The principle of travel three speed control and maximum flow cut-off control is shown in figure 12-59, and the travel sequence diagram (s and H modes).
1. When mode s is selected
(1) When the travel pressure switch and the upper pressure switch are in the 0n position, the controller will not output control signals to the travel switching solenoid valve. At this time, the displacement of the main pump is the standard (middle) displacement, and the swashplate of the travel motor is in the low displacement position.
(2) High speed walking state (when in the medium speed walking state, press the change-over switch again to turn to the high-speed walking state). The walking change-over solenoid valve is in the 0n position, and the swashplate of the walking motor is in the high displacement position.
(3) Low speed walking state (when in high-speed walking state, press the change-over switch again to turn into low-speed walking state).
Once the travel switch is switched, the maximum flow cut-off solenoid valve is turned on (on), so as to realize the maximum flow cut-off control. When the swashplate of the traveling motor is at the low displacement position, the main pump realizes the maximum flow cut-off control.
When the upper pressure switch is in the on position, the maximum flow cut-off solenoid valve is not on (off), so the maximum flow cut-off control cannot be realized.
2. When h mode is selected
(1) When traveling at medium speed, the swashplate of the traveling motor is at the low displacement position, and the output flow of the main pump is the standard (medium) flow.
(2) When traveling at high speed, the swashplate of the travel motor is at the high displacement position.
(3) When walking at low speed, the maximum flow cut-off control of main pump output is realized, which is the same as that in S mode.
3. When l and f modes are selected
The walking sequence diagram (L and f modes) is shown in figure 12-61.
(1) When traveling at medium speed, the swashplate of the traveling motor is at the low displacement position, and the output flow of the main pump is the standard (medium) flow.
(2) When traveling at high speed, the swashplate of the travel motor is at the high displacement position.
(3) When walking at low speed, the maximum flow cut-off control of the main pump output is realized.
4. When mode f is selected
When f mode is selected, the signal of the upper pressure switch can be used to realize the maximum flow cut-off control of the main pump output.
(1) When the excavator travels at medium speed, operate the travel control handle separately, the swashplate of the travel motor is at the low displacement position, and the output flow of the main pump is the standard (medium) flow; when the upper working device is operated alone, the maximum flow cut-off control of the main pump output is realized; while the excavator is walking, the upper working device also acts, and the swashplate of the traveling motor is at the low displacement position to realize the maximum flow cut-off control of the main pump output.
(2) When the excavator is traveling at high speed, the traveling joystick is operated separately, the swashplate of the traveling motor is at the low displacement position, and the output flow of the main pump is the standard (medium-range) flow; when the upper working device is operated separately, the maximum flow cut-off control of the main pump output is realized: while the excavator is traveling, the upper working device also acts to realize the maximum flow cut-off control of the main pump output.
(3) When the excavator travels at low speed, the travel joystick is operated separately, and the swashplate of the travel motor is at the low displacement position to realize the maximum flow cut-off control of the main pump output. When the upper working device is operated separately, the maximum flow cut-off control of the main pump output is realized.
While the excavator is traveling, the upper working device also acts. The swashplate of the traveling motor is at the low displacement position, and the output flow of the main pump is the standard (medium) flow.
Table 12-5 shows the relationship among the traveling speed of excavator, the displacement of traveling motor and the output flow of main pump.
The walking speed and power mode are independent of each other, and the walking speed varies with the walking mode and power mode
