JPH0332973Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air flow meter for an internal combustion engine.

In an internal combustion engine using an electronically controlled fuel injection device that supplies fuel to the engine through a fuel injection valve,
The opening and closing of the injection valve is controlled according to the amount of intake air taken into the engine, and an intake air flow meter is provided to measure the amount of intake air. As such an intake air flow meter, a rotatable flap is provided in the intake air passage, and since this flap rotates according to the amount of intake air, a voltage at a level corresponding to the rotation of the flap is generated using a potentiometer. There is an air flow meter to do this.

By the way, in electronically controlled fuel injection devices,
The amount of fuel injected at one time is approximately determined by the output voltage level of the air flow meter, that is, the amount of intake air.A fuel injection pulse corresponding to this amount of fuel injection is generated by the control circuit, and electromagnetic injection is performed according to the pulse width of the fuel injection pulse. Fuel is injected and supplied to the engine by driving the valve. This injection supply typically consists of one engine cycle (intake, compression, explosion, exhaust).
The fuel injection is performed twice during this period, and the fuel amount required by the engine is achieved by two injections. This is because even if the injection capacity of the electromagnetic injection valve is increased, there is a limit, so when the engine is running at high speed, the required amount of fuel cannot be supplied by one injection per engine cycle, and the injection capacity of the electromagnetic injection valve is This is also because if the fuel injection amount is large, the injection amount will not be proportional to the pulse width of the fuel injection pulse in the portion where the injection amount is small. However, the electromagnetic injection valve causes a delay in operation with respect to the supplied fuel injection pulse due to the influence of the inductance of the electromagnetic coil.
That is, a valve opening delay and a valve closing delay occur. Therefore, when the engine speed becomes higher than a predetermined speed, and the air-fuel ratio of the engine-required mixture is particularly rich, the fuel injection pulse width increases and the period of one engine cycle shortens. Due to the delay in operation, the next fuel injection pulse may be supplied before the electromagnetic injection valve closes, and the valve may remain open and fuel may be injected and released. As fuel is injected and released, the air-fuel ratio of the air-fuel mixture becomes richer and richer, resulting in a decrease in engine output. For this reason, conventionally, the output voltage characteristic of the air flow meter, which is predetermined to make the air-fuel ratio of the required air-fuel mixture leaner, has been changed to prevent the fuel from being injected. The solid line a in FIG. 1 is the output voltage characteristic of the air flow meter that is predetermined to satisfy the air-fuel ratio, and the solid line b is the output voltage characteristic of the air flow meter that has been changed to make the air-fuel ratio leaner. In addition, in Fig. 1, U is the output voltage,
_UB is the voltage applied to the potentiometer, and Q is the intake air amount. Moreover, the broken line C is the limit line at which the injection is released.

However, in such air flow meters, the output voltage characteristics have been changed by trimming the resistance of the potentiometer, but due to the structure of the potentiometer, it is compatible with the high rotation range of the engine where fuel is injected and released. Since it is not possible to change only the output voltage characteristics of the intake air amount portion, there is a problem in that the air-fuel ratio becomes lean even in the medium rotation range of the engine.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an air flow meter that can prevent fuel from being injected and released without adversely affecting the air-fuel ratio in a medium engine speed range.

The air flow meter according to the present invention has a stopper that prevents the slider of the potentiometer from rotating when the flap rotates beyond a predetermined angle.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 2 and 3.

In FIG. 1, a case 1 has an air passage 2 having a square cross section and a damper chamber 3 in which a part of the air passage 2 projects outward in a fan shape. A shaft 4 is rotatably supported upstream of the air passage 2 and near the boundary with the damper chamber 3. flap 5
consists of two plates (one end is the flap plate 6,
At the other end, a damper plate 7) is connected to the shaft 4 at a predetermined angle. flap plate 6
rotates in the air passage 2 according to the intake air flow rate,
It also has a backflow valve 8 for backfire. The damper plate 7 rotates within the damper chamber 3 and uses the expansion and contraction action of the air in the damper chamber 3 to close the flap 5.
It eases the overall pulsation. The shaft 4 is biased by a helical spring (not shown) in a direction opposite to the direction of rotation of the flap 5 caused by the intake air flow.
The potentiometer is configured to actuate the potentiometer. The potentiometer is housed in a potentiometer chamber formed by the case 1.

FIG. 3 shows the potentiometer section. In FIG. 3, reference numeral 9 denotes a potentiometer chamber formed by the case 1, and within the potentiometer chamber 9, an insulating substrate 10 is fixed to the case 1. A pattern is formed on the insulating substrate 10 by arc-shaped resistance plates 11 and the like, and contacts 12 are in contact with the resistance plates 11. The contactor 12 is fixed to a slider 13, and the slider 13 is adapted to rotate in conjunction with the shaft 4 of the flap 5. Further, a stopper 14 is provided within the rotation angle of the slider 13 to prevent the slider 13 from rotating beyond a predetermined angle. stopper 1
Reference numeral 4 is a screw member, and the blocking position can be adjusted.

In the air flow meter according to the present invention having the above configuration, the flap 5 is normally moved to an angle where the return torque of the helical spring is balanced with the pressure of the intake air flowing in the directions of arrows A and B depending on the open state of the throttle valve. Rotate and slider 1
3 also rotates in the direction of arrow C in conjunction with flap 5. The contactor 12 moves while contacting the resistance plate 11 as the slider 13 rotates. Therefore, since the voltage U _B is applied between both ends of the resistive plate 11, the output voltage U obtained through the contact 12 has a level corresponding to the rotation angle of the flap 5. However, if the amount of intake air increases and the flap 5 is able to rotate over a predetermined angle, for example, from 0 to 100 degrees, when it rotates over 80 degrees, the slider 13 will move as shown by the broken line D in FIG. The rotation is prevented by contacting the stopper 14 at a predetermined angular position. Therefore, even if the flap 5 rotates by a predetermined angle or more, the output voltage U remains at the voltage level when the flap 5 is at a predetermined angular position, as shown in the output voltage characteristics shown in FIG. Incidentally, the broken line d in FIG. 4 is the limit line for releasing the fuel. Therefore, when the amount of intake air increases and the engine speed rises to a high engine speed where fuel is injected and released due to the activation delay of the electromagnetic injection valve as in the past, the intake air is supplied to the control circuit that generates the fuel injection pulse. Since the output voltage U of the air flow meter is at the voltage level when the flap 5 is at a predetermined angular position, the fuel injection pulse width does not increase so much that the fuel is injected and released.

Note that the rotation of the slider 13 is caused by the stopper 14.
Even if the flap 5 is prevented by a predetermined angle, the flap 5 will rotate by a predetermined angle or more if a predetermined torque or more is applied.

As described above, the air flow meter according to the present invention can prevent fuel from being injected and released without adversely affecting the air-fuel ratio in the middle engine speed range, unlike conventional methods.

Furthermore, in the air flow meter according to the present invention, the slider of the potentiometer is in contact with the stopper, and the stopper is not in direct contact with the flap made of a soft material, so deformation and damage to the flap can be prevented. .

Furthermore, since the slider is prevented from rotating by the stopper and the flap itself is not stopped from rotating beyond a predetermined angle, the intake air amount is prevented from being restricted by the flap, which may adversely affect the engine output. do not have.

[Brief explanation of the drawing]

Fig. 1 is an output voltage characteristic diagram of a conventional air flow meter, Figs. 2 and 3 are diagrams showing an embodiment of the air flow meter of the present invention, and Fig. 4 is an output voltage characteristic diagram of the air flow meter according to the present invention. . Explanation of the symbols of the main parts, 1...Case, 2...
Intake air path, 3... Damper chamber, 5... Flap, 9... Potentiometer chamber, 10... Insulating board, 11... Resistance plate, 12... Contact, 13...
Slider, 14...stopper.

Claims (1)

[Scope of utility model registration request] a flap provided in an intake air passage of an internal combustion engine that rotates in accordance with the air flow rate; a potentiometer that includes a slider that rotates in conjunction with the flap and generates an output voltage at a level that corresponds to the rotation of the slider; An air flow meter comprising: a stopper that comes into contact with the slider and prevents rotation of the slider without inhibiting rotation of the flap when the flap rotates by a predetermined angle or more.