JPS63219902A - Control device for hydraulic actuator - Google Patents

Abstract

PURPOSE:To prevent any faulty speed control that may occur in a crawling range due to a variation in a pump discharge by determining the pump discharge through an engine rotational speed, and controlling a duty-ratio depending on the engine rotational speed. CONSTITUTION:A control range setting unit 21 optionally setting the speed control range of a lift cylinder 1 is provided, an output signal from the control range setting unit 21 is inputted into a determining unit 22 provided with a signal inputted from a position detecting unit 23, and an output signal from the determining unit 22 and a signal from a rotational speed detecting unit 25 for detecting the rotational speed of an engine E are inputted into a calculating unit 24. This constitution enables a duty-ratio to be controlled depending on an engine rotational speed proportional to a pump discharge, and thus variation in the pump discharge has no effect on its speed control.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device most suitable for controlling the operating speed of a lift cylinder of an agricultural tractor, for example.

(Prior Art) For example, the conventional agricultural tractor n shown in FIG.
The operating speed of the lift arm for raising and lowering the implement i was configured to be controlled by a control device shown in FIG.

FIG. 4 is a hydraulic circuit diagram for controlling a single-acting lift cylinder 1 used in an agricultural tractor. A pressure chamber 1a of the lift cylinder 1 is connected to a pump P via a supply passage 2. As shown in FIG. This supply passage 2 is provided with a check valve 3 that allows flow only from the pump P to the lift cylinder I.

Note that the pump P is connected to the engine E of the tractor n.
The amount of discharge changes depending on the rotational speed.

The supply passage 2 on the upstream side of the check valve 3 is connected to a branch passage 4 connected to the tank T.
This branch passage 4 is provided with an o-F/<lub 5. In addition, the branch passage 4 on the upstream side of the unload valve 5 includes a pilot passage 6 that communicates with one pilot chamber 5a of the unload valve 5, and a bypass that communicates with the first electromagnetic on/off valve 7 of the normal oven. It is connected to passage 8. A pilot passage 9 communicating with the other pilot chamber 5b of the unload valve 5 is connected to this bypass passage 8, and an orifice 10 is provided upstream of the connection point.

Now, when the first electromagnetic on/off valve 7 is maintained at the normal position shown in the figure, the oil discharged from the pump P flows from the bypass passage 8 to the tank T via the first electromagnetic on/off valve 7. At this time, a pressure difference is generated before and after the orifice IO, and the high pressure on the upstream side acts on one pilot chamber 5a, and the low pressure on the downstream side acts on the other pilot chamber 5b. Therefore, the unload valve 5 switches against the spring and maintains the open position shown in FIG. 1, thereby unloading the oil discharged from the pump P.

In the above state, when an on-off signal maintaining a predetermined duty ratio is input to the first TrL magnetic on/off valve 7, the signal passes through the first TrL magnetic on/off valve 7 according to the average on time. Flow rate is controlled. That is, the flow rate flowing into the pilot passage 8 is controlled by the first electromagnetic on/off valve 7, and the differential pressure across the orifice 10 changes depending on the controlled flow rate. The flow rate to be unloaded from the unload valve 5 is determined according to the change in this differential pressure. Then, the flow rate other than the unloaded flow rate and the flow rate flowing out from the first electromagnetic on/off valve 7 is supplied to the lift cylinder 1 via the check valve 3. Therefore, the duty ratio of the signal input to the first electromagnetic on/off valve 7 determines the unloaded flow rate, and the remaining amount of the total discharge amount of the pump P excluding the unloaded flow rate. A flow rate will be supplied to the lift cylinder 1. In other words, the lift cylinder l
As the duty ratio approaches 10 oz, the relative opening of the first electromagnetic on/off valve 7 becomes smaller. Once the first electromagnetic on/off valve 7 is closed, the unload valve 5 is also closed, so the flow rate supplied to the lift cylinder 1 increases, and the operating speed increases accordingly.

Conversely, the smaller the above duty ratio, the lower the first
The relative opening degree of the electromagnetic on/off valve 7 increases. Therefore, the degree of opening of the unload valve 5 also increases, and the flow rate to be unloaded increases accordingly. As the unloaded flow rate increases, the flow rate supplied to the lift cylinder l decreases, and its operating speed becomes slower.

However, unlike the case shown in FIG. 4, if the first electromagnetic on/off valve 7 is normally closed, the relationship between the duty ratio and its opening degree will be reversed.

Further, in the supply passage 2, a branch passage 11 connected to the tank T is also connected to the downstream side of the check valve 3, and this branch passage 11 is provided with a hold valve 12. This hold valve 12 blocks the flow from the pressure chamber 1a of the lift cylinder 1 to the tank T when it is in the normal position shown.

Hold the lift cylinder l at the current position. Furthermore, a pilot passage 13 communicating with one of the pilot chambers 12a of the hold valve 12 is connected to the branch passage 11, and a normally closed second electromagnetic on/off valve is connected to the branch passage 11.
A bypass passage 15 communicating with the off valve 14 is connected. A pilot passage 16 communicating with the other pilot chamber 12b of the hold valve 12 is connected to this bypass passage 15, and an orifice 17 is provided upstream of the connection point.

Now, if the second electromagnetic on/off valve 14 maintains the normal position shown in the figure, no flow will occur in the bypass passage 15, so no differential pressure will occur before and after the orifice 17, and both pilots of the hold valve 12 will The pilot pressures acting on each of the chambers 12a and 12b become equal, and the hold valve 12 is held at the normal position shown in the figure by the action of the spring.

In the above state, when an on/off signal maintaining a predetermined duty ratio is input to the second electromagnetic on/off valve 14,
Depending on its average on time, the second? l! The flow rate through the magnetic on-off valve 14 is controlled. When the flow rate flowing into the pilot passage 15 is controlled by the second electromagnetic on-Φoff valve 14 in this manner, the differential pressure before and after the orifice 17 changes depending on the controlled flow rate.

The flow rate to be unloaded from the hold pulp 12 is determined according to the change in this differential pressure. Therefore, the flow rate flowing out from the pressure chamber 1a is controlled according to the duty ratio, which is the average on time of the second electromagnetic on-off valve 14, but when the lift cylinder 1 is lowered, the duty ratio is The closer it gets to 100%, the faster the rate of decline becomes.

However, in this case, if the second electromagnetic on/off valve is used as a normal oven, the relationship between its opening degree and duty ratio will be opposite to that described above.

When stopping the lift cylinder 1, it is necessary to decelerate near the stop position to alleviate the shock.In particular, the site side demands that the lift cylinder 1 be moved at high speed to the target position. However,
In this case, the shock mitigation near the stop position is
It becomes a big problem.

Therefore, in this conventional device, the stop position of the lift cylinder 1 is set, and when the lift cylinder 1 reaches the vicinity of the stop position, it is turned on.
The duty ratio of the off signal is set to a certain constant value to reduce the speed of the lift cylinder I. In other words, the duty ratio in the vicinity of the stop position is fixedly determined, and when the lift cylinder reaches the vicinity of the stop position, the operating speed corresponding to the duty ratio is maintained.

(Problems to be Solved by the Invention) However, if the duty ratio at the position where slow speed control is required is fixed, there is a problem that the speed control in the slow speed range will be disrupted due to changes in the pump discharge amount. .

An object of the present invention is to provide an apparatus that controls the duty ratio in the slow speed range in accordance with the engine rotation speed and eliminates the above-mentioned conventional problems.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an electromagnetic on-
A control device that controls the speed of a hydraulic actuator according to a duty ratio of a signal input to an off valve, comprising: a position detection unit that detects the current position of the hydraulic actuator; and a control area that sets a speed control area of the hydraulic actuator. A setting section, a rotation speed detection section that detects the rotation speed of the engine that is the driving source of the pump, and a comparison between the output signal of the position detection section and the output signal of the control range setting section to determine whether the actuator is in the control range. and a calculation unit that calculates the duty ratio of the on/off signal to be output to the electromagnetic on/off valve when the hydraulic actuator is in the control range, depending on the engine rotation speed. I have to.

(Action of the present invention) The present invention determines the pump discharge amount based on the engine rotation speed, and determines the duty ratio according to the discharge amount, that is, the engine rotation speed.

(Effects of the present invention) As described above, the duty ratio can be controlled according to the engine speed, which is proportional to the pump discharge amount, so even if the condition of the pump discharge amount changes, the speed control will not be affected. .

(Embodiment of the present invention) The first embodiment shown in FIG. 1.2 controls the lift cylinder l shown in FIG. is used to control the rising speed of the lift cylinder l. Its hydraulic circuit is the same as before. Therefore, for the description of this hydraulic circuit, the conventional description will be used as is.

In this embodiment, a control range setting section 21 is provided to arbitrarily set the speed control range of the lift cylinder 1 as a hydraulic actuator, and an output signal of this setting section 21 is input to a determination section 22. . Furthermore, in addition to the signal from the setting section 21, a signal from a position detection section 23 that detects the position of the lift cylinder 1 is also input to the determination section 22.

The determination unit 22 determines whether the current position of the lift cylinder 1 is within an arbitrarily set speed control range.

The output signal of the determination section 22 is input to the calculation section 24, and a signal from a rotation speed detection section 25 that detects the rotation speed of the engine E is also input to the calculation section 24. and,
The calculation result of the calculation section 24 is input to the oscillation section 26, and the lift cylinder 1 is controlled according to the duty ratio of the on/off signal output from the oscillation section 2B.

The manner of control under the above configuration will be explained based on the flowchart shown in FIG.

First, in step 1, a target stop position of the lift cylinder 1 is determined, a control range is determined based on the target stop position, and the control range is input to the control range setting section 21.

Further, in step 2, the current position of the lift cylinder I is detected by the position detecting section 23, and the position signal detected by the current position detecting section 23 is input to the determining section 22.

In step 3, the determination unit 22 determines whether the position signal of the lift cylinder 1 detected by the 1-position detection unit 23 is within the control range input to the control range setting unit 21. If the lift cylinder 1 has not reached the control range, the process moves to step 4, where the duty ratio of the on/off signal to the electromagnetic on-off valve 7 is set at 100 $, and continuous energization is repeated.

Contrary to the above, if the lift cylinder 1 has reached the control range, a signal to that effect is input to the calculation section 24, and the process moves to step 5, where the rotation speed of the engine E is detected by the rotation speed detection section 25. The detection signal is input to the calculation section 24.

Then, in step 6, it is determined whether the duty ratio A of the on/off signal output to the electromagnetic on-off valve 7 is appropriate under the rotational speed of the engine E, and if it is appropriate, the process proceeds to step 7. The oscillator 26 is operated according to the output signal of the duty ratio A, and the operating speed of the electromagnetic on/off valve 7 is controlled.

If it is determined that the duty ratio A is not appropriate compared to the rotation speed of the engine E, the process moves to step 8, and it is determined whether the duty ratio B is appropriate according to the rotation speed of the engine E. If it is appropriate, the process moves to step 9, where the oscillation section 2B is operated in accordance with the output signal of the duty ratio B, and the operating speed of the electromagnetic on/off valve 7 is controlled. If it is determined that the duty ratio B is not appropriate compared to the rotational speed of the engine E, the process proceeds to step 10, where a signal of the duty ratio C is output, and the oscillation section 26 is operated in accordance with the signal, and the electromagnetic Controls the operating speed of the on-off valve 7.

In any case, according to the control device of this embodiment, the duty ratio of the electromagnetic on/off valve 7 can be controlled according to the rotational speed of the engine E, that is, the change in the discharge amount of the pump P. Even if there is a change in conditions such as a change in , the speed of the lift cylinder l can be accurately controlled.

[Brief explanation of the drawing]

Drawings 1 and 2 show embodiments of this invention.
Figure 2 is a block diagram of the control circuit, Figure 2 is a flowchart, Figures 3 and 4 show conventional equipment, Figure 3 is a side view of an agricultural tractor, and Figure 4 is a diagram of the hydraulic control circuit. be. 1... Lift cylinder as a hydraulic actuator,
P... pump, E... engine, 7... electromagnetic on/off valve, 21... control range setting section, 22... determination section, 23... position detection section, 24... Arithmetic unit, 25...
・Rotation speed detection section.

Claims (1)

[Claims] In a control device that controls the speed of a hydraulic actuator according to the duty ratio of a signal input to an electromagnetic on/off valve, a position detection unit that detects the current position of the hydraulic actuator and a speed control range of the hydraulic actuator are set. A control range setting section that detects the rotation speed of the engine that is the drive source of the pump, a rotation speed detection section that detects the rotation speed of the engine that is the drive source of the pump, and a comparison between the output signal of the position detection section and the output signal of the control range setting section to control the actuator. a determination unit that determines whether the hydraulic actuator is within the control range, and a calculation unit that calculates the duty ratio of the on/off signal output to the electromagnetic on/off valve according to the engine rotation speed when the hydraulic actuator is within the control range. Control loading of hydraulic actuators with.