Steering force controller for power steering apparatus

A steering force controller for power steering apparatus including a servo valve for controlling the distribution of an oil pressure from a discharge port of a pump to a power cylinder through a relative rotation of a pair of valve members, a reaction mechanism for producing a steering reaction in accordance with an oil pressure supplied to an oil pressure reaction chamber and a pressure controlling mechanism for controlling the oil pressure which is supplied to the oil pressure reaction chamber;

• the pressure controlling mechanism comprising a spool valve slidably fitted in an internal bore within a housing, a solenoid connected to the spool valve for causing a reciprocating displacement thereof, a pair of low pressure chambers formed at the opposite ends of the spool valve and communicating with a tank associated with the pump, a distribution passage formed around an external peripheral surface of the spool valve, a feed passage opening into a surface of the housing against which the spool valve slides and communicating with the discharge port of the pump, a reaction passage opening into the sliding surface and communicating with the oil pressure reaction chamber, and a discharge passage opening into the sliding surface and communicating with the tank, the feed passage and the reaction passage and the discharge passage opening into the sliding surface in a sequential order as viewed in the axial direction of the spool valve, the distribution passage being effective to increase a channel area between the reaction passage and the feed passage and to reduce a channel area between the reaction passage and the discharge passage in accordance with a displacement of the spool valve in one direction by the solenoid, in which the feed passage and the reaction passage and the discharge passage open into the sliding surface from the housing side, respectively, and in which the distribution passage which is formed around the external peripheral surface of the spool valve communicates with the reaction passage and also extends to the opposite sides of the reaction passage as viewed in the axial direction thereof where it opens, and in which one side of the opening of the distribution passage can be brought into overlying relationship with the feed passage while the other side of the opening can be brought into overlying relationship with the discharge passage.

A steering force controller for power steering apparatus including a servo valve for controlling the distribution of an oil pressure from a discharge port of a pump to a power cylinder through a relative rotation of a pair of valve members, a reaction mechanism for producing a steering reaction in accordance with an oil pressure supplied to an oil pressure reaction chamber and a pressure controlling mechanism for controlling the oil pressure which is supplied to the oil pressure reaction chamber;

• the pressure controlling mechanism comprising a spool valve slidably fitted in an internal bore within a housing, a solenoid connected to the spool valve for causing a reciprocating displacement thereof, a pair of low pressure chambers formed at the opposite ends of the spool valve and communicating with a tank associated with the pump, a distribution passage formed around an external peripheral surface of the spool valve, a feed passage opening into a surface of the housing against which the spool valve slides and communicating with the discharge port of the pump, a reaction passage opening into the sliding surface and communicating with the oil pressure reaction chamber, and a discharge passage opening into the sliding surface and communicating with the tank, the feed passage and the reaction passage and the discharge passage opening into the sliding surface in a sequential order as viewed in the axial direction of the spool valve, the distribution passage being effective to increase a channel area between the reaction passage and the feed passage and to reduce a channel area between the reaction passage and the discharge passage in accordance with a displacement of the spool valve in on direction by the solenoid, in which the feed passage and the reaction passage open into the sliding surface from the housing side, and in which the discharge passage is formed around the external peripheral surface of the spool valve together with the distribution passage, the distribution passage comprising an annular groove which provides a communication between the feed passage and the reaction passage, and a land which limits a communication between the reaction passage and the discharge passage.

A steering force controller for power steering apparatus including a servo valve for controlling the distribution of an oil pressure from a discharge port of a pump to a power cylinder through a relative rotation of a pair of valve members, a reaction mechanism for producing a steering reaction in accordance with an oil pressure supplied to an oil pressure reaction chamber and a pressure controlling mechanism for controlling the oil pressure which is supplied to the oil pressure reaction chamber;

• the pressure controlling mechanism comprising a spool valve slidably fitted in an internal bore within a housing, a solenoid connected to the spool valve for causing a reciprocating displacement thereof, a pair of low pressure chambers formed at the opposite ends of the spool valve and communicating with a tank associated with the pump, a distribution passage formed around an external peripheral surface of the spool valve, a feed passage opening into a surface of the housing against which the spool valve slides and communicating with the discharge port of the pump, a reaction passage opening into the sliding surface and communicating with the oil pressure reaction chamber, and a discharge passage opening into the sliding surface and communicating with the tank, the feed passage and the reaction passage and the discharge passage opening into the sliding surface in a sequential order as viewed in the axial direction of the spool valve, the distribution passage being effective to increase a channel area between the reaction passage and the feed passage and to reduce a channel area between the reaction passage and the discharge passage in accordance with a displacement of the spool valve in one direction by the solenoid, in which the low pressure chambers formed at the opposite ends of the spool valve communicate with each other through an internal path formed to extend axially through the spool valve, the internal path communicating with the discharge passage which opens into the sliding surface.