The traveling system is composed of traveling hydraulic motor, two-speed hydraulic motor regulating valve, parking brake, brake valve, traveling reducer (final transmission), etc.
1. Walking hydraulic motor
The traveling hydraulic motor is a residual disc type axial variable plunger motor, which is composed of a drive shaft, a motor housing, a fixed core guide sleeve, a swash plate, a plunger, a cylinder block, an oil distribution plate, and a rear cover. The structure is shown in Figure 3- 22 shown. The technical parameters of the traveling hydraulic motor are shown in Table 3-2.
1—drive shaft; 2—motor housing; 3 fixed core guide sleeve; 4—swash plate; 5—plunger; 6—cylinder block; 7—oil distribution plate; 8—rear cover;
9—regulator valve; 10—spring; 11—brake spring; 12—brake piston; 13—steel plate; 14—friction plate;
15—regulator piston; 16—spring; 17—check valve spring; 18—check valve;
19—Balance valve; 20—Balance valve return spring; 21—Safety valve
Figure 3-22 Walking hydraulic motor
2. Working principle of two-speed hydraulic motor
The high and low speed conversion of the traveling hydraulic motor is realized by changing the displacement of the hydraulic motor by the regulator valve 9 according to whether the solenoid valve of the traveling speed works. The working principle of the two-speed hydraulic motor is shown in Figure 3-23.
4—swash plate; 8—rear cover; 9—regulator valve; 10—spring; 15a—upper regulator piston;
15b—lower regulator piston; 22—check valve Figure 3-23 Working principle of two-speed hydraulic motor
① High torque at low speed (LO). The driving speed solenoid valve does not work, the regulator valve 9 is pushed to the right by the spring 10, the pressure oil from the travel control valve pushes the check valve 22 to the rear cover 8 through the a port on the regulator valve 9, and enters the upper regulator at the same time The bottom of the piston 15a moves the regulator piston 15a to the right and pushes the swash plate 4 to rotate to the maximum swash plate angle. The pressure oil in the lower regulator piston is discharged to the motor housing through the orifice b on the regulator valve 9. The motor displacement reaches the maximum, and the system is at low speed (LO) at this time.
② High speed (Hi) low torque. When the driving speed solenoid valve works, the pilot pressure oil from the pilot pump flows to port P, pushing the regulator valve 9 to move to the left. Therefore, most of the pressure oil from the travel control valve passes through the passage c on the regulator valve 9 and enters the bottom of the lower regulator piston 15b, causing the piston 15b to move to the right and pushing the swash plate 4 to the smallest swash plate inclination angle. position. At the same time, the pressure oil at the bottom of the upper regulator piston 15a flows to the motor housing through the orifice d in the regulator valve 9. The motor displacement reaches the minimum and the system is at high speed (Hi).
1. Parking brake
The parking brake is installed in the traveling hydraulic motor and is a normally closed disc brake. Its structure is shown in Figure 3-22. The working principle of the brake is shown in Figure 3-24.
① When the walking control lever is operated to start walking, the pressure oil from the hydraulic pump enters the walking hydraulic motor and the walking brake valve through the walking control spool. The pressure oil flowing into the brake valve moves the balance spool of the valve and flows into a of the brake piston 12
The chamber overcomes the force of the spring 11 and pushes the brake piston to the right. At this time, the friction plate 14 and the steel plate 13 are separated, and the brake is released.
②When the travel control lever stops walking in the neutral position, the travel control valve stops supplying oil to the travel motor and travel brake valve, the balance spool of the travel brake valve returns to the neutral position, and the pressure oil in chamber a of the brake piston 12 The brake piston orifice drains to the housing. The brake spring 12 pushes the brake piston to the left. At this time, the friction plate 14 and the steel plate 13 are pressed together, and the brake is applied.
2. Brake valve
The brake valve is composed of a one-way valve, a balance valve and a safety valve. It is installed in the back cover of the traveling hydraulic motor. Its structure is shown in Figure 3-22.
The working principle of balance valve and check valve is shown in Figure 3-25.
11—spring; 12—brake piston; 13T initial ": 14—friction plate; 19—balance valve Figure 3-24 Working principle of parking brake (part of Figure 3-22)
When operating the walking control lever, the pressure oil from the walking control valve enters the Pa port. When the one-way valve 18a is opened, it flows from the motor inlet Ma to the outlet Mb, but the oil outlet of the motor is closed by the one-way valve 18b and the balance valve 19. The oil stops flowing and the motor does not rotate. When the pressure in the motor oil inlet increases, when the pressure in the S] cavity is greater than the moving pressure of the balance valve core, the balance valve 19 moves to the right, Mb communicates with the Ma port, and the motor starts to rotate.
When the excavator goes downhill, due to the influence of the machine's own weight, the motor will rotate under no load, causing the motor inlet pressure to drop. When the pressure of the & cavity is less than the pressure of the balance spool movement, the balance spool 19 moves to the left under the action of the return spring, the outlet is throttled, the pressure on the outlet side rises, the motor rotates, and resistance is generated to prevent the motor from losing control , And make the motor control the rotation speed according to the output flow of the hydraulic pump.
The function of the safety valve is that when the excavator stops driving or goes downhill, the oil circuit of the hydraulic motor outlet is closed by the balance valve, but the motor continues to rotate under the action of inertial force. Therefore, the safety valve opens to relieve pressure to prevent pipelines and other The component is damaged.
3. Walking reducer
The walking reducer, also known as the final drive, is composed of two-stage planetary gears, with a compact structure and a large reduction ratio. Its structure is shown in Figure 3-26. 
1—Oil level plug; 2-Drain plug; No. 3-1 sun gear; No. 4-2 sun gear; No. 5-2 planet carrier;
6—Side cover; No. 7—1 planet carrier; 8—Drive wheel ring gear; 9—Floating oil seal; 10—Travel motor;
11-wheel hub; 12-1 planetary gear; 13-gear ring; 14-2 planetary gear
Figure 3-26 Walking reducer
