JPS634079Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a hydraulic circuit for an aerial work vehicle, and particularly to a hydraulic circuit in which switching valves are provided at the upper and lower parts of the boom of the aerial work vehicle.

2. Description of the Related Art As a conventional aerial work vehicle, for example, there is one shown in FIG. 1, and as a hydraulic circuit for this vehicle, for example, a circuit as shown in FIG. 2 is known. To explain this hydraulic circuit, reference numeral 1 denotes a body of an aerial work vehicle, and a hydraulic pump 9 is mounted on this body 1. A boom 2 whose elevation angle can be changed is rotatably installed at the rear end of the vehicle body 1, and an upper switching valve 3 is disposed at the upper part of the boom 2. This upper switching valve 3 and the hydraulic pump 9 are connected via an outgoing pipe line 6, and a lower switching valve 4 disposed at the bottom of the boom 2 is interposed in the middle of this outgoing pipe line 6. . The upper switching valve 3 and the lower switching valve 4 are connected to an oil tank 10 installed in the vehicle body 1 via a return pipe line 7.
is connected to. 5 is a hydraulic actuator, and the lower chamber 19 of this hydraulic actuator 5, the upper switching valve 3, and the lower switching valve 4 are connected to the upper chamber 2 through a first pipe line 21.
0, the upper switching valve 3, and the lower switching valve 4 are connected to each other by a second pipe line 22. Further, the lower switching valve 4 and the return pipe line 7 are connected by a third pipe line 23. As a result, when the upper switching valve 3 or the lower switching valve 4 switches to the first operating position, the hydraulic fluid discharged by the hydraulic pump 9 flows down from the upper switching valve 3 or the lower switching valve 4 through the first pipe line 21. room 19
The hydraulic oil in the upper chamber 20 flows into the second pipe line 22,
Since the oil is discharged to the return pipe line 7 via the upper switching valve 3 or the lower switching valve 4 and the third pipe line 23, the hydraulic actuator 5 is extended. On the other hand, when the upper switching valve 3 or the lower switching valve 4 switches to the second operating position, the hydraulic oil discharged by the hydraulic pump 9 is supplied to the upper chamber 20, and the hydraulic oil in the lower chamber 19 is transferred to the return pipe 7. The hydraulic actuator 5 is reduced in size. Furthermore, when the upper and lower switching valves 3, 4 are in the non-operating position,
Hydraulic oil discharged from the hydraulic pump 9 is circulated to the oil tank 10 via the lower switching valve 4, the outgoing line 6, the upper switching valve 3, and the returning line 7.

However, in such a conventional hydraulic circuit, when the upper and lower switching valves 3 and 4 are in the non-operating position, the hydraulic fluid discharged from the hydraulic pump 9 is transferred to the lower switching valve 4, the outgoing pipe line 6, and the upper Since the oil returns to the oil tank 10 via the switching valve 3 and the return pipe 7, there is a drawback that the pipe resistance is large, and therefore the discharge pressure of the hydraulic pump 9 becomes high, and the power consumption of the hydraulic pump 9 becomes large. Ta. Therefore, a circuit as shown in FIG. 3 has been proposed as a hydraulic circuit to solve these drawbacks. This hydraulic circuit has a bypass valve 12 interposed in the outgoing line 6 between the hydraulic pump 9 and the lower switching valve 4, and the upper and lower switching valves 3,
When all 4 are in the non-operating position, the hydraulic pump 9
The hydraulic oil discharged from the pump is discharged to the return pipe 7 via the bypass valve 12 and the bypass pipe 13.

However, in such a hydraulic circuit, the bypass valve 12 is switched each time either the upper or lower switching valves 3, 4 are in the operating position, so the problem is that the life of the bypass valve 12 is shortened. It was hot.

This idea was made by focusing on the problems of the conventional technology, and consists of a hydraulic pump 9 mounted on the vehicle body and an upper switching valve 3 disposed on the upper part of the boom.
, an outgoing pipe line 6 connecting the hydraulic pump 9 and the upper switching valve 3, a lower switching valve 4 disposed at the bottom of the boom and interposed in the outgoing pipe line 6, an upper switching valve 3, and a lower switching valve. 4 and 9 A return pipe 7 connecting the oil tanks 10 and the above-mentioned outgoing pipe 6 between the lower switching valve 4 and the upper switching valve 3 interpose the hydraulic oil that has passed through the lower switching valve 4 into the return pipe. 7 and a bypass valve 14 that can be directly bypassed, and when the upper switching valve 3 is in the non-operating position, the bypass valve 14 directs hydraulic oil to the outgoing pipe 6.
The purpose of the present invention is to solve the above-mentioned problems by making it possible to bypass from the pipe to the return pipe 7 and supplying hydraulic oil to the upper switching valve 3 when the upper switching valve 3 is in the operating position. There is.

This invention will be explained below based on the drawings.

Figures 4 and 5 are diagrams showing an embodiment of this invention. Note that the same parts as in the conventional hydraulic circuit shown in FIGS. 1 and 2 are denoted by the same numbers, and a description thereof will be omitted.

14 is a bypass valve, and this bypass valve 14
is interposed in the vicinity of the lower switching valve 4 between the upper switching valve 3 and the lower switching valve 4 in the middle of the outgoing pipe line 6 that connects the hydraulic pump 9 and the upper switching valve 3. A bypass line 15 is disposed between the bypass valve 14 and the return line 7. Further, the bypass valve 1
4 is controlled by a detection means 24 that detects the operating state of the upper switching valve 3, and is configured to switch the outflow direction. As shown in detail in FIG. 5, this detection means 24 includes an operating lever 16 for operating the upper operating valve 3, a cam 17 connected to and interlocking with this operating lever 16, and a cam 17 that is in constant contact with the cam 17. and a micro switch 18 that is activated by the displacement of the cam 17 and switches the bypass valve 14 via a drive circuit (not shown), and is configured to detect the operation of the upper switching valve 3 through the displacement of the cam 17. .

Next, the action will be explained.

When the operating lever 16 of the upper switching valve 3 is in the neutral position, the upper switching valve 3 is in the non-operating position. The detection means 24 detects that the upper switching valve 3 is in the non-operating position, and the solenoid of the bypass valve 14 is in a non-energized state. As a result, the bypass valve 14 is in the first position, and the hydraulic oil is bypassed from the outgoing line 6 to the incoming line 7. Then,
When the lower switching valve 4 is in the non-operating position, that is, when the upper switching valve 3 and the lower switching valve 4 are both in the non-operating position, the hydraulic fluid discharged from the hydraulic pump 9 flows through the lower switching valve 4, The oil flows into the oil tank 10 via the outbound line 6, bypass valve 14, bypass line 15, and return line 7, and the hydraulic actuator 5 does not operate.
In such a case, the piping through which the hydraulic oil circulates becomes shorter and the resistance of the piping decreases, so that the power consumption of the hydraulic pump 9 decreases. On the other hand, when the upper switching valve 3 is in the non-operating position and the lower switching valve 4 is in the operating position, the hydraulic oil discharged from the hydraulic pump 9 is transferred to the outgoing pipe 6, the lower switching valve 4, and the lower switching valve 4. , flows into the upper chamber 20 or lower chamber 19 of the hydraulic actuator 5 through the first pipe line 21 or the second pipe line 22, and operates the hydraulic actuator 5. Further, this hydraulic oil flows out from the lower chamber 19 or upper chamber 20 of the hydraulic actuator 5, and flows out from the second pipe line 22 or the first pipe line 21,
The oil is returned to the oil tank 10 via the lower switching valve 4, the third pipe line 23, and the return pipe line 7.

On the other hand, when the upper switching valve 3 is in the operating position,
A micro switch 18 is actuated via a cam 17 that is interlocked with an operating lever 16 that operates the upper switching valve 3. As a result, the solenoid of the bypass valve 14 is energized and the bypass valve 14 is in the second position.
The hydraulic oil flows out into the return pipe 7 only through the upper switching valve 3. As a result, the hydraulic oil discharged from the hydraulic pump 9 is transferred to the outgoing pipe line 6, the lower switching valve 4, and the bypass valve 1.
4. It flows into the hydraulic actuator 5 through the upper switching valve 3 to operate it, and also flows into the oil tank 10 through the upper switching valve 3 and the return pipe 7. In this way, the solenoid of the bypass valve 14 is energized only when the upper switching valve 3 is in the operating position, and since the bypass valve 14 is switched, the number of operations of the bypass valve 14 is reduced compared to the conventional one, and its lifespan is extended.

As explained above, according to this idea,
Its configuration includes a hydraulic pump 9 mounted on the vehicle body,
An upper switching valve 3 disposed at the top of the boom, an outgoing pipe line 6 connecting the hydraulic pump 9 and the upper switching valve 3,
A lower switching valve 4 disposed at the lower part of the boom and interposed in the return pipe 6, and a return pipe 7 connecting the upper switching valve 3, the lower switching valve 4, and the oil tank 10.
and a bypass valve 14 which is interposed in the outgoing pipe line 6 between the lower switching valve 4 and the upper switching valve 3 and is capable of directly bypassing the hydraulic oil that has passed through the lower switching valve 4 to the returning pipe line 7. When the switching valve 3 is in the non-operating position, the bypass valve 14 diverts hydraulic oil from the outgoing pipe line 6 to the returning pipe line 7.
Since hydraulic oil is supplied to the upper switching valve 3 when the upper switching valve 3 is in the operating position, the pipe resistance is reduced when the upper switching valve is not operated, and the hydraulic pump In addition, since the bypass valve is switched and controlled only depending on the operating state of the upper switching valve, the life of the bypass valve is also improved.

[Brief explanation of the drawing]

Figure 1 is a side view of a vehicle for aerial work, and Figure 2 is a hydraulic circuit diagram showing an example of the hydraulic circuit of a conventional vehicle for aerial work.
FIG. 3 is a hydraulic circuit diagram showing another hydraulic circuit of a conventional aerial work vehicle, FIG. 4 is a hydraulic circuit diagram showing an embodiment of the hydraulic circuit of the aerial work vehicle according to the present invention, and FIG. FIG. 3 is a perspective view showing a detection means in the hydraulic circuit according to the present invention. 1...Vehicle body, 2...Boom, 3...Upper switching valve, 4...Lower switching valve, 6...Outward pipe line, 7...Return pipe line, 9...Hydraulic pump, 14...Bypass valve.

Claims (1)

[Scope of utility model registration request] A hydraulic pump 9 mounted on the vehicle body, an upper switching valve 3 arranged on the upper part of the boom, an outgoing pipe 6 connecting the hydraulic pump 9 and the upper switching valve 3, and an outgoing pipe 6 arranged on the lower part of the boom and A lower switching valve 4 interposed in the outgoing pipe line 6, an upper switching valve 3, and a lower switching valve 4
The hydraulic oil that has passed through the lower switching valve 4 is interposed between the return pipe line 7 connecting the oil tank 10 and the lower switching valve 4 and the upper switching valve 3, and the outgoing pipe line 6 between the lower switching valve 4 and the upper switching valve 3. A bypass valve 14 that can be directly bypassed is provided, and when the upper switching valve 3 is in the non-operating position, the bypass valve 14 allows hydraulic oil to bypass from the outgoing pipe line 6 to the returning pipe line 7, and the upper switching valve 3 A hydraulic circuit for an aerial work vehicle, characterized in that hydraulic oil is supplied to an upper switching valve 3 when the valve is in an operating position.