Electronically controlled power steering system

• US 4,828,065 A
• Filed: 05/04/1988
• Issued: 05/09/1989
• Est. Priority Date: 05/13/1987
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Ishihara, Satoru, Yokote, Masatsugu, Ito, Hideo, Kawagoe, Kenji
• Primary Examiner(s): Pekar, John A.
• Application Number:
  US07/190,067
• Time in Patent Office: 370 Days
• Field of Search: 180/142, 180/141, 364/424.01
• US Class Current: 180/422
• CPC Class Codes: B62D 5/065 characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist
• CPC Class Codes: B62D 6/02 responsive only to vehicle speed

Abstract

An electronically controlled power steering system comprises a vehicle speed sensor, a steering wheel angle sensor, a power steering gear including a control valve, a bypass valve for regulating a flow rate of hydraulic fluid supplied to the control valve of the power steering gear in response to a control signal generated by a controller. The controller is operative responsive to sensor output signals of the sensors for generating the control signal. With the controller, the control signal is varied in response to the vehicle speed and the steering wheel angle when the steering wheel angle is less than a predetermined value, but this varying tendency of the control signal in response to the steering wheel angle is restrained when the steering wheel angle is not less than the predetermined value.

Claims

1. An electronically controlled power steering system for a vehicle including a steering wheel, comprising:

a vehicle speed sensor means for generating a vehicle speed indicative signal indicative of the vehicle speed;

a steering wheel angle sensor means for generating a steering wheel angle indicative signal indicative of a steering wheel angle of the steering wheel;

a source of pressurized hydraulic fluid;

a power steering gear including a control valve supplied with pressurized hydraulic fluid from said source;

a bypass valve means for regulating a flow rate of hydraulic fluid to be supplied to said power steering gear in response to a control signal; and

a controller means responsive to said vehicle speed indicative signal and said steering wheel angle indicative signal for generating said control signal, said controller means being operative to vary said control signal in response to said vehicle speed indicative signal and said steering wheel angle indicative signal when said steering wheel angle indicative signal is less than a predetermined value, but restraining the varying tendency of said control signal in response to said steering wheel angle indicative signal when said steering wheel angle indicative signal is not less than said predetermined value.

2. An electronically controlled power steering system for a vehicle including a steering wheel, comprising:

a vehicle speed sensor means for generating a vehicle speed indicative signal indicative of the vehicle speed;

a steering wheel angle sensor means for generating a steering wheel angle indicative signal indicative of a steering wheel angle of the steering wheel;

a source of pressurized hydraulic fluid;

a power steering gear including a control valve supplied with pressurized hydraulic fluid from said source;

a bypass valve means for regulating a flow rate of hydraulic fluid to be supplied to said power steering gear in response to a control signal; and

a controller means responsive to said vehicle speed indicative signal and said steering wheel angle indicative signal for generating said control signal, said controller means including a memory storing a first group of data which is a function of varying vehicle speed value, said first group of data being predetermined for a zero steering wheel angle, said memory storing a second group of data which is a function of varying vehicle speed value, said second group of data being predetermined for a predetermined steering wheel angle that is larger than the zero steering wheel angle, said memory also storing a third group of data including a coefficient variable from zero to one in proportion to varying steering wheel angle when the steering wheel angle is less than said predetermined steering wheel angle, and fixed to one when the steering wheel angle is not less than said predetermined steering wheel angle, said controller means being operative to look up said first and second group of data in response to a given vehicle speed value indicated by said vehicle speed indicative signal and said third group of data in response to a given steering wheel angle value indicated by said steering wheel angle indicative signal to determine a target data which falls between said first and second group of data when the steering wheel angle value indicated by said steering wheel angle indicative signal is less than said predetermined steering wheel angle and which is included by said second group of data when the steering wheel angle value indicated by said steering wheel indicative signal is not less than said predetermined steering wheel angle, siad controller means being operative also to vary said control signal in response to said target data determined.

3. An electronically controlled power steering system as claimed in claim 2, wherein said controller means is operative also to vary said control signal in response to a first derivative of steering wheel angle.

4. A method of controlling the degree of power assist in an electronically controlled power steering system for a vehicle including a steering wheel, said power steering system comprising:

a vehicle speed sensor means for generating a vehicle speed indicative signal indicative of the vehicle speed;

a steering wheel angle sensor means for generating a steering wheel angle indicative signal indicative of a steering wheel angle of the steering wheel;

a source of pressurized hydraulic fluid;

a power steering gear including a control valve supplied with pressurized hydraulic fluid from said source;

a bypass valve means for regulating a flow rate of hydraulic fluid to be supplied to said power steering gear in response to a control signal; and

a controller means responsive to said vehicle speed indicative signal and said steering wheel angle indicative signal for generating said control signal,

said method comprising the steps of;

storing a first group of data which is a function of varying vehicle speed value, said first group of data being predetermined for a zero steering wheel angle;

storing a second group of data which is a function of varying vehicle speed value, said second group of data being predetermined for a predetermined steering wheel angle that is larger than the zero steering wheel angle;

storing a third group of data including a coefficient variable from zero to one in proportion to varying steering wheel angle when the steering wheel angle is less than said predetermined steering wheel angle, and fixed to one when the steering wheel angle is not less than said predetermined steering wheel angle;

looking up said first and second group of data in response to a given vehicle speed value indicated by said vehicle speed indicative signal and said third group of data in response to a given steering wheel angle value indicated by said steering wheel angle indicative signal to determine a target data which falls between said first and second group of data when the steering wheel angle value indicated by said steering wheel angle indicative signal is less than said predetermined steering wheel angle and which is included by said second group of data when the steering wheel angle value indicated by said steering wheel indicative signal is not less than said predetermined steering wheel angle; and

varying said control signal in response to said target data determined.