. It is possible to provide an electric vehicle having a similar structure.

The drive device according to any of the above embodiments can be used as a drive device for the vehicle 100, for example, as shown in FIG. The example of FIG. 7 is an example of a rear-wheel drive vehicle, but as already described, it can be used for a front-wheel drive vehicle or a four-wheel drive vehicle, and it can be applied to a propeller shaft connecting the front and rear axles to torque the front and rear wheels. It can be used for the purpose of dynamically adjusting the allocation.

Alternatively, the drive device according to any of the above embodiments can be used for any application in which a torque difference needs to be generated between a pair of drive shafts. For example, as shown in FIG. 8, it can be used for driving the foot 110 of a bipedal walking robot. If the thighs TA and TB are extended downward from the pair of drive shafts 1A and 1B, respectively, and the legs LA and LB are swingably connected to the lower ends thereof, the leg 110 of the bipedal walking robot is configured. If the differential 3 is fixed to the robot and a torque difference is generated between the pair of drive shafts 1A and 1B, one of the legs LA and LB kicks the ground backward and the other is swung forward. By changing the application of the electric current and reversing the motor, such operations can be alternately performed, so that the drive device can be used for the purpose of walking the robot.

Of course, it can be used for each of a plurality of pairs of legs of a multi-legged robot, or it can be used for driving an arm.

Although some embodiments have been described, it is possible to modify or modify the embodiments based on the above disclosure contents.

A drive device that is driven by only a pair of motors and is capable of remarkable torque vectoring is provided.

Claims (7)

A pair of drive shafts that can rotate around the shaft,
A pair of motors that are coaxial with the pair of drive shafts and generate torque around the shafts, respectively.
A pair of side gears that are drivenly coupled to any one of the pair of drive shafts, a casing that is gear-coupled to the pair of side gears to allow a differential between the pair of drive shafts, and a casing that can rotate around the shaft. With a differential with
A pair of planetary gear sets, each of which is a first gear fixedly coupled to the casing, meshes with the first gear, and is drivenly coupled to any one of the pair of motors. A third gear that receives the input and is drivenly coupled to one of the pair of drive shafts, meshes with the second gear, decelerates the input, and outputs the input to the drive shaft. A pair of planetary gear sets with gears,
A drive device equipped with. The drive device according to claim 1, wherein the first gear is an outer gear or a sun gear that meshes with the second gear. The driving device according to claim 1, wherein the second gear is an outer gear or a planetary gear that meshes with the third gear. The driving device according to claim 1, wherein the second gear includes a planetary gear, and the first gear and the third gear are outer gears having internal teeth that mesh with the second gear. The second gear includes a carrier that rotatably supports the planetary gear, each of the pair of motors includes a rotor that drives the second gear, and the carrier is fixedly coupled to the rotor. Item 4 drive device. The driving device according to claim 1, wherein the casing is not drivenly coupled to a power source other than the pair of motors. The drive device according to claim 1, wherein the differential is any of a bevel gear type, a face gear type, and a double pinion gear type.

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