JP3003958B2 - Load sensing hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load sensing hydraulic circuit.

[0002]

2. Description of the Related Art A machine equipped with a load sensing hydraulic circuit , for example, a hydraulic excavator, is a variable displacement hydraulic pump 1 driven by a power source such as an engine as shown in FIG.
(Hereinafter referred to as " pump 1" ) and a hydraulic actuator 2 (hereinafter referred to as " pump 1" ) driven by pressure oil discharged from the pump 1.
An actuator 2 ), a closed center type directional control valve 3 for switching the direction of pressure oil sent from the pump 1 to the actuator 2, a regulator 4 and an LS valve 5 for controlling the flow rate of pressure oil discharged from the pump 1. (Load Se
nsing) .

The directional control valve 3 has three positions. Each position is connected to a shuttle valve 10 via a port R at each position, and a pilot circuit 11 is connected to the shuttle valve 10. Pressure compensating valves 21a and 21b are provided at the outlet port of the direction switching valve 3, and the branch circuit 11a of the pilot circuit 11 is connected to the pressure compensating valves 21a and 21b. The discharge pressure of the pump 1 PP (hereinafter referred to as "pump discharge pressure PP") is guided to the other end of the LS valve 5 through the pilot circuit 9, the maximum pressure PLS (hereinafter "maximum load of the load pressures of the actuators
Pressure PLS "hereinafter) is a one end of the LS valve 5 through the pilot circuit 11, the pressure compensating valves 21a, are led to and 21b. Incidentally, the spring 5a for differential pressure setting is disposed at one end of the LS valve 5.

The flow rate QA supplied to the actuator is:
If the opening area of the directional control valve is A, the pump discharge pressure is PP, the actuator load pressure is PLS, and the flow coefficient is c, it can be expressed by the following equation. QA = c * A * (PP-PLS) 1/2 and the differential pressure (PP-P
Since LS) is controlled to be constant, the flow rate QA is controlled in accordance with the opening area A of the directional control valve, that is, the operation amount of the operation lever 15 . Differential pressure in the temporary (PP -PLS)
Is set to 20 kg /
Assuming cm2, QA=c.times.A.times.20@1/2. still,
The above set values are predetermined by design according to the overall configuration of the hydraulic circuit.
It is a round value (especially from the discharge port of the pump 1 to the direction switching valve 3
Loss pressure to outlet and pilot circuit 9 to LS valve 5
Value higher than the combined pressure with the internal loss pressure), the spring force of the spring 5a
(Not shown, hereinafter referred to as "spring force PSS")
Get stuck.

[0005]

As described above, in the load sensing hydraulic circuit, the differential pressure (PP-PLS) is controlled to be constant, so that the pump discharge amount QP is equal to the opening area of the directional control valve. A, that is, control is performed in accordance with the operation amount of the operation lever, and there is no loss of flow rate. By the way ,
When the operation lever 15 is held at the neutral position while the pump 1 is driven, the direction switching valve 3 is also at the neutral position, and the pressure PLS of the pilot circuit 11 becomes 0 kg / cm2.
Therefore, L is set so that the pump discharge pressure PP itself becomes the set value.
S valve 5 is replaced Ri switching regulator 4 reduces the swash plate angle of <br/> pump 1 In response to this, reduce the pump discharge amount QP
That it has to.

However , the operation lever 15 is moved from the neutral state.
When the operating position is suddenly operated, the load pressure PLS rapidly increases. Then, the differential pressure in the LS valve 5 (PP -PLS) is that less than the set value <br/>. Therefore, the LS valve 5 is connected to the regulator 4.
On the other hand, the pump swash plate angle is sharply increased until the differential pressure (PP-PLS) returns to the set value, and the pump discharge amount QP is rapidly increased.
Then, the pump discharge pressure PP is rapidly increased . As a result, a large shock is generated, and such a shock is repeated each time the operation lever 15 is suddenly operated from the neutral state to the operating position, thereby increasing operator fatigue.

The present invention pays attention to the above-mentioned conventional problems, and does not generate a large shock even if the operating lever is suddenly operated, can reduce the fatigue of the operator, and if necessary, mount the actuator with high precision. An object of the present invention is to provide a load sensing hydraulic circuit that can be finely moved.

[0008]

Means for Solving the Problems] Load Sensing grayed oil pressure circuit according to the present invention in order to achieve the above object, (1) in a first, direction switching the discharge oil of the variable displacement hydraulic pump
Stopped or operable intermittently by switching the valve
Hydraulic actuator and oil on one end
A spring having a predetermined spring force PSS in the entire pressure circuit configuration
A spring force PSS and a hydraulic actuator
Variable pressure hydraulic pressure on the other end
In response to pump discharge pressure PP, "PP> PLS + PSS"
The output of the variable displacement hydraulic pump is reduced, while "P
When P <PLS + PSS, the discharge amount of the variable displacement hydraulic pump is
Load sensing hydraulic circuit with increasing LS valve
Switch from stop to operation of the hydraulic actuator
It has a first means for detecting a time comparatively, the first means
Connected in a signal manner, and when switching from the first means.
When the information is received, it gradually increases at one end side of the LS valve at a predetermined speed.
A second means for applying a force Pi (= 0 to Pmax),
Further, the spring disposed on one end side of the LS valve is described as “PS ≒ PSS
−Pmax ”.
It is a sign. (2) Secondly, in the first load sensing hydraulic circuit,
In addition, the second means uses an LS valve from a separately provided hydraulic pump.
Proportional control valve installed in the pilot circuit to one end
When, a signal connected to the first means, the first means
When the information at the time of switching is received, the
An exciting current that increases gradually at a constant speed is given,
Pilot gradually increases in accordance with the excitation current
A controller for generating the hydraulic pressure Pi (= 0 to Pmax)
It is characterized by having. (3) Third, the first load sensing hydraulic circuit
The second means selects and uses predetermined speeds different from each other.
It is characterized by having a plurality freely . (4) Fourth, in the second load sensing hydraulic circuit,
In this case, the controller sets a predetermined speed different from each other in advance.
In addition to storing a plurality of speeds,
Selectable readout, and at the specified readout speed
And a changeover switch for gradually increasing the exciting current.
It is a sign .

[0009]

[Operation and Effect] (1) According to the first configuration, the following
Use effect. Iwayu
Fully illustrates the conventional load sensing hydraulic circuit
You. That is, the LS valve is variable when “PP> PLS + PSS”.
The displacement of the displacement hydraulic pump is reduced, while "PP <
Increased discharge of variable displacement hydraulic pump at "PLS + PSS"
Let it. As a result, “PP ≒ PLS + PSS” is obtained.
Pressure (PP 方向 PLS + PSS) and outlet pressure at the directional control valve
The differential pressure from the PLS (PP-PLS) is "PP-PLS = (PLS +
(PSS) −PLS = PSS ”and is constant (PSS = constant)
Because). Note that, in the preceding configuration, the load pressure PLS
The reason is that when there are multiple actuators, the maximum load pressure P
Refers to LS. In such a load sensing hydraulic circuit,
The first configuration is characterized by a post-stage configuration. Its features and
Means that the second means receives the switching information from the first means.
The force Pi at one end of the LS valve gradually increases at a predetermined speed.
(= 0 to Pmax) and a force that gradually increases
The maximum force Pmax of Pi and the spring force PSS are determined by
The entire hydraulic circuit in a conventional load sensing hydraulic circuit
With respect to the spring force PSS determined in advance by the configuration, "PS ≒ PSS-P
max ” . That is, variable capacity type
To increase the hydraulic pump discharge, for example,
To increase the pump discharge pressure PP to the same as
It is to become a "PP <PLS + PSS," but, on the other hand
In the first configuration, "PP <PLS + PS + Pi" holds.
Since the force Pi increases gradually at a predetermined speed,
It takes more time than the conventional technology for the constant speed.
You. Note that the flow rate QA passing through the directional control valve is “(PLS + P
S + Pi) 1/2 ", so that the predetermined speed
Actuator actuation compared to the prior art by the degree
It naturally takes time to start. That is, the first configuration
According to this, even if the operation lever is suddenly operated,
No shock occurs, reducing operator fatigue
It becomes a load sensing hydraulic circuit that can . (2) The second configuration gradually increases at a predetermined speed in the first configuration.
Configuration example in which increasing force Pi is achieved by pilot hydraulic pressure
It is. That is, the controller switches from the first means.
When the time information is received, the electromagnetic proportional control valve is gradually increased at a predetermined speed.
To increase the exciting current, which
Pilot oil pressure Pi that gradually increases according to the increase of the exciting current
(= 0 to Pmax). Therefore, its effect
The result is the same as the first configuration. The pilot oil pressure
Since hydraulic pressure is used, hydraulic pressure is applied to the load sensing hydraulic circuit.
The advantage of ease of handling with overlapping systems results.

(3) According to the third configuration, the first configuration
Second means can select and use different predetermined speeds
Have a plurality . Therefore, select a predetermined speed as necessary.
Thus, the shock reduction mode described in the first configuration can be achieved.
Mode, conventional shock mode, and other modes
Move the actuator with high precision
You can also. Specifically, for example, each hydraulic excavator
For seed work (crushing work, slope finishing work, etc.)
Efficient work can be performed based on the optimal speed mode. (4) The fourth configuration gradually increases at a predetermined speed in the third configuration.
Configuration example in which increasing force Pi is achieved by pilot hydraulic pressure
It is. In this case, the controller is actually a microcomputer
First, the microcomputers differ from each other.
A plurality of predetermined speeds are stored in advance. And
A changeover switch is added to the microcomputer. Turn off the changeover switch
By switching, you can select from multiple predetermined speeds
And read it from memory and read this
The excitation current is gradually increased at a predetermined speed.
You. Therefore, the same effect as in the third configuration can be obtained .

[0011]

EXAMPLES The following examples with reference to the accompanying drawings. FIG. 1 is a diagram of a first embodiment , and only one directional control valve 3 , an actuator 2 and the like are typically shown. Immediately
Chi, pressure pump 1, to be sent hydraulic excavator boom pump 1 is driven by pressure oil to discharge, the arms, and an actuator 2 for a work machine or swivel such as a bucket, the pump 1 to the actuator 2 A closed center type directional control valve 3 for switching the direction of oil, a regulator 4 for controlling the flow rate of pressurized oil discharged from the pump 1, and an LS valve 5
And

The directional control valve 3 is connected to the pump 1 by a circuit 6 and to the oil tank 7 by a circuit 8. Incidentally, 6a is a circuit directed to another direction switching valve not shown, and 8a is a return circuit thereof. Other end of the LS valve 5 receives a pump discharge pressure PP is connected to the pilot circuit 9 which is branched from the circuit 6,
One end is received through the shuttle valve 10 and the pilot circuit 11 to the maximum load pressure PLS among the actuators. Provided on one end of the LS valve 5, the top and the pump discharge pressure PP
A spring 5 for setting a differential pressure (PP- PLS ) from the high load pressure PLS
a is a spring having a smaller tension than a spring (the spring force P SS) used in a normal load sensing hydraulic circuit ( hereinafter referred to as a spring).
"Spring force PS" ) is used. Further, separately by <br/> provided with leads from the hydraulic pump 12 to one end of the LS valve 5 pilot circuit 13 to the electromagnetic proportional control valve 14 (hereinafter "EPC valve 1
4 (Electric Proportional Control) ”).

In the vicinity of the driver's seat, a pilot pressure proportional control valve 16 (hereinafter referred to as a "PPC valve 16 (Pilot Proportional Control) " ) that applies a pilot pressure to the left end or the right end of the direction switching valve 3 by operating the operation lever 15. ) Is provided, and a pressure switch 18 is provided in a branch circuit 17a of a pilot circuit 17 extending from the PPC valve 16 to the direction switching valve 3.
8a is connected to the controller 19. The output wiring 19 a of the controller 19 is connected to the solenoid of the EPC valve 14.

Next, the operation of the above configuration will be described. Because the operator was that operates the working machine on the temporary working machine operating lever 1
5 is operated from the neutral position (that is, the actuator stop position)
When the position is suddenly operated, the pilot pressure is transmitted from the PPC valve 16 to the direction switching valve 3, and the pressure switch 18 detects this and outputs a detection signal to the controller 19. Upon receiving the detection signal, the controller 19 outputs a command current (hereinafter, referred to as “ excitation current”) to the solenoid of the EPC valve 14.

Here, the control characteristics of the EPC valve 14 and the LS valve
FIG. 2 shows the relationship with the set value ( set pressure) of No. 5 . When the operation lever 15 is at the neutral position, the exciting current flowing from the controller 19 to the EPC valve 14 is 0 mA. <br/> a detection signal to enter into the controller 19 of the pressure switch 18, becomes EmA exciting current is gradually increased, the outlet pressure Pi of EPC valve 14 in response to this is a PiE. Therefore, LS
The control force PLSE (= PLS + PS + Pi) applied to the actuator load pressure acting side of the valve 5 gradually increases in correspondence with the exciting current. Thus, an example of the required time when the pump discharge amount QP increases from the minimum value to the maximum value is 0.5 seconds as shown by the solid line in FIG. Toes
As the pump discharge QP gradually increases, the shock
No. In contrast, the conventional load sensing hydraulic circuit (L
Control applied to the actuator load pressure acting side of S valve 5
The required time in force (PLS + PSS) ones), as to shown by a dotted line in the figure, a 0.1 to 0.2 seconds, the pump discharge amount QP increases rapidly, a large shock. still,
In FIG. 3, the above-mentioned PS, PSS and Pmax are clearly divided.
Although FIG. 3 does not show these relationships,
It is shown in FIG. That is, in FIG. 3, both (conventional and first)
The maximum discharge QP of the embodiment) is equal. Incidentally, in the first embodiment,
The maximum discharge QP is obtained by gradually increasing the outlet pressure Pi from "0 to Pmax".
At the time of "Pi = Pmax ". Place
As described above, the pump discharge amount QP is calculated as “QP = c × A ×
(PP -PLS) 1/2 ". FIG. 3 shows the direction switching.
Since the opening area A of the valve 3 is the same for both, FIG.
Pump discharge QP depends only on differential pressure (PP-PLS)
are doing. This differential pressure (PP-PLS) is used in the first embodiment.
Is "PS + Pmax", while "PSS" is conventionally
It is. That is, since the maximum discharge QP of both is equal,
3 is that PS, PSS and Pmax are "PS + Pmax = PSS".
The illustration includes the relationship.

FIG. 4 shows a second embodiment. The basic configuration is the same as that of the first embodiment (FIG. 1), and is different.
Where is is connected mode switch 20 for Switching Operation recombination the buffer mode and precision mode controller 19, optionally by changing disconnect the the mode selection switch 20, the buffer mode, either the precise mode You can choose to.

When the buffer mode is selected by operating the mode changeover switch 20, the buffer mode program of the controller 19 is operated when the detection signal is inputted from the pressure switch 18 to the controller 19 by operating the operation lever 15. The control of the controller 19 in this case is based on the first
Is as in Example, the rise time required for the pump discharge amount QP is 0.5 seconds. Therefore, when changing turn off the mode switch 20 to a precision mode, when a detection signal from the pressure switch 18 to the controller 19 is input, precision mode program controller 19 is operated. In this case, the controller 19 outputs the signal to the EPC valve 14.
The exciting current rapidly increases, and the pilot pressure Pi applied to the actuator load pressure acting side of the LS valve 5 accordingly.
Rises rapidly, and as shown by the dotted line in FIG. 3, the pump discharge amount QP reaches the maximum value in 0.1 to 0.2 seconds. The precision mode is suitable for inching excavation, excavation by giving a shock, and the like because the work machine has good responsiveness.

[0018]

As described above , according to the first embodiment of the present invention, the control force applied to the actuator load pressure acting side of the LS valve can be varied by the EPC valve, the controller, or the like. Therefore, the rise of the pump discharge amount (increase rate of the pump discharge amount) can be easily changed. Therefore, the rise of the pump discharge amount is
Can be delayed than for grayed oil pressure circuit, the shock is reduced, can be improved and operator fatigue relief safety. Therefore, work efficiency is improved and continuous work for a long time is possible.

According to a second embodiment according to the present application, the rise time required for the pump discharge quantity, as a precision mode that requires a smaller buffer mode of shock, a sensitive response, provided at least two levels any since to be able to select, by the work object or for selecting an optimum mode from among a plurality of modes in accordance with the work, you can move the actuator as intended by the operator, improving the operability and work efficiency Can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram of a first embodiment .

FIG. 2 is a diagram illustrating relationships among an exciting current, an EPC valve outlet pressure, and a pressure acting on a load pressure side of an LS valve.

FIG. 3 is a diagram illustrating a relationship between a pump discharge amount and time.

FIG. 4 is a diagram of a second embodiment .

FIG. 5 is a diagram of a conventional load sensing hydraulic circuit example .

[Explanation of symbols]

1: Variable displacement hydraulic pump, 2: Actuator, 3:
Directional switching valve 4: Regulator 5: LS valve 9, 1
1, 13, 17: pilot circuit, 12: hydraulic pump,
14: Electromagnetic proportional control valve (EPC valve), 15: Operation lever, 18: Pressure switch, 19: Controller, 20:
Mode switch.

Claims (4)

(57) [Claims] 1. Discharge oil from a variable displacement hydraulic pump (1)
Intermittent stop or operation due to switching of the directional control valve (3)
With a movable hydraulic actuator (2)
In addition, a spring force PSS which is predetermined on one end side by the entire configuration of the hydraulic circuit.
And a spring (5a) having a spring force PSS
And the load pressure PLS of the hydraulic actuator (2), and
The other end receives the discharge pressure PP of the variable displacement hydraulic pump (1).
Variable displacement hydraulic pump when “PP> PLS + PSS” (1)
The discharge amount (Qp) of the ink is reduced, while “PP <PLS + PSS”
Increase the discharge volume (Qp) of the variable displacement hydraulic pump (1)
In the load sensing hydraulic circuit having the LS valve (5), switching from the stop to the operation of the hydraulic actuator (2)
A first means for detecting time; a signal means connected to the first means;
LS valve (5)
A force Pi (= 0 to Pmax) that gradually increases at a predetermined speed is applied to the end side.
A second means (14, 19) for operating the LS valve (5).
The spring (5a) arranged on the side
A load sensing hydraulic circuit having a satisfactory spring force PS . 2. The load sensing hydraulic circuit according to claim 1,
In road, second means (14, 19) are pilot circuit leading from separately by providing a hydraulic pump (12) to one end of the LS valve (5) (1
The signal is connected to the electromagnetic proportional control valve (14) provided in 3) and the first means (18), and the first means (18)
When the information at the time of switching is received from the
(14) is given an exciting current that gradually increases at a predetermined speed, thereby
Increase gradually in the pilot circuit (13) as the exciting current gradually increases
That pilot hydraulic Pi (= 0~Pmax) Ru is generated controller (19) and load sensing hydraulic circuit, characterized in Rukoto to have a. 3. The load sensing hydraulic circuit according to claim 1 , wherein the second means (14, 19) comprises a predetermined speed different from each other.
A load sensing hydraulic circuit having a plurality of degrees that can be selected and used freely . 4. The load sensing hydraulic circuit according to claim 2,
On the road, the controller (19)
In addition to storing a plurality of degrees in advance,
Selectable reading speed from home and read speed
Switch (20) that gradually increases the exciting current
Load sensing hydraulic circuit you characterized by.