JP7803260B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine.

An exhaust treatment device that purifies the exhaust gas from an internal combustion engine is installed in the exhaust passage. There is technology that detects when the exhaust treatment device has been removed based on the temperature of the exhaust passage (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-106028

Condensed water can form in the exhaust passage, causing the temperature sensor to become wet. This makes it difficult to accurately detect the temperature. This reduced accuracy in temperature detection also makes it difficult to accurately detect the removal of the exhaust treatment device. Therefore, the objective is to provide a control device for an internal combustion engine that can determine if the temperature sensor has become wet.

The above objective can be achieved by an exhaust treatment device that purifies the exhaust gas of an internal combustion engine, a control device for an internal combustion engine that includes a first temperature sensor provided in an exhaust passage, a first acquisition unit that acquires a differential value of the temperature detected by the first temperature sensor, and a determination unit that determines whether the first temperature sensor has been exposed to water based on the differential value.

The first acquisition unit may acquire a first-order or second-order derivative of the temperature, and the determination unit may determine that the first temperature sensor has been exposed to water if the first-order derivative of the temperature is greater than a predetermined value or if the sign of the second-order derivative of the temperature changes.

The system may include a first temperature sensor provided in the exhaust passage upstream of the exhaust treatment device, a second temperature sensor provided downstream of the exhaust treatment device, a second acquisition unit that acquires parameters based on the temperatures detected by the first temperature sensor and the second temperature sensor, a correction unit that corrects the parameters when it is determined that the first temperature sensor has been exposed to water, and a detection unit that detects an abnormality in the exhaust treatment device based on the corrected parameters.

The second acquisition unit may acquire the parameter based on an integral value of the temperature detected by the first temperature sensor and an integral value of the temperature detected by the second temperature sensor, and when it is determined that the first temperature sensor is wet, the correction unit may correct the parameter by correcting the integral value of the temperature detected by the first temperature sensor, and the detection unit may detect an abnormality in the exhaust treatment device based on the corrected parameter.

The determination unit determines whether the second temperature sensor has been exposed to water, and if it is determined that the second temperature sensor has been exposed to water, the correction unit corrects the parameter by correcting the integrated value of the temperature detected by the second temperature sensor, and the detection unit may detect an abnormality in the exhaust treatment device based on the corrected parameter.

It is possible to provide a control device for an internal combustion engine that can determine whether a temperature sensor is wet.

FIG. 1 is a schematic view illustrating a vehicle according to an embodiment. FIG. 2 is a flowchart illustrating the processing executed by the ECU. 3A is a diagram illustrating an example of temperature, and FIG. 3B is a diagram illustrating an example of a differential value of temperature. 4(a) and 4(b) are diagrams illustrating examples of the relationship between temperature and fuel pressure.

The control device for an internal combustion engine according to this embodiment will now be described with reference to the drawings. FIG. 1 is a diagram illustrating a vehicle 100 according to this embodiment. As shown in FIG. 1, the vehicle 100 has an internal combustion engine 10 and an ECU (Electronic Control Unit) 30.

An internal combustion engine 10 burns fuel, such as gasoline, to generate power. An intake passage 12 and an exhaust passage 14 are connected to the internal combustion engine 10. Air flows through the intake passage 12 and is introduced into the internal combustion engine 10. A throttle valve 16 and an air flow meter 18 are provided in the intake passage 12, arranged in this order from upstream to downstream. As the opening of the throttle valve 16 increases, the air flow rate in the intake passage increases. As the opening decreases, the air flow rate decreases. The air flow meter 18 detects the air flow rate. An acceleration sensor 26 detects the attitude and acceleration of the vehicle 100 in which the internal combustion engine 10 is installed.

Exhaust gas generated by combustion flows through the exhaust passage 14 and is discharged outside the vehicle. A temperature sensor 22 (first temperature sensor), an exhaust treatment device 20, and a temperature sensor 24 (second temperature sensor) are provided in the exhaust passage 14, arranged in this order from upstream to downstream. The exhaust treatment device 20 may have, for example, a GPF (Gasoline Particulate Filter) to capture particulate matter in the exhaust. The exhaust treatment device 20 may also include a catalyst. The catalyst purifies substances such as carbon monoxide (CO) and nitrogen oxides (NOx). The exhaust treatment device 20 may also have a DPF (Diesel Particulate Filter).

The portion of the exhaust passage 14 upstream of the exhaust treatment device 20 is referred to as region 14a, and the portion downstream of the exhaust treatment device 20 is referred to as region 14c. The position between regions 14a and 14c is referred to as region 14b. Temperature sensor 22 is located in region 14a upstream of the exhaust treatment device 20 and detects the temperature on the upstream side. Temperature sensor 24 is located in region 14c downstream of the exhaust treatment device 20 and detects the temperature on the downstream side. Temperature sensors 22 and 24 are inserted from the outside to the inside of the exhaust passage 14 and are provided on, for example, the upper half of the wall of the exhaust passage 14. Down is the direction in which gravity acts, and up is the opposite direction to down.

ECU 30 is a control device that includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and other storage devices, and performs various controls by executing programs stored in the ROM and storage devices.

The ECU 30 controls the opening of the throttle valve 16. The ECU 30 obtains the air flow rate from the air flow meter 18. The ECU 30 obtains the attitude and acceleration of the vehicle 100 from the acceleration sensor 26. The ECU 30 obtains the temperature of the exhaust passage 14 from the temperature sensors 22 and 24.

Exhaust gas contains moisture. When the exhaust gas is cooled, the moisture condenses, producing condensed water. The ECU 30 obtains the amount of condensed water produced in the exhaust passage 14 and the distribution of the condensed water in each of the regions 14a, 14b, and 14c. The ECU 30 stores the processing program shown in Figure 2, and stores, for example, a threshold value for the differential value and a threshold value for the area ratio. The ECU 30 stores the temperature detected when the temperature sensor 22 is not exposed to water.

The ECU 30 functions as a first acquisition unit that acquires a differential value of the temperature detected by the temperature sensor 22. The differential value of the temperature includes a first-order differential value and a second-order differential value. The ECU 30 functions as a determination unit that determines whether the temperature sensor 22 has been exposed to condensed water based on the differential value. Exposure to water means that water has fallen on the sensor. The ECU 30 functions as a second acquisition unit that acquires parameters based on the temperatures detected by the temperature sensor 22 and the temperature detected by the temperature sensor 24. The ECU 30 functions as a detection unit that detects an abnormality in the exhaust treatment device 20 based on the parameters. An abnormality could be, for example, damage to the exhaust treatment device 20 or the exhaust treatment device 20 being removed. The ECU 30 functions as a correction unit that corrects the parameters.

(process)
2 is a flowchart illustrating the processing executed by the ECU 30. The ECU 30 acquires the amount of condensed water in the exhaust passage 14 based on, for example, the temperature of the exhaust passage 14, the operating time of the internal combustion engine 10, and the intake air volume (step S10). The lower the temperature, the more likely condensed water is to occur. The condensed water moves from region 14a to region 14c by the exhaust and is discharged outside the vehicle 100. The condensed water evaporates due to heat generated by the internal combustion engine 10. As the operating time increases and the intake air volume increases, the amount of condensed water decreases. As the vehicle 100 tilts from the horizontal direction, the condensed water moves downward (in the direction of gravity). The ECU 30 updates the amount of condensed water.

The ECU 30 acquires the temperatures detected by the temperature sensors 22 and 24 (step S12). The ECU 30 acquires a parameter R based on the temperatures (step S14). The parameter R is used to detect an abnormality in the exhaust treatment device 20.

The ECU 30 obtains a derivative value of the temperature detected by the temperature sensor 22 (step S16). The derivative value includes a value obtained by first-order and second-order derivatives of the detected temperature with respect to time. The ECU 30 determines whether the temperature sensor 22 has been exposed to water based on the derivative value (step S18). If the determination is affirmative (Yes), the ECU 30 corrects the parameter R (step S20).

After step S20, or if a negative determination (No) is made in step S18, the ECU 30 uses the parameter R to determine whether an abnormality has occurred in the exhaust treatment device 20. Specifically, the ECU 30 determines whether the parameter R is equal to or greater than the threshold value Rth (step S22). If the determination is positive, the ECU 30 determines that the exhaust treatment device 20 is normal (step S24). If the determination is negative, the ECU 30 determines that the exhaust treatment device 20 is abnormal (step S26). After step S24 or S26, the processing in FIG. 2 ends.

(Water exposure determination)
3A is a diagram illustrating temperature. The horizontal axis represents time, and the vertical axis represents temperature. The temperature detected by the temperature sensor 22 that is not exposed to water is designated as T1 and is represented by a solid line. The temperature detected by the temperature sensor 22 that is exposed to a large amount of condensed water is designated as T1a and is represented by a dotted line. The temperature detected by the temperature sensor 22 that is exposed to a small amount of condensed water is designated as T1b and is represented by a dashed line.

When water is present, temperatures T1a and T1b are lower than temperature T1 when water is not present. This is because heat around the temperature sensor 22 is absorbed by condensed water. The greater the amount of water exposure, the greater the temperature drop. The less water exposure, the smaller the temperature drop. Before time t2, temperature T1a is lower than T1. The condensed water is washed downstream and evaporates, disappearing from around the temperature sensor 22. As the amount of condensed water decreases, temperature T1a rises sharply around time t2, becoming approximately the same as T1. Temperature T1b drops below temperature T1 at time t1, and then rises to approximately the same as T1. The temperature detected by temperature sensor 24 is designated as T2. Because the heat of the exhaust gas is absorbed by the exhaust treatment device 20, temperature T2 is lower than temperature T1.

Figure 3(b) is a diagram illustrating temperature derivatives. The vertical axis represents the first-order derivative of each of the temperatures T1, T1a, and T1b in Figure 3(a) with respect to time. The solid line represents the derivative DT1 of T1. The dotted line represents the derivative DT1a of T1a. The dashed line represents the derivative DT1b of T1b. The horizontal axis represents time.

In response to an increase in temperature T1a, the differential value DT1a becomes larger than the differential value DT1, then decreases and becomes approximately the same as the differential value DT1. In response to a temporary decrease in temperature T1b, the differential value DT1b becomes smaller than the differential value DT1, then rises sharply and becomes larger than the differential value DT1, then decreases again and becomes approximately the same as the differential value DT1.

The ECU 30 may store a threshold value Dth for the derivative value. In the example of FIG. 3(b), the derivative values DT1a and DT1b are greater than the threshold value Dth. The ECU 30 determines that the temperature sensor 22 has been exposed to water (step S18 in FIG. 2). As shown in FIG. 3(b), the derivative values DT1a and DT1b increase and decrease. When the first-order derivative value increases, the second-order derivative value takes a positive sign (+). When the first-order derivative value decreases, the second-order derivative value takes a negative sign (-). The first-order derivative value DT1b of the temperature T1b repeatedly increases and decreases in a short period of time. The sign of the second-order derivative value of the temperature T1b also changes. Because the sign changes, the ECU 30 may determine that the temperature sensor 22 has been exposed to water.

(Abnormality detection)
4(a) and 4(b) are diagrams illustrating examples of temperatures. Fig. 4(a) shows an example in which the exhaust treatment device 20 is normal. Fig. 4(b) shows an example in which an abnormality has occurred in the exhaust treatment device 20, and the exhaust treatment device 20 has been removed.

In the example of FIG. 4A, the temperature T2 detected by the temperature sensor 24 rises to T0 at time t3. Temperature T0 is, for example, higher than the dew point of the exhaust gas. The ECU 30 calculates the integrals (areas of the graph) of temperatures T1 and T2 over the range from time 0 to t3. The integral value of temperature T1 is set to S1, and the integral value of temperature T2 is set to S2. The ECU 30 calculates a parameter R based on the integral values S1 and S2 (step S14 in FIG. 2). The parameter R is, for example, the ratio (area ratio) of S1 to S2, and is expressed by the following equation (1):
R=S1/S2 (1)
If the parameter R is equal to or greater than the threshold value Rth, the ECU 30 determines that the exhaust treatment device 20 is normal (step S24 in FIG. 2).

In the example of Figure 4(b), the exhaust treatment device 20 has been removed. The heat of the exhaust is not absorbed by the exhaust treatment device 20. The temperature T2 detected by the temperature sensor 24 rises more quickly than in the example of Figure 4(a) and reaches T0 at time t4. The ECU 30 calculates the integral values S1 and S2 from time 0 to t4 to calculate the parameter R. The parameter R in Figure 4(b) is smaller than in the example of Figure 4(a) and is less than the threshold value Rth. The ECU 30 determines that there is an abnormality in the exhaust treatment device 20 (step S26).

The temperature T1a in Figure 4(a) is an example in which the temperature sensor 22 is wet, and is lower than the temperature T1. The integral value S1a of T1a is smaller than the integral value S1 of T1. As a result, the parameter R (= S1a/S2) obtained using the integral value S1a is smaller than the normal value (S1/S2) and may be less than the threshold value Rth. This may result in an erroneous determination that the exhaust treatment device 20 is abnormal, even though it is normal.

The ECU 30 stores the behavior of the temperature T1 when there is no water exposure. When the ECU 30 determines that the temperature sensor 22 has been exposed to water, it corrects the integral value (step S20). Specifically, the difference between the integral value S1a of the temperature T1a and the integral value S1 of the temperature T1 (the shaded area in Figure 4(a)) is added to the integral value S1a of the temperature T1a, making the integral value S1a approximately the same size as S1. The corrected parameter R is obtained by substituting the integrated value after the addition into equation (1). By comparing the corrected parameter R with the threshold value Rth, highly accurate abnormality detection is possible.

According to this embodiment, the ECU 30 determines whether the temperature sensor 22 has been exposed to water based on the derivative value of the temperature detected by the temperature sensor 22 (step S18). As shown in Figure 3(a), when the temperature sensor 22 is exposed to water, the temperature behavior changes from when it is not exposed to water. As shown in Figure 3(b), the temperature derivative value also changes in response to the change in temperature behavior. Based on the derivative value, the ECU 30 can accurately determine whether the temperature sensor 22 has been exposed to water.

As shown in Figure 3(a), when the amount of water exposure is large, the temperature T1a is lower than the temperature T1 when there is no water exposure, and rises sharply at time t2. As shown in Figure 3(b), the derivative value DT1a becomes greater than the threshold value Dth. The ECU 30 determines water exposure when the derivative value DT1a is equal to or greater than the threshold value Dth. As shown in Figure 3(a), when the amount of water exposure is small, the temperature T1b drops and then rises immediately. As shown in Figure 3(b), the derivative value DT1b changes sharply. The sign of the value obtained by second-order differentiation of temperature T1b changes between negative and positive. The ECU 30 determines water exposure based on the change in sign. When the temperature sensor 22 is exposed to water, the temperature behavior changes, and changes sharply. Using the temperature derivative value enables accurate determination of water exposure.

As shown in Figure 4(a), when the temperature sensor 22 is exposed to water, the temperature behavior changes. Because the temperature integral value changes, the value of parameter R also changes. When the ECU 30 determines that the temperature sensor 22 is exposed to water, it corrects parameter R. An abnormality in the exhaust treatment device 20 is detected based on the corrected parameter R. This makes it possible to suppress a decrease in the accuracy of abnormality detection.

Parameter R is the ratio between integral value S1 and integral value S2 (Equation (1)). When temperature sensor 22 is exposed to water, integral value S1 becomes a smaller value S1a than the actual value, and parameter R also becomes smaller. ECU 30 corrects parameter R by correcting integral value S1a to bring it closer to the value S1 when there is no water exposure. Parameter R is corrected to a larger value. This can suppress a decrease in the accuracy of abnormality detection. ECU 30 performs correction so that the corrected integral value is larger than integral value S1a before correction. The greater the amount of condensed water and the greater the air volume, the more likely temperature sensor 22 is exposed to water and the more likely it is to output a lower temperature. The greater the amount of condensed water and the greater the air volume, the more ECU 30 increases the amount added to the integral value, correcting the integral value to a larger value. ECU 30 may multiply parameter S1a/S2 calculated using integral value S1a by a coefficient or may perform addition. It is estimated that the temperature detected by the temperature sensor 22 when water is present will be lower than the temperature when there is no water exposure. The integral value S1 and parameter R will decrease. The ECU 30 performs a correction to increase parameter R. The ECU 30 detects an abnormality in the exhaust treatment device 20 based on the corrected parameter R. This makes it possible to suppress a decrease in the accuracy of abnormality detection.

The temperature sensor 24 may also be exposed to water. Water exposure changes the behavior of the temperature T2 detected by the temperature sensor 24. The ECU 30 may determine whether the temperature sensors 22 and 24 are exposed to water (step S18 in Figure 2). If water exposure occurs, the ECU 30 may correct not only the integral value S1 but also the integral value S2 (step S20). The greater the amount of condensed water and the greater the intake air volume, the more condensed water flows downstream of the exhaust passage 14, and the greater the amount of water exposure to the temperature sensor 24. As heat around the temperature sensor 24 is absorbed by the condensed water, the integral value S2 of the temperature T2 decreases. The parameter R decreases. The ECU 30 corrects the integral value S2 to increase. The parameter R is corrected to a larger value. The greater the amount of condensed water and the greater the air volume, the greater the amount of addition to the integral value S2, correcting the integral value S2 to a larger value. By having the ECU 30 correct the temperatures detected by the temperature sensors 22 and 24, the parameter R becomes a more accurate value. Abnormalities in the exhaust treatment device 20 can be detected accurately.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims.

REFERENCE SIGNS LIST 10 internal combustion engine, 12 intake passage, 14 exhaust passage, 14a, 14b, 14c area, 16 throttle valve, 18 air flow meter, 20 exhaust treatment device 22 temperature sensor (first temperature sensor), 24 temperature sensor (second temperature sensor), 26 acceleration sensor, 30 ECU, 100 vehicle

Claims (4)

an exhaust treatment device that purifies exhaust gas from the internal combustion engine and a first temperature sensor are provided in the exhaust passage;
a first acquisition unit that acquires a differential value of the temperature detected by the first temperature sensor;
a determination unit that determines whether the first temperature sensor is wet based on the differential value ,
the first temperature sensor is provided in the exhaust passage upstream of the exhaust treatment device, and the second temperature sensor is provided downstream of the exhaust treatment device,
a second acquisition unit that acquires a parameter based on the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor;
a correction unit that corrects the parameter when it is determined that the first temperature sensor is wet;
a detection unit that detects an abnormality in the exhaust treatment device based on the corrected parameters. the first acquisition unit acquires a first-order differential value or a second-order differential value of the temperature,
2. The control device for an internal combustion engine according to claim 1, wherein the determination unit determines that the first temperature sensor has been exposed to water when the value obtained by first differentiating the temperature is greater than a predetermined value or when the sign of the value obtained by second differentiating the temperature changes. the second acquisition unit acquires the parameter based on an integral value of the temperature detected by the first temperature sensor and an integral value of the temperature detected by the second temperature sensor;
When it is determined that the first temperature sensor is wet, the correction unit corrects the parameter by correcting an integral value of the temperature detected by the first temperature sensor;
The control device for an internal combustion engine according to claim 1 , wherein the detection unit detects an abnormality in the exhaust treatment device based on the corrected parameters. The determination unit determines whether the second temperature sensor is wetted,
When it is determined that the second temperature sensor is wet, the correction unit corrects the parameter by correcting an integral value of the temperature detected by the second temperature sensor;
The control device for an internal combustion engine according to claim 3 , wherein the detection unit detects an abnormality in the exhaust treatment device based on the corrected parameters.