JP2550365Y2 - Hydraulic circuit of hydraulic lifting device - Google Patents

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 hydraulic elevating device for elevating a work floor in an aerial work vehicle or the like.

[0002]

2. Description of the Related Art There are many types of high-place work vehicles that raise and lower a work floor vertically and move an operator who is on the work floor to a high place. Such a work floor is moved up and down. The hydraulic elevating device to be driven is configured as shown in FIG. The hydraulic lifting device includes a hydraulic cylinder C and a hydraulic circuit 30 for supplying and discharging hydraulic oil to and from the hydraulic cylinder C.
It is composed of The hydraulic cylinder C is of a so-called single-acting type, and receives a supply of pressure oil discharged from the hydraulic pump 31 to extend and raise a work floor (not shown). Allowed to be reduced by the weight of the work floor, lowering the work floor.

For this reason, the hydraulic circuit 30 includes a supply / discharge shared line 33 which is directly connected to the hydraulic cylinder C and circulates pressure oil supplied / discharged to / from the hydraulic cylinder C, and a supply / discharge shared line 33. The hydraulic oil discharged from the hydraulic cylinder C through the common supply / discharge line 33 is drained to the hydraulic oil tank 35 by the ascending supply line 34 for supplying hydraulic pressure discharged from the hydraulic pump 31 to the hydraulic cylinder C via the hydraulic pump C. And a discharge line 36 for normal lowering.
Therefore, the ascending open / close valve 34a attached on the ascending supply line 34 is opened to open the ascending supply line 34, and the descending on / off valve 36a usually attached on the descending discharge line 36 is closed. If the discharge line 36 for normal descending is closed in this way, the hydraulic cylinder C can be extended to raise the work floor.
Further, if the ascending supply line 34 is closed and the normal descending discharge line 36 is opened, the hydraulic cylinder C can be reduced and the work floor can be lowered.

As shown in FIGS. 3B and 3C,
Normally, the discharge line 36
A restrictor 37 for limiting the discharge flow rate of the pressure oil flowing through the inside is attached. As a result, when lowering the work floor,
The descending speed can be suppressed appropriately.

Further, as shown in FIG. 3 (A), the hydraulic oil discharged from the hydraulic cylinder C via the common supply / discharge line 33 bypasses the normal descending discharge line 36 in the hydraulic circuit 30. An emergency lowering discharge line 38 for draining the direct pressure oil tank 35 is provided. For this reason, for example, when the opening / closing valve 36a for descent breaks down and cannot be opened, if the stop valve 38a mounted on the discharge line 38 for emergency descent is opened, the discharge line 36 for normal descent is opened. The work floor can be lowered even without it.

[0006] Conventionally, as shown in FIG.
The downstream end of the emergency descending discharge line 38 is connected to the downstream end of the throttle 37 in the normal descending discharge line 36, and the opening of the stop valve 38a adjusts the pressure oil from the emergency descending discharge line 38. The discharge flow rate was restricted so that the descent speed of the work floor could be suppressed even in an emergency. Also, as shown in FIG. 3C, the discharge flow from the emergency descending discharge line 38 is connected to the upstream of the restrictor 37 in the normal descending discharge line 36 so as to reduce the discharge flow rate.
In some cases, it could be restricted by 7.

While the work floor is being lifted, the weight of the work floor is supported by the hydraulic pressure in the supply / discharge line 33 and the other hydraulic lines 34, 36, 38. If the pressure oil inside the line flows out at a large flow rate due to breakage of the line or the like, the work floor may fall suddenly. For this reason, a fuse valve (emergency lowering prevention means) 39 is provided on the common supply / discharge line 33 at a position close to the hydraulic cylinder C. The fuse valve 39 closes the common supply / discharge line 33 using a difference in pilot pressure generated on the left and right sides of the spool when the flow rate of the pressure oil discharged from the common supply / discharge line 33 exceeds a predetermined regulation flow rate. It works as follows. With such a fuse valve 39, it is possible to prevent the work floor from dropping as described above.

[0008]

However, in the circuit configuration in which the downstream end of the emergency descent discharge line 38 is connected as shown in FIG. 3B, if the opening of the stop valve 38a is too large, The discharge flow rate from the hydraulic cylinder C may exceed the regulated flow rate. In this case, there is a problem that the fuse valve 39 is closed and the work floor cannot be lowered. Before the start of work, a start-up inspection (opening / closing valves 34a, 36
a) is often performed), but in the circuit configuration to which the downstream end of the emergency descent line 38 is connected as shown in FIG. At the time of inspection, it is impossible to experimentally create a state in which hydraulic oil with a flow rate exceeding the regulated flow rate flows out of the hydraulic cylinder C,
There is a problem that the operation check of the fuse valve 39 cannot be performed.

The present invention has been made in view of such a problem, and it is possible to surely lower the work floor smoothly even in an emergency, and to check the operation of the emergency lowering prevention means at the start of work inspection. It is an object of the present invention to provide a hydraulic circuit of a hydraulic elevating device capable of performing the operation.

[0010]

In order to achieve the above-mentioned object, in the hydraulic circuit of the present invention, the discharge flow rate of the hydraulic oil from the normal descending discharge line is set to at most the first descending discharge line. While the first throttle means for suppressing the flow rate is provided, the second throttle means for suppressing the discharge flow rate of the pressure oil from the emergency descending discharge line to the second flow rate at the maximum is provided on the emergency descending discharge line. Then, the first flow rate and the second flow rate are individually set so that the sum of the first flow rate and the second flow rate is smaller than the regulated flow rate, but the sum of the first flow rate and the second flow rate is smaller than the regulated flow rate at which the emergency descent prevention means operates. I have.

[0011]

According to such a hydraulic circuit, in a normal operation, when discharging the pressurized oil only from the discharge line for normal descending, the discharge flow rate is smaller than the regulated flow rate by the operation of the first throttle means. It can be suppressed to the first flow rate or less. Therefore, the work floor can be lowered at an appropriate speed. Further, when the pressurized oil is discharged only from the emergency descending discharge line such as when the normal descending discharge line cannot be opened as described above, the discharge flow rate is regulated by the operation of the second throttle means. The flow rate can be suppressed to a second flow rate lower than the flow rate. For this reason, the hydraulic oil can be discharged from the hydraulic cylinder without operating the emergency descent prevention means, and the work floor can be lowered at an appropriate speed. Further, at the start of inspection, etc., by discharging the pressurized oil from both the normal descending discharge line and the emergency descending discharge line, it is possible to discharge a flow rate exceeding the regulated flow rate from both lines. Therefore, the operation of the emergency descent prevention means can be checked.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows an aerial work vehicle 10 provided with a hydraulic circuit according to the present invention. The aerial work vehicle 10 is configured based on a traveling carriage 11 that can travel freely using hydraulic pressure. A hydraulic lifting device 12 is mounted on the upper surface of the traveling vehicle 11. The hydraulic lifting device 12 is vertically mounted on a front portion of the traveling vehicle 11 and can be telescopically extended and retracted.
And a work floor 14 horizontally mounted on the upper part of the elevating post 13. The lifting post 13 has a built-in hydraulic cylinder C. The lifting post 13 expands and contracts with the expansion and contraction of the hydraulic cylinder C, and the work floor 14 moves up and down. An operator (not shown) riding on the work floor 14 of the aerial work vehicle 10 lifts the lifting post 13
Through the operation of the operation device 15 attached to the upper part of the vehicle, the traveling carriage 11 can be moved or the work floor 14 can be moved up and down to an arbitrary height.

The hydraulic cylinder C is a single-acting hydraulic cylinder as shown in FIG. That is, the pressurized oil is supplied to the bottom side oil chamber Ca to perform the extension operation and raise the work floor 14 as described above. On the other hand, by allowing the pressurized oil to be discharged from the bottom side oil chamber Ca, the pressure is reduced by the weight of the work floor 14 and the work floor 14 is lowered.

It is the hydraulic circuit 20 according to the present invention that supplies and discharges the pressure oil to and from the hydraulic cylinder C. The hydraulic circuit 20 is a conventional hydraulic circuit (FIG. 3).
), And such a portion will be described briefly. The hydraulic circuit 20 includes a supply / discharge shared line 23 connected directly to the bottom oil chamber Ca of the hydraulic cylinder C at the upper end, and a rising supply line 24 connected to the lower end of the shared supply / discharge line 23. A lowering discharge line 26 and an emergency lowering discharge line 28 are provided.

The ascending supply line 24 is connected to the hydraulic pump 21
, And is opened and closed by an ascending opening / closing valve 24a which receives an operation signal from the operating device 15 and operates to switch. The discharge line 26 for normal descent is connected to the pressure oil tank 2
5, and is opened and closed by a lowering opening / closing valve 26 a that receives an operation signal from the operating device 15 and that performs a switching operation. The emergency descending discharge line 28 is connected to the lower part of the normal descending discharge line 26 so that the pressure oil tank 2
The opening / closing operation and the flow path area adjustment are performed by a stop valve 28a which is manually operated.

At a position close to the hydraulic cylinder C in the common supply / discharge line 23, a fuse valve (emergency descent prevention means) 29 is attached. The fuse valve 29 has two spool positions having a left movement position (open position) for opening the common supply / discharge line 23 and a right movement position (close position) for closing the common supply / discharge line 23.
The pilot hydraulic pressure is guided to the left side of the spool from a position near the bottom oil chamber Ca in the common supply / discharge line 23, while the pilot hydraulic pressure is guided to the right side of the spool from the lower side of the common supply / discharge line 23. A spring 29a is attached to the right side of the spool so as to bias the spool to the left movement position. For this reason, the fuse valve 29 includes a pilot hydraulic pressure (hereinafter referred to as a right pilot hydraulic pressure) acting on the right side of the spool and a spring 29a.
As long as the resultant force with the urging force is greater than the pilot hydraulic pressure acting on the left side of the spool (hereinafter, referred to as left pilot hydraulic pressure), it is located at the open position.

The reason why the spool is switched to the closed position when the left pilot oil pressure exceeds the resultant force is that the lower part of the fuse valve 29 in the common supply / discharge line 23 is ruptured or the like, so that the hydraulic oil is released therefrom. Is discharged at an excessive flow rate, and is limited to an “emergency state” in which the right pilot oil pressure is extremely reduced. The amount of pressure oil flowing out of the common supply / discharge line 23 for switching the spool of the fuse valve 29 to the closed position in this manner is referred to as a “regulated flow rate”.

The lowering discharge line 26 is generally lower (downstream side) than the lowering opening / closing valve 26a and higher than the connection with the emergency lowering discharge line 28 (upstream side).
Is provided with a first aperture 27a. This first
The throttle 27a narrows the flow passage area of the discharge line 26 so that only pressurized oil having a flow rate of the first flow rate Q1 at the maximum flows out from the discharge line 26 for normal descending. The first flow rate Q1 is smaller than the above “regulated flow rate”.

A second throttle 27 is located downstream of the stop valve 28a in the emergency descending discharge line 28.
b is attached. The second throttle 27b narrows the flow area of the discharge line 28 so that only the pressurized oil having the second flow rate Q2 flows out from the emergency descending discharge line 28 at the maximum. Note that the second flow rate Q2 is also smaller than the above “regulated flow rate”. However, the first flow rate Q1 and the second flow rate Q
The sum of 2 is greater than the “regulated flow rate”.

In the hydraulic circuit 20 configured as described above,
In the case of performing a normal work at a high place, if the ascending opening / closing valve 24 a is opened to open the ascending supply line 24, the pressure oil discharged from the hydraulic pump 21 is supplied through the supply / discharge shared line 23. Since the oil is supplied to the bottom oil chamber Ca of the cylinder C, the work floor 14 can be raised. On the other hand, if the ascending opening / closing valve 24a is closed and the descending opening / closing valve 26a is opened, the pressure oil is discharged from the bottom side oil chamber Ca via the common supply / discharge line 23 and the normal descending discharge line 26. So work floor 1
5 can be lowered. Here, the first aperture 27a
, The discharge flow rate is suppressed to the first flow rate Q1 or less, so that the work floor 14 can be slowly lowered without switching the fuse valve 29 to the closed position and operating it.

In the case where the lowering opening / closing valve 26 fails and the pressurized oil cannot be discharged from the normal lowering discharge line 26, the stop valve 28a can be appropriately opened to open the bottom side oil chamber Ca. Supply / discharge shared line 2
Since the pressure oil is discharged through the discharge line 3 and the emergency lowering discharge line 28, the work floor 14 can be lowered. Here, the stop valve 2 is operated by the operation of the second throttle 27b.
Even when 8a is fully opened, the discharge flow rate can be suppressed to the second flow rate Q2 or less, so that the work floor 14 can be slowly lowered without switching and operating the fuse valve 29 to the closed position.

Further, before performing such high-place work, it is necessary to check the operation of the opening / closing valves 24a, 26a and the like as a start-up inspection. In this hydraulic circuit 20, the work floor 14 is slightly raised. In this state, the lowering opening / closing valve 26 is opened and the stop valve 28a is opened to near the fully open state, so that the pressure oil can be discharged from both the normal lowering discharge line 26 and the emergency lowering discharge line 28. it can. Since the total discharge flow rate (Q1 + Q2) at this time exceeds the "regulated flow rate" as described above, an "emergency state" can be created on a test basis, so that the fuse valve 29 can be switched to the closed position and actuated. it can. Therefore, if this hydraulic circuit 20 is used, the operation check of the fuse valve 29 can be performed as a start-up inspection.

[0023]

As described above, in the hydraulic circuit according to the present invention, the maximum discharge flow rate from the discharge line for normal descent is set to the first flow rate smaller than the regulated flow rate at which the descent of the work floor is prevented by the emergency descent prevention means. And the maximum discharge flow rate from the emergency descent discharge line is also suppressed to the second flow rate which is smaller than the regulated flow rate. For this reason, if this hydraulic circuit is used, the hydraulic oil can be discharged through the normal descending discharge line during normal work, and the pressure oil can be discharged through the emergency descending discharge line because the normal descending discharge line cannot be used. Even when the oil is discharged, the work floor can be smoothly lowered without operating the emergency lowering prevention means. Further, in this hydraulic circuit, the sum of the first flow rate and the second flow rate is larger than the regulated flow rate. Therefore, by discharging the pressurized oil from both the normal descending discharge line and the emergency descending discharge line,
The emergency descent prevention means can be activated experimentally.
Therefore, by using the hydraulic circuit of the present invention, it is possible to easily check the operation of the emergency descent prevention means at the time of starting inspection of the hydraulic elevating device or the like.

[Brief description of the drawings]

FIG. 1 is a side view of an aerial work vehicle equipped with a hydraulic circuit of a hydraulic lifting device according to the present invention.

FIG. 2 is a configuration diagram of the hydraulic circuit.

FIG. 3A is a configuration diagram of a conventional hydraulic circuit, and FIGS.
(C) is a diagram showing a part of (A).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Aerial work platform 14 Work floor 20 Hydraulic circuit 23 Supply / discharge shared line 24 Ascending supply line 26 Normal descending discharge line 27a First restrictor 27b Second restrictor 28 Emergency descending discharge line 29 Fuse valve (emergency descending prevention means) C hydraulic cylinder

Claims (1)

(57) [Scope of request for utility model registration] The work floor is raised by receiving and supplying pressure oil into a cylinder and extending the work floor, while the discharge of the pressure oil from within the cylinder is allowed to increase the work floor. A hydraulic circuit of a hydraulic elevating device comprising a single-acting hydraulic cylinder which is reduced by the weight of the single-acting hydraulic cylinder. A supply / discharge shared line for circulating pressure oil supplied / discharged, a rising supply line for supplying pressure oil to the single-acting hydraulic cylinder via the shared supply / discharge line, A discharge line for normal lowering for draining the pressure oil discharged from the single-acting hydraulic cylinder through a line, and a pressure oil discharged from the single-acting hydraulic cylinder through the supply / discharge shared line. Through And a very depressing discharge line for draining bypassing the lowering exhaust line, attached to the supply and discharge common line on,
When the discharge flow rate of the pressure oil from the single-acting hydraulic cylinder exceeds a predetermined regulated flow rate, the supply / discharge shared line is closed to stop the discharge of the pressure oil from the single-acting hydraulic cylinder, Emergency lowering prevention means for preventing the lowering of the work floor, and a first throttle means for suppressing the discharge flow rate of the pressurized oil in the normal lowering discharge line to a first flow rate at the maximum on the normal lowering discharge line. On the other hand, on the emergency descending discharge line, there is provided a second throttle means for suppressing a discharge flow rate of the pressure oil in the emergency descending discharge line to a maximum of a second flow rate, wherein the first flow rate and the second Although the flow rate alone is smaller than the regulated flow rate, the first flow rate and the second
A hydraulic circuit for a hydraulic elevating device, wherein the sum of the flow rates is set to be greater than the regulated flow rate.