JP3403548B2 - Construction machine control circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in a construction machine such as a hydraulic excavator, and a state where gravity acts on the meter-out side and a state where load reaction force acts on the meter-in side can selectively occur. The present invention relates to a control circuit that includes an actuator and that controls the drive of the actuator according to the load sensing differential pressure.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a control circuit of a conventional construction machine of this type. This conventional example is provided, for example, in a hydraulic excavator, and includes a variable displacement hydraulic pump 1 as a hydraulic pump and the hydraulic pump 1
Driven by the pressure oil discharged from, the state in which gravity acts on the meter-out side by the load 7 such as an arm as shown by an arrow 9 and the grounding of the load 7 as shown by an arrow 10 An actuator, for example, an arm cylinder 6, which can selectively generate a state in which the reaction force of the load 7 acts is provided.

Also, the hydraulic pump 1 to the arm cylinder 6
Meter-in variable throttle 3A for controlling the flow of pressure oil supplied to the tank, a meter-out variable throttle 3B for controlling the flow of pressure oil returned from the arm cylinder 6 to the tank 8, the downstream side of the meter-in variable throttle 3A and the arm cylinder. 6 is connected to the meter-in side 6a of the arm cylinder 6, and the meter-out main conduit 6B is connected to the upstream side of the meter-out variable throttle 3B and the meter-out side 6b of the arm cylinder 6. When gravity is acting on the out side 6b, a regeneration pipe 6C capable of supplying pressure oil from the meter-out main pipe 6B to the meter-in main pipe 6A, and a passage flow rate of the regeneration pipe 6C can be controlled. The control throttle 3C and the regeneration conduit 6C are provided to prevent backflow of pressure oil from the meter-in main conduit 6A to the meter-out main conduit 6B. And a check valve 30.

Further, the supply flow rate to the meter-in variable throttle 3A is controlled by the discharge pressure PP of the hydraulic pump 1 and the arm cylinder 6.
Load pressure differential pressure Δ which is the differential pressure from the load pressure PLO
A flow rate control means that can be controlled according to PLS, for example, a regulator 2 that controls the tilt angle of the hydraulic pump 1 is provided. The load pressure PLO of the arm cylinder 6 is guided to one pilot chamber of the regulator 2 via the detection pipeline 4, and the discharge pressure of the hydraulic pump 1 to the other pilot chamber of the regulator 2 via the detection pipeline 5. PP is introduced, and the discharge amount QPO of the hydraulic pump 1 is adjusted so that the load sensing differential pressure ΔPLS, which is the differential pressure between the discharge pressure PP and the load pressure PLO, becomes a target set pressure difference determined by the biasing force of the spring 2A.
Is controlled.

In this conventional example, the load 7 is the arrow 9 in FIG.
As shown in FIG. 2, the load 7 lowers the gravity of the arm cylinder 6 and the pressure for controlling the drive of the arm cylinder 6 is generated on the meter-out side 6b of the arm cylinder 6, that is, the meter-out during regeneration. Part of the pressure oil flowing through the main pipeline 6B is supplied to the regeneration pipeline 6C,
Meter check line 6A through check valve 3D and control throttle 3C
Is supplied to. At this time, the regulator 2 drives according to the discharge pressure PP of the hydraulic pump 1 and the load pressure PLO of the arm cylinder 6, and the load sensing differential pressure (ΔPLS = PP−
The discharge flow rate QPO of the hydraulic pump 1 is controlled so that (PLO) becomes a set differential pressure determined by the urging force of the spring 2A. The characteristic line 11 in FIG. 4 is the load sensing differential pressure Δ at this time.
The relationship between PLS and pump discharge flow rate QPO is shown.
Therefore, at the time of this regeneration, the regeneration flow rate QS supplied from the regeneration pipeline 6C and the discharge flow rate QPO supplied from the hydraulic pump 1 are combined (QPO + QS) and supplied to the meter-in main pipeline 6A.

In this way, the regeneration flow rate QS is changed to the discharge flow rate QPO.
The gravitational energy of the load 7 is utilized to increase the operating speed of the arm cylinder 6 by merging with
Cavitation is prevented from occurring on the meter-in side 6a of the arm cylinder 6. The operating speed of the arm cylinder 6 depends on the pressure in the meter-out main pipe line 6B, that is, the weight of the load 7, and the opening area of the meter-out variable throttle 3B provided in the meter-out main pipe line 6B, that is, from the meter-out variable throttle 3B to the tank. 8 and the opening area of the control aperture 3C provided in the regeneration conduit 6C, that is, the regeneration flow rate QS. Characteristic line 12 of FIG.
Indicates the flow rate supplied to the arm cylinder 6 at this time.

When the load 7 descends and is grounded in a state of being positioned in the air as described above, the reaction force of the load 7 acts as shown by an arrow 10, whereby the meter cylinder side 6a of the arm cylinder 6 is acted. A state in which a pressure that controls the drive of the arm cylinder 6 is generated, that is, a state in which the regeneration is canceled is set. In this state, the regeneration flow rate does not flow from the meter-out main pipeline 6B to the regeneration pipeline 6C. Therefore, the load sensing differential pressure ΔPLS is applied to the meter-in main pipeline 6A.
Based on the above, only the discharge flow rate QPO of the hydraulic pump 1 is supplied, and this relatively small flow rate (corresponding to the characteristic line 11 in FIG. 4) is supplied to the arm cylinder 6.

A known technique of this type is disclosed in, for example, JP-A-63-83808.

[0009]

As described above, in the conventional example illustrated in FIG. 3, the regeneration flow rate QS.
Is determined by the pressure of the meter-out main pipeline 6B, that is, the weight of the load 7, and the weight of the load 7 can change as the position of the load 7 drops. Therefore, the regeneration flow rate QS is not constant in most cases, and in some cases, the regeneration flow rate QS decreases, and the flow rate flowing into the meter-in side 6a of the arm cylinder 6 becomes insufficient, causing cavitation on the meter-in side 6a. It may happen. When such cavitation occurs, undesirable vibrations are applied to the hydraulic equipment and pipelines that make up the control circuit, and the durability of these hydraulic equipments and pipelines deteriorates.

The present invention has been made in view of the above-mentioned situation in the prior art, and an object thereof is to provide a control circuit for a construction machine capable of increasing the flow rate supplied to the actuator during regeneration. .

[0011]

In order to achieve this object, the invention according to claim 1 of the present invention is driven by a hydraulic pump and pressure oil discharged from the hydraulic pump, and gravity is applied to the meter-out side. And a state in which a reaction force of the load acts on the meter-in side can selectively occur, a meter-in variable throttle for controlling the flow of pressure oil supplied from the hydraulic pump to the actuator,
A meter-out variable throttle that controls the flow of pressure oil returned from the actuator to the tank, a meter-in main conduit that connects the downstream side of the meter-in variable throttle and the meter-in side of the actuator, and an upstream of the meter-out variable throttle. Side is connected to the meter-out side of the actuator, and when gravity acts on the meter-out side, pressure oil can be supplied from the meter-out main line to the meter-in main line. A regeneration pipeline, a control throttle capable of controlling a flow rate of the regeneration pipeline, and a supply flow rate to the meter-in variable throttle are load sensing which are differential pressures between a discharge pressure of the hydraulic pump and a load pressure of the actuator. A control circuit for a construction machine, comprising: a flow control means capable of controlling according to a differential pressure; A separate control throttle is provided in the regeneration pipeline portion located downstream of the tine variable throttle and between the meter-in main pipeline and the regeneration pipeline located between the other control throttle and the control throttle. A detection pipeline for detecting the pressure of a part is provided, and the flow rate control means is driven according to the pressure detected by this detection pipeline.

[0012]

According to the first aspect of the present invention, the regeneration flow rate does not flow in the regeneration pipe when the regeneration is canceled in the state where the reaction force of the load acts on the meter-in side of the actuator. The pressure in the regeneration pipe section located between the other control throttle becomes equal to the load pressure of the actuator,
This load pressure is detected by the detection line. Therefore, the flow rate control means is driven according to the load sensing differential pressure that is the differential pressure between the discharge pressure of the hydraulic pump and the load pressure, and the flow rate flowing into the meter-in variable throttle is the flow rate according to the load sensing differential pressure. This flow rate is supplied to the actuator.

Further, at the time of regeneration in a state where gravity acts on the meter-out side of the actuator, a part of the pressure oil flowing in the meter-out main pipeline flows in the regeneration pipeline. At this time, a control throttle and another control throttle are provided. The pressure of the regeneration pipe portion located between the two is higher than the above-mentioned load pressure by the pressure loss of another control throttle. This high pressure is detected in the detection line. Therefore, the above-mentioned flow rate control means is controlled according to the pressure difference between the discharge pressure of the hydraulic pump and the pressure higher than the load pressure by the pressure loss of another control throttle. At this time, the load sensing differential pressure becomes smaller than that at the time of releasing the regeneration described above, and the flow rate control means drives to increase the flow rate flowing into the meter-in variable throttle in order to reach the predetermined set differential pressure. Accordingly, the meter-in side of the actuator can be supplied with a relatively large flow rate obtained by combining the passage flow rate and the regeneration flow rate, which are larger than the passage flow rate of the meter-in variable throttle at the time of releasing the regeneration described above.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control circuit for a construction machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment corresponding to the invention according to claims 1, 2, 5, and 6 of a control circuit for a construction machine of the present invention. FIG. 2 is a diagram showing the characteristics obtained in the embodiment shown in FIG.

FIG. 1 is drawn corresponding to FIG. 3 described above, and shows an embodiment adapted to a hydraulic excavator. In FIG. 1, the same components as those shown in FIG. 3 described above are designated by the same reference numerals. That is, this FIG.
In the embodiment shown in FIG. 2 as well, the variable displacement hydraulic pump 1 and a state in which the load 7 is driven by the pressure oil discharged from the hydraulic pump 1 and the gravity of the load 7 acts on the meter-out side and the load 7 on the meter-in side. An actuator, such as an arm cylinder 6, that can selectively generate a state in which a reaction force acts is provided.

The meter-in variable throttle 3A for controlling the flow of pressure oil supplied to the arm cylinder 6 and the tank 8 are also provided.
Meter-out variable throttle 3B for controlling the flow of pressure oil returned to the meter, meter-in main conduit 6A connecting the downstream side of the meter-in variable throttle 3A and the meter-in side 6a of the arm cylinder 6, and the upstream side of the meter-out variable throttle 3B. And a meter-out main conduit 6B that connects the meter-out side 6b of the arm cylinder 6 to each other, and when gravity acts on the meter-out side 6b of the arm cylinder 6, the meter-out main conduit 6B connects to the meter-in main conduit 6A. A regeneration pipe 6C capable of supplying pressure oil to the control pipe, a control throttle 3C capable of controlling the flow rate of the regeneration pipe 6C, and a regeneration pipe 6C. The meter-in main pipe 6A to the meter-out main pipe 6B are provided. And a check valve 30 for preventing the backflow of the pressure oil to the.

The flow rate supplied to the meter-in variable throttle 3A is the load sensing differential pressure ΔP which is the differential pressure between the discharge pressure PP of the hydraulic pump 1 and the load pressure PLO of the arm cylinder 6.
A flow rate control means that can be controlled according to LS, for example, a regulator 2 that controls the tilt angle of the hydraulic pump 1 is provided.
The target set differential pressure of the load sensing differential pressure is
It is determined by the biasing force of the spring 2A. The above configuration is the same as that of the conventional example shown in FIG.

In this embodiment, in particular, another control throttle 13 is provided in the portion of the regeneration pipeline 6C located between the control throttle 3C and the meter-in main pipeline 6A downstream of the meter-in throttle 3A. DLS indicates the pressure loss of the other control throttle 13. Further, there is provided a detection conduit 14 for detecting the pressure in the regeneration conduit 6C portion located between another control diaphragm 13 and the control diaphragm 3C.

In one pilot chamber of the regulator 2, the load pressure PL of the arm cylinder 6 is passed through the detection pipe line 14.
O, or a pressure obtained by adding a pressure loss DLS of another control throttle 13 to the load pressure PLO as described later, is introduced, and the other pilot chamber of the regulator 2 is discharged to the other pilot chamber via the detection conduit 5 and the discharge pressure PP of the hydraulic pump 1. And the discharge amount QPO (or QPO) in which the load sensing differential pressure ΔPLS matches the set differential pressure determined by the urging force of the spring 2A.
The regulator 2 is driven and the tilt angle of the hydraulic pump 1 is controlled so that the QQP is larger than that.

In the embodiment thus constructed, the load 7 is changed from the state in which it is located in the air as shown by the arrow 9 in FIG.
When the pressure for controlling the drive of the arm cylinder 6 is generated on the meter-out side 6b of the arm cylinder 6 due to the gravity of the load 7, a part of the pressure oil flowing through the meter-out main pipe line 6B is generated at the time of regeneration. , Regeneration line 6
C is supplied to the meter-in pipe line 6A through the check valve 3D and the control throttle 3C. This operation is shown in FIG.
This is equivalent to the conventional example shown in.

At this time, the regeneration conduit 6C located between the control diaphragm 3C and another control diaphragm 13 by the detection conduit 14
The pressure of the part is detected. This pressure is applied to the arm cylinder 6
It is a comparatively high pressure obtained by adding the pressure loss DLS to the load pressure PLO. Further, the discharge pressure PP of the hydraulic pump 1 is detected by the detection conduit 5. The regulator 2 is driven according to the discharge pressure PP detected by the detection pipeline 5, the load pressure PLO detected by the detection pipeline 14, and the pressure including the pressure loss DLS.
At this time, the load sensing differential pressure ΔPLS is ΔPLS = PP− (PLO + DLS). That is, apparently, the load sensing differential pressure is
The value is smaller than the set differential pressure.

When the above equation is modified, ΔPLS + DLS = PP-PLO, and the differential pressure created by the flow rate of the meter-in variable throttle 3A becomes larger than the set differential pressure by the pressure loss DLS, and the regulator 2 discharges the hydraulic pump 1. The amount is increased, and the increased discharge amount QPX (> the above-mentioned discharge amount QPO) is caused to flow into the meter-in variable aperture 3A. Figure 2
The characteristic line 16 indicates the characteristic of the pump discharge amount during such regeneration. During this regeneration, as shown by the characteristic line 17 in FIG. 2, the regeneration flow rate QS supplied from the regeneration pipeline 6C and the discharge flow rate QP supplied from the hydraulic pump 1.
X is merged (QPX + QS) and supplied to the meter-in main pipeline 6A.

Thus, the regeneration flow rate QS is changed to the discharge flow rate QPX.
By merging with the arm cylinder 6, the gravitational energy of the load 7 can be used for increasing the operating speed of the arm cylinder 6, and the flow rate supplied to the arm cylinder 6 can be increased during this regeneration, and thus the arm cylinder 6 can be increased.
It is possible to suppress the occurrence of cavitation on the meter-in side 6a.

When the load 7 descends and is placed in the air while being grounded as described above, the reaction force of the load 7 acts as shown by an arrow 10 in FIG. A state in which a pressure for controlling the drive of the arm cylinder 6 is generated on the meter-in side 6a, that is, a state in which the regeneration is canceled. In this state, the meter-out main pipeline 6
The regeneration flow rate does not flow from B to the regeneration conduit 6C. Further, the pressure detected by the detection conduit 14 is the load pressure PLO. Along with this, regulator 2 without this regeneration
The load-sensing differential pressure ΔPLS that is led to ΔPLS is ΔPLS = PP-PLO. Therefore, the pump discharge pressure PP and the load pressure PLO are connected to the meter-in variable throttle 3A and the meter-in main conduit 6A.
Only the discharge flow rate QPO of the hydraulic pump 1 based on the load sensing differential pressure ΔPLS considering only the above is supplied, and this relatively small flow rate (corresponding to the characteristic line 15 in FIG. 2) is supplied to the arm cylinder 6.

According to this embodiment, as described above, during the regeneration in which the pressure for controlling the drive of the arm cylinder 6 is generated on the meter-out side 6b of the arm cylinder 6, the pump discharge flow rate QPO at the time of the regeneration cancellation is lower than the pump discharge flow rate QPO. The pump discharge flow rate QPX, which is a large flow rate, can be supplied to the meter-in variable throttle 3A, whereby the meter-in side 6 of the boom cylinder 6 can be supplied.
It is possible to suppress the occurrence of cavitation of a, reduce the damage due to cavitation of the hydraulic equipment and the pipeline forming the control circuit, and improve the durability of these hydraulic equipment and the pipeline.

In the above embodiment, the meter-in diaphragm 3
As a flow rate control means capable of controlling the supply flow rate to A according to the load sensing differential pressure ΔPLS, which is the differential pressure between the discharge pressure PP of the hydraulic pump 1 and the load pressure PLO of the arm cylinder 6, the inclination of the hydraulic pump 1 is controlled. Regulator 2 that controls the turning angle
However, the present invention is not limited to this configuration.

For example, the hydraulic pump for supplying the pressure oil for driving the actuator such as the arm cylinder 6 is a fixed displacement hydraulic pump, and the flow rate control means is provided in the discharge pipe line of the fixed displacement pump, and one pilot portion is provided. Is the discharge pressure of the hydraulic pump and the load pressure PL on the other pilot part.
O may be constituted by an unload valve provided respectively.

Further, for example, the above-mentioned flow rate control means is constituted by a pressure compensating valve for controlling the differential pressure across the meter-in variable throttle 3A, which is the differential pressure between the upstream pressure and the downstream pressure.
The discharge pressure of the hydraulic pump may be applied to one pilot portion, and the load pressure PLO may be applied to the other pilot portion.

In the above embodiment, the arm cylinder 6 is used as the actuator, but the actuator is not limited to the arm cylinder 6 and may be a boom cylinder, or the arm cylinder 6 and the boom cylinder. It may be both.

Further, in the above embodiment, the hydraulic excavator was mentioned as the construction machine, but the present invention is not limited to the hydraulic excavator, and is provided with a load sensing system and has the same function as the arm or boom of the hydraulic excavator. Any construction machine provided with members can be applied.

[0031]

Since the present invention is configured as described above, it is possible to increase the flow rate supplied to the actuator at the time of reproduction, and as a result, the occurrence of cavitation on the meter-in side of the actuator is generated as compared with the prior art. It is possible to suppress the damage and to reduce damage due to cavitation of the hydraulic equipment and the pipeline that configure the control circuit, and it is possible to improve the durability of these hydraulic equipment and the pipeline as compared with the related art.

[Brief description of drawings]

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

FIG. 2 is a diagram showing characteristics obtained in the embodiment shown in FIG.

FIG. 3 is a circuit diagram showing an example of a control circuit of a conventional construction machine.

FIG. 4 is a diagram showing characteristics obtained in the conventional example shown in FIG.

[Explanation of symbols]

1 Variable displacement hydraulic pump 2 Regulator (flow control means) 2A spring 3A meter-in variable aperture 3B meter-out variable aperture 3C control diaphragm 3D check valve 5 detection lines 6 arm cylinder (actuator) 6a Meter-in side 6A meter-in main pipeline 6b Meter-out side 6B meter-out main pipeline 6C regeneration pipe 7 load 8 tanks 13 Separate control diaphragm 14 Detection line 15 characteristic line 16 characteristic lines 17 characteristic line

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) E02F 9/22 F15B 11/02

Claims (6)

(57) [Claims] 1. A hydraulic pump and a state where gravity is applied to a meter-out side and a state where a reaction force of a load is applied to a meter-in side are selectively generated by being driven by hydraulic oil discharged from the hydraulic pump. Actuator, a meter-in variable throttle that controls the flow of pressure oil supplied from the hydraulic pump to the actuator, a meter-out variable throttle that controls the flow of pressure oil returned from the actuator to the tank, and the meter-in variable throttle Of the meter-in side of the actuator, the meter-in main conduit that connects the meter-in side of the actuator and the meter-in side of the actuator, and the meter-out main conduit that connects the upstream side of the meter-out variable throttle and the meter-out side of the actuator. When operating, pressure oil from the meter-out main pipeline to the meter-in main pipeline Of the hydraulic pump, a control throttle capable of controlling the flow rate of passage through the regeneration pipeline, and a supply flow rate to the meter-in variable throttle, which is the difference between the discharge pressure of the hydraulic pump and the load pressure of the actuator. In a control circuit of a construction machine, which comprises a flow control means capable of controlling according to a load sensing differential pressure which is a pressure, the control throttle is located between the control throttle and the meter-in main pipeline downstream of the meter-in variable throttle. In the regeneration pipeline, another control throttle is provided, and a detection pipeline for detecting the pressure in the regeneration pipeline located between the other control throttle and the control throttle is provided. A control circuit for a construction machine, characterized in that the flow rate control means is driven according to the detected pressure. 2. The construction machine according to claim 1, wherein the hydraulic pump is a variable displacement hydraulic pump, and the flow rate control means is a regulator for controlling a tilt angle of the variable displacement hydraulic pump. Control circuit. 3. The construction according to claim 1, wherein the hydraulic pump comprises a fixed displacement hydraulic pump, and the flow rate control means is an unload valve provided in a discharge conduit of the fixed displacement hydraulic pump. Machine control circuit. 4. The flow rate control means is a pressure compensating valve for controlling a front-rear differential pressure which is a differential pressure between an upstream pressure and a downstream pressure of the meter-in variable throttle. The control circuit of the described construction machine. 5. The construction according to claim 1, wherein the regeneration pipe is provided with a check valve for preventing a backflow from the meter-in main pipe to the meter-out main pipe. Machine control circuit. 6. The construction machine is a hydraulic excavator, and the actuator is at least one of a boom cylinder that drives a boom and an arm cylinder that drives an arm. The control circuit of the construction machine described in.