On the basis of the conventional HPS system, an additional set of hydraulic counterforce device constitutes the electronically controlled hydraulic station hydraulic counterforce ECHPS system.

The hydraulic counterforce device includes solenoid valve, piston, etc.. In the upper part of the spool there is a piston sleeve, they can move axially, but can not rotate relative to each other. A V-shaped groove is machined in both the lower end of the piston and the upper end of the valve sleeve, and a roller is placed in the groove. Said piston forms a reaction chamber with the upper part of the steering gear housing, which is equipped with a spring. A solenoid valve controlled by a vehicle speed signal is mounted on the passage between the reaction force chamber and the steering gear oil port. At low speeds, the solenoid valve will automatically close and the counterforce will not work. At this point the system works in the same state as a conventional HPS system. As the vehicle speed increases, the solenoid valve gradually opens, and a certain pressure is formed in the reaction chamber. At this time, the electronically controlled hydraulic station, due to the combined effect of spring force and hydraulic pressure, the axial force of the roller column is larger, so that the steering wheel torque required to produce the same relative angle between the spool and the valve sleeve becomes larger, that is, the steering assistance is reduced. The larger the opening of the solenoid valve, the smaller the throttle resistance, the larger the pressure in the reaction chamber, the larger the steering wheel torque required, the same relative angle between the valve sleeve and spool, the smaller the steering assistance.

A check valve is installed between the passage of the reaction chamber and the return port. Rotate the steering wheel so that the piston moves upward relative to the spool, then the pressure in the reaction chamber further increases, and at this time the check valve opens, so that the pressure in the reaction chamber does not exceed the set value, to avoid overburdening the steering maneuver.

The spring in the reaction chamber can improve the road feeling in the middle position of the steering wheel.

Principle of steering system of electronically controlled hydraulic station.

(1) Low speed steering or parking steering.

When the ECU steers from low speed or parking steering, when the vehicle speed is low or zero, when the ECU receives a small vehicle speed signal from the speed sensor, the ECU delivers a large current to the solenoid valve, and the solenoid valve's valve port opens, reducing the hydraulic reaction force on the control valve shaft. At this point in time, a small steering sensation is given to the driver. At this point in time, the driver only needs to apply a smaller steering wheel force, i.e. the torque is the same as that of the torsion bar. So at low speed steering, a smaller steering disk force can be utilized to produce a larger hydraulic assist.

Second, when steering at medium and high speeds small.

Vehicles in the middle speed driving process, the steering wheel from straight down to a small amount of rotation state, that is, small steering, the control valve shaft according to the torsion angle of the torsion bar rotation, so that the oil pressure in the rotary valve becomes larger, the oil through the fluid flow control valve into the hydraulic reaction chamber. When the vehicle speed is increased, the ECU receives the medium-high speed signal from the speed sensor, the ECU that is, the current delivered to the solenoid valve is reduced, and the solenoid valve opening is reduced until it closes, and the large oil pressure generated by the rotary valve is transmitted to the hydraulic reaction chamber through the hydraulic control valve, and the hydraulic reaction chamber piston of the electronically controlled hydraulic station by the hydraulic control valve acts on the hydraulic reaction chamber, which transmits the hydrodynamic reaction force to the steering wheel, and gives the driver a medium steering feeling.

Third, the middle and high speed big steering.

Middle and high speed big steering, that is, middle and high speed steering wheel turning angle is larger, the oil pressure in the rotary valve further becomes larger. At the same time, because in the middle and high speed when the solenoid valve is closed or closed smaller, and in the big steering due to high oil pressure and close the liquid flow control valve. So the increase in pressure within the hydraulic response chamber of the electronically controlled hydraulic station is only due to the increase in fluid flow through the pipe orifice. Therefore, when the steering angle becomes larger, the hydraulic reaction force of the electronically controlled hydraulic station also increases, and when the steering angle is larger, the reaction force of the turntable remains larger to alert the driver.