JP2010008087A - Signal processing circuit and rolling bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal processing circuit which suppresses ripple noise and a rolling bearing device equipped with this circuit. <P>SOLUTION: The signal processing circuit 10 for processing signals output from displacement sensors 7 arranged as a group of one pair in a hub unit 100 and providing it to an ECU, includes an amplification part 11 for differentially amplifying two signals based on the signals output from the one pair of displacement sensors, and outputting a smooth signal whose keytone is a sinusoidal waveform, a rectification part 12 for rectifying the output from the amplification part 11 and extracting a direct current component, and an adjustment part 13 for linearizing the output of the rectification part 12. In this case, since the two signals whose amplitudes and phases are different from each other according to a displacement amount are not rectified directly, and rectification is performed on the basis of the smooth signal which is obtained by performing the differential amplification of the two signals and whose keytone is a sinusoidal waveform, a waveform before rectification is prevented from containing a waveform part which would be an origin of low-frequency ripple noise. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a circuit for processing a signal output from a displacement sensor provided in a rolling bearing device.

  In recent years, in the field of automobiles, information on loads acting on wheels has been required in order to perform operation control during traveling. In order to obtain such information, a displacement sensor is provided in the wheel rolling bearing device (hub unit) (see, for example, Patent Document 1).

  In such a rolling bearing device, an inner shaft that is a movable raceway is rotatably supported by a fixed raceway on the vehicle body via a rolling element, and a wheel is attached to the inner shaft. A plurality of displacement sensors (provided in a pair of two pairs in the axial direction) are provided opposite to the outer periphery of the end of the inner shaft, and the inner shaft is generated when a load is applied to the wheel. The displacement in the radial and axial directions is output as a change in inductance. And the signal processing circuit connected to these displacement sensors produces | generates the DC signal which shows a displacement based on the change of an inductance, and provides the said signal to ECU (electronic control unit). Thereby, the ECU can determine the load acting on the wheel.

JP 2007-127253 A

  In the signal processing circuit as described above, signals output from the pair of displacement sensors are two signals having sin waveforms with different amplitudes and phases. In such rectification processing for extracting a DC component from the two signals, a method of generating X and Y signals combined with the other signal every half cycle and differentially amplifying them is used. More specifically, the peak portion (half cycle) of one of the two signals is connected to the valley portion (half cycle) of the other signal to form an X signal. A process is performed in which the waveform of the Y signal is switched by connecting the valley portion of one signal after the portion, and the X and Y signals are input to the differential amplifier circuit.

However, when the above-described waveform replacement is performed on two signals having different amplitudes and phases, the joint portion is not smooth. A DC output obtained by signal processing from a waveform having such a joint includes ripple noise with a low frequency, and there is a problem that the output is not linear.
In view of such a conventional problem, an object of the present invention is to provide a signal processing circuit for suppressing ripple noise and a rolling bearing device including the signal processing circuit.

  The present invention is a signal processing circuit that processes signals output from a pair of displacement sensors arranged to detect a displacement of an axis of a rotating body, and converts the signals output from the pair of displacement sensors. Amplifying unit that differentially amplifies two signals based on the output and outputs a smooth signal based on a sin waveform; a rectifying unit that rectifies an output from the amplifying unit to extract a DC component; and an output of the rectifying unit And an adjusting unit for linearizing the.

The signal processing circuit configured as described above is based on a sin waveform obtained by differentially amplifying two signals without subjecting the two signals having different amplitudes and phases depending on the amount of displacement to rectification. Rectification is performed based on the smooth signal. Therefore, it is possible to prevent the waveform before rectification from including a waveform portion that is the basis of ripple noise having a low frequency.
Note that the sin waveform here refers to a shape, and does not mean to exclude the cos waveform. The cos waveform is the same as the sin waveform.

In the signal processing circuit, the rectifier may generate a signal that follows the phase shift of the sin waveform from the reference clock signal, and perform rectification based on the signal.
In this case, since rectification is performed at the timing following the phase shift, there is no waveform step at the rectification switching point. Therefore, there is no loss in subsequent amplification, and the amplification efficiency is improved as compared with the case where there is a step.

The rolling bearing device of the present invention includes a displacement sensor and the signal processing circuit as described above.
In this case, the displacement of the shaft of the rotating body that is rotatably supported by the rolling bearing device can be accurately detected by the signal processing circuit in which the ripple noise is suppressed.

  According to the signal processing circuit of the present invention and the rolling bearing device including the signal processing circuit, it is possible to prevent the waveform before rectification from including a waveform portion that is the basis of low-frequency ripple noise. Ripple noise can be suppressed.

  Hereinafter, a signal processing circuit and a rolling bearing device according to an embodiment of the present invention will be described with reference to the drawings. First, the overall structure of the rolling bearing device will be described.

<< Overall structure of rolling bearing device >>
FIG. 1 is a cross-sectional view of a hub unit which is a kind of rolling bearing device. The hub unit 100 is attached to a vehicle. In the attached state, the right side in FIG. 1 is the outer side of the vehicle (outside of the vehicle), and the left side is the inner side of the vehicle (inside of the vehicle).
In FIG. 1, the direction along the central axis C of the hub unit 100 is defined as the Y-axis direction, the direction perpendicular to the paper surface perpendicular thereto is defined as the X-axis direction, and the vertical direction perpendicular to both the Y-axis direction and the X-axis direction. Is the Z-axis direction. Therefore, in a state where the hub unit 100 is attached to the automobile, the X-axis direction is the front-rear horizontal direction of the wheel, the Y-axis direction is the left-right horizontal direction (axial direction) of the wheel, and the Z-axis direction is the vertical direction.

  The hub unit 100 includes an outer ring 1, an inner shaft 2, an inner ring member 3, a nut 4, and a rolling element 5 as main structural parts. The outer ring 1 has a cylindrical part 1a and a flange part 1b extending radially outward from a part of the outer peripheral surface of the cylindrical part 1a. The flange portion 1b is fixed to a vehicle body side fixing member (not shown), whereby the hub unit 100 is fixed to the vehicle body. The inner shaft 2 has a main shaft portion 2a that is inserted into the outer ring 1 and a flange portion 2b that is on the outer side of the vehicle and extends radially outward. This flange part 2b becomes an attachment part of the wheel of a wheel or a brake disc.

  A cylindrical inner ring member 3 is fitted on the inner side of the inner shaft 2 on the vehicle inner side, and a nut 4 is screwed onto a male screw portion 2d formed on the end of the inner shaft 2, whereby the inner ring member 3 is fitted. Is fixed to the inner shaft 2. The rolling elements 5 have a double-row configuration including a plurality of balls arranged in the circumferential direction. The balls in each row are held at predetermined intervals in the circumferential direction by a cage (not shown). The outer raceway surface 1c and the inner raceway surfaces 2c and 3c form an angle with respect to the rolling element 5, and an angular ball bearing is configured.

  In the hub unit 100, the outer ring 1 is a fixed race that is fixed to a fixing member on the vehicle body side. Further, the inner shaft 2 and the inner ring member 3 are rotating raceways that are rotatably supported by the outer ring 1 via rolling elements 5. The outer ring 1, the inner shaft 2 and the inner ring member 3 are arranged coaxially (center axis C).

  On the other hand, the hub unit 100 is a radial component between the target member 6 and a cylindrical target member (detected portion) 6 that is externally fitted to the inner side end of the inner ring member 3 as a component related to the sensor function. And a displacement sensor 7 disposed opposite to each other in the radial direction. The displacement sensor 7 is attached to a cylindrical case 8, and the case 8 is attached to the outer ring 1. A cap 9 that closes the opening on the left end side of the case 8 is attached. The target member 6 is disposed coaxially with the inner shaft 2 and the inner ring member 3 and rotates integrally therewith. The displacement sensor 7 is provided to obtain a load acting on the rotating raceway (inner shaft 2 and inner ring member 3) from the wheel, and includes a coil that constitutes an inductance that changes in accordance with the displacement of the target member 6. Yes.

  In FIG. 1, the target member 6 is a cylindrical member as a whole, but a circumferential groove 6a is formed on the outer peripheral surface thereof. When the target member 6 is displaced in the axial direction due to the presence of the circumferential groove 6a, the size of the gap between the two rows of the displacement sensors 7 and the target member 6 changes, and the displacement is detected as a change in inductance. be able to.

FIG. 2 is a layout view of the displacement sensor 7 viewed from the left end side of FIG. As shown in FIG. 2, two pairs of displacement sensors 7 are arranged along the X axis and the Z axis. Further, these two pairs of displacement sensors 7 are provided in two rows in the axial direction (Y direction) of FIG.
Here, the displacement sensor 7 is indicated by a sign indicating the location (front of the X axis: f, rearward r of the X axis, upper side of the Z axis: t, lower side of the Z axis b, vehicle inner side: i, vehicle outer side o). , There are eight displacement sensors fi, fo, ri, ro, ti, to, bi, bo shown in FIG. For example, if the output of each displacement sensor is expressed as [fi] if it is the output of the displacement sensor fi, the displacement can be obtained as follows.

That is, the radial displacement Xi on the vehicle inner side can be obtained based on the differential outputs of [fi] and [ri], for example, [fi] − [ri].
The radial displacement Zi on the vehicle inner side can be obtained based on a differential output of [bi] and [ti], for example, [bi]-[ti].
Similarly, the radial displacement Xo on the vehicle outer side can be determined based on [fo]-[ro], and the radial displacement Zo on the vehicle outer side can be determined based on [bo]-[to]. .

  On the other hand, the axial displacement Y is a differential output of [fi] and [fo], a differential output of [ri] and [ro], a differential output of [ti] and [to], or [bi], [ bo] can be obtained based on the differential output. It can also be obtained based on the differential output of the sum of [fi], [ri], [ti], [bi] and the sum of [fo], [ro], [to], [bo]. it can.

<< Signal Processing Circuit According to First Embodiment >>
Next, a signal processing circuit (first embodiment) for processing signals output from the two displacement sensors 7 in order to obtain the above displacement will be described based on the circuit diagram of FIG. The signal processing circuit may be mounted on the hub unit 100 as a part of the hub unit 100, or may be another individual connected from the hub unit 100 via a cable or the like.

  In FIG. 3, the signal processing circuit 10 includes an amplifying unit 11 that differentially amplifies two signals based on signals output from the pair of displacement sensors 7 and outputs a smooth signal based on a sin waveform, and an amplifying unit. 11 includes a rectification unit 12 that rectifies the output from 11 and extracts a DC component, and an adjustment unit 13 that linearizes the output of the rectification unit 12. Two signals (IN−, IN +) are input from the pair of displacement sensors 7 to the amplifying unit 11. Moreover, the output of the adjustment part 13 is provided to ECU which is not shown in figure.

  The signal processing circuit 10 shown in the circuit diagram of FIG. 3 includes an operational amplifier (not shown), a resistor or variable resistor R, a capacitor C, and an analog switch 12b. First, the amplification unit 11 includes a resonance circuit 11a that changes a change in inductance in the pair of displacement sensors 7 into a voltage signal, a buffer circuit 11b that performs impedance conversion, and a differential amplification circuit 11c that performs differential amplification of two signals. It is configured. An oscillation signal synchronized with the clock signal is given to the resonance circuit 11a.

The rectifying unit 12 includes an inverting circuit 12a that inverts a signal voltage, an analog switch 12b, and a differential amplifier circuit 12c. The analog switch 12b receives the signal itself output from the amplifying unit 11 and a signal obtained by inverting the signal by the inverting circuit 12a. The analog switch 12b is supplied with a clock signal (CLK), and the switch is switched in synchronization with the clock signal.
The adjustment unit 13 is an offset / gain adjustment circuit.

FIG. 4 is an example of a waveform diagram showing signal waveforms at various parts on the circuit of FIG. 3, in which the amount of displacement decreases from the + state when viewed from the reference value, and further increases toward the − state. Is shown. The clock signal is a pulse signal having a constant frequency as shown. Further, the input signals “IN +” and “IN−” from the displacement sensor 7 have opposite phases and amplitudes. That is, when the amount of displacement is +, the voltage phase of “IN +” advances from the clock signal and the amplitude increases as the amount of displacement increases, whereas the voltage phase of “IN−” lags behind the clock signal as the amount of displacement increases. The amplitude decreases. On the contrary, when the displacement amount is −, “IN +” has a voltage phase that is delayed from the clock signal and decreases in amplitude as the displacement amount is large, but “IN−” has a voltage phase that advances from the clock signal as the displacement amount is large. The amplitude increases.
The relationship between the phase and the amplitude may be reversed depending on the relationship between the resonance frequency of the resonance circuit 11a and the frequency of the clock signal.

  The two input signals “IN +” and “IN−” are differentially amplified by the differential amplifier circuit 11c and are directly input to the analog switch 12b. A signal obtained by inverting this is also an input signal to the analog switch 12b. If one of these two input signals is “analog switch IN +” and the other is “analog switch IN−”, these become a smooth signal waveform based on a sin waveform as shown, and the phase of the two signals -The coincidence point of the amplitude is a neutral point (reference value) where the displacement amount is zero.

  The analog switch 12b performs switch switching every half cycle in synchronization with the clock signal. As a result, the input signal is full-wave rectified and output, and becomes “analog switch OUT +” and “analog switch OUT−” shown in the figure. Further, these two signals are differentially amplified by the differential amplifier circuit 12c to become the “differential amplifier OUT” shown in the figure. This signal is obtained by extracting a DC component from the input of the analog switch 12b, and has a sign and a peak value corresponding to the sign (positive / negative) and absolute value of the displacement amount for each half cycle of the clock signal. Further, in this signal, a phase shift from the clock signal included in the input of the analog switch 12b appears as a step for each half cycle of the clock signal. This step is steep and is constituted by a high frequency component.

  The adjustment unit 13 (offset gain adjustment circuit) has a function of a low-pass filter and a function of giving a signal in a predetermined voltage range to an ECU (not shown). Remove components and linearize. Accordingly, the output signal “offset gain OUT” is a straight line passing through the neutral point (zero point) as shown in the figure. Thus, a linear output without ripple noise is obtained.

  According to the signal processing circuit 10 configured as described above, two signals (IN +, IN−) having different amplitudes and phases are not subjected to rectification, but the two signals are differentially amplified. Rectification is performed based on smooth signals ("analog switch IN +" and "analog switch IN-") based on the obtained sin waveform. Therefore, it is possible to prevent the waveform before rectification from including a waveform portion that is the basis of ripple noise having a low frequency. That is, a signal processing circuit that suppresses ripple noise can be provided.

  From another point of view, the crosstalk and capacitor component of the analog switch 12b increase ripple noise during switching. In this embodiment, the analog switch 12b is arranged separately from the resonance circuit 11a. Therefore, impedance separation is performed, and thereby ripple noise can be suppressed.

  Further, by using such a signal processing circuit 10, the displacement of the inner shaft 2 that is rotatably supported by the hub unit 100, that is, the force (tire force) acting on the wheel, while suppressing ripple noise, It can be detected accurately.

<< Signal Processing Circuit According to Second Embodiment >>
Next, a signal processing circuit (second embodiment) having another circuit configuration will be described with reference to the circuit diagram of FIG. In the figure, the amplification unit 11 and the adjustment unit 13 of the signal processing circuit 10 are the same as those in the first embodiment (FIG. 3). The inverting circuit 12a, the analog switch 12b, and the differential amplifier circuit 12c of the rectifying unit 12 are the same as those in the first embodiment. The difference from the first embodiment is that a phase clock tracking circuit 12d is provided. The circuit 12d generates a signal that follows the phase shift (shift from the reference clock signal) of the phase output from the amplifying unit 11, and the rectifying unit 12 performs rectification based on the signal. It will be.

  Specifically, the phase clock tracking circuit 12d is configured by connecting a resistor R, a capacitor C, a comparator COMP, a flip-flop circuit FF, and an exclusive OR circuit EXOR as illustrated. The output signal of the differential amplifier circuit 11c in the amplifier 11 is input to the phase clock tracking circuit 12d, and the analog switch 12b performs switch switching in synchronization with the output signal of the phase clock tracking circuit 12d.

  FIG. 6 is an example of a waveform diagram showing signal waveforms at various parts on the circuit of FIG. 5, in which the amount of displacement decreases from the + state as viewed from the reference value, and further increases toward the − state. Is shown. In the figure, the clock signal, the input signals “IN +” and “IN−” from the displacement sensor 7, and the input signals “analog switch IN +” and “analog switch IN−” to the analog switch 12 b are the first embodiment ( This is similar to FIG.

  The comparator COMP of the phase clock tracking circuit 12d compares the signal of the “analog switch IN +” with a predetermined value to obtain the illustrated binary signal “COMP OUT”. The phase of the “COMP OUT” signal is slightly shifted from that of the clock signal, similarly to the “analog switch IN +”. The “COMP OUT” signal and the clock signal are input to the flip-flop circuit FF. The output “FF OUT” of the flip-flop circuit FF becomes 0 when the rise of the “COMP OUT” signal is earlier than that of the clock signal, and from this state, the rise of the “COMP OUT” signal as compared with the clock signal. Becomes 1 when the state becomes slower.

The exclusive OR circuit EXOR calculates the exclusive OR of “FF OUT” and “COMP OUT” and outputs an “EXOR OUT” signal as shown in the figure.
In this way, the phase clock follower circuit 12d outputs an “EXOR OUT” signal that follows the phase shift of the input signal “analog switch IN +”, and the analog switch 12b performs switch switching in synchronization with the signal. The flip-flop circuit FF plays a role of generating a polarity signal, and regenerates the polarity origin in order to repair the “separation” of the phase relationship with the clock signal lost due to the phase shift tracking.

  Then, the analog switch 12b performs switch switching in synchronization with the “EXOR OUT” signal. As a result, full-wave rectification is performed in synchronization with the phase of the input signal, resulting in “analog switch OUT +” and “analog switch OUT−” shown in the figure. Further, these two signals are differentially amplified by the differential amplifier circuit 12c to become the “differential amplifier OUT” shown in the figure. This signal is obtained by extracting a DC component from the input of the analog switch 12b, and has a sign and a peak value corresponding to the sign (positive / negative) and absolute value of the displacement amount, respectively. Further, in this signal, there is no step at the rectification switching point. Therefore, there is no amplification loss, and the amplification efficiency in the subsequent stage (adjustment unit 13) is improved as compared with the case where there is a step.

  The adjustment unit 13 removes a high frequency component from the “differential amplification OUT” signal and linearizes it. Therefore, the output signal “offset gain OUT” is a straight line passing through the neutral point (zero point) as shown in the figure. Thus, a linear output without ripple noise is obtained.

In the second embodiment as described above, similarly to the first embodiment, it is possible to provide the signal processing circuit 10 that suppresses ripple noise.
Further, since the rectification is performed at the timing following the phase shift, there is no waveform step at the rectification switching point. Therefore, there is no loss in subsequent amplification, and the amplification efficiency is improved as compared with the case where there is a step.

  In addition, although the signal processing circuit of each said embodiment demonstrated as what processes the output signal of the displacement sensor 7 attached to the hub unit 100, it detects not only the hub unit 100 but the displacement of the axis | shaft of a rotary body. Therefore, the present invention can be applied as a signal processing circuit that processes signals output from a displacement sensor arranged in a one-to-one pair.

It is sectional drawing of the hub unit which is a kind of rolling bearing apparatus. FIG. 2 is a layout diagram of a displacement sensor viewed from the left end side of FIG. 1. 1 is a circuit diagram of a signal processing circuit according to a first embodiment. It is an example of the wave form diagram which shows the signal waveform in each part on the circuit of FIG. It is a circuit diagram of the signal processing circuit which concerns on 2nd Embodiment. FIG. 6 is an example of a waveform diagram showing signal waveforms at various parts on the circuit of FIG. 5.

Explanation of symbols

2 Inner shaft 7 Displacement sensor 10 Signal processing circuit 11 Amplifying unit 12 Rectifying unit 13 Adjusting unit 100 Rolling bearing device

Claims (3)

A signal processing circuit for processing signals output from displacement sensors arranged in a one-to-one pair to detect displacement of a shaft of a rotating body,
An amplifier that differentially amplifies two signals based on the signals output from the pair of displacement sensors and outputs a smooth signal based on a sin waveform;
A rectification unit that rectifies the output from the amplification unit and extracts a DC component;
A signal processing circuit comprising: an adjustment unit that linearizes an output of the rectification unit.   The signal processing circuit according to claim 1, wherein the rectifying unit generates a signal that follows a phase shift of the sin waveform from a reference clock signal, and performs rectification based on the signal.   A rolling bearing device comprising the displacement sensor and the signal processing circuit according to claim 1.

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