JP2009174400A - Fuel property detection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel property detection device for an internal combustion engine capable of maintaining detection accuracy of fuel properties and detecting abnormality occurring on a fuel property sensor. <P>SOLUTION: During execution of air-fuel ratio feed back control based on output of an A/F sensor 17 after completion of warming up of the internal combustion engine 1, properties of fuel of which properties have been already known is detected by the fuel property sensor 100, and output error of the fuel property sensor 100 is corrected based on comparison between the detected fuel properties and the known fuel properties. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel property detection device used for an internal combustion engine.

  2. Description of the Related Art In recent years, so-called flexible fuel vehicles (FFV) that can run with ethanol fuel or a mixed fuel of gasoline and ethanol (hereinafter referred to as ethanol mixed fuel) based on a gasoline engine have become widespread. This FFV uses an optical or capacitive fuel property sensor to detect the fuel density and ethanol concentration, and feeds back the detected fuel property for more precise engine control. We are trying to reduce the occurrence.

  Gasoline and alcohol-mixed fuel have different properties, and the alcohol concentration or the component ratio in the alcohol-mixed fuel is not necessarily constant, and therefore there is a possibility that the fuel property will be different each time fuel is supplied to the engine. On the other hand, when the fuel property changes, for example, the theoretical air-fuel ratio changes. Therefore, it is necessary to correct the air-fuel ratio according to the fuel properties.

  A fuel property sensor is disposed in the fuel supply path from the fuel tank to the fuel injection valve, a correction coefficient corresponding to the fuel property detected by the fuel property sensor is determined, and air-fuel ratio control is performed using this correction factor. Such an internal combustion engine is known (see Patent Document 1). In this way, good air-fuel ratio control can be maintained regardless of the nature of the fuel supplied.

Japanese Patent Laid-Open No. 5-5446

  By the way, in the optical fuel property sensor, it is avoided that the optical system such as the prism and the reflecting mirror is contaminated with the fuel or the like, and the detection accuracy is not lowered due to the deterioration of the light source (LED) and the light receiving element (photodiode) with time. I can't. In order to maintain good air-fuel ratio control, it is necessary to maintain the detection accuracy of the optical fuel property sensor, and to reliably detect an abnormality in the optical fuel property sensor.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel property detection device for an internal combustion engine capable of maintaining the detection accuracy of the fuel property and detecting an abnormality occurring in the fuel property sensor. There is to do.

  A fuel property detection device for an internal combustion engine according to the present invention includes a fuel property sensor that detects the property of fuel supplied to the internal combustion engine, and an air-fuel ratio feedback control based on the output of the air-fuel ratio sensor after the warm-up of the internal combustion engine is completed. The fuel property sensor detects the fuel property of a known fuel during the execution of the fuel, and corrects the output error of the fuel property sensor based on the comparison between the detected fuel property and the known fuel property. It is characterized by having.

  In the above configuration, the correction means calculates a correction coefficient for matching the detected fuel property with the known fuel property, and if the correction factor is not within a predetermined range, the fuel property sensor is abnormal. It is possible to adopt a configuration having an abnormality detection means for determining that there is.

  In the above configuration, the fuel tank is connected to a main tank that stores fuel, a fuel supply path that supplies the fuel in the main tank to the internal combustion engine and is provided with the fuel property sensor, and the fuel supply path that is upstream of the fuel property sensor. Further, a sub-tank for storing fuel with a known property, a fuel supply passage downstream of the fuel property sensor, and the main tank, and a recovery passage for collecting fuel with a known property supplied from the sub-tank. A bypass passage connecting the upstream side of the sub-tank of the fuel supply passage and the downstream side of the recovery passage, the bypass passage, and a first and a first that selectively open and close the fuel supply passage corresponding to the bypass passage. 2 valve means, a third valve means for opening and closing a passage between the sub tank and the fuel supply path, and a fourth valve means for opening and closing the recovery path. You can adopt a configuration.

  According to the present invention, it is possible to obtain a fuel property detection device for an internal combustion engine capable of detecting an abnormality occurring in a fuel property sensor while maintaining the detection accuracy of the fuel property.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view showing an internal combustion engine to which the present invention is applied. As shown in the figure, the internal combustion engine 1 generates power by burning a mixture of fuel and air inside a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. To do. The internal combustion engine 1 is a multi-cylinder engine for a vehicle (only one cylinder is shown), and is a spark ignition type internal combustion engine.

  In the cylinder head of the internal combustion engine 1, an intake valve Vi for opening and closing the intake port and an exhaust valve Ve for opening and closing the exhaust port are provided for each cylinder. Each intake valve Vi and each exhaust valve Ve are opened and closed by a camshaft (not shown). A spark plug 7 for igniting the air-fuel mixture in the combustion chamber 3 is attached to the top of the cylinder head for each cylinder.

  The intake port of each cylinder is connected to a surge tank 8 serving as an intake air collecting chamber via a branch pipe for each cylinder. An intake pipe 13 that forms an intake manifold passage is connected to the upstream side of the surge tank 8, and an air cleaner 9 is provided at the upstream end of the intake pipe 13. An air flow meter 5 for detecting the intake air amount and an electronically controlled throttle valve 10 are incorporated in the intake pipe 13 in order from the upstream side. An intake passage is formed by the intake port, the surge tank 8 and the intake pipe 13.

  An injector (fuel injection valve) 12 that injects fuel into the intake passage, particularly into the intake port, is provided for each cylinder. The fuel injected from the injector 12 is mixed with intake air to form an air-fuel mixture. The air-fuel mixture is sucked into the combustion chamber 3 when the intake valve Vi is opened, compressed by the piston 4, and ignited and burned by the spark plug 7. It is done. The configuration of the fuel supply system that supplies fuel to the injector 12 will be described later.

  On the other hand, the exhaust port of each cylinder is connected to an exhaust pipe 6 forming an exhaust collecting passage through a branch pipe for each cylinder, and a catalyst 11 made of a three-way catalyst is attached to the exhaust pipe 6. An exhaust passage is formed by the exhaust port, the branch pipe, and the exhaust pipe 6. An A / F sensor 17 for detecting the exhaust air / fuel ratio is installed upstream of the catalyst 11.

  The above-described spark plug 7, throttle valve 10, injector 12, and the like are electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 20. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like, all not shown. In addition to the air flow meter 5 and the A / F sensor 17 described above, the ECU 20 includes a crank angle sensor 14 for detecting the crank angle (phase) of the internal combustion engine 1 and an accelerator for detecting the accelerator opening, as shown in the figure. An opening sensor 15, a throttle opening sensor 19 for detecting the opening of the throttle valve 10, and other various sensors are electrically connected via an A / D converter or the like (not shown). The ECU 20 controls the ignition plug 7, the throttle valve 10, the injector 12, etc. so as to obtain a desired output based on the detection values of various sensors, etc., and the ignition timing, fuel injection amount, fuel injection timing, throttle opening. Control the degree etc. The throttle opening is normally controlled to an opening corresponding to the accelerator opening. Further, the ECU 20 constitutes correction means and abnormality detection means.

The catalyst 11 is a harmful component in the exhaust gas when the air-fuel ratio A / F of the exhaust gas flowing into the catalyst 11 is close to the stoichiometric air-fuel ratio (stoichiometric, for example, A / F = 14.6) of the gasoline that is the reference fuel. NOx, HC and CO are simultaneously purified. Further, the catalyst 11 has an oxygen storage capacity (O ₂ storage capacity). When the air-fuel ratio of the inflowing exhaust gas becomes larger than the stoichiometric ratio, that is, when it becomes lean, it adsorbs and holds the excess oxygen present in the exhaust gas, and the inflow When the air-fuel ratio of the exhaust gas becomes smaller than stoichiometric, that is, when it becomes rich, the adsorbed oxygen is released.

  The ECU 20 controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing into the catalyst 11 coincides with the stoichiometry during normal operation of the internal combustion engine (after warming up). Specifically, the ECU 20 sets a target air-fuel ratio equal to the stoichiometry, and is injected from the injector 12 so that the pre-catalyst air-fuel ratio detected by the A / F sensor 17 matches the stoichiometry. Feedback control of the fuel injection amount.

  Here, similarly, when alcohol is mixed in the fuel, the air-fuel ratio is feedback-controlled so that the actual sensor output matches the sensor output value equivalent to the gasoline stoichiometry. Since alcohol contains oxygen, the fuel injection amount increases accordingly, and the numerical theoretical air-fuel ratio becomes smaller than the value when gasoline fuel is used (14.6), but as a result, the air-fuel ratio is actually used. The alcohol fuel stoichiometric (for example, 12.0) is controlled. When using alcohol fuel, the numerical value of the air / fuel ratio is different from that when using gasoline fuel, and the oxygen concentration in the exhaust gas and sensor output are the same, resulting in the same gas state (lean, stoichiometric, rich). It becomes.

  The fuel supply system 40 includes a main tank 50, a sub tank 60, a fuel supply path 70, a bypass path 72, a recovery path 74, bypass valves VA and VB, open / close valves VC and VD, a fuel property sensor 100, and the like.

  The main tank 50 stores fuel and supplies the fuel to the injector 12 through the connected fuel supply path 70. As this fuel, gasoline or an alcohol mixed fuel obtained by mixing alcohol with gasoline is used.

  The fuel property sensor 100 is provided in the middle of the fuel supply path 70. The fuel property sensor 100 detects the alcohol concentration in the fuel passing through the fuel supply path 70 and outputs it to the ECU 20.

  Here, as the fuel property sensor 100, for example, an optical sensor as shown in FIG. 2 or FIG. 3 is used.

  A fuel property sensor 100A shown in FIG. 2 includes a light source 101 and a light receiving unit 102 provided on a glass plate 104, a reflection plate 103 facing the light source 101 and the light receiving unit 102 with a fuel supply path 71 interposed therebetween. In the fuel property sensor 100A having such a structure, for example, if the glass surface of the glass plate 104 becomes dirty, the refraction angle of reflected light from the reflection plate 103 may change, and the reflection surface of the reflection plate 103 may change. When it gets dirty, the reflection angle of light changes, which causes a decrease in detection accuracy (detection sensitivity).

  The fuel property sensor 100B shown in FIG. 3 is provided on the glass plate 105 and the glass plate 106 so that the fuel supply path 71 is sandwiched between the glass plates 105 and 106, and the light source 101 and the light receiving unit 102 are opposed to each other. In the fuel property sensor 100B having such a structure, for example, dirt on the glass surfaces of the glass plates 105 and 106 that come into contact with the fuel absorbs light from the light source 101 and causes a decrease in detection accuracy (detection sensitivity).

  The sub-tank 60 stores fuel having a known property connected to the fuel supply path 70 upstream of the fuel property sensor 100. Here, the fuel having a known property is, for example, an alcohol mixed fuel having an alcohol concentration of a predetermined value.

  The recovery path 74 connects the fuel supply path 70 downstream of the fuel property sensor 100 and the main tank 50, and is provided for recovering fuel having a known property supplied from the sub tank 60 to the main tank 50.

  The bypass passage 72 connects the upstream side of the sub-tank 60 of the fuel supply path 70 and the downstream side of the recovery path 74 to bypass the fuel supplied from the main tank 50 without passing through the fuel property sensor 100 side. Is provided.

  The bypass valves VA and VB are provided at the upstream end and the downstream end of the bypass passage 72, respectively, and selectively open and close the bypass passage 72 and the fuel supply passage 71 corresponding to the bypass passage 72 according to a control signal from the ECU 20. To do. The fuel supply passage 71 corresponding to the bypass passage 72 is a portion of the fuel supply passage 70 that branches from the bypass passage 72 and merges again. When the bypass valves VA and VB open the bypass passage 72, the fuel supply passage 71 is closed, the fuel from the main tank 50 passes through the bypass passage 72, and the fuel from the main tank 50 passes through the fuel property sensor 100. No longer. When the bypass valves VA and VB close the bypass passage 72, the fuel supply passage 71 is opened, and the fuel from the main tank 50 passes through the fuel supply passage 71.

The on-off valve VC opens and closes a passage between the sub tank 60 and the fuel supply passage 71 in accordance with a control signal from the ECU 20.
The on-off valve VD is provided in the middle of the recovery path 74 and opens and closes the recovery path 74 in accordance with a control signal from the ECU 20.

Next, the operation of the fuel supply system 40 will be described with reference to FIGS.
During normal operation of the internal combustion engine 1, as shown in FIG. 4, the fuel property is detected by the fuel property sensor 100, and the fuel property is determined based on the detection result of the fuel property sensor 100. The bypass passage 72 is closed by bypass valves VA and VB. The on-off valves VC and VD are also closed. Thereby, the fuel FL from the main tank 50 is supplied to the injector 12 through the fuel supply path 70. The fuel property detected by the fuel property sensor 100 is used, for example, for air-fuel ratio control before the internal combustion engine 1 is warmed up.

  On the other hand, after the warm-up of the internal combustion engine 1 is completed, sensitivity correction of the fuel property sensor 100 and the like are executed during the execution of the air-fuel ratio feedback control based on the output of the A / F sensor 17. Since the A / F sensor 17 is activated after the warm-up of the internal combustion engine 1 is completed, the air-fuel ratio control can be performed without using the output of the fuel property sensor 100. When the sensitivity of the fuel property sensor 100 is corrected, as shown in FIG. 5, the detection of the property of the fuel FL from the main tank 50 by the fuel property sensor 100 is interrupted, and the property of the fuel SFL whose property supplied from the sub tank 60 is known. Is detected. The bypass passage 72 is opened by bypass valves VA and VB. In addition, the open / close valves VC and VD are opened. As a result, the fuel FL from the main tank 50 is supplied to the injector 12 through the bypass passage 72, and the fuel SFL having a known property from the sub tank 60 passes through the fuel property sensor 100 and then passes to the main tank 50 through the recovery passage 74. Collected.

Next, an example of sensitivity correction processing by the ECU 20 as the fuel property detection device will be described with reference to a flowchart shown in FIG.
First, it is determined whether the warm-up of the internal combustion engine 1 has been completed based on the state of the A / F sensor activation flag indicating whether the A / F sensor 17 has been activated (step S1). Drives the bypass valves VA and VB (step S2) and opens the bypass passage 72 (bypass mode). As a result, the fuel from the main tank 50 flows through the bypass passage 72 bypassing the fuel supply passage 71 provided with the fuel property sensor 100.

Next, the open / close valve VC is opened (step S3). As a result, the fuel SFL having a known property is supplied to the fuel supply passage 71.
Next, the release valve VD is opened (step S4). As a result, the fuel SFL having a known property from the sub-tank 60 passes through the fuel property sensor 100 and is then recovered to the main tank 50 through the recovery path 74.

  Next, it is determined whether the change in the sensor output from the fuel property sensor 100 is saturated (the sensor output becomes constant), and the sensitivity is corrected when the change in the sensor output is saturated (step S6). Specifically, the detected fuel property obtained from the sensor output of the fuel property sensor 100 is compared with the known property of the fuel SFL, and the output error of the fuel property sensor 100 is corrected. That is, the deviation of the property detected by the fuel property sensor 100 is corrected based on the known property of the fuel SFL. In order to correct the sensor output error of the fuel property sensor 100, for example, a sensitivity correction coefficient to be multiplied with the sensor output of the fuel property sensor 100 is obtained.

  In step S6, by correcting the sensor output error of the fuel property sensor 100, when detecting the property of the fuel from the main tank 50, it becomes possible to detect with high accuracy, and the air-fuel ratio control until the warm-up is completed is more precise. Can be executed.

Next, an example of the abnormality detection process accompanying the sensitivity correction process by the ECU 20 as the fuel property detection device will be described with reference to the flowchart shown in FIG.
Steps S11 to S15 are the same as the processing in FIG.
In step S16, a sensitivity correction coefficient K for multiplying the sensor output of the fuel property sensor 100 is calculated.

  Next, it is determined whether the sensitivity correction coefficient K does not exceed a predetermined threshold value, that is, whether the sensitivity correction coefficient K is within a predetermined range (step S17). If the sensitivity correction coefficient K for correcting the sensor output error of the fuel property sensor 100 is not within the predetermined range, it can be determined that the sensor output error is also large, so the fuel property sensor 100 determines that there is an abnormality. , MIL (malfunction indicator light) is turned on to notify the driver.

  As described above, the abnormality of the fuel property sensor 100 is determined based on the sensitivity correction coefficient K calculated to correct the sensor output error of the fuel property sensor 100, so that the output error is accurate within a relatively small range. The property detection can be maintained, and the abnormality can be detected when the output error becomes relatively large.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows an example of an optical fuel property sensor. It is a figure which shows the other example of an optical fuel property sensor. It is a figure which shows operation | movement of the fuel supply system at the time of fuel property determination. It is a figure which shows operation | movement of the fuel supply system at the time of a sensitivity correction | amendment. It is a flowchart which shows an example of the process sequence at the time of the correction | amendment of the output error of a fuel property sensor. It is a flowchart which shows an example of the process sequence at the time of abnormality detection of a fuel property sensor.

Explanation of symbols

20 ... ECU (correction means, abnormality detection means)
40 ... Fuel supply system 50 ... Main tank 60 ... Sub tank 70 ... Fuel supply passage 72 ... Bypass passage 74 ... Recovery passage 100 ... Fuel property sensors VA, VB ... Bypass valves VC, VD ... Open / close valves

Claims (3)

A fuel property sensor for detecting the property of fuel supplied to the internal combustion engine;
After the completion of warm-up of the internal combustion engine, during the execution of the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor, the fuel property of the fuel whose property is known is detected by the fuel property sensor, and the detected fuel property is known. Correction means for correcting the output error of the fuel property sensor based on the comparison with the fuel property;
A fuel property detection device for an internal combustion engine. The correction means calculates a correction coefficient for matching the detected fuel property with the known fuel property,
When the correction coefficient is not within a predetermined range, the fuel property sensor has an abnormality detection means that determines that the fuel property sensor is abnormal.
The fuel property detecting device for an internal combustion engine according to claim 1. A main tank for storing fuel;
A fuel supply path for supplying fuel in the main tank to the internal combustion engine and provided with the fuel property sensor;
A sub-tank connected to the fuel supply path upstream of the fuel property sensor and storing fuel having a known property;
A recovery path for connecting the fuel supply path downstream of the fuel property sensor and the main tank, and recovering fuel having a known property supplied from the sub tank;
A bypass passage connecting the upstream side of the sub tank of the fuel supply path and the downstream side of the recovery path;
First and second valve means for selectively opening and closing the bypass passage and a fuel supply passage corresponding to the bypass passage;
Third valve means for opening and closing a passage between the sub tank and the fuel supply passage;
Fourth valve means for opening and closing the recovery path;
The fuel property detection device for an internal combustion engine according to claim 1 or 2, characterized by comprising:

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