Machine element or mechanism – Control lever and linkage systems – Multiple controlled elements
Reexamination Certificate
2000-05-30
2001-11-27
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Multiple controlled elements
C074S473370
Reexamination Certificate
active
06321615
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a manual range-type transmission that incorporates a top cover assembly having a single shift rail, reverse bias, and shift housing.
Much effort is expended on designing transmissions that increases robustness and reliability while making the transmission easier to assemble and service. Manual transmissions incorporate many separate, non-integrated systems to achieve these ends.
In a manual range-type transmission for heavy duty trucks there is a set of gears in a main transmission section and a set of range gears that are actuated selectively to put the main transmission gears in either low or high range. After shifting through the main gears in low range, the operator may range shift to make available the main gears in high range, or vice versa. In this manner, the number of gears available to the vehicle operator is effectively doubled.
For the range gears to operate properly it is desirable that the transmission be in neutral (none of the main gears engaged) when a range shift occurs. Some prior art systems incorporate a three shift rail assembly that includes a check shaft that locks out the range gears when the main gears are not in neutral. However, these systems increase the shift effort necessary by the operator and still permits undesired range shifting in some instances.
Many manual transmissions for heavy duty truck applications do not have shift levers that automatically return to the neutral position when moved out of gear. The problem is that after the vehicle operator has moved the shift lever out of gear there is no feed back in the shift lever to indicated to the operator where he is in the shift pattern.
Further, manual transmissions may incorporate reverse biasing to indicate to the vehicle operator that the reverse gear is about to be engaged. This information is conveyed to the operator by a reverse biasing mechanism that increases resistance as the shift lever is moved in a horizontal direction towards a reverse gear position. Thus, while gear shifting the operator is alerted as to when the reverse gear is being approached. The operator can avoid inadvertently shifting into the reverse gear. Prior art systems incorporate additional components to achieve reverse biasing.
Moreover, manual transmissions include shift forks that are operatively connected to the shift lever. As the shift lever is moved throughout the shift pattern, a shift fork is selectively engaged and moves a clutch collar into engagement with a gear thereby causing a gear shift. The shift forks are often supported by the shift rail and typically include many fasteners and other components to attach the shift forks to the shift lever. These additional fasteners and components can make the transmission more difficult to shift and to manufacture and repair.
Therefore, what is needed is an assembly that integrates these functions into one conveniently manufactured and repairable assembly while still maintaining a reliable and durable transmission having an acceptable shift feel.
SUMMARY OF THE INVENTION
The present invention provides a top cover assembly for a manual transmission having a plurality of gears including a reverse gear. The top cover assembly comprises a shift rail assembly, a reverse biasing assembly, and a shift housing assembly. The shift rail assembly includes a housing, and a shift rail that defines a longitudinal axis and is supported by the housing. The shift rail moves axially between a plurality of shift positions for selectively placing one of the gears in driving engagement. The shift rail assembly further includes a contoured surface and a sensing device for coacting with the contoured surface producing a first electronic signal in response to the shift rail being in a predetermined shift position.
The shift rail also includes another contoured surface and a detent pin for coacting with the contoured surface that acts to rotationally center the shift rail and an operatively connected shift lever to predetermined positions.
The reverse biasing assembly comprises a shift sleeve and shift lever for shifting the gears. The shift lever has a first lower shift force when moved to shift at least one of the forward gears. The reverse biasing assembly also utilizes the shift rail of the shift rail assembly and is operatively connected to the shift sleeve and shift lever. The shift rail rotates about the longitudinal axis when the shift lever is moved to shift the gears. An interlock supported by the shift rail and shift sleeve rotates with the shift rail. A detent engages the interlock for creating a higher shift force than the first lower shift force when the shift lever is moved to shift the reverse gear.
The shift housing assembly shares the use of the shift sleeve and shift lever. The shift housing assembly comprises a shift housing having a channel and a shift fork for engaging the plurality of gears. The shift fork is selectively engageable by the shift sleeve and shift lever. A shift bar interconnects the shift sleeve and the shift fork and slidingly engages the channel such that when the shift lever actuates the shift sleeve and, in turn, the shift bar, the shift bar moves along the channel causing the shift fork to engage and shift into a desired gear.
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Carlson & Gaskey & Olds
Fenstermacher David
ZF Meritor LLC
LandOfFree
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