JPS628015A - Encoder - Google Patents

Abstract

PURPOSE:To make it possible to inexpensively obtain a precise output wave form, by such a simple structure that a magnetic core having rectangular magnetizing characteristics is arranged in concentrically opposed relation to a ring shaped multipolar magnetic field generation means so as to provided an appropriate gap. CONSTITUTION:A ring shaped multipolar magnetic field generation means 1 has magnetic poles N, S successively and alternately formed along the circumference thereof at relatively large appropriate pitches and a rotary shaft 4 is mounted to said means 1 to form a rotor R. A large number of magnetic cores 3 having rectangular magnetizing characteristics are arranged outside the rotor R in concentrical relation to said means so as to hold relatively large appropriate gaps from the magnetic poles N, S. Further, one coil 2 is wound through the magnetic cores 3 to form a magnetic sensor along with the magnetic cores 3. A terminal is provided to the coil 2 and received in a case 5 along with the magnetic cores 3. When the magnetic poles N, S of the means 1 approach the magnetic cores 3 and are separated therefrom with the revolution of the rotor R, the magnetic cores 3 are magnetized by the magnetic fields due to the magnetic poles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an encoder, and particularly to an improvement of a rotary encoder that can obtain a highly accurate waveform output.

[Conventional technology]

Rotary or linear encoders, synchronizers, resolvers, etc. are used to detect position feedback signals in automatic control systems, and rotary encoders are often used to detect arm positions and axis positions of industrial robots and NC machine tools. It is used.

Such encoders include optical encoders and magnetic encoders, and magnetic encoders include gear type encoders and drum type encoders. However, with the optical type, the resolution can be increased by cutting the slits into smaller pieces or making the pitch finer, but there are limits to this.

In addition, there are also effects such as misalignment between the stationary plate and the rotating plate due to temperature rise, etc., and there is a limit to the improvement of resolution.Of the magnetic types, gear type types can be manufactured at low cost, but the tooth profile is poor. Since the waveform is not constant, the pitch accuracy is poor and the resolution is limited. Furthermore, among the magnetic types, the drum type has magnetic poles N and S alternately magnetized along the circumference on the outer periphery of the drum 21, as shown in FIG. 8, and maintains an appropriate gap between these magnetic poles. A magnetoresistive drop element 22 (magnetic sensor) is provided. In this case, in order to increase the resolution,
Although the pitch of the magnetic poles N-8 can be made finer, it is necessary to reduce the gap between the magnetoresistive drop element 22 and the magnetic pole NS. However, if this gap is made too small, there is a problem in that even slight variations in the gap cause variations in the detection output, resulting in poor accuracy.

Since there is a limit to improving resolution through subdivision such as slits, magnetization, and tooth profile engraving, it is possible to further subdivide the information obtained by the encoder using interpolation for applications that require high resolution. The one that responds to this is JP-A-5
This is disclosed in Japanese Patent Application Laid-Open No. 8-85118, Japanese Patent Application Laid-Open No. 59-211822, etc.

By the way, in conventional industrial robots and various automatic machine tools, the axes and arms are driven by motors via reduction gears.For example, a rotary encoder is connected to this motor to detect the rotation of the motor. By doing this, the position information of the shaft and arm is obtained. In this case, since a speed reducer was used, even if there was a longitudinal error in detecting the motor rotational position, there was almost no negative effect on the detection accuracy of the shaft or arm position. However, using a motor with extremely low rotation speed,
When the reduction ratio is extremely small, or when a reduction gear is not required, such as in a direct drive motor, the accuracy of detecting the motor rotational position has a significant effect on the accuracy of detecting the position of the arm or axis. A position detector is required.

For example, when direct drive motors are used in industrial robots, etc., a resolution of 1 million pulses/rotation or more is required, but there are no practical encoders that can meet this requirement, and expensive synchro resolvers and the like are not available. It is used.

[Problem to be solved]

In order to obtain a practical encoder with high resolution for precise position detection, it is necessary to obtain a precise output waveform and interpolate it with a simple configuration. The purpose of this invention is to provide an inexpensive encoder with a simple structure that can obtain a suitable output waveform.

[Means for solving problems]

This invention uses a magnetic type to simplify the structure of the encoder, making it compact and inexpensive, and the magnetic core for sensing magnetism is also small and inexpensive. and,
The magnetic pole pitch is not subdivided for high resolution, and the magnetic pole pitch is set relatively large, so that the gap between the magnetic pole and the magnetic core can be made relatively large. By using a highly sensitive magnetic core, this gap is made relatively large, thereby preventing a decrease in accuracy due to variations in the gap. Furthermore, a very precise output waveform is obtained by using a large number of magnetic cores and configuring the output to be averaged.0 The ring-shaped multipolar magnetic field generating means 1 shown in FIG. It is possible to sequentially and alternately form magnetic poles N and S at relatively large appropriate pitches along the circumference. A rotating shaft 4 is attached to form a rotor R. On the outside of the rotor R, a large number of magnetic cores 3 having square magnetization characteristics are arranged concentrically with the ring-shaped multipolar magnetic field generating means 1 while maintaining a relatively large gap with the magnetic poles N and S. It is set up. Then, one coil 2 is passed through these magnetic cores 3.
is wound, and forms a magnetic sensor together with the magnetic core 3. The coil 2 is provided with a terminal 2a and is housed together with the magnetic core 3 in a case 5.

Incidentally, the magnetic material used as the magnetic core generally has a magnetization characteristic with hysteresis as shown in Fig. 3a, but the magnetic core 3 used in this invention has no hysteresis and has no rising and falling characteristics as shown in Fig. 3b. extremely steep,
It has a so-called square characteristic. Good sensitivity is obtained by using it in this steep region.

[For production]

As the coil 2 moves, the magnetic core 3 is magnetized by the magnetic field generated by these magnetic poles, and the inductance of the coil 2 changes.

By the way, since the magnetic core 3 has good sensitivity, the magnetic core 3 and the magnetic pole N,
Since the gap of S is relatively large, it is well magnetized even by a minute magnetic field, and since this gap is relatively large, it is not easily affected by variations in the magnetic field. will also be uniform. Moreover, since a large number of magnetic cores 3 are provided for one coil 2, the fluctuation in inductance seen from the terminal 2a of the coil 2 is the sum of the fluctuations in inductance caused by the fluctuations in the magnetization of the individual magnetic cores 3. . Therefore, variations in inductance due to the individual magnetic cores 3 include variations due to the dimensions of the cores, variations in the gap with the ring-shaped multipolar magnetic field generating means 1, variations in the magnetic pole pitch of the ring-shaped multipolar magnetic field generating means 1, etc. Even if
The variations in inductance seen from the terminal 2a are averaged by smoothing out these variations. Therefore, terminal 2a
When a voltage is applied to , the waveform becomes a very precise waveform that fluctuates uniformly.

[Example 1] The ring-shaped multipolar magnetic field generating means has magnetic poles N and S along the circumference.
A ring-shaped multi-pole magnet is magnetized so that 2-phase magnets appear alternately, and the axial direction of the magnetic core 3 is set to face the NS direction of the magnet of the ring-shaped multi-pole magnetic field generating means, in order to obtain a two-phase output. An example in which these configurations are made into a two-unit system will be described.

The cylindrical hollow casing 5a and the substantially disc-shaped lid 5b are made of stainless steel and are fixed with screws 6.
A shield case 5 is formed.

Inside the casing 5a, there is a flat ring-shaped holder 7 made of Duracon, a stator St made of a coil 2 wound around a magnetic core 3 and hardened with epoxy resin 8, a ring-shaped holder 9 made of Duracon made of a flat plate, The stator and the flat ring-shaped holder 10 made of Duracon are sequentially fitted and fixed with screws 11. Although not all are shown in FIG. Amorphous magnetic cores 3 are arranged radially, and coils 2 are sequentially wound in series around the cores, and then hardened with epoxy resin 8. The coils 2 are provided with terminals 2a. The amorphous magnetic core 3 is, for example, 0
．． It is a magnetic core with a length of 4 cm consisting of three wires with a diameter of 1 wm, and is a so-called zero magnetostrictive magnetic core with typical square magnetization characteristics. This characteristic is described in the Japanese Journal of Applied Magnetics V o
t, 7 + N o -2+ 1988. Then, an enameled wire with a diameter of 0.1 mm is wound 10 times to form a minute magnetic sensor with a diameter of about 1 mm.

Next, a rotating shaft 12 made of a non-magnetic material is supported in the shield case 5 by bearings 18a and 18b.
A flat plate-shaped Duracon ring-shaped holder 15 made of Giniracon, a ring-shaped sag net 1, and a flat plate-shaped Duracon ring-shaped holder 16 are fitted in order, and a circumferential ring with a rotation stopper (not shown) is fitted in order. The magnetic poles are sequentially magnetized in N and S directions, and are made up of, for example, 100 magnetic poles, although not all are shown.

The gap G between the ring-shaped multipolar magnet 1 and the magnetic core 3 is set to, for example, 3 mm in order to obtain the optimum magnetic field strength (10 to 20 Gauss). For example, a suitable encoder can be obtained by connecting it to the two-core multivibrator bridge introduced in the above-mentioned Japanese Journal of Applied Magnetics.

[Other Examples]

The coil 2 is wound as shown in Figures 1 and 2.
Although it is possible to wind the magnetic core around this coil 2, it is common to wind it in series as in the previous embodiment, or to wind it in a waveform as shown in Fig. 6, or to wind it in other ways. You can also do that.

The method of magnetizing the ring-shaped multipolar magnet 1 is not limited to one in which N and S appear alternately along the circumference, but also in a direction perpendicular to the circumference as shown in Figures 7a and 7b. In other words, one side (front or back) of the ring is magnetized with N, and the other side (back or front) is magnetized with S, and the axial direction of the magnetic core 3 is parallel to the magnetized N and S directions of the ring-shaped seat gun 1. It can be set up so that Again, coil 2
The winding method is not limited to series winding, but also wave winding,
It can be other.

In order to obtain two-phase output, a ring-shaped multipolar magnet 1
The combination of magnetic core 3 and coil 2 is not only made into two sets, but also made into one set, as shown in Fig. 9.
It is also possible to use two coils 2b and 20, and to sequentially wind each coil one pitch at a time, and to change the winding direction. In this case as well, the winding method is not limited to series winding, but may be waveform winding or other winding methods. In addition, when obtaining a one-phase output, the combination of the ring-shaped multipolar magnet 1, the magnetic core 3, and the coil 2 is
It goes without saying that you can string them together, but if you want to get even more output, you can string them together. In addition, magnetic core 3
The number of magnetic poles does not necessarily have to be the same as the number of individual magnetic poles of the ring-shaped multi-pole magnet 1, but can be provided at an appropriate pitch, and the number of coils 2 can be other than one or two.

The structure of the stator S7 is not limited to the magnetic core 3 and the coil 2, but the rotary shaft R can be fitted to the magnetic core 3 and the coil 2, and the ring-shaped multipolar magnet 1 can be used as the stator St. .

The magnetic core 3 only needs to have zero magnetostriction, and is not limited to amorphous material; however, at present, an amorphous magnetic core is optimal.

When the coil 2 is wound around the magnetic core 3, it can be encapsulated and solidified with epoxy resin, or it can be encapsulated in other resins or other non-magnetic and insulating materials, or it can be made into a block shape made of these materials. It can be supported by the following materials.

The number of magnetic poles, magnetic cores, gaps between them, etc. can also be determined as appropriate.

Although the case 5 does not necessarily have to be a shield case, it is generally a shield case to prevent the influence of surrounding magnetic noise. The support material and structure for supporting the ring-shaped multipolar magnet 1 and the stator St, and the method of fixing with screws, etc., can also be appropriately selected.

The ring-shaped magnetic field generating means is not limited to one formed by magnetizing a large number of magnetic poles in a ring shape. For example, as shown in FIG. b may be attached to the coil 18 so that a current flows through the coil 18.

Although this invention can be implemented in a linear encoder, there is little benefit in smoothing out gap variations.

〔Effect of the invention〕

Since the magnetic pole pitch is relatively large, the gap between the magnetic core and the magnetic poles is relatively large, and a highly sensitive magnetic core is used, magnetic flux due to variations in this gap and eccentricity of the rotor and stator is reduced. Since the influence of distribution variations can be reduced, highly accurate detection can be achieved. Therefore,
Since the resolution of conventional magnetic encoders is increased, problems with accuracy caused by extremely fine magnetization pitches are eliminated. Furthermore, since a large number of magnetic cores are used to make the fluctuations in the coil inductance uniform, a highly accurate output waveform can be obtained. In addition, since it is a magnetic type with a simple structure and uses a simple, small, and inexpensive magnetic core as a sensor, an encoder with a simple structure, small size, and low cost is obtained despite using a large number of magnetic cores. be able to.

[Brief explanation of drawings]

The drawings show the configuration, embodiments, and prior art of the present invention, and FIG. 1 is a cross-sectional view, FIG. 2 is a view in the direction of arrows, and FIG.
Fig. 4 and Fig. 3b are characteristic diagrams, Fig. 4 is a sectional view, Fig. 5 is a view in the direction of the arrows, Fig. 6 and Fig. 7a are plan views, Fig. 7b is a sectional view, Fig. 8, Fig. 9, and FIG. 10 is a plan view. In the drawings, 1 is a ring-shaped multipolar magnet (ring-shaped multipolar magnetic field generating means), 2 is a coil, 3 is a magnetic core, N and S are magnetic poles, R is a rotor, and St is a stator.

Claims (9)

[Claims] (1) A ring-shaped multipolar magnetic field generating means is provided, a magnetic core having square magnetization characteristics is arranged concentrically facing the ring-shaped multipolar magnetic field generating means with an appropriate gap maintained, and this magnetic core An encoder comprising a coil wound so as to straddle the ring, and rotatably supporting either the ring-shaped multipolar magnetic field generating means or the magnetic core around which the coil is wound. (2) The encoder according to claim 1, wherein the magnetic core having the square magnetization characteristic is an amorphous magnetic core. (3) The ring-shaped multipolar magnetic field generating means is formed by alternately magnetizing magnetic poles N and S along the circumference, and the magnetic core is arranged such that its axial direction faces the NS direction of the magnetic poles. An encoder according to claim 1, comprising: (4) The ring-shaped multipolar magnetic field generating means is formed by sequentially magnetizing magnetic poles N and S in a direction perpendicular to the circumference along the circumference, and the axis of the magnetic core is in the NS direction of the magnetic poles. The encoder according to claim 1, wherein the encoder is arranged in parallel with the encoder. (5) The encoder according to claims 3 and 4, wherein the coil is wound in series. (6) The encoder according to claims 3 and 4, wherein the coil is wound in a waveform. (7) The encoder according to claim 3, wherein the coil is wound concentrically with the ring-shaped multipolar magnetic field generating means, and the magnetic core is wound around the ring-shaped multipolar magnetic field generating means. (8) The magnetic core and the coil are used as a stator, a rotating shaft is attached to the ring-shaped multipolar magnetic field generating means to form a rotor, and this rotor is inserted inside the stator so that the rotor can freely rotate around the shaft. An encoder according to claim 1, which is supported by: (9) The ring-shaped multipolar magnetic field generating means is used as a stator, a rotating shaft is attached to the magnetic core and the coil to form a rotor, and this rotor is inserted inside the stator so that the rotor can freely rotate around the shaft. An encoder according to claim 1, which is supported by: