• Final Drives motor

How the final drive motor works

The weight of medium and large crawler excavators is generally above 20t. The inertia of the machine is very large. It will bring a big impact to the hydraulic system during the start and stop of the machine. Therefore, the travel control system must be improved to adapt to this. Kind of working conditions. The traveling motor generally adopts a high-speed motor plus a planetary reducer or a cycloidal pin reducer, and the control of the circuit of the hydraulic motor part has its own characteristics. The control circuit of the travel motor is shown in Figure 1. The motor is equipped with a high-voltage automatic variable device. When the high-speed gear is engaged, the circuit is connected to the manual shift port to oil, pushing the shift valve to the left to make the final drives become small displacement; When the resistance increases and the oil pressure rises to the set value, the oil pushes the shift valve to the right, and the motor automatically changes to a large displacement low speed gear to increase the torque. Therefore, the motor can automatically change the gear as the walking resistance changes.

This type of motor can automatically change gears as the walking resistance changes.

This type of motor can automatically change gears as the walking resistance changes.

(2) The hydraulic oil enters the balance valve through the orifice and moves it to the left to open the brake oil passage to release the brake. This action also turns on the oil return passage of the final drive motor B port.

(3) The hydraulic oil enters the buffer piston chamber through the intermediate orifice of the safety valve, pushing the buffer piston to the left side. If the system pressure exceeds the set pressure (10.2 MPa) of this safety valve at this time, the safety valve will open in an instant and serve as a buffer.

(4) If the motor overspeed (for example, when going downhill), the pump does not have time to supply oil, then the pressure at port A is lowered, the balance valve moves to the right under the action of the spring force, and the oil return passage of the small motor is closed, thereby limiting the rotation speed of the motor. https://www.spfinaldrives.com/



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