Machine element or mechanism – Control lever and linkage systems – Multiple controlled elements
Patent
1993-11-24
1995-02-14
Herrmann, Allan D.
Machine element or mechanism
Control lever and linkage systems
Multiple controlled elements
74473R, 74477, F16H 5904, F16H 6336
Patent
active
053884779
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a gearshift device for electrically controlled transmissions having a shifting lever pivotable in two parallel planes and guided in slides that are provided with a cross link only in the area of a neutral shifting position. Said shifting lever meshes in the existing shifting position. It is also jointed on a gearshift shaft that is rotatably mounted substantially perpendicularly to the shifting lever and connected therewith by a joint. If the shifting lever is moved from the existing shifting positions, it causes the gearshift shaft with cams, that actuate microswitches which produce signals for the shift of gear, to rotate. A locking disc, which is locked by a locking solenoid in accordance with its position and a specific admissible speed, is also connected with the gearshift shaft.
BACKGROUND OF THE INVENTION
Such gearshift devices are preferably used in heavy industrial motor vehicles and omnibuses. Such devices have been disclosed in DT 25 02 578 C3. Here, the forward gears are situated in a swivel plane of the shifting lever and the reverse gears in another swivel plane parallel therewith. In automatically shifting transmissions, the automatically shifting driving steps are conveniently situated in one swivel plane and the gears to be manually shifted in the other.
Especially in construction site vehicles, it is required that a quick shift from one gear to the other and in the opposite direction of travel be possible. Inadmissible downshifts and reversing operations at too high traveling speeds must be avoided.
Although the gearshift device known already has a detent solenoid which is activated in accordance with the shifting position and the correspondingly admissible speed, the control of said detent solenoid requires a high cost of control in order to ensure that the shifting cycle is not hindered in the admissible limits.
The problem to be solved by the invention is to design a downshift lock for a gearshift device so that it is easier to control, without hindering the gearshifting cycle.
SUMMARY OF THE INVENTION
The point of departure of the invention is that in transmissions for construction machines, a reversing operation below a speed admissible for a second gear is desirable and admissible for the maneuverability of the vehicle. In the selector switch according to the invention, the detent solenoid is not activated in said range so that the reversing operation can be carried out without hindrance. If the speed is above the admissible speed for the second gear, the detent solenoid is activated and engages a stop on the locking disc as soon as the latter is in a position corresponding to the shifting position for the first gear. As long as the detent solenoid is activated, it is not possible to shift to the neutral position and thus no reversing operation can be effected. The reversing lock design is thus effective both in a shift from a forward to a reverse direction and from a reverse to a forward direction.
Since the detent solenoid is always activated above the speed admissible for a second gear but the locking disc has no stops or detents for the detent solenoid in the shifting positions that correspond to the shifting positions for the higher gears, the reversing lock is inactive in said shifting positions. In order to avoid accidental downshifts over several gears, an electrical-mechanical step-by-step gearshift mechanism which, with a periodically controlled locking solenoid, engages the locking disc and briefly locks the locking disc in a given gear position upon a shift into that gear position only allowing a shift from one hear to the next and preenting too swift a shift through a plurality of gears. Such step-by-step gearshift mechanisms are known per se for gearshift devices, DT 23 36 784 A1. The expense for regulation is very low due to the two mutually independent locking systems.
To avoid damages caused by improper use on the locking device, a pushbutton is fastened on the shifting lever over a rubber buffer member. By virtue
REFERENCES:
patent: 3894443 (1975-07-01), Beig et al.
patent: 4126055 (1978-11-01), Forsyth
patent: 4401866 (1983-08-01), Kaminski
patent: 4455885 (1984-06-01), Beig
patent: 4569246 (1986-02-01), Katayama et al.
patent: 4631984 (1986-12-01), Jones
patent: 5063817 (1991-11-01), Bogert
patent: 5078020 (1992-01-01), Hasegawa
Frei Walter
Hardtle Wilhelm
Schwarz Gunter
Herrmann Allan D.
ZF Friedrichshafen AG
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