For tire-type construction machinery, in order to expand the working area and increase the overall stability, it is necessary to extend the outriggers on the frame to the outside of the tire to support the whole. The outriggers include frog, H, X and radial. Here only a hydraulic circuit of the H-type outrigger is used as an example to illustrate some characteristics of the hydraulic circuit of the outrigger mechanism of Hitachi excavator.
H-type legs consist of four groups of hydraulic cylinders, each group includes a horizontal hydraulic cylinder and a vertical hydraulic cylinder. In Figure 2-5 (a), the horizontal hydraulic cylinder 1 pushes out the outriggers, and the vertical hydraulic cylinder 2 pushes up the frame to suspend the tires, so that the entire work frame is supported by the outrigger mechanism.
Figure 2-5 (b) is a hydraulic circuit diagram of the outrigger mechanism. The manual directional valve 2 controls the expansion and contraction of the four horizontal hydraulic cylinders 5. When the horizontal hydraulic cylinder operates, the outrigger mechanism has not yet worked, the tire has not left the ground, the load resistance is not large, and only needs to reach the appropriate position, so the control of the horizontal hydraulic cylinder is very simple. The manual directional valve 3 controls the lifting and lowering of the four vertical hydraulic cylinders 6. The six-position six-way rotary valve can control four vertical hydraulic cylinders separately, so that when the ground is uneven, the vertical hydraulic cylinders can be adjusted to different lifts while keeping the working frame horizontal. When the rotary valve is in the I position, it controls four hydraulic cylinders at the same time; in the port, dish, IV, and V positions, it controls the hydraulic cylinders 6a, 6b, 6c, and 6d; while in the VI position, the four hydraulic cylinders are free of liquid In and out, then the outriggers support the frame in the ideal working position. 4 bidirectional hydraulic locks 7 each control a vertical hydraulic red, when the legs support the frame static
Figure 2-5 Outrigger mechanism
At the end of time, the liquid in the upper cavity of the vertical hydraulic cylinder is subjected to gravity load. In order to avoid the settlement of the frame, it is necessary to use the hydraulic control check valve connected to the upper cavity for locking to prevent the commonly known "soft leg" phenomenon; when the tire supports the frame When the liquid in the lower chamber of the vertical hydraulic cylinder bears the weight of the outrigger itself, in order to prevent the outrigger from falling to the ground and prevent the phenomenon commonly known as "leg drop", it is necessary to use a hydraulic control check valve connected to the lower chamber for locking.
