JPH067057B2 - Encoder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an encoder, in particular, a rotary encoder for obtaining a highly accurate waveform output.

(Prior Art) Rotary or linear encoders, synchros, resolvers, etc. are used to detect position feedback signals in automatic control systems, and detect arm positions and axis positions of industrial robots and NC machine tools. Rotary encoders are often used in.

Such encoders include an optical type and a magnetic type, and a magnetic type includes a gear type and a drum type. However, in the optical type, the resolution can be increased by finely cutting the slit or finely pitching it, but there is a limit to that.
In addition, there is a limit to the improvement of resolution due to the influence of misalignment between the fixed plate and the rotating plate due to temperature rise and the like. The gear type among the magnetic types can be manufactured at low cost, but if the tooth profile is poor, the waveform accuracy is not constant and the pitch accuracy is poor and the resolution is limited. Of the magnetic type, the drum type is, for example, on the outer peripheral portion of the drum 21 as shown in FIG.
A magnetic sensor, for example, a magnetoresistive element 22 (magnetic sensor) is arranged so as to be magnetized so that magnetic poles N and S are alternately arranged along the circumferential direction, and a gap G is appropriately maintained facing the magnetic pole surface. There is. When the drum 21 rotates, the magnetoresistive element 22 outputs a pulse train having a period corresponding to the arrangement pitch of the magnetic poles, and by counting the pulse train, a detection output indicating the rotation angle of the drum 21 is obtained. Has become.

In this case, the pitch of the magnetic poles N and S can be made fine in order to increase the resolution, but the effective distribution range of the magnetic flux in the radial direction of the drum 21 becomes smaller as the magnetic pole pitch decreases, so the magnetoresistive element 22 It is necessary to reduce the gap between the magnetic pole NS and the magnetic pole NS. However,
If this gap is made too small, there is a problem in that the detection output will fluctuate even if the gap fluctuates even slightly, and the accuracy will deteriorate.

Since there is a limit to the improvement of resolution by subdivision such as slitting, magnetization, and engraving of tooth profile, the information obtained by the encoder is further subdivided by the interpolation method, and the application that requires high resolution. Japanese Patent Laid-Open No. Sho 5
No. 8-85113 and Japanese Patent Laid-Open No. 59-212822.

By the way, in conventional industrial robots and various automatic machine tools, a shaft and an arm are driven by a motor via a speed reducer. For example, a rotary encoder is connected to this motor to detect rotation of the motor. By this, the position information of the axis and the arm is obtained. In this case, since the reduction gear is used, even if there are many small errors in the detection of the motor rotation position, there is almost no adverse effect on the detection accuracy of the shaft or arm position. However, using an extremely low speed motor,
When the reduction gear ratio is extremely small, or when a speed reducer is not required like a direct drive motor in particular, the detection accuracy of the motor rotation position directly affects the position detection accuracy of the arm and axis, so it has an extremely high resolution. A position detector is required.

For example, when a direct drive motor is used for an industrial robot or the like, although a resolution of 1 million pulses / revolution or more is required, there is no practical encoder that meets this requirement, and an expensive synchro resolver or the like is used. It is used.

(Problems to be solved) In order to obtain a practical encoder having a high resolution for performing precise position detection, it is necessary to obtain a precise output waveform and interpolate it with a simple configuration. Therefore, the present invention is intended to provide an inexpensive encoder with a simple structure capable of obtaining a precise output waveform.

(Means for Solving Problems) The present invention adopts a magnetic system for simplifying the structure of the encoder to make it small and inexpensive, and the magnetic core for sensing magnetism is also small and inexpensive. There is. And
The magnetic pole pitch is not subdivided for high resolution, and the magnetic pole pitch is made relatively large so that the gap between the magnetic pole and the magnetic core can be made relatively large. Then, by using a magnetic core having high sensitivity, this gap is made relatively large to prevent a decrease in accuracy due to variations in the gap. The output is averaged by using more magnetic cores,
A very precise output waveform is obtained by adding some ideas to how to connect the coils wound around these magnetic cores.

The ring-shaped multipole magnetic field generating means 1 of FIG. 1 has a relatively large appropriate angular pitch θ ₁ along its circumference as shown in FIG. 2a.
The magnets are sequentially magnetized into N and S alternately. The rotary shaft 4 is attached to the center to form the rotor R. On the outside of the rotor R, a large number of magnetic cores 3 having a magnetization characteristic with a small hysteresis are divided into two stages, and a relatively large gap G is maintained between the magnetic poles N and S and the axial direction is opposed to the magnetic poles. In this way, they are arranged concentrically with the ring-shaped multipole magnetic field generating means 1. Pitch θ of array of magnetic cores 3
₂ is usually the same as the angular pitch θ ₁ of the magnetic pole arrangement, but may be an integral multiple. Further, the ring-shaped multipole magnetic field generating means 1 may be provided on the stator side and the magnetic core 3 may be provided on the rotor side.

The coils 2i (i;
1 to n) are wound, and as shown in FIG. 3, these coils 2i are sequentially connected to the adjacent first stage (in the figure, upper stage) and the second stage (in the figure, lower diagram). And is wound around the magnetic core 3 to form the detection coils 2a and 2b. The connection of the detection coils 2a and 2b is shown in detail in FIG. 2b. In FIG. 2b, the upper and lower parts indicate the first and second steps, and the symbols a and b attached to both ends of the coil 2i indicate the outer end and the inner end of the coil 2i as seen on the stator St. Show. Also,
T ₁₁ and T ₁₂ indicate lead terminals of the coil 2a, and T ₂₁ and T ₂₂ indicate lead terminals of the coil b.

Because it is thus connected, the coil 2a, the 2b, the output between the terminals _{T 11 ~T 12, T 21 ~T} 22 will those that are 180 degrees out of phase.

By the way, in general, a magnetic material serving as a magnetic core has a magnetization characteristic having hysteresis as shown in FIG. 4a, but the magnetic core 3 used in the present invention has no hysteresis and rises and falls as shown in FIG. 4b. Good sensitivity is obtained by using it in an extremely steep region.

(Operation) As the rotor R rotates, when the magnetic poles N and S of the ring-shaped multipole magnetic field generating means 1 move closer to and away from a certain magnetic core 3,
The magnetic core 3 magnetizes the magnetic field generated by these magnetic poles, and the inductance of the coil 2i changes. By the way, since the magnetic core 3 has a high sensitivity, it is well magnetized even for a minute magnetic field due to the relatively large gap between the magnetic core 3 and the magnetic poles N and S, and the gap is comparatively adaptive. It is hard to receive, so coil 2
The variation of the inductance of i is uniform for all magnetic poles. Moreover, the magnetic core 3 includes one coil 2a, 2
Since a large number are provided for b, the coils 2a, 2b
The variation of the inductance seen from the terminals T ₁₁ , T ₁₂ or T ₂₁ , T ₂₂ of is the sum of the variation of the inductance due to the variation of the magnetization of each magnetic core 3. Therefore, variations in the inductance due to the individual magnetic cores 3 include variations due to the size of the magnetic cores, variations in the gap with the ring-shaped multipole magnetic field generation means 1, variations in the magnetic pole pitch of the ring-shaped multipole magnetic field generation means 1, and the like. Even if the terminals T ₁₁ , T ₁₂ or T ₂₁ , T
The variation of the inductance seen from ₂₂ is averaged after smoothing out these variations. Also, the first-stage magnetic core 3
Since the coil 2i wound around the coil 2i and the coil 2i wound around the second-stage magnetic core 3 are sequentially and alternately connected,
The inductance change due to a slight swing of the outer peripheral portion in the rotor axis direction during the rotation of the rotor R is also canceled. Thus when a voltage is applied between the between the terminals T ₁₁ through T ₁₂ or T ₂₁ through T _22, its waveform respectively a very precise waveform that varies uniformly.

(Embodiment 1) The ring-shaped multipole magnetic field generating means has magnetic poles N and S along the circumference.
In order to obtain a two-phase output by making the axial center of the magnetic core 3 face the NS direction of the magnetic poles of the ring-shaped multipolar magnetic field generating means. An example will be given in which the configuration of (2) is a double type.

The substantially cylindrical hollow casing 5a and the substantially disk-shaped lid 5b are made of stainless steel and are fixed by screws 6,
The case 5 is formed.

Inside the casing 5a, a substantially plate-shaped resin ring-shaped holder 7, a coil 2i is wound around and connected to a large number of magnetic cores 3, and detection coils 2a and 2b are formed and fixed in a ring shape fixed with epoxy resin. child St _1, substantially plate-shaped resin ring holder 9, the stator St ₁ and made in the same manner, 90 stator St ₂ provided by shifting the position by half a pole pitch to obtain the output of the phase shift, The plate-shaped resin ring-shaped holder 10 is sequentially fitted and fixed by the screw 11.

The stator St ₁ and the stator St ₂ have the same structure. 100 amorphous magnetic cores 3 are radially arranged at an angular pitch θ _{2 as} shown in FIG. 6, and are arranged at the same position as shown in FIG. To 2
The coil 2i (i = 1 to 100) is wound around each stage. The pitch angle θ ₂ is the same as the pitch angle θ ₁ of the magnetic poles described later. These coils 2i are the first-stage ones, the second-stage ones, the first-stage ones next to each other, the second-stage ones, the first-stage ones, the second-stage ones next to each other ... , Etc. are sequentially and alternately contacted in series with the outer peripheral side end comrades or the inner peripheral side end comrades, and in FIG.
= 100, the detection coils 2a and 2b are formed. The epoxy resin 8 is solidified, and each coil 2 is provided with terminals T ₁₁ , T ₁₂ and T ₂₁ , T ₂₂ . The amorphous magnetic core 3 is, for example, a wire 3 having a diameter of 0.1 mm.
It is a so-called zero magnetostrictive magnetic core which is a magnetic core made of a book and having a length of 4 mm and having a typical square-shaped magnetic characteristic with a small hysteresis. This characteristic is the Vol.
7, No. 2, 1983.
Then, wind 0.1mm diameter enamel wire 10 times and
It is a magnetic sensor with a small diameter.

Next, a non-magnetic rotating shaft 12 is rotatably supported on the case 5 by bearings 13a and 13b. The rotating shaft 12 has a substantially plate-shaped resin holder 14, a ring-shaped multipolar magnet 1, Almost flat resin ring-shaped holder 15, ring-shaped multi-pole magnet 1, flat resin ring-shaped holder 16
Are fitted one by one, and a rotation stopper (not shown) is applied, and then fixed by a nut 17 to form a rotor R.

As shown in FIG. 6, the ring-shaped multi-pole magnet 1 is magnetized into N and S at an angular pitch θ ₁ sequentially in the circumferential direction, and is made up of, for example, 100 magnetic poles, although not entirely shown.
The gap G between the ring-shaped multipole magnet 1 and the magnetic core 3 is, for example, 3 mm in order to obtain the optimum magnetic field strength (10 to 20 Gauss). Then, for example, a suitable encoder can be obtained by connecting with the two-core multivibrator bridge introduced in the above-mentioned Japanese Journal of Applied Magnetics.

By the way, such an encoder is connected to the above-described two-core multivibrator bridge to function as follows. That is, the two sides of the two-core multivibrator bridge, which are composed of magnetic sensors, are respectively formed by the magnetic core and the coil of the encoder of the present embodiment.
As shown in the figure.

The operation of this two-core multi-vibrator bridge is well known, so it will not be described in detail. However, assuming that the rotor R is rotating at a constant speed, each coil 2a, 2b of the stator St ₁ will be described.
Since the magnetic field passing through changes periodically, the output signal Eout changes periodically with respect to time t as shown in FIG. The cycle T of this change is determined according to the angular pitch θ ₁ of the magnetic poles of the rotational speed, and the rotation angle of the rotor in units of the angular pitch θ ₁ can be detected by counting the number of peaks of this output. . Further, by sampling this output in one cycle T and obtaining the digitized (internally searched) value ED, it is possible to detect a fine angle at the angle pitch θ ₁ or less. The decrease in the accuracy of the peaks and valleys of the output signal is obtained from the magnetic core and coil of the stator St ₂ provided with a 90 ° phase shift, and another two magnetic core multivibrator bridge connected to the magnetic core and coil. However, this is a known point.

(Other Embodiments) The coil 2 is usually wound in series as shown in FIGS. 5 to 6 and also in corrugated winding as shown in FIG. You can also do it. In addition,
Although the magnetic poles N and S are simplified and shown in FIG.
This is no different from the figures and FIG. Further, the magnetic cores 3 are alternately shown in the first and second stages.

To obtain two-phase output, a ring-shaped multi-pole magnet 1
Not only is the combination of the magnetic core 3 with the magnetic core 3 and the coils 2a and 2b two, but this combination is one, and as shown in FIG. 9, two coils 2a ₁ and 2a ₂ are provided, and the coils 2a are sequentially arranged. It is also possible to wind each coil at every pitch and change the winding direction. Also in this case, the winding method is not limited to serial winding, but may be corrugated winding or the like. Note that in FIG. 9 as in FIG.
The magnetic poles are shown in a simplified manner, and the magnetic cores 3 are alternately shown only in the first and second stages. Further, in order to obtain a one-phase output, the ring-shaped multipole magnet 1, the magnetic core 3 and the coil 2 are used.
Of course, the combination with and may be one line, and if more outputs are desired, many lines can be connected. Further, the magnetic core 3 is not necessarily the ring-shaped multipole magnet 1
The number of individual magnetic poles does not have to be the same as the number of individual magnetic poles, and they can be provided at an appropriate pitch, and the number of coils 2 can be one or other than two.

The stator St is not limited to the magnetic core 3 and the coil 2, but the rotating shaft R may be fitted to the magnetic core 3 and the coil 2 so that the ring-shaped multipole magnet 1 serves as the stator St.

The magnetic core 3 may be of zero magnetostriction and is not limited to amorphous, but at present, an amorphous magnetic core is most suitable.

In addition to winding the coil 2 around the magnetic core 3 and encapsulating it with epoxy resin to solidify it, encapsulating it with another resin or other non-magnetic and insulative material, or a block shape made of these materials It can be supported by the material.

The number of magnetic poles, magnetic cores, and gaps between them can be appropriately determined.

The case 5 does not necessarily have to be a shield case, but is generally a shield case in order to prevent the influence of magnetic noise in the surroundings. The support material for supporting the ring-shaped multi-pole magnet 1 and the stator St, the structure, and the method of fixing with a screw or the like can also be appropriate.

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, and for example, magnetic bodies 19a and 19b are provided on a coil 18 wound in a ring shape as shown in FIG. For example, the coil 18 may be attached so that an electric current is passed through the coil 18.

The present invention can be applied to a linear encoder, but there is little merit in smoothing the gap variation.

(Advantages of the Invention) Since the magnetic pole pitch is relatively large, the gap between the magnetic core and the magnetic pole is relatively large, and a magnetic core with high sensitivity is used, variations in the gap and eccentricity between the rotor and the stator are caused. Since it is possible to reduce the influence of variations in the magnetic flux distribution due to, for example, accurate detection can be performed. Therefore, in order to increase the resolution in the conventional magnetic encoder, there is no problem in accuracy caused by making the magnetizing pitch extremely fine. Further, since a large number of magnetic cores are used and the variation of the coil inductance is made uniform by the way of winding the coil wound around the magnetic cores, a very accurate output waveform can be obtained. Since the magnetic type is used to simplify the structure, and the magnetic core that is simple, small, and inexpensive is used as the sensor, an encoder that is simple, small, and inexpensive can be obtained despite the large number of magnetic cores being used. be able to.

[Brief description of drawings]

The drawings show the constitution, embodiments and prior art of the present invention, wherein FIG. 1 is a sectional view, FIGS. 2a and 3 are arrow views, FIG. 2b is a connection diagram, FIG. 4a and FIG. FIG. 4b is a characteristic view, FIG. 5 is a cross-sectional view, FIGS. 6 and 7 are arrow views, FIGS. 8, 9 and 10 are plan views, FIG. 11 is a circuit diagram, and FIG. Is a waveform diagram and FIG. 13 is a plan view. In the drawing, 1 is a ring-shaped multipole magnet (ring-shaped multipole 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, St ₁ and St ₂ are stators. is there.

Claims (6)

[Claims] 1. A stator and a rotor facing each other, wherein the rotor or the stator has magnetic poles N alternately arranged along the circumference.
A ring-shaped multipolar magnetic field generating means is provided, and a plurality of magnetic cores made of a magnetic material having a magnetization characteristic with a small hysteresis are provided on the stator or the rotor. Are arranged in two stages with a pitch corresponding to the magnetic pole pitch, and the axial direction thereof faces the magnetic poles. A coil is wound around this magnetic core, and these coils are adjacent to each other in one stage. The first magnetic core, the second magnetic core, the first magnetic core, etc., and the adjacent second magnetic core, the first magnetic core, and the second magnetic core, which are wound around the magnetic core, are sequentially connected in this order. An encoder formed by forming two sets of detection coils. 2. A magnetic core having a magnetization characteristic of small hysteresis, which is an amorphous magnetic core.
The encoder according to the item. 3. The encoder according to claim 3, wherein the coil is wound in series. 4. The encoder according to claim 3, wherein the coil is wound in a waveform. 5. The magnetic core and coil are used as a stator, and a rotating shaft is attached to the ring-shaped multipole magnetic field generating means to form a rotor. The rotor is inserted inside the stator to be rotatable. The encoder according to claim 1, which is axially supported. 6. The ring-shaped multipole magnetic field generating means serves as a stator, and a rotating shaft is attached to the magnetic core and the coil to form a rotor. The rotor is inserted inside the stator to be rotatable. The encoder according to claim 1, which is axially supported by the encoder.