JPH0137603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic cylinder control device using an electromagnetic proportional valve.

(Prior Art) Conventionally, as an example of controlling a hydraulic actuator using an electromagnetic proportional valve, a control device for an aerial work vehicle as shown in FIG.
No. (Japanese Unexamined Patent Publication No. 56-097604).

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 controller 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.
It can be freely increased or decreased by the vertical movement of each poppet 10a, 11a in conjunction with 0, 11.

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.

(Problems to be Solved by the Invention) By the way, as shown in FIG. It has a dead zone A.

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, in order to ensure stability in the neutral position,
Between the plunger 21a and the double-acting piston 13,
A spring 44 is provided on the outer periphery of a small diameter portion formed by a step portion 40 formed by coupling the plunger 21a and a connecting rod 43 and a flange portion 41 of the connecting rod 43.

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 42 is displaced leftward from the neutral position, for example,
While the holder 45 is stopped by the stop surface 47, the holder 46 is displaced in conjunction with the flange portion 41, so that the spring 44 is compressed by an amount proportional to the displacement force.

Conversely, when the plunger is displaced from the neutral position to the right, the holder 46 is stopped by the stopper surface 48, but the holder 45 is now displaced, so the spring 44 is similarly proportional 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, 31, 32 are sliding resistors connected to the control lever 9, 33, 34
1 is an amplifier circuit, and 10 and 11 are electromagnetic proportional solenoids interposed in the hydraulic valve 8.

The sliding resistors 31 and 32 are connected to the control lever 9 so as to exhibit resistance changes independently of each other. For example, when the control lever 9 is tilted to the right from the neutral position, the tilting angle of the control lever 9 is changed by the amplifier circuit 33. Electromagnetic proportional solenoid 1 according to
Only the current to zero increases gradually 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 amplifier circuits 33 and 34 are constructed in exactly the same way, only the amplifier circuit 34 will be shown in detail in the drawings and will be specifically explained.

Sliding terminal voltage signal A of the sliding resistor 32 that changes proportionally according to the tilt angle of the control lever 9
is amplified by an amplifier 35 and transistors 36 and 37, and then sent to the electromagnetic proportional solenoid 1 as a current signal.
1.

At that time, use the control lever 9 as described above.
In order to quickly stroke the plunger 21a of the hydraulic valve 8 to the upper limit of the neutral dead zone of the switching valve 21 in order to narrow the dead zone width of the control lever 9, after the tilting angle of the control lever 9 reaches a predetermined value, the safe When the intentional dead zone is exceeded, the comparator 38 adds a predetermined additional voltage to the voltage from the sliding resistor 32 based on the magnitude relationship between the sliding terminal voltage signal A and the predetermined reference voltage signal B. The current is supplied to the amplifier 35, and a predetermined current is forcibly added to the current flowing to the electromagnetic proportional solenoid 11 for correction.

After the neutral dead zone is exceeded, the rate of change of the current supplied to the electromagnetic proportional solenoid 11 is controlled by a variable resistor for adjusting the amplification factor so that the plunger 21a strokes at an appropriate rate with respect to the tilting of the control lever 9. Set to a predetermined value using VR-1.

In addition, regarding the dead band width of the control lever 9 to prevent valve operation due to careless contact, etc., the reference voltage signal B is applied via the variable resistor VR-2.
By increasing or decreasing the value of , the width can be freely adjusted.

In addition, if the neutral dead zone of the switching valve 21 with respect to the stroke of the plunger 21a is large, the additional voltage is increased correspondingly by the variable resistor VR-3, and the additional current to the electromagnetic proportional solenoid 11 is further increased. do it. FIG. 5 shows the output current of the controller section 7 with respect to the tilt angle of the control lever 9.

As you can see from the diagram, the control lever 9
When the output current I passes through an intentional dead zone set for safety, the output current I rises rapidly, and when the plunger 21a is stroked to the upper limit of the neutral dead zone of the switching valve 21, the tilt angle of the control lever 9 is changed. The control current value is increased proportionally in response to the increase in valve 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 of the control lever 9 is reduced. By the way, focusing on the control range where the flow rate from the hydraulic valve 8 is maximum, the control current value I ₂ that provides the maximum flow rate changes due to machining errors of the valve components, so it is set large in advance ( I ₃ ) must;
This increases the dead zone width in the maximum flow rate range.

In other words, due to machining errors in the valve components, even when the control current value is I ₂ , the plunger may not stroke the specified amount and the maximum flow rate cannot be obtained. so that the maximum value _I3 can be obtained. In this case, the control lever range from the current value I ₂ to I ₃ becomes a so-called dead zone, which narrows the effective control angle range of the control lever accordingly, and as a result, the valve control accuracy for a unit tilt angle decreases. There were cases where the

The present invention aims to solve such conventional problems.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a passage provided with an orifice for introducing pilot oil into two pressure chambers partitioned by a double-acting piston, and a passage provided with an orifice for introducing pilot oil into two pressure chambers partitioned by a double-acting piston. 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 controller 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 increases the current to further move the hydraulic valve to its full stroke in the maximum tilt angle region.

(Function) Based on the above configuration, the drive current rises rapidly in the maximum tilt angle range of the control lever, so that the hydraulic valve reliably makes a full stroke in response to the control lever. In this case, even if the control range of the current value itself is the same as before, the dead zone will be reduced in the region where the control current value rises rapidly as described above, so the tilt angle of the control lever will be adjusted accordingly. In other words, the effective tilting angle of the control lever corresponding to the same current value control width is expanded compared to the conventional one.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As shown in FIG. 6, in the present invention, the sliding resistance 32 input to the amplifier 35 in the valve maximum flow region
The output value from the comparator 50 is combined with the output E from the comparator 50 to cause the solenoid excitation current I to rise rapidly in the maximum tilt angle range of the control lever 9.

The comparator 50 compares the output A of the sliding resistor 32 with the reference voltage signal D set via the variable resistor VR-4, and turns on when the set value is exceeded.

This voltage value is adjusted to a predetermined value E using a variable resistor VR- ₅ , and as shown in FIG. Add to input voltage A so that

With this configuration, until the tilting angle of the control lever 9 reaches the maximum tilting angle, only the output value C of the comparator 38 is added to the output A of the sliding resistor 32, as in the case of FIG. However, when the maximum tilting angle is reached and the comparator 50 is turned on, the output value E is added together with the output value C, so the output current I rises rapidly at that point, and the plunger 21a is instantaneously turned on. The current value I ₃ required to make a full stroke including the error can be obtained.

As a result, as shown in FIG.
As the output of the control lever 9, the control current I, which has a slope proportional to the combined value of the voltages A and C, must be increased in proportion to the angle of the control lever 9, exceeding _I2 and reaching _I3 .
In the present invention, the angle of the control lever 9 up to θ ₃ , which is even larger than θ ₂ , can be set as _an effective control angle. This allows the dead zone to be made that much narrower.

In this way, by reducing the dead zone between the neutral position and the maximum tilt angle of the control lever 9, the effective control angle range expands accordingly, which also makes it possible to improve the control accuracy of the unit lever tilt angle. becomes.

(Effects of the Invention) As described above, according to the present invention, it is possible to reliably fully stroke the plunger (hydraulic valve) at the maximum tilt angle of the control lever while reducing the dead zone in the vicinity. , control accuracy is also improved by expanding the effective tilt angle of the control lever.

[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 FIG. 5 is a diagram showing its operating characteristics. FIG. 6 is a circuit diagram of the controller section of the present invention, and FIG. 7 is a characteristic diagram showing the controller output current with respect to the tilting angle of the control lever. 3... Upper tower, 4... Lower tower, 5, 6... Hydraulic cylinder, 7... Controller section, 8... Hydraulic valve, 9... Control lever, 10, 11...
Electromagnetic proportional solenoid, 10a, 11a... poppet, 12... double acting cylinder, 13... double acting piston, 14, 15... pressure chamber, 14a, 15a...
Pressure chamber outlet, 16...Pilot oil pressure supply passage, 17, 18...Orifice, 21...Switching valve, 21a...Plunger, 31, 32...Sliding resistance, 33, 34...Amplification circuit, 35... ...Amplifier, 36, 37...Transistor, 38, 50...
...Comparator, 39...Position limiter,
VR-1, VR-2, VR-3, VR-4, VR-5
...variable resistance.

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 A hydraulic cylinder control device, characterized in that the controller section is equipped with a circuit that adds a current that rises in order to further stroke the hydraulic valve to a full stroke in the angle turning region.