JPH049892B2 - - 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). A first control valve 5 includes a left travel valve 5a, a swing valve 5b, an arm valve 5c, a boom 2nd 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 the driver's 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 through a pipe connecting the left and right travel motors to the left and right travel valves of the first and second control valves. A switching valve is installed to switch between independent and parallel exhaust.
Further, a first pilot switching valve for opening and closing each of the pipes branched from the most upstream side of the first and second control valves and connected to the switching valve, respectively, and a first pilot switching valve for opening and closing each of the pipes at the most downstream side of the neutral passage. At the same time, the first and second pilot switching valves are provided with a second pilot switching valve with the closed positions reversed, and the pilot pipe lines of the first and second pilot switching valves are switched independently and in parallel with the switching valves. It is characterized in that it is connected to a switching valve that is switched in conjunction with the operation to supply and cut off pilot pressure.

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, which includes a left travel valve 5a, a turning valve 5b, and an arm valve 5.
c, has a boom 2nd speed valve 5d and a main relief valve 5e; the first pilot switching valve 5f is connected to a branch passage branched from the most upstream neutral passage of the control valve 1, and the second pilot switching valve 5g is connected to a control valve. It is placed at the lowest downstream of the neutral passage No. 1.

Reference numeral 6 denotes a second control valve to which pressure oil is supplied from the second hydraulic pump 2, including a right-hand travel valve 6a,
Boom 1st speed valve 6b, bucket valve 6
c. It has a main relief valve 6d, and the first pilot switching valve 6e is placed in a branch circuit branching from the neutral passage at the most upstream side of the control valve 2, and the second pilot switching valve 6f is placed at the most downstream side of the neutral passage of the control valve 2. It is arranged in

Numerals 7 and 8 are conduits that lead pressure oil from the first pilot switching valves 5f and 6f, and are connected to check valves 9 and 6, respectively.
It merges into a merging pipe line 10 connected to a switching valve 21, which will be described later, via 9'. 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 is a pilot pipe connecting the first pilot switching valve 5f, 6e and the second pilot switching valve 5g, 6f to the switching valve 20, and 20 is the pilot pressure of the first and second pilot switching valve 5f, 6e, 5g, 6f. In the neutral position, pilot pressure is not generated in the pilot line 19 connected to the tank, so the first pilot selector valves 5f and 6e are closed and the second The pilot switching valves 5g and 6f are in an open state. Therefore, 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 first pilot switching valves 5f and 6e are closed. to the open state, and the second pilot switching valves 5g and 6f
is switched from the open state to the closed 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, and the pipe 14, respectively; The supply/discharge pipe line 15 is the pipe line 16
and conduit 17 are connected to conduit 18, respectively. Further, the merging pipes 10 are respectively connected to the tank passages.

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 are connected to the other conduit 13 and conduit 15, respectively.
will be blocked. In this way, in the case of a parallel circuit, the supply direction of pressure oil to the left and right motors is switched to enable forward and reverse running.

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 first and second pilot switching valves 5f, 6e, 5g, 6
The switching position of f 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, the first pilot switching valves 5f and 6e are closed, and the second pilot switching valves 5g and 6f are held open. On the other hand, in the embodiment shown in FIG. 5, the pilot line 19 and the pilot hydraulic pressure source are connected at the neutral position of the switching valve 20, and the pilot pressure closes the first pilot switching valves 5f and 6e. 2 Pilot switching valve 5
They are the same except that g and 6f are held open.

In the above embodiment, each of the pilot pipe lines connecting the first and second pilot switching valves 5f, 6e, 5g, and 6f and the switching valve 20 and the pipe line connecting the first pilot switching valve and the switching valve 16 are An embodiment has been described in which the pilot pipes of the first and second pilot switching valves are connected to the two switching valves 15 linked to the switching valve 16 without merging the pilot pipes of the first and second pilot switching valves. Therefore, the switching valve 16 can be switched separately from the first logic valve to the switching valve 16.
In this example, the pilot pressure for switching the first and second pilots 5f, 6e, 5g, and 6f 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 introducing it from the first or second hydraulic pump.

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

1 When driving straight ahead independently; (a) When switching the switching valve 21 to the "A" position,
The confluence 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 15 is connected to the pipe 14.
are respectively connected to the conduit 16, and the conduit 11 and the conduit 17 form a block. Also, since the switching valve 20 linked to the switching valve 21 is also switched to the "A" position, in the embodiment shown in FIG.
is supplied with pressure oil from the pilot pump 3, and in the embodiment shown in FIG.
The supply of pressure oil to is cut off, the first pilot switching valves 5f and 6e are switched to the "A" position,
Also, the second pilot switching valves 5g and 6f are also "A".
Switch to position. As a result, the pressure oil of the first hydraulic pump 1 and the second hydraulic pump 2 flows through the first pilot switching valves 5f and 6e, the pipes 7 and 8, and the check valves 9 and 9', respectively, and flows into the confluence pipe 10. Then, the same amount is divided into the pipe line 12 and the pipe line 18 via the switching valve 21, and flows into the left and right travel motors. Also, the return oil from the left and right running motors returns to the tank through the pipes 14 and 16, the switching valve 21, the pipes 13 and 15, the left running valve 5a, or the right running valve 6a, respectively. . As described above, the same pressure and the same amount of pressure oil are supplied to the left and right travel motors, so that the left and right travel motors move 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. The vehicle will go straight in the reverse direction.

2 If other operations are performed at the same time while driving straight; (a) If turning is performed simultaneously while driving straight, set the switching valve 21 to “A” (forward) or “B”.
(reverse) position and when the turning valve 5b is switched, the switching valve 20, the first pilot switching valves 5f, 6e, and the second pilot switching valves 5g, 6f are switched to the above-mentioned 1-(a) and 1-(b). ), the turning valve 5b forms a parallel circuit for the left and right travel motors and the first pump 1, and forms an independent circuit for the second hydraulic pump 2. This means that the travel drive pressure is generally lower at the beginning of the turn, so the turning is accelerated by that pressure, and most of the discharge amount of the first hydraulic pump 1 flows into the left and right travel motors. is the above inflow amount +
The total pressure oil discharge amount of the second hydraulic pump 2 is divided.

Note that the rotation speed increases, and the first hydraulic pump 1
If the rotation motor consumes the entire discharge amount of
The discharge amount of the first hydraulic pump 1 does not flow to the left and right travel motors at all, and only the discharge amount of the second hydraulic pump 2 is diverted to the left and right travel motors. At this time, since there is a check valve 9 in the pipe line 7, the pressure oil of the second hydraulic pump 2 will not flow back to the first pump group side.

Therefore, even if a turning operation is performed while traveling straight, it is possible to perform a turning operation while maintaining straight traveling.
Further, the traveling speed does not decrease suddenly, but gradually decreases, and finally decreases only to an amount corresponding to the discharge amount of the second hydraulic pump 2, and does not decrease any further.

(b) In the case of simultaneous arm operation while traveling straight; It is possible to operate the arm while traveling straight in exactly the same way as in 2-(a) above. In addition, when the arm drive pressure is greater than the traveling drive pressure, such as when escaping from a muddy area, the pressure on the first hydraulic pump 1 side may not rise sufficiently, and the retracting force of the arm may not be utilized. In this case, if a suitable restrictor is installed in the passage corresponding to the conduit 7, the arm retraction pressure will increase and the arm retraction force can be used, which is effective for escaping from mud.

(c) In the case of simultaneously operating the boom while traveling straight; Same as in 2-(a) and 2-(b) above, it is possible to operate the boom while maintaining straight traveling. Also, in this case, as in 2-(b), if the boom drive pressure > travel drive pressure, the boom may not be able to be operated, so if a restrictor is installed appropriately in the passage corresponding to pipe 8, the above drawback can be overcome. It will be resolved.

(d) In the case of simultaneous bucket and tot operation while traveling straight; Similar to 2-(c) above, 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 in the same way as in the past, 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 variable capacity pumps may also be used.Furthermore, the switching valves 20 and 21 are shown as being manually operated, but they can be pilot operated. It may be a valve or a solenoid valve. Furthermore, the first pilot switching valves 5f, 6e and the second pilot switching valves 5g, 6
Although f 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 invention. In the figure: 1...first hydraulic pump, 2...second hydraulic pump, 3...pilot pump, 4...
(For pilot pump) Relief valve, 5...
1st control valve, 5a...Valve for left running, 5b...Swivel valve, 5c...Valve for arm, 5d...Valve for boom 2nd speed, 5e...Main relief valve, 5f...1st pilot switching Valve, 5g...Second pilot switching valve, 6...Second control valve, 6a...Right travel valve,
6b...Boom 1st speed valve, 6c...Bucket valve, 6d...Main relief valve, 6e
……1st pilot switching valve, 6f…2nd pilot switching valve, 7…(1st pump of 1st pump group)
Pipe line that leads pressure oil from the pilot switching valve, 8...
... Pipe (guiding pressure oil from the first 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... Left running supply/discharge pipe, 15, 16, 17, 18... Right running supply/discharge pipe, 19... Pilot pipe, 20... (first pilot switching valve and first 2) switching valve for controlling the pilot 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 for switching 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, and the first and second control valves 5 and 6 are First pilot switching valves 5f and 6e for opening and closing the pipes, respectively, are provided in the pipes branching from the most upstream side and connecting to the parallel/independent switching valve 21,
Second pilot switching valves 5g and 6f are provided at the most downstream side of the neutral passage to open and close the passage, respectively.
and second pilot switching valves 5f, 6e, 5g, 6f
A switching valve 2 which reverses the opening and closing positions of the pilot switching valves 5f, 6e, 5g, and 6f and switches the pilot pipes 19 of the first and second pilot switching valves 5f, 6e, 5g, and 6f independently from the parallel valves.
The switching valve 20 is connected to a switching valve 20 that is switched in conjunction with the independent/parallel switching operation of the switching valve 2, and is opened and closed alternately in response to switching of the switching valve 21.
1, both the first pilot switching valves 5f, 6e on the first control valve 5 side and the second control valve 6 side, or the left and right travel valves 5a, on the first control valve 5 side and the second control valve 6 side. It is possible to selectively supply pressure oil to the left and right travel motors from 6a, and when the motors are parallel, both the first
Pressure oil is supplied to the motor by merging from the pilot switching valves 5f and 6e, and the left and right travel valves 5a and 6a
A hydraulic circuit for a hydraulic excavator, characterized in that no pressure oil is supplied from the.