JPH047414B2 - - 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) Conventional hydraulic excavator directional valve groups 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. Further, there is a problem that the actuator does not operate when another actuator with a high load pressure is 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 for driving 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. 5 is a second directional valve group, which includes a first boom directional valve 5a and a bucket directional valve 5.
b, and a directional control valve 5c for left and right travel (hereinafter described as right travel), which are similarly connected in parallel. Therefore, the first
As with the group, there is no problem functionally even if the order of the above-mentioned directional control valves is changed.

The conventional hydraulic circuit configured as described above has the following problems. That is, () when the vehicle is traveling straight, that is, when the left travel direction switching valve 4d and the right travel direction changeover valve 5c are simultaneously operated in the same direction and the arm is to be operated, the arm direction changeover valve 4b and the left travel direction changeover valve 4b are operated in the same direction at the same time. Since the directional switching 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 the left running directional switching valve accordingly flows. As the amount of pressure oil flowing 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, since the turning direction switching valve 4a and the left running direction switching valve 4d are connected in parallel, the turning direction is smaller than the left running direction switching valve 4d side. Pressure oil flows toward the switching 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 while traveling straight, the bucket directional control valve 5b and the right-hand directional control valve 5c are connected in parallel, so the load is lighter compared to the right-hand directional control valve 5c. The pressure oil flows to the bucket directional switching valve 5b side, and the pressure oil flowing to the right running directional switching valve decreases accordingly, and the speed of the right running motor becomes slower than the speed of the left running motor, making straight running 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, a swing directional control valve, an arm directional control valve, and a second boom 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. Downstream of these switching valves, one of the left and right running direction switching valves (hereinafter described as the left running direction switching valve) is connected in tandem via a throttle and a load check valve.

In the other group of directional valves, a first boom directional valve and a bucket directional valve are connected in parallel. Therefore, there is no functional problem even if the order of these switching valves is changed. Then, downstream of these switching valves, the other one of the left and right running direction switching valves (hereinafter described as the right running direction switching valve) is connected in tandem via a throttle and a load check valve.

The pressure oil from each hydraulic pump is supplied 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 valve and the load check valve of the left-hand travel directional control valve which is tandemly connected to the upstream of the group and the downstream via the throttle and load check valve, and when the control valve is switched, one side The pressure oil from the hydraulic pump is the first and second
The pressure oil of the other hydraulic pump is supplied to the upstream side of the first and second directional valve groups, and the pressure oil is supplied between the left and right traveling directional valves and the load check valve downstream of the first and second directional valve groups. It is possible to supply each.

(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, 6 is a switching valve for the first and second valves.
is arranged between the hydraulic pumps 1, 2 and the first and second directional switching valve groups 4, 5, and the switching valve 6 switches the connection between the hydraulic pumps 1, 2 and the switching valve groups 4, 5. . The switching method of this switching valve may be manual operation by the operator's hands, pedal operation using the foot, or electric or hydraulic type.

4f is a throttle provided in series with the road check valve 4e for the left travel directional change valve 4d, and 5e is a throttle provided in series with the road check valve 5d for the right travel directional change valve 5c. Relief valves 12 and 13 regulate the maximum pressure of the hydraulic pumps 1 and 2.

With this configuration, (a) When the switching valve 6 is in the A position, the pressure oil of the first hydraulic pump 1 passes through the pipe 7 to the swing directional switching valve of group 4 of the first directional switching valve. 4a,
While being supplied in parallel to the arm directional switching valve 4b and the second boom directional switching valve 4c,
A left travel directional control valve 4d and a load check valve 4 are tandemly connected to the most downstream side through a conduit 9 via a throttle 4f and a load check valve 4e.
It is supplied between e. On the other hand, the pressure oil of the second hydraulic pump 2 passes through the line 8 to the first boom directional valve 5 of the second directional valve group 5.
a and the bucket directional control valve 5b, and is supplied through the conduit 10 to the throttle 5e.
and a right-hand travel direction switching valve 5c which is tandemly connected to the most downstream side via the road check valve 5d.
and the load check valve 5d.

(b) Also, when the switching valve 6 is switched to the B position, the pressure oil of the first hydraulic pump 1 passes through the pipe line 7 to the first
The pipe line 8
through the first of group 5 of the second directional valve
The pressure oil of the second hydraulic pump 2 is supplied to the boom directional control valve 5a and the bucket directional control valve 5b in parallel, and the pressure oil of the second hydraulic pump 2 is supplied to the lowest downstream of the first directional control valve group 4 through the pipe 9. It is supplied between the left travel direction switching valve 4d and the load check valve 4e, which are connected in tandem via the throttle 4f and the load check valve 4e, and the conduit 10
is supplied between the right travel directional control valve 5c and the load check valve 5d, which are connected in tandem through the throttle 5e and the load check valve 5d to the most downstream side of the second directional control valve group 5. There is.

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

(A) If only the left travel direction change valve 4d and the right travel direction change valve 5c are operated at the same time with the changeover valve 6 in position A as shown in Figure 2, the The pressure oil from the first 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 distributed from the center bypass passage of the first directional valve group 4. The air is supplied to the left travel direction switching valve 4d which is connected in tandem through the throttle 4f and 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 center bypass passage of the group 5 of the second directional switching valve. The air is supplied to the right travel direction switching valve 5c connected in tandem through the throttle 5e and the road check valve 5d. Further, the pressure oil that has passed through the pipe line 10 is supplied between the right-hand travel direction switching valve 5c and the road check valve 5d, and is then supplied to the right-hand travel direction change-over 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 driving straight, the arm directional switching valve 4d should be moved to the right or left. When the switch is made, the pressure oil from the first hydraulic pump 1 is supplied to the arm as explained in the conventional hydraulic circuit, and the pressure oil supplied to the left travel motor decreases accordingly, reducing the speed of the left travel motor. meandering.

Therefore, before operating the arm directional switching valve 4d, the switching valve 6 is switched to the B position shown in the figure.

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 8 is then passed from the center bypass passage of the group 4 of the first directional control valve, through the throttle 4f and the load check valve 4e, and then flows to the left side which is connected in tandem. Directional switching valve 4d
The pressure oil that has passed through the pipe line 8 is passed from the center bypass passage of the second directional valve group 5 through the throttle 5e and the road check valve 5d to the right-hand directional directional control valve 5c connected in tandem.
supplied to Further, the pressure oil from the second hydraulic pump 2 is distributed to a pipe line 9 and a pipe line 10 via a switching valve 6, and a pressure oil load check valve 4e and a left travel direction switching valve 4d, which are passed through the pipe line 9. The pressure oil that has passed through the pipe line 10 is supplied to the right-hand direction change-over valve 5c from between the road check valve 5d and the right-hand 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. Moreover, the pressure oil that has passed through the pipe line 8 is passed from the center bypass passage of the second directional valve group 5 to the throttle 5e,
It is also supplied to the right travel direction switching valve 5c via the road check valve 5d. Moreover, the pressure oil from the hydraulic pump 2 is transferred to the pipe line 9 and the pipe line 1 via the switching valve 6.
The pressure oil that has passed through the pipe line 9 is supplied to the left travel direction switching valve 4d from between the road check valve 4e and the left travel direction change valve 4d, and the pressure oil that has passed through the pipe line 10 is supplied to the left travel direction changeover valve 4d. Load check valve 5d
The fuel is supplied to the right travel direction changeover valve 5c from between the right travel direction changeover valve 5c 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 the amount of oil is distributed to the left and right travel motors due to the inherent straightness of the crawler itself, which is a traveling body. is evenly distributed to keep the vehicle running straight.

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 the arm can maintain straight travel 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 straightness by operating the switching valve 6. Since it is basically the same as the explanation, it will be omitted.

3 has basically the same configuration as the embodiment shown in FIG. 2, but the difference is that in the embodiment shown in FIG. This allows the switching to be performed automatically. The structure of the differences will be described below.

11 is a pilot pump, 14 is a relief valve that regulates the maximum pressure of the pilot pump 11, 15
16 is a travel auxiliary switching valve that is interlocked with the right-hand directional change-over valve 5c, 16 is a travel auxiliary change-over valve that is interlocked with the left-hand directional change-over valve 4d, and 17 is the pilot pump 1.
1 and the travel assist switching valve 15;
Numerals 8 and 19 are conduits connecting the travel assist switching valves 15 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 that requires independence for traveling is operated; 22 is a pipe connecting the auxiliary switching valve 21 and This is a conduit connecting the operating section of the switching valve 6. Next, its effect will be explained.

(A) When only traveling straight ahead, the pilot pump 11 is activated by switching the left travel direction switching valve 4d to state A (or B) and the right travel direction change valve 5c to state A (or B). The pressure oil from the
(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 A (blocked) and no pressure oil is introduced into the pipe line 22, so the switching valve 6 maintains the state A. Continue. Therefore, as explained in the embodiment shown in FIG.
The operation is the same as in item (A), and the operation is the same as that of a conventional hydraulic circuit.

(B) When operating other actuators that require independence at the same time as straight-line travel, such as an arm,
In conjunction with the operation of the arm switching valve 4b, the auxiliary switching valve 21 is switched to the B position, and the pressure oil is guided to the operation part of the switching valve 6 via the auxiliary switching valve 21 and through the pipe 22. switch to position B. Therefore, the state is the same as that in item (B) in the embodiment shown in FIG. 2, and the operation is the same as that described in the same item. This also applies to actuators other than the arm.

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

(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 hydraulic 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 control various actuators other than the travel motors. Since the supply is given priority, it is possible to operate the various actuators for purposes other than driving, 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...
Pipeline, 8...Pipeline, 9...Passway, 10...Passage,
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. A first directional valve group 4 and a second directional valve group 5 controlling direction and flow rate.
In a hydraulic circuit of a construction machine such as a hydraulic excavator that is equipped with a plurality of directional valves divided into two groups, the first directional valve group 4 includes a swing directional valve 4a, a swing directional valve 4a,
The arm directional switching valve 4b, the second boom directional switching valve 4c, etc. are connected in parallel in random order, and one traveling directional switching valve 4d is throttled 4f downstream of these.
and load check valves 4e, and the second directional control valve group 5 is connected to the first
The boom directional switching valve 5a and the bucket directional switching valve 5b, etc. are connected in parallel in random order, and the other running directional switching valve 5c is connected downstream of these in tandem via a throttle 5e and a road check valve 5d, between the first and second hydraulic pumps and the first and second directional valve groups;
A state in which pressure oil from the second hydraulic pump can be independently supplied between the upstream side of the first and second directional valve groups and between the traveling directional valve and the load check valve located downstream; Pressure oil from one of the first and second hydraulic pumps is connected upstream of the first and second directional valve groups, and pressure oil from the other hydraulic pump is connected to the first and second directional valve groups. A hydraulic circuit for a construction machine such as a hydraulic excavator, characterized in that a switching valve 6 is provided between a traveling direction switching valve and a road check valve provided downstream of a valve group, which can be switched to a state in which supply is possible. 2 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 such as a hydraulic excavator that is equipped with a plurality of directional valves divided into a first directional valve group and a second directional valve group, the first directional valve group 4 The swing direction change valve 4a, the arm direction change valve 4b, the second boom direction change valve 4c, etc. are connected in parallel in random order, and one of the traveling direction change valves 4d is throttled downstream of these (4
f) and are connected in tandem through the load check valve 4e, and the second directional valve group 5 connects the first boom directional valve 5a, bucket bucket directional valve 5b, etc. in parallel in random order, The other traveling directional control valve 5c is throttled 5 downstream of these.
e and the load check valve 5d, and the first and second hydraulic pumps,
The pressure oil from the first and second hydraulic pumps is transferred between the first and second groups of directional valves and the traveling directional valves upstream and downstream of the first and second groups of directional valves. and the load check valve, and pressurized oil from either the first or second hydraulic pump is connected upstream of the first and second directional valve groups. , a switching valve that can be switched to a state in which pressure oil from the other hydraulic pump can be supplied between the traveling directional switching valve and the road check valve, which are provided downstream of the first and second directional switching valve groups. 6 is provided, and a directional switching valve 4 for left and right travel is provided.
The traveling auxiliary switching valves 16 and 15 that are linked to the left and right running directional switching valves 4d and 5c are connected by a pipe 20 to the auxiliary switching valve 21 that is linked to an actuator that requires independence for running, and the left and right running directional switching valves 4d and 5c are connected in the same direction. When at least one actuator that requires independence for travel is operated, the travel assist switching valve 1
6, 15 and an auxiliary switching valve 21, pressure oil from a pilot pump 11 is guided to a pilot port of a switching valve 6 for switching.