Detection device of rotational angle or position

Abstract

To provide a detection device of a rotational angle or a position that can realize both of an increase in the detection precision of the rotational angle or the position and a decrease in the delay of a filter output signal.SOLUTION: A detection device comprises sensors 1, 2 for outputting at least one of a sine signal and a cosine signal as a sensor signal v2 according to rotation or reciprocating motion of a detected body 5, a bandpass filter 3 that includes a high-pass filter 33 and a low-pass filter 34 and allows the sensor signal v2 to be inputted, a position detection circuit 4 for detecting a rotational angle or a position of the detected body 5 by input of a filter output signal v3 obtained by removing noise from the sensor signal v2 by the bandpass filter 3, and a frequency detection circuit 31 for detecting the frequency of rotation or reciprocating motion of the detected body 5 by input of the sensor signal v2, and adjusts the time constant of the high-pass filter 33 according to the frequency of rotation or reciprocating motion of the detected body 5 detected by the frequency detection circuit 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a detection device for detecting the rotation angle or position of a detection object. [Background technology]

[0002] Patent Document 1 discloses a rotation angle detection device that uses a low-pass filter (hereinafter abbreviated as LPF) to remove noise from sine and cosine signals output as sensor signals from a rotation angle sensor in response to the rotation of a rotating body.

[0003] 23 is a block diagram showing the configuration of a conventional rotation angle detection device that uses an LPF to remove noise from sine and cosine signals output as sensor signals from a rotation angle sensor in response to the rotation of a rotating body. In this rotation angle detection device, the LPF removes noise from the sine and cosine signals output as sensor signals from the rotation angle sensor in response to the rotation of the rotating body, and the filter output signals are input to a rotation angle detection circuit.

[0004] In such a rotation angle detection device, in order to improve the accuracy of angle detection, it is necessary to set the cutoff frequency of the LPF to a value that is as low as possible while still allowing the maximum frequency component of the sensor signal to pass.

[0005] For example, as shown in Figure 24, the rotation frequency of the rotor is assumed to be in the range of 0 to 4 kHz. In this case, the cutoff frequency f C2 Therefore, the cutoff frequency f of the LPF must be set to be higher than 4 kHz. C2 To compare the cutoff frequency f C2 The frequency characteristics of the LPF gain when set to 12 kHz are shown by the solid line in Fig. 24, and the cutoff frequency f C2 The frequency characteristics of the LPF gain when set to 48 kHz are shown by the broken line in Figure 24. Then, the cutoff frequency f C2The LPF with cutoff frequency f set to 48kHz has a wider passband than the LPF with cutoff frequency f set to 12kHz, so the noise in the filter output signal will be larger. C2 Using an LPF set to 12 kHz will result in a higher S / N ratio (signal-to-noise ratio) than an LPF set to 48 kHz, and the rotation angle of the rotor can be detected with higher accuracy. Therefore, the time constant of the LPF is determined by the target angle detection accuracy and resolution. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-009590 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above-mentioned conventional technology, the use of an LPF causes a phase delay in the filter output signal. The phase delay θ2 of the filter output signal of the LPF is calculated by the relational expression shown in Equation 9 below, which is expressed as follows: C2 Therefore, the more the LPF reduces noise, the longer the delay time increases, and the target delay time cannot be achieved.

[0008] In this way, in a rotation angle detection device that uses an LPF for noise removal, the cutoff frequency f C2 Lowering the cutoff frequency f of the LPF reduces noise, but increases the phase delay of the filter output signal. C2 Increasing θ can reduce the phase delay of the filter output signal, but increases noise. In other words, in a rotation angle detection device that uses an LPF for noise removal, there is a trade-off between increasing the accuracy of angle detection and reducing the delay of the filter output signal.

[0009] Furthermore, even in a position detection device in which sine signals and cosine signals are output as sensor signals from a position sensor in response to the reciprocating motion of a detected object, if an LPF is used to remove noise from the sine signals and cosine signals output as sensor signals, there is a trade-off between increasing the accuracy of position detection and reducing the delay in the filter output signals.

[0010] Therefore, the present invention aims to provide a rotation angle or position detection device that solves the above-mentioned omission and can achieve both high accuracy in detecting the rotation angle or position and reduced delay in the filter output signal. [Means for solving the problem]

[0011] The rotation angle or position detection device of the present invention comprises a sensor that outputs at least one of a sine signal and a cosine signal as a sensor signal in accordance with the rotation or reciprocating motion of a detectable object, a band-pass filter having a low-pass filter and a high-pass filter with an adjustable time constant, to which the sensor signal is input, a position detection circuit that detects the rotation angle or position of the detectable object by inputting a filter output signal obtained by removing noise from the sensor signal by the band-pass filter, and a frequency detection circuit that detects the frequency of the rotation or reciprocating motion of the detectable object by inputting the sensor signal or the filter output signal, and is characterized in that the time constant of the high-pass filter is adjusted in accordance with the frequency of the rotation or reciprocating motion of the detectable object detected by the frequency detection circuit.

[0012] The present invention narrows the passband of the bandpass filter by adjusting the time constant of the high-pass filter in accordance with the frequency of the rotation or reciprocating motion of the object to be detected, and the phase delay caused by the low-pass filter can be offset by the phase advance caused by the high-pass filter, thereby achieving both high accuracy in detecting the rotation angle or position and reduced delay in the filter output signal.

[0013] In one aspect of the rotation angle or position detection device according to the present invention, the low-pass filter may have a changeable time constant, and the time constant of the low-pass filter may be adjusted according to the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit.

[0014] According to this aspect, by adjusting the time constant of the low-pass filter in accordance with the frequency of the rotation or reciprocating motion of the object to be detected, the pass band of the band-pass filter is narrowed, thereby further improving the accuracy of detection of the rotation angle or position.

[0015] In one aspect of the rotation angle or position detection device of the present invention, when the frequency of the rotation or reciprocating motion of the object detected by the frequency detection circuit falls below a first threshold, the function of the high-pass filter may be disabled.

[0016] According to this aspect, it is possible to reduce the maximum resistance value of the variable resistor and the maximum capacitance of the variable capacitor used in the high-pass filter.

[0017] In one aspect of the rotation angle or position detection device according to the present invention, when the function of the high-pass filter is disabled, the time constant of the low-pass filter may be fixed to a predetermined value.

[0018] According to this aspect, the delay of the filter output signal can be suppressed by disabling the function of the high-pass filter and fixing the time constant of the low-pass filter to a predetermined value in a state where only a phase delay occurs due to the low-pass filter.

[0019] In one aspect of the rotation angle or position detection device according to the present invention, even if the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit changes from a value equal to or less than the first threshold to a value greater than the first threshold, the function of the high-pass filter may be kept disabled until the frequency becomes equal to or greater than a second threshold that is greater than the first threshold.

[0020] According to this aspect, even under usage conditions in which the frequency of the rotation or reciprocating motion of the object to be detected repeatedly rises and falls across the first threshold, it is possible to prevent the high-pass filter function from being frequently switched between disabled and enabled in a short period of time.

[0021] In one aspect of the rotation angle or position detection device according to the present invention, the rotation angle or position of the object to be detected may be calculated from a sine signal and a cosine signal of the filter output signal and output.

[0022] In one aspect of the rotation angle or position detection device according to the present invention, even if the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit changes from a value equal to or less than the first threshold value to a value greater than the first threshold value, the function of the high-pass filter may be kept disabled and the time constant of the low-pass filter may be kept fixed at the predetermined value until the frequency becomes equal to or greater than a second threshold value that is greater than the first threshold value.

[0023] According to this aspect, even under usage conditions in which the frequency of the rotation or reciprocating motion of the object to be detected repeatedly rises and falls across the first threshold, it is possible to prevent the high-pass filter function from being frequently disabled and enabled in a short period of time, and the low-pass filter time constant from being frequently switched between a specified value and a non-specified value in a short period of time.

[0024] In one aspect of the rotation angle or position detection device of the present invention, the frequency detection circuit may detect the frequency of the rotation or reciprocating motion of the object to be detected by counting the number of pulses of a reference clock included in multiple periods, a single period, a half period, or a quarter period of the sensor signal.

[0025] In one aspect of the rotation angle or position detection device according to the present invention, the sensor may be an inductive type or a magnetoelectric conversion element type sensor.

[0026] According to this aspect, even with an inductive or magnetoelectric conversion element sensor that generates a small output signal, it is possible to detect the rotation angle or position with high precision.

[0027] In one aspect of the rotation angle or position detection device according to the present invention, the sensor may be an inductive sensor of an electromagnetic induction type or a self-inductance type. [Effects of the Invention]

[0028] The present invention can provide a rotation angle or position detection device that can achieve both high precision in detecting a rotation angle or position and reduced delay in a filter output signal. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a block diagram showing the configuration of a rotation angle detection device according to a first embodiment. [Figure 2] 2 is a block diagram showing the configuration of a frequency tracking bandpass filter circuit of the rotation angle detection device of the first embodiment. FIG. [Figure 3] 1 is a block diagram showing a first configuration example of an FN conversion circuit of a frequency tracking bandpass filter circuit of a rotation angle detection device according to a first embodiment. FIG. [Figure 4] FIG. 4 is a block diagram showing a configuration of a second configuration example of an FN conversion circuit of a frequency tracking bandpass filter circuit of the rotation angle detection device of the first embodiment. [Figure 5] 3A to 3C are diagrams illustrating the operation of a first configuration example of an FN conversion circuit of a frequency tracking bandpass filter circuit of the rotation angle detection device of the first embodiment. [Figure 6] 4A to 4C are diagrams illustrating the operation of a second configuration example of the FN conversion circuit of the frequency tracking bandpass filter circuit of the rotation angle detection device of the first embodiment. [Figure 7] FIG. 1 is a circuit diagram illustrating a first example of a configuration of a high-pass filter. [Figure 8] FIG. 10 is a circuit diagram showing a second configuration example of a high-pass filter. [Figure 9] 3 is a circuit diagram showing an example of the configuration of a low-pass filter of the rotation angle detection device of the first embodiment. FIG. [Figure 10]10A and 10B are diagrams illustrating a method for changing the time constants of a high-pass filter and a low-pass filter. [Figure 11] 3A and 3B are diagrams illustrating a method for adjusting the time constants of a high-pass filter and a low-pass filter in accordance with the rotation frequency of a rotating body in the rotation angle detection device of the first embodiment. [Figure 12] 4 is a diagram showing the relationship between the rotation frequency of a rotor and the cutoff frequencies of a high-pass filter and a low-pass filter in the rotation angle detection device of the first embodiment. FIG. [Figure 13] 10A and 10B are diagrams illustrating the frequency characteristics of the phase lead of a high-pass filter and the frequency characteristics of the phase lag of a low-pass filter. [Figure 14] FIG. 10 is a diagram illustrating frequency characteristics of the gain of a high-pass filter and a low-pass filter. [Figure 15] 3A to 3C are diagrams illustrating the operation of a high-pass filter and a low-pass filter in a low frequency band in the rotation angle detection device of the first embodiment. [Figure 16] FIG. 10 is a block diagram showing the configuration of a frequency tracking bandpass filter of a rotation angle detection device according to a second embodiment. [Figure 17] FIG. 10 is a circuit diagram showing an example of the configuration of a low-pass filter of a rotation angle detection device according to a second embodiment. [Figure 18] 10A and 10B are diagrams illustrating a method for changing the time constant of a high-pass filter. [Figure 19] 10A and 10B are diagrams illustrating a method for adjusting the time constant of a high-pass filter in accordance with the rotation frequency of a rotor in a rotation angle detection device according to a second embodiment. [Figure 20] 10 is a diagram illustrating the relationship between the rotation frequency of a rotor and the cutoff frequencies of a high-pass filter and a low-pass filter in the rotation angle detection device of the second embodiment. FIG. [Figure 21] 10A and 10B are diagrams illustrating the operation of a high-pass filter and a low-pass filter in a low frequency band in the rotation angle detection device of the second embodiment. [Figure 22] FIG. 10 is a block diagram showing the configuration of a position detection device according to a third embodiment. [Figure 23]FIG. 1 is a block diagram showing the configuration of a conventional rotation angle detection device using a low-pass filter. [Figure 24] FIG. 10 is a diagram illustrating the frequency characteristics of the gain of a low-pass filter. DETAILED DESCRIPTION OF THE INVENTION

[0030] First Embodiment A rotation angle detection device 10 according to a first embodiment of the present invention will be described below with reference to FIGS. 1 to 15. The rotation angle detection device 10 can be used to detect the rotation angle of a rotating body, such as the rotor of an electric motor. FIG. 1 is a block diagram showing the configuration of the rotation angle detection device 10. As shown in FIG. 1, the rotation angle detection device 10 includes a sensor body 1, a signal processing circuit 2, a frequency tracking bandpass filter (hereinafter abbreviated as BPF) circuit 3, and a rotation angle detection circuit 4. The sensor body 1 can be an inductive sensor that detects the displacement of a conductor caused by the rotation of a rotating body 5, which is the object to be detected. The inductive sensor used as the sensor body 1 may be either an electromagnetic induction type or a self-inductance type. The sensor body 1 may also be a magnetoelectric conversion element type sensor using a magnetoresistive element or a Hall element.

[0031] The sensor main body 1 outputs a voltage v1 obtained by amplitude modulating (AM) a high-frequency carrier into a sine signal and a cosine signal. The signal processing circuit 2 demodulates and amplifies the AM-modulated voltage v1 input from the sensor main body 1 and outputs the sine signal and the cosine signal as a sensor signal v2. Therefore, the combination of the sensor main body 1 and the signal processing circuit 2 functions as a single rotation angle sensor that outputs a sine signal sin θ and a cosine signal cos θ as the sensor signal v2 according to the rotation angle θ of the rotor 5. For example, the sine signal and the cosine signal that change by one period as the rotor 5 rotates once are output as the sensor signal v2. The sensor signal v2 is input to the BPF circuit 3, and the filter output signal v3, from which noise has been removed, is input to the rotation angle detection circuit 4. The rotation angle detection circuit 4 then receives the filter output signal v3, detects the rotation angle of the rotor 5 from the filter output signal v3, and outputs an output signal va representing the rotation angle. The rotation angle detection circuit 4 corresponds to the "position detection circuit" set forth in the claims.

[0032] Fig. 2 is a block diagram showing the configuration of a frequency tracking BPF circuit 3. As shown in Fig. 2, the BPF circuit 3 includes an FN conversion circuit 31, a switching determination circuit 32, a high-pass filter (hereinafter abbreviated as HPF) 33, and an LPF 34. The HPF 33 includes a resistance value control circuit 35, and the LPF 34 includes a resistance value control circuit 36. The HPF 33 and the LPF 34 are connected in series, and the sensor signal v2 has noise removed by the HPF 33 and the LPF 34 before being output from the BPF circuit 3 as a filter output signal v3.

[0033] The sensor signal v2 is also input to the FN conversion circuit 31. The FN conversion circuit 31 is a circuit that outputs a count value N corresponding to the frequency of the sensor signal v2. A block diagram of a first configuration example of the FN conversion circuit 31 is shown in FIG. 3, and a block diagram of a second configuration example of the FN conversion circuit 31 is shown in FIG. 4. The FN conversion circuit 31 may have either the first configuration example shown in FIG. 3 or the second configuration example shown in FIG. 4.

[0034] FIG. 5 is a diagram illustrating the operation of the first configuration example of the FN conversion circuit 31. When the FN conversion circuit 31 has the configuration of the first configuration example shown in FIG. 3, the sine and cosine signals of the sensor signal v2 are converted by the pulse conversion circuit into a pulse signal v2p with a duty ratio of 50 percent, as shown in FIG. 5. The pulse width of this pulse signal v2p corresponds to a half period of the sensor signal v2. A pulse train v2t corresponding to the pulse width of the pulse signal v2p is generated by performing a logical AND operation on the pulse signal v2p and the clock signal CLK. A counter counts the number of reference clock pulses included in the pulse train v2t to obtain a count value N. This count value N corresponds to the rotational frequency of the rotating body 5, and therefore the first configuration example of the FN conversion circuit 31 shown in FIG. 3 functions as a frequency detection device that detects the rotational frequency of the rotating body 5.

[0035] FIG. 6 illustrates the operation of the second configuration example of the FN conversion circuit 31. When the FN conversion circuit 31 has the configuration of the second configuration example shown in FIG. 4, the pulse conversion circuit converts the sine signal v2s and cosine signal v2c of the sensor signal v2 into pulse signals v2ps and v2pc, respectively, with a duty ratio of 50 percent, as shown in FIG. 6. Then, by performing an exclusive OR operation on the pulse signals v2ps and v2pc, a pulse signal v22p having a frequency twice that of the pulse signals v2ps and v2pc is obtained. The pulse width of this pulse signal v22p corresponds to one-quarter of the period of the sensor signal v2. In the second configuration example of the FN conversion circuit 31, a pulse train v2t corresponding to the pulse width of the pulse signal v2p is generated by performing a logical AND operation on the pulse signal v22p and the clock signal CLK. In the second configuration example of the FN conversion circuit 31, a counter counts the number of reference clock pulses included in the pulse train v2t to obtain a count value N. Since this count value N corresponds to the rotation frequency of the rotor 5, the second configuration example of the FN conversion circuit 31 shown in FIG.

[0036] As described above, the FN conversion circuit 31 can obtain the count value N corresponding to the rotation frequency of the rotor 5 in either of the configurations of Configuration Example 1 shown in FIG. 3 and Configuration Example 2 shown in FIG. 4. However, the measurement frequency of the count value N in Configuration Example 2 shown in FIG. 4 is twice that of Configuration Example 1 shown in FIG. 3. Therefore, Configuration Example 2 shown in FIG. 4 can improve the calculation speed of the count value N and suppress delays due to signal processing compared to Configuration Example 1 shown in FIG. 3. In this way, when Configuration Example 2 shown in FIG. 4 is used as the FN conversion circuit 31, the frequency of the clock signal CLK can be set to at least twice that of Configuration Example 1 shown in FIG. 3, thereby ensuring the same or better detection accuracy of the rotation frequency of the rotor 5.

[0037] 2, the count value N calculated by the FN conversion circuit 31 is input to the switching determination circuit 32. The switching determination circuit 32 is a determination circuit for switching between enabling and disabling the function of the HPF 33. When the count value N is smaller than a switching value Nth, the switching determination circuit 32 enables the function of the HPF 33, and when the count value N is equal to or greater than the switching value Nth, the switching determination circuit 32 disables the function of the HPF 33.

[0038] FIG. 7 is a circuit diagram showing a first configuration example of the HPF 33. FIG. 8 is a circuit diagram showing a second configuration example of the HPF 33. The HPF 33 may have either the first configuration example shown in FIG. 7 or the second configuration example shown in FIG. 8. The HPF 33 includes a capacitor C1 and a variable resistor R1 in either the first configuration example shown in FIG. 7 or the second configuration example shown in FIG. 8. The HPF 33 can vary the time constant by varying the resistance value of the variable resistor R1. Note that the resistance value control circuit 35 shown in FIG. 2 is not shown in FIGS. 7 and 8.

[0039] When the HPF 33 has the configuration of Configuration Example 1 shown in Fig. 7, the switching determination circuit 32 can disable the function of the HPF 33 by shorting the capacitor C1. When the HPF 33 has the configuration of Configuration Example 2 shown in Fig. 8, the switching determination circuit 32 can disable the function of the HPF 33 by skipping the HPF 33.

[0040] 9 is a circuit diagram showing an example configuration of the LPF 34. The LPF 34 includes a capacitor C2 and a variable resistor R2. The time constant of the LPF 34 can be varied by varying the resistance value of the variable resistor R2. Note that the resistance value control circuit 36 ​​shown in FIG. 2 is omitted from FIG. 9.

[0041] 10 is a diagram illustrating a method for changing the time constants of the HPF 33 and the LPF 34. As shown in FIG. 10, the variable resistor R1 of the HPF 33 is a resistor R 10 , resistance R 11 , resistance R 12 ...Resistance R 1(nー1) The resistor R 11 The resistance value of resistor R 10 Resistance value of 2 1 times the resistance R 12 The resistance value of resistor R 10 Resistance value of 2 2 times the resistance R 13 The resistance value of resistor R 10 Resistance value of 2 3 times the resistance R 1(nー1) The resistance value of resistor R 10 Resistance value of 2 (n-1) The resistance value control circuit 35 of the HPF 33 is a resistor R 10 ~Resistance R 1(n-1) By selecting resistors to be shorted from the n resistors in the 10 From 1 to (2 n For example, the resistance value control circuit 35 of the HPF 33 can vary the resistance R 10 By shorting out all resistors except for R 10 In addition, the resistance value control circuit 35 of the HPF 33 can be set to 1 times the resistance R 10 ~Resistance R 1(n-1) By not shorting any of the n resistors, the resistance value of the variable resistor R1 is set to the resistance R 10 (2 nSince the time constant of the HPF 33 is the product of the resistance value of the variable resistor R1 and the capacitance value of the capacitor C1, the resistance value control circuit 35 of the HPF 33 can change the time constant of the HPF 33 by varying the resistance value of the variable resistor R1.

[0042] The variable resistor R2 of the LPF 34 is 20 , resistance R 21 , resistance R 22 ...Resistance R 2(n-1) The resistor R 21 The resistance value of resistor R 20 Resistance value of 2 1 times the resistance R 22 The resistance value of resistor R 20 Resistance value of 2 2 times the resistance R 23 The resistance value of resistor R 20 Resistance value of 2 3 times the resistance R 2(nー1) The resistance value of resistor R 20 Resistance value of 2 (n-1) The resistance value control circuit 36 ​​of the LPF 34 is 20 ~Resistance R 2(n-1) By selecting resistors to be shorted from the n resistors in the 20 From 1 to (2 n For example, the resistance value control circuit 36 ​​of the LPF 34 can vary the resistance R 20 By shorting out all resistors except for R 20 In addition, the resistance value control circuit 36 ​​of the LPF 34 can be set to 1 times the resistance R 20 ~Resistance R 2(n-1) By not shorting any of the n resistors, the resistance value of the variable resistor R2 is set to the resistance R 20 (2 n Since the time constant of the LPF 34 is the product of the resistance value of the variable resistor R2 and the capacitance value of the capacitor C2, the resistance value control circuit 36 ​​of the LPF 34 can change the time constant of the LPF 34 by varying the resistance value of the variable resistor R2.

[0043] 11 is a diagram illustrating a method for adjusting the time constants of the HPF 33 and the LPF 34 in accordance with the rotation frequency of the rotor 5 in the rotation angle detection device 10. The resistance value control circuit 36 ​​of the LPF 34 adjusts the cutoff frequency f C2 The time constant of the LPF 34 is adjusted so that (x) follows the fluctuation of the rotation frequency x of the rotor 5. For example, when the rotation frequency x of the rotor 5 decreases from x1 to x2 to x3 as shown in FIG. 11, the resistance control circuit 36 ​​of the LPF 34 adjusts the cutoff frequency of the LPF 34 to f C2 (x1), and the cutoff frequency of LPF34 is f C2 (x2), and the cutoff frequency of LPF34 is f C2 The time constant of the LPF 34 is adjusted to be (x3).

[0044] The resistance control circuit 36 ​​of the LPF 34 is configured to, for example, calculate the rotation frequency x and the cutoff frequency f of the LPF 34. C2 The time constant of the LPF 34 may be adjusted in accordance with fluctuations in the rotation frequency x so that the relationship of (x) satisfies the relationship shown in Equation 1 below.

[0045]

number

[0046] When the resistance value control circuit 36 ​​of the LPF 34 adjusts the time constant of the LPF 34 so that the relationship of Equation 1 holds, the rotation frequency x of the rotor 5 and the cutoff frequency f of the LPF 34 are C2 The relationship with (x) is shown in FIG. 12. In this case, from Equation 1, the cutoff frequency f C2 (x) is proportional to the rotation frequency x of the rotor 5. The proportionality constant of Equation 1 is 2.65, which is greater than 1. Therefore, as shown in FIG. 12, the cutoff frequency f C2 (x) is always higher than the rotation frequency x. Therefore, as shown in FIG. 11, the cutoff frequency f of the LPF 34 at the rotation frequency x1 C2(x1) is higher than the rotation frequency x1, and the cutoff frequency f C2 (x2) is higher than the rotation frequency x2, and the cutoff frequency f of the LPF 34 at the rotation frequency x3 C2 (x3) is higher than the rotation frequency x3.

[0047] The resistance control circuit 35 of the HPF 33 controls the cutoff frequency f of the HPF 33 in response to fluctuations in the rotation frequency x of the rotor 5. C1 The time constant of the HPF 33 is adjusted to follow (x) so as not to cause a delay in the filter output signal v3 from the BPF circuit 3. For example, when the rotation frequency x of the rotor 5 decreases from x1 to x2 to x3 as shown in FIG. 11, the resistance control circuit 35 of the HPF 33 adjusts the cutoff frequency of the HPF 33 to f C1 (x1), and the cutoff frequency of HPF33 is f C1 (x2), and the cutoff frequency of HPF33 is f C1 Adjust the time constant of HPF33 so that it becomes (x3).

[0048] The resistance control circuit 36 ​​of the LPF 34 controls the rotation frequency x and the cutoff frequency f of the LPF 34. C2 When the time constant of the LPF 34 is adjusted in accordance with the fluctuation of the rotation frequency x so that the relationship of (x) becomes the relationship shown in Equation 1, the resistance value control circuit 35 of the HPF 33 is C1 The time constant of the HPF 33 is adjusted in accordance with fluctuations in the rotation frequency x so that the relationship of (x) satisfies the relationship shown in Equation 2 below.

[0049]

number

[0050] The resistance value control circuit 35 of the HPF 33 adjusts the time constant of the HPF 33 so that the relationship of Equation 2 holds, and the rotation frequency x of the rotor 5 and the cutoff frequency f of the HPF 33 C1The relationship between the HPF 33 and the cutoff frequency f (x) is as shown in FIG. 12. The proportionality constant in Equation 2 is the reciprocal of 2.65, which is smaller than 1. Therefore, as shown in FIG. 12, C1 (x) is always lower than the rotation frequency x. Therefore, as shown in FIG. 11, the cutoff frequency f C1 (x1) is lower than the rotation frequency x1, and the cutoff frequency f of HPF33 at rotation frequency x2 C1 (x2) is lower than the rotation frequency x2, and the cutoff frequency f of HPF33 at rotation frequency x3 C1 (x3) is lower than the rotation frequency x3.

[0051] Rotation frequency x and cutoff frequency f of LPF34 C2 When (x) satisfies the relationship shown in Equation 1, the rotation frequency x and the cutoff frequency f of the HPF33 C1 If (x) satisfies the relationship shown in Equation 2, the phase delay θ2 caused by the LPF 34 can be offset by the phase lead θ1 caused by the HPF 33, thereby preventing delay of the filter output signal v3 caused by the BPF circuit 3. The reason why the relationship between Equation 1 and Equation 2 enables the phase delay θ2 caused by the LPF 34 to be offset by the phase lead θ1 caused by the HPF 33 will be explained below.

[0052] If the capacitance value of the capacitor C1 of the HPF33 is C1 and the resistance value of the variable resistor R1 is R1, the cutoff frequency of the HPF33 is f C1 For (x), the following equation 3 holds:

[0053]

number

[0054] When the angular frequency of the rotor 5 is ω, the following equation 4 holds for the phase lead θ1 generated by the HPF 33.

[0055]

number

[0056] If the capacitance value of the capacitor C2 of the LPF 34 is C2 and the resistance value of the variable resistor R2 is R2, the cutoff frequency f C2 For (x), the following equation 5 holds:

[0057]

number

[0058] Regarding the phase delay θ2 caused by the LPF 34, the following equation 6 holds true.

[0059]

number

[0060] Regarding the angular frequency ω and the rotational frequency x, the following equation 7 holds true:

[0061]

number

[0062] From equations 3, 4 and 7, the following equation 8 holds true for the phase lead θ1 caused by the HPF 33.

[0063]

number

[0064] From equations 5, 6, and 7, the following equation 9 holds true for the phase delay θ2 caused by the LPF 34.

[0065]

number

[0066] From Equation 8 and Equation 9, in order to cancel out the phase lead θ1 and the phase lag θ2 and make the delay caused by the BPF circuit 3 zero, the following Equation 10 must be satisfied.

[0067]

number

[0068] Rotation frequency x and cutoff frequency f of LPF34 C2 When (x) satisfies the relationship shown in Equation 1, the rotation frequency x and the cutoff frequency f of the HPF33 C1 If (x) satisfies the relationship shown in Equation 2, the cutoff frequency f C1 (x) and the cutoff frequency f of LPF34 C2 (x) is related to the cutoff frequency f C2 If the relationship in Equation 1 holds for (x), the cutoff frequency f C1 Since the relationship of Equation 2 holds for (x), the phase delay θ2 caused by the LPF 34 can be offset by the phase advance θ1 caused by the HPF 33.

[0069] For example, if the rotation frequency x is 4 kHz, then the cutoff frequency f of LPF 34 is C2 The time constant of the LPF 34 is adjusted so that (x) is 10.6 kHz, and the cutoff frequency f of the HPF 33 is calculated from Equation 2. C1 The time constant of the HPF 33 is adjusted so that (x) is 1.5 kHz. C1 The frequency response of the phase lead by the HPF33 adjusted so that (x) is 1.5 kHz, and the cutoff frequency f C2 The solid line shows the frequency characteristics of the phase delay caused by the LPF 34 adjusted so that (x) is 10.6 kHz. C1 HPF33 adjusted so that (x) is 1.5kHz, and the cutoff frequency f C2 The frequency characteristics of the phase shift of the BPF circuit 3 combined with the LPF 34 adjusted so that (x) is 10.6 kHz are shown by the dashed line in Fig. 13. When the rotation frequency x is 4 kHz, the BPF circuit 3 does not cause any phase lead or lag, as shown in Fig. 13.

[0070] Figure 14 shows the cutoff frequency f C1 The frequency characteristics of the gain of HPF33 when (x) is adjusted to 1.5 kHz and the cutoff frequency f of LPF34 C2 The frequency characteristics of the gain of the LPF 34 when (x) is adjusted to 10.6 kHz are shown by solid lines.

[0071] If the gain of the HPF 33 is G1, the following equation 11 holds.

[0072]

number

[0073] If the gain of the LPF 34 is G2, the following equation 12 holds true.

[0074]

number

[0075] From the formulas 3, 7, and 11, the following formula 13 holds for the gain G1 of the HPF 33.

[0076]

number

[0077] From the equations 5, 7, and 12, the following equation 14 holds true for the gain G2 of the LPF 34.

[0078]

number

[0079] From equation 13, the rotation frequency x is the cutoff frequency f of HPF33. C1 When the rotation frequency x is sufficiently higher than (x), the gain G1 of the HPF 33 is constant at 1. In other words, when the rotation frequency x is sufficiently higher than 1.5 kHz, which is the cutoff frequency of the HPF 33, the gain G1 of the HPF 33 is constant at 1, as shown in FIG.

[0080] Furthermore, from Equation 14, the rotation frequency x is equal to the cutoff frequency f C2 When the rotation frequency x is sufficiently lower than (x), the gain G2 of the LPF 34 is constant at 1. In other words, when the rotation frequency x is sufficiently lower than 10.6 kHz, which is the cutoff frequency of the LPF 34, the gain G2 of the LPF 34 is constant at 1, as shown in FIG.

[0081] Because BPF circuit 3 has HPF 33 and LPF 34 connected in series, the frequency characteristics of the gain of BPF circuit 3 exhibit a transmission frequency characteristic centered around 4 kHz, as shown by the dashed line in Fig. 14. Therefore, BPF circuit 3 can pass the 4 kHz rotation frequency x without attenuating it while narrowing the passband.

[0082] In this way, the rotation angle detection device 10 narrows the pass band of the BPF circuit 3 by adjusting the time constants of the HPF 33 and the LPF 34 in accordance with the rotation frequency of the rotor 5, and can offset the phase delay θ2 caused by the LPF 34 with the phase advance θ1 caused by the HPF 33, thereby achieving both high precision in rotation angle detection and reduced delay in the filter output signal v3. Furthermore, because the rotation angle detection device 10 can narrow the pass band of the BPF circuit 3 in this way, it can detect the rotation angle with high precision even when a rotation angle sensor with a small output signal is used for the sensor main body 1.

[0083] 12 does not accurately depict the operation of the HPF 33 and the LPF 34 in the low frequency range where the rotation frequency x of the rotor 5 is 1000 Hz or less. The accurate operation of the HPF 33 and the LPF 34 in the low frequency range where the rotation frequency x of the rotor 5 is 1000 Hz or less is depicted in FIG.

[0084] As already described, the switching determination circuit 32 of the BPF circuit 3 shown in Fig. 2 enables the function of the HPF 33 when the count value N is smaller than the switching value Nth, and disables the function of the HPF 33 when the count value N is equal to or greater than the switching value Nth. This switching value Nth for the count value N corresponds to the first threshold value xth1 of the rotation frequency x shown in Fig. 15. When the count value N rises above the switching value Nth, that is, when the rotation frequency x of the rotating body 5 falls below the first threshold value xth1, the switching determination circuit 32 disables the function of the HPF 33.

[0085] When the rotation frequency x of the rotor 5 is in a low frequency range equal to or lower than the first threshold value xth1, the cutoff frequency f C1 If we try to adjust (x) to a value lower than the rotation frequency x, then, according to Equation 3, a very large resistance value is required for the variable resistor R1 of the HPF 33. In particular, when the rotation frequency x is zero, the cutoff frequency f C1 To set (x) to zero, it would be necessary to set the variable resistance R1 of the HPF 33 to infinity, which is difficult to achieve. Therefore, in the rotation angle detection device 10, when the rotation frequency x drops below the first threshold value xth1, the switching determination circuit 32 disables the function of the HPF 33. By disabling the function of the HPF 33 in this way when the rotation frequency x of the rotor 5 drops below the first threshold value xth1, the rotation angle detection device 10 can reduce the maximum resistance value of the variable resistance R1 used in the HPF 33.

[0086] When the switching determination circuit 32 of the BPF circuit 3 disables the function of the HPF 33, the resistance value control circuit 36 ​​of the LPF 34 determines the cutoff frequency f C2The time constant of the LPF 34 is fixed to a predetermined value so that (x) becomes a fixed value f0. When the rotation frequency x falls below the first threshold value xth1 and the function of the HPF 33 is disabled, the BPF circuit 3 does not produce a phase lead θ1 due to the HPF 33, and only a phase lag θ2 due to the LPF 34 occurs. Therefore, when the function of the HPF 33 is disabled, it is necessary to reduce the phase lag θ2 due to the LPF 34. Therefore, the predetermined value of the time constant of the LPF 34, which is fixed when the function of the HPF 33 is disabled, is set to a value smaller than the time constant of the LPF 34 immediately before it was disabled. From Equation 5, when the time constant of the LPF 34 becomes smaller, the cutoff frequency f of the LPF 34 C2 Therefore, the fixed value f0 is set to the cutoff frequency f of the LPF 34 immediately before the function of the HPF 33 is disabled, as shown in FIG. C2 The rotation angle detection device 10 sets the predetermined value of the time constant of the LPF 34, which is fixed when the function of the HPF 33 is disabled, to a value smaller than the time constant of the LPF 34 immediately before the HPF 33 is disabled, thereby making it possible to reduce the phase delay θ2 caused by the LPF 34 when the function of the HPF 33 is disabled.

[0087] 15, the rotation angle detection device 10 may further include a second threshold value xth2 higher than the first threshold value xth1. When the second threshold value xth2 is included, even if the rotation frequency x of the rotor 5 changes from a value equal to or less than the first threshold value xth1 to a value greater than the first threshold value xth1, the switching determination circuit 32 does not immediately enable the function of the HPF 33, but continues to disable the function of the HPF 33 until the value becomes higher than the second threshold value xth2, and the cutoff frequency f of the LPF 34 C2 When the rotation frequency x becomes higher than the second threshold value xth2, the switching decision circuit 32 of the BPF circuit 3 switches the function of the HPF 33 to be valid, and the resistance value control circuit 36 ​​of the LPF 34 switches the cutoff frequency f C2 (x) is switched from a fixed value f0 to the value calculated by Equation 1. In other words, the cutoff frequency f C2When the rotation frequency x falls below the first threshold value xth1, (x) rises to a fixed value f0 as shown by the solid line in FIG. 15, and when the rotation frequency x rises above the second threshold value xth2, (x) falls from the fixed value f0 as shown by the dashed line in FIG. 15.

[0088] By setting the second threshold value xth2 in this manner, the rotation angle detection device 10 can prevent the function of the HPF 33 from being frequently disabled and enabled in a short period of time and prevent the time constant of the LPS 34 from being frequently switched between a predetermined value and a non-predetermined value, even under usage conditions in which the rotation frequency x of the rotating body 5 repeatedly rises and falls across the first threshold value xth1.

[0089] <Second embodiment> Next, a rotation angle detection device 20 according to a second embodiment of the present invention will be described with reference to Figures 16 to 21. The rotation angle detection device 20 of the second embodiment has the same configuration as the rotation angle detection device 10 of the first embodiment, except that the resistor R2 of the LPF 34a is a fixed resistor and the device 20 does not include a resistance value control circuit 36 ​​for the resistor R2. Therefore, the same components as those in the rotation angle detection device 10 of the first embodiment are denoted by the same reference numerals and will not be described again.

[0090] Fig. 16 is a block diagram showing the configuration of the BPF circuit 3a of the rotation angle detection device 20. Fig. 17 is a circuit diagram showing an example configuration of the LPF 34a of the BPF circuit 3a. As shown in Figs. 16 and 17, the LPF 34a of the BPF circuit 3a differs from the LPF 34 of the BPF circuit 3 of the rotation angle detection device 10 of the first embodiment in that the resistor R2 is a fixed resistor and the LPF 34a does not include a resistance value control circuit for the resistor R2. Therefore, in the rotation angle detection device 20, the time constant of only the HPF 33 is adjusted in accordance with the rotation frequency of the rotor 5.

[0091] 18 is a diagram illustrating a method for changing the time constant of the HPF 33. The resistance value control circuit 35 of the HPF 33 controls the resistance R 10 ~Resistance R 1(n-1) By selecting resistors to be shorted from the n resistors in the 10From 1 to (2 n Since the time constant of the HPF 33 is the product of the resistance value of the variable resistor R1 and the capacitance value of the capacitor C1, the resistance value control circuit 35 of the HPF 33 can change the time constant of the HPF 33 by varying the resistance value of the variable resistor R1.

[0092] 19 is a diagram illustrating a method for adjusting the time constant of the HPF 33 in accordance with the rotation frequency of the rotor 5 in the rotation angle detection device 20. The resistance value control circuit 35 of the HPF 33 adjusts the cutoff frequency f C1 The time constant of the HPF 33 is adjusted so that (x) follows the fluctuation of the rotation frequency x of the rotor 5. For example, when the rotation frequency x of the rotor 5 decreases from x1 to x2 to x3 as shown in FIG. 19, the resistance control circuit 35 of the HPF 33 adjusts the cutoff frequency of the HPF 33 to f C1 (x1), and the cutoff frequency of HPF33 is f C1 (x2), and the cutoff frequency of HPF33 is f C1 The time constant of the HPF 33 is adjusted so that the cutoff frequency f of the LPF 34a is (x3). C2 maintains a constant value and does not fluctuate.

[0093] For example, the LPF 34a has a cutoff frequency f C2 In this case, the time constant may be set so that the cutoff frequency f of the HPF 33 is always 10.7 kHz. C1 The time constant of the HPF 33 is adjusted in accordance with the rotation frequency x so that the relationship of (x) satisfies the relationship shown in the following equation 15.

[0094]

number

[0095] Cutoff frequency f of LPF34a C2If is fixed at 10.7kHz, then from equation 10, the rotation frequency x and the cutoff frequency f of HPF33 are C1 If (x) satisfies the relationship shown in Equation 15, the phase delay θ2 caused by the LPF 34a can be offset by the phase advance θ1 caused by the HPF 33.

[0096] The resistance control circuit 35 of the HPF 33 adjusts the time constant of the HPF 33 so that the relationship of Equation 15 holds, and the rotation frequency x of the rotor 5 and the cutoff frequency f of the HPF 33 are C1 The relationship between (x) and the cutoff frequency f of the HPF 33 is shown in FIG. C1 (x) is a quadratic function of the rotation frequency x.

[0097] In this way, the rotation angle detection device 20 narrows the passband of the BPF circuit 3a by adjusting the time constant of the HPF 33 in accordance with the rotation frequency of the rotor 5, and the phase delay θ2 caused by the LPF 34a can be offset by the phase advance θ1 caused by the HPF 33, so it is possible to achieve both high accuracy in angle detection and reduced delay in the filter output signal v3. Unlike the rotation angle detection device 10 of the first embodiment, which adjusts the time constants of the HPF 33 and the LPF 34 in accordance with the rotation frequency x of the rotor 5, the rotation angle detection device 20 does not adjust the time constant of the LPF 34a, and therefore has the advantage of being easier to control than the rotation angle detection device 10 of the first embodiment.

[0098] 20 does not accurately depict the operation of the HPF 33 in the low-frequency range where the rotation frequency x of the rotor 5 is 1000 Hz or less. The accurate operation of the HPF 33 in the low-frequency range where the rotation frequency x of the rotor 5 is 1000 Hz or less is depicted in FIG. 21.

[0099] As in the rotation angle detection device 10 of the first embodiment, in the rotation angle detection device 20 of the second embodiment, the switching determination circuit 32 of the BPF circuit 3a enables the function of the HPF 33 when the count value N is smaller than the switching value Nth, and disables the function of the HPF 33 when the count value N is equal to or greater than the switching value Nth. This switching value Nth of the count value N corresponds to the first threshold value xth1 of the rotation frequency x shown in Fig. 21. When the count value N rises above the switching value Nth, that is, when the rotation frequency x of the rotating body 5 falls below the first threshold value xth1, the switching determination circuit 32 disables the function of the HPF 33.

[0100] When the rotation frequency x of the rotor 5 is in a low frequency range equal to or lower than the first threshold value xth1, the cutoff frequency f C1 If we try to adjust (x) to a value lower than the rotation frequency x, then, according to Equation 3, a very large resistance value is required for the variable resistor R1 of the HPF 33. In particular, when the rotation frequency x is zero, the cutoff frequency f C1 To set (x) to zero, it would be necessary to set the variable resistance R1 of the HPF 33 to infinity, which is difficult to achieve. Therefore, in the rotation angle detection device 20, when the rotation frequency x drops below the first threshold value xth1, the switching determination circuit 32 disables the function of the HPF 33. By disabling the function of the HPF 33 in this way when the rotation frequency x of the rotor 5 drops below the first threshold value xth1, the rotation angle detection device 20 can reduce the maximum resistance value of the variable resistance R1 used in the HPF 33.

[0101] 21, the rotation angle detection device 20 may further include a second threshold xth2 that is greater than the first threshold xth1. When the second threshold xth2 is included, even if the rotation frequency x of the rotor 5 changes from a value equal to or less than the first threshold xth1 to a value greater than the first threshold xth1, the switching determination circuit 32 does not immediately enable the function of the HPF 33, but continues to disable the function of the HPF 33 until the rotation frequency x becomes greater than the second threshold xth2. When the rotation frequency x becomes greater than the second threshold xth2, the switching determination circuit 32 of the BPF circuit 3a enables the function of the HPF 33.

[0102] By setting the second threshold value xth2 in this manner, the rotation angle detection device 20 can prevent the function of the HPF 33 from being frequently switched between disabled and enabled in a short period of time, even under conditions in which the rotation frequency x of the rotor 5 repeatedly rises and falls across the first threshold value xth1.

[0103] <Third embodiment> Next, a position detection device 30 according to a third embodiment of the present invention will be described with reference to Fig. 22. The position detection device 30 of the third embodiment has the same configuration as the rotation angle detection device 10 of the first embodiment, except that it includes a sensor main body 1b that detects the position of a reciprocating detection object 5b, and includes a position detection circuit 4b instead of the rotation angle detection circuit 4. Therefore, the same components as those in the rotation angle detection device 10 of the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0104] FIG. 22 is a block diagram showing the configuration of a position detection device 30. The position detection device 30 can be used to detect the position of a reciprocating detection object 5b. As shown in FIG. 22, the position detection device 30 includes a sensor main body 1b, a signal processing circuit 2, a frequency tracking BPF circuit 3, and a position detection circuit 4b. The sensor main body 1b can be an inductive sensor that detects the displacement of a conductor caused by the reciprocating motion of the detection object 5b. The inductive sensor used as the sensor main body 1b can be either an electromagnetic induction type or a self-inductance type. Furthermore, the sensor main body 1b can also be a magnetoelectric conversion element type sensor using a magnetoresistance effect element or a Hall element.

[0105] The sensor main body 1b outputs a voltage v1 obtained by amplitude modulating (AM) a high-frequency carrier into a sine signal and a cosine signal. The signal processing circuit 2 demodulates and amplifies the AM-modulated voltage v1 input from the sensor main body 1b and outputs the sine signal and the cosine signal as a sensor signal v2. Therefore, the combination of the sensor main body 1b and the signal processing circuit 2 functions as a single rotation angle sensor that outputs a sine signal sinα and a cosine signal cosα as the sensor signal v2 in accordance with the position α of the reciprocating stroke of the object to be detected 5b. For example, the sine signal and the cosine signal that change by one period as the object to be detected 5b reciprocates are output as the sensor signal v2. The sensor signal v2 is input to the BPF circuit 3, and the filter output signal v3, which has been filtered by the BPF circuit 3, is input to the position detection circuit 4b. The position detection circuit 4b then detects the position of the object to be detected 5b from the filter output signal v3 and outputs a position output signal va. The position detection circuit 4b corresponds to the "position detection circuit" set forth in the claims.

[0106] The BPF circuit 3 of the position detection device 30 is the same as the BPF circuit 3 of the rotation angle detection device 10 of the first embodiment. The position detection device 30 adjusts the time constants of the HPF 33 and the LPF 34 in accordance with the frequency of the reciprocating motion of the detection object 5b. The method of adjusting the time constants of the HPF 33 and the LPF 34 in the position detection device 30 is the same as the method of adjusting the time constants of the HPF 33 and the LPF 34 in the rotation angle detection device 10 of the first embodiment.

[0107] Therefore, the position detection device 30 narrows the pass band of the BPF circuit 3 by adjusting the time constants of the HPF 33 and the LPF 34 in accordance with the frequency of the reciprocating motion of the object to be detected 5b, and the phase delay θ2 caused by the LPF 34 can be offset by the phase advance θ1 caused by the HPF 33, thereby achieving both high accuracy in position detection and reduced delay in the filter output signal v3. Furthermore, because the position detection device 30 can narrow the pass band of the BPF circuit 3 in this way, it is possible to achieve high accuracy in position detection even when a position sensor with a small output signal is used for the sensor main body 1b.

[0108] Furthermore, similar to the rotation angle detection device 10 of the first embodiment, the position detection device 30 is provided with a second threshold value xth2 shown in FIG. 15, which makes it possible to prevent the function of the HPF 33 from being frequently switched between disabled and enabled in a short period of time and to prevent the time constant of the LPS 34 from being frequently switched between a predetermined value and a non-predetermined value, even under conditions in which the frequency x of the reciprocating motion of the object to be detected 5b repeatedly rises and falls across the first threshold value xth1.

[0109] <Supplementary information on the embodiment> The rotation angle or position detection device of the present invention is not limited to the above-described embodiment and can be embodied in various forms within the scope of the present invention. For example, the HPF and LPF may employ variable capacitors instead of variable resistors to make the time constant variable. Furthermore, the frequency detection circuit that detects the frequency of the object to be detected may count the number of reference clock pulses contained in one cycle of the sensor signal v2, or may count the number of reference clock pulses contained in multiple cycles of the sensor signal v2.

[0110] [Configuration of the invention] [Configuration 1] a sensor that outputs at least one of a sine signal and a cosine signal as a sensor signal in response to the rotation or reciprocating motion of an object to be detected; a band-pass filter having a low-pass filter and a high-pass filter with a changeable time constant, to which the sensor signal is input; a position detection circuit that detects the rotation angle or position of the object to be detected by inputting a filter output signal obtained by removing noise from the sensor signal by the band pass filter; a frequency detection circuit that detects a frequency of the rotation or reciprocating motion of the detection object by receiving the sensor signal or the filter output signal; A rotation angle or position detection device, characterized in that the time constant of the high-pass filter is adjusted in accordance with the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit. [Configuration 2] The rotation angle or position detection device according to configuration 1, The low-pass filter has a variable time constant, A rotation angle or position detection device, characterized in that the time constant of the low-pass filter is adjusted in accordance with the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit. [Configuration 3] The rotation angle or position detection device according to configuration 1 or 2, A rotation angle or position detection device characterized in that when the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit falls below a first threshold, the function of the high-pass filter is disabled. [Configuration 4] The rotation angle or position detection device according to configuration 3, A rotation angle or position detection device, characterized in that, when the function of the high-pass filter is disabled, the time constant of the low-pass filter is fixed to a predetermined value. [Configuration 5] The rotation angle or position detection device according to configuration 3 or 4, A rotation angle or position detection device characterized in that, even when the frequency of the rotation or reciprocating motion of the object to be detected by the frequency detection circuit changes from a value below the first threshold to a value above the first threshold, the function of the high-pass filter continues to be disabled until the frequency becomes equal to or above a second threshold that is greater than the first threshold. [Configuration 6] The rotation angle or position detection device according to any one of configurations 1 to 5, A rotation angle or position detection device, characterized in that the rotation angle or position of the object to be detected is calculated from the sine signal and cosine signal of the filter output signal and outputted. [Configuration 7] The rotation angle or position detection device according to configuration 4, A rotation angle or position detection device characterized in that, even when the frequency of the rotation or reciprocating motion of the object to be detected by the frequency detection circuit changes from a value below the first threshold to a value above the first threshold, the function of the high-pass filter continues to be disabled and the time constant of the low-pass filter continues to be fixed at the predetermined value until the frequency becomes equal to or above a second threshold that is greater than the first threshold. [Configuration 8] The rotation angle or position detection device according to any one of configurations 1 to 7, A rotation angle or position detection device characterized in that the frequency detection circuit detects the frequency of the rotation or reciprocating motion of the object to be detected by counting the number of pulses of a reference clock contained in multiple periods, a single period, a half period, or a quarter period of the sensor signal. [Configuration 9] The rotation angle or position detection device according to any one of configurations 1 to 8, A rotation angle or position detection device, characterized in that the sensor is an inductive type or a magnetoelectric conversion element type sensor. [Configuration 10] The rotation angle or position detection device according to configuration 9, A rotation angle or position detection device, wherein the sensor is an inductive sensor of an electromagnetic induction type or a self-inductance type. [Explanation of symbols]

[0111] 1, 1b sensor body, 2 signal processing circuit, 3, 3a BPF circuit, 4 rotation angle detection circuit, 4b position detection circuit, 5 rotating body, 5b detected body, 10, 20 rotation angle detection device, 30 position detection device, 31 FN conversion circuit, 32 switching determination circuit, 33 HPF, 34, 34a LPF, 35, 36 resistance value control circuit.

Claims

1. a sensor that outputs at least one of a sine signal and a cosine signal as a sensor signal in response to the rotation or reciprocating motion of an object to be detected; a band-pass filter having a low-pass filter and a high-pass filter with a variable time constant, to which the sensor signal is input; a position detection circuit that detects the rotation angle or position of the object to be detected by inputting a filter output signal obtained by removing noise from the sensor signal by the band pass filter; a frequency detection circuit that detects a frequency of the rotation or reciprocating motion of the detection object by receiving the sensor signal or the filter output signal; A rotation angle or position detection device, characterized in that the time constant of the high-pass filter is adjusted in accordance with the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit.

2. 2. The rotation angle or position detection device according to claim 1, The low-pass filter has a variable time constant, A rotation angle or position detection device, characterized in that the time constant of the low-pass filter is adjusted in accordance with the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit.

3. 3. The rotation angle or position detection device according to claim 1 or 2, A rotation angle or position detection device characterized in that when the frequency of the rotation or reciprocating motion of the object to be detected detected by the frequency detection circuit falls below a first threshold, the function of the high-pass filter is disabled.

4. 4. The rotation angle or position detection device according to claim 3, A rotation angle or position detection device, characterized in that, when the function of the high-pass filter is disabled, the time constant of the low-pass filter is fixed to a predetermined value.

5. 4. The rotation angle or position detection device according to claim 3, A rotation angle or position detection device characterized in that, even when the frequency of the rotation or reciprocating motion of the object to be detected by the frequency detection circuit changes from a value below the first threshold to a value above the first threshold, the function of the high-pass filter is continued to be disabled until the frequency becomes equal to or above a second threshold that is greater than the first threshold.

6. 3. The rotation angle or position detection device according to claim 1 or 2, A rotation angle or position detection device, characterized in that the rotation angle or position of the object to be detected is calculated from the sine signal and cosine signal of the filter output signal and outputted.

7. 5. The rotation angle or position detection device according to claim 4, a rotation angle or position detection device characterized in that, even when the frequency of the rotation or reciprocating motion of the object to be detected by the frequency detection circuit changes from a value below the first threshold to a value above the first threshold, the function of the high-pass filter continues to be disabled and the time constant of the low-pass filter continues to be fixed at the predetermined value until the frequency becomes equal to or above a second threshold that is greater than the first threshold.

8. 3. The rotation angle or position detection device according to claim 1 or 2, A rotation angle or position detection device characterized in that the frequency detection circuit detects the frequency of the rotation or reciprocating motion of the object to be detected by counting the number of pulses of a reference clock contained in multiple periods, a single period, a half period, or a quarter period of the sensor signal.

9. 3. The rotation angle or position detection device according to claim 1 or 2, A rotation angle or position detection device, characterized in that the sensor is an inductive type or a magnetoelectric conversion element type sensor.

10. 10. The rotation angle or position detection device according to claim 9, A rotation angle or position detection device, characterized in that the sensor is an inductive sensor of an electromagnetic induction type or a self-inductance type.

Images