JP2010112200A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of restraining an excessive rise in the temperature of an engine body when setting the air-fuel ratio of exhaust gas supplied to an NOx storage catalyst to the rich or stoichiometric air-fuel ratio. <P>SOLUTION: This control device of the internal combustion engine reduces a combustion quantity of fuel in a combustion chamber, and increases unburnt fuel supplied to the NOx storage catalyst, by changing an injection pattern D to an injection pattern E of delaying the injection timing of after-injection, when the temperature of the engine body of the internal combustion engine becomes a predetermined allowable value or more, when performing rich control by the injection pattern D having the after-injection for setting the air-fuel ratio of the exhaust gas to the rich or stoichiometric air-fuel ratio by increasing the injection quantity of the fuel injected into the combustion chamber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

In an internal combustion engine such as a diesel engine or a gasoline engine, fuel is burned in the engine body, and exhaust gas containing pollutants is discharged. In addition to carbon monoxide (CO), unburned hydrocarbons (HC), and particulates (PM), exhaust gas pollutants include nitrogen oxides (NO _x ). As one method for removing nitrogen oxides, it has been proposed that a NO _x storage catalyst be disposed in the engine exhaust passage.

_The NO _X storage catalyst, the air-fuel ratio of the exhaust gas is when greater than the stoichiometric air-fuel ratio, i.e., the air-fuel ratio of the exhaust gas is occluded NO _X when the lean. On the other hand, when the air-fuel ratio in the exhaust gas is smaller than the stoichiometric air-fuel ratio, that is, when the air-fuel ratio of the exhaust gas is rich or the stoichiometric air-fuel ratio, the stored NO _x is released and included in the exhaust gas. NO _x is reduced and purified by the reducing agent. Diesel engines, etc., during normal operation air-fuel ratio of the exhaust gas is lean, NO _X storage catalyst occludes NO _X in the exhaust gas. After the NO _X storage is continued, the NO _x can be reduced and purified by setting the air-fuel ratio of the exhaust gas to a rich or stoichiometric air-fuel ratio at a predetermined time.

The exhaust gas of an internal combustion engine may contain sulfur oxide (SO _x ). In this case, the NO _X storage catalyst stores SO _X simultaneously with NO _X storage. When SO _x is occluded, the storable amount of NO _x decreases. Thus, so-called sulfur poisoning occurs in the NO _x storage catalyst. In order to eliminate this sulfur poisoning, a sulfur poisoning recovery process for releasing SO _x is performed. SO _X is occluded in the NO _X storage catalyst in a stable state as compared to the NO _X. For this reason, in the sulfur poisoning recovery process, the temperature of the NO _x storage catalyst is raised, and then the exhaust gas having a rich air-fuel ratio or the exhaust gas having the stoichiometric air-fuel ratio is supplied to release SO _x .

Patent In 2005-291057 discloses a storage reduction NO _X catalyst provided in an exhaust passage of a diesel engine, a reducing agent supply means for supplying a reducing agent to the NO _X catalyst, for detecting the NO _X catalyst temperature exhaust An exhaust gas purification device including a temperature sensor and poisoning recovery time determination means is disclosed. In this apparatus, when the SO _X poisoning is recovered, the amount of the reducing agent added to the NO _X storage reduction catalyst is relatively large when the detected temperature from the exhaust temperature sensor is lower than the target temperature. When the map of 1 is selected and the detected temperature from the exhaust temperature sensor reaches the target temperature, the reducing agent is added using the second map that has an amount of reducing agent that is smaller than the amount added by the first map. Is disclosed.

JP-A-2005-291057

For example, an internal combustion engine such as a diesel engine is operated in a state where the air-fuel ratio of exhaust gas is lean during normal operation. In such an internal combustion engine, when performing NO _X release processing or sulfur poisoning recovery processing, the air-fuel ratio of the exhaust gas is made rich or stoichiometric by increasing the injection amount into the combustion chamber of the internal combustion engine. can do. At this time, at least a part of the increased amount of fuel injected into the combustion chamber is converted into a light reducing agent under high temperature and high pressure in the combustion chamber. For this reason, a light reducing agent suitable for the NO _x storage catalyst can be supplied.

  However, when the air-fuel ratio of the exhaust gas is made rich or stoichiometric, the temperature of the engine body rises and exceeds the allowable value on the high temperature side, and overheating may occur. It is preferable that this can be avoided.

  In the above Japanese Patent Application Laid-Open No. 2005-291057, it is considered that the temperature of the catalyst and the temperature of the catalyst carrier become high during the sulfur poisoning recovery process, but the temperature of the engine body is considered. Not.

The present invention, in an internal combustion engine having _the NO _X storage catalyst, prevents the air-fuel ratio of the exhaust gas supplied to the NO _X storage catalyst when the rich or the stoichiometric air-fuel ratio, the temperature of the engine body is excessive increase internal combustion An object of the present invention is to provide an engine control device.

The control apparatus for an internal combustion engine according to the first aspect of the present invention occludes NO _x contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the engine exhaust passage of the internal combustion engine is lean, and the exhaust gas flowing in air-fuel ratio of the gas is arranged the NO _X storing catalyst to release the NO _X was occluded becomes the stoichiometric air-fuel ratio or rich, the control device of the internal combustion engine so as to inject fuel into a combustion chamber, fuel is injected into the combustion chamber When the temperature of the engine body of the internal combustion engine exceeds a predetermined allowable value when rich control is performed to increase the air-fuel ratio of the exhaust gas to a rich or stoichiometric air-fuel ratio by increasing the injection amount of Reduces the amount of fuel burned in the combustion chamber and increases the amount of unburned fuel supplied to the NO _x storage catalyst. With this configuration, when the air-fuel ratio of the exhaust gas supplied to the NO _x storage catalyst is made rich or the stoichiometric air-fuel ratio, it is possible to suppress an excessive increase in the temperature of the engine body.

In the above invention, when the temperature of the engine body of the internal combustion engine exceeds a predetermined allowable value during rich control, the air-fuel ratio of the exhaust gas flowing into the NO _X storage catalyst is changed. Without reducing the amount of fuel combustion in the combustion chamber, it is preferable to increase the amount of unburned fuel supplied to the NO _x storage catalyst. With this configuration, it is possible to avoid an increase in the processing time of the NO _x release processing and sulfur poisoning recovery processing that require supply of a reducing agent.

  In the above invention, when the rich control is performed in the combustion chamber by performing the auxiliary injection at the combustible timing after the main injection in addition to the main injection, the temperature of the engine body of the internal combustion engine is set to a predetermined allowable value. When the value exceeds the value, the combustion amount of the auxiliary injection can be reduced.

In the above invention, by delaying the injection timing of the auxiliary injection, it is possible to reduce the combustion amount of the auxiliary injection and increase the unburned fuel supplied to the NO _x storage catalyst.

In the above invention, in the combustion chamber, in addition to the main injection, the first auxiliary injection for injecting fuel at a combustible time after the main injection and the second auxiliary injection for injecting fuel after the first auxiliary injection are performed. When the temperature of the engine body of the internal combustion engine exceeds a predetermined allowable value during the rich control, the injection amount of the second auxiliary injection is decreased by decreasing the injection amount of the first auxiliary injection. By increasing the amount, the amount of fuel burned in the combustion chamber can be reduced and the amount of unburned fuel supplied to the NO _x storage catalyst can be increased.

In the above invention, the fuel addition means that is arranged upstream of the NO _x storage catalyst in the engine exhaust passage and adds fuel in the engine exhaust passage is arranged to reduce the fuel injection amount in the combustion chamber and By increasing the amount of fuel added by the adding means, the unburned fuel supplied to the NO _x storage catalyst can be increased.

The control apparatus for an internal combustion engine according to the second aspect of the present invention occludes NO _x contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the engine exhaust passage of the internal combustion engine is lean, and the exhaust gas flowing in air-fuel ratio of the gas is arranged the NO _X storing catalyst to release the NO _X occluding becomes the stoichiometric air-fuel ratio or rich, when the SO _X amount occluded exceeds the allowable amount predetermined for the NO _X storing catalyst , together with increasing the temperature of the NO _X storage catalyst to sO _X releasable sO _X release temperature, so as to perform the sulfur poisoning recovery process by the air-fuel ratio of the exhaust gas flowing into the NO _X storage catalyst the stoichiometric air-fuel ratio or rich In the control apparatus for an internal combustion engine, the control of delaying the injection timing of the main injection of fuel injected into the combustion chamber and the control of performing auxiliary injection at the combustible timing after the main injection in the sulfur poisoning recovery process Small The _the NO _X storage catalyst and the temperature maintaining control for maintaining the above SO _X release temperature, the period during which performing temperature maintenance control, to increase the injection quantity of fuel injected into the combustion chamber at regular intervals by also performing one and Thus, the rich control is performed to make the air-fuel ratio of the exhaust gas rich or the stoichiometric air-fuel ratio. When the temperature of the engine body of the internal combustion engine becomes equal to or higher than a predetermined allowable value, the rich control performed at regular intervals is suspended and a period for maintaining the temperature maintenance control is interposed. With this configuration, when the air-fuel ratio of the exhaust gas supplied to the NO _x storage catalyst is made rich or the stoichiometric air-fuel ratio, it is possible to suppress an excessive increase in the temperature of the engine body.

  In the above invention, there is provided a control device for an internal combustion engine in which a cooling means for cooling the engine body and a cooling capacity detecting means for detecting the cooling capacity of the cooling means are arranged, the cooling detected by the cooling capacity detecting means It is preferable to change the amount of combustion in the combustion chamber in accordance with the capacity. With this configuration, the heat generation amount of the engine body can be adjusted according to the capacity of the cooling means.

  In the above invention, the cooling means preferably includes a cooling capacity adjusting means for adjusting the cooling capacity. With this configuration, it is possible to more effectively prevent the temperature of the engine body from excessively rising.

According to the present invention, in an internal combustion engine having _the NO _X storage catalyst, suppress the air-fuel ratio of the exhaust gas supplied to the NO _X storage catalyst when the rich or the stoichiometric air-fuel ratio, the temperature of the engine body is excessive increase It is possible to provide a control device for an internal combustion engine.

(Embodiment 1)
With reference to FIG. 1 to FIG. 9, the control apparatus for an internal combustion engine in the first embodiment will be described.

  FIG. 1 shows an overall view of a compression ignition type internal combustion engine in the present embodiment. In the present embodiment, a diesel engine disposed in an automobile will be described as an example. The internal combustion engine includes an engine body 1. The engine body 1 includes a combustion chamber 2 for each cylinder and an electronically controlled fuel injection valve 3 for injecting fuel into each combustion chamber 2. The engine body 1 includes an intake manifold 4 and an exhaust manifold 5.

  The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 via the intake duct 6. An inlet of the compressor 7 a is connected to an air cleaner 9 via an intake air amount detector 8. A throttle valve 10 driven by a step motor is disposed in the intake duct 6. Further, an intake air cooling device 11 for cooling intake air flowing through the intake duct 6 is disposed around the intake duct 6.

On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7. The outlet of the exhaust turbine 7 b is connected to the NO _x storage catalyst 17 through the exhaust pipe 12. A particulate filter 16 for collecting particulates in the exhaust gas is disposed in the engine exhaust passage downstream of the NO _x storage catalyst 17. In the embodiment shown in FIG. 1, the oxidation catalyst 13 is disposed in the engine exhaust passage downstream of the particulate filter 16.

  An EGR passage 18 is arranged between the exhaust manifold 5 and the intake manifold 4 for exhaust gas recirculation (EGR). An electronically controlled EGR control valve 19 is disposed in the EGR passage 18. Further, an EGR cooling device 20 for cooling the EGR gas flowing in the EGR passage 18 is disposed around the EGR passage 18.

  Each fuel injection valve 3 is connected to a common rail 22 via a fuel supply pipe 21. The common rail 22 is connected to a fuel tank 24 via an electronically controlled fuel pump 23 having a variable discharge amount. The fuel stored in the fuel tank 24 is supplied into the common rail 22 by the fuel pump 23. The fuel supplied to the common rail 22 is supplied to the fuel injection valve 3 through each fuel supply pipe 21.

  The electronic control unit 30 is composed of a digital computer. The control device for the internal combustion engine in the present embodiment includes an electronic control unit 30. The electronic control unit 30 includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35, and an output port 36 connected to each other by a bidirectional bus 31. The ROM 32 is a read-only storage device and stores information such as a map necessary for control in advance. The CPU 34 can perform arbitrary calculations and determinations. The RAM 33 is a readable / writable storage device, and can store information such as an operation history or temporarily store a calculation result.

Downstream of the NO _X storage catalyst 17, a temperature sensor 26 for detecting the temperature of the NO _X storage catalyst 17 is arranged. A temperature sensor 27 for detecting the temperature of the oxidation catalyst 13 or the particulate filter 16 is disposed downstream of the oxidation catalyst 13. The output signals of these temperature sensors 26 and 27 are input to the input port 35 via the corresponding AD converter 37.

  The particulate filter 16 is provided with a differential pressure sensor 28 for detecting the differential pressure across the particulate filter 16. Output signals of the differential pressure sensor 28 and the intake air amount detector 8 are input to the input port 35 via the corresponding AD converters 37.

  Connected to the accelerator pedal 40 is a load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40. The output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °.

  A water temperature sensor 58 disposed in an engine cooling device that cools the engine body is connected to the input port 35 via a corresponding AD converter 37. A vehicle speed sensor 60 that detects the speed of the automobile and an outside air temperature sensor 61 that measures the outside air temperature are connected to the input port 35 via the corresponding AD converter 37. On the other hand, the output port 36 is connected to the fuel injection valve 3, the step motor for driving the throttle valve 10, the EGR control valve 19, and the fuel pump 23 through corresponding drive circuits 38.

  The oxidation catalyst 13 is a catalyst having oxidation ability for purifying exhaust gas. The oxidation catalyst 13 includes, for example, a base body having a partition wall extending in the exhaust gas flow direction inside a cylindrical case body. The substrate is formed in a honeycomb structure, for example. A coating layer made of, for example, porous oxide powder is formed on the surface of the substrate, and a noble metal catalyst such as platinum Pt is supported on the coating layer. CO or HC contained in the exhaust gas is oxidized by the oxidation catalyst 13 and converted into harmless substances such as water and carbon dioxide.

  The particulate filter 16 is a filter that removes particulate matter (particulates) such as carbon particulates and ionic particulates such as sulfate contained in the exhaust gas. The particulate filter has, for example, a honeycomb structure and has a plurality of flow paths extending in the gas flow direction. In the plurality of channels, the channels whose downstream ends are sealed and the channels whose upstream ends are sealed are alternately formed. The partition walls of the flow path are formed of a porous material such as cordierite. Particulates are captured when the exhaust gas passes through the partition walls.

  Particulate matter is collected on the particulate filter 16 and oxidized. The particulate matter gradually deposited on the particulate filter 16 is oxidized and removed by raising the temperature to, for example, about 600 ° C. in an atmosphere containing excess air.

In the example of the apparatus shown in FIG. 1, when the differential pressure ΔP before and after the particulate filter 16 detected by the differential pressure sensor 28 exceeds the allowable value P _X , the amount of particulate matter deposited on the particulate filter 16 is It is judged that the allowable amount was exceeded. When the amount of the particulate matter exceeds the allowable amount, the temperature of the particulate filter 16 is raised under the lean air-fuel ratio of the exhaust gas, thereby oxidizing and removing the deposited particulate matter.

  The control apparatus for an internal combustion engine in the present embodiment includes air-fuel ratio detection means for detecting the air-fuel ratio in the combustion chamber. The control device for the internal combustion engine in the present embodiment detects the intake air amount by the intake air amount detector 8. Further, the control device controls the amount of fuel injected by the fuel injection valve 3. The control device detects the air-fuel ratio in the combustion chamber. The air-fuel ratio detecting means for detecting the air-fuel ratio in the combustion chamber is not limited to this form, and any means for detecting the air-fuel ratio in the combustion chamber can be adopted.

The control device for the internal combustion engine may include air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas. For example, by disposing an air-fuel ratio sensor in the middle of the engine exhaust passage, it is possible to detect the air-fuel ratio of the exhaust gas flowing into the NO _x storage catalyst.

  FIG. 2 shows a schematic diagram of the engine cooling device in the present embodiment. The internal combustion engine in the present embodiment includes an engine cooling device as a cooling means for cooling the engine body 1. The engine cooling device is formed so that cooling water flows through a system formed by piping. The engine cooling device is configured such that when the water pump 52 is driven, the cooling water sequentially flows through the oil cooler 53, the cylinder block 54, and the cylinder head 55 and flows into the thermo case 56. Further, the engine cooling device is driven by the water pump 52 so that the cooling water passes through the intake air cooling device 11 disposed in the intake passage and the EGR cooling device 20 disposed in the EGR passage 18. It is formed so as to flow into the case 56.

  The thermocase 56 is provided with a water temperature sensor 58 for measuring the temperature of the cooling water. In the present embodiment, a thermostat 57 is disposed in the thermocase 56. When the water temperature of the cooling water becomes equal to or higher than a predetermined determination value, the on / off valve is opened by the thermostat 57 and the cooling water flows to the radiator 51. The radiator 51 is a radiator that cools the cooling water. A fan 59 for forcibly sending air to the radiator 51 is disposed on the front side of the radiator 51. As the fan 59 rotates, the cooling water is forcibly cooled. The cooling water cooled by the radiator 51 is formed so as to go to the water pump 52. In this way, the water pump 52 is driven so that the cooling water circulates inside the engine cooling device.

  With reference to FIGS. 1 and 2, the output port 36 of the electronic control unit 30 is connected to the water pump 52 via a corresponding drive circuit 38. The output port 36 is connected to the fan 59 via a corresponding drive circuit 38. As described above, the water pump 52 and the fan 59 are controlled by the electronic control unit 30.

  The control apparatus for an internal combustion engine in the present embodiment includes a cooling capacity detecting means for detecting the cooling capacity of the engine cooling apparatus. The cooling capacity detecting means in the present embodiment is at least one of the temperature of the cooling water detected by the water temperature sensor 58, the vehicle speed detected by the vehicle speed sensor 60, and the outside air temperature detected by the outside air temperature sensor 61. Is used so that the cooling capacity of the engine cooling device can be calculated.

  The engine cooling device in the present embodiment includes a cooling capacity adjusting means for adjusting the cooling capacity. In the present embodiment, the cooling capacity can be adjusted by changing the rotational speed of the water pump 52. By increasing the rotation speed of the water pump 52, the flow rate of the circulating cooling water can be increased. By increasing the circulating flow rate of the cooling water, it is possible to increase the heat dissipation capability of the radiator 51 and improve the cooling capability. Further, the cooling capacity can be adjusted by controlling the driving and stopping of the fan 59. By driving the fan 59, the heat dissipation capability in the radiator 51 can be increased, and the cooling capability can be improved. The cooling capacity adjusting means is not limited to this form, and any cooling capacity that cools the engine body may be adjusted.

FIG. 3 is a schematic cross-sectional view of the NO _x storage catalyst. The NO _X storage catalyst 17 has a catalyst carrier 45 made of alumina, for example, supported on a substrate. A noble metal catalyst 46 is dispersed and supported on the surface of the catalyst carrier 45. A layer of NO _x absorbent 47 is formed on the surface of the catalyst carrier 45. As the noble metal catalyst 46, for example, platinum Pt is used. The components constituting the NO _x absorbent 47 are selected from, for example, alkali metals such as potassium K, sodium Na and cesium Cs, alkaline earths such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y. At least one of these is used.

The ratio of air and fuel (hydrocarbon) supplied to the engine intake passage, the combustion chamber, or the engine exhaust passage upstream of the NO _x storage catalyst is referred to as the exhaust gas air-fuel ratio (A / F). When the fuel ratio is lean (when greater than the stoichiometric air-fuel ratio), NO contained in the exhaust gas is oxidized on the noble metal catalyst 46 to become NO ₂ . NO ₂ is occluded in the NO _x absorbent 47 in the form of nitrate ions NO ₃ ⁻ .

In contrast, (smaller when the stoichiometric air-fuel ratio) air when fuel ratio is rich of the exhaust gas or becomes the stoichiometric air-fuel ratio, the reaction reverse to the oxygen concentration in the exhaust gas decreases (NO ₃ ^- → NO Go to ₂ ). _The NO _X absorbent in the 47 nitrate ions NO ₃ ^- are released from _the NO _X absorbent 47 in the form of NO _2. The released NO _x is reduced to N ₂ by unburned HC and CO contained in the exhaust gas.

In the operating example of the present embodiment, to detect the _the NO _X storage amount stored in _the NO _X storage catalyst. For example, a map of the accumulated amount of NO _x per unit time with the engine speed N and the required torque TQ as functions is built in the ROM 32 of the electronic control unit 30. By integrating the storage amount of the NO _X per unit is calculated time in accordance with the operating conditions, it is possible to detect _the NO _X storage amount stored in the NO _X storage catalyst. Before absorbing capability of the NO _X absorbent 47 becomes saturated, when _the NO _X storage amount reaches the predetermined amount, by temporarily make the air, the NO _X from _the NO _X absorbent 47 It can be released and reduced.

FIG. 4 shows another schematic cross-sectional view of the NO _x storage catalyst. The exhaust gas contains SO _x , that is, SO ₂ . When this SO ₂ flows into the NO _x storage catalyst 17, it is oxidized in the noble metal catalyst 46 to become SO ₃ . The SO ₃ is absorbed in _the NO _X absorbent 47, for example, while bonding with the barium carbonate BaCO _3, and diffuses in the NO _X absorbent 47 in sulfate ions SO ₄ ^2-form, generating the sulfate BaSO ₄ To do. Since the NO _x absorbent 47 has strong basicity, the sulfate BaSO ₄ is stable and difficult to decompose, and the sulfate BaSO ₄ remains without being decomposed simply by making the exhaust gas air-fuel ratio rich. . For this reason, if the use of the NO _x storage catalyst is continued, the sulfate BaSO ₄ in the NO _x absorbent 47 increases. The amount of NO _x that can be absorbed by the NO _x storage catalyst decreases. In this way, sulfur poisoning occurs in the NO _x storage catalyst 17.

In order to eliminate sulfur poisoning, a sulfur poisoning recovery process for releasing SO _x from the NO _x storage catalyst is performed. In the sulfur poisoning recovery process, the air-fuel ratio of the exhaust gas flowing into the NO _X storage catalyst 17 the temperature of the NO _X storage catalyst 17 in a state of being raised to a temperature capable of SO _X release the stoichiometric air-fuel ratio or rich Thus, a treatment for releasing SO _x from the NO _x storage catalyst is performed.

In the present embodiment, control when performing sulfur poisoning recovery processing will be described. The control device for an internal combustion engine in the present embodiment detects the SO _X storage amount accumulated in the NO _X storage catalyst. For example, a map of the accumulated amount of SO _x per unit time that has the engine speed N and the required torque TQ as functions is built in the ROM 32 of the electronic control unit 30. By integrating the SO _X storage amount per unit is calculated time in accordance with the operating conditions, it is possible to detect the SO _X storage amount stored in the NO _X storage catalyst. When the SO _X storage amount of the NO _X storage catalyst reaches a predetermined amount, sulfur poisoning recovery processing is performed.

  The control device for an internal combustion engine in the present embodiment is formed so as to be able to control the injection pattern of fuel injected into the combustion chamber. That is, the fuel injection amount and the injection timing of the electronic fuel injection valve 3 can be controlled. The sulfur poisoning recovery process of the present embodiment is performed by controlling the fuel injection pattern in the combustion chamber.

  FIG. 5 shows a fuel injection pattern during normal operation of the internal combustion engine in the present embodiment. The injection pattern A is a fuel injection pattern during normal operation. During normal operation, the main injection FM is performed at a compression top dead center TDC. That is, main injection FM is performed when the crank angle is approximately 0 °. Further, in order to stabilize the combustion of the main injection FM, the pilot injection FP is performed before the main injection FM. The pilot injection FP is performed, for example, in a range where the crank angle is approximately 10 ° to approximately 40 ° before the compression top dead center TDC. During normal operation, as shown in the injection pattern B, the pilot injection FP may not be performed, and the operation may be performed only with the main injection FM. In this embodiment, an injection pattern in which pilot injection FP is performed will be described as an example.

FIG. 6 is a time chart of operation control for performing sulfur poisoning recovery processing in the internal combustion engine of the present embodiment. Up to time t ₀ is normal operation. From time t ₀ to time t ₁ , the temperature of the NO _x storage catalyst is increased so that the temperature of the NO _x storage catalyst becomes equal to or higher than the SO _x release temperature. From time t ₁ to time t ₃ , SO _X is released by making the air-fuel ratio of the exhaust gas rich or stoichiometric while maintaining the temperature of the NO _X storage catalyst at or above the SO _X release temperature. . After time t ₃ , the sulfur poisoning recovery process is terminated and normal operation is performed. The temperature raising time from time t ₀ to time t ₁ is, for example, several tens of seconds, and the time for releasing SO _x from time t ₁ to time t ₃ is, for example, about several tens of minutes.

When operating with the injection pattern A during normal operation, the air-fuel ratio of the exhaust gas is lean. The operation of the internal combustion engine is continued and it is detected that SO _x has accumulated to a predetermined amount, and the temperature rise of the NO _x storage catalyst is started at time t ₀ . From time t ₀ to time t ₁ , temperature increase control for increasing the temperature of the NO _x storage catalyst is performed.

FIG. 7 shows an injection pattern for increasing the temperature of the NO _x storage catalyst or maintaining the increased temperature. In the injection pattern C, the injection timing of the main injection FM is delayed from the compression top dead center TDC. That is, the injection timing of the main injection FM is retarded. As the injection timing of the main injection FM is retarded, the injection timing of the pilot injection FP is also retarded. By delaying the injection timing of the main injection FM, the temperature of the exhaust gas can be raised. Further, after the main injection FM, after injection FA as auxiliary injection is performed. The after injection FA is performed at a combustible time after the main injection. The after injection FA is performed, for example, in a range where the crank angle after compression top dead center is approximately 40 °, for example, in the range where the crank angle after compression top dead center is approximately 20 ° to approximately 30 °. By performing after-injection FA, the afterburning period becomes longer and the temperature of the exhaust gas can be raised. Further, the amount of combustion in the combustion chamber can be increased and the temperature of the exhaust gas can be raised.

Referring to FIG. 6, the temperature of the NO _x storage catalyst can be raised by raising the temperature of the exhaust gas during the period from time t ₀ to time t ₁ . The temperature of the NO _x storage catalyst is raised to the SO _x release temperature. For example, the temperature is raised to 600 ° C. Further, during the period from time t ₁ to time t _3, by performing the injection pattern C, temperature maintenance control for maintaining the NO _x storage catalyst at the SO _x release temperature or higher can be performed. When operating with the injection pattern C, the air-fuel ratio of the exhaust gas is lean. The temperature rise of the NO _x storage catalyst is not limited to this form, and any method can be adopted.

When the temperature of the NO _X storage catalyst reaches the SO _X release temperature, rich control is performed to make the air-fuel ratio of the exhaust gas rich or the stoichiometric air-fuel ratio in order to release SO _X while performing temperature maintenance control.

FIG. 8 shows an injection pattern for enriching the air-fuel ratio of the exhaust gas in the present embodiment. The injection pattern D is an injection pattern in a period from time t ₁ to time t ₂ . When the injection pattern D is compared with the combustion pattern C, the injection amount of the after injection FA is increased. By increasing the injection amount of the after injection FA, the air-fuel ratio of the exhaust gas can be made rich. In the present embodiment, rich control is performed by increasing the injection amount of the after injection FA. However, the present invention is not limited to this mode, and for example, the injection amount of the main injection FM may be increased.

Referring to FIG. 6, SO _X can be released by performing rich control. During the period from time t ₁ to time t ₂ , rich control is performed at regular intervals when temperature maintenance control is performed. SO _X is released while repeating the injection pattern D and the injection pattern C.

In the rich control, the amount of combustion in the combustion chamber increases by increasing the injection amount of the after injection FA. At least a part of the increased fuel is converted into light unburned fuel (HC), CO, or the like under high temperature and high pressure in the combustion chamber. Thus, light unburned fuel (HC) or CO can be supplied to the engine exhaust passage as a reducing agent. Light unburned fuel, CO, and the like are excellent in reducing properties and are preferable as reducing agents. In the NO _x storage catalyst, SO _x is released by supplying the reducing agent.

  On the other hand, in rich control, the amount of combustion in the combustion chamber increases, so the temperature of the engine body 1 rises. Further, during rich control, the fuel injection pattern may be changed and the intake air amount may be reduced to achieve a target air-fuel ratio. That is, referring to FIG. 1, the throttle valve 10 disposed in the intake passage of the internal combustion engine may be throttled. By reducing the throttle valve 10, the intake air amount can be reduced and the air-fuel ratio can be reduced. At this time, the temperature of the exhaust gas further increases.

  As the temperature of the engine body 1 increases, the temperature of the cooling water in the engine cooling device also increases. In the present embodiment, the temperature of the cooling water in the engine cooling device has reached a predetermined allowable value on the high temperature side. The allowable value of the coolant temperature is preferably set to a low temperature that includes a margin with respect to the limit value of the operating range of the engine cooling device. The allowable value is preferably set to a low temperature so that the limit value of the operation range is not exceeded while the temperature of the cooling water exceeds the allowable value and is controlled to decrease the temperature.

The control apparatus for an internal combustion engine according to the present embodiment controls the amount of fuel burned in the combustion chamber when the temperature of the engine body of the internal combustion engine exceeds a predetermined allowable value during rich control. while decreasing, increasing the unburned fuel supplied to _the NO _X storage catalyst. In this embodiment, the water temperature sensor 58 of the engine cooling system, coolant temperature is detected that it is now more than the allowable value, to change the injection pattern in the combustion chamber at time t _2.

With reference to FIGS. 6 and 8, in a period from time t ₂ to time t _3, by changing the injection pattern D to the injection pattern E, repeated the injection pattern C and injection pattern E. Rich control is performed by the injection pattern E. Compared with the injection pattern D, the injection pattern E delays the injection timing of the after injection FA. That is, the after injection FA is retarded. By adopting this injection pattern, the amount of fuel combustion in the combustion chamber can be reduced. In the present embodiment, it is possible to suppress the combustion amount of the fuel injected by the auxiliary injection from decreasing and the engine body from being overheated. Or it can suppress that the cooling water of an engine cooling device overheats.

Further, when the after injection FA is retarded, the unburned fuel supplied to the NO _x storage catalyst increases, and the air-fuel ratio of the exhaust gas can be maintained in a rich state. By performing the injection pattern E and making the air-fuel ratio of the exhaust gas rich, SO _x can be released.

Here, the NO _x storage catalyst carries a metal catalyst for oxidizing NO _x as described above. Unburned fuel supplied to the NO _x storage catalyst is oxidized on the surface of the metal catalyst. At this time, heat generated by the oxidation reaction occurs, and the temperature of the NO _x storage catalyst can be maintained. That is, the temperature of the exhaust gas decreases as the amount of combustion in the combustion chamber decreases, but the oxidation reaction in the NO _X storage catalyst increases, so that the temperature of the NO _X storage catalyst is maintained at the SO _X release temperature. Can do.

A suitable reducing agent can be supplied to the NO _x storage catalyst by combusting at least a part of the increased amount of fuel injected into the combustion chamber. In the present embodiment, a suitable reducing agent can be supplied by burning at least part of the fuel injected by the after injection. However, since the amount of fuel combustion in the combustion chamber increases, the temperature of the engine body excessively rises. For this reason, by changing the injection pattern, it is possible to suppress the engine body from being overheated while supplying the reducing agent to the NO _x storage catalyst. Thus, in the present embodiment, while continuing the release of SO _X, it is possible to prevent the engine body becomes excessive temperature.

For the end of the sulfur poisoning recovery process, for example, the remaining SO _x amount is calculated based on the integrated value of the time when the air-fuel ratio of the exhaust gas is rich. Then, when the SO _X storage amount remaining in the NO _X storage catalyst reaches a predetermined value, the sulfur poisoning recovery process is terminated. Referring to FIG. 6, the sulfur poisoning recovery process is completed at time t ₃ . The normal operation is performed by returning the injection pattern to the injection pattern A.

  Referring to FIG. 8, in the present embodiment, injection pattern E is employed to lower the coolant temperature of the engine cooling device while maintaining a state where the air-fuel ratio of the exhaust gas becomes rich. For example, the injection pattern F may be adopted.

  The injection pattern F is an injection pattern in which the post injection FPO is performed by stopping the injection of the after injection FA. The post-injection is an auxiliary injection similar to the after-injection, but the post-injection affects the engine output, while the post-injection has a feature that does not contribute to the engine output. The post-injection FPO is an injection performed, for example, when the crank angle after compression top dead center is in the range of approximately 90 ° to approximately 120 °. By changing the injection pattern D to the injection pattern F, the injection timing of the auxiliary injection is delayed. By stopping the post-injection FA and performing the post-injection FPO, the air-fuel ratio of the exhaust gas can be maintained rich while reducing the amount of combustion in the combustion chamber.

In the present embodiment, the injection timing of at least a part of the fuel injected into the combustion chamber is delayed. In particular, when the auxiliary injection for injecting fuel is performed after the main injection in the combustion chamber, the injection timing of the auxiliary injection is delayed. With this control, the amount of fuel burned in the combustion chamber can be reduced, and unburned fuel supplied to the NO _x storage catalyst can be increased.

Further, in the present embodiment, the injection amount of one auxiliary injection remains substantially the same, and the injection timing of auxiliary injection is delayed. With this control, the air-fuel ratio of the exhaust gas flowing into the NO _x storage catalyst can be kept substantially constant even when the injection pattern is switched. Without changing the air-fuel ratio of the exhaust gas flowing into the NO _X storage catalyst, in order to be able to supply the reducing agent to the NO _X storage catalyst, to continue the release of SO _X without delay sulfur poisoning recovery process it can.

  Referring to FIG. 6, in the present embodiment, when the coolant temperature of the engine cooling device becomes equal to or higher than a predetermined determination value on the high temperature side, the operation is continued by switching from injection pattern D to injection pattern E. However, the present invention is not limited to this mode, and when the coolant temperature of the engine cooling device becomes equal to or lower than a predetermined determination value on the low temperature side after switching the injection pattern, the injection pattern E is returned to the injection pattern D. It doesn't matter. By performing this control, the time for supplying a lighter reducing agent can be lengthened.

  In the above description, the engine main body is prevented from being overheated by changing the combustion injection pattern. However, the present invention is not limited to this mode, and control of the engine cooling device may be used in combination. Next, control of the engine cooling device in the present embodiment will be described.

  FIG. 9 shows a first flowchart for explaining the control of the engine cooling device in the present embodiment. FIG. 9 shows the control during the sulfur poisoning recovery process. In step 101, the coolant temperature of the engine cooling device is detected. In step 102, it is determined whether or not the temperature of the cooling water is equal to or higher than an allowable value.

  In step 102, when the temperature of the cooling water of the engine cooling device is not less than the allowable value, the routine proceeds to step 103. In step 103, it is determined whether or not the cooling capacity of the engine cooling device is maximum. For example, it is determined whether or not the rotation speed of the water pump 52 is maximum, or whether or not the fan 59 that cools the radiator 51 is driven. In step 103, when the cooling capacity of the cooling device is not the maximum, the routine proceeds to step 111.

  In step 111, the cooling capacity of the cooling device is improved. For example, a predetermined amount of the rotation speed of the water pump 52 is increased. Alternatively, when the fan 59 that cools the radiator 51 is not driven, the fan 59 is driven. Thus, the cooling device in the present embodiment can avoid the engine body from becoming overheated by the cooling capacity adjusting means adjusting the cooling capacity.

  In step 103, when the cooling capacity of the engine cooling device is maximum, the routine proceeds to step 104. In step 104, the vehicle speed and the outside air temperature are detected. In step 105, the cooling capacity detecting means calculates the cooling capacity of the engine cooling device based on the vehicle speed and the outside air temperature. In the present embodiment, the maximum cooling capacity of the engine cooling device is calculated. In step 106, an injection pattern in the combustion chamber that can avoid overheating of the engine body is selected according to the cooling capacity of the engine cooling device.

  For example, the crank angle for retarding the auxiliary injection performed after the main injection is selected. Referring to FIG. 8, it is selected whether to adopt the injection pattern E that retards the after injection FA or the injection pattern F that stops the after injection FA and performs the post injection FPO. Alternatively, a retarded crank angle for retarding the after injection FA is selected. The amount of combustion in the combustion chamber can be reduced by delaying at least a part of the auxiliary timing in the auxiliary injection. Thus, the cooling capacity of the engine cooling device can be calculated, and the amount of combustion in the combustion chamber can be adjusted according to the cooling capacity.

  In step 107, the engine body can be prevented from being overheated by changing to the injection pattern in the combustion chamber selected according to the cooling capacity of the cooling device. The control shown in FIG. 9 is performed, for example, every predetermined period.

  FIG. 10 shows a second flowchart for explaining the control of the engine cooling device in the control device for the internal combustion engine in the present embodiment. In the control shown in FIG. 10, when the engine cooling device has sufficient cooling capacity, the amount of fuel combustion in the combustion chamber is increased. For example, according to the control shown in FIG. 9, the temperature of the cooling water in the engine cooling device is lowered to a predetermined determination value after a predetermined period after the combustion pattern is changed so that the amount of fuel combustion in the combustion chamber is reduced. In this case, it is possible to control to increase the amount of fuel combustion in the combustion chamber.

  In step 102 shown in FIG. 9, when the temperature of the cooling water of the engine cooling device is less than the allowable value, the routine proceeds to step 121 shown in FIG. In step 121, the vehicle speed and the outside air temperature of the automobile are detected. In step 122, the maximum value of the cooling capacity of the engine cooling device is calculated by the cooling capacity detecting means based on the vehicle speed and the outside air temperature. Further, the remaining capacity of the cooling capacity of the engine cooling device is calculated based on the current driving state of the engine cooling device. In calculating the remaining capacity of the cooling capacity, for example, the temperature of the cooling water, the rotational speed of the water pump 52, or whether the fan 59 is driven is referred to.

  In step 123, it is determined whether the remaining capacity of the engine cooling device is equal to or greater than a predetermined determination value. When the remaining capacity of the engine cooling device is less than a predetermined determination value, this control is terminated. When the remaining capacity of the engine cooling device is equal to or greater than a predetermined determination value, the routine proceeds to step 124. In step 124, an injection pattern that increases the amount of combustion within the cooling capacity of the engine cooling device is selected.

  As an injection pattern for increasing the combustion amount in the combustion chamber, for example, referring to FIG. 8, when the injection pattern E is adopted during the rich control, control for reducing the angle at which the after injection FA is retarded is performed. Do. Alternatively, when the injection pattern F is employed, the post injection FPO is stopped and the after injection FA is performed. Alternatively, the post injection FPO is reduced and the after injection FA is added. In this way, the amount of combustion in the combustion chamber can be increased by advancing at least part of the auxiliary injection timing.

In step 125, the combustion quantity in the combustion chamber is increased by changing to the selected injection pattern. As described above, when the cooling capacity of the engine cooling device is high, it is possible to perform control to increase the amount of fuel combustion in the combustion chamber. By increasing the amount of combustion in the combustion chamber, more light reducing agent can be supplied to the NO _x storage catalyst.

  In step 124 and step 125, when the cooling capacity of the engine cooling device has sufficient capacity, control for improving the cooling capacity of the engine cooling device may be performed in addition to the control for increasing the combustion amount in the combustion chamber. .

In this way, by changing the amount of fuel combustion in the combustion chamber according to the cooling capacity of the cooling device, the NO _x storage catalyst has many high-quality reducing agents while avoiding overheating of the engine cooling device. Can be supplied.

  The temperature detection means for detecting the temperature of the engine body in the present embodiment detects the coolant temperature of the engine cooling device, but is not limited to this form, and any means for detecting the temperature of the engine body is adopted. can do.

(Embodiment 2)
With reference to FIGS. 11 to 13, the control device for the internal combustion engine in the second embodiment will be described. The internal combustion engine in the present embodiment is the same as the internal combustion engine in the first embodiment. In the present embodiment, control when performing sulfur poisoning recovery processing will be described.

FIG. 11 is a time chart of operation control when performing the sulfur poisoning recovery process in the present embodiment. Control of normal operation until time t ₀ and temperature increase control from time t ₀ to time t ₁ are the same as in the first embodiment.

In this embodiment, between time t ₁ and time t ₃ , the temperature maintenance control injection pattern for maintaining the temperature of the NO _x storage catalyst at the SO _x release temperature or higher and the air-fuel ratio of the exhaust gas are rich. The rich control injection pattern is different from that of the first embodiment.

FIG. 12 shows an injection pattern for maintaining the NO _X storage catalyst at the SO _X release temperature or higher. In the injection pattern G, main injection FM, after injection FA as auxiliary injection, and post injection FPO are performed. The after injection FA corresponds to the first auxiliary injection performed after the main injection, and the post injection FPO corresponds to the second auxiliary injection performed after the first auxiliary injection. Referring to FIG. 11, the air-fuel ratio of the exhaust gas when operating with the injection pattern G is lean.

FIG. 13 shows an injection pattern when the air-fuel ratio of the exhaust gas is made rich in the sulfur poisoning recovery process of the present embodiment. At time t ₂ from time t _1, when the air-fuel ratio of the exhaust gas rich, the injection pattern H is adopted. The injection pattern H is controlled so that the injection amount of the after injection FA is larger than the injection pattern G shown in FIG.

Referring to FIG. 11, in the period from time t ₁ to time t ₂ , SO _X is released by adopting injection pattern H. As SO _X is released, the water temperature of the engine cooling device rises. It detects that the water temperature of the engine cooling system is equal to or greater than the allowable value, and changing the injection pattern at time t _2. In the period from time t ₂ to time t ₃ , the injection pattern for enriching the air-fuel ratio of the exhaust gas is changed from the injection pattern H to the injection pattern I.

Referring to FIG. 13, as compared with injection pattern H, injection pattern I decreases the injection amount of after injection FA and increases the injection amount of post injection FPO. By changing from the injection pattern H to the injection pattern I, the amount of fuel combustion in the combustion chamber can be reduced, and overheating of the engine body can be suppressed. Moreover, an increasing number of unburned fuel supplied to the NO _X storing catalyst, the temperature of the NO _X storage catalyst can be maintained above SO _X release temperature.

  Thus, in the rich control in the present embodiment, the first auxiliary injection for injecting fuel after the main injection and the second auxiliary injection for injecting fuel after the first auxiliary injection are performed. The injection amount of the first auxiliary injection is decreased to increase the injection amount of the second auxiliary injection. The injection timing of at least a part of the fuel injected into the combustion chamber is delayed. With this control, the amount of combustion in the combustion chamber can be reduced.

When detecting the cooling capacity of the engine cooling device and adjusting the combustion amount in the combustion chamber, the combustion amount in the combustion chamber is changed by changing the ratio of the injection amount of the after injection FA and the injection amount of the post injection FPO. Can be adjusted. For example, when the temperature of the engine body is lowered in step 106 and step 107 in FIG. 9, the amount of combustion in the combustion chamber can be reduced by decreasing the injection amount of the after injection FA and increasing the post injection FPO. . Alternatively, when the engine cooling device has a surplus capacity, the amount of combustion in the combustion chamber increases by increasing the injection amount of the after injection FA and decreasing the post injection FPO in steps 124 and 125 of FIG. Thus, many high-quality reducing agents can be supplied to the NO _x storage catalyst.

  Other configurations, operations, and effects are the same as those in the first embodiment, and thus description thereof will not be repeated here.

(Embodiment 3)
With reference to FIG. 14, a control apparatus for an internal combustion engine in the third embodiment will be described. The internal combustion engine in the present embodiment is the same as the internal combustion engine in the first embodiment. In the present embodiment, control when performing sulfur poisoning recovery processing will be described.

In FIG. 14, the time chart of the operation control which performs the sulfur poisoning recovery process of this Embodiment is shown. Normal control operation until time t _0, Atsushi Nobori control from time t ₀ to time t _1, the temperature maintaining control by the injection pattern C from time t ₁ to time t _2, the and the rich control by the injection pattern D is This is the same as the operation control in the first embodiment.

In the present embodiment, it is detected that the temperature of the cooling water in the engine cooling device has become an allowable value, and the injection pattern D performed at regular intervals is paused between time t ₂ and time t _3. The injection pattern C is continued. By continuing the injection pattern C, the temperature of the cooling water in the engine cooling device is lowered, but the temperature of the NO _x storage catalyst can be maintained at the SO _x release temperature or higher. Air-fuel ratio of the exhaust gas becomes lean, the release of SO _X is stopped. Thus, in the present embodiment, although the release of SO _x is stopped, standby temperature rise is performed while maintaining the temperature of the NO _x storage catalyst at a high temperature.

At time t ₃ , it is detected that the coolant temperature of the engine cooling device has dropped to a predetermined determination value, and the control for repeating the injection pattern D and the injection pattern C is resumed. At time t ₄ , it is detected that the storage amount of SO _X has become equal to or less than the determination value, and the sulfur poisoning regeneration process is terminated.

In this way, by detecting that the temperature of the engine body has become high when performing rich control at regular intervals, and interposing a period in which rich control is suspended and temperature maintenance control is continued, It can control that a main part becomes overheated. Moreover, the _the NO _X storage catalyst it is possible to maintain the high temperature of at least SO _X release temperature, there is no need to again raise the temperature of the _the NO _X storage catalyst can be performed in a short time sulfur poisoning recovery process. In the present embodiment, one standby temperature increase is interposed, but the present invention is not limited to this, and the standby temperature increase may be interposed twice or more.

  When the internal combustion engine includes an engine cooling device, fuel injection for performing rich control can be stopped instead of changing the fuel injection pattern in the first embodiment. For example, in step 106 and step 107 in FIG. 9, instead of changing the injection pattern, the injection pattern for performing the rich control can be paused to perform the temperature maintenance control.

  In the present embodiment, the injection pattern C is adopted as the temperature maintenance control and the injection pattern D is adopted as the rich control. However, the present invention is not limited to this form. For example, as in the second embodiment, the temperature The injection pattern G may be adopted as the maintenance control, and the injection pattern H may be adopted as the rich control.

  Other configurations, operations, and effects are the same as those in the first or second embodiment, and thus description thereof will not be repeated here.

(Embodiment 4)
With reference to FIGS. 15 to 17, the control apparatus for an internal combustion engine in the fourth embodiment will be described. The internal combustion engine in the present embodiment is the same as the internal combustion engine in the first embodiment. In the present embodiment, it will be described NO _X release processing for releasing NO _X.

FIG. 15 is a time chart of the first operational control in the present embodiment. Up to time t ₁ is normal operation. In the combustion chamber, the injection pattern A shown in FIG. 5 is adopted.

It is detected that the NO _x storage amount has reached a predetermined determination value, and release of NO _x is started at time t ₁ . In the release of NO _x , rich control is performed to enrich the air-fuel ratio of the exhaust gas by performing the injection pattern D shown in FIG. 8 during the period from time t ₁ to time t ₂ . In other words, the air-fuel ratio of the exhaust gas is made rich by retarding the main injection FM and adding the after injection FA.

During normal operation, the temperature of the engine body may be high. That is, the coolant temperature of the engine cooling device may be high. For example, in a driving state in which climbing a steep uphill at a slow vehicle speed for a long time at a high temperature such as midsummer, the water temperature of the engine cooling device becomes high. When in this state, when the NO _X release process of the NO _X storage catalyst, there is a case where the temperature of the coolant of the engine cooling system exceeds the allowable value. In operation example shown in FIG. 15, the water temperature of the cooling water reaches the allowable value, the injection pattern of the rich control is changed at time t _2.

In the period from time t ₂ to time t _3, the injection pattern E shown in FIG. 8 is employed to make the air-fuel ratio of the exhaust gas rich. That is, an injection pattern in which the injection timing of the after injection FA is delayed is adopted. By changing the injection pattern D to the injection pattern E, the amount of fuel combustion in the combustion chamber can be reduced. As a result, the coolant temperature of the engine cooling device can be lowered. Further, although the amount of fuel burned in the combustion chamber decreases, the amount of unburned fuel supplied to the engine exhaust passage increases, so that the air-fuel ratio of the exhaust gas can be kept rich.

Similarly to the sulfur poisoning recovery process, in the NO _x release process, by changing the injection pattern D to the injection pattern E, it is possible to avoid overheating the engine body while continuing to release NO _x. Can do. The engine cooling device can also be controlled in the same manner as in the sulfur poisoning recovery process.

  In the example shown in FIG. 15, it is detected that the coolant temperature of the engine cooling device has reached the allowable value on the high temperature side, and the injection pattern D is changed to the injection pattern E. However, the present invention is not limited to this form. As in the first embodiment, the injection pattern D may be changed to the injection pattern F. In other words, the control may be performed to stop the after injection FA and add the post injection FPO.

At time t ₃ , it is detected that the NO _X storage amount has decreased to a predetermined determination value, and the NO _X release process is terminated. After time t ₃ , the normal operation is performed by the injection pattern A.

FIG. 16 shows a time chart of the second operational control in the present embodiment. In the second operation control, the operation is performed with the injection pattern A in order to perform the normal operation until time t ₁ . From time t ₁ to time t ₂ , the injection pattern D is employed as rich control in order to release NO _x . The injection pattern A and the injection pattern D are repeated at regular intervals.

In the second operation control detects that the temperature of the coolant has reached the allowable value at time t _2, the has a longer time between the injection pattern D together at time t ₃ from time t _2. The time of the injection pattern A interposed between the injection patterns D is lengthened. That is, in the NO _X release process, while doing rich control to make the air-fuel ratio of the exhaust gas rich at regular intervals, and increase the interval between the rich control.

  By increasing the interval between the injection patterns to make the air-fuel ratio of the exhaust gas rich, it is possible to secure a time for cooling the cooling water of the engine cooling device and to prevent the engine body from becoming overheated. it can. In the control of the engine cooling device, in steps 106 and 107 in FIG. 9, the interval between the rich controls can be increased instead of changing the injection pattern.

In the operation example shown in FIG. 16, the operation is continued from time t ₂ to time t ₃ while performing control to increase the time between the rich controls, but the coolant temperature of the cooling device is predetermined. If it falls to this determination value, the time between rich controls may be shortened again.

FIG. 17 shows a time chart of the third operational control in the present embodiment. In the third operation control, the normal operation is continued with the injection pattern A until time t ₁ . From time t ₁ to time t ₂ , NO _X is released by repeating injection pattern D and injection pattern A.

In the third operation control it detects that the temperature of the cooling water of the engine cooling system at time t ₂ has reached the allowable value, during the period from the time t ₂ to time t _3, the air-fuel ratio of the exhaust gas Rich control to make it rich has stopped. That is, during the period from time t ₂ to time t ₃ , the operation is performed only with the injection pattern A. During this period, emission of the NO _X is paused.

At time t ₃ , it is detected that the water temperature of the engine cooling device has dropped to a predetermined determination value, and rich control is performed to make the air-fuel ratio of the exhaust gas rich again. In the period from time t ₃ to time t _4, and repeated again the injection pattern D and the injection pattern A. Thus, by interposing the stop period during which the rich control is stopped, the engine body can be prevented from being overheated. It is detected that the NO _X storage amount has reached a predetermined determination value at time t ₄ , and the NO _X release process is terminated. Normal operation is being performed at time t ₄ later.

  The engine cooling device can be controlled by stopping the rich control performed at regular intervals in step 106 and 107 in FIG. 9 instead of changing the injection pattern.

  Other configurations, operations, and effects are the same as in any of the first to third embodiments, and thus description thereof will not be repeated here.

(Embodiment 5)
An internal combustion engine control apparatus according to Embodiment 5 will be described with reference to FIGS. The internal combustion engine in the present embodiment is provided with a fuel addition valve for adding fuel into the engine exhaust passage.

FIG. 18 shows a schematic diagram of the internal combustion engine in the present embodiment. The internal combustion engine in the present embodiment is disposed in the engine exhaust passage upstream of the NO _x storage catalyst 17 and includes a fuel addition valve 15 as fuel addition means for adding fuel into the engine exhaust passage. The fuel addition valve 15 is formed so as to inject fuel toward the inside of the exhaust pipe 12. In the present embodiment, the same fuel as the fuel of the engine body 1 is injected, but the present invention is not limited to this, and a fuel different from the fuel of the engine body 1 may be used. The output port 36 of the electronic control unit 30 is connected to the fuel addition valve 15 via a corresponding drive circuit 38. The fuel addition valve 15 in the present embodiment is controlled by the electronic control unit 30.

FIG. 19 shows a time chart when performing sulfur poisoning recovery processing in the internal combustion engine of the present embodiment. Normal control operation until time t _0, the temperature increase control until time t _1, and the temperature maintaining control and rich control from time t ₁ to time t ₂ is the same as in the first embodiment.

  In the sulfur poisoning recovery process of the present embodiment, when the water temperature of the engine cooling device reaches an allowable value, the amount of fuel injected into the combustion chamber is reduced and the amount of fuel added by the fuel addition valve is reduced. Control to increase.

In time t _2, the detects that the water temperature of the engine cooling system has reached the allowable value, stops the rich control by injection pattern D. During the period from time t ₂ to time t ₃ , the temperature maintenance control of the injection pattern C is continued. By stopping the injection pattern D, the amount of fuel combustion in the combustion chamber is reduced, and the temperature of the engine body can be lowered. The air-fuel ratio of the exhaust gas discharged from the combustion chamber becomes lean.

On the other hand, by adding fuel from the fuel addition valve 15, the air-fuel ratio of the exhaust gas at the inlet of the NO _X storage catalyst 17 is made rich. By performing this control, the release of SO _x can be continued. In this way, the amount of fuel burned in the combustion chamber is reduced, and the amount of unburned fuel supplied to the NO _x storage catalyst is increased.

Also in this embodiment, while the temperature of the exhaust gas drops in the period from time t ₂ to time t _3, since the unburned fuel supplied to the NO _X storage catalyst is increased, in the NO _X storing catalyst Oxidation reaction is promoted. Due to the reaction heat of this oxidation reaction, the NO _x storage catalyst can be maintained at the SO _x release temperature or higher.

At time t ₃ , it is detected that the temperature of the cooling water in the engine cooling device has dropped to a predetermined low-temperature determination value, and rich control using the injection pattern D is resumed. The control of repeating the injection pattern D and the injection pattern C is resumed. At time t ₄ , it is detected that the amount of SO _X stored in the NO _X storage catalyst has decreased to a predetermined amount, and the sulfur poisoning regeneration process is terminated. After time t ₄ , normal operation is performed with the injection pattern A.

Also in the sulfur poisoning recovery process of the present embodiment, the amount of combustion in the combustion chamber can be reduced, and the engine body can be prevented from overheating. Further, by adding fuel from the fuel supply valve, it is possible to continue the SO _X release.

Further, in the present embodiment, the fuel addition is performed so that the air-fuel ratio of the exhaust gas at the NO _x storage catalyst inlet is substantially the same during the period during which the injection pattern D is performed and the period during which fuel is added by the fuel addition valve. The amount added by the valve is controlled. With this control, the air-fuel ratio of the exhaust gas flowing into the NO _x storage catalyst can be kept substantially constant.

FIG. 20 shows a time chart when NO _X is released in the internal combustion engine of the present embodiment. Normal operation is performed by the injection pattern A until time t ₁ . In the period from time t ₁ to time t ₂ , NO _x is released by performing rich control with the injection pattern D, as in the operation example of the fourth embodiment.

In NO _X emission process of the present embodiment, the temperature of the coolant of the engine cooling system at time t ₂ is detected to have reached the allowable value, and stops the rich control by injection pattern D. That is, the injection pattern D performed every fixed period is stopped and the injection pattern A is continued. The air-fuel ratio of the exhaust gas discharged from the combustion chamber becomes lean. On the other hand, the air-fuel ratio of the exhaust gas is made rich by adding fuel from the fuel addition valve 15 between time t ₂ and time t ₃ . By adding fuel from the fuel addition valve 15, the air-fuel ratio of the exhaust gas flowing into the NO _x storage catalyst can be made rich.

Also in the NO _x releasing process of the present embodiment, the amount of combustion in the combustion chamber can be reduced, and the engine body can be prevented from being overheated. Further, NO _x release can be continued by adding fuel from the fuel addition valve.

In the present embodiment, at time t ₃ , it is detected that the temperature of the cooling water of the engine cooling device has dropped to a predetermined determination value, and the addition of fuel from the fuel addition valve 15 is stopped. Further, the rich control by the injection pattern D is resumed. That is, the control of repeating the injection pattern D and the injection pattern A is resumed. At time t ₄ , it is detected that the NO _X storage amount has dropped to a predetermined determination value, and the NO _X release process is terminated.

  In the control of the engine cooling apparatus, instead of changing the injection pattern for performing the rich control, the injection by the injection pattern for performing the rich control can be stopped and the fuel can be added by the fuel addition valve. For example, in steps 106 and 107 of FIG. 9, instead of changing the injection pattern, the rich control injection pattern in the combustion chamber is stopped and fuel is added from the fuel addition valve, so that the temperature of the engine body is excessively increased. Can be suppressed.

In the present embodiment, as control for enriching the air-fuel ratio of the exhaust gas flowing into the NO _x storage catalyst, control for increasing the amount of fuel injected into the combustion chamber or control for adding fuel from the fuel addition valve is performed. Either one is adopted, but it is not limited to this form, and both controls may be used in combination. The temperature of the engine body can be adjusted by changing the ratio between the amount of fuel injected in the combustion chamber and the amount of fuel injected from the fuel addition valve. In the control of the engine cooling device, for example, in steps 106 and 107 in FIG. 9 or steps 124 and 125 in FIG. 10, the amount of fuel injected into the combustion chamber and the fuel addition valve in accordance with the cooling capacity of the engine cooling device. The temperature of the engine body can be adjusted by changing the ratio with the amount of fuel injected from the engine.

  Other configurations, operations, and effects are the same as those in the first to fourth embodiments, and thus description thereof will not be repeated here.

  In the respective drawings described above, the same or corresponding parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. The above embodiments can be combined. Further, in the embodiment, changes included in the scope of claims are intended.

1 is a schematic diagram of an internal combustion engine in a first embodiment. 1 is a schematic view of an engine cooling device that cools an engine main body in a first embodiment. _The NO _X storage catalyst is an enlarged schematic sectional view of the NO _X storage catalyst when absorbing NO _{X. The} NO _X storage catalyst is an enlarged schematic sectional view of the NO _X storage catalyst when absorbing the SO _X. It is an injection pattern when the internal combustion engine performs normal operation. 3 is a time chart of operation control for performing sulfur poisoning recovery processing in the first embodiment. It is an injection pattern when performing temperature rise of the NO _x storage catalyst. 6 is an injection pattern when the air-fuel ratio of exhaust gas in the first embodiment is made rich. 3 is a first flowchart illustrating control of the engine cooling device in the first embodiment. 6 is a second flowchart illustrating control of the engine cooling device in the first embodiment. 6 is a time chart when performing a sulfur poisoning recovery process in the second embodiment. FIG. 6 is an injection pattern when the NO _X storage catalyst in Embodiment 2 is maintained at a temperature equal to or higher than the SO _X release temperature. It is an injection pattern when making the air-fuel ratio of exhaust gas rich in Embodiment 2. 10 is a time chart of operation control for performing sulfur poisoning recovery processing in the third embodiment. 10 is a time chart of first operational control for performing NO _X release processing in the fourth embodiment. 12 is a time chart of second operational control for performing NO _X release processing in the fourth embodiment. 10 is a time chart of third operational control for performing NO _X releasing processing in the fourth embodiment. FIG. 10 is a schematic view of an internal combustion engine in a fifth embodiment. 10 is a time chart of operation control for performing sulfur poisoning recovery processing in the fifth embodiment. 12 is a time chart of operation control for performing NO _X release processing in the fifth embodiment.

Explanation of symbols

1 engine body 2 combustion chamber 3 fuel injection valve 13 oxidation catalyst 15 fuel addition valve 16 particulate filter 17 NO _X storing catalyst 21 the fuel supply pipe 26 temperature sensor 27 temperature sensor 28 differential pressure sensor 30 the electronic control unit 51 radiator 52 water pump 58 Water temperature sensor 59 Fan 60 Vehicle speed sensor 61 Outside air temperature sensor

Claims (9)

NO _x contained in the exhaust gas is occluded when the air-fuel ratio of the inflowing exhaust gas is lean in the engine exhaust passage of the internal combustion engine, and the occluded NO when the air-fuel ratio of the inflowing exhaust gas becomes the stoichiometric air-fuel ratio or rich _In a control device for an internal combustion engine in which a NO _X storage catalyst that releases _X is arranged and fuel is injected into a combustion chamber,
The temperature of the engine body of the internal combustion engine is set to a predetermined allowable value when rich control is performed to make the air-fuel ratio of the exhaust gas rich or the stoichiometric air-fuel ratio by increasing the amount of fuel injected into the combustion chamber. In the case of the above, a control apparatus for an internal combustion engine, which reduces the amount of fuel burned in the combustion chamber and increases the amount of unburned fuel supplied to the NO _x storage catalyst. When performing the rich control, if the temperature of the engine body of the internal combustion engine exceeds a predetermined allowable value, without changing the air-fuel ratio of the exhaust gas flowing into the NO _X storage catalyst, 2. The control device for an internal combustion engine according to claim 1, wherein the combustion amount of the fuel in the combustion chamber is decreased and the unburned fuel supplied to the NO _x storage catalyst is increased.   In the combustion chamber, when the rich control is performed by performing the auxiliary injection at the combustible time after the main injection in addition to the main injection, the temperature of the engine body of the internal combustion engine exceeds a predetermined allowable value. 3. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion amount of the auxiliary injection is reduced when it becomes. 4. The internal combustion engine according to claim 3, wherein the combustion amount of the auxiliary injection is decreased and the unburned fuel supplied to the NO _X storage catalyst is increased by delaying the injection timing of the auxiliary injection. 5. Control device. In the combustion chamber, in addition to the main injection, the rich control is performed by performing a first auxiliary injection for injecting fuel at a combustible time after the main injection and a second auxiliary injection for injecting fuel after the first auxiliary injection. When the temperature of the engine body of the internal combustion engine becomes equal to or higher than a predetermined allowable value, the injection amount of the first auxiliary injection is decreased to reduce the injection amount of the second auxiliary injection. by increasing, while decreasing the combustion amount of fuel in the combustion chamber, characterized in that increasing the unburned fuel supplied to the NO _X storing catalyst, the control apparatus for an internal combustion engine according to claim 1 or 2. A fuel addition means that is disposed upstream of the NO _x storage catalyst in the engine exhaust passage and that adds fuel to the engine exhaust passage is disposed to reduce the amount of fuel injected into the combustion chamber and to reduce the fuel generated by the fuel addition means. 6. The control device for an internal combustion engine according to claim 1, wherein unburned fuel supplied to the NO _X storage catalyst is increased by increasing the amount of addition of NO. NO _x contained in the exhaust gas is occluded when the air-fuel ratio of the inflowing exhaust gas is lean in the engine exhaust passage of the internal combustion engine, and the occluded NO when the air-fuel ratio of the inflowing exhaust gas becomes the stoichiometric air-fuel ratio or rich _When the NO _X storage catalyst that releases _X is disposed, and the amount of SO _X stored in the NO _X storage catalyst exceeds a predetermined allowable amount, the temperature of the NO _X storage catalyst can be reduced to SO _{X that} can release SO _X. In the control device for an internal combustion engine that raises the discharge temperature and makes the air-fuel ratio of the exhaust gas flowing into the NO _x storage catalyst the stoichiometric air-fuel ratio or rich and performs the sulfur poisoning recovery process,
NO _x occlusion by performing at least one of control for delaying the injection timing of the main injection of fuel injected into the combustion chamber and control for performing auxiliary injection at the combustible timing after the main injection during the sulfur poisoning recovery process The temperature maintenance control for maintaining the catalyst at the SO _X release temperature or higher, and the period during which the temperature maintenance control is being performed, the amount of fuel injected into the combustion chamber is increased at regular intervals to enrich the air-fuel ratio of the exhaust gas. Or it is formed to perform rich control to the stoichiometric air-fuel ratio,
When the temperature of the engine body of the internal combustion engine is equal to or higher than a predetermined allowable value, the rich control performed every predetermined period is suspended, and a period for maintaining the temperature maintenance control is interposed. Control device for internal combustion engine.   A control device for an internal combustion engine in which a cooling means for cooling an engine body and a cooling capacity detecting means for detecting the cooling capacity of the cooling means are arranged, corresponding to the cooling capacity detected by the cooling capacity detecting means The control device for an internal combustion engine according to any one of claims 1 to 7, wherein a combustion amount in the combustion chamber is changed.   9. The control apparatus for an internal combustion engine according to claim 8, wherein the cooling means includes cooling capacity adjusting means for adjusting the cooling capacity.

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