JPH0647958B2 - Engine fuel supply controller - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel supply control device for an engine.

(Prior Art) Generally, in a deceleration state in which the output demand of the engine rapidly changes, it is necessary to control the fuel supply amount accurately in accordance with the change of intake air in the deceleration state.

As a conventional fuel supply control device for this type of engine,
For example, the one described in JP-A-56-6032 is known. This device detects the intake air amount by an air flow meter provided on the upstream side of the throttle valve, and controls the fuel supply amount according to the intake air amount per one rotation. Then, when the intake air amount changes in the decreasing direction, the fuel amount is increased and corrected according to the changing speed to avoid leaning of the air-fuel mixture immediately after deceleration. This will be described later in detail (see FIG. 3), but immediately after deceleration, there is a deviation in the correlation between the output of the air flow meter and the intake air amount actually sucked into the combustion chamber (hereinafter referred to as the effective intake amount). Because. In this case, the effective intake air amount is larger than the output of the air flow meter. Therefore, at the time of deceleration, the difference between the two is estimated by the decrease rate of the intake air amount, and the fuel amount is increased and corrected according to the estimation result.

However, in such a conventional fuel supply control apparatus for an engine, since the fuel amount is increased and corrected according to the decreasing speed of the intake air amount, the intake air amount immediately before deceleration becomes relatively stable. The air-fuel ratio of the air-fuel mixture can be appropriately corrected when decelerating from the state in which the air-fuel ratio is reduced. There was a problem that it would be appropriate.

That is, if the air-fuel ratio before deceleration is stable, the air-fuel ratio can be appropriately corrected even if the fuel increase correction is performed only in accordance with the reduction rate of the intake air amount. However, in the case where the air-fuel ratio is fluctuating or the degree of decrease is different, the intake air amount is different before the start of deceleration and during deceleration, even if the decreasing speed of the intake air amount is the same. Therefore, it is difficult to maintain the air-fuel ratio of the air-fuel mixture at an appropriate value during deceleration simply by increasing the amount of the fuel to be corrected according to the decreasing speed.

On the other hand, the deviation of the correlation between the detected value of the intake air amount and the effective intake air amount also occurs during acceleration, and as a method of estimating the deviation of the correlation during acceleration and correcting the fuel supply amount,
For example, the one described in JP-A-58-8239 is known. This device calculates the fuel supply amount for each predetermined time based on the intake air amount and the number of revolutions, and at the time of acceleration, the (previous) fuel supply amount before the predetermined time (actually supplied amount. Amount) and the fuel supply amount calculated this time (hereinafter referred to as “calculated supply amount”) is obtained (hereinafter, this is referred to as weighting calculation, and the calculation method will be described in detail later), and the average value is calculated as By setting the effective supply amount, the air-fuel mixture becomes rich immediately after acceleration.
It avoids the conversion and leaning. The cause of the enrichment is that there is an inertial force in the measuring plate of the air flow meter (the plate that is rotationally driven by the flow of the intake air and measures its flow rate). Immediately after acceleration, the measuring plate overshoots and the effective intake The output of the air flow meter is larger than the amount. Therefore, more fuel than necessary is supplied to the combustion chamber, the air-fuel ratio of the air-fuel mixture becomes rich, and so-called rich spike occurs. The reason for the leaning is that the two are displaced again immediately after the overshoot. That is,
The overshoot phenomenon is attenuated with time after acceleration, and the output of the air flow meter approaches the value of the effective intake amount. At this time, if all of the fuel injected from the injector is taken into the combustion chamber, the air-fuel ratio will be an appropriate value, but in reality, part of the injected fuel will adhere to the wall surface of the intake pipe and the air-fuel ratio will become lean. , So-called lean spike occurs. Therefore, at the time of acceleration, the above-mentioned weighted average is sequentially executed to correct the problem caused by the difference between the two.

However, this device only corrects the fuel supply amount during acceleration to prevent enrichment or leaning of the air-fuel ratio, and it is difficult to maintain the air-fuel ratio at an appropriate value in a rapid deceleration state. Further, the weighting calculation is relatively effective as a method for correcting the above-mentioned deviation between the two, but if the calculation is simply performed without considering the connection relationship between the engine and the external load, for example, the rotation fluctuation becomes large. In some cases (details will be described later), new problems may occur.

(Object of the invention) Therefore, the present invention corrects the detected value of the intake state so as to correspond to the effective intake amount by executing a weighting calculation when the external load is connected when shifting to a predetermined deceleration state. As a result, even when shifting to deceleration conditions from various operating conditions, the amount of fuel that always corresponds to the effective intake amount is always supplied to make the air-fuel ratio of the air-fuel mixture appropriate, and the operability of the engine is improved. When the external load is not connected, the weighting calculation is stopped to prevent the engine rotation fluctuation.

(Structure of the Invention) FIG. 1 is an overall structure diagram for clarifying the present invention.

a is an intake state detecting means for detecting the state of intake air taken into the engine, b is a rotational speed detecting means for detecting the rotational speed of the engine, c is an operating state detecting means for detecting the operating state of the engine, d is a connection state detecting means for detecting a connection state between the engine and an external load, and e is a correction signal output when the engine shifts to a deceleration state until the deceleration is stopped if the external load is connected. On the other hand, if the external load is not connected, the correction signal generating means for outputting the correction signal until a predetermined time elapses, and f, when the correction signal is not input, changes the output of the intake state detecting means to the intake air state. When the correction signal is input, the output of the intake state detecting means is corrected so as to correspond to the current state of the intake air based on the state of the intake air before a predetermined time. Together, output correction means for sequentially executing the correction at predetermined timings, g is storage means for storing the output of the output correction means at each predetermined timing as corresponding to the state of intake air, and h is output correction Means and a supply amount calculation means for calculating the fuel supply amount based on the output of the rotation speed detection means, and i is a fuel supply means for supplying fuel to the engine based on the output of the supply amount calculation means.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 9 are views showing the first embodiment of the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes an engine, intake air is supplied to each cylinder from an air cleaner 2 through an intake pipe 3, and fuel is injected by an injector (fuel supply means) 4 based on an injection signal Si. The flow rate Qa of the intake air is an air flow meter (intake state detecting means)
5 and is controlled by the throttle valve 6 in the intake pipe 3. Further, the opening Cv of the throttle valve 6 is detected by a throttle opening sensor (operating state detecting means) 7, and the rotation speed N of the engine 1 is detected by a crank angle sensor (rotation speed detecting means) 8. Further, the connection state between the engine 1 and the external load is detected by the connection state detecting means 9, and the connection state detecting means 9 detects the neutral switch 10 and the clutch switch 11.
It is composed of The neutral switch 10 detects that the gear of the manual transmission is in the neutral position and outputs the neutral signal Sn, and the clutch switch 11 detects the disengaged state of the clutch and outputs the clutch signal Sc. The signals from the air flow meter 5, the throttle valve opening sensor 7, the crank angle sensor 8, the neutral switch 10 and the clutch switch 11 are input to the control unit 12, which controls the correction signal generating means, the output correcting means, It has a function as a storage unit and a supply amount calculation unit.

The control unit 12 includes a CPU 13, ROM 14, RAM
15 and I / O port 16 The CPU 13 executes I / O according to the program written in the ROM 14.
The necessary external data is fetched from the port 16 and arithmetic processing is performed while exchanging data with the RAM 15, and the data processed as necessary is the I / O port.
Output to 16. The I / O port 16 has the sensors 5 and
The signals from 7, 8, and 9 are input, and the injection signal Si is output from the I / O port 16. ROM14 is C
Stores the calculation program in PU13, RAM
Reference numeral 15 stores data used for calculation in the form of a map or the like.

Next, the operation will be described.

Generally, in an EGI type engine, since the amount of fuel corresponding to the engine load is injected in synchronization with the rotation, it is necessary to detect the state of intake air per rotation (state of engine load). There is. Therefore, a sensor that detects the intake air amount is provided. However, the output of the sensor is accurately correlated with the actual intake state during steady operation, but the correlation is deviated during rapid deceleration operation. This is because the measuring plate of the sensor is forcibly displaced under the influence of the inertia of the intake air. That is, when the throttle valve is fully closed at timing t _{1 as} shown in FIG. 3 (a), the pressure in the intake pipe on the downstream side of the throttle valve approximates the effective intake amount as shown in FIG. 3 (b). Gradually decreases. At this time, the flow rate of the air that has passed through the measuring plate of the sensor immediately after the throttle valve is fully closed suddenly changes.Therefore, when the throttle valve is fully closed, the flow rate that is much smaller than the original air flow rate is detected. As shown by the solid line in FIG. 3 (c), the output of the sensor sharply decreases at the timing t ₁ and then gradually returns to the effective intake amount (broken line (Y) in the figure).
Is equivalent to this). As a result, an error in the shaded portion in FIG. 3 (c) occurs between the sensor output and the effective intake air amount, and the two do not correlate accurately. Further, since such an error varies depending on the degree of deceleration, conventionally, the fuel supply amount has been increased and corrected according to the decreasing speed of the sensor output. However, it is difficult to uniformly determine the influence of the above-mentioned inertia of the intake air (which is also related to the flow rate at that time) only with the decreasing speed, and the fuel supply amount is not necessarily corrected appropriately.

Therefore, in this embodiment, focusing on the advantage of the weighting operation,
By applying this during deceleration, the output of the sensor is approximated to the effective intake air amount very accurately.

FIG. 4 is a flow chart showing a program for controlling the fuel supply amount written in the ROM ₁₄ , P _{1 to} P in the figure.
₁₀ shows each step of the flowchart. This program is executed once for each engine revolution.

First reads the rotational speed N and the intake air amount Qa in _{P 1, then,} P 2 to P ^- determines operating conditions of the engine 1 in ₄ consisting operating state discrimination flow UHF. P 2 _{to P} ^- In _4, respectively to determine the following conditions.

P _2: throttle valve 6 or fully closed. That is, it is determined whether the engine 1 has shifted to the deceleration state.

P _3: whether the gear is in the neutral position.

P ^- ₄ : Is the clutch connected?

Then, from these determination results, it is determined which of the following A, B and C states the operating state of the engine 1 corresponds to,
Depending on the state, proceed to different steps.

A state: When the throttle valve 6 is not fully closed in _{P 2.} This state corresponds to when the engine 1 is not in the decelerating state. In this case, the process proceeds to _{P 5.}

B state: the throttle valve 6 in the _{P 2} is fully closed. At P ₃ the gear is in a position other than neutral and at P ₄ the clutch is engaged. This state is when the external load is connected during deceleration, and at this time, the process proceeds to P ₆ .

C Condition: throttle valve 6 at P ₂ is fully closed, when the gear is in the neutral position P _3, alternatively the throttle valve 6 is fully closed in P _2, in the position gear other than neutral in P ₃ When the clutch is disengaged at P ₄ . This condition is when the no external load is connected during deceleration, the time proceeds to P _20.

Now, in the A state, the output Qa of the air flow meter 5
There replacing the output Qa of this air flow meter 5 to the correction intake air amount Qe at P ₅ and judged to be substantially approximate to the effective intake air amount. Here, the corrected intake air amount Qe is a correction value when the output Qa of the air flow meter 5 is corrected so as to approximate the effective intake air amount, and in the A state, Qa = effective intake air amount, so Qa = Qe To do.

On the other hand, in the B state, the output Qa of the air flow meter 5
Is determined not to be close to the effective intake air amount, the flow proceeds to a correction flow EF consisting of P ₆ and P ₇ , and the output Qa is corrected.
In the correction flow EF, first, at P ₆ , the previous intake air amount Q _a-1 (corresponding to the previous effective intake air amount) is read, and then at P ₇ , the current correction intake air amount Qe is calculated according to the following equation. Calculate

Qe = Qa · n / m + (Q _a−1 ) · (m−n) / m In the formula, the previous intake air amount (Q _a−1 ) and the output Qa of the air flow meter 5 of this time are respectively expressed. Predetermined weighting factor (n / m and (mn) / m correspond to this)
The output Qa of the air flow meter 5 at this time is corrected to correspond to the effective intake air amount by multiplying by and obtaining the sum thereof. Here, m and n are set to optimum values by, for example, experiments. As an example, a case where m = 8 and n = 3 is set will be described later in detail with reference to FIG.

After calculating the correction intake air amount Qe in step _{P 5} or _{P 7,} the process proceeds to _{P 9} of the present correction intake air amount Qe at _{P 8} as the old correction intake air amount (Q _a-1), according to the following expressions _{P 9} The fuel supply amount Te is calculated.

Te = K · Qe / N (where K is a constant, and at P ₁₀ , an injection signal Si having a pulse width corresponding to the fuel supply amount Te is output.

FIG. 5 is a timing chart when the state A is changed to the state B.

In FIG. 5, at timing t ₂ during operation at Qa = Qo.
When the state changes from state A to state B, the air flow meter 5
Output Qa changes as shown by the curve C, and a deviation occurs from the effective intake amount shown by the curve D. Therefore, a weighting operation based on the above equation is executed for each engine revolution so as to correct this deviation. In the equation, when m = 8 and n = 3 are set, the weighting calculation for each rotation after the timing t ₂ is sequentially as follows and the corrected intake air amount Qe (where Qe = Q ₁ , Q ₂ , Q ₃ ...) is determined.

That is, the timing t ₂ after in this operation, Qa of the air flow meter 5 is corrected based on the correction intake air amount Qe even while reducing the weight amounted reversed until the time t _2. Therefore, as shown by the curve E in the figure, the corrected intake air amount Q
The value of e (Qe = Q ₁ , Q ₂ , Q ₃ ...) Can be accurately approximated to the value of the effective intake amount shown by the curve D. Further, this calculation is based on the intake air amount Qo before the start of deceleration, and the corrected intake air amount Qe that is close to the effective intake air amount can be obtained regardless of the operating conditions for deceleration. As a result, the air-fuel ratio of the air-fuel mixture in the decelerated state can always be made appropriate, and drivability can be improved. Then, the steady state from the decelerated state reaches the timing t ₃ (e.g., idle state) to migrate, the output Qa of the timing t ₂ becomes as before Qa = Qe air flow meter 5 again is to approximate the effective intake air amount .

In the present embodiment, an example in which m = 8 and n = 3 is set has been shown, but FIG. 6 shows changes in the corrected intake air amount Qe when these values are changed. In FIG. 6, a curve G represents a case where n / m is large, a curve H represents a case where n / m is appropriate, and a curve I represents a case where n / m is small.

Although the present embodiment shows an example in which the steady state is decelerated to the idle state, the application of the present invention is not limited to the deceleration to the idle state. For example, the present invention can be applied to all cases where the steady state is decelerated to the vicinity of the idle state or when the deceleration causes a deviation in the correlation between the output of the air flow meter 5 and the effective intake amount.

Furthermore, in the present embodiment, the weighting calculation is executed for the intake air amount, but the present invention is not limited to this, and the same effect can be obtained by executing the weighting calculation for the fuel supply amount, for example.

Further, in the present invention, the weighting calculation is limited within a predetermined time when no load is applied to correct the deviation from the effective intake air amount while suppressing the rotational fluctuation.

First, the background of this embodiment will be described.

In general, when the throttle valve opening is constant and the rotation speed N changes, the pressure in the intake pipe (hereinafter referred to as intake pressure) changes according to the change in the rotation speed N as shown in FIGS. 7 (a) and 7 (b). P fluctuates, and a phase difference between the two occurs. This is because the intake pipe has a predetermined volume, and if the volume is zero, for example, no phase shift occurs. On the other hand, such a deviation leads to the effect of suppressing engine speed fluctuations during no-load operation. For example, in FIG. 7, when the rotation speed N when there is no rotation fluctuation is N = No and the intake pressure P is P = Po, the intake pressure P is higher at the timing t ^- ₄ than when there is no rotation fluctuation. (P> Po), on the contrary, at the timing t ₅ , the intake pressure P is low (P <Po). Therefore, No, when injecting fuel, which is calculated according to Po, the timing t ^- ₄ In the air-fuel ratio of the mixture is leaner shifted to the rich side at the timing t _5. Here, the air-fuel ratio of the air-fuel mixture corresponding to No and Po shows the relationship between the torque and the air-fuel ratio.
At the point, the air-fuel ratio deviates to the lean side from the point X at the timing t ₄ when the rotation increases, so the fluctuation range ΔA /
After that, the torque is reduced according to F, and the increase in rotation is suppressed. On the other hand, the timing t ₅ In the air-fuel ratio rotation is reduced for shift to the rich side of the X point, the rotation torque is increased to increase. That is, even when the rotation speed N changes due to a cause such as a deviation in the correlation between the output of the air flow meter and the effective intake amount, the torque is appropriately controlled and the rotation fluctuation is suppressed by the above-described phase deviation. It

However, when the weighting calculation is performed according to the deviation of the correlation, the torque fluctuation based on the air-fuel ratio fluctuation also decreases.
Therefore, even if the rotation speed N changes, the torque is not properly controlled, and the rotation fluctuation cannot be suppressed. As a result, when the weighting calculation is executed during no-load operation, a large swell occurs in the rotation speed N as compared with the case where the calculation is not executed as shown by the curve J in FIG. 9 (the curve K corresponds to this). However, there occurs a problem that the rotation fluctuation becomes large.

On the other hand, if the weighting calculation is stopped in order to avoid such a rotation fluctuation, the degree of deviation between the output of the air flow meter and the effective intake amount becomes large when the engine is idling in the idle state and immediately after the engine stall or An extreme decrease in the rotation speed N occurs.

Therefore, according to the present invention, when the throttle valve 6 shifts from the predetermined opening degree to the fully closed state when there is no load, the weighting calculation is executed within the predetermined time, and thereafter the weighting calculation is stopped, thereby deviating from the execution intake air amount. Is corrected to prevent an extreme decrease in the number of revolutions N, while suppressing a rotational fluctuation.

Therefore, in the flow of FIG. 4, in the C state, P ₂₀
The elapsed time T after the throttle valve 6 is fully closed (after shifting to the deceleration state) is compared with the predetermined time To. T ≦ T
When o, the flow proceeds to the correction flow EF, and when T> To, the process proceeds to P ₅ . Therefore, in the C state, the weighting calculation is executed within the predetermined time T to correct the output of the air flow meter 5, and the air-fuel ratio of the air-fuel mixture is maintained at an appropriate value.
As a result, it is possible to prevent the engine stall and the extreme decrease in the number of revolutions even in the case such as immediately after the idling in the idle state. When the predetermined time T has elapsed, the weighting calculation is stopped. Therefore, the torque in the idle state is appropriately controlled by the above-described principle, and the rotation fluctuation is suppressed. As a result, drivability can be improved.

(Effect) According to the present invention, the output of the intake state detecting means can be appropriately corrected to be approximated to the effective intake amount, and the air-fuel ratio of the air-fuel mixture during deceleration can always be made appropriate to improve the operability of the engine. Can be improved.

Moreover, it is possible to suppress the rotational fluctuation while maintaining the air-fuel ratio of the air-fuel mixture at an appropriate value by correcting the deviation from the effective intake air amount during deceleration under no load.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of the present invention, FIGS. 2-9 are diagrams showing a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram thereof, and FIGS. 3 (a)-(c) are Timing chart for explaining the operation, FIG. 4 is a flow chart showing a program of the fuel supply amount control, FIG. 5 is a diagram showing a change state of the intake air amount, and FIG. 6 is a weighting coefficient of the weighting calculation. FIG. 7 (a) and FIG. 7 (b) are timing charts showing the changing states of the rotational speed and the intake pressure when FIG. 8 is changed, and FIG. 8 shows the torque and the air-fuel ratio. FIG. 9 is a diagram showing the relationship, and FIG. 9 is a diagram showing the changing state of the rotation speed. 1 ... Engine, 4 ... Fuel supply means, 5 ... Intake state detection means, 7 ... Operating state detection means, 8 ... Rotation speed detection means, 9 ... Coupling state detection means, 12 ... Control unit ( Correction signal generation means, storage means, supply amount calculation means).

Claims (1)

[Claims] 1. A) intake state detecting means for detecting the state of intake air drawn into the engine, b) rotational speed detecting means for detecting the engine speed, and c) operation for detecting the operating state of the engine. State detection means, d) connection state detection means for detecting a connection state between the engine and an external load, and e) correction when the engine shifts to a deceleration state until the deceleration is stopped if the external load is connected. A signal is output, and on the other hand, if an external load is not connected, a correction signal generation unit that outputs a correction signal until a predetermined time elapses, and f) Intake the output of the intake state detection unit when the correction signal is not input. When the correction signal is input, on the other hand, it is not corrected as the one corresponding to the state of the air. On the other hand, when the correction signal is inputted, the intake state detecting means of the intake state detecting means is made to correspond to the present state of the intake air based on the state of the intake air before a predetermined time. Output correction means for correcting the force and sequentially executing the correction at predetermined timings; and g) storage means for storing the output of the output correction means at predetermined timings as corresponding to the state of intake air, h) a supply amount calculation means for calculating the fuel supply amount based on the outputs of the output correction means and the rotation speed detection means, and i) a fuel supply means for supplying fuel to the engine based on the output of the supply amount calculation means. A fuel supply control device for an engine, comprising: