JPH01163438A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform optimum control responding to opening and closing of a suction control valve, by a method wherein, in the feed of fuel, the magnitude of the correction factor of correction of fuel loading is varied by opening and closing of a suction control valve. CONSTITUTION:In a transient operation state, e.g. acceleration and deceleration running of an engine, the opening and closing state of a suction control valve is discriminated by an SCV state discriminating means, and the magnitude of a correction factor by a correction factor calculating means 2 is varied by opening and closing of a suction control valve 32. Correction of a fuel feed amount under the transient state of an engine responds to the state of the suction control valve to perform optimum control, resulting in prevention of disturbance of an air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device for an engine equipped with an intake control valve, that is, a throttle valve downstream of a throttle valve and upstream of an intake valve for controlling intake air.

[Prior Art] In an internal combustion engine, the air-fuel ratio is basically controlled to the stoichiometric air-fuel ratio. Therefore, for example, in an electronically controlled fuel injection type internal combustion engine, the basic fuel injection amount to bring the air-fuel ratio to the stoichiometric air-fuel ratio is controlled by the rotational speed. It is calculated using the intake pipe pressure as a load factor. In order to prevent the air-fuel ratio from becoming rough during transient operation such as during acceleration operation, it is common to add an increase or decrease correction to the basic fuel injection amount. On the other hand, an internal combustion engine that uses an intake control valve is known as an internal combustion engine that enables combustion with an air-fuel mixture whose air-fuel ratio is extremely leaner than the stoichiometric air-fuel ratio. For example, see Japanese Patent Application Laid-Open No. 60-62640. In such a lean-burn internal combustion engine, the amount of intake air changes depending on the opening and closing of the intake control valve even if the intake pipe pressure remains the same. Therefore, the optimal value of the fuel increase correction factor (correction coefficient and correction amount for correcting the basic fuel injection amount) to prevent the air-fuel ratio from becoming rough during transient periods changes depending on whether the intake control valve is open or closed. It should be. However, in the conventional technology, the same increase correction factor was used regardless of whether the intake control valve was open or closed as long as the acceleration/deceleration state was the same. For example, a roughness occurs in the air-fuel ratio when the intake control valve is opened, and conversely, if the optimum value is set when the intake control valve is opened, a roughness occurs in the air-fuel ratio when the intake control valve is closed.

An object of this invention is to prevent the air-fuel ratio from becoming rough during transient operation, regardless of whether the intake control valve is open or closed.

[Means for Solving the Problems] In FIG. 1, the air-fuel ratio control device for a lean-burn internal combustion engine of the present invention includes an intake control valve 3 driven by intake pipe negative pressure.
2, a fuel supply means 26, a fuel supply amount calculation means 1 that calculates the amount of fuel introduced into the engine from the fuel supply means 26 according to the intake pipe pressure, and whether the intake control valve 32 is in an open state or a closed state. The intake control valve state determining means 2 determines whether the intake control valve 32 is open or closed, and the fuel supply amount calculating means 1 determines the fuel supply amount according to the result of the determination by the intake control valve state determining means 2 as to whether the intake control valve 32 is open or closed. [Embodiment] Consisting of a correction factor calculation means 2 that makes the correction factor used in calculation variable in size [Embodiment] In FIG. 2, 10 is a cylinder block, and 12 is a cylinder bore. 12a and 12b are intake boats, 14a
, 14b are exhaust ports, and each boat has a so-called 4-valve configuration in which intake valves 16a, 16b and exhaust valves 18a, 18b are provided. The first intake boat 12a is of a so-called helical type, and is configured to have a shape convenient for forming an intake swirl. Second intake boat 12
b is a straight type. The intake boats 12a and 12b are connected to a throttle body 23 via an intake pipe 20 and a surge tank 22. A throttle valve 24 is installed within the throttle body 23. A fuel injector 26 is installed in the intake pipe 20 adjacent to the intake bows 12a and 12b of each cylinder.
The exhaust boats 14a and 14b are connected to the exhaust manifold 28. Note that 30 is a distributor.

An intake control valve 32 as a butterfly valve is provided on the straight intake boat 12b. When the intake control valve 32 is in the closed state, intake air is introduced only from the helical intake boat 12a, a swirl S is formed in the cylinder bore 12, and combustion of an ultra-lean mixture is achieved. When the intake control valve 32 is opened, air is introduced from both intake control valves 12a and 12b, and the swirl is eliminated. A lever 34 is attached to the valve shaft of the intake control valve 32 of each cylinder, and is connected to a negative pressure actuator 38 via a rond 36. The negative pressure actuator 38 is composed of a diaphragm 40 and a spring 41. When no negative pressure is applied to the diaphragm 40, the diaphragm 40 is pushed downward in the figure by the action of the spring 41, and the intake control valve 32 is placed in the open position. When negative pressure is applied to the diaphragm 40, the diaphragm 40 is pulled against the spring 41, and the intake control valve 32 assumes a position that closes the intake boat 12b.

The diaphragm 40 includes a negative pressure delay valve 42 and an electromagnetic three-way valve 44.
, and the surge tank 2 via the negative pressure maintenance check valve 46.
It is connected to No. 2 negative pressure extraction boat 22a. Negative pressure delay valve 4
2 is configured by arranging an orifice 42a and a check valve 42b in parallel, and the rate at which atmospheric pressure is introduced into the diaphragm 40,
That is, the opening speed of the intake control valve 32 is controlled to an appropriate value. On the other hand, the check valve 46 maintains the negative pressure applied to the diaphragm 40. Solenoid valve 44
is equipped with three boats 44a, 44b, and 44c, and when electricity is removed, the boats 44a and 44b are communicated, and the diaphragm 40 is communicated with the negative pressure boat 22a, and when electricity is applied, the boats 44a and 44c are communicated. , the diaphragm 40 is in communication with the atmosphere (filter 48). The solenoid valve 44 is driven by the control circuit 50 and controls the operation of the intake control valve 32.

The control circuit 50 is configured as a microcomputer system, for example, and controls the injector 26 and the solenoid valve 44 according to the present invention. The intake pipe pressure sensor 52 is installed in the surge tank 22 and measures the intake pipe pressure PM.
Generates a signal according to the Crank angle sensor 54,5
6 is provided in the distributor 30, the first crank angle sensor 54 is for detecting the reference position and generates a signal every 720 degrees of the engine crankshaft, and the second crank angle sensor 56 is for detecting the crank angle. For example, it generates a signal every 30 degrees and is useful for knowing the engine speed NE. Water temperature sensor 57 generates a signal according to engine cooling water temperature TIIH. Further, an air-fuel ratio sensor 58 such as a so-called lean sensor is provided in the exhaust manifold 28, and a signal corresponding to the air-fuel ratio Ox is obtained.

59 is a throttle valve wide opening switch (■L switch), which is turned ON when the throttle valve 24 is depressed to an opening corresponding to the full load, and is normally OFF. The control circuit 50 executes necessary arithmetic processing based on the signals from these sensors, and controls the driving of the injector and the solenoid valve.

The operation of the control circuit 50 will be explained below using a flowchart. FIG. 3 shows a routine for driving the intake control valve (SCV) 32. This routine may be located within the main routine. In step 70, the opening/closing conditions for the intake control valve 32 are determined. Intake control valve 32
As is well known, the valve is closed when the engine is under partial load and at low speed, and at this time the air-fuel ratio is controlled to the lean side. When the engine is under high load or at high speed, the intake control valve is opened.
At this time, the air-fuel ratio is controlled to be richer than when the intake control valve 32 is closed. The details of the opening/closing range of the intake control valve 32 are not directly related to this invention, so a description thereof will be omitted.

In step 72, it is determined whether the operating range of the intake control valve determined in step 70 is in the closed region. If the intake control valve is in the closed region, the process proceeds to step 74, and YSCV=1.
is set. Here, YSCV is a flag indicating whether the intake control valve 32 is closed (1) or open (0). In step 76, a signal to turn off the solenoid valve 44 is output. Therefore, the solenoid valve 44 assumes the black port position, and the negative pressure of the negative pressure port 22a of the surge tank 22 is applied to the check valve 46. Negative pressure is applied to the diaphragm 40 through the check valve 42b of the delay valve 42, the diaphragm 40 is attracted against the spring 42, and the intake control valve 32 is closed. Note that once the negative pressure that closes the intake control valve 32 is generated, this negative pressure is maintained by the function of the check valve 46, and the intake control valve 32 is closed even if the negative pressure in the port 22a is not sufficient to close the valve. Valve can be retained.

If it is in the open region of the intake control valve 32, step 7
2, proceed from step 72 to step 78, and YSCV
= 0, and a signal to turn off the solenoid valve 44 is output. Therefore, the solenoid valve 44 assumes the white port position, atmospheric pressure is applied from the air filter 48 to the diaphragm 40 through the orifice 42a of the negative pressure delay valve, the diaphragm 40 is lowered by the spring 42, and the intake control valve 32 is opened. The orifice 42a appropriately regulates the opening speed of the intake control valve 32.

FIG. 4 shows a fuel injection routine, and this routine is started when the crank angle sensors 54 and 56 detect a point slightly before the fuel injection timing for each cylinder at the crank angle. That is, in a four-cylinder internal combustion engine, the process is performed every 180 degrees in terms of crank angle. In step 90, every very short interval (e.g. l -2slsec)
From the current value PM of the intake pipe pressure measured by the pressure sensor 52 which is D-converted (i.e. 180 degrees in crank angle)
intake pipe pressure measurement value PMOO difference DLP measured before
M.

That is, a transient pressure change is calculated. Note that the measured value PM of the pressure sensor 52 is blunted by a filter circuit (not shown) or software processing. In step 92, the engine water temperature contribution KI at 1 is used as the weighting coefficient when detecting the fuel increase due to pressure change.
THW is calculated.

The value of this KIT)l- changes depending on the water temperature THW, and the value of KIT)l- for THW is stored in the memory of the control circuit 50.
A map of the values of II-□ is stored, and the water temperature sensor 5
7, the value of KITH- corresponding to the actually measured water temperature THW is calculated by interpolation.

In step 94, the engine speed contribution KI at 1 is used as a weighting coefficient when calculating the fuel increase due to pressure change.
NE is calculated. This value of KINE changes according to the rotational speed NE, and a map of the value of KINH with respect to NE is stored in the memory of the control circuit 5°, and is actually measured from the time interval of the 30° pulse of the crank angle sensor. The value of KINE corresponding to the engine speed NE is similarly calculated by interpolation. In step 96, KITHW calculated in step 92 and II calculated in step 94 are
The sum of NH is the weighting coefficient K for calculating the fuel increase due to pressure change.
It is assumed that l.

In step 98, 2T)IN is calculated as the engine coolant temperature contribution in the weighting coefficient when calculating the fuel increase based on the time integral term of the pressure change DLPH. Similarly, THW-
There is a 2THW map, and interpolation calculations are performed. In step 100, 2NB is calculated as the rotation speed contribution in the weighting coefficient when calculating the fuel increase amount due to the time integral term of the pressure change OLPM. There is a map of NE-K2NH, and a similar interpolation operation will be performed. In step 102, the value calculated in step 98 is 2Tl+-
The product of 2NE and 2NE calculated in step 100 becomes 2 as the weighting coefficient for calculating the fuel increase amount by the integral term accompanying the time decay of the pressure change OLPM.

In step 104, the pressure difference integral value DLPMi is
It is calculated by Mz "OLPM + K 3

Physically, this equation has the meaning of the sum of pressure changes (that is, intake air amount changes) up to the previous time. That is, in FIG. 5(a), the solid line shows the actual change in intake pipe pressure in a transient state, and the broken line shows the intake pipe pressure PM after annealing.
shows. The fuel injection amount is calculated based on this smoothed intake pipe pressure value. Therefore, if the fuel injection amount is calculated using the smoothed value, the air-fuel ratio will be transiently rough. Therefore, it is necessary to increase the amount by the difference between the actual intake pipe pressure and the annealed value. Figure 5 (b) shows the correction amount. In the embodiment of this invention, the amount is increased using an addition method.

That is, the amount of change in the intake pipe pressure is calculated, and based on this, the correction amount to be added to the basic injection amount is calculated. Fifth
In Figure (c), DLPM indicates the difference in intake pipe pressure between the current and previous injections, and this corresponds to the increase in the injection amount between the previous injection and the current injection. On the other hand, DLPM is the sum of pressure changes up to the previous time, and corresponds to the sum of the fuel injection amounts up to the previous time. Therefore, the sum of the weighting coefficients Kl corresponding to each of DLPM and DLPM multiplied by 2, K I
XDLPMt K 2 XDLP gate i is the total pressure change during the transient period.

Then, if the conversion coefficient from intake pipe pressure to fuel injection amount is C, then CX (K I XDLPMt plus 2DLP) becomes the transient increase value.

The problem here is that the intake control valve 3 as in the present invention
In an internal combustion engine equipped with 2, the amount of intake air is not the same at the same intake pipe pressure depending on whether the intake control valve 32 is open or closed.

That is, Figure 6 explains this situation, and (a) is P
The solid line shows the change in M, and (b) shows the change in the intake air amount when the intake control valve 32 is open, and the broken line shows the change when the intake control valve 32 is closed.

Therefore, if the conversion coefficient C of the intake pipe pressure car fuel injection amount is the same value depending on whether the intake control valve 32 is opened or closed, then
If the value of C is set to the optimum value when the intake control valve 32 is closed, the transient roughness of the air-fuel ratio is almost suppressed when the intake control valve 32 is closed, as shown in (c), but the intake control valve 32 is closed. When the valve 32 is open, the air-fuel ratio becomes more uneven as shown by the solid line. This invention prevents the air-fuel ratio from becoming rough regardless of whether the intake control valve is open or closed by switching the conversion coefficient C of the intake pipe pressure fuel injection amount depending on whether the intake control valve is open or closed.

In step 106, it is determined whether YSCV=O or not. When yscv=o, that is, when the intake control valve 32 is open, the process advances to step 10B, where C=52 and YSCV=
1, that is, when the intake control valve 32 is closed, the process advances to step 110, where C=35. The specific value of C here has no meaning, and since the amount of intake air is larger when the intake control valve 32 is open than when it is closed, the conversion coefficient C of the intake pipe pressure car fuel injection amount is also when the intake control valve 32 is open. is simply larger than at the time of closure and is a fitting constant.

In step 112, the additional increase correction value TPAE- is
AEW = CX (K I XDLPM+K 2 XD
LPMi). In step 114, the basic fuel injection amount Tp is calculated. As is well known, the basic fuel injection amount is determined by the intake pipe pressure and the rotational speed and is a value that makes the air-fuel ratio the stoichiometric air-fuel ratio. The memory of the control circuit 50 has a map of the basic fuel injection amount for each combination of intake pipe pressure and rotational speed, and the basic fuel injection amount for the current intake pipe pressure and rotational speed is calculated by interpolation. At this time,
The basic injection amount may also be determined from each map depending on whether the 5VC32 is open or closed.

In step 116, the final fuel injection amount TAU is changed to TAU-
(T p +TPAEW) is calculated by xα+β. Here, α and β collectively represent various correction coefficients and correction amounts whose explanations are omitted because they are not directly related to the present invention.

For example, α includes a lean correction coefficient determined from PM-NE in order to make the air-fuel ratio ultra-lean when the SCv is closed. In step 118, a fuel injection signal is generated, which fuel injection signal has a duration such that the fuel injection quantity calculated in step 116 is obtained.

In step 120, the current PM value is transferred to PMO, and in step 122, the current DLPM,
is put into DLPM=-r.

In the embodiment, an additive type transient increase correction has been described, but the idea of the present invention can also be used in a system that performs a proportional type transient increase correction. In this proportional type increase correction, transient increase correction is performed by multiplying the basic fuel injection amount by an increase correction coefficient.

Although this embodiment has been described with respect to a lean burn, the present invention is not limited thereto, and can also be applied to an internal combustion engine operating at a normal air-fuel ratio.

〔Effect of the invention〕

According to this invention, by changing the correction factor for the fuel supply amount during transient periods depending on whether the intake control valve is open or closed, the air-fuel ratio becomes unstable during transient operation regardless of whether the intake control valve is open or closed. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is an overall schematic diagram of an embodiment of the invention. FIGS. 3 and 4 are flowcharts illustrating the operation of the control circuit of the present invention. FIG. 5 is a diagram illustrating the principle of additive transient increase correction according to the present invention. FIG. 6 is a diagram illustrating the transient air-fuel ratio control characteristics according to the present invention. 12a, 12b...Intake port 22...Surge tank 26...Fuel injector 32...Intake control valve 38...Negative pressure actuator 44...3-way solenoid valve 46...For maintaining negative pressure Check valve 50...Control circuit 52...Intake pipe pressure sensor 54.56...Crank angle sensor

Claims (1)

[Claims] An intake control valve driven by intake pipe negative pressure, a fuel supply means, a fuel supply amount calculation means for calculating the amount of fuel introduced into the engine from the fuel supply means according to the intake pipe pressure, and an intake control valve that is opened. An intake control valve state determining means determines whether the intake control valve is open or closed, and a fuel supply amount calculating means supplies fuel according to the result of determining whether the intake control valve is open or closed by the intake control valve state determining means. An air-fuel ratio control device for an internal combustion engine, comprising a correction factor calculation means that makes a transient correction factor used when calculating the amount variable.