JP2003165699A - Hydraulic circuit of vehicle for high lift work - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate operation backlash of a work platform even when a vehicle is stored with the work platform positioned in a high position, and prevent malfunction of a delay in action occurring to an input from an operation device. <P>SOLUTION: The hydraulic circuit of the vehicle for high lift work is provided with an ABT connection type swinging motor control valve 64 controlling swinging operation of the work platform by changing oil passages for hydraulic oil fed to a swinging motor 42 by a first hydraulic pump P1, an unloading valve 43 changing between feeding of the hydraulic oil from the first hydraulic pump P1 to a P port of the swinging motor control valve 64 and returning of the hydraulic oil to a reservoir T, and a check valve CV provided in a discharge oil passage L4 reaching the reservoir T from a confluence S of an oil passage L2 connected with a T port of the swinging motor control valve 64 and an oil passage L3 connected with a T port of the unloading valve 43 and allowing a flow of the hydraulic oil from a confluence S side to a reservoir T side and prohibiting a flow of the hydraulic oil from the reservoir T side to the confluence S side when a pressure of the hydraulic oil exceeds a preset cracking pressure. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for an aerial work vehicle in which a work platform for mounting an operator is attached to a tip end portion of a boom provided on a traveling body, and more specifically, to a work platform The present invention relates to a hydraulic circuit for eliminating a play.

[0002]

2. Description of the Related Art An aerial work vehicle has a structure in which a boom is provided on a traveling body which is movable by wheels and the like, and a work platform for mounting a worker is attached to a tip portion of the boom. The boom can be undulated, expanded and contracted (or bent and stretched), swiveled, etc., and its operation is controlled by an operating device (lever, etc.) provided on the workbench.
Can be done from For this reason, the worker on the workbench can move the workbench to a desired position by an operation performed by himself / herself, and can perform work at a high position at an arbitrary position.

The workbench is rotatably attached to a vertical post that is provided at the tip of the boom and is held almost vertically at all times. A swinging motor (hydraulic motor) built in the workbench is used as a hydraulic pressure. By driving, the workbench can be swung around the vertical post. For this reason, the operator on the workbench can perform not only the raising and lowering, extension and contraction, and the turning operation of the boom, but also the swinging operation of the workbench to adjust the posture of the workbench and make the work easy. .

FIG. 6 shows an example of a conventional hydraulic circuit relating to the swinging operation of a workbench, in which hydraulic oil discharged and supplied from a hydraulic pump 101 provided in a traveling body is extended in a boom 102. An oil passage (generally a flexible hose) is provided to guide the swing motor 103. An electromagnetically driven three-position switching valve 104 for controlling the operation of the swing motor 103 is provided in the workbench, and an operating device (for example, a lever) provided in the workbench is provided.
The spool of the switching valve 104 can be electrically moved by the operation of. Hydraulic pump 1
The pump oil passage 201 connected to 01 is P of the switching valve 104.
The T port of the switching valve 104 is connected to the oil tank 105 through the discharge oil passage 202.
The A and B ports of the switching valve 104 are the oil passages 203,
It is connected to the swing motor 103 by 204. Oil passage 20 connecting the switching valve 104 and the swing motor 103
Double pilot check valve 10 in 3,204
6 is provided, and a relief valve 107 is provided in the oil passage 205 branched from the pump oil passage 201 so that the pressure in the pump oil passage 201 does not exceed a predetermined pressure (relief set pressure). .

In such a configuration, the hydraulic oil discharged from the hydraulic pump 101 into the pump oil passage 201 reaches the oil passage 203 or 204 via the switching valve 104, and after rotating the swing motor 103. , Oil passage 204 or 20
After returning from 3 to the switching valve 104, the oil is discharged from the discharge oil passage 202 to the oil tank 105. By rotating the spool of the switching valve 104 from the normal position (the position shown in FIG. 6) to the switching position moved to the right or the switching position moved to the left, the rotation direction of the swing motor 103 can be switched. Further, when the spool of the switching valve 104 is located at the normal position, both oil passages 203 and 204 connected to both ports of the swing motor 103 communicate with the oil tank 105, and the double pilot is provided in these oil passages 203 and 204. Since the check valve 106 is provided, the swing motor 103 is hydraulically locked.

[0006]

In an aerial work vehicle having a hydraulic circuit having such a conventional structure, there are
Some vehicles store the vehicle with the workbench positioned at a high place. When the vehicle is stored with the workbench positioned at a high position in this manner (generally, the state is kept overnight), the hydraulic oil in the oil passages 203 and 204 leaks from the gap of the switching valve 104 due to its own weight. Swinging motor 1
A vacuum region is created in 03. When a vacuum region is created in the swinging motor 103 in this way, the work table is loosened. Such operation rattling of the work table may cause a problem such as an operation delay with respect to an input from the operating device, and it has been desired to solve such a problem.

The present invention has been made in view of the above problems, and eliminates the rattling of the workbench even when the workbench is located at a high position and the vehicle is stored. It is an object of the present invention to provide a hydraulic circuit for an aerial work vehicle that can prevent a problem in which an operation delay with respect to the input of is generated.

[0008]

A hydraulic circuit for an aerial work vehicle according to the present invention comprises a traveling body, a boom on which the hoisting motion is freely performed, and a vertical swing at the tip of the boom. A hydraulic circuit for an aerial work vehicle that is composed of a vertical post that is freely supported and is held almost vertically regardless of the hoisting angle of the boom, and a workbench that is rotatably attached to the vertical post. Then, the hydraulic actuator (for example, the swing motor 42 in the embodiment) that swings the workbench around the vertical post and the oil passage of the working oil supplied from the hydraulic pump to the hydraulic actuator are switched to change the neck of the workbench. A first switching valve (for example, a swing motor control valve 64 in the embodiment) that performs swing operation control, and hydraulic oil from a hydraulic pump is supplied to the P port of the first switching valve or returned to an oil tank. Second switching valve for Kano switching (e.g., unload valve 43 in the embodiment)
And an oil passage connected to the T port of the first switching valve (for example, the oil passage L2 in the embodiment) and an oil passage connected to the T port of the second switching valve (for example, the oil passage L3 in the embodiment). It is provided in the discharge oil passage (for example, the oil passage L4 in the embodiment) from the point to the oil tank, and the pressure of the working oil flow from the confluence side to the oil tank side exceeds a preset cracking pressure. A first check valve (for example, the check valve CV in the embodiment) that allows the case and prohibits the flow of the hydraulic oil from the oil tank side to the confluence side is provided.

According to the hydraulic circuit for an aerial work vehicle according to the present invention, the oil discharged from the hydraulic pump is supplied to the hydraulic actuator via the first switching valve. Therefore, it is possible to swing the work table by operating the spool of the first switching valve. However, the discharge oil of the hydraulic pump is supplied to the P port of the first switching valve or is supplied to the oil tank. A second switching valve for switching between returning and returning is provided, and from the confluence point of the oil passage connected to the T port of the first switching valve and the oil passage connected to the T port of the second switching valve to the oil tank. In the discharge oil path to reach, the flow of hydraulic oil from this confluence side to the oil tank side is allowed when the pressure exceeds a preset (own) cracking pressure, and this confluence point from the oil tank side is allowed. Check valve that prohibits the flow of hydraulic oil to the side (first check valve)
Is provided, the workbench is located at a high position to store the vehicle, and the hydraulic oil in the hydraulic actuator leaks from the gap of the first switching valve to prevent the hydraulic fluid from flowing between the hydraulic actuator and the first switching valve. Even if a vacuum region is created in the oil passage between them, if the spool of the first switching valve is placed in the normal position when the hydraulic pump is started next time, the discharge oil of the hydraulic pump Passes through the gap of the first switching valve and enters the hydraulic actuator until the first check valve rises to a pressure for opening the discharge oil passage, and fills the vacuum region. Therefore, even when the vehicle is stored with the workbench positioned at a high position, the backlash of the workbench can be eliminated, and a problem in which an operation delay with respect to an input from the operation device can be prevented.

Here, the pressure of the flow of the hydraulic oil from the oil tank side to the hydraulic actuator side is preset in each of the two oil passages connecting the first switching valve and the hydraulic actuator. ) A second check valve (for example, a check valve CV1 constituting the double pilot check valve DCV in the embodiment, which allows the cracking pressure to be exceeded and prohibits the flow of the working oil discharged from the hydraulic actuator side to the oil tank side). ，
When CV2) is provided, the cracking pressure set for the first check valve is set to be higher than the cracking pressure set for the second check valve. With such a configuration, the second check valve connects the first switching valve and the hydraulic actuator before the pressure in the discharge oil passage increases and the first check valve opens the discharge oil passage. Since the oil passage is opened, the above-mentioned second check valve is provided in each of the two oil passages that connect the first switching valve and the hydraulic actuator. The effect can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. 2 is a side view of an aerial work vehicle including a hydraulic circuit according to an embodiment of the present invention, and FIG. 3 is a block diagram showing a control system of the aerial work vehicle. As shown in FIG. 2, an aerial work vehicle 1 according to the present embodiment has a traveling body 10 including a pair of left and right front wheels 11 and rear wheels 12, a revolving structure 20 provided on the traveling structure 10, and a revolving structure. A boom 30 is attached to the upper part of the body 20 by means of a foot pin 21 so as to be vertically swingable, and a work board 40 for mounting a worker is attached to the tip of the boom 30.

The revolving structure 20 is attached to the traveling structure 10 so as to be rotatable 360 degrees about a vertical axis.
By hydraulically driving the turning motor 13 built into the 0, the turning operation can be performed in the horizontal plane. Boom 30
The multiple boom members are assembled in a nested manner,
By hydraulically driving the built-in telescopic cylinder 31, the telescopic cylinder 31 can be telescopically operated in the longitudinal direction. A hoisting cylinder 22 is provided between the boom 30 and the revolving structure 20, and the hoisting cylinder 22 can be hydraulically driven to hoist the boom 30 in the upper and lower planes.

A vertical post is provided at the tip of the boom 30. The vertical post is supported by the tip of the boom 30 so as to be swingable up and down, and is kept in a substantially vertical position by a leveling device (not shown) regardless of the hoisting angle of the boom 30. The workbench 40 is rotatably attached to the vertical post 32 via a workbench holder (bracket) 41. By hydraulically driving a swinging motor 42 provided in the workbench holder 41, The entire workbench 40 can be swung around the vertical post 32.

The rear wheels 12 of the traveling body 10 are connected to a rotary shaft of a traveling motor 14 incorporated in the traveling body 10. The rear wheel 12 is supplied by supplying hydraulic pressure to the traveling motor 14 to drive the rotating shaft. Can be rotated to start and stop the traveling body 10 and adjust the speed during traveling. Further, the front wheels 11 are connected to a rotating shaft of a steering motor 15 built in the traveling body 10 via a link mechanism (not shown). By supplying hydraulic pressure to the steering motor 15 to drive the rotating shaft, the front wheels 11 are driven. The traveling body 10 can be steered by changing the direction of 11.

Operation box 5 provided on the workbench 40
Within 0, a hoisting operation lever 51 for issuing a hoisting command of the boom 30, a telescopic operation lever 52 for issuing a telescopic command of the boom 30, and a turning operation for issuing a turning command of the boom 30 (of the turning body 20). An operation lever 53 and a swing operation lever 54 for issuing a swing command of the workbench 40 are provided. Here, when the hoisting operation lever 51 is tilted in the front-rear direction, an operation command signal for expanding and contracting the hoisting cylinder 22 is output accordingly. When the telescopic operation lever 52 is tilted in the front-rear direction, the telescopic cylinder 3 is correspondingly output.
An operation command signal for expanding and contracting 1 is output. Also,
When the turning operation lever 53 is tilted in the left-right direction, an operation command signal for rotating the turning motor 13 in the forward and reverse directions is output accordingly, and when the swinging operation lever 54 is tilted in the left-right direction, the swinging operation lever 53 is swung accordingly. An operation command signal for rotating the motor 42 in the forward and reverse directions is output. Then, each of these operation command signals is input to the workbench movement control unit 71 of the controller 70 as shown in FIG.

The operation box 50 also has a traveling lever 55 for issuing traveling commands for the traveling body 10 (starting, stopping and speed adjustment commands during traveling), and a steering lever 56 for issuing steering instructions for the traveling body 10. Is provided. Here, when the traveling lever 55 is tilted in the front-rear direction, an operation command signal for rotating the traveling motor 14 in the forward and reverse directions is output accordingly, and when the steering lever 56 is tilted in the left-right direction, the steering motor is accordingly responded. An operation command signal for rotating 15 in the forward and reverse directions is output. And
These operation signals are transmitted to the controller 7 as shown in FIG.
0 is input to the traveling control unit 72. Further, the operation box 50 is provided with an engine start switch 57 for starting the engine E provided in the traveling body 10 and an engine stop switch 58 for stopping the engine E. The operation signals of the switches 57 and 58 are, as shown in FIG.
3 is input.

When the engine start switch 57 is operated, the engine control unit 73 of the controller 70 accordingly starts the engine E, and when the engine stop switch 58 is operated, the engine control unit 73 stops the engine E. When the engine E starts, this causes the first and second
The hydraulic pumps P1 and P2 are driven to drive both hydraulic pumps P1 and P1.
The hydraulic oil is discharged from P2. The hydraulic oil discharged from the first hydraulic pump P1 into the first pump oil passage L1 is the undulating cylinder control valve 61, the telescopic cylinder control valve 62, the swing motor control valve 63, and the swing motor control valve 6.
4 is supplied to the undulating cylinder 22, the telescopic cylinder 31, the swing motor 13, and the swing motor 42, and the hydraulic oil discharged from the second hydraulic pump P2 into the second pump oil passage L11 is the traveling motor control valve 65, It is supplied to the traveling motor 14 and the steering motor 15 via the steering motor control valve 66.

Worktable movement control section 71 of controller 70
Are levers 51 to 51 operated by an operator M who is on the workbench 40.
The control valves 61 to 64 are electromagnetically driven according to the respective operation command signals output by the operation of 54.
As a result, the undulating cylinder 22, the telescopic cylinder 31, the turning motor 13, and the swinging motor 42 have the first hydraulic pump P1.
The hydraulic oil is supplied from each of them to perform the operation corresponding to the operation of the corresponding lever. In addition, the traveling control unit 72 of the controller 70 controls the control valve 65, in response to each operation command signal output by the operation of the levers 55, 56 by the worker M.
66 is electromagnetically driven, so that the traveling motor 14 and the steering motor 15 have the second hydraulic pump P2.
The hydraulic oil is supplied from each of them to perform the operation corresponding to the operation of the corresponding lever. Therefore, the worker M who is on the workbench 40 operates the levers 51 to 54 from the operation box 50 to raise, retract, and swing the boom 30, or swing the workbench 40 to work at a desired position. In addition, the traveling body 10 can be freely moved by operating the traveling lever 55 and the steering lever 56.

Further, as shown in FIG. 2, a hoisting angle detector 81 for detecting the hoisting angle of the boom 30 and a length detector 82 for detecting the length of the boom 30 are provided in the boom 30 for traveling. A swing angle detector 83 that detects the swing angle of the boom 30 with respect to the traveling body 10 (of the swinging body 20) is provided near the swinging motor 13 inside the body 10. Information about the hoisting angle and length of the boom 30 and the turning angle of the swinging body 10 detected by the detectors 81, 82, and 83 are all input to the position calculating unit 74 of the controller 70 (see FIG. 3).

The position calculating section 74 of the controller 70 calculates the position of the workbench 40 with respect to the traveling body 10 based on the input hoisting angle, length and turning angle information of the boom 30. The workbench 40 is stored in the storage unit 75 of the controller 70.
Of the allowable movement area, that is, the movement area of the work table 40 in which the work table 40 can be moved within a range in which the traveling body 10 does not fall, is stored in advance. Calculated workbench 40
Is compared with the data of the allowable movement area stored in the storage unit 75, and an operation command signal that causes the workbench 40 to deviate from the allowable movement area is ignored. For this reason, the swinging operation of the swinging body 20 and the hoisting and extending / contracting operation of the boom 30 such that the workbench 40 deviates from the permissible movement area are not performed, and the worker M feels at ease in the up / down, extending / contracting, and turning operations of the boom 30. It can be performed.

Next, the hydraulic circuit according to the present invention provided in the aerial work vehicle 1 will be described with reference to FIG. As described above, from the first hydraulic pump P1 to the first pump oil passage L1
The pressure oil discharged inside reaches the swing motor control valve 64 via an unload valve 43 (not shown in FIG. 3), and then to the swing motor 42 via this swing motor control valve 64. It is being supplied. here,
The unload valve 43 is provided below the boom 30, that is, on the traveling body 10 side, and the swing motor control valve 64 is provided above the boom 30, that is, on the workbench 40 side.

The swing motor control valve 64 is an ABT connection type electromagnetically driven three-position switching valve as shown in FIG. Therefore, when the spool is in the normal position (position shown in FIG. 1), the P port (pump port) is blocked and both the A and B ports connected to the swing motor 42 and the T port (tank port) are communicated. , When the spool is located at the switching position moved to the right, connect the P port to the A port of the swing motor 42, connect the B port of the swing motor 42 to the T port, and move the spool to the switching position moved to the left. When it is located, the P port is connected to the B port of the swing motor 42 and the A port of the swing motor 42 is connected to the T port.

When the spool is in the normal position (position shown in FIG. 1), the unload valve 43 connects the P port, the T port, and the A port connected to the P port of the swing control valve 64 with the B port connected. When the spool is connected to the plugged oil passage and located at the switching position where the spool has moved to the right, the P port is connected to the A port and the B port is connected to the T port. Here, the spool operation of the unload valve 43 is adapted to interlock with the spool operation of the swing motor control valve 64. When the spool of the swing motor control valve 64 is located at the normal position, the unload valve 43 The spool is located in the normal position and the swing motor control valve 64
When the spool of the unload valve 43 is located at the switching position moved to the right or left, the spool of the unload valve 43 is located at the switching position moved to the right.

Check valves CV1 and CV2 are provided in the two oil passages L5 and L6 connecting the swing motor control valve 64 and the swing motor 42, respectively. Oil passage (L5
Alternatively, a double pilot check valve DCV that receives the pilot pressure from L6) to open its own oil passage is configured. These check valves CV1 and CV2 allow the flow of hydraulic oil from the oil tank T side to the swing motor 42 side when the pressure exceeds a preset (own) cracking pressure, and also the swing motor 42. The flow of hydraulic oil discharged from the oil side to the oil tank T side is prohibited.
The check valves CV1 and CV2 close their own oil passages when no pressure is applied to the other oil passages. Therefore, when the oil passage located below the double pilot check valve DCV is broken, the swing motor 42 is operated. It is fixed (hydraulic lock) to the posture at that time. Further, in the oil passage L7 that branches from the first pump oil passage L1 and returns to the oil tank T, the oil passage L7 is provided when the pressure in the first pump oil passage L1 reaches a predetermined pressure (relief set pressure). A main relief valve R that opens to the oil tank T is provided.

An oil passage L2 connected to the T port of the swing motor control valve 64 and an oil passage L3 connected to the T port of the unload valve 43 are located below the boom 30 (that is, the traveling body 10).
A check valve CV is provided in the discharge oil passage L4 from the junction S to the oil tank T. The check valve CV allows the flow of hydraulic oil from the side of the confluence S to the side of the oil tank T when the pressure exceeds a preset (own) cracking pressure, and also allows the flow of hydraulic oil from the side of the oil tank T to the confluence. Prohibit the flow of hydraulic oil to the S side. Here, the cracking pressure of the check valve CV is adjusted to be higher than the cracking pressures of the two check valves CV1 and CV2 forming the double pilot check valve DCV.

In the hydraulic circuit having such a configuration, the first
The pressure oil discharged from the hydraulic pump P1 is the first pump oil passage L.
From 1 to the unload valve 43. Here, when the spool of the swing motor control valve 64 is located at the normal position, the spool of the unload valve 43 is also located at the normal position.
The A, B, and T ports are all in communication.
In such a state, the pressure oil supplied from the first hydraulic pump P1 into the first pump oil passage L1 is discharged from the oil passage L3 through the discharge oil passage L3.
Since it returns to the oil tank T via 4 the swing motor 42 does not operate.

When the spool of the swing motor control valve 64 is located at the switching position which is moved rightward or leftward from the normal position, the unload valve 43 is used.
The spool is located at the switching position, which is moved to the right from the normal position. In such a state, the pressure oil supplied from the first hydraulic pump P1 into the first pump oil passage L1 drives the swing motor 42 via the swing motor control valve 64, and then the swing motor control valve 64. Then, it returns to the oil tank T via the oil passage L2 and the discharge oil passage L4. Like this first
The oil discharged from the hydraulic pump P1 is supplied to the swing motor 42 via the swing motor control valve 64 of the ABT connection type, and the workbench 40 normalizes the spool of the swing motor control valve 64. By moving to the position moved to the right or left from the position, the swinging operation can be performed in either the forward or reverse (left and right) directions.

By the way, when the work vehicle 1 for aerial work is to be stored at a predetermined position after the work is completed, the hoisting cylinder 22 is extended to bring the boom 30 into a posture of a high hoisting angle and the work table 40.
To be in a high position. When such a posture is maintained for a long time (for example, all night), the hydraulic oil in the swing motor 42 leaks through the gap between the double pilot check valve DCV and the swing motor control valve 64, and the swing motor 42 and the swing motor 42. Oil passage L5 connecting to the control valve 64
A vacuum region is created in L6. However, in the present hydraulic circuit, the unload valve 43 that switches whether the discharge oil of the first hydraulic pump P1 is supplied to the P port of the swing motor control valve 64 or returned to the oil tank T.
Is provided in the discharge oil passage L4 from the junction S of the oil passage L2 connected to the T port of the swing motor control valve 64 and the oil passage L3 connected to the T port of the unload valve 43 to the oil tank T. Since the above-mentioned check valve CV is provided, when the first hydraulic pump P1 is started next time, the spool of the swing motor control valve 64 is positioned at the normal position (the position where the A, B and T ports are communicated). If so, the discharge oil of the first hydraulic pump P1 passes through the gap of the swing motor control valve 64 before the check valve CV rises to the pressure for opening the discharge oil passage L4, and the swing motor 42 is discharged. It penetrates inside and fills its vacuum region. Therefore, even when the vehicle is stored with the workbench 40 positioned at a high position, the operation rattling of the workbench 40 is eliminated, and an operation delay with respect to an input from the operation device (pivot operation lever 54) occurs. It becomes possible to prevent a defect.

FIG. 4 shows a modified example of the hydraulic circuit according to the above-described embodiment. Check valves CV11 and CV12 are provided in two oil passages L5 and L6 connecting the swing motor control valve 64 and the swing motor 42, respectively. The counter balance valves CBV1 and CBV2 having the above are provided instead of the above-mentioned double pilot check valve DCV. Here, both check valves CV11 and CV12 allow the flow of hydraulic oil from the oil tank T side to the swing motor 42 side when the pressure exceeds a preset (own) cracking pressure, and The flow of hydraulic oil discharged from the swing motor 42 side to the oil tank T side is prohibited, and both sequence valves SV11 and SV12 operate by receiving the pilot pressure of the oil passage (L5 or L6) of the other party. It is like this. Even in the hydraulic circuit having such a configuration, the T of the swing motor control valve 64 is
In the discharge oil passage L4 from the junction S of the oil passage L2 connected to the port and the oil passage L3 connected to the T port of the unload valve 43 to the oil tank T, the operating oil from the junction S side to the oil tank T side By providing a check valve CV that allows the flow of the hydraulic oil when the pressure exceeds a preset (own) cracking pressure and prohibits the flow of the hydraulic oil from the oil tank T side to the confluence S side, It is possible to obtain the same effect as that of the above-described embodiment.

Next, another embodiment of the hydraulic circuit according to the present invention will be described with reference to FIG. The aerial work vehicle to which the hydraulic circuit shown here is applied is the aerial work vehicle 1 described above.
And its description is omitted. In the hydraulic circuit according to this embodiment, the pressure oil discharged into the first pump oil passage L21 by the first hydraulic pump P1 is the above-mentioned A.
It is supplied to the swing motor 42 through a BT connection type swing motor control valve 64. A first pump oil passage L2 connecting the first hydraulic pump P1 and the swing motor control valve 64
An unload valve 243 is provided in the branch oil passage L22 that branches from 1 and returns to the oil tank T. Here, both the swing motor control valve 64 and the unload valve 243 are provided below the boom 30, that is, on the traveling body 10 side.

The unload valve 243 connects the P port and the T port when the spool is in the normal position (the position shown in FIG. 5), and is in the P position when the spool is moved to the left. Prohibit the flow of hydraulic oil from port to T port (In this example, the check valve allows the flow of hydraulic oil from T port to P port, but the P port and T port are shut off. May be). Here, the spool operation of the unload valve 243 is performed by the swing motor control valve 6
The spool of the swing motor control valve 64 is in the normal position (see FIG. 5).
Position), the spool of the unload valve 243 is in the normal position, and when the spool of the swing motor control valve 64 is in the switching position, which is moved to the right or to the left, the unload valve 243.
The spool is located at the switching position that is moved to the left.

Check valves CV21 and CV22 are respectively provided in the two oil passages L23 and L24 connecting the swing motor control valve 64 and the swing motor 42, and an oil passage L25 branched from the oil passage L5 is provided. Sequence and check valves SCV1 and SCV2 are provided in each of the oil passages L26 branched from the oil passage L6. Here, both check valves CV21 and CV22 allow the flow of hydraulic oil from the oil tank T side to the swing motor 42 side when the pressure exceeds a preset (own) cracking pressure, and The flow of hydraulic oil discharged from the swing motor 42 side to the oil tank T side is prohibited, and the sequence and check valve SCV
1 and SCV2 receive the pilot pressure from the oil passage (L23 or L24) of the other party and open their own oil passages.

Further, these sequence and check valves SCV1 and SCV2 have their own oil passage (L23 or L23).
24) receives the pilot pressure from 24) to open its own oil passage, and the swing motor 42 is in an overloaded state (when the work table 40 comes into contact with an obstacle and the swing operation cannot be performed, the work table 40 The oil passage L23 and the oil passage L25 (or the oil passage L24 and the oil passage L26) are prevented from bursting when the time reaches the end of the swingable range. Therefore, each of the sequence and check valves SCV1 and SCV2 receives the pilot pressure from its own oil passage and receives its own oil pressure rather than the pilot pressure when opening its own oil passage by receiving the pilot pressure from the other oil passage. The pilot pressure when opening the road is set to be higher. In addition, the first pump oil passage L
In the oil passage L27 branching from 21 and returning to the oil tank T,
A main relief valve R that opens the oil passage L27 to the oil tank T when the pressure in the first pump oil passage L21 reaches a predetermined pressure (relief set pressure) is provided.

An oil passage L28 connected to the T port of the swing motor control valve 64 (or a common drain oil passage L2 for the above two sequence and check valves SCV1 and SCV2).
9) and the branch oil passage L22 from the first pump oil passage L21
Are joined below the boom 30 (that is, on the traveling body 10 side), and a check valve CV is provided in the discharge oil passage L30 from the joining point S to the oil tank T. The check valve CV allows the flow of hydraulic oil from the side of the confluence S to the side of the oil tank T when the pressure exceeds a preset (own) cracking pressure, and also allows the flow of hydraulic oil from the side of the oil tank T to the confluence. Prohibit the flow of hydraulic oil to the S side. Here, the cracking pressure of the check valve CV is the cracking pressure of the two check valves CV21, CV22 (or the check valves CV121, CV222 in the two sequence and check valves SCV1, SCV2) provided in the oil passages L23, L24. Has been adjusted to be larger than.

In the hydraulic circuit having such a configuration, the first
The pressure oil discharged from the hydraulic pump P1 is the first pump oil passage L.
From 21 to the swing motor control valve 64,
From the branch oil passage L22 to the unload valve 243. Here, when the spool of the swing motor control valve 64 is located at the normal position, the unload valve 243
The spool is also in the normal position, and the pressure oil supplied from the first hydraulic pump P1 into the first pump oil passage L21 passes from the branch oil passage L22 through the discharge oil passage L30 to the oil tank T.
Therefore, the swing motor 42 does not operate.

When the spool of the swing motor control valve 64 is located at the switching position which is moved rightward or leftward from the normal position, the unload valve 24 is operated.
The spool No. 3 is located at the switching position, which is moved to the right from the normal position. In such a state, the branch oil passage L22 is blocked by the unload valve 243, so that pressure builds up in the first pump oil passage L21, and the oil discharged from the first hydraulic pump P1 passes through the swing motor control valve 64. After driving the swing motor 42 via the route, the sequence and check valve SCV1 or SCV2 returns to the oil tank T via the common drain oil passage L29 and the discharge oil passage L30. As described above, in the present hydraulic circuit, the discharge oil from the first hydraulic pump P1 is supplied to the swing motor 42 via the swing motor control valve 64 of the ABT connection type.
The worktable 40 can be swung in either forward or reverse (left and right) directions by moving the spool of the swinging motor control valve 64 to the position moved to the right or left from the normal position. It is similar to the case of the form.

A workbench 40 for storing the aerial work vehicle 1
In the hydraulic circuit according to the present embodiment, whether the discharge oil of the first hydraulic pump P1 is supplied to the P port of the swing motor control valve 64 even if the hydraulic oil is placed at a high place for a long time. An unload valve 243 for switching between returning to the oil tank T is provided, and a confluence point of an oil passage L28 connected to the T port of the swing motor control valve 64 and an oil passage L22 connected to the T port of the unload valve 243. In the discharge oil passage L30 from S to the oil tank T, the flow of the hydraulic oil from the confluence S side to the oil tank T side is allowed when the pressure exceeds a preset (own) cracking pressure. In addition, since the check valve CV for prohibiting the flow of the hydraulic oil from the oil tank T side to the confluence S side is provided, the swing motor control is performed when the first hydraulic pump P1 is started next time. If the spool of the lube 64 is positioned at the normal position (the position where the A, B, and T ports are communicated), the discharge oil of the first hydraulic pump P1 becomes the pressure at which the check valve CV opens the discharge oil passage L30. Until it rises, it passes through the gap of the swing motor control valve 64 and enters the swing motor 42 to fill the vacuum region. Therefore, the same effect as the hydraulic circuit according to the above-described embodiment can be obtained.

Although the preferred embodiments of the present invention have been described above, the scope of the present invention is not limited to the above. For example, in the above-described embodiment, the swing motor control valve 64 that controls the operation of the swing motor 42.
Although the neutral type is the ABT connection type, the neutral type may be the PTAB connection type or another form. Further, the swing motor control valve 64 is configured to electromagnetically drive the spool, but this is an example, and may be hydraulically driven or mechanically driven by a manual operation. Further, the configuration of the unload valve 43 is not necessarily limited to that shown in the above-described embodiment, and hydraulic fluid from the hydraulic pump (first hydraulic pump P1) is supplied to the P port of the swing motor control valve 64. Other forms may be used as long as they are switched to the oil tank T.

The hydraulic actuator for swinging the workbench 40 around the vertical post 32 is an angle limiting type actuator in the above-mentioned embodiment,
This may be a rotary hydraulic motor or hydraulic cylinder. Further, the swing motor control valve 64 is located above the boom 30 (that is, on the workbench 40 side) in the previous embodiment.
In the following embodiments, it is assumed that the swing motor control valve 64 is positioned above the boom 30. It does not matter whether it is located below 30.

Further, in the above-described embodiment, the oil tank T side is provided in each of the two oil passages L5, L6 (or the oil passages L23, L24) connecting the swing motor control valve 64 and the swing motor 42. From the swing motor 42 side to the swing motor 42 side when the pressure exceeds a preset cracking pressure, and the flow of the working oil discharged from the swing motor 42 side to the oil tank T side is prohibited. Although the check valves CV1 and CV2 (or CV11, CV12 or CV21, CV22) are provided, these check valves may not necessarily be provided. However, when these check valves are provided, as described above, the cracking pressure of the check valve CV provided in the discharge oil passage L4 (or L30) is determined by the check valves CV1, CV2 (or CV11, CV12).
Alternatively, it must be higher than the cracking pressure of CV21, CV22).

[0041]

As described above, according to the hydraulic circuit for an aerial work vehicle according to the present invention, the discharge oil of the hydraulic pump is first
A second switching valve for switching between supplying to the P port of the switching valve and returning to the oil tank is provided. An oil passage connected to the T port of the first switching valve and a T of the second switching valve are provided. In the discharge oil passage from the junction with the oil passage connected to the port to the oil tank, allow the flow of hydraulic oil from this junction to the oil tank if the pressure exceeds a preset cracking pressure. In addition, since there is a check valve (first check valve) that prohibits the flow of hydraulic oil from the oil tank side to the confluence side, store the vehicle with the workbench positioned at a high position. Even if the hydraulic oil in the hydraulic actuator leaks from the gap of the first switching valve and a vacuum region is created in the oil passage between the hydraulic actuator and the first switching valve, the hydraulic pressure Start pump If the spool of the first switching valve is positioned at the normal position, the oil discharged from the hydraulic pump will be discharged from the first switching valve until the pressure at which the first check valve opens the discharge oil passage increases. Through the gap to enter the hydraulic actuator and fill the vacuum area. Therefore, even when the vehicle is stored with the workbench positioned at a high position, the backlash of the workbench can be eliminated, and a problem in which an operation delay with respect to an input from the operation device can be prevented.

Here, in each of the two oil passages connecting the first switching valve and the hydraulic actuator, the flow of the hydraulic oil from the oil tank side to the hydraulic actuator side is set at a preset cracking pressure. If a second check valve that allows the flow rate of hydraulic oil to exceed the limit and prohibits the flow of hydraulic oil discharged from the hydraulic actuator side to the oil tank side is provided, the cracking pressure set for the first check valve is set. However, the cracking pressure is set to be higher than the cracking pressure set for these second check valves. With such a configuration, the second check valve connects the first switching valve and the hydraulic actuator before the pressure in the discharge oil passage increases and the first check valve opens the discharge oil passage. Since the oil passage is opened, the first switching valve and the hydraulic actuator are connected to each other.
Even when the second check valve as described above is provided in each of the oil passages of the book, the above effect can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a hydraulic circuit according to an embodiment of the present invention.

FIG. 2 is a side view of an aerial work vehicle including the hydraulic circuit shown in FIG.

FIG. 3 is a block diagram showing a control system of this aerial work vehicle.

FIG. 4 is a hydraulic circuit diagram showing a modified example of the above hydraulic circuit.

FIG. 5 is a diagram showing a hydraulic circuit according to another embodiment of the present invention.

FIG. 6 is a hydraulic circuit diagram showing a conventional hydraulic circuit for an aerial work vehicle.

[Explanation of symbols]

1 aerial work vehicle 10 traveling body 20 revolving structure 30 boom 32 vertical post 40 worktable 42 swinging motor (hydraulic actuator) 43 unloading valve (second switching valve) 64 swinging motor control valve (first switching valve) ) 70 controller P1 first hydraulic pump (hydraulic pump) DCV double pilot check valve CV check valve (first check valve) CV1, CV2 check valve (second check valve) T oil tank

Continued front page    (72) Inventor Masakatsu Maeda             41-1, Higashimine Sugawa, Shinji Village, Tone-gun, Gunma Prefecture               Aichi Corporation Shinjiko             Inside the hall F-term (reference) 3F333 AA08 AA15 AB01 AB04 AC01                       BB03 BB08 BB23 BB26 BD02                       BE02 CA21 FA09 FA16 FA20                       FA22 FA28 FD03 FD08 FD09                       FE08 FE09 FH08

Claims (2)

[Claims] 1. A traveling body, a boom on which the hoisting motion and the like are freely provided, and a boom which is supported by a tip end portion of the boom so as to be vertically swingable. A hydraulic circuit for an aerial work vehicle comprising a vertical post held vertically and a worktable rotatably attached to the vertical post, wherein the worktable is necked around the vertical post. A hydraulic actuator for swinging operation, a first switching valve for switching the oil passage of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator to control swinging operation of the workbench, and hydraulic oil from the hydraulic pump. A second switching valve for switching between supplying to the P port of the first switching valve or returning to the oil tank, an oil passage connected to the T port of the first switching valve, and the second switching valve. It is provided in a discharge oil passage extending from a confluence point with an oil passage connected to a port to the oil tank, and the pressure of a working oil flow from the confluence side to the oil tank side exceeds a preset cracking pressure. A hydraulic circuit for an aerial work vehicle, which is provided with a first check valve that allows the case and prohibits the flow of hydraulic oil from the oil tank side to the confluence side. 2. The pressure of the flow of hydraulic oil from the oil tank side to the hydraulic actuator side is preset in each of two oil passages connecting the first switching valve and the hydraulic actuator. A second check valve is provided that allows the cracking pressure to exceed when it exceeds the cracking pressure and prohibits the flow of hydraulic oil discharged from the hydraulic actuator side to the oil tank side, and the cracking pressure set in the first check valve. Is higher than the cracking pressure set in the second check valve, the hydraulic circuit for an aerial work vehicle according to claim 1, wherein