WO2014172175A1

WO2014172175A1 - Variable speed differential drive

Info

Publication number: WO2014172175A1
Application number: PCT/US2014/033605
Authority: WO
Inventors: Robert Benjey
Original assignee: Eaton Corp
Current assignee: Eaton Corp
Priority date: 2013-04-16
Filing date: 2014-04-10
Publication date: 2014-10-23
Anticipated expiration: 2015-10-16

Abstract

A differential drive assembly constructed in accordance to one example of the present disclosure includes a ring gear, a sun gear, an input member and a differential. The ring gear can be rotatably mounted to a housing. The sun gear can be meshingly engaged to the ring gear through a planet carrier having a plurality of planet gears. The input member can be selectively engaged to the ring gear. The differential can be driven by the planet carrier. The sun gear can provide a first rotatable input to the differential and the input member can provide a second rotatable input to the differential causing the differential to be selectively driven at variable speed.

Description

VARIABLE SPEED DIFFERENTIAL DRIVE

FIELD

[0001] The present disclosure relates generally to traction modifying differential devices and more particularly to a variable speed differential drive.

BACKGROUND

[0002] It has been increasingly desirable to have overdrive ratios in a number of the highest gears in a transmission to gain improved fuel economy. In some examples when this is done, the remaining gears are too few to cover the range of needed ratio change leading to large undesirable gear to gear steps.

[0003] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

SUMMARY

[0004] A differential drive assembly constructed in accordance to one example of the present disclosure includes a ring gear, a sun gear, an input member and a differential. The ring gear can be rotatably mounted to a housing. The sun gear can be meshingly engaged to the ring gear through a planet carrier having a plurality of planet gears. The input member can be selectively engaged to the ring gear. The differential can be driven by the planet carrier. The sun gear can provide a first rotatable input to the differential and the input member can provide a second rotatable input to the differential causing the differential to be selectively driven at variable speed.

[0005] According to additional features, the input member of the differential drive assembly can be a worm gear. In other examples, the input member can be a spur gear. In still other configurations, the input member can be a hydraulic pump. The differential drive assembly can further include a hydraulic motor. The hydraulic pump can be configured in one example to pump oil to the hydraulic motor based on rotation of the ring gear. The hydraulic motor can be configured to introduce a rotary torque onto the differential based on rotation of the ring gear.

[0006] According to other features, the differential drive assembly can further comprise a valve positioned between the hydraulic pump and the hydraulic motor. The valve can be movable between (i) an open position that permits oil flow between the hydraulic pump and the hydraulic motor, and (ii) a closed position that precludes oil flow between the hydraulic pump and the hydraulic motor.

[0007] According to other configurations, the hydraulic motor of the differential drive assembly can be configured to pump oil to a transmission oil pump based on rotation of the ring gear. The differential drive assembly can be arranged in a front transaxle. The differential drive assembly can be mounted in a front wheel drive vehicle.

[0008] A differential drive assembly constructed in accordance to another example of the present disclosure can include a ring gear, a sun gear, a hydraulic pump, a differential, and a hydraulic motor. The ring gear can be rotatably mounted to a housing. The sun gear can be meshingly engaged to the ring gear through a planet carrier having a plurality of planet gears. The hydraulic pump can be selectively coupled to the ring gear. The differential can be driven by the planet carrier. The hydraulic motor can be selectively coupled to the differential and configured to introduce rotary torque onto the differential based on oil communicated from the hydraulic pump in response to rotation of the ring gear.

[0009] According to additional features, the differential drive assembly can further include a valve positioned between the hydraulic pump and the hydraulic motor. The valve can be movable between (i) an open position that permits oil flow between the hydraulic pump and the hydraulic motor, and (ii) a closed position that precludes oil flow between the hydraulic pump and the hydraulic motor.

[0010] In other arrangements, the differential drive assembly can further include an accumulator fluidly connected between the hydraulic pump and the hydraulic motor. The differential drive assembly can additionally include an overriding clutch positioned between the hydraulic motor and the differential. The differential drive assembly can be arranged in a front transaxle. [0011] According to another configuration, a differential drive assembly according to the present disclosure can include a ring gear, a sun gear, an input member, a hydraulic pump and a differential. The ring gear can be rotatably mounted to a housing. The sun gear can be meshingly engaged to the ring gear through a planet carrier having a plurality of planet gears. The input member can be selectively engaged to the ring gear. The hydraulic pump can be coupled to the input member. The differential can be driven by the planet carrier. The sun gear can provide a first rotatable input to the differential and the input member can provide a second rotatable input to the differential causing the differential to be selectively driven at variable speed. The hydraulic pump can be configured to pump oil to a transmission oil pump based on rotation of the ring gear.

[0012] According to additional features, the differential drive assembly can further include a valve positioned between the hydraulic pump and the transmission oil pump. The valve can be movable between (i) an open position that permits oil flow between the hydraulic pump and the transmission oil pump, and (ii) a closed position that precludes oil flow between the hydraulic pump and the transmission oil pump. The differential drive assembly can be arranged in a front transaxle. The differential drive assembly can be mounted in a front wheel drive vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0014] FIG. 1 is a side schematic depiction of a variable speed differential assembly constructed in accordance to one example of the present disclosure;

[0015] FIG. 2 is a cross-sectional representation of a variable speed differential assembly constructed in accordance to another example of the present disclosure;

[0016] FIG. 3 is a cross-sectional representation of a variable speed differential assembly constructed in accordance to another example of the present disclosure;

[0017] FIG. 4 is a cross-sectional representation of a variable speed differential assembly constructed in accordance to another example of the present disclosure; [0018] FIG. 5 is a cross-sectional representation of a variable speed differential assembly constructed in accordance to another example of the present disclosure; and

[0019] FIG. 6 is a cross-sectional representation of a variable speed differential assembly constructed in accordance to another example of the present disclosure.

DETAILED DESCRIPTION

[0020] With initial reference to FIGS. 1 a variable speed differential drive assembly is shown and generally identified at reference numeral 10. The variable speed differential drive assembly 10 can be arranged in a front transaxle of a vehicle. In this regard, the variable speed differential drive assembly 10 can be mounted in a front wheel drive vehicle. The variable speed differential drive assembly 10 generally includes a planetary drive 12, a sun gear 14, a ring gear 16, an input member or worm gear 18 and a motor 20. The planetary drive 12 comprises a plurality of planet gears 22 that rotate between the sun gear 14 and the ring gear 16. A transmission output member 26 drives the planetary drive 12 by way of a chain member 30. The planetary drive 12 drives a differential (not shown in FIG. 1 ). The ring gear 16 is rotatably received in a housing 34. The ring gear 16 is permitted to rotate in a counter clockwise direction relative to the housing 34 as viewed in FIG. 1. In this regard, the variable speed differential drive assembly 10 allows the engine speed to increase for a given output or axle speed. The worm gear 18 is driven by the motor 20. The motor 20 may be an electric or a hydraulic motor. The worm gear 18 driven by the motor 20 can be designed to allow some amount of back driving (or no back driving) depending on the reduction desired, the amount of torque desired to move the ring gear 16, torque needed to overcome the static friction or other variable. The differential configuration shown in FIG. 1 therefore has two inputs: the sun gear 14 and the worm gear 18. In other examples, such as disclosed herein, this may be accomplished using a spur gear. By allowing the ring gear 16 to rotate, the "fulcrum" is moved allowing greater engine speed for a given axle speed. Explained further, a ratio of 1 :1.x can be achieved based on a given application.

[0021] In another example configuration of FIG. 1 , the worm gear 18 could be replaced by a gear to backdrive the motor 20. In this configuration, the ring gear 16 would drive the motor 20 as a generator. The motor 20 could be using energy to hold the ring gear 16 stationary. When the ring gear 16 is allowed to slip, the gear (in place of the worm 18) would backdrive the motor 20 to create electrical energy. The electrical energy can be used to power a traction motor used to input torque back into the system.

[0022] Turning now to FIG. 2, a variable speed differential drive assembly constructed in accordance to another example of the present disclosure is shown and generally identified at reference 1 10. The variable speed differential drive assembly 1 10 generally includes a planetary drive 1 12, a sun gear 1 14, a ring gear 1 16, an input member or spur gear 1 18, a hydraulic pump 1 19 and a hydraulic motor 120. The sun gear 1 14 is driven by an input gear 121. The planetary drive 1 12 comprises a plurality of planet gears 122 that are rotatably mounted to a planetary or differential carrier 131 and are configured to rotate between the sun gear 1 14 and the ring gear 116. The planetary drive 1 12 drives a differential carrier 131 of a differential 132. The ring gear 1 16 is rotatably received in a housing 134. A bearing 135 is mounted between the housing 134 and the ring gear 1 16.

[0023] The ring gear 1 16 can be controlled by the spur gear 118 connected to the hydraulic pump 1 19. When the hydraulic pump is blocked, such as by valve 136, the ring gear 1 16 stops being driven by the spur gear 1 18. The flow therefore adjusts the rotation of the ring gear 1 16 and the speed change of the engine relative to the axle speed. This allows more engine power to be delivered to the vehicle wheels achieving higher speed and torque as the engine "climbs" its torque curve. The hydraulic motor 120 has an overrunning clutch 140 between it and the differential carrier 131 since the carrier 131 must overrun it when the ring gear 1 16 is stopped. For reverse, the overrunning clutch 140 will drive the motor 120 as a pump and thus a reverse flow valve 142 is added to prevent hydraulic lock. A park pawl 144 can selectively mesh with the ring gear 1 16. The park pawl 144 is added since when the engine if off and oil is not supplied to the hydraulic pump 120, the oil pressure can leak down and allow the ring gear 1 16 to rotate which bypasses the existing up-stream parking pawl.

[0024] With reference to FIG. 3, a variable speed differential drive assembly constructed in accordance to another example of the present disclosure is shown and generally identified at reference 210. The operation of the variable speed differential drive assembly 210 is similar to the variable speed differential 1 10 described above. Like reference numerals increased by 100 have been used to denote similar components. The variable speed differential drive assembly 210 generally includes a planetary drive 212, a sun gear 214, a ring gear 216, an input member or hydraulic pump 219 and a hydraulic motor 220. The sun gear 214 is driven by an input gear 221. The planetary drive 212 comprises a plurality of planet gears 222 that are rotatably mounted to a planetary or differential carrier 231 and are configured to rotate between the sun gear 214 and the ring gear 216. The planetary drive 212 drives a differential carrier 231 of a differential 232. The ring gear 216 is rotatably received in a housing 234. The hydraulic pump 219 is a positive displacement pump. In this example however a bearing is not needed around the ring gear 216. The hydraulic pump 219 is located within the differential. A valve 236 can control the oil that is communicated to and from the hydraulic pump. When valve 236 is in a closed position, hydraulic lock results and the ring gear 216 will not rotate. When the valve 236 is open, fluid is permitted to flow which allows the ring gear 216 to slip and the hydraulic pump 219 to operate as a positive displacement pump. The hydraulic motor 220 has an overrunning clutch 240 between it and the differential carrier 231 since the carrier 231 must overrun it when the ring gear 216 is stopped.

[0025] With reference to FIG. 4, a variable speed differential assembly constructed in accordance to another example of the present disclosure is shown and generally identified at reference 310. The operation of the variable speed differential drive assembly 310 is similar to the variable speed differential drive assembly 100 described above. Like reference numerals increased by 200 have been used to denote similar components. The variable speed differential drive assembly 310 generally includes a planetary drive 312, a sun gear 314, a ring gear 316, an input member or spur gear 318, a hydraulic pump 319 and a transmission oil pump 320. The sun gear 314 is driven by an input gear 321. The planetary drive 312 comprises a plurality of planet gears 322 that are rotatably mounted to a planetary or differential carrier 331 and are configured to rotate between the sun gear 314 and the ring gear 316. The planetary drive 312 drives a differential carrier 331 of a differential 332. The ring gear 316 is rotatably received in a housing 334. In the configuration shown in FIG. 4, pumped oil is allowed to return to the transmission oil pump 320 to supplement its energy needs when the hydraulic pump 319 is running. Otherwise, there is no flow and the transmission pump 320 operates as normal. This configuration may reduce the transmission pump energy draw when the ring gear 316 is rotating. Note that the parking pawl 344 is still on the ring gear 316 to ensure a fail-safe operation should oil leak down in the hydraulic pump 319.

[0026] According to the present teachings, when the ring gear 316 slips, the hydraulic pump 319 begins to pump fluid to the transmission oil pump 320. The hydraulic pump 319 therefore acts as a motor. When valve 336 is in a closed position, hydraulic lock results and the ring gear 316 will not rotate. When the valve 336 is open, fluid is permitted to flow which allows the ring gear 316 to slip and the hydraulic pump 319 to operate as a pump. In this regard, oil is urged into the transmission oil pump 320. When the ring gear 316 is permitted to slip, the system is otherwise loosing energy. The configurations shown herein, such as shown in FIG. 4, captures the energy and puts it back into the system. In the configuration of FIG. 4, the energy is returned to the system through the transmission oil pump 320.

[0027] With reference to FIG. 5, a variable speed differential drive assembly constructed in accordance to another example of the present disclosure is shown and generally identified at reference 410. The operation of the variable speed differential drive assembly 410 is similar to the variable speed differential drive assembly 100 described above. Like reference numerals increased by 300 have been used to denote similar components. The variable speed differential drive assembly 410 generally includes a planetary drive 412, a sun gear 414, a ring gear 416, an input member or worm gear 418, and a hydraulic pump 419. The sun gear 414 is driven by an input gear 421. The planetary drive 412 comprises a plurality of planet gears 422 that are rotatably mounted to a planetary or differential carrier 431 and are configured to rotate between the sun gear 414 and the ring gear 416. The planetary drive 412 drives a differential carrier 431 of a differential 432. The ring gear 416 is rotatably received in a housing 434. Rotational energy may be recovered via an electrical bus 448 (and/or by the hydraulic pump 419). The pitch of the worm gear 418 can be adjusted to change the motor requirements for torque and speed as well as adjusting the static friction loss.

[0028] With reference to FIG. 6, a variable speed differential drive assembly constructed in accordance to another example of the present disclosure is shown and generally identified at reference 510. The operation of the variable speed differential drive assembly 510 is similar to the variable speed differential drive assembly 200 described above. Like reference numerals increased by 300 have been used to denote similar components. The variable speed differential drive assembly 510 generally includes a planetary drive 512, a sun gear 514, a ring gear 516, an input member or worm gear 518, and a hydraulic pump 519. The sun gear 514 is driven by an input gear 521. The planetary drive 512 comprises a plurality of planet gears 522 that are rotatably mounted to a planetary or differential carrier 531 and are configured to rotate between the sun gear 514 and the ring gear 516. The planetary drive 512 drives a differential carrier 531 of a differential 532. The ring gear 516 is rotatably received in a housing 534. The hydraulic motor 520 has an overrunning clutch 540 between it and the differential carrier 531 since the carrier 531 must overrun it when the ring gear 516 is stopped. An accumulator 550 can be located between the hydraulic pump 519 and the hydraulic motor 520. The accumulator 550 can be used to balance flow conditions between the hydraulic pump 519 to the hydraulic motor 520.

[0029] According to the present teachings, when the ring gear 516 slips, the hydraulic pump 519 begins to pump fluid. When valve 536 is in a closed position, hydraulic lock results and the ring gear 516 will not rotate. When the valve 536 is open, fluid is permitted to flow which allows the ring gear 516 to slip and the hydraulic pump 519 to operate as a pump. In this regard, oil is urged into the accumulator 550 and the hydraulic motor 520. The hydraulic motor 520 introduces a rotary torque onto the differential carrier 531. The torque introduced onto the differential carrier 531 is communicated to the axles that rotate with the differential carrier 531.

[0030] When the ring gear 516 is permitted to slip, the system is otherwise loosing energy. The configurations shown herein, such as shown in FIG. 6, captures the energy and puts it back into the system.

[0031] In other examples of this disclosure, an existing planetary final drive of a differential may be used as a portion of the reduction mechanism. In other examples, reduced gear reduction may be used between each primary gear to maintain optimum engine efficiency thus improving fuel economy. A variable reduction can be implemented and/or an additional gear range. The variable reduction can be a bolt-on assembly instead of a differential replacement.

[0032] In any of the examples described above, a shift strategy may be implemented according to a given application. In one example, a variable under drive can be provided for launch and subsequently a 1 :1 ratio can be provided through all the primary gears. A small amount of under drive may be added in the primary gears if necessary. In another example, the transmission could shift in and out of under drive "splitting" the primary drives as necessary.

[0033] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

CLAIMS What is claimed is:

1. A differential drive assembly comprising:

a ring gear rotatably mounted to a housing;

a sun gear meshingly engaged to the ring gear through a planet carrier having a plurality of planet gears;

an input member selectively engaged to the ring gear; and

a differential driven by the planet carrier;

wherein the sun gear provides a first rotatable input to the differential and the input member provides a second rotatable input to the differential causing the differential to be selectively driven at variable speed.

2. The differential drive assembly of claim 1 wherein the input member is a worm gear.

3. The differential drive assembly of claim 1 wherein the input member is a spur gear.

4. The differential drive assembly of claim 1 wherein the input member is a hydraulic pump.

5. The differential drive assembly of claim 4, further comprising a hydraulic motor.

6. The differential drive assembly of claim 5 wherein the hydraulic pump is configured to pump oil to the hydraulic motor based on rotation of the ring gear.

7. The differential drive assembly of claim 6 wherein the hydraulic motor is configured to introduce a rotary torque onto the differential based on rotation of the ring gear.

8. The differential drive assembly of claim 7, further comprising a valve positioned between the hydraulic pump and the hydraulic motor, wherein the valve is movable between (i) an open position that permits oil flow between the hydraulic pump and the hydraulic motor, and (ii) a closed position that precludes oil flow between the hydraulic pump and the hydraulic motor.

9. The differential drive assembly of claim 4, wherein the hydraulic pump is configured to pump oil to a transmission oil pump based on rotation of the ring gear.

10. The differential drive assembly of claim 1 wherein the differential drive assembly is arranged in a front transaxle.

1 1. The differential drive assembly of claim 1 wherein the differential drive assembly is mounted in a front wheel drive vehicle.

12. A differential drive assembly comprising:

a ring gear rotatably mounted to a housing;

a hydraulic pump selectively coupled to the ring gear;

a differential driven by the planet carrier; and

a hydraulic motor selectively coupled to the differential and configured to introduce rotary torque onto the differential based on oil communicated from the hydraulic pump in response to rotation of the ring gear.

13. The differential drive assembly of claim 12, further comprising:

a valve positioned between the hydraulic pump and the hydraulic motor, wherein the valve is movable between (i) an open position that permits oil flow between the hydraulic pump and the hydraulic motor, and (ii) a closed position that precludes oil flow between the hydraulic pump and the hydraulic motor.

14. The differential drive assembly of claim 13, further comprising:

an accumulator fluidly connected between the hydraulic pump and the hydraulic motor.

15. The differential drive assembly of claim 12, further comprising:

an overrunning clutch positioned between the hydraulic motor and the differential.

16. The differential drive assembly of claim 12 wherein the differential drive assembly is arranged in a front transaxle.

17. A differential drive assembly comprising:

a ring gear rotatably mounted to a housing;

an input member selectively engaged to the ring gear; a hydraulic pump coupled to the input member; and

a differential driven by the planet carrier, wherein the sun gear provides a first rotatable input to the differential and the input member provides a second rotatable input to the differential causing the differential to be selectively driven at variable speed; wherein the hydraulic pump is configured to pump oil to a transmission oil pump based on rotation of the ring gear.

18. The differential drive assembly of claim 17, further comprising:

a valve positioned between the hydraulic pump and the transmission oil pump, wherein the valve is movable between (i) an open position that permits oil flow between the hydraulic pump and the transmission oil pump, and (ii) a closed position that precludes oil flow between the hydraulic pump and the transmission oil pump.

19. The differential drive assembly of claim 17 wherein the differential drive assembly is arranged in a front transaxle.

20. The differential drive assembly of claim 17 wherein the differential drive assembly is mounted in a front wheel drive vehicle.