Electric vehicle, and method of controlling electric vehicle

Abstract

An electric vehicle (10a; 10b) comprising an annular wheel (12, 14) rotatable around a rotation axis (26) an annular support element (46) enclosing the rotation axis (26) and supporting the wheel (12, 14) radially inside of the wheel (12, 14) with respect to the rotation axis (26); and a plurality of electric motors (44) supported on the support element (46) offset from the rotation axis (26) and positioned radially inside of the wheel (12, 14) with respect to the rotation axis (26), each electric motor (44) being arranged to directly drive the wheel (12, 14). A method of controlling an electric vehicle (10a; 10b) is also provided.

Description

[0001] ELECTRIC VEHICLE, AND METHOD OF CONTROLLING

[0002] ELECTRIC VEHICLE

[0003] Technical Field

[0004] The present disclosure generally relates to electric vehicles. In particular, an electric vehicle comprising an annular support element and a plurality of electric motors directly driving an annular wheel, such electric vehicle in the form of an electric bicycle, and a method of controlling an electric vehicle, are provided.

[0005] Background

[0006] Electric bicycles typically have wheels supported via spokes on central hubs. The spokes and hubs occupy the centers of the wheels. Moreover, the spokes may pose a danger to the driver when the wheels rotate.

[0007] DE 202010012992 Ui discloses a hubless electric bicycle comprising an electric motor with a drive roller or a drive gear on a drive shaft. The drive roller or drive gear transmits engine torque to a wheel.

[0008] Summary

[0009] One object of the invention is to provide an improved electric vehicle.

[0010] A further object of the invention is to provide an improved method of controlling an electric vehicle.

[0011] These objects are achieved by the electric vehicle according to appended claim 1 and by the method according to appended claim 22.

[0012] The invention is based on the realization that by providing a plurality of electric motors inside of a hubless wheel of an electric vehicle to directly drive the wheel, a design of the electric vehicle can be made more slim and the electric vehicle can be driven in a more agile, reliable and efficient manner. The term plurality refers to at least two.

[0013] According to a first aspect, there is provided an electric vehicle comprising an annular wheel rotatable around a rotation axis; an annular support element enclosing the rotation axis and supporting the wheel radially inside of the wheel with respect to the rotation axis; and a plurality of electric motors supported on the support element offset from the rotation axis and positioned radially inside of the wheel with respect to the rotation axis, each electric motor being arranged to directly drive the wheel.

[0014] The provision of a plurality of electric motors to independently drive each wheel directly has been found to have several advantages. This enables resting one electric motor at light driving conditions of the electric vehicle which in turn allows the resting electric motor to cool. In this manner, the lifetime of the electric motors can be increased. The electric motors can be controlled to operate alone or in combination to provide an optimal drive of the wheel for a wide range of driving conditions. The electric motors may be driven simultaneously at heavier driving conditions, such as when driving uphill, and can then be driven one at a time at lighter driving conditions.

[0015] Moreover, since a plurality of electric motors are used, a rating of each electric motor can be lower in comparison with an electric motor used as an only motor to potentially drive the wheel. This in combination with the direct drive of the wheel by each electric motor enables a very slim design of the electric vehicle.

[0016] Since the wheel is annular and supported by the annular support element, the wheel may be referred to as a hubless or centerless wheel. The wheel is not connected to a central hub provided at the rotation axis. Thus, the wheel does also not comprise any spokes. Since both the wheel and the support element are annular, and thereby also hollow, an empty central space is provided at the rotation axis. This space can be utilized for a wide range of purposes, including storage. For example, shopping bags maybe carried inside of the wheel. Alternatively, or in addition, an electric energy storage for the electric vehicle, such as a battery, may be carried inside of the wheel. Such energy storage may be an auxiliary energy storage in addition to an already existing energy storage of the electric vehicle.

[0017] For each wheel, the electric vehicle may comprise a cover, such as an annular cover. The cover may protect and cover the support element and the electric motors. The electric vehicle may comprise two wheels and corresponding support elements and electric motors for each wheel. The cover may be fixed to the support element.

[0018] Each electric motor may have a gear ratio to the wheel of at least 5:1, such as at least 7:1. In cases where the gear ratio is 5:1, the electric motor rotates five turns during one turn of the wheel.

[0019] Each electric motor may be positioned radially within the support element with respect to the rotation axis. Thus, the support element may extend radially outside of the electric motors and radially inside of the electric motors with respect to the rotation axis.

[0020] Two adjacent electric motors maybe angularly spaced from each other with an angle of at least 60 degrees with respect to the rotation axis. According to one variant, all electric motors arranged to drive the wheel are substantially evenly distributed angularly, or evenly distributed angularly, with respect to the rotation axis.

[0021] Two electric motors of the plurality of electric motors may be positioned below a horizontal center line of the wheel. By positioning the electric motors below the horizontal center line, an efficiency of the electric motors can be increased since a play between an electric motor and the wheel will be smaller below the horizontal center line than above the horizontal center line due to gravity.

[0022] The electric vehicle may further comprise an electronic control system configured to control the electric motors in an alternating manner to drive the wheel. Thus, during operation of the electric vehicle, the control system may control the electric motors such that only a first group of the plurality of motors drives the wheel for a first time period, and such that only a second group of the plurality of motors, different from the first group, drives the wheel for a second time period, e.g., following the first time period. Each group of electric motors may comprise one, several or all of the electric motors. The electric motors can thus be controlled in an alternating manner by the control system to drive the wheel.

[0023] The control system may comprise at least one data processing device and at least one memory having at least one computer program stored therein, the at least one computer program comprising program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform, or command performance of, various operations as described herein, such as to control the electric motors in an alternating manner.

[0024] The plurality of electric motors may include three electric motors. For example, in cases where the electric vehicle comprises three electric motors associated with each wheel, the three electric motors may be angularly spaced from each other at an angle of 120 degrees with respect to the rotation axis. In cases where the electric vehicle comprises four or six electric motors associated with each wheel, the four or six electric motors may be angularly spaced from each other at an angle of 90 degrees or 60 degrees, respectively, with respect to the rotation axis.

[0025] An inner radius of the support element with respect to the rotation axis may be at least 50 %, such as at least 65 %, of an outer radius of the wheel with respect to the rotation axis.

[0026] Each electric motor may comprise a stator and a rotor. In these cases, each stator may be fixed to the support element. The rotor may be rotatable about a rotor axis parallel with the rotation axis. The wheel may comprise a toothed element. In these cases, each electric motor associated with the wheel may directly drive the toothed element. The toothed element may comprise, or be constituted by, a timing belt. Alternatively, or in addition, the toothed element may be mainly composed of rubber or polymers, such as nylon plastic. The toothed element may be injection molded.

[0027] In addition to the toothed element, the wheel may comprise a rim. The toothed element may be secured to the rim. The wheel may also comprise a tire defining the outer radius of the wheel. The toothed element may comprise a toothed track concentric with the rotation axis. In these cases, each rotor may comprise a rotor gear meshing with the toothed track. The rotor gear may be injection molded.

[0028] The toothed element may comprise a first bearing track and a second bearing track, each concentric with the rotation axis. In these cases, the toothed track may be positioned between the first and second bearing tracks.

[0029] Alternatively, the direct drive could be provided in other ways than through the use of a toothed element, for example through friction or magnetism.

[0030] The electric vehicle may further comprise a plurality of bearings mechanically between the support element and the wheel for supporting rotation of the wheel around the rotation axis. The electric vehicle may for example comprise at least three bearings, such as three sets of bearings angularly spaced from each other with an angle of 120 degrees with respect to the rotation axis, four sets of bearings angularly spaced from each other with an angle of 90 degrees with respect to the rotation axis, or six sets of bearings angularly spaced from each other with an angle of 60 degrees with respect to the rotation axis. In any case, each set of bearings may comprise one or two bearings. Two bearings of a set may be concentric with each other.

[0031] At least one of the bearings may engage the first bearing track and at least one of the bearings may engage the second bearing track. The bearings may be rolling-element bearings.

[0032] Each electric motor may be an outrunner. Thus the rotor may be positioned radially outside of the stator with respect to the rotor axis.

[0033] The support element may comprise a truss structure. The truss structure may provide an optimized strength for a given mass. The truss structure may for example be provided in a disc, e.g., by cutting out material from a solid disc, e.g., by laser. According to some examples, each support element comprises two discs offset from each other along the rotation axis, e.g., parallel with each other. Each electric motor and each bearing may be positioned partly or entirely between the discs. The discs may be flat or conical. The truss structure may be provided in one or both of the discs.

[0034] The support element may be made of metal, such as steel. Each disc may have a thickness of at least 3 mm.

[0035] The support element may comprise a plurality of motor openings. In these cases, each electric motor may be received in one of the motor openings.

[0036] The support element may comprise a plurality of triangular openings.

[0037] The electric vehicle may further comprise a light source fixed to the support element, e.g., fixed to the cover which in turn is fixed to the support element.

[0038] The electric vehicle may be an electric bicycle. As some conceivable alternatives, the electric vehicle may be moped or motorbike.

[0039] According to a second aspect, there is provided a method of controlling an electric vehicle, the method comprising providing an electric vehicle according to the first aspect, where the electric vehicle comprises the control system and a plurality of electric motors arranged to directly drive the wheel; and controlling, by the control system, the electric motors in an alternating manner to drive the wheel. Brief Description of the Drawings

[0040] Further details, advantages and aspects of the present disclosure will become apparent from the following description taken in conjunction with the drawings, wherein:

[0041] Fig. i: schematically represents a perspective side view of an electric bicycle;

[0042] Fig. 2: schematically represents a partial side view of the electric bicycle;

[0043] Fig. 3: schematically represents a partial perspective view of an annular support element of the electric bicycle;

[0044] Fig. 4: schematically represents a perspective view of the support element;

[0045] Fig. 5: schematically represents a partial perspective cross-sectional view of a toothed element of the electric bicycle;

[0046] Fig. 6: schematically represents further a partial side view of the electric bicycle;

[0047] Fig. 7: schematically represents a partial perspective view of the electric bicycle;

[0048] Fig. 8: schematically represents a partial side view of an electric bicycle according to a further example; and

[0049] Fig. 9: is a flowchart outlining general steps of a method.

[0050] Detailed Description

[0051] In the following, an electric vehicle comprising an annular support element and a plurality of electric motors directly driving an annular wheel, such electric vehicle in the form of an electric bicycle, and a method of controlling an electric vehicle, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

[0052] Fig. 1 schematically represents a perspective side view of an electric bicycle 10a according to one example. The electric bicycle 10a is one example of an electric vehicle according to the present disclosure. The electric bicycle 10a comprises an annular front wheel 12 and an annular rear wheel 14. The electric bicycle 10a further comprises a frame 16 and pedals 18 for driving a sprocket 20 at the rear wheel 14 via a belt 22 in a conventional manner.

[0053] Each wheel 12, 14 is a hubless wheel providing a central space 24. The electric bicycle 10a may for example provide for a storage of 50 liters inside of the front wheel 12 and 50 liters inside of the rear wheel 14. The ability to store items in both wheels 12, 14 enables a center of gravity of the electric bicycle 10a plus carried weight to be centered, or close to centered, between the respective rotation axis 26 of the wheels 12, 14. This in turn enables an improved dynamic performance of the electric bicycle 10a.

[0054] The front and rear wheels 12, 14 have corresponding designs in this example. Unless otherwise indicated, the descriptions of the rear wheel 14 also apply to the front wheel 12. In the following, the rear wheel 14 will be described in great detail and will simply be referred to as the wheel 14.

[0055] The electric bicycle 10a further comprises an electric energy storage 28, such as one or more batteries. The energy storage 28 is here provided in the frame 16.

[0056] The electric bicycle 10a further comprises an electronic control system 30. The control system 30 is here provided in the frame 16. The control system 30 of this example comprises a data processing device 32 and a memory 34. The memory 34 has a computer program stored therein. The computer program comprises program code which, when executed by the data processing device 32, causes the data processing device 32 to perform, or command performance of, various operations as described herein.

[0057] The wheel 14 comprises a tire 36. An annular cover 38 is positioned on both sides of the wheel 14 radially inside of the tire 36 with respect to the rotation axis 26. The wheel 14 rotates relative to the cover 38. The wheel 14 of this example further comprises two light sources, here exemplified as two light strips 40 (only one associated with the wheel 14 is shown in Fig. 1). Each light strip 40 is here annular and concentric with a respective rotation axis 26. Each light strip 40 is fixed to an associated cover 38.

[0058] The light strips 40 may function as turn signals. Thus, when a driver intends to turn right, a light strip 40 on a right side of the wheel 14 can be controlled, e.g., by the control system 30, to provide a particular light signal (such as blinking or emitting light of a particular color). Correspondingly, when a driver intends to turn left, a light strip 40 on a left side of the wheel 14 can be controlled to provide a corresponding light signal.

[0059] Fig. 1 further shows an outer radius 42 of the wheel 14, here a radial distance from the rotation axis 26 to an outer periphery of the tire 36.

[0060] Fig. 2 schematically represents a partial side view of the electric bicycle 10a. As shown, the electric bicycle 10a comprises a plurality of electric motors 44 for directly driving the wheel 14. With direct drive is meant that each electric motor 44 directly contacts and drives the wheel 14, as opposed to when an intermediate transmission is provided between the electric motors 44 and the wheel 14.

[0061] Each electric motor 44 is electrically powered from the energy storage 28. The control system 30 is configured to control each electric motor 44 independently. Each electric motor 44 may be of identic design and rating. Thus, when a description is given for one of the electric motor 44, this description applies also to all other electric motors 44, unless otherwise indicated.

[0062] In this specific and non-limiting example, the electric bicycle 10a comprises six electric motors 44. The electric motors 44 are here positioned at the two, four, six, eight, ten and twelve o'clock positions with respect to the rotation axis 26. Each pair of two adjacent electric motors 44 are angularly spaced from each other with an angle of 60 degrees with respect to the rotation axis 26. The electric motors 44 are thus evenly distributed angularly with respect to the rotation axis 26.

[0063] Each electric motor 44 may provide a torque of at least 0.5 Nm and / or less than 3 Nm. Each electric motor 44 may for example provide a torque of 0.8 Nm, 1.5 Nm or 2 Nm. Each electric motor 44 may have a power of 100 W to 300 W, such as 200 W. Each electric motor 44 may have a diameter of less than 100 mm, such as 50 mm.

[0064] During operation of the electric bicycle 10a, the control system 30 may control the electric motors 44 such that only a first group of the six electric motors 44 drives the wheel 14 for a first time period, and such that only a second group of the six electric motors 44, different from the first group, drives the wheel 14 for a second time period, e.g., following the first time period. Each group of electric motors 44 may comprise one, several or all of the electric motors 44. For example, only the electric motors 44 at the two, six and ten o'clock positions may be driven during the first time period, and only the electric motors 44 at the four, eight and twelve o'clock positions may be driven during the second time period. The electric motors 44 can thus be controlled in an alternating manner by the control system 30 to drive the wheel 14. This allows cooling of the non-driven electric motors 44 and a consequentially increased lifetime of the electric motors 44. During a third time period, e.g., following the second time period, all electric motors 44 may be controlled to drive the wheel 14 to thereby provide a high power drive. During a fourth time period, e.g., following the third time period, only one of the electric motors 44 may drive the wheel 14. The one electric motor 44 currently driving the wheel 14 may be alternated.

[0065] The electric bicycle 10a further comprises an annular support element 46. The support element 46 is only partly shown in Fig. 2. Similarly to the wheel 14, the support element 46 encloses the rotation axis 26 and is concentric with the rotation axis 26. The support element 46 is here arranged radially inside of the wheel 14 and supports rotation of the wheel 14 around the rotation axis 26. All electric motors 44 are secured to the support element 46 offset from the rotation axis 26. The support element 46 serves to efficiently transfer heat away from the electric motors 44. All electric motors 44 are positioned radially within the support element 46 with respect to the rotation axis 26. This means that the support element 46 extends both radially above and radially below the electric motors 44.

[0066] Fig. 2 further shows an inner radius 48 of the support element 46. The inner radius 48 amounts to at least 50 % of the outer radius 42 of the wheel 14, here to approximately 72 % thereof. This implies that the space 24 inside of the wheel 14 is quite large and that the arrangement of the electric motors 44 in the support element 46 is very compact.

[0067] As shown in Fig. 2, the wheel 14 of this example further comprises a rim 50 and a toothed element 52 secured to the rim 50, such as by rivets. The tire 36 is secured to the rim 50. The electric motors 44 are arranged to directly contact and drive the toothed element 52.

[0068] The electric bicycle 10a of this example further comprises a plurality of bearings 54, here exemplified as rolling-element bearings, for supporting rotation of the wheel 14 around the rotation axis 26. The electric bicycle 10a of this example comprises twelve bearings 54 but only six bearings 54 are visible in Fig. 2. In this example, the bearings 54, here a pair of two concentric bearings 54, are positioned at the one, three, five, seven, nine and eleven o'clock positions with respect to the rotation axis 26. Each pair of two bearings 54 are thus evenly distributed angularly with respect to the rotation axis 26. In this example, all bearings 54 are of the same design and rating. Thus, when a description is given for one bearing 54, this description applies also to all remaining bearings 54, unless otherwise indicated.

[0069] A first race of each bearing 54 is fixed to the support element 46. A second race of each bearing 54 contacts and rotates along with the wheel 14, here the toothed element 52 thereof. Thus, the bearings 54 are provided mechanically between the support element 46 and the wheel 14. Fig. 2 shows that both the electric motors 44 and the bearings 54 are positioned radially within the support element 46 with respect to the rotation axis 26. The support element 46, the electric motors 44 and the bearings 54 are protected by the covers 38 (Fig. 1). The covers 38 are here fixed to the support element 46.

[0070] Fig. 2 further shows a horizontal center line 56 (which is horizontal when the electric bicycle 10a is on a horizontal surface). In this example, three of the electric motors 44 (at the four, six and eight o'clock positions) are positioned geodetically below the horizontal center line 56. Due to the gravity of the electric bicycle 10a, some play may occur between the electric motors 44 above the horizontal center line 56 (at the two, ten and twelve o'clock positions). By positioning some electric motors 44 below the horizontal center line 56, the propulsion efficiency by these electric motors 44 is increased.

[0071] Fig. 3 schematically represents a partial perspective view of the support element 46. In Fig. 3, a first disc 58a of the support element 46 is shown. Except for a bracket 60 for mounting the support element 46 to the frame 16, the first disc 58a is annular and concentric with the rotation axis 26.

[0072] The first disc 58a of this example comprises a plurality of motor openings 62. Each motor opening 62 is circular in this example. Each electric motor 44 is received in one of the motor openings 62.

[0073] The first disc 58a of this example further comprises a plurality of triangular openings 64. Some triangular openings 64 point towards the rotation axis 26 and some triangular openings 64 point away from the rotation axis 26. As shown, the motor openings 62 and the triangular openings 64 are alternatingly provided around a circumference of the support element 46. A plurality of triangular openings 64, here four, are provided between each pair of adjacent motor openings 62.

[0074] Due to the motor openings 62 and the triangular openings 64, the first disc 58a provides one example of a truss structure 66. The truss structure 66 comprises a plurality of beams interconnected at nodes. In this example, the illustrated shape of the first disc 58a is provided by cutting out the motor openings 62 and the triangular openings 64 from a solid substantially annular disc, e.g., by laser. The first disc 58a maybe made of steel and / or may have a thickness of at least 3 mm.

[0075] The truss structure 66 provides several advantages in combination. The support element 46 is provided with a very high strength to weight ratio. Moreover, the support element 46 serves as cooling fins to efficiently conduct heat away from the electric motors 44. In addition, the motor openings 62 and the triangular openings 64 contribute to air circulation and an enhanced cooling of the electric motors 44.

[0076] Fig. 4 schematically represents a perspective view of the support element 46. In addition to the first disc 58a, the support element 46 of this example further comprises a second disc 58b and an intermediate member 68, here exemplified as a cylinder. As shown in Fig. 4, also the second disc 58b and the intermediate member 68 has a truss structure 66. In this example, the second disc 58b differs from the first disc 58a in that instead of the motor openings 62, the second disc 58b comprises a pair of slits 70 associated with each electric motor 44.

[0077] Each of the first and second discs 58a, 58b of this example is flat and oriented in a respective plane transverse to the rotation axis 26. The first and second discs 58a, 58b are thus parallel and offset from each other along the rotation axis 26. The intermediate member 68 is concentric with the rotation axis 26 and interconnects the first and second discs 58a, 58b. The intermediate element 68 may define the inner radius 48 of the wheel 14. Although the truss structure 66 is provided in each of the first and second discs 58a, 58b and the intermediate element 68 in this example, the truss structure 66 may be provided in only one or two of these elements.

[0078] Fig. 5 schematically represents a partial perspective cross-sectional view of the toothed element 52. As mentioned, the toothed element 52 is fixed to the rim 50 in this example. The toothed element 52 of this example comprises a toothed track 72. The toothed track 72 is annular and concentric with the rotation axis 26.

[0079] The toothed element 52 of this example further comprises a first bearing track 74a and a second bearing track 74b. Each of the first and second bearing tracks 74a, 74b is annular and concentric with the rotation axis 26. The toothed track 72 is positioned between the first and second bearing tracks 74a, 74b along the rotation axis 26. Each of the first and second bearing tracks 74a, 74b is a flat-bottomed recess in the toothed element 52. The first bearing track 74a is axially limited (with respect to the rotation axis 26) by an annular first edge 76a on the one hand, and by the toothed track 72 on the other hand. The second bearing track 74b is axially limited by a second edge 76b on the one hand, and by the toothed track 72 on the other hand.

[0080] The toothed track 72 protrudes radially inward beyond the first and second bearing tracks 74a, 74b with respect to the rotation axis 26. The toothed element 52 of this example is a timing belt made of injection molded nylon plastic. Optionally, a core of the toothed element 52 is made of a different material, e.g., a non-polymeric material.

[0081] Fig. 6 schematically represents further a partial side view of the electric bicycle 10a. In Fig. 6, it can be seen that each electric motor 44 comprises a stator 78 and a rotor 80. The stator 78 is fixed to the support element 46. The rotor 80 is rotatable relative to the stator 78 around a rotor axis 82. The rotor axis 82 is here parallel with the rotation axis 26. As shown in Fig. 6, the rotor 80 is positioned radially outside of the stator 78 with respect to the rotor axis 82. Each electric motor 44 is thus an outrunner in this example. The use of outrunners has been found particularly advantageous for the electric bicycle 10a of this implementation since it enables a positioning of the electric motors 44 inside of a support element 46 of a small size, both radially and axially with reference to the rotation axis 26. Fig. 7 schematically represents a partial perspective view of the electric bicycle 10a. Each electric motor 44 is mounted in a respective motor opening 62 of the support element 46, here in the first disc 58a thereof. The entirety of each electric motor 44 is here contained within the axially outer boundaries of the support element 46 with respect to the rotation axis 26. Thus, the electric motors 44 do not protrude axially outside of a space spanned by the first and second discs 58a, 58b.

[0082] In Fig. 7, it can be seen that in this example, the rotor 80 is positioned axially within the stator 78 with respect to the rotor axis 82. Fig. 7 further shows that the rotor 80 comprises a rotor gear 84. The rotor gear 84 includes external teeth meshing with the toothed track 72 (including internal teeth). The rotor gear 84 of this example is made of injection molded nylon plastic.

[0083] In this example, each electric motor 44 has a gear ratio to the wheel 14 of at least 7:1. This means that for one full turn of the wheel 14, the rotor gear 84 makes at least seven turns, such as ten turns.

[0084] Fig. 7 further denotes two of the bearings 54 as a first bearing 54a and a second bearing 54b. As shown, the first and second bearings 54a, 54b are concentric and oriented in respective planes transverse to the rotation axis 26 (and transverse to the rotor axis 82). One or both of the first and second bearings 54a, 54b may also be referred to with reference numeral "54". The bearings 54 are entirely accommodated inside of the support element 46 both axially and radially with respect to the rotation axis 26.

[0085] Each bearing 54 comprises a first race and a second race, here exemplified as an inner race 86 and an outer race 88, respectively. The inner race 86 is fixed to the support element 46. The outer race 88 is rotatable relative to the inner race 86 and rotates along with the rotation of the wheel 14.

[0086] In this example, each bearing 54 further comprises a bushing 90. The bushing 90 is annular and fixed to the outer race 88 radially outside of the outer race 88. The bushing 90 of this example is made of injection molded nylon plastic. In this example, the bushing 90 of the first bearing 54a runs in and frictionally engages the first bearing track 74a, and the bushing 90 of the second bearing 54b runs in and frictionally engages the second bearing track 74b.

[0087] Fig. 8 schematically represents a partial side view of a electric bicycle 10b according to a further example. The electric bicycle 10b differs from the electric bicycle 10a in that each wheel 12, 14 comprises only three electric motors 44. The electric motors 44 are here positioned at the four, eight and twelve o'clock positions with respect to the rotation axis 26. If each electric motor 44 provides a maximum torque of at least 0.5 Nm and all three electric motors 44 are driven simultaneously when the electric bicycle 10b travels uphill, each electric motor 44 may operate at below 50 % of its rated load.

[0088] Fig. 9 is a flowchart outlining general steps of a method. The method comprises a step of providing S10 an electric vehicle 10a; 10b comprising an annular wheel 12, 14 rotatable around a rotation axis 26; an annular support element 46 enclosing the rotation axis 26 and supporting the wheel 12, 14 radially inside of the wheel 12, 14 with respect to the rotation axis 26; a plurality of electric motors 44 supported on the support element 46 offset from the rotation axis 26 and positioned radially inside of the wheel 12, 14 with respect to the rotation axis 26, each electric motor 44 being arranged to directly drive the wheel 12, 14; and an electronic control system 30 configured to control the electric motors 44.

[0089] The method further comprises a step S12 of controlling, by the control system 30, the electric motors 44 in an alternating manner to drive the wheel 12, 14.

[0090] While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts maybe varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.

Claims

CLAIMS1. An electric vehicle (10a; lob) comprising:- an annular wheel (12, 14) rotatable around a rotation axis (26);- an annular support element (46) enclosing the rotation axis (26) and supporting the wheel (12, 14) radially inside of the wheel (12, 14) with respect to the rotation axis (26); and- a plurality of electric motors (44) supported on the support element (46) offset from the rotation axis (26) and positioned radially inside of the wheel (12, 14) with respect to the rotation axis (26), each electric motor (44) being arranged to directly drive the wheel (12, 14).

2. The electric vehicle (10a; 10b) according to claim 1, wherein each electric motor (44) has a gear ratio to the wheel (12, 14) of at least 5:1.

3. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein each electric motor (44) is positioned radially within the support element (46) with respect to the rotation axis (26).

4. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein two adjacent electric motors (44) are angularly spaced from each other with an angle of at least 60 degrees with respect to the rotation axis (26).

5. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein two electric motors (44) are positioned below a horizontal center line (56) of the wheel (12, 14).

6. The electric vehicle (10a; 10b) according to any of the preceding claims, further comprising an electronic control system (30) configured to control the electric motors (44) in an alternating manner to drive the wheel (12, 14).

7. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein the plurality of electric motors (44) include three electric motors (44).

8. The electric vehicle (10a; lob) according to any of the preceding claims, wherein an inner radius (48) of the support element (46) with respect to the rotation axis (26) is at least 50 % of an outer radius (42) of the wheel (12, 14) with respect to the rotation axis (26).

9. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein each electric motor (44) comprises a stator (78) and a rotor (80), and wherein each stator (78) is fixed to the support element (46).

10. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein the wheel (12, 14) comprises a toothed element (52).

11. The electric vehicle (10a; 10b) according to claims 9 and 10, wherein the toothed element (52) comprises a toothed track (72) concentric with the rotation axis (26), and wherein each rotor (80) comprises a rotor gear (84) meshing with the toothed track (72).

12. The electric vehicle (10a; 10b) according to claim 11, wherein the toothed element (52) comprises a first bearing track (74a) and a second bearing track (74b), each concentric with the rotation axis (26), and wherein the toothed track (72) is positioned between the first and second bearing tracks (74a, 74b).

13. The electric vehicle (10a; 10b) according to any of the preceding claims, further comprising a plurality of bearings (54) mechanically between the support element (46) and the wheel (12, 14) for supporting rotation of the wheel (12, 14) around the rotation axis (26).

14. The electric vehicle (10a; 10b) according to claims 12 and 13, wherein at least one of the bearings (54) engages the first bearing track (74a) and at least one of the bearings (54) engages the second bearing track (74b).

15. The electric vehicle (10a; 10b) according to claim 13 or 14, wherein the bearings (54) are rolling-element bearings.

16. The electric vehicle (10a; lob) according to any of the preceding claims, wherein each electric motor (44) is an outrunner.

17. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein the support element (46) comprises a truss structure (66).

18. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein the support element (46) comprises a plurality of motor openings (62), and wherein each electric motor (44) is received in one of the motor openings (62).

19. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein the support element (46) comprises a plurality of triangular openings (64).

20. The electric vehicle (10a; 10b) according to any of the preceding claims, further comprising a light source (40) fixed to the support element (46).

21. The electric vehicle (10a; 10b) according to any of the preceding claims, wherein the electric vehicle (10a; 10b) is an electric bicycle.

22. A method of controlling an electric vehicle (10a; 10b), the method comprising:- providing (S10) an electric vehicle (10a; 10b) according to claim 6; and- controlling (S12), by the control system (30), the electric motors (44) in an alternating manner to drive the wheel (12, 14).