JPS61262278A - Solenoid valve control circuit - Google Patents

Abstract

PURPOSE:To obtain the half opened state even with opening/closing type solenoid valves by intermittently driving the switch elements connected in series with the solenoids. CONSTITUTION:The switching elements 26-29 for the flow of electric current in solenoids 13-17 are connected in series, and a circuit for generating the continuous driving signals and a circuit 31 for generating an intermittent driving signal are provided. Further, a switch 35 for selectively providing the both driving signals supplied from these circuits into the switching elements 26-29 is provided. With such constitution, the perfect opened state and the half opened state of a solenoid valve 12 can be obtained by the operation of the switch 35.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a solenoid valve control circuit used in a hydraulic circuit for a front loader, etc., and the present invention relates to a solenoid valve control circuit used in a hydraulic circuit for a front loader, etc. It has been made possible.

<Prior Art> Hydraulic circuits using electromagnetic valves are widely used not only in front loaders mounted on tractors, etc., but most of them are of a simple open/close type.

This open/close type solenoid valve has a structure that switches from closed to open or from closed to open when a predetermined value of excitation current is passed through the solenoid, and only the total flow rate can be switched.

<Problem to be solved by the invention> - Therefore, when a conventional solenoid valve is used, its operation causes a rapid change in flow rate, which causes a shock in the operation of the device controlled by it, resulting in delicate and fine movements. It was difficult to control.

There are also proportional control valves that can control the flow rate, but they are very complicated and have the drawback of being cost-limited.

The present invention was provided for the purpose of solving such conventional problems.

Means for Solving the Problems> As a means for solving the above-mentioned problems, the present invention provides an opening/closing solenoid valve that operates when a predetermined value of excitation current is passed through the solenoid. The switch elements for causing the current to flow are connected in series, and a circuit that generates a continuous drive signal and a circuit that generates an intermittent drive signal are provided, and both drive signals from these circuits are selectively transmitted. A changeover switch is provided for applying the power to the switch element.

<Function> In FIG. 1, when the changeover switch 35 is on the contact side, the switch element 27 is in the on state, so when the down switch 21 is turned on, the solenoid 14 is energized and the solenoid valve 12 is on the down side. Fully open. When the changeover switch 35 is switched to the contact a side, the pulse generation circuit 31 generates an intermittent pulse signal, and the switch element 27 repeats on/off operations. Therefore, if the lowering switch 21 is turned on at this time, the solenoid 14 will repeat energization and demagnetization.
The solenoid valve 12 is in a half-open state on the descending side. That is, by operating the changeover switch 35, the solenoid valve 12 can be selected between fully open and half open, and the flow rate can be controlled.

<Example> The invention will now be described in detail with reference to the illustrated embodiments.

FIG. 2 shows a packet-type front loader for mounting on a tractor, where 1 is the tractor, 2 is the front wheel, and 3 is the rear wheel. Reference numeral 4 denotes a pair of left and right booms, which are attached to the tractor 1 via a mounting frame 5 and can be raised and lowered by a pair of left and right boom cylinders 6. A packet 7 is pivotally supported at the tip of the boom 4 and can be rotated by a pair of left and right packet cylinders 8.

FIG. 3 shows a hydraulic circuit, where 9 is a hydraulic pump, which is driven by an engine 10. 11 is a relief valve. 12
is an open/close type solenoid valve for the boom cylinder 6, and has a solenoid 13 for raising and a solenoid 14 for lowering. 15 is an open/close type solenoid valve for the packet cylinder 8, and has a dumping solenoid 16 and a scooping solenoid 17. 1
A pressure switch 8 is connected to detect the oil pressure of the hydraulic pump 9 rather than the electromagnetic valve 13. This pressure switch 13 is set to a set pressure P2 that is higher than the pressure P1 on the hydraulic pump 9 side when the boom 4 is raised in a no-load state. Reference numeral 19 denotes a control valve device for a hydraulic device for lifting and lowering the working machine.

Figure 1 shows the control circuit of the solenoid valve 12.15.
The ascending solenoid 13 of No. 2 is connected to the ascending switch 20 and the contact point a of the pressure switch 18, and the descending solenoid 14 is connected to the descending switch 21 and the contact point a of the pressure switch 18. The pressure switch 18 closes a contact a when the detected oil pressure is higher than a set pressure P2, and closes a contact when the detected oil pressure is lower than the set pressure P2. A dump switch 22 is connected to the dump solenoid 16 of the solenoid valve 15, and a scoop switch 23 is connected to the scoop solenoid 17, respectively. Reference numeral 24 denotes a floating changeover switch, which has two contacts a and b for selectively selecting manual control by switches 20 and 21 and floating control by pressure switch 18.

Switch elements 26 to 29 are connected to each of the solenoids 13 to 17, respectively, for causing current of a predetermined value to flow therein. The switch elements 26 to 29 are composed of two Darlington-connected transistors Tr1 and Tr2. 30 is a resistor for continuously applying a base drive signal to the transistors Tr1 of the switching elements 26-29. 31 is a pulse generation circuit for giving an intermittent base drive signal to the transistor Tr1 via the resistor 32, and the number of pulses is controlled by the variable resistor 33,
The configuration is such that the pulse width can be adjusted respectively. The duty ratio of the pulse signal generated by this pulse generating circuit 31 is adjusted with resistors 33 and 34 as appropriate so that the spool can be maintained at an intermediate position between fully closed and fully open, taking into account the operation delay of the solenoid valve 12.15. . 35 is a transistor Tr1
This is a changeover switch for selecting a base drive signal to be added to the base drive signal, and has a contact a connected to a resistor 30 and a contact a connected to a resistor 32.

4 and 5 show the control lever 36 and each switch 20,
21.22.23.24.35 is shown. The control lever 36 is attached to the top plate of the control box 37 via a spherical pivot 38 so as to be freely operable in the front-back and left-right directions, and is resiliently supported at the center by a spring (not shown).

The lower end of the control lever 36 is inserted through elastic pieces 41 and 42 into ring-shaped operating bodies 39 and 40 provided in upper and lower stages. The actuating body 39, 40 is supported slidably in all directions by a support member 43 in the control box 37, with the up switch 20 in front of the actuating body 39, and the down switch 21, 40 in the rear. A dump switch 22 is provided on the left, and a scoop switch 23 is provided on the right. Further, a changeover switch 24 is provided in front of the operating body 40. When the control lever 36 is tilted around the pivot portion 38 in any direction, front, back, left, or right up to the first stage tilt angle, the switches 20, 21, 22, and 23 are turned on via the operating body 39, and the second When you tilt forward to the tilt angle of the step,
Switch via operating body 40? 4 is the contact point, so the switch is made to the contact point a. A changeover switch 35 is incorporated in the grip portion 44 at the upper end of the control lever 36 so as to be linked to a push button 45, and is configured to switch from contact A to contact a when the push button 45 is pressed. There is.

Next, the operation of the above configuration will be explained.

When excavating and loading earth and sand, operate the control lever 36 back and forth, left and right, and move the tractor 1 while positioning the boom 4 and packet 7 as shown in solid lines in Figure 2 by expanding and contracting the boom cylinder 6 and packet cylinder 8. Move forward. When dirt enters the packet 7, the packet 7 is rotated upward by the contraction operation of the packet cylinder 8 to scoop it up, and the boom 4 is raised and transported by the expansion and contraction operation of the boom cylinder 6, and then the packet 7 to dump the earth and sand.

When the push button 45 of the control lever 36 is not pressed, the changeover switch 35 is on the contact side, so the transistors T of the switch elements 26 to 29 are connected from the resistor 30 through the contact.
A base drive signal is continuously applied to r1, and each of the switch elements 26 to 29 is continuously turned on.

Further, when the push button 45 of the control lever 36 is pressed, the changeover switch 35 is switched from contact to contact a, and the pulse signal generated by the pulse generation circuit 31 is transmitted to the transistor Tr1 via the resistor 32 and contact a. Added as base drive signal. Therefore, each of the switches 26 to 29 repeats on/off operations in synchronization with the pulses generated by the pulse generating circuit 31.

Therefore, in normal cases, the control lever 36 is operated without pressing the push button 45. For example, when the control lever 36 is operated forward (arrow A) to the first stage position, the lowering switch 21 is activated via the operating body 39, the lowering solenoid 14 is energized, and the solenoid valve 12 is lowered. It is fully opened to the side, the boom cylinder 6 is retracted, and the boom 4 is lowered. When the control lever 30 is operated to the left (arrow B), the scoop switch 23 is actuated by the operating body 39, the scoop solenoid 17 is energized, the solenoid valve 15 is fully opened to the scoop side, and the packet cylinder 8 is contracted. The packet 7 rotates upward. If the control lever 36 is operated backwards (arrow C), the boom 4 will rise in the same way and move to the right (D
If you operate as shown by the arrow), the packet 7 will be dumped downward.

During the lowering movement of the boom 4, the pushbutton 4 of the control lever 36
When 5 is pressed, the selector switch 35 switches to contact a side,
- Since the switch element 27 repeats on/off operations, an excitation current of a predetermined value flows intermittently through the lowering solenoid 14 as shown in FIG. 6(^). Therefore, the lowering solenoid 1
4 repeats excitation and demagnetization, and due to the delay in operation at that time, the spool maintains a half-open position as shown in Figure 6 (B), so the flow rate of hydraulic oil supplied to the boom cylinder 6 is reduced to about half. The operating speed of the boom cylinder 6 decreases. Therefore, the descending speed of the boom 4 becomes slower, and for example,
The packet 7 can be made to touch the ground slowly. In other words, when the pushbutton 45 is pressed, the spool of the solenoid valve 12.15 becomes half-open in any case, making it easier to control the front loader compared to the conventional method of simply opening and closing, allowing for more precise work. Kudzu can be done.

Next, after the packet 7 is grounded on the ground, when running the packet 7 while following the undulations of the ground to perform leveling work, etc., the control lever 36 is moved from the first stage as shown in FIG. The tilting operation is performed further forward (arrow A) to the second stage, and the contact a of the changeover switch 24 is closed to shift to floating control.

That is, when the contact a of the changeover switch 24 is closed with the packet 7 grounded, the contact a of the pressure switch 18 is closed, so the lowering solenoid 14 of the solenoid valve 12 is activated and the solenoid valve 12 is switched in the lowering direction. Then, pressure oil is supplied to the boom cylinder 6 in the contraction direction, and the pressure on the discharge side of the hydraulic pump 9 begins to rise as shown in FIG. and,
When the pressure exceeds the set pressure P2, the pressure switch 18
The contact is switched to contact a, and the lifting solenoid 13 of the solenoid valve 12 is energized. Therefore, as shown in FIG. 7, the solenoid valve 12 changes from neutral to rising, but the pressure rises until it becomes neutral, and then gradually decreases.

That is, when the electromagnetic valve 12 is on the downward side, the boom cylinder 6 is pushing down the packet 7 so that it touches the ground, so the pressure increases. However, when it passes neutral and begins to switch to the upward side, the pressing force is released and acts in the upward direction, so the pressure decreases until it reaches the rising pressure P1 with no load.

Then, while the pressure is decreasing, the pressure switch 18 switches from contact a to contact again at the set pressure P2, and the solenoid valve 12 switches from the ascending side to the descending side, and the boom cylinder 6 moves as described above. It moves in the contraction direction again. Therefore,
``The pressure begins to rise again and the same operation is repeated. As a result, the boom 4 is maintained in a floating state so that the packet 7 follows the undulations of the ground, so that the desired work can be performed. If the switches 22 and 23 are operated during this floating control, packet operation is also possible.

8 to 10 show a second embodiment of the present invention, in which when the control lever 36 is operated to the first stage, the solenoid valves 12, 1
5 is in a half-open state, and when the second stage is operated, it is in a fully open state, so that the flow rate changes according to the amount of operation of the control lever 36.

That is, as shown in FIG. 8, four changeover switches 46 to 49 are provided corresponding to each of the switch elements 26 to 29, and each of the changeover switches 46 to 49 has a contact a on the normally open side connected to a resistor 3.
0 and the normally closed side contacts are connected to a resistor 32, respectively. As shown in FIGS. 9 and 10, these changeover switches 46 to 49 are arranged on the front, rear, left and right sides of the actuating body 41, respectively, in vertical phase correspondence with the switches 20 to 23. When the second stage is operated, the actuating body 41 operates the contact to switch to the contact a side.

The changeover switch 24 is built into a grip portion 44 of the control lever 36 and is operated by a push button 45.

In this case, for example, move the control lever 36 forward (arrow A).
When the operation is performed to the first stage, the lowering switch 21 is turned on, so that the solenoid valve 12 is operated on the lowering side to a half-open state by the on/off operation of the switch element 27. Then, when the control lever 36 is further operated from the first stage to the second stage,
Since the changeover switch 47 is in contact, it switches to contact a, so
The switch element 27 remains on, and the solenoid valve 12
goes from half-open to fully open. Therefore, although it is an open/close type solenoid valve 12, it can be used in a proportional control manner according to the amount of operation of the control lever 36.

<Effects of the Invention> According to the present invention, the switching element connected in series with the solenoid is driven intermittently using an intermittent drive signal to repeatedly excite and demagnetize the solenoid. Despite this, a half-open state can be obtained and the flow rate can be controlled in stages. Further, since it is only necessary to select between continuous and intermittent drive signals to be applied to the switch elements using a changeover switch, the operation is easy to handle and can be carried out easily.

[Brief explanation of drawings]

1 to 7 show a first embodiment of the present invention, in which FIG. 1 is an electric circuit diagram, FIG. 2 is an overall side view, FIG. 3 is a hydraulic circuit diagram, and FIG. 4 is a hydraulic circuit diagram. 5 is a sectional view of a part of the control lever, FIG. 5 is a layout diagram of a switch, FIGS. 6 and 7 are explanatory diagrams of operation, and FIGS. 8 to 10 show a second embodiment. 8 is an electric circuit diagram, FIG. 9 is a sectional view of a part of the control lever, and FIG. 10 is a layout diagram of the switch. 4...Boom, 6...Boom cylinder, 7...Packet, 8...Packet cylinder, 12.15...
Solenoid valve, 13-17... Solenoid, 18... Pressure switch, 26-29... Switch element, 31...
Pulse generation circuit, 35... changeover switch, 36...
control lever.

Claims (1)

[Claims] 1. In an open/close type solenoid valve that operates when a predetermined excitation current is passed through a solenoid, a switch element for causing the current to flow is connected in series with the solenoid, and a circuit that generates a continuous drive signal and an intermittent drive signal are connected in series to the solenoid. 1. A solenoid valve control circuit comprising: a circuit for generating drive signals; and a changeover switch for selectively applying both drive signals from these circuits to a switch element.