JPH07286805A - Rotational position detector - Google Patents

Abstract

PURPOSE:To detect the reference position and angle of a rotating body based on the output of one sensor which detects the angle information of the rotating body. CONSTITUTION:The rotational position detector is provided with an electromagnetic pickup 2 which obtains information from a rotating body 1 formed out of teeth 1a arranged at regular intervals and a part 1b from which one of the teeth 1a is chipped off and a signal processing means 3 which shapes the waveform of signals obtained from the pickup 2 into a square wave, and a counter (timer) 4 which measures the period between two pieces of angle information. In addition, the detector is provided with a storing means 5 which stores measured periods and predicted period values, a predicted period value calculating means 6 which predicts the next period based on the past period stored in the storing means 5, and a comparing means 7 which compares an actually measured period with a predicted period value. Moreover, the detector is also provided with a reference position discriminating means 8 which discriminates whether or not the measured period value is a reference position based on the compared results of the comparing means 7 and a reference position signal outputting means 9 which outputs a reference position signal when the reference position is discriminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a rotational position, and more particularly to a control device for an internal combustion engine or the like, which is suitable for detecting a rotational position for ignition control and fuel injection control.

[0002]

2. Description of the Related Art As a method of providing reference position markings between angular markings arranged at equal intervals around a rotating body, the angle markings are usually formed as teeth, in which at least one reference marking is missing. Formed as. Japanese Patent Application Laid-Open No. 61-502557 can be cited as a conventional technique for detecting the reference position by using the missing angle marking on the rotating body. In this conventional technique, at least four pieces of continuous information used to represent the cycle of an angle are measured and stored, and three difference values are obtained from these four pieces of information, and an intermediate difference between the three difference values is obtained. It is an angular position detection device that compares a value with a difference value before and after and identifies a reference position based on the result. In other conventional techniques, when the cycle of detected angle information exceeds a predetermined threshold value, it is determined as a reference position.

[0003]

However, in the above-mentioned prior art, at least four pieces of information used for detecting the reference position of the rotating body are required, and these pieces of information are required in the rotating position detecting device. However, there is a problem that the load imposed by the memory and calculation of is increased as the rotation speed is increased.

[0004]

According to the present invention, the number of pieces of information used for detecting the reference position of the rotating body is at least 2.
Let's do it. Further, a means for predicting the next information based on these two pieces of information and identifying the reference position by comparing with the information actually measured is used.

[0005]

By the above means, the reference position can be identified based on a small amount of information.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system block diagram of the present invention.

Reference numeral 1 is a rotor, 1a is teeth arranged at equal intervals, and 1b is a missing tooth.

Reference numeral 2 is an electromagnetic pickup for obtaining information from the teeth 1a arranged at equal intervals.

Reference numeral 3 is a signal processing means, which is a waveform shaping circuit for shaping the signal obtained from the electromagnetic pickup 2 into a rectangular wave.

Reference numeral 4 is a counter (timer) for measuring the cycle between angle information.

Reference numeral 5 is a storage means for storing the measured period and the obtained period predicted value.

Reference numeral 6 is a cycle prediction value calculation means for predicting the next cycle based on the past cycle stored in the storage means.

Reference numeral 7 is a comparison means for comparing the measured actual cycle with the predicted cycle.

Reference numeral 8 is a reference position judging means for judging whether or not the measured period value is the reference position based on the comparison result of the comparing means 7.

Reference numeral 9 is a reference position signal output means for outputting a reference position signal when the reference position is identified.

Next, the operation of the system shown in FIG. 1 will be described with reference to the signal diagram shown in FIG.

(A) shows teeth arranged on the circumference of the rotating body as an angle information source. (B) shows the output waveform of the above-mentioned electromagnetic pickup, θ is the angle between the teeth arranged at equal intervals, and kθ is the angle between the teeth of the missing part.
This output waveform is shaped into a rectangular wave as shown in (c) through a waveform shaping circuit. Further, after storing the counter state at the rising edge of the rectangular wave (c), the counter is reset and restarted. The waveform of the counter is shown in (d), and the stored counter value represents the period between teeth. In the present invention, at least two cycle values are stored, and the next cycle value is predicted based on these values. The method of predicting the cycle value will be described below.

A flow chart of the reference position detection logic of the present invention is shown in FIG. 3 and will be described below.

In step S1, the two measured cycle values (time) t (n-a) and t (n-a-b) are stored.

In step S2, the next cycle is predicted. The predicted value is obtained as a function of the two past cycle values measured in step S1 as in the formula shown below.

P (n) = f (t (na), t (nab)) (1) Here, P (n) is the periodic value t at the next time (n).
It is a predicted value of (n).

T (na) and t (nab) are measured period values at times (na) and (nab), respectively.
As a method of obtaining P (n), for example, the following formula can be given.

P (n) = αt (n−a) −t (n−a−b) (2) α is a coefficient.

In step S3, the actual (next) cycle t
Measure (n).

In step S4, the relationship between the actually measured value and the predicted value is examined to determine whether or not the actually measured value falls within a predetermined range of the predicted value as shown in the following inequality.

ΒP (n) ≦ t (n) ≦ γP (n) (3) The coefficients β and γ shown in this equation are selected in consideration of the error caused by the change in the rotation speed. When the above relationship is established,
It is determined that t (n) is the reference position.

In addition to this, the following relationships can be mentioned.

P (n) + ε ≦ t (n) ≦ P (n) −ε (4) Here, ε is the lower limit value of the predetermined range.

In step S5, t (n) is determined to be the reference position, and the reference position signal is output.

In step S6, the equation (3) is established, and t
When (n) is identified as the reference position, the next predicted value is obtained as a function of the previously predicted value and the previously measured value as follows.

P (n + 1) = f (P (n + 1-a), t (n + 1-a-b)) (5-1) P (n + 2) = f (t (n + 2-a), P (n + 2-) a−b)) (5-2) P (n + 3) and subsequent ones are based on the equation (1). Therefore, only when the reference position is identified, the formula (5-
The operations 1 and 2) must be performed.

Another embodiment of the present invention will be described with reference to FIG.

FIGS. 4 (a) and 4 (b) correspond to FIGS. 2 (c) and 2 (d), respectively, which are the output waveform of the electromagnetic pickup and the waveform of the timer, respectively. Further, (c) is the waveform of the identified reference position signal, and (d) is a prediction value calculation permission flag. In this embodiment, immediately after the reference position is identified, the prediction calculation of the cycle value is not performed within a predetermined angle period (for example, during mθ shown in the figure). For example, FIG. 4 (d)
There is a method of providing a prediction value calculation permission flag as described above, turning it off immediately after the reference position determination, and turning it on after a predetermined angle period has elapsed. By doing so, it is not necessary to store the past predicted value, and the burden of calculation can be reduced. Also,
In this embodiment, the calculation of the predicted value is performed by the above-mentioned formula (1)
Although it is performed according to (4), since the predicted value calculation is not performed within a predetermined period after the reference position determination, it is not necessary to perform the calculation by the equations (5-1, 2). A flow chart of this embodiment is shown in FIG.

[0035]

According to the present invention, in the above-described rotational position detecting device, the reference position signal can be accurately detected based on at least two pieces of information even in a sudden rotational fluctuation state or the like.

[Brief description of drawings]

FIG. 1 is a system block diagram of the present invention.

FIG. 2 is a signal diagram showing the operation of the system.

FIG. 3 is a flowchart of the first embodiment.

FIG. 4 is a signal diagram of Example 2.

FIG. 5 is a flowchart of a second embodiment.

[Description of Reference Signs] 1 ... Rotating body, 1a ... Teeth arranged at equal intervals, 1b ... Missing teeth, 2 ... Electromagnetic pickup, 3 ... Signal processing means,
4 ... Counter, 5 ... Storage means, 6 ... Cycle predicted value calculation means, 7 ... Comparison means, 8 ... Reference position determination means, 9 ... Reference position signal output means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Ishii 2520 Takaba, Katsuta City, Ibaraki Prefecture Hitachi Ltd. Automotive Equipment Division

Claims (8)

[Claims] 1. A rotary body which has a large number of angular information provided at equal intervals and in which the angular information at a reference position is omitted from the angular information, and the angular information of the rotary body is detected.
One sensor, signal processing means for processing a signal of the output of this sensor, a counter for measuring the cycle of each angle information based on the output of this signal processing means, and a storage device for storing the value of the measured cycle. And a calculating device for calculating a stored value, wherein the reference position is identified based on at least two stored cycle values. 2. The rotational position detecting device according to claim 1, wherein a cycle of the next angle information is predicted by using a stored value of at least two cycles. 3. The rotational position detecting device according to claim 2, wherein at least one of the cycle prediction values is stored. 4. The rotational position detecting device according to claim 2, wherein the period predicted value and the period actually measured value are compared, and the reference position is identified based on the result. 5. The rotational position detecting device according to claim 2, wherein the cycle predicted value and the cycle actually measured value are compared, and when the cycle actually measured value is within a predetermined range of the cycle predicted value, the cycle is determined. A rotational position detecting device characterized by determining an actually measured value as a reference position. 6. The rotational position detecting device according to claim 5, wherein when the reference position is determined, the next cycle predicted value is obtained based on the previous cycle predicted value and the previous cycle actually measured value. Rotational position detector. 7. The rotational position detecting device according to claim 2, wherein the cycle predicted value is not calculated during a predetermined period immediately after the reference position is determined. 8. The rotational position detecting device according to claim 7, wherein when the predetermined period has elapsed, the calculation of the cycle predicted value is restarted.