Machine element or mechanism – Gearing – With fluid drive
Patent
1990-04-05
1991-04-23
Diehl, Dwight
Machine element or mechanism
Gearing
With fluid drive
192 4R, F16H 4706
Patent
active
050091263
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a hydrostatic-mechanical drive system and a method for the operation thereof.
THE RELATED ART
Comfortable driving and operational safety of modern vehicles carrying agricultural and construction machines require that the vehicle be drivable in various speed ranges according to traffic, that it can be safely parked, and that it can be ready to perform these functions with a high degree of reliability. The transmission and the brake components of agricultural and construction vehicles are highly exposed to the dangers of dirt and damage. The complex functions which have to be performed by modern agricultural and construction vehicles require the operation of a great number of regulating units and increase the possibility of human error during the operation of these vehicles.
It is known (DE-OS No. 34 25 757) to have a hydrostatic-mechanical drive system equipped with an adjustable reducing gear ratio, so that the regulating elements shift the adjustable hydrostatic gearbox automatically, depending on changes in the reducing ratio of a mechanical gearbox.
Further, from DE-A-No. 31 49 473 a hydrostatic drive system has become known, which has a hydraulic motor with variable delivery and wherein a spring-loaded parking brake triggered by the pressure medium from the high-pressure segment is mounted on the driven shaft of the hydraulic motor. If the pressure of the pressure medium surpasses a certain value, the hydraulic motor is reset in a position for increased delivery, whereby for the braking of the vehicle a high braking force is supposed to be produced.
SUMMARY OF THE INVENTION
It is the object of the present invention to create an operationally safe combination of a hydrostatic-mechanical multirange drive system with a mechanical parking brake and to make the control of the hydrostatic-mechanical multirange drive and of the parking brake especially user-friendly.
According to the invention, this objective is achieved by incorporating a mechanical parking brake into a mechanical two-step gearbox, the parking brake acting directly upon the driven shaft of the mechanical two-step gearbox, and by the fact that for the actuation of the parking brake pressure medium is branched off from the high-pressure segment of the hydrostatic cycle via a pressure duct and that a 3/2-way valve is switched which actuates a cylinder of the parking brake with the pressure of a servo hydraulic pump of the hydrostatic gearbox or connects it to a pressure-free return duct.
Since the parking brake acts directly upon the driven shaft of the two-step mechanical gearbox, when the brake is engaged the vehicle is prevented from unintentionally rolling away, independently of the fact that one speed is engaged. Because the parking brake is incorporated in the mechanical gearbox housing , it is possible to achieve a particularly compact construction of the gearbox and the parking brake, affording considerably improved safety for the parking brake against damage or dirt.
Since the actuation of the parking brake depends on the operational condition of the hydrostatic gearbox, a particularly safe operation of the parking brake is insured and for the driver the operation of the vehicle is simplified by one regulated quantity.
According to the invention, the arrangement of the mechanical gearbox with parking brake and hydrostatic drive and the actuation of the regulating unit for the adjustable hydromotor and the shifting of the mechanical two-step gearbox with the same hydraulic pressure medium used for the actuation of the parking brake lead to a particularly operationally safe drive system and method for controlling such a drive system.
BRIEF DESCRIPTION OF THE DRAWING
In the FIGS. 1 to 3, embodiment examples of the invention are represented.
DETAILED DESCRIPTION
FIG. 1 is a general view of a drive system of a vehicle. It comprises a drive engine 1, which via a drive shaft 2 drives a servo hydraulic pump 3 for the production of servo pressure and via a shaft extension 2' drives a
REFERENCES:
patent: 2741351 (1956-04-01), Fletcher et al.
patent: 3864991 (1975-02-01), Nembach
patent: 4187739 (1980-02-01), Hamma et al.
patent: 4192199 (1980-03-01), Hamma et al.
patent: 4528871 (1985-07-01), Nembach
patent: 4899542 (1990-02-01), Iino
patent: 4939954 (1990-07-01), Walzer et al.
Meisinger Erwin
Zimmer Jurgen
Diehl Dwight
Dubno Herbert
Zahnfabrik Friedrichshafen AG
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