Diagnosis and Elimination of High and Low Speed Disengagement Faults of ZL30

Diagnosis and Elimination of High and Low Speed Disengagement Faults of ZL30

I. Fault Phenomenon:

A ZL30E loader often experiences disengaging at high and low speeds during operation, which eventually leads to the entire machine being unable to work or move, seriously affecting the progress of the project.

Ii. Principle of High and Low Gear Shifting Structure:

The ZL30 transmission adopts a structure that combines fixed-axis power shift and mechanical fork structure to achieve four forward gears and two reverse gears. The mechanical fork structure is mainly used to achieve the conversion mechanism between high and low speeds. Its structure is as shown in the figure

It is mainly composed of bracket 1, fork shaft 2, fork 4, etc. When the loader needs to change its high and low speeds, the position of the fork shaft is altered to change the fork's push of the high and low speed meshing sleeves, achieving gear meshing. Then, by changing the on-off state of the oil circuit of the variable speed control valve, gear shifting is realized.

Bracket 1 is fixed to the transmission box with bolts. The 2-end of the fork shaft is connected to the fork through the set screw 3. The set screw is connected to the fork with steel wire to prevent it from falling off. The shape of the fork shaft is shown in Figure 2. The steel ball 7 is positioned in the gear positioning slot through the spring 8 and the plug 6, and locked in the positioning slot of a certain gear to achieve the transformation between high and low gears.

Iii. Fault Analysis

According to the structural principle analysis, the reasons for the high and low speed disengagement fault are as follows:

(1) The positioning ball slot of the fork shaft gear is worn flat, making it impossible to position the steel ball.

(2) The steel balls are severely worn.

(3) Spring damage.

(4) The depth of the positioning hole of the locking screw is insufficient, resulting in the screw being unable to lock the fork.

(5) The locking screw is stripped.

Iv. Troubleshooting

When the entire high and low speed mechanism was removed from the transmission, it was found that the fork and the screw had fallen off and dropped into the transmission oil pan, and the screw positioning was also severely worn. After removing the fork and the screw, it was found that the thread had stripped. Thus, it was determined that the cause of the high and low speed disengagement was due to insufficient depth of the screw positioning hole. The fork shaft was removed, the positioning hole was drilled deeper, and the screw was replaced. Install the high and low speed mechanisms, debug them, and resume normal operation. This machine has not experienced any gear disengagement within 1,000 hours of operation.