Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-12-16
2001-06-26
Rivell, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C091S37500R
Reexamination Certificate
active
06250334
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a centering device for a steering valve of an automotive vehicle, said device comprising an elastic torsion bar having a first end portion connected to a drive shaft and a second end portion connected to a driven shaft which is connected to a valve bushing of the steering valve, a rotary slide formed integrally on the drive shaft being inserted in the valve bushing so that, by a limited displacement of the drive shaft relative to the driven shaft, pressure oil can be fed to a servo element.
The invention also concerns a centering device of the aforesaid type in which the rotary slide is supported on cage-guided needle rollers of a needle roller bearing.
BACKGROUND OF THE INVENTION
A centering device of the pre-cited type known from DE 43 00 612 A1 comprises a spring element in the form of a metal folding bellows which is connected at one end to an end element which is fixed on the drive shaft. The other end of the metal folding bellows is connected to a centering element. The centering element which is axially spring-mounted through the metal folding bellows presses through rolling elements against a second centering element which is fixed on an end element. This end element connects the torsion bar to the driven shaft. The fact that the rolling elements roll in angular grooves of the centering elements results in the production of a resetting force which is determined by the relative rotation of the two shafts and is added to the torsional force of the torsion bar. A centering device of this type effects an exact adjustment of the two shafts, and thus also of the steering valve, at the hydraulic center. This prior art centering device is suitable for rotary slide or rotary piston structures and assures a perfect straight-ahead driving behavior.
A drawback of the above construction, however, is that the spring element in the form of a folding bellows is expensive to manufacture and its connection to the centering element and the torsion bar is work-intensive and thus also involves high costs.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to create a centering device which has a substantially uncomplicated structure so that it is also simpler to manufacture.
This and other objects and advantages of the invention will become obvious from the following detailed description.
SUMMARY OF THE INVENTION
The invention achieves the above objects by the fact that a needle roller bearing is arranged between the drive shaft and the valve bushing, said needle roller bearing having an outer bearing ring which is configured as a thin-walled sleeve which comprises, in at least one peripheral section, an elastically yielding raceway convexity deviating from the circular shape, and said peripheral section comprises an angular groove which is situated radially opposite an angular groove disposed in an associated portion of the drive shaft.
The advantage of the invention resides in the fact that a needle roller bearing is utilized as a spring means for producing the resetting force. This resetting force for adjusting the longitudinal valve at the hydraulic center is created by the resilient peripheral sections of the thin-walled sleeve so that the metal folding bellows as well as the first and the second centering elements and the rolling elements arranged therebetween according to the prior art solution are all dispensable. Due to the non-circular peripheral sections with their angular grooves and due to the angular grooves of the drive shaft, a relative rotation of the two shafts releases a resetting force which causes the rolling elements to snap exactly into the angular grooves of the drive shaft and the elastic sleeve, so that a highly precise adjustment of the hydraulic center of the steering valve is obtained. Thus, the needle roller bearing arranged between the drive shaft and the valve bushing fulfils a locking function.
According to a further feature of the invention, the outer bearing ring comprises, in three equally spaced peripheral sections, a raceway convexity deviating from the circular shape. This symmetric configuration results in a particularly uniform distribution of the resetting force.
According to another feature of the invention, the angular groove of the drive shaft is formed by a separate inner bearing ring.
According to still another feature of the invention, the bearing on which the rotary slide is supported is configured as a sliding or a rolling bearing.
In another solution, the invention achieves its objects by the fact that a centering element received in a needle roller bearing and connected to the driven shaft and the torsion bar is arranged between the driven shaft and the torsion bar, said needle roller bearing having an outer bearing ring which is configured as a thin-walled sleeve which comprises, in at least one peripheral section, an elastically yielding raceway convexity deviating from the circular shape, and said peripheral section comprises an angular groove which is situated radially opposite an angular groove disposed in an associated portion of the drive shaft.
In this case, too, according to a further feature of the invention, the outer bearing ring comprises, in three equally spaced peripheral sections, a raceway convexity deviating from the circular shape. This symmetric configuration results in a particularly uniform distribution of the resetting force.
According to still another feature of the invention, the torsion bar and the centering element are configured in one piece with each other. This has the advantage that no force-locked connection has to be made between the torsion bar and the centering element during the assembly of the centering device.
According to a final feature of the invention, the angular groove of the centering element is formed by a separate inner bearing ring.
The invention will now be described more closely with the help of the following examples of embodiment represented in the drawings.
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patent: 5964315 (1999-10-01), Suzuki et al.
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Abraham Uwe
Jennes Peter
Zernickel Alexander
Bierman, Muserlian and Lucas
Ina Walzlager Schaeffler OHG
Rivell John
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