WO2021215980A1 - Tondeuse à gazon et roue d'entraînement de tondeuse à gazon - Google Patents

Tondeuse à gazon et roue d'entraînement de tondeuse à gazon Download PDF

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Publication number
WO2021215980A1
WO2021215980A1 PCT/SE2021/050330 SE2021050330W WO2021215980A1 WO 2021215980 A1 WO2021215980 A1 WO 2021215980A1 SE 2021050330 W SE2021050330 W SE 2021050330W WO 2021215980 A1 WO2021215980 A1 WO 2021215980A1
Authority
WO
WIPO (PCT)
Prior art keywords
lawnmower
wheel
torque
members
wheel member
Prior art date
Application number
PCT/SE2021/050330
Other languages
English (en)
Inventor
Lars EDERFORS
Original Assignee
Husqvarna Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Husqvarna Ab filed Critical Husqvarna Ab
Priority to DE112021000267.8T priority Critical patent/DE112021000267T5/de
Publication of WO2021215980A1 publication Critical patent/WO2021215980A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B15/00—Wheels or wheel attachments designed for increasing traction
    • B60B15/02—Wheels with spade lugs
    • B60B15/10—Wheels with spade lugs with radially-adjustable spade lugs; Control mechanisms therefor
    • B60B15/12—Wheels with spade lugs with radially-adjustable spade lugs; Control mechanisms therefor involving cams or eccentric hoops
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01D—HARVESTING; MOWING
    • A01D34/00—Mowers; Mowing apparatus of harvesters
    • A01D34/006—Control or measuring arrangements
    • A01D34/008—Control or measuring arrangements for automated or remotely controlled operation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B15/00—Wheels or wheel attachments designed for increasing traction
    • B60B15/02—Wheels with spade lugs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B2900/00—Purpose of invention
    • B60B2900/70—Adaptation for
    • B60B2900/721—Use under adverse external conditions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Y—INDEXING SCHEME RELATING TO ASPECTS CROSS-CUTTING VEHICLE TECHNOLOGY
    • B60Y2200/00—Type of vehicle
    • B60Y2200/20—Off-Road Vehicles
    • B60Y2200/22—Agricultural vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Y—INDEXING SCHEME RELATING TO ASPECTS CROSS-CUTTING VEHICLE TECHNOLOGY
    • B60Y2200/00—Type of vehicle
    • B60Y2200/40—Special vehicles

Definitions

  • the present disclosure relates to lawnmower comprising at least one drive wheel and a propulsion motor configured to rotate the drive wheel.
  • the present disclosure further relates to a drive wheel for a lawnmower.
  • a walk-behind mower is a lawnmower usually comprising an elongated handle allowing a user to push, and/or to guide, the lawnmower. Some walk-behind mowers comprise a propulsion arrangement configured to drive one or more drive wheels of the lawnmower. Walk-behind mowers lacking a propulsion arrangement are sometimes referred to as “push mowers”.
  • a riding mower is a mower comprising a seat for a user, a steering device, such as a steering wheel, and a motor configured to provide motive power to the riding mower. Usually, riding mowers are used to mow bigger lawns, gardens, parks, sports fields, golf courts or the like.
  • Self-propelled autonomous robotic lawnmowers have become increasingly popular, partly because they usually are capable of performing work which previously was made manually.
  • a self-propelled robotic lawnmower is capable of navigating in an area in an autonomous manner, i.e. without the intervention of a user.
  • the robotic lawnmower may move in a systematic and/or random pattern to ensure that the area is completely covered.
  • Some robotic lawnmowers require a user to set up a boundary wire around an area that defines the area to be operated by the robotic lawnmower.
  • Such robotic lawnmowers use a sensor to locate the boundary wire and thereby the boundary of the area to be operated. When such a robotic lawnmower reaches the boundary wire, the robotic lawnmower is usually stopped and then operated in a direction opposite to the direction of travel that the robotic lawnmower had at the time of the detection of the boundary wire.
  • robotic lawnmowers may comprise other types of positioning units and sensors, for example sensors for detecting an event, such as a collision with an object within the area.
  • sensors for detecting an event such as a collision with an object within the area.
  • the robotic lawnmower is usually stopped and then operated in a direction opposite to the direction of travel that the robotic lawnmower had at the time of the detection of the collision.
  • Traction is a problem associated with lawnmowers comprising driven wheels. Many areas comprise more or less slopes which add to the problem of traction, especially in wet conditions.
  • Another problem associated with robotic lawnmowers is wear and tear of the area operated by the robotic lawnmower.
  • wheel slip of one or more wheels of the lawnmower may cause unwanted marks in the area operated by the lawnmower.
  • the presence of slopes in an area operated may significantly increase the probability of unwanted marks in the area due to an increased risk of wheel slip.
  • the lack of traction may adversely affect the coverage of an area operated by the robotic lawnmower.
  • the lack of traction may affect the travelling direction of the lawnmower. That is, wheel slip of one or more wheels of the robotic lawnmower may cause unexpected changes of the travel direction of the robotic lawnmower, which, due to the topography of the area, may result in that some parts of the area are operated more frequently, and some other parts of the area are operated less frequently.
  • a further problem associated with lawnmowers in general is the build-up of matter, such as cuttings, onto various components of the lawnmower.
  • matter, such as cuttings may stick to the wheels of the lawnmower and to portions of the lawnmower surrounding the wheels. If so, rotation of the wheels may become blocked.
  • build up of matter onto a wheel may adversely affect the traction of the wheel.
  • a lawnmower comprising at least one drive wheel and a propulsion motor configured to rotate the drive wheel.
  • the drive wheel comprises a first wheel member connected to the propulsion motor and a second wheel member comprising a ground engaging surface configured to abut against a ground surface during operation of the lawnmower.
  • the drive wheel further comprises a number of grip enhancing members movably arranged relative to the ground engaging surface between a retracted and an extracted position.
  • the drive wheel further comprises a mechanism configured to move the grip enhancing members between the retracted and the extracted position based on a torque between the first and second wheel members.
  • a lawnmower is provided capable of obtaining an automatic control of the position of the grip enhancing members, and thereby also of the grip of the drive wheel, based on the need for traction. That is, the risk of wheel slip is higher when the torque between the first and second wheel members is high, compared to when the torque between the first and second wheel members is low.
  • the grip enhancing members can be moved to the extracted position when the torque between the first and second wheel members is high, i.e. when there is a need for higher wheel grip.
  • the grip enhancing members can be moved to the retracted position when the torque between the first and second wheel members is low, i.e. when the need for wheel grip is low.
  • the gravitational force acting on the lawnmower decreases the traveling speed of the lawnmower.
  • the torque between the first and second wheel members increases when the lawnmower reaches the uphill slope.
  • the first wheel member is connected to the propulsion motor and the second wheel member comprises the ground engaging surface. Accordingly, as a result of the increased torque between the first and second wheel members, the mechanism can move the grip enhancing members to the extracted position. Thereby the grip of the drive wheel can be significantly enhanced, and the risk of wheel slip can thereby be significantly reduced when the lawnmower is traveling up the uphill slope.
  • the torque between the first and second wheel members decreases, and the mechanism can, as a result thereof, move the grip enhancing members to the retracted position.
  • the need for traction is lower when traveling on a flat area than when traveling along an uphill slope. In this manner, an automatic control of the position of the grip enhancing members is provided based on the need for traction.
  • the gravitational force on the lawnmower acts in a direction wanting to increase the traveling speed of the lawnmower.
  • the lawnmower is controlled to operate at constant speed, or at least is provided with a maximum propulsion speed of the propulsion motor, the torque between the first and second wheel members increases when the lawnmower reaches the downhill slope.
  • the first wheel member is connected to the propulsion motor and the second wheel member comprises the ground engaging surface.
  • the mechanism can move the grip enhancing members to the extracted position.
  • the increased torque between the first and second wheel members in the start-up phase may cause the mechanism to move the grip enhancing members to the extracted position.
  • the torque between the first and second wheel members then decreases as the travel speed of the lawnmower increases.
  • the mechanism may move the grip enhancing members to the retracted position.
  • the risk of wheel slip is greater at the start-up phase of the lawnmower as compared to when the lawnmower is travelling at constant speed along a sufficiently flat area.
  • an automatic control of the position of the grip enhancing members can be provided based on the need for traction.
  • the control of the position of the grip enhancing members, based on the torque between the first and second wheel members, is particularly advantageous if the lawnmower is to initiate propulsion in a steep slope, for example after having stopped in a steep slope. Accordingly, due to the features of the lawnmower according to the embodiments herein, a lawnmower is provided having conditions for improved traction when needed. As a further result, a lawnmower is provided capable of operating areas having greater slope inclinations. In this manner, a lawnmower is provided capable of matching demands of customers and the topology of their gardens. Furthermore, since the lawnmower is capable of reducing the risk of wheel slip, a lawnmower is provided having a reduced probability of making unwanted marks in the operated area.
  • the mechanism is configured to move the grip enhancing members between the retracted and the extracted position based on the torque between the first and second wheel members, any matter stuck onto the grip enhancing members may be removed from the grip enhancing members when the grip enhancing members are moved to the retracted position. In this manner, the risk of build-up of matter onto the drive wheel is significantly reduced as compared to such a solution.
  • the lawnmower in view of a solution comprising stationary spikes or studs arranged on the drive wheel, the lawnmower can be operated with the grip enhancing members in the retracted position when the need for traction is lower. Thereby, wear and tear of an area operated can be reduced. Moreover, the lawnmower can be operated with the grip enhancing members in the retracted position when traveling on hard surfaces such as pavement. In this manner, wear and tear of the grip enhancing members and of the hard surface can be reduced. Moreover, vibration of the lawnmower can be reduced when traveling on such surfaces.
  • the grip enhancing members may remove matter stuck onto surfaces surrounding the drive wheel, such as fenders, mudguards, and the like, when the grip enhancing members are in the extracted position. In this manner, it can be ensured that a clearance space is obtained around the drive wheel when the grip enhancing members are in the retracted position.
  • a lawnmower is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.
  • the first wheel member is configured to rotate relative to the second wheel member between a first and a second position based on the torque between the first and second wheel members.
  • a simple and low cost mechanism configured to move the grip enhancing members between the retracted and the extracted position based on the rotational position of the first wheel member relative to the second wheel member.
  • the mechanism is configured to move the grip enhancing members to the retracted position upon rotation of first wheel member to the first position, and wherein the drive wheel comprises one or more elastic members configured to bias the first wheel member towards the first position.
  • the grip enhancing members can be moved to the retracted position in a simple, reliable, and efficient manner.
  • any matter stuck onto the grip enhancing members may be removed from the grip enhancing members in an efficient manner when the torque between the first and second wheel members is below a threshold torque.
  • the grip enhancing members are lockable in at least one of the retracted position and the extracted position.
  • a user-friendly lawnmower is provided allowing a user to lock the grip enhancing members in at least one of the retracted position and the extracted position.
  • a user may want to lock the grip enhancing members in the extracted position when cutting in wet conditions, when cutting less sensitive areas, when cutting undulated areas having a high proportion of steep slopes, and/or when wanting to aerate a lawn.
  • a user may want to lock the grip enhancing members in the retracted position in dry conditions, and/or when cutting flatter areas.
  • the mechanism is configured to move the grip enhancing members to the extracted position when a torque having a first torque direction rises above a first threshold torque, and wherein the lawnmower is accelerated in a forward direction of the lawnmower when a torque having the first torque direction is applied onto the first wheel member.
  • a lawnmower is provided capable of improving the grip in the forward direction thereof in an efficient manner, when needed.
  • the mechanism is configured to move the grip enhancing members to the extracted position when a torque between the first and second wheel members having a second torque direction rises above a second threshold torque, and wherein the lawnmower is accelerated in a reverse direction of the lawnmower when a torque having the second torque direction is applied onto the first wheel member.
  • a lawnmower is provided capable of improving the grip in the reverse direction thereof in an efficient manner, when needed.
  • one of the first and second threshold torques is lower than the other of the first and second threshold torques.
  • a lower propulsion torque in one of the mowing directions of the lawnmower is required for moving the grip enhancing members to the retracted position than what is required in the other mowing direction.
  • the second threshold torque is lower than the first threshold torque.
  • a lower propulsion torque in the reverse direction of the lawnmower is required for moving the grip enhancing members to the extracted position than what is required in the forward direction of the lawnmower.
  • the lawnmower is to initiate propulsion in the reverse direction in a steep slope, for example after having stopped in a steep slope.
  • the grip enhancing members are more likely to be moved to the extracted position when travelling in the forward direction down a slope.
  • the mechanism is transferable to a state in which the mechanism keeps the grip enhancing members in the retracted position also when a torque is applied onto the first wheel member in one of the first and second torque directions exceeding the respective threshold torque.
  • a user can prevent the grip enhancing members from moving to the extracted position upon propulsion in one of the mowing directions of the lawnmower, i.e. in one of the forward direction and the reverse direction. In this manner, a more user-friendly lawnmower is provided.
  • the mechanism is configured to move the grip enhancing members in radial directions of the drive wheel.
  • an enhanced grip can be provided in a simple and efficient manner.
  • conditions are provided for a simple and low cost mechanism for moving the grip enhancing members between the retracted and the extracted position.
  • the grip enhancing members are formed as elongated rods.
  • an enhanced grip can be provided in a simple and efficient manner.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the grip enhancing members are movably arranged in through holes of the second wheel member.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • any matter stuck onto the grip enhancing members can be removed from the grip enhancing members in an efficient manner when the grip enhancing members are moved towards the retracted state.
  • the lawnmower comprises a cleaning device configured to clean the ground engaging surface and/or the grip enhancing members during operation of the lawnmower.
  • a cleaning device may for example comprise a brush arrangement comprising a brush configured to rotate relative to the ground engaging surface during operation of the lawnmower.
  • the brush may comprise a brush body and a number of bristles arranged on the brush body.
  • the bristles may be configured to abut against the grip enhancing members when the grip enhancing members are in the extracted position and the brush body is rotating.
  • the bristles may be configured to abut against portions of the grip enhancing members upon rotation of the brush body when the grip enhancing members are in the retracted position.
  • the bristles may be configured to abut against the ground engaging surface upon rotation of the brush body. In this manner, the ground engaging surface and/or the grip enhancing members can be cleaned during operation of the lawnmower. As a result, the risk of build-up of matter onto the drive wheel is further minimized.
  • the second wheel member comprises a number of stationary friction enhancing elements protruding from the ground engaging surface, and wherein the grip enhancing members are arranged in areas between the stationary friction enhancing elements.
  • the drive wheel may roll over a hard surface without the grip enhancing members touching the hard surface, at least when the grip enhancing members are in the retracted position.
  • the grip enhancing members can be provided in a hard material, such as a metal material, without risking damage of hard surfaces and/or components of the drive wheel.
  • the mechanism comprises a number of cam surfaces and a number of followers each abutting against a cam surface. Thereby, a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the first wheel member comprises the cam surfaces.
  • a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost- efficient manner while being capable improving the grip in an efficient manner when needed.
  • one or more of the grip enhancing members is/are attached to a follower.
  • a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • two or more of the grip enhancing members are attached to one follower of the number of followers. In this manner, a further simpler and more cost-efficient mechanism can be provided.
  • the mechanism comprises a number of elastic members forcing the followers against the cam surfaces.
  • the forcing of the followers against the cam surfaces may bias the first wheel member towards a position relative to the second wheel member in which the grip enhancing members assume the retracted position.
  • a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the cam surfaces are curve-shaped in a plane perpendicular to a rotation axis of the drive wheel.
  • a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the curve-shape of the cam surfaces is arranged such that an actuation speed of the grip enhancing members is higher close to the retracted position than the actuation speed close to the extracted position.
  • the grip enhancing members can be moved in a quick manner from the retracted position and with a greater force as they approach the extracted position.
  • the higher actuation speed close to the retracted position may be obtained by arranging the cam surfaces in such a manner that the followers abut against portions of the cam surfaces having steeper angles relative to tangential directions of the drive wheel when the grip enhancing members are close to the retracted position as compared to when the grip enhancing members are close to the extracted position.
  • the cam surfaces are arc-shaped in a plane perpendicular to a rotation axis of the drive wheel.
  • a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the arc-shaped cam surfaces may ensure that an actuation speed of the grip enhancing members is higher close to the retracted position than the actuation speed close to the extracted position. In this manner, the grip enhancing members can be moved in a quick manner from the retracted position and with a greater force as they approach the second position.
  • the drive wheel comprises the same number of cam surfaces as the number of followers.
  • a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • a follower of the number of followers is configured to assume a position between two adjacent cam surfaces when the torque between the first and second wheel members is below a threshold torque.
  • a simple, efficient, and reliable mechanism is provided having conditions for moving the grip enhancing members to the extracted position based on the torque between the first and second wheel members in two torque directions.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the cam surfaces are arranged such that the followers are closer to an rotation axis of the drive wheel when the torque between the first and second wheel members is below a threshold torque, than when the torque between the first and second wheel members exceeds the threshold torque.
  • the mechanism comprises a plurality of arms arranged between the first and second wheel members, and wherein at least a number of the plurality of arms are configured to move based on the torque between the first and second wheel members so as to cause the movement of the grip enhancing members between the retracted and the extracted position.
  • a simple, efficient, and reliable mechanism is provided.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • At least a number of the plurality of arms are configured to be subjected to elastic deformation when the torque between the first and second wheel members rises above a threshold torque.
  • a simpler and more reliable mechanism can be provided circumventing the need for hinges, cam surfaces, and the like.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the mechanism is a compliant mechanism.
  • a simpler and more reliable mechanism can be provided circumventing the need for hinges, cam surfaces, and the like.
  • a drive wheel is provided having conditions and characteristics suitable for being manufactured and assembled in a cost-efficient manner while being capable improving the grip in an efficient manner when needed.
  • the lawnmower is a self-propelled robotic lawnmower.
  • a robotic lawnmower is provided capable of obtaining an automatic control of the position of the grip enhancing members, and thereby also of the grip of the drive wheel, based on the need for traction in a simple and efficient manner.
  • the control of the position of the grip enhancing members based on the torque between the first and second wheel members is particularly advantageous if the robotic lawnmower is to initiate propulsion in a steep slope, for example after having stopped at a boundary wire positioned in a steep slope.
  • a robotic lawnmower since the robotic lawnmower has conditions for improved traction, a robotic lawnmower is provided capable of operating areas having greater slope inclinations. In this manner, the robotic lawnmower allows for the placement of boundary wires in slopes having greater a slope inclinations than would be possible otherwise. In this manner, a robotic lawnmower is provided capable of matching demands of customers and the topology of their gardens.
  • the robotic lawnmower can be operated with the grip enhancing members in the retracted position when traveling on hard surfaces such as pavement or the top surface of a charging station. In this manner, wear and tear of the grip enhancing members and of the hard surface can be reduced. Moreover, vibration of the robotic lawnmower can be reduced when traveling on such surfaces.
  • the lawnmower comprises a control arrangement configured to control operation of the propulsion motor, and wherein the control arrangement is configured to selectively perform a control operation in which the propulsion motor is controlled to apply a torque onto the first wheel member causing a movement of the grip enhancing members towards the extracted position.
  • a lawnmower is provided capable of actively moving the grip enhancing members to the retracted position.
  • the grip can be improved when determined necessary, for example based on input data.
  • lawnmower is provided having improved conditions for navigating in areas having a high risk of wheel slip, such as undulated areas.
  • control arrangement is configured to determine whether to perform the control operation based on input data.
  • a lawnmower is provided capable of actively moving the grip enhancing members to the retracted position based on input data.
  • a lawnmower is provided having further improved conditions for navigating in areas having a high risk of wheel slip, such as undulated areas.
  • the input data is representative of a current or impending slope inclination at the location of the lawnmower and/or a current or impending inclination angle of the lawnmower.
  • a lawnmower is provided having improved conditions for operating in steep slopes. That is, if the data indicates presence of a current or impending slope inclination exceeding a threshold inclination, the control arrangement may perform the control operation to actively move the grip enhancing members to the extracted position. Thereby, the grip is significantly improved and the risk of wheel slip in the slope is significantly reduced.
  • the input data is representative of one or more of traction conditions at the location of the lawnmower, weather conditions at the location of the lawnmower, and humidity at the location of the lawnmower.
  • a lawnmower is provided having improved conditions for operating under conditions with increased risk of wheel slip.
  • the input data is representative of presence of wheel slip of one or more wheels of the lawnmower.
  • a lawnmower is provided capable of actively improving the grip of the drive wheel in case wheel slip of one or more wheels of the lawnmower is detected.
  • a lawnmower is provided having improved conditions for navigating in areas having a high risk of wheel slip, such as undulated areas.
  • the control operation comprises stopping the lawnmower before controlling the propulsion motor to apply the torque onto the first wheel member.
  • a lawnmower is provided having further improved conditions for regaining grip after wheel slip of one or more wheels of the lawnmower is detected. This because it is ensured that the ground engaging surface of the second wheel member is stationary relative to the ground surface before initiating propulsion.
  • a lawnmower is provided having further improved conditions for navigating in areas having a high risk of wheel slip, such as undulated areas. Moreover, the risk of unwanted marks in the operated area is reduced.
  • the object is achieved by a drive wheel for a lawnmower, wherein the lawnmower comprises a propulsion motor configured to rotate the drive wheel.
  • the drive wheel comprises a first wheel member configured to be connected to the propulsion motor of the lawnmower and a second wheel member comprising a ground engaging surface configured to abut against a ground surface during operation of the lawnmower.
  • the drive wheel further comprises a number of grip enhancing members movably arranged relative to the ground engaging surface between a retracted and an extracted position.
  • the drive wheel further comprises a mechanism configured to move the grip enhancing members between the retracted and the extracted position based on a torque between the first and second wheel members.
  • a drive wheel is provided capable of obtaining an automatic control of the position of the grip enhancing members, and thereby also of the grip of the drive wheel, based on the need for traction.
  • a drive wheel is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.
  • the drive wheel according to the second aspect of the invention is combinable with any one of the features of the drive wheel of the lawnmower according to the first aspect of the invention. That is, the drive wheel according to the second aspect of the invention may comprise one or more of the features, functions, and advantages of the drive wheel of the lawnmower described herein.
  • Fig. 1 schematically illustrates a lawnmower according to some embodiments
  • Fig. 2 illustrates a perspective view of a drive wheel of the lawnmower illustrated in Fig. 1 ,
  • Fig. 3 illustrates a perspective view of a first wheel member of the drive wheel illustrated in Fig. 2,
  • Fig. 4 illustrates a perspective view of a second wheel member of the drive wheel illustrated in Fig. 2,
  • Fig. 5 illustrates the first wheel member illustrated in Fig. 3 rotated to a second position
  • Fig. 6 illustrates the second wheel member illustrated in Fig. 4 with grip enhancing members in an extracted position
  • Fig. 7 illustrates a drive wheel according to some further embodiments of the present disclosure.
  • Fig. 8 illustrates the drive wheel illustrated in Fig. 7 with a first wheel member rotated to a second position.
  • Fig. 1 schematically illustrates a lawnmower 1 according to some embodiments.
  • the lawnmower 1 is a self-propelled autonomous robotic lawnmower 1 capable of navigating and cutting grass in an autonomous manner in an area without the intervention or the control of a user.
  • the self- propelled autonomous robotic lawnmower 1 is in some places herein referred to as “the robotic lawnmower 1” or simply the “lawnmower 1”.
  • the robotic lawnmower 1 is configured to be used to cut grass in areas used for aesthetic and recreational purposes, such as gardens, parks, city parks, sports fields, lawns around houses, apartments, commercial buildings, offices, and the like.
  • the lawnmower 1 may be another type of lawnmower 1, such as a walk-behind mower or a riding mower.
  • the lawnmower 1 comprises a lawnmower chassis 2 and a number of wheels 3, 6 supporting the lawnmower chassis 2 by abutting against a ground surface 22 during operation of the lawnmower 1. In Fig. 1, only two wheels 3, 6 are visible. However, according to the illustrated embodiments, the lawnmower 1 comprises four wheels 3, 6, namely two drive wheels 3 and two support wheels 6.
  • the drive wheels 3 of the lawnmower 1 may each be powered by a propulsion motor 4 of the lawnmower 1 to provide motive power and/or steering of the lawnmower 1.
  • the lawnmower 1 may thus comprise one propulsion motor 4 per drive wheel 3, wherein the propulsion motor/motors 4 is/are configured to rotate a drive wheel 3.
  • the lawnmower 1 may comprise a transmission between the respective propulsion motor 4 and drive wheel 3.
  • the propulsion motor/motors 4 may comprise an electrical motor.
  • a longitudinal direction Id of the lawnmower 1 is indicated.
  • the longitudinal direction Id of the lawnmower 1 extends in a longitudinal plane LP of the lawnmower 1.
  • the longitudinal plane LP is parallel to a ground surface 22 when the lawnmower 1 is positioned in an intended use position onto a flat ground surface 22, as illustrated in Fig. 1.
  • the longitudinal direction Id of the lawnmower 1 is parallel to a forward direction fd of travel of the lawnmower 1 as well as a reverse direction rd of travel of the lawnmower 1, as is further explained herein.
  • a horizontal plane hp at the location of the lawnmower 1 is indicated.
  • the drive wheels 3 of the lawnmower 1 are non- steered wheels having a fix rolling direction in relation to the lawnmower chassis 2.
  • the respective rolling direction of the drive wheels 3 of the lawnmower 1 is substantially parallel to the longitudinal direction Id of the lawnmower 1.
  • the support wheels 6 are non-driven wheels.
  • the support wheels 6 can pivot around a respective pivot axis such that the rolling direction of the respective support wheel 6 can follow a travel direction of the lawnmower 1.
  • the lawnmower 1 may be referred to as a four- wheeled rear wheel driven lawnmower 1. According to further embodiments, the lawnmower 1 may be provided with another number of wheels 3, 6, such as three wheels. Moreover, according to further embodiments, the lawnmower 1 may be provided with another configuration of driven and non-driven wheels, such as a front wheel drive or an all-wheel drive.
  • the lawnmower 1 comprises a cutting unit 10 configured to cut vegetation during operation of the lawnmower 1.
  • the cutting unit 10 comprises a cutting disc provided with a number of cutting members arranged at a periphery of the cutting disc.
  • the lawnmower 1 comprises a motor configured to rotate the cutting unit 10.
  • the motor may comprise an electric motor.
  • the motor is not illustrated in Fig. 1 for the reason of brevity and clarity.
  • the cutting unit 10 is configured to rotate in a cutting plane substantially parallel to the longitudinal plane LP of the lawnmower 1.
  • the angle between the cutting plane and the longitudinal plane LP may be less than 7 degrees. As indicated in Fig.
  • the drive wheel 3 comprises a first wheel member 5 and a second wheel member 7.
  • the first wheel member 5 is connected to the propulsion motor 4. As indicated above, the first wheel member 5 may be connected to the propulsion motor 4 via a transmission, or the like.
  • the second wheel member 7 comprises a ground engaging surface T.
  • the ground engaging surface 7’ is configured to abut against a ground surface 22 during operation of the lawnmower 1.
  • the ground engaging surface 7’ may also be referred to as a rolling surface 7’ of the drive wheel 3. This because the ground engaging surface 7’ is configured to roll against the ground surface 22 during operation of the lawnmower 1.
  • Fig. 2 illustrates a perspective view of a drive wheel 3 of the lawnmower 1 illustrated in Fig.
  • the drive wheel 3 is configured to rotate around a rotation axis ax during operation of the lawnmower 1.
  • the rotation axis ax is also indicated in Fig. 1.
  • the drive wheel 3 comprises a number of grip enhancing members 8.
  • the grip enhancing members 8 are movably arranged relative to the ground engaging surface 7’ between a retracted and an extracted position. In Fig. 2, the grip enhancing members 8 are illustrated in the retracted position.
  • the drive wheel 3 further comprises a mechanism 9 configured to move the grip enhancing members 8 between the retracted position and the extracted position based on a torque between the first and second wheel members 5, 7, as is further explained herein.
  • the first wheel member 5 is configured to rotate relative to the second wheel member 7 between a first and a second position based on the torque between the first and second wheel members 5, 7.
  • the mechanism 9 is configured to move the grip enhancing members 8 to the retracted position upon rotation of first wheel member 5 to the first position and is configured to move the grip enhancing members 8 to the extracted position upon rotation of first wheel member 5 to the second position, as is further explained herein.
  • Fig. 3 illustrates a perspective view of the first wheel member 5 of the drive wheel 3 illustrated in Fig. 2.
  • the first wheel member 5 comprises a shaft interface 14 for the connection to a drive shaft.
  • the drive shaft may thus be connected to the propulsion motor 4 indicated in Fig. 1 , for example via a transmission.
  • the mechanism 9 comprises a number of cam surfaces 11 and a number of followers 13.
  • the first wheel member 5 comprises the cam surfaces 11.
  • the mechanism 9 comprises the same number of cam surfaces 11 as the number of followers 13. That is, according to the illustrated embodiments, the mechanism 9 comprises six cam surfaces 11 and six followers 13.
  • the mechanism 9 may comprise another number of cam surfaces 11 and followers 13, such as a number between three and twenty.
  • the followers 13 are illustrated in positions corresponding to positions obtained when the drive wheel is in the assembled state and the grip enhancing members 8 are in the retracted state.
  • the first wheel member 5 is in the first position relative to the second wheel member when the grip enhancing members 8 are in the retracted state.
  • the followers 13 have been included in Fig. 3 to improve understanding of the operating principle of the mechanism 9.
  • the grip enhancing members 8 are attached to the followers 13.
  • two grip enhancing members 8 are attached to one follower 13.
  • another number of grip enhancing members 8 may be attached to each follower 13, such as one, three, four, or the like.
  • Fig. 4 illustrates a perspective view of the second wheel member 7 of the drive wheel 3 illustrated in Fig. 2.
  • the followers 13 are illustrated in positions corresponding to positions obtained when the drive wheel is in the assembled state and the grip enhancing members 8 are in the retracted state, i.e. when the first wheel member 5 is in the first position relative to the second wheel member 7.
  • the grip enhancing members 8 are movably arranged in through holes 17 of the second wheel member 7.
  • the through holes 17 of the second wheel member 7 are provided through the ground engaging surface 7’ of the drive wheel.
  • the through holes 17 are provided in directions substantially coinciding with radial directions R of the drive wheel.
  • the grip enhancing members 8 are formed as elongated rods. Therefore, the grip enhancing members 8, as referred to herein, may also be referred to as studs 8.
  • the followers 13 are slidably arranged in radial directions R of the drive wheel in pockets 18 of the second wheel member 7. Thus, according to the illustrated embodiments, the followers 13 are rotationally locked in relation to the second wheel member 7 and the cam surfaces 11 are rotationally locked in relation to the first wheel member 5.
  • the mechanism 9 comprises a number of elastic members 15.
  • the elastic members 15 are configured to force the followers 13 against the cam surfaces 11.
  • the mechanism 9 comprises one elastic member 15 per follower 13, wherein the elastic member 15 is attached to the follower 13.
  • the elastic member 15 and the follower 13 may be provided in one piece of continuous material, such as a polymeric material.
  • elastic members 15 are formed as a respective leaf spring abutting against a radially inner surface of the second wheel member 7.
  • the elastic members 15 may comprise a coil spring, or the like.
  • the grip enhancing members 8 may be provided in a metal material, such as a steel material. Due to these features, the drive wheel can be manufactured and assembled in a cost-efficient manner while being capable of significantly enhancing the grip, as is further explained herein.
  • each follower 13 of the number of followers 13 is configured to assume a position between two adjacent cam surfaces 11 when the grip enhancing members 8 are in the retracted state, i.e. when the first wheel member 5 is in the first position relative to the second wheel member 7.
  • the followers 13 are illustrated in such positions.
  • the cam surfaces 11 are arranged such that the followers 13 are closer to an rotation axis ax of the drive wheel 3 when the grip enhancing members 8 are in the retracted state, than when the grip enhancing members 8 are in the extracted state.
  • the cam surfaces 11 are arc-shaped in a plane P perpendicular to a rotation axis ax of the drive wheel. As is further explained herein, according to further embodiments, the cam surfaces 11 may have another curve-shape in the plane P perpendicular to the rotation axis ax of the drive wheel.
  • Fig. 5 illustrates the first wheel member 5 illustrated in Fig. 3 rotated to the second position.
  • the first wheel member 5 has been rotated clockwise in Fig. 5 from the first position to the second position relative to a second wheel member.
  • the cam surfaces 11 are arranged such that the followers 13, and thus also the grip enhancing members 8, are located further from the rotation axis ax of the drive wheel 3 when the first wheel member 5 is in the second position, than when the first wheel member 5 is in the first position as illustrated in Fig. 3.
  • the followers 13 have been included in Fig. 5 to improve understanding of the operating principle of the mechanism 9.
  • Fig. 6 illustrates the second wheel member 7 illustrated in Fig. 4 with the grip enhancing members 8 in the extracted position. That is, in relation to the second wheel member 7 illustrated in Fig. 4, the grip enhancing members 8 have been moved to the extracted position by the abutting contact between the cam surfaces 11 and the followers 13.
  • the mechanism 9 is configured to move the grip enhancing members 8 to the extracted position upon rotation of first wheel member 5 to the second position relative to the second wheel member 7.
  • the elastic members 15 have been compressed as a result of the movement of the grip enhancing members 8 to the extracted position.
  • the elastic members 15 are configured to force the followers 13 against the cam surfaces 11 , the elastic members 15 apply a counter torque between the first and second wheel members 5, 7 acting to displace the first wheel member 5 towards the first position relative to the second wheel member 7 when the first wheel member 5 is in a position between the first and second positions.
  • the elastic members 15 are configured to bias the first wheel member 5 towards the first position.
  • the number of elastic members 15, the spring coefficients thereof, and the profile of the cam surfaces 11 thus determines the torque which has to be overcome in order to displace the first wheel member 5 towards the second position so as to move the grip enhancing members 8 to the extracted position.
  • the torque referred to in the previous sentence is in some places herein also referred to as a threshold torque.
  • a first and a second torque direction Td1, Td2 are indicated.
  • the lawnmower 1 is accelerated in a forward direction fd of the lawnmower 1 when a torque having the first torque direction Td1 is applied onto the first wheel member 5.
  • the first torque direction Td1 thus coincides with the forward rotational direction of the drive wheel 3, as referred to above.
  • the second torque direction Td2 is opposite to the first torque direction Td1.
  • the lawnmower 1 is accelerated in a reverse direction rd of the lawnmower 1 when a torque having the second torque direction Td2 is applied onto the first wheel member 5.
  • the second torque direction Td2 thus coincides with the reverse rotational direction of the drive wheel 3, as referred to above.
  • the mechanism 9 is configured to move the grip enhancing members 8 to the extracted position when a torque having a first torque direction Td1 rises above a first threshold torque.
  • the number of elastic members 15, the spring coefficients thereof, and the profile of the cam surfaces 11 thus determines the magnitude of the first threshold torque. Accordingly, when the propulsion motor 4 of the lawnmower 1 applies a torque onto the first wheel member 5 in the first torque direction Td1 exceeding the first threshold torque, the first wheel member 5 is rotated from the first position, as illustrated in Fig. 3, to the second position, illustrated in Fig. 5. As a result the grip enhancing members 8 are displaced from the retracted position, as illustrated in Fig. 3, to the extracted position, illustrated in Fig. 5. As indicated in Fig.
  • the mechanism 9 is configured to move the grip enhancing members 8 in radial directions R of the drive wheel 3.
  • the grip enhancing members 8 are distributed around the circumference of the ground engaging surface 7’ of the second wheel member 7 of the drive wheel 3. Since the grip enhancing members 8 protrudes further out from the ground engaging surface 7’ when in the extracted position, the grip of the drive wheel 3 is significantly improved.
  • the second wheel member 7 comprises a number of stationary friction enhancing elements 19 protruding from the ground engaging surface T.
  • the grip enhancing members 8 are arranged in areas 23 between the stationary friction enhancing elements 19.
  • the drive wheel 3 may roll over a hard surface without the grip enhancing members 8 touching the hard surface, at least when the grip enhancing members 8 are in the retracted position.
  • the lawnmower 1 comprises a control arrangement 21.
  • the control arrangement 21 is configured to control operation of the propulsion motor 4.
  • the control arrangement 21 may be configured to selectively perform a control operation in which the propulsion motor 4 is controlled to apply a torque onto the first wheel member 5 in the first torque direction Td1 or the second torque direction Td2 exceeding the first threshold torque or a second threshold torque, as is further explained herein.
  • the lawnmower 1 is illustrated as positioned onto a flat ground surface 22 being substantially parallel to a horizontal plane hp at the location of the lawnmower 1.
  • the torque between the first and second wheel members 5 is illustrated as positioned onto a flat ground surface 22 being substantially parallel to a horizontal plane hp at the location of the lawnmower 1.
  • the mechanism 9 will move the grip enhancing members 8 to the extracted position, as explained above. Thereby, the grip of the drive wheel 3 can be significantly improved when needed, i.e. such as when traveling up the uphill slope.
  • the first threshold torque may be set to a level such that the grip enhancing members 8 are moved to the extracted position when the lawnmower 1 is travelling at constant velocity up an uphill slope having a certain slope inclination.
  • the first threshold torque may be set to a level such that the grip enhancing members 8 are moved to the extracted position when the lawnmower 1 is travelling at constant velocity up an uphill slope having a slope inclination within the range of 7-13 degrees.
  • the torque between the first and second wheel members 5, 7 is higher than when travelling at constant speed.
  • the first threshold torque may be set to a sufficiently high level such that the lawnmower 1 can initiate propulsion in the forward direction fd when starting on a flat ground surface 22 without causing movement of the grip enhancing members 8 to the extracted position.
  • a control arrangement 21 of the lawnmower 1 can select whether to move the grip enhancing members 8 to the extracted position in a start-up phase of the lawnmower 1 by selecting the magnitude of the torque applied onto the first wheel member 5.
  • each follower 13 is in a position between two adjacent cam surfaces 11 when the first wheel member 5 is in the first position relative to the second wheel member 7, as seen in Fig. 3.
  • the first wheel member 5 is rotationally arranged relative to the second wheel member 7 in an opposite rotational direction from the first position towards a third position.
  • the difference between the second and third position is that the followers 13 are abutting against different cam followers 11 when the first wheel member 3 is rotated towards the third position than when the first wheel member 3 is rotated towards the second position.
  • each follower 13 is configured to cooperate with two adjacent cam surfaces 11 during operation of a lawnmower 1 comprising the drive wheel 3.
  • the first wheel member 5 rotates counterclockwise from the first position towards the third position.
  • the wording clockwise and counterclockwise as used herein only constitutes examples, as understood by a person skilled in the art, because the rotational direction of the first wheel member 5 relative to the second wheel member 7 depends the side of the lawnmower 1 at which the drive wheel 3 is intended to be arranged.
  • the third position is similar to the second position, illustrated in Fig. 5 in the sense that the followers 13 are displaced in radial directions R towards top surfaces of cam surfaces 11 when the first wheel member 5 is rotated towards the third position.
  • the mechanism 9 is configured to move the grip enhancing members 8 to the extracted position when a torque between the first and second wheel members 5, 7 having a second torque direction Td2 rises above the second threshold torque.
  • the number of elastic members 15, the spring coefficients thereof, and the profile of the cam surfaces 11 thus determines the magnitude of the second threshold torque. Accordingly, when the propulsion motor 4 of the lawnmower 1 applies a torque onto the first wheel member 5 in the second torque direction Td2 exceeding the second threshold torque, the first wheel member 5 is rotated from the first position, as illustrated in Fig. 3, to the third position. As a result, the grip enhancing members 8 are displaced from the retracted position towards the extracted position.
  • the cam surfaces 11 arranged on either side of the followers 13 comprise the same cam profile shapes, meaning that, according to the illustrated embodiments, the first and second threshold torques have the same magnitude.
  • the cam surfaces 11 arranged on either side of the followers 13 may be provided with different cam profile shapes. In this manner, one of the first and second threshold torques can be made lower than the other of the first and second threshold torques.
  • the second threshold torque is lower than the first threshold torque.
  • a lower torque applied onto the first wheel member 5 in the second torque direction Td2 is required for moving the grip enhancing members 8 to the extracted position than what is required moving the grip enhancing members 8 to the extracted position when a torque is applied onto the first wheel member 5 in the first torque direction Td1.
  • the lawnmower 1 is to initiate propulsion in the reverse direction rd up a steep uphill slope, for example after having stopped in such a slope.
  • the drive wheel 3 comprises a rotation limiting assembly 24,
  • the rotation limiting assembly 24, 26 is configured to lock the first wheel member 5 from rotating relative to second wheel member 7 past the second position and past the third position.
  • the rotation limiting assembly 24, 26 comprises a number of protrusions 24 arranged on the first wheel member 5 and a number of arc-shaped slots 26 arranged on the second wheel member 7.
  • the number of protrusions 24 may be arranged on the second wheel member 7 and a number of arc-shaped slots 26 may be arranged on the first wheel member 5.
  • Each protrusion 24 of the number of protrusion 24 extends into a slot 26 of the number of arc shaped slots 26 when the drive wheel 3 is in an assembled state.
  • Each slot 26 of the number of arc-shaped slots 26 comprises a first and a second stop surface 31 , 32.
  • the protrusions 24 are configured to abut against a first stop surface 31 of the slots 26 when the first wheel member 5 is in the second position relative to the second wheel member 7. In this manner, the first wheel member 5 is prevented from rotating past the second position.
  • the protrusions 24 are configured to abut against a second stop surface 32 of the slots 26 when the first wheel member 5 is in the third position relative to the second wheel member 7. In this manner, the first wheel member 5 is prevented from rotating past the third position.
  • the rotation limiting assembly 24, 26 comprises four slots 26 and four protrusions 24. According to further embodiments, the rotation limiting assembly 24, 26 may comprise another number of slots 26 and protrusions 24, such as one, two, three, five, or the like.
  • the rotation limiting assembly 24, 26 may comprise other types of components or structures than slots 26 and protrusions 24 for preventing rotation the first wheel member 5 relative to second wheel member 7 past the second position and past the third position.
  • the drive wheel 3 may lack a rotation limiting assembly.
  • the first wheel member 5 can be rotated relative to the second wheel member 7 with the grip enhancing members 8 in the extracted position, with the only limitation being the abutting force of the followers 13 against the cam surfaces 11.
  • a pulsating force can be applied onto a ground surface 22 via the ground engaging surface 7’ and the grip enhancing members 8 upon rotation of the first wheel member 5 relative to the second wheel member 7.
  • Such a pulsating force can facilitate take off of the lawnmower 1.
  • wheel slip of the ground engaging surface 7’ and the grip enhancing members 8 relative to the ground surface 22 can be further avoided.
  • the lawnmower 1 comprises a locking assembly allowing a locking of the grip enhancing members 8 in at least one of the retracted position and the extracted position.
  • a locking assembly may comprise means for locking the first wheel member 5 in one or more of the first, second, and third positions relative to the second wheel member 7.
  • a locking assembly may comprise one or more fastening elements screwed into the protrusions 24 of the rotation limiting assembly 24, 26 which can be tightened in order to lock the first wheel member 5 from rotating relative to the second wheel member 7.
  • the mechanism 9 is transferable to a state in which the mechanism 9 keeps the grip enhancing members 8 in the retracted position also when a torque is applied onto the first wheel member 5 in one of the first and second torque directions Td1, Td2 exceeding the respective threshold torque. Thereby, a user can prevent the grip enhancing members 8 from moving to the extracted position upon propulsion in one of the forward direction fd and the reverse direction rd of the lawnmower 1.
  • the torque applied to the first wheel member 5 towards the first position by the engagement between the followers 13 and the cam surfaces 11 is higher when the first wheel member 5 is in a region close to the first position than when the first wheel member 5 is in a region of the second or third positions.
  • the torque applied to the first wheel member 5 towards the first position gradually decreases upon rotation of the first wheel member 5 from the first position towards any of the second or third positions.
  • an actuation speed of the grip enhancing members 8 is higher close to the retracted position than the actuation speed close to the extracted position. In this manner, the grip enhancing members 8 can be moved in a quick manner from the retracted position and with a greater force as they approach the extracted position.
  • the followers 13 are positioned at a top surface of a cam surface 11 when the first wheel member 5 is in the first position relative to the second wheel member 7, as well as when the first wheel member 5 is in the third position relative to the second wheel member 7.
  • substantially no torque is applied to the first wheel member 5 towards the first position by the engagement between the followers 13 and the cam surfaces 11 when the first wheel member 5 is in the second or third position.
  • the grip enhancing members 8 can be kept in the extracted position until the propulsion motor applies a torque onto the first wheel member 5 in a direction from the second or third positions towards the first position.
  • the rotation limiting assembly 24, 26 may be arranged such that the followers 13 are positioned at other portions of the cam surfaces 11 , than the top surfaces thereof, when the first wheel member 5 is in the first or third positions.
  • the cam surfaces 11 may be provided with other cam profiles than arc-shaped cam profiles.
  • the cam surfaces 11 of the mechanism 9 may comprise one or more sections in which substantially no torque is applied to the first wheel member 5 towards the first position by the engagement between the followers 13 and the cam surfaces 11.
  • Such one or more sections may comprise a recess, a dent, a flat section, or the like, resulting in substantially no torque applied to the first wheel member 5 towards the first position when a follower 13 is biased against the section.
  • the grip enhancing members 8 can be kept in an extracted position, or in a partially extracted position, until the propulsion motor applies a torque onto the first wheel member 5 in a direction from the current position.
  • Fig. 7 illustrates a drive wheel 3 according to some further embodiments of the present disclosure.
  • the drive wheel 3 illustrated in Fig. 7 may comprise the same features, functions, and advantage as the drive wheel 3 explained with reference to Fig. 1 - Fig. 6, with some differences explained below. Also some mutual features will be explained in the following.
  • the drive wheel 3 comprises a first wheel member 5 and a second wheel member 7.
  • the first wheel member 5 comprises a shaft interface 14 for the connection to a drive shaft.
  • the drive shaft may thus be connected to the propulsion motor 4 indicated in Fig. 1 , for example via a transmission.
  • the drive wheel 3 is configured to rotate around a rotation axis ax during operation of the lawnmower 1.
  • the rotation axis ax is also indicated in Fig. 1.
  • the second wheel member 7 comprises a ground engaging surface 7’ configured to abut against a ground surface 22 during operation of the lawnmower 1.
  • the ground engaging surface 7’ is only schematically illustrated.
  • the ground engaging surface 7’ of the drive wheel 3 may be provided at a ring attached to the outer circumference of the second wheel member 7.
  • the drive wheel 3 comprises a number of grip enhancing members 8.
  • the grip enhancing members 8 are movably arranged relative to the ground engaging surface 7’ between a retracted and an extracted position. In Fig. 7, the grip enhancing members 8 are illustrated in the retracted position.
  • the outer ring may be provided with thorough holes for the grip enhancing members 8.
  • the drive wheel 3 further comprises a mechanism 9 configured to move the grip enhancing members 8 between the retracted position and the extracted position based on a torque between the first and second wheel members 5, 7, as is further explained herein.
  • the mechanism 9 comprises a plurality of arms 25 arranged between the first and second wheel members 5, 7. At least a number of the plurality of arms 25 are configured to move when the first wheel member 5 rotates relative to the second wheel member 7.
  • the first wheel member 5 is illustrated in a first position relative to the second wheel member 7 in which the mechanism 9 is configured to position the grip enhancing members 8 in the retracted position.
  • the mechanism 9 is configured to bias the first wheel member 5 towards the first position. Accordingly, the first wheel member 5 will assume the first position relative to the second wheel member 7 when there is no torque between the first and second wheel members 5, 7.
  • Fig. 8 illustrates the drive wheel 3 illustrated in Fig. 7 with the first wheel member 5 rotated to a second position. That is, in relation to the drive wheel 3 illustrated in Fig. 7, the first wheel member 5 has been rotated counterclockwise from the first position to a second position.
  • the mechanism 9 has moved the grip enhancing members 8 in radial directions R of the drive wheel 3 to the extracted position as a result of the rotation of the first wheel member 5 to the second position.
  • the mechanism 9 comprises a set of actuating members 27 which are moved in the radial directions R of the drive wheel 3 upon rotation of the first wheel member 5 from the first position.
  • the grip enhancing members 8 are attached to the actuating members 27. According to the illustrated embodiments, two grip enhancing members 8 are attached to one actuating member 27. However, according to further embodiments, another number of grip enhancing members 8 may be attached to each actuating member 27.
  • the arms 25 are configured to be subjected to elastic deformation when the first wheel member 5 rotates from the first position illustrated in Fig. 7. In this manner, the arms 25 apply a counter torque acting to displace the first wheel member 5 towards the first position when the first wheel member 5 is rotated therefrom.
  • a mechanism 9 is provided causing movement of the grip enhancing members 8 between the retracted and the extracted position based on the torque between the first and second wheel members 5, 7.
  • the first wheel member 5 can also be rotated clockwise from the first position illustrated 7 towards a third position.
  • Such a third position is similar to the second position illustrated in Fig. 8 with the difference that at least some of the arms 25 are moved in an opposite direction as compared to the arms 25 illustrated in Fig. 8.
  • the mechanism 9 is a compliant mechanism, meaning that the arms 25 referred to above are provided in one piece of continuous material and that the arms 25 are configured to bend upon a relative rotation between the first and second wheel members 5, 7.
  • joints 25’ between the arms 25 are bent upon rotation of the first wheel member 5 from the first position.
  • the arms 25 are configured to bend to assume a curved shape when the first wheel member 5 rotates from the first position.
  • the magnitude of the first and second threshold torques may be obtained by adapting the number of arms 25, the stiffness of the arms 25, the stiffness of the joints 25’ between the arms 25, the positions of the arms 25, and the length of the arms 25.
  • the arms 25, the joints 25’, the actuating members 27, the first wheel member 5, and the second wheel member 7 may be provided in a polymeric material.
  • the arms 25, the joints 25’, the actuating members 27, the first wheel member 5, and the second wheel member 7 may be provided in one piece of continuous material.
  • the grip enhancing members 8 may be provided in a metal material, such as steel.
  • the lawnmower 1 illustrated in Fig. 1 may comprise one or more drive wheels 3 explained with reference to Fig. 2 - Fig. 6, or one or more drive wheels 3 explained with reference to Fig. 7 or Fig. 8.
  • the two drive wheels 3 may be of identical design, or identical but mirrored design.
  • the lawnmower 1 comprises a control arrangement 21 configured to control operation of the propulsion motor 4.
  • the control arrangement 21 is configured to selectively perform a control operation in which the propulsion motor 4 is controlled to apply a torque onto the first wheel member 5 causing a movement of the grip enhancing members 8 towards the extracted position.
  • the control arrangement 21 may cause movement of the grip enhancing members 8 towards the extracted position by applying a torque onto the first wheel member 5 exceeding one of the first and second threshold torques.
  • control arrangement 21 is configured to determine whether to perform the control operation based on input data.
  • the control arrangement 21 may be configured to receive the input data from a sensor 28 arranged on the lawnmower 1 and/or may be configured to receive the input data from an external communication unit 38.
  • the input data is representative of a current or impending slope inclination at the location of the lawnmower 1 and/or a current or impending inclination angle of the lawnmower 1.
  • the sensor 28 arranged on the lawnmower 1 may be configured to sense a current inclination angle of the lawnmower 1 relative to a horizontal plane hp at the location of the lawnmower 1.
  • the sensor 28 may be configured to sense the orientation of the lawnmower 1 relative the gravitational field at the location of the lawnmower 1.
  • the sensor 28 may comprise an accelerometer.
  • the senor 28 may be configured to sense angular displacements of the lawnmower 1.
  • the sensor 28 may comprise a gyroscope.
  • the control arrangement 21 may be arranged to obtain reference values at one or more predetermined locations, such as at a charging dock.
  • the sensor 28 may obtain the current inclination angle by monitoring changes in inclination angle, for example by sensing changes in inclination angle of the lawnmower 1 and comparing such changes with one or more reference values.
  • control arrangement 21 may be configured to obtain a current or impending slope inclination at the location of the lawnmower 1 and/or a current or impending inclination angle of the lawnmower 1 by receiving such data from an external source 38, and/or by comparing the current position of the lawnmower 1 and a map comprising data indicative of slope inclination angles at the area.
  • the inclination angle of the lawnmower 1, as referred to herein, may be an inclination angle between the longitudinal direction Id of the lawnmower 1 and the horizontal plane hp at the location of the lawnmower 1.
  • control arrangement 21 may be configured to perform the control operation if a current or impending slope inclination at the location of the lawnmower 1 , and/or a current or impending inclination angle of the lawnmower 1 , exceeds a threshold inclination. In this manner, a lawnmower 1 is provided having improved conditions for operating in steep slopes.
  • the input data may be representative of one or more of traction conditions at the location of the lawnmower 1 , weather conditions at the location of the lawnmower 1 , and humidity at the location of the lawnmower 1.
  • the control arrangement 21 may be configured to input such input data from a sensor 28 arranged on the lawnmower 1 and/or from an external communication unit 38. The control arrangement 21 may thus use such input data when determining whether to perform the control operation. In this manner, a lawnmower 1 is provided having improved conditions for operating under conditions with increased risk of wheel slip.
  • the input data may be representative of presence of wheel slip of one or more wheels 3, 6 of the lawnmower 1, i.e. wheel slip of the drive wheels 3 and/or of the support wheels 6.
  • the control arrangement 21 may be configured to input such input data by monitoring electrical quantities of one or more propulsion motors 4 of the lawnmower 1.
  • the control arrangement 21 may be configured to input such input data from a positioning unit of the lawnmower 1, and/or an inclination angle sensor of the lawnmower 1.
  • the control arrangement 21 may determine whether to perform the control operation based on data representative of presence of wheel slip of one or more wheels 3, 6 of the lawnmower 1. If the data indicates presence of wheel slip of one or more wheels 3, 6 of the lawnmower 1 , the control arrangement 21 may perform the control operation.
  • the control operation comprises stopping the lawnmower 1 before controlling the propulsion motor 4 to apply the torque onto the first wheel member 5.
  • a lawnmower 1 is provided having further improved conditions for regaining grip after wheel slip of one or more wheels 3, 6 of the lawnmower 1. This because it is ensured that the ground engaging surface 7’ of the second wheel member 7 is stationary relative to the ground surface 22 before initiating propulsion.
  • a lawnmower 1 is provided having further improved conditions for navigating in areas having a high risk of wheel slip, such as undulated areas. Moreover, the risk of unwanted marks is reduced in the operated area.
  • control performed by the control arrangement 21 described herein may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in the control arrangement 21, ensures that the control arrangement 21 carries out the desired control.
  • the computer program is usually part of a computer program product which comprises a suitable digital storage medium on which the computer program is stored.
  • the control arrangement 21 may comprise a calculation unit which may take the form of substantially any suitable type of processor circuit or microcomputer, e.g. a circuit for digital signal processing (digital signal processor, DSP), a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions.
  • a calculation unit may represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.
  • the control arrangement 21 may further comprise a memory unit, wherein the calculation unit may be connected to the memory unit, which may provide the calculation unit with, for example, stored program code and/or stored data which the calculation unit may need to enable it to do calculations.
  • the calculation unit may also be adapted to store partial or final results of calculations in the memory unit.
  • the memory unit may comprise a physical device utilised to store data or programs, i.e. , sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit may comprise integrated circuits comprising silicon-based transistors.
  • the memory unit may comprise e.g. a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g. ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments.
  • the control arrangement 21 is connected to components of the lawnmower 1 for receiving and/or sending input and output signals.
  • These input and output signals may comprise waveforms, pulses, or other attributes which the input signal receiving devices can detect as information and which can be converted to signals processable by the control arrangement 21. These signals may then be supplied to the calculation unit.
  • One or more output signal sending devices may be arranged to convert calculation results from the calculation unit to output signals for conveying to other parts of the control system and/or the component or components for which the signals are intended.
  • Each of the connections to the respective components of the lawnmower 1 for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, or some other bus configuration, or a wireless connection.
  • the lawnmower 1 comprises a control arrangement 21 but might alternatively be implemented wholly or partly in two or more control arrangements or two or more control units.
  • the computer program product may be provided for instance in the form of a data carrier carrying computer program code for performing the desired control when being loaded into one or more calculation units of the control arrangement 21.
  • the data carrier may be, e.g. a CD ROM disc, or a ROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non- transitory manner.
  • the computer program product may furthermore be provided as computer program code on a server and may be downloaded to the control arrangement 21 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems.
  • the control arrangement 21 may be configured to control propulsion of the lawnmower 1, and steer the lawnmower 1, so as to navigate the lawnmower 1 in an area to be operated.
  • the lawnmower 1 may further comprise one or more sensors arranged to sense a magnetic field of a wire, and/or one or more positioning units, and/or one or more sensors arranged to detect an impending or ongoing collision event with an object.
  • the one or more positioning units may comprise a space based satellite navigation system such as a Global Positioning System (GPS), The Russian GLObal NAvigation Satellite System (GLONASS), European Union Galileo positioning system, Chinese Compass navigation system, or Indian Regional Navigational Satellite System.
  • GPS Global Positioning System
  • GLONASS The Russian GLObal NAvigation Satellite System
  • European Union Galileo positioning system Chinese Compass navigation system
  • Indian Regional Navigational Satellite System Indian Regional Navigational Satellite System
  • control arrangement 21 may be configured to obtain data from, or may comprise, one or more positioning units utilizing a local reference source, such as a local sender and/or a wire, to estimate or verify a current position of the lawnmower 1.
  • the lawnmower 1 may comprise a communication unit connected to the control arrangement 21.
  • the communication unit may be configured to communicate with a remote communication unit 38 to receive instructions therefrom and/or to send information thereto.
  • the communication may be performed wirelessly over a wireless connection such as the internet, or a wireless local area network (WLAN), or a wireless connection for exchanging data over short distances using short-wavelength, i.e. ultra-high frequency (UHF) radio waves in the industrial, scientific, and medical (ISM) band from 2.4 to 2.485 GHz.
  • a wireless connection such as the internet, or a wireless local area network (WLAN), or a wireless connection for exchanging data over short distances using short-wavelength, i.e. ultra-high frequency (UHF) radio waves in the
  • the control arrangement 21 may be configured to control propulsion of the lawnmower 1, and steer the lawnmower 1, so as to navigate the lawnmower 1 in a systematic and/or random pattern to ensure that an area is completely covered, using input from one or more of the above described sensors and/or units.
  • the lawnmower 1 may comprise one or more batteries arranged to supply electricity to components of the lawnmower 1.
  • the one or more batteries may be arranged to supply electricity to propulsion motors 4 of the lawnmower 1 by an amount controlled by the control arrangement 21.
  • the one or more batteries may be arranged to supply electricity a motor configured to power the cutting unit 10.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental Sciences (AREA)
  • Harvester Elements (AREA)

Abstract

Est divulguée une tondeuse à gazon (1) comprenant au moins une roue d'entraînement (3) et un moteur de propulsion (4) conçu pour faire tourner la roue d'entraînement (3). La roue d'entraînement (3) comprend un premier élément de roue (5) relié au moteur de propulsion (4), un second élément de roue (7) comprenant une surface de mise en contact avec le sol (7') conçue pour venir en butée contre une surface de sol (22) pendant le fonctionnement de la tondeuse à gazon (1), et un certain nombre d'éléments d'amélioration de préhension (8) agencés mobiles par rapport à la surface de mise en contact avec le sol (7') entre une position rétractée et une position extraite. La roue d'entraînement (3) comprend en outre un mécanisme (9) conçu pour déplacer les éléments d'amélioration de préhension (8) entre la position rétractée et la position extraite sur la base d'un couple entre les premier et second éléments de roue (5, 7). La présente divulgation concerne en outre une roue d'entraînement (3) destinée à une tondeuse à gazon (1).
PCT/SE2021/050330 2020-04-21 2021-04-12 Tondeuse à gazon et roue d'entraînement de tondeuse à gazon WO2021215980A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE112021000267.8T DE112021000267T5 (de) 2020-04-21 2021-04-12 Rasenmäher und Rasenmäherantriebsrad

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE2050451A SE544294C2 (en) 2020-04-21 2020-04-21 Lawnmower and lawnmower drive wheel
SE2050451-0 2020-04-21

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WO2021215980A1 true WO2021215980A1 (fr) 2021-10-28

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DE (1) DE112021000267T5 (fr)
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1828163A (en) * 1930-12-08 1931-10-20 Andrew R Taylor Wheel
US4601519A (en) * 1985-10-04 1986-07-22 Andrade Bruce M D Wheel with extendable traction spikes and toy including same
US20080161968A1 (en) * 2007-01-01 2008-07-03 Babatunde Olanipekun Adegbile BT' Smart Machine (BTSM)
US20140371975A1 (en) * 2012-01-13 2014-12-18 Robert Bosch Gmbh Autonomous Implement
JP2015167491A (ja) * 2014-03-06 2015-09-28 株式会社筑水キャニコム 斜面作業車両用車輪
US20150366130A1 (en) * 2013-02-20 2015-12-24 Husqvarna Ab A Robotic Work Tool Configured for Improved Turning in a Slope, a Robotic Work Tool System, and a Method for Use in the Robot Work Tool
CN207630863U (zh) * 2017-11-29 2018-07-20 刘纪琴 一种园林维护机械用安全高效防滑轮

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1828163A (en) * 1930-12-08 1931-10-20 Andrew R Taylor Wheel
US4601519A (en) * 1985-10-04 1986-07-22 Andrade Bruce M D Wheel with extendable traction spikes and toy including same
US20080161968A1 (en) * 2007-01-01 2008-07-03 Babatunde Olanipekun Adegbile BT' Smart Machine (BTSM)
US20140371975A1 (en) * 2012-01-13 2014-12-18 Robert Bosch Gmbh Autonomous Implement
US20150366130A1 (en) * 2013-02-20 2015-12-24 Husqvarna Ab A Robotic Work Tool Configured for Improved Turning in a Slope, a Robotic Work Tool System, and a Method for Use in the Robot Work Tool
JP2015167491A (ja) * 2014-03-06 2015-09-28 株式会社筑水キャニコム 斜面作業車両用車輪
CN207630863U (zh) * 2017-11-29 2018-07-20 刘纪琴 一种园林维护机械用安全高效防滑轮

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Publication number Publication date
DE112021000267T5 (de) 2022-09-29
SE544294C2 (en) 2022-03-29
SE2050451A1 (en) 2021-10-22

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