JP3265945B2 - Catalyst deterioration diagnosis device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for diagnosing deterioration of a catalyst of an internal combustion engine, and more particularly to a device for diagnosing deterioration or abnormality of a normal catalyst at a low atmospheric pressure. The present invention relates to a catalyst deterioration diagnosis device for an internal combustion engine, which can avoid an increase in maintenance costs such as replacement of a catalyst body, and can improve the accuracy of deterioration diagnosis and improve reliability.

[0002]

2. Description of the Related Art In an internal combustion engine mounted on a vehicle, a catalyst is provided in an exhaust passage, and a first O2 sensor and a second O2 sensor serving as exhaust sensors are respectively provided in upper and lower exhaust passages of the catalyst.
In some cases, two sensors are provided and control means for performing feedback control so that the air-fuel ratio becomes a target value based on the first detection signal and the second detection signal output from the first O2 sensor and the second O2 sensor. As a result, in the internal combustion engine, the exhaust gas purification efficiency of the catalyst body is improved, and the exhaust emission harmful component value is reduced.

[0003] Japanese Patent Application Laid-Open No. 6-14686 discloses a technique for reducing the value of harmful exhaust components emitted from an internal combustion engine.
There is one disclosed in Japanese Patent Application Publication No. 5 (JP-A) No. 5 (1994).

This publication discloses a lean response delay time, a rich response delay time, a rich determination delay time, a rich determination delay time, and a lean determination delay time based on the first detection signal and the second detection signal of the first O2 sensor and the second O2 sensor. The deterioration state of the catalyst body is determined based on the deterioration determination value calculated based on the above.

[0005]

In the catalyst deterioration diagnosis apparatus for an internal combustion engine disclosed in the above publication, the lower limit value of the engine load is set by the intake pressure or the like as a condition for executing the diagnosis. This is because when the catalyst body deterioration diagnosis is performed at a low load, the catalyst temperature decreases, and as shown in FIG.
This is to prevent the output of the second O2 sensor from becoming an output at the time of a low purification rate in which the catalyst has deteriorated even though it is a new catalyst.

However, the engine load during traveling at a constant vehicle speed differs between when the atmospheric pressure is normal pressure (low altitude) and when the atmospheric pressure is low pressure (high altitude), as shown in FIG. For this reason, in the low pressure state, the catalyst deterioration diagnosis is performed at a lower load than in the normal pressure state. In the region shown by the diagonal lines in FIG. 10, the function of the catalyst body is normal. There is an inconvenience that an erroneous diagnosis of deterioration or abnormality is made.

[0007] Such an erroneous diagnosis has a disadvantage that the maintenance cost is increased due to unnecessary replacement of the catalyst body and the like, and there is a disadvantage that the accuracy and reliability of the deterioration diagnosis are reduced.

[0008]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, the present invention provides a first exhaust sensor provided in an exhaust passage upstream and downstream of a catalyst provided in an exhaust passage of an internal combustion engine. And a second exhaust sensor.
Control means for performing feedback control so that the air-fuel ratio becomes a target value based on the first detection signal and the second detection signal output from the exhaust sensor and the second exhaust sensor is provided, and the intake pressure is equal to or higher than a predetermined lower limit. In the internal combustion engine provided with a diagnosis unit in the control means for executing the deterioration diagnosis of the catalyst when the diagnosis execution condition is satisfied as one condition, the deterioration diagnosis of the catalyst is prevented when the atmospheric pressure is low. In order to correct the lower limit value with the atmospheric pressure, a corrected lower limit value is obtained, and when the intake pressure is less than the corrected lower limit value, execution of the deterioration diagnosis of the catalyst is prohibited. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION
Control means is provided for performing feedback control so that the air-fuel ratio becomes a target value based on the first detection signal and the second detection signal output from the first exhaust sensor and the second exhaust sensor on the upstream and downstream sides of the catalyst body. The control unit is provided with a diagnosis unit that executes a deterioration diagnosis of the catalyst when a diagnosis execution condition is satisfied in which one condition is that the pressure is equal to or higher than a preset lower limit value. This diagnostic unit calculates the corrected lower limit by correcting the lower limit with the atmospheric pressure to prevent deterioration diagnosis of the catalyst when the atmospheric pressure is low, and determines the corrected lower limit when the intake pressure is less than the corrected lower limit. Prohibits the execution of the deterioration diagnosis. As a result, the catalyst deterioration diagnosis device prohibits the execution of the deterioration diagnosis of the catalyst when the atmospheric pressure is low, such as at a high altitude, and prevents the erroneous diagnosis that the normal catalyst is deteriorated or abnormal. are doing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 6 show an embodiment of a catalyst deterioration diagnosis apparatus according to the present invention. In FIG. 6, 2 is an internal combustion engine, 4 is an intake passage, and 6 is an exhaust passage. The intake passage 4 of the internal combustion engine 2 is formed by an air cleaner 8, an air flow meter 10, a throttle body 12, and an intake manifold 14 which are sequentially connected from the upstream side. A throttle valve 16 is provided in the intake passage 4 in the throttle body 12. The intake passage 4 is communicated with a combustion chamber 18 of the internal combustion engine 2.

The exhaust passage 6 communicating with the combustion chamber 18 of the internal combustion engine 2 includes an exhaust manifold 20, an upstream exhaust pipe 22, a catalytic converter 24, and a downstream exhaust pipe 26 which are sequentially connected from the upstream side. It is formed. A catalyst body 28 is provided in the exhaust passage 6 in the catalytic converter 24.

The internal combustion engine 2 is provided with a fuel injection valve 30 directed toward the combustion chamber 18. The fuel injection valve 30
The fuel supply passage 34 communicates with the fuel tank 36 via the fuel distribution passage 32. The fuel in the fuel tank 36 is pumped by a fuel pump 38 and a fuel filter 40
Then, the dust is removed, and the dust is supplied to the fuel distribution passage 32 by the fuel supply passage 34 and distributed to the fuel injection valve 30.

The fuel distribution passage 32 is provided with a fuel pressure adjusting section 42 for adjusting the fuel pressure. The fuel pressure adjusting unit 42 adjusts the fuel pressure to a predetermined value by the intake pressure introduced from the pressure guiding passage 44 communicating with the intake passage 4, and returns excess fuel to the fuel tank 36 through the fuel return passage 46.

The fuel tank 36 is provided with a passage 4 for the fuel vapor.
8, a two-way valve 50 and a canister 52 are provided in communication with the intake passage 4 of the throttle body 12 in the middle of the evaporative fuel passage 48. The throttle body 12 is provided with a bypass passage 54 bypassing the throttle valve 16, and an idle air amount control valve 56 is provided in the middle of the bypass passage 54. Reference numeral 58 denotes an air regulator, reference numeral 60 denotes a power steering switch, reference numeral 62 denotes an air amount control valve for power steering,
4 is a blow-by gas passage, and 66 is a PCV valve.

The air flow meter 10 and the fuel injection valve 3
The idle air amount control valve 56 and the power steering air amount control valve 62 are connected to a control unit 68 as control means. The control unit 68 includes a crank angle sensor 70,
Distributor 72 and throttle opening sensor 74
, A knock sensor 76, a water temperature sensor 78, and a vehicle speed sensor 80, respectively. Reference numeral 82 denotes an ignition coil, and reference numeral 84 denotes an ignition power unit.

In the internal combustion engine 2, a first O 2 sensor 8, which is an exhaust sensor for detecting an oxygen concentration as an exhaust component value, is provided in the exhaust passage 6 on the upstream side and the downstream side of the catalyst body 28.
6 and a second O2 sensor 88 are provided. These first O
The 2 sensor 86 and the second O2 sensor 88 are provided so as to be connected to the control section 68.

The control unit 68, as shown in FIG.
The operation of the fuel injection valve 30 is feedback-controlled based on the first detection signal and the second detection signal output from the sensor 86 and the second O2 sensor 88 so that the air-fuel ratio becomes a target value. Thereby, the exhaust gas purification efficiency by the catalyst body 28 is improved, and the emission harmful component value is reduced.

Reference numeral 90 denotes a dashpot, and reference numeral 9 denotes a dashpot.
2 is a thermofuse, 94 is an alarm relay, 96 is a warning light, 98 is a diagnosis switch,
100 is a TS switch, 102 is a diagnosis lamp, 104 is a main switch, 106
Is a battery.

In such an internal combustion engine 2, as shown in FIG. 5, the control section 68 is provided with a diagnosis section 108 for diagnosing the deterioration state of the catalyst body 28, and is provided with an atmospheric pressure sensor 110 connected thereto. . The diagnosing unit 108 is configured to perform a diagnosis execution condition when one condition that the engine load EC, which is the intake pressure, is equal to or more than a preset lower limit value ECL is satisfied.
The deterioration diagnosis of the catalyst body 28 is executed. This diagnostic unit 108
Is obtained by correcting the lower limit value ECL by the atmospheric pressure pa so as to prevent the deterioration diagnosis of the catalyst body 28 when the atmospheric pressure pa is low, to obtain the corrected lower limit value ECLnew, and the engine load EC is less than the corrected lower limit value ECLnew. In this case, the execution of the deterioration diagnosis of the catalyst body 28 is prohibited.

The lower limit value ECL is, as shown in FIG.
This is a value set by the engine speed Ne at atmospheric pressure in a standard state, and is set in the control unit 68.

Next, the diagnosis of the catalyst deterioration determining apparatus will be described with reference to FIG.

The internal combustion engine 2 is started (step 200).
When the determination starts, a predetermined catalyst deterioration diagnosis execution condition is read (step 202), and it is determined whether or not the catalyst deterioration diagnosis execution condition is satisfied (step 204).

As shown in FIG. 2, the condition for executing the catalyst deterioration diagnosis is that the condition is within the catalyst deterioration diagnosis region set by the engine load EC and the engine speed Ne, and that the warm-up of the internal combustion engine 2 has been completed. The intake air temperature is equal to or higher than a set value (intake air temperature ≧ set value), the first feedback control is being performed by the first O2 sensor 86, and at a constant speed (intake air amount, throttle opening, fuel injection amount, The change amount of the engine load EC such as the intake pressure is equal to or less than the set value),
Is determined based on whether or not all of the above are satisfied.

In the above judgment (step 204), if either one is not satisfied and the judgment is NO, the process returns to the reading of the catalyst deterioration diagnosis execution condition (step 202). In the determination (step 204), if all are satisfied and YES, the atmospheric pressure sensor 110 detects the atmospheric pressure p.
is measured (step 206), and the lower limit ECL of the engine load EC is corrected based on the atmospheric pressure pa, and the corrected lower limit E is corrected.
CLnew is calculated (step 208).

The calculation of the corrected lower limit value ECLnew is shown in FIG.
Atmospheric pressure-engine speed correction map (Kpa)
And ECLnew = ECL * Kpa.

The actual engine load EC is compared with the corrected lower limit value ECLnew, and it is determined whether or not a catalyst deterioration diagnosis is to be performed (step 210).
It is determined whether EC ≦ ECH (step 212).

In this determination (step 212), if the engine load EC is equal to or more than the corrected lower limit value ECLnew and equal to or less than the upper limit value ECH and YES, a catalyst deterioration diagnosis is executed (step 214) and the process ends (step 21).
6).

On the other hand, when the engine load EC is less than the corrected lower limit value ECLnew or exceeds the upper limit value ECH and the result of the determination (step 212) is NO, execution of the catalyst deterioration diagnosis is prohibited, and execution of the catalyst deterioration diagnosis is performed. The process returns to the condition reading (step 202).

As described above, the diagnostic unit 1 provided in the control unit 68
08, a diagnosis of deterioration of the catalyst body 28 is executed when a diagnosis execution condition is satisfied in which one condition is that the engine load EC, which is the intake pressure, is equal to or higher than a preset lower limit value ECL. When the temperature is low, the lower limit ECL of the engine load EC is determined by the atmospheric pressure pa to prevent the deterioration diagnosis of the catalyst body 28
Is corrected to obtain a corrected lower limit value ECLnew. If the engine load EC is less than the corrected lower limit value ECLnew, execution of the deterioration diagnosis of the catalyst body 28 is prohibited, and the engine load EC
Is greater than the upper limit value ECH, the execution of the deterioration diagnosis of the catalyst body 28 is prohibited.

Thus, this catalyst deterioration diagnosis apparatus prohibits the execution of the deterioration diagnosis of the catalyst body 28 when the atmospheric pressure is low such as at a high altitude, thereby erroneously determining that the normal catalyst body 28 is deteriorated or abnormal. Diagnosis can be prevented.

For this reason, the catalyst deterioration diagnosis apparatus can prevent the erroneous diagnosis that the normal catalyst body 28 is deteriorated or abnormal when the atmospheric pressure is low, and replace the catalyst body 28 due to the erroneous diagnosis. It is possible to prevent the inconvenience of being performed, to avoid an increase in maintenance costs, to improve the accuracy of the deterioration diagnosis, and to improve the reliability.

It should be noted that the present invention is not limited to the above-described embodiment, and various applications and modifications are possible. For example,
In the above-described embodiment, as shown in FIG. 4, the calculation of the corrected lower limit value ECLnew is obtained from the atmospheric pressure-engine speed correction map (Kpa) according to ECLnew = ECL * Kpa, and whether or not the catalyst deterioration diagnosis is performed. However, as shown in FIGS. 7 to 9, the corrected lower limit value ECLnew
Can be determined to determine whether or not to perform catalyst deterioration diagnosis.

In FIG. 7, when the internal combustion engine 2 is started and the determination (step 300) is started, a predetermined catalyst deterioration diagnosis execution condition is read (step 302), and it is determined whether or not the catalyst deterioration diagnosis execution condition is satisfied. Judgment (Step 30)
4) Yes.

In the determination (step 304), if any one of the conditions is not satisfied and the determination is NO, the process returns to the reading of the catalyst deterioration diagnosis execution condition (step 302). In the determination (step 304), if all are satisfied and the result is YES, the atmospheric pressure pa is measured (step 30).
6), the lower limit value EC of the engine load EC is calculated based on the atmospheric pressure pa.
L is corrected, and a corrected lower limit value ECLnew is calculated (step 308).

The calculation of the corrected lower limit value ECLnew is shown in FIG.
As shown in FIG. 9, the ECLnew is calculated based on the atmospheric pressure correction coefficient (Kpa1) and the engine speed correction coefficient (Kpa2).
= ECL * Kpa1 * Kpa2.

The actual engine load EC is compared with the corrected lower limit value ECLnew, and it is determined whether or not to execute the catalyst deterioration diagnosis (step 310).
It is determined whether EC ≦ ECH (step 312).

In this determination (step 312), if the engine load EC is equal to or more than the corrected lower limit value ECLnew and equal to or less than the upper limit value ECH, and the determination is YES, a catalyst deterioration diagnosis is executed (step 314) and the process ends (step 31).
6).

On the other hand, in the above judgment (step 312), if the engine load EC is smaller than the corrected lower limit value ECLnew or larger than the upper limit value ECH and is NO, execution of the catalyst deterioration diagnosis is prohibited, and execution of the catalyst deterioration diagnosis is performed. The process returns to the condition reading (step 302).

Thus, the present catalyst deterioration diagnosis apparatus prohibits the execution of the deterioration diagnosis of the catalyst body 28 when the atmospheric pressure is low such as at a high altitude, thereby erroneously determining that the normal catalyst body 28 is deteriorated or abnormal. Diagnosis can be prevented.

Therefore, this catalyst deterioration diagnosis apparatus can prevent the erroneous diagnosis that the normal catalyst 28 is deteriorated or abnormal when the atmospheric pressure is low, and replace the catalyst 28 due to the erroneous diagnosis. It is possible to prevent inconveniences that may occur, to avoid an increase in maintenance costs, to improve the accuracy of deterioration diagnosis, and to improve reliability.

[0042]

As described above, the catalyst deterioration diagnosing apparatus of the present invention prohibits the execution of the catalyst deterioration diagnosis when the atmospheric pressure is low, such as at high altitude, and determines that the normal catalyst is deteriorated or abnormal. Erroneous diagnosis is prevented.

For this reason, the catalyst deterioration diagnosis apparatus can prevent the erroneous diagnosis that the normal catalyst is deteriorated or abnormal when the atmospheric pressure is low, and can replace the catalyst due to the erroneous diagnosis. In addition, it is possible to avoid an increase in the maintenance cost of the apparatus, improve the accuracy of the deterioration diagnosis, and improve the reliability.

[Brief description of the drawings]

FIG. 1 is a flowchart of a diagnosis of a catalyst deterioration diagnosis apparatus for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a catalyst deterioration diagnosis area.

FIG. 3 is a diagram showing a setting of a lower limit value of an engine load, which is a condition for executing a catalyst body deterioration diagnosis.

FIG. 4 is a view showing an atmospheric pressure-engine speed correction map for obtaining a corrected lower limit value.

FIG. 5 is a block diagram of a catalyst deterioration diagnosis device.

FIG. 6 is a schematic configuration diagram of a catalyst deterioration diagnosis device.

FIG. 7 is a flowchart of a diagnosis of a catalyst deterioration diagnosis apparatus according to another embodiment.

FIG. 8 is a diagram showing an atmospheric pressure correction coefficient.

FIG. 9 is a diagram showing an engine speed correction coefficient.

FIG. 10 is a diagram showing a catalyst deterioration diagnosis area based on intake pressure and engine speed.

[Explanation of symbols]

 2 Internal combustion engine 4 Intake passage 6 Exhaust passage 24 Catalytic converter 28 Catalyst 30 Fuel injection valve 68 Control unit 86 First O2 sensor 88 Second O2 sensor 108 Diagnosis unit

Claims (1)

(57) [Claims] A first exhaust sensor and a second exhaust sensor are provided in an exhaust passage upstream and downstream of a catalyst body provided in an exhaust passage of an internal combustion engine, respectively, and the first exhaust sensor and the second exhaust sensor are provided. preset output first detection signal and the second control means is provided Rutotomoni intake pressure at which the air-fuel ratio based on a detection signal to feedback control so that the target value of
Diagnosis condition that one condition is not less than the lower limit
Execute the catalyst body deterioration diagnosis when the running condition is satisfied.
In an internal combustion engine provided in the control unit diagnosis unit that, large
In order to prevent deterioration diagnosis of the catalyst body when the atmospheric pressure is low,
The lower limit is corrected by the atmospheric pressure to obtain a corrected lower limit.
Because, the catalyst deterioration diagnosis apparatus for an internal combustion engine when the intake pressure is lower than the corrected lower limit value, characterized in that prohibits execution of the deterioration diagnosis of the catalytic body.