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Electronic power steering system EPS
Overview
| Fig. 4.43. The main elements of the electronic steering system EPS: 1 - the electromagnetic valve; 2 - pump; 3 - the gauge of speed of the car; 4 - a control unit
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Electronic power steering system (EPS) contains the same elements as the steering system with hydraulic booster. In addition, the power steering unit and the control unit on the front panel under a radio receiver provided the solenoid valve (Fig. 4.43). To control the flow of fluid in the steering mechanism of the solenoid valve is powered by the current supplied from the control unit, which receives signals from VSS (vehicle speed sensor). The EPS system performs the normal functions of a steering in the event of a system failure. EPS performs electronic control of the supply of current to the solenoid of the bypass valve, adjusting the amount of fluid in the cylinder on the basis of signals from sensor control and thus, changing the force applied depending on the hydraulic pressure, which in turn depends on the vehicle speed.
| Fig. 4.44. Location of the block (1) Management (EPSCM)
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The control unit (EPSCM) is mounted on the center console under the radio (Fig. 4.44).
Solenoid Valve
| Fig. 4.45. Solenoid Valve: 1 - hydraulic control unit; 2 - the torsion bar; 3 - rotary valve; 4 - of the oil pump; 5 - right chamber of the cylinder; 6 - left chamber of the cylinder; 7 - to the reservoir; 8 - the solenoid valve; 9 - pusher; 10 - the piston; 11 - Spring
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The steering mechanism is a solenoid valve to control the flow of fluid in the hydraulic system of the power steering (Fig. 4.45). The electromagnetic valve includes a spring, the piston and the pusher. The input current signals coming from the control unit EPS, varies from 0 to 1 A, depending on the vehicle speed. When the ignition current begins to flow through the solenoid valve, resulting in piston is lifted in contact with a pusher which overcomes the resistance of the spring. As vehicle speed increases, decreases current flow - the piston under the action of a spring lowers. When lifting the piston closes the opening of the liquid feed, the full fluid pressure is transmitted to the cylinder. But when the piston is lowered opening is opened, the liquid is drained from the valve to the tank through the opening in the rotary valve.
A WARNING If you need to remove the steering EPS, in order to avoid damage, ensure that the connector is disconnected. |
The functioning of the electronic steering system EPS Left turn (counter clockwise).
| Fig. 4.46. The circuit operation of the electronic steering system EPS control when a left turn: 1 - pump; 2 - a tank; A - at a low speed; B - at a high speed; and - the supply of fluid to the port "B"; b - the supply of fluid from the port "A"; c - from the oil pump; d - on the right cylinder tube; e - port "A"; f - port "B"; g - to the left of the cylinder tube; h - right chamber of the cylinder; i - I left chamber of the cylinder; j - the gap is closed; k - the supply of liquid from the "A"; l - the supply of liquid to the "B"; m - the gap opened
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Steering oil pump creates the pressure and fluid flows into the rotary valve. The interaction of the rotating wheels and tires rotated torsion resistance. At high vehicle speed fluid from the rotary valve is supplied to the electromagnetic valve through the bottom opening and exits through the upper opening portion for connection to the piston (fig. 4.46). At this time, the piston is pushed back, so that the force of the pusher spring force larger solenoid valve. The liquid passes through the clearance between the piston and the side wall and into the rotary valve and then discharged into the tank through the drain hole between the rotary valve and the torsion bar. Thus, the pressure generated by the pump, does not affect the force applied to the steering wheel. With decreasing vehicle speed piston aperture connecting the left and right compartments, gradually closes and the fluid pressure created by the pump is transmitted to the left compartment. Thus, the force applied to the steering wheel is reduced. Right turn (clockwise).
| Fig. 4.47. The circuit operation of the electronic steering system EPS control when the right turn: 1 - pump; 2 - a tank; A - at a low speed; B - at a high speed; and - the supply of fluid to the port "B"; b - the supply of fluid from the port "A"; c - from the oil pump; d - to the tube right cylinder; e - port "A"; f - port "B"; g - on the right cylinder tube; h - right chamber of the cylinder; i - I left chamber of the cylinder; j - the gap is closed; k - the supply of liquid from the "A"; l - the supply of liquid to the "B"; m - the gap opened
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Electronic steering EPS control when the right turn operates in the reverse operation in the left turn (Fig. 4.47).
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