Drive unit with a fan-flywheel, power unit and a hand-held power tool with such a drive unit
Patent Information
- Application Number
- PCT/SE2026/010001
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-20
- Filing Date
- 2026-01-08
- Publication Date
- 2026-08-27
Smart Images
Figure SE2026010001_27082026_PF_FP_ABST
Abstract
Description
[0001] Drive Unit, Power Unit, and Hand-Held Power Tool
[0002] TECHNICAL FIELD
[0003] The present disclosure relates to drive unit for a hand-held power tool. The present disclosure further relates to a power unit for a hand-held power tool, as well as a hand-held power tool.
[0004] BACKGROUND
[0005] Hand-held power tools are tools designed to be operated by one or two hands of a user. Examples of hand-held power tools include chain saws, circular saws, pole saws, string trimmers, brush cutters, hedge trimmers, and combi-trimmers. Hand-held power tools are for example used in industry, construction, and home gardening, as well as for various household and property maintenance tasks.
[0006] A common feature of hand-held power tools is that they comprise a tool which can be driven by a power source other than solely manual labour. The power source may for example comprise a motor, such as a combustion engine, an electric motor, a pneumatic motor, or the like. Traditionally, hand-held power tools such as chain saws, circular saws, trimmers, hedge trimmers, and combi-trimmers, have typically been powered by combustion engines. These engines are most often compact two-stroke internal combustion models.
[0007] However, in recent years, advancements in battery technology have encouraged a shift towards electric motors in hand-held power tools. High-capacity and high-discharge batteries, such as lithium-ion batteries, have made it possible for electric tools to achieve performance levels comparable to, or even exceeding, those of tools powered by combustion engines. Electric motors can offer advantages in terms of reduced emissions, lower noise levels, increased efficiency, and reduced vibration levels, which may contribute to improved usability and comfort for a user. These benefits have made electric hand-held power tools an attractive alternative to traditional designs.
[0008] However, the transition to electric hand-held power tools may introduce new challenges that need to be addressed. For example, electric motors and their associated components, such as batteries, power electronics, and wiring, can generate significant heat during operation. Effective cooling solutions may therefore be required to ensure reliable and safe operation over time. Insufficient cooling can potentially lead to overheating, which may reduce the lifespan or performance of sensitive components.In addition, vibrations caused by resonance frequencies during operation may impact both user comfort and the durability of the power tool. Addressing such vibrations may require careful design considerations to ensure that the power tool can operate effectively without introducing excessive wear or discomfort.
[0009] Another aspect to consider is the potential risk of clogging in cooling channels or paths of the hand-held power tool. That is, hand-held power tools are often used in environments where debris, such as dust, grass, or sawdust, may enter the power tool. This can hinder airflow and reduce cooling efficiency, potentially compromising the powertool's performance or leading to damage to critical components.
[0010] Another problem associated with hand-held power tools is the need for compact designs. Hand-held power tools are often used in environments where manoeuvrability and ease of handling are important, such as in tight spaces or during extended periods of use. A compact design may help reduce the overall weight and size of the power tool, which can improve user comfort and minimise operator fatigue. However, achieving compactness can also complicate the implementation of effective cooling systems. As mentioned, components such as motors, batteries, and power electronics generate heat during operation, and the reduced space in compact designs may limit airflow and put limitations on the arrangement of efficient cooling paths.
[0011] Another drawback of electric motors is that they normally produce a relatively low starting torque. In colder weather conditions, lubricants such as oil and grease may obtain higher viscosity, increasing resistance within moving parts of the hand-held power tool. This increased resistance can require a higher torque to initiate motor rotation. If the motor cannot produce sufficient torque to overcome this resistance, the motor may fail to initiate rotation and may thereby remain stationary, potentially leaving the hand-held power tool inoperable and causing delays in completing tasks. Moreover, if electrical power is supplied to the motor while it remains stationary, components such as motor windings or power electronics may experience overheating or overcurrent conditions, potentially leading to damage. This can thus compromise the reliability of the hand-held power tool and may result in additional maintenance or repair requirements.
[0012] Moreover, hand-held power tools are preferably designed to minimise the risk of damage to sensitive components during use, such as electronic circuits, electrical conductors, and connections. Furthermore, a design of a hand-held power tool that facilitates efficientproduction processes and minimises costs can be advantageous in making the power tools competitive in the market and more accessible to a wide range of users.
[0013] SUMMARY
[0014] It is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks. The object is achieved by the subject-matter of the appended independent claim(s).
[0015] According to a first aspect of the present disclosure, the object is achieved by a drive unit for a hand-held power tool. The drive unit comprises an electric motor comprising an output shaft for powering a tool of the hand-held power tool, a fan-flywheel unit arranged on the output shaft of the electric motor, and a fan scroll structure enclosing the fan-flywheel unit. The drive unit further comprises a motor casing at least partially enclosing the electric motor, and a motor cooling path extending through the motor casing. The fan-flywheel unit comprises a number of radially acting fan blades configured to generate an airflow through the motor cooling path and into the fan scroll structure upon rotation of the output shaft.
[0016] Thereby, a drive unit is provided capable of providing a high cooling efficiency of the electric motor, mitigate resonance vibrations, and enable a compact design of a hand-held power tool.
[0017] A high cooling efficiency of the electric motor can be provided because the drive unit comprises the fan-flywheel unit arranged on the output shaft of the electric motor, and the fan scroll structure enclosing the fan-flywheel unit, wherein the fan-flywheel unit comprises the radially acting fan blades configured to generate an airflow through the motor cooling path and into the fan scroll structure upon rotation of the output shaft. In other words, due to these features, it can be ensured that a cooling stream of air is efficiently drawn through the motor cooling path and into the fan scroll structure upon rotation of the output shaft to thereby cool the electric motor. This may help maintain optimal operating temperatures for the electric motor and associated components, reducing the risk of overheating.
[0018] Moreover, due to the number of radially acting fan blades, and the feature that the fan scroll structure encloses the fan-flywheel unit, a high air pumping efficiency of can be obtained. A high air pumping efficiency can enhance cooling performance by improving airflow through the motor cooling path. Additionally, a high air pumping efficiency can contribute to lower energy consumption and reduced noise levels during operation of the hand-held power tool.The drive unit is capable of mitigating resonance vibrations because the fan-flywheel unit is arranged on the output shaft of the electric motor. More specifically, the fan-flywheel unit can act as a stabilising mass, helping to dampen oscillations and counterbalance rotational imbalances that may otherwise amplify vibrations. By mitigating resonance vibrations, the drive unit can provide a more user-friendly hand-held power tool by reducing discomfort and operator fatigue during use, particularly over extended use periods. Additionally, lower vibration levels may help protect internal components from excessive wear, potentially extending the lifespan of the hand-held power tool and reducing the need for maintenance thereof.
[0019] Furthermore, a compact design of the drive unit, and thereby also of a hand-held power tool comprising the drive unit, is enabled because of the features that the fan-flywheel unit is arranged on the output shaft of the electric motor, the fan scroll structure encloses the fanflywheel unit, and the fan-flywheel unit comprises the radially acting fan blades configured to generate an airflow through the motor cooling path and into the fan scroll structure upon rotation of the output shaft. A compact design of the drive unit can enhance manoeuvrability and ease of handling of a hand-held power tool, which may be particularly beneficial in tight spaces or during extended periods of use. This configuration can also optimise the arrangement of other components and structures within the hand-held power tool such as, batteries, power electronics, and cooling paths, thereby enabling a smaller and more lightweight hand-held power tool without compromising performance or reliability.
[0020] In addition, the configuration of the drive unit can enable a design providing a reduced risk of clogging in cooling paths of a hand-held power tool by minimising the accumulation of debris, such as dust, grass, or sawdust, which can help maintain consistent airflow and cooling efficiency, thereby supporting reliable operation and preventing potential overheating of components of the hand-held power tool.
[0021] Moreover, the configuration of the drive unit enables a design which protects sensitive components, such as electronic circuits, connections, and electrical wires, against potential damage. This is because the fan-flywheel unit is arranged on the output shaft. In other words, the configuration enables the fan-flywheel unit to be positioned on a first axial side of the electric motor, with components responsible for electrical supply to the electric motor located on an opposite, second axial side. In this manner, sensitive components, such as electronic circuits, connections, and electrical wires, can be protected against potential damage during use of a hand-held power tool comprising the drive unit.Furthermore, the configuration of the drive unit can enable efficient manufacturing and assembly processes of the drive unit, which can help to reduce production costs and make the power tool more accessible and competitive in the market.
[0022] Accordingly, a drive unit 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.
[0023] Optionally, the fan-flywheel unit is formed in a single piece of material. Thereby, manufacturing complexity can be reduced, and the risk of imbalances or mechanical failure due to assembly inconsistencies may be minimised. This may also contribute to a more durable and reliable fan-flywheel unit, and thereby also a more durable and reliable drive unit.
[0024] Optionally, the fan-flywheel unit is made of metal. Thereby, the fan-flywheel unit can exhibit higher durability and resistance to wear compared to non-metallic materials. Additionally, the metallic structure may enhance conductive heat transfer from the electric motor via the output shaft thereof, supporting better cooling performance. The weight provided by the metal can also increase the flywheel inertia of the fan-flywheel unit, which may help stabilise the rotation of the output shaft, reduce vibrations, and improve the overall operational smoothness of the hand-held power tool.
[0025] Optionally, the weight of the fan-flywheel unit exceeds 70 grams or exceeds 90 grams. Thereby, a relatively high flywheel inertia can be achieved, which may help stabilise the rotation of the output shaft, reduce vibrations, and improve the overall operational smoothness of the hand-held power tool.
[0026] Optionally, the diameter of the fan-flywheel unit exceeds 55 millimetres or exceeds 70 mm. Thereby, a fan-flywheel unit is provided having conditions for generating high airflow and achieving high air pumping efficiency, while also ensuring a relatively high flywheel inertia of the fan-flywheel unit.
[0027] Optionally, the radio between the diameter of the fan-flywheel unit and the axial thickness of the fan-flywheel unit is within the range of 2.5 - 5.5 or is within the range of 3.5 - 4.5.
[0028] Thereby, a fan-flywheel unit is provided having proportions that enable high airflow generation and high air pumping efficiency, while also providing high flywheel inertia to stabilise motor operation and reduce vibrations.Optionally, the motor cooling path extends through the electric motor, and / or at least partially around the electric motor. Thereby, it can be ensured that air flowing through the motor cooling path can cool the electric motor in an efficient manner which can reduce the risk of overheating and help maintain optimal operating temperatures, thereby contributing to the reliability and performance of the drive unit.
[0029] Optionally, the fan-flywheel unit comprises a disc-shaped body portion, and wherein the fan blades protrude axially from a surface of the disc-shaped body portion. Thereby, it can be ensured that the fan blades efficiently can generate a radial airflow upon rotation of fanflywheel unit, ensuring effective cooling of the motor and associated components. Moreover, the axial protrusion of the blades from the disc-shaped body portion allows for a compact design while obtaining a high air pumping efficiency, enabling efficient cooling without significantly increasing the overall size of the drive unit.
[0030] Optionally, the fan-flywheel unit comprises a first side facing the electric motor and a second side facing away from the electric motor, and wherein the fan blades are arranged on the first side of the fan-flywheel unit. Thereby, it can be ensured that the fan blades efficiently generate a radial airflow upon rotation of the fan-flywheel unit, ensuring a consistent flow of air through the cooling path. This consistent airflow may help reduce the risk of overheating, maintain optimal operating temperatures, and contribute to the overall reliability and performance of the drive unit.
[0031] Optionally, the drive unit comprises a clutch, wherein the clutch comprises a driving member and a driven member, and wherein the driving member is attached to the fan-flywheel unit. Thereby, the initiation of rotation of the electric motor can be facilitated by allowing the motor to rotate independently of the driven member during the initial phase of operation. This can reduce the load on the motor, ensuring reliable operation even under conditions of increased internal resistance, such as during cold weather.
[0032] Additionally, the inclusion of a clutch provides further advantages by enabling controlled engagement between the motor and the driven member. This may reduce wear on both motor and tool components, enhance operational smoothness, and extend the service life of the hand-held power tool. In addition, since the driving member is attached to the fanflywheel unit, the clutch can be effectively cooled through conductive heat transfer between the driving member and the fan-flywheel unit, which can reduce the risk of overheating theclutch. Furthermore, since the driving member is attached to the fan-flywheel unit, the driving member can contribute to the flywheel effect of the fan-flywheel unit.
[0033] Optionally, the fan-flywheel unit comprises a first side facing the electric motor and a second side facing away from the electric motor, and wherein the driving member is mounted on the second side of the fan-flywheel unit. Thereby, the heat transfer from the driving member to the fan-flywheel unit can be further improved, as the mounting position facilitates direct thermal conduction between the driving member of the clutch and the fan-flywheel unit. This can reduce the risk of overheating the clutch by dissipating heat more effectively.
[0034] Furthermore, a direct mounting of the driving member to the fan-flywheel unit circumvents the need for a clutch adapter or similar intermediate components, simplifying the design as well as the assembling process of the drive unit.
[0035] Optionally, the drive unit comprises a fan scroll housing comprising the fan scroll structure, and wherein the clutch is arranged inside the fan scroll housing. Thereby, a further efficient cooling of the clutch can be ensured because the airflow generated by the fan-flywheel unit is directed to pass over the clutch. This airflow can further aid in dissipating heat from the clutch during operation, further reducing the risk of overheating. The arrangement within the fan scroll housing can also provide additional protection to the clutch from external contaminants, such as dust or debris, further contributing to the reliability and longevity of the drive unit.
[0036] Optionally, the fan scroll housing comprises an air outlet, and wherein the fan scroll housing forms a clutch cooling path extending from the fan scroll structure, through and / or around portions of the clutch, to the air outlet. Thereby, a controlled cooling path is provided, allowing the airflow generated by the fan-flywheel unit to effectively pass over and carry heat away from the clutch to the air outlet. This configuration can ensure consistent cooling, improving the clutch's reliability and performance during extended operation, and enhancing the overall durability of the drive unit.
[0037] According to a second aspect of the present disclosure, the object is achieved by a power unit for a hand-held power tool, wherein the power unit comprises an external casing and a drive unit according to some embodiments of the first aspect of the present disclosure, wherein the drive unit is arranged inside the external casing.
[0038] Since the power unit comprises a drive unit according to some embodiments of the first aspect of the present disclosure, a power unit is provided that enables improved coolingefficiency of the electric motor with high pumping efficiency, mitigated resonance vibrations, and a compact design suitable for a hand-held power tool comprising the power unit.
[0039] In addition, the configuration of the drive unit arranged inside the external casing of the power unit can enable a design providing a reduced risk of clogging in cooling paths of the power unit by minimising the accumulation of debris, such as dust, grass, or sawdust, which can help maintain consistent airflow and cooling efficiency, thereby supporting reliable operation and preventing potential overheating of components of the power unit.
[0040] Moreover, the configuration of the drive unit arranged inside the external casing of the power unit enables efficient manufacturing and assembly processes of the power unit, which could help to reduce production costs and make the power tool more accessible and competitive in the market.
[0041] Accordingly, a power unit 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.
[0042] Optionally, the drive unit comprises an air outlet, wherein the fan scroll structure is configured to direct air from the fan-flywheel unit to the air outlet, and wherein the power unit comprises an outflow path extending between the air outlet of the drive unit and one or more air outlets of the external casing. Thereby, a directed and efficient removal of heated air can be achieved, helping to maintain optimal operating temperatures of the drive unit. Moreover, the outflow path can ensure that heated air is effectively expelled from the power unit, reducing the risk of overheating and contributing to the reliability and performance of the hand-held power tool.
[0043] Optionally, the power unit comprises power electronics configured to regulate the electric power supply to the electric motor, and wherein the power electronics is arranged in the outflow path. Thereby, the cooling airflow can also dissipate heat generated by the power electronics during operation. This may help maintain the reliability of the power electronics, reducing the risk of overheating and ensuring consistent power delivery to the electric motor, even during demanding operating conditions.
[0044] Optionally, the power unit comprises a battery attachment section configured to attach a battery for supplying electricity to the electric motor, and wherein the outflow path extends through and / or around the battery attachment section. Thereby, a battery attached to thebattery attachment section can benefit from the cooling airflow, helping to dissipate heat generated by the battery during operation. This may prolong the service life of the battery and support consistent performance, particularly during extended and / or intensive use.
[0045] According to a third aspect of the present disclosure, the object is achieved by a hand-held power tool comprising a drive unit according to some embodiments of the first aspect of the present disclosure or a power unit according to some embodiments of the second aspect of the present disclosure.
[0046] Thereby, a hand-held power tool is provided with conditions for improved cooling efficiency of the electric motor, mitigated resonance vibrations, and a compact design. The integration of a drive unit or power unit within the hand-held power tool can help reduce the risk of overheating and ensure reliable operation, even during extended or demanding use.
[0047] Additionally, the configuration can minimise the accumulation of debris in cooling paths, supporting consistent airflow and enhancing the overall performance and durability of the power tool. Furthermore, the efficient design and assembly of the power tool may contribute to reduced manufacturing costs, making the power tool more accessible and competitive in the market.
[0048] Optionally, the hand-held power tool is an outdoor power tool, such as a pole saw, a string trimmer, or a brush cutter. Thereby, an outdoor power tool is provided having at least some of the above-mentioned advantages.
[0049] Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.
[0050] BRIEF DESCRIPTION OF THE DRAWINGS
[0051] Various aspects of the present disclosure, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:
[0052] Fig. 1 illustrates a perspective view of a hand-held power tool according to some embodiments,
[0053] Fig. 2 illustrates an enlarged perspective view of a power unit of the hand-held power tool illustrated in Fig. 1,
[0054] Fig. 3 illustrates a perspective view of a drive unit of the power unit depicted in Fig. 1 and Fig. 2,Fig. 4 illustrates an exploded view of components of the drive unit according to the embodiments illustrated in Fig. 3, wherein the components are shown in a perspective view, Fig. 5 illustrates an exploded view of components of the drive unit according to the embodiments illustrated in Fig. 3, wherein the components are shown straight from the side in a direction perpendicular to an output shaft of an electric motor of the drive unit,
[0055] Fig. 6 illustrates a perspective view of a fan-flywheel unit of the drive unit illustrated in Fig. 3 - Fig. 5,
[0056] Fig. 7 illustrates a side view of the fan-flywheel unit illustrated in Fig. 6, in which the fanflywheel unit is shown straight from the side in a direction perpendicular to a rotation axis of the fan-flywheel unit,
[0057] Fig. 8 illustrates a partial assembly of the drive unit according to the embodiments illustrated in Fig. 3 - Fig. 5,
[0058] Fig. 9 illustrates a cross section of the power unit of the hand-held power tool illustrated in Fig. 1,
[0059] Fig. 10 illustrates components of a drive unit according to some further embodiments, and Fig. 11 illustrates a partial assembly of the drive unit according to the embodiments illustrated in Fig. 10.
[0060] DETAILED DESCRIPTION
[0061] Aspects of the present disclosure will now be described more fully. Like reference signs refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity.
[0062] Fig. 1 illustrates a perspective view of a hand-held power tool 10 according to some embodiments of the present disclosure. According to the illustrated embodiments, the handheld power tool 10 is a brush cutter, i.e. a hand-held power tool 10 comprising a tool 50 in the form of a circular saw blade designed for cutting vegetation such as brush, grass, or similar vegetation in outdoor environments. A brush cutter may also be referred to as a brush saw. The circular saw blade can optionally be replaced with a trimmer head comprising trimmer line, allowing the tool 50 to be adapted for different cutting tasks. When the handheld power tool 10 comprises a tool in the form of a trimmer head with trimmer line, the handheld power tool 10 may also be referred to as a string trimmer.
[0063] However, according to further embodiments, the hand-held power tool 10, as referred to herein, may be another type of hand-held power tool 10, such as a chainsaw, pole saw, pole hedge trimmer, grass trimmer, coffee shaker, or olive shaker.For reasons of brevity and clarity, the hand-held power tool 10 is in some places herein simply referred to as the power tool 10. According to the embodiments illustrated in Fig. 1, the power tool 10 comprises two handles hi, h2. In the following, these are referred to as a first handle hi and a second handle h2.
[0064] The feature that the power tool 10 is “hand-held” means that the power tool 10 is configured to be supported by one or two hands of a user during operation. As understood from the above, since the power tool 10 according to the illustrated embodiments comprises the first and second handles hi , h2, the power tool 10 is configured to be supported by two hands of a user during operation thereof, i.e., by one hand grabbing the first handle hi and the other hand grabbing the second handle h2. However, according to further embodiments, the power tool 10 may comprise one handle only.
[0065] The power tool 10 further comprises a power unit 2. As is further explained herein, the power unit 2 comprises a drive unit with an electric motor for powering the tool 50 of the power tool 10. The power tool 10 further comprises an elongated body portion 35, which connects the power unit 2 to a tool portion 50’ of the power tool 10. The tool 50 is attached to the tool portion 50’ of the power tool 10. The elongated body portion 35 may alternatively be referred to as a shaft assembly or pole shaft assembly. The elongated body portion 35 houses a drive shaft for transmitting rotational power from the electric motor of the power unit 2 to the tool portion 50’, thereby driving the tool 50.
[0066] According to the embodiments illustrated in Fig. 1, the power unit 2 comprises a battery attachment section 24 configured to attach a battery for supplying electricity to the electric motor of the power unit 2. In Fig. 1 , no battery is attached to the battery attachment section 24. According to further embodiments, the power unit 2 of the power tool 10 may comprise other means of supplying electricity to the electric motor, such as a cable with a connector for connection to an external power source, for example an external power grid.
[0067] The first handle hi and the second handle h2 are part of a handle assembly 30. According to the embodiments illustrated in Fig. 1, the handle assembly 30 is arranged on the elongated body portion 35. The handle assembly 30 further comprises a throttle actuator 31 located on the first handle hi . The throttle actuator 31 is configured to enable a user to control the power output of the electric motor of the power unit 2 to control the power delivered to the tool 50. To prevent unintentional actuation of the throttle actuator 31, the handle assembly 30 also comprises a locking mechanism including a button 33. The locking mechanism isconfigured such that the button 33 must be pressed to allow actuation of the throttle actuator 31.
[0068] Fig. 2 illustrates an enlarged perspective view of the power unit 2 of the hand-held power tool 10 illustrated in Fig. 1. In Fig. 2 a battery 26 is attached to the battery attachment section 24 of the power unit 2. The battery 26 may comprise a number of rechargeable battery cells, such as lithium-ion cells, configured to supply electric power to the electric motor of the power unit 2. The battery 26 may be removably attached to the battery attachment section 24, allowing for easy replacement or recharging when depleted. Additionally, the battery 26 can include a protective casing to safeguard the battery cells against external impacts, dust, or moisture during operation of the hand-held power tool 10. The battery 26, as referred to herein, may also be referred to as a battery pack.
[0069] Fig. 3 illustrates a perspective view of a drive unit 1 of the power unit 2 depicted in Fig. 1 and Fig. 2. As is indicated in Fig. 2, the power unit 2 comprises an external casing 12. The drive unit 1 illustrated in Fig. 3 is arranged inside the external casing 12 of the power unit 2 illustrated in Fig. 1 and Fig. 2.
[0070] The external casing 12 comprises one or more air outlets 21 and one or more air inlets 41. According to the embodiments illustrated in Fig. 1 and Fig. 2, the one or more air outlets 21 are formed by a perforated section of the external casing 12. Likewise, the one or more air inlets 41 are formed by a perforated section of the external casing 12. However, according to further embodiments, the one or more air outlets 21 , and / or the one or more air inlets 41 , may be formed in another manner, such as by incorporating a number of through holes into the external casing 12 or into a separate piece that is attached to the external casing 12 of the power unit 2.
[0071] As indicated in Fig. 3, the drive unit 1 comprises an air inlet 14 and an air outlet 11. The air inlet 14 is fluidly connected to the one or more air inlets 41 of the external casing 12 via an internal airflow path of the power unit 2, as is further explained herein. Furthermore, as is further explained herein, the air outlet 11 is fluidly connected to the one or more air outlets 21 of the external casing 12 via an internal outflow path of the power unit 2.
[0072] Fig. 4 illustrates an exploded view of components of the drive unit 1 according to the embodiments illustrated in Fig. 3, wherein the components are shown in a perspective view.As can be seen in Fig. 4, the drive unit 1 comprises an electric motor 4. The electric motor 4 may be a brushless DC motor. A brushless DC motor offers advantages such as higher efficiency, reduced maintenance, and lower heat generation compared to brushed motors, as it does not rely on physical brushes to transfer electrical current. This type of motor may also provide improved durability and longer operational life, particularly during extended or intensive use. However, according to further embodiments, the electric motor 4 of the drive unit 1 may be a brushed DC motor or another suitable type of electric motor.
[0073] The drive unit 1 further comprises a fan-flywheel unit 3. The fan-flywheel unit 3 is configured to be attached to an output shaft of the electric motor 4. Moreover, the drive unit 1 comprises a motor casing 6 for supporting the electric motor 4 and a fan scroll housing 15. The motor casing 6 at least partially encloses the electric motor 4 when the drive unit 1 is assembled. The fan scroll housing 15 comprises a fan scroll structure 5. The fan scroll structure 5 is configured to enclose the fan-flywheel unit 3 when the drive unit 1 is assembled.
[0074] Furthermore, the drive unit 1 comprises a motor cover 16. According to the illustrated embodiments, the motor cover 16 comprises the air inlet 14 of the drive unit 1. The motor cover 16, as referred to herein, may also be referred to as an air conductor. According to the illustrated embodiments, the motor cover 16 and the fan scroll housing 15 are configured to be attached to the motor casing 6 such that these components together form a structure that fully encloses the electric motor 4. The motor cover 16, the fan scroll housing 15, and the motor casing 6 may be attached to each other using a number of fastening elements, such as bolts or screws.
[0075] Fig. 5 illustrates an exploded view of components of the drive unit 1 according to the embodiments illustrated in Fig. 3, wherein the components are shown straight from the side in a direction perpendicular to the output shaft 4’ of the electric motor 4. That is, in Fig. 5, the output shaft 4’ of the electric motor 4 can be seen.
[0076] As mentioned, the fan-flywheel unit 3 is configured to be attached to the output shaft 4’ of the electric motor 4. According to the illustrated embodiments, the output shaft 4’ comprises a conical engagement section 4” configured to engage a conical inner engagement section of a centrally arranged through-hole of the fan-flywheel unit 3.
[0077] Fig. 6 illustrates a perspective view of the fan-flywheel unit 3 of the drive unit 1 illustrated in Fig. 3 - Fig. 5. In Fig. 6, the centrally arranged through-hole 61 of the fan-flywheel unit 3 can be seen.The feature that the through-hole 61 of the fan-flywheel unit 3 is centrally arranged means that the centre axis of the through-hole 61 coincides with a rotation axis of the fan-flywheel unit 3. Below, simultaneous reference is made to Fig. 1 - Fig. 6, if not indicated otherwise.
[0078] According to the illustrated embodiments, the output shaft 4’ of the electric motor 4 is configured to protrude through the through-hole 61 of the fan-flywheel unit 3 when the drive unit 1 is assembled.
[0079] Moreover, as indicated in Fig. 5, the fan-flywheel unit 3 is configured to be attached to the output shaft 4’ of the electric motor 4 using a nut 54 treaded onto a treaded portion 64 of the output shaft 4’. By tightening the nut 54, the conical inner engagement section of a centrally arranged through-hole 61 of the fan-flywheel unit 3 is clamped against the conical engagement section 4” of the output shaft 4’. In this manner, the fan-flywheel unit 3 can be securely attached to the output shaft 4’ with high precision so as to avoid a wobbling motion of the fan-flywheel unit 3 upon rotation of the output shaft 4’.
[0080] As understood from the above, according to the illustrated embodiments, the fan-flywheel unit 3 is directly attached to the output shaft 4’ of the electric motor 4, meaning that the fanflywheel unit 3 is in direct abutting contact with the output shaft 4’ when the drive unit 1 is assembled. However, according to further embodiments, the fan-flywheel unit 3 may be attached to the output shaft 4’ of the electric motor 4 in another manner.
[0081] As indicated in Fig. 5 and Fig. 6, the fan-flywheel unit 3 comprises a number of radially acting fan blades 13.
[0082] Fig. 7 illustrates a side view of the fan-flywheel unit 3 illustrated in Fig. 6, in which the fanflywheel unit 3 is shown straight from the side in a direction perpendicular to the rotation axis Ax of the fan-flywheel unit 3. That is, in Fig. 7, the rotation axis Ax of the fan-flywheel unit 3 has been marked. Below, simultaneous reference is made to Fig. 1 - Fig. 7, if not indicated otherwise.
[0083] The feature that the radially acting fan blades 13 are “radially acting” means that the fan blades 13 are configured to direct airflow primarily in radial directions relative to the rotation axis Ax of the fan-flywheel unit 3. In other words, upon rotation of the fan-flywheel unit 3, the fan blades 13 are designed to move air primarily outward from the centre of the fan-flywheel unit 3 towards its periphery.Moreover, in these embodiments, the fan-flywheel unit 3 comprises a disc-shaped body portion 23, wherein the fan blades 13 protrude axially from a surface 23’ of the disc-shaped body portion 23. The feature that the fan blades 13 protrude axially from the surface 23’ of the disc-shaped body portion 2 means that the fan blades 13 extend in a direction parallel to the rotation axis Ax of the fan-flywheel unit 3. In other words, the fan blades 13 are oriented to project away from the surface 23’ of the disc-shaped body portion 23 along the axial direction of the fan-flywheel unit 3. The axial direction of the fan-flywheel unit 3 is parallel to the rotation axis Ax of the fan-flywheel unit 3. This configuration allows the fan blades 13 to efficiently interact with the surrounding air during rotation of the fan-flywheel unit 3, contributing to the generation of a radial airflow for cooling purposes, as is further explained herein.
[0084] Moreover, according to the illustrated embodiments, the fan-flywheel unit 3 is formed in a single piece of material. The feature that the fan-flywheel unit 3 is formed in a single piece of material means that the disc-shaped body portion 23, the fan blades 13, and also any possibly additional structural elements of the fan-flywheel unit 3 are integrally manufactured as one continuous piece. This configuration can provide enhanced structural integrity and durability of the fan-flywheel unit 3 by eliminating joints or connections between separate components, which might otherwise weaken the overall structure or become points of failure during operation.
[0085] Additionally, in these embodiments, the fan-flywheel unit 3 is made of metal. The feature that the fan-flywheel unit 3 is made of metal means that it is composed of a metallic material, such as aluminium or steel. This provides several advantages, including high durability, resistance to wear, and the ability to efficiently dissipate heat from the electric motor 4’ via thermal conduction. The metallic composition can also support high-precision manufacturing, ensuring smooth operation of the fan-flywheel unit 3 during rotation.
[0086] According to the illustrated embodiments, the weight of the fan-flywheel unit 3 is approximately 116 grams. However, according to further embodiments, the fan-flywheel unit 3 may have another weight, such as a weight exceeding 70 grams or exceeds 90 grams under normal gravitational conditions on Earth's surface. Due to a relatively high weight of the fan-flywheel unit 3, the fan-flywheel unit 3 can efficiently function as a flywheel. A heavier fan-flywheel unit 3 can provide greater rotational inertia, which helps stabilise the operation of the electric motor 4 by reducing fluctuations in rotational speed and mitigating resonance vibrations.Moreover, according to the illustrated embodiments, the diameter d1 of the fan-flywheel unit 3 is approximately 82 millimetres. However, according to further embodiments, the fanflywheel unit 3 may have another diameter d1 , such as a diameter d1 exceeding 55 millimetres or exceeding 70 millimetres. The diameter d1 of the fan-flywheel unit 3 can be measured in directions perpendicular to the rotation axis Ax of the fan-flywheel unit 3. The relatively large diameter d1 of the fan-flywheel unit 3 can contribute to improved airflow generation. In other words, a relatively large diameter d1 allows the fan blades 13 to efficiently move more air during rotation of the fan-flywheel unit 3 around the rotation axis Ax. Additionally, a relatively large diameter d1 can increase the rotational inertia of the fanflywheel unit 3, further supporting the functioning as a flywheel to stabilise the operation of the electric motor 4 by reducing fluctuations in rotational speed and mitigating resonance vibrations.
[0087] Furthermore, according to the illustrated embodiments, the ratio between the diameter d1 of the fan-flywheel unit 3 and the axial thickness t1 of the fan-flywheel unit 3 is approximately 4.2. However, according to further embodiments, the fan-flywheel unit 3 may be provided with a different ratio between the diameter d1 of the fan-flywheel unit 3 and the axial thickness t1 of the fan-flywheel unit 3, such as a radio within the range of 2.5 - 5.5 or within the range of 3.5 - 4.5.
[0088] The axial thickness t1 of the fan-flywheel unit 3 can be measured along directions parallel to the rotation axis Ax of the fan-flywheel unit 3. The feature that this ratio is within these ranges means that the fan-flywheel unit 3 has proportions that can support both flywheel action and airflow generation. A larger diameter d1 relative to the axial thickness t1 (i.e. , a larger ratio) may enhance the flywheel effect by increasing rotational inertia, contributing to stable motor operation. Conversely, a larger axial thickness t1 (i.e., a smaller ratio) may mainly support the generation of radial airflow, as greater axial thickness t1 may allow the fan blades 13 to interact more effectively with the surrounding air during rotation.
[0089] As can be seen in Fig. 4 and Fig. 5, according to these embodiments, the drive unit 1 comprises a clutch 7. The clutch 7 comprises a driving member 17 and a driven member 27. As indicated in Fig. 4 and Fig. 6, the fan-flywheel unit 3 comprises two threaded holes 36’. According to these embodiments, the driving member 17 is configured to be mounted onto the fan-flywheel unit 3 using bolts threaded into the threaded holes 36’ of the fan-flywheel unit 3.Fig. 8 illustrates a partial assembly 70 of the drive unit 1 according to the embodiments illustrated in Fig. 3 - Fig. 5. The partial assembly 70 depicted in Fig. 8 comprises the motor casing 6, the electric motor 4, the fan-flywheel unit 3, and the driving member 17 of the clutch. Below, simultaneous reference is made to Fig. 1 - Fig. 8, if not indicated otherwise.
[0090] As indicated in Fig. 5 and Fig. 7, the fan-flywheel unit 3 comprises a first side S1. The fan blades 13 are arranged on the first side S1 of the fan-flywheel unit 3, and the first side S1 of the fan-flywheel unit 3 faces the electric motor 4 when the drive unit 1 is assembled.
[0091] The fan-flywheel unit 3 further comprises a second side S2. The second side S2 is opposite to the first side S1 and faces away from the electric motor 4 when the drive unit 1 is assembled. In these embodiments, the driving member 17 is mounted on the second side S2 of the fan-flywheel unit 3. As is best seen in Fig. 8, in these embodiments, the driving member 17 is mounted onto the fan-flywheel unit 3 using a pair of bolts 36. Each of the pair of bolts 36 is threaded into one of the treaded holes 36’ of the fan-flywheel unit 3. One of the bolts 36 is also indicated in Fig. 4. According to further embodiments, the driving member 17 of the clutch may be attached or mounted to the fan-flywheel unit 3 in another manner.
[0092] Since the driving member 17 of the clutch 7 is mounted onto the fan-flywheel unit 3, the driving member 17 co-rotates with the fan-flywheel unit 3 and shares the same rotation axis Ax as the fan-flywheel unit 3. In this manner, the driving member 17 of the clutch 7, as well as the bolts 36, add some flywheel effect to the fan-flywheel unit 3.
[0093] According to the illustrated embodiments, the clutch 7 is a centrifugal clutch. The driving member 17 comprises two friction elements 37, 37’ and a spring 38. The spring 38 of the driving member 17 applies a biasing force onto the two friction elements 37, 37’ in a direction towards the rotation axis Ax of the driving member 17.
[0094] According to the illustrated embodiments, the driven member 27 of the clutch 7 is drum shaped. In more detail, the driven member 27 comprises an inner cylindrical surface, which is arranged concentrically around the driving member 17. The inner surface of the driven member 27 is positioned to receive and interact with the two friction elements 37, 37’ when they move outward.
[0095] That is, when the driving member 17 rotates with the fan-flywheel unit 3, centrifugal force acts on the two friction elements 37, 37’, causing them to move radially outward against the biasing force of the spring 38. At lower rotational speeds, the spring 38 keeps the two frictionelements 37, 37’ retracted, such that no contact, or substantially no contact, is made with the inner surface of the driven member 27. In this condition, rotational power is not transferred from the driving member 17 to the driven member 27.
[0096] When the rotational speed of the driving member 17 increases, the centrifugal force overcomes the inward biasing force of the spring 38, causing the two friction elements 37, 37’ to move radially outward. As the two friction elements 37, 37’ move radially outward, they engage the inner cylindrical surface of the driven member 27. The contact between the two friction elements 37, 37’ and the inner surface of the driving member 17 enables torque transfer from the driving member 17 to the driven member 27.
[0097] This configuration allows the clutch 7 to engage automatically as the rotational speed of the driving member 17 increases, facilitating smooth and efficient torque transfer. Additionally, when the rotational speed decreases, the spring 38 pulls the two friction elements 37, 37’ back towards the rotation axis Ax, thereby disengaging the driving member 17 from the driven member 27. In this manner, the centrifugal clutch 7 provides reliable power transmission while preventing the electric motor 4 from being subjected to excessive loads at low speeds or during startup.
[0098] Fig. 9 illustrates a cross section of the power unit 2 of the hand-held power tool 10 illustrated in Fig. 1. Moreover, in Fig. 9, a portion of the elongated body portion 35 of the power tool 10 is seen. In Fig. 9, the cross section is made in a plane comprising the rotation axis Ax of the electric motor 4. Below, simultaneous reference is made to Fig. 1 - Fig. 9, if not indicated otherwise.
[0099] In Fig. 9, a portion of a drive shaft 39 is also seen. The drive shaft 39 is connected to the driven member 27 of the clutch 7 and to the tool portion 50’ of the power tool 10 so as to transfer rotation and torque between the driven member 27 and a tool 50 attached to the tool portion 50’. According to the illustrated embodiments, the electric motor 4, the driving member 17 of the clutch 7, the driven member 27 of the clutch 7 and the drive shaft 39 shares the same rotation axis Ax. According to the embodiments illustrated in Fig. 9, the drive shaft 39 is connected to the driven member 27 of the clutch 7 via a splined interface and is configured to co-rotate with the driven member 27 of the clutch 7.
[0100] As mentioned, and as is seen in Fig. 9, the power unit 2 comprises an external casing 12, wherein the drive unit 1 is arranged inside the external casing 12. The power unit 2 comprises a number of airflow paths inside the external casing 12. Moreover, as mentioned,the drive unit 1 comprises an air inlet 14 and an air outlet 11. The air inlet 14 of the drive unit 1 is fluidly connected to the one or more air inlets 41 of the external casing 12 indicated in Fig. 1 and Fig. 2. The airflow path between the air inlet 14 of the drive unit 1 and the one or more air inlets 41 of the external casing 12 cannot be seen in Fig. 9 because this airflow path extends mainly in a direction coinciding with the viewing direction of Fig. 9.
[0101] Moreover, the drive unit 1 of the power unit 2 comprises a motor cooling path p1 extending through the motor casing 6. According to the illustrated embodiments, the motor cooling path p1 extends through the motor casing 6 by extending through the electric motor 4. That is, in more detail, the motor cooling path p1 extends through a space formed between a rotor and a stator of the electric motor 4. The rotor is connected to the output shaft 4’. According to the illustrated embodiments, the stator comprises wire windings configured to generate a magnetic field when electric current is supplied to the windings. This magnetic field interacts with permanent magnets of the rotor, causing the rotor and the connected output shaft 4’ to rotate. However, according to further embodiments, the rotor may comprise wire windings and the stator may comprise permanent magnets. In such embodiments, the wire windings of the rotor generate a magnetic field when electric current is supplied therethrough, wherein the magnetic field interacts with the permanent magnets of the stator, causing the rotor and the connected output shaft 4’ to rotate.
[0102] In these embodiments, the cooling path p1 may also extend through and / or around the wire windings of the stator. The stator, the rotor, and the wire windings have not been provided with reference signs in Fig. 9 for reasons of brevity and clarity. Moreover, according to some embodiments, the motor cooling path p1 may alternatively or additionally extend least partially around the electric motor 4, such as at least partially around a casing of the electric motor 4, or at least partially around a stator of the electric motor 4.
[0103] The number of radially acting fan blades 13 is configured to generate an airflow through the motor cooling path p1 and into the fan scroll structure 5 of the fan scroll housing 15 upon rotation of the output shaft 4’. The fan scroll structure 5 is configured to direct air from the fan-flywheel unit 3 to the air outlet 11 along an airflow path p2 indicated in Fig. 9. According to the illustrated embodiments, inner delimiting surfaces of the fan scroll housing 15 defines the fan scroll structure 5. The wording fan scroll structure 5 implies that the fan scroll structure 5 comprises curved or spiral-like surfaces configured to guide and direct the airflow efficiently from the fan-flywheel unit 3 towards the air outlet 11. According to some embodiments, the fan scroll structure 5 may have a volute shape, where the cross-sectional area of the airflow path p2 gradually increases towards the air outlet 11. This design canreduce airflow resistance and improve air pumping efficiency and thereby also cooling performance.
[0104] According to the illustrated embodiments, the fan scroll structure 5 is integrated into the fan scroll housing 15 as a single piece, which can provide structural integrity and simplify the manufacturing and assembling process. However, according to further embodiments, the fan scroll structure 5 may comprise separate components that are assembled into the fan scroll housing 15.
[0105] Moreover, according to the embodiments illustrated in Fig. 9, the clutch 7 is arranged inside the fan scroll housing 15. In other words, the fan scroll housing 15 encloses the clutch 7, including the driven member 27 and the driving member 17 thereof. Moreover, in these embodiments, the fan scroll housing 15 forms a clutch cooling path p3 extending from the fan scroll structure 5, through and / or around portions of the clutch 7, to the air outlet 11. As can be seen in Fig. 9, according to the illustrated embodiments, the clutch cooling path p3 branches off from the airflow path p2 of the fan scroll structure 5, wherein air flowing through the clutch cooling path p3 rejoins the airflow path p2 of the fan scroll structure 5 before exiting through the air outlet 11.
[0106] The power unit 2 comprises an outflow path p4 extending between the air outlet 11 of the drive unit 1 and one or more air outlets 21 of the external casing 12. In other words, the air outlet 11 of the drive unit 1 is fluidly connected to the one or more air outlets 21 of the external casing 12 via the outflow path p4 indicated in Fig. 9.
[0107] The power unit 2 comprises power electronics 44 configured to regulate the electric power supply to the electric motor 4. According to the illustrated embodiments, the power electronics 44 is arranged in the outflow path p4. In this manner, efficient cooling of the power electronics 44 can be provided. The power electronics 44 may comprise components such as a motor controller, inverters, and / or voltage regulators, which may be responsible for adjusting and managing the flow of electric power to the electric motor 4. A number of electrical wires 51 of the electric motor 4 is indicated in Fig. 3 - Fig. 5, and Fig. 8. As understood from the above, power electronics 44 configured to regulate the electric power supply to the electric motor 4 by regulating the electric power supply in the number of electrical wires 51.
[0108] The battery attachment section 24 of the power unit 2 is also seen in Fig. 9, as well as an example battery 26 attached to the battery attachment section 24. The battery 26 comprisesa number of battery cells, which can be seen in Fig. 9, and is configured to supply electricity to the electric motor 4 by an amount controlled by the power electronics 44. The battery cells have not been provided with reference signs in Fig. 9 for reasons of brevity and clarity.
[0109] According to the embodiments illustrated in Fig. 9, the outflow path p4 extends through and around the battery attachment section 24. Moreover, in these embodiments, the battery attachment section 24 is configured to accommodate a battery 26 with internal cooling channels surrounding the battery cells of the battery 26. In other words, according to the illustrated embodiments, the outflow path p4 of the power unit 2 extends through the internal cooling channels of the battery 26 when the battery 26 is attached to the battery attachment section 24 of the power unit 2. In this manner, efficient cooling of the battery cells of the battery 26 can be provided upon operation of a power tool 10 comprising the power unit 2.
[0110] Fig. 10 illustrates components of a drive unit T according to some further embodiments. The power tool 10 illustrated in Fig. 1 may comprise a drive unit T according to the embodiments illustrated in Fig. 10 instead of the drive unit 1 explained with reference to Fig. 3 - 9. In other words, the drive unit T illustrated in Fig. 10 may be arranged inside the power unit 2 explained with reference to Fig. 1 - Fig. 9.
[0111] The drive unit T illustrated in Fig. 10 comprises the same features, functions, and advantages as the drive unit 1 explained with reference to Fig. 2 - 9 with only some differences. For reasons of brevity and clarity, only the differences are explained in detail below.
[0112] The drive unit T according to the embodiments illustrated in Fig. 10 lacks a clutch. Instead, as is further with reference to Fig. 11 below, the fan-flywheel unit 3 is configured to be directly connected to a drive shaft of the hand-held power tool.
[0113] Apart from the clutch, the drive unit T may comprise the same components as the drive unit T explained with reference to Fig. 3 - 9, such as a motor cover 16, an electric motor 4, a motor casing 6, and a fan-flywheel unit 3. Moreover, even though not visible in Fig. 10, the drive unit T may comprise a fan scroll housing 15 as explained with reference to Fig. 3 - 9 above.
[0114] The fan-flywheel unit 3 of the drive unit T may be identical to the fan-flywheel unit 3 explained with reference to Fig. 3 - 9 or may be a variant thereof with possible modifications as further explained below.According to the embodiments illustrated in Fig. 10, the fan-flywheel unit 3 is configured to be attached to the output shaft 4’ of the electric motor 4 in the same manner as described with reference to Fig. 6, i.e., by using a nut 54 treaded onto a treaded portion 64 of the output shaft 4’.
[0115] Fig. 11 illustrates a partial assembly 71 of the drive unit T according to the embodiments illustrated in Fig. 10. The partial assembly 71 depicted in Fig. 11 comprises the motor casing 6, the electric motor 4, and the fan-flywheel unit 3. Moreover, Fig. 11 depicts an attachment member 42 and a portion of a drive shaft 39’. The drive shaft 39’ may be arranged inside an elongated body portion 35 of a hand-held power tool 10 as explained with reference to Fig. 1 and Fig. 9.
[0116] Below, simultaneous reference is made to Fig. 1 , Fig. 10, and Fig. 11, if not indicated otherwise. The attachment member 42 is attached to the second side S2 of the fan-flywheel unit 3 using two bolts 36 each tightened into the two threaded holes 36’ of the fan-flywheel unit 3.
[0117] The drive shaft 39’ is connected to the attachment member 42 via a splined interface 45. According to the embodiments illustrated in Fig. 11 , the splined interface 45 is formed between inner splines of the attachment member 42 and outer splines of the drive shaft 39’. However, according to further embodiments, this may be the other way around. Moreover, the drive shaft 39’ may be connected to the attachment member 42 in another manner than by using a splined interface 45, such as another type of keyed interface, a friction fit, or a threaded connection.
[0118] As understood from the above, according to the embodiments illustrated in Fig. 10 and Fig.
[0119] 11 , the rotor of the electric motor 4, the fan-flywheel unit 3, the attachment member 42, and the drive shaft 39’ are arranged to always co-rotate during rotation of the rotor of the electric motor 4. Moreover, in these embodiments, these components are arranged to rotate around the same rotation axis.
[0120] Since these components are arranged to always co-rotate with the rotor of the electric motor 4, they collectively contribute to a flywheel effect. Thereby, the fan-flywheel unit 3 of the drive unit T according to the embodiments illustrated in Fig. 10 and Fig. 11 can be made lighter than what is specified in some examples explained with reference to Fig. 7, while stillmaintaining the desired flywheel effect. As an example, the fan-flywheel unit 3 of the drive unit 1' may have a weight below 70 grams or even below 50 grams.
[0121] The lighter weight may be achieved through material selection for the fan-flywheel unit 3, such as by using an aluminium alloy or a polymeric material. As an alternative, or in addition, the lighter weight may be obtained through dimensions and / or design adjustments, such as reducing the thickness of non-critical portions of the fan-flywheel unit 3.
[0122] It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended independent claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended independent claims.
[0123] As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components, or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions, or groups thereof.
Claims
CLAIMS1. A drive unit (1 , 1 ’) for a hand-held power tool (10), the drive unit (1 , 1 ’) comprising:an electric motor (4) comprising an output shaft (4’) for powering a tool (50) of the hand-held power tool (10),a fan-flywheel unit (3) arranged on the output shaft (4’) of the electric motor (4), a fan scroll structure (5) enclosing the fan-flywheel unit (3),a motor casing (6) at least partially enclosing the electric motor (4), anda motor cooling path (p1) extending through the motor casing (6),and wherein the fan-flywheel unit (3) comprises a number of radially acting fan blades (13) configured to generate an airflow through the motor cooling path (p1) and into the fan scroll structure (5) upon rotation of the output shaft (4’).
2. The drive unit (1 , T) according to claim 1 , wherein the fan-flywheel unit (3) is formed in a single piece of material.
3. The drive unit (1 , T) according to claim 1 or 2, wherein the fan-flywheel unit (3) is made of metal.
4. The drive unit (1 , T) according to any one of the preceding claims, wherein the weight of the fan-flywheel unit (3) exceeds 70 grams or exceeds 90 grams.
5. The drive unit (1 , T) according to any one of the preceding claims, wherein the diameter (d1 ) of the fan-flywheel unit (3) exceeds 55 millimetres or exceeds 70 mm.
6. The drive unit (1 , T) according to any one of the preceding claims, wherein the radio between the diameter (d1) of the fan-flywheel unit (3) and the axial thickness (t1) of the fan-flywheel unit (3) is within the range of 2.5 - 5.5 or is within the range of 3.5 - 4.5.
7. The drive unit (1 , T) according to any one of the preceding claims, wherein the motor cooling path (p1) extends through the electric motor (4), and / or at least partially around the electric motor (4).
8. The drive unit (1 , T) according to any one of the preceding claims, wherein the fanflywheel unit (3) comprises a disc-shaped body portion (23), and wherein the fan blades (13) protrude axially from a surface (23’) of the disc-shaped body portion (23).
9. The drive unit (1 , T) according to any one of the preceding claims, wherein the fanflywheel unit (3) comprises a first side (S1) facing the electric motor (4) and a secondside (S2) facing away from the electric motor (4), and wherein the fan blades (13) are arranged on the first side (S1) of the fan-flywheel unit (3).
10. The drive unit (1, T) according to any one of the preceding claims, wherein the drive unit (1, 1’) comprises a clutch (7), wherein the clutch (7) comprises a driving member (17) and a driven member (27), and wherein the driving member (17) is attached to the fanflywheel unit (3).
11. The drive unit (1) according to claim 10, wherein the fan-flywheel unit (3) comprises a first side (S1) facing the electric motor (4) and a second side (S2) facing away from the electric motor (4), and wherein the driving member (17) is mounted on the second side (S2) of the fan-flywheel unit (3).
12. The drive unit (1 ) according to claim 10 or 11 , wherein the drive unit (1 ) comprises a fan scroll housing (15) comprising the fan scroll structure (5), and wherein the clutch (7) is arranged inside the fan scroll housing (15).
13. The drive unit (1) according to claim 12, wherein the fan scroll housing (15) comprises an air outlet (11), and wherein the fan scroll housing (15) forms a clutch cooling path (p3) extending from the fan scroll structure (5), through and / or around portions of the clutch (7), to the air outlet (11).
14. A power unit (2) for a hand-held power tool (10), wherein the power unit (2) comprises an external casing (12) and a drive unit (1, T) according to any one of the preceding claims, wherein the drive unit (1, T) is arranged inside the external casing (12).
15. The power unit (2) according to claim 14, wherein the drive unit (1, T) comprises an air outlet (11), wherein the fan scroll structure (5) is configured to direct air from the fanflywheel unit (3) to the air outlet (11), and wherein the power unit (2) comprises an outflow path (p4) extending between the air outlet (11 ) of the drive unit (1 , 1 ’) and one or more air outlets (21) of the external casing (12).
16. The power unit (2) according to claim 15, wherein the power unit (2) comprises power electronics (44) configured to regulate the electric power supply to the electric motor (4), and wherein the power electronics (44) is arranged in the outflow path (p4).
17. The power unit (2) according to claim 15 or 16, wherein the power unit (2) comprises a battery attachment section (24) configured to attach a battery (26) for supplyingelectricity to the electric motor (4), and wherein the outflow path (p4) extends through and / or around the battery attachment section (24).
18. A hand-held power tool (10) comprising a drive unit (1, 1’) according to any one of the claims 1 - 13 or a power unit (2) according to any one of the claims 14- 17.
19. The hand-held power tool (10) according to claim 18, wherein the hand-held power tool (10) is an outdoor power tool, such as a pole saw, a string trimmer, or a brush cutter.