JPS60182324A - Air-fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To control air-fuel ratio to a good condition, by obtaining a quantity of fuel in accordance with the speed of an engine and its throttle valve opening or the pressure of an intake pipe in the range of operation of the engine where a quantity of intake air can not be measured due to pulsation. CONSTITUTION:A quantity of fuel is normally obtained in accordance with the signal of an intake air amount sensor 1 outputting a frequency in proportion to a quantity of air. The quantity of intake air can not be accurately detected in the operative range of an engine where pulsation of the intake air and its blow back are increased. In the range such as described, the quantity of fuel is obtained in accordance with a signal from a speed sensor 2 and a load sensor 3 which detects a throttle valve opening or the pressure of an intake pipe. In this way, air-fuel ratio can be controlled to a good condition even in the range with a large level of pulsation.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a device for controlling the mixing ratio (air-fuel ratio) between the amount of air required for complete combustion of fuel and the amount of fuel in an engine. In particular, the present invention relates to an air-fuel ratio control device for an engine that can perform good air-fuel ratio control even in engine conditions in which intake air amount detection is difficult.

[Prior art]

In general, the intake air amount of an engine varies over a wide range and constantly fluctuates due to various factors, so it is technically difficult to measure it stably and accurately over the entire range. In particular, when the engine condition is low speed and high load, the intake air pulsates greatly and is also affected by blowback, so the error in intake air amount detection is large. Therefore, since the air-fuel ratio error is significant, there is a risk that the engine output will be completely reduced or that the engine will be damaged due to abnormal combustion.

Conventionally, in order to avoid such inconveniences, measures have been taken to completely reduce pulsation by inserting a resonator of considerable size into the engine's intake air passage, or by increasing the passage length. was.

However, such a method has a large side effect such as completely impeding mountability, and such countermeasures often have the disadvantage that the structure becomes complicated and large, making it uneconomical.

Therefore, there has been a demand for more effective countermeasures, but
There is still no accurate and easy way to do so.

[Summary of the invention]

In view of the above points, the present invention has been made in order to solve such problems, eliminate such drawbacks, and satisfy the above-mentioned requirements. In addition, it is possible to supply fuel without the influence of intake pulsation, and there is no shock caused by switching, and good engine output can be obtained, and the configuration is simplified. Accordingly, the present invention aims to provide an air-fuel ratio control device for an engine that can greatly improve performance at a low price.

In order to achieve such an object, the present invention generates a frequency corresponding to the true intake air amount from the engine speed and throttle valve opening or intake pipe pressure in a region where intake air amount cannot be measured due to pulsation. This system injects fuel in synchronization with the frequency, and detects at least one of the engine intake air amount, engine speed, and throttle valve opening or intake pipe pressure, which represents the engine load, to determine the appropriate air flow. This system calculates the amount of fuel that corresponds to the fuel ratio and controls the fuel injection solenoid valve to supply the desired fuel to the engine.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of an engine air-fuel ratio control device according to the present invention, and only the parts necessary for explanation are shown.

In the figure, 1 is an intake air amount sensor that detects the engine intake air amount and generates a frequency fa proportional to the air amount; 2 is a rotation sensor that detects the engine rotation speed and generates an output N';
3 is a load sensor that detects at least one of the throttle valve opening or intake pipe pressure representing the engine load and generates an output θ; 4 is the output N of this rotation speed sensor 2 and the load sensor 3
A first calculation unit receives the output θ of the output θ and outputs a frequency fb and a state determination output S based on both or one of the outputs N and θ; Frequency fb from first calculation unit 4
and a switching unit which inputs the state discrimination output S and selects the frequency fa or frequency fb by referring to the state of the state discrimination output S and outputs the frequency f; 6 detects the engine cooling water temperature and outputs the frequency f; ■Temperature sensor that generates 7 is output A
The air-fuel ratio sensor 8 receives the frequency f from the switching section 5, the output WT of the temperature sensor 6, and the output A/F of the air-fuel ratio sensor 7, and receives the frequency ft- to generate a predetermined pulse width. 9 is an amplifier that amplifies the power of the pulse train obtained by the second calculation unit 8; 10 is the output of this amplifier 9; This is a fuel injection solenoid valve that is controlled to open and close by a fuel injection valve to supply the desired fuel to the engine.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIGS. 2 and 3. In Figure 2, the horizontal axis is the intake air amount Qa of the engine, and the vertical axis is the frequency fa, which is proportional to the intake air amount.
3 shows an example of the output of the intake air amount sensor 1 shown in FIG. 1 expressed as k. FIG. 3 shows an example of a method of driving the solenoid valve 10 shown in FIG.

First, as shown in Fig. 2, the intake air amount sensor 1 is of a type that generates a frequency fa' proportional to the intake air amount Qa of the engine, and is rarely known, for example, one that detects the Karman vortex frequency. Melt. In addition, in this Figure 2, QAmi
n and famin indicate the minimum point of the intake air amount Qa and the frequency fa, respectively.

As shown in Fig. 3, the method of controlling the fuel supply amount using the frequency fa is to use a pulse train with the frequency fi shown in (b), which is proportional to the frequency fa shown in (a), and the pulse width τ. , when the fuel injection solenoid valve 10 is controlled to fully open, the fuel supply amount Qf becomes Q t QCf i・τ, and since f i tx f aoc QB, Q
4 oc fast (X: expressed as Qa fist.

That is, the fuel supply amount Qf can constitute an air-fuel ratio in proportion to the intake air amount Qa.

Furthermore, the air-fuel ratio can be controlled to a desired value by changing the pulse width τ.

Now, the output frequency fa of the intake air amount sensor 1 is given to the switching section 5, and this switching section 5 changes the output frequency fa of the intake air amount sensor 1 according to the output state of the state determination output S from the first calculation section 4. It consists of something like a gate mechanism that allows passage and blocking.

The explanation will now be made assuming that the frequency fa is in a passing state.

First, the output frequency f=fa of the switching unit 5 is given to the second calculation unit 8, and this second calculation unit 8 has a branching function, and the frequency fa from the intake air amount sensor 1 is given to the second calculation unit 8. is converted into a frequency fi at which the fuel injection solenoid valve 1o can operate. Further, this second calculating section 8 has a second function of calculating and deriving the pulse width τ (see FIG. 3) according to the air-fuel ratio required by the engine.

A frequency fi proportional to the frequency fa obtained by the second arithmetic unit 8 having such first and second functions.
, a pulse train with a pulse width τ is output from the second arithmetic unit 8, and this pulse train is power amplified by the amplifier 9, and then
Controls the opening of the fuel injection solenoid valve 10. Since this solenoid valve 10 discharges fuel approximately proportional to the valve opening time, the amount of fuel supplied to the engine is Q("fi・τocQB・
As mentioned above, the engine can be operated at the required air-fuel ratio.

In FIG. 1, the second calculation unit 8 includes the output WT of the cooling water temperature sensor 6 and the output A/ of the air-fuel ratio sensor 7.
F is input. These inputs are evaluated by the second calculation unit 8VC and used as parameters for determining the required value of the air-fuel ratio, so as to influence the pulse width τ for driving the solenoid valve 10.

The present invention has been described above by taking as an example a device that performs air-fuel ratio control using an intake air amount sensor 1f that generates an output frequency fak proportional to the intake air amount of an engine.
Since the intake air amount of an engine varies over a wide range and constantly fluctuates due to various factors, it is technically difficult to measure it stably and accurately over the entire range. In addition, when the engine condition is low speed and high load, the intake air pulsates greatly and blows back, resulting in a large error in intake air amount detection.

In Figure 4, the horizontal axis represents the throttle valve opening θ which is the output of the load sensor 3, and the vertical axis represents the throttle valve opening θ and the output frequency fa of the intake air amount sensor 1. FIG. 2 is an explanatory diagram showing the relationship between the engine speed Nk and the engine speed Nk parameter output from the speed sensor 2.

In FIG. 4, in the zone S+ on the left side separated by the dashed line, there is little pulsation of intake air and the amount of intake air can be detected accurately, and in the zone S2 on the right side, due to the pulsation of intake air and blowback, The output is significantly shifted upward and downward relative to the true output (dashed line).

In such zone S2, an air-fuel ratio error occurs,
There is a risk of engine damage due to a decrease in engine output or abnormal combustion.

The present invention has been made to improve the above disadvantages, and will be explained below.

In FIG. 1, a first calculation section 4 receives outputs from a rotational speed sensor 2 and a load sensor 3, and its first function is to determine the state of the engine.

That is, when the state of the engine is in the zone Sl to the left of the dashed line in FIG. 4, the state determination output S = S
! Also, when entering the right zone S2, the state determination output 5=82'! Output z. Here, this fourth
The dash-dotted line in the figure can be easily determined by experiment. Next, the second function of the first calculation unit 4 is to operate in a region where the engine state is S = Sz, that is, in a region where an error occurs in the output of the intake air amount sensor 1 due to intake pulsation, etc. In this case, the frequency fb is generated based on the engine rotational speed N, which is the output of the rotational speed sensor 2, and the throttle valve opening degree θ, which is the output of the load sensor 3. This frequency fb is necessary because it simulates the true intake air amount shown by the broken line in FIG. Here, the true amount of intake air can be easily determined from an experimental value by inserting a resonator or a damper into the intake air passage of the engine to completely suppress intake pulsation. In addition, there are various well-known means for generating the frequency fb output from the first calculation section 4, and detailed explanation thereof will be omitted.
A timer device or a timer program that can preset the period T='/fbk corresponding to is suitable.

Next, when the state determination output S from the first calculation section 4 is S = S r, the switching unit 5 passes the frequency faIt from the intake air amount sensor 1, and the state determination output S is S = S.
When z, the frequency f from the first calculation unit 4.

This is a switch means that allows the signal to pass through and outputs it to the second arithmetic unit 8 at the subsequent stage. Therefore, the second calculation section 8Fi changes depending on the output frequency fa of the intake air amount sensor 1 in a region corresponding to zone 81 shown in FIG. 4 where there is no intake pulsation, and in a region corresponding to zone 82 shown in FIG. In the corresponding region, the fuel injection solenoid valve 1
Since a drive pulse train of zero is generated, a desired air-fuel ratio can always be achieved.

It is expected that the true intake air volume (see the broken line in Figure 4) will vary due to various factors such as engine manufacturing variations and atmospheric pressure. , for example, can be easily corrected by using the output A/F' of the air-fuel ratio sensor 7 for feedback control.

Further, in the above embodiment, the case where the throttle valve opening θ, which is the output of the load sensor 3, is used as an input to the switching unit 5 was explained as an example, but the present invention is not limited to this, and the intake air It is obvious that the same function can be achieved by the pressure P in the tube (not shown).

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the engine can be operated without using complicated means such as inserting a resonator of considerable size into the engine intake path or increasing the passage length. The system detects at least one of the throttle valve opening or intake pipe pressure, which is representative of the intake air volume, the rotational speed, and the engine load, calculates the fuel volume that will give an appropriate air-fuel ratio, and controls the magnetic valve for fuel injection. A simple configuration that supplies the desired fuel to the engine enables fuel supply that eliminates the effects of intake pulsation.
Furthermore, when switching from frequency fa to frequency fb or vice versa, the frequency is uniformly and continuously switched, so there is no shock caused by switching, and good engine output can be obtained. In the air-fuel ratio control device using one microprocessor per unit, there is a calculation means or the above-mentioned state discrimination output that generates the frequency fb and the state discrimination output S based on the engine rotation speed output N generated by the rotation speed sensor and the output θ generated by the load sensor. The switching means that refers to the state of S and selects either the frequency fa proportional to the air amount or the frequency fb mentioned above and outputs the frequency f is configured by software together with other components, so the configuration is simplified. In addition, it can be made smaller, the price can be reduced, and the power and performance can be greatly improved, so the practical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an engine air-fuel ratio control device according to the present invention, FIGS. 2 to 4 are explanatory diagrams of the operation of the embodiment shown in FIG. 1, and FIG. Fig. 1 shows an example of the output of the intake air amount sensor, Fig. 3 shows an example of the driving method of the solenoid valve shown in Fig. 1, and Fig. 4 shows the relationship between the throttle valve opening and the output frequency of the intake air amount sensor in the total rotation speed and total harameter. Draw a diagram. 1--Intake amount sensor, 2--Rotation speed sensor, 3
...Load sensor, 4...First calculation section, 5...
...Switching unit, 8...Second calculation unit, 9...Amplifier, 10...Solenoid valve. Agent Masuo Oiwa (15)

Claims (3)

[Claims] (1) An intake air amount sensor that detects the total engine intake air amount and generates a first frequency proportional to the air amount; a rotation speed sensor that detects the engine rotation deposit and generates the first output; A representative throttle valve opening degree fc is obtained by detecting at least one of the intake pipe pressures and outputting a second output lI: the generated load sensor, the first output obtained by the rotation speed sensor, and the load sensor. a first calculation means that generates a second frequency and state discrimination output based on both or either of the second outputs obtained by;
a switching means for selecting which of the first frequency and the second frequency 71)-'& and outputting a third frequency with reference to the state of the discrimination output obtained by the first calculation means; , a second calculation means that receives the third frequency obtained by the switching means and generates a pulse train of a fourth frequency having a predetermined pulse width and proportional to the third frequency; An engine air conditioner comprising: an amplifier that amplifies the power of the pulse train obtained by the second calculation means; and an electromagnetic valve that is controlled to open and close by the output of the amplifier and supplies desired fuel to the engine. Fuel ratio control device. (2) A first device that generates a second frequency and state determination output based on either or both of the first output obtained by the rotation speed sensor and the second output obtained by the load sensor. The air-fuel ratio control for an engine according to claim 1, wherein the calculation means is configured such that the state determination output obtained by the calculation means can determine that the state of the engine is high load. Device. (3) The switching means for selecting either the first frequency or the second frequency by referring to all the states of the state discrimination output obtained by the first calculation means and outputting the third frequency is a gate circuit. 1. An air-fuel ratio control device for an engine according to claim 1, wherein the second frequency can be selected depending on a low-speed, high-load state of the engine.