Shift by wire transmission shift control system

At least one implementation of a gear shift control system includes an output mechanism coupled to a vehicle transmission, a first drive member coupled to the output mechanism to drive the output mechanism to shift between gears of the transmission and a drivetrain. The drivetrain may include a first input driven by the drive member during a first mode of operation of the gear shift control system and an output coupled to both the first input and the output mechanism to drive the output mechanism as commanded by the drive member. During a second mode of operation of the gear shift control system a second input is coupled to the output. A second drive member is coupled to the second input to drive the output mechanism through the second input and the output during the second mode of operation to cause a transmission gear shift.

TECHNICAL FIELD

The present disclosure relates generally to a gear shift system for a vehicle transmission.

BACKGROUND OF THE DISCLOSURE

In some vehicles, a gear shift lever in a passenger compartment of the vehicle can be moved by an operator of the vehicle to shift the vehicle transmission between its park gear and other gears, such as reverse, neutral and forward drive gears. The shift lever is mechanically coupled to the transmission through a cable that transmits the shift level movement to a transmission shift mechanism. Other vehicles use a so-called “shift-by-wire” system wherein an operator shift lever or shift control unit is not physically coupled to the transmission shift mechanism by a cable. Instead, the shift control unit is electrically coupled to a shift actuator that is arranged to shift the transmission upon receipt of a signal from the shift control unit that a transmission gear shift is desired by the operator. If electrical power is lost to the vehicle, or to the electrical circuit of the vehicle from which electricity is supplied to the shift-by-wire system, then the ability of the operator to control shifting of the transmission via the shift control unit is also lost.

SUMMARY OF THE DISCLOSURE

A gear shift control system permits a driver to control shifting among the gears of a vehicle transmission. The gear shift control system is a shift-by-wire system where shifting among and between the transmission gears may be accomplished with one or more electrical components and without a direct physical linkage between the driver and transmission. If electrical power is lost in the vehicle, the gear shift control system provides a mechanism to shift the vehicle transmission into park even if the driver is not able to directly command such a shift due to the lack of electrical power. In at least some implementations, the gear shift control system also enables normal, driver controlled shifting of the transmission when electrical power is restored.

At least one implementation of a gear shift control system includes an output mechanism coupled to a vehicle transmission, a first drive member coupled to the output mechanism to drive the output mechanism to shift between gears of the transmission and a drivetrain. The drivetrain interconnects the drive member and the output mechanism so that the output mechanism is driven by the drive member through the drivetrain. The drivetrain may include a first input driven by the drive member during a first mode of operation of the gear shift control system and an output coupled to both the first input and the output mechanism to drive the output mechanism as commanded by the drive member. During a second mode of operation of the gear shift control system a second input is coupled to the output. The drivetrain may also include a second drive member coupled to the second input to drive the output mechanism through the second input and the output during the second mode of operation to cause a transmission gear shift. In at least one implementation, the transmission is shifted into park during the second mode of operation, and this may occur even if electrical power is not available to the shift control system.

In at least some implementations, the gear shift control system may include a first drive member including an electric motor, an output shaft coupled to a vehicle transmission and to the first drive member to be driven for rotation by the first drive member, and a planetary gear set. The gear set is coupled to the first drive member and the output shaft, and has three intermeshed gear elements which may include a ring gear, a sun gear and at least one planet gear. A first of the gear elements is coupled to the first drive member and is driven for rotation by the first drive member, and a second of the gear elements is coupled to the output shaft for rotation with the output shaft. A second drive member is coupled to a third of the gear elements to drive the output shaft through the third gear element and the first gear element, wherein during a first mode of operation the transmission is shifted between park and other gears by causing the first drive member to rotate the output shaft through the second gear element and the first gear element when a transmission gear shift is desired, and during a second mode of operation, the transmission is shifted to park by the second drive member which drives the output shaft through the third gear element and first gear element.

A method of shifting a vehicle transmission between park and other transmission gears is also disclosed. The method may include providing a planetary gear set having a sun gear, a ring gear and one or more planet gears meshed with the sun and ring gears and carried by a carrier, and providing an output shaft coupled to the carrier for corotation with the carrier. One of the sun gear or the ring gear may be driven while holding against rotation the other one of the sun gear and ring gear during a first mode of operation wherein the output shaft is rotated to cause shift the transmission gear between park and drive gears. For the sake of discussion, the sun gear will be considered to be driven in the above example while the ring gear is held against rotation. Continuing with this example, the ring gear may also be driven while the sun gear is held so that it does not rotate to rotate the output shaft in a direction to shift the transmission to park during a second mode of operation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring in more detail to the drawings,FIG. 1shows a transmission shifting system10including an actuator12that is controlled by an operator of a vehicle to command a gear shift of the transmission14, for example to shift the transmission among and between park, neutral, reverse and forward drive gears. The shifting system10may be a so-called “shift by wire” system where an operator command for a gear shift is transmitted to an electric motor16of the actuator12, and the motor16drives an output mechanism, such as an output shaft18(FIG. 3), of the actuator12that is coupled to a shift mechanism of the transmission14to shift among the transmission gears. The output mechanism may be any device or component that may couple, directly or indirectly, the actuator to a shift mechanism of the transmission. Should electric power be lost in the vehicle, or at least in an electrical circuit of the vehicle electric system that includes the motor16, then the ability of the vehicle operator to control shifting of the vehicle transmission may also be lost. In this situation, it may be desirable to shift the transmission14into park so that any motion of the vehicle can be stopped and further motion prevented until the electric power is restored to the actuator motor16.

As shown inFIGS. 2-4and9-13, the actuator12may include a housing20, which is shown in phantom inFIG. 2to expose internal components. The actuator may also include a main drive element that, through a drivetrain22, drives the output shaft18to shift the transmission14. The main drive element may be any device capable of causing a shift of the transmission in response to an operator of the vehicle's request. The drivetrain may be any device or devices that interface with the main drive element and the transmission to facilitate shifting the transmission. In at least one implementation, the main drive element includes the electric motor16and a drive gear24, shown here as a worm that is rotated by the motor. The worm24in this implementation is meshed with a first input26of the drivetrain22, which, in this implementation, is shown as a worm gear having external teeth28that mesh with teeth30on the worm24. Further, in the implementation shown, the drivetrain22includes a planetary gear set and the first input includes a sun gear29that is coupled to the worm gear26. Accordingly, rotation of the worm24causes rotation of the worm gear26and sun gear29.

As shown inFIGS. 3,5,6and7, the sun gear29includes teeth31adapted to be meshed with an output32of the drivetrain22. In the implementation shown, the output32includes one or more planet gears meshed with the sun gear29so that rotation of the sun gear29causes rotation of the planet gears32. The planet gears32are carried for rotation about shafts or pins34that are connected to a carrier36. The carrier36, in turn, is coupled to the output shaft18such as by one or more keys of the carrier36being received in complementary keyways38formed in the output shaft18, for corotation of the carrier36and output shaft18. In this way, movement of the planet gears32around the sun gear29causes rotation of the output shaft18. In the implementation shown three planet gears32are provided, although any desired number may be used.

As best shown inFIG. 6, the planet gears32are also meshed with a second input40of the drivetrain22. The second input, in the implementation shown, includes a ring gear40having inwardly extending teeth42meshed with complementary teeth44of the planet gears32. During a normal or first mode of operation of the actuator12in which the gears of the transmission14are shifted as commanded by an operator of the vehicle, the planet gears32move relative to the ring gear40about the inner circumference of the ring gear40, and the ring gear is held so that it does not rotate. In at least one implementation, the ring gear40is held against rotating in one direction by engagement of a stop surface46carried by the ring gear with an adjacent structure, such as a tab or flange48of the carrier36. And the ring gear40may be held against rotation in a second direction, that is opposite to the first direction, by a locking mechanism50.

The locking mechanism50may be any device capable of inhibiting or preventing rotation of the ring gear, and it may be releasable to selectively permit rotation of the ring gear40in the second direction during a second mode of operation. In at least one implementation, the actuator's second mode of operation causes the transmission14to be shifted to park when electric power to the motor16is lost. During this second mode of operation, the lock mechanism50is released so that the ring gear40can rotate, the sun gear29is held in place and the ring gear40is driven in the second direction. Rotation of the ring gear40causes a corresponding movement of the planet gears32and both the ring gear40and planet gears32rotate relative to the sun gear29. This movement of the planet gears32causes rotation of the output shaft18and a corresponding movement of the shift mechanism20of the transmission14until the transmission is shifted into park. The sun gear29may be held in place by the motor16which, while not operating, resists or prevents rotation of the worm24to which the sun gear29is coupled via the worm gear26. Of course, a separate lock mechanism may be used to hold the sun gear29during the second mode of operation, if desired. The position of the actuator after the second mode of operation is shown inFIG. 10.

In the implementation shown, for example in FIGS.2and7-13, the locking mechanism50is a torsion spring that is coiled around the exterior of the ring gear40and has one fixed leg52and one movable leg54. The fixed leg52is attached to or otherwise held immobile by an adjacent structure, which could be the housing20or other portion of the actuator12or a structure not related to the actuator. The movable leg54may be moved relative to the fixed leg52. In its normal state, without movement of the movable leg54relative to the fixed leg52, the spring50provides a force that prevents or at least inhibits or limits rotation of the ring gear40in the second direction. However, when the movable leg54is moved away from the fixed leg52, the force of the spring50on the ring gear40is relieved or at least sufficiently reduced to permit rotation of the ring gear40in the second direction.

Rotation of the ring gear40in the second direction is accomplished by a second drive element56which may be any device that can provide a suitable rotational force on the ring gear40. In the implementation shown, the second drive element is a spring which is called herein a return spring56because its function is to return the transmission14to park. While any suitable spring could be used, the return spring56is shown as a torsion spring in the illustrated example. As shown inFIG. 4(and other views), the return spring56has a first end58bearing on the ring gear40, such as at a shoulder60of the ring gear40to bias the ring gear40for rotation in the second direction. A second end (not shown) of the return spring bears on a bracket62, which may be attached to another structure and held against rotation. Accordingly, when the force of the locking mechanism50on the ring gear40is relieved, the return spring56rotates the ring gear40in the second direction which causes the output shaft18to rotate and return the transmission14to park.

As best shown inFIGS. 9-13, a release mechanism64is provided to release the ring gear locking mechanism50and permit rotation of the ring gear40. As noted above, the illustrated embodiment of the locking mechanism is a torsion spring50that is released by moving the movable leg54in a direction tending to unwind the spring50. To move the movable leg54, a third drive element66is provided which engages and moves the leg54as noted. The third drive element66, in at least one implementation, includes a small electric motor that rotates an actuator68to selectively engage and move the movable leg. As shown, the actuator68includes a cam lobe70that engages and displaces the movable leg54when the actuator68is rotated. While the motor66could directly drive the actuator68, in the version shown, the motor66drives a worm72which in turn drives a worm gear of the actuator68. The motor66may be driven by electrical power charged and stored, for example, in one or more capacitors or other charge storage device. Accordingly, even if electric power in the vehicle is not otherwise functioning, the stored charge can be used to drive the release mechanism motor66.

As shown inFIGS. 11 and 12, a third mode of operation may be employed after the second mode of operation is complete and the vehicle transmission14is returned to park. The third mode of operation resets the actuator12so that the normal or first mode of operation can again commence when electrical power is restored to the main motor. In more detail, during the recovery or third mode of operation, the ring gear40is rotated in the first direction to the position it was in prior to the return to park (that is, the second) mode of operation. This winds the return spring56so that the necessary force can again be provided for a subsequent return to park event, if electrical power to the main motor16is again lost.

To return the ring gear40to its starting position, the output shaft18is held immobile, the ring gear40is not locked and the main motor16is energized to rotate the sun gear29. Rotation of the sun gear29causes a corresponding rotation of the planet gears32which in turn rotate the ring gear40back toward its starting position and thereby winds the return spring56. This may be readily seen, for example, by comparing the position of the first end58of the spring56inFIG. 10with its position inFIG. 11.

The output shaft18may be locked by any suitable mechanism during the third mode of operation. In the implementation shown, another torsion spring74is used to hold the output shaft18against rotation when desired, as shown inFIGS. 7-9. Like the ring gear torsion spring50, the output shaft torsion spring74includes a body76coiled about the output shaft18, a fixed leg78and a movable leg80. In its at rest position, the spring74provides a force on the shaft18that inhibits or prevents the shaft18from rotating. When the movable leg80is moved in direction tending to unwind the spring74, the force on the shaft18is reduced or relieved and the shaft18can rotate relative to the spring74. To selectively move the movable leg80, a release mechanism64may be used. The release mechanism64, in the implementation shown, is the same mechanism64used to release the ring gear torsion spring50.

As shown inFIG. 9, the actuator68includes a second cam lobe82arranged to selectively engage and displace the movable leg80during a portion of the rotation of the actuator68. In this example, the second cam lobe82may engage and move the movable leg80to relieve the spring force on the output shaft18during at least the first mode of operation, as shown, for example, inFIG. 9. This permits the output shaft18to rotate relative to the spring74so that shifting of the transmission14can be accomplished under operator command. The second cam lobe82may be moved for the third mode of operation so that the movable leg80moves in a direction tending to further wind the spring74onto the output shaft18and the spring force is applied to the shaft18to inhibit or prevent the shaft from rotating in one direction.

The cam lobe82, which cannot be directly seen in the views ofFIGS. 10-13, is shown in dashed lines inFIGS. 10-13to illustrate the movement and certain positions of the cam lobe82as the actuator68rotates. For example, inFIG. 12, the nose of the cam lobe82is shown not engaged with the movable leg80, and in that position the spring74prevents rotation of the output shaft18. InFIG. 13, the nose of the cam lobe82is engaged with and displacing the movable leg80so that the spring74does not prevent rotation of the output shaft18.

With the output shaft18held in position, the carrier36does not rotate during the third mode of operation. Instead, the planet gears32only rotate around their shafts34. When the main motor16is energized to drive the sun gear29, the rotation of the sun gear29is transmitted to the ring gear40via the rotating planet gears32. This returns the ring gear40to its starting position (e.g. the position it was in before the second mode of operation), which also winds the return spring56as noted above.

After the ring gear40is returned to its starting position, the release mechanism64can move the first cam70out of engagement with the movable leg54of the ring gear locking mechanism50, as is shown inFIG. 12, to re-lock the ring gear40and prevent it from rotating. Continued rotation of the release mechanism64may also move the second cam82into engagement with the movable leg80of the output shaft locking mechanism74, as shown inFIG. 13, to displace the movable leg80and thereby unlock and permit rotation of the output shaft18. In this way, the actuator components (e.g. motors, drivetrain, output shaft, release mechanism and locking mechanisms) are positioned and arranged to permit future shifting of the transmission14in the first mode of operation, as commanded by a vehicle operator under the power of the main motor16.

While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. For example, while the drivetrain22was shown and described as a planetary gear set, other arrangements are possible. Also, while the first input was described as being the sun gear29, the second input the ring gear40and the output the planet gears32, the gears could be arranged differently so that the different gears define different ones of the inputs and output. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.