DE102021000407B3 - Electrical auxiliary drive for a bicycle, and an electric bicycle or a bicycle ergometer with such an electrical auxiliary drive - Google Patents

Abstract

The present invention relates to an electric auxiliary drive (10) for a bicycle, in particular a pedelec, or for a bicycle ergometer and a bicycle, in particular a pedelec, or a bicycle ergometer with such an auxiliary drive. The electric auxiliary drive has a stator (12) and a rotor (14). A torque applied by a driver can be transmitted to the rotor (14) via a transmission element (16) and a torque transmission element (18), the transmission element (16) and the torque transmission element (18) being coupled to one another in the axial direction and being coaxial with respect to the axis of rotation of the rotor are arranged, wherein the torque transmission element (18) has at least one magnetostrictive area (181). A first sensor device (20) is configured to measure a torque transmitted to the torque transmission element (18) in the magnetostrictive region of the torque transmission element (18) and to transmit a resulting torque signal to a control unit (34) of the electric auxiliary drive (10), wherein the torque signal corresponds to a torque-induced magnetic flux at the magnetostrictive region (181). The control unit (34) is configured to control an assist torque for the driver from the electric assist drive from the torque signal. The first sensor device (34) is configured to measure the torque-induced magnetic flux on the torque transmission element (18) from the outside on the magnetostrictive region (181) of the torque transmission element (18).

Description

The present invention relates to an electric auxiliary drive for a bicycle, in particular a pedelec, or for a bicycle ergometer and a bicycle, in particular a pedelec, or a bicycle ergometer with such an electric auxiliary drive.

The use of electric auxiliary drives for vehicles and bicycles, such as city e-bikes, gravel bikes and pedelecs, is constantly increasing. In the case of pedelecs or e-bikes, the electric auxiliary drives are usually arranged in the frame, so-called central motor, or on the rear wheel hub, so-called rear-wheel hub motor. The torque applied by a driver and the angular velocity or cadence are important for the control of an electric auxiliary drive. The detection of the torque and the cadence enables the power applied by the driver to be recorded. For the harmonious control of an electric auxiliary drive in pedelecs and e-bikes, it is known to record the power input by the driver and to use a suitable software algorithm to generate a torque request for the auxiliary drive.

The torque can be measured, for example, by sensors based on strain gauges. Here, using one or more strain gauges attached directly to the shaft, a change in resistance caused by strain is measured on the outer peripheral surface of the shaft with a bridge circuit or other well-known device. However, these are error-prone due to the direct contact with the rotating shaft and usually have a high mechanical complexity. The signals are usually transmitted to a control unit by cable arrangements, which makes assembly on a pedelec more difficult. In addition, they are relatively expensive.

Nowadays, torque measurement using non-contact torque sensors is mostly based on the magnetostrictive principle. This enables a simplified and improved detection of the torque. Magnetostriction is a property of ferromagnetic (iron-based, magnetizable) materials that causes materials to change shape or size when a magnetic field is present. This magnetostrictive effect can be used to measure torque. Magnetostriction is based on the interaction of magnetic fields. Such systems often have a simple mechanical structure and are also inexpensive to produce.

US 2013/0 049 444 A1 discloses a hub for a bicycle with a torque transmission element, wherein a torque is transmitted to a magnetostrictive region of the torque transmission element. A sensor device with at least one sensor is arranged inside the hub to measure the torque-induced magnetic flux at the magnetostrictive region.

The object of the invention is to provide an electric auxiliary drive and an electric bicycle or a bicycle ergometer with such an electric auxiliary drive, with the auxiliary drive providing an auxiliary torque in a simplified and improved manner through improved torque measurement and also a simple mechanical structure and inexpensive production of the electric auxiliary drive with a torque measuring device or power measuring device.

This object is achieved by an electrical auxiliary drive with the features of claim 1 and by an electrically operated bicycle or a bicycle ergometer with such an electrical auxiliary drive with the features of claim 11. Advantageous developments result from the dependent claims, the description and the figures.

Accordingly, an electric auxiliary drive for a bicycle, in particular a pedelec, or for a bicycle ergometer is proposed, having a stator and a rotor. Torque applied by a driver can be transmitted to the rotor via a gear element and a torque transmission element, the gear element and the torque transmission element adjoining one another in the axial direction and being arranged coaxially with respect to the axis of rotation of the rotor. The torque transmission element has at least one magnetostrictive area. A first sensor device is configured to measure a torque transmitted to the torque transmission element at the magnetostrictive region of the torque transmission element and to transmit a resulting torque signal to a control unit of the electric auxiliary drive. The torque signal corresponds to a torque-induced magnetic flux at the magnetostrictive region. The controller is configured to control an assist torque to the driver from the electric assist drive from the torque signal. The first sensor device is configured to measure the torque-induced magnetic flux on the torque-transmitting element from the outside at the magnetostrictive region of the torque-transmitting element.

Contrary to the solutions known from the prior art, the torque can be measured from the outside on the torque transmission element with such an arrangement. As a result, the assembly of the first sensor device can be simplified. It is also advantageous that the first sensor device can be fixed directly on a printed circuit board of the electrical auxiliary drive. As a result, complex cabling from the sensor device to the printed circuit board can be avoided, which in turn reduces the effort involved in installing the torque measurement.

The magnetostrictive region is configured such that the torque applied to the torque-transmitting element is transmitted to the magnetostrictive region, which includes at least one magnetically polarized region. The magnetostrictive area extends at least partially along the outer peripheral surface of the torque transmission element. The magnetostrictive region may be endowed with an effective uniaxial magnetoelastic anisotropy and magnetically polarized in the circumferential direction, producing a field that varies with applied stress from the torque input. When torque is applied to the torque-transmitting element, the circumferential magnetic orientation at the magnetostrictive region is reoriented such that a helical magnetic orientation is created that has both circumferential and axial components. The magnetostrictive area thus has a torque-exposed magnetic material, which emits the torque-dependent magnetic flux and can be measured by the first sensor device.

Advantageously, the circumferential magnetizations can be reduced by suitable conditioning of the shaft material, e.g. B. be provided by permanent or current magnets. The torque transmission element with the magnetostrictive area is formed at least partially from a ferromagnetic material that is suitable for generating a magneto-elastic effect and, in particular, contains nickel (Ni). An industrial steel such as X200r13 or similar material can be used. With this type of torque transmission element, the circumferential magnetization can be in the shaft material itself. Consequently, the torque transmission element can do without an additional sleeve or ring element.

The first sensor device is mounted in such a way that it is responsive to the change in the original orientation of the magnetization. In one example, the sensors of the sensor device can be set in such a way that it measures the axial component of the magnetization in order to determine the magnitude of the torque input therefrom. The change in the axial component is therefore proportional to the torque applied to the torque transmission element, particularly in the magnetostrictive range.

The rotating torque-transmitting element is carried by a non-rotating fixed axle. This can be attached to a frame of the bicycle. The torque transmission element is preferably designed as a sleeve and is arranged coaxially with respect to the fixed axis of the electric auxiliary drive. The fixed axis also forms the axis of rotation for the rotor of the electric auxiliary drive.

By installing the torque sensor device outside of the bottom bracket, the accessible torque value is not limited to a torque that is applied via the left or right pedal crank, ie via a single pedal crank, as is usual with mid-motors. In contrast to the torque sensor devices that are installed in the bottom bracket spindle, a total value of the torque acting on the freewheeling wheel can be determined.

The system on which the invention is based generates the control signal for the auxiliary drive from the detection of the torque. This makes it possible to dynamically control an electric auxiliary drive in such a way that an auxiliary torque is output by the electric auxiliary drive based on the detected torque. The electric assist drive processes the sensed torque command signal to determine what torque to assist in transferring to the freewheeling wheel. Depending on the torque signal, the control unit controls the level of the auxiliary torque that is to be output in support of the electric auxiliary drive. Depending on the auxiliary torque to be delivered, the control unit regulates the current with which the rotor is driven in order to generate the desired auxiliary torque. The auxiliary torque is transmitted to the freewheeling wheel via the rotor and, for example, spokes. The electric power assist rotor has spoke sockets for attaching spokes to the rotor.

For example, the support of the electric auxiliary drive can be activated with an auxiliary torque when a threshold torque applied by a driver is exceeded. For example, the threshold values of the torque or the power can be set in such a way that the electric auxiliary drive provides the driver with an auxiliary torque supported, which is easy on the driver's joints in the desired torque range. Conversely, support for the electric auxiliary drive can also be deactivated if the torque applied by the driver exceeds a specific threshold value.

The control unit is an electronic component and can be part of the power electronics of the electric auxiliary drive. The control unit is configured to receive the data recorded by the sensor device, in particular the torque signal, and to control the electric auxiliary drive based thereon. Depending on the detected torque signal, the control unit can set an auxiliary torque, which is to be supplied to the bicycle by the electric auxiliary drive as a supporting torque for the rider. In addition, the control unit can receive further data from further sensor devices. For example, the control unit can detect the rotor position and angular velocity of the rotating system from a further sensor device. By detecting the angular velocity, the control unit can regulate the power to be delivered by the electric auxiliary drive. For example, the control unit can be configured in such a way that it does not add more than a power applied and/or adjustable by the driver.

The transmission element can transmit the pedaling force exerted by a driver, so that a torque can be transmitted to a free-wheeling wheel. In one example, the gearing element includes a rear gear element (e.g., multi-gear cassette). In a further example, the transmission element has a freewheel. Alternatively, the freewheel can also be arranged in the bottom bracket, so that the electric auxiliary drive does not require a freewheel. As a result, components and the effort involved in installing them in the electric auxiliary drive can be reduced.

Outside or from the outside is to be understood in such a way that the sensor device is not arranged within the area between the axis of rotation and the torque transmission element, but is arranged outside of the axis of rotation and the torque transmission element. In other words, outside or outside of the torque transmission element is to be understood in such a way that the surface normal of the outer peripheral surface of the torque transmission element, which is arranged coaxially around the axis of rotation, points away from transversely with respect to the axis of rotation.

By arranging the sensor device outside of the torque transmission element, the magnetostrictive area can be arranged on the outer peripheral surface of the torque transmission element. As a result, the torque-induced magnetic flux can be measured from the outside by the sensor device. The sensor means are thus not mounted inside a hub assembly. In this way it can be avoided that the signals from internal sensors have to be routed to the control unit via cables. Furthermore, it is advantageous that the installation of the sensors is more time- and cost-efficient.

The electric auxiliary drive has a housing with side walls in order to protect the interior of the electric auxiliary drive from environmental influences, in particular moisture and dirt. The stator, in particular the stator carrier, and the rotor can partially form the housing. As a result, in particular the power electronics and the torque sensor device can be protected from environmental influences by the housing. The integration of the sensor device in the electric auxiliary drive makes use of the fact that the sensor device has to be integrated inside bicycle components, such as a hollow shaft or a hub, in order to protect them from environmental influences. As a result, the mechanical structure for the torque measurement can be simplified in a significant way.

The electric auxiliary drive can be an electric DC motor that works with 12 V or 36 V or 48 V operating voltage. In one example, the electric auxiliary drive is a direct-rotor motor.

The term bicycle in the sense of this description means a pedelec and all other types of bicycles that have an electric drive, in particular an electric auxiliary drive. These can also be referred to as e-bikes. The term bicycle also includes cargo bikes with a front and/or rear axle with at least two free-wheeling wheels.

The term non-rotatable is understood to mean that one component is fixed to another component and has no relative movement with respect to this other component.

According to one embodiment, the torque transmission element has a hollow shaft and a measuring sleeve, which are arranged coaxially with respect to the axis of rotation of the rotor. The measuring sleeve is arranged on the outside in relation to the hollow shaft and the axis of rotation and has the magnetostrictive area. The hollow shaft is non-rotatably coupled to the gear element and the measuring sleeve, so that the torque can be transmitted to the measuring sleeve.

The measuring sleeve is therefore to be understood as a separate sleeve that encloses the hollow shaft. With this type of torque transmission element, the circumferential magnetization is only in the measuring sleeve to form the magnetostrictive area.

The torque is transmitted via the gear element to the hollow shaft, which is non-rotatably coupled to the measuring sleeve. The rotating system essentially consists of the gear element, the hollow shaft, the measuring sleeve and the rotor. When the torque is applied to the measuring sleeve, the magnetostrictive area is twisted and the magnetization changes as a result. The magnetostrictive portion is configured such that the torque applied to the measurement sleeve is transferred to the magnetostrictive portion, which includes at least one magnetically polarized portion. The magnetostrictive area extends at least partially along the outer peripheral surface of the measuring sleeve. Advantageously, the circumferential magnetizations can be reduced by suitable conditioning of the shaft material, e.g. B. be provided by permanent or current magnets. This generates circumferential magnetizations that can be detected with a magnetoelastic sensor. The measuring sleeve is formed at least partially from a ferromagnetic material that is suitable for generating a magneto-elastic effect and contains, in particular, nickel (Ni). An industrial steel such as X200r13 or similar material can be used. In this embodiment, only the measuring sleeve needs to be made of such a material. As a result, the magnetostrictive area can be manufactured more cost-effectively.

The sensor device is set in such a way that a torque-induced change in magnetization can be measured in the magnetostrictive range.

According to one embodiment, the sensor device is arranged on the stator in a rotationally fixed manner. The sensor device thus has a fixed assignment to the stator, the stator having a fixed arrangement to the frame of the bicycle, in particular the pedelec.

According to one embodiment, the sensor device measures the torque-induced magnetic flux at the magnetostrictive area in a contactless manner.

Contactless can also be understood as non-contact.

The sensor device has at least one magnetoelastic sensor. In one example, this is based on what is known as inverse magnetostriction, ie the change in magnetization is measured by mechanical stresses as a result of the torsion on the torque transmission element. According to a further embodiment of the invention, the at least one magnetoelastic sensor is a vector sensor. In particular, the vector sensor is one of the following: a Hall effect, a magnetoresistance, a magnetotransistor, a magnetodiode, or a MAGFET sensor. The magnetic field sensor is in particular a fluxgate magnetometer. These magnetic field sensors have proven to be particularly suitable for use in an electric auxiliary drive.

In one example, the sensor device has at least one magnetic field sensor. Preferably four magnetic field sensors are used, two being arranged diametrically opposite to the other two with respect to the torque transmission element. This can improve the accuracy of the torque measurement.

According to one embodiment, the sensor device and the control unit are connected to a printed circuit board, which is non-rotatably connected to the stator. The stator can also provide the stationary fixation for the control unit of the electric auxiliary drive. The sensor device, for example a sensor circuit board, can thus advantageously be combined with the control unit, which is provided on a circuit board, to form one assembly. As a result, the mechanical and acoustic engineering structure for the torque measurement can be simplified.

According to one embodiment, a magnetized pole ring is provided to measure rotor position. The pole ring is arranged coaxially around the axis of rotation, the magnetized pole ring being non-rotatably connected to the rotor or the torque transmission element or a torque support element.

For the efficient operation of the electric auxiliary drive, in addition to the detection of the torque, the detection of the angular velocity and the rotor position are important. Power is a product of angular velocity and torque. This allows performance to be determined. On the one hand, the power exerted by a driver can be determined. On the other hand, based on this, the power of the electric auxiliary drive can be determined as a function of the desired auxiliary torque. Furthermore, the angular velocity measurement can be used to determine the speed of the bicycle, the distance traveled by the rider, and other desired ones to measure parameters. The fast and accurate detection of the rotor position is important in order to determine how the rotor, or the individual rotor windings, are in relation to the stator. For efficient and direct application of the auxiliary torque, it is desirable that the rotor winding of the rotor which is best positioned with respect to the stator (e.g. centered over a permanent magnet of the stator) is energized. This is particularly relevant when starting off or on an incline, since in these situations direct and efficient support for the driver with the auxiliary torque immediately facilitates starting off.

In the prior art, sensorless implementations, but also implementations with sensors, are known. Systems with sensors have the advantage that they can detect a rotor position as soon as the rotor is in motion. This allows the rotor position to be quickly determined and the rotor winding best positioned in relation to the stator to be located. Sensorless systems, on the other hand, can only measure a rotor position after a full or at least partial revolution of the rotating system. Sensor-based conversions are particularly important for electric auxiliary drives, which are arranged in a rear wheel, in particular on a rear wheel hub, since they run at low speeds and the efficient use of the electric auxiliary drive depends on the direct and precise measurement of the rotor position.

In order to determine the position of the rotor of electrical auxiliary drives, in particular external rotor motors, sensors, for example Hall elements, are usually arranged in notches in the stator in the vicinity of the rotors. The slot notches or the sensors are located on the outer radius of the stator. The rotor magnets generate the magnetic fields required for the sensors to measure the angular velocity. The position of the rotor can be determined according to the arrangement of the Hall elements and a mathematical transformation. The transmission of the position signals is wired to a control unit, in particular the electrical-mechanical connection is ensured by means of plug connectors or soldered connections. In addition, the use of adhesives to reduce mechanical stress or vibration is common and requires additional processing steps.

The proposed pole ring allows the location of the measurement to be transferred in the direction of the axis of rotation. The measurement of the angular velocity is therefore no longer dependent on the magnetic poles of the rotor. The magnetized pole ring has a large number of pole pairs. The pole ring preferably has a number of pole pairs equal to the number of pole pairs of the rotor. The sensors required for measuring the angular velocity, for example Hall elements, are preferably arranged on a printed circuit board attached to the stator in the vicinity of the pole ring.

The variant of position detection using a pole ring near the axis of rotation thus enables a very compact, integrated and low-interference measurement of the angular velocity.

Alternatively, the angular velocity can also be measured using a quadrature encoder (QEP). However, this sensor technology is often significantly more expensive and only delivers a usable position signal after a full revolution of the rotor.

According to one embodiment, the pole ring is sprayed on. As a result, a pole ring can be attached to a component of the rotary system in a simple manner without additional connecting means.

According to one embodiment, a second sensor device is connected to the control unit in order to detect the position of the pole ring by changing the magnetic field emitted by the pole ring, preferably without contact.

The second sensor device can have at least one Hall sensor in order to generate a position signal when the sensor detects a magnetic field emitting through the poles of the pole ring. The at least one Hall sensor is arranged directly on the printed circuit board, which is firmly fixed to the stator.

The position of the at least one Hall element is coordinated with the position of the magnetized pole ring in such a way that the at least one Hall element has the same radial spacing as the poles of the pole ring in relation to the axis of rotation. Thus, at least one pole of a pole pair and a Hall element face each other at a small distance in the axial direction at the time of the measurement. In a further example, a multiplicity of Hall elements can be arranged on the printed circuit board. The Hall elements are arranged in a circular path on the printed circuit board. The radius of the circular path on which the Hall elements are arranged thus essentially corresponds to the mean radius of the pole ring.

The arrangement of the Hall elements on the printed circuit board eliminates the need for an additional circuit board to accommodate the sensors, in comparison to the known solutions for measuring the angular velocity on the outer radius of the stator special Hall elements. The sensors can thus be arranged directly on the circuit board of the power electronics, in particular soldered. This eliminates the need for cables and/or other connectors. In addition, the components and transmission paths are rigid and firmly installed, which improves the mechanical structure. Furthermore, the production costs can also be reduced through better automation and the omission of work steps such as gluing in the sensors or the subsequent application of adhesive to fix cables and lines. The omission of plug connectors also increases operational reliability.

The pole ring thus enables the sensors, in particular Hall elements, to be arranged directly on the power electronics. This eliminates the need to arrange the sensors on the outer radius of the stator. In this way, the rotor position or the angular velocity of the rotor can be detected with just one additional sensor on the printed circuit board. As a result, the mechanical structure for measuring the angular velocity can be simplified and manufactured more cost-effectively.

According to one embodiment, the electric auxiliary drive is arranged directly in a free-wheeling rear wheel of a bicycle, so that an auxiliary torque can be transmitted via the rotor to the free-wheeling rear wheel.

Due to the direct integration on the rear wheel, the axis of the electric auxiliary drive forms the axis of the free-wheeling wheel at the same time. In addition, the torque transmission element and the rotor form the hub of the freewheeling wheel. As a result, the number of components can be reduced and the complexity of the torque measurement can be reduced.

According to one embodiment, the electric auxiliary drive can be connected to a second transmission element, so that the auxiliary torque can be transmitted to the freewheeling rear wheel via the second transmission element.

In such an arrangement, the electric auxiliary drive is arranged on a frame structure of a bicycle, in particular a pedelec, between the bottom bracket and the rear axle. The torque applied by a driver is transmitted via the first transmission element to the electric auxiliary drive and is transmitted via a second transmission element to at least one freewheeling rear wheel. In one example, the pedelec can have a rear axle with two free-wheeling wheels. In this arrangement, the torque is transmitted to the free-wheeling rear wheels via the second transmission element and preferably a differential.

If the electric auxiliary drive is activated, a total torque from a torque applied by the driver and the auxiliary torque of the electric auxiliary drive is transmitted to the at least one freewheeling rear wheel. If the electric auxiliary drive is deactivated, the torque applied by a driver is not supported by the electric auxiliary drive, but is transmitted via the first gear element via the electric auxiliary drive and the second gear element to the at least one freewheeling rear wheel.

In a further example, the electric auxiliary drive can be arranged on a frame structure of a bicycle, in particular a pedelec in the bottom bracket or between the bottom bracket and the rear axle, the electric auxiliary drive being connected via the first transmission element in order to detect the torque applied by the driver and from it derive or regulate the auxiliary torque according to the invention. The electric auxiliary drive or the control unit can control the auxiliary torque with the desired auxiliary torque by an electrical signal to at least one motor which is arranged on the rear axle or on a free-wheeling rear wheel or on a free-wheeling rear wheel. According to this arrangement, the auxiliary torque is not transmitted by a second transmission element. Furthermore, it is advantageous that the chain, which couples the first transmission element and the bottom bracket, can be made shorter since the distance between the first transmission element and the bottom bracket is shorter compared to an arrangement of the electric auxiliary drive in the rear wheel or on the rear axle. Furthermore, no chain is required to transmit the auxiliary torque to the rear axle, since the auxiliary torque is transmitted to the at least one motor as an electrical signal a bicycle battery can be used. The transmission of the auxiliary torque is transmitted to the at least one motor via the electrical signal.

Furthermore, an electrically operated bicycle, in particular a pedelec or a bicycle ergometer, is proposed, which has an electric auxiliary drive and a battery. The battery is configured to power the electric assist drive.

Based on the determined torque applied by the driver, an auxiliary torque, which is used by the electric auxiliary drive to support the driver, can be provided to the bicycle. This is advantageous for the operation and control of the electric auxiliary drive.

In a further example, the electric auxiliary drive can be used for a bicycle ergometer or home trainer. The driver drives the rotor of the electric auxiliary drive. The control unit is configured in such a way that the pedaling resistance for a user of the bicycle ergometer can be adjusted by changing a magnetic field which is generated by the electric auxiliary drive. In one example, the control unit can be configured to set the current to the rotor windings in such a way as to regulate the strength of the magnetic field. This makes it possible to set or simulate different training intensities. For example, a training can be set in which the driver trains with a constant power (e.g. 150W). In another example, different driving situations such as uphill gradients on mountains, descents or different wind conditions can be simulated by setting the respective pedaling resistance via the control unit. In another example, an additional flywheel mass may be coupled to the rotor to improve the weight distribution of the rotating mass and provide a realistic driving experience.

Further advantages and features of the present invention can be seen from the following description of preferred exemplary embodiments. The features described there can be implemented on their own or in combination with one or more of the features set out above, insofar as the features do not contradict one another. The following description of preferred exemplary embodiments is carried out with reference to the accompanying drawings.

• 1A-1B zeigen eine perspektivische Ansicht und eine Seitenansicht eines erfindungsgemäßen Hilfsantriebs gemäß einer Ausführungsform,
• 2 zeigt eine Schnittansicht des elektrischen Hilfsantriebs gemäß einer Ausführungsform;
• 3A-3B zeigen zwei alternative Ausführungsformen für die Anordnung eines Polrings des erfindungsgemäßen Hilfsantriebs in jeweils einer Schnittansicht, und
• 4 zeigt eine alternative Anordnung des elektrischen Hilfsantriebs an einem Pedelec mit einer zweirädrigen Hinterachse gemäß einer Ausführungsform.

Preferred further embodiments of the invention are explained in more detail by the following description of the figures. show:

• 1A-1B show a perspective view and a side view of an auxiliary drive according to the invention according to one embodiment,
• 2 shows a sectional view of the electric auxiliary drive according to an embodiment;
• 3A-3B show two alternative embodiments for the arrangement of a pole ring of the auxiliary drive according to the invention, each in a sectional view, and
• 4 shows an alternative arrangement of the electric auxiliary drive on a pedelec with a two-wheel rear axle according to one embodiment.

Preferred exemplary embodiments are described below with reference to the figures. Elements that are the same, similar or have the same effect are provided with identical reference symbols in the different figures, and a repeated description of these elements is sometimes dispensed with in order to avoid redundancies.

1A shows a perspective view of the electric auxiliary drive 10. 1B shows a front or rear view of the electric auxiliary drive according to the invention 10.

In a first embodiment, the electric auxiliary drive 10 according to the invention can be arranged directly on a free-wheeling rear wheel (not shown), so that an auxiliary torque can be transmitted via the rotor 14 to the free-wheeling rear wheel. In this embodiment, the torque applied by a cyclist to the pedals and the pedal cranks is transmitted to the rotor 14 via the transmission element 16 . The rotor has a multiplicity of spoke receptacles 141 which connect a rim of the rear wheel (not shown) to the rotor 14 via spokes. The electric auxiliary drive 10 is in this arrangement about a fixed axis 17 (see section view AA in, for example 2 ) designed. The fixed axis 17 can be fixed to a mount, the so-called dropout 19, of the bicycle. As shown here, a cable assembly 21 is provided to provide power to the electric assist drive and to transmit data from the electric assist drive 10 to a cycle computer (not shown). Furthermore, other elements such as a disc for a disc brake can also be fixed to the electric auxiliary drive.

The electric auxiliary drive 10 has a housing 11 with side walls in order to protect the interior of the electric auxiliary drive 10 from environmental influences, in particular moisture and dirt. The rotor 14 and the stator carrier can partially form the housing 11 . As a result, in particular the power electronics and the torque sensor device can be protected from environmental influences by the housing 11 .

The system on which the invention is based generates the control signal for the electric auxiliary drive 10 from the detection of the torque. This makes it possible to dynamically control an electric auxiliary drive 10 in such a way that an auxiliary torque is emitted by the electric auxiliary drive 10 based on the detected torque will. The electric assist drive 10 processes the sensed torque command signal to determine what torque to assist the freewheeling wheel via the rotor 14 to transfer to the freewheeling wheel.

For example, the support of the electric auxiliary drive 10 can be activated with an auxiliary torque when a threshold value of a torque applied by a driver is exceeded. For example, the threshold values can be set in such a way that the electric auxiliary drive supports the driver with an auxiliary torque, so that driving the pedelec in the desired torque range is easy on the driver's joints. Conversely, the support of the electric auxiliary drive 10 can also be deactivated if the torque applied by the driver exceeds a specific threshold value. In addition, the control unit can receive further data from further sensor devices. For example, the control unit can detect the angular velocity and the rotor position of the rotating system from a further sensor device. As a result, the control unit can be configured to regulate power to be output by the electric auxiliary drive. For example, the control unit can be configured in such a way that it does not add more than a power applied and/or adjustable by the driver.

2 shows a sectional view AA of the electric auxiliary drive 10 for a bicycle, in particular a pedelec or for a bicycle ergometer according to a first embodiment. The electric auxiliary drive 10 has a stator 12 and a rotor 14 . The torque applied by a driver can be transmitted to the rotor 14 via the transmission element 16 and a torque transmission element 18 . The transmission element 16 and the torque transmission element 18 are coupled to one another in the axial direction and are arranged coaxially with respect to the axis of rotation D of the rotor 14 . Torque transmission element 18 has at least one magnetostrictive area 181 . Furthermore, the electric auxiliary drive 10 has a sensor device 20 which is configured to measure a torque transmitted to the torque transmission element 18 in the magnetostrictive region 181 of the torque transmission element 18 and to transmit a resulting torque signal to a control unit 34 of the electric auxiliary drive 10, wherein the torque signal corresponds to a torque-induced magnetic flux at the magnetostrictive region 181 . The control unit 34 is configured to determine an auxiliary torque for the driver from the electric auxiliary drive from the torque signal and to control the rotor 14 accordingly. The sensor device 20 is configured to measure the torque-induced magnetic flux on the torque-transmitting element 18 from the outside at the magnetostrictive area 181 of the torque-transmitting element 18 .

Contrary to the solutions known from the prior art, the torque can be measured from the outside on the torque transmission element 18 with such an arrangement. As a result, the assembly of the sensor device 20 can be simplified. It is also advantageous that the sensor device 20 can be arranged directly on a printed circuit board 36 of the electrical auxiliary drive 10 . As a result, complex wiring from the sensor device to the printed circuit board 36 can be avoided, which in turn reduces the assembly effort for the torque measurement.

Due to the direct integration on the rear wheel, the axis 17 of the electric auxiliary drive forms the axis of the free-wheeling wheel at the same time. In addition, the torque-transmitting element 18 and the rotor 14 form the hub of the freewheeling wheel. As a result, the number of components can be reduced and the complexity of the torque measurement can be reduced.

The magnetostrictive region 181 extends at least partially along the outer peripheral surface of the torque-transmitting element 18. The magnetostrictive region 181 can be equipped with an effective uniaxial magnetoelastic anisotropy and magnetically polarized in the circumferential direction, which creates a field that varies with applied mechanical stress from the torque input. When torque is applied to torque-transmitting member 18, the circumferential magnetic orientation at magnetostrictive region 181 is reoriented such that a helical magnetic orientation is created that has both circumferential and axial components.

The sensor device 20 is mounted in such a way that it is responsive to the change in the original orientation of the magnetization. In one example, the sensors of the sensor device 20 can be adjusted in such a way that it measures the axial component of the magnetization in order to determine the magnitude of the torque input therefrom. The change in the axial component is thus proportional to the torque input to the torque transmission element 18, in particular in the magnetostrictive area 181. The arrangement of the sensor device 20 outside of the torque transmission element 18 allows the magnetostrictive area 181 to be on the outer peripheral surface of the torque transmission element 18 are arranged. As a result, the torque-induced magnetic flux can be measured from outside by the sensor device 20 .

The torque transmission element 18 is coupled in a torque-proof manner to the rotor 14 and the transmission element 16 via a freewheel 161 and a freewheel body 162 . The torque transmission element 18 and the transmission element 16 are rotatably mounted on the fixed axle 17 . The rotor 14 thus rotates about the axis of rotation D of the fixed axis 17. The stator 12 is fixed to the fixed axis 17. In the structure according to this invention, the torque applied by a rider via cranks (not shown) which are non-rotatably connected to a front gear (not shown) is introduced via a chain (not shown) and a rear gear 163 which is non-rotatably connected to the Freewheel body 162 is connected, applied to the torque transmission element 18. Torque transmission element 18 is coupled to freewheel body 162 . The pedal cranks together with the gear element 16 form the drive side. The rotor 14 of the electric auxiliary drive 10 forms the output side. The torque transmission element 18 is therefore arranged between the output side and the input side in relation to the power flow.

The control unit 34 is arranged on a circuit board 36 on the stator 12 . The printed circuit board 36 is designed in such a way that it can be arranged around the axis 17 or the torque transmission element 18 . Alternatively, the circuit board 36 can also be designed as a circuit board without recesses and can be arranged, for example, above or below or to the side in relation to the axis. A sensor device 20 is fixed to the printed circuit board 36 transversely to the printed circuit board 36 . At least one magnetic field sensor can be arranged over the outer peripheral surface of the torque transmission element 18 . As a result, a torque-induced magnetic flux in the magnetostrictive region 181 of the torque transmission element 18 can be measured without contact on the outside of the torque transmission element 18 in relation to the axis of rotation D and in the radial direction. The sensors are usually arranged inside a hub of a rear wheel. The signal recorded by the sensors must be transmitted to a control unit with cables. The arrangement of the sensor device 20 according to the invention makes it possible to dispense with signal transmission by means of cables.

According to the 2 In the example shown, the torque transmission element 18 has a hollow shaft 182 and a measuring sleeve 183 which are arranged coaxially with respect to the axis of rotation D of the rotor 14 . The measuring sleeve 183 is arranged on the outside in relation to the hollow shaft 182 and fixed axis 17 and has the magnetostrictive area 181 . The hollow shaft 182 is arranged on the outside in relation to the fixed axle 17 . The hollow shaft 182 is coupled to the transmission element 16 and the measuring sleeve 183 in a torque-proof manner, so that the torque can be transmitted to the measuring sleeve 183 .

The measuring sleeve 183 is therefore to be understood as a separate sleeve which encloses the hollow shaft 182 . With this type of torque transmission element, the circumferential magnetization is only in the measuring sleeve 183 in order to form the magnetostrictive area 181 of the torque transmission element 18 .

The torque is transmitted via the transmission element 16 to the hollow shaft 182 which is coupled to the measuring sleeve 183 in a torque-proof manner. The rotating system thus consists essentially of the gear element 16, the hollow shaft 182, the measuring sleeve 183 and the rotor 14. In other words, the power flow or the torque input runs from the gear element 16 via the hollow shaft 182 and the measuring sleeve 183 to the rotor 14.

For example, the measuring sleeve 183 and the hollow shaft 182 are connected to one another via a fastening element 54, which can have one or more screws or pins. Alternatively, the measuring sleeve 183 and the hollow shaft 182 can be formed integrally. In one example, the torque-transmitting member 18 may be manufactured using forging. The desired circumferential magnetizations for the magnetostrictive region 181 can be achieved, for example, by suitable conditioning of the shaft material, e.g. B. be provided by permanent or current magnets.

The hollow shaft 182 and the measuring sleeve 183 are mounted on the fixed axle 17 via bearings 40 .

When the torque is applied to the measuring sleeve 183, the magnetostrictive area 181 is twisted and the magnetization is therefore changed. The magnetostrictive portion 181 is configured such that the torque applied to the measurement sleeve 183 is transmitted to the magnetostrictive portion 181, which includes at least one magnetically polarized portion. Magnetostrictive region 181 extends at least partially along the outer peripheral surface of measuring sleeve 183.

The sensor device 20 is set such that the torque-induced changes of the magnetization in the magnetostrictive area 181 can be measured. in the in 2 In the example shown, the sensor device 20 is arranged on the stator 12 in a rotationally fixed manner. The sensor device 20 thus has a fixed assignment to the stator 12, the stator 12 having a fixed arrangement to the frame of the bicycle, in particular the pedelec. The sensor device 20 preferably measures the torque-induced magnetic flux at the magnetostrictive region 181 in a contactless manner.

The sensor device 20 has at least one magnetoelastic sensor. This is based on so-called inverse magnetostriction, i.e. the measurement of the change in magnetization due to mechanical stresses as a result of the torsion on the torque transmission element 18 or the measuring sleeve 183.

According to the example shown here, the sensor device 20 and the control unit 34 are connected to a circuit board 36 which is non-rotatably connected to the stator 14 . The stator 12 thus provides the stationary fixation for the control unit 34 of the electric auxiliary drive 10 on the printed circuit board 36 . Thus, the sensor device 20, shown here as a sensor board arranged perpendicularly to the printed circuit board, can advantageously be combined with the control unit 34 to form an assembly. As a result, the mechanical and acoustic engineering structure for the torque measurement can be simplified.

In the example shown here, the rotor 14 has pole heads 142 for magnetic scanning of the stator 12 . Each pole head 142 of the rotor 14 may be provided above a magnetic pole pair 121 of the stator 12 in equal proportions.

Furthermore, the electric auxiliary drive 10 has a torque support element 38 or stator carrier. The torque support element 38 is preferably formed integrally with the stator 12 . The torque support element 38 also acts as a heat sink, which can dissipate the heat of the electric auxiliary drive 10 in an efficient manner. This is advantageous since the magnetic field can be adversely affected if the temperature is too high.

Rear wheel hub motors in particular have an overheating problem at high power outputs or slow speeds. The waste heat from the motor windings and power electronics (especially MOSFETs) leads to high temperatures in the motor if the power output is not regulated. These temperatures can demagnetize the magnets, damage the electronics, splices or press fits and thus impair the function of the motor or put it out of operation altogether.

The cooling of the power electronics (MOSFETs) can thus be ensured via the torque support element 38 as a heat sink and/or via the motor housing.

In 2 A magnetized pole ring 42 according to a first embodiment is shown for measuring the angular velocity of the rotor 14. FIG. The pole ring 42 is arranged coaxially around the axis of rotation D, the pole ring 42 being connected to the measuring sleeve 183 in a rotationally fixed manner in the direction of the side of the transmission element 16 . The measuring sleeve 183 has a portion that extends radially outward with respect to the axis of rotation D and an annular recess to fix the pole ring 42 .

A second sensor device 44 , preferably a Hall sensor, arranged opposite pole ring 42 is arranged on sensor device 20 . The second sensor device 44 is arranged on the sensor circuit board on which the first sensor device 20 is also arranged

The second sensor device 44 is also connected to the control unit 34 in order to detect the position of the pole ring 42 or the rotor 14 by changing the magnetic field emitted by the pole ring 42, preferably without contact. The position of the at least one sensor, preferably a Hall sensor, of second sensor device 44 is matched to the position of magnetized pole ring 42 in such a way that the sensor has the same radial spacing as the poles of pole ring 42 in relation to axis of rotation D. Thus, at least one pole of the pole ring 42 and the sensor face each other at a small distance in the axial direction at the time of the measurement. When the sensor detects that a pole of the pole ring 42 has passed, a position signal is generated, which is transmitted to the control unit 34 via the printed circuit board 36 .

3A shows a pole ring 42 in an electric auxiliary drive 10 according to a second embodiment, the structure of the electric auxiliary drive 10 apart from the alternative arrangement of the pole ring 42 with the in 2 structure shown is identical. In this exemplary embodiment, pole ring 42 is disposed on torque support member 38 . In this case, the torque support element 38 has an annular recess 39 in order to arrange the pole ring 42 coaxially about the axis of rotation D. The sensor, preferably a Hall sensor, is arranged directly on the circuit board 36 . Such an arrangement has the advantage that the pole ring 42 in a simple manner on the stator 12 and the associated Hall sensor can be arranged directly on the printed circuit board 36. The direct arrangement of the sensors of the second sensor device 44 on the circuit board eliminates the need for an additional circuit board to accommodate the sensors, in comparison to the known solutions for measuring the angular velocity at the outer radius of the stator. The sensors of the second sensor device 44 can be soldered, for example, to the printed circuit board 36 of the power electronics. This eliminates the need for cables and/or other connectors. In addition, the components and transmission paths are rigid and firmly installed, which improves the mechanical structure.

3B shows a further alternative arrangement of the pole ring 42. The pole ring 42 is arranged coaxially around the measuring sleeve 183 at one end of the measuring sleeve 183 in the direction of the torque support element 38. The sensor of the second sensor device 44 is arranged on the circuit board 36 . As a result, the pole ring 42 can be attached to the measuring sleeve 183 centrally in relation to the axis of rotation, which enables a compact arrangement of the pole ring 42 with a small diameter and a correspondingly smaller number of pole pairs. As a result, cost-effective production can be achieved.

In the 3A and 3B Arrangements of the second sensor device 44 on the printed circuit board 36 shown have the additional advantage that the pole ring 42 and the second sensor device 44 are spaced apart or shielded from the first sensor device 20, so that the second sensor device 44 and the first sensor device 20 do not interfere with one another. Thereby, the measurement accuracy of the angular velocity of the rotor 14 can be improved.

4 shows an alternative arrangement of the electric auxiliary drive 10. In such an arrangement, the electric auxiliary drive 10 is arranged on a frame arrangement 30 of a bicycle, in particular a pedelec, between the bottom bracket 48 and the rear axle 46. The torque applied by a driver is transmitted to the electric auxiliary drive 10 via the first gear element 16 and to at least one freewheeling rear wheel 52 via a second gear element 28 . In the example shown here, the pedelec has a rear axle 46 with two free-wheeling wheels 52 . In this arrangement, torque is transmitted to the freewheeling rear wheels 52 via the second transmission element 28 and a differential 32 .

As far as applicable, all individual features that are presented in the exemplary embodiments can be combined with one another and/or exchanged without departing from the scope of the invention.

Reference List

10

electric auxiliary drive

11

Housing

12

stator

121

pole pairs of the stator

14

rotor

141

spoke mount

142

Pole heads of the rotor

16

first gear element

161

freewheel

162

freehub body

163

gear

17

fixed axis

18

torque transmission element

181

magnetostrictive area

182

hollow shaft

183

measuring sleeve

19

Bicycle frame dropout

20

first sensor device

21

cable arrangement

22

circuit board

26

torque support element

28

second gear element

30

frame assembly

32

differential

34

control unit

36

circuit board

37

MOSFET circuits

38

torque support element

39

recess

40

warehouse

42

pole ring

44

second sensor device

46

rear axle

48

bottom bracket

52

free wheel

54

fastener

Claims (11)

Electrical auxiliary drive (10) for a bicycle, in particular a pedelec, or for a bicycle ergometer, having a stator (12) and a rotor (14), with a torque applied by a rider being transmitted via a gear element (16) and a torque transmission element (18). can be transmitted to the rotor (14), the transmission element (16) and the torque transmission element (18) being coupled to one another in the axial direction and being arranged coaxially in relation to the axis of rotation of the rotor, the torque transmission element (18) having at least one magnetostrictive region (181 ) has, - a first sensor device (20) which is configured to measure a torque transmitted to the torque transmission element (18) at the magnetostrictive region (181) of the torque transmission element (18) and send a torque signal resulting therefrom to a control unit (34) to transmit the electric auxiliary drive (10), wherein the torque signal rotates a torque induced magnetic flux at the magnetostrictive region (181), wherein the control unit (34) is configured to control from the torque signal an assist torque to the driver from the electric assist drive; characterized in that the first sensor device (20) is configured to measure the torque-induced magnetic flux on the torque-transmitting element (18) from the outside at the magnetostrictive region (181) of the torque-transmitting element (18). Electrical auxiliary drive (10) according to claim 1 , wherein the torque transmission element has a hollow shaft (182) and a measuring sleeve (183) which are arranged coaxially with respect to the axis of rotation (D) of the rotor (14), the measuring sleeve (183) having the magnetostrictive area and with respect to the hollow shaft ( 182) and the axis of rotation (D) is arranged on the outside and the hollow shaft (182) is non-rotatably coupled to the gear element (16) and the measuring sleeve (183), so that the torque can be transmitted to the measuring sleeve (183). Electrical auxiliary drive (10) according to claim 1 or 2 , wherein the first sensor device (20) is arranged in a rotationally fixed manner on the stator (12). Electrical auxiliary drive (10) according to any one of the preceding claims, wherein the first sensor device (20) measures the torque-induced magnetic flux at the magnetostrictive region (181) without contact. Electrical auxiliary drive (10) according to one of the preceding claims, wherein the first sensor device (20) and the control unit (34) are connected to a printed circuit board (36) which is non-rotatably connected to the stator (12). The electric power assist drive (10) of any preceding claim, further comprising a magnetized pole ring (42) to sense rotor position, the pole ring (42) being coaxial about the axis of rotation (D), the magnetized pole ring (42) non-rotatable is connected to the rotor (14) or the torque transmission element (18) or a torque support element (38). Electrical auxiliary drive (10) according to claim 6 , wherein the magnetized pole ring (42) is sprayed on. Electrical auxiliary drive (10) according to one of Claims 6 or 7 , wherein a second sensor device (20) is connected to the control unit (34) in order to detect the position of the pole ring (42) by changing the magnetic field emitted by the pole ring (42), preferably without contact. Electrical auxiliary drive (10) according to one of the preceding claims, wherein the electrical auxiliary drive (10) is arranged directly in a free-wheeling rear wheel of a bicycle, so that an auxiliary torque can be transmitted via the rotor (14) to the free-wheeling rear wheel. Electrical auxiliary drive (10) according to one of Claims 1 - 8th , The electric auxiliary drive (10) being connectable to a second transmission element (28), so that the auxiliary torque can be transmitted to the freewheeling rear wheel via the second transmission element (28). Electrically operated bicycle or a bicycle ergometer having an electrical auxiliary drive (10) according to one of the preceding claims and a battery.

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