SE2250460A1

SE2250460A1 - In-wheel arrangement

Info

Publication number: SE2250460A1
Application number: SE2250460A
Authority: SE
Inventors: Magnus Öhrlund; Martin Elonsson; Mats Svensson; Pär-Ola Svensson
Original assignee: Husqvarna Ab
Priority date: 2022-04-14
Filing date: 2022-04-14
Publication date: 2023-10-15
Also published as: WO2023198339A1

Abstract

The present invention relates to an in-wheel arrangement (300) for a work tool (100), such as a lawn mower. The in-wheel arrangement comprises a support member (310), attachable to the work tool, a stator assembly (320), a rotor assembly (330) configured to at least partly enclose the stator assembly in an inner space (338) of the rotor assembly and a bearing assembly (340). The rotor assembly is rotatably supported on the support member by means of the bearing assembly for rotation of the rotor assembly about a rotation axis (A). The rotor assembly comprises a rotor portion (332), configured to at least partly enclose the stator assembly, and a motor cover portion (334), configured to at least partly cover a first axial side (324) of the stator assembly. The rotor assembly is rotatably supported by the bearing assembly only between a first end portion (312) of the support member and the first axial side of the stator assembly. The present invention further relates to a work tool, such as a lawn mower, comprising at least one in-wheel arrangement according to the invention.

Description

TECHNICAL FIELD The present invention relates to an in-wheel arrangement for a work tool, such as a lawn mower. The present invention further relates to a work tool, such as a lawn mower, comprising at least one in-wheel arrangement as described herein. The work tool may be an outdoor work tool or an indoor work tool. The work tool may be adapted to be driven by a user or may be adapted to run by itself as a robotic work tool.

BACKGROUND Outdoor work tools, such as lawn mowers, are commonly used. Other examples of outdoor work tools, in which the disclosed in-wheel arrangement is applicable, are ball collectors, mine sweepers and farming equipment. lt is also known to use indoor work tools, such as a concrete grinding machine. The work tool may be adapted to be driven by a user or may be adapted to run by itself as a robotic work tool.

The work tool comprises a plurality of wheels, e.g. two, three, four, six or eight wheels. At least one of the wheels is drivably connected to an electric motor assembly. Often, two or four wheels are drivably connected. The drivably connected wheels may be connected to a respective electric motor assembly. The work tool may comprise at least one electric power source, such as a battery. The electric power source is typically rechargeable and the work tool may thus visit a charging station to recharge the electric power source.

A commonly used electric motor assembly drivably connected to a wheel of the work tool include a gearbox, which may generate uncomfortable noise. Further, the life time of the gearbox may be less than that of the other parts of the electric motor assembly, thus deciding the actual life time of the electric motor assembly. Depending on the configura- tion of the gearbox, it may be technically complex and thus cumbersome to manufacture. Typically, the whole electric motor assembly has to be replaced, although only the gear- box has broken down or is worn out.

Patent document US 2020/0346488 A1 discloses an in-wheel arrangement with a rim cover assembly having a waterproof structure. The in-wheel arrangement includes a rim, a shaft, a motor assembly and a cover. The shaft passes through a centre of the rim. The motor assembly is disposed in an inner portion of the rim and includes a stator connected to the shaft and a rotor disposed to be wrapped around the stator and configured to rotate. The stator receives external power, and a lead line for providing the power passes through a centre of the shaft and is connected to the stator. When the power is supplied to the stator, the rotor rotates. The rim is connected to the rotor and is rotated together with the rotor. Accordingly, a tyre located on an outer wheel of the rim is rotated. A first bearing is disposed at a front end portion of the shaft and a second bearing is disposed at a rear end portion of the shaft, the bearings facilitating the rotation of the rotor. The first bearing is located in front of the stator and the second bearing is located behind the stator. lt is generally desirable that an in-wheel arrangement is durable and simple to service. lt is also desirable that the components can be replaceable separate from each other, such that the in-wheel arrangement does not have to be replaced as a whole because only a single component, or a few components, being broken down or worn out.

Even if a configuration like the in-wheel arrangement of US 2020346488 A1 avoids problems previously associated with the gearbox, since such a motor assembly is not associated with a gearbox, the in-wheel arrangement is still complex. lt is thus desirable to provide an in-wheel arrangement being less complex, thus being easy to manufacture, easy to service and/or easy to repair. lt is further desirable to have a lower manufacturing cost, a lower service cost and a lower repair cost as compared to prior art solutions.

SUMMARY The above object may be achieved with in-wheel arrangement for a work tool, such as a lawn mower according to claim 1 or with a work tool, such as a lawn mower, according to claim 18. Variations of the invention are set out in the dependent claims and in the following description.

The in-wheel arrangement for a work tool, such as a lawn mower, according to the invention comprises: - a support member, attachable to the work tool, the support member comprising a first end portion, attachable to the work tool, and an opposite second end portion, - a stator assembly, comprising a stator directly or indirectly attachable to the second end portion of the support member, - a rotor assembly, configured to at least partly enclose the stator assembly in an inner space of the rotor assembly, and - a bearing assembly.

The rotor assembly is rotatably supported on the support member by means of the bearing assembly for rotation of the rotor assembly about a rotation axis. The rotor assembly comprises: - a rotor portion, comprising or being constituted by a rotor and being configured to at least partly enclose the stator assembly, and - a motor cover portion, configured to at least partly cover a first axial side of the stator assembly, which first axial side is adapted to face the first end portion of the support member. Further, the rotor assembly is rotatably supported by the bearing assembly only between the first end portion of the support member and the first axial side of the stator assembly.

The in-wheel arrangement according to the invention is intended to be used as a part of a work tool, such as a lawn mower. The work tool may be an outdoor work tool or an indoor work tool. Examples of outdoor Work tools, in Which the disclosed in-wheel arrangement is applicable, are lawn mowers, ball collectors, mine sweepers and farming equipment. Examples of indoor work tools, in which the disclosed in-wheel arrangement is applicable, are concrete grinding machines. The work tool may be adapted to be driven by a user and/or it may be adapted to run by itself as a robotic work tool. The in-wheel arrangement may be comprised in a Wheel of the work tool, form the wheel or comprise the wheel. The in-wheel arrangement according to the invention may be sold, maintained and/or repaired as a standalone unit, e.g. as a spare part.

The support member may be a shaft, which may be solid or hollow. The support member may have a straight configuration or a curved configuration. The support member is used to attach the in-wheel arrangement to the work tool. Hence, the first end portion of the support member is attachable to the work tool. The opposite end portion, i.e. the second end portion, thus faces away from the main part of the work tool. lf the support member is hollow, thus forming a tubular structure, an inner bore can be used to ventilate in-wheel arrangement, e.g. if any moisture may have entered.

The stator assembly is adapted to be stationary in relation to a main part of the work tool.

Accordingly, the stator assembly is stationary in relation to the support member. The stator assembly is configured to be attached to the second end portion of the support member.

The rotor assembly, on the other hand, is configured to be rotatable in relation to the main part of the work tool and, thereby, also rotatable in relation to the support member. Hence, the rotor assembly is rotatably supported on the support member by means of the bearing assembly for rotation of the rotor assembly about the rotation axis. lf the support member has a straight configuration, such as a shaft, the rotation axis of the rotor assembly typically coincides with an axial direction of the shaft.

As mentioned above, the rotor assembly comprises the rotor portion and the motor cover portion. The rotor portion comprises, or is constituted by, the rotor, which together with the stator of the stator assembly forms an in-wheel motor assembly, also known as a hub motor assembly. Thereby, the rotor portion at least partly, preferably completely, encloses the stator assembly, such that the rotor encloses the stator.

The motor cover portion is configured to at least partly cover the first axial side of the stator assembly, i.e. the axial side facing towards the main part of the work tool. Hence, the motor cover portion may assume the shape of a circular disc, where the support member goes through an opening in the centre.

The rotor portion and the motor cover portion may be two separate components that are attachable to each other. As an alternative, they may together form a single unitary component. The rotor portion and the motor cover portion together at least partly cover the circumference and the first axial side of the stator assembly, such that the inner space is formed in the rotor assembly, in which inner space the stator assembly is located.

The rotor assembly is rotatably supported by the bearing assembly only between the first end portion of the support member and the first axial side of the stator assembly. Hence, there is no bearing at a second axial side of the stator assembly, i.e. at the axial side facing away from the main part of the work tool. The bearing assembly may comprise one, two, three or more bearings. lf only a single bearing, the single bearing is configured to extend along the direction of the rotation axis. lf two or more bearings, they are located interspaced, or next to each other, as seen along the rotation axis.

The in-wheel arrangement according to the invention makes a compact configuration of the in-wheel arrangement possible. lt is further less complex than prior art in-wheel arrangements. lt is easier and/or cheaper to manufacture than prior art in-wheel arrange- ments, e.g. by having fewer parts to assemble. The components are replaceable separate from each other, such that the in-wheel arrangement does not have to be replaced as a whole because only a single component, or a few components, being broken down or worn out. The in-wheel arrangement according to the invention is easy to service, resulting in lower costs for service. Further, the in-wheel arrangement according to the invention is easy to repair, resulting in lower costs for repair. lt is thereby advantageous that the components are individually replaceable, i.e. separately from each other. By repairing and/or byjust replacing a single component rather than the whole in-wheel arrangement, the in-wheel arrangement according to the invention is more environ- mentally-friendly than prior art solutions, thereby influencing the LCA, i.e. life-cycle analysis, in a positive way.

The in-wheel arrangement according to the invention may form a stand-alone functional unit. lt can comprise a number of components being used to propel the work tool, which components according to prior art technology have been provided separate from each other. The in-wheel arrangement according to the invention makes it possible to configure the work tool as a modular system arrangement.

By locating the bearing assembly on the first axial side of the stator assembly only, the space at the second axial side can be used for other components. As further described herein, the space at the second axial side can e.g. be used for a rotation sensor arrange- ment, being used to sense the rotation position of the rotor assembly. As an alternative or a complement, the space at the second axial side can be used for a control unit, which also is further described herein. The control unit is configured to control the in-wheel motor assembly, but may in addition control other functions of the in-wheel arrangement and/or functions of the work tool not associated with the in-wheel arrangement.

The in-wheel arrangement according to the invention is less prone to failures than prior art solutions, thus extending the MBTF, i.e. mean time between failures, being the predicted elapsed time between inherent failures of a system during normal system operation.

Further, according to the invention, an in-wheel arrangement is provided with low risk of electromagnetically disturbing other equipment in the vicinity. The in-wheel arrangement according to the invention uses less electrical wiring than prior art solutions, such as e.g. the in-wheel arrangement of US 2020346488 A1. The electromagnetic emissions may be kept at a minimum.

The in-wheel arrangement according to the invention may operate in a silent way, thereby reducing, or preferably avoiding, the risk of generating noise.

The bearing assembly may have an extension along the rotation axis in the range of 3%- 40% of an inner diameter of the rotor, preferably in the range of 5%-35%, more preferably in the range of 10%-30%, most preferably in the range of 15%-25%. lfjust having a single bearing, the extension is the width of the bearing. lf having more than one bearing, such as two bearings, the extension is taken as the width/s of the individual bearings plus the interspace/s in between the bearings as seen along the rotation axis. Purely as an example, being usable for an in-wheel arrangement of a robotic lawn mower, the extension along the rotation axis may be in the range of 5-55 mm, preferably 10-45 mm, more preferably 15-35 mm, most preferably 20-30 mm.

The bearing assembly may comprise a first bearing and a second bearing being inter- spaced by a c-c distance along the rotation axis being in the range of 3%-35% of the inner diameter of the rotor, preferably in the range of 5%-30%, more preferably in the range of 10%-25%, most preferably in the range of 15%-20%. The distance is measured as a centre-to-centre distance, i.e. from the centre of the first bearing to the centre of the second bearing. lf more than two bearings are provided, the distance is measured as the c-c distance between the outermost bearings. Purely as an example, being usable for an in-wheel arrangement of a robotic lawn mower, the c-c distance along the rotation axis may be in the range of 5-50 mm, preferably 10-40 mm, more preferably 15-30 mm, most preferably 20-25 mm.

The rotor assembly may comprise a circumferential traction portion adapted to surround the rotor portion, the circumferential traction portion being provided with traction means, such as a traction pattern and/or a tyre attached to, or integrated with, the circumferential traction portion. The circumferential traction portion may be made of plastics, preferably of injection-moulded plastics. The plastics may be fibre-reinforced, e.g. glass-fibre reinforced.

The circumferential traction portion is intended to be in contact with the ground in order to be able to propel the Work tool. The circumferential traction portion may be provided with traction means, such as a traction pattern or studs, forming part of the circumferential traction portion. Alternatively, or as a complement, the circumferential traction portion may comprise a tyre. The tyre may be a separate component, which is mounted to the circumferential traction portion. Alternatively, the tyre may be manufactured at the same time as the circumferential traction portion, e.g. by means of double injection moulding.

The rotor assembly may comprise a wheel cover portion, adapted to at least partly cover the second axial side of the stator assembly, the second axial side being on the axially opposite side of the stator assembly with respect to the first axial side. The wheel cover portion is adapted to be directly or indirectly attached to the rotor portion by a wheel cover attachment means, which preferably is releasable and reattachable, such as a screw and a corresponding receiving bore in the rotor portion.

The wheel cover portion may be made of plastics, preferably of injection-moulded plastics.

The plastics may be fibre-reinforced, e.g. glass-fibre reinforced.

The wheel cover portion and the circumferential traction portion may form a single unitary component, which optionally may include the tyre attached to, or integrated with, the circumferential traction portion. Accordingly, the wheel cover portion and the circum- ferential traction portion may be manufactured together, e.g. by means of injection moulding. Optionally, also the tyre may be manufactured in the same step, e.g. by means of double injection moulding.

The rotatable rotor assembly may thus comprise two housing members together forming a housing, where a first housing member may comprise the motor cover portion and the rotor portion, which optionally may be formed as a single unitary unit, e.g. of die-cast aluminium. A second housing member may then comprise the Wheel cover portion and the traction portion, which optionally may be formed as a single unitary unit, and also as an option include the tyre. lf the support member is hollow, the inner bore can be used to ventilate the housing, e.g. if any moisture may have entered the housing.

Alternatively, the traction portion can be included in the first housing portion, such that the first housing member comprises the motor cover portion, the rotor portion and the traction portion. The second housing member may then comprise the wheel cover portion.

The first and the second housing member together enclose the inner space containing the stator assembly. The second housing member is removable from the first housing member without prior removal of the stator. Further, the second housing member is reattachable to the first housing member, such that the rotor assembly can be closed again, e.g. by the wheel cover attachment means, such as the screw and the correspon- ding receiving bore of the rotor portion disclosed herein. This contributes to easy service and repair of the in-wheel arrangement according to the invention.

The in-wheel arrangement may further comprise a control unit, which is adapted to be located at or adjacent to the second end portion of the support member. The control unit is configured to control the in-wheel motor assembly, but may in addition control other functions of the in-wheel arrangement and/or of the work tool, such as a malfunction monitor function, wear and health self-diagnosis, temperature monitoring, precipitation monitoring, power management. The control unit may be an electronic control unit comprising a processor and a memory. The memory may comprise instructions execut- able by the processor. The control unit may comprise hardware, or hardware and soft- ware. The control unit may be adapted for wired and/or wireless communication. Data may be stored in the memory of the control unit, in a memory of the work tool, in a memory of a remote central unit and/or in the cloud.

The in-wheel arrangement comprising the control unit offers a decentralized system func- tion, which may be connected via serial communication like a field bus to other systems of the work tool. lt represents a stand-alone subsystem, which can be pre-tested before it is assembled to the work tool.

The control unit may comprise a printed circuit board, preferably without an opening for the support member. Since the control unit is located at or adjacent to the second end portion of the support member, it is located axially outside of and adjacent to the second axial side of the stator assembly, i.e. the axial side facing outwards. Hence, the printed circuit board does not need to have an opening for the support member. This is in contrast to prior art in-wheel arrangements, in which the printed circuit board typically has an opening for the support member, such that the support member can pass through the printed circuit board. The location of the printed circuit board is facilitated by having the bearing assembly on one axial side only. This makes it possible to minimize the size of the printed circuit board. Also, the control unit is located inside of the housing formed by the first and second housing members.

The in-wheel arrangement may further comprise an electrical wire, adapted to be connected to the control unit. ln that case, the support member of the in-wheel arrange- ment is preferably hollow such that the electrical wire can extend through the support member from a first end of the support member to a second end of the support member, the second end being opposite to the first end. Hence, the electrical wire extends the whole way through the support member, from the first end to the second end. There is thus no need to make an opening in the tubular wall of the hollow support member for allowing passage of an electrical wire, which is known from prior art solutions.

The electrical wire may comprise at least one electrical connector for attachment to the control unit, the electrical connector and the hollow support member being sized such that the electrical connector is movable through the hollow support member, i.e. through its bore. This contributes to easy mounting, easy service and/or easy repair of the in-wheel arrangement.

The electrical wire is adapted to be releasably attached to the control unit, preferably also reattachably attached, e.g. by means of the electrical connector of the electrical wire cooperating With a corresponding electrical connector of the control unit. The other end of the electrical wire is connectable to the work tool.

The in-wheel arrangement may further comprise at least one electrical connection assembly configured to electrically connect the stator and the control unit, the electrical connection assembly preferably being releasable, more preferably the electrical connec- tion assembly being releasable and reattachable. This contributes to easy mounting, easy service and/or easy repair of the in-wheel arrangement.

The in-wheel arrangement may further comprise a rotation sensor arrangement located at the rotation axis for measurement of a rotational position of the rotor assembly relative to the stator assembly. The rotation sensor arrangement can also be used to measure a distance travelled by the in-Wheel arrangement and thereby also by the work tool. The rotation sensor arrangement may e.g. be a magnetic sensor arrangement or an optical sensor arrangement. This location of the rotation sensor arrangement makes it possible to detect the rotation of the rotor assembly with high accuracy. Since, it is possible to detect the rotational position of the rotor assembly relative to the stator assembly when the work tool is to start moving, the risk of starting with a jerk, is reduced or preferably avoided. This differs from prior art rotation sensor arrangements, Which are located in an off-axis position.

Further, this location of the rotation sensor makes odometry possible, i.e. it is possible to estimate change in position over time. lt is e.g. possible to detect that the circumferential traction portion, with its optional tyre, spins or slips at the contact with the ground. Moreover, it is possible to dispense with a commutation sensor, such as a Hall sensor. Accordingly, it is possible to provide a sophisticated control of the in-wheel motor assembly, which allows for a lower energy consumption, less noise, and a more exact control than for prior art systems.

The rotation sensor arrangement may comprise a sensed member, such as a magnet, located on the rotor assembly at the rotation axis. The sensed member may be comprised in the wheel cover portion, e.g. held by the wheel cover portion. The sensed member may be put in place When manufacturing the wheel cover portion.

The rotation sensor arrangement may further comprise a sensor, configured to sense a relative rotational orientation of the sensed member about the rotation axis with respect to the sensor, the sensor being directly or indirectly attached to the stator assembly and located at the rotation axis. Hence, the sensor cooperates with the sensed member, e.g. a magnetic sensor cooperating with a magnet. The sensor contributes to the advantages mentioned above for the rotation sensor arrangement.

The sensor of the rotation sensor arrangement may be attached to, or form a part of, the printed circuit board of the control unit. The control of the rotation sensor arrangement may thus be one of the functions performed by the control unit in the in-wheel arrange- ment according to the invention. 11 The present invention further relates to a work tool, such as a lawn mower, comprising at least one in-wheel arrangement as described herein, preferably comprising two or four in- wheel arrangements as described herein. Other examples of work tools, in which the disc|osed in-wheel arrangement is applicable, are ball collectors, mine sweepers, farming equipment and concrete grinding machines. The work tool may be adapted to be driven by a user or may be adapted to run by itself as a robotic work tool. The work tool may be an outdoor work tool or an indoor work tool. The in-wheel arrangement may be comprised in a wheel of the work tool, form the wheel or comprise the wheel.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will hereinafter be further explained by means of non-limiting examples with reference to the appended drawings wherein: Fig. 1 illustrates a work tool comprising an in-wheel arrangement.

Fig. 2 shows a schematic overview of an exemplary work area.

Fig. 3 illustrates an exploded view of the in-wheel arrangement of Fig. 1.

Fig. 4 illustrates a cross-sectional view of the in-wheel arrangement of Fig. 1. Fig. 5 illustrates a cross-sectional view of an alternative in-wheel arrangement. lt should be noted that the appended drawings are not necessarily drawn to scale and that the dimensions of some features of the present invention may have been exaggerated for the sake of clarity.

DETAILED DESCRIPTION The invention will in the following be exemplified by embodiments. lt should however be realized that the embodiments are included in order to explain principles of the invention and not to limit the scope of the invention, defined by the appended claims. Details from two or more of the embodiments may be combined with each other. lt should be noted that even though the description given herein will be focused on a robotic lawn mower, the teachings herein may also be applied to any type of work tool, such as for example ball collectors, mine sweepers, farming equipment or concrete grinding machines. The work tool may be adapted to be driven by a user and/or may be 12 adapted to run by itself as a robotic work tool. The work tool may be an outdoor work tool or an indoor work tool.

Figure 1 schematically illustrates a work tool exemplified as a robotic lawn mower 100. Figure 2 shows a schematic overview of an exemplary work area 201, e.g. a garden, in which the work tool, illustrated as the robotic lawn mower 100, may be set to operate.

The work area 201 is delimited by a boundary. ln the illustrated embodiment, the work area 201 is enclosed by a boundary wire 203 with the purpose of keeping the robotic lawn mower 100 inside the work area 201. An electric control signal may be transmitted through the boundary wire 203, thereby generating an electromagnetic field emanating from the boundary wire 203. The robotic lawn mower 100 is in that case typically arranged with one or more control signal sensors (not shown) adapted to sense the control signal. The work area 201 is typically arranged such that the robotic lawn mower 100 can dock with a charging station 205.

Alternatively, or as a complement, the work area 201 may be delimited by a virtual boundary, e.g. provided by a map application or stored coordinates in the robotic lawn mower 100. Hence, the robotic lawn mower 100 may as an option comprise a navigation system that is adapted for satellite navigation by means of GPS, i.e. Global Positioning System, or some other GNSS system, i.e. Global Navigation Satellite System, for example using RTK, i.e. Real Time Kinematic. ln addition to this, the navigation system can be adapted for navigation by means of a local base station that e.g. can be housed in the charging station 205 and provide a navigation signal that further increases the navigation accuracy.

The robotic lawn mower has a main body 110 and a plurality of wheels. ln the illustrated embodiment, the robotic lawn mower 100 has four wheels, two front wheels, whereof one front wheel 120 and two rear wheels 130, 140 are visible in the illustrated perspective. The rear wheels 130, 140 comprise in-wheel arrangements 300 according to the inven- tion, which are further described herein. One of the rear wheels 130 is illustrated separate from the rest of the robotic lawn mower 100 in order to illustrate how the in-wheel arrange- ment 300 is attached to the rest of the robotic lawn mower 100. 13 The robotic lawn mower 100 may be a multi-chassis type or a mono-chassis type. A multi- chassis type comprises more than one body part being movable with respect to one another. A mono-chassis type comprises only one main body part. ln the illustrated embodiment, the robotic lawn mower 100 is of a mono-chassis type, having the main body 110.

The robotic lawn mower 100 comprises a grass cutting device 150, such as a rotating blade or a disc with a plurality of separate cutting members, e.g. rotating blades, driven by a cutter motor. The energy of each cutting member typically is below 2 Joule when cutting. The weight of each cutting member is typically in the ranges of 1-5 grams, such as e.g. 3.4 grams. Thickness is typically the range of 0.5-1.0 mm, such as e.g. 0.63 mm.

The robotic lawn mower 100 comprises at least one rechargeable electric power source 160 for providing power to the in-wheel arrangements 300 and/or the cutter motor. The rechargeable electric power source 160 is arranged to be charged by means of received charging current from the charging station 205, received through charging skids or other suitable charging connectors. lnductive charging without galvanic contact, only by means of electric contact, is also conceivable. The rechargeable electric power source 160 may comprise one or more batteries that can be separately arranged or be arranged in an integrated manner to form a combined battery.

The robotic lawn mower 100 may, as an option, comprise at least one environmental detection sensor, e.g. an imaging sensor such as a camera device, which is adapted to provide images of the environment around the robotic lawn mower 100. Other examples of commonly used environmental detection sensors in work tools are a radar sensor, an IR sensor, an ultrasonic sensor and/or a Lidar sensor. The one or more environmental detection sensors are helpful when the robotic lawn mower 100 moves around in order to help its navigation ability.

Figures 3-4 schematically illustrate the in-wheel arrangement 300 of Figure 1 as seen in an exploded view, as in Figure 3, and in a cross-sectional, as in Figure 4.

The in-wheel arrangement 300 comprises a support member 310, attachable to the robotic lawn mower 100, a stator assembly 320, a rotor assembly 330 configured to at least partly enclose the stator assembly 320 in an inner space 338 of the rotor assembly 14 330 and a bearing assembly 340. The rotor assembly 330 is rotatably supported on the support member 310 by means of the bearing assembly 340 for rotation of the rotor assembly 330 about a rotation axis A.

The support member 310, illustrated as a hollow shaft forming a tubular structure, com- prises a first end portion 312 with a first end 314, the first end portion 312 being attach- able to the robotic lawn mower 100, and an opposite second end portion 316 with a second end 318, facing away from the robotic lawn mower 100. ln the illustrated embodi- ment, the support member 310 is a straight shaft. Hence, the rotation axis A coincides with an axial direction of the shaft. lfthe support member 310 is hollow, as is illustrated, an inner bore of it can be used to ventilate the in-Wheel arrangement 300, e.g. if any moisture may have entered.

The stator assembly 320 with its stator 322 is attached to the second end portion 316 of the support member 310. The stator assembly 320 is adapted to be stationary in relation to a main part of the work tool 100. Accordingly, the stator assembly 320 is also stationary in relation to the support member 310.

The rotor assembly 330 comprises a rotor portion 332, configured to at least partly enclose the stator assembly 320. Hence, the rotor assembly 330 at least partly encloses the stator assembly 320 in the inner space 338 of the rotor assembly 330. The rotor assembly 330 further comprises a motor cover portion 334, configured to at least partly cover a first axial side 324 of the stator assembly 320, which first axial side 324 is adapted to face the first end portion 312 of the support member 310. Hence, the motor cover portion 334 in the illustrated embodiment assumes the shape of a circular disc, where the support member 310 goes through an opening in the centre.

The rotor assembly 330 is configured to be rotatable in relation to the main part of the work tool 110 and, thereby, also rotatable in relation to the support member 310. Hence, the rotor assembly 330 is rotatably supported on the support member 310 by means of the bearing assembly 340 for rotation of the rotor assembly 330 about the rotation axis. lf the support member 310 has a straight configuration, such as the illustrated hollow shaft, the rotation axis A of the rotor assembly 330 coincides with the axial direction of the shaft.

The rotor portion 332 comprises, or is constituted by, a rotor 336, which together with the stator 322 of the stator assembly 320 forms an in-wheel motor assembly, also known as a hub motor assembly. The rotor portion 332 encloses the stator assembly 320, such that the rotor 336 encloses the stator 322. The rotor 336 has an inner diameter a, as seen in Figure 4.

The rotor portion 332 and the motor cover portion 334 may be two separate components that are attachable to each other. As an alternative, as is the case for the illustrated embodiment, they may together form a single unitary component. The rotor portion 332 and the motor cover portion 334 together at least partly cover the circumference and the first axial side 324 of the stator assembly 320, such that the inner space 338 is formed in the rotor assembly 330, in which inner space 338 the stator assembly 320 is located.

The rotor assembly 330 is rotatably supported by the bearing assembly 340 only between the first end portion 312 of the support member 310 and the first axial side 324 of the stator assembly 320. Hence, there is no bearing at a second axial side 326 of the stator assembly 320, i.e. at the axial side facing away from the main part of the work tool 100.

The bearing assembly 340 may comprise one, two, three or more bearings. ln the illustrated embodiment, there are two bearings, a first bearing 342 and a second bearing 344, with the second bearing 344 being closest to the first end portion 312 of the support member 310. The first bearing 342 and the second bearing 344 are located interspaced in relation to each other as seen along the rotation axis A, with a c-c distance, i.e. a centre- to-centre distance, d being in the range of 3%-35% of the inner diameter a of the rotor, preferably in the range of 5%-30%, more preferably in the range of 10%-25%, most preferably in the range of 15%-20%, please see Figure 4. Purely as an example, being usable for the in-wheel arrangement 300 of the illustrated robotic lawn mower 100, the c-c distance along the rotation axis may be in the range of 5-50 mm, preferably 10-40 mm, more preferably 15-30 mm, most preferably 20-25 mm.

The rotor assembly 330 comprises a circumferential traction portion 352 surrounding the rotor portion 332. The circumferential traction portion 352 is integrated with a tyre 354.

The circumferential traction portion 352 may be made of plastics, e.g. injection-moulded 16 plastics. The plastics may be fibre-reinforced, e.g. glass-fibre reinforced. The circum- ferential traction portion 352 with the integrated tyre 354 may be made by double injection moulding.

The rotor assembly 330 further comprises a wheel cover portion 356, adapted to at least partly cover the second axial side 326 of the stator assembly 320. The wheel cover portion 356 is attached to the rotor portion 332 by a wheel cover attachment means, which preferably is releasable and reattachable, e.g. a screw (not illustrated) going through a bore 358 and gripping into a corresponding receiving bore 362 in the rotor portion 332.

The wheel cover portion 356 of the illustrated embodiment may be made of plastics, which may be fibre-reinforced, e.g. glass-fibre reinforced. ln the illustrated embodiment, the Wheel cover portion 356 and the circumferential traction portion 352 form a single unitary component, which includes the integrated tyre 354. For example, the Wheel cover portion 356, the circumferential traction portion 352 and the integrated tyre 354 are manufactured by means of double injection moulding. ln the illustrated embodiment, the rotatable rotor assembly 330 comprises two housing members together forming a housing 364, where a first housing member 366 comprises the motor cover portion 334 and the rotor portion 332, formed as a single unitary unit, e.g. of die-cast aluminium. A second housing member 368 comprises the wheel cover portion 356 and the traction portion 352 with its integrated tyre 354. A sealing 369 seals between the first and second housing members 366, 368. lfthe support member 310 is hollow, as is illustrated, the inner bore of it can be used to ventilate the housing 364, e.g. if any moisture may have entered the housing 364.

The first and the second housing member 366, 368 together enclose the inner space 338 containing the stator assembly 320. The second housing member 368 is removable from the first housing member 366 without prior removal of the stator 322. Further, the second housing member 368 is reattachable to the first housing member 366, such that the rotor assembly 330 can be closed again, e.g. by the wheel cover attachment means, such as the screw and the corresponding receiving bore 362 of the rotor portion 332, thereby closing the housing 364. This contributes to easy service and repair of the in-wheel arrangement 300 according to the invention. 17 The in-wheel arrangement 300 further comprises a control unit 370, which is adapted to be located at or adjacent to the second end portion 316 of the support member 310. The control unit 370 is configured to control the in-wheel motor assembly 300, but may in addition control other functions of the in-wheel arrangement 300 and/or of the work tool 100, such as a malfunction monitor function, wear and health self-diagnosis, temperature monitoring, precipitation monitoring, power management. The control unit 370 may be an electronic control unit comprising a processor and a memory. The memory may comprise instructions executable by the processor. The control unit may comprise hardware or hardware and software. The control unit 370 may be adapted for wired and/or wireless communication.

The control unit 370 comprises a printed circuit board 372. Since the control unit 370 is located at the second end portion 316 of the support member 310, it is located axially outside of and adjacent to the second axial side 326 of the stator assembly 320. Hence, the printed circuit board 372 does not need to have an opening for the support member 310. The location of the printed circuit board 372 is facilitated by having the bearing assembly 340 on one axial side only. Further, the control unit 370 is located inside of the housing 364 formed by the first and second housing members 366, 368.

An electrical wire 373 is adapted to be connected to the control unit 370. Since the support member 310 is hollow, the electrical wire 373 can extend the whole way through the support member 310 from the first end 314 to the second end 318.

The electrical wire 373 comprises an electrical connector 374 for attachment to the control unit 370, the electrical connector 374 and the hollow support member 310 being sized such that the electrical connector 374 is movable through the hollow support member 310, i.e. through its bore. The electrical wire 373 is releasably and reattachably attached to the control unit 370, by means of the electrical connector 374 of the electrical wire 373 cooperating with a corresponding electrical connector 376 of the control unit 370. The other end 375 of the electrical wire 373 is connectable to the work tool 100.

The in-wheel arrangement 300 further comprises at least one electrical connection assembly 378 configured to electrically connect the stator 322 and the control unit 370, 18 the electrical connection assembly 378 being releasable and reattachable. This contri- butes to easy mounting, easy service and/or easy repair of the in-wheel arrangement 300.

The in-wheel arrangement 300 further comprises a rotation sensor arrangement 380 located at the rotation axis A for measurement of a rotational position of the rotor assembly 330 relative to the stator assembly 320. The rotation sensor arrangement 380 comprises a sensed member, such as a magnet 382, located on the rotor assembly 330 at the rotation axis A. ln the illustrated embodiment, the sensed member 382 is comprised in the wheel cover portion 356, held by the wheel cover portion 356. The rotation sensor arrangement 380 further comprises a sensor 384, configured to sense a relative rotational orientation of the sensed member 382 about the rotation axis A with respect to the sensor 384, the sensor 384 being directly or indirectly attached to the stator assembly 320 and located at the rotation axis A. Hence, the sensor 384 cooperates with the sensed member 382. The sensor 384 is attached to the printed circuit board 372 of the control unit 370 or forms part of to the printed circuit board 372. The rotation sensor arrangement 380 is a non-contact assembly with an air gap between the sensed member 382 and the sensor 384. The control of the rotation sensor arrangement 380 is one of the functions performed by the control unit 370 in the in-wheel arrangement 300 according to the invention. The rotation sensor arrangement 380 can also be used to measure a distance travelled by the in-wheel arrangement 300 and thereby also by the work tool 100.

Figure 5 illustrates a cross-sectional view of an alternative in-wheel arrangement 300'. lt has most details in common with the in-wheel arrangement 300 illustrated in Figures 3-4. Hence, the in-wheel arrangement 300' of Figure 5 comprises a support member 310', a stator assembly 320' and a rotor assembly 330', which comprises a rotor portion 332' and a motor cover portion 334'. The rotor portion 332' comprises, or is constituted by, a rotor 336' having an inner diameter a'.

However, the in-wheel arrangement 300' of Figure 5 differs from that of Figures 3-4 as regards the bearing assembly 340'. lnstead of having two separate bearings 342, 344 as illustrated in Figures 3-4, there is only a single bearing being a double-bearing, i.e. with two rows 342', 344' of bearing balls included in a single bearing. Hence, the c-c distance d' is much less than the c-c distance d illustrated in Figures 4 and 5. 19 The bearing assembly 344' of Figure 5 has an extension b' along the rotation axis A', i.e. a width of the single bearing illustrated in Figure 5, being in the range of 3%-40% of an inner diameter of the rotor, preferably in the range of 5%-35%, more preferably in the range of 10%-30%, most preferably in the range of 15%-25%. lf more than one bearing, as in Figure 4, such as two bearings 342, 344, the extension b of the bearing assembly 340 is taken as the width/s of the individual bearings 342, 344 plus the interspace/s in between the bearings as seen along the rotation axis A. Purely as an example, being usable for an in-wheel arrangement 300, 300' of a robotic lawn mower 100, the extension b, b' along the rotation axis A, A' may be in the range of -55 mm, preferably 10-45 mm, more preferably 15-35 mm, most preferably 20-30 mm.

Further modifications of the invention within the scope of the appended claims are feasible. As such, the present invention should not be considered as limited by the embodiments and figures described herein. Rather, the full scope of the invention should be determined by the appended claims, with reference to the description and drawings.

Claims

1.An in-wheel arrangement (300) for a work tool (100), such as a lawn mower, the in-wheel arrangement (300) comprising - a support member (310), attachable to the work tool (100), the support member (310) comprising a first end portion (312) attachable to the Work tool (100), and an opposite second end portion (316), - a stator assembly (320), comprising a stator (322) attachable to the second end portion (316) of the support member (310), - a rotor assembly (330) configured to at least partly enclose the stator assembly (320) in an inner space (338) of the rotor assembly (330), and - a bearing assembly (340), wherein the rotor assembly (330) is rotatably supported on the support member (310) by means of the bearing assembly (340) for rotation of the rotor assembly (330) about a rotation axis (A), and wherein the rotor assembly (330) comprises - a rotor portion (332), comprising or being constituted by a rotor (336) and being configured to at least partly enclose the stator assembly (320), and - a motor cover portion (334), configured to at least partly cover a first axial side (324) of the stator assembly (320), which first axial side (324) is adapted to face the first end portion (312) of the support member (310), characterized in that the rotor assembly (330) is rotatably supported by the bearing assembly (340) only between the first end portion (312) of the support member (310) and the first axial side (324) of the stator assembly (320).

2.The in-wheel arrangement (300) according to claim 1, wherein the bearing assembly (340) has an extension (b) along the rotation axis (A) in the range of 3%-40% of an inner diameter (a) of the rotor (336), preferably in the range of 5%- 35%, more preferably in the range of 10%-30%, most preferably in the range of 15%-25%.

3.The in-wheel arrangement (300) according to claim 1 or 2, wherein the bearing assembly (340) comprises a first bearing (342) and a second bearing (344) interspaced by a c-c distance (d) along the rotation axis being in the range of 3%-35% of the inner diameter (a) of the rotor (336), preferably in the range of 5%-30%, more preferably in the range of 10%-25%, most preferably in the range of 15%-20%.

4.The in-wheel arrangement (300) according to any one of the preceding claims, wherein the rotor assembly (330) further comprises a circumferential traction portion (352) adapted to surround the rotor portion (332), the circumferential traction portion (352) being provided with traction means, such as a traction pattern and/or a tyre (354) attached to, or integrated with, the circumferential traction portion (352).

5.The in-wheel arrangement (300) according to any one of the preceding claims, wherein the rotor assembly (330) further comprises a wheel cover portion (356), adapted to at least partly cover a second axial side (326) of the stator assembly (320), the second axial side (326) being on the axially opposite side of the stator assembly (320) With respect to the first axial side (324), the wheel cover portion (334) being adapted to be directly or indirectly attached to the rotor portion (332) by a wheel cover attachment means, which preferably is releasable and reattach- able, such as a screw and a corresponding receiving bore (362) of the rotor portion (332).

6.The in-wheel arrangement (300) according to claim 5, wherein the wheel cover portion (356) is made of plastics, preferably of injection-moulded plastics.

7.The in-wheel arrangement (300) according to claim 5 or 6, wherein the wheel cover portion (356) and the circumferential traction portion (352) form a single unitary component.

8.The in-wheel arrangement (300) according to any one of the preceding claims further comprising a control unit (370), wherein the control unit (370) is adapted to be located at or adjacent to the second end portion (316) of the support member (310).

9.The in-wheel arrangement (300) according to claim 8, wherein the control unit (370) comprises a printed circuit board (372), preferably without an opening for thesupport member (310).

10.The in-wheel arrangement (300) according to claim 8 or 9 further comprising an electrical wire (373), adapted to be connected to the control unit (370), the support member (310) of the in-wheel arrangement (300) being hollow, the electrical wire (373) being adapted to extend through the support member (310) from a first end (314) of the support member (310) to a second end (318) of the support member (310), the second end (318) being opposite to the first end (314).

11.The in-wheel arrangement (300) according to claim 10, the electrical wire (373) comprising at least one electrical connector (374) for attachment to the control unit (370), the electrical connector (374) and the hollow support member (310) being sized such that the electrical connector (374) is movable through the hollow support member (310).

12.The in-wheel arrangement (300) according to claim 10 or 11, wherein the electrical wire (373) is adapted to be releasably attached to the control unit (370), preferably also reattachably attached, e.g. by means of the electrical connector (374) of the electrical wire (373) cooperating with a corresponding electrical connector (376) of the control unit (370).

13.The in-wheel arrangement (300) according to any one of claims 8-12 further comprising at least one electrical connection assembly (378) configured to electrically connect the stator (322) and the control unit (370), the electrical connection assembly (378) preferably being releasable, more preferably the electrical connection assembly (378) being releasable and reattachable.

14.The in-wheel arrangement (300) according to any one of the preceding claims further comprising a rotation sensor arrangement (380) located at the rotation axis (A) for measurement of a rotational position of the rotor assembly (330) relative to the stator assembly (320).

15.The in-wheel arrangement (300) according to claim 14, wherein the rotation sensor arrangement (380) comprises a sensed member (382), such as a magnet,located on the rotor assembly (330) at the rotation axis (A).

16. The in-wheel arrangement (300) according to claim 15, wherein the rotation sensor arrangement (380) further comprises a sensor (384), configured to sense a relative rotational orientation of the sensed member (382) about the rotation axis (A) with respect to the sensor (384), the sensor (384) being directly or indirectly attached to the stator assembly (320) and located at the rotation axis (A).

17. The in-wheel arrangement (300) according to claim 16, when dependent on claim 9, wherein the sensor (384) is attached to, or forms a part of, the printed circuit board (372) of the control unit (370).

18. Awork tool (100), such as a lawn mower, comprising at least one in-wheel arrangement (300) according to any one of the preceding claims, preferably comprising two or four in-wheel arrangements (300) according to any one of the preceding claims.