JP7163670B2 - Signal processor and sensor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device used in, for example, a rotation detection device using changes in electrical signals due to eddy current loss, and a sensor device provided with the same.

For example, Patent Literature 1 discloses a rotation detection device that detects the rotation speed of a turbocharger mounted on a vehicle. The rotation detection device includes an eddy current sensor having a sensor top (a coil wound around a ferrite core), a resonant circuit connected to the eddy current sensor, and a turbocharger (blade) adjacent to the sensor top. An eddy current is generated in the rotor, and the rotation speed of the turbocharger is detected from a change in an electric signal due to the eddy current loss.

Japanese Patent No. 5645207

However, in the above-configured rotation detection device, the electrical signal from the eddy current sensor has the same waveform when the sensor fails due to disconnection or the like and when the turbocharger is not rotating. Stops cannot be distinguished from electrical signals. Therefore, if it is erroneously determined that the turbocharger is not rotating due to the failure of the sensor, for example, if the engine equipped with the turbocharger is controlled, the turbocharger or the engine may malfunction or fail. .

SUMMARY OF THE INVENTION In view of the circumstances as described above, an object of the present invention is to provide a signal processing device capable of distinguishing failure of a sensor from stoppage of a detection target such as a turbocharger, and a sensor device having the same. .

To achieve the above object, a signal processing device according to one aspect of the present invention is a signal processing device electrically connected to a detection coil for signal detection, and includes an oscillation circuit and a detection section.
The oscillation circuit outputs a first sine wave signal when the detection coil is not broken, and has a lower frequency and an amplitude than the first sine wave signal when the detection coil is broken. Output a large second sinusoidal signal.
The detection unit detects rotation of the detection target based on whether the amplitude of the first sine wave signal exceeds a predetermined threshold, wherein the threshold is the rotation of the detection target. It is set to a value that is larger than the amplitude of the first sine wave signal and smaller than the amplitude of the second sine wave signal when stopped.

The detection unit includes: a first detection circuit for detecting a first amplitude higher than a reference potential in a sine wave signal; a second detection circuit for detecting a second amplitude lower than the reference potential; a differential amplifier circuit that amplifies the difference between the output signal of the detection circuit and the output signal of the second detection circuit; and a binarization circuit that binarizes the output of the differential amplifier circuit based on the threshold value. , may have

As described above, according to the present invention, it is possible to distinguish between a failure of a sensor and a stoppage of an object to be detected such as a turbocharger.

1 is a block diagram schematically showing the configuration of a sensor device according to one embodiment of the present invention; FIG. 1 is a circuit diagram showing a configuration example of an oscillation circuit; FIG. FIG. 4 is a schematic diagram showing a comparison of sine wave signals of the oscillation circuit when the detection coil is not disconnected (solid line) and when the detection coil is disconnected (chain line). 1 is a circuit diagram showing one configuration example of a detection circuit and a differential amplifier circuit; FIG. FIG. 4 is a diagram schematically showing output waveforms of an oscillation circuit, a differential amplifier circuit, and a binarization circuit during turbocharger rotation; FIG. 4 is a diagram schematically showing output waveforms of an oscillation circuit, a differential amplifier circuit, and a binarization circuit when a detection coil is disconnected;

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram schematically showing the configuration of a sensor device 100 according to one embodiment of the invention. A sensor device 100 includes a sensor top 10 and a signal processing device 20 . In this embodiment, the sensor device 100 is a rotation detection device that detects the rotational speed or number of rotations of the rotating blades T in the turbocharger.

The sensor top 10 is, for example, a protruding eddy current sensor, and has a detection coil L1 for signal detection arranged close to the rotating blade T made of metal. The detection coil L1 is formed of a resin-coated copper wire such as enameled wire wound around a magnetic core made of a soft magnetic material such as ferrite. The detection coil L1 is connected to the oscillation circuit 21 of the signal processing device 20, and generates a magnetic field that causes an eddy current in the rotating blade T, which is an object to be detected.

The signal processing device 20 has an oscillation circuit 21 and a detection section 22 . The detection section 22 has a detection circuit 221 , a differential amplifier circuit 222 , a binarization circuit 223 and a frequency division circuit 224 .

FIG. 2 is a circuit diagram showing a configuration example of the oscillation circuit 21. As shown in FIG. As shown in the figure, the oscillator circuit 21 is composed of, for example, a Colpitts-type oscillator circuit, and has a bipolar transistor Q, a first capacitor C10, a second capacitor C20, and a coil L2.

A first capacitor C10 is connected between the emitter of the bipolar transistor Q and the ground terminal, a second capacitor C20 is connected between the collector and the emitter of the bipolar transistor Q, and a coil L2 is connected between the bipolar transistor Q and the ground terminal. is connected between the collector and the base of the A resistor R and a detection coil L1 are connected in parallel with the first capacitor C10 between the emitter of the bipolar transistor Q and the ground terminal.

The oscillation circuit 21 receives a voltage from the power supply (Vcc), and is determined by the combined capacitance of the first capacitor C10 and the second capacitor C20 and the combined inductance of the detection coil L1 and the coil L2. oscillates at an oscillation frequency f0 represented by The oscillation frequency f0 is not particularly limited, and is, for example, 3.5 MHz.

The oscillation circuit 21 outputs a sine wave signal with an oscillation frequency f0 as a detection signal. The rotating blade T facing the detection coil L1 passes through a position affected by the magnetic field generated by the current flowing through the detection coil L1. When the rotating blade T is positioned facing the detection coil L1, the eddy current induced in the rotating blade T causes eddy current loss. Due to this influence, the voltage V of the detection signal output from the oscillation circuit 21 changes. By detecting the voltage change of the detection signal due to this eddy current loss with the detector 22, the rotation of the rotating blade T is detected as described later.

On the other hand, in this type of rotation detection device, the sensor top (detection coil L1) may break. When the detection coil L1 is disconnected, the combined inductance of the oscillation circuit increases as expressed by the following equation (2). As a result, the oscillation frequency f0 decreases and the impedance of the oscillation circuit increases, so that the signal voltage (V) increases compared to before the disconnection of the sensor top.

FIG. 3 is a schematic diagram showing a comparison of the sine wave signal of the oscillation circuit 21 when the detection coil L1 is not disconnected and when the detection coil L1 is disconnected. The solid line in the figure represents the voltage waveform of the oscillation circuit 21 in the normal state, and is hereinafter also referred to as the first sine wave signal W1. The chain double-dashed line in the figure represents the voltage waveform of the oscillation circuit 21 when the detection coil L1 is disconnected, and is hereinafter also referred to as the second sine wave signal W2.

For example, when the detection coil L1 is disconnected, the oscillation frequency of the oscillation circuit 21 drops from the normal 3.5 MHz (first frequency) to 500 kHz (second frequency), and the signal voltage drops to 6 V. (Normal time) to 8V.
Since FIG. 3 is a schematic diagram, the relative ratio of the frequencies of the sinusoidal signals W1 and W2 does not necessarily match the above example.

Next, the detection unit 22 will be described. FIG. 4 is a circuit diagram showing one configuration example of the detection circuit 221 and the differential amplifier circuit 222. As shown in FIG.

The detection circuit 221 has a first detection circuit 221A and a second detection circuit 221B.

The first detection circuit 221A has capacitors C1, C2, C3, a diode D1, and a resistor R1. A diode D1, a capacitor C2 and a resistor R1 are connected in parallel between a first signal line S1 connected to the oscillation circuit 21 and a GND potential (hereinafter referred to as a reference potential). The diode D1 directs current flow from the reference potential to the first signal line. The capacitor C2 and the resistor R1 form an integration circuit F1 that detects a first amplitude higher (positive potential) than the reference potential in the sine wave signal (detection signal) output by the oscillation circuit 21 .

The second detection circuit 221B has capacitors C4, C5, C6, a diode D2, and a resistor R2. A diode D2, a capacitor C4 and a resistor R2 are connected in parallel between a second signal line S2 connected to the oscillation circuit 21 and the reference potential. The diode D2 directs current flow from the second signal line S2 toward the reference potential. The capacitor C5 and the resistor R2 form an integration circuit F2 that detects a second amplitude lower (negative potential) than the reference potential in the sine wave signal output from the oscillation circuit 21. FIG.

The differential amplifier circuit 222 amplifies the difference between the output signal of the first detection circuit 221A and the output signal of the second detection circuit 221B. The differential amplifier circuit 222 has an operational amplifier OP, resistors R3, R4, R5 and R6, and a bias power supply E. The resistor R3 is connected between the first signal line S1 of the detection circuit 221 and the input terminal (non-inverting input terminal) of the operational amplifier OP, and the resistor R4 is connected between the second signal line S2 of the detection circuit 221 and the operational amplifier OP. is connected between the inverting input terminal of A resistor R5 is a negative feedback resistor of the operational amplifier OP, and a resistor R6 is connected between the bias power supply E and the input terminal (non-inverting input terminal) of the operational amplifier OP.

The binarization circuit 223 includes a comparator that compares the output of the differential amplifier circuit 222 with a predetermined potential. The predetermined potential is a threshold (Vth) for detecting the amplitude of the first sine wave signal W1 that changes as the rotating blade T approaches the sensor top 10. FIG. A binarization circuit 223 binarizes the first sine wave signal W1 depending on whether or not its amplitude exceeds the threshold value (Vth). That is, the amplitude of the first sine wave signal W1 changes as the rotating blade T approaches and separates from the sensor top 10 due to the rotation of the rotary blade T, and the change in amplitude is binarized based on the threshold value (Vth). Generate the resulting pulse signal. The frequency of the generated pulse signal is determined by the rotational frequency of the rotating plate T, and is, for example, 50 Hz to 72 kHz.

A frequency dividing circuit 224 divides the output of the binarizing circuit 223 by a predetermined frequency dividing ratio. Thereby, a detection signal corresponding to the rotation speed of the rotating blade T is obtained. The obtained detection signal is output to an ECU (Electronic Control Unit) 30, and the rotation speed of the rotating blade T is detected. Note that the frequency dividing circuit 224 may be provided in the ECU 30 .

5A to 5D are diagrams schematically showing output waveforms of the oscillation circuit 21, the differential amplifier circuit 222, and the binarization circuit 223 when the turbocharger rotates. (B) is an enlarged view of the neutral point (P part) of the voltage fluctuation in (A), the envelope curve on the positive potential side of the sine wave signal W1. (C) shows the output waveform of the differential amplifier circuit 222, and (D) shows the output waveform of the binarization circuit 223, respectively.

The first detection circuit 221A detects the positive voltage side of the first sine wave signal W1 output from the oscillation circuit 21 . The second detection circuit 221B detects the negative voltage side of the first sine wave signal W1 output from the oscillation circuit 21. FIG. The first sine wave signal W1 is a high-frequency signal whose amplitude decreases when the rotating blade T approaches the sensor top 10 and increases when the rotating blade T moves away from the sensor top 10 . Therefore, when the turbocharger is rotating, the amplitude of the first sine wave signal W1 changes periodically according to the rotation of the rotating blades T, as shown in FIG. 5(A). The differential amplifier circuit 222 outputs a waveform signal whose amplitude is maximized when the rotating blade T approaches, as shown in FIG. 5(C). As shown in FIG. 5(D), the binarization circuit 223 generates a pulse signal in which the output of the differential amplifier circuit 222 exceeds the threshold value Vth as "1" and the area below the threshold value Vth as "0". and outputs this to the frequency dividing circuit 224 as information on the number of revolutions of the rotating blade T. FIG.

The threshold Vth is set to a value larger than the amplitude of the first sine wave signal W1, as shown in FIG. set. When the rotating blade T stops rotating, the amplitude of the first sinusoidal signal W1 does not change. In this case, since the output of the differential amplifier circuit 222 is a constant value, the output (pulse signal) of the binarization circuit 223 is not output.

On the other hand, in this type of conventional rotation detection device, when the sensor top is disconnected, the signal waveform output from the oscillation circuit 21 to the detection circuit 221 has the same shape as when the turbocharger stops rotating. and turbocharger shutdown.
In this embodiment, as will be described later, the threshold Vth for detecting the rotation of the rotating blades T is set to a value smaller than the amplitude of the second sine wave signal W2.

6A to 6D are diagrams schematically showing output waveforms of the oscillation circuit 21, the differential amplifier circuit 222, and the binarization circuit 223 when the detection coil L1 is disconnected. Envelope on the positive potential side of the waveform, (B) is an enlarged view of the neutral point (P part) of the voltage fluctuation in (A). (C) shows the output waveform of the differential amplifier circuit 222, and (D) shows the output waveform of the binarization circuit 223, respectively.

When the detection coil L1 is disconnected, the oscillation circuit 21 outputs a second sine wave signal W2 as a detection signal. As shown in FIG. 6(A), the amplitude of the detection signal does not fluctuate and remains constant, as when the turbocharger stops rotating. On the other hand, as described above, the second sine wave signal W2 has a lower frequency and a larger amplitude than the first sine wave signal W1.

Therefore, in this embodiment, the threshold value Vth of the binarization circuit 223 is set to a value smaller than the amplitude of the second sine wave signal W2, as shown in FIG. 6B. That is, the threshold Vth is set to a value that is larger than the amplitude of the first sine wave signal W1 and smaller than the amplitude of the second sine wave signal W2 when the rotating blades T stop rotating. As a result, even when the detection coil L1 is disconnected, the binarization circuit 223 can output a pulse waveform signal obtained by extracting a signal component equal to or higher than the threshold value Vth from the output signal of the differential amplifier circuit 222 (Fig. 6(C), (D)). Since this pulse waveform signal corresponds to the frequency of the second sine wave signal W2 (for example, about 500 Hz), its frequency band is different from that of the pulse signal (50 Hz to 72 kHz) detected during turbocharger rotation. Thereby, the ECU 30 can detect the failure of the sensor top 10 .

The method of adjusting the frequency and voltage of the second sine wave signal W2 is not particularly limited.

As described above, according to the present embodiment, failure of the sensor top 10 and stoppage of the turbocharger can be distinguished. As a result, an erroneous determination that the turbocharger is not rotating due to a malfunction of the sensor top 10 is avoided, so that malfunction or failure of the turbocharger or the engine due to the erroneous determination can be prevented.

Furthermore, according to the present embodiment, since a failure of the sensor top 10 can be detected from the detection signal of the oscillation circuit 21, it is not necessary to separately provide a terminal for outputting an abnormality detection signal of the sensor top 10 to the oscillation circuit 21. Therefore, a single output terminal can output a normal detection signal and an abnormal detection signal.

Although the embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to the above-described embodiments and can be modified in various ways.

For example, in the above embodiment, the oscillation circuit 21 is configured by a Colpitts-type oscillation circuit as shown in FIG. may be employed.

Further, in the above embodiments, the rotating blades of a turbocharger are used as an example of a detection target of the rotational speed, but the detection target is not limited to this. may

Furthermore, in the above embodiment, an eddy current sensor is used as an example of the sensor top 10. However, the sensor top 10 is not limited to this. may apply.

DESCRIPTION OF SYMBOLS 10... Sensor top 20... Signal processing apparatus 21... Oscillation circuit 22... Detection part 30... ECU
DESCRIPTION OF SYMBOLS 100... Sensor apparatus 221... Detection circuit 221A... 1st detection circuit 221B... 2nd detection circuit 222... Differential amplifier circuit 223... Binarization circuit 224... Frequency division circuit L1... Detection coil

Claims (3)

A signal processing device electrically connected to a detection coil for signal detection,
A first sine wave signal is output when the detection coil is not disconnected, and a second sine wave signal having a lower frequency and a larger amplitude than the first sine wave signal is output when the detection coil is disconnected. an oscillation circuit that outputs a wave signal;
A first detection circuit for detecting a first amplitude higher than a reference potential in a sine wave signal, a second detection circuit for detecting a second amplitude lower than the reference potential, and an output of the first detection circuit. a differential amplifier circuit for amplifying a difference between the signal and the output signal of the second detection circuit, the output of the differential amplifier circuit exceeds a predetermined threshold, wherein the threshold is greater than the amplitude of the first sine wave signal when the rotation of the detection target is stopped a detector set to a value that is large and smaller than the amplitude of the second sine wave signal;
A signal processing device comprising: The signal processing device according to claim 1,
The signal processing device , wherein the detection unit further includes a binarization circuit that binarizes the output of the differential amplifier circuit based on the threshold. A signal processing device according to claim 1 or 2;
A sensor device comprising: a detection coil electrically connected to the signal processing device.

Images