JPH11336705A - Automatic pressure rising device for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the frequency of pressure rising to obtain a pressure rising circuit which holds down the life of a hydraulic device or the like within a practical range by selecting a pressure rising mode, and controlling the relief pressure to rise when high load continues more than designated time and the oil pressure of the main oil path is a designated value or more. SOLUTION: Acoording to the respective signals X1, X2, and X3 from a pressure rising mode-selecting switch 24, a pressure sensor 21 of a branch oil path 20 and a rack sensor 23 for detecting load of an engine 3, a controller 22 outputs solenoid current Y1 to a solenoid 8C of a solenoid valve 8. When an operator turns on a switch 24, high load of the engine continues more than designated time and the oil pressure of an oil path 4 becomes high above a designated value, the output Y1 is automatically turned on and the relief pressure of a relief valve 6 rises. When the pressure rising state continues more than designated time, the output Y1 is automatically turned off to release the pressure rising state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a hydraulic booster for increasing the hydraulic pressure of hydraulic oil for construction machinery. More specifically, it belongs to the technical field of control technology for increasing the relief pressure of a relief valve connected to an output oil passage of a hydraulic pump.

[0002]

2. Description of the Related Art Hydraulic oil has been conventionally used when a large load is applied to attachments when working with construction machines, for example, when digging hard ground, when digging up rocks or the roots of trees, or when hanging loads. , That is, means for temporarily increasing the relief pressure of the main relief valve. This means that if the hydraulic oil pressure is always operated at a high pressure, it is necessary to make the hydraulic pump, hydraulic motor and other hydraulic equipment withstand high pressure, which increases the cost of the hydraulic circuit and conversely, the hydraulic equipment This is because if only the relief pressure of the main relief valve is increased without any change, problems occur in the life and durability of the hydraulic equipment used.

As a conventional hydraulic circuit for temporarily increasing the hydraulic pressure of hydraulic oil for use, for example, a hydraulic circuit as shown in FIG. 5 is known. This circuit uses a booster circuit for boosting the relief pressure.
Call. Hereinafter, the conventional device 1 will be described with reference to FIGS.

In FIG. 5, a hydraulic pump 1 and an auxiliary hydraulic pump 2 are driven by an engine 3. In the oil passage 4 of the hydraulic pump 1, a plurality of switching control valves 5a, 5b,. . . Is provided. The oil passage 4 is connected to a relief valve 6 via a branch passage.
Is provided to limit the maximum oil pressure in the oil passage 4. The relief valve 6 is configured such that the relief pressure changes according to the pilot pressure of the oil passage 7 acting on the pilot port 6a.

[0005] The oil passage 7 is connected to the auxiliary hydraulic pump 2 and the oil tank T via an electromagnetic valve 8. The solenoid 8c of the solenoid valve 8 is connected to the output terminal of the controller 10 via a wiring 9, and the input terminal thereof is connected to a boost switch 11 for increasing the relief pressure of the relief valve 6. Further, the controller 10 is connected to the battery 12 and the ground.

The controller 10 outputs a solenoid current Y1 as shown in FIG. 6 to an output terminal based on an on / off signal X1 from the boost switch 11. That is, the ON signal X
1 if the time t is less than or equal to t2, the solenoid current Y1 is output for the time t. If the time t is longer than t2, the time t is output.
Two solenoid currents are output.

FIG. 7 is a graph showing the performance of the hydraulic pump 1. The rated maximum discharge flow Q2 and the rated maximum discharge pressure P2 are determined based on the capacity of the hydraulic pump 2, the pressure resistance of the hydraulic equipment used, and the like. Further, the arrows in the figure show the change in the discharge pressure and the maximum discharge pressure P3 when the boost switch 11 is turned on, and the dotted line in the figure shows the characteristic curve of the hydraulic pump 1 when the boost switch 11 is turned on.

[0008] The conventional device 1 functions as follows by the configuration described above. That is, when the boost switch 11 is turned on (closed), the controller 10 outputs a solenoid current to the wiring 9. As a result, the solenoid valve 8 switches from the state a to the state b, pressure oil flows from the auxiliary pump 2 into the pilot port 6a, and the relief pressure of the relief valve 6 increases to P3, resulting in a characteristic curve indicated by a dotted line in FIG. . Boost switch 1
When 1 is turned off within time t2, the controller 10 sets the solenoid current to 0, and the boost state is released. Also,
Even if the boost switch is turned on for the time t2 or more, when the time t2 elapses, the solenoid current becomes 0, and the boost state is released.

FIG. 8 shows a published patent application No. 60-10960.
No. 5 discloses an example of a booster circuit used for a hoist drum. Hereinafter, it is referred to as a conventional circuit 2. The same components as those described in the conventional circuit 1 are denoted by the same reference numerals, and the description will be simplified. 8, a switching control valve 5 for controlling a hydraulic motor 12 is connected to an output oil passage 4 of a hydraulic pump 1, and a branch oil passage is provided and a relief valve 6 is connected. The relief valve 6 is connected so as to change the relief pressure by changing the oil pressure in the oil path 13 on the back pressure side. Oilway 1
Reference numeral 3 is connected to the auxiliary pump 2 via switching valves 14 and 15 connected in cascade.

The switching valve 14 can be switched by a hydraulic cylinder 16 so as to communicate with the auxiliary pump 2 or the oil tank T, and the switching valve 15 is communicated with the auxiliary pump 2 or the oil tank T by the oil pressure in the oil passage 4. Connected to be. In addition, a relief valve 17 for keeping the discharge pressure constant is connected to the auxiliary pump 2. The pilot port of the switching valve 15 is connected to the oil passage 4 so that the oil pressure in the oil passage 4 becomes constant pressure P
When the pressure rises above o, the hydraulic pressure of the auxiliary pump 2
Are connected so as to act on the back pressure oil passage 13.

Further, the hydraulic cylinder 1 is
6 is connected to a hydraulic circuit 19. The hydraulic circuit 19 is a control circuit that switches the switching valve 14 from the auxiliary pump 2 side to the oil tank T after the predetermined time t2 has elapsed when the oil pressure in the oil passage 4 (or the oil passage 18) reaches the rated pressure.

The conventional circuit 2 is configured as described above and functions as shown in FIG. That is, when the hydraulic motor 12 is operated by operating the switching control valve 5, the oil pressure in the oil passage 4 increases. When the oil pressure rises above a certain pressure Po, the switching valve 15
Is switched, the hydraulic pressure of the auxiliary pump 2 acts on the back pressure side of the relief valve 6, and the relief pressure increases to Pc. Further, when the hydraulic pressure of the oil passage 4 rises and reaches the rated pressure Pa, the hydraulic circuit 19 is operated to slowly extend the hydraulic cylinder 16 over a predetermined time t2 so that the switching valve 14 communicates with the oil tank. Switch to. As a result, the back pressure of the relief valve 6 becomes zero, and the pressure increase is released.

[0013]

As described above,
The conventional circuit 1 has a problem that an operator must operate a switch in order to perform boosting, and if another operation is required while operating the operation lever, the operation of the operation lever becomes complicated. Further, when the boost switch is turned on, the pressure is constantly increased, so that the frequency of the boost is increased, and there is a problem that the life of the hydraulic equipment or the like is shortened. In the conventional circuit 2, it is not necessary to operate a switch or the like during operation of the operation lever because the boosting circuit automatically boosts the pressure. However, if the hydraulic pressure of the main oil passage rises to a predetermined value or more, the pressure is automatically raised at all times. Therefore, boosting is performed even when unnecessary. Therefore, there has been a problem that the frequency of pressure increase is high and the life of the hydraulic device is shortened.

SUMMARY OF THE INVENTION The present invention has been made under the above-described background, and provides a condition for boosting, reducing the frequency of boosting, and keeping the life of hydraulic equipment and the like within a practical range. It is intended to provide a circuit.

[0015]

The present invention employs the following means to solve the above-mentioned problems. That is, claim 1
The described invention provides a circuit for increasing the hydraulic pressure of a main oil passage of a construction machine, a solenoid valve for controlling a relief pressure of a relief valve connected to the main oil passage, and a hydraulic pressure detection for detecting a hydraulic pressure of the main oil passage. Means, a load detection means for detecting a load of an engine driving the main pump, a boost mode selection switch, and a controller for controlling the solenoid valve based on the results of the hydraulic pressure detection means, the load detection means, and the selection switch. The controller is characterized in that when the boost mode is selected, the high load continues for a predetermined time or more, and the relief pressure is increased when the hydraulic pressure of the main oil passage is equal to or more than a predetermined value.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, when the pressure increase of the relief valve continues for a predetermined time or more, control is performed so as to cancel the pressure increase.

[0017]

FIG. 1 shows a configuration of an embodiment of the present invention, and FIG. 2 shows a flowchart of a controller of the present embodiment. FIG. 3 shows a performance curve of the hydraulic pump, and FIG. 4 shows a performance curve of the engine. An embodiment of the present invention will be described below with reference to FIGS. In these figures, the same components as those of the above-described conventional device are denoted by the same reference numerals, and detailed description is omitted.

In FIG. 1, a branch oil passage 20 is provided from the oil passage 4 of the hydraulic pump 1 to which a pressure sensor 21 is connected.
The output of the pressure sensor 21 is connected to the input terminal of the controller 22. Further, the output of the rack sensor 23 is connected to the input terminal of the controller 22 to detect the load of the engine 3. Further, a selection switch 2 for selecting a boost mode
4 is also connected to the input of the controller 22.
The output of the controller 22 is connected to the solenoid 8c of the solenoid valve 8.

The controller 22 outputs a solenoid current Y1 based on the signal X1 from the selection switch 24, the signal X2 from the pressure sensor 21, and the signal X3 from the rack sensor 23. The procedure for determining the output Y1 is shown in the flowchart of FIG. The determination procedure is performed at regular time intervals, during which time the output Y1 keeps the same value. Hereinafter, the determination procedure of FIG. 2 will be described. In step S1, if the switch signal X1 is on, step S2 is executed, and if it is off, step S3 is executed. In step S2, first, the rack sensor signal X
2, the load factor F of the engine 3 is obtained, and the obtained load factor F is compared with a load factor F1 of a predetermined value. If F ≧ F1, the load is regarded as high, and if F <F1, the load is low.

There are various methods for determining the load factor of the engine. In the present embodiment, the current fuel flow rate X3 is determined as follows. That is, it is determined by F = X3 / (QH-QL). Here, QH is the fuel flow rate at the rated point A in the engine performance curve of FIG. 4, and QL is the fuel flow rate at the no-load point B. The values of QH, QL, and F1 are recorded in a memory in advance. If the engine has a low load, steps S4 and S5 are executed. If the engine has a high load, step S6 is executed.

In step S3, the flag memory Sf and the elapsed time t are reset to "0". In step S4, the output Y1 is turned off, and no boost is performed. In step S5, the flag memory Sf is read out, and if "0", step S6 is executed, and if other than "0", step S8 is executed. In step S6, if the elapsed time t is longer than the predetermined time t1, "1" is set in the flag memory Sf in step S7. If it is smaller than the time t1, the process returns without doing anything. That is,
"1" is set in the flag memory Sf when the high load of the engine continues for the time t1 or more.
Repeat steps until. The time t1 is recorded in the memory in advance.

In step S8, the flag memory Sf is read out, and if "1", step S9 is executed, and if "2" or "3", step S10 is executed. Step S9
Then, the hydraulic pressure signal X2 of the oil passage 4 is compared with a predetermined hydraulic pressure P1, and if X2 is larger than P1, steps S11, S12
Execute If smaller than P1, step S13 is executed. The hydraulic pressure P1 is equal to the rated pressure P2 as shown in FIG.
It is predetermined by a smaller value. Step S11
Then, "2" is set in the flag memory Sf, and in S12, the output Y1 is turned on. Thereby, the relief pressure of the relief valve 6 is increased to P3. FIG. 3 shows P1, P2, P
FIG. 3 is a diagram showing a relationship of No. 3; In FIG. 3, the dotted line indicates the horsepower input from the engine. In step 13, the flag memory Sf is reset to "0" and the process returns.

In step 10, the flag memory Sf is read and if "2", step S14 is executed, and if "3", the process returns. In step S14, the elapsed time t is compared with the time t2. If the time t is longer than t2, steps S15 and S16 are executed.
Is ON, and the flag memory Sf remains at 2). Therefore,
The boosting time t ′ (= t−t1) is the longest time t3 (= t2−
t1) It is limited to the following. The time t2 is a predetermined time recorded in the memory in advance.

In step 15, "3" is set in the flag memory Sf, and in step S16, the output Y1 is turned off.
Thereby, the pressure increase of the relief valve 6 is released. When "3" is set in the flag memory Sf, the voltage is not boosted until the selection switch 24 is turned off or until the engine 3 becomes low load and step 3 is executed again.

This embodiment functions as follows by the above configuration. That is, when the operator turns on the boost mode selection switch 24 and the high load of the engine continues for the time t1 or more and the oil pressure of the oil passage 4 becomes a high pressure of P1 or more, the output Y1 is automatically turned on and the relief valve is turned on. The relief pressure of No. 6 is increased. If the boost state continues for time t3 or more, output Y1
Is automatically turned off and the boost is released. Further, once the pressure is increased, the voltage is not increased no matter how long the high load state of the engine continues while the selection switch 24 is kept on.

In this embodiment, since the boost mode selection switch is provided as described above, the boost can be performed only when the operator desires, and the boost is automatically performed. Further, the load condition of the engine is also monitored as a requirement for increasing the pressure, and since the increase in pressure is limited, fatigue of the device is reduced, and an effect of making the failure less likely to be obtained is obtained.

Although the embodiments and examples of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to this example, and the design can be changed within a range not departing from the gist of the present invention. The present invention is included in the present invention. For example, the function of the controller 22 is not limited to the above case. If the high load state of the engine continues for the time t1 or more after the single boost, the algorithm may be changed so that the boost can be performed again. This case is also included in the scope of the present invention.

[0028]

As described above, according to the configuration of the present invention, the step-up mode selection switch is provided, so that the step-up operation can be performed only when the operator desires. The effect can be obtained when is facilitated. In addition, the load condition of the engine is also monitored as a requirement for increasing the pressure, and since the increase in pressure is limited, fatigue of the device is reduced, and an effect that a failure hardly occurs is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a boosting determination procedure of a controller according to the embodiment.

FIG. 3 shows a performance curve of the hydraulic pump of the present embodiment.

FIG. 4 shows criteria for determining a load factor in the present embodiment.

FIG. 5 is a diagram showing a configuration of a conventional device 1.

FIG. 6 is a diagram showing a boost determination by a controller of the conventional device 1.

FIG. 7 shows a performance curve of the hydraulic pump of the conventional device 1.

FIG. 8 shows a configuration of a conventional device 2.

FIG. 9 shows a boost condition of the conventional device 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Auxiliary hydraulic pump 3 Engine 4 Main oil passage 5a, 5b Switching control valve of actuator 6 Relief valve 8 Solenoid valve 21 Main oil passage pressure sensor (oil pressure detecting means) 22 Controller 23 Rack sensor (load detecting means) 24 Mode selection switch

Claims (2)

[Claims] In a circuit for increasing a hydraulic pressure of a main oil passage of a construction machine, an electromagnetic valve for controlling a relief pressure of a relief valve connected to the main oil passage, and a hydraulic pressure detection for detecting a hydraulic pressure of the main oil passage. Means, a load detection means for detecting a load of an engine driving the main pump, a boost mode selection switch, and a controller for controlling the solenoid valve based on the results of the hydraulic pressure detection means, the load detection means, and the selection switch. A construction machine, wherein the controller controls to increase the relief pressure when the boost mode is selected, the high load continues for a predetermined time or more, and the hydraulic pressure of the main oil passage is a predetermined value or more. Automatic booster. 2. The automatic booster for a construction machine according to claim 1, wherein the controller controls so as to release the boost when the boost of the relief valve has continued for a predetermined time or more.