JPH0128176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit for civil engineering construction machines such as hydraulic excavators and cranes.

A hydraulic excavator will be described below as an example of a civil engineering construction machine to which the present invention is applied.

FIG. 1 is a front view of the hydraulic excavator, and FIG. 2 is a plan view thereof. In the figure, 91 and 92 are crawlers, 93 is a revolving body rotatably supported by a traveling body having crawlers 91 and 92, 99 is a boom rotatably supported by the revolving body 93, and 98 is rotatable by a boom 99. 97 is arm 9
bucket rotatably supported on 8, 80,90
50 is a swing hydraulic motor for rotating the rotating structure 93; 70 is a boom hydraulic cylinder for rotating the boom 99; 40 is for rotating the arm 98. 60 is a bucket hydraulic cylinder for rotating the bucket 97. 4 is a prime mover attached to the revolving body 93. This prime mover 4 drives actuators such as the arm hydraulic cylinder 40.

FIG. 3 is a diagram showing a hydraulic circuit of a conventional hydraulic excavator. In the figure, 1 and 2 are pumps connected to the prime mover 4, and 10 and 20 are pumps 1 and 2, respectively.
11 is a left traveling switching valve connected to the traveling hydraulic motor 80 , 12 is a bucket switching valve connected to the bucket hydraulic cylinder 60 , and 13 is a boom switching valve connected to the boom hydraulic cylinder 70 The switching valves 11 to 13 are connected in parallel. 23 is a swing switching valve connected to the swing hydraulic motor 50, 22 is a right travel switching valve connected to the travel hydraulic motor 90, 24 is an arm switching valve connected to the arm hydraulic cylinder 40, and 21 is a boom hydraulic cylinder 70. The connected boom speed increasing switching valves include boom speed increasing switching valve 21 and boom switching valve 1.
3 and can be operated in conjunction with each other. Also,
The switching valves 21 to 24 are connected in parallel. 10
0 is a tank, A and B are relief valves connected to the pumps 1 and 2, respectively, and E is a throttle provided in a pipe line s connecting the arm switching valve 24 and the arm hydraulic cylinder 40. Note that the bucket hydraulic cylinder 60, boom hydraulic cylinder 70, and travel hydraulic motors 80 and 90 are omitted. The arm hydraulic cylinder 40 is connected to the arm switching valve 24 by the pipes s and t, and the swing motor 50 is connected to the swing switching valve 23 by pipes m and n. Also, a and b are discharge side pipes of the pumps 1 and 2, z is a parallel pipe of the switching valve group 20, and e and f are tank communication pipes of the switching valve groups 10 and 20.

Next, in the conventional hydraulic circuit, the arm switching valve 2
4 and the swing switching valve 23 are operated individually or in combination, the effects will be explained.

When the arm direction switching valve 24 is operated independently to the 24a side, the pressure oil of the pump 2 is transferred to the discharge side pipe b and the parallel pipe z.
It then enters the arm switching valve 24 and flows into the bottom side chamber of the arm hydraulic cylinder 40 through the pipe t, and the arm 98 clouds. At this time, the pressure oil in the rod side chamber of the arm hydraulic cylinder 40 returns to the tank 100 through the throttle E, the pipe s, the arm direction switching valve 24, and the tank communication pipe f. Moreover, when the arm direction switching valve 24 is operated independently to the 24b side, the pressure oil of the pump 2 enters the arm direction switching valve 24 from the discharge side pipe b and the parallel pipe z, passes through the pipe s and the throttle E, and is transferred to the arm. It flows into the rod side chamber of the hydraulic cylinder 40, and the arm 98 dumps. At this time, the pressure oil in the bottom side chamber of the arm hydraulic cylinder 40 is supplied to the tank 100 from the pipe t, the arm direction switching valve 24, and the tank communication pipe f.
Return to

Next, the arm direction switching valve 24 is operated to the 24a side, and the swing switching valve 23 is moved to the 23a or 23a side.
Move to side b. Normally, when the arm 98 is clouded, the arm 98's own weight is applied to the arm hydraulic cylinder 4.
Since it acts on the side that pushes out the zero rod, the load pressure is small. As a result, the pressure in the bottom side chamber of the arm hydraulic cylinder 40 becomes low, while the swing hydraulic motor 5
Since the pressure at the time of startup of the pump 0 is high, the pressure oil of the pump 2 flows from the parallel pipe z to the arm switching valve 24 side and does not flow to the swing switching valve 23 side, and the swing hydraulic motor 50 does not rotate at a predetermined speed. There's a problem. In order to prevent this, in the hydraulic circuit shown in FIG. 3, the back pressure in the pipe line s of the arm hydraulic cylinder 40 is increased by providing a restriction E in the pipe line s, and the pressure in the bottom side chamber of the hydraulic cylinder 40 is set to be higher than the load pressure. Increase it by the amount of pressure added. Therefore, the pressure in the bottom side chamber of the hydraulic cylinder 40 becomes sufficient to start the swing hydraulic motor 50, and the pressure oil of the pump 2 passes through the discharge side pipe b and the parallel pipe z, and part of the pressure oil is is the swing direction switching valve 2
3. Swing hydraulic motor 50 from pipe m or pipe n
The oil flows into the tank 1 from pipe n or pipe m, tank communication pipe f, and rotates the swing hydraulic motor 50.
Return to 00. The remaining pressure oil flows into the bottom side chamber of the arm hydraulic cylinder 40 through the arm switching valve 24 and the pipe t, and the arm 98 clouds. Pressure oil in the rod side chamber of the arm hydraulic cylinder 40 returns to the tank 100 through the throttle E, the pipe s, and the tank communication pipe f.

When the arm direction switching valve 24 is operated to the 24b side and the swing switching valve 23 is operated to the 23a or 23b side, the pressure oil from the pump 2 passes through the discharge side pipe b and the parallel pipe z, and part of the pressure oil is flows into the swing hydraulic motor 50 from the swing direction switching valve 23 through pipe m or pipe n, rotates the swing hydraulic motor 50, and
Or tank 10 from pipe m and tank communication pipe f
Return to 0. The remaining pressure oil flows into the rod chamber side of the arm hydraulic cylinder 40 through the arm switching valve 24, pipe s, and throttle E, dumping the arm 98, and the pressure oil in the bottom side chamber flows through the pipe t and the arm switching valve. 24, return to the tank 100 from the tank communication pipe f. At this time, the pressure oil in the pipe s is higher than the load pressure by the amount throttled by the throttle E.

The hydraulic circuit of the conventional hydraulic excavator described above has a restriction E in the pipe line s connecting the arm hydraulic cylinder 40 and the arm direction switching valve 24, so that the revolving body 93 can be rotated and the arm 98 can be rotated in the cloud. At this time, sufficient pressure to start the swing motor 40 can be built up on the bottom side of the arm hydraulic cylinder 40, so that the swing body 93 can swing at a predetermined speed.

However, when operating the arm 98 alone or when dumping the arm 98 and rotating the rotating body 93, which usually have a large arm load, the throttle E acts on the hydraulic circuit connected to the arm hydraulic cylinder 40. pressure becomes higher than necessary,
There are problems in that the pressure loss in the circuit increases, the temperature in the hydraulic circuit increases, and the fuel consumption rate of the prime mover also worsens.

This invention was made in view of the problems of the conventional hydraulic circuit described above, in which a plurality of actuators are connected to a hydraulic power source through respective directional control valves, and at least two of the directional control valves are connected to a hydraulic power source. In a hydraulic circuit of a civil engineering construction machine that is connected in parallel to the hydraulic power source, a first directional control valve located upstream of the directional control valves connected in parallel to the hydraulic power source and a first directional control valve located downstream A center bypass conduit is provided that connects in series a second directional control valve located on the side, a first input port of the first directional control valve and a first input port of the second directional control valve. and the first hydraulic pressure source connected to the hydraulic power source.
a parallel pipe line is provided, and a second pipe line of the first directional control valve is provided.
and a second input port of the second directional control valve, and a second parallel pipe connected to the hydraulic power source, and the second parallel pipe connects the hydraulic power source to the second input port of the second directional control valve. A pressure generating means for generating pressure on the upstream side between the connection point of and the second input port of the second directional control valve is provided, and the second parallel pipe is connected to the spool of the second directional control valve. A passage is provided that connects the center bypass line and the second parallel line when the center bypass line is in a position to connect the line and the output port of the second directional valve.

An embodiment of the present invention will be described below with reference to FIGS. 4 to 7. FIG. 4 is a sectional view of the directional control valves 21 to 24 housed in one valve block V. In the figure, a hydraulic source 2 indicates a pump 2;
3' and 24' indicate the spools of the swing switching valve 23 and the arm switching valve 24, respectively. z _a and z _b are parallel pipes,
f _a and f _b are tank communication pipes, r is a center bypass pipe, s' and t' are ports communicating with connection pipes s and t to the arm hydraulic cylinder 40 shown in FIG. 3, m',
n' indicates a port communicating with connecting pipes m and n to the swing motor 50. F is a relief valve provided in the parallel pipe line _zb between the swing switching valve 23 and the arm switching valve 24, K is a passage provided in the spool 24', and J is a check valve provided in the passage F.

If the circuit configuration of FIG. 4 is shown strictly as a circuit, it becomes the hydraulic circuit shown in FIG. 5. In FIG. 5, the same reference numerals as in FIGS. 3 and 4 indicate the same or equivalent components.

Next, the operation of the present invention will be explained.

(1) Arm independent operation (a) When the arm switching valve 24 is operated to the 24a side When the arm switching valve 24 is operated to the 24a side in Fig. 5, that is, when the arm switching valve 24 is operated to the 24a side in Fig. 4, the spool 2
4' is moved in the I direction to the state shown in FIG.
, opens the check valve J, enters the port t', and passes through the pipe t to the arm hydraulic cylinder 40.
flows into the bottom side chamber of and clouds the arm 98. Pressure oil in the rod side chamber of the arm hydraulic cylinder 40 returns to the tank 100 through the pipe s, port s', and tank communication pipe _fa .

(b) When the arm switching valve 24 is operated to the 24b side In Fig. 5, when the arm switching valve 24 is operated to the 24b side, that is, in Fig. 4, the spool 2
When moving in the direction of 4', pump 2
The pressure oil passes through discharge side pipe b, parallel pipe z _a , port s', pipe s, and reaches arm hydraulic cylinder 4.
Enter 0's rod side room and dump arm 98. Pressure oil in the bottom side chamber of the arm hydraulic cylinder 40 is supplied to the pipe t, port t', and tank communication pipe.
Return to tank 100 through f _b .

(2) Combined operation of arm and swing (a) When the arm switching valve 24 is moved in the I direction in Fig. 4 and the swing switching valve 23 is moved in the direction shown in Fig. 7, the pump 2 The pressure oil passes through the discharge side pipe b, a part of the pressure oil is supplied to the swing motor 50 via the parallel pipe z _a , port m', and pipe m, and the other pressure oil is supplied to the swing motor 50 through the parallel pipe
z _b , relief valve F, check valve J, port
t', and is supplied to the bottom side chamber of the arm hydraulic cylinder 40 via the pipe t. At this time, due to the action of the relief valve F, even if the load on the arm 98 is low, the pressure in the parallel pipe line _zb can be ensured to be high enough to rotate the swing motor 50, so the swing motor 50 is rotated at a predetermined speed. The arm 98 also clouds. Pressure oil in the rod side chamber of the arm hydraulic cylinder 40 returns to the tank 100 through pipe s, port s', and tank communication pipe f _a , and pressure oil returned from the swing motor 50 returns to pipe n, port n', and the tank. communication pipe
Return to tank 100 from f _b . Furthermore, when the arm switching valve 24 is moved in the I direction in FIG. 4 and the swing switching valve 23 is moved in the I direction,
Performs a similar action.

(b) When the arm switching valve 24 is moved in the direction and the swing switching valve 23 is moved in the I direction or the direction, the pressure oil of the pump 2 passes through the discharge side pipe b, and a part of the pressure oil flows through the parallel pipe. z _a or z _b , port m' or n', pipe m or n to the swing motor 50, and other pressure oil is supplied to the parallel pipe
It is supplied to the rod side chamber of the arm hydraulic cylinder 40 via z _a , port s', and pipe s. The arm 98 dumps, and the load at this time is large, so the pressure in the parallel pipe z _a is high, and the swing motor 5
0 rotates at a predetermined speed. Also in this case, since the pressure oil does not pass through the relief valve F, the pressure loss in the circuit is small.

As described above, according to the present invention, pressure loss in the hydraulic circuit can be reduced during operations other than simultaneous rotation of the cloud of the arm 98 and the revolving body 93, thereby reducing the temperature rise of the hydraulic circuit and the fuel consumption of the prime mover. This can prevent the consumption rate from deteriorating.

FIG. 8 is a sectional view showing another embodiment of the present invention;
FIG. 9 is a diagram strictly showing the circuit configuration of FIG. 8. In the figure, H is a throttle valve provided in place of the relief valve F in FIGS. 4 and 5. When performing a combined operation of the cloud of the arm 98 and the rotation of the rotating body 93, the pressure oil of the pump 2 is supplied from the parallel pipe _zb to the bottom side chamber of the arm hydraulic cylinder 40 via the throttle valve H, and the throttle valve H The pressure in the parallel line z _b is increased by throttling it. For other effects, please refer to the 4th section.
It is similar to that shown in FIG.

Although the above-mentioned embodiment has been described using an example of the swing of a hydraulic excavator and an arm, other combinations of actuators may be used. Further, even if the present invention is applied to a hydraulic circuit of a civil engineering construction machine other than a hydraulic excavator, similar effects can be obtained.

As explained above, according to the present invention, when a plurality of actuators connected in parallel to a hydraulic power source via directional control valves are operated simultaneously, even if the load when driving one actuator in one direction is small. , high enough pressure can be built up in the parallel conduit to drive other actuators, and
During individual operation of each actuator and combined operation in a direction other than the one direction described above, pressure loss in the hydraulic circuit can be minimized, temperature rise in the hydraulic circuit can be prevented, and fuel consumption rate of the prime mover can be improved.

[Brief explanation of drawings]

Fig. 1 is a front view of a hydraulic shovel, Fig. 2 is a plan view thereof, Fig. 3 is a diagram showing a hydraulic circuit of a conventional hydraulic excavator, and Fig. 4 is a hydraulic circuit used in a hydraulic excavator according to the present invention. A cross-sectional view of the directional control valve, Fig. 5 is a hydraulic circuit diagram strictly showing the circuit configuration of the directional control valve shown in Fig. 4, and Figs. 6 and 7 show the operation of the directional control valve shown in Fig. 4. The explanatory diagram, FIG. 8, is a sectional view showing another embodiment of the present invention, and FIG. 9 is a diagram strictly showing the circuit configuration of FIG. 8. 1, 2...Hydraulic source (pump), 23...Swivel switching valve,
23'...Spool, 24...Arm switching valve, 24'...
Spool, 40...Arm hydraulic cylinder, 50...Swivel motor, z _a , z _b ... Parallel pipe line, r... Center bypass pipe line, F... Relief valve, H... Throttle valve, K... Passage.

Claims (1)

[Claims] 1. A plurality of actuators are connected to a hydraulic power source via respective directional switching valves, and at least two of the directional switching valves are connected in parallel to the hydraulic power source. In the hydraulic circuit of civil engineering and construction machinery, a first directional switching valve located on the upstream side and a second directional switching valve located on the downstream side of the directional switching valves connected in parallel to the hydraulic power source. a center bypass conduit connecting the first directional control valve in series with the first input port of the first directional control valve and the first input port of the second directional control valve and connected to the hydraulic pressure source; a first parallel pipe line connected to the second input port of the first directional valve and the second input port of the second directional valve, and connected to the hydraulic power source. A second parallel pipe is provided, and pressure is generated on the upstream side between the connection point of the second parallel pipe with the hydraulic pressure source and the second input port of the second directional control valve. generating means is provided, and when the spool of the second directional control valve is at a position where the second parallel pipe line and the output port of the second directional control valve are connected, the center bypass pipe and the above A hydraulic circuit for a civil engineering construction machine, characterized in that a passageway is provided to connect the second parallel conduit. 2. A hydraulic circuit for civil engineering and construction machinery according to claim 1, characterized in that a relief valve is used as the pressure generating means. 3. The hydraulic circuit for civil engineering and construction machinery according to claim 1, characterized in that a throttle valve is used as the pressure generating means.