Machine element or mechanism – Control lever and linkage systems – Multiple controlled elements
Reexamination Certificate
2000-08-07
2002-03-19
Bucci, David A. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Multiple controlled elements
C074S473210, C074S473100
Reexamination Certificate
active
06357316
ABSTRACT:
The invention relates to a shifting device for pinion gear change transmissions.
BACKGROUND OF THE INVENTION
To shift pinion gear change transmission, selector forks are used, as a rule, in order, by means of transmission devices, to transmit shifting movements from a shift lever to the positive-fit couplings of the transmission. The shifting movements are transmitted to the shift lever according to known H gear shift patterns. The transmission device must have few transmission losses and small volume and be well damped to ensure the shifting comfort required in modem vehicles. It must reliably prevent the possibility of several gears being simultaneously actuated. One other function is the conversion of the shifting movement on the shift lever (path and force) to the path and force needed by the arrangement of the positive-fit couplings on the output shift and/or countershaft and the configuration thereof in the form of dog clutch control or synchronizer units.
Shifting devices of this kind can be divided in the following sub-groups:
Selector forks for transmitting the shifting force to the sliding sleeves of the positive-fit couplings. The positive-fit couplings, often synchronized, are as a rule disposed on shafts of the transmission and selectively connect pinions with the shafts. Selector forks transmit the shifting force to the sliding sleeves by sliding bearings. This requires a wear-resistant material. To keep the weight and costs low, selector forks are often made of die-cast aluminum or compound material and in place of the low-friction bearing is a sprayed molybdenum or provided with crossheads shoes. In the gear shift mechanism with a central shifting rail proposed, e.g. in U.S. Pat. No. 4,621,537, the gate selection and gear shift demand precise machining and hardened edges directly on the selector fork. This requires different costly selector forks made of malleable cast iron. Another disadvantage of this design is the many low-friction bearing places between central shifting rail and selector forks which mainly when cold can lead to tough selection and shifting.
Longitudinal guides for transmitting the shifting force to the selector forks. Two basic principles are known:
a) rails firmly connected each with one selector fork. The rails slide in the transmission housing and transmit only forces in the longitudinal direction. There are rails made of pipes, round steel, or as stamped or bending parts.
b) a central rail which slides in the transmission housing and transmits longitudinal and rotational movement. All selector forks slide on the rail. The choice of which selector fork is to be coupled with the shifting rail for shifting and the locking of the non-actuated selector forks in this neutral position in longitudinal direction are effected by shaped and locking parts between shifting rail and selector forks.
Gates and gear shift make possible the selection of the gate in which lies the desired gear and the shifting of the gear by moving the shift lever. Three basic principles are known:
a) selection and locking between the central rails and the selector forks such as shown in EP 0 395 241. At the same time, strict requirements are imposed on the selector forks in relation to precise machining and strength of the material. This results in expensive machining and great weight. Many friction places generate which can have a negative effect upon the shifting comfort.
b) selection of the desired shifting rail by shifting finger or lever fastened upon a separate selection shaft. The gears are locked by separate means such as pins and balls or pawls between the selector forks and shifting rails. This type is often used in pinion gear change transmissions of passenger cars and light industrial vehicles.
c) selection and locking by a so-called switching comb. The switching comb consists of several flat segments of which alternatively one is connected with a selector fork and one firmly connected with the housing in shifting direction. The shifting finger that slides through said switching comb can only actuate the desired gear when its position coincides in shifting direction with the flat segment of the selector fork. In other positions, the selector forks remain locked. Such a shifting system is shown by way of example in DE 30 00 577 C2. The shifting device is often used in transmissions of commercial vehicles.
Connection of different switches and sensors to indicate the transmission situations (for ex., neutral position reverse gear, etc.).
Connection of different selector units. For different vehicles different selector units are used such as lever shifts, turning-shaft shifts, cable-controlled and hydrostatic shifting mechanisms. To make possible installing on a pinion gear change transmission different selector units, a unitary interface must be obtained between pinion gear change transmission and selector units.
Due to movements of the sliding sleeves or jerks on the vehicle the shifting parts can be excited in a manner such that an engaged gear trips during the drive. To prevent this, the shifting parts of each gate are fixed by means of spring-loaded detents in the “neutral” and “gear in” positions. This constitutes an added expense, since a separate detent of the positions again takes place in the selector unit.
It is often necessary in pinion gear change transmissions to construct different ratio series, so-called high gear or direct gear designs. Here the low-loss direct lock-up clutch, e.g. in a 5-gear transmission is the 4
th
gear in the high gear transmission and the 5
th
gear in a direct gear transmission. This requires, e.g. a reversal of shifting direction of the selector forks concerned. In shifting systems with central shifting rail, this is not possible and in shifting systems with several shifting rails, it involves substantial cost. The change of the gear shift pattern, e.g. for right-hand and left-hand steering, is also very expensive in the gear shifts with central shifting rail.
The problem on which the invention is based is to indicate a gear shift device which makes possible that the selecting and shifting forces are transmitted with low friction, reliably and economically between different selector units and the sliding sleeves of the separating clutch. The device should offer simple possibilities of designing gear shift for direct and high gear transmissions and different gear shift patterns, and a clear modulation of the gear shift sections.
The problem is solved with the shifting device for pinion gear change transmissions of the present invention.
SUMMARY OF THE INVENTION
In the inventive shifting device, all selectorforks are guided by means of a longitudinal guide firmly connected with the housing parts and actuated by profiled metal plates sliding on said mechanism. The profiled metal plates slide on their other end into a switching comb fastened upon the longitudinal guide and having locking plates as teeth. Between the teeth a shifting finger and an automatic locking device are displaced by shifting means and either interact with the profiled metal plates for shifting the gear or block with the locking plates the non-shifted gates and gears.
In an advantageous embodiment, the longitudinal guide has a profile in the shape of a triangle which consists of a rolled or drawn metal pipe.
In another advantageous embodiment, the selector forks are made of die-cast aluminum or compound material and the guide between the longitudinal guide and the selector forks is integrated directly in the selector fork.
In another advantageous embodiment, the selector forks have plugged-in low-friction bearings.
In another advantageous embodiment, the selectorforks have rollers as longitudinal guide.
In another advantageous embodiment, the profiled metal plates are fixed in shifting direction with the selector forks by means of driver pins and the position of the profiled metal plates in selecting direction is determined by means of spacer discs.
In another advantageous embodiment, the profiled metal plates are connected with positive fit with the sel
Bucci David A.
Davis & Bujold P.L.L.C.
Joyce William C
ZF Friedrichshafen AG
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