JP2596216B2 - Four-phase differential rotation sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-phase differential rotation sensor, and more particularly to a four-phase differential rotation sensor in which eight MR elements are arranged in a rotation detection direction.

[0002]

2. Description of the Related Art FIG. 8 is a schematic view showing an example of a conventional four-phase differential rotation sensor. In the four-phase differential rotation sensor 51,
When the pitch of the teeth of the rotation detecting gear is P, the MR elements 52 to 59 are set to P / 4, P / 4, P / 4, 3P / 4, P /
They are arranged in eight rows at intervals of 4, P / 4 and P / 4.

FIG. 9 is an equivalent circuit diagram of the four-phase differential rotation sensor 51. When the teeth of the rotation detection gear move in the detection direction, output signals having respective neutral voltage values are obtained from the output terminals of the A phase, the B phase, the notA phase, and the notB phase.

FIG. 10 is a conceptual diagram showing a state of a magnetic bias c applied to the four-phase differential rotation sensor 51. 60 is
It is a substrate. The magnetic bias c has high uniformity at the center portion, but has low uniformity at the end portions (it becomes stronger at the end portions). Therefore, the MR elements 52, 53, 58, 5
9 has a stronger magnetic bias than the MR elements 54, 55, 56, 57.

[0005]

In the above-described conventional four-phase differential rotation sensor 51, the interval at which the MR elements 52 to 59 are arranged is 9P / 4 as a whole, and there is a problem that the size in the detection direction is large.

Further, since the rows of the MR elements 52 to 55 and the rows of the MR elements 56 to 59 are spaced from each other at the center and are arranged near both ends, the uniformity of the magnetic bias applied to each MR element is improved. And the amount of adjustment required to obtain a predetermined neutral voltage value increases.

Further, since the magnetic bias c changes in a direction in which the magnetic bias c decreases with a rise in temperature, the resistance values of the MR elements 52 to 59 change in a direction in which the resistance decreases. However, since the uniformity of the magnetic bias c is low, the degree of change of the magnetic bias c is also low, and the MR elements 52 and
Although the resistance values of 53, 58 and 59 are considerably small, the resistance values of the MR elements 54, 55, 56 and 57 near the center are only slightly reduced. Then, for the A phase and the B phase, the resistance values of the MR elements 52 and 53 on the power supply Vin side become considerably small, and the resistance values of the MR elements 54 and 55 on the Gnd side become slightly small. It changes to Vin side. On the other hand, for the notA phase and the notB phase, the resistance values of the MR elements 58 and 59 on the Gnd side become considerably small, and the resistance values of the MR elements 56 and 57 on the power supply Vin side become slightly small, so that the neutral voltage value is Gnd. Change to the side. That is, the direction of the temperature change of the neutral voltage value of the A phase and the B phase is opposite to the direction of the temperature change of the neutral voltage value of the notA phase and the notB phase. Therefore, A phase and notA phase, B phase
Differential amplification of the neutral voltage value of the phase and notB phases causes a problem that a large temperature drift occurs.

An object of the present invention is to provide an improved four-phase differential rotation sensor in which the size in the detection direction can be reduced, the amount of adjustment can be reduced, and the temperature drift can be reduced.

[0009]

The four-phase differential rotation sensor according to the present invention has high uniformity at the center portion, and is closer to the end portion.
Four-phase differential in which eight rows of first to eighth MR elements are sequentially arranged at equal intervals in a magnetic bias that is stronger than at the center.
In the rotation sensor, a first terminal of a first MR element is connected to a power supply or Gnd, and a second terminal of the first MR element is connected to an A-phase output terminal and a first terminal of a third MR element. Connecting a first terminal of the second MR element to a power supply or Gnd, connecting a second terminal of the second MR element to a B-phase output terminal and a first terminal of a fourth MR element, The third M
Connecting the second terminal of the R element to Gnd or a power supply, connecting the second terminal of the fourth MR element to Gnd or a power supply,
Connecting the first terminal of the fifth MR element to the output terminal of the notA phase and the second terminal of the seventh MR element; connecting the second terminal of the fifth MR element to Gnd or a power supply; MR
A first terminal of the element is connected to the output terminal of the notB phase and a second terminal of the eighth MR element, a second terminal of the sixth MR element is connected to Gnd or a power supply, First
A circuit is formed by connecting the terminal to the power supply or Gnd and connecting the first terminal of the eighth MR element to the power supply or Gnd.
Then, the first to eighth MR elements are magnetically biased.
And a first MR element and a second MR element
The seventh MR element and the element on one end side of the magnetic bias.
This is characterized in that the eighth MR element is arranged on the other end side of the magnetic bias .

[0010]

In the four-phase differential rotation sensor according to the present invention, by setting the interval at which the MR elements are arranged to be P / 4, the A-phase and the P-phase can be preferably used.
B-phase, notA-phase, and notB-phase signals can be extracted.

At this time, the size in the detection direction is 7P / 4, which is smaller than that of the conventional four-phase differential rotation sensor.

Further, since the MR elements are centrally arranged, the uniformity of the magnetic bias is increased, and the amount of adjustment required to obtain a predetermined neutral voltage value can be reduced.

Further, A phase, B phase, notA phase, not
Since the MR elements on the power supply side (or Gnd side) of the B phase are located at the end side, and the MR elements on the Gnd side (or power supply side) are located at the center side, the A phase and the notA
The neutral voltage values of the phases B, B and notB all change to the power supply side (or Gnd side) due to the temperature rise. Therefore, the temperature change is canceled by the differential amplification, and the temperature drift is reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. It should be noted that the present invention is not limited by this.

FIG. 1 is a schematic diagram of a four-phase differential rotation sensor 1 according to one embodiment of the present invention.

In this four-phase differential rotation sensor 1, the MR elements 2, 3, 4, 5, 6, 7, 8, and 9 are arranged in eight rows at equal intervals. When the pitch of the teeth of the rotation detecting gear is P, the interval is P / 4. Therefore, the size in the detection direction is 7P / 4, and the conventional four-phase differential rotation sensor 5 is used.
About 78% of 1.

The four-phase differential rotation sensor 1 includes an MR element 2
Is connected to the power supply Vin, the second terminal of the MR element 2 is connected to the A-phase output terminal and the first terminal of the MR element 4, and the first terminal of the MR element 3 is connected to the power supply Vin. The second terminal of the MR element 3 is connected to the B-phase output terminal and the MR element 5.
And the second terminal of the MR element 4 is connected to G
nd, the second terminal of the MR element 5 is connected to Gnd, the first terminal of the MR element 6 is connected to the output terminal of the notA phase, and the second terminal of the MR element 8. The second terminal is connected to Gnd, and the first terminal of the MR element 7 is no.
connected to the output terminal of the tB phase and the second terminal of the MR element 9,
The second terminal of the MR element 7 is connected to Gnd,
The first terminal of the element 8 is connected to the power supply Vin, and the first terminal of the MR element 9 is connected to the power supply Vin.

The arrangement of the A-phase and B-phase MR elements 2, 3, 4, and 5 is the same as that of the conventional four-phase differential rotation sensor 51. Therefore, if the teeth of the rotation detection gear T move in the detection direction, the A-phase,
The same output signal as the neutral voltage value of phase B is obtained from the output terminals of phase A and phase B.

Next, for the notA phase, the teeth of the rotation detecting gear T face the MR element 2 on the power supply Vin side of the A phase, and the teeth of the rotation detecting gear T face the MR element 4 on the Gnd side. Of the nota phase power supply Vin side
The R element 8 faces the concave portion of the tooth of the rotation detecting gear T,
The convex part of the tooth of the rotation detecting gear T faces the nd side MR element 6. Therefore, an output signal obtained by inverting the A-phase output signal is obtained from the notA-phase output terminal. Similarly, n
An output signal obtained by inverting the B-phase output signal is obtained from the otB-phase output terminal.

FIG. 2 shows an equivalent circuit of the four-phase differential rotation sensor 1. FIG. 3 is a conceptual diagram illustrating a state of the magnetic bias C applied to the four-phase differential rotation sensor 1. Reference numeral 10 denotes a substrate. Note that the distribution of the magnetic bias C is generally shown in FIG.
It is widely known that a state like
Shape of bias magnet, bias magnet and substrate
Depending on the distance). The magnetic bias C has high uniformity at the center portion, but has low uniformity at the end portions (it becomes stronger at the end portions). However, since the MR elements 2 to 9 are arranged at equal intervals and the size in the detection direction is small, the MR elements 2 to 9 are located at the center of the magnetic bias C. Therefore, a magnetic bias having a relatively high uniformity is applied, and the amount of adjustment required to obtain a predetermined neutral voltage value can be small.

Further, since the magnetic bias C changes in a direction in which the magnetic bias C becomes weaker as the temperature rises, the resistance of the MR elements 52 to 59 changes in a direction in which the resistance becomes smaller. However, since the degree of uniformity of the degree of change in the magnetic bias is low, the resistance values of the MR elements 2, 3, 8, 9 near the ends are considerably small, but the MR elements 4, 5, 6, 7 near the center. Is only slightly reduced (however, since the magnetic bias is more uniform than before, the difference in change is smaller than before). Then, the resistance values of the MR elements 2, 4, 8, and 9 on the power supply Vin side of the A phase, the B phase, the notA phase, and the notB phase become G.
Since the resistance values are much smaller than the resistance values of the NG-side MR elements 4, 5, 6, and 7, the A-phase, B-phase, notA-phase, and no
All neutral voltage values of the tB phase drift to the power supply Vin side. Such drift in the same direction is canceled out by the differential amplification, so that the temperature drift eventually decreases.

Phase A at a temperature of 25 to 80 ° C., no
Actual measured values of the neutral voltage values of the tA phase, the B phase, and the notB phase are shown in FIGS. The value measured by the four-phase differential rotation sensor 1 of the present invention is indicated by ○, and the value measured by the conventional four-phase differential rotation sensor 51 is indicated by △. M is an average value and σ is an average error.

In the four-phase differential rotation sensor 1 of the present invention, the amount of drift due to a temperature change is smaller than that of the conventional four-phase differential rotation sensor 51. The directions of temperature change (positive / negative on the vertical axis in the figure) are A phase, notA phase, B phase, n phase.
It is in the otB phase.

Since the MR elements 2 to 9 are concentrated at the center and the distance to the rotation detecting gear T is short even at the end MR elements 2 and 9, there is also an advantage that the peak-to-peak output signal becomes large. . Further, since the output signal is obtained by detecting the narrow range of the rotation detecting gear T, the phase difference can be detected more accurately.

As another embodiment of the present invention, a power supply Vin and Gnd of the four-phase differential rotation sensor 1 are connected in reverse.

[0026]

According to the four-phase differential rotation sensor of the present invention, the size in the detection direction is reduced. Therefore, the overall chip size can be reduced. Further, since the MR elements are concentrated at the center and the distance to the subject (for example, the rotation detecting gear) is short even at the end MR elements, the peak-to-peak of the output signal increases. Further, since an output signal is obtained by detecting a narrow range of the subject, the phase difference can be accurately detected. In addition, since the uniformity of the magnetic bias applied to the MR element is high, the amount of adjustment required to obtain a predetermined neutral voltage value can be small. Further, since the directions of the temperature drifts are the same for the four-phase output signals, they can be canceled by differential amplification, and the temperature characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of a four-phase differential rotation sensor according to the present invention.

FIG. 2 is an equivalent circuit diagram of the four-phase differential rotation sensor of FIG.

FIG. 3 is a conceptual diagram showing a state of a magnetic bias applied to the four-phase differential rotation sensor of FIG.

FIG. 4 is a characteristic diagram of a neutral voltage value of an A-phase.

FIG. 5 is a characteristic diagram of a neutral voltage value of a notA phase.

FIG. 6 is a characteristic diagram of a neutral voltage value of a B phase.

FIG. 7 is a characteristic diagram of a neutral voltage value of a notB phase.

FIG. 8 is a schematic view of an example of a conventional four-phase differential rotation sensor.

FIG. 9 is an equivalent circuit diagram of the four-phase differential rotation sensor of FIG.

FIG. 10 is a conceptual diagram showing a state of a magnetic bias applied to the four-phase differential rotation sensor of FIG.

[Explanation of symbols]

 1 4-phase differential rotation sensor 2-9 MR element A A-phase output terminal B B-phase output terminal C Magnetic bias T Rotation detection gear Vin Power supply.

Claims (1)

(57) [Claims] (1) The uniformity is high in the central part, and
In 4 retardation Dokai rolling sensors sequentially disposed eight columns of MR element from the first to the eighth equidistantly in a magnetic bias is stronger than in the very central portion, the power supply first terminal of the first MR element Or the second terminal of the first MR element is connected to the A-phase output terminal and the first terminal of the third MR element, and the first terminal of the second MR element is connected to a power supply or Gnd. And the second M
A second terminal of the R element is connected to a B-phase output terminal and a first terminal of the fourth MR element, a second terminal of the third MR element is connected to Gnd or a power supply, Element 2
The terminal of the fifth MR element is connected to the output terminal of the notA phase and the second terminal of the seventh MR element.
And the second terminal of the fifth MR element is connected to Gn.
d or the power supply, and the first terminal of the sixth MR element is connected to n
The output terminal of the otB phase is connected to the second terminal of the eighth MR element, the second terminal of the sixth MR element is connected to Gnd or a power supply, and the first terminal of the seventh MR element is connected to a power supply or G
nd, and a circuit formed by connecting the first terminal of the eighth MR element to a power supply or Gnd.
The eighth MR element is disposed at the center of the magnetic bias,
The first MR element and the second MR element are
A seventh MR element and an eighth MR element are
A four-phase differential rotation sensor, wherein the four-phase differential rotation sensor is arranged on the other end side of the bias .