JP2008002332A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expedite warming-up of a catalyst after starting an engine, and to properly urge air-fuel mixture combustion at that time. <P>SOLUTION: An internal combustion engine 10 is provided with an ignition timing delay means for warming up the catalyst, an ozone supply means 40 supplying ozone into intake air, and a control means controlling a delay quantity of ignition timing and a supply amount of ozone on the basis of difference in temperature between the temperature of the catalyst 38 and a reference temperature when the temperature of the catalyst 38 is lowered than the reference temperature. By delaying the ignition timing, after burning is generated, and warming-up of the catalyst is urged. At that time, ozone is supplied into the intake air by the ozone supply means 40, therefore combustibility of the air-fuel mixture is enhanced by ozone. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine having a catalyst for exhaust gas purification.

  Conventionally, in a spark ignition type internal combustion engine such as a gasoline engine, the basic ignition timing determined according to the operating state is advanced or retarded by starting correction, knocking correction, etc., and the ignition timing is determined. Yes. When the temperature of the exhaust gas purifying catalyst is lower than its activation temperature, such as when the engine is cold started, the basic ignition timing is corrected to retard the ignition, thereby delaying the combustion timing of the air-fuel mixture. It is possible to warm up.

  On the other hand, Patent Literature 1 discloses a compression ignition type internal combustion engine provided with a self-ignition promoter supplying means for supplying ozone as a fuel self-ignition promoter into a combustion chamber. In this engine, the supply amount of the self-ignition accelerator from the self-ignition accelerator supply means is increased as the cooling water temperature of the engine is lower.

  Furthermore, Patent Document 2 discloses a combustion characteristic improving method for an internal combustion engine in which ozone is supplied to a combustion chamber to burn the fuel.

JP 2002-276404 A Japanese Patent Laid-Open No. 02-191858

  However, when the catalyst is warmed up by retarding the ignition timing as described above, if the ignition retard amount is made larger than a predetermined amount, the combustibility of the air-fuel mixture will deteriorate. As a result, the amount of CO and HC in the exhaust gas increases, which is not preferable.

  Therefore, the present invention provides a control device for an internal combustion engine that promotes catalyst warm-up while appropriately burning an air-fuel mixture.

  In order to solve the above problems, an internal combustion engine control apparatus according to the present invention is an ignition timing retarding means for retarding an ignition timing for catalyst warm-up in an internal combustion engine control apparatus having an exhaust gas purifying catalyst. Ozone supply means for supplying ozone during intake, temperature detection means for detecting or estimating the temperature of the catalyst, and the temperature of the catalyst detected or estimated by the temperature detection means is lower than a predetermined reference temperature A temperature difference deriving means for obtaining a temperature difference from the reference temperature, a control means for controlling a retard amount of the ignition timing and an ozone supply amount based on the temperature difference obtained by the temperature difference deriving means; It is characterized by providing.

  According to the above configuration, when the temperature of the catalyst falls below the predetermined reference temperature, the retard amount of the ignition timing and the ozone supply amount are controlled based on the temperature difference from the reference temperature. Thereby, when the temperature of the catalyst is lower than the reference temperature, the ignition timing is retarded and ozone is supplied into the intake air. By retarding the ignition timing in this way, afterburning occurs and catalyst warm-up can be promoted. On the other hand, since ozone is supplied into the intake air, it becomes possible to continue to properly burn the air-fuel mixture.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a conceptual diagram of a vehicle engine system to which the control device for an internal combustion engine of the present embodiment is applied. An internal combustion engine (engine) 10 according to the present embodiment is a port injection type spark ignition internal combustion engine, which is an in-line four-cylinder engine.

  In the engine 10, air (intake air) drawn from the intake port is introduced into the intake passage 14 via the air cleaner 12. The air flows into the surge tank 18 while its flow rate is adjusted by the opening of the throttle valve 16, and is branched into the intake manifold 22 that is branched and formed corresponding to the cylinder 20. The intake passage 14 is formed by a surge tank 18, an intake manifold 22, an intake pipe 23 connected upstream of them, and the like. A fuel injection valve 24 is disposed in the intake manifold 22. The fuel injected by the fuel injection valve 24 is mixed with the diverted air, and an ignition plug 28 that is operated by the control of the ignition coil 26 via the intake valve 25 is provided in the combustion chamber 30 provided in the upper center. Inhaled. However, the throttle valve 16 of this embodiment is operated in conjunction with the amount of depression of the accelerator pedal, and increases or decreases the opening degree of the intake passage 14.

  In the combustion chamber 30 of each cylinder 20, the air-fuel mixture is ignited by a spark plug 28. A flame generated by the ignition gradually propagates to the entire air-fuel mixture, and normally the entire air-fuel mixture burns. Exhaust gas generated by the combustion is discharged through an exhaust valve 31 to an exhaust manifold 32 that is branched corresponding to each cylinder 20. The exhaust gas is purified by passing through a catalytic converter 38 disposed in the middle of an exhaust pipe 36 that defines an exhaust passage 34 together with the exhaust manifold 32, and is discharged into the atmosphere.

The catalytic converter 38 is filled with an exhaust gas purification catalyst. A three-way catalyst used as an exhaust gas purification catalyst is composed of an oxidation catalyst such as platinum (Pt) or palladium (Pd), a reduction catalyst such as rhodium (Rh), and a promoter such as ceria (CeO ₂ ). The Then, CO and HC contained in the exhaust gas are purified by water (H ₂ O) and carbon dioxide (CO ₂ ) by the action of the oxidation catalyst, and NOx contained in the exhaust gas is nitrogen (N ₂ ) by the action of the reduction catalyst. And purified by oxygen (O ₂ ). Note that the exhaust gas purification catalyst in the catalytic converter 38 needs a heating state of, for example, 400 ° C. to 600 ° C. in order to function effectively. However, when the catalyst temperature exceeds such an activation temperature, for example, reaches a temperature exceeding 800 ° C., there is a problem that the catalyst function deteriorates.

Further, ozone supply means 40 is provided to supply ozone (O ₃ ) during intake, that is, to supply ozone so that the mixture before combustion contains ozone. The ozone supply means 40 has an ozone generator 41, and the ozone generated by the ozone generator 41 is supplied to the portion of the intake passage 14 on the downstream side of the throttle valve 16 in this embodiment. Specifically, the ozone generator 41 includes a pump, a discharger, and a pulse power source, and is operated by a control output of an electronic control unit (ECU) 44 described later. The ozone generator 41 removes dust and the like in the discharger, takes in air from the outside by a pump, and generates corona discharge between a pair of electrodes in the discharger by power supply from a pulse power source. Thereby, corona discharge acts on the air in the discharger, and ozone which is a kind of oxygen active component is generated. More specifically, electrons collide with oxygen molecules (O ₂ ) in the air to generate oxygen atoms, which combine with the oxygen molecules to generate ozone. The ozone generated in this way is supplied to the intake passage 14 via a discharge passage 46 having a nozzle shape that constitutes a part of the ozone supply means 40, and is introduced through the air cleaner 12 (intake air). And mix. However, in the ozone generator 41, the power supplied to the discharger is controlled to an appropriate value so as to generate and supply a predetermined amount of ozone. In the present embodiment, the pulse power source includes a battery in which electricity generated by the alternator using the power from the engine 10 is stored.

  Further, the intake pipe 23 is provided with a bypass air passage 47 that bypasses the throttle valve 16 and supplies air. The flow rate of air flowing through the bypass air passage 47 is controlled by an idle speed control valve (ISCV) 48. The ISCV 48 is closed at times other than the idling operation, and the opening degree is controlled so that the engine speed becomes a predetermined target idling speed at the idling operation.

  The ECU 44 is provided as described above to perform fuel injection control, ignition timing control, ozone supply control, and the like. The ECU 44 is constituted by a microcomputer including a CPU, a ROM and a RAM for recording various programs and data, an input interface circuit, and an output interface circuit. The input interface circuit includes a knock sensor 52 for detecting high-frequency vibration caused by knocking transmitted to the cylinder block 50, an intake pressure sensor 54 for detecting intake pressure downstream of the throttle valve 16, and an accelerator pedal depression operation. The throttle position sensor 56 for detecting the opening degree of the throttle valve 16 that is opened and closed in conjunction, the accelerator position sensor 58 for detecting the depression amount of the accelerator pedal, that is, the accelerator opening degree, and the cylinder block 50 are provided. The crank position sensor 64 for detecting the crank rotation signal of the crankshaft 62 to which the piston 60 is connected via the connecting rod, and the cylinder block 50 are provided with the temperature of the cooling water (cooling water temperature) of the engine 10. Water temperature to detect Capacitors 66, such as the O2 sensor 67 for detecting the oxygen concentration in the exhaust gas flowing through upstream of the catalytic converter 38 is connected via the electrical wiring. An idle switch 68 that is turned on when the throttle valve 16 is fully closed is also connected. In the present embodiment, the crank position sensor 64 is used as a rotational speed sensor for detecting the rotational speed of the engine 10. The output interface circuit of the ECU 44 is connected to the fuel injection valve 24, the ignition coil 26 with a built-in igniter, the ozone generator 41, the ISCV 48, etc., and based on the data obtained by the above various sensors, etc. Has been made controllable. Note that the ECU 44 of this embodiment has a built-in timer device for measuring time.

  In the engine 10, during normal operation, the intake pressure based on the output signal from the intake pressure sensor 54, the engine speed based on the output signal from the crank position sensor 64, that is, the operation expressed by the engine load and the engine speed. Based on the state, the basic fuel injection amount, the basic fuel injection timing, the basic ignition timing, and the like are set. At that time, the basic values are corrected by the coolant temperature of the engine 10 and the like, and the fuel injection amount, the fuel injection timing, and the ignition timing targeted for control are derived, and the operation of the fuel injection valve 24, the ignition plug 28, etc. Is controlled.

  By the way, when starting the engine 10 is started, if the engine 10 is cooled to a temperature lower than a predetermined temperature, that is, during a cold start in which the cooling water temperature is lower than the predetermined temperature, the warm-up of the engine 10 should be promoted. The engine 10 is rotated at a higher speed (for example, 1500 rpm; hereinafter referred to as “idle speed”) than in a normal idle state (for example, 800 rpm; hereinafter referred to as “idle speed”). The operation is shifted to the first idle state where the operation is performed at “the first idle rotation speed”, and the operation is performed at the first idle rotation speed. Operating the engine 10 at a high speed is achieved by increasing the amount of injected fuel and increasing the amount of intake air supplied to the combustion chamber 30. The fuel injection amount increase correction at this time is performed based on the cooling water temperature obtained based on the output signal from the water temperature sensor 66. In general, the fuel injection amount increase correction amount is set to be larger as the cooling water temperature is lower. An increase in the intake air amount can be realized by increasing the opening of the ISCV 48. It should be noted that the air-fuel ratio (A / F) of the air-fuel mixture is set rich (excessive fuel) for a predetermined time immediately after the engine is started so as to preferentially maintain a stable combustion state.

  On the other hand, when the engine 10 is in the first idle state, the cooling water temperature of the engine 10 is low as described above, and the temperature of the exhaust gas purification catalyst (catalyst temperature) of the catalytic converter 38 is activated. In many cases, the temperature is lower than a predetermined reference temperature which is the minimum value of the temperature. In such a case, the ignition timing is retarded in order to warm up the catalyst quickly to the catalyst activation temperature. At the same time, when retarding the ignition timing, the engine 10 supplies ozone during intake so that the air-fuel mixture is properly combusted. Hereinafter, an example of this control will be described with reference to FIGS. 2 is a control flowchart of the present embodiment, FIG. 3 is a graph showing the relationship between the cooling water temperature, the ignition delay amount, and the ozone supply amount for the catalyst warm-up control. FIG. It is a time chart regarding the engine speed, ignition retard amount, and ozone supply amount at the time of start-up and thereafter in an idle state. Note that the routine of FIG. 2 is generally repeated for each combustion cycle.

  The ECU 44 first proceeds to step S201, and determines whether or not it is in the fast idle state. The ECU 44 receives a signal indicating that the engine is in an ON state from the idle switch 68, determines that the time measured from the start of the engine 10 (at the start of cranking) is equal to or less than a predetermined time, and receives a signal from the water temperature sensor 66. When it is determined that the coolant temperature of the engine 10 obtained based on the output signal is a predetermined value, which is less than 80 ° C. in the present embodiment, it is determined that the engine 10 is in the idle state immediately after the cold start, that is, the fast idle state. To do. That is, in this embodiment, since the cooling water temperature and the catalyst temperature are generally in a correspondence relationship, the catalyst temperature is estimated by detecting the cooling water temperature instead of directly detecting the catalyst temperature. That is, when the cooling water temperature is lower than the predetermined value, the catalyst temperature is lower than the predetermined reference temperature. This reference temperature is 400 ° C., for example.

  If it is determined that the engine is in the fast idle state, the process proceeds to step S203, and an ignition delay amount is derived as a correction amount for the basic ignition timing stored in advance in the ROM. The ignition retard amount at this time has a corresponding relationship with the coolant temperature of the engine 10 as schematically shown in FIG. Based on the detected coolant temperature of the engine 10, the ECU 44 searches the mapped data stored in advance in the ROM as shown in FIG. In the present embodiment, the basic ignition timing θ0 at this time is defined as 5 ° before top dead center (BTDC) and the maximum ignition retardation amount ΔθH is defined as 15 °. Therefore, the ignition timing is increased from 5 ° before top dead center. The range is set to 10 ° after the dead point. In this embodiment, the ignition delay amount varies when the coolant temperature is between the temperature TwH and the temperature TwL (<TwH), and when the coolant temperature is lower than the temperature TwL, the ignition delay amount is the maximum ignition delay amount. When ΔθH is constant and the cooling water temperature is higher than the temperature TwH, the ignition retardation amount for warming up the catalyst is “0” (see FIG. 3A). Thus, determining the ignition retardation amount based on the cooling water temperature means that the temperature difference between the cooling water temperature when the cooling water temperature is below a predetermined temperature of, for example, 80 ° C. and the predetermined temperature, that is, the catalyst temperature is This means that the retard amount of the ignition timing is determined based on the temperature difference between the catalyst temperature when the temperature is below the reference temperature and the reference temperature.

  Next, in step S205, the ozone supply amount is derived. As shown in FIG. 3B, the ozone supply amount is obtained by searching the mapped data stored in the ROM in advance with the ignition retardation amount obtained in step SS203. The ozone supply amount is generally proportional to the ignition retard amount, and the ozone supply amount is set to increase as the ignition retard amount increases. In the present embodiment, when the ignition retard amount obtained in step S203 is “0”, the ozone supply amount is set to “0”. The determination of the ozone supply amount in this way is based on the temperature difference when the cooling water temperature is lower than the predetermined temperature, that is, the temperature difference when the catalyst temperature is lower than the reference temperature. It means to ask for quantity.

  In step S207, a correction value for the opening of the ISCV 48 is obtained. By searching a map (not shown) stored in the ROM in advance with the ozone supply amount obtained in step S205, a correction value for the opening of the ISCV 48 is obtained. This is to reduce the opening of the ISCV 48 by the amount of ozone supplied in step S209, which will be described later, to reduce the amount of intake air flowing through the intake passage 14 and to obtain a desired target idle speed. .

  In step S209, ignition is performed using the ignition timing corrected with the ignition delay amount obtained in step S203, and ozone is inhaled from the ozone supply means 40 by the ozone supply amount obtained in step S205. Will be supplied. At the same time, the opening degree of the ISCV 48 is controlled based on the correction value obtained in step S207.

  In the present embodiment, as shown in FIG. 4, first, the state transitions to the idle state at time t1. When the coolant temperature up to this time t1 is lower than the temperature TwL, the engine speed is set and controlled at the speed NeH which is the maximum value of the first idle speed. On the other hand, after the engine speed reaches the first idle speed at time t1, the ignition retard amount is gradually increased at time t2 after a very short predetermined time has elapsed. This makes it possible to maintain combustion stability even when the ignition timing is retarded. More specifically, in the present embodiment, the ignition delay amount obtained in step S203 is increased by 1 ° each time the routine of FIG. 2 reaches step S209, that is, by 1 °. The ignition timing is retarded to be reflected. When the ignition delay amount finally obtained in step S203 is reached, thereafter, in step S209, the ignition delay amount itself obtained in step S203 is retarded from the basic ignition timing. The supply of ozone is performed corresponding to the execution of the ignition retard amount.

  On the other hand, when the cooling water temperature reaches the temperature TwL at time t3 and then rises to the temperature TwH at time t4, as shown in FIG. 2, the result is negative in step S201, and the process proceeds to step S211. The ignition timing retarding and the ozone supply for are terminated. Along with this, the opening correction of the ISCV 48 is also ended, and the engine is operated in the idle state after warming up. That is, the operation is performed at the idle speed NeS, and the control for warming up the catalyst is completed.

  As described above, in the present embodiment, when the catalyst temperature is low and the engine is in the fast idle state, the ignition timing is delayed by a predetermined ignition delay amount for catalyst warm-up, so that afterburning occurs. As the ignition retard amount increases, the temperature of the exhaust gas reaching the exhaust passage 34 increases, so that the catalyst warm-up is promoted. On the other hand, since ozone is supplied in response to retarding the ignition timing, the amount of ozone in the air-fuel mixture increases as the ignition retard amount increases. Since the air-fuel mixture containing ozone is ignited, the combustion reaction proceeds by ozone having a strong oxidation reaction, and the combustion of the air-fuel mixture is completed better. Therefore, it is possible not only to prevent misfire, but also to prevent the amount of CO and HC in the exhaust gas from increasing. In addition, since the combustion of the air-fuel mixture is maintained well by ozone in this way, it is possible to further increase the ignition retard amount and further promote catalyst warm-up.

  In this way, it is possible to retard the ignition timing and cause sufficient afterburning while appropriately burning the air-fuel mixture, so that the exhaust gas temperature can be raised to a desired high temperature when the catalyst is warmed up. It becomes possible. Therefore, it is possible to quickly warm the catalyst without providing the catalyst arrangement position upstream of the exhaust passage, for example, at the exhaust manifold outlet. In addition, since it is not necessary to place the catalyst on the upstream side of the exhaust passage, even after the catalyst is warmed up, even if the exhaust gas temperature is high during other operating conditions at high load or high speed, it is more than necessary. Thus, the catalyst can be prevented from being heated. Thereby, it becomes possible to appropriately prevent the catalyst temperature from reaching the deterioration temperature of the catalyst.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this does not limit this invention. In the above embodiment, the catalyst temperature is estimated and controlled based on the engine coolant temperature, but the catalyst temperature may be estimated based on other factors. Alternatively, a sensor for directly measuring and detecting the catalyst temperature may be provided in the catalytic converter 38 itself or in the vicinity thereof. That is, in the above embodiment, the catalyst warm-up is performed when it is determined that the cooling water temperature is lower than the predetermined temperature in the fast idle state. However, the catalyst temperature is directly obtained and the obtained catalyst temperature is the reference temperature. The catalyst may be warmed up when it is determined that it is lower than the lower limit.

  In the above embodiment, the catalyst warm-up is performed in the fast idle state, but the application of the present invention is not limited to this state. In addition, whenever it is necessary to warm up the catalyst, similarly, the ignition timing may be retarded to promote afterburning, and ozone may be supplied to improve combustion.

  In the above embodiment, the ozone supply means 40 is provided to supply ozone to the intake passage 14, but the present invention is not limited to this. The present invention includes providing ozone supply means at various locations such as an intake port, an intake manifold, and an arbitrary location of an intake pipe upstream of the intake port in order to supply ozone to the intake air. For example, ozone may be supplied into the intake air that has already been taken into the combustion chamber 30, or ozone may be supplied into the air-fuel mixture already formed in the combustion chamber 30. That is, the present invention does not exclude not only providing the ozone supply means 40 so as to supply ozone in the intake passage 14 but also supplying ozone directly to the combustion chamber 30.

  Moreover, the ozone supply means 40 is not limited to the said embodiment, You may substitute by the apparatus which generates and supplies ozone. For example, a reactor may be provided as ozone supply means in the middle of the intake passage so as to form a part of the intake passage. More specifically, a reactor including an insulator case forming an intake passage, a center electrode disposed along the central axis of the case, and a high voltage power source connected to the center electrode by a metal wire is sucked into the reactor. In the middle of the passage, by controlling the high-voltage power supply to apply a desired high voltage to the center electrode, it discharges to the air flowing through the intake passage and generates ozone in the intake air. good.

  In the above embodiment, the internal combustion engine to which the present invention is applied is an intake port injection type spark ignition type internal combustion engine, but it may be a cylinder injection type spark ignition type internal combustion engine. The present invention does not limit the number of cylinders and the cylinder arrangement of the engine to which the present invention is applied.

  Furthermore, in the above embodiment, the intake air amount is adjusted by controlling the ISCV 48 in the idle state. However, in the case of an engine not provided with the bypass air passage 47, the opening degree of the throttle valve 16 is controlled. You may go by doing. In this case, the throttle valve 16 is electronically controlled so that the depression operation of the accelerator pedal and the opening / closing operation of the throttle valve 16 can be separated and electronically controlled.

  In the above embodiment, the present invention has been described with a certain degree of concreteness, but various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.

1 is a conceptual diagram of an engine system to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. It is an example of the control flowchart of this embodiment. 4 is a graph conceptually showing the relationship between cooling water temperature, ignition retard amount, and ozone supply amount for catalyst warm-up control. 3 is a time chart conceptually showing changes in engine speed, ignition retardation amount, and ozone supply amount during cold start and in an idle state thereafter.

Explanation of symbols

10 Engine 38 Catalytic converter 40 Ozone supply means

Claims (1)

In a control device for an internal combustion engine having a catalyst for purifying exhaust gas,
Ignition timing retarding means for retarding the ignition timing for warming up the catalyst;
Ozone supply means for supplying ozone during inhalation;
Temperature detecting means for detecting or estimating the temperature of the catalyst;
Temperature difference deriving means for obtaining a temperature difference from the reference temperature when the temperature of the catalyst detected or estimated by the temperature detection means is lower than a predetermined reference temperature;
Control means for controlling the retard amount of the ignition timing and the ozone supply amount based on the temperature difference obtained by the temperature difference deriving means;
A control device for an internal combustion engine, comprising:

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