For tire type construction machinery, in order to expand the working area and increase the overall stability, it is necessary to extend outriggers to the outside of the tire on the frame to support the whole. The outriggers are frog, h, X and radial. Here, only one hydraulic circuit of H-type outrigger is taken as an example to illustrate some characteristics of the hydraulic circuit of Hitachi excavator outrigger mechanism.
H-type outrigger is composed of four groups of hydraulic cylinders, each group includes a horizontal hydraulic cylinder and a vertical hydraulic cylinder. In Fig. 2-5 (a), the horizontal hydraulic cylinder 1 pushes out the outrigger, and the vertical hydraulic cylinder 2 lifts the frame to suspend the tire, so that the whole operation frame works under the support of the outrigger mechanism.
Figure 2-5 (b) is the hydraulic circuit diagram of outrigger mechanism. The manual change-over valve 2 controls the expansion and contraction of four horizontal hydraulic cylinders 5. When the horizontal hydraulic cylinder acts, the outrigger mechanism does not work, the tire does not leave the ground, the load resistance is small, and it can be extended to the appropriate position, so the control of the horizontal hydraulic cylinder is very simple. The manual change-over valve 3 controls the lifting of four vertical hydraulic cylinders 6. The six position six way rotary valve can control four vertical hydraulic cylinders respectively, so as to adjust the vertical hydraulic cylinder in different lift and keep the working frame horizontal when the ground is uneven. When the rotary valve is in position I, four hydraulic cylinders are controlled at the same time; Control hydraulic cylinders 6a, 6b, 6C and 6D respectively at port, dish, IV and V positions; At VI position, there is no liquid in and out of the four hydraulic cylinders. At this time, the outrigger supports the frame at the ideal working position. Four two-way hydraulic locks 7 each control a vertical hydraulic red when the outrigger supports the frame
During the stop, the liquid in the upper chamber of the vertical hydraulic cylinder bears the 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 chamber to lock and prevent the commonly known "soft leg" phenomenon; when the tire supports the frame, the liquid in the lower chamber of the vertical hydraulic cylinder bears the weight of the outrigger itself, so as to avoid the outrigger falling to the ground and prevent the commonly known "leg falling" Therefore, the hydraulic control check valve connected to the lower chamber needs to be used for locking.
