JPH09170484A - Abnormality detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect abnormality even when a noise is superposed on a reference signal inputted from a camshaft sensor. SOLUTION: The input number of crank angle signals from a crankshaft sensor is counted in a crank angle signal counter CN, and also the input number of reference signals from a camshaft sensor is counted in a reference signal counter CG. The crank angle signal counter CN is compared with a predetermined judged value KCN (=12) at the input timing t1 of the reference signals except for timing that the reference signal counter CG is turned from 0 into 1, and abnormality is judged that is exists when CN ≠ KCN so as to set abnormal flag XDPOS=1. In this case, both crank angle signal counter CN and reference signal counter CG are cleared to be 0. After that, the reference signal counter CN is turned from 0 into 1 at timing t2 that the normal reference signal is inputted so that the foregoing abnormality judgement may not be executed so as retain XDPOS=1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine abnormality detecting apparatus for detecting an abnormality of a system for detecting the rotational state of an internal combustion engine (engine).

[0002]

2. Description of the Related Art Generally, in a 4-cycle engine, the entire stroke from intake to exhaust is completed by rotating the crankshaft twice.
In the meantime, the camshaft makes one revolution by two revolutions of the crankshaft. While the engine is rotating, the crankshaft sensor provided on the crankshaft side outputs a crank angle signal (pulse signal) at every predetermined crank angle, and the camshaft sensor provided on the camshaft side makes one revolution of the camshaft ( The reference signal is output once every two revolutions of the crankshaft, and the reference position of the crankshaft (for example, the top dead center of the specific cylinder) is detected by this reference signal. Furthermore, by counting the crank angle signal output from the crankshaft sensor with reference to this reference signal,
The crank angle is detected, the cylinder is discriminated based on the detected crank angle, and ignition timing control and fuel injection control are performed.

Therefore, even if either of the crank angle signal and the reference signal becomes abnormal, the correct crank angle cannot be detected and normal engine control cannot be performed. Therefore, when either the crank angle signal or the reference signal becomes abnormal, it is necessary to immediately detect the abnormality and take fail-safe measures, and various abnormality detection devices for that purpose have been proposed in the past. There is.

For example, in Japanese Patent Laid-Open No. 63-61754, the crank angle signals output from the output of the reference signal from the crankshaft sensor to the output of the next reference signal are counted, and An apparatus for determining whether or not there is an abnormality in a crank angle signal by comparing a count value with a predetermined determination value is disclosed. However, this device can detect only the abnormality of the crank angle signal on the assumption that the reference signal is correctly output, and cannot detect the abnormality of the reference signal at all.

Therefore, in order to solve this drawback, Japanese Patent Publication No. 63-45044 proposes a method of using a crank angle signal and a reference signal to mutually monitor the presence or absence of an abnormality between these two signals. There is. That is, in this device, if no crank angle signal is input before the next reference signal is input after one reference signal is input, it is determined that the crank angle signal is abnormal, and one reference signal input After that, if the next reference signal is not input before the count value of the crank angle signal reaches the predetermined number, it is determined that the reference signal is abnormal.

[0006]

However, in the above-described abnormality detecting device, the normal determination condition is that the next reference signal is input before the count value of the crank angle signal reaches a predetermined number after inputting one reference signal. , To determine whether the reference signal is normal or abnormal depending on whether or not this condition is satisfied, noise is mixed in the reference signal line, for example, and noise (false reference signal) is input before the next regular reference signal is input. Even if is input, the normality determination condition described above is satisfied, and the abnormality cannot be detected.

The present invention has been made in consideration of such circumstances, and therefore an object thereof is to detect an abnormality even when noise is mixed in the reference signal line, and to detect the abnormality. An object of the present invention is to provide an abnormality detection device for an internal combustion engine that can improve the performance.

[0008]

In order to achieve the above object, in an abnormality detecting device for an internal combustion engine according to claim 1 of the present invention, the number of times the crank angle signal is inputted from the crankshaft rotation detecting means is determined by the crank angle signal. Counting by the counting means, the first
The abnormality determining means compares the count value of the number of times of input of the crank angle signal by the crank angle signal counting means with a predetermined determination value at the timing of inputting the reference signal from the camshaft rotation detecting means, and when both do not match. It is determined that there is an abnormality. That is, noise is mixed in the reference signal line, for example, and noise (false reference signal) is input before the next regular reference signal is input.
Is input, the count value of the number of times the crank angle signal is input at the input timing does not match the predetermined determination value, and it is determined that there is an abnormality. Thereby, even if noise is mixed in the reference signal line, the abnormality can be detected, and the reliability of the abnormality detection can be improved.

In this case, the predetermined judgment value is defined by
As described above, the number of times the crank angle signal is input during two rotations of the crankshaft may be set. This has 2 crankshafts
This is because the camshaft makes one revolution during rotation and one reference signal is output from the camshaft rotation detecting means (in other words, the next regular reference signal is input after one reference signal is input. This is because the crankshaft rotates twice.

Further, according to a third aspect of the present invention, the count value of the number of times of inputting the crank angle signal by the crank angle signal counting means is compared with the predetermined determination value at the timing of inputting the crank angle signal from the crankshaft rotation detecting means. And a second abnormality determining means for determining that there is an abnormality when the count value is larger than the predetermined determination value. With this configuration, for example, when the reference signal is no longer input due to a failure of the camshaft rotation detecting means, a disconnection of the reference signal line, or the like, the count value of the number of times the crank angle signal counting means inputs the crank angle signal becomes It is determined that there is an abnormality at the time when the determination value is exceeded (that is, when the crankshaft has rotated two or more times since the previous reference signal was input), and an abnormality in which the reference signal is not input is also detected.

Further, in the present invention, the number of times the reference signal is input from the camshaft rotation detecting means is counted by the reference signal counting means, and the count value of the reference signal counting means is initialized in the initialization process when starting the internal combustion engine. Is reset to an initial value, and the reference signal is also applied when the second abnormality determining means determines that the count value of the number of times the crank angle signal is input by the crank angle signal counting means is larger than the predetermined determination value. The count value of the counting means is reset to the initial value. As a result, the count value of the number of times the crank angle signal is input at the next reference signal input timing is a value corresponding to two revolutions of the crankshaft, depending on whether the count value immediately before the reference signal counting means is the initial value. Can be determined.

Further, in the present invention, the reference signal counting means counts the number of input times of the reference signal with the initial value set to 0, and returns the counted value to 1 when the counted value exceeds 2.
Thus, while the normal reference signal is being input, the count value of the reference signal counting means is 1 → 2 → 1 → 2 → 1 → ....
It changes like

By utilizing the counting characteristic of the reference signal counting means, in the sixth abnormality determining means, the first abnormality determining means determines the reference signal counting means at the input timing of the reference signal from the camshaft rotation detecting means. The abnormality is determined at the input timing of the reference signal other than the timing at which the count value of becomes 0 to 1. That is, the position where the count value of the reference signal counting means is initialized to 0 is not the position where the normal reference signal is output, and therefore becomes 1 after the count value of the reference signal counting means is initialized to 0. Until then, it is unknown how much the crankshaft will rotate, and it is not possible to make an abnormality determination. Therefore, in claim 6, the abnormality determination is performed by the first abnormality determination means at the input timing of the reference signal other than the timing when the count value of the reference signal counting means changes from 0 to 1. Thereby, it is possible to determine the abnormality each time the crankshaft makes two revolutions.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, the schematic configuration of the entire engine control system will be described with reference to FIG. An air flow meter 14 is provided on the upstream side of an intake pipe 13 of an engine 11 which is an internal combustion engine, and an intake air amount measured by the air flow meter 14 is converted into a voltage signal by a potentiometer 15 and output. An intake air temperature sensor 16 for detecting the intake air temperature and a throttle valve 17 are provided downstream of the air flow meter 14. The injector 1 for injecting fuel is introduced into the intake manifold 12 for introducing the intake air that has passed through the throttle valve 17 into each cylinder.
9 are provided.

On the other hand, the exhaust pipe 21 of the engine 11 is provided with an air-fuel ratio sensor 22 for detecting the air-fuel ratio of exhaust gas and a three-way catalyst 23 for purifying exhaust gas. A water temperature sensor 25 that detects the cooling water temperature is attached to the water jacket 24 that cools the engine 11. Further, a high voltage secondary current of the ignition coil 28 is supplied to a distributor 27 that distributes a high voltage current to the spark plug 26 of each cylinder of the engine 11.

A signal rotor 32 for detecting a crank angle is attached to the crankshaft 31 of the engine 11, and an electromagnetic pickup type crankshaft sensor 33 (crankshaft rotation detecting means) is opposed to the outer periphery of the signal rotor 32. It is arranged to. The signal rotor 32
Protrusions 32a, which are the same in number as the number of cylinders (six cylinders in this embodiment), are formed on the outer circumference of the crankshaft 31 at equal intervals.
With the rotation of the crankshaft sensor 33, the projection 32a is detected by a detection coil (not shown) in the crankshaft sensor 33 every time the projection 32a faces the crankshaft sensor 33.
Outputs a pulse signal as a crank angle signal.

A cam shaft 35 is connected to the crank shaft 31 via a timing belt 34, and the crank shaft 3
The cam shaft 35 makes one rotation in two rotations of one. A signal rotor 36 for detecting a reference position is attached to the camshaft 35, and an electromagnetic pickup type camshaft sensor 37 (camshaft rotation detecting means) is arranged so as to face the outer periphery of the signal rotor 36. ing. A single protrusion 36a is formed on the outer periphery of the signal rotor 36, and the protrusion 36a faces the cam shaft sensor 37 every time the cam shaft 35 makes one rotation, and is protruded by a detection coil (not shown) therein. 36a is detected, and a pulse signal is output from the camshaft sensor 37 as a reference signal.

Output signals from the various sensors described above are read into an electronic control circuit (hereinafter abbreviated as "ECU") 38 through an input / output circuit 39. The ECU 38 is mainly composed of a microcomputer, and includes a CPU 40 and an R
The OM 41, the RAM 42, the backup RAM 43, the timer 44, etc. are provided, and the cam shaft sensor 37 to the cam shaft 35
The crankshaft sensor detects the reference position of the crankshaft 31 (for example, the top dead center of a specific cylinder) based on the reference signal output once per rotation (two rotations of the crankshaft 31), and uses this as a reference. By counting the crank angle signal from 33, the crank angle is detected, the cylinder is discriminated by the crank angle signal, and the ignition timing control and the fuel injection control are performed.

By executing the abnormality detection routine shown in FIG. 2, the ECU 38 detects abnormality of the crank angle signal from the crankshaft sensor 33 and abnormality of the reference signal from the camshaft sensor 37. This abnormality detection routine is executed as follows every predetermined time (for example, every 5 ms).

First, in step 101, it is judged whether or not it is the initialization processing performed immediately after the ignition switch (not shown) is turned on. If it is the initialization processing, the routine proceeds to step 102, where the crank angle signal is output. The counter CN and the reference signal counter CG are both initialized and set to the initial value (0), and this routine ends. Here, the crank counter CN is a counter that counts the crank angle signals input from the crankshaft sensor 33, and corresponds to the crank angle signal counting means in the claims. Further, the cam counter CG is a counter that counts the reference signal input from the cam shaft sensor 37, and corresponds to the reference signal counting means in the claims.

On the other hand, after the initialization processing, every time this routine is executed, a "No" determination is made in step 101, and in steps 103 and 113, the reference signal from the camshaft sensor 37 and the crankshaft sensor 33 are output. It is determined whether or not any one of the crank angle signals is input. If neither the reference signal nor the crank angle signal has been input, this routine is terminated without performing the subsequent processing.

On the other hand, when the crank angle signal is input from the crankshaft sensor 33, step 103 → 1
The process proceeds in the order of 13 → 114, and it is determined whether or not it is the stall determination. If it is the stall determination, the process proceeds to step 102 as in the initialization process described above, and the crank angle signal counter CN and the reference The signal counter CG is initialized together and set to the initial value (0), and this routine is finished. If it is not the stall determination, the routine proceeds from step 114 to step 115, the crank angle signal counter CN is incremented by 1, and in the following step 116, it is determined whether or not the crank angle signal counter CN has overflowed, that is, the upper limit value (eg, 255) It is determined whether or not the above has been reached, and if overflow occurs, the routine proceeds to step 117, where the crank angle signal counter CN is fixed at the upper limit value, and step 1
Proceed to 18.

In step 118, the crank angle signal counter CN is compared with a predetermined determination value KCN stored in the ROM 41 in advance to determine whether or not the crank angle signal counter CN exceeds the predetermined determination value KCN. Here, the determination value KCN is the number of times the normal crank angle signal output from the crankshaft sensor 33 is input while the crankshaft 31 makes two rotations (the camshaft 35 makes one rotation), and in this embodiment, KCN = Twelve. Then, if CN ≦ KCN, it is determined to be “No” in step 118, it is determined that the system is normal, and this routine is ended.

If CN> KCN, it means that the reference signal to be input by that time has not been input. In this case, it is estimated that some abnormality such as a failure of the camshaft sensor 37 or disconnection of the reference signal line has occurred and the reference signal is no longer input, and the routine proceeds to step 119, where the abnormality flag XDPOS is abnormal. Is set to "1" indicating that the reference signal counter C
The G is initialized to the initial value (0), and this routine ends. The processing of steps 118 and 119 functions as the second abnormality determining means in the claims.

On the other hand, when the reference signal is input from the camshaft sensor 37, steps 103 to 104 are performed.
And the reference signal counter CG is incremented by 1,
In the following step 105, it is determined whether or not the reference signal counter CG has exceeded the upper limit value “2”. If CG> 2, the process proceeds to step 106 and the reference signal counter CG is set to 1
Return to Thus, while the normal reference signal is being input, the count value of the reference signal counter CG is 1 → 2 → 1 →
It changes in the order of 2 → 1 → …….

Then, in the next step 107, it is judged whether or not it is the timing when the reference signal counter CG changes from 0 (initial value) to 1, and if it is the timing from 0 to 1, the process proceeds to step 108, Crank angle signal counter C
N is compared with the predetermined determination value KCN (12 in this embodiment) to determine whether CN = KCN. Here, if CN = KCN, it is determined that the system is normal, the process proceeds to step 111, the abnormality flag XDPOS is cleared, XDPOS = 0 (no abnormality), and in the subsequent step 112, the crank angle signal counter The CN is initialized to the initial value (0), and this routine is finished. If it is determined in step 108 that CN ≠ KCN, the abnormality flag XDPOS is not cleared, and the process proceeds to step 112, where the crank angle signal counter CN is initialized and this routine ends.

On the other hand, if it is determined to be "No" in step 107, that is, if it is determined to be the input timing of the reference signal other than the timing when the reference signal counter CG changes from 0 to 1, the process proceeds to step 109, The crank angle signal counter CN is compared with the predetermined determination value KCN to determine whether CN = KCN. Where C
If N = KCN, the number of crank angle signal inputs from the input of one reference signal to the input of the next reference signal is two revolutions of the crankshaft 31 (one revolution of the camshaft 35).
Means that the number of signals of the minute matches. In this case,
When it is determined that the system is normal, the process proceeds to step 111, the abnormality flag XDPOS is cleared, and XDPOS = 0
As (no abnormality), the process proceeds to step 112.

If in step 109, CN ≠ KC
If N is determined, the number of crank angle signal inputs from the input of one reference signal to the input of the next reference signal is the number of signals of two rotations of the crankshaft 31 (one rotation of the camshaft 35). Means disagreement with. In such a state, for example, noise mixed in the reference signal line (false reference signal) is input before the next regular reference signal is input, or noise mixed in the crank angle signal line is cranked. It occurs when it is counted as an angle signal. In this case, it is determined that there is an abnormality and step 11
In step 112, the abnormality flag XDPOS is set to "1" indicating that there is an abnormality, and in the subsequent step 112, the crank angle signal counter CN is initialized and this routine is ended.
The processing of steps 109 to 111 functions as the first abnormality determining means in the claims.

The process of the abnormality detection routine of FIG. 2 described above will be specifically described with reference to the time charts of FIGS. 3 to 5.

(1) Normal Case FIG. 3 is a time chart showing the behavior in a normal case after the ignition switch is turned on. In the example of FIG. 3,
Immediately after the ignition switch is turned on, initialization processing is first performed, and both the crank angle signal counter CN and the reference signal counter CG are initialized and set to an initial value (0). After that, each time the crank angle signal is input from the crankshaft sensor 33 when the engine 11 is started, the crank angle signal counter CN is incremented by one.
Then, at time t2, when the first reference signal is input from the camshaft sensor 37, the reference signal counter CG is incremented by 1 and CG = 1, but the reference signal counter C
At the timing when G changes from 0 to 1, the abnormality determination is not performed, and the abnormality flag XDPOS = 0 (no abnormality) is maintained. Then, every time a reference signal is input from the camshaft sensor 37, the crank angle signal counter CN is initialized and returned to zero.

Then, the reference signal counter CG is changed from 0 to 1
At the input timing of the reference signal other than the timing, the crank angle signal counter CN sets the predetermined determination value KCN.
(Eg 12) and if CN = KCN then 1
This means that the number of input of the crank angle signal from the input of one reference signal to the input of the next reference signal is equal to the number of signals of two rotations of the crankshaft 31 (one rotation of the camshaft 35). . In this case, the system is determined to be normal, and the abnormality flag XDPOS = 0 (no abnormality) is maintained.

Also, every time a crank angle signal is input from the crankshaft sensor 33, a crank angle signal counter CN
Has exceeded a predetermined determination value KCN (for example, 12). In the example of FIG. 3, the crank angle signal counter C
Every time N reaches a predetermined judgment value KCN, a reference signal is input and the crank angle signal counter CN is initialized to 0. Therefore, the crank angle signal counter CN does not exceed the judgment value KCN, and the system does not operate normally. It is determined that there is, and the abnormality flag XDPOS = 0 (no abnormality) is maintained.

When the reference signal counter CG which is counted up each time the reference signal is input exceeds the upper limit value of 2, the reference signal counter CG is returned to 1. As a result, the reference signal counter CG changes in the order of 1 → 2 → 1 → 2 → 1 → ... While the normal reference signal is input.

(2) When noise is mixed in the reference signal line FIG. 4 is a time chart showing the behavior when noise is mixed in the reference signal line. In the example of FIG. 4, noise is mixed into the reference signal line at time t1, and at that time, the crank angle signal counter CN outputs a predetermined judgment value KCN (for example, 1).
Although it is compared with 2), since CN ≠ KCN, it is determined that there is an abnormality. In this case, the abnormality flag XDPOS
Is set to "1" indicating that there is an abnormality, and the crank angle signal counter CN and the reference signal counter CG are both initialized and returned to the initial value (0).

After that, at time t2, the next normal reference signal is input. At this timing, the reference signal counter C
Since G is the timing from 0 to 1, the abnormality determination is not performed, and the abnormality flag XDPOS is maintained at "1" indicating that there is an abnormality. Then, every time a reference signal is input from the camshaft sensor 37, the crank angle signal counter CN is initialized and returned to zero.

After that, when there is no noise input and the next regular reference signal is input at time t3, this timing is the input timing of the reference signal other than the timing when the reference signal counter CG changes from 0 to 1. Therefore, the abnormality determination is performed by comparing the crank angle signal counter CN and the predetermined determination value KCN. In this case, since CN = KCN, it is determined to be normal, and the abnormality flag XDPOS is reset to "0" indicating no abnormality.

(3) When no reference signal is input FIG. 5 is a time chart showing the behavior when no reference signal is input from the camshaft sensor 37. Even when the reference signal is not input, every time the crank angle signal is input from the crankshaft sensor 33, the crank angle signal counter CN
Has exceeded a predetermined determination value KCN (for example, 12). After the time t1, the crank angle signal counter CN exceeds the predetermined determination value KCN, so it is determined that there is an abnormality, and the abnormality flag XDPOS is set to "1" indicating that there is an abnormality. After that, the crank angle signal counter CN is incremented by 1 each time a crank angle signal is input from the crankshaft sensor 33, and fixed at the upper limit value at time t2 when the count value reaches the upper limit value (for example, 255). To be done.

In this example, the upper limit value of the crank angle signal counter CN is set to 255, but the predetermined judgment value KC
A value exceeding N (13 or more in this embodiment) can be freely set. Increasing the upper limit of the crank angle signal counter CN has an advantage that the elapsed time after the abnormality detection can be determined from the count value of the crank angle signal counter CN.

(4) When the crank angle signal is missing or when the crank angle signal is not input This example is not shown, but is determined to be abnormal as described above. That is, in this case, since the count value of the crank angle signal counter CN becomes smaller than the count value in the normal case, the crank angle signal counter CN is set to a predetermined determination value KCN (for example, 1 at the input timing of the reference signal).
When compared with 2), CN ≠ KCN, and it is determined that there is an abnormality.

(5) When noise is mixed in the crank angle signal line This example, though not shown, is determined to be abnormal as in the above. That is, in this case, since the count value of the crank angle signal counter CN is larger than the count value in the normal case, the crank angle signal counter CN is set to a predetermined determination value KCN (for example, 12) at the input timing of the reference signal.
When compared with, CN ≠ KCN, and it is determined that there is an abnormality.

By the way, the above-mentioned Japanese Patent Publication No. 63-4504.
According to the technique of Japanese Patent No. 4, it is impossible to detect the abnormality when noise is mixed in the signal line.

In the above example, the six-cylinder engine is 60
Although the crank angle signal is input for each ° C A, for example, the crank angle signal may be input for each 30 ° C (in this case, the determination value KCN = 24).

In addition, the present invention can be applied to engines having various numbers of cylinders, and the input pulse interval of the crank angle signal may be appropriately changed according to the number of cylinders. Furthermore, the present invention is not limited to a gasoline engine, but can be applied to various internal combustion engines such as a diesel engine and a gas engine.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing flow of an abnormality detection routine.

FIG. 3 is a time chart showing the behavior in a normal case after the ignition switch is turned on.

FIG. 4 is a time chart showing the behavior when noise is mixed in the reference signal line.

FIG. 5 is a time chart showing the behavior when a reference signal is not input from the camshaft sensor.

[Explanation of symbols]

11 ... Engine (internal combustion engine), 31 ... Crank shaft, 32
... signal rotor for detecting crank angle, 33 ... crankshaft sensor (crankshaft rotation detecting means), 34 ... timing belt, 35 ... camshaft, 36 ... signal rotor for detecting reference position, 37 ... camshaft sensor (camshaft) Rotation detecting means) 38 ... Electronic control circuit (crank angle signal counting means,
Reference signal counting means, first abnormality determining means, second abnormality determining means).

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Satoshi Koike 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd. (72) Inventor Nobuo Sakurada 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Stock Company (72) Inventor Kazuo Tanaka 4-1-2 Hiranocho Chuo-ku, Osaka City Osaka Gas Co., Ltd. (72) Inventor Keihito Taniguchi 19-18 Sakuradacho, Atsuta-ku, Nagoya City Toho Gas Co., Ltd.

Claims (6)

[Claims] 1. A crankshaft rotation detecting means for outputting a plurality of crank angle signals per revolution of a crankshaft of an internal combustion engine, and a camshaft which rotates at a rate of once every two revolutions of the crankshaft, A camshaft rotation detecting means for outputting one reference signal per one rotation of the camshaft, and the number of times the crank angle signal is inputted from the crankshaft rotation detecting means, and the counted value is counted by the camshaft rotation detecting means. Crank angle signal counting means which is reset each time a reference signal is input from the cam shaft rotation detecting means An abnormality detecting device for an internal combustion engine, comprising: a first abnormality determining means that determines that there is an abnormality when the two values do not match each other. 2. The abnormality detection device for an internal combustion engine according to claim 1, wherein the predetermined determination value is set to the number of times the crank angle signal is input during two revolutions of the crankshaft. . 3. The count value of the number of times the crank angle signal is input by the crank angle signal counting means at the timing of inputting the crank angle signal from the crankshaft rotation detecting means is compared with the predetermined determination value to obtain the count value. The abnormality detection device for an internal combustion engine according to claim 1 or 2, further comprising a second abnormality determination unit that determines that there is an abnormality when the value is larger than the predetermined determination value. 4. A reference signal counting means for counting the number of times of inputting a reference signal from the camshaft rotation detecting means is provided, and the count value of the reference signal counting means is initialized by an initialization process at the time of starting the internal combustion engine. When the second abnormality determining means determines that the count value of the number of times the crank angle signal is input by the crank angle signal counting means is larger than the predetermined determination value, the reference signal counting means The abnormality detection device for an internal combustion engine according to claim 3, wherein the count value is reset to an initial value. 5. The reference signal counting means counts the number of input times of the reference signal with the initial value set to 0, and returns the count value to 1 when the count value exceeds 2. An abnormality detection device for an internal combustion engine according to item 1. 6. The first abnormality determining means includes a timing of inputting a reference signal from the camshaft rotation detecting means,
The abnormality detection device for an internal combustion engine according to claim 5, wherein the abnormality determination is performed at an input timing of a reference signal other than a timing when the count value of the reference signal counting means becomes 0 to 1.