JP2008255951A - Sulfur concentration determination device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sulfur concentration determination device of an internal combustion engine capable of prematurely determining the sulfur concentration of a fuel supplied thereto. <P>SOLUTION: An engine system of this embodiment comprises: a catalyst 38 capable of storing and discharging the oxygen contained in an exhaust gas; an oxygen sensor 66 for detecting the air-fuel ratio of the exhaust gas after passing through the catalyst 38; a lubrication detection sensor 91 for determining the presence or absence of lubrication; and an ECU 4 for determining the sulfur concentration of the present supplied fuel according to the previous output value of the oxygen sensor while the previously supplied fuel is used and the present output value of the oxygen sensor while the present supplied fuel is used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sulfur concentration determination device for an internal combustion engine.

2. Description of the Related Art Conventionally, there has been known a catalyst deterioration detection device in which an air-fuel ratio sensor or an oxygen sensor is disposed downstream of a three-way catalyst disposed in an exhaust passage of an internal combustion engine.
For example, Patent Document 1 discloses that the deterioration of the catalyst is detected based on the average value of the trajectory length before and after refueling of the output value from the oxygen sensor arranged on the downstream side of the three-way catalyst, and high sulfur gasoline. A catalyst deterioration detection device for determining the use of a catalyst is disclosed.
In this apparatus, high sulfur gasoline can be detected by utilizing the fact that the three-way catalyst is temporarily deteriorated due to the use of high sulfur gasoline and the trajectory length of the output of the oxygen sensor becomes long. Specifically, the value obtained by adding a predetermined value to the average value of the trajectory length of the output of the oxygen sensor calculated after the current refueling and the average value of the trajectory length of the output of the oxygen sensor calculated after the previous refueling Is used to determine the use of high sulfur gasoline.

JP 2003-148137 A

  However, in the apparatus disclosed in Patent Document 1, use of high sulfur gasoline can be determined only after a predetermined number of times of refueling has been performed. Therefore, there is a problem that it cannot be determined that high-sulfur gasoline has been used at an early stage.

  Accordingly, an object of the present invention is to provide a sulfur concentration determination device for an internal combustion engine that can determine the sulfur concentration of fuel supplied at an early stage.

The above-described objects include a catalyst capable of occluding and releasing oxygen in exhaust gas, an oxygen sensor for detecting the oxygen concentration of exhaust gas after passing through the catalyst, an oil supply determining means for determining the presence or absence of fuel supply, and a previous fuel supply. Sulfur concentration determination means for determining the sulfur concentration of fuel supplied this time based on the previous output value of the oxygen sensor during use of fuel and the current output value of the oxygen sensor during use of fuel supplied this time It can achieve by the sulfur concentration determination apparatus of the internal combustion engine characterized by comprising.
When high-sulfur fuel is used, the catalyst temporarily deteriorates, and the air-fuel ratio of the exhaust gas after passing through the catalyst varies between before the high-sulfur fuel is used and after the high-sulfur fuel is used. . Therefore, since the output of the oxygen sensor also fluctuates, the sulfur concentration of the fuel supplied this time can be determined based on the previous output value and the current output value. Moreover, since it can be determined if the previous output value and the current output value can be grasped before and after refueling, the sulfur concentration of the fuel refueled this time can be determined early.

Further, in the above configuration, the sulfur concentration determination means may employ a configuration in which the determination is performed based on a change between an intermediate value of the amplitude of the previous output value and an intermediate value of the amplitude of the current output value.
By comparing the intermediate value of the amplitude of the output value of the oxygen sensor, the detection accuracy of the deterioration of the catalyst is improved. This facilitates the determination of the sulfur concentration of the fuel that has been refueled this time.

In the above configuration, the exhaust gas temperature sensor for detecting the temperature of the exhaust gas is provided, and the sulfur concentration determination means includes a change in the intermediate value when an output value of the exhaust gas temperature sensor is equal to or higher than a predetermined value, and the exhaust gas temperature. A configuration in which the determination is performed based on the change in the intermediate value when the output value of the sensor is less than the predetermined value can be employed.
For example, when the fuel supplied this time is oxygen-containing fuel, since the fuel contains oxygen, the air-fuel ratio of the exhaust gas may fluctuate and the sulfur concentration of the fuel flow may be erroneously determined. Further, the decrease in the oxygen releasing function due to catalyst deterioration is more remarkable at low temperatures than when the exhaust gas is at a temperature higher than a predetermined temperature. Therefore, the oxygen-containing fuel is determined by making a determination based on the change in the intermediate value when the output value of the exhaust temperature sensor is equal to or greater than the predetermined value and the change in the intermediate value when the output value of the exhaust temperature sensor is less than the predetermined value. Even when oil is supplied, it is possible to prevent an erroneous determination of the sulfur concentration.

  ADVANTAGE OF THE INVENTION According to this invention, the sulfur concentration determination apparatus of the internal combustion engine which can determine the sulfur concentration of the fuel supplied fuel early can be provided.

  Embodiments according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an engine system according to the present embodiment. A multi-cylinder in-cylinder injecting gasoline engine (hereinafter abbreviated as “engine”) 2 mounted on an automobile and its electronic control unit ( Hereinafter, the schematic configuration of the ECU 4 is referred to as “ECU”. In FIG. 1, the configuration of one cylinder is mainly shown.
Here, the output of the engine 2 is finally transmitted as a driving force to the wheels via a transmission (not shown). The engine 2 is provided with a fuel injection valve 12 that directly injects fuel into the combustion chamber 10 and an ignition plug 14 that ignites the injected fuel.

Fuel is stored in the fuel tank 90. The fuel stored in the fuel tank 90 is pumped to the fuel injection valve 12 through a delivery pipe (not shown).
The fuel tank 90 is provided with a fuel supply detection sensor 91. The fuel supply detection sensor 91 outputs a predetermined output to the ECU 4 by opening and closing the fuel supply cap. Thereby, ECU4 can determine the presence or absence of fuel supply. Further, the ECU 4 stores the presence / absence of refueling as a history.

  The intake port 16 connected to the combustion chamber 10 is opened and closed by driving an intake valve (not shown). A surge tank 22 is provided in the middle of the intake passage 20 connected to the intake port 16, and a throttle valve 26 whose opening degree is adjusted by a throttle motor 24 is provided upstream of the surge tank 22.

  The intake air amount is adjusted by the opening of the throttle valve 26 (throttle opening TA). The throttle opening degree TA is detected by a throttle opening degree sensor 28, and the intake pressure PM in the surge tank 22 is detected by an intake pressure sensor 30 provided in the surge tank 22 and read into the ECU 4.

  The exhaust port 32 connected to the combustion chamber 10 is opened and closed by driving an exhaust valve (not shown). The exhaust passage 36 connected to the exhaust port 32 performs oxidation of unburned components (HC, CO) and reduction of nitrogen oxide (NOx) in the exhaust gas, and has a three-way catalyst having oxygen storage and release functions. A start catalyst 38 is provided. Further, a NOx occlusion reduction catalyst 40 is provided in the exhaust passage 36 downstream of a start catalyst (hereinafter simply referred to as “catalyst”) 38.

  Further, in the exhaust passage 36, an exhaust temperature sensor 63 and an air-fuel ratio sensor 64 are disposed upstream of the catalyst 38, a first oxygen sensor 66 is disposed between the catalyst 38 and the NOx storage reduction catalyst 40, and a NOx storage reduction catalyst. A second oxygen sensor 68 is disposed downstream of the sensor 40. As the air-fuel ratio sensor 64, a linear air-fuel ratio sensor that outputs a voltage signal corresponding to the air-fuel ratio of the exhaust gas flowing into the catalyst 38 is used. Both oxygen sensors 66 and 68 are sensors that detect whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio based on the residual oxygen concentration in the exhaust gas. Further, the temperature of the exhaust gas flowing into the catalyst 38 can be detected by the exhaust temperature sensor 63.

The ECU 4 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the operation of the entire engine. The ECU 4 functions as a sulfur concentration determination unit, which will be described in detail later.
In addition to the throttle opening sensor 28 and the intake pressure sensor 30, the ECU 4 inputs a signal from an accelerator opening sensor 56 that detects the amount of depression of the accelerator pedal 44 (accelerator opening ACCP). Further, the ECU 4 receives signals from an engine speed sensor 58, an air-fuel ratio sensor 64, a first oxygen sensor 66, and a second oxygen sensor 68 that detect the engine speed NE from the rotation of the crankshaft 54, respectively.

  The ECU 4 appropriately controls the fuel injection timing, the fuel injection amount, and the throttle opening TA of the engine 2 based on the detection contents from the various sensors described above. As a result, the combustion mode is switched between stratified combustion and homogeneous combustion. In the present embodiment, the combustion mode is determined based on a map of the engine speed NE and the load factor eklq during normal operation excluding conditions such as cold. Here, the “load factor” indicates the ratio of the current load to the maximum engine load, and is obtained from a map using, for example, the accelerator opening ACCP and the engine speed NE as parameters.

  When the combustion mode is set to stratified combustion, the throttle valve 26 is in a considerably open state, and control is performed so that an amount of fuel considerably smaller than the stoichiometric air-fuel ratio with respect to the intake air amount is injected in the latter half of the compression stroke. Is done. As a result, at the ignition timing, the ignitable rich air-fuel mixture that exists in the vicinity of the ignition plug 14 is ignited and stratified combustion is performed.

  On the other hand, when the combustion mode is set to homogeneous combustion, the opening degree of the throttle valve 26 is adjusted according to the degree of the accelerator opening degree ACCP, and an amount of fuel in which the air-fuel ratio of the engine becomes the stoichiometric air-fuel ratio is taken into the intake stroke. It is controlled to be injected inside. As a result, at the ignition timing, the entire combustion chamber 10 is occupied, the engine air-fuel ratio is the stoichiometric air-fuel ratio, and a homogeneous air-fuel mixture is ignited to perform homogeneous combustion.

  In order to enhance the oxidation / reduction ability of the catalyst 38, the ECU 4 sets the fuel injection amount to the output of the air-fuel ratio sensor 64 or the output thereof so that the air-fuel ratio of the exhaust gas flowing into the catalyst 38 becomes the stoichiometric air-fuel ratio. Feedback control is performed based on the output of the first oxygen sensor 66. Moreover, ECU4 performs the sulfur concentration determination process which determines the sulfur concentration contained in fuel.

  Next, the oxygen storage reaction and the oxygen release reaction in the catalyst 38 will be described. When fuel-lean exhaust gas flows into the catalyst 38, excess oxygen in the exhaust gas is occluded by a catalyst carrier (for example, composed of a noble metal such as Pt, Pd, Rh, Ce). On the other hand, when a fuel-rich exhaust gas, that is, a reducing gas (for example, CO, HC) flows into the catalyst 38, the reducing gas is oxidized by oxygen released from the catalyst carrier and discharged as CO2 or H2O.

  By the way, it is known that the reaction rate of the oxygen storage reaction is larger than the reaction rate of the oxygen releasing reaction in the catalyst. This tendency becomes more prominent as the degree of deterioration of the catalyst increases. That is, when the catalyst 38 is deteriorated by poisoning with sulfur contained in the fuel, the reaction rate of the oxygen release reaction in the catalyst 38 is greatly reduced. For this reason, with a deteriorated catalyst, the reaction rate of the oxygen release reaction is very small compared to the reaction rate of the oxygen storage reaction. Therefore, the output value of the first oxygen sensor 66 varies between when the catalyst is deteriorated and when it is not deteriorated.

Next, the sulfur concentration determination process executed by the ECU 4 will be described.
FIG. 2 is a flowchart showing an example of the sulfur concentration determination process executed by the ECU 4.
The ECU 4 determines whether there is a refueling history (step S1).
If there is a refueling history, the ECU 4 determines whether or not the sub-feedback learning after refueling has been completed (step S2).
Here, the sub-feedback learning is a process for the ECU 4 to calculate an intermediate value of the amplitude of the output value of the first oxygen sensor 66 based on the output value from the first oxygen sensor 66.

FIG. 3 is a conceptual explanatory diagram of sub-feedback learning.
First, before specifically explaining the sub-feedback learning, the fluctuation of the air-fuel ratio of the exhaust gas before and after passing through the catalyst 38 will be explained.
As shown in FIG. 3, the output value of the first oxygen sensor 66 behaves alternately in a lean state and a rich state. For example, when the output value of the first oxygen sensor 66 is in a rich state, the air-fuel ratio of the exhaust gas before passing through the catalyst 38 is in a lean state, and the exhaust gas in the lean state is converted into oxygen by the catalyst 38. Occluded, the output value of the first oxygen sensor 66 becomes rich. Therefore, in this case, the output value of 64 indicates a lean state, and the output value of the first oxygen sensor 66 indicates a rich state.

  When the output value of the first oxygen sensor 66 is in the lean state, the air-fuel ratio of the exhaust gas before passing through the catalyst 38 is in a rich state, and the exhaust gas in the rich state is converted into oxygen by the catalyst 38. Released to a lean state. Therefore, in this case, the output value of 64 indicates a rich state, and the output value of the first oxygen sensor 66 indicates a lean state.

As shown in FIG. 3, the ECU 4 has a steady value R1 in the rich state of the output value of the first oxygen sensor 66 (hereinafter referred to as “previous output value”) when the fuel supplied last time is used. The intermediate value M1 is calculated based on the steady value L1 in the lean state. Thereby, the intermediate value of the amplitude of the output value of the first oxygen sensor 66 can be calculated.
Similarly, the ECU 4 has a steady state value R2 in the rich state of the output value of the first oxygen sensor 66 (hereinafter referred to as “current output value”) when the fuel supplied this time is used, and in the lean state. The intermediate value M2 is calculated based on the steady-state value L2.
Thus, the sub feedback learning process is completed by calculating the intermediate value M2 (Yes in step S2).
Note that the intermediate value M1 of the previous output value is calculated and stored by the ECU 4 while the engine 2 is being driven by the fuel supplied last time.

When the sub-feedback learning process is completed, the intermediate value M1 is compared with the intermediate value M2 (step S3).
As shown in FIG. 3, when the intermediate values M1 and M2 are compared, it can be seen that the intermediate value M2 is output to the richer side than the intermediate value M1. This is because the sulfur contained in the fuel temporarily deteriorates the catalyst 38 and the oxygen release rate of the catalyst 38 decreases. Thereby, it can be determined that the fuel supplied this time has a higher sulfur concentration in the fuel than the fuel supplied last time (step S4).
Specifically, when the difference between the intermediate values M1 and M2 is greater than or equal to a predetermined value, it is determined that the concentration of sulfur contained in the fuel is greater than the previously refueled fuel, and when the difference is less than the predetermined value, It is determined that there is no change in the sulfur concentration.

As described above, when the high sulfur fuel is used, the catalyst 38 is temporarily deteriorated, and the air-fuel ratio of the exhaust gas after passing through the catalyst 38 is the same as before the high sulfur fuel is used. It fluctuates after and after. Accordingly, since the output of the first oxygen sensor 66 also fluctuates, the sulfur concentration of the fuel supplied this time can be determined based on the previous output value and the current output value. Moreover, since it can be determined if the previous output value and the current output value can be grasped before and after refueling, the sulfur concentration of the fuel refueled this time can be determined early.
Further, since the sulfur concentration of the fuel is determined based on the fluctuation between the intermediate value of the amplitude of the previous output value and the intermediate value of the current output value, the detection accuracy of the deterioration of the catalyst 38 is improved. This facilitates the determination of the sulfur concentration of the fuel that has been refueled this time.

Next, step S3 will be described in more detail.
The ECU 4 determines the sulfur concentration based on the change in the intermediate value when the output value of the exhaust temperature sensor 63 is equal to or higher than the predetermined value and the change in the intermediate value when the output value of the exhaust temperature sensor 63 is less than the predetermined value. Make a decision.
Specifically, the intermediate value fgsfbBC of the fuel supplied last time and the intermediate value fgsfbAC of the fuel supplied this time calculated with the output value of the exhaust temperature sensor 63 being less than 700 degrees, and the exhaust temperature sensor The ECU 4 determines the sulfur concentration based on the intermediate value fgsfbBH of the fuel supplied last time and the intermediate value fgsfbAH of the fuel supplied this time calculated in a state where the output value of 63 indicates 700 degrees or more.
Using the above values, calculation is made according to the following equation.
(FgsfbAC-fgsfbBC) / (fgsfbAH-fgsfbBH) …… (1)
When the value calculated by the above formula (1) is larger than the predetermined value, it is determined that the sulfur concentration contained in the fuel is larger than the fuel refueled last time, and when the value is less than the predetermined value, the sulfur concentration is determined. It is determined that there is no change.

Here, the above formula shows the ratio of the change in the intermediate value when the exhaust gas is low temperature (less than 700 degrees) to the change in the intermediate value when the exhaust gas is high temperature (700 degrees or more). Yes.
That is, when the calculated value by the above formula (1) is equal to or larger than the predetermined value, it indicates that the fluctuation is larger at the low temperature than the middle value when the exhaust gas is high. . In addition, when the calculated value by the above formula (1) is less than the predetermined value, it indicates that the fluctuation of the intermediate value at the high temperature and the fluctuation of the intermediate value at the low temperature are substantially the same. ing.

  The reason for determining the sulfur concentration using such an equation is that, for example, when the fuel supplied this time is an oxygen-containing fuel, oxygen is contained in the fuel, so the combustion stoichiometric air-fuel ratio of the exhaust gas is Fluctuating, there is a risk of misjudging the sulfur concentration of the fuel stream. In addition, the decrease in the oxygen release function due to the sulfur poisoning deterioration of the catalyst becomes more conspicuous when the exhaust gas is at a lower temperature than when the exhaust gas is higher than a predetermined temperature. Therefore, by determining the sulfur concentration using the above equation (1), when oxygen-containing fuel is used, the calculated value by the above equation (1) is a small value regardless of the temperature of the exhaust gas. It becomes. By calculating as described above, it is possible to prevent erroneous determination of the sulfur concentration even when oxygen-containing fuel is supplied.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

  For example, the ECU 4 grasps the value of the sulfur concentration corresponding to the output value (intermediate value) of the first oxygen sensor 66, and the intermediate value of the amplitude of the previous output value and the intermediate value of the amplitude of the current output value are obtained. Based on the fluctuation, the sulfur concentration of the fuel supplied this time may be specifically determined.

It is the schematic diagram which showed the structure of the engine system which concerns on a present Example. It is the flowchart which showed an example of the sulfur concentration determination process which ECU performs. It is a conceptual explanatory drawing of sub feedback learning.

Explanation of symbols

2 Engine 4 ECU (Sulfur concentration determination means)
DESCRIPTION OF SYMBOLS 10 Combustion chamber 12 Fuel injection valve 14 Spark plug 16 Intake port 20 Intake passage 22 Surge tank 24 Throttle motor 26 Throttle valve 28 Throttle opening sensor 30 Intake pressure sensor 32 Exhaust port 36 Exhaust passage 38 Catalyst 40 NOx storage reduction catalyst 44 Accelerator pedal 54 crankshaft 56 accelerator opening sensor 58 engine speed sensor 63 exhaust temperature sensor 64 air-fuel ratio sensor 66 first oxygen sensor 68 second oxygen sensor 90 fuel tank 91 oil supply detection sensor

Claims (3)

A catalyst capable of storing and releasing oxygen in the exhaust gas;
An oxygen sensor for detecting the oxygen concentration of the exhaust gas after passing through the catalyst;
Refueling determination means for determining the presence or absence of refueling;
Based on the previous output value of the oxygen sensor during the use of the previously refueled fuel and the current output value of the oxygen sensor during the use of the currently refueled fuel, the sulfur concentration of the fuel refueled this time is determined. An apparatus for determining sulfur concentration of an internal combustion engine, comprising: a sulfur concentration determining means.   The said sulfur concentration determination means performs the said determination based on the fluctuation | variation of the intermediate value of the amplitude of the said last output value, and the intermediate value of the amplitude of the said current output value, The said determination is characterized by the above-mentioned. A sulfur concentration determination device for an internal combustion engine. An exhaust temperature sensor for detecting the temperature of the exhaust gas;
The sulfur concentration determination means is based on the change in the intermediate value when the output value of the exhaust temperature sensor is greater than or equal to a predetermined value and the change in the intermediate value when the output value of the exhaust temperature sensor is less than the predetermined value. The determination of sulfur concentration in an internal combustion engine according to claim 2, wherein the determination is performed.

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