Process for actuating the steering cylinders of mobile plant and

Motor vehicles – Steering gear – No mechanical connection between steering shaft and steering...

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Details

180405, B62D 500

Patent

active

061316873

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a process for actuating the steering cylinders of mobile machines, in particular wheel loaders, graders, mobile excavators or the like.
Wheel loaders, but also other machines starting with a certain size have two separate control systems because of safety requirements as well as legal regulations. In this case, the second system, which is frequently called an emergency control system, becomes operational only if the primary system cannot meet its function as designed due to a defect or interference. Thus, the primary system must be designed such that it meets all legal and technical driving requirements, in particular also for low steering system speeds. The emergency steering system is non-functioning during this operating condition, but requires energy because of the constant transfer by pumping of its feed current. In addition, expensive emergency valves and flow-through indicators are required, which become effective when the primary system fails. Even though the emergency control system as a rule is used rarely or never and thus is not employed frequently, it can occur that this system fails rather than the main system, so that its failure must be indicated as well. Furthermore, the additional components such as emergency valves and flow-through indicator result in pressure losses, which have a negative effect on the energy balance.


SUMMARY OF THE INVENTION

It is the object of the invention to design a process for actuating the steering cylinders of mobile machines as well as the steering system of mobile machines in such a way that the previously described disadvantages for the most part are avoided, and this in particular for specific operating conditions, e.g. for low drive motor speeds.
With a process for actuating the steering cylinders of mobile machines, in particular wheel loaders, graders, mobile excavators or the like, this object is achieved by bringing together the feed currents of two hydraulic pumps either continuously or, depending on predetermined parameters, discontinuously and by supplying the resulting feed current to at least one steering gear actuating the steering cylinders, wherein if one pump fails, the feed current from the still active pump(s) is prevented from flowing back by at least one return element that is inserted into the respective pressure line for the individual pumps.
Advantageous improvements of the process according to the invention can be seen in the following description of the invention.
The object is furthermore achieved with a steering system for mobile machines, in particular for wheel loaders, graders, mobile excavators or the like by having at least two hydraulic pumps that can be operated, at least one steering gear, one or more steering cylinders as well as the pumps, the steering gear and the hydraulic lines that connect the cylinder or cylinders, wherein the individual hydraulic lines are brought together to form a joint feed line that is connected to the steering gear and wherein return elements are provided in the individual hydraulic lines.
Advantageous improvements of the steering system according to the invention will be apparent from the detailed description.
Owing to the fact that both steering systems now can work together either continuously or discontinuously, depending on predetermined operating conditions, it is possible to ensure a sufficient feed current even for a low drive engine speed.
The following advantages are achieved with the invention: smaller. emergency steering system used so far, are no longer necessary. of each of the two systems is indicated in a simple way. be reduced.
Depending on the respective type of machine, the most varied types of pumps can be used, for example pumps with constant feed volume, such as gear pumps or the like, and pumps with changeable, meaning controllable, feed volume. Type and selection of the pump(s) in this case depends on the type of use.
For a preferred use, the invention resorts to pumps with a feed volume that can be controlled starti

REFERENCES:
patent: 3719249 (1973-03-01), Becker et al.
patent: 3935918 (1976-02-01), Hicks et al.
patent: 3952510 (1976-04-01), Peterson
patent: 3958657 (1976-05-01), McBurnett
patent: 4044786 (1977-08-01), Yip
patent: 4476677 (1984-10-01), Hanshaw
patent: 4517800 (1985-05-01), Karakama et al.
patent: 4553389 (1985-11-01), Tischer
patent: 4618017 (1986-10-01), Liebert et al.
patent: 4762195 (1988-08-01), McBurnett
Automotive Engineering, vol. 89, No. 9, Sep. 1981, Dallas, Texas, US; "Emergency steering: which system is the best?" pp. 46-51.

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