JP4506325B2 - Magnetic encoder - Google Patents

Description

  The present invention relates to a magnetic encoder used in a detection device that detects the rotation of a rotating member provided in, for example, an automobile, a home appliance, or the like.

  Some magnetic encoders are used, for example, to detect the rotational speed of a car wheel. FIG. 5 shows a conventional example of a magnetic encoder. In FIG. 5, there is a signal output unit 101 serving as a reference point, and the signal output unit 101 is a wide portion having a width twice the normal width. In addition to the signal output unit 101, a plurality of regions having a normal width are formed, and these portions indicate the position and rotation angle in the rotation direction from the reference point. Moreover, there exists a thing like patent document 1. FIG. In Patent Document 1, a signal output portion of a reference point protrudes in a convex shape, and a predetermined magnetic pole pattern continues in other portions, and this magnetic pole pattern portion indicates a position and a rotation angle in a rotation direction from the reference point. Yes.

  In such a magnetic encoder, the magnetic field is detected by one sensor. For this reason, since the signal output from the sensor is only a pulse accompanying rotation, the rotation speed can be detected, but the rotation direction of normal rotation or reverse rotation cannot be determined.

If there are two sensors for detecting the magnetic field, it is possible to discriminate between normal rotation and reverse rotation based on the two output signals, but the number of parts increases and the cost increases.
JP 7-74020 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic encoder capable of discriminating the rotation direction of normal rotation or reverse rotation without increasing the number of parts.

In order to achieve the above object, the present invention adopts the following configuration. That is,
Rotating relative to the detection means for detecting the magnetic field,
A magnetic encoder having a track in which a magnetization pattern in which a narrow pitch of a pair of magnetic poles and a wide pitch of a pair of magnetic poles are repeated is repeated at least two times.

  According to this, it is possible to determine the rotation direction of normal rotation or reverse rotation with one track and one detection means.

The detection means specifies the magnetic pole at the start of rotation, and measures the interval time between the magnetic field changes when counting the number of magnetic field changes when the magnetic pole of the track after the rotation starts is reversed by five. And
Based on the measurement result, the first interval time and the third interval time between the magnetic field changes are compared, and the second interval time and the fourth interval time between the magnetic field changes are compared. Compare with the interval time,
It is preferable to determine whether the rotation is normal or reverse.

According to this, as a result of comparison between the first interval time and the third interval time between the magnetic pole and magnetic field change at the start of rotation, the second interval time and the fourth interval between the magnetic field changes. Based on the three parameters of the comparison result with time, it is possible to determine the forward or reverse rotation direction with one track and one detection means.

  Comparison result between the magnetic pole at the start of rotation, the first interval time and the third interval time between the magnetic field changes, and the second interval time and the fourth interval between the magnetic field changes. It is preferable to discriminate between forward and reverse rotations using a discriminant that can discriminate between forward and reverse rotations using the comparison result with time as a parameter.

  According to this, as a result of comparison between the first interval time and the third interval time between the magnetic pole and magnetic field change at the start of rotation, the second interval time and the fourth interval between the magnetic field changes. One track for deriving the above three parameters by discriminating the rotation direction of the normal rotation or the reverse rotation with a discriminant in which the three parameters of the comparison result with the time correspond to the rotation direction of the normal rotation or the reverse rotation in advance. Other than the one detection means, no other parts are required, and as a result, the forward or reverse rotation direction can be determined without increasing the number of parts.

  According to the present invention, the rotation direction of normal rotation or reverse rotation can be determined without increasing the number of parts.

  FIG. 1 is a partial perspective view of a magnetic encoder according to an embodiment. The magnetic encoder 1 according to the embodiment is one annular member that rotates with respect to one detection means 2 that detects the strength of a magnetic field. What is necessary is just to select the magnitude | size of the magnetic encoder 1 suitably with the rotating member to attach.

  The detection means 2 uses a magnetic sensor. A magnetic sensor is a sensor that detects magnetic energy. Specifically, a magnetic head using an electromagnetic induction action, a differential transformer, a Hall element using an action that converts magnetic force into electricity, an MR element ( A magnetoresistive effect element) or the like is preferable.

  The magnetic encoder 1 has a row of tracks 7 in which a magnetization pattern in which a narrow pitch 3, 4 of a pair of magnetic poles and a wide pitch 5, 6 of a pair of magnetic poles are repeated is repeated four times. It should be noted that the number of repetitions of the magnetization pattern in which the narrow pitches 3 and 4 of the pair of magnetic poles and the wide pitches 5 and 6 of the pair of magnetic poles are continuous may be at least two. I'm not bound by it.

  The track 7 is arranged over the entire circumference on the annular outer peripheral surface of the magnetic encoder 1. In the track 7, magnetic poles that are S poles and N poles are alternately arranged on the circumference.

  The track 7 uses the change in the magnetic field when the magnetic poles of the N pole and the S pole are reversed as a pulse, counts the number of pulses to determine the rotational speed information, and rotates the magnetic encoder 1 in the forward or reverse rotation. Information that identifies the direction is determined. As shown in FIG. 2, the track 7 has a narrow pitch 3, 4 of a pair of magnetic poles at intervals of 90 ° of 0 ° to 90 °, 90 ° to 180 °, 180 ° to 270 °, and 270 ° to 360 °. And a wide pitch 5, 6 of the pair of magnetic poles, which are repeated every 90 °. Then, with respect to the pattern width of the narrow pitches 3 and 4 of the pair of magnetic poles and the wide pitches 5 and 6 of the pair of magnetic poles at intervals of 90 °, P1 is the narrow pitch 3 of the N pole and P2 is the narrow width of the S pole When pitches 4 and P3 are determined as N-pole wide pitch 5 and P4 as S-pole wide pitch 6, a relational expression P1 = P2 <P3 = P4 is established.

  Note that the relationship of P1 to P4 is not limited to the above formula in the present embodiment, and it is sufficient that the relational expression of P1≈P2 << P3≈P4 is satisfied.

  In this embodiment, as shown in FIG. 1, the magnetic field of the track 7 is detected by the detection means 2 from the outside of the outer peripheral surface of the magnetic encoder 1.

  FIG. 3 shows a digital output signal obtained by converting the detection result of the detection means 2 into a pulse by a Hall IC or the like. As shown in FIG. 3, assuming that the N pole is Hi and the S pole is Lo, the output signal of the first track 7 can obtain a periodic waveform at intervals of 90 °.

  In the magnetic encoder 1 of this configuration, when the magnetic pole is reversed when the magnetic pole at the start of rotation is specified and the number of pulses of the magnetic field change when the magnetic pole of the track 7 after the rotation is reversed is counted five times. By measuring the interval time between the magnetic field change pulses, it is possible to determine the rotation direction of normal rotation or reverse rotation.

  Hereinafter, a method for discriminating the rotation direction of normal rotation or reverse rotation at the start of rotation according to the present embodiment will be described.

  First, the magnetic pole at the start of rotation is specified. Since the N pole is Hi and the S pole is Lo, for example, in A, B, C, and D showing the rotation start position shown in FIG. 3, A is Hi, B is Lo, C is Hi, and D is Lo. Identified.

  The points A, B, C, and D in FIG. 3 are identified as four because the position at the start of rotation is classified as any one of A to D regardless of where in the track 7 the rotation starts. Is. That is, A is the rotation start position from the N pole narrow pitch 3, B is the rotation start position from the S pole narrow pitch 4, C is the rotation start position from the N pole wide pitch 5, and D is the S pole. The rotation start position from the wide pitch 6 is shown.

  Next, the first and second interval times of the magnetic field change pulse when the magnetic pole of the track 7 after the rotation is reversed is t1, the second and third interval times are t2, and the third and fourth intervals are the same. The interval time between the pulses of the magnetic field change is measured with t3 as the interval time and t4 as the fourth and fifth interval times. For example, the case where the rotation starts from the point A in FIG. 3 with the rotation direction as normal rotation is as shown by t1 to t4 in FIG. t1 to t4 are measured in the same way for both forward rotation and reverse rotation.

  And based on the measurement result of t1-t4, the length of time of t1 and t3 is compared, and the length of time of t2 and t4 is compared. The comparison result may be obtained by a relationship based on an inequality that indicates the length of time between the two. Examples of comparison results are t1 <t3, t2> t4, and the like.

  In this way, the Hi or Lo signal at the start of rotation, the comparison result between t1 and t3, and the comparison result between t2 and t4 are obtained as three parameters.

  Here, the three parameters of the Hi or Lo signal at the start of rotation, the comparison result of t1 and t3, and the comparison result of t2 and t4 rotate in the forward or reverse rotation direction at the start positions A to D. It has been confirmed that each combination is different. FIG. 4 is a table showing the relationship between the three parameters and the forward or reverse rotation direction at the start positions A to D.

  For this reason, a discriminant as shown in FIG. 4 having three parameters in advance, the Hi or Lo signal at the start of rotation, the comparison result of t1 and t3, and the comparison result of t2 and t4, is prepared. Can be determined with reference to the discriminant of FIG. 4 to determine the forward or reverse rotation direction.

As described above, as long as the three parameters are obtained, the rotational direction of forward rotation or reverse rotation can be determined by a discriminant in which the three parameters correspond to the rotational direction of forward rotation or reverse rotation in advance. Other than the one track 7 and the one detecting means 2 for guiding the above, no other parts are required. As a result, the rotation direction of the forward rotation or the reverse rotation can be determined without increasing the number of parts.

  The above method is sufficiently established when the rotational speed of the magnetic encoder 1 is constant. However, when the rotational speed changes, even if there is a speed change between at least P1 and P3, the “interval time of P1” By appropriately setting the magnitude of the coefficient α of P3 = αP1 so that the “interval time of P3” is established, the forward or reverse rotation direction can be determined in the same manner as described above.

The perspective view which shows a part of magnetic encoder which concerns on embodiment. The figure which shows the magnetization pattern of the magnetic encoder which concerns on embodiment. The figure which shows the output signal of the magnetic encoder which concerns on embodiment. Three parameters of Hi or Lo signal at the start of rotation of the magnetic encoder according to the embodiment, comparison result of t1 and t3, comparison result of t2 and t4, and normal rotation or reverse rotation at the start positions A to D The figure which showed the relationship with a rotation direction. The perspective view which shows a part of magnetic encoder of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic encoder 2 Detection means 3 N pole narrow pitch 4 S pole narrow pitch 5 N pole wide pitch 6 S pole wide pitch 7 Track

Claims (3)

Rotating relative to the detection means for detecting the magnetic field,
A magnetic encoder comprising a track in which a magnetization pattern in which a narrow pitch of a pair of magnetic poles and a wide pitch of a pair of magnetic poles are repeated is repeated at least two times. The detection means specifies the magnetic pole at the start of rotation, and measures the interval time between the magnetic field changes when counting the number of magnetic field changes when the magnetic pole of the track after the rotation starts is reversed by five. And
Based on the measurement result, the first interval time and the third interval time between the magnetic field changes are compared, and the second interval time and the fourth interval time between the magnetic field changes are compared. Compare with the interval time,
The magnetic encoder according to claim 1, wherein forward / reverse rotation is discriminated.   Comparison result between the magnetic pole at the start of rotation, the first interval time and the third interval time between the magnetic field changes, and the second interval time and the fourth interval between the magnetic field changes. 3. The magnetic encoder according to claim 2, wherein the forward / reverse of rotation is discriminated using a discriminant that can discriminate between forward and reverse of rotation using a comparison result with time as a parameter.

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