DE10020247B4 - Rotary encoder for a rotor, in particular a balancing motor vehicle wheel - Google Patents

Abstract

Wheel balancing machine for a motor vehicle wheel to be balanced, which is to be connected in a rotationally fixed manner to a main shaft (12) of the wheel balancing machine which is rotatable about an axis of rotation (8) and has a circular cylindrical surface (5), with a rotational angle position of the main shaft (12) connected to the main shaft (12) ) around the axis of rotation, detecting the angle of rotation encoder, the light-emitting emitter (1) and angle of rotation increments, which are arranged at equal angular intervals on a circumferential surface that can be rotated about the axis of rotation (8) and via which the light emitted by the emitter is fed to a detector (3) , and with an evaluation device (4) connected to the detector (3), which evaluates signals of the detector (3) for a rotation angle detection, characterized in that the rotation angle increments are designed as reflectors (2), the reflectors (2) on webs (11) between two on the circular cylindrical surface (5) au flying material strips (9) are arranged, are formed and are integrally connected to the material strips (9) to form a flexible band (10), or on the outside of a rigid ...

Description

The invention relates to a rotary encoder for a rotor, in particular a motor vehicle to be balanced, with an emitter and reflectors, which are arranged in the form of reflective surfaces on a rotatable circular path at equal angular intervals from each other and reflect light emitted by the emitter, at least one detector which reflected the Receives light and provides corresponding signals, and a connected to the at least one detector evaluation, which evaluates the signals for a rotation angle detection.

[State of the art]

Such a rotary encoder is known (Ram S. Krishnan et al, A Miniature Surface Mount Optical Reflective Optical Shaft Encoder, Hewlett-Packard Journal, December 1996, pages 1 to 6). In the known rotary encoder, the reflectors to maintain their planar reflective surfaces are arranged in an annular ring on one side of a fixed to the rotor, in particular a shaft connected to the disc about the axis of rotation of the disc and the rotor. This results in an additional device overhead and space requirements for a functionally correct arrangement of the reflectors relative to the emitter and the detector or the detectors, since the reflective surfaces extend in a plane perpendicular to the axis of rotation.

When detecting the angular position, rotational speed and direction of rotation of a main shaft on a balancing machine, incremental encoders are used in which light sensors face one or more light sources, in particular in the form of light-emitting diodes. Between the light source and sensors a hole, slotted or toothed disc is arranged, which rotates with the main shaft of the balancing machine ( US 4,457,172 ). In addition to the additional angle encoder, an additional zero mark as a hole, slot or tooth and an associated detector are required to detect the absolute angular positions of the rotor. In this arrangement too, the elements indicating the angular increments extend in a plane perpendicular to the axis of rotation.

US 5,329,121 shows an apparatus for position encoding a shaft in which a multi-faceted polygon mirror is mounted on the shaft and a light beam is directed onto the facets. The facets of the polygon mirror reflect the light beam so that a light spot is generated on a linear matrix detector. An analog-to-digital converter is connected to the linear matrix detector and a microprocessor, the microprocessor calculating the position of the wave based on the data from the analog-to-digital converter.

US 2 685 083 A shows a photoelectric signal generator for position indicator.

US 2 586 540 A shows a torsion measuring the torsion or a transmitted torque of a shaft by means of a light beam.

US 5,471,054 A shows an encoder for providing a calibrated measuring capability of a rotating or linear movement of an object using a light beam.

EP 0 185 619 B1 shows a device for indicating the relative positions in a given direction between a reference point and a test point, which are spaced apart and movable relative to each other. The device has a reference surface, a test surface and a lighting means and utilizes the moiré effect.

OBJECT OF THE INVENTION

The object of the invention is to provide a Radauswuchtmaschine with a rotary encoder of the type mentioned, in which a reduced device complexity and space is required.

This object is achieved by a Radauswuchtmaschine according to claim 1.

In the invention, the reflectors of the rotary encoder, which are formed by reflective surfaces or surface portions, arranged on the circumference of a circular cylindrical surface of a rotating part rotating with the rotor or on a circular cylindrical surface of the rotor.

During the rotation of the rotary member or rotor, the reflecting surfaces, which are arranged successively on the circumference of the circle, successively passed through the emitter preferably continuously emitted beam. The reflective surfaces are configured in their sequence to direct discrete reflected rays to the detector. This achieves an increment in angular positions which correspond to the respective reflective surface sections. The respective surface sections can adjoin one another directly and have a continuous reflective hand with features that distinguish the individual surface sections. For this purpose, the respective surface sections may have surface configurations deviating from the circular cylindrical shape. However, it can also circular cylindrical surfaces be used for the respective surface portions, wherein the radius of the respective circular cylindrical surface deviate from the radius of the circle, which has the circular cylindrical surface on which the surface portions are arranged. The radius of the respective surface portion may lie between infinity, ie between a flat surface, and the radius of the circular cylindrical surface on which the reflectors are arranged. However, it is also possible that the surface portions have a parabolic or elliptical cross-section. Furthermore, the reflective surface sections may have a convex or concave profile relative to the emitter or detector. Preferably, the reflective surface portions are arranged on a flexible band immediately adjacent to each other, this flexible band is wound around the circular cylindrical surface of the rotor or rotary member.

In one embodiment, the reflectors are formed on surfaces of webs extending parallel to the axis of the circular cylindrical surface. For this purpose, the webs are arranged between two strips of material and connected to these in one piece to form a band. This band has flat or curved surfaces in the region of the webs and the strips of material. When bending the tape to be placed on the circular cylinder surface, the surfaces of the material strip of the circular cylindrical shape adapt. However, the webs can maintain their flat surfaces. The width of the bars, d. H. their extent in the circumferential direction of the circular cylindrical surface is a fraction of a millimeter, for example about 0.3 mm. When looping the band with the reflectors having webs around the rotor or to the rotating with the rotor rotating part requires virtually no space, as a result, the rotor diameter or diameter of the rotary member is only slightly increased by the thickness of the belt. The reflectors have equal angular distances from each other. To achieve an absolute angular reference, there may be an angular distance deviating from the remaining equal angular distances between two reflectors. As a result, for example, a zero mark is achieved. The created in the invention polygon mirror whose reflectors (reflecting surfaces) are arranged around the circumference of the circular cylindrical surface, can also be formed from a rigid molding, in particular plastic. The reflecting surface portions of the reflectors can be produced by metal deposition, in particular galvanic metal deposition. In particular, the molded part may be a plastic injection-molded part, preferably in sleeve form. The molded part can form the rotating part rotating with the rotor. Since the immediately juxtaposed reflective surface sections are distinguished by the detector, a continuous reflective coating can be used.

In a preferred manner, the beam (light beam) emitted onto the respective reflectors is focused so that its focal point lies on the flat surface of the respective reflector. The reflected beam from the respective reflector is deflected during the rotation, within the surface of the respective reflector in response to the changing angle of rotation and can thereby be received by a plurality of detectors arranged in series. Instead of the plurality of detectors, it is also possible for a detector to comprise a plurality of light-sensitive sensors, to which the reflected beam deflected by the respective reflector strikes in succession during the rotation. The detectors, or sensors are arranged side by side in the direction of rotation substantially. They can also be arranged in a straight line. Preferably, however, they are located on a circular arc around the axis of rotation. A reversal of the direction of rotation can be recognized by the fact that the light beam is directed to the sensor or detector longer, at which the direction of rotation reversal takes place. The signals emitted by the detectors or sensors are evaluated accordingly.

[Examples]

With reference to the figures, the invention will be explained in more detail on an embodiment. It shows:

1 a schematic representation of an embodiment of the rotary encoder, viewed in the axial direction;

2 the rotary encoder perpendicular to the axial direction;

3 a band with reflectors, which can be used in the embodiment;

4 a sectional representation of a second embodiment;

5 a detail from the in 4 illustrated embodiment;

6 a third embodiment; and

7 a fourth embodiment.

The rotary encoder shown in the figures has an emitter 1 , which preferably continuously light in the direction of reflectors 2 sending out. The reflectors 2 reflect the light and the reflected light is from one or more detectors 3 receive. The reflectors 2 become of discrete reflective surfaces or area sections on a belt 10 formed and are, for example, on bars 11 between two continuous stripes 9 are arranged ( 3 ). The ribbon 10 may consist of metal, in particular hard nickel or a metallized plastic film ( 3 ). The surfaces of the two strips 9 and the bridges 11 are flat (plan) trained. To achieve the angle coding for a rotor 6 becomes the band 10 around a turned part 7 which, for example, as the main shaft 12 a balancing machine may be formed. For this purpose, the belt is located on a circular cylinder surface 5 of the turned part 7 or the main shaft 12 the balancing machine. The main shaft 12 or the rotating part 7 are non-rotatable with the rotor 6 , which may be a motor vehicle wheel, for example. This is done in a known manner by fastening and / or clamping means. If the imbalance of the main shaft is to be determined, this forms the rotor. In the arrangement of the band 10 on the circular cylinder surface 5 the continuous strips of material fit 9 of the band to the circular cylinder surface 5 at. The surfaces on the webs 11 , in particular the reflective outer or inner surfaces which the reflectors 2 form, maintain their flat (plane) property and act as a Poligonspiegel, between the reflective surfaces non-reflective portions with in the circumferential direction of the circular cylindrical surface 5 lie. As a result, equal angular distances between the reflectors 2 reached. The non-reflective sections between the reflectors 2 are removed by appropriate material removal from the tape 10 won, so the webs 11 arise. In the arrangement on the circular cylinder surface 5 The bridges extend 11 and the reflectors formed thereon 2 in the axial direction, ie parallel to the axis 8th around which the rotor 6 as well as the turned part 7 or the main shaft 12 rotate.

The webs can be made by so-called electroforming. In this case, the metallic strip is coated with a photosensitive resist and by subsequent exposure by means of a mask, the structures are transferred to the resist. On the after development, non-resistive surfaces of the metal structure is carried out by electrodeposition and thus the formation of the webs.

This achieves the arrangement of a Poligonspiegels around the circular cylindrical surface of the rotor 6 rotatably connected rotary part 7 or the main shaft 12 a balancing machine. During rotation, the angular position of the respective mirror surface of a reflector changes 7 to the emitter 1 and the at least one detector 3 , The emitter 1 In particular, it sends focused light to the rotating circular cylinder surface 5 out. The light hits the reflective flat surfaces of the reflectors 2 , That of the reflectors 2 reflected light is from at least one detector 3 receive and this generates a corresponding signal. This is in one to the detector 3 connected evaluation device 4 evaluated for a rotation angle detection. The evaluation of the detector 3 The signals supplied can also be used to determine the speed and direction of rotation of the rotor 6 be evaluated.

For an absolute angular reference to the rotor 6 or the rotary part 7 in (main shaft 12 ), the angular distance between two reflectors can be obtained 2 deviate from the same angular distances between the other reflectors. This achieves, for example, a zero position at which, for example, a rotary angle counter of the rotary encoder is set to zero.

In the in the 4 and 5 illustrated embodiment, the flat surfaces of the reflectors 2 on the outside of a rigid molding 13 educated. This molding 13 is preferably formed by a plastic injection molded part and has a sleeve shape. The molding 13 can be placed on a rotor or a part connected to the rotor. In the illustrated embodiment of the 4 and 5 is the sleeve-shaped molding on the main shaft 12 the Auswuchtmaschine put on.

In the in the 6 and 7 Illustrated embodiments, the reflectors 2 with respect to the emitter 1 or the detector 3 convex curved surface sections ( 6 ) or concavely curved surface sections ( 7 ) educated. The reflectors 2 forming surface sections can be strung together directly on a tape 10 or a molding 13 be provided. By means of a continuous reflective coating to reach the reflector property. Since the individual reflectors are geometrically distinguishable from one another at their abutting edges, discrete surface sections are obtained even with a continuous reflective coating, which can be evaluated in the evaluation device to determine the individual angles of rotation.

The emitter 1 and the detector 3 are in one unit 20 arranged. This unit 20 is together with the evaluation device 4 on a carrier plate 21 arranged. The emitter 1 sends a focused beam of light 14 on the respective, the component 20 opposite reflector 2 as it also in detail from the 6 can be seen. When rotating around the axis of rotation 8th becomes one from the respective reflector 2 reflected beam 15 deflected in dependence on the rotation angle change with different deflection angles and meets in the deflection direction side by side arranged photosensitive sensors 16 . 17 . 18 and 19 , which at the detector 3 are to be provided ( 5 ). Thus, that of a respective reflector 2 reflected beam 15 when rotated in one direction in succession to the sensors 16 to 19 on. The first sensor 16 and the third sensor 18 are connected to a differential amplifier, which as an output signal in 4 with A designated output delivers. The second sensor 17 and the fourth sensor 19 are connected to a further differential amplifier which receives an output signal B ( 4 ). As a result, the differences in brightness at the respective sensors, while a mirror surface of the reflector 2 on the unit 20 moved past, evaluated.

When the rotor or the main shaft 12 continues to rotate, the reflected light beam no longer hits the sensors. However, it is the case of the subsequent reflector 2 reflected light beam 15 again when changing the angular position of the rotor successively to the sensors 16 to 19 , Preferably, there are 256 reflectors 2 on the circumference of the molded part 13 intended. The absolute angle reference to the rotor 7 or to the main shaft 12 may be due to an irregularity in the division of the sealing surfaces around the axis 8th be won. This point can be, for example, the zero position of the position counter in the rotary encoder.

A reversal of the direction of rotation can be detected by the fact that, in the case of a change of state of the output signal A, the instantaneous state of the output signal B (FIG. 4 ) is evaluated.

The rotary encoder (incremental encoder) of the invention is insensitive to axial displacements. The number of signal lines and end noise filters can be reduced to a respective number of two. The one from the reflectors 2 formed polygon mirror can, as explained, be designed as a relatively thin sleeve or band, which increases the diameter of the rotary member or rotor only slightly. One achieves a space-saving arrangement of the rotary encoder.

LIST OF REFERENCE NUMBERS

1

emitter

2

reflector

3

detector

4

evaluation

5

Circular cylindrical surface

6

rotor

7

turned part

8th

axis

9

strips of material

10

tape

11

Stege

12

main shaft

13

molding

14

emitted beam

15

reflected beam

16

sensor

17

sensor

18

sensor

19

sensor

20

unit

21

support plate

Claims (22)

Wheel balancing machine for a vehicle wheel to be balanced, which rotatably with a about a rotation axis ( 8th ) rotatable and a circular cylindrical surface ( 5 ) having main shaft ( 12 ) of the wheel balancing machine, with one with the main shaft ( 12 ), the angular position of the main shaft ( 12 ) about the axis of rotation detecting rotary encoder which emits a light emitting emitter ( 1 ) and rotational angle increments, which on one about the axis of rotation ( 8th ) rotatable circular peripheral surface are arranged at equal angular intervals from one another and via which the light emitted by the emitter a detector ( 3 ), and with one to the detector ( 3 ) connected evaluation device ( 4 ), which signals of the detector ( 3 ) evaluates for a rotation angle detection, characterized in that the rotation angle increments as reflectors ( 2 ) are formed, wherein the reflectors ( 2 ) on webs ( 11 ) between two on the circular cylindrical surface ( 5 ) lying strips of material ( 9 ) are arranged, are formed and with the strips of material ( 9 ) in one piece into a flexible band ( 10 ) or on the outside of a rigid thin sleeve ( 13 ), which on the circular cylindrical surface ( 5 ) of the main shaft ( 12 ) of the wheel balancing machine, are formed in immediately adjacent reflective surface portions. Wheel balancing machine according to claim 1, characterized in that the reflectors ( 2 ) at parallel to the axis ( 8th ) of the circular cylindrical surface ( 5 ) extending surface sections are formed. Wheel balancing machine according to claim 1 or 2, characterized in that the surfaces of the reflectors ( 2 ) are rectangular or square. Wheel balancing machine according to one of claims 1 to 3, characterized in that the reflectors ( 2 ) are formed by surface portions which deviate from a circular cylindrical surface. Wheel balancing machine according to one of claims 1 to 4, characterized in that the reflectors ( 2 ) are formed by flat surfaces. Wheel balancing machine according to one of claims 1 to 5, characterized in that the sectional view of the reflectors ( 2 ) in an axis of rotation ( 8th ) vertical plane is a polygon. Wheel balancing machine according to claim 6, characterized in that the polygon has the same polygon sides. Wheel balancing machine according to one of claims 1 to 3, characterized in that the reflectors ( 2 ) of cylinder surface sections, in particular circular cylindrical surface sections are formed whose cylinder axes parallel to the axis of rotation ( 8th ). Wheel balancing machine according to claim 8, characterized in that the radius of a respective circular cylindrical surface portion between infinity (plan) and the radius of the circular path is, on which the reflectors ( 2 ), wherein the radius of a respective circular cylindrical surface section is not equal to the radius of the circular path. Wheel balancing machine according to one of claims 1 to 4, characterized in that the reflectors ( 2 ) forming surface sections with respect to the emitter ( 1 ) or the detector ( 3 ) have a convex or concave course, respectively. Wheel balancing machine according to claim 1, characterized in that the belt ( 10 ) consists of plastic and at least in the area of the reflectors ( 2 ) or webs ( 11 ) is formed reflective. Wheel balancing machine according to claim 1, characterized in that the belt ( 10 ) consists of metal, in particular hard nickel. Wheel balancing machine according to one of claims 1, 11 or 12, characterized in that the webs ( 11 ) by removal of material from the planar surface having band ( 10 ) are formed. Wheel balancing machine according to claim 13, characterized in that the webs ( 11 ) are made by electro-forming. Wheel balancing machine according to claim 1, characterized in that the sleeve ( 13 ) consists of plastic. Wheel balancing machine according to claim 15, characterized in that the sleeve ( 13 ) is a plastic injection molded part. Wheel balancing machine according to one of claims 1 to 16, characterized in that on the respective reflectors ( 2 ) emitted beam ( 14 ) is focused. Wheel balancing machine according to one of claims 1 to 17, characterized in that at the detector ( 3 ) several photosensitive sensors ( 16 - 19 ) are provided, which during the rotor rotation of a respective reflector ( 2 ) reflected beam ( 15 ) received. Wheel balancing machine according to claim 18, characterized in that the sensors ( 16 - 19 ) are arranged side by side substantially in the direction of rotation. Wheel balancing machine according to claim 18 or 19, characterized in that that of a respective reflector ( 2 ) reflected beam ( 15 ) in turn in one direction on the sensors ( 16 - 19 ). Wheel balancing machine according to one of claims 18 to 20, characterized in that four photosensitive sensors ( 16 . 17 . 18 . 19 ) are arranged side by side in the direction of rotation and are connected in such a way that brightness differences between the first sensor ( 16 ) and the third sensor ( 18 ) and between the second sensor ( 17 ) and the fourth sensor ( 19 ) be evaluated. Wheel balancing machine according to claim 1, characterized in that between at least two along the circular cylindrical surface ( 5 ) arranged reflectors ( 2 ) is provided from the other equal angular intervals deviating angular distance.

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