Machine element or mechanism – Gearing – Interchangeably locked
Patent
1989-07-21
1991-04-02
Diehl, Dwight
Machine element or mechanism
Gearing
Interchangeably locked
192 53F, F16H 338, F16D 2306
Patent
active
050038346
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a multi-range transmission for motor vehicles, with a first gear and a second gear located next to one another on a common shaft, with synchronizing devices located between the gears and movable axially with respect to them for matching the speed of the gears, whereby one actuating element of the synchronizing devices rotates with the first gear, however, rotable only within a limited portion of the circumference, and with a circumferential friction surface which can be brought into contact with an opposing friction surface of the second gear when moved axially.
Transmissions of the type described are generally known as synchromesh transmissions.
With customary transmissions of this type, the first gear rotates with the shaft, the second gear rotates freely on the shaft. The second gear meshes with a third gear which is located on and rotates with a second shaft which is parallel to the first one. The synchronizing devices are usually synchronizing rings which rotate with the first gear and can rotate within a limited angle of rotation with respect to the gear. A shift sleeve surrounding the external toothing of the gears can be made to slide by a shift fork, whereby the shift sleeve has internal toothing which positively engages in the external toothing of the first and second gear, thus connecting the gears so they rotate together.
Before this unirotating connection can be made, however, the shift sleeve slides the synchronizing ring--which usually has a conical friction surface--against the opposing surface of the second gear so that, if there is a difference in rotational speed between the first and second gear, a friction moment is induced which rotates the synchronizing ring by a stated finite angle of rotation with respect to the first gear. In this rotated state, the synchronizing ring prevents further axial movement of the shift sleeve so the respective shift range cannot be engaged until the first and second gears both rotate at the same speed. Only after this is the case--the friction moment has therefore reached zero--can the synchronizing ring rotate back to the initial, unrotated, position (for example, as a result of the force of a suitable return spring), clearing the axial path for the shift sleeve so the first and second gear can engage with each other, thus also engaging the desired shift range.
From the above description explaining the operation of customary synchromesh transmissions, it follows that the synchronizing procedure is highly dependent on how the vehicle drive executes the change of shift range by operating the shift lever; if the shift sleeve is moved relatively forcibly, thus thrusting the synchronizing ring with great force against the opposing surface of the second gear, a relatively large friction moment occurs immediately and the speed matching occurs relatively quickly. Conversely, the speed of the two gears is matched relatively slowly if the shift sleeve is moved with only a slight axial actuating force. This obviously influences the time required for the range change because the spreed gradient of the gear which is to be accelerated or slowed depends on the amount of the friction moment and directly influences the shift time.
The wear on the friction surfaces of the synchronizing ring and the opposing surface as well as the wear on the toothing also naturally depend on the force with which the shift sleeve is moved axially.
The objective of the invention is to further develop a transmission of the type described so that the synchronizing procedure takes place independently of the shift force applied by the driver.
This objective is implemented by the invention as follows: the actuator has a first surface which is slanted from the radial plane; it meets with an opposing, second, inclined surface which rotates with the first gear in such a manner that an axial force is applied by the actuator against the opposing friction surface when friction occurs.
The invention completely fulfills this objective in the manner stated above. When the driver w
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Martin Felix
Muller Erich R.
Priwitzer Gunther
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