The Composition of Hydraulic Power Steering System

The hydraulic power steering system is mainly composed of a constant flow valve, steering gear, steering cylinder, and gear pump. The oil in and out of the two cylinders of the electromechanical big stone is controlled by the steering valve. The steering valve is installed at the lower end of the steering gear, and the constant flow valve is installed on the left side of the steering valve. The steering valve, steering gear, and constant flow valve are connected to one body and mounted on the rear frame. The steering spool moves up and down with the rotation of the steering wheel, and the maximum moving distance of the spool is 3mm.

How Hydraulic Power Steering System Works

(1) When the steering wheel of the loader does not rotate.

The steering servo valve is in the neutral position. The oil output from the gear pump enters the middle groove 14 of the steering gear inlet through the high-pressure chamber of the constant flow valve and the one-way valve of the steering gear. The neutral position is normally open, but the opening is very small, about 0.15mm, which is equivalent to a throttle. The steering servo valve has five grooves, the middle groove 14 is for oil intake, 9 and 10 are respectively connected with the upper and lower chambers of the steering cylinder, and 15 and 16 are communicated with the oil return port 13. The pressure oil entering 14 enters the steering cylinder through the "normally open" axial clearance, and the pressure oil output by the gear pump communicates with the two working chambers of the steering cylinder through the constant flow valve and the tiny opening of the steering servo valve and then passes through the follow-up valve. The tiny opening of the valve is returned to the tank. Due to the throttling effect of the small opening, the hydraulic pressure of the two working chambers of the steering hydraulic cylinder is equal, so the oil pressure in the front and rear chambers of the cylinder is equal, and the piston rod of the steering hydraulic cylinder does not move, so the front and rear frames are kept at a certain In the relative angular position, there is no rotation, and the machine runs in a straight line or with a certain turning radius. At this time, the feedback lever, the sector gear in the steering gear, and the rack nut does not move.

(2) When the steering wheel rotates

The annular groove of the constant current spool moves down to the Aojian drill, which drives the gardening of Suiyan.com to overcome the strong capital and move. The moving distance The direction of the follow-up valve is reversed, and the pressure oil output by the steering pump enters a certain working chamber of the steering hydraulic cylinder through the constant-flow valve and the follow-up valve. Return to the fuel tank, and the steering rod extends or retracts to make the body move. Because the front frame rotates relative to the rear frame, the follower rod connected to the front frame drives the rocker arm to move forward and backward, the tug drives the sector gear to rotate, and the rack nut drives the direction shaft and the follower valve core to move in the opposite direction. Eliminate the relative movement error between the valve core and the valve body, so that the follower valve returns to the middle position, the follower valve no longer passes oil to the hydraulic cylinder, the movement of the steering hydraulic cylinder stops, and the front and rear frames maintain a certain steering angle. If you want to increase the steering angle, you can only continue to turn the steering wheel, so that the spool of the follower valve and the valve body continues to maintain the relative displacement error, so that the follower valve is opened until the maximum steering angle. The hydraulic power steering system is a follow-up system, its input signal is the displacement of the follow-up valve spool through the direction shaft, the output is the swing angle of the front frame, and the feedback mechanism is the follow-up rod, rocker arm, sector gear, tooth bar nut and direction shaft.

With the rotation of the steering wheel, since the rack, sector gear, steering rocker arm, and follower rod on the steering rod are connected to the front frame, the rack nut is fixed at this moment, so the steering screw acts relative to the rack nut. Rotation produces upward or downward movement at the same time. The plane washers and plane ball bearings installed on both ends of the steering valve compress the return spring and the one-way valve of the steering gear as the steering rod moves up or down, and gradually open the steering cylinder cavity 9 or 10 to release the high pressure. The oil is fed to one cavity of the steering cylinder, while the other cavity of the cylinder returns oil through 10 or 9.

When the pressure oil enters the steering cylinder, since the piston rod cavity and the largest area cavity of the left and right steering cylinders are cross-connected by the high-pressure oil camp, the two steering cylinders generate a moment in the same direction relative to the hinge pin, causing the front and rear beams to deflect relative to each other. When the front and rear frames have relative deflection and displacement, they are immediately sprayed back to the follower rod installed on the front frame, and the probe arm connected to the other end of the follower rod drives the sector gear and rack nut in the steering gear to move upwards and downwards. move, thus driving the screw to move up and down, like this. The steering spool returns to the neutral position under the action of the return spring, and the oil passage for the pressure oil to continue to supply oil to the steering cylinder is cut off, and the loader stops the steering movement. Only when you continue to turn the steering wheel will valve 9 or 10 be opened again to continue steering.

Steering system control process

Steering unit manipulation can be summarized as follows:

Turn the steering wheel -- the steering valve core slides up (or down), that is, the steering valve -- open the oil to enter the steering cylinder through the steering valve, and the cylinder moves -- the front and rear frames rotate relative to its connecting pin -- the steering starts, The movement of the follow-up mechanism fixed at the hinge point of the front frame - the other end of the follow-up mechanism, the arm shaft, the sector gear, and the movement of the rack nut - the steering valve core slides linearly, that is, the steering valve is closed. It can be seen that the relative deflection of the front and rear frames always lags behind the rotation of the steering wheel for a short period, that the continued relative rotation of the front and rear frames can be stopped. The rotation of the front and rear frames is realized by the movement of the follow-up mechanism, which is called "follow-up" feedback movement.

Steering assistance should first ensure that the pressure and flow of the steering system are constant, but during the operation of the engine, the size of the throttle changes, and the fuel supply and pressure of the steering gear pump to the steering system will also change. This contradiction can be solved by constant current valve repair.

When the amount of oil supplied by the steering pump 2 is too much, the liquid flow through the throttle plate can restrict the excessive oil from flowing into the steering gear, and flows through the groove 17 of the constant current valve core, enters the right end of the valve core through the oblique hole, and pushes the valve core Move to the left until the two chambers 17 and 7 are connected, and 7 is the low-pressure chamber connected with the oil pool. At this time, the valve core acts as an overflow, overflowing the excess oil from the oil pump into the oil tank.
If the pressure of the oil supply of the oil pump passing through the throttle plate exceeds the rated value, the overpressured oil enters into people 5 and 6 through the orifice. The valve of the pressure regulating spool of the pilot safety valve can be opened. The pressure difference increases and the pressure of oil flowing from 3 through 17 through the small hole in the valve core exceed the sum of the oil pressure and elastic force of the 5-chamber. The lake can be moved to the left until 17 and 7 are connected, at which time the pressure of the steering system is immediately reduced to the rated value. As the pressure of the system drops to the rated value, the pressure of the 6-chamber also decreases, and the pilot safety net core moves to the left under the action of the bomb until the valve is closed again. The extremely high quality of logistics and the network center of the hospital can guarantee the transfer to the internal system for the low health of the micro-health, and the stable and safe power flow network of the first security country ensures the constant and safe pressure of the steering system, and the change of the pressure of the peach fruit system is more sensitive and safe and reliable. guarantee.

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