JPS6124730A - Hydraulic circuit for construction machine such as hydraulic shovel - Google Patents

Abstract

PURPOSE:To ensure straight running and operation of other actuators, by providing a switching valve which feeds pressure oil from a second hydraulic pump to a running motor and pressure oil from a first hydraulic pump to actuators other than that for running. CONSTITUTION:A hydraulic circuit consists of a first hydraulic pump 1, a second hydraulic pump 2, a first direction switching valve group 4, and a second direction switching valve group 5, and is provided on the upper stream side of the group 5 with a switching valve 5e. In case actuators other than that for running are operated as a vehicle runs straight, the valve 5e is switched from a position A to a position B, pressure oil from the pump 2 is fed through a line 9, a valve 5d, and a line 10 to a right running motor and is fed through a line 7, the valve 5e, and a line 10 to a left running motor to ensure straight running. Meanwhile, pressure oil from the pump 1 is fed to actuators other than that for running to ensure operation of the actuators only for running.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic circuit for construction machinery such as a hydraulic excavator.

(Prior art) When another actuator is operated while the construction machine is running, the hydraulic circuit of a conventional hydraulic excavator has all directional control valves connected in parallel, so the actuator operated with a lighter load will be activated. The amount of oil supplied to the travel motor side is
The amount of oil supplied to the other traveling motor side is less than that of the other one, and the motor meanders.

Another drawback is that if another actuator with a high load pressure is operated while the vehicle is running, that actuator will not operate.

FIG. 9 is a hydraulic circuit diagram of a conventional hydraulic excavator, which will be briefly described below. 1 is a first hydraulic pump, 2 is a second hydraulic pump, 3 is a first hydraulic pump. This is a prime mover that drives the second hydraulic pumps 1 and 2. Reference numeral 4 denotes a first group of directional control valves, which includes a main relief valve 4a, a turning direction control valve 4b, an arm direction control valve 4c, a second boom direction control valve 4d, and a left travel direction control valve 4e. These directional control valves 4b to 4e are connected in parallel.

Reference numeral 5 denotes a second group of directional switching valves, which includes a main relief valve 5a, a first boom directional switching valve 5b, a bucket directional switching valve 5c, and a right travel directional switching valve 5e. ~5d are connected in parallel. 6 is a pipe connecting the first hydraulic pump l and the main inlet port P1 of the first directional valve group 4; 7 is the main inlet port of the second hydraulic pump 2 and the second directional valve group 5 This is a conduit connecting Pl.

The hydraulic circuit of such a conventional hydraulic excavator has the following problems. That is, ■) Left travel direction switching valve 4e and right travel direction change valve 5d.
If you operate the arm while driving straight ahead with the arm operated in the same direction,
Since the arm directional switching valve 4c and the left running directional switching valve 4e are connected in parallel, the arm has a lighter load compared to the left running directional switching valve 4e in terms of arm drive pressure (travel driving pressure). The pressure oil of the first hydraulic pump 1 tends to flow toward the direction switching valve 4c. As a result, the speed of the front travel motor becomes slower than the speed of the right travel motor, and although the arm moves, it is unable to travel straight.

If the arm drive pressure is higher than the travel drive pressure, the pressure applied to the arm cylinder will be insufficient, so even if the vehicle can travel straight, the arm will not move.

2) When performing a turning operation while traveling straight, the left travel direction changeover valve 4e and the turning direction changeover valve 4b are connected in parallel, so if the turning drive pressure is equal to the travel drive pressure, the left travel direction will be changed. The pressure oil of the first hydraulic pump 1 tends to flow to the swing direction switching valve 4b side, which has a lighter load than the switching valve 4e side. As a result, the speed of the front travel motor is slower than the speed of the right travel motor, and although the vehicle can turn, it cannot travel straight.

In addition, if the turning drive pressure is greater than the running drive pressure, the pressure applied to the swing motor is insufficient, and even if the vehicle can travel straight, it cannot perform a turning operation.

3) When operating the bucket while traveling straight, the right travel direction switching valve 5d and the bucket direction change valve 5c are connected in parallel, so if the bucket drive pressure is the travel drive pressure, the right travel The pressure oil of the second hydraulic pump 2 tends to flow to the bucket directional switching valve 5c side, which has a lighter load than the directional switching valve 5d side. As a result, the right travel motor speed is slower than the left travel motor speed, and the bucket moves, but cannot travel straight.

Furthermore, if the bucket drive pressure is greater than the travel drive pressure, the pressure applied to the bucket lower cylinder will be insufficient, and the bucket will not move even if it can travel straight.

4) When operating the boom while traveling straight, the left travel directional control valve 4e and the second boom directional change valve 4d, and the right travel directional control valve 5d and the first boom directional change valve 5d. are each connected in parallel, so the boom drive pressure <
When the driving pressure is the same, the first and second boom directional control valves 5b and 4d, which have a lighter load, are moved toward the first and second boom directional control valves 5b and 4d. The pressure oil of the second hydraulic pumps 1 and 2 flows, and the boom moves, but cannot travel.

Also, if the boom driving pressure is greater than the travel driving pressure, the pressure applied to the boom cylinder will be insufficient and the boom will not move even if it can travel straight.

(Problems to be Solved by the Invention) The present invention attempts to solve the above-mentioned problems of the known technology, and even if other actuators are activated while driving, it is possible to drive straight ahead, and the other actuators are also activated. The objective is to provide a hydraulic circuit that can operate reliably.

(Means for Solving the Problems) The present invention has been made to solve the problems of the hydraulic circuits of conventional hydraulic excavators as described above, and the first means for solving the problems is as follows. That is, among the two directional valve groups that control the pressure oil of the actuator, one directional valve group includes a swing directional valve, an arm directional valve, a second boom directional valve, etc. A plurality of directional switching valves are connected in parallel in random order, and one of the left and right directional switching valves (hereinafter referred to as "travelling") is connected in tandem at the most downstream side of each of the directional switching valves.

A throttle and a load check valve are provided in series in the tandem passage connected to the left travel direction change valve, and a pressure oil inflow port is provided between the left travel direction change valve and the load check valve.

In addition, a plurality of directional control valves such as the first boom directional control valve and bucket directional control valve are connected in parallel in random order to the second directional control valve group, and left and right control valves are connected at the lowest downstream of each of the above directional control valves. Connect the other travel direction switching valve (hereinafter referred to as right travel) in tandem. A throttle and a load check valve are provided in series in the tandem passage connected to the right-hand travel direction switching valve, and a pressure oil boat is provided between the right-hand travel direction change-over valve and the load check valve.

Furthermore, a switching valve is provided upstream of either the first or second directional switching valve group, and the switching valve causes the first or second directional switching valve group. The flow of pressure oil from the second hydraulic pump is switched as follows. In other words, when the switching valve is in the one (A) position, the pressure oil of each hydraulic pump is directly or via the switching valve connected to the main inlet boat of each directional switching valve group, each traveling directional switching valve, and the load check. Each pressure oil inlet port between the valve and the valve is supplied with the pressure oil. Also, the switching valve is connected to the other side (B
) position, the pressure oil of one hydraulic pump is transferred to the main inlet port of one directional valve group that is not equipped with a directional valve and the downstream stage of the directional valve of the other directional valve group that is equipped with the directional valve. The pressure oil of the other hydraulic pump is supplied to the neutral passage of the first hydraulic pump through a switching valve, and the pressure oil of the other hydraulic pump is supplied directly or via the switching valve to the neutral passage of the first hydraulic pump. It is designed to be supplied between the left and right traveling direction changeover valves and the load check valve of the second direction changeover valve group.

Next, the second solution is as follows. That is, among the two directional control valve groups that control the pressure oil of the actuator, the first directional control valve group includes a left travel directional control valve, a turning directional control valve, an arm directional control valve, and a second directional control valve. A plurality of directional switching valves such as the boom directional switching valve No. 2 are connected in parallel in random order. A throttle and a load check valve are provided in series in the parallel passage connected to the left travel directional change valve, and a pressure oil inflow port is provided between the left travel directional change valve and the load check valve. Further, a plurality of directional switching valves such as a right travel directional switching valve, a first boom directional switching valve, and a bucket directional switching valve are connected in parallel in random order to the second directional switching valve group. A throttle and a load check valve are provided in series in the parallel passage connected to the right-hand travel directional change-over valve, and a pressure oil flow port is provided between the right-hand travel directional change-over valve and the load check valve.

Furthermore, a switching valve is provided on the upstream side of either the first or second directional switching valve group, and the switching valve pass allows the first or second directional switching valve group to be connected to the first or second directional switching valve group. The flow of pressure oil of the second hydraulic pump can be switched as follows. In other words, when the switching valve is in the one (A) position, the pressure oil of each hydraulic pump is directly or via the switching valve connected to the main inlet boat of each directional switching valve group, each traveling directional switching valve, and the load check. Each pressure oil inlet port between the valve and the valve is supplied with the pressure oil. When the switching valve is switched to the other position (B), the pressure oil of one hydraulic pump is transferred between the main inlet boat of the directional valve group without the switching valve and the other directional switching valve group with the switching valve. are respectively supplied to the neutral passages downstream of the switching valves of the valve group via the switching valves,
Pressure oil from the other hydraulic pump is supplied to the first hydraulic pump either directly or via a switching valve. The problems of the conventional hydraulic circuit are solved by supplying the oil between the left and right traveling direction switching valves and the load check valve of the second directional switching valve group.

(Embodiment of the first solution) An embodiment of a hydraulic circuit for a construction machine such as a hydraulic excavator according to the present invention will be described below.

FIG. 1 is a hydraulic circuit diagram of a first embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram of a second embodiment of the present invention, and FIG. 3 is a hydraulic circuit diagram of a third embodiment of the present invention. FIG. 4 is a hydraulic circuit diagram of a fourth embodiment of the present invention. In these figures, the ninth
Components that are the same as those in the conventional example shown in the figure are designated by the same reference numerals.

First embodiment circuit (Fig. 1): ① is the first hydraulic pump, 2 is the second hydraulic pump, 3 is the first hydraulic pump. This is a prime mover that drives the second hydraulic pumps 1 and 2.

Reference numeral 4 denotes a first directional control valve group, in which a main relief valve 4a, a swing directional control valve 4b, an arm directional control valve 4c, and a second boom directional control valve 4d are connected in parallel. One of the left and right (left) running directional switching valves 4e is connected in tandem to the most downstream of the directional switching valves 4b, 4c, and 4d. 4f is a throttle provided in the tandem passage of the left travel direction switching valve 4e, 4g is a load check valve similarly provided in the tandem passage, and the throttle 4f and the load check valve 4g are provided in series with each other.

Reference numeral 5 designates a second group of directional valves, including a main relief valve 5a, a first boom directional valve 5b, a bucket directional valve 5c, and either the left or right (right) traveling directional valve. 5d and a switching valve 5e. The first boom directional switching valve 5b and the bucket directional switching valve 5c are connected in parallel, but the right travel directional switching valve 5d is the parallel-connected directional switching valve 5b, 5c.
are connected in tandem downstream of the

The switching valve 5e is provided downstream of the main relief valve 5a of the second directional switching valve group 5 and most upstream of the other directional switching valves. From the first and second hydraulic pumps 1 and 2 to the first. This switches over the supply of pressure oil to the second directional valve group 4.5.

5f is a throttle provided in the tandem passage of the right travel switching valve 5d;
5g is a load check valve similarly provided in the tandem passage, and the throttle 5f and the load check valve 5g are connected in series.

Reference numeral 8 denotes a pipe line that branches from the pipe line 6 connecting the first hydraulic pump 51 and the main inlet boat Pl of the first directional switching valve group 4, and connects to the Al port of the switching valve 5e. 9 is the second
A pressure oil flow branched from the pipe 7 connecting the hydraulic pump 2 and the main inlet boat P of the second directional valve group 5, and connected between the right travel directional valve 5d and the load check valve 5g. This is a conduit that connects to the human port P2. 10 is B of the switching valve 5e! This is a pipe line that connects the boat and the pressure oil inflow port P2 connected between the left travel direction switching valve 4e and the load check valve 4g.

With the above configuration, (a) When the switching valve 5e is in the A position (the state shown in FIG. 1), the pressure oil of the first hydraulic pump 1 passes through the pipe line 6 to the first
to the main inlet boat Pt of directional valve group 4.

where the main inlet boat P of group 4 of the first directional valve
! The pressure oil that has flowed is supplied in parallel to the turning direction switching valve 4b, the arm direction switching valve 4c, and the second boom direction switching valve 4d, and is supplied in tandem to the left running direction switching valve 4e. In addition, the pipe line 8, the 〇 port of the switching valve 5e,
The pressure oil is supplied through the B□ boat pipe line 10 of the switching valve 5e to the pressure oil flow port P2 of the left travel direction switching valve 4e.

The pressure oil of the hydraulic pump 2 of the external cylinder 2 is supplied through the line 7 to the main inlet port Pl of the group 5 of the second directional control valve. Here, the pressure oil flowing into the main inlet boat P1 of the second directional switching valve group 5 passes through the switching valve 5e, and is supplied in parallel to the first boom directional switching valve 5b and the bucket directional switching valve 5c, The pressure oil is supplied in tandem to the right-hand directional change-over valve 5d, and is also supplied to the pressure oil flow port P2 of the right-hand directional change-over valve 5d through a conduit 9.

(b) When the switching valve 5e is switched to the B position, the pressure oil of the first hydraulic pump 1 flows through the pipe 6 to the main inlet boat Pl of the group 4 of the first directional switching valve for turning. It is supplied in parallel to the directional switching valve 4b, the arm directional switching valve 4c, and the second boom directional switching valve 4d, and in tandem to the left running directional switching valve 4e. The A8 boat 5e is supplied in parallel to the first boom directional switching valve 5b and the bucket directional switching valve 5c via the switching valve 5e, and in tandem to the right travel directional switching valve 5d. On the other hand, the pressure oil of the second hydraulic pump passes through the conduit 7 to the main inlet port PI of the group 5 of the second directional switching valve, the switching valve 5e, the Bl boat of the switching valve 5e, and the pipework 0. The pressure oil flows into the pressure oil flow port P2 of group 4 of the first directional switching valve, and is supplied to the left travel directional switching valve 4e. A second group of directional valves 5 together via line 9
Pressure oil flows to the flow man port P2, and the right travel direction switching valve 5d
is supplied to In other words, the pressure oil of the first hydraulic pump 1 is supplied to the swing directional valve 4b, the arm directional valve 4c1, the second boom directional valve 4d, and the first boom directional valve 5.
b, and the bucket directional switching valve 5c in parallel, and is supplied in tandem to the left and right running directional switching valves 4e and 5d. - Pressure oil from the hydraulic pump of the power cylinder 2 is supplied preferentially to the left and right travel direction switching valves 4e and 5d.

(Operation of the first embodiment) A) When only the left travel direction changeover valve 4e and the right travel direction changeover valve 5d are operated at the same time with the changeover valve 5e set to the A position as shown in FIG. The effect is similar to that of a conventional hydraulic circuit. That is, the pressure oil from the first hydraulic pump 1 is distributed to the pipe line 6 and the pipe line 8, and the pressure oil that has passed through the pipe line 6 flows to the main inlet boat Pl of the first directional valve group 4, It passes through the neutral passage, the tandem passage, the throttle 4f, the load check valve 4g, and is supplied to the left travel direction switching valve 4e. In addition, the pressure oil passing through the pipe 8 is transferred to the Al port of the switching valve 5e of the second directional valve group 5, the switching valve 5e, the Bl boat of the switching valve 5e, and the pipe 10 to the first directional switching valve. The pressure oil passes through the pressure oil inlet port P2 of No. 4 and is supplied to the left travel direction switching valve 4e. That is, the entire amount of pressure oil from the first hydraulic pump 1 is supplied to the left travel direction switching valve 4e.

The pressure oil from the hydraulic pump 2 of the external cylinder 2 is supplied to the pipe 7 and the pipe 9.
The pressure oil that has passed through the pipe line 7 flows to the main inlet port P□ of group 5 of the second directional switching valve, passes through the switching valve 5e, passes through the neutral passage, and from the tandem passage to the throttle 5f and the load check valve 5g. It is supplied to the right travel direction switching valve 5d through the. Further, the pressure oil that has passed through the pipe line 9 flows to the pressure oil flow port P2 of the second directional switching valve group 5, and is supplied to the right travel directional switching valve 5d. That is, the entire amount of pressure oil from the second hydraulic pump 2 flows to the right travel direction switching valve 5d.

B) When operating the left running directional switching valve 4e and the right running directional switching valve 5d in the same direction to perform other operations, such as arm operation, while driving straight, the arm directional switching valve 4c
When switched to the right or left, pressure oil from the first hydraulic pump 1 is also supplied to the arm via the pipe 6, and the pipe 8, the AI port of the switching valve 5e, the switching valve 5e, the switching valve B, the port, the pipe line 10, and the left travel direction switching valve 4e are supplied, but the pressure oil supplied to the left travel motor decreases by the amount supplied to the arm, and the speed of the left travel motor decreases, causing it to meander. .

Therefore, before operating the arm directional switching valve 4c, the switching valve 5e 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 4c with the switching valve 5e switched to the B position, the pressure oil in the first hydraulic pump 1 flows through the pipe line 6 and The pressure oil that has been distributed to the pipe line 8 and passed through the pipe line 6 flows to the main inlet port Pl of the group 4 of the first directional valve, passes through the neutral passage, and from the tandem passage to the throttle 4f and the load check valve 4.
g, and is supplied to the left travel direction switching valve 4e. In addition, the pressure oil that has passed through the pipe line 8 passes through the A1 port of the switching valve 5e of group 5 of the second directional switching valve, the switching valve 5e, the neutral passage, and the tandem passage to the throttle 5f and the load check valve 5.
g, and is supplied to the right travel direction switching valve 5d.

Further, the pressure oil from the second hydraulic pump 2 is distributed to the pipe line 7 and the pipe line 9, and the pressure oil that has passed through the pipe line 7 flows to the main inlet port Pl of the group 5 of the second directional switching valve 5e. , B12 of the switching valve 5e, and flows through the pipe line 10 to the pressure oil inflow port hP2 of the group 4 of the first directional switching valve, and is supplied to the left-hand travel directional switching valve 4e. Further, the pressure oil that has passed through the pipe line 9 flows to the pressure oil flow port P2 of the group 5 of the second directional switching valve, and is supplied to the right travel directional switching valve 5d. In other words, the first
The pressure oil of the 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 4e and the right travel direction changeover valve 5d.

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 control valve 4c is operated from this state, the pressure oil from the first hydraulic pump 1 is distributed to the pipe line 6 and the pipe line 8, and the pressure oil that has passed through the pipe line 6 is transferred to the first direction control valve. is supplied to the arm directional control valve 4d in group 4. In addition, the pressure oil that has passed through the pipe 8 is throttled from the tandem passage through the A and port of the switching valve 5e of group 5 of the directional switching valve 2, the switching valve 5e, the neutral passage, and the right-hand directional switching valve 5d. 5f, supplied via load check valve 5g. Further, the pressure oil from the second hydraulic pump 2 is distributed to the pipe line 7 and the pipe line 9, and the pressure oil that has passed through the pipe line 7 is switched to flow to the main inlet boat P of the group 5 of the second directional control valve. The oil flows through the valve 5e, the B□ boat of the switching valve 5e, and the pipe line 10 to the pressure oil inlet port P2 of the group 4 of the first directional switching valve, and is supplied to the left travel directional switching valve 4e. Further, the pressure oil passing through the pipe line 9 flows to the pressure oil inlet port (P2) of group 5 of the second directional control valve,
It is supplied to the right travel direction switching valve 5d. In other words, the pressure oil of the first hydraulic pump 1 is supplied to the arm direction switching valve 4c and the right travel direction changeover valve 5d, and the pressure oil of the second hydraulic pump 2 is supplied to the left and right travel direction changeover valve 4e and the right travel direction changeover valve 5d. 5d, and the amount of pressure oil supplied to the -direction switching valve 5d for running to the right is received as increasing, but due to the straightness of the crawler itself, the pressure oil flowing to the pipe 9 is This is less than the amount of pressure oil flowing through the pipe 10, and the amount of oil supplied to the left and right travel directional control valves 4e, 5d is evenly distributed to maintain straight travel.

At this time, if the drive 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 the straightness can be maintained while moving the arm. 0 or conversely, if the drive pressure of the arm is higher than the travel drive pressure, the drive pressure of the arm is secured by the throttles 4f and 5f, and the excess oil other than that used to move the arm is distributed equally to the left and right travel motors as mentioned above. Therefore, it is possible to maintain straightness while moving the arm.

C) Next, when performing a turning operation while traveling straight, or a bucket operation to create a boom movement, it is possible to operate other actuators while maintaining straight travel by operating the switching valve 5e. Since this is basically the same as the above explanation, the explanation will be omitted.

FIG. 2 shows a second embodiment. This is basically the same configuration as the embodiment shown in FIG. 1, but the difference is that in the first embodiment, the pipe line 9 was configured outside the group 5 of the second directional control valve. In this case, a passage 5h is provided inside the second directional valve group 5, and the pipe line 9 is omitted.

FIG. 3 shows a third embodiment, which is similar to the first embodiment shown in FIG.
The operation is basically the same as in the first embodiment, but the difference is that in the first embodiment, the pipe line 8 was connected to the AI boat on the downstream side of the switching valve 5e, but in this embodiment, the pipe line 8 was connected to the AI boat on the downstream side of the switching valve 5e. P on the side
3 boats are installed, and the first hydraulic pump 1 is connected to the P3 port.
A pipe line 11 that can supply pressure oil is provided.

FIG. 4 shows a fourth embodiment, which has basically the same configuration as the third embodiment shown in FIG. 3, except that in the third embodiment, the pipe line 9 is The passage 5h' is provided inside the second directional valve group 5, and the conduit 9 is omitted, instead of being configured outside the second directional valve group 5.

In the above embodiments, 1) the switching valve 5e is provided in the group 5 of the second directional switching valves; however, it is of course possible to provide the switching valve 5e on the group 4 side of the first directional switching valves.

2) Regarding the operation method of the switching valve 5e, although it is shown as a manual type in the diagram of this embodiment, when traveling and other operations that require independence from traveling are simultaneously applied, electric, hydraulic, link, etc. It is also possible to use a method of automatically switching using the following. (Embodiment of the second solution) FIGS. 5 to 8 are embodiments corresponding to the second solution of the present invention. These differ from the first to fourth embodiments in the connection relationship between the traveling direction switching valve and other direction switching valves. First, the fifth embodiment shown in FIG. 5 will be described.

In FIG. 5, 1 is a first hydraulic pump, 2 is a second hydraulic pump, 3 is a first hydraulic pump, and 3 is a first hydraulic pump. The prime mover that drives the second hydraulic pump 1.2 is a group of first directional valves 4, which consists of a main relief valve 4a, one for left and right travel (hereinafter described as for topsoil travel). Directional switching valve 4e
, a directional switching valve for swing 4b, a directional switching valve for arm 4c, and a second directional switching valve for boom 4d, and unlike the previous embodiment, these directional switching valves 4b to 4e are all connected in parallel.

Reference numeral 5 denotes a second directional switching valve group, which is composed of a main relief (lube 5a), a directional switching valve 5d for the left and right travel (hereinafter described as the left travel), and a first boom directional valve 5d. These are the switching valve 5b and the directional switching valve 5c for buckets 1 to 5c, and these directional switching valves 5b to 5d are also connected in parallel. 6 is the first hydraulic pump 1 and the first directional switching valve. A pipe line 7 connecting the main inlet port PI of group 4 is a pipe line connecting the second hydraulic pump 2 and the main inlet port PI of the second directional valve group 5.

4f is a throttle provided in the parallel passage of the left travel direction switching valve 4e, 4g is a load check valve similarly provided in the parallel passage, and the throttle 4f and the load check valve 4g are provided in series with each other. Reference numeral 5e denotes a switching valve which is provided downstream of the main relief valve 5a of the second directional switching valve group 5 and at the most upstream position of the other directional switching valves. From 1st. Switching occurs in the state of the flow of pressure oil to the second directional valve group 4.5.

5f is a throttle provided in the parallel passage of the right travel direction switching valve 5d, 5g is a load check valve similarly provided in the parallel passage, and the throttle 5f and the load check valve 5g are connected in series. Reference numeral 8 denotes a pipe branched from the pipe 6 connecting the first hydraulic pump 1 and the main inlet port Pl of the first directional switching valve group 4, and connected to the Al boat of the switching valve 5e. 9' branches from the pipe line 7 connecting the second hydraulic pump 2 and the main inlet boat PM of the second directional valve group 5;
This is a pipe line that connects the pressure oil inflow port P2 connected between the right-hand directional switching valve 5d and the port check valve 5g. 10' is the left-hand BIl port of the switching valve 5e. This is a conduit that connects the pressure oil boat P2 connected between the direction switching valve 4e and the load check valve 4g.

With this configuration, (a) when the switching valve 5e is in the A position in FIG. flows into the main entrance boat pt. Here, the pressure oil flowing into the main inlet port Pl of the first directional valve group 4 is supplied to the left travel directional valve 4e, the swing directional valve 4b, the arm directional valve 4c, and the second boom directional valve. It is supplied in parallel to the valve 4d, and the pipe 8, the A0 port of the switching valve 5e, the switching valve 5e, and the switching valve 5e.
The pressure oil is supplied to the left travel directional switching valve 4e, which is connected in parallel through a conduit 10' to the Bl boat P2, through a throttle 4f and a load check valve 5g.

On the other hand, the pressure oil of the second hydraulic pump 2 flows through line 7 to the main inlet boat Pl of the second group 5 of directional valves.

where the main inlet boat P of group 5 of the second directional valve
The pressure oil flowing into the pipe 9 passes through the switching valve 5e and is supplied in parallel to the right travel directional switching valve 5d, the first boom directional switching valve 5b, and the bucket directional switching valve 5c.
It is connected in parallel through the throttle 5f and the load check valve 5g. The pressure oil of the right travel direction switching valve 5d is supplied to the drift boat P2.

) Also, when the switching valve 5e is switched to the B position, the pressure oil of the first hydraulic pump 1 flows through the pipe 6 to the main inlet port Pt of the group 4 of the first directional switching valve, and the left The Al boat of the switching valve 5e is supplied in parallel to the running directional switching valve 4e, the turning directional switching valve 4b, the arm directional switching valve 4c, and the second boom directional switching valve 4d.
Right' through the switching valve 5e, the first travel direction switching valve 5d,
Boom directional control valve 5b and bucket directional control valve 5
c in parallel.

On the other hand, the pressure oil of the second hydraulic pump passes through line 7 to the main inlet port of the second group of directional valves, Po, to the directional valves 5
e, flows through the B□ port of the switching valve 5e and the pipe 1° to the pressure oil inlet port P2 of group 4 of the first directional switching valve;
It is supplied to the left travel direction switching valve 4b, and the pipe line 9
The oil flows to the pressure oil boat P2 of group 5 of the second directional switching valve, and is supplied to the right travel directional switching valve 5b.

In other words, the pressure oil of the first hydraulic pump 1 is supplied to the left running direction switching valve 4e, the turning direction switching valve 4b, and the arm direction switching valve 4.
c, is supplied in parallel to the second boom directional switching valve 4d, the right travel directional switching valve 5d, the first boom directional switching valve 5b, and the bucket directional switching valve 5c, and the second hydraulic pressure '□
The pressure oil of the pump is controlled by the left and right travel direction switching valves 4e,
It will be supplied in priority to 5d.

(Operation of the fifth embodiment) A) With the switching valve 5e in the A position as shown in Fig. 5,
When only the left running direction switching valve 4e and the right running direction switching valve 5d are operated at the same time: The same effect as in the conventional hydraulic circuit is obtained. In other words, the pressure oil from the first hydraulic pump l is distributed to the pipe line 6 and the pipe line 8, and the pressure oil that has passed through the pipe line 6 is distributed to the first hydraulic pump l.
flows into the main inlet port Pl of group 4 of the directional valve;
It is supplied from the parallel passage through the throttle 4f and the load check valve 4g to the left travel direction switching valve 4e. Further, the pressure oil passing through the pipe 8 is transferred to the switching valve 5 of the second directional switching valve group 5.
e, the first directional valve group 4 via the switching valve 5e, the Bl port of the switching valve 5e, and the pipe 10'.
Pass through the hydraulic oil drift boat P2, and turn to the left travel directional control valve 4e.
is supplied to That is, the entire amount of pressure oil from the first hydraulic pump 1 is supplied to the left travel direction switching valve 4e.

On the other hand, the pressure oil from the second hydraulic pump 2 is supplied to pipes 7 and 9.
', the pressure oil that has passed through line 7 flows into the main inlet boat P□ of group 5 of second directional valves,
It is supplied through the parallel passage e through the throttle 5f and the right travel direction switching valve 5dl through the load check valve register. The pressure oil passing through line 9' is also transferred to group 5 of the second directional valve.
The hydraulic pressure inflow port P2 flows into the right-hand travel direction switching valve 5d.
is supplied to That is, the entire amount of pressure oil from the second hydraulic pump 2 flows to the right travel direction switching valve 5d.

B) Directional switching valve 4e for left travel and directional switching valve 5 for right travel
d in the same direction to perform other operations, such as arm operation, while traveling straight: When the arm directional control valve 4c is switched to the right or left, pressure oil from the first hydraulic pump l is also applied to the arm. The pressure oil supplied to the left travel motor decreases accordingly, and the speed of the left travel motor decreases, causing it to meander.

Therefore, before operating the arm directional switching valve 4c, the switching valve 5e 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 4c with the switching valve 5e switched to the B position, the pressure oil in the first hydraulic pump 1 flows through the pipe line 6 and The pressure oil that has been distributed to pipe 8 and passed through pipe 6 flows to the main port Pl of group 4 of the first directional switching valve, passes through the throttle 4f and load check valve 4g from the parallel passage, and then passes through the left-hand directional switching valve. 4e, and the pressure oil that has passed through the pipe line 8 is supplied to A□ of the switching valve 5e of group 5 of the second directional switching valve.
It is supplied from the parallel passage via the port, the switching valve 5e, and the neutral passage, through the throttle 5f, and the load check valve 5g to the right-hand direction switching valve 5d. Further, the pressure oil from the second hydraulic pump is distributed to line 7 and line 9', and the pressure oil that has passed through line 7 is transferred to the main inlet port P of group 5 of the second directional control valve.
Flow switching valve 5e to x, Bl boat of switching valve 5e, pipe l
The oil flows through O to the pressure oil flow port P2 of group 4 of the first directional switching valve, and is supplied to the left travel directional switching valve 4e. Further, the pressure oil that has passed through the pipe line 9' flows to the pressure oil flow port P2 of group 5 of the second directional switching valve, and is supplied to the right travel directional switching valve 5d.

In other words, the pressure oil of the first hydraulic pump 1 and the second hydraulic pump 2
The pressure oils merge and are supplied in parallel to the left travel direction changeover valve 4e and the right travel direction changeover valve 5d. At this time, it appears that the amount of oil from pumps 1 and 2 is not divided equally 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. Straight running is maintained.

When the arm directional switching valve 4c is operated from this state, the pressure oil from the first hydraulic pump 1 is distributed to the pipe line 6 and the pipe line 8, and the pressure oil that has passed through the pipe line 6 is switched to the first direction switching valve. It is also supplied to the arm directional control valve 4c in valve group 4.

In addition, the pressure oil that has passed through the pipe 8 passes through the A0 boat of the switching valve 5e of group 5 of the second directional switching valve, the switching valve 5e, and the neutral passage to the right-hand directional switching valve 5d and is then throttled 5f through the parallel passage. Supplied via load check valve 5g. Also, the pressure oil from the second hydraulic pump 2 is distributed to line 7 and line 9', and the pressure oil passing through line 7 is delivered to the main inlet port P! of group 5 of the second directional valve. The oil flows through the switching valve 5e, port 81 of the switching valve 5e, and pipe 10' to the hydraulic inlet port P2 of the first directional switching valve group 4, and is supplied to the left-hand directional switching valve 4e. Further, the pressure oil passing through the pipe 9' is transferred to the pressure oil flow port P of group 5 of the second directional control valve.
2, and is supplied to the right travel direction switching valve 5d. In other words, the pressure oil of the first hydraulic pump l is supplied to the arm directional control valve 4.
c and the right travel direction switching valve 5d, and the second hydraulic pump 2.
Pressure oil will be supplied to the left and right travel direction switching valves 4b and 5b, and more pressure oil will be supplied to the right travel direction changeover valve 5d. Due to the linearity of the crawler itself, the pressure oil flowing into the pipe 9' is smaller than the pressure oil flowing into the pipe 10', and the amount of oil supplied to the left and right travel directional control valves 4e and 5d is evenly distributed, allowing the crawler to travel straight. Can keep 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 running drive pressure, the drive pressure of the arm is secured by the throttles 4f and 5f, and the excess oil other than that used to move the arm is distributed equally to the left and right drive motors, as described above. This allows you to maintain straightness while moving the arm.

C) Next, when performing a turning operation, a movement toward a boo, a bucket operation, etc. while traveling straight, it is possible to operate other actuators while maintaining straightness by operating the switching valve 5e. Since this is basically the same as the above explanation, the explanation will be omitted.

FIG. 6 shows a sixth embodiment, which has basically the same configuration as the embodiment shown in FIG. 5, except that in the first embodiment, the conduit 9' is The difference is that the passage 5h is provided inside the second directional valve group 5, whereas the conduit 9' is omitted, whereas the passage 5h is provided outside the second directional valve group 5.

FIG. 7 shows a seventh embodiment, which has basically the same effect as the fifth embodiment shown in FIG. 5, but the difference is that in the fifth embodiment, the pipe line 8 is switched. A1 downstream of valve 5e
A port P is provided on the upstream side of the switching valve 5e, and a conduit 11' to which pressure oil from the first hydraulic pump 1 can be supplied is provided. FIG. 8 shows an eighth embodiment, which has basically the same configuration as the seventh embodiment shown in FIG. 7, except that in the seventh embodiment, the pipe 9' The passage 5h was provided outside the second directional valve group 5, but the passage 5h was provided inside the second directional valve group 5, and the pipe line 9' was omitted.

(Effects of the Invention) Since the hydraulic circuit of the present invention has the above-described configuration, when operating an actuator other than traveling while traveling straight, switching the switching valve will switch between the first and second hydraulic pumps. The pressure oil from one of the hydraulic pumps can be equally distributed to the left and right travel motors independently of the other actuators, and the pressure oil from the other hydraulic pump can be distributed equally to the left and right travel motors independently of the other actuators. Since the supply is given priority to traveling, various actuators other than traveling can be reliably operated while traveling straight without meandering, and efficient work can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of a first embodiment of the present invention. FIG. 2 is a hydraulic circuit diagram of the second embodiment. FIG. 3 is a hydraulic circuit diagram of the third embodiment. FIG. 4 is a hydraulic circuit diagram of the fourth embodiment. FIG. 5 is a hydraulic circuit diagram of the fifth embodiment. FIG. 6 is a hydraulic circuit diagram of the sixth embodiment. FIG. 7 is a hydraulic circuit diagram of the seventh embodiment. FIG. 8 is a hydraulic circuit diagram of the eighth embodiment. FIG. 9 is a conventionally known hydraulic circuit diagram. , in the figure: 1 First hydraulic pump 2 Second hydraulic pump 3 Prime mover 4 First directional valve group 4a, 5a Main relief valve 4b Directional switching valve for swing 4c Directional switching valve for arm 4d For second boom Directional switching valve 4e Left running directional switching valve 4f Throttle 4g Load check valve 5 Second directional switching valve group 5b First boom directional switching valve 5c Bucket directional switching valve 5d Right running directional switching valve 5e Switching valve 5f Throttle 5g Load check valve 5h Pipe line 6.7, 8, 9, 9', 10
, 10' , 11 pipes or more

Claims (1)

[Claims] [1] Two hydraulic pumps, a first hydraulic pump and a second hydraulic pump, and driven by these hydraulic pumps, characterized by the following structural requirements 1) to 3): A first directional valve group (4) and a second directional valve group (4) that control the direction of pressure oil supplied to the plurality of actuators.
5) A hydraulic circuit for construction machinery such as a hydraulic excavator. 1) The first directional valve group (4) includes a swing directional valve (4b), an arm directional valve (4c), and a second directional valve (4c).
A plurality of directional control valves such as the boom directional control valve (4d) are connected in parallel in random order, and one traveling direction control valve (4e) is connected at the lowest downstream of these parallel connected control valve groups.
) are connected in tandem, and the tandem passage is provided with a throttle and a load check valve in series, and the second directional valve group (5) has a first boom directional valve (5b) and a bucket directional valve. A plurality of directional switching valves such as valves (5c) are connected in parallel in random order, and the other traveling directional switching valve (5d) is placed at the lowest downstream of the switching valve group connected in parallel.
are connected in tandem, and a throttle and a load check valve are provided in series in the tandem passage, 2) upstream of either the first directional valve group (4) or the second directional valve group (5). 3) one hydraulic pump (1 or 2) is connected to the main inlet port (P_1) of one of the directional valve groups (4 or 5);
It is connected to the switching valve (5e), and the other hydraulic pump (2
Or 1) is connected between the switching valve (5e) and the travel directional switching valve (5d) and the load check valve (5g) of the other directional valve group (5 or 4), and By switching, one hydraulic pump (1 or 2) is connected to one of the travel directional valves (4e) of the directional valve group (4 or 5).
or 5d) and the load check valve (4g or 5g) and the other directional valve group (5 or 4).
e) and the other hydraulic pump (2 or 1) is connected to the neutral passage downstream of the switching valve (5e) of the other group (5 or 4) of the directional valve and Group (4 or 5) driving directional valve (4e or 5e)
and the load check valve (4g). [2] Supply to two hydraulic pumps, a first hydraulic pump and a second hydraulic pump, and a plurality of actuators driven by these hydraulic pumps, characterized by the following structural requirements 1) to 3): A hydraulic circuit for a construction machine such as a hydraulic excavator, which includes a first directional switching valve group and a second directional switching valve group that control the direction of pressure oil. 1) The first directional valve group includes one travel directional valve (4e), a swing directional valve (4b), an arm directional valve (4c), and a second boom directional valve (4c). 4
Connect multiple directional valves such as d) in parallel in random order,
A throttle (4f) and a load check valve (4g) are provided in series in the parallel passage connected to the traveling direction switching valve (4e), and the second direction switching valve group (5) is connected to the other traveling direction. Switching valve (5d), first boom directional switching valve (
5b) and a bucket directional control valve (5c) are connected in parallel in random order, and a throttle (5f) and a load check valve (5g) are connected to the parallel passage connected to the travel directional control valve (5d). ) are provided in series, 2) a switching valve (5e) is provided upstream of either the first directional valve group (4) or the second directional valve group (5), 3) one The hydraulic pump (1 or 2) is connected to the main inlet port (P_1) of one group of directional valves (4 or 5) and the directional valve (5e), and the other hydraulic pump (2 or 1) The switching valve (5e) is connected between the traveling direction switching valve (5d) and the load check valve (5g) of the other directional switching valve group (5 or 4), and by switching the switching valve (5e), one side hydraulic pump (1 or 2) between the travel directional valve (4e or 5d) and load check valve (4g or 5g) of one directional valve group (4 or 5) and the other directional valve group (5 or 4) switching valve (5e)
and the other hydraulic pump (2 or 1) in the neutral passage downstream of
the directional valves (5 or 4) of the other directional valve group (5 or 4)
5e) and between the traveling directional control valve (4e) and load check valve (4g) of one of the directional control valve groups (4 or 5). did.