JPH09303191A - Abnormality diagnosing device of intake air temperature sensor for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make abnormality diagnosable of an intake air temperature sensor when an internal combustion engine is operated, by determining a decision value based on a difference previously from a normal intake air temperature sensor, so as to decide whether abnormality is provided or not of the intake air temperature sensor from a difference between both detected intake air temperatures of the actual intake air temperature sensor. SOLUTION: An intake air temperature sensor 20 detects a temperature of intake air introduced to an internal combustion engine. A first decision means 15, 27, 28, 30 decides a first operating condition with this temperature of intake air depending on a temperature of the outside air. A second decision means 22, 28, 30 decides a second operating condition with an intake air temperature depending on heat generation of the internal combustion engine. An arithmetic means 30 obtains a difference between a second detection intake air temperature detected when in the second operating condition and a first detection intake air temperature detected when in the first operating condition. An abnormality decision means 30, 29, from the difference obtained by the arithmetic means 30 and a predetermined decision value, decides whether abnormality is provided or not in the intake air temperature sensor 20. In this way, at each time using an automobile, the intake air temperature sensor 20 can be surely diagnosed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality diagnosis device for an intake air temperature sensor for an internal combustion engine, which detects the temperature of intake air supplied to the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine for an automobile, an ECU (Electronic Control Unit) is used in order to optimize performances such as output characteristics, fuel consumption characteristics and exhaust characteristics under various conditions.
The air-fuel ratio is controlled by. In this air-fuel ratio control, the basic injection amount of fuel for obtaining an appropriate air-fuel ratio is determined based on the rotation speed of the internal combustion engine and the intake air amount.
Further, in the air-fuel ratio control, the basic fuel injection amount is corrected based on the intake air temperature. That is, the basic injection amount is corrected so as to be proportional to the actual volume of the intake air, based on the intake temperature corresponding to the density of the intake air. As a result, even if the intake air temperature changes, highly accurate air-fuel ratio control can be performed.

By the way, the intake air temperature is measured by an intake air temperature sensor provided in the intake pipe. Therefore, it is known that the intake air temperature THA detected by the intake air temperature sensor has a value substantially equal to the wall temperature of the intake pipe cooled by the intake air.
Therefore, there is an error between the intake air temperature THA detected by the intake air temperature sensor and the actual intake air temperature (hereinafter referred to as the actual intake air temperature). This error becomes small when the vehicle is running with the internal combustion engine completely warmed up, and becomes large when the vehicle is stopped and idling. Therefore,
Since the correction amount determined based on the intake air temperature THA varies depending on the usage state of the vehicle, the control accuracy of the air-fuel ratio control is not stable.

In order to eliminate the error in the correction amount due to the error between the intake air temperature THA measured by the intake air temperature sensor and the actual intake air temperature as described above, the intake air temperature estimation of the internal combustion engine is disclosed in JP-A-2-112739. A device has been proposed. In this intake air estimation device, the actual intake air temperature is estimated from the measured intake air temperature THA, the amount of heat received by the intake pipe from the outside, etc., using an arithmetic expression set based on a physical model describing the behavior of the intake air temperature sensor. There is. According to this estimation device, the actual intake air temperature can be estimated with high accuracy in various usage states of the automobile. Therefore, the basic injection amount can be corrected with high accuracy based on the actual intake air temperature regardless of the state of use of the vehicle, so that highly accurate air-fuel ratio control can be stably performed.

[0005]

By the way, when the use period of the automobile becomes long, the detection characteristic of the intake air temperature sensor itself deteriorates due to aging. That is, the ratio of the change in the detection signal output by the intake air temperature sensor to the change in the intake air temperature detected becomes small. Therefore, an error between the intake air temperature estimated based on the detected intake air temperature THA and the actual intake air temperature becomes large, and it becomes impossible to obtain an appropriate correction amount.
As a result, highly accurate air-fuel ratio control cannot be performed stably, and exhaust characteristics and output characteristics deteriorate.

Such a problem also occurs when the electric wire inside the intake air temperature sensor is initially used in a state where the connection is not good, and when the connection is improved for some reason. Occurs. In this case, the amount of change in the output voltage output by the intake air temperature sensor becomes large, so that the error between the estimated intake air temperature and the actual intake air temperature becomes large.

The present invention has been made to solve the above problems, and an object thereof is to provide an abnormality diagnosis device for detecting an abnormality of an intake air temperature sensor for an internal combustion engine.

[0008]

In order to solve the above problems, the present invention provides an intake air temperature sensor for detecting the intake air temperature of intake air introduced into an internal combustion engine and an intake air temperature of intake air introduced into the internal combustion engine. A first determining means for determining a first operating condition that depends on the outside air temperature, a second determining means that determines a second operating condition for which the intake air temperature depends on the heat generation of the internal combustion engine, and the first determining means. The difference between the second detected intake air temperature detected by the intake air temperature sensor under the second operating condition and the first detected intake air temperature detected by the intake air temperature sensor under the first operating condition; It is composed of a calculating means for obtaining and an abnormality determining means for determining whether or not there is an abnormality in the intake air temperature sensor from the difference obtained by the calculating means and a predetermined determination value.

Therefore, according to the present invention, the intake air temperature sensor detects the intake air temperature of the intake air introduced into the internal combustion engine. The first determining means determines a first operating condition in which the intake air temperature of the intake air introduced into the internal combustion engine depends on the outside air temperature. Second
Determination means determines the second operating condition in which the intake air temperature depends on the heat generation of the internal combustion engine. The calculating means detects the second detected intake air temperature detected by the intake air temperature sensor under the second operating condition and the first detected intake air temperature detected by the intake air temperature sensor under the first operating condition. Find the difference from the temperature. The abnormality determining means determines whether or not there is an abnormality in the intake air temperature sensor based on the difference obtained by the calculating means and a predetermined determination value.

That is, the difference between the two detected intake air temperatures of the abnormal intake air temperature sensor has a deviation from the difference between the two detected intake air temperatures of the normal intake air temperature sensor. Therefore, if the determination value is determined in advance based on the difference between the normal intake air temperature sensors, the abnormality of the intake air temperature sensor is determined from the difference between the detected intake air temperatures of the actual intake air temperature sensor.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of a water-cooled gasoline engine system mounted on an automobile. This water-cooled gasoline engine system includes the diagnosis device for the intake air temperature sensor of the present invention.

The engine 1 comprises a cylinder block 2 and a cylinder head 3. A piston 5 is arranged in a cylinder bore 4 provided in the cylinder block 2, and a combustion chamber 6 is formed above the piston 5. Combustion chamber 6
Is equipped with a spark plug 7 and an intake port 8
And an exhaust port 9 are provided. An intake pipe 10 is connected to the intake port 8, and an intake valve 11 for opening and closing the intake pipe 10 is provided. An exhaust pipe 12 is connected to the exhaust port 9 and an exhaust valve 13 for opening and closing the exhaust pipe 12 is provided. The cylinder block 2 is provided with a cooling water jacket 14, and the cooling water jacket 14 is provided with a water temperature sensor 15 for measuring the cooling water temperature THW.

Intake pipe 10 connected to the intake port 8
From the upstream side toward the intake port 8, the air cleaner 16, the throttle valve 17, the surge tank 18
And a fuel injection injector 19 are sequentially provided. The air for air-fuel mixture (hereinafter, simply referred to as intake air) introduced into the air cleaner 16 is introduced into the injector 19 side with the pulsation smoothed by the surge tank 18 after the intake amount is controlled by the throttle valve 17. It Then, the fuel injected from the injector 19 is mixed and introduced into the intake port 8.

An intake air temperature sensor 20 for detecting the intake air temperature THA is provided downstream of the air cleaner 16, and an air flow meter 21 for detecting the intake air amount Q is provided further downstream thereof. A throttle sensor 22 for detecting a throttle opening TA and an idle position is arranged near the throttle valve 17.

An exhaust pipe 12 connected to the exhaust port 9
A catalytic converter 23 is connected to. An oxygen sensor 24 for detecting the oxygen concentration OX in the exhaust gas is arranged on the exhaust port 9 side of the catalytic converter 23.

A distributor 25 is arranged in the engine 1. The distributor 25 has
The igniter 26 is electrically connected. The distributor 25 applies the high voltage output from the igniter 26 to the spark plug 7. Distributor 2
5, a rotation speed sensor 27 for detecting the rotation speed NE of the engine is arranged.

Further, a vehicle speed sensor 28 for detecting the vehicle speed SPD is provided in the transmission (not shown). Further, the intake air temperature sensor 2 is provided on the instrument plate (not shown).
An indicator 29 for warning 0 abnormality is provided.

The water-cooled gasoline engine system performs various controls such as air-fuel ratio control, ignition timing control, idle speed control, etc. based on the detection signals from the respective sensors.
tronicControl Unit) 30.

Next, the electrical construction of the water-cooled gasoline engine system will be described. The water temperature sensor 15 outputs a detection signal corresponding to the cooling water temperature THW to the ECU 30.

The intake air temperature sensor 20 outputs a detection signal according to the intake air temperature THA to the ECU 30. The air flow meter 21 outputs a detection signal according to the intake air amount Q to the ECU 30. The throttle sensor 22 outputs a detection signal corresponding to the throttle opening TA to the ECU 30. Further, the throttle sensor 22 outputs an idle signal iDL when the throttle valve 17 is in the idle position.

The oxygen sensor 15 outputs a detection signal corresponding to the oxygen concentration Ox in the exhaust gas to the ECU 30. The rotation speed sensor 27 outputs a detection signal corresponding to the engine rotation speed NE to the ECU 30.

The vehicle speed sensor 28 outputs a detection signal corresponding to the vehicle speed SPD to the ECU 30. The indicator 29 is
It is turned on by a signal from the ECU 30. Next, the ECU 3
The configuration of 0 will be described in detail with reference to FIG.

The ECU 30 is a central processing unit (hereinafter C
PU) 41, read only memory (hereinafter referred to as ROM) 42, write / read memory (hereinafter referred to as RAM) 4
3, a backup write / read memory (hereinafter referred to as backup RAM) 44 and a timer counter 45. The ECU 30 also includes an external input device 46 and an external output device 47. These are connected to each other by a bus 48.

The ROM 42 stores respective control programs for ignition timing control, air-fuel ratio control, idle speed control and the like. The intake air temperature sensor diagnostic routine is stored in the ROM 42. RAM43
Temporarily stores the calculation result of the CPU 41. The backup RAM 44 stores the stored data. The timer counter 45 counts the count values C and D, respectively. Further, the timer counter 45 outputs an interrupt signal to the CPU 41 at a predetermined cycle.

In the external input device 46, the above-mentioned respective sensors, that is, the water temperature sensor 15, the intake air temperature sensor 20, the air flow meter 21, the throttle sensor 22, and the oxygen sensor 2 are provided.
4, a rotation speed sensor 27 and a vehicle speed sensor 28 are connected to each other.

On the other hand, the injector 19, the igniter 26, and the indicator 29 are connected to the external output device 47, respectively. The ECU 30 uses the engine 1
When the engine is started, the above-mentioned control programs control the injector 19 and the igniter 26 based on the detection signals from the sensors 15, 20 to 22, 24, 27 and 28, thereby controlling the ignition timing and the air-fuel ratio. Well-known controls such as control and idle control are performed.

Further, the ECU 30 repeatedly executes the intake air temperature sensor diagnostic processing by the intake air temperature sensor diagnostic routine in response to a periodic interrupt signal from the timer counter 45 while the engine 1 is operating.

That is, as the intake air temperature sensor diagnostic processing, EC
U30 has a water temperature THW of 80 which is detected by the water temperature sensor 20.
° Determine if it is above. The ECU 30 determines that the engine 1 is in the completely warmed-up state when the water temperature THW is 80 ° or more.

When it is determined that the engine 1 is in the completely warmed-up state, the ECU 30 causes the vehicle speed S detected by the vehicle speed sensor 28 to be detected.
It is determined whether or not the state in which PD is equal to or higher than a predetermined speed (for example, 80 km) and the rotation speed NE detected by the rotation speed sensor 27 is equal to or higher than a predetermined rotation speed (for example, 3000 rpm) continues for a predetermined time T1 or more. .

By the way, this vehicle speed SPD is 80 km / h.
Under the condition that the speed NE is 3000 rpm or less and continues for a predetermined time T1 or more (hereinafter referred to as the first operating condition), the actual intake air temperature at that time is generally almost equal to the outside air temperature, that is, the outside air temperature. Is known to depend on. That is, for example, 80 km / h or more and 3
When running for 1 hour at 000 rpm or less, if the outside air temperature is 10 ° C, the intake air temperature at that time is about 10 ° C.
If the outside air temperature is -16 ° C, the intake air temperature at that time is approximately -16 ° C.

In the present embodiment, the environmental temperature (outside air temperature) Td used by the automobile is, for example, Tdmin to Tdm.
Ax, and the range is used as one of the data for determining whether the intake air temperature sensor 20 is normal.

The ECU 30 determines that the engine 1 is completely warmed up, the vehicle speed SPD is 80 km / h or more and the rotation speed N is N.
When the state in which E is 3000 rpm or less continues for a predetermined time T1 or more (under the first operating condition), the intake air temperature THA detected by the intake air temperature sensor 20 at that time (hereinafter, in order to distinguish from the intake air temperature THA under other conditions) First detected intake air temperature THA
1) is stored in the RAM 43.

Further, the ECU 30 determines that the vehicle speed SPD detected by the vehicle speed sensor 28 is 0 and the throttle sensor 2
2 is for a predetermined time T when the idle signal iDL is output.
2 Determine whether or not to continue.

By the way, under the condition that the idling signal iDL is output at the vehicle speed SPD of 0 km / h for a predetermined time T2 or longer (hereinafter referred to as the second operating condition), the actual intake air temperature at that time is generally used. It is known that is substantially equal to the temperature Te of the engine 1 in the completely warmed-up steady state, that is, depends on the temperature Te of the engine 1. The engine temperature Te in the steady state changes relative to the outside air temperature Td at each time. That is, the steady-state engine temperature (that is, intake air temperature) Te is relatively low when the outside air temperature Td is low, and is relatively high when the outside air temperature Td is high.

In the present embodiment, the environmental temperature (outside air temperature) Td used by the automobile is, for example, Tdmin to Tdm.
Ax, and the engine temperature Te in the steady state changes relative to this between Temin and Temax. The range of the change is used as one of the data for determining whether the intake air temperature sensor 20 is normal.

When the ECU 30 is in the fully warmed state and the idling signal iDL is output at the vehicle speed SPD of 0 km / h for a predetermined time T2 or more (second
RAM), the intake air temperature THA detected by the intake air temperature sensor 20 at that time (hereinafter, referred to as a second detected intake air temperature THA2 to be distinguished from the intake air temperature THA under other conditions) is stored in the RAM.
It is supposed to be stored in 43.

Next, the ECU 30 controls the intake air temperature sensor 2
In order to determine whether 0 is normal, the difference between the first detected intake air temperature THA1 and the second detected intake air temperature THA2 stored in the RAM 43 is calculated, and the difference value ΔTHA (= TH
A2-THA1) is stored in the RAM 43. ECU 30
Compares the difference value ΔTHA with the lower limit value THAL and the upper limit value THAU which are preset determination values, and determines whether the intake air temperature sensor 20 is normal based on the comparison result. The lower limit THAL and the upper limit THAU are obtained as follows in the present embodiment.

That is, the above-mentioned vehicle speed SPD is 80 km /
It has been stated that the actual intake air temperature at that time is substantially equal to the outside air temperature under the first operating condition in which the state where the rotational speed NE is h or more and the rotational speed NE is 3000 rpm or less continues for the predetermined time T1 or more. If the environmental temperature (outside air temperature) Td used by the vehicle is Tdmin to Tdmax, the outside air temperature (intake air temperature)
Has also stated that it varies the range from Tdmin to Tdmax.

On the other hand, the above-mentioned vehicle speed SPD is 0 km / h.
In the second operating condition in which the idling signal iDL is output for a predetermined time T2 or longer, the actual intake air temperature at that time is almost equal to the temperature Te of the engine 1 in the steady state in the fully warmed state. It was It is known that the steady-state engine temperature Te changes relative to the outside air temperature. This steady-state engine temperature (that is, intake air temperature) is relatively low when the outside air temperature Td is low, and is relatively high when the outside air temperature Td is high. In addition, the ambient temperature (outside temperature) Td is set to Tdmin to Tdmax.
Then, it is also stated that the steady-state engine temperature Te changes correspondingly between Temin and Temax.

The lower limit value THAL is a value which is the difference (= Temin-Tdmax) between the lowest engine temperature Temin and the highest outside air temperature Tdmax. Further, the upper limit value THAU is a value which is a difference (= Temax-Tdmin) between the highest engine temperature Temax and the lowest outside air temperature Tdmin. The lower limit value THAL and the upper limit value THAU
Are stored in the ROM 42.

The ECU 30 determines that the intake air temperature sensor 20 is abnormal when the difference value ΔTHA becomes smaller than the lower limit value THAL. Further, the ECU 30 determines that the difference value ΔT
When HA becomes larger than the upper limit value THAU, it is determined that the intake air temperature sensor 20 is abnormal.

That is, when the detection characteristic of the intake air temperature sensor 20 deteriorates due to secular change, a difference value calculated from the first detected intake air temperature THA1 and the second detected intake air temperature THA2 obtained by the intake air temperature sensor 20. ΔTHA (= THA2-
It is known that the absolute value of THA1) becomes small.
Then, when the difference value ΔTHA becomes smaller than the lower limit value THAL, it is determined that the intake air temperature sensor 20 has deteriorated due to aging and has become abnormal due to the above reason.

Further, when the connection state of the electric wire inside the intake air temperature sensor 20 becomes good for some reason (initially, the intake air sensor 20 is set so that it is adjusted and set in a poor connection state and operates normally. It may have been done),
It is known that the difference value ΔTHA becomes large.
Then, when the difference value ΔTHA becomes larger than the upper limit value THAU, it is determined that the intake air temperature sensor 20 is abnormal due to the above reason.

In this embodiment, the water temperature sensor 1
5, rotation speed sensor 27, vehicle speed sensor 28 and ECU 30
The first determination means is configured by the throttle sensor 2
2, the vehicle speed sensor 28, and the ECU 30 constitute a second determining means. Further, the ECU 30 constitutes a calculation means and an abnormality determination means.

Next, the operation of the intake air temperature sensor abnormality diagnosis device configured as described above will be described with reference to the flow chart of the intake air temperature sensor diagnosis routine shown in FIG. First, E
The CU 30 resets the count values C and D of the timer counter 45 to 0 and clears the intake air temperature sensor abnormality flag FTHA by an initial routine that is executed immediately after the ignition is turned on.

While the engine 1 is operating, the ECU 30
In step 10, based on the detection signal from the water temperature sensor 15, it is determined whether the water temperature THW has reached 80 ° or more. The ECU 30 ends the intake air temperature sensor diagnosis process when the water temperature THW is less than 80 °. On the other hand, ECU
When the water temperature THW is 80 ° or more, the No. 30 judges that the engine 1 is in the fully warmed-up state, and the next step 11
Move on to.

In step 11, the ECU 30 determines that the vehicle speed SPD detected by the vehicle speed sensor 28 is 80 km or more and the rotational speed NE detected by the rotational speed sensor 27 is 3000.
Determine if it is below rpm. The ECU 30
When this condition is satisfied, the count value C is incremented in the next step 12. Then, the ECU 30
In the next step 13, it is determined whether the count value C has reached the count value CK. The ECU 30 displays the count value C
Is less than the count value CK, the intake air temperature sensor diagnosis routine is ended.

On the other hand, when the count value C is equal to the count value CK in step 13, the ECU 30 determines the vehicle speed S
PD is 80 km or more, and rotation speed NE is 300
The state of 0 rpm or less continued for a predetermined time T1,
That is, it is determined that the first operating condition has been reached, and the routine proceeds to the next Step 14.

In step 14, the ECU 30 stores the intake air temperature THA detected by the intake air temperature sensor 20, that is, the first detected intake air temperature THA1 in the RAM 43.
Further, the ECU 30 determines in step 11 that the vehicle speed S
PD is 80km or more and rotation speed NE is 3000rp
When it is not less than m, the process proceeds to step 15. Then, in step 15, the ECU 30 determines whether the vehicle speed SPD is 0 and the idle signal iDL is output. If this condition is not established, the ECU 30 ends the intake air temperature sensor diagnosis routine.

On the other hand, the ECU 30 determines in step 15 that the vehicle speed SPD is 0 and the idle signal iDL is
Is output, the process proceeds to the next step 16 to increment the count value D. And the ECU 30
Is the count value D in the next step 17,
Determine if K. When the count value D is less than the count value DK, the ECU 30 ends the intake air temperature sensor diagnosis routine.

On the other hand, when the count value D is equal to the count value DK in step 17, the ECU 30 determines the vehicle speed S
If PD is 0 and the idle signal iDL is output for a predetermined time T2, that is, if the second operating condition is satisfied, the routine proceeds to the next step 18.

In step 18, the ECU 30 stores in the RAM 43 the intake air temperature THA detected by the intake air temperature sensor 20, that is, the second detected intake air temperature THA2. Next, in step 19, the ECU 30 obtains a difference value ΔTHA (= THA2-THA1) from the first intake air temperature THA1 and the second intake air temperature THA2 stored in the RAM 43, and the difference value ΔTHA is not less than the lower limit value THAL. Yes, and
It is determined whether or not it is less than or equal to the upper limit value THAU. ECU
30, the difference value ΔTHA is not less than the lower limit value THAL,
If it is equal to or lower than the upper limit value THAU, it is judged that the intake air temperature sensor 20 is normal, and the intake air temperature abnormality diagnosis routine is ended.

On the other hand, the ECU 30 determines in step 19 that the intake air temperature sensor 20 is abnormal when the difference value ΔTHA is smaller than the lower limit value THAL or when the difference value ΔTHA is larger than the upper limit value THAU. Then, in step 20, the intake air temperature sensor abnormality flag FTHA is set to "1" and the intake air temperature sensor abnormality diagnosis processing is ended.

The ECU 30 controls the intake air temperature sensor abnormality flag F.
The indicator 29 is lit while THA is “1”. Therefore, the indicator 29 is turned on until the ignition is turned off, and the indicator 29 is turned on to warn of the abnormality of the intake air temperature sensor 20.

As described in detail above, according to the abnormality diagnosis device for the intake air temperature sensor of the present embodiment, the following effects can be obtained. (A) The ECU 30 determines, based on the water temperature THW detected by the water temperature sensor 15, that the engine 1 is in the fully warmed state, and then the vehicle speed SPD detected by the vehicle speed sensor 28.
Is greater than or equal to a predetermined value and the rotational speed NE detected by the rotational speed sensor 27 is less than or equal to the predetermined value for a predetermined time T1, that is, it is determined whether the first operating condition is satisfied. When it is determined that the first operating condition is satisfied, the ECU 30 stores the first detected intake air temperature THA1 which is the detected value of the intake air temperature sensor 20 at that time.

Further, the ECU 30 determines that the vehicle speed SPD detected by the vehicle speed sensor 28 is 0 and the throttle sensor 2
2 detects the idle signal iDL for a predetermined time T2
It is determined whether or not the operation is continued, that is, whether or not the second operating condition is satisfied. When the ECU 30 determines that the second operating condition is satisfied, the ECU 30 determines that the intake air temperature sensor 20
The second intake air temperature THA2 that is the detected value of is stored.

Then, the ECU 30 obtains a difference value ΔTHA (= THA2-THA1) which is a difference between the second intake air temperature THA2 and the first intake air temperature THA1, and the difference value ΔTHA is set to the lower limit value THAL and the upper limit value. It is determined whether the difference value ΔTHA of the normal intake air temperature sensor 20 set by THAU is within the range. This determines whether or not the intake air temperature sensor 20 is abnormal.

Therefore, the intake air temperature sensor 20 changes with time.
When the detection characteristic of is deteriorated, the difference value ΔTHA becomes the lower limit value TH.
Since it is smaller than AL, it is possible to detect an abnormality in the detection characteristic. If the connection state of the electric wire inside the intake air temperature sensor 20 becomes good for some reason, the difference value ΔTH
Since A becomes larger than the upper limit value THAU, it is possible to detect an abnormality in the detection characteristic.

(B) Under the first operating condition in which the actual intake air temperature is substantially equal to the outside air temperature Td, the engine 1 is completely warmed up, and the vehicle is driven for a predetermined time T1 at a predetermined rotational speed NE or lower and a predetermined vehicle speed SPD or higher. I set it when I did. A second operating condition in which the actual intake air temperature is substantially equal to the engine temperature Te is set when the vehicle is stopped and the idle state continues for a predetermined time T2. Therefore, since the operating condition is always achieved each time the vehicle is used, the intake air temperature sensor 20 can be reliably diagnosed.

(C) Since the intake air temperature sensor diagnosis routine is executed by the ECU 30 which performs air-fuel ratio control, ignition timing control and idle speed control, it is necessary to separately provide a control unit for executing the intake air temperature sensor diagnosis routine. Absent. As a result, since the control units are integrated and the number is reduced, the number of parts and the number of assembling steps can be reduced.

It should be noted that the present invention is not limited to the above-described embodiment, but can be configured as follows. (1) The first operating condition may be set immediately after the engine 1 is started from the cooling state, and the second operating condition may be set when the engine 1 is in a stopped state and is completely warmed up by idling. Also in this case, under the first operating condition, the actual intake air temperature becomes substantially equal to the outside air temperature Td, and under the second operating condition,
The actual intake air temperature becomes almost equal to the engine temperature Te. According to this configuration, the intake air temperature sensor 20 can be diagnosed before the vehicle actually travels, so that measures such as repair can be taken at an early stage.

(2) Instead of using the water temperature THW to determine that the engine 1 is completely warmed up, a predetermined vehicle speed S
The determination may be made when the condition for continuing the PD and the rotational speed NE for a predetermined time is satisfied.

(3) The calculated difference value ΔTHA may be determined based on only the lower limit value THAL. In this case, it is possible to diagnose deterioration of the detection characteristic due to the secular change of the intake air temperature sensor 20.

(4) Lower limit THAL and upper limit THA
U may be set in consideration of variations in the detected values of the individual intake air temperature sensors 20. That is, the first operating condition and the second operating condition are set within a range in which variations in the output value of the normal intake air temperature sensor 20 are added, and the lower limit value THAL and the upper limit value THAU are set based on each range. . In this case, abnormality diagnosis can be performed in consideration of variations in the detection characteristics of the individual intake air temperature sensors 20.

(5) Although the intake air temperature sensor diagnosis is performed by the ECU 30 that performs air-fuel ratio control, ignition timing control, and idle speed control, it may be performed by a separately provided control unit. In this case, the conventional ECU
It is possible to perform the abnormality diagnosis of the intake air temperature sensor 20 without redesigning.

Further, in the ECU 30, a C different from the CPU 41 is provided.
A PU may be provided and the CPU may perform abnormality diagnosis of the intake air temperature sensor. In this case, the external input circuit 46
Also, the external output circuit 47 can be shared.

(6) The present invention is not limited to the water-cooled gasoline engine system, but may be applied to an oil-cooled or air-cooled gasoline engine system. Further, it may be embodied in a diesel engine system or an LPG engine system of each cooling system.

The technical ideas other than the claims that can be grasped from the above embodiment will be described below together with their effects. (1) In the abnormality diagnosis device for an intake air temperature sensor for an internal combustion engine according to claim 1, the first determination means determines that the water temperature is equal to or higher than a preset water temperature THW, and then the vehicle speed SPD. Is equal to or higher than the preset vehicle speed SPD and the rotational speed NE is equal to or lower than the preset rotational speed NE, which continues for a preset time T1 or longer.
The second determination means determines that the water temperature has become equal to or higher than the preset water temperature THW, and the vehicle speed SPD is 0, and It is determined that the second operating state in which the idling state continues for a preset time T2 or longer is established.

According to this structure, the intake air temperature sensor can be reliably diagnosed every time the vehicle is used. (2) In the invention according to claim 1, the intake air temperature sensor abnormality diagnosis device is provided with an abnormality display means 29 for displaying that the intake air temperature sensor 20 is abnormal based on the determination result of the abnormality determination means. According to this configuration, the abnormality of the intake air temperature sensor 20 can be visually recognized.

(3) Claim 1 or supplementary notes (1), (2)
The intake air temperature sensor abnormality diagnosing device described in (1) is for a water-cooled internal combustion engine. With this configuration, it is possible to diagnose an abnormality in the intake air temperature sensor of the water-cooled internal combustion engine.

[0071]

According to the first aspect of the present invention, the abnormality of the intake air temperature sensor can be diagnosed when the internal combustion engine is operating.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a water-cooled gasoline engine system including an abnormality diagnosis device for an intake air temperature sensor.

FIG. 2 is a block diagram showing an electrical configuration.

FIG. 3 is a flowchart of an intake air temperature sensor abnormality diagnosis routine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 15 ... Water temperature sensor which comprises 1st determination means, 20 ... Intake temperature sensor, 22 ... Throttle sensor which comprises 2nd determination means, 27 ... 1st
A rotation speed sensor that constitutes the determination means, 28 ... A vehicle speed sensor that constitutes the first determination means and the second determination means, 30 ...
ECU as first determining means, second determining means and abnormality determining means, THA1 ... First detected intake air temperature, THA2 ...
Second detected intake air temperature, THAL ... Lower limit value as judgment value,
THAU ... Similarly, the upper limit.

Claims (1)

[Claims] 1. An intake air temperature sensor for detecting an intake air temperature of intake air introduced into an internal combustion engine, and a first operation condition in which an intake air temperature of intake air introduced into the internal combustion engine depends on an outside air temperature. Determining means for determining the second operating condition in which the intake air temperature depends on the heat generation of the internal combustion engine, and the second detecting means for detecting the second operating condition under the second operating condition. Calculation means for obtaining a difference between the detected intake air temperature of No. 2 and the first detected intake air temperature detected by the intake air temperature sensor under the first operating condition; An abnormality diagnosis device for an intake air temperature sensor for an internal combustion engine, comprising: abnormality determination means for determining whether or not the intake air temperature sensor is abnormal from the determined value.