JP2012112318A - Device for detecting deterioration of catalyst of internal combustion engine - Google Patents

Abstract

Even when the temperature of the catalyst decreases when fuel is supplied to the catalyst, the deterioration of the catalyst is detected more accurately.
In a catalyst deterioration detection device for an internal combustion engine that detects deterioration of a catalyst having an oxidation function provided in an exhaust passage of an internal combustion engine, fuel supply means for supplying fuel to the catalyst, and an amount of fuel supplied to the catalyst Obtained by the temperature obtaining means, the temperature obtaining means for obtaining the temperature of the catalyst, the oxygen amount obtaining means for obtaining the amount of oxygen flowing into the catalyst, and the temperature obtaining means within the period during which the fuel is supplied to the catalyst If the value obtained by dividing the fuel amount acquired by the fuel amount acquisition means at the highest temperature by the oxygen amount acquired by the oxygen amount acquisition means is equal to or less than a predetermined value, the catalyst is deteriorated. Determination means for determining.
[Selection] Figure 6

Description

  The present invention relates to a catalyst deterioration detection device for an internal combustion engine.

  A technique for determining deterioration of the oxidation catalyst by calculating the amount of heat generated by the oxidation of the fuel based on the temperature upstream and downstream of the oxidation catalyst when the fuel is added to the oxidation catalyst is known. (For example, refer to Patent Document 1).

  By the way, when the temperature of the exhaust gas is as low as 300 ° C. as in a diesel engine, the filter is regenerated by increasing the temperature to 600 ° C. by adding fuel. However, when the temperature of the catalyst is high, the reaction rate of the fuel is high even if the catalyst is deteriorated, so that there is not much difference in calorific value between the normal catalyst and the deteriorated catalyst. In addition, when the temperature of the catalyst is raised, the fuel addition amount is gradually increased to the final target temperature. However, if the catalyst is deteriorated to some extent, the catalyst reacts per unit time. Exceeding the possible amount of fuel may reduce the temperature of the catalyst. Even in such a case, since the degree of deterioration may be within an allowable range, it may not be necessary to determine that the catalyst has deteriorated.

JP 2009-156049 A JP 2009-191789 A JP-A-10-212934

  The present invention has been made in view of the above problems, and more accurately detects deterioration of a catalyst even when the temperature of the catalyst is lowered when fuel is supplied to the catalyst. For the purpose.

In order to achieve the above object, a catalyst deterioration detection apparatus for an internal combustion engine according to the present invention comprises:
In a catalyst deterioration detection device for an internal combustion engine for detecting deterioration of a catalyst having an oxidation function provided in an exhaust passage of the internal combustion engine,
Fuel supply means for supplying fuel to the catalyst;
Fuel amount acquisition means for acquiring the amount of fuel supplied to the catalyst by the fuel supply means;
Temperature acquisition means for acquiring the temperature of the catalyst;
Oxygen amount acquisition means for acquiring the amount of oxygen flowing into the catalyst;
The amount of fuel acquired by the fuel amount acquisition unit when the temperature acquired by the temperature acquisition unit reaches a maximum during the period in which fuel is supplied to the catalyst by the fuel supply unit is acquired by the oxygen amount acquisition unit. Determination means for determining that the catalyst is deteriorated when the value divided by the amount of oxygen to be performed is equal to or less than a predetermined value;
Is provided.

When fuel is added into the exhaust gas by the fuel supply means, the fuel flows into the catalyst together with the exhaust gas. When the fuel is oxidized by the catalyst, heat is generated and the temperature of the catalyst rises. By the way, the number of reaction sites on the catalyst surface decreases as the catalyst deteriorates. As a result, the amount of fuel that can be oxidized by the catalyst per unit time is reduced. Then, when more fuel than the amount of fuel that can be oxidized per unit time by the catalyst is supplied, surplus fuel covers the reaction site, and the reaction amount of the fuel decreases. When the amount of fuel added exceeds the amount of fuel that can be oxidized by the catalyst, the amount of reaction in the catalyst decreases, and the temperature of the catalyst decreases.

  Since the number of catalyst sites decreases as the deterioration of the catalyst progresses, there is a correlation between the amount of fuel supplied when the temperature of the catalyst starts to decrease and the degree of deterioration of the catalyst. Therefore, if the amount of fuel supplied immediately before the temperature of the catalyst decreases, that is, when the temperature of the catalyst reaches the maximum, is acquired, even if the temperature of the catalyst subsequently decreases, the degree of deterioration of the catalyst is detected. be able to. Further, by using a value obtained by dividing the fuel amount acquired by the fuel amount acquiring unit when the temperature acquired by the temperature acquiring unit becomes the highest by the oxygen amount acquired by the oxygen amount acquiring unit, the internal combustion engine It is possible to determine the deterioration of the catalyst regardless of the operating state. That is, since the amount of oxygen in the exhaust changes depending on the operating state of the internal combustion engine, the amount of oxidizable fuel also changes. Since the degree of deterioration of the catalyst can be detected according to this change, the detection accuracy can be increased.

  The predetermined value may be an upper limit value when the catalyst is deteriorated. This may be a value when the degree of deterioration of the catalyst exceeds the limit.

Further, in order to achieve the above object, a catalyst deterioration detection device for an internal combustion engine according to the present invention comprises:
In the present invention, in the catalyst deterioration detection device for an internal combustion engine that detects deterioration of the catalyst having an oxidation function provided in the exhaust passage of the internal combustion engine,
Fuel supply means for supplying fuel to the catalyst;
Temperature acquisition means for acquiring the temperature of the catalyst;
A determination unit that determines that the catalyst has deteriorated when a maximum value of the temperature acquired by the temperature acquisition unit is equal to or less than a predetermined value within a period in which fuel is supplied to the catalyst by the fuel supply unit; ,
Is provided.

  A value obtained by dividing the amount of fuel acquired by the fuel amount acquisition unit when the temperature acquired by the temperature acquisition unit becomes the highest by the amount of oxygen acquired by the oxygen amount acquisition unit, and the temperature acquired by the temperature acquisition unit Since there is a correlation with the maximum value, the deterioration of the catalyst can be determined based on the maximum value of the temperature. Thereby, deterioration of a catalyst can be determined more easily. The predetermined value in this case can be an upper limit value when the catalyst is deteriorated. This may be a value when the degree of deterioration of the catalyst exceeds the limit.

  In the present invention, the determination means can make a determination when a difference between a target temperature of the catalyst and a maximum value of the temperature acquired by the temperature acquisition means is larger than a predetermined value. That is, when the difference between the target temperature of the catalyst and the maximum value of the temperature acquired by the temperature acquisition means is larger than a predetermined value, the catalyst temperature is treated as being lowered. Here, when the deterioration of the catalyst proceeds, the difference between the target temperature when the fuel is supplied to the catalyst and the maximum value of the actual temperature increases. For this reason, when this difference is large, the catalyst may be deteriorated. By performing the deterioration determination at this time, the deterioration determination can be performed at an appropriate time. The predetermined value here is an upper limit value of the difference that is not required to determine the deterioration of the catalyst.

In the present invention, when the temperature acquired by the temperature acquisition unit decreases by a predetermined value or more during the period in which fuel is supplied to the catalyst by the fuel supply unit, the temperature acquired by the temperature acquisition unit is The temperature immediately before the decrease can be set to the maximum value. The predetermined value here is a lower limit value that can be regarded as a decrease in the temperature of the catalyst. As described above, when the temperature is decreased by a predetermined value or more, the temperature immediately before the decrease is set to the maximum value, so that the influence when the temperature fluctuates due to other than the deterioration of the catalyst can be eliminated.

  According to the present invention, even when the temperature of the catalyst is lowered when fuel is supplied to the catalyst, the deterioration of the catalyst can be detected more accurately.

It is a figure which shows schematic structure of the internal combustion engine which concerns on an Example, its intake system, and an exhaust system. It is the time chart which showed transition of the temperature (outlet gas temperature) of the exhaust gas downstream from the catalyst. It is the time chart which showed transition of the target temperature of the catalyst and the temperature (outlet gas temperature) of the exhaust gas flowing out from the catalyst. It is the figure which showed the relationship between the degree of deterioration of a catalyst, and the maximum value of the value (HC amount / O ₂ amount) which divided HC amount per unit time by O ₂ amount. FIG. 4 is a diagram showing the relationship between the degree of catalyst deterioration and the maximum temperature of catalyst 3. It is the flowchart which showed the flow of the deterioration determination of the catalyst which concerns on an Example.

  Hereinafter, a specific embodiment of a catalyst deterioration detection apparatus for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake system and exhaust system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a diesel engine. Note that this embodiment can also be applied to a gasoline engine.

An exhaust passage 2 is connected to the internal combustion engine 1. A catalyst 3 is provided in the middle of the exhaust passage 2. The catalyst 3 may be any catalyst that has a function of oxidizing fuel, and is, for example, an oxidation catalyst, a three-way catalyst, or a NOx catalyst. In this embodiment, the catalyst 3 corresponds to the catalyst having an oxidation function in the present invention.

  An addition valve 4 for injecting fuel (light oil) as fuel in the exhaust is attached to the exhaust passage 2 upstream of the catalyst 3. The addition valve 4 is opened by a signal from the ECU 10 described later and injects fuel into the exhaust. In this embodiment, the addition valve 4 corresponds to the fuel supply means in the present invention.

  An upstream temperature sensor 5 that measures the temperature of exhaust gas is attached to the exhaust passage 2 downstream of the addition valve 4 and upstream of the catalyst 3. Further, a downstream temperature sensor 6 for measuring the temperature of the exhaust is attached to the exhaust passage 2 downstream of the catalyst 3. The upstream temperature sensor 5 measures the temperature of the exhaust gas flowing into the catalyst 3. The downstream temperature sensor 6 measures the temperature of the exhaust gas flowing out from the catalyst 3. The temperature of the catalyst 3 can be detected by the downstream temperature sensor 6. In the present embodiment, the downstream temperature sensor 6 corresponds to the temperature acquisition means in the present invention.

  The exhaust passage 2 downstream of the downstream temperature sensor 6 is provided with a filter 7 that collects particulate matter (PM) in the exhaust.

An intake passage 8 is connected to the internal combustion engine 1. The intake passage 8 is provided with an air flow meter 9 that outputs a signal corresponding to the flow rate of air flowing through the intake passage 8.
The air flow meter 9 measures the intake air amount of the internal combustion engine 1.

  The internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 controls the operation state of the internal combustion engine 1 according to the operation conditions of the internal combustion engine 1 and the request of the driver.

  In addition to the above sensors, the ECU 10 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 11 by the driver to detect the engine load, and an accelerator position sensor 12 for detecting the engine speed. 13 are connected via electric wiring, and the output signals of these various sensors are input to the ECU 10. On the other hand, the addition valve 4 is connected to the ECU 10 via electric wiring, and the opening / closing timing of the addition valve 4 is controlled by the ECU 10.

Then, when the amount of PM collected by the filter 7 reaches a threshold value, the ECU 10 supplies fuel from the addition valve 4 to the catalyst 3 to increase the temperature of the exhaust. Thereby, since the temperature of the filter 7 can be raised, PM can be oxidized and removed from the filter 7. Thus, the filter 7 is regenerated by supplying fuel from the addition valve 4 to the catalyst 3. In this embodiment, the deterioration of the catalyst 3 is determined when the filter 7 is regenerated. Not only the regeneration of the filter 7 but also the deterioration of the catalyst 3 can be determined if the fuel is supplied to the catalyst 3 to raise the temperature of the catalyst 3. For example, it is possible to determine the deterioration of the catalyst 3 even when the sulfur reduction of the NOx storage reduction catalyst is recovered.

  FIG. 2 is a time chart showing the transition of the exhaust gas temperature (outlet gas temperature) downstream of the catalyst 3. The temperature of the exhaust gas may be the temperature of the catalyst 3. The solid line indicates a normal case where the catalyst is not deteriorated, and the alternate long and short dash line indicates a case where the catalyst is deteriorated. Other conditions are the same for the solid line and the alternate long and short dash line. The inlet gas temperature is the temperature of the exhaust gas flowing into the catalyst 3, and is, for example, 300 ° C. The target temperature is a final target value of the temperature of the exhaust gas flowing out from the catalyst 3, and is 600 ° C., for example.

  The amount of fuel added from the addition valve 4 is set so that the temperature of the catalyst 3 becomes the target temperature when the catalyst 3 is normal. Then, when the catalyst 3 is normal, the temperature of the catalyst 3 coincides with the target temperature after a sufficient time has elapsed since the start of fuel addition. On the other hand, when the catalyst 3 is deteriorated, the temperature starts to rise after the temperature rises to some extent, and the temperature of the catalyst 3 becomes substantially equal to the gas temperature.

  Here, conventionally, after a sufficient time has elapsed since the start of fuel addition (see “determination region” in FIG. 2), the catalyst 3 is determined based on whether or not the temperature of the catalyst 3 is the target temperature. 3 was judged for deterioration. However, even if the degree of deterioration of the catalyst 3 is low and within the allowable range, the temperature of the catalyst 3 may not reach the target temperature as shown by the one-dot chain line in FIG. In such a case, it is not necessary to determine that the catalyst 3 has deteriorated.

  FIG. 3 is a time chart showing the transition of the target temperature of the catalyst 3 and the temperature of the exhaust gas flowing out from the catalyst 3 (outgas temperature). The solid line indicates the target temperature of the catalyst 3, and the alternate long and short dash line indicates the outgas temperature. In FIG. 3, the target temperature is increased stepwise in accordance with the fuel oxidizing ability of the catalyst 3. In accordance with this target temperature, the amount of fuel added from the addition valve 4 per unit time is increased stepwise. This is performed by increasing the valve opening time of the addition valve 4 or the time for adding fuel from the addition valve 4 in a stepwise manner.

When the target temperature is switched to a higher temperature, the fuel per unit time added from the addition valve 4 is increased. If the catalyst 3 is normal, the reaction amount of the fuel in the catalyst 3 increases, so the outgas temperature rises and converges to a temperature corresponding to the fuel addition amount at that time. On the other hand, after the target temperature increases and the fuel addition amount increases, the outgas temperature may decrease (see the circled portion in FIG. 3). This is considered to be due to the following reasons.

  That is, as the catalyst 3 deteriorates, the number of reaction sites on the catalyst surface decreases. As a result, the amount of fuel (HC) that can be oxidized per unit time in the entire catalyst 3 is reduced. Then, when more fuel than the amount of fuel that can be oxidized per unit time by the catalyst 3 is supplied, surplus fuel covers the reaction site, and the entire catalyst 3 can be oxidized per unit time. The amount of (HC) is further reduced.

  Therefore, immediately after the target temperature becomes high, the fuel addition amount is increased, and when the fuel addition amount exceeds the amount of fuel that can be oxidized by the catalyst 3, the reaction amount in the catalyst 3 is reduced. The temperature drops.

  Since the number of sites of the catalyst 3 decreases as the deterioration of the catalyst 3 progresses, the amount of fuel (HC) that can be oxidized per unit time in the entire catalyst 3 decreases as the degree of deterioration of the catalyst 3 increases. Therefore, if the maximum value of the amount of fuel that can be reacted by the entire catalyst 3 can be acquired, the degree of deterioration of the catalyst 3 can be detected even if the temperature of the catalyst 3 subsequently decreases. The maximum value of the amount of fuel that can react with the entire catalyst 3 can be acquired as the fuel supply amount immediately before the temperature drops.

Further, in this embodiment, rather than using it as a whole by oxidizable per unit time fuel (HC) of the catalyst 3, based on the amount of HC ratio O ₂ amount (HC amount / O ₂ volume) The deterioration determination of the catalyst 3 is performed. By using this ratio, it is possible to determine the deterioration of the catalyst 3 regardless of the operating state of the internal combustion engine 1. That is, since the amount of O ₂ in the exhaust gas changes depending on the operating state of the internal combustion engine 1, the oxidizable HC amount also changes. Since the degree of deterioration of the catalyst 3 can be detected according to this change, the detection accuracy can be increased. When the HC amount is used as it is, the deterioration determination of the catalyst 3 may be performed when the internal combustion engine 1 is in a predetermined operation state. Thereby, the influence of the amount of O ₂ in the exhaust can be ignored.

FIG. 4 is a graph showing the relationship between the degree of deterioration of the catalyst 3 and the maximum value of the HC amount per unit time divided by the O ₂ amount (HC amount / O ₂ amount).

By detecting the maximum value of (HC amount / O ₂ amount) per unit time and comparing this value with a threshold value, it can be determined whether or not the catalyst 3 has deteriorated. That is, it can be determined that the catalyst 3 is normal if the maximum value of (HC amount / O ₂ amount) is larger than the threshold value, and that the catalyst 3 is deteriorated if the maximum value is less than the threshold value. When fuel injection from the addition valve 4 and stopping are repeated, the amount of HC can be calculated by dividing the fuel addition amount for a predetermined period by the predetermined period. Further, the O ₂ amount can be obtained based on the flow rate of the exhaust gas and the air-fuel ratio upstream of the catalyst 3. The flow rate of the exhaust gas can be calculated based on the intake air amount obtained by the air flow meter 9 and the fuel supply amount to the internal combustion engine 1. Further, the air-fuel ratio upstream of the catalyst 3 can be obtained, for example, by attaching an air-fuel ratio sensor. Note that the O ₂ amount may be estimated based on the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load).

FIG. 5 is a graph showing the relationship between the degree of deterioration of the catalyst 3 and the maximum temperature of the catalyst 3. The maximum temperature of the catalyst 3 may be a temperature at which the temperature decrease of the catalyst 3 starts. The temperature at which the temperature decrease of the catalyst 3 starts may be the maximum value of the temperature of the catalyst 3 or the temperature of the exhaust gas downstream of the catalyst 3. Here, since there is a correlation between the maximum value of (HC amount / O ₂ amount) and the maximum temperature of the catalyst 3, the deterioration of the catalyst 3 can also be determined according to the maximum temperature of the catalyst 3. That is, if the maximum temperature of the catalyst 3 is higher than the threshold value, the catalyst 3 is normal, and if the maximum temperature is lower than the threshold value, the catalyst 3 is normal.
Can be determined to have deteriorated. Thus, the deterioration of the catalyst 3 can be determined according to the maximum temperature of the catalyst 3.

  FIG. 6 is a flowchart showing a flow for determining deterioration of the catalyst 3 according to this embodiment. This routine is executed by the ECU 10 every predetermined time.

In step S101, it is determined whether or not the filter 7 is being regenerated. That is, it is determined whether or not fuel is supplied from the addition valve 4. In this step, it is determined whether or not the precondition for determining the deterioration of the catalyst 3 is satisfied. In addition, it is not limited to regeneration of the filter 7, but it may be determined whether or not the fuel is being supplied, for example, at the time of recovery from sulfur poisoning of the NOx storage reduction catalyst. If an affirmative determination is made in step S101, the process proceeds to step S102, and if a negative determination is made, the deterioration determination of the catalyst 3 cannot be performed, and thus this routine is ended.

  In step S102, a previous value (previous annealing temperature TDO) that is a value obtained by smoothing the temperature downstream of the catalyst 3 (annealing temperature TD) is calculated. When the previous annealing temperature TD has been calculated, the previous annealing temperature TD is directly used as the “previous annealing temperature TDO”. Further, at the first time, the temperature downstream of the catalyst 3 is set to the “previous annealing temperature TDO”. The downstream temperature from the catalyst 3 is obtained by the downstream temperature sensor 6.

In step S103, a value obtained by smoothing the temperature downstream of the catalyst 3 (annealing temperature TD) is calculated. Here, the reason why the temperature is set downstream of the catalyst 3 is to remove influences such as errors and disturbances. The annealing temperature TD is obtained by the following equation.
TD ← TD + (Temperature downstream from catalyst 3−TD) × Coefficient Here, the coefficient is set in advance. Further, the annealing process may be performed by another calculation formula.

In step S104, a difference ΔTD between the annealing temperature TD and the previous annealing temperature TDO is calculated. That is, the difference ΔTD is obtained by the following equation.
ΔTd ← TD-TDO

  In step S105, it is determined whether or not the difference ΔTD is less than a predetermined value. This predetermined value is a lower limit value of a range in which the temperature can be assumed not to decrease, and is (−25 ° C.), for example. That is, in this step, it is determined whether or not the temperature downstream of the catalyst 3 (which may be the temperature of the catalyst 3) is lowered.

  It may be determined whether the difference between the target temperature of the catalyst 3 and the maximum value of the temperature of the catalyst 3 obtained by the downstream temperature sensor 6 is greater than a predetermined value. This predetermined value is an upper limit value in a range in which the catalyst 3 can be considered normal. If the difference between the target temperature of the catalyst 3 and the maximum temperature of the catalyst 3 obtained by the downstream temperature sensor 6 is larger than a predetermined value, even if the temperature of the catalyst 3 actually increases, It may be determined that the temperature of the catalyst 3 has reached the maximum value at the time of this determination.

  If an affirmative determination is made in step S105, the process proceeds to step S106, and if a negative determination is made, the process proceeds to step S112.

  In step S106, the supplied HC amount GHC is calculated. The supplied HC amount GHC is the amount of fuel supplied from the addition valve 4 per unit time. In this embodiment, the ECU 10 that processes step S106 corresponds to the fuel amount acquisition means in the present invention.

In step S107, the passing O ₂ amount GO2 is calculated. The passage O ₂ amount GO2 is the amount of O ₂ that passes through the catalyst 3 per unit time, and is calculated based on, for example, the flow rate of exhaust gas and the air-fuel ratio of exhaust gas upstream of the catalyst 3. In this embodiment, the ECU 10 that processes step S107 corresponds to the oxygen amount acquisition means in the present invention.

In step S108, the supplied HC amount GHC is divided by the passing O ₂ amount GO2.

  In step S109, it is determined whether or not the value (GHC / GO2) calculated in step S108 is equal to or less than a predetermined value. The predetermined value here is an upper limit value in a range where the catalyst 3 is normal. This predetermined value corresponds to the threshold value in FIG. That is, in this step, it is determined whether or not the catalyst 3 has deteriorated.

  When an affirmative determination is made in step S109, the process proceeds to step S110 and it is determined that the catalyst 3 has deteriorated. In this case, a catalyst deterioration flag that is turned ON when it is determined that the catalyst 3 is deteriorated may be set to ON. In this embodiment, the ECU 10 that processes steps S109 and S110 corresponds to the determination means in the present invention.

  If a negative determination is made in step S109, the process proceeds to step S111 and the fuel addition method is switched. That is, although it is not necessary to determine that the catalyst 3 has deteriorated, it is considered that the oxidation ability of the catalyst 3 has been reduced, and therefore, the method is switched to a method in which the catalyst 3 can easily react with fuel. For example, the catalyst 3 may be heated using a heater. Further, the temperature of the exhaust from the internal combustion engine 1 may be increased.

  In step S112, it is determined whether the filter 7 is being regenerated. In this step, it is determined whether or not the temperature of the catalyst 3 continues to rise. When an affirmative determination is made in step S112, the temperature of the catalyst 3 continues to rise, so the process proceeds to step S113, where it is determined that the catalyst 3 is normal. In this case, the catalyst deterioration flag may be turned off. On the other hand, if a negative determination is made in step S112, the process returns to step S102.

  As described above, according to the present embodiment, the deterioration determination of the catalyst 3 is performed based on the fuel addition amount when the temperature of the catalyst 3 reaches the maximum when the fuel is added to the catalyst 3. Even when the temperature of the catalyst 3 subsequently decreases, the deterioration can be determined with high accuracy.

  In addition, the deterioration determination can be performed based on the maximum temperature of the catalyst 3, and in this case, the determination can be made more easily.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust passage 3 Catalyst 4 Addition valve 5 Upstream temperature sensor 6 Downstream temperature sensor 7 Filter 8 Intake passage 9 Air flow meter 10 ECU
11 Accelerator pedal 12 Accelerator opening sensor 13 Crank position sensor

Claims (4)

In a catalyst deterioration detection device for an internal combustion engine for detecting deterioration of a catalyst having an oxidation function provided in an exhaust passage of the internal combustion engine,
Fuel supply means for supplying fuel to the catalyst;
Fuel amount acquisition means for acquiring the amount of fuel supplied to the catalyst by the fuel supply means;
Temperature acquisition means for acquiring the temperature of the catalyst;
Oxygen amount acquisition means for acquiring the amount of oxygen flowing into the catalyst;
The amount of fuel acquired by the fuel amount acquisition unit when the temperature acquired by the temperature acquisition unit reaches a maximum during the period in which fuel is supplied to the catalyst by the fuel supply unit is acquired by the oxygen amount acquisition unit. Determination means for determining that the catalyst is deteriorated when the value divided by the amount of oxygen to be performed is equal to or less than a predetermined value;
A catalyst deterioration detection device for an internal combustion engine. In a catalyst deterioration detection device for an internal combustion engine for detecting deterioration of a catalyst having an oxidation function provided in an exhaust passage of the internal combustion engine,
Fuel supply means for supplying fuel to the catalyst;
Temperature acquisition means for acquiring the temperature of the catalyst;
A determination unit that determines that the catalyst has deteriorated when a maximum value of the temperature acquired by the temperature acquisition unit is equal to or less than a predetermined value within a period in which fuel is supplied to the catalyst by the fuel supply unit; ,
A catalyst deterioration detection device for an internal combustion engine.   3. The internal combustion engine according to claim 1, wherein the determination unit performs determination when a difference between a target temperature of the catalyst and a maximum temperature acquired by the temperature acquisition unit is larger than a predetermined value. Catalyst deterioration detector.   The temperature immediately before the temperature acquired by the temperature acquisition unit decreases when the temperature acquired by the temperature acquisition unit falls below a predetermined value within the period during which fuel is supplied to the catalyst by the fuel supply unit. The catalyst deterioration detection device for an internal combustion engine according to any one of claims 1 to 3, wherein a maximum value is set.

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