JPS6362984A - Hydraulic device - Google Patents

Abstract

PURPOSE:To reduce a difference between amounts of oil, circulated in the time of operation start and its end, by first conducting an excitation current larger than a normal control current in a solenoid valve thereafter the control current in the solenoid valve. CONSTITUTION:When an instruction of up-down moving a cultivator 5 is output, it is decided whether the instruction is for operation of up or down, and when it is for operation of up, further a device decides whether or not an instruction of setting an excitation current is output. A lift arm 17 is lifted by an up opera tion valve 20, but a regular control current is conducted after the excitation current of large value is conducted only for a predetermined time when up operation is started, consequently the device, in which a flow amount of oil in the time of operation start is almost equal to that after the time of operation start, actuates the lift arm 17 to be smoothly lifted. Also in case of lowering, similarly the device controls a down operation valve 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electronically controlled hydraulic system used in agricultural machines and the like.

[Prior Art] A hydraulic system equipped with a proportional solenoid valve as a control valve, in which the amount of oil flowing increases in proportion to the energization time, is used as a work machine lifting device for a tractor, etc.

[Problems to be Solved by the Invention] Figure 5 is a graph showing the characteristics of an example of this type of proportional solenoid valve. Pressure oil does not start flowing until t has elapsed and the current reaches a certain amount.
Even when the amount of current is the same, the flow ψ of the pressure oil differs when increasing and decreasing the amount of current. This characteristic results from the combined influence of the hysteresis phenomenon of the solenoid itself and the hysteresis phenomenon of the valve itself.

For example, if a proportional solenoid valve with the characteristics shown in Figure 5 is used in a hydraulic system for raising and lowering the work equipment of a powered agricultural machine, the pressure oil will not start flowing even if the position lever for raising and lowering the work equipment is slightly moved. The work equipment remains stationary, but if you move the lever a little more from this position (
At point A in the figure) the pressure oil begins to flow and the working equipment suddenly starts operating. Therefore, the working machine lifting device equipped with such a proportional solenoid valve has a problem in that it is difficult to finely adjust the vertical position of the making device, and this tends to be dangerous.

[Means for Solving the Problems] In order to solve the problem 1-, the present invention provides a hydraulic system having the following configuration. In other words, the hydraulic system according to the present invention is a hydraulic system having a proportional solenoid valve in which the amount of oil flowing increases or decreases in proportion to energization, and when an output command is issued, an excitation current larger than a normal control current is first applied. The present invention is characterized in that it includes a control device that energizes the solenoid valve with radio waves and then energizes the solenoid valve with a control gI electric field.

[Function] When an output command is issued, a large excitation current is applied to the valve solenoid for a certain period of time, and then a regular control current is applied. The difference is reduced and stable operation is obtained.

[Example] The embodiments shown in the drawings will be described below.

Figure 1 shows an embodiment of a power agricultural machine equipped with a hydraulic system according to the present invention.
l is provided with a link device 3 at the rear of the fuselage 2,
A working machine (a tiller in this example) 5 is attached to the link device 3.

The link device 3 has one top link 10 and a pair of left and right lower links 11.11, and the top link IO is connected to the mast 13 of the tiller 4II5, and the lower link 11.11 is connected to the mast 13 of the tiller 4II5.
are attached to the mounting frame 14 of the tiller 5, respectively. The lower link 11.11 is suspended from the hydraulic lift arm 17 of the tractor 2 by a lift rod te, is connected to its intermediate portion.

The tractor 1 includes a link device 71 and a hydraulic device 1 for lower movement.
9 is A@L, and the lift arm 1 is moved by the hydraulic pressure of this hydraulic system.
7 can be rotated up and down.

The L-lower operation of the work machine is performed using a position lever 24 provided on the side of the operator's seat 23. A lift arm angle sensor 27 is provided at the base of the lift arm 17 to detect the rotation angle of the lift arm. There is.

As a control valve for the hydraulic system 19, a proportional solenoid valve whose pressure oil flow rate changes in proportion to the energization by a pulse is used, and this proportional solenoid valve is provided for raising and lowering the work equipment, respectively. ing. When moving the lift arm 17, the second lifting valve 20 is opened to feed pressure oil into the extension side cylinder chamber of the driving hydraulic cylinder, and the lowering valve 21 is closed to circulate the pressure oil to the tank. let Conversely, when moving the lift arm 17 downward, the ascending valve 20 is closed, and the descending valve 21 is opened to send pressure oil into the contraction side cylinder chamber of the hydraulic cylinder.

FIG. 2 is a block diagram showing the control U4 mechanism of the hydraulic system 19, and shows the detection signal of the lift arm angle sensor 27 (the signal that controls the setting position of the tiller by the position lever 24 (φ is the A/D conversion signal). The angle of the lift arm 17 set by the position lever 24 is compared with the actual rotation angle of the lift arm 17 detected by the angle sensor 27. - Open/close signals ■ and ■ are output to the external valve 20 and the lowering valve 21. When the open signal is output to the valve 20.21, a large excitation current is passed through the valve solenoid for a certain period of time. After that, a predetermined control current is caused to flow. Fig. 4 is a waveform diagram of an example of the pulse current for energizing the solenoid, and in this example, the pulse energization time and non-energization time of the control current are shown. The ratio of excitation currents is 5:5, and the same ratio of excitation currents is 9=1.These ratios are arbitrary, and the most suitable one can be selected.

Next, the operation of this hydraulic system 13 will be explained based on the flowchart shown in FIG. First, position lever 2
4 and the detected value of the lift arm angle sensor 27, it is determined whether the tiller 5 is to be kept at the current position (neutral). When a neutral command is issued, both valves 20 and 2
1 to "close" to stop the lift arm 17,
At this time, an excitation request is issued. If there is a command to raise or lower the tiller a5, it is determined whether the command is to raise or lower, and if it is "raise", it is further determined whether there is a command to set an excitation radio wave. If this command is given, the excitation current supply time for applying excitation current to the solenoid is set. If there is no command, control current is applied. In either case, the lift arm 17 rises, but when the lift arm 17 begins to rise, a large excitation current is applied for a predetermined period of time, and then a regular control current is applied, so the flow rate of pressure oil at the start of operation and thereafter is reduced. Almost equally, the lift arm 17 is designed to move upward smoothly. The same applies to the case of "downward", and the control performed on the ascending valve 20 in the above operation is performed on the descending valve 21. lift arm 17
When the movement to the set position is completed, the control radio waves are cut off.

In this embodiment, a hydraulic system for a power agricultural machine has been described, but it goes without saying that the hydraulic system control device according to the present invention can be used for other systems.

[Effects of the Invention] As is clear from the above description, the hydraulic system according to the present invention energizes the solenoid valve with an exciting radio wave larger than the normal control current when an output command is issued, and then changes the control current to the solenoid valve. A control device is provided to energize the
This eliminates the effects of hysteresis on valves and solenoids, making it possible to achieve smooth and accurate operation.

[Brief explanation of drawings]

FIG. 1 is a side view of an agricultural machine that is an embodiment of the present invention;
Fig. 2 is a block diagram showing the control mechanism of the hydraulic system, Fig. 3 is a flowchart showing its operation, Fig. 4 is a waveform diagram showing an example of the solenoid excitation current, and Fig. 5 is a proportional solenoid This is a graph showing the flow characteristics of the valve. l...tractor 2...body 3...link device 5...tiller 17...lift arm 19...
・Hydraulic system 20... Solenoid valve for lifting 21
... Lowering solenoid valve 24 ... Position lever 27 ... Lift arm angle sensor

Claims (1)

[Claims] (1) In a hydraulic system that has a proportional solenoid valve in which the amount of oil flowing increases or decreases in proportion to the amount of energization, when an output command is issued, an excitation current that is larger than the normal control current is first energized to the solenoid valve. , and then a control device for supplying a control current to a solenoid valve.