DE102022002546B3 - Torque detection device, electric drive and method - Google Patents

Abstract

A torque detection device (108), in particular for an electric drive (100), is presented, comprising a main shaft (114), a main ring (120) which extends around the main shaft (114) at a radial distance from the latter, and a plurality of preferably similar spoke-shaped lamellae (118), which connect the main shaft (114) to the main ring (120) and which are designed to transmit a torque acting on the main shaft (114) to the main ring (120), the slats (118) being proportional to the introduced Torque deform, a toothed disk (122) which is connected to the main shaft (114) and is arranged parallel to the plurality of slats (118), a detection device (124) which is designed to output an electrical signal which varies depending on the Deformation of the slats (118) changes, as well as an evaluation device (126) which is designed to read in the electrical signal, evaluate it and output at least one signal which represents a torque acting on the main shaft (114). Furthermore, an electric drive with such a torque detection device 108 is presented. A method for determining a torque, in particular of an electric drive, is also presented.

Description

Technical area

The present invention relates to a torque detection device, in particular for an electric drive, an electric drive and a method for determining a torque.

State of the art

The use of electric auxiliary drives for vehicles and bicycles, for example city e-bikes, gravel bikes, cargo bikes, S-Pedelecs and Pedelecs, is constantly increasing. In pedelecs or e-bikes, the electric auxiliary drives are usually arranged in the frame, so-called mid-motor, or on the rear wheel hub, so-called rear-wheel hub motor, or on the front wheel hub, so-called front-wheel hub motor. The torque applied by a driver and the angular velocity or cadence are important for controlling an electric auxiliary drive. The recording of the torque and the cadence enables the power applied by the driver to be recorded. In order to harmoniously control an electric auxiliary drive in pedelecs and e-bikes, it is known to record the power provided by the driver and to generate a control request (support of the driver with the electric motor; motor voltage/torque/speed) for the auxiliary drive using a suitable software algorithm.

Torque measurement can be carried out, for example, using sensors based on strain gauges. Using one or more strain gauges attached directly to the shaft, a change in resistance caused by strain is measured on the outer circumferential surface of the shaft with a bridge circuit or other well-known device. However, these are prone to errors due to direct contact with the rotating shaft and usually have a high level of mechanical complexity. The signals are usually transmitted to a control unit through cable arrangements, which makes installation 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 simplified and improved detection of the torque. Magnetostriction is a property of ferromagnetic (e.g. iron-based, magnetizable) materials that allows materials to reversibly change their 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 therefore often easy to manufacture. Such systems are, for example, in the US 2013 / 0 049 444 A1 or the DE 10 2021 000 407 B3 disclosed.

The subsequently published one DE 10 2021 003 644 B3 discloses an electric auxiliary drive for a bicycle with a sensor device which has a magnetostrictive sensor which is positioned and configured in such a way as to measure a torque-induced magnetic flux at the magnetostrictive region in a non-contact manner, the measuring region being designed in particular integrally in the side wall of the rotor.

DE 10 2010 017 851 A1 discloses a torsion module for a torque detection device of a steering system. This allows the torque exerted on the steering wheel in a motor vehicle to be recorded as an input variable for electric power steering systems. The torque detection device has a spoke wheel with an inner ring and an outer ring, between which bending spokes with a spring element are arranged.

Description of the invention

The object of the present invention is to provide a cost-effective and low-maintenance solution for a torque measuring device, particularly suitable for a bicycle, e-bike or pedelec of the generic type, which is improved or at least represents an alternative embodiment. The aim is for the measuring device to also be suitable for cargo bikes, S-Pedelecs or velomobiles, including two-lane vehicles or generally L1e, L2e and L6e.

The task is solved by the subjects of the independent claims. Advantageous developments of the invention are specified in the dependent claims, the description and the accompanying figures. In particular, the independent claims of one claim category can also be developed analogously to the dependent claims of another claim category.

A torque detection device according to the invention has a main shaft, a main ring spaced radially from the main shaft and a plurality of preferably similar spoke-shaped lamellae. The slats are designed to transmit a torque acting on the main shaft to the main ring, whereby the Deform the slats in a predetermined or derivable relationship to the applied torque. The behavior can, for example, be proportional, progressive or degressive, depending on the geometry and material used. So it can also be described with a polynomial. The slats connect the main shaft with the main ring that extends radially around the main shaft. Furthermore, the torque detection device has a toothed disk connected to the main shaft. Furthermore, the torque detection device has a detection device and an evaluation device. The detection device is designed to output an electrical signal which changes depending on the deformation of the slats. The evaluation device is designed to read in the electrical signal, evaluate it and output or provide at least one signal which represents a torque acting on the main shaft.

A main shaft can be understood as a hub. A main ring can be understood as a rim. So you can imagine that, for example, in a bicycle tire, the hub forms a unit with the rim by means of spokes, and in the torque detection device the main shaft (hub) forms a unit with the main ring (rim) by means of the slats (spokes), with the special feature that a torque-dependent deformation of the slats is desired, whereby the deformation can be proportional or directly proportional to the torque introduced. The deformation can also be progressive or degressive in relation to the applied torque. The deformation can be determined mathematically from the applied torque. The toothed washer is aligned transversely to the axis of the main shaft. The toothed disk is thus arranged parallel to the plane of extension of the plurality of slats. The toothed disk can also extend in the same plane as a plurality of preferably similar spoke-shaped lamellas in the spaces between the plurality of spoke-shaped lamellas and can also be formed as a plurality of toothed lamellas. A deformation of the slats that is proportional to the torque introduced can be understood as a deformation that has a predefined ratio of torque to deformation. This can therefore be described mathematically.

The torque detection device is particularly suitable for an electric drive or hybrid drive (electric drive to support muscle power). The electric drive can be a motor for an e-bike, Pedelec cargo bike, S-Pedelec, moped, motorcycle, light motorcycle, velomobile, or even light motor vehicle, including two-lane vehicles or generally L1e, L2e and L6e. The term e-bike (abbreviation for English electric bike, i.e. electric bike) commonly refers to a single-track vehicle with an electric motor, in particular the electric bicycle (a bicycle with an electric auxiliary motor), sometimes also as a pedelec and speed pedelec (S-Pedelec, up to 45 km/h). In a special embodiment, the electric drive can also be an electric drive of a machine.

Drehmoment M (Nm); Drehzahl n (1/s); Leistung P (W); PI = 3,14The torque detection device is also suitable for detecting torques cheaply and accurately in other areas of application in which a measurement of a torque on a rotating body is required. The rotating body does not require any electronics or wireless connection technology with the static sensor (e.g. fork light barrier) to record the torque and speed. The method can generally be used to measure the power of any rotating shaft: $$P=2\cdot PI\cdot M\cdot n$$

Torque M (Nm); speed n (1/s); power P (W); PI = 3.14

Areas of application here are: industrial robots (measurement of torque and angular velocity in the joints), performance measurement of electric motors or combustion engines, torque measurement in automobiles or motorcycles for performance measurement or control of electronic auxiliary systems such as ABS, ASR or torque vectoring.

A number of lamella teeth aligned transversely to the direction of extension of the lamellas are arranged on an end region of the plurality of lamellas facing away radially from the main shaft or on the main ring. Furthermore, a number of reference teeth, which are arranged in the outer edge region of the toothed disk and are aligned transversely to the main extension of the toothed disk, are formed. The lamella teeth can be formed in one piece with the associated lamella or the main ring. The reference teeth can be formed in one piece with the toothed washer. The reference teeth can be arranged on an annular plane extending around the axis of the main shaft and the reference teeth can be arranged on a further annular plane extending around the axis of the main shaft. The annular plane and the further annular plane can be arranged parallel to one another in one plane or preferably in two annular planes spaced apart from one another. The reference teeth are aligned parallel to the lamellar teeth. If the toothed washer is parallel to a plane spanned by the slats is shaped, the number of reference teeth can extend through openings between the slats. The arrangement of the reference teeth and the lamellar teeth in the manner described enables the detection device to make do with a single sensor, such as a fork light barrier, in order to detect a relative displacement of the lamellar teeth to the reference teeth, the relative displacement being directly proportional to deform the slats due to the torque acting on the main shaft.

The number of reference teeth and the number of lamellar teeth can be the same. The number of lamella teeth can also correspond to the number of lamellae. The number of lamella teeth can correspond to an integer multiple of the number of lamellas.

The main shaft, the slats and the main ring can be made in one piece. These can be produced, for example, as a cast part, an injection molded part, a solidly formed component, in an additive manufacturing process or by machining. The toothed washer can also be made. The toothed pulley and the unit consisting of the main shaft, plates and main ring can only be firmly coupled or connected to one another in the area of the main shaft. Alternatively, the main shaft, the slats, the main ring and the toothed washer can be made in one piece. For example, such a unit can be punched out of spring steel or similar, lasered or similarly shaped. In this case, the slats and the spoke-shaped elements of the toothed pulley lie in a plane aligned transversely to the main shaft. The spoke-shaped elements of the toothed pulley are aligned in the direction of the main ring, but are not connected to it. Only when the slats are deformed can the spoke-shaped elements of the toothed disk come into contact, which can provide additional support to absorb the (maximum) torque.

The detection device can have a number of Hall sensors. This means that the detection device can sense without contact and the motor phases can be controlled correctly. This also works when the engine is at a standstill to directly energize the correct phases in order to start the electric motor in an energy-efficient manner. The number can mean one or a plurality. A Hall sensor (also Hall probe or Hall sensor, after Edwin Hall) uses the Hall effect to measure magnetic fields. Hall sensors consist of the thinnest possible, crystalline, doped semiconductor layers that usually have four electrodes on the sides. A current is fed in through the two opposite electrodes; the two electrodes located orthogonally to them serve to decrease the Hall voltage. If a magnetic field running perpendicular to the layer flows through such a Hall sensor, it delivers an output voltage that is proportional to the (signed) amount of the vector product of the magnetic flux density and current. The cause is the Lorentz force on the moving majority charge carriers in the layer. The vector product is proportional to the current, to the charge carrier mobility and inversely proportional to the layer thickness (the thinner the layer, the greater the charge carrier velocity and the Lorentz force). The electric field that develops between the measuring electrodes is in equilibrium with the Hall voltage and prevents further charge carrier separation.

The detection device can have one or a plurality of optical sensors. The optical sensors can be a light barrier or fork light barrier. In optoelectronics, a light barrier is a system that detects the interruption of a light beam and displays it as an electrical signal. In this way, the detection device detects moving objects, i.e. here the reference teeth and the lamella teeth, without contact. Light barriers consist of a light source (the transmitter) and a sensor (the receiver) for this radiation. The light barrier can be a through-beam light barrier, retro-reflective light barrier or a light grid. With through-beam light barriers, the transmitter and receiver face each other. These include fork couplers and fork light barriers, in which the transmitter and receiver are already pre-assembled at a distance of 3-120 mm from each other. With a retro-reflective light barrier, the transmitter and receiver are located parallel to each other in a common housing. With retro-reflective sensors, the light signal is reflected back at a reflector on the opposite side. Small retro-reflective photoelectric sensors are also known as reflex couplers; they often work with reflective, self-adhesive film marks on moving parts. The light signal is reflected back via the object to be detected. The switching distance therefore depends on the reflection properties of the object surface. Here too, the transmitter and receiver are located parallel to each other in a common housing. In addition to the simple versions with just one light beam, there are also so-called light grids or light curtains that work with several parallel light beams.

Electric motors can be controlled using Hall sensors. This begins from a standstill in which the switching state is returned to the status of the (three) motor phases via the Hall sensor can be closed. The motor phases (usually called UVW in German or ABC in English) are then controlled by the motor controller so that the electric motor begins to rotate.

The use of the optical sensors in combination with the design of the teeth that correctly matches the number of poles of the motor brings the following advantages: No Hall sensors have to be placed on the outside of the stator between the electrical sheet teeth. A challenge is the wiring past the windings to the controller or motor cable out of the motor for an external controller. These cables could become damaged and disable the engine. Furthermore, conventional Hall sensors are located at the hottest point of an electric motor and can be thermally destroyed when the motor is under high load. The use of optical sensors with a suitable toothed pulley can happen outside the thermally hottest point of the engine. This means that the influence of temperature is no longer relevant and the motor can be operated with higher performance. There is also no need to install additional cables or circuit boards for the conventional Hall sensors. Optionally, the optical sensors can be installed on the same board as an internal motor controller in order to create the cheapest, fail-safe electric motor possible.

The detection device can have a plurality of sensors, in particular Hall sensors or optical sensors such as light barriers, and the evaluation device can be designed, in addition to the sensor signal, which represents the torque acting on the main shaft, at least one representing the direction of rotation and, in addition or alternatively, the speed of rotation To output signal or signals. The detection device can therefore not only detect the torque, but also the direction of rotation and, additionally or alternatively, the speed of rotation. In this way, the evaluation device or in particular a downstream control device can be supplied with further information and the control can thus be optimized.

The detection device can be designed to determine a zero crossing of the main wave. An additional sensor can be provided for this purpose. Alternatively or additionally, the zero crossing can be detected through a special design (different width of the teeth) of individual reference teeth and/or lamellar teeth and a corresponding signal evaluation. Optionally, the two methods can also be combined to create redundancy and thus increase reliability.

The slats can have a thickness in the circumferential direction of less than 8 mm, in particular less than 5 mm, in particular less than 3 mm, in particular less than 2 mm. This can describe the minimum thickness in the circumferential direction. The thickness can vary in the radial direction. In this way, the bending characteristic and the fatigue strength can be optimized. With the same goal and also to optimize weight, additional recesses such as holes or similar can be provided.

The slats can have different thicknesses in their radial extent. The slats can be made thinner in a central area than in the end areas. The slats can each have a thickness in the middle region that is at least 20%, particularly advantageously at least 25%, reduced than an average thickness in the end regions. In this way, optimal deformation can be achieved while at the same time optimizing strength (for transmitting torque) and long-term load capacity.

At least one stop can be provided, which limits the deformation of the slats and transmits a torque that exceeds the limited deformation to the main ring by means of positive locking. A plurality of stops can be provided. In particular, one stop can be provided for each slat. The stops can be shaped in such a way that at least 50%, in particular at least 80%, of the longitudinal extent of the respective assigned lamella rests on a stop surface of the respective stop. This means that the slats can be supported from a defined maximum torque. In this way, a torque that exceeds the defined maximum torque can also be transmitted without overloading the torque detection device.

The evaluation device can be set up to calibrate the read-in electrical signal. For this purpose, information about the zero crossing can be evaluated. In this way, an offset at zero crossing can be determined and this can be subtracted from the signal to be calibrated. Alternatively, a complete signal curve of a complete revolution can also be used for calibration. A lookup table or a calibration signal or calibration signal curve can be determined and saved in order to subsequently continuously calibrate the electrical signal of the detection device. The signal representing torque acting on the main shaft can be determined using the calibrated signal.

An electric drive, especially for a vehicle such as a bicycle, a pede lec, S-Pedelec or a light motor vehicle, has a stator and a rotor, with a torque applied by a driver of the vehicle being transferable to the rotor via a gear element. A variant of a previously described torque detection device is provided. Furthermore, the electric drive has a control device which is designed to control an auxiliary torque for the driver from the electric drive depending on the torque signal.

The main ring and the large number of particularly similar spoke-shaped lamellas can be part of the rotor shaped as a rotor bell. This saves parts and simplifies assembly.

A method for determining a torque, in particular of an electric drive, has at least the steps of sensing, providing and evaluating. In the sensing step, an angular displacement relative to a torque is sensed and an electrical signal representing the angular displacement and thus the torque is provided at an interface. The torque acts on a main shaft, which is connected via a plurality of preferably similar spoke-shaped lamellas to a main ring, which is arranged at a radial distance from the main shaft and extending around it. The slats are designed to transmit a torque acting on the main shaft to the main ring. The slats deform in proportion to the applied torque. In the providing step, the electrical signal generated in the sensing step is provided at an interface. In the step of evaluating the electrical signal, this is read in by the interface and evaluated in an evaluation device. At least one signal is determined which represents the torque acting on the main shaft. This is provided at an output so that it can be read by a control device and used to control, in particular, an electric drive.

In an optional calibration step, the electrical signal can be calibrated to a zero point, in particular using a zero crossing. The torque acting on the main shaft can be determined in the evaluating step using the calibrated signal.

Using the electrical signal and additionally or alternatively using the calibrated signal, an angular velocity of the main shaft and additionally or alternatively a direction of rotation can be determined.

Short character description

• 1 eine offene Darstellung eines elektrischen Antriebs gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 2 eine isometrische Darstellung eines elektrischen Antriebs gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 3 Teile einer Drehmomenterfassungseinrichtung gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 4 eine Drehmomenterfassungseinrichtung gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 5 - 7 jeweils einen Ausschnitt einer Drehmomenterfassungseinrichtung gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 8 - 13 jeweils eine Drehmomenterfassungseinrichtung (ohne Erfassungs- und Auswerteeinrichtung) gemäß Ausführungsbeispielen der vorliegenden Erfindung;
• 14 einen Ausschnitt einer Drehmomenterfassungseinrichtung gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 15 ein Ablaufdiagramm eines erfindungsgemäßen Verfahrens gemäß einem Ausführungsbeispiel der vorliegenden Erfindung; und
• 16 Signalverläufe eines elektrischen Signals und eines kalibrierten Signals gemäß einem Ausführungsbeispiel der vorliegenden Erfindung.

The inventive idea will be described in more detail below with reference to the figures. However, the following description is to be viewed as purely an example. The invention is determined solely by the subject matter of the claims. Advantageous exemplary embodiments of the invention are explained below with reference to the accompanying figures. The same reference numbers are used for elements that are the same or have the same effect. Furthermore, for the sake of easier readability and assignment, reference numbers are also used for features if they are not shown in the figure described. Also, not all reference symbols are always shown in similar figures if these features are already clearly designated from the previous figures. Show it:

• 1 an open representation of an electric drive according to an embodiment of the present invention;
• 2 an isometric view of an electric drive according to an embodiment of the present invention;
• 3 Parts of a torque detection device according to an embodiment of the present invention;
• 4 a torque detection device according to an embodiment of the present invention;
• 5 - 7 each a section of a torque detection device according to an exemplary embodiment of the present invention;
• 8th - 13 each a torque detection device (without detection and evaluation device) according to exemplary embodiments of the present invention;
• 14 a section of a torque detection device according to an exemplary embodiment of the present invention;
• 15 a flowchart of a method according to the invention according to an exemplary embodiment of the present invention; and
• 16 Signal curves of an electrical signal and a calibrated signal according to an exemplary embodiment of the present invention.

Detailed description of the figures and description of the invention

There are different ways to measure torque on rotating components. The torque detection device shown here shows torque measurements on a rotating component, with the detection electronics (detection device possibly integrated with the evaluation device) remaining static. Advantageously, no slip ring or wireless transmission and energy supply are necessary when the electronics rotate. The torque detection device follows the basic idea of two toothed disks, with one toothed disk deforming flexibly to the other toothed disk with increasing torque. This changes the tooth spacing, which can preferably be detected via an optical sensor (e.g. fork light barrier, but also inductively with less accuracy and at the same time less sensitivity to dirt) with a high detection rate using state-of-the-art microcontrollers (the microcontroller can also be used as an A/D converter; a dedicated A/D converter can also be used for increased accuracy). The displacement of the teeth lying one above the other or next to one another is recorded as a duty cycle by the sensor (detection device) and is proportional to the torque applied. The duty cycle (duty cycle) indicates the ratio of the pulse duration to the period length for a periodic sequence of pulses according to standardization. The duty cycle is specified as a ratio of the number dimension with a value range of 0 to 1 or 0 to 100%. In this case, the duty cycle is independent of the rotation speed.

Such a torque detection device is suitable for all technical challenges in which torques of rotating components must be recorded cheaply and efficiently with static electronics, such as e-bike motors, both hub motors (direct rotor or geared motors) and mid-mounted motors of any design. Use is also generally conceivable in mechanical engineering, for measuring torque (e.g. for precise performance determination or service life recording) of torque-loaded components.

Previously more expensive and complex torque measurements on rotating components can be realized more simply and cost-effectively with the described torque detection device. The torque detection device can also potentially detect torques of 0 to 2,500 Nm at speeds of 0 to 15,000 rpm (revolutions per minute), depending on the design of the sensor. In one variant, for example, it can be 400 Nm and 500 rpm. The torque detection device can also be equipped with two to three additional tracks and adopt the functionality of common Hall sensors in electric motors or be used instead of them.

As explained, the described torque detection device can be used as a torque sensor system in e-bike motors, or to control the motor support by measuring the torque applied by the driver.

The basic idea for the torque detection device consists of the arrangement of the toothed disks, including the use of the toothed disk or the lamellas as a reinforcing pointer for the torque detection. The use of just one fork light barrier (it also works with two separate paths that deform relative to each other) to measure the torque via the displacement of the teeth relative to each other. The torque is measured as a duty cycle and is proportional to the torque applied.

The sensor works with metallic alloys (aluminum, steel, etc.) as well as with all plastics. Even a design made of wooden components, CFRP or ceramic materials is possible. This results in a particularly wide range of applications.

1 shows a partial exploded view of an electric drive 100 according to an exemplary embodiment of the present invention. The electric drive 100 for a bicycle or cargo bike has a stator 102 and a rotor 104. In comparison to a standard electric drive, the electric drive shown here is set up to transmit a torque applied by a driver to the rotor 104 via a gear element 106. The stator 102 has slots and windings. The power electronics (evaluation device 108 and control device 110 are arranged inside the motor (electric drive 100). Also not visible is the one torque detection device 108, which provides its corresponding signal (representing the torque) to the power electronics. The control device 110 is designed to be a To control auxiliary torque for the driver depending on the torque signal. The rotor 104 is designed as a rotor bell 112 with magnets.

The in 1 Electric drive 100 already shown is in 2a shown closed as a wheel hub motor with cassette drive. The rotor bell 112 rotates about the fixed wheel hub axis 116. The casing rotates about the wheel hub axis 116 The cassette holder represents the main shaft 114. A gear element 106, not shown (in the form of a pinion), can be plugged onto the cassette holder in order to transfer the torque applied by the driver of the e-bike (from the crank via a chain or a belt) to the wheel hub motor transmitted.

2 B and 2c show two different exemplary embodiments as an exploded view, 2d and 2e each show a sectional view.

3 shows main shaft 114, plates 118, main ring 120, toothed washer 122, plate teeth 128 and reference teeth 130 of a torque detection device according to an exemplary embodiment of the present invention in a one-piece version. The toothed washer 122 corresponds to the main shaft 114, on which the reference teeth 130 are arranged directly. The slats 118 are created by cutting out a trapezoid (elongated recess in the radial direction with a small recess transverse to it at the outer end in the circumferential direction, the recesses being slot-shaped). The disk teeth 128 are arranged on the main ring 120, ie radially on the outside of the disk. Slat teeth 128 and reference teeth 130 are arranged parallel to one another and transversely to the main extension surface of the slats 118. In this exemplary embodiment, a large fork light barrier is used, so that the teeth 128, 130 that belong to one another (ie lying in a radial straight line) run within the fork light barrier when the disk rotates. The disadvantage of the large fork light barrier is offset by the manufacturing advantage, especially if the teeth 128, 130 are produced by stamping and bending. This means that the integrated component can be completely manufactured in one stamping and bending step.

4 shows a torque detection device according to an embodiment of the present invention. The toothed disk 122 is arranged parallel (in the picture behind) the slats 118 or a plane spanned by the slats 118. The plate teeth 128 and the reference teeth 130 are arranged in pairs at a short distance from one another; the arrangement is clearer than the one below 5 refer to. The reference teeth 130 extend through the openings between two adjacent slats 118.

Each plate tooth 128 and an associated reference tooth 130 are arranged in pairs. The disk tooth 128 is arranged further outwards, viewed radially from the main shaft 114. In the radial direction there is a transmitter 125a (located below in the picture and therefore closer to the shaft) and on the opposite side, so to speak after the teeth (lamella teeth 128, reference teeth 130) or located radially on the outside, there is a receiver 125b of a detection device 124 or .A light barrier 125 (as part of the detection device 124) is arranged. When the teeth 128, 130 rotate, first one of the two teeth and then at the end the other tooth covers the beam of the light barrier. The overlap area varies and therefore the duty cycle varies.

The two rows of teeth (the number of reference teeth 130 and the number of lamellar teeth 128) are aligned between the redundant two (or more) pieces of fork light barriers 125 (as a detection device 124) and thus always rotate through the light barrier 125. The inner toothed disk 122 is amplified like a pointer on a measuring instrument. The overlap is important for compensating for manufacturing tolerances in the case of teeth that are not perfectly manufactured, so that only one edge of each tooth 128, 130 is visible to the sensor 125. The front edge of one of the teeth as it passes through the sensor 125 and the rear edge of the other tooth are relevant for the sensor.

In 6 the detection device 124 with a light barrier 125 can be seen in section. The light barrier 125 is arranged on a circuit board on which a second light barrier is also arranged at a distance from the first light barrier. If the distance does not exactly match the distance between the teeth 128, 130, a direction of rotation can already be calculated from the two signals. The reliability of the sensor can also be increased by a plurality of sensors 125 and the redundancy created in this way, and the torque detection device 108 can thus become more robust. The evaluation device 126 can be arranged on the same circuit board 134. A microcontroller on the circuit board 134 can also take over the tasks of the detection device 124 and the evaluation device 126.

In 7 one can see that the toothed washer 122 is coupled or connected to the unit consisting of the main shaft 114, the plurality of disks 118 and the main ring 120 in the area of the main shaft 114, but does not undergo any deformation due to a torque acting on the main shaft 114.

8th and 9 show the same exemplary embodiment, once in the unloaded state and once in the loaded state. In the unloaded state, as in 8th is shown, the slats are aligned straight in the radial direction. When a torque acts on the torque detection device 108, the slats 118 deform as shown in 9 is visible. On the Toothed disk 122, stops 132 are formed, which extend into the space between two slats 118. A stop surface of the stop 132 facing the assigned lamella 118 is curved and thus corresponds to the deformation of the lamella 118 at the maximum load at the end of the measuring range, for example 100 Nm. At a higher load, the slats 118 are no longer deformed; the torque is supported by means of the stop 132 or the stops 132.

The stop 132 could also be shaped differently, for example between the toothed disk 122 and the main ring 120, so that a torque could then also be transmitted directly to the main ring 120 via the toothed disk 122. Other alternatives are conceivable. It is always about supporting the slats so that they only deform elastically, do not undergo plastic deformation and are loaded above the tensile load limit.

10 shows a variant that is made from a spring steel sheet. The slats 118 and the toothed disk 122 are arranged in one plane. In this exemplary embodiment, the toothed disk 122 consists of slats or spokes, which are not attached to the main ring 120 and therefore ideally do not experience any deformation, except after the maximum measuring range. Once this is achieved, the slats or spokes of the toothed disk 122 can also support the main ring 120. A two-part design with two disks arranged in parallel is also conceivable. Also that in 11 The exemplary embodiment shown follows this idea. Alternating slats are formed, with a connection to the main ring (then these are slats 118) and in which there is no connection to the main ring 120 (then these are part of the toothed washer 122). The detection device 124 is set up to detect a relative movement of the two different slats. This way the effective torque can be determined.

12 and 13 show further alternative embodiments according to the present invention.

14 shows a variant with additional rows of teeth. Through a special arrangement of the teeth, additional information can be recorded with the fork light barriers 125 and the downstream signal evaluation.

15 shows a flowchart of a method according to an exemplary embodiment of the present invention. The process includes at least three process steps. In the first step S1 of sensing, an angular displacement relative to a torque is sensed and an electrical signal representing the angular displacement and thus the torque is generated, which is provided in the second step S2. In the third step S3 of evaluating the electrical signal, the electrical signal is read in at an interface of an evaluation device 126, evaluated in the evaluation device and at least one signal is output which represents the torque acting on the main shaft. In 16 Corresponding signals representing the torque are shown. This shows 16a an uncalibrated signal from a large number of revolutions. Both an offset and a crank revolution are visible. In 16b the signal is calibrated. For this purpose, the torque detection device has an additional device that detects a zero crossing of the main shaft. This can be done via a special design of the teeth 128, 130 or preferably via an additional sensor. This can be, for example, a Hall sensor or an optical sensor. With the additional information about the zero crossing, the signal can be easily calibrated. A human rider typically does not produce constant torque, even when using special bicycle pedals connected to the rider's shoe (so-called click pedals). Since a higher torque can be generated in the downward movement than in the horizontal movement, the torque signal looks similar to a sine wave. You can see four crank revolutions with a constant force or torque, then a strong increase in torque, which then drops slightly for the next three crank revolutions. The signal can then be further processed for the control device, for example subjected to smoothing, so that the controlled motor drives the bicycle evenly.

Reference symbol list

100

Electric drive, wheel hub motor

102

stator

104

rotor

106

Gear element

108

Torque detection device

110

Control device

112

Rotor bell

114

Main shaft, cassette holder

116

Wheel hub axle

118

slats

120

main ring

122

toothed washer

124

Detection device

125

Light barrier, fork light barrier

125a

Light barrier transmitter

125b

Receiver of the light barrier

126

Evaluation device

128

Lamellar teeth

130

Reference teeth

132

attack

134

circuit board

S1 to S3

Procedural steps

Claims (15)

Torque detection device (108), in particular for an electric drive (100), having - a main shaft (114), - a main ring (120), which extends around the main shaft (114) at a radial distance from it, - a plurality of preferably similar spoke-shaped slats (118), which connect the main shaft (114) to the main ring (120) and which are designed to transmit a torque acting on the main shaft (114) to the main ring (120), whereby deform the slats (118) in a predeterminable manner to the applied torque, - a toothed disk (122) which is connected to the main shaft (114) and is arranged parallel to the plurality of slats (118), - a detection device (124) which is designed to output an electrical signal which changes depending on the deformation of the slats (118), - an evaluation device (126) which is designed to read in the electrical signal, evaluate it and output at least one signal which represents a torque acting on the main shaft (114), whereby - a number of lamella teeth (128) aligned transversely to the direction of extension of the lamellae (118) are arranged on an end region of the plurality of lamellas (118) facing away radially from the main shaft (114) or on the main ring (120), and - a number of reference teeth (130) which are arranged in the outer edge region of the toothed disk (122) and are aligned transversely to the main extension of the toothed disk (122), - The reference teeth (130) are aligned parallel to the plate teeth (128). Torque detection device (108) according to the preceding claim, wherein - The number of reference teeth (130) extend through openings between the slats (118). Torque detection device (108) according to one of the preceding claims, wherein the detection device (124) has a number of Hall sensors. Torque detection device (108) according to one of Claims 1 or 2 , wherein the detection device (124) has an optical sensor or a plurality of optical sensors, in particular light barriers. Torque detection device (108) according to one of the preceding claims, wherein the detection device (124) has a plurality of sensors and the evaluation device (126) is designed to provide at least one sensor signal representing the direction of rotation and/or the torque acting on the main shaft (114). Output signal representing rotational speed. Torque detection device (108) according to one of the preceding claims, wherein the detection device (124) is designed to determine a zero crossing of the main shaft (114), in particular by means of an additional sensor and/or by a special design of individual reference teeth (130) and/or or lamellar teeth (128). Torque detection device (108) according to one of the preceding claims, wherein the slats (118) have a thickness in the circumferential direction of less than 8 mm, in particular less than 5 mm, in particular less than 3 mm, in particular less than 2 mm. Torque detection device (108) according to the preceding claim, wherein the slats (118) have a different thickness in the radial extent, are in particular thinner in a central region than in the end regions, in particular in the central region have a thickness reduced by at least 20% than a middle one Thickness in the end areas. Torque detection device (108) according to one of the preceding claims, wherein at least one stop (132) is provided which limits the deformation of the slats (118) and transmits a torque that exceeds the limited deformation to the main ring (120) by means of positive locking, in particular where a stop (132) is provided for each slat and the stops (132) are shaped in such a way that at least 50% of the Longitudinal extension of the respective assigned lamella rests on a stop surface of the respective stop (132). Torque detection device (108) according to one of the preceding claims, wherein the evaluation device (126) is set up to calibrate the read-in electrical signal, in particular using the zero crossing, and the signal representing the torque acting on the main shaft (114) using the calibrated signal determine. Electric drive (100), in particular for a vehicle such as a bicycle, a Pedelec, an S-Pedelec or a light motor vehicle - a stator (102) and a rotor (104), wherein a torque applied by a driver can be transmitted to the rotor (104) via a gear element (16), - A torque detection device (108) according to one of the preceding claims. - A control device (110), which is designed to control an auxiliary torque for the driver from the electric drive (100) depending on the torque signal. Electric drive (100) according to the preceding claim, wherein the main ring (120) and the plurality of, in particular, similar spoke-shaped slats (118) are part of the rotor (104) shaped as a rotor bell (112). Method for determining a torque, in particular of an electric drive (100), comprising at least the following steps: a) Sensing (S1) an angular displacement relative to a torque and providing an electrical signal representing the angular displacement and thus the torque, the torque acting on a main shaft (114) which has a plurality of preferably similar spoke-shaped slats (118). radially spaced from the main shaft (114) and connected to the main ring (120) extending around it, the slats (118) being designed to transmit a torque acting on the main shaft (114) to the main ring (120), and wherein the Deform the slats (118) in proportion to the torque introduced, with a number of slat teeth (128) aligned transversely to the direction of extension of the slats (118) on an end region of the plurality of slats (118) facing away radially from the main shaft (114) or on the main ring (120). are arranged, and a number of reference teeth (130) which are arranged in the outer edge region of the toothed disk (122) and are aligned transversely to the main extension of the toothed disk (122), the reference teeth (130) being parallel to the lamellar teeth (128) are aligned, b) providing (S2) the electrical signal, and c) evaluating (S3) the electrical signal, wherein the electrical signal is read in at an interface of an evaluation device (126), is evaluated in the evaluation device (126) and at least one signal is output which represents the torque acting on the main shaft (114). represented. Method according to the preceding claim, with a step of calibrating, in which the electrical signal is calibrated to a zero point, in particular using a zero crossing, and wherein the torque acting on the main shaft (114) in the step of evaluating (S3) using the calibrated signal is determined. Method according to one of the two preceding claims, wherein an angular velocity of the main shaft (114) is determined using the electrical signal and/or the calibrated signal.

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