JPS5916529Y2 - engine fuel supply system - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fuel supply system for an engine in which a fuel pump is arranged in a fuel pipe that communicates a fuel tank with a carburetor float chamber.

Conventionally, in order to prevent vapor lock or percolation that occurs in the fuel supply system at high temperatures, the discharge side of the fuel pump installed in the fuel pipe that communicates the fuel tank and the carburetor float chamber with the suction side of the fuel tank or the fuel pump. In the former case, the fuel is always returned to the fuel tank, or only when the temperature is high via a temperature-sensitive valve, and in the latter case, the return is made when the temperature is high.

However, if the engine is stopped after driving under high-temperature conditions and left for a while, the temperature in the engine compartment will rise and a large amount of paper will be generated in the fuel supply system.

When cranking to restart the engine, the fuel pump pumps most of these vapors along with the fuel into the carburetor float chamber, disrupting the fuel level and making the mixture too rich, making it difficult to restart. becomes.

In the conventional device described above, if the capacity of the fuel pump or the diameter of the return passage is set to eliminate such problems, it will be possible to cover the range of low rotational speeds, that is, low fuel consumption, but on the other hand, it will be possible to cover the range of low rotation speeds, that is, low fuel consumption, but on the other hand, acceleration or This causes a problem that the absolute value of supplied fuel is insufficient during high-speed, high-load operation.

The present invention solves these problems and provides a fuel supply system that can supply appropriate fuel not only when restarting the engine at high temperatures but also during normal driving.

Embodiments will be described below with reference to the accompanying drawings.

FIG. 1 shows a system diagram of an example in which the fuel is constantly circulated.

The system is supplied from a fuel tank 1 to a carburetor 3 via a fuel pump 2, and is equipped with a return passage 4 and a bypass passage 5, and this bypass passage 5 is connected to six control valves, a third
Control opening/closing by referring to the diagram (closed during normal engine operation)
.

7 is a temperature detection switch (e.g. water temperature switch) that opens when the water temperature rises, 8 is an ignition switch, 9 and 10 are relays, and relay 10 is connected to the neutral terminal N of the alternator and shuts off when the engine starts. It is designed to function as an engine start cranking detection device.

Next, its function will be explained.

When the engine water temperature is higher than a predetermined value (for example, 50°C) (water temperature switch 7 is off, therefore the contact of relay 9 is on), relay 1 is turned on when cranking the ignition switch.
Since the contact 0 is on, the solenoid of the control valve 6 is turned on, the valve 6' is opened, and most of the fuel is returned to the pump suction side through the bypass passage 5.

That is, the function of the fuel pump is substantially stopped.

Further, paper generated in the fuel passage between the fuel pump 2 and the carburetor float chamber 3 returns to the tank 1 via the return passage 4.

The float chamber will not be disturbed by the paper.

When the engine starts up due to the fuel remaining in the float chamber or the intake system, current flows to the N terminal circuit of the alternator, which opens the relay 10, which turns off the solenoid of the control valve 6 and bypasses the fuel. Normally supplied to the vaporizer.

In conditions other than the above, the control valve 6 does not work during cranking or during engine starting.

In the explanation, the engine cooling water temperature is used as the engine temperature signal, but oil temperature, engine room temperature, fuel temperature, etc. can also be used as the signal.

Also, a hydraulic signal may be used instead of the rotational speed.

Furthermore, it is within the scope of the invention to use a cranking switch-on signal instead of an ignition switch-on signal.

As described above, according to this device, a side passage is provided upstream and downstream of the fuel pump, and a solenoid valve controlled by an engine temperature switch is provided in the side passage, and the solenoid valve is operated when the cranking detection device and the engine temperature switch are closed. Since the engine is activated, it has excellent advantages such as improving the startability of the engine at high temperatures and enabling high-load operation at high temperatures.

That is, restartability under heat-resistant conditions is improved, and the cranking time until starting can be shortened.

FIG. 2 shows another embodiment, in which the electromagnetic pump 2 is used as the fuel pump, and the electromagnetic pump 2 operates when the ignition switch 8 is turned on.

When restarting under high temperature conditions, the engine water temperature switch 7 is turned on, and when the starter switch 11 is turned on to crank the engine, the relay 12 is activated to turn off the electromagnetic pump circuit and the electromagnetic pump is not activated.

In the figure, reference numeral 13 denotes a control valve. By opening the return passage 4 through bimetal operation at high temperatures, paper generated in the fuel passage between the fuel pump 2 and the carburetor float chamber 3 passes through the valve 13 to the tank 1. Return to

Note that for the purpose of the present invention, various combinations as shown below are possible.

Temperature detection device (1) Engine water temperature switch, (2) Engine room temperature switch, (3) Oil temperature detection switch, (4) Fuel temperature switch, Engine start cranking detection device (1) Ignition switch + alternator terminal (1st (Example in the figure), (2) Starter switch, (3) Rotation speed switch (ex 400 rpm or less),
(4) Oil pressure switch, fuel pump function stop device (1) Fuel pump bypass + electromagnetic (cutoff) valve, (2) Ten electromagnetic (cutoff) valves that connect the fuel pump discharge side and return passage (3) Fuel pump direct connection make it stop.

(Example in Figure 2) (4) Shut off the fuel passage on the float chamber hole opening side.

[Brief explanation of drawings]

FIGS. 1 and 2 are schematic diagrams each illustrating an embodiment of the present invention, and FIG. 3 is a sectional view of an example of the control valve used in FIG. 1. 1...fuel tank, 2...fuel pump or electromagnetic pump, 3...carburizer, 4...
・Return passage, 5...Bypass passage, 6...
... Control valve, 7 ... Temperature detection switch, 8 ... Ignition switch, 9
...Relay, 10 ...Relay (cranking detection switch), 11 ...Starter switch, 12 ...Relay

Claims (1)

[Scope of utility model registration request] In an engine fuel supply system in which a fuel pump is installed in a fuel pipe that communicates between the fuel tank and the carburetor float chamber, there is a return passage that returns fuel from the fuel passage between the fuel pump and the carburetor float chamber to the tank, and a return passage that returns fuel to the float chamber. a fuel pump function locking device that substantially stops the fuel supply of the engine, and an engine temperature detection device having a contact point that activates when the temperature is higher than a predetermined temperature in an electric circuit that activates the fuel pump function locking device; An engine start cranking detection device is provided with a contact that operates during cranking, and both contacts work together so that the fuel pump function stop device is configured to operate only during start cranking when the temperature is high. Features: Engine fuel supply system.