Motor with characteristic curve expansion, and table height and seat height adjustment device with such motor

Abstract

The invention relates to an electric machine (10), in particular for height adjustment of tables or seats, and to a table height adjustment device and a seat height adjustment device, comprising permanent magnets (12) which are arranged in a stator housing (11) and which form an excitation magnetic field (13), and comprising a rotor (14) which is arranged radially within the permanent magnets (12) and which has an electric winding (15), the rotor forms a rotor magnetic field (17) when the rotor is energized, and the rotor magnetic field (17) is rotated by a rotation angle from a neutral position relative to the excitation magnetic field (13) in order to generate a characteristic curve expansion (21) between a counter-clockwise rotation and a clockwise rotation of the electric machine (10).

Description

Technical Field

[0001] The invention relates to an electric motor with a characteristic curve expansion as well as a table height adjustment device and a seat height adjustment device having such a motor. Background Art

[0002] DE 10 2013 200 248 A1 discloses a method for designing an electric motor, wherein the manufacturing and design effort is to be reduced by adapting to a number of different application possibilities. The speed-torque characteristic curve of the electric motor is designed in such a way that different operating points can be achieved for the respective application. A disadvantage of such a method for designing an electric motor is that the electric motor is designed relatively large and therefore also relatively expensive due to the intended application with maximum drive power. This disadvantage is to be eliminated by the invention described below. Summary of the invention

[0003] In contrast, the electric machine according to the invention having the features of the independent claim has the advantage that, due to the characteristic curve expansion of the electric motor, a lower total power can be designed for a specific application than without the characteristic curve expansion. Since a higher torque is available in one direction of rotation of the electric motor than in the opposite direction of rotation, the efficiency of the electric motor can be optimized in the desired operating range in such a way that the required current requirement is reduced for this purpose. The reduced current requirement can reduce the installation space of the electric motor and thus its costs. The required power requirement of the power supply unit for energizing the electric motor is also correspondingly reduced.

[0004] Advantageous developments and improvements of the embodiments specified in the independent claims can be achieved by the measures listed in the dependent claims. Such an electric motor can be used particularly advantageously for an adjusting device with a load requirement that depends on the direction of rotation. Thus, for example, the first direction of rotation of the electric motor can be used for an adjusting movement of a component to be adjusted against the force of gravity, wherein a higher torque must be applied than in the case of a second direction of rotation for adjusting a movable component in the direction of gravity. In this case, the electric motor can be optimized only for the lifting operation against the force of gravity, since for the lowering operation it is not important that only a lower torque is provided in the second direction of rotation by the characteristic curve expansion, since the adjusting movement is supported by gravity here.

[0005] For the drive device according to the invention, a cost-effective DC motor (direct current motor) can be used, wherein an armature winding is arranged on the rotor and is electrically connected to the commutator disk of the commutator. Electric carbon brushes abut against the commutator, via which the electric coils are alternately energized. By intervening in the commutation, such a DC motor can be designed very easily in such a way that a characteristic curve expansion that depends on the direction of rotation can be achieved.

[0006] The characteristic curve expansion can be achieved, for example, by commutator twisting, wherein the commutator is fastened to the rotor shaft in such a way that it is twisted by a certain commutator twist angle relative to the neutral region of the commutator. In this case, the commutator is rotated out of a neutral position relative to the coils, wherein the characteristic curve expansion can be set by the size of the commutator twist angle as the expansion angle. Since the commutator is only fastened to the rotor shaft in such a way that it is twisted by the commutator twist angle, no changes to the production line are required in such a production process.

[0007] In a further advantageous embodiment, the characteristic curve expansion can be achieved by twisting the brushes relative to the neutral region of the commutator, wherein all, in particular two, brushes are positioned in such a way that they are twisted by a corresponding brush twist angle relative to the neutral position of the commutator. In this embodiment, the position of the brush fastening on the brush holder is modified accordingly. In the case of eight commutator disks, the brushes can be fastened to the brush holder, for example, in such a way that they are twisted by a maximum of + / -22.5°, in particular by 5° to 15°, relative to the neutral position of the commutator.

[0008] The angle between two brushes is preferably approximately 180°, wherein the brushes or the commutator can be arranged rotated by the extension angle relative to the neutral position of the coil with respect to the external excitation magnetic field.

[0009] The neutral position of the commutator relative to the electric coil is in particular defined in such a way that the electric coil is penetrated by the maximum possible magnetic flux of the permanent magnetic field, and the commutator and the brushes are arranged in such a way that the coil is energized to the maximum extent in this position. The plane of the electric coil is perpendicular to the radial center axis of the permanent magnetic field.

[0010] The electric machine preferably has exactly two magnetic poles on the stator, wherein the rotor advantageously has eight rotor teeth and eight electrical coils of the electrical winding, wherein the rotor is designed rotationally symmetrically with eight identical rotor poles.

[0011] For example, exactly two permanent magnets are arranged at the stator of the motor, and these two permanent magnets form two magnetic poles of the excitation field. Alternatively, four magnetic poles can also be arranged in the stator, wherein in particular two magnetic poles can also be constructed in a sequential pole-arrangement mode. The rotor preferably has eight rotor poles, which are formed by eight rotor teeth. The rotor also has eight commutator-discs, which are connected to the corresponding electrical coils of the rotor. Alternatively, the rotor can also have more or fewer rotor poles, wherein the number of commutator-discs also changes. For the structural scheme of the characteristic curve-expansion, the commutator-torsion angle during commutator-torsion or the brush-torsion angle during brush-torsion depends on the number of commutator-discs.

[0012] The electric motor according to the invention with an extended characteristic curve can be used very advantageously for adjusting the height of tables, chairs or other furniture, since a correspondingly greater drive torque is required for a lifting movement than for a lowering movement. Thus, the direction of rotation of the electric motor which is optimized with respect to the maximum drive torque can be used for the lifting movement, without causing disadvantages when the furniture part is lowered.

[0013] Likewise, electric machines with extended characteristic curves can also be used to adjust movable components in motor vehicles, wherein oppositely arranged directions of movement require different drive torques. Here, the direction of rotation with the maximum drive torque can be used, for example, for seat height adjustment or backrest adjustment against the force component of gravity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention is explained in more detail in the following description with reference to the exemplary embodiments shown in the drawings.

[0015] in:

[0016] Figure 1 Schematically shows an expanded diagram of a characteristic curve of an electric machine,

[0017] Figure 2 A diagram schematically shows the superposition of the excitation magnetic field and the rotor field of the electric machine, and

[0018] Figure 3 An exemplary embodiment for setting an expansion angle for characteristic curve expansion is schematically shown. DETAILED DESCRIPTION

[0019] exist Figure 1Schematically, the division of the characteristic curve of the electric motor 10 is shown in . The torque m provided by the electric motor 10 in Nm is shown increasing from left to right on the x-axis 25. The rotational speed n of the electric motor in 1 / min is shown increasing from bottom to top on the y-axis 26 on the left. The torque characteristic curves 20, 22 are shown as thick lines, which extend as straight lines from the upper left to the lower right. According to the present invention, the torque characteristic curve 20 for counterclockwise rotation (solid line) is constructed differently from the torque characteristic curve 22 for clockwise rotation of the electric motor 10 (dashed line), which is manifested as a characteristic curve expansion 21. The torque characteristic curve 20 for counterclockwise rotation continuously provides a higher torque m and is therefore located above the torque characteristic curve 22 for clockwise rotation of the electric motor 10. In Figure 1 The working range 40 for lifting a table or a chair is marked between about 5Nm and 7Nm. In the working range 40 for lifting, the extension between counterclockwise rotation and clockwise rotation is, for example, about + / -10% to 15% of the theoretical average value between the two torque characteristic curves 20, 22. This means that, compared with the corresponding clockwise rotation of the motor 10, the counterclockwise rotation of the motor 10 here provides a 20%-30% higher torque m for lifting a table or a chair at a specific speed n. The working range 42 for lowering a table or a chair is, for example, in the range between 0.5Nm and 2Nm. Since the characteristic curve 20 is used for counterclockwise rotation in this example for lifting, the characteristic curve 22 is used for clockwise rotation for lowering. In the lowering working range 42, the motor 10 provides a lower torque at a specific speed n according to the characteristic curve 22 for clockwise rotation. However, this is not important for the lowering operation, because when the table or the seat is lowered, it causes an inertial operation, so that a high drive torque is not required here.

[0020] In addition, Figure 12 shows the current consumption 32 for counterclockwise rotation with respect to torque m, which current consumption extends from the lower left to the upper right. The right y-axis 27 on the right side shows the motor current I of the motor 10 in A. The current consumption 32 for clockwise rotation is shown as a dashed thin line and also extends from the lower left to the upper right with a greater slope. The current consumption 30, 32 is also extended like the torque characteristic curves 20, 22, so that the motor 10 has a lower current consumption for counterclockwise rotation in the lifting operation in the working range for lifting 40 than when the motor 10 rotates clockwise, but the clockwise rotation is only used for the lowering operation. In this embodiment, the current consumption 32 for counterclockwise rotation and the current consumption 30 for clockwise rotation are approximately the same in the lowering working range 42, wherein the current required in the lowering operation is relatively low due to the inertia operation. Since the size of the electric machine 10 must be designed for the lifting operation, the direction of rotation (counterclockwise rotation 20) with a higher available torque can be used as the basis for the design of the maximum required torque due to the torque characteristic curve expansion 21. This can correspondingly reduce the current consumption of the electric machine 10 and thus its size.

[0021] Figure 2 The cross section of an electric machine 10 is schematically shown, wherein two permanent magnets 12 are arranged opposite each other in a stator housing 11 of a stator 18. These permanent magnets 12 form an excitation magnetic field 13, which serves to drive a rotor 14 supported in the stator housing 11 in rotation. The rotor 14 schematically has only one electrical winding 15 here, which forms a magnetic rotor field 17 when it is energized. During operation of the electric machine 10, the rotor field 17 is superimposed on the excitation field 13 to form a total magnetic field 16, in which a deformation of the induction curve in the air gap 44 between the rotor 14 and the stator magnets 12 occurs. By setting the expansion angle of the electric machine 10, the neutral region of the commutator 50 is shifted by an angle φ relative to the electrical coil 54 between the induction component of the excitation field 13 and the rotor field 17, which causes the characteristic curve expansion 21 of the electric machine 10.

[0022] exist Figure 31 shows the principle of the commutator twist relative to the coil 54, which causes the characteristic curve expansion 21 between the counterclockwise rotation and the clockwise rotation of the electric machine 10. On the left side, a rotor 14 is shown, which has, for example, eight rotor teeth extending in the radial direction 7 and eight rotor slots 19, into which the electrical winding 15 is inserted. In addition, a commutator 50 with a commutator hook 52 is fastened to the rotor 14, which is connected to the coil 54 of the electrical winding 15. The commutator hook 52 is formed on the commutator disk 56, which is electrically insulated from each other. Brushes 60 are in contact with the commutator disk 56 in order to energize the electrical coils 54 one after another. In the middle of the image, the commutator 50 with eight commutator disks 56 is schematically shown in a circumferential direction 9. Each commutator disc 56 is connected to an end of the electric coil 54 so that the motor current I flows from the first brush 60 through the electric coil 54 to the second brush 60. Figure 3 On the right side in FIG. 1 , a permanent magnet 12 is shown, which forms an excitation field 13, which is schematically shown in the middle image relative to the electric coil 54. The extent of the excitation field 13 in the axial direction 8 corresponds essentially to the axial length of the permanent magnet 12. When the rotor 14 rotates, the cross section of the coil loop is displaced through the excitation field 13 in the circumferential direction 9. Figure 3 In the right-hand image, the rotor 14 again has eight rotor slots 19, wherein only the electrical coils 54 are schematically shown as wire windings. The two brushes 60 are offset by 180° relative to one another here, so that the two brushes 60 are arranged axially exactly opposite each other at the first commutator gap 61 between the first commutator disk 56 and at the second commutator gap 62 between the fifth commutator disk 56. Figure 3The right-hand image of shows the state of the neutral position of the electric coil 54 relative to the commutator 50. In order to now generate the characteristic curve expansion 21, the commutator 50 is displaced, for example, relative to the rotor slots 19 and therefore relative to the electric coils 54 by an angle ψ of the commutator twist 66, so that the commutator 50 is fastened, for example, to the rotor shaft in a manner twisted by an angle ψ relative to the neutral position of the electric coils 54. The commutator 50 is fastened, for example, to the rotor shaft in a manner twisted by an angle ψ relative to the rotor slots 19 to such an extent that the coils 54, instead of being in the neutral position, no longer generate a maximum magnetic flux with the aid of an applied brush current in their geometrically symmetrical center position relative to the stator magnetic field 13. In this case, in the case of a rotor 14 having, for example, eight electric coils 54 and eight commutator disks 56, the angle ψ of the commutator twist 66 is in particular approximately 5° to 15°, preferably approximately 9°, wherein the two brushes 60 have in particular a brush angle of approximately 180° relative to one another. Thus, by selecting the angle ψ of the commutator rotation 66 , the characteristic curve expansion 21 can be set, whereby the two directions of rotation of the electric machine 10 provide different torques.

[0023] As an alternative to the commutator twist 66, the characteristic curve expansion 21 can also be generated by fastening the brush 60 to the brush holder in a manner that is twisted in the circumferential direction 9 relative to the neutral position of the commutator 50. To generate the characteristic curve expansion 21, the brush 60 can be fastened to the stator housing 11, for example, in a manner that is twisted by an angle ψ as an expansion angle relative to the neutral position of the commutator 50 and therefore also in particular relative to the neutral position of the rotor slots 19. As a result, the commutation of the electrical coil 54 can also be influenced in such a way that different characteristic curves 20, 22, 30, 32 are generated for counterclockwise and clockwise rotation of the electric machine 10.

[0024] It should be noted that various combinations of the individual features are possible with respect to the embodiments shown in the drawings and in the description. Thus, for example, the specific construction, arrangement and number of the electric coil 54 together with the commutator 50 and the construction and number of the permanent magnets 12 can be changed accordingly. The characteristic curve expansion 21 can be achieved by different measures, wherein the commutation of the electric motor 10 is changed in such a way that a higher drive torque should be provided along the first rotation direction of the electric motor 10 than along the oppositely arranged rotation direction of the electric motor 10. The present invention is particularly suitable for height adjustment of tables or seats or furniture, but can also be used for other adjustment drives, wherein different drive torques are required along different adjustment directions. Thus, the electric motor 10 according to the present invention can also be used, for example, for a unit in a motor vehicle, in particular for adjusting a component of a vehicle seat.

Claims

1. An electric motor (10), in particular for adjusting the height of a table or a chair, comprising: stator (18), wherein A permanent magnet (12) is arranged in the stator housing (11), which forms an excitation magnetic field (13), and a rotor (14) arranged radially within the permanent magnets (12), the rotor having an electrical winding (15) which forms a rotor magnetic field (17) when current is supplied to the rotor, It is characterized in that The rotor magnetic field (17) is twisted by an expansion angle relative to the excitation magnetic field (13) from a neutral position in order to generate a characteristic curve expansion (21) between counterclockwise rotation and clockwise rotation of the electric machine (10).

2. The electric machine (10) according to claim 1, characterized in that By means of the characteristic curve expansion (21), the electric machine (10) provides a higher drive torque in a lifting operation range (40) in just one direction of rotation with a lower current requirement than a drive torque in a lowering operation range (42) in an opposite direction of rotation.

3. The electric machine (10) according to claim 1 or 2, characterized in that: The rotor (14) has a commutator (50) with commutator plates (56) insulated from one another, wherein the commutator plates (56) are connected to the electrical coils (54) of the electrical winding (15) and brushes (60) for energizing the electrical coils (54) abut against the commutator (50).

4. The electric machine (10) according to any one of the preceding claims, characterized in that The rotor magnetic field (17) is twisted relative to the excitation magnetic field (13) by a commutator twist (66), wherein a neutral region of the commutator (50) is arranged in such a way that it is twisted relative to the electrical coil (54) by a commutator twist angle (ψ), in particular 5° to 15°, and in which neutral region the rotor magnetic field (17) of the energized electrical coil (54) is oriented parallel to the excitation magnetic field (13), the commutator twist angle corresponding to the expansion angle.

5. The electric machine (10) according to any one of the preceding claims, characterized in that The rotor magnetic field (17) is twisted relative to the excitation magnetic field (13) by brush twisting (66), wherein the commutator (50) is fastened to the rotor (18) in the neutral region of the commutator (50) and the brushes (60) are arranged relative to the commutator (50) at a brush twist angle that corresponds to the spread angle.

6. The electric machine (10) according to any one of the preceding claims, characterized in that Precisely two brushes (60) abut against the commutator (50), which are arranged relative to one another at a brush angle (α) of approximately 180°.

7. An electric machine (10) according to any one of the preceding claims, characterized in that In the neutral region of the commutator (50), at least one electric coil (54) has a coil axis which extends along a radial perpendicular midline of the excitation magnetic field (13).

8. An electric machine (10) according to any one of the preceding claims, characterized in that Exactly two stator poles are formed on the stator (18), and exactly eight rotor poles and eight electric coils (54) are formed on the rotor (14).

9. Table height adjustment device having an electric motor (10) according to any one of the preceding claims, characterized in that A characteristic curve expansion (21) is generated between the two rotation directions of the electric motor (10), and a rotation direction with lower current consumption for the lifting movement of the table and a further rotation direction with higher current consumption for the lowering movement of the table are provided.

10. A seat height adjustment device, in particular in a motor vehicle, having an electric motor (10) according to any one of the preceding claims, characterized in that A characteristic curve expansion (21) is generated between two rotation directions of the electric motor (10), and a rotation direction with lower current consumption for the lifting movement of the seat and a further rotation direction with higher current consumption for the lowering movement of the seat are provided.

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