JP2780053B2 - Starter fuel supply for carburetor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting fuel supply device for a carburetor in which starting fuel is automatically supplied in relation to starting conditions of an engine.

[Prior Art] According to the starting fuel supply device for a carburetor in a small internal combustion engine according to Japanese Patent Application Laid-Open No. 63-299026 filed by the present applicant,
At the start of the engine, a normally closed solenoid on-off valve disposed between a fuel chamber of the carburetor and a passage connecting the intake passage is energized and opened, and starting fuel is supplied to the intake passage simultaneously with cranking of the engine. Since the rich mixture is supplied to the engine, the engine is started smoothly. When the engine reaches an idle speed higher than the cranking speed, the voltage or current of the primary coil of the flywheel magnet exceeds a predetermined value. Based on a signal such as the voltage of the primary coil, the power to the solenoid on-off valve is cut off, the solenoid on-off valve is closed, and the supply of the starting fuel is stopped.

However, the ignition circuit of the engine uses a transistor system or CD.
Since the output characteristics of the flywheel magnet differ depending on the ignition method, the electric circuit for the solenoid on-off valve must be provided.
If an electric circuit that is compatible with any of the ignition methods is provided, the circuit becomes complicated and large, and a mounting portion for the engine is restricted.

[Problems to be Solved by the Invention] An object of the present invention is to provide a carburetor which has a simple structure and can be applied to any ignition type engine, and in which starting fuel is automatically supplied according to the starting conditions of the engine. To provide a starting fuel supply device.

Means for Solving the Problems In order to achieve the above object, the configuration of the present invention relates to an internal combustion engine that supplies starting fuel from a fuel chamber of a carburetor to an intake passage through a normally-closed electromagnetic on-off valve. A thermistor that detects a temperature change of the coil as a resistance change is disposed in proximity to a coil of the electromagnetic on-off valve, and a switch that is linked to a closing operation of a start switch for driving a starter motor with respect to a power battery and the electromagnetic open-close valve. A coil and a switching transistor are connected in series, a base voltage of the switching transistor is controlled by the thermistor, and when the temperature of the coil of the electromagnetic on-off valve is lower than a predetermined value, the switching transistor is turned on, When the coil temperature of the on-off valve exceeds a predetermined value, the switching transistor is turned off.

[Action] When the engine is started, the solenoid on-off valve is energized and opens. With the cranking of the engine, the starting fuel is supplied from the fuel chamber of the carburetor to the intake passage of the carburetor via the electromagnetic on-off valve, and a rich mixture is supplied to the engine, so that the engine is started smoothly.

The amount of the rich mixture supplied to the engine depends on the temperature and the ambient temperature of the engine. At low temperatures, a large amount of the rich mixture is supplied, and at high temperatures, the engine is started with little or no supply. .

When the temperature of the coil reaches a predetermined value due to the energization of the coil of the solenoid on-off valve, the solenoid on-off valve is closed by a signal of this temperature. The time required for the coil temperature to reach the predetermined value is longer as the ambient temperature is lower. Accordingly, the period during which the solenoid on-off valve is open becomes longer, and the amount of starting fuel increases. In this way, the amount of rich mixture supplied to the engine is automatically controlled in accordance with the ambient temperature of the engine, so that the engine can be started smoothly at any ambient temperature.

FIG. 1 is a schematic configuration diagram of a starting fuel supply device according to an embodiment of the present invention in the case of a diaphragm type carburetor. The starting fuel supply device includes a diaphragm type fuel pump A, a fuel supply mechanism B, and an electromagnetic opening and closing mechanism for opening and closing a passage between the fuel chamber 26 and the fuel storage chamber 10 of the fuel supply mechanism B in the main body 4 of the carburetor 1. A valve C and a control circuit D for the solenoid on-off valve C are provided.

The carburetor 1 has a cylindrical portion 7 crossing the intake passage 9 of the main body 4,
The rotary throttle valve 8 is supported rotatably and axially movable. A throttle valve 8 having a throttle hole 8a has a lever 2 connected to a small-diameter shaft portion on the upper end side, and a follower hanging from the lever 2 is urged by a spring (not shown) to a cam 3a formed on a lid 3 closing a cylindrical portion 7. Engaged. When the throttle valve 8 is rotated by the lever 2 to increase the opening, the rod valve 5 connected to the throttle valve 8 rises, the opening of the fuel injection hole 6 increases, the fuel amount increases, and the engine 31 The output is increased.

A fuel reservoir 10 for holding the starting fuel is formed at the bottom of the cylindrical portion 7, that is, below the throttle valve 8, and the fuel in the fuel reservoir 10 at the start of the engine 31 passes through the gap between the cylindrical portion 7 and the throttle valve 8 through the intake passage. 9
Is sucked into. The fuel reservoir 10 preferably accommodates a porous member such as ceramics.

The fuel pump A has a diaphragm 28 inside the carburetor body 4.
The pulsating pressure introducing chamber and the pump chamber are partitioned by the pulsating pressure introducing chamber, and the pulsating pressure introducing chamber is connected to the crank chamber of the engine 31. The pump chamber is connected to the fuel tank 18 via a check valve 27 and a pipe 16,
The fuel supply mechanism B is connected to a fuel chamber 26 called a metering chamber via a check valve 24, a passage 15, and an inflow valve 23.

The fuel supply mechanism B has a diaphragm inside the carburetor body 4.
The fuel chamber 26 and the atmosphere chamber 20 are defined by 19. Fuel chamber
The lever 21 is supported by a support shaft 22 inside 26. lever
One end of 21 is urged by the spring to the diaphragm 19, while the other end is engaged with the inflow valve 23 and urged to close the inflow valve 23. The fuel chamber 26 communicates with the fuel injection hole 6 of the fuel supply pipe via the fuel jet 25. Further, the fuel chamber 26 is communicated with the above-described fuel reservoir 10 via the throttle 17 inserted into the passage 11 and the electromagnetic on-off valve C.

The solenoid on-off valve C is a normally-closed type and has a starting switch.
When the switch 34 is closed, power is supplied to the relay coil 35a from the power supply battery 36, the switch 35b is closed, the control circuit D is operated, the coil 12 of the solenoid on-off valve C is excited, and the solenoid on-off valve C is opened. . Power battery 36 to switch 35b
, The electric power is supplied to the starting motor 29, whereby the engine 31 is cranked. Further, the current of the primary coil of the flywheel magnet 30 is controlled by the ignition circuit 32 at the same time as the engine cranking, and an ignition voltage is applied from the secondary coil to the ignition plug 40.

FIG. 2 shows a control circuit D of the solenoid on-off valve C. In FIG. 2, 41 to 44 are resistors, 45 is a thermistor as a temperature sensing element for sensing the temperature of the coil 12, 46 is a Zener diode, 47,
48 is a transistor, 49 is a diode for suppressing a surge voltage, and 12 is a coil of the solenoid on-off valve C. Transistor 48
, Whose base voltage is controlled by the thermistor 12, acts as a switching transistor for opening and closing the electromagnetic on-off valve C.

Next, the operation of the starting fuel supply device according to the present invention will be described. When the start switch 34 is closed in FIG.
The relay 35 operates and the switch 35b closes. Power Battery 3
From 6 the starting motor 29 is energized and the engine is cranked. Immediately after the start switch 34 is closed, the temperature of the coil 12 is equal to the ambient temperature, and the resistance value of the thermistor 45 for detecting the temperature of the coil 12 is high, so that the base voltage of the transistor 47 is high and the transistor 47 is turned on. , The transistor 48 applied to the base of the collector voltage of the transistor 47 is also turned on, and the coil 12 is energized to
Opens. Accordingly, in FIG. 1, the starting fuel is supplied from the fuel chamber 26 of the fuel supply mechanism B to the fuel reservoir 10 of the carburetor via the throttle 17 of the passage 11 and the electromagnetic switching valve C. Further, the starting fuel in the fuel storage chamber 10 is sucked into the intake passage 9 and a rich air-fuel mixture is supplied to the engine 31, so that the engine is started smoothly.

When power is supplied to the coil 12 from the power battery 36, the coil
12 generates heat, and the temperature of the coil 12 gradually increases. coil
The temperature of 12 is detected by a thermistor 45. When the temperature exceeds a predetermined value, the transistor 47 is turned off and the transistor 48 is also turned off, so that the power supply to the coil 12 is cut off, the solenoid on-off valve C is closed, and the starting fuel is supplied. Is stopped.

As shown in FIG. 3, the energizing time of the coil 12 and the coil 12
The relationship with the temperature is that the longer the energizing time, the higher the temperature of the coil 12 and the higher the voltage of the power battery 36, the faster the temperature of the coil 12 rises (the power battery of a small internal combustion engine has 7.2 volts, 6 volts and 4.8 volts are installed.)

If the ambient temperature is 0 ° C, the temperature of coil 12 will be a predetermined value.
The energizing time until the temperature rises to tn ° C. is sl, whereas when the ambient temperature is t ° C. higher than 0 ° C., the energizing time until the temperature of the coil 12 rises to the predetermined value tn ° C. is s2. . When the voltage of the power supply battery 36 is 7.2 volts, as described above, the lower the ambient temperature, the longer the energizing time until the coil temperature reaches a predetermined value.Therefore, the amount of the starting fuel in proportion to this energizing time, that is, The amount of the rich mixture supplied to the engine also increases, and the engine is started smoothly.

When the voltage of the power supply battery 36 is low, the energization time is prolonged, and the supply amount of the starting fuel is increased. However, when the battery voltage is low, the cranking speed decreases, the boost pressure decreases, and the intake amount of starting fuel per unit time decreases. Therefore, the energizing time of the coil 12 (opening time of the solenoid on-off valve) increases. By doing so, sufficient starting fuel is supplied.

After the engine is started, the electromagnetic on-off valve C is closed as described above, and the supply of the starting fuel from the fuel reservoir 10 is stopped.
Then, the fuel in the fuel chamber 26 is supplied to the engine 31 through the fuel jet 25, the fuel injection hole 6, the throttle 8a of the throttle valve 8, and the intake passage 9. This fuel amount is adjusted by turning the lever 2.

When the diaphragm 28 of the fuel pump A vibrates up and down due to the pulsating pressure of the crank chamber of the engine, the fuel in the fuel tank 18 is sucked into the pump chamber via the pipe 16 and the check valve 27, and further, the check valve 24 and the passage 15. The fuel is supplied to the fuel chamber 26 via the inflow valve 23. The inflow valve 23 is opened and closed with the swing of the lever 21 receiving the force of the atmospheric pressure spring received by the diaphragm 19, and the fuel chamber 26 is opened.
A predetermined amount of fuel is maintained at a pressure slightly higher than the atmospheric pressure.

In the above, the case of the diaphragm type vaporizer has been described. However, the present invention can be applied to a float type vaporizer.

[Effects of the Invention] As described above, the present invention provides an internal combustion engine that supplies starting fuel from a fuel chamber of a carburetor to a intake passage via a normally closed electromagnetic on-off valve, in the vicinity of a coil of the electromagnetic on-off valve. A thermistor for detecting a temperature change of the coil as a resistance change is provided, and a switch interlocked with a closing operation of a start switch for driving a start motor with respect to a power supply battery, a coil of the solenoid on-off valve, and a switching transistor are connected in series. Connected, the base voltage of the switching transistor is controlled by the thermistor, and when the temperature of the coil of the solenoid on-off valve is lower than a predetermined value, the switching transistor is turned on, and the temperature of the coil of the solenoid on-off valve becomes a predetermined value. Since the switching transistor is turned off when the voltage exceeds the threshold value, the following effects are obtained.

(A) Since the starting fuel corresponding to the temperature condition is supplied, the engine can be started reliably and easily.

(B) Since it does not use the primary coil signal of the flywheel magnet of the engine, the transistor method, CDI
It can be used regardless of the configuration of the ignition circuit such as the method.

(C) Since the configuration of the control circuit is simple, the size is reduced.
It is possible to configure integrally with the electromagnetic on-off valve.

(D) Since it is not necessary to directly measure the temperature of the engine, wiring of the engine is reduced, assembly with the engine is simplified, and the area around the engine is compact.

(E) It can be used in engines with different battery voltages, and can cope with voltage changes due to insufficient charging.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a starting fuel supply device for a carburetor according to the present invention, FIG. 2 is an electric circuit diagram of the starting fuel supply device of the carburetor, and FIG. FIG. 4 is a diagram illustrating a relationship between the temperature of the coil and the temperature of the coil. C: solenoid on-off valve, 1: carburetor, 9: intake passage, 10: fuel reservoir, 1
2: Coil, 26: Fuel chamber

Claims (1)

(57) [Claims] An internal combustion engine for supplying starting fuel from a fuel chamber of a carburetor to an intake passage via a normally closed solenoid on-off valve,
A switch disposed in proximity to a coil of the electromagnetic on / off valve for detecting a temperature change of the coil as a resistance change, and a switch interlocked with a closing operation of a start switch for driving a starter motor with respect to a power battery; The coil and the switching transistor are connected in series, and the base voltage of the switching transistor is controlled by the thermistor, and when the temperature of the coil of the solenoid on-off valve is lower than a predetermined value, the switching transistor is turned on. The starting fuel supply device for a carburetor, wherein the switching transistor is turned off when the temperature of the coil of the solenoid on-off valve exceeds a predetermined value.