JPH0689704B2 - Intake pipe internal pressure detection device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an operating state control device for an internal combustion engine, and more particularly to a device for detecting an engine intake pipe internal pressure included in such a device.

BACKGROUND ART In a device that controls the operating state of an internal combustion engine by controlling the amount of fuel supplied to the internal combustion engine or controlling the amount of intake air, the so-called intake pipe internal pressure downstream of the throttle valve and engine speed The engine parameters are detected and an electrical signal representing each engine parameter is obtained.

On the other hand, a so-called microcomputer is often used in order to perform such operating state control more quickly and accurately.
OM or RAM or the like storage means, according to a predetermined operation program stored in advance in the storage means,
For example, the CPU operates in synchronization with the so-called TDC (Top Dead Center) timing of the engine, and the engine parameters such as the intake pipe internal pressure signal are sampled in synchronization with the operation to obtain sample values. Then, the operation state of the engine is adjusted by storing this in the storage means and reading it out to perform a calculation operation and adjusting the valve opening time of the fuel injection valve according to the calculation result.

However, the operating state of the internal combustion engine is changing every moment, and in particular, the intake pipe internal pressure is an important parameter, and it is not easy to detect this with only a single sample value and perform accurate operating state control. .

Therefore, a method of predicting or estimating the actual intake pipe internal pressure by making a correction calculation of the present value among the sample values of the intake pipe internal pressure by the sample value before the previous value is conceivable.

However, if the mode of the correction calculation in such a prediction method is fixed irrespective of the engine state, the prediction result of the correction calculation may be used for controlling the engine operating state such as the fuel supply amount control depending on the engine operating state. There may be cases where it is not appropriate. In particular, immediately after the engine is started, the temperature of the fuel adhering wall surface of the intake pipe is lower than that during normal operation, and the vaporization rate of the fuel is low. Therefore, the prediction calculation result of the intake pipe internal pressure is often not appropriate. For example, a part of the fuel injected from the injector adheres to the wall surface of the intake pipe and is then sucked into the cylinder. During steady operation of the engine, the fuel adhering to the wall surface is in an equilibrium state (the amount of fuel newly adhering to the wall surface is equal to the amount of fuel sucked into the cylinder from the wall surface), and therefore correction for the adhering fuel is unnecessary. However, since the fuel injection amount increases at the time of engine acceleration, the amount of newly adhering fuel increases compared to the amount sucked into the cylinder from the wall surface.
The equilibrium state of the deposited fuel is broken. Therefore, in the fuel injection amount based on the predicted intake pipe internal pressure value that only considers the detection delay of the intake pipe internal pressure detector, the amount of fuel supplied to the cylinder is insufficient by the change amount of the adhered fuel, and the air-fuel ratio becomes lean. On the other hand, when the engine decelerates, the fuel injection amount decreases, so the amount of newly adhering fuel decreases compared to the amount sucked into the cylinder from the wall surface.Therefore, a prediction considering only the detection delay of the intake pipe pressure detector The fuel injection amount based on the intake pipe internal pressure value becomes excessive and the air-fuel ratio becomes rich.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to predict the intake pipe internal pressure and simultaneously perform detection feed compensation of the intake pipe internal pressure detector during engine transient operation and correction of intake pipe wall surface adhering fuel. It is to provide a detection device.

In the intake pipe internal pressure detection apparatus according to the present invention, the intake pipe internal pressure downstream of the throttle valve of the internal combustion engine is detected, an intake pipe internal pressure signal representing the detected internal pressure is generated, and the fluctuation amount of the intake pipe internal pressure signal level is calculated. The pressure signal is corrected on the basis of the pressure fluctuation amount and the correction coefficient, and includes a start-up detection means (step S ₄₀ ) for detecting the start-up of the internal combustion engine,
Set the correction coefficient to the initial value in response to the detection output of immediately after the start due immediately after the start detecting means (step S _41), gradually allowed to decrease within a predetermined time period from immediately after starting the correction coefficient (Step S ₄₂ to S ₇₀₎ that Is characterized by.

Examples Hereinafter, examples will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a fuel injection type internal combustion engine including an intake pipe internal pressure detection device according to the present invention. Reference numeral 1 denotes an air filter, and intake air passing through the filter 1 passes through an intake pipe 2 and an engine 3 Is supplied to the intake pipe 2, and the amount of air is adjusted by the throttle valve 4 provided in the intake pipe 2. Reference numeral 5 denotes, for example, a potentiometer, and a throttle opening sensor that generates an output voltage at a level corresponding to the opening (θ _TH ) of the throttle valve 4, and 6 an absolute pressure W in the intake pipe 2 downstream of the throttle valve 4. _An absolute intake pressure sensor that generates an output voltage of a level according to _BA , a cooling water temperature sensor 7 that generates an output voltage of a level corresponding to the cooling water temperature of the engine 3, and 8 of a crankshaft (not shown) of the engine 3 A crank angle sensor that generates a pulse signal (TDC signal) when the rotation angle is a top dead sensor (TDC), 9 is an exhaust pipe, and 10 is a three-way catalyst. 11
Is an injector, which is provided in the intake pipe 2 in the vicinity of an intake valve (not shown) of the engine 3 so as to inject and supply the fuel to the engine 3 in an amount corresponding to the input pulse time. The output voltages of the throttle opening sensor 5, the intake absolute pressure sensor 6, the cooling water temperature sensor 7, and the crank angle sensor 8 are input to the control circuit 12.

The control circuit 12 is composed of, for example, a microprocessor or a microcomputer, and the fuel obtained by multiplying the basic fuel injection time Ti and the basic fuel injection time Ti by an increase or decrease correction coefficient according to a predetermined program described later. Fuel injection time T corresponding to increased injection amount
Performs OUT arithmetic processing.

FIG. 2 is a block diagram showing a specific configuration of the control circuit 12. In FIG. 2, the control circuit 12 has a CPU (central processing circuit) 13 that performs digital calculation processing according to a program described later. An input / output bus 14 is connected to the CPU 13, and a data signal or an address signal is input / output to / from the CPU 13 via the input / output bus 14. The input / output bus 14 includes an A / D converter 15, an MPX (multiplexer) 16, a counter 17, a ROM (read only memory) 18, a RAM (random access memory) 19, and a drive circuit 20 for the injector 11. Each is connected. The MPX 16 selectively outputs one of the output signals of the sensors 5 to 7 via the level conversion circuit 21 according to a command from the CPU 13 to the A / D converter 15
It is a switch for relay supply to. The A / D converter 15 converts the supplied analog signal into digital data in synchronization with the TDC pulse. The counter 17 measures the generation cycle of the TDC signal of the crank angle sensor 8 supplied via the waveform shaping circuit 22. It is well known that the output pulse of the crank angle sensor 8 is synchronized with the engine rotation and the engine speed Ne can be obtained based on this output pulse.

FIG. 3 shows an operation program executed by the CPU 13 in synchronization with the TDC timing, for example. In this program, first, engine speed data Ne (N) obtained based on the TDC signal is calculated (step
S ₁ ). As a method of obtaining Ne (N), various methods are known, such as a method of resetting the integrating circuit with a pulse synchronized with the engine speed to obtain a voltage representing the engine speed and sampling this. . Sample value data Ne of engine speed thus obtained
(N) and the sample value data P _BA (N) of the intake pipe internal pressure P _BA obtained via the A / D converter 15 are stored in a predetermined area of the RAM 19 (step S ₂ ).

Next, the previously stored value P _BA (N-1) and the two-preceding value P _BA (N
-2), the last-previous value P _BA (N-3), etc., and the current value (N)
Performing a prediction operation that forms the correction (Step S _3). This prediction calculation will be described later with reference to FIG. After the _PBA prediction calculation is completed, the increase coefficient K _AST after start and the temperature correction coefficient
K _TW , atmospheric pressure correction coefficient K _PA , O ₂ feedback correction coefficient K
Various correction factors such as ₀₂ are calculated (step S ₄ ).
Next, sample value data θ of throttle opening θ _{TH
Take in TH} (N) and store it in RAM 19 (step
S ₅ ). Then Ne (N) and P predicted in step S ₃
A basic value Ti of the valve opening time of the injection valve 11 is calculated by a predetermined calculation formula or a map search based on _BA (step S ₆ ). The final injection time T OUT is calculated by, for example, multiplying the obtained basic value Ti by the above correction coefficient (step S ₇ ),
Supplying valve-opening command to the drive circuit 20 (step S _8), whereby it is of the ejector 11 is opened actuated.

FIG. 4 shows a subroutine program of the _PBA prediction calculation by the CPU 13 described above. First, the change detection sample number intervals m ₁ , m ₂ (m ₁ <m ₂ ) are set to 2 and 3, for example. Preliminary (step S ₁₀ ) Current value P _BA (N) and guard value P
Compare with _GD (step S ₁₁ ). If P _BA (N) is P
_If it is larger than _GD , the prediction calculation is not performed with P _BA = P _BA (N) (step S ₁₂ ). When P _BA (N) is less than P _GD compares the after-start enrichment coefficient K _AST and the reference value K _ASTR1 (step S _13), during the start-up period when the K _AST is smaller than K _ASTR1 Therefore, the prediction calculation is not performed again with the operation of step S ₁₂ , that is, P _BA = P _BA (N). If what, during a predetermined period after the start is in an unstable state P _BA with an increase in engine speed is decreased, rather the P _BA by prediction calculation during this period will be predicted rather small engine This is because it is not preferable because the instability of is increased. When K _AST ≧ K _ASTR1, it is determined that the predetermined period after the start has ended, the throttle opening data θ _TH (N) is compared with the idle reference opening θ _ID , and the engine rotation data Ne (N) is compared with the idle discrimination value N _A (step S ₁₄ ). Now θ
_{If TH} (N) ≤ θ _ID and Ne (N) <N _A ,
Change in P _BA ΔP _BA = P _BA (N) -P _BA (Nm ₁ ) (step S ₁₅ ). By comparing the absolute value of ΔP _BA with the reference value ΔPr, is the engine in a transient operating state? to determine whether (step S _16). Since the absolute value of [Delta] P _BA is sufficiently small change in P _BA when equal to or less than the reference value ΔPr engine is determined to be in the substantially steady operating condition, and P _BA (N) without prediction of P _BA ( step S _12). As long as the absolute value of ΔP _BA is larger than ΔPr, the correction coefficient φ is set to φ ₀ (step S ₁₇ ), then ΔP _BA is compared with the guard value ΔP _GHO (step S ₁₈ ), and ΔP _BA is ΔP _{GHO and} above Δ
_Set P _BA = ΔP _GHO (step S ₁₉ ). However, when the value of ΔP _BA is negative, it is natural that ΔP _GHO also becomes negative.

Next, if the throttle opening data θ _TH (N) exceeds θ _ID or if the engine speed data Ne (N) becomes N _A or more, Ne (N) is compared with the high speed discrimination value N _Z1 (step
S ₂₀ ). When Ne (N) exceeds N _Z1 , the engine is in the high-speed mode, and prediction calculation is not performed, and P _BA = P BA (N) is set (step S ₁₂ ). When Ne (N) is N _Z1 or less, the engine speed is in the medium speed range, and ΔP _BA = P _BA (N) −P _BA
(N−m ₂ ) (step S ₂₁ ). As mentioned above, m ₂
Is 3, for example. The absolute value of ΔP _BA thus obtained is compared with the reference value ΔPr (step S ₂₂ ). ｜ ΔP _BA | ＞ ΔPr
If it is, it is determined whether P _BA is positive or negative (step S ₂₃ ). If P _BA is zero or positive, such as when the engine is in an accelerated state, φ = φ _H is set (step S ₂₄ ),
Compared to [Delta] P _BA and the guard value P GH ₁ (step S _25), ΔP _BA
≧ [Delta] P _GH1 if a ΔP _BA = ΔP GH ₁ (step S _26),
If ΔP _BA <ΔP CG ₁ , proceed directly to the next step. If ΔP _BA is negative, such as under engine deceleration, φ = φ _L is set (step S ₂₇ ), and ΔP _BA is compared with the guard value ΔP _GL1 (step S ₂₈ ). ΔP _BA is Δ
When P _GL1 or less, ΔP _BA is made equal to ΔP _GL1 (step S ₂₉ ), and when ΔP _BA is larger than ΔP _GL1, 0> ΔP _BA >
It is ΔP _GL1 , and the value of ΔP BA is left unchanged, and the process proceeds to the next step.

The prediction calculation of P _BA using φ and ΔP _BA thus obtained is
This is performed by the formula P _BA = P _BA (N) + φ · ΔP _BA (step S ₃₀ ). The resulting P _BA compared to last guard value P _PRD (step S _31), and P _BA> P _PRD If P _BA = P _PRD (step S _32), and ends as if P _BA ≦ P _PRD .

In the above operation, the hitting To corrected by predicting a current value P _BA (N), the current value at the time of low-speed rotation, such as during idling of the engine P _BA (N) and the second preceding value P _BA (N 2) and the The difference ΔP _BA is used, and the current value P is used in the medium speed range.
The difference between _BA (N) and the value P _BA (N 3) two before two is ΔP _BA . What happens is that if the correction cycle is fixedly synchronized with the TDC-synchronized sampling cycle, the fluctuation cycle of the actual _PBA does not change much even if the engine speed increases.
When the increase in the engine speed is corrected period becomes too short with respect to the fluctuation period of the P _BA, excessively increasing predict the variation of P _BA, P _BA after predicted next P _BA (N + 1)
Is greatly exceeded, and once P
_This is because the phenomenon of re-estimating _BA to a small extent occurs, and the P _BA after the prediction includes an extra fluctuation as compared with the fluctuation of the actual P _BA . In other words, when the engine speed is reduced the time interval of the TDC pulse rises is widely in TDC speed conversion is taken up interval of the sample value of the underlying P _BA for the prediction of P _BA real For the fluctuation of P _BA, the predictive calculation is performed by the sample value P _BA (N) generated at a substantially constant time interval regardless of the fluctuation of the engine speed.

FIG. 5 shows a subroutine program for calculating the correction coefficients φ _O , φ _H , and φ _L used in the above-described prediction calculation subroutine. In this subroutine,
First, it is determined whether or not the initialization condition that the engine is just after starting (cranking) is satisfied (step S ₄₀ ),
If the initialization condition is satisfied, φ ₀ = φ _O2 , φ _H =
Initialize φ _H2 , φ _L = φ _L2 (step S ₄₁ ). Note that φ _O2 , φ _H2 , and φ _L2 are, for example, 6.0, 6.0, and 4.5. If the initialization condition is not satisfied after the start (cranking) state is finished, φ _H and φ _H1 are compared (step _S42 ), and if φ _H ≦ φ _H1 , φ _H is left unchanged as φ _H
(Step S ₄₃ ). Here, φ _H1 is set to 2.0, for example. If φ _H> φ _H1, determining parameter Itafai is to determine 0 or not (step S _44), and Itafai = 0 if the count value C? = C _TW n (Step S _45). As shown below, C _TW n is preset to a value of C _TWO , C _TW1 , or C _TW2 according to the engine temperature T _W by another routine program.

Then, at the 1 Itafai (step S _46), the value of phi _H is maintained. Then, in the case of ηφ = 1, Cφ is to determine whether the zero (step S _47), (step ₄₈₎ as C?-1 if C? Is not zero, phi _H intact maintained (Step S ₄₃ ). C? = 0 if, it means that the down counting ends, keep in a ηφ = 0 (step S _49), by subtracting the [Delta] [phi _H from phi _H as a new phi _H (step S _50). By the above calculation from step 42 to step S ₅₀ , φ _H changes according to the number of TDCs as shown by the stepwise solid line in FIG. 6, and φ _H2 to φ _H1
Reach

Similarly for φ _L and φ _D , steps S ₅₂ to S ₆₀ and S
_The calculation is performed by ₆₂ to S ₇₀ , and finally φ _L is φ
The _L1, phi _O is set to phi _01. The values of φ _L1 and φ _O1 are set to 1.5 and 3.0, for example. After all, φ _O > φ
The relationship is _H > φ _L. By doing this,
While ensuring the responsiveness of _PBA correction at idle, while compensating for the _PBA increasing side correction in the medium speed range, it compensates for the response delay of the control system and the dripping / adhesion phenomenon of fuel in the intake system in advance. _{This is} to compensate in advance for the response delay of the control system and the fuel evaporation phenomenon in the intake system when correcting the _BA decreasing side.

Further, since the values of φ _O , φ _H , and φ _L are gradually decreased immediately after the engine is started, the fuel adhesion rate is large and the fuel vaporization rate is high because the temperature around the combustion chamber is low immediately after the engine is started. Since it is also low, it is possible to obtain sufficient fuel supply by predicting P _{BA a} little.

FIG. 7 is a subroutine program for calculating the increase coefficient K _AST after starting. That is, first, it is determined that the engine is immediately after cranking by detecting a change of the starter switch from ON to OFF (step S
₈₀ ). When the engine is immediately after cranking, the value of the parameter C _AST is stored in the predetermined storage area according to T _W.
Obtained from the C _AST table (step S ₈₁ ). In addition, C _AST
An example of the table is shown in the graph of FIG. In addition,
Value of from C _AST0 not C _AST4 is 1.7,1.5,1.3,1.2,1.15 example. Thus, when C _AST is found, determine the K _AST as _{K AST = C AST · K W} . (Step S ₈₂ ). Next, the slope switching _values K _ASTR0 and K _ASTR1 are calculated by the following equation (step
S ₈₃ ). That is, K _ASTR0 = (K _AST -1) R _AST0 +1 K _ASTR1 = (K _AST -1) R _AST1 +1 where R _AST0 and R _AST1 are constants, for example 0.5 and 0.3.
Is.

On the other hand, in the next cycle immediately after cranking, compared with the engine temperature (cooling water temperature) T _W cryogenic determination value T _WDP (step S _84), when T _W becomes smaller than T _WDP is a K _AST K
By comparing the _ASTR0 (step S _85), if K _AST is greater than K _ASTR0, and ΔK _AST = D _KAST0 (step
S ₈₆ ). If K _AST is less than or equal to K _{ASTR 0} , then K _AST and K
_Compare the magnitude with _ASTR1 (step ₈₇ ) and find that K _AST is K
If it is _larger than _ASTR1 , then K _ASTR0 > K _AST is K _ASTR1 ,
_Set ΔK _AST = D _KAST1 (step S ₈₈ ). K _AST ≤ K _ASTR1
Then, ΔK _AST = D _KAST2 is set (step S ₈₉ ).

When the engine temperature T _W is higher T _WDP by comparing the magnitudes of K _AST and K _ASTR0 (step S _90), and ΔK _AST = D _KAST1 when the K _AST> K _ASTR0, the K _AST ≦ K _ASTR0 When ΔK _AST = D
_Set to _KAST2 (step S ₈₉ ). ΔK _AST thus obtained
To obtain K _AST −ΔK _AST and a new K _AST (step S
₉₁ ). Now, D _KAST0 ＞ D _KAST1 ＞ D _KAST2 and T _W <
In the case of T _WDP , the change of K _AST is as shown by the solid line in Fig. 9.
When T _W ≧ T _WDP , the change of K _AST is as shown by the alternate long and short dash line in FIG.

Compare K _AST thus obtained with 1 (step
S ₉₂ ), if K _AST ≤ 1, then K _AST = 1 (step
If S ₉₃ ), K _AST ≧ 1, the process ends.

As it is clear from Figure 9, time to K _AST reaches K _ASTR1 from an initial value immediately after cranking is necessarily regarded as a predetermined period after engine start.

It should be noted that an independent variable K is prepared in order to know the predetermined period after the engine is started, and this is set to TD immediately after engine cranking.
A predetermined value may be subtracted (down-counted) for each C pulse, and when the variable K reaches a predetermined reference value, the predetermined period may be ended after the start.

EFFECTS OF THE INVENTION As is clear from the above, the intake pipe internal pressure detection device according to the present invention is obtained by multiplying the difference between the sample value of the intake pipe internal pressure signal between the present value and the previous sample value by the correction coefficient. The corrected current value obtained by adding the correction amount to the current value is used as the intake pipe internal pressure, and the correction coefficient is gradually decreased from the initial value immediately after the engine is started until a predetermined period of time elapses. An intake pipe internal pressure detection value that can compensate for a large fuel adhesion rate or a small fuel vaporization rate at low temperatures in the vicinity of the engine combustion chamber from immediately after the start up to the elapse of a predetermined period can be calculated as a predicted value. Therefore, the detection delay of the intake pipe internal pressure detector during the transient operation of the engine is compensated, and the intake pipe internal pressure detected value thus obtained is used for the transient state control of the internal combustion engine so that the fuel adhering to the intake pipe wall surface during the engine transient operation is Can be corrected. In particular, it is possible to compensate for the shortage of the amount of fuel supplied to the cylinder due to the change in the adhered fuel during engine acceleration, and to prevent the lean air-fuel ratio. In addition, during deceleration of the engine, it is possible to prevent the rich air-fuel ratio due to the intake of the adhered fuel into the cylinder.

[Brief description of drawings]

1 and 2 are block diagrams showing an operating state control device for an internal combustion engine including an intake pipe internal pressure detecting device according to the present invention, and FIG. 3 is an operation of the operating state control device shown in FIGS. 1 and 2. 4 is a flow chart showing a program, FIGS. 4 and 5 are flow charts showing an operation program of the intake pipe internal pressure detecting apparatus according to the present invention, and FIG. 6 is a state of fluctuation of the correction coefficient obtained by the program shown by the flow chart of FIG. FIG. 7 is a flow chart showing a correction coefficient calculation program used in the program shown in the flow chart of FIG.
FIG. 9 is a graph showing changes in parameters used in the program of FIG. 7 with respect to the engine temperature, and FIG. 9 is a graph showing changes in correction coefficient obtained by the program of FIG. Explanation of symbols for main parts 1 ... Intake filter 2 ... Intake pipe 4 ... Throttle valve 5 ... Throttle opening sensor 6 ... Intake absolute pressure sensor 7 ... Cooling water temperature sensor 8 ... Crank angle sensor 9 ... Exhaust pipe 10 ... Three-way catalyst

Claims (3)

[Claims] 1. A pressure detector for generating an intake pipe internal pressure signal representing an intake pipe internal pressure downstream of a throttle valve of an internal combustion engine, a pressure fluctuation amount calculating means for calculating a fluctuation amount of the intake pipe internal pressure signal, and the inside of the intake pipe. An intake pipe internal pressure detection device, comprising: a correction unit that corrects a pressure signal based on the fluctuation amount and a correction coefficient to obtain an intake pipe internal pressure detection value for use in operating state control of the internal combustion engine. Immediately after starting the engine is detected, the correcting means sets the correction coefficient to an initial value according to a detection output immediately after starting by the immediately after starting detecting means, and sets the correction coefficient to a predetermined value immediately after starting. An intake pipe internal pressure detection device characterized by gradually decreasing within a period. 2. The intake pipe internal pressure detection device according to claim 1, wherein the correction means reduces the correction coefficient at a reduction rate determined according to the engine temperature. 3. The intake pipe internal pressure detection device according to claim 1, wherein the correction means determines the initial value and a correction coefficient after that in accordance with an engine operating state.