JP6999336B2 - Hydraulic circuit - Google Patents

Description

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 vertical direction under the influence of gravity. Considering the drive characteristics of such a boom, various types of hydraulic circuits have been proposed as hydraulic circuits connected to the hydraulic cylinders for driving the boom.

For example, the energy-saving device of 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 a boom cylinder, and is provided with a negative control throttle in an oil passage leading to a tank. The sensor is installed on the upstream side of the negative control aperture. In this energy-saving device, the rotation speed of the engine that drives the hydraulic pump is controlled based on the negative pressure detected by the sensor, and energy saving is achieved.

Further, in the lowering regeneration circuit of the boom of the hydraulic excavator described in Patent Document 2, a throttle is provided in the tank return oil passage on the boom bottom side at the boom lowering position of the directional control valve, and the supply oil passage to the boom rod side is provided. A diaphragm is provided. In addition, a reclaimed oil passage that connects the tank return oil passage and the supply oil passage is provided, and a check valve is interposed in this reclaimed oil passage. According to this regenerative circuit, the return oil from the boom bottom side can be returned to the boom rod side via the regenerative oil passage by increasing the pressure by the throttle during the boom lowering operation, so that it is from the hydraulic pump. The oil supply can be reduced.

Further, in the hydraulic circuit described in Patent Document 3, when the boom is lowered without a force acting against the lowering of the boom, the first switching valve opens the first center bypass oil passage and discharges the first hydraulic pump. While reducing the amount, the 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 that opposes the descent of the boom is acting, the first center bypass oil passage is closed by the first switching valve and the pump discharge amount is increased.

Japanese Unexamined Patent Publication No. 2007-333017 Japanese Unexamined Patent Publication No. 10-089317 Japanese Unexamined Patent Publication No. 11-247236

In the above-mentioned conventional hydraulic circuit, measures have been taken such as suppressing the supply amount of hydraulic oil supplied from the hydraulic source (hydraulic pump) when the boom is lowered, but the configuration is simplified, the cost is reduced, and the energy is saved. There is room for further improvement regarding.

For example, in a device that controls the output of hydraulic oil of a hydraulic pump based on the detection result of a sensor, such as the energy-saving device of Patent Document 1, since the installation of the sensor is indispensable, the device configuration becomes complicated and the cost increases. .. Further, in the regenerative circuit of Patent Document 2, even when the boom can be lowered by using its own weight, for example, when the boom is lowered while the bucket is in the air, the hydraulic pump to the boom cylinder (particularly the boom). Oil is supplied to the rod side). Supplying hydraulic oil, which is not originally required, from the hydraulic pump to the boom cylinder causes energy loss, so that optimum energy saving is not always achieved. Further, 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 acting, the pressure oil from the hydraulic pump is supplied to the boom cylinder, which causes energy loss. There is.

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

One aspect of the present invention is connected to a hydraulic source that supplies hydraulic oil to the oil passage, and a hydraulic cylinder having a piston rod, a head-side chamber, and a rod-side chamber that support a support member driven in the vertical direction. It is a hydraulic circuit and is equipped with a selector valve that communicates with the head side chamber and switches the oil passage according to the pressure of the hydraulic oil from the head side chamber, and a connecting path that communicates between the head side chamber and the rod side chamber. The selector valve relates to a hydraulic circuit that cuts off 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 communicate the hydraulic 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 communication path may communicate the head-side chamber with the tank passage, and the rod-side chamber may communicate with the tank passage and communicate with the head-side chamber via the tank passage and the communication path.

The selector valve may allow the hydraulic source to communicate with 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 source may be a negative control type hydraulic pump that changes the supply amount of the hydraulic oil according to the pressure of the hydraulic oil in the bypass passage.

The hydraulic circuit further comprises a directional switching valve that switches the oil passage between the hydraulic source and the hydraulic cylinder, and the selector valve may be provided inside the directional switching valve.

The support member may be a boom.

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

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

An embodiment 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 size, scale, etc. are shown differently from those actually shown for ease of 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 the boom, and the subject of the present invention is the boom. It is not limited to the hydraulic circuit for drive control of.

1 to 4 are circuit diagrams showing a circuit configuration example of the hydraulic circuit 10 according to the embodiment of the present invention. FIG. 1 shows a state in which the boom direction switching valve 30 is arranged at the neutral position b and the arm direction switching valve 31 is arranged at the neutral position b. 2 and 4 show a state in which the boom direction switching valve 30 is arranged at the reverse drive position c and the arm direction switching valve 31 is arranged at the neutral position b, and FIG. 2 shows a state in which the boom 71 is a bucket. A case where the boom 71 is away from the ground together with the arm 72 (hereinafter, also referred to as “aerial state”) is shown, and FIG. 4 shows a state in which the boom 71 is in contact with the ground via the bucket 73 and the arm 72 (hereinafter, “the air”). It is also referred to as "grounded state"). FIG. 3 shows a state in which the boom direction switching valve 30 is arranged at the reverse drive position c and the arm direction switching valve 31 is arranged at the reverse drive position c.

Note that FIGS. 1 to 4 show the oil passage configuration 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 hydraulic cylinder 75 for the arm is shown in both the circuit diagram and the external view, but these refer to the same hydraulic cylinder 75 for the arm.

The hydraulic circuit 10 shown in FIGS. 1 to 4 is connected to a hydraulic source 12, a boom hydraulic cylinder 74, and an arm hydraulic cylinder 75, and provides an oil passage 11 between the hydraulic source 12 and the boom hydraulic cylinder 74. A boom directional switching valve 30 for switching and an arm directional switching valve 31 for switching the oil passage 11 between the hydraulic source 12 and the hydraulic cylinder 75 for the arm are provided. In the present specification, the term oil passage 11 is a general term for passages through which hydraulic oil is flowed. 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 composed of spool valves. The direction switching valves 30 and 31 shown in FIGS. 1 to 4 switch the oil passage 11 according to the pilot hydraulic pressure applied to the spool, but may be configured by another valve body (electromagnetically driven type spool valve or the like). .. Although a bucket direction switching valve is also provided between the hydraulic source 12 and the bucket hydraulic cylinder 76, the bucket direction is shown in FIGS. 1 to 4 in order to simplify the overall configuration and facilitate understanding. The switching valve is omitted, and detailed description of the drive control of the bucket directional switching valve and the bucket hydraulic cylinder 76 will be omitted below. However, the connection mode of the bucket directional switching valve and the bucket hydraulic cylinder 76 to the oil passage 11 and the supply mode of the hydraulic oil can be the same as those of the arm directional switching valve 31 and the arm hydraulic cylinder 75.

The hydraulic source 12 is composed of a variable displacement hydraulic pump that supplies hydraulic oil to the oil passage 11, and the amount of hydraulic oil supplied to the oil passage 11 can be increased or decreased under the control of the regulator 13. The hydraulic source 12 of the present embodiment is 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 composed of 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 uses the hydraulic oil from the hydraulic 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 supply amount of the hydraulic oil from the hydraulic source 12. Increase.

The oil passage 11 extending from the hydraulic source 12 includes an oil passage 11a extending toward the boom direction switching valve 30 (hereinafter, also referred to as “main oil passage”) and two oil passages branching from the main oil passage 11a (hereinafter, “main oil passage”). (Also referred to as "branch oil passage") 11b, 11c, the main oil passage 11a and the branch oil passage 11b, 11c are connected in parallel to the hydraulic source 12. One of the branch oil passages 11b is intended to be communicated with the bypass passage 22 (particularly, the first bypass passage 22a) via the boom direction switching valve 30, depending on the operating state of the boom direction switching valve 30. The communication and disconnection between the branch oil passage 11b and the bypass passage 22 are controlled. The other branch oil passage 11c is intended to be communicated with the arm hydraulic cylinder 75 via the arm direction switching valve 31, and the branch oil passage 11c is intended to be communicated with the arm hydraulic cylinder 75 according to the operating state of the arm direction switching valve 31. Communication and disconnection between the arm and the hydraulic cylinder 75 for the arm are controlled.

The boom hydraulic cylinder 74 has a piston rod 81 and a cylinder tube 82. The piston rod 81 has a piston portion 81a arranged in the cylinder tube 82, and a rod portion 81b provided integrally with the piston portion 81a and extending from the inside to the outside of the cylinder tube 82. A boom 71 is rotatably connected to one tip 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 upward by increasing the amount of protrusion of the piston rod 81 from the cylinder tube 82, and the boom 71 is driven downward 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 so that hydraulic oil does not leak between the rod side chamber 83 and the head side chamber 84 in the cylinder tube 82, and the inside of the cylinder tube 82. Is provided so that it can be moved.

The arm hydraulic cylinder 75 is basically configured in the same manner as the boom hydraulic cylinder 74 described above, and has a movable piston rod 75a, a variable capacity rod-side chamber 75b, and a head-side chamber 75c. Although the bucket hydraulic cylinder 76 is not shown as a circuit diagram, it is basically configured in the same manner as the boom hydraulic cylinder 74 and the arm hydraulic cylinder 75 described above, and is a movable piston rod. And a rod-side chamber and a head-side chamber with variable capacitance.

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 is provided with the boom direction switching valve 30 arranged at the reverse drive position c. And the rod-side chamber 83 are communicated with each other via the communication path 23. That is, the head-side chamber 84 is communicated with the tank passage 21 connected to the tank 14 via the connecting 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 communicate with each other or shut off from each other via the tank passage 21 and the connecting path 23, depending on the driving state of the boom direction switching valve 30.

A line relief make-up valve 43 is provided in the oil passage 11 between the tank passage 21 and the rod-side chamber 83. The line relief make-up valve 43 includes a check valve 41 and a pressure control valve 45 provided in parallel with 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 flow of hydraulic oil from the tank passage 21 side toward the rod side chamber 83 side, but allows the flow of hydraulic oil from the rod side chamber 83 side toward the tank passage 21 side. Do not allow. The pressure control valve 45 of the line relief make-up valve 43 has an oil passage 11 and a tank on the rod side chamber 83 side 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. When the pressure of the hydraulic oil in the oil passage 11 on the rod side chamber 83 side is equal to or less than the predetermined valve opening pressure, the oil passage 11 on the rod side chamber 83 side and the tank passage are communicated with each other. The communication with the oil passage 11 on the 21 side is cut off.

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 is passed through the check valve 41 of the line relief make-up valve 43. Hydraulic oil flows from the oil passage 11 on the 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 pressure of the hydraulic oil in the oil passage 11 on the tank passage 21 side and from the valve opening pressure of the pressure control valve 45 of the line relief make-up valve 43. If it is also small, 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 larger than the valve opening pressure of the pressure control valve 45 of the line relief make-up valve 43. If it is large, the pressure control valve 45 opens, and hydraulic oil flows from the oil passage 11 on the rod side chamber 83 side to the oil passage 11 on the tank passage 21 side.

In this way, 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 the oil passage on the rod side chamber 83 side. When the pressure of the hydraulic oil in the rod side 11 becomes excessive, the hydraulic oil escapes from the oil passage 11 on the rod side chamber 83 side to the oil passage 11 on the tank passage 21 side, and the pressure of the hydraulic oil in the rod side chamber 83 becomes excessive. It also has a function to prevent. 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 make-up valve 43. On the other hand, when the boom direction switching valve 30 is arranged at the reverse drive position c, the connecting path 23 communicates the head side chamber 84 with the tank passage 21. Therefore, when the boom direction switching valve 30 is arranged at the reverse drive position c, the head side chamber 84 and the rod side chamber 83 are the oil passage 11 including the communication path 23 and the tank passage 21, and the line relief. It communicates with each other via the make-up valve 43. 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 connecting path 23 and the pressure of the hydraulic oil in the rod side chamber 83 is large or small. Depending on the relationship and the magnitude of the hydraulic oil pressure in the rod-side chamber 83, the hydraulic oil flow between the tank passage 21 (and thus the head-side chamber 84) and the rod-side chamber 83 can be adjusted appropriately. can.

The hydraulic circuit 10 further includes 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. With the boom direction switching valve 30 arranged at the reverse drive position c, the selector valve 40 communicates with the head side chamber 84 via the oil passage 11 (particularly the connecting path 23) and operates from the head side chamber 84. The oil passage 11 is switched according to the oil pressure (the pressure of the hydraulic oil in the connecting 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 has the hydraulic pressure source 12 and the rod side chamber 83. Block the communication between (see the sign "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 has the hydraulic pressure source 12 and the rod side chamber 83. (See the sign "f" in FIG. 4).

Further, in the selector valve 40, when the pressure of the hydraulic oil from the head side chamber 84 is equal to or higher than the switching pressure (see the sign “e” in FIG. 2), the hydraulic source 12 is set to the bypass passage 22 (particularly, the first bypass passage 22a). When the hydraulic oil pressure from the head-side chamber 84 is lower than the switching pressure, the communication is cut off between the hydraulic source 12 and the bypass passage 22 (see the 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 configured by the same tank. The bypass passage 22 shown in FIGS. 1 to 4 is provided with an arm direction switching valve 31, and the bypass passage 22 has a first bypass passage 22a on the upstream side of the arm direction switching valve 31 and an arm direction. It is divided into a second bypass oil passage 22b on the downstream side of the switching valve 31. Both ends of the first bypass passage 22a are controlled to open and close by the boom direction switching valve 30 and the arm direction switching valve 31, respectively. Further, one end of the second bypass oil passage 22b 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 directional control valve 31 for the arm.

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 appliances as appropriate. For example, a check valve 41 is provided in the main oil passage 11a and the branch oil passage 11c. Further, a throttle 42 is provided in the connecting path 23, and the throttle 42 is provided on the downstream side (that is, the tank 14 side) of the connecting path 23 from the portion connected to the selector valve 40. Therefore, the switching of the oil passage 11 (see the symbols “e” and “f” shown in FIGS. 1 to 4) by the selector valve 40 is the operation of the connecting passage 23 whose pressure is increased by the throttle 42 provided in the connecting passage 23. It is done according to the pressure of the oil. Further, 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 (that is, the tank 14 side) of the second bypass oil passage 22b from the portion connected to the negative control oil passage 24. Therefore, the control of the hydraulic pressure source 12 by the regulator 13 is performed according to the pressure of the hydraulic 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 the predetermined valve opening pressure. Open to increase the flow of hydraulic oil towards the tank 14.

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

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

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

Next, as shown in FIG. 2, the boom directional switching valve 30 is arranged at the reverse drive position c, the arm directional switching valve 31 is arranged at the neutral position b, and the boom 71 is in the air 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. Further, under the influence of gravity, the piston rod 81 descends due to the weight of the boom 71 and the like, 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 communicating with the head side chamber 84 increases. It becomes equal to or more 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, blocks the communication between the hydraulic source 12 (particularly the main oil passage 11a) and the rod side chamber 83, and branches oil. The hydraulic pressure source 12 is communicated with the first bypass passage 22a via the path 11b. On the other hand, the arm direction switching valve 31 cuts off 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 them is cut off, and the first bypass passage 22a and the second bypass oil passage 22b are communicated with each other.

In this case, the high-pressure hydraulic oil discharged from the head-side chamber 84 is flowed toward the tank 14 via the connecting path 23 and the tank passage 21, and the connecting path 23, the tank passage 21, and the line relief make-up valve 43. It is supplied (that is, regenerated) to the boom hydraulic cylinder 74 via (particularly the check valve 41). As a result, the shortage of the amount and pressure of the hydraulic oil in the rod-side chamber 83 whose volume increases with the lowering of the piston portion 81a is compensated for, and the boom 71 can be lowered by utilizing its own weight. On the other hand, the hydraulic oil discharged from the hydraulic 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 source 12 is suppressed to a low level to save energy. Can be done.

Next, as shown in FIG. 3, the boom directional switching valve 30 is arranged at the reverse drive position c, the arm directional switching valve 31 is also arranged at the reverse drive position c, and the boom 71 is in the air together with the bucket 73 and the arm 72. The case where it is in is explained. In this case, as in the case shown in FIG. 2 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 sign "e" in FIGS. 1 to 4. Therefore, the boom direction switching valve 30 cuts off the communication between the rod side chamber 83 and the hydraulic source 12 (particularly the main oil passage 11a), and makes the hydraulic source 12 into the bypass passage 22 via the branch oil passage 11b. Communicate. On the other hand, the directional control valve 31 for the arm communicates the rod-side chamber 75b and the tank passage 21, and communicates the head-side chamber 75c and the hydraulic source 12 (particularly the branch oil passage 11c) with the first bypass passage 22a and the first. 2 The communication with the bypass oil passage 22b is cut off.

In this case, the high-pressure hydraulic oil discharged from the head-side chamber 84 is the boom hydraulic cylinder 74 via the connecting path 23, the tank passage 21, and the line relief make-up valve 43, as in the case shown in FIG. 2 above. The boom 71 descends using its own weight. On the other hand, a part of the hydraulic oil discharged from the hydraulic source 12 is supplied to the head side chamber 75c via the branch oil passage 11c. Further, the hydraulic oil discharged from the rod-side chamber 75b 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, in driving the hydraulic cylinder 74 for the boom, the own weight of the boom 71 or the like is used, and the high-pressure hydraulic oil discharged from the head side chamber 84 and the rod side chamber 75b is used, and the hydraulic oil from the hydraulic source 12 is used. It is not necessary to use the hydraulic oil to drive the hydraulic cylinder 75 for the arm. Therefore, the hydraulic oil newly supplied from the hydraulic source 12 can be efficiently used for driving the hydraulic cylinder 75 for the arm, and energy saving can be achieved. Since the second bypass oil passage 22b is shut off 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, which is negative. The control type hydraulic source 12 increases the supply amount of hydraulic oil. Thereby, 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 arranged at the reverse drive position c, the arm direction switching valve 31 is arranged at the neutral position b, and the boom 71 is grounded via the bucket 73 and the arm 72. The case of being 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 the grounded state, the weight of the boom 71 or the like cannot be basically used in the downward drive of the piston rod 81. Therefore, 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 communicating with the head-side chamber 84 becomes smaller than the switching pressure of the selector valve 40. Therefore, the selector valve 40 takes the state indicated by the sign “f” in FIG. 4, allows the hydraulic pressure source 12 to communicate with the rod side chamber 83 via the main oil passage 11a, and the hydraulic source 12 (particularly the branch oil passage 11b). The communication between the bypass passage 22 and the bypass passage 22 (particularly the first bypass passage 22a) is cut off. On the other hand, the arm direction switching valve 31 cuts off 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 them is cut off, and the first bypass passage 22a and the second bypass oil passage 22b are communicated with each other.

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 applied to the head side chamber 84. The pressure becomes higher than the pressure of the hydraulic oil, the piston portion 81a receives a downward force, and the boom 71 is lowered. The head-side chamber 84 is communicated to the tank passage 21 via the connecting 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, so that the head-side chamber 84 is connected to the head side. No hydraulic oil is 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 connecting path 23 and the tank passage 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 to the tank 14, the tank passage 21, and the head-side chamber 84. Further, 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 type hydraulic source 12 increases the supply amount of the hydraulic oil. Thereby, a sufficient amount and sufficient pressure of hydraulic oil can be supplied to the rod side chamber 83 via the main oil passage 11a.

Although detailed description will be omitted, when the boom direction switching valve 30 is arranged 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 communicates with the tank passage 21, and the communication between the branch oil passage 11b and the first bypass passage 22a is cut off. 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 to 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 arranged 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, and the arm hydraulic cylinder 75 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 cut off. In this case, the hydraulic oil discharged from the hydraulic source 12 is supplied to the rod side chamber 75b, the hydraulic oil discharged from the head side chamber 75c flows out to the tank passage 21, the protrusion amount of the piston rod 75a is reduced, and the arm The 72 is swung in the ascending direction with the connection point with the boom 71 as a fulcrum. Further, the bypass passage 22 is cut off by the directional control valve 30 for the boom and / or the directional switching valve 31 for the arm, and the negative control type hydraulic source 12 increases the supply amount of the hydraulic oil to supply a sufficient amount and sufficient pressure of the hydraulic oil. It can be supplied to the head side chamber 84 and / or the rod side chamber 75b.

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

5 to 8 are partial cross-sectional views showing an example of the boom direction switching valve 30 and the selector valve 40. FIG. 5 shows a state in which the boom 71 is in the grounded state and the boom direction switching valve 30 is arranged at the neutral position b. FIG. 6 shows a state in which the boom 71 is in the air and the boom direction switching valve 30 is arranged at the reverse drive position c. FIG. 7 shows a state in which the boom 71 is in the grounded state and the boom direction switching valve 30 is arranged at the reverse drive position c. FIG. 8 shows a state in which the boom direction switching valve 30 is arranged at the positive drive position a. The boom directional switching valve 30 and the selector valve 40 shown in FIGS. 5 to 8 are not necessarily structurally and functionally the same as the boom directional switching valve 30 and the selector valve 40 shown in FIGS. 1 to 4 described above. Although they do not match, they generally correspond to the boom direction switching valve 30 and the selector valve 40 shown in FIGS. 1 to 4. Therefore, those skilled in the art can fully understand the structures and functions of the boom directional control 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 inside the spool 50. The spool 50 is formed with a plurality of land portions and a plurality of notches (including a groove portion in the spool 50 in which the selector valve 40 is housed and a hole portion connecting the outside of the spool 50), and the spool with respect to the main body portion 51. The oil passage 11 is switched according to the relative slide position of 50. A plurality of land portions and a plurality of notches are also formed in the selector valve 40, and the oil passage 11 is switched according to the slide position of the selector valve 40 relative to the spool 50.

The main body 51 is communicated with a tank passage 52 communicated with the tank passage 21, a first actuator passage 53 communicated with the rod side chamber 83, a bridge passage 58 communicated with the hydraulic source 12, and a branch oil passage 11b. 1st upstream unload passage 54 and 2nd upstream unload passage 56, 1st downstream unload passage 55 and 2nd downstream unload passage 57 communicated with 1st bypass passage 22a, and head side chamber. A second actuator passage 59 communicating with the 84 is formed. Although not shown, the main body 51 also has a tank communication passage that communicates with the tank 14 on the side opposite to the bridge passage 58 (on the right side in FIGS. 5 to 8) via the second actuator passage 59. It is formed.

A connecting path 23 is further formed in the spool 50. One end of the connecting path 23 (the left end of FIGS. 5 to 8) communicates with one end of the selector valve 40 (the right end of FIGS. 5 to 8), and the other end of the connecting path 23. The portion (the right end portion in FIGS. 5 to 8) communicates with the notch portion 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 slide position of the selector valve 40 is the force of the hydraulic oil from the connecting 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 is determined according to the elastic force. Therefore, the hydraulic oil is not supplied from the connecting path 23 to one end of the selector valve 40, or the force of the hydraulic oil from the connecting path 23 acting on one end of the selector valve 40 is the force of the selector valve 40. In a state 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 is arranged at the right position in FIGS. 5 to 8.

For example, when the boom directional control valve 30 is arranged at the neutral position b (see FIG. 1), the boom directional 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 connecting passage 52, and the second actuator passage 59 is cut off from the bridge passage 58 and the tank connecting passage (not shown) via the land portion of the spool 50. On the other hand, the first upstream unload passage 54 and the first downstream unload passage 55 communicate with each other via the notch of the spool 50 and the notch of the selector valve 40, and communicate with the second upstream unload passage 56. The second downstream unload passage 57 communicates with each other via a notch in the spool 50. Therefore, 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 is passed through the branch oil passage 11b to the first upstream side unload passage 54 and the second upstream side unload passage. It flows into 56 and flows out to the first bypass passage 22a via the first downstream unload passage 55 and the second downstream unload passage 57.

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

On the other hand, when the boom 71 is in the air and the boom direction switching valve 30 is arranged 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. Is placed in. That is, the spool 50 is arranged to the right of the position shown in FIG. 5 by the pilot pressure. Further, the hydraulic oil from the head side chamber 84 flows into the connecting path 23 through the second actuator passage 59, pushes the selector valve 40 to compress the switching spring 60, and positions the selector valve 40 at the left position in FIG. Place it. As a result, the first actuator passage 53 is cut off from the bridge passage 58 via the land portion of the spool 50. Further, the second actuator passage 59 is cut off from the bridge passage 58 via the land portion of the spool 50, and is connected to the tank connecting passage (not shown) via the notch portion of the spool 50 and the connecting path 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 of the spool 50 and the notch of the selector valve 40, and communicate with the second upstream unload passage 56. The second downstream unload passage 57 communicates with each other via a notch in the spool 50. Therefore, 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 side unload passage 54 and the second upstream side unload passage 56 from the branch oil passage 11b. And flows out to the first bypass passage 22a via the first downstream side unload passage 55 and the second downstream side unload passage 57. On the other hand, the hydraulic oil discharged from the head-side chamber 84 flows into the tank communication passage (not shown) through the connecting path 23, and flows from the tank communication passage into the tank communication passage indicated by the symbol 52 in FIG. It is supplied (regenerated) from the tank communication passage 52 to the rod side chamber 83 via the first actuator passage 53.

Further, when the boom 71 is in the grounded state and the boom direction switching valve 30 is arranged at the reverse drive position c (see FIG. 4), the boom direction switching valve 30 and the spool 50 are arranged as shown in FIG. To. That is, the spool 50 is basically arranged at the same position as shown in FIG. 6 with respect to the main body 51 by the pilot pressure. However, the force applied to the selector valve 40 by the hydraulic oil flowing from the head side chamber 84 to the connecting path 23 via the second actuator passage 59 is smaller than the force applied to the selector valve 40 by the switching spring 60, and the selector valve 40 Is pushed by the switching spring 60 and is arranged at the right position in FIG. 7. As a result, the first actuator passage 53 communicates with the bridge passage 58 via the notch of the spool 50 and the notch of the selector valve 40. Further, the second actuator passage 59 is cut off from the bridge passage 58 via the land portion of the spool 50, and is connected to the tank connecting passage (not shown) via the notch portion of the spool 50 and the connecting path 23. On the other hand, the first upstream side unload passage 54 and the first downstream side unload passage 55 are cut off from each other via the land portion of the spool 50 and the land portion of the selector valve 40, and become the second upstream side unload passage 56. The second downstream unload passage 57 is cut off from each other via the land portion of the spool 50. Therefore, 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 cut off 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 passage (not shown) through the connecting passage 23, and the tanks (symbols “14” in FIGS. 1 to 4 (not shown) are not shown from the tank communication passage. See).

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 arranged to the left of the position shown in FIG. 5 by the pilot pressure. As a result, the rod-side chamber 83 is communicated with the tank passage 21 via the first actuator passage 53 and the tank communication passage 52, and the head-side chamber 84 is communicated with the hydraulic 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 blocked 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 downward. 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 potential energy of the boom 71 or the like can be effectively used, and the boom lowering operation can be performed with energy efficiency.

Further, the selector valve 40 communicates the hydraulic pressure source 12 with 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 (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 that 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 descends and touches the ground and the pressure of the hydraulic oil from the head side chamber 84 is lower than the switching pressure of the selector valve 40, the pressure side from the hydraulic source 12 to the rod side. Since the piston rod 81 can be lowered by the hydraulic oil supplied to the chamber 83, the work of compacting the ground by the bucket 73 and lifting the body of the hydraulic excavator 70 can be efficiently performed.

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 switching valve 30, and the boom directional switching valve 30 and the selector valve 40 are integrally configured. A selector valve 40 may be provided on the outside, and the boom direction switching valve 30 and the selector valve 40 may be separated from each other.

Further, FIGS. 1 to 4 show a hydraulic circuit 10 mainly connected to the boom hydraulic cylinder 74 and the arm hydraulic cylinder 75, but the bucket hydraulic cylinder 76 and other hydraulic cylinders 70 are configured. A hydraulic actuator (for example, a traveling hydraulic motor for driving a wheel (crawler) or a turning hydraulic motor for turning a 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, the oil passages extending from the hydraulic source 12 are branched, and these branch oil passages connected in parallel to the hydraulic source 12 are connected to each hydraulic actuator via a direction switching valve such as a spool valve. You may connect. Further, an oil passage branched from a bypass passage communicating with the tank 14 (see the symbol “22” in FIGS. 1 to 4) may be connected to each hydraulic actuator via a directional control valve.

In addition, various modifications may be added to each element of the above-described embodiment and modification. Further, an embodiment including a component other than the above-mentioned components may also be included in the embodiment of the present invention. Further, an embodiment of the present invention may also include a form in which some of the above-mentioned components are not included. In addition, an embodiment of the present invention may also include some components included in one embodiment of the present invention and some components included in other embodiments of the present invention. Therefore, the components included in each of the above-described embodiments and modifications and the embodiments of the present invention other than the above may be combined, and the embodiments related to such combinations may also be included in the embodiments of the present invention. .. Further, the effect produced by the present invention is not limited to the above-mentioned effect, and a peculiar effect according to the specific configuration of each embodiment can be exhibited. In this way, various additions, changes and partial deletions can be made to each element described in the claims, the specification, the abstract and the drawings without departing from the technical idea and purpose of the present invention. Is.

10 hydraulic circuit, 11 oil passage, 11a main oil passage, 11b branch oil passage, 11c branch oil passage, 12 hydraulic source, 13 regulator, 14 tank, 21 tank passage, 22 bypass passage, 22a first bypass passage, 22b second Bypass oil pressure passage, 23 connecting 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 1st actuator passage, 54 1st upstream unload passage, 55 1st downstream unload passage, 56 2nd upstream unload Passage, 57 2nd downstream unload passage, 58 bridge passage, 59 2nd actuator passage, 60 switching spring, 70 hydraulic excavator, 71 boom, 72 arm, 73 bucket, 74 boom hydraulic cylinder, 75 arm hydraulic cylinder, 75a piston rod, 75b rod side chamber, 75c head side chamber, 76 bucket hydraulic 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 that supplies hydraulic oil to an oil passage, a piston rod that supports a support member that is driven in the vertical direction, and a hydraulic cylinder that has a head-side chamber and a rod-side chamber.
A selector valve that communicates with the head-side chamber and switches the oil passage according to 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 is provided.
The selector valve is a hydraulic circuit that cuts off 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 hydraulic circuit according to claim 1, wherein 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. The communication path communicates the head-side chamber to the tank passage.
The hydraulic circuit according to claim 1 or 2, wherein the rod-side chamber communicates with the tank passage and communicates with the head-side chamber via the tank passage and the connecting path. The hydraulic circuit according to any one of claims 1 to 3, wherein the selector valve communicates the hydraulic 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 circuit according to claim 4, wherein the hydraulic source is a negative control type hydraulic pump that changes the supply amount of the hydraulic oil according to the pressure of the hydraulic oil in the bypass passage. Further provided with a directional switching valve for switching the oil passage between the hydraulic source and the hydraulic cylinder.
The hydraulic circuit according to any one of claims 1 to 5, wherein the selector valve is provided inside the direction switching valve. The hydraulic circuit according to any one of claims 1 to 6, wherein the support member is a boom.

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