JPH05106604A - Hydraulic circuit for load-body elevation device - Google Patents

Abstract

PURPOSE:To shorten the pressure accumulation time length of the accumulator in a hydraulic circuit for a hydraulic crane, by causing the communication between the accumulator and a bottom-side chamber of a cylinder and the communication between the bottom-side chamber thereof and a rod-side chamber thereof when the load body is lowered. CONSTITUTION:When a load body 12 is kept stopped at the lowered end, a controller 25 detects that the load body 12 is located at the lowered end, by a signal inputted via a signal line 34 from a lowered end limit switch 32. It starts causing a pressure accumulation in an accumulator 1 by driving an electric motor 3 and a hydraulic pump 2, and opening solenoid valves 20 to 22. When the controller 25 detects that the pressure in the accumulator 1 has become high enough to cause the load body 12 to rise, by a signal inputted via a signal line 27 from a pressure switch 24, it stops the rotation of the electric motor 3 and closes the solenoid valves 20 to 22. When, thereafter, a rise switch 29 is operated, the load body 12 rises.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a load raising / lowering device which is provided in a hydraulic machine such as a hydraulic crane or a hydraulic excavator and which raises / lowers a heavy load.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing an example of a hydraulic circuit of a conventional load lifting device. In this prior art, a cylinder 8 having a piston 9 for moving a load 12 as a heavy object up and down, an accumulator 1 for supplying pressure oil to a bottom side chamber 10 of the cylinder 8 through a flow path 6, and an accumulator 1 of the accumulator 1 are provided. A directional control valve 1 which is provided on the downstream side and controls the direction of pressure oil supplied to the bottom side chamber 10 of the cylinder 8.
3 and a hydraulic pump 2 for supplying pressure oil to the accumulator 1
And an electric motor 3 for driving the hydraulic pump 2. Between the connecting portion 14 of the accumulator 1 and the flow path 6 and the hydraulic pump 2, the connecting portion 14 from the hydraulic pump 2 is provided.
A check valve 4 is provided which can conduct only in the direction. 5
Is a relief valve that sets the maximum pressure of the circuit. The rod-side chamber 11 of the cylinder 8 described above is connected to the reservoir via the flow path 7.

The operation of the prior art thus configured is as follows.

When the load 12 is to be raised, the solenoid 13sa of the directional control valve 13 is excited to energize the left position 13a.
To connect the accumulator 1 to the bottom side chamber 10 of the cylinder 8 via the flow path 6. As a result, pressure oil is supplied from the accumulator 1 to the bottom side chamber 10 of the cylinder 8, the piston 9 extends, and the load 12 rises. Along with this, the oil in the rod side chamber 11 of the cylinder 8 flows to the reservoir via the flow path 7.

When lowering the load body 12,
The solenoid 13sb of the direction control valve 13 is excited to switch to the right position 13b, and the bottom side chamber 10 of the cylinder 8 is connected to the reservoir via the flow path 6. As a result, the load body 12 contracts the piston 9 of the cylinder 8 by its own weight,
Oil in the bottom side chamber 10 of the cylinder 8 flows to the reservoir via the flow path 7. Along with this, the rod side chamber 1 of the cylinder 8
1 sucks oil from the reservoir through the flow path 6 and the direction control valve 13, and the load 12 descends.

When the load 12 is stopped,
Both the solenoids 13sa and 13sb of the directional control valve 13 are not excited and are kept at the neutral position 13c. As a result, the pressure oil flowing through the flow path 6 communicating with the bottom side chamber 10 of the cylinder 8 is cut off, and the load 12 is stopped.

The pressure oil is supplied to the accumulator 1 when the load body 12 is stopped or lowered, that is, the directional control valve 13 cuts off the flow path 6 communicating with the bottom side chamber 10 of the cylinder 8. Sometimes, this is done by driving the hydraulic pump 2 by driving the electric motor 3.

[0008]

In the prior art described above, when the load 12 is repeatedly raised and lowered at high speed, the capacity of the hydraulic pump 2 for supplying pressure oil to the accumulator 1 is large. Since it is relatively small, there is a problem that the storage pressure of the accumulator 1 takes time.

Further, the potential energy held by the load body 12 after being raised causes the oil in the bottom side chamber 10 of the cylinder 8 to flow into the reservoir via the flow passage 6 and the direction control valve 13 when the load body 12 descends. Therefore, most of them are discarded as pressure loss, and there is also a problem of poor efficiency.

The present invention has been made in view of the above-mentioned situation in the prior art, and its purpose is to effectively utilize the potential energy that the load body has after the load is raised, and to reduce the storage pressure of the accumulator. An object of the present invention is to provide a hydraulic circuit for a load lifting device that can reduce the time required.

[0011]

To achieve this object, the present invention comprises a cylinder for raising and lowering a load, an accumulator for driving the cylinder, and a hydraulic source for supplying pressure oil to the accumulator. In the hydraulic circuit of the load raising / lowering device, there are provided a first communication means for communicating the accumulator with the bottom side chamber of the cylinder when the load is lowered, and a bottom side chamber and a rod side chamber of the cylinder when the load is lowered. The second communication means communicates with the second communication means.

[0012]

Since the present invention has the above-mentioned structure, when the load is lowered, the pressure in the cylinder is increased by communicating the bottom side chamber and the rod side chamber of the cylinder through the second communicating means. Further, the load body can be lowered by being guided to the first communication means, whereby the potential energy possessed by the load body after being raised can be effectively utilized and the storage pressure of the accumulator can be improved. The time required can be shortened.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic circuit of a load lifting device according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention, and FIG. 2 is a diagram showing operations of three electromagnetic switching valves provided in the embodiment shown in FIG.

In the embodiment shown in FIG. 1 as well, as in the prior art shown in FIG.
A cylinder 8 having a bottom side chamber 10 and a rod side chamber 11 for raising and lowering the load body 12, and an accumulator 1 for supplying pressure oil to the bottom side chamber 10 of the cylinder 8.
Hydraulic pump 2 for supplying pressure oil to this accumulator 1
A flow path 6 that connects the electric motor 3 that drives the hydraulic pump 2, the accumulator 1 and the bottom side chamber 10 of the cylinder 8, and a flow path 7 that connects the rod side chamber 11 of the cylinder 8 and the reservoir, and the cylinder 8 A check valve 4 for preventing the flow of pressure oil from the bottom chamber side 10 toward the hydraulic pump 2;
And a relief valve 5 for setting the pressure of the circuit.

Further, in this embodiment, the flow path 23 connecting the flow path 6 and the flow path 7 and the flow path 6 downstream of the connection point 14 are further provided.
A first electromagnetic switching valve 20 provided in a portion having an open position and a closed position; and a first electromagnetic switching valve having a open position and a closed position provided in a part of the flow path 7 downstream of a connection point of the flow paths 7 and 23. 2 electromagnetic switching valve 21, a third electromagnetic switching valve 22 provided in the flow path 23 and having an open position and a closed position, a pressure sensor 24 for detecting the pressure in the accumulator 1, and a rise of the load body 12. An ascending switch 29 for instructing an operation, a descending switch 30 for instructing a descending operation of the load body 12, a stop switch 31 for instructing a stopping operation of the load body 12, and detecting that the load body 12 has descended to the lowermost end. The descending end limit switch 32, the ascending end limit switch 33 that detects that the load 12 has risen to the uppermost end, the above-mentioned first electromagnetic switching valve 20, second electromagnetic switching valve 21, and third electromagnetic switching. Valve 22, pressure The controller 25, which is connected to the server 24, the raising switch 29, the lowering switch 30, the stop switch 31, the lowering end limit switch 32, and the raising end limit switch 33, and has a calculation and logic judgment function, and the controller 25 and 1 electromagnetic switching valve 2
0, the second electromagnetic switching valve 21, the signal lines 26a, 26b and 26c connecting the third electromagnetic switching valve 22, the signal line 27 connecting the controller 25 and the pressure sensor 24, the controller 25 and the electric motor 3 to each other. It includes a signal line 28 for connection, a signal line 34 for connecting the controller 25 and the lower limit switch 32, a signal line 35 for connecting the controller 25 and the upper limit switch 35, and the like.

The above-mentioned flow path 6 and the first electromagnetic switching valve 2
Reference numeral 0 constitutes a first communication means for communicating the accumulator 1 when the load 12 is descending with the bottom side chamber 10 of the cylinder 8. Further, the flow path 23 and the third electromagnetic switching valve 22 described above constitute a second communication unit that connects the bottom side chamber 10 and the rod side chamber 11 of the cylinder 8 when the load body 12 descends.

The relationship of the opening / closing operations of the first electromagnetic switching valve 20, the second electromagnetic switching valve 21, and the third electromagnetic switching valve 22 described above is preset as shown in FIG. That is, when the load 12 is raised, the first electromagnetic switching valve 20 is in the communication (open) position, the second electromagnetic switching valve 21 is in the communication (open) position, and the third electromagnetic switching valve 22 is in the blocking (closed) position. When the load 12 descends, the first electromagnetic switching valve 20 is in the open (open) position and the second electromagnetic switching valve 21 is closed (closed).
Position, the third electromagnetic switching valve 22 is driven to the communication (open) position, and when the load 12 is stopped, all the electromagnetic switching valves 20,
21 and 22 are driven to the cutoff (closed) position.

The operation of the embodiment thus constructed is as follows.

That is, for example, when the load body 12 is stopped at the descending end, the controller 25 causes the load body 12 to move to the descending end by the signal output from the descending end limit switch 32 via the signal line 34. Is detected, and a signal for starting the electric motor 3 to start accumulator 1 pressure accumulation is output to the electric motor 3 via the signal line 28 to drive the hydraulic pump 2. The controller 25
When it is detected by the signal output from the pressure switch 24 via the signal line 27 that the pressure in the accumulator 1 is large enough to raise the load 12, the motor 3 is instructed to stop. Output the signal. In addition,
When the load body 12 is stopped, as shown in FIG. 2, all the electromagnetic switching valves 20, 21, 22 are in a shut-off state.

In order to raise the load 12, it is sufficient to operate the raising switch 29.
The signal output from 9 causes the controller 25 to
To the electromagnetic switching valve 20 and the second electromagnetic switching valve 21 of
A signal is sent via each of a and 26b to bring the first electromagnetic switching valve 20 and the second electromagnetic switching valve 21 into a communication state. In this way, the first electromagnetic switching valve 20 and the second electromagnetic switching valve 21 are made to communicate with each other and the third electromagnetic switching valve 22 is cut off, whereby the accumulator 1 discharges the pressure oil, and this pressure oil It is guided to the bottom side chamber 10 of the cylinder 8 through the flow path 6 and the first electromagnetic switching valve 20, and the piston 9
To stretch. The oil in the rod-side chamber 11 of the cylinder 8 flows through the flow path 7 and the second electromagnetic switching valve 21 into the reservoir, whereby the load 12 rises. The load 12 is stopped by outputting a signal from the rising end limit switch 33 or the stop switch 31 to the controller 25, and the controller 25 causes the first electromagnetic switching valve 20 and the second electromagnetic switching valve 21 to operate. Is the third electromagnetic switching valve 22
These electromagnetic switching valves 20, so as to cut off together with
The signal is output to 21 and 22.

Here, the cylinder 8 when the load 12 is raised
The pressure Pbu in the bottom side chamber 10 is Ab · Pbu = W
Therefore, Pbu = W / Ab (1) However, Ab: bottom side pressure receiving area of the piston 9 W: weight of the load body 12 and the piston 9. Therefore, the pressure in the bottom side chamber 10 of the cylinder 8, the flow path 6, and the accumulator 1 after the load body 12 is raised is as described above ( From formula (1), it is almost W / Ab.

The above operation is similar to that of the above-mentioned conventional technique, but the operation of the load body 12 when the load body 12 descends, which is a feature of this embodiment, is as follows.

When lowering the load 12, the lower switch 30 may be operated. The signal from the lowering switch 30 causes the controller 25 to output signal lines 26a and 26c.
Through the first electromagnetic switching valve 20 and the third electromagnetic switching valve 22.
A signal for bringing the second electromagnetic switching valve 21 into a disconnected state is output through the signal line 26b. Thereby, the accumulator 1 and the bottom side chamber 10 of the cylinder 8 communicate with each other, and the bottom side chamber 1 of the cylinder 8 communicates with each other.
0 and the rod side chamber 11 communicate with each other. Along with this, the pressure Pbd in the bottom side chamber 10 of the cylinder 8 and the pressure Prd in the rod side chamber 11 become equal, and the pressure Pbd in the bottom side chamber 10 of the cylinder 8 is Pbd = (Ar / Ab) from Ab · Pbd = Ar · Prd + W. -Prd + (W / Ab) = (Ar / Ab) -Pbd + (W / Ab) (2). However, Ab: bottom side pressure receiving area of the piston 9, Ar: rod side pressure receiving area of the piston 9, W: weight of the load body 12 and the piston 9, therefore, from the equations (1) and (2), such load body 1
2, the pressure P of the bottom chamber 10 of the cylinder 8 is lowered.
The relationship between b and the pressure Pacc in the accumulator 1 after rising is Pbd> Pacc (= Pbu).

As a result, the bottom chamber 10 of the cylinder 8 is
The oil inside passes through the flow path 6 and a part of the oil flows inside the third electromagnetic switching valve 22.
To the rod-side chamber 11 and the rest is accumulated in the accumulator 1 via the first electromagnetic switching valve 20.
2 descends.

As described above, in this embodiment, when the load 12 is lowered, part of the oil in the bottom chamber 10 is caused to flow into the rod chamber 11 and the rest is accumulated in the accumulator 1. The potential energy that the load body 12 has after being raised can be effectively used for accumulating the accumulator 1, and the time required for accumulating the accumulator 1 by the hydraulic pump 2 can be shortened.

[0026]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to effectively utilize the potential energy that the load body has after the load is raised, and to shorten the time required for accumulator pressure storage. Therefore, there is an effect that it is more economical than the conventional one and that the load can be easily raised and lowered at high speed.

[Brief description of drawings]

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

FIG. 2 is a diagram showing operations of three electromagnetic switching valves provided in the embodiment shown in FIG.

FIG. 3 is a circuit diagram showing an example of a hydraulic circuit of a conventional load lifting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Accumulator 2 Hydraulic pump 4 Check valve 6 Flow path 7 Flow path 8 Cylinder 10 Bottom side chamber 11 Rod side chamber 12 Load body 20 First electromagnetic switching valve 21 Second electromagnetic switching valve 22 Third electromagnetic switching valve 23 Flow channel 24 Pressure Sensor 25 Controller 29 Up Switch 30 Down Switch 31 Stop Switch 32 Down End Limit Switch 33 Up End Limit Switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Morio Oshina 650 Kazunachicho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd.Tsuchiura factory (72) Inventor Mitsuo Sonoda 650 Jinmachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Company's Tsuchiura factory (72) Inventor Hideyo Kato 650 Kintachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd.Tsuchiura factory (72) Inventor Takayuki Kubota 650 Kintachi-machi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. (72) Inventor Yasuki Tsuriga 650 Kintate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd.

Claims (1)

[Claims] 1. A hydraulic circuit of a load lifting device having a cylinder for raising and lowering a load, an accumulator for driving the cylinder, and a hydraulic power source for supplying pressure oil to the accumulator. It is characterized by comprising: first communication means for communicating the accumulator and the bottom side chamber of the cylinder; and second communication means for communicating the bottom side chamber of the cylinder and the rod side chamber when the load is lowered. Hydraulic circuit for load lifting device.