The invention relates to a multi-turn angle measurement device for measuring multiple revolutions of a shaft. The invention is based on a multi-turn angle measurement that comprises a single turn detection using optics and a multi-turn detection that uses magnetic scanning.

The invention is based on EP 1 391 696 A2, which describes a multi-turn angle measurement device with an optical single-turn scanning function and a magnetic multi-turn scanning function.

The disadvantage of the known multi-turn angle measurement device is that it uses transmission gears that are complex and have some play, which uses a worm wheel, which interacts with the other transmission gears with significant play, resulting in only an inadequate multi-turn angle scanning with correspondingly fast wear of the gears.

Another disadvantage is the fastening of the permanent magnets in the transmission design, which leads to a non-compact design, because the permanent magnets are arranged with mounts of their own above the transmission gears and not integrated in them.

Furthermore, the installation costs are high because the magnets must be adhered to the code carrier, which is arranged outside the transmission design, which increases the total height and is associated with the risk that it can be lost, i.e. when the adhesive fails after an extended service life.

Furthermore, the adhesion process is associated with a certain amount of play, which cannot be minimized due to the machine processing.

The known multi-turn angle measurement device is furthermore characterized by the fact that the optic single-turn scanning function is arranged on the one side of a conductor plate while the magnetically working multi-turn angle scanning function is arranged on the opposite side. This results in a compact design, which cannot, however, be minimized any further.

The invention is therefore, based on this printed prior art document, based on the task to further develop a multi-turn angle measurement device of the type described above that has a much more compact design and thus allows for a cost-effective production with an arrangement of the permanent magnets that has as little play as possible.

To solve the assigned task, the invention is characterized by the technical teaching of claim1.

The feature of the invention is that the permanent magnets are directly integrated into the transmission design, so they are directly embedded into the respective assigned transmission gear with an overmold, and the respective transmission gear itself, which holds the respective permanent magnet, is secured on the assigned axle with a snapping mechanism.

Compared to prior art, this technical teaching has the advantage that it is now easily possible to fasten the respective permanent magnets on the transmission gear without any play because the invention provides that the respective permanent magnet is embedded in the plastic material of the transmission gear with an overmold.

This results in a particularly simple and compact design because the permanent magnet is directly inserted into the injection mold during the production of the transmission gear and embedded into the plastic during the production of the transmission gear when the plastic is injected into the mold.

Consequently, the complex and fragile adhesive bonds described in prior art are no longer necessary, and the custom-fit orientation of the permanent magnet on the transmission gear is always the same and does not have the play that must be tolerated when using adhesive bonds.

According to a further feature of the invention, the magnetization of the permanent magnets takes place directly in the injection mold, i.e. after the molding of the permanent magnet in the plastic material of the transmission gear, which has the advantage that the magnetic force that is generated is always the same and does not deviate from other molded permanent magnets in other transmission gears.

According to a further feature of the invention, a snapping connection is created between the transmission gear holding the embedded permanent magnet and the axle on which the transmission gear is rotatably positioned.

To keep the description simple, the description below will only be using the term “magnetic transmission gear,” which means that at least one permanent magnet is embedded by overmolding in the transmission gear which is made from plastic and not magnetically conductive.

In a preferred embodiment, the permanent magnet remains exposed only on a front side, i.e. the lower front side, where a specific distance to a Hall element arranged below it, which must be exactly adhered to, is to be provided.

The front side of the permanent magnet embedded in the plastic material of the transmission gear is therefore substantially exposed and only has the retaining lugs which extend only partially from the front side of the permanent magnet that is exposed there.

Consequently, a completely exposed front side of the permanent magnet is formed at a precisely defined distance from a Hall element.

To ensure that this distance does not change, a further feature is that the pivot bearing of the magnetic transmission gear is formed by a fixed axle, which is firmly anchored in a carrier plate.

It is, for example, injected into the carrier plate and stably guided along a longer axial length in a manner that protects it against bending so that the axle is protected against bending and, in the axial direction, injected into the carrier plate in a completely fixed manner.

One advantage is that a snapping mechanism is provided as a pivot bearing between this fixed axle and the magnetic transmission gear, which results in a particularly easy positioning.

This makes the assembly very easy since the magnetic transmission gear is simply placed onto an annular groove of the axle, the diameter of which decreases and is thus held in place there.

In a kinematic reversal, it is also possible, however, that the axle holds an annular ring, the diameter of which increases, which engages at the inner circumference of the bore in the magnetic transmission gear with an assigned annular groove, the diameter of which decreases.

Consequently, it is a simple plug-on, which is normally associated with the disadvantage of some axial play.

This is where the invention, which provides that the axle is made of magnetically conductive material, comes in so that a constant reciprocal pull exists between the permanent magnet embedded at a small distance from the front side of the axle and located below the axle and the magnetically conductive material of the fixed axle.

This ensures that the permanent magnet embedded in the magnetic transmission gear always exerts a tensile force on the axle and therefore pretensions the entire magnetic transmission gear with a certain axial pretension vis-A-vis the snapping mechanism and that it can furthermore come in contact with a fixed housing.

The stop is formed in such a way that a certain front side of the magnetic transmission gear may rub against the stop surface of the fixed housing, but this stop always remains in place and does not have any axial play.

The technical teaching that the magnetic transmission gear is fixed on the magnetically conductive axle due to the magnetic holding force and pretension has the advantage that a distance, which is free from play, which always remains the same, and which is unchangeable, exists between the front side of the permanent magnet and the Hall element below it.

This ensures an always constant application of a constant permanent magnetic force on the Hall sensors without a weakening of the magnetic field or a deviation of the reciprocal distance between the permanent magnets and the magnetically sensitive surface of the Hall element.

The magnetic pull between the transmission gear holding the permanent magnet and the magnetically conductive axle is only claimed, however, in exceptional cases because the exactness of the snapping mechanism is chosen so precisely that an axial displacement between the magnetic transmission gear and the axle onto which the transmission gear is placed cannot occur from the start.

Only in exceptional cases, for example if oscillations or vibrations were to occur, the magnetic tensile force between the upper front side of the permanent magnet and the opposite front side of the magnetically conductive axle may help generate an additional holding force, which is superimposed on the holding force of the snapping mechanism.

Embedding permanent magnets into magnetically neutral plastic material of the magnetic transmission gear is particularly easy and cost effective, and the result cannot be compared with the complex assembly process according to the object of EP 1 391 696 A2 where, in a multi-step fastening process, the permanent magnet must be attached to the corresponding magnetic transmission gear.

As known from prior art, a one-level arrangement is known for multi-turn angle rotary encoders, which means that the conductor plate comprises an optic single-turn scanning function on its one side and a magnetically working multi-turn scanning function on the opposite side.

This results in a particularly compact design.

In special application cases, however, it is preferred that a two-level design is provided instead of the one-level design with a single conductor plate. According to a further feature of the invention, this design is characterized by the fact that a total of two conductor plates are arranged at a distance from each other.

Such a two-level design is preferred especially when the space for the arrangement of the components on the single conductor plate no longer suffices, and it is necessary to use the second conductor plate.

In this case, two printed circuits board are arranged parallel to each other at a reciprocal distance. A relatively large micro-controller or higher components may be arranged on the second conductor plate, which cannot be accommodated on one level and with a single conductor plate.

Such a two-level design is characterized by the fact that, once again in the manner described above, the optic single-turn scanning function is arranged on the one side of the conductor plate arranged in the middle (first level), and the magnetic multi-turn scanning function is arranged on the opposite side in the known manner, but a second conductor plate is arranged in the space above, i.e. beyond the magnetic multi-turn scanning function and above a transmission, which is part of the magnetic multi-turn scanning function.

In this case, the magnetic scanning no longer takes place on the lower conductor plate, but the scanning is moved so that the reduction gear is now facing upward and offers the opportunity that the upward facing permanent magnets of the magnetic transmission gears now make it possible that a further conductor plate is arranged above this transmission, which forms the cover plate of the housing at the same time and on whose underside the Hall sensors are now arranged, which interact with the transmission-side permanent magnets that are embedded in the magnetic transmission gears.

In the aforementioned one-level design, however, it is also possible to arrange a second conductor plate on top of the upper front side of the transmission if there is enough space.

In the two-level version, however, the magnetic scanning and the optical scanning must be separated from each other in the area of a single conductor plate and are now only used for the optic scanning on the one conductor plate, which is arranged in the central region of the multi-turn rotary encoder, and the other, further conductor plate, which delimits the upper side of the housing, is now used for the magnetic scanning of the multi-turn rotary encoder.

This also results in the advantage of a compact design because the upper conductor plate with the Hall sensors below it is located directly opposite the magnetic transmission gears of the transmission.

The invention assumes that a reduction gear with three magnetically driven transmission gears is present, wherein a permanent magnet is embedded in each magnetic transmission gear as described above.

This means that when three magnetic transmission gears arranged in a transmission design are used, a reduction of the angle of a shaft at a ratio of 1:16 to the first magnetic transmission gear, and then based on this gear, a further reduction of 1:16 to the second magnetic transmission gear, and based on that gear, a further reduction of 1:16 to the third magnetic transmission gear takes place.

In total, therefore, the reduction takes place at a ratio of 1:4096.

The invention is naturally not limited to the arrangement of three reduction gears.

Only two transmission gears or more than three may be used instead.

This is while only one exemplary embodiment in which three transmission gears are arranged in a reduction design of a transmission is described in further detail. The invention is not limited to this embodiment, however.

It is important in any event that each magnetic transmission gear has the previously mentioned embedded permanent magnet and that the receiving configuration with an axial pretension is present.

In a further development of the present invention, a suitable evaluation circuit is provided for this purpose as well, wherein the signals from the individual permanent magnets (which are present in triplicate and integrated in the reduction configuration of the transmission) are now evaluated in a particularly advantageous manner.

To this purpose, an evaluation circuit is provided which provides for a first sensor in a first step, into which the respective Hall sensor is embedded, wherein, in a preferred design, a total of four Hall sensor elements are arranged in a specific matrix and embedded in the sensor.

Such a sensor is therefore assigned to each step with a matrix of Hall sensors. For the evaluation circuit, it is important that the output of the first step is directly connected to the input of the second sensor step and that the output of the second sensor step is directly connected to the input of the third sensor step, whose output directly emits the composite single-turn and multi-turn code word in a serial form.

This also allows for a Daisy chain progression of the sensor signals through all sensor steps, which is new and inventive over prior art.

In the prior art, a parallel evaluation of the individual steps is performed in a central module, which must be separately integrated as the evaluation module, while in the present invention, a particularly compact and simple design is provided due to the fact that the evaluation circuits for the matrix-like arranged Hall sensors are arranged in the sensors at the same time.

Consequently, a central evaluation instance is no longer necessary, which saves space on the conductor plate and leads to a further improvement of the compact design.

The signals that are emitted at the output of the respective sensor step and fed into the input of the subsequent sensor step are digital data words, which are serially processed and which are serially transmitted from the one sensor step to the next.

With regard to the single-turn evaluation circuit, it is important that the output of the single-turn evaluation circuit is directly connected to form the input of the first multi-turn evaluation circuit so that the signals of the single-turn evaluation circuit form the input of the first sensor step of the multi-turn evaluation.

It was stated above that a stable, axial safeguard against a displacement of the magnetic transmission gear is provided by the magnetic tensile force that acts on the magnetic axle.

If such a fastening with a magnetic pretension on the axle is not desired, it may be provided in another design in which each Hall sensor is surrounded by a distance-creating spacer ring at its outer circumference, and the permanent magnet, which is embedded in the magnetic transmission gear, is placed directly, without play, on the spacer ring.

This results in a certain degree of friction, however, which is acceptable because the materials are self-lubricating.

Instead of a pretensioned, play-free positioning, which is pretensioned by the magnetic force, a second design therefore provides that the magnetically pretensioned positioning of the magnetic transmission gear is not present and that it is now fully positioned on the respective spacer ring on the side of the conductor plate without a snapping connection as a pivot bearing.

The object of the present invention is not only described in the individual claims but must also be viewed as a combination of the individual claims with each other.

All information and features disclosed in the documentation, including the abstract, and especially the spatial configuration shown in the drawings are claimed as essential to the invention, as far as they are novel over prior art either individually or in combination.

Hereinafter, the invention will be described in further detail on the basis of just one execution path. The drawings and their description provide further features that are essential to the invention and advantages of the invention.

