Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine capable of executing diagnosis of a catalyst while satisfying an exhaust gas law even in any operation state.SOLUTION: And a ECU10 configured to perform active air / fuel ratio control for diagnosing degradation of the catalytic converter 42 when a diagnosis-time exhaust gas emission amount is less than a predetermined target value, the diagnosis-time exhaust gas emission amount being a value obtained by adding a maximum value of an exhaust gas emission amount per mileage assumed when degradation of the catalytic converter 42 is diagnosed to an exhaust gas emission amount per mileage in a current drive cycle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] Patent Document 1 describes an active air-fuel ratio control method as a method for diagnosing an abnormality in a catalyst arranged in the exhaust passage of an internal combustion engine, in which the air-fuel ratio of the exhaust gas supplied to the catalyst is alternately and actively switched between rich and lean in response to the output of a post-catalyst sensor that detects the exhaust air-fuel ratio downstream of the catalyst reversing to lean or rich. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-255490 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as described above, such active air-fuel ratio control fluctuates the air-fuel ratio from the stoichiometric air-fuel ratio, which raises concerns about an increase in regulated components contained in exhaust gas.

[0005] Therefore, depending on the operating conditions in the current drive cycle, implementing active air-fuel ratio control for catalyst diagnosis may result in the amount of emissions of regulated components contained in exhaust gas in that drive cycle no longer meeting regulations.

[0006] Until now, European regulations required that catalyst and sensor diagnosis be completed and emissions regulations be met when vehicles were driven in an exhaust gas mode representative of normal driving. However, future European regulations will require that emissions regulations be met regardless of driving conditions.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device for an internal combustion engine that can execute catalyst diagnosis while satisfying exhaust gas regulations regardless of the operating state. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a control device for an internal combustion engine comprising an internal combustion engine, a catalyst for purifying exhaust gas from the internal combustion engine, and a control unit that performs active air-fuel ratio control for diagnosing deterioration of the catalyst, wherein the control unit performs deterioration diagnosis of the catalyst when the exhaust gas emission at the time of diagnosis, which is the sum of the exhaust gas emission per distance traveled in the current drive cycle and the maximum value of the exhaust gas emission per distance traveled that is expected if deterioration diagnosis of the catalyst is performed, is less than a predetermined target value. [Effects of the Invention]

[0009] In this way, according to the present invention, catalyst diagnosis can be performed while complying with exhaust gas regulations, regardless of the operating state. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with an internal combustion engine control device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a control block diagram of a process for determining a diagnosis execution enabling condition of a control device for an internal combustion engine according to an embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing the procedure of catalyst diagnosis control processing in the control device for an internal combustion engine according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A control device for an internal combustion engine according to one embodiment of the present invention is a control device for an internal combustion engine that includes an internal combustion engine, a catalyst that purifies exhaust gas from the internal combustion engine, and a control unit that performs active air-fuel ratio control for diagnosing catalyst deterioration, and the control unit is configured to perform catalyst deterioration diagnosis when the exhaust gas emission at the time of diagnosis, which is the sum of the exhaust gas emission per driving distance in the current drive cycle and the maximum value of the exhaust gas emission per driving distance that is expected if catalyst deterioration diagnosis is performed, is less than a predetermined target value.

[0012] As a result, the control device for an internal combustion engine according to one embodiment of the present invention can diagnose the catalyst while satisfying exhaust gas regulations regardless of the operating state. [Example]

[0013] Hereinafter, a control device for an internal combustion engine according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0014] In FIG. 1, a vehicle 1 equipped with an internal combustion engine control device according to one embodiment of the present invention is configured to include an engine 2 as an internal combustion engine, an intake pipe 3, an exhaust pipe 4, and an ECU (Electronic Control Unit) 10 as a control unit.

[0015] The engine 2 is formed with a cylinder 21 as a cylinder. A piston 22 that can reciprocate up and down within the cylinder 21 is housed in the cylinder 21. A combustion chamber 23 is provided above the cylinder 21.

[0016] The engine 2 is a so-called four-stroke gasoline engine in which a piston 22 performs a series of four strokes, consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, during two reciprocating motions of the piston 22 in the cylinder 21.

[0017] The piston 22 is connected to the crankshaft 2a via a connecting rod 24. The connecting rod 24 converts the reciprocating motion of the piston 22 into the rotational motion of the crankshaft 2a. The engine 2 is configured as a drive source for the vehicle 1.

[0018] The engine 2 is provided with a spark plug 25, an intake port 26, and an exhaust port 27. The spark plug 25 is fixed to the cylinder head with an electrode protruding into the combustion chamber 23, and the ignition timing of the spark plug 25 is adjusted by the ECU 10.

[0019] An injector 28 is provided in the intake port 26. The injector 28 is a so-called port injection type fuel injection valve that injects fuel supplied from a fuel tank (not shown) by a fuel pump into the combustion chamber 23.

[0020] An intake manifold 35 is provided in the intake port 26. The intake manifold 35 is connected to the intake pipe 3. An intake passage 3a in the intake pipe 3, which will be described later, is connected to the intake port 26 via the intake manifold 35. An intake valve 26a is provided in the intake port 26. The intake valve 26a is configured to open and close so as to connect or disconnect the intake passage 3a and the combustion chamber 23.

[0021] The exhaust port 27 is connected to an exhaust passage 4a in the exhaust pipe 4, which will be described later. An exhaust valve 27a is provided in the exhaust port 27. The exhaust valve 27a is configured to open and close so as to connect or block the exhaust passage 4a and the combustion chamber 23 to each other.

[0022] The intake pipe 3 is connected to the engine 2 via an intake manifold 35, and an intake passage 3a is formed inside the intake pipe 3. In the intake pipe 3, an intake temperature sensor 31, an air flow sensor 32, an air cleaner 33, a throttle valve 34, and an intake pressure sensor 36 are attached in this order from the upstream side in the air intake direction.

[0023] The intake air temperature sensor 31 is electrically connected to the ECU 10, detects the temperature of the intake air, and outputs the detection result to the ECU 10. The air flow sensor 32 is electrically connected to the ECU 10, detects the intake air volume, which is the flow rate of the intake air flowing through the intake passage 3a, and outputs the detection result to the ECU 10.

[0024] The air cleaner 33 filters out impurities such as dust contained in the intake air. The throttle valve 34 is electrically connected to the ECU 10, and the throttle opening is controlled in response to a command signal from the ECU 10, thereby adjusting the amount of intake air to the engine 2.

[0025] The intake pressure sensor 36 is electrically connected to the ECU 10 , detects the pressure of the intake air in the intake manifold 35 , and outputs the detection result to the ECU 10 .

[0026] The exhaust pipe 4 is connected to the engine 2 and has an exhaust passage 4a formed therein. In order from the upstream side in the exhaust flow direction of the exhaust, an air-fuel ratio sensor 41, a catalyst 42, an O2 sensor 43, and a NOx sensor 44 are attached to the exhaust pipe 4. The air-fuel ratio sensor 41 and the O2 sensor 43 are arranged in the exhaust pipe 4 so as to sandwich the catalyst 42 therebetween.

[0027] The air-fuel ratio sensor 41 is a sensor that detects the air-fuel ratio of the exhaust gas upstream in the exhaust direction from the catalyst 42, and is configured by, for example, an A / F sensor. The catalyst 42 is configured by a three-way catalyst that purifies the exhaust gas.

[0028] The O2 sensor 43 is a sensor that detects the air-fuel ratio of the exhaust gas downstream in the exhaust direction from the catalyst 42. The NOx sensor 44 is a sensor that detects the NOx concentration in the exhaust gas.

[0029] The ECU 10 is composed of a computer unit having a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, etc., input ports, and output ports.

[0030] The ROM of the computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the ECU 10. That is, the CPU executes the program stored in the ROM using the RAM as a work area, causing the computer unit to function as the ECU 10 in this embodiment.

[0031] In addition to the intake temperature sensor 31, air flow sensor 32, intake pressure sensor 36, air-fuel ratio sensor 41, O2 sensor 43, and NOx sensor 44 mentioned above, various sensors such as a throttle sensor 11, a crank angle sensor 12, a vehicle speed sensor 13, and an atmospheric pressure sensor 14 are connected to the ECU 10.

[0032] The throttle sensor 11 detects the throttle opening, which is the opening of the throttle valve 34. The crank angle sensor 12 detects the rotation angle of the crankshaft 2a of the engine 2 (hereinafter referred to as "crank angle"). The ECU 10 calculates the engine speed, which is the number of revolutions of the engine 2, based on information indicating the crank angle input from the crank angle sensor 12. The vehicle speed sensor 13 detects the vehicle speed, which is the speed of the vehicle 1. The atmospheric pressure sensor 14 detects the pressure of the atmosphere.

[0033] The ECU 10 is connected to various devices such as a spark plug 25, an injector 28, a throttle valve 34, and the like.

[0034] The ECU 10 performs a deterioration diagnosis of the catalyst 42 when a predetermined diagnosis execution condition is met. The predetermined diagnosis execution condition is that the engine operating range defined by the engine speed and engine load is in a stable range where stable combustion can be ensured. Alternatively, the predetermined diagnosis execution condition may be that the rate of change over time of each of the engine speed and engine load is equal to or less than a certain amount. Alternatively, the predetermined diagnosis execution condition may be that the two aforementioned conditions are satisfied.

[0035] When diagnosing the deterioration of the catalyst 42, the ECU 10 performs active air-fuel ratio control that alternately switches the air-fuel ratio of the exhaust gas flowing into the catalyst 42 between rich and lean.

[0036] In this embodiment, the ECU 10 performs a deterioration diagnosis of the catalyst 42 when the exhaust gas emission amount at the time of diagnosis, which is the sum of the exhaust gas emission amount per driving distance in the current drive cycle and the maximum value of the exhaust gas emission amount per driving distance expected when a deterioration diagnosis of the catalyst 42 is performed, is less than a predetermined target value, determining that the diagnosis executable condition is met.

[0037] For example, the ECU 10 performs a deterioration diagnosis of the catalyst 42 when the respective diagnosis execution enabling conditions are met for all of the regulated components contained in the exhaust gas.

[0038] For example, the ECU 10 performs the deterioration diagnosis of the catalyst 42 only when the following formula, which indicates the diagnosis executable condition, is satisfied for all of the regulated components contained in the exhaust gas.

[0039]

number

[0040] GasTarget [mg / km] is the target emission amount of the regulated component, and the regulated value or a target value that is expected to clear the regulation is set. GasNow mass [mg] is the emission amount of the regulated component in the current driving cycle. GasNow distance [km] is the distance traveled in the current drive cycle. GasWorst mass [mg] is the maximum amount of emission of the regulated component when the deterioration diagnosis of the catalyst 42 is performed. GasWorst distance [km] is the minimum distance traveled while the deterioration diagnosis of the catalyst 42 is being carried out.

[0041] The process of determining whether or not a diagnosis can be performed using this formula will be described with reference to Fig. 2. Fig. 2 shows an example of CO as a regulated component.

[0042] The ECU 10 multiplies the amount of exhaust gas per distance in the current drive cycle indicated by V1 by the travel distance in the current drive cycle indicated by V2 to calculate the amount of CO emissions in the current drive cycle indicated by V3.

[0043] The ECU 10 calculates the amount of CO emissions by multiplying the current exhaust flow rate indicated by V4 by the CO concentration found from a correspondence map of CO concentration for a diagnostic target λ indicated by V5. The correspondence map of CO concentration for λ corresponds to the CO concentration when enriched to λ for diagnosis.

[0044] ECU10 multiplies the calculated CO emissions by 1.0 x 10 -6 to make the units uniform, multiply this by the value obtained by dividing the density of CO, which is a regulated component shown in V6, by the density of air shown in V7, and then multiply this by the longest rich time corresponding to the new catalyst 42 at the time of diagnosis shown in V8, to calculate the maximum amount of CO emissions at the time of deterioration diagnosis of the catalyst 42 shown in V9.

[0045] The ECU 10 calculates the braking distance by squaring the vehicle speed indicated by V10 and dividing the result by 256,000, and sets the calculated braking distance as the minimum value of the travel distance while the deterioration diagnosis of the catalyst 42 indicated by V11 is being performed.

[0046] In this embodiment, the minimum value of the travel distance during the deterioration diagnosis of the catalyst 42 is assumed to be a case where the vehicle is suddenly decelerated and stopped immediately after the start of the diagnosis.

[0047] ECU10 multiplies the target CO exhaust gas regulation value indicated by V12 by a safety factor that takes into account measurement errors and the like indicated by V13, and sets the result as the target exhaust gas amount indicated by V14.

[0048] If the value obtained by dividing the sum of the CO2 emissions in the current drive cycle indicated by V3 and the maximum CO2 emissions during the deterioration diagnosis of the catalyst 42 indicated by V9 by the sum of the mileage in the current drive cycle indicated by V2 and the minimum mileage while the deterioration diagnosis of the catalyst 42 is being performed indicated by V11 is less than the target exhaust gas amount indicated by V14, ECU 10 sets the value indicated by V15 to "True", and otherwise sets it to "False".

[0049] The catalyst diagnosis control process performed by the control device for an internal combustion engine according to this embodiment configured as described above will be described with reference to Fig. 3. The catalyst diagnosis control process described below is started when the ECU 10 starts operating, and is executed at preset time intervals.

[0050] In step S1, the ECU 10 determines whether or not the diagnostic execution enabling conditions are met for all the restricted components.

[0051] If it is determined that the diagnosis execution conditions are met for all the restricted components, the ECU 10 executes the process of step S2. If it is determined that the diagnosis execution conditions are not met for all the restricted components, the ECU 10 executes the process of step S1.

[0052] In step S2, the ECU 10 determines whether or not a standard diagnosis execution condition is met.

[0053] If it is determined that the standard diagnosis execution conditions are met, the ECU 10 executes the process of step S3. If it is determined that the standard diagnosis execution conditions are not met, the ECU 10 executes the process of step S1.

[0054] In step S3, the ECU 10 starts a deterioration diagnosis of the catalyst 42. After executing the process of step S3, the ECU 10 executes the process of step S4.

[0055] In step S4, the ECU 10 determines whether or not a standard diagnosis execution condition is met.

[0056] If it is determined that the standard diagnosis execution conditions are met, the ECU 10 executes the process of step S5. If it is determined that the standard diagnosis execution conditions are not met, the ECU 10 suspends the deterioration diagnosis of the catalyst 42 and executes the process of step S1.

[0057] In step S5, the ECU 10 determines whether the deterioration diagnosis of the catalyst 42 has been completed.

[0058] If it is determined that the deterioration diagnosis of the catalyst 42 has been completed, the ECU 10 ends the catalyst diagnosis control process. If it is determined that the deterioration diagnosis of the catalyst 42 has not been completed, the ECU 10 executes the process of step S4.

[0059] Thus, in this embodiment, the ECU 10 performs a deterioration diagnosis of the catalyst 42 when the exhaust gas emission amount at the time of diagnosis, which is the sum of the exhaust gas emission amount per driving distance in the current drive cycle and the maximum value of the exhaust gas emission amount per driving distance expected when a deterioration diagnosis of the catalyst 42 is performed, is less than a predetermined target value.

[0060] This allows the determination of whether or not to perform a deterioration diagnosis of the catalyst 42 to be made taking into account the increase in regulated components contained in the exhaust gas due to active air-fuel ratio control as a deterioration diagnosis of the catalyst 42, thereby making it possible to perform a diagnosis of the catalyst 42 while satisfying exhaust gas regulations regardless of the operating conditions.

[0061] In this embodiment, an example has been described in which ECU 10 performs various determinations and calculations based on various sensor information, but this is not limited to this. Vehicle 1 may be provided with a communication unit capable of communicating with an external device such as an external server, and various determinations and calculations may be performed by the external device based on the detection information of various sensors transmitted from the communication unit. The determination results and calculation results may be received by the communication unit, and various controls may be performed using the received determination results and calculation results.

[0062] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0063] 1 vehicle 2 engines 10 ECU (control unit) 11 Throttle sensor 12 Crank angle sensor 13 Vehicle speed sensor 14 Atmospheric pressure sensor 31 Intake air temperature sensor 32 Air flow sensor 36 Intake pressure sensor 41 Air-fuel ratio sensor 42 Catalyst 43 O2 sensor 44 NOx sensor

Claims

[Claim 1] A control device for an internal combustion engine, comprising: an internal combustion engine; a catalyst that purifies exhaust gas from the internal combustion engine; and a control unit that performs active air-fuel ratio control for diagnosing deterioration of the catalyst, The control unit is a control device for an internal combustion engine that performs a deterioration diagnosis of the catalyst when the diagnostic exhaust gas emission amount, which is the sum of the exhaust gas emission amount per driving distance in the current drive cycle and the maximum value of the exhaust gas emission amount per driving distance expected when a deterioration diagnosis of the catalyst is performed, is less than a predetermined target value.

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