JPH078770U - Differential coil type rotation detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To stabilize the rotation pulse output by eliminating the temperature drift and drift over time of the differential coil type rotation detector. [Structure] The differential coil type rotation detector comprises a combination of a gear 1 and a pair of cores 2 and 3. The gear 1 is made of a magnetic material and is attached to a rotary shaft to be detected. Coils 5 and 6 are wound around the pair of cores 2 and 3, respectively.
The magnetic resistance of the magnetic circuit formed by one core 2 and the teeth 7 of the gear 1 and the magnetic resistance of the magnetic circuit formed by the other core 3 and the teeth 7 of the gear 1 follow the rotation of the gear 1. It changes differentially. The oscillator circuit 10 applies alternating voltages Φ and Φ ⁻ to both ends of a pair of coils 5 and 6 connected in series. The AC amplifier 11 amplifies the AC signal output from the midpoint M of the pair of coils 5 and 6. The synchronous rectification circuit 12 rectifies and smoothes the amplified AC signal in synchronization with the alternating voltage Φ, and converts the AC signal into a DC signal. The comparison circuit 13 sends the DC signal to A
A rectangular wave pulse output R is generated by comparison with the midpoint potential of the C amplifier 11.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a differential coil type rotation detector. More specifically, the present invention relates to an electric processing technique of a signal output from a pair of coils.

[0002]

[Prior art]

 The magnetic circuit configuration of the conventional differential coil type rotation detector will be briefly described with reference to FIG. The differential coil type rotation detector comprises a combination of a gear 1 made of a magnetic material and a pair of cores 2 and 3. The gear 1 is attached to a rotary shaft 4 which is a detection target. Examples of the rotating shaft 4 include a wheel shaft of a train. Coils 5 and 6 are wound around the pair of cores 2 and 3, respectively. The magnetic resistance of the magnetic circuit formed by one core 2 and the teeth 7 of the gear 1 and the magnetic resistance of the magnetic circuit formed by the other core 3 and the teeth 7 of the gear 1 follow the rotation of the gear 1. It changes differentially. In such a configuration, a pulse output corresponding to the movement of the teeth 7 of the rotating gear 1 can be obtained by differentially comparing the inductances of the coils 5 and 6 wound around the cores 2 and 3.

FIG. 6 is a block diagram showing an example of a conventional electric circuit configuration connected to the magnetic circuit configuration shown in FIG. A resistor 101 is connected to one coil 5. The resistor 102 is also connected to the other coil 6. An oscillator circuit 10 3 is connected to both coils 5 and 6. A connection point 104 between the coil 5 and the resistor 101 is connected to one input terminal of a differential amplifier circuit 106 via a rectifier circuit 105. A connection point 107 between the coil 6 and the resistor 102 is connected to the other input terminal of the differential amplifier circuit 106 via a rectifier circuit 108. The differential amplifier circuit 106 is connected to the comparison circuit 109. The differential amplifier circuit 106 and the comparison circuit 109 are supplied with a predetermined reference voltage from the reference voltage generation circuit 110. In this configuration, the same alternating voltage is applied from the oscillator circuit 103 to the pair of coils 5 and 6. The output from the connection point 104 is rectified and smoothed by the rectifying circuit 105. Similarly, the output from the connection point 107 is also rectified and smoothed by the rectification circuit 108. The pair of rectified and smoothed signals are differentially amplified with a predetermined reference voltage as a midpoint. The differentially amplified signal is compared with a predetermined reference voltage by the comparison circuit 109, and a rectangular wave pulse output is obtained.

[0004]

[Problems to be solved by the device]

 In the conventional electric circuit configuration described above, the signal line from each coil 5, 6 to the differential amplifier circuit 106 is divided into two systems. The differential amplifier circuit 106 dc-amplifies the signal rectified and smoothed by the rectifier circuits 105 and 108. Therefore, the signal transmitted through the electric circuit shown in FIG. 6 is susceptible to the drift of each circuit element. That is, there is a problem that an error occurs in rotation detection due to the influence of temperature drift and drift over time such as the resistance values of the resistors 101 and 102 connected in series with the coils 5 and 6 and the offset of the differential amplifier circuit 106. .

[0005]

[Means for Solving the Problems]

 The following measures were taken in order to solve the above-mentioned problems of the conventional technique. That is, the differential coil type rotation detector according to the present invention basically comprises a combination of a gear made of a magnetic material attached to a rotary shaft to be detected and a pair of cores each wound with a coil. Consists of. In this combination, the reluctance of the magnetic circuit formed by one core and the teeth of the gear and the reluctance of the magnetic circuit formed by the other core and the teeth of the gear are associated with the rotation of the gear. It is arranged so that it changes differentially. By differentially comparing the inductance of the coils wound around each core, a pulse output corresponding to the movement of the teeth of the rotating gear is obtained. In such a configuration, the present differential coil type rotation detector includes an oscillation circuit, an AC amplifier, a synchronous rectification circuit, and a comparison circuit as an electric circuit configuration. The oscillator circuit applies an alternating voltage across the pair of coils connected in series. The AC amplifier amplifies the AC signal output from the midpoint of the pair of coils. The synchronous rectification circuit performs direct current smoothing on the amplified AC signal in synchronization with the alternating voltage and converts it into a DC signal. The comparator circuit compares the DC signal with the midpoint potential of the AC amplifier to generate a rectangular wave pulse output. Preferably, the oscillating circuit applies a rectangular wave alternating voltage to a pair of coils connected in series.

[0006]

[Action]

 In the differential coil type rotation detector according to the present invention, the pair of coils are connected in series, and the alternating voltage for driving is applied from the oscillation circuit to both ends thereof. As a feature of the present invention, an AC signal is directly extracted from the midpoint of a pair of coils connected in series. The amplitude of this AC signal changes as the gear rotates. Further, this AC signal is AC amplified by an AC amplifier. The AC amplified AC signal is synchronously rectified and then compared with a reference voltage during AC amplification to be converted into a rectangular wave pulse output. Therefore, in this electric circuit configuration, there is one signal path from the midpoint of the pair of coils to the output terminal, and it is less affected by the variation in the characteristics of individual circuit elements as compared with the two systems. Also, unlike the conventional method, the output from the coil is not amplified by DC but is amplified by AC. Therefore, stable rotation pulse output with less drift can be obtained without being affected by offset.

[0007]

【Example】

 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the basic configuration of a differential coil type rotation detector according to the present invention. As shown in the figure, this rotation detector is composed of a magnetic circuit section and an electric circuit section. The magnetic circuit section is composed of a combination of a gear 1 and a pair of cores 2 and 3. The gear 1 is made of a magnetic material and is attached to a rotary shaft (not shown) to be detected. A coil 5 is wound around one core 2. A coil 6 is also wound around the other core 3. The pair of coils 5 and 6 are connected to each other in series via a midpoint M. Teeth 7 are formed at a predetermined pitch P along the circumferential direction at the peripheral end of the gear 1. On the other hand, the core 2 has a pair of magnetic poles formed at intervals equal to an integer multiple of the arrangement pitch P of the teeth 7. Similarly, the other core 3 also has a pair of magnetic poles at the same intervals. In this example, the distance between the pair of magnetic poles is set to be equal to the arrangement pitch P of the teeth 7. These magnetic poles are arranged to face the teeth 7 of the gear 1 via a predetermined air gap. The pair of cores 2 and 3 are displaced from each other by a half phase with respect to the arrangement pitch P of the teeth 7. That is, as shown, when the magnetic pole of one core 2 is aligned with the top of the tooth 7, the magnetic pole of the other core 3 is aligned with the valley 9 of the tooth 7. With this arrangement, the magnetic resistance of the magnetic circuit formed by the core 2 and the tooth 7 on one side and the magnetic resistance of the magnetic circuit formed by the core 7 and the tooth 7 on the other side cause the rotation of the gear 1. It changes differentially with it.

Next, the electric circuit section includes an oscillation circuit 10, an AC amplifier 11, a synchronous rectification circuit 12, a comparison circuit 13, and a reference voltage generation circuit 14. The oscillator circuit 10 applies an alternating voltage Φ to a terminal on the coil 6 side of a pair of coils connected in series, and applies an alternating voltage Φ ⁻ having a 180 ° phase difference from Φ to a terminal on the coil 5 side. The oscillation frequency of the oscillation circuit 10 is set sufficiently higher than the rotation speed of the gear 1. In this example, the oscillator circuit 10 generates an alternating voltage having a rectangular wave. By adopting a rectangular wave, the configuration of the electric circuit section is simplified. In some cases, an alternating voltage such as a sine wave or a triangular wave may be used. The AC amplifier 11 amplifies the AC signal output from the midpoint M of the pair of coils 5 and 6. The synchronous rectification circuit 12 rectifies and smoothes the amplified AC signal in synchronization with the alternating voltage Φ and converts it into a DC signal. The comparator circuit 13 compares the DC signal with the midpoint potential of the AC amplifier 11 to generate a rectangular wave pulse output R. The reference voltage generation circuit 14 supplies a predetermined reference voltage V0 to the AC amplifier 11 and the comparison circuit 13. This reference voltage V0 defines the midpoint potential of the AC amplifier 11.

Next, the operation of the differential coil type rotation detector will be described in detail. Continuing to refer to FIG. 1, the operation of the magnetic circuit section will be described first. When the gear 1 rotates, the air gap between the cores 2 and 3 and the tops 8 and the valleys 9 of the facing teeth 7 changes, and the permeance of the magnetic path formed by the cores 2 and 3 and the gear 1 changes. Changes. At this time, since the pair of cores 2 and 3 are in opposite phases with respect to the positions of the teeth 7 facing each other, the permeance of each magnetic path changes differentially with respect to the rotation of the gear 1. Therefore, when alternating voltage Φ, Φ ⁻ is applied to a pair of coils 5 and 6 connected in series to drive, the impedance of each coil 5 and 6 changes in a similar manner as the permeance changes. To do. At this time, the potential at the midpoint M of the coils 5 and 6 connected in series (midpoint potential) is determined by the divided voltage value of the impedance of the respective coils 5 and 6. When the impedances are equal, the midpoint potential becomes 1/2 of the alternating voltage Φ and is constant. When a difference occurs in impedance, an AC signal having a frequency proportional to the alternating voltage Φ with an amplitude proportional to the difference is taken out from the midpoint M. At this time, the direction of the impedance (polarity) can be determined by comparing the phases of the AC signal and the alternating voltage Φ.

Next, the operation of the electric circuit section will be described in detail with reference to FIG. 2 (A), (B), (C), (D), and (E) show the states that change with the rotation of the gears over time. For each state, the waveform of the amplified AC signal, the waveform schematically showing the synchronization processing process, and the DC signal waveform are shown. The state (A) corresponds to the arrangement relationship between the gear and the core shown in FIG. That is, one core 2 is aligned with the top 8 of the tooth 7, and the other core 3 is aligned with the valley 9 of the tooth 7. At this time, the impedance difference between the pair of coils 5 and 6 is maximum, and the amplitude of the AC signal is also maximum. The AC signal shown in FIG. 2 represents a waveform after AC amplification, and unnecessary DC components such as offset are removed. In this example, the AC signal in the state (A) has the same phase as the alternating voltage Φ. The AC signal is synchronously processed based on the alternating voltage Φ. That is, the peak level of the AC signal is sequentially sampled. After this, rectification and smoothing is performed to obtain a corresponding DC signal. As shown, this DC signal has a predetermined voltage level VA with respect to the midpoint potential V0.

The state (B) is a state in which the gear 1 is rotated clockwise from the state (A) by about 1/8 of the alignment pitch P of the teeth 7. At this time, the tooth tops 8 are separated from the magnetic poles of the one core 2 and the tooth tops 8 are close to the magnetic poles of the other core 3. Therefore, the impedance difference between the coils 5 and 6 tends to decrease, and the amplitude of the AC signal also decreases. As a result, the voltage level VB of the corresponding DC signal is lower than the voltage level VA in the state (A 1).

In the state (C), the gear 1 is further rotated by P / 8 minutes from the state (B). That is, it is a time point when P / 4 minutes have progressed from the state (A). At this time, all the magnetic poles of both cores 2 and 3 are aligned with the boundary between the top portion 8 and the valley portion 9. In other words, the pair of cores 2 and 3 are located at equilibrium points with respect to the teeth 7 of the gear 1. As a result, the impedance difference between the coils 5 and 6 disappears, and the AC signal becomes constant at a level of 1/2 of the alternating voltage Φ. Therefore, the corresponding DC signal has a level V C equal to the midpoint potential V 0.

The state (D) is when the gear 1 further rotates clockwise by P / 8 minutes, and an impedance difference appears again between the pair of coils 5 and 6. However, as compared with the state of (B) described above, the magnitude relationship (polarity) of impedance becomes opposite. Therefore, the AC signal in the state (D) has a reverse polarity with respect to the alternating voltage Φ. When this AC signal is synchronized, a minimum peak level is sampled. Therefore, the corresponding DC signal is at the negative level VD having the same magnitude as the voltage level VB in the above-mentioned state (B) and the opposite polarity.

(E) is the time when the gear 1 further rotates clockwise by P / 8 minutes from the state of (D). In other words, the gear 1 has rotated P / 2 minutes from the initial state (A). At this time, the magnetic poles of the core 2 are aligned with the valleys 9, while the magnetic poles of the core 3 are aligned with the tops 8. Therefore, the impedance difference between the coils 5 and 6 becomes maximum again, but the polarities are opposite. Therefore, the corresponding DC signal has a negative polarity and a maximum absolute level V E.

FIG. 3 shows changes in the level of the DC signal in each of the above-described states over time, and the DC signal periodically fluctuates with respect to the midpoint potential V0 according to the rotation of the gear. That is, in the state of (A), the DC signal is at the maximum level, in the state of (B), it is at the intermediate level, in the state of (C), it is at the midpoint potential level, and in the state of (D), it is at the negative intermediate level. In the case of (E), it reaches the minimum level. During this time, the gear rotates P / 2 minutes. When the gear further rotates, the DC signal starts rising from the minimum level and reaches the maximum level when it rotates again for P / 2 minutes. The comparison circuit 13 compares the DC signal, which fluctuates in this manner, with the midpoint potential V0 to obtain a rectangular wave pulse output R 1. As shown in the figure, when the gear rotates by one pitch P, one rectangular wave pulse is output.

Finally, FIG. 4 shows a specific example of the synchronous rectification circuit 12 as a reference. As shown in the figure, the synchronous rectification circuit 12 is composed of an analog switch SW, a capacitor CC, and a high-impedance buffer BUF. The analog switch SW opens and closes in response to the alternating voltage Φ supplied from the oscillation circuit 10, and synchronously samples the AC signal output from the AC amplifier 11. The sampled signal is charged in the capacitor CC and rectified and smoothed. The terminal voltage of the capacitor CC is taken out via the buffer BUF and a DC signal is obtained.

[0017]

[Effect of device]

 As described above, according to the present invention, a pair of differential coils are connected in series and an alternating voltage is applied to drive them. The AC signal is directly extracted from the midpoint of the coils connected in series, subjected to AC amplification, synchronous rectification, and comparison processing to obtain a rectangular wave pulse output in response to the rotation of the gear. Unlike the conventional method, there is only one signal transmission path, and AC amplification is performed. Therefore, according to the present invention, it is possible to obtain a stable rotation pulse output with less drift.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a differential coil type rotation detector according to the present invention.

FIG. 2 is an operation explanatory view of the differential coil type rotation detector shown in FIG.

FIG. 3 is likewise an operation explanatory view.

4 is a block diagram showing an example of a synchronous rectification circuit included in the differential coil type rotation detector shown in FIG.

FIG. 5 is a schematic diagram showing a general magnetic circuit configuration of a conventional differential coil type rotation detector.

FIG. 6 is a block diagram showing an electric circuit configuration of a conventional differential coil type rotation detector.

[Explanation of symbols]

 1 Gear 2 Core 3 Core 4 Rotation Shaft 5 Coil 6 Coil 7 Tooth 8 Top 9 Valley 10 Oscillation Circuit 11 AC Amplifier 12 Synchronous Rectifier 13 Comparison Circuit 14 Reference Voltage Generation Circuit

Claims (2)

[Scope of utility model registration request] 1. A combination of a gear made of a magnetic material attached to a rotary shaft to be detected and a pair of cores each wound with a coil, and formed by one core and teeth of the gear. The magnetic resistance of the magnetic circuit and the magnetic resistance of the magnetic circuit formed by the other core and the teeth of the gear are arranged so as to change differentially with the rotation of the gear. In the differential coil type rotation detector that obtains pulse output corresponding to the movement of the teeth of the rotating gear by comparing the inductances of the wound coils differentially, apply an alternating voltage across the pair of coils connected in series. An oscillating circuit to be applied, an AC amplifier for amplifying the AC signal output from the midpoint of the pair of coils, and a synchronous rectifying circuit for rectifying and smoothing the amplified AC signal in synchronism with the alternating voltage to convert it into a DC signal. A differential coil type rotation detector which comprises a comparison circuit for generating a pulse output of the square wave the DC signal compared to the midpoint potential of the AC amplifier. 2. The differential coil type rotation detector according to claim 1, wherein the oscillation circuit generates an alternating voltage of a rectangular wave.