JPH05263806A - Hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To facilitate inching operations of a boom without being affected by a direction control valve for increasing arm speeds when an arm cylinder and a boom cylinder are complexly operated in floor excavation works and the like by construction machines. CONSTITUTION:A direction control valve 26 for a boom cylinder is connected to each arm speed increasing direction control valve 5 in file from the upstream side of a first hydraulic pump, a pressure control valve 30 compensating pressure to the direction that the boom cylinder 2 is extended, is provided for the spool 27 of a direction control valve 26 for the boom cylinder. The pressure control valve 30 is provided coaxially with the spool 27 at the downstream of the opening of the spool 27, in addition, the spring 32 of the pressure control valve 30 is disposed at the center side of the spool 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a construction machine, and more particularly to a hydraulic circuit of a construction machine in which hydraulic circuit systems of a plurality of hydraulic pumps are connected in parallel.

[0002]

2. Description of the Related Art A conventional hydraulic circuit for this type of construction machine is shown in FIG.
Shown in. The directional control valve 3 for the boom cylinders 2 and 2 and the directional control valve 5 for increasing the speed of the arm cylinder 4 are connected in tandem from the upstream side to the hydraulic circuit system of the first hydraulic pump 1.
Further, a directional control valve 7 for increasing the speed of the boom cylinders 2, 2 and a directional control valve 8 for the arm cylinder 4 are connected in parallel to the hydraulic circuit system of the second hydraulic pump 6 from the upstream side. Then, the hydraulic circuit system of the first hydraulic pump 1 and the hydraulic circuit system of the second hydraulic pump 6 are connected via a confluent oil passage 9 for boom cylinder acceleration and a confluent oil passage 10 for arm cylinder acceleration. It is connected.

In the conventional hydraulic circuit, throttle valves 11 and 12 are provided downstream of the directional control valves 5 and 8, respectively, a pilot pressure P _R is led to a pilot oil passage 15, and a pilot pressure P _L to a pilot oil passage 16. derive the activates the respective regulator 17 and 18 constitute a hydraulic circuit of a negative control for changing the discharge amount Q ₂ of the first hydraulic pump 1 discharge quantity Q ₁ and the second hydraulic pump 6 ..

In the illustrated state, each directional control valve 3, 5,
All of 7 and 8 are in the neutral position, and as shown in the graph of FIG. 13, the pilot pressures P _R and P _L are P _R =
P _R1, P _L = P _L1, and the discharge amount Q ₂ of the first discharge amount of the hydraulic pump 1 Q ₁ and the second hydraulic pump 6 becomes each minimum amount min. Here, for example, when the directional control valve 3 for the boom cylinder is switched to the position of 3a and the directional control valve 7 for boom cylinder acceleration is switched to the position of 7a, the discharge oil of the first hydraulic pump 1 is Directional control valve 3
As shown in the graph of FIG. 13, the pilot pressure P _R derived from the throttle valve 11 does not flow downstream from P _R = P _R2
And the discharge amount Q ₁ of the first hydraulic pump 1 becomes the maximum amount max. Similarly, the pilot pressure P _L derived from the throttle valve 12 also decreases to P _L = P _L2, and the discharge amount Q _{2 of} the second hydraulic pump 6 also reaches the maximum amount max.

Then, the oil discharged from the second hydraulic pump 6 merges with the oil discharged from the first hydraulic pump 1 via a merged oil passage 9, and passes through an oil passage 19 to one of the oil ports of the boom cylinders 2, 2. It flows into 2a and 2a. Therefore, the boom cylinders 2, 2
Grows while being accelerated. The oil flowing out from the other oil ports 2b, 2b of the boom cylinders 2, 2 returns to the tank 21 from the oil passage 20 through the directional control valve 3 (this hydraulic circuit can accelerate only when the boom cylinder 2 extends).

The same applies to the operation of the arm cylinder 4. By switching the directional control valve 8 for the arm cylinder and the directional control valve 5 for accelerating the arm cylinder, the arm cylinder is operated to the open side or the closed side. (This hydraulic circuit can increase the speed when the arm cylinder 4 is opened or closed).

[0007]

As described above, the hydraulic circuit of the conventional construction machine is connected to the hydraulic circuit systems of a plurality of hydraulic pumps to perform a composite operation. For example, in FIG.
In the case of so-called floor excavation work in which the toe 24 of the bucket is horizontally moved while simultaneously operating the boom 22 and the arm 23 of the power shovel shown in FIG. 4, the directional control valve 8 for the arm cylinder shown in FIG. The directional control valve 5 for accelerating the arm cylinder is gradually switched from the neutral position to the full stroke side of 8a and 5a, and the directional control valve 3 for the boom cylinder and the directional control valve 7 for increasing the boom cylinder are provided.
Is controlled by fine movement operation in accordance with the movement of the arm 23, as shown in FIG.

However, as shown in FIG. 12, since there is a directional control valve 5 for increasing the speed of the arm cylinder downstream of the directional control valve 3 for the boom cylinder, the discharge amount Q _{1 of the} first hydraulic pump 1 is increased.
Is supplied to the boom cylinders 2 and 2, and the discharge amount Q ₂ of the second hydraulic pump 6 is increased by the oil passage 25.
According to the difference between the load pressure of 2 and the load pressure of the arm cylinder 4, most of it is supplied to the arm cylinder 4, and the remaining part is supplied from the merging oil passage 9 to the boom cylinders 2, 2. Therefore, the flow rate supplied to the boom cylinders 2 and 2 is influenced and changed by the operation of the directional control valve 5 for accelerating the arm cylinder, and the fine movement operation of the boom 22 becomes difficult.

Therefore, in floor digging work of construction machinery,
A technical problem to be solved for facilitating the fine movement operation of the boom arises when the arm cylinder and the boom cylinder are combinedly operated, and the present invention aims to solve this problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned problems, and comprises a plurality of hydraulic pumps, and a hydraulic circuit system for the first hydraulic pump is provided for the boom cylinder from the upstream side. The directional control valve and the directional control valve for accelerating the arm cylinder are connected in tandem, and the directional control valve for accelerating the boom cylinder and the directional control valve for the arm cylinder are connected in parallel from the upstream side to the hydraulic circuit system of the second hydraulic pump. Connect and connect between the downstream side of the directional control valve for boom cylinder acceleration and the upstream side of the directional control valve for boom cylinder, and the upstream side of the directional control valve for arm cylinder acceleration and the direction for arm cylinder. In the hydraulic circuit connected to the upstream side of the control valve by a confluent oil passage, pressure compensation is performed in the spool of the directional control valve for the boom cylinder in the direction in which the boom cylinder extends. That the pressure control valve provided in the spool coaxially downstream of the spool openings, and is intended to provide a hydraulic circuit for a construction machine characterized in that a spring of the pressure control valve to the center side of the spool.

[0011]

When the directional control valve for the boom cylinder is switched to the extending direction of the boom cylinder, the opening area of the directional control valve, that is, the operation amount of the directional control valve, is controlled by the pressure control valve built in the directional control valve. Proportional flow passes through. Therefore, when the directional control valve for the arm cylinder and the directional control valve for increasing the arm cylinder are operated, and further, the directional control valve for the boom cylinder and the directional control valve for increasing the boom cylinder are finely operated. Also, the flow rate proportional to the operation amount of the directional control valve for the boom cylinder flows through the boom cylinder without being influenced by the operation amount of the directional control valve for increasing the arm cylinder, and the fine movement operation of the boom is facilitated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. For convenience of explanation, the same components as those of the conventional technique are designated by the same reference numerals and the description thereof will be omitted. FIG. 1 shows a hydraulic circuit of a construction machine. Reference numeral 26 is a directional control valve for the boom cylinders 2 and 2. The configuration other than the directional control valve 26 for the boom cylinder is the conventional one shown in FIG. It is the same as the hydraulic circuit of.

2 and 3 show the details of the directional control valve 26 for the boom cylinder. In the illustrated state, the spool 27 is in the neutral position C, and the discharge oil passage 28 of the first hydraulic pump 1 is an arm. It communicates with the oil passage 29 to the directional control valve 5 for cylinder acceleration. Direction control valve 2 for the boom cylinder
The spool 31 of the pressure control valve 30 is provided inside the spool 27 of No. 6 coaxially with the spool 27, and the spring 32 of the pressure control valve 30 is arranged on the center side of the spool 27 of the direction control valve 26.

Here, the directional control valve 26 for the boom cylinder is in the neutral position C, and the boom cylinder 2,
2 is not operating, the oil pressure P _{P of the} discharge oil passage 28 is
Comparing with the oil pressure P _B of the oil passage 19 to the boom cylinders 2 and 2, P _P > P _B. Therefore, the pressure oil in the discharge oil passage 28 is sent to the directional control valve 5 for accelerating the arm cylinder via the oil passage 29, and a part of the pressure oil in the discharge oil passage 28 passes through the check valve 33, so that the oil passage It branches to 34, 34. The pressure oil in one of the oil passages 34 passes through a pilot oil passage 35 provided in the spool 31 and is led to the right end portion of the spool 31. Further, the pressure oil in the oil passage 19 is led out to the pilot oil passage 37 through the throttle 36, but the resultant force of the pilot pressure P _u of the pilot oil passage 37 and the spring force F _S of the spring 32 is the pilot oil passage. Since it is smaller than the pilot pressure P _{P of} 35, the spool 31 moves to the left in the drawing against the pressure of the spring 32, and as shown in FIGS. 2 and 3, the pressure control valve built in the spool 27. 30 acts on the closing side.

On the other hand, the directional control valve 26 for the boom cylinder is in the neutral position C, and the boom cylinders 2, 2 are
When the holding pressure P _B in the oil passage 19 is high in a suspended state,
P _P <P _B. Therefore, similarly to the above, the discharge oil passage 28
Is sent to the directional control valve 5 for accelerating the arm cylinder through the oil passage 29. However, the pilot pressure P that has been drawn from the oil passage 19 through the throttle 36 to the pilot oil passage 37
_Since the resultant force of _u and the spring force F _S of the spring 32 is larger than the pilot pressure P _P of the pilot oil passage 35, the spool 3
5 moves to the right in the figure, and as shown in FIGS. 4 and 5,
The pressure control valve 30 built in the spool 27 acts on the opening side.

Next, when the directional control valve 26 for the boom cylinder is switched from the neutral position C to the boom extension position A, the entire spool 27 slides to the left in the drawings, as shown in FIGS. 6 and 7. However, the discharge oil passage 28 and the oil passage 29 are cut off, and the pressure oil does not flow from the discharge oil passage 28 to the directional control valve 5 for arm acceleration. Therefore, the pressure oil in the discharge oil passage 28 passes through the check valve 33 and branches into the oil passages 34, 34. The pressure oil in one of the oil passages 34 passes through the throttle 36 to pass from the oil passage 19 to one of the oil ports 2a, 2 of the boom cylinders 2, 2.
It flows into a and the boom cylinders 2 and 2 extend. Then, the oil flowing out from the other oil ports 2b, 2b of the boom cylinders 2, 2 returns from the oil passage 20 to the tank 21 via the direction control valve 26. A part of the pressure oil that has passed through the throttle 36 is led to the pilot oil passage 37, and the resultant force of the pilot pressure P _u and the spring force F _S of the spring 32 opposes the pilot pressure P _P of the pilot oil passage 35.

The flow rate Q flowing into the boom cylinder 2 is represented by the following equation.

[0018]

[Equation 1]

The balance of the spool 31 of the pressure control valve 30 is expressed by the following equation.

[0020]

[Equation 2]

Therefore, from (1 expression) and (3 expression),

[0022]

[Equation 3]

Here, the flow coefficient C and the spring force F_SIs constant
Therefore, the flow rate Q flowing into the boom cylinder 2 is
It is proportional to the opening area a of the control valve 26. That is, boom siri
The flow rate proportional to the operation amount of the direction control valve 26 for
It flows to the cylinder 2. Therefore, the first hydraulic pump 1
The discharge pressure is low and the pilot pressure P in the pilot oil passage 37 is_u
And the spring force F of the spring 32_SThe resultant force with the pilot oil passage 3
Pilot pressure P of 5_PIf it is much larger, then FIG.
As shown in FIG. 7, the spool 31 of the pressure control valve 30 is
Moving to the center right, the pressure control valve 30 acts on the open side.
On the other hand, the discharge pressure of the first hydraulic pump 1 is high, and
Pilot pressure P on the oil passage 37_uAnd spring of 32
Force F_SThe resultant force is the pilot pressure of the pilot oil passage 35.
P _PIf it becomes much smaller, as shown in FIG. 8 and FIG.
The spool 31 of the pressure control valve 30 moves to the left in the drawing,
The force control valve 30 acts on the closing side.

Thus, the directional control valve 2 for the boom cylinder
The pressure control valve 30 built into the spool 27 of No. 6 prevents a large flow rate from passing through with respect to the operation amount of the directional control valve 26 when the directional control valve 26 is operated toward the boom extension side. 3) so as to maintain the relationship shown in FIG. 7 within the range between the state shown in FIG. 7 and the state shown in FIG.
Will move accordingly.

Thus, when performing a floor excavation work with a construction machine, the directional control valve 26 for the boom cylinder is operated while operating the directional control valve 8 for the arm cylinder and the directional control valve 5 for increasing the arm cylinder. When you operate the
Unlike the conventional type, the flow rate proportional to the operation amount of the directional control valve 26 flows through the boom cylinders 2 and 2 without being influenced by the operation amount of the directional control valve 5 for increasing the arm cylinder, and the fine movement operation of the boom is performed. Becomes extremely easy.

Next, when the directional control valve 26 for the boom cylinder is switched from the neutral position C to the boom retracted position B, as shown in FIGS. 10 and 11, the entire spool 27 slides to the right in the drawings. Then, the discharge oil passage 28 and the oil passage 29
Are cut off, and pressure oil does not flow from the discharge oil passage 28 into the directional control valve 5 for accelerating the arm. Therefore, the discharge oil passage 28
11 passes through the check valve 33 and branches into the oil passages 34, 34, and one oil passage 34 becomes a dead end as shown in FIG. 11, but the other oil passage 34 passes through the bypass oil passage 38. To communicate with the oil passage 20. That is, the pressure oil in the discharge oil passage 28 is transferred from the oil passage 20 to the other oil port 2 of the boom cylinders 2, 2.
b, 2b, and the boom cylinders 2, 2 contract.

The oil flowing out from one of the oil ports 2a, 2a of the boom cylinders 2, 2 passes through the throttle 36 of the directional control valve 26 from the oil passage 19 and returns to the tank 21, and part of it is piloted. It is led to the oil passage 37 and generates the pilot pressure P _u . Further, the oil in the pilot oil passage 35 returns to the tank 21 together with the oil from the oil passage 19, so that the spool 31 of the pressure control valve 30 moves to the right in the figure.

The present invention can be modified in various ways without departing from the spirit of the present invention, and it goes without saying that the present invention covers the modifications.

[0029]

Since the present invention is configured as described in detail in the above embodiment, the directional control valve for the arm cylinder and the directional control valve for accelerating the arm cylinder when the floor excavation work is performed by the construction machine. Even if the boom cylinder directional control valve is finely operated while operating, the operation amount of the arm cylinder speed-up directional control valve is not affected.

Therefore, a flow rate proportional to the operation amount of the directional control valve for the boom cylinder flows in the boom cylinder, the fine movement operation of the boom becomes extremely easy, and the operability of the hydraulic circuit of the construction machine is improved.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a construction machine according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of the spool of the directional control valve when the directional control valve for the boom cylinder is in the neutral position and the boom is not operating.

FIG. 3 is a sectional view of the spool in the state shown in FIG.

FIG. 4 is a hydraulic circuit diagram of the spool of the directional control valve when the directional control valve for the boom cylinder is in the neutral position and the boom is under load.

5 is a cross-sectional view of the spool in the state shown in FIG.

FIG. 6 is a hydraulic circuit diagram of the spool of the directional control valve when the directional control valve for the boom cylinder is in the boom extension position and the pressure control valve in the spool acts on the opening side.

FIG. 7 is a sectional view of the spool in the state shown in FIG.

FIG. 8 is a hydraulic circuit diagram of the spool of the directional control valve when the directional control valve for the boom cylinder is in the boom extended position and the pressure control valve in the spool acts on the closing side.

9 is a sectional view of the spool in the state shown in FIG.

FIG. 10 is a hydraulic circuit diagram of the spool of the directional control valve when the directional control valve for the boom cylinder is in the boom contracted position.

11 is a sectional view of the spool in the state shown in FIG.

FIG. 12 is a hydraulic circuit diagram of a conventional construction machine.

FIG. 13 is a graph showing the relationship between pilot pressure and the discharge amount of a hydraulic pump.

FIG. 14 is a side view showing a state in which a power shovel, which is an example of a construction machine, is performing floor digging work.

FIG. 15 is a side view showing a state in which a power shovel as an example of a construction machine is performing floor digging work.

[Explanation of symbols]

 1 First Hydraulic Pump 2 Boom Cylinder 4 Arm Cylinder 5 Arm Cylinder Directional Control Valve for Accelerating 6 Second Hydraulic Pump 7 Directional Control Valve for Boom Cylinder Acceleration 8 Directional Control Valve for Arm Cylinder 9, 10 Confluence Oil passage 26 Direction control valve for boom cylinder 27 Spool 30 Pressure control valve 31 Spool 32 Spring 35, 37 Pilot oil passage

Claims (1)

[Claims] 1. A plurality of hydraulic pumps are provided, wherein a directional control valve for boom cylinder and a directional control valve for accelerating arm cylinder are connected in tandem from the upstream side to a hydraulic circuit system of the first hydraulic pump, and a second hydraulic pump is provided. Connect the boom cylinder speed-up directional control valve and the arm cylinder directional control valve in parallel from the upstream side to the hydraulic circuit system of the hydraulic pump, and connect the boom cylinder speed-up directional control valve downstream and the boom cylinder directional control valve. A hydraulic circuit is connected between the upstream side of the directional control valve and between the upstream side of the directional control valve for increasing the arm cylinder and the upstream side of the directional control valve for the arm cylinder, respectively. In the spool of the directional control valve for the boom cylinder, a pressure control valve for compensating the pressure in the extending direction of the boom cylinder is provided coaxially with the spool downstream of the spool opening. A hydraulic circuit for a construction machine, in which the spring of the force control valve is arranged on the center side of the spool.