JPH0221604Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a pressure fluid circuit used in construction machines such as hydraulic excavators.

Construction machinery, for example, a hydraulic excavator, includes various parts such as a traveling device, a swing device, a boom, a bucket, and an earth removal plate, and each of these parts is operated by supplying and discharging pressure fluid from a pressure fluid source. It is the composition. The operating conditions of each of the above parts are different, such as when one device is operating while the other is not operating due to large differences in operating pressure between the operating parts. A two-pump type pressure fluid source is used in which two pumps are operated in parallel to provide a pressure fluid circuit tailored to the conditions and to use power efficiently.

In such a hydraulic excavator, the traveling device and the earth removal plate perform soil removal work while traveling, so the earth removal plate must be operated while the excavator is traveling.
When the pressure fluid to the actuator of the earth removal plate is connected to one of the pressure fluid circuits of the traveling device, the flow rate of the pressure fluid supplied to that traveling device is reduced, so that the traveling direction of the hydraulic excavator is bent. To prevent this, there is a pressure fluid circuit shown in FIG. 5 (Utility Model Application No. 54-201).

The pressure fluid circuit shown in FIG.
are two pumps, a first pump 1a' and a second pump 1b', a first circuit 7' is connected to the discharge side of the first pump 1a', and a second circuit 10 is connected to the discharge side of the second pump 1b'. Connect ′. This first circuit 7' includes switching valves 30a' and 31 for the second boom, swing and travel.
This is a circuit in which a' and 32a' are connected in parallel, and includes an unload circuit 24a' and a supply circuit 22a'. The second circuit 10' is a circuit in which the first boom, bucket, and traveling switching valves 30b', 31b', and 32b' are connected in parallel, and includes an unload circuit 24b' and a supply circuit 22b'.
b'. The switching valve 5' for the soil removal plate includes check valves 8a', 8b', and
Apertures 4a' and 4b' are inserted in series and connected to their connection point.

This pressure fluid flows through the first circuit 7' and the second circuit 1.
0' operating switching valves 32a' and 32b',
While the construction machine is running, the soil discharge plate can be operated by operating the soil discharge plate switching valve 5'. Note that the check valves 8a' and 8b' provided at the most downstream side of the supply circuits 22a' and 22b' prevent the pressure in either the first circuit 7' or the second circuit 10' from becoming higher than the other pressure. This is to prevent pressure fluid from flowing from one side to the other when the
By making the opening areas of a' and 4b' sufficiently small, the flow rate to the soil removal plate can be kept almost constant regardless of the magnitude of the running load.

As described above, when the switching valve of either the first circuit 7' or the second circuit 10' is operated, the pressure fluid circuit described above is switched to the unload circuit 24a' or the unload circuit 24a'.
Since either b' is closed, the earth removal plate can be operated.

However, when the switching valves of the first circuit 7' and the second circuit 10' are in the neutral position, the first pump 1a',
The discharge side of the second pump 2a' is discharged into the tank via the unloading circuits 24a' and 24b' of the first circuit and the second circuit 10', so it is no longer possible to operate only the earth removal plate. . Therefore, in order to operate the earth removal plate, it must be operated simultaneously with one of the other actuators, which makes the operation complicated.

The present invention solves the above-mentioned problems by making it possible to operate the earth removal plate alone and simultaneously with other actuators.

In the present invention, a first circuit and a second circuit formed by a plurality of switching valves are connected to a first pump as a pressure fluid source and a second pump as a pressure fluid source.
The unload circuit that connects the pump to the tank and the input side of the switching valve of the first and second circuits are connected to the first and second circuits.
a supply circuit connected to the second pump;
The two supply circuits are connected at their most downstream sides, and there is a non-return check between the upstream side of this connection point and the downstream side of the most downstream switching valve of the first and second circuits, with the direction of the connection point being the forward direction. A pressure fluid circuit including a third circuit in which a valve and a throttle are arranged in series and a switching valve whose input side is connected to this connection point, the switching valve of the third circuit having an unload circuit connected to a tank. However, one of the unload circuits of the first circuit or the second circuit is connected to the unload circuit of the third circuit.

The present invention having the above-mentioned technical means provides a switching valve for one or both of the first circuit, the second circuit, or the third circuit.
Even if either of the switching valves in the circuit is operated, both or one of the first pump and the second pump of the pressure fluid source is connected to the switching valve in the third circuit, so the switching valve in the third circuit is operated. The actuator to be
It can be operated simultaneously with the first circuit and the second circuit or independently.

Hereinafter, FIG. 1 showing an embodiment of this invention will be described.

The pressure fluid circuit shown in FIG. 1 includes a first pump 1a, a second pump 1a, and a second pump 1a, which are operated in parallel by an engine (not shown) and have a first discharge circuit 3a and a second discharge circuit 3b connected to their discharge sides. A first circuit 7 consisting of a pressure fluid source 2 consisting of a pump 1b, a first discharge circuit 3a, directional control valves 30a, 31a, 32a and a relief valve 6 to which actuators of each part of the hydraulic excavator are connected; Directional switching valves 30b, 31b, to which the second discharge circuit 3b and actuators (not shown) of each part of the hydraulic excavator are connected;
32b and a relief valve 9, an actuator for driving the earth discharge plate, and a throttle 4 in the first discharge circuit 3a and the second discharge circuit 3b.
a, 4b via check valves 8a, 8b, and a discharge circuit 15 connected to the tank T.

Directional switching valves 30a, 31a, 32 of the first circuit 7
18a, 19a; 20a,
21a; and the first discharge circuit 3a; and the first discharge circuit 3
A first supply circuit 22a branching from a and a first discharge circuit 23a connected to the discharge circuit 15 are connected and have a neutral position B and switching positions C and D. The directional switching valves 30a, 31a, 32a connect the first discharge circuit 3a to the tank T when in the neutral position B, and form a first unloading circuit 24a which is closed when operated to the switching position C or D. When any or all of them are operated to switching position C or D, one load circuit is connected to the first supply circuit 22a branched from the first discharge circuit 3a, and the other first load circuit is connected to the discharge circuit. The first connected to 15
It is configured to be connected to the discharge circuit 23a.

Directional switching valves 30b, 31b, 3 of second circuit 10
2b is a second load circuit 16b, 17b, 18b, 1 that supplies and discharges pressure fluid to each actuator (not shown) of the first boom, bucket, and traveling device, respectively.
9b, 20b, 21b; and a second supply circuit 22b and a discharge circuit 15 branching from the second discharge circuit 3b.
It has a neutral position B and switching positions C and D. These directional control valves 30b, 31b, 32b are in neutral position B
, the second discharge circuit 3b is connected to the tank T to form a second unload passage 24b that is closed when operated to the switching position C or D, and any or all of them are switched to the switching position C or D. When operated in D, one of the second load circuits is connected to the second discharge circuit 3.
It is connected to a second supply circuit 22b branching from b, and the other of the second load circuits is connected to a second discharge circuit 23b connected to the discharge circuit 15.

The directional control valve 5 of the third circuit 14 is connected to the third load circuit 2 connected to an actuator that operates the earth removal plate.
5, 26, and check valves 8a, 8b and throttles 4a, 4b in the first supply circuit 22a and second supply circuit 22b, respectively.
The third supply circuit 13 and the third discharge circuit 27 connected to the discharge circuit 15 are connected through the third supply circuit 13 and have a neutral position B and switching positions C and D. This directional switching valve 5 has an unload passage 28c that communicates only when it is in the neutral position B. This unloading passage 2
8c, the first unload circuit 24a communicates with the third unload circuit 28. The third unload circuit 28 is connected to a second unload circuit 24b connected to the tank T. Further, when the switching position C or D is operated, the first unload circuit 2
4a is closed, one of the third load circuits 25, 26 is connected to the third supply circuit 13, and the other is connected to the third discharge circuit 27.

Next, the first circuit 7, the second circuit 10 and the third circuit 1
Directional switching valves 30a, 31a, 32a constituting 4
The directional control valves 30b, 31b, 32b and the directional control valve 5 will be described with reference to FIGS. 2 and 3 (E-A cross section in FIG. 2) and FIG. 4 (Ro-Ro cross section in FIG. 2). However, since each directional control valve has almost the same configuration, only the directional control valve 30a will be described, and for the other directional control valves, the same numbers will be used for the same parts as the directional control valve 30a, and the letters "e", " f”, “g”, “h”, “i”, “j” and “k”
Subscript and state as necessary.

The directional switching valve 30a includes a spool 37e having a plurality of land portions and a small diameter portion, and this spool 37.
The valve body 35e has an inner hole 36e into which the valve body 35e is slidably inserted.

In the inner hole 36e of the valve body 35e, load circuits 16a and 17 are connected as shown in FIG. 4 of the Ro-Ro cross section of FIG.
load passages 38e and 39e to which a is connected, and a supply passage 33 to which the relief valve 6 and the first discharge circuit 3a are connected.
a, a passage 40e connected to the supply passage 33a of the supply body 34a, and a passage 4 of the directional control valve 31a.
When the passage 41e connected to 0f and each switching valve are connected, the supply port 4 forms the first supply circuit 22a.
2e via a load check valve 43e, and a discharge passage 45e that forms the first discharge circuit 23a when the respective switching valves are connected in series.
open respectively. The spool 37e has land portions 47e, 48e, 49e, 50e, 51e and small diameter portions 52e, 53e, 54e, 55e, and the spool 37e is in the neutral position shown in FIGS. 2 and 4 (see FIG. 1). In the case of the neutral position B), the small diameter portions 53e and 54e communicate with the passages 40e and 41e. In addition, the passages 40e, 40f, 40 of each switching valve
g, 40k and passages 41e, 41f, 41g, 41
When k is in communication, a first unload circuit 24a is formed. When the spool 37e is operated to the right, the land portions 48e and 49e close the space between the passages 40e and 41e, and the small diameter portions 52e and 55e connect the load passages 16a and 17a to the bridge passage 44e and the discharge passage 45e, respectively. (Switching position C in FIG. 1) Also, when the spool 37e is operated to the left from the neutral position B, the land portions 49e and 50e are moved to the passage 4.
A small diameter portion 52 closes the space between 0e and 41.
e, 55e are the discharge passage 45e and the bridge passage 44
Connect to each of e. Note that 57e (57
h) is an overload relief valve, and 58e (5
8h) is an anti-cavitation valve which is provided only on the directional control valves 30a and 30b as shown in FIG.

Valve body 35k of the directional switching valve 5 forming the third circuit 14 and the directional switching valve 32b forming the second circuit 10
The connecting body 60 provided between the valve body 35j and the third
As shown in the figure, a passage 61 that communicates the passages 41j and 41k, a passage 62 (third discharge circuit 27 in FIG. 1) that connects the discharge passages 45k and 45j,
Both passages 61 and 62 are connected to the tank T (discharge circuit 15 in FIG. 1), and at the connection surface between the connecting body 60 and the valve body 35j,
A hole 63 is provided at a position that coincides with the supply port 42j, and the supply hole 42j and the hole 63 are connected via the aperture 4b that is engaged with the connection surface. Further, the supply port 42k of the valve body 35g is a throttle 4 provided between the supply port 42g of the valve body 35g and the supply port 42k of the valve body 35k.
a, connected to a bridge passage 44k via a supply port 42k and a load check valve 43k. The hole 63 of the connecting body 60 is connected to the bridge passage 44 via a check valve 64 and a passage 65 (third supply circuit 13 in FIG. 1).
The configuration is to connect to k. Note that the apertures 4a and 4b
have the same configuration and lock at the connecting surface. It has a flange 66 and a throttle hole 67 inside it, and the supply port 42
j, the structure has cylindrical portions 68 and 69 that fit into the hole 63.

The operation of this embodiment having the above configuration will be described. Each direction switching valve 3 of the first, second, and third circuits
0a, 31a, 32a, 30b, 31b, 32b
and 5, when the pressure fluid source 2 is driven in the neutral position B, the discharge fluid of the first pump of the pressure fluid source 2 flows through the first discharge circuit 3a, the first and third unload circuits 24a and 28, and the discharge It flows out via circuit 15 into tank T. Further, the discharge pressure fluid of the second pump is supplied to the second discharge circuit 3b and the second unload circuit 24.
b and flows into the tank T via the discharge circuit 15.

In order to operate only the earth removal plate, the spool 37k of the directional switching valve 5 is operated in the right direction to the switching position C, and the third unloading circuit 28 is moved to the spool 37k.
One load circuit 25 of the third load circuits 25 and 26 is connected to the bridge passage 44k, and the other load circuit 26
is connected to the discharge circuit 27. At this time, the second unload circuit 24b is connected to the tank T via the discharge circuit 15. Therefore, the pressure fluid discharged from the first pump 1a of the pressure fluid source 2 is transferred to the first discharge circuit 3.
a, first supply circuit 22a, throttle 4a, load check valve 43k (check valve 8a) bridge passage 44k
Load path 38k One load circuit 2 of the third load circuit
5 to the actuator for driving the earth removal plate. From the actuator for driving the earth removal plate, the other load circuit 26 of the third circuit, the load passage 39k,
From the discharge circuit 15 to the tank T via the discharge passage 45k
leaks to. At this time, the operating speed of the earth removal plate becomes a value corresponding to the amount of restriction of the restriction 4a.

Next, a case will be described in which the earth removal plate is operated while the traveling device is in operation. Directional switching valve 32 of first circuit 7
a and the directional switching valve 32b of the second circuit 10 are simultaneously operated to the switching position D, the first unload circuit 24a is closed, and the load circuits 21a, 2 are closed.
0a are connected to the first supply circuit 22a and the first discharge circuit 23a, respectively. Similarly, the second unload circuit 2
4b is closed, and the load circuits 21b, 20
b are the second supply circuit 22b and the second discharge circuit 23, respectively.
Connect to b. Therefore, the discharge pressure fluid of the first and second pumps 1a and 1b of the pressure fluid source 2 flows into the actuator of the traveling device via the directional control valves 32a and 32b, and the discharge side of the actuator of the traveling device It flows out to the tank T via the directional switching valves 32a, 32b, the first and second discharge circuits 23a, 23b, and the discharge circuit 15. Therefore, the actuator of the traveling device operates, but the operating speed at this time has a value corresponding to the amount of operation of the directional control valves 32a, 32b. When the directional control valve 5 of the third circuit 14 is operated to the switching position C while the actuator of the traveling device is in operation, the load circuits 25 and 26 for the earth removal plate actuator are connected to the third supply circuit 4 and the third discharge circuit. 27, at this time, the first pump
A part of the discharge pressure fluid 1a is supplied to the first supply circuit 22
a, flow into the bridge passage 44k via the throttle 4a and the load check valve 43k, and the discharge pressure fluid of the second pump 1b flows through the second supply circuit 22b and the throttle 4.
b, check valve 8b (check valve 64 in Fig. 3), third supply circuit 13 (path 65 in Fig. 3), bridge passage 44
As in the case described above, it flows into the actuator for the earth removal plate. In this way, the earth removal plate can be operated simultaneously with the traveling device. At this time, the speed of the earth removal plate becomes a speed corresponding to the sum of the amounts of restriction of the restrictors 4a and 4b. At this time, the flow rate of the pressure fluid to the traveling device decreases, but by making the throttling amounts of the throttles 4a and 4b the same, no curving or the like will occur.

As described above, according to this invention, a pressure fluid source having a plurality of pumps is provided with a third circuit connecting the unload circuits of the first and second circuits connected to the discharge pressure fluid of each pump, and Third
a circuit between the pressure fluid source and a third circuit;
Since it is configured via a check valve, it has the effect that the third circuit and the first or second circuit can be operated simultaneously or independently.

[Brief explanation of the drawing]

FIG. 1 is a pressure fluid circuit diagram of one embodiment of this invention, FIG. 2 is a cross-sectional view of a switching valve constituting the pressure fluid circuit of FIG. 1, and FIG.
FIG. 4 is a cross-sectional view of Rollo in FIG. 2. FIG. 5 shows a conventional pressure fluid circuit diagram. 1a...first pump, 1b...second pump, 2
...Pressure fluid source, 3a, 3b...Discharge circuit, 4
a, 4b... Throttle valve, 7... First circuit, 10...
Second circuit, 14...Third circuit, 16a, 17a,
18a, 19a, 20a, 21a, 25, 26...
...Load circuit, 16b, 17b, 18b, 19b,
20b, 21b, 13...Third supply circuit, 22a
...First supply circuit, 22b...Second supply circuit, 2
4a...first unload circuit, 24b...second unload circuit, 28...third unload circuit, 3
0a, 31a, 32a, 5... Directional switching valve, 30
b, 31b, 32b... Directional switching valve.

Claims (1)

[Claims for Utility Model Registration] A first circuit formed by a plurality of directional control valves and a second circuit formed by a plurality of directional control valves.
an unload circuit connecting a first pump and a second pump of the pressure fluid source to the tank when the directional valves of the first circuit and the second circuit are in neutral positions; a supply circuit that connects the input side of the two-circuit directional control valve to the first and second pumps, the two supply circuits are connected at the most downstream side, and the upstream side of this connection point and the first , a check valve restrictor whose connection point is directed forward is provided in series between the most downstream side of the second circuit, and a third circuit is provided with a switching valve whose input side is connected to this connection point. In the fluid circuit, the switching valve of the third circuit has an unload passage communicating with the tank when the switching valve of the third circuit is in a neutral position, and one of the unloading circuit of the first circuit or the second circuit is connected to the switching valve of the third circuit. A pressure fluid circuit characterized in that it communicates with an unload passage of the.