KR102575846B1 - Hydraulic circuit for construction machine and construction machine - Google Patents

Abstract

Provided is a hydraulic circuit for construction machinery that can quickly operate multiple actuators simultaneously by efficiently using oil.
The hydraulic circuit 30 for a construction machine is a hydraulic circuit for a construction machine to operate the first actuator 23D and the second actuator 23F using oil from the pump 12. The hydraulic circuit for construction machinery includes a first direction control valve (53D) for supplying and distributing oil to the first actuator, a second direction control valve (53F) for supplying and discharging oil to the second actuator, and return oil from the first actuator. It has a regeneration passage 45 that leads to the second direction change valve.

Description

Hydraulic circuit for construction machinery and construction machinery {HYDRAULIC CIRCUIT FOR CONSTRUCTION MACHINE AND CONSTRUCTION MACHINE}

The present invention relates to a hydraulic circuit for construction machinery for operating a first actuator and a second actuator using oil from a pump, and in particular to a hydraulic circuit capable of quickly operating the second actuator in parallel with the operation of the first actuator. It's about hydraulic circuits. Additionally, the present invention relates to a construction machine having this hydraulic circuit.

Conventionally, a construction machine that drives each part by a plurality of actuators and a hydraulic circuit that operates the plurality of actuators in the construction machine are known. Hydraulic oil is discharged from one or more pumps and is usually supplied to more actuators than the number of pumps. The hydraulic circuit has a plurality of direction change valves installed corresponding to each of the plurality of actuators. In such a hydraulic circuit, in order to stably operate a plurality of actuators, a parallel supply circuit connecting a plurality of direction change valves through a parallel oil passage or a tandem supply circuit connecting a plurality of direction change valves through a serial oil passage are used. has been hired Additionally, the hydraulic circuit disclosed in Patent Document 1 includes a regeneration circuit that re-supplies return oil discharged from one actuator to the direction change valve corresponding to the actuator.

Japanese Patent Publication No. 2011-179541

However, when one actuator is operated simultaneously with another actuator, the operation speed may be reduced compared to the case where the one actuator is operated alone. The present invention was made in consideration of these points, and its purpose is to provide a hydraulic circuit for construction machinery that can quickly operate a plurality of actuators simultaneously by efficiently using oil.

The hydraulic circuit for construction machinery according to the present invention,

A hydraulic circuit for a construction machine for operating a first actuator and a second actuator using oil from a pump,

a first direction change valve supplying and distributing the oil to the first actuator;

a second direction change valve supplying and distributing the oil to the second actuator;

and a regeneration passage that guides return oil from the first actuator to the second direction switching valve.

The hydraulic circuit for construction machinery according to the present invention,

an unloading passage connected to the pump and passing through the first direction change valve and the second direction change valve in this order;

further comprising a tandem supply passage connected to a position between the first direction control valve and the second direction control valve of the unload passage, and guiding the oil in the unload passage to the second direction control valve,

The regeneration passage may be connected to a position between the first direction control valve and the second direction control valve of the unload passage or to the tandem supply passage.

The hydraulic circuit for construction machinery according to the present invention,

a supply main line passage connected to the pump, the first supply branch passage connecting the supply main line passage to the first direction switching valve, and the second supply connecting the supply main line passage to the second direction switching valve. further comprising a supply passage having a branch passage,

The tandem supply passage may be connected to the supply passage.

In the hydraulic circuit for construction machinery according to the present invention,

The tandem supply passage is connected to the second supply branch passage,

The throttle may be installed at a position in the second supply branch passage that is upstream from the position where the tandem supply passage is connected.

The hydraulic circuit for construction machinery according to the present invention,

a supply main line passage connected to the pump, the first supply branch passage connecting the supply main line passage to the first direction switching valve, and the second supply connecting the supply main line passage to the second direction switching valve. further comprising a supply passage having a branch passage,

The regeneration passage may be connected to the supply passage.

In the hydraulic circuit for construction machinery according to the present invention, the regeneration passage may be connected to the second supply branch passage.

The hydraulic circuit for construction machinery according to the present invention,

Further comprising an actuator passage connecting the first direction change valve to the first actuator,

The regeneration passage may be connected to the actuator passage.

In the hydraulic circuit for construction machinery according to the present invention,

The first actuator is a cylinder for driving the boom,

The return oil may be oil that flows out from the cylinder when the boom is lowered.

In the hydraulic circuit for construction machinery according to the present invention, the return oil may be oil flowing out from the piston side chamber of the cylinder.

The construction machine according to the present invention is provided with any one of the hydraulic circuits for construction machines according to the present invention described above.

According to the present invention, by using return oil from one actuator, a plurality of actuators can be operated simultaneously and quickly.

1 is a diagram showing a hydraulic circuit of a construction machine and an actuator that is operated by receiving operating oil from the hydraulic circuit.
Figure 2 is a hydraulic circuit diagram for explaining the operation of a direction change valve for a boom included in the hydraulic circuit shown in Figure 1.
Figure 3 is a hydraulic circuit diagram for explaining a modified example of a direction change valve for a boom.
Figure 4 is a hydraulic circuit diagram for explaining a regeneration passage included in the hydraulic circuit of Figure 1.
Fig. 5 is a hydraulic circuit diagram showing the same hydraulic circuit as Fig. 4 in a state different from that of Fig. 4;
Figure 6 is a hydraulic circuit diagram showing the same hydraulic circuit as Figure 4 in a state different from Figures 4 and 5;
Figure 7 is a hydraulic circuit diagram showing the same hydraulic circuit as Figure 4 in a state different from Figures 4 to 6.
FIG. 8 is a view corresponding to FIG. 4 and is a hydraulic circuit diagram showing a modified example of a regeneration passage.
Fig. 9 is a hydraulic circuit diagram showing the same hydraulic circuit as Fig. 8 in a state different from that of Fig. 8;

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 9 are diagrams for explaining an embodiment of the present invention.

The construction machine 1 is a machine for performing construction work. The construction machine 1 is, for example, a hydraulic excavator. The construction machine 1 includes pumps 11 and 12, a tank 15, and actuators 21A, 22B, 21C, 23D, 23E, and 23F (hereinafter, also referred to as actuators 21A to 23F). and a hydraulic circuit 30 for construction machinery.

The pumps 11 and 12 are hydraulic pumps that discharge oil (pressure oil, hydraulic oil). As an example, the pumps 11 and 12 are of a variable capacity type. In the pumps 11 and 12, the capacity changes as the tilting angle of the swash plate changes, and when the capacity changes, the discharge amount (the amount of oil discharged per rotation of the input shaft) changes. The pumps 11 and 12 may be composed of two pumps, a first pump 11 and a second pump 12. The pumps 11 and 12 are, for example, split pumps. A split pump is a pump in which multiple pumps are driven by one input shaft. In the split pump, the first pump 11 and the second pump 12 are integrated. In a split pump, the discharge amount of the first pump 11 and the discharge amount of the second pump 12 are equal. However, the pumps 11 and 12 do not have to be split pumps. The first pump 11 and the second pump 12 may be separate units. The input shaft of the first pump 11 and the input shaft of the second pump 12 may or may not be common. The discharge amount of the first pump 11 and the discharge amount of the second pump 12 may be the same or different.

Tank 15 stores oil. Tank 15 supplies oil to pumps 11 and 12. The oil discharged from the pumps 11 and 12 and passed through the actuators 21A to 23F is returned to the tank 15. Oil discharged from the pumps 11 and 12 and not passing through the actuators 21A to 23F is returned to the tank 15.

Actuators 21A to 23F drive the moving parts of the construction machine 1. The actuators 21A to 23F are hydraulic actuators that operate by supplying oil from the pumps 11 and 12. Types of actuators (21A to 23F) include hydraulic motors and hydraulic cylinders. When the construction machine 1 is a hydraulic excavator, the uses of the actuators 21A to 23F include traveling, turning, boom up and down, arm up and down, and bucket rotation. Additionally, in the illustrated example, the actuators 21A to 23F are divided into a first group of actuators 21A and 21C, a second group of actuators 22B, and a third group based on the passage through which oil is supplied. It is classified into actuators (23D, 23E, 23F).

The first group of actuators 21A and 21C operate by supplying oil from the first pump 11. In the example shown in FIG. 1 , oil is not supplied from the second pump 12 to the first group of actuators 21A and 21C. In the illustrated example, the first group of actuators 21A and 21C includes a right-side travel motor 21A (one travel motor) and a turning motor 21C. The right traveling motor 21A (one traveling motor) is a hydraulic motor for driving the construction machine 1. The right-side travel motor 21A is a hydraulic motor for driving the crawler on the right side of the undercarriage provided in the construction machine 1. The turning motor 21C is a hydraulic motor for turning the upper turning body with respect to the lower traveling body. Additionally, the swing motor 21C may be used as a second group of actuators.

The second group of actuators 22B operates by supplying oil from the second pump 12. In the example shown in FIG. 1 , oil is not supplied from the first pump 11 to the second group of actuators 22B. In the illustrated example, the second group of actuators 22B includes a left travel motor 22B (the other travel motor). The left traveling motor 22B (the other traveling motor) is a hydraulic motor for driving the construction machine 1. The left traveling motor 22B is a motor for driving the crawler on the left side of the undercarriage provided in the construction machine 1. Additionally, the motor 21A for right travel may be used as the second group of actuators, and the left travel motor 22B may be used as the first group of actuators.

The third group of actuators 23D, 23E, and 23F can be supplied with oil from the first pump 11 and can also be supplied with oil from the second pump 12. The third group of actuators 23D, 23E, and 23F operate by supplying oil from both or one of the first pump 11 and the second pump 12. In the illustrated example, the third group of actuators 23D, 23E, and 23F includes a boom cylinder 23D, an arm cylinder 23E, and a bucket cylinder 23F. The arm cylinder 23E is a cylinder for undulating (raising and lowering, rotating) the arm with respect to the boom. The boom cylinder 23D is a cylinder for undulating (raising, lowering, rotating) the boom with respect to the upper rotating body. In addition, in the example shown in FIGS. 1 and 2, as will be described in detail later, when performing an operation to lower the boom (“in the case of boom lowering”), the boom cylinder 23D is the second group of actuators. It works similarly to The bucket cylinder 23F is a hydraulic cylinder for rotating the bucket with respect to the arm.

In addition, the construction machine 1 may be provided with actuators (for example, “dozer”, etc.) other than the actuators 21A to 23F described above.

The hydraulic circuit 30 for construction machinery is a hydraulic circuit for controlling the operation of a plurality of actuators 21A to 23F. The hydraulic circuit 30 for construction machinery is connected to the first pump 11, the second pump 12, the tank 15, and a plurality of actuators 21A to 23F. “Connection” may be a direct connection or an indirect connection (connection through a channel, etc.) (the same applies hereinafter). The hydraulic circuit 30 for a construction machine is configured integrally, for example, in a block shape (roughly rectangular parallelepiped shape). The hydraulic circuit 30 for construction machinery has a plurality of direction change valves 51A, 52B, 51C, 53D, 53E, 53F (hereinafter referred to as direction change valves 51A to 53F), as will be described later. The entire hydraulic circuit 30 may be referred to as a “directional change valve.” The hydraulic circuit 30 for construction machinery includes passages 31 to 45, direction change valves 51A to 53F, pressure detection units 75, and throttles 71E, 71F, 72E, 72F [hereinafter, throttle ( 71E ~ 72F)].

Here, the passages 31 to 45 are oil passages (channels, pipes). Passages 31 to 45 include unload passages 31 and 32, tank passages 35, supply passages 41 to 43, tandem supply passages 37Ea, 37Eb, 37Fa and 37Fb, and regeneration passages 45. Includes.

The unload passages 31 and 32 are passages (bypass passages) for returning the discharge oil of the pumps 11 and 12 to the tank 15 without passing through the actuators 21A to 23F. However, from the unloading passages 31 and 32, a tandem supply passage (tandem supply passage 37Ea for the first arm, tandem supply passage 37Eb for the second arm, tandem supply passage 37Fa for the first bucket, which will be described later) When oil flows through the tandem supply passage 37Fb for two buckets, the discharge oil of the pumps 11 and 12 passes through the actuators 23E to 23F. Two unloading passages (31, 32) are installed. That is, the hydraulic circuit 30 for construction machinery shown is of the so-called dual bypass type. The unload passages 31 and 32 have a first unload passage 31 and a second unload passage 32. The first unload passage 31 is connected to the first pump 11. The second unload passage 32 is connected to the second pump 12.

The tank passage 35 is a passage for returning oil to the tank 15. The tank passage 35 is connected to the tank 15, the first unload passage 31, and the second unload passage 32. The tank passage 35 is connected to each of the plurality of direction change valves 51A to 53F. The tank passage 35 is connected to the most downstream portions of the first unload passage 31 and the second unload passage 32. The “most downstream portion” refers to a direction change valve on the most downstream side (the side away from the pumps 11 and 12) among the plurality of direction change valves 51A to 53F (in FIG. 1, the direction change valve for bucket 53F). It is the part downstream.

The supply passages 41 to 43 are passages for supplying the discharge oil of the pumps 11 and 12 to the actuators 21A to 23F. The supply passages 41 to 43 include a first supply passage 41, a second supply passage 42, and a joining supply passage 43.

The first supply passage 41 is a passage for supplying the discharge oil of the first pump 11 to the first group of actuators 21A and 21C and the third group of actuators 23D, 23E and 23F. In the illustrated example, the first supply passage 41 joins the second supply passage 42 and is a third group of directional control valves for supplying and distributing oil to the third group of actuators 23D, 23E, and 23F. It is connected to (53D, 53E, 53F). The joined portion of the first supply passage 41 and the second supply passage 42 forms the combined supply passage 43. That is, the joining supply passage 43 forms a part of the first supply passage 41. The first supply passage 41 is connected to the first pump 11. In the illustrated example, the first supply passage 41 joins the first unload passage 31 and is connected to the first pump 11. The first supply passage 41 is connected to the most upstream part of the first unload passage 31. The above-mentioned “most upstream part of the first unload passage 31” refers to the most upstream direction change valve among the direction change valves 51A to 53F through which the first unload passage 31 passes (in FIG. 1, the direction change for right driving) It is a part upstream (on the first pump 11 side) from the valve 51A. The first supply passage 41 has a first supply main line passage 41α and first supply branch passages 41A, 41C, 41D, 41E, and 41F.

The first supply main line passage 41α is a passage capable of supplying oil to two or more direction change valves among the first group of direction change valves 51A and 51C and the third group of direction change valves 53D, 53E and 53F. am. The first supply branch passages 41A, 41C, 41D, 41E, 41F are in one direction among the first group of direction change valves 51A, 51C and the third group of direction change valves 53D, 53E, 53F. This is a passage that can supply oil only to the switching valve. The first supply branch passages 41A, 41C, 41D, 41E, and 41F are connected to the first supply main line passage 41α. The first supply branch passages 41A, 41C, 41D, 41E, 41F include a supply branch passage 41A for right travel, a supply branch passage 41C for turning, and a supply branch passage 41D for the first boom, A supply branch passage 41E for the first arm and a supply branch passage 41F for the first bucket are included.

The second supply passage 42 is a passage for supplying the discharge oil of the second pump 12 to the second group of actuators 22B and the third group of actuators 23D, 23E, and 23F. In the illustrated example, the second supply passage 42 joins the first supply passage 41 and is a third group of directional control valves for supplying and distributing oil to the third group of actuators 23D, 23E, and 23F. It is connected to (53D, 53E, 53F). The joined portion of the first supply passage 41 and the second supply passage 42 forms the combined supply passage 43. That is, the joining supply passage 43 forms a part of the second supply passage 42. The second supply passage 42 is connected to the second pump 12. In the illustrated example, the second supply passage 42 joins the second unload passage 32 and is connected to the second pump 12. The second supply passage 42 is connected to the most upstream part of the second unload passage 32. The second supply passage 42 has a second supply main line passage 42α and second supply branch passages 42B, 42D, 42D1, 42E, and 42F.

The second supply main line passage 42α is a passage that can supply oil to two or more direction control valves among the second group of direction control valves 52B and the third group of direction control valves 53D, 53E, and 53F. The second supply branch passages (42B, 42D, 42D1, 42E, 42F) are one of the second group directional control valves 52B and the third group directional control valves 53D, 53E, 53F. This is a passage that can supply oil only to (any one of 52B, 53F, 53D, or 53E). The second supply branch passages 42B, 42D, 42D1, 42E, and 42F are connected to the second supply main line passage 42α. The second supply branch passages 42B, 42D, 42D1, 42E, and 42F include a supply branch passage 42B for the left travel (supply branch passage for the other travel), a supply branch passage 42D for the second boom, and a second supply branch passage 42D for the second boom. 2. It includes a supply branch passage 42D1 for lowering the boom, a supply branch passage 42E for the second arm, and a supply branch passage 42F for the second bucket.

The second boom supply branch passage 42D joins the above-described first boom supply branch passage 41D to form a boom combined supply passage 43D, and is connected to the boom direction change valve 53D. That is, the boom merging supply passage 43D forms a part of the first boom supply branch passage 41D and a part of the second boom supply branch passage 42D.

The second arm supply branch passage 42E joins the above-described first arm supply branch passage 41E to form the arm merge supply passage 43E, and is connected to the arm direction change valve 53E. That is, the arm joining supply passage 43E forms a part of the first arm supply branch passage 41E and a part of the second arm supply branch passage 42E.

The second bucket supply branch passage 42F joins the above-described first bucket supply branch passage 41F to form a bucket bucket supply branch supply passage 43F, and is connected to the bucket direction change valve 53F. That is, the bucket merge supply passage 43F forms a part of the first bucket supply branch passage 41F and a part of the second bucket supply branch passage 42F.

On the other hand, the second supply branch passage 42D1 for lowering the boom is a separate path from the second boom supply branch passage 42D, and connects the second supply main line passage 42α and the boom direction change valve 53D. The second supply branch passage 42D1 for boom lowering is connected to the boom direction change valve 53D without merging with the boom supply branch passage 42D. In addition, as will be described later, the supply branch passage 42D1 for lowering the second boom is omitted, and the boom supply is supplied from the supply passage 42 through the second boom supply branch passage 42D both when the boom is raised and lowered. Oil may be supplied to the direction change valve 53D.

The tandem supply passages 37Ea, 37Eb, 37Fa, and 37Fb are passages for supplying oil (surplus oil) flowing through the unload passages 31 and 32 to one of the one-way switching valves 51A to 53F. In the illustrated example, the tandem supply passages 37Ea, 37Eb, 37Fa, 37Fb are connected to the unload passages 31 and 32 and the supply passages 41 to 43, and the unload passages 31 and 32 and the supply passages ( 41 to 43) are connected.

In the example shown in FIG. 1, the first arm tandem supply passage 37Ea is connected to the first unload passage 31 and the first arm supply branch passage 41E, and the first unload passage 31 and the first supply passage 41. The second arm tandem supply passage 37Eb is connected to the second unload passage 32 and the second arm supply branch passage 42E, and connects the second unload passage 32 and the second supply passage 42. Connecting. The first bucket tandem supply passage 37Fa is connected to the first unload passage 31 and the first bucket supply branch passage 41F, and connects the first unload passage 31 and the first supply passage 41. Connecting. The second bucket tandem supply passage 37Fb is connected to the second unload passage 32 and the second bucket supply branch passage 42F, and connects the second unload passage 32 and the second supply passage 42. Connecting.

As shown in FIG. 1, the 1st arm tandem supply passage 37Ea is connected to the 1st unloading passage 31 at the connection position 37Ea-1. Connection position 37Ea-1 is a position on the first unloading passage 31 between the direction change valve 53E for arms and the "other direction change valve" different from the direction change valve 53E for arms. This “other direction change valve” is a direction change valve upstream (upstream in the first unload passage 31) from the arm direction change valve 53E. Specifically, the connection position 37Ea-1 is located between the turning direction switching valve 51C and the boom direction changing valve 53D.

The first arm tandem supply passage 37Ea is connected to the first arm supply branch passage 41E of the first supply passage 41 at the connection position 37Ea-2. A first arm throttle 71E is installed in the first arm supply branch passage 41E. The connection position 37Ea-2 is located between the arm first throttle 71E and the arm direction change valve 53E in the first arm supply branch passage 41E. However, even if the first arm tandem supply passage 37Ea is connected to the second arm supply branch passage 42E or the arm combined supply passage 43E rather than the first arm supply branch passage 41E, do.

The second arm tandem supply passage 37Eb is connected to the second unload passage 32 at the connection position 37Eb-1. The connection position 37Eb-1 is located between the direction control valve 53D for booms and the direction control valve 53E for arms in the second unloading passage 32. The second arm tandem supply passage 37Eb is connected to the second arm supply branch passage 42E of the second supply passage 42 at the connection position 37Eb-2. A second arm throttle 72E is installed in the second arm supply branch passage 42E. The connection position 37Eb-2 is located between the second arm throttle 72E and the arm confluence supply passage 43E in the second arm supply branch passage 42E.

The first bucket tandem supply passage 37Fa is connected to the first unload passage 31 at the connection position 37Fa-1. Connection position 37Fa-1 is located between the direction control valve 53E for arms and the direction control valve 53F for buckets in the first unload passage 31. The first bucket tandem supply passage 37Fa is connected to the first bucket supply branch passage 41F of the first supply passage 41 at the connection position 37Fa-2. A first throttle 71F for buckets is installed in the first bucket supply branch passage 41F. The connection position 37Fa-2 is located between the first bucket throttle 71F and the bucket merging supply passage 43F in the first bucket supply branch passage 41F.

The second bucket tandem supply passage 37Fb is connected to the second unload passage 32 at the connection position 37Fb-1. Connection position 37Fb-1 is located between the direction control valve 53E for arms and the direction control valve 53F for buckets in the second unloading passage 32. The second bucket tandem supply passage 37Fb is connected to the second bucket supply branch passage 42F of the second supply passage 42 at the connection position 37Fb-2. A second bucket throttle 72F is installed in the second bucket supply branch passage 42F. The connection position 37Fb-2 is located between the second throttle 72F for buckets and the convergence supply passage 43F for buckets in the second bucket supply branch passage 42F.

In addition, the “connection position” refers to the connection position in the circuit and does not mean the physical position (arrangement) (the same applies hereinafter). Additionally, the connection positions of the tandem supply passages 37Ea, 37Eb, 37Fa, and 37Fb are not limited to the example shown, and various changes are possible.

The regeneration passage 45 is a passage for effective use of return oil from one actuator (the first actuator). The regeneration passage 45 explained here guides return oil from one actuator (first actuator) to a direction change valve for supplying and distributing oil to another actuator (second actuator). In the example shown, the regeneration passage 45 can recover at least part of the return oil from the boom cylinder 23D as one actuator (the first actuator) without returning it to the tank 15. The regeneration passage 45 guides the recovered return oil to the bucket cylinder 23F as another actuator (second actuator).

As shown in FIG. 2, the boom cylinder 23D and the boom direction change valve 53D that supplies and distributes oil to the boom cylinder 23D are connected to the first actuator passage 61D and the second actuator passage 62D. are connected by Among these, the first actuator passage 61D is connected to the piston side chamber 23Dp of the boom cylinder 23D. The second actuator passage 62D is connected to the rod side chamber 23Dr of the boom cylinder 23D. The rod side thread 23Dr is a thread on the side through which the rod r in the cylinder penetrates. In the piston side chamber 23Dp, the rod r is not disposed inside. Therefore, the change in internal volume accompanying the movement of the piston p is greater in the piston side chamber 23Dp than in the rod side chamber 23Dr. In the example shown, the regeneration passage 45 is connected to the first actuator passage 61D at one end 45-1, and can recover a large amount of return oil from the boom cylinder 23D. The regeneration passage 45 is connected to the second unload passage 32 at the other end 45-2. The regeneration passage 45 is connected to a position between the arm direction change valve 53E and the bucket direction change valve 53F in the second unload passage 32.

On the regeneration passage 45, a switching valve 47 is installed. The switching valve 47 opens and closes the regeneration passage 45 and switches between supplying oil through the regeneration passage 45 and stopping the supply of oil. The switching valve 47 may be a valve that switches between a state in which the regeneration passage 45 is opened and a state in which the regeneration passage 45 is closed. Additionally, the regeneration passage 45 may be a valve that can adjust the opening of the regeneration passage 45. The switching valve 47 can be a spool valve, similar to the direction switching valves 51A to 53F described later.

Check valves are disposed in the passages 31 to 45. The check valve prevents reverse flow of oil from the direction change valves 51C, 53D, 53E, and 53F to the supply passages 41 and 42 and the unload passages 31 and 32. The check valve is disposed in, for example, the supply branch passage 41C for the swing, the supply branch passage 41D for the first boom, the supply branch passage 41E for the first arm, and the supply branch passage 41F for the first bucket. . The check valve is disposed in, for example, the second boom supply branch passage 42D, the boom lowering supply branch passage 42D1, the second arm supply branch passage 42E, and the bucket supply branch passage 42F. The check valve has, for example, a tandem supply passage for the first arm (37Ea), a tandem supply passage for the second arm (37Eb), a tandem supply passage for the first bucket (37Fa), and a tandem supply passage for the second bucket (37Fb). is placed in A check valve is arranged, for example, in the regeneration passage 45.

The direction change valves 51A to 53F are valves that change the flow rate and direction (adjust the flow rate or change the direction) of the oil supplied from the pumps 11 and 12 to the actuators 21A to 23F. The direction change valves 51A to 53F are valves that supply and discharge oil to the actuators 21A to 23F. The direction change valves 51A to 53F supply the discharge oil of the pumps 11 and 12 to the actuators 21A to 23F. The direction change valves 51A to 53F discharge (return) the oil discharged by the actuators 21A to 23F to the tank 15. The direction change valves 51A to 53F are disposed between the pumps 11 and 12 and the actuators 21A to 23F. Each of the direction change valves (51A to 53F) can be a spool valve. A spool valve is a valve that changes the flow rate and direction of oil depending on the stroke amount (position) of the spool.

These direction change valves 51A to 53F determine the presence or absence of connection between the passages (part of passages 31 to 45) connected to the direction change valves 51A to 53F, and the opening of the connection, depending on the stroke amount of the spool. Switch degrees (valve opening). More specifically, the direction switching valves 51A to 53F place the flow path in either a “blocked state” or a “connected state”. The “blocked state” is a state in which the flow paths are not connected to each other (blocked state). The “connected state” is a state in which the flow paths are connected (connected state). This “connection state” includes a “fully open state” and a “throttled state.” The “fully open state” is a state in which the valve opening degree is maximum. “The state in which the valve opening is at its maximum” means that when the spool of the direction change valve (51A to 53F) is stroked from one end to the other end, the valve opening changes in various ways, and this valve opening is at its maximum. It is in a state of being. For example, a “fully open state” is a state in which the flow path is not constricted (or almost unconstricted). The “throttled state” is a state (excluding the blocked state) in which the flow path is constricted compared to the “fully open state” described above.

The direction change valves 51A to 53F operate in accordance with the operation (lever operation) by the operator of the construction machine 1. The switching positions of the direction switching valves 51A to 53F are switched according to lever operation. The switching positions of the direction change valves 51A to 53F include a neutral position and an operating position.

(Neutral position) The neutral position is a switching position when the lever is not operated (when the lever operation amount is zero, for example). When the switching position is the neutral position, the direction switching valves 51A to 53F do not distribute oil to the actuators 21A to 23F.

(Operating position) The operating position is a switching position when the lever is operated (when the lever operation amount is not zero, for example). When the switching position is the operating position, the direction switching valves 51A to 53F distribute oil to the actuators 21A to 23F. When the switching position is the operating position, the direction switching valves 51A to 53F change the amount of oil supplied to the actuators 21A to 23F in accordance with the lever operation amount.

The direction change valves 51A to 53F include a first group of direction change valves 51A and 51C, a second group of direction change valves 52B, and a third group of direction change valves 53D, 53E and 53F. is included. In the example shown in FIG. 1, the direction change valves 51A to 53F include, in order from the upstream side to the downstream side in the unloading passages 31 and 32, a direction change valve 51A for right-hand travel and a left-hand travel. A direction change valve 52B for a direction change valve, a direction change valve 51C for a swing, a direction change valve 53D for a boom, a direction change valve 53E for an arm, and a direction change valve 53F for a bucket are included.

The first group of direction change valves 51A and 51C are valves that change the flow rate and direction of oil flowing from the first pump 11 to the first group of actuators 21A and 21C. The first group of directional valves 51A and 51C supplies oil to the first group of actuators 21A and 21C. The first group of direction control valves 51A, 51C is connected to the first supply passage 41, the first unload passage 31, and the tank passage 35. The direction change valves 51A, 51C of the first group may be connected to the second unload passage 32 as shown, and may not be connected to the second unload passage 32.

The first group of direction control valves 51A and 51C operate as follows.

(Neutral position) When the switching position is the neutral position, the first group of direction switching valves 51A and 51C do not distribute oil to the first group of actuators 21A and 21C. Specifically, when the switching position is the neutral position, the first group of direction switching valves 51A, 51C places the first unloading passage 31 in a fully open state, and the first supply passage 41 and The tank passage 35 is placed in a blocked state.

(Operating position) When the switching position is the operating position, the first group of direction switching valves 51A and 51C distribute oil to the first group of actuators 21A and 21C. Specifically, when the switching position is the operating position, the first group of direction switching valves 51A, 51C puts the first unloading passage 31 in a blocked state or a throttled state. In addition, when the switching position is the operating position, the first group of direction switching valves 51A, 51C places the first supply passage 41 and the tank passage 35 in a connected state (fully open state or throttled state). . As a result, the discharge oil of the first pump 11 flows through the first supply passage 41, and the oil flowing through the first supply passage 41 is supplied to the first group of actuators 21A and 21C, and the first group of actuators 21A and 21C The oil discharged from the actuators 21A and 21C flows into the tank passage 35.

(Neutral position and operating position) The first group of direction change valves 51A, 51C connected to the second unload passage 32 maintain the second unload passage 32 in a fully open state, regardless of the switching position. do.

In the example shown in Fig. 1, the first group of direction control valves 51A and 51C includes a right-hand travel direction control valve 51A and a turning direction control valve 51C. The right-hand travel direction control valve 51A (one travel direction control valve) distributes oil to the right-hand travel motor 21A. The direction change valve 51A for right travel is connected to the supply branch passage 41A for right travel of the first supply passage 41 . The turning direction change valve 51C distributes oil to the turning motor 21C. The turning direction change valve 51C is connected to the turning supply branch passage 41C of the first supply passage 41.

The second group direction change valve 52B is a valve that changes the flow rate and direction of oil flowing from the second pump 12 to the second group actuator 22B. The second group of directional control valves 52B supplies oil to the second group of actuators 22B. The second group of direction control valves 52B is connected to the second supply passage 42, the second unload passage 32, and the tank passage 35. The second group of direction change valves 52B is connected to the first unload passage 31. The second group of direction change valves 52B do not need to be connected to the first unload passage 31 (not shown).

This second group of direction control valves 52B operates as follows.

(Neutral position) When the switching position is the neutral position, the second group of direction selector valves 52B do not distribute oil to the second group of actuators 22B. Specifically, when the switching position is the neutral position, the second group of direction switching valves 52B keeps the second unloading passage 32 in a fully open state and also opens the second supply passage 42 and the tank passage. (35) is set to blocked.

(Operating position) When the switching position is the operating position, the second group of direction switching valves 52B supplies oil to the second group of actuators 22B. Specifically, when the switching position is the operating position, the second group of direction switching valves 52B puts the second unloading passage 32 in a blocked state or a throttled state. Additionally, when the switching position is the operating position, the second group of direction switching valves 52B places the second supply passage 42 and the tank passage 35 in a connected state (fully open state or throttled state). As a result, the discharge oil of the second pump 12 flows through the second supply passage 42, the oil flowing through the second supply passage 42 is supplied to the second group of actuators 22B, and the second group of actuators 22B Oil discharged from (22B) flows into the tank passage (35).

(Neutral position and operating position) The second group of direction switching valves 52B connected to the first unloading passage 31 maintains the first unloading passage 31 in a fully open state, regardless of the switching position.

In the example shown in FIG. 1, the second group of direction control valves 52B includes a left-hand travel direction control valve 52B. The left-hand travel direction change valve 52B distributes oil to the left-hand travel motor 22B. The left travel direction change valve 52B is connected to the left travel supply branch passage 42B of the second supply passage 42.

The third group of direction change valves (53D, 53E, 53F) control the flow rate and direction of oil flowing from the first pump 11 and the second pump 12 to the third group of actuators (23D, 23E, 23F). It is a valve that changes . The third group of directional valves 53D, 53E, and 53F supplies oil to the third group of actuators 23D, 23E, and 23F. The third group of direction change valves (53D, 53E, 53F) includes a first supply passage (41) and a second supply passage (42), a first unload passage (31), a second unload passage (32), and , connected to the tank passage 35. In the illustrated example, the third group of actuators 23D, 23E, and 23F are connected by a joining supply passage 43 formed by joining the first supply passage 41 and the second supply passage 42. The third group of direction control valves 53D, 53E, and 53F are located downstream from the first group of direction control valves 51A, 51C and the second group of direction change valves 52B (unload passages 31, 32). It is placed on the downstream side of [. The direction change valves of the third group are similar to the direction change valves 52B of the second group in some switching positions, such as the boom lowering position 53Dc (see Fig. 2) of the direction change valve for boom 53D described later. It's okay to operate. In the example shown in FIG. 1, the third group of direction control valves 53D, 53E, and 53F includes a boom direction change valve 53D, an arm direction change valve 53E, and a bucket direction change valve ( 53F) is included.

The boom direction change valve 53D distributes oil to the boom cylinder 23D. The boom direction change valve 53D is disposed on the downstream side of the other direction change valves along the unloading passages 31 and 32. Specifically, the boom direction change valve 53D is disposed on the downstream side of the swing direction change valve 51C. As shown in FIG. 2, the boom direction change valve 53D is connected to the first boom supply branch passage 41D and the second boom supply branch passage 42D through the boom combined supply passage 43D. Additionally, the boom direction change valve 53D is connected to the boom lowering supply branch passage 42D1. The switching position of the boom direction change valve 53D includes a neutral position (53Da) and an operating position (53Db, 53Dc). The operating positions 53Db and 53Dc include a boom raising position 53Db and a boom lowering position 53Dc. The boom raising position 53Db is a transition position selected when raising the boom. The boom lowering position 53Dc is a transition position selected when lowering the boom.

As shown in FIG. 1, the arm direction change valve 53E distributes oil to the arm cylinder 23E. The arm direction change valve 53E is disposed on the downstream side of the other direction change valve. Specifically, the arm direction switching valve 53E is disposed on the downstream side of the boom direction switching valve 53D. As shown in FIG. 1, the arm direction change valve 53E connects the first arm supply branch passage 41E and the second arm supply branch passage 42E through the arm confluence supply passage 43E. is connected to

As shown in FIG. 1, the bucket direction change valve 53F distributes oil to the bucket cylinder 23F. The bucket direction change valve 53F is disposed on the downstream side of the other direction change valve. Specifically, the bucket direction switching valve 53F is disposed on the downstream side of the arm direction switching valve 53E. As shown in FIG. 1, the bucket direction change valve 53F connects the first bucket supply branch passage 41F and the second bucket supply branch passage 42F through the bucket confluence supply passage 43F. is connected to

The outline of the operation of the third group of direction control valves 53D, 53E, and 53F shown in FIG. 1 is as follows, excluding the boom lowering position 53Dc of the boom direction change valve 53D. The third group of direction change valves 53D, 53E, 53F is operated through the lever (operation of the third group of direction change valves 53D, 53E, 53F) through the first unloading passage 31 and the second unloading passage. Adjust the opening degree of the passage 32. By adjusting this opening degree, the third group of direction change valves 53D, 53E, 53F allows the flow of water flowing in from the first supply passage 41 and the second supply passage 42 through the combined supply passage 43. Adjust the oil flow rate. The third group of direction change valves 53D, 53E, and 53F adjusts the flow rate of the oil supplied to the third group of actuators 23D, 23E, and 23F by adjusting the flow rate.

The arm direction change valve 53E operates as follows.

(Neutral position) When the switching position is the neutral position, the arm direction switching valve 53E does not distribute oil to the arm cylinder 23E. Specifically, the neutral position places the first unload passage 31 and the second unload passage 32 in a fully open state, and puts the joining supply passage 43 and the tank passage 35 in a blocked state.

(Operating position) When the switching position is the operating position, the arm direction switching valve 53E distributes oil to the arm cylinder 23E. Specifically, the operating position puts the first unloading passage 31 and the second unloading passage 32 in a blocked state or a constricted state. In addition, the operating position is such that the combined supply passage 43 and the tank passage 35 are in a connected state (fully open state or constricted state). As a result, in principle, the oil flowing through the first supply passage 41 and the oil flowing through the second supply passage 42 join in the combined supply passage 43. Then, the oil flowing through the combined supply passage 43 is supplied to the arm cylinder 23E, and the oil discharged from the arm cylinder 23E flows into the tank passage 35.

The bucket direction change valve 53F operates as follows.

(Neutral position) When the switching position is the neutral position, the bucket direction switching valve 53F does not distribute oil to the bucket cylinder 23F. Specifically, the neutral position places the first unload passage 31 and the second unload passage 32 in a fully open state, and puts the joining supply passage 43 and the tank passage 35 in a blocked state.

(Operating position) When the switching position is the operating position, the bucket direction switching valve 53F distributes oil to the bucket cylinder 23F. Specifically, the operating position sets the 1st unloading passage 31 in a connected state (fully open state or a constricted state), and sets the 2nd unloading passage 32 in a blocked state or a constricted state. In addition, the operating position is such that the combined supply passage 43 and the tank passage 35 are in a connected state (fully open state or constricted state). As a result, in principle, the oil flowing through the first supply passage 41 and the oil flowing through the second supply passage 42 join in the combined supply passage 43. In particular, in the operating position, the second unloading passage 32 is in a blocked state, so that the inflow of oil from the second supply passage 42 into the joining supply passage 43 is promoted. Then, the oil flowing through the combined supply passage 43 is supplied to the bucket cylinder 23F, and the oil discharged from the bucket cylinder 23F flows into the tank passage 35.

The operation of the boom direction change valve 53D shown in FIG. 2 will be described.

(Neutral position) When the switching position is the neutral position (53Da), the boom direction switching valve 53D does not distribute oil to the boom cylinder 23D. Specifically, the neutral position 53Da places the first unload passage 31 and the second unload passage 32 in a fully open state, and the combined supply passage 43 and the tank passage 35 are in a blocked state. Do this.

[Boom raising position 53Db] When the switching position is the boom raising position 53Db, the boom direction change valve 53D distributes oil to the boom cylinder 23D. Specifically, the boom raising position 53Db puts the first unloading passage 31 and the second unloading passage 32 in a blocked state or a constricted state. Additionally, the boom raising position 53Db places the combined supply passage 43 and the tank passage 35 in a connected state (fully open state or constricted state). As a result, in principle, the oil flowing through the first supply passage 41 and the oil flowing through the second supply passage 42 join in the combined supply passage 43. Then, the oil flowing through the combined supply passage 43 is supplied to the boom cylinder 23D, and the oil discharged from the boom cylinder 23D flows into the tank passage 35. As a result, the boom rises.

[Boom lowering position 53Dc] In the example shown in FIGS. 1 and 2, when the boom lowering position 53Dc is selected, the direction change valve 53D for the boom is the second group direction change valve 52B. ) functions similarly to When the switching position is the boom lowering position 53Dc, the boom direction change valve 53D supplies oil to the boom cylinder 23D from the second supply passage 42, and supplies oil to the boom cylinder 23D through the confluence supply passage 43 (confluence for boom). Oil is not supplied from the supply passage 43D to the boom cylinder 23D. That is, when the boom is lowered, oil is supplied to the boom direction change valve 53D from only the second supply passage 42 among the first supply passage 41 and the second supply passage 42.

Specifically, the boom lowering position 53Dc places the first unloading passage 31 in a fully open state (maintains it in a fully open state). The boom lowering position 53Dc places the boom merging supply passage 43D (merging supply passage 43) in a blocked state. Additionally, similarly to the second group of direction change valves 52B, the boom lowering position 53Dc places the second unloading passage 32 in a blocked or restricted state. In addition, similarly to the second group of direction change valves 52B, the boom lowering position 53Dc is in a state where the boom lowering supply branch passage 42D1 (second supply passage 42) and the tank passage 35 are connected. (fully open or throttled). As a result, the discharge oil of the second pump 12 flows through the boom lowering supply branch passage 42D1 (second supply passage 42), and the oil flowing through the boom lowering supply branch passage 42D1 flows into the boom cylinder 23D. ) and the oil discharged from the boom cylinder 23D flows into the tank passage 35. As a result, the boom descends.

Additionally, when the boom lowering position 53Dc is selected, the boom direction change valve 53D may be modified to function similarly to the first group of direction change valves 51A and 51C. In this case, it is structured as follows. The supply branch passage 42D1 for boom lowering is connected to the first supply passage 41, not the second supply passage 42. The boom lowered position 53Dc maintains the second unload passage 32, but not the first unload passage 31, in a fully open state. When the boom is lowered, among the first supply passage 41 and the second supply passage 42, the combined supply passage 43D1 for boom lowering is provided only from the first supply passage 41, not from the second supply passage 42. Oil is supplied to

In addition, an example in which the passage for supplying oil to the boom direction change valve 53D and the boom cylinder 23D changes between the boom raising position 53Db and the boom lowering position 53Dc is shown in FIGS. 1 and 2. did. However, it is not limited to this example, and as shown in FIG. 3, oil is applied to the boom direction change valve 53D and the boom cylinder 23D between the boom raising position 53Db and the boom lowering position 53Dc. The supply channel may be common. In the example shown in Fig. 3, from the example shown in Figs. 1 and 2, the supply branch passage 42D1 for boom lowering is deleted, and in both cases of boom raising and boom lowering, from the combined supply passage 43D for the boom. Oil is supplied to the direction change valve (53D) for the boom. The direction change valve 53D for the boom shown in FIG. 3 is configured in the same manner as the direction change valve 53F for the bucket shown in FIG. 1 .

The pressure detection unit 75 is provided to control the capacity of the pumps 11 and 12 shown in FIG. 1 (perform negative control). The pressure detection unit 75 detects the pressure (negative control pressure) at the most downstream portion of the unloading passages 31 and 32. The pressure detection unit 75 detects the pressure of the lower one of the first unload passage 31 and the second unload passage 32. According to the pressure detected by the pressure detection unit 75, the discharge amounts of the pumps 11 and 12 are adjusted. More specifically, the more oil flows (used) from the pumps 11 and 12 to the actuators 21A to 23F, the less oil flows through the unload passages 31 and 32, which is detected by the pressure detection unit 75. The pressure decreases. Therefore, the capacity of the pumps 11 and 12 is controlled (the tilting angle is changed) so that the lower the pressure detected by the pressure detection unit 75, the larger the discharge amount of the pumps 11 and 12. Additionally, the hydraulic circuit 30 for construction machinery may be configured such that the capacity of the pumps 11 and 12 is controlled by positive control. Additionally, in the hydraulic circuit 30 for construction machinery, capacity control of the pumps 11 and 12 does not need to be performed.

Throttles 71E to 72F are disposed in the first supply passage 41 and the second supply passage 42. These throttles 71E to 72F adjust the supply amount of oil flowing into the third group of direction change valves 53D to 53F through the combined supply passage 43 to the first supply passage 41 or the second supply passage ( 42) It is installed with the sole purpose of adjusting it. In the illustrated example, the throttles 71E to 72F include a first throttle 71E for the arm, a second throttle 72E for the arm, a first throttle 71F for the bucket, and a second throttle 72F for the bucket. It is included.

The first arm throttle 71E is disposed in the first arm supply branch passage 41E. The first arm throttle 71E is located inside the first supply passage 41 outside the area downstream from the first arm supply branch passage 41E to prevent the oil pressure from lowering. It is installed for By installing the first throttle 71E for the arm, sufficient oil is supplied from the first supply passage 41 to the first group of direction change valves 51A, 51C and the third group of direction change valves 53D, 53F. It can be secured. On the other hand, when the first arm throttle 71E is installed, the oil supplied to the arm direction change valve 53E through the arm first throttle 71E is reduced. In this regard, by providing the tandem supply passage 37Ea for the first arm, not only the first throttle 71E for the arm but also the directional control valve 53E for the arm is provided through the tandem supply passage 37Ea for the first arm. It becomes possible to supply sufficient oil.

The second arm throttle 72E is disposed in the second arm supply branch passage 42E. The second arm throttle 72E is located inside the second supply passage 42 outside the area downstream from the second arm supply branch passage 42E to prevent the oil pressure from lowering. It is installed for By installing the second throttle 72E for the arm, it is possible to ensure sufficient oil supply from the second supply passage 42 to the second group of direction change valves 52B and the third group of direction change valves 53D and 53F. You can. On the other hand, when the second arm throttle 72E is installed, the oil supplied to the arm direction change valve 53E through the arm second throttle 72E is reduced. In this regard, by providing the tandem supply passage 37Eb for the second arm, not only the second throttle 72E for the arm but also the directional control valve 53E for the arm is provided through the tandem supply passage 37Eb for the second arm. It becomes possible to supply sufficient oil.

The first bucket throttle 71F is disposed in the first bucket supply branch passage 41F. The first bucket throttle 71F is used to prevent the oil pressure from lowering inside the first supply passage 41 outside the area downstream from the first bucket supply branch passage 41F. It is installed for By installing the first throttle 71F for the bucket, sufficient oil is supplied from the first supply passage 41 to the first group of direction change valves 51A, 51C and the third group of direction change valves 53D, 53E. It can be secured. Meanwhile, when the first throttle 71F for the bucket is installed, the oil supplied to the direction change valve 53F for the bucket through the first throttle 71F for the bucket is reduced. In this regard, by providing the tandem supply passage 37Fa for the first bucket, not only the first throttle 71F for the bucket, but also the direction change valve 53F for the bucket through the tandem supply passage 37Fa for the first bucket. It becomes possible to supply sufficient oil.

The second bucket 72F throttle is disposed in the second bucket supply branch passage 42F. The second bucket throttle 72F is used to prevent the oil pressure from lowering inside the second supply passage 42 outside the area downstream from the second bucket supply branch passage 42F. It is installed for By installing the second throttle 72F for the bucket, sufficient oil supply from the second supply passage 42 to the second group of direction change valves 52B and the third group of direction change valves 53D and 53E can be secured. You can. Meanwhile, when the second throttle 72F for the bucket is installed, the oil supplied to the direction change valve 53F for the bucket through the second throttle 72F for the bucket is reduced. In this regard, by providing the tandem supply passage 37Fb for the second bucket, not only the second throttle 72F for the bucket, but also the direction change valve 53F for the bucket through the tandem supply passage 37Fb for the bucket. It becomes possible to supply sufficient oil.

By the way, the hydraulic circuit 30 for construction machinery described above is used to operate a plurality of actuators. Also, it is assumed that a situation in which both one actuator and another actuator are operated simultaneously may occur frequently. For example, in a power excavator, which is a typical example of construction machinery 1, a boom supports an arm and a bucket. And, in many cases where the bucket is driven, the boom or arm is also driven simultaneously. And, when using one actuator (first actuator) and another actuator (second actuator) simultaneously, the construction machine 1 and the hydraulic circuit 30 for construction machine described above operate both one actuator and the other actuator. At the same time, a design has been made to operate quickly.

Hereinafter, the design will be explained with reference to FIGS. 4 to 7. In the following description, one actuator is also called a first actuator, and the other actuator is also called a second actuator. Additionally, the direction change valve that supplies and distributes oil to one actuator is also called a first direction change valve, and the direction change valve that supplies and distributes oil to another actuator is also called a second direction change valve. In addition, the supply branch passage connected to the first direction switching valve from the supply main passage of the supply passage is also called a first supply branch passage, and the supply branch passage connected to the second direction switching valve from the supply main passage of the supply passage is, It is also called the second supply branch passage. And, the first actuator in the following description is the boom cylinder 23D of the hydraulic circuit 30 for construction machinery described above. In addition, the second actuator in the following description is the bucket cylinder 23F. 4 to 7 show, for convenience of explanation, a direction change valve 53D for the boom forming the first direction change valve, a direction change valve 53E for the bucket forming the second direction change valve, and these direction change valves 53D. Among the components connected to , only the components necessary for explanation are extracted and shown. In addition, for convenience of explanation, the boom direction change valve 53D in the following description and FIGS. 4 to 7 is assumed to have a simpler structure as shown in FIG. 3 .

4 to 7, in the hydraulic circuit 30 for construction machinery described above, the unloading passage (second unloading passage) 32 connected to the pump (second pump) 12 is the first unloading passage (second unloading passage) 32. It passes through the direction change valve (direction change valve for boom) 53D and the second direction change valve (direction change valve for bucket) 53E in this order. Additionally, the supply passage (second supply passage) 42 connected to the pump 12 is connected to the boom direction change valve 53D and the bucket direction change valve 53F. The supply passage 42 includes a supply main line passage (second supply main passage) 42α connected to the pump 12, and a first supply branch passage (supply branch passage for the second boom) branched from the supply main passage 42α. (42D) and a second supply branch passage (supply branch passage for the second bucket) 42F. The first supply branch passage 42D is connected to the boom direction control valve 53D, and the second supply branch passage 42F is connected to the bucket direction change valve 53F. On the supply branch passage 42F for the bucket, a throttle (second throttle for the bucket) 72F is installed.

Additionally, the hydraulic circuit 30 for a construction machine has a tandem supply passage (tandem supply passage for the second bucket) 37Fb. The tandem supply passage 37Fb is connected at one end to a position between the boom direction change valve 53D and the bucket direction change valve 53F of the unload passage 32. The tandem supply passage 37Fb is connected to the supply passage 42. That is, the tandem supply passage 37Fb guides the oil in the unload passage 32 to the bucket direction change valve 53F. In the illustrated example, the tandem supply passage 37Fb is connected to a second supply branch passage (second bucket supply branch passage 42F) at its other end. The throttle 72F is installed at a position in the second supply branch passage 42F that is upstream of the connection position 37Fb-2 where the tandem supply passage 37Fb is connected.

In the hydraulic circuit 30 for a construction machine shown in Fig. 4, the boom direction change valve 53D is in the neutral position, and the bucket direction change valve 53F is also in the neutral position. In the state shown in FIG. 4, the boom direction change valve 53D does not supply or discharge oil to the boom cylinder 23D. Additionally, the bucket direction change valve 53F does not supply or distribute oil to the bucket cylinder 23F.

Next, the operation of the hydraulic circuit 30 for construction machinery in the state shown in FIG. 5 will be described. In the hydraulic circuit 30 for a construction machine shown in FIG. 5, the direction change valve (first direction change valve) 53D for the boom is at the boom raising position 53Db (see FIG. 3) among the operating positions, and the bucket The directional control valve (second directional control valve) 53F is in the operating position. The boom direction change valve 53D blocks or restricts the unloading passage 32 and connects the supply passage 42 to the boom cylinder (first actuator) 23D. By blocking or throttling the unload passage 32, the oil discharged from the pump 12 is promoted to flow into the supply passage 42. The oil sent to the supply passage 42 is supplied to the boom cylinder 23D through the boom direction change valve 53D, and the boom cylinder 23D raises the boom.

In addition, the power excavator, which is the construction machine 1, typically has a boom supporting the arm and bucket. Additionally, the bucket also holds and supports heavy objects such as rocks. As a result, when raising the boom, it is necessary to drive the boom with a very large driving force compared to when lowering the boom. Therefore, when raising the boom, the boom direction change valve 53D supplies oil to the piston side chamber Dp of the boom cylinder 23D and discharges oil from the rod side chamber Dr of the boom cylinder 23D. The rod side chamber Dr is penetrated by the rod. Therefore, the cross-sectional area at a cross-section perpendicular to the operating direction of the rod r is larger in the piston side chamber Dp, which is not penetrated by the rod, than in the rod side chamber Dr. When sending hydraulic oil of the same pressure to the boom cylinder 23D, by setting the piston side chamber Dp to high pressure, the boom cylinder 23D can exert a greater driving force. Between the boom cylinder 23D and the boom direction change valve 53D, two actuator passages 61D and 62D are provided. In the boom raising position shown in FIG. 4, the boom direction change valve 53D connects the supply passage 42 to the first actuator passage 61D connected to the piston side chamber Dp of the boom cylinder 23D. Thereby, the boom can be raised more quickly and more stably.

Next, the operation of the bucket cylinder 23F and the bucket direction change valve 53F in the state shown in FIG. 5 will be described. The bucket direction change valve 53F in the operating position blocks or restricts the unloading passage 32 and connects the supply passage 42 to the bucket cylinder 23F. The oil sent from the pump 12 to the supply passage 42 is supplied to the bucket cylinder 23F through the bucket direction change valve 53F, and the bucket cylinder 23F drives the bucket.

Here, in the power excavator, which is the construction machine 1, the force required to drive the arm and the boom supporting the bucket is usually significantly greater than the force required to drive the bucket. On the other hand, the boom direction change valve 53D and the bucket direction change valve 53F are both connected to the supply passage 42 and receive oil supply from the supply passage 42. Therefore, a throttle 72F is provided in the bucket supply branch passage 42F to suppress the amount of oil flowing from the supply main line passage 42α into the bucket supply branch passage 42F. Conversely, the throttle 72F ensures a sufficient amount of oil flowing from the supply main line passage 42α to the boom supply branch passage 42D. As a result, it becomes possible to quickly and stably perform the boom raising operation and the bucket operation in parallel.

However, when oil is supplied to the bucket direction change valve 53F through the bucket supply branch passage 42F in which the throttle 72F is installed, a pressure loss occurs in the throttle 72F. Therefore, as shown in FIG. 6, in all cases including the case where the boom cylinder 23D is not driven, supplying oil to the bucket direction change valve 53F through the throttle 72F is inefficient, thereby reducing fuel efficiency. It is not ideal in terms of things like this. In order to deal with this problem, as shown in FIGS. 4 to 7, the hydraulic circuit 30 for construction machinery has a tandem supply passage (tandem supply passage for the second bucket) 37Fb.

In the hydraulic circuit 30 for a construction machine shown in FIG. 6, the boom direction change valve 53D is in the neutral position, and the bucket direction change valve 53F is in the operating position. Therefore, in the state shown in FIG. 6, the boom direction change valve 53D does not supply or distribute oil to the boom cylinder 23D. The boom direction change valve 53D opens the unloading passage 32. For this reason, the bucket direction change valve 53F can use the oil flowing through the unload passage 32 through the tandem supply passage 37Fb. In particular, since the connection position 37Fb-2 of the tandem supply passage 37Fb to the boom supply branch passage 42D is located on the downstream side of the throttle 72F, the bucket direction change valve 53F has a pressure loss. A small amount of high-pressure oil is supplied.

Moreover, in the state shown in FIG. 5, the unloading passage 32 is closed by the boom direction change valve 53D disposed upstream of the connection position 37Fb-1 with the tandem supply passage 37Fb. . Additionally, the switching valve 47 on the regeneration passage 45 is also closed. Therefore, in the state where the boom raising operation and the bucket operation are performed simultaneously as shown in FIG. 5, oil is not supplied to the bucket direction change valve 53F through the tandem supply passage 37Fb. For this reason, as described above, oil is supplied from the bucket supply branch passage 42F to the bucket direction change valve 53F at a flow rate controlled by the throttle 72F.

Next, the operation of the hydraulic circuit 30 for construction machinery in the state shown in FIG. 7 will be described. In the hydraulic circuit 30 for a construction machine shown in FIG. 7, the boom direction change valve 53D is at the boom lowering position 53Db (see FIG. 3) among the operating positions, and the bucket direction change valve 53F is in the operating position. The boom direction change valve 53D blocks or restricts the unloading passage 32 and connects the supply passage 42 to the boom cylinder 23D. By blocking or throttling the unload passage 32, the oil discharged from the pump 12 is promoted to flow into the supply passage 42. The oil sent to the supply passage 42 is supplied to the boom cylinder 23D through the boom direction change valve 53D, and the boom cylinder 23D lowers the boom.

On the other hand, the bucket direction change valve 53F is in the operating position, blocks or restricts the unloading passage 32, and connects the supply passage 42 to the bucket cylinder 23F. The oil sent from the pump 12 to the supply passage 42 is supplied to the bucket cylinder 23F through the bucket direction change valve 53F. However, due to the throttle 72F, the oil in the supply passage 42 flows more easily to the boom direction change valve 53D than to the bucket direction change valve 53F. That is, in this hydraulic circuit 30 for construction machinery, driving the boom is given priority over driving the bucket. Therefore, the bucket direction change valve 53F cannot operate the bucket cylinder 23F at high speed only with the oil supplied from the supply passage 42.

However, when the boom shown in FIG. 7 is lowered, the switching valve 47 installed on the regeneration passage 45 opens the regeneration passage 45. Therefore, oil discharged from the boom cylinder 23D, that is, return oil, flows into the area between the boom direction change valve 53D and the bucket direction change valve 53F in the unload passage 32. A tandem supply passage 37Fb is connected to the area between the boom direction change valve 53D and the bucket direction change valve 53F in the unload passage 32. Accordingly, the return oil from the boom cylinder 23D can additionally pass through the tandem supply passage 37Fb and the bucket supply branch passage 42F and flow into the bucket direction change valve 53F. That is, in the state shown in FIG. 7, the bucket cylinder 23F is supplied not only by oil supplied from the supply passage 42, but also by return oil from the boom cylinder 23D supplied through the regeneration passage 45. It works. For this reason, both the boom cylinder 23D and the bucket cylinder 23F can be operated simultaneously and quickly.

In the unloading passage 32 of the illustrated hydraulic circuit 30 for construction machinery, the area receiving return oil from the regeneration passage 45 is closed on the upstream side by the boom cylinder 23D and is also closed by the bucket cylinder ( It is closed on the downstream side by 23F). Therefore, the return oil supplied to the unload passage 32 can be efficiently used to operate the bucket cylinder 23F.

In addition, the connection position 45-2 of the regeneration passage 45 to the unloading passage 32 is located on the bucket supply branch passage 42F downstream from the position where the throttle 72F is installed. Therefore, the return oil can be efficiently used to operate the bucket cylinder 23F without causing a pressure loss in the throttle 72F.

In particular, in the example shown, return oil from the boom cylinder 23D when the boom is lowered is used. Unlike the raising motion of the boom shown in FIG. 5, the lowering motion of the boom shown in FIG. 7 is also assisted by the dead weight of the boom itself. Therefore, the lowering operation of the boom is performed quickly with low driving force from the boom cylinder 23D. From this tendency, the second actuator passage 62D, which receives oil when the boom is lowered, is connected to the rod side chamber Dr of the boom cylinder 23D. Conversely, the first actuator passage 61D, which receives oil when the boom is raised, communicates with the piston side chamber Dp of the boom cylinder 23D, and the boom cylinder 23D can express high driving force when the boom rises. there is.

The regeneration passage 45 is connected to the first actuator passage 61D. The regeneration passage 45 recovers the return oil discharged from the piston side chamber Dp of the boom cylinder 23D to the first actuator passage 61D when the boom is lowered. Since the rod r is not disposed inside the piston side chamber 23Dp, the change in internal volume accompanying the movement of the piston p is greater in the piston side chamber 23Dp than in the rod side chamber 23Dr. That is, when lowering the boom, the flow rate discharged from the piston side chamber 23Dp of the boom cylinder 23D becomes greater than the flow rate supplied to the rod side chamber 23Dr of the boom cylinder 23D. That is, a large amount of return oil discharged from the boom cylinder 23D can be used to operate the bucket cylinder 23F. Therefore, the hydraulic circuit 30 for a construction machine can very efficiently reuse the return oil from the boom cylinder 23D in the other bucket cylinders 23F. As a result, both the boom cylinder 23D and the bucket cylinder 23F can be operated simultaneously and very quickly.

In the present embodiment described above, the hydraulic circuit 30 for a construction machine includes a first direction change valve (boom direction change valve 53D) for supplying and distributing oil to the first actuator (boom cylinder 23D), A second direction control valve (bucket direction control valve (53F)) supplies and discharges oil to the second actuator (bucket cylinder (23F)), and return oil from the first actuator (boom cylinder (23D)) is supplied to the second actuator (bucket cylinder (23F)). It has a regeneration passage 45 leading to the direction change valve 53F. By guiding the return oil from the first actuator (boom cylinder 23D) to the second direction control valve (bucket direction control valve 53F) using the regeneration passage 45, the first actuator [boom cylinder 23D )] and the second actuator [bucket cylinder 23F] are operated simultaneously, not only the first actuator [boom cylinder 23D] but also the second actuator [bucket cylinder 23F] is quickly stabilized. It can work just fine. Moreover, since the operation of the second actuator (bucket cylinder 23F) is assisted using return oil without increasing the output of the pump 12, it is also preferable from the viewpoint of energy saving.

In addition, in this embodiment, the hydraulic circuit 30 for construction machinery further includes an unload passage 32 and a tandem supply passage 37Fb. The unloading passage 32 is connected to the pump 12, and further controls the first direction control valve (boom direction control valve 53D) and the second direction control valve (bucket direction control valve 53F) in this order. pass in series. The tandem supply passage 37Fb is connected to a position between the first direction change valve 53D and the second direction change valve 53F in the unload passage, and switches the oil in the unload passage 32 to the second direction. Guided to valve (53F). And the regeneration passage 45 is connected to a position between the first direction control valve 53D and the second direction control valve 53F in the unload passage 32. The second directional valve (bucket directional valve 53F) supplies and distributes oil to the second actuator (bucket cylinder 23F), and the first valve supplies and distributes oil to the first actuator (boom cylinder 23D). When located downstream along the unloading passage 32 from the direction change valve (direction change valve for boom 53D), there is a possibility that the operation of the second actuator 23F may become slow during operation of the first actuator 23D. There is. In this regard, according to the present embodiment, the return oil from the first actuator 23D is diverted to the second direction connected to the unload passage 32 and the tandem supply passage 37Fb using the regeneration passage 45. It can be supplied to the valve (53F). Therefore, the second actuator 23F can be quickly operated in parallel with the first actuator 23D.

Additionally, at a position downstream of the first direction change valve (boom direction change valve 53D) in the unloading passage 32, two or more direction change valves (arm direction change valve 53E and bucket direction change valve) (53F)] is connected to the regeneration passage 45 through the tandem supply passage 37Fb, respectively, these two or more direction change valves [arm direction change valve 53E and bucket direction change valve 53F )], return oil from the first actuator 53D can be supplied. As a result, two or more actuators (arm cylinder 23E and bucket cylinder 23F) that supply and receive oil using these two or more direction change valves 53E, 53F are operated in parallel with the first actuator 23D. , it can be operated quickly.

In addition, in this embodiment, the hydraulic circuit 30 for construction machinery further has a supply passage 42, and this supply passage 42 includes a supply main line passage 42α connected to the pump 12, and , the supply main line passage 42α is connected to a first supply branch passage (boom supply branch passage 42D) connected to the first direction switching valve (boom direction switching valve 53D), and the supply main line passage 42α is connected to a second direction switching valve (boom direction switching valve 53D). It has a second supply branch passage (bucket supply branch passage 42F) connected to the direction change valve (bucket direction change valve 53F). And the tandem supply passage 37Fb is connected to the supply passage 42. In this embodiment, the return oil from the first actuator (boom cylinder 23D) flows into the supply passage 42 through the regeneration passage 45 and the tandem supply passage 37Fb. Therefore, by adjusting the check valve arrangement of the hydraulic circuit 30 for construction machinery shown in FIG. 1, the return oil from the first actuator 23D is transferred to the second direction change valve 53F communicated with the supply passage 42. ), it also becomes possible to supply to the first direction switching valve 53D connected to the supply passage 42. Thereby, both the first actuator 23D and the second actuator 23F can be operated quickly.

In addition, by adjusting the check valve arrangement of the hydraulic circuit 30 for construction machinery shown in FIG. 1, the second direction change valve supplied with the return oil from the first actuator 23D is changed to the first direction change valve ( It is not limited to the direction switching valves 53E and 53F arranged on the upstream side of 53D), and it can also be used as the direction switching valve 52B arranged on the downstream side of the first direction switching valve 53D. In addition, when three or more direction change valves 52B, 53D, 53E, 53F are connected to the supply passage 42 through the supply branch passages 42B, 42D, 42E, 42F, these three or more direction change valves 52B , 53D, 53E, 53F), return oil from the first actuator 23D can be supplied. As a result, three or more actuators (22B, 23D, 23E, 23F) that supply and receive oil can be operated simultaneously and quickly using these three or more direction change valves (52B, 53D, 53E, 53F).

Moreover, in this embodiment, the tandem supply passage 37Fb is connected to the second supply branch passage (bucket supply branch passage 42F) of the supply passage 42. And the throttle 72F is installed at a position on the upstream side of the position where the tandem supply passage 37Fb is connected in the second supply branch passage 42F. Therefore, the return oil from the first actuator (boom cylinder 23D) can be supplied to the second directional valve (bucket directional valve 53F) without causing pressure loss in the throttle 72F. As a result, the second actuator (bucket cylinder 23F) can be operated quickly and efficiently in parallel with the first actuator (boom cylinder 23D).

In addition, in this embodiment, the first actuator (boom cylinder 23D) is a cylinder for driving the boom, and the regenerated return oil is the oil that flows out from the cylinder when the boom is lowered. When the boom is lowered, the pressure of the return oil from the first actuator 23D can usually be made higher than the pressure expected from the pump's capacity due to the self-weight of the boom. By using this high-pressure return oil, the second actuator (bucket cylinder 23F) can be operated quickly and stably. Additionally, by effectively using the self-weight of the boom, the second actuator (bucket cylinder 23F) can be operated more effectively, thereby realizing significant energy savings.

Additionally, in this embodiment, the regenerated return oil is the oil flowing out from the piston side chamber 23Dp of the cylinder. Compared to the rod side chamber 23Dr, the piston side chamber 23Dp has a larger cross-sectional area at a cross-section perpendicular to the moving direction of the piston p to the extent that the rod r is not penetrated therethrough. That is, as the piston p moves, a large amount of return oil flows out from the piston side chamber 23Dp. By using this large amount of return oil, the second actuator (bucket cylinder 23F) can be operated quickly and efficiently.

Additionally, it is possible to make various changes to the above-described embodiment. Hereinafter, an example of a modification will be described with reference to the drawings. In the following description and the drawings used in the following description, the same symbols as those used for the corresponding parts in the above-described embodiment are used for parts that can be configured similarly to the above-described embodiment, and there is overlap. Omit the necessary explanation.

In the above-described embodiment, an example has been shown in which the regeneration passage 45 is connected to the second unload passage 32 at the other end 45-2, but the other end (45-2) is not limited to this example. In 45-2), it may be connected to the tandem supply passage 37Fb. According to this modification, the same effects as those of the above-described embodiment can be ensured.

Additionally, the regeneration passage 45 may be connected to the supply passage 42 at the other end 45-2. In the modification shown in FIGS. 8 and 9, the regeneration passage 45 is connected to the main supply passage 42α of the supply passage 42 at the other end 45-2. According to this modification, using the regeneration passage 45, the return oil from the first actuator (boom cylinder 23D) is supplied to the second directional control valve (bucket directional control valve) connected to the supply passage 42. (53F)]. Therefore, the second actuator (bucket cylinder 23F) can be operated quickly in parallel with the first actuator (boom cylinder 23D).

Furthermore, according to this modification, the return oil from the first actuator 23D is supplied not only to the second direction control valve 53F but also to the first direction control valve (boom direction control valve (boom direction control valve)) communicated with the supply passage 42. 53D)] can also be supplied to itself. Therefore, both the first actuator (boom cylinder 23D) and the second actuator (bucket cylinder 23F) can be operated quickly. In addition, the second direction change valve that receives return oil from the first actuator 23D is not limited to the direction change valves 53E and 53F disposed upstream of the first direction change valve 53D, and the second direction change valve 53E and 53F are It can also be used as a direction change valve 52B disposed downstream of the one-way change valve 53D. In addition, when three or more direction change valves (52B, 53D, 53E, 53F) are connected to the supply passage 42 through the supply branch passages (42B, 42D, 42E, 42F), these three or more direction change valves ( Return oil from the first actuator 23D can be supplied to 52B, 53D, 53E, and 53F). As a result, three or more actuators that supply and receive oil can be operated simultaneously and quickly using these three or more direction change valves 52B, 53D, 53E, and 53F. As a specific example, as shown in FIGS. 8 and 9, if the regeneration passage 45 is connected to the main supply passage 42α of the supply passage 42 at the other end 45-2, the boom cylinder Return oil from (23D) can be supplied to one or more of the direction change valve for the boom (53D), the direction change valve for the arm (53E), the direction change valve for the bucket (53F), and the direction change valve for left travel (52B). there is.

Additionally, the regeneration passage 45 may be connected to the bucket supply branch passage 42F of the supply passage 42 at the other end 45-2, and according to this modification, one embodiment described above The same effect can be obtained. In addition, the return oil from the first actuator (boom cylinder 23D) can be supplied to the second directional valve (bucket directional valve 53F) through a short path without causing a large pressure loss. . Therefore, the return oil from the first actuator (boom cylinder 23D) can be efficiently used for the operation of the second actuator (bucket cylinder 23F), thereby further promoting energy saving.

In addition, although several modifications to the above-described embodiment have been described above, it is naturally possible to apply a plurality of modifications in appropriate combination.

1: Construction machinery
11: first pump
12: second pump
15: Tank
21A: Right driving motor
22B: Motor for left driving
21C: Swivel motor
23D: Cylinder for boom (first actuator)
23E: Cylinder for arm
23F: Cylinder for bucket (second actuator)
30: Hydraulic circuit for construction machinery
31: first unloading passage
32: second unloading passage
35: Tank passage
37Ea: Tandem supply passage for first arm
37Eb: Tandem supply passage for second arm
37Fa: Tandem supply passage for first bucket
37Fb: Tandem supply aisle for second bucket (tandem supply aisle)
41: first supply passage
41α: First supply main line passage
41D: Supply branch passage for first boom
41E: Supply branch passage for first arm
41F: Supply branch passage for first bucket
42: second supply passage
42α: Second supply main line passage
42D: Supply branch passage for the second boom (first supply branch passage)
42D1: Supply branch passage for lowering the second boom
42E: Supply branch passage for second arm
42F: Supply branch passage for the second bucket (second supply branch passage)
43D: Joining supply channel for boom
43E: Joining supply passage for arms
43F: Combined supply aisle for buckets
45: Regeneration passage
47: diverter valve
51A: Directional valve for right-hand drive
52B: Directional valve for left-hand driving
51C: Swivel directional valve
53D: Directional valve for boom (first directional valve)
53E: Directional valve for arm
53F: Directional valve for bucket (second directional valve)
61D: first actuator passageway
62D: second actuator passageway
71E: First throttle for arm
72E: Second throttle for arm
71F: 1st throttle for bucket
72F: Second throttle for bucket
75: pressure detection unit

Claims (10)

A hydraulic circuit for a construction machine for operating a first actuator and a second actuator using oil from a pump,
a first direction change valve supplying and distributing the oil to the first actuator;
a second direction change valve supplying and distributing the oil to the second actuator;
a regeneration passage that guides return oil from the first actuator to the second direction control valve;
A supply main line passage connected to the pump, a first supply branch passage connecting the supply main line passage to the first direction switching valve, and a second supply branch passage connecting the supply main line passage to the second direction switching valve. A supply passage having,
an unloading passage connected to the pump and passing through the first direction change valve and the second direction change valve in this order;
A tandem connected to a position between the first direction control valve and the second direction control valve in the unload passage and the second supply branch passage, and guiding the oil in the unload passage to the second direction control valve. Provide a supply passage,
A hydraulic circuit for a construction machine, wherein the throttle is installed at a position in the second supply branch passage that is upstream of the position where the tandem supply passage is connected. According to paragraph 1,
The hydraulic circuit for a construction machine, wherein the regeneration passage is connected to a position between the first direction control valve and the second direction control valve of the unload passage or to the tandem supply passage. According to paragraph 1,
The hydraulic circuit for a construction machine, wherein the regeneration passage is connected to the supply passage. According to paragraph 1,
The hydraulic circuit for a construction machine, wherein the regeneration passage is connected to the second supply branch passage. According to paragraph 4,
The hydraulic circuit for a construction machine, wherein the regeneration passage is located downstream of a position in the second supply branch passage where the throttle is installed. According to any one of claims 1 to 5,
Further comprising an actuator passage connecting the first direction change valve to the first actuator,
A hydraulic circuit for a construction machine, wherein the regeneration passage is connected to the actuator passage. According to any one of claims 1 to 5,
The first actuator is a cylinder for driving the boom,
The return oil is oil flowing out from the cylinder when the boom is lowered. In clause 7,
The hydraulic circuit for construction machinery, wherein the return oil is oil flowing out from a piston side chamber of the cylinder. A construction machine provided with a hydraulic circuit for a construction machine according to any one of claims 1 to 5.
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