JPH061465U - Two-stage relief valve circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] When the hydraulic circuit of the cylinder that operates the boom of a construction machine that has a boom, an arm, and a bucket has two hydraulic pumps and operating valves, contracts the cylinder that operates the boom. The pressure to be applied is controlled in two steps. [Structure] A relief valve provided in the middle of the pipe for supplying hydraulic oil to contract the cylinder that operates the boom,
It is a two-stage relief circuit that is a relief valve that can be switched to two stages of low pressure or high pressure by operating pilot hydraulic pressure.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic circuit for operating a working machine of a construction machine, and more particularly to a two-stage relief valve circuit used in the hydraulic circuit.

[0002]

[Prior art]

 FIG. 3 is a side view showing an example of excavation work of a power shovel. In FIG. 3, reference numeral 101 is a traveling device, and 103 is an upper revolving structure capable of revolving around a revolving center 102. The upper revolving superstructure 103 has a boom 104 which has a part 104a as a center of rotation and which is lifted by expansion and contraction of a rod 105a of a hydraulic cylinder 105. Further, the arm 106 is pivotally attached to the tip portion 106a of the boom 104, and the bucket 109 attached to the tip portion 109a of the arm 106 can be moved back and forth by expanding and contracting the rod 107a of the hydraulic cylinder 107. . The bucket 109 is pivotally attached at 109a, and can be rotated up and down by expanding and contracting the rod 108a of the hydraulic cylinder 108. The driver appropriately operates the boom 104 and the arm 106, pushes the bucket 109 in the direction of arrow P, pulls it in the direction of arrow Q, and scoops the soil into the bucket.

FIG. 4 is a hydraulic circuit diagram for operating the hydraulic cylinder 105 for operating the boom 104 up and down. In FIG. 4, 121 is a hydraulic pump, and 131 is an operation valve that controls the discharge oil of the hydraulic pump 121. Further, 125 is another hydraulic pump, and 141 is an operation valve for controlling the oil discharged from the hydraulic pump 125. The operation valves 131 and 141 have three-step operation positions of A, B, and C, respectively, and the position and the intermediate position thereof can be obtained by the pilot hydraulic pressure. Reference numeral 171 is a hydraulic pump for pilot operation, and 172 is a control valve for pilot operation. The control valve 172 can send the pilot hydraulic pressure to the pipe 174 or the pipe 177 by operating the operation lever 173.

When the operating lever 173 of the control valve 172 is operated to discharge the hydraulic oil from the hydraulic pump 171 to the pipe 174, the discharged hydraulic oil is supplied to the operating valves 131 and 141 via the pipes 175 and 176. As a result, the operation valve 131 is operated in the A position direction and the operation valve 141 is operated in the B position direction. At this time, the hydraulic oil from the hydraulic pump 121 reaches the pipe 134 via the pipes 122 and 132 and the check valve 133, while the hydraulic oil from the hydraulic pump 125 reaches the pipe 143 via the pipes 126 and 142. They are merged and introduced through a pipe 144 to the side of the cylinder 105 where the rod 105a is extended (hereinafter referred to as the bottom side). The two hydraulic pumps 121 and 125 are used to operate the cylinder 105, because when the rod 105a is extended, that is, when the boom is raised, it is desired to move the cylinder 105 earlier than other cylinders for the convenience of work. When the rod 105a of the cylinder 105 extends in this way, the hydraulic oil on the rod 105a side (hereinafter referred to as the head side) flows back to the tank 128 via the pipes 172 and 151, the operation valve 141, and the pipe 171.

Reference numerals 135 and 145 are relief valves, which are valves for automatically escaping to the tanks 137 and 147 if the hydraulic pressure pushing the bottom side of the cylinder 105 becomes higher than the set pressure. Further, 136 and 146 are check valves, which are valves for sucking hydraulic oil from the tanks 137 and 147 to prevent negative pressure if the pressure on the bottom side of the cylinder 105 becomes negative.

Next, when the operating lever 173 of the control valve 172 is operated to discharge the hydraulic oil from the hydraulic pump 171 to the pipe 177, the discharged hydraulic oil causes the operating valves 131 and 141 to move in the opposite direction to the above. As a result, the operation valve 131 takes the B position and the operation valve 141 takes the A position. At this time, since the operation valve 131 does not have a pipe for discharging the hydraulic oil from the hydraulic pump 121, it simply returns to the tank 124 via the pipe 123. However, the hydraulic oil from the hydraulic pump 125 is introduced to the side (head side) where the rod 105a of the cylinder 105 is contracted via the pipes 126, 151 and 152. At this time, the hydraulic oil on the bottom side of the cylinder 105 does not flow to the pipe 134 because the check valve 133 is provided on the pipe 134 side, and the entire amount passes through the pipes 144 to 143 and 142, the operation valve 141 and the pipe 127, and the tank 128. Reflux to. The operation of the relief valve 153 and the check valve is the same as described above.

When the bucket 109 is to be excavated in the direction shown by the arrow Q in the form as shown in FIG. 3, some force must be applied also in the direction shown by the arrow P. For that purpose, it is necessary to apply pressure to the direction in which the rod 105a of the cylinder 105 is contracted, that is, to the head side. However, the set pressure of the relief valve 153 is usually set to be slightly lower than the set pressure of the relief valves 135 and 145 due to the adjustment of the operation of the cylinders 107 and 108. For example, when the set pressure of the relief valves 135 and 145 is 300 kg / cm 2, the set pressure of the relief valve 153 is 240 kg / cm 2.

[0008]

[Problems to be solved by the device]

 However, depending on the work, the force of arrow P may be increased to perform root cutting, mass cutting, twist turning, etc., but as described above, it was set slightly lower than the set pressure of the relief valves 135, 145. In the pressure circuit, there has been a problem that the operations such as root cutting, mass cutting, and twist turning cannot be sufficiently performed. That is, there was a problem that excavation while relieving the pressure on the head side of the cylinder 105 and the operations such as the root cutting and the mass cutting are contradictory actions. The present invention is intended to solve this problem.

[0009]

[Means for solving problems]

 The pressure relief valve for the head side has a low pressure and a high pressure so that the pressure on the head side of the cylinder can be operated both in a low state and in a high state. It is designed to be adjustable in steps.

[0010]

【Example】

 FIG. 1 is an explanatory view of one embodiment of the present invention. In addition, about the code | symbol in a figure, the same code | symbol is used about what is functionally the same as the conventional technology. In FIG. 1, 53 is a relief valve that can change the relief pressure in two stages. The relief valve 53 has a relief pressure acting only by the spring action and a function of increasing the relief pressure higher than that when only the spring action is exerted by pressurizing the pilot pressure to the high-pressure device 56. Reference numeral 1 is a switching valve for selecting which of the above two-stage relief pressures is selected. The switching valve 1 has two positions A and B, and switching is electrically performed by a solenoid 2. Reference numeral 4 is a switch for activating the solenoid 2, 5 is a power source, 3 and 6 are electric wirings. It should be noted that the switching of the switching valve 1 does not necessarily need to be performed electrically, and may be performed manually although not shown. As a hydraulic pressure source for sending the pilot hydraulic pressure to the high-pressure device 56, a part thereof is taken out from a pipe 178 for sending hydraulic oil from the hydraulic pump 171 to the control valve 172, and is led to the switching valve 1 by the pipe 11. Now, when the position of the switching valve 1 is at B as shown in the figure, the pilot pressure is not applied to the high-pressure device, so that the relief valve 53 relieves with the relief pressure only by the spring action. When the position of the switching valve 1 is switched to the position A, the hydraulic oil guided by the pipe 11 is guided to the pipe 12 and the high-pressure device 56 is operated so that the relief valve 53 has a higher hydraulic pressure than when only the spring action is performed. Will be relief. In this state, if the switching valve 1 is switched to the position B again, the pilot pressure guided by the pipe 12 acting on the high-pressure device 56 is returned to the tank 13 and thus the relief valve 53. The relief pressure returns to the relief pressure only by the spring action.

As described above, the relief pressure of the relief valve 53 can be switched to two stages because the pressure applied to the side that contracts the rod 105a of the cylinder 105, that is, the head side is switched to two stages. Therefore, it is possible to perform both the normal excavation work and the work of pressing the bucket 109 in FIG. 3 more strongly than usual.

FIG. 2 shows another embodiment, which is an application example of FIG. FIG. 2 is a circuit diagram of a structure in which hydraulic oil from both the pump 121 and the pump 125 is sent to the pipe 83 on the head side of the cylinder 105. That is, when the pilot hydraulic oil from the control valve 172 is guided to the pipe 177 and the operation valve 31 is in the B position and the operation valve 141 is in the A position, the hydraulic oil from the pump 121 passes through the pipes 91 and 92, The hydraulic oil from the pump 125, which has come through the pipes 151 and 82, joins and is guided to the head side of the cylinder 105 by the pipe 83. 93 is a relief valve whose relief pressure is set to be the same as that of the relief valves 135 and 145. 94 is a check valve and 95 is a tank. Also in this case, the relief valve 53 operates in the same manner as the relief valves 135, 145, 93 by applying a pilot pressure to the high-pressure increasing device 56, as described above with reference to FIG. A high relief pressure is obtained, so that the force of the bucket 109 in the direction of arrow P can be switched between two steps, as in the case of FIG.

[0013]

[Effect of device]

 Since the present invention is configured as described above, the hydraulic cylinder enables two types of operation by using a relief valve in which the relief pressure can be switched in two stages as compared with the conventional technique, and thus, the construction of a construction machine. Two types of work have been made possible: normal excavation work and work that specifically requires the bucket to be pressed down strongly. This means that the working capacity of construction machinery can be greatly expanded, so its practical value is extremely high.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention.

FIG. 2 is an explanatory view of another embodiment of the present invention.

FIG. 3 is a side view of a schematic view of a construction machine according to the present invention.

FIG. 4 is a hydraulic circuit diagram of a conventional technique.

[Explanation of symbols]

 31 Operation Valve 53 Relief Valve 56 High Pressure Device 82 Piping 83 Piping 91 Piping 92 Piping 93 Relief Valve 104 Boom 105 Cylinder 106 Arm 107 Cylinder 108 Cylinder 109 Bucket 121 Hydraulic Pump 122 Piping 125 Hydraulic Pump 126 Piping 131 Operation Valve 132 Piping 134 Piping 135 Relief valve 141 Operation valve 142 Piping 143 Piping 144 Piping 145 Relief valve 151 Piping 152 Piping 171 Hydraulic pump

Claims (2)

[Scope of utility model registration request] 1. A construction machine having a boom, an arm, and a bucket, each of which is operated by using a cylinder, has a hydraulic circuit of a cylinder for operating the boom, which has two systems of hydraulic pumps, operating valves, and the like. In the hydraulic circuit for operation of the cylinder, which uses only one of the two systems for the oil supply pipe for extending, the two oil systems are joined together for oil supply, and the oil supply pipe for contracting the cylinder uses only one system of the two systems. A two-stage relief valve circuit that uses a relief valve that can be switched to a two-stage relief pressure by operating pilot hydraulic pressure as a relief valve provided in the middle of the pipe that contracts the cylinder. 2. A hydraulic circuit of a cylinder for operating a boom of a construction machine having a boom, an arm, and a bucket, each of which uses a cylinder, has two systems of hydraulic pumps, operating valves, relief valves, and the like. The oil supply pipe for extending the cylinder and the oil supply pipe for contracting the cylinder are provided in the middle of the pipe for contracting the cylinder in the hydraulic circuit for operation of the cylinder, which is used by merging two systems. Either one of the relief valves can be operated by operating pilot pressure.
Uses a relief valve that can switch to a two-stage relief pressure 2
Stage relief valve circuit.