JPH01242921A - Magnetic absolute rotary encoder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] "Field of Industrial Application" The present invention relates to a magnetic rotary encoder among rotary encoders used for detecting rotational speed, angle, and position of FA-related equipment such as machine tools and robots. Among them, there is an absolute type that can detect the absolute position from the reference position.

"Prior Art" An absolute rotary encoder outputs an electrical signal that encodes an absolute rotational position (angle) according to a certain rule.

Generally, the absolute position is often expressed using a binary code or a Gray code.

Further, in a magnetic rotary encoder, it is common to use a drum or disk having a required number of absolute signal tracks subjected to @magnetism corresponding to the output signal.

, Here, an example of the conventional technique will be explained according to FIG. The magnetic absolute rotary encoder shown in FIG. 6 has 9 bits and 360 divisions. It consists of a rotary drum 1 having absolute signal tracks 4a to 41 equal to the number of bits, and a magnetic sensor 2 fixed to a sensor stand 3 so as to be disposed opposite to each other at a certain distance.

The drum 1 is connected to a rotating shaft 5 such as a motor via a coupling 6, and rotates together with the rotating shaft.

Each track of the drum 1 is magnetized in a predetermined manner.

A magnetic sensor corresponding to each track is arranged to detect the surface magnetic field of each track.

If a magnetoresistive element (hereinafter referred to as an MR element) is used as a magnetic sensor, the property of the MR element that its resistance value decreases by applying a magnetic field perpendicular to its longitudinal direction can be utilized.

FIG. 7 shows a developed view showing how the drum is magnetized and a plan view of the MR element.

Here, the presence or absence of magnetization was made to correspond to the output signal Hu, ""[P', and a dalay code was used to encode the output signal.

Magnetization is performed with a pitch L, and this pitch corresponds to the minimum unit. That is, in this example, the drum diameter is LX3
60 (number of divisions).

In order to detect the surface magnetic field of the drum, MR elements are arranged corresponding to each track: Rat, Ra2, Rb1, Rb2""...
- It is important that the MR elements installed as R11 and R12 and corresponding to a certain track are separated by L/2 in order to cancel the pulsation of resistance change.

Further, as shown in FIG. 8, each MR element is connected to a fixed resistor in order to extract the resistance change due to the magnetic field as an intermediate potential between the DC voltage 1E and ground.

For example, the resistors Ra1 and Ra2 exhibit resistance changes as shown in FIG. 9 when the drum shown in FIG. 7 is detected. When Ral and Ra2 are connected to a fixed resistor R as shown in Figure 8, MR
The intermediate potential between the element and the fixed resistor changes as shown in eal and ee2 in FIG. The difference between these two potentials (eal-ee2
>, an output va with the pulsation canceled can be obtained.

This is waveform-shaped to obtain the output Va.

Do the same with other tracks, ■b, VC...
Vi is obtained.

"Problem to be Solved by the Invention" Considering the length of the minimum unit when the absolute position changes sequentially in the above-mentioned magnetic absolute rotary encoder, as is clear from FIGS. 7 and 9, 2. 1~
"Htt→"Lee (or "Lpa→"H
″), so the accuracy of the minimum unit is 1~
It is decided by easy magnetization accuracy. Therefore, in order to increase the accuracy of the smallest unit, that is, the resolution of the rotary encoder, it is necessary to improve the minute pitch magnetization accuracy of all 1-racks and the absolute position accuracy of magnetization between each track. Highly technically difficult.

On the other hand, the signal “HTl 14 L It
, the boundary between magnetization and non-magnetization was unclear, making it difficult to improve accuracy.

Furthermore, a method of increasing the number of signal tracks has been proposed in order to improve accuracy, but this method has the disadvantage that the encoder itself becomes larger.

"Means for Solving the Problem" An electronic circuit that provides a strobe signal track on the drum of a magnetic absolute rotary encoder separately from the 7-bus unit signal track, and latches the absolute signal in synchronization with this strobe signal. It is distinctive in that it has been added.

In the magnetic absolute rotary encoder of the present invention, the state of the output signal is determined by the state of the absolute signal output at the rising edge (or falling edge, or both) of the strobe signal, and the change in the output signal is determined by the state of the absolute signal output when the strobe signal rises (or falls, or both). Since the output signal accuracy is determined by the accuracy of the strobe signal, a more accurate output signal can be obtained than in the past.

Since the output signal does not depend on the state of the output signal of the absolute signal track other than when it is latched by the strobe signal, the formation of the absolute signal section is easy and inexpensive.

"Example" An embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a schematic diagram of a 9-hit, 360-division magnetic absolute rotary encoder according to the present invention.

A coupling 6 connects the rotating shaft 5 of the rotating body 8 to be detected and the drum 1 of the magnetic absolute rotary encoder.
The drum 1 rotates like a rotating body. Drum 1 has the same absolute signal 1- as in the conventional technology.
It consists of racks 4a to 41 and a strobe signal track 7, which is a feature of the present invention.

The magnetic sensor 2 is fixed to a sensor stand 3 and placed in the λ1 direction at a distance from the drum 1.

FIG. 2 shows a developed view showing how the drum is magnetized and a plan view of the magnetic sensor (MR element). The spacing between the magnetic poles is constant.

The MR elements are connected by wiring as shown in FIG.

The waveforms of each part at this time are shown in FIG.

The resistance change of the MR element in the absolute signal section and the waveforms of each section are the same as in the conventional example, so they will not be explained here.

The resistance changes of the MR elements Rsl and Rs2 for the strobe signal track are as shown in FIG.

The intermediate potential e between Rsl and Rs2 has a periodic waveform 17 as shown in FIG. 4, and is further waveform-shaped to obtain VS.

This VS lasts one period 'C'J, which coincides with the minimum unit of the absolute signal.

FIG. 5 shows a circuit diagram (a) of an electronic circuit added according to the present invention and its timing chart (b).

The slave signal e becomes Vs in the waveform shaping circuit 9,
In this case, the latch circuit that latches the absolute 1 signal output at the rising edge of Vs (10 in Figure 5 (a>
> or [] Even if the period of the absolute 1 signal output Va, Vb, VC... is slightly distorted as shown in Fig. 5(b), ■8o, Vb0, ■ ,. By aligning the period with the strobe signal, the minimum unit of time can be made the same.

Also, if you do this, Va, Vb, Vo...
etc., the rise and fall are inevitable, and even if chattering occurs, the Va will not come out. , Vb.・・・・・・
・It does not appear as it is.

For VS, the minimum unit accuracy of the period is determined by the magnetization accuracy of only the strobe signal track.

The minimum unit of the conventional 7 Bsorieux 1.1Δ is a different 2
It is necessary to achieve high precision on one track, and achieving high precision over the entire circumference requires increasing precision on all 1 to 3 tracks, which is very difficult. However, in the present invention, the magnetization of the strobe signal Since only the accuracy needs to be increased, it is easier and cheaper to apply magnetization than the conventional technology.

In this way, by adding a rack and a simple electronic circuit to the strobe signal 1 (), it is possible to easily and inexpensively manufacture a magnetic absolute rotary encoder that outputs a highly accurate absolute signal.

The latch timing for the STRO-1 signal depends on the cycle of the STRO-1 signal and the magnitude relationship and phase of the absolute signal's minimum unit, and the rise and fall of the STRO-7 signal also depends on the cycle of the STRO-1 signal and the phase of the absolute signal.
It is also possible to use both, or the rising or falling edge of a signal whose frequency has been appropriately divided. It is most effective to latch or GJ in the middle of the minimum unit of the absolute signal.

In the embodiment, a drum-type magnetic rotary encoder is used, but the present invention (A-disk type can also be applied.
It can also be applied to linear encoders.

"Effects of the invention J Magnetic absolute rotary encoder" - Adding a slow-lobe signal track to the conventional °shi in the d3,
By adding an electronic circuit to detect this and latching the Abflue1 signal output using the strobe signal output obtained by this electronic circuit, the encoder output pulse accuracy can be determined by the strobe pulse precision of 1σ, making it easy to use. Moreover, it is possible to produce 1q of high-precision absolute signals at low cost.

[Brief explanation of the drawing]

FIG. 1 is a general W1B configuration diagram of an embodiment of the present invention, FIGS. 2 to 5 are explanatory diagrams of the embodiment, and FIGS. 6 to 9 are explanatory diagrams of a prior art. In the figure: 1...Magnetic drum 2...Magnetic sensor 1J4...Absolute go 1-signal l/rack 7...S1~lobe signal track Patent applicant Takadake Seisakusho Co., Ltd. Rα2 'J11 vomiting 4 Fig. VIG- "J Eye 3>

Claims (1)

[Claims] In a magnetic absolute rotary encoder that detects the absolute position of a rotating body, a strobe signal track that provides positioning timing is provided separately from the absolute signal track that has a position information signal, and the strobe signal is used to generate an absolute signal. A magnetic absolute rotary encoder with high positional accuracy obtained by adding a latching electronic circuit and latching the absolute signal with a strobe signal near the middle of the absolute signal's smallest unit.