A Brief Discussion on Fault Detection and Maintenance of the Vibration System of XCMG YZ18S Roller

Our company has a XCMG YZ18S vibratory roller, which is fully hydraulically operated. However, recently during the construction at the site, there was suddenly no vibration. Based on this situation, we analyzed and diagnosed.

First, inspect the vibration control system. The vibration of the YZ18S vibratory roller is achieved by controlling the vibration motor with a vibration solenoid valve. Only when the vibration solenoid valve is opened does the oil circuit of the vibration motor open, and vibration can be achieved. Let's start from the simplest aspect and test the vibrating solenoid valve first. Through the measurement by a professional electrician, it was found that the vibration solenoid valve opened and closed normally, indicating that the fault did not lie with the vibration solenoid valve.

Secondly, test the vibration hydraulic circuit. We loosened the oil inlet pipe of the vibration motor and operated the vibration system. We found that very little oil was flowing out of the oil inlet pipe and the oil pressure was very low. From this, it can be determined that the fault lies in the vibration pump and its transmission part, and thus the fault of the vibration motor can be eliminated.

Iii. Inspect the vibration pump and its drive system. The YZ18S vibratory roller is equipped with a German Deutz F6L913 engine. The engine power is transmitted through the transfer case to drive the vibratory pump and the walking pump. First, we remove the vibration pump. After the vibration pump was removed and cleaned thoroughly, we found that the splines on the pump shaft of the vibration pump and the splines inside the gear sleeve meshing with it were basically ground smooth. The reason for the problem lies precisely here. The splines of the pump shaft and the gear sleeve are worn flat, which is equivalent to cutting off the power transmitted from the transfer case to the vibration pump, thus making it impossible to drive the vibration pump to work normally.

Iv. Maintenance Methods. The vibration pump of the YZ18S vibratory roller adopts the German Rexroth A2F63 vibratory pump. Considering that the cost of replacing the pump shaft is too high, the maintenance cost is too large, and besides, the spare parts need to be ordered, which delays the time and affects the construction and production. Let's analyze it and decide to use wire cutting technology to repair the pump shaft and gear sleeve, and in this way, there is no need to disassemble the vibrating pump. (Note: The Rexroth A2F63 pump must be re-calibrated on the test bench after disassembly.)" This is both simple and convenient. The specific maintenance method is as follows: We contacted the wire cutting machinery processing factory, discussed and calculated with them, and decided to open three keyways of appropriate width, depth and length on each of the pump shaft and gear sleeve. (Note: The moderate width, depth and length of the keyway mean that the strength of the pump shaft and gear sleeve should not be damaged.)"

V. Determination of the repair dimensions of the keyways opened on the pump shaft and gear sleeve.

First, we measure the diameter of the pump shaft, which is 35mm. Then, based on the diameter of the pump shaft, we roughly determine the size of the connecting flat key. Considering that the pump shaft is not too thick, the width and depth dimensions of the flat key should not be too large. Otherwise, it will reduce the strength of the pump and cause the pump shaft to break. First, we decided to use a flat key connection with a width × height of 6× 6mm. Because the pump shaft and the gear sleeve were originally connected by splines, in order not to weaken the strength of the pump shaft, a multi-key connection is adopted. After meticulous and thorough research with the workers, it was decided to use three flat keys for connection (three keyways are opened at intervals of 120 degrees along the circumference of the pump shaft). The splines of the original pump shaft and the gear sleeve are connected by through keys. Even if the three flat keys are opened, the strength of the shaft will not be damaged. Therefore, it was decided to open the keyway. The keyway dimensions for the shaft and gear sleeve are: width × height 6× 6mm. For key connections, choose the tighter key connection. The processing dimensions can be determined by referring to the design manual based on the tolerance fit dimensions of the shaft, gear sleeve and key.

Then we carry out the strength check calculation of the construction.

(1) Check the extrusion strength of the key.

According to the formula: key connection p=2T/Dkl≤ [p]

T - Pump shaft torque (which can be found on the pump's nameplate), D - shaft diameter.

K - the height of the connection between the key and the gear sleeve, taking K=h/2=3 mm, l - the working length of the key.

[p] Refer to the design manual and take [p] =40MPa

(2) Check the shear strength of the key

According to the formula: τ=2T/Dbl≤ [τ]

T - Pump shaft torque, b - key width, D - shaft diameter. The working length of the L-key.

Refer to the design manual and take [p] =90MPa

Through the above calculation, the key connection strength is verified to be qualified.

Six. According to the dimensions determined by the calculation, process three high-strength flat keys and connect the vibration pump and the gear sleeve through the keys. After the pump and the gear sleeve were assembled by key connection, we smoothly installed the pump behind the transfer case. After installation, the test was conducted again. The excitation force was restored and the excitation effect was obvious. The repair was successful.

Vii. Analysis of Fault Causes. On the one hand, due to the fact that our company's YZ18S vibratory roller has been working on construction sites for a long time, with poor working conditions and a lot of dust, the gear oil in the transfer case has become too dirty, and the wear of abrasive particles has gradually worn out the splines between the pump shaft and the gear sleeve. On the other hand, it may also be due to the lack of gear oil in the transfer case or the failure to replenish or replace the gear oil in time, resulting in insufficient oil and causing the splines between the pump shaft and the gear sleeve to wear out due to poor lubrication. Therefore, it is reminded that all operators should frequently check the oil level in the transfer case and change the oil in time to prevent similar situations from happening again.

Since we repaired this YZ18S vibratory roller, it has been working normally and the vibration system has never malfunctioned again.