JPS644796Y2 - - Google Patents

Description

[Detailed explanation of the idea] (Application field) The present invention relates to a hydraulic control device for an aerial work vehicle.

(Prior art) Generally, in the case of an aerial work vehicle equipped with a work platform at the tip of the boom, control valves are provided on the vehicle side and the work platform side, and these control valves on the vehicle side and the work platform side control the ups and downs of the boom. It is configured to control boom-related operations such as extension and contraction or swinging, and to control tool operations such as swinging the workbench and crimping overhead wires and other workbench-related operations using a workbench-side control valve.

However, when the boom-related operations are controlled by the work platform side control valve, the piping length is approximately four times longer than the boom length compared to when the vehicle side control valve is operated. There is a disadvantage that pressure loss occurs due to conduit resistance, and boom-related operations become slow.

In particular, when reducing the boom extension/retraction hydraulic cylinder, the rod is thick due to buckling tension (there is a large area difference between the rod side oil chamber and the piston back pressure side oil chamber), so the piston back pressure side oil The pressure oil flowing out from the chamber has a small pressure and a large flow rate,
This tendency is particularly noticeable.

(Purpose) The present invention has been made in view of the above points, and its purpose is to improve the operating speed of boom-related operations.

(Configuration) The present invention branches a bypass circuit to an oil reservoir from at least one of the supply circuits to the hydraulic actuator for boom-related operation, and the bypass circuit includes a check valve and a pressure oil switch in the supply circuit. The operating control valves are arranged in sequence.

(Example) Examples will be described below based on the drawings.

As shown in FIG. 1, a swivel base 3 is mounted on the body 2 of the aerial work vehicle 1 so that the swivel can be controlled by a swivel motor (not shown). The proximal end is pivoted so that it can be raised and lowered freely.

The boom 4 has a luffing angle controlled by a luffing cylinder 5 disposed between it and the swivel base 3, and
A telescopic cylinder (not shown) is built in and is provided in a multi-stage telescopic manner with variable length, and a workbench 6 is installed at the tip of the boom 4a via a connecting member 7.

Although not explained in detail, the workbench 6 is configured so that it always maintains a horizontal state in response to the up-and-down movement of the boom 4, and is also rotated by a swing cylinder (not shown). .

In addition, stabilizing legs 8 are provided at four locations on both the front and rear sides of the vehicle body 2, and these stabilizing legs 8 are provided so as to be able to extend laterally by means of outrigger cylinders (not shown), and downwardly by means of a jack cylinder. They are provided to be extendable and retractable, and each support the vehicle body 2 during work.

The above-mentioned aerial work vehicle 1 is equipped with hydraulic equipment as shown in the hydraulic system diagram of FIG. 2. First, as the actuators that are supplied with pressure oil and perform various operations, there is a stabilizer leg actuator A on the vehicle body 2 side, which consists of an outrigger cylinder 9 of the stabilizer leg 8 and a jack cylinder 10 that extends and contracts vertically, and a boom 4.
A boom-related actuator B includes a hoisting cylinder 5 that raises and lowers the swivel table 3, a swing motor 11 that turns the swivel table 3, and a telescopic cylinder 12 that extends and retracts the boom 4.
3 and a crimping device 15 connected via a pressure intensifier (booster) 14.

Further, as control valves for controlling the operation of each of the above-mentioned actuators, on the vehicle body 2 side, there is a stabilizing gear control valve V1 for the stabilizing leg actuator A, and a luffing control valve V for the boom-related actuator B.
2. A vehicle-side control valve D consisting of a swing control valve V3 and a telescoping control valve V4 is provided, while a swing control valve V5 and a work control valve V6 for the actuator C for workbench-related operation are provided on the workbench 6 side. In addition, a work platform side control valve E consisting of a levitation control valve V7, a swing control valve V8, and a telescopic control valve V9 corresponding to the vehicle side control valve D described above is provided.

The hydraulic system for each of the actuators and control valves includes a first pump P1 that is driven by engine power via a power extraction device 16 as a pressure oil source.
and a second pump P driven by an electric motor 17.
2 (emergency pump), the first pump P1
The second pump P2 is connected to the stability gear control valve V1, and the stability gear control valve V1 is connected to the outrigger cylinder 9 and the jack cylinder 10, while the stability gear control valve V1 is connected to the vehicle side control valve V1. D
It is connected to the workbench side control valve E via.

By operating each of the above control valves, the boom 4 is rotated, raised and extended (boom-related operations) from the vehicle side or the workbench side, and swinging and crimping operations (workbench-related operations) are performed from the workbench side. It is something.

Next, the hydraulic circuit of the telescopic cylinder 12 will be described in detail with reference to FIG. First pump P1 or second pump
Pressure oil from the pump P2 passes from the vehicle side control valve D (telescopic control valve V4) to the piping device 18 that follows the expansion and contraction of the boom 4, and then from the workbench side control valve E (telescopic control valve V9) to the oil reservoir T. Piping is connected so that it returns to the The telescoping control valve V4 and the telescoping cylinder 12 are connected via an extension side supply circuit 19 and a contraction side supply circuit 20, and between the telescoping control valve V9 and the telescoping cylinder 12, a piping device 1 is connected.
They are connected via an expansion side supply circuit 19' and a contraction side supply circuit 20' which pass through the circuit 8.

By the way, a bypass circuit 21 to the oil reservoir T is branched from the extension side supply circuit 19, and this bypass circuit 21 has a check valve 22.
and an operation control valve 23 are arranged in this order.

The operation control valve 23 is controlled to be switched to the left position or the right position in response to pilot pressure guided from the supply circuits 19 and 20 through the pilot pipes 19a and 20a.

The check valve 22 only allows flow from the extension side supply circuit 19 toward the operation control valve 23 (oil reservoir T), and its operation pressure (cracking pressure) is set slightly higher than that of the operation control valve. has been done.

(Description of operation) Next, to explain the operation of the embodiment, first, when the engine (not shown) is started and the power take-off device 16 is operated, the first pump P1 is driven and the pressure oil can be supplied. Become.

Next, the stabilizer leg control valve V1 is switched to extend the outrigger cylinder 9 and the jack cylinder 10 to support the vehicle body 2. Then, the operator is placed on the workbench 6, and the control valves V2, V3, By switching control of V4 or the control valves V7, V8, and V9 on the workbench side, the workbench 6 can be moved to an appropriate spatial position and various high-place work can be performed.

Here, for example, when controlling the contraction of the boom 4 on the work platform 6 side, it is sufficient to switch the telescopic control valve V9 to the right position, and as a result, the pressure oil from the first pump is reduced through the telescopic control valve V9. The piston rod side oil chamber 12 of the telescopic cylinder 12 via the side supply circuit 20'.
supplied to a. At the same time, the pilot pipe 20a
Since pilot pressure is also supplied to the actuation control valve 23 via the actuation control valve 23, the actuation control valve 23 is switched to the right position.

Therefore, the drained oil from the piston back pressure side oil chamber 12b of the telescopic cylinder 12 is directly transferred to the oil reservoir T via the bypass circuit 21 in which the actuation control valve 23 is disposed.
Since the cylinder returns to , the telescopic cylinder 12 contracts.

On the other hand, when extending the boom on the workbench 6, the extension control valve V9 may be switched to the left position. At this time, the pressure oil from the first pump P1 is supplied to the piston back pressure side oil chamber 12b of the telescopic cylinder 12, and at the same time is switched to the left position of the operation control valve 23 via the pilot pipe 19a. That is, check valve 2
The cracking pressure of the actuation control valve 23 is set slightly higher than that of the actuation control valve 23.
After switching to the left position, the check valve 22 opens, and at this time the bypass circuit 21 is cut off.

Therefore, the pressure oil from the first pump from the extension side supply circuit 19 does not return to the oil reservoir T via the bypass circuit 21, and is reliably supplied to the piston back pressure side oil chamber 12b of the telescoping cylinder 12. . Further, the drained oil from the piston rod side oil chamber 12a returns to the oil reservoir T via the boom contraction side supply circuit 20 and the telescopic control valve V9, thereby extending the telescopic cylinder 12, that is, the boom.

In this example, the bypass circuit was branched only from the extension side supply circuit of the boom telescoping cylinder, but a bypass circuit equipped with a check valve and an operation control valve may also be branched from the contraction side supply circuit. In addition, the present invention may be used in other hydraulic actuators for boom-related operation, such as a luffing cylinder or a swing motor.

(Effects) As described above, in the present invention, pressure oil can be directly returned to the oil reservoir via the bypass circuit from the supply circuit from the hydraulic actuator for boom-related operations, so the operation of boom-related operations is possible. The speed can be increased as much as possible.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is an overall side view of the aerial work vehicle, FIG. 2 is a hydraulic system diagram thereof, and FIG. 3 is a hydraulic circuit diagram of a telescopic cylinder. 4... Boom, 6... Workbench, 12... Telescopic cylinder, 21... Bypass circuit, 23... Operation control valve.

Claims (1)

[Scope of claim for utility model registration] (1) A work platform is installed at the tip of the boom, and pressure oil from a hydraulic pump driven by an engine is supplied to the boom via a vehicle-side control valve or a work platform-side control valve. In the aerial work vehicle capable of supplying oil to a hydraulic actuator for related operation, a bypass circuit to an oil reservoir is branched from at least one of the supply circuits communicating the control valve and the hydraulic actuator for boom-related operation, and the bypass circuit is connected to the oil reservoir. includes an actuation control valve that is switched by pressure oil from the supply circuit, and a check valve that has a higher operating pressure than the switching pressure of the actuation control valve and allows flow only from the supply circuit to the actuation control valve. A hydraulic control device for an aerial work vehicle, characterized by being equipped with a valve. (2) The hydraulic control device for an aerial work vehicle according to claim 1, wherein the bypass circuit is at least branched from the extension-side high-pressure circuit of the boom extension/retraction hydraulic cylinder.