JP2005002958A - Secondary air supply device and internal combustion engine controller having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary air supply device having a failure detection function capable of judging leakage failure of piping and the like downstream of a shut-off valve discriminating from other failure, and to provide an internal combustion engine controller having the secondary air supply device. <P>SOLUTION: From pressure behavior during AI (secondary air) supply, from a difference between pressure during the supply and pressure at the time when AP (air pump) is driven with an ASV (air switching valve) closed after stop, or from A/F (air-fuel ratio) in an exhaust pipe after the stop of supply, a case (case 3) where failure such as leakage (disengagement of a hose) on a downstream side of the ASV is discriminated from normal condition (case 1) and from closing failure of the ASV (case 2) aside from failure of other AI equipment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary air supply device that supplies secondary air to an upstream side of an exhaust purification device that is disposed in an exhaust system of an internal combustion engine, and a control device for an internal combustion engine that includes the secondary air supply device. The present invention relates to a secondary air supply device capable of detecting abnormality of its constituent parts and a control device for an internal combustion engine provided with the same.
[0002]
[Prior art]
As an exhaust gas purification device for an internal combustion engine, a device is known in which a three-way catalyst is disposed in an exhaust system to purify the exhaust gas by reducing CO, HC, and NOx components. Further, by pumping air from the air pump to a secondary air supply passage having an on-off valve connected to the exhaust pipe, the secondary air is supplied into the exhaust pipe to increase the oxygen concentration, and HC in the exhaust gas, A technique for promoting the purification of exhaust gas by oxidizing CO is known.
[0003]
In such a secondary air supply device, if an abnormality occurs in components such as an air pump or an on-off valve, the exhaust gas purification efficiency decreases, and emissions deteriorate. Therefore, it is necessary to determine the abnormality early. . Therefore, as a technique for detecting this type of abnormality, a technique disclosed in Patent Document 1 is known.
[0004]
This technology detects the pressure behavior in the secondary air supply passage during operation control and non-operation control of the secondary air supply device, respectively, and diagnoses the fault location according to the combination of pressure and pressure pulsation. is there.
[0005]
[Patent Document 1]
JP 2003-83048 A (paragraphs 0019 to 0058, FIGS. 1 to 7)
[0006]
[Problems to be solved by the invention]
In general, the downstream side of the open / close valve of the secondary air supply system is connected to the exhaust system piping and a flexible hose. This facilitates manufacture and maintenance, but increases the possibility of leakage due to disconnection or damage of the hose as compared to the case of using a fixed pipe made of metal or the like. For this reason, it is necessary to detect these leakage faults. However, in the above technique, when leakage occurs, it is erroneously determined that the on-off valve is closed abnormally, and there is a possibility that accurate determination cannot be performed.
[0007]
Therefore, the present invention relates to a secondary air supply device having a failure detection function capable of distinguishing and determining a leakage failure in piping or the like downstream of an on-off valve from other failures, and an internal combustion engine equipped with the secondary air supply device. It is an object to provide a control device.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a secondary air supply apparatus according to the present invention includes an air pump, a pressure sensor, and an on-off valve arranged upstream from a supply pipe connected to an exhaust system of an internal combustion engine. 2 is a secondary air supply device that supplies secondary air, and includes a failure diagnosis unit that determines a failure state of its component parts from pressure and pressure fluctuation during secondary air supply control and non-supply control. In the secondary air supply apparatus, when it is determined that there is no pressure pulsation due to exhaust gas from the pressure detected by the pressure sensor during secondary air supply control, the failure diagnosis unit sets the detected pressure value as the first predetermined value. When the detected pressure value is larger than the first predetermined value, the on-off valve closing failure is detected. When the detected pressure value is smaller than the second predetermined value, the on-off valve closing failure is detected. And air pump stop failure And both when located between the first predetermined value and a second predetermined value, and judging, respectively when there leakage at off valve downstream.
[0009]
When there is a leak on the downstream side of the opening / closing valve of the secondary air supply device, and when the air pump and the opening / closing valve are operating normally, the air discharged from the air pump flows out from the leakage portion. As a result, the detection value of the pressure detection means during the secondary air supply control in this case is lower than when there is no leakage downstream of the on-off valve, but is higher than when the air pump is stopped. Indicates. In addition, since this leakage portion exists, the upstream side of the on-off valve and the exhaust system do not actually communicate with each other, so that they are not affected by pressure fluctuations in the exhaust system. Therefore, pressure pulsation due to exhaust does not occur in the pressure detected by the pressure detection means. Therefore, the presence of leakage can be determined from this condition.
[0010]
Alternatively, when the failure diagnosis unit determines that there is no pressure pulsation due to exhaust during the secondary air supply control, and the pressure difference when the air pump is driven both during the opening / closing valve opening control and during the closing control, a predetermined value In the above case, it may be determined that there is a leak downstream of the on-off valve.
[0011]
When the on-off valve and the air pump are operating normally, if the air pump is forcibly operated with the on-off valve closed, the pressure detected by the pressure detection means will be greater than when the on-off valve is open. Get higher. At this time, since the downstream side of the on / off valve is blocked from the pressure detecting means by the on / off valve, the pressure detecting means is not affected by the downstream of the on / off valve. That is, the pressure behavior at this time is not related to the presence or absence of leakage downstream of the on-off valve. As described above, when the air pump is operated with the opening / closing valve opened, the pressure value is higher in the case of no leakage downstream of the opening / closing valve than in the case of leakage. As a result, the difference in pressure when the air pump is activated when the valve is opened and when the valve is closed is higher when there is leakage than when there is no leakage. Therefore, the presence of leakage can be determined also from this condition.
[0012]
In addition, an air-fuel ratio sensor disposed in the exhaust system is further provided, and the failure diagnosis unit determines that the on-off valve is closed due to pressure and pressure fluctuations during secondary air supply control and non-supply control. If it is determined from the output of the air-fuel ratio sensor after the end of the secondary air supply control that the lean state is greater than or equal to a predetermined value, it may be determined that there is a leak downstream of the on-off valve.
[0013]
If a leaking part exists downstream of the on-off valve, the exhaust pipe and the atmosphere communicate with each other through the leaking part. As a result, even after the secondary air supply control, the atmosphere flows into the exhaust system that is normally at a negative pressure, and the air-fuel ratio of the exhaust gas shifts to the lean side from the original control state. Therefore, the presence of leakage can be determined also from this condition.
[0014]
The control apparatus for an internal combustion engine according to the present invention includes the secondary air supply device according to the present invention, and when the failure diagnosis unit determines that the leak is downstream of the on-off valve, the air-fuel ratio feedback In the fuel learning control according to the above, the learning value is richly corrected and the control is performed.
[0015]
As described above, if there is a leak downstream of the on-off valve, the exhaust air-fuel ratio shifts to the lean side. If the exhaust air-fuel ratio continues to be lean, the exhaust purification performance of the exhaust purification catalyst deteriorates and the emission deteriorates.Therefore, the learned value is richly corrected in the fuel learning control by the air-fuel ratio feedback. Is controlled in a predetermined state to suppress the deterioration of emission.
[0016]
When the failure diagnosis unit determines that the leak is downstream of the on-off valve, it is preferable to further stop fuel learning and fuel abnormality determination. When there is an inflow from a leak point in this way, fuel learning and fuel abnormality determination cannot be performed accurately, so learning and abnormality determination are prohibited and emissions are deteriorated during cold start and non-feedback control. Suppress.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.
[0018]
FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine equipped with a secondary air supply device according to the present invention. The secondary air supply device 1 is attached to a multi-cylinder gasoline engine (hereinafter simply referred to as an engine) 2 that is an internal combustion engine. This engine 2 is a four-cycle engine. Here, an intake pipe 20 and an exhaust pipe 21 are attached to the engine 2, and a throttle 24 is disposed in the intake pipe 20 and connected to an intake filter 25. An air flow meter 26 for measuring an air amount (primary air amount) is disposed between the intake filter 25 and the throttle 24. On the other hand, an exhaust purification device 22 composed of a three-way catalyst is disposed downstream of the exhaust pipe 21, and an O for detecting the oxygen concentration in the exhaust both upstream and downstream of the exhaust purification device. ₂ Sensors 31 and 32 are arranged. O ₂ Instead of sensors, A / F sensors, linear O ₂ A sensor may be used. Further, the engine 2 is provided with a rotation speed sensor 27 for detecting the rotation speed Ne, and its output is input to the engine ECU 23.
[0019]
The secondary air supply apparatus 1 includes a position between the intake filter 25 and the throttle 24 in the intake pipe 20, the engine 2 in the exhaust pipe 21, and the upstream side O. ₂ A secondary air supply passage 11 that connects the sensor 31 is provided. In the secondary air supply passage 11, a flexible piping portion 11b such as a rubber hose or a flexible hose is disposed between the fixed piping portions 11a and 11c made of metal or ceramic. An electric motor driven air pump (AP) 12, an air switching valve (ASV) 13, and a reed valve that is a check valve are provided on the upstream fixed piping portion 11 a of the secondary air supply passage 11 from the intake pipe 20 side. RV) 14 is arranged. And the pressure sensor 15 is arrange | positioned between AP12 and ASV13. A pipe 16 extending from the downstream side of the throttle 24 of the intake pipe 20 is connected to the ASV 13, and a three-way valve 17 is disposed on the pipe 16. The other port of the three-way valve 17 is connected to the outside air via a pipe 18 and a filter 19.
[0020]
The control device 10 that controls the operation of the secondary air supply device 1 is composed of a CPU, a RAM, and the like, and is connected to exchange information with an engine ECU 23 that controls the engine. O ₂ The output signals of the sensors 31 and 32 are input, and the motor driving of the AP 12 and the opening and closing of the three-way valve 17 are controlled. Note that the control device 10 may form part of the engine ECU 23. The control device 10 includes a failure diagnosis device according to the present invention. Note that the failure diagnosis unit can be made independent of the control device 10 and may be incorporated in another system, for example, a vehicle failure diagnosis device.
[0021]
The secondary air supply device 1 executes secondary air supply control (hereinafter referred to as AI control) when a predetermined condition is satisfied. This predetermined condition is, for example, that the fuel concentration is high at the time of cold start or the like, the air-fuel ratio (A / F) is small, and the exhaust purification device 22 has not sufficiently raised its function. The state where it is hard to be demonstrated is mentioned. When such a condition is satisfied, the control device 10 controls the three-way valve 17 to connect the pipe 16 to the intake pipe 20, thereby introducing the negative pressure in the intake pipe 20 to the ASV 13 and opening the ASV 13. In addition to controlling, the AP 12 is driven. Thereby, part of the air that has passed through the air filter 25 is guided into the exhaust pipe 21 via the secondary air supply passage 11. As a result, the oxygen concentration in the exhaust gas increases, the A / F increases, the secondary combustion of the HC and CO in the exhaust gas in the exhaust pipe 21 is promoted, the exhaust gas is purified, and the exhaust gas temperature increases. As a result, the temperature increase of the three-way catalyst of the exhaust purification device 22 is promoted, and the deterioration of the emission is suppressed. In place of the combination of the ASV 13 and the three-way valve 17, a solenoid valve can be directly used for the ASV 13 portion.
[0022]
The secondary air supply apparatus according to the present invention includes a failure diagnosis unit that detects an abnormality in the component parts, that is, the AP 12, the ASV 13, the RV 14, and the secondary air supply passage 11. Specifically, the control device 10 detects a failure of the component based on the pressure behavior detected by the pressure sensor 15 disposed on the secondary air supply passage 11.
[0023]
Hereinafter, some of the failure diagnosis operations will be described in detail. First, the first control mode of the failure diagnosis operation will be described with reference to the processing flow of FIG. This failure diagnosis process is repeatedly executed at a predetermined timing from when the vehicle power is turned on until the process is started by the control device 10 until the failure detection is completed.
[0024]
First, it is determined whether a condition (AI execution condition) for executing AI control is satisfied (step S2). This execution condition is determined by the engine coolant temperature, the intake air temperature, the elapsed start time, the battery voltage, the load condition, etc. sent from the engine ECU 23. Here, the AI execution condition is not satisfied even when the condition for ending the AI control is satisfied.
[0025]
When it is determined that the AI execution condition is satisfied, the process proceeds to step S4 to determine whether or not the AI control is being executed. When the AI control is being executed, the process proceeds to step S6, and it is determined whether or not an abnormality detection condition during the AI execution is satisfied. This abnormality detection condition is satisfied when a predetermined elapsed time has elapsed from the start of AI execution, the vehicle speed, the load, and the engine speed are within a predetermined range, and it is determined that the engine is in an idling state.
[0026]
If the abnormality detection condition during execution of AI is satisfied, the pressure value P and the pressure average value (smoothing value) Psm are read (step S8). This pressure annealing value Psm is Psm = {(n−1) × Psm_old + Ps} / where Ps is the pressure value detected at the current time step and Psm_old is the calculation result of the pressure annealing value at the previous time step. n. FIG. 3 shows the time variation of Psm and Ps thus obtained together. Here, the time step Δt is sufficiently short (for example, 4 × Δt ≦ T) with respect to the length T of the pressure fluctuation cycle, and the coefficient n for obtaining the annealing value is sufficiently large (for example, When n × Δt ≧ 2 × T), Psm is a value that approximates the average value of the pressure values Ps within the sampling period (n × Δt). When the number of time steps after the start of processing is less than n, the number of time steps may be used instead of n. By performing the calculation using the annealing value in this way, it is not necessary to store the pressure value in the past time step, the required memory amount can be reduced, the calculation is simplified, and the control is performed. Computer resources in the apparatus 10 can be effectively used.
[0027]
Next, the pressure pulsation integrated value ΔPsum is calculated (step S10). This pressure pulsation integrated value ΔPsum can be expressed as ΔPsum = (n−1) / n × ΔPsum_old + | Ps−Psm |, where the pressure pulsation integrated value in the previous time step is ΔPsum_old. This is an annealing value of a value Σ | Ps−Psm | obtained by integrating the absolute value of the difference between the pressure value Ps and the average value (more precisely, the pressure annealing value Psm) for n time steps. In order to accurately obtain the integrated value of n time steps, it is necessary to store each difference value for n times. By using the smoothed value in this way, the above-described pressure smoothed value can be obtained. As in the case of the calculation, it is not necessary to store the calculation results in the past n time steps, the required amount of memory can be reduced, the calculation is simplified, and the computer in the control device 10 can be reduced. Resources can be used effectively.
[0028]
In addition, when there is a margin in computer resources, it is also possible to store n time step values and accurately calculate an average value and an integrated value. In this embodiment, the pressure pulsation integrated value ΔPsum is used for the determination of the pressure pulsation, but a predetermined interval of the length Lps of the plotted line locus when Ps is plotted on the coordinate axis of time t-pressure p. The integrated value may be used (an annealed value may be used in actual calculation). This Lps is √ (Δt for one time step. ² + (Ps-Ps_old) ² ) (Ps_old is the previous value of the pressure Ps). Of course, the pressure pulsation may be obtained from the amplitude value of the actual pressure within the predetermined period (difference between the maximum pressure value and the minimum pressure value).
[0029]
Next, the presence or absence of pulsation is determined by comparing the pressure pulsation integrated value ΔPsum and the threshold value ΔP0 (step S12). ΔP0 is set to a value that can accurately identify the pulsation caused by the exhaust pulsation transmitted to the pressure sensor 15 through the secondary air supply passage 11 from the measurement error of the pressure sensor 15 and the pulsation accompanying the discharge pressure fluctuation of the air pump 12. . If ΔPsum exceeds ΔP0, it is determined that there is pulsation and the ASV 13 is normally opened, and the routine proceeds to step S14. In step S14, the presence or absence of a pressure increase is determined by comparing the pressure smoothing value Psm with a threshold value P0 (second predetermined value in the present invention). Here, P0 is set to a value slightly higher than atmospheric pressure. When Psm exceeds P0, it is determined that a pressure increase due to the discharge pressure is observed with the operation of AP12, and the process proceeds to step S16, and the air flow rate by AP12 from this pressure-annealed value Psm. Q is calculated. The correspondence between Psm and Q is grasped in advance as shown in the diagram of FIG. 4 and stored in the RAM or the like in the control device 10 in a map format or a function format.
[0030]
Next, the air amount Q thus obtained is compared with a threshold value Q0 (step S18). Here, the necessary and sufficient amount of Q0 is set as the secondary air supply amount. If Q is equal to or greater than Q0, it is determined that the secondary air supply amount is sufficient, the process proceeds to step S20, and 1 is set to the flag XAIONOK indicating that the device is functioning normally during execution of AI control. Then, a flag indicating the end of AI failure detection is set (step S24), and the process is terminated.
[0031]
If Q is less than Q0 in step S18, it is determined that the air supply amount has decreased, 1 is set in the flag XFAILOWN indicating the flow rate decrease (step S22), and the process proceeds to step S24. End post-processing.
[0032]
On the other hand, if the pressure smoothing value Psm is less than or equal to the threshold value P0 in step S14, no pressure increase due to the discharge pressure of the AP 12 is observed, so it is determined that the AP 12 is not operating, and the step The process proceeds to S26, XFAPOFF indicating an off failure of the AP 12 is set to 1 (step S26), and the process is terminated after the process proceeds to step S24.
[0033]
If ΔPsum is equal to or smaller than the threshold value ΔP0 in step S12, it is determined that there is no pressure pulsation and communication between the air supply passage 11 and the exhaust pipe 21 is hindered downstream of the pressure sensor 15. Then, the process proceeds to step S28, and the pressure smoothed value Psm is compared with the threshold value P1 (first predetermined value in the present invention). This P1 is set to a value larger than the aforementioned P0. If Psm exceeds P1, it is determined that the AP 12 is operating, but the downstream ASV 13 remains closed, and the process proceeds to step S30 where the ASV 13 close abnormality flag XFASVCL is set to 1. Is set, and the process is terminated after the process proceeds to step S24.
[0034]
On the other hand, when Psm is less than P1, the process proceeds to step S32, and the pressure smoothed value Psm is compared with the threshold value P0. When Psm exceeds P0, the AP 12 is operating and the ASV 13 is normally opened, but the hose disconnection or the like occurs in the flexible piping portion 11b downstream thereof, and the air supply passage 11 is exhausted. It determines with having fallen into the state which is not connected to the pipe | tube 21, transfers to step S34, sets 1 in the hose disconnection abnormality flag XFAILAK, transfers to step S24, and complete | finishes a process.
[0035]
On the other hand, if Psm is equal to or less than P0, it is determined that there is no discharge pressure of AP12, and it is inoperative, 1 is set to the close abnormality flag XFASVCL of ASV13 (step S36), and 1 is set to the off failure flag XFAPOFF of AP12. (Step S38) Each is set, and the process proceeds to Step S24 to end the process.
[0036]
If the determination result is NO in steps S2, S4, and S6, in any case, the process proceeds to step S40, and it is determined whether or not AI failure detection is completed. If the determination result is yes, the process is terminated, and only when it is not detected, the process returns to the beginning, and the detection process is continued.
[0037]
According to this failure diagnosis processing, it is possible to distinguish and determine leakage abnormality from piping on the downstream side of the ASV 13 such as hose disconnection from other failure states. In addition, it is possible to accurately determine the abnormality of other component parts.
[0038]
Next, a second control mode of the failure diagnosis operation will be described with reference to the processing flow of FIG. This process has the same basic part as the process flow shown in FIG. 2, but is different in that determination of hose disconnection or the like is performed in the AI control stop state. Therefore, this processing is repeatedly executed at a predetermined timing by the control device 10 after the vehicle is turned on.
[0039]
First, unlike the first control mode, first, the pressure value P, the pressure smoothing value Psm, and the pressure pulsation integrated value ΔPsum are detected by performing the processes of steps S8 and S10. The processing in steps S2 to S26 is the same as that in the first embodiment. On the other hand, if ΔPsum is equal to or smaller than the threshold value ΔP0 in step S12, it is estimated that the ASV 13 is closed, and the pressure annealing value Psm is compared with the threshold value P0 (step S32). ). If Psm exceeds P0, it is determined that the AP 12 is operating, the process proceeds to step S30, the ASB13 close abnormality flag XFASVCL is set to 1, and the process proceeds to step S24. On the other hand, if Psm is equal to or less than P0, it is determined that the AP 12 is also inoperative, and the ASV 13 close abnormality flag XFASVCL is set to 1 (step S36) and the AP 12 off failure flag XFAPOFF is set to 1 (step S38). Then, the process proceeds to step S24.
[0040]
After step S24 ends, the process proceeds to step S25, the pressure value during AI control is stored in the Paspop, and the process ends.
[0041]
Further, when the process proceeds from step S2 to S6 to S40 and it is determined that the failure determination during the AI control is completed, first, the process proceeds to step S42, and whether or not the hose disconnection detection process is completed. Determine. If the detection process has been completed, the subsequent process is skipped and the process is terminated.
[0042]
If the detection process has not been completed, the AP 12 operation flag XAP is first turned on in step S44, and the valve opening flag XASV of the ASV 13 is turned off to operate the AP 12 while the ASV 13 is closed. And it is determined whether the operation time of AP12 in the valve closing state of ASV13 exceeds predetermined time (step S46). If the operating time is less than or equal to the predetermined time, the pressure value is not stable, and hose disconnection cannot be detected accurately, so that the subsequent processing is skipped and terminated until the predetermined time is reached. When the predetermined time is reached, the process proceeds to step S48, and the pressure smoothing value Psm at the time when the ASV 13 is closed is stored in Pasvoff. Then, a difference ΔP between the pressure smoothing value Pasvoff at the time of closing the ASV 13 and the pressure smoothing value Pasvop at the time of AI control (stored in step S25) is calculated (step S50).
[0043]
Subsequently, ΔP thus obtained is compared with a threshold value α (step S52). This α is set to a value smaller than the difference between the pressures when the AP 12 is operated while the ASV 13 is closed and the ASV 13 is opened when the ASV 13 is functioning normally. If ΔP is smaller than α and the pressure difference between the two is small, it is determined that the pipe is clogged or ASV 13 is closed abnormally, the process proceeds to step S54, and the ASV 13 closed abnormal flag XFASVCL set in the failure determination during AI control is determined. Check out. When the ASV 13 closing abnormality flag XFASVCL is set to 1, it is determined that the ASV 13 is due to a valve closing abnormality, the process proceeds to step S64, and the flag indicating that the hose disconnection detection is completed is set. The process ends. On the other hand, if the close abnormality flag XFASVCL of the ASV 13 is 0, that is, if it is determined that the ASV 13 is functioning normally in the failure determination during the AI control, it is determined that the pipe is clogged, and the process proceeds to step S56 and the pipe is clogged. After setting the flag XFAIJAM to 1, the process is terminated via step S64.
[0044]
If it is determined in step S52 that ΔP is greater than α, the process proceeds to step S58, and the closed abnormality flag XFASVCL of the ASV 13 set in the failure determination during AI control is checked. When the value of XFASVCL is set to 0, that is, when it is determined that the ASV 13 is functioning normally in the failure determination during the AI control, the pressure ΔP is determined based on whether the ASV 13 is open or closed. This is due to a difference from the state, and the device is determined to be normal, and the process is terminated as it is via step S64.
[0045]
When the value of XFASVCL is determined to be 1 in step S58, it is a case where the ASV 13 is determined to be in a closed state in the failure determination during AI control, but in reality, the ASV 13 is open during AI control. It is determined that there is a leak on the downstream side of the ASV 13, and XFASVCL is changed to 0 indicating no valve closing abnormality (step S60), and 1 is set to the hose disconnection abnormality flag XFAILAK (step S62). The process is terminated via step S64.
[0046]
Also in this process, it is possible to detect an abnormality in the piping on the downstream side of the ASV 13 such as a hose disconnection in distinction from the abnormality of other components. Therefore, accurate device abnormality determination can be performed.
[0047]
Next, a third control mode of the failure diagnosis operation will be described with reference to the processing flow of FIG. Although this process has the same basic part as the process flow shown in FIG. 2, the determination of hose disconnection detection performed when AI control is stopped is determined by O instead of the pressure sensor 15. ₂ The difference is that it is performed by the sensor 31 (or A / F sensor).
[0048]
Specifically, as shown in FIG. 6, the processing from step S2 to S40 is almost the same as in the second embodiment shown in FIG. 5, and the pressure value P, the pressure annealing value Psm, and the pressure pulsation The only difference is that the processing of step S8 and step S10 for detecting the integrated value ΔPsum is performed between step S6 and step S12 as in the first embodiment shown in FIG.
[0049]
If it is determined in step S40 that the failure determination during the AI control has been completed, first, the process proceeds to step S66, where it is determined whether the hose disconnection detection process has ended. Then, it is determined whether or not a predetermined time has elapsed after the end of the AI control (step S68). When the operation time is equal to or shorter than the predetermined time, it is determined that the influence of AI control remains on the A / F behavior in the exhaust pipe 21, and the subsequent hose disconnection detection process is skipped and the process ends.
[0050]
If it is determined in step S68 that the predetermined time has elapsed, it is determined that the influence of AI control does not remain on the A / F behavior in the exhaust pipe 21, and the process proceeds to step S70 to determine failure during AI control. The set ASV 13 close abnormality flag XFASVCL is checked. When XFASVCL is 0, the failure determination during the AI control is normal, it is determined that there is no hose disconnection, the process proceeds to step S80, and a flag value indicating that the detection of the hose disconnection has ended. Set to exit.
[0051]
On the other hand, when XFASVCL is 1, that is, when it is determined that the ASV 13 is closed in the failure determination during the AI control, there is a possibility that the hose is actually disconnected. First, air-fuel ratio feedback control is stopped (step S72), A / F in the exhaust pipe 21 is calculated from the oxygen concentration measured by the O2 sensor 31, and this is compared with the threshold value β. This threshold value β is set slightly leaner than the A / F value in the exhaust pipe 21 in a standard state when AI is not controlled.
[0052]
If the calculated A / F in the exhaust pipe 21 is less than the threshold value β (in the case of the rich side), there is no unexpected air inflow into the exhaust pipe 21, so it is determined that there is no hose disconnection and the process proceeds to step S80. And a flag value indicating that the detection of the hose disconnection has been completed is set and the process ends. On the other hand, if the A / F is greater than or equal to the threshold value β, that is, deviates to the lean side, air inflow occurs due to the air suction effect due to the exhaust pulsation from the leaked portion into the exhaust pipe 21 due to the hose disconnection or the like. XFASVCL is changed to 0 indicating that there is no valve closing abnormality (step S76), the hose disconnection abnormality flag XFAILAK is set to 1 (step S78), and the process is terminated via step S80. To do.
[0053]
According to this control mode, a failure such as a hose disconnection can be determined as a failure of another device as in the other control modes described above. Further, unlike the other embodiments, even when the ASV 13 is closed, there is an advantage that the hose disconnection can be detected independently.
[0054]
As described here, when leakage occurs on the downstream side of the ASV 13 such as hose disconnection, air flows into the exhaust pipe 21 from the leaked part even after the AI supply is stopped due to the air suction effect due to exhaust pulsation. The exhaust A / F shifts to the lean side. FIG. 7 is a control flow showing control corresponding to such a deviation of the exhaust A / F. This control is performed by the control device 10 in cooperation with the engine ECU 23, and is repeatedly executed at a predetermined timing after the vehicle is turned on.
[0055]
First, it is determined whether or not AI device failure detection (including hose disconnection detection) has been completed. If failure detection has not ended, the subsequent processing is skipped and the process ends. If the failure detection has been completed, it is determined in steps S84 and S86 whether 1 is set in either the open abnormality flag XFASVOP or the hose disconnection abnormality flag XFAILAK of ASV13. Here, the setting of the open abnormality flag XFASVOP of the ASV 13 is, for example, that the pressure behavior measured by the pressure sensor 15 when the ASV 13 is controlled to be closed and the AP 12 is operated when the AI supply is stopped has the same tendency as during the AI supply control. In this case, XFASVOP may be set to 1 considering that the valve opening failure of the ASV 13 occurs.
[0056]
If both the determination results in steps S84 and S86 are no, that is, if there is no open failure of the ASV 13 and there is no hose disconnection, the process is terminated as it is. If it is determined that any failure has occurred, the routine proceeds to step S80 where the fuel control value (fuel learning value) in the engine ECU 23 is corrected to the rich side and used. A / F inside is prevented from shifting to the lean side. Then, the learning in the fuel feedback is prohibited (step S90), the detection by the on-board diagnostic (OBD) system of the fuel property is stopped (step S92), and the process is ended. This suppresses emission deterioration during cold start due to incorrect learning or when feedback control is open.
[0057]
FIG. 8 shows changes in pressure value and A / F with time when the AI device is normal (case 1), when the ASV 13 is closed (case 2), and when the hose is disconnected (case 3). It is a timing chart which shows.
[0058]
In case 1, the pressure behavior measured by the pressure sensor 15 during the AI supply control has a pulsation associated with the exhaust pulsation, and the average pressure (annealing value) is higher than P1. When the ASV 13 is closed while the AP 12 is operated, the average pressure (annealing value) increases by ΔPa. On the other hand, when the secondary air is supplied, the A / F shifts to a leaner side than the stoichiometric point due to the supplied secondary air, but substantially coincides with the stoichiometric point when the supply is stopped.
[0059]
In case 2, since the ASV 13 is closed, a high pressure is exhibited as in the AP operation when the ASV 13 is closed in the case 1 regardless of the control state. That is, the valve closing abnormality can be detected because the pressure value during the valve opening control is high and there is no pulsation.
[0060]
In case 3, the hose is disengaged on the downstream side of the ASV 13, so that the pulsation of the exhaust pipe 2 is not transmitted to the pressure sensor 15, so that no pressure pulsation is observed. Lower. In the first control mode, the difference in the behavior is utilized to detect the hose disconnection. Further, since the pressure behavior when the ASV 13 is closed is the same as in the cases 1 and 2, the pressure difference ΔPb between the valve opening and the valve closing becomes larger than that in the case 1. In the second control mode, the hose disconnection is detected by utilizing the difference in behavior. On the other hand, since the A / F corrects the fuel control amount to the rich side in anticipation of the supply at the time of AI supply, the A / F in the exhaust pipe 21 is not actually supplied in this case. Shifts to the rich side. In addition, after the AI supply is stopped, the outside air enters the exhaust pipe 2 from the leaked part by the air suction accompanying the exhaust pulsation, so that the A / F shifts to the rich side. In the third control mode, the difference in behavior is utilized to detect the hose disconnection.
[0061]
In the above description, the leak determination on the downstream side of the ASV 13 such as hose disconnection is performed using any of the differences in behavior, but more accurate failure determination can be performed by performing determination by combining a plurality of behavior differences. It can be carried out.
[0062]
【The invention's effect】
As described above, according to the present invention, the pressure behavior during AI supply, the difference between the pressure during supply and the pressure when the AP is driven with the ASV closed after the stop, or after the supply is stopped A failure such as a leak (disconnection of the hose) on the downstream side of the ASV 13 can be determined from the A / F in the exhaust pipe separately from other AI device failures.
[0063]
At the time of leakage determination, air flows into the exhaust pipe. Therefore, it is preferable to prevent the A / F in the exhaust pipe from shifting to the lean side by performing rich correction of the learning value in the fuel learning control. . Further, it is preferable to stop the fuel learning and the fuel abnormality determination to suppress the deterioration of the emission at the cold start.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a configuration of an internal combustion engine equipped with a secondary air supply device according to the present invention.
FIG. 2 is a processing flow of the first control mode in FIG. 1;
3 is a diagram schematically showing a pressure behavior pattern at the position of the pressure sensor in FIG. 1. FIG.
FIG. 4 is a diagram showing the relationship between pressure and air flow rate.
FIG. 5 is a processing flow of the second control mode in FIG. 1;
FIG. 6 is a processing flow of the third control mode in FIG. 1;
FIG. 7 is a flowchart illustrating fuel control in the apparatus of FIG.
FIG. 8 is a timing chart showing pressure values and A / F with time according to AI supply / stop control in three cases with different states of AI equipment in the apparatus of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Secondary air supply device, 2 ... Engine, 10 ... Control device, 11 ... Secondary air supply passage, 12 ... Air pump (AP), 13 ... Air switching valve (ASV), 14 ... Reed valve (RV), 15 DESCRIPTION OF SYMBOLS ... Pressure sensor, 16 ... Piping, 17 ... Three-way valve, 18 ... Piping, 19 ... Filter, 20 ... Intake pipe, 21 ... Exhaust pipe, 22 ... Exhaust gas purification device, 23 ... Engine ECU, 24 ... Throttle, 25 ... Intake filter , 26 ... Air flow meter, 27 ... Rotational speed sensor, 31, 32 ... O ₂ Sensor.

Claims (5)

An air pump, a pressure sensor, and an on-off valve are arranged from an upstream side on a supply pipe connected to an exhaust system of an internal combustion engine, and supply secondary air to the exhaust system. In the secondary air supply apparatus including a failure diagnosis unit that determines a failure state from the pressure and pressure fluctuation at the time of secondary air supply control and non-supply control,
When the failure diagnosis unit determines that there is no pressure pulsation due to exhaust gas from the pressure detected by the pressure sensor during secondary air supply control, the detected pressure value is set to a first predetermined value and a second smaller than the first predetermined value. Compared with each of the predetermined values, if the detected pressure value is larger than the first predetermined value, the valve closing failure of the on-off valve, and if the detected pressure value is smaller than the second predetermined value, the valve closing failure of the on-off valve The secondary air supply device characterized in that it is determined that there is a leak downstream of the on-off valve when both the stop failure of the air pump is between the first predetermined value and the second predetermined value. An air pump, a pressure sensor, and an on-off valve are arranged from an upstream side on a supply pipe connected to an exhaust system of an internal combustion engine, and supply secondary air to the exhaust system. In the secondary air supply apparatus including a failure diagnosis unit that determines a failure state from the pressure and pressure fluctuation at the time of secondary air supply control and non-supply control,
The failure diagnosing unit determines that there is no pressure pulsation due to exhaust during secondary air supply control, and a pressure difference when the air pump is driven both during the opening / closing valve opening control and during the closing control is predetermined. A secondary air supply device that determines that there is a leak downstream of the on-off valve when the value is greater than or equal to the value. An air pump, a pressure sensor, and an on-off valve are arranged from an upstream side on a supply pipe connected to an exhaust system of an internal combustion engine, and supply secondary air to the exhaust system. In the secondary air supply apparatus including a failure diagnosis unit that determines a failure state from the pressure and pressure fluctuation at the time of secondary air supply control and non-supply control,
An air-fuel ratio sensor disposed in the exhaust system;
The failure diagnosis unit determines that the on / off valve is closed due to pressure and pressure fluctuations during secondary air supply control and non-supply control, and the air-fuel ratio sensor after the secondary air supply control ends. A secondary air supply device characterized by determining that there is a leak downstream of the on-off valve when it is determined that the lean state is greater than or equal to a predetermined value based on the output of. A control device for an internal combustion engine,
The internal combustion engine includes the secondary air supply device according to any one of claims 1 to 3,
A control apparatus for an internal combustion engine, wherein when the failure diagnosis unit determines that the leakage is downstream of the on-off valve, the learning value is richly corrected in fuel learning control by air-fuel ratio feedback. The control device for an internal combustion engine according to claim 1, wherein when the failure diagnosis unit determines that the leak is downstream of the on-off valve, fuel learning and fuel abnormality determination are further stopped.

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