Fluid handling – Systems – Multi-way valve unit
Patent
1998-03-05
1999-11-02
Michalsky, Gerald A.
Fluid handling
Systems
Multi-way valve unit
91375R, 91375A, F15B 910
Patent
active
059751363
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a steering valve with an input shaft, an output shaft and a torsionally elastic element connected at one end to the input shaft and at the other end to the output shaft.
Steering valves, particularly so-called rotary disk type valves, are used by preference in power-assisted steering systems. Here, for example, hydraulic control means are used to shift hydraulic steering bores relative to each other as a function of the relative torsion between input and output shaft, which in turn depends on the spring characteristic of the torsionally elastic element, such that hydraulic fluid flow occurs. Other control types are conceivable.
In order to be able to use such systems in a defined controlled manner, a wide variety of measures are taken to detect signals by means of sensors. However, in practice, no direct measured values are generated but only indirect functional variables based on which the respective desired value can be determined. It is desirable, for example, to generate steering torque dependent electrical signals and use these for steering control. For this purpose, the steering torque can be converted into a measurable relative motion of two components by means of a torsion element of a steering device of the generic class or the strain can be measured directly on the surface of the torsion element. Various inexpensive methods for measuring strain with great accuracy are known. However, their use for measuring steering torques is problematic because the steering shaft (input shaft) is not only subject to torsion but also to bending and in a conventional torsion element with a round cross-section, the surface tensions due to bending moments compared to the surface tensions due to torsional moments are too small.
Mechanical decoupling of the two stress types, for example by means of a multiple bearing arrangement of the steering shaft or a guide bush, not only substantially increases the costs to build the steering device but, due to unavoidable bearing friction, can also lead to unacceptable hysteresis in the steering torque signal.
DE 27 34 182 A1 describes a device for measuring steering torques and steering angles in vehicles. A steering shaft and a dynamo hub that can be connected thereto are arranged in the steering wheel area to measure steering torques. An additional measuring element comprises an upper and a lower ring which are connected to each other by spokes that are arranged in fish-trap fashion and provided with strain gauges. Such an additional measuring element entails a redesign of conventional steering valves and a substantial increase in size. A torque sensor is disclosed in EP 0575634 A1.
Thus, it is the object of the present invention to further develop a steering valve of the generic class so that on the one hand steering torques result in easily measurable surface strains on a component and on the other hand bending stresses of the steering shaft (input shaft) do not appreciably influence the measuring result.
To solve this technical problem, the invention proposes that the torsionally elastic element be made of a plurality of separately arranged strips.
The solution according to the invention makes it possible that steering moments essentially result in a bending stress of the strips with easily measurable surface strains, whereas bending moments on the steering shaft (input shaft) essentially cause only tensile or compressive stresses of the strips with surface strains that are very minor by nature.
The solution according to the invention now makes it possible to evaluate the mechanical strain of at least two of the strips forming a torsion element by means of measurements and thus precisely to measure, for example, the steering torque.
The invention proposes to arrange the strips such that they extend in axial direction of the input and output shaft, respectively, and are spaced apart from each other. It is particularly advantageous if the strip arrangement is ring-shaped.
The described advantageous embodiment of the invention thus replaces a convent
REFERENCES:
patent: 5103715 (1992-04-01), Phillips
patent: 5307892 (1994-05-01), Phillips
"Freqeunzanaloge Drehmomentmessung mit Oberflachenwellen-Resonatoren", .TM.Technisches Messen, 58 (1991) Sep., No. 9, Munchen, DE, pp. 329-334.
Michalsky Gerald A.
TRW Fahrwerksysteme GmbH & Co. KG
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