JP3832288B2 - Exhaust gas purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device that performs exhaust gas purification in a direct injection internal combustion engine that injects fuel directly into a combustion chamber, and more particularly to an exhaust gas purification device that is suitable for use in exhaust gas purification during super lean combustion.
[0002]
[Prior art]
At present, a spark ignition type cylinder injection type internal combustion engine that directly injects fuel into a combustion chamber has been developed. This in-cylinder injection type internal combustion engine can be operated in an extremely lean region (at the time of ultra-lean combustion operation) in which the air-fuel ratio is extremely large as compared with a conventional lean burn internal combustion engine (lean burn engine). Can be set as a lean region, and fuel efficiency can be further improved.
[0003]
[Problems to be solved by the invention]
However, in such an in-cylinder injection internal combustion engine, fuel is injected during the compression stroke, and stratified combustion is established, thereby burning in an extremely lean mixture (oxygen-excess atmosphere) (combustion at an air-fuel ratio of 30 or more) In this combustion, when compared with the same fuel amount, the amount of air in the cylinder is larger and the calorific value is smaller than that of a conventional lean combustion internal combustion engine (burning in a lean region at an air-fuel ratio of about 22). Therefore, depending on the operating state, the exhaust temperature may be low (about 150 degrees), and there is a problem that the temperature of the catalyst provided in the exhaust passage decreases and exhaust gas purification efficiency deteriorates.
[0004]
By the way, as a technique for raising the temperature of the catalyst, the temperature of the catalyst is detected, and when the detected temperature is lower than the catalyst activation temperature, the air-fuel ratio is forcibly set to the stoichiometric air-fuel ratio, thereby setting the catalyst temperature. A technique for rapidly raising the temperature to the activation temperature has been proposed (Japanese Patent Laid-Open No. 3-948).
However, this prior art is intended for a conventional lean-burn internal combustion engine, and is intended for early catalyst activation at the time of cold start. Therefore, during normal operation in a direct injection internal combustion engine However, it cannot solve the specific problem of lowering the exhaust temperature.
[0005]
The present invention was devised in view of such problems, and in a direct injection internal combustion engine that performs ultra lean combustion, suppresses a decrease in the temperature of a catalyst that purifies exhaust gas, and prevents deterioration of exhaust gas purification efficiency. It is an object of the present invention to provide an exhaust gas purification device that can perform the above-mentioned.
[0006]
[Means for Solving the Problems]
  For this reason, the exhaust gas purifying apparatus of the present invention according to claim 1 injects fuel directly into the combustion chamber and performs stratified super lean combustion having an air-fuel ratio larger than the stoichiometric air-fuel ratio in accordance with the operating state. A specific operation provided in the engine and disposed in the exhaust passage of the engine to purify exhaust gas, and detecting or predicting a temperature drop of the catalyst by detecting the temperature of the catalyst or causing a temperature drop A temperature drop detecting means for detecting a temperature drop of the catalyst after the temperature of the catalyst reaches a catalyst activation temperature and activated by detecting a state and estimating a temperature drop of the catalyst; and the temperature drop detection Temperature drop suppression means that operates so as to suppress the temperature drop of the catalyst when the temperature drop of the catalyst is detected by the means, the in-cylinder injection internal combustion engine includes the layered super lean combustion The stoichiometric operation mode in which the premixed combustion whose combustion air-fuel ratio is smaller than that of the stratified super-lean combustion is switched according to the operating state, and the stoichiometric operation mode or the theory of operation is performed near the stoichiometric air-fuel ratio in order to perform the premixed combustion. A lean operation mode in which operation is performed at an air-fuel ratio greater than the air-fuel ratio, and the temperature decrease suppression means has a temperature of the catalyst that is lower than a first set value in accordance with an output from the temperature decrease detection means, or Switch engine operation to lean operation mode for premixed combustion when expected to be lower,furtherThe engine when the temperature of the catalyst is predicted to be lower or lower than a second set value set as a temperature lower than the first set value according to the output from the temperature drop detecting means Is switched to the stoichiometric operation mode of the premixed combustion.
[0007]
This temperature decrease suppression means injects additional fuel during the switching means (temperature decrease suppression mode switching means for switching the operation mode) for switching the combustion state of the engine (stratified super lean combustion and premixed combustion) or during the exhaust stroke of the engine. The additional fuel injection control means is preferable.
When the temperature drop detecting means is a means for directly detecting the temperature of the catalyst, the temperature drop is detected when the temperature drop detecting means detects that the catalyst temperature is lower than a preset temperature. It is preferable that the combustion state is premixed combustion for a predetermined time by the lowering suppression means. In this case, it becomes possible to prevent the exhaust gas purification efficiency from deteriorating.
[0008]
Further, the temperature drop and the temperature drop degree of the catalyst may be detected by the temperature drop detection means, and the time for premixed combustion by the temperature drop suppression means may be made variable according to the temperature drop degree. When the degree of temperature decrease is small, it is possible to reduce the time for premixed combustion while preventing the exhaust gas purification efficiency from deteriorating, and to minimize the deterioration of fuel consumption.
[0009]
In addition, after switching the operation mode (after control by the temperature drop suppression means), it is conceivable to return to the normal operation mode by actually detecting the catalyst temperature. In this case, when the temperature rising gradient of the catalyst is steep, it is preferable to lower the set temperature for returning to the normal mode to prevent the catalyst from becoming overheated.
Further, when the temperature decrease detecting means is a means for estimating the temperature of the catalyst, for example, the temperature of the catalyst or the temperature decrease is estimated by the duration of the stratified super lean combustion in which the exhaust gas temperature decreases, and the temperature decrease suppressing means May be premixed combustion for a certain period of time after a lapse of a predetermined time from setting to stratified super lean combustion. In this case, a very simple control specification can be obtained.
[0010]
  When this engine has the stoichiometric operation mode, it is preferable to switch to the stoichiometric operation mode, and when it has the lean operation mode, it is preferable to switch to the lean operation mode.
  According to a second aspect of the present invention, the exhaust gas purifying apparatus of the present invention is provided in a direct injection internal combustion engine that directly injects fuel into a combustion chamber and performs stratified super-lean combustion having an air / fuel ratio larger than the stoichiometric air / fuel ratio in accordance with operating conditions. A catalyst disposed in the exhaust passage of the engine for purifying exhaust gas, and detecting or predicting a temperature drop of the catalyst by detecting the temperature of the catalyst, or detecting a specific operating state causing the temperature drop Then, by estimating the temperature drop of the catalyst, the temperature drop detection means for detecting the temperature drop of the catalyst after the catalyst temperature reaches the catalyst activation temperature and is activated, and the temperature drop detection means Temperature drop suppression means that operates to suppress the temperature drop of the catalyst when a temperature drop of the catalyst is detected, and the in-cylinder injection internal combustion engine includes the layered super-lean combustion, the layered combustion The premixed combustion with a combustion air-fuel ratio smaller than that of lean combustion is switched according to the operating state. The premixed combustion is performed in a stoichiometric operation mode in which operation is performed at the stoichiometric air-fuel ratio and an air pressure larger than the stoichiometric air-fuel ratio. The temperature drop detecting means is configured to detect the temperature drop of the catalyst and detect or predict the temperature drop of the catalyst by having two operation modes of a lean operation mode that operates at a fuel ratio, and the temperature drop The suppression means sets the operation mode as the lean operation mode when the temperature drop detection means predicts that the temperature of the catalyst is lower than or lower than the preset first set value.And thenWhen the temperature drop detecting means predicts that the temperature of the catalyst is lower or lower than the second set value set to a temperature lower than the first set value, the operation mode is set to the stoichiometric mode. It is characterized by the operation mode.
[0011]
Preferably, the first set value and the second set value are variable according to the output from the temperature drop detection means. For example, when the temperature decrease gradient is steep, it is preferable to increase the second set value and operate the temperature decrease suppression means early so as to prevent the catalyst purification efficiency from being deteriorated.
According to a third aspect of the present invention, the exhaust gas purifying apparatus of the present invention is provided in a direct injection internal combustion engine that directly injects fuel into a combustion chamber and performs stratified super-lean combustion having an air / fuel ratio larger than the stoichiometric air / fuel ratio in accordance with operating conditions. A catalyst disposed in the exhaust passage of the engine for purifying exhaust gas, and detecting or predicting a temperature drop of the catalyst by detecting the temperature of the catalyst, or detecting a specific operating state causing the temperature drop Then, by estimating the temperature drop of the catalyst, the temperature drop detection means for detecting the temperature drop of the catalyst after the catalyst temperature reaches the catalyst activation temperature and is activated, and the temperature drop detection means Temperature drop suppression means that operates to suppress the temperature drop of the catalyst when a temperature drop of the catalyst is detected, and the in-cylinder injection internal combustion engine includes the layered super lean combustion and the layered super lean combustion. The premixed combustion having a combustion air-fuel ratio smaller than that of the lean combustion is switched in accordance with the operating state, and the temperature decrease suppressing means is a first means for switching between the stratified super lean combustion and the premixed combustion. And a second means for injecting additional fuel at least during the exhaust stroke of the engine, and the temperature drop suppressing means selects the first means when the engine is in a steady operation state and While switching from lean combustion to the premixed combustion, the second means is selected when the engine is in a low load operation state.
[0012]
In the steady running operation state, the temperature decrease suppressing means switches the engine combustion state to premixed combustion (execution of the first means), and may include a low load operation state (idle operation state) including a deceleration fuel cut. In the case of (preferably), it is preferable to inject additional fuel (execution of the second means) during the exhaust stroke of the engine.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, with reference to FIGS. 1-5, the exhaust gas purification apparatus as 1st Embodiment of this invention is demonstrated.
The configuration of a cylinder injection type internal combustion engine provided with the exhaust gas purifying apparatus is as shown in FIG. 3, and is an internal combustion engine having four strokes of intake, compression, expansion and exhaust in one operation cycle, that is, a four-cycle engine. And it is a spark ignition type and is configured as a cylinder injection engine (cylinder injection internal combustion engine) that directly injects fuel into the combustion chamber.
[0014]
An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1 so as to communicate with each other. The intake passage 2 and the combustion chamber 1 are controlled to communicate with each other by an intake valve 4, and the exhaust passage 3 and the combustion chamber 1 are connected. The communication is controlled by the exhaust valve 5.
The intake passage 2 is provided with an air cleaner 6 and a throttle valve 7 in order from the upstream side, and the exhaust passage 3 is provided with an exhaust gas purification catalytic converter 9 as an exhaust gas purification catalyst in order from the upstream side. A muffler (silencer) (not shown) is provided. The intake passage 2 is provided with a surge tank 2a.
[0015]
Further, an exhaust gas recirculation device (hereinafter referred to as an EGR device) 10 is provided. That is, the exhaust gas recirculation passage 10b is provided so as to connect the surge tank 2a portion of the intake passage 2 and the upstream side of the exhaust passage 3, and an EGR valve 10a is attached to the exhaust gas recirculation passage 10b.
The flow rate of exhaust gas (also referred to as exhaust gas, exhaust gas, or exhaust gas) from the exhaust passage 3 to the intake passage 2 can be controlled by the EGR valve 10a. The EGR valve 10a is controlled according to the operating state of the engine.
[0016]
Further, the opening degree of the throttle valve 7 changes in accordance with the amount of depression of an accelerator pedal (not shown), whereby the amount of air introduced into the combustion chamber 1 is adjusted. Reference numeral 16 denotes an idle speed control valve (ISC valve), which is provided in a bypass passage 16A that bypasses the throttle valve installation portion of the intake passage 2 and is driven to open and close by a stepper motor (not shown). Alternatively, the idle speed at the time of substantially full closing is finely adjusted.
[0017]
50 is an air bypass valve (ABV), which is provided in a bypass passage 50A that connects the intake passage 2 upstream of the throttle valve 7 and the surge tank 2a so as to bypass the throttle valve 7 installation portion of the intake passage 2. The air-fuel ratio can be adjusted by adjusting the intake air amount separately from the throttle valve 7.
The injector (fuel injection valve) 8 is arranged so that its opening faces the combustion chamber 1 so as to directly inject fuel toward the combustion chamber 1 in the cylinder. Naturally, this injector 8 is provided for each cylinder. For example, if the engine of this embodiment is an in-line four-cylinder engine, four injectors 8 are provided.
[0018]
With such a configuration, the air sucked through the air cleaner 6 according to the opening of the throttle valve 7 is sucked into the combustion chamber 1 by opening the intake valve 4, and the sucked air and the injector 8 in the combustion chamber 1. The fuel directly injected from the fuel is mixed, and the ignition plug 35 is ignited at an appropriate timing in the combustion chamber 1 to be combusted to generate engine torque. CO, HC, NO in the exhaust gas is discharged to the exhaust passage 3 and discharged by a catalytic converter (hereinafter also simply referred to as catalyst) 9_xAfter these three harmful components are purified, they are silenced by a muffler and released to the atmosphere.
[0019]
In particular, this engine is an engine that can perform a saving operation while keeping the air-fuel ratio lean. During lean operation, the normal three-way catalyst alone can reduce NO in the exhaust gas._xCatalyst 9 cannot be sufficiently purified, the catalyst 9_xThe catalyst 9A and the three-way catalyst 9B are combined. In other words, lean NO_xDownstream of the catalyst 9A, CO, HC and NO in the exhaust gas under the stoichiometric air-fuel ratio_xA three-way catalyst 9B having a three-way function capable of purifying the catalyst is provided.
[0020]
This is a three-way catalyst 9B lean NO_xIt is placed downstream of the catalyst 9A and lean NO_xNO at catalyst 9A_xLean NO while not impeding purification_xThis is to ensure that CO and HC that could not be sufficiently purified by the catalyst can be purified. Lean NO_xIf the catalyst has a three-way function, lean NO_xOnly one catalyst may be arranged.
[0021]
By the way, the engine will be further described. The engine is configured such that the intake air flow that flows into the combustion chamber 1 from the intake passage 2 forms a vertical vortex (reverse tumble flow). However, a small amount of fuel is collected only in the vicinity of the spark plug 35 disposed at the center of the top of the combustion chamber 1 and separated from the spark plug 35 while using the longitudinal vortex. In this portion, an extremely lean air-fuel ratio can be obtained, and only the vicinity of the spark plug 35 is set to a stoichiometric air-fuel ratio or a rich air-fuel ratio, thereby realizing stable stratified combustion (stratified super-lean combustion) and fuel. Consumption can be suppressed. The optimum fuel injection timing in this case is the latter half of the compression stroke where the air flow is weak.
[0022]
In order to obtain a high output from the engine, the fuel from the injector 8 is homogenized in the entire combustion chamber 1, and the entire combustion chamber 1 is premixed with a stoichiometric air-fuel ratio or a lean air-fuel ratio. It is sufficient to perform combustion. Of course, the stoichiometric air-fuel ratio can provide higher output than the lean air-fuel ratio, but in these cases, fuel injection is performed at a timing at which fuel atomization and vaporization are sufficiently performed. As a result, high output can be obtained efficiently. The optimum fuel injection timing in such a case is set so that the fuel injection is completed at the initial stage or the first half of the intake stroke so that the atomization and vaporization of the fuel can be promoted using the intake air flow.
[0023]
Incidentally, various sensors are provided for controlling the engine. First, on the intake passage 2 side, an air flow sensor 11 for detecting the intake air amount from Karman vortex information, an intake air temperature sensor 12 for detecting the intake air temperature, and an atmospheric pressure sensor 13 for detecting the atmospheric pressure are provided in the air cleaner portion. A potentiometer type throttle sensor 14 for detecting the opening degree of the throttle valve 7, an idle switch 15 for detecting an idling state, and the like are provided in the throttle valve arrangement portion.
[0024]
Further, on the exhaust passage 3 side, the oxygen concentration in the exhaust gas (O₂Oxygen concentration sensor 17 (hereinafter simply referred to as O)₂ Sensor 17) and a downstream side portion of the catalyst 9 has a temperature θ of the catalyst or the vicinity thereof._CC(Hereafter, catalyst temperature θ_CCA catalyst temperature sensor (high temperature sensor) 26 is provided as a catalyst temperature detecting means for detecting the above.
[0025]
Further, as other sensors, a water temperature sensor 19 for detecting the engine cooling water temperature or a crank angle sensor 21 for detecting a crank angle as shown in FIG. 2 (the crank angle sensor 21 is also a rotation speed sensor for detecting the engine speed). And a TDC sensor (cylinder discrimination sensor) 22 for detecting the top dead center of the first cylinder (reference cylinder) is provided in the vicinity of each cam.
[0026]
Detection signals from these sensors are input to an electronic control unit (ECU) 23.
Note that the ECU 23 includes a voltage signal from the accelerator position sensor 24 that detects the amount of depression of the accelerator pedal and a battery sensor 25 that detects the voltage of the battery, and a cranking switch that detects a start time (or an ignition switch (key switch)). A signal from 20 is also input.
[0027]
By the way, the hardware configuration of the ECU 23 is as shown in FIG. 2. The ECU 23 has a CPU 27 as a main part thereof. The intake air temperature sensor 12, the atmospheric pressure sensor 13, the throttle sensor 14, and the O 27 are connected to the CPU 27.₂ Detection signals from the sensor 17, the water temperature sensor 19, the accelerator position sensor 24, the catalyst temperature sensor 26, and the battery sensor 25 are input via the input interface 28 and the analog / digital converter 30, and the airflow sensor 11 and crank angle sensor. 21, detection signals from the TDC sensor 22, the idle switch 15, the cranking switch 20, the ignition switch and the like are input via the input interface 29.
[0028]
Further, the CPU 27 holds the stored contents while the ROM 31 for storing program data and fixed value data, the RAM 32 to be updated and sequentially rewritten, the free running counter 48 and the battery are connected via the bus line. Thus, data is exchanged with a battery backup RAM (not shown) backed up.
[0029]
The data in the RAM 32 is erased and reset when the ignition switch is turned off.
Further, the fuel injection control signal based on the calculation result by the CPU 27 is output to the solenoid (injector solenoid) 8a of the injector 8 via the (in this case, four) injection driver (fuel injection valve driving means) 34 for each cylinder. It has come to be.
[0030]
Now, paying attention to the fuel injection control (air-fuel ratio control), the fuel injection control signal calculated by the CPU 27 is output via the driver 34, and, for example, the four injectors 8 are sequentially driven.
Due to the characteristics of the in-cylinder injection engine as described above, in this engine, as a mode of fuel injection, in order to realize lean operation by stratified super lean combustion and improve fuel efficiency (particularly, in the latter half of the compression stroke) The late-stage injection mode (late-lean operation mode) in which fuel injection is performed and the lean-injection by premixed combustion, and the early-stage injection in which fuel is injected during the intake stroke (especially in the first half of the intake stroke) in order to obtain output by slow acceleration Mode (first lean operation mode) and stoichiometric operation (stoichiometric air-fuel ratio operation) by premixed combustion, and fuel injection during the intake stroke to improve output compared to the first injection mode (stoichio operation mode) ) And is switched according to the operating state of the engine.
[0031]
In the late lean operation mode, the exhaust gas temperature is particularly lowered, and this is called a specific operation state. Further, the switching of the operation mode described above means switching of the combustion state of the engine (switching between stratified super lean combustion and premixed combustion).
For such fuel injection control (injector drive control), as shown in the block diagram of FIG. 1, the ECU 23 sets the operation mode setting means 106 for selecting the injection mode (operation mode) and the setting of the fuel injection amount. There is provided a fuel injection control means 101 for performing the following.
[0032]
As shown in FIG. 1, the operation mode setting means 106 has a function (normal operation mode setting means) 107 for selecting an injection mode during normal operation and an injection mode for suppressing the temperature drop of the catalyst 9. And a switching function (temperature drop suppression mode switching means) 108.
Among these, in the normal operation mode setting means 107, the injection mode is set to the engine speed (rotation speed) Ne detected from the engine speed sensor 21, various sensors 104, etc., and the accelerator pedal depression amount θ._ACCBased on the above, the target output torque T of the engine is set, and either the early injection mode or the late injection mode is selectively set according to the engine speed Ne or the target output torque T. For example, when the engine speed Ne is low and the target torque T is low, the late injection mode is set, and when either the engine speed Ne or the target torque T is not low, the pre-injection mode or stoichiometric mode is set.
[0033]
Further, the temperature drop suppression mode switching means 108 is a characteristic component of the in-cylinder injection internal combustion engine for exhaust gas purification, and when the temperature drop of the catalyst 9 is determined by the temperature drop determination means 105 described later. In addition, the normal operation mode set by the normal operation mode setting means 107 is switched to the operation mode for suppressing temperature decrease, and has a function of suppressing the temperature decrease of the catalyst 9. Therefore, the temperature drop suppression mode switching means 108 constitutes a temperature drop suppression means 110 that operates so as to suppress the temperature drop of the catalyst 9.
[0034]
As shown in FIG. 1, the temperature drop suppression mode switching means 108 is based on the information from the normal operation mode setting means 107, the temperature drop determination means 105, which will be described later, and the throttle sensor 14. The mode is switched to the first lean operation mode as a temperature drop suppressing operation mode. Since switching of the operation mode corresponds to switching of the combustion state of the engine, switching the late lean operation mode to the first lean operation mode means switching the stratified super lean combustion to the premixed combustion.
[0035]
This is because the exhaust gas temperature is greatly influenced by the operation mode selected by the normal operation mode setting means 107 (that is, the air-fuel ratio at the time of operation), and the closer to the stoichiometric operation mode (theoretical air-fuel ratio), the per unit weight of the intake air. The amount of fuel increases (therefore, the amount of heat generated increases) and the exhaust gas temperature increases, so that the exhaust gas at a higher temperature is brought closer to the catalyst 9 by switching the operation mode using this property. The amount of heat transferred from the exhaust gas to the catalyst 9 is increased so as to be discharged, the temperature drop of the catalyst 9 is suppressed, and the purification efficiency of the catalyst 9 is prevented from deteriorating.
[0036]
Here, when the late lean operation mode in which the exhaust gas temperature is low is selected as the normal operation mode, the first lean operation mode in which the exhaust gas temperature is higher than that in the late lean operation mode is switched to. This is because the exhaust gas temperature becomes the lowest in the late lean operation mode in which combustion is performed with the air-fuel mixture, and thus the temperature of the catalyst 9 is significantly reduced.
[0037]
Further, the temperature drop suppression mode switching means 108 takes in information from the throttle sensor 14 as well. This is because it is preferable to set the control by the temperature drop suppression mode switching means 108 to be performed in a constant load state (steady operation state).
This is because the normal operation mode is switched during acceleration that is not in a steady operation state, and it is not particularly necessary to perform temperature decrease suppression control by switching the operation mode by the temperature decrease suppression mode switching means 108. In addition, when the vehicle is decelerating in a non-steady operation state, there is an operation state such as decelerating fuel cut.At the time of this fuel cut, the fuel necessary to raise the exhaust temperature when the operation mode is switched is cut, so the exhaust temperature It is because it cannot raise. Also, if mode switching control is executed even during deceleration and an attempt is made to prohibit operation mode switching control only during deceleration fuel cut, the control becomes complicated. In addition, about the low load driving | running state containing such a deceleration fuel cut, it is preferable to perform temperature fall suppression control as shown in 4th Embodiment mentioned later.
[0038]
For this reason, the temperature drop suppression mode switching means 108 determines whether or not the change amount ΔTPS of the throttle opening during a certain time is equal to or less than the reference value TP1 of the change amount of the throttle opening (ΔTPS ≦ TP1). Whether or not the vehicle is in a steady operation state is determined. Note that the change amount ΔTPS is obtained, for example, by the difference between the throttle opening value in the previous detection cycle and the throttle opening value in the current detection cycle. The reference value TP1 is set as a value close to 0.
[0039]
In addition, the temperature drop suppression mode switching means 108 is connected to the catalyst temperature θ._CCTherefore, the ECU 23 is provided with a temperature decrease determination means 105 for determining a temperature decrease of the catalyst 9. The temperature drop determination means 105 and the catalyst temperature sensor 26 described above constitute a temperature drop detection means 111.
This temperature decrease determination means 105 once sets the catalyst temperature θ._CCAfter reaching the temperature necessary for activating the catalyst 9 (catalytic activation temperature) and activating, the catalyst temperature θ_CCBased on the detection information from the catalyst temperature sensor 26 that detects this, the temperature drop of the catalyst 9 is determined.
[0040]
For this reason, the temperature drop determination means 105 determines the catalyst temperature θ_CCIs a preset set temperature θ₁By determining whether or not (θ_CC≦ θ₁), The temperature drop of the catalyst 9 is determined.
Where the set temperature θ₁Is set as a value higher than the catalyst activation temperature, for example, a value obtained by adding a predetermined temperature (for example, 50 ° C.) at the catalyst activation lower limit temperature. This catalyst activation lower limit temperature is the lean NO._XIn the case of a catalyst, it is about 400 degrees. The value of the predetermined temperature is a value determined by the response delay and response accuracy of the catalyst temperature sensor 26, and varies depending on the system. Moreover, the catalyst activity minimum temperature of a catalyst changes with catalyst components etc.
[0041]
The temperature drop determination means 105 is controlled by the temperature drop suppression mode switching means 108 as the temperature drop suppression means 110 under the control of the catalyst temperature θ._CCIn order to determine whether or not the temperature of the catalyst 9 has sufficiently increased, the temperature increase of the catalyst 9 is determined based on detection information from the catalyst temperature sensor 26 that detects the temperature of the catalyst 9.
For this reason, the temperature drop determination means 105 determines the catalyst temperature θ_CCIs a preset set temperature θ₂By determining whether or not (θ_CC≧ θ₂), Catalyst temperature θ_CCWhether or not has risen is determined.
[0042]
Where the set temperature θ₂Is the end condition of the temperature drop suppression control, and the catalyst temperature θ_CCAs shown in FIG. 9A, the set temperature θ is₁Is set as a larger value (higher temperature). Set temperature θ₂Is the set temperature θ₁You may set as the same value.
Such set temperature θ₁, Θ₂Is set, for example, as shown in FIG. In FIG. 9A, curve A indicates the catalyst temperature θ._CCShows changes. Moreover, in the figure, the injection period indicates the injection period based on the first lean operation mode for temperature drop suppression.
[0043]
As shown in FIG. 9 (a), the catalyst temperature θ_CCDecreases and the set temperature θ₁In the case of the following, the temperature reduction control is performed by switching to the first lean operation mode by the temperature suppression control mode switching means 108 (the injection period is shown in the figure), and thereby the catalyst temperature θ_CCRises and the set temperature θ₂When it becomes above, temperature fall suppression control is complete | finished and it is made to return an operation mode to a normal operation mode (here, it returns to a late lean operation mode). And again, the catalyst temperature θ_CCDecreases and the set temperature θ₁In the following cases, similar control is repeated.
[0044]
Incidentally, as shown in FIG. 1, the ECU 23 is provided with a fuel injection control means 101. The fuel injection control in the fuel injection control means 101 will be described. In the fuel injection control means 101, the fuel injection amount is the fuel injection time (injector drive time, which is called injector drive pulse width in actual control). ) T_AUThe engine load (intake air amount per stroke) Q / Ne and the target air-fuel ratio (A / F, AF) First, the basic drive time t_pIs calculated.
[0045]
t_p= (Q / Ne) × (1 / AF) × (α_AIR/ Α_FUEL) X (1 / G_INJ)
The engine load Q / Ne is the intake air amount per stroke, and the intake air amount Q detected by the air flow sensor 11 is divided by the engine speed Ne detected by the engine speed sensor (crank angle sensor) 21. Is required.
Α_AIRIs the air density, α_FUELIs fuel density, G_INJIs the injector gain.
[0046]
And fuel injection time t_AUIs calculated by the following equation.
t_AU= T_pXf + t_D
In addition, f is various fuel correction coefficients, and this fuel correction coefficient f is the engine cooling water temperature detected by the water temperature sensor 19, the intake air temperature detected by the intake air temperature sensor 12, and the large pressure detected by the atmospheric pressure sensor 13. It is set according to the atmospheric pressure. T_DIs the injector dead time.
[0047]
Since the exhaust gas purification apparatus as the first embodiment of the present invention is configured as described above, for example, as shown in FIG. 4, the fuel injection control is performed based on the operation mode set by the normal operation mode setting means 107. Is done.
This control is executed at every fixed crank angle, and first, the processes of steps A10 to A30 are performed. That is, in step A10, the engine load Q / Ne (that is, the intake air amount per stroke) is calculated from the intake air amount Q detected by the air flow sensor 11 and the rotation speed sensor 21 and the engine rotation speed Ne. Next, at step A20, as shown in the above equation, based on this engine load Q / Ne, the basic drive time t_pCalculate In step A30, the basic drive time t_pThe fuel injection time t is multiplied by various fuel correction coefficients K, etc._AUIs calculated.
[0048]
Based on this, fuel injection (step A40) is performed.
Next, temperature reduction suppression control by the exhaust gas purifying apparatus, that is, switching control to the temperature decrease suppression operation mode by the temperature decrease suppression mode switching means 108 will be described with reference to the flowchart of FIG. This control is executed at regular intervals.
[0049]
First, in step B10, it is determined whether or not the operation mode selected by the normal operation mode setting means 107 is the late lean operation mode. As a result of the determination, if the late lean operation mode is selected, the process proceeds to step B20. If the late lean operation mode is not selected, the process proceeds to step B60.
In step B20, the catalyst temperature θ_CCIs the set temperature θ₁It is determined whether or not the catalyst temperature θ_CCIs the set temperature θ₁If not, the process proceeds to step B30, and it is determined whether or not the change amount ΔTPS of the throttle opening is equal to or less than a reference value TP1 of the change amount of the throttle opening in order to determine whether or not the steady operation state is present. .
[0050]
As a result of this determination, if the change amount ΔTPS is less than or equal to the reference value TP1, the process proceeds to step B40. If the change amount ΔTPS is not less than or equal to the reference value TP1, the process returns without performing temperature decrease suppression control because the steady operation state is not established.
On the other hand, as a result of the determination in step B20, the catalyst temperature θ_CCIs the set temperature θ₁If not, the process returns because the temperature drop suppression control is not necessary.
[0051]
In step B40, the lower-level lean operation mode as the normal operation mode is switched to the first-term lean operation mode for temperature decrease suppression by the temperature decrease suppression mode switching means 108 to perform the temperature decrease suppression control, and the flag F is set in step B50. Set to 1. Here, the flag F is set to 1 when the temperature decrease suppression control is being performed, is set to 0 when the temperature decrease suppression control is not being performed, and is set to 0 at the time of initial setting.
[0052]
By the way, if the late lean operation mode is not selected in step B10, the process proceeds to step B60. In step B60, it is determined whether or not the flag F is 1. If the flag F is 1 as a result of this determination, the process proceeds to step B60. (F = 1) proceeds to step B70, and returns if the flag F is not 1.
In Step B70, it is determined whether or not the change amount ΔTPS of the throttle opening is equal to or less than a reference value TP1 of the change amount of the throttle opening, in order to determine whether or not the steady operation state is present. As a result of this determination, if the change amount ΔTPS is equal to or less than the reference value TP1, the process proceeds to step B80, and the catalyst temperature θ_CCIs the set temperature θ₂It is determined whether or not the catalyst temperature θ is reached._CCIs the set temperature θ₂If it is determined that it is below, the process further proceeds to step B90, the temperature decrease suppression control is terminated, and the flag F is reset to 0 in step B100.
[0053]
In step B80, the catalyst temperature θ_CCIs the set temperature θ₂If it is determined that it is not below, the process returns, and the temperature decrease suppression control is continued.
On the other hand, if it is determined in step B70 that the change amount ΔTPS is not equal to or less than the reference value TP1, the process proceeds to step B90, the temperature decrease suppression control is terminated, and the flag F is reset to 0 in step B100.
[0054]
After the end of the temperature decrease suppression control, the operation mode is set back to the normal operation mode setting means 107 (here, the latter lean operation mode which is the original operation mode).
As described above, in the exhaust gas purifying apparatus of the present embodiment, when the temperature decrease of the catalyst 9 is detected by the temperature decrease determining unit 105 as the temperature decrease detecting unit 111, the temperature decrease suppressing unit 110 as the temperature decrease suppressing unit 110 is used. By operating the mode switching means 108, there is an advantage that it is possible to prevent the deterioration of the catalyst purification efficiency accompanying the decrease in the exhaust gas temperature peculiar to the direct injection internal combustion engine.
[0055]
That is, the engine operating mode is set by the temperature drop suppression mode switching means 108 as the temperature drop suppression means 110 in accordance with the outputs from the normal operation mode setting means 107 and the temperature drop determination means 105 as the temperature drop detection means 111. By switching, it is possible to suppress a decrease in exhaust gas temperature due to stratified super-lean combustion, thereby preventing an increase in catalyst purification efficiency accompanying a decrease in exhaust gas temperature.
[0056]
Next, a modification of the first embodiment will be described.
In the exhaust gas purifying apparatus of the first embodiment described above, one set temperature for determining the temperature drop of the catalyst 9 is provided. In this modification, the catalyst temperature θ_CCIn order to perform temperature decrease suppression control according to the above, two set values, a first set value and a second set value set as a temperature lower than the first set value, are provided, and the catalyst temperature θ_CCIs switched to the first lean operation mode as the temperature decrease suppressing operation mode, and the temperature decrease of the catalyst 9 is sufficiently suppressed in this operation mode. That is, the catalyst temperature θ_CCIs switched to the stoichiometric operation mode as the operation mode for suppressing the temperature drop when the value is lower than or lower than the second set value.
[0057]
According to the exhaust gas purification apparatus of this modification, the catalyst temperature θ_CCIs slightly lower than the set temperature, the operation mode is set to the lean operation mode in consideration of the deterioration of fuel consumption, so that the exhaust gas purification efficiency of the catalyst 9 can be maintained, and the catalyst temperature θ_CCIs considerably lower than the set temperature, the exhaust gas purification efficiency of the catalyst 9 is extremely deteriorated. Therefore, the operation mode is set to the stoichiometric operation mode, and the catalyst temperature θ is positively increased._CCThere is an advantage that the deterioration of the purification efficiency of the catalyst 9 can be prevented by raising the temperature of the catalyst.
[0058]
Next, the second embodiment will be described. As shown in FIG. 6, the exhaust gas purification apparatus of this embodiment is different from that of the first embodiment described above in the temperature drop determination means 105 as the temperature drop detection means 111. .
That is, in this embodiment, the temperature decrease determination unit 105 detects the temperature decrease degree (temperature decrease gradient) of the catalyst 9 based on the detection information from the catalyst temperature sensor 26, predicts the temperature decrease of the catalyst 9, The set temperature θ1 is changed according to the detected temperature decrease degree, and the catalyst temperature θ_CCIs determined to be less than or equal to the preset temperature θ1,_CCAfter the catalyst reaches the catalyst activation temperature and is activated, the catalyst temperature θ_CCIt is determined whether or not the battery has fallen.
[0059]
For this reason, as shown in FIG._CCA Δθ calculation unit 105A having a function of calculating the time change amount Δθ of the catalyst is detected. The detection information from the catalyst temperature sensor 26 is read at regular intervals by the Δθ calculation unit 105A, and the catalyst temperature θ in the current reading cycle is read._CCAnd catalyst temperature θ in the previous reading cycle_CCΔθ (catalyst temperature θ_CCThe degree of temperature decrease is detected by calculating the amount of time change Δθ).
[0060]
Based on the information from the Δθ calculation unit 105A, the temperature drop of the catalyst 9 is predicted and the set temperature θ1 is changed, and the catalyst temperature θ is changed by the set temperature θ1._CCIn order to determine whether or not the temperature has decreased, the temperature decrease determination means 105 is further provided with a θ1, θ2 reading unit 105B and a determination unit 105C.
The θ1 reading unit 105B is configured such that the catalyst temperature θ calculated by the Δθ calculation unit 105A_CCThe setting temperature θ1 has a function of reading the set temperature θ1 from the map [θ1 = G (Δθ)] on the basis of the time change amount Δθ._CCIs less than or equal to the set temperature θ1 read by the θ1, θ2 reading unit 105B (θ_CC≦ θ1), catalyst temperature θ_CCIt has a function of determining whether or not the decrease has occurred.
[0061]
The temperature drop determination means 105 is controlled by the temperature drop suppression mode switching means 108 as the temperature drop suppression means 110 under the control of the catalyst temperature θ._CCTo determine whether the catalyst temperature has risen sufficiently_CCThe temperature rise of the catalyst 9 is predicted by detecting the temperature rise degree (temperature rise gradient) of the catalyst 9 based on the detection information from the catalyst temperature sensor 26 for detecting the catalyst temperature θ._CCWhether or not has risen is also determined. That is, the set temperature θ2 is changed according to the degree of temperature decrease, and the catalyst temperature θ_CCIs determined to be equal to or higher than the set temperature θ2 to thereby determine the catalyst temperature θ._CCWhether or not has risen is determined.
[0062]
Therefore, the detection information from the catalyst temperature sensor 26 is read at regular intervals by the Δθ calculation unit 105A included in the temperature decrease determination unit 105, and the catalyst temperature θ in the current detection cycle is read._CCAnd catalyst temperature θ in the previous detection cycle_CC(Catalyst temperature θ_CCThe degree of temperature rise is detected by calculating the amount of time change Δθ).
[0063]
Then, the θ1, θ2 reading unit 105B and the determination unit 105C included in the temperature decrease determination unit 105 predict the temperature increase of the catalyst 9 based on the information from the Δθ calculation unit 105A, and change the set temperature θ2. The catalyst temperature θ depends on the set temperature θ2._CCIt also has a function of determining whether or not has risen.
That is, the θ1 reading unit 105B performs the catalyst temperature θ calculated by the Δθ calculation unit 105A._CCAnd a function of reading the set temperature θ2 from the map [θ2 = G (Δθ)] on the basis of the time change amount Δθ, and the determination unit 105C has the catalyst temperature θ._CCIs determined to be equal to or higher than the set temperature θ2 read by the θ1, θ2 reading unit 105B (θ_CC≧ θ2), catalyst temperature θ_CCIt also has a function of determining whether or not has risen.
[0064]
Here, the set temperature θ2 is an end condition of the temperature decrease suppression control, and the catalyst temperature θ_CCIs set to a value (higher temperature) that is higher than the set temperature θ2 of the first embodiment because it is for preventing the catalyst temperature from rising excessively. . That is, if the heat-resistant temperature of the catalyst is about 800 ° C, it is preferable that the predetermined temperature is about 200 ° C and the set temperature θ2 is about 600 ° C. Of course, since the heat-resistant temperature varies depending on the catalyst, the set temperature θ2 is preferably set as appropriate according to the catalyst.
[0065]
These set temperatures θ1 and θ2 are set as shown in FIG. 9B, for example. In FIG. 9B, curves A and B indicate the catalyst temperature θ._CCCurve A shows the catalyst temperature θ_CCThe curve B shows the catalyst temperature θ._CCIt shows the case where the change of is abrupt.
As shown by this curve A, the catalyst temperature θ_CCWhen the change of the temperature is gradual, the set temperature θ described in the first embodiment is described with reference to FIG.₁, Θ₂The set temperatures θ1 and θ2 are set in the same manner as described above. On the other hand, as shown by curve B, the catalyst temperature θ_CCWhen the change of A is abrupt, the set temperature θ1 is set so as to become larger (so that the temperature becomes higher) by the map [θ1 = G (Δθ)], and the set temperature θ2 is set to the map [θ2 = G (Δθ)] Is set to be smaller (so that the temperature is lower).
[0066]
This is the catalyst temperature θ_CCWhen the temperature drop is abrupt, by setting the set temperature θ1 to a high temperature, the temperature drop suppression control is started early, and the catalyst temperature θ1_CCIs prevented from excessively decreasing and the purification efficiency of the catalyst 9 is deteriorated._CCWhen the temperature rises suddenly, the temperature drop suppression control is terminated early by setting the set temperature θ2 to a low temperature, and the catalyst temperature θ_CCThis is to prevent the excessive increase of the amount.
[0067]
To explain further, making the set temperature θ1 variable in this way means making the time for continuing the first lean operation mode for temperature drop suppression variable, and as described above, setting the set temperature θ1 to a high temperature. When the temperature is set and the set temperature θ2 is set to a low temperature, it is possible to shorten the time during which the lean operation mode for suppressing temperature decrease is continued and to suppress the deterioration of fuel consumption.
[0068]
In addition, by setting the set temperature θ2 high, the catalyst can be sufficiently heated, and the temperature drop suppression control can be prevented from being complicated.
In addition, about the other structure in the exhaust gas purification apparatus in this embodiment, since it is the same as that of the above-mentioned 1st Embodiment, the description is abbreviate | omitted here. The exhaust gas purification apparatus as the second embodiment of the present invention is configured as described above, and the fuel injection control based on the operation mode set by the normal operation mode setting means 107 is the same as in the first embodiment described above. Therefore, the description thereof is omitted.
[0069]
Further, the temperature decrease suppression control by the exhaust gas purifying apparatus of the present embodiment, that is, the switching control to the temperature decrease suppression operation mode by the temperature decrease suppression mode switching means 108 will be described with reference to the flowchart of FIG. This control is executed at regular intervals.
First, in step D10, it is determined whether or not the operation mode selected by the normal operation mode setting means 107 is the late lean operation mode. As a result of the determination, if the late lean operation mode is selected, the process proceeds to step D20. If the late lean operation mode is not selected, the process proceeds to Step D80.
[0070]
In Step D20, the catalyst temperature detection mode (see FIG. 8) is executed by the Δθ calculator 105A, and the catalyst temperature θ_CCThe amount of change Δθ in a certain time is calculated. That is, as shown in FIG. 8, at step E10, the catalyst temperature θ_CCAnd based on this, in step E20, the catalyst temperature θ_CCThe amount of change Δθ over a certain period of time is calculated.
[0071]
In step D30, the set temperature θ1 is read from the map based on the change amount Δθ calculated in step D20 by the θ1, θ2 reading unit 105B, and the process proceeds to step D40. In Step D40, the catalyst temperature θ is determined by the determination unit 105C._CCIs less than or equal to the set temperature θ1, and as a result of this determination, the catalyst temperature θ_CCWhen the temperature is equal to or lower than the set temperature θ1, the process proceeds to step D50.
[0072]
In addition, since the process after step D50, ie, the process from step D50 to step D70, is the same as step B30 to step B50 in the flowchart (see FIG. 5) showing the temperature suppression control in the first embodiment described above, The description is omitted here.
On the other hand, as a result of the determination in step D40, the catalyst temperature θ_CCIf the temperature is not equal to or lower than the set temperature θ1, the process returns because the temperature drop suppression control is not necessary.
[0073]
By the way, when the late lean operation mode is not selected in step D10, the process proceeds to step D80. In step D80, it is determined whether or not the flag F is 1. If the flag F is 1 as a result of this determination, the process proceeds to step D80. (F = 1) proceeds to step D90, and returns if the flag F is not 1.
In Step D90, it is determined whether or not the change amount ΔTPS of the throttle opening is equal to or less than a reference value TP1 of the change amount of the throttle opening, in order to determine whether or not the steady operation state is present. As a result of this determination, when the change amount ΔTPS is equal to or smaller than the reference value TP1, the process proceeds to step D100, and the catalyst temperature detection mode (see FIG. 8) is executed by the Δθ calculation unit 105A, and the catalyst temperature θ_CCThe amount of change Δθ in a certain time is calculated. That is, as shown in FIG. 8, at step E10, the catalyst temperature θ_CCAnd based on this, in step E20, the catalyst temperature θ_CCThe amount of change Δθ over a certain period of time is calculated.
[0074]
In step D110, the set temperature θ2 is read from the map based on the change amount Δθ calculated in step D100 by the θ1, θ2 reading unit 105B, and the process proceeds to step D120.
In step D120, the catalyst temperature θ is determined by the determination unit 105C._CCIs equal to or higher than the set temperature θ2, and as a result of this determination, the catalyst temperature θ_CCIs determined to be equal to or higher than the set temperature θ2, the process further proceeds to step D130, the temperature decrease suppression control is terminated, and the flag F is reset to 0 in step D140.
[0075]
In step D120, the catalyst temperature θ_CCWhen it is determined that the temperature is not equal to or higher than the set temperature θ2, the process returns and continues the temperature decrease suppression control.
On the other hand, if it is determined in step D90 that the variation ΔTPS is not equal to or less than the reference value TP1, the process proceeds to step D130, the temperature decrease suppression control is terminated, and the flag F is reset to 0 in step D140.
[0076]
Note that after the end of the temperature decrease suppression control, the operation mode (here, the late lean operation mode) set by the normal operation mode setting means 107 is restored.
Thus, in the exhaust gas purifying apparatus of the present embodiment, when the temperature decrease of the catalyst 9 is determined by the temperature decrease determining unit 105 as the temperature decrease detecting unit 111, the temperature decrease suppressing unit 110 as the temperature decrease suppressing unit 110 is used. By operating the mode switching means 108, there is an advantage that it is possible to prevent the deterioration of the catalyst purification efficiency accompanying the decrease in the exhaust gas temperature peculiar to the cylinder injection type internal combustion engine.
[0077]
That is, the engine operating mode is set by the temperature drop suppression mode switching means 108 as the temperature drop suppression means 110 in accordance with the outputs from the normal operation mode setting means 107 and the temperature drop determination means 105 as the temperature drop detection means 111. By switching, it is possible to suppress a decrease in exhaust gas temperature due to stratified super-lean combustion, thereby preventing an increase in catalyst purification efficiency accompanying a decrease in exhaust gas temperature.
[0078]
Next, a third embodiment will be described. As shown in FIG. 10, the exhaust gas purifying apparatus of this embodiment is different from that of the first embodiment described above in the temperature drop determination means 105 as the temperature drop detection means 111. .
That is, in this embodiment, the temperature decrease determination unit 105 estimates the temperature decrease of the catalyst 9 based on the duration after the lean operation in the late lean operation mode set by the normal operation mode setting unit 107 is started. Is configured to do. The temperature drop of the catalyst 9 is estimated based on the set time T1 after the start of the lean operation in the late lean operation mode.₀This is done by determining whether or not this is the case.
[0079]
As described above, in this embodiment, the catalyst temperature θ is determined by the duration of the late lean operation mode (stratified super lean combustion) in which the exhaust gas temperature decreases._CCAlternatively, the temperature decrease of the catalyst 9 is estimated, and the temperature decrease suppression control is performed based on this estimation.
For this reason, when the late lean operation mode is set by the normal operation mode setting means 107, the temperature decrease determination means 105 starts the timer 109A to measure the duration. Then, the count value t1 by the timer 109A is the set time T₀If this is the case, the catalyst temperature θ_CCThe signal is sent to the temperature drop suppression mode switching means 108.
[0080]
Since the duration t1 is measured by the timer 109A as shown in FIG. 10, the duration t1 indicates the count value of the timer 109A. Also, the set time T₀Is set to about 30 seconds, for example.
Further, the temperature decrease determination means 105 is configured such that the duration t1 from the start of the lean operation in the late lean operation mode is the set time T₀In such a case, it also has a function of resetting a timer 109A described later.
[0081]
Further, the temperature decrease determination unit 105 performs the temperature decrease of the catalyst 9 by the temperature decrease suppression control based on the duration time after the lean operation in the first lean operation mode set by the temperature decrease suppression mode switching unit 108 is started. Is suppressed and the temperature decrease suppression control can be terminated, that is, the catalyst temperature θ_CCIt also has a function of determining whether or not has risen sufficiently.
[0082]
The determination as to whether or not the temperature decrease suppression control can be terminated is based on the set time T2 after the start of the lean operation in the first lean operation mode.₁This is done by determining whether or not this is the case.
This is because the catalyst temperature θ depends on the duration t1 of the above-described late lean operation mode (stratified super lean combustion)._CCAlternatively, similarly to the estimation of the temperature decrease of the catalyst 9, the catalyst temperature θ is determined by the duration t2 after the lean operation in the first lean operation mode is started._CCAlternatively, the temperature rise of the catalyst 9 is estimated.
[0083]
For this reason, when the temperature drop determination means 105 is switched to the previous lean operation mode by the temperature drop suppression mode switching means 108, the timer 109B is started to measure the duration. Then, the count value (ie, duration) t2 by the timer 109B is equal to the set time T₁If this is the case, the catalyst temperature θ_CCIt is determined that the temperature has risen, and the signal is sent to the temperature drop suppression mode switching means 108.
[0084]
Since the duration t2 is measured by the timer 109B as shown in FIG. 10, the duration t2 corresponds to the count value of the timer 109B. Also, the set time T₁Is set to about 90 seconds, for example.
In addition, the temperature decrease determination unit 105 determines that the duration t2 after the start of the lean operation in the first lean operation mode is the set time T₁In such a case, it also has a function of resetting a timer 109B described later.
[0085]
In addition, about the other structure in the exhaust gas purification apparatus in this embodiment, since it is the same as that of the above-mentioned 1st Embodiment, the description is abbreviate | omitted here.
The exhaust gas purification apparatus as the third embodiment of the present invention is configured as described above, and the fuel injection control based on the operation mode set by the normal operation mode setting means 107 is the same as in the first embodiment described above. Therefore, the description thereof is omitted.
[0086]
Further, temperature reduction suppression control by the exhaust gas purifying apparatus of this embodiment, that is, switching control to the temperature reduction suppression operation mode by the temperature reduction suppression mode switching means 108 will be described with reference to the flowchart of FIG. This control is executed at regular intervals.
First, in step C10, it is determined whether or not the operation mode selected by the normal operation mode setting means 107 is the late lean operation mode. As a result of the determination, if the late lean operation mode is selected, the process proceeds to step C20. If the late lean operation mode is not selected, the process proceeds to Step C70.
[0087]
In step C20, the duration (count value of the timer 109A) t1 after the start of the lean operation in the late lean operation mode selected by the normal operation mode setting means 107 is set to the set time T.₀It is determined whether or not the above is satisfied, and as a result of this determination, the duration t1 is set to the set time T.₀When it is above, the process proceeds to Step C30 to reset the count value t1 of the timer 109A, and further proceeds to Step C40.
[0088]
In addition, since the process after step C40, ie, the process from step C40 to step C60, is the same as step B30 to step B50 in the flowchart (see FIG. 5) showing the temperature suppression control in the first embodiment described above, The description is omitted here.
On the other hand, as a result of the determination in step C20, the duration t1 is equal to the set time T₀If not, the temperature drop suppression control is not necessary and the process returns.
[0089]
When the late lean operation mode is not selected in step C10, the process proceeds to step C70. In step C70, it is determined whether the flag F is 1. If the flag F is 1, as a result of the determination. (F = 1) proceeds to step C80, and returns if the flag F is not 1.
In Step B80, it is determined whether or not the change amount ΔTPS of the throttle opening is equal to or less than a reference value TP1 of the change amount of the throttle opening, in order to determine whether or not the steady operation state is present.
[0090]
As a result of this determination, if the change amount ΔTPS is equal to or less than the reference value TP1, the process proceeds to step C90, and the duration from when the lean operation in the first lean operation mode selected by the temperature decrease suppression mode switching means 108 is started. (Count value of timer 109B) t2 is set time T₁It is determined whether or not the above is satisfied, and as a result of this determination, the duration t2 is set to the set time T.₁When it is above, the process proceeds to Step C100 to reset the count value t2 of the timer 109B, and further proceeds to Step C110 to end the temperature decrease suppression control, and the flag F is reset to 0 in Step C120.
[0091]
In step C90, the duration t2 is set to the set time T.₁If it is determined that the above is not reached, the process returns, and the temperature decrease suppression control is continued.
On the other hand, if the change amount ΔTPS is not equal to or less than the reference value TP1 in step C80, the process proceeds to step C110, the temperature decrease suppression control is terminated, and the flag F is reset to 0 in step B100.
[0092]
Note that after the end of the temperature decrease suppression control, the operation mode (here, the late lean operation mode) set by the normal operation mode setting means 107 is restored.
In this way, the exhaust gas purifying apparatus of the present embodiment is for temperature reduction suppression as the temperature decrease suppression means 110 when the temperature decrease of the catalyst 9 is estimated by the temperature decrease determination means 105 as the temperature decrease detection means 111. By operating the mode switching means 108, there is an advantage that it is possible to prevent the deterioration of the catalyst purification efficiency accompanying the decrease in the exhaust gas temperature peculiar to the cylinder injection type internal combustion engine.
[0093]
That is, the engine operation mode is switched by the temperature drop suppression mode switching means 108 as the temperature drop suppression means 110 in accordance with the outputs from the temperature drop determination means 105 as the normal operation mode setting means 107 and the temperature drop detection means 111. Accordingly, it is possible to suppress a decrease in the exhaust gas temperature due to the stratified super-lean combustion, and there is an advantage that it is possible to prevent the catalyst purification efficiency from being deteriorated due to the decrease in the exhaust gas temperature.
[0094]
Next, a fourth embodiment will be described. As shown in FIG. 12, the exhaust gas purifying apparatus of this embodiment is different from the first embodiment described above in that the temperature drop suppressing means 110 is different, so that the operation mode setting means 106 and The structure of the fuel injection control means 101 is different.
That is, in this embodiment, instead of configuring the temperature decrease suppression means 110 as having a function (temperature decrease suppression mode switching means) 108 for performing switching control to the temperature decrease suppression operation mode, FIG. As shown in FIG. 4, the function (additional fuel injection control) of performing additional fuel injection control after the expansion stroke of each cylinder, that is, during the opening of the exhaust valve 5 in the exhaust stroke (specifically, between the end of the expansion stroke and the exhaust stroke). (Injection control means) 102 is configured.
[0095]
That is, in addition to fuel injection for combustion in a normal combustion chamber, additional fuel is injected to activate the catalyst 9. In this additional fuel injection, by supplying an air-fuel mixture containing unburned fuel components to the catalyst 9, the unburned fuel components in the air-fuel mixture are burned by the catalyst 9, the temperature of the catalyst 9 is increased, and the catalyst 9 This is intended to suppress the temperature drop.
[0096]
For this reason, the operation mode setting means 106 is configured to have only the same function as the normal operation mode setting means 107 of the first embodiment. Therefore, the description of the operation mode setting unit 106 is omitted here.
Further, as shown in FIG. 12, the fuel injection control means 101 is added to suppress the temperature drop of the normal fuel injection control means 103 having the same function as the fuel injection control means 101 of the first embodiment and the catalyst 9. And a function (additional fuel injection control means) 102 for performing fuel injection control.
[0097]
This additional fuel injection control means 102 is a characteristic component in the exhaust gas purification apparatus of the present embodiment. In the additional fuel injection control means 102, the temperature of the catalyst 9 once reaches the catalyst activation temperature and is activated. When the temperature determination of the catalyst 9 is determined by the decrease determination means 105, the temperature decrease of the catalyst 9 is suppressed by controlling to perform additional fuel injection in the exhaust stroke of each cylinder. Therefore, the additional fuel injection control unit 102 functions as a temperature decrease suppressing unit 110 that operates so as to suppress the temperature decrease of the catalyst 9.
[0098]
In this additional fuel injection control means 102, as shown in FIG. 12, additional fuel injection control is performed based on information from the temperature drop determination means 105 and the operation mode setting means 106 so as to suppress the temperature drop of the catalyst 9. Therefore, the ECU 23 is provided with a temperature decrease determination means 105 for determining the temperature decrease of the catalyst 9.
This temperature decrease determination means 105 has the same function as that of the first embodiment, but in this embodiment, the catalyst temperature θ is further reduced._CCIs combustible temperature θ₀It is also configured to have a function of determining whether or not the above is true.
[0099]
Where the flammable temperature θ₀Is the minimum temperature required for the catalyst 9 to react and burn. Catalyst temperature θ_CCIs combustible temperature θ₀It is also determined whether or not the above is the combustible temperature θ₀This is because the unburned fuel supplied by the additional fuel injection does not burn on the catalyst 9 below.
The temperature decrease determination unit 105 and the catalyst temperature sensor 26 constitute a temperature decrease detection unit 111.
[0100]
Further, the additional fuel injection control means 102 controls to perform additional fuel injection within the exhaust stroke of each cylinder when the lean operation mode is set by the operation mode setting means 106 (specific operation state). Information indicating that the lean operation mode is set from the operation mode setting means 106 is taken in. Here, the specific operation state set in the lean operation mode means a low load operation state including a deceleration fuel cut, and the low load operation state includes an idle operation state.
[0101]
This is particularly true when the lean operation mode is set and the exhaust gas temperature decreases and the catalyst temperature θ_CCIt is because it is easy to fall. On the other hand, when the lean operation mode is set, there is a feature that the amount of oxygen used for the main combustion in the normal operation is small and the amount of surplus oxygen is large, and this surplus oxygen is used as temperature decrease suppression control of the catalyst 9. It is also intended to be used for combustion by additional fuel injection.
[0102]
In the additional fuel injection control means 102, when the lean operation mode is set by the operation mode setting means 106 and the temperature decrease of the catalyst 9 is determined by the temperature decrease determination means 105, the additional fuel injection in the exhaust stroke is performed. Injection start time T_INJAs come to be determined. Here, the injection start time T_INJIs determined by an injector drive time t described later._PLUSWhen setting the basic drive time t_BThis is because it is necessary to correct the above.
[0103]
Injection time of additional fuel at this time (total injection time in one operation cycle) t_exIs the fuel amount M corresponding to the surplus oxygen remaining after the main combustion_fuelInjector drive time t so that is injected_PLUSIs set. This is because when the additional fuel is burned by the catalyst 9, the surplus oxygen remaining after the main combustion is completely burned by the additional fuel so that the temperature of the catalyst 9 can be increased efficiently.
[0104]
This injector drive time t_PLUSSetting is performed as follows. That is, injector drive time t_PLUSIs set to a basic driving time t which is basic in the additional fuel injection in the exhaust stroke._B, Injection start time T_INJ, Catalyst temperature θ_CCThe correction is performed by the following.
Here, the basic drive time t_BIs the amount of fuel M that can be injected into the surplus oxygen after main combustion._fuelIs calculated based on That is, the amount of oxygen remaining after the main combustion is determined from the intake air amount Q per one cylinder cycle determined by the normal fuel injection control means 103 and the target air-fuel ratio (target A / F). Based on fuel amount M_fuelIs calculated.
[0105]
Fuel amount M_fuelIs obtained by the following equation.
M_fuel= Q × (1 / theoretical air / fuel ratio-1 / target air / fuel ratio)
Also, the injection start time T in the exhaust stroke_INJIs corrected by the injection start time T_INJAnd correction coefficient K₂Correction coefficient K from a preset map from₂This correction coefficient K₂The basic drive time t_BMultiplied by (t_B× K₂)
[0106]
The catalyst temperature θ_CCIs corrected by the catalyst temperature θ_CCAnd correction coefficient K_ThreeCorrection coefficient K from a preset map from_ThreeThis correction coefficient K_ThreeThe basic drive time t_BMultiplied by (t_B× K_Three)
In this way, the injector drive time t in the exhaust stroke_PLUSIs obtained by the following equation.
[0107]
t_PLUS= T_B× K₂× K_Three
The injection start time T set in this way_INJAnd injector drive time t_PLUSAccordingly, the additional fuel injection is performed in the exhaust stroke separately from the normal fuel injection.
In addition, about the other structure in the exhaust gas purification apparatus in this embodiment, since it is the same as that of the above-mentioned 1st Embodiment, the description is abbreviate | omitted here.
[0108]
The exhaust gas purification apparatus as the fourth embodiment of the present invention is configured as described above, and the fuel injection control based on the operation mode set by the operation mode setting means 106 performs the normal operation of the first embodiment described above. Since the fuel injection control is performed in the same manner as the fuel injection control based on the operation mode set by the mode setting means 107, the description thereof is omitted.
[0109]
Further, temperature decrease suppression control by the exhaust gas purifying apparatus of this embodiment, that is, additional fuel injection control by the additional fuel injection control means 102 will be described with reference to the flowchart of FIG. This control is executed at regular intervals.
First, in Step F1, it is determined whether or not the flag F is 0. If the flag F is 0, the process proceeds to Step F10. If the flag F is not 0, the process proceeds to Step F80. Here, the flag F is set to 1 when the temperature decrease suppression control is being performed, is set to 0 when the temperature decrease suppression control is not being performed, and is set to 0 at the time of initial setting.
[0110]
In Step F10, the catalyst temperature θ_CCIs combustible temperature θ₀Set temperature θ₁It is determined whether or not (θ₀≦ θ_CC≦ θ₁). As a result, the catalyst temperature θ_CCIs combustible temperature θ₀Set temperature θ₁If not, the process proceeds to step F15, the flag F is set to 1, the process proceeds to step F20, and the catalyst temperature θ_CCIs combustible temperature θ₀Set temperature θ₁If not, the process returns without performing the temperature drop suppression control.
[0111]
Then, in step F20, it is determined whether or not the operation mode set by the operation mode setting means 106 is the lean operation mode. If the result of this determination is that the operation mode is lean, the process proceeds to step F30 to suppress the temperature drop. In order to perform the exhaust stroke injection control as the control, the processing from step F30 to F70 is performed. If it is not the lean operation mode, the exhaust stroke injection control as the temperature decrease suppression control is not performed, and the routine proceeds to step F90 and the flag F is set to 0. Reset to and return.
[0112]
By the way, in Step F80, the catalyst temperature θ is controlled by the temperature decrease suppression control._CCRises and the catalyst temperature θ_CCIs the set temperature θ₂It is determined whether or not the above has been reached. As a result, the catalyst temperature θ_CCIs the set temperature θ₂If not, the process proceeds to step F20 to continue the exhaust stroke injection control as the temperature decrease suppression control, and the catalyst temperature θ_CCIs the set temperature θ₂In the case above, in order to end the exhaust stroke injection control as the temperature decrease suppression control, the process proceeds to step F90, the flag F is reset to 0, and the process returns.
[0113]
As the exhaust stroke injection control, the processes from Step F30 to F70 are performed. In Step F30, the injection start timing T of additional fuel injection in the exhaust stroke is performed._INJTo decide. In step F40, the intake air amount Q and the target A / F per cylinder / cycle are read.
Next, in step F50, the amount of oxygen remaining after main combustion is obtained from the intake air amount Q per cylinder and the target A / F, and the fuel amount M is determined based on this oxygen amount._fuelIs calculated. In step F60, the basic drive time t of additional fuel injection in the exhaust stroke_BInjection start time T_INJ, Catalyst temperature θ_CCThe injector drive time t in the exhaust stroke is corrected by_PLUSSet.
[0114]
Based on this setting, additional fuel injection is performed in the exhaust stroke (step F70). Further, in order to simplify the control, the injection start time may be fixed (for example, 120 ° ATDC may be considered as the fixed time).
In this way, in the exhaust gas purifying apparatus of this embodiment, the temperature decrease of the catalyst 9 is detected by the temperature decrease determining means 105 constituting the temperature decrease detecting means 111 and the catalyst 9 is detected by the output from the operation mode setting means 106. When a lean operation mode [a specific operation state (low load operation state including a deceleration fuel cut)] is detected, the additional fuel injection control unit 102 as the temperature decrease suppression unit 110 detects at least the engine. By injecting the additional fuel during the exhaust stroke, there is an advantage that the temperature of the catalyst 9 can be surely increased and the purification efficiency of the catalyst 9 can be prevented from deteriorating.
[0115]
Next, a fifth embodiment will be described. As shown in FIG. 14, the exhaust gas purifying apparatus of this embodiment is different from that of the above-described fourth embodiment in the temperature decrease determination means 105 as the temperature decrease detection means 111. .
That is, in this embodiment, the temperature decrease determination unit 105 detects the temperature decrease degree (temperature decrease gradient) of the catalyst 9 based on the detection information from the catalyst temperature sensor 26, and the set temperature θ1 according to the temperature decrease degree. The catalyst temperature θ is temporarily changed according to the set temperature θ1._CCAfter the catalyst reaches the catalyst activation temperature and is activated, the catalyst temperature θ_CCIt is determined whether or not the battery has fallen.
[0116]
For this reason, as shown in FIG. 14, the temperature decrease determination unit 105 has the same configuration as the temperature decrease determination unit 105 of the second embodiment described above, but further has a catalyst temperature θ._CCIs combustible temperature θ₀It is also configured to have a function of determining whether or not the above is true. Here, the description of the same configuration as the temperature decrease determination unit 105 of the second embodiment is omitted.
[0117]
In addition, since it is the same as that of the above-mentioned 4th Embodiment about the other structure in the exhaust gas purification apparatus in this embodiment, the description is abbreviate | omitted here.
The exhaust gas purification apparatus as the fifth embodiment of the present invention is configured as described above, and the fuel injection control based on the operation mode set by the normal operation mode setting means 107 is the same as in the first embodiment described above. Therefore, the description thereof is omitted.
[0118]
Further, temperature decrease suppression control by the exhaust gas purifying apparatus of this embodiment, that is, additional fuel injection control by the additional fuel injection control means 102 will be described with reference to the flowchart of FIG. This control is executed at regular intervals.
First, in step G10, the Δθ calculation unit 105A executes the catalyst temperature detection mode (see FIG. 8), and the catalyst temperature θ_CCThe amount of change Δθ in a certain time is calculated. That is, as shown in FIG. 8, at step E10, the catalyst temperature θ_CCAnd based on this, in step E20, the catalyst temperature θ_CCThe amount of change Δθ over a certain period of time is calculated.
[0119]
Next, in Step G15, it is determined whether or not the flag F is 0. If the flag F is 0, the process proceeds to Step G20, and if the flag F is not 0, the process proceeds to Step G90. Here, the flag F is set to 1 when the temperature decrease suppression control is being performed, is set to 0 when the temperature decrease suppression control is not being performed, and is set to 0 at the time of initial setting.
In step G20, the set temperature θ1 is read from the map based on the change amount Δθ calculated in step D20 by the θ1, θ2 reading unit 105B, and the process proceeds to step G30. Here, the map in which the set temperature θ1 is variable is basically a catalyst temperature θ._CCIs set so as to increase the set temperature θ1 when the amount of change Δθ greatly changes to the temperature lowering side (that is, when the temperature decreasing degree is large).
[0120]
In Step G30, the catalyst temperature θ is determined by the determination unit 105C._CCIs combustible temperature θ₀It is determined whether or not the temperature is equal to or lower than the set temperature θ1, and as a result of this determination, the catalyst temperature θ_CCIs combustible temperature θ₀When the temperature is equal to or lower than the set temperature θ1, the process proceeds to step G35, the flag F is set to 1, and the process proceeds to step G40._CCIs combustible temperature θ₀When the temperature is not lower than the set temperature θ1, the temperature drop suppression control is not performed and the process returns.
[0121]
Then, in step G40, it is determined whether or not the operation mode set by the operation mode setting means 106 is the lean operation mode. If the result of this determination is the lean operation mode, exhaust as temperature decrease suppression control. In order to perform the stroke injection control, the processing from step G45 to G80 is performed, and if it is not the lean operation mode, the exhaust stroke injection control is not performed as the temperature decrease suppression control, and the process proceeds to step G110 to reset the flag F to 0 To return.
[0122]
In step G90, the θ1, θ2 reading unit 105B reads the set temperature θ2 from the map based on the change amount Δθ calculated in step G10, and the process proceeds to step G100. Here, the map in which the set temperature θ2 is variable is basically a catalyst temperature θ._CCWhen the amount of change Δθ greatly changes toward the temperature rise side (that is, when the temperature rise degree is large), the set temperature θ2 is set to be low.
[0123]
In step G100, the catalyst temperature θ is controlled by the temperature decrease suppression control._CCRises and the catalyst temperature θ_CCIs determined to be equal to or higher than the set temperature θ2. As a result, the catalyst temperature θ_CCIs not equal to or higher than the set temperature θ2, the process proceeds to step G40 to continue the exhaust stroke injection control as the temperature decrease suppression control, and the catalyst temperature θ_CCIs equal to or higher than the set temperature θ2, the exhaust stroke injection control as the temperature decrease suppression control is not performed, the process proceeds to step G110, the flag F is reset to 0, and the process returns.
[0124]
As the exhaust stroke injection control, the processing from Step G45 to G80 is performed, which corresponds to Step F30 to Step F70 of the exhaust stroke injection control described with reference to FIG. 13 in the fourth embodiment. Therefore, the description thereof is omitted here.
As described above, in the exhaust gas purification apparatus of the present embodiment, the same effect as that of the fourth embodiment can be obtained, and by making the set temperature θ1 variable, at least from the early stage when the degree of catalyst temperature decrease is large. By injecting additional fuel during the exhaust stroke of the engine, there is an advantage that the temperature of the catalyst 9 can be surely increased, and the purification efficiency of the catalyst 9 can be prevented from deteriorating. Further, by making the set temperature θ2 variable, even when the catalyst temperature suddenly rises due to the catalyst temperature decrease suppression control, the catalyst temperature decrease suppression control is stopped at an early stage to prevent the catalyst from overheating. There is also an advantage that can be done.
[0125]
Next, the sixth embodiment will be described. The exhaust gas purification apparatus of this embodiment is a combination of the above-described first embodiment and the fourth embodiment as shown in FIG. This is configured to prevent the temperature of the catalyst from being lowered efficiently and reliably at the time of a low load operation including the deceleration fuel cut (including the idling operation) during the steady running operation in which the catalyst temperature decrease is predicted. .
[0126]
In this embodiment, the fuel injection control means 101 is configured in the same manner as in the fourth embodiment, and the other configurations are the same as those in the first embodiment. The temperature decrease suppressing mode switching means (first means) 108 and the additional fuel injection control means (second means) 102 constitute a temperature decrease suppressing means 110. These temperature decrease suppressing mode switching means 108 or additional means are added. The temperature drop suppression control by the fuel injection control means 102 is switched depending on the operating state.
[0127]
More specifically, when the catalyst temperature becomes lower than a predetermined temperature by the catalyst temperature sensor 26, and thereafter the engine operating state is determined from the output of the throttle sensor 14 or the like, and the operating state at that time is a steady running operating state, In the case of the low load operation state (including the idling operation state) including the deceleration fuel cut, the temperature decrease suppression unit 110 performs the temperature decrease suppression control by the temperature decrease suppression mode switching unit 108 as the temperature decrease suppression unit 110. The additional fuel injection control means 102 performs temperature drop suppression control.
[0128]
Since the exhaust gas purifying apparatus of the present embodiment is configured as described above, the temperature reduction suppression control and the additional fuel injection control means 102 by switching the operation mode (combustion state) by the temperature reduction suppression mode switching means 108. The temperature decrease suppression control by injecting additional fuel is selectively performed according to the operating state of the engine, so that the temperature decrease of the catalyst 9 can be reliably performed while suppressing the deterioration of fuel consumption to a minimum. There is an advantage that a reduction in the purification efficiency of the catalyst can be prevented.
[0129]
The present invention is not limited to the above-described embodiments. For example, in the first embodiment, the temperature decrease suppression control is operated and stopped according to the temperature of the catalyst. May be started in accordance with the temperature of the catalyst, and then the temperature decrease suppression control may be terminated depending on the duration of the temperature decrease suppression control, that is, the time after the operation mode is switched. Good.
[0130]
In the exhaust gas purification apparatuses of the first, second, third, and sixth embodiments, the operation mode selected as the operation mode for suppressing temperature decrease is the first lean operation mode. However, the present invention is not limited to this, and the temperature of the catalyst The operation mode may be switched stepwise from the previous lean operation mode to the stoichiometric operation mode according to the rise, and the catalyst temperature θ_CCIn a situation where it is necessary to rapidly increase the stoichiometric operation mode, the stoichiometric operation mode may be selected directly from the late lean operation mode. This is a lean NO that has a higher catalyst activation temperature and a narrow activation temperature range than the three-way catalyst 9B._XThis is particularly effective for suppressing the temperature drop of the catalyst 9A.
[0131]
In the exhaust gas purifying apparatus of the first, second, third, and sixth embodiments, the catalyst temperature θ_CCWhen the catalyst temperature θ is very low_CCIn order to raise the temperature, first, the operation mode may be switched to the stoichiometric operation mode as the operation mode for suppressing temperature decrease. In this case, when it is detected or estimated that the catalyst temperature has risen to some extent in order to prevent excessive temperature rise of the catalyst 9, it is preferable to further switch to the first lean operation mode as the operation mode for suppressing temperature decrease. .
[0132]
Furthermore, in the exhaust gas purification apparatuses of the first, second, third, and sixth embodiments, the late lean operation mode is selected as the normal operation mode, but the exhaust gas temperature is lowered depending on the operation state in the first lean operation mode. Alternatively, the operation mode may be switched to the stoichiometric operation mode as the operation mode for suppressing temperature decrease. Further, in the exhaust gas purification apparatus of the first, second, third, and sixth embodiments, it is described that the engine is provided in an engine that switches the late lean operation mode, the first lean operation mode, and the stoichiometric operation mode as the normal operation mode. Is configured to switch between the second lean operation mode and the first lean operation mode, the first lean operation mode may be set as the operation mode for suppressing the temperature drop, and the engine is operated in the second lean operation mode. When configured to switch between the operation mode and the stoichiometric operation mode, the stoichiometric operation mode may be set as the temperature decrease suppressing operation mode.
[0133]
Further, in the exhaust gas purification apparatuses of the first, second, third, and sixth embodiments, the temperature decrease suppression control is performed by the temperature decrease suppression mode switching means 108 in the steady operation state by incorporating the detection information from the throttle sensor 14. However, without such a determination, the catalyst temperature θ_CCWhether or not to perform control may be determined based on only the above.
[0134]
Further, as a temperature drop suppression means, some cylinders of the engine are configured as stratified super-lean combustion in which fuel is injected during the compression stroke, and other cylinders are injected with fuel during the intake stroke to perform stoichiometric or fuel-rich air. Unmixed components (CO, HC, H) discharged from stoichiometric or fuel-rich cylinders as premixed combustion at the fuel ratio₂Etc.) and O discharged from the cylinder of fuel lean₂The temperature of the catalyst may be increased by an oxidation reaction due to the above, and the temperature of the catalyst may be increased efficiently for each operating state in combination with each of the operating states described above.
[0135]
【The invention's effect】
As described above in detail, according to the exhaust gas purification apparatus of the present invention, the in-cylinder injection is performed by operating the temperature decrease suppressing means when the temperature decrease detecting means determines that the temperature of the catalyst is decreased. There is an advantage that it is possible to prevent the deterioration of the catalyst purification efficiency accompanying the decrease in the exhaust gas temperature peculiar to the internal combustion engine.
[0136]
In addition, an inexpensive system without an additional device can suppress a decrease in exhaust gas temperature due to layered super-lean combustion, thereby preventing deterioration in catalyst purification efficiency due to a decrease in exhaust gas temperature. There are advantages.
According to the exhaust gas purification apparatus of the present invention as set forth in claim 2, when the catalyst temperature is slightly lower than the set temperature, the operation mode is set to the lean operation mode in consideration of deterioration of fuel consumption, and the exhaust gas purification of the catalyst is performed. In addition to maintaining the efficiency, if the catalyst temperature is significantly lower than the set temperature, the exhaust gas purification efficiency of the catalyst will be extremely deteriorated. Therefore, the operation mode is set to the stoichiometric operation mode, and the catalyst temperature is positively changed. There is an advantage that the temperature can be raised to prevent the catalyst purification efficiency from being deteriorated.
[0137]
According to the exhaust gas purifying apparatus of the present invention as set forth in claim 3, by selectively performing the switching of the combustion state and the additional fuel injection, the temperature of the catalyst is surely lowered while suppressing the deterioration of fuel consumption. There is an advantage that (decrease in the purification efficiency of the catalyst) can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a main configuration of a control system of an exhaust gas purification apparatus as a first embodiment of the present invention.
FIG. 2 is a control block diagram in the exhaust gas purification apparatus as the first embodiment of the present invention.
FIG. 3 is an overall configuration diagram of an exhaust gas purification apparatus as a first embodiment of the present invention.
FIG. 4 is a flowchart for explaining fuel injection control of the exhaust gas purifying apparatus as the first embodiment of the present invention.
FIG. 5 is a flowchart for explaining temperature decrease suppression control of the exhaust gas purification apparatus as the first embodiment of the present invention.
FIG. 6 is a control block diagram schematically showing a main configuration of a control system of an exhaust gas purifying apparatus as a second embodiment of the present invention.
FIG. 7 is a flowchart for explaining temperature decrease suppression control of the exhaust gas purifying apparatus as the second embodiment of the present invention.
FIG. 8 is a flowchart for explaining a catalyst temperature detection mode in temperature drop suppression control of the exhaust gas purifying apparatus as the second embodiment of the present invention.
FIG. 9 is a diagram for explaining a set temperature used in an exhaust gas purification apparatus as an embodiment of the present invention, and (a) is a set temperature θ.₁, Set temperature θ₂, (B) are for explaining the set temperature θ1 and the set temperature θ2, respectively.
FIG. 10 is a control block diagram schematically showing a main configuration of a control system of an exhaust gas purification apparatus as a third embodiment of the present invention.
FIG. 11 is a flowchart for explaining temperature decrease suppression control of an exhaust gas purifying apparatus as a third embodiment of the present invention.
FIG. 12 is a control block diagram schematically showing a main configuration of a control system of an exhaust gas purifying apparatus as a fourth embodiment of the present invention.
FIG. 13 is a flowchart for explaining temperature decrease suppression control of the exhaust gas purifying apparatus as the fourth embodiment of the present invention.
FIG. 14 is a control block diagram schematically showing a main configuration of a control system of an exhaust gas purification apparatus as a fifth embodiment of the present invention.
FIG. 15 is a flowchart for explaining temperature decrease suppression control of an exhaust gas purification apparatus as a fifth embodiment of the present invention.
FIG. 16 is a control block diagram schematically showing a main configuration of a control system of an exhaust gas purifying apparatus as a sixth embodiment of the present invention.
[Explanation of symbols]
1 Combustion chamber
2 Intake passage
2a Surge tank
3 Exhaust passage
4 Intake valve
5 Exhaust valve
6 Air cleaner
7 Throttle valve
8 Injector (fuel injection valve)
8a Injector solenoid
8b Injector solenoid switching transistor
9 Exhaust gas purification catalytic converter as exhaust gas purification catalyst
9A lean NO_xcatalyst
9B Three-way catalyst
10 Exhaust gas recirculation device (EGR device)
10b Exhaust gas recirculation passage
10a EGR valve (exhaust gas recirculation means)
11 Air flow sensor
12 Intake air temperature sensor
13 Atmospheric pressure sensor
14 Throttle sensor
15 Idle switch
16 Idle speed control valve (ISC valve)
16A bypass
17 Oxygen concentration sensor (O₂ Sensor)
19 Cooling water temperature sensor
20 Cranking switch or ignition switch
21 Crank angle sensor (engine speed sensor)
22 TDC sensor (cylinder discrimination sensor)
23 Electronic control unit (ECU)
24 Accelerator position sensor
25 Battery sensor
26 Catalyst temperature sensor (catalyst temperature detection means)
27 CPU
28, 29 Input interface
30 Analog / Digital Converter
31 ROM
32 RAM
34 Injection driver (fuel injection valve drive means)
35 Spark plug
50 Air bypass valve (ABV)
50A bypass
101 Fuel injection control means
102 Additional fuel injection control means (temperature drop suppression means)
103 Normal fuel injection control means
104 Various sensors
105 Temperature drop determination means (temperature drop detection means)
105A Δθ calculation unit
105B θ1, θ2 reading part
105C judgment part
106 Operation mode setting means
107 Normal operation mode setting means
108 Mode switching means for suppressing temperature drop
109A timer
109B timer
110 Temperature drop suppression means
111 Temperature drop detection means

Claims (3)

The fuel is directly injected into the combustion chamber, and is provided in a direct injection internal combustion engine that performs stratified super-lean combustion having a larger air-fuel ratio than the stoichiometric air-fuel ratio according to the operating state,
A catalyst disposed in the exhaust passage of the engine for purifying exhaust gas;
By detecting the temperature of the catalyst and detecting or predicting a decrease in the temperature of the catalyst, or by detecting a specific operation state that causes a temperature decrease and estimating the temperature decrease of the catalyst, the temperature of the catalyst is changed to the catalyst. A temperature drop detecting means for detecting a temperature drop of the catalyst after reaching the activation temperature and being activated;
A temperature drop suppression means that operates to suppress a temperature drop of the catalyst when a temperature drop of the catalyst is detected by the temperature drop detection means;
The in-cylinder injection internal combustion engine is
The stratified super-lean combustion and the premixed combustion having a combustion air-fuel ratio smaller than that of the stratified super-lean combustion are switched according to the operation state,
In order to perform the premixed combustion, a stoichiometric operation mode that operates near the stoichiometric air-fuel ratio or a lean operation mode that operates at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
The temperature decrease suppressing means controls the operation of the engine when the temperature of the catalyst is predicted to be lower or lower than a first set value in accordance with the output from the temperature decrease detecting means. Switching to the lean operation mode of combustion, and further, the temperature of the catalyst becomes lower or lower than a second set value set as a temperature lower than the first set value in accordance with the output from the temperature drop detecting means. An exhaust gas purifying apparatus characterized by switching the operation of the engine to the premixed combustion stoichiometric operation mode when it is predicted. The fuel is directly injected into the combustion chamber, and is provided in a direct injection internal combustion engine that performs stratified super-lean combustion having a larger air-fuel ratio than the stoichiometric air-fuel ratio according to the operating state,
A catalyst disposed in the exhaust passage of the engine for purifying exhaust gas;
By detecting the temperature of the catalyst and detecting or predicting a decrease in the temperature of the catalyst, or by detecting a specific operation state that causes a temperature decrease and estimating the temperature decrease of the catalyst, the temperature of the catalyst is changed to the catalyst. A temperature drop detecting means for detecting a temperature drop of the catalyst after reaching the activation temperature and being activated;
A temperature drop suppression means that operates to suppress a temperature drop of the catalyst when a temperature drop of the catalyst is detected by the temperature drop detection means;
The in-cylinder injection internal combustion engine is configured to perform switching between the stratified super lean combustion and the premixed combustion having a combustion air-fuel ratio smaller than that of the stratified super lean combustion in accordance with an operating state.
The premixed combustion has two operation modes, a stoichiometric operation mode that operates at a stoichiometric air-fuel ratio and a lean operation mode that operates at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
The temperature drop detection means is configured to detect or predict the temperature drop of the catalyst by detecting the temperature of the catalyst,
The temperature decrease suppression unit sets the operation mode to the lean operation mode when the temperature decrease detection unit predicts that the temperature of the catalyst is lower than or lower than a preset first set value. When And then When the temperature drop detecting means predicts that the temperature of the catalyst will be lower or lower than the second set value set to a temperature lower than the first set value, the operation mode is set to the stoichiometric mode. An exhaust gas purification apparatus characterized by being in an operation mode. The fuel is directly injected into the combustion chamber, and is provided in a direct injection internal combustion engine that performs stratified super-lean combustion having a larger air-fuel ratio than the stoichiometric air-fuel ratio according to the operating state,
A catalyst disposed in the exhaust passage of the engine for purifying exhaust gas;
By detecting the temperature of the catalyst and detecting or predicting a decrease in the temperature of the catalyst, or by detecting a specific operation state that causes a temperature decrease and estimating the temperature decrease of the catalyst, the temperature of the catalyst is changed to the catalyst. A temperature drop detecting means for detecting a temperature drop of the catalyst after reaching the activation temperature and being activated;
A temperature drop suppression means that operates to suppress a temperature drop of the catalyst when a temperature drop of the catalyst is detected by the temperature drop detection means;
The in-cylinder injection internal combustion engine is configured to perform switching between the stratified super-lean combustion and the premixed combustion having a combustion air-fuel ratio smaller than that of the stratified super-lean combustion in accordance with an operating state,
The temperature drop suppression means includes first means for switching between the stratified super lean combustion and the premixed combustion, and second means for injecting additional fuel after the expansion stroke of the engine,
The temperature drop suppressing means selects the first means when the engine is in a steady operation state and switches from the stratified super lean combustion to the premixed combustion, while the engine temperature is low when the engine is in a low load operation state. An exhaust gas purifying apparatus, wherein two means are selected.

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