JP2527424B2 - Magnetic rotary encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic rotary encoder, and more particularly to a magnetic rotary encoder that detects the rotational state of a member to be detected by magnetic means.

[Prior Art] In the field of automatic control, closed-loop control that detects the state of a controlled member and performs control according to the detected state and closed-loop control that does not detect the state of the controlled member are known as control methods. There is. Generally, when high-precision control is required, closed-loop control is usually performed.

In particular, various encoders such as those using an optical detection method or those using a magnetic detection method are known as elements for detecting the physical state of the controlled member. In particular, encoders that detect physical motion states can be classified into those that detect linear motions and those that detect rotary motions (hereinafter referred to as RE elements).

FIG. 9 shows the structure of a RE element according to the conventional magnetic detection method.

The illustrated RE element is of a drum type, and a plurality of magnetic tracks 7 magnetized at a predetermined recording wavelength are provided on a magnetic sheet 3 wound around the circumferential side surface of a cylindrical magnetic drum 2. The magnetic head 4 is arranged to face these tracks. Here, three magnetoresistive effect elements (hereinafter referred to as MR elements) 5 provided in the magnetic head 4 are arranged to face three magnetic tracks 7. A rotating shaft 1 is provided at the center of the magnetic drum 2, and the rotating shaft 1 is directly (or via a reduction gear or the like) coupled to a rotating shaft of a motor 6, which is a member to be detected.

[Problems to be Solved by the Invention] A plurality of magnetic tracks are provided because a pattern such as a gray code is formed by the plurality of tracks in order to detect the absolute rotational position of the RE element (that is, the member to be detected). However, in the conventional configuration as shown in FIG. 9, it is necessary to increase the length of the magnetic drum 2 in order to increase the number of tracks, and it is difficult to configure a thin and small RE element. .

Further, in order to improve the detection accuracy of the RE element, a method is known in which a plurality of magnetoresistive effect elements are opposed to one magnetic track and the detection outputs are averaged. Since it is formed on the side surface of the magnetic drum, there is a problem that it is difficult to arrange the magnetoresistive effect elements so that the distances between the plurality of magnetoresistive effect elements and the magnetic drum are all equal.

[Means for Solving Problems] In order to solve the above problems, according to the present invention, in a magnetic rotary encoder that magnetically detects a rotational state of a detected object, the magnetic rotary encoder is coupled to the detected object, A rotating body having a plurality of concentric circular tracks each having a magnetization pattern of a magnetization wavelength λ on a plane perpendicular to the rotation axis, and a pitch provided for the plurality of tracks and having a narrow pitch with respect to the magnetization wavelength λ. n in parallel with λ / 2 × 1 / n
(N is an integer greater than or equal to 2) The structure provided with the detection body which has a some detection means which consists of a magnetoresistive effect element was employ | adopted.

[Operation] According to such a configuration, since a plurality of concentric circular tracks having a magnetization pattern are formed on a plane perpendicular to the rotation axis of the rotating body, the rotating body can be configured in a flat shape, and the entire device can be formed. Does not have the problem of becoming large or thick.

Further, since the magnetization pattern is formed on the plurality of concentric tracks at the same magnetization wavelength λ, it is possible to configure the detecting means including the magnetoresistive effect element under the same condition for each track.

[Examples] Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 1 is a perspective view showing the structure of an RE element adopting the present invention. Here, the RE element integrated with the motor, which is the member to be detected, is shown.

Reference numeral 6 in the drawing denotes a motor as a member to be detected, and a rotating body 2 is fixed to a rotation shaft 1 of the motor. The magnetic track is formed on a magnetic sheet 3 provided on the lower surface of the rotating body 2 facing the disk-shaped magnetic head 4 provided on the upper surface of the motor 6. The magnetization information of the magnetic track provided on the lower surface of the magnetic sheet 3 is detected by the MR element 5 formed on the magnetic head 4.

FIG. 2 shows the structure of the magnetic tracks provided on the lower surface of the magnetic sheet of FIG. 1 and the MR element 5 for detecting them.

Four magnetic tracks are concentrically formed on the magnetic sheet. In these magnetic tracks, a region 7 is a portion where a magnetization signal having a wavelength λ is recorded and the signal output is turned on when the MR element 5 detects the magnetization signal. A region 8 is a region formed by performing AC erasing after recording the magnetized region 7 in advance, and is a portion where the detection output signal from the MR element 5 is turned off.

Hereinafter, the four tracks on the magnetic sheet 3 will be referred to as a first track, a second track ... A fourth track from the inside. A circular magnetic sheet 3 is formed on the first to fourth tracks to form a signal ON / OFF pattern at a cycle of 2π / 2, 2π / 4, 2π / 8, 2π / 16, and this is used for absolute position detection. Gray code.

Further, in FIG. 2, the MR element 5 is shown as ai, bi, ci, .... Here, i indicates the track number. For example, for the outermost fourth track,
Eight MR elements 5 a4 to h4 are arranged on the upper surface of the magnetic head 4 on the motor 6. MR elements a1 to a4 are located at the position where the ON signals of all tracks start, which is the reference position when detecting each track.
Are arranged in a straight line along the radial direction of the magnetic sheet 3.

Among the above MR elements, especially MR elements b1, b2, b3, b4 are
Magnetization pitch 2 of each track to improve detection accuracy
It is arranged every π / 2, 2π / 4, 2π / 8, 2π / 16. That is, one ai and one bi are arranged in the adjacent ON pattern (magnetization area 7) and OFF pattern (AC erasing area 8) of each track, and the detection signals are extracted by combining the outputs of these two elements. I am trying.

Such an arrangement of the MR element 5 can be expanded by combining two MR elements ci and di. In that case, MR elements ai and ci,
The bi and di are arranged so as to be at the same position relative to an arbitrary ON / OFF magnetization pattern.

In this embodiment, all tracks after the second track are
The MR elements ci and di are provided, and the MR elements ai and ci and bi and di are arranged point-symmetrically to each other. Therefore, ei, fi and gi, hi of the fourth track are MR elements for output compensation which have been further added.

FIG. 3 is an enlarged and linear view of the second track and MR element 5 of FIG. 2 to show the connection state of the MR element 5. The MR elements a2, b2, c2, d2 of the second track are connected in series as shown in the figure, and the voltage V is applied to the terminals k, l at both ends of this series connection, and the midpoint potential m0 is applied from the midpoint terminal m.
Take out. This connection state is shown as a circuit diagram in FIG. In FIG. 4, the MR element 5 is indicated by a resistance symbol.

Similar to FIG. 4, FIG. 5 shows the connection state of the MR element 5 of the fourth track. Here, the midpoint voltage V0 is MR
It is taken out from between the elements g4 and h4.

FIG. 6 shows the physical configuration of the MR element 5.
As shown in the figure, the MR element 5 is formed on the magnetic sheet 3 by a film forming technique in a shape in which a plurality of magnetic elements having a high magnetic permeability are alternately folded. The pattern width of the illustrated MR element 5 corresponds to exactly one half wavelength of the magnetization wavelength λ of the magnetic track.

 FIG. 7 shows the manner of detection in the above configuration.

The uppermost part of FIG. 7 shows the magnetization pattern of the magnetic track and the pattern of the MR element 5, the middle part shows the output signal of the MR device when only one MR device is used, and the lowermost part shows the same track as described above. 3 shows the detection output when a plurality of MR elements are arranged and connected.

The output of the MR element p1 shown in the uppermost stage of FIG. 7 becomes a detection waveform having a period of λ / 2 as shown in the middle stage of FIG. Further, since the five MR elements p to s in FIG. 7 are arranged at a pitch of ⅕ of λ / 2, the respective outputs are out of phase by λ / 10 as shown in the lower stage of FIG. Output waveform. When these five MR elements p to s are connected in series as described above, the combined output waveform thereof becomes a substantially flat constant voltage level as indicated by the symbol u in the lower part of FIG.

Generally, for n sinusoidal magnetic signals, n MR elements are
When they are arranged at a pitch of / 2 x 1 / n and they are connected in series, the composite output waveform becomes almost flat as described above. Therefore, according to the above embodiment, a stable detection output waveform can be obtained. When the MR element 5 enters the erased area 8 of the magnetic track in FIG. 7, the combined output waveform of the MR element 5 becomes 0.
Therefore, it is possible to reliably detect ON / OFF of the magnetization.
This will be described in detail below.

Now, when the MR elements a2, b2, c2, d2 in FIG. 3 are in the positions shown, the MR elements a2 and c2 are in the position of the detection signal ON and have a resistance value R0-ΔR when receiving the magnetic field. There is. On the other hand, MR element
b2 and d2 are in the AC-erased region 8, the resistance value does not change, and the resistance value at this time is the initial value R0. In this case, the value of total output voltage V0 is Y1 Can be shown as

When the MR element of FIG. 3 moves 2π / 4 with respect to the magnetized region 7, the resistance values of the MR elements a2 and c2 become R0. The output voltage Y2 at this time is Therefore, in the second track, an output pulse composed of the output voltages of Y1 and Y2 that appear alternately at a pitch of 2π / 4 during one rotation of the magnetic sheet 3 is obtained.

FIG. 8 shows the output waveform of each MR element when the first to fourth tracks are detected over the entire circumference of the magnetic sheet 3.

As mentioned above, the magnetization pattern of each magnetic track is 2π /
Since it is set to 2, 2π / 4, 2π / 8, 2π / 16, which is an integral multiple of 2, the number of magnetization region detection pulses of the MR element 5 in charge of each track is counted and If binary number data in which the count value is the most significant bit and the count value of the fourth track is the least significant bit is constructed, this data can be used as 4-bit data indicating the absolute rotation position of the rotary shaft 1 of the motor 6. it can.

According to the above configuration, since the magnetizing signal forming portion of the RE element can be configured to have a flat shape as in the conventional case, the entire RE element can be configured to be small and thin, and as shown in FIG. It can be incorporated into an element such as a motor.

Further, according to the present embodiment, since a plurality of MR elements are arranged point-symmetrically with respect to one magnetic track, it is possible to suppress the output fluctuation due to the inclination of the rotating magnetic sheet 3. That is, in the motor 6 of the present embodiment, it is possible that the spacing between the MR element and the magnetic track changes due to thrust rattling of the rotating shaft 1 and the output voltage fluctuates. If this is done, the spacing of a certain MR element will become wider, and if the output drops, the spacing of the MR element located in a point-symmetrical position with that will narrow and the output will increase. Are balanced and spacing losses are compensated.
According to this configuration, not only the spacing loss but also the output reduction due to the pattern configuration of the MR element on the substrate, the dimensional error of the element, the error of the element mounting position, and the like can be compensated. This compensation effect increases as the number of MR elements arranged in point symmetry increases, so the number of elements may be increased or decreased according to the desired detection accuracy.

[Effect] As is apparent from the above, according to the present invention, in a magnetic rotary encoder that magnetically detects the rotational state of a detected body, the planes that are coupled to the detected body and are perpendicular to the rotation axis are magnetized. A rotating body having a plurality of concentric circular tracks having a magnetization pattern of wavelength λ, and the magnetization wavelength λ provided for the plurality of tracks, respectively.
In contrast, a detector having a plurality of detectors composed of n (n is an integer of 2 or more) magnetoresistive elements arranged in parallel at a narrow pitch λ / 2 × 1 / n is adopted. The rotating body can be formed in a flat shape, and the entire device can be formed in a significantly small size and a thin shape. Further, since the detection means composed of the magnetoresistive effect element can be configured under the same condition for each of the plurality of tracks of the rotating body, the detection output from each detection means is uniform and the detection means are the same. Because it can be manufactured under the conditions of
The excellent effect that the manufacturing is easy and the manufacturing accuracy can be improved can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of an RE element adopting the present invention,
2 is a top view showing the structure of the magnetic sheet shown in FIG. 1, FIG. 3 is an explanatory view showing the arrangement of the magnetic tracks and MR elements shown in FIG. 2, and FIGS. 4 and 5 show MR elements. FIG. 6 is a circuit diagram showing an electrical connection state, FIG. 6 is an explanatory diagram showing a relationship between a magnetized area of a magnetic track, an AC erased area and an MR element, and FIG. 7 is an explanation showing a position detecting operation in an embodiment of the present invention. FIG. 8 is a waveform diagram showing the output waveform of the RE element at the time of detecting the absolute position in this embodiment, and FIG. 9 is a perspective view showing the configuration of the conventional RE element. 1 ... Rotation axis, 2 ... Rotating body 3 ... Magnetic sheet, 4 ... Magnetic head 5 ... MR element, 6 ... Motor 7 ... Magnification region, 8 ... Motor

Front page continued (72) Inventor Hideto Sano 1248 Shimokage Mori, Chichibu City, Canon Electronics Co., Ltd. JP-A-59-108193 (JP, A) JP-A-62-34302 (JP, A) JP-A-60-102520 (JP, A)

Claims (1)

(57) [Claims] 1. A magnetic rotary encoder for magnetically detecting a rotational state of a detected body, comprising a plurality of concentric circles each having a magnetization pattern of a magnetization wavelength λ on a plane which is coupled to the detected body and is perpendicular to a rotation axis. And a rotor provided with tracks, and n arranged in parallel with each other at a narrow pitch λ / 2 × 1 / n with respect to the magnetization wavelength λ.
(N is an integer of 2 or more), and a detection body having a plurality of detection means composed of a plurality of magnetoresistive effect elements.