JPS635214A - Magnetic encoder apparatus - Google Patents

Abstract

PURPOSE:To detect an accurate position by providing objects to be detected each having a first region with a cyclical magnetized pattern and a second region having a different pattern in plural rows in an adjacent state. CONSTITUTION:A region having no cyclical magnetized pattern provided thereto is constituted of AC erasure regions 6 and three tracks 4 are provided on a rotor 1. The magnetized regions 5 of three tracks 4 and the circumferential pitches of the AC erasure regions 6 are determined by weighting so as to be capable of detecting the absolute rotary position of the rotor 1 as an absolute address comprising a three-bit binary number. In order to detect the magnetized patterns of three tracks 4, three MR (magnetic resistance effect element) sensors 3 are respectively arranged on a magnetic head substrate 2 in opposed relation to the tracks 4. Each of the MR sensors 3 provided on the substrate 1 consists of a plurality of MR elements wherein the direction of the magnetic flux of each magnetized region is right-angled to an easily magnetizable axis direction and, since the MR elements of each row are arranged at an azimuth angle thetaequal to the azimuth angle 7 of each magnetized region 5, a position can be detected accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic encoder device, and particularly to a magnetic encoder device that detects the relative position between a detected object and a detected object.

C prior art] 'The magnetoresistive element C (hereinafter referred to as MR element) is made of Ni-Fe.
, a change in the applied magnetic field is detected by a change in resistance of a thin film element such as Ni-Co. Therefore, when used as various encoder devices, a permanent magnet or the like can be used as a magnetic field generating means, and the structure is simpler and more durable than a photo sensor, which requires a power source such as an LED, and requires a consumable light source element. It is also possible to construct an excellent encoder device.

When used as a rotary encoder, the circumferential surface of the cylindrical rotor 1 is divided into multiple (three in this case) tracks 4 as shown in Fig. 11, and these are reversely magnetized with magnetization patterns of different pitches. A configuration has been considered in which leakage magnetic flux from the magnetization pattern of each track 4 is detected by an MR sensor 3 on the substrate 2 arranged along the circumferential surface.

Of course, with this configuration, it is also possible to measure the rotational speed of the rotor l.

Detection of changes in the magnetic field is performed by a bridge circuit as shown in FIG. 12. The resistor R1 in FIG. 12 corresponds to the resistance of the MR sensor 2, and this resistor R1 is connected to a temperature compensation resistor R2 having the same temperature resistance coefficient. are connected in series. Furthermore, by forming a bridge circuit with resistors R3 and R4 that form a reference voltage from the power supply voltage E, and detecting the voltage difference at each voltage division point with a differential amplifier A, changes in the magnetic field can be output as an electrical signal. .

[Problems to be Solved by the Invention] With the above configuration, the leakage magnetic flux 4a from the magnetization pattern of the track 4 shown in FIG. 13 is applied to the MR element arranged nearby. Therefore, if magnetization patterns with various long and short periods are provided for absolute position detection as shown in Figure 1, the longer the period, the smaller the magnetic flux density at the center of magnetization is than at the end a, as shown in Figure 14. Therefore, the magnetic flux of the MR element cannot be detected. As a result, if the rotor is stopped and raised so that the MR element is located at the center of Bi magnetization, there is a problem that accurate position detection cannot be performed.

Furthermore, in order to reduce the size and cost of a magnetic encoder, it is necessary to narrow the track width of the magnetization pattern and the distance between adjacent tracks. However, if the track width is narrowed, the MR sensor facing the magnetization pattern of each track will be affected by the cocoon talk from other adjacent tracks due to the slight eccentricity that occurs when the rotor rotates, making it impossible to accurately detect the position. was there.

[Means for Solving the Problems] In order to solve the above problems, one aspect of the present invention is to create a periodic magnetization pattern with a predetermined pitch in an encoder device that detects the relative position between a detected object and a detected object. and a second region having at least a pattern different from the above-mentioned periodic magnetization pattern. A configuration was adopted in which the azimuth angles were set to different values.

[Function] According to the above configuration, crosstalk between detected objects can be significantly reduced by using azimuth angles caused by different azimuth angles of adjacent detected objects. Further, physical states such as absolute position and velocity can be digitally detected with high efficiency by a sensor using a magnetoresistive element as described above.

[Embodiment] The present invention will be described in detail below based on an embodiment shown in one drawing. In this embodiment, a configuration of a rotary encoder for detecting a rotational interlocking state is shown as an encoder.

FIG. 1 shows the configuration of the rotor portion of a rotary encoder adopting the present invention. In this embodiment, instead of providing a plurality of tracks with different magnetization period patterns on the rotor 1 as in the conventional case, , 0 tracks in which a magnetized region 5 provided with a magnetization pattern with a common pitch for each track having a different azimuth angle with respect to adjacent tracks, and a region 6 provided with at least a periodic magnetization pattern are arranged at alternating W. In the embodiment, a region in which no periodic magnetization pattern is provided is constituted by an AC erase region 6, and three tracks 4 are provided on the rotor lk.

The magnetization areas of the three tracks 4 and the circumferential pitch of the erase area 6 are weighted and determined so that the absolute rotational position of the rotor 1 can be detected as an absolute address consisting of a 3-bit binary number. In order to detect the magnetization patterns of the three tracks 4, three MR sensors 3 are arranged on the magnetic head substrate z, facing each track 4, respectively. The MR sensor 3 provided on the substrate 2 is composed of a plurality of MR elements in which the direction of the magnetic flux of the magnetized region and the direction of the axis of easy magnetization are perpendicular. As shown in FIG. 2, the MR sensor 3 is formed by forming a thin film of an alloy such as iron-nickel or nickel-cobalt into a zigzag shape by a method such as vapor deposition or etching. Alternatively, the MRX' elements of each strip are independent MR elements 6a and 6b.

6c, . . . and may be made conductive by other methods.

Each strip of MR elements can be considered as a series connection of a plurality of MR elements arranged at a pitch p. The MR elements of each strip are arranged with an azimuth angle θ equal to the azimuth angle of the magnetized region 5 on the rotor l.

Individual M:R elements 6a constituting the MR sensor 3 in FIG.
, 6b, . . . , the detection circuit shown in FIG. 12 is connected to one of the tracks 4, which is composed of a magnetized region 5 having a magnetization pitch of 2P and an erased region 6 as shown in FIG.
Let us consider the case where the rotor 1 is rotated and scanned. In this case, as shown by reference numeral 70 in FIG. 3, the output becomes 0 at every half pitch P of the magnetization pitch 2P.

As mentioned above, the MR sensor 3 has individual MR elements 6a, 6
Since it can be considered as a series connection of b,..., MR
When a detection circuit as shown in FIG. 12 is connected to the sensor 3, the combined output waveform is generated by the MR element 6a, as shown in FIG.
6b, 6c, . . . output waveform 8a whose phase is shifted by pitch P.

8b, 8c, . . . are combined to form a waveform 8e.

That is, when the track 4 is scanned by the MR sensor 3, an output waveform approximately approximate to a rectangular wave can be obtained corresponding to the la magnetized region and the erased region 6.

Of course, the combined output of MR sensor 3 is different from that of the conventional single MR sensor.
The rise is sharper at the break between magnetization and erasure region, which is larger than when the element is used as a detection element.

A pulse with a falling edge can be obtained.

Therefore, the detection accuracy does not become unstable depending on the mounting position of the MR sensor as in the conventional case, and highly accurate position detection or rotation speed detection is always possible.

Furthermore, in the above configuration, since the magnetization pattern having an azimuth angle and the MR sensors formed in the direction intersecting the direction of the magnetic flux of this magnetization pattern are opposed to each other, the track width of the magnetization pattern and the adjacent track Even if the tracks are placed close to each other, or even if the tracks are placed adjacent to each other, the slight eccentricity that occurs when the rotor rotates will cause the MR sensor holding each track to be affected by the interference from other adjacent tracks. In this sense too, because it is not affected by crosstalk.

Highly accurate position detection and rotation speed detection are possible. Furthermore, since the track density or track width can be made smaller than in the conventional method, there is an advantage that the rotor can be made smaller and the entire encoder can be made smaller and lighter.

In order to confirm the effect of the above azimuth angle setting, the following experiment was conducted.

As shown in FIG. 5, the output was examined when a magnetized region 5 having an azimuth angle θ was scanned by an MR sensor 3 having no azimuth angle. In this case, the output of the MR sensor 3 decreased significantly as the azimuth angle 0 of the magnetization pattern 5 increased. The dependency of the output of the sensor 3 on the azimuth angle is as shown in FIG. That is, the larger the azimuth angle, the greater the output decreases, and if the absolute value of the azimuth angle is 106 or more, an S/N ratio of 60 dB or more could be obtained.

Therefore, as shown in FIG. 7, if the azimuth angle θ of the MR sensor 3 and the azimuth angle 0 of the magnetized region of the track 4 are made equal, output characteristics without azimuth loss can be obtained.

As shown in FIG. 8, by setting different azimuth angles θ' to the tracks 4' and 4' adjacent to the track 4, even if the MR sensor 3 causes a track deviation, the adjacent tracks 4' will be fixed.

It was possible to obtain an output waveform 12a that is not affected by the magnetization pattern of 4'.

Next, the MR element 8a that constitutes the MR sensor 3.

The optimum combination of the pitches 6b, 6c, . . . and the magnetization pitch of the magnetized region 5 is considered.

FIG. 9 shows M R− with respect to the magnetization pitch 2P of the magnetization region 5.
1! The figure shows the results of measuring the output while varying the number of MR elements 6a, 6b, 6c (7) of the sensor 3.

In FIG. 9, P=10p, that is, MR elements 6a, 6b,
The pitch p of ... is 1/10 of the local pitch P of the magnetized region 5
In this example, in FIG. 9, the reference numeral 13a is 6.
Books, number 13b is 8 books, number 13c is 10 books, number 13
d shows a combined output waveform when an MR element is constructed from 12 elements.

As is clear from FIG. 9, the waveform 13c is closest to a rectangular wave and is a suitable waveform.

Therefore, in this case, the number n of MR elements is n=10
is appropriate.

Generalizing, if there is a relationship between the magnetization pitch P of the track and the pitch p of the MR sensor as P=np, it is better to configure the MR element with n elements. In other words,
The MR sensor may be configured such that n elements are arranged at equal intervals between one S pole and one N pole of the magnetization pattern of the track.

As described above, according to this embodiment, by giving different azimuth angles to adjacent tracks and giving the same azimuth angle to the corresponding MR elements, the influence of crosstalk caused by rotor eccentricity etc. It is possible to perform highly accurate detection operations based on highly efficient signal reproduction. Therefore, the manufacturing cost of the device can be significantly reduced because the precision of the parts of the mechanism is not required in the past. Further, due to the reduction in crosstalk, the track width and pitch can be reduced by omitting the guard band, so that the rotor, and therefore the entire device, can be significantly reduced in size and weight.

FIG. 10 shows a configuration for compensating the temperature-resistance characteristics of the MR element. Figure 10 shows an MR thin film formed on a substrate.
Shows the shape of the sensor.

In FIG. 10, the MR sensor 3 is formed as a thin film in the same shape as described above, and adjacent to this, the MR sensor 3 is formed at the same temperature as the MR sensor 3.
A resistor 14d having a resistance coefficient is formed to have an area suitable for desired compensation characteristics. The resistor 14d is also formed to have the same azimuth angle as the MR sensor 3. This resistor 14d.

It is used as the temperature compensation resistor R2 of the bridge circuit shown in FIG.
The middle point of the series connection of 4d is taken out from the terminal 14c. Therefore, by connecting resistors R3+R4 and differential amplifier A to this, the detection circuit shown in FIG. 12 can be easily constructed. Connection points of terminals 14a to 14c in FIG. 14 are indicated by the same reference numerals in FIG. 12.

In this embodiment, the first region having a periodic magnetization pattern with a predetermined pitch is shown in FIGS. 1, 3, 4, and 5.
The regions 5 and 1 disclosed in the figure and other drawings, and the second region having a pattern different from the periodic magnetization pattern with a predetermined pitch are designated as the AC erase region 6;
As shown in 6 in FIGS. 5(A) to 5(CB), the area may have a magnetic pattern having a different azimuth angle from area 5. In this case, it is necessary that the region 6 has an azimuth angle that is different from the azimuth angle of the region 5 of the adjacent track. Also, bees finer than area 5.

The pitch pattern may be so fine that it cannot be detected by the MR element due to the spacing loss that occurs between the MR element and the medium. Such a pitch is determined by the distance between the MR element and the medium, the element sensitivity, and the characteristics of the magnetized region. It should be optimized depending on the situation.

For example, if the distance between the MR element and the medium is 0.11 layers, and the stripe width of the element is 10p, the pitch of region 6 is
It is fine if the pitch is less than or equal to the height of the pitch.

Although a single-tally encoder has been described above as an example, the same technique as described above can also be applied to a linear encoder in which the track to be detected is arranged in a straight line. Further, even if the configuration is such that the detection object side moves instead of the detection object side, the same effect as described above can be obtained. Furthermore, it goes without saying that the number of detected object tracks is not limited to three trees.

[Effects] As is clear from the above description, according to the present invention, in an encoder device that detects the relative position between a detected object and a detected object, a first magnetization pattern having a periodic magnetization pattern with a predetermined pitch is used. A plurality of adjacent detection objects each having a first region and a second region having at least a pattern different from the periodic magnetization pattern described above are provided, and the azimuth angles of the plurality of adjacent detection objects are set relative to each other. By adopting a configuration in which different values are set, it is possible to effectively prevent the effects of crosstalk between objects to be detected and the negative effects of a decrease in parts and assembly precision, and also to reduce the distance between objects to be detected. It is possible to obtain the excellent advantage that the entire device can be significantly reduced in size and weight.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main structure of a rotary encoder as an example of a magnetic encoder device employing the present invention;
Fig. 2 is an explanatory diagram showing the configuration of the MR sensor in Fig. 1, Figs. 3 and 4 are explanatory diagrams showing the detection operation of the MR sensor in the apparatus shown in Fig. 1, and Figs. is a diagram explaining the effect of the azimuth angle, Figure 5 is an explanatory diagram showing the magnetization pattern on the rotor and an MR sensor without an azimuth angle, and Figure 6 is an illustration showing the output of the MR sensor when the azimuth angle is set. Both the diagram and FIG. 7 are explanatory diagrams showing the magnetization pattern with the azimuth angle set and the MR sensor, and FIGS. 8 and 9 are explanatory diagrams each showing the state of output synthesis of multiple MR elements.
Figure 1θ is an explanatory diagram showing different configurations of the MR element.
The following figures explain the conventional configuration: Figure 11 is an external perspective view of a rotary encoder, Figure 12 is a circuit diagram of a detection circuit used in the configuration of Figure 11, Figures 13 and 14.
The figure is a conventional line. An explanatory diagram showing this operation, Fig. 15 (A),
(B) is an explanatory diagram showing a different embodiment of the present invention. 1... Rotor 2... Magnetic head board 3.
...MR sensor 5...Magnetized region 6...AC erasing region 14d...Resistor P-g 4ε Plant 5 Kinuta! E Recycling port 12 of the drawing/discharging 21. i Figure 13 Figure 15

Claims (1)

[Claims] An encoder device that detects a relative position between a detected object and a detected object includes a first region having a periodic magnetization pattern with a predetermined pitch, and a second region having a pattern different from at least the periodic magnetization pattern. What is claimed is: 1. A magnetic encoder device characterized in that a plurality of adjacent detection objects having a region are provided, and the azimuth angles of the plurality of adjacent detection objects are set to different values.