Motor vehicles – Including one or more ski-like or runner members – With at least one surface-engaging propulsion element
Patent
1987-02-09
1988-10-04
Love, John J.
Motor vehicles
Including one or more ski-like or runner members
With at least one surface-engaging propulsion element
91434, 180143, B62D 506
Patent
active
047750227
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to an apparatus for controlling steering power in a power steering system which is used in an automobile.
PRIOR ART
It is generally preferred that the steering power of a power steering system which is used in an automobile is greatly reduced when the automobile is at rest or running at a very low speed while it assumes an increased value when running at higher speeds.
To this end, an arrangement as shown in FIG. 1 is employed in which a main pump 1 supplies hydraulic oil to a power steering system while a subpump 2 of a reduced size which is driven by a countershaft of a transmission, separately from the pump 1, supplies oil to an oil presssure reaction chamber 3, with a fixed throttle 5 disposed in a branch extending from the oil path to the reaction chamber 3 and leading to a tank 4 so that as the vehicle speed increases, the number of revolutions of the subpump 2 increases to increase a discharge flow therefrom, thus increasing the throttle pressure across the fixed throttle 5 to increase the pressure applied to the reaction chamber 3, which is effective to increase the steering force which is needed during the high speed running.
However, as a result of achieving an increase in the throttle pressure in response to the vehicle speed which represents a primary function, even though an excellent centering effect (the effect of providing a resistance to the steering wheel at the central position) is achieved, there results a disadvantage that as the steering wheel is operated, the corresponding pressure rise response (a rate of change in auxiliary power), which remains the same as it is fixed, causes a rapid reduction in the resistance experienced when operating the steering wheel, causing an unstable steering response.
As another consideration, it is preferred that the pressure produced by the subpump is raised to the order of several tens of kilograms per square centimeter in order to achieve the required steering response of the steering wheel under the high speed running condition, but the combination of a reduced discharge flow and an increased pressure results in an increased power loss of the subpump. The oil pressure reaction chamber may be provided with a seal which prevents an oil leakage from the reaction chamber. However, when subjected to a pressure on the order of several tens of kilograms per square centimeter during the time the vehicle is running at high speeds, the seal is continuously exposed to such pressure to be urged outward and expanded, thus producing a frictional resistance between the seal and its mating sealing surface. Such resistance disadvantageously causes a frictional feeling.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a steering force controlled by a power steering system, which is needed to operate a steering wheel and which is greatly reduced when the vehicle is at rest or running at low speeds while being increased when the vehicle is running at higher speeds by means of a hydraulic oil from an oil pressure reaction chamber, to prevent a rapid reduction in the resistance experienced when operating the steering wheel under high speed conditions to thereby enhance a positive steering feeling while simultaneously eliminating a frictional feeling associated with the seal or the like.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a conventional arrangement;
FIG. 2 is a schematic view of an arrangement according to the invention;
FIG. 3 is a longitudinal section of a pressure responsive valve according to one embodiment of the invention as illustrated in FIG. 2; and
FIG. 4 graphically shows the relationship between a reaction pressure of the oil pressure reaction chamber and the angular displacement through which the steering wheel is operated.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 2 and 3, an embodiment of the invention will be described. Reference numeral 10 represents a main pump which supplies a hydraulic oil to a power steering system 11, and 12
REFERENCES:
patent: 3994361 (1976-11-01), Nishikawa et al.
patent: 4000785 (1977-01-01), Nishikawa et al.
patent: 4293051 (1981-10-01), Nishikawa
patent: 4601358 (1986-07-01), Kozuka et al.
patent: 4632204 (1986-12-01), Honaga et al.
patent: 4640380 (1987-02-01), Daido et al.
Hirakushi Shuzo
Matsubara Hideo
Adams Bruce L.
Koyo Jidoki Kabushiki Kaisha
Love John J.
Watts Charles R.
Wilks Van C.
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