1. Generation of turning force
The high-pressure oil supplied from the hydraulic pump flows into the oil cylinder and valve plate through the valve housing of the motor. When the oil flow passes through the Y-Y oil circuit-end connected to the upper and lower ends of the plunger, high-pressure oil is formed. As shown in Figure 1-77, high-pressure oil generates pressure (F1=pxA, where p refers to providing pressure and A refers to pressure area), acting on the plunger.
In the case of a swash plate with an inclination angle a, F is divided into a local pushing pressure N and a local radial pressure W. w generates torque, T=W:xR, because the Y-Y oil circuit is connected together through the upper and lower ends of the plunger, as shown in Figure 1-77 (a).
The total torque (2 W:xR}) is generated from each plunger (4~5) at the one-end of high pressure to generate the turning force. The torque is converted into slewing force through the plunger to the cylinder, because the cylinder includes a slewing shaft and a spline, and the slewing shaft rotates to send the slewing force.
2. The relief valve works
The overflow valve performs the following two functions.
① When driving the hydraulic motor, the relief valve makes the pressure meet the standard, for example, the extra oil generated due to inertial acceleration goes to the bypass oil passage.
②When the inertia stops, the relief valve stops the equipment according to the brake pressure generated at the predetermined end.
As shown in Figure 1-78, the chamber A is always connected to the oil port A of the motor. If the port pressure increases, the pressure pushes the bracket A.
If the pressure is greater than the set spring pressure, the bracket A is separated from the connection surface of the seat A, so the oil in the chamber A flows into the oil port B.
3. The brake works
As shown in Figure 1-79, the modern excavator brake applies the pressure provided by the spool in the valve housing to the brake plunger and releases the brake.
When the pressure is not working, the brake still runs straight.
The frictional force between the plates fixed on the axle housing generates a braking force, and the brake plunger and the friction plate are connected by a spline on the outer end of the cylinder.
When the pressure does not act on the plunger parts, the brake spring presses the brake plunger, and the oil in the brake chamber flows into the leakage oil port of the motor through the hole. At this time, the brake plunger presses the friction plate, the separation plate in the middle of the axle housing and the brake plunger according to the pressure of the 10 brake springs, and finally generates friction.
Frictional force helps the brake to fix the rotating shaft connected by the cylinder and the operation spline.
4. Balance valve
Av is the oil port connected to the hydraulic pump, Bv is the oil port connected to the oil tank.
As shown in Figure 1-80, the oil for the hydraulic pump presses the check valve Av port → Cv port, and is supplied to the hydraulic motor through the port L to run it. However, the oil pressure outside the pump increases and is transmitted to the spring chamber M through the channel G, because the brake is working.
If the pressure in the chamber M is greater than the spring force holding the spool neutral, the spool moves to the right.
The oil in the chamber N is sent to the chamber M through the hole I, and flows to the oil tank through the channel G. Therefore, the spool moves to the right, so does the oil flow from the K port to the Bv port.
5. Automatic switch work (normal speed)
As shown in Figure 1-81, because there is no pilot control pressure, the spool does not work.
6. Automatic switch operation (high speed)
At normal speed, if hydraulic oil flows into the high-speed switch pressure port through the internal passage of the spool (external pilot control pressure p=35kgf/cm?), the spool moves from right to left.
At high speed, the rotation pressure of the motor DI exceeds 250kgf/cm'. When the pressure of the spool 1 (pressure p1) is greater than the spool 2, the spool 1 is pushed out, and then the spool 2 moves from the left to the right. The switch works.
