JP2002206256A - Hydraulic device for backhoe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the ascent operation of a boom under heavy load to be favorably carried out without bringing about a lack of a flow rate in a hydraulic device for a backhoe wherein the valve sections of a front device and right and left travel devices are connected to a variable displacement pump, wherein a valve section for slewing is connected to a fixed displacement pump, and which is constituted so as to control the discharge flow rate of the variable displacement pump under a load sensing system operating by taking the negative pressurization of the front working device as a control signal. SOLUTION: A control valve V5 for the confluence of pressure oil to the ascent side of a boom cylinder C1 is connected to the fixed displacement pump P3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backhoe hydraulic device provided with a load sensing system.

[0002]

2. Description of the Related Art As a backhoe hydraulic device, valve sections of a front device and left and right traveling devices are connected to a variable displacement pump, and a turning valve section is connected to a constant displacement pump. It has been proposed to control the discharge flow rate of a variable displacement pump using a load sensing system that operates using negative pressure as a control signal.

[0003]

The load sensing system is based on the discharge pressure and the maximum load pressure so as to maintain the difference between the discharge pressure and the maximum load pressure of the variable displacement hydraulic pump at a set value. The discharge rate of the pump is automatically changed by the flow control unit, which is an effective means for energy saving operation and improving operability.However, since the maximum flow rate is set according to the traveling speed, As in the case of lifting a large amount of soil that has been scooped up by a bucket, a shortage of flow rate is apt to occur during a lifting operation of a boom with a large load, and the working efficiency may be reduced.

[0004] It is a main object of the present invention to enable a lifting operation of a boom with a large load to be performed favorably without causing a flow rate shortage.

[0005]

Means for Solving the Problems [Configuration, Function and Effect of the Invention According to Claim 1]

(Structure) In the invention according to claim 1, the valve sections of the front device and the left and right traveling devices are connected to a variable displacement pump, and the turning valve section is connected to a constant displacement pump. In a backhoe hydraulic device configured to control the discharge flow rate of the variable displacement pump by a load sensing system that operates by using a negative pressure in the front device as a control signal, the constant displacement pump may have a boom cylinder lift. A valve section for converging hydraulic oil to the side is connected.

(Operation) According to the above configuration, when raising the boom cylinder, the pressurized oil from the constant displacement type pump can be combined with the boom cylinder, and when the soil removed from the bucket is greatly lifted. As described above, the insufficient flow rate can be compensated for in the raising operation of the boom with a large load.

(Effect) Therefore, according to the first aspect of the present invention, even if the maximum flow rate of the variable displacement pump is suppressed corresponding to the traveling speed, the boom raising operation can be performed smoothly and promptly. This is effective for improving work efficiency.

[Structure, operation and effect of the invention according to claim 2]

(Structure) In the backhoe hydraulic device according to the second aspect of the present invention, in the first aspect of the present invention, the swiveling valve section and the pressure oil merging valve section are connected to a fixed displacement pump. They are connected in parallel.

(Operation) According to the above configuration, when turning while raising the boom, the pressure oil of the constant displacement pump can be supplied to the turning valve section and the pressure oil merging valve section, respectively. Becomes

(Effects) Therefore, according to the second aspect of the present invention, the turning operation while raising the boom can be performed smoothly and promptly, which is more effective in improving work efficiency.

[Structure, operation and effect of the invention according to claim 3]

(Structure) In the backhoe hydraulic device according to a third aspect of the present invention, in the second aspect of the invention, the pressure oil from a constant displacement pump is preferentially supplied to the pressure oil merging valve section. It is configured so that:

(Operation) According to the above configuration, when turning while raising the boom, the pressure oil of the constant displacement pump can be supplied to the valve section for turning and the valve section for converging the pressure oil, respectively. Although possible, merging to the boom cylinder is performed preferentially to the turning operation.

(Effect) Therefore, according to the third aspect of the present invention, it is possible to more reliably and promptly raise the boom when turning while raising the boom,
It is more effective for improving work efficiency.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an overall side view of a backhoe. This backhoe is mounted on an upper part of a traveling machine base 2 equipped with a pair of left and right crawler type traveling devices 1L, 1R so that a swivel base 5 equipped with an engine 3 and an operating unit 4 can fully rotate around a vertical axis P1. This turntable 5
Is equipped with a front device 9 in which a boom 6, an arm 7, and a bucket 8 are sequentially connected to each other, and an earth removal plate 10 for dozer work is provided at a front portion of the traveling machine base 2. I have.

The left and right traveling devices 1L and 1R are driven in forward and reverse directions by traveling hydraulic motors ML and MR, respectively, and the swivel table 3 is driven to pivot left and right by a turning hydraulic motor MT. The boom 6, arm 7, and bucket 8 of the front device 6 are driven by a boom cylinder C1, an arm cylinder C2, and a bucket cylinder C3, respectively, and the entire front device 9 is rotated about a vertical axis P2 by a swing cylinder C4. And is driven to swing left and right. The earth discharging plate 10 is driven up and down by a dozer cylinder C5.

FIG. 2 shows a hydraulic circuit for driving the various hydraulic actuators described above. In the figure, V
1 is a control valve for left running, V2 is a control valve for right running, V3 is a control valve for turning, V4 is a control valve for dozer, V5 is a control valve for boom confluence, and V6 is a control valve for arm. , V7 is the control valve for the boom, V8
Is a control valve for a bucket, V9 is a control valve for a swing, V10 is a control valve for an auxiliary work, and control valves V1 and V2 for the left and right traveling are provided on a control tower 12 in front of a driver's seat 11 on the left and right. A manually operated type in which the spool is directly switched by the traveling lever 13 is employed, and the control valves V4, V9, V10 for dozer, swing, and auxiliary work are operated by lever operation or pedal operation. A manually operated spool that directly operates the spool is used, and for turning, merging,
Each of the control valves V3, V5, V6, V7, V8 for the arm, boom, and bucket is of a hydraulic pilot operation type, and a pair of left and right operations provided on the control tower 12 so as to be able to perform a cross operation. An opening degree corresponding to the lever operation amount is operated by a pilot pressure supplied from a pilot valve (not shown) operated by the operating lever 14.

The valve block group of the control valves V1 to V10 is connected in parallel with an inlet block B1, an outlet block B2, and an intermediate spacer block B3, and connected to each other by an internal oil passage. Here, the inlet block B1 is interposed between the valve block of the control valve V1 for left running and the valve block of the control valve V2 for right running, and the block B2 for outlet is connected to the control valve V9 for auxiliary work. Is connected as an end block to the outside of the valve block.

The pressure oil supply unit 15 includes an engine 3
Hydraulic pumps P1, P2, P3 driven by
And a pilot pump P4, and the pump group and the inlet block B1 are connected by piping. An axial plunger type pump is used for the pumps P1 and P2, and is configured as a variable displacement type in which the discharge amount can be changed by changing the angle of each swash plate.
The flow rates of the pumps P1 and P2 are controlled by a load sensing system to be described later, and the flow rate control unit 16 is connected to the inlet block B1. The pump P3 is mainly used for turning and dozer work, and a constant displacement gear pump is used. The pilot pump P4 is a pilot pressure supply pump composed of a gear pump having a constant capacity. The pilot pump P4 supplies a pilot base pressure to a pilot valve (not shown) and a pilot oil passage a1 connected to a valve spool of the traveling section. A pilot pressure for detecting valve operation is supplied to a pilot oil passage a2 connected to a valve spool of the load sensing section.

The load sensing system controls the discharge amount of the pump in accordance with the work load pressure and discharges hydraulic power required for the load from the pump, thereby saving power and improving operability. In this example, the system is configured to function for the arm section, the boom section, the bucket section, the swing section, and the auxiliary work section of the front device 6. Here, the pressure compensating valve CV is provided after the spool of each control valve V6 to V10 in each section.
Are connected to each other to use an after-orifice type load sensing system. In this example, the unload valve V11 of the load sensing system is used.
And a relief valve V12 are incorporated in the most downstream outlet block B2.

The flow control unit 16 is provided with a flow compensation valve V13, and the pressure oil supply unit 15 is provided with a flow compensation piston Ac and a horsepower control piston Ap for adjusting the flow rates of the pumps P1 and P2. The maximum negative pressure of the load detection line in each section is transmitted to the flow compensation valve V13 of the flow control unit 16 as a control signal pressure PLS, and the signal pressure PLS and the pumps P1 and P2 are transmitted. The difference from the discharge pressure PPS is the flow compensation valve V13
Pumps P 1,
The discharge flow rate of P2 is controlled.

In this example, the flow control unit 1
6, the control differential pressure applied to the flow rate compensating valve V13 is, as shown in FIG.
When the rotation speed of the engine 3 increases and the discharge amount of the pilot pump P4 increases, the control differential pressure component provided by the differential pressure piston 18 increases, and the pumps P1, P2 When the rotational speed of the engine 3 decreases and the discharge amount of the pilot pump P4 decreases, the control differential pressure component provided by the differential pressure piston 18 decreases, and The discharge flow rates of P1 and P2 are controlled to be reduced.

As described above, the front working device 9
Each section belongs to the load sensing system, while the traveling section, the turning section, and the dozer section are configured by open circuits.

That is, the inlet block B1 incorporates pilot-type flow switching valves V14 and V15, and when the vehicle is not running, as shown in FIG. 3, the hydraulic oil from the pumps P1 and P2 is used. Is the flow path switching valve V
After being merged at 14, the oil is supplied to the load sensing system via the oil passage d, and the pressure oil from the pump P3 is supplied to the turning section, the dozer section, and the merging section. When the traveling section is used without using the section of the load sensing system, as shown in FIG. 5, the pressure rises in the pilot oil passage a1, and the flow path switching valve V14 is switched, so that the pump P
The hydraulic oil from P1 and P2 is supplied independently to the section for the right traveling hydraulic motor MR and the section for the left traveling hydraulic motor ML, and the hydraulic oil from the pump P3 is supplied to the turning section, the dozer section, And it is supplied to the junction section. In other words, a three-pump drive mode similar to the conventional three-pump type can be realized to perform traveling, turning, or dozer work with a minimum change in speed.

When the front device 9 which is a load sensing system is operated while traveling, the pressure rises in the pilot oil passage a2, and the flow passage switching valve V15 is switched as shown in FIG. After passing through the turning section, the dozer section, and the merging section, the pressure oil flows into the spacer block B3 via the flow path switching valve V15, and is supplied to the section of the load sensing system.

A control valve V3 for turning, a control valve V4 for dozer, and a control valve V5 for boom confluence
Is connected in parallel with the pump P3, and the oil passage b derived from the control valve V5 is connected to the boom cylinder C
1 is connected to the oil passage c on the boom raising side. The control valve V5 is switched in conjunction with the operation of the boom control valve V7 in the boom raising direction so that the pressure oil of the pump P3 joins the oil path c on the rising side of the boom cylinder C1. Is configured. In addition, the relief pressure of the pump P3 is reduced by the pumps P1, P2
Since the pressure is set lower than the relief pressure on the side, a load check valve Vc that allows only the flow in the merging direction is interposed in the merging oil passage b.

[Alternative Embodiment] As shown in FIG. 7, a control valve V5 for merging is replaced with a control valve V8 for turning.
By connecting the control valve V4 for the dozer to the control valve V4 in tandem, and by interposing a throttle s in the parallel oil passage to the control valve V5, it is possible to preferentially join the boom cylinder C1. .

[Brief description of the drawings]

FIG. 1 is an overall side view of a backhoe.

FIG. 2 is an overall hydraulic circuit diagram.

FIG. 3 is a partially omitted hydraulic circuit diagram.

FIG. 4 is a hydraulic circuit diagram of a dosing sensing system.

FIG. 5 is a hydraulic circuit diagram in a state where only traveling is performed.

FIG. 6 is a hydraulic circuit diagram showing a state in which front work and running are performed.

FIG. 7 is a hydraulic circuit diagram in another embodiment.

[Explanation of symbols]

 9 Front device C1 Boom cylinder P1, P2 Variable displacement pump P3 Constant displacement pump

Claims (3)

[Claims] 1. A valve section for a front device and left and right traveling devices is connected to a variable displacement pump, and a valve section for turning is connected to a constant displacement pump to control negative pressure in the front device. A backhoe hydraulic device configured to control the discharge flow rate of the variable displacement pump by a load sensing system that operates as a signal, wherein the constant displacement pump includes a valve section for converging hydraulic oil to a rising side of a boom cylinder. A backhoe hydraulic device, characterized by being connected to a backhoe. 2. The backhoe hydraulic device according to claim 1, wherein the turning valve section and the pressure oil merging valve section are connected in parallel to a constant displacement pump. 3. The backhoe hydraulic device according to claim 2, wherein a pressure oil from a constant displacement pump is preferentially supplied to the pressure oil merging valve section.