Steering system with auxiliary power assist

Claim 2

In combination with a vehicle steering system having an engine driven servo pump (2 or 102) supplying fluid at a flow rate that is an inverse function of engine speed above a predetermined value, at least one control valve (5 or 105) through which the fluid is supplied to a servo motor (3), a torsion spring connected to the control valve for resisting displacement thereof with an increasing bias (27 or 127) and means (28) to which a manual effort is applied for displacing the control valve against the bias of said torsion spring, the improvement including flow regulating surface means (25, 26, or 125, 126) formed on the control valve for varying the output flow rate to the servo motor as a function of displacement of the control valve, whereby the manual effort required to meet increasing steering resistance at engine speeds above said predetermined value increases more rapidly than the increase in the steering effort at engine speeds below said predetermined value.

Claim 3

The combination of claim 1, wherein said control valve includes an axially displaceable valve operating piston (5).

Claim 4

The combination of claim 1, wherein said control valve includes a rotary valve operating piston (105).

Claim 5

In a fluid power steering system having an engine driven pump (2), servo motor means (3) to which pressurized fluid is conducted from the pump under an operating flow rate that varies as an inverse function of pump operating speed, control valve means (5) displaceable between limit positions from a neutral position for supply of said pressurized fluid to the servo motor means, spring means (27) connected to the control valve means for resisting displacement thereof from the neutral position with a bias that is proportional to said displacement of the control valve means and valve actuating means (28) connected to the control valve means for displacement thereof against the bias of the spring means under a manual effort that is a direct function of said bias; and reaction force control means for varying the quantity flow rate of fluid supplied to the servo motor means, including flow throttling means (25 or 26) connected to the control valve means for controlling flow of the fluid supplied to the servo motor means as a direct function of said displacement of the control valve means, whereby the manual effort required for displacement of the control valve means is limited to substantially the same maximum value throughout the operating speed range of the pump.

Claim 6

In a fluid power steering system having an engine driven pump (2), servo motor means (3) to which pressurized fluid is conducted from the pump under an operating flow rate that varies as an inverse function of pump operating speed, control valve means (5) displaceable between limit positions from a neutral position for supply of said pressurized fluid to the servo motor means, spring means (27) connected to the control valve means for resisting displacement thereof from the neutral position with a bias that is proportional to said displacement of the control valve means and valve actuating means (28) connected to the control valve means for displacement thereof against the bias of the spring means under a manual effort that is a direct function of said bias; and reaction force control means for varying the quantity flow rate of fluid supplied to the servo motor means, including flow throttling means (25 or 26) connected to the control valve means for controlling flow of the fluid supplied to the servo motor means as a direct function of said displacement of the control valve means, whereby the manual effort required for displacement of the control valve means is limited to substantially the same maximum value throughout the operating speed range of the pump.

Claim 7

The combination of claim 4, wherein said control valve means includes a valve body having inlet and outlet ports respectively connected to the pump and the servo motor means and exhaust ports, and a valve element connected to the valve actuating means and displaceable from the neutral position to block one of the exhaust ports, said flow throttling means including regulating surface formations on the valve element forming variable flow passages between the inlet and exhaust passages, said flow passages being fully blocked in said limit positions of the valve element.