JPH09177592A - Atmospheric pressure estimating device in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the atmospheric pressure with a high precision without being influenced by the detection error of throttle valve opening even when it is large. SOLUTION: When a throttle opening is a prescribed value or less (S1), and an internal combustion engine is in steady state or constant traveling state (not in accelerating or decelerating state) (S2), the average value α 1 of feedback correction quantity α in air-fuel ratio feedback control within a prescribed period is calculated (S4) in the state where EGR is forcedly started (S3). The average value α 2 of feedback correction quantity α in air-fuel ratio feedback control within a prescribed period is calculated (S6) in the state where EGR is forcedly stopped (S5). Thereafter, on the basis of the deviation (α2-α1) of the average values of feedback correction quantity changed by ON/OFF of EGR, the atmospheric pressure Pa is estimated in reference to a map or by arithmetic operation (S7).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine provided with a fuel supply device for setting a basic fuel supply amount based on, for example, an intake air flow rate to the engine, and more particularly to a large amount necessary for correcting the fuel supply amount and the like. The present invention relates to a technique for estimating atmospheric pressure.

[0002]

2. Description of the Related Art Conventionally, as an electronically controlled fuel supply device for an internal combustion engine, there is one which sets a basic fuel supply amount based on an intake air flow rate to the engine (referred to as an L-JETRO system). That is, based on the intake air flow rate, the fuel supply amount corresponding to the intake charging efficiency is set by correction based on the intake temperature, etc., and an injection pulse signal corresponding to the fuel supply amount is output to the electromagnetic fuel injection valve to output the fuel. The supply is controlled.

By the way, when correcting the fuel supply amount in consideration of the intake charging efficiency, it is necessary to detect the atmospheric pressure which changes depending on the altitude at which the vehicle is traveling. As a method of detecting the atmospheric pressure, there is a method of directly detecting the atmospheric pressure by an atmospheric pressure sensor, but it is costly to provide a new atmospheric pressure sensor for detecting the atmospheric pressure. Therefore, as a method of estimating the atmospheric pressure using an existing sensor, an intake air flow rate to the engine detected as a mass flow rate by an air flow meter, and a volume flow rate obtained from the opening degree of the throttle valve and the engine rotation speed are used. A method for estimating the atmospheric pressure from the intake air flow rate and the intake air temperature by calculation has been developed (see the flowchart of FIG. 5; details will be described later).

[0004]

However, in the potentiometer type throttle sensor generally used for detecting the opening of the throttle valve, the allowable range of variation in sensor output with respect to the opening of the throttle valve is defined as shown in FIG. In such a case, as shown in FIG. 7, the opening degree detection error due to the output variation becomes larger on the low opening side where the output is smaller, and it is difficult to detect the opening degree with high accuracy on the low opening side.

Therefore, the intake air flow rate as the volume flow rate obtained from the throttle valve opening and the engine rotation speed is also
Due to the detection error of the throttle valve opening, there is a large error particularly on the low opening side, and there is a risk that the atmospheric pressure estimation accuracy using the intake air flow rate as the volume flow rate may be reduced. Therefore, in view of the above conventional problems, the present invention provides a large internal combustion engine capable of highly accurately estimating the atmospheric pressure without being affected by the detection error even when the throttle valve opening detection error is large. An object is to provide an atmospheric pressure estimation device.

[0006]

Therefore, according to the invention described in claim 1, as shown in FIG. 1, an exhaust gas recirculation means A for performing exhaust gas recirculation for causing a part of exhaust gas of the engine to be sucked into the engine again, and an engine. In the internal combustion engine including the air-fuel ratio feedback control means B that corrects the basic fuel supply amount so that the air-fuel ratio of the air-fuel mixture that is supplied to the target air-fuel ratio approaches the target air-fuel ratio, whether the condition for estimating the atmospheric pressure is satisfied. When it is determined by the estimation condition determination means C for determining whether or not the exhaust gas recirculation control means D for controlling the operation of the exhaust gas recirculation means, and the atmospheric pressure estimation condition are satisfied by the estimation condition determination means, Deviation calculating means E for controlling exhaust gas recirculation by the exhaust gas recirculation control means, and calculating a deviation of the correction amount of the air-fuel ratio feedback control within a predetermined period during execution and non-execution of exhaust gas recirculation.
Atmospheric pressure estimating means F for estimating atmospheric pressure based on the deviation
It was composed including and.

With this configuration, when it is determined by the estimation condition determination means that the atmospheric pressure estimation condition is satisfied,
The exhaust gas recirculation control means turns ON / OFF the exhaust gas recirculation,
The atmospheric pressure is estimated with high accuracy by the atmospheric pressure estimation means based on the deviation of the correction amount of the air-fuel ratio feedback control when the exhaust gas recirculation is turned on / off. According to a second aspect of the present invention, the estimated condition determining means includes an effect detecting means for detecting the magnitude of the effect of the atmospheric pressure variation on the intake negative pressure of the engine, and the engine is operating in a substantially constant steady state. A condition for estimating the atmospheric pressure when the steady state detection means detects the steady state of the engine, and the steady state detection means detects the steady state of the engine. It is determined that is established.

In this way, it is possible to determine a state in which the fluctuation of the intake negative pressure due to the fluctuation of the atmospheric pressure and the fluctuation of the engine operating state is small, so that the change of the correction amount of the air-fuel ratio feedback control by turning the exhaust gas recirculation on / off. Is calculated with high accuracy. The invention according to claim 3 is provided with an opening degree detecting means for detecting a throttle opening degree of a throttle valve interposed in the intake passage, and the influence detecting means has a predetermined throttle opening degree detected by the opening degree detecting means. When the value is less than or equal to the value, it is detected that the influence of atmospheric pressure fluctuation is small.

With this arrangement, the existing throttle sensor can detect the magnitude of the influence of the atmospheric pressure variation on the suction negative pressure.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In FIG. 2 showing a system configuration of an embodiment of an atmospheric pressure estimation device according to the present invention, an internal combustion engine 1
The air is sucked in through the air cleaner, the intake duct 2, and the intake manifold 3, which are not shown. The intake duct 2 is provided with a throttle valve 4 that opens and closes in conjunction with an accelerator pedal (not shown), and the throttle valve 4 controls the intake air flow rate to the internal combustion engine 1. .

Further, the intake manifold 3 is provided with an electromagnetic fuel injection valve 5 for each cylinder. The fuel injection valve 5 intermittently injects and supplies the fuel adjusted to a predetermined pressure by a pressure regulator (not shown) to the engine in response to an injection pulse signal from a control unit 6 containing a microcomputer. Further, in the internal combustion engine 1, from the viewpoint of environmental protection and improvement of fuel consumption, a part of the exhaust gas is introduced into the intake system for recirculation, and the exhaust gas is mixed with the combustion mixture to lower the combustion temperature to reduce NOx. An exhaust gas recirculation device is provided for reducing the amount of generation and improving the thermal efficiency by improving the cycle efficiency. The structure of this exhaust gas recirculation device includes an exhaust manifold 7 of the internal combustion engine 1.
An EGR passage 8 that communicates with the intake manifold 3 is provided, and the EGR passage 8 is opened and closed by an EGR control valve 9. The EGR control valve 9 is a diaphragm type valve that is opened by applying suction negative pressure to the engine against the biasing force of the coil spring in the valve closing direction. A negative pressure introducing passage 10 that communicates with the downstream intake duct 2 is provided, and the negative pressure introducing passage 1 is provided.
The valve is opened by introducing a negative suction pressure of the internal combustion engine 1 to the pressure chamber via 0.

In the negative pressure introducing passage 10, the EGR control solenoid 1 whose opening is controlled by the duty of the drive pulse signal from the control unit 6
1 is installed, and this EGR control solenoid 11
The opening degree of the EGR control valve 9, that is, the exhaust gas recirculation (hereinafter, referred to as EGR) amount can be controlled through the opening degree control.

Further, reference numeral 12 is a diaphragm type B which determines the negative pressure for controlling the EGR control valve 9 by operating the diaphragm by the exhaust pressure and the manifold negative pressure.
It is a PT valve. The EGR passage 8, the EGR control valve 9, the negative pressure introduction passage 10, the EGR control solenoid 11, and the BPT valve 12 constitute exhaust gas recirculation means.

By the way, the control unit 6 includes
Signals from various sensors are input to perform fuel injection control and EGR control. As these various sensors, a hot wire type air flow meter 2 is provided which is provided in the intake duct 2 on the upstream side of the throttle valve 4 and detects the intake air flow rate Q.
0 (steady state detection means), a rotation speed sensor 21 (steady state detection means) for detecting the engine rotation speed Ne by extracting a rotation signal from the crankshaft, and a throttle valve TVO attached to the throttle valve 4 to adjust the throttle opening TVO. A throttle sensor 22 (influence detecting means and steady state detecting means) for detecting, an intake air temperature T to the engine provided in the intake duct 2
Intake air temperature sensor 23 for detecting the temperature, a water temperature sensor 24 provided in the water jacket of the internal combustion engine 1 for detecting a cooling water temperature Tw representing the engine temperature, and an oxygen concentration in the exhaust gas which is interposed in the exhaust manifold 7. The air-fuel ratio sensor that detects the air-fuel ratio of the intake air-fuel mixture by
An O ₂ sensor) 25 and the like are provided.

Then, for fuel injection control, the control unit 6 calculates the basic fuel supply amount Tp based on the detected intake air flow rate Q and the engine rotation speed Ne, and further, the cooling water temperature Tw and the throttle opening TVO. And the estimated atmospheric pressure Pa, etc. are used to make a correction in consideration of the intake charging efficiency, and based on the output of the O ₂ sensor 25, air-fuel ratio feedback control is performed to bring the air-fuel ratio of the intake air-fuel mixture close to the ideal air-fuel ratio. The effective fuel supply amount Te is calculated, and an injection pulse signal corresponding to the effective fuel supply amount Te is supplied to the fuel injection valve 5. The control unit 6 and the O ₂ sensor 25 form an air-fuel ratio feedback control means.

Further, as the EGR control, the control unit 6 obtains the EGR amount by referring to a map or the like based on the detected intake air flow rate Q and the engine rotation speed Ne, and a drive pulse signal corresponding to this EGR amount. Is supplied to the EGR control solenoid 11.
The control unit 6 includes an estimation condition determining means,
It has functions as an exhaust gas recirculation control means, a deviation calculation means, and an atmospheric pressure estimation means.

Here, in order to clarify the problems of the conventional atmospheric pressure estimation processing and to clarify the necessity of the present invention, the conventional atmospheric pressure estimation processing will be described below with reference to the flowchart of FIG. . In step 10 (abbreviated as S10 in the figure. The same applies hereinafter), the throttle opening TVO is read from the throttle sensor 22.

In step 11, the engine rotation speed Ne is read from the rotation speed sensor 21. In step 12, the map or the like in which the volume flow rate (intake air flow rate) V to the engine is stored in advance using the throttle opening TVO and the engine rotation speed Ne as parameters, and the throttle opening TVO and the throttle opening TVO read in steps 10 and 11 are referred to. The volume flow rate V is searched based on the engine rotation speed Ne.

In step 13, the air flow meter 20
Read the mass flow rate (intake air flow rate) Q from the engine to the engine.
In step 14, the intake air temperature sensor 23 detects the intake air temperature T.
Read. In step 15, the retrieved volumetric flow rate V,
Based on the read mass flow rate Q and intake air temperature T, the atmospheric pressure Pa is estimated by the following equation.

Pa = func (Q · T / V) where func (x) is the atmospheric pressure Pa with x as a parameter.
Shows a function or a map for obtaining By performing such atmospheric pressure estimation processing, atmospheric pressure can be estimated without newly providing an expensive atmospheric pressure sensor. However, as described above, when the throttle valve 4 is at a low opening, the throttle sensor 2
Since the opening degree detection error of 2 is large, the accuracy of the volume flow rate V decreases, and as a result, the estimation accuracy of the atmospheric pressure Pa decreases.

Therefore, according to the present invention, the atmospheric pressure estimation process of the flowchart shown in FIG. 3 is performed in addition to the atmospheric pressure estimation process shown in FIG. The pressure can be estimated. Hereinafter, the details of the atmospheric pressure estimation processing according to the present invention will be described in detail. This atmospheric pressure estimation processing is performed paying attention to the fact that the EGR amount changes due to the influence of the atmospheric pressure, and particularly when the EGR is forcibly turned ON / OFF in the intake state where the influence of the atmospheric pressure is small. The atmospheric pressure can be estimated with high accuracy based on the deviation of the feedback correction amount α of the air-fuel ratio feedback control.

In step 1, it is judged whether or not the throttle opening TVO read from the throttle sensor 22 is less than or equal to a predetermined value θ, and if it is less than or equal to a predetermined value θ (TVO ≦ θ), the process proceeds to step 2 and a predetermined value is obtained. If it is larger than the value θ, the process of step 1 is repeated. That is, the throttle opening TV
If O is equal to or smaller than the predetermined value θ, the suction negative pressure on the downstream side of the throttle valve 4 is equal to or larger than the predetermined value, and it is considered that the influence of the atmospheric pressure is small. By performing the atmospheric pressure estimation process, it is possible to improve the atmospheric pressure estimation accuracy. It should be noted that this determination method may be any method as long as it can be determined from the output of the intake pressure sensor that directly detects the suction negative pressure, as long as it can be determined that the influence of atmospheric pressure is small. The process of step 1 corresponds to the influence detecting means.

In step 2, the internal combustion engine 1 is in a steady state,
That is, it is determined whether or not the vehicle is in the constant speed traveling state (when not in the acceleration / deceleration state), and if it is the steady state, the process proceeds to step 3, and if it is not the steady state, the process returns to step 1. This determination is made based on, for example, the intake air flow rate Q read from the eflow meter 20, and also the throttle sensor 22.
The determination can be made based on the angular speed ω (opening change speed) of the throttle valve 4 calculated from the output of the throttle valve 4 or the change in engine operation such as the engine speed Ne read from the speed sensor 21. . The process of step 2 corresponds to the steady state detecting means, and the process of steps 1 and 2 constitutes the estimation condition determining means.

In step 3, the control unit 6
To supply the duty of the drive pulse signal to the EGR control solenoid 11 to forcibly start the EGR. In step 4, the average value α1 of the feedback correction amount α in the air-fuel ratio feedback control within a predetermined period (for example, time, cumulative rotation speed) is calculated while EGR is being performed.

In step 5, the control unit 6
To stop supplying the duty of the drive pulse signal to the EGR control solenoid 11 and forcibly stop the EGR. In step 6, the average value α2 of the feedback correction amount α in the air-fuel ratio feedback control within a predetermined period (for example, time, cumulative rotation speed) is calculated in a state where EGR is not performed.

In step 7, the atmospheric pressure Pa is estimated by referring to or calculating a map or the like based on the deviation (α2-α1) of the average value of the feedback correction amount α which changes depending on ON / OFF of the EGR. The processing of steps 3 to 7 (first half) corresponds to the deviation calculating means, and the processing of step 7 (second half) corresponds to the atmospheric pressure estimating means.

According to the atmospheric pressure estimation process described above, the atmospheric pressure is not affected by the detection error of the throttle valve opening on the low opening side of the throttle valve, which could not be accurately estimated in the prior art. The estimation can be performed with high accuracy. Also,
Since the atmospheric pressure can be estimated by the existing sensor, the cost does not increase due to the addition of new parts. Therefore, by using the atmospheric pressure estimation process according to the present invention together with the conventional atmospheric pressure estimation process, the atmospheric pressure estimation can be performed with high accuracy over the entire opening of the throttle valve 4.

Next, an atmospheric pressure estimation process in which a part of the flowchart of FIG. 3 is modified is shown in the flowchart of FIG.
This is because instead of the exhaust gas recirculation device composed of the EGR control solenoid 11 or in addition to the exhaust gas recirculation device, the valve timing of the exhaust valve is changed so that the exhaust gas discharged from the engine is returned to the inside of the cylinder. It is applied to an internal combustion engine having an internal EGR for returning. FIG.
The steps that are different from the atmospheric pressure estimation processing shown in the flowchart of 1 are briefly described below.

In step 3 ', the internal EGR is forcibly started by changing the valve timing of the exhaust valve.
In step 4, the average value α1 of the feedback correction amount α in the air-fuel ratio feedback control within the predetermined period is calculated while EGR is being performed. In step 5 ', the internal EGR is forcibly stopped by changing the valve timing of the exhaust valve.

The effect of such atmospheric pressure estimation processing is shown in FIG.
Since it is the same as that of the flowchart of FIG.

[0031]

As described above, according to the first aspect of the present invention, the exhaust gas recirculation control means controls the exhaust gas recirculation when the estimated condition judgment means determines that the atmospheric pressure estimation condition is satisfied. ON / OFF, exhaust recirculation ON / O
Since the atmospheric pressure is estimated by the atmospheric pressure estimating means based on the deviation of the correction amount of the air-fuel ratio feedback control at the time of FF, on the low opening side of the throttle valve where the atmospheric pressure cannot be estimated with high accuracy in the past, The atmospheric pressure can be estimated with high accuracy without being affected by the detection error of the throttle valve opening.
That is, if the atmospheric pressure estimation of the present invention is performed, the atmospheric pressure can be estimated with high accuracy over the entire opening of the throttle valve.

Further, since the atmospheric pressure is estimated by the existing sensor, there is no increase in cost due to the addition of new parts. According to the second aspect of the present invention, the atmospheric pressure is estimated only when the variation of the suction negative pressure due to the variation of the atmospheric pressure and the variation of the engine operating state is small. Therefore, the exhaust gas recirculation is turned on. The change in the correction amount of the air-fuel ratio feedback control due to ON / OFF is calculated with high accuracy, so that the atmospheric pressure estimation accuracy can be further improved.

According to the third aspect of the present invention, the existing throttle sensor detects the magnitude of the influence of the fluctuation of the atmospheric pressure on the suction negative pressure, so that the cost does not increase due to the addition of new parts.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claim 1 of the present invention.

FIG. 2 is a system configuration diagram showing an embodiment of an atmospheric pressure estimation device according to the present invention.

FIG. 3 is a flowchart showing an atmospheric pressure estimation process of the above.

FIG. 4 is a flowchart showing another atmospheric pressure estimation process of the above.

FIG. 5 is a flowchart showing a conventional atmospheric pressure estimation process.

FIG. 6 is a diagram showing an output variation of the throttle sensor.

FIG. 7 is a diagram showing variations in opening detection due to variations in output.

[Explanation of symbols]

1 Internal Combustion Engine 6 Control Unit 8 EGR Passage 9 EGR Control Valve 10 Negative Pressure Introduction Passage 11 EGR Control Solenoid 12 BPT Valve 20 Air Flow Meter 21 Rotation Speed Sensor 22 Throttle Sensor 25 O ₂ Sensor

Claims (3)

[Claims] Claim: What is claimed is: 1. Exhaust gas recirculation means for performing exhaust gas recirculation for sucking a part of engine exhaust gas into the engine again, and correcting the basic fuel supply amount so that the air-fuel ratio of the air-fuel mixture supplied to the engine approaches a target air-fuel ratio. In an internal combustion engine including: an air-fuel ratio feedback control unit that performs: an estimation condition determination unit that determines whether a condition for estimating atmospheric pressure is satisfied; and an exhaust gas recirculation control unit that controls the operation of the exhaust gas recirculation unit. When the estimation condition determining means determines that the atmospheric pressure estimation condition is satisfied, the exhaust gas recirculation control means controls exhaust gas recirculation, and the exhaust gas recirculation is performed within a predetermined period during execution and non-execution of the exhaust gas recirculation. An internal combustion engine including: a deviation calculating means for calculating a deviation of a correction amount of the fuel ratio feedback control; and an atmospheric pressure estimating means for estimating an atmospheric pressure based on the deviation. Atmospheric pressure estimation device in. 2. The estimation condition determining means detects the magnitude of the influence of atmospheric pressure fluctuations on the suction negative pressure of the engine, and detects that the engine is operating in a substantially constant steady state. The steady state detecting means is included, and when the influence detecting means detects that the influence is small and the steady state detecting means detects the steady state of the engine, the condition for estimating the atmospheric pressure is satisfied. The atmospheric pressure estimation device for an internal combustion engine according to claim 1, wherein the atmospheric pressure estimation device determines. 3. An opening detecting means for detecting a throttle opening of a throttle valve interposed in an intake passage, wherein the influence detecting means has a throttle opening detected by the opening detecting means of a predetermined value or less. The atmospheric pressure estimation device for an internal combustion engine according to claim 2, wherein it is detected that the influence of the fluctuation of atmospheric pressure is small.