JPS62153536A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the exhaust emission by smoothing the air fuel ratio in transition by making the fundamental fuel injection itself close to the engine demand value by taking into consideration of the adhesion of fuel due to the variation of the suction pipe pressure and the engine temperature. CONSTITUTION:The weighted average value of the intake pipe pressure at present is calculated from the intake pipe pressure at present and the weighted average value of the intake pipe pressure which is detected in the past, by the detection signal of a pressure sensor 6, in an electronic control circuit 44. The fundamental intake pipe pressure which is corrected according to the engine temperature by the detection signal of a water temperature sensor 34 is determined by adding the first weighted average value to the value which is obtained by subtracting the second weighted average value in which the constant corresponding to the weight is increased, from the first weighted average value in which the constant corresponding to the weight is decreased. Then, the fundamental fuel injection is determined from the fundamental suction pipe pressure and the engine speed. Then, the fuel injection corresponding to the engine demand value is obtained.

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 in particular, the basic fuel injection amount is determined based on intake pipe pressure (absolute pressure) and engine speed. The present invention relates to a fuel injection amount control device for an internal combustion engine that changes the twist 1 injection amount itself to increase or decrease during a transient period.

[Prior Art] Conventionally, fuel injection amount control has been performed in which a basic fuel injection amount is determined based on intake pipe pressure PM and engine speed NE, and fuel is injected by correcting the basic fuel injection amount based on intake air temperature, engine cooling water temperature, etc. The device is known. In order to improve acceleration response during acceleration, such a fuel injection amount control device detects the amount of change in PM and injects fuel in an amount proportional to this amount of change either synchronously with the crank angle or asynchronously with the crank angle. The amount is being increased (Japanese Unexamined Patent Application Publication No. 60-35154).

[Problem to be solved] In the above-mentioned acceleration increase based on the temporal change amount ΔPM of the intake pipe pressure, a relatively constant time constant is required to remove the minimum pulsating component of the intake pipe pressure in order to improve engine control responsiveness. The pressure signal may be input to the control circuit through a small (for example, 3 to 51 sec) filter. In this case, since the pulsating component cannot be completely removed by the filter, the amount of change ΔPM
fluctuates depending on the remaining pulsation component, and even in a steady state of operation, the amount of fuel may be increased excessively. 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 smaller, and I due to the amount of change ΔPM
The amount of W cannot be achieved. Even in this latter stage of acceleration, the amount of change Δ
If an attempt is made to increase the amount by PM, there is a problem in that complicated control such as making the time constant of the filter variable is required.

In addition, the present inventors conducted research on fuel injection during transient times and found that it is better to match the basic fuel injection amount to the engine's required injection amount than to increase the fuel injection amount by acceleration increase or asynchronous injection. Since the fuel injection amount is corrected over the entire range of operating conditions, it has been found that this method is very effective for smoothing the air-fuel ratio during sudden transients and reducing exhaust emissions.

The present invention was made based on the above findings in order to solve the above problems, and an object of the present invention is to provide a fuel injection amount control device for an internal combustion engine that has better acceleration performance than the conventional one.

[Means for Solving the Problems] ] In order to achieve the two-pronged object, the present invention includes a rotation speed detection means for detecting the engine rotation speed, a pressure detection means for detecting the intake pipe pressure, and a pressure detection means for detecting the intake pipe pressure. The weight of the first weighted average value detected in the past is increased, and the first weighted average value detected in the past of the intake pipe pressure and the current intake pipe pressure are
I7) II! A first average value detection means for detecting the average value, and a second weighted average value detected in the past of the intake pipe pressure is weighted more heavily than the first average value detection means to detect the intake pipe pressure. a second average value detection means for detecting a current second weighted average value using a second weighted average value detected in the past and a current intake pipe pressure; The currently detected second weighted average value of the intake pipe pressure is subtracted from the weighted average value of 1 to determine the difference, and the difference and the first weighted average value are added to determine the basic intake pipe pressure. The basic intake pipe pressure calculation means calculates the basic intake pipe pressure, and the basic fuel injection amount calculation means calculates the basic fuel injection amount based on the engine speed and the basic intake pipe pressure.

Here, in the present invention, if a sudden acceleration is performed immediately after a sudden deceleration such as a gear change, the second weighted average value P M (b
), as shown in Figure 2, the basic intake pipe pressure PM undershoots the intake pipe pressure PM for a while after acceleration starts, and the basic fuel injection iTP is calculated to be small. , there is a risk that lean spikes may occur at the beginning of acceleration during rapid transients. Therefore, in the present invention, the basic intake pipe pressure calculation means converts the value of the second weighted average value P M (b) into the first weighted average value P at the change point of acceleration/deceleration.
The weighted average value PM(b) with poor responsiveness is calculated from the weighted average value PM(a) with good responsiveness by doing as follows, which is preferably the value of M(a). This prevents unduplication of the basic intake pipe pressure at the beginning of acceleration when transitioning from deceleration to acceleration and overshoot at the beginning of deceleration of the basic intake pipe pressure when transitioning from acceleration to deceleration, and prevents basic fuel injection even during sudden transients. It is possible to achieve smoothing of the air-fuel ratio by bringing the amount close to the value required by the engine, and also to reduce exhaust emissions during sudden transients.

In addition, when performing sudden acceleration as described above, the basic intake pipe pressure immediately after acceleration ends overshoots the intake pipe pressure, but if the amount of overshoot of this basic intake pipe pressure becomes excessive, acceleration becomes rich. Exhaust emissions may deteriorate.

Therefore, in the present invention, it is preferable that the difference be made smaller during acceleration than in normal operating conditions.

Furthermore, the amount of fuel that adheres to the inner wall of the intake manifold decreases as the engine temperature increases due to engine water temperature, engine oil salt, etc., as the amount of evaporation increases. When changing the value or the magnitude of the difference, it is preferable to change the difference so that it becomes smaller as the engine temperature becomes higher.

FIG. 3, which corresponds to the embodiment, shows changes in the basic intake pipe pressure when the weighted average value and constant are changed as described above.

[Operation] The operation of the present invention will be explained with reference to FIG. It is assumed that the intake pipe pressure PM changes as shown in FIG. 1, and the first weighted average value and the second weighted average value are expressed by the following general formula.

PMi, + (K-1)PML-(PML=□... (1) Here, PML is the current intake pipe pressure detected by the pressure detection means, and PMLt is the intake pipe pressure detected in the past. The weighted average value, P M t, is the current weighted average value of the intake pipe pressure, and 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. The first weighted average value PM (a) approximately follows the intake pipe pressure PM as shown in FIG. 1, but the second weighted average value PM (b
) has worse followability than the first weighted average value PM(a). Therefore, the basic value determined by adding the first weighted average value PM(a) to the value obtained by subtracting the second weighted average value PM(b) from the first weighted average value PM(a). As shown in FIG. 1, the intake pipe pressure PM reaches a substantially maximum value near the end of the change in the intake pipe pressure PM, and reaches a minimum after a predetermined period of time has elapsed from the start and end of the change. Therefore, the basic intake pipe pressure PM gradually increases from the beginning of acceleration to the end of acceleration, and after the end of acceleration, the basic intake pipe pressure PM gradually decreases. Therefore, the basic fuel injection amount determined by the basic intake pipe pressure PM and the engine speed corresponds to the engine required value.

[Effects of the Invention] As explained above, according to the present invention, since the basic fuel injection amount itself is brought close to the engine required value, smoothing of the air-fuel ratio during transient times becomes possible, and exhaust emissions during transient times are reduced. This has the effect of being able to reduce the

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

Note that in the following embodiments, an example will be described in which a weighted average value is detected by calculation. FIG. 4 schematically shows an internal combustion engine equipped with a fuel injection 1 external control device according to each embodiment of the present invention.

This engine is controlled by a '1L child control circuit such as a microcomputer, and is controlled by an air cleaner (
A throttle valve 8 is arranged on the lower housing side (not shown),
An idle switch lO is attached to this throttle valve 8, which turns on when the throttle valve is fully closed (idle position).
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 built-in filter such as an RC filter with a small time constant (for example, 3 to 5 m5ec) and good responsiveness for removing pressure pulsation components.

Note that this filter may be provided between the pressure sensor and the control circuit described below, or may be provided so as to bypass the throttle valve 8 and communicate the upstream side of the throttle valve with the surge tank 12 on the upstream side of the throttle valve. A bypass path 14 is provided. An idle speed control (ISO) valve 16B whose opening degree is adjusted by a pulse motor 16A having a four-pole stator is attached to this bypass path 14. The surge tank 12 is connected to the engine 20 via an intake manifold 18 and an intake port 22.
It communicates with the combustion chamber. 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 port 26 and an exhaust manifold 28 to a catalyst device ff1 (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 3
4 detects the engine cooling water temperature and outputs a water temperature signal.

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 7200 CA, and the rotation angle sensor 48 outputs an engine rotation speed signal, for example, every 30' CA.

As shown in FIG. 5, the electronic control circuit 44 includes a central processing unit (MPU) 60 and a read-only memory (ROM).
62, random access φ memory (RAM) 64.
Backup RAM (BU-RAM) 66, input/output capotro 8. It is configured to include an input port (0° output port) 72, 74, and 76, and a bus 78 such as a data bus or a control bus that connects these. Input/Output Capotro 8
for.

Analog-to-digital (A/D) converter 78. The pressure sensor 6 and the cooling water temperature sensor 34 are connected via a multiplexer 80 and buffers 82 and 84. MPU6
0 is multiplexer 80 and (A/D) converter 78
, the output of the pressure sensor 6 and the output of the water temperature sensor 34 are sequentially converted into digital signals and stored in the RAM 64.

Therefore, multiplexer 84. The (A/D) converter, the MPU 60, and the like act as sampling means that samples the pressure sensor output at predetermined time intervals. 02 sensor is connected to the input port door 0 via a comparator 88 and a buffer 86, and a waveform shaping circuit 90 is also connected to the input port door 0.
A cylinder discrimination sensor 46 and a rotation angle sensor 48 are connected thereto, and an idle switch IO is also connected thereto.

The output port door 2 is connected to the igniter 42 via the 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 ISO valve pulse motor 16A via a drive circuit 96.
It is connected to the. In addition.

98 is a clock, and ioo is a timer. Above ROM6
2 stores in advance a control routine program, etc., which will be explained below.

Next, the processing routine of this embodiment will be explained.

FIG. 8 shows a weighted average value calculation routine executed by an interrupt every time A/D conversion is completed.

In step 114, this time it is converted into ^/D and stored in the RAM.
The intake pipe pressure PMi stored in , and the weighted average value P M (a
) L t * PM (b) Taking L-1, the weighted average value PM (a) L , PM (b)
L The intake pipe pressure PM(a)L is calculated based on the following formula and has good responsiveness to changes in intake pipe pressure.
The amount of change ΔPM(a) is calculated.

P M (a) L =□...(2) PML+83P
M(b)&s PM(b) L=□...(3) ΔPM(a)=PM(a)r, -PM(a) L-t・
...(4) In the next step 116, the contents of register XN are loaded into register xO, and in step 118, the amount of change ΔPM(a)
Determine whether or not is greater than or equal to 0. When the amount of change ΔPM(a) is 0 or more, that is, when the intake pipe pressure is constant or increasing, the amount of change ΔPM(a) and the reference value PMACC for determining whether or not the acceleration state is in step 120 are determined. Compare. Then, when ΔPM(a)>PMACC, the contents of register XN are set to 1 in step 122, and ΔPM(a)>PMACC is satisfied.
When P M (a)≦PMACC, the contents of register XN are set to O in step 124. As a result, when the acceleration is above a predetermined value, the contents of register XN are set to 1.

When the amount of change ΔP M (a) is determined to be less than 0 in step 118, that is, when the intake pipe pressure decreases,
In step 126, the amount of change ΔPM(a) is compared with a reference value PMDEC for determining whether or not the vehicle is in a deceleration state. Then, when ΔPM(a)<PMDEC, step 12
8, set the contents of register XN to -l, and set ΔP M
(a) When ≧PMDEC, the contents of register XN are set to O in step 124. As a result, when the deceleration exceeds a predetermined value, the contents of register XN are set to -1.

Next, in step 130, it is determined whether the deceleration state has changed to the acceleration state by determining whether the contents of the register xO are -1 and the contents of the register XN are 1. When it is determined that the deceleration state has changed to the acceleration state, in step 134, the weighted average value PM(a)L, which is responsive to changes in intake pipe pressure, is set to Weighted average value PM(b) with poor responsiveness
Set as the value of L. On the other hand, when the determination in step 130 is negative, in step 132 it is determined whether the contents of register xO are 1 and the contents of register XN are -1, thereby determining whether the acceleration state has changed to the deceleration state. to decide. When it is determined that the acceleration state has changed to the deceleration state, the weighted average values PM(a) and L are changed to the weighted average value PM(b) in step 134 in the same manner as described above.
Set as the value of L.

As a result of the above, at the change point of acceleration/deceleration, the weighted average value PM
(a) The values of L and weighted average value PM (b) L are made the same, and 1. Weighted average value PM (b) L is calculated from the value of weighted average value PM (a) L with good responsiveness. will be resumed.

Figure 6 shows the fuel injection amount calculation routine.
In step 101, it is determined whether the register XN is in an acceleration state by determining whether the contents are 1 or not. If the contents of the register Let the intake pipe pressure PM & be the basic intake pipe pressure PMτ. Step 101
When it is determined that the vehicle is in an accelerated state, a constant A is calculated in step 102. That is, as shown in step 110 of the subroutine in FIG. 7, the current engine cooling water temperature THW that has been A/D converted and stored in the RAM is fetched, and in step 112, the map shown in FIG. 9 is searched and engine cooling is performed. A constant A corresponding to the water temperature Tl(W) is calculated by interpolation. This constant A is set to decrease as the engine cooling water temperature increases.

Then, in the first step 104, the value of the constant A is set to 112, and in step 106, the basic intake pipe pressure PMτ is calculated based on the following equation.

PM = PM (a) L + A life (PM (a) L - PM (b) t, ) ...-
(5) In the next step 108, the current engine rotation aNE stored in the RAM is taken in, and basic fuel injection is performed as before based on the basic intake pipe pressure PM calculated as above and the engine rotation 11NE. Calculate the quantity TP. After that, the fuel injection amount TAU is obtained by adding the increase/decrease in the fuel injection amount and limiting the upper and lower limits of the fuel injection amount.
Inject fuel in an amount equivalent to AU.

As a result of controlling as described above, the weighted average value P M (
a) , P M (b) and basic intake pipe pressure P
M changes as shown in Figure 3.

As mentioned above, the weighted average value PM(a
) and the weighted average value P M (b) are made equal, so the weighted average value P M (b) with poor responsiveness is calculated from the weighted average value PM (a) with good responsiveness. This prevents the 7-d shoot at the beginning of the acceleration of the basic intake pipe pressure when transitioning from deceleration to acceleration, and the 0-8 shoot at the beginning of the deceleration of the basic intake pipe pressure when transitioning from acceleration to deceleration, and even during sudden transitions, the basic intake pipe pressure It is possible to achieve a smooth air-fuel ratio by bringing the fuel injection amount close to the value required by the engine, and to reduce exhaust emissions during sudden transients.

In addition, since the constant A during acceleration is smaller than that under steady running conditions, it is possible to prevent the air-fuel ratio from becoming rich during acceleration due to excessive overshoot of the basic intake pipe pressure during acceleration. Exhaust emissions can be reduced. Furthermore, since the constant A is changed according to the engine cooling water temperature, when the engine power level is low, the fuel injection amount increases, and when considering the amount of fuel applied to the intake manifold, the engine temperature changes. Also, the amount of fuel supplied to the engine can be made approximately equal to the engine required value over the entire operating range.

Note that the intake pipe pressure may be calculated only during acceleration/deceleration, and the basic fuel injection amount may be determined based on the basic intake pipe pressure only during acceleration/deceleration to control the fuel injection amount. In addition, although the example in which the first and second weighted average values are detected by calculation has been described above, the first and second weighted average values are detected using two RC filters with different time constants. It may also be detected.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention in detail. Fig. 2 is a diagram for explaining the case where the basic intake pipe pressure of the present invention is asodashooting, etc., Fig. 3 is a diagram showing the case when the weighted average value is changed, etc., and Fig. 4 is a diagram for explaining the case where the basic intake pipe pressure of the present invention is asoda shoot. A schematic diagram of an engine equipped with a fuel injection amount control device according to an embodiment, FIG. 5 is a block diagram showing details of the control circuit of FIG. 4, and FIGS. 6 to 8 show processing routines of the above embodiment. The flowchart, FIG. 9, is a diagram showing a map of constant A. 6...Pressure sensor. 24...Fuel injection valve, 34...Water temperature sensor.

Claims (4)

[Claims] (1) A rotation speed detection means for detecting the engine rotation speed, a pressure detection means for detecting the intake pipe pressure, and a first weighted average value detected in the past of the intake pipe pressure is increased to increase the weight of the intake pipe pressure. A first method for detecting a current first weighted average value using the first weighted average value detected in the past and the current intake pipe pressure.
means for detecting the average value of the intake pipe pressure, and a second
A weighted average value of the weighted average value is weighted more heavily than the first average value detection means, and a second weighted average value detected in the past of the intake pipe pressure and the current intake pipe pressure are combined to obtain a current second weighted value. a second average value detection means for detecting an average value; and a second average value detection means for detecting an average value; basic intake pipe pressure calculating means for calculating basic intake pipe pressure by calculating the basic intake pipe pressure by calculating the difference and the first weighted average value; basic fuel injection amount calculation means for calculating the injection amount;
A fuel injection amount control device for an internal combustion engine. (2) The basic intake pipe pressure calculation means sets the second weighted average value to the first weighted average value at a change point of acceleration/deceleration. The fuel injection amount control device for the internal combustion engine described above. (3) The basic intake pipe pressure calculation means controls the fuel injection amount of the internal combustion engine according to claim (1) or (2), which makes the difference smaller during acceleration than in the normal operating state. Device. (4) The fuel injection amount control for an internal combustion engine according to claim 2 or 3, wherein the basic intake pipe pressure calculation means corrects the difference so that it becomes smaller as the engine temperature increases. Device.