JP2020026960A - Speed sensor for railroad vehicle - Google Patents

Abstract

To provide a speed sensor for a railroad vehicle which enables miniaturization of an object to be detected while retaining detection accuracy.SOLUTION: A speed sensor 10 for a railroad vehicle comprises: a magnetic resistance element 11 which converts rotational motion of a gear 1 as an object to be detected including a magnetic body into a signal; and a multiplication and waveform generation circuit 12 which multiplies frequency of the signal. Also, the speed sensor 10 for the railroad vehicle may comprise two magnetic resistance elements 11. The magnetic resistance elements 11 may output respective sinusoidal signals which are different in phase from each other by 90 degrees.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a speed sensor for a railway vehicle.

  In a railway vehicle speed sensor, a magnetoresistive element detects rotation of a detection target (eg, a gear) and converts the rotation into a pulse train. Since the output signal is one pulse per gear tooth, the rotation angle resolution is a value obtained by dividing 360 ° by the number of gear teeth.

  In such a configuration, the speed detection accuracy depends on the resolution of the rotation angle, and therefore it is necessary to increase the number of gear teeth. For this reason, the gears become large, and as a result, the entire device including the gears becomes large.

  On the other hand, it is known to use a frequency multiplication technique in a speed detection device in order to improve speed detection accuracy. Patent Document 1 discloses an example of such a technique.

JP 2010-236965 A

  Conventionally, in a speed sensor for a railway vehicle, only increasing the size of a gear in order to improve speed detection accuracy has been studied, and there has been a problem that the gear cannot be downsized while maintaining the detection accuracy. .

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a speed sensor for a railway vehicle that can reduce the size of an object to be detected while maintaining detection accuracy. .

A speed sensor for a railway vehicle according to the present invention includes a magnetoresistive element that converts a rotational motion of a detection target including a magnetic material into a signal, and a multiplying circuit that multiplies the frequency of the signal.
According to a specific aspect, the device includes two of the magnetoresistive elements, and each of the magnetoresistive elements outputs a sine wave signal having a phase different from each other by 90 degrees.

  ADVANTAGE OF THE INVENTION Since the speed sensor for railway vehicles which concerns on this invention can obtain the signal of a high frequency from a small to-be-detected object by multiplying the frequency of a detection signal, the gear can be miniaturized, maintaining detection accuracy. Can be.

FIG. 2 is a diagram illustrating an example of a configuration of a speed sensor according to Embodiment 1 of the present invention. FIG. 2 is a diagram illustrating an example of output signals of a conventional and the speed sensor of FIG. 1.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows an example of a configuration of a speed sensor 10 according to Embodiment 1 of the present invention. The speed sensor 10 is a speed sensor for a railway vehicle. The speed sensor 10 has a function of detecting the speed of a railway vehicle equipped with the detected object by converting the rotational motion of the detected object including the magnetic material into a signal.

  In the present embodiment, the gear 1 is used as an example of the detection target. The gear 1 is configured to include, for example, a magnetic material, and is configured to have a shape in which the magnetic permeability changes periodically in a circumferential direction, although not particularly illustrated. The gear 1 is rotatable in both a direction corresponding to the forward movement of the railway vehicle and a direction corresponding to the backward movement of the railway vehicle.

  The speed sensor 10 includes a magnetoresistive element 11. The magnetoresistive element 11 converts a magnetic resistance or a change thereof depending on the rotation angle of the gear 1 into a signal (for example, a voltage signal). The magnetoresistive element 11 is configured using, for example, an SMR (semiconductor magnetoresistive element).

  In the present embodiment, the magnetoresistive element 11 includes two magnetoresistive elements, and these two magnetoresistive elements are provided at different phases (A phase and B phase) with respect to the period of the change in the magnetic permeability of the gear 1. Preferably, these two magnetoresistive elements are configured to output a sine wave signal whose phases are different from each other by 90 degrees. For example, when one magnetoresistive element outputs a sin θ signal (A phase) with respect to the rotation angle θ of the gear 1, the other magnetoresistive element outputs a cos θ signal (B phase).

  The speed sensor 10 includes a multiplication and waveform generation circuit 12. The multiplication and waveform generation circuit 12 multiplies the frequency of a signal (for example, a voltage signal). In the example of FIG. 1, two input signals are each subjected to frequency multiplication, and two output signals are output.

  FIG. 2 shows an example of output signals of the conventional speed sensor and the speed sensor 10 of FIG. FIG. 2A shows an example of an output signal of a conventional speed sensor. The output signal of the magnetoresistive element is shaped and output as a pulse wave.

  FIG. 2B is an example of an output signal of the speed sensor 10 according to Embodiment 1 of the present invention (that is, an output signal of the multiplication and waveform generation circuit 12). In this example, the multiplication ratio is 2, and therefore, the number of pulses of the output signal is twice that of the conventional example. By counting the number of pulses, it is possible to detect the rotation speed of the gear 1, that is, the moving speed of the railway vehicle, with twice the accuracy compared to the related art.

  Further, as shown in FIG. 2B, in the first embodiment, the phase of the A-phase output and the phase of the B-phase output are shifted by 90 °, so that the rotation direction of the gear 1 (that is, the traveling direction of the railway vehicle). Can be determined.

  Each phase output may be used as it is as a pulse representing the speed of the railway vehicle, or may be input to any component that outputs or displays the speed value.

  In the first embodiment shown in FIGS. 1 and 2, the following modifications can be made.

  The multiplication ratio of the multiplication and waveform generation circuit 12 can be set to an arbitrary value. In the first embodiment (FIG. 2), the multiplication ratio is 2, and therefore, the speed sensor 10 outputs two pulses for one tooth of the gear. Assuming that the multiplication ratio is n, it is possible to output n pulses to one tooth of the gear. Note that n can be appropriately determined according to the application and the specific circuit configuration, and may be, for example, a natural number of 2 or more or a real number of 1 or more.

  According to the speed sensor of the present invention, the size of the gear 1 can be reduced. For example, when the multiplication ratio is 2 as shown in FIG. 2, a speed sensor having the same detection accuracy as the conventional one can be configured using a gear having half the number of teeth of the conventional one. As a result, the entire device including the gears can be reduced in size, and the degree of freedom in design can be improved in a limited space.

  In the first embodiment, the magnetoresistance element 11 includes two magnetoresistance elements, but the number of magnetoresistance elements may be three or more. In applications where it is not necessary to determine the rotation direction of the gear 1, the number of magneto-resistive elements may be one. In that case, the gear 1 may be rotatable in only one direction.

  The multiplying and waveform generating circuit 12 may have only the function of multiplying the frequency of the signal, or may omit the waveform generating function. That is, a simple multiplying circuit may be used instead of the multiplying and waveform generating circuit 12.

  1 gear (object to be detected), 10 speed sensor for railway vehicle, 11 magnetoresistive element, 12 multiplication and waveform generation circuit (multiplication circuit).

Claims (2)

A magnetoresistive element that converts the rotational movement of the detection target including the magnetic substance into a signal,
A multiplier circuit for multiplying the frequency of the signal,
A speed sensor for a railway vehicle, comprising: Comprising two magneto-resistive elements,
Each of the magnetoresistive elements outputs a sine wave signal having a phase different from each other by 90 degrees.
The speed sensor for a railway vehicle according to claim 1.

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