JP2008045459A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of reducing emission of HC generated at the start of the internal combustion engine. <P>SOLUTION: Oxygen concentration in suction air supplied into a combustion chamber during a predetermined period of time in start of the internal combustion engine is controlled to enrich oxygen and is raised (thickened) by an oxygen concentration raising device 500, and combustion of air fuel mixture is activated. Consequently, HC emitted from the engine is reduced and HC emission quantity is reduced by shortening catalyst warming up period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that reduces harmful gases such as hydrocarbons when the internal combustion engine of an automobile is started.

  In recent years, a technique for reducing hydrocarbons (hereinafter referred to as HC) discharged at the time of starting from an internal combustion engine mounted on an automobile has been proposed from the viewpoint of reducing emissions. For example, in an internal combustion engine using gasoline as a fuel, at the start of the internal combustion engine, the catalyst temperature of the catalyst device provided in the exhaust pipe is increased to activate the catalyst, and harmful gases such as HC contained in the exhaust gas are activated. A technology that reduces emissions is known (catalyst warm-up technology). In order to warm up the catalyst at an early stage, a technique is known in which the ignition temperature is intentionally significantly retarded (retarded) to increase the exhaust temperature (see Patent Document 1 and Patent Document 2).

  However, if the ignition timing is greatly retarded (retarded) as described above to make the combustion worse, the catalyst can be warmed up early, but the combustion is worsened and the combustion itself is not stable. Conversely, the amount of HC increases.

  Therefore, in order to solve this problem, in an internal combustion engine in which the ignition timing is retarded at the start of the engine and the exhaust gas temperature is raised, hydrogen is added to the main fuel when the exhaust gas temperature is raised to retard the ignition timing. In addition, there is a technology that raises the exhaust gas temperature, burns HC that may be discharged unburned due to the combustion promotion effect of hydrogen addition, and reduces the HC emission amount (see Patent Document 3).

JP-A-8-218852 JP-A-11-315741 JP 2005-48631 A

  The catalyst warm-up control by the ignition timing retard can warm the catalyst early, and after that, the HC reduction effect by the activated catalyst is great. However, as described in Patent Document 3, a large amount of HC is discharged when the ignition timing is retarded. In addition, from the viewpoint of combustion stability, the region where the retarding is possible is limited, and the effect above a certain level is obtained. Difficult to get. On the other hand, as described in Patent Document 3, the method of adding hydrogen to the fuel has a problem in the method of generating and storing hydrogen from the viewpoint of safety because hydrogen itself has self-ignitability. It is necessary to control the amount of hydrogen more precisely in order to add hydrogen.

  The present invention has been made in view of the above, and an object of the present invention is to increase the combustion temperature by enriching the intake air with oxygen when starting the internal combustion engine to burn HC, and from the internal combustion engine. An object of the present invention is to provide a control device for an internal combustion engine capable of reducing the amount of HC discharged, reducing the time until catalyst warm-up, and reducing the amount of HC emission.

  In order to achieve the above object, a control device for an internal combustion engine according to the present invention comprises a catalyst device for purifying exhaust gas, and in the internal combustion engine that burns a mixture of fuel and air in a combustion chamber, the internal combustion engine is started. An oxygen concentration raising means for enriching oxygen in the intake air supplied into the combustion chamber during the control is provided.

  The present invention can reduce the generation of hydrocarbons at the time of combustion by increasing the oxygen concentration of the intake air when starting the engine, and can reduce the emission of hydrocarbons when the catalyst is not activated. The exhaust temperature can be increased, and the warm-up time of the catalyst can be shortened.

  The oxygen concentration increasing means in the control device for an internal combustion engine according to the present invention is characterized in that oxygen in the intake air is enriched until a predetermined time elapses after the internal combustion engine is started. Can be controlled more easily.

  The oxygen concentration increasing means in the control device for an internal combustion engine of the present invention enriches oxygen in the intake air until the detected temperature of the catalyst device or the estimated temperature of the catalyst device becomes a predetermined value or higher after the internal combustion engine is started. The oxygen enrichment control can be performed until a temperature at which the catalyst is reliably activated is obtained by a detection sensor or the like that detects the temperature of the catalyst device.

  The oxygen concentration increasing means in the control apparatus for an internal combustion engine according to the present invention includes an oxygen enriched film provided in a bypass passage provided in an intake pipe of the internal combustion engine, and an air amount for controlling an air flow rate passing through the oxygen enriched film. And the control means, and the oxygen concentration raising means can be made compact by the oxygen-enriched film.

  The oxygen concentration increasing means in the control device for an internal combustion engine of the present invention is composed of an ozone generator connected to the intake pipe of the internal combustion engine and an air amount control means for controlling the ozone flow rate generated from the ozone generator. The oxygen concentration of the intake air can be increased by the ozone generated from the ozone generator.

  Furthermore, the control device for an internal combustion engine according to the present invention is characterized in that ignition timing retard control is performed at the time of engine start, and the exhaust temperature is controlled by synergistic action of enriching intake air and ignition timing retard. The catalyst warm-up can be further increased by increasing the amount of catalyst, and the amount of HC discharged when the ignition timing retard control is performed can be reduced by enriching the intake air with oxygen.

  According to the control apparatus for an internal combustion engine of the present invention, when the internal combustion engine is started, by increasing the oxygen concentration in the intake air, the combustion speed increases, the combustion temperature increases, and HC burns. HC discharged from the engine can be reduced, and at the same time, the combustion temperature becomes higher, the exhaust temperature becomes higher and the catalyst warm-up time can be shortened, and the activated catalyst can reduce the HC emission amount.

  Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a control device for an internal combustion engine according to a first embodiment of the present invention, and is a schematic configuration diagram showing an oxygen concentration raising device 500 together with a direct injection engine 2 provided in an intake pipe.

  The engine 2 forms a combustion chamber 101c for each cylinder by a cylinder block 101b, a piston 101a, and the like. The air introduced into each combustion chamber 101c is taken in from the inlet portion 102a of the air cleaner 102, the intake air amount sensor 25, the throttle body 140 in which the electric throttle valve 140a for controlling the intake flow rate is accommodated, and the oxygen concentration raising device 500. And is distributed to the intake pipes 107 connected to the respective combustion chambers 101c, and then led from the intake valves 121 to the combustion chambers 101c.

  The intake air amount sensor 25 detects the intake flow rate and outputs the detected signal to the ECU (engine control device) 11. A throttle sensor 27 for detecting the opening degree of the electric throttle valve 140a is attached to the throttle body 140, and its signal is also output to the ECU 11.

  Fuel such as gasoline is supplied from the fuel tank 50, is primarily pressurized by the fuel pump 51, is regulated to a constant pressure by the fuel pressure regulator 52, and is secondarily pressurized to a high pressure by the high pressure pump 300.

  The secondary pressurized fuel is injected into the combustion chamber 101 c from the fuel injection valve (injector) 54 provided in each combustion chamber 101 c via the pressure accumulation chamber 53. A fuel pressure sensor 56 is attached to the secondary pressurized fuel pipe.

  The fuel injected into the combustion chamber 101c is ignited and burned by spark discharge of the spark plug 109 by the ignition signal that has been increased in voltage by the ignition coil 108, and is discharged from the exhaust valve 120 to the exhaust pipe 209.

  The exhaust pipe 209 is provided with, for example, an air-fuel ratio sensor 208 that linearly detects an oxygen concentration in the exhaust gas and outputs a detection signal to the ECU 11, an exhaust gas purification catalyst 210 that is a catalyst device, and the like. Yes. The exhaust gas purification catalyst 210 is provided with a temperature detection sensor 211, and its detection signal is output to the ECU 11.

  A crank angle sensor 24 is attached to the crankshaft 101d of the engine 2 and outputs a signal representing the rotational position of the crankshaft 101d to the ECU 11. A cam angle sensor 117 is attached to the cam shaft 100 of the exhaust valve 120 and outputs a reference angle signal representing the rotational position of the cam shaft to the ECU 11.

  The ECU 11 controls the fuel injection width, fuel injection timing, and the like of the fuel injection valve 54 based on the signal from the intake air amount sensor 25, the engine coolant temperature detected by the water temperature sensor 28, the detection signal of the air-fuel ratio sensor 208, and the like. To do. Reference numeral 212 denotes a cam shaft of the intake valve 121.

  Here, an oxygen concentration raising device 500, which is a component of the control device for an internal combustion engine according to the embodiment of the present invention, will be described with reference to FIG.

  The oxygen concentration raising apparatus 500 includes an oxygen enriched film 501 and a flow rate control valve 503, and a bypass 502 is provided in the intake pipe 107, and the oxygen enriched film 501 is disposed in the bypass 502. Further, the bypass 502 is provided with a flow rate control valve 503 as an air amount control means for controlling the flow rate of the bypass 502 downstream of the oxygen-enriched membrane 501. Here, the flow rate control valve 503 is not limited to the butterfly type as shown in FIG. 2, and may be an ON / OFF type as long as it can control the flow rate of the bypass 502. In the present embodiment, the oxygen concentration increasing device 500 is provided in the bypass provided in the intake pipe 107, but may be configured to be directly disposed in the intake pipe 107.

  The oxygen-enriched film 501 is a film that allows oxygen to permeate well and separates oxygen and nitrogen. As the oxygen-enriched film 501, for example, a silicon film is generally known. As shown in FIG. 3, when a pressure difference is provided on the upstream and downstream sides of the oxygen-enriched film 501 and air is allowed to pass therethrough, the oxygen-enriched film 501 passes oxygen better than nitrogen. As a result, the oxygen concentration can be increased. If a pressure difference is forcibly provided upstream and downstream of the oxygen-enriched membrane 501, the amount of oxygen-enriched air can be increased, and a means (not shown) using a compressor or the like is also effective as the means. .

  Next, the effect of using the oxygen concentration raising apparatus 500 including the oxygen-enriched film 501 will be described with reference to FIGS.

  FIG. 3 shows the concentration ratio of oxygen and nitrogen upstream and downstream of the oxygen-enriched film 501, and the concentration ratio of nitrogen and oxygen is usually about 79:21 in the natural atmosphere. As shown in FIG. 3, when air is passed through the oxygen-enriched film 501, the oxygen concentration is increased on the downstream side, that is, an oxygen-enriched state (for example, an oxygen concentration of 25%) is obtained.

Incidentally, the combustion rate v can be generally expressed by the following equation.
[Formula 1]
v = k (fuel molecular formula) ^m (O ₂ ) ⁿ exp (−E / RT)
Here, k is a rate constant, R is a gas constant, E is a total activation energy, T is a temperature, and m and n are constants.

  That is, it can be seen that the combustion rate v is a function of the oxygen concentration, in other words, the oxidation reaction (combustion) is promoted as the oxygen concentration increases, although it is not unique.

  FIG. 4 shows the relationship between the time after starting the internal combustion engine and the combustion temperature when the oxygen concentration in the intake air is changed. As shown in FIG. 4, when compared at the same time after starting, it can be seen that the combustion temperature increases as the oxygen concentration increases. In other words, since the catalyst temperature is proportional to the combustion temperature, the vertical axis can be considered as the catalyst temperature for exhaust gas purification, and the time for the catalyst to reach the predetermined temperature becomes faster as the oxygen concentration increases, and the catalyst warm-up performance Will improve dramatically.

  FIG. 5 shows the relationship between the time after starting the internal combustion engine and the hydrocarbons (HC) discharged from the engine. When the oxygen concentration is increased, the flame temperature rises, the quenching in the cooling region near the chamber wall of the combustion chamber 101c decreases, and the amount of HC emission decreases due to the decrease in quenching due to the improvement in combustibility. In the present invention, the amount of HC emission can be reduced by the above effects. For example, when oxygen enrichment is performed at 25%, HC is reduced compared to the case where oxygen enrichment is not performed. Even if is not activated, less HC is released into the atmosphere.

  Control at start-up in the control device for the internal combustion engine when the oxygen concentration increasing device 500 is operated will be described using the flowchart of FIG.

  In step 601, it is determined whether or not the engine is in a starting state. If the engine is stopped, this routine is terminated. If it is determined in step 601 that the engine is started (starting control is in progress), the process proceeds to step 602, where it is determined whether the temperature of the exhaust gas purification catalyst 210 is equal to or lower than a predetermined value. When the temperature of the exhaust gas purifying catalyst 210 is higher than a predetermined value, this routine is finished. When the temperature of the exhaust gas purifying catalyst 210 is equal to or lower than the predetermined value, the routine proceeds to step 603, where oxygen enrichment control is performed by the oxygen concentration raising device 500 for raising the oxygen concentration of the intake air.

  In the oxygen enrichment control in step 603, the ECU 11 controls the flow rate control valve 503 shown in FIG. 2, bypasses the intake air amount to the bypass 502, and passes the oxygen enriched membrane 501, thereby allowing oxygen in the intake air to pass through. The concentration is increased (intensified), the intake air having a high oxygen concentration and the fuel are mixed, and the mixture is sucked into the combustion chamber 101c and combusted.

  In step 604, it is determined whether or not the temperature of the exhaust gas purification catalyst 210 is equal to or higher than a predetermined value. If the temperature is lower than the predetermined value, step 604 is continued. If the temperature is higher than the predetermined value, the process proceeds to step 605. End the oxygen enrichment control.

  In this flowchart, the temperature of the exhaust gas purification catalyst 210 is measured by the temperature detection sensor 211, but the temperature of the exhaust gas purification catalyst 210 estimated from the engine information such as the output value of the water temperature sensor 28 is used. You may do it. The determination may be made using the output value of the water temperature sensor 28 itself. That is, the relationship between the temperature of the exhaust gas purifying catalyst 210 and the output value of the water temperature sensor 28 is as shown in FIG. 7, and reaches the temperature at which the exhaust gas purifying catalyst 210 is activated from the output value of the water temperature sensor 28. When it is estimated that the oxygen enrichment control is performed, the oxygen enrichment control is terminated.

  Further, the predetermined value of the catalyst temperature in step 604 of FIG. 6 may be set to a temperature at which the exhaust gas purification catalyst 210 is sufficiently activated and the HC emission amount from the exhaust gas purification catalyst 210 is sufficiently reduced. desirable.

  In the above embodiment, ignition timing retard control is not performed when the engine is started. However, if ignition timing retard control is performed, the exhaust temperature can be increased by ignition timing retard and combustion is achieved by enriching intake air with oxygen. Because the combustion speed can be increased by increasing the speed, the catalyst warm-up time can be further shortened, and even if ignition timing retard control is performed, the combustion temperature can be increased, so that HC is burned and discharged from the engine. HC can be reduced.

  Next, the oxygen enrichment control by the oxygen concentration raising apparatus 500 will be described with reference to the flowchart of FIG.

  In step 801, it is determined whether or not the engine is started (during start control). If it is determined that the engine is stopped, this routine is terminated. If it is determined in step 801 that the engine has been started (starting control is in progress), the process proceeds to step 802, where oxygen enrichment control by the oxygen concentration raising apparatus 500 is started. The oxygen enrichment control method is as described in detail in FIG.

  In step 803, it is determined whether or not a predetermined time has elapsed after the engine is started. If the predetermined time has not elapsed, this step is continued. If the predetermined time has elapsed, the process proceeds to step 804 and the oxygen enrichment control is performed. finish.

  In this embodiment, the oxygen enrichment control is performed for a predetermined time from the start of the period. However, the oxygen enrichment control may be performed until the integrated value of the engine speed from the start of the start reaches a predetermined value. .

  The present invention is to reduce the HC until the catalyst warms up at the time of cold start of the internal combustion engine. For this reason, the oxygen concentration in the intake air is increased (concentrated). A sufficient effect can be obtained only by performing oxygen enrichment control.

  FIG. 9 shows a second embodiment according to the present invention, and is a schematic configuration diagram showing a direct injection engine 2 provided with an oxygen concentration raising device 500 '. The difference from the first embodiment shown in FIG. 1 is that the oxygen concentration raising device 500 ′ is arranged at a location different from the intake pipe 107, and the air enriched by the oxygen concentration raising device 500 ′ is taken in. The details of the configuration of the in-cylinder injection engine 2 and the like are as described in the description of the first embodiment shown in FIG.

  An oxygen concentration raising apparatus 500 'in the present embodiment will be described with reference to the schematic diagram of FIG.

The oxygen concentration increasing device 500 ′ is provided in parallel with the intake pipe 107, and the oxygen concentration increasing device 500 ′ includes an ozonizer 1001 and a compressor 1002. The ozonizer 1001 is a device that generates ozone (O ₃ ) from air in the atmosphere. Ozonization technology using an ozonizer is realized by applying a high-frequency high voltage between a linear discharge electrode provided on the surface of an alumina ceramic and a plate-like induction electrode provided inside to generate creeping discharge. The technology to make it known is known. The ozonizer is known to have a higher ozone concentration as the flow rate through the ozonizer increases. Therefore, as in the present invention, the compressor 1002 is provided to control the air flow rate to generate ozone with a higher concentration. be able to.

As can be seen from the molecular formula of ozone, when ozone is added to the intake air, oxygen enrichment of the intake air can be expected.
As for the control flow, the same concept as in the first embodiment can be applied, and therefore detailed description is not necessary here.

  In the above embodiment, an in-cylinder injection type gasoline engine is used. However, the present invention is not limited to this, and is not limited to a type of an internal combustion engine such as a spark ignition engine or a compression ignition engine. it can. Further, the present invention can also be applied to a so-called idle stop vehicle, a hybrid vehicle, or the like that includes an engine automatic start / stop device.

  Further, the fuel is not limited to gasoline, and any fuel having an oxidation reaction such as light oil and natural gas can be applied.

  In the present invention, any means for enriching oxygen can be applied as long as it is a means for increasing (increasing) the oxygen concentration, such as using an oxygen cylinder.

The block diagram of the engine control system which shows 1st Embodiment in the control apparatus of the internal combustion engine which provided the oxygen concentration raising apparatus which concerns on this invention. The figure which shows the principal part in the control apparatus of the internal combustion engine which provided the oxygen concentration raising apparatus which concerns on this invention. The figure which shows the outline of the principle of an oxygen enrichment film | membrane. The figure which shows the relationship between the time after engine starting, and combustion temperature when the oxygen concentration in intake air is changed. The figure which shows the relationship between the time after engine starting when the oxygen concentration in intake air is changed, and HC discharge | emission amount discharged | emitted from an engine. The flowchart which shows the oxygen enrichment control based on a catalyst temperature in the control apparatus of the internal combustion engine which concerns on this invention. The figure which shows the relationship between the time after engine starting, a catalyst inlet temperature, a catalyst temperature, and an engine water temperature. The flowchart which shows the oxygen enrichment control based on engine starting time in the control apparatus of the internal combustion engine which concerns on this invention. The block diagram of the engine control system which shows 2nd Embodiment in the control apparatus of the internal combustion engine which provided the oxygen concentration raising apparatus which concerns on this invention. Schematic of the oxygen concentration raising apparatus using an ozone generator.

Explanation of symbols

2 In-cylinder injection engine, 11 ECU (engine control unit), 24 engine speed sensor, 25 intake air flow rate sensor, 27 throttle valve opening sensor, 28 engine water temperature sensor, 50 fuel tank, 51 fuel pump, 52 fuel pressure regulator , 53 Pressure accumulator, 54 Fuel injection valve, 56 Fuel pressure sensor, 100 Control unit, 101a Piston, 101b Each cylinder, 101c Combustion chamber, 101d Crankshaft, 102 Air cleaner, 106 Collector, 107 Intake pipe, 108 Ignition coil, 109 Ignition plug 117 cam angle sensor, 120 exhaust valve, 121 intake valve, 140 throttle body, 140a electronic throttle valve, 208 air-fuel ratio sensor, 209 exhaust pipe, 210 catalyst, 300 high pressure fuel pump, 500 oxygen concentration Temperature increasing device, 501 oxygen-enriched membrane, 502 bypass intake pipe, 503 flow control valve, 1001 ozone generator (ozonizer), 1002 compressor

Claims (7)

A control device for an internal combustion engine that includes a catalyst device that purifies exhaust gas and burns a mixture of fuel and air in a combustion chamber,
The control apparatus for an internal combustion engine, comprising oxygen concentration raising means for enriching oxygen in intake air supplied into the combustion chamber when the internal combustion engine is started.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the oxygen concentration increasing means enriches oxygen in intake air until a predetermined time has elapsed after the internal combustion engine is started.   2. The control of an internal combustion engine according to claim 1, wherein the oxygen concentration increasing means enriches oxygen in the intake air until an integrated value of the engine speed from the start of the internal combustion engine reaches a predetermined value. apparatus.   The oxygen concentration increasing means enriches oxygen in intake air until the detected temperature of the catalyst device or the estimated temperature of the catalyst device becomes a predetermined value or higher after the internal combustion engine is started. Item 2. A control device for an internal combustion engine according to Item 1.   The oxygen concentration increasing means is composed of an oxygen-enriched film provided in a bypass passage provided in the intake pipe of the internal combustion engine, and an air amount control means for controlling the flow rate of air passing through the oxygen-enriched film. 5. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.   The oxygen concentration raising means comprises an ozone generator connected to an intake pipe of the internal combustion engine, and an air amount control means for controlling the flow rate of ozone generated from the ozone generator. Item 5. The control device for an internal combustion engine according to any one of Items 1 to 4.   The control device for an internal combustion engine according to any one of claims 1 to 6, wherein the control device performs ignition timing retard control.

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