Power transfer mechanism for 4WD vehicles with low effort mode shift system

Patent metadata

Field	Value
Publication number	US-9216649-B2
Application number	US-201414279666-A
Country	US
Kind code	B2
Filing date	May 16, 2014
Priority date	Jun 13, 2012
Publication date	Dec 22, 2015
Grant date	Dec 22, 2015

Abstract

A power transfer mechanism for a four-wheel drive vehicle includes a first shaft for transferring torque to a first driveline, a second shaft for transferring torque to a second driveline, and a transfer mechanism driving the second shaft. A mode clutch drivingly connects the first shaft to the transfer mechanism and includes a clutch gear-driven by the transfer mechanism and a mode sleeve. A sprocket associated with the transfer mechanism has internal spline teeth meshed with external spline teeth on the second shaft with a predetermined amount of backlash therebetween. A ball cam mechanism centers the backlash and permits relative rotation of the transfer mechanism and the mode sleeve to circumvent a blocked mode shift.

First claim

What is claimed is:

1. A power transfer mechanism for a four-wheel drive vehicle having a powertrain, a first driveline for driving a pair of first wheels and a second driveline for driving a pair of second wheels, the power transfer mechanism comprising:
a first shaft adapted to transmit drive torque from the powertrain to the first driveline;
a second shaft adapted to be coupled to the second driveline;
a transfer mechanism including a first transfer component rotatably mounted on the first shaft, a second transfer component mounted on the second shaft, and a torque transmission component interconnecting the first and second transfer components;
a mode clutch for selectively coupling the first transfer component for driven rotation with the first shaft, the mode clutch including a clutch gear fixed to the first transfer component and having clutch gear teeth, and a mode sleeve fixed via a sliding spline connection for rotation with the first shaft and having mode sleeve teeth, wherein the mode sleeve is operable in a released position to disengage the mode sleeve teeth from the clutch gear teeth for releasing the transfer mechanism from driven connection with the first shaft, and wherein the mode sleeve is operable in an engaged position to engage the mode sleeve teeth with the clutch gear teeth for coupling the transfer mechanism for driven connection with the first shaft; and
a backlash interface connection disposed between the second transfer component and the second shaft to permit a predetermined amount of angular movement therebetween so as to reduce an axial force required to move the mode sleeve from the released position into the engaged position, the backlash interface connection including external shaft spline teeth formed on the second shaft, a plurality of recesses formed between certain adjacent pairs of the external shaft spline teeth with a retention chamber formed in each recess, internal spline teeth formed in a central aperture of the second transfer component and which are interdigitated with the external shaft spline teeth, a plurality of ramped cam seats formed between adjacent pairs of the internal spline teeth and which are aligned with respect to the plurality of recesses, and a plurality of spring-biased cam followers at least partially disposed in each of the retention chambers and biased into engagement with a corresponding one of the ramped cam seats so as to establish a predefined amount of angular clearance between each set of interdigitated shaft spline teeth and internal spline teeth to define a predetermined amount of backlash between the second transfer component and the second shaft;
wherein the second transfer component is rotatable through the backlash to align the clutch gear teeth with the mode sleeve teeth to circumvent a blocked movement of the mode sleeve from the released position into the engaged position.

2. The power transfer mechanism of claim 1 , wherein the predetermined amount of backlash defines about eight degrees of relative rotation between the second transfer component and the second shaft.

3. The power transfer mechanism of claim 1 , wherein the internal spline teeth on the second transfer component are centered relative to the shaft spline teeth when the followers are centrally-disposed within the ramped cam seats.

4. The power transfer mechanism of claim 1 wherein the first transfer component is a first sprocket, the second transfer component is a second sprocket, and the torque transmission component is a belt or chain interconnecting the first sprocket for rotation with the second sprocket.

5. The power transfer mechanism of claim 4 wherein the spring-biased cam followers include a spring and a ball at least partially retained in each of the recesses, and wherein each ball is biased by the spring into engagement with a central portion of a corresponding one of the ramped cam seats to centrally locate and align the internal spline teeth of the second sprocket relative to the external shaft teeth on the second shaft.

6. The power transfer mechanism of claim 5 wherein each of the ramped cam seats includes a pair of cam surfaces configured to displace the balls inwardly against the biasing force of the springs in response to rotational movement of the second sprocket relative to the second shaft in response to translational movement of the mode sleeve from the released position toward the engaged position.

7. The power transfer mechanism of claim 1 wherein the mode clutch assembly further includes a synchronizer that is operably disposed between the mode sleeve and the clutch gear.

8. The power transfer mechanism of claim 1 further comprising a power-operated actuator operable for moving the mode sleeve between the released and engaged positions, a mode select mechanism for permitting a vehicle operator to select between a two-wheel drive mode established when the mode sleeve is in the released position and a four-wheel drive mode established when the mode sleeve is in the engaged position, and a controller for receiving a mode signal from the mode select mechanism indicative of the selected drive mode and controlling operation of the power-operated actuator in response to the mode signal.

9. A power transfer mechanism for a four-wheel drive vehicle having a powertrain, a first driveline for driving a pair of first wheels and a second driveline for driving a pair of second wheels, comprising:
a first shaft adapted to transmit drive torque from the powertrain to the first driveline;
a second shaft adapted to be coupled to the second driveline;
a transfer mechanism including a first sprocket rotatably supported on the first shaft, a second sprocket mounted on the second shaft, and an endless chain or belt interconnecting the first and second sprockets;
a mode clutch for selectively coupling the first sprocket to the first shaft and including a clutch gear coupled to the first sprocket and having clutch gear teeth, and a mode sleeve coupled for rotation with the first shaft and axially moveable relative to the clutch gear between first and second positions and having mode sleeve teeth, wherein the mode sleeve is operable in the first position to disengage the mode sleeve teeth from engagement with the clutch gear teeth and is operable in the second position to engage the mode sleeve teeth with the clutch gear teeth; and
a backlash interface connection disposed between the second sprocket and the second shaft to permit a predetermined amount of relative angular travel therebetween so as to reduce an axial force required to move the mode sleeve from the first position to the second position, the backlash interface connection including internal sprocket spline teeth formed on the second sprocket that are interdigitated with external spline teeth formed on the second shaft and defining a centered position with a predefined clearance between the interdigitated spline teeth, a plurality of circumferentially-aligned retention chambers formed in a face surface on one of the second sprocket and the second shaft, a plurality of circumferentially-aligned cam seats formed in a face surface on the other one of the second sprocket and the second shaft, and spring-biased cam followers partially disposed in the retention chambers and centrally positioned in engagement with the cam seats when the interdigitated spline teeth are centrally positioned;
wherein the second sprocket is rotatable through the predetermined backlash to assist in aligning the clutch gear teeth with the mode sleeve teeth to circumvent a blocked movement of the mode sleeve from the first position to the second position.

10. The power transfer mechanism of claim 9 wherein the internal mode sleeve teeth engage

Assignees

• Magna Powertrain America Inc

Inventors

• Beasock Randolph E
• Bradford Jr Thomas E

Classifications

• B60K2023/0858

  with electric means, e.g. electro-hydraulic means · CPC title

• B60K17/344

  having a transfer gear · CPC title

• B60K23/08 Primary

  for changing number of driven wheels {, for switching from driving one axle to driving two or more axles (B60K17/3515 takes precedence)} · CPC title

• Y10T74/19074

  Single drive plural driven · CPC title

• B60K17/3467

  combined with a change speed gearing, e.g. range gear · CPC title