JP2011127280A - Hydraulic circuit of working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a working machine capable of preventing a traveling device from being operated when using an external oil pressure source by a simple configuration. <P>SOLUTION: This hydraulic circuit of the working machine is constituted by providing first selector valves 19a, 19b in a traveling circuit 42b connecting a running motor 10 with a control valve 8 and connecting an external hydraulic fluid introducing passage 63a connected with the external oil pressure source with the first selector valves 19a, 19b. Second selector valves 20a, 20b are installed on a control valve 8 side more than the first selector valves 19a, 19b in the traveling circuit 42b, and a first flow passage 60a formed by branching from a main circuit 43a is connected with the second selector valves 20a, 20b. The first selector valves 19a, 19b can be freely switched to a first position for communicating the running motor 10 with the control valve 8 and a second position for communicating the external hydraulic fluid introducing passage 63a with the control valve 8. The second selector valves 20a, 20b can be freely switched to a third position for communicating the running motor 10 with the control valve 8 and a fourth position for communicating the running motor 10 with the first flow passage 60a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic circuit for a work machine that operates by receiving supply of hydraulic oil from an external hydraulic source as well as a hydraulic source mounted on the work machine.

  Conventionally, in hydraulically driven work machines such as hydraulic excavators, a technique for driving a hydraulic device without relying on an engine (internal combustion engine) has been proposed assuming use in a closed space such as indoors or in a tunnel. ing. For example, Patent Literature 1 discloses an electric hydraulic excavator that drives a hydraulic pump by supplying power from an external power source. In this technique, an electric motor is driven by connecting a power feeding device of a building where indoor work is performed and a hydraulic excavator with a detachable power cable, and the hydraulic pump is driven by this electric motor. In addition, when the power cable is disconnected, the electric motor is driven by the auxiliary battery.

On the other hand, in such an electric hydraulic excavator, a large electric motor having a sufficient output for operating the hydraulic device is required, which may increase the manufacturing cost. Such a problem becomes significant in a hybrid hydraulic excavator equipped with an electric motor and an engine for driving the electric motor.
Therefore, a technique for driving a hydraulic device by receiving pressure oil supply instead of receiving power supply from the outside has been studied. For example, in Patent Document 2, a movable external hydraulic unit is connected to a valve on the construction vehicle side, and the working machine is operated by supplying hydraulic oil from the external hydraulic unit instead of the hydraulic pump mounted on the construction vehicle. Techniques for making them disclosed are disclosed. In this technique, it is said that it can be used as a normal construction vehicle by releasing the connection between the valve and the external hydraulic unit.

JP 2004-225355 A Japanese Utility Model Publication No. 2-50450

  By the way, the hydraulic pump of the hydraulic excavator is generally provided in the pump room of the upper swing body, and hydraulic oil is supplied from here to the front working machine, the swing device in front of the machine body, and the travel device of the lower travel body. Further, since the upper swing body is mounted so as to be swingable with respect to the lower traveling body, swivel joints are provided at these connecting portions. For example, the hydraulic oil flow path that connects the hydraulic pump and the traveling device is provided inside the swivel joint so that the hydraulic oil flow path is not blocked by the turning operation of the airframe.

  On the other hand, in the technique of Patent Document 2, a connection pipe through which hydraulic oil from an external hydraulic unit circulates is connected to a valve. Therefore, when hydraulic oil is supplied from a lower traveling body located below the machine body, the connection pipe is swiveled. Need to be inserted into the joint. That is, it is necessary to provide a hydraulic oil flow path from the external hydraulic unit in addition to the hydraulic oil flow path used when driving the traveling device with a hydraulic pump inside the swivel joint, and the structure is complicated. There is.

In particular, since high-pressure hydraulic fluid flows in the drive circuit of the hydraulic device mounted on the hydraulic excavator, the larger the number of hydraulic fluid channels arranged across the upper swing body and the lower traveling body, the larger the hydraulic fluid. An expensive swivel joint must be used, making it difficult to keep manufacturing costs low.
In addition, when supplying high-pressure hydraulic fluid from the outside of the hydraulic excavator, it may be desired to prevent the hydraulic excavator from moving from the viewpoint of protecting the hydraulic circuit. On the other hand, as described in Patent Document 2, in the configuration in which hydraulic fluid from the outside is introduced into the valve, the valve may be operated by operating the travel lever, and the hydraulic fluid may be supplied to the travel device. That is, in order to prevent the operation of the traveling device with the technique of Patent Document 2, valve control different from valve control during normal work is required, and there is a problem that the circuit configuration and control configuration become complicated.

One of the purposes of this case was created in view of such problems, and is to enable the use of an external hydraulic power source with a simple configuration, or the operation of the traveling device when the external hydraulic power source is used. Is to prevent.
In addition, the present invention is not limited to the above-mentioned object, and is an operational effect derived from each configuration shown in the embodiment for carrying out the invention, which will be described later. Can be positioned.

  The disclosed hydraulic circuit for a work machine is a hydraulic circuit for a work machine that supplies hydraulic oil discharged from a hydraulic source to a travel motor and a hydraulic actuator via a control valve and discharges the hydraulic oil to a tank via the control valve. An external hydraulic oil introduction path connected to an external hydraulic power source provided separately from the hydraulic power source, and a running circuit connecting the travel motor and the control valve, and the external hydraulic oil Connected to the introduction path and provided to be switchable between two positions: a first position where the travel motor and the control valve communicate with each other, and a second position where the external hydraulic oil introduction path and the control valve communicate with each other. A first switching valve having a valve body, a first flow path formed by branching from a main circuit connecting the hydraulic pressure source and the control valve, and a control valve side of the traveling circuit rather than the first switching valve. And connected to the first flow path, A second switching valve having a valve body provided to be switchable between two positions, a third position for communicating the control valve and the control valve, and a fourth position for communicating the traveling motor and the first flow path; A first merging check valve that is interposed closer to the hydraulic power source than a branch point with the first flow channel in the main circuit, and prevents backflow from the control valve side to the hydraulic power source side; And a second merging check valve that prevents backflow from the main circuit side to the second switching valve side.

For example, when the hydraulic power source is used, the valve body of the first switching valve is set to the first position, and the valve body of the second switching valve is set to the third position. When the external hydraulic power source is used, the valve body of the first switching valve is set to the second position, and the valve body of the second switching valve is set to the fourth position.
Further, the hydraulic circuit of the disclosed working machine is interposed on an external return flow path connected to an external tank provided separately from the tank, and a return circuit connecting the control valve and the tank. Connected to the external return flow path, and is switchable between a fifth position for communicating the control valve and the tank, and a second position for communicating the control valve and the external return flow path. And a return switching valve having a valve body.

For example, when the hydraulic pressure source is used, the valve body of the return switching valve is set to the fifth position. When using an external hydraulic power source, the valve body of the return switching valve is set to the sixth position.
Further, the hydraulic circuit of the disclosed working machine includes a pilot circuit that generates a pilot pressure for setting an operation amount of the hydraulic actuator, and a second flow that is branched from the first flow path and connected to the pilot circuit. And a pressure reducing valve interposed on the second flow path.

Further, the hydraulic circuit of the disclosed working machine includes a negative control pressure detecting unit that detects the working hydraulic pressure of the center bypass in the control valve as a negative control pressure, and the external control based on the negative control pressure detected by the negative control pressure detection unit. An external negative control device for controlling the flow rate of hydraulic fluid from the hydraulic source is further provided.
Further, the hydraulic circuit of the disclosed working machine is characterized in that the first switching valve is provided in a lower traveling body of the working machine and the second switching valve is provided in an upper swing body of the working machine. It is said.

  According to the hydraulic circuit of the disclosed working machine, the hydraulic oil supplied from the external hydraulic source is introduced into the traveling circuit and introduced into the main circuit through the first flow path, so that not only the hydraulic source but also the external hydraulic pressure is introduced. The hydraulic actuator can be driven using the power source. Further, it is possible to reliably prevent the traveling device from operating when the external hydraulic power source is used.

It is a figure which shows the hydraulic shovel and the external hydraulic device to which the hydraulic circuit which concerns on one Embodiment is applied, (a) is a side view of a hydraulic shovel, (b) is a side view of an external hydraulic device. FIG. 2 is a hydraulic circuit diagram and a block configuration diagram of the hydraulic excavator in FIG. FIG. 2 is a hydraulic circuit diagram and a block configuration diagram of the external hydraulic device in FIG.

Hereinafter, an embodiment of a hydraulic control device for a work machine will be described with reference to the drawings. However, the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not clearly shown in the embodiment described below. That is, the present embodiment may be variously modified and implemented without departing from the spirit of the invention.
[1. overall structure]
The present invention is applied to a hydraulic excavator 70 (work machine) shown in FIG. The hydraulic excavator 70 includes a lower traveling body 71 equipped with a crawler traveling device and an upper swing body 72 mounted on the lower traveling body 71. The upper turning body 72 is installed on the lower traveling body 71 so as to be turnable via a turning device. A rotary joint 16 (swivel joint) in which a flow path for hydraulic oil is formed is provided at a connection portion between the lower traveling body 71 and the upper swing body 72.

  A front work machine 80 provided so as to extend forward of the vehicle is provided on the vehicle front side of the upper turning body 72, and a cab 74 on which an operator gets on the left side of the vehicle body is provided. A counterweight 73 for balancing the weight of the aircraft is provided at the rear end of the upper swing body 72, and an engine room 75 is provided on the front side of the aircraft. Inside the engine room 75, an engine 3 (internal combustion engine) is arranged.

  In the pump room adjacent to the engine room 75, main pumps 5 and 6 and a pilot pump 7 which are hydraulic drive sources of various hydraulic devices mounted on the hydraulic excavator 70 are provided. The main pumps 5 and 6 and the pilot pump 7 are connected to the output shaft of the engine 3 via the pump drive 4. The pump drive 4 functions as a transmission that distributes the power generated by the engine 3 to the pumps 5, 6, and 7 and adjusts the rotational speed and torque. When the engine 3 is operated, the main pumps 5 and 6 and the pilot pump 7 are driven, and hydraulic oil discharged from the main pumps 5 and 6 and the pilot pump 7 is supplied to a hydraulic circuit described later.

  The front work machine 80 includes a boom 81 whose base end is pivotally supported by the upper swing body 72, an arm 82 pivotally supported at the distal end of the boom 81, and a bucket 83 pivotally supported at the distal end of the arm 82. Have. A pair of boom cylinders 11 is interposed between the boom 81 and the upper swing body 72, and the boom 81 is driven in the vertical direction by an expansion / contraction operation. Similarly, the arm cylinder 12 and the bucket cylinder 13 drive the arm 82 and the bucket 83 by an expansion / contraction operation, respectively. An operation lever for inputting the operation amount of these hydraulic actuators is arranged in the cab 74.

  The frame of the lower traveling body 71 is provided with joints 27a, 27b, and 27c (hose joints) for receiving hydraulic oil supply from outside the airframe when the engine 3 is stopped. Since the main pumps 5 and 6 and the pilot pump 7 do not operate when the engine 3 is stopped, hydraulic oil introduced from these joints 27a and 27b is supplied to a hydraulic circuit described later and discharged from the joint 27c.

An external hydraulic device 90 for supplying hydraulic oil when the engine 3 is stopped is shown in FIG. The external hydraulic device 90 is a power generation unit provided separately from the hydraulic excavator 70, and has a function of supplying hydraulic oil instead of the main pumps 5, 6 and the pilot pump 7.
Inside the external hydraulic device 90, an external electric motor 31, an external pump drive 32, external main pumps 33 and 34, and an external pilot pump 35 that are operated by receiving electric power from the outside are provided. The external main pumps 33 and 34 and the external pilot pump 35 are connected to the output shaft of the external electric motor 31 via the external pump drive 32 and are driven by the external electric motor 31.

  In addition, the external hydraulic device 90 is provided with external joints 49a, 49b, and 49c (hose joints) as hydraulic oil inlets and outlets with the hydraulic excavator 70. For example, when the engine 3 of the hydraulic excavator 70 is stopped, the external joints 49a, 49b, 49c and the joints 27a, 27b, 27c on the hydraulic excavator 70 side are connected by a hose or the like to form a hydraulic circuit.

[2. Excavator hydraulic circuit]
FIG. 2 shows an overall configuration of the excavator side hydraulic circuit 1 related to the driving of the excavator 70.
The excavator side hydraulic circuit 1 is a circuit that constitutes a hydraulic oil flow path from the pair of main pumps 5 and 6 to various actuators and a hydraulic oil flow path from the pilot pump 7 to the pilot circuit 15. As examples of various actuators, a boom cylinder 11, an arm cylinder 12, a bucket cylinder 13, travel motors 9 and 10, and a swing motor 14 are shown in FIG. 2. The traveling motors 9 and 10 are respectively provided in the left and right traveling devices of the lower traveling body 71.

  A main control valve 8 (control valve) incorporating a plurality of control valves is provided on a hydraulic circuit between the main pumps 5 and 6 and various actuators. The main control valve 8 is a valve unit in which a plurality of valves for controlling the flow rate and flow direction of hydraulic oil to various actuators are incorporated. The hydraulic oil discharged from the main pumps 5 and 6 is supplied to each actuator via the main control valve 8, and return oil from each actuator flows to the tank 40 via the main control valve 8.

Hereinafter, the hydraulic fluid passage between the main pumps 5 and 6 and the main control valve 8 is referred to as main circuits 43a and 43b, and the hydraulic fluid passage between the main control valve 8 and the traveling motors 9 and 10 is referred to as a main fluid passage. This is referred to as travel circuits 42a and 42b. The hydraulic oil flow path between the main control valve 8 and the tank 40 is called a return circuit 44.
Each of the main pumps 5 and 6 is provided with regulators 5a and 6a (swash plate control mechanism) for controlling the discharge flow rate and the discharge pressure by adjusting the inclination angle of the tilting swash plate. The regulators 5a and 6a reduce or increase the discharge flow rate of the main pumps 5 and 6 so as to correspond to the level of the center bypass working hydraulic pressure (negative control pressure) in the main control valve 8, and output the main pumps 5 and 6 respectively. It has a function to keep it constant. Hereinafter, the hydraulic fluid passages connecting the center bypass of the main control valve 8 and the regulators 5a and 6a are referred to as negative control circuits 45a and 45b.

In the negative control circuits 45a and 45b, pressure sensors 28a and 28b for detecting the negative control pressure are interposed. One pressure sensor 28 a detects the negative control pressure P ₁ generated by the hydraulic fluid supplied from one main pump 5, and the other pressure sensor 28 b detects the negative control pressure generated by the hydraulic fluid supplied from the other main pump 6. to detect the P _2. These negative control pressures P ₁ and P ₂ detected by the pressure sensors 28a and 28b are transmitted to the data processor 29 described later.

The main circuits 43a and 43b have the same configuration, and the traveling circuits 42a and 42b have the same configuration. Here, one main circuit 43a and the travel circuit 42b will be described in detail as a representative, and overlapping description of the other main circuit 43b and the travel circuit 42a will be partially omitted.
A first flow path 60a is branched from the middle of the main circuit 43a. A first merging check valve 22a is interposed closer to the main pump 5 than the branch point between the main circuit 43a and the first flow path 60a, and the backflow of hydraulic oil to the main pump 5 is prevented. Further, a second merging check valve 23a is also interposed on the first flow path 60a. Accordingly, the flow direction of the hydraulic oil is limited to the direction from the main pump 5 and the first flow path 60a toward the main control valve 8. The first flow path 60b is also branched from the main circuit 43b, and a first merging check valve 22b and a second merging check valve 23b are provided.

  Two kinds of switching valves are interposed in the traveling circuit 42b. In the traveling circuit 42b, the flow path on the inflow side where the hydraulic oil is directed to the traveling motor 10 and the flow path on the outflow side from which the hydraulic oil is discharged from the traveling motor 10 form a pair. Switching valve is provided. Those interposed on the traveling motor 10 side are called first switching valves 19a and 19b, and those interposed on the main control valve 8 side are called second switching valves 20a and 20b.

The first switching valves 19a and 19b are disposed below the rotary joint 16 (lower traveling body 71 side), and the second switching valves 20a and 20b are disposed above the rotary joint 16 (upper swing body 72 side). . The first switching valves 19a and 19b and the second switching valves 20a and 20b are both configured to be able to switch the position of the spool (valve element) to two positions.
The other end of the external hydraulic oil introduction path 63a having one end connected to the joint 27a is connected to the first switching valves 19a and 19b. The spool positions of the first switching valves 19a and 19b include a first position a for connecting the traveling motor 10 and the main control valve 8, and a second position for connecting the external hydraulic oil introduction path 63a to the main control valve 8 side. b.

A first flow path 60a is connected to the second switching valves 20a and 20b. In the spool positions of the second switching valves 20a and 20b, there are a third position c for connecting the travel motor 10 and the main control valve 8, and a fourth position d for connecting the first flow path 60a to the travel motor 10 side. Provided.
Here, the flow path connecting the first switching valves 19a and 19b and the second switching valves 20a and 20b is referred to as a connection path 46. When the spool position of the first switching valves 19a and 19b is the second position, the external hydraulic oil introduction path 63a and the connection path 46 communicate with each other. At this time, if the spool position of the second switching valves 20a and 20b is the fourth position, the connection path 46 and the first flow path 60a communicate with each other, that is, the external hydraulic oil introduction path 63a and the first flow path 60a are connected. . The connection path 46 is formed inside the rotary joint 16 (swivel joint).

The first position “a” and the third position “c” are positions where the hydraulic oil passage is formed when the excavator 70 is normally driven (for example, when the main pumps 5 and 6 are operated). On the other hand, the second position “b” and the fourth position “d” are positions that form a hydraulic fluid passage supplied from the external hydraulic device 90.
The first switching valves 17a and 17b in the traveling circuit 42a have functions corresponding to the first switching valves 19a and 19b in the traveling circuit 42b, respectively. Similarly, the second switching valves 18a and 18b in the traveling circuit 42a have functions corresponding to the second switching valves 20a and 20b in the traveling circuit 42b. A flow path connecting the first switching valves 17a and 17b and the second switching valves 18a and 18b is referred to as a connection path 47. Similar to the connection path 46, the connection path 47 is formed inside the rotary joint 16.

  A return switching valve 21 is interposed on the return circuit 44. The return switching valve 21 is connected to the other end of the external return flow path 62 having one end connected to the joint 27c. At the spool position of the return switching valve 21, a fifth position e for communicating the main control valve 8 and the tank 40 and a sixth position f for communicating between the main control valve 8 and the external return flow path 62 are provided.

The fifth position e is a position for forming a return path of hydraulic oil to the tank 40 when the excavator 70 is normally driven. On the other hand, the sixth position f is a position where a return path to the external hydraulic device 90 is formed.
The second flow path 61a is formed by branching from the second switching valve 20a, 20b side with respect to the second merging check valve 23a in the first flow path 60a. The second flow path 61 a is a flow path for supplying hydraulic oil flowing through the first flow path 60 a to the pilot circuit 15 of the hydraulic excavator 70, and is connected to the pilot flow path 48 that connects the pilot pump 7 and the pilot circuit 15. Is done. A second flow path 61b for supplying hydraulic oil to the pilot circuit 15 is also branched from the first flow path 60b.

  A third merging check valve 24 is interposed closer to the pilot pump 7 than the connection point between the pilot circuit 15 and the second flow path 61a, thereby preventing backflow of hydraulic oil to the pilot pump 7 side. Further, a fourth merging check valve 25a is also interposed on the second flow path 61a. Therefore, the flow direction of the hydraulic oil is limited to the direction from the pilot pump 7 and the second flow path 61a toward the pilot circuit 15.

Further, a pressure reducing valve 26 is interposed on the pilot circuit 15 side of the fourth merging check valve 25a on the second flow path 61a. As a result, the reduced hydraulic pressure of the first flow path 60 a is introduced into the pilot circuit 15.
Similarly, a fourth merging check valve 25b is also interposed in the second flow path 61b. In addition, the pressure reducing valve 26 is arrange | positioned downstream (pilot circuit 15 side) from the confluence | merging point of the two 2nd flow paths 61a and 61b.

The excavator 70 is provided with a data processor 29 and a transmitter 30. The data processor 29 is an electronic control unit for processing information transmitted to the external hydraulic apparatus 90, and is provided as an LSI device in which a known microprocessor, ROM, RAM, and the like are integrated. The data processor 29 reads the negative control pressures P ₁ and P ₂ detected by the pressure sensors 28a and 28b, performs A / D conversion and the like, and generates transmission data. The transmission data generated here is transmitted from the transmitter 30 by wireless communication.

[3. External hydraulic circuit]
FIG. 3 shows the overall configuration of the external hydraulic circuit 2 built in the external hydraulic device 90.
In the external hydraulic circuit 2, the hydraulic oil discharge ports of the pair of external main pumps 33 and 34 are connected to the external joints 49a and 49b, respectively, and are connected to the joints 27a and 27b of the excavator side hydraulic circuit 1 through the hoses 52a and 52b. Is done. Further, the joint 27c of the excavator side hydraulic circuit 1 is connected to the external joint 49c via the hose 52c. An external oil cooler 37 is interposed on the external return flow path 65 that connects the joint 27 c and the external tank 41.

The external pilot pump 35 supplies hydraulic oil to the external pilot relief circuit 36. The external pilot relief circuit 36 is a relief circuit provided for circuit protection.
Each of the external main pumps 33 and 34 is provided with external regulators 33a and 34a (swash plate control mechanism) for controlling the discharge flow rate and the discharge pressure by adjusting the inclination angle of the tilting swash plate. The external regulators 33a and 34a decrease or increase the discharge flow rate of the external main pumps 33 and 34 so as to correspond to the negative control pressure on the hydraulic excavator 70 side, and keep the output of the external main pumps 33 and 34 constant. It has a function. That is, the same control as the negative control performed by the main pumps 5 and 6 of the excavator side hydraulic circuit 1 is performed for the external main pumps 33 and 34.

  The pilot hydraulic fluid for negative control in the external regulators 33 a and 34 a is introduced from the external pilot relief circuit 36. External electromagnetic proportional pressure reducing valves 39a and 39b are interposed on the flow path between the external pilot relief circuit 36 and the external regulators 33a and 34a. The external electromagnetic proportional pressure reducing valves 39a and 39b have a function of controlling the hydraulic pressure on the external pilot relief circuit 36 side and supplying hydraulic oil with an appropriate pressure to the external regulators 33a and 34a side.

The external hydraulic device 90 is provided with a receiver 50 and a proportional valve driver 51. The receiver 50 receives transmission data from the transmitter 30 of the excavator 70 and inputs it to the proportional valve driver 51. The proportional valve driver 51 is an electronic control device that controls the opening degree of the external electromagnetic proportional pressure reducing valves 39a and 39b based on input transmission data.
Here, the proportional valve driver 51 controls the external electromagnetic proportional pressure reducing valves 39a and 39b so that hydraulic oil having the same pressure as the negative control pressures P ₁ and P _{2 of the} excavator 70 is supplied to the external regulators 33a and 34a. . Therefore, the external main pump 33 serves as a working oil supply source as a substitute for the main pump 5, and the external main pump 34 serves as a working oil supply source as a substitute for the main pump 6.

[4. Action, effect]
[4-1. When the engine 3 is operating]
When the engine 3 of the excavator 70 is operated, the first switching valves 17a and 17b of the traveling circuit 42a and the first switching valves 19a and 19b of the traveling circuit 42b are set to all the spool positions and the first position a. At the same time, all the spool positions and the third position c of the second switching valves 18a and 18b of the traveling circuit 42a and the second switching valves 20a and 20b of the traveling circuit 42b are set. The spool position of the return switching valve 21 is the fifth position e.

  The main pumps 5 and 6 of the excavator 70 are driven by the engine 3, and hydraulic oil discharged from the main pumps 5 and 6 flows to the main circuits 43a and 43b side. Since the second flow check valves 23a and 23b are interposed in the first flow paths 60a and 60b branched from the main circuits 43a and 43b, the hydraulic oil is prevented from flowing out to the first flow paths 60a and 60b. , Flows into the main control valve 8 side.

  Accordingly, hydraulic oil is supplied to the travel circuits 42a and 42b in response to an operation input to a travel operation lever (not shown). For example, the operating oil is supplied to the travel motor 9 via the second switching valve 18a and the first switching valve 17a, and the return oil returns to the main control valve 8 via the first switching valve 17b and the second switching valve 18b. . When the rotation direction of the traveling motor 9 is the reverse direction, the flow direction of the hydraulic oil is reversed.

  Similarly, when the travel motor 10 is driven, hydraulic oil is supplied, for example, via the second switching valve 20a and the first switching valve 19a, and the return oil is supplied to the main control via the first switching valve 19b and the second switching valve 20b. Return to valve 8. The distribution direction of the hydraulic oil depends on the rotation direction of the traveling motor 10. The hydraulic oil that has returned to the main control valve 8 flows through the return circuit 44 and is discharged to the tank 40 via the return switching valve 21.

  When a boom operation lever or an arm operation lever (not shown) is operated, hydraulic oil is supplied to the boom cylinder 11 or the arm cylinder 12 according to the operation amount and operation direction, and the boom 81 or the arm 82 is operated. it can. The discharge flow rates of the main pumps 5 and 6 are controlled in accordance with the center bypass operating hydraulic pressure (negative control pressure) of the main control valve 8. Therefore, normal operation of the hydraulic excavator 70 is possible.

[4-2. During operation of external hydraulic device 90]
At the time of driving by the external hydraulic device 90, all the spool positions and the second position b of the first switching valves 17a and 17b of the traveling circuit 42a and the first switching valves 19a and 19b of the traveling circuit 42b are set. At the same time, all the spool positions and the fourth position d of the second switching valves 18a and 18b of the traveling circuit 42a and the second switching valves 20a and 20b of the traveling circuit 42b are set. The spool position of the return switching valve 21 is a sixth position f.

Further, as shown in FIG. 3, the joints 27a, 27b, and 27c of the excavator side hydraulic circuit 1 are connected to the external joints 49a, 49b, and 49c of the external hydraulic circuit 2 by the hoses 52a, 52b, and 52c, respectively. 90 is connected to an external power source.
The main pumps 5 and 6 of the excavator 70 are stopped and do not discharge hydraulic oil. Instead, hydraulic oil discharged from the external main pumps 33 and 34 is introduced into the excavator side hydraulic circuit 1.

  For example, the hydraulic oil discharged from one external main pump 33 is introduced into the external hydraulic oil introduction path 63a via the hose 52a. At this time, since the spools of the first switching valves 19a and 19b of the traveling circuit 42b are both in the second position b, the hydraulic oil is introduced into both connection paths 46. Further, since the spools of the second switching valves 20a and 20b are both in the fourth position d, the hydraulic fluid in the connection path 46 is introduced into the first flow path 60a, and is connected to the main circuit via the second merging check valve 23a. 43a. Since the first junction check valve 22a is interposed in the main circuit 43a, the hydraulic oil is prevented from flowing out to the main pump 5 side, and flows into the main control valve 8 side.

  Similarly, the hydraulic oil discharged from the other external main pump 34 is introduced into the external hydraulic oil introduction path 63b via the hose 52b, and the first switching valves 17a and 17b and the second switching valve 18a, 18b is introduced into the first flow path 60b and supplied to the main circuit 43b via the second merging check valve 23b. Moreover, the backflow of hydraulic fluid to the main pump 6 side is prevented by the first merging check valve 22b.

  Further, the working oil is diverted from the first flow paths 60 a and 60 b to the second flow paths 61 a and 61 b, and the working oil decompressed by the pressure reducing valve 26 is supplied to the pilot circuit 15. Therefore, when the boom operation lever or the arm operation lever is operated, the hydraulic oil is supplied to the boom cylinder 11 or the arm cylinder 12 according to the operation amount and the operation direction, and the boom 81 or the arm 82 is operated. it can.

On the other hand, hydraulic oil from the external hydraulic oil introduction passages 63a and 63b flows through the traveling circuits 42a and 42b, and hydraulic oil is supplied to the traveling motors 9 and 10 in the second switching valves 18a, 18b, 20a, and 20b. Is cut off. Therefore, even if an operation input to the travel operation lever is made by mistake, the operation of the travel motors 9 and 10 can be reliably prevented.
Information on the center bypass operating hydraulic pressures (negative control pressures) P ₁ and P ₂ of the main control valve 8 is wirelessly transmitted from the transmitter 30 of the hydraulic excavator 70 to the external hydraulic device 90. In the external hydraulic device 90, the external electromagnetic proportional pressure reducing valves 39a and 39b are controlled according to the negative control pressures P ₁ and P ₂ of the hydraulic excavator 70, and the discharge flow rates of the external main pumps 33 and 34 are controlled.

  As described above, according to the hydraulic circuit of the disclosed working machine, the hydraulic fluid supplied from the external main pumps 33 and 34 (external hydraulic power source) is introduced into the travel circuits 42a and 42b, and the first flow paths 60a and 60b are provided. Thus, the hydraulic actuator can be driven using not only the main pumps 5 and 6 but also the external main pumps 33 and 34 by introducing them into the main circuits 43a and 43b. Further, the operation of the traveling motors 9 and 10 when using the external main pumps 33 and 34 can be reliably prevented.

In order to switch the hydraulic circuit from the mode using the main pumps 5 and 6 to the mode using the external main pumps 33 and 34, the first switching valves 17a, 17b, 19a and 19b, and the second switching valves 18a and 18b are used. , 20a, 20b and the return switching valve 21 need only be changed all at once, and the switching operation can be easily performed.
Moreover, the main pump is provided by interposing the first merging check valves 22a and 22b and the second merging check valves 23a and 23b on the upstream sides of the connecting portions between the main circuits 43a and 43b and the first flow paths 60a and 60b. 5 and 6 and the flow direction of the hydraulic oil from the external main pumps 33 and 34 can be set uniquely, and the operation of the hydraulic circuit can be stabilized.

  In addition, the disclosed hydraulic circuit has a circuit configuration in which hydraulic fluid supplied from the external main pumps 33 and 34 is supplied not only to the main circuits 43 a and 43 b but also to the pilot circuit 15. Therefore, the external main pumps 33 and 34 can function not only as substitutes for the main pumps 5 and 6 but also as substitutes for the pilot pump 7. Furthermore, since the hydraulic pressure in the second flow paths 61a and 61b is reduced by the pressure reducing valve 26 and supplied to the pilot circuit 15, there is no problem in generating the pilot pressure related to the boom operation and the arm operation. It can provide almost the same operational feeling as when driving.

Further, since the discharge flow rates of the external main pumps 33 and 34 are controlled according to the negative control pressures P ₁ and P ₂ , the same operational feeling as during normal operation of the hydraulic excavator 70 is possible even when the boom 81 and the arm 82 are operated. Can be secured. Further, since the outputs of the external main pumps 33 and 34 are constant, an appropriate hydraulic fluid flow rate can be ensured even if a large load fluctuation occurs.

Further, when the hydraulic oil is supplied from the external main pumps 33 and 34, the return oil from the main control valve 8 is returned to the external tank 41 through the external return flow path 62 and the hose 52c. The hydraulic oil flow rate can be secured.
In the disclosed hydraulic circuit, the first switching valves 17a, 17b, 19a, and 19b are disposed below the rotary joint 16, and the second switching valves 18a, 18b, 20a, and 20b are disposed above the rotary joint 16. . That is, when hydraulic oil is supplied from the external hydraulic device 90, the hydraulic fluid passage for driving the traveling motors 9 and 10 during the driving operation is diverted as a power introduction passage for the entire hydraulic excavator 70. Therefore, the internal flow path of the rotary joint 16 that connects the lower traveling body 71 and the upper turning body 72 can be effectively used. Further, the present invention can be applied without changing the number of channels and the channel cross-sectional area formed inside the rotary joint 16, and the existing rotary joint can be used as it is.

[5. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
The method of switching the spool positions of the first switching valves 17a, 17b, 19a, 19b, the second switching valves 18a, 18b, 20a, 20b and the return switching valve 21 in the above-described embodiment is arbitrary, and may be configured to switch manually. Alternatively, it may be configured to be automatically switched. In the former case, the mode can be switched with a simple configuration, and the cost can be further reduced. In the latter case, it is conceivable to use an electromagnetic switching valve as the switching valve and a switching control device (switching control means) that electrically controls the electromagnetic switching valve. As a function required for the switching control device, a switch operation or insertion of the hoses 52a, 52b, 52c into the joints 27a, 27b, 27c is detected, and a control signal for changing the spool position of the electromagnetic switching valve is output. And so on. With such a configuration, the switching operation of the main pumps 5 and 6 and the external main pumps 33 and 34 can be automatically performed, and convenience can be improved.

  The present invention can be applied to work machines having a traveling motor and a hydraulic actuator (for example, a hydraulic excavator, a hydraulic crane, a vehicle including a hydraulic traveling device in a lower traveling body, etc.).

1 Excavator side hydraulic circuit 2 External hydraulic circuit 3 Engine 5, 6 Main pump (hydraulic source)
5a, 6a Regulator 7 Pilot pump 8 Main control valve (control valve)
9, 10 Traveling motor 15 Pilot circuit 16 Rotary joint 21 Return switching valve 22a, 22b First merge check valve 23a, 23b Second merge check valve 24 Third merge check valve 25a, 25b Fourth merge check valve 26 Pressure reducing valve 28a, 28b Pressure sensor (negative control pressure detection means)
29 Data processor 30 Transmitter 33, 34 External main pump (external hydraulic power source)
33a, 34a External regulator (external negative control device)
35 External pilot pump 36 External pilot relief circuit 39a, 39b External electromagnetic proportional pressure reducing valve 42a, 42b Travel circuit 43a, 43b Main circuit 44 Return circuit 45a, 45b Negative control circuit 46, 47 Connection path 48 Pilot flow path 50 Receiver 51 Proportional valve Driver 60a, 60b First flow path 61a, 61b Second flow path 62 External return flow path 63a, 63b External hydraulic oil introduction path 65 External return flow path 70 Hydraulic excavator (work machine)
90 external hydraulic device P _1, P ₂ negative control pressure

Claims (5)

A hydraulic circuit of a work machine that supplies hydraulic oil discharged from a hydraulic source to a travel motor and a hydraulic actuator via a control valve and discharges the hydraulic oil to a tank via the control valve,
An external hydraulic oil introduction path connected to an external hydraulic source provided separately from the hydraulic source;
A first position that is interposed on a travel circuit that connects the travel motor and the control valve and is connected to the external hydraulic oil introduction path, and that communicates the travel motor and the control valve; and the external operation A first switching valve having a valve body switchably provided at two positions of the second position for communicating the oil introduction path and the control valve;
A first flow path branched from a main circuit connecting the hydraulic pressure source and the control valve;
A third position interposed between the first switching valve and the control valve side of the travel circuit and connected to the first flow path to communicate the travel motor and the control valve; and the travel motor; A second switching valve having a valve body that can be switched to two positions of the fourth position to communicate with the first flow path;
A first merging check valve that is interposed closer to the hydraulic power source than a branch point with the first flow path in the main circuit, and prevents backflow from the control valve side to the hydraulic power source side;
A hydraulic circuit for a work machine, comprising a second merging check valve interposed in the first flow path and preventing a backflow from the main circuit side to the second switching valve side. An external return flow path connected to an external tank provided separately from the tank;
A fifth position that is interposed on a return circuit that connects the control valve and the tank and is connected to the external return flow path, and communicates the control valve and the tank; and the control valve and the external 2. The hydraulic circuit for a work machine according to claim 1, further comprising a return switching valve having a valve body that is switchably provided at two positions of the sixth position for communicating with the return flow path. A pilot circuit for generating a pilot pressure for setting an operation amount of the hydraulic actuator;
A second flow path branched from the first flow path and connected to the pilot circuit;
The hydraulic circuit for a working machine according to claim 1 or 2, further comprising a pressure reducing valve interposed on the second flow path. Negative control pressure detecting means for detecting the hydraulic pressure of the center bypass in the control valve as a negative control pressure;
The external negative control means for controlling the hydraulic oil flow rate from the external hydraulic source based on the negative control pressure detected by the negative control pressure detection means, further comprising external negative control control means. A hydraulic circuit for a work machine according to claim 1. The first switching valve is provided in the lower traveling body of the work machine,
The hydraulic circuit for a work machine according to any one of claims 1 to 4, wherein the second switching valve is provided in an upper swing body of the work machine.

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