JPH047412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a hydraulic circuit such as a hydraulic excavator, and in particular to a hydraulic circuit such as a hydraulic excavator, which is equipped with a plurality of actuators, and which does not travel straight even if other actuators other than those for traveling are activated while the vehicle is traveling. However, each actuator also relates to a hydraulic circuit that allows normal operation.

(Technical Background of the Invention) The directional control valve groups of conventional hydraulic excavators are connected in parallel to each other. Therefore, the amount of oil supplied to the travel motor side of the directional valve group that activated the actuator, such as the arm with a light load, is greater than the amount of oil supplied to the travel motor side of the other directional valve group. It becomes less and meandering. or,
There was a problem in that the actuator did not operate when other actuators with high load pressure were operated.

The above problem will be explained in more detail below with reference to FIG.

FIG. 1 is a circuit diagram of a conventional hydraulic excavator.
1 is a first hydraulic pump, 2 is a second hydraulic pump, and 3 is a prime mover that drives the first and second hydraulic pumps 1 and 2. 4 is a group of first directional switching valves, including a swing directional switching valve 4a, an arm directional switching valve 4b, and a second directional switching valve 4b.
Boom directional switching valve 4c, one direction switching valve 4 for left and right travel (hereinafter described as left travel)
It is composed of d. These directional control valves are connected in parallel.

Therefore, there is no functional problem even if the order of the directional control valves is changed. Reference numeral 5 designates a second group of directional switching valves, including a first boom directional switching valve 5a, a bucket directional switching valve 5b, and the other directional switching valve 5 for left and right travel (hereinafter described as right travel).
It is composed of C and is also connected in parallel. Therefore, as with the first directional valve group, there is no functional problem even if the order of the directional valves is changed.

The conventional hydraulic circuit configured as described above has the following problems.

) When traveling straight ahead, that is, when operating the left running direction switching valve 4d and the right running direction switching valve 5c in the same direction at the same time and attempting to operate the arm, the arm direction switching valve 4b and the left running direction switching valve Since the valves 4d are connected in parallel, pressure oil flows to the arm directional switching valve 4b side, which has a lighter load compared to the left running directional switching valve 4d, and that amount of pressure flows to the left running directional switching valve. As the oil level decreases, the speed of the left travel motor becomes slower than the speed of the right travel motor, making it impossible to travel straight. Furthermore, if the running drive pressure is lower than the arm movement pressure, the pressure applied to the arm cylinder will be insufficient and the arm will not be able to move.

) When performing a turning operation while traveling straight ahead, since the turning direction switching valve 4a and the left running direction switching valve 4d are connected in parallel, the turning direction switching valve 4a and the left running direction switching valve 4d are connected in parallel. Pressure oil flows toward the valve 4a side, and the amount of pressure oil flowing to the left travel direction switching valve decreases by that amount, and the speed of the left travel motor becomes slower than the right travel motor speed, making it impossible to travel straight. Furthermore, if the travel drive pressure is lower than the swing drive pressure, the pressure applied to the swing motor will be insufficient, making it impossible to perform a swing operation.

) When operating the bucket truck while traveling straight, the bucket truck directional control valve 5b and right travel directional control valve 5c are connected in parallel, so the bucket truck has a lighter load compared to the right travel directional control valve 5c. The amount of pressure oil flowing to the right-hand direction switching valve 5b is reduced accordingly, and the speed of the right-hand motor becomes slower than that of the left-hand motor, making straight-line travel impossible. Furthermore, if the running drive pressure is lower than the bucket movement pressure, the pressure applied to the bucket cylinder is insufficient and bucket operation cannot be performed.

) When operating the boom while traveling straight,
Since the boom directional switching valve 5a and the right running directional switching valve 5c are connected in parallel, and the second boom directional switching valve 4c and the left running directional switching valve 4d are connected in parallel, the right and left running directional switching valves are connected in parallel. The pressure oil flowing to the directional control valves becomes equal, but if the running drive pressure is lower than the boom movement pressure, sufficient pressure oil is applied to the first and second boom directional control valves 4c and 5a to raise the boom. Because I can't do it,
A situation arises in which the boom cylinder does not extend.

(Objective of the Invention) The present invention has been made to solve the various problems mentioned above, and even when other actuators are activated while driving, it is possible to maintain straight running, and the other actuators can also operate sufficiently. The present invention aims to provide such a hydraulic circuit.

(Summary of the Invention) The present invention has been made to solve the problems of the conventional hydraulic circuit as described above. In the directional control valve group, at least one of the swing directional control valve, the arm directional control valve, the second boom directional control valve, etc., and one traveling directional control valve are sequentially connected in parallel. Therefore, there is no functional problem even if the order of these directional control valves is changed. Then, a throttle and a load check valve are inserted in series into a parallel passage connected to a determined one of the left and right running direction switching valves (hereinafter described as left running direction switching valve).

In the other group of directional control valves, at least one of the first boom directional control valve and the bucket directional control valve is connected in parallel to the other travel directional control valve. Therefore, there is no functional problem even if the order of these switching valves is changed. Then, a throttle and a load check valve are inserted in series into the parallel passage connected to the other of the left and right travel direction switching valves (hereinafter described as right travel direction switching valves).

The pressure oil from each hydraulic pump is transferred to these first and second directional valve groups via a switching valve provided between the switching valve group and the first and second hydraulic pumps. is supplied between the upstream of the group and the load check valve of each travel directional control valve connected via the throttle and load check valve, and when the control valve is switched, one hydraulic pressure is supplied. Pressure oil from the pump is supplied upstream of the first and second directional valve groups, and pressure oil from the other hydraulic pump is supplied to the left and right travel directional valves of the first and second directional valve groups. and the load check valve.

(Embodiments of the Invention) Hereinafter, embodiments of a hydraulic circuit for a construction machine such as a hydraulic excavator according to the present invention will be described. FIG. 2 is a hydraulic circuit diagram of a first embodiment of the present invention, and FIG. 3 is a hydraulic circuit diagram of a second embodiment of the present invention. Note that in these figures, the same components as those shown in FIG. 1 described above are designated by the same reference numerals, and the explanation thereof will be omitted.

Now, in FIG. 2, reference numeral 6 denotes a switching valve, which is disposed between the first and second hydraulic pumps 1 and 2 and the first and second directional switching valve groups 4 and 5. The connections between the hydraulic pumps 1 and 2 and the switching valve groups 4 and 5 are switched. Note that the switching method of this switching valve is arbitrary, and the switching may be performed manually by the operator's hands or by pedal operation with the foot, but as described later, it is preferable to perform the switching operation automatically using hydraulic pilot control. Preferably, electrical control is also possible.

4f is a throttle provided in the parallel passage for the left travel directional control valve 4d in series with the road check valve 4e;
Reference numeral 5e denotes a throttle provided in the parallel passage for the right travel direction switching valve 5c in series with the road check valve 5d. 12 and 13 are relief valves and hydraulic pumps 1 and 2
Regulate the maximum pressure of

With this configuration, (a) When the switching valve is in the A position (the state shown in the figure), the pressure oil of the first hydraulic pump 1 flows through the pipe 7 to the group 4 of the first directional switching valve. arm directional switching valve 4a, arm directional switching valve 4b and second
It is supplied in parallel to the boom directional switching valve 4c and the left running directional switching valve 4d, and is also supplied to the throttle 4f and the load check valve 4e through the pipe 9.
It is supplied between the left travel directional switching valve 4d and the road check valve 4e, which are connected in parallel via the valve. On the other hand, the pressure oil of the second hydraulic pump 2 passes through the pipe line 8 to the first boom directional control valve 5a, the bucket directional control valve 5b, and the right travel directional control valve of the second directional control valve group 5. 5c in parallel, and
0 through the throttle 5e and the load check valve 5d.
It is supplied between the right-hand travel direction switching valve 5c and the road check valve 5d, which are connected in parallel via the valve.

(b) Also, when switching the switching valve to position B, the first
The pressure oil of the hydraulic pump 1 passes through the line 7 to the swing directional valve 4 of the first directional valve group 4.
a, arm directional switching valve 4b, second boom directional switching valve 4c, and left running directional switching valve 4d
At the same time, it is supplied to the first boom directional control valve 5a, the bucket directional control valve 5b, and the right travel directional control valve 5c of the second directional control valve group 5 in parallel through the conduit 8. Pressure oil from the second hydraulic pump 2 is supplied to the first directional valve group 4 through a pipe 9 to a left-hand directional directional valve connected in parallel via a throttle 4f and a load check valve 4e. 4d and the load check valve 4e, and is connected in parallel to the second directional control valve group 5 through the conduit 10 via the throttle 5e and the load check valve 5d. Switching valve 5c
and the load check valve 5d.

(Function) The function of the hydraulic circuit configured as described above will be explained.

A) When only the left travel direction changeover valve 4d and the right travel direction changeover valve 5c are operated at the same time with the changeover valve 6 in position A as shown in FIG. The pressure oil from the hydraulic pump 1 is distributed to the pipe line 7 and the pipe line 9 via the switching valve 6, and the pressure oil that has passed through the pipe line 7 is transferred from the parallel passage of the group 4 of the first directional valve to the throttle 4f.
It is supplied to the left travel direction switching valve 4d connected in parallel through the road check valve 4e. Further, the pressure oil that has passed through the pipe line 9 is supplied between the left travel direction changeover valve 4d and the road check valve 4e, and is then supplied to the left travel direction changeover valve 4d.
That is, the entire amount of pressure oil from the first hydraulic pump 1 is supplied to the left travel direction switching valve 4d. Further, the pressure oil of the second hydraulic pump 2 is distributed to the pipe line 8 and the pipe line 10 via the switching valve 6, and the pressure oil that has passed through the pipe line 8 is distributed to the group 5 of the second directional switching valve.
The air is supplied from the center bypass passage through the throttle 5e and the load check valve 5d to the right-hand direction switching valve 5c connected in parallel. In addition, the pressure oil that has passed through the pipe 10 is transferred to the right-hand travel direction switching valve 5c.
and the road check valve 5d, and is supplied to the right travel direction switching valve 5c. That is, the entire amount of pressure oil from the second hydraulic pump 2 is also supplied to the right travel direction switching valve 5c.

B) When operating the left running directional switching valve 4d and the right running directional switching valve 5c in the same direction to perform another operation, such as an arm operation, while traveling straight, the arm directional switching valve 4b is switched to the right or left. and,
As explained in the conventional hydraulic circuit, the pressure oil from the first hydraulic pump 1 is supplied to the arm, and the pressure oil supplied to the left travel motor decreases by that amount, and the speed of the left travel motor decreases, causing it to meander. .

Therefore, before operating the arm directional switching valve 4b, the switching valve 6 is switched from the illustrated position to the B position.

First, to explain the flow of pressure oil in each hydraulic pump before operating the arm directional switching valve 4b with the switching valve 6 switched to the B position, the pressure oil in the first hydraulic pump 1 flows through the switching valve 6. The pressure oil that has passed through the pipe line 7 and the pipe line 7 is then passed from the parallel passage of the first directional control valve group 4 through the throttle 4f and the load check valve 4e to the parallel-connected left-hand drive oil. The pressure oil that is supplied to the directional control valve 4d and passed through the conduit 8 is passed from the parallel passage of the second directional control valve group 5 through the throttle 5e and the load check valve 5d to the right-hand direction control valve connected in parallel. 5c.
Moreover, the pressure oil from the second hydraulic pump 2 is transferred to the switching valve 6.
is distributed to conduit 9 and conduit 10 via conduit 9
The pressure oil that has passed through is supplied to the left travel direction switching valve 4d from between the road check valve 4e and the left travel direction changeover valve 4d, and the pressure oil that has passed through the pipe line 10 is supplied to the left travel direction changeover valve 4d between the road check valve 4e and the right travel direction changeover valve 4d. It is supplied to the right-hand travel direction change-over valve 5c from between the direction change-over valve 5c and the direction change-over valve 5c. In other words, the pressure oil of the first hydraulic pump 1 and the pressure oil of the second hydraulic pump 2 are combined and supplied in parallel to the left travel direction changeover valve 4d and the right travel direction changeover valve 5c. At this time, it seems that the amount of oil from pumps 1 and 2 is not equally divided between the left and right travel motors, but due to the inherent straightness of the crawler itself, the total amount of oil is divided equally and it runs straight. is maintained.

When the arm directional switching valve 4b is operated from this state, the pressure oil from the hydraulic pump 1 is distributed to the pipe line 7 and the pipe line 8 via the switching valve 6, and the pressure oil that has passed through the pipe line 7 is distributed to the first pipe line 7 and the pipe line 8. Group 4 of directional valves
It is supplied to the inner arm directional switching valve 4b. Further, the pressure oil that has passed through the pipe line 8 is supplied from the parallel passage of the second directional switching valve group 5 to the right-hand travel directional switching valve 5c via the throttle 5e and the load check valve 5d. Further, the pressure oil from the hydraulic pump 2 is distributed to the pipe line 9 and the pipe line 10 via the switching valve 6, and the pressure oil that has passed through the pipe line 9 is distributed between the road check valve 4e and the left travel direction switching valve 4d. is supplied to the left running directional control valve 4d, and the conduit 10
The pressure oil that has passed through is supplied to the right travel direction changeover valve 5c from between the road check valve 5d and the right travel direction changeover valve 5c.

At this time, of the pressure oil from the hydraulic pump 1 mentioned above, the pressure oil that has passed through the pipe line 8 is transferred to the pipe lines 9 and 10.
Since the oil is communicated with each other via the switching valve 6, it is also distributed to the left travel direction switching valve 4d, and due to the inherent straightness of the crawler itself, the amount of oil is equalized between the left and right travel motors. to maintain straight running.

At this time, if the driving pressure of the arm is low, the entire amount of pressure oil from the hydraulic pump 1 is supplied to the arm, and the pressure oil from the hydraulic pump 2 is evenly distributed to the left and right travel motors, so that straight forward movement can be maintained while moving the arm.

On the other hand, if the drive pressure of the arm is higher than the travel drive pressure, the drive pressure of the arm is secured by the throttle 5e, and as mentioned above, the excess oil other than that used to move the arm is distributed equally to the left and right travel motors. It is possible to maintain straightness while moving the arm.

C) Next, when performing a turning operation, boom operation, bucket operation, etc. while traveling straight, it is possible to operate other actuators while maintaining straight travel by operating the switching valve 6. Since it is basically the same as the explanation, it will be omitted.

FIG. 3 shows an embodiment of the invention in which the switching valve 6 can be switched by pilot hydraulic control.

Since the basic circuit is exactly the same as that shown in FIG. 2, only the pilot hydraulic pressure control circuit is added, only the added portion will be explained.

14 is a relief valve that regulates the maximum pressure of the pilot pump 11, and 15 is a right-hand travel direction switching valve 5c.
16 is a travel assist switching valve that is interlocked with the left travel direction selector valve 4d, 17 is a pipe connecting the pilot pump 11 and the travel assist switching valve 15, and 18 and 19 are travel assist valves. Switching valve 1
This is a conduit connecting 5 and 16. 20 is a pipe connecting the traveling auxiliary switching valve 16 and the auxiliary switching valve 21 which operates in conjunction with the directional switching valve when at least one actuator independent of travel is activated; 22 is a pipe connecting the auxiliary switching valve 21 and the auxiliary switching valve 21; This is a conduit connecting the operating section of the switching valve 6.

Next, its effect will be explained.

A) When traveling only straight ahead, switch the left travel directional selector valve 4d to state A (or B) and the right travel directional selector valve 5c to state A (or B), and the pilot pump 11 will The pressure oil is transferred to the pipe 19 via the travel assist switching valve 15.
(or conduit 18), travels through the traveling assist switching valve 16, passes through the conduit 20, and reaches the auxiliary switching valve 21. However, since the other actuators are not operating at this time, the auxiliary switching valve 21 is maintained in the state of A (blocked) and no pressure oil is introduced into the pipe line 22, so the switching valve 6 continues to maintain the state of A. .
Therefore, A) explained in the embodiment of FIG. 2 above.
The operation is similar to that of the conventional hydraulic circuit.

B) When operating another independent actuator, such as an arm, at the same time as straight-ahead travel, the auxiliary switching valve 21 is switched to position B in conjunction with the operation of the arm switching valve 4b, and the pressure oil is switched to the auxiliary switching valve. 21 and a conduit 22 to the operating section of the switching valve 6 to switch the switching valve 6 to the B position. Therefore, the state is the same as in item B) in the embodiment shown in FIG. 2 described above, and the operation is the same as described in the same item. This also applies to actuators other than the arm.

C) When the left running directional switching valve 4d is set to state A (or B) and the right running directional switching valve 5c is set to B (or A), the pressure oil of the pilot pump 11 is transferred to the running auxiliary switching valve 15. However, since the travel assist switching valve 16 is blocked, the pipe 20 is
Pilot pressure is not introduced to the valve, and the switching valve 6 does not switch. Therefore, it has the same function as a conventional hydraulic circuit.

D) Even when one side of the vehicle is operated, the pressure oil from the pilot pump 11 is not guided to the conduit 20 as explained in section C) of the embodiment in FIG. 2, so the function is the same as that of a conventional hydraulic circuit. It is.

(Effects of the Invention) Since the hydraulic circuit of the present invention has the above-described configuration, when actuating other actuators other than traveling while traveling straight, the first and second hydraulic pressures can be changed by switching the switching valve. The pressure oil from one of the pumps is distributed equally to the left and right travel motors independently of the other actuators, and the pressure oil from the other hydraulic pump is used to travel to various actuators other than the travel motor. Since the vehicle is supplied with priority to the vehicle, various actuators other than travel can be operated reliably while traveling straight without meandering, ensuring efficient work.

[Brief explanation of drawings]

Figure 1 shows a conventional hydraulic circuit. FIG. 2 shows an embodiment circuit of the present invention. FIG. 3 also shows the circuit of the second embodiment. In the figure: 1...First hydraulic pump, 2...Second hydraulic pump, 3...Motor, 4...First directional switching valve group, 4a...Swivel directional switching valve, 4b
... Directional switching valve for arm, 4c... Directional switching valve for second boom, 4d... Directional switching valve for left travel, 4e
...Load check valve, 4f... Throttle, 5... Second directional switching valve group, 5a... First boom directional switching valve, 5b... Directional switching valve for bucket, 5c
...Right travel direction switching valve, 5d... Road check valve, 5e... Throttle, 6... First switching valve, 7...
Pipe line, 8...Pipe line, 9...Pipe line, 10...Pipe line,
11...Pilot pump, 12...Relief valve, 13...Relief valve, 14...Relief valve,
15... Traveling assistance switching valve, 16... Traveling assistance switching valve, 17... Pipe line, 18...... Pipe line, 19...... Pipe line, 20...... Pipe line, 21...... Auxiliary switching valve.

Claims (1)

[Claims] 1. Pressure oil supplied to two hydraulic pumps, a first hydraulic pump 1 and a second hydraulic pump 2, and a plurality of actuators driven by pressure oil from these hydraulic pumps. In a hydraulic circuit for a construction machine equipped with a plurality of directional valves divided into a first directional valve group 4 and a second directional valve group 5 that control direction and flow rate, the first directional valve group 4 includes a plurality of directional switching valves 4a to 4, including one running directional switching valve 4d.
4d are connected in parallel, and a throttle 4f and a load check valve 4e are inserted in series into the parallel passage connected to the one traveling direction switching valve 4d, and the second direction switching valve group 5 has the other one. A plurality of directional switching valves 5a to 5c including a traveling directional switching valve 5c.
5c are connected in parallel, and a throttle 5e and a load check valve 5d are inserted in series into the parallel passage connected to the other traveling direction switching valve 5c, and the first and second hydraulic pumps 1, 2 and 1st,
The pressure oil from both hydraulic pumps 1 and 2 is supplied between the second directional valve groups 4 and 5 and the upstream side of each directional valve group 4 and 5 independently.
Directional switching valve 4 for travel that belongs to the switching valve group
d, 5c and load check valves 4e, 5d, and one hydraulic pump 1 or 2.
Pressure oil from the other hydraulic pump 2 or 1 is applied between both travel directional control valves 4d, 5c and road check valves 4e, 5d. A hydraulic circuit for a construction machine such as a hydraulic excavator, characterized in that it is provided with a switching valve 6 which can be switched to a state B in which supply is possible. 2. Construction of a hydraulic excavator, etc. according to claim 1, wherein the first directional switching valve group 4 includes a swing directional switching valve 4a, an arm directional switching valve 4b, and a second boom directional switching valve 4c. Machine hydraulic circuit. 3. A hydraulic circuit for a construction machine such as a hydraulic excavator according to claim 1 or 2, wherein the second directional valve group 5 includes a first boom directional valve 5a and a bucket directional valve 5b. 4 Claims in which the directional control valve 6 inserted between the first and second hydraulic pumps 1 and 2 and the first and second directional control valve groups 4 and 5 is manually operable. A hydraulic circuit for a construction machine such as a hydraulic excavator according to items 1 to 3. 5 Controls the direction and flow rate of pressure oil supplied to two hydraulic pumps, the first hydraulic pump 1 and the second hydraulic pump 2, and a plurality of actuators driven by the pressure oil from these hydraulic pumps. In a hydraulic circuit of a construction machine equipped with a plurality of directional valves divided into a first directional valve group 4 and a second directional valve group 5, the first directional valve group 4 includes one of the directional valves. A plurality of directional switching valves 4a to 4a including a traveling directional switching valve 4d.
4d are connected in parallel, and a throttle 4f and a load check valve 4e are inserted in series into the parallel passage connected to the one traveling direction switching valve 4d, and the second direction switching valve group 5 has the other one. A plurality of directional switching valves 5a to 5c including a traveling directional switching valve 5c.
5c are connected in parallel, and a throttle 5e and a load check valve 5d are inserted in series into the parallel passage connected to the other traveling direction switching valve 5c, and the first and second hydraulic pumps 1, 2 and 1st,
Pressurized oil from both hydraulic pumps 1 and 2 is supplied between the second directional valve groups 4 and 5 independently to the upstream side of each directional valve group 4 and 5, and
Directional switching valve 4 for travel that belongs to the switching valve group
d, 5c and load check valves 4e, 5d, and one hydraulic pump 1 or 2.
Pressure oil from the other hydraulic pump 2 or 1 is applied between both travel directional control valves 4d, 5c and road check valves 4e, 5d. A switching valve 6 is provided which can be switched to a state B in which supply is possible, respectively, and is interlocked with travel auxiliary switching valves 16 and 15 that are interlocked with the left and right travel direction switching valves 4d and 5c, and an actuator that is independent for travel. Auxiliary switching valve 2
1 is connected by a conduit 20, both the left and right travel direction switching valves 4d and 5c are switched in the same direction, and when at least one actuator that is independent of travel is operated, the travel assist switching valve 16,1
5 and an auxiliary switching valve 21 to guide pressure oil from a pilot pump 11 to a pilot port of the switching valve 6 to switch the switching valve 6.