Motor vehicles – Including one or more ski-like or runner members – With at least one surface-engaging propulsion element
Patent
1986-10-27
1989-01-10
Bertsch, Richard A.
Motor vehicles
Including one or more ski-like or runner members
With at least one surface-engaging propulsion element
91375A, 180132, B62D 602, B62D 504, B62D 500
Patent
active
047967153
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a power assist steering device (hereinafter simply "power steering device") and more particularly to a hydraulic reaction pressure device in the power steering device wherein pressurized oil from a pump driven by the engine is controlled by a vehicle speed. This pressurized oil is supplied to a hydraulic reaction pressure chamber so that a resistance at steering time is changed in response to the vehicle speed. This invention relates more particularly to the hydraulic reaction pressure device having a centering function to coincide a valve neutral position with a neutral position of the reaction pressure device (a position where the hydraulic reaction does not functions with respect to the relative displacement of the valve).
DESCRIPTION OF THE PRIOR ART
In the rotary valve employed in hydraulic power assisting device for the power steering system, the neutral positions of the output and input shafts of the valve are, as shown in FIGS. 3 and 4, preferably axis X--X of a plurality of, for example, eight number of ditches 51 provided on a valve body 51 of the output shaft and axis Y--Y of a convex 52B of a plurality, for example eight number of ditches 52A. In other words, two gaps a and a' formed between the projections 51B of each ditch 51A of the valve body 51, and each convex 52B of the input shaft 52 are preferably a=a'. Although the condition a=a' at one ditch 51A is available, it is difficult to coincide the axe at all the other ditches in view of a mechanical finishing accuracy, and an accumulated error of the valve body 51 and the input shaft 52 becomes deviated state as shown in FIG. 5. FIG. 5 is a graph showing an angular position .theta. of the ditch at an abscissa and the accumulated error e at a vertical axis, and showing the finishing accumulated error of each ditch 51A and 52A when the valve roates from K point to J point and further to K point.
FIGS. 1 and 2 show the hydraulic pressure reaction device of a conventional power steering device in cross section, but this hydraulic reaction pressure device is formed as V-shape ditch 60 in cross section othogonal to an outer periphery of the input shaft 52, and a plurarity of the reaction chambers 58 which extend radialy toward the V-ditchs 60 are formed in the valve body 51. Each reaction chamber 58 has a ball 59, which is pressedly pushed against the V-ditch by the pressurized oil. As apparent from the above description, in this conventional device, it is almost impossible to coincide the axe of all the reaction members to each axis of the valves in view of the mechanical finishing accuracy and an adjusting error at an assembly process. In a practical automobiles, when the valve body 51 of the output shaft and the input shaft 52 take respective positions neutral, a slight gap .DELTA.l is created between a right hand slant surface of the V-ditch 60 and the ball 59 as shown in FIG. 7 with respect to the axe of the reaction member and the valve. This gap may be also created in a left hand slant surface instead of the V-ditch 60, but for the convenience of the explanation, the right hand slant surface is mentioned. When the ball 59 is affected by the pressurized oil with an accelleration of the vehicle speed, the ball 59 is pushed radially and inwardly, and this ball 59 rotates the input shaft 52 in the counter clockwise direction in a cam functional manner so as to take a condition shown in FIG. 6. Because a torsion rod 53 has an weak power to hold the condition shown in FIG. 7 for the input shaft 52, it is shifted by pushing power of the pressurized oil. As a result, the valve is relatively displaced. As shown in FIG. 8, where an input torque is indicated at an abscissa and the pressing power is indicated at a vertical line, the neutral position (the lowest circuit pressure) of the valve deviates to a right hand 0.fwdarw.0', and a pressure difference of P' is created at the original valve neutral position. This P' is generated as a pressure difference of left and right cylinders CYL1, and CYL2 (
REFERENCES:
patent: 3998131 (1976-12-01), Adams
patent: 4034825 (1977-07-01), Adams
patent: 4535678 (1985-08-01), Thomsen et al.
patent: 4557342 (1985-12-01), Drutchas
patent: 4560023 (1985-12-01), Kirby
patent: 4601358 (1986-07-01), Kozuka et al.
patent: 4621704 (1986-11-01), Kozuka
Futaba Takeshi
Noguchi Masahiko
Adams Bruce L.
Bertsch Richard A.
Koyo Jidoki Kabushiki Kaisha
Wilks Van C.
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