Patent Description:
Examples of winding structures used in electrical machines are shown in <CIT> or <CIT>.

Coil windings of an electric motor currently applied to a power tool are mostly copper wires with circular cross-sections. When the preceding coil windings are wound on a stator core, on the one hand, a slot fill factor of the electric motor is relatively low due to the shape of the coil windings, affecting the overall efficiency of the electric motor. On the other hand, the electric motor in operation generates a large amount of heat, and a gap between coils reduces the thermal conductivity of the electric motor, affecting the heat dissipation effect of the electric motor.

To solve the deficiencies of the related art, the present application provides a brushless motor suitable for a power tool, and the preceding brushless motor can effectively improve the working efficiency of the power tool and effectively suppress a temperature rise while reducing power consumption.

To achieve the preceding object, the present application adopts the technical solutions described below.

A power tool includes: a housing; and an electric motor disposed in the housing, wherein output power of the electric motor is greater than or equal to <NUM> W and less than or equal to <NUM> W The electric motor includes at least a stator, a rotor, and a plurality of coil windings disposed on the stator, a cross-section of each of the plurality of coil windings is non-circular, and a slot fill factor of the electric motor is greater than or equal to <NUM>%.

In one example, the stator includes a stator core formed by stacking a plurality of stator laminations and an insulating member disposed on the stator core, and each of the plurality of coil windings is wound on the insulating member.

In one example, an outer diameter of the plurality of stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>; and an inner diameter of the plurality of stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>.

In one example, a stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>.

In one example, the stator core is formed by joining a plurality of split cores into which the stator core is split in a circumferential direction of the stator core.

In one example, the cross-section of each of the plurality of coil windings includes a rectangle, an ellipse, or a gradient shape.

In one example, a cross-sectional area of each of the plurality of coil windings is configured to be less than or equal to <NUM><NUM>.

In one example, a rotational speed of the electric motor is greater than or equal to <NUM> rpm and less than or equal to <NUM> rpm.

In one example, output torque of the electric motor is greater than or equal to <NUM> N·m and less than or equal to <NUM> N·m.

In one example, a high efficiency region of motor efficiency accounts for <NUM>% or more, and the high efficiency region is a region in which the motor efficiency is greater than or equal to <NUM>%.

In one example, the electric motor includes a printed circuit board and a conductive assembly disposed on the printed circuit board, and the conductive assembly is used for achieving electrical connections between the plurality of coil windings.

In one example, the conductive assembly includes a conductive member and a copper foil, the copper foil is disposed on the printed circuit board, and the conductive member is connected in parallel to the copper foil.

In one example, a sum of cross-sectional areas of the conductive member and the copper foil is Scu, a sum of cross-sectional areas of coil windings soldered in correspondence with the conductive member and the copper foil is Sw, and Scu ≥ Sw.

In one example, a thickness of the printed circuit board satisfies that <NUM> ≤ h ≤ <NUM>.

In one example, the electric motor is a brushless motor driven by a driver circuit to operate.

In the technical solutions of the present application, the brushless motor in which the cross-section of the coil winding is non-circular is applied to the handheld power tool, a table power tool, and the outdoor tool so that the slot fill factor of the brushless motor is improved, thereby improving the proportion of the high efficiency region of the motor efficiency and effectively suppressing the temperature rise while improving the working efficiency of the power tool.

The present application is described below in detail in conjunction with drawings and examples.

<FIG> and <FIG> show examples of power tools in the present application, such as an electric drill, a table saw, and a smart mower. Actually, an electric motor in the present application is applicable to a handheld power tool such as an electric drill, an electric wrench, an electric screwdriver, an electric hammer drill, an electric circular saw, and a sander, a table tool such as a table saw, and an outdoor tool such as a mower, a snow thrower, a grass trimmer, a pair of electric shears, a pruner, and a chain saw. Apparently, the following examples are part, not all, of examples of the present application.

<FIG> shows a handheld power tool as an example of the present application. The handheld power tool is particularly the electric drill. An electric drill <NUM> can provide at least torque to assist in driving a screw into a workpiece and may provide an impact force to perform an impact operation to satisfy usage requirements of a user.

Referring to <FIG> and <FIG>, the electric drill <NUM> includes a housing <NUM> formed with a grip <NUM> for the user to hold. An end of the grip <NUM> is connected to a power supply interface for accessing a direct current power supply or an alternating current power supply. In some examples, the power supply interface is connected to a battery pack <NUM> detachably connected to the housing <NUM>. Of course, the power supply interface may also access alternating current power, such as mains power. In this example, the battery pack <NUM> is used as an energy source for the electric drill <NUM>. Specifically, a rated output voltage of the battery pack <NUM> is greater than or equal to <NUM> V. Further, a main control switch <NUM> is disposed on the grip <NUM> and used for controlling the start and stop of the electric drill <NUM>. Of course, in some examples, the main control switch <NUM> can implement a speed regulation function, and the user controls a rotational speed of the electric drill <NUM> by controlling a stroke by which the main control switch <NUM> is pressed. An accommodation space (not shown in the figure) is formed in the housing <NUM> along a direction of a first straight line <NUM>, and a fan <NUM>, an electric motor <NUM>, and a transmission assembly (not shown in the figure) are disposed in the accommodation space in sequence. The electric motor <NUM> is supported by the housing <NUM> and drives an output shaft (not shown in the figure) to drive a drill bit to rotate. In this example, the electric motor <NUM> is configured to be a brushless motor, and the electric motor <NUM> is replaced with the brushless motor <NUM> in the following description.

Referring to <FIG>, the brushless motor <NUM> in this example is configured to be an outer rotor brushless motor received in the housing <NUM> in a posture parallel to the first straight line <NUM>. Specifically, the brushless motor <NUM> includes a stator <NUM>, a rotor <NUM> disposed on an outer side of the stator <NUM>, and an electric motor shaft <NUM>. The stator <NUM> has a stator core <NUM>, an insulating member <NUM> disposed on the stator core <NUM>, and multiple coil windings <NUM> wound on the stator core <NUM> with insulating members <NUM> between the coil windings <NUM> and the stator core <NUM>. The rotor <NUM> is disposed on an outer circumferential side of the stator <NUM>. Specifically, multiple permanent magnets <NUM> are uniformly distributed on an inner side of the rotor <NUM>.

In some examples, a structure of the stator core <NUM> is configured to be an integral structure. In another example, the structure of the stator core <NUM> is configured to be a split structure. In this example, the structure of the stator core <NUM> is configured to be the split structure. Specifically, the structure of the stator core <NUM> in this example is preferably configured to be a spliced structure. Next, the specific structure and splicing manner of the stator core <NUM> in this example are described.

In some examples, referring to <FIG>, the stator core <NUM> is formed by joining multiple split cores 411a into which the stator core <NUM> is split in a circumferential direction of the stator core <NUM>. The split core 411a is formed with a straight groove 4112b and a boss 4112c extending along a direction of the electric motor shaft <NUM>. When the multiple split cores 411a are assembled into the stator core <NUM>, the straight groove 4112b on each split core 411a forms a snap-fit structure with the boss 4112c of a split core 411a adjacent to the each split core 411a, thereby limiting the stator core <NUM> on a plane perpendicular to the electric motor shaft <NUM>.

In some examples, referring to <FIG>, a stack length L of the stator core <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length L of the stator core <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length L of the stator core <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length L of the stator core <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length L of the stator core <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. Referring to <FIG> and <FIG>, the stator core <NUM> is formed by stacking multiple stator laminations <NUM> in a direction parallel to the electric motor shaft <NUM>. The stator core <NUM> further includes fixing pins <NUM> for fixing the multiple stator laminations <NUM>. The stator lamination <NUM> is provided with a through hole <NUM> through which the fixing pin <NUM> can penetrate to fix the stator lamination <NUM>.

In some examples, referring to <FIG>, an outer diameter D1 of the stator laminations <NUM> is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter D1 of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter D1 of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter D1 of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. An inner diameter D2 of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the inner diameter D2 of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the inner diameter D2 of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>.

Referring to <FIG> and <FIG>, the stator core <NUM> further includes multiple stator teeth <NUM> extending circumferentially inwards, and the insulating members <NUM> are disposed on the multiple stator teeth <NUM>. Specifically, the insulating member <NUM> includes a front side insulator 412a and a rear side insulator 412b. Here, the coil winding <NUM> is wound on the stator tooth <NUM> with the front side insulator 412a and the rear side insulator 412b between the coil winding <NUM> and the stator tooth <NUM>. Specifically, the front side insulator 412a is sleeved on a front side of the stator tooth <NUM>, and the rear side insulator 412b is sleeved on a rear side of the stator tooth <NUM>. The coil winding <NUM> is wound back and forth on the front side insulator 412a and the rear side insulator 412b, that is, the coil winding <NUM> is wound on the stator tooth <NUM> with the front side insulator 412a and the rear side insulator 412b between the coil winding <NUM> and the stator tooth <NUM>.

Next, a shape of the coil winding <NUM> on the stator <NUM>, a manner in which the coil winding <NUM> is wound on the stator <NUM>, and a wiring manner are described in detail with reference to <FIG>.

In this example, a cross-section 413a of the coil winding <NUM> is non-circular. Specifically, the cross-section of the coil winding <NUM> may be configured to be one of or a combination of a rectangle, an ellipse, or a gradient shape. Preferably, in this example, the cross-section 413a of the coil winding <NUM> is a rectangle, and a cross-sectional area of the coil winding <NUM>, that is, an area of the rectangle, is configured to be less than or equal to <NUM><NUM>. In some examples, the cross-sectional area 413a of the coil winding <NUM> is configured to be less than or equal to <NUM><NUM>. The cross-section 413a of the coil winding <NUM> is a cross section of one coil winding in a plane perpendicular to a current direction flowing through the one coil winding.

The multiple split cores 411a are assembled along the circumferential direction into the stator core <NUM>, and a manner in which adjacent split cores 411a are mounted is described in detail above and is not repeated here. Referring to <FIG>, one split core 411a is used as an example, and the coil winding <NUM> is wound on the stator tooth <NUM> and formed with a wire inlet end <NUM> and a wire outlet end <NUM>. In the assembly process of the stator <NUM>, the coil winding <NUM> is wound on the stator tooth <NUM> of each split core 411a, and then all the split cores 411a on which the coil windings <NUM> are wound are limited and fixed through the preceding snap-fit structures and assembled into the stator <NUM>. Preferably, in this example, the brushless motor <NUM> is configured to be a three-phase brushless motor, and the stator core <NUM> is composed of <NUM> split cores 411a.

<FIG> shows the stator core <NUM> on which the coil windings <NUM> are wound. The coil winding <NUM> wound on each split core 411a is formed with the wire inlet end <NUM> and the wire outlet end <NUM>. If any split core 411a of the stator core <NUM> is defined as <NUM>#, the other split cores are defined as a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, a split core <NUM>#, and a split core <NUM># in sequence along a counterclockwise direction. The coil winding <NUM> is wound on each split core and each coil winding <NUM> is formed with the wire inlet end <NUM> and the wire outlet end <NUM>. As an example, the split core <NUM>#, the split core <NUM>#, the split core <NUM>#, the split core <NUM>#, and the coil windings <NUM> wound on the split cores are used as one phase of the three-phase brushless motor <NUM>. The split core <NUM>#, the split core <NUM>#, the split core <NUM>#, the split core <NUM>#, and the coil windings <NUM> wound on the split cores are used as one phase of the three-phase brushless motor <NUM>. The split core <NUM>#, the split core <NUM>#, the split core <NUM>#, the split core <NUM>#, and the coil windings <NUM> wound on the split cores are used as one phase of the three-phase brushless motor <NUM>. The three phases of the three-phase brushless motor <NUM> are formed by the preceding distribution method. Of course, those skilled in the art can adopt other numbers of split cores or other distribution methods for electrical connections, which is not limited in the present application.

Referring to <FIG>, the three-phase brushless motor <NUM> further includes a printed circuit board <NUM>. The printed circuit board <NUM> is fixedly disposed on a side of the stator <NUM> and used for implementing conductive connections between the coil windings <NUM> on the stator core <NUM> of the three-phase brushless motor <NUM>.

One phase of the three-phase brushless motor <NUM> is used as an example. Referring to <FIG>, the coil winding <NUM> on the split core <NUM># enters at 1a, exits at 1b, is wound along an extension direction of the stator tooth <NUM>, enters at 2a, and exits at 2b to form a first layer of winding, and the coil winding <NUM> forms a second layer of winding according to this winding rule and finally exits at 3b to form a third layer of winding. Since a width of the stator tooth <NUM> in the extension direction of the stator tooth <NUM> is basically consistent, the space for placing the coil winding <NUM> and between two adjacent stator teeth <NUM> gradually decreases in the extension direction of the stator tooth <NUM>. Thus, a length of the first layer of winding in the extension direction of the stator tooth <NUM> is greater than a length of the second layer of winding in the extension direction of the stator tooth <NUM>. The length of the second layer of winding in the extension direction of the stator tooth <NUM> is greater than a length of the third layer of winding in the extension direction of the stator tooth <NUM>.

In this example, the coil windings <NUM> are wound in the preceding winding manner, which can ensure that a slot fill factor of the brushless motor <NUM> is greater than or equal to <NUM>%.

Specifically, referring to <FIG>, the coil winding <NUM> on the split core <NUM># has the wire inlet end <NUM> at 1a and the wire outlet end <NUM> at 3b. The coil winding <NUM> on the split core <NUM># has the wire inlet end <NUM> at 4a and the wire outlet end <NUM> at 5b. A conductive connection is implemented between the wire outlet end <NUM> at 3b of the coil winding <NUM> on the split core <NUM># and the wire inlet end <NUM> at 4a of the coil winding <NUM> on the split core <NUM># through the printed circuit board <NUM>. Similarly, the coil winding <NUM> on the split core <NUM># has the wire inlet end <NUM> at 5a and the wire outlet end <NUM> at 6b. The coil winding <NUM> on the split core <NUM># has the wire inlet end <NUM> at 7a and the wire outlet end <NUM> at 8b. A conductive connection is implemented between the wire outlet end <NUM> at 6b of the coil winding <NUM> on the split core <NUM># and the wire inlet end <NUM> at 7a of the coil winding <NUM> on the split core <NUM># through the printed circuit board <NUM>. In some examples, a conductive connection is implemented between the wire outlet end <NUM> at 5b of the coil winding <NUM> on the split core <NUM># and the wire inlet end <NUM> at 5a of the coil winding <NUM> on the split core <NUM># through the printed circuit board <NUM>. The preceding wiring manner is the wiring of one phase of the brushless motor <NUM>. It is to be understood that the wiring manners for the other two phases are similar to the preceding wiring manner and are not repeated here.

In some examples, a conductive assembly is arranged on the printed circuit board <NUM> and used for implementing electrical connections between the coil windings <NUM>. Referring to <FIG>, the conductive assembly includes a conductive member <NUM> and a copper foil <NUM>. The copper foil <NUM> is disposed on the printed circuit board <NUM> and connected in parallel to the conductive member <NUM>. The conductive member <NUM> and the copper foil <NUM> replace wires and connections of the coil windings <NUM> around an outer circumference of the stator core <NUM> in the related art, thereby effectively reducing the crossing between wires and simplifying connections. On the other hand, the following is avoided: lead-in wires and lead-out wires of multiple coil windings in a relevant structure are arranged along the direction of the electric motor shaft and occupy a relatively large space in height. The present application can effectively reduce the space occupied at an end of the electric motor, simplify wiring, and reduce the overall height of the electric motor, thereby improving the power density and connection efficiency of the electric motor. The conductive member <NUM> and the copper foil <NUM> are disposed on the printed circuit board <NUM> so that the structural connections are stable and reliable, and a risk and a cost are reduced. In some examples, the conductive member <NUM> and the copper foil <NUM> can be soldered to the coil windings <NUM>.

In some examples, a sum of cross-sectional areas of the conductive member <NUM> and the copper foil <NUM> is Scu, and a sum of cross-sectional areas of coil windings <NUM> soldered in correspondence with the conductive member <NUM> and the copper foil <NUM> is Sw, and Scu ≥ Sw. When the coil windings <NUM> consists of multiple coils with the same cross-sectional area, Sw = N × S0. N denotes a number of wires of the coil windings <NUM> at a solder joint, in other words, N denotes the number of strands of the multiple coils. S0 denotes a cross-sectional area of a single wire of the coil windings <NUM>. When the coil winding includes only one coil, N is <NUM>. The cross-sectional areas of the conductive member <NUM> and the copper foil <NUM> are increased to be greater than the cross-sectional areas of the coil windings <NUM> soldered to the conductive member <NUM> and the copper foil <NUM>, so as to ensure that a large current on the coil winding <NUM> can stably pass through the conductive member <NUM> and the copper foil <NUM>. It is to be noted that the cross-sectional area refers to an area of a cross-section basically perpendicular to a flow direction of the current.

In some examples, the copper foil <NUM> and the conductive member <NUM> are connected to the winding on each tooth of the stator core <NUM>, the coil windings <NUM> on teeth belonging to the same phase are connected in series and in parallel through the copper foil <NUM> and the conductive member <NUM>, and then phases are connected in a delta shape, a Y shape, or other shapes, so as to form inlet and outlet wires of the electric motor. In the solution, for each phase of the electric motor, when the current is relatively large, the copper foil <NUM> and the conductive member <NUM> are not burned by the large current. In some examples, the electric motor is a three-phase electric motor.

In an example, multiple grooves <NUM> recessed radially inwards are arranged on an outer circumference of the printed circuit board <NUM>, and the conductive member <NUM> extends into grooves <NUM> and is connected to the coil windings <NUM>, so as to facilitate soldering of the coil windings <NUM>.

Since copper has good electrical conductivity, in an example, the conductive member <NUM> is a strip of copper, thereby improving the electrical conductivity and the performance of the electric motor. In other examples, the conductive member <NUM> may be replaced with other conductive wires or metal stampings, so as to implementing the connections between the coil windings <NUM>.

In an example, as shown in <FIG>, when the number of the coil windings <NUM> is relatively large, resulting in a large number of solder joints, the conductive member <NUM> is soldered on an upper surface and a lower surface of the printed circuit board <NUM>, so as to perform a double-sided arrangement, avoid overcrowding due to a single-sided arrangement, and facilitate a layout; when the number of the coil windings <NUM> is relatively small, in another example, the conductive member <NUM> is soldered on the upper surface or the lower surface of the printed circuit board <NUM>, so as to perform the single-sided arrangement and simplify the structure. The conductive member <NUM> is specifically arranged according to actual situations, which is not limited.

In an example, a thickness of the printed circuit board <NUM> satisfies that <NUM> ≤ h ≤ <NUM>, where the thickness refers to a thickness of the printed circuit board <NUM> itself, excluding thicknesses of the soldered conductive member <NUM> and solder joints, thereby avoiding the following case: the thickness of the printed circuit board <NUM> is so large that the electric motor is heightened, or the thickness of the printed circuit board <NUM> is so small that structural strength is affected. In this manner, reliability is ensured when the conductive member <NUM> is carried, and the layout of the conductive member <NUM> and the copper foil <NUM> is facilitated when multilayer wiring is adopted.

In some examples, as shown in <FIG>, when the printed circuit board <NUM> is relatively thick, the multilayer wiring may be adopted, that is, the conductive member <NUM> is arranged on both the upper surface and the lower surface of the printed circuit board <NUM>, and the copper foil <NUM> is arranged in an inner layer of the printed circuit board <NUM> through a processing process of the printed circuit board <NUM>. In an example, the printed circuit board <NUM> is provided with a threading through hole <NUM> and the conductive member <NUM> penetrates through the threading through hole <NUM> so that the routing of the conductive member <NUM> on the upper surface and the lower surface is achieved, thereby reducing the number of conductive members <NUM> and the number of solder joints.

In an example, as shown in <FIG>, multiple conductive members <NUM> are disposed on the printed circuit board <NUM> and insulation distances are provided between the multiple conductive members <NUM>. A certain insulation distance needs to be ensured between conductive members <NUM>, thereby avoiding an insulation failure in a severe working condition. For a magnitude of the insulation distance, reference is made to the related art and the details are not repeated here.

In consideration of a dimension of the electric motor, in an example, an outer diameter of the printed circuit board <NUM> is less than or equal to an outer diameter of the stator core <NUM>, thereby reducing the space occupied by the printed circuit board <NUM> and facilitating installation.

In some examples, the printed circuit board <NUM> can be fixedly connected to an end of the stator core <NUM>, and the printed circuit board <NUM> is fixed to the stator core <NUM> so that the structure is mounted stably.

In an example, as shown in <FIG>, a first region and a second region are provided on the printed circuit board <NUM>, the first region is covered with the copper foil <NUM>, and the second region is provided with at least one heat dissipation hole <NUM>, so as to achieve heat dissipation, improve safety, and extend a service life; the copper foil <NUM> and the heat dissipation hole <NUM> are disposed in different regions, so as to prevent the copper foil <NUM> from covering the heat dissipation hole <NUM>. The first region and the second region are arranged according to actual situations, which is not limited. In some examples, the heat dissipation hole <NUM> and the threading through hole <NUM> are different and may be different in magnitude, shape, or the like, and a foolproof setting is performed so as to avoid a routing error of the conductive member <NUM>.

The brushless motor <NUM> in the preceding examples is the outer rotor brushless motor, and the technical solution in the present application may also be applied to an inner rotor brushless motor. The specific structure of the inner rotor brushless motor is described below in conjunction with <FIG>.

Referring to <FIG>, the inner rotor brushless motor includes a stator <NUM>, where the stator <NUM> includes a stator core <NUM>, an insulating member <NUM> disposed on the stator core <NUM>, and a coil winding <NUM> wound on the insulating member <NUM>. The stator core <NUM> is formed by joining multiple split cores 511a into which the stator core <NUM> is split in a circumferential direction of the stator core <NUM>. Specifically, the split core 511a is formed with a straight groove and a boss extending along a direction of an electric motor shaft. When the multiple split cores 511a are assembled into the stator core <NUM>, the straight groove on each split core 511a forms a snap-fit structure with the boss of a split core 511a adjacent to the each split core 511a, thereby limiting the stator core <NUM> on a plane perpendicular to the electric motor shaft. The preceding limiting principle is similar to that of the brushless motor in the preceding example and is not repeated here.

Referring to <FIG>, the coil winding <NUM> is wound on the stator core <NUM> with the insulating member <NUM> between the coil winding <NUM> and the stator core <NUM>. The coil winding <NUM> on the split core 511a is wound on the stator tooth along an extension direction of the stator tooth and forms a first layer of winding, and the coil winding <NUM> forms a second layer of winding according to this winding rule until the last layer of winding is formed. Since the width of the stator tooth in the extension direction of the stator tooth is basically consistent, the space for placing the coil winding <NUM> and between two adjacent stator teeth gradually decreases in the extension direction of the stator tooth. Thus, a length of the last layer of winding wound on the stator tooth along the extension direction of the stator tooth is the smallest. It is to be understood that a length of the first layer of winding along the extension direction of the stator tooth, a length of the second layer of winding along the extension direction of the stator tooth, until a length of the last layer of winding along the extension direction of the stator tooth gradually decrease.

In this example, a cross-section of the coil winding <NUM> is non-circular. Specifically, the cross-section of the coil winding <NUM> may be configured to be one of or a combination of a rectangle, an ellipse, or a gradient shape. In this example, the cross-section of the coil winding <NUM> is a rectangle, and a cross-sectional area of the coil winding <NUM>, that is, an area of the rectangle, is configured to be less than or equal to <NUM><NUM>. In some examples, the cross-sectional area of the coil winding <NUM> is configured to be less than or equal to <NUM><NUM>.

Referring to <FIG>, the electric drill <NUM> further includes a driver circuit <NUM> and a control module <NUM>, which are used for controlling and driving the brushless motor <NUM> to operate. Driven by a drive signal outputted by the control module <NUM>, the driver circuit <NUM> distributes a voltage to phases of windings on the stator <NUM> of the brushless motor <NUM> according to a certain logical relationship such that the brushless motor <NUM> starts and generates continuous torque. Specifically, the driver circuit <NUM> includes multiple electronic switches. In some examples, the electronic switches include field-effect transistors (FETs). In other examples, the electronic switches include insulated-gate bipolar transistors (IGBTs). In some examples, the driver circuit <NUM> is a three-phase bridge circuit. The driver circuit <NUM> includes three electronic switches Q1, Q3, and Q5 provided as high-side switches and three electronic switches Q2, Q4, and Q6 provided as low-side switches. The driver circuit <NUM> is a circuit that switches energized states of the phases of windings of the brushless motor <NUM> and controls energized currents of the phases of windings to drive the brushless motor <NUM> to rotate. The turn-on sequence and time of each phase of windings depend on a position of the rotor <NUM> of the brushless motor <NUM>. To make the brushless motor <NUM> rotate, the driver circuit <NUM> has multiple driving states. In a driving state, stator windings of the electric motor <NUM> generate a magnetic field, and the control module <NUM> outputs a control signal based on different positions of the rotor to control the driver circuit <NUM> to switch between the driving states. Therefore, the magnetic field generated by the stator windings rotates to drive the rotor to rotate, thereby driving the brushless motor <NUM>.

In some examples, output power of the brushless motor <NUM> using the preceding technical solution ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor <NUM> ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor <NUM> ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor <NUM> ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor <NUM> ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor <NUM> ranges from <NUM> W to <NUM> W.

In some examples, a rotational speed of the brushless motor <NUM> using the preceding technical solution ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor <NUM> ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor <NUM> ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor <NUM> ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor <NUM> ranges from <NUM> rpm to <NUM> rpm.

In some examples, output torque of the brushless motor <NUM> using the preceding technical solution ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor <NUM> ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor <NUM> ranges from <NUM> N·m to <NUM> N m. In some examples, the output torque of the brushless motor <NUM> ranges from <NUM> N·m to <NUM> N·m.

In the preceding technical solution of the present application, the brushless motor in which the cross-section of the coil winding is non-circular is applied. Compared with a conventional electric motor in which a cross-section of a coil winding is circular, the brushless motor in the present application has a higher slot fill factor so that the proportion of a high efficiency region of the efficiency of the brushless motor is higher. Next, two brushless motors with the same volume are used as an example. It is assumed that one of the brushless motors is a common electric motor, that is, the cross-section of the coil winding is circular. The common electric motor is simply referred to as a round wire motor. It is assumed that the other brushless motor is the brushless motor provided in the present application, and the cross-section of the coil winding is a rectangle. An inner diameter of a copper wire in the coil winding of the round wire motor is set to <NUM>. A copper wire in the coil winding of a flat wire motor has a width of <NUM> and a thickness of <NUM>. In addition, the two brushless motors have the same number of winding turns of the coil winding on the stator core. Table <NUM> is an effect comparison table of the round wire motor and the flat wire motor.

As can be seen from Table <NUM>, compared with the round wire motor with the same specification, the flat wire motor has a smaller gap and a larger contact area between coils due to the rectangular cross-section of the coil winding so that the thermal conductivity between the coil windings of the flat wire motor is better and the temperature rise of the electric motor can be effectively suppressed.

On the other hand, as can be seen from the test results, compared with the round wire motor with the same specification, the flat wire motor has a significantly higher slot fill factor than the round wire motor so that the flat wire motor has lower power consumption and higher working efficiency.

In this example, the high efficiency region of the motor efficiency of the brushless motor with a rectangular cross-section of the coil winding accounts for <NUM>% or more. The high efficiency region of the brushless motor is a region in which the motor efficiency is greater than or equal to <NUM>%.

<FIG> and <FIG> show the motor efficiency maps of the round wire motor and the flat wire motor, respectively. The round wire motor and the flat wire motor have basically the same specifications. The round wire motor and the flat wire motor with the specifications that the outer diameter of the stator laminations is <NUM> and the stack length of the stator core is <NUM> are used as an example. An area of the high efficiency region of the flat wire motor is significantly greater than an area of the high efficiency region of the round wire motor. In the test, a ratio of the area of the high efficiency region in which the efficiency of the flat wire motor is greater than <NUM>% to the area of the high efficiency region in which the efficiency of the round wire motor is greater than <NUM>% is greater than or equal to <NUM>. It is to be understood that the high efficiency region of the motor efficiency of the flat wire motor is increased by a factor of <NUM> relative to that of the round wire motor. Thus, the flat wire motor has a larger high efficiency region than the round wire motor. Therefore, the flat wire motor provided in the present application can improve the working efficiency of the power tool when applied to the power tool.

That the coil winding with a non-circular cross-section is applied to the brushless motor and the preceding brushless motor is applied to the power tool to improve the working efficiency of the power tool is described in detail in the preceding examples. On the one hand, the cross-section of the coil winding of the brushless motor is configured to be non-circular so that the gap between coils becomes smaller and the contact area between coils becomes larger. In this manner, the thermal conductivity of the brushless motor is better and the temperature rise of the brushless motor can be effectively suppressed. On the other hand, the brushless motor in the present application has a higher slot fill factor so that the proportion of the high efficiency region of the motor efficiency of the brushless motor in the present application is higher, and the brushless motor can improve the working efficiency of the whole machine when applied to the power tool.

In fact, the technical solution of the present application with respect to the brushless motor can also be applied to other types of power tool. <FIG> shows a second example of the power tool of the present application. The power tool is a table tool, in particular, a table saw <NUM>. The table saw <NUM> includes a table <NUM> with a workplane <NUM> on which a workpiece can be placed. Specifically, the workplane <NUM> is an upper surface of the table <NUM> and for a user to perform a cutting operation on. A hole is formed on the workplane <NUM>. The table saw <NUM> further includes a saw blade <NUM> for cutting the workpiece. The saw blade <NUM> passes through the hole and extends. The table saw <NUM> further includes an electric motor for supplying power, and the saw blade <NUM> is driven by the electric motor disposed below the workplane <NUM> to rotate to implement a cutting function. The saw blade <NUM> is used for cutting the workpiece pushed along the workplane <NUM> and in contact with the saw blade <NUM>, such as wood. Specifically, the electric motor is preferably configured to be a brushless motor. In some examples, the table saw <NUM> further includes a power supply device (not shown in the figure) electrically connected to the table saw <NUM> to supply electrical energy to the table saw <NUM>. The power supply device may be a battery pack or a mains connector. In this example, preferably, the power supply device is configured to be the battery pack, where the battery pack is detachably connected to the table saw <NUM>. Specifically, a rated output voltage of the battery pack is greater than or equal to <NUM> V.

The electric motor in this example is similar in structure to the brushless motor in the first example and is not described in detail here. It is to be noted that the cross-section of the coil winding of the brushless motor is a rectangle, and the cross-sectional area of the coil winding, that is, the area of the rectangle, is configured to be less than or equal to <NUM><NUM>. In some examples, the cross-sectional area of the coil winding is configured to be less than or equal to <NUM><NUM>.

Specifically, the stack length of the stator core of the brushless motor is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. The outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. The inner diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the inner diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the inner diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>.

Specifically, the output power of the brushless motor using the preceding technical solution ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor ranges from <NUM> W to <NUM> W In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m.

In this example, the high efficiency region of the motor efficiency of the brushless motor using the preceding technical solution accounts for <NUM>% or more. The high efficiency region of the brushless motor is a region in which the motor efficiency is greater than or equal to <NUM>%.

In fact, the technical solution of the present application with respect to the brushless motor can also be applied to other types of power tool. <FIG> shows a third example of the power tool of the present application. The power tool is an outdoor tool, in particular, a riding mower <NUM>. Specifically, the riding mower <NUM> includes a rack <NUM>, a seat <NUM>, a power output assembly <NUM>, a moving assembly <NUM>, an operating device <NUM>, and a power supply device <NUM>.

The rack <NUM> is used for carrying the seat <NUM> and at least partially extends in a front and rear direction. The seat <NUM> is used for an operator to sit on and is mounted to the rack <NUM>.

The power output assembly <NUM> includes a first electric motor for driving a mowing element to rotate at a high speed and a second electric motor for driving the moving assembly <NUM> to move. The power supply device <NUM> is used for powering the first electric motor, the second electric motor, and other electronic assemblies on the riding mower <NUM>.

In some examples, the power supply device <NUM> is disposed on a rear side of the seat <NUM> on the rack <NUM>. In some examples, the power supply device <NUM> includes multiple battery packs for supplying power to the power tool. In this example, preferably, a rated output voltage of the battery pack is configured to be greater than or equal to <NUM> V.

The operating device <NUM> is used by the operator to control the riding mower <NUM> to move and/or determine whether the riding mower <NUM> enters a working state.

In this example, preferably, the first electric motor or the second electric motor is configured to be a brushless motor and is similar in structure to the brushless motor in the first example, which is not described in detail here. It is to be noted that, in this example, the cross-section of the coil winding of the brushless motor is a rectangle, and the cross-sectional area of the coil winding, that is, the area of the rectangle, is configured to be less than or equal to <NUM><NUM>. In some examples, the cross-sectional area of the coil winding is configured to be less than or equal to <NUM><NUM>.

Specifically, the stack length of the stator core of the brushless motor is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the stack length of the stator core is greater than or equal to <NUM> and less than or equal to <NUM>. The outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the outer diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. The inner diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the inner diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the inner diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>. In some examples, the inner diameter of the stator laminations is greater than or equal to <NUM> and less than or equal to <NUM>.

Specifically, the output power of the brushless motor using the preceding technical solution ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor ranges from <NUM> W to <NUM> W In some examples, the output power of the brushless motor ranges from <NUM> W to <NUM> W In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the rotational speed of the brushless motor ranges from <NUM> rpm to <NUM> rpm. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m. In some examples, the output torque of the brushless motor ranges from <NUM> N·m to <NUM> N·m.

Claim 1:
A power tool (<NUM>, <NUM>, <NUM>), comprising:
a housing (<NUM>); and
an electric motor (<NUM>) disposed in the housing, wherein output power of the electric motor is greater than or equal to <NUM> W and less than or equal to <NUM> W;
wherein the electric motor comprises at least a stator (<NUM>), a rotor (<NUM>), and a plurality of coil windings (<NUM>) disposed on the stator,
characterized in that
a cross-section (413a) of each of the plurality of coil windings is non-circular, and a slot fill factor of the electric motor is greater than or equal to <NUM>%.