JPH0313421B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electronically controlled fuel injection device for an internal combustion engine, and in particular, a vane type fuel injection device that measures the intake air amount by the opening amount of a measuring plate provided in an intake air passage, which is suitable for use in an automobile internal combustion engine. The present invention relates to an improvement in an electronically controlled fuel injection device for an internal combustion engine that calculates a basic fuel injection amount according to an engine load determined from an engine intake air amount and engine rotation speed detected by an air flow meter.

[Conventional technology]

One of the methods for supplying an air-fuel mixture at a predetermined air-fuel ratio to the combustion chamber of an internal combustion engine (referred to as an engine) is to use a so-called electronically controlled fuel injection device.
In this method, an injector for injecting fuel into the engine is installed in the intake manifold or throttle body of the engine, for example, in several or one engine cylinder, and the valve opening time of the injector is controlled according to the operating state of the engine. By doing so, an air-fuel mixture with a predetermined air-fuel ratio is supplied to the engine combustion chamber. There are various types of such electronically controlled fuel injection devices, but in recent years, particularly, digital electronically controlled fuel injection devices in which the electronic control circuit has been digitalized have been developed. In such an electronically controlled fuel injection device,
Under normal conditions, the engine load is determined as the intake air amount per engine revolution based on the engine intake air amount detected using an air flow meter etc. and the engine rotation speed detected from the engine rotation signal input from the distributor. The basic fuel injection quantity calculated according to Synchronous injection is taking place. In addition, in order to improve startability or responsiveness immediately after acceleration, in addition to normal synchronous injection, asynchronous injection is performed in which a predetermined amount of injection is performed only immediately after receiving a signal from a sensor according to the driving condition. ing. The synchronous injection time during which the injector is open in response to the synchronous injection is, for example, determined by the engine load (=intake air amount/engine speed) determined from the intake air amount from the air flow meter and the rotation signal from the distributor. Based on the basic injection time calculated accordingly, depending on the signal from each sensor,
It is determined by multiplying the injection time by a correction coefficient to correct the injection time according to the engine state at that time, such as during acceleration, and then adding the invalid injection time to correct for the injector operation delay due to voltage fluctuation. . For example, in order to improve engine startability, the basic injection time is corrected at the time of engine startup by setting it to a predetermined time regardless of the intake air amount and engine speed when starting the engine. In order to stabilize the engine rotation, the amount is increased for a certain period of time after the engine starts, and the increase in amount is compensated for after starting.Furthermore, when the intake air temperature is low, the air density increases and the air amount increases. In order to prevent deviations in the fuel ratio, the intake air temperature is corrected by increasing the amount when the intake air temperature is low.
In addition, in order to ensure drivability when cold, the amount of cooling water is increased when the temperature is low to compensate for the warm-up increase.Furthermore, in order to prevent sluggishness immediately after acceleration and improve acceleration performance, the amount of cooling water is increased when the temperature is low. By increasing the amount for a certain period of time immediately after, the acceleration amount increase during warm-up is corrected.
In addition, to increase engine output at high loads,
By increasing the throttle valve opening at a high load such as 60° or more, the output is corrected. Furthermore, in order to bring the air-fuel ratio of the mixture to a predetermined air-fuel ratio, for example near the stoichiometric air-fuel ratio, the amount of air in the exhaust gas is increased. The air-fuel ratio feedback is corrected by changing the increase ratio according to the oxygen concentration. Additionally, in order to prevent overheating of the catalytic converter and save fuel consumption, or to forcibly reduce vehicle speed, fuel injection is stopped and fuel is cut during engine braking or when vehicle speed exceeds the specified maximum speed. is being used. Such an electronically controlled fuel injection device, particularly a digital electronically controlled fuel injection device, is characterized in that it is possible to control the fuel injection amount extremely precisely.

[Problem to be solved by the invention]

However, the conventional electronically controlled fuel injection system, especially the detection of the intake air amount, is
As shown in the figure, a measuring plate 12b that is fixed to a rotatable shaft 12a and inserted into an intake air (intake) passage, and a return that biases the measuring plate 12b in a direction to close the intake passage. a spring 12c and the shaft 1
Potentiometer 12d disposed at one end of 2a
The potentiometer 12d controls the opening amount (opening degree) of the measuring plate 12b, which is determined by the balance between the force in the opening direction caused by the air flowing in the intake passage and the force in the closing direction caused by the return spring 12c. In the case where the vane type air flow meter 12 detects the intake air amount and outputs it as the intake air amount, the measuring plate 12b is is too open,
The intake air amount of the engine was overestimated, and the fuel injection amount was also excessive, resulting in so-called overrich conditions. In the figure, 12e is a compensation plate. In order to prevent the above-mentioned drawbacks, a full load stopper is installed in the air flow meter to prevent the measuring plate from opening too much, or the maximum value τmax of the fuel injection amount is set. However, it was not always possible to achieve sufficient effects.
In particular, in the latter method, if the maximum value τmax is kept constant regardless of the engine speed, as shown by the two-dot chain line A in Fig. 3, the restriction of the fuel injection amount is hardly effective at high engine speeds. gone,
After all, it becomes overrich and the engine output decreases. On the other hand, it is also possible to change the maximum value τmax in two stages depending on the engine speed, as shown by the dashed line B or the dashed line C in FIG. If the maximum value τmax at high engine speeds is set to a relatively small value in order to obtain sufficient output, the restriction by τmax becomes too effective in the mid-engine speed range, resulting in a relatively lean air-fuel ratio.
As shown by the dashed line B in FIG. 4, the exhaust gas temperature may rise when the engine is rotating mid-rotation.
Furthermore, as shown by the broken line C in Fig. 3, if the maximum value τmax at high engine speeds is set to a relatively large value in order to prevent the exhaust gas temperature from rising in the middle engine speed range, overflow occurs at high engine speeds. The problem is that the engine becomes rich and the engine output decreases. The amount of fuel actually injected from the engine injector is corrected using various increase correction coefficients. Furthermore, since these various increase correction coefficients are calculated independently of each other, even when the above-mentioned overrich error in the detected intake air amount is relatively small, these other various If the corrections made by the increase correction coefficients overlap to increase the fuel injection amount, there is also the problem that the amount of fuel actually injected from the engine injector becomes overrich. The present invention has been made to eliminate the above-mentioned drawbacks of the conventional technology, and it is possible to perform accurate fuel injection and improve exhaust gas temperature and engine engine performance regardless of the intake air amount detection error of the vane air flow meter due to the pulsation of the enriched air. In addition to easily achieving a point that is compatible with output, even when the fuel injection amount is overlapping and increased by various increase coefficients, it is possible to ensure that the actual amount of fuel injected from the engine injector is corrected. It is an object of the present invention to provide an electronically controlled fuel injection device for an internal combustion engine that can prevent excessive fuel injection and reliably prevent excessive increases in exhaust gas temperature.

[Means to solve the problem]

The present invention provides a vane air flow meter that measures the intake air amount of an engine based on the opening amount of a measuring plate provided in an intake air passage, a rotation speed sensor that detects the engine rotation speed, and an injector that injects fuel into the engine. Then, the basic fuel injection time is calculated according to the engine load determined from the engine intake air amount and engine speed, and the basic fuel injection time is corrected with various increase correction coefficients to obtain the effective synchronous injection time. , the fuel injection signal is set such that the maximum value is limited so as not to exceed the effective synchronous injection time, taking into account the increase in fuel amount to lower the exhaust gas temperature, which is set to decrease as the engine speed increases. The above object is achieved by including an electronic control circuit that outputs the fuel injection signal to the injector.

[Effect]

FIG. 8A is a diagram showing the relationship between the actual intake air amount and the intake air amount detected by the vane air flow meter. In FIG. 8A, point b is the lowest actual intake air amount, ie, the lowest engine speed, at which overrichness occurs due to the pulsation of intake air that occurs at high engine speeds. Strictly speaking, the amount of intake air and engine speed are assumed to be proportional, although there are certain errors. In this figure, the broken line shows the hypothetical relationship between the actual intake air amount and the intake air amount detected by the air flow meter, and the solid line shows the actual intake air amount detected by the air flow meter. This shows the relationship between As shown in this figure, at an actual intake air amount larger than point b, the actual intake air amount and the intake air amount detected by the air flow meter are no longer proportional. That is, the deviation is caused by the occurrence of excessive opening of the measuring plate of the air flow meter due to the above-mentioned intake pulsation. Figure 8B shows the relationship between the actual intake air amount, that is, the engine speed, and the deviation amount of the intake air amount detected by the vane type air flow meter, that is, the relationship between the actual intake air amount, that is, the engine speed, and the deviation amount of the intake air amount detected by the vane type air flow meter. FIG. 3 is a diagram showing deviations that occur. This point b in FIG. 8B is the same as the point b in FIG.
Similar to point b in , this is the lowest actual intake air amount, that is, the lowest engine speed at which the measuring plate of the air flow meter opens too much due to intake pulsation. If a deviation occurs due to excessive opening of the measuring plate of the air flow meter due to intake pulsation as shown in FIG. 8B, the actual intake air amount will be smaller than the value detected by the air flow meter. Therefore, if the fuel injection amount is controlled based on this detected value, the actual air-fuel ratio will become overrich compared to the target air-fuel ratio, resulting in a decrease in engine output. Therefore, in the present invention, the maximum value τmax is decreased from point a in FIG. 3 as shown by the solid line D at higher engine speeds. Note that point a in FIG. 3 is the minimum actual intake air amount, that is, the minimum engine speed at which over-richness of the air-fuel ratio occurs due to the air flow meter's measuring plate opening too much due to intake pulsation in FIGS. 8A and 8B. This corresponds to point b. As shown in FIG. 3, the maximum value τmax of the fuel injection amount is usually a slightly larger constant value τu with some margin. However, in the present invention, overrich occurs. The maximum value τmax is greatly reduced in the region of high engine speed from point a, and the maximum value τmax controls the air-fuel ratio appropriately to prevent the temperature of the exhaust gas from rising. Further, the maximum value τmax shown by the solid line D in the high engine speed range from point a in FIG. 3 has a characteristic of downward sloping to the right. This is because, as shown in FIG. 8B, the amount of deviation of the intake air amount due to overrichness detected by the vane air flow meter increases on the higher engine speed side than point b. Due to the downward sloping characteristic of the solid line D in FIG. 3, by determining the maximum value τmax according to the engine speed, it is possible to prevent the exhaust gas temperature from increasing without reducing the engine output. Furthermore, in the present invention, in order to prevent overriching of the amount of fuel actually injected from the engine injector using the maximum value of the fuel injection amount,
The fuel injection amount corrected and determined by various increase correction coefficients, that is, the effective synchronous injection time, is limited to prevent overriching. These various increase correction coefficients are calculated independently according to various engine operating conditions, and
It is used to increase (or decrease in some cases) the amount of fuel injected. Therefore, if the increase in fuel injection amount overlaps due to these various increase correction coefficients, even if the influence of the error in the intake air amount detection value (overrich deviation in intake air amount detection) is relatively small. Even if this is not the case, the amount of fuel injected from the engine injector will eventually become overrich. If the amount of fuel injected from the injector of the engine becomes overrich, the temperature of the exhaust gas of the engine increases. Note that the degree of increase in the engine exhaust gas temperature changes depending on the engine rotation speed and the like. However, in the present invention, the fuel injection amount corrected by various increase correction coefficients, that is, the effective synchronous injection time, is limited so that overrich does not occur. Therefore, it is possible to reliably prevent an excessive increase in the amount of fuel actually injected from the injector of the engine, and to reliably prevent an excessive rise in exhaust temperature. In addition, as a method for preventing an excessive increase in the amount of fuel actually injected from the injector of such an engine, there is a method of prioritizing each increase using various increase correction coefficients as described above,
Possible methods include mutually adapting each increase value using various increase correction coefficients to various operating conditions and finding a reasonable point for each increase value. However, all of these methods are very complex,
There is also a question as to whether an excessive increase in the amount of fuel injection can be reliably prevented. However, the method of the present invention for limiting the amount of fuel injection determined by correcting it using various increase correction coefficients, that is, the effective synchronous injection time so as not to become excessive, is extremely simple and actually An excessive increase in the amount of fuel injected from the fuel can be reliably prevented. Further, according to the method of the present invention, there is no problem of unnecessarily restricting the increase in fuel injection amount that is made when the exhaust gas temperature of the engine decreases.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. An embodiment of the electronically controlled fuel injection device for an internal combustion engine according to the present invention is, as shown in FIGS. a vane type air flow meter 12 such as the above, and a distributor 14 that generates a pulse signal according to engine rotation.
Cooling water temperature sensor 16 that detects engine cooling water temperature
and disposed within the air flow meter 12,
An intake air temperature sensor 18 that detects the engine intake air temperature, a throttle position sensor 22 that detects the opening of a throttle valve 20 disposed in the intake passage 10 and changes in the throttle valve opening, and A starter switch 24 that generates a signal, an oxygen concentration sensor 28 disposed in the exhaust passage 26 that detects the oxygen concentration in exhaust gas, and a vehicle running speed that is detected from the rotational speed of the shaft of the transmission 30. vehicle speed sensor 32 and engine intake manifold 34
an injector 36 for injecting fuel into the interior;
The basic fuel injection time is calculated according to the engine load (= intake air amount / engine rotation speed) determined from the engine intake air amount and engine rotation speed, and the fuel injection time is corrected according to the engine condition etc. Further, a digital controller outputs a fuel injection signal to the injector 36 by limiting the corrected fuel injection time so that it does not exceed a maximum value τmax of the fuel injection time set as a function of engine speed and engine cooling water temperature. It is composed of an electronic control circuit 38. In FIG. 5, 40 is an air cleaner, 42 is a surge tank, 44 is a spark plug, 46 is a catalytic converter, and in FIG. 6, 48 is a battery. The digital electronic control circuit 3 shown in FIG.
8, as shown in detail in FIG. 6, the air flow meter 12 (including the intake air temperature sensor 18), the cooling water temperature sensor 16, and an analog-to-digital converter for converting analog signals output from the battery 48 into digital signals. (A/D) converter 50 and an input interface for inputting digital signals output from the distributor 14, throttle position sensor 22, starter switch 24, oxygen concentration (O ₂ ) sensor 28, and vehicle speed sensor 32. an ace circuit 52, a central processing circuit (CPU) 54,
The results of calculations in the read-only memory (ROM) 56, random access memory (RAM) 58, and central processing circuit 54 are transferred to the injector 36.
The output interface circuit 60 converts the fuel injection signal into a fuel injection signal suitable for output to the fuel injection system. The operation will be explained below with reference to FIG. First, the digital electronic control circuit 38 controls the air flow meter 1.
2-output intake air amount Q and distributor 14
Based on the engine rotation speed N calculated from the output, the basic injection time T _P according to the engine load (=Q/N) is calculated using the following formula. T _P =K・Q/N (1) where K is a coefficient. Furthermore, by correcting the basic injection time T _P using the following formula according to the signals from each sensor,
Calculate the effective synchronous injection time τ1. τ1=T _P・f(A/F)・f(WL)・f(THA)・{1+f(ASE)
+f(AEW)+f(OTP)}{1-f(RS)}...(2) Here, f(A/F) is the air-fuel ratio correction coefficient, f
[WL) is the warm-up increase correction coefficient, f (THA) is the intake air temperature correction coefficient, f (ASE) is the after-start increase correction coefficient), f (AEW) is the warm-up acceleration increase correction coefficient, f
(OTP) is the overheat (output) increase coefficient, f
(RS) is the weight loss coefficient. Next, in accordance with the output of the cooling water temperature sensor 16, when the cooling water temperature is high, for example over 70° C., the engine speed is first read. after that,
The maximum value τmax is obtained by converting the engine speed and the maximum value τmax of the fuel injection amount from the engine speed as shown by the solid line D in FIG. The relationship between the engine speed and the maximum value τmax of the fuel injection amount, shown by the solid line D in FIG. 3, is stored in the read-on memory 56 as a map. Compare this τmax and the above τ ₁ , and τ ₁
If τmax exceeds τmax, τmax read from the table is set to _τ1 . Further, τ ₁ obtained in this way is compared with the upper limit value τu of τmax, and if τ ₁ exceeds u, this τu is set as τ ₁ . In addition, when the cooling water temperature is low (70°C or less), instead of reading out the table value of τmax shown by the solid line D in Figure 3 as described above, the upper limit τu of τmax and _τ1 are compared, and τ If ₁ exceeds τu, this τu is taken as τ ₁ . Effective synchronous injection time τ ₁ obtained in this way
As shown in the following equation, the synchronous injection time τs is calculated by adding the invalid injection time τv corresponding to the response delay time of the injector 36 when the battery voltage decreases. τs = τ ₁ + τv ... (3) A fuel injection signal corresponding to this synchronous injection time τs is output to the injector 36, and the injector 36 is opened for the synchronous injection time τs in synchronization with the engine rotation, and the intake manifold of the engine is opened. Fuel is injected into 34. In this embodiment, the maximum value τmax of the fuel injection time is changed not only according to the engine speed but also according to the engine coolant temperature, so especially when the engine coolant temperature is low, τmax
is not restricted more than necessary, a good fuel increase correction is performed, and fuel injection control suitable for the engine cooling water temperature is performed. Note that τmax may be constant regardless of the engine cooling water temperature. In the above embodiment, when the engine cooling water temperature is low (70°C or less), τmax is made to match τu and is constant regardless of the engine speed, but when the engine cooling water temperature is low,
Of course, you may use a different table than the one used when the temperature is high.

【Effect of the invention】

As explained above, according to the present invention, it is possible to perform accurate fuel injection due to the pulsation of the intake air, regardless of the intake air amount detection error of the vane type air flow meter, and therefore, the exhaust gas temperature and engine output can be accurately injected. In addition, even if the fuel injection amount is overlapping and increased due to various increase coefficients, the amount of fuel actually injected from the engine injector can be reliably adjusted using a simple control method. This has the excellent effect of preventing an excessive increase in the amount of gas and reliably preventing an excessive rise in exhaust gas temperature.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view showing the configuration of an air flow meter used in a conventional electronically controlled fuel injection device, Fig. 2 is a sectional view thereof, and Fig. 3 is a conventional example and an embodiment of the present invention. A diagram showing the relationship between the engine speed and the maximum value of the fuel injection amount,
FIG. 4 is a diagram similarly showing the relationship between engine speed and exhaust gas temperature, and FIG. 5 is an implementation of an electronically controlled fuel injection device in which the electronically controlled fuel injection method for an internal combustion engine according to the present invention is adopted. Sectional view, partially in block diagram, showing an internal combustion engine with an example arrangement, No. 6
FIG. 7 is a block diagram showing the circuit configuration of the embodiment, FIG. 7 is a flowchart showing the fuel injection time calculation routine in the embodiment, and FIG.
is a diagram showing the relationship between the actual intake air amount and the intake air amount detected by the vane type air flow meter, and Figure 8B shows the deviation amount between the actual intake air amount and the intake air amount detected by the vane type air flow meter. FIG. 12... Air flow meter, 14... Distributor, 16... Cooling water temperature sensor, 18...
Intake air temperature sensor, 22... Throttle position sensor, 24... Starter switch, 28...
Oxygen concentration sensor, 32...Vehicle speed sensor, 36...
Injector, 38...Digital electronic control circuit,
a...Minimum engine speed that reduces the maximum value τmax, b...Minimum actual intake air amount (minimum engine speed) at which overrich occurs.

Claims (1)

[Scope of Claims] 1. A vane air flow meter that measures the intake air amount of the engine based on the opening amount of a measuring plate provided in the intake air passage, a rotation speed sensor that detects the engine rotation speed, and a fuel in the engine. The system calculates the basic fuel injection time according to the engine load determined from the injector that injects the engine, the intake air amount of the engine, and the engine speed, and corrects the basic fuel injection time with various increase correction coefficients to make it effective. The effective synchronous injection time is limited so that the effective synchronous injection time does not exceed the maximum value, which is set at least as the engine speed becomes higher, taking into account the increase in fuel amount to lower the exhaust gas temperature. An electronically controlled fuel injection device for an internal combustion engine, comprising: an electronic control circuit that outputs the fuel injection signal as a fuel injection signal to the injector.