JPS6355336A - Fuel injection quantity controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To supply fuel accurately in the initial stage of acceleration, by incrementing the injection quantity at the start of acceleration thereafter decreasing the injection quantity gradually to a quantity corrected on the basis of a weighted average value of the pressure in an intake tube. CONSTITUTION:An intake tube pressure signal is inputted from a pressure sensor 6 to a controller 44. At first, the controller 44 takes in first and second weighted average values PM(a)i-1, PM(b)i-1 being stored in current intake tube pressure PMi RAM64 inputted through a filter 7. Then, current weighted average values PM(a)i, PM(b)i are operated according to a specific formula. Furthermore, an increment or decrement coefficient is operated based on the difference between PM(a)i and PM(b)i and corrected by a gradually decreasing correction quantity B. Consequently, the injection quantity is incremented in the initial stage of acceleration, resulting in the improvement of operationability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection amount control device for an internal combustion engine, and more particularly to a fuel injection amount control device for an internal combustion engine that performs acceleration increase.

[Prior art] Conventionally, the basic fuel injection amount is determined based on intake pipe pressure (absolute pressure) PM and engine rotational speed NE, and the basic fuel injection amount is corrected based on intake air temperature, engine cooling water temperature, etc., and fuel is injected. Fuel injection amount control devices are known. In such a fuel injection amount control device, in order to improve the acceleration response during acceleration, the amount of change ΔPMt! in the intake pipe pressure PM is controlled. J is detected and this amount of change ΔPM
It is practiced to increase the amount of fuel in proportion to (Japanese Patent Application Laid-Open No. 60-35154).

In the conventional acceleration increase described above, since the intake pipe pressure PM increases at a substantially constant rate during acceleration, the amount of change ΔPM in the intake pipe pressure becomes substantially constant, and a substantially constant amount of fuel is increased. However, since the intake pipe pressure at the beginning of acceleration is small and the intake pipe pressure at the end of acceleration is high, the amount of evaporation of the injected fuel increases at the beginning of acceleration and the amount of fuel adhering to the inner wall of the intake manifold decreases, but at the end of acceleration In this case, the amount of evaporation of the injected fuel decreases, and the amount of fuel that adheres to the inner wall of the intake manifold increases.

Therefore, if a substantially constant amount of fuel is injected during acceleration as in the past, the air-fuel ratio of the air-fuel mixture supplied to the engine combustion chamber at the beginning of acceleration will be richer than the engine required value, and at the end of acceleration, the air-fuel ratio of the mixture supplied to the engine combustion chamber will become richer than the engine required value. The air-fuel ratio becomes leaner than the engine requirement.

For this reason, although the air-fuel ratio is controlled to the engine-required value in some regions during acceleration, the air-fuel ratio is no longer controlled to the engine-required value throughout the entire region during acceleration, resulting in the problem that acceleration performance is still not good. there were. Furthermore, in the acceleration increase based on the temporal change amount ΔPM of the intake pipe pressure, in order to improve engine control responsiveness, a relatively small time constant (for example, 3 ~5m5e
c) The pressure signal may be input to the control circuit through a filter. In this case, since the pulsating component cannot be completely removed by the filter, the amount of change ΔPM will fluctuate depending on the remaining pulsating component, and the amount of fuel may be increased even during steady operation. . On the other hand, if the threshold value for increasing the amount of fuel is increased to solve this problem, the amount of fuel cannot be increased during slow acceleration or the like. In addition, when the engine temperature is relatively low, it is necessary to increase the amount of fuel injection as the intake pipe pressure increases even in the late acceleration period when the change in intake pipe pressure is small. Since the amount of change ΔPM is small, the amount of change ΔPM becomes small and it becomes impossible to increase the amount by the amount of change ΔPM.

If an attempt is made to increase the amount of change ΔPM even in this latter stage of acceleration, complicated control such as making the time constant of the filter variable is required. There is a problem.

For this reason, the present applicant uses a first weighted average value that changes approximately following changes in intake pipe pressure and a second weighted average value that gradually follows changes in intake pipe pressure. ,
We have previously proposed a fuel injection amount control device for an internal combustion engine that can control the air-fuel ratio to the level required by the engine during acceleration (Japanese Patent Application No. 60-295836).

Here, a fuel injection amount control device proposed by the present applicant will be explained. It is assumed that the intake pipe pressure PM changes as shown in FIG. 2, and the first weighted average value and the second weighted average value are expressed by the following general formula.

PML + (K -1)PML -t・ ・ ・
(1) Here, PML is the current intake pipe pressure detected by the pressure detection means, PML-t is the weighted average value of the intake pipe pressure detected in the past, and PM is the currently detected intake pipe pressure. Weighted average value, K is a constant corresponding to the weight.

In the above equation (1), the constant K is made small (for example, 4
), the first weighted average value PM(a) can be detected, and when the constant K is increased (for example, 64), the second weighted average value PM(b) can be detected. First weighted average value P
M(a) approximately follows the intake pipe pressure PM as shown in FIG. Therefore, the amount of increase in the fuel injection amount determined based on the value obtained by subtracting the second weighted average value PM(b) from the first weighted average value PM(a) is As shown in FIG. 2, it reaches a substantially maximum value near the end of the change in the intake pipe pressure PM, and reaches a minimum at the time when the change in the intake pipe pressure PM starts and after a predetermined time has elapsed from the time the change in the intake pipe pressure PM ends. For this reason, the increase in fuel injection amount is gradually increased from the beginning of acceleration to the end of acceleration, and after the end of acceleration, the increase in fuel injection amount is gradually decreased. 6 [Invention [Problems to be Solved] Considering in more detail the amount of fuel supplied to the combustion chamber at the beginning of acceleration by the above-mentioned fuel injection amount control device, it is found that at the beginning of acceleration, the intake pipe pressure is small. The fuel has evaporated and almost no fuel is attached to the inner wall of the intake manifold. Therefore, if the increased amount of fuel is injected in this state as described above,
Most of the injected fuel temporarily adheres to the inner wall of the intake manifold near the start of acceleration, then evaporates and is supplied to the combustion chamber. That is, the above-mentioned fuel injection amount control device has a problem in that near the start of acceleration, the amount of fuel supplied is insufficient by the amount that adheres to the inner wall of the intake manifold, resulting in deterioration of drivability and exhaust emissions.

The present invention has been made to solve the above-mentioned problems.1 The present invention is an internal combustion engine that improves the fuel injection amount control device previously proposed by the applicant so that the fuel supply amount does not become insufficient even near the start of acceleration. The purpose of the present invention is to provide a fuel injection amount control device.

[Means for Solving the Problems] In order to achieve the above object, an uninvented configuration includes a pressure detection means for detecting the intake pipe pressure, and a first weighted average value of the intake pipe pressure detected in the past. a first average value detection means for detecting a current first weighted average value based on a first weighted average value detected in the past of the intake pipe pressure by increasing the weight and the current intake pipe pressure; The weight of the second weighted average value detected in the past of the pipe pressure is heavier than the first average value detection means, and the second weighted average value detected in the past of the intake pipe pressure and the current intake pipe pressure are calculated. and a second average value detection means for detecting a current second weighted average value of the intake pipe pressure from the currently detected first weighted average value of the intake pipe pressure. A calculation means for determining an increase amount of the fuel injection amount based on a deviation obtained by subtracting the average value, and a correction amount for increasing the increase amount at the start of acceleration and then gradually decreasing it to an increase amount determined based on the deviation. The fuel injection device includes a correction amount setting means and a fuel injection means for increasing the fuel injection amount based on the correction amount and the increase amount.

Here, the lower the engine temperature represented by engine cooling water temperature and engine oil salt, etc., the less the amount of fuel evaporation. , set the correction amount so that the speed at which the increase is gradually reduced as the engine temperature decreases, or set the correction amount such that the increase at the start of acceleration becomes large as the engine temperature decreases. It is preferable to set the correction amount so that the speed at which the increase is gradually reduced becomes slower as the engine temperature decreases.

[Operation] According to the present invention, the first weighted average value PM(a) and the second weighted average value PM are calculated based on the above equation (1).
(b) is detected, and the deviation of the weighted average value is calculated by subtracting the current second weighted average value detected from the average value PM(a) for the current first weight detected by the calculation means. The amount of increase in the fuel injection amount is calculated based on this deviation.

On the other hand, the correction amount setting means sets a correction amount that increases the amount of increase in the fuel injection amount at the start of acceleration and then gradually reduces the amount of increase to an amount determined based on the deviation. Then, the fuel injection means increases the fuel injection amount based on the correction amount set by the correction amount setting means and the increase amount of the fuel injection amount calculated by the calculation means. The fuel injection amount is increased by an amount larger than the amount of increase determined by the deviation of the weighted average value, and then this increase amount is reduced to the amount of increase determined by the deviation of the weighted average value. In this way, the amount of increase in the fuel injection amount near the start of acceleration is increased, so even if some of the injected fuel adheres to the inner wall of the intake manifold, the remaining fuel is supplied to the combustion chamber, and the fuel injection amount is increased at the beginning of acceleration. It is possible to accurately supply the fuel required by the engine.

[Effects of the Invention] As explained above, according to the present invention, since the amount of increase in the fuel injection amount is increased near the start of acceleration, there is no shortage of fuel even near the start of acceleration.
The effect is that drivability and exhaust emissions near the start of acceleration can also be improved.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 schematically shows an internal combustion engine equipped with a fuel injection amount control device according to an embodiment of the present invention.

This engine is controlled by an electronic control circuit such as a microcomputer, and a throttle valve 8 is arranged downstream of an air cleaner (not shown). ), and a surge tank 12 is provided downstream of the throttle valve 8. A diaphragm type pressure sensor 6 is attached to this surge tank 12. This pressure sensor 6 has a small time constant for removing pressure pulsation components (for example,
A filter (FIG. 4) composed of a CR filter or the like with good response and 3 to 5 m5 ec) is connected. In addition,
This filter may be built into the pressure sensor, or a bypass passage 14 may be provided to bypass the throttle valve 8 and communicate between the upstream side of the throttle valve and the surge tank 12 on the downstream side of the throttle valve. ing.

An I5C (idle speed control) valve 16B whose opening degree is allfM is attached to this bypass path 14 by a pulse motor 16A having a four-pole stator. The surge tank 12 is communicated with the combustion chamber of the engine 20 via an intake manifold 18 and an intake boat 22. A fuel injection valve 24 is attached to each cylinder or cylinder group so as to protrude into the intake manifold 18.

The combustion chamber of the engine 20 is communicated via an exhaust bow 26'R and an exhaust manifold 28 to a catalyst device (not shown) filled with a three-way catalyst. An 02 sensor 30 is attached to the exhaust manifold 28 and outputs a signal that is inverted from the stoichiometric air-fuel ratio. A cooling water temperature sensor 34 is attached to the engine block 32 so as to penetrate through the engine block 32 and protrude into the water jacket. This cooling water temperature sensor 34
detects the engine cooling water temperature and outputs a water temperature signal, which represents the engine temperature. Note that the engine oil temperature may be detected to represent the engine temperature.

A spark plug 38 is attached to each cylinder so as to penetrate the cylinder head 36 of the engine 20 and protrude into the combustion chamber. The spark plug 38 is connected via a distributor 40 and an igniter 42 to an electronic control circuit 44 composed of a microcomputer or the like.

Inside the distributor 40, a cylinder discrimination sensor 46 and a rotation angle sensor 48 are installed, each of which is composed of a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing. In the case of a six-cylinder engine, the cylinder discrimination sensor 46 outputs a cylinder discrimination signal, for example, every 720'CA, and the rotation angle sensor 48 outputs an engine rotation speed signal, for example, every 30'CA.

As shown in FIG. 4, the electronic control circuit 44 is connected to the central processing bag W.
1 (MPU) 60, read-only memory (ROM)
) 62 , random access memory (RAM) 64
, backup RAM (BU-RAM) 66, input/output capotro 8. Input port door 0, output port) 72, 74.7
6 and a data bus and control bus stop 8 that connect these. An analog-digital (A/D) converter 78 and a multiplexer 80 are connected in sequence to the input/output capotro 8. The pressure sensor 6 is connected to the multiplexer 80 via a filter 7 and a buffer 82 which are composed of a resistor R and a capacitor C, and the cooling water temperature sensor 34 is also connected via a buffer 84 . The MPU 60 controls the multiplexer 80 and the (A/D) converter 78 to sequentially convert the output of the pressure sensor 6 and the output of the water temperature sensor +34 inputted via the filter 7 into digital signals and store them in the RAM 64.
to be memorized. Therefore, multiplexer 84. (A/D
) The converter, the MPU 60, etc. act as sampling means for sampling the pressure sensor output at predetermined time intervals. The O2 sensor 30 is connected to the input port door 0 via a comparator 88 and a buffer 86, and the cylinder discrimination sensor 46 and the rotation angle sensor 48 are also connected via a waveform shaping circuit 90. Also, the idle switch 10 is connected to the input port door 0. There is. The output port door 2 is connected to the igniter 42 via a drive circuit 92, the output port door 4 is connected to the fuel injection valve 24 via a drive circuit 94, and the output port door 6 is connected to the pulse motor of the ISO valve via a drive circuit 96. -6A is connected. Note that 98 is a clock and 99 is a timer. The ROM 62 stores in advance a control routine program, etc., which will be explained below.

Next, a control routine will be described in which the present invention is applied to the above engine and a weighted average value is detected by calculation. In addition, although the following description uses numerical values that do not hinder the present invention, the present invention is not limited to these numerical values.

FIG. 5 shows a part of the main routine. In step 102, for example, the current intake pipe pressure P M L is inputted via a full tough signal that is A/D converted and stored in the RAM at predetermined time intervals. , take in the first weighted average value PM(a) L-t and the second weighted average value PM(b) c-t which were previously calculated and stored in the RAM;
In step 104 and step 106, the first weighted average values PM(a)L and PM
(b) Calculate L, and replace PM (a) t, , PM (b) L calculated in step 108 with the previous weighted average values PM (a) L t, PM (b) Le, and store them in RAM. to be memorized.

PML +3PM (a) L t PM (a) L = □ ... (2) PML + 63 PM (b) L t PM (b) L = □ ... (3) Figure 6 shows the output of the rotation angle sensor 48. is generated (
For example, it shows an interrupt routine executed by an interrupt signal (generated every revolution of the engine). In step 114, the current intake pipe pressure PML, engine speed NE, and weighted average value PM(a) L, PM(b) L stored in the RAM are loaded, and in step 112, the intake pipe pressure PM& and engine speed are read. Basic fuel injection amount TP based on NE as before
Calculate. In the next step 114, from the first weighted average value PM (a) L to the second weighted average value PM
(b) Calculate the fuel injection amount increase/decrease coefficient FTCPM based on the deviation ΔPM obtained by subtracting L. Then, in the next step 116, the fuel injection amount TAU is calculated according to the following equation.

TAU=TP・(1+FTCPM)・FAF・・
(4) Note that FAF is an air-fuel ratio feedback correction coefficient for controlling the air-fuel ratio to the stoichiometric air-fuel ratio based on the O2 sensor output.

Next, the routine for calculating the increase/decrease coefficient FTCPM in step 114 will be explained in detail with reference to FIG. First, in step 120, the current second weighted average value PM(b)L is subtracted from the current first weighted average value PM(a)4 to calculate the deviation ΔPM of the weighted average value. This deviation ΔPM takes a positive value during acceleration,
In step 122, which is a zeroth order which takes a negative value during deceleration, a water temperature correction coefficient KTC (≧1) corresponding to the current cooling water temperature is calculated from the map shown in FIG. 7 by interpolation. Then, in step 124, the increase/decrease coefficient FT is calculated based on the following formula.
Calculate CPM.

FTCPM4-A・ΔPM-KTC (5) where A is a positive constant.

In step 126, it is determined whether the increase/decrease coefficient FTCPM is O or not. When the increase/decrease coefficient FTCPM is O, that is, when the deviation ΔPM is O, it is determined that the operating state is steady, and the correction amount B is set to O in step 128. Return later.

On the other hand, when it is determined in step 126 that the increase/decrease coefficient FTCPM is not O, that is, when the deviation ΔPM≠O, it is determined that acceleration or deceleration is occurring, and it is determined in step 130 whether or not the correction amount B is O. When the correction amount B is 0, that is, at the start of acceleration or deceleration, the initial value corresponding to the current engine cooling water temperature is calculated from the map shown in Table 1 below by interpolation, and this initial value is used as the correction amount B. be the value of

Table 1 As understood from Table 1, the initial value of the correction amount B increases as the engine cooling water temperature decreases.

In the next step 134, the increase/decrease coefficient FTCPM calculated in step 124 is multiplied by the correction amount B to obtain the increase/decrease coefficient FTCPM.
Correct TCPM.

On the other hand, when it is determined in step 130 that the correction amount B is not 0, that is, after setting the correction amount B to a value other than O, in step 136 the current engine cooling water temperature is determined from the map shown in Table 2 below. A corresponding attenuation value C is calculated by interpolation.

Table 2 Then, in step 138, the attenuation value C is subtracted from the correction amount B to attenuate the correction amount B, and in step 140, the correction M H
It is determined whether the value of has become less than 1 (the minimum value of the correction amount B), and if the value of the correction amount B is less than 1, the value of the correction amount B is set to 1 in step 142 and the process proceeds to step 134. ,
If it is determined in step 140 that the value of correction iB is 1 or more, the process directly advances to step 134.

As can be understood from Table 2, the damping value C decreases as the engine cooling water temperature decreases, and therefore the attenuation speed of the correction amount B becomes slower as the engine cooling water temperature decreases.

(4) above using the increase/decrease coefficient calculated as above.
After calculating 1 TAU of fuel injection based on the formula, fuel injection is performed by controlling the drive circuit 94 according to a fuel injection routine (not shown) to open the fuel injection valve for a time corresponding to the fuel injection amount TAU.

As explained above, the correction value B is set to a large value at the start of acceleration and is then gradually attenuated to l, so the increase/decrease coefficient FTCPM during acceleration is around the time at the start of acceleration, as shown by the broken line in Figure 2. becomes a large value. Therefore, even if the injected fuel adheres to the inner wall of the intake manifold, the air-fuel ratio can be controlled to the engine-required value.

On the other hand, near the start of deceleration, the increase/decrease coefficient FTCP
M becomes a large negative value, and the fuel injection amount is significantly reduced. This prevents the air-fuel ratio from becoming overrich due to evaporation of the fuel near the inner wall of the intake manifold at the start of deceleration.

In the above, an example was explained in which the increase/decrease coefficient is corrected by multiplication using a value of 1 or more as the correction value B, but as shown in Table 3, the increase/decrease coefficient is corrected by division using a value of 1 or less as the correction value B. The coefficients may be corrected.

Table 3 Note that in this case, the attenuation value is added to the correction value B and the attenuation value is gradually attenuated until it becomes 1.

In addition, although the example in which the initial value of the correction amount and the damping speed are changed according to the engine cooling water temperature has been described above, the initial value may be kept constant and the damping speed may be changed according to the engine cooling water temperature. The value may be changed depending on the engine cooling water temperature to make the damping speed constant, or the initial value and the damping speed may be made constant.

In addition, although the example in which the weighted average value is detected by calculation has been described above, the first and second weighted average values may be detected using two filters with different time constants. Furthermore, the filter output may be used as it is as the first weighted average value.

[Brief explanation of the drawing]

Fig. 1 is a flowchart of a routine for calculating FTCPM in an embodiment of the present invention, Fig. 2 is a diagram showing changes in weighted average values during acceleration, etc., and Fig. 3 is applicable to the embodiment of the present invention. A schematic diagram of the engine, FIG. 4 is a block diagram of the control circuit of FIG. 3, and FIG. 5 is a flowchart showing the main routine of the above embodiment.
FIG. 6 is a flowchart showing the fuel injection amount calculation routine of the above embodiment, and FIG. 7 is a diagram showing a KTC map. 6... Pressure sensor, No. 24 fuel injection valve, 34... Water temperature sensor. Figure 1 Figure 2 (FTCPMI Figure 5 Figure 6 Figure 7 Oiromizu: J (@C)

Claims (3)

[Claims] (1) A pressure detection means for detecting intake pipe pressure, and a first weighted average value of intake pipe pressure detected in the past by increasing the weight of the first weighted average value detected in the past of intake pipe pressure. a first average value detection means for detecting a current first weighted average value of the intake pipe pressure and the current intake pipe pressure; The current second weighted average value detected in the past of the intake pipe pressure and the current intake pipe pressure are
a second average value detection means for detecting a weighted average value of;
a calculation means for determining an increase amount of the fuel injection amount based on a deviation obtained by subtracting a currently detected second weighted average value of the intake pipe pressure from a currently detected first weighted average value of the intake pipe pressure; and an acceleration start. a correction amount setting means for setting a correction amount for increasing the increase amount and then gradually decreasing it to an increase amount determined based on the deviation; and increasing the fuel injection amount based on the correction amount and the increase amount. fuel injection means;
A fuel injection amount control device for an internal combustion engine. (2) The fuel injection amount control device for an internal combustion engine according to claim (1), wherein the correction amount is set so that the amount of increase at the start of acceleration increases as the engine temperature decreases. (3) Claims (1) or (2), wherein the correction amount is set so that the speed at which it is gradually decreased to the increase amount determined based on the deviation becomes slower as the engine temperature becomes lower. The fuel injection amount control device for the internal combustion engine described above.