Nissan Motor Company Limited

Tokiyoshi Yanai

Yutaka Aoyama

Masafumi Nakayama

Hirotsugu Yamaguchi

Masato Fukino

Moritsune Nakata

Megumu Higuchi

Yasuhiro Niikura

Nobuteru Hitomi

Akihiko Sano

Yasuji Shibahata

Koichi Takahashi

Kunihiko Morikawa

Manabu Tsunematsu

Koichi Takahasi

A torque distribution control device includes two rotational speed differential responsive type control couplings each having various transfer torque characteristics which differ in the ratio of a transfer torque to a rotational speed differential. The control device selects one of the torque transfer characteristics in response to a signal supplied thereto. When turning the outer wheel side control coupling is supplied with a signal for selecting the transfer torque characteristic that produces a maximum transfer torque for a given rotational speed differential, and the inner wheel side control coupling is supplied with a signal for attaining a non-slip rotational speed differential and for selecting the transfer torque characteristic that produces a transfer torque equal to that produced by the outer wheel side control coupling when the non-slip rotational speed differential is obtained. When the vehicle is running straight ahead, both control couplings are supplied with signals for selecting the transfer torque characteristics that produce maximum transfer torque for a given rotational speed differential.

Torque distribution control device

A pair of orifices of different orifice sizes is provided between each pressure chamber and an accumulator chamber. A larger one serves as a variable orifice and a smaller one as a fixed orifice. The variable orifice becomes effective when a control circuit is functioning properly for variably controlling an axial position of a valve spool. The fixed orifice becomes effective when the control circuit malfunctions and allows the valve spool to be moved into a predetermined position. In another embodiment, a single orifice cooperates with the valve spool to serve as both a variable orifice and a fixed orifice.

Rotational speed differential responsive type control coupling

A transfer torque control device for a rotational speed responsive type control coupling is provided for providing a desired variation of a transfer torque in response to a variation of a rotational speed differential. The control coupling has orifices for restricting fluid flow therethrough and for thereby producing a transfer torque between first and second axle shafts. The transfer torque control device controls the orifices in such a manner that the openings of the orifices are varied successively in response to variations of the rotational speed differential to obtain the desired torque transfer characteristic.

Rotational speed differential responsive type control coupling with

In order to simplify the construction of a power steering system and simultaneously allow for unassisted steering in the event that the motor or the like of the system malfunctions, the differential gear which establishes the drive connection between the auxiliary motor, the steering input shaft and the steering output shaft is such that when the element of the differential gear which is connected to a variable speed motor is not driven by the motor, an essentially 1:1 drive is established between the steering input and output shafts while at this time the motor driven element is braked only by the friction and other natural resistances which occur in the system. Further, the differential gear is such as to have a relatively low responsiveness to the rotational speed of the motor and thus eliminates the need for a reduction gear between the motor and the differential gear.

Steering system for automotive vehicle or the like

This automotive vehicle power-steering system can positively compensate for resistance to the return of a steering linkage from an operating position to its neutral rest position after the vehicle turns a corner, and can enhance a steerability of the vehicle. The system includes a controller ordering a power-assist actuator to reduced the steering angular deviation of a steering wheel to zero when the controller receives a zero-level signal from a steering torque sensor and non-zero-level signal from a steering angular deviation sensor. The method for the system includes a step of controlling the power-assist actuator to generate a return-assist force counteracting the resistance and variable according to vehicle conditions.

Automotive vehicle power-steering system and method

An input shaft and an output shaft can rotate relative to each other. Pressure supplied to a pressure-responsive actuator depends on the axial position of a movable valve member. A transmission arrangement serves to move the valve member only in the axial direction as the input and output shafts rotate relative to each other. The valve member and each of the input and output shafts are wholly outside one another.

Power steering system

An inventive electrical motor-assisted power-steering system is compact while still providing adequate steering assist force. The system can also act as a manual steering system in the event of failure of an electrical motor. The system includes a steering gear with a shaft rotated manually via a steering shaft, a worm driven by the electrical motor operating in response to rotation of the steering shaft, and a worm wheel fixed to the steering gear shaft and meshing with the worm. The lead angle of the worm is selected to be larger than the friction angle between the worm and the worm wheel so that the worm wheel can drive the worm freely if the motor should fail.

Electrical motor type power-steering system

In a vehicle the steering system includes a steering gear housing transversely mounted relative to the vehicle body by means of a plurality of gear housing mount insulators. Each of the gear housing mount insulators elastically supports the gear housing in such a manner as to allow transverse displacement of the gear housing with respect to the vehicle body. A damper is provided to restrain the transverse displacement allowed by the gear housing mount insulators.

Steering system controlling transverse displacement of a gear housing

A vehicular power steering system is provided with a steering effort control system which controls the degree of power assistance by controlling the supply of hydraulic fluid to the hydraulic power actuator unit. The steering effort control system monitors the speed of the vehicle and the angular velocity of the steering wheel, and controls the quantity of the fluid supply in accordance with the monitored variables. The fluid supply quantity is determined so as to satisfy the following three conditions: (1) The steering must become heavier as the vehicle speed increases; (2) however, a sufficient amount of the fluid must be supplied even when the steering wheel is turned rapidly; and (3) the driver must be given a feel about the lateral acceleration of the vehicle during a turn.

Vehicular power steering having steering effort control system

A steering pressure control apparatus for a power-assisted steering system for a vehicle including a steering power cylinder to develop a steering assistance fluid pressure, comprising a detecting unit operative to detect a state in which the steering wheel is held in an angular position turned from the straight-ahead position thereof through an angle smaller than a predetermined value and to produce an output signal when the that predetermined state is detected; and a control unit responsive to the output signal from the detecting unit and operative to control the steering assistance fluid pressure to be developed in the steering power cylinder so that the steering assistance fluid pressure is lower or higher in the presence of the signal than in the absence of the signal.

Steering assistance pressure control apparatus

In a method of manufacturing a rack for a variable ratio rack and pinion steering gear, having a preforming process for preparing a rack blank having a plurality of teeth which are formed to a shape corresponding approximately to the shape desired in the finished rack and a finishing process for converting the teeth to the finished shape by cold forming in a die having a shape which is the exact counterpart of the finished shape, the preformed rack teeth are shaped to have top lands which are level with those in the finished shape and bottom lands that are deeper than those of same. The rack teeth in the preformed shape are all wider at the top areas than in the finished shape, and the ratio of the widths at the root areas of the rack teeth in the preformed shape to those in the finished shape varies in proportion to the variation of the steering ratio such that a rack tooth for a higher steering ratio is given the above-mentioned ratio that is larger.

Method of manufacturing racks for variable ratio steering gears

A steering control apparatus for a power-assisted vehicle steering system for a vehicle, comprising a steering pressure pump, a power cylinder, a pressure control valve operative to direct fluid under pressure from the pump to the power cylinder to develop in the cylinder a differential fluid pressure to produce a controlled degree of hydraulic steering assistance, and a fluid flow control valve bypassing the pressure control valve between the suction and delivery ports of the pump, wherein the differential fluid pressure to be developed in the power cylinder or the flow rate of the fluid to be discharged through the flow control valve is variable in two or more different basic modes in each of which the differential fluid pressure or the fluid flow rate is further continuously variable so that the vehicle driver is enabled to steer the vehicle with a manual steering effort continuously variable with, for example, the vehicle speed.

Steering control apparatus

In a vehicular power steering system, the hydraulic fluid supply to a hydraulic power actuator is controlled in accordance with the vehicle speed and the angular velocity of the steering wheel. Preferably, the fluid supply is reduced so that the steering effort becomes heavier as the vehicle speed increases while the fluid supply is increased when the angular velocity of the steering wheel is high. To control the fluid supply, there is provided, in a power steering system, a bypass valve means for draining a portion of the fluid flow to bypass the power actuator, and control means for producing a control signal to control the bypass valve means in accordance with the vehicle speed and the angular velocity of the steering wheel.

Vehicular power steering system

In accordance with the present invention, there is provided a novel and improved variable ratio rack and pinion steering gear wherein the pinion has teeth of variable shape and size and the rack has teeth at least in part of variable shape and size. The teeth of the pinion are correctly meshable with a uniformly toothed rack profile and adapted to provide variable pitch circles. The teeth of the rack are adapted to be generated by using the profile of the pinion teeth in a manner to provide a desired variable ratio between the pinion and the rack.

Variable ratio rack and pinion steering gear

A control apparatus for a power-assisted steering system, comprising a power cylinder having pressure acting chambers respectively communicating with the control ports of a pressure control valve having inlet and outlet ports respectively communicable with the delivery and suction ports of a pump, and first and second flow control valves each having an inlet port and a discharge port communicating with the suction port of the pump, each flow control valve including a control pressure acting chamber communicating with a pressure acting chamber of the power cylinder to develop a differential pressure variable with a differential pressure between the pressure acting chambers of the cylinder, and a valve member movable in response to the differential pressure acting thereon and urged to provide communication between the inlet and discharge ports of each flow control valve, the inlet port of the first flow control valve being in constant communication with the delivery port of the pump and the inlet port of the pressure control valve, the inlet port of the second flow control valve being in constant communication with the outlet port of the pressure control valve, the valve member of each flow control valve being operative to block the communication between the inlet and discharge ports of the valve when the differential pressure is higher than a predetermined value, the second flow control valve further comprising a bypass providing constant communication between the outlet port of the pressure control valve and the suction port of the pump independently of the valve member.

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Yokosuka, Japan

Tokiyoshi Yanai