Connecting element for connecting a motor shaft of a motor to a rotary encoder and motor

A connecting element for connecting a motor shaft of a motor to an encoder shaft of a rotary encoder which is designed to detect a rotational position and/or a rotational speed of the motor shaft has a connecting region which runs in an annular shape around a connecting axis and has two end sides which lie axially opposite one another, an outer side facing away from the connecting axis and an inner side facing the connecting axis. In addition, the connecting element has at least one fan blade which protrudes radially from the outer side of the connecting region.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is the U.S. National Stage of International Application No. PCT/EP2017/070828, filed Aug. 17, 2017, which designated the United States and has been published as International Publication No. WO 2018/059825 and which claims the priority of European Patent Application, Serial No. 16191465.0, filed Sep. 29, 2016, pursuant to 35 U.S.C. 119(a)-(d).

BACKGROUND OF THE INVENTION

The invention relates to the connection of a motor shaft of a motor to a rotary encoder which is embodied to detect a rotational position and/or a rotational speed of the motor shaft.

Motors often comprise a rotary encoder for the purpose of detecting a rotational position and/or a rotational speed of a motor shaft of the motor. A rotary encoder of a motor is frequently exposed to high temperatures produced as a result of the operation of the motor and capable of causing a failure of the rotary encoder due to excessive temperature.

JP H08 163826 A discloses a rotating electric machine with a rotation detector. Fins of a fan are coupled to a rotary shaft of the machine for the purpose of guiding air around the rotation detector in order to cool the latter.

The object underlying the invention is to disclose an improved connection of a motor shaft of a motor to a rotary encoder which is embodied to detect a rotational position and/or a rotational speed of the motor shaft.

SUMMARY OF THE INVENTION

According to one aspect of the invention, the object is achieved by a connecting element for connecting a motor shaft of a motor to an encoder shaft of a rotary encoder which is embodied to detect a rotational position and/or a rotational speed of the motor shaft. The connecting element has a connecting region which runs in an annular shape around a connecting axis and has two end sides which lie axially opposite one another, an outer side facing away from the connecting axis and an inner side facing toward the connecting axis. At least one fan blade protrudes radially from the outer side of the connecting region, Each end side of the connecting region has at least one coupling recess which extends radially from the inner side to the outer side of the connecting region.

Advantageous embodiments of the invention are the subject matter of the dependent claims.

The connecting element advantageously enables a motor shaft of a motor to be connected to the encoder shaft of a rotary encoder and a simultaneous cooling of the rotary encoder. The cooling is effected by means of at least one fan blade which is arranged externally on the connecting element. During a rotation of the motor shaft, the connecting element, and consequently also the at least one fan blade, is set into rotation, such that the fan blade generates an air flow in the region of the rotary encoder which cools the rotary encoder. This advantageously results in the rotary encoder being cooled precisely when said cooling of the rotary encoder is required, that is to say when the motor is in operation so that the motor shaft rotates. In particular, therefore, no additional power connection is required for the cooling by means of the at least one fan blade.

The coupling recesses in the end sides of the connecting region advantageously enable positive-locking connections of the connecting element to the motor shaft and the encoder shaft to be realized by means of motor shaft and encoder shaft studs protruding from the motor shaft and the encoder shaft respectively and projecting radially into the coupling recesses. In particular, positive-locking connections of the connecting element to the motor shaft and the encoder shaft of said type permit axial displacements of the motor shaft and the encoder shaft relative to the connecting element, with the result that temperature-induced changes in length of the motor shaft and the encoder shaft can be compensated for by the connecting element.

One embodiment of the invention provides a plurality of fan blades protruding radially from the outer side of the connecting region and distributed at regular intervals along a circle around the connecting axis. The cooling function of the connecting element is advantageously magnified by means of a plurality of fan blades as compared to just one fan blade. A uniform distribution of the fan blades around the circumference of the connecting element advantageously prevents unbalances that would be caused by an uneven distribution of the fan blades.

A further embodiment of the invention provides that each fan blade has substantially the shape of a prism with a triangular base area which stands out vertically from the outer side of the connecting region. This advantageously enables the fan blades to be produced in a simple manufacturing process and with a stable design.

A further embodiment of the invention provides that each end side of the connecting region has precisely two coupling recesses that are disposed radially opposite one another. In this arrangement, the two coupling recesses of a first end side are offset by, for example, 90 degrees relative to the coupling recesses of the second end side. This advantageously increases the stability of the positive-locking connections of the connecting element to the motor shaft and the encoder shaft. Furthermore, a symmetric loading of the connecting element by the motor shaft and the encoder shaft is achieved.

A further embodiment of the invention provides that each coupling recess has an axial depth which is roughly half as great as the axial extension of the connecting region. This produces a twofold advantage: firstly, it prevents the stability of the connecting element from being significantly reduced due to an excessively large axial depth of the coupling recesses; secondly, a sufficient depth of the coupling recesses is realized to enable reliable positive-locking connections of the connecting element to the motor shaft and the encoder shaft.

A further embodiment of the invention provides that the connecting region has at least one axially extending, groove-like indentation in each wall bounding a coupling recess and starting from an end side of the connecting region. Groove-like indentations of said type in walls of the coupling recesses advantageously facilitate axial displacements of the motor shaft end and the encoder shaft end relative to the connecting element in order to compensate for temperature-induced changes in length by reducing the friction between the connecting element and the motor shaft and the encoder shaft. The reduction in friction is achieved on the one hand by a reduction in the size of the friction surfaces between the connecting element and the motor shaft and between the connecting element and the encoder shaft. Furthermore, the indentations can accommodate a lubricant that is used for lubricating the coupling recesses, thereby further reducing the friction between the connecting element and the motor shaft and the encoder shaft.

A further embodiment of the invention provides that the connecting region has at least one cutout which extends axially from an end side and spaced apart from the outer side and the inner side. This advantageously enables the mass of the connecting element to be reduced and the stability of the connecting element to be increased.

A further embodiment of the invention provides that the connecting element is formed as a single, integral unit. This advantageously enables the stability of the connecting element to be increased and the manufacturing costs of the connecting element to be reduced.

A further embodiment of the invention provides that the connecting element is fabricated from a plastic material. This advantageously enables the mass and the manufacturing costs of the connecting element to be reduced for example compared to a fabrication of the connecting element from metal.

A motor according to the invention comprises a motor shaft having a motor shaft longitudinal axis, a rotary encoder for detecting a rotational position and/or a rotational speed of the motor shaft, and a connecting element according to the invention. The rotary encoder comprises an encoder shaft having an encoder shaft longitudinal axis. The connecting element connects a motor shaft end of the motor shaft on the encoder shaft side and an encoder shaft end of the encoder shaft on the motor shaft side to one another in that it is connected in a positive-locking manner in each case to the motor shaft end and to the encoder shaft end, wherein a first end side of the connecting region of the connecting element faces toward the motor shaft, the second end side of the connecting region of the connecting element faces toward the rotary encoder, and the connecting axis of the connecting element coincides with the motor shaft longitudinal axis and the encoder shaft longitudinal axis.

One embodiment of the motor provides that each end side of the connecting region has at least one coupling recess which extends radially from the inner side to the outer side of the connecting region, the motor shaft end has, for each coupling recess of the first end side, a motor shaft stud projecting radially into the coupling recess, and the encoder shaft end has, for each coupling recess of the second end side, an encoder shaft stud projecting radially into the coupling recess.

The advantages of a motor according to the invention will become apparent from the advantages of a connecting element according to the invention that have already been cited hereinabove.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Parts corresponding to one another are labeled with the same reference numerals in all the figures.

FIG. 1shows a schematic sectional view of a motor1, which is an electric motor. The motor1comprises a motor housing3, a motor shaft5, a rotor7arranged on the motor shaft5, a stator9arranged around the rotor7on the motor housing3, two motor shaft bearings11,13for mounting the motor shaft5, a rotary encoder15for detecting a rotational position and/or a rotational speed of the motor shaft5, a connecting element17for connecting the motor shaft5to an encoder shaft19of the rotary encoder15, and an encoder cover21.

FIG. 2shows an enlarged detail ofFIG. 1in the region of the connecting element17.

FIG. 3shows a perspective sectional view of the motor1illustrated inFIG. 1in the region of the rotary encoder15.

FIG. 4shows a perspective view of the connecting element17.

The motor shaft5is mounted by means of the motor shaft bearings11,13so as to be rotatable about a motor shaft longitudinal axis23of the motor shaft5. A first motor shaft bearing11is arranged on a first bearing shield27of the motor housing3facing toward the rotary encoder15. The second motor shaft bearing13is arranged on a second bearing shield29of the motor housing3facing away from the rotary encoder15. On the rotary encoder side, the motor shaft5has a bore31extending along the motor shaft longitudinal axis23.

The rotary encoder15is mounted so as to be rotatable about an encoder shaft longitudinal axis25which coincides with the motor shaft longitudinal axis23.

The encoder cover21is embodied in a pot-like shape and seals off an end of the motor housing3on the rotary encoder side. The encoder cover21protects the rotary encoder15against influences from the environment of the motor1.

The connecting element17connects a motor shaft end33of the motor shaft5on the encoder shaft side to an encoder shaft end35of the encoder shaft19on the motor shaft side, such that the encoder shaft19co-rotates with the motor shaft5. The motor shaft end33and the encoder shaft end35have at least approximately equal outer diameters and are spaced apart from one another.

The connecting element17comprises a connecting region39which runs in an annular shape around a connecting axis37, as well as a plurality of fan blades41. The connecting axis37coincides with the motor shaft longitudinal axis23and the encoder shaft longitudinal axis25. The connecting region39has two end sides43,45which lie axially opposite one another, an outer side47facing away from the connecting axis37, and an inner side49facing toward the connecting axis37. A first end side43of the connecting region39faces toward the motor shaft5, while the second end side45faces toward the rotary encoder15. The fan blades41protrude radially from the outer side47of the connecting region39. The terms radially and axially refer in this context to the connecting axis37.

The fan blades41are distributed at regular intervals along a circle around the connecting axis47on the outer side47of the connecting region39. In the exemplary embodiment illustrated inFIG. 4, the connecting element17has four fan blades41. However, alternative exemplary embodiments of the connecting element17may also have a different number of fan blades41. Each fan blade41has substantially the shape of a prism with a triangular base area which stands out vertically from the outer side47of the connecting region39. During a rotation of the motor shaft5, the fan blades41generate an air flow, indicated by arrows inFIG. 1, which distributes colder air from the region of the encoder cover21around the rotary encoder15and thereby advantageously cools the rotary encoder15.

Each end side43,45of the connecting region39of the connecting element17has two coupling recesses51which extend radially in each case from the inner side49to the outer side47of the connecting region39and are disposed radially opposite one another. The coupling recesses51of the first end side43are offset by 90 degrees relative to the coupling recesses51of the second end side45. Each coupling recess51has an axial depth which is roughly half as great as the axial extension of the connecting region39.

For each coupling recess51of the second end side45of the connecting region39, the encoder shaft end35has an encoder shaft stud53projecting radially into the coupling recess51. Each encoder shaft stud53is part of an encoder shaft attachment55which annularly surrounds the encoder shaft end35and is press-fitted onto the encoder shaft end35. The engagement of the encoder shaft studs53into the coupling recesses51of the second end side45of the connecting region39causes the encoder shaft end35to be connected to the connecting element17in a positive-locking manner.

Analogously thereto, for each coupling recess51of the first end side43of the connecting region39, the motor shaft end33has a motor shaft stud57projecting radially into the coupling recess51. Each motor shaft stud57is part of a motor shaft attachment59which annularly surrounds the motor shaft end33and is press-fitted onto the motor shaft end33. The engagement of the motor shaft studs57into the coupling recesses51of the first end side43of the connecting region39causes the motor shaft end33to be connected to the connecting element17in a positive-locking manner.

The positive-locking connections of the motor shaft end33and the encoder shaft end35to the connecting element17enable axial displacements of the motor shaft end33and the encoder shaft end35relative to the connecting element17, such that temperature-induced changes in length of the motor shaft5and the encoder shaft19can be compensated for by the connecting element17.

In order to facilitate such axial displacements of the motor shaft end33and the encoder shaft end35relative to the connecting element17, the connecting element17has axially extending groove-like indentations61in each wall bounding a coupling recess51and starting from an end side43,45of the connecting region39. The friction between the connecting element17and the motor shaft end33and the encoder shaft end35is advantageously reduced by the indentations61as a result of a reduction in the size of the friction surfaces between the connecting element17and the motor shaft end33and the encoder shaft end35. Furthermore, the indentations61can accommodate a lubricant which is used for lubricating the coupling recesses51, thereby further reducing the friction between the connecting element17and the motor shaft end33and the encoder shaft end35.

Optionally, the connecting region39has a plurality of cutouts63which extend axially in each case from an end side43,45and spaced apart from the outer side47and from the inner side49. This advantageously enables the mass of the connecting element17to be reduced.

The connecting element17is preferably fabricated from a plastic material and formed as a single, integral unit, and produced in an injection molding process, for example.

Although the invention has been illustrated and described in more detail on the basis of preferred exemplary embodiments, the invention is not limited by the disclosed examples and other variations may be derived herefrom by the person skilled in the art without leaving the scope of protection of the invention.