JP2007016730A - Internal combustion engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology for early increasing temperatures in lean combustion cylinders of an internal combustion engine which performs rich combustion and lean combustion to early increase the temperature of an exhaust gas purifying catalyst at cold start. <P>SOLUTION: At cold start, this internal combustion engine control device sets an air-fuel ratio in a cylinder (#1) as part of four cylinders to be rich and an air-fuel ratio in cylinders (#2-#4) as at least part of the other remaining cylinders to be lean for giving reaction between exhaust materials exhausted from the cylinder (#1) where the air-fuel ratio is rich and exhaust materials exhausted from the cylinders (#2-#4) where the air-fuel ratio is lean to increase the temperature of the exhaust gas purifying catalyst. Herein, a cylinder temperature control means is provided for independently changing the temperatures in the cylinders where the air-fuel ratio is lean and in the cylinder where the air-fuel ratio is rich. When increasing the temperatures in the cylinders, the cylinder temperature control means distributes a high temperature cooling water stored in a regenerating system 9 into only the cylinders (#2-#4) where the air-fuel ratio is lean at cold start. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that controls the internal combustion engine to raise the temperature of an exhaust purification catalyst during a cold start.

  The exhaust system of an automobile engine is provided with a catalytic converter located immediately after the exhaust manifold or under the floor, and HC (hydrocarbon) in the exhaust gas by an exhaust purification catalyst such as a three-way catalyst built in the catalytic converter. , CO (carbon monoxide) and NOx (nitrogen oxide) are simultaneously purified and reduced.

At the time of cold start where the exhaust gas temperature is low and the catalyst temperature is low, the rich combustion and the lean are divided by dividing the air-fuel ratio into a plurality of cylinders and lean cylinders in the plurality of cylinders. A technology that simultaneously performs combustion, oxidizes CO in rich exhaust gas and O ₂ (oxygen) in lean exhaust gas, and heats the catalyst quickly with the heat generated by this reaction. It is disclosed in Patent Document 1.
JP 2002-332833 A JP-A-8-144801 JP 2002-276420 A

  When performing the technique disclosed in Patent Document 1, it is preferable to make the difference in air-fuel ratio between the rich cylinder and the lean cylinder as large as possible. In accordance with this, it is also desirable to increase the lean degree of the air-fuel ratio even in the cylinder where the air-fuel ratio is lean. However, at the time of cold start, the cylinder is cold, and there is a possibility that the cylinder temperature of the cylinder having the lean air-fuel ratio is not good. Therefore, the lean combustion is deteriorated in the cylinder, which may cause the worst misfire. For this reason, the lean degree of the air-fuel ratio cannot be increased in the cylinder that makes the air-fuel ratio lean during cold start.

  Therefore, in order to increase the leanness of the air-fuel ratio in the cylinder that makes the air-fuel ratio lean from the cold start, the temperature of the cylinder that makes the air-fuel ratio lean is raised to a temperature suitable for lean combustion at the cold start. It is hoped that

  An object of the present invention is to quickly increase the temperature of a cylinder that performs lean combustion in an internal combustion engine that simultaneously performs rich combustion and lean combustion in order to quickly increase the temperature of the exhaust purification catalyst at the time of cold start. Is to provide.

  In order to achieve the above object, in the control apparatus for an internal combustion engine according to the present invention, during cold start, the air-fuel ratio of some of the plurality of cylinders is made rich, and the remaining one of the remaining cylinders At least a part of the air-fuel ratio is lean, and the exhaust gas discharged from the cylinder that makes the air-fuel ratio rich and the exhaust gas discharged from the cylinder that makes the air-fuel ratio lean react with each other to raise the temperature of the exhaust purification catalyst A control apparatus for an internal combustion engine, comprising: a cylinder temperature control means capable of independently changing a temperature of a cylinder that makes the air-fuel ratio lean and a temperature of the cylinder that makes the air-fuel ratio rich. .

In the control device for the internal combustion engine configured as described above, at the time of cold start where the catalyst temperature is low,
Rich combustion and lean combustion are performed simultaneously by having two sets of a cylinder that makes the air-fuel ratio rich with respect to the stoichiometric air-fuel ratio and a cylinder that makes lean in a plurality of cylinders, and CO in the exhaust gas of rich combustion, O _{2 in} the exhaust gas of lean combustion is oxidized and the temperature of the exhaust purification catalyst is raised quickly by the heat generated by this reaction.

  However, at the time of cold start, the cylinder is cold, and there is a possibility that the cylinder temperature of the cylinder having the lean air-fuel ratio is not good. Therefore, the lean combustion is deteriorated in the cylinder, which may cause the worst misfire.

  Therefore, the control apparatus for an internal combustion engine according to the present invention includes cylinder temperature control means that can independently change the temperature of the cylinder that makes the air-fuel ratio lean and the temperature of the cylinder that makes the air-fuel ratio rich. The temperature control means raises the temperature of the cylinder that makes the air-fuel ratio lean at the time of cold start.

Therefore, the cylinder having lean air-fuel ratio is heated at the cold start, so that lean combustion can be facilitated without misfiring. For this reason, the cylinder with lean air-fuel ratio can perform lean combustion with increasing lean degree from the cold start, and the difference in air-fuel ratio with the rich cylinder can be increased. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

  A heat medium can flow through each of the plurality of cylinders, and the cylinder temperature control means controls the flow of the heat medium, thereby controlling the temperature of the cylinder that makes the air-fuel ratio lean and the air temperature. It is preferable that the temperature of the cylinder that makes the fuel ratio rich can be changed independently. Thereby, with a simple configuration, the temperature of the cylinder that makes the air-fuel ratio lean and the temperature of the cylinder that makes the air-fuel ratio rich can be changed independently.

  It is preferable that the heat medium circulated by the cylinder temperature control means is high-temperature cooling water that is heated when warm and stored in the heat storage system. Thereby, it is possible to raise the temperature of the cylinder by circulating the heat medium with a simple configuration.

  The cylinder temperature control means causes the high-temperature cooling water stored in the heat storage system to flow through the cylinder that makes the air-fuel ratio lean at the time of cold start to raise the temperature of the cylinder that makes the air-fuel ratio lean. Is preferred.

As a result, the cylinder having lean air-fuel ratio is heated at the cold start, so that lean combustion can be facilitated without misfire. For this reason, the cylinder with lean air-fuel ratio can perform lean combustion with increasing lean degree from the cold start, and the difference in air-fuel ratio with the rich cylinder can be increased. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

  Here, when the amount of the cooling water stored in the heat storage system is limited, it is preferable that the high-temperature cooling water is circulated only to the cylinder having the lean air-fuel ratio. If the high-temperature cooling water is circulated to all the cylinders at the time of cold start, all the high-temperature cooling water is supplied before the temperature of the cylinder that makes the air-fuel ratio lean which requires an early temperature increase rises. This is because it may disappear.

In the cold start, the cylinder temperature control means stops the flow of the low-temperature heat medium to the cylinder having the air-fuel ratio as lean, and the low-temperature heat medium flows through the cylinder as the lean air-fuel ratio. It is preferable to raise the temperature faster than the cylinders that are present.

  For example, when there is no high-temperature cooling water even if a heat storage system is provided, or in the case of an internal combustion engine that is supplied with cooling water as a heat medium by a mechanical pump driven by a crankshaft, the empty When cooling water is supplied to a cylinder having a lean fuel ratio, the cylinder is cooled because the cooling water is at a low temperature. Therefore, it is impossible to quickly raise the temperature of the cylinder. Therefore, for the cylinders that should be heated up early, the low-temperature cooling water is stopped from flowing so that the temperature is raised quickly.

As a result, the cylinder having lean air-fuel ratio is heated at the cold start, so that lean combustion can be facilitated without misfire. For this reason, the cylinder with lean air-fuel ratio can perform lean combustion with increasing lean degree from the cold start, and the difference in air-fuel ratio with the rich cylinder can be increased. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

  According to the present invention, in an internal combustion engine that simultaneously performs rich combustion and lean combustion in order to quickly raise the temperature of the exhaust purification catalyst during cold start, the temperature of the cylinder that performs lean combustion can be raised quickly.

  Specific examples of the present invention will be described below.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 and its cooling water circulation system according to this embodiment. The internal combustion engine 1 is a spark ignition type internal combustion engine (gasoline engine) using gasoline as fuel, and is mounted on an automobile or the like.

  The internal combustion engine 1 is an in-line four cylinder in which four cylinders of a first cylinder (# 1) to a fourth cylinder (# 4) are arranged in series. In-engine cooling water passage 2 (2a, 2b, 2c, 2d), which is a passage through which cooling water as a heat medium flows in each cylinder (# 1, # 2, # 3, # 4) of the internal combustion engine 1 However, the cooling water is provided so as to flow on the outer periphery of the combustion chamber.

  The engine cooling water passage 2 is provided with an on-off valve 3 (3a, 3b, 3c, 3d) that circulates the cooling water when opened and blocks the circulation of the cooling water when closed. The on-off valve 3 is controlled to be opened and closed by a command signal from the ECU 14 described later.

  As shown in FIG. 1, the engine cooling water passage 2 of the internal combustion engine 1 includes a first circulation path 5 that guides the cooling water to the heater core 4 for heating the vehicle interior and a second circulation that guides the cooling water to the radiator 6. The passage 7 is connected to the first bypass passage 8 through which the cooling water passes through the cylinder block of the internal combustion engine 1. In addition, a second bypass passage 10 that bypasses the heater core 4 and guides cooling water to the heat storage system 9 is connected to the first circulation passage 5.

  The first circulation path 5, the second circulation path 7, the first bypass passage 8, and the second bypass passage 10 merge before the internal combustion engine 1, and an electric water pump 11 is provided at the junction. The electric water pump 11 uses a battery (not shown) as a drive source. When a voltage is applied according to a command signal from the ECU 14 described later, the engine water coolant passage 2 supplies a flow of coolant corresponding to the applied voltage. To send.

  Here, a heat storage system 9 is provided in the middle of the second bypass passage 10. The heat storage system 9 includes a heat retaining container that can retain the cooling water stored in the interior surrounded by a heat insulating material that insulates the interior from the outside for a long time.

  A three-way valve 12 is provided at a branch position between the first circulation path 5 and the second bypass passage 10. The three-way valve 12 can move the valve position by a command signal from the ECU 14 to be described later. When the cooling water is circulated through both the first circulation path 5 and the second bypass path 10, the cooling water is supplied to the second bypass path 10. Select whether to circulate and prevent the cooling water from flowing through the first circulation path 5 or to circulate the cooling water through the first circulation path 5 and prevent the cooling water from flowing through the second bypass passage 10 it can.

  For example, when the electric water pump 11 is driven in a state where the valve position of the three-way valve 12 is set so that the coolant flows through the second bypass passage 10, the coolant flows into the heat storage system 9, and the heat storage system 9 The cooling water stored in the engine is sent into the engine cooling water passage 2. In the heat storage system 9, new cooling water is stored in place of the stored cooling water.

  In the second circulation path 7, a thermostat 13 is provided in addition to the radiator 6. When the temperature of the cooling water detected by the thermostat 13 does not reach a predetermined temperature (about 80 to 90 ° C.), the thermostat 13 is closed and the flow of the second circulation path 7 is blocked. Thereby, the cooling water circulates through the first circulation path 5 and the bypass path 8. On the other hand, when the temperature of the cooling water detected by the thermostat 13 has reached a predetermined temperature, the thermostat 13 is opened and the cooling water is also circulated through the second circulation path 7.

The internal combustion engine 1 includes an electronic control unit (ECU: Electronic) that controls the internal combustion engine 1 and the like.
Control Unit) 14 is also provided. The ECU 14 is an arithmetic logic operation circuit including a CPU, ROM, RAM, backup RAM, and the like.

  The ECU 14 is electrically connected to the electric water pump 11, and the ECU 14 can control the circulating flow rate of the cooling water by controlling the electric water pump 11. The ECU 14 is electrically connected to the on-off valve 3 and the three-way valve 12, and the ECU 14 can change the cooling water circulation path in the cooling water circulation system by controlling the on-off valve 3 and the three-way valve 12. It has become. Furthermore, the ECU 14 can also execute well-known fuel injection amount control by controlling an electrically connected fuel injection valve (not shown).

  FIG. 2 is a diagram illustrating a cooling water circulation path during normal operation of the internal combustion engine 1. During normal operation of the internal combustion engine 1, the ECU 14 opens the on-off valves 3 (3 a to 3 d) of all the engine cooling water passages 2, causes the cooling water to flow through the first circulation passage 5, and the second bypass passage 10. Then, the valve position of the three-way valve 12 is set so that the cooling water does not flow, and the electric water pump 11 is driven. As a result, when the temperature of the cooling water reaches a predetermined temperature and the thermostat 13 is opened, the cooling water flows as indicated by the arrows shown in FIG. Thereby, the cooling water flows through the heater core 4 and the radiator 6.

  Next, a case where high-temperature cooling water (hereinafter sometimes referred to as “hot water”) is recovered in the heat storage system 9 will be described. The cooling water recovery is performed when the temperature of the cooling water becomes high during normal operation of the internal combustion engine 1 or when the operation of the internal combustion engine 1 is stopped.

FIG. 3 is a diagram illustrating a circulation path of hot water during cooling water recovery. At the time of cooling water recovery, the ECU 14 opens the on-off valves 3 (3 a to 3 d) of all the engine cooling water passages 2, and the valve positions of the three-way valves 12 so that the cooling water flows at least through the second bypass passage 10. And the electric water pump 11 is driven. As a result, the cooling water flows as shown by the arrows in FIG. Thereby, the cooling water stored in the heat storage system 9 is sent into the engine cooling water passage 2, and new cooling water (hot water) is stored in the heat storage system 9 in place of the stored cooling water.

By the way, in the present embodiment, at the time of cold start where the catalyst temperature is low, the cylinders that make the air-fuel ratio richer than the stoichiometric air-fuel ratio in the four cylinders (# 1 to # 4) of the internal combustion engine 1 (this embodiment) Then, the rich combustion and the lean combustion are performed at the same time by dividing into two sets of cylinders that are # 1 cylinders and cylinders that are lean (in this embodiment, cylinders # 2, # 3, and # 4). Let it be done. This is because the CO in the rich combustion exhaust gas and the O ₂ in the lean combustion exhaust gas are oxidized and the temperature of the exhaust purification catalyst is raised quickly by the heat generated by this reaction. The control for simultaneously performing rich combustion and lean combustion for each cylinder is referred to as cylinder-specific rich / lean control.

  However, at the time of cold start, the cylinder is cold, and there is a possibility that the cylinder temperature of the second to fourth cylinders (# 2 to # 4) that performs lean combustion is not good. Therefore, lean combustion deteriorates in the second to fourth cylinders (# 2 to # 4), which may cause the worst misfire.

  Therefore, in the present embodiment, at the time of cold start of the internal combustion engine 1, before performing the rich / lean control for each cylinder, the hot water stored in the heat storage system 9 is subjected to lean combustion for the second to fourth cylinders ( It supplies only to the engine cooling water passages 2b to 2d of # 2 to # 4) to raise the temperature of the second to fourth cylinders (# 2 to # 4).

  Here, in this embodiment, since the amount of hot water that can be stored in the heat storage system 9 is limited, hot water is supplied only to the second to fourth cylinders (# 2 to # 4) that have a lean air-fuel ratio. Make it available for distribution. If hot water is circulated through all the cylinders during cold start, all of the hot water is supplied before the temperature of the second to fourth cylinders (# 2 to # 4), which requires an early temperature increase, may be insufficient. Because there is.

  Note that the rich / lean control for each cylinder is usually desired control, but if the lean combustion is performed at the extremely low temperature, misfire is likely to occur. Therefore, the control is not performed at the extremely low temperature. In other words, if catalyst warm-up is required, rich / lean control for each cylinder is performed except at extremely low temperatures. On the other hand, at the very low temperature, even if catalyst warm-up is necessary, the normal catalyst warm-up control is performed without performing the rich / lean control for each cylinder. Here, the normal catalyst warm-up control is to perform ignition delay and perform catalyst warm-up by raising the exhaust gas temperature.

  The above-described control for supplying warm water stored in the heat storage system 9 to the in-engine cooling water passage of the cylinder that performs lean combustion and causing the temperature of the cylinder to rise during the cold start is referred to as preheating. The preheating is executed before the rich / lean control for each cylinder when the exhaust purification catalyst such as the three-way catalyst of the exhaust system of the internal combustion engine 1 is warmed up when the internal combustion engine 1 is cold-started. FIG. 4 is a diagram showing a circulation path of hot water when the internal combustion engine 1 is preheated.

  In executing the preheating, the ECU 14 closes the on-off valve 3a of the first cylinder (# 1) and opens the on-off valves 3b, 3c, 3d of the second to fourth cylinders (# 2 to # 4). The valve position of the three-way valve 12 is set so that the cooling water flows at least through the second bypass passage 10, and the electric water pump 11 is driven. As a result, warm water flows as shown by the arrows in FIG.

Thereby, the warm water stored in the heat storage system 9 flows out of the heat storage system 9, and is supplied to the engine cooling water passages 2b to 2d of the second to fourth cylinders (# 2 to # 4). A part of the heat of the hot water is transmitted to the wall surface of the combustion chamber, and the temperature of the second to fourth cylinders (# 2 to # 4) of the internal combustion engine 1 rises.

  Such preheat control is determined as follows. Hereinafter, the control at the time of catalyst warm-up will be specifically described based on FIG.

  FIG. 5 is a flowchart showing a control routine of control during catalyst warm-up. This routine is stored in advance in the ECU 14 and is executed by the ECU as an interrupt process triggered by a predetermined time interval or input of a pulse signal from the crank position sensor.

  In this routine, the ECU 14 first determines in step (hereinafter referred to as “S”) 101 whether or not catalyst warm-up is necessary. For example, when the temperature of the catalyst estimated or detected based on the elapsed time since the previous stop of the internal combustion engine 1, various data, the detection temperature of the temperature sensor attached to the exhaust purification catalyst, etc. is lower than the activation temperature, the catalyst It is determined that warm-up is necessary.

  If it is determined in S101 that the catalyst needs to be warmed up, the process proceeds to S102, and it is determined whether or not the rich / lean control for each cylinder is requested.

  If it is determined in S102 that the cylinder-by-cylinder rich / lean control is required, the process proceeds to S103, where the on-off valve 3a of the first cylinder (# 1) that makes the air-fuel ratio rich is closed, and the air-fuel ratio is reduced. The on-off valves 3b to 3d of the second to fourth cylinders (# 2 to # 4) that are lean are opened.

  Further, after S103, the process proceeds to S104, the valve position of the three-way valve 12 is set so that the cooling water flows at least through the second bypass passage 10, the electric water pump 11 is driven, and the cooling water is allowed to flow. Then, the warm water flows as indicated by the arrows shown in FIG. 4, and the warm water is supplied to the engine coolant passages 2b to 2d of the second to fourth cylinders (# 2 to # 4). Thereby, the heat of warm water is transmitted to the combustion chamber wall surface, and the second to fourth cylinders (# 2 to # 4) of the internal combustion engine 1 are heated.

  After the control of S104, the process proceeds to S105, and the rich / lean control for each cylinder is started. That is, the air-fuel ratio in each cylinder is controlled so that rich combustion is performed in the first cylinder (# 1) and lean combustion is performed in the second to fourth cylinders (# 2 to # 4).

At this time, since the cylinder temperatures of the second to fourth cylinders (# 2 to # 4) are increased by S103 and S104, lean combustion is easily performed without misfiring. For this reason, the second to fourth cylinders (# 2 to # 4) increase the lean degree from the cold start and increase the air-fuel ratio difference from the first cylinder (# 1) that performs rich combustion as much as possible. Yes. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

  On the other hand, if it is determined in S102 that the rich / lean control for each cylinder is not requested, the process proceeds to S106, and normal catalyst warm-up control is performed.

  On the other hand, if it is determined in S101 that catalyst warm-up is not necessary, the process proceeds to S107, and various catalyst warm-up controls such as cylinder rich / lean control and normal catalyst warm-up control are not performed.

Note that, in the rich / lean control for each cylinder in S105, the ignition delay that is the normal catalyst warm-up control in S106 may be performed at the same time, and the ignition timing can be arbitrarily determined. As a result, the temperature of the exhaust purification catalyst is raised early at the time of cold start, so that the function of the exhaust purification catalyst can be exhibited early even at the time of cold start.

As described above, in the present embodiment, the second to fourth cylinders (# 2 to # 4) that perform the lean combustion in the cylinder-by-cylinder rich / lean control are heated at the cold start due to the preheat, so misfire This makes it easy to perform lean combustion without doing so. For this reason, in the second to fourth cylinders (# 2 to # 4), lean combustion can be performed with the lean degree increased from the cold start, and the difference in air-fuel ratio from the first cylinder (# 1) is increased. can do. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

  The cooling water supplied from the heat storage system at the time of cold starting is usually warm water. However, when the cooling water recovery is performed after a short period of operation or when the temperature of the hot water is decreased due to the preheating, the temperature of the cooling water stored in the heat storage system may be low. If the cooling water is supplied to the cylinder when the cooling water in the heat storage system is low, the cylinder is cooled by the low-temperature cooling water, and the cylinder cannot be heated to a temperature suitable for lean combustion. Therefore, in this embodiment, an example is shown in which different control is performed according to the temperature of the cooling water stored in the heat storage system. The detailed description of the configuration described in the first embodiment is omitted.

  In this embodiment, as shown in FIGS. 6 and 7, a water temperature sensor 15 is provided near the outlet of the heat storage system 9 in the second bypass passage 10. A water temperature sensor 15 is electrically connected to the ECU 14, and an output signal of the water temperature sensor 15 is input to the ECU 14.

  In this embodiment, when the exhaust purification catalyst is warmed up when the internal combustion engine 1 is cold-started, the preheat or cooling water supply cylinder selection control is executed before performing the cylinder rich / lean control.

  In the preheating, when the cooling water stored in the heat storage system 9 is high-temperature hot water, the hot water stored in the heat storage system 9 is used when the internal combustion engine 1 is cold-started as in the first embodiment. Is supplied to the engine coolant passages 2b to 2d of the second to fourth cylinders (# 2 to # 4). FIG. 6 is a diagram showing a circulation path of hot water when the internal combustion engine 1 is preheated. The circulation path of the hot water in such a case is as shown by the one-dot chain arrow shown in FIG.

  When the above preheating is performed, the used hot water loses heat correspondingly, and the temperature of the hot water decreases. In this way, when preheating is continued and the temperature of the hot water becomes low, or when the cooling water is low from the beginning of the cold start, the following cooling water supply cylinder selection control is performed.

  The cooling water supply cylinder selection control is different from preheating when the cooling water stored in the heat storage system 9 is low-temperature cooling water (hereinafter sometimes referred to as “cold water”). Before performing the rich / lean control for each cylinder at the time of starting, the chilled water is supplied only to the engine coolant water passage 2a of the first cylinder (# 1) that makes the air-fuel ratio rich, and the second to second air-fuel ratios are made lean. It is not supplied to the engine coolant passages 2b to 2d of the fourth cylinders (# 2 to # 4).

  In executing the cooling water supply cylinder selection control, the ECU 14 opens the on-off valve 3a of the first cylinder (# 1), and the on-off valves 3b to 3d of the second to fourth cylinders (# 2 to # 4). Is closed and the electric water pump 11 is driven.

FIG. 7 is a diagram illustrating a cooling water circulation path when the cooling water supply cylinder selection control of the internal combustion engine 1 is executed. The circulation path of the cold water in such a case is as shown by the one-dot chain arrow shown in FIG.

  Thus, in the coolant supply cylinder selection control, the coolant is not supplied to the engine coolant passages 2b to 2d of the second to fourth cylinders (# 2 to # 4). # 4) is not cooled. For this reason, it is possible to prevent the lean combustion from becoming difficult due to the low temperature of the cylinder.

  In this cooling water supply cylinder selection control, low-temperature cooling water must be supplied to the engine cooling water passages 2b to 2d of the second to fourth cylinders (# 2 to # 4) having at least the lean air-fuel ratio. As described above, the cooling water may or may not be supplied to the in-engine cooling water passage 2a of the first cylinder (# 1).

  Control during catalyst warm-up including such preheating and cooling water supply cylinder selection control is determined as follows. Hereinafter, the control at the time of catalyst warm-up will be specifically described based on FIG. In addition, since the process of S201-S207 in a present Example is the same as the process of S101-S107 in Example 1, the detailed description is abbreviate | omitted.

  When the rich / lean control for each cylinder is requested in S202, the process proceeds to S210, and it is determined whether or not the temperature T of the cooling water stored in the heat storage system 9 is higher than the predetermined temperature Tf (T> Tf). . The temperature T of the cooling water stored in the heat storage system 9 can be determined by comparing the history of measurement results measured by the water temperature sensor 15 at the end of the previous operation with a predetermined temperature Tf registered in the ECU 14 in advance. . Further, the temperature T of the cooling water is measured by the water temperature sensor 15 and can be determined by comparing the measurement result with a predetermined temperature Tf registered in the ECU 14 in advance.

  When it is determined that T> Tf in S210 (Yes), the process proceeds to S203, and the same control as in the first embodiment is performed.

  On the other hand, when it is determined that T ≦ Tf in S210 (No), the process proceeds to S211 and the on-off valve 3a of the first cylinder (# 1) is opened, and the second to fourth cylinders (# 2 to # 4) are opened. The on-off valves 3b to 3d are closed.

  Further, after S211, the process proceeds to S204, and the electric water pump 11 is driven and the cooling water is allowed to flow while making the valve position of the three-way valve 12 arbitrary. Then, cold water flows as shown by the arrows in FIG. 7, and the cold water is supplied only to the engine coolant passage 2a of the first cylinder (# 1).

  As a result, the first cylinder (# 1) is cooled by the cold water, but the cold water is not supplied to the engine coolant passages 2b to 2d of the second to fourth cylinders (# 2 to # 4). The fourth cylinder (# 2 to # 4) is not cooled. For this reason, it is possible to prevent the lean combustion from becoming difficult due to the low temperature of the cylinder, and it is possible to facilitate the lean combustion without causing misfire.

For this reason, the second to fourth cylinders (# 2 to # 4) can perform lean combustion with an increased lean degree from the cold start, and the difference in air-fuel ratio from the first cylinder (# 1) is increased. can do. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

As described above, also in the present embodiment, the preheat or the coolant supply cylinder selection control can facilitate the lean combustion without misfire of the cylinder that performs the lean combustion in the rich / lean control for each cylinder. For this reason, lean combustion can be performed with the lean degree increased from the time of cold start in the cylinder, and the air-fuel ratio difference from the cylinder that performs rich combustion can be increased. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

  The internal combustion engine 1 according to the present embodiment does not include a heat storage system but includes a mechanical pump that operates as the crankshaft rotates as a cooling water pump. Detailed descriptions of the configurations described in the first and second embodiments are omitted.

  In the present embodiment, as shown in FIG. 9, the internal combustion engine 1 does not include a heat storage system, and the cooling water only circulates through the first circulation path 5, the second circulation path 7, and the first bypass path 8. is there. Therefore, the cooling water is cold water at the cold start. Further, since the mechanical pump 16 operates as the crankshaft rotates, the cooling water continues to circulate while the internal combustion engine 1 is operating.

  The cooling water supply cylinder selection control in the present embodiment is the same as the cooling water supply cylinder selection control in the second embodiment. When the internal combustion engine 1 is cold started, the cold water is rich in the air-fuel ratio of the internal combustion engine 1. Is supplied to the engine coolant passage 2a of the first cylinder (# 1), and the engine coolant passages 2b to 2d of the second to fourth cylinders (# 2 to # 4) having a lean air-fuel ratio Do not supply.

  FIG. 9 is a diagram showing a cooling water circulation path when the cooling water supply cylinder selection control of the internal combustion engine 1 is executed. The circulation path of the cold water in such a case is as shown by the one-dot chain arrow shown in FIG. In this embodiment, because the mechanical pump 16 is used, the cooling water continues to circulate while the internal combustion engine 1 is operating. Therefore, in the cooling water supply cylinder selection control in this embodiment, the first cylinder (# 1 The cooling water is supplied to the in-engine cooling water passage 2a.

  Such control during catalyst warm-up is determined as follows. Hereinafter, the control at the time of catalyst warm-up will be specifically described based on FIG. In addition, since the process of S301-S307 in a present Example is the same as the process of S101-S107 in Example 1, the detailed description is abbreviate | omitted.

  If it is determined in S302 that the cylinder-by-cylinder rich / lean control is requested, the process proceeds to S310, where the on-off valve 3a of the first cylinder (# 1) is opened and the second to fourth cylinders (# 2) are opened. The on-off valves 3b to 3d of .about. # 4) are closed.

  In addition, after S310, the internal combustion engine 1 is operated, and the mechanical pump 16 is driven in accordance with this operation to flow cold water. And cold water flows like the arrow shown in FIG. 9, and cold water is supplied only to the engine cooling water channel | path 2a of a 1st cylinder (# 1).

  As a result, the first cylinder (# 1) is cooled by the cold water, but the cold water is not supplied to the engine coolant passages 2b to 2d of the second to fourth cylinders (# 2 to # 4). The fourth cylinder (# 2 to # 4) is not cooled. For this reason, it is possible to prevent the lean combustion from becoming difficult due to the low temperature of the cylinder, and it is possible to facilitate the lean combustion without causing misfire.

For this reason, the second to fourth cylinders (# 2 to # 4) can perform lean combustion with an increased lean degree from the cold start, and the difference in air-fuel ratio from the first cylinder (# 1) is increased. can do. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

As described above, also in this embodiment, the coolant supply cylinder selection control can facilitate the lean combustion without misfire of the cylinder that performs the lean combustion in the rich / lean control for each cylinder. For this reason, lean combustion can be performed with the lean degree increased from the time of cold start in the cylinder, and the air-fuel ratio difference from the cylinder that performs rich combustion can be increased. Therefore, the oxidation reaction between CO in the rich combustion exhaust gas and O ₂ in the lean combustion exhaust gas can be promoted, and the temperature of the exhaust purification catalyst can be raised quickly.

  In the above embodiment, the cylinders with lean air-fuel ratio in the rich / lean control for each cylinder are set to three cylinders (# 2 to # 4). However, the present invention is not limited to this, and one cylinder or two cylinders may be used. it can. Further, the total number of cylinders is not limited to the four cylinders in the embodiment. Further, not only the total cylinders are divided into cylinders that make the air-fuel ratio lean and cylinders that make the air-fuel ratio rich, but in addition to that, you may have a cylinder that makes the air-fuel ratio the stoichiometric air-fuel ratio. .

  In the first to third embodiments described above, the open / close valves 3 (3a, 3b, 3c, 3d) are provided in all four cylinders of the first cylinder (# 1) to the fourth cylinder (# 4). ing. However, if the cylinder in which the air-fuel ratio is rich or the stoichiometric air-fuel ratio is determined in the third embodiment, the opening / closing valve 3 may not be provided in the cylinder.

1 is a diagram illustrating a schematic configuration of an internal combustion engine according to a first embodiment. FIG. 3 is a diagram illustrating a flow of cooling water during normal operation in the internal combustion engine according to the first embodiment. It is a figure which shows the flow of the cooling water at the time of the cooling water collection | recovery in the internal combustion engine which concerns on Example 1. FIG. It is a figure which shows the flow of the warm water at the time of the preheating execution in the internal combustion engine which concerns on Example 1. FIG. FIG. 3 is a flowchart showing a control routine for control during catalyst warm-up according to the first embodiment. It is a figure which shows the flow of the warm water at the time of the preheating execution in the internal combustion engine which concerns on Example 2. FIG. It is a figure which shows the flow of the cold water at the time of the cooling water supply cylinder selection control execution in the internal combustion engine which concerns on Example 2. FIG. FIG. 9 is a flowchart showing a control routine for control during catalyst warm-up according to a second embodiment. FIG. 10 is a diagram illustrating a flow of cold water when executing a cooling water supply cylinder selection control in an internal combustion engine according to a third embodiment. FIG. 9 is a flowchart showing a control routine for control during catalyst warm-up according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 (2a, 2b, 2c, 2d) Engine cooling water passage 3 (3a, 3b, 3c, 3d) Open / close valve 4 Heater core 5 Circulation path 6 Radiator 7 Circulation path 8 First bypass path 9 Heat storage system 10 2 Bypass passage 11 Electric water pump 12 Three-way valve 13 Thermostat 14 ECU
15 Water temperature sensor 16 Mechanical pump

Claims (6)

During cold start, the air-fuel ratio of some cylinders of the plurality of cylinders is made rich, the air-fuel ratio of at least some of the remaining cylinders is made lean, and the air-fuel ratio is exhausted from the cylinders that are rich A control device for an internal combustion engine, wherein the exhaust gas discharged from a cylinder having a lean air-fuel ratio is reacted to raise the temperature of the exhaust purification catalyst.
A control apparatus for an internal combustion engine, comprising: cylinder temperature control means capable of independently changing a temperature of a cylinder having a lean air-fuel ratio and a temperature of a cylinder having a rich air-fuel ratio.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the cylinder temperature control means raises the temperature of a cylinder having the air-fuel ratio as lean at the time of cold start. A heat medium can flow through each of the plurality of cylinders,
The cylinder temperature control means is capable of independently changing a temperature of a cylinder that makes the air-fuel ratio lean and a temperature of the cylinder that makes the air-fuel ratio rich by controlling the flow of the heat medium. The control apparatus for an internal combustion engine according to claim 1 or 2.   The control apparatus for an internal combustion engine according to claim 3, wherein the heat medium circulated by the cylinder temperature control means is high-temperature cooling water that is heated during warming and stored in a heat storage system.   The cylinder temperature control means causes the high-temperature cooling water stored in the heat storage system to flow through the cylinder that makes the air-fuel ratio lean at the time of cold start to raise the temperature of the cylinder that makes the air-fuel ratio lean. The control apparatus for an internal combustion engine according to claim 4.   In the cold start, the cylinder temperature control means stops the flow of the low-temperature heat medium to the cylinder having the air-fuel ratio as lean, and the low-temperature heat medium flows through the cylinder having the air-fuel ratio as lean. The control device for an internal combustion engine according to claim 3, wherein the temperature is raised earlier than a cylinder that is present.

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