JPS60253630A - Oil-pressure circuit for rocking of slewing body of slewing working vehicle - Google Patents

Abstract

PURPOSE:To miniaturize rocking cylinders by a method in which a slewing base is pivotally supported in a rocking manner around the horizontal axis on a traveler, two rocking cylinders are provided, the bottom chamber and the rod chamber are led to each other, and a counterbalance valve is provided. CONSTITUTION:In an oil-pressure shovel capable of excavating vertical trenches in sloped or ungraded ground, a rocking plate 9 is pivotally supported in a rocking manner around the horizontal axis on the frame 2 of a traveler 1, and a slewing base and a front mechanism are provided on the rocking plate 9. Two rocking cylinders 20 are also provided between the frame 2 and the rocking plate 9 and connected to the pressure oil of an oil-pressure pump 14 through a rocking control valve 15 and a counter balance valve 26. The bottom chamber of one cylinder is led to the rod chamber of the other cylinder. The rocking cylinders can thus be miniaturized and the chattering of the rocking control valve and the runaway of the slewing body can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a hydraulic circuit for swinging a revolving body in a revolving work vehicle such as a hydraulic excavator.

[Background of the invention]

2. Description of the Related Art There is a hydraulic excavator in which a revolving body on which a front member is disposed is swingable relative to a traveling body in order to enable excavation of vertical trenches on slopes or uneven terrain.

FIGS. 4 and 5 show the structure of a conventionally known hydraulic excavator of this type. FIG. 4 is a side view showing the overall structure of a conventionally known hydraulic excavator of this type, and FIG. 5 is a sectional view of the swinging section of this hydraulic excavator as seen from the front side.

In these figures, 1 is a running body, 2 is a frame of the running body 1, 3 is a guide shaft arranged in front of this frame 2, 4 is a drive shaft arranged behind the frame 2, and 5
is an upper roller provided above the frame 2, 6 is a lower roller provided below the frame 2, and 7 is mounted on the guide shaft 3, drive shaft 4, upper roller 5, and lower roller 6. Tracks.

8 is a fulcrum formed above the central part of the frame 2; 9
10 is a rotating body mounted on the upper surface of the swinging plate 9; 11 is a rotating body 1;
0 is a pivot shaft attached to the swing plate 9 so as to rotate 360 degrees, 12 is a front member provided on the rotating body 10, and 13° 13a are both ends of the frame 2 and the swing plate 9. is provided between the swing plate 9 and the traveling body 1.
It is a hydraulic cylinder that swings against the

This hydraulic excavator includes hydraulic equipment such as a prime mover, a hydraulic pump, and a directional control valve, a travel motor that drives the drive shaft 4, a swing motor that swings the swing structure 10, and a hydraulic cylinder that operates the front member. An actuator is arranged (not shown). By controlling the pressure oil supplied to this actuator (not shown) with a directional control valve (not shown), the traveling body 1 and the rotating body 10 are
, the front member 12 may be operated alone or in combination as appropriate to perform desired work such as excavation. For example, when excavating a trench on a slope or uneven ground, a swinging hydraulic cylinder]3. 'By operating I3a accordingly,
When the revolving body lO provided with the front member J2 is swung to a horizontal position, the front member 12 can be operated vertically, making it possible to excavate a vertical trench regardless of the inclination of the traveling body l. Become.

FIG. 6 is a circuit diagram showing a hydraulic circuit for operating a swinging hydraulic cylinder provided in a conventional hydraulic excavator of this type.

In this figure, 14 is the hydraulic cylinder 13° 13a.
15 is a swinging direction switching valve that controls the direction of pressure oil supplied from the hydraulic pump 14 to the hydraulic cylinders 1.3 and 138; 16.16a is an output of the direction switching valve 15; [] and the swinging hydraulic cylinder 13,1
A pipe line 17.17a connects this pipe line 16,
A relief valve is interposed between 16a, 18 is a center joint provided between traveling body 1 and rotating body 10 and inserted through the pipes 16 and 16a, and 19 is an oil tank.

As shown in FIG. 6, in the conventional swinging work vehicle, a single-acting hydraulic cylinder is used as the swinging hydraulic cylinder 13.13a for swinging the swinging body 1, and the swinging directional control valve 15 is Two outlet lines 16, 16a are connected to the respective hydraulic cylinders 13, 13 via a center joint 18.
connected to a.

In such a swinging hydraulic cylinder, by switching the swinging directional control valve 15 to the switching position A, the pressure oil from the hydraulic pump 14 is transferred to the above-described swinging directional control valve 15, the center joint 18, and the pipe line 16. It is supplied to one swinging hydraulic cylinder 13 provided at the left end of the swinging plate 9,
The pressure oil filled in the other swinging hydraulic cylinder 13a provided at the right end of the swinging plate 9 is discharged by the pressing force of the swinging plate 9, and the pressure oil is discharged from the pipe 16a and the swinging directional control valve 15.
, and is returned to the oil tank 19 via the center joint 18. As a result, the s# plate 9°, that is, the rotating body 1o can be tilted to the right with respect to the traveling body 1. On the contrary, when the swinging directional control valve 15 is switched to the switching position B,
Pressure oil from the hydraulic pump 14 is supplied to the swinging directional control valve 15. The swing plate 9 is connected to the center joint 18 through the conduit 16a.
Said other swinging hydraulic cylinder i provided at the right end of
The pressure oil supplied to 3a and filled in the -force swinging hydraulic cylinder 13 provided at the left end of the swing plate 9 is discharged by the pressing force of the swing plate 9, and is discharged from the pipe line 16, Swinging directional control valve 15. It is returned to the oil tank 19 via the center joint 18. As a result, the rocking plate 9,
That is, the rotating body 10 can be tilted to the left with respect to the running body 1.

However, as described above, in the conventional hydraulic circuit for swinging a swinging body, a single-acting hydraulic cylinder is used as the swinging hydraulic cylinder.

When the rotating body 10 is swung and the center of gravity moves from the fulcrum 8 to the inclined side, (the full load acts on the swinging hydraulic cylinder on the IJI slanted side and the fulcrum 8, and the other swinging hydraulic cylinder is involved in bearing the load. Therefore, the swinging hydraulic cylinder 13,
13a, it must be equipped with a large-capacity hydraulic cylinder that can handle this shared load, which not only increases manufacturing costs but also requires a large installation space, which has the disadvantage of being subject to moderate design constraints. be.

In order to make this situation clearer, FIG. 7 schematically shows the loads acting on the swinging hydraulic cylinders 13, 13a and the fulcrum 8. As shown in FIG. 7, the rocking plate 9 is rocked to the left, and the center of gravity W of the rocking plate 9 (rotating body 10) is moved to the left side of the fulcrum 8 and a distance L from the fulcrum 8. case,
R1 is the reaction force acting on the swinging hydraulic cylinder 13 installed at a distance l from the fulcrum 8 on the left side of the fulcrum 8; R2 is the reaction force acting on the fulcrum 8; Swinging hydraulic cylinder 13a provided at a distance of 1
If the reaction force acting on the oscillation plate 9 is R3, then R1=WXL/I R2=-W (1-L/1) R3=0, and the reaction force is applied to the oscillation hydraulic cylinder 13a provided on the right side of the oscillation plate 9. It can be seen that the swinging hydraulic cylinder 13 provided on the left side of the swinging plate 9 bears a large load.

Further, as described above, in the conventional hydraulic circuit for swinging a swinging body, the magnitude of the load applied to the swinging hydraulic cylinder changes as the swinging plate 9 swings, and the swinging directional control valve 15 The pipes 15, 15a connecting the oscillating hydraulic cylinder 13.1.3a must be routed through the center joint 18, and the pipes 16, 16a are long and narrow in diameter to supply pressure oil. Since the suction resistance of the hydraulic cylinder is large, there is a drawback that negative pressure is likely to be generated in the swinging hydraulic cylinder as the swinging plate 9 swings.

For example, when switching the swing direction switching valve 15 to switching position A and swinging the swing plate 9 tilted to the left to the right, the center of gravity of the swing plate 9 moves from the left side of the fulcrum 8 to the right side. Then, the load on the swing plate 9 is transferred to the right swing hydraulic cylinder 13a.
Then, the pressure oil in the swinging hydraulic cylinder 13a is pushed out and the swinging hydraulic cylinder 13a suddenly tilts to the right. In this case, pressure oil proportional to the tilting speed of the rocking plate 9 is not supplied to the leftward swinging hydraulic cylinder 13 due to the large suction resistance, and the rightward swinging hydraulic cylinder 13 becomes negative pressure.

When the swinging hydraulic cylinder 13 becomes negative pressure, the swinging directional control valve 15 may chattering or the swinging plate 9 may
．． In other words, a serious problem will occur in that the swinging motion of the revolving structure 1O becomes unstable.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned actual state of the prior art, and an object of the present invention is to provide a hydraulic circuit for swinging an upper revolving body in a revolving work vehicle that is highly stable, compact and economical. That is.

[Summary of the invention]

In order to achieve the above object, the present invention provides a double-acting hydraulic cylinder as a hydraulic cylinder disposed between a frame of a traveling body and both ends of a rocking plate pivotally supported on the frame. A counterbalance valve is interposed between the hydraulic cylinder and a swinging direction switching valve that controls the direction of pressure oil supplied to the hydraulic cylinder, and two outlet pipes of the counterbalance valve are connected to each other. One of the outlet pipes is connected to a rond side chamber of a hydraulic cylinder arranged on one side of the swing plate and a bottom side chamber of a hydraulic cylinder arranged on the other side of the swing plate, and the two outlet pipes are connected to each other. The other outlet pipe is connected to a bottom side chamber of a hydraulic cylinder arranged on one side of the swing plate and a rond side chamber of a hydraulic cylinder arranged on the other side of the swing plate. .

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings. In this embodiment, the same members as shown in FIGS. 4 to '6rgJ are designated by the same reference numerals.

FIG. 1 is a circuit diagram showing a hydraulic circuit for swinging a rotating body according to the present invention, and FIG. 2 is a sectional view showing the configuration of a swinging section of a swinging work vehicle according to the present invention.

Reference numeral 20.20a is a swinging hydraulic cylinder for swinging the revolving structure 1o, and a double-acting hydraulic cylinder is used. That is, the swinging hydraulic cylinders 20, 20a have their interiors connected to the bottom side chambers 22, 22 by the pistons 21.21a.
a and a rod side chamber 23.degree. 23a, and by selectively supplying pressure oil to the bottom side chamber 22.degree. It has become. 24 and 25 are the swinging directional control valve 15 and the swinging hydraulic cylinder 20.
．． 20a, and these two pipes 2
4 and 25, one pipe line 24 is connected to the rod side chamber 23 of one swinging hydraulic cylinder 2o and the bottom side chamber 22a of the other swinging hydraulic cylinder 20a, and the other pipe line 25 is It is connected to the bottom side chamber 22 of the one hydraulic cylinder 2o and the rod side chamber 23a of the other hydraulic cylinder 20a. Reference numeral 26 denotes a counterbalance valve, which is interposed in the pipe line 24.25 between the swinging directional control valve 15 and the relief valve 17.17a.

In this hydraulic circuit, when the swinging directional control valve 15 is switched to the switching position A, the pressure in the pipe line 24 increases, and when this pressure reaches the operating pressure of the counterbalance valve 26, the pilot signal 26a causes the counterbalance valve 26 to is switched to the switching position a, and the pressure oil from the hydraulic pump 14 is transferred to one of the swinging hydraulic cylinders 2o provided at the left end of the swinging plate 9.
and the bottom side chamber 22a of the other swinging hydraulic cylinder 20a. Further, the pressure oil in the bottom side chamber 22 of one swinging hydraulic cylinder 2o and the rod side chamber 23a of the other swinging hydraulic cylinder 20a is changed as the pressure oil is supplied to the rod side chamber 23 and the bottom side chamber 22a.
The oil is returned to the oil tank 19 via the counterbalance valve 26 and the swinging directional control valve 15, and is transferred to the swinging plate 9, that is, the rotating body 1.
o is tilted to the left. In this case, when the center of gravity of the rotating body 10 moves to the left with the swinging of the swinging Fi9, the rod side chamber 23 of one swinging hydraulic cylinder 20 and the bottom of the other swinging hydraulic cylinder 20a receive the load. The pressure in the side chamber 22a, that is, the pressure in the pipe line 24, decreases, but when this pressure falls below the operating pressure of the counterbalance valve 26, the counterbalance valve 26 is switched to the neutral position by the pilot signal 26a, and the pipe line is opened again. Pressure oil is not returned to the oil tank 19 from the bottom side chamber 22 of the one swinging hydraulic cylinder 20 and the rod side chamber 23a of the other swinging hydraulic cylinder 208 until the pressure of 24 reaches the operating pressure of the counterbalance valve 26. will be stopped. By repeating the above actions.

The rocking plate 9 (swivel body 10) can be smoothly rocked to the left. On the contrary, the swing direction switching valve 15 is switched to the switching position B.
In this case, the pressure oil is controlled in exactly the same manner as described above, and the swing plate 9 (swivel body io) can be smoothly rocked to the left.

In this way, since the counterbalance valve 26 is interposed in the pipes 24 and 25 that connect the hydraulic cylinders 20 and 20a and the swinging directional control valve 15, the pressure in the pipe 24 (25) causes the counterbalance valve 26 to operate. Returning of the pressure oil from the return side of the swinging hydraulic cylinders 20, 20a is stopped until the pressure is reached, and as the swinging plate 9 swings, the weight of the rotating body IO acts on the swinging hydraulic cylinders 20, 20a. Even if the pressure oil supply side of the swing hydraulic cylinders 20, 20a becomes negative pressure.

Therefore, chattering of the swinging direction switching valve 15 and runaway of the rotating structure 10 in the swinging direction can be prevented.

In addition, since the double-acting hydraulic cylinder 20.20a is used as the swinging hydraulic cylinder, the swinging plate 9, that is, the rotating body 10
The weight of the fulcrum 8 and the two swinging hydraulic cylinders 20, 2
0a, the load burden shared by each swinging hydraulic cylinder is smaller than when using a conventional single-acting swinging hydraulic cylinder 13°13a. It will be enough.

The reaction forces acting on the fulcrum 8 and the swinging hydraulic cylinder 20.20a are schematically shown in FIG. When the rocking plate 9 is rocked to the left and the center of gravity W of the rocking plate 9 (swivel body 10) moves to the left side of the fulcrum 8 and the distance from the fulcrum 8 is L, the fulcrum is on the left side of the fulcrum 8. R1 is the reaction force acting on the swinging hydraulic cylinder 13, which is located at a distance of 1 from the fulcrum 8, R2 is the reaction force acting on the fulcrum 8, and is located on the right side of the fulcrum 8 at a distance of 1 from the fulcrum 8. Let R3 be the reaction force acting on the provided swinging hydraulic cylinder 13a, and let α (>1) be the ratio between the piston area on the bottom side and the piston area on the rond side of the swinging hydraulic cylinder 13.13a.

R1=WX L/lX (E/(1+a)R2=
W(1-L/l X(1-α)/(1+α))R3=W
XL/l It can be seen that the load burden shared by 20a is smaller than in the conventional case.

〔Effect of the invention〕

As described above, the hydraulic circuit for swinging the upper revolving body in the swing work vehicle of the present invention uses a double-acting hydraulic cylinder as the hydraulic cylinder that operates the swinging plate, and the hydraulic circuit is supplied to this hydraulic cylinder from the hydraulic pump. Outlet side pipe of the swinging directional control valve that controls pressure oil.

Since they are connected to the bottom side chamber of one hydraulic cylinder and the rod side chamber of the other hydraulic cylinder, the weight of the rocking plate can be shared between the connecting pin of the fulcrum and the two hydraulic cylinders, which is different from the conventional single-acting hydraulic cylinder. Compared to the case where cylinders are used, the weight to be shared by one hydraulic cylinder is reduced. Therefore.

The hydraulic cylinder can be downsized, manufacturing costs can be reduced, and the degree of freedom in design can be improved. In addition, a counterbalance valve was installed in the pipe connecting the swinging directional control valve and the swinging hydraulic cylinder.
The swinging hydraulic cylinder does not become a negative pressure, and chattering of the swinging directional control valve and runaway of the rotating body during swinging operation can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing the configuration of a swinging part of a swing work vehicle equipped with the hydraulic circuit of the present invention, and FIG. 3 is a hydraulic circuit of the present invention. FIG. 4 is a schematic diagram showing the load distribution acting on the swinging part of a swinging work vehicle equipped with Figure 5 is a sectional view from the front side showing the structure of the swinging part of the hydraulic excavator shown in Figure 4, Figure 6 is a circuit diagram showing a conventional hydraulic circuit for swinging a swinging body, and Figure 7 is a diagram of a conventional swinging unit. FIG. 3 is a schematic diagram showing load distribution acting on the swinging portion of the work vehicle. 1: Running body, 2: Frame, 3: Guide shaft, 4: Drive shaft,
5: Upper roller, 6: Lower roller, 7: Track, 8: Fulcrum, 9
: Rocking plate, 10: Swivel body, 11: Swivel shaft, 12: Front member, 13, 13a: Hydraulic cylinder for rocking, ]4: Hydraulic pump, 15: J! ! Dynamic directional valve, 16.16a
: Outlet pipe, 17° 17a: Relief valve, 18: Center joint, 19 Ni oil tank, 20.20a: Hydraulic cylinder, 2i, 21a: Piston, 22, 22a: Bottom side chamber, 23, 23a: Rod side chamber, 24.25j Pipe line, 26: Counter balance valve Fig. 2 Fig. 3 Fig. 5 Fig. 6 Fig. 7

Claims (1)

[Claims] Two swinging hydraulic cylinders are arranged between the frame of the traveling body and both ends of a swinging plate that is swingably provided on the upper part of the frame, and pressure oil is supplied to the second swinging hydraulic cylinder. In a hydraulic circuit for swinging a swinging body of a swinging work vehicle, which is equipped with a hydraulic pump for supplying hydraulic oil, and a swinging direction switching valve for controlling the direction of pressure oil supplied from the hydraulic pump to the swinging hydraulic cylinder, "C1" is connected to the frame. A double-acting hydraulic cylinder is used as the hydraulic cylinder disposed between both ends of the swinging plate, and a counterbalance valve is interposed between this hydraulic cylinder and the swinging direction switching valve, and the counterbalance One of the two outlet pipes of the valve is connected to a rond side chamber of a hydraulic cylinder arranged on one side of the swing plate and a bottom side chamber of a hydraulic cylinder arranged on the other side of the swing plate. , the other of the two outlet pipes is connected to a bottom side chamber of a hydraulic cylinder arranged on one side of the swing plate and a rond side chamber of a hydraulic cylinder arranged on the other side of the swing plate. A hydraulic circuit for swinging a revolving body of a revolving work vehicle, characterized by: