초록 ▼

If a first control valve 71 is arranged so as to change between a flow position A and a throttling position C by a fluid for switching purpose guided through a pilot channel 77, the flow area of a first intermediate channel can be changed in two steps. As a result, the injection-valve opening pressu

If a first control valve 71 is arranged so as to change between a flow position A and a throttling position C by a fluid for switching purpose guided through a pilot channel 77, the flow area of a first intermediate channel can be changed in two steps. As a result, the injection-valve opening pressure and time of a first relief valve 48 change between two types of values, whereby the physical shock occurring when a crawler vehicle stops can be switched between two types of shock.

대표청구항 ▼

[ What is claimed is:] [1.] A relief mechanism includinga pair of supply/discharge channels connecting a hydraulic actuator to a changeover valve;a connection channel connecting together the supply/discharge channels;a first relief valve provided at some point in the connection channel; wherein when

[ What is claimed is:] [1.] A relief mechanism includinga pair of supply/discharge channels connecting a hydraulic actuator to a changeover valve;a connection channel connecting together the supply/discharge channels;a first relief valve provided at some point in the connection channel; wherein when the internal pressure of one supply/discharge channel reaches a relief pressure level, the first relief valve is opened and permits fluid to escape from the supply/discharge channel to the other supply/discharge channel, whereas when the internal pressure of the latter supply/discharge channel decreases to a given pressure level lower than the relief pressure level, the first relief valve is opened only during the time period over which the fluid is flowing to a first intermediate channel from the latter supply/discharge channel, to thereby permit fluid to escape from the latter supply/discharge channel to the former supply/discharge channel;a second relief valve provided at some point in the connection channel in shunt with the first relief valve, wherein when the internal pressure of the latter supply/discharge channel reaches the relief pressure level, the second relief valve is opened, to thereby permit fluid to escape from the latter supply/discharge channel to the former supply/discharge channel, whereas when the internal pressure of the former supply/discharge channel decreases to a given pressure level lower than the relief pressure level, the second relief valve is opened only during the time period over which fluid is flowing to the latter supply/discharge channel from the former supply/discharge channel; anda cylinder connecting the first intermediate channel to a second intermediate channel, wherein when a piston housed therein is moved to a stroke end as a result of being pressed by the fluid that has flowed from the first and second intermediate channels, the cylinder stops the influx of the fluid from the first and second intermediate channels, the improvement being characterized by comprising:first and second control valves which are provided at some points in the first and second intermediate channels of the foregoing relief mechanism and can be switched between a flow position at which smooth flow of fluid is permitted and a throttling position at which fluid flows in a throttled manner; anda pilot channel for guiding fluid for switching purposes to the first and second control valves.