JPS626286Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a device for returning excess fuel from the fuel sent to the carburetor of an internal combustion engine to a fuel tank.

Generally, fuel is sent from the fuel tank to the float chamber of the carburetor using a fuel pump, but since the fuel flow rate supplied from the carburetor to the engine varies greatly depending on the engine operating condition, The capacity of the pump is set so that there will be no shortage of fuel even when the required fuel flow rate is at its maximum.

Therefore, in areas where the required fuel flow rate is low, such as during idling, excess fuel is returned to the fuel tank via the bypass passage.

In order to control the flow rate of the returned fuel according to the operating conditions, a device as shown in FIG. 1 has been proposed (Japanese Utility Model Publication No. 103663/1983).

The fuel in the fuel tank 1 is passed through a filter 2 in a supply pipe 5 and then sent to a carburetor (float chamber) 4 by a fuel pump 3.

Fuel is supplied to the engine as a mixture from the carburetor 4, but excess fuel is returned to the fuel tank 1 via the variable flow valve 10 of the return pipe 6.

The variable flow path valve 10 is composed of a solenoid valve whose operation is controlled via the vehicle speed switch relay 9, and the ignition switch 8
In the ON state, a vehicle speed switch (not shown) closes when the vehicle speed is below a predetermined low speed range, and the relay 9
When the contact 9a turns on, the flow path variable valve 10
is energized to open and increase the return fuel flow.

Therefore, especially when the engine is restarted in a high-temperature atmosphere, a large amount of fuel vapor accumulated in the fuel system piping is sent into the carburetor float chamber immediately after startup, causing the fuel vapor to flow into the carburetor main nozzle, air bleed, or air vent. By being forced out of the tube, these fuels and vapors overflow into the intake passage, causing the mixture to temporarily become overrich.
This tends to make restarting difficult.
In such a case, the opening degree of the variable flow path valve 10 is increased to make it easier for the vapor to flow through the return pipe 6, thereby preventing over-concentration of the air-fuel mixture and improving the restart characteristics.

On the other hand, if the variable flow path valve 10 closes while the vehicle speed switch relay 9 is turned OFF and the variable flow path valve 10 is closed, the fuel is returned only through the small-diameter orifice 10a, which prevents more return fuel than necessary from flowing out from the carburetor 4. Therefore, sufficient fuel can be supplied to the engine even at high speeds and high loads.

However, in this device, the opening degree of the variable flow path valve (variable orifice) 10 is controlled by the vehicle speed switch relay 9, so even when driving under high load in a low speed gear, if the vehicle speed is low, the flow path will change. The variable valve 10 would open, and in such a case, the engine required fuel flow rate could not be ensured, resulting in a lack of engine output.

The present invention provides a return fuel control system that solves the above-mentioned problems by increasing the return fuel flow only in low speed and low load regions where the required fuel flow rate of the engine is low.

An embodiment in which the present invention is applied to an engine with an automatic transmission will be described below with reference to the drawings.

15 in the figure is an inhibitor relay, which is energized when the gear shift position of the automatic transmission is in parking or neutral range, and its contact 15a is
Turns on.

A series circuit including a vacuum switch 16 and a rotation speed switch 17 is interposed in parallel with the inhibitor relay 15.

Vacuum switch 16 senses suction negative pressure and turns ON when the negative pressure exceeds a predetermined value corresponding to low load such as when idling, and rotation speed switch 1
Reference numeral 7 also turns on the ignition pulse of the ignition coil in a low rotational speed range below a predetermined value, and these two switches 16 and 17 constitute means for detecting a low speed and low load state.

Relay 18 is the inhibitor relay 15 above.
contact 15a is turned on, or both vacuum switch 16 and rotation speed switch 17 are turned on.
When the temperature reaches 1, the contact point 18a is closed and the flow path variable valve 10 is energized to open.

Regarding other components, the same parts as in FIG. 1 are given the same reference numerals, and the operation will be explained next.

When the engine is started, the gear shift position of the transmission is in neutral or parking range, so relays 15 and 18 are turned ON, energizing the flow path variable valve 10, and the diameter of the orifice through which the return fuel passes is expanded. increases.

Furthermore, even when the gear position of the transmission is in the drive range, under low load conditions such as idling, both the vacuum switch 16 and the rotation speed switch 17 are turned on, and similarly, the contact 18a of the relay 18 is turned on.
is closed, and the flow path variable valve 10 is energized.

In this way, in an area where the engine requires less fuel (the shaded area in Fig. 3), the flow path variable valve 10 is opened wide to ensure that the excess fuel is returned to the fuel tank 1, which can be used, for example, to prevent overflow when the engine is restarted at a high temperature. Prevent the phenomenon.

On the other hand, while the vehicle is running (the transmission is in the drive range), if either the vacuum switch 16 or the rotation speed switch 17 is turned OFF, the relay 13 is not energized and the flow path variable valve 10 is closed. , fuel is returned only from the small diameter orifice 10a.

Therefore, even at low speeds and high loads when the engine speed is low but the throttle valve is open and the suction negative pressure is weak, the fuel flow rate required by the engine can be maintained without increasing the return fuel as in the conventional case. can be secured.

As described above, according to the present invention, a means for detecting a low speed and low load condition is provided, and the opening degree of the flow path variable valve is increased only during low speed and low load conditions, thereby preventing the overburden phenomenon at the time of a high temperature restart. This has the effect of reliably avoiding fuel supply shortages at low speeds and high loads.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional device. FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram showing its operating characteristics. 1...Fuel tank, 3...Fuel pump, 4...
Vaporizer, 5... Supply piping, 6... Return piping, 10
... Variable flow path valve, 15 ... Inhibitor relay, 16 ... Vacuum switch, 17 ... Rotation speed switch, 18 ... Drive relay.

Claims (1)

[Scope of utility model registration request] In a fuel return device that returns part of the fuel supplied from a fuel tank to an engine via a supply pipe by a fuel pump to the fuel tank via a return pipe, a flow path variable valve is provided in the middle of the return pipe. At the same time, an engine suction negative pressure detection means and a rotation speed detection means are provided, and the opening degree of the variable flow path valve is adjusted at low speed and low load of the engine when the suction negative pressure is above a predetermined value and the rotation speed is below a predetermined value. A return fuel control device for an internal combustion engine configured to increase the opening degree and decrease the opening degree in other conditions.