JPH0456883B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a hydraulic actuator drive device for driving a hydraulic actuator provided in a hydraulic working machine or the like.

[Background of the invention]

2. Description of the Related Art Hydraulic working machines, such as hydraulic excavators, include a front mechanism driven by a plurality of hydraulic actuators, and the front mechanism is arbitrarily driven to perform a predetermined work. This will be explained using a diagram.

FIG. 10 is a side view of the schematic configuration of the hydraulic excavator. In the figure, 1 is the lower traveling body, 2 is the upper revolving body,
3 indicates the front mechanism. The front mechanism 3 includes a boom 4 rotatably supported by the upper revolving body 2, an arm 5 rotatably supported by the boom 4, and a bucket 6 rotatably supported by the arm 5. 7 is a boom cylinder that drives the boom 4; 8 is an arm cylinder that drives the arm 5; and 9 is a bucket cylinder that drives the bucket 6. The drive circuits for each of these hydraulic cylinders will be explained by exemplifying the drive circuit for the bucket cylinder 9.

FIG. 11 is a hydraulic circuit diagram of the bucket drive device. In the figure, 9 is the bucket cylinder shown in FIG. 10, 10 is the hydraulic pump, 11 is the directional control valve interposed between the hydraulic pump 10 and the bucket cylinder 9, and 11a and 11b are the pilot ports of the directional control valve 11. It is. 12 is a relief valve that defines the maximum value of the discharge pressure of the hydraulic pump 10, and 12a is a spring for setting the relief pressure.

13 is a control lever that is manually operated by the operator; 14 is a push part that is integrated with the control lever 13; and 15 is a control lever 13 and the push part 14.
A fulcrum that rotatably supports in the directions of arrows A and B, 1
6 is in contact with both ends of the push part 14 and the operating lever 13
This is a stopper that restricts the rotation of the Reference numeral 17 indicates a pilot hydraulic pressure source, and 18a and 18b indicate the pilot hydraulic pressure source 17 and each pilot port 11 of the directional control valve 11.
a pilot valve interposed between a and 11b, 19
a, 19b are the push part 14 and each pilot valve 18
The spring 20 is a tank mounted between the springs a and 18b.

Now, the hydraulic excavator operator is pressing control lever 1.
3 in the direction of arrow A, the pusher 14
rotates downward to deflect the spring 19a and generate the output oil pressure P _a of the pilot valve 18a. This pressure P _a is applied to the pilot port 1 of the directional valve 11.
1a, the directional control valve 11 is switched to the left position, and pressure oil from the hydraulic pump 10 is supplied to the rod side of the bucket cylinder 9. As a result, the bucket cylinder 9 is driven in the direction of retracting its rod. When the operating lever 13 is rotated in the direction of arrow B, the directional control valve is switched to the right position by the output oil pressure _Pb of the pilot valve 18b, and the bucket cylinder 9 is driven in the direction of extending the rod.

Here, the operating amount S of the operating lever 13, the pilot pressure P _a (P _b ) output from the pilot valve 18a
And the flow rate Q of the pressure oil supplied to the bucket cylinder 9 will be explained. Pilot valve 18a, 1
8b constitutes a kind of pressure reducing valve, and the spring 19a
When the spring flexes, pressure P _a is generated at the output port against the spring force, and as the spring force increases further,
The output port of the pilot valve 18a is connected to the pilot oil pressure source 17 (pressure P ₀ ) to increase the oil pressure P _a . Further, when the spring force of the spring 19a decreases from this state, the output port of the pilot valve 18a is connected to the tank 20, and the pressure P _a decreases. The spring force of the spring 19a is proportional to the amount of deflection thereof, and the amount of deflection is proportional to the amount of downward movement of the push portion 14, that is, the amount of operation S of the operating lever 13. Therefore, the pressure P _a (P _b ) at the output port of the pilot valves 18a, 18b is proportional to the operating amount S of the operating lever 13.

FIG. 12 is a characteristic diagram showing the relationship between the operating amount of the operating lever and the output port pressure of the pilot valve.
The horizontal axis is the manipulated variable S, and the vertical axis is the pressures P _a and P _b . The operating lever 13 has a slight play in both directions of arrows A and B around the neutral position, but when the operating lever 13 is operated beyond this play, the pressure increases in proportion to the amount of operation, and finally The maximum pressure (discharge pressure of the pilot hydraulic pressure source 17) reaches P ₀ . Further, even if the operating lever 13 is operated, the pressure remains constant at the value _P0 . When the manipulated variable reaches the value _S0 , the end of the pushing part 14 collides with the stopper 16 and stops. Therefore, the operation amount S of the operation lever 13 is -
The range is S ₀ <S < S ₀ .

Figure 13 is a characteristic diagram showing the relationship between the output pressure of the pilot valve and the flow rate of hydraulic pressure supplied to the bucket cylinder, with the output pressures P _a and P _b on the horizontal axis and the flow rate Q on the vertical axis. . Pilot valves 18a, 18b
When pressure P _a (P _b ) is generated at the output port of , the directional control valve 11 is switched to the left position. The directional control valve 11 has a structure that throttles a metering orifice in proportion to the pilot pressure P _a (P _b ) transmitted to the pilot ports 11a, 11b, and the flow from the hydraulic pump 10 passes through this throttled orifice. Hydraulic pressure is supplied to the bucket cylinder 9. and,
The supply flow rate begins to gradually increase when the pressure P _a reaches the value P _t , and at a pressure lower than the pressure P ₀ the orifice is fully opened and reaches the maximum flow rate Q ₀ .

FIG. 14 is a characteristic diagram showing the relationship between the operating amount of the operating lever and the supply flow rate to the bucket cylinder,
The manipulated variable S is plotted on the horizontal axis, and the flow rate Q is plotted on the vertical axis.
The characteristics shown in FIG. 14 are naturally obtained from the characteristics shown in FIGS. 12 and 13, and the maximum flow rate Q ₀ can be achieved with a manipulated variable smaller than the manipulated variable S ₀ at which the pushing portion 14 of the flow rate Q collides with the stopper 16. becomes. Since the flow rate Q of hydraulic pressure supplied to the bucket cylinder 9 is proportional to the driving speed of the bucket cylinder 9, after all,
By operating the operating lever, the operator of the hydraulic excavator can control the speed of the bucket cylinder according to the characteristics shown in FIG.

By the way, if the bucket 6 hits a hard rock during work, the pressure in the circuit will increase even if the operating amount is increased, and once it reaches the set pressure of the relief valve 12, the pressure will not increase beyond that, and the bucket 6 will stop working. Stop. Despite this, it is common for the operator to further operate the operating lever to set the operating amount to the maximum operating amount S ₀ and then apply force to the operating lever in order to move the operating lever. This is because although the drive control of the bucketed cylinder by the operation lever 13 is the speed control of the bucketed cylinder as described above, the operator intuitively perceives the drive control as controlling the force of the bucketed cylinder. Because there is. Such sensations not only naturally arise from natural sensations that match the sensations humans experience when moving an object, but also
This also occurs due to the following reasons.

That is, the operation of the operating lever 13 is performed by the springs 19a,
This is done against the spring force of 19b. This state is shown in FIG. In the figure, the horizontal axis shows the operating amount S, and the vertical axis shows the operating force f applied to the operating lever 13.
In other words, when the operator increases the operating amount S of the operating lever 13, an operating force f proportional to the amount S is required. It causes sensation.

The situation regarding such operational feeling is exactly the same not only when driving a bucket cylinder but also when driving a hydraulic actuator of a hydraulic excavator or other working machine. From this point of view, especially when the load is extremely large, the operation in the conventional hydraulic circuit shown in FIG. This has the disadvantage that it leads to deterioration of the process, which in turn leads to a decrease in work efficiency.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to eliminate the above-mentioned conventional drawbacks,
It is an object of the present invention to provide a hydraulic actuator drive device capable of driving a hydraulic actuator in accordance with an operator's operating feeling and improving operability.

[Summary of the invention]

In order to achieve the above object, the present invention includes a hydraulic actuator, a flow rate control mechanism that controls the drive flow rate of the hydraulic actuator, and an operating section that is operated by an operator to drive the flow rate control mechanism. a variable pressure setting mechanism that sets the maximum pressure of the hydraulic circuit including the hydraulic actuator and the flow rate control mechanism; and a variable pressure setting mechanism that sets the set pressure of the variable pressure setting mechanism when the operating force of the operating section exceeds a predetermined value. The present invention is characterized in that it includes a set pressure changing means for increasing the set pressure.

When the operating force applied to the operating section by the operator exceeds a predetermined value, the set pressure set in the variable pressure setting mechanism increases in accordance with the operating force. As a result, the driving force of the hydraulic actuator is increased, and it is possible to perform work that matches the operator's sense of operation.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a hydraulic circuit diagram of a bucket cylinder driving device according to an embodiment of the present invention. In the figure, the 11th
Components that are the same as those shown in the figures are given the same reference numerals and explanations will be omitted. 22 is a strain gauge attached to the side surface of the operating lever 13 (the side surface in the direction of arrow A), and when the operating amount S is S>0, the compressive stress is measured.
Further, when S<0, tensile stress is applied. When the strain gauge 22 receives compressive stress, its resistance becomes the value ΔR
(ΔR>0), and increases by the value ΔR (ΔR<0) when subjected to tensile stress. 23 is an electromagnetic relief valve provided in place of the relief valve 12 shown in FIG. The electromagnetic relief valve 23 has a proportional solenoid, and by supplying a current I to the proportional solenoid, an electromagnetic force (a force corresponding to the spring force of the spring 12a of the relief valve 12) proportional to the supplied current I is generated. As a result, the relief pressure _PR can be set in proportion to the supply current I. Since such electromagnetic relief valves are well known, detailed explanation will be omitted. A pressure setting section 24 supplies a current to the electromagnetic relief valve 23 to set a relief pressure based on the resistance value of the strain gauge 22. The configuration of this pressure setting section 24 is shown in the next figure.

FIG. 2 is a circuit diagram showing a specific example of the pressure setting section shown in FIG. 1. In the figure, 22 is the strain gauge shown in FIG. 1, 25 is a bridge circuit with the strain gauge 22 on one side, and 26a, 26b, and 26c are bridge circuits 2.
It is a resistance that constitutes many sides of 5. The resistance value of the strain gauge 22 is R ₀ when the strain gauge 22 is not receiving any stress, and the resistance value of the strain gauge 22 is R 0 when the strain gauge 22 is not receiving any stress.
The resistance values of b and 26c are selected to be the same value R ₀ as above. Among the connection points a to d of each resistor, a predetermined voltage V _S is applied between the connection points b and d, and the output signal ΔV of the bridge circuit 25 is applied between the connection points a and c.
is taken out. 27 is a differential amplifier that inputs the signal ΔV and outputs the signal V _A based on the signal; 28;
29 is a function generator having predetermined characteristics, and 30 is an amplifier.

Next, the operation of this embodiment will be explained with reference to the characteristic diagrams shown in FIGS. 3 to 9. First, each characteristic diagram will be explained. As mentioned earlier, the resistance value of the strain gauge 22 is a value ΔR proportional to the applied stress.
This change ΔR and the bridge circuit 25
The relationship between the output voltage (potential difference between connection points a and c) ΔV is expressed by the following equation.

ΔV=k・ΔR・V _S (k>0 proportional constant) Therefore, the output voltage ΔV is proportional to the operating force f applied to the operating lever 13, and the output of the differential amplifier 27
V _A is also proportional to the operating force f.

FIG. 3 is a characteristic diagram showing the relationship between the operating force and the output voltage of the differential amplifier, with the operating force f on the horizontal axis and the output voltage V _A on the vertical axis. When the operating lever 13 is operated until the pusher 14 comes into contact with the stopper (operating amount S ₀ ), the operating force becomes the value f ₀ as shown in FIG. _A0
is output. As shown, the voltage V _A is the operating force f
is proportional to.

FIG. 4 is a characteristic diagram of the function generator 28, in which the horizontal axis represents the output voltage V _A of the differential amplifier 27, and the vertical axis represents the output voltage V _B of the function generator 28. As is clear from the figure, the output voltage V _B of the function generator 28
is proportional to the absolute value of the input voltage V _A , and the voltage V _A0 , −
Outputs voltage V _B0 when V _A0 is input.

FIG. 5 is a characteristic diagram of the function generator 29, in which the horizontal axis represents the output voltage V _B of the function generator 28, and the vertical axis represents the output voltage V _C of the function generator 29. The output voltage V _C is constant at the value V _C0 until the input voltage V _B reaches a value V _B1 greater than the value V _B0 , and the input voltage V _B
From V _B1 to the value V _B2 , the value V _C0 is proportional to the input voltage V _B
The voltage V _C1 changes from V C1 to the value V C1, and when the input voltage V _B is equal to or higher than V _B2 , the value V _C1 remains constant. That is, function generator 2
8, the operating force f is a value _f1 slightly larger than the value _f0 .
A voltage proportional to this is output from ₂ to the value f2, and a constant value is output when the operating force f is greater than that.

FIG. 6 is a characteristic diagram showing the output characteristics of the amplifier (same as the output characteristics of the pressure setting section), where the horizontal axis represents the output voltage V _C of the function generator 29, and the vertical axis represents the output current I of the amplifier 30. It is attached. There is a proportional relationship between the output voltage V _C and the output current I, as shown in Figure 5.
Since the output voltage V _C of the function generator 29 changes between the value V _C0 and the value V _C1 , the output current I also changes between the proportional values I ₀ and I ₁ .

FIG. 7 is a characteristic diagram of the electromagnetic relief valve 23,
The horizontal axis shows the supply current I, and the vertical axis shows the electromagnetic relief valve 23.
The set pressure P _R is determined. The two are in a proportional relationship, and as mentioned above, since the current I changes between the values I ₀ and I ₁ , the set pressure P _R also has a proportional value P _R0 ,
P varies between _R1 .

FIG. 8 is an output characteristic diagram of the pressure setting section, in which the horizontal axis indicates the operating force f of the operating lever 13, and the vertical axis indicates the output current I of the pressure setting section 24 (output current of the amplifier 30). From the characteristic diagrams shown in Figs. 3 to 6, when the operating force is less than f ₁ , the output current is constant at the value I ₀ , when the operating force is above f ₂ , the output current is constant at the value I ₁ , and when the operating force is f ₁ , f ₂
It can be seen that the output current changes in proportion to this between.

FIG. 9 is a characteristic diagram showing the relationship between the operating force of the operating lever and the set pressure of the electromagnetic relief valve, with the operating force f on the horizontal axis and the set pressure P _R on the vertical axis. 7th
8 and the characteristic diagram shown in FIG. 8, the relationship between the operating force f and the set pressure P _R is similar to the relationship between the operating force f and the output current I of the pressure setting section 24 shown in FIG. 8. I understand that. That is, when the operating force is less than f ₁ , the set pressure P _R0 is constant, when the operating force is more than f ₂ , the set pressure P _R1 is constant, and between the operating forces f ₁ and f ₂ , the set pressure changes proportionally.

Here, when the operating force of the operating lever 13 is from 0 to f ₁ , the set pressure P _R0 of the electromagnetic relief valve 23 due to the output current I ₀ of the pressure setting unit 24 is the setting of the relief valve of the conventional device shown in FIG. It is determined to be equal to the pressure. Currently working on the hydraulic excavator, Bucket 6
Suppose the tip of the ball hits a solid rock. At this time, the operator operates the operating lever 13 until the pushing part 14 hits the stopper 16, based on the feeling of controlling the force described earlier, and also presses the pushing part 14 and the stopper 16.
Even after the lever 13 is engaged, force is further applied to the operating lever 13. In this case, the speed is controlled until the push part 14 of the operating lever 13 hits the stopper 16;
After that, further force is applied to the operating lever 13, and when the operating force exceeds the value f, the pressure setting section 2 responds accordingly.
The output current of 4 exceeds the value I ₀ and the solenoid relief valve 23
The set pressure exceeds the set pressure P _R0 under normal conditions.
Therefore, the pressure in the circuit increases, and the driving force of the bucket cylinder 9, which is represented by the product of flow rate and pressure, also increases, and the force with which the bucket 6 attempts to move the solid rock also increases. As a result, the control is a force control that matches the operator's sense, and operability (operational feeling)
becomes extremely better. If the rock does not move, if the operating force of the operating lever 13 by the operator increases,
The set pressure also increases in proportion to this, allowing greater force to be exerted. If the rock does not move even when the operating force reaches the value _f2 , even if the operator applies more force to the operating lever 13, the set pressure remains constant at the value P _R1 , protecting the components of the hydraulic circuit.

Here, the set pressure P _R1 is determined by the horsepower of the engine that drives the hydraulic pump 10, but since the normal set pressure P _R0 is set with a considerable margin for the output horsepower of the engine, Set pressure P _R1
can be set to a somewhat large value, and a correspondingly large force can be generated.

As described above, in this embodiment, the relief valve is equipped with an electromagnetic relief valve, the operating force applied to the operating lever is detected by a strain gauge, and current is supplied from the pressure setting section to the electromagnetic relief valve in response to this operating force. Since the hydraulic excavator operator is able to change the set pressure by using the hydraulic excavator, when a situation that requires a large amount of force occurs during work, the operator of the hydraulic excavator can perform an operation that is consistent with his/her operating feeling, improving operability and improving work efficiency. will improve. In addition, since the set pressure of the electromagnetic relief valve is changed only when force is applied to the operating lever after the pushing part of the operating lever contacts the stopper, the setting pressure of the electromagnetic relief valve is changed every time the pushing part of the operating lever touches the stopper. It is possible to prevent the set pressure from being changed and to prevent the operational feeling from being deteriorated due to frequent changes in the maximum pressure of the hydraulic circuit.

In addition, in the description of the above embodiment, the driving of a bucket cylinder of a hydraulic excavator was explained as an example.
It is obvious that it can be applied to various hydraulic actuators of various work machines.

Further, although the above embodiments have been explained by exemplifying a fixed pump, the present invention can of course also be applied to a variable displacement pump. In this case, the regulator that controls the tilting of the variable displacement pump receives the discharge pressure of the variable displacement pump as well as the pressure on the higher pressure side of the outputs of the two pilot valves to perform predetermined control. In the case of a variable displacement pump, since tilting control is performed, there is more leeway in setting the set pressure of the electromagnetic relief valve than in a fixed pump.

Furthermore, in the explanation of the above embodiment, an example was given in which the set pressure of the electromagnetic relief valve when the operating force is small is equal to the set pressure of the normal relief valve, but the set pressure of the normal relief valve is Since it is set to a fairly high value for the state,
Select the set pressure of the electromagnetic relief valve when the operating force is small to a value lower than the set pressure of the normal relief valve, and set the maximum set pressure of the electromagnetic relief valve to a value equal to the set pressure of the normal relief valve. You can also do that. In this case, an energy saving effect occurs.

Furthermore, in the explanation of the above embodiment, an example was explained in which a hydraulic pilot valve was used to detect the operating amount of the operating lever, but a potentiometer was used to detect the operating amount, and the directional control valve was operated based on this. It may also be controlled. Moreover, a variable discharge amount pump may be used as the flow rate control mechanism without using the directional switching valve.

〔Effect of the invention〕

As described above, in the present invention, the set pressure of the variable pressure setting mechanism is changed in accordance with the operating force of the operating section that operates the hydraulic actuator.
The hydraulic actuator can be driven in accordance with the operator's operating sense, and operability can be improved.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of a bucket cylinder drive device according to an embodiment of the present invention, FIG. 2 is a block diagram of a specific example of the pressure setting section shown in FIG. 1, and FIGS.
Figures 5 and 6 are characteristic diagrams of each circuit element shown in Figure 2, Figure 7 is a characteristic diagram of the electromagnetic relief valve shown in Figure 1, and Figures 8 and 9 are characteristic diagrams of each circuit element shown in Figure 1. The characteristic diagram of the output current of the pressure setting unit and the set pressure of the electromagnetic relief valve with respect to the operating force of the operating lever shown in the figure, Fig. 10 is a side view of the schematic configuration of a hydraulic excavator, and Fig. 11 is a conventional bucket cylinder drive device. Fig. 12 is the hydraulic circuit diagram of the pilot valve shown in Fig. 11, Fig. 13 is the output characteristic diagram of the pilot valve shown in Fig.
Figure 4 is an output characteristic diagram of the directional control valve shown in Figure 11;
FIG. 15 is an operation characteristic diagram of the operating lever shown in FIG. 11. 9...Bucket cylinder, 11...Directional switching valve, 13...Operation lever, 14...Pushing part, 16
... Stopper, 18a, 18b ... Pilot valve, 22 ... Strain gauge, 23 ... Electromagnetic relief valve, 24 ... Pressure control section.

Claims (1)

[Scope of Claims] 1. A device comprising a hydraulic actuator, a flow rate control mechanism that controls the drive flow rate of the hydraulic actuator, and an operating section that is operated by an operator to drive the flow rate control mechanism, wherein the hydraulic actuator and the flow rate control mechanism are operated by an operator. a variable pressure setting mechanism that sets the maximum pressure of a hydraulic circuit including a flow rate control mechanism; and a set pressure change that increases the set pressure of the variable pressure setting mechanism when the operating force of the operating section exceeds a predetermined value. A hydraulic actuator drive device comprising: means. 2. The hydraulic actuator drive device according to claim 1, wherein the variable pressure setting mechanism is an electromagnetic relief valve. 3. In claim 1, the set pressure changing means includes a strain gauge that generates a strain in accordance with the operating force when the operating section is further operated from the restriction position, and A hydraulic actuator drive device comprising: a pressure setting section that generates a signal to increase the set pressure of the variable pressure setting mechanism.