JPH0410535B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a hydraulic circuit for construction machinery such as a hydraulic excavator. (Prior art) When other actuators are activated while the construction machine is running, the hydraulic circuit of a conventional hydraulic excavator has all directional control valves connected in parallel.
The amount of oil supplied to the drive motor side that activated the actuator with a light load becomes smaller than the oil pressure supplied to the other drive motor side, causing meandering.
Another drawback is that if another actuator with a high load pressure is operated while the vehicle is running, that actuator will not operate. Also, if another actuator in the same directional valve group as the travel motor side is activated during a pivot turn, if the load pressure on that actuator is low, the pivot turn will not be possible, and the load pressure on that actuator will be high. In this case, pivot turns could be made, but the other actuators did not operate. Figure 4 is a hydraulic circuit diagram of a conventional hydraulic excavator.
This will be briefly explained below. 1 is a first hydraulic pump, 2 is a second hydraulic pump, 3 is a first and a second hydraulic pump.
This is the prime mover that drives the hydraulic pumps 1 and 2. 4
is a group of first directional switching valves, which includes a main relief valve 4a, a directional switching valve for left travel motor 4b, a directional switching valve for swing motor 4c, a directional switching valve for arm cylinder 4d, and a directional switching valve for second boom cylinder. The directional control valves 4b to 4e are connected in parallel. 4f
is a neutral passage, 4g is a parallel passage, and 4h is a return passage. Reference numeral 5 designates a second group of directional control valves, including a main relief valve 5a and a directional control valve 5 for the right travel motor.
b. It consists of a first boom cylinder directional switching valve 5c and a bucket cylinder directional switching valve 5d, and each of the directional switching valves 5b to 5d are connected in parallel. 5f is neutral passage, 5g is parallel passage, 5h
is the return passage. 6 is the main inlet port P ₁ of the group 4 of the first hydraulic pump 1 and the first directional valve
A pipe line 7 connects the second hydraulic pump 2 and the main inlet port _P1 of the second directional valve group 5. The hydraulic circuit of such a conventional hydraulic excavator has the following problems. That is, (1) While operating the left travel motor directional selector valve 4b and the right travel motor directional selector valve 5b (a) When operating the arm; The arm cylinder directional selector valve 4d and the left travel motor directional selector valve 4b are connected in parallel, so in the relationship of arm cylinder drive pressure < left travel motor drive pressure, the first arm cylinder directional control valve 4d side, which has a lighter load than the left travel motor directional control valve 4b side, is connected in parallel. The pressure oil of the hydraulic pump 1 tends to flow. As a result, the speed of the left travel motor becomes slower than the speed of the right travel motor, and although the arm moves, straight travel or spin turns are not possible. Furthermore, in the relationship of arm cylinder drive pressure > left travel motor drive pressure, the pressure applied to the arm cylinder is insufficient, so even if straight travel or spin turns are possible, the arm cannot be moved. (b) When performing a turning operation; Since the direction switching valve 4c and the left travel motor direction change valve 4b are connected in parallel, in the relationship of swing motor drive pressure < left travel motor drive pressure, the left travel motor direction change valve 4b side The hydraulic pressure of the first hydraulic pump 1 tends to flow to the direction switching valve 4c side for the swing motor, which has a lighter load compared to the directional control valve 4c, and as a result, the left travel motor speed becomes slower than the right travel motor speed, and although the swing moves, the straight travel does not occur. Unable to run or spin turns. If the relationship is that swing motor drive pressure>left drive motor drive pressure, the pressure applied to the swing motor will be insufficient, so even if it is possible to run straight or spin turn, it will not be possible to complete a turn. (c) When performing bucket operation; Since the bucket cylinder directional control valve 5d and the right travel motor directional control valve 5b are connected in parallel, the bucket cylinder drive pressure < the right travel motor drive pressure. When you're in a relationship,
Directional switching valve 5 for the bucket cylinder, which has a lighter load compared to the directional switching valve 5b for the right travel motor.
The pressure oil of the second hydraulic pump 2 tends to flow to the d side. As a result, the right travel motor speed becomes slower than the left travel motor speed, and although the bucket moves, it is unable to travel straight or spin turns. Also, bucket cylinder driving pressure>
If this is the case with the right travel motor drive pressure, the pressure applied to the bucket cylinder will be insufficient, so even if the vehicle can travel straight or spin turn, it will not be able to move the bucket. (d) When operating the boom; the left traveling motor directional switching valve 4b and the second boom cylinder directional switching valve 4e are the same as the right traveling motor directional switching valve 5b and the first boom cylinder directional switching valve. 5c are connected in parallel, so if the boom cylinder drive pressure is less than the travel motor drive pressure, the first and second boom cylinder directional control valves 4 have a light load.
c, 5c, the first and second hydraulic pumps 1,
Each of the two pressure oils flows, and the boom moves, but cannot run or spin turn.
If the relationship is boom cylinder drive pressure>travel motor drive pressure, the pressure applied to the boom cylinder will be insufficient and the boom will not be able to move even if it can travel straight or spin turn. (2) When pivoting or arm operation is performed by operating only the left travel motor directional control valve 4b, the left travel motor directional control valve 4b and the swing motor directional control valve 4c or the arm cylinder Since it is connected in parallel with the direction switching valve 4d, if the swing motor drive pressure or arm cylinder drive pressure is less than the left travel motor drive pressure, the load will be lower than that on the left travel motor direction change valve 4b. The hydraulic pressure of the first hydraulic pump 1 flows to the light swing motor directional switching valve 4c side or the arm cylinder directional switching valve 4d side, and as a result, the swing or arm moves, but the left travel motor does not move and a pivot turn is not possible. That will happen. Also, if there is a relationship of swing motor drive pressure or arm cylinder drive pressure>travel motor drive pressure,
The pressure applied to the swing motor or arm cylinder is insufficient, and even if the pivot turn is possible, the swing or arm will not move. (3) When operating only the right travel motor directional control valve 5b and operating the bucket belt when making a pivot turn, the bucket cylinder directional control valve 5d
and the right travel motor directional switching valve 5b are connected in parallel, so when the bucket cylinder drive pressure < the right travel motor drive pressure, the load is lighter compared to the right travel motor directional switching valve 5b side. A second directional control valve for the bucket cylinder is installed on the 5d side.
Pressure oil from the hydraulic pump 2 will flow, and the bucket will move, but the right travel motor will not move and a pivot turn will not be possible. Furthermore, if the relationship is that bucket cylinder drive pressure>right travel motor drive pressure, the pressure applied to the bucket cylinder will be insufficient and the bucket will not move even if a pivot turn can be made. (4) When operating the boom when making a pivot turn by operating only the left travel motor directional change valve 4b or the right travel motor directional change valve 5b, the left travel motor directional change valve 4b and the second boom cylinder Since the directional control valve 4e or the right motor directional control valve 5b and the first boom cylinder directional control valve 5c are connected in parallel, the relationship is such that boom cylinder drive pressure < left or right motor drive pressure. If there is, the second boom cylinder directional control valve 4e side or the first boom cylinder directional switch has a lighter load compared to the left travel motor directional control valve 4b side or the right travel motor directional change valve 5b side. Pressure oil from the first hydraulic pump 1 or the second hydraulic pump flows to the valve 5c side. As a result, the boom moves, but the left travel motor or the right travel motor does not move, making it impossible to make a pivot turn. When operating the left travel motor to drive the boom, if the relationship is boom cylinder drive pressure>left travel motor drive pressure, in order to drive the boom, the pressure oil of the second hydraulic pump 2 must be transferred to the first boom. The pressure oil of the first hydraulic pump 1 flows through the cylinder directional switching valve 5c, and in order to drive the left running motor, the pressure oil of the first hydraulic pump 1 flows through the left running motor directional switching valve 4b. In other words, it is an independent circuit, and the boom drive and left travel motor can perform pivot turns at the same time. Also, when operating the right travel motor to drive the boom, the boom cylinder drive pressure>
In the case of the right travel motor drive pressure, the pressure oil of the first hydraulic pump 1 flows through the second boom cylinder directional control valve 4e to drive the boom, and to drive the right travel motor. , second
Pressure oil from the hydraulic pump 2 flows through the right travel motor directional switching valve 5b. In other words, it becomes an independent circuit, allowing simultaneous operation of boom drive and pivot turn by the right travel motor. (Problems to be Solved by the Invention) The present invention attempts to solve the problems in the known technology, and even if other actuators are activated while driving, it is possible to drive straight, and the other actuators can also be reliably activated. The present invention aims to provide a hydraulic circuit which is capable of operating the directional control valve, and which enables both actuators to operate reliably even if the other actuators in the group of directional control valves are operated while only one travel motor is being driven. It is. (Means for Solving the Problems) The present invention has been made to solve the problems of the hydraulic circuit of the conventional hydraulic excavator as described above.
The 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 has one of the directional control valves for the left and right travel motors on the upstream side. Directional switching valves for actuators that are subject to combined operation with traveling, such as directional switching valves for the swing motor, arm cylinder, and second boom cylinder, are connected to the directional switching valve for the traveling motor via a check valve for preventing backflow. Connect in series with. The directional switching valves for the swing motor, arm cylinder, and second boom cylinder are connected in parallel. Further, a logic valve for blocking the neutral passage is provided at the most downstream position of the neutral passage after the directional switching valve for the swing motor. The second group of directional control valves includes, for example, a directional control valve for an actuator that is to be operated in combination with the upstream movement of a predetermined directional control valve for the other of the left and right running motors. The directional control valves for the boom cylinder and the bucket cylinder are connected in series to the directional control valve for the travel motor via a check valve for preventing backflow. The directional switching valves for the first boom cylinder and the bucket cylinder are connected in parallel. or,
A logic valve for blocking the neutral passage is provided at the most downstream of the neutral passage downstream from the first boom cylinder directional switching valve. Furthermore, a switching valve is provided upstream of the travel motor directional switching valve of either the first or second directional switching valve group, and this switching valve controls the pressure oil of the first and second hydraulic pumps. The flow is switched as follows. For the sake of explanation, it is assumed that the switching valve is provided in a group of second directional switching valves. In other words, when the switching valve is in (a) position A, the first hydraulic pump is
A first inlet port of a group of directional valves enters the first inlet port of the group of directional valves and is supplied to the neutral passage, and a second hydraulic pump enters a first inlet port of the second group of directional valves and is supplied with the neutral passage. is supplied to the neutral path. (b) When the switching valve is switched to the B position, the first
a hydraulic pump enters the first inlet port of the first directional valve and is supplied to the neutral passage;
It enters the second inlet port of the second group of directional valves and is fed via said directional valves to the neutral passage. Further, the second hydraulic pump enters the first inlet port of the second directional valve and, through the said directional valve, connects the directional valves other than the left-hand drive motor directional valve of the first directional valve group. It is supplied to the parallel passage and the parallel passages of the directional control valves other than the right-hand travel motor directional control valve of the second directional control valve group. and when the most upstream directional valve of the second group of directional valves switches from position A to position B, the logic in the neutral passage downstream of each of the first and second groups of directional valves Each of the valves also switches to block the neutral passage, solving the problems of conventional hydraulic circuits. (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. 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 invention, and Fig. 3 is a hydraulic circuit diagram of a third embodiment of the invention. It is. In these figures, the same components as in the conventional example shown in FIG. 4 are designated by the same reference numerals. (First Embodiment) In the first embodiment shown in FIG. 1; 1 is a first hydraulic pump, 2 is a second hydraulic pump, 3 is the first and second hydraulic pumps 1, 2, and a pilot. This is the prime mover that drives the hydraulic pump 10. 4 is a group of first directional valves,
A main relief valve 4a, a directional switching valve 4b for the left running motor from the upstream side, and a directional switching valve 4 for the swing motor.
Directional switching valves are provided in this order: c, arm cylinder directional switching valve 4d, and second boom cylinder directional switching valve 4e. Each direction switching valve 4 for the swing motor, arm cylinder, and second boom cylinder is subject to combined operation with traveling with these directional switching valves.
c to 4e are connected in series to the left travel motor directional switching valve 4b. In addition, each direction switching valve 4c to 4e for the swing motor, arm cylinder, and second boom cylinder
Since they are connected in parallel, the order may be changed. 4f is a neutral passage, 4g is a parallel passage,
It is connected to the second inlet port Po. 4h is a return passage, and 4i is a logic valve provided downstream of the neutral passage 4f. 4j is a check valve for preventing backflow provided in a passage connecting the neutral passage 4f and the parallel passage 4g of the other directional switching valves 4c to 4e, which are provided in series below the left travel motor directional switching valve 4b; It is arranged so that it flows freely from 4f to parallel passage 4g and does not flow in the opposite direction. Reference numerals 4b', 4c', and 4d' designate auxiliary valves that operate in conjunction with the directional switching valves 4b to 4d for the left travel motor, the swing motor, and the arm cylinder. 4k is a check valve installed in the parallel passage 4g, which allows fluid to flow freely from the second inlet port Po side, but does not flow in the opposite direction. Reference numeral 5 denotes a second directional control valve group, which includes a main relief valve 5a, a directional control valve 5 for the right traveling motor from the upstream, a directional control valve 5c for the first boom cylinder, and a directional control valve 5d for the bucket cylinder.
The directional switching valves 5 for the first boom cylinder and for the bucket cylinder are provided in this order, and these directional switching valves are used for combined operation with traveling.
c and 5d are connected in series to the right travel motor directional switching valve 5b. Note that since the directional switching valves for the first boom cylinder and the bucket cylinder are connected in parallel, the order may be changed. 5e is a switching valve provided upstream of the right travel motor directional switching valve 5b, which allows the first,
The supply state of pressure oil of the second hydraulic pumps 1 and 2 is switched. 5f is neutral passage, 5g is parallel passage, 5
h is a return passage, and 5i is a logic valve provided downstream of the neutral passage 5f. 5j is a check valve for preventing backflow provided in a passage connecting the neutral passage 5f and the parallel passage 5g of the other directional switching valves 5c and 5d, which are provided in series downstream of the directional switching valve 5b for the right travel motor; It is constructed so that it flows freely from the to the parallel passage 5g and does not flow in the opposite direction. Reference numeral 5k denotes a check valve provided in the parallel passage 5g, which is installed so that fluid can flow freely from the switching valve 5e side and cannot flow in the opposite direction.
Reference numerals 5b', 5c', and 5d' designate auxiliary valves that operate in conjunction with the directional switching valves 5b to 5d for the right travel motor, the first boom cylinder, and the bucket cylinder. 6 is a conduit connecting the first hydraulic pump 1 and the first inlet port _P1 of the first directional valve group 4; 7 is a pipe connecting the second hydraulic pump 2 and the first inlet port P ₁ of the second directional valve group 5; 8 is the first hydraulic pump 1 and the second directional valve group 5; A pipe line 9 connects the second inlet port P2 of the switching valve _5e and the first outlet port Po of the switching valve 5e.
2nd inlet port Po of group 4 of directional valve
It is a conduit that connects the 10 is a pilot pump, 11 is a relief valve that limits the maximum pressure of the pilot pump 10, 12 is a pipe line that guides the pressure oil of the pilot pump 10 to the switching valve 5e and the auxiliary valve 5c', and 13 is the pipe line. A pipe branching from 12 and connecting to the auxiliary valve 5b', 14 a pipe connecting the outlet side of the auxiliary valve 5b' and the auxiliary valve 4b', and 15 a pipe line connecting the auxiliary valve 5b'.
This is a conduit connecting the outlet of c' and the auxiliary valve 5d'. 1
6 is a pipe connecting the outlet of the auxiliary valve 5d' and the auxiliary valve 4d', 17 is a pipe connecting the outlet of the auxiliary valve 4d' and the auxiliary valve 4c', and 18 is a pipe connecting each of the auxiliary valves 4b' and 4c'. A pipe line 19 connecting the outlet is a pipe line connecting the pipe line 18 and the tank. Here, when the pressure in the pipe line 12 increases, the directional control valve 5e is moved from the A position to the B position.
Switch to position. 5e' is an auxiliary valve for operating the logic valves 4i, 5i in conjunction with the switching valve 5e. A conduit 20 and conduits 21 and 22 branching from the conduit 20 are connected to the auxiliary valve 5e' and logic valves 4i and 5i, respectively. 23 is a pipe connecting the outlet of the auxiliary valve 5e' and the tank. With this configuration, the flow of pressure oil generated by the first and second hydraulic pumps 1 and 2 by the switching valve 5e is as follows. (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 flows through the pipe 6.
through the first of group 4 of the first directional valve.
It is supplied to the inlet port _P1 , passes through the neutral passage 4f, and flows to the tank port T. It is also connected to the parallel passage 4g via a backflow prevention check valve 4j upstream of the swing motor directional switching valve 4c. Further, the pressure oil of the first hydraulic pump 1 is supplied through the line 8 to the second inlet port _P2 of the second group 5 of directional valves, but is blocked by the directional valve 5e. The pressure oil of the second hydraulic pump 2 is supplied through 7 to the first inlet port P ₁ of the second group 5 of directional valves, and flows to the tank port T through the directional valve 5e and the neutral passage 5f.
It is also connected to the parallel passage 5g via a backflow prevention check valve 5j upstream of the first boom cylinder directional switching valve 5c. (b) When the pressure in the pipe line 12 increases and the switching valve 5e switches to the B position, the auxiliary valve 5e' is also switched in conjunction with this. Then, the logic valves 4i and 5i are also switched, and the neutral passages 4f and 5f are closed. In this state, the pressure oil of the first hydraulic pump 1 passes through the pipe line 6, is supplied to the first inlet port _P1 of the group 4 of the first directional control valve, and is supplied to the neutral passage 4f.
flows to Note that since the logic valve 4i is switched, the pressure oil flowing through the neutral passage 4f does not flow downstream of the logic valve 4i. The pressure oil from the first hydraulic pump 1 passing through the pipe 8 is supplied to the second inlet port _P2 of the second directional valve group, and flows into the neutral passage 5f via the switching valve 5e. In addition, since the logic valve 5i is also switched, the neutral passage 5f
The pressure oil that flows through does not flow downstream of the logic valve 5i. That is, the pressure oil of the first hydraulic pump 1 is exclusively supplied to the left and right travel motor directional switching valves 4b and 5b. On the other hand, the pressure oil of the second hydraulic pump 2 is supplied through the line 7 to the first inlet port _P1 of the group 5 of the second directional control valves, and is then connected to the parallel path 5g and the second direction via the control valve 5e. Supplied to the outlet port Po of the switching valve. The pressure oil coming out of this port Po passes through the pipe 9 and is supplied to the second inlet port Po of the group 4 of the first directional control valve, and also flows into the parallel passage 4g.
That is, the pressure oil of the second hydraulic pump 2 is exclusively supplied to the actuator directional switching valves 4c to 4e, 5c, and 5d other than the left and right travel motor switching valves 4b and 5b. (Second Embodiment) FIG. 2 shows a second embodiment of the present invention. This is basically the same configuration as the embodiment shown in FIG. 1, but the difference is that the structure of the switching valve 5e is different. To explain this, when the switching valve 5e switches to the B position, the pressure oil of the second hydraulic pump 2, that is, the directional switching valves 4c for actuators other than the directional switching valves 4b and 5b for the left and right travel motors. The surplus of the pressure oil supplied to ~4e, 5c, and 5d is supplied to the directional switching valves 4b and 5b for the left and right travel motors via the throttle and check valve provided in series inside the switching valve 5e. by doing,
The purpose is to make it possible to effectively utilize the pressure oil of the second pressure oil pump 2. (Third Embodiment) FIG. 3 shows a third embodiment of the present invention. This also has basically the same configuration as the embodiment shown in FIG. 1, but the difference is that each of the parallel passages 4g and
Passage 4 connecting 5g and neutral passages 4f and 5f
5j, respectively, and throttles 4l, 5l and check valves 4k, 5k are provided in series in the passages 4j, 5j. In addition, each check valve 4k, 5
k is parallel passage 4g, 5g to neutral passage 4f,
Although pressure oil can freely flow through 5f, it is prevented from flowing in the opposite direction. With the above configuration, when the switching valve 5e is switched to the B position, the pressure oil of the second hydraulic pump 2, that is, the directional switching valves 4c for actuators other than the directional switching valves 4b and 5b for the left and right travel motors. ~4e and 5
The surplus of pressure oil supplied to channels c and 5d is transferred to passage 4.
The pressure oil of the second pressure oil pump 2 is supplied to the directional control valves 4b and 5b for the left and right travel motors through the throttles 4m and 5m and check valves 4n and 5n provided in the left and right travel motors. It can be used effectively. In addition, in the circuit diagrams of the respective embodiments shown in FIGS. 1 to 3 above, in order to operate the switching valve 5e, the combination of movements of the auxiliary valves 4b' to 4d' and 5b' to 5d' is required. Although a configuration has been described in which the pressure oil of the pilot pump 10 is raised, the circuit combinations are not limited to those shown in these circuit diagrams, and other circuit combinations may be used. Of course, it may be performed using a mechanical or electrical method. (Operation of the invention) The operation of the embodiment will be explained below with reference to FIG. (A) Directional switching valve 4b or 5b for the traveling motor on one side, or directional switching valve 4 for the traveling motor on both sides
b, 5b, but do not switch the other actuator directional control valves 4c to 4e, 5c, 5d, that is, in the case of single travel operation; the pressure oil of the pilot pump 10 is supplied to the auxiliary valve 5.
c', 5d', 4d', and 4c' are in the open state, so they return to the tank, no hydraulic pressure is generated in the pipe line 12, and the switching valve 5e remains in the state shown in the figure, and the first hydraulic pump 1 The pressure oil is supplied to the left travel motor directional control valve 4b via the pipe line 6, the first inlet port P ₁ of the first directional control valve group 4, and the neutral passage 4f. Further, the pressure oil of the second hydraulic pump 2 is supplied to the right travel motor directional control valve 5b via the pipe line 7, the first inlet port P ₁ of the second directional control valve group 5, and the neutral passage 5f. If only one of the directional switching valves 4b or 5b for the traveling motor on one side is switched, the pressure oil supplied to the directional switching valve 4b or 5b for the traveling motor that was not switched is further transferred to the neutral passage 4f or It will return to the tank through 5f. Therefore, the same operation as a conventional hydraulic circuit is possible. (B) When the directional switching valves 4c to 4e, 5c, and 5d for the other actuators are switched without switching the left and right travel motor directional switching valves 4b and 5b (state shown); Pressure oil of the pilot pump 10 is auxiliary valve 4
Since b' and 5b' are open, they return to the tank,
No hydraulic pressure is generated in the pipe line 12, and the switching valve 5e
remain as shown in the figure, and the neutral passages 4f and 5f of the first and second directional valve groups 4 and 5 are directional valves for actuators other than the travel motor directional valves 4b and 5b. 4c~4e,
5c or 5d, the pressure oil of the first hydraulic pump 1 is supplied to the pipe 6, the first inlet port P ₁ of the first directional valve group 4, the neutral passage 4f, and the left travel motor. directional switching valve 4b,
It is supplied in parallel to the directional switching valves 4c to 4e for the swing motor, arm cylinder, and boom cylinder through a check valve 4j provided in a passage connecting the neutral passage 4f and the parallel passage 4g. Moreover, the pressure oil of the second hydraulic pump 2 is supplied to the pipe line 7, the second
The first inlet port of group 5 of the directional valve
P ₁ , the switching valve 5e, the neutral passage 5f, the right travel motor directional switching valve 5b, and the check valve 5j for preventing backflow provided in the passage connecting the neutral passage 5f and the parallel passage 5g to the first boom cylinder and the bucket. each direction switching valve 5c for the cylinder,
5d in parallel. Therefore, the same operation as a conventional hydraulic circuit is possible. (C) Manipulate the left and right travel motor directional control valves 4b and 5b to set the directional control valve 4 for other actuators.
When switching c to 4e, 5c, and 5d, for example, when switching the rotation motor directional control valve 4c; the pressure oil of the pilot pump 10 is supplied to the auxiliary valves 4b'
4c' and 5b', the hydraulic pressure in the pipe line 12 rises to the set pressure of the relief valve 11, the switching valve 5e switches to the B position, and the logic valves 5i and 4i switch as well. The pressure oil of the first hydraulic pump 1 is supplied to the left travel motor directional control valve 4b via the pipe line 6, the first inlet port P ₁ of the first directional control valve group 4, and the neutral passage 4f. Note that, since the neutral passage 4f is blocked by the left travel motor directional switching valve 4b, the pressure oil of the first hydraulic pump 1 is not supplied to the subsequent directional switching valves 4c to 4e. On the other hand, the first hydraulic pump 1 supplied to the pipe line 8
The pressure oil is supplied to the right travel motor directional switching valve 5b through the second inlet port P ₂ of the second directional switching valve group 5, the switching valve 5e, and the neutral passage 5f. In addition, the direction switching valve 5 for the right travel motor
Since the neutral passage 5f is blocked by b, the pressure oil of the first hydraulic pump 1 is not supplied to the subsequent directional control valves 5c and 5d. The pressure oil of the second hydraulic pump 2 passes through line 7 to the first inlet port of group 5 of the second directional valve.
P ₁ and is supplied to the parallel passage 5g of the second directional valve group 5 and the outlet port Po by the switching valve 5e. Pressure oil from the second hydraulic pump 2 supplied to the parallel passage 5g is supplied in parallel to the directional switching valves 5c and 5d for the first boom cylinder and the bucket cylinder. Also, the second directional valve group 5
The pressure oil of the second hydraulic pump 2 supplied to the outlet port Po of the first directional valve is connected to the parallel passage 4g via the second inlet port Po of the group 4 of the first directional valve via the pipe line 9, and is connected to the swing motor. It will be supplied in parallel to each switching valve 4c, 4d, 4e for the boom cylinder, arm cylinder, and second boom cylinder. To summarize the above, the pressure oil of the first hydraulic pump 1
These directional valves 4b,
If 5b is switched in the same direction, straight traveling will be maintained. Further, the pressure oil of the second hydraulic pump 2 is supplied to directional switching valves 4c to 4e, 5 for actuators other than the left and right travel motor directional switching valves 4b, 5c.
c, 5d. In this case, other actuator directional control valves 4d, 4
Since the valves e, 5c, and 5d are not operated, the entire amount is supplied to the swing motor directional switching valve 4c. This means that travel and other actuators are completely independent. (D) Any of the travel motor directional control valves 4b or 5b and the other actuator directional control valves 4
c - When 4e, 5c, and 5d are switched; (For the sake of explanation, a case will be explained in which the left traveling motor directional switching valve 4b and the swing motor directional switching valve 4c are switched). The pressure oil of the pilot pump 10 is supplied to the auxiliary valve 4.
b' and 4c', the hydraulic pressure in the pipe line 12 rises to the set pressure of the relief valve 11, and the switching valve 5e is switched (to position B), and at the same time the logic valves 5i and 4i are also switched off. Because it changes,
The pressure oil of the first hydraulic pump 1 is supplied to the line 6, the first inlet port P ₁ of the group 4 of the first directional valve,
It is supplied to the left travel motor directional switching valve 4b through the neutral passage 4f. Note that since the neutral passage 4f is blocked by the left travel direction switching valve 4b, the pressure oil of the first hydraulic pump 1 is not supplied to the subsequent direction switching valves 4c to 4e. On the other hand, the first hydraulic pump 1 supplied to the pipe line 8
The pressure oil in the second directional valve of group 5
Inlet port P ₂ , neutral passage 5 via switching valve 5e
However, since the neutral passage 5f is blocked by the logic valve 5i, it is supplied to the parallel passage 5g via the check valve 5j. However, since the pressure oil supplied to the parallel passage 5g does not operate the directional switching valves 5c and 5d for the first boom cylinder and the bucket cylinder, there is also a check valve 5k in the parallel passage 5g.
Therefore, it will not flow anywhere. In other words, the entire pressure oil of the first hydraulic pump 1 flows to the left travel motor directional switching valve 4b. The pressure oil of the second hydraulic pump 2 passes through line 7 to the first inlet port of group 5 of the second directional valve.
P ₁ and is supplied to the parallel passage 5g of the second directional valve group 5 and the outlet passage Po by the switching valve 5e. The pressure oil from the second hydraulic pump 2 supplied to the parallel passage 5g is supplied to the directional switching valves 5c and 5d for the first boom cylinder and the bucket cylinder. Further, the pressure oil of the second hydraulic pump 2 supplied to the outlet port Po of the group 5 of the second directional control valve is transferred to the second inlet port Po of the group 4 of the first directional control valve via the pipe line 9. The switching valves 4 for the swing motor, the arm cylinder, and the second boom cylinder are connected through the parallel passage 4g.
c, 4d, and 4e in parallel. Here, each direction switching valve 4d, 4 for the arm cylinder, the second boom cylinder, the first boom cylinder, and the bucket cylinder is installed.
Since the pumps e, 5c, and 5d are not operated, the entire pressure oil of the second hydraulic pump 2 is supplied to the swing motor directional switching valve 4c. This means that travel and other actuators are completely independent. (E) When the directional switching valve 4b for the left traveling motor and the directional switching valve 5b or 5c for the bucket cylinder or the first boom cylinder are switched;
(For purposes of explanation, we will explain the case where the left travel motor directional control valve 4 and the bucket cylinder directional control valve 5d are switched.) The pressure oil of the pilot pump 10 is supplied to the auxiliary valve 4.
Since it is shut off by b' and 5d', the hydraulic pressure in the pipe line 12 rises to the set pressure of the relief valve 11.
The switching valve 5e is switched to the B position, and at the same time the logic valves 5i and 4i are also switched. First hydraulic pump 1
The pressure oil is supplied to the left travel motor directional control valve 4b via the pipe line 6, the first inlet port P ₁ of the first directional control valve group 4, and the neutral passage 4f.
Note that since the neutral passage 4f is blocked by the left traveling motor directional switching valve 4b, the pressure oil of the first hydraulic pump 1 is not supplied to the subsequent directional switching valves 4c to 4e. On the other hand, the pressure oil from the first hydraulic pump 1 supplied to the pipe line 8 side is supplied to the neutral passage 5f via the second inlet port P ₂ of the second directional valve group 5 and the switching valve 5e. Since the neutral passage 5f is blocked by the bucket cylinder directional switching valve 5d, the water does not flow into the return passage. Further, this pressure oil is transferred from the neutral passage 5f downstream of the right travel motor directional control valve 5b to the parallel passage 5 via the check valve 5j.
Since it is connected to g, the left travel motor drive pressure <
Due to the bucket cylinder drive pressure, it does not flow to the 5g side, and the pressure oil of the first hydraulic pump 1 is exclusively used for the left travel motor switching valve 4b. Further, if the travel motor drive pressure>bucket cylinder drive pressure, the entire pressure oil of the first hydraulic pump 1 will flow to the parallel passage 5g side. On the other hand, the pressure oil of the second hydraulic pump 2 is supplied to the first inlet port _P1 of the group 5 of the second directional valves through the line 7, and the second
directional valve group 5 parallel passage 5g
and is supplied to the exit port Po. Among these, the pressure oil supplied to the outlet port Po is passed through the pipe line 9 to the second inlet port Po of the first directional valve group 4, and then to the parallel passage 4g and the check valve 4.
It is supplied to K, but since nothing is used, it does not flow anywhere. Further, the pressure oil supplied to the parallel passage 5g flows in its entirety to the bucket cylinder directional control valve 5d via the check valve 5k. In other words, if the left travel motor drive pressure <bucket cylinder drive pressure, the first
The pressure oil of the hydraulic pump 1 is exclusively used for the left travel motor directional switching valve 4b, and the pressure oil of the second hydraulic pump 2 is exclusively used for the bucket cylinder directional switching valve 5d, so that they operate independently and reliably. If the left travel motor drive pressure > the bucket cylinder drive pressure, the entire amount of pressure oil from the first and second hydraulic pumps 1 and 2 is supplied to the bucket cylinder directional control valve 5d. It does not flow to valve 4b and the left travel motor is not driven. The effects of the combination of operations (A) to (E) above are summarized as follows.

【table】

[Table] Also, in the above table, (1) *1 indicates that the pressure oil of the second hydraulic pump 2 is not used effectively. (2) *2 indicates that the pressure oil of the second hydraulic pump 1 is not used effectively. In all other combinations, the pressure oil of the first and second hydraulic pumps 1 and 2 is effectively utilized. (3) Conditional OK means that if the drive pressure on the actuator side other than the drive is higher than the drive pressure of the drive motor, both will operate reliably. (Effects of the Invention) Since the present invention has the above-described configuration, when an actuator other than the drive actuator is operated during the drive operation, the switching valve 5e and the logic valves 5i and 4i are switched by the pilot pressure. , Pressure oil from one of the first and second hydraulic pumps is supplied exclusively to the drive independently from the other actuators, and pressure oil from the other hydraulic pump is supplied exclusively to other actuators other than the drive. I decided to do so. Therefore, the operation of straight-ahead driving, spin turns, and pivot turns can cause problems such as meandering during straight driving, stopping of one-sided driving motor during spin-turns, and stopping of travel during pivot turns due to the operation of other actuators other than driving. This allows for reliable travel operation and other actuator operations other than travel, ensuring efficient work.

[Brief explanation of drawings]

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.
FIG. 3 is a hydraulic circuit diagram of a third embodiment of the present invention. FIG. 4 is a conventionally known hydraulic circuit diagram. In the figure; 1...first hydraulic pump, 2...
2nd hydraulic pump, 3... Prime mover, 4... First directional valve group, 4a, 5a... Main relief valve, 4b... Directional switching valve for left travel motor, 4c... Directional switching for swing motor Valve, 4d...
Directional switching valve for arm cylinder, 4e... Directional switching valve for second boom cylinder, 4f... Neutral passage,
4g...Parallel passage, 4h...Return passage, 4i
...Logic valve, 4j...Check valve, 4k...
Check valve, 4l...passage, 4m...throttle, 4n
...Check valve, 5...Second directional switching valve group, 5b...Directional switching valve for right travel motor, 5c...
...First boom cylinder directional control valve, 5d...
Directional switching valve for bucket cylinder, 5e...Switching valve, 5f...Neutral passage, 5g...Parallel passage,
5h...Return passage, 5i...Logic valve, 5j...
...check valve, 5k...check valve, 5l...passage, 5m...throttle, 5n...check valve, 10...
...Pilot pump, 11...Relief valve, 1
2, 13, 14, 15, 16, 17, 18, 1
9, 20, 21, 22, 23...Pipe line.

Claims (1)

[Claims] 1. Two hydraulic pumps, a first hydraulic pump and a second hydraulic pump, and these hydraulic pumps, which are characterized by the following structural requirements (1) to (4): A hydraulic circuit for a construction machine such as a hydraulic excavator, which includes a first directional valve group 4 and a second directional valve group 5 that control the direction of pressure oil supplied to a plurality of driven actuators. (1) In the first group 4 of directional control valves, a directional control valve 4b for one of the left and right travel motors is arranged upstream, and a directional control valve 4b for the travel motor is disposed downstream thereof. A plurality of actuator directional control valves, such as a swing motor directional control valve 4c, an arm cylinder directional control valve 4d, and a second boom cylinder directional control valve 4e, are connected in series by a neutral passage 4f. In the group 5 of the two directional switching valves, the other determined directional switching valve 5 for the left and right running motors is disposed upstream,
Downstream thereof, directional control valves for a plurality of actuators, such as a first boom cylinder directional control valve 5c and a bucket cylinder directional control valve, which are subject to combined operation with traveling, are connected in series through a neutral passage 5f. (2) A neutral passage 4 is connected to these serially connected passages.
Check valves 4j and 5j for preventing backflow in the direction in which pressure oil freely flows from f and 5f are provided downstream of the travel motor directional control valves 4b and 5b, respectively; A logic valve 4 downstream of the neutral passages 4f, 5f of groups 4, 5 normally opens the neutral passages 4f, 5f, and closes the neutral passages 4f, 5f when the neutral passages 4f, 5f are switched.
(4) Group 5 of the second directional control valve or the first
A switching valve 5e having the following functions (a), (b), and (c) is provided upstream of one of group 4 of directional switching valves. (a) The switching valve 5e has an auxiliary valve 5 interlocked with it.
e', and by switching the auxiliary valve 5e', the logic valves 4i, 5i are opened or closed. (b) Normally, the pressure oil from one hydraulic pump (1 or 2) is supplied only to the neutral passage (4f or 5f) of one directional valve group (4 or 5), and the pressure oil from the other hydraulic pump ( 2 or 1) is supplied to the neutral passage (5f or 4) via the switching valve 5e of the other directional valve group (5 or 4).
f). (c) When the switching valve 5e is switched, the pressure oil of one hydraulic pump (1 or 2) flows between the neutral passage (4f or 5f) of one directional switching valve group (4 or 5) and the other. The group of directional control valves (5 or 4) is supplied to the neutral passage (5f or 4f) via the control valve 5e, and the pressure oil of the other hydraulic pump (2 or 1) is supplied to the group of directional control valves (5 or 4). The parallel passage (5g or 4g) of the other directional valve group (5 or 4) and the parallel passage (4g or 4g) of one directional valve group (4 or 5) are 5g). 2 Group 5 of the second directional valve or the first
When the switching valve 5e provided upstream of one of the directional switching valve groups 4 is switched, a part of the pressure oil from the other hydraulic pump (5 or 4) is transferred to the inside of the switching valve 5e. A hydraulic excavator, etc. according to claim 1, characterized in that the hydraulic excavator, etc. has a passage configured to allow pressure oil to flow toward the hydraulic pump (4 or 5), and is provided with a throttle and a check valve in series in this passage. construction machinery hydraulic circuit. 3 Passages 4l and 5l connecting the parallel passages 4g and 5g and the neutral passages 4f and 5f are provided in the first and second directional valve groups 4 and 5, respectively, and the parallel passages 4g and 5l are connected to these passages 4l and 5l. Claim 1 characterized in that check valves 4n and 5n are provided in a direction that allows flow from 5g to only neutral passages 4f and 5f, and throttles 4m and 5m are provided in series with these check valves 4n and 5n, respectively. Hydraulic circuit of construction machinery such as hydraulic excavator described.