JPS5833401B2 - Hydraulic cylinder control device - Google Patents

Description

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

2. Description of the Related Art Conventionally, as an example of controlling a hydraulic actuator using an electromagnetic proportional valve, there is an aerial work vehicle as shown in FIG. 1, for example.

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.

Both hydraulic cylinders 5 or 6 are connected to a controller section 7 and a hydraulic valve 8 responsive to the controller section 7 as shown in FIG.
The expansion and contraction operation can be freely controlled by the control lever 9 via the control lever 9.

I'll explain this now.

The hydraulic valve 8 is composed of a switching valve 21 and a position limiter 49.

The controller section 7 proportionally increases or decreases the current flowing to the electromagnetic proportional solenoids 1o and ii provided in the position limiter 49 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 flowing to the electromagnetic proportional solenoid 10 gradually increases from zero in accordance with the tilt angle.

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 49 has a mutually symmetrical annular pressure chamber 14.15 partitioned by the double-acting piston 13 inside the double-acting cylinder 12, and both pressure chambers 14.1
5 has a pilot oil pressure supply passage 16, an orifice 17,
Pilot hydraulic pressure is introduced through steps 18 and the like.

and an outlet 14a of each pressure chamber 14,15.

The cross-sectional area of 15a is the electromagnetic proportional relenoid 10.1 described above.
It can be freely increased or decreased by vertical movement of each poppet 10a, 11a interlocked with 1.

For example, if a current flows through the electromagnetic proportional renoid 10, the popetsu N
When Oa moves upward, the cross-sectional area of the outlet 14a becomes relatively smaller than that of the outlet 15a, and a pressure difference is generated 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 forces of the springs 19 and 20 are balanced.

The amount of movement at this time, that is, the stroke amount of the double-acting piston 130 increases proportionally in accordance with the current flowing through the electromagnetic proportional solenoid 10.

Conversely, current flows through the electromagnetic proportional solenoid 11 and the poppet 1
When 1a 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, the plunger 21 of the switching valve 21 is connected to the double-acting piston 13 via a connecting rod 50 that moves integrally with the double-acting piston 13.
a is connected, and this switching valve 21 is connected to the double acting piston 13.
That is, depending on the amount of displacement of the plunger 21a, hydraulic oil is sent from the hydraulic pump (not shown) to the hydraulic cylinders 5 and 6, hydraulic oil is returned from the hydraulic cylinders 5 and 6 to the oil tank (not shown), and hydraulic oil is The quantitative ratio of the hydraulic oil that bypasses the hydraulic cylinder 5.6 from the pump and returns to the hydraulic tank is regulated.

As a result of such operation of the hydraulic valve 8, the hydraulic cylinders 5,
The flow rate of hydraulic oil in the extension direction to 6 increases, and conversely, the flow rate of hydraulic oil in the contraction direction increases in accordance with the current flowing through the electromagnetic solenoid 11.

On the other hand, since the stroke position of the hydraulic cylinders 5 and 60, that is, the elevation angle of the upper tower 3 (or lower tower 4), is adjusted by the amount of hydraulic oil supplied, for example, the control lever 9 is moved to the neutral position. When the current to the electromagnetic solenoid 10 is increased by tilting it to the right, the amount of hydraulic oil also increases, 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 mπ or more from the neutral position.

Therefore, even if the control lever 9 is tilted from the neutral position, the hydraulic cylinder 5.6 cannot extend or retract until the plunger 21a is displaced beyond the neutral dead zone.

Therefore, in order to narrow the range in which the control lever 9 is insensitive to the expansion and contraction movement of the hydraulic cylinder 5.6 that occurs in this way, that is, the amount of hydraulic oil supplied thereto, the displacement of the plunger 21a from the neutral position is First, by receiving this with a relatively weak spring 20, the plunger 21a is made to stroke quickly to the upper limit of its neutral dead zone A in response to the tilting movement of the control lever 9.

After the upper limit of the neutral dead zone A is exceeded, the plunger 21a is displaced by the spring 20 and the relatively strong spring 19, so that the hydraulic cylinder 5 is moved at an appropriate rate with respect to the tilting of the control lever 9. ，
The flow rate of hydraulic oil to 6 can be changed.

In order to obtain stability in the neutral position, an initial load of a predetermined magnitude is also given to the weak spring 19, and therefore, until the differential pressure due to the pilot oil moving to the double-acting piston 13 exceeds a predetermined value, The plunger 21a is designed to maintain a neutral position.

However, in the conventional device as described above, two springs 19°202 are required, especially in the hydraulic valve 8, so the structure becomes complicated, and the number of parts increases and the assembly process becomes complicated. In addition, the initial load to ensure stability in the neutral position is combined with the dead zone A of the plunger itself shown in Figure 3, and the control lever 9
The dead zone of the supply flow rate characteristics to the cylinders 5 and 6 with respect to the tilt angle is increased.

In other words, the dead band width corresponds to the sum of the dead band until the plunger starts to move due to the initial load and the dead band from when the plunger starts moving until the oil begins to flow, so the control lever must be adjusted until the supply flow rate is sufficient to accommodate this dead band. The tilt angle is extremely large.

The present invention has been made in view of the conventional situation, and the reduction of the dead band width of the control lever is realized by changing the response characteristics of the electromagnetic proportional solenoid to the tilting movement of the control lever in the controller section, thereby reducing the hydraulic pressure. We aim to provide a hydraulic cylinder control device for aerial work vehicles, etc. using an electromagnetic proportional valve, which has a valve structure that does not require a spring for reducing dead band width, reduces the number of parts, and simplifies the assembly process. purpose.

In the present invention, descriptions of the same parts as in FIGS. 1 to 3 will be omitted with reference to those figures, and the main parts of the controller section and position limiter section, which are different from the conventional device, will be explained in the fourth section.
and FIG. 5, respectively, and the following description will be made based on these.

In FIG. 4, 3L32 is a sliding resistor connected to a control lever, 33.34 is an amplifier circuit, and 10.11 is an electromagnetic proportional solenoid installed in a hydraulic valve similar to that in FIG.

The sliding resistors 31 and 32 are connected to the control lever so as to exhibit resistance changes independently of each other. For example, when the control lever is tilted to the right from the neutral position, the amplifier circuit 3
3, only the current flowing to the electromagnetic proportional solenoid 10 gradually increases from zero according to the tilt angle of the control lever.

Conversely, when tilting to the left from the neutral position, only the current flowing 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.

The sliding terminal voltage signal A of the sliding resistor 32, which changes proportionally according to the tilting angle of the control lever, is amplified by an amplifier 35 and a transistor 36, 37, and then supplied to the electromagnetic proportional solenoid 11 as a current signal. Ru.

At that time, in order to quickly stroke the plunger of the hydraulic valve to the upper limit of the neutral dead zone of the switching valve, in order to narrow the width of the dead zone of the control lever as described above.
After the tilt angle of the control lever reaches a predetermined value, i.e., beyond the intentional dead zone for safety, the control lever is , the comparator 38 supplies a predetermined additional voltage in addition to the voltage of the sliding resistor 32 to the amplifier 35, and compulsorily adds a predetermined current 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 VR- 1 to a predetermined value.

If it is necessary to provide a dead band width for the control lever in order to prevent valve operation due to careless contact, etc., you can freely adjust the width by increasing or decreasing the value of the reference voltage signal B via the variable resistor vR-2. It is possible to adjust its width.

Furthermore, if the neutral dead zone of the switching valve with respect to the stroke of the plunger is large, the added voltage may be correspondingly increased by the variable resistor VR3 to further increase the added current to the electromagnetic solenoid 11.

FIG. 7 shows a comparison diagram of the prior art and the present invention with respect to the output current of the controller section with respect to the tilting angle of the control lever.

In the conventional case, since the output current to the electromagnetic solenoid is linearly proportional to the control lever tilt angle from the beginning, the current value i until it passes the dead zone.

In order to obtain this, the tilting angle θ2 of the control lever required is considerably larger than the tilting angle θ1 of the present invention.

In the present invention, the predetermined current value i.

To obtain this, a predetermined current value can be added to the current corresponding to the control lever tilt angle using variable resistor ■R-3, so the angle range of the dead zone can be made as small as desired.In other words, From the viewpoint of safety and responsiveness, the angular range of the dead zone that is intentionally provided with respect to the total tilt angle of the control lever can be freely set, for example, to 10%.

Note that if the additional current is applied from the beginning when the control lever is in the neutral position, the hydraulic valve will start operating as soon as the control lever is tilted even slightly, which is not desirable from a safety point of view, so please take this into account. This provides an appropriate dead zone as described above.

According to such a controller section, the hydraulic valve is controlled by the fifth
As shown in the figure, it is now possible to create a structure that does not require a spring to reduce the width of the dead zone, which reduces the number of parts and simplifies the assembly process compared to the conventional method.At the same time, the control lever can be tilted. The width of the dead zone of the flow rate around the corner can be reduced.

Specifically, this position limiter 39 includes a single spring 44 on the outer periphery of a small diameter portion formed by a step portion 40 formed by coupling the flange 42 and the 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 the plunger 42 is moved from the neutral position to the left, for example. When displaced, the holder 45 is stopped by the stop surface 47, whereas the holder 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 is displaced from the neutral position to the right, the holder 46 is stopped by the stop surface 48, but the holder 45 is now displaced, so the spring 44 similarly contracts in proportion to the displacement force. It is.

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, and therefore the differential pressure of the pilot oil acting on the double-acting piston 13 is The plunger 42 stably maintains its neutral position until the initial load is exceeded.

However, when the control lever is tilted from the neutral position, as described above, by operating the additional voltage of the comparator 38, the plunger 42 quickly strokes to the upper limit of the neutral dead zone of the switching valve that regulates the flow rate to the hydraulic cylinder. Therefore, the dead zone of the flow rate supplied to the hydraulic cylinder of the control lever is within a range that is necessary for safety and does not impede operability.

For example, as shown in FIG. 6, in the present invention, the dead zone F1 at the oil amount change F in the hydraulic cylinder with respect to the tilting angle of the control lever is the same as the dead zone F1 at the oil amount change G when the above-mentioned addition voltage operation is not performed. It can be made smaller than the dead zone G1.

As explained above, in the present invention, the tilting of the control lever from the neutral position is corrected by adding the current supplied to the electromagnetic proportional solenoid installed in the hydraulic valve when the tilting angle is greater than or equal to a predetermined tilting angle. The plunger of the hydraulic valve can be quickly displaced up to the upper limit of the neutral dead zone of the hydraulic valve with respect to the amount of oil in the hydraulic cylinder without intervening a spring to reduce the dead zone, and the expansion and contraction operation of the hydraulic cylinder can be controlled. The dead zone of the lever can be reduced to a necessary and sufficient value.

Therefore, the structure of the hydraulic valve can be particularly simplified, and the number of parts can be reduced and the assembly process can be simplified compared to the conventional method.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the aerial work vehicle, Figure 2 is a sectional view of the main parts of the hydraulic valves etc. that control the hydraulic cylinders in Figure 1, and Figure 3 is a characteristic diagram showing the operation of the hydraulic valves in Figure 2. ,
Fig. 4 is a circuit diagram of the controller section in the device of the present invention, Fig. 5 is a sectional view of the main parts of the hydraulic valve, Fig. 6 is a characteristic diagram showing its operation, and Fig. 7 shows the combination of the control lever and the controller. FIG. 3... Upper tower, 4... Lower tower, 5, 6...
... Hydraulic cylinder, 1 ... Controller section, 8 ... Hydraulic valve, 9 ... Control lever, 10, 11 ... Electromagnetic solenoid,
10a, Ila...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...Comparator,
39...Hydraulic valve, 42...Plunger, 44...Spring, 49...
Position limiter, VR-1, VR-2, VR-3...
...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 electromagnetic channels 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 having a proportional solenoid and having a dead zone that adjusts the flow rate of hydraulic fluid to the hydraulic cylinder according to the displacement of the double-acting piston;
In a control device equipped with a controller unit that proportionally increases/decreases the drive current to both electromagnetic proportional solenoids by tilting the control lever, when the control lever is tilted from a neutral position at a tilt angle greater than or equal to a predetermined tilt angle, A hydraulic cylinder control device characterized in that a controller section includes a circuit that adds and corrects a predetermined current corresponding to a dead zone width of a hydraulic valve to both electromagnetic proportional solenoid drive currents.