JP2002277282A - Absolute encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absolute encoder which can reduce the number of magnetized tracks without lowering its resolution and which can be manufactured at low costs. SOLUTION: The absolute encoder 20 is provided with a magnetic drum 22 on which the magnetized tracks 25 are arranged along the circumferential direction, and a magnetism detection sensor 23 which is arranged relatively so as to be capable of detecting the magnetized tracks 25 on the magnetic drum 22 and which comprises MR elements 14a, 14b. The magnetized tracks 25 are magnetized so as to comprise absolute encoder codes Ci (serial data) indicating an absolution rotation angle as the rotation position of the magnetic drum 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute encoder.

[0002]

2. Description of the Related Art Conventionally, a magnetic drum having two or more rows of magnetization patterns magnetized as an absolute encoder and a detector using a magnetoresistive effect element (hereinafter referred to as an MR element) for reading the magnetization pattern of the magnetic drum are known. A combined magnetic absolute encoder has been proposed.

In general, in order to obtain a resolution of 2 n in this type of absolute encoder, n magnetized tracks are required. In such a case, as shown in FIG. 4, a plurality of magnetized tracks 51 on which 1-bit absolute information is recorded are arranged in the axial direction on the outer periphery of the magnetic drum 50, and the number of the magnetized tracks is arranged on the magnetic drum 50. A magnetic sensor in which MR elements (magnetoresistive elements) 52 of the number of bits corresponding to
The absolute value is output by combining the signals obtained from.

That is, if the data is 10 bits,
Ten magnetized tracks 51 are provided, and ten MR elements 52 are provided corresponding to each magnetized track. As a result, an absolute encoder having a resolution of 2 to the 10th power (= 1024) is obtained.

[0005]

However, conventionally, M
It is necessary to arrange the same number of R elements in the axial direction of the magnetic drum as the number of magnetized tracks, and the number of MR elements is correspondingly arranged in the same number. Therefore, the cost is high, and the axial length of the magnetic drum is long. There was a problem.

An object of the present invention is to reduce the number of magnetized tracks without lowering the resolution,
An object of the present invention is to provide an inexpensive absolute encoder.

[0007]

According to a first aspect of the present invention, there is provided a rotating body having a magnetized track along a circumferential direction, and a magnetoresistive element which is disposed relatively to the magnetized track of the rotating body. In an absolute encoder provided with a detector including, the gist track is magnetized so as to have serial data indicating a rotation angle which is a rotation position of a rotating body. Things.

According to a second aspect of the present invention, in the first aspect, when the serial data is rotated in any of a clockwise direction and a counterclockwise direction of the rotating body, a rotation angle corresponding to the rotating direction is provided. Is readable.

According to a third aspect of the present invention, in the first aspect, the magnetized track includes serial data indicating a clockwise rotation angle of the rotating body and serial data indicating a counterclockwise rotation angle. Two rows are provided, and a pair of magnetoresistive elements are provided so as to be opposed to the two rows of magnetized tracks, respectively.

(Operation) According to the first aspect of the present invention,
By reading the serial data with the detector, it is possible to detect the number of rotation angles of the rotating rotator.

According to the second aspect of the invention, when the rotating body rotates clockwise or counterclockwise, the serial data corresponding to the rotating direction is detected by the detector corresponding to the magnetized track. , The rotation angle (absolute rotation angle) of the rotating rotator can be detected.

According to the third aspect of the invention, when the rotating body rotates clockwise or counterclockwise, the serial data of the magnetized track corresponding to the rotation direction corresponds to the rotation direction. By reading the read magnetoresistive element, the rotation angle (absolute rotation angle) of the rotating rotator can be detected.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of an absolute encoder embodying the present invention will be described below with reference to FIGS.

FIG. 1 is an explanatory perspective view of an essential part of an absolute encoder, FIG. 2A is an explanatory view of a magnetized track, and FIG.
(B), (c) is an explanatory diagram when a pair of MR elements detects magnetic data.

An absolute encoder 20 includes a magnetic drum 22 as a rotating body integrally connected to a rotating shaft 21.
And MR elements 24a and 24b as magnetoresistive elements
And a magnetic detection sensor 23 as a detector having (see FIG. 1). The rotating shaft 21 is operatively connected to an output shaft (not shown).
Rotation in either clockwise or counterclockwise direction is enabled.

The magnetic drum 22 is adapted to rotate around the axis of the rotating shaft 21, and one magnetized track 25 is provided on the peripheral surface thereof. The rotating shaft 21 is supported by a support plate (not shown) via a pivot bearing.

The magnetized track 25 will be described. FIG.
As shown in (a), the magnetized track 25 is
In order to indicate the absolute rotation angle which is the absolute rotation position of No. 2, the absolute encoder code Ci having a predetermined number of bits n
(I = 1, 2,..., M) are magnetized as a serial code in a belt shape in the circumferential direction. In the present embodiment, n
= 10. Therefore, according to the present embodiment, 0.35 (degree) (= 36)
0/1024) is set.
In the present embodiment, 2 to the nth power is m. That is, m is 1024 in the present embodiment.

Further, the absolute encoder code Ci of the present embodiment is obtained by reading the absolute encoder code Ci during the clockwise rotation.
W data Cia and CCW data Cib read at the time of counterclockwise rotation are included, and both data are arranged alternately.

The CW data Cia is configured as 10-bit serial data arranged so as to be detected in the order of X0 to X9 when read by the MR element 24a when the magnetic drum 22 rotates clockwise. (See FIG. 2A). X0 is the start of serial data,
X9 means the end, and the suffixes attached to X2 to X8 between them indicate the order counted from the start. or,
1 and 2A, the arrow CW indicates the magnetic drum 22.
The rotation of the (magnetized track 25) indicates the clockwise direction, and the arrow CCW indicates that the rotation of the magnetic drum 22 (the magnetized track 25) indicates the counterclockwise direction.

The CCW data Cib is configured as 10-bit serial data arranged so as to be detected in the order of X0 to X9 when read by the MR element 24b when the magnetic drum 22 rotates counterclockwise. (See FIG. 2A).

Then, between CW data Cia and CCW data Cib where i belongs to the same group, X0 to X9
Are matched to each other. That is, for example, when i = 1, X0 to X of the CW data C1a
9 and the values of X0 to X9 of the CCW data C1b are the same.

In this embodiment, for convenience of explanation, i
It is said that the CW data Cia and the CCW data Cib that match the same group belong to the same set, and if i does not match, they belong to another set.

As shown in FIG. 2A, CW data Cia
A start code ST is arranged between the start X0 of the CCW data Cib belonging to another adjacent group and the start X0 of the CCW data Cib belonging to another adjacent group.

A stop code SP is arranged between X9 at the end of CW data Cia belonging to the same group and X9 at the end of CCW data Cib. Each of the start code ST and the stop code SP is composed of 4 bits.

In this embodiment, for example, the start code ST is "1001" and the stop code SP is "011".
Start code ST and stop code S, such as "0"
P is a value whose code is inverted for each bit. As a result, the start code ST and the stop code SP can be read as the start code ST and the stop code SP both when read from the clockwise direction and when read from the counterclockwise direction.

As described above, one set of serial data structures in the present embodiment (that is, in this embodiment, every 0.35 (degrees)) has a start code ST, The CW data Cia, the stop code SP, and the CCW data Cib are combined in an order. When data is read in the counterclockwise direction, one set of serial data structures includes a start code ST, CCW data Cib, stop code SP, and CC
It is constructed by combining the order of the W data Cib.

As described above, 1024 sets of serial data are arranged in the circumferential direction of the magnetic drum 22. Therefore, with this configuration, the absolute rotational position can be read in both the clockwise direction and the counterclockwise direction.

The MR element 24a and the MR element 24b have 14
Bits are arranged apart from each other in the circumferential direction of the magnetic drum 22 and at a predetermined distance from the magnetic drum 22. That is, the magnetic drum 22
Is rotated in either direction, CW data Cia
The start code ST (start bit) and the stop code SP (stop code) adjacent to (or CCW data Cib) can be read simultaneously.

Further, the MR elements 24a and 24b are connected to an arithmetic unit 26. Then, when the magnetic drum 22 rotates clockwise, the MR element 24a sequentially outputs detection signals of the start code ST, the CW data Cia, the stop code SP, and the CCW data Cib to the arithmetic unit 26 in each group. Then, the arithmetic unit 26 analyzes this detection signal and outputs a rotation angle code representing the absolute rotation position.

When the magnetic drum 22 rotates counterclockwise, the MR element 24b sets the start code ST, CCW data Cib, stop code SP, and CW of each set.
The detection signal of the data Cia is sequentially output to the arithmetic unit 26. Then, the arithmetic unit 26 analyzes this detection signal,
Outputs the rotation angle code indicating the absolute rotation position.

(Operation) The operation of the absolute encoder 20 configured as described above will be described. When the rotation shaft 21 rotates clockwise, the MR of the magnetic detection sensor 23
Each absolute encoder code Ci is read via the element 24a. That is, as shown in FIG.
In the present embodiment, the detection signal of each set of the start code ST, the CW data Cia, the stop code SP, and the CCW data Cib is sequentially output to the arithmetic unit 26 every time the rotation is performed every 0.35 (degree).

On the other hand, each absolute encoder code Ci is read via the MR element 24b. That is, as shown in FIG.
Each time it rotates every (degree), each set of start code ST,
The detection signals of the CW data Cia, the stop code SP, and the CCW data Cib are sequentially output to the arithmetic unit 26.

The arithmetic unit 26 regards the data following the start code ST and the data up to the stop code SP in the read data of each set as data indicating an absolute rotation angle in this rotation direction. Interpret. That is, the arithmetic unit 26 sequentially calculates the absolute rotation angle, which is the absolute rotation position, for each set based on the data, and outputs the result to a control device (not shown).

The MR element 24a and the MR element 24b
, The detection data obtained at the same time is shifted by 14 bits. The arithmetic unit 26 calculates the absolute rotation angle based on the data read 14 bits ahead, calculates the absolute rotation angle based on the data read later, and calculates the absolute rotation angle only when both match. The angle is output to the control device. Thereby, the arithmetic unit 26 can calculate an accurate absolute rotation angle.

When the rotating shaft 21 rotates counterclockwise, the absolute encoder code Ci is read through the MR element 24a of the magnetic sensor 23. That is, in this embodiment, each time the rotation is performed every 0.35 (degrees), each set of the start code ST, the CCW data Cib,
The detection signals of the stop code SP and the CW data Cia are sequentially output to the arithmetic unit 26.

On the other hand, the MR element 24 of the magnetic detection sensor 23
Each absolute encoder code Ci is read via b. That is, in the present embodiment, the detection signal of each set of the start code ST, the CCW data Cib, the stop code SP, and the CW data Cia is sequentially output to the arithmetic unit 26 every time the rotation is performed every 0.35 (degrees).

The arithmetic unit 26 regards the data following the start code ST in the read data of each set and up to the stop code SP as data indicating the absolute rotation angle in this rotation direction. Interpret. That is, the arithmetic unit 26 sequentially calculates the absolute rotation angle, which is the absolute rotation position, for each set based on the data, and outputs the result to a control device (not shown).

The MR element 24b and the MR element 24a
, The detection data obtained at the same time is shifted by 14 bits. The arithmetic unit 26 calculates the absolute rotation angle based on the data read 14 bits ahead, calculates the absolute rotation angle based on the data read later, and calculates the absolute rotation angle only when both match. The angle is output to the control device. Thereby, the arithmetic unit 26 can calculate an accurate absolute rotation angle.

Next, the features of this embodiment will be described below. (1) In the absolute encoder of the present embodiment, the magnetic drum 22 (rotating body) on which the magnetized tracks 25 are arranged along the circumferential direction and the magnetized tracks 25 of the magnetic drum 22 are relatively arranged so as to be detectable. MR element 2
A magnetic detection sensor 23 (detector) including 4a and 24b (magnetoresistive elements) is provided. The magnetized track 25 was magnetized so as to have an absolute encoder code Ci (serial data) indicating an absolute rotation angle which is a rotation position of the magnetic drum 22.

As a result, the number of magnetized tracks 25 can be reduced. For this reason, the axial length of the magnetic drum 22 can be reduced. In addition, since the space for providing the MR element can be reduced, the size of the absolute encoder can be reduced.

Since the number of MR elements can be reduced, the cost can be reduced. That is, as compared with a conventional absolute encoder having the same resolution, the number of magnetized tracks can be reduced, the number of MR elements can be reduced, and the size and cost can be reduced.

(2) In the present embodiment, the absolute encoder code C
When i (serial data) is rotated in either the clockwise direction or the counterclockwise direction of the magnetic drum 22 (rotating body), the absolute rotation angle (rotation angle) corresponding to the rotation direction can be read. Provided.

That is, one set (0.3 in this embodiment)
5 (degrees), when read in the clockwise direction, the serial data structure is constructed by combining the start code ST, CW data Cia, stop code SP, and CCW data Cib in this order. When data is read in the counterclockwise direction, one set of serial data structures is constructed by combining a start code ST, CCW data Cib, stop code SP, and CW data Cia in this order. With this configuration, the absolute rotational position can be read in both the clockwise direction and the counterclockwise direction.

As a result, no matter which direction the motor rotates, only one magnetized track 25 is required, so that the axial length of the magnetic drum 22 can be reduced. (3) In the present embodiment, on the premise of the configuration described in (2) above, the MR element 24a and the MR element 24b are arranged with a predetermined number of bits separated. Then, the arithmetic unit 26 calculates
The absolute rotation angle calculated based on the previously input CW data C1a (or CCW data Cib) and the CW data C1 related to the MR element input with a delay of a predetermined number of bits
Only when the absolute rotation angles calculated based on a (or the CCW data Cib) are the same, is output to a control device (not shown).

As a result, the control device can perform various controls based on the accurate absolute rotation angle. Here, the predetermined number of bits means a pair of MR elements 24a and 24b.
Indicates the number of bits at which the start code ST (start bit) and the stop code SP (stop code) adjacent to the CW data Cia (or CCW data Cib) can be read simultaneously.

(4) In this embodiment, the start code ST is "1001" and the stop code SP is "011".
Start code ST and stop code S, such as "0"
P has the same number of bits, and is a value whose code is inverted for each bit.

As a result, even if the start code ST and the stop code SP are read from the clockwise direction or from the counterclockwise direction, both the start code ST and the stop code SP become the start code S.
T and stop code SP can be interpreted.

(5) In this embodiment, since serial data is adopted, for example, two 10
Numerous absolute rotation angles of the power can be represented. (6) In the present embodiment, serial data is adopted, and the absolute rotation angle is indicated by a code included in the serial data.

In a conventional absolute encoder,
In some cases, an incremental phase is provided on another magnetized track, and the absolute rotation angle is calculated by logic using this incremental phase.

On the other hand, in the present embodiment, there is no need to provide a magnetized track constituting the incremental phase, provide a sensor therefor, or use other logic for using it. Therefore, the configuration can be simplified.

(7) In this embodiment, when the magnetic drum 22 as a rotating body is stopped, the absolute rotation angle is
The configuration cannot be detected. However, the magnetic drum 2
When the rotation starts, the MR elements 24a and 24b detect the serial data as serial data, so that the absolute rotation angle in the rotation operation can be detected.

Such an absolute encoder 20
Can be used, for example, when the power steering handle control device detects an absolute rotation angle as a steering angle.

In this case, since the rotation within one rotation is detected by the absolute encoder 20, the rotation is usually 4
It is difficult to detect the absolute angle of lock-to-lock of the steering shaft that rotates. Therefore, if the rotation of the steering shaft is reduced through a speed reducer having a reduction ratio of 1/4 so that the rotation of the absolute encoder 20 falls within one rotation, the absolute angle of the steering shaft can be detected.

The embodiment of the present invention is not limited to the above embodiment, but may be modified as follows. (1) In the first embodiment, n is set to 10;
May be set to 8 or larger than 10. n
Is increased, the resolution of the absolute encoder can be increased.

(2) In the first embodiment, two MR elements are used.
Although the number is provided, the calculation of the absolute rotation angle may be performed by one if a countermeasure against disturbance or the like is taken. (3) In the first embodiment, the magnetic drum 22 is used. However, a disk may be used instead of the magnetic drum 22, and the magnetization track 25 may be provided on a plane on the disk.

(4) In the first embodiment, when a single magnetized track 25 is read clockwise as a set of serial data structures, the start code ST, the CW data Cia, the stop code SP,
Constructed with a combination of the order of the CCW data Cib. or,
When read in the counterclockwise direction, the start code ST, CCW
Data Cib, stop code SP, CW data Cia
It was constructed by the combination of the order.

Instead, two magnetized tracks 25a, 25b are formed on the peripheral surface of the magnetic drum 22 as shown in FIG.
Are arranged side by side, and on each of the magnetized tracks 25a and 25b,
Serial data for clockwise and counterclockwise directions may be constructed.

In this case, when read in a clockwise direction as one set of serial data structures in one magnetized track 25a, the order of the start code ST, CW data Cia, stop code SP, and CW data Cia is sequentially determined. , And this set is set to 2 n powers.

When read in the other magnetized track 25b in a counterclockwise direction as a set of serial data structures, the start code ST and the CCW data Ci are read.
b, stop code SP, and CCW data Cib. This set is defined as 2 n.

Then, the MR element 24 is used as a magnetoresistive element for each of the magnetized tracks 25a and 25b.
a, 24b are arranged relative to each other. Even with this configuration, the number of magnetized tracks can be reduced, the number of MR elements can be reduced, and the size can be reduced as compared with the conventional absolute encoder having the same resolution as the conventional one. Cost can be reduced.

In the first embodiment, clockwise CW data Cia and counterclockwise CCW data Cib are alternately arranged on a single magnetized track 25. On the other hand, in the present embodiment, the CW data C1a and the CC data
Since the W data Cib is provided, the capacity for arranging data in each magnetized track increases accordingly, and the resolution can be higher than in the first embodiment.

The present embodiment also provides the effects (6) and (7) of the embodiment shown in FIG. next,
Technical ideas other than the inventions described in the claims that can be understood from the first embodiment and another embodiment will be described below together with their effects.

(1) The serial data according to any one of claims 1 to 3, wherein the serial data is a code indicating an absolute rotation angle of the rotating body, and a start code and a stop code are provided at a start end and an end of the code. And both codes are composed of codes with the same number of bits, and are interpreted as a start code and a stop code whether read from the clockwise direction or from the counterclockwise direction. An absolute encoder configured to obtain the absolute encoder.

In this case, the start code and the stop code are read from the sensor in the clockwise direction or the counterclockwise direction by the sensor.
Can be interpreted as a stop code.

[0065]

As described in detail above, according to the first to third aspects, it is possible to provide an absolute encoder which can reduce the number of magnetized tracks without lowering the resolution and can reduce the cost. Can be.

According to the second aspect of the present invention, the clockwise direction,
Even if the rotating body rotates in any of the counterclockwise directions, the number of magnetized tracks can be reduced, and the axial length of the magnetic drum can be reduced.

According to the third aspect of the present invention, the capacity for arranging data is increased, and the resolution can be increased.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view of a main part in an embodiment of the present invention.

FIG. 2A is an explanatory view of a magnetized track, and FIGS.
(C) is an explanatory diagram when a pair of MR elements detects magnetic data.

FIG. 3 is an explanatory perspective view of a main part in another embodiment.

FIG. 4 is an explanatory perspective view of a main part showing a conventional example.

[Explanation of symbols]

20 ... absolute encoder, 21 ... rotary axis, 22
... Magnetic drum (rotating body), 23 ... Magnetic detection sensor (detector), 24a, 24b ... MR element (Magnetoresistance effect element), 25 ... Magnetic track 26 ... Calculator, Ci ... Absolute encoder code, C1a ... CW Data, Cib ... CCW data.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Terabe 1-1-1, Asahi-machi, Kariya-shi, Aichi Toyota Machine Works Co., Ltd. Koki Co., Ltd. F term (reference) 2F077 AA30 AA31 AA37 NN03 NN24 PP14 QQ01 QQ13 QQ15 RR03 RR13 RR23 RR29

Claims (3)

[Claims] 1. An absolute encoder comprising a rotating body having magnetized tracks arranged along a circumferential direction and a detector arranged relative to the rotating body so as to detect the magnetized tracks and including a magnetoresistive element. An absolute encoder, wherein the magnetized track is magnetized so as to have serial data indicating a rotation angle which is a rotation position of the rotating body. 2. The method according to claim 1, wherein the serial data is provided so that a rotation angle corresponding to the rotation direction can be read when the rotation body rotates in any of a clockwise direction and a counterclockwise direction. The absolute encoder according to claim 1, wherein: 3. The magnetized tracks are provided in two rows, one for serial data indicating a clockwise rotation angle of the rotating body, and the other for serial data indicating a counterclockwise rotation angle. 2. The absolute encoder according to claim 1, wherein a pair of elements are provided so as to face the two rows of magnetized tracks, respectively.