WO2018170906A1

WO2018170906A1 - Power tools with integrated circuit boards

Info

Publication number: WO2018170906A1
Application number: PCT/CN2017/078146
Authority: WO
Inventors: Hei Man Raymond LEE; Jian Wei He; Li Feng Wang
Original assignee: Tti (Macao Commercial Offshore) Limited
Priority date: 2017-03-24
Filing date: 2017-03-24
Publication date: 2018-09-27
Also published as: CN211908570U; AU2017405808A1; EP3602750A4; EP3602750A1; AU2017405808A2

Abstract

A brushless motor (22) includes a casing (34) which at least partially accommodates a stator and a rotor, an end cap (40) located adjacent to an end of the brushless motor; and a circuit board (32) which contains a controller for the brushless motor. The circuit board is located outside of a region defined by the end cap and the casing. As the circuit board is placed outside of the casing and the end cap, there is no need to configure a separate heat-sink for the circuit board, but the end cap to which the circuit board is mounted becomes a large heat-sink for the circuit board. This provides improved heat dissipation efficiency for both the circuit board and the stator /rotor of the motor.

Description

Power Tools with Integrated Circuit Boards

FIELD OF INVENTION

This invention relates to electric power tools, and in particular battery-powered power tools with brushless motor and their internal structures.

BACKGROUND OF INVENTION

Electric power tools are widely used in various applications such as building, construction and interior decoration. These power tools provide necessary tool functions to the user using the driving power generated by the on-board drive motor. At the same time, the power tools are usually manufactured to be compact and light-weight, so that the user has no difficulty in carrying and manipulating them.

However, the internal structures of traditional power tools are usually complicated and are somehow made disorderly. For example, many traditional power tools use brushless motors as the drive motor, which requires one or more circuit board to carry motor sensors and motor controller for the normal operation of the brushless motor. However, the circuit board is usually placed within the casing of the motor, and special heat dissipation component (e.g. a heatsink) has to be designed for the circuit board and also be placed within the casing. This increases the complexity of the motor structure, as well as reduces the efficiency of heat dissipation.

SUMMARY OF INVENTION

In the light of the foregoing background, it is an object of the present invention to provide an alternate power tool design which eliminates or at least alleviates the above technical problems.

Accordingly, in one aspect of the invention there is provided a brushless motor which includes a casing which at least partially accommodates a stator and a rotor, an end cap located adjacent to an end of the brushless motor； and a circuit board which contains a controller for the brushless motor. The circuit board is located outside of a region defined by the end cap and the casing.

Preferably, the circuit board is located further away from the stator or rotor than the end cap along a longitudinal direction defined by a motor shaft.

More preferably, the circuit board is located at an outermost position at the end of the brushless motor with respect to the rotor or stator.

According to one specific implementation, the circuit board has a contour substantially the same as that of the end cap.

According to another specific implementation, the circuit board further contains a plurality of vias which are adapted to receive struts on the end cap, such that the circuit board is securely mounted on the end cap.

According to one variation of the preferred embodiments, the circuit board further contains a plurality of surface-mount elements configured on a surface of the circuit board.

According to another variation of the preferred embodiments, a Hall sensor, a power control device, and a logic controller are configured on the circuit board.

According to a further variation of the preferred embodiments, the end cap is manufactured using die casting.

According to another aspect of the present invention, there is provided a power tool which contains a tool housing, and a brushless motor as described above. The brushless motor is fixedly mounted to the tool housing and adapted to drive one or more movable part in the power tool.

There are many advantages to the present invention, and apparently the major advantage is that the brushless motor according to the present invention provides improved heat dissipation for both the circuit board, and the interior parts of the motor such as the stator and the rotor. As the circuit board is placed outside of the motor casing and the end cap, there is no need to configure a separate heatsink for the circuit board, but the end cap to which the circuit board is mounted becomes a large heatsink for the circuit board. The end cap is preferably made by die casting to increase heat dissipation efficiency. The circuit board as it is exposed to the outside of the motor structure is also benefited to have a better heat dissipation to surrounding environment itself.

As the circuit board is no longer located within the motor, and in particular adjacent to the stator or rotor, there is now created air flow paths starting and ending around the two end caps of the motor. The air flow paths are formed by gaps between the end caps and the stator /rotor, and as a result of the circuit board placed outside of the motor structure. Such air flow paths further enhance the cooling efficiency on the stator and rotor of the motor.

BRIEF DESCRIPTION OF FIGURES

The foregoing and further features of the present invention will be apparent from the following description of preferred embodiments which are provided by way of example only in connection with the accompanying figures, of which:

Fig. 1 is a perspective view of a handheld power tool according to a first embodiment of the present invention.

Fig. 2a shows the perspective view of the structure of the drive motor in the power tool in Fig. 1.

Fig. 2b shows the perspective view of the structure in Fig. 2a from another viewing angle.

Fig. 2c shows the perspective view of the structure in Fig. 2a from a further viewing angle.

Fig. 3 is a side view of the structure in Fig. 2a.

Fig. 4 is a cross-sectional view of the structure in Fig. 2a along a plane in which the axis of rotation of the motor shaft is located.

Fig. 5a is a front view of the circuit board in the structure in Fig. 2a.

Fig. 5b is a rear view of the circuit board in Fig. 5a.

Fig. 6 shows a side view of the internal structure of an electric tool according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

As used herein and in the claims, “couple” or “connect” refers to electrical coupling or connection either directly or indirectly via one or more electrical means unless otherwise stated.

Terms such as “horizontal” , “vertical” , “upwards” , “downwards” , “above” , “below” and similar terms as used herein are for the purpose of describing the invention in its normal in-use orientation and are not intended to limit the invention to any particular orientation.

Referring now to Fig. 1, the first embodiment of the present invention is an electric power tool which is designed to be handheld. The power tool has a casing which contains a main portion 20 and a handle portion 28. There is an electric drive motor 22 mounted inside the main portion 20, and the drive motor 22 is configured to driving one or more movable parts in the power tool, such as any intermediate gear mechanism (not shown) and ultimately the tool bit holder 24. The main portion 20 extends substantially along an axial direction defined by the motor shaft (not shown) of the drive motor 22. The handle portion 28 is connected to and extends from the main portion along a substantially downward direction, but which is inclined from the vertical direction perpendicular to the axial direction. A trigger 26 is configured on the handle portion 28 where the trigger 26 is exposed to the outside for the user’s manipulation to turn on/off the power tool. At the bottom of the handle portion 28, there is a battery pack 30 which is detachably connected to the power tool to supply power to the electrical circuit inside the power tool.

Turning now to Fig. 2a-2c and Fig. 3, the structure of the drive motor of the electric tool as described above is clearly shown with other components of the electric tool hidden. The drive motor is a brushless DC motor, which contains two

end caps

38, 40 located approximately at two end of the motor. The drive motor further contains a casing 34 which is configured to accommodate at least partially the essential parts of the motor such as the rotor and the stator (both not shown) . The casing 34 is located between the two

end caps

38, 40. In particular, there are grooves (not shown) formed on the exterior circumference of the casing 34 and these grooves receive a number of elongated screws 44 which have their two ends extending into the end cap 38 and end cap 40 respectively. The end cap 38 and end cap 40 are therefore firmly connected together by the screws 44. On an end of the motor there is mounted a fan 42 which is covered by the end cap 38. The end caps 38, 40 and the casing 34 are aligned along the axis of rotation defined by the motor shaft 52.

A circuit board 32 of the motor is configured at another end of the motor adjacent to the end cap 40. In particular, the circuit board 32 is exposed outside of the casing 34 and the end cap 40, and is in fact located at an outermost position on the respective end of the motor. In other words, the circuit board 32 is located further away from the stator or rotor than the end cap 40 along a longitudinal direction defined by the motor shaft 52. As the circuit board 32 is not placed within the casing 34 and the end caps 38, 40, the size of the circuit board 32 is slightly larger than that of the casing 34 or the end caps 38, 40. The contour of the upper part 41 of the circuit board 32 follows closely with that of the end cap 40, so that they have an identical shape. On the other hand, the lower part 43 of the circuit board 32 extends beyond the end cap 40. The circuit board 32 is mounted to the motor by having one or more struts 36 extending from the end cap 40 into corresponding vias (not shown) on the circuit board 32, thereby holding the circuit board 32 to the end cap 40 firmly. On the circuit board 32, there is a plurality of surface-mount (SMT) elements 50 such as resistors, ICs and capacitors which are electrically connected. A connecting wire 47 extends from the circuit board 32 and has a connector 46 on the free end of it. The connecting wire 47 allows the circuit board 32 to connect electrically to other components in the electric tool such as the battery pack or the trigger described in Fig. 1.

Turning now to Fig. 4, in the cross-sectional view one can see that the shaft 52 is rotatably supported by bearings 54 on the end caps 38, 40 respectively. A rotor 58 is mounted on the motor shaft 52 which contains magnets 64. Outside of the rotor 58 there is a stator 62 which contains windings 60 that cooperate with the magnets 64 in the rotor 58.The structure and working principle of the stator and rotor structure in brushless motors are well-known to skilled persons, and thus no further descriptions will be provided here. However, one should note that the motor structure shown in Fig. 4 effectively provides an air path indicated by the arrow 66. The air from external environment may enter into the interior of the motor from one end of the motor and exits another end, at locations between the end caps 38, 40 and the rotor /stator. Such an air path can be formed since there is no circuit board placed within the motor which would otherwise obscure the air flow. Without the circuit board, there is allowed sufficient gap between each one of the end caps 38, 40 and the rotor /stator, so that air could flow through such gap.

Figs. 5a and 5b show the circuit board 32 independently. The circuit board 32 has a substantially oval shape, and there are both SMT elements 50 as well as non-SMT elements on the circuit board 32. For example, the SMT elements 50 include a microcontroller 53, and the non-SMT elements include a capacitor 55. Among the SMT elements 50 and non-SMT elements, there are a Hall sensor, a power control device, and a logic controller configured on the circuit board.

In the embodiment described above, the circuit board 32 is placed outside of the motor casing and the end caps, so there is no need to configure a separate heatsink for the circuit board 32. Instead, as the circuit board 32 is directly mounted to the end cap 40 the end cap 40 becomes the heatsink for the circuit board 32. In other words, the end cap 40 becomes a much larger heatsink than separate heatsinks used in traditional brushless motors. Such a configuration not only simplifies the structure of the motor, but also greatly enhances the heat dissipation efficiency of the motor. The heat dissipation is further improved by the air path created between the end caps 38, 40 and the rotor /stator as mentioned above.

Turning now to Fig. 6, a portion of an electric tool according to another embodiment of the present invention is illustrated. The drive motor 122 and the main portion 120 are both arranged along the axial direction of the motor shaft (not shown) . The drive motor 122 is a brushless DC motor, which is located at the rear end of the main portion 120 and covered by an end cap 140 of the main portion 120. The drive motor 122 contains a casing 134 which is made by die casting. The casing 134 supports other components of the motor 122 on the main portion 120. A circuit board 132 of the motor 122 is configured at an end of the motor 122 adjacent to the end cap 140. The circuit board 132 is mounted to the casing 134 by having one or more struts 136 extending from the casing 134 into corresponding vias (not shown) on the circuit board 132, thereby holding the circuit board 132 firmly. As a result, the circuit board 132 is mechanically connected to the drive motor 122. On the circuit board 132, there is a plurality of surface-mount (SMT) elements (not shown) such as resistors, ICs and capacitors which are electrically connected.

The exemplary embodiments of the present invention are thus fully described. Although the description referred to particular embodiments, it will be clear to one skilled in the art that the present invention may be practiced with variation of these specific details. Hence this invention should not be construed as limited to the embodiments set forth herein.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and do not limit the scope of the invention in any manner. It can be appreciated that any of the features described herein may be used with any embodiment. The illustrative embodiments are not exclusive of each other or of other embodiments not recited herein. Accordingly, the invention also provides embodiments that comprise combinations of one or more of the illustrative embodiments described above. Modifications and variations of the invention as herein set forth can be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated by the appended claims.

Claims

A brushless motor, comprising:

a) a casing which at least partially accommodates a stator and a rotor；

b) an end cap located adjacent to an end of the brushless motor； and

c) a circuit board which comprises a controller for the brushless motor；

wherein the circuit board is located outside of a region defined by the end cap and the casing.
The brushless motor according to claim 1, wherein the circuit board is located further away from the stator or rotor than the end cap along a longitudinal direction defined by a motor shaft.
The brushless motor according to claim 2, wherein the circuit board is located at an outermost position at the end of the brushless motor with respect to the rotor or stator.
The brushless motor according to any one of the preceding claims, wherein the circuit board has a contour substantially the same as that of the end cap.
The brushless motor according to any one of the preceding claims, wherein the circuit board further comprises a plurality of vias which are adapted to receive struts on the end cap, such that the circuit board is securely mounted on the end cap.
The brushless motor according to any one of the preceding claims, wherein the circuit board further comprises a plurality of surface-mount elements configured on a surface of the circuit board.
The brushless motor according to any one of the preceding claims, wherein a Hall sensor, a power control device, and a logic controller are configured on the circuit board.
The brushless motor according to any one of the preceding claims, wherein the end cap is manufactured using die casting.
A power tool, comprising:

a) a tool housing； and

b) a brushless motor as defined in any one of claims 1-8； the brushless motor fixedly mounted to the tool housing and adapted to drive one or more movable part in the power tool.