JPH0223713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixture metering device for supplying a mixture of air and fuel at an appropriate mixture ratio to an internal combustion engine.
The present invention provides an inexpensive air-fuel mixture metering device capable of supplying fuel without delay.

Conventionally, a carburetor or a fuel injection device has been used as a device for metering and supplying an air-fuel mixture to an internal combustion engine. The carburetor has been used as a mixture regulating device for a long time, but it is a mechanism that mechanically regulates the quantity of the mixture using ventilate pressure, and is compatible with a wide range of engine conditions such as low-speed jets, accelerator pumps, etc. A complicated mechanism has been added for this purpose. Since it is difficult for this type of mechanism to harmonize with each other, the seemingly contradictory proposition of achieving recent exhaust gas regulation values and maintaining vehicle drivability has almost reached its limit.

In order to easily accomplish this proposition, fuel injection systems that electrically control the mixture ratio have been adopted and are replacing conventional carburetors. There are various types of fuel injection systems, but basically they measure the engine's intake air volume or intake pipe internal pressure electrically or mechanically, and then inject pressurized fuel to mix it with the air. It is something. The required amount of fuel is often calculated electronically, and it is obvious that this calculation can be easily achieved even if the setting of the mixture ratio is complicated, especially when this calculation is performed by a control device using a microcomputer. be. In addition, various parameters such as engine temperature, air temperature, or exhaust gas components can be measured to perform high-level air-fuel mixture adjustment, so it is possible to improve engine starting performance at low temperatures, automate or speed up warm-up, improve fuel efficiency, etc. It greatly contributes to improved performance, and there is no question that it will become the mainstream of air-fuel mixture control devices for automobiles in the future.

However, conventionally used fuel injection devices have the following drawbacks. First, in the air flow rate detector that detects the amount of intake air based on the opening degree of the movable air valve installed in the intake air passage, the rotating shaft of the movable air valve is worn out and the measured value changes over time. Second, the movable air valve needs to be a highly accurate mechanism that can respond to the range of changes in the amount of intake air and measure a 40 to 50 times measurement range within an error of a few percent or less. Thirdly, if the braking force of the movable air valve is set to respond to the low air flow velocity corresponding to the idle state of the engine, measurement errors will occur in response to vehicle body vibration, so it will effectively stop when the engine is close to the idle state. Fourthly, the response of the movable air valve is delayed in response to dynamic changes in the air flow rate, and the delay in calculating the required amount of fuel and the response of the fuel supply means cause the mixture ratio to change. For example, excessive errors may occur. The fourth drawback is that it has a serious negative effect on the drivability of the car, so a mechanism for detecting acceleration, such as a means for detecting the opening speed of an air throttle valve, is added, and this output is used to supply additional fuel. Although it is normal to do so, it is undesirable because it complicates the mechanism and increases the price.

This invention has been made to improve the above-mentioned drawbacks, and below, FIG. 1 shows the configuration of an embodiment of the air-fuel mixture metering device, and FIG.
An embodiment of the present invention will be described with reference to the drawings and FIG.

In Fig. 1, 1 is an accelerator pedal, 2 is a mixer installed in the intake passage of the engine, 2-1 is a communication hole for pressure detection, and 2-2 is connected to the accelerator pedal 1 through a push rod 2-8. An air throttle valve that moves up and down in conjunction with each other is inserted into a ventilate formed in the intake passage of the engine, and controls the cross-sectional area SA of section A in the figure to adjust the amount of intake air in the engine. Reference numeral 2-3 denotes a needle valve for metering fuel, which is fitted into the end of the fuel passage 2-5 constituting a movable valve port formed in the air throttle valve, and is connected to the needle valve 2-3 and the fuel passage 2-5. Accordingly, a fuel control valve with a variable opening area is constructed.

Numerals 2-4 and 2-6 are fuel passages, and fuel is discharged from the end outlet of the fuel passage 2-6 to a section A in the intake air passage, where it is mixed and atomized into the air flow. A spring 2-7 is arranged to press the air throttle valve 2-2 to the closed side and throttle the air flow when the accelerator pedal 1 is released.

Reference numeral 3 denotes an electric controller which generates a fuel pressure control signal based on the output of the pressure detector 4. Reference numeral 5 denotes a fuel pressure controller comprising, for example, an electric pump, which is driven by the fuel pressure control signal.

Next, the operation of the apparatus shown in FIG. 1 will be explained. When the accelerator pedal 1 is opened and closed to control the output of the engine, the air throttle valve 2-2 moves up and down, changing the air passage area S _A. That is, part A constitutes a ventilate with a variable cross-sectional area.

Therefore, the air flow rate Q _A passing through part A is expressed by the following formula.

Q _A = S _A・v _n (1) However, v _n is the air flow velocity in the ventilate section A, and it is known that the following relationship holds approximately with the pressure P ₁ in the A section. Here, P ₀ represents the pressure upstream of the air throttle valve, that is, approximately atmospheric pressure, k is the specific heat ratio, g is the gravitational acceleration,
γ ₀ represents the air density. Air flow velocity is determined by equation (2).
It can be seen that v _n can be obtained by measuring the A part pressure P ₁ .

Figure 2 shows this relationship. It can be seen from FIG. 2 that v _n converges to a constant value below a certain value of pressure P ₁ - approximately P ₁ /P ₀ =0.5. Therefore, the pressure detection range is limited to wide variations in air flow rate - from approximately 40 to
It can be seen that a range of 0.5P ₀ to approximately twice P ₀ is suitable for 50 times -.

Next, the fuel passage 2-5 is raised and lowered by the upper and lower movements of the air throttle valve 2-2, and the area of the metering orifice portion A' of the fuel control valve is formed by the needle valve 2-3.
Since S _A ′ is configured to be interlocked, S _A ′=
There is a relationship kS _A ′.

However, k is a constant. Amount of fuel applied to part A′
Q _F is expressed as Q _F =S _A ′·v _n ′ (3) where v _n ′ is the fuel flow velocity. If we set Q _A /Q _F =μ (4) to obtain a predetermined mixing ratio, then from (1), (3), and (4), v _n ′=S _A /S _A ′・v _n /μ (5 ) becomes. Substituting the relationship S _A ′=kS _A into equation (5) yields v _n ′=1/k・μ・v _n (6). According to equation (6), it can be seen that in order to obtain a predetermined mixture ratio, the fuel flow rate v _n ' needs to be made proportional to the air flow rate v _n . On the other hand, the fuel flow velocity v _n ′ is expressed by the following equation (7).

v _n ′=√2 _f ( ₂ − ₈ )≒√2 _f ( ₂ − ₁ )(7
) Here, γ _f is the fuel density, P ₂ is the upstream pressure of the orifice part A', that is, the output pressure of the fuel pressure controller 5, and P ₈
is the downstream pressure of the orifice part A' and the fuel discharge part pressure, and in the configuration shown in Fig. 1, the pressure of the ventilate part A is P ₁
almost equal to

From equations (6) and (7), the following relational expression is obtained: P ₂ = 1/2gγ _f k ² μ ² v _n ² +P ₁ (8). Therefore, if the fuel pressure of P ₂ is controlled according to the relationship of equation (8), a predetermined mixture ratio μ can be obtained.

Therefore, based on the output P ₁ of the pressure detector (4), the electric controller (3) calculates the air flow velocity v _n based on equation (2),
Next, the required fuel pressure P ₂ is calculated based on equation (8) using the air flow velocity v _n and the pressure P ₁ , and an electric signal corresponding to this output is given to the fuel pressure controller 5 to control the fuel pressure.
By obtaining P ₂ it becomes possible to generate a predetermined mixing ratio μ. In addition, in this embodiment, by providing the fuel discharge port in the ventilate part,
By setting P ₈ ≒ P ₁ , there is no need to adjust the pressure of P ₈ , and at the same time, fuel is discharged at the point where the air flow velocity is maximum, improving fuel atomization.
This configuration is not the main feature of the present invention, and does not necessarily require this configuration.

Next, the transient operation of the device of the present invention will be explained with reference to FIG. The air flow rate Q _A increases rapidly when the accelerator pedal is pressed suddenly, and then increases gradually as the engine speed increases. The diagram shows that the air flow velocity v _n once slows down due to a sudden increase in the cross-sectional area S _A of the ventilate section, and then increases as Q _A gradually increases. In the same figure, the cross section of the fuel orifice
S _A ′ communicates with area S _A and changes without delay,
On the other hand, the fuel flow velocity v _n ' has a delay time td with respect to the air flow velocity v _n . This delay td includes the aforementioned delay time of the fuel pressure controller 5, calculation delay in the electric controller 3, etc., but it is also possible to proactively generate a delay time to obtain a desired delay time td. Now, the fuel flow rate Q _F is expressed as v _n ′ × S _A ′ according to equation (3), so the response is as shown in Q _F in Figure 3, and the amount of fuel is statically lower than the required amount during the time td. Also, an excess amount of fuel will flow, making it possible to increase the amount of fuel required when the engine suddenly accelerates. This increase requires a balance between the level of exhaust gas regulations and the level required from drivability, and this adjustment can be made by adjusting the delay time td. Furthermore, in order to gradually reduce the increase in fuel amount, it is also possible to delay the fuel flow velocity v _n ' through, for example, a first-order delay element, thereby producing a response as shown by the broken line at v _n ' in FIG.

As is clear from the above description, the air-fuel mixture metering device of the present invention has the following effects.

The first effect is that it has a mechanism that does not cause changes in measured values over time due to wear and tear, such as with a movable air valve. The second effect is that the range of 40 to 50 times the intake air amount is not directly measured, but only twice (0.5P ₀ to P ₀ )
Since the amount of intake air can be calculated by measuring a pressure range of approximately The third effect is that in the past, if the sensitivity of the movable air valve was increased too much, it would respond to vehicle body vibration and cause measurement errors, making it virtually difficult to detect the air flow rate near the idle state. Since the air throttle valve 2-2 is linked to the accelerator pedal and has a mechanism that does not respond to the air flow velocity, it is possible to set the force without being affected by vehicle body vibration. The fourth effect is that the opening area of the fuel control valve changes in conjunction with the air throttle valve, so
This means that the air flow rate measurement delay and the fuel supply means delay contribute to the acceleration increase required when the engine accelerates, and that an arbitrary function can provide an acceleration increase without delay. Therefore, it is not necessary to provide a mechanism for detecting acceleration and to additionally supply fuel, and it is also a great advantage that the mechanism can be simplified.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure shows a correlation characteristic diagram between the ventilator pressure and the air flow velocity, and FIG. 3 shows a transient operation diagram of the apparatus shown in FIG. 1. 1... Accelerator pedal, 2... Mixer, 2-2
... Air throttle valve, 2-3 ... Metering needle valve, 3
. . . electric controller, 4 . . . pressure detector, 5 . . . fuel pressure controller.

Claims (1)

[Claims] 1. An air throttle valve 2-2 that is disposed in a ventilate section formed in an intake passage of an engine and changes the opening area of the ventilate section in conjunction with the accelerator pedal.
and fuel control valves 2-3 and 2-5 whose opening areas are controlled to increase in accordance with an increase in the opening area of the ventilate section in conjunction with the air throttle valve, and the air flow velocity of the ventilary section is maximized. a pressure detector 4 that detects the pressure at or around the maximum throttle part; an electric controller 3 that receives the output of the pressure detector and generates a fuel pressure control output corresponding to the output; It is composed of a fuel pressure controller 5 that controls the fuel supply pressure to the fuel control valve, and a discharge port 2-6 that discharges the fuel metered by the fuel control valve to the intake passage of the engine and mixes it with air.
A mixture adjusting device that controls the mixture ratio of air and fuel to a predetermined value. 2. The air-fuel mixture metering device according to claim 1, wherein the fuel discharge port is provided at or around the maximum constriction portion of the ventilate portion.