JP2019015328A - Wheel drive device - Google Patents

Abstract

To attain a structure capable of measuring driving torque of a wheel even in a stop state of a vehicle.SOLUTION: A wheel drive device comprises: a housing 1; a differential device 2 arranged in the housing 1, and into which torque from a drive source is input; a pair of drive shafts 3 where an input shaft part 16 constituting each base end part is connected to each side gear 15 constituting the differential device 2, and which is configured to transmit torque from each side gear 15 to right and left wheels; and a pair of torque sensors 4 each arranged around each input shaft part 16 in the housing 1, and configured to use a reverse magnetostrictive effect occurring at each input shaft part 16, to measure torque acting on each drive shaft 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wheel drive device mounted on a vehicle such as an automobile.

  Conventionally, in order to ensure the running stability of a vehicle such as an automobile, for example, the rotational speed of the wheel, the acceleration of the vehicle, the yaw rate, and the like are detected, and using these detection results, the braking system of each wheel and each wheel are detected. There is known a method for controlling the distribution of the drive torque (see, for example, Japanese Patent Application Laid-Open No. 2008-144788).

JP 2008-144788 A

  The rotational speed of the wheel, the acceleration of the vehicle body, and the yaw rate are not generated when the vehicle is stopped. For this reason, for example, when the vehicle starts, there is a problem that it is difficult to appropriately control the distribution of driving torque to each wheel.

  This invention is made | formed in view of the above situations, The objective is to implement | achieve the structure which can measure the driving torque of a wheel regarding a wheel drive device, even if a vehicle is a stop state.

The wheel drive device of the present invention includes a housing, a differential device, a pair of drive shafts, and a pair of torque sensors.
The differential device is disposed in the housing, and outputs a torque input unit to which torque from a drive source such as an engine is input, and outputs torque input to the torque input unit, and is mutually differential. And a pair of torque output units allowed to rotate.
In the pair of drive shafts, input shaft portions constituting respective base end portions are coupled to the torque output portions, and torque is transmitted from the torque output portions to the left and right wheels.
The pair of torque sensors are arranged one by one around the input shaft portions in the housing, and torque acting on the drive shafts using the inverse magnetostrictive effect generated in the input shaft portions. Measure.

  In the wheel drive device of the present invention, the differential device is rotatably supported in the housing by a plurality of rolling bearings with respect to the housing, and at least one of the pair of torque sensors. The torque sensor may be configured to be supported by a rolling bearing adjacent to the torque sensor among the plurality of rolling bearings.

  According to the wheel driving device of the present invention, the driving torque of the wheel can be measured even when the vehicle is stopped.

FIG. 1 is a cross-sectional view of a wheel drive device according to a first example of an embodiment. FIG. 2 is a cross-sectional view of the wheel drive device according to the second example of the embodiment.

[First example of embodiment]
A first example of the embodiment will be described with reference to FIG.
The wheel drive device of this example is mounted on an automobile and is arranged on the downstream side of the transmission with respect to the transmission direction of the engine output torque, and transmits the torque that has passed through the transmission to the left and right wheels (front wheels or rear wheels). Used to do.

  Such a wheel drive device includes a housing 1, a differential device 2, a pair of drive shafts 3, and a pair of torque sensors 4.

  The differential device 2 is disposed in the housing 1 and includes a differential case 5, a ring gear 6, and a differential gear mechanism 7.

  The differential case 5 is configured in a cylindrical shape as a whole, and its axially intermediate portion is a spherical shell-like case body 8, and both axially opposite side portions are cylindrical cylindrical portions 9. Yes. Further, the differential case 5 has a flange portion 10 that extends radially outward from the outer peripheral surface of the case body 8.

  The differential case 5 is rotatably supported with respect to the housing 1 by a rolling bearing 11 that is externally supported by each cylindrical portion 9. The housing 1 has through-holes 12 communicating with the inside and the outside of the housing 1 in the peripheral portion of each cylindrical portion 9. Each rolling bearing 11 is supported by being fitted into these through holes 12.

  That is, each of the rolling bearings 11 includes an inner ring 17 that is a race ring that is externally supported by the cylindrical portion 9, an outer ring 18 that is a race ring that is internally supported by the through hole 12, and an outer peripheral surface of the inner ring 17. And a plurality of rolling elements 19 disposed between the inner ring raceway formed on the inner ring and the outer ring raceway formed on the inner peripheral surface of the outer ring 18. In the illustrated example, a tapered roller bearing is used as the rolling bearing 11. However, when the present invention is carried out, other types such as a ball bearing can be used as the rolling bearing 11.

  The ring gear 6 corresponds to a torque input portion and is fixedly coupled to the flange portion 10. The ring gear 6 meshes with a gear (not shown) that inputs torque to the differential device 2 such as an output gear of a transmission (not shown).

  The differential gear mechanism 7 is housed inside the case body 8 and includes a pinion shaft 13, a pair of pinion gears 14, and a pair of side gears 15 each corresponding to a torque output portion. The pinion shaft 13 is disposed so as to penetrate the central portion in the axial direction of the case main body 8 in the radial direction, and both end portions in the axial direction are coupled and fixed to the case main body 8. The pair of pinion gears 14 is fitted on both ends of the pinion shaft 13 so as to be able to rotate relative to the pinion shaft 13. The pair of side gears 15 are arranged on both sides in the axial direction inside the case body 8 so as to be coaxial with the case body 8 and capable of relative rotation with respect to the case body 8. Each pair of side gears 15 is a pair of pinion gears. 14 is engaged. Accordingly, the pair of side gears 15 is allowed to rotate differentially with each other.

  The pair of drive shafts 3 are for transmitting drive torque from the differential device 2 to the left and right wheels, and each has an input shaft portion 16 at the base end portion. These input shaft portions 16 are inserted into the housing 1 through the respective through holes 12 and are inserted into the differential case 5 through the respective cylindrical portions 9, and the respective base end portions thereof are respectively connected to the respective side gears 15. Thus, the torque transmission is possible by spline fitting or the like.

  The pair of torque sensors 4 are for measuring the torque transmitted by each drive shaft 3 and are arranged in the housing 1. Each of the pair of torque sensors 4 is formed in an annular shape, and is disposed one by one around the input shaft portion 16 of each drive shaft 3. More specifically, each torque sensor 4 is disposed around a portion of each input shaft portion 16 that protrudes in the axial direction from the radially inner side of each cylindrical portion 9 of the differential case 5. Each torque sensor 4 is internally fitted and supported in a portion of each through hole 12 of the housing 1 that is closer to the outside of the housing 1 than the rolling bearing 11, and each detection portion is connected to each input shaft portion 16. It is made to face and face the outer peripheral surface that is the detected portion. Each torque sensor 4 is of a magnetostrictive type having a plurality of coils constituting a bridge circuit, and the magnitude and direction of the torque transmitted by each drive shaft 3 is generated in each input shaft portion 16. Measure using the inverse magnetostriction effect. For this reason, each input shaft part 16 has at least a detected part made of a material having magnetostriction characteristics such as an iron-based alloy.

  The wheel drive device of this example applies torque from the engine to the ring gear 6, the differential case 5, the pinion shaft 13, the pair of pinion gears 14, the pair of side gears 15, and the pair of drive shafts 3 in the order of traveling of the automobile. Communicate and rotate left and right wheels. Further, the differential device 2 allows differential rotation between the pair of side gears 15, that is, differential rotation of the left and right wheels, according to the driving state of the automobile.

  Further, in this example, since the torque transmitted by each drive shaft 3 can be measured by each torque sensor 4, in order to ensure the running stability of the vehicle using the measurement results of these torques. (For example, optimal distribution of driving torque to each wheel and brake control of each wheel during deceleration). In particular, in this example, since each torque sensor 4 is a magnetostrictive sensor, when the vehicle is traveling, that is, when each drive shaft 3 is rotating, when the vehicle is stopped, That is, even when each drive shaft 3 is not rotating, the torque transmitted by each drive shaft 3 can be measured. For this reason, not only when the vehicle is running, but also when the vehicle is stopped, the measurement result of the torque transmitted by each drive shaft 3 is used to ensure the running stability of the vehicle. Can be controlled.

Moreover, when using the wheel drive device of this example in combination with a belt-type continuously variable transmission, the following effects can be achieved.
In the belt type continuously variable transmission, it is necessary to control the clamping pressure of the belt according to the transmission torque of the pulley. On the other hand, in addition to the transmission torque being input from the engine, the transmission torque may be input (reverse input) from each tire. Here, the transmission torque input from the engine to the pulley can be estimated from the accelerator opening and the engine speed, but the torque input from each tire to the pulley cannot be estimated. Therefore, at present, a certain amount of margin is provided for the minimum clamping pressure required in the driving state in preparation for the transmission torque being input from each tire to the pulley.
On the other hand, when the wheel drive device of this example is used in combination with a belt-type continuously variable transmission, before the transmission torque is input from each tire to the pulley, the transmission torque is 4 can be measured. Therefore, if the belt-type continuously variable transmission is controlled using the measurement result of the transmission torque, the clamping pressure margin can be reduced. If the margin can be reduced, over-pressing of the belt against the pulley can be avoided, so that transmission torque loss at the pulley and the support bearing can be reduced. Furthermore, since the pump pressure that generates the clamping pressure can be lowered, the pump loss can also be reduced. As a result, it can contribute to the improvement of the fuel consumption of the automobile.

  In this example, each torque sensor 4 is disposed in the housing 1. More specifically, each torque sensor 4 is disposed on the radially inner side of each through hole 12 that communicates the inside and outside of the housing 1. For this reason, compared with the structure where each torque sensor 4 is arranged outside the housing 1, the wheel drive device can be reduced in size and the risk of damage such as a stepping stone hitting each torque sensor 4 can be kept low. In this example, since the torque is measured using the inverse magnetostriction effect generated in the input shaft portion 16 of each drive shaft 3, for example, the inverse magnetostriction of an expensive magnetostrictive film deposited on the outer peripheral surface of the input shaft portion 16 is used. Compared to a structure that measures the torque by using the effect, the manufacturing cost can be sufficiently suppressed.

  When the present invention is carried out, a compression work hardened layer is formed by, for example, performing shot peening on the detected portion of the outer peripheral surface of the input shaft portion 16 that faces the detecting portion of the torque sensor 4. You can also. By forming such a compression work hardened layer, the mechanical characteristics and magnetic characteristics of the detected part are improved, and the sensitivity and hysteresis of the torque measurement by the torque sensor 4 can be improved. Note that since the shot peening process can be performed at a lower cost than the formation of the magnetostrictive film, the manufacturing cost can be suppressed even when the configuration for forming the compression-processed hardened layer is employed.

[Second Example of Embodiment]
A second example of the embodiment will be described with reference to FIG.
In this example, each torque sensor 4 a is supported and fixed to an inner ring 17 that constitutes the rolling bearing 11 adjacent to itself among the rolling bearings 11. In this example having such a configuration, each torque sensor 4a can be handled integrally with each rolling bearing 11, so that the assembly work of the wheel drive device can be facilitated.
When the present invention is carried out, the torque sensor 4 a can be supported and fixed to the outer ring 18 constituting the rolling bearing 11.
Other configurations and operations are the same as those in the first example of the embodiment.

DESCRIPTION OF SYMBOLS 1 Housing 2 Differential apparatus 3 Drive shaft 4, 4a Torque sensor 5 Differential case 6 Ring gear 7 Differential gear mechanism 8 Case main body 9 Cylindrical part 10 Flange part 11 Rolling bearing 12 Through-hole 13 Pinion shaft 14 Pinion gear 15 Side gear 16 Input shaft part 17 Inner ring 18 Outer ring 19 Rolling element

Claims (2)

A housing;
A torque input unit to which torque from a drive source is input; and a pair of torque output units that output torque input to the torque input unit and are allowed to perform differential rotation with each other, A differential device disposed in the housing;
A pair of drive shafts coupled to the respective torque output portions with input shaft portions constituting respective base end portions, and transmitting torque from the respective torque output portions to the left and right wheels;
A pair of torque sensors that are arranged one by one around each input shaft portion in the housing and measure the torque acting on each drive shaft by utilizing the inverse magnetostrictive effect generated in each input shaft portion. And with,
Wheel drive device. The differential device is rotatably supported in the housing by a plurality of rolling bearings with respect to the housing.
At least one torque sensor of the pair of torque sensors is supported by a rolling bearing adjacent to the torque sensor among the plurality of rolling bearings.
The wheel drive device according to claim 1.

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