JPH09217646A - Crank angle sensor signal period measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a period measured erroneously due to noise and signal omission at the time of providing engine rotation information by measuring a period of a crank angle signal. SOLUTION: A crank angle sensor transmits a crank angle signal for each specified crank angle synchronously with rotation of an engine. A timer measures a period of the crank angle signal. Thereafter, (n) pieces (but n=3) of the past newest cycles measured by the aforementioned timer are memorized by a period memory means. Thereafter, a central value at the time when (n) pieces of period memory values are aligned in a size order is computed, and it is provided an engine rotation information. However, a change proportion of the measured periods is computed by a change proportion computing means, and only when the change proportion is higher than a specified threshold value, the aforementioned central value is provided as the engine rotation information, and except it, the newest values are provided as the engine rotation information. An average value can be used in place of the central value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crank angle sensor signal cycle measuring device for measuring the cycle of a crank angle signal from a crank angle sensor mounted on a vehicle engine and providing it as engine rotation information.

[0002]

2. Description of the Related Art A conventional crank angle sensor signal cycle measuring device is provided with a crank angle sensor for generating a crank angle signal for each predetermined crank angle in synchronization with engine rotation, and a timer for measuring the cycle of the crank angle signal. Then, the cycle of the crank angle signal is provided as engine rotation information, and this information is used for calculation of the engine rotation speed and time control between crank angle signals.

[0003]

However, in the conventional crank angle signal cycle measuring device, the crank angle sensor is used to provide a signal generating protrusion or a signal generating plate provided on the signal disk plate which rotates in synchronization with the engine rotation. The crank angle signal is generated magnetically or optically by detecting slits, etc., but due to noise on the output line and signal dropout, the correct cycle of the crank angle signal required as engine rotation information. May not be measured,
There is a problem that control may be performed based on an incorrect cycle.

Specifically, the crank angle signal (1) shown in FIG.
When noise is generated as in the case of (3), the measurement cycle is shortened, and by using this value for control, malfunction occurs. When the signal is omitted as in the case of the crank angle signal (2) in FIG. 6, the measurement cycle becomes long, causing a malfunction like the above. In addition, the control unit for engine control is RA
After M is cleared and the operation is started, after the engine key is turned off, a self-shutoff period is provided to secure the control unit power supply for a predetermined time for controlling the cooling system and the like. Since the control unit power is automatically turned off after the end of, the control unit power will never be turned off if the engine key is turned on and restarted before the self-shutoff period ends. R
The AM is not cleared, and the engine may be slightly reversed in the extremely low rotation speed range when the engine is stopped, so normal operation cannot be guaranteed.

Therefore, extremely low rotation range (200 to less than 300 rpm)
It is considered that the RAM is forcibly cleared when the engine is turned on and restarted during the self-shutoff period. However, in order to detect that it is in the relevant rotation range, As information, it is required to correctly measure the cycle of the crank angle signal. The present invention has been made in view of such conventional problems, and an object thereof is to provide a crank angle sensor signal period measuring device with a fail-safe function.

[0006]

Therefore, in the invention according to claim 1, as shown in FIG. 1, a crank angle sensor for generating a crank angle signal for each predetermined crank angle in synchronization with the engine rotation, and a crank angle sensor. In a crank angle sensor signal cycle measuring device, which is provided with a timer for measuring the cycle of an angle signal and provides the cycle of a crank angle signal as engine rotation information, the cycle measured by the timer is the latest n cycles from the latest cycle. (However, n ≧ 3) cycle storing means for storing,
A median value calculating means for calculating a median value when n cycle storage values are arranged in descending order is provided, and the median value is provided as engine rotation information.

That is, instead of providing the measured period as it is, a median value of the past n period stored values is calculated and provided, so that the wrong measured value is eliminated. In the invention according to claim 2, as also shown in FIG. 1, a change rate calculating means for calculating a change rate of the latest value of the cycle measured by the timer from the previous value and a predetermined change rate. A switching means is provided which, when compared with the threshold value, provides the median value as engine rotation information only when the rate of change is larger than a predetermined threshold value, and otherwise provides the latest value as engine rotation information. It is characterized by

That is, only when the rate of change is large, it is considered that the wrong measured value may be included, and the process of calculating the median value is performed. In other cases, the measured period is provided as it is. In the invention according to claim 3, an average value calculating means for calculating an average value of n periodic memory values is provided in place of the median value calculating means, and the average value is used in place of the median value. Characterize.

By using the median value, it is possible to completely eliminate erroneous measurement values, but even if an average value is used instead of the median value, the influence of erroneous measurement values can be reduced, so that it is substantially the same. You can expect a great effect.

[0010]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of an embodiment of the present invention.
The crank angle sensor 1 magnetically or optically detects protrusions or slits for signal generation provided on a signal disk plate that rotates in synchronization with engine rotation, and a predetermined crank angle (for example, 10 ° CA). A pulse-shaped crank angle signal is generated every time.

A crank angle signal from the crank angle sensor 1 is input to an engine control unit 2 built in a microcomputer. The control unit 2 measures the cycle of the crank angle signal and processes it to obtain engine rotation information. Furthermore, the control unit 2
Based on this information, calculates the engine speed and controls the time between crank angle signals, and issues control outputs to various actuators.

The control unit 2 has a throttle opening information (TVO) detected by a throttle sensor and a G value for measuring and processing the cycle of the crank angle signal.
Acceleration information (G) detected by the sensor is also input. The control unit 2 measures and processes the cycle of the crank angle signal by a timer processing routine (FIG. 3) and a cycle measurement processing routine (FIG. 4 or 5).

FIG. 3 is a flowchart of the timer processing routine. This timer processing routine has a predetermined time interval (Δ
It is executed every t) and the timer TM is incremented by the time interval (TM = TM + Δt). FIG. 4 is a flowchart of the cycle measurement processing routine (first embodiment). This cycle measurement processing routine is executed in synchronization with the generation of the crank angle signal.

In step 1 (denoted as S1 in the figure; the same applies hereinafter), the value of the timer TM is read to measure the cycle T ₀ = TM of the crank angle signal. Step 2
Then, in order to start the measurement of the next cycle, the timer TM is cleared (TM = 0). In step 3, the change rate (absolute value) ΔT ₀ = | T ₀ −T ₋₁ | of the latest value T ₀ of the measured cycle from the previous value T ₋₁ is calculated. This portion corresponds to the change rate calculation means.

In step 4, throttle opening information (T
The threshold value x is calculated by referring to a table or a map from VO), acceleration information (G), and the like. In step 5, the change rate ΔT ₀ is compared with the threshold value x. As a result of the comparison, if the change rate ΔT ₀ ≦ threshold value x, step 6
Then, the cycle T output as engine rotation information is set to the latest measured value T ₀ (T = T ₀ ). This portion corresponds to the switching means.

When the change rate ΔT ₀ > the threshold value x, the process proceeds to step 7. In step 7, the cycle storage value T ₀ , which stores the measured three cycles from the latest three cycles,
T _-1, reorders T _-2 of the size order, the maximum value T _H, the middle value (median) T _M, the minimum value and T _L. As a result, the median value T _M when arranged in descending order is calculated.
This part corresponds to the median calculating means.

Then, in step 8, the period T output as the engine rotation information is set to the median value T _M when arranged in descending order (T = T _M ). Then, if necessary, in step 9, T ₀ = T. After this, in step 10, the measured three cycles from the latest one are stored, so that T _-2 = T _-1 , T _-1 = T ₀ is processed. This part corresponds to the cycle storage means.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flow chart of the cycle measurement processing routine (second embodiment). Here, instead of the median value calculating means, an average value calculating means for calculating an average value of n periodic memory values is provided, and the average value is used instead of the median value. Therefore, only steps 7 and 8 are different.

In step 7, the measured period is the period stored value T ₀ , which is stored for the past three from the latest one.
The average value Tave of T ₋₁ and T ₋₂ is calculated by the following formula. Tave = (T ₀ + T _-1 + T _-2 ) / 3 This portion corresponds to the average value calculating means. Then, in step 8, the cycle T output as the engine rotation information is set to the average value Tave (T = Tave).

As described above, even if the average value is used instead of the median value, the influence of an erroneous measurement value can be reduced, so that substantially the same effect can be expected. In the above embodiment, the measured period is stored from the latest three in the past, but any number n may be stored as long as it is three or more. Further, when calculating the median value, it is more convenient to use an odd number, but even if it is an even number, the average value of the two central values may be taken.

[0021]

As described above, according to the invention of claim 1, the measured period is not provided as it is, but the median value of the past n stored period values is calculated, and this is calculated. By providing the information, it is possible to eliminate an erroneous measurement value and optimize engine rotation information.

According to the second aspect of the present invention, it is assumed that the wrong measured value may be included only when the change rate is large, and the process of calculating the median value is performed. In other cases, the measured cycle is left as it is. By providing the information, it is possible to obtain the effect that the latest information can be provided as much as possible under normal circumstances. According to the invention of claim 3, instead of the median,
By using the average value, it is possible to reduce the influence of wrong measurement values, and it is possible to expect substantially the same effect.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram of an embodiment of the present invention.

FIG. 3 is a flowchart of a timer processing routine.

FIG. 4 is a flowchart of a cycle measurement processing routine (first embodiment).

FIG. 5 is a flowchart of a cycle measurement processing routine (second embodiment).

FIG. 6 is a diagram showing a conventional problem.

[Explanation of symbols]

 1 Crank angle sensor 2 Control unit

Claims (3)

[Claims] 1. A crank angle sensor for generating a crank angle signal for each predetermined crank angle in synchronism with engine rotation, and a timer for measuring a cycle of the crank angle signal. In the crank angle sensor signal cycle measuring device provided as above, the cycle measured by the timer is stored from the latest n cycles (where n ≧ 3) from the latest cycle, and n cycle memory values are stored. A crank angle sensor signal cycle measuring device, comprising: a median value calculating means for calculating a median value when arranged in order, and providing the median value as engine rotation information. 2. A change rate calculating means for calculating a change rate of the latest value of the period measured by the timer from a previous value, and the change rate is compared with a predetermined threshold value to obtain a predetermined change rate. 2. The crank according to claim 1, further comprising switching means for providing the median value as engine rotation information only when the threshold value is larger than the threshold value and for providing the latest value as engine rotation information otherwise. Angle sensor signal cycle measuring device. 3. A mean value calculating means for calculating an average value of n periodic memory values is provided in place of the median value calculating means, and the mean value is used in place of the median value. The crank angle sensor signal cycle measuring device according to claim 1 or 2.