Troubleshooting methods for pavers that cannot move

A TiTAn423 paver produced by Shaanxi Construction in 2000, when the engine was started, the throttle was set to the rated speed, the knob switch S6 was set to the working position, the steering potentiometer was centered, the speed potentiometer was selected at 2m/min, and the driving control lever was in the forward position, the following fault occurred: When the emergency stop button is pressed (the above steps are called the initial operation), the paver shows that the left track does not move, the right track moves rapidly, and the machine makes a sharp left turn.

The walking system of the paver mainly consists of a walking computer, two walking pumps, two walking motors, a track walking mechanism and a speed sensor, etc. Among them, the walking computer keeps the walking speed of the paver constant, thus meeting the construction requirements. To identify the cause of the fault, we conducted the following fault diagnosis based on the structure and working principle of the walking system.

(1) Release the brake. First, push in the black knob of the two-position four-way valve on the transfer case that serves as a brake and turn it clockwise to put the paver into the initial operating state. At this time, the pressure oil of the right walking pump reaches the brake cylinder, and the brake is released. The braking of the machine is released, and the following phenomenon occurs: the left track does not move, the right track moves rapidly, and the machine turns sharply to the left. This phenomenon indicates that the malfunction was not caused by the braking system.

(2) Apply emergency measures. The emergency transfer switch S70 behind the main control console distribution box was moved upwards to put the machine in the initial operation state. However, the following phenomenon occurred: the left track moved forward slowly, while the right track moved forward rapidly, resulting in a sharp left turn. The fault was not resolved. This indicates that the malfunction was not caused by the walking computer.

(3) Swap the plugs of the solenoid valve coils of the left and right walking pumps to put the machine in the initial operating state. At this moment, the left track remained stationary while the right track moved rapidly, causing the machine to make a sharp left turn.

(4) Unplug the coil of the solenoid valve of the right walking pump to put the machine in the initial operating state. At this point, the left track remained stationary while the right track moved forward rapidly, causing the machine to make a sharp left turn. When the switch S70 was set to the upward position and the machine was put into the initial operation state, the left track moved forward slowly while the right track moved forward rapidly, causing the machine to make a sharp left turn.

(5) The plug of the solenoid valve coil of the left walking pump was unplugged to put the machine in the initial operation state. As a result, the left track did not move, while the right track moved rapidly, causing the machine to make a sharp left turn. Switch S70 to the upward position and put the machine in the initial operation state. At this time, the left track remains stationary while the right track moves rapidly, causing the machine to make a sharp left turn.

The above situation indicates that the machine malfunction might be caused by the right-walking pump, that is, the right-walking pump has been continuously outputting a large flow rate in a single direction (the forward direction).

When switch S70 is in the normal position (i.e., set to the downward position) and the machine is in the initial operating state, due to the protective function of the walking computer, the left walking pump has no flow output. However, because the right walking pump is constantly outputting a large flow in one direction, the machine makes a sharp left turn. When the emergency measure (switch S70 is set to the upward position) is applied and the machine is put into the initial operation state, since neither the left nor the left walking pump is controlled by the walking computer, the left walking pump has a relatively small flow output, causing the left track to move forward slowly. However, due to the large flow output in a single direction of the right walking pump, the machine also turns left.

(6) To further verify the correctness of the fault diagnosis, we carried out the following operations:

When the emergency transfer switch is set to the normal position (switch S70 is set to the downward position), start the engine and adjust the throttle to the rated speed. Set the knob switch S6 to the working position, center the steering potentiometer, set the speed potentiometer to 2m/min, push the driving control lever to the reverse position, and press the release emergency stop button. At this point, the left track remains stationary while the right track moves forward rapidly, and the machine makes a sharp left turn. Apply the emergency measure (switch S70 to the upward position) and perform the above reverse operation. At this time, the left track slowly retracts, the right track rapidly moves forward, and the machine makes a sharp left turn.

This verification further indicates that the swash plate of the right-walking pump has always been in a position with a large flow output in a single direction (forward direction).

The possible reason for the right-walking pump's swash plate remaining in a single-direction high-flow output position all the time is that there is a problem with the solenoid valve. (If it is not a problem with this valve, the entire right-walking pump must be removed to the test bench for inspection.) So, we removed the solenoid valve of the right walking pump, cleaned it and reinstalled it. During the test run, the fault was eliminated.