KR20190030160A - Hydraulic circuit - Google Patents

Abstract

Provided is a hydraulic circuit, which can perform an action (a descending action in particular) of a supporting member including a boom at a high energy efficiency. The hydraulic circuit (10) is provided with a selector valve (40) communicating with a head side chamber (84), and switching a flow path (11) corresponding to pressure of a working oil from the head side chamber (84); and a connecting route (23) communicating the head side chamber (84) and a rod side chamber (83). When the pressure of the working oil from the head side chamber (84) is above a switching pressure, the selector valve (40) blocks the communication between a hydraulic pressure source (12) and the rod side chamber (83).

Description

Hydraulic circuit {HYDRAULIC CIRCUIT}

The present invention relates to a hydraulic circuit connected to a hydraulic cylinder.

The boom of the hydraulic excavator is driven up and down in the substantially vertical direction under the influence of gravity. Various types of hydraulic circuits have been proposed as hydraulic circuits to be connected to the hydraulic cylinders for boom driving in consideration of the driving characteristics of such booms.

For example, the energy saving device of the construction machine disclosed in Patent Document 1 is provided with a control valve (direction switching valve) for controlling the supply of pressure to the boom cylinder and a negative control orifice provided in the flow path to the tank , And a sensor is provided on the upstream side of the negative control orifice. In this energy saving device, based on the negative control pressure detected by the sensor, the number of revolutions of the engine that drives the hydraulic pump is controlled, thereby saving energy.

In the descent regeneration circuit of the boom of the hydraulic excavator described in Patent Document 2, the orifice is provided in the tank return flow path on the boom bottom side at the boom descent position of the direction control valve, and the orifice is provided in the supply flow path to the boom rod side Is installed. Further, a regeneration flow path for communicating the tank return flow path and the supply flow path is provided, and a check valve is interposed in the regeneration flow path. According to this regeneration circuit, the return oil from the boom bottom side can be returned to the boom rod side through the regeneration flow path by increasing the pressure by the orifice during the boom lowering operation, so that the oil supplied from the hydraulic pump can be reduced .

In the hydraulic circuit disclosed in Patent Document 3, when the boom is lowered in a state in which a force against the downward force of the boom is not applied, the first center bypass passage is opened by the first switching valve, While the discharge amount is reduced, the discharge oil from the elongation side oil chamber is supplied to the cylinder reduction side oil chamber via the regeneration circuit. On the other hand, when a force against the fall of the boom is applied, the first center bypass passage is closed by the first switching valve, and the pump discharge amount is increased.

Japanese Patent Laid-Open No. 2007-333017 Japanese Patent Application Laid-Open No. 10-089317 Japanese Patent Application Laid-Open No. 11-247236

In the above-described conventional hydraulic circuit, when the boom is lowered, the supply amount of the hydraulic oil supplied from the hydraulic pressure source (hydraulic pump) is designed to be reduced. However, further improvement is required for simplification of construction, There is room for.

For example, in an apparatus for controlling the output of the hydraulic oil of the hydraulic pump based on the detection result of the sensor as in the energy saving device of Patent Document 1, the installation of the sensor is essential, so that the apparatus configuration is complicated and the cost is increased. In the regeneration circuit of Patent Document 2, even when the boom can be lowered by using its own weight, for example, when the boom is lowered in a state where the bucket is in the air, the boom cylinder (particularly, the boom rod side) Oil is supplied. Supplying the hydraulic fluid from the hydraulic pump to the boom cylinder, which is not originally required in this way, results in loss of energy, so that optimum energy saving is not necessarily achieved. Also in the hydraulic circuit of Patent Document 3, when the boom is lowered in a state in which the force against the fall of the boom is not applied, the oil pressure from the hydraulic pump is supplied to the boom cylinder, resulting in loss of energy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic circuit capable of performing an operation (particularly a lowering operation) of a support member such as a boom with high energy efficiency.

One aspect of the present invention is a hydraulic circuit connected to a hydraulic cylinder having a hydraulic source for supplying hydraulic oil to a hydraulic passage, a piston rod for supporting a support member to be driven in a vertical direction, a head side chamber and a rod side chamber, A selector valve communicating with the chamber and switching the flow path in accordance with the pressure of the working oil from the head side chamber and a connecting path communicating between the head side chamber and the rod side chamber, And the communication between the hydraulic pressure source and the rod-side chamber is blocked when the switching pressure is equal to or higher than the switching pressure.

The selector valve may communicate the hydraulic pressure source and the rod-side chamber when the pressure of the hydraulic oil from the head-side chamber is lower than the switching pressure.

The connecting passage may communicate the head side chamber to the tank passage, the rod side chamber may communicate with the tank passage, and may communicate with the head side chamber through the tank passage and the connecting passage.

The selector valve may communicate the oil pressure source with the bypass passage when the pressure of the operating oil from the head side chamber is equal to or higher than the switching pressure.

The hydraulic pressure source may be a negative control type hydraulic pump that changes the supply amount of the hydraulic fluid according to the pressure of the hydraulic fluid in the bypass passage.

The hydraulic circuit further includes a direction switching valve for switching the flow path between the hydraulic pressure source and the hydraulic cylinder, and the selector valve may be provided inside the direction switching valve.

The supporting member may be a boom.

According to the present invention, the operation (particularly the lowering operation) of the support member such as the boom can be performed with high energy efficiency.

Fig. 1 is a circuit diagram showing an example of a circuit configuration of a hydraulic circuit. Fig. 1 shows a state in which the boom directional control valve is disposed at the neutral position and the arm directional control valve is disposed at the neutral position.
Fig. 2 is a circuit diagram showing an example of a circuit configuration of a hydraulic circuit. Fig. 2 shows a state in which the boom directional control valve is disposed at the reverse drive position and the arm directional control valve is disposed at the neutral position. Fig.
Fig. 3 is a circuit diagram showing an example of the circuit configuration of the hydraulic circuit. Fig. 3 shows a state in which the boom directional control valve is disposed at the reverse drive position and the arm directional control valve is disposed at the reverse drive position.
Fig. 4 is a circuit diagram showing an example of the circuit configuration of the hydraulic circuit. Fig. 4 shows a state in which the boom directional control valve is disposed at the reverse drive position and the arm directional control valve is disposed at the neutral position. Fig.
5 is a partial cross-sectional view showing an example of a directional switch valve and a selector valve for a boom and shows a state in which the boom is in the grounded state and the directional switch valve for the boom is disposed in the neutral position.
6 is a partial cross-sectional view showing an example of a directional switch valve and a selector valve for a boom and shows a state in which the boom is in the air state and the boom directional control valve is disposed in the reverse drive position.
7 is a partial cross-sectional view showing an example of a directional switch valve and a selector valve for a boom and shows a state in which the boom is in the grounded state and the directional switch valve for boom is disposed in the reverse drive position.
8 is a partial cross-sectional view showing an example of a directional switch valve and a selector valve for a boom and shows a state in which a boom directional control valve is disposed at a forward drive position.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. Elements shown in the drawings may include elements whose size and scale are different from the actual ones in order to facilitate understanding.

Hereinafter, a case where the present invention is applied to a hydraulic circuit for driving control of a hydraulic excavator (particularly, a boom) will be described. However, the present invention can be effectively applied to a hydraulic circuit for driving control of a hydraulic cylinder having a piston rod that supports a support member driven in a vertical direction other than a boom. The present invention is not limited to the hydraulic circuit.

1 to 4 are circuit diagrams showing an example of the circuit configuration of a hydraulic circuit 10 according to an embodiment of the present invention. Fig. 1 shows a state in which the boom directional control valve 30 is disposed at the neutral position b and the arm directional control valve 31 is disposed at the neutral position b. 2 and 4 show a state in which the boom direction switching valve 30 is disposed at the reverse driving position c and the arm direction switching valve 31 is disposed at the neutral position b, (Hereinafter also referred to as " air condition ") with the bucket 73 and the arm 72, and Fig. 4 shows a case in which the boom 71 is in the state of being separated from the ground (Hereinafter also referred to as " grounded state ") through contact with the ground surface through the insulating film 72. 3 shows a state in which the boom direction switching valve 30 is disposed at the reverse drive position c and the arm direction switching valve 31 is disposed at the reverse drive position c.

1 to 4 show the flow path configuration as a circuit diagram and the hydraulic excavator 70 (particularly, the boom 71, the arm 72 and the bucket 73) are shown as external views. Therefore, although Figs. 1 to 4 show both the circuit diagram and the external view of the arm hydraulic cylinder 75, they refer to the same hydraulic cylinder 75 for arm.

The hydraulic circuit 10 shown in Figs. 1 to 4 is connected to a hydraulic pressure source 12, a hydraulic cylinder 74 for a boom and a hydraulic cylinder 75 for an arm. The hydraulic circuit 12 and the boom hydraulic cylinder 74 A boom directional control valve 30 for switching the flow path 11 between the oil pressure source 12 and the arm hydraulic cylinder 75 and an arm direction switching valve 31 for switching the flow path 11 between the oil pressure source 12 and the arm hydraulic cylinder 75 . In this specification, the term " flow path 11 " is a generic name of a passage through which working fluid flows, and includes, for example, branch paths 11b and 11c, tank path 21, bypass path 22, 23, the negative control flow path 24 and the directional control valves 30, 31 constitute the flow path 11 as well.

The boom direction switching valve 30 and the arm direction switching valve 31 are constituted by spool valves. The directional control valves 30 and 31 shown in Figs. 1 to 4 switch the oil passage 11 according to the pilot oil pressure applied to the spool, but may be constituted by other valve bodies (electromagnetic drive type spool valves or the like) . In addition, the bucket direction changeover valve is provided between the hydraulic source 12 and the hydraulic cylinder 76 for the bucket. However, in order to simplify the entire structure and facilitate understanding, the bucket direction changeover valve is omitted in Figs. And the detailed description of the drive control of the bucket directional control valve and the bucket hydraulic cylinder 76 will be omitted. However, the connection mode of the bucket directional control valve and the hydraulic cylinder 76 for the bucket with respect to the oil passage 11 and the supply mode of the hydraulic oil may be the same as those of the oil directional directional control valve 31 and the oil hydraulic cylinder 75.

The hydraulic pressure source 12 is constituted by a variable displacement hydraulic pump that supplies hydraulic oil to the hydraulic oil passage 11 and can increase or decrease the supply amount of hydraulic oil to the hydraulic oil passage 11 under the control of the regulator 13. The hydraulic source 12 of the present embodiment is configured so that the pressure of the operating oil of the negative control flow passage 24 connected to the bypass passage 22 (particularly, the second bypass passage 22b) communicated with the tank 14 And the pressure of the working oil of the second bypass flow path 22b) of the working fluid. The flow rate of the hydraulic fluid flowing through the second bypass passage 22b increases and the pressure of the operating oil of the second bypass passage 22b and the negative control passage 24 increases, 12 to be supplied with the hydraulic oil. On the other hand, since the flow rate of the hydraulic fluid flowing through the second bypass passage 22b is reduced and the pressure of the hydraulic fluid in the bypass passage 22 and the negative control passage 24 is reduced, the regulator 13 is moved from the hydraulic pressure source 12 Thereby increasing the supply amount of the operating oil.

The oil passage 11 extending from the oil pressure source 12 includes a passage 11a extending from the boom directional control valve 30 (hereinafter also referred to as a "main passage") and a passage 11b branched from the main passage 11a The main flow path 11a and the branch flow paths 11b and 11c are connected in parallel to the oil pressure source 12. The main flow path 11a and the branch flow paths 11b and 11c are connected to each other. The one branch flow passage 11b is intended to communicate with the bypass passage 22 (particularly the first bypass passage 22a) through the boom directional control valve 30 and the operation of the boom directional control valve 30 The communication between the branch passage 11b and the bypass passage 22 is controlled according to the state. The other branching flow path 11c is intended to be connected to the hydraulic cylinder 75 for the female through the female direction switching valve 31 and is connected to the branching flow path 11c in accordance with the operating state of the female direction switching valve 31, And the oil hydraulic cylinder 75 are controlled.

The boom hydraulic cylinder 74 has a piston rod 81 and a cylinder tube 82. The piston rod 81 includes a piston portion 81a disposed in the cylinder tube 82 and a rod portion 81b integrally provided with the piston portion 81a and extending outwardly from the inside of the cylinder tube 82 ). A boom 71 is rotatably connected to one end of the rod portion 81b, and the piston rod 81 supports the boom 71 from below in the vertical direction. The boom 71 is driven to ascend by increasing the amount of projection of the piston rod 81 from the cylinder tube 82 and by reducing the amount of projection of the piston rod 81 from the cylinder tube 82, Down. The internal space of the cylinder tube 82 is partitioned into a rod-side chamber 83 and a head-side chamber 84 via a piston portion 81a. The piston portion 81a is a portion of the rod-side chamber 83 and the head-side chamber 84 so as not to leak the working oil between the rod-side chamber 83 and the head- And is movably provided in the cylinder tube 82 while sealing each of them.

The hydraulic cylinder 75 for the arm is basically constructed in the same manner as the hydraulic cylinder 74 for the boom described above and includes a piston rod 75a movably provided and a rod side chamber 75b and a head side chamber 75c, . Although not shown schematically as a circuit diagram, the bucket hydraulic cylinder 76 basically includes a piston rod configured in the same manner as the above-described hydraulic cylinder 74 for boom and the hydraulic cylinder 75 for arm, Side chamber and a head-side chamber.

The connecting path 23 is provided in the hydraulic circuit 10 (particularly, the directional switch valve 30 for the boom) of the present embodiment. In the state where the boom directional switch valve 30 is disposed at the reverse drive position c, The chamber 84 and the rod-side chamber 83 communicate with each other through the connecting passage 23. That is, the head-side chamber 84 communicates with the tank passage 21 connected to the tank 14 through the connecting passage 23 formed in the directional valve 30 for the boom. On the other hand, the rod-side chamber 83 communicates with the tank passage 21 without passing through the boom directional control valve 30. The rod side chamber 83 and the head side chamber 84 are communicated with each other or blocked from each other through the tank passage 21 and the connecting passage 23 depending on the driving state of the directional valve 30 for the boom.

A line relief makeup valve 43 is provided in the flow path 11 between the tank passage 21 and the rod side chamber 83. The line relief makeup valve 43 is provided with a check valve 41 and a pressure control valve 45 which are provided in parallel to the flow path 11 on the tank passage 21 side and the flow path 11 on the rod side chamber 83 side, ). The check valve 41 of the line relief make-up valve 43 allows the flow of the operating oil from the tank passage 21 side toward the rod chamber 83 side, but flows from the rod side chamber 83 side to the tank passage 21 ) Of the operating fluid. The pressure control valve 45 of the line relief make-up valve 43 is configured such that the pressure of the working fluid in the flow path 11 on the rod side chamber 83 side is larger than the predetermined valve opening pressure, When the pressure of the working oil in the flow path 11 on the rod side chamber 83 side is equal to or lower than the predetermined valve opening pressure, the rod side chamber 83 (83) communicates with the flow path 11 on the side of the tank passage 21 And the flow passage 11 on the tank passage 21 side.

The check valve 41 of the line relief makeup valve 43 is connected to the oil passage 11 on the side of the rod side chamber 83 in the case where the pressure of the hydraulic oil in the oil passage 11 on the tank passage 21 side is larger than the hydraulic oil pressure on the oil passage 11 on the rod side chamber 83 side The hydraulic oil flows from the oil passage 11 on the tank passage 21 side to the oil passage 11 on the rod side chamber 83 side. On the other hand, the pressure of the hydraulic oil in the oil passage 11 on the rod-side chamber 83 side is larger than the hydraulic oil pressure on the oil passage 11 on the tank passage 21 side and the pressure control valve 45 The flow of the hydraulic fluid between the flow path 11 on the rod side chamber 83 side and the flow path 11 on the tank path side 21 side is controlled by the line relief makeup valve 43 . The pressure of the hydraulic oil in the oil passage 11 on the rod side chamber 83 side is larger than the hydraulic oil pressure on the oil passage 11 on the tank passage 21 side and the pressure control valve 45 of the line relief make- The pressure control valve 45 is opened so that the hydraulic oil flows into the oil passage 11 on the tank passage 21 side from the oil passage 11 on the rod side chamber 83 side.

The line relief makeup valve 43 has a function of supplying the hydraulic oil from the oil passage 11 on the tank passage 21 side to the oil passage 11 on the rod side chamber 83 side while preventing the reverse flow, Side chamber 83 to the oil passage 11 on the side of the tank passage 21 when the pressure of the hydraulic fluid in the oil passage 11 on the side of the rod-side chamber 83 is excessive, And has a function of preventing the pressure of the operating fluid of the chamber 83 from becoming excessive. The valve opening pressure of the pressure control valve 45 of the line relief makeup valve 43 is set to the upper limit of the permissible pressure of the working oil in the flow path 11 on the rod side chamber 83 side and the rod side chamber 83 side .

As described above, the rod-side chamber 83 communicates with the tank passage 21 by opening the line relief make-up valve 43. On the other hand, when the boom directional control valve 30 is disposed at the reverse drive position c, the connection passage 23 communicates the head-side chamber 84 with the tank passage 21. The head side chamber 84 and the rod side chamber 83 are connected to each other via the connecting passage 23 and the tank passage 21 when the directional switching valve 30 for boom is disposed at the reverse drive position c. (11) and the line relief makeup valve (43). The line relief make-up valve 43 is provided so that the pressure difference between the pressure of the working oil discharged from the head side chamber 84 to the tank passage 21 through the connecting passage 23 and the pressure of the working oil in the rod- The flow of the hydraulic fluid between the tank passage 21 (and hence the head-side chamber 84) and the rod-side chamber 83 is appropriately adjusted depending on the magnitude of the pressure and the magnitude of the pressure of the hydraulic fluid in the rod- .

The hydraulic circuit (10) also has a selector valve (40). In the hydraulic circuit 10 shown in Figs. 1 to 4, a selector valve 40 is provided inside the boom directional control valve 30. As shown in Fig. The selector valve 40 communicates with the head side chamber 84 via the flow path 11 (particularly, the connecting passage 23) while the boom directional control valve 30 is disposed at the reverse drive position c, (The pressure of the operating oil in the connecting passage 23 in Figs. 1 to 4) from the side chamber 84. [0070] When the pressure of the hydraulic oil supplied to the selector valve 40 from the head side chamber 84 (that is, the pressure of the hydraulic oil in the connecting passage 23) is equal to or higher than the predetermined switching pressure, (See "e" in FIG. 2) between the rod-side chamber 12 and the rod-side chamber 83. On the other hand, when the pressure of the hydraulic oil supplied from the head side chamber 84 to the selector valve 40 (that is, the pressure of the hydraulic oil in the connecting passage 23) is lower than the switching pressure, ) And the rod-side chamber 83 (see the symbol " f " in Fig. 4).

2), the selector valve 40 opens the hydraulic pressure source 12 to the bypass passage 22 (specifically, the selector valve 40 is closed) when the pressure of the operating oil from the head side chamber 84 is equal to or higher than the switching pressure And the communication between the oil pressure source 12 and the bypass passage 22 is blocked when the pressure of the working oil from the head side chamber 84 is lower than the switching pressure 4 " f "). The bypass passage (22) is a flow passage (11) communicating with the tank (14). The tank 14 connected to the bypass passage 22 and the tank 14 connected to the aforementioned tank passage 21 are constituted by the same tank. The bypass passage 22 shown in Figs. 1 to 4 is provided with a direction switch valve 31 for the arm. The bypass passage 22 is connected to the first bypass And is divided into a passage 22a and a second bypass passage 22b on the downstream side of the arm direction switching valve 31. [ Both end portions of the first bypass passage 22a are controlled to be opened and closed by the boom direction changeover valve 30 and the arm direction changeover valve 31, respectively. One end of the second bypass passage 22b is connected to the arm direction switching valve 31 and the other end of the second bypass passage 22b is connected to the tank 14. [ One end of the second bypass passage 22b is controlled to be opened and closed by the direction selector valve 31 for the direction of the arm.

The check valve 41, the orifice 42, the pressure control valve 45, and other mechanisms are also suitably installed in the hydraulic circuit 10 shown in Figs. For example, a check valve 41 is provided in the main flow path 11a and the branch flow path 11c. An orifice 42 is provided in the connection passage 23 and the orifice 42 is located on the downstream side of the connecting passage 23 connected to the selector valve 40 (that is, on the side of the tank 14) Respectively. Therefore, the switching of the flow path 11 (see the symbols "e" and "f" shown in FIGS. 1 to 4) by the selector valve 40 is performed by the orifice 42 provided in the connection path 23 Is performed in accordance with the pressure of the operating oil in the connecting passage 23 which is increased. A discharge control valve 44 having an orifice 42 and a pressure control valve 45 is provided in the second bypass passage 22b. The orifice 42 of the discharge control valve 44 is provided downstream of the portion of the second bypass passage 22b connected to the negative control flow passage 24 (that is, on the side of the tank 14). The control of the oil pressure source 12 by the regulator 13 is performed in accordance with the pressure of the operating oil of the negative control flow path 24 whose pressure is increased by the orifice 42 provided in the second bypass flow path 22b. The pressure control valve 45 of the discharge control valve 44 is opened and closed in accordance with the pressure of the operating oil of the second bypass passage 22b and the pressure of the operating oil of the second bypass passage 22b is lower than a predetermined valve opening pressure Thereby increasing the flow rate of the operating oil toward the tank 14. [

Next, the operation of the hydraulic circuit 10 will be described.

First, as shown in Fig. 1, a case in which both the boom directional control valve 30 and the arm directional control valve 31 are disposed at the neutral position b will be described. In this case, the communication between the oil pressure source 12 and the boom hydraulic cylinder 74 is blocked by the boom directional control valve 30, and the communication between the oil pressure source 12 and the oil hydraulic cylinder 75 is switched And is shut off by the valve 31. That is, the boom directional control valve 30 interrupts the communication between the head side chamber 84 and the tank passage 21, and between the rod side chamber 83 and the oil pressure source 12 (particularly, the main passage 11a) And the branch passage 11b and the first bypass passage 22a are communicated with each other. The direction selector valve 31 for the arm blocks the communication between the rod side chamber 75b of the arm hydraulic cylinder 75 and the tank passage 21 and the communication between the head side chamber 75c of the arm hydraulic cylinder 75 and the branch The communication between the first bypass passage 22a and the second bypass passage 22b is interrupted.

In this case, the oil pressure source 12 is connected to the first bypass passage 22a through the branch passage 11b, and the first bypass passage 22a is connected to the second bypass And is connected to the flow path 22b. The oil pressure source 12 is communicated with the tank 14 and the negative control flow path 24 through the branch passage 11b and the bypass passage 22. [ The amount of the hydraulic fluid flowing through the bypass passage 22 is increased to increase the pressure of the hydraulic oil in the negative control passage 24 . Therefore, the oil pressure source 12 suppresses the supply amount of the operating oil under the control of the regulator 13. As a result, the amount of the hydraulic fluid flowing through the bypass passage 22 is reduced, and the pressure of the hydraulic oil in the negative control passage 24 is lowered, thereby saving energy.

2, the boom directional control valve 30 is disposed at the reverse drive position c, the arm directional control valve 31 is disposed at the neutral position b, and the boom 71 is positioned at the bucket 73, And the arm 72 are in a public state. In this case, the head side chamber 84 communicates with the connecting passage 23 and communicates with the tank passage 21 through the connecting passage 23. The piston rod 81 is lowered due to the weight of the boom 71 or the like under the influence of gravity and the pressure of the hydraulic fluid in the head side chamber 84 is increased so that the connection path 23 communicating with the head side chamber 84, The pressure of the operating oil of the selector valve 40 becomes equal to or higher than the switching pressure of the selector valve 40. Therefore, the selector valve 40 takes the state indicated by the symbol "e" in FIGS. 1 to 4 and interrupts the communication between the hydraulic oil source 12 (particularly, the main passage 11a) and the rod-side chamber 83 , And the oil pressure source 12 is communicated with the first bypass passage 22a through the branch passage 11b. On the other hand, the direction selector valve 31 for the arm interrupts the communication between the rod-side chamber 75b and the tank passage 21 of the hydraulic cylinder 75 for the arm and the head-side chamber 75c of the hydraulic cylinder 75 for arm The communication between the branch passages 11c is cut off and the first bypass passage 22a and the second bypass passage 22b are communicated with each other.

In this case, the high-pressure hydraulic fluid discharged from the head side chamber 84 flows toward the tank 14 through the connecting passage 23 and the tank passage 21, and flows through the connecting passage 23, the tank passage 21, And is supplied (that is, regenerated) to the hydraulic cylinder 74 for the boom via the line relief makeup valve 43 (particularly the check valve 41). As a result, the amount of working oil and the insufficient pressure in the rod-side chamber 83 whose volume increases with the descent of the piston portion 81a are supplemented, and the boom 71 can be lowered using its own weight . On the other hand, the hydraulic oil discharged from the hydraulic pressure source 12 is sent toward the tank 14 via the bypass passage 22, and the supply amount of the hydraulic oil from the negative control hydraulic oil source 12 is suppressed to be low, .

Next, as shown in Fig. 3, the boom direction changeover valve 30 is disposed at the reverse drive position c and the arm direction changeover valve 31 is also disposed at the reverse drive position c, And the arm 72 are in a public state will be described. 2, the head-side chamber 84 communicates with the tank passage 21 via the connecting passage 23, and the pressure of the hydraulic fluid in the connecting passage 23 is transmitted to the selector valve (not shown) 40, and the selector valve 40 assumes the state indicated by the symbol " e " in Figs. The directional switching valve 30 for the boom cuts off the communication between the rod-side chamber 83 and the hydraulic oil source 12 (in particular, the main passage 11a), and the hydraulic source 12 through the branch passage 11b And communicates with the bypass passage (22). On the other hand, the direction selector valve 31 communicates the rod-side chamber 75b with the tank passage 21, communicates the head-side chamber 75c with the oil pressure source 12 (particularly, the branch passage 11c) The communication between the first bypass passage 22a and the second bypass passage 22b is blocked.

In this case, the high-pressure hydraulic fluid discharged from the head-side chamber 84 passes through the connecting passage 23, the tank passage 21, and the line-relief makeup valve 43 in the same manner as in the case shown in Fig. Is supplied to the cylinder 74, and the boom 71 descends using its own weight. On the other hand, a part of the hydraulic fluid discharged from the hydraulic pressure source 12 is supplied to the head side chamber 75c through the branch passage 11c. The working oil discharged from the rod-side chamber 75b is sent to the tank passage 21 and then is discharged to the tank 14 or supplied to the rod-side chamber 83 via the line relief make-up valve 43 . The boom 71 and the like are used for driving the boom hydraulic cylinder 74 and the high pressure hydraulic fluid discharged from the head side chamber 84 and the rod side chamber 75b is used to drive the hydraulic pressure source 12 May not be used for driving the hydraulic cylinder 75 for the arm. Accordingly, the operating fluid newly supplied from the oil pressure source 12 can be efficiently used for driving the oil hydraulic cylinder 75, thereby saving energy. The amount of the hydraulic fluid flowing through the second bypass passage 22b is reduced and the pressure of the hydraulic fluid in the negative control passage 24 is reduced by the second bypass passage 22b, The negative pressure source 12 of the negative control type increases the supply amount of the operating oil. As a result, a sufficient amount and a sufficient pressure of working fluid can be supplied to the head-side chamber 75c through the branch passage 11c.

4, the boom directional control valve 30 is disposed at the reverse drive position c, the arm directional control valve 31 is disposed at the neutral position b, and the boom 71 is positioned at the bucket 73, And the arm 72 in the ground state. In this case, the head side chamber 84 communicates with the connecting passage 23 and communicates with the tank passage 21 through the connecting passage 23. However, since the boom 71 is in the grounded state, the weight of the boom 71 or the like can not basically be used in the downward movement of the piston rod 81. [ The pressure of the working oil in the connecting passage 23 communicating with the head side chamber 84 becomes smaller than the switching pressure of the selector valve 40. Therefore, 4, the selector valve 40 communicates the hydraulic pressure source 12 to the rod-side chamber 83 through the main flow channel 11a and the hydraulic pressure source 12 (Particularly, the branch passage 11b) and the bypass passage 22 (particularly, the first bypass passage 22a). On the other hand, the direction selector valve 31 for the arm interrupts the communication between the rod-side chamber 75b and the tank passage 21 of the hydraulic cylinder 75 for the arm and the head-side chamber 75c of the hydraulic cylinder 75 for arm The communication between the branch passages 11c is cut off and the first bypass passage 22a and the second bypass passage 22b are communicated with each other.

4, the hydraulic fluid discharged from the hydraulic pressure source 12 is supplied to the rod-side chamber 83 so that the pressure of the hydraulic fluid in the rod- The pressure of the working oil in the side chamber 84 is larger than the pressure of the working oil in the side chamber 84, and the piston 81a receives the downward force and the boom 71 is lowered. The head side chamber 84 communicates with the tank passage 21 through the connecting passage 23 but since the pressure of the hydraulic fluid discharged from the head side chamber 84 is smaller than the pressure of the hydraulic fluid in the rod side chamber 83, The operating oil is not sent from the side chamber 84 to the rod side chamber 83. The operating fluid discharged from the head side chamber 84 is sent toward the tank 14 through the connecting passage 23 and the tank passage 21. [ The check valve 41 of the line relief make-up valve 43 prevents the back flow of the hydraulic fluid from the rod side chamber 83 toward the tank 14, the tank passage 21 and the head side chamber 84 . Further, the hydraulic pressure source 12 is disconnected from the bypass passage 22 (particularly, the first bypass passage 22a) by the directional valve 30 for the boom. As a result, the amount of the hydraulic fluid flowing through the second bypass passage 22b is reduced, so that the pressure of the hydraulic oil in the negative control hydraulic passage 24 is lowered, and the negative control hydraulic pressure source 12 increases the hydraulic oil supply amount. As a result, a sufficient amount and sufficient pressure of operating fluid can be supplied to the rod-side chamber 83 through the main flow path 11a.

The hydraulic source 12 is connected to the head side chamber 84 of the boom hydraulic cylinder 74 via the main flow path 11a when the directional switching valve 30 for the boom is disposed at the forward drive position a, And the rod side chamber 83 of the boom hydraulic cylinder 74 communicates with the tank passage 21 and the communication between the branch passage 11b and the first bypass passage 22a is cut off. In this case, the hydraulic fluid discharged from the hydraulic pressure source 12 is supplied to the head side chamber 84, the hydraulic fluid discharged from the rod side chamber 83 flows out to the tank passage 21, (81). On the other hand, when the female direction change-over valve 31 is disposed at the forward drive position a, the oil pressure source 12 is communicated with the rod-side chamber 75b of the female hydraulic cylinder 75 through the branch passage 11c, The head side chamber 75c of the first bypass passage 75 communicates with the tank passage 21 and the communication between the first bypass passage 22a and the second bypass passage 22b is cut off. In this case, the hydraulic fluid discharged from the hydraulic pressure source 12 is supplied to the rod-side chamber 75b, the hydraulic fluid discharged from the head-side chamber 75c flows out to the tank passage 21, The arm 72 is pivoted in the upward direction with the point of connection with the boom 71 as a fulcrum. Further, the bypass passage 22 is blocked by the boom directional control valve 30 and / or the arm directional control valve 31, and the negative control type hydraulic pressure source 12 increases the supply amount of the hydraulic oil, The working fluid of sufficient pressure can be supplied to the head side chamber 84 and / or the rod side chamber 75b.

Next, a concrete configuration example of the directional switching valve 30 for the boom and the selector valve 40 will be described.

5 to 8 are partial cross-sectional views showing an example of the directional switch valve 30 and the selector valve 40 for the boom. 5 shows a state in which the boom 71 is in a grounded state and the directional valve 30 for boom is disposed in the neutral position b. 6 shows a state in which the boom 71 is in the air condition and the directional valve 30 for boom is disposed at the reverse drive position c. 7 shows a state in which the boom 71 is in a grounded state and the directional valve 30 for boom is disposed in the reverse drive position c. 8 shows a state in which the boom directional control valve 30 is disposed at the forward drive position a. The boom directional switch valve 30 and the selector valve 40 shown in Figs. 5 to 8 are not necessarily strictly limited to the boom directional switch valve 30 and the selector valve 40 shown in Figs. 1 to 4 But does correspond roughly to the boom directional switch valve 30 and the selector valve 40 shown in Figs. 1 to 4. Fig. Therefore, those skilled in the art can fully understand the structure and function of the boom directional switch valve 30 and the selector valve 40 shown in Figs. 5 to 8 based on the following description.

The boom directional control valve 30 shown in Figs. 5 to 8 includes a spool 50 and a main body portion 51 for slidably holding the spool 50 inwardly. A selector valve (40) is slidably installed in the spool (50). The spool 50 is formed with a plurality of land portions and a plurality of notches (including a hole portion connecting the groove portion in the spool 50 in which the selector valve 40 is accommodated to the outside of the spool 50) The flow path 11 is switched in accordance with the relative slide position of the spool 50 with respect to the portion 51. The selector valve 40 also has a plurality of land portions and a plurality of notches, and the flow path 11 is switched according to the relative slide position of the selector valve 40 with respect to the spool 50.

The main body portion 51 is provided with a tank communicating passage 52 communicating with the tank passage 21, a first actuator passage 53 communicating with the rod chamber 83, a bridge passage communicating with the oil pressure source 12 58, a first upstream-side unloading passage 54 and a second upstream-side unloading passage 56 communicating with the branching passage 11b, a first downstream-side unloading passage 55 communicating with the first bypass passage 22a, A second downstream unloading passage 57, and a second actuator passage 59 communicating with the head side chamber 84 are formed. 5 to 8) communicating with the tank 14 through the second actuator passage 59 and on the side opposite to the bridge passage 58 (on the right side in Figs. 5 to 8) A communication path is also formed.

The spool (50) is further provided with a connecting passage (23). 5 to 8) communicates with one end (the right end in Figs. 5 to 8) of the selector valve 40, and the other end of the connecting passage 23 (Right end portion in Figs. 5 to 8) communicates with a notch portion formed in the spool 50. Fig. A switching spring 60 (elastic body) is provided at the other end of the selector valve 40 (the left end in Figs. 5 to 8). The slide position of the selector valve 40 is determined by the force of the operating oil from the connecting passage 23 acting on one end of the selector valve 40 and the force acting on the other end of the selector valve 40 , And is determined according to the elastic force of the switching spring (60). Therefore, the state in which the hydraulic oil is not supplied to the one end of the selector valve 40 from the connecting passage 23, or the force of the hydraulic oil from the connecting passage 23, which acts on one end of the selector valve 40, The selector valve 40 is pressed by the switching spring 60 and is disposed at the rightward position in Figs. 5 to 8 in a state where the selector valve 40 is smaller than the elastic force of the switching spring 60 applied to the other end of the valve 40. Fig.

For example, when the boom directional control valve 30 is disposed at the neutral position b (see Fig. 1), the boom directional control valve 30 and the selector valve 40 are arranged as shown in Fig. The rod side chamber 83 is disconnected from the bridge passage 58 and the tank communication passage 52 via the land portion of the spool 50 and the second actuator passage 59 is blocked from the bridge passage 58 and the tank communication (Not shown). On the other hand, the first upstream-side unloading passage 54 and the first downstream-side unloading passage 55 communicate with each other through the notch of the spool 50 and the notch of the selector valve 40, The first downstream side unloading passage 56 and the second downstream side unloading passage 57 communicate with each other through cutouts of the spool 50. The hydraulic fluid from the hydraulic pressure source 12 is not supplied to either of the rod side chamber 83 and the head side chamber 84 and flows through the first upstream side unloading passage 54 and the second Side unloading passage 56 and flows out to the first bypass passage 22a through the first downstream-side unloading passage 55 and the second downstream-side unloading passage 57. [

When the directional switch valve 30 for the boom is disposed at the neutral position b, the connection passage 23 communicates with the head-side chamber 84 through the second actuator passage 59. The operating fluid from the head side chamber 84 flows into the connecting passage 23 through the second actuator passage 59 and the selector valve 40 is moved in accordance with the pressure of the operating oil of the connecting passage 23 All. 5 shows a state in which the boom 71 is in the grounded state and the pressure of the hydraulic fluid flowing into the connecting passage 23 from the head side chamber 84 is low and the selector valve 40 is pressed by the switching spring 60, As shown in Fig. However, when the boom 71 is in the air condition and the pressure of the operating oil flowing into the connecting passage 23 from the head side chamber 84 is high, the selector valve 40 is connected to the operating oil from the connecting passage 23 And is disposed in the left direction. The rod side chamber 83 is also blocked from the bridge passage 58 and the tank communication passage 52 and the second actuator passage 59 is blocked from the bridge passage 58 and the tank communication passage The first upstream side unloading passage 54 and the first downstream side unloading passage 55 communicate with each other through the cutout portion of the spool 50 and the cutout portion of the selector valve 40 and the second upstream side unloading passage 56 and the second downstream-side unloading passage 57 are communicated with each other through the notch of the spool 50.

On the other hand, when the boom 71 is in the air condition and the boom directional control valve 30 is disposed at the reverse drive position c (see Figs. 2 and 3), the boom directional control valve 30 and the spool 50 Are arranged as shown in Fig. That is, the spool 50 is disposed on the right side of the position shown in Fig. 5 by the pilot pressure. The operating fluid from the head side chamber 84 flows into the connecting passage 23 through the second actuator passage 59 and presses the selector valve 40 to compress the switching spring 60, In the leftward direction in Fig. As a result, the first actuator passage 53 is blocked from the bridge passage 58 through the land portion of the spool 50. The second actuator passage 59 is blocked from the bridge passage 58 through the land portion of the spool 50 and is connected to the tank communication passage (not shown) through the cutout portion of the spool 50 and the connecting passage 23 . On the other hand, the first upstream-side unloading passage 54 and the first downstream-side unloading passage 55 communicate with each other through the notch of the spool 50 and the notch of the selector valve 40, The first downstream side unloading passage 56 and the second downstream side unloading passage 57 communicate with each other through cutouts of the spool 50. The hydraulic fluid from the hydraulic pressure source 12 is not supplied to either of the rod side chamber 83 and the head side chamber 84 and is supplied from the branch passage 11b to the first upstream side unloading passage 54 and the second upstream side Side unloading passage 56 and flows out to the first bypass passage 22a through the first downstream side unloading passage 55 and the second downstream side unloading passage 57. [ On the other hand, the operating oil discharged from the head-side chamber 84 flows into the tank communication passage (not shown) through the connecting passage 23 and flows into the tank communication passage indicated by reference numeral 52 in Fig. 6 And is supplied (regenerated) from the tank communication passage 52 to the rod-side chamber 83 through the first actuator passage 53.

7), the boom directional control valve 30 and the spool 50 are disposed in the reverse drive position c (see Fig. 4), and when the boom 71 is in the grounded state and the boom directional control valve 30 is disposed in the reverse drive position c As shown in FIG. That is, the spool 50 is disposed at a position basically the same as the position shown in Fig. 6 with respect to the main body portion 51 by the pilot pressure. The force exerted on the selector valve 40 by the hydraulic fluid flowing into the connecting passage 23 from the head side chamber 84 through the second actuator passage 59 is transmitted to the selector valve 40 The selector valve 40 is pressed by the switching spring 60 and is disposed at the rightward position of Fig. The first actuator passage 53 is communicated with the bridge passage 58 through the notch of the spool 50 and the cutout portion of the selector valve 40. [ The second actuator passage 59 is blocked from the bridge passage 58 through the land portion of the spool 50 and is connected to the tank communication passage (not shown) through the cutout portion of the spool 50 and the connecting passage 23, Respectively. On the other hand, the first upstream-side unloading passage 54 and the first downstream-side unloading passage 55 are blocked from each other through the land portion of the spool 50 and the land portion of the selector valve 40, 56 and the second downstream-side unloading passage 57 are cut off from each other through the land portion of the spool 50. The working oil from the hydraulic pressure source 12 is supplied to the rod side chamber 83 through the bridge passage 58 and the first actuator passage 53 and the branch passage 11b is supplied from the first bypass passage 22a . On the other hand, the hydraulic fluid discharged from the head-side chamber 84 flows into the tank communication passage (not shown) through the connecting passage 23 and is discharged from the tank communication passage through a tank Quot;).

When the boom direction switching valve 30 is disposed at the forward drive position a, the boom direction switching valve 30 and the spool 50 are arranged as shown in Fig. That is, the spool 50 is disposed in the leftward direction from the position shown in Fig. 5 by the pilot pressure. The rod side chamber 83 communicates with the tank passage 21 through the first actuator passage 53 and the tank communication passage 52 and the head side chamber 84 communicates with the bridge passage 58 and the 2 actuator passage 59 and the first upstream side unloading passage 54 and the second upstream side unloading passage 56 communicate with the first downstream side unloading passage 55 and the second downstream side unloading passage 56, Is blocked from the downstream side unloading passage (57).

As described above, according to the hydraulic circuit 10, the directional switching valve 30 for boom and the selector valve 40, when the boom 71 in the air condition is driven to descend, the head side chamber 84, And the hydraulic oil is supplied from the hydraulic pressure source 12 to the hydraulic cylinder 74 for the boom. Therefore, the boom can be lowered with high energy efficiency by effectively utilizing the potential energy of the boom 71 or the like.

The selector valve 40 also communicates the oil pressure source 12 and the rod-side chamber 83 when the pressure of the hydraulic oil from the head-side chamber 84 is lower than the switching pressure of the selector valve 40 Reference). In this case, even if the weight of the boom 71 or the like can not be used for lowering the piston rod 81, the hydraulic oil is supplied from the oil pressure source 12 to the rod-side chamber 83, The piston rod 81 can be lowered. Therefore, even if the bucket 73 of the hydraulic excavator 70 is lowered to be grounded and the pressure of the working oil from the head side chamber 84 is lower than the switching pressure of the selector valve 40, The piston rod 81 can be lowered by the hydraulic oil supplied to the rod-side chamber 83 from the hydraulic pump 70. Therefore, the work for lifting the base of the hydraulic excavator 70 by lifting the ground surface by the bucket 73 And can be performed efficiently.

The present invention is not limited to the above-described embodiments and modifications.

For example, in the above-described embodiment, the selector valve 40 is provided inside the boom directional control valve 30 and the boom directional control valve 30 and the selector valve 40 are integrally formed. However, The selector valve 40 may be provided outside the switching valve 30 and the boom directional control valve 30 and the selector valve 40 may be separated from each other.

1 to 4 show a hydraulic circuit 10 mainly connected to a hydraulic cylinder 74 for a boom and a hydraulic cylinder 75 for an arm. The hydraulic circuit 10 for a bucket, the hydraulic excavator 70, (For example, a traveling hydraulic motor for driving a wheel (crawler) or a pivoting hydraulic motor for pivotally driving a structure above the crawler) may be connected to the hydraulic circuit 10. The manner of connection of these hydraulic actuators to the hydraulic circuit 10 is not particularly limited. For example, even if these branched flow paths branched from the oil pressure source 12 are branched and connected to each other in parallel with the oil pressure source 12, they can be connected to the respective hydraulic actuators through the direction switching valves such as spool valves do. The flow paths branched from the bypass passage (refer to 22 in Figs. 1 to 4) communicating with the tank 14 may be connected to the respective hydraulic actuators through the direction switching valves.

Various modifications may be made to the elements of the above-described embodiment and modifications. Also, aspects including components other than the above-described components may be included in the embodiments of the present invention. Also, forms in which some of the above-mentioned components are not included may be included in the embodiments of the present invention. Also, aspects including some components included in some embodiments of the present invention and some components included in other embodiments of the present invention may be included in embodiments of the present invention. Therefore, the components included in each of the above-described embodiments and modifications, and those of the embodiments of the present invention other than those described above may be combined, and a form according to such a combination may be included in the embodiments of the present invention. Also, the effects exerted by the present invention are not limited to the effects described above, and specific effects according to the specific configurations of the embodiments can be exhibited. As described above, various additions, alterations, and partial deletions are possible to each element described in the claims, the specification, the summary, and the drawings without departing from the spirit and scope of the present invention.

10: Hydraulic circuit
11: Euro
11a: Main flow path
11b:
11c:
12: Hydraulic source
13: Regulator
14: Tank
21: tank passage
22: Bypass passage
22a: first bypass passage
22b: the second bypass passage
23: Connection route
24: Negative control Euro
30: Directional switching valve for boom
31: Directional switch for female
40: selector valve
41: check valve
42: Orifice
43: Line Relief Makeup Valve
44: Discharge control valve
45: Pressure control valve
50: spool
51:
52: tank communication path
53: first actuator passage
54: first upstream-side unloading passage
55: first downstream side unloading passage
56: second upstream-side unloading passage
57: second downstream side unloading passage
58: Bridge passage
59: second actuator passage
60: switching spring
70: Hydraulic shovel
71: Boom
72: Cancer
73: Bucket
74: Hydraulic cylinder for boom
75: Hydraulic cylinder for arm
75a: Piston rod
75b: rod-side chamber
75c: head side chamber
76: Hydraulic cylinder for bucket
81: Piston rod
81a:
81b:
82: Cylinder tube
83: Rod side chamber
84: Head side chamber
a: Jeongdong-dong location
b: Neutral position
c: reverse drive position

Claims (7)

A hydraulic circuit connected to a hydraulic cylinder having a hydraulic source for supplying hydraulic oil to a hydraulic passage, a piston rod for supporting a support member to be driven in a vertical direction, a head side chamber and a rod side chamber,
A selector valve communicating with the head side chamber and switching the flow path according to the pressure of the hydraulic oil from the head side chamber;
And a connecting passage for communicating the head-side chamber and the rod-side chamber,
Wherein the selector valve interrupts the communication between the hydraulic source and the rod-side chamber when the pressure of the hydraulic oil from the head-side chamber is equal to or higher than the switching pressure. The method according to claim 1,
And the selector valve communicates the hydraulic source with the rod-side chamber when the pressure of the hydraulic oil from the head-side chamber is lower than the switching pressure. 3. The method according to claim 1 or 2,
The connecting passage communicates the head side chamber to the tank passage,
And the rod-side chamber communicates with the tank passage, and communicates with the head-side chamber through the tank passage and the connecting passage. 4. The method according to any one of claims 1 to 3,
Wherein the selector valve communicates the hydraulic pressure source with the bypass passage when the pressure of the working oil from the head side chamber is equal to or higher than the switching pressure. 5. The method of claim 4,
Wherein the hydraulic pressure source is a negative control type hydraulic pump that changes the supply amount of the hydraulic oil in accordance with the pressure of the hydraulic oil in the bypass passage. 6. The method according to any one of claims 1 to 5,
Further comprising a direction switching valve for switching the flow path between the hydraulic source and the hydraulic cylinder,
And the selector valve is installed inside the direction switching valve. 7. The method according to any one of claims 1 to 6,
Wherein the support member is boom.

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