JP5347581B2 - Rotational speed sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation number sensor which can detect not only a rotation rate but also a rotation direction. <P>SOLUTION: The rotation number sensor includes, at the rear stage of a comparator 30 which compares an output signal from a differential amplifier circuit 29 to a predetermined voltage to output a rectangular wave signal, a comparison means including a rising-edge detection means 32, a falling-edge detection means 34, and a comparator 36 for detecting the rising edge and falling edge of an output signal from the comparator 30 and comparing them with each other. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a rotation speed sensor that detects a rotation speed by a change in magnetism.

  This type of conventional rotational speed sensor is configured as shown in FIGS.

  FIG. 7 is a side sectional view of a conventional rotational speed sensor, FIG. 8 is a top view of a magnetoresistive element in the rotational speed sensor, and FIG. 9 is a circuit diagram of the magnetoresistive element in the rotational speed sensor.

  7 to 9, reference numeral 1 denotes a magnet. On the magnetic pole surface of the magnet 1, a first magnetoresistive element 2 and a second magnetoresistive element 3 are provided as shown in FIG. Further, a third magnetoresistive element 4 and a fourth magnetoresistive element 5 serving as a bias resistance are provided at the end of the magnetic pole surface of the magnet 1 at a position where no magnetic force is generated in the magnet 1, and The first magnetoresistive element 2, the second magnetoresistive element 3, the third magnetoresistive element 4 and the fourth magnetoresistive element 5 are electrically connected to form a bridge circuit as shown in FIG. It is composed. In addition, a power supply electrode 6, a first output electrode 7, a second output electrode 8 and a GND electrode 9 are provided on the upper surface of the magnet 1, and in a state where a voltage is applied to the bridge circuit from the power supply electrode 6, A change in resistance value of the first magnetoresistive element 2 and the second magnetoresistive element 3 that changes due to the change is output as a potential difference between the first output electrode 7 and the second output electrode 8. Reference numeral 10 denotes a resin base. The base 10 has the magnet 1 at one end and the first magnetoresistive element 2, the second magnetoresistive element 3, the third magnetoresistive element 4 and the first magnetoresistive element on the magnetic pole face of the magnet 1. 4, a bridge circuit composed of four magnetoresistive elements 5 is fixed, and a circuit component 11 is provided on the side surface. From the sine waveform output from the first output electrode 7 and the second output electrode 8 by the circuit component 11. The output signal is converted into a pulse waveform. Further, a connection terminal 12 is provided at the other end of the substrate 10, and a pulse signal output from the circuit component 11 is output by this connection terminal 12. Reference numeral 13 denotes a case. The case 13 accommodates the base body 10 inside, and is provided with a connector terminal 14 integrally. The connector terminal 14 electrically connects one end to the connection terminal 12 of the base body 10. The other end protrudes outward.

  Next, the operation of the conventional rotational speed sensor configured as described above will be described.

  As shown in FIG. 7, the conventional rotational speed sensor has a gear 15 having a convex portion 16 and a concave portion 17 provided on the surface at a position facing the outer bottom surface of the case 13, and the rotation of the gear 15. Thus, a change in magnetic force from the magnet 1 toward the gear 15 is detected as a change in resistance value of the first magnetoresistive element 2 and the second magnetoresistive element 3 provided in the magnet 1.

  At this time, as shown in FIG. 9, since the block circuit is configured, the potential difference generated in the first output electrode 7 and the second output electrode 8 has a sine waveform as shown in FIG. Then, this sine waveform is converted into a pulse waveform by the circuit component 11 provided on the base 10, and output from the connector terminal 14 to a counterpart computer or the like to detect the rotational speed of the main shaft or the like of an automobile (not shown). there were.

As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laid-Open No. 11-51695

  However, in the conventional rotational speed sensor described above, although the rotational speed can be detected, but the rotational direction cannot be detected, when the rotational speed sensor is used for detecting the rotational speed of the axle of the automobile, the vehicle speed is detected. Although the vehicle speed can be detected, the moving direction of the automobile cannot be detected.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a rotation speed sensor that can detect the rotation speed and also can detect the rotation direction.

  In order to achieve the above object, the present invention has the following configuration.

The invention according to claim 1 of the present invention is a constant current generating means, a pair of magnetoresistive elements connected in series with the constant current generating means, and a buffer circuit for outputting an upstream voltage of the pair of magnetoresistive elements A pair of resistors connected in series with the buffer circuit, a differential amplifier circuit that compares and outputs the potential difference between the midpoint potential of the pair of magnetoresistive elements and the midpoint potential of the pair of resistors, and A comparator that compares the output signal from the differential amplifier circuit with a predetermined voltage and outputs a rectangular wave signal; and a rising edge detection means that detects a rising edge of the output signal from the comparator at a subsequent stage of the comparator ; and the fall detecting means detects the falling of the output signal from the comparator, a second comparator connected to the buffer circuit, before the said rise detecting means A first switch that connects the buffer circuit and the second comparator when the rising edge of the output signal is detected; and the buffer circuit and the buffer circuit when the falling edge of the output signal is detected by the falling edge detecting means A comparison means having a second switch for connecting to the second comparator is provided.

Rotational speed sensor of the present invention by this arrangement, it is possible to detect the rotational speed by the output signal from the comparator, an excellent effect that the comparison means provided downstream of the comparator can detect the rotation direction It is what you play.

  Hereinafter, a rotation speed sensor according to an embodiment of the present invention will be described with reference to the drawings.

  1 is an exploded perspective view of a rotational speed sensor according to an embodiment of the present invention, FIG. 2 is a sectional side view of the same, FIG. 3 is a circuit block diagram of the rotational speed sensor, and FIG. 4 is a circuit diagram of the rotational speed sensor. is there.

  1-4, 21 is a magnet. Reference numeral 22 denotes a first magnetoresistive element, and the first magnetoresistive element 22 is provided on the magnetic pole surface of the magnet 21. Reference numeral 23 denotes a second magnetoresistive element. The second magnetoresistive element 23 is disposed on the magnetic pole surface of the magnet 21 with a predetermined distance from the first magnetoresistive element 22. The magnetoresistive element 22 and the second magnetoresistive element 23 are electrically connected in series. Reference numeral 24 denotes a processing circuit composed of an IC, and the processing circuit 24 is provided with a constant current generating means 25 shown in FIGS. The constant current generating means 25 supplies a constant current to the first magnetoresistive element 22 and the second magnetoresistive element 23. Further, the processing circuit 24 is provided with a buffer circuit 26, which generates the same voltage as the voltage generated upstream of the first magnetoresistive element 22. Reference numeral 27 denotes a first resistor. A voltage generated from the buffer circuit 26 is applied to the first resistor 27, and a second resistor 28 is connected in series to the first resistor 27. ing. The processing circuit 24 is provided with a differential amplifier circuit 29. The differential amplifier circuit 29 is generated between the first magnetoresistive element 22 and the second magnetoresistive element 23. The midpoint potential is input to the non-inverting input terminal 29a, and the midpoint potential generated between the first resistor 27 and the second resistor 28 is input to the inverting input terminal 29b, and the potential difference between the two is compared. Is output.

  Further, the processing circuit 24 is provided with a comparator 30, which compares the output signal from the differential amplifier circuit 29 with a predetermined threshold value and outputs a comparison pulse signal consisting of high and low. Yes. Further, the differential amplifier circuit 29 and the comparator 30 constitute a comparison pulse generation circuit 31. The processing circuit 24 is provided with a rising edge detection means 32 comprising a positive edge trigger type synchronous flip-flop, and the rising edge detection means 32 switches the output signal from the comparator 30 from low to high. Sometimes the first switch 33 is turned on to output the output signal from the buffer circuit 26. Further, the processing circuit 24 is provided with a falling detection means 34 composed of a negative trigger type synchronous flip-flop, and the falling detection means 34 changes the output signal from the comparator 30 from high to low. When switching, the output signal from the buffer circuit 26 is output by turning on the second switch 35. Further, the processing circuit 24 is provided with a comparator 36, which connects the output signal via the first switch 33 to the inverting input terminal 37 and outputs the signal via the second switch 35. Is connected to the non-inverting input terminal 38 to compare the two and output an on / off output signal. The rising detection means 32, the falling detection means 34, the first switch 33, the second switch 35, and the comparator 36 constitute a comparison means.

  Reference numeral 39 denotes a resin base. The base 39 fixes the magnet 21, the first magnetoresistive element 22 and the second magnetoresistive element 23 to the end portions, and the first resistor 27 and the second magnetoresistive element on the side surface. A resistor 28 and a processing circuit 24 are provided, and a connection terminal 40 is provided at an end opposite to the end to which the magnet 21 is fixed. Reference numeral 41 denotes a resin case. The case 41 accommodates the base 39 inside, and is provided with a connector terminal 42 so as to protrude outward. The connector terminal 42 is a connection terminal 40 on the base 39. And is electrically connected. Reference numeral 43 denotes a lid which closes the opening of the case 41.

  Next, a method for assembling the rotational speed sensor according to the embodiment of the present invention configured as described above will be described.

  First, the first magnetoresistive element 22 and the second magnetoresistive element 23 are formed on the magnetic pole surface of the magnet 21 by vapor deposition through a Si substrate (not shown).

  Next, the connection terminal 40 is installed in a mold (not shown) to form a base 39 integrally provided with the connection terminal 40.

  Next, the magnet 21 is fixed to the base 39 on the side opposite to the side where the connector terminal 42 is provided.

  Next, the first resistor 27, the second resistor 28, and the processing circuit 24 are mounted on the side surface of the base 39.

  Next, after the base 39 is accommodated inside a case 41 in which the connector terminals 42 are integrally formed in advance, the connection terminals 40 in the base 39 are soldered to the connector terminals 42 in the case 41.

  Finally, the opening of the case 41 is closed with a lid 43.

  Next, the operation of the rotational speed sensor according to the embodiment of the present invention constructed and assembled as described above will be described.

  As shown in FIG. 5, a gear 48 on the other side is provided on the side facing the outer bottom surface of the case 41, and convex portions 49 and concave portions 50 are alternately provided on the surface of the gear 48. . As the gear 48 rotates, the magnetic force passing through the first magnetoresistive element 22 and the second magnetoresistive element 23 changes. Due to the change in the magnetic force, the first magnetoresistive element 22 and the second magnetoresistive element 23 are changed. The resistance value of the element 23 changes. The first magnetoresistive element 22 and the second magnetoresistive element 23 are loaded with a constant voltage by a constant current generating means 25. Therefore, with the rotation of the gear 48, the voltage shown in FIG. 6A is generated in the first magnetoresistive element. Similarly, the voltage shown in FIG. 6B is also generated in the second magnetoresistive element 23. Then, from the buffer circuit 26, a first resistor 27 and a second resistor 28 to which the voltage shown in FIG. 6C, which is the sum voltage of FIG. 6A and FIG. 6B, is connected in series. To be applied. As a result, the intermediate potential between the first resistor 27 and the second resistor 28 becomes an output signal shown in FIG. 6D and is input to the inverting input terminal 29 b of the differential amplifier circuit 29. On the other hand, the midpoint potential of the first magnetoresistive element 22 and the second magnetoresistive element 23 becomes an output signal shown in FIG. 6E and is input to the non-inverting input terminal 29a in the differential amplifier circuit 29. . The difference voltage between FIG. 6D and FIG. 6E is input to the comparator 30. As a result, as shown in FIG. 6F, the comparator 30 has a midpoint potential between the first resistor 27 and the second resistor 28 and the first magnetoresistive element 22 and the second magnetoresistive element 23. When the potential becomes higher than the midpoint potential, a high signal is output. On the other hand, the midpoint potentials of the first resistor 27 and the second resistor 28 become the first magnetoresistive element 22 and the second magnetoresistive element 23, respectively. When the potential becomes lower than the midpoint potential, a low signal is output. That is, the rotation speed of the gear 48 can be measured by measuring the pulse waveform composed of the high and low signals.

  Here, consider the case where the gear 48 rotates in the positive direction and the case where it rotates in the negative direction.

  When the gear 48 is rotating in the forward direction, when the rectangular wave shown in FIG. 6 (f) rises, a signal is input to the synchronous input terminal 32a in the rise detection means 32, and the first switch 33 is turned on. Become. As a result, a high signal is output from the comparator 36. On the other hand, when the rectangular wave falls, a signal is inputted to the synchronous input terminal 34a in the fall detecting means 34, and the second switch 35 is turned on. As a result, a low signal is output from the comparator 36.

  Similarly, when the gear 48 is rotating in the negative direction, when the rectangular wave shown in FIG. 6 (f) rises, a signal is input to the synchronous input terminal 34a in the fall detection means 34, and the second The switch 35 is turned on. As a result, a low signal is output from the comparator 36. On the other hand, when the rectangular wave falls, a signal is inputted to the synchronous input terminal 32a in the rise detection means 32, and the first switch 33 is turned on. As a result, a high signal is output from the comparator 36. That is, the rotation direction of the gear 48 can be detected by comparing the output signal from the comparator 30 and the output signal from the comparator 36.

  As described above, in the rotation speed sensor according to the embodiment of the present invention, the rising edge detecting means 32 for detecting and comparing the rising edge and the falling edge of the output signal from the comparator 30 and the falling edge detection are provided after the comparator 30. Since the comparison means including the means 34 and the comparator 36 is provided, the number of rotations can be detected by the output signal from the comparator 30, and the rising detection means 32 and the falling detection means 34 provided at the subsequent stage of the comparator 30. In addition, the rotation direction can be detected by the comparison means including the comparator 36 and the like.

  The rotational speed sensor according to the present invention has an effect that it can detect the rotational speed and also the rotational direction, and is particularly useful as a rotational speed sensor that detects the rotational speed by a change in magnetism. It will be.

The disassembled perspective view of the rotation speed sensor in one embodiment of this invention Side sectional view of the same rotation speed sensor Circuit block diagram of the same rotation speed sensor Circuit diagram of the same rotation speed sensor Side sectional view showing a state in which the counter gear is arranged in the same rotational speed sensor (A)-(h) Output waveform diagram of the same rotation speed sensor Side sectional view showing a state in which a counter gear is arranged on a conventional rotational speed sensor Top view of magnetoresistive element in the same rotational speed sensor Circuit diagram of magnetoresistive element in the same rotational speed sensor The figure which shows the sine waveform output from the magnetoresistive element in the rotation speed sensor

DESCRIPTION OF SYMBOLS 22 1st magnetoresistive element 23 2nd magnetoresistive element 25 Constant current generation means 26 Buffer circuit 27 1st resistance 28 2nd resistance 29 Differential amplifier circuit 30, 36 Comparator 32 Rise detection means 33 1st switch 34 Falling detection means 35 Second switch

Claims (3)

Constant current generating means, a pair of magnetoresistive elements connected in series with the constant current generating means, a buffer circuit for outputting the upstream voltage of the pair of magnetoresistive elements, and a pair connected in series with the buffer circuit And a differential amplifier circuit that compares and outputs the potential difference between the midpoint potential of the pair of magnetoresistive elements and the midpoint potential of the pair of resistors, and outputs an output signal from the differential amplifier circuit to a predetermined voltage. And a comparator that outputs a rectangular wave signal, and a rise detection means that detects the rise of the output signal from the comparator, and a rise that detects the fall of the output signal from the comparator. The rising edge of the output signal is detected by the falling edge detecting means, the second comparator connected to the buffer circuit, and the rising edge detecting means. A first switch connecting the buffer circuit and the second comparator, and connecting the buffer circuit and the second comparator when the falling detection unit detects a falling edge of the output signal. A rotation speed sensor provided with a comparison means having a second switch . 2. The rotational speed sensor according to claim 1, wherein the rising edge detection means is a positive edge trigger type synchronous flip-flop, and the falling edge detection means is a negative trigger type synchronous flip-flop. The rotational speed sensor according to claim 2, wherein the first switch is connected to the inverting input terminal of the second comparator, and the second switch is connected to the non-inverting input terminal of the second comparator.

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