JP2008069730A - Exhaust emission control device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure correct feedback control even when using an active oxygen component generating device 40 together. <P>SOLUTION: A catalytic unit 30 is provided in an exhaust passage 20. The active oxygen component generating device 40 having a discharge pipe 41 for discharging an active oxygen component is provided upstream of the catalytic unit 30 in the exhaust passage 20. A control means 100 is provided for controlling the active oxygen component generating device 40. The control means 100 has an air-fuel ratio feedback control function of feedback-controlling an actual air-fuel ratio based on the detection of an air-fuel ratio sensor SW10 arranged upstream of the discharge pipe 41 in the exhaust passage 20 so that the actual air-fuel ratio reaches a predetermined target air-fuel ratio. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device for an engine.

  The main components of the unpurified gas discharged from the engine are hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx).

  These components are purified by a catalyst provided in the engine. The purification rate by this catalyst depends on the exhaust temperature of the engine. That is, after the engine is warmed up, the purification rate becomes high. However, during cold operation until the engine is started and sufficiently warmed up, the activity of the catalyst noble metal is low, and the oxygen storage / release function of the oxygen storage material (OSC) is not fully exhibited. In practice, it is difficult to obtain a sufficient purification rate. For this reason, in many cases, two manifold catalysts (closed coupled catalyst) and an underfloor catalyst connected immediately below the exhaust manifold are provided. Here, the purpose of the manifold catalyst is to raise the temperature as quickly as possible after the engine is started. However, although it is “as fast as possible”, there is a limit to the lower temperature limit at which the catalytic noble metal is activated, and in general, only about 50% of exhaust gas can be purified at around 250 ° C.

  On the other hand, Patent Document 1 and Patent Document 2 describe a method in which an exhaust gas component can be reacted with an active oxygen component such as ozone to purify exhaust gas even at a temperature lower than the above temperature. .

Specifically, in Patent Document 1, in the NOx storage reduction catalyst, a discharge unit and a hydrogen supply unit are provided on the upstream side, and oxygen radicals or ozone is generated by the discharge unit to oxidize NO to NO ₂ . to occlude NO ₂ in NOx-absorbing material and reducing the NO ₂ released from the NOx-absorbing material with hydrogen from a hydrogen supply means is described.

Patent Document 2 describes that a hydrocarbon is reacted with ozone to convert the hydrocarbon mainly into CO, and further oxidized with a subsequent catalyst to be converted into CO ₂ . Specific examples thereof include those having a built-in plasma generator in the exhaust passage, or supplying ozone into the exhaust passage from an active oxygen component generator (Ozonizer) disposed outside the exhaust passage. Has been.

In addition, as an ozonizer as an active oxygen component production | generation apparatus, as shown in patent document 3, the thing of a silent discharge type is common.
JP 2005-344688 A JP-A-2005-207316 Japanese Patent Laid-Open No. 9-156904

  By the way, when controlling the air-fuel ratio of the engine, an oxygen concentration sensor for air-fuel ratio control is provided immediately upstream of the exhaust gas catalyst in the exhaust passage, and a value detected by this oxygen concentration sensor is used as a feedback element to obtain a predetermined value. Feedback control is performed on the target air-fuel ratio. However, when the active oxygen component generating apparatus as described above is used in combination with an engine, the active oxygen component generating apparatus introduces air to make a part of the active oxygen component, and the generated active oxygen component and The introduced residual air component may act as a disturbance, and accurate feedback control may be hindered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an engine exhaust gas purification device that can ensure accurate feedback control even when an active oxygen component generation device is used in combination.

  In order to solve the above problems, the present invention provides a catalyst unit that is disposed in an exhaust passage and purifies exhaust gas in the exhaust passage, and discharges an active oxygen component upstream of the catalyst unit in the exhaust passage. An active oxygen component generator having a discharge pipe, an operating state determining means for determining an operating state of the engine, an air-fuel ratio sensor disposed upstream of the discharge pipe in the exhaust passage, and the exhaust passage An upstream oxygen concentration sensor disposed between the discharge pipe and the catalyst unit, and control means for controlling the operation of the active oxygen component generation device based on the operating state determined by the operating state determining means; And the control means feedback-controls the actual air-fuel ratio so as to reach a predetermined target air-fuel ratio based on detection of the operating state determination means and the air-fuel ratio sensor. The engine exhaust having a feedback control function and a concentration adjusting function for adjusting the concentration of the active oxygen component discharged from the active oxygen component generating device based on the detection of the upstream oxygen concentration sensor It is a gas purification device. In this aspect, the upstream oxygen concentration sensor can perform feedback control of the active oxygen component generation device, and the active oxygen component generation device is disposed upstream of the position where the active oxygen component is discharged into the exhaust passage. Since the air-fuel ratio sensor can feedback control the engine air-fuel ratio, the air-fuel ratio sensor detects the oxygen concentration independent of the discharge amount of the active oxygen component while supplying the necessary and sufficient active oxygen component. The fuel ratio can be controlled to a predetermined target air-fuel ratio, and there is no possibility of adversely affecting the combustion characteristics of the engine body.

  In a preferred aspect, the control means sets the air-fuel ratio to the target air-fuel ratio based on the output value of the upstream oxygen concentration sensor during the initial operation period of the active oxygen component generation device during the cold operation of the engine body. The concentration of the active oxygen component is increased until the active oxygen component generating device is subsequently operated, and the amount of air supplied to the active oxygen component generating device is reduced to suppress the concentration of the active oxygen component. It is. In this aspect, since the concentration of the active oxygen component is increased during the initial operation period of the active oxygen component generation device, it is possible to quickly purify HC and CO, and during the operation period after the initial operation period has elapsed. By reducing the concentration to the necessary and sufficient active oxygen concentration, it is possible to prevent the active oxygen component from being excessively released.

  In a preferred aspect, the control means suppresses the amount of air added to the extent that the air-fuel ratio downstream of the discharge pipe in the exhaust passage becomes an air excess state than the target air-fuel ratio. . In this embodiment, while ensuring the minimum necessary active oxygen component, the active oxygen concentration is suppressed as much as possible to save power consumption and adverse effects due to excessive active oxygen components (for example, oxidation of exhaust system components). And a decrease in sensor sensitivity).

  In a preferred embodiment, the catalyst unit includes a NOx storage catalyst. In this aspect, the lean state increases on the downstream side of the air-fuel ratio sensor due to the active oxygen component discharged from the active oxygen component generation device. Therefore, during the generation of the active oxygen component, NOx in the exhaust gas is converted into a NOx storage catalyst. To be adsorbed. On the other hand, in a rich (or stoichiometric air-fuel ratio) state during steady operation where no active oxygen component is generated, NOx release or reduction purification can be performed by the NOx storage catalyst.

  As described above, according to the present invention, while supplying a necessary and sufficient active oxygen component, the oxygen concentration independent of the discharge amount of the active oxygen component is detected by the air-fuel ratio sensor, and the original actual air-fuel ratio is set to a predetermined target. As a result of being able to control the air-fuel ratio, there is a remarkable effect that accurate feedback control can be ensured even when the active oxygen component generator is used together.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of an engine including an apparatus according to an embodiment of the present invention.

  Referring to FIG. 1, a plurality of cylinders 2 are provided in an engine body 1 of a spark ignition gasoline engine shown in FIG. Each cylinder 2 is formed with a combustion chamber 2a. In each combustion chamber 2a, an intake port 3 and an exhaust port 4 are opened, and an intake valve 5 and an exhaust valve 6 are provided in these ports. Furthermore, an ignition plug 7 is provided for each combustion chamber 2a.

  The engine body 1 is connected to an intake passage 10 for supplying fresh air to each cylinder 2 and an exhaust passage 20 for leading exhaust gas from each cylinder 2.

  The intake passage 10 is configured to introduce fresh air into each cylinder 2 via an unillustrated intake manifold having an intake passage for each cylinder connected to the intake port 3 of each cylinder 2. An intake shutter valve 11 is provided upstream of the intake passage 10, and the valve opening amount is controlled by a stepping motor 12.

  Next, the exhaust passage 20 is configured to discharge burned gas from each cylinder 2 via an unillustrated exhaust manifold having an exhaust passage for each cylinder connected to the exhaust port 4 of each cylinder 2. Yes. A catalyst unit 30 is connected to the downstream side of the exhaust passage 20.

  As shown in Table 1, the catalyst unit 30 includes a three-way catalyst 31 and a Pt / Rh catalyst 33 that is disposed downstream of the three-way catalyst 31 and contains a NOx storage function as a NOx catalyst. Yes.

  Next, in this embodiment, an ozonizer (an example of an active oxygen component generation device) 40 that supplies ozone as an active oxygen component to the exhaust passage 20 is provided.

  Referring to FIG. 1, the ozonizer 40 includes a discharge pipe 41 connected upstream of the catalyst unit 30 in the exhaust passage 20, an ozone generation unit 42 provided in the middle of the discharge pipe 41, an ozone An air pump 43 that supplies air for generating ozone to the generation unit 42; an air flow meter 44 that is disposed between the air pump 43 and the ozone generation unit 42 and that measures the amount of air supplied by the air pump 43; A power supply unit 45 that applies a high voltage to the generation unit 42 is provided. In the illustrated embodiment, an adjustment valve 41a is provided on the downstream side of the ozone generation unit 42 of the discharge pipe 41, and the exhaust gas does not flow back to the discharge pipe 41 when the ozonizer 40 is stopped by the adjustment valve 41a. It is configured as follows.

  The ozone generation unit 42 has, for example, a cylindrical earth electrode and an application electrode disposed concentrically within the earth electrode. By applying a high voltage to the application electrode by the power supply unit 45, the ozone generation unit 42 A silent discharge is generated between the electrodes, and ozone is generated from the air between the electrodes.

  The air pump 43 introduces outside air into the discharge pipe 41 and supplies fresh air (introduced outside air) to the ozone generation unit 42 so that the ozone discharge amount (feed amount) from the discharge pipe 41 can be adjusted. It is.

  The air flow meter 44 outputs a signal indicating the amount of air supplied from the air pump 43 and inputs it to the engine control unit 100 described later in detail.

  The power supply unit 45 applies a high voltage to the application electrode of the ozone generation unit 42 by being controlled by an engine control unit 100 described later. The power supply unit 45 is configured to output a signal corresponding to an applied voltage during power supply to an engine control unit 100 described later.

  In order to detect the operating state of the engine body 1, a pair of crank angle sensors SW1 and a water temperature sensor SW2 are provided at predetermined locations of the engine body 1.

  The crank angle sensor SW1 detects the engine rotational speed Ne based on a detection signal output from one side, and also detects the rotational direction and phase (crank) of the crankshaft 8 based on a detection signal out of phase output from both sides. The angle CA) is detected.

  The water temperature sensor SW2 detects the temperature of the cooling water of the engine body 1.

  The intake passage 10 is provided with an air flow meter SW3 disposed between the air cleaner of the intake passage 10 and the intake shutter valve 11 in order to detect the air flow rate immediately after passing through an unillustrated air cleaner. .

  Further, the engine is provided with an accelerator opening sensor SW4 that detects the depression amount of an accelerator pedal 50 (not shown).

On the other hand, in the exhaust passage 20, an air-fuel ratio sensor SW 10 for controlling the air-fuel ratio is disposed upstream of the ozone discharge pipe 41 in the exhaust passage 20. In the present embodiment, the air-fuel ratio sensor SW10 is arranged on the upstream side of the discharge pipe 41, so that the engine can be used regardless of the amount of active oxygen components and residual air components discharged into the exhaust passage 20 by the ozonizer 40. The air-fuel ratio of the main body 1 can be feedback controlled. The illustrated air-fuel ratio sensor SW10 is embodied by an oxygen concentration sensor, detects the oxygen concentration based on the number of oxygen atoms contained in the exhaust gas discharged to the exhaust passage 20, and outputs a corresponding detection value _LSL0 later. Output to the engine control unit 100.

  Further, oxygen concentration sensors SW11 and SW12 and exhaust temperature sensors SW31 and SW32 for estimating the temperature of the catalyst unit 30 are arranged on the upstream side and the downstream side of the catalyst unit 30, respectively.

The oxygen concentration sensors SW11 and SW12 are mainly used for controlling the concentration of the active oxygen component generated by the ozonizer 40. The upstream oxygen concentration sensor SW11 detects the oxygen concentration based on the number of oxygen atoms before purification of the exhaust gas containing ozone and oxygen discharged from the discharge pipe 21, and an engine control unit, which will be described later, with a corresponding detection value _LSL1. 100 to output to 100. Further, the downstream oxygen concentration sensor SW12 is disposed on the downstream side of the catalyst unit 30, detects the oxygen concentration based on the number of oxygen atoms contained in the exhaust gas after being purified by the catalyst unit 30, and the corresponding detection value. L _SL2 is output to an engine control unit 100 described later.

  Note that the air-fuel ratio sensor SW10 and the oxygen concentration sensors SW11 and SW12 are oxygen sensors with heaters that heat the sensor element to at least 250 ° C. or more so as to function even when the exhaust gas temperature is low.

  The exhaust temperature sensors SW31 and SW32 are used for calculating the temperature difference between the front and rear of the catalyst unit 30 and detecting the temperature of the catalyst unit 30, and the upstream temperature sensor SW31 is configured to detect the upstream detection value T1 downstream. The side temperature sensor SW32 is configured to output the downstream detection value T2 to the engine control unit 100 described later.

  Next, the engine control unit 100 will be described.

  The engine control unit 100 includes a CPU 101, a memory 102, a counter timer group 103, an interface 104, and a microprocessor having a bus 105 that connects these units 101 to 104.

  In addition to the engine operation switch SS, various sensors including the above-described sensors are connected to the interface 104 as input elements. By receiving detection signals from the engine operation switch SS and sensors, the operation state is changed. Judgment is now possible. The interface 104 is connected to an unillustrated controller and driver as output elements, and through these units, the ignition timing of the ignition plug 7, the stepping motor 12 of the intake shutter valve 11, the ozonizer 40, etc. It is comprised so that it can drive.

  The memory 102 stores programs and data for controlling the entire engine. By executing such a program based on a flowchart described later in detail, the engine control unit 100 controls the operation / stop control of the engine starting with the operation of the ozonizer 40 based on the ON / OFF operation of the engine operation switch SS. The control means that governs it is functionally configured.

  In this embodiment, a well-known fuel injection system for injecting fuel from a fuel injection valve (not shown) is provided, and the engine control unit 100 determines the fuel injection timing and fuel injection by the fuel injection system according to the operating state. The amount can be controlled.

  FIG. 2 is a graph showing the relationship between the amount of ozone generated and the power consumption of the ozonizer 40 as the active oxygen component generator according to the embodiment of FIG.

  Next, referring to FIG. 2, in this embodiment, in order to control the ozonizer 40, the relationship between the power consumption of the ozonizer 40 and the amount of generated ozone is shown in FIG. 2 based on experimental data. And is stored in the memory 102 of the engine control unit 100 as a control map. In the illustrated example, for example, when the power consumption is 120 W, the generated ozone amount is 12 ml / min. This amount of 12 ml / min seems to be a small value at first glance, but is an amount equivalent to about 0.1% in the exhaust gas flow rate of the engine. Considering that the amount of oxygen contained in the exhaust gas at the time of low engine rotation is 0.6%, the effect of oxidizing and purifying HC and CO is sufficiently obtained even with an ozone amount of 12 ml / min. It is done. Therefore, depending on the exhaust gas temperature, even an ozone amount of 12 ml / min may be excessively supplied. Therefore, in the present embodiment, the fuel injection amount and the air addition amount are controlled so that the ozone amount is reduced as much as possible and the necessary and sufficient supply amount is maintained.

  Next, a control example of this embodiment by the engine control unit 100 will be described.

  FIG. 3 is a flowchart illustrating an example of operation control according to the embodiment of FIG. 1.

  Referring to FIG. 3, when engine operation switch SS is turned ON and this operation control is executed, engine control unit 100 executes initialization of each part (step S1).

Next, the engine control unit 100 reads a signal from the input element described above and grasps the operating state (step S2). Next, the engine control unit 100 determines whether or not the ozonizer 40 is operating (step S3), and if it is operating, the ozonizer 40 is turned off (step S4). When the operation of the ozonizer 40 is stopped, or when it is determined in step S3 that the ozonizer 40 is not operating, the engine control unit 100 sets the target air-fuel ratio Ls based on the operating state (step S5). The target air-fuel ratio Ls is a control target for feedback control of the fuel injection amount based on the detection value L _SL0 of the air-fuel ratio sensor SW10. For example, the center air-fuel ratio is set to λ = 1 and periodically fluctuates. It is set to a state where periodic fluctuations in the air-fuel ratio are suppressed.

Next, the engine control unit 100 controls the fuel injection amount with respect to the target air-fuel ratio Ls, using the detection value L _SL0 of the air-fuel ratio sensor SW10 and the input value from the air flow meter SW3 as feedback elements (step S6). Next, the engine control unit 100 determines whether or not the engine operation switch SS has been switched to OFF (step S7). If switched, the control is terminated, and if not switched to step S1. Return and repeat the above control.

  FIG. 4 is a flowchart showing an example of operation control of the ozonizer executed in parallel with the operation control of FIG.

  Referring to FIG. 4, engine control unit 100 reads signals from various sensors (step S10), and determines whether or not it is during a cold start operation from the read values (step S11). The determination condition in step S11 is a condition for operating the ozonizer 40 until the catalyst unit 30 reaches a predetermined activation temperature (300 ° C. in the present embodiment). Whether or not it is during a cold start is, for example, the rotational speed Ne of the engine body 1 estimated by the crank angle sensor SW1, the in-cylinder temperature of the engine body 1 estimated by the water temperature sensor SW2, or each exhaust temperature sensor SW31. The temperature is determined based on the temperature of the catalyst unit 30 estimated from the detected values T1 and T2 of the SW32.

  If it is determined in step S11 that the engine is not cold start, the engine control unit 100 executes a cold start ozone generation operation subroutine (step S12). This cold start ozone generation operation subroutine is a program for purifying exhaust gas by ozone until the catalyst unit 30 reaches the activation temperature and performs the desired catalytic action by operating the ozonizer 40. is there.

  If it is determined in step S11 that the activation condition is not satisfied, or if the cold start ozone generation operation subroutine in step S12 is terminated, the engine control unit 100 performs the Pt / Rh catalyst containing the NOx occlusion material. A regeneration operation determination subroutine (step S14) is executed.

  In the Pt / Rh catalyst activation operation subroutine containing the NOx storage material, by operating the ozonizer 40, the NOx stored in the Pt / Rh catalyst 33 containing the NOx storage material is released and the NOx storage material is contained. This is a program for recovering the purification performance of the Pt / Rh catalyst 33 to a desired level.

  Next, the engine control unit 100 determines whether or not the regeneration operation condition of the Pt / Rh catalyst 33 containing the NOx storage material is satisfied (step S15).

  If it is determined in step S15 that the Pt / Rh catalyst regeneration operation condition containing the NOx storage material is satisfied, the engine control unit 100 performs the Pt / Rh catalyst regeneration operation subroutine containing the NOx storage material (step S16). Execute. This Pt / Rh catalyst regeneration operation subroutine containing NOx occlusion material releases and purifies NOx occluded by the Pt / Rh catalyst 33 containing NOx occlusion material of the catalyst unit 30 and Pt / Rh containing NOx occlusion material. This is a program for recovering the NOx storage capacity of the Rh catalyst 33.

  If it is determined in step S15 that the Pt / Rh catalyst regeneration operation condition containing the NOx storage material is not satisfied, or if the Pt / Rh catalyst activation operation subroutine containing the NOx storage material in step S16 is terminated, the engine The control unit 100 returns to step S11 and repeats the above-described determination and subroutine.

  Next, each subroutine in FIG. 4 will be described in detail.

  FIG. 5 is a flowchart illustrating an example of a cold start ozone generation operation subroutine in the flowchart of FIG. 4. FIG. 6 is a timing chart showing an example of executing the flowchart of FIG.

  Referring to FIGS. 5 and 6, in the illustrated cold start time ozone generation operation subroutine, engine control unit 100 first turns on ozonizer 40 (step S120) and sets the air addition amount to the maximum value (step S120). Step S121). As a result, as shown in FIG. 6, the air-fuel ratio (oxygen concentration) detected by the upstream oxygen concentration sensor SW11 rapidly rises to the lean side.

Next, the engine control unit 100 reads the detection value L _SL1 of the upstream oxygen concentration sensor SW11 (step S122), and the atmosphere in the exhaust passage 20 downstream from the ozone discharge pipe 41 is the target air-fuel ratio set in step S5. The process waits for reaching Ls (step S123), and if not, repeats the steps after step S121. As described above, when the engine body 1 is cold-started, the ozonizer 40 is fully operated and the active oxygen concentration is increased, so that the purification rate of HC and CO can be increased as quickly as possible. As shown in FIG. 6, in this embodiment, the initial operation period IT is from the timing t1 when the ozonizer 40 is turned on to the timing t2 that satisfies the condition of step S213.

In step S123, when the detection value L _SL1 of the upstream oxygen concentration sensor SW11 reaches the target air-fuel ratio Ls set in step S5, the engine control unit 100 reduces the air addition amount (step S124). As a result, as shown in FIG. 6, the value L _SL1 detected by the upstream oxygen concentration sensor SW11 remains at the target air-fuel ratio Ls, during which the detection of the air-fuel ratio sensor SW10 detected as the actual air-fuel ratio by the control of step S6. The value L _SL0 reaches the target air-fuel ratio Ls.

  Next, the engine control unit 100 determines whether or not the necessary and sufficient air addition amount has been reached based on the following equation (1) (step S125).

dL _SL1 −dL _SL0 = Lt−Ls (1)
However, dL _SL0 is a differential value of the value L _SL0 detected by the air-fuel ratio sensor SW10,
dL _SL1 is a differential value of the value L _SL1 detected by the upstream oxygen concentration sensor SW11,
Lt is an oxygen concentration control air-fuel ratio.

  As shown in FIG. 6, the oxygen concentration control air-fuel ratio Lt has an air-excess atmosphere (for example, λ = 1.02 to 1.03) more than the target air-fuel ratio Ls by the air-fuel ratio sensor SW10 according to the operating state of the engine. It is a control target set to be. By setting the active oxygen component discharged from the ozone discharge pipe 41 in equation (1), the necessary and sufficient ozone supply amount is maintained until the activation temperature at which the three-way catalyst 31 is activated, It is possible to prevent the ozone from being excessively discharged while ensuring the exhaust performance.

  In step S125, if the values detected by the air-fuel ratio sensor SW10 and the upstream oxygen concentration sensor SW11 do not satisfy the expression (1) (NO in step S125), the process returns to step S124 and the amount of air added Continue to reduce. On the other hand, if the values detected by the air-fuel ratio sensor SW10 and the upstream oxygen concentration sensor SW11 satisfy the expression (1) in step S125 (YES in step S125), the air addition amount is kept constant. (Step S126). As a result, it is possible to purify HC and CO and promote activation of the three-way catalyst 31 while preventing excessive ozone from being supplied from the ozonizer 40.

  Next, the engine control unit 100 determines whether or not a predetermined end condition is satisfied (step S127). Here, the termination condition is a condition where it can be determined that the three-way catalyst 31 has reached the activation temperature and has reached a state where a predetermined purification ability can be exhibited. In this embodiment, this end condition is determined using the upstream and downstream oxygen concentration sensors SW11 and SW12. However, separately or in combination with this, determination using the temperature of the catalyst unit 30 estimated from the detected values T1 and T2 of the upstream and downstream exhaust temperature sensors SW31 and SW32 may be used. Further, the determination by timer setting using the counter timer group 103 may be used.

  If it is determined in step S125 that the end condition is satisfied, the engine control unit 100 turns off the ozonizer 40 (step S126) and returns to the main routine as indicated by the timing t3 in FIG. On the other hand, if it is determined that the end condition is not satisfied, the process returns to step S126 and waits for the end condition to be satisfied.

  5 is executed, the ozone discharged from the ozonizer 40 to the exhaust passage 20 reacts with CO and HC in the exhaust gas to purify these harmful substances, Due to the reaction heat between ozone and CO, the three-way catalyst 31 of the catalyst unit 30 is heated and quickly reaches the activation temperature.

  As described above, in the present embodiment, the air-fuel ratio sensor SW10 disposed upstream of the discharge pipe 41 in the exhaust passage 20, and the discharge pipe 41 and the catalyst unit 30 in the exhaust passage 20 are connected. The engine control unit 100 includes an upstream oxygen concentration sensor SW11 disposed between the engine control unit 100 and the engine control unit 100 based on the detection of the sensors SW1 to SW4, SW11, SW12, SW31, SW32, etc. An air-fuel ratio feedback control function for feedback control of the fuel ratio and a concentration adjustment function for adjusting the concentration of ozone discharged from the ozonizer 40 based on detection by the upstream oxygen concentration sensor SW11 are provided. For this reason, in the present embodiment, the upstream oxygen concentration sensor SW11 can execute feedback control of the ozonizer 40, and the air-fuel ratio sensor disposed upstream of the position where the ozonizer 40 discharges ozone into the exhaust passage 20. Since the air / fuel ratio of the engine body 1 can be feedback controlled by the SW 10, the oxygen concentration independent of the ozone discharge amount is detected by the air / fuel ratio sensor SW 10 while supplying the necessary and sufficient ozone to the exhaust passage 20. The air-fuel ratio can be controlled to a predetermined target air-fuel ratio Ls, and there is no possibility of adversely affecting the combustion characteristics of the engine body 1.

  In the present embodiment, during the initial operation period IT of the ozonizer 40 during the cold operation of the engine body 1, the ozone concentration is increased until the air-fuel ratio reaches the target air-fuel ratio based on the output value of the air-fuel ratio sensor SW10. During the subsequent operation of the ozonizer 40, the amount of air added to the ozonizer 40 is reduced to suppress the ozone concentration. For this reason, in the present embodiment, the ozone concentration is increased during the initial period IT (period t1 to t2 in FIG. 6) of the ozonizer 40, so that HC and CO can be quickly purified, During the operation period after the initial movement period IT, the ozone can be prevented from being excessively released by reducing the concentration to the necessary and sufficient active oxygen concentration.

  Further, in the present embodiment, the amount of air added is suppressed so that the air-fuel ratio downstream of the discharge pipe 41 in the exhaust passage 20 is in an excess air state than the target air-fuel ratio Ls. For this reason, in the present embodiment, the active oxygen concentration is suppressed as much as possible while securing the minimum necessary ozone, and power consumption can be saved and harmful effects caused by excessive ozone can be prevented.

  In the present embodiment, the catalyst unit 30 includes a Pt / Rh catalyst 33 containing a NOx storage material as a NOx storage catalyst. For this reason, in this embodiment, it becomes possible to perform NOx release or reduction purification by the Pt / Rh catalyst 33 containing the NOx storage material. That is, because the ozone discharged from the ozonizer 40 increases the lean state downstream of the air-fuel ratio sensor SW10, the NOx in the exhaust gas contains the NOx occlusion material during the ozone generation. To be adsorbed. On the other hand, in a rich (or stoichiometric air-fuel ratio) state during steady operation where ozone is not generated, NOx can be released or reduced and purified by the Pt / Rh catalyst 33 containing the NOx storage material.

  As described above, according to the present embodiment, while supplying necessary and sufficient ozone, the air concentration sensor SW10 detects an oxygen concentration that does not depend on the discharge amount of ozone, and the original actual air fuel ratio is set to a predetermined target air fuel ratio. As a result of being able to control to Ls, there is a remarkable effect that accurate feedback control can be ensured even when the ozonizer 40 is used together.

1 is an overall configuration diagram of an engine including an apparatus according to an embodiment of the present invention. It is a graph which shows the relationship between the ozone generation amount and power consumption of the ozonizer as an active oxygen component production | generation apparatus which concerns on embodiment of FIG. It is a flowchart which shows an example of the operation control which concerns on embodiment of FIG. It is a flowchart which shows the operation control example of the ozonizer performed in parallel with the operation control of FIG. 5 is a flowchart showing an example of a cold start-time ozone generation operation subroutine in the flowchart of FIG. 4. It is a timing chart which shows an example which performed the flow chart of Drawing 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Cylinder 2a Combustion chamber 3 Intake port 4 Exhaust port 5 Intake valve 6 Exhaust valve 7 Spark plug 8 Crankshaft 10 Intake passage 11 Intake shutter valve 12 Stepping motor 20 Exhaust passage 21 Discharge pipe 30 Catalyst unit 31 Three-way catalyst 32 Particulate filter 33 Pt / Rh catalyst containing NOx storage material (NOx storage catalyst)
40 Ozonizer (active oxygen component generator)
41 Ozone discharge pipe 42 Ozone generation unit 43 Air pump 44 Air flow meter 45 Power supply unit 100 Engine control unit Ao Accelerator opening CA Crank angle Ls Target air-fuel ratio Lt Air addition amount control air-fuel ratio SW10 Air-fuel ratio sensor SW11 Upstream oxygen concentration sensor SW12 Downstream oxygen concentration sensor SW31 Upstream temperature sensor SW32 Downstream temperature sensor SW4 Accelerator opening sensor

Claims (4)

A catalyst unit disposed in the exhaust passage and purifying the exhaust gas in the exhaust passage;
An active oxygen component generator having a discharge pipe for discharging an active oxygen component upstream of the catalyst unit in the exhaust passage;
An operating state determining means for determining the operating state of the engine;
An air-fuel ratio sensor disposed upstream of the discharge pipe in the exhaust passage;
An upstream oxygen concentration sensor disposed between the discharge pipe and the catalyst unit in the exhaust passage;
Control means for controlling the operation of the active oxygen component generation device based on the operation state determined by the operation state determination means,
The control means includes an air-fuel ratio feedback control function that feedback-controls an actual air-fuel ratio so as to reach a predetermined target air-fuel ratio based on detection of the operating state determination means and the air-fuel ratio sensor, and an upstream oxygen concentration sensor An exhaust gas purifying apparatus for an engine having a concentration adjusting function for adjusting the concentration of the active oxygen component discharged from the active oxygen component generating device based on the detection. The exhaust gas purification apparatus for an engine according to claim 1,
In the initial operation period of the active oxygen component generation device during the cold operation of the engine body, the control means determines the active oxygen component until the air-fuel ratio reaches the target air-fuel ratio based on the output value of the upstream oxygen concentration sensor. In the subsequent operation of the active oxygen component generating device, the amount of air added to the active oxygen component generating device is reduced to suppress the concentration of the active oxygen component. An exhaust gas purification device for an engine that is characterized. The exhaust gas purification apparatus for an engine according to claim 2,
The control means suppresses the amount of air added to the extent that an air-fuel ratio downstream of the discharge pipe in the exhaust passage becomes an air-excess state than the target air-fuel ratio. Engine exhaust gas purifier. The exhaust gas purification apparatus for an engine according to any one of claims 1 to 3,
The exhaust gas purification apparatus for an engine, wherein the catalyst unit includes a NOx storage catalyst.

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