JPH0411689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit for a hydraulic excavator. The objectives are: (1) To enable the vehicle to travel straight without meandering by simply operating a single lever or pedal.

(2) Even if other operations such as turning, arm, boom, or bucket operations are performed at the same time during the straight-line operation, the straight-line performance of the hydraulic excavator can be maintained, and this improves the functionality of the hydraulic excavator. It can be used for multiple purposes, and it also reduces driver fatigue.
The present invention aims to provide a hydraulic circuit for a hydraulic excavator that improves work efficiency.

FIG. 1 shows a conventional hydraulic circuit, where 1 is a first hydraulic pump and 2 is a second hydraulic pump, each of which is driven by an engine (not shown). 5 is a first control valve, which includes a left and right travel valve 5a, a swing valve 5b, an arm valve 5c, and a boom 2.
It has a speed valve 5d and a main relief valve 5e. A second control valve 6 includes a right travel valve 6a, a boom 1st speed valve 6b, a bucket valve 6c, and a main relief valve 6d.

Now, with this conventional hydraulic circuit, (1) When driving straight, the left and right travel valves 5a and 6a must be constantly turned on and held in the same direction at the same time, which increases driver fatigue. It was hot.

(2) If other operations are performed while traveling straight, the discharge amount of the hydraulic pump on the operation side will be diverted to other operations, so the speed of the travel motor on the operation side will decrease and the meandering will occur. There was a drawback.

The present invention improves the drawbacks of the conventional hydraulic circuit, and its structure can be summarized as follows.

That is, in the hydraulic circuit of a hydraulic excavator having two pumps and two control valves, pressure oil is supplied to the left and right travel motors in a pipe connecting the left and right travel motors of the first and second control valves. Equipped with a switching valve that switches supply and discharge independently and in parallel.
and a pilot switching valve for opening and closing the neutral passages is provided at the most downstream of the neutral passages of the first and second control valves, and a pipe line branching from the front stage of the pilot switching valve is connected to the switching valve, and The pilot pipe line of the pilot switching valve is connected to a switching valve that is switched in conjunction with the independent/parallel switching operation of the switching valve, and pilot pressure is supplied and cut off.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydraulic circuit of a hydraulic shovel according to the present invention will be described below with reference to the embodiments shown in FIG. In FIG. 2, 1 is a first hydraulic pump, 2 is a second hydraulic pump, and 3 is a pilot pump, each of which is driven by an engine (not shown). 4 is a relief valve for the pilot pump.

5 is a first control valve to which pressure oil is supplied from the first hydraulic pump 1, a left/right travel valve 5a;
It has a swing valve 5b, an arm valve 5c, a boom second speed valve 5d, and a main relief valve 5e, and a first pilot switching valve 5f is disposed at the most downstream position of the neutral passage.

Reference numeral 6 denotes second control valves to which pressure oil is supplied from the second hydraulic pump 2, including a right travel valve 6a, a boom 1st speed valve 6b, a bucket valve 6c,
It has a main relief valve 6d, and a pilot switching valve 6e is disposed at the most downstream side of the neutral passage.

Numerals 7 and 8 are conduits for guiding pressure oil from the pilot switching valves 5f and 6e, and a confluence pipe 10 is connected to a switching valve 21, which will be described later, via check valves 9 and 9', respectively.
are merging with. 11 and 12, 13 and 14 are supply and discharge pipes for left travel, and 15 and 16 and 17 and 18 are supply and discharge pipes for right travel.

19 are pilot switching valves 5f, 6e and switching valve 2
0 and 20 are switching valves that control the pilot pressure of the pilot switching valves 5f and 6e.In the neutral position, the pilot pipe 19 is connected to the tank and no pilot pressure is generated in the pipe 19. Since the pilot switching valves 5f and 6e are in an open state, the pressure oil of the first and second hydraulic pumps 1 and 2 does not flow to the pipe line 10 side.

When the switching valve 20 is switched to the "A" or "B" position, the pilot line 19 is connected to the pilot pump 3, pressure oil is supplied from the pump 3, and the pilot switching valves 5f and 6e are changed from the open state to the closed state. state, and the pressure oil from the first and second hydraulic pumps 1 and 2 flows into the pipe line 10.

Reference numeral 21 denotes a parallel/independent switching valve that is switched in conjunction with the switching valve 20, and in the neutral position, the left running supply/discharge pipe 11 is connected to the pipe 12, the pipe 13 is connected to the pipe 14, and the right running supply/discharge pipe 11 is connected to the pipe 14. The supply/discharge pipe line 15 is the pipe line 16
The conduit 17 is connected to the conduit 18, and the confluence conduit 10 is connected to the tank passage.

Next, when the switching valve 21 is switched to the "A" position, the confluence pipe 10 is connected to the pipe 12 and the pipe 18, the pipe 13 is connected to the pipe 14, and the pipe 15 is connected to the pipe 16. The other conduit 11 and conduit 17 are blocked. Conversely, when switched to the "ro" position, the confluence pipe 10 is connected to the pipes 14 and 16, the pipe 11 is connected to the pipe 12, and the pipe 17 is connected to the pipe 18.
and the other pipes 13 and 15 respectively.
will be blocked. In this way, in the case of a parallel circuit, the direction of supply of pressure oil to the motor is changed, and backward running is possible.

Fig. 3 shows another embodiment of the internal connection of the switching valve 21, and when the switching valve 21 is switched to the "A" and "B" positions, the pipes other than those connected to the pressure oil supply side pipe 10 are shown. All have a structure that connects them to the tank.

FIG. 4 shows another embodiment of the interlocking method of the switching valve 20 and the switching valve 21, in which the switching valve 20 is used as an auxiliary valve for the switching valve 21 so that it can be directly switched.

Furthermore, FIG. 5 shows another embodiment of the present invention, in which the switching positions of the pilot switching valves 5f, 6e and the supply of pilot pressure are partially changed from those in FIG. 2.

That is, in the embodiment shown in FIG. 2, when the switching valve 20 is in the neutral position, the pilot line 19 is opened to the tank;
While the pilot switching valves 5f and 6e are held open, in the embodiment shown in FIG.
They are the same except that the pilot line 19 and the pilot hydraulic pressure source are connected at the neutral position of the pilot valve, and the pilot pressure is used to hold the pilot switching valves 5f and 6e open.

In the above embodiment, the pilot switching valve 5
An embodiment has been described in which the pilot pipes connecting the pilot pipes f, 6e and the switching valve 20 are merged and then guided to the switching valve 20. In this example, the pilot pressure for switching the pilot switching valves 5f and 6e is derived from the pilot pump 3. It goes without saying that changes can be made without departing from the gist of the present invention, such as directing it from the second hydraulic pump.

The present invention has the above structure and its operation will be explained below.

1. When traveling straight ahead independently: (a) When the switching valve 21 is switched to the "A" position, the merging pipe 10 is connected to the pipe 12 and the pipe 18, and the pipe 13 is connected to the pipe 14. , and the pipe line 15 is connected to the pipe line 16, respectively, and the pipe line 11 and the pipe line 1 are connected to each other.
7 becomes a block. Also, since the switching valve 20 linked to the switching valve 21 is also switched to the "A" position, the second
In the embodiment shown, the pilot pipe 19 is supplied with pressure oil from the pilot pump 3, and in the embodiment shown in FIG. Switch to "A" position. As a result, the pressure oil of the first hydraulic pump 1 and the second hydraulic pump 2 flows through the conduit 7 and the conduit 8, respectively, into the confluence conduit 10, and then flows into the conduit 12 and the conduit 18 via the switching valve 21. It is divided into equal amounts and flows into the left and right travel motors.
Also, the return oil from the left and right travel motors is connected to pipe 1, respectively.
4 and the pipe line 16, and the pipe line 13 via the switching valve 21.
and returns to the tank through the pipe 15, the left-hand travel valve 5a, and the right-hand travel valve 6a. Therefore, the same pressure and the same amount of pressure oil are supplied to the left and right travel motors, and the vehicle moves straight in the forward direction at the same speed.

(b) When the switching valve 21 is switched to the "ro" position, the direction of pressure oil supply to the travel motors is reversed from the explanation in item (a) above, but in the same way, the left and right travel motors are at the same speed. This will cause you to go straight in the reverse direction.

2 If other operations are performed simultaneously while traveling straight: (a) If turning is simultaneously performed while traveling straight, switch the switching valve 21 to the "A" (forward) or "B" (reverse) position, and also turn the Valve 5b
When switched, the switching valve 20 and the pilot switching valves 5f and 6e become the same as explained in 1-(a) and 1-(b) above, and the swing valve 5b and the pilot switching valve 5f form a tandem circuit, The pressure oil of the first pump does not flow to the pilot switching valve 5f side, but flows entirely to the swing motor side. Further, the entire pressure oil of the second hydraulic pump 2 is diverted to the left and right travel motors.
Therefore, pressure oil from independent hydraulic pumps is used for turning and traveling, and straight-line traveling is possible even when turning is performed.

(b) In the case of simultaneous arm operation while traveling straight; It is exactly the same as 2-(a) above, and arm operation is possible while traveling straight.

(c) In the case of simultaneous boom operation while traveling; The above procedure is the same as in 2-(a) and 2-(b) except that the hydraulic pump on the pressure oil supply side is replaced, so operate the boom in 1st gear while traveling straight. is possible.

(d) In the case of simultaneous bucket and tot operations while traveling straight; This is the same as 2-(c) above, and it is possible to perform bucket and tot operations while maintaining straight travel.

As described above, in the present invention, the switching valve 21 and the switching valve 20 can be easily operated by allowing the switching of the merging from the first and second pumps and the running direction by operating only one lever or pedal. Furthermore, even if other operations are performed during the above operation, the straightness of travel can be maintained, allowing the hydraulic excavator to be used for multiple purposes.

In addition, when performing the same traveling operation as before, selector valve 2
This can be done by operating the left and right travel valves 5a and 6a, as in the conventional case, without operating the valves 0 and 21. Also,
In Figures 2 and 5, the first and second hydraulic pumps 1 and 2 are shown as fixed capacity pumps, but they may be variable capacity pumps, and the switching valves 20 and 21 are shown as manually operated, but they are pilot operated valves. Alternatively, a solenoid valve may be used. Furthermore, the pilot switching valve 5f,
Although 6e is integrated with the first and second control valves 5 and 6, they may of course be placed separately.

In the above embodiments, a hydraulic excavator has been described, but it goes without saying that the present invention can also be applied to machines such as hydraulic crawler cranes, etc., in which traveling is driven by a hydraulic motor and other operations are driven by a hydraulic motor or a hydraulic cylinder.

[Brief explanation of drawings]

Figure 1 shows the hydraulic circuit of a conventional hydraulic excavator. FIG. 2 shows a hydraulic circuit according to the present invention. Figure 3 shows switching valve 2.
Other embodiments of 1. FIG. 4 shows another embodiment of the method of interlocking two switching valves. FIG. 5 shows another embodiment of the present invention. In the figure: 1...first hydraulic pump, 2...second hydraulic pump, 3...pilot pump, 4...relief valve (for pilot pump), 5...first control valve, 5a...valve for left travel, 5b...for turning Valve, 5c...Arm valve, 5d...Boom 2nd speed valve, 5e...Main relief valve,
5f...Pilot switching valve, 6...Second control valve, 6a...Right travel valve, 6b...Boom 1
speed valve, 6c...bucket valve, 6d...main relief valve, 6e...pilot switching valve,
7... Pipe line (guiding pressure oil from the pilot switching valve of the first pump group), 8... Pipe line (guiding pressure oil from the pilot switching valve of the second pump group),
9, 9'... Check valve, 10... Merging pipe (of pipe 7 and pipe 8), 11, 12, 13, 14... Supply/discharge pipe for left running, 15, 16, 17, 18... Right running Supply/discharge pipe line, 19...Pilot pipe line, 20...
(For controlling pilot switching valves 5f and 6e)
Switching valve, 21... switching valve.

Claims (1)

[Claims] 1 In the hydraulic circuit of a hydraulic excavator having two pumps and two control valves, the left and right travel valves 5 of the first and second control valves 5 and 6
A switching valve 21 that switches the supply and discharge of pressure oil to the left and right travel motors independently and in parallel is provided in the pipe connecting the left and right travel motors to the left and right travel motors. A pilot switching valve 5 that opens and closes the neutral passage, respectively, at the most downstream side of the neutral passage.
f, 6e, and the pilot switching valve 5
The pipes 7 and 8 branched from the front stage of the pilot switching valves 5f and 6e are connected to the switching valve 21, and the pilot switching valves 5f and 6e are connected to the switching valve 21.
The pilot pipe 19 of 6e is connected to the switching valves 5f and 6.
The switching valve 20 is connected to the switching valve 20 which is switched in conjunction with the independent/parallel switching operation of e, and is opened and closed alternately in response to switching of the switching valve 21.
By switching 1, both the pilot switching valves 5f and 6e on the first control valve 5 side and the second control valve 4 side are closed, both pilot switching valves are shut off, and pressure oil is supplied from the preceding stage to the traveling motor. , a hydraulic circuit for a hydraulic excavator characterized in that no pressure oil is supplied from the left and right travel valves.