JPH07159426A - Rotating speed detector - Google Patents

Abstract

PURPOSE:To reduce detection errors of rotating speed by controlling fluctuation amplitude and swell of an output signal caused by rotor eccentricity. CONSTITUTION:Output of a detection part 2 is rectified by a rectifier 3. Direct current drift is removed from the output of the rectifier 3 by a next stage low area shutdown filter 4. The amplitude fluctuation of the output of the detection part 2 can be controlled by logarithmically compressing the output of the low area shutdown filter 4 by means of a logarithmic amplifier 5. The output of the logarithmic amplifier 5 is compared with reference voltage Vf input from a reference voltage generation part 15 in a comparator 6. When the output of the logarithmic amplifier 5 exceeds a reference voltage Vf, the comparator 6 outputs a signal, the output signal becomes detection output in accordance with a recess and a projection of a rotor and rotating speed detection of small detection errors caused by rotor eccentricity is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation speed detecting device which is attached to a wheel of an automobile, a transmission or the like to detect the rotation speed of a wheel shaft or a drive shaft.

[0002]

2. Description of the Related Art In recent years, automobiles have been equipped with an anti-lock brake system, an automatic transmission, a navigation system, etc., and these devices detect the traveling speed of the automobile and perform various controls. Driving speed detection is becoming more important.

By the way, in order to detect the traveling speed of an automobile as described above, heat resistance, environment resistance, etc. are taken into consideration.
Generally, a magnetic detection device is used rather than an optical or contact detection device. For example, a rotor that is fixed to a rotating shaft (axle) that is inserted substantially in the center and rotates integrally with this rotating shaft is installed in a magnetic field, and the rotation speed of the rotating shaft (that is, running speed ) Is used to detect the rotational speed.

As the rotation speed detecting device as described above,
There is a so-called magnet pickup type (hereinafter abbreviated as MPU type) rotation speed detecting device as shown in FIG. This MPU type rotation speed detecting device is configured such that a concavo-convex portion 1a is formed on a surface of a substantially cylindrical metal rotor 1 in a circumferential direction.
Is provided to fix the rotor 1 to the rotating shaft, and a detecting portion 2 having a permanent magnet 16 disposed in the vicinity thereof is provided to rotate the rotor 1 in a magnetic field generated by the permanent magnet 16. Allows the rotor 1 to run along the circumferential direction.
The uneven portion 1a provided on the surface extracts the induced electromotive force generated in the magnetic detection coil 17 of the detection unit 2 as an output signal by changing the magnetic field. This output signal is shown in FIG. 1 because the uneven portions 1a are provided at equal intervals.
As shown in FIG. 8, the sine wave signal has a peak value and a period proportional to the rotation speed of the rotor 1. That is, when the number of revolutions is 2n and 0.5n with respect to the number of revolutions n of the rotor 1, the crest value and the cycle are respectively larger or smaller than in the case of the number of revolutions n. And the output signal is
Compared with the reference voltage by a comparator (not shown)
The rotation speed of the rotary shaft is detected by converting the pulse signal into 0 "and" 1 "and then counting the pulse. However, in the above-mentioned MPU system rotation speed detecting device, as shown in FIG. In addition, since the output signal of the detection unit 2 is proportional to the rotation speed (rotation speed n) of the rotor 1, an output signal of a sufficient level cannot be obtained at a low speed, and the detection sensitivity of the rotation speed decreases in proportion to the speed. Therefore, there is a problem that it cannot be detected just before the rotation of the rotor 1 is stopped.

Therefore, in order to be able to detect even a low speed range without causing such a problem, a change in the magnetic field is detected by a Hall element or a magnetoresistive element, or a high frequency current is passed through a coil to generate a high frequency wave. A magnetic field is generated, the rotor 1 is arranged in this high frequency magnetic field, and the eddy current generated on the surface of the rotor 1 by the high frequency magnetic field is changed by the rotation of the rotor 1, and the change in the impedance or Q factor of the coil caused thereby is detected. The method of doing is adopted.

A specific example of the above-mentioned detection method using the high-frequency magnetic field (hereinafter, abbreviated as high-frequency magnetic field method) will be briefly described with reference to FIGS. 20 and 21. In the rotation speed detecting device shown in FIG. 20, the rotor 1 is rotated in a high-frequency magnetic field generated by driving the coil 19 with the high-frequency oscillator 18, so that the rotor 1 faces the coil 19 in the circumferential direction. The magnetic flux of the high-frequency magnetic field penetrates the surface, which causes the rotor 1
Eddy currents are generated on the surface along the circumferential direction of. On the other hand, the magnetic field generated by the eddy current adversely affects the high-frequency magnetic field, and the impedance and Q factor of the coil 19 change, and the oscillation amplitude of the coil 19 by the high-frequency oscillator 18 changes.

However, since the uneven portion 1a is provided on the surface of the rotor 1 along the circumferential direction, the distance between the uneven portion 1a of the rotor 1 and the coil 19 changes as the rotor 1 rotates, The magnetic flux passing through the surface of the rotor 1 along the circumferential direction changes according to the rotation of the rotor 1. As a result, the magnitude of the eddy current generated on the surface of the rotor 1 changes, so that the oscillation output of the high-frequency oscillator 18 changes according to the rotation speed of the rotor 1, and the rotation of the rotor 1 is detected by detecting the change. The speed can be detected. That is, the oscillation amplitude of the high frequency signal obtained by the signal detecting resistor R provided in the detection unit 2 changes in a cycle according to the rotation speed of the rotor 1 (see FIGS. 21A and 22). The output is rectified by the rectifier 20 (see FIGS. 21B and 22), and the output is further passed through the low-pass filter 21.
The detection output is obtained by filtering with (FIG. 21 (c) and FIG. 2).
2). Therefore, unlike the conventional MPU method,
Since the output level of the detection output does not change depending on the rotation speed of the rotor 1 (see FIG. 19), it is possible to detect a wide range of rotation speeds from low speed just before stop to high speed. It should be noted that the output of the rectifier 20 can be held at its peak value, or a frequency component twice as high as the original oscillation can be removed from the output by a filter to obtain a detection output corresponding to the rotation speed of the rotor 1. Further, as the high frequency magnetic field method, FIG.
Also, a configuration as shown in FIG. 24 has been proposed.
That is, the output of the detection unit 2 is rectified by the rectifier 20, the output of the rectifier 20 is further amplified by the amplifier 25, the output of the amplifier 25 is compared with the reference voltage by the comparator 24, and the uneven portion 1a of the rotor 1 is obtained. According to this, the corresponding detection output is obtained.

[0008]

However, by improving the detection sensitivity in the low speed range by the above-mentioned structure, the fluctuation of the amplitude of the detection output and the undulation due to the eccentricity of the rotor 1 become remarkable, and the detection error of the rotation speed is increased. There is a problem that such things occur. In the above MPU method, FIG.
As shown in (a), the amplitude of the output voltage fluctuates due to the eccentricity of the rotor 1, and since the rotor 1 is made of metal, the output voltage is affected by the parts other than the uneven portion 1a of the rotor 1. Swell occurs. As a result, the detection output does not occur even though the peak value level exceeds the reference voltage, and a detection error occurs (see FIG. 25 (b)).

In the high frequency magnetic field method, the influence of the eccentricity of the rotor 1 is slightly different from that of the MPU method. That is, since the gap between the Hall element or the magnetoresistive element or coil 19 for detecting the change in the magnetic field and the uneven portion 1a of the rotor 1 is not constant due to the eccentricity of the rotor 1, as shown in FIG. When the length is long, the amplitude of the output voltage is small, and when the gap length is short, the amplitude is large. Furthermore, since the output voltage is undulated due to the influence of the portion other than the uneven portion 1a of the rotor 1 and the output voltage has a DC drift due to the undulation, the peak value level exceeds the reference voltage. Without the detection output, a detection error occurs (see FIG. 26B).

On the other hand, with respect to the above problem of the high frequency magnetic field method, as shown in FIG.
6 and the detectors 22 and 22 respectively connected to the detector 6, and the detector 2 is configured, and the outputs obtained from the detectors 22 and 22 of the detector 2 are input to the differential amplifier 23, and the differentially amplified output is provided. A so-called differential type rotation speed detection device capable of suppressing the occurrence of undulations as shown in FIG. 28 is proposed by comparing with the reference voltage in the comparator 24 to obtain a detection output according to the rotation speed. ing. But,
In the differential type, the two magnetic detection elements 26, 2
Since it is difficult to make the gap between 6 and the rotor 1 completely equal, a slight undulation occurs. Further, it is impossible to suppress the amplitude fluctuation of the output voltage due to the change of the gap length. Furthermore, it is necessary that the characteristics of the two magnetic detection elements 26, 26, which are Hall elements, magnetoresistive elements, etc., be the same, and the characteristics of the two magnetic detection elements 26, 26 are the same, or the two detectors 22, The driving conditions of No. 22 must be adjusted, and it is necessary to solve the problems other than the above-mentioned undulations and output amplitude fluctuations, which causes an extra cost increase.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotation speed detecting device in which fluctuations in output signal amplitude and undulation due to eccentricity of a rotor are suppressed to reduce rotation speed detection errors. Is.

[0012]

In order to achieve the above object, the rotor of the present invention rotates integrally with a rotating shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotating direction. A detection unit including a magnetic detection element that detects a change in magnetic field caused by rotation of the rotor; a rectifier that rectifies the output of the detection unit; a low-frequency cutoff filter that removes a direct current component from the output of the rectifier; A rotating rotor provided with a logarithmic amplifier for logarithmically compressing the output of the band cutoff filter, and a comparator for comparing the output of the logarithmic amplifier with a reference value and outputting a signal only when the output of the logarithmic amplifier exceeds the reference value. It is characterized in that a detection output corresponding to the unevenness of is obtained from the output of the comparator.

In order to achieve the above-mentioned object, a second aspect of the present invention provides a rotor that rotates integrally with a rotary shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction. A detection unit including a magnetic detection element that detects a change in the generated magnetic field, a rectifier that rectifies the output of the detection unit, a coupling capacitor that removes a direct current component from the output of the rectifier, and an output of the rectifier that passes through this coupling capacitor. An amplifier for amplifying, a switch circuit for connecting and disconnecting the output of the rectifier input to the amplifier, a comparing section for comparing the output of the amplifier with two different reference values according to the changing direction of the output of the amplifier, and the switch. An oscillator for periodically controlling ON / OFF of the circuit is provided, and a detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparison unit.

In order to achieve the above object, a third aspect of the present invention provides a rotor that rotates integrally with a rotating shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction. A detection unit including a magnetic detection element that detects a change in the generated magnetic field, a pair of rectifying and smoothing units that rectifies and smoothes the output of the detection unit through a coupling capacitor that removes a direct current component from the output of the detection unit, and a pair of these A pair of switch circuits for connecting / disconnecting the output of the detection unit input to the rectifying / smoothing unit, a differential amplifier for differentially amplifying the output of the pair of rectifying / smoothing unit, and an amplifier according to the direction in which the output of the differential amplifier changes. And a comparator for comparing two different reference values with each other, and an oscillator for controlling the pair of switch circuits to be turned on and off periodically and alternately. Comparison above And wherein the obtaining the output.

[0015]

According to the first aspect of the invention, the rotor is rotated integrally with the rotating shaft in the magnetic field and a large number of irregularities are formed at regular intervals in the rotational direction, and a change in the magnetic field caused by the rotation of the rotor is detected. And a rectifier that rectifies the output of the detector, a low-pass filter that removes a direct current component from the output of the rectifier, and a logarithmic amplifier that logarithmically compresses the output of the low-pass filter. , A comparator for comparing the output of this logarithmic amplifier with a reference value and outputting a signal only when the output of the logarithmic amplifier exceeds the reference value, and the detection output corresponding to the unevenness of the rotating rotor is Since it is obtained from the output, the swell contained in the output of the detection unit can be removed by the low-pass filter, and the output of the low-pass filter is logarithmically compressed by the logarithmic amplifier. Te, it is possible to suppress amplitude fluctuations in the output of the detecting unit due to the eccentricity of the rotating rotor.

According to the second aspect of the invention, the rotor that rotates together with the rotating shaft in the magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction, and the change in the magnetic field caused by the rotation of the rotor are detected. And a rectifier that rectifies the output of the detector, a coupling capacitor that removes a direct current component from the output of the rectifier, an amplifier that amplifies the output of the rectifier that passes through the coupling capacitor, and an amplifier. Switch circuit for connecting and disconnecting the output of the rectifier input to the circuit, a comparing section for comparing the output of the amplifier with two different reference values according to the changing direction of the output of the amplifier, and a switching circuit for periodically turning on and off the switch circuit. Since the detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparison unit, it is included in the output of the detection unit by the coupling capacitor. Ripple can be eliminated, and the input to the amplifier is interrupted by the switch circuit that is periodically turned on and off by the oscillator, so amplitude fluctuations in the output of the detector due to eccentricity of the rotating rotor can be suppressed. it can.

According to the third aspect of the invention, the rotor that rotates integrally with the rotating shaft in the magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction, and the change in the magnetic field caused by the rotation of the rotor are detected. A pair of rectifying and smoothing sections for rectifying and smoothing the output of the detecting section through a coupling capacitor that removes a direct current component from the output of the detecting section; A pair of switch circuits that intermittently output the output of the detection unit, a differential amplifier that differentially amplifies the outputs of the pair of rectifying and smoothing units, and an output of the amplifier and two phases depending on the direction in which the output of the differential amplifier changes. A comparison unit that compares different reference values, and an oscillator that controls the pair of switch circuits to be alternately turned on and off periodically,
Since the detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparison unit, the undulation included in the output of the detection unit can be removed by the coupling capacitor. The rectifying and smoothing signals are alternately output from each rectifying and smoothing section depending on the on / off timing, and while one of the rectifying and smoothing sections is operating, the other rectification is performed. The smoothing section does not operate, and the output of the rectifying and smoothing section that is operating is higher than the output of the rectifying and smoothing section that is not always operating in absolute value level. With dynamic amplification, it is possible to obtain a detection output in which the positive and negative are alternately inverted corresponding to the unevenness of the rotating rotor, and to suppress the amplitude fluctuation of the output of the detection unit due to the eccentricity of the rotor. It can be.

[0018]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit block diagram of this embodiment, and FIG. 2 shows a specific schematic circuit diagram. As shown in FIG. 1, the rotation speed detection device according to the present embodiment includes a detection unit 2 whose output changes according to the uneven portion 1 a of the rotor 1 due to the rotation of a rotor 1 (not shown), and a detection unit 2. A rectifier 3 for rectifying the output,
A low-frequency cutoff filter 4 for removing DC drift from the output of the rectifier 3, a logarithmic amplifier 5 for logarithmically compressing the output of the low-frequency cutoff filter 4, a reference input from the output of the logarithmic amplifier 5 and a reference voltage generator 15. And a comparator 6 which compares the voltage Vf and outputs a signal when the output of the logarithmic amplifier 5 exceeds the reference voltage Vf. Power is supplied to the detection unit 2 from an external power supply (not shown) via an input protection circuit 27. The input protection circuit 27 is for protecting the detection unit 2 from a surge input from the external power supply. is there.
Here, the detection unit 2 is of any of the MPU method described in the conventional example, the high frequency magnetic field method using a Hall element, a magnetoresistive element, and a coil, and the differential method using a differential amplifier. Also, the technical idea of the present invention can be applied. Further, the rotor 1 may be made of metal and resin other than metal as long as it can be used in each of the above methods, and the material of the rotor 1 is not the subject matter of the present invention.

As shown in FIG. 2, the logarithmic amplifier 5 in this embodiment is composed of an operational amplifier IC ₁ .
The low-frequency cutoff filter 4 is provided at the inverting input terminal of the operational amplifier IC _1.
Is input, the reference voltage Vf created in the reference voltage generator 15 is input to the non-inverting input terminal, and a capacitor C ₁ and a feedback resistor are provided between the output terminal and the inverting input terminal of the operational amplifier IC _1. R ₁ and two diodes D ₁ and D ₂ are connected in parallel in opposite directions.

In the above configuration, the low-frequency cutoff filter 4 detects the frequency component below the frequency of the output of the detection unit 2 at the lowest limit of the rotation speed of the rotor 1 which can be detected by the detection unit 2.
Is removed from the output of the detection unit 2, and the low-frequency cutoff filter 4 can remove the swell of the output of the detection unit 2 including the DC drift. Further, the output of the low-frequency cutoff filter 4 is logarithmically compressed by the logarithmic amplifier 5, and the logarithmically compressed output and the reference voltage Vf are compared by the comparator 6, and when the output of the logarithmic amplifier 5 exceeds the reference voltage Vf. The output of the comparator 6 becomes H level, and as shown in FIG. 3B, a pulsed detection output corresponding to the uneven portion 1a of the rotor 1 can be obtained. Therefore,
In the logarithmic amplifier 5, the amplitude variation of the output of the detection unit 2 due to the eccentricity of the rotor 1 is logarithmically compressed at the same time as the original output of the detection unit 2 corresponding to the uneven portion 1a of the rotor 1, thereby the amplitude variation of the output of the detection unit 2. Can be suppressed, and the dynamic range of the comparator 6 with respect to the output of the detection unit 2 can be widened. As a result, the detection error due to the eccentricity of the rotor 1 can be reduced,
Further, the rotational speed of the rotor 1 which is affected by the eccentricity of the rotor 1 on the detection output can be suppressed to a value that sufficiently exceeds the upper limit of the rotational speed of the rotor 1 that can be detected by the detection unit 2.

When the detection unit 2 of the MPU type is used, the DC cutoff filter 4 can be omitted because the MPU type detection unit 2 itself has a function of relatively removing the DC drift. Therefore, by directly logarithmically amplifying the output of the detection unit 2 by the logarithmic amplifier 5, it is possible to reduce extreme amplitude fluctuations and undulations. Further, although the low-frequency cutoff filter 4 is connected to the front stage of the logarithmic amplifier 5 in this embodiment, it may be connected to the rear stage of the logarithmic amplifier 5.

(Embodiment 2) A circuit block diagram of this embodiment is shown in FIG. 4, and a concrete schematic circuit diagram is shown in FIGS. 5 (a) and 5 (b). As shown in FIG. 4, the rotation speed detection device according to the present exemplary embodiment includes a detection unit 2, a rectifier 3 that rectifies the output of the detection unit 2, and an output of the rectifier 3 via a coupling capacitor C ₀ for cutting a DC component. Two comparators 6a for comparing the amplifier 7 connected to the end and two different comparison voltages V ₁ and V _{2 obtained by} dividing the output of the amplifier 7 and the reference voltage Vf input from the reference voltage generator 15 from each other. , 6b, and RS flip-flops FF to which the output signals of these two comparators 6a, 6b are input to the set terminal and the reset terminal, respectively, and the connection point between the coupling capacitor C ₀ and the amplifier 7 is connected to the switch circuit 8. The switch circuit 8 is connected to the reference voltage generator 15 via an oscillator 9 which is an astable multivibrator. In the present embodiment, as in the case of the first embodiment, the detection unit 2 is either an MPU method, a high frequency magnetic field method using a Hall element, a magnetoresistive element or a coil, or a differential amplification method using a differential amplifier. It may be of a system.

As shown in FIG. 5A, in this embodiment, the amplifier 7 is composed of an operational amplifier IC ₂ .
The output of the rectifier 3 is input to the inverting input terminal, and the reference voltage Vf is input to the non-inverting terminal. Also, two comparators 6a, 6b is constituted by an operational amplifier IC _3, IC _4, respectively, an operational amplifier I of one of the comparators 6a
The comparison voltage V ₁ divided by the reference voltage Vf is inputted to the inverting input terminal of C _{3, and} the comparison voltage V divided by the reference voltage Vf is inputted to the inverting input terminal of the operational amplifier IC ₄ of the other comparator 6b. ₂ is entered. Further, the output terminal of the amplifier 7 is connected to the non-inverting input terminal of the one comparator 6a and the inverting input terminal of the other comparator 6b. The output terminal of the one comparator 6a is an RS flip-flop FF.
Of the comparator 6b, and the output terminal of the other comparator 6b is connected to the reset terminal R.

The switch circuit 8 outputs the output of the oscillator 9.
Equipped with an analog switch SW that turns contacts on and off according to
I am. However, as shown in FIG.
Densa C₀To the analog switch SW connected in series with
Inverter IC_FiveInput the output of the oscillator 9 via
It is also possible to configure it. Next, in the above configuration
The circuit operation according to FIG. 6 will be described with reference to FIGS.
To do. Now, for the sake of explanation, the rotor 1 rotates at a constant speed.
It is assumed that a pair of the uneven portions 1a of the rotor 1
The cycle T of the output of the detection unit 2 due to the unevenness of 1
Below, abbreviated as ms). Also, the eccentricity of the rotor 1
The swell due to the rotation of the rotor 1 is generated as shown in Fig. 6 (b).
Each half cycle of the rolling cycle is greatly undulating, and this swell
Between the valley part (negative swell) and the mountain part (positive swell)
Period t₁, T ₂Are set to 50 ms, and the oscillator 9 output
Force cycle is 100 microseconds (hereinafter abbreviated as μs)
It In this case, the analog switch of the switch circuit 8
SW is the half cycle (50 μs) of the output of the oscillator 9.
It turns on, turns off in the next half cycle, and turns off every 50 μs.
Turn off and on repeatedly.

Here, as shown in FIG. 6 (b), when the output of the detector 2 is constantly increasing (when the convex portion of the rotor 1 is close to the detector 2), the period is Since it becomes a half cycle (500 μs) of the cycle T of the detection output, the period (500 μs) is set to the cycle (100 μs) of the output of the oscillator 9.
The number of positive pulses equal to the value divided by s) (500/100 = 5 in this case) is output from the amplifier 7. The pulse width of this pulse is proportional to the detection output of the detection unit 2,
It does not exceed the half cycle (50 μs) of the output of the oscillator 9.

On the contrary, when the concave portion of the rotor 1 is close to the detecting portion 2, the output of the detecting portion 2 constantly decreases, and during that period, the same number of negative pulses as the positive pulse is amplified. It is output from 7. Therefore, the oscillator 9
If the oscillation frequency is constant, the number of positive and negative pulses output from the amplifier 7 during the constant period depends on the rotation speed of the rotor 1. However, the positive and negative signs represent the sign for the reference voltage Vf.

Since the output pulse of the amplifier 7 is input to the non-inverting input of the one comparator 6a, the amplifier 7
The output pulse of 1 is a negative pulse, and the other comparator 6b outputs a signal only when the output pulse of the amplifier 7 is a positive pulse. Therefore, since the output Q of the RS flip-flop FF is inverted when the output pulse of the amplifier 7 is inverted, the output Q becomes an output according to the rotation speed of the rotor 1. That is, the pair of comparators 6a for comparing the output of two different comparison voltages V _1, V ₂ and amplifier 7, the comparison unit is constituted by 6b, the pair of comparators 6a, the comparator unit consisting 6b output It is possible to obtain a detection output corresponding to the uneven portion 1a of the rotor 1.

As described above, according to the above configuration, the detection unit 2
The swell and DC drift that occur in the output of the amplifier 7 are removed by the coupling capacitor C ₀ , and the operation of the switch circuit 8 that is on / off controlled by the oscillator 9 causes the amplifier 7 to operate.
Since the variation that makes the reference voltage Vf zero level is always input to the input side of, the amplitude variation of the detection output due to the eccentricity of the rotor 1 is reduced.

(Embodiment 3) A circuit block diagram of this embodiment is shown in FIG. 7, and a concrete schematic circuit diagram is shown in FIG. The basic configuration of this embodiment is the same as that of the second embodiment, the common parts are denoted by the same reference numerals, the description thereof will be omitted, and only different points will be described. The rotational speed detection device in this embodiment is different from that of the second embodiment in that it has only one comparator and does not have an RS flip-flop FF. Comparator 6c in this embodiment is fed back the output to the non-inverting input terminal via a feedback resistor Rf inputs the reference voltage Vf to a non-inverting input terminal of the operational amplifier IC _6.

In the above configuration, the voltage input to the non-inverting input terminal of the comparator 6c, that is, the comparison voltage changes depending on the output state of the comparator 6c, and the output level of the comparator 6c is L.
At the level, the comparison voltage V ₁ lower than the reference voltage Vf
On the contrary, when the output level of the comparator 6c is H level, the comparison voltage V ₂ is higher than the reference voltage Vf. That is, one comparator 6c has two different comparison voltages V ₁ and V ₂ , and the two comparators 6 described in the second embodiment are different.
The operations of a and 6b can be performed by one comparator 6c. Therefore, the amplifier 7 outputs a fixed number of positive and negative pulses having the reference voltage Vf at the zero level according to the rotation speed of the rotor 1, and the output pulse of the amplifier 7 changes the comparison voltage V ₂ of the comparator 6c in the positive direction. The output of the comparator 6c becomes L level when the voltage exceeds the value
When the output pulse of ₁ exceeds the comparison voltage V ₁ of the comparator 6c in the negative direction, the output becomes H level. That is, the output of the comparator 6c is inverted only when the output pulse of the amplifier 7 is inverted, and the output pulse corresponding to the rotation speed of the rotor 1 is output from the comparator 6c. Therefore, Example 2
Similar to the case of (3), it is possible to remove the undulation of the detection output and the amplitude fluctuation.

(Embodiment 4) A circuit block diagram of this embodiment is shown in FIG. 9, and a concrete schematic circuit diagram is shown in FIG. The basic configuration of this embodiment is the same as that of the third embodiment, the common portions are denoted by the same reference numerals, the description thereof will be omitted, and only different points will be described. The rotation speed detecting device in this embodiment is different from that of the third embodiment in that the oscillator 9 is a monostable multivibrator, and in order to generate a trigger signal of this monostable multivibrator, a delay circuit 10 and a logic circuit are used. This is the point where the circuit 11 is connected to the output terminal of the comparator 6c.

In the above configuration, the output of the amplifier 7 is the comparator 6
When the positive comparison voltage V ₂ at c is exceeded in the positive direction (see FIG. 11 (f)), the output of the comparator 6c is inverted and H
The output level of the logic circuit 11 rises to the H level (see (b) in the figure). On the other hand, the comparator 6
The output of c is delayed by the delay circuit 10 for a certain time and then input to the logic circuit 11, and the output from the delay circuit 10 is H level.
Since the output of the logic circuit 11 is inverted to the L level when rising to the level, a pulse signal (trigger signal) having a pulse width equal to a constant delay time in the delay circuit 11 is eventually output from the logic circuit 11 to the oscillator 9. (See (d) in the figure).

Each time the trigger signal is input, a pulse signal having a constant pulse width is output from the oscillator 9 composed of a monostable multivibrator (see (e) in the same figure), and the switch circuit is activated by this pulse signal. The analog switch SW 8 is turned on and the amplifier 7 receives the reference voltage V
f is input. Further, when the output of the oscillator 9 is turned off, the analog switch SW of the switch circuit 8 is turned off, and the signal corresponding to the output of the detection unit 2 is output from the amplifier 7 (see (f) in the figure). When the output of the amplifier 7 exceeds the negative comparison voltage V ₁ in the comparator 6c in the negative direction, the output of the comparator 6c is inverted and becomes the L level. The output pulse corresponding to (a) is output from the comparator 6c (see (g) in the figure). Therefore, as in the case of the second and third embodiments, the output of the comparator 6c is not affected by the swell or fluctuation included in the output of the detection unit 2, in other words, from the output of the detection unit 2. It is possible to remove undulations and amplitude fluctuations. The voltage across the coupling capacitor C ₀ is the reference voltage V every time the analog switch SW is turned on.
Since it is reset to f, the DC drift in the coupling capacitor C ₀ is canceled each time.

(Embodiment 5) A circuit block diagram of this embodiment is shown in FIG. 12, and a concrete schematic circuit diagram is shown in FIG. The rotational speed detection device in this embodiment includes a detection unit 2, coupling capacitors C ₀ and C ₀ that are connected in parallel to the output terminal of the detection unit 2 and remove a DC component from the output of the detection unit 2, and these coupling capacitors C. Rectifying and smoothing units 12 and 13 for rectifying and smoothing the output of the detecting unit 2 via ₀ and C _0, and the respective rectifying and smoothing units 12 and 1.
Switch circuits 8a and 8b which are connected to the input terminal of 3 and connect and disconnect the output of the detection unit 2, and these two rectification smoothing units 12 and
It is connected to a differential amplifier 14 that differentially amplifies the output of 13, a comparator 6c that compares the output of the differential amplifier 14 with two different comparison voltages V ₁ and V _2, and an output terminal of the comparator 6c. The D flip-flop DFF and the oscillator 9 for supplying a clock signal to the D flip-flop DFF are provided. The rectifying / smoothing units 12 and 13 may be those that perform peak hold or synchronous rectification.

[0035] The switch circuit 8a, 8b respectively provided with switching elements Q _1, Q _2, the control terminals of the switching elements Q _1, Q ₂ are connected to the output terminal of the oscillator 9. However, the control terminal of the switching element Q ₁ of the rectifying / smoothing unit 12 is connected to the oscillator 9 via the inverter IC _10.
Is connected to the output end of. That is, since the two switching elements Q ₁ and Q ₂ are alternately turned on and off with respect to the output of the oscillator 9, the rectifying and smoothing units 12 and 13 alternately detect the detection unit 2 in synchronization with the output of the oscillator 9. The operation of rectifying and smoothing the output is performed.

Next, the operation of this embodiment will be described with reference to FIG. As shown in FIGS. 14A and 14B, the output of the detection unit 2 is a signal that changes according to the uneven portion 1 a of the rotor 1, and this output signal now includes undulation due to eccentricity of the rotor 1. It is assumed that The output signal is inputted through the coupling capacitor C _0, C ₀ into two rectifying and smoothing portion 12, 13. On the other hand, the rectifying / smoothing unit 12, 1
The switching element Q ₁ is the input end of the 3, Q ₂ switch circuit 8a comprising, 8b are connected, the switching elements Q _1, Q ₂ are controlled to be turned on and off by oscillator 9. Therefore, according to the on / off timings of the switching elements Q ₁ and Q ₂ determined by the oscillation cycle of the oscillator 9, the two rectifying / smoothing sections 12 and 13 are rectified and smoothed as shown in FIGS. The signals are output alternately.

When the switching elements Q ₁ and Q ₂ are off, the input sides of the rectifying / smoothing sections 12 and 13 are short-circuited, so that one rectifying / smoothing section 12 (or the rectifying / smoothing section 13).
Of the other rectifying / smoothing unit 13 (or the rectifying / smoothing unit 12) does not operate, and the output of the rectifying / smoothing unit 12 (or the rectifying / smoothing unit 13) in operation does not always operate. The absolute value level is higher than the output of the smoothing unit 13 (or the rectifying / smoothing unit 12). Therefore, when the outputs of the two rectifying / smoothing sections 12 and 13 are differentially amplified by the differential amplifier 14, it is possible to obtain an output in which the positive and negative are alternately inverted from the differential amplifier 14.

The output of the differential amplifier 14 is compared with the comparator 6
Input to c, as described in Example 3 and Example 4.
The output of the differential amplifier 14 is the positive / negative comparison voltage of the comparator 6c.
Pressure V ₁, V₂Comparator 6c depending on the direction over
The output of is inverted. Therefore, the output of this comparator 6c is D
Input to flip-flop DFF, oscillation cycle of oscillator 9
By latching the output of the comparator 6c in synchronization with
Then, as shown in (f) and (g) of FIG.
The output according to the signal is the output Q of the D flip-flop DFF.
You can get it. The differential amplifier 14
When the output of is large enough, the output of the differential amplifier 14
It is also possible to input directly to the D flip-flop DFF.
Yes, in that case, the comparator 6c can be omitted.
It

In the above structure, the undulations and fluctuations contained in the detected output can be removed by differentially amplifying the outputs of the two rectifying / smoothing sections 12 and 13 at time intervals synchronized with the oscillation cycle of the oscillator 9. it can. Note that FIG. 15 and FIG.
6, the oscillator 9 is also used as an oscillator for high-frequency magnetic field generation used in the detection unit 2, or the output of the oscillator 9 is frequency-divided to perform frequency conversion, and two rectifying / smoothing units 12, 13 may be used for the operation timing. The comparator 6c in the present embodiment may be replaced with a comparison section composed of two comparators 6a and 6b as described in the second embodiment.

By the way, in the first to fifth embodiments described above, the detection unit 2 is of the type that detects the rotation of the rotor 1 by magnetism, but for example, an optical sensor or the like is used for the detection unit 2. The technical idea of the present invention can also be applied to a system that detects the distance from the rotor 1.

[0041]

According to the first aspect of the present invention, a rotor that rotates integrally with a rotating shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction, and a change in the magnetic field caused by the rotation of the rotor are detected. And a rectifier that rectifies the output of the detector, a low-pass filter that removes a direct current component from the output of the rectifier, and a logarithmic amplifier that logarithmically compresses the output of the low-pass filter. , A comparator for comparing the output of this logarithmic amplifier with a reference value and outputting a signal only when the output of the logarithmic amplifier exceeds the reference value, and the detection output corresponding to the unevenness of the rotating rotor is Since it is obtained from the output, the swell and DC drift of the output of the detector caused by the eccentricity of the rotor and the axis deviation can be removed by the low cutoff filter. The by logarithmically compressed by the logarithmic amplifier, it is possible to suppress amplitude fluctuations in the output of the detecting unit due to the eccentricity of the rotating rotor. As a result, it is possible to reduce the detection error of the rotation speed due to the eccentricity of the rotor, and it is possible to improve the detection accuracy of the rotation speed. Further, since the influence of the rotor axis deviation and the eccentricity can be reduced, there is an effect that precision is not required for mounting the magnetic detection element and the application of the rotation speed detection device can be expanded. Furthermore, when a so-called differential type is used as the detection unit, there is no need to align or adjust the characteristics of the two magnetic detection elements, which has the effect of reducing the cost.

According to a second aspect of the present invention, a rotor that rotates integrally with a rotating shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction, and a magnetic field that detects changes in the magnetic field caused by the rotation of the rotor. A detection unit including a detection element, a rectifier that rectifies the output of the detection unit, a coupling capacitor that removes a direct current component from the output of the rectifier, an amplifier that amplifies the output of the rectifier that passes through this coupling capacitor, and an input to the amplifier. Switch circuit for connecting and disconnecting the output of the rectifier, a comparing section for comparing the output of the amplifier and two different reference values according to the changing direction of the output of the amplifier, and the on / off control of the switch circuit periodically. It is equipped with an oscillator, and the detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparison unit, so the ridges included in the output of the detection unit by the coupling capacitor. Can be removed, further, since the input of the switch circuit is periodically turned on and off controlled by the oscillator to the amplifier is interrupted, it is possible to suppress variation in output of the detector due to the eccentricity of the rotating rotor. As a result, it is possible to reduce the detection error of the rotation speed due to the eccentricity of the rotor, and it is possible to improve the detection accuracy of the rotation speed. Further, since the influence of the rotor axis deviation and the eccentricity can be reduced, there is an effect that precision is not required for mounting the magnetic detection element and the application of the rotation speed detection device can be expanded. Furthermore, when a so-called differential type is used as the detection unit, there is no need to align or adjust the characteristics of the two magnetic detection elements, which has the effect of reducing the cost. According to a third aspect of the present invention, there is provided a rotor that rotates integrally with a rotating shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction, and a magnetic detection element that detects a change in the magnetic field caused by the rotation of the rotor. A detection section provided, a pair of rectification smoothing sections for rectifying and smoothing the output of the detection section through a coupling capacitor that removes a direct current component from the output of the detection section, and an output of the detection section input to these pair of rectification smoothing sections. A pair of switch circuits, a differential amplifier that differentially amplifies the output of the pair of rectifying and smoothing units, and an output of the differential amplifier and two different reference values according to the changing direction of the output of the differential amplifier. Since a comparison section for comparison and an oscillator for controlling the pair of switch circuits to be alternately turned on and off periodically are provided, the detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparison section. , Combined The swell included in the output of the detection unit can be removed by the capacitor, and the pair of rectifying / smoothing units are periodically on / off controlled by the oscillator. The rectified and smoothed signals are output alternately.While one rectifying and smoothing section is operating, the other rectifying and smoothing section does not operate, and the output of the operating rectifying and smoothing section is not always operating. The absolute value level becomes higher than the output of the smoothing unit, and if the outputs of the two rectifying and smoothing units are differentially amplified by the differential amplifier, the detection output in which the positive and negative are alternately inverted corresponding to the unevenness of the rotating rotor is obtained. It is possible,
It is possible to suppress the fluctuation of the output of the detection unit due to the eccentricity of the rotor. As a result, it is possible to reduce the detection error of the rotation speed due to the eccentricity of the rotor, and it is possible to improve the detection accuracy of the rotation speed. Further, since the influence of the rotor axis deviation and the eccentricity can be reduced, there is an effect that precision is not required for mounting the magnetic detection element and the application of the rotation speed detection device can be expanded. Furthermore, when a so-called differential type is used as the detection unit, there is no need to align or adjust the characteristics of the two magnetic detection elements, which has the effect of reducing the cost.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a first embodiment.

FIG. 2 is a specific schematic circuit diagram of the above.

FIG. 3 is a diagram for explaining the operation of the above, FIG.
Is a waveform diagram of the output voltage of the detection unit, and (b) is a waveform diagram of the detected output of the rotation speed.

FIG. 4 is a circuit block diagram showing a second embodiment.

5A and 5B are specific schematic circuit diagrams of the above.

6A to 6D are waveform diagrams for explaining the operation of the same.

FIG. 7 is a circuit block diagram showing a third embodiment.

FIG. 8 is a specific schematic circuit diagram of the above.

FIG. 9 is a circuit block diagram showing a fourth embodiment.

FIG. 10 is a specific schematic circuit diagram of the above.

11A to 11G are waveform charts for explaining the operation of the same.

FIG. 12 is a circuit block diagram showing a fifth embodiment.

FIG. 13 is a specific schematic circuit diagram of the above.

14A to 14G are waveform charts for explaining the operation of the same.

FIG. 15 is a circuit block diagram showing another example of the above.

16 is a specific schematic circuit diagram of what is shown in FIG.

FIG. 17 shows a conventional example, and is a schematic configuration diagram of a so-called MPU type rotation speed detection device.

FIG. 18 is a diagram showing an output waveform of the above.

FIG. 19 is a diagram showing the relationship between the rotational speed of the rotor and the output voltage in the above.

FIG. 20 illustrates another conventional example and is a schematic configuration diagram of a so-called high-frequency magnetic field type rotation speed detection device.

21 (a) to 21 (c) are waveform charts showing the output of each part of the above.

FIG. 22 is a waveform chart showing the output of each unit of the above.

FIG. 23 is a schematic configuration diagram showing another example of a so-called high-frequency type rotation speed detection device.

FIG. 24 is a specific schematic circuit diagram of what is shown in FIG. 23.

FIG. 25A is an output voltage waveform diagram of the detection unit and FIG. 25B is a rotational speed detection output waveform diagram of the MPU method shown in FIG.

FIG. 26A is an output voltage waveform diagram of the detection unit of the MPU system shown in FIG. 20, and FIG. 26B is a rotational speed detection output waveform diagram.

FIG. 27 shows still another conventional example, and is a schematic configuration diagram showing a so-called differential type rotation speed detection device.

FIG. 28 is a diagram for explaining the above operation,
(A) is an output voltage waveform diagram of a detection part, (b) is a detection output waveform diagram of a rotation speed.

[Explanation of symbols]

 2 Detector 3 Rectifier 4 Low-frequency cutoff filter 5 Logarithmic amplifier 6 Comparator Vf Reference voltage

Claims (3)

[Claims] 1. A rotor provided with a rotating shaft that rotates together with a rotating shaft in a magnetic field and in which a large number of irregularities are formed at regular intervals in the rotating direction, and a magnetic detecting element for detecting a change in the magnetic field caused by the rotation of the rotor. The detection unit, a rectifier that rectifies the output of the detection unit, a low-frequency cutoff filter that removes DC components from the output of the rectifier, a logarithmic amplifier that logarithmically compresses the output of this low-frequency cutoff filter, and the output of this logarithmic amplifier. A comparator that outputs a signal only when the output of the logarithmic amplifier exceeds a reference value compared with the reference value, and a detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparator. Rotation speed detection device. 2. A rotor, which is integrally rotated with a rotating shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction, and a magnetic detection element for detecting a change in the magnetic field caused by the rotation of the rotor. A detector, a rectifier that rectifies the output of the detector, a coupling capacitor that removes DC components from the output of the rectifier, an amplifier that amplifies the output of the rectifier that passes through this coupling capacitor, and an output of the rectifier that is input to the amplifier. A switch circuit that connects and disconnects the amplifier, a comparator that compares the output of the amplifier with two different reference values according to the changing direction of the output of the amplifier, and an oscillator that periodically controls ON / OFF of the switch circuit. A rotation speed detection device, wherein a detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparison unit. 3. A rotor, which is integrally rotated with a rotating shaft in a magnetic field and has a large number of irregularities formed at regular intervals in the rotational direction, and a magnetic detection element for detecting a change in the magnetic field caused by the rotation of the rotor. The detection unit, a pair of rectification smoothing units that rectify and smooth the output of the detection unit via a coupling capacitor that removes DC components from the output of the detection unit, and the output of the detection unit that is input to the pair of rectification smoothing units is intermittently connected. A pair of switch circuits, a differential amplifier that differentially amplifies the outputs of the pair of rectifying and smoothing units, and compares the output of the amplifier and two different reference values according to the changing direction of the output of the differential amplifier. A rotation comprising a comparator and an oscillator for controlling the pair of switch circuits to be alternately turned on and off periodically, and a detection output corresponding to the unevenness of the rotating rotor is obtained from the output of the comparator. Speed detection apparatus.