Electric tool, electric motor and rotor assembly thereof

The invention provides a power tool, a motor and a rotor assembly of the motor. The rotor assembly includes a rotating shaft, and a rotor body, a limiting member and a cooling fan fixed on the rotating shaft, the limiting member and the cooling fan are respectively arranged at both axial ends of the rotor body, the rotor body includes a rotor core and magnets fixed in the rotor core, the limiting member and the cooling fan jointly limit an axial displacement and a radial displacement of the magnets.

FIELD OF THE INVENTION

The invention relates to the field of electric technology, and in particular, to rotor assemblies, motors having the rotor assemblies, and power tools having the motors.

BACKGROUND OF THE INVENTION

A rotor of an inner rotor motor usually includes a rotor core and a ring magnet that is sleeved around the rotor core, and the ring magnet is fixed to the rotor core by gluing. The ring magnet is positioned in the axial direction by means of holders fixed to a rotating shaft. However, in some application fields, such as the field of power tools, the motor is required to have a relatively high rotational speed. In order to avoid the ring magnet cracking or even flying off under the high-speed rotation of the rotor, in the prior art, an upper sleeve and a lower sleeve are usually sleeved on the periphery of the ring magnet, which inevitably increases the magnetic resistance, the air gap between the rotor and the stator, the material cost and assembly process of the motor.

SUMMARY OF THE INVENTION

In view of this, the present invention aims to provide a rotor assembly that can solve the above problems, a motor having the rotor assembly, and a power tool having the motor.

For this reason, the present invention provides a rotor assembly, which includes a rotating shaft, and a rotor body, a limiting member and a cooling fan fixed on the rotating shaft, the limiting member and the cooling fan are respectively arranged at both axial ends of the rotor body, the rotor body includes a rotor core and magnets fixed in the rotor core, the limiting member and the cooling fan jointly limit an axial displacement and a radial displacement of the magnets.

In some embodiments, the cooling fan abuts first axial ends of the magnets.

In some embodiments, the cooling fan includes protrusions integrally formed therewith and extending towards the rotor body, the protrusions abut the first axial ends of the magnets.

In some embodiments, the rotor core defines mounting holes for mounting the magnets, and positioning holes respectively communicated with the mounting holes, each of the positioning holes is located on a side of a corresponding one of the mounting holes, the protrusions are at least partially inserted into the positioning holes to abut the magnets, respectively.

In some embodiments, each protrusion comprises a stop portion, and the stop portion abuts against the first axial end of the corresponding magnet, to prevent the magnet from moving towards the cooling fan.

In some embodiments, a radial dimension of one end of each protrusion close to the cooling fan is larger than a radial dimension of a free end of the protrusion to form the stop portion, the stop portion is an inclined surface or a step.

In some embodiments, the cooling fan further comprises a base, the protrusions are integrally formed on the base and completely inserted into the rotor core, the base directly abuts the first axial ends of the magnets.

In some embodiments, each positioning hole is arranged in a center of a side of the corresponding mounting hole facing the rotating shaft or away from the rotating shaft.

In some embodiments, the cooling fan includes a flange integrally formed therewith and extending toward the rotor body, the flange is deformed by the pressing of the rotor core during the installation of the rotor assembly, and at least partially abuts against the axial ends of the magnets.

In some embodiments, the rotor core defines mounting holes for mounting the magnets, and at least parts of the flange are embedded in bottoms of the mounting holes of the rotor core after being deformed to abut the magnets.

In some embodiments, the limiting member abuts against second axial ends of the magnets opposite to the first axial ends directly or through an elastic washer.

In some embodiments, the rotor core defines mounting holes for mounting the magnets and positioning holes respectively communicated with the mounting holes, each of the positioning holes is located on a side of a corresponding one of the mounting holes, the limiting member includes protrusions extending toward the rotor body, the protrusions are at least partially inserted into the positioning holes to abut the magnets, respectively.

The present invention also provides a motor, includes a stator and the above-mentioned rotor assembly, the rotor assembly is rotatably arranged in the stator.

The present invention also provides a power tool, includes the above-mentioned motor.

In the rotor assembly provided by the embodiment of the present invention, the magnets can be installed and fixed in the rotor core only by means of mechanical assembly, the number of components of the rotor assembly is reduced, the assembly is convenient, and the manufacturing cost is effectively reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments, so as to make the technical solutions and beneficial effects of the present invention clearer. It can be understood that the drawings are only provided for reference and explanation, and are not used to limit the present invention. The dimensions shown in the drawings are only for the convenience of clear description, and do not limit the proportional relationship.

FIG.1shows an assembled, perspective view of a rotor assembly100according to a first embodiment of the present invention. The rotor assembly100includes a rotating shaft4, and a rotor body1, a limiting member2and a cooling fan3fixed on the rotating shaft4. The limiting member2and the cooling fan3are respectively arranged at both ends of the rotor body1in the axial direction.

Referring toFIGS.2,3aand3bsimultaneously, the rotor body1includes a rotor core11and a plurality of magnets12inserted into the rotor core11in the axial direction. The plurality of magnets12are arranged in the rotor core11at circumferential intervals around the rotating shaft4. In this embodiment, the length of the magnet12in the axial direction of the rotating shaft4is approximately equal to the axial length of the rotor core11, that is, two ends of the magnet12in the axial direction are substantially flush with two axial ends of the rotor core11in the axial direction, respectively. Both ends of the magnet12in the axial direction of the rotating shaft4respectively abut against the limiting member2and the cooling fan3, to prevent the magnet12from moving relative to the rotor core11. In other embodiments, the length of the magnet12may also be slightly smaller than the axial length of the rotor core11.

Referring toFIGS.4aand4bsimultaneously, the rotor core11is substantially cylindrical, and is provided with mounting holes111for mounting the magnets12, the mounting holes111extend axially and penetrate the rotor core11. The plurality of mounting holes111are arranged circumferentially around the rotating shaft4. In this embodiment, the cross section of the mounting hole111is substantially rectangular, and protrusions are provided at both ends for restricting the circumferential movement of the magnet. The rotor core11further defines a positioning hole112at the center of the radial inner side of each mounting hole111, and the positioning hole112communicates with the corresponding mounting hole111. In this embodiment, the positioning holes112extend perpendicular to the radial inner sides of the corresponding mounting holes111, and the positioning holes112also penetrate the rotor core11in the axial direction. In other embodiments, the axial length of the positioning holes112may be smaller than the axial length of the rotor core11, that is, the positioning holes112only extend a certain distance in the axial direction from one end face of the rotor core11, and does not penetrate through the other end face of the iron core11. Preferably, the positioning holes112are located at the centers of the radial inner sides of the mounting holes111. The magnets12are inserted into the mounting holes111. In this embodiment, the rotor body1includes four magnets12, and the magnets12are in the shape of rectangular plates. Correspondingly, there are four mounting holes111, which are evenly spaced along the circumference of the rotor core11, and are arranged in a square shape together. It can be understood that the specific numbers of the mounting holes111and the positioning holes112and the specific positional relationship between them can be set according to actual needs.

The cooling fan3includes a base31and a number of blades33on the outer periphery of the base. The base31has a substantially circular shape, and is disposed facing the rotor body1. A side of the base31facing the rotor body1has a plurality of protrusions32extending toward the rotor body1. The protrusions32can be at least partially inserted into the positioning holes112of the rotor core11and abut the magnets12installed in the corresponding mounting holes111. Referring toFIG.5at the same time, the radially outer side of an end of each protrusion32close to the base31has an outwardly extending inclined surface321, so that the radial dimension of the end of the protrusion32close to the base31is larger than the radial dimension of a free end of the protrusion32, the inclined surface321abuts against an end of the magnet12installed in the mounting hole111, thereby restricting the axial movement of the magnet12toward the cooling fan3and the movement of the magnet12in the radial direction. The arrangement of the protrusions32and their inclined surfaces321enables the corresponding magnets12to be pressed in the mounting holes111of the rotor core11, and the arrangement of the inclined surfaces321can allow certain assembly deviations, thereby reducing the requirements for machining accuracy. In this embodiment, the protrusions32are made of plastic, preferably, integrally injection-molded with the base31and the blades33.

In this embodiment, the protrusions32have inclined surfaces321for axially and radially limiting the magnets12. In other embodiments, the inclined surfaces321can be replaced by steps, and the steps abut on the ends of the magnets12, which can limit the axial movement of the magnets12in the direction towards the cooling fan3. The inclined surfaces321or the steps constitute stop portions of the protrusions32, and act as stops for the axial end portions of the magnets.

In other embodiments, the positioning holes112may be arranged on the radial outer sides of the mounting holes111, in this case, the inner sides of the protrusions abut the magnets, and the radial inner sides of the ends of the protrusions close to the base31may be provided with corresponding inclined surfaces in order to limit the axial movement of the magnets12toward the cooling fan3and the movement of the magnets12in the radial direction. In other embodiments, the radially inner and outer sides of the end of each protrusion near the base31are provided with inclined surfaces to limit the axial movement of the magnet12toward the cooling fan3and the movement of the magnet12in the radial direction. It can be understood that the arrangement of the protrusions and their inclined surfaces can be designed according to actual requirements.

The limiting member2is fixed on the rotating shaft4, which is located at the other end of the rotor body1. A surface of the limiting member2facing the rotor body1is a limiting surface21, and the limiting surface21abuts against the other axial end of the rotor body1and abuts against the other ends of the magnets12, thereby limiting the axial movement of the magnets toward the limiting member2. In this way, the limiting member2cooperates with the cooling fan3to limit the axial displacement of the magnets12. In this embodiment, the cross section of the limiting member2is circular. Preferably, the radius of the limiting surface21of the limiting member2is greater than the shortest distance between the magnets12and the axis of the rotating shaft4, and is not greater than the diameter of the rotor core11. In other embodiments, the limiting member2may also be provided with protrusions to engage in the positioning holes, and the radial movement and/or axial movement of the magnets12is restricted by the protrusions at one end of the limiting member2.

In the present invention, the above-mentioned arrangement of the limiting member2and the protrusions32on the cooling fan3enables the magnets12installed in the mounting holes111of the rotor core11to be reliably fixed in the mounting holes111only by means of mechanical fixing. Glue-free assembly of the magnets12in the rotor core11is realized, and the magnets12can be kept in proper positions, the number of components in the rotor assembly100is reduced, the assembly process is simple, and the cost is effectively reduced.

FIGS.6and7illustrate a rotor assembly100according to a second embodiment of the present invention. The main difference between this embodiment and the above-mentioned embodiment is that a washer5is arranged between the rotor body1and the limiting member2. Preferably, the shape of the washer5can be matched with the limiting surface21of the limiting member2, so the above description about the limiting surface21is also applicable to the washer5. Preferably, the washer5is made of elastic materials such as rubber, which can provide limited elastic preloading force for the magnets12arranged in the rotor core11.

In addition, in this embodiment, the protrusions32of the cooling fan3extend perpendicularly from the base31, that is, the protrusions32do not have inclined surfaces. In the present embodiment, the protrusions32are completely inserted into the positioning holes112, so that both ends of the rotor core11in the axial direction of the rotating shaft4abut against the washer5and the surface of the base31, respectively. Both ends of the magnets12installed in the rotor core11in the axial direction of the rotating shaft4are respectively limited by the limiting member2and the cooling fan3, to prevent axial movement of the magnets12relative to the rotor core11. The elastic preloading force of the washer5can press the magnets12assembled in the rotor core11towards the cooling fan3, thereby pressing the magnets12against the base31of the cooling fan3without any gap, so the design of the washer5allows a certain assembly deviation, thereby reducing the requirements for machining accuracy.

FIG.8shows a cooling fan3′ of a rotor assembly100′ of a third embodiment of the present invention. Comparing the rotor assembly100′ of the third embodiment with the rotor assembly100of the first embodiment, the main difference is that the protrusions32′ of the base31′ of the cooling fan3′ may or may not be provided with inclined surfaces for abutting against the magnets12according to the situation, and a side of the base31′ facing the rotor body1further includes a flange34′ integrally injection-molded with the base31′ and surrounding the plurality of protrusions32′. The height of the flange34′ in the axial direction is lower than the height of the protrusions32′. When installing the rotor assembly100′, the rotor core11and the magnets12inserted into the mounting holes111are pressed toward the cooling fan3′ by an air press or a hydraulic press, and the protrusions32′ are at least partially inserted into the rotor core11. The rotor core11presses the flange34′, so that the flange34′ is squeezed and deformed and partially embedded in the bottom of each mounting hole111of the rotor core11. Therefore, the movement in the radial direction of the magnets12accommodated in the rotor core11can be restricted by the protrusions32′, and the movement in the axial direction can be restricted by at least the deformed portions of the flange34′ fitted in the mounting holes111of the rotor core11and the limiting member2. Thus, the magnets12can be better fixed.

In this embodiment, the flange34′ is annular. In other embodiments, the flange34′ can be designed in other shapes or form a plurality of intermittent flanges according to the arrangement of the mounting holes111, and the height and width of the flange can be designed differently according to requirements.

FIG.9shows a motor300having the rotor assembly of the present invention, which includes a stator200and the rotor assembly100disposed inside the stator200and rotatable relative to the stator200. The motor300of the present invention is suitable for, but not limited to, power tools.

FIG.10shows a power tool400having the motor300of the present invention, which may be, for example, an electric drill, which includes a drill body401, the motor300mounted in the drill body401, and a drill bit402driven by the motor300. The motor300of the present invention can also be applied to other power tools.

The above are only preferred specific implementations of the present invention. The protection scope of the present invention is not limited to the above-listed examples. Any person skilled in the art can obviously obtain the technology within the technical scope disclosed in the present invention. Simple changes or equivalent replacements of the solutions fall within the protection scope of the present invention.