Toyoda Koki Kabushiki Kaisha

Jtekt Corporation

Toyota Jidosha Kabushiki Kaisha

Kenichi Fukumura

Mikio Suzuki

Kyosuke Haga

Hideya Kato

Yoshiharu Inaguma

Katsuhisa Mori

Jiro Nakano

Yutaka Mori

Shinji Takeuchi

Hajime Kamimae

Seiho Kawakami

Kaname Saito

Miko Suzuki

A method of heat-treating a rack bar includes a step of continuously conveying a rack bar provided with a rack teeth portion and a ball screw portion by a quenching means, and a step of sequentially applying a quenching treatment to each circumferential surface of the rack teeth portion and the ball screw portion. The quenching treatment is preferably and sequentially applied to each entire circumferential surface of the rack teeth portion and the ball screw portion.

Heat-treated rack bar

A first system and a second system include a first motor and a second motor for driving a steering mechanism in dependence on the rotational manipulation of a steering wheel. A first ECU and a second ECU mutually monitor abnormalities of the systems each to stop an abnormal system. When the respective systems are normal, the first ECU and the second ECU drivingly control the first motor and the second motor of their own systems to drive the steering mechanism by cooperation of the respective motors. When either one of the both systems is abnormal, the ECU of the other system solely drivingly controls the motor of its own system thereby to drive the steering mechanism. Thus, it can be realized to make the systems low in cost irrespective of the provision of the plural systems.

Steering control device and steering control method of motor vehicle

An electrically operated power steering apparatus for an automotive vehicle having a steering wheel to be operated by the vehicle operator includes a motor and a power supply restricting device. The motor applies a drive force thereof to a torque transmitting system so as to assist a steering torque applied to the steering wheel by the vehicle operator. The power supply restricting device utilizes a temperature of a heated portion of the electrically operated power steering apparatus which emits heat as a result of a supply of an electric power to the motor, at a reference point of time, as an initial temperature of the heated portion, utilizes a plurality of electric power-related values each of which is related to at least one of a current and a voltage value of the motor, as a plurality of physical quantities related to temperature increases of the heated portion each of which is an increase of the temperature of the heated portion from that at the reference point of time, and restricts the electric power supply to the motor such that an actual value of the temperature of the heated portion does not exceed a predetermined upper limit thereof.

Electrically operated power steering apparatus selectively restricting electric power supply to motor by using initial value and subsequent increase of temperature of heated portion therein

A hydraulic power steering apparatus includes a fluid pump, a power cylinder, a reservoir, and a control valve connected to the pump via a supply passage including a high pressure hose and connected to the reservoir via a drain passage. The power steering apparatus also includes a bypass passage provided between the supply passage and the drain passage, and a check valve which is disposed in the bypass passage to allow operation fluid to flow only in a direction from the drain passage to the supply passage. The power steering apparatus can supply a sufficient amount of operation fluid to the power cylinder even when a steering wheel is abruptly turned or when an opposing force is input from a tire.

Hydraulic power steering apparatus

A hydraulic power steering system includes a pump, a flow control valve, and a bypass control valve. The flow control valve responds to a pressure drop across a metering orifice disposed in a fluid supply passage so as to control the flow rate of operating fluid by bypassing a part of the operating fluid to a reservoir. A spring chamber of the flow control valve is connected to the supply passage through a control orifice. The bypass control valve is disposed between the spring chamber and the reservoir so as to increase the amount of bypassed fluid by controlling the pressure in the spring chamber. The bypass control valve has a control spool, a load pressure introduction port connected to the upstream side of the control orifice for leading the load pressure to a first end of the control spool and a pilot port connected to the downstream side of the control orifice for leading the pressure in the spring chamber of the flow control valve to a second end of the control spool. Moreover, a pressure receiving area of the second end of the control spool is smaller than that of the first end of the control spool. Accordingly, a spring having a small spring constant can be used in the bypass control valve, even when the control spool is controlled within a short stroke. Further, the control spool, the load pressure introduction port, and the pilot port are formed in a sleeve.

A power steering apparatus having a fluid source for discharging pressurized fluid, a power cylinder, a control valve responsive to operation of a steering wheel for supplying the power cylinder with pressurized fluid from the fluid source, and a reservoir. The control valve has a first control portion for controlling the flow of pressurized fluid from the fluid source to the reservoir, and a second control portion for controlling the flow of pressurized fluid to the power cylinder. The first control portion has two paths connecting the fluid source and the reservoir, each of the paths being formed with at least one variable orifice of a center-open type which opens when the control valve is in a neutral state. The second control portion has two supply paths communicating with the fluid source and a pair of chambers of the power cylinder, each of the supply paths being formed with a variable orifice of a center-close type which closes when the control valve is in the neutral state, and two drain paths communicating with the pair of chambers and the reservoir, each of the drain paths being formed with a variable orifice of a center-open type which opens when the control valve is in the neutral state.

A hydraulic power steering system includes a pump, a flow control valve, and a bypass control valve. The flow control valve responds to a pressure drop across a metering orifice disposed in a fluid supply passage so as to control the flow rate of operational fluid by bypassing part of the operational fluid to a reservoir. A spring chamber of the flow control valve is connected to the supply passage through a control orifice. The bypass control valve is disposed between the spring chamber and the reservoir so as to increase the amount of bypassed fluid by controlling the pressure in the spring chamber. The bypass control valve has a control spool, a load pressure introduction port connected to the upstream side of the control orifice for leading the load pressure to a first end of the control spool and a pilot port connected to the downstream side of the control orifice for leading the pressure in the spring chamber of the flow control valve to a second end of the control spool. Moreover, a pressure receiving area of the second end of the control spool is smaller than that of the first end of the control spool. Accordingly, a spring having a small spring constant can be used in the bypass control valve, even when the control spool is controlled within a short stroke.

A power steering apparatus for a motor vehicle is provided with a metering orifice arranged on a supply passage and a flow control device in parallel relation with the metering orifice. The flow control valve includes a spool and a spring and moves the spool against the force of the spring in response to the pressure difference across the metering orifice for returning an excess part of operating fluid discharged from an engine-driven pump to an intake side of the pump so as to keep the flow rate towards a power assist gear unit almost constant regardless of changes in rotational speed of the pump. A drooping device cooperating with the flow control valve is provided comprising a control orifice at the upstream of the metering orifice and a bypass valve in communication with a spring chamber of the flow control valve retaining the spring. When the pressure difference across the control orifice exceeds a predetermined value with the increase in the pump rotational speed to a predetermined speed, the bypass valve operates to drain the pressure in the spring chamber. The load acting on the pump is thereby relieved. A bypass control valve is responsive to the pressure at the downstream of the metering orifice so as to restrict the draining of the pressure in the spring chamber when the power assist gear unit is brought into operation.

Power steering apparatus for a vehicle

A power steering apparatus having a hydraulic pump for outputting a pressurized fluid, an assist force generation mechanism hydraulically connected to the pump through a supply passage to generate an assist force in response to rotation of a steering wheel, wherein the assist force generation mechanism has a characteristic that the back pressure thereof increases when the steering wheel is rotated. The power steering apparatus further comprises a flow control valve having a spool which is moved in response to a pressure drop at a metering orifice disposed in the middle of the supply passage, so as to control the flow rate of the pressurized fluid to be constant. The spring chamber of the flow control valve is connected to a reservoir through a drain passage, and a drain valve is disposed in the drain passage for allowing the flow of pressurized fluid from the spring chamber to the reservoir when the back pressure of the assist force generation mechanism is low, and for prohibiting the flow of the pressurized fluid when the back pressure of the assist force generation mechanism increases.

Growing community of inventors

Aichi-ken, Japan

Kenichi Fukumura