JPH0346682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic cylinder control device using an electromagnetic proportional valve.

Conventionally, as a device for controlling a hydraulic actuator using an electromagnetic proportional valve, for example, a control device for an aerial work vehicle as shown in FIG.
- Proposed as No. 1223.

That is, it has an upper tower 3 and a lower tower 4, each of which has a workbench 2 for the worker 1 attached to its tip, and when these two towers are raised and lowered appropriately using hydraulic cylinders 5 and 6, the workbench 2 can be moved freely up and down.

Then, both hydraulic cylinders 5 or 6
The expansion and contraction operation thereof can be freely controlled by a control lever 9 via a controller section 7 and a hydraulic valve 8 responsive to the controller section 7 as shown in the figure.

To explain this now, the hydraulic valve 8 is
It is composed of a switching valve 21 and a position limiter 39. The controller section 7 proportionally increases or decreases the current to the electromagnetic proportional solenoids 10 and 11 provided in the position limiter 39 in accordance with the tilt angle of the control lever 9.

For example, when the control lever 9 is tilted to the right from the neutral position, the current to the electromagnetic proportional solenoid 10 gradually increases from zero according to the tilt angle, except for a dead zone described below. Conversely, when tilting to the left from the neutral position, the current to the electromagnetic proportional solenoid 11 gradually increases from zero.

On the other hand, the position limiter 39 is
2 has mutually symmetrical annular pressure chambers 14 and 15 partitioned by a double-acting piston 13, and both pressure chambers 14 and 15 are equipped with a pilot oil pressure supply passage 16, orifices 17 and 18, etc. Afterwards, pilot hydraulic pressure was introduced.

And the outlets 14a, 1 of each pressure chamber 14, 15
The cross-sectional area of 5a is that of the electromagnetic proportional solenoid 1 described above.
Each poppet 10a, 1 is interlocked with a solenoid plunger 10b, 11b which moves up and down by 0, 11.
It can be freely increased or decreased by vertical movement of 1a.

For example, when a current flows through the electromagnetic proportional solenoid 10 and the poppet 10a moves upward, the cross-sectional area of the outlet 14a becomes relatively smaller than that of the outlet 15a, creating a pressure difference between the pressure chambers 14 and 15.

As a result, the double-acting piston 13 moves rightward and stops at a position where this moving force and the elastic force of the spring 44 are balanced.

The amount of movement at this time, that is, the amount of stroke of the double-acting piston 13 increases in proportion to the current flowing through the electromagnetic proportional solenoid 10.

Conversely, when a current flows through the electromagnetic proportional solenoid 11 and the poppet 11a moves upward, the double-acting piston 13 moves to the left.

In this way, the double-acting piston 13 moves left and right with a stroke amount that corresponds to the current flowing through the electromagnetic proportional solenoids 10 and 11, that is, the tilt angle of the control lever 9.

Further, a plunger 21a of a switching valve 21 is connected to the double-acting piston 13 via a connecting rod 43 that moves integrally with the double-acting piston 13.
1 is a double-acting piston 13, that is, a plunger 21a
According to the amount of displacement of The quantitative ratio of the hydraulic oil that bypasses the hydraulic cylinders 5 and 6 and returns to the hydraulic tank is regulated.

As a result of such operation of the hydraulic valve 8, the flow rate of hydraulic oil in the extending direction to the hydraulic cylinders 5 and 6 increases depending on the current flowing through the electromagnetic proportional solenoid 10, and conversely, the flow rate of hydraulic oil in the extending direction increases depending on the current flowing through the electromagnetic proportional solenoid 11. Accordingly, the flow rate of hydraulic oil in the contraction direction increases.

On the other hand, the stroke positions of the hydraulic cylinders 5 and 6,
That is, since the elevation angle of the upper tower 3 (or lower tower 4) is adjusted by the amount of hydraulic oil supplied, for example, the current to the electromagnetic solenoid 10 can be changed by tilting the control lever 9 from the neutral position to the right. As the amount increases, the amount of hydraulic oil also increases, and the hydraulic cylinder 5,
6 extends, and the upper tower 3 (or lower tower 4) rises.

Conversely, if the control lever 9 is tilted to the left, the upper tower 3 (or lower tower 4) will fall.

By the way, as shown in FIG. 3, for example, the aforementioned switching valve 21 has a neutral dead zone A when the flow rate of the hydraulic oil to the hydraulic cylinders 5 and 6 changes with respect to the stroke of the plunger 21a from the neutral position.

That is, in this case, the switching valve 21 can change the flow rate of the hydraulic oil only after the plunger 21a has stroked approximately 2.5 mm or more from the neutral position.

Therefore, even if the control lever 9 is tilted from the neutral position, the hydraulic cylinders 5 and 6 cannot be extended or retracted until the plunger 21a is displaced beyond the neutral dead zone.

Therefore, it is necessary to narrow the width of the dead band of the control lever 9 more than necessary for the expansion and contraction of the hydraulic cylinders 5 and 6 that occurs in this way, that is, the amount of hydraulic oil supplied to the hydraulic cylinders, and to improve the stability in the neutral position. In order to ensure this, there is a stepped portion 4 between the plunger 21a and the double-acting piston 13, which is formed by coupling the plunger 21a and the connecting rod 43.
0 and the flange portion 41 of the connecting rod 43
A spring 4 is attached to the outer periphery of the small diameter portion formed by
It is equipped with 4.

The spring 44 is held between stepped cylindrical holders 45 and 46 that are slidably fitted to the stepped portion 40 and the flange portion 41, and when the plunger 21a is displaced leftward from the neutral position, for example, While the holder 45 is stopped by the stop surface 47, the boulder 46 is displaced in conjunction with the flange portion 41, so the spring 44 is compressed by an amount proportional to the displacement force.

Conversely, when the plunger 21a is displaced rightward from the neutral position, the holder 46 is stopped by the stop surface 48, but the holder 45 is now displaced, so the spring 44 is similarly activated in proportion to the displacement force. It shrinks.

At this time, in order to obtain stability in the neutral position, the spring 44 is held between the holders 45 and 46 with a predetermined initial load, so that the pilot oil acting on the double-acting piston 13 is reduced. Plunger 42 stably holds its neutral position until the differential pressure exceeds this initial load.

However, the dead zone width corresponds to the sum of the dead zone until the plunger 21a starts to move due to the initial load and the dead zone until the oil starts to flow after it starts moving, so it may become too large than necessary.
Therefore, in order to reduce the width of the dead zone of the control lever, the responsive characteristics of the electromagnetic proportional solenoids 10 and 11 to the tilting movement of the control lever 9 are changed in the controller section 7 as shown in FIG.

That is, in FIG. 4, 50 and 51 are potentiometers (sliding resistance) connected to the control lever 9, 7A and 7B are controller parts, 10,
11 is an electromagnetic proportional solenoid installed in the hydraulic valve 8.

The potentiometers 50 and 51 are connected to the control lever 9 so as to show resistance changes independently of each other. For example, when the control lever 9 is tilted to the right from the neutral position, the controller section 7A controls the tilt angle of the control lever 9. Accordingly, only the current to the electromagnetic proportional solenoid 10 gradually increases from zero.

Conversely, when tilting to the left from the neutral position, only the current to the electromagnetic proportional solenoid 11 gradually increases from zero.

Since the controller sections 7A and 7B are constructed in exactly the same way, only the controller section 7B will be shown in detail in the drawings and will be specifically explained.

Comparators 56 to 58 are turned on when the output of the potentiometer 51 via the buffer circuit 54 changes from 0, making the analog switch 55 conductive.

The comparator 57 turns on when the potentiometer output exceeds the neutral dead band, turns on the analog switch 61, and inputs the output of the current I ₁ setting device 59 to the adder circuit 63.

Comparator 58 is turned on, for example, by the same setting value as comparator 56 , turns on analog switch 62 , and synthesizes the dither signal from oscillation circuit 60 into adder circuit 63 .

The adder circuit 63 adds the above-mentioned additional current _I1 to the potentiometer output via the buffer circuit 54, corrects it so that a rise after the neutral dead zone is obtained, powers it up with an amplifier 64, and further adds power transistor etc. A drive circuit 6 consisting of
Enter 5.

Therefore, the drive circuit 65 outputs a drive current corresponding to the operation amount of the control lever 9 plus a correction value to the electromagnetic proportional solenoid 11 .

Therefore, FIG. 5 shows the output current of the controller section 7 with respect to the tilt angle of the control lever 9. However, the dither signal is omitted.

As you can see from the diagram, the control lever 9
After passing the intentional dead zone A provided for safety, the output current I suddenly rises to _I1 , and this causes the plunger 21a to be stroked to the upper limit of the neutral dead zone of the switching valve 21. From then on, the control lever 9 The control current value is increased proportionally according to the tilting angle of the valve, thereby increasing the pulp flow rate.

In this way, the characteristics of the output current with respect to the input voltage (control lever tilting angle) are controlled, and as a result, the neutral dead zone A of the control lever 9 is reduced.

By the way, if we focus on the control range where the output amount from the hydraulic valve 8 is maximum, the control current value I ₃ that provides the maximum flow rate will change due to machining errors of the valve components, so it should be set large in advance to account for the variation. This increases the required dead zone width in the maximum flow rate range.

In other words, due to machining errors in valve components, even when the control current value is I _{3 ,} the plunger may not stroke the specified amount and the maximum flow rate cannot be obtained. When I ₄ (I ₄ >I ₃ ) is set, the increase rate of the output current becomes large in a normal valve as shown in FIG. 5A. For this reason, _the rate of increase in the flow rate from the hydraulic valve ₈ also changes from _the solid line in _FIG . becomes.

This means that the dead zone given between the lever amount and the large tilting angle θmax expands from B to C, thereby narrowing the range of effective control angle of the control lever, and as a result, the unit tilting angle The accuracy of valve control for angles was reduced.

In order to solve this problem, the present invention suddenly increases the input voltage near the maximum tilt angle of the control lever to obtain the output current necessary for a full valve stroke, thereby reducing the dead band. It is an object of the present invention to provide a hydraulic cylinder control device that achieves reduction and concomitant improvement in control accuracy.

In order to achieve the above object, the present invention provides a passageway equipped with an orifice for introducing pilot oil into two pressure chambers partitioned by a double-acting piston, and increases or decreases the cross-sectional area of the outlet of pilot oil from both pressure chambers. It has two electromagnetic proportional solenoids that displace the double-acting piston, and a hydraulic valve that has a dead band that adjusts the flow rate of hydraulic oil to the hydraulic cylinder according to the displacement of the double-acting piston. In a control device equipped with a controller unit that controls the increase/decrease of the drive current to the proportional solenoid, the drive current for both electromagnetic proportional solenoids is adjusted to the dead band width of the hydraulic valve over a predetermined range with respect to tilting of the control lever from the neutral position. A circuit that adds and corrects the current according to the maximum tilt angle range, a circuit that adds a rising current to further stroke the hydraulic valve to full stroke in the maximum tilt angle range, and an increase rate of output current after a predetermined tilt angle in the effective control angle range of the control lever. The controller section is equipped with a circuit that changes the

Therefore, in the present invention, the current increases rapidly near the maximum tilt angle of the control lever to ensure that the hydraulic valve (its plunger) is fully stroked. This reduces the dead zone near the maximum tilt angle. In addition, since the rate of increase in the output current is changed at a predetermined tilting angle in the effective control angle range of the control lever, the rate of increase in the flow rate relative to the tilting angle of the control lever is small in the region where the rate of increase is small. , accurate flow control is possible.

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 6, the comparator 73 turns on when the potentiometer output reaches around the maximum lever tilt angle, turns on the analog switch 75, and adds the output of the current I ₂ setting device 70 to the adding circuit 63. input.

Since the other parts are the same as those in FIG. 4, the same parts are given the same reference numerals and the explanation will be omitted.

Note that this example uses the controller section 7 in FIG.
Since A and 7B have exactly the same configuration, one of them is used in common to simplify the circuit.

That is, 70 is a potentiometer that is linked to the control lever 9, and the potentiometer slider is set to be at the neutral origin when the lever is at its neutral point, so that the lever 9 can be tilted in either direction. also outputs an output proportional to the angle.

Reference numeral 71 denotes a direction discrimination circuit that compares the output of the potentiometer 70 with a reference voltage at a neutral point to discriminate the left/right operation direction of the control lever 9. Based on the discrimination result, a solenoid selection circuit (relay) 76, which will be described later, is switched. , a control current from the drive circuit 65 is supplied to the electromagnetic proportional solenoid 10 or 11.

72 is an absolute value circuit, which generates an absolute output depending only on the angle (deviation) of the output of the potentiometer 70 inputted through the buffer circuit 54 even if the output is switched in any direction from the neutral point. do.

The adder circuit 63 adds the above-mentioned additional currents I ₁ and I ₂ to the potentiometer absolute output from the absolute value circuit 72 and corrects it so that a rise after the neutral dead zone or a rise near the maximum tilt angle is obtained. , this is powered up by an amplifier 64 and further inputted to a drive circuit 65 composed of power transistors and the like.

Therefore, regardless of the direction in which the control lever 9 is operated, the output of the drive circuit 65 will be the one corresponding only to the amount of operation plus a correction value.

This output determines which electromagnetic proportional solenoid 1
The selection circuit 76 selects whether to drive 0 or 11.

The selection circuit 76 is switched by the output of the direction determination circuit 71 which determines the direction in which the control lever 9 is tilted, and thereby a drive current is supplied to either the electromagnetic proportional solenoid 10 or 11.

Therefore, only one drive current controller is required, and the circuit is simplified.

With the above configuration, until the tilting angle of the control lever 9 reaches θ ₂ before the maximum tilting angle θmax, the potentiometer output is set to the I ₁ setting device 59, as in the case of FIG. Only the output current value I ₁ is added, but when the comparator 73 is turned on when it reaches θ ₂ before the maximum tilt angle θmax, the output current is sufficiently large compared to the above output current value I ₁ . Since the value I ₂ is also added, the output current I rises rapidly at that point, and the current value I ₂ necessary to instantaneously make the plunger 21a fully stroke including the error is obtained.

As a result, as shown by the broken line in _{FIG .} Since the output current had to be increased proportionally up to _I4 , the angle of the control lever 9 had to exist as a dead zone when the angle was above a predetermined value _θ3.However , in the present invention, the angle of the control lever 9 can be maintained as an effective control angle up to θ ₂ , which is even larger than θ _3. In other words, the dead zone can be made that much narrower.

In this way, by reducing the dead zone near the neutral position and maximum tilting angle of the control lever 9, the effective control angle range expands by that amount, thereby improving the control accuracy of the unit lever tilting angle. It becomes possible.

By the way, in the effective control angle range of the control lever 9, since the rate of increase in the output current I with respect to the lever tilting angle is constant, the rate of increase in the flow rate with respect to the lever tilting angle is also constant.

In this case, the rate of increase in the flow rate determines the moving speed of the work platform 2 on which the worker 1 stands, and if the tilting operation is performed by an inexperienced operator, the initial movement speed will be too fast and the work platform workers may feel a sense of fear.

In other words, since speed control at startup requires fine operations, it is necessary to become proficient in the operations.

Therefore, in order to easily perform fine operations without having to become familiar with the operation, a circuit is provided in which the increase rate of the output current value is changed after the control lever 9 reaches a predetermined tilt angle within the effective control angle range, as shown in FIG. and is provided between the analog switch 55 and the adder circuit 63.

This circuit is composed of variable resistors 80 and 82 and a level shifter 81. The level shifter 81 and the variable resistor 82 are connected in series, and the variable resistor 80 is connected in parallel.

Variable resistors 80 and 82 control the increase rate of output current I
G ₁ , G ₂ (Specifically, G ₁ and G ₂ are the ratio of the output current value I and the input voltage V, but since the input voltage V corresponds to the lever tilting angle, here the output current I and the lever (described as a ratio of tilt angles) are each set to a predetermined value.

The level shifter 81 becomes conductive when a potentiometer output corresponding to a predetermined lever tilt angle θ ₄ (θ ₁ <θ ₄ <θ ₂ ) within the effective control angle range is reached.

Note that _θ4 is set within a range of 50 to 70% of the maximum tilt angle θmax of the control lever 9, and in this example, θmax is set to 30°, and 20°, which is two-thirds of that, is set as _θ4 . .

Therefore, as shown in FIG. 7A, the output current I increases at an increasing rate G 1 by the variable resistor 80 up to θ ₄ , and after θ ₄ , the output current I increases by the increase rate G ₁ +G with the addition of G ₂ by the variable resistor ₈₂ . Increase by ₂ .

Therefore, the flow rate is as shown in Figure 7B.
With Qa set to Sakai, the increase rate changes from small to large, and Qa
is set within the range of 25-55% of the total flow rate, and in this example is set to 50%.

In other words, when the lever tilt angle is θ ₄ or less, the rate of increase in flow rate is set smaller than before, and in this range the movement speed of the workbench is slow, making it easy to control the speed at startup. .

In this example, the range in which the increase rate of the flow rate is set to be small is from θ ₁ to θ ₄ , but the setting range can be freely set as long as the lever tilt angle is between θ ₁ and θ ₂ .

As described above, according to the present invention, it is possible to reliably fully stroke the plunger (hydraulic valve) near the maximum tilt angle of the control lever while reducing the dead zone in the vicinity, and as a result, the dead zone of the control lever can be reduced. Control accuracy is also improved by expanding the effective tilt angle. Furthermore, since the movement speed of the workbench can be set small within a predetermined range of the effective tilting angle of the lever, it is also possible to obtain the effect of improving operability within this range.

Additional Relationship The present invention is disclosed in Japanese Patent Application No. 56-58021 (Patent No. 1551800).
(Japanese Patent Publication No. 01-37603), its components are ``a passage provided with an orifice for introducing pilot oil into two pressure chambers partitioned by a double-acting piston, and a A hydraulic valve has two electromagnetic proportional solenoids that displace a double-acting piston by increasing or decreasing the exit cross-sectional area of pilot oil, and has a dead zone that adjusts the flow rate of hydraulic oil to a hydraulic cylinder according to the displacement of the double-acting piston. In a control device equipped with a controller unit that increases or decreases the drive current to both electromagnetic proportional solenoids by tilting the control lever, the electromagnetic proportional solenoids increase or decrease over a predetermined range with respect to the tilting of the control lever from the neutral position. The main part of the invention is that the controller section is equipped with a circuit that adds and corrects the drive current according to the width of the dead zone of the hydraulic valve, and a circuit that adds a current that rises to further stroke the hydraulic valve in the maximum tilt angle region. In addition, it is an invention that achieves the same purpose as this, and satisfies the requirements for an additional patent as stipulated in Article 31, Item 1 of the Patent Law.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the aerial work vehicle, FIG. 2 is a sectional view of the main part of the hydraulic valve that controls the hydraulic cylinder in FIG. 1, and FIG. 3 is a characteristic diagram showing the operation of the hydraulic valve in FIG. 2. FIG. 4 is a circuit diagram of a controller section that controls this hydraulic valve, and FIGS. 5A and 5B are characteristic diagrams showing its output current and the flow rate of hydraulic oil to the hydraulic cylinder, respectively. FIG. 6 is a circuit diagram of the controller section of the present invention, and FIGS. 7A and 7B are characteristic diagrams showing the output current and the flow rate of hydraulic oil to the hydraulic cylinder with respect to the tilting angle of the control lever, respectively. 3... Upper tower, 4... Lower tower, 5, 6... Hydraulic cylinder, 7, 7A, 7B... Controller section, 8...
...Hydraulic valve, 9...Control lever, 1
0, 11...Electromagnetic proportional solenoid, 10a, 11
a...Poppet, 12...Double acting cylinder, 13...
...Double acting piston, 14, 15...Pressure chamber, 14
a, 15a... Pressure chamber outlet, 16... Pilot hydraulic pressure supply passage, 17, 18... Orifice, 2
1...Switching valve, 21a...Plunger, 39...
Position limiter, 50, 51, 70... Potentiometer, 55, 61, 75... Analog switch, 56, 57, 73... Comparator, 59... I ₁
Setting device, 63...Addition circuit, 64...Amplification circuit,
65...Drive circuit, 80, 82...Variable resistor, 8
1...Level shifter.

Claims (1)

[Claims] 1. A passage equipped with an orifice that introduces pilot oil into two pressure chambers partitioned by a double-acting piston, and two electromagnets that displace the double-acting piston by increasing or decreasing the exit cross-sectional area of the pilot oil from both pressure chambers. A hydraulic valve with a proportional solenoid and a dead band that adjusts the flow of hydraulic oil to the hydraulic cylinder according to the displacement of the double-acting piston, and a control lever that increases or decreases the drive current to both electromagnetic proportional solenoids by tilting the control lever. A control device equipped with a controller unit includes a circuit that adds and corrects both electromagnetic proportional solenoid drive currents according to a dead band width of a hydraulic valve over a predetermined range with respect to tilting of a control lever from a neutral position, and The controller is equipped with a circuit that adds a rising current to further stroke the hydraulic valve to full stroke in the angle rotation range, and a circuit that changes the increase rate of the output current at a predetermined tilt angle in the control lever's effective control angle range. A hydraulic cylinder control device characterized by: