Troubleshooting the problem that the paver cannot move

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A TITAN423 paver produced by Shaanxi Construction in 2000. When the engine is started and the accelerator is placed at the rated speed, the toggle switch S6 is placed in the working gear position, the steering potentiometer is centered, the speed potentiometer is selected at 2m/min, and the travel joystick is in the forward position, the following fault occurs.: When the emergency stop button is pressed (the above steps are called initial operations), the left track of the paver does not move, the right track moves forward rapidly, and the machine turns sharply to the left. The paver traveling system mainly consists of a traveling computer, two traveling pumps, two traveling motors, a crawler traveling mechanism, and a speed sensor. The traveling computer keeps the traveling speed of the paver at a constant speed to meet construction requirements. In order to find the cause of the fault, we conduct the following fault diagnosis based on the structure and working principle of the walking system. (1) Release the brake. First, push the black knob of the two-position four-way valve that acts as a brake on the transfer case and turn it clockwise to put the paver in the initial operating state. At this time, the pressure oil from the right traveling pump reaches the brake cylinder, opens the brake, and the machine's brake is released. The following phenomenon occurs.: The left crawler track does not move, the right crawler track moves forward quickly, and the machine turns sharply to the left. This phenomenon indicates that the fault is not caused by the braking system. (2) Use emergency measures. Turn the emergency transfer switch S70 behind the distribution box of the main console to the upward position to put the machine in the initial operating state. The following phenomenon occurs.: The left crawler track moved forward slowly, and the right crawler track moved forward quickly, causing a sharp left turn and the fault could not be eliminated. This shows that the fault is not caused by the walking computer. (3) Replace the plugs of the solenoid valve coils of the left and right traveling pumps so that the machine is in the initial operating state. At this time, the left crawler track did not move and the right crawler track moved forward rapidly, causing the machine to turn sharply to the left. (4) Unplug the solenoid valve coil plug of the right traveling pump to put the machine in the initial operating state. At this time, the left crawler track does not move and the right crawler track moves forward quickly, causing the machine to turn sharply to the left. ； Turn switch S70 to the upward position and put the machine in the initial operating state. As a result, the left crawler track moved forward slowly and the right crawler track moved forward rapidly, causing the machine to turn sharply to the left. (5) Unplug the solenoid valve coil plug of the left traveling pump to put the machine in the initial operating state. As a result, the left crawler track did not move and the right crawler track moved forward rapidly, causing the machine to turn sharply to the left. ； Turn switch S70 to the upward position and put the machine in the initial operating state. At this time, the left crawler track does not move and the right crawler track moves forward rapidly, causing the machine to turn sharply to the left. The above situation shows that the machine failure may be caused by the right traveling pump, that is, the right traveling pump has been outputting a large flow in one direction (forward direction). When switch S70 is in the normal position (that is, moved to the downward position) and the machine is in the initial operating state, due to the protection of the traveling computer, the left traveling pump has no flow output, but the right traveling pump has been outputting large flow in one direction, causing the machine to turn sharply to the left. ； When emergency measures are taken (switch S70 is moved to the upward position) and the machine is in the initial operating state, since the left and right walking pumps are not controlled by the walking computer, the left walking pump has a smaller flow output, causing the left track to move forward slowly. However, due to the large flow output of the right walking pump in one direction, the machine also turns to the left. (6) In order to further verify the correctness of the fault judgment, we performed the following operations: When the emergency switch is in the normal position (switch S70 is moved to the down position), start the engine and adjust the accelerator to the rated speed. Place the toggle switch S6 in the working gear position, the steering potentiometer in the middle, and the speed potentiometer set at 2m/min. Push the travel joystick to the reverse position and press the release emergency stop button. At this time, the left crawler track does not move, the right crawler track moves forward quickly, and the machine turns sharply to the left. ； Use emergency measures (turn switch S70 to the upward position) and perform the above-mentioned retreat operation. At this time, the left crawler track slowly retreats, the right crawler track moves forward quickly, and the machine turns sharply to the left. This verification further explains: The swash plate of the right traveling pump is always in the output position of large flow in one direction (forward direction). The possible reason why the swash plate of the right traveling pump is always in the one-way large flow output position is that there is a problem with the solenoid valve (if it is not a problem with the valve, the entire right traveling pump can only be removed and put on the test bench for inspection). Therefore, we removed the solenoid valve of the right traveling pump, cleaned it and reinstalled it. The fault was eliminated during the test run.