JPH07110007A - Hydraulic driving device for construction vehicle - Google Patents

Abstract

PURPOSE:To provide a hydraulic driving device for a construction vehicle, which can surely supply pressure oil discharged from a first hydraulic pump during going-straight of the vehicle to a working actuator via a first direction switching valve for the work. CONSTITUTION:A piston accommodating chamber 39 is formed in a valve main body 31 of a first direction switching valve 4A for the work, while a piston 40 is accommodated in this piston accommodating chamber 39 in such a manner that the piston 40 is able to move in the longitudinal direction of a spool 35. In addition, a stroke restricting stopper 41 is placed at one end of the piston 40 in such a manner that the stopper 41 faces one end of the spool 35. At the same time, the valve main body 31 is provided with a pair of pilot pressure oil introducing ports 42, 43 for introducing the pilot pressure oil to both sides of the piston accommodating chamber 39 partitioned by the piston 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for construction vehicles.

[0002]

2. Description of the Related Art A construction vehicle such as a hydraulic excavator is generally equipped with a working hydraulic actuator such as a boom cylinder or an arm cylinder and a hydraulic motor as a traveling hydraulic actuator. A conventional hydraulic drive system that drives an actuator has a configuration as shown in FIG.

In FIG. 5, reference numeral 1 is an engine mounted on a construction vehicle such as a hydraulic excavator, and an output shaft 1a of the engine 1 is connected to a first hydraulic pump 2A and a second hydraulic pump 2B. . These hydraulic pumps 2
Among the A and 2B, the pressure oil discharged from the first hydraulic pump 2A is supplied to the first hydraulic system 3A, and the pressure oil discharged from the second hydraulic pump 2B is supplied to the second hydraulic system 3B. It has become.

The first hydraulic system 3A is a tandem circuit 12A.
The tandem circuit 12A includes a first hydraulic drive actuator 9 such as a boom hoisting cylinder.
Is provided with a work direction switching valve 4A, and a first travel direction switching valve 5A for driving and controlling the first travel hydraulic motor 6A is provided downstream of the first work control valve 4A. .

On the other hand, the second hydraulic system 3B has a tandem circuit 12B, and the tandem circuit 12B is provided with a second working direction switching valve 4B for driving and controlling a working hydraulic actuator 9 such as a boom hoisting cylinder. A second traveling direction switching valve 5B for driving and controlling the second traveling hydraulic motor 6B is provided upstream of the second working direction switching valve 4B.

In FIG. 5, reference numeral 7 indicates the upstream side of the second traveling directional control valve 5B and the first working directional control valve 4A.
Is a bypass line that is connected to the upstream side of the first traveling direction switching valve 5A, and the pressure from the second hydraulic pump 2B is applied to the bypass line 7 when the traveling straight ahead function is activated. A straight traveling switching valve 8 for supplying oil to the first traveling direction switching valve 5A is provided.

In the hydraulic drive device having such a structure, the operating valve 11 is operated at the same time as the traveling operation to move the spool of the first working direction switching valve 4A from the neutral position to the left and right switching positions by the pilot pressure. Then, the spool of the straight travel switching valve 8 moves to the right side in the figure by the pilot pressure oil from the pilot pump 10, and the pressure oil discharged from the second hydraulic pump 2B is used for the first travel via the bypass line 7. It is supplied to the direction switching valve 5A. Therefore, the pressure oil discharged from the first hydraulic pump 2A is independently supplied to the working hydraulic actuator 9, and the pressure oil discharged from the second hydraulic pump 2B is independently supplied to the left and right traveling hydraulic actuators 6A and 6B. Therefore, the traveling hydraulic actuator 6
Since A and 6B are not affected by the load fluctuation of the working hydraulic actuator, there is an advantage that stable traveling can be performed.

[0008]

However, the first working directional control valve 4A of the hydraulic drive system described above has a full stroke of the spool in order to suppress shock when the actuator is operated and improve the operation feeling. Since the center bypass has a structure that is not completely closed, when the first work direction switching valve 4A is operated during traveling, the load on the work actuator driven by the first work direction switching valve 4A is increased. Is the first traveling hydraulic motor 6
When the load is larger than A, the first hydraulic pump 2A
The pressure oil discharged from the tank flows through the tandem circuit 12A to the first traveling hydraulic motor 6A, and it becomes difficult for the pressure oil to flow from the first work direction switching valve 4A to the work hydraulic actuator. There was a problem that would not work.

The present invention has been made in view of the above-mentioned problems, and the pressure oil discharged from the first hydraulic pump during straight traveling is reliably transferred to the working hydraulic actuator via the first working direction switching valve. It is an object of the present invention to provide a hydraulic drive system for a construction vehicle that can be supplied to

[0010]

In order to solve the above problems, the present invention provides an engine, a first hydraulic pump driven by the engine, and a flow of pressure oil discharged from the first hydraulic pump. A first working direction switching valve for driving and controlling a working hydraulic actuator by switching the first working direction switching valve, a first traveling direction switching valve provided on the downstream side of the first working direction switching valve, and A second hydraulic pump driven by the engine; a second working directional control valve for driving and controlling a working hydraulic actuator by switching the flow of pressure oil discharged from the second hydraulic pump; A second traveling direction switching valve provided upstream of the second working direction switching valve, an upstream side of the second traveling direction switching valve and a downstream side of the first working direction switching valve. And the first A bypass line connecting the upstream side of the traveling direction switching valve, a traveling straight traveling switching valve provided in the bypass line, the first working direction switching valve and the second working direction switching valve are piloted. In a hydraulic drive system for a construction vehicle, comprising a control valve which is switched by pressure oil, a piston accommodating chamber is formed in a valve body of the first working direction switching valve, and a piston is accommodated in the piston accommodating chamber. The work direction switching valve is provided so as to be movable in the longitudinal direction of the spool, a stroke regulating stopper is provided at one end of the piston so as to face one end of the spool, and both sides of a piston storage chamber partitioned by the piston are provided. A pair of pilot pressure oil introduction ports for introducing pilot pressure oil are provided in the valve body, and one of the pilot pressure oil introduction ports is provided with Connect the pilot line branched from a pilot circuit Sakuben, characterized in that connecting the pilot line branched from the pilot circuit of the other in the straight traveling switching valve of the pilot pressure oil introduction port.

[0011]

According to the present invention, a piston accommodating chamber is formed in the valve body of the first working direction switching valve, and the piston can be moved in the longitudinal direction of the spool of the first working direction switching valve. The piston is provided with a stroke restriction stopper facing one end of the spool, and a pair of pilot pressure oil introduction ports for introducing pilot pressure oil to both sides of the piston storage chamber partitioned by the piston. A pilot pipe provided on the valve body and connected to one side of the pilot pressure oil introduction port with a pilot line branched from the pilot circuit of the operating valve, and to the other side of the pilot pressure oil introduction port from the pilot circuit of the straight-travel switching valve. By connecting the road, if the work direction switching valve is not operated at the same time as the traveling operation, operate the operation valve with a full stroke. The stroke of the work direction switching valve is restricted so that the tandem circuit is not completely closed.When the work direction switching valve and the traveling operation are operated simultaneously, the stroke restriction is released and the tandem circuit is completely closed. Can be cut.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are diagrams showing an embodiment of the present invention, and FIG. 1 is a diagram showing a schematic configuration of a hydraulic drive system for a construction vehicle according to an embodiment of the present invention. In the figure, reference numeral 1 is an engine mounted on a construction vehicle such as a hydraulic excavator, and an output shaft 1a of the engine 1 is connected to a first hydraulic pump 2A and a second hydraulic pump 2B. Of these hydraulic pumps 2A and 2B, the pressure oil discharged from the first hydraulic pump 2A is fed to the first hydraulic system 3A, and the pressure oil discharged from the second hydraulic pump 2B is fed to the second hydraulic system 3B. It is being supplied.

The first hydraulic system 3A is a tandem circuit 12A.
The tandem circuit 12A includes a first hydraulic drive actuator 9 such as a boom hoisting cylinder.
Is provided with a work direction switching valve 4A, and a first travel direction switching valve 5A for driving and controlling the first travel hydraulic motor 6A is provided downstream of the first work control valve 4A. .

On the other hand, the second hydraulic system 3B has a tandem circuit 12B, and the tandem circuit 12B is provided with a second working direction switching valve 4B for driving and controlling a working hydraulic actuator 9 such as a boom hoisting cylinder. A second traveling direction switching valve 5B for driving and controlling the second traveling hydraulic motor 6B is provided upstream of the second working direction switching valve 4B.

Further, in FIG. 1, reference numeral 7 indicates the upstream side of the second traveling direction switching valve 5B and the first working direction switching valve 4A.
Is a bypass line that is connected to the upstream side of the first traveling direction switching valve 5A. The bypass line 7 has a second line when the traveling operation and the working direction switching valve are simultaneously operated. There is provided a straight traveling switching valve 8 for supplying pressure oil from the hydraulic pump 2B to the first traveling direction switching valve 5A.

Reference numeral 10 is a pilot pump, 11 is an operation valve for supplying pilot pressure oil to the pilot ports of the work direction switching valves 4A and 4B through a pilot circuit 14, and 13 is a traveling direction switching valve 5B and a work direction valve. This is a pilot circuit that supplies pilot pressure oil discharged from the pilot pump 10 to the pilot port of the straight traveling switching valve 8 when the direction switching valves 4A and 4B are switched.

FIG. 2 is a diagram showing the construction of the first working direction switching valve 4A. The valve body 31 of the first working direction switching valve 4A has a first hydraulic pressure as shown in FIG. Pump 2A
A pressure oil inlet 32 into which the pressure oil discharged from the pressure oil flows in is provided, and a first pressure oil outlet 33 and a second pressure oil outlet 3 from which the pressure oil flowing from the pressure oil inlet 32 flows out.
4 (see FIG. 1) are provided. Of these pressure oil outlets 33, 34, the first pressure oil outlet 33 is the above-mentioned first
The tandem circuit 1 is installed at the pressure oil inlet of the traveling directional control valve 5A.
2A, and the second pressure oil outlet 24 is connected to the working actuator 9 via a hydraulic line.

On the other hand, a spool 35 is provided inside the valve body 31 of the first working direction switching valve 14A so as to be movable in the longitudinal direction. This spool 35 has a pressure oil inlet 3
The flow of the pressure oil flowing from 2 is switched, and when the pilot pressure oil from the operation valve 11 is introduced into the first pilot pressure chamber 36 formed at the left end portion of the valve body 31,
The spool 35 moves to the right in the figure against the urging force of the spool return spring 37, restricts the pressure oil flowing out from the first pressure oil outlet 33 to the downstream side, and works from the second pressure oil outlet 34. The pressure oil is made to flow out to the hydraulic actuator 19 for use.

When pilot pressure oil from the operation valve 22 is introduced into the second pilot pressure chamber 38 formed at the right end of the valve body 31, the spool 35 moves to the left in the figure. .

Further, in FIG. 2, reference numeral 39 is a valve body 31.
Is a piston storage chamber formed at the left end of the piston storage chamber 39. A piston 40 is stored in the piston storage chamber 39.
The piston 40 is movable in the longitudinal direction of the spool 35, and a stroke restricting stopper 41 is projectingly provided at one end of the piston 40. The stroke regulating stopper 41 regulates the stroke of the spool 35 and faces one end of the spool 35.

Further, in the valve body 31 of the first working direction switching valve 4A, pilot pressure oil introduction ports 42 and 43 for introducing pilot pressure oil to both sides of the piston storage chamber 39 partitioned by the piston 40. Is provided. Of these pilot pressure oil introduction ports 42, 43, the pilot pressure oil introduction port 42 is connected to a pilot line 45 branched from the pilot circuit 14 of the operation valve 11, and the pilot pressure oil introduction port 43 is switched for straight traveling. A pilot line 46 branched from the pilot circuit 13 of the valve 8 is connected.

In such a structure, when pilot pressure oil is introduced into the pilot pressure oil introduction port 42 of the first working direction switching valve 4A, the piston 40 housed in the piston housing chamber 39 moves to the left side in the figure. Moving. At this time, when the spool 35 is moved to the right side in the drawing by the pilot pressure oil introduced into the pilot pressure chamber 36 of the first work direction switching valve 4A, one end of the spool 35 is stroke-regulated as shown in FIG. The stopper 41 for contact. This regulates the stroke of the spool 35.

Further, the pilot pressure oil is introduced into the pilot pressure oil introduction port 43 by running while the pilot pressure oil is introduced into the pilot pressure oil introduction ports 36 and 42 of the first work direction switching valve 4A. When done, Fig. 4
As shown in, the piston 40 housed in the piston housing chamber 39 moves to the right side in the figure. This allows the spool 35
Since the stroke restriction is released and the spool 35 makes a full stroke, the pressure oil discharged from the first hydraulic pump 2A is discharged even when the load of the work hydraulic actuator 9 is larger than the load of the first traveling hydraulic motor 6A. The pressure oil discharged from the first hydraulic pump 2A does not flow through the tandem circuit 12A to the first traveling direction switching valve 5A, and the working oil is discharged through the first working direction switching valve 4A. The actuator 9 can be reliably supplied, and the working hydraulic actuator 9 can be reliably operated.

[0024]

As described above, according to the present invention, a piston accommodating chamber is formed in the valve body of the first working direction switching valve, and the piston is housed in the piston accommodating chamber in the longitudinal direction of the spool of the working direction switching valve. A stroke restriction stopper is provided at one end of the piston so as to face one end of the spool, and a pair of pilot pressure oils for introducing pilot pressure oil to both sides of the piston storage chamber partitioned by the piston. An inlet port is provided on the valve body, and one side of the pilot pressure oil inlet port is connected to the pilot line branched from the pilot circuit of the operating valve, and the other side of the pilot pressure oil inlet port is branched from the pilot circuit of the straight-ahead switching valve. By connecting the pilot line, the operation feeling is good as before when only the work direction switching valve is operated. Therefore, when the traveling operation and the work direction switching valve are simultaneously operated, even if the load of the working hydraulic actuator is larger than the load of the traveling hydraulic motor, the pressure oil can be reliably supplied to the working hydraulic actuator. A hydraulic drive system for a construction vehicle can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a hydraulic drive system for a construction vehicle according to an embodiment of the present invention.

FIG. 2 is a first hydraulic drive system for a construction vehicle according to the embodiment.
The figure which shows the structure of the working direction switching valve.

FIG. 3 is an operation explanatory view of the first work direction switching valve shown in FIG.

FIG. 4 is an operation explanatory view of the first work direction switching valve shown in FIG.

FIG. 5 is a diagram showing a schematic configuration of a conventional hydraulic drive system for a construction vehicle.

[Description of Reference Signs] 1 ... Engine 2A ... First hydraulic pump 2B ... Second hydraulic pump 4A ... First work direction switching valve 4B ... Second work direction switching valve 5A ... First traveling direction Switching valve 5B ... Second traveling direction switching valve 31 ... Valve body 35 ... Spool 36 ... First pilot pressure oil chamber 38 ... Second pilot pressure oil chamber 39 ... Piston storage chamber 40 ... Piston 41 ... Stroke restriction stopper 42, 43 ... Pilot pressure oil introduction port 45, 46 ... Pilot line

Claims (1)

[Claims] Claim: What is claimed is: 1. An engine, a first hydraulic pump driven by this engine, and a first hydraulic pump for driving and controlling a working hydraulic actuator by switching the flow of pressure oil discharged from the first hydraulic pump. Work direction switching valve, a first traveling direction switching valve provided downstream of the first work direction switching valve, a second hydraulic pump driven by the engine, and the second Second work direction switching valve for driving and controlling a work hydraulic actuator by switching the flow of pressure oil discharged from the second work hydraulic pump, and the second work direction switching valve provided upstream of the second work direction switching valve. A second traveling direction switching valve, an upstream side of the second traveling direction switching valve, a downstream side of the first working direction switching valve, and an upstream side of the first traveling direction switching valve. Bypass line connecting to And a straight travel switching valve provided in the bypass line, and an operating valve for switching the first working direction switching valve and the second working direction switching valve with pilot pressure oil. In a hydraulic drive system for a construction vehicle, a piston housing chamber is formed in the valve body of the first working direction switching valve, and the piston can be moved in the piston housing chamber in the longitudinal direction of the spool of the working direction switching valve. A pair of pilot pressure oils are provided at one end of the piston so as to face the one end of the spool, and to introduce pilot pressure oil to both sides of the piston storage chamber partitioned by the piston. An introduction port is provided in the valve body, and a pilot line branched from the pilot circuit of the operation valve is provided at one of the pilot pressure oil introduction ports. A hydraulic drive system for a construction vehicle, characterized in that a pilot line branched from a pilot circuit of the traveling straight-ahead switching valve is connected to the other of the pilot pressure oil introduction ports.