JP2015004353A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine having two banks, which includes a secondary air supply device and can suppress deterioration in exhaust emission without spoiling durability of an air control valve of the device even when determining an abnormality of the air control valve.SOLUTION: An internal combustion engine, when determining an abnormality of an air control valve, drives an air pump while maintaining opening commands to respective air control valves, and increases an amount of intake air for a bank on a side where abnormality determination is made. Further, it executes first catalyst warming-up control for the bank on the side where abnormality determination is made, and second catalyst warming-up control for a bank on a side where no abnormality determination is made. The first catalyst warming-up control includes: control for forming a high-concentration area where fuel concentration of a part of a combustion chamber rises and a low-concentration area which is lower in concentration of fuel than the high-concentration area by injecting the fuel from an in-cylinder fuel injection valve in a compressing stroke while keeping a lean air-fuel ratio as the combustion air-fuel ratio in the whole cylinder; and control for delaying an ignition period. The second warming-up control includes control for forming a homogeneous mixed gas in the whole cylinder to burn the mixed gas at the lean air-fuel ratio.

Description

  The present invention is an internal combustion engine having two banks, an in-cylinder fuel injection valve that injects fuel into each combustion chamber, an exhaust purification catalyst disposed in each exhaust pipe, and each exhaust pipe The present invention relates to an internal combustion engine including a secondary air supply device that supplies secondary air.

It is known to arrange an exhaust purification catalyst in an exhaust pipe of an internal combustion engine to purify components such as carbon monoxide (CO), hydrocarbon (HC) or nitrogen oxide (NO _x ) contained in the exhaust gas. . The exhaust purification catalyst has an activation temperature at which exhaust gas components can be purified with high efficiency. Immediately after the internal combustion engine is stopped for a long period of time and immediately after starting, the exhaust purification catalyst is below the activation temperature, and it is preferable to raise the exhaust purification catalyst to the activation temperature or higher at an early stage.

  When starting an internal combustion engine, oxygen is supplied to the exhaust gas flowing out of the combustion chamber by supplying secondary air to the exhaust pipe by the secondary air supply device in order to promote warm-up of the exhaust purification catalyst. It is known to do. By oxidizing carbon monoxide or the like contained in the exhaust gas, the temperature of the exhaust gas can be raised and the temperature of the exhaust purification catalyst can be raised in a short time.

  In an internal combustion engine equipped with such a secondary air supply device, when secondary air is required, if the secondary air is not supplied to the exhaust pipe, activation of the desired exhaust purification catalyst cannot be obtained, and conversely In addition, if the secondary air is supplied to the exhaust pipe while the temperature is sufficiently high and the exhaust purification catalyst is activated, the exhaust purification catalyst may overheat. Therefore, an air control valve capable of blocking the passage of the secondary air is disposed in the secondary air supply pipe that is in fluid communication with the exhaust pipe and causes the circulation of the secondary air, and the exhaust pipe is controlled by controlling the air control valve. Appropriate supply of secondary air to the air is carried out.

  If the operation of the air control valve is abnormal, the secondary air may not be properly supplied, and exhaust emission may deteriorate or the catalyst may overheat. Accordingly, development of an internal combustion engine having an air control valve abnormality determining means for diagnosing abnormality of the air control valve is underway.

JP 2005-299515 A

  By the way, the development of a secondary air supply device that can diagnose an abnormality of the air control valve as described above also for an internal combustion engine having two banks such as a V-type internal combustion engine. Is underway.

  For example, Patent Document 1 is a secondary air supply device that supplies secondary air to each exhaust pipe of an internal combustion engine having two banks, and is located on each exhaust pipe downstream of the air pump and the air pump. A secondary air supply pipe having an air control valve capable of blocking the passage of the secondary air is attached, the pressure between the air pump of one secondary air supply pipe and the air control valve, and the other A differential pressure sensor capable of detecting the differential pressure between the air pump of the secondary air supply pipe and the pressure of the air control valve is provided, and the passage of the secondary air to the exhaust pipe of one bank is performed while the air pump is driven. Based on the pulsation of the pressure detected by the differential pressure sensor at that time, the air control valve to be controlled is closed and the air control valve that controls the passage of secondary air to the exhaust pipe of the other bank is opened. To diagnose air control valve abnormalities Unishi was secondary air supply apparatus is disclosed.

  However, in the air control valve abnormality diagnosing means disclosed in Patent Document 1, when diagnosing the abnormality of the air control valve, the passage of secondary air to the exhaust pipe of one of the two banks Since the air control valve for controlling the air is closed, the secondary air is not introduced into the exhaust pipe of the one bank, and the exhaust pipe on the other bank side where the air control valve is opened and the secondary air is introduced Compared with the warm-up of the exhaust purification catalyst installed in the exhaust gas, the warm-up of the exhaust purification catalyst installed in the exhaust pipe on the one bank side where the secondary air is not introduced causes a delay and adversely affects the exhaust emission. May be affected. Further, in the air control valve abnormality diagnosis means disclosed in Patent Document 1, the air control valve is always opened and closed when the air control valve abnormality diagnosis is executed. This may be accompanied by an increase in the number of opening / closing operations of the air control valve, and may impede the durability of the air control valve itself.

  In view of the above problems, the present invention is an internal combustion engine having two banks, and includes a secondary air supply device that supplies secondary air to each exhaust pipe. An air control valve abnormality determining means capable of determining an abnormality of the air control valve without closing the air control valve for controlling the passage of secondary air to each exhaust pipe. In addition, an object of the present invention is to provide an internal combustion engine having an air control valve abnormality determining means that can suppress deterioration of exhaust emission when determining abnormality of the air control valve.

According to the first aspect of the present invention, an internal combustion engine having two banks, an in-cylinder fuel injection valve for injecting fuel into each combustion chamber, and an exhaust purification catalyst disposed in each exhaust pipe And an internal combustion engine comprising a secondary air supply device that supplies secondary air to each exhaust pipe,
The secondary air supply device provides a secondary air supply pipe that is bifurcated from a single pipe portion to a branch portion, and a secondary air that is disposed in the single pipe portion and that passes through the branch portion to each exhaust pipe. An air pump, an air control valve disposed in each of the branch portions, for controlling passage of secondary air to the exhaust pipes, and a single pipe portion downstream of the air pump. A pressure sensor that is disposed and detects a pressure between the air pump and the air control valve;
The internal combustion engine includes air control valve abnormality determining means for determining abnormality of the air control valve based on a pressure behavior detected by the pressure sensor of the secondary air supply device, and each bank of the two banks. Intake air amount control means capable of individually controlling the intake air amount of
The air control valve abnormality determining means is
When the abnormality determination of the air control valve is performed, the air pump is driven while maintaining an opening command to the air control valve disposed in each of the branch portions, and one air subject to abnormality determination The back pressure in the exhaust pipe of the bank on the abnormality determination side, which becomes the bank on the side where the inflow of secondary air is controlled by the control valve, is controlled by the other air control valve that is not subject to the abnormality determination. In order to make it larger than the back pressure of the exhaust pipe of the abnormality determination non-execution side bank that becomes the bank on the side of the abnormality determination, the intake air amount to the abnormality determination execution side bank is increased,
For the abnormality determination side bank, the fuel air-fuel ratio as a whole in the cylinder is a lean air-fuel ratio, and fuel is injected from the in-cylinder fuel injection valve in the compression stroke, and the fuel concentration in a part of the combustion chamber increases. A first catalyst comprising: a control for forming a high concentration region and a low concentration region in which the fuel concentration is lower than the high concentration region; and a control for increasing the temperature of exhaust gas flowing out of the combustion chamber by retarding the ignition timing Execute warm-up control,
The abnormality determination non-execution side bank includes a control for forming a homogeneous air-fuel mixture in the entire cylinder and burning it at a rich air-fuel ratio so that exhaust gas containing unburned components flows out to the exhaust pipe. An internal combustion engine that performs catalyst warm-up control is provided.

  That is, in the first aspect of the invention, the air control valve abnormality determining means for determining abnormality of the air control valve that controls the passage of the secondary air to each exhaust pipe of the internal combustion engine having two banks includes the air When determining an abnormality in the control valve, the air pump is driven while maintaining an opening command to both air control valves disposed in each of the branch portions of the secondary air supply pipe, and In order to make the back pressure in the exhaust pipe larger than the back pressure of the exhaust pipe in the abnormality determination non-execution side bank, the intake air amount to the abnormality determination execution side bank is increased. An abnormality determination execution side air control valve that controls the inflow of secondary air into the exhaust pipe of the abnormality determination execution side bank when the intake air intake amount for the abnormality determination execution side bank is increased. In the case where there is no abnormality such as closed adhesion, the amplitude of the pressure pulsation detected by the pressure sensor changes to a large one as the exhaust pulsation amplitude increases. On the other hand, when there is an abnormality such as closed adhering on the abnormality determination execution side air control valve, the pressure pulsation change due to the increase in the intake air amount is not detected by the pressure sensor.

  Therefore, if the intake air amount is increased with respect to the bank for performing abnormality determination, it is necessary to close any air control valve by monitoring the presence or absence of such a pressure pulsation change. It is possible to determine whether or not there is an abnormality in the air determination control side air control valve based on the pressure behavior detected by the pressure sensor. Therefore, according to such an air control valve abnormality determining means, it is possible to reduce the number of times of operation of the air control valve, and to suppress deterioration in durability of the air control valve itself, and It is possible to suppress the change in the air flow noise of the secondary air caused by the opening / closing operation of the air control valve at the time of abnormality determination, and it is possible to improve the merchantability.

  By the way, when determining the abnormality of the air control valve, when increasing the intake air amount to the abnormality determination execution side bank as described above, the back pressure of the exhaust pipe of the abnormality determination execution side bank is not abnormal determination. Since it becomes higher than the back pressure of the exhaust pipe of the implementation side bank, the secondary air supplied by the air pump flows unevenly to the exhaust pipe of the abnormality determination non-execution side bank. If the secondary air supply pipe does not have a backflow prevention means such as a backflow prevention valve, or if it does not function even if it has a backflow prevention means, the abnormality determination implementing bank In some cases, a reverse flow of the exhaust gas may occur and the reverse flow toward the exhaust pipe of the bank not performing abnormality determination may occur via the secondary air supply pipe. As a result, lean gas flows in the bank on which the abnormality determination non-execution is performed, and the temperature rise of the exhaust purification catalyst is delayed, and there is a concern that exhaust emission may deteriorate.

  Based on this, when the air control valve abnormality determining means of the present invention determines the abnormality of the air control valve, the abnormality determination side bank sets the lean air-fuel ratio as the entire combustion air-fuel ratio in the cylinder. In the compression stroke, fuel is injected from the in-cylinder fuel injection valve to form a high concentration region where the fuel concentration in a part of the combustion chamber is increased and a low concentration region where the fuel concentration is lower than the high concentration region (so-called stratified lean) Combustion control) and first catalyst warm-up control including control for increasing the temperature of exhaust gas flowing out of the combustion chamber by retarding the ignition timing. On the other hand, for the bank not performing abnormality determination, control is performed to form a homogeneous air-fuel mixture in the entire cylinder and burn at a rich air-fuel ratio so that exhaust gas containing unburned components flows out to the exhaust pipe ( The second catalyst warm-up control including the homogeneous rich combustion control) is executed.

  According to such an air control valve abnormality determination means of the present invention, in the abnormality determination execution side bank, although secondary air is not introduced, hydrocarbons are obtained by so-called stratified lean combustion control and ignition timing retardation control. The exhaust gas temperature can be increased while reducing the exhaust gas etc., and since the intake air amount is increased, it is possible to suppress a decrease in the engine speed accompanying the retarded ignition timing, This makes it possible to suppress the deterioration of exhaust emissions without causing any problems in engine operation. On the other hand, in the bank not performing abnormality determination, exhaust gas containing unburned components such as carbon monoxide can be discharged into the engine exhaust passage by so-called homogeneous rich combustion control, and the unburned components are discharged into the secondary air. As a result of the oxidation, it is possible to raise the temperature of the exhaust gas and raise the temperature of the exhaust purification catalyst in a short time, and to suppress the deterioration of the exhaust emission. Further, according to the air control valve abnormality determination means of the present invention, the backflow prevention means such as the backflow prevention valve can be eliminated, so that the cost can be reduced and the configuration can be simplified.

  According to a second aspect of the present invention, when the air control valve abnormality determining means determines that the air control valve is abnormal, the air control valve abnormality determining means opens the air control valve disposed in each of the branch portions. In order to make the back pressure in the exhaust pipe of the abnormality determination execution side bank larger than the back pressure of the exhaust pipe of the abnormality determination non-execution side bank while driving the air pump while maintaining the command, The second catalyst warming-up means executed for the abnormality determination non-execution side bank, while increasing the intake air amount to the abnormality determination non-execution side bank and reducing the intake air amount for the abnormality determination non-execution side bank, In addition to controlling the exhaust gas containing unburned components to flow into the exhaust pipe to form a homogeneous air-fuel mixture throughout the cylinder and combusting it at a rich air-fuel ratio, the ignition timing is advanced in accordance with the reduction in the intake air amount. Including control to horn The internal combustion engine according is provided in claim 1.

  According to the third aspect of the present invention, while the combustion air-fuel ratio of the entire cylinder is the first rich air-fuel ratio, fuel is injected from the in-cylinder fuel injection valve in the compression stroke, and the fuel concentration in a part of the combustion chamber increases. When the abnormality determination of the air control valve is executed from the engine operation state including the control to form the high concentration region and the low concentration region where the fuel concentration is lower than the high concentration region, the abnormality determination non-execution side bank So that the rich air-fuel ratio of the homogeneous air-fuel mixture formed in the cylinder by the second catalyst warm-up means executed with respect to the engine becomes the second rich air-fuel ratio richer than the first rich air-fuel ratio. An internal combustion engine according to claim 2 is provided which is controlled.

  According to the fourth aspect of the present invention, the intake air amount control means has an independent throttle valve disposed for each bank of the two banks, and the independent throttle valve allows the two banks to control the intake air amount. The internal combustion engine according to any one of claims 1 to 3, wherein the amount of intake air to each bank is individually controlled.

  According to the fifth aspect of the present invention, the intake air amount control means has a variable valve mechanism that can adjust the closing timing of the intake valve, and each of the two banks is controlled by the variable valve mechanism. The internal combustion engine according to any one of claims 1 to 3, wherein the intake air amount to the bank is individually controlled.

  According to the invention described in each claim, in the internal combustion engine having two banks, the internal combustion engine having a secondary air supply device that supplies secondary air to each exhaust pipe, the secondary to each exhaust pipe It is possible to determine the abnormality of the air control valve without performing the closing operation of the air control valve that controls the passage of air, and suppress the deterioration of the exhaust emission when determining the abnormality of the air control valve. It has the common effect of making things possible.

1 is a schematic view of an embodiment of an internal combustion engine of the present invention. It is the schematic of one Embodiment of the engine main body cylinder part in the internal combustion engine of this invention. The operation timing of each device of the air pump, the first air control valve, and the second air control valve at the time of abnormality determination by the air control valve abnormality determination means in the present embodiment, and the intake air to each bank by the intake air amount control means It is a figure which shows an example of the time chart of quantity control. FIG. 5 is a diagram illustrating an example of a behavior of pressure detected by a pressure sensor during an air control valve abnormality determination period when normal driving of an air pump is confirmed and there is no abnormality in a first air control valve and a second air control valve. is there. The behavior of the pressure detected by the pressure sensor during the air control valve abnormality determination period when the normal operation of the air pump is confirmed and there is no abnormality in the second air control valve, but there is an abnormality in the first air control valve. It is a figure which shows an example. The behavior of the pressure detected by the pressure sensor during the air control valve abnormality determination period when the normal operation of the air pump has been confirmed and there is no abnormality in the first air control valve, but there is an abnormality in the second air control valve. It is a figure which shows an example. It is a figure which shows an example of the time chart of the switching timing of the 1st catalyst warm-up control by the air control valve abnormality determination means in this embodiment, and a 2nd catalyst warm-up control.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of an embodiment of an internal combustion engine of the present invention, and FIG. 2 is a schematic diagram of an embodiment of an engine body cylinder portion in the internal combustion engine of the present invention. 1 and 2, 1 is an internal combustion engine, 2a is a first bank, 2b is a second bank, 3 is an engine main body cylinder section, 4 is a cylinder block, 5 is a piston, 6 is a cylinder head, 7 is a combustion chamber, 8 is an intake valve, 9 is an exhaust valve, 10 is an ignition device, 11 is a cylinder fuel injection valve, 12 is a port fuel injection valve, 13 is an intake port, 14 is an exhaust port, 15a is a first exhaust pipe, and 15b is a first exhaust pipe. 2 exhaust pipe, 16a is a first exhaust purification catalyst, 16b is a second exhaust purification catalyst, 17 is a secondary air supply device, 18 is an air pump, 19 is a pressure sensor, 20 is a secondary air supply pipe, and 21a is a first air. A control valve, 21b is a second air control valve, 22 is an ECU, and 23 is an intake air amount control means.

  The internal combustion engine of the present embodiment is an internal combustion engine 1 having two banks 2a and 2b, and is arranged in a cylinder fuel injection valve 11 for injecting fuel into each combustion chamber 7 and exhaust pipes 15a and 15b. Exhaust purification catalysts 16a and 16b, and a secondary air supply device 17 for supplying secondary air to the exhaust pipes. The secondary air supply device includes a secondary air supply pipe 20 that is bifurcated from a single pipe portion into a branch portion, and an air pump that is disposed in the single pipe portion and that provides secondary air to each exhaust pipe via the branch portion. 18, a first air control valve 21 a and a second air control valve 21 b, which are air control valves disposed in each of the branch portions and control passage of secondary air to each exhaust pipe, and more than the air pump 18. A pressure sensor 19 is provided in the single pipe portion on the downstream side to detect the pressure between the air pump and the air control valve. The internal combustion engine further includes air control valve abnormality determining means for determining abnormality of the air control valve based on the behavior of pressure detected by the pressure sensor 19 of the secondary air supply device 17, and each of the two banks. It further includes an intake air amount control means 23 capable of individually controlling the intake air amount.

  In the present embodiment, as can be understood from FIG. 1, the intake air amount control means 23 is configured to have independent throttle valves disposed for each of the two banks. The amount of intake air to each bank is controlled individually. The intake air amount control means for individually controlling the intake air amount to each of the two banks is not limited to this, and in another embodiment, the closing timing of the intake valve can be adjusted. A variable valve mechanism may be provided, and the intake air amount to each of the two banks may be individually controlled by the variable valve mechanism.

A first exhaust pipe 15a and a second exhaust pipe 15b are connected to the first bank 2a and the second bank 2b. The first exhaust pipe 15a and the second exhaust pipe 15b are provided with a first exhaust purification catalyst 16a and a second exhaust purification catalyst 16b using a three-way catalyst, and purify HC, CO, and NO _{x in} the exhaust. Is doing. For this purpose, an O ₂ sensor for detecting the oxygen concentration in the exhaust gas is attached to the first exhaust pipe 15a and the second exhaust pipe 15b on the upstream side of the exhaust purification catalyst. The exhaust gas purified by the first exhaust purification catalyst 16a and the second exhaust purification catalyst 16b is exhausted through the assembled exhaust pipe.

  The first exhaust pipe 15a and the second exhaust pipe 15b are provided with a secondary air supply port, and the downstream end of the secondary air supply tube 20 is connected to the secondary air supply port. The secondary air supply pipes 20 are gathered at the upstream end and connected to a single pipe gathering secondary air supply pipe. The upstream end of the aggregated secondary air supply pipe is connected to the discharge side of the air pump 18. The suction side of the air pump 18 is connected to the air cleaner via an air intake pipe.

  The ECU 22 is a microcomputer, but includes a backup RAM that remains stored even when the power is turned off. The ECU 22 is connected to the pressure sensor 19, the first air control valve 21 a, the second air control valve 21 b, the intake air amount control means 23, etc. related to the present invention, and performs abnormality diagnosis as described later. Performs a number of general controls.

  Hereinafter, an embodiment of control of abnormality diagnosis executed by the air control valve abnormality determination means in the internal combustion engine of the present invention in the above hardware configuration will be described. First, the concept of this diagnosis will be described. This diagnosis basically controls the air control valves 21a and 21b, the air pump 18 and the intake air amount control means 23, and the air control valves 21a and 21b disposed in the branch portions of the secondary air supply pipe 20, respectively. The air pump 18 is driven while maintaining the opening command to 21b, and in the exhaust pipe of the abnormality determination execution side bank that becomes the bank on the side where the inflow of secondary air is controlled by one air control valve that is the target of abnormality determination. Abnormality judgment is made so that the back pressure is larger than the back pressure of the exhaust pipe of the non-execution side bank that becomes the bank on the side where secondary air inflow is controlled by the other air control valve that is not subject to abnormality judgment The intake air amount to the execution side bank is increased, and abnormality of the air control valve is determined based on the behavior of the pressure detected by the pressure sensor 19 at that time.

  In the present embodiment, the air pump 18, the first air control valve 21a, and the second air are used to determine the abnormality of the air control valves of the first air control valve 21a and the second air control valve 21b in one diagnosis. Each device of the control valve 21b and the intake air amount control means 23 is operated. FIG. 3 shows the operation timing of each device of the air pump 18, the first air control valve 21 a, and the second air control valve 21 b and the intake air amount control at the time of abnormality determination by the air control valve abnormality determination means in this embodiment. It is a figure which shows an example of the time chart of intake air amount control with respect to each bank by the means.

  As can be understood from FIG. 3, when determining an abnormality of the air control valve in the present embodiment, the air control valve abnormality determining means first confirms that the air pump 18 is normally driven (ON) and the first air Abnormality of the first air control valve 21a that controls the supply of secondary air to the first exhaust pipe 15a when the engine is in an engine operating state in which an opening command is issued to the control valve 21a and the second air control valve 21b. In order to determine whether or not there is an abnormality due to close adhesion, in particular, the air pump 18 drive and the opening command for the first air control valve 21a and the second air control valve 21b are maintained, and the amount of intake air to the first bank 2a is maintained. The engine operation in this state is executed for a first predetermined period. Then, in the second predetermined period following the first predetermined period, the second air control valve 21b that controls the supply of the secondary air to the second exhaust pipe 15b is checked for abnormality, particularly, whether there is an abnormality due to closed adhesion. Therefore, the intake air amount to the second bank 2b is increased while maintaining the drive of the air pump 18 and the opening command of the first air control valve 21a and the second air control valve 21b. Then, at least over the first predetermined period and the second predetermined period, the pressure sensor 19 tracks the pressure behavior in the secondary air supply pipe 20, and based on the pressure behavior, the first air control valve 21a and the second air pressure control valve 21a. The presence or absence of abnormality of each air control valve of 2 air control valve 21b is determined. Here, the first predetermined period and the second predetermined period are within a range in which the influence of the variation in the detection data can be reduced based on an evaluation test or analysis evaluation that is performed in advance. It shall be set appropriately.

  Incidentally, there is a case where further improvement in the determination accuracy of the air control valve abnormality determination is required from the viewpoint of exhaust emission regulations. Based on this, in one embodiment of the air control valve abnormality determining means in the internal combustion engine of the present invention, the air control valve abnormality determining means, when determining the abnormality of the air control valve, the air control valve 21a, While maintaining the opening command to 21b, the air pump 18 is driven to increase the intake air amount to the abnormality determination execution side bank and to decrease the intake air amount to the abnormality determination non execution side bank.

  In this way, by increasing the intake air amount for the abnormality determination execution side bank and decreasing the intake air amount for the abnormality determination non-execution side bank, The exhaust pulsation and the exhaust pulsation change that occurs at the time of abnormality determination can have a larger amplitude change, and the determination accuracy of the air control valve abnormality determination can be further improved. FIG. 3 shows an embodiment in which the intake air amount for the abnormality determination execution side bank is increased and the intake air amount for the abnormality determination non-execution side bank is decreased.

  FIG. 4 shows the first predetermined period which is an air control valve abnormality determination period when normal driving (ON) of the air pump 18 is confirmed and there is no abnormality in the first air control valve and the second air control valve. It is a figure which shows an example of the behavior of the pressure which a pressure sensor detects in a 2nd predetermined period. FIG. 5 shows the air control valve abnormality determination period when the normal operation (ON) of the air pump is confirmed and there is no abnormality in the second air control valve, but there is an abnormality in the first air control valve. It is a figure which shows an example of the behavior of the pressure which a pressure sensor detects in a 1st predetermined period and a 2nd predetermined period. FIG. 6 shows the air control valve abnormality determination period when the normal operation (ON) of the air pump is confirmed and there is no abnormality in the first air control valve, but there is an abnormality in the second air control valve. It is a figure which shows an example of the behavior of the pressure which a pressure sensor detects in a 1st predetermined period and a 2nd predetermined period.

  As can be understood from FIGS. 4 to 6, when the normal drive (ON) of the air pump 18 is confirmed and there is no abnormality in the first air control valve 21a and the second air control valve 21b, that is, the first control valve 21a. When both the second control valve 21b are opened, the behavior of the pressure detected by the pressure sensor 19 during the first predetermined period and the second predetermined period, which are the air control valve abnormality determination period, is the abnormality determination execution side. A tendency for the amplitude of the pressure pulsation detected by the pressure sensor to increase as the amplitude of the exhaust pulsation on the abnormality determination side increases due to the increase in the intake air amount of the bank Will be shown.

  On the other hand, the normal operation (ON) of the air pump 18 has been confirmed, and there is no abnormality in the second air control valve 21b serving as the abnormality determination non-execution side air control valve. When there is an abnormality in the first air control valve 21a, that is, when the first air control valve 21a is closed and fixed, fluid communication between the exhaust pipe of the abnormality determination execution side bank and the secondary air supply pipe is established. Because of being shut off, the pressure behavior detected by the pressure sensor 19 during the first predetermined period, which is the air control valve abnormality determination period, is a pressure pulsation caused by an increase in intake air amount to the abnormality determination execution side bank. The change in the amplitude increase of the pressure sensor 19 tends to be not detected by the pressure sensor 19. The first air control valve 21a, which has been confirmed to be normally driven (ON) of the air pump 18 and is an abnormality determination non-execution side air control valve, has no abnormality, but the abnormality determination execution side air control valve is the first. 2 When there is an abnormality in the air control valve 21b, that is, when the second air control valve 21b is closed and fixed, the fluid communication between the exhaust pipe and the secondary air supply pipe of the abnormality determination execution side bank is cut off. Therefore, the behavior of the pressure detected by the pressure sensor 19 during the second predetermined period, which is the air control valve abnormality determination period, is the amplitude of the pressure pulsation caused by the increase in the intake air amount with respect to the abnormality determination side bank. This indicates a tendency that the increase change is not detected by the pressure sensor 19.

  Therefore, by increasing the intake air amount with respect to the abnormality determination execution side bank, it is possible to monitor the presence or absence of such a pressure pulsation change without requiring any air control valve closing operation. Based on the pressure behavior detected by the pressure sensor, it is possible to determine whether there is an abnormality in the abnormality determination execution side air control valve. Therefore, according to such an air control valve abnormality determining means, it is possible to reduce the number of times of operation of the air control valve, and to suppress deterioration in durability of the air control valve itself, and It is possible to suppress the change in the air flow noise of the secondary air caused by the opening / closing operation of the air control valve at the time of abnormality determination, and it is possible to improve the merchantability.

  By the way, as described above, when determining the abnormality of the air control valve, when increasing the intake air amount to the abnormality determination execution side bank as described above, the exhaust pipe of the abnormality determination execution side bank Since the back pressure becomes higher than the back pressure of the exhaust pipe of the abnormality determination non-execution side bank, the secondary air supplied by the air pump 18 is biased toward the exhaust pipe of the abnormality determination non-execution side bank. . If the secondary air supply pipe 20 does not have a backflow prevention means such as a backflow prevention valve, or if it does not function even if it has a backflow prevention means, the abnormality determination execution side There may be a case where a reverse flow of the exhaust gas of the bank and a reverse flow toward the exhaust pipe of the bank on the abnormality determination non-execution side via the secondary air supply pipe 20 may occur. As a result, lean gas flows in the bank on which the abnormality determination non-execution is performed, and the temperature rise of the exhaust purification catalyst is delayed, and there is a concern that exhaust emission may deteriorate.

  Based on this, when the air control valve abnormality determining means of the present invention determines the abnormality of the air control valve, in the abnormality determination executing side bank, the combustion air-fuel ratio as the whole in-cylinder is made the lean air-fuel ratio. In the compression stroke, fuel is injected from the in-cylinder fuel injection valve to form a high concentration region where the fuel concentration in a part of the combustion chamber is increased and a low concentration region where the fuel concentration is lower than the high concentration region (so-called stratified lean) Combustion control) and first catalyst warm-up control including control for increasing the temperature of exhaust gas flowing out of the combustion chamber by retarding the ignition timing. On the other hand, for the bank not performing abnormality determination, control is performed to form a homogeneous air-fuel mixture in the entire cylinder and burn at a rich air-fuel ratio so that exhaust gas containing unburned components flows out to the exhaust pipe ( The second catalyst warm-up control including the homogeneous rich combustion control) is executed.

  According to such an air control valve abnormality determination means of the present invention, in the abnormality determination execution side bank, although secondary air is not introduced, hydrocarbons are obtained by so-called stratified lean combustion control and ignition timing retardation control. The exhaust gas temperature can be increased while reducing the exhaust gas etc., and since the intake air amount is increased, it is possible to suppress a decrease in the engine speed accompanying the retarded ignition timing, This makes it possible to suppress the deterioration of exhaust emissions without causing any problems in engine operation. On the other hand, in the bank not performing abnormality determination, exhaust gas containing unburned components such as carbon monoxide can be discharged into the engine exhaust passage by so-called homogeneous rich combustion control, and the unburned components are discharged into the secondary air. As a result of the oxidation, it is possible to raise the temperature of the exhaust gas and raise the temperature of the exhaust purification catalyst in a short time, and to suppress the deterioration of the exhaust emission. Further, according to the air control valve abnormality determination means of the present invention, the backflow prevention means such as the backflow prevention valve can be eliminated, so that the cost can be reduced and the configuration can be simplified.

  FIG. 7 is a diagram illustrating an example of a time chart of the switching timing between the first catalyst warm-up control and the second catalyst warm-up control by the air control valve abnormality determination unit in the present embodiment. As can be understood from FIG. 7, the intake air amount is increased in the first predetermined period which is the start period of the air control valve abnormality determination period and the abnormality determination execution bank becomes the first bank 2a. With respect to the first bank 2a, the combustion air-fuel ratio as a whole in the cylinder is a lean air-fuel ratio, and fuel is injected from the cylinder fuel injection valve in the compression stroke to increase the fuel concentration in a part of the combustion chamber. The first catalyst warming includes control for forming a concentration region and a low concentration region in which the fuel concentration is lower than that of the high concentration region, and control for increasing the temperature of exhaust gas flowing out of the combustion chamber by retarding the ignition timing. Machine control is executed. On the other hand, the secondary air provided by the air pump 18 is biased due to the back pressure difference and is supplied to the exhaust pipe in an uneven state. Second catalyst warm-up control including control for forming a homogeneous air-fuel mixture in the entire cylinder and combusting at a rich air-fuel ratio is performed so that exhaust gas containing components flows out to the exhaust pipe.

  In addition, in the second predetermined period following the first predetermined period, in which the abnormality determination performing bank is switched from the first bank 2a to the second bank 2b, the intake air intake amount is increased. The catalyst warm-up control of the bank 2b is performed from the second catalyst warm-up control to the first catalyst warm-up control, that is, the combustion air-fuel ratio as a whole in the cylinder is set to the lean air-fuel ratio, and the fuel is injected from the cylinder fuel injection valve in the compression stroke. Control that forms a high-concentration region in which the fuel concentration in a portion of the combustion chamber is increased by injection and a low-concentration region in which the fuel concentration is lower than the high-concentration region, and exhaust gas that flows out of the combustion chamber by retarding the ignition timing Switching to first catalyst warm-up control including control for increasing the temperature of the gas. On the other hand, the secondary air provided by the air pump 18 is unevenly supplied to the exhaust pipe due to the back pressure difference, and the first bank 2a serving as the abnormality determination non-execution side bank is unburned. Second catalyst warm-up control including control for forming a homogeneous air-fuel mixture in the entire cylinder and combusting at a rich air-fuel ratio is performed so that exhaust gas containing components flows out to the exhaust pipe.

  Incidentally, as in this embodiment, when the intake air amount for the abnormality determination execution side bank is increased and the intake air amount for the abnormality determination non-execution side bank is decreased, abnormality determination is not performed. The second catalyst warm-up means executed for the side bank forms a homogeneous air-fuel mixture in the entire cylinder and burns at a rich air-fuel ratio so that exhaust gas containing unburned components flows out to the exhaust pipe. In addition to the control, it includes control for advancing the ignition timing in accordance with a reduction in the intake air amount.

  According to such an air control valve abnormality determination means of the present invention, in the abnormality determination execution side bank, although secondary air is not introduced, hydrocarbons are obtained by so-called stratified lean combustion control and ignition timing retardation control. The exhaust gas temperature can be increased while reducing the exhaust gas etc., and since the intake air amount is increased, it is possible to suppress a decrease in the engine speed accompanying the retarded ignition timing, This makes it possible to suppress the deterioration of exhaust emissions without causing any problems in engine operation. On the other hand, in the bank not performing abnormality determination, exhaust gas containing unburned components such as carbon monoxide can be discharged into the engine exhaust passage by so-called homogeneous rich combustion control, and the unburned components are discharged into the secondary air. As a result of the oxidation, it is possible to raise the temperature of the exhaust gas and raise the temperature of the exhaust purification catalyst in a short time, and to suppress the deterioration of the exhaust emission. Further, according to the air control valve abnormality determination means of the present invention, the backflow prevention means such as the backflow prevention valve can be eliminated, so that the cost can be reduced and the configuration can be simplified.

  As described above, according to the present invention, in the internal combustion engine having the two banks 2a and 2b, the internal combustion engine including the secondary air supply device 17 that supplies the secondary air to the exhaust pipes 15a and 15b. It is possible to determine the abnormality of the air control valve without performing the closing operation of the air control valves 21a and 21b for controlling the passage of the secondary air to each exhaust pipe, and to determine the abnormality of the air control valve It is also possible to suppress the deterioration of exhaust emission during the operation. That is, an internal combustion engine having two banks, which is equipped with a secondary air supply device, and even when an abnormality of the air control valve of the device is determined, the exhaust emission is deteriorated without impairing the durability of the air control valve. It is also possible to provide an internal combustion engine that can also suppress the above.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2a 1st bank 2b 2nd bank 3 Engine main body cylinder part 11 In-cylinder fuel injection valve 13 Intake port 14 Exhaust port 15a 1st exhaust pipe 15b 2nd exhaust pipe 16a 1st exhaust purification catalyst 16b 2nd exhaust purification catalyst 17 Secondary air supply device 18 Air pump 19 Pressure sensor 20 Secondary air supply pipe 21a First air control valve 21b Second air control valve 23 Intake air amount control means

Claims (5)

An internal combustion engine having two banks, an in-cylinder fuel injection valve for injecting fuel into each combustion chamber, an exhaust purification catalyst disposed in each exhaust pipe, and secondary air to each exhaust pipe In an internal combustion engine comprising a secondary air supply device for supplying,
The secondary air supply device provides a secondary air supply pipe that is bifurcated from a single pipe portion to a branch portion, and a secondary air that is disposed in the single pipe portion and that passes through the branch portion to each exhaust pipe. An air pump, an air control valve disposed in each of the branch portions, for controlling passage of secondary air to the exhaust pipes, and a single pipe portion downstream of the air pump. A pressure sensor that is disposed and detects a pressure between the air pump and the air control valve;
The internal combustion engine includes air control valve abnormality determining means for determining abnormality of the air control valve based on a pressure behavior detected by the pressure sensor of the secondary air supply device, and each bank of the two banks. Intake air amount control means capable of individually controlling the intake air amount of
The air control valve abnormality determining means is
When the abnormality determination of the air control valve is performed, the air pump is driven while maintaining an opening command to the air control valve disposed in each of the branch portions, and one air subject to abnormality determination The back pressure in the exhaust pipe of the bank on the abnormality determination side, which becomes the bank on the side where the inflow of secondary air is controlled by the control valve, is controlled by the other air control valve that is not subject to the abnormality determination. In order to make it larger than the back pressure of the exhaust pipe of the abnormality determination non-execution side bank that becomes the bank on the side of the abnormality determination, the intake air amount to the abnormality determination execution side bank is increased,
For the abnormality determination side bank, the fuel air-fuel ratio as a whole in the cylinder is a lean air-fuel ratio, and fuel is injected from the in-cylinder fuel injection valve in the compression stroke, and the fuel concentration in a part of the combustion chamber increases. A first catalyst comprising: a control for forming a high concentration region and a low concentration region in which the fuel concentration is lower than the high concentration region; and a control for increasing the temperature of exhaust gas flowing out of the combustion chamber by retarding the ignition timing Execute warm-up control,
The abnormality determination non-execution side bank includes a control for forming a homogeneous air-fuel mixture in the entire cylinder and burning it at a rich air-fuel ratio so that exhaust gas containing unburned components flows out to the exhaust pipe. An internal combustion engine that performs catalyst warm-up control. The air control valve abnormality determining means is
When determining an abnormality in the air control valve, the air pump is driven while maintaining an opening command to the air control valve disposed in each of the branch portions, and the exhaust pipe in the bank for performing the abnormality determination is In order to increase the back pressure of the exhaust pipe of the abnormality determination non-execution side bank, the intake air amount to the abnormality determination execution bank is increased and the abnormality determination non-execution side bank Reduce the intake air volume,
The second catalyst warm-up means executed for the abnormality determination non-execution bank forms a rich air-fuel mixture in the entire cylinder so that exhaust gas containing unburned components flows out to the exhaust pipe. 2. The internal combustion engine according to claim 1, wherein the internal combustion engine includes control for burning at an air-fuel ratio and control for advancing the ignition timing in accordance with a reduction in the intake air amount. The combustion air-fuel ratio as a whole in the cylinder is the first rich air-fuel ratio, and the high-concentration region where the fuel concentration in the combustion chamber is increased by injecting fuel from the in-cylinder fuel injection valve in the compression stroke, and the high-concentration region In the case where the abnormality determination of the air control valve is executed from the engine operation state including the control for forming the low concentration region where the fuel concentration is low,
The rich air-fuel ratio of the homogeneous air-fuel mixture formed in the cylinder by the second catalyst warm-up means executed for the abnormality determination non-execution side bank is a second rich air-fuel ratio that is richer than the 1 rich air-fuel ratio. The internal combustion engine according to claim 2, wherein the internal combustion engine is controlled to have a rich air-fuel ratio.   The intake air amount control means has an independent throttle valve disposed for each bank of the two banks, and individually controls the intake air amount to each bank of the two banks by the independent throttle valve. The internal combustion engine according to any one of claims 1 to 3.   The intake air amount control means has a variable valve mechanism capable of adjusting the closing timing of the intake valve, and individually controls the intake air amount to each of the two banks by the variable valve mechanism. An internal combustion engine according to any one of claims 1 to 3.

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