JPH0261326A - Intake controller for internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an intake air control device for an internal combustion engine that can use a mixture of different types of fuel, such as gasoline and alcohol.

<Prior Art> An example of this type of intake control device for an internal combustion engine is the one disclosed in Japanese Patent Laid-Open No. 56-98540.

This product is designed to use a mixture of gasoline and alcohol, and is equipped with a capacitive alcohol sensor that detects the alcohol concentration in the fuel, and supplies fuel based on the detected value of the alcohol sensor. In addition to controlling the fuel supply amount, a 0□ sensor is installed to detect the air-fuel ratio from the oxygen concentration in the exhaust gas, and during predetermined operation, feedback correction is performed on the fuel supply amount so that the air-fuel ratio approaches the target air-fuel ratio. ing.

Incidentally, in recent years, for the purpose of improving fuel efficiency and purifying exhaust gas, some engines have been designed to control the air-fuel ratio so that the actual air-fuel ratio becomes thinner than the stoichiometric air-fuel ratio in the low-speed, low-load operating region of the engine.

In this case, some engines are equipped with a swirl control valve in the intake passage to give a swirl to the intake air in order to improve the mixability of fuel and air in order to obtain stable combustibility even when the air-fuel ratio is made lean.

<Problems to be Solved by the Invention> However, in the conventional internal combustion engines that are compatible with the use of different types of fuels as described above, there is no one equipped with a swirl control valve as described above, so it is difficult to sufficiently dilute the air-fuel ratio. For example, when using a mixed fuel of alcohol and gasoline, the combustion stability increases as the alcohol concentration increases, and the required swirl characteristics differ.
Conventionally, dilution control that takes full advantage of such characteristics has not been performed.

The present invention was made in view of these conventional problems, and it is possible to dilute the air-fuel ratio by controlling the opening of a swirl control valve installed in the intake passage in an internal combustion engine that can use different types of fuel. It is an object of the present invention to provide an intake air control device for an internal combustion engine, which can improve fuel economy by solving the above-mentioned problems.

<Means for Solving the Problems> Therefore, the present invention provides an internal combustion engine that can be used by mixing different types of fuel as shown in FIG. An intake control device having a swirl control valve that increases intake turbulence when the valve is closed, comprising: an operating state detecting means for detecting an operating state; a fuel concentration detecting means for detecting a concentration of reference fuel supplied to the engine; An opening control means for controlling the opening of the swirl control valve according to the operating state of the engine detected by the operating state detecting means and the reference fuel concentration detected by the fuel concentration detecting means. .

<Operation> The opening control means determines whether lean combustion is in a stable region based on the operating state of the engine detected by the operating state detecting means and the reference fuel concentration detected by the fuel concentration detecting means. Based on the result of the determination, the opening degree (including switching between fully closed and fully open) of the swirl control valve installed in the intake passage is controlled.

In this way, the opening degree of the swirl control valve can be appropriately controlled with respect to the reference fuel concentration, and as a result, the dilution caused by the intake swirl can be matched to the fuel concentration and promoted as much as possible.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 2 showing the configuration of one embodiment, an air flow meter 3 is installed in an intake passage 2 of an engine 1 to detect the intake air flow rate in the intake passage 2 from the upstream side. Throttle valve 4. A pressure sensor 14 is sequentially provided to detect the intake negative pressure of intake air. Further, swirl control valves 6 are provided near the intake valves 5 at branch points to each cylinder, and air is taken in through these. Further, a fuel injection valve 7 is provided between the swirl control valve 6 and the intake valve 5 for each cylinder, and fuel is injected and supplied by this.

Further, the engine 1 is provided with a water temperature sensor 8 that detects the cooling water temperature of the engine 1, and a crank angle sensor 9 that is attached to a crankshaft or a distributor (not shown) and outputs a pulse signal for each unit crank angle of the engine 1. Further, the exhaust passage 10 is provided with an 02 sensor 11 that detects the oxygen concentration in the exhaust gas and detects the air-fuel ratio.

Here, the air flow meter 3. The pressure sensor 14, the water temperature sensor 8, the crank angle sensor 9, and the like constitute operating state detection means.

Further, in a fuel supply pipe 12 that communicates with the fuel injection valve 7 and supplies fuel to the engine 1, the concentration of alcohol as a reference fuel in the mixed fuel of alcohol and gasoline flowing through the fuel supply pipe 12 is detected. An alcohol sensor 13 is provided as a fuel concentration detection means.

Detection signals from these sensors are input to a control unit 15 with a built-in microcomputer, and various calculations are performed.

Furthermore, the swirl control valve 6 is composed of a valve body 20 having a notch 20a as shown in FIG. Increase the turbulence (hereinafter referred to as swirl control). The support shaft 21 is common to all cylinders, and supports the valve bodies 20 of several cylinders. And for opening and closing track,
An output rod of a diaphragm type negative pressure actuator (not shown) is connected to the support shaft 21 . In the negative pressure actuator, intake negative pressure downstream of the throttle valve 4 or atmospheric pressure upstream of the throttle valve 4 is selectively introduced into the electromagnetic valve 16.

Therefore, the control unit 15 controls the solenoid valve 16.
ON/OF by controlling the duty of energization to
Swirl control can be performed by controlling the opening degree of the swirl control valve 6 including F.

Here, the stability limit in the lean burn range varies depending on the concentration of the reference fuel, and the required swirl characteristics also vary accordingly. For example, if the concentration of alcohol as a reference fuel is 8.
Comparing 5% mixed fuel (hereinafter referred to as M85) and gasoline, M2S has a higher air-fuel ratio (λ) of 0.
Stable combustion can be performed up to a lean range of about 2. Furthermore, the emissions of HC, NO, etc. contained in the exhaust gas are also M.
Compared to gasoline, 2S can be suppressed to about 60%, especially in the lean burn range. Therefore, when performing lean burn in engine 1 to improve fuel efficiency, the stability limit of lean burn will differ depending on the concentration of the reference fuel.
Along with this, the required swirl characteristics also differ. In other words, the higher the stability, the smaller the required swirl.

Additionally, during warm-up, the target air-fuel ratio and the opening degree of the swirl control valve associated with it vary depending on the concentration of the reference fuel.In other words, the water temperature at the starting point of lean burn control varies depending on the concentration. It's for a reason.

Next, control of the swirl control valve 6 will be explained with reference to the flowchart shown in FIG.

In step 1 (marked as S in the figure, the same applies hereafter),
Cooling water temperature T of engine 1 based on the signal from water temperature sensor 8
w, the rotational speed N of the engine 1 detected by the crank angle sensor 9, and the intake negative pressure P of the intake air detected by the pressure sensor 14 are read. Therefore, step 1 also constitutes an operating state detection means.

In step 2, the A/D converted value of the alcohol concentration detection signal from the alcohol sensor 13 is read.

Therefore, step 2 constitutes fuel concentration detection means.

In step 3, the lean combustion start cooling water temperature TWL is determined from the detected alcohol concentration value using a map.

In step 4, the cooling water temperature Tw is the lean combustion start cooling water > 1
It is determined whether the value is equal to or greater than TWL.

Then, the cooling water temperature Tw is the lean combustion start cooling water temperature TW.
If it is greater than or equal to L, the process proceeds to step 5, where a lean air-fuel ratio λ for performing lean combustion is determined. In addition, the lean air-fuel ratio λ,
is determined from the map according to the concentration of alcohol as the reference fuel.

Swirl control for sufficiently mixing fuel and intake air to perform lean combustion will be described below.

In step 6, from the swirl map shown in FIGS. 5 and 6, the rotational speed Ns of the engine 1 that performs ON/OFF control of the swirl control valve 6 for each detected alcohol concentration value is determined.
, and the range of the intake negative pressure Ps of the intake air. That is,
Swirl control valve according to the gasoline swirl map for gasoline to M15 fuel, the M30 swirl map for M15 to M45 fuel, the M60 swirl map for M45 to M70 fuel, and the M85 swirl map for fuel with higher alcohol concentration. 6 ON/OF
Perform F control. For example, in the case of the swirl map for gasoline shown in FIG. 5, each of the above maps is configured so that the intake negative pressure P is between 150 mmHg and the rotational speed N is 320 O from a no-load state.
When the rotational speed is below r p m, the swirl control valve 6 is closed to cause swirl.

Here, the range of the rotational speed Ns and the intake negative pressure Ps of the intake air that causes the swirl is designed to cause the swirl to occur up to high loads because the closer the range is to gasoline, the worse the combustion stability is.

Then, in step 7 and step 8, the engine 1
The rotation speed N and the intake negative pressure P of the intake air are respectively Ns-P.
If it is within the range that causes swirl compared to s,
Proceeding to step 9, the solenoid valve 16 is turned OFF to close the swirl control valve.

When the solenoid valve 16 is OFF, intake negative pressure is introduced into the negative pressure working chamber of the negative pressure actuator, the swirl control valve 6 is closed, and the swirl is strengthened.

On the other hand, in step 4, when the cooling water temperature Tw is less than the lean combustion start cooling water temperature TWL, the process proceeds to step 10, where the throttle valve 4 is opened so that the stoichiometric air-fuel ratio λ is reached in order to stabilize combustion, and in step 11, Solenoid valve 16
Turn ON and open the swirl control valve 6.

Further, in step 7 and step 8, the rotation speed N
, when the intake negative pressure P of the intake air is outside the range that causes swirl compared to Ns and PS, respectively, step 11 is performed.
, and open the swirl control valve 6.

In the portion explained above, steps 3 to 11 correspond to the opening control means.

In this way, in an internal combustion engine that uses a mixed fuel of alcohol and gasoline, even if the concentration of alcohol differs, it is possible to select the optimum air-fuel ratio according to the concentration of alcohol and provide an appropriate swirl. .

Furthermore, there is one in which the opening degree of the swirl control valve 6 can be adjusted.

The control of the swirl control valve 6 in this case will be explained with reference to the flowchart shown in FIG. Regarding the same steps as in the flowchart shown in FIG. 4,
The same step numbers will be given and the explanation will be omitted.

In step 1, the cooling water temperature Tw of the engine 1, the rotational speed N, and the basic injection amount Tp calculated in a separate routine are read.

In step 2, the A/D converted value of the alcohol concentration detection signal from the alcohol sensor 13 is read.

In step 3, the lean combustion start cooling water temperature T W L is determined from the detected alcohol concentration value using a map.

In step 4, it is determined whether the cooling water temperature Tw is equal to or higher than the lean combustion starting cooling water temperature Tw, and if it is equal to or higher than the lean combustion starting cooling water temperature Tw, the process proceeds to step 21.

In step 21, it is determined whether the engine is being warmed up by comparing the cooling water temperature Tw and the warm-up completion temperature Two. If the cooling water temperature Tw is equal to or higher than the warm-up completion temperature Two, it is determined that the engine 1 has been warmed up and the process proceeds to step 22.

In step 22, assuming that engine l has been warmed up, an intermediate flag F, which will be described later, is set to F=0. Then, in step 23, the engine 1 as shown in FIG.
A target air-fuel ratio λ for performing lean combustion is determined from a lean-burn air-fuel ratio map at the time of completion of warm-up for each alcohol concentration detection value using a grid of the shaft torque corresponding to the load Tp and the rotational speed N.

In step 24, the required swirl ratio S is determined from a swirl map in which the target air-fuel ratio λ for performing lean combustion determined in step 23 and the detected alcohol concentration are used as a grid. Here, the required swirl ratio S is set to be increased by about 1 in the case of gasoline compared to the case of M2S, for example.

In step 25, based on the required swirl ratio S,
The opening degree θ of the swirl control valve 6 is determined.

Then, in step 26, the control unit 15 performs duty control to energize the solenoid valve 16 to achieve the opening degree θ, and swirl control is performed.

Next, the process proceeds to step 27, where lean air-fuel ratio control is performed so that the target air-fuel ratio λ□ obtained in step 23 is achieved.

On the other hand, in step 21, if the cooling water temperature Tw is less than the warm-up completion temperature Two, it is determined that the engine 1 is being warmed up, and the process proceeds to step 31.

In step 31, it is determined whether the engine 1 is being warmed up and the temperature is equal to or higher than the temperature Tws at which swirl should be started.

If the cooling water temperature Tw is equal to or higher than the swirl start temperature Tws, the process proceeds to step 32.

In step 32, the intermediate flag F, which indicates that the engine 1 is being warmed up and the cooling water temperature is equal to or higher than the swirl start temperature Tws, is set to F=1, and the process proceeds to step 33.

In step 33, first, the target air-fuel ratio λ8 at the time of completion of warm-up under the same conditions as found in step 23 is found. That is, as shown in FIG. 8, the target air-fuel ratio for lean combustion is determined from the lean-burn air-fuel ratio map at the time of completion of warm-up for each alcohol concentration detection value using the load TP and rotational speed N of the engine 1 as a grid. Find λ.

In step 34, the target air-fuel ratio λ during warm-up is determined. is the target air-fuel ratio λ□ at the end of warm-up for each alcohol concentration detection value mentioned above.
and an air-fuel ratio map (not shown) at the start of lean combustion when the air-fuel ratio is set to λ=1.

Then, in step 35, it is determined whether or not the intermediate flag F is up, and if it is, the process proceeds to step 24.

On the other hand, if the cooling water temperature Tw is less than the swirl start temperature Tws in step 31, the intermediate flag F is not set.
Jump to step 33.

Therefore, if the cooling water temperature Tw is less than the swirl start temperature Tws, in step 35, since F=O, the process proceeds to step 36, where swirl control is not performed and the swirl control valve 6 is fully opened. Next, step 37 Proceed to
Lean air-fuel ratio control is performed in accordance with the target air-fuel ratio λ for performing lean combustion during warm-up determined in step 34.

Therefore, steps 3 to 26 and steps 31 to
Step 36 constitutes an opening control means.

Further, in step 4, if the cooling water temperature Tw is less than the lean combustion start cooling water temperature TWL, the combustion is not stable, so normal air-fuel ratio control is performed.

That is, the process proceeds to step 41, where the load T of the engine 1 (not shown) is
A target air-fuel ratio λN for carrying out normal air-fuel ratio control is set as a stoichiometric air-fuel ratio from an air-fuel ratio map for each alcohol concentration detection value using p and rotational speed N as a grid.

Then, proceed to step 42 and do not add swirl (
With the swirl control valve 6 fully open), the process proceeds to step 43, where stoichiometric air-fuel ratio control is performed.

In this way, in the internal combustion engine 1 that can use a mixed fuel of alcohol and gasoline, which are different fuels, the swirl control valve 6
It becomes possible to control the opening and closing of the opening, thereby making it possible to vary the required swirl characteristics. Therefore, even if the stability limit of lean combustion differs depending on the concentration of alcohol, which is the reference fuel, the dilution caused by intake swirl can be promoted as much as possible by matching it with the concentration of alcohol, thereby improving fuel efficiency. There is an effect.

In addition, during warm-up, the water temperature at the start point of lean burn control and the water temperature at which swirl should start differ depending on the alcohol concentration, so the target air-fuel ratio and the associated opening degree θ of the swirl control valve 6 Although it varies depending on the concentration of alcohol, since the opening degree of the swirl control valve 6 is linearly controlled, in this case as well, the dilution caused by the intake swirl can be matched to the concentration of alcohol and promoted as much as possible. Fuel efficiency can be improved.

<Effects of the Invention> As described above, according to the present invention, the opening control means is controlled based on the operating state of the engine detected by the operating state detecting means and the reference fuel concentration detected by the fuel concentration detecting means. The structure is designed to determine whether lean combustion is in the region where lean combustion can be performed stably and to control the opening degree of the swirl control valve.
As a result of being able to appropriately control the opening degree of the swirl control valve with respect to the reference fuel concentration, the dilution caused by the intake swirl can be matched to the fuel concentration and promoted as much as possible. This has the effect of making it possible to improve fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing the configuration of the swirl control valve, and FIGS. 4 and 7 are control diagrams. 5 and 6 are diagrams showing the control area for opening and closing of the swirl control valve, and FIG. 8 is a diagram showing an example of a lean burn air-fuel ratio map for each alcohol concentration. ■... Engine 2... Intake passage 3... Air flow meter 6... Swirl control valve 8... Water temperature sensor 9... Crank angle sensor 13... Alcohol sensor 14... Pressure sensor 16 ...Solenoid valve 15...Control unit

Claims (1)

[Scope of Claims] An intake control device for an internal combustion engine that can be used by mixing different types of fuel, which includes a swirl control valve that is interposed in an intake passage leading to an intake valve and increases intake turbulence when the intake passage is closed. An operating state detecting means for detecting an operating state; a fuel concentration detecting means for detecting a concentration of reference fuel supplied to the engine; and an operating state of the engine detected by the operating state detecting means and the fuel concentration. 1. An intake air control device for an internal combustion engine, comprising: a reference fuel concentration detected by a detection means; and an opening control means for controlling the opening of the swirl control valve in accordance with the reference fuel concentration detected by the detection means.