JP2019052664A - Hydraulic circuit - Google Patents

Abstract

A hydraulic circuit capable of performing an operation (particularly, a descending operation) of a support member such as a boom with energy efficiency. A hydraulic circuit (10) communicates with a head-side chamber (84) and switches a hydraulic path (11) according to the pressure of hydraulic oil from the head-side chamber (84). And a communication path 23 for communicating the The selector valve 40 cuts off the communication between the hydraulic pressure source 12 and the rod-side chamber 83 when the pressure of the hydraulic oil from the head-side chamber 84 is equal to or higher than the switching pressure. [Selection diagram] FIG.

Description

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

  The boom of a hydraulic excavator is driven up and down in a substantially vertical direction under the influence of gravity. In consideration of such boom drive characteristics, various types of hydraulic circuits have been proposed as hydraulic circuits connected to boom-driving hydraulic cylinders.

  For example, the energy saving device for a construction machine described in Patent Document 1 is provided with a control valve (direction switching valve) for controlling the supply of pressure oil to the boom cylinder, and with a negative control throttle in the oil passage leading to the tank. The sensor is installed upstream of the negative control diaphragm. In this energy-saving device, the number of revolutions of the engine that drives the hydraulic pump is controlled based on the negative control pressure detected by the sensor to save energy.

  Further, in the boom lowering regeneration circuit of the hydraulic excavator described in Patent Document 2, a throttle is provided in the tank return oil path on the boom bottom side and the supply oil path to the boom rod side in the boom lowering position of the direction control valve. A diaphragm is provided. In addition, a regeneration oil passage is provided for communicating the tank return oil passage and the supply oil passage, and a check valve is interposed in the regeneration oil passage. According to this regeneration circuit, during the boom lowering operation, the return oil from the boom bottom side can be returned to the boom rod side via the regeneration oil path by increasing the pressure by the throttle, Supply oil can be reduced.

  Further, in the hydraulic circuit described in Patent Document 3, when the boom is lowered in a state where the force against the lowering of the boom is not applied, the first center bypass oil passage is opened by the first switching valve to discharge the first hydraulic pump. While reducing the amount, oil discharged from the extension side oil chamber is supplied to the cylinder reduction side oil chamber via the regeneration circuit. On the other hand, when a force resisting the lowering of the boom is working, the first center bypass oil passage is closed by the first switching valve, and the pump discharge amount is increased.

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

  The conventional hydraulic circuit described above has been devised to reduce the amount of hydraulic oil supplied from the hydraulic power source (hydraulic pump) during the boom lowering operation, but the configuration is simplified, the cost is reduced, and energy is saved. There is room for further improvement.

  For example, in an apparatus that controls the output of hydraulic oil of a hydraulic pump based on the detection result of a sensor, such as the energy saving apparatus of Patent Document 1, since the installation of the sensor is essential, the apparatus configuration becomes complicated and the cost increases. . Further, in the regeneration circuit of Patent Document 2, even when the boom can be lowered using its own weight, for example, when the boom is lowered while the bucket is in the air, the boom cylinder (particularly the boom cylinder) Oil is supplied to the rod side. Thus, supplying hydraulic oil that is not essentially required from the hydraulic pump to the boom cylinder causes an energy loss, and therefore, optimum energy saving is not necessarily achieved. Also in the hydraulic circuit of Patent Document 3, when the boom is lowered in a state where the force against the lowering of the boom is not working, the pressure oil from the hydraulic pump is supplied to the boom cylinder, which causes energy loss. Yes.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a hydraulic circuit capable of energy efficient operation of a support member such as a boom (particularly descending operation).

  One embodiment of the present invention is connected to a hydraulic pressure source that supplies hydraulic oil to an oil passage, and a piston rod that supports a support member driven in a vertical direction, a hydraulic cylinder having a head side chamber and a rod side chamber. A hydraulic circuit, comprising a selector valve that communicates with the head side chamber and switches the oil path according to the pressure of the hydraulic oil from the head side chamber, and a communication path that communicates between the head side chamber and the rod side chamber. The selector valve relates to a hydraulic circuit that blocks 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 selector valve may cause the hydraulic pressure source and the rod side chamber to communicate with each other when the hydraulic oil pressure from the head side chamber is lower than the switching pressure.

  The communication path may communicate the head side chamber with the tank passage, the rod side chamber may communicate with the tank passage, and may communicate with the head side chamber via the tank passage and the communication path.

  The selector valve may connect the hydraulic pressure source to the bypass passage when the pressure of the hydraulic 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 amount of hydraulic oil supplied according to the pressure of the hydraulic oil in the bypass passage.

  The hydraulic circuit may further include a direction switching valve that switches an oil path between the hydraulic source and the hydraulic cylinder, and the selector valve may be provided inside the direction switching valve.

  The support member may be a boom.

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

FIG. 1 is a circuit diagram showing a circuit configuration example of a hydraulic circuit, and shows a state in which a boom direction switching valve is disposed at a neutral position and an arm direction switching valve is disposed at a neutral position. FIG. 2 is a circuit diagram showing a circuit configuration example of the hydraulic circuit, showing a state in which the boom direction switching valve is disposed in the reverse drive position and the arm direction switching valve is disposed in the neutral position. The case where is in the air. FIG. 3 is a circuit diagram showing a circuit configuration example of the hydraulic circuit, and shows a state in which the boom direction switching valve is disposed at the reverse drive position and the arm direction switching valve is disposed at the reverse drive position. FIG. 4 is a circuit diagram showing a circuit configuration example of a hydraulic circuit, showing a state in which the boom direction switching valve is disposed in the reverse drive position and the arm direction switching valve is disposed in the neutral position. Shows the case where is in a grounded state. FIG. 5 is a partial cross-sectional view illustrating an example of a boom direction switching valve and a selector valve, showing a state where the boom is in a grounded state and the boom direction switching valve is disposed in a neutral position. FIG. 6 is a partial cross-sectional view showing an example of a boom direction switching valve and a selector valve, showing a state where the boom is in the air and the boom direction switching valve is disposed at the reverse drive position. FIG. 7 is a partial cross-sectional view illustrating an example of a boom direction switching valve and a selector valve, showing a state where the boom is in a grounded state and the boom direction switching valve is disposed at a reverse drive position. FIG. 8 is a partial cross-sectional view showing an example of the boom direction switching valve and the selector valve, and shows a state in which the boom direction switching valve is arranged at the positive drive position.

  Embodiments of the present invention will be described with reference to the drawings. It should be noted that the elements shown in each drawing may include elements whose sizes and scales are different from those actually shown for easy understanding.

  Below, the case where this invention is applied with respect to the hydraulic circuit for drive control of a hydraulic shovel (especially boom) is demonstrated. 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 the boom, and the application target of the present invention is a boom It is not limited to the hydraulic circuit for driving control.

  1 to 4 are circuit diagrams showing circuit configuration examples of a hydraulic circuit 10 according to an embodiment of the present invention. FIG. 1 shows a state in which the boom direction switching valve 30 is disposed at the neutral position b and the arm direction switching 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 drive position c and the arm direction switching valve 31 is disposed at the neutral position b. FIG. FIG. 4 shows a case where the boom 71 and the arm 72 are separated from the ground (hereinafter also referred to as “air condition”), and FIG. 4 shows a state where the boom 71 is in contact with the ground via the bucket 73 and the arm 72 (hereinafter “ In this case, it is also referred to as “grounded state”. FIG. 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, the oil path configuration is shown as a circuit diagram, while the hydraulic excavator 70 (particularly, the boom 71, the arm 72, the bucket 73, etc.) is shown as an external view. Therefore, in FIGS. 1 to 4, the arm hydraulic cylinder 75 is shown in both a circuit diagram and an external view, and these indicate the same arm hydraulic cylinder 75.

  The hydraulic circuit 10 shown in FIGS. 1 to 4 is connected to the hydraulic source 12, the boom hydraulic cylinder 74, and the arm hydraulic cylinder 75, and passes through an oil path 11 between the hydraulic source 12 and the boom hydraulic cylinder 74. A boom direction switching valve 30 for switching, and an arm direction switching valve 31 for switching the oil passage 11 between the hydraulic source 12 and the arm hydraulic cylinder 75 are provided. In this specification, the term oil passage 11 is a general term for passages through which hydraulic oil flows, and for example, branch oil passages 11b and 11c, tank passage 21, bypass passage 22, communication passage 23, negative control oil passage 24, and The hydraulic oil passages in the direction switching valves 30 and 31 also constitute the oil passage 11.

  The boom direction switching valve 30 and the arm direction switching valve 31 are constituted by spool valves. The direction switching valves 30 and 31 shown in FIGS. 1 to 4 switch the oil passage 11 in accordance with the pilot oil pressure applied to the spool, but may be constituted by other valve bodies (such as electromagnetically driven spool valves). . Although a bucket direction switching valve is also provided between the hydraulic power source 12 and the bucket hydraulic cylinder 76, in order to simplify the overall configuration and facilitate understanding, the bucket direction is shown in FIGS. The switching valve is omitted, and a detailed description of drive control of the bucket direction switching valve and the bucket hydraulic cylinder 76 is omitted below. However, the connection mode of the bucket direction switching valve and bucket hydraulic cylinder 76 to the oil passage 11 and the supply mode of hydraulic oil can be the same as those of the arm direction switching valve 31 and the arm hydraulic cylinder 75.

  The hydraulic source 12 is configured by a variable displacement hydraulic pump that supplies hydraulic oil to the oil passage 11, and can increase or decrease the amount of hydraulic oil supplied to the oil passage 11 under the control of the regulator 13. The hydraulic pressure source 12 of the present embodiment is configured such that the pressure of the hydraulic oil in the negative control oil passage 24 connected to the bypass passage 22 (particularly the second bypass oil passage 22b) communicating with the tank 14 (that is, the operation of the second bypass oil passage 22b). It is constituted by a negative control type hydraulic pump that changes the supply amount of hydraulic oil according to the oil pressure). For example, as the flow rate of the hydraulic oil flowing through the second bypass oil passage 22b increases and the pressure of the hydraulic oil in the second bypass oil passage 22b and the negative control oil passage 24 increases, the regulator 13 increases the amount of hydraulic oil from the hydraulic power source 12. Reduce supply. On the other hand, as the flow rate of the hydraulic oil flowing through the second bypass oil passage 22b decreases and the pressure of the hydraulic oil in the bypass passage 22 and the negative control oil passage 24 decreases, the regulator 13 reduces the amount of hydraulic oil supplied from the hydraulic source 12. Increase.

  The oil passage 11 extending from the hydraulic pressure source 12 includes an oil passage 11a (hereinafter also referred to as “main oil passage”) extending toward the boom direction switching valve 30 and two oil passages (hereinafter referred to as “main oil passage”) branched from the main oil passage 11a. The main oil passage 11a and the branch oil passages 11b, 11c are connected in parallel to the hydraulic power source 12. One branch oil passage 11 b is intended to communicate with the bypass passage 22 (particularly the first bypass passage 22 a) via the boom direction switching valve 30, and depends on the operating state of the boom direction switching valve 30. Thus, communication and blocking between the branch oil passage 11b and the bypass passage 22 are controlled. The other branch oil passage 11 c is intended to communicate with the arm hydraulic cylinder 75 via the arm direction switching valve 31, and the branch oil passage 11 c depends on the operating state of the arm direction switching valve 31. And communication between the hydraulic cylinder 75 and the arm hydraulic cylinder 75 are controlled.

  The boom hydraulic cylinder 74 has a piston rod 81 and a cylinder tube 82. The piston rod 81 has a piston part 81 a disposed in the cylinder tube 82 and a rod part 81 b provided integrally with the piston part 81 a and extending from the inside to the outside 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 up by increasing the amount of protrusion of the piston rod 81 from the cylinder tube 82, and the boom 71 is driven down by reducing the amount of protrusion of the piston rod 81 from the cylinder tube 82. 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 seals each of the rod side chamber 83 and the head side chamber 84 in the cylinder tube 82 so that the working oil does not leak between the rod side chamber 83 and the head side chamber 84 in the cylinder tube 82. Is provided to be movable.

  The arm hydraulic cylinder 75 is basically configured in the same manner as the boom hydraulic cylinder 74 described above, and includes a piston rod 75a movably provided, a variable volume rod side chamber 75b, and a head side chamber 75c. The bucket hydraulic cylinder 76 is not shown as a circuit diagram, but is basically the same as the boom hydraulic cylinder 74 and the arm hydraulic cylinder 75 described above, and is a movably provided piston rod. And a variable volume rod side chamber and a head side chamber.

  The hydraulic circuit 10 (particularly, the boom direction switching valve 30) of the present embodiment is provided with a communication path 23, and the head side chamber 84 in a state where the boom direction switching valve 30 is disposed at the reverse drive position c. And the rod-side chamber 83 are communicated with each other via a communication path 23. That is, the head side chamber 84 is communicated with the tank passage 21 connected to the tank 14 through the communication path 23 formed in the boom direction switching valve 30. On the other hand, the rod side chamber 83 communicates with the tank passage 21 without passing through the boom direction switching valve 30. Therefore, the rod-side chamber 83 and the head-side chamber 84 are communicated with each other via the tank passage 21 and the communication passage 23 according to the driving state of the boom direction switching valve 30 or are mutually blocked.

  A line relief makeup valve 43 is provided in the oil passage 11 between the tank passage 21 and the rod side chamber 83. The line relief makeup valve 43 includes a check valve 41 and a pressure control valve 45 provided in parallel to the oil passage 11 on the tank passage 21 side and the oil passage 11 on the rod side chamber 83 side. The check valve 41 of the line relief make-up valve 43 allows the hydraulic oil to flow from the tank passage 21 side to the rod side chamber 83 side, but the hydraulic oil to flow from the rod side chamber 83 side to the tank passage 21 side. Is not allowed. When the pressure of the hydraulic oil in the oil passage 11 on the rod side chamber 83 side is larger than a predetermined valve opening pressure, the pressure control valve 45 of the line relief make-up valve 43 is connected to the oil passage 11 and the tank on the rod side chamber 83 side. The oil passage 11 on the side of the passage 21 is communicated. When the pressure of the hydraulic oil in the oil passage 11 on the side of the rod side chamber 83 is equal to or lower than a predetermined valve opening pressure, the oil passage 11 on the side of the rod side chamber 83 and the tank passage The communication with the oil passage 11 on the 21 side is blocked.

  When the pressure of the hydraulic oil in the oil passage 11 on the tank passage 21 side is larger than the pressure of the hydraulic oil in the oil passage 11 on the rod side chamber 83 side, the tank passage 21 passes through the check valve 41 of the line relief makeup valve 43. The hydraulic oil flows from the oil passage 11 on the side into 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 pressure of the hydraulic oil in the oil passage 11 on the tank passage 21 side and the opening pressure of the pressure control valve 45 of the line relief make-up valve 43. Is smaller, the flow of hydraulic oil between the oil passage 11 on the rod side chamber 83 side and the oil passage 11 on the tank passage 21 side is blocked by the line relief make-up valve 43. The pressure of the hydraulic oil in the oil passage 11 on the rod side chamber 83 side is larger than the pressure of the hydraulic oil in the oil passage 11 on the tank passage 21 side, and is higher than the valve opening pressure of the pressure control valve 45 of the line relief makeup valve 43. When it is larger, the pressure control valve 45 is opened, and hydraulic oil flows from the oil passage 11 on the rod side chamber 83 side into the oil passage 11 on the tank passage 21 side.

  Thus, the line relief make-up valve 43 has a function of supplying 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 backflow, and an oil passage on the rod side chamber 83 side. When the pressure of the hydraulic oil 11 is excessive, the hydraulic oil is released from the oil path 11 on the rod side chamber 83 side to the oil path 11 on the tank path 21 side, and the pressure of the hydraulic oil in the rod side chamber 83 becomes excessive. It also has a function to prevent this. Therefore, the valve opening pressure of the pressure control valve 45 of the line relief make-up valve 43 is determined based on the upper limit of the allowable pressure of the hydraulic oil in the rod side chamber 83 and the oil passage 11 on the rod side chamber 83 side.

  As described above, the rod side chamber 83 communicates with the tank passage 21 via the line relief makeup valve 43. On the other hand, when the boom direction switching valve 30 is disposed at the reverse drive position c, the communication path 23 communicates the head side chamber 84 with the tank passage 21. Therefore, when the boom direction switching valve 30 is disposed at the reverse drive position c, the head side chamber 84 and the rod side chamber 83 are connected to the oil passage 11 including the communication passage 23 and the tank passage 21, and the line relief. The makeup valve 43 communicates with each other. In particular, by providing the line relief make-up valve 43, the magnitude between the pressure of the hydraulic oil discharged from the head side chamber 84 to the tank passage 21 via the communication path 23 and the pressure of the hydraulic oil in the rod side chamber 83 is small. The flow of hydraulic oil between the tank passage 21 (and thus the head side chamber 84) and the rod side chamber 83 can be appropriately adjusted according to the relationship and the pressure of the hydraulic oil in the rod side chamber 83. it can.

  The hydraulic circuit 10 further 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 direction switching valve 30. In a state in which the boom direction switching valve 30 is disposed at the reverse drive position c, the selector valve 40 communicates with the head side chamber 84 via the oil passage 11 (particularly the communication passage 23), and the operation from the head side chamber 84 is performed. The oil passage 11 is switched in accordance with the oil pressure (the hydraulic oil pressure in the communication passage 23 in FIGS. 1 to 4). For example, 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 communication path 23) is equal to or higher than a predetermined switching pressure, the selector valve 40 is connected to the hydraulic source 12 and the rod side chamber 83. Is disconnected (see symbol “e” in FIG. 2). 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 communication path 23) is lower than the switching pressure, the selector valve 40 is connected to the hydraulic source 12 and the rod side chamber 83. Are communicated (see symbol “f” in FIG. 4).

  Further, when the pressure of the hydraulic oil from the head side chamber 84 is equal to or higher than the switching pressure (see the reference “e” in FIG. 2), the selector valve 40 causes the hydraulic source 12 to enter the bypass passage 22 (particularly the first bypass passage 22a). When the pressure of the hydraulic oil from the head side chamber 84 is lower than the switching pressure, the communication between the hydraulic source 12 and the bypass passage 22 is shut off (see symbol “f” in FIG. 4). The bypass passage 22 is an oil passage 11 communicating with the tank 14. The tank 14 connected to the bypass passage 22 and the tank 14 connected to the tank passage 21 described above are constituted by the same tank. The bypass passage 22 shown in FIGS. 1 to 4 is provided with an arm direction switching valve 31. The bypass passage 22 includes a first bypass passage 22a upstream of the arm direction switching valve 31 and an arm direction. The second bypass oil passage 22b is divided downstream of the switching valve 31. Both ends of the first bypass passage 22a are controlled to be opened and closed by a boom direction switching valve 30 and an arm direction switching valve 31, respectively. One end of the second bypass oil passage 22 b is connected to the arm direction switching valve 31, and the other end is connected to the tank 14. One end of the second bypass oil passage 22b is controlled to open and close by the arm direction switching valve 31.

  The hydraulic circuit 10 shown in FIGS. 1 to 4 is further provided with a check valve 41, a throttle 42, a pressure control valve 45, and other devices as appropriate. For example, a check valve 41 is provided in the main oil passage 11a and the branch oil passage 11c. In addition, a throttle 42 is provided in the communication path 23, and the throttle 42 is provided on the downstream side of the connection path 23 connected to the selector valve 40 (that is, on the tank 14 side). Therefore, the switching of the oil passage 11 (see symbols “e” and “f” shown in FIGS. 1 to 4) by the selector valve 40 is performed by operating the communication passage 23 whose pressure is increased by the throttle 42 provided in the communication passage 23. This is done according to the oil pressure. The second bypass oil passage 22b is provided with a discharge control valve 44 having a throttle 42 and a pressure control valve 45. The throttle 42 of the discharge control valve 44 is provided on the downstream side (i.e., the tank 14 side) of the second bypass oil passage 22b where it is connected to the negative control oil passage 24. Therefore, the control of the hydraulic power source 12 by the regulator 13 is performed according to the pressure of the working oil in the negative control oil passage 24 whose pressure is increased by the throttle 42 provided in the second bypass oil passage 22b. The pressure control valve 45 of the discharge control valve 44 opens and closes according to the pressure of the hydraulic oil in the second bypass oil passage 22b, and when the pressure of the hydraulic oil in the second bypass oil passage 22b is larger than a predetermined valve opening pressure. Open and increase the flow rate of hydraulic oil toward the tank 14.

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

  First, the case where both the boom direction switching valve 30 and the arm direction switching valve 31 are arranged at the neutral position b as shown in FIG. 1 will be described. In this case, the communication between the hydraulic source 12 and the boom hydraulic cylinder 74 is blocked by the boom direction switching valve 30, and the communication between the hydraulic source 12 and the arm hydraulic cylinder 75 is performed by the arm direction switching valve 31. Blocked. That is, the boom direction switching valve 30 blocks communication between the head side chamber 84 and the tank passage 21, and blocks communication between the rod side chamber 83 and the hydraulic source 12 (particularly the main oil path 11a). The branch oil passage 11b is communicated with the first bypass passage 22a. Further, the arm direction switching valve 31 blocks communication between the rod side chamber 75b of the arm hydraulic cylinder 75 and the tank passage 21, and between the head side chamber 75c of the arm hydraulic cylinder 75 and the branch oil path 11c. The first bypass passage 22a and the second bypass oil passage 22b are communicated with each other.

  In this case, the hydraulic pressure source 12 is connected to the first bypass passage 22a via the branch oil passage 11b, and the first bypass passage 22a is connected to the second bypass oil passage 22b via the arm direction switching valve 31. Therefore, the hydraulic pressure source 12 is communicated with the tank 14 and the negative control oil passage 24 via the branch oil passage 11 b and the bypass passage 22. Accordingly, when the boom direction switching valve 30 and the arm direction switching valve 31 are initially disposed at the neutral position b, the amount of hydraulic oil flowing through the bypass passage 22 increases, and the hydraulic oil pressure in the negative control oil passage 24 increases. Go up. Therefore, the hydraulic source 12 suppresses the amount of hydraulic oil supplied under the control of the regulator 13. As a result, the amount of hydraulic fluid flowing through the bypass passage 22 is reduced, the pressure of the hydraulic fluid in the negative control oil passage 24 is lowered, and energy saving is achieved.

  Next, as shown in FIG. 2, the boom direction switching valve 30 is disposed at the reverse drive position c, the arm direction switching valve 31 is disposed at the neutral position b, and the boom 71 is brought into the air state together with the bucket 73 and the arm 72. A case will be described. In this case, the head-side chamber 84 communicates with the communication path 23 and communicates with the tank passage 21 via the communication path 23. Also, the piston rod 81 descends due to the weight of the boom 71 and the like under the influence of gravity, the pressure of the hydraulic oil in the head side chamber 84 increases, and the pressure of the hydraulic oil in the communication path 23 communicated with the head side chamber 84 increases. It becomes more than the switching pressure of the selector valve 40. For this reason, the selector valve 40 takes the state indicated by the symbol “e” in FIGS. 1 to 4, shuts off the communication between the hydraulic source 12 (particularly the main oil passage 11 a) and the rod side chamber 83, and the branched oil. The hydraulic power source 12 is communicated with the first bypass passage 22a through the passage 11b. On the other hand, the arm direction switching valve 31 blocks communication between the rod side chamber 75b of the arm hydraulic cylinder 75 and the tank passage 21, and connects the head side chamber 75c of the arm hydraulic cylinder 75 and the branch oil passage 11c. The communication between the first bypass passage 22a and the second bypass oil passage 22b is communicated.

  In this case, the high-pressure hydraulic oil discharged from the head side chamber 84 is caused to flow toward the tank 14 via the communication path 23 and the tank path 21, and the communication path 23, the tank path 21 and the line relief make-up valve 43. (In particular, the boom hydraulic cylinder 74 is supplied (that is, regenerated) via the check valve 41). Thus, the shortage of hydraulic oil and pressure in the rod-side chamber 83 whose volume increases with the lowering of the piston portion 81a is compensated, and the boom 71 can be lowered using its own weight. On the other hand, the hydraulic oil discharged from the hydraulic power source 12 is sent to the tank 14 via the bypass passage 22, and the supply amount of the hydraulic oil from the negative control type hydraulic power source 12 is kept low, thereby saving energy. Can do.

  Next, as shown in FIG. 3, the boom direction switching valve 30 is disposed at the reverse driving position c, the arm direction switching valve 31 is also disposed at the reverse driving position c, and the boom 71 is in the air state together with the bucket 73 and the arm 72. The case will be described. In this case, similarly to the case shown in FIG. 2 described above, the head side chamber 84 communicates with the tank passage 21 via the communication path 23, and the pressure of the hydraulic oil in the communication path 23 becomes equal to or higher than the switching pressure of the selector valve 40. The selector valve 40 takes the state indicated by the reference numeral “e” in FIGS. Therefore, the boom direction switching valve 30 blocks communication between the rod-side chamber 83 and the hydraulic source 12 (particularly the main oil passage 11a), and connects the hydraulic source 12 to the bypass passage 22 via the branch oil passage 11b. Communicate. On the other hand, the arm direction switching valve 31 communicates the rod-side chamber 75b and the tank passage 21, communicates the head-side chamber 75c and the hydraulic pressure source 12 (particularly the branch oil passage 11c), and connects the first bypass passage 22a and the first passageway. 2 The communication with the bypass oil passage 22b is blocked.

  In this case, the high-pressure hydraulic oil discharged from the head-side chamber 84 is boom hydraulic cylinder 74 via the communication path 23, the tank passage 21, and the line relief make-up valve 43 as in the case shown in FIG. The boom 71 descends using its own weight. On the other hand, a part of the hydraulic oil discharged from the hydraulic power source 12 is supplied to the head side chamber 75c through the branch oil passage 11c. The hydraulic oil discharged from the rod side chamber 75 b is sent to the tank passage 21, and then discharged to the tank 14 or supplied to the rod side chamber 83 via the line relief make-up valve 43. As described above, the boom hydraulic cylinder 74 is driven by its own weight, such as the boom 71, and high pressure hydraulic oil discharged from the head side chamber 84 and the rod side chamber 75 b is used. The hydraulic oil need not be used for driving the arm hydraulic cylinder 75. Accordingly, the hydraulic oil newly supplied from the hydraulic power source 12 can be efficiently used for driving the arm hydraulic cylinder 75, and energy saving can be achieved. Since the second bypass oil passage 22b is blocked by the arm direction switching valve 31, the amount of hydraulic oil flowing through the second bypass oil passage 22b is reduced, and the pressure of the hydraulic oil in the negative control oil passage 24 is lowered. The control type hydraulic pressure source 12 increases the amount of hydraulic oil supplied. As a result, a sufficient amount and sufficient pressure of hydraulic oil can be supplied to the head side chamber 75c via the branch oil passage 11c.

  Next, as shown in FIG. 4, the boom direction switching valve 30 is disposed at the reverse drive position c, the arm direction switching valve 31 is disposed at the neutral position b, and the boom 71 is grounded via the bucket 73 and the arm 72. A case in a state will be described. In this case, the head-side chamber 84 communicates with the communication path 23 and communicates with the tank passage 21 via the communication path 23. However, since the boom 71 is in a grounded state, the weight of the boom 71 or the like cannot be basically used in the downward driving of the piston rod 81. Accordingly, the pressure of the hydraulic oil in the head side chamber 84 becomes relatively small, and the pressure of the hydraulic oil in the communication path 23 communicated with the head side chamber 84 becomes smaller than the switching pressure of the selector valve 40. For this reason, the selector valve 40 takes the state indicated by the symbol “f” in FIG. 4 to connect the hydraulic pressure source 12 to the rod side chamber 83 via the main oil passage 11a, and the hydraulic power source 12 (particularly, the branched oil passage 11b). And the bypass passage 22 (particularly, the first bypass passage 22a) are blocked. On the other hand, the arm direction switching valve 31 blocks communication between the rod side chamber 75b of the arm hydraulic cylinder 75 and the tank passage 21, and connects the head side chamber 75c of the arm hydraulic cylinder 75 and the branch oil passage 11c. The communication between the first bypass passage 22a and the second bypass oil passage 22b is communicated.

  When the hydraulic circuit 10 takes the state shown in FIG. 4 described above, the hydraulic oil discharged from the hydraulic source 12 is supplied to the rod side chamber 83, and the pressure of the hydraulic oil in the rod side chamber 83 is increased in the head side chamber 84. The pressure of the hydraulic oil becomes larger, the piston portion 81a receives a downward force, and the boom 71 is lowered. The head side chamber 84 communicates with the tank passage 21 via the communication path 23, but the pressure of the hydraulic oil discharged from the head side chamber 84 is smaller than the pressure of the hydraulic oil in the rod side chamber 83. The hydraulic oil is not sent from the chamber 84 to the rod side chamber 83. Therefore, the hydraulic oil discharged from the head side chamber 84 is sent toward the tank 14 via the communication path 23 and the tank path 21. The check valve 41 of the line relief make-up valve 43 prevents the backflow of hydraulic oil from the rod side chamber 83 toward the tank 14, the tank passage 21 and the head side chamber 84. The hydraulic pressure source 12 is shut off from the bypass passage 22 (particularly, the first bypass passage 22a) by the boom direction switching valve 30. Therefore, the amount of hydraulic oil flowing through the second bypass oil passage 22b decreases, the pressure of the hydraulic oil in the negative control oil passage 24 decreases, and the negative control hydraulic source 12 increases the supply amount of hydraulic oil. Thus, a sufficient amount and sufficient pressure of hydraulic fluid can be supplied to the rod side chamber 83 via the main oil passage 11a.

  Although a detailed description is omitted, when the boom direction switching valve 30 is disposed at the positive drive position a, the hydraulic source 12 is communicated with the head side chamber 84 of the boom hydraulic cylinder 74 via the main oil passage 11a. The rod side chamber 83 of the boom hydraulic cylinder 74 is communicated with the tank passage 21, and the communication between the branch oil passage 11b and the first bypass passage 22a is blocked. In this case, the hydraulic oil discharged from the hydraulic source 12 is supplied to the head side chamber 84, the hydraulic oil discharged from the rod side chamber 83 flows out into the tank passage 21, and the boom 71 is raised together with the piston rod 81. On the other hand, when the arm direction switching valve 31 is disposed at the positive drive position a, the hydraulic source 12 is communicated with the rod side chamber 75b of the arm hydraulic cylinder 75 via the branch oil passage 11c. The head side chamber 75c is communicated with the tank passage 21, and the communication between the first bypass passage 22a and the second bypass oil passage 22b is blocked. In this case, the hydraulic oil discharged from the hydraulic power source 12 is supplied to the rod side chamber 75b, the hydraulic oil discharged from the head side chamber 75c flows out into the tank passage 21, and the protruding amount of the piston rod 75a is reduced. 72 is swung in the ascending direction with a connection point with the boom 71 as a fulcrum. Further, the bypass passage 22 is shut off by the boom direction switching valve 30 and / or the arm direction switching valve 31, and the negative control type hydraulic power source 12 increases the supply amount of the hydraulic oil so that a sufficient amount and sufficient pressure of the hydraulic fluid is supplied. It can be supplied to the head side chamber 84 and / or the rod side chamber 75b.

  Next, specific configuration examples of the boom direction switching valve 30 and the selector valve 40 will be described.

  5 to 8 are partial cross-sectional views showing examples of the boom direction switching valve 30 and the selector valve 40. FIG. 5 shows a state in which the boom 71 is in a grounded state and the boom direction switching valve 30 is disposed at the neutral position b. FIG. 6 shows a state where the boom 71 is in the air and the boom direction switching valve 30 is disposed at the reverse drive position c. FIG. 7 shows a state in which the boom 71 is in a grounded state and the boom direction switching valve 30 is disposed at the reverse drive position c. FIG. 8 shows a state in which the boom direction switching valve 30 is disposed at the positive drive position a. The boom direction switching valve 30 and the selector valve 40 shown in FIGS. 5 to 8 are not necessarily strictly structurally and functionally different from the boom direction switching valve 30 and the selector valve 40 shown in FIGS. Although they do not coincide, they generally correspond to the boom direction switching valve 30 and the selector valve 40 shown in FIGS. Therefore, those skilled in the art can fully understand the structures and functions of the boom direction switching valve 30 and the selector valve 40 shown in FIGS. 5 to 8 based on the following description.

  The boom direction switching valve 30 shown in FIGS. 5 to 8 includes a spool 50 and a main body 51 that slidably holds the spool 50 inside. A selector valve 40 is slidably provided 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 and the outside of the spool 50). The oil passage 11 is switched according to 50 relative slide positions. The selector valve 40 is also formed with a plurality of land portions and a plurality of notches, and the oil passage 11 is switched according to the relative slide position of the selector valve 40 with respect to the spool 50.

  The main body 51 communicates with a tank communication path 52 that communicates with the tank path 21, a first actuator path 53 that communicates with the rod side chamber 83, a bridge path 58 that communicates with the hydraulic power source 12, and a branch oil path 11b. A first upstream unload passage 54, a second upstream unload passage 56, a first downstream unload passage 55 and a second downstream unload passage 57 communicated with the first bypass passage 22a, and a head chamber. A second actuator passage 59 communicating with 84 is formed. Although not shown in the figure, the main body 51 also has a tank communication path that communicates with the tank 14 on the side opposite to the bridge path 58 (the right side in FIGS. 5 to 8) via the second actuator path 59. Is formed.

  A communication path 23 is further formed in the spool 50. One end (the left end in FIGS. 5 to 8) of the communication path 23 communicates with one end (the right end in FIGS. 5 to 8) of the selector valve 40, and the other end of the communication path 23. The portion (the right end portion in FIGS. 5 to 8) communicates with a notch formed in the spool 50. 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). As will be described later, the sliding position of the selector valve 40 depends on the force of the hydraulic oil from the communication path 23 acting on one end of the selector valve 40 and the switching spring 60 acting on the other end of the selector valve 40. It depends on the elastic force. Therefore, the state in which hydraulic oil is not supplied from the communication path 23 to one end of the selector valve 40 or the force of the hydraulic oil from the communication path 23 acting on one end of the selector valve 40 causes the selector valve 40 to In a state where it is smaller than the elastic force of the switching spring 60 applied to the other end, the selector valve 40 is pushed by the switching spring 60 and arranged at the right position in FIGS.

  For example, when the boom direction switching valve 30 is arranged at the neutral position b (see FIG. 1), the boom direction switching valve 30 and the selector valve 40 are arranged as shown in FIG. That is, the rod-side chamber 83 is cut off from the bridge passage 58 and the tank communication passage 52 through the land portion of the spool 50, and the second actuator passage 59 is cut off from the bridge passage 58 and the tank communication passage (not shown). On the other hand, the first upstream unload passage 54 and the first downstream unload passage 55 communicate with each other via the notch portion of the spool 50 and the notch portion of the selector valve 40, and the second upstream unload passage 56 The second downstream unload passage 57 is communicated with each other via a notch portion of the spool 50. Accordingly, the hydraulic oil from the hydraulic source 12 is not supplied to either the rod side chamber 83 or the head side chamber 84, and the first upstream unload passage 54 and the second upstream unload passage via the branch oil passage 11b. 56 and flows out to the first bypass passage 22a through the first downstream unload passage 55 and the second downstream unload passage 57.

  When the boom direction switching valve 30 is disposed at the neutral position b, the communication path 23 communicates with the head-side chamber 84 via the second actuator path 59. Accordingly, the hydraulic oil from the head side chamber 84 flows into the communication path 23 via the second actuator passage 59, and the selector valve 40 is slid in accordance with the pressure of the hydraulic oil in the communication path 23. In FIG. 5, the boom 71 is in a grounded state, the pressure of the hydraulic oil flowing into the communication path 23 from the head side chamber 84 is low, and the selector valve 40 is pushed to the right by the switching spring 60. It is shown. However, when the boom 71 is in the air and the pressure of the hydraulic oil flowing into the communication path 23 from the head side chamber 84 is high, the selector valve 40 is pushed by the hydraulic oil from the communication path 23 and arranged on the left side. Is done. Also in this case, the rod side chamber 83 is cut off from the bridge passage 58 and the tank communication passage 52, and the second actuator passage 59 is cut off from the bridge passage 58 and the tank communication passage (not shown), and the first upstream unload passage. 54 and the first downstream unload passage 55 are communicated with each other via a notch portion of the spool 50 and a notch portion of the selector valve 40, and a second upstream unload passage 56, a second downstream unload passage 57, Are communicated with each other via a notch portion of the spool 50.

  On the other hand, when the boom 71 is in the air and the boom direction switching valve 30 is disposed at the reverse drive position c (see FIGS. 2 and 3), the boom direction switching valve 30 and the spool 50 are as shown in FIG. Placed in. That is, the spool 50 is disposed on the right side of the position shown in FIG. 5 by the pilot pressure. Further, the hydraulic oil from the head side chamber 84 flows into the communication path 23 via the second actuator passage 59, presses the selector valve 40, compresses the switching spring 60, and moves the selector valve 40 to the left position in FIG. Arrange. As a result, the first actuator passage 53 is blocked from the bridge passage 58 via the land portion of the spool 50. The second actuator passage 59 is disconnected from the bridge passage 58 via the land portion of the spool 50 and is connected to a tank communication passage (not shown) via the notch portion of the spool 50 and the communication passage 23. On the other hand, the first upstream unload passage 54 and the first downstream unload passage 55 communicate with each other via the notch portion of the spool 50 and the notch portion of the selector valve 40, and the second upstream unload passage 56 The second downstream unload passage 57 is communicated with each other via a notch portion of the spool 50. Therefore, the hydraulic oil from the hydraulic power source 12 is not supplied to either the rod side chamber 83 or the head side chamber 84, and the first upstream unload passage 54 and the second upstream unload passage 56 from the branch oil passage 11b. Into the first bypass passage 22a through the first downstream unload passage 55 and the second downstream unload passage 57. On the other hand, the hydraulic oil discharged from the head side chamber 84 flows into the tank communication path (not shown) via the communication path 23, and flows from the tank communication path into the tank communication path indicated by reference numeral 52 in FIG. The tank communication passage 52 is supplied (regenerated) to the rod side chamber 83 through the first actuator passage 53.

  When the boom 71 is in a grounded state and the boom direction switching valve 30 is disposed at the reverse drive position c (see FIG. 4), the boom direction switching valve 30 and the spool 50 are disposed as shown in FIG. The That is, the spool 50 is arranged at the same position as the position shown in FIG. However, the force applied to the selector valve 40 by the hydraulic oil flowing into the communication path 23 from the head side chamber 84 via the second actuator passage 59 is smaller than the force applied by the switching spring 60 to the selector valve 40, and the selector valve 40 Is pushed by the switching spring 60 and disposed at the right position in FIG. Thus, the first actuator passage 53 is communicated with the bridge passage 58 via the notch portion of the spool 50 and the notch portion of the selector valve 40. The second actuator passage 59 is disconnected from the bridge passage 58 via the land portion of the spool 50 and is connected to a tank communication passage (not shown) via the notch portion of the spool 50 and the communication passage 23. On the other hand, the first upstream unload passage 54 and the first downstream unload passage 55 are blocked from each other via the land portion of the spool 50 and the land portion of the selector valve 40, and the second upstream unload passage 56 The second downstream unload passage 57 is blocked from each other via the land portion of the spool 50. Accordingly, the hydraulic oil from the hydraulic source 12 is supplied to the rod side chamber 83 via the bridge passage 58 and the first actuator passage 53, and the branch oil passage 11b is blocked from the first bypass passage 22a. On the other hand, the hydraulic oil discharged from the head-side chamber 84 flows into the tank communication path (not shown) via the communication path 23, and from the tank communication path, a tank (not shown “14” in FIGS. 1 to 4). Flow towards).

  When the boom direction switching valve 30 is arranged at the positive 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 on the left side of the position shown in FIG. 5 by the pilot pressure. As a result, the rod side chamber 83 communicates with the tank passage 21 via the first actuator passage 53 and the tank communication passage 52, and the head side chamber 84 communicates with the hydraulic power source 12 via the bridge passage 58 and the second actuator passage 59. The first upstream unload passage 54 and the second upstream unload passage 56 are cut off from the first downstream unload passage 55 and the second downstream unload passage 57, respectively.

  As described above, according to the hydraulic circuit 10, the boom direction switching valve 30, and the selector valve 40 described above, the high-pressure hydraulic oil discharged from the head-side chamber 84 when the boom 71 in the air is driven to descend. Is supplied to the rod side chamber 83, and no new hydraulic oil is supplied from the hydraulic source 12 to the boom hydraulic cylinder 74. Therefore, the position energy of the boom 71 and the like can be effectively used, and the boom lowering operation can be performed with high energy efficiency.

  Further, when the pressure of the hydraulic oil from the head side chamber 84 is lower than the switching pressure of the selector valve 40, the selector valve 40 causes the hydraulic source 12 and the rod side chamber 83 to communicate (see FIG. 4). In this case, even if the weight of the boom 71 or the like cannot be used for lowering the piston rod 81, the hydraulic oil (pressure oil) is supplied from the hydraulic source 12 to the rod side chamber 83, so the piston rod 81 including the piston portion 81a. Can be lowered. Therefore, for example, even when the bucket 73 of the hydraulic excavator 70 is lowered and grounded, and the pressure of the hydraulic oil from the head side chamber 84 is lower than the switching pressure of the selector valve 40, Since the piston rod 81 can be lowered by the hydraulic oil supplied to the chamber 83, the work of pressing the ground with the bucket 73 and lifting the body of the excavator 70 can be performed efficiently.

  In addition, this invention is not limited to the above-mentioned embodiment and modification.

  For example, in the above-described embodiment, the selector valve 40 is provided inside the boom direction switching valve 30 and the boom direction switching valve 30 and the selector valve 40 are integrally configured. A selector valve 40 may be provided outside, and the boom direction switching valve 30 and the selector valve 40 may be separated from each other.

  1 to 4 show the hydraulic circuit 10 mainly connected to the boom hydraulic cylinder 74 and the arm hydraulic cylinder 75, the bucket hydraulic cylinder 76 and other components constituting the hydraulic excavator 70 are shown. A hydraulic actuator (for example, a traveling hydraulic motor that drives a wheel (crawler), or a turning hydraulic motor that drives a turning structure above the crawler) may be connected to the hydraulic circuit 10. The connection mode of these hydraulic actuators to the hydraulic circuit 10 is not particularly limited. For example, an oil passage extending from the hydraulic source 12 is branched, and these branch oil passages connected in parallel to the hydraulic source 12 are connected to the respective hydraulic actuators via direction switching valves such as spool valves. You may connect. Further, an oil passage branched from a bypass passage (see reference numeral “22” in FIGS. 1 to 4) communicating with the tank 14 may be connected to each hydraulic actuator via a direction switching valve.

  Various modifications may be made to each element of the above-described embodiment and modification examples. In addition, embodiments including components other than the above-described components can also be included in the embodiments of the present invention. Further, a form in which some of the above-described components are not included can also be included in the embodiment of the present invention. Moreover, the form containing the one part component included in one embodiment of this invention and the one part component included in other embodiment of this invention can also be contained in embodiment of this invention. Therefore, the constituent elements included in each of the embodiments and modifications described above and the embodiments of the present invention other than those described above may be combined, and the embodiment related to such combinations may also be included in the embodiments of the present invention. . Moreover, the effect produced by the present invention is not limited to the above-described effect, and a specific effect corresponding to the specific configuration of each embodiment can be exhibited. As described above, various additions, modifications, and partial deletions may be made to each element described in the claims, the description, the abstract, and the drawings without departing from the technical idea and spirit of the present invention. It is.

DESCRIPTION OF SYMBOLS 10 Hydraulic circuit, 11 Oil path, 11a Main oil path, 11b Branch oil path, 11c Branch oil path, 12 Hydraulic source, 13 Regulator, 14 Tank, 21 Tank path, 22 Bypass path, 22a 1st bypass path, 22b 2nd Bypass oil passage, 23 connection passage, 24 negative control oil passage, 30 boom direction switching valve, 31 arm direction switching valve, 40 selector valve, 41 check valve, 42 throttle, 43 line relief make-up valve, 44 discharge control Valve, 45 pressure control valve, 50 spool, 51 main body, 52 tank communication passage, 53 first actuator passage, 54 first upstream unload passage, 55 first downstream unload passage, 56 second upstream unload Passage, 57 second downstream unload passage, 58 bridge passage, 59 second door Couture passage, 60 switching spring, 70 hydraulic excavator, 71 boom, 72 arm, 73 bucket, 74 hydraulic cylinder for boom, 75 arm hydraulic cylinder, 75a piston rod, 75b rod side chamber, 75c head side chamber, 76 hydraulic pressure for bucket Cylinder, 81 Piston rod, 81a Piston part, 81b Rod part, 82 Cylinder tube, 83 Rod side chamber, 84 Head side chamber, a Positive drive position, b Neutral position, c Reverse drive position

Claims (7)

A hydraulic circuit connected to a hydraulic source for supplying hydraulic oil to the oil passage, and a piston rod supporting a vertically driven support member, a hydraulic cylinder having a head side chamber and a rod side chamber,
A selector valve that communicates with the head-side chamber and switches the oil passage in accordance with the pressure of the hydraulic oil from the head-side chamber;
A communication path for communicating the head side chamber and the rod side chamber,
The selector valve is a hydraulic circuit that blocks communication between the hydraulic pressure source and the rod side chamber when the pressure of the hydraulic oil from the head side chamber is equal to or higher than a switching pressure.   2. The hydraulic circuit according to claim 1, wherein when the pressure of the hydraulic oil from the head side chamber is lower than the switching pressure, the selector valve causes the hydraulic source to communicate with the rod side chamber. The communication path connects the head side chamber to a tank passage,
The hydraulic circuit according to claim 1, wherein the rod side chamber communicates with the tank passage and communicates with the head side chamber via the tank passage and the communication path.   The hydraulic circuit according to any one of claims 1 to 3, wherein the selector valve communicates the hydraulic pressure source with a bypass passage when the pressure of the hydraulic oil from the head side chamber is equal to or higher than the switching pressure.   The hydraulic circuit according to claim 4, wherein the hydraulic pressure source is a negative control type hydraulic pump that changes a supply amount of the hydraulic oil according to a pressure of the hydraulic oil in the bypass passage. A directional switching valve that switches the oil path between the hydraulic source and the hydraulic cylinder;
The hydraulic circuit according to claim 1, wherein the selector valve is provided inside the direction switching valve.   The hydraulic circuit according to claim 1, wherein the support member is a boom.

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