CN117704026A

CN117704026A - Differential limiting device

Info

Publication number: CN117704026A
Application number: CN202211344760.5A
Authority: CN
Inventors: 广田功; 内田升; 舟根彻; 川合阳辅
Original assignee: GKN Driveline International GmbH
Current assignee: GKN Driveline International GmbH
Priority date: 2022-09-09
Filing date: 2022-10-31
Publication date: 2024-03-15
Also published as: JP2024039294A

Abstract

The invention provides a differential limiting device for limiting the differential motion between a pair of output shafts driven by a pair of power sources respectively and independently. The device is provided with: a pair of transmission bodies rotatable independently of each other, each of the transmission bodies including: a gear member drivingly coupling one of the power sources to one of the output shafts; and a brake body rotatable with respect to the gear member to perform friction braking on the gear member; and a cam structure that is sandwiched between the pair of brake bodies, converts a differential motion between the brake bodies into an axial pressing force, and presses the brake bodies against the gear member.

Description

Differential limiting device

Technical Field

The present invention relates to a differential limiting device that limits a differential between drive wheels that can be applied to a vehicle that includes a power source for each drive wheel.

Background

In a vehicle using an internal combustion engine, a configuration is generally employed in which torque is distributed from one power source to a plurality of drive wheels. However, such a configuration is not essential, and an electric vehicle is exemplified as an example, but the vehicle may be provided with a power source independent for each driving wheel.

Vehicles having motors for each drive wheel have been studied since the end of the 19 th century, and several of them have been put to practical use. By independently controlling the torque applied to each driving wheel, it is possible to control the posture of the vehicle such as to prevent side slip, and by actively generating a torque difference, it is possible to orient the travel of the vehicle irrespective of the steered wheel (torque vector distribution).

International patent application publication WO2020/179202A1 discloses a related art.

In a vehicle in which each drive wheel is provided with an electric motor, it is not easy to make the vehicle travel straight unexpectedly. This is because it is not easy to completely match the outputs of the left and right motors.

Detecting the direction of travel of the vehicle and dynamically and closely controlling the motor output is one solution. However, the vehicle is running straight for a large part of its running time, and it can be said that it is over-specification to continue such precise control. In addition, in case of failure of control, the vehicle may display an action which is not desired by the driver.

Disclosure of Invention

The technology disclosed below provides a mechanical differential limiting device that reduces the burden on the control system.

A differential limiting device for limiting a differential motion between a pair of output shafts driven by a pair of power sources, respectively, comprises: a pair of transmission bodies rotatable independently of each other, each of the transmission bodies including: a gear member drivingly coupling one of the power sources to one of the output shafts; and a brake body rotatable with respect to the gear member to perform friction braking on the gear member; and a cam structure that is sandwiched between the pair of brake bodies, converts a differential motion between the brake bodies into an axial pressing force, and presses the brake bodies against the gear member.

Preferably, the gear member and the brake member each have a tapered surface around a corresponding shaft, and the tapered surfaces are fitted to face each other, thereby forming a tapered clutch that receives the pressing force. Further, the brake bodies preferably each include: a plurality of brake pads surrounding the gear member and arranged around an axis; and a ring that generates frictional force with respect to the gear member by applying force in a direction in which the plurality of brake pads are concentrated. Further preferably, the brake body includes bridge members that engage with the plurality of brake pads, respectively, so that the brake body follows the brake pads. Alternatively, it is preferable that the cam structure includes cam surfaces extending in the circumferential direction, which are formed on the brake body, respectively, and cam balls capable of rolling on the cam surfaces.

The effects of the present invention are as follows.

The differential limiting device reduces the burden on the control system and does not interfere with advanced control such as torque vectoring.

Drawings

FIG. 1 illustrates a schematic view of a powertrain and a vehicle including a differential limiting device according to one embodiment.

Fig. 2 shows a front view of the differential limiting device.

Fig. 3 shows a front cross-sectional view of the differential limiting device.

Fig. 4 is a perspective view of one transmission body of the differential limiting device.

Fig. 5 is an exploded perspective view of the transfer body.

Fig. 6 shows an exploded perspective view of an assembly including a brake pad.

Detailed Description

Several exemplary embodiments are described below with reference to fig. 1-6. It should be noted in particular that the drawings are not necessarily drawn to scale precisely, and therefore the dimensional relationships are not limited to the illustrated case. In the following description and the scope of the appended claims, unless otherwise specified, the shaft means the rotation axis of the differential limiting device, and terms "radial direction" and "circumferential direction" are defined with respect to the shaft, respectively.

Referring mainly to fig. 1, a vehicle includes, for example, a pair of driving wheels WR and WL, and motors MR and ML are provided for each driving wheel independently. In the illustrated example, the rear wheels are driving wheels, but the front wheels may be driving wheels, or the driving wheels may be four or more wheels, or the motors may be four or more wheels.

The motors MR, ML may be directly coupled to the driving wheels WR, WL, respectively, but appropriate gear sets GR, GL may be interposed as shown in the figure. Since the gear sets GR and GL can be reduction gear sets each composed of a plurality of gears, the torque of the motors MR and ML is multiplied and transmitted to the driving wheels WR and WL. In the illustrated example, the gear sets GR, GL are 4-stage gear sets, respectively, but may be 3 or less stages, or may be 5 or more stages. Typically, the combination of all gears is a reduction gear, or a portion of the combination may not be a reduction gear. Alternatively, the gear sets GR, GL may also each include a transmission. Further, the gear sets GR and GL may be connected to each other through a gear mechanism such as a planetary gear.

At least one gear shaft of the gear sets GR, GL is coupled to each other by a differential limiting device 1, the differential between them being limited. If the differential limiting device 1 is interposed in the first stage of the gear shaft, the differential is more effectively limited, but since the gear shaft is at the highest speed, the differential limiting device 1 is consumed more. Alternatively, the differential limiting device 1 may be interposed in the final stage, but the effect of limiting the differential becomes smaller. If benefits and adverse effects are considered, it is appropriate that the differential limiting device 1 is sandwiched between intermediate stages. In the illustrated example, the differential limiting device 1 is sandwiched in the third stage of the 4-stage gear set.

Referring to fig. 2 in conjunction with fig. 1, the differential limiting device 1 is basically configured by a pair of transmission bodies 3 that are rotatable about axes X independently of each other, and a cam structure 5 interposed between the transmission bodies 3. The transmission body 3 includes gear members 7, and forms a part of the gear group GR or GL, respectively, to transmit torque to the drive wheels WR or WL. The transmission bodies 3 are also provided with respective braking bodies 9 to cooperate with the cam structures 5, thereby limiting the mutual differential motion.

Referring to fig. 3 in conjunction with fig. 1 and 2, the gear member 7 has a structure similar to a gear wheel, and constitutes a gear by driving engagement with an output shaft. The output shaft has, for example, a spline 7S on its inner periphery and gear teeth 7T on its outer periphery that mesh with gears of the preceding stage or the following stage. The gear teeth 7T may be directly engraved on the outer periphery of the gear member 7, or may be combined with the gear member 7 separately. Although not necessary, the gear member 7 is provided with a boss portion 7B, which can be used for support by a bearing. Of course, the support by the bearing may be performed instead of or in other places.

A spring 27 for biasing the brake body 9 toward the cam structure 5 can be provided. The spring 27 is interposed between the gear member 7 and the brake body 9, for example.

Further, referring to fig. 4, the transmitting body 3 includes a braking body 9 on a side facing the other transmitting body 3, and the gear member 7 has a structure for accommodating the braking body 9. The brake 9 is coupled to the gear member 7 so as to be fitted therein, but is rotatable relative to the gear member. The brake body 9 may further include a groove-shaped cam surface 15 extending in the circumferential direction on a side facing the other brake body 9.

Referring mainly to fig. 3, the cam structure 5 includes cam balls 17 corresponding to the cam surfaces 15, and the cam balls 17 can roll on both the cam surfaces 15 to convert the differential motion between the transmission bodies 3 into an axial pressing force. However, the cam structure 5 is not limited to the cam ball 17, and may be provided with a rolling element such as a cylinder or a cone, or may be another suitable structure. The cam structure 5 may be a structure fixedly formed on one or both of the brake bodies 9, or may be a structure that converts a differential motion into a pressing force by sliding each other.

The pressing force generated by the cam structure 5 is used to press the braking body 9 toward the gear member 7. The combination of the gear member 7 and the brake 9 constitutes a friction clutch 13, and when a pressing force acts, the brake 9 generates a braking force against the gear member 7. The friction clutch 13 may be, for example, a cone clutch. Referring to fig. 5 in conjunction with fig. 3, the cone clutch is constituted by, for example, a cone surface 21 formed on the outer peripheral surface of the brake body 9 and a cone surface 23 correspondingly formed on the inner surface of the gear member 7, and the friction material 25 can be interposed therebetween. Although not necessarily, the friction member 25 includes a projection 25P projecting toward the gear member 7, and the gear member 7 includes a recess 7R correspondingly, and the friction member 25 may be locked against rotation relative to the gear member 7 by engagement with each other. Alternatively, the friction member 25 may be stopped against the braking body 9.

The brake body 9 further includes an assembly 11. The assembly 11 is interposed between the gear member 7 and the brake member 9, for example, and is locked to the gear member 7 by an engagement member such as a C-ring 39. Alternatively, other means may be used instead of the engaging member, or the gear member 7 may be integrated with the brake body 9.

Referring to fig. 6 in conjunction with fig. 5, the assembly 11 includes at least a plurality of brake pads 29 arranged around the shaft and a ring 31 fitted so as to apply force in a direction in which they are concentrated. The brake piece 29 surrounds and fits with the hub portion on the inner peripheral side of the gear member 7. However, the friction material 35 may be interposed between the hub portion and the brake pad 29. The friction material 35 may include a circumferential groove 37 for accommodating the brake pad 29, and the brake pad 29 is fitted into the circumferential groove 37 to secure a large friction area.

The friction material 35 further includes a projection 35P projecting toward the gear member 7, and the gear member 7 includes a recess 7Q, and the friction material 35 is locked against rotation relative to the gear member 7 by engagement with each other. By the urging force of the ring 31, the brake pads 29 frictionally generate a braking force against the friction material 35, and further generate a friction braking force against the gear member 7.

The assembly 11 is further provided with a bridge 33 for connecting the brake pad 29 to the brake body 9. The bridge 33 may be formed in a substantially annular shape around the shaft, and may include a protruding piece 33P for engagement with the brake pad 29. Correspondingly, the brake pads 29 can each be provided with a recess 29R. The engagement of the brake pads 29 with the bridge 33 may take other suitable forms. In any case, play to such an extent that the engagement of the brake pads 29 is not hindered can be provided.

Referring mainly to fig. 3, the bridge 33 is coupled to the stopper body 9 at an end opposite to the tab 33P. For example, the braking body 9 is provided with a corresponding shoulder, to which the bridge 33 is coupled, for example by interference fit. That is, the brake body 9 is driven by the brake pad 29 by sandwiching the bridge 33, and therefore the brake pad 29 is driven by the brake body 9.

As described above, in the present embodiment, both the brake by the brake pad 29 and the brake by the friction clutch 13 act on the transmission body 3. Alternatively, a structure using only one of them may be employed.

When the differential motion between the transmission members 3 is small and the torque difference applied by the motors MR and ML is also small, the brake by the brake pad 29 acts to restrict the differential motion between the right and left transmission members 3, and the differential motion restriction device 1 thereby urges the vehicle to move straight. Therefore, the differential limiting device 1 can reduce the burden of precise control of the control system of the vehicle.

When traction force is lost by one drive wheel due to the vehicle traveling on a rough road or the like, the differential motion between the transmission bodies 3 increases, and the cam structure generates a pressing force to actuate the friction clutch 13. Therefore, the braking force increases, and the differential limiting device 1 further limits the differential motion between the right and left transmitting bodies 3. At this time, the torque of the motor on the side where the traction force is lost also flows into the drive wheels that ensure traction force via the differential limiting device 1, so the vehicle can easily pass through a rough road. This operation is particularly similar to the operation of the torque-sensitive limiting differential in the conventional vehicle, and has an advantage that the driver of the conventional vehicle can easily grasp the operation of the vehicle.

On the other hand, the differential limiting capability exhibited by the differential limiting device 1 is not so large, and when the electric motors MR, ML actively exhibit a torque difference, the differential can be easily generated. Therefore, the differential limiting device 1 does not interfere with advanced control such as torque vector distribution.

Although the embodiments have been described, modifications and variations of the embodiments can be made based on the above disclosure.

Claims

1. A differential limiting device for limiting a differential motion between a pair of output shafts driven by a pair of power sources, the differential limiting device comprising:

the pair of transmission bodies are rotatable independently of each other, and each of the pair of transmission bodies includes: a gear member drivingly coupling one of the power sources to one of the output shafts; and a brake body rotatable with respect to the gear member to perform friction braking on the gear member; and

and a cam structure which is sandwiched between the pair of braking bodies, converts a differential motion between the braking bodies into an axial pressing force, and presses the braking bodies against the gear member.

2. The differential limiting device according to claim 1, wherein,

the gear member and the brake body each have a tapered surface around a corresponding shaft, and the tapered surfaces are fitted to face each other, thereby forming a tapered clutch that receives the pressing force.

3. The differential limiting device according to claim 1, wherein,

the brake body includes: a plurality of brake pads surrounding the gear member and arranged around an axis; and a ring that generates frictional force with respect to the gear member by applying force in a direction in which the plurality of brake pads are concentrated.

4. A differential limiting device according to claim 3, wherein,

the brake bodies each include a bridge that engages with the plurality of brake pads to cause the brake bodies to follow the brake pads.

5. The differential limiting device according to claim 1, wherein,

the cam structure includes cam surfaces extending in a circumferential direction, each of the cam surfaces being formed on the brake body, and cam balls capable of rolling on the cam surfaces.