DE102009023395B4 - Code disc for an encoder - Google Patents

Abstract

Encoder for measuring the rotational movement of a shaft, comprising a code disk (11, 11 ', 11' ', 11' '', 11 '' '') for mounting on the shaft, the code disk (11, 11 ', 11' ') , 11 '' ', 11' '' ') has an annular scanning region (12, 12' '', 12 '' '') in which a scale is formed from essentially spiral-shaped parallel lines (13) in that the helical lines (13) of the scale are designed such that they intersect an imaginary line (14) such that the tangents (16) applied to the helical lines (13) at the intersections (15) are perpendicular to the imaginary line (14) and parallel to each other.

Description

The present invention relates to an encoder for measuring the rotational movement of a shaft, comprising a code disk for mounting on the shaft, wherein the code disk has an annular sensing area in which a scale is formed from substantially helical, parallel lines.

Usually, code disks for encoders or angle encoders are designed such that the scale, which is scanned by a sensor of the encoder, is formed by lines running radially outwards. The strokes are therefore not parallel to each other, but run concentrically, the extension of the lines leads through the center of the code disc. The bars of the scale are thus formed as circle segments or wedge-shaped segments. In order to enable a simple scanning of the scale with a sensor, code disks are therefore known which have very many lines. In this case, the circle segments converge to almost parallel lines. A disadvantage of these code disks is that they are only suitable for very large or optical encoders. Small designs of such code discs are not feasible.

It is also known to form encoders in such a way that the scanning of the code disks is not in the axial but in the radial direction of the code disk. However, the length increases with these encoders, the production becomes more complicated and thus also increase the cost.

Furthermore, there are encoders which have predistorted sensors, so that the sensors follow the circular shape of the code disc or of the strokes to be scanned. However, these sensors have only a low flexibility and can therefore only be used for a code disk diameter.

There are also smart sensors available that can read both concentric circle segments and parallel lines. However, these sensors are relatively expensive.

The US Pat. No. 6,163,147 A deals with a sensor having two sensor elements whose distance and position are known to the axis of rotation of a circular multipolar magnetic encoder which is mounted on a shaft. These sensors measure the signals of the encoder whose sensing regions of opposite polarity are formed by transitions in the form of spirals.

wobei a der Abstand der Striche des Maßstabs voneinander und n die Anzahl der Striche des Maßstabs ist. Liegt der Innenradius der Codescheibe nahe dem optischen Radius, so verlaufen die entlang der archimedischen Spiralen ausgebildeten Striche des Maßstabs nicht mehr äquidistant zueinander und es werden keine klaren Signale mehr erzeugt.In the US 5 017 776 A An optical encoder is disclosed in which the scale of the code disc to be scanned is formed by helical windows and spokes of identical shape. The front edges and trailing edges of the windows, which are viewed in the direction of rotation of the disk, run essentially parallel to one another and are each designed as sections of an Archimedean spiral. If the radius of the Archimedean spirals is sufficiently large that the Archimedean spirals are almost tangential, the spirals are essentially equidistant from each other. However, especially in cramped conditions on the code disk, the course of the edges along the Archimedean spiral is not optimal. This is especially true with code disks having an inner radius which is close to the optical radius of the code disk. The optical radius k of the code disk is defined in this context as follows: $k=\frac{\alpha \cdot \mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DE102009023395B4\_0015.png"\; state="\{\{state\}\}">n</figure-callout>}}{2\pi }.$

where a is the distance of the bars of the scale from one another and n is the number of bars of the scale. If the inner radius of the code disk is close to the optical radius, then the bars of the scale formed along the Archimedean spirals are no longer equidistant from each other and clear signals are no longer generated.

It is therefore the object of the present invention to provide an encoder with a code disk, which overcomes the disadvantages of the previously known encoder, so that reliable signals of good quality can be provided.

For this purpose, it is provided according to the invention that the helical bars of the scale are designed such that they intersect an imaginary straight line such that the tangents applied to the spiral lines at the intersections are perpendicular to the imaginary straight line and parallel to one another.

Because the spiral strokes, or the tangents applied to them, are parallel to one another in the region of the imaginary straight lines and thus equidistant from one another, the rotational movements of the code disc can be converted into an equidistant linear scale. Therefore, a linear sensor can be used to scan the code disk. Due to the rectilinear line image, even with small radii of the code disk, i. at radii that are close to the optical radius of the code disk, uniform interpolation signals are generated. In addition, the code disk can be used in all types of encoders in which a scale is scanned locally. The code disc can therefore be used for inductive encoders, optical encoders (reflective and transmissive) and capacitive encoders.

ist, wobei a der Abstand zwischen den Strichen des Maßstabs und n die Anzahl der Striche des Maßstabs ist. Wenn die Striche des Maßstabs als Kreisevolventen ausgebildet sind, erfüllen sie diese Anforderung. Der Linearsensor kann dann einfach entlang einer Tangente, die z.B. an dem inneren Rand des kreisringförmigen Abtastbereichs anliegt, ausgerichtet werden.In an advantageous embodiment it can be provided that the imaginary straight line forms a circle tangent to a circle with the radius concentric with the annular scanning region $k=\frac{\alpha \cdot \mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DE102009023395B4\_0015.png"\; state="\{\{state\}\}">n</figure-callout>}}{2\pi }$

where a is the distance between the bars of the scale and n is the number of bars of the scale. If the bars of the scale are trained as circle involutes, they fulfill this requirement. The linear sensor can then be easily aligned along a tangent, for example, which bears against the inner edge of the annular scanning region.

gebildet sind, mit $k=\frac{\alpha \cdot n}{2\pi },$

wobei a der Abstand zwischen den Strichen des Maßstabs, n die Anzahl der Striche des Maßstabs und C eine Konstante ist. Durch diese Gleichung wird eine bevorzugte Form der als Kreisevolventen ausgebildeten spiralförmigen Striche des Maßstabs beschrieben. Der Radius r der Codescheibe darf dabei nicht kleiner als k werden, da sonst der Radikand negativ wird. Dabei entspricht k dem optischen Radius der Codescheibe. Auf diese Weise können die spiralförmigen Striche einfach in der gewünschten Kurvenform erzeugt werden.In a preferred embodiment of the invention it is provided that the helical bars of the scale according to the equation $$\mathrm{\Phi }\left(\text{r}\right)=\pm \frac{\sqrt{{\text{r}}^2-k^2}}{k}\mp \text{arctan}\frac{\sqrt{{\text{r}}^2-k^2}}{k}+C$$

are formed with $k=\frac{\alpha \cdot \mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DE102009023395B4\_0015.png"\; state="\{\{state\}\}">n</figure-callout>}}{2\pi }.$

where a is the distance between the bars of the scale, n is the number of bars of the scale, and C is a constant. This equation describes a preferred form of helical bars of the scale formed as circle involutes. The radius r of the code disk must not be smaller than k, otherwise the radicand becomes negative. Here, k corresponds to the optical radius of the code disk. In this way, the spiral strokes can be easily generated in the desired curve shape.

It may further be provided that the helical bars of the scale are formed as a pseudo-random-cyclic code. It can then be realized with a single track on the code disc an absolute encoder or an encoder with index. Thereby, the absolute position of the shaft can be specified, on which the code disk is mounted.

In yet another advantageous embodiment it can be provided that the track width, the track pitch or the intensity of the scale is modulated. This allows a better transferability of the signals.

In a further advantageous embodiment, the encoder comprises a linear sensor for scanning the scale of the code disk. By the already described inventive scale of the code disk, which makes it possible to implement rotational movements in an equidistant linear scale, relatively inexpensive linear sensors can be used as motion detectors. Since the scale of the code disk is formed by parallel lines, linear sensors can be used even with small circular code disks, whereby for micro motors encoders with relatively coarse line widths can be used without a radial scanning of the code disks is required.

In an advantageous variant it can be provided that the linear sensor is aligned along the imaginary straight line. In the area of the imaginary line, the spiral lines of the scale run exactly parallel to each other, so that very exact signals can be generated.

However, it may also turn out to be positive to arrange the linear sensor slightly twisted in relation to the imaginary straight line. The angle between the longitudinal extension of the linear sensor and the imaginary line is preferably about 0.1 ° to 5 °. This allows slightly rounder signals to be generated (anti-aliasing).

ist, wobei a der Abstand zwischen den Strichen des Maßstabs und n die Anzahl der Striche des Maßstabs ist. Die Striche sind dann als Kreisevolventen ausgebildet, so dass einfach ein äquidistanter Abstand zwischen den Strichen eingestellt werden kann und der Maßstab leicht erzeugt werden kann.In a preferred embodiment it can be provided that the imaginary straight line forms a circle tangent to a circle with the radius $k=\frac{\alpha \cdot \mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DE102009023395B4\_0015.png"\; state="\{\{state\}\}">n</figure-callout>}}{2\pi }$

where a is the distance between the bars of the scale and n is the number of bars of the scale. The strokes are then designed as circle involutes, so that simply an equidistant distance between the strokes can be set and the scale can be easily generated.

In a further variant it can be provided that the encoder is designed as an optical encoder, wherein the code disk has an outer diameter in the range of about 2 mm to 140 mm, and the width of the bars of the scale of the code disk in a range of about 0.05 mm to 1 mm. This makes it possible to produce optical encoders in high-resolution variants for micro and small motors. The scale of the code disk is finely structured and is made, for example, by electroforming, sputtering, photolithography, photoresist, or other fine patterning. The reading of the scale is done with an integrated circuit. Especially for code discs that are in the upper range of the specified diameter sizes, by scanning many successive bars of the scale is a particular advantage. A better phase determination for the interpolation is then possible, and it is possible to scan longer pseudo-random codes or other codes.

However, it can also be provided that the encoder is designed as an optical encoder, wherein the code disk has an outer diameter in the range of about 30 mm to 500 mm and the width of the bars of the scale of the code disk is more than 1 mm. In this way, larger, discrete optical encoder can be made. The production of the code disk is done for example by injection molding. As a code disk but also a structured plastic part or a stamped part can be used. As a sensor of the encoder then discretely constructed photodiodes are used. As a result, a favorable production of the encoder is possible. Due to the special spiral shape of the bars of the scale of the code disc but still a high signal accuracy is achieved.

Advantageously, it can also be provided that the encoder is designed as an inductive encoder, wherein the code disk has an outer diameter in a range of about 10 mm to 150 mm and the width of the bars of the scale of the code disk in a range of about 0.1 mm to 3 mm, preferably 1.2 mm. The code disc thus has very filigree structures. It is thus possible to produce highly integrated encoders with filigree structures. Thanks to the special spiral shape of the scales of the scale specified above, very accurate signals are generated.

In yet another embodiment, it can be provided that the encoder is designed as an inductive encoder, wherein the outer diameter of the code disk is in a range of about 30 mm to 500 mm and the width of the bars of the scale is greater than 3 mm and a maximum of about 30 mm. Here, too, larger inductive encoders can be provided, which are then constructed discretely and discretely arranged coils. By using the code disk according to the invention with the new spiral shape of the bars of the scale, it is thus possible to produce cost-effective inductive encoder, which nevertheless have a high signal accuracy.

Furthermore, the invention also relates to an electric motor with a code disk described above. The encoder's linear sensor can be external to the motor, which is very popular with printers and motors in hermetically sealed packages. It is then an open or externally realized encoder. This encoder has the advantages already described.

In a further variant it can be provided that an electric motor has an encoder described above. In this case, the encoder is integrated in the electric motor. The electric motor thus has the advantages already described. Thus, it is possible to provide micromotors which have encoders with a relatively coarse linewidth and which can be scanned with a linear sensor. This provides simple, low-cost engines.

• 1 Codescheibe mit einem Maßstab gemäß dem Stand der Technik,
• 2 Codescheibe mit dem erfindungsgemäßen Maßstab,
• 3a Vergrößerung eines Ausschnitts des Maßstabs aus 1,
• 3b Vergrößerung eines Ausschnitts des Maßstabs aus 2,
• 4 Codescheibe mit Kennzeichnung der Sensorpositionen,
• 5 weitere Ausführungsform einer erfindungsgemäßen Codescheibe,
• 6 optischer Encoder mit einer erfindungsgemäßen Codescheibe, und
• 7 induktiver Encoder mit einer erfindungsgemäßen Codescheibe.

In the following the invention will be explained in more detail with reference to a drawing. Show it:

• 1 Coded disc with a scale according to the prior art,
• 2 Code disc with the scale according to the invention,
• 3a Enlargement of a section of the scale 1 .
• 3b Enlargement of a section of the scale 2 .
• 4 Code disc with identification of the sensor positions,
• 5 further embodiment of a code disc according to the invention,
• 6 optical encoder with a code disk according to the invention, and
• 7 inductive encoder with a code disk according to the invention.

The code discs or encoders are not shown to scale.

1 shows a code disc 1 with an annular scanning area 2 , In the annular scanning region 2 is a scale of essentially helical, parallel lines 3 arranged. The spiral lines 3 are like in the US 5 017 776 A described trained. Each of the spiral strokes 3 follows the equation r = k · φ. Where r is the radius and φ is the angle of rotation. This equation represents an Archimedean spiral. Each of the strokes 3 is thus formed as part of an Archimedean spiral. An Archimedean spiral represents the trajectory of a point traveling at a constant velocity on a straight line passing through the center of a circular disk, while the disk is rotated at a constant speed. An Archimedean spiral is characterized by the fact that its winding distance is constant. If the radius r assumes large values, so that the Archimedean spiral already runs almost tangentially to a circle, then the lines are essentially equidistant from each other. The distance of the lines to each other is determined in such a way that first the solder is cut on the lines and the distance between two lines corresponds to the distance of the solder between the two lines. Especially for small radii r there is no common solder for adjacent strokes, which are formed according to an Archimedean spiral. These lines are therefore not equidistant from each other.

definiert. Die Striche 13 verlaufen also jeweils n äquidistant zueinander, so dass über die gesamte Breite des Abtastbereichs 12 der Abstand zwischen zwei nebeneinander liegenden Strichen 13 konstant ist. Der Abstand zwischen zwei Strichen 13 wird dabei so bestimmt, dass zunächst das Lot auf die zwei Striche gefällt wird. Das Lot steht senkrecht auf beide Striche 13. Der Abstand zwischen den Strichen 13 ist dann die Strecke auf dem Lot zwischen den zwei Schnittpunkten des Lots mit den Strichen 13. 2 shows a code disc 11 according to the present invention. The code disc 11 also includes an annular sensing region 12 , in which parallel, spiral-shaped lines 13 are formed. Also the code disc 11 is designed as a circular ring. The spiral lines 13 Form a scale that can be read by a sensor of an encoder. Each of the strokes 13 has a constant distance a to the next stroke 13 on, by an angle Δφ from the first bar 13 is moved. The angle Δφ is given by the number n of bars of the scale and is given by the equation $\Delta \phi =\frac{2\pi }{n}$

Are defined. The strokes 13 Thus, in each case, n run equidistant from each other so that over the entire width of the scanning region 12 the distance between two adjacent lines 13 is constant. The distance between two bars 13 is determined so that first the lot is felled on the two strokes. The perpendicular is perpendicular to both strokes 13 , The distance between the strokes 13 then the stretch is on the lot between the two intersections of the lot with the strokes 13 ,

The spiral lines 13 of the scale are thus designed so that they are an imaginary line 14 cut in such a way that in the intersections 15 to the spiral lines 13 created tangents 16 perpendicular to the imaginary line 14 and run parallel to each other. The tangents 16 are therefore equidistant to each other. Such an imaginary line exists for any juxtaposed strokes 13 , Because the tangents 16 Equidistant to each other, they can be read with a linear sensor. As a sensor of an encoder with the code disk according to the invention, therefore, a linear sensor can be used.

gebildet sind. Die Konstante k ist folgendermaßen definiert: $k=\frac{\alpha \cdot n}{2\pi }.\text{k}$

entspricht dem Minimalradius, den der innere Rand des kreisringförmigen Abtastbereichs 12 mindestens annehmen muss, da sonst der Radikand der obigen Gleichung negativ wird. Dabei ist a der gewünschte Abstand zwischen den Strichen 13 des Maßstabs und n die Anzahl der Striche 13 des Maßstabs. Die gedachte Gerade 14 ist dann vorzugsweise eine Tangente an einen Kreis mit dem Minimalradius k. Preferably, the helical strokes 13 of the scale trained as Kreisvolventen. This can be achieved by making the spiral strokes 13 of the scale according to the equation $$\mathrm{\Phi }\left(\text{r}\right)=\pm \frac{\sqrt{{\text{r}}^2-k^2}}{k}\mp \text{arctan}\frac{\sqrt{{\text{r}}^2-k^2}}{k}+C$$

are formed. The constant k is defined as follows: $k=\frac{\alpha \cdot \mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DE102009023395B4\_0015.png"\; state="\{\{state\}\}">n</figure-callout>}}{2\pi },\text{k}$

corresponds to the minimum radius that the inner edge of the annular scanning region 12 at least, otherwise the radical of the above equation becomes negative. Where a is the desired distance between the bars 13 scale and n the number of strokes 13 of the scale. The imaginary straight line 14 is then preferably a tangent to a circle with the minimum radius k.

The spiral path of the circle involutes or spiral lines 13 can be described by the development of circle tangents on the outside of a circle. When a tangent is rolled to a circle on the circle, the point of the circle tangent to which the circle tangent originally attached to the circle describes a spiral curve, the circle involute. In the present case, the circle on which the circle tangent is unrolled, a radius k, with $k=\frac{\alpha \cdot n}{2\pi },$

As already described, the constant k represents the optical radius or the minimum radius of the code disk 11 dar. The inner radius _i of the scanning area 12 the code disc 11 must not be smaller than the optical radius k, otherwise the radical of the equation given above would be negative. The code disk according to the invention 11 is characterized by the fact that even in the region where the code disc's radius is very close to the optical radius k, good sampling of the code disc is still possible.

3a shows an enlarged portion of the code disk 1 according to the closest prior art 1 , 3b shows an enlarged portion of the code disc according to the invention 11 out 2 , In this comparison, the difference between the scale known from the prior art according to 1 and the scale according to the invention, as described in 2 shown clearly.

Although circle involutes and Archimedean spirals approach each other more and more with increasing number of turns. Especially in the small angle range and small radii but strong differences between the course of a Kreisvolvente and an Archimedean spiral exist.

As in 3b shown are the spiral lines 13 the scale of the code disc 11 designed so that they with an imaginary line 14 intersections 15 respectively. The imaginary straight line 14 is preferably a circular tangent to the inner circular edge of the scanning area 12 , This inner circle of the scanning region preferably has the radius k, ie the minimum radius. In the intersections 15 can be tangents 16 to the spiral lines 13 be created. These tangents 16 are perpendicular to the imaginary line 14 as well as parallel to each other. The distance a between two adjacent tangents 16 is always the same and corresponds to the distance a between two adjacent bars 13 , The tangents 16 are therefore equidistant.

As in 3a This is in the known from the prior art scale of the code disk 1 not the case. Here are the intersections of the lines 3 with an imaginary straight line 4 , or the Kreistangenten, to the strokes 3 created tangents 6 not parallel to each other. The tangents 6 close with the imaginary line 4 different angles, and therefore are not equidistant from each other.

From this comparison, it is therefore easy to see that the scale with the spiral lines 13 makes the present invention rotational movements in an equidistant linear scale feasible. This makes it possible to use relatively inexpensive linear sensors for scanning the scale of the code disk 11 use. The linear sensors usually have a certain longitudinal extension and therefore touch the strokes 13 applied tangents. The determined spiral shape of the strokes 13 is easy to use even for code disks in the tightest of conditions. The code disc 11 with a scale of spiral, substantially parallel lines 13 as they are in the 2 and 3b can be used in all types of encoders in which a scale is scanned locally. An appropriately designed code disk can therefore be used for inductive, optical (reflective and transmissive), capacitive and eddy-current encoders.

4 shows a further embodiment of a code disc according to the invention 11 ' , The code disc 11 ' essentially corresponds to the code disk already described, so that the same reference numerals are used for the same components or elements. The code disc 11 ' has an annular scanning region 12 on. In the scanning area 12 are eight spiral-shaped, parallel lines 13 formed the scale of the code disk 11 ' form. The angle Δφ to the adjacent bars 13 are each shifted to each other, that is 45 °. The distance a between the bars 13 is 1.2 mm. The sensitivity of the code disk 11 ' is therefore 37.5 ° / mm.

As already described, the spiral lines are 13 Scale formed such that they intersect an imaginary straight line such that in the intersections of the spiral lines 13 applied tangents are equidistant to each other and perpendicular to the line and parallel to each other. The spiral lines 13 are therefore again trained as circle involute. The circle involutes follow the equation already given. Will the code disk 11 ' used in an encoder, the respective sensor of the encoder is arranged in the region of a first of the imaginary line. The imaginary straight line is preferably again as a tangent to one with the annular scanning region 12 formed concentric circle. Preferably, the circle has the radius k, where k is the minimum radius. In 4 this circle corresponds to the inner edge of the scanning area 12 ,

In 4 two sensor positions are shown. The rectangle represents the possible position of an optical linear sensor 17 dar. The optical linear sensor 17 spans almost the entire width of the circular scan area. The linear sensor 17 then detects a majority of the spiral lines 13 so that the code disk 11 ' can be reliably scanned even with contamination and reliably a position signal can be generated. The square indicates the possible position of an inductive linear sensor 18 on. The inductive linear sensor 18 is along another of the imaginary straights 14 arranged, which is formed such that the spiral to the strokes 13 in the intersections with the line 14 applied tangents perpendicular to the further straight line 14 and parallel to each other and thus are arranged equidistant from each other. Also the other imaginary straight line 14 is preferably as a tangent to one with the annular scanning region 12 concentric circle with the minimum radius k, particularly preferably as a tangent to the inner edge of the scanning 12 educated. The optical linear sensor 17 and the inductive linear sensor 18 so touch the tangents 16 at the intersections of the spiral lines or circle involutes 13 with the imaginary line on the lines 13 issue. This produces an accurate, reliable signal.

By scanning the parallel tangents 16 For example, a linear sensor can be used even on small circular code discs. The outer diameter d _a the code disc 11 ' is freely selectable in wide ranges and is preferably in a range of about 2 mm to 140 mm. For example, an encoder with a code disc with 3 mm outer diameter can be realized as an optical encoder with a 256 dpi sensor. An encoder with a code disc with 10 mm outer diameter can be realized as inductive encoder with 1.2 mm pitch. Furthermore, for example, an optical encoder with a code disk with 30 mm diameter can be realized with pseudo-random-cyclic code and a 180 dpi track. As 4 shows, the code disks can 11 ' be used with relatively coarse line widths even for micro motors, without a radial scanning of the code discs is required. But there are also code discs with larger outer diameters possible.

5 shows yet another embodiment of a code disk 11 " for an inductive encoder. This encoder is preferably used in a flat motor. The code disc 11 " is by a mounted on the rotor of the flat motor Printed circuit board (PCB) formed. The code disc 11 " has an outer diameter of about 90 mm. The scale of the code disc 11 " consists of 200 strokes 13 together. The distance a between the bars 13 is about 1.2 mm. The code disc 11 " therefore has a sensitivity of 1.5 ° / mm. The angle Δφ to the adjacent bars 13 are each shifted to each other, here is 1.8 °. The optical radius k is here 38.2 mm and does not correspond to the inner radius of the scanning range of the code disk, but was chosen so that a round line number results. The active sensor area is approx. 2.5 mm x 2.5 mm. Preferably, the scale is formed by a copper layer applied to the base material of the printed circuit board (usually FR4, ie glass fiber plates impregnated with epoxy resin).

folgen, ist auch dann möglich, wenn weniger Striche verlangt werden als theoretisch möglich sind, wo also die Striche schräg statt konzentrisch verlaufen.Even for large code disks worth the mentioned procedure. The formation of the scale of the code disk 11 " by parallel helical strokes corresponding to the equation $$\mathrm{\Phi }\left(\text{r}\right)=\pm \frac{\sqrt{{\text{r}}^2-k^2}}{k}\mp \text{arctan}\frac{\sqrt{{\text{r}}^2-k^2}}{k}+C$$

is possible even if fewer strokes are required than are theoretically possible, ie where the strokes are oblique instead of concentric.

As already described, an encoder with a code disk according to the invention for scanning the scale of the code disk can be equipped with a linear sensor. The linear sensor of the encoder is then preferably arranged so that it scans the scale of the code disk along the imaginary line and is therefore aligned along the imaginary line. But it can also be provided to arrange the linear sensor slightly twisted to the imaginary line. It will then get something rounder signals (anti-aliasing). The imaginary line is preferably formed as a tangent to a circle with the minimum radius k.

The invention also relates to an optical encoder with the code disk according to the invention and with a linear sensor for reading the code disk. Such an optical encoder can be produced as a high-resolution variant for micro and small motors. The code disk is formed as described above and has an outer diameter in the range of about 2 mm to 140 mm. The width of the bars of the scale of the code disc is in a range of 0.05 mm to 1 mm. The code disk is then so finely structured and is prepared for example by electroforming, sputtering, photolithography, photoresist or other fine structuring measures. The sensor of the optical encoder is formed in this case by an integrated circuit.

Especially with code discs having an outer diameter in the upper half of the specified range, the scanning of many successive bars of the scale creates a particular advantage. It is then possible a better phase determination for the interpolation, also there is the possibility to scan longer pseudo-random or other codes.

6 shows an example of a high-resolution optical encoder 19 with a code disk according to the invention 11 ''' , The code disc 11 ''' again comprises an annular scanning region 12 "' with spiral lines 13 , The spiral lines 13 are in turn formed as circle involutes on the inner circular edge of the scanning area 12 '''' The circle involutes, or the spiral lines 13 follow the equation already given. The encoder 19 is also circular and has an opening in the middle 20 on, so the encoder 19 can be plugged onto a shaft. The scanning range 12 ''' the code discs 11 ''' is in the outer area of the encoder 19 arranged. The one next to the opening 20 arranged area of the encoder 19 has no measuring standard. The code disc 11 ''' is preferably formed as a disk with 256 dpi. The line spacing of the bars 13 the scale is 0.1 mm. The encoder 19 is thus implemented as an encoder with a 256 dpi sensor. The diameter of the code disc 11 ''' is preferably 3 mm. The shaft to which the encoder 19 can be plugged, has a shaft diameter of 1 mm. On the encoder 19 is the position of the linear sensor 17 specified. The linear sensor 17 is aligned along the imaginary line, which is designed so that the tangents to the spiral lines 13 in the intersections of the spiral lines 13 with the imaginary line are equidistant to each other. Preferably, the imaginary line is a tangent to the inner edge of the scanning area 12 ''' the code disc 11 ''' , or to one with the annular scanning region 12 ''' concentric circle with the minimum radius k. Since the encoder is designed as an optical encoder, the sensor is an optical linear sensor 17 used. As in 6 clearly recognizable, the linear sensor feels 17 the distance between four lines, ie four periods. The active area of the sensor is about 0.4 mm x 0.2 mm.

But it is also possible to produce the code disks according to the invention with the trained as described above spiral scale scale with larger diameters for larger optical encoder. The code discs then have an outer diameter in the range of about 30 mm to 500 mm and the width of the bars of the scale of the code disk is greater than 1 mm. So these code discs have coarser structures and can be made for example by injection molding. It is also conceivable to use structured plastic parts or stamped parts as code discs. The optical encoders with these code disks can be constructed discretely. The sensor used is preferably discrete photodiodes. These larger encoders are very cheap to manufacture. By using the code disc according to the invention with the newly developed shape of the helical strokes, which follow the equation given above, a high signal accuracy is achieved.

It is also possible to equip inductive encoders with the code disks according to the invention. Thus, the code disk for an inductive encoder, for example, be designed so that it has very filigree structures. The outer diameter of the code disk is then in a range of about 10 mm to 150 mm, the width of the bars of the scale of the code disk is in a range of about 0.1 to 3 mm. Such a code disk is used in highly integrated encoders.

7 shows an example of such a highly integrated inductive encoder 22 , The inductive encoder 22 again has a code disk 11 ''' 'with a circular scanning area 12 ''' ' on. In the scanning area 12 ''' 'are the spiral strokes 13 arranged here also as circle involutes to the inner circular edge of the scanning area 12 ''' are trained. The circle involutes 13 follow the equation already given. The encoder 22 is also circular in shape and has an opening in its center 21 on, by means of which he can be plugged onto a shaft. The inductive encoder 22 has 16 spiral strokes 13 on, the outside diameter of the code disk 11 ''' 'is 15.3 mm. This encoder is again designed so that the code disc or the scanning 12 "" the code disc not to the center of the encoder 22 ie up to the opening 21 , extends. The distance between every two of the spiral lines 13 is preferably 1.2 mm. On the code disc 11 ''' 'is the position of the linear sensor 18 specified. The linear sensor 18 is again along a tangent to the inner circular edge of the scanning area 12 "" aligned. The inductive encoder 22 is preferably formed as a mounted on the shaft of an inner rotor carrier with a glued printed circuit board (PCB).

For larger motors discretely constructed inductive encoders are used which have code disks with coarser structures. These code discs have an outer diameter in the range of about 30 mm to 500 mm. The spiral lines 13 The scale of these code discs have line widths of more than 3 mm and a maximum of about 30 mm.

Furthermore, it is also possible to use the code disks constructed according to the invention in capacitive encoders. The code disks used in capacitive encoders also have an outside diameter of about 10 to 140 mm. Codewheels with filigree structures with a line width of the spiral lines in the range of 0.1 to 3 mm are used for encoders up to 60 mm in diameter. These encoders are used for small motors, where they can be installed in the motor or attached to the motor. Codewheels with coarser structures with line widths up to 50 mm are used for capacitive encoders with a diameter of up to 500 mm. These encoders are suitable for larger motors and can also be mounted on the motors or installed in the motors.

Advantageously, the spiral lines 13 of the scale of the code disk formed as a pseudo-random-cyclic code. In this way, with a single track, a code disc for an absolute encoder or an encoder with index can be realized. In addition, it can be provided that a type of modulation, for example amplitude modulation, phase modulation or pulse width modulation, is realized. It is also possible to modulate the track width, the track pitch or the intensity of the scale. An analog or digital modulation is possible. The code discs according to the invention can be produced in any way. For example, it is possible to produce a code disk in which electroformed metal is mounted on a dielectric. The code disk can also be produced by laser marking or by machining. Further manufacturing methods are PCB production, for example etching and photochemistry, or photolithography.

Preferably, an encoder with the code disk according to the invention is used in an electric motor for determining the position of the motor shaft.

It can also be provided to equip an electric motor with the code disk according to the invention. The linear sensor is then located external to the motor. This is especially relevant for printers and motors in hermetically sealed housings. The encoder is then open or external realized.

Claims (15)

Encoder for measuring the rotational movement of a shaft, comprising a code disk (11, 11 ', 11'',11''', 11 '''') for mounting on the shaft, the code disk (11, 11 ', 11'') , 11 ''',11'''') has a circular ring-shaped scanning region (12, 12''', 12 ''''), in which a scale from is formed in substantially helical, parallel bars (13), characterized in that the helical lines (13) of the scale are designed such that they intersect an imaginary line (14) such that the tangents (16) applied to the helical lines (13) at the intersections (15) are perpendicular to the imaginary line (14) and parallel to each other. Encoder after Claim 1 , characterized in that the imaginary straight line (14) has a circular tangent to a with the annular sensing area (12, 12 ''',12'''') concentric circle with the minimum radius $k=\frac{\alpha \cdot n}{2\pi }$

where a is the distance between the bars (13) of the scale and n is the number of bars (13) of the scale. Encoder after Claim 1 or 2 , characterized in that the spiral lines (13) of the scale according to the equation $$\mathrm{\Phi }\left(\text{r}\right)=\pm \frac{\sqrt{{\text{r}}^2-k^2}}{k}\mp \text{arctan}\frac{\sqrt{{\text{r}}^2-k^2}}{k}+C$$

are formed with $k=\frac{\alpha \cdot n}{2\pi }.$

where a is the distance between the bars (13) of the scale and n is the number of bars (13) of the scale. Encoder after one of the Claims 1 to 3 , characterized in that the helical bars (13) of the scale are formed as a pseudo-random cyclic code. Encoder after one of the Claims 1 to 4 , characterized in that the track width, the track pitch or the intensity of the scale is modulated. Encoder after one of the Claims 1 to 5 , characterized in that the encoder comprises a linear sensor for scanning the scale of the code disc (11, 11 ', 11'',11''', 11 ''''). Encoder after Claim 6 , characterized in that the linear sensor along the imaginary line (14) is aligned. Encoder after Claim 6 , characterized in that the linear sensor is slightly rotated relative to the imaginary line (14). Encoder after one of the Claims 6 to 8th , characterized in that the imaginary straight line (14) a circle tangent to a with the annular sensing area (12, 12 ''',12'''') concentric circle with the radius $k=\frac{\alpha \cdot n}{2\pi }$

where a is the distance between the bars (13) of the scale of the code disc and n is the number of bars (13) of the scale. Encoder (19) after one of Claims 6 to 9 , characterized in that the encoder is formed as an optical encoder, the code disk (11 ''') has an outer diameter in the range of about 2 to 140 mm and the width of the lines (13) of the scale of the code disk in a range of about 0th , 05 mm to 1 mm. Encoder after one of the Claims 6 to 9 , characterized in that the encoder is designed as an optical encoder, the code disk has an outer diameter of about 30 to 500 mm and the width of the bars of the scale of the code disk is greater than 1 mm. Encoder (22) after one of Claims 6 to 9 , characterized in that the encoder is formed as an inductive encoder, the code disc (11 '''') has an outer diameter in a range of about 10 mm to 150 mm and the width of the bars of the scale of the code disc in a range of about 0 , 1 mm to 3 mm. Encoder after one of the Claims 6 to 9 , characterized in that the encoder is designed as an inductive encoder, the outer diameter of the code disk in a range of about 30 mm to 500 mm and the width of the bars of the scale of the code disk is greater than 3 mm and a maximum of about 30 mm. Encoder (22) to Claim 12 , characterized in that the width of the bars of the scale of the code disc is 1.2 mm. Electric motor with a shaft and an encoder for measuring the rotational movement of the shaft according to one of Claims 1 to 14 ,

Images