JPS5982570A - Fuel filtering unit with automatic drain - Google Patents

Abstract

PURPOSE:To prevent a coil from being heated by providing a thermistor with positive characteristics on a drain solenoid valve control circuit between the solenoid valve of a fuel filtering unit with an automatic drain and the power supply, and reducing an electric current immediately after opening said drain solenoid valve to a degree that the opened condition of the valve can be maintained. CONSTITUTION:If the level of the separated water rises and detecting electrodes 34, 35 are immersed in it, potential difference arises across a resister R1, a transistor Tr1 is made conductive, and the resultant current ignites a thyristor TH. Then, an electric current flows through a thermistor 53 with positive characteristics located between the power supply 52 and a drain solenoid valve 4, opening the valve. Since the thermistor is heated and the value of its resistance is increased when an electric current flows through it, the flow of a current to an exciting coil 45 is reduced, after a short time, due to the resistance of the thermistor, maintaining less flow of a current than that when the operation is started, while the draining is continued. Thereby, the coil can be prevented from being heated, and its size can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-draining fuel filter equipped with water level sensing means for use in internal combustion engines.

The fuel filter has the function of removing dust contained in fuel oil such as light oil and separating water from the fuel oil. A water reservoir for storing this separated water is provided at the bottom of the casing, and when 1L of separated water accumulates above a certain level, the water level is notified to the user, and the drain solenoid valve is automatically opened to drain the separated water. A device is known that discharges fuel to the outside from the bottom of the fuel filter.

However, in such a device, the initial excessive current required to open the drain solenoid valve continues to flow until the drain is completed, and the power consumption of the power source is high. Also, if there is garbage in the drained water, the garbage will partially block the drain port of the drain 1 magnetic valve, and it will take time to drain the water, during which time the valve will remain open. The excessive current continues to flow through the excitation coil inside the valve, causing the excitation coil to generate heat, or burning out, which may impair the functions of the drain 1 and the rod valve. Therefore, since the hJJm coil was made thicker, the drain solenoid valve had to be made larger.

The present invention solves these drawbacks and provides a fuel filter with an automatic drain device, which includes a circuit that reduces the current to enough to maintain the valve open immediately after the drain solenoid valve is opened. The automatic/automatic drainage fuel filter device 1 shown in FIG. The fuel filter main body 2 has a filter body 12 pressed by a spring 17 disposed within a metal cup-shaped housing 11, and an outlet section 14 provided with a screw mechanism in the central upright portion and an outlet section 14 provided around the outlet section 14. A sheet 15 consisting of a cover plate having a plurality of inlets 13 and a shroud plate 16 crimped to the periphery of the open end of the casing 11 is fixed in a liquid-tight manner.

The water level detection device 3 includes a high-position water level detection electrode 62 at the upper end of a synthetic resin cylinder, and a low-position water level detection electrode 63 at the lower end thereof, and terminals 34 and 35 connected to the respective electrodes.
It is inserted into the lower closed part of the metal casing 11. Also, there is a flag sheet 18 at the bottom of the casing 11.
A drain electromagnetic valve 4 is disposed on the plug seat 18 via a packing 41 to open and close a drain passage 43 formed in the plug seat 18. The drain solenoid valve 4 consists of a valve 44 with a gasket 42 at its tip, an excitation coil 45 that operates the valve 44, and a spring 46 that always biases the valve 44 in the closing direction. i#lei coil 45
are separated from drain passages 45' and 48 by a diaphragm 47.

Drain electromagnetic valve control circuit 5f: As shown in FIG. 2, 52 is a power source whose one end is grounded, and the single power terminal 51a of the switch 51 is connected to the non-grounded terminal of the power source 52. The anode side of the dimate D1 is connected to the other terminal 51b of the switch 51, and the cathode side of the diode I)1 is connected to the resistor R1r.
It is connected to the high position water level detection terminal 34 via R2.

ZnR is a varistor whose one end is connected to the switch terminal 51b and the other end is grounded. The transistor Tr1, which has a connection point of the wire at the cathode terminal of the dimate D1, has its pace connected to the connection point of the resistors R1 and R2, and its collector is grounded via the diode D2 and the resistors R5 and R4. The twiristor TH whose gate is connected to the connection point of the resistor R3 and the resistor R4 is connected to the transistor Tr2 whose anode is connected to the cathode terminal of the diode D1 and the resistor R6.
The J-sword is connected to the ground via a resistor R7. A resistor R5 is connected between the cathode and gate of this thyristor TH.

The transistor Tr3 whose pace is connected to the connection point A of the thyristor TH and the resistor R7 has its collector connected to the display circuit,
The emitter is grounded. The display circuit is connected to the drain electromagnetic valve 4 via a positive characteristic thermistor 56 whose one end is connected to the timemate D1, and a diode D3 arranged in parallel with this.
The other end of the display lamp LP is connected to the transistor Tr3, and in the rotary drainage fuel filter device 1 constructed as described above, the fuel oil is supplied to the filter body 2 at the population 16.
The water flows into the casing 11 through the filter body 12 and flows out through the outlet 14. Water droplets in the fuel oil are separated by the filter 12 and collected at the bottom of the cooling sink 11. Casing 11
While the water level detection electrode 52 is in contact with the fuel oil, the electrical conductivity of the fuel is low and the resistance between the detection electrode 62 and the metal casing 110 is extremely large. A potential difference necessary to operate the transistor Tr1 is not generated in the resistor R1, and the drain xi valve 4 is not operated.

When the separated water gradually rises and immerses the high-position water level detection electrode 32, a current flows from the t-electrode 62 to the metal casing 11 due to the high conductivity of the water. Then, a potential difference sufficient to operate the transistor Trl is generated in the resistor R1, and the transistor Tr1 is made conductive. transistor 1゛r1
When becomes conductive, the amplified current flows through the resistor R3 to the gate of the thyristor 7 and 11, causing the thyristor TH to fire. The fired thyristor TH causes current to flow through the transistor Tr5, making the transistor Tr5 conductive. When the transistor Tr5 becomes conductive, the positive characteristic Yrmister 53 disposed between the power source 52 and the drain solenoid valve 4 is turned on.
A current flows through. The valve 4 is connected to the excitation coil 45 of the drain solenoid valve 4.
An excessive current necessary to operate the valve 4 flows to open the valve 44 and start draining the water accumulated at the bottom of the casing 11. When the water reaches the bottom of the casing 11, the indicator lamp LP lights up to indicate that the water is being drained. .

When current flows through the positive characteristic thermistor 53, the thermistor generates heat and increases its resistance value. After this short-term resistance value increase, the current to the exciting coil 45 becomes smaller due to the resistance of the thermistor, and the current lower than that at the start of operation is maintained while draining continues. When the separated water is discharged, the electrical conductivity between the low water level detection electrode 66 and the metal part casing 11 decreases due to the fuel oil, and the resistance increases, making the transistor Tr2 non-conductive. Then, thyristor TH, h transistor Tr
s also becomes non-conductive, cutting off the current in the excitation coil 45 of the drain electromagnetic valve 4, closing the valve 44, and extinguishing the lamp LP.

As described above, in the present invention, a positive temperature coefficient thermistor is provided in the connection circuit between the power source and the drain solenoid valve, so that water separated by the filter reaches the high-position water level electrode and activates the drain solenoid valve control circuit. When opening the drain solenoid valve, the excessive current required to open the valve is passed for a short period of time while the resistance increases due to the heat generated by the thermistor, and after the resistance value has increased, it is held just enough to keep the valve open. The current can be lowered. As a result, excessive current flows through the coil for only a short period of time regardless of the drainage time, so that heat generation in the coil can be prevented and power consumption can be reduced. Furthermore, since the drainage function can be achieved even if the excitation coil is made small, the drainage solenoid valve itself has the advantage of being able to be made smaller in size and lighter in size.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an automatic drainage fuel filter device which is an embodiment of the present invention. Figure 2 is a wiring diagram of the drainage solenoid valve control circuit. 1. Automatic drainage fuel filter device 2.
...Fuel filter body 6...Water level detection device 4...Drainage solenoid valve 5...
... Drainage solenoid valve control circuit 11 ... Gold PA cup-shaped case song 62 ... Akane position water level detection ring and others 66 ... Low position water level detection electrode 45 ... ...
・Exciting coil 53...Positive characteristic thermistor

Claims (1)

[Claims] 5. An automatic drainage fuel filter device characterized in that a positive temperature coefficient thermistor is disposed in a valve control circuit in a housing which is liquid-tightly fixed to a sheet having a fuel oil inlet and outlet and a gold kj4a cup-shaped casing.