JP2000027692A - Method and device for detecting intake pipe pressure in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To predict an actual intake pipe pressure. SOLUTION: An engine speed NE and a throttle opening degree TA are read (200). An intake pipe pressure PMTA is computed in a steady-state, corresponding to NE and TA (202). A factor (n) relating to weighing is computed (204). A previously computed weight average value PMSMi-1 is read, and then, a weight average value PMSMi at the present time is computed from PMSMi=((n-1).PMSMi-1+PMTA)/n (206 to 210). A time T msec from the present time to a time for predicting an intake pipe pressure is divided by a computation cycle period Δt(=8 msec) in a routine so as to compute a frequency T/Δt (212). With the repetitions of the above-mentioned computation by the frequency T/Δt (214), an intake pipe pressure (intake pipe pressure in a state nearer the steady-state than the present time) is predicted at a time subsequent from the present time by T msec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for detecting an intake pipe pressure of an internal combustion engine, and more particularly, to an intake pipe of an internal combustion engine for detecting an intake pipe pressure based on a throttle opening and an engine speed. The present invention relates to a pressure detection method and device.

[0002]

2. Description of the Related Art Conventionally, an intake pipe detection method for an internal combustion engine has been used for a fuel injection amount control method for an internal combustion engine. A conventional fuel injection amount control method for an internal combustion engine detects an intake pipe pressure and an engine speed, calculates a basic fuel injection time based on the detected intake pipe pressure and the engine speed, and calculates the basic fuel injection time. The fuel injection time is obtained by correcting the injection time according to the intake air temperature, the engine cooling water temperature, or the like, and the fuel injection amount is controlled by opening the fuel injection valve for a time corresponding to the fuel injection time. In this fuel injection amount control method, a diaphragm type pressure sensor is attached to an intake pipe, and a time constant of 3 to 5 msec is used to remove an engine pulsation component.
The output of the pressure sensor is processed through the filter to detect the intake pipe pressure, and the basic fuel injection time is calculated based on the detected intake pipe pressure and the engine speed detected by the rotational speed sensor. I have to.

However, since there is a response delay due to the diaphragm of the pressure sensor and a response delay due to the time constant of the filter, during a transient operation such as acceleration or deceleration, the intake pipe pressure detected with respect to the actual intake pipe pressure fluctuation is detected. There is a time lag in the fluctuation of. For this reason, during acceleration, the throttle valve is suddenly opened and the actual intake pipe pressure rises sharply, whereas the detected intake pipe pressure has a time delay, and the intake pipe pressure is smaller than the actual intake pipe pressure. As a result, the basic fuel injection time is calculated, so that the air-fuel ratio becomes over lean, the acceleration responsiveness deteriorates, and the exhaust emission deteriorates. Conversely, during deceleration, since the throttle valve is rapidly closed, the intake pipe pressure drops rapidly, so the basic fuel injection time is calculated based on the intake pipe pressure that is larger than the actual intake pipe pressure, and the air-fuel ratio , The exhaust emission deteriorates as well as the driver liability deteriorates. In order to prevent the air fuel ratio from being over-lit or over-lean, various increase / decrease corrections such as acceleration increase and deceleration decrease are performed. It was impossible to completely control the target air-fuel ratio.

On the other hand, a method of calculating the basic fuel injection time based on the throttle opening and the engine speed by using the throttle opening as a physical quantity having no time delay from the actual value (Japanese Patent Laid-Open No. 59-28031). And the intake pipe pressure corresponding to the throttle opening and the engine speed are stored, and the intake pipe pressure is determined in consideration of the partial pressure of exhaust gas during exhaust gas recirculation according to a signal obtained from a pressure sensor. The fuel injection amount is controlled by making a correction (Japanese Patent Application Laid-Open No.
No. 39948).

[0005]

However, the throttle valve is usually arranged at a position where the pressure sensor is mounted and at a position upstream of the engine combustion chamber, and the air passing through the throttle valve is located at the position where the pressure sensor is mounted and the engine combustion position. There is a time delay before reaching the chamber, and the throttle opening degree advances in phase with the change in the actual intake air amount due to the volume between the throttle valve and the intake valve. For this reason, the intake pipe pressure P determined by the throttle opening and the engine speed is determined.
(TA, NE) is the actual intake pipe pressure P as shown in FIG.
The value has a phase advanced. Here, PM is the intake pipe pressure obtained from the pressure sensor. As shown in FIG. 4, the basic fuel injection amount TP (TA, NE) determined by the throttle opening and the engine speed has a phase in which the change in the throttle opening advances with respect to the change in the actual intake air amount. Therefore, it becomes larger than the required fuel injection amount. Therefore, if the fuel injection amount is controlled based on the throttle opening and the engine speed,
At the time of acceleration, the fuel injection amount becomes larger than the required value and the air-fuel ratio becomes overlit. At the time of deceleration, the fuel injection amount becomes smaller than the required value and the air-fuel ratio becomes over lean. Further, even when the acceleration increase correction is performed, the increase value becomes as shown by the oblique line in FIG. 4, and the above-described phase advance cannot be corrected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an intake pipe pressure having no phase advance and delay using a throttle opening having no response delay with respect to an actual intake pipe pressure change. An object of the present invention is to provide a method and a device for detecting an intake pipe pressure of an internal combustion engine, which can predict an actual intake pipe pressure.

[0007]

According to the first aspect of the present invention, an intake pipe pressure in a steady state is calculated at a predetermined cycle based on a throttle opening and an engine speed.
A weighting coefficient is calculated using the time constant for the change in the intake pipe pressure during the transition and the predetermined period, and the weight of the weighted average value calculated in the past is increased, and the weighted average value calculated in the past is calculated. A current weighted average value is calculated using the intake pipe pressure in the steady state and the coefficient relating to the weight, and a predicted value of the intake pipe pressure for a predetermined period ahead of the calculation time is repeatedly calculated. The current weighted average value obtained by the previous calculation at the time of each calculation to be performed is used as the weighted average value calculated in the past.

According to a second aspect of the present invention, in the first aspect of the invention, at least one of a differential value of the throttle opening and a differential value of the engine speed is calculated, and the calculation is repeated using the differential value. At least one of the throttle opening and the engine rotation speed at each calculation time to be performed is predicted, and at the time of each calculation to repeat the calculation, at least one of the predicted throttle opening and the predicted clearance rotation speed is calculated. This is used to predict the intake pipe pressure in the steady state before the predetermined period.

According to a third aspect of the present invention, in the first aspect, the throttle opening and the engine speed or
The coefficient relating to the weight is calculated using the intake pipe pressure and the engine speed in the steady state.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the intake pipe pressure in the steady state is PMTA, and the coefficient relating to the weight is n.
And then, characterized by calculating from the following equation the actual intake pipe pressure PMSM _i of the current.

PMSM _i = ((n−1) · PMSM _i−1 +
PMSM) / n where PMSM _i-1 is the current weighted average value obtained by the previous calculation in each of the above-described repeated calculations.

According to a fifth aspect of the present invention, there is provided a throttle opening detecting means for detecting a throttle opening, a rotational speed detecting means for detecting an engine rotational speed, the detected throttle opening and the detected engine rotation. Intake pipe pressure calculating means for calculating the intake pipe pressure in a steady state at a predetermined cycle based on the speed; and calculating a coefficient relating to weight using a time constant relating to a change in the intake pipe pressure during transition and the predetermined cycle. Weighting coefficient calculating means, weighting the weighted average value calculated in the past, and using the weighted average value calculated in the past, the intake pipe pressure in the steady state, and a coefficient relating to the weight to calculate the current weight. An average value is calculated, a predicted value of the intake pipe pressure for a predetermined period ahead of the calculation time point is repeatedly calculated, and the current weighted average value obtained by the previous calculation at the time of each of the repeated calculations is calculated in the past. Used as computed weighted average value, and a, and intake pipe pressure estimated value predicting means for obtaining.

According to a sixth aspect of the present invention, in accordance with the fifth aspect of the present invention, there is provided an arithmetic means for calculating at least one of a differential value of the throttle opening and a differential value of the engine speed, and using the calculated differential value. Prediction means for predicting at least one of the throttle opening and the engine rotational speed at each calculation time point at which the calculation is repeated. In this case, the intake pipe pressure in the steady state before the predetermined period is predicted using at least one of the predicted throttle opening and the predicted engine rotation speed.

According to a seventh aspect of the present invention, in the fifth aspect of the present invention, the weight coefficient calculating means uses the throttle opening and the engine speed, or the intake pipe pressure and the engine speed in a steady state. , And calculates a coefficient related to the weight.

According to an eighth aspect of the present invention, in the invention according to any one of the fifth to seventh aspects, the intake pipe pressure predicted value predicting means sets the intake pipe pressure in the steady state to P.
MTA, if the coefficient for the weighting is n, the is intended for calculating the following equation to actual intake pipe pressure PMSM _i of the current.

PMSM _i = ((n−1) · PMSM _i−1 +
PMSM) / n where PMSM _i-1 is the current weighted average value obtained by the previous calculation in each of the above-described repeated calculations.

First, for reference, the actual intake pipe pressure is
The principle to be determined will be described. As shown in FIG.
Intake of the engine E from the throttle valve Th via the surge tank S
Considering the intake system up to the valve, the air pressure in the intake system (intake pipe
Absolute pressure) is P [mmHgabs.], And the volume of the intake system is V
[L], the weight of air existing in the intake system is Q [g],
The absolute temperature of air in the air system is T [° K], and the atmospheric pressure is Pc
[MmHgabs.] And the combustion system of the engine E from the intake system.
ΔQ is the weight of air per unit time sucked into₁[G / se
c], is drawn into the intake system through the throttle valve Th
Air weight per unit time is ΔQ_Two[G / sec]
Within a short time Δt, the weight of the air in the intake system becomes (ΔQ_Two−ΔQ ₁)
Δt changes, and at this time, the pressure of the air in the intake system changes by ΔP
The air in the intake system is voile
The following equation (1) is obtained by applying the law of

[0018]

(Equation 1)

Here, R is a gas constant.

On the other hand, since PV = Q · RT, the above equation (1) is modified to obtain the following equation (2).

[0021]

(Equation 2)

Here, assuming that the flow coefficient is ψ and the opening area of the throttle valve (throttle opening) is A, the air weight ΔQ2 per unit time passing through the throttle valve is expressed by the following equation (3). Assuming that the volume is VS, the engine speed is NE [rpm], and the suction efficiency is η, the air weight ΔQ1 per unit time drawn into the combustion chamber of the engine is expressed by the following equation (4).

[0023]

(Equation 3)

By substituting the above equations (3) and (4) into the equation (2), the following equation (5) is obtained.

[0025]

(Equation 4)

Here, taking the limit of Δt → 0,

[0027]

(Equation 5)

## EQU1 ##

Now, considering the response in the vicinity of the pressure P0 (と し て PC), assuming that the pressure has changed from P0 to P0 + P, P0 + P (where P is a small value) is substituted for P in the above equation (6). By substitution, the following equation (7) is obtained.

[0030]

(Equation 6)

Here,

[0032]

(Equation 7)

Therefore, the above equation (7) becomes the following equation (9).

[0034]

(Equation 8)

Here,

[0036]

(Equation 9)

Then, the above equation (9) becomes as follows.

[0038]

(Equation 10)

If the above equation (12) is transformed as in the following equation (13), and both sides are integrated, and the integration constant is C, the following equation (14) is obtained.
An expression is obtained.

[0040]

[Equation 11]

Here, when t = 0, the initial value of P is P0, so that the integration constant C is as follows from the above equation (14).

[0042]

(Equation 12)

When P is obtained from the above equations (14) and (15), the following is obtained.

[0044]

(Equation 13)

Where e is the base of the natural logarithm.

Accordingly, the opening area A of the throttle valve, that is, the throttle opening TA, the engine speed NE, and the elapsed time t from the time when the throttle opening changes are measured to determine the above (1).
By substituting into the equation (6), the actual intake pipe pressure P can be obtained. Then, based on the actual intake pipe pressure P and the engine rotational speed NE obtained in this way, for example, a calculation shown in the following equation is performed to obtain a basic fuel injection time TP.
The basic fuel injection time TP is corrected according to the intake air temperature, the engine cooling water temperature, etc., to obtain the fuel injection time, and the fuel injection valve is opened for a time corresponding to the fuel injection time to obtain the fuel required by the engine. Can be injected.

[0047]

[Equation 14]

Where K is a constant.

FIG. 2 is a graph showing the intake pipe pressure P in the above equation (16).
In the limit of P0, t → ∞ (steady state), it is the output of the first-order lag element where P = b / a (intake pipe pressure PMTA in the steady state). Accordingly, the intake pipe pressure PMTA in the steady state is calculated based on the throttle opening TA and the engine speed NE, and the intake pipe pressure PMTA in the steady state is calculated by the following equation (1).
The actual intake pipe pressure may be calculated by processing with the first-order lag element represented by the transfer function G (s) in the equation (7).

[0050]

(Equation 15)

Here, s is an operator of Laplace transform, and T is a time constant.

That is, the intake pipe pressure in the steady state is calculated on the basis of the throttle opening and the engine speed every predetermined cycle, and the calculated intake pipe pressure in the steady state is processed by the first-order lag element. Thus, the intake pipe pressure using the elapsed time as a variable can be calculated.

As described above, since the actual intake pipe pressure is predicted and the fuel injection amount is controlled based on the intake pipe pressure and the engine rotation speed, the amount of fuel corresponding to the actual intake air amount can be reduced. Injection can be performed, whereby the air-fuel ratio can be controlled to the target air-fuel ratio to prevent the air-fuel ratio from being over-lit or over-lean during transition.

Next, another reference example will be described with reference to FIG. As shown in FIG. 6, the intake pipe pressure calculating means A is based on the throttle opening TA detected by the throttle opening detecting means and the engine rotational speed detected by the rotational speed detecting means.
Thus, the intake pipe pressure PMTA in the steady state is calculated. The intake pipe pressure PMTA in the steady state calculated by the intake pipe pressure calculation means A is corrected by the correction means B by a response delay of the intake pipe pressure in the transient state. A primary delay element can be used as this correction means. The intake pipe pressure corrected by the correction means B is input to the basic fuel injection time calculation means C, and the basic fuel injection time TP is calculated based on the engine speed NE input to the basic fuel injection time calculation means. . Then, the fuel injection amount is controlled by the fuel injection amount control means based on the basic fuel injection time TP.

As described above, since the pressure sensor and the filter are not used, it is possible to inject the required amount of fuel by predicting the actual intake pipe pressure with a simple structure and accurately.

Next, the operation of the first embodiment will be described.

According to the present invention, the intake pipe pressure in a steady state is calculated at a predetermined cycle based on the throttle opening and the engine speed, and a time constant relating to a change in the intake pipe pressure during transition and the predetermined cycle are used. To calculate a coefficient relating to the weight.

Then, the weight of the weighted average value calculated in the past is increased, and the weighted average value calculated in the past, the intake pipe pressure in the steady state and the coefficient relating to the weight are used to calculate the current weighted average value. A value is calculated, and a predicted value of the intake pipe pressure for a predetermined period ahead of the time of the calculation is repeatedly calculated, and a current weighted average value obtained by a previous calculation in each of the repeated calculations is calculated in the past. It is obtained by using the obtained weighted average value.

That is, for example, by repeating the calculation of the weighted average value a predetermined number of times obtained by dividing the predetermined period by the predetermined period, the intake pipe pressure ahead of the predetermined period can be obtained. Further, for example, if a predetermined period is taken from the time of calculation to the time when the amount of air taken into the engine combustion chamber is determined, the actual intake pipe pressure at the time when the amount of intake air is determined can be predicted.

The basic fuel injection time is calculated on the basis of the predicted value of the intake pipe pressure and the engine speed in the predetermined period, and the fuel injection amount is controlled based on the calculation result. Is also good.

Here, at least one of the differential value of the throttle opening and the differential value of the engine speed is calculated, and the calculation is repeated at each calculation time point using the differential value. At least one of the throttle opening and the engine rotation speed is predicted, and at the time of each calculation of repeating the calculation, at least one of the predicted throttle opening and the predicted clearance rotation speed is used for the predetermined period. The intake pipe pressure in the previous steady state may be predicted.

In this case, even if at least one of the throttle opening and the engine speed changes during the predetermined period and the intake pipe pressure in the steady state changes, the intake air in the steady state before the predetermined period changes. Since the pipe pressure is predicted, it is possible to predict the predicted value of the intake pipe pressure a predetermined period ahead of the calculation time with higher accuracy.

Further, the coefficient relating to the weight may be calculated by using the throttle opening and the engine speed, or the intake pipe pressure and the engine speed in a steady state.

[0064] Furthermore, as according to claim 4, PMTA the intake pipe pressure at the steady state, the coefficient regarding weight is n, the following equation of the actual intake pipe pressure PMSM _i of the current (to be described later (23) ) May be calculated.

PMSM _i = ((n−1) · PMSM _i−1 +
PMTA) / n where PMSM _i-1 is the current weighted average value obtained by the previous calculation in each of the above-described repeated calculations.

Next, the principle of the present invention will be described. When the first-order lag element is represented by a block diagram, it is as shown in FIG. 5, where x (t) is an input, y (t) is an output, and T is a time constant. It is represented by the following equation.

[0067]

(Equation 16)

Here, t2 is the current operation timing,
If t1 is the past calculation timing, the following equation (21) is obtained.

[0069]

[Equation 17]

In the above (21), x (t2) is the intake pipe pressure PMTA in a steady state, y (t2) is the current actual intake pipe pressure PMSMi, and y (t1) is the past actual intake pipe pressure PMSMi. Assuming that the calculation cycle is -1, t2-t1 (= Δt),

[0071]

(Equation 18)

Assuming that T / Δt = n, the following (2)
3) is obtained.

[0073]

[Equation 19]

That is, the above equation (23) is obtained by calculating a weighted average where the weight of the past actual intake pipe pressure PMSMi-1 is n-1 and the weight of the intake pipe pressure PMTA in the steady state is 1. , The current actual intake pipe pressure PMSMi
Can be calculated. The coefficient n relating to the weight is obtained by the ratio between the time constant T and the operation period Δt.

Therefore, based on the throttle opening and the engine speed, the intake pipe pressure PM in the steady state at a predetermined period Δt is determined.
TA is calculated, and a coefficient n relating to weight is calculated by a time constant T relating to a change in the intake pipe pressure during a transition and a predetermined period Δt,
The weight of the weighted average value PMSMi-1 calculated in the past is increased, and the weighted average value PMSMi-1 calculated in the past, the intake pipe pressure PMTA in the steady state, and a coefficient n relating to the weight are calculated.
By calculating the weighted average value PMSMi according to the above equation (23), the current actual intake pipe pressure can be obtained.

Then, the basic fuel injection time is calculated based on the weighted average value (current actual intake pipe pressure) calculated as described above and the engine speed, and based on the calculated basic fuel injection time. Alternatively, the fuel injection amount may be controlled.

As understood from the above equations (10) and (16), the time constant T = 1 / a decreases as the engine speed NE increases, and decreases as the throttle opening TA increases. . Thus, the time constant is the throttle opening T
It is represented by a function using A and the engine speed NE as variables.
Accordingly, if the calculation cycle Δt is fixed, the coefficient n relating to the weight can be determined by a function using the throttle opening TA and the engine speed NE as variables. It should be noted that the intake pipe pressure P in a steady state is determined by the throttle opening TA and the engine speed NE.
Since the MTA is uniquely determined, the intake pipe pressure PM in the steady state is replaced with the throttle opening TA and the engine speed NE.
Coefficient n relating to weight according to TA and engine speed NE
May be determined.

The amount of air supplied to the engine combustion chamber is determined at the end of intake, that is, when the intake valve is closed. However, a predetermined time is required to calculate the fuel injection time, and a predetermined flight time is required before the fuel injected from the fuel injection valve reaches the combustion chamber, and the amount of air supplied to the combustion chamber is required. When the fuel injection amount is calculated when is determined, a time delay occurs. Therefore, conventionally, the basic fuel injection time is calculated using the intake pipe pressure before the air amount supplied to the combustion chamber is determined. For this reason, an amount of fuel suitable for the amount of air actually sucked into the combustion chamber is no longer injected, and during acceleration, the fuel injection amount is controlled by an intake pipe pressure smaller than the intake pipe pressure at which the intake air amount is determined. Therefore, the air-fuel ratio becomes lean, and at the time of deceleration, the fuel injection amount is controlled by the intake pipe pressure having a value larger than the intake pipe pressure at which the intake air amount is determined, so that the air-fuel ratio becomes rich.

On the other hand, assuming that the throttle opening degree TA and the engine speed NE do not change in the above equation (23), the period from when the weighted average value is calculated until the intake air amount is determined, that is, the weighted average value calculation The intake pipe pressure PMTA in a steady state is constant from time to a predetermined time ahead. Therefore, by repeatedly calculating the weighted average value of the above equation (23), the actual intake pipe pressure at the time of determining the intake air amount can be predicted. Therefore, in the present invention, the number of calculations is obtained by dividing the time from when the intake pipe pressure in the steady state is calculated to the time when the amount of air taken into the engine is determined by the calculation cycle Δt. By repeating the calculation of the weighted average of equation (23), the weighted average value at the time when the amount of air taken into the engine is determined, that is, the actual intake pipe pressure at the time when the amount of air taken into the engine is determined, is calculated. It is preferable to control the fuel injection amount by prediction.

In the above description, it is assumed that the throttle opening and the engine speed do not change between the time of calculating the fuel injection time and the time when the amount of air taken into the engine is determined. However, the throttle opening and the engine speed are not changed. Is changed, the throttle opening and / or the engine speed at the time of the next fuel injection time calculation is calculated by using the differential value of the throttle opening at the time of calculating the fuel injection time and / or the differential value of the engine speed. By predicting the intake pipe pressure in a steady state when the intake air amount is determined and repeating the calculation of the weighted average value to predict the actual intake pipe pressure as described above, the throttle opening and the The accuracy of the predicted value of the actual intake pipe pressure when the engine rotation speed fluctuates is further improved (see the invention described in claim 2).

The fuel injected from the fuel injection valve is:
Since all of the fuel adhering to the engine wall surface such as the inner wall surface of the intake manifold and the like is not supplied to the combustion chamber, it is preferable to control the fuel injection amount by correcting the fuel adhesion amount. The amount of fuel adhesion depends on the magnitude of the intake pipe pressure. When the intake pipe pressure is small, the amount of fuel evaporation increases because the amount of fuel evaporation increases, and when the intake pipe pressure is large, the amount of fuel evaporation decreases. Therefore, the fuel adhesion amount increases. For this reason, in this aspect, the amount of change in the amount of fuel adhering to the engine wall surface is predicted from the actual intake pipe pressure calculated by the weighted average,
It is preferable to correct the fuel injection amount corresponding to the change amount and supply the engine with an amount of fuel corresponding to the actual intake air amount drawn into the engine. The amount of fuel adhering to the wall surface also changes depending on the engine temperature and the engine rotation speed. (If the engine temperature is high, the amount of fuel evaporation increases, the amount of fuel adhesion decreases, and if the engine rotation speed increases, the air flow velocity decreases. (The amount of fuel deposition decreases as the evaporation rate increases, and the amount of fuel deposition decreases.) Therefore, the amount of change in the amount of fuel deposition may be determined as a function of the engine temperature or the engine rotation speed. Since the fuel injection amount is not stable, the correction amount of the fuel injection amount may be attenuated over time so that the fuel adhesion amount at the time of the current injection is reflected in the next and subsequent injections.

As described above, in the present invention, since the actual intake pipe pressure is predicted by calculating the weighted average value at a predetermined cycle, it is possible to measure the elapsed time from the time when the throttle opening changes. The actual intake pipe pressure can be predicted.

By controlling the air-fuel ratio to the target air-fuel ratio even during the transition, deterioration of acceleration response, drivability, exhaust emission and the like can be prevented.

The inventions according to claims 5 to 8 have the same functions and effects as the inventions according to claims 1 to 4, respectively.
Since the effect is achieved, the description is omitted.

[0085]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 7 is a schematic diagram of the internal combustion engine according to the present embodiment.

A throttle valve 8 is arranged downstream of the air cleaner (not shown). A throttle opening sensor 10 for detecting the opening of the throttle valve 8 is attached to the throttle valve 8. Throttle opening sensor 1
Numeral 0, as shown in the equivalent circuit of FIG. 8, comprises a contact 10B fixed to the rotary shaft of the throttle valve 8 and a variable resistor 10A having one end connected to a power source and the other end grounded. As the opening of the throttle valve 8 changes, the contact state between the contact 10B and the variable resistor 10A changes, and a voltage corresponding to the opening of the throttle valve 8 is obtained from the contact 10B. ing. A temperature sensor 14 composed of a thermistor for detecting the temperature of intake air is attached to the intake pipe wall on the upstream side of the throttle valve 8. A surge tank 12 is disposed downstream of the throttle valve 8, and the surge tank 12 is provided with an intake manifold 18,
Engine body 20 through intake port 22 and intake valve 23
Of the combustion chamber 25. The intake manifold 24 is provided with the fuel injection valve 2 so as to correspond to each cylinder.
4 are mounted so that fuel can be injected independently for each cylinder, for each cylinder group, or simultaneously for all cylinders.

The combustion chamber 25 includes an exhaust valve 27, an exhaust port 2
6 and an exhaust manifold 28 are connected to a catalyst device (not shown) filled with a three-way catalyst.
The exhaust manifold 28 is provided with an O2 sensor 30 that detects the concentration of residual oxygen in the exhaust gas and outputs a signal inverted from a value corresponding to the stoichiometric air-fuel ratio.

The cylinder block 32 is provided with a cooling water temperature sensor 34 such as a thermistor for detecting the engine cooling water temperature representing the engine temperature so as to protrude into the water jacket. A spark plug 3 is provided in the cylinder block 36 so as to project into each combustion chamber 25.
8 are attached. The ignition plug 38 is connected to a control circuit 4 composed of a microcomputer or the like via a distributor 40 and an igniter 42 having an ignition coil.
4 is connected. A cylinder discriminating sensor 46 and a rotation angle sensor 48 each composed of a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing are attached to the distributor 40. Cylinder discrimination sensor 46
Outputs a cylinder discrimination signal every 720 ° CA, for example, and the rotation angle sensor 48 outputs a rotation angle signal every 30 ° CA, for example. Then, the engine speed can be calculated from the cycle of the rotation angle signal.

As shown in FIG. 9, the control circuit 44 composed of a micro computer or the like includes a micro processing unit (MPU) 60, a read only memory (ROM) 62, and a random access memory (RA).
M) 64, backup RAM (BU-RAM) 66,
Input / output port 68, input port 70, output port 72,
74 and a bus 75 such as a data bus and a control bus for connecting them. An analog-digital (A / D) converter 78 and a multiplexer 80 are sequentially connected to the input / output port 68, and the multiplexer 80 is connected to the intake air temperature sensor 1 via a buffer 82.
4 is connected, and a buffer 84 and a buffer 8 are connected.
5, a water temperature sensor 34 and a throttle opening degree sensor 10 are connected. Also, input / output port 6
Numeral 8 is connected to an A / D converter 78 and a multiplexer 80, and sequentially A / D converts the outputs of the intake air temperature sensor 14, the water temperature sensor 34 and the throttle opening degree sensor 10 at predetermined intervals in accordance with a control signal from the MPU. Control.

The input port 70 is connected to the O 2 sensor 30 via a comparator 88 and a buffer 86, and the cylinder discriminating sensor 46 via a waveform shaping circuit 90.
And a rotation angle sensor 48 are connected. The output port 72 is connected to the igniter 42 via a drive circuit 92, and the output port 74 is connected to the combustion chamber 24 via a drive circuit 94.

The ROM 62 stores a control routine program described below and the throttle opening T shown in FIG.
A and a map of the intake pipe pressure PMTA in a steady state defined by the engine speed NE and the engine speed NE shown in FIG.
E and the map of the coefficient n relating to the weight determined by the intake pipe pressure PMTA (or the throttle opening TA) in the steady state, and the actual intake pipe pressure PMSM and the engine speed N
The map of the basic fuel injection time TP determined by E is stored in advance. The map of the intake pipe pressure PMTA in the steady state shown in FIG. 10 sets the throttle opening TA and the engine rotation speed NE, and measures the intake pipe pressure corresponding to the set throttle opening TA and the engine rotation speed NE. , Using the value when the intake pipe pressure is stable.
The map of the coefficient n relating to the weight shown in FIG. 11 measures the time constant T at the time of the response of the intake pipe pressure (indicative response) when the throttle valve is opened in a step-like manner. The measured value and the calculation routine shown in FIG. From the execution cycle Δtsec of
/ Δt (≒ n) is obtained by obtaining the engine rotation speed NE and the actual intake pipe pressure PMTA (or throttle opening TA). Then, the map of the basic fuel injection time TP in FIG. 12 is created by setting the engine speed and the intake pipe pressure and measuring the basic fuel injection time TP that becomes the target air-fuel ratio.

Next, the fuel injection time calculation routine shown in FIG. 13 will be described. This routine is executed every predetermined time (for example, 8 msec). The throttle opening TA (for example, 8 ms) which has been A / D converted in step 100
At step 102, the intake pipe pressure PMTA in a steady state corresponding to the throttle opening TA and the engine speed NE is calculated from the map in FIG. Next Step 104
Now, the intake pipe pressure PMTA calculated in step 102
A coefficient n relating to the weight is calculated from the map shown in FIG. 11 based on and the engine speed NE taken in step 100. When the map of the coefficient n relating to the weight is determined by the throttle opening and the engine speed, the step 104
Then, the coefficient n relating to the weight may be calculated based on the throttle opening TA and the engine speed NE taken in step 100. In the next step 106, step 102
, The coefficient n relating to the weight calculated in step 104, and the previous weighted average value P calculated in step 106 during the previous execution of this routine.
The current weighted average value PMSMi is calculated using MSMi-1 and the equation (23) described above. In the next step 108, the basic fuel injection time TP is calculated from the map shown in FIG. 12 based on the current weighted average value PMSMi and the engine speed NE. Then, the next step 110
Correction coefficient FK determined by intake air temperature, engine cooling water temperature, etc.
Is multiplied by the basic fuel injection time TP to calculate the fuel injection time TAU. Then, in a control routine (not shown), when the predetermined crank angle is reached, the fuel injection valve is opened for a time corresponding to the fuel injection time TAU to execute the fuel injection.

FIG. 14 shows a routine for calculating the ignition advance angle θ by interruption every predetermined crank angle. In FIG. 14, the same parts as those in FIG. 13 are denoted by the same reference numerals, and description thereof will be omitted. In step 112, the weighted average value PMSMi calculated this time and the engine speed NE are calculated.
Then, the basic ignition advance θBASE is calculated. The basic ignition advance angle θBASE may be calculated by an arithmetic expression, or a map may be created in the same manner as the basic fuel injection time and calculated from this map. Then, in the next step 114, the ignition advance angle θ is obtained by multiplying the basic ignition advance angle θBASE by a correction coefficient IK determined by the intake air temperature, the engine cooling water temperature and the like. Then, in an ignition timing control routine (not shown), the ignition is executed by turning off the igniter at the basic ignition advance angle θ.

FIGS. 15A and 15B show a comparison between the change in the air-fuel ratio when acceleration is not performed and the change in the air-fuel ratio according to the present embodiment when acceleration is not performed conventionally. Weighted average value P in the present embodiment for obtaining the injection amount
5 shows a difference between MSM and a conventional detected intake pipe pressure PM. As can be understood from FIG. 15, the air-fuel ratio of the conventional example has a lean spike during acceleration, but the air-fuel ratio of the present embodiment is substantially flat.

As described above, in the present embodiment, the fuel injection amount and the ignition timing are controlled by predicting the actual intake pipe pressure, so that the fuel injection amount can be accurately controlled without using a pressure sensor or a filter. And ignition timing control.

Next, a second embodiment in which the present invention is applied to the internal combustion engine will be described.
An embodiment will be described. This embodiment predicts the actual intake pipe pressure when the intake air amount is determined (when the intake valve is fully closed) by repeating the calculation of the weighted average value a predetermined number of times, and controls the fuel injection amount based on the predicted intake pipe pressure. It is something to do. FIG. 16 shows a routine executed every predetermined time (8 msec in the present embodiment) to calculate a predicted value PMSM2 of the intake pipe pressure when the intake air amount is determined. In step 200, the engine rotational speed NE is acquired, and the throttle opening TA is subjected to A / D conversion to acquire the throttle opening TA. In step 202, FIG.
From the map shown in the figure, the engine speed NE and the throttle opening T
The intake pipe pressure PMTA in the steady state corresponding to A is calculated. In the next step 204, a coefficient n relating to weighting is calculated from the map shown in FIG. Next Step 20
In step 6 and in step 208, the previously calculated weighted average value PMSMi-1 stored in the register PMSM1 is calculated as R
The weighted average value PMSMi is read out from the AM and calculated based on the above equation (23), and the weighted average value PMSMi is stored in the register PMSM1 in step 210. In the next step 212, the number of calculations T / Δt is calculated by dividing the time Tmsec from the current time to the intake pipe pressure prediction time by the calculation cycle Δt (= 8 msec) of the routine of FIG. The predicted time Tmsec can be a time from the current time to the determination of the intake air amount, that is, a time from the current time to the closing of the intake valve. If the fuel is not injected independently for each cylinder, the combustion from the fuel injection valve is performed. Although it is determined in consideration of the fuel flight time to the chamber, etc., even if the crank angle from the present time to the prediction destination is the same, the predicted time Tmsec becomes shorter as the engine speed increases, so that the engine speed, etc. It is preferable to vary according to the operating conditions (for example, it becomes shorter as the engine speed increases). In the next step 214, the calculation of the above equation (23) is repeatedly executed T / Δt times, and in step 216, the calculated value is used as the predicted intake pipe pressure value PMSM2.
And By repeatedly executing the weighted average value in this manner, the latest weighted average value approaches the intake pipe pressure value in the steady operation state, so that the number of calculations of the weighted average value is determined from the current time to It is possible to predict the previous intake pipe pressure (the intake pipe pressure in a state closer to a steady state than at the present time).

FIG. 17 shows a predetermined crank angle (for example, 120 crank angles).
FIG. 1 shows a routine for calculating the fuel injection time TAU for each of the engine speed NE and the predicted intake pipe pressure value PMSM2 calculated in step 216.
The basic fuel injection time TP is calculated from the map shown in FIG.
Then, in step 220, the above step 110 is performed.
The fuel injection time TAU is calculated in the same manner as described above.

Since the throttle opening and the engine speed may change when Tmsec elapses from the current time, the throttle opening ahead of Tmsec is calculated using the differential value of the throttle opening and the differential value of the engine speed. The accuracy is further improved by estimating the intake pipe pressure in the steady state before Tmsec by estimating the engine speed and the engine rotational speed, and repeating the calculation of the weighted average value.

FIG. 18 and FIG. 19 show the weighted average value calculated as described above and the predicted value PMSM2 after the lapse of Tmsec. FIG. 18 shows the predicted value and the theoretical value 16 msec later, but the predicted value is substantially equal to the theoretical value.
Although the A / D conversion timing of the throttle opening may coincide with the fuel injection time calculation timing, it is shifted by a time corresponding to the maximum calculation cycle Δt. Therefore, the deviation time may be averaged (0 + Δt) / 2 to predict the intake pipe pressure T ± Δt / 2 hours ahead.

Next, a third embodiment will be described. In the present embodiment, the amount of fuel adhering to the engine wall is predicted and the fuel injection amount is corrected.

The amount of fuel adhering to the engine wall surface without being sucked into the engine combustion chamber is determined by the intake pipe pressure when the intake valve is closed. For example, the intake pipe pressure accelerates from the state of PM1 to the state of PM2. In this case, assuming that the fuel adhesion thickness at each intake pipe pressure is T1 and T2, the fuel adhesion thickness is T
The amount of fuel supply to the wall surface required to increase from 1 to T2 is determined irrespective of the throttle opening speed, the number of fuel injections, and the like. Therefore, in this embodiment, as shown in FIG. 22, the total amount of the injection amount to be supplied to the wall when the pressure is changed from a certain reference intake pipe pressure (for example, 0 mmHgabs) to an arbitrary intake pipe pressure is shown in FIG. The intake pipe pressure when fully closed is stored in the ROM in advance in the form of a map.

FIG. 20 shows a fuel injection amount calculation routine executed at a predetermined crank angle (360 ° CA) according to the present embodiment.
The basic fuel injection time TP is calculated from the predicted value PMSM2 of the intake pipe pressure and the engine speed NE calculated in the same manner as described above. In the next step 232, a correction coefficient FK of the fuel injection amount determined by the intake air temperature, the engine cooling water temperature and the like is calculated. In the next step 234, a fuel adhesion amount FMWET from the map shown in FIG. 22 to the engine wall surface corresponding to the predicted intake pipe pressure value PMSM2 is calculated. And the next step 23
In step 6, the fuel injection time TAU is obtained by multiplying the basic fuel injection time by the correction coefficient FK and adding a value obtained by subtracting the previous fuel adhesion FMWETOLD from the fuel adhesion FMWET obtained this time as a correction addition value. . This correction addition amount indicates a change amount of the fuel adhesion amount caused by a change of the intake pipe pressure. Then, in step 238, the fuel adhesion amount FMWET obtained this time is stored in the RAM as the previous adhesion amount FMWETOLD.

By controlling the fuel injection amount as described above, the amount of fuel indicated by the hatched portion as shown in FIG. 21 is increased, whereby the fuel having a thickness equal to the fuel adhesion thickness adheres to the inner wall surface of the engine. Even so, the fuel supplied to the engine according to the correction addition amount becomes the required value. FIG. 24 shows a change in the throttle opening, the predicted value of the intake pipe pressure, and the air-fuel ratio. In the present embodiment, the air-fuel ratio is small with no lean spike as in the conventional example shown by the broken line. Has become.

Next, a fourth embodiment will be described. In the above-described third embodiment, the fuel injection amount is controlled by the fuel adhesion amount for each injection. However, in consideration of the fact that the adhesion of the fuel to the engine wall surface is not instantaneously stabilized, in the present embodiment, The amount of fuel supply to the combustion chamber is made equal to the required value by attenuating the correction addition amount in each injection with time so as to be reflected in the next and subsequent injections. FIG.
Shows a fuel injection calculation routine of the present embodiment,
For example, it is executed every predetermined crank angle (360 ° CA). In FIG. 25, the same parts as those in FIG. After calculating the fuel adhesion amount FMWET in step 234, the correction addition amount FAE is calculated in step 240 according to the following equation. FAEOLD is the correction addition amount calculated last time, FM
WEOLD is the previously calculated amount of fuel adhering to the wall surface.

In the above equation (24), the previous correction addition amount FAE
Since OLD is multiplied by 0.2, the previous correction addition amount is attenuated by 80%, and 20% of the previous correction addition amount is reflected in the current correction addition amount. In addition, an optimal method of this damping is selected by the engine, and may be attenuated by a predetermined amount every predetermined crank angle (360 ° CA in the above example) as described above, or by a predetermined amount every predetermined time. You may make it attenuate one by one.

In the next step 242, the basic fuel injection time, the correction coefficient FK, and the correction addition amount FAE are set in the same manner as described above.
Is used to calculate the fuel injection time TAU. In step 244, the correction addition amount FAE is stored in the RAM as the previous correction addition amount FAEOLD, and the fuel adhesion amount FMWET is stored in the RAM.
D is stored in the RAM.

Although FIG. 22 shows an example in which the amount of fuel adhesion is determined according to the intake pipe pressure when the intake valve is fully closed, the amount of fuel adhesion also changes according to the engine speed. May be stored as a map that changes the intake pipe pressure and the engine speed as variables. Further, the amount of fuel adhesion varies depending on the engine temperature, and the lower the engine temperature, the greater the amount of fuel adhesion. Therefore, the engine temperature may be further determined as a variable. In the above-described embodiment, an example in which the intake pipe pressure is predicted by the weighted average value has been described. However, the intake pipe pressure may be predicted according to the above equation (16). The intake pipe pressure may be predicted by processing with the elements.

[0108]

As described above, according to the present invention, since the predicted value of the intake pipe pressure is determined a predetermined period earlier, the intake air pressure is determined from the present time until the intake air amount is determined as the predetermined period. This has the effect that the actual intake pipe pressure when the air amount is determined can be predicted.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of a reference example.

FIG. 2 is a diagram showing a change of an actual intake pipe pressure in an intake system with respect to time;

FIG. 3 is a diagram showing a difference between an intake pipe pressure determined by a conventional throttle opening and an engine speed and an actual intake pipe pressure.

FIG. 4 is a diagram showing a difference between a fuel injection amount and a required fuel injection amount determined by a conventional throttle opening and an engine rotation speed.

FIG. 5 is a block diagram for explaining another reference example.

FIG. 6 is a block diagram for explaining still another reference example.

FIG. 7 is a schematic diagram showing an internal combustion engine.

FIG. 8 is an equivalent circuit diagram of a throttle opening sensor.

FIG. 9 is a block diagram showing details of the control circuit of FIG. 8;

FIG. 10 is a diagram showing a map of intake pipe pressure in a steady state.

FIG. 11 is a diagram showing a map of coefficients relating to weighting of a weighted average value.

FIG. 12 is a diagram showing a map of a basic fuel injection time.

FIG. 13 is a flowchart showing a fuel injection amount calculation routine according to the first embodiment.

FIG. 14 is a flowchart illustrating an ignition advance calculation routine according to the first embodiment;

FIGS. 15 (1) and (2) are diagrams showing changes in the air-fuel ratio and the intake pipe pressure between the conventional example and the first embodiment.

FIG. 16 is a flowchart illustrating a routine for calculating a predicted value of the intake pipe pressure according to the second embodiment.

FIG. 17 is a flowchart illustrating a fuel injection time calculation routine according to the second embodiment.

FIG. 18 is a diagram illustrating a change in a predicted value and the like of an intake pipe pressure according to the second embodiment.

FIG. 19 is a diagram showing changes in predicted values and the like of the intake pipe pressure according to the second embodiment.

FIG. 20 is a flowchart showing a fuel injection time calculation routine according to the third embodiment.

FIG. 21 is a diagram showing a relationship between a fuel wall thickness and an intake pipe pressure.

FIG. 22 is a diagram showing a map of a correction injection amount.

FIG. 23 is a diagram showing a map of a correction injection amount.

FIG. 24 is a diagram showing changes in the air-fuel ratio and the like of the third embodiment in comparison with a conventional example.

FIG. 25 is a flowchart showing a fuel injection amount calculation routine according to a fourth embodiment.

[Explanation of symbols]

 8 Throttle valve 10 Throttle opening sensor 48 Rotation angle sensor

Claims (8)

[Claims] An intake pipe pressure in a steady state is calculated in a predetermined cycle based on a throttle opening and an engine rotation speed, and weighting is performed using a time constant relating to a change in the intake pipe pressure during transition and the predetermined cycle. The weight of the weighted average value calculated in the past is weighted, and the current weight is calculated using the weighted average value calculated in the past, the intake pipe pressure in the steady state, and the coefficient related to the weight. The average value is calculated, and the predicted value of the intake pipe pressure for a predetermined period ahead of the calculation time is repeatedly calculated, and the current weighted average value obtained by the previous calculation in each of the repeated calculations is calculated in the past. An intake pipe pressure detection method for an internal combustion engine, which is obtained by using the calculated weighted average value. 2. A method for calculating at least one of a differential value of a throttle opening and a differential value of an engine rotational speed, and using the differential value, repeatedly calculates the throttle opening and the engine rotational speed at each calculation time point at which the calculation is repeated. At least one of the predicted throttle opening and the predicted clearance speed is used at the time of each calculation of repeating at least one of the above calculations, and the intake pipe in a steady state ahead of the predetermined period is used. The method according to claim 1, wherein the pressure is predicted. 3. The internal combustion engine according to claim 1, wherein a coefficient relating to the weight is calculated using a throttle opening and an engine speed, or an intake pipe pressure and an engine speed in a steady state. Intake pipe pressure detection method. 4. The intake pipe pressure in the steady state is determined by PMT.
A, the coefficients for the weighting is n, the intake pipe of an internal combustion engine according to any one of claims 1 to 3, characterized in that for calculating the following equation to actual intake pipe pressure PMSM _i Current Pressure detection method. PMSM _i = ((n−1) · PMSM _i−1 + PMTA) /
n Here, PMSM _i-1 is the current weighted average value obtained by the previous calculation in each of the above-described repeated calculations. 5. A throttle opening detecting means for detecting a throttle opening, a rotating speed detecting means for detecting an engine speed, and a predetermined value based on the detected throttle opening and the detected engine speed. Intake pipe pressure calculating means for calculating the intake pipe pressure in a steady state in a cycle; weight coefficient calculating means for calculating a coefficient relating to weight using a time constant relating to a change in the intake pipe pressure during transition and the predetermined cycle; The weight of the weighted average value calculated in the past is increased, and the current weighted average value is calculated using the weighted average value calculated in the past, the intake pipe pressure in the steady state, and the coefficient related to the weight, The predicted value of the intake pipe pressure for a predetermined period from the time of the calculation is calculated by repeating the calculation, and at the time of each of the repeated calculations, the current weighted average value obtained by the previous calculation is calculated by the weighted average calculated in the past. Using the value, an intake pipe pressure detecting device for an internal combustion engine provided with an intake pipe pressure estimated value predicting means for obtaining. 6. A calculating means for calculating at least one of a differential value of a throttle opening and a differential value of an engine rotation speed, and a throttle opening at each calculation time point at which the calculation is repeated using the calculated differential value. Prediction means for predicting at least one of the degree and the engine rotation speed, wherein the intake pipe prediction value prediction means performs the calculation repeatedly to repeat the calculation, the predicted throttle opening and the predicted throttle opening degree. The intake pipe pressure detection device for an internal combustion engine according to claim 5, wherein the intake pipe pressure in a steady state before the predetermined period is predicted using at least one of the engine rotation speeds. 7. The weight coefficient calculating means calculates a coefficient relating to the weight using a throttle opening and an engine speed, or an intake pipe pressure and an engine speed in a steady state. Item 6. An intake pipe pressure detecting device for an internal combustion engine according to Item 5. Wherein said intake pipe pressure estimated value predicting means, PMTA the intake pipe pressure at the steady state, when the coefficient for the weighting is n, the following equation of the actual intake pipe pressure PMSM _i of the current The intake pipe pressure detection device for an internal combustion engine according to any one of claims 5 to 7, wherein the calculation is performed. PMSM _i = ((n−1) · PMSM _i−1 + PMTA) /
n Here, PMSM _i-1 is the current weighted average value obtained by the previous calculation in each of the above-described repeated calculations.