JP6764377B2 - Air-fuel ratio sensor diagnostic device for internal combustion engine - Google Patents

Description

The present invention relates to an air-fuel ratio sensor diagnostic device for an internal combustion engine.

As a means for reducing harmful exhaust gas from automobiles and improving fuel efficiency and drivability, a feedback type air-fuel ratio control device that controls the air-fuel ratio based on information on the exhaust gas component of an internal combustion engine such as an engine has been put into practical use. ing.

In the above air-fuel ratio control device, an abnormality in the exhaust gas component or an abnormality in the control system may not be properly controlled due to a failure or deterioration of the air-fuel ratio sensor itself used. In particular, since the air-fuel ratio sensor is installed immediately after the engine is exhausted, it is easily deteriorated because it is affected by high temperature, high pressure, vibration, poor fuel, and the like.

In particular, automobiles destined for North America must comply with OBDII regulations (a law that requires the installation of in-vehicle self-diagnosis devices), and when the above air-fuel ratio sensor fails to exceed 1.5 times the exhaust regulation value. , It is necessary to promptly warn the driver of the abnormality and urge repair.

Therefore, when the detection accuracy of the air-fuel ratio sensor deteriorates for some reason, it is necessary to take appropriate measures such as replacing the sensor.

The response characteristics of the air-fuel ratio sensor must be maintained in a normal state in order to satisfactorily control the actual air-fuel ratio at the ternary points of the three-way catalyst by the air-fuel ratio feedback control, and this response abnormality must be detected. Is an essential technique in the OBDII regulation.

Therefore, for the diagnosis of the response characteristic of the air-fuel ratio sensor, it is required by the OBDII regulation to detect six deterioration modes. Measures for detecting these six deterioration modes are required.

Here, regarding the diagnosis of the response characteristic, there is known a technique capable of detecting the response characteristic of the air-fuel ratio sensor by dividing it into a wasted time and an nth-order delay characteristic (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2005-307961

There are six deterioration modes shown in FIG. 4 in which the response characteristics of the air-fuel ratio sensor are abnormal. This is a legal requirement of OBDII regulation and must be detected. Details of the six deterioration modes (1) to (6) are as follows.

(1) Abnormal rich → lean response time (2) Abnormal lean → rich response time (3) Abnormal rich → lean / lean → rich bilateral response time (4) Abnormal rich → lean wasted time (5) Abnormal lean → rich wasted time (6) Rich-> Lean / Lean-> Rich Both-sided Waste Time Abnormality There is a demand for a means for accurately detecting these, but the technology disclosed in Patent Document 1 is regulated by OBDII (On-Board Diagnostics II). Accurate diagnosis of the response characteristics of the air-fuel ratio sensor for the six degradation modes is not considered.

An object of the present invention is to provide an air-fuel ratio sensor diagnostic device for an internal combustion engine capable of accurately diagnosing the response characteristics of an air-fuel ratio sensor for six deterioration modes of OBD regulation.

In order to achieve the above object, the air-fuel ratio sensor diagnostic apparatus of the internal combustion engine of the present invention has a target air-fuel ratio changing unit that changes the target air-fuel ratio of the feedback control into a rectangular wave shape, and a target based on the output signal of the air-fuel ratio sensor. A first time constant calculation unit that calculates the first time constant when the air fuel ratio rises, and a second time constant that calculates the second time constant when the target air fuel ratio falls based on the output signal of the air fuel ratio sensor. In the time constant calculation unit of 2, the first waste time calculation unit that calculates the first waste time when the target air fuel ratio rises based on the output signal of the air fuel ratio sensor, and the output signal of the air fuel ratio sensor. A second waste time calculation unit that calculates a second waste time when the target air-fuel ratio falls based on the above, and at least one of the first time constant and the second time constant, or the first time constant. An air-fuel ratio sensor diagnostic device including a response deterioration determination unit for determining the presence or absence of response deterioration of the air-fuel ratio sensor based on at least one of the wasted time of 1 and the second wasted time. The response deterioration determination unit includes a first response deterioration determination unit that determines the presence or absence of the first response deterioration of the air fuel ratio sensor for the six deterioration modes of the OBD regulation based on the first time constant, and the second response deterioration determination unit. The second response deterioration determination unit that determines the presence or absence of the second response deterioration of the air-fuel ratio sensor for the six deterioration modes of the OBD regulation based on the time constant of, and the first time constant and the second time. Regarding the six deterioration modes of the OBD regulation based on the constant, the third response deterioration determination unit for determining the presence or absence of the third response deterioration of the air fuel ratio sensor, and the six OBD regulation based on the first waste time. Deterioration Mode A fourth response deterioration determination unit that determines the presence or absence of a fourth response deterioration of the air fuel ratio sensor, and a first of the air fuel ratio sensors for six deterioration modes of OBD regulation based on the second waste time. A fifth response deterioration determination unit for determining the presence or absence of response deterioration of 5, and a sixth of the air-fuel ratio sensor for the six deterioration modes of the OBD regulation based on the first waste time and the second waste time. It is composed of a sixth response deterioration determination unit that determines the presence or absence of response deterioration, and the first time constant calculation unit differentiates the output signal of the air-fuel ratio sensor, cuts less than zero, and squares it. , Integrate and take the inverse number to calculate the first time constant, and the second time constant calculation unit differentiates the output signal of the air-fuel ratio sensor, cuts zero or more, and 2 Calculate the second time constant by multiplying, integrating, and taking the inverse number. ..

According to the present invention, it is possible to accurately diagnose the response characteristics of the air-fuel ratio sensor for the six deterioration modes of OBD regulation. Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is a block diagram of the air-fuel ratio sensor diagnostic apparatus of the internal combustion engine according to the embodiment of this invention. It is a figure which shows an example of the structure of the air-fuel ratio sensor diagnostic apparatus and the internal combustion engine system by embodiment of this invention. It is a figure which shows the operation of the existing LAF sensor response deterioration diagnosis. It is a figure which shows 6 deterioration modes of a LAF sensor. It is a figure for demonstrating a tentative response deterioration index and a response deterioration index. It is a figure which shows the processing process of the formula (3) of FIG. It is the relationship between the response deterioration index and the time constant. It is a timing chart which detects the wasted time of a LAF sensor. It is a flowchart (1) of the air-fuel ratio sensor diagnostic apparatus according to embodiment of this invention. It is a flowchart (2) of the air-fuel ratio sensor diagnostic apparatus according to embodiment of this invention. It is a flowchart (3) of the air-fuel ratio sensor diagnostic apparatus according to embodiment of this invention. It is a flowchart (4) of the air-fuel ratio sensor diagnostic apparatus according to embodiment of this invention. It is a flowchart (5) of the air-fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (6) of the air-fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (7) of the air-fuel ratio sensor diagnostic apparatus according to embodiment of this invention. It is a flowchart (8) of the air-fuel ratio sensor diagnostic apparatus according to embodiment of this invention.

Hereinafter, the configuration and operation of the air-fuel ratio sensor diagnostic apparatus for the internal combustion engine according to the embodiment of the present invention will be described with reference to the drawings. The air-fuel ratio sensor diagnostic device according to the present embodiment is a diagnostic device that accurately diagnoses the above-mentioned six deterioration modes in the response deterioration diagnosis of the air-fuel ratio sensor attached to the internal combustion engine, and is used to strengthen vehicle self-diagnosis regulations. On the other hand, it is an essential technology.

FIG. 1 shows a block diagram of an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to an embodiment of the present invention. The air-fuel ratio is detected by the air-fuel ratio detecting means of the block 101. The diagnostic area is determined by the diagnostic area determining means of block 102. The diagnostic area determining means determines whether or not the operating state such as the rotation speed of the internal combustion engine and the load of the internal combustion engine is within a predetermined range. The operation of the diagnostic area determination means will be described in detail with reference to FIG.

The air-fuel ratio is changed to rich or lean by the target air-fuel ratio changing means of the block 103. The rich-to-lean response time constant detecting means of the block 104 detects the time constant until the target lean air-fuel ratio is reached. The lean → rich response time constant detecting means of the block 105 detects the time constant until the target rich air-fuel ratio is reached. The rich → lean waste time detecting means of the block 106 detects the waste time until the target lean air-fuel ratio is reached. The lean → rich wasted time detecting means of the block 107 detects the wasted time until the target rich air-fuel ratio is reached.

The air-fuel ratio sensor response deterioration determining means 1 of the block 108 determines the rich → lean response abnormality by comparing the rich → lean response time constant with a predetermined value. The air-fuel ratio sensor response deterioration determining means 2 of the block 109 determines the lean → rich response abnormality by comparing the lean → rich response time constant with a predetermined value. The air-fuel ratio sensor response deterioration determining means 3 of the block 110 determines the rich-> lean / lean-> rich bilateral response abnormality by comparing the rich-> lean response time and the lean-> rich response time constant with a predetermined value.

The air-fuel ratio sensor response deterioration determining means 4 of the block 111 determines the rich → lean wasted time abnormality by comparing the rich → lean wasted time with a predetermined value. The air-fuel ratio sensor response deterioration determining means 5 of the block 112 determines the lean → rich wasted time abnormality by comparing the lean → rich wasted time with a predetermined value. The air-fuel ratio sensor response deterioration determining means 6 of the block 113 determines the rich-> lean / lean-> rich bilateral waste time abnormality by comparing the rich-> lean waste time and the lean-> rich waste time with a predetermined value.

The above is the outline of the embodiment of the present invention, and will be described below from the internal combustion engine system which is the object of the embodiment of the present invention.

FIG. 2 shows the configuration of the air-fuel ratio sensor diagnostic apparatus and the internal combustion engine system according to the embodiment of the present invention. The internal combustion engine system includes an internal combustion engine, an intake system, and an exhaust system, and the internal combustion engine is equipped with an ignition device 201, a fuel injection device 202, and a rotation speed detection device 203.

The air flowing in from the air cleaner 200 has a flow rate adjusted by the throttle valve 213, then measured by the flow rate detecting device 204 (flow rate detecting means), and is injected from the fuel injection device 202 at a predetermined angle. It is mixed and supplied to each cylinder 214. Further, an air-fuel ratio sensor 205 such as a LAF sensor (Linear Air-Fuel ratio sensor) and a three-way catalyst 206 are attached to the exhaust system, and the exhaust gas is purified by the three-way catalyst 206 and then put into the atmosphere. It is discharged. The internal combustion engine control device 207 takes in the rotation speed Ne of the ring gear or the plate 208 by the output signal Qa of the flow rate detection device 204 and the rotation speed detection device 203 (rotation speed detection means), calculates the fuel injection amount Ti, and fuels. Controls the injection amount of the injection device.

Further, the internal combustion engine control device 207 detects the air-fuel ratio (A / F) in the internal combustion engine from the air-fuel ratio sensor 205, and corrects the fuel injection amount Ti so that the air-fuel ratio in the internal combustion engine becomes the theoretical air-fuel ratio. Air-fuel ratio feedback control is performed. Further, the air-fuel ratio after the catalyst is detected by the oxygen sensor 215.

On the other hand, the fuel in the fuel tank 209 is sucked and pressurized by the fuel pump 210 and then guided to the fuel inlet of the fuel injection device 202 through the fuel pipe 212 provided with the pressure regulator 211, and the excess fuel is used. Is returned to the fuel tank 209. The above is the target internal combustion engine system.

The internal combustion engine control device 207 of FIG. 2 includes a clock, a microcomputer (MPU: Micro Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a timer / counter, an interface I / O, and an A / D conversion. It consists of a device, output circuit, digital input (port), analog input (port), etc.

Next, the present invention will be specifically described. FIG. 3 shows the operation of the existing LAF sensor response deterioration diagnosis. In this diagnosis, the time after the diagnosis area is established is measured, and the number of rich lean reversals during that period is measured. When the counter value of the number of rich lean inversions is equal to or greater than the determination value (NG determination value) when the predetermined determination time elapses after the diagnosis area is established, it is determined to be normal, and if it is less than the determination value, it is determined to be NG. judge. In the case of FIG. 3, the normal operation is shown.

However, with this method, it is not possible to discriminate the deterioration of the 6 modes shown in FIG. 4 as OBDII regulation compliant. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to an embodiment of the present invention aims to determine deterioration in the six modes shown in FIG. 4 and detect an abnormality.

First, the methods for detecting the response time delays (1), (2), and (3) shown in FIG. 4 will be described.

The principle is shown in FIG. Shake the target air-fuel ratio from rich to lean and lean to rich at predetermined time intervals. At that time, if the equation (1) is established and arranged, the tentative response deterioration index IDXtpm is as follows.

In equation (1), T> τ holds, so equation (2) holds.

Therefore, it can be seen that the tentative response deterioration index IDXtpp is a parameter that is inversely proportional to the time constant τ of the response speed. Therefore, by taking the reciprocal of Eq. (2), the response deterioration index IDX proportional to the time constant τ can be obtained (see Eq. (3)).

Next, FIG. 6 will be described. FIG. 6 shows the processing process of the formula (3) described with reference to FIG. The reciprocal of the final value obtained by differentiating, cutting the negative side, squaring and integrating becomes a response deterioration index proportional to the time constant τp at the time of rich → lean response. Note that A in FIG. 6 represents the final value obtained by integration.

In addition, the reciprocal of the final value obtained by differentiating, cutting the positive side, squaring, and integrating becomes a response deterioration index proportional to the time constant τm at the time of lean → rich response.

Next, FIG. 7 will be described. FIG. 7 shows a temporary response deterioration index and a response deterioration index when the response of the LAF sensor signal is actually deteriorated. The figure on the left is a false response deterioration index, and it can be seen that the relationship is inversely proportional to the time constant. From this, if the reciprocal is taken, the response deterioration index proportional to the time constant can be calculated (see the figure on the right).

When the rich → lean response deterioration index becomes larger than the predetermined NG threshold value, it is determined that the rich → lean response is abnormal. Further, when the lean → rich response deterioration index becomes larger than the predetermined NG threshold value, it is determined that the lean → rich response is abnormal.

Next, FIG. 8 will be described. FIG. 8 shows the methods for detecting the wasted time delays (4), (5), and (6) shown in FIG. Detects a state in which the LAF sensor signal does not change at all when the target air-fuel ratio changes from rich to lean, or a state in which the LAF sensor signal does not change at all when the target air-fuel ratio changes from lean to rich.

From the time when the target air-fuel ratio changes from rich to lean, the rich → lean waste time timer Dp is incremented, and the time until the predetermined value αp is exceeded is measured. This is integrated every predetermined cycle, and if it exceeds a predetermined threshold value, it is determined that the rich → lean wasted time is abnormal. In addition, the lean → rich waste time timer Dm is incremented from the time when the target air-fuel ratio changes from lean to rich, and the time until the target air-fuel ratio falls below the predetermined value αm is measured. This is integrated every predetermined cycle, and when the predetermined threshold is exceeded, it is determined that the lean → rich wasted time is abnormal.

Hereinafter, the flowchart of the present invention will be described.

FIG. 9 shows a flowchart of this embodiment. FIG. 9 is a flowchart for determining the diagnostic area.

In step 901, it is checked whether the rotation speed of the internal combustion engine is within a predetermined range. In step 902, it is checked whether the load of the internal combustion engine is within a predetermined range. In step 903, it is checked whether the water temperature is within a predetermined range. In step 904, it is checked whether the vehicle speed is within the predetermined range. In step 905, it is checked whether the intake air temperature is within the predetermined range.

In step 906, it is checked whether the atmospheric pressure is equal to or higher than a predetermined value. In step 907, it is checked whether the battery voltage is within a predetermined range. Check if the fuel is being cut in step 908. In step 909, it is checked whether the air-fuel ratio control feedback is in progress. Check if the sensor used in step 910 is faulty.

If all the conditions of steps 901 to 910 are satisfied in step 911, it is determined that the area is within the diagnostic area. If even one is out of the range, it is determined in step 912 that the area is out of the diagnostic area.

Next, the flowchart of FIG. 10 will be described. FIG. 10 shows a process of storing the LAF sensor signal in the RAM of the microcomputer. Here, the LAF sensor signal is input every 10 ms. For example, the MPU of the internal combustion engine control device 207 stores the air-fuel ratio (A / F) indicated by the LAF sensor signal in the RAM as a variable LAF. In this embodiment, an example of operating in a 10 ms task is shown, but the present invention is not limited to this.

Next, the flowchart of FIG. 11 will be described. FIG. 11 is a flowchart for detecting rich → lean response deterioration (detection of (1) in FIG. 4).

In step 1101, it is determined whether the diagnostic area is established. If it is not in the diagnostic area, the squared value integrated value Ip is cleared in step 1102. If it is a diagnostic area, the process proceeds to the steps after step 1103, and the difference value of LAF is calculated in step 1103. If the difference value of the LAF shows a negative value in step 1104, a process of making it zero is executed. In step 1105, the squared value is calculated.

In step 1106, the squared value is added to the squared value integrated value Ip. In step 1107, when N reaches the predetermined cycle, the process proceeds to step 1108, and when N does not reach the predetermined cycle, the process ends without executing the subsequent processing (N is calculated in FIG. 14). In step 1108, a predetermined value is divided by Ip to calculate a diagnostic index τp proportional to the time constant. In step 1109, if the τp is larger than the NG threshold value, it is determined to be abnormal in step 1110, and if it is less than or equal to that, it is determined to be normal in step 1111.

In other words, the MPU of the internal combustion engine control device 207 has a time constant (first) when the target air-fuel ratio rises (rich → lean) based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). It functions as a rich → lean response time constant detecting means 104 (first time constant calculation unit) for calculating (time constant). In the present embodiment, the diagnostic index τp proportional to the time constant is calculated, but the τp when the proportional constant is 1 is the time constant itself when the target air-fuel ratio rises (rich → lean).

Specifically, the rich-to-lean response time constant detection means 104 (first time constant calculation unit) differentiates the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor), cuts below zero, and cuts the value below zero. By squaring, integrating, and taking the reciprocal, the time constant (first time constant) when the target air-fuel ratio rises (rich → lean) is calculated.

Since the time constant is approximated with a first-order delay, the logic is simplified. Therefore, the calculation can be performed at high speed.

Next, the flowchart of FIG. 12 will be described. FIG. 12 is a flowchart for detecting lean → rich response deterioration (detection of (2) in FIG. 4).

In step 1201, it is determined whether the diagnostic area is established. If it is not in the diagnostic area, the squared value integrated value Im is cleared in step 1202. If it is a diagnostic area, the process proceeds to the steps after step 1203, and the difference value of LAF is calculated in step 1203. If the difference value of the LAF shows a positive value in step 1204, the process of making it zero is executed. In step 1205, the squared value is calculated.

In step 1206, the squared value is added to the squared value integrated value Im. In step 1207, when N reaches the predetermined cycle, the process proceeds to step 1208, and when N does not reach the predetermined cycle, the process ends without executing the subsequent processing (N is calculated in FIG. 14). In step 1208, a predetermined value is divided by Im to calculate a diagnostic index τm proportional to the time constant. In step 1209, if the τm is larger than the NG threshold value, it is determined to be abnormal in step 1210, and if it is less than or equal to that, it is determined to be normal in step 1211.

In other words, the MPU of the internal combustion engine control device 207 has a time constant (second) when the target air-fuel ratio falls (lean → rich) based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). It functions as a lean → rich response time constant detecting means 105 (second time constant calculation unit) for calculating (time constant). In the present embodiment, the diagnostic index τm proportional to the time constant is calculated, but τm when the proportional constant is 1 is the time constant itself when the target air-fuel ratio falls (lean → rich). ..

Specifically, the lean-to-rich response time constant detection means 105 (second time constant calculation unit) differentiates the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor), cuts zero or more, and cuts it. By squaring, integrating, and taking the reciprocal, the time constant (second time constant) when the target air-fuel ratio falls (lean → rich) is calculated.

The detection of (3) in FIG. 4 is regarded as an abnormality when the abnormality is determined in step 1110 of FIG. 11 and the abnormality is determined in step 1210 of FIG.

Next, the flowchart of FIG. 13 will be described. FIG. 13 is a flowchart of control for swinging the target air-fuel ratio at predetermined time intervals.

In step 1301, it is determined whether the diagnostic area is established. If it is not in the diagnostic area, the target air-fuel ratio is normally calculated by the air-fuel ratio feedback control in step 1303. If it is a diagnostic area, the process proceeds to the steps after step 1302, and in step 1302, the target air-fuel ratio is set to the lean value. Next, in step 1304, it is checked whether the timer Ta has reached a predetermined time, and if not, 10 ms is added to the Ta in step 1306. If it has been reached, the target air-fuel ratio is set to the rich value in step 1305. Next, in step 1307, it is checked whether the timer Tb has reached a predetermined time, and if not, 10 ms is added to the Tb in step 1308. If it has reached, the Ta and Tb are cleared to zero in step 1309.

In other words, the MPU of the internal combustion engine control device 207 functions as a target air-fuel ratio changing means 103 (target air-fuel ratio changing unit) for changing the target air-fuel ratio of the feedback control into a rectangular wave shape.

Next, the flowchart of FIG. 14 will be described. FIG. 14 is a flowchart for calculating N. N is a variable that is incremented each time the target air-fuel ratio changes by one cycle. It is determined in step 1401 whether the diagnostic area is established. If it is not in the diagnostic area, N is cleared to zero in step 1404. If it is a diagnostic area, the rising edge of the target air-fuel ratio is checked in step 1402. If it is a rising edge, increment N. If it is not a rising edge, no processing is applied to N.

Next, the flowchart of FIG. 15 will be described. FIG. 15 is a flowchart for detecting rich → lean waste time deterioration (detection of (4) in FIG. 4).

First, it is determined in step 1501 whether the diagnostic area is established. If it is a diagnostic area, it is checked in step 1502 whether the flag Rp is 1. If it is not in the diagnostic area, the flag Rp is set to zero in step 1508. If the flag Rp is zero in step 1502, the rising edge of the target air-fuel ratio is checked in step 1505, and if it is satisfied, the flag Rp is set to 1 in step 1506.

Going back, if the flag Rp is 1 in step 1502, the LAF is compared with the rich value + αp value (threshold value determined to be wasted time) in step 1503. As a result of the comparison, if the LAF is small, it is determined that the waste time state is reached, and 10 ms is added to the waste time timer Dp in step 1504.

Next, the falling edge of the target air-fuel ratio is checked in step 1507, and if it is satisfied, Rp is set to zero in step 1508. If unsuccessful, it is checked in step 1509 whether N has reached a predetermined cycle, and if so, the wasted time timer Dp is compared with the NG threshold value in step 1510. As a result of the comparison, if the wasted time timer Dp is larger than the NG threshold value, it is determined as abnormal in step 1511. If it is equal to or less than the NG threshold value, it is determined to be normal in step 1512.

In other words, the MPU of the internal combustion engine control device 207 is wasted time (first) when the target air-fuel ratio rises (rich → lean) based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). It functions as a rich → lean waste time detecting means 106 (first waste time calculation unit) for calculating (wasted time). In the present embodiment, the sum (integrated value) of the wasted time in the predetermined period N when the target air-fuel ratio rises (rich → lean) is calculated, but the sum of the wasted time when N = 1 is calculated. , It is the wasted time itself when the target air-fuel ratio rises (rich → lean).

Specifically, the rich → lean waste time detecting means 106 (first waste time calculation unit) starts from the rise of the target air-fuel ratio until the air-fuel ratio becomes the sum of the rich value and the αp value (first threshold value). Is measured as wasted time (first wasted time). Specifically, the rich → lean wasted time detecting means 106 (first wasted time calculation unit) calculates the sum of the wasted time (first wasted time) in the predetermined period N. As a result, even if the wasted time as noise enters the total, the influence can be suppressed.

Next, the flowchart of FIG. 16 will be described. FIG. 16 is a flowchart for detecting lean → rich waste time deterioration (detection of (5) in FIG. 4).

First, it is determined in step 1601 whether the diagnostic area is established. If it is a diagnostic area, it is checked in step 1602 whether the flag Rm is 1. If it is not in the diagnostic area, the flag Rm is set to zero in step 1608. If the flag Rm is zero in step 1602, the falling edge of the target air-fuel ratio is checked in step 1605, and if it is satisfied, the flag Rm is set to 1 in step 1606.

Going back, if the flag Rm is 1 in step 1602, the LAF is compared with the lean value −αm value (threshold value determined to be wasted time) in step 1603. As a result of the comparison, if the LAF is small, it is determined that the waste time state is reached, and 10 ms is added to the waste time timer Dm in step 1604.

Next, the rising edge of the target air-fuel ratio is checked in step 1607, and if it is satisfied, Rm is set to zero in step 1608. If unsuccessful, it is checked in step 1609 whether N has reached a predetermined cycle, and if so, the wasted time timer Dm is compared with the NG threshold value in step 1610. As a result of the comparison, if the wasted time timer Dm is larger than the NG threshold value, it is determined as abnormal in step 1611. If it is equal to or less than the NG threshold value, it is determined to be normal in step 1612.

The detection of (6) in FIG. 4 is regarded as abnormal when the abnormality is determined in step 1511 of FIG. 15 and the abnormality is determined in step 1611 of FIG.

In other words, the MPU of the internal combustion engine control device 207 determines the wasted time (second wasted time) when the target air-fuel ratio falls based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). It functions as a lean → rich waste time detecting means 107 (second waste time calculation unit) for calculation. In the present embodiment, the total amount of wasted time during a predetermined period N when the target air-fuel ratio falls (lean → rich) is calculated, but the total amount of wasted time when N = 1 is the target air-fuel ratio. It becomes the waste time itself when it falls (lean → rich).

Specifically, the lean → rich waste time detecting means 107 (second waste time calculation unit) sets the air-fuel ratio at the sum of the lean value and the −αp value (second threshold value) after the target air-fuel ratio falls. The time until it becomes is measured as a wasted time (second wasted time). Specifically, the lean → rich wasted time detecting means 107 (second wasted time calculation unit) calculates the sum of the wasted time (second wasted time) in the predetermined period N.

Then, the MPU of the internal combustion engine control device 207 has a time constant (first time constant) when the target air-fuel ratio rises (rich → lean) and a time constant (first time constant) when the target air-fuel ratio falls (lean → rich). At least one of (2 time constants), or wasted time when the target air-fuel ratio rises (rich → lean) (first wasted time) and wasted time when the target air-fuel ratio falls (second waste) Response deterioration determination unit for determining the presence or absence of response deterioration of the air-fuel ratio sensor 205 based on at least one of (time) (air-fuel ratio sensor response deterioration determination means 1 (108) to air-fuel ratio sensor response deterioration determination means 6 ( It functions as 113)).

This makes it possible to accurately diagnose the response characteristics of the air-fuel ratio sensor for the six deterioration modes of OBD regulation.

Specifically, the air-fuel ratio sensor response deterioration determination means 1 (108) as the first response deterioration determination unit is based on the time constant (first time constant) when the target air-fuel ratio rises (rich → lean). , It is determined whether or not the response deterioration (first response deterioration) of the air-fuel ratio sensor 205 is present. Specifically, in the air-fuel ratio sensor response deterioration determining means 1 (108), when the time constant (first time constant) when the target air-fuel ratio rises (rich → lean) is larger than the threshold value (third threshold value). , It is determined that there is a response deterioration (first response deterioration) of the air-fuel ratio sensor 205.

As a result, the response deterioration of the air-fuel ratio sensor 205 can be accurately detected from the time constant (response time delay) when the target air-fuel ratio rises (rich → lean).

The air-fuel ratio sensor response deterioration determination means 2 (109) as the second response deterioration determination unit is based on the time constant (second time constant) when the target air-fuel ratio falls (lean → rich). It is determined whether or not there is a response deterioration (second response deterioration) of 205. Specifically, in the air-fuel ratio sensor response deterioration determining means 2 (109), the time constant (second time constant) when the target air-fuel ratio falls (lean → rich) is larger than the threshold value (fourth threshold value). In this case, it is determined that there is a response deterioration (second response deterioration) of the air-fuel ratio sensor 205.

As a result, the response deterioration of the air-fuel ratio sensor 205 can be accurately detected from the time constant (response time delay) when the target air-fuel ratio falls (lean → rich).

The air-fuel ratio sensor response deterioration determination means 3 (110) as the third response deterioration determination unit reduces the time constant (first time constant) and the target air-fuel ratio when the target air-fuel ratio rises (rich → lean). The presence or absence of response deterioration (third response deterioration) of the air-fuel ratio sensor 205 is determined based on the time constant (second time constant) at the time of (lean → rich). Specifically, in the air-fuel ratio sensor response deterioration determining means 3 (110), the time constant (first time constant) when the target air-fuel ratio rises (rich → lean) is larger than the threshold value (third threshold value). Moreover, when the time constant (second time constant) when the target air-fuel ratio falls (lean → rich) is larger than the threshold value (fourth threshold value), the response deterioration of the air-fuel ratio sensor 205 (third response deterioration). Is determined to exist.

As a result, the response deterioration of the air-fuel ratio sensor 205 is accurately detected from the time constant (response time delay) when the target air-fuel ratio rises (rich → lean) and the time constant when the target air-fuel ratio falls (lean → rich). can do.

The air-fuel ratio sensor response deterioration determination means 4 (111) as the fourth response deterioration determination unit is based on the wasted time (first wasted time) when the target air-fuel ratio rises (rich → lean). It is determined whether or not there is a response deterioration (fourth response deterioration). Specifically, in the air-fuel ratio sensor response deterioration determining means 4 (111), the sum of the wasted time (first wasted time) when the target air-fuel ratio rises (rich → lean) is greater than the threshold value (fifth threshold value). If it is large, it is determined that there is a response deterioration (fourth response deterioration) of the air-fuel ratio sensor 205.

As a result, the response deterioration of the air-fuel ratio sensor 205 can be accurately detected from the wasted time (wasted time delay) when the target air-fuel ratio rises (rich → lean).

The air-fuel ratio sensor response deterioration determination means 5 (112) as the fifth response deterioration determination unit has a response deterioration (second waste time) of the air-fuel ratio sensor 205 based on the wasted time (second wasted time) when the target air-fuel ratio falls. The presence or absence of the fifth response deterioration) is determined. Specifically, the air-fuel ratio sensor response deterioration determining means 5 (112) is empty when the sum of the wasted time (second wasted time) when the target air-fuel ratio falls is larger than the threshold value (sixth threshold value). It is determined that the response deterioration of the fuel ratio sensor 205 (fifth response deterioration) is present.

As a result, the response deterioration of the air-fuel ratio sensor 205 can be accurately detected from the wasted time (wasted time delay) when the target air-fuel ratio falls (lean → rich).

The air-fuel ratio sensor response deterioration determination means 6 (113) as the sixth response deterioration determination unit reduces the wasted time (first wasted time) and the target air-fuel ratio when the target air-fuel ratio rises (rich → lean). Based on the wasted time (second wasted time), it is determined whether or not there is a response deterioration (sixth response deterioration) of the air-fuel ratio sensor 205. Specifically, in the air-fuel ratio sensor response deterioration determining means 6 (113), the sum of the wasted time (first wasted time) when the target air-fuel ratio rises (rich → lean) is greater than the threshold value (fifth threshold value). If the total of wasted time (second wasted time) when the target air-fuel ratio falls is larger than the threshold value (sixth threshold value), the response deterioration of the air-fuel ratio sensor 205 (sixth response deterioration) is Judge that there is.

As a result, the response of the air-fuel ratio sensor 205 from the wasted time (waste time delay) when the target air-fuel ratio rises (rich → lean) and the wasted time (waste time delay) when the target air-fuel ratio falls (lean → rich). Deterioration can be detected accurately.

As described above, according to the present embodiment, the response characteristics of the air-fuel ratio sensor can be accurately diagnosed for the six deterioration modes of the OBD regulation.

It should be noted that each of the above configurations, functions (means), etc. may be realized by hardware, for example, by designing a part or all of them with an integrated circuit. Further, each of the above configurations, functions (means), etc. may be realized by software by the processor (MPU) interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

When the MPU of the internal combustion engine control device 207 detects the response deterioration of the six deterioration modes of the air-fuel ratio sensor, the warning lamp or the like may be turned on to notify the driver of the warning. For example, six lamps for notifying the first to sixth response deterioration may be provided, or one lamp may be provided, and the lighting state (color, blinking) thereof depends on the combination of the presence or absence of the first to sixth response deterioration. ) May be changed.

Moreover, the embodiment of the present invention may have the following aspects.

(11) The air-fuel ratio correction coefficient is calculated based on the signal of the catalyst provided in the exhaust system of the internal combustion engine and the air-fuel ratio sensor before the catalyst for detecting the concentration of a specific component in the exhaust gas, and the reference fuel. In the control device of the internal combustion engine having the air-fuel ratio feedback control means for correcting the supply amount, the target air-fuel ratio changing means, the means for detecting the rich → lean response time constant of the pre-catalyst air-fuel ratio sensor, and the pre-catalyst air Means for detecting the lean → rich response time constant of the fuel ratio sensor, means for detecting the rich → lean wasted time of the pre-catalyst air-fuel ratio sensor, and detecting lean → rich wasted time of the pre-catalyst air-fuel ratio sensor. A means for detecting the response deterioration of the air-fuel ratio sensor, a means for determining the response deterioration of the air-fuel ratio sensor based on the results of the means for detecting the response time constant and the means for detecting the wasted time, and a means for determining the response deterioration of the air-fuel ratio sensor. An air-fuel ratio sensor diagnostic device for an internal combustion engine, characterized by having.

(12) The target air-fuel ratio changing means is characterized by changing from rich to lean, changing from lean to rich after a predetermined time, and repeating changing from rich to lean again after a predetermined time. (11) The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine.

(13) The means for detecting the rich → lean response time constant of the pre-catalyst air-fuel ratio sensor differentiates the pre-catalyst air-fuel ratio sensor signal while executing the target air-fuel ratio changing means, and cuts the signal below zero. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), which comprises squared, then integrated, and detects the rich → lean response time constant from the reciprocal thereof.

(14) The means for detecting the lean → rich response time constant of the pre-catalyst air-fuel ratio sensor differentiates the pre-catalyst air-fuel ratio sensor signal while executing the target air-fuel ratio changing means, and cuts the signal above zero. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), wherein the air-fuel ratio sensor diagnostic apparatus of the internal combustion engine is characterized in that it integrates after squares and detects the lean → rich response time constant from the reciprocal thereof.

(15) The means for detecting the rich → lean wasted time of the pre-catalyst air-fuel ratio sensor determines the time required to reach a predetermined value from the time when the target air-fuel ratio is changed to lean while the target air-fuel ratio changing means is being executed. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), which measures and detects rich → lean waste time.

(16) The means for detecting the lean → rich wasted time of the pre-catalyst air-fuel ratio sensor determines the time required to reach a predetermined value from the time when the target air-fuel ratio is changed to rich while executing the target air-fuel ratio changing means. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), which measures and detects lean → rich wasted time.

(17) The diagnostic area determining means has a rotation speed within a predetermined range, an engine load within a predetermined range, a water temperature within a predetermined range, a vehicle speed within a predetermined range, an intake air temperature within a predetermined range, and an atmospheric pressure within a predetermined value. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), wherein the battery voltage is within a predetermined range, the fuel is not cut, the air-fuel ratio is fed back, and the sensor used is not failed. ..

(18) The internal combustion engine according to (13), wherein the air-fuel ratio sensor response deterioration determining means determines that the rich → lean response is abnormal when the response time constant of (13) is longer than the NG threshold value. Air-fuel ratio sensor diagnostic device.

(19) The empty of the internal combustion engine according to (14), wherein the air-fuel ratio sensor response deterioration determining means determines a lean → rich response as abnormal when the response time of (14) is longer than the NG threshold value. Fuel ratio sensor diagnostic device.

(20) The air-fuel ratio sensor response deterioration determining means is characterized in that when the response times of (13) and (14) are longer than the NG threshold value, the rich-> lean / lean-> rich bilateral response is determined to be abnormal. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (13) and (14).

(21) The internal combustion engine according to (15), wherein the air-fuel ratio sensor response deterioration determining means determines that the rich → lean wasted time is abnormal when the wasted time in (15) is longer than the NG threshold value. Air-fuel ratio sensor diagnostic device.

(22) The internal combustion engine according to (16), wherein the air-fuel ratio sensor response deterioration determining means determines that the lean → rich wasted time is abnormal when the wasted time of (16) is longer than the NG threshold value. Air-fuel ratio sensor diagnostic device.

(23) The air-fuel ratio sensor response deterioration determining means is characterized in that when the wasted time of (15) and (16) is longer than the NG threshold value, the rich → lean / lean → rich bilateral waste time is determined as abnormal. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (15) and (16).

For example, the target air-fuel ratio is swung from rich to lean or lean to rich, and at that time, the air-fuel ratio sensor signal is differentiated, squared and then integrated, and the response time constant is detected from the reciprocal. In addition, when it is made rich or lean, the time until a predetermined value is reached from that time point is measured. By doing so, the six deterioration modes shown in FIG. 4 can be accurately diagnosed.

101: Air-fuel ratio detecting means 102: Diagnosis area determining means 103: Target air-fuel ratio changing means 104: Rich → lean response time constant detecting means 105: Lean → rich response time constant detecting means 106: Rich → lean wasted time detecting means 107: Lean → rich wasted time detecting means 108: air-fuel ratio sensor response deterioration determining means 1
109: Air-fuel ratio sensor response deterioration determination means 2
110: Air-fuel ratio sensor response deterioration determination means 3
111: Air-fuel ratio sensor response deterioration determination means 4
112: Air-fuel ratio sensor response deterioration determination means 5
113: Air-fuel ratio sensor response deterioration determination means 6
200: Air cleaner 201: Ignition device 202: Fuel injection device 203: Rotation speed detection device 204: Flow rate detection device 205: Pre-catalyst oxygen sensor 206: Catalyst 207: Internal combustion engine control device 208: Plate or ring gear 209: Fuel tank 210 : Fuel pump 211: Pressure regulator 212: Fuel pipe 213: Throttle valve 214: Cylinder 215: Post-catalyst oxygen sensor

Claims (4)

A target air-fuel ratio changer that changes the target air-fuel ratio of feedback control into a rectangular wave shape,
A first time constant calculation unit that calculates the first time constant when the target air-fuel ratio rises based on the output signal of the air-fuel ratio sensor, and
A second time constant calculation unit that calculates a second time constant when the target air-fuel ratio falls based on the output signal of the air-fuel ratio sensor, and
A first waste time calculation unit that calculates the first waste time when the target air-fuel ratio rises based on the output signal of the air-fuel ratio sensor, and
A second waste time calculation unit that calculates a second waste time when the target air-fuel ratio falls based on the output signal of the air-fuel ratio sensor, and
The response of the air-fuel ratio sensor based on at least one of the first time constant and the second time constant, or at least one of the first wasted time and the second wasted time. A response deterioration determination unit that determines the presence or absence of deterioration, and an air-fuel ratio sensor diagnostic device provided .
The response deterioration determination unit
A first response deterioration determination unit that determines the presence or absence of a first response deterioration of the air-fuel ratio sensor for six deterioration modes of OBD regulation based on the first time constant.
A second response deterioration determination unit that determines the presence or absence of a second response deterioration of the air-fuel ratio sensor for the six deterioration modes of the OBD regulation based on the second time constant.
A third response deterioration determination unit that determines the presence or absence of a third response deterioration of the air-fuel ratio sensor for the six deterioration modes of the OBD regulation based on the first time constant and the second time constant.
A fourth response deterioration determination unit that determines the presence or absence of a fourth response deterioration of the air-fuel ratio sensor for the six deterioration modes of the OBD regulation based on the first waste time.
A fifth response deterioration determination unit that determines the presence or absence of a fifth response deterioration of the air-fuel ratio sensor for the six deterioration modes of the OBD regulation based on the second waste time.
Consists of a sixth response deterioration determination unit that determines the presence or absence of a sixth response deterioration of the air-fuel ratio sensor for the six deterioration modes of OBD regulation based on the first waste time and the second waste time. Being done
The first time constant calculation unit calculates the first time constant by differentiating the output signal of the air-fuel ratio sensor, cutting below zero, squaring, integrating, and taking the reciprocal. And
The second time constant calculation unit calculates the second time constant by differentiating the output signal of the air-fuel ratio sensor, cutting zero or more, squaring, integrating, and taking the reciprocal. An air-fuel ratio sensor diagnostic device for an internal combustion engine. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1.
The first waste time calculation unit is
An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, characterized in that the time from when the target air-fuel ratio rises until the air-fuel ratio reaches the first threshold value is measured as the first waste time. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1.
The second waste time calculation unit is
An air-fuel ratio sensor diagnostic device for an internal combustion engine, characterized in that the time from when the target air-fuel ratio falls until the air-fuel ratio reaches a second threshold value is measured as the second waste time. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1 .
The first waste time calculation unit is
The time from when the target air-fuel ratio rises until the air-fuel ratio reaches the first threshold value is measured as the first wasted time, and the sum of the first wasted time in a predetermined period is calculated.
The second waste time calculation unit is
The time from when the target air-fuel ratio falls until the air-fuel ratio reaches the second threshold value is measured as the second waste time, and the sum of the second waste time in a predetermined period is calculated.
The first response deterioration determination unit is
When the first time constant is larger than the third threshold value, it is determined that there is a first response deterioration of the air-fuel ratio sensor.
The second response deterioration determination unit is
When the second time constant is larger than the fourth threshold value, it is determined that there is a second response deterioration of the air-fuel ratio sensor.
The third response deterioration determination unit is
When the first time constant is larger than the third threshold value and the second time constant is larger than the fourth threshold value, it is determined that there is a third response deterioration of the air-fuel ratio sensor.
The fourth response deterioration determination unit is
When the sum of the first wasted time is larger than the fifth threshold value, it is determined that there is a fourth response deterioration of the air-fuel ratio sensor.
The fifth response deterioration determination unit is
When the sum of the second wasted time is larger than the sixth threshold value, it is determined that there is a fifth response deterioration of the air-fuel ratio sensor.
The sixth response deterioration determination unit is
When the total sum of the first wasted time is larger than the fifth threshold value and the total sum of the second wasted time is larger than the sixth threshold value, it is determined that there is a sixth response deterioration of the air-fuel ratio sensor. An air-fuel ratio sensor diagnostic device for an internal combustion engine.

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