Shift device for a manual transmission

Abstract: A transmission shift rail comprising a control rail (20) and a shift fork (40) are provided. The shift fork (40) is not translated when the control rail (20) is translated in a first shift plane. The shift fork (40) is translated when the control rail (20) is translated in a second shift plane. The shift fork (40) is translated when the control rail (20) is rotated to the first shift plane.

Description: This invention relates to a manual transmission shift mechanism, and more particularly to a shift rail and shift fork design for such a transmission. EP-A-0 786 610 describes a shift mechanism which axially moves a shift fork upon rotational movement of a shift rail. The shift fork in EP-A-0 786 610 is moved when the shift rail is rotated, but not when the rail is moved axially. It would be desirable to provide a design which accommodates axial movement of a shift fork with either a rotational movement of the shift rail or an axial movement of the shift rail. According to the present invention, there is provided a shift mechanism, comprising a shift rail rotatable about its axis between first and second shift planes and translatable along its axis in each shift plane, a shift fork mounted for translation parallel to the axis of the shift rail, means operative to permit translation of the shift rail when in the first shift plane without corresponding translation of the shift fork; and means operative to cause translation of the shift fork in response to rotation of the shift rail (20) into the first plane; characterised by means connecting the shift rail when in the second shift plane for translation with the shift fork to enable the shift fork to be moved by the shift rail. The invention provides a manual transmission shift rail design which enables axial movement of a shift fork with either a rotational movement of a shift rail or an axial movement of the same shift rail. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an example of a shift pattern for a shift mechanism according to the present invention; Figure 2 is a planar view of a shift rail and shift fork; Figure 3 is an end view of the shift rail and shift fork shown in Figure 2; Figure 4 is an alternative embodiment of a shift mechanism according to the present invention; Figure 5 is a schematic diagram for a transmission using the shift mechanism of Figure 4; and Figure 6 is a shift pattern for the transmission shown in Figure 5. As shown in Figure 1, a manual transmission shift pattern 53 includes a neutral plane 51 extending laterally. A plurality of shift planes 52, 54, 56, 58 extend perpendicular to the neutral plane 51. A selector 50 travels in the planes 51, 52, 54, 56, 58 of the shift pattern 53 to select a desired gear ratio. During movement of the shift lever 50 in the fore and aft direction of the shift planes 52, 54, 56, 58, one of a plurality of shift forks (not shown) are normally moved to engage or disengage a gear ratio in a manner known to one skilled in the art. EP-A-0 786 610 describes a method and apparatus to shift a gear ratio when moving within the neutral plane 51. Figure 2 illustrates a shift rail assembly 10 of a shift mechanism of one embodiment of the present invention. The shift rail assembly 10 includes a shift rail 20 which has a shift rail sleeve 30 slidably mounted thereupon. A shift fork 40 is slidably and rotatably mounted to the shift rail sleeve 30. A shift fork finger 60 is pinned to the shift rail 20 with a pin 62. The shift rail finger 60 engages a slot 64 in the shift fork 40 via an extension 63 when the shift rail 20 is rotated to the appropriate plane illustrated in Figure 3 as the 5 th gear plane, in a manner known to one skilled in the art. Thus, when the extension 63 engages the fork 40 and the shift rail 20 is translated axially, the present invention enables a fore/aft movement of the shift fork 40 corresponding with the fore/aft movement of the shift rail 20. In a preferred embodiment, the shift rail sleeve 30 acts as a control rail, because it is the rotation of the shift rail sleeve 30 that causes translation of the shift fork 40. In an alternative embodiment, the shift rail 20 may act as the control rail, performing this function. The planes illustrated in Figure 3 illustrate a rail configuration compatible with the shift pattern illustrated in Figure 1. One skilled in the art appreciates several different configurations are available depending on the transmission layout. The present invention further accommodates fore/aft movement of the shift fork 40 upon a rotational movement of the shift rail 20 in a manner similar to that described in EP-A-0 786 610. The shift fork 40 includes a cam slot 42. A cam pin 47 is secured to the shift rail sleeve 30 and projects through the cam slot 42. The shift rail sleeve 30 includes an axial slot 31 through which a rotation pin 32 projects. The rotation pin 32 is secured to the shift rail 20 and moves axially and rotatably therewith. The shift rail sleeve 30 is prevented from moving axially via a slot 34 and pin 33 arrangement. The pin 33 is secured to the transmission case 70. The slot 34 extends circumferentially about a portion of the rail sleeve 30 to permit relative rotational movement of the sleeve 30 to the case 70. As the shift rail 20 moves fore/aft, the rotation pin 32 translates axially in the axial slot 31, while the sleeve 30 remains stationary due to the pin 33 and slot 34. However, as the rail 20 rotates, the rotation pin 32 engages the axial slot 31 to rotate the sleeve 30 therewith. As the sleeve 30 rotates, the cam pin 47 rotates therewith. As the rail 20 rotates in a counter-clockwise manner, as shown in Figure 3, the cam pin 47 rotates to the left as shown in Figure 2. The cam pin 47 eventually engages a ramp portion 45 of the cam slot 42 causing the shift fork 40 to move rearwardly, as shown in Figure 2, when the shift lever 50 is moved from the 1, 2 point 52 to the R/Cl plane 56 as illustrate in Figure 1. Cam pin 47 is then engaged in the R/Cl position 46 of the cam slot. As the shift rail 20 is rotated in a clockwise direction, the pin 47 returns to the horizontal portion 43 of the cam slot 42 as illustrated in Figure 2. The shift fork 40 then moves in the opposite direction to disengage the gear set which was engaged at the R/Cl position 46. As the shift rail 20 is rotated further clockwise, the cam pin 47 moves to a position corresponding to the 5 th gear shift plane 58. This position 48 is in the rightward portion of the cam slot 42 and illustrated in Figure 2. As the shift lever 50 moves forward in the 5 th gear plane 58 to select the 5 th gear, the shift rail moves in a forward direction as illustrated in Figure 2. As the shift rail rotates to the 5 th gear plane, the 5 th shift finger 60 engages the shift fork 40 as described above. As the shift rail 20 moves forward, the 5 th shift finger 60 causes the shift fork 40 to move forward therewith. The cam pin 47 remains stationery as the rail moves forward thus causing the cam pin 47 to end up in the 5 th gear position 44 of the cam slot 42. Thus, the shift fork 40 moves in the second direction to engage the 5 th gear (verses the opposite direction in which the R/Cl reduction was engaged). One skilled in the art recognises that the present invention may be adapted as described in EP-A-0 786 610 to include a cam plate as illustrated in Figures 6-14 of that publication. Figures 4-6 show a double-disconnect reverse transmission diagram and shift pattern according to another embodiment of the present invention. The double disconnect enables both the driving and driven gears to be drivably disengageable. In Figure 5, a first reverse synchroniser 80 engages the driven gear of the reverse pinion-gear pair 81 rotatably supported on the output shaft 82 during the motion of the shift lever laterally, as shown in Figure 6, from the 5/6 position 83 to the reverse plane 84. When the gearshift lever is moved forward as shown in Figure 6 from the neutral position in the reverse plane 84 to the R position 85, the second reverse synchroniser 86 is moved to the right, as shown in Figure 5, to engage the driving gear of the reverse pinion-gear pair 81. The reverse pinion-gear pair 81 is then driven through a chain or idler gear (not shown) as is well known in the art. The engagement of the first reverse pinion 80 is caused by a translation pin as shown in the prior embodiments engaging the translation slot of the rotation cam or rotation plate 87 shown in Figure 4. Thus, as described in the prior embodiments and in EP-A-0 786 610, when the lever 89 is moved from the 5/6 position 83 to the reverse plane 56, the first reverse synchroniser engages the reverse gear 81 mounted on the output shaft 82. The second reverse synchroniser 86 is moved in a conventional manner, either by using a shift fork mounted on the shift rail, or a shift fork mounted on a parallel rail and moved through the use of a shift finger, both of which are well known in the art to drivably engage the output shaft 82.

Claims: A shift mechanism, comprising: a shift rail (20) rotatable about its axis between first and second shift planes (56, 58) and translatable along its axis in each shift plane, a shift fork (40) mounted for translation parallel to the axis of the shift rail (20), means (30,31,32) operative to permit translation of the shift rail (20) when in the first shift plane (56) without corresponding translation of the shift fork (40); and means (45,47) operative to cause translation of the shift fork (40) in response to rotation of the shift rail (20) into the first plane (56); characterised by means (60,63,64;60') connecting the shift rail (20) when in the second shift plane (58) for translation with the shift fork (40) to enable the shift fork (40) to be moved by the shift rail (20). A shift mechanism as claimed in claim 1, wherein the means operative to cause translation of the shift fork (40) in response to rotation of the shift rail (20) into the first plane (56) comprise a cam slot (42) having a portion (45) traversing the shift fork (40) in an oblique manner and a pin (47) extending radially from the shift rail (20) to engage with the cam slot (42). A shift mechanism as claimed in claim 1 or 2, wherein the means operative to permit translation of the shift rail (20) when in the first shift plane without corresponding translation of the shift fork (40) comprises; a shift rail sleeve (30); and a pin and axial slot coupling (31, 32) acting between the shift rail (20) and the shift rail sleeve (30) thereby preventing rotation relative to one another. A shift mechanism as claimed in claim 3, wherein the shift rail sleeve is supported by the shift rail and the shift fork is supported by a second rail adjacent the shift rail (Figure 4). A shift mechanism as claimed in claim 3, further comprising: a radial groove (34) in the shift rail sleeve (30); and sleeve translation prevention means (33) being fixed against translation and extending into the radial groove (34). A shift mechanism as claimed in claim 5, wherein the shift fork (40) is encased within a transmission case; and the translation preventing means is a pin (33) projecting from the transmission case 70 and extending into the radial groove 34 of the shift rail sleeve (30). A shift mechanism as claimed in any preceding claim, wherein the coupling means operative to connect the shift rail (20) when in the second shift plane to the shift fork (40) to enable the shift fork to be moved by the shift rail comprises a finger slot (64) in the shift fork (40), and a shift rail finger (60) carried on the shift rail (20) such that the shift rail finger engages the finger slot when the shift rail is rotated to a predetermined angle for translation of the shift fork when the shift rail is translated. A shift mechanism as claimed in any preceding claim further comprising an input shaft, a countershaft, an output shaft, a pinion and gear pair, and a first synchroniser axially movable by the shift fork for producing an output ratio to the output shaft.

Inventors: HOFFMAN DONALD EDWARD, HOFFMAN, DONALD EDWARD
Applicants: FORD GLOBAL TECH LLC, FORD GLOBAL TECHNOLOGIES, LLC
Application year: 1998
Main classification: F16H63
IPC codes: F16H63