JPS5830671A - Noise detecting device in rotational speed detector - Google Patents

Abstract

PURPOSE:To detect for sure if any noise is mixed in or not in a rotational speed detector by setting two different slice levels for an electromagnetic pickup output and by the correspondence of output when the rotational speed is over a set speed. CONSTITUTION:The output of an electromagnetic pickup 1 is detected based on slice levels S1 and S2 (S2>S1) by calculation circuits 11 and 14 and is converted into rotational speed n1 or n2. The level S1 is set up so that the output wave height value reaches it at a low speed rotation A, and the level S2 is set up higher enough that an expected noise levels and high enough so that wave height value reaches it at a high speed rotation (=N) B. In the low speed area where n1<N2, rotational speed n1 is adopted. If n1not equal to N2, in the high speed area where n1>=N2, noises detected only by the level S1 is judged to be included in n1 and alarm 20 is issued, and n2 is adopted as the rotational speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotation speed detection W&wrinkle noise detection device using an electromagnetic pickup as a rotation signal sensor.

As an electromagnetic pickup for a conventional rotation signal sensor,
For example, the one shown in FIG. 4 is widely known. (
For example, June 0, 1970, Nissan Automatic Single Issue Technical Explanation Buttocks rKceg I, Series Engine'' P, 17-P, 21
) That is, the electromagnetic pickup is equipped with a one-wire permanent magnet 2 and a coil 3, and an electromotive force is generated in the coil 3 due to a change in magnetic flux density that occurs when a magnetic body 4 crosses within the magnetic field generated by the permanent magnet 2. The voltage draws a sine wave as shown in FIG. 2(A)K. The peak value Vp of the sine wave is proportional to the rotating speed (IIL) at which the magnetic body 4 moves, and at the same time is inversely proportional to the distance t between the permanent magnet 2 and the magnetic body 4.

Therefore, when detecting the rotation speed based on the output of an electromagnetic pickup, the peak value Vp may be detected, or the sine wave may be rectified and smoothed and connected to a voltmeter. In mass-produced products such as , it is difficult to manage t related to the wave height value VP, so generally, the number of waves (frequency) or the period of waves within a certain time is measured.
Converts to rotational speed.

That is, the predetermined slice level is set to 8 as shown in Fig. 2 (A), and the wave is determined as shown in Fig. 2 (B) depending on whether the nine waves from the electromagnetic pickup cross the slice level S or not. Detects its presence and converts it into rotational speed.

Therefore, if the slice level S is set at a level such that the sine wave from the electromagnetic pickup crosses even at the lowest rotation, the rotation speed can be detected regardless of the wave height value Vp.

However, when using an electromagnetic pickup, as shown in Figure 3 (A), even in the □ section where the output is supposed to have no signal, noise may be generated due to a slight change in magnetic flux, or noise may be generated from other circuits. There is a noise that sometimes gets mixed in, and when this noise becomes larger than the slice level S, the noise is treated as the same as the rotation signal, so the rotation speed can be accurately detected as shown in Figure 3 (B). The problem is that you won't be able to do it.

In particular, when the noise is generated from an electromagnetic pickup, as shown in Figure 4, the peak value of the noise increases as the rotation increases.
ns (in Figure 4, Vnl is the peak value of noise generated due to the influence of other electrical components, regardless of the rotation speed) also increases, so it is possible to detect the lowest rotation and eliminate noise at the highest rotation. It is necessary to select a slice level so that it will not be detected, and a circuit that moves the slice level as the rounding rotation increases will need to be devised. However, this cannot be prevented if unexpected noise gets mixed in, and if the output of this type of rotation speed detection circuit is used as an input to an engine control device, the engine will be controlled using a high-speed signal. However, there are problems such as a decrease in control accuracy and the generation of erroneous control signals.

The present invention has focused on such conventional problems and aims to enable detection of noise mixed into the output of an electromagnetic pickup. Therefore, in the present invention, two slices having different slice levels for the output of the electromagnetic pickup are used.
Two rotation speed calculation circuits are provided, and the slice level of one is set to a level much higher than possible noise, and the outputs of the two rotation speed calculation circuits match at the rotation speed at which the peak value reaches that slice level. In view of this, it is also possible to detect noise contamination when there is a discrepancy.

Hereinafter, the present invention will be explained based on the diagram.

FIG. 5 shows an embodiment of the invention.

The output of the electromagnetic pickup 1 is input to the rotation signal detection section 12 of the rotation speed calculation circuit 11 having a slice level S1,
The value detected based on the slice level S1 is converted into a rotation speed n1 (digital value or analog value) by the rotation speed converter 13 at the next stage. Further, the output of the electromagnetic pickup 1 is inputted to the rotation signal detection section 15 of the rotation speed calculation circuit 14 having a slice level Sm (>Ss), detected based on the slice level SsK, and the nine values are obtained by the rotation speed conversion section 16 of the next stage. is converted to rotational speed J. - In addition, Fig. 6 (A).

As shown in (B), the slice level 8 plate is set to the level at which the wave height reaches at low rotation (A), and the slice level Sma is set much higher than the noise level observed. The peak value is made to reach at the time of rotation (B).

The output n1 of the rotation speed calculation circuit 11 is compared with a predetermined rotation speed Nm (the rotation speed at which the peak value reaches the slice level Sl) in the judgment unit 11, and when nl<Na3, the output circuit 18 (J)nt is Output.

When n1≧Nm in the judgment unit 17, the judgment unit 1s determines nl and the output n! of the rotation speed calculation circuit 140. It is determined whether nl:1g is obtained. And il
When l:ill, the output circuit 18 outputs nl.

At the time of n14n1, the warning device 20 such as a warning lamp is activated, and the determination unit 21 determines whether nl(0), and when nl(0), nl is output from the output circuit 22. When n!=0, output circuit 1
8 outputs nl.

That is, as shown in the table below.

nl (Nx ″−@H′−′−″knee″−′−−−
------------------1-Output n1 The reasons for doing this are described below.

As described above, as the rotation speed increases, the number of waves in the output of the electromagnetic pickup 1 increases over time, and the peak value of the waves also increases. The relationship is shown in FIG. That is, the peak value increases in direct proportion to the rotational speed from 0 to several thousand rotations.

On the other hand, since the rotation speed calculation circuit 11 uses 81 as the slice level, it does not detect a rotation signal when the rotation speed is less than N1 (rotation speed calculation value 0), and detects a rotation signal that is directly proportional to the rotation speed when the rotation speed is N or more. Detect. Therefore, the rotation speed calculation value nsa
The result is as shown by the solid line in FIG.

Moreover, the rotation speed calculation circuit 14 is S! is set as a slice level, so when the rotation speed is less than N3, no rotation signal is detected (rotation speed calculation value 0), and when the rotation speed is higher than N1, a rotation signal that is directly proportional to the rotation speed is detected. Therefore, the rotation speed calculation value n! is as shown by the broken line in FIG.

Therefore, when the number of rotations is N or more, essentially nl = J.

On the other hand, the noise on the output side of electromagnetic big ag 1 has a fourth
As shown in the figure, the one proportional to the rotation speed (Vnl),
There are two types, one that occurs regardless of the number of rotations (Vns), but in either case, the difference from the sine wave peak value Vp usually increases as the number of rotations increases.

Therefore, if S3 is set to a sufficiently large value without noise, when the rotation speed is N1 or higher, the output nl of the rotation speed calculation circuit 14 with Ss as the slice level becomes an output with higher gI reliability. In the case of nl)J, it can be detected that noise is mixed on the nl side.

Therefore, in the determination unit 1T, n1≧N! When it is detected that nl and n3 have been reached, the judgment unit 19 compares nl and n3, and if nl'enl, it is determined that nl processes a signal containing noise and is a friend, so the rotation The warning device 20 is activated when the noise detection device picks up noise, and a warning is given to the driver and the like. At this time, the judgment unit 21 confirms that n snow' = o, and if nl) is 0, it is determined that nl is the correct rotation speed and outputs n5t-, and n
If 3 = 0, the output of the electromagnetic pickup 1 will be detected due to a disconnection or poor contact, and therefore n
Even if l contains noise, an emergency process is performed to temporarily output it.

As explained above, according to the present invention, a rotation speed calculation circuit for checking that calculates the rotation speed at a slice level that sufficiently avoids noise is provided, and its output is compared with the output of the normal rotation speed calculation circuit. Since noise intrusion is detected based on the difference, it is possible to reliably detect whether or not noise is being picked up, and by notifying the driver etc. of this, it is possible to prevent driving based on incorrect information. Can be done.

[Brief explanation of the drawings] Figure 1 is a schematic diagram of a conventional electromagnetic pickup, and Figure 2 (A
), (B) a Diagram showing the output waveform of the electromagnetic pickup and the signal processed waveform, Figure 3 (A), (B) a Diagram showing the output waveform and signal processed waveform when noise is mixed, Figure 4 Figure 5 is a circuit diagram showing an embodiment of the present invention, Figures 6 (A) and (B
) is a diagram showing the relationship between the output waveform and slice level at low and simple rotations, Figure 7 is a diagram showing the relationship between rotation speed and wave height value, etc., and Figure 8 is a diagram showing the relationship between rotation speed and rotation speed calculation value. It is a figure showing a relationship. 1... Electromagnetic pickup 11.14... Rotation speed calculation circuit 18.22... Output circuit 21...
Warning device patent applicant Fujio Sasa Karasu, patent attorney representing Nissan Motor Co., Ltd.

Claims (1)

[Claims] A rotation speed detection device that uses an electromagnetic pickup as a rotation signal sensor to detect the rotation speed based on its output, wherein at least 42 rotation speed calculation circuits having different slice levels for the output of the electromagnetic pickup are provided, and these rotation speed calculation circuits are provided. Noise detection of a rotation speed detection device, characterized in that it is detected whether or not there is noise in the output of an electromagnetic pickup based on whether or not the respective outputs match when the output of the electromagnetic pickup is equal to or higher than a predetermined rotation speed. Device.