JPH05248404A - Hydraulic circuit for construction machinery - Google Patents

Abstract

PURPOSE:To enlarge the maximum preset flow without spreading the size of a variable displacement hydraulic pump and ensure the metering region of an actuator widely. CONSTITUTION:A hydraulic circuit for construction machinery is provided with a detecting means 33 for detecting the rotational frequency N of an engine 21, a detecting means 34 for detecting the discharge pressure P of a variable displacement hydraulic pump 22, and detecting means 24, 26 for detecting the operation strokes theta1, theta2 of operating levers 23, 25. According to a detection value of each detecting means, an electric signal Ep is output to a regulator 28 and electric signals Ec1, Ec2, Ec3, Ec4 are output to driving means 35, 40 of flow control valves 31, 32 to control them. When the maximum required flow by operation of the operating levers 23, 25 exceeds the maximum discharge of the variable displacement hydraulic pump 22, a control unit 27 controls the maximum required flow to a flow rate which can be discharged by the variable displacement hydraulic pump 22.

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 construction machine in which a plurality of actuators are connected to respective flow control valves and a variable displacement hydraulic pump supplies pressure oil to the actuators. Related to the hydraulic circuit.

[0002]

2. Description of the Related Art A conventional hydraulic circuit of this type of construction machine is shown in FIG. The variable displacement hydraulic pump 2 is driven by the engine 1, the operation signals of the operation levers 3 and 4 are input to the control unit 5, and the control unit 5 outputs an electric signal to the regulator 6 to operate the operation levers 3 and 4. Pressure oil corresponding to the stroke is discharged to the flow rate control valves 7 and 8. Flow control valve 7
As the spool driving means 9 and 10, the solenoids 9a and 9b and 10a and 10 are provided at both ends of each spool.
b is provided, and the solenoid 9a or 9b, or 10a or 1 from the control unit 5 is operated by operating the operation levers 3 and 4.
An electric signal is output to 0b to drive and control the spools of the flow control valves 7 and 8 to any position. Then, the spools of the flow control valves 7 and 8 are moved according to the operation of the operation levers 3 and 4, and the discharge oil of the variable displacement hydraulic pump 2 is led to the actuators 11 and 12.

FIG. 9 shows the discharge amount Qp of the variable displacement hydraulic pump 2.
Is a graph showing the relationship between the discharge pressure P and the discharge pressure P, and the curve changes in the direction of the arrow as the rotation speed N of the engine 1 decreases. In the hydraulic circuit of a general construction machine, in order to ensure the speed at the time of independent operation of each actuator 11 and 12,
The spool stroke (opening area) of the flow rate control valves 7 and 8 with respect to the operation levers 3 and 4 is set at the A position where the engine speed Nmax and the pump discharge pressure P are relatively low.

In a normal operation, the total value of the operation strokes of the operation levers 3 and 4 is proportional to the discharge amount of the variable displacement hydraulic pump 2 as shown in the graph of FIG.

[0005]

In the hydraulic circuit of the conventional construction machine, when the load pressure of the actuator 11 or 12 increases and the discharge amount of the variable displacement hydraulic pump 2 decreases to the position B in FIG. When the engine 1 is used at a reduced rotation speed, or when a combined operation is performed, the operation lever 3
When the discharge amount of the variable displacement hydraulic pump 2 is insufficient with respect to the required flow rates of 4 and 4, the operation stroke of the operation lever 3 or 4 is 100 as shown at the position C in the graph of FIG.
The pump discharge amount saturates at an intermediate point where
Even if the spool stroke of the flow control valve 7 or 8 is further moved by the operating lever 3 or 4, the actuator 1
The flow rate of pressure oil to 1 or 12 does not increase.

Therefore, as shown in the graph of FIG. 12, the operating speed of the actuator 11 or 12 does not increase at the intermediate position D of the operation stroke of the operation lever 3 or 4.
The so-called metering region (range of S in FIG. 12) becomes narrow, and the operability is significantly deteriorated. Therefore, there is a technical problem to be solved in order to increase the maximum set flow rate and enlarge the metering area for controlling the speed of the actuator without increasing the size of the variable displacement hydraulic pump. Aims to solve this problem.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above-mentioned object, and a flow control valve is connected to each of a plurality of actuators, driven by an engine, and an equal flow control is performed. In the hydraulic circuit of the construction machine, which is provided with a variable displacement hydraulic pump that supplies pressure oil to the actuator via the valve and is provided with an operation lever for operating the drive means of the spool of each flow control valve, A detection means for detecting the discharge pressure of the variable displacement hydraulic pump; and a detection means for detecting the operation stroke of the operating lever. Based on the detection value of each detection means, a regulator for the variable displacement hydraulic pump and When the maximum required flow rate due to the operation of the operation lever exceeds the maximum discharge rate of the variable displacement hydraulic pump by controlling the drive means of each flow rate control valve, the maximum required flow rate is controlled. The hydraulic circuit of the construction machine provided with a control unit that allows the flow rate to be the dischargeable flow rate of the variable displacement hydraulic pump, and electromagnetic proportional valves at both ends of the spool of the flow rate control valve, and an electric signal from the control unit. The hydraulic circuit of the construction machine equipped with the drive means for the flow control valve, which operates the solenoid proportional valve by the output of the control valve and controls and derives the pilot pressure from the hydraulic source at both ends of the spool of the flow control valve. Is provided.

[0008]

When the drive means for the spool of the flow control valve is operated by the operating lever and the actuator is operated, the control section determines the characteristic curve (PQ curve) of the hydraulic pump from the engine speed and the pump discharge pressure. ) Is calculated and the maximum discharge amount of the variable displacement hydraulic pump is obtained. Then, an electric signal to the drive means of the spool of the flow rate control valve is controlled according to the maximum required flow rate required by the actuator by operating the operation lever.

When the maximum required flow rate of the actuator exceeds the maximum discharge rate of the variable displacement hydraulic pump, the electric signal to the drive means of the flow rate control valve is corrected to reduce the spool stroke and the operation lever is operated. Reduce actuator speed to stroke to ensure metering area.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows a hydraulic circuit of a construction machine, in which a variable displacement hydraulic pump 22 is driven by an engine 21.
The operation signal E is detected by the detection means 24 that drives the control lever 23 and detects the operation stroke of the one operation lever 23 and the detection means 26 that detects the operation stroke of the other operation lever 25.
θ ₁ and E θ ₂ are input to the control unit 27, and the electric signal E is sent to the regulator 28 under the control of the control unit 27 described later.
p is output. The tilt angle of the variable displacement hydraulic pump 22 is changed by the operation of the regulator 28 based on the electric signal Ep, and the flow paths 31 and 3 are controlled by the oil passages 29 and 30.
Pressure oil is discharged to 2.

A detecting means 33 for detecting the number of revolutions N of the engine 21 (= the number of revolutions of the variable displacement hydraulic pump 22) is provided at a connecting portion between the engine 21 and the variable displacement hydraulic pump 22, and the variable displacement hydraulic pump is provided in an oil passage 29. Detection means 34 for detecting the discharge pressure P of 22 is provided. The equality detecting means 33 and 34 are
The engine speed N and the pump discharge pressure P are output to the control unit 27 as electrical signals.

Drive means 35 for the spool of the flow control valve 31
As a result, the solenoid proportional valves 36 and 37 are arranged at the pilot pressure receiving portions at both ends of the spool, respectively. The solenoid 38 of the solenoid proportional valve 36 and the solenoid 39 of the solenoid proportional valve 37 are connected to the electric signals Ec ₁ and Ec ₂ from the controller 27. Turned on and off by. Further, the spool driving means 4 of the flow control valve 32
The solenoid proportional valves 41 and 42 are arranged at the pilot pressure receiving portions at both ends of the spool, respectively, and the solenoid 43 of the solenoid proportional valve 41 and the solenoid 44 of the solenoid proportional valve 42 are connected to the electric signals Ec ₃ and Ec from the control unit 27. Turned on and off by ₄ .

Then, from the hydraulic power source 45 to the pilot oil passage 4
The pilot oil passing through 6 is led out to one pilot pressure receiving portion of the spool of the flow rate control valve 31 via the electromagnetic proportional valve 36, and the pilot oil passing through the pilot oil passage 47 is flowed via the electromagnetic proportional valve 37. The spool of the control valve 31 is led to the other pilot pressure receiving portion. Further, the pilot oil passing through the pilot oil passage 48 is
The pilot oil which is led to one pilot pressure receiving portion of the spool of the flow control valve 32 through the pilot oil passage 49 is led to the other pilot pressure receiving portion of the spool of the flow control valve 32 via the electromagnetic proportional valve 42. To be done. The drive means 35 of the equal flow rate control valve 31 and the drive means 40 of the flow rate control valve 32 respectively have an electric signal Ec ₁ from the control section 27,
It is controlled by Ec ₂ , Ec ₃ , and Ec ₄ , but in the illustrated state, the spools of both flow control valves 31 and 32 are in the neutral positions 31a and 32a, and the flow control valves 31 and 3 are
Oil passages 29 and 3 because 2 is a center closed type
The pressure oil of 0 is in a state of being cut off from the actuators 50 and 51.

Next, the control of the hydraulic circuit of the construction machine of the present invention
The control procedure in the section 27 will be described. The control unit 2
7 is a CPU having a memory function, an arithmetic function, and a logical judgment function
Are formed by the setting means 27a, the calculating means 27b, the discrimination
It comprises means 27c and output means 27d. Control unit 2
In the setting means 27a of No. 7, as shown in the graph of FIG.
Detecting means 24 and 26 of the operating levers 23 and 25, respectively
Operation stroke θ detected by₁And θ₂And each
Electrical signals output from the detection means 24 and 25 to the control unit 27
Issue Eθ ₁And Eθ₂Set the relationship with and as shown in Figure 3.
To the electrical signal Eθ₁And Eθ₂And each flow control valve 31 and
Required flow rate Q of each of 32₁And Q₂Relationship with
It In addition, as shown in FIG.
The relationship between the signal Ep and the discharge amount Qp of the variable displacement hydraulic pump 22
As shown in Fig. 5, each solenoid proportional valve is set.
Signal Ec to the solenoids 38, 39, 43, 44 of
₁, Ec₂, Ec₃, Ec_FourAnd each flow control valve 31
And 32 spool strokes (ie required flow rate Q₁Over
And Q₂) And the relationship with. Furthermore, from the detection means 33
From the detected engine speed N of the engine 21 and the detection means 34
Based on the detected discharge pressure P of the variable displacement hydraulic pump 22,
The characteristic curve (PQ curve) of the hydraulic pump shown in FIG. 9 is set.
Set.

Next, in the computing means 27b of the control unit 27,
Operating strokes of operating levers 23 and 24 θ ₁ and θ ₂
The required flow rates Q ₁ and Q ₂ for the flow control valves 31 and 32 are calculated from the above, and the maximum dischargeable flow rate Qpmax of the variable displacement hydraulic pump 22 is calculated from the characteristic curve (PQ curve) of the hydraulic pump. At the same time, the maximum required flow rate total value ΣQmax is calculated from the maximum required flow rates Q ₁ max and Q ₂ max, and the maximum required flow rate total value ΣQmax is the maximum dischargeable amount of the variable displacement hydraulic pump 22. When the flow rate exceeds Qpmax, the variable displacement hydraulic pump 2
A ratio K between the maximum dischargeable flow rate Qpmax of 2 and the total value ΣQmax of the maximum required flow rates is calculated. Then, the electric signals Ec ₁ , Ec ₂ , Ec ₃ and Ec ₄ to the solenoids 38, 39, 43 and 44 of the respective solenoid proportional valves are respectively multiplied by K to correct.

On the other hand, in the discriminating means 27c of the control unit 27,
The total value ΣQmax of the maximum required flow rates described above and the maximum flow rate Qpmax of the variable displacement hydraulic pump 22 that can be discharged are compared to determine the magnitude. Further, the output means 2 of the control unit 27
In 7d, the electric signal Ep to the regulator 28 that changes the discharge amount of the variable displacement hydraulic pump 22 is output, and the electric signals Ec ₁ and Ec ₂ to the solenoids 38 and 39 of the solenoid proportional valve of the driving means 35, and the driving means. Electrical signals Ec ₃ and E to the solenoids 43 and 44 of the 40 solenoid proportional valve
Output c ₄ .

FIG. 6 is a flow chart of the control procedure of the control unit 27. First, the detection means 24 and 26 operate the operation stroke θ ₁ of the operation lever 23 and the operation lever 25.
The operation stroke θ ₂ is read, and the operation strokes θ ₁ and θ ₂ are converted into electric signals Eθ ₁ and Eθ ₂ and input to the control unit 27. At the same time, the detecting means 33 reads the rotational speed N of the engine 21, converts it into an electric signal and inputs it to the control section 27, and the detecting means 34 reads the discharge pressure P of the variable displacement hydraulic pump 22 into an electric signal. The converted data is input to the control unit 27 (step 10).
1).

Next, the setting means 27a of the control unit 27 sets the relationship between the operation strokes θ ₁ and θ ₂ and the electric signals Eθ ₁ and Eθ ₂ as shown in FIG. As described above, the relationship between the electric signals Eθ ₁ and Eθ ₂ and the required flow rates Q ₁ and Q _{2 of the} flow rate control valves 31 and 32 is set. In addition, as shown in FIG. 4, the relationship between the electric signal Ep to the regulator 28 and the discharge amount Qp of the variable displacement hydraulic pump 22 is set, and as shown in FIG. The relationship between the electric signals Ec ₁ , Ec ₂ , Ec ₃ , and Ec ₄ to 43 and 44 and the required flow rates Q ₁ and Q ₂ of the flow rate control valves 31 and 32 is set. Further, as shown in FIG. 9, a characteristic curve (PQ curve) of the hydraulic pump is set by the rotation speed N of the engine 21 and the discharge pressure P of the variable displacement hydraulic pump 22 (step 102).

On the basis of the read data and setting data, the calculating means 27b of the control unit 27 calculates the maximum dischargeable flow rate Qpmax of the variable displacement hydraulic pump 22 from the characteristic curve (PQ curve) of the hydraulic pump. (Step 1
03). At the same time, the total value ΣQmax of the maximum required flow rates is calculated from the maximum values Q ₁ max and Q ₂ max of the required flow rates for the flow rate control valves 31 and 32 regardless of the operation strokes θ ₁ and θ ₂ (step 104). ..

Then, the actual operation strokes θ ₁ and θ
The total value Q of the required flow rates Q ₁ and Q ₂ corresponding to ₂ is calculated, and the electric signals Ec ₁ and Ec ₂ to the drive means 35 are set in accordance with the required flow rate Q ₁ of the flow rate control valve 31. , Electric signals Ec ₃ and Ec ₄ to the drive means 40 are set in accordance with the required flow rate Q ₂ of the flow rate control valve 32 (step 105).

The discriminating means 27c of the control unit 27 compares the total value ΣQmax of the maximum required flow rates with the maximum dischargeable flow rate Qpmax, and discharges the maximum possible flow rate Qpmax.
Is greater than or equal to the maximum required flow rate ΣQmax (step 106). Here, the variable displacement hydraulic pump 22
Of the maximum required flow rate ΣQmax or more, the variable displacement hydraulic pump 2
The value of the discharge amount Qp of 2 is set as the total value Q of the required flow rates (step 107).

On the other hand, the maximum required flow rate ΣQmax is the variable capacity.
Exceeding the maximum flow rate Qpmax that can be discharged by the hydraulic pump 22
The discharge amount Qp of the variable displacement hydraulic pump 22,
It is set to Qpmax (step 108). And Qpm
A ratio K between ax and ΣQmax is calculated (step 10
9), electric signal Ec to each driving means 35 and 40₁, E
c ₂, Ec₃, Ec_FourIs corrected (step 110).

An electric signal E to the regulator 28 of the variable displacement hydraulic pump 22 is output by the output means 27d of the control unit 27.
p for outputting the solenoid 3 of the solenoid valve of the driving means 35.
The electric signals Ec ₁ and Ec ₂ to 8 and 39 and the electric signals Ec ₃ and Ec ₄ to the solenoids 43 and 44 of the solenoid proportional valve to the driving means 40 are output (step 11).
1).

That is, if the maximum required flow rate ΣQmax is within the maximum dischargeable flow rate Qpmax of the variable displacement hydraulic pump 22, the electric signal Ep from the control unit 27 causes the regulator 28 to operate and the discharge amount of the variable displacement hydraulic pump 22. It is controlled so that Qp becomes the total value Q of the required flow rates. Further, the electromagnetic proportional valves 36 and 37 are actuated by the electric signals Ec ₁ and Ec _2, and the drive means 35 of the one flow rate control valve 31.
Is controlled. Then, the spool moves from the position of 31a to the other 31b or 31c direction, the amount of movement thereof changes under the control of the driving means 35, and pressure oil is led to the actuator 50.

The electric proportional signals Ec ₃ and Ec ₄ actuate the solenoid proportional valves 41 and 42, and the drive means 40 of the other flow control valve 32 is controlled. And the spool is 32a
Moves from the position of 3 to the other direction of 32b or 32c, the amount of movement changes under the control of the driving means 35, and pressure oil is led to the actuator 51. Therefore, as shown by the solid line in FIG. 7, the actuators 50 and 51 operate at the actuator speed corresponding to the operation strokes θ ₁ and θ ₂ of the operation levers 23 and 25.

On the other hand, when the maximum required flow rate ΣQmax exceeds the maximum dischargeable flow rate Qpmax of the variable displacement hydraulic pump 22, the electric signal Ep from the control unit 27 operates the regulator 28 to discharge the variable displacement hydraulic pump 22. The discharge amount is controlled so that the amount Qp becomes the maximum dischargeable flow rate Qpmax. Further, the electromagnetic proportional valves 36 and 37 are actuated by the electric signals Ec ₁ and Ec ₂ corrected by multiplication by K, and the drive means 35 of the one flow rate control valve 31 is controlled. Then, the spool moves from the position of 31a to the other 31b or 31c direction, and the movement amount is the driving means 35.
By the control of 1), the pressure oil is changed to be smaller than that in the case of ΣQmax ≦ Qpmax described above, and pressure oil is led to the actuator 50.

The electric signal Ec ₃ corrected by multiplying K
And Ec ₄ actuate the solenoid proportional valves 41 and 42, and the drive means 40 of the other flow control valve 32 is controlled. Then, the spool moves from the position of 32a to another 32b or 32c.
The amount of movement is changed by the control of the drive means 35 to be smaller than that in the case of ΣQmax ≦ Qpmax described above, and the pressure oil is led to the actuator 51. Therefore, as shown by the chain double-dashed line in FIG.
The actuator speed with respect to the operation strokes θ ₁ and θ ₂ of Nos. 25 and 25 is reduced, and the metering area can always be secured.

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 one embodiment, the operation is performed when the load pressure of the actuator suddenly rises, when the combined operation is performed, or when the engine speed is reduced. When the maximum required flow rate of the actuator due to lever operation exceeds the maximum discharge rate of the variable displacement hydraulic pump, the displacement of the spool of the flow rate control valve with respect to the operation stroke of the operating lever decreases and the variable displacement hydraulic pump can discharge. The flow rate will be Therefore, the metering area for controlling the actuator can be always secured, 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 graph showing a relationship between an operation stroke θ ₁ (θ ₂ ) of an operation lever and an electric signal Eθ ₁ (Eθ ₂ ) output to a control unit.

FIG. 3 is a graph showing a relationship between an electric signal Eθ ₁ (Eθ ₂ ) and a required flow rate Q ₁ (Q ₂ ) of a flow control valve.

FIG. 4 is an electric signal E output from the control unit to the regulator.
The graph which shows the relationship between p and the discharge amount Qp of a variable displacement hydraulic pump.

FIG. 5: Electric signal E to the solenoid of each solenoid proportional valve
_{c 1, Ec 2 (Ec 3} , Ec 4) and a graph showing the relationship between the spool stroke of the flow control valve.

FIG. 6 is a flowchart showing a control procedure of a control unit.

FIG. 7 is a graph showing the relationship between the operation stroke θ ₁ (θ ₂ ) of the operation lever and the actuator speed.

FIG. 8 is a hydraulic circuit diagram of a conventional construction machine.

FIG. 9 is a graph showing the relationship between the discharge amount Qp and the discharge pressure P of the variable displacement hydraulic pump.

FIG. 10 is a graph showing a relationship between a total value of operation lever strokes and a discharge amount of a variable displacement hydraulic pump.

FIG. 11 is a graph showing the relationship between the operation lever stroke and the spool stroke.

FIG. 12 is a graph showing the relationship between the operation lever stroke and the actuator speed.

[Explanation of symbols]

Reference Signs List 21 engine 22 variable displacement hydraulic pump 23,25 operation lever 24,26 (operation stroke) detection means 27 control unit 28 regulator 31, 32 flow control valve 33 (engine speed) detection means 34 (variable displacement hydraulic pump) Detecting means 35, 40 Driving means 36, 37, 41, 42 Electromagnetic proportional valve 45 Hydraulic power source 50, 51 Actuator θ ₁ , θ ₂ Operating stroke N Engine speed P Discharge pressure of variable displacement hydraulic pump Qp Variable displacement hydraulic pump Discharge rate Qpmax Maximum dischargeable flow rate of variable displacement hydraulic pump ΣQmax Total value of maximum required flow rate of actuator Eθ ₁ , Eθ ₂ Electric signal from operation stroke detection means Ep Electric signal to regulator Ec ₁ , Ec ₂ Electromagnetic proportional valve electric signals Ec ₃ to the solenoid, Ec ₄ solenoid proportional solenoid valve Electrical signal to the de

Claims (2)

[Claims] 1. A variable displacement hydraulic pump, which is connected to a plurality of actuators and is connected to a flow control valve, is driven by an engine, and supplies pressure oil to the actuators through the equal flow control valves, and the respective flow control is provided. In a hydraulic circuit of a construction machine equipped with an operating lever for operating a driving means of a valve spool, a detecting means for detecting an engine speed, a detecting means for detecting a discharge pressure of a variable displacement hydraulic pump, and an operating lever Detecting means for detecting the operation stroke of the control means, and controlling the regulator of the variable displacement hydraulic pump and the drive means of each flow rate control valve based on the detection value of each detection means, thereby controlling the maximum required flow rate by operating the operation lever. A control unit is provided so that the maximum required flow rate is a flow rate that can be discharged by the variable displacement hydraulic pump when the maximum discharge amount of the variable displacement hydraulic pump is exceeded. A hydraulic circuit for construction machinery. 2. An electromagnetic proportional valve is arranged at each end of the spool of the flow control valve, the electromagnetic proportional valve is operated by the output of an electric signal from the control unit, and a hydraulic power source is provided at both ends of the spool of the flow control valve. 2. The hydraulic circuit for a construction machine according to claim 1, further comprising a flow control valve driving means for controlling and deriving a pilot pressure from the valve.