Change-gear transmissions and so-called X-Y shifting devices therefor are well known in the prior art. Briefly, X-Y gear change actuators or shifters are devices which control the X-X (or selection directional) and the Y-Y (or engage/not-engaged directional) positions of a shift control member such as a shift finger or the like. Typically, in shift-by-wire systems adapted for use with change-gear transmissions, two separate electric motors are used to control the X-X and Y-Y positioning of the shift control member, and thus the selection of gears through which the transmission input and output shafts operably communicate. The transmission input and output shafts are in operable communication when in power transmitting engagement with each other. Typically, the transmission input shaft is selectively engaged, for example through a master friction clutch C, to the output shaft of a prime mover such as a gasoline or diesel engine E (FIG. 30).
Referring to FIG. 30, in manual change-gear transmission types, when the master friction clutch C is engaged, the input shaft of the transmission T rotates with and in the same direction as the engine output shaft. The transmission may include one or more countershafts operably disposed between the transmission input and output shafts, which are selectively engaged at different gear ratios through the respectively selected gears.
Typically X-Y shifter S is mounted to the transmission T and manually controlled as a slave device electrically connected to the operator's shift lever interface L or an intermediate controller module M, or is under the control of a system controller of a fully or partially automated transmission system. Typically, in manual transmission applications, the shift lever L is manipulated through an X-Y or H-pattern that simulates the corresponding X-Y positioning of the shift control member within the transmission.
As is known, the purpose of an X-Y shifter S is to properly position the shift control member by moving it along paths on which different sets of gears that that may be engaged and disengaged, and on which the gears of the selected set are brought into and out of power transmitting engagement with the transmission input and output shafts. In a manual change-gear transmission T, for example, the shift finger may be positioned along the X-direction between different “gates” in which a respective set of gears is engageable and disengageable, and along the Y-direction between the neutral gear and gear engagement positions in the selected gate.
The progressive selection of forward gears in manual change-gear transmissions T is typically through at least portions of at least one H-shaped shift pattern. For example in a one-reverse-speed, six-forward-speed manual transmission (i.e., a six-speed manual transmission), progression from first through sixth gear usually involves the operator's corresponding movement of the shift lever L through an interface 44 including a pair of H-shaped patterns (FIG. 30) that share a common central longitudinal leg extending along the Y-direction. The lateral crossbars of each H pattern extend along the X-direction, and are aligned and connected across the shared central longitudinal leg. In such a six-speed transmission, the reverse shift lever position is typically laterally outward of the forward gear H patterns, along the direction of the aligned cross-bars in the X-direction, and also longitudinally along a short Y-direction leg. Thus, a six speed manual transmission T, for example, typically includes four longitudinal legs or gates, each defined by a respective leg of shift finger travel in the Y-direction, with the legs spaced from each other along the X-direction.
Relative to the shift lever's (L) usual orientation as installed in a vehicle, in the exemplary six-speed manual transmission T, the six forward speed shift lever gear positions have a forwardmost position in which gears 1, 3, and 5 are located, and a rearwardmost position in which gears 2, 4, and 6 are located, the forwardmost and rearwardmost positions located on opposite sides of the central, neutral gear positions. The four gates may be respectively identified A-D, and in the example pattern of shift lever interface 44 herein discussed the reverse gear lever position RA is located to the left, along gate A, and adjacent to the second gear position 2B. The movement of the shift control member in the transmission may directly correspond to movement of the shift lever L in X-Y directions. That is, the shift lever and shift control member may be correspondingly moved through similar shift patterns substantially simultaneously to engage a particular ratio and/or drive direction.
By way of example, referring to FIG. 30, assuming a six-speed manual transmission is engaged in first gear (position 1B) and a shift to second gear (position 20 is required (i.e., a “1-2” shift), the shift lever and shift control member are each correspondingly moved in its respective Y-Y direction along gate B from the 1B-3C-5D position to neutral gear position NB to disengage first gear, then continued along gate B to the RA-2B-4C-6D position to engage second gear. If a further shift to third gear (position 3C) is required (i.e., a “2-3” shift), the shift lever and shift control member are each correspondingly moved in the respective Y-Y direction along gate B from the RA-2B-4C-6D position to neutral gear position NB to disengage second gear, then moved to neutral gear position NC of gate C, and then continued along gate C to the 1B-3C-5D position to engage third gear.
In prior shift-by-wire systems, a typical X-Y gear change actuator S includes a first motor for moving the shift control member or shift finger in the X-X direction and a second motor for moving the shift control member in the Y-Y direction. The first and second motors may be electric motors and/or fluid motors controlled by solenoids or the like. The X-Y position of the shift control member may be indicated by sensors that communicate with an electronic control unit (“ECU”) in controller module M, which controls a motor driver and a switching device for individually connecting the motor driver, to the first and second motors one at a time. The ECU is preferably microprocessor-based, and receives and processes input signals according to logic rules to issue command output signals as described, for example, in U.S. Pat. Nos. 4,361,060 and 4,595,986, the disclosures of which are expressly incorporated herein by reference. Through this control arrangement, the first and second motors of the prior gear change actuator S are each respectively dedicated to positioning the shift control member in the X and Y directions, and are individually controlled only one at a time, rather than simultaneously. Moreover, to effect quick, effective positioning of the shift control member between various positions along its X and Y directions, one of the first and second motors is typically larger than the other, for the motors are matched to the requirements of moving the shift control member in its X or Y direction in view of physical characteristics associated with shifting between gates (X-direction movement), and the positions along each gate (Y-direction movement).
For example, within a prior manual gear-change transmission T, each gate may be respectively provided with a gear change mechanism through which gear changes in that gate are accomplished through movement of a shift rail and fork assembly that is coupled to a control collar or ring. Typically, each shift rail extends along a shift rail axis. As is well known, movement of the shift rail along its axis in the Y-direction effects movement of its fork, and the control collar it is coupled to, therealong. The fork is typically defined by a pair of fingers that are joined at a hub section and define therebetween a U-shaped opening in which the control collar is received and relative to which it is axially fixed. The fork fingers extend about the circumference of its respective control collar and are disposed in a circumferential collar groove, the distal ends of the fingers disposed in the groove interfacing the opposing axial sides that define the collar groove. Each control collar is concentric with and rotatably fixed about the transmission mainshaft or output shaft and is rotatable relative to its fork, which positions the collar axially along the mainshaft or output shaft axis.
The respective control collar of each gate slides between a neutral gear position in which it is rotatably fixed to the transmission mainshaft or output shaft but is not operably engaged with the input shaft, and at least one gear engagement position. In each gear engagement position, the control collar remains rotatably fixed to the transmission mainshaft and is also operably engaged with the transmission input shaft, typically by being coupled to a gear of a gear train that is driven by the input shaft. The geartrain ordinarily provides gear reduction and rotation direction changes between the transmission input and output shafts. Thus, each control collar serves as a dog clutch for its respective gear change mechanism, through which the input and output shafts are selectively rotatably interconnected.
In this example, the movements of each shift rail and fork assembly is imparted by corresponding shift control member movements between shift positions in the respective gate, which is driven by the actuator motor solely dedicated to Y-direction motion of the gear change mechanism. Shift finger movement in the X-direction between different gates, which occurs only when the gear change mechanisms of all gates are each in their respective neutral gear position, is driven by the motor solely dedicated to X-direction motion of the gear change mechanism.
Relative to the selected gate, the shift finger engages the shift rail of its gear change mechanism, for example by its finger tip being received between interfacing sidewalls of a slot formed in the shift rail. The shift finger may extend radially from, and be fixed to, a rotatable and axially moveable cylindrical shift rod. The tip of the shift finger bears against the opposite sidewalls of the shift rail slot, and angular movement of the shift rod about its axis moves the shift finger tip in Y-direction, correspondingly forcing the shift rail to be moved axially along the Y-direction, which effects corresponding movement of the shift fork and the control collar engaged thereby. Axial movement of the control collar effects gear engagement or disengagement in that gate, as described above. Because the shift rod is also axially displaceable in the X-direction along its axis, the shift finger may be moved between aligned, adjacent slots of the various shift rails, which are generally arranged to move axially in parallel relative to one another. The slots of all shift rails are aligned along the X-direction, and each may receive the shift finger tip, only when the shift rails and control collars are all in their respective neutral gear positions.
The six-speed manual gear-change transmission T as described above is further described below, and is an example of one transmission type to which a gear change actuator according to the present invention may be adapted for use.
A problem with prior shift-by-wire gear change actuators S used with such transmissions T is that they require two motors, each individually coupled to the shift rod for respectively performing shift control member movements in X and Y directions. Moreover, these two motors may differ from one another, which complicates the design and assembly of the gear change actuator, and carries attendant costs. Moreover, performing each of the shifting and selecting functions with a single, respectively dedicated motor may require at least one of the two motors to be undesirably large and high in inertia, and compromise the dynamic performance of the shifter actuator and the transmission gear change mechanism.
Thus, there is a need for an improved shift-by-wire gear change actuator that simplifies the design and assembly, and accommodates the use of identical and relatively smaller and less expensive motors, which may also be of relatively lower inertia.