JPS5827174Y2 - Automatic drainage failure alarm device in fuel filter - Google Patents

Description

[Detailed description of the invention] This invention is used in fuel filters, especially devices that electrically sense water accumulated in the filter for filtering fuel oil in internal combustion engines and automatically drain it by operating a solenoid valve. The present invention relates to an automatic drainage failure warning device for a fuel filter that detects failure and warns of the failure.

Glass wool, etc., which has the function of separating water from oil, is used as a filter element called a water separation oil filter, and the water contained in oil is separated by the difference in specific gravity from the oil without passing through the filter element. In a fuel filter configured to be stored below the fuel filter, there is a device that electrically senses when water reaches a certain level and opens a solenoid valve to automatically drain the water out of the filter (for example, Utility Model Law filed in 1973 by the applicant
-66 Publication).

However, with this automatic drainage system, if the operation control circuit of the solenoid valve used there or the solenoid valve itself fails, the solenoid valve will remain open and discharge not only water but also fuel oil. This resulted in a very dangerous situation, so it was not put into practical use.

The purpose of this invention is to provide an automatic drain alarm device to prevent fuel oil from being discharged due to the continued open state of the solenoid valve, which is a defect found in the conventional automatic drain device for fuel filters. , temperature-sensing elements are arranged downstream of the solenoid valve and outside the drainage pipe in the fuel filter's drainage pipe, and a detection circuit that detects waste water using the temperature-sensing element and a detection signal of this detection circuit are measured in advance. A delay circuit whose delay time is set to be almost the same as the normal drainage completion time, and an alarm that issues an alarm using the output signal of this delay circuit, ensure that the solenoid valve remains open even after the normal drainage time has elapsed. It's happening! The reason is that it is possible to warn of the state.

Examples of this invention will be described below with reference to the drawings.

In Fig. 1, the configuration of the fuel filter and the installation position of the temperature sensing element are shown. Reference numeral 1 is the upper lid of the fuel filter, and a fuel filler port 2 is provided on its circumference, and a fuel discharge port 3 is provided in the center. ing.

Reference numeral 4 denotes a lower lid forming a bottom container of the fuel filter, and a cylindrical body 5 made of a transparent material such as glass is held in an oil-tight manner between this and the upper lid 1.

A drain hole 6 for draining water is provided at the lowest center of the lower lid 4, and a solenoid valve 7 for opening and closing the drain hole 6 is provided.

Reference numeral 8 denotes a drainage conduit connected to the drain hole 6 for guiding drained water to the outside of the filter.

A filter element 9 is disposed within the filter so as to come into contact with the upper lid 1 by means of a spring 10 installed on the inner surface of the lower lid 4.

Reference numerals 11 and 12 designate electrodes, which are arranged within the filter along the inner wall of the body 5 with some spacing between them.

13 and 14 are temperature sensing elements such as thermistors; one temperature sensing element 13 is installed downstream of the solenoid valve 7 within the drainage pipe 8, and the other temperature sensing element 14 is installed near the outer wall surface of the drainage pipe 8. It is installed in

In the above configuration, fuel oil flows into the filter from the filtered fuel port 2, is filtered by the filter element 9, flows out from the discharge port 3, and is guided to the injection pump (not shown).

At this time, the water separated from the fuel oil accumulates at the bottom of the filter.

FIG. 2 shows an example of a circuit for detecting that a certain amount of water has accumulated in the filter, automatically opening the solenoid valve T, and discharging the water to the outside of the filter.

In FIG. 2, the drainage circuit is shown.

15.16.17 are bridge resistors, and this resistor 1
A bridge circuit is formed by 5.16, 17 and electrodes 11, 12, and exhibits high resistance when oil is in contact with electrodes 11.12.

The branch point P between the resistor 15 and the electrodes 11 and 12 is the operational amplifier 1.
The branch point Q of the resistor 16 and resistor 17 is connected to the negative input terminal of the amplifier 8, and the branch point Q of the resistor 16 and the resistor 17 is connected to the positive input terminal of the operational amplifier 18, respectively.

The operational amplifier 18 acts as a comparator,
A positive feedback resistor 19 is provided.

The output of the operational amplifier 18 is connected to the base of a switching transistor 210 via a resistor 20, and the emitter of the transistor 21 is connected to the electromagnetic valve 7.

A diode 22 for preventing back electromotive force is connected to this solenoid valve 7.
are connected in parallel.

In this configuration, when there is no water in the filter, the space between the electrodes 11 and 12 is filled with fuel oil, which is a poor conductor, so the resistance between the electrodes 11 and 12 is large.
The voltage pV at which branch point P of this and the resistor 15 is approximately equal to the power supply voltage, and this is applied to the negative input terminal of the operational amplifier 18.

Further, the voltage qV at the branch point Q with the bridge resistor 16.17 is applied to the negative input terminal of the operational amplifier 18,
The value of each bridge resistor 15.16°17 is the pV value q
Since the output level of the operational amplifier 18 is set to be higher than the VO value, the output level of the operational amplifier 18 is at a low level when no water is accumulated.

Water gradually collects in the filter, and the water level rises to the electrode 11.
12, the resistance between the electrodes 11, 12 decreases rapidly, and the pVO value decreases accordingly, so that the value of pV becomes lower than the value of qV.

As a result, the output of the operational amplifier 18 becomes high level, the transistor 21 becomes conductive, the solenoid valve 7 is operated, and the solenoid valve 7 is opened to start draining water.

As drainage continues and the water level falls and electrodes 11.12 are filled with fuel oil, which is a poor conductor, the electrodes 1
The resistance between 1.12 and 12 increases, and the voltage pV at point P also increases, making pV higher than qV, but the resistor 19 prevents positive feedback and gives hysteresis to the input/output characteristics of the operational amplifier 18. Therefore, the output level of the operational amplifier 18 does not immediately return to the low level, but until the pV rises to the predetermined voltage value set by the resistor 19... In order to maintain the high level, the transistor 21 maintains a conductive state, and the solenoid valve 7 is in an open state.

When the voltage pV at point P is increased to a predetermined voltage value by the resistor 19, the output of the operational amplifier 18 becomes low level, the transistor 21 becomes non-conductive, the solenoid valve 7 is closed, and the drainage work is completed.

As is clear from the above description, the time to start draining can be controlled by the values of the resistors 15, 16, 17 and the electrodes 11, 12, and the time to finish draining can be controlled by the value of the positive feedback resistor 19, respectively.

If a failure occurs in the electronic circuit that controls such drainage work or in the solenoid valve 7 itself, and the solenoid valve 7 does not return to the closed state even after drainage is completed, fuel oil may flow and this is dangerous. This idea for detecting a fault condition will be explained with reference to FIG.

In FIG. 3, the detection circuit of this invention is shown, 13.
14 is a temperature sensing element such as a thermistor placed in the drain pipe 8 as described above, 23 and 24 are bridge resistors that form a bridge with the thermistor, and 25 is an operational amplifier, with the resistor 23 and the sensor connected to its positive input terminal. Temperature element 13 Which branch point N(7) Voltage n
V is applied, and a resistor 24 and a temperature sensing element 1 are connected to the negative input terminal.
4. The voltage mV is applied to which branch point M, and a detection circuit is formed by each of these elements.

26 and 27 are a resistor and a capacitor forming a delay circuit, and in this embodiment, this resistor 26 and capacitor 2
7 forms a relaxation oscillation circuit together with resistors 28 and 29 and a unijunction transistor (hereinafter referred to as UJT) 30, and determines the time constant of this circuit.

31 is a known bistable multivibrator, and the U
It is activated by the trigger pulse output from JT30.

Reference numeral 32 denotes an alarm, which is formed by a buzzer, a lamp, etc., and is configured to be activated by a pulse signal output from the bistable multivibrator 31.

In this configuration, the negative input terminal of the operational amplifier 25 has a
The voltage mV at which branch point M is applied to the resistor 24 and the temperature sensing element 13 such as a thermistor, and the voltage nV at which branch point N of the resistor 23 and the temperature sensing element 14 such as thermistor is applied to the positive input terminal of the operational amplifier 25. is applied, but these pressures are set such that when the solenoid valve 1 is in the closed state, mV is higher than nV, that is, the output level of the operational amplifier 25 is at a low level. Resistance value is set.

When the electromagnetic valve 7 is opened and drainage starts, the temperature sensing element 13 comes into direct contact with the drainage flow, causing its heat dissipation characteristics to change and its resistance to increase, thereby increasing the voltage nV at point N. Therefore, the voltage nV at the N point is higher than the voltage mV at the M point.

Therefore, the output level of the operational amplifier 25 changes from a low level to a high level, and the output level of the operational amplifier 25 changes from a low level to a high level.
It is charged to 7.

Here, the voltage of the UJT 30 rises with the time constant of the resistor 26 and the capacitor 27, and when it reaches the peak voltage, it is biased in the emitter & tJ [direction, and the voltage between the voltage of the UJT 30 and the base of the resistor 29 side increases. The operating resistance drops and capacitor 27 discharges through the emitter.

This discharge continues until the emitter voltage is cut off,
By repeating the same operation as above, the UJT
A trigger pulse is generated at the output of 30.

This trigger pulse activates the bistable multivibrator 31, which subsequently causes an alarm 32 such as a lamp or buzzer to blink intermittently.

With this configuration, if the time constant determined by the resistor 26 and capacitor 27 is set to be almost the same as the drain completion time measured in advance in the normal state, the solenoid valve I will be activated after the drain is finished. When closed, the resistance of the temperature sensing element 13 such as a thermistor decreases, and with the start of drainage, the voltage nV at point N was higher than the voltage mV at point M, but the voltage nV at point N increased to point M. The voltage suddenly becomes lower than the voltage mV of , and the output of the operational amplifier 25 becomes low level.

Therefore, charging of the capacitor 27 is stopped, and the UJT 30
The emitter voltage does not reach the peak voltage, the UJT 30 is inactive, and the alarm 32 does not issue an alarm signal.

However, even after the drainage force is discharged, the solenoid valve 7 remains open, and while the fuel oil is being discharged, the capacitor 27 is charged with this as described above, and the emitter voltage of the UJT 30 reaches its peak. When the voltage exceeds the voltage, the UJT 30 is activated and the alarm 32 can issue an abnormality alarm.

Note that if the time constant is set too short, an alarm will be issued even though fuel oil has not been discharged during the water discharge process. It is desirable to set it slightly longer than the time.

Furthermore, although an example has been described in which the delay circuit is incorporated into the relaxation oscillation circuit as a time constant setting circuit, it goes without saying that the delay circuit of the present invention is not limited to this.

Furthermore, although we have described the case where a UJT or a bistable multivibrator that forms a relaxation oscillation circuit is inserted between the alarm and the delay circuit, these are not necessarily essential elements in this invention, and other switching elements may be used. This circuit may be used and replaced with another appropriate circuit, or may be omitted depending on the configuration of the delay circuit.

In this way, according to this invention, it is possible to detect a malfunction in the solenoid valve operation of the automatic drainage device in the fuel filter, and to minimize the discharge of fuel oil outside the filter. This is the first time that it has become possible to put it into practical use.

[Brief explanation of the drawing]

The figure shows an embodiment of this invention and an automatic fuel filter drainage system which is the premise of this invention. FIG. 3 is a circuit diagram of an automatic drainage alarm device. 7...Solenoid valve, 8...Drainage pipe, 11
．． 12... Electrode, 13, 14... Temperature sensing element, 23.24... Resistance, 25...
Arithmetic amplifier, 26... Resistor, 27...
Capacitor, 30... Unijunction transistor, 31... Bistable multivibrator, 32... Alarm.

Claims (1)

[Scope of utility model registration request] A pair of electrodes is placed inside the fuel filter, and when these electrodes are immersed in water separated from oil, the resistance value changes between the two electrodes, and electrically indicates that a certain amount of water has reached a certain level in the fuel filter. In an automatic fuel filter drainage fault alarm system, the detection signal opens a solenoid valve to discharge water through a drainage pipe. A detection circuit that detects drainage using a temperature sensing element installed outside the conduit, a delay circuit whose delay time is set to be almost the same as the completion time of drainage, which is activated by the detection signal of this detection circuit, and a delay circuit which is activated by the signal of this delay circuit. 1. An automatic drainage failure alarm device for a fuel filter, characterized in that it is comprised of an alarm that