Electric tool and walking equipment

Abstract

The utility model discloses an electric tool and walking equipment, and the electric tool comprises a working part which is configured to have a maximum output rotating speed, and a motor which is configured to have a maximum rotating speed; the transmission assembly is configured with a transmission ratio; the driving circuit comprises one or more driving switches; a controller for outputting a control signal to control one or more drive switches of the drive circuit; wherein at least one driving switch in the driving circuit comprises a wide bandgap semiconductor switch, and the ratio of the required maximum rotating speed of the motor to the maximum rotating speed of the motor is smaller than or equal to 0.9. The electrical performance of the motor system of the electric tool is good.

Description

Technical Field

[0001] The present application relates to an electric tool and a walking device. Background Art

[0002] In the related technology, there are some products that require low voltage, high speed and high power. In order to improve the power density of the motor, the product is generally designed from the aspects of increasing the motor speed and reducing the motor copper loss.

[0003] This section provides background information related to the present application which is not necessarily prior art. Utility Model Content

[0004] One object of the present application is to solve or at least alleviate part or all of the above problems. The object of the present application is to provide an electric tool and walking equipment with a high efficiency motor system and a stable operation motor system.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] An electric tool comprises: a motor, wherein the motor is configured with a maximum speed; the maximum speed is a motor performance parameter; a drive circuit, used to drive the motor to output power; the drive circuit comprises one or more drive switches, and the power-on state of the coil winding is switched by turning the drive switches on and off; the product of the maximum output speed of the working part and the transmission ratio is limited to the required maximum speed of the motor; at least one drive switch in the drive circuit comprises a wide bandgap semiconductor switch and the ratio of the required maximum speed of the motor to the maximum speed of the motor is less than or equal to 0.9.

[0007] In one embodiment, it includes: a working component for realizing the function of an electric tool; the working component is configured with a maximum output rotation speed.

[0008] In one embodiment, a motor is used to drive a working component; the motor includes a stator, a rotor and a coil winding.

[0009] In one embodiment, a transmission assembly is mechanically connected to the motor and the working component; the transmission assembly is configured with a transmission ratio.

[0010] In one embodiment, a DC power supply provides electrical energy to the motor.

[0011] In one embodiment, a controller is connected to the driving circuit; the controller is used to output a control signal to control one or more driving switches of the driving circuit.

[0012] In one embodiment, at least one driving switch in the driving circuit includes a wide bandgap semiconductor switch and a ratio of a required maximum speed of the motor to a maximum speed of the motor is less than or equal to 0.85.

[0013] In one embodiment, at least one driving switch in the driving circuit includes a wide bandgap semiconductor switch and a ratio of a required maximum speed of the motor to a maximum speed of the motor is less than or equal to 0.8.

[0014] In one embodiment, the cross-section of each coil winding is a non-circular cross-section.

[0015] In one embodiment, the controller controls the ratio between the on-time and the off-time of the driving switch based on a pulse width modulation (PWM) signal, and the frequency of the pulse width modulation (PWM) signal is greater than 12 KHz.

[0016] In one embodiment, the controller controls the ratio between the on-time and the off-time of the driving switch based on a pulse width modulation (PWM) signal, and the dead time between the driving switches is less than or equal to 50 ns.

[0017] In one embodiment, the nominal output power of the motor is greater than or equal to 120W and less than or equal to 5000W.

[0018] In one embodiment, the maximum rotation speed of the motor is greater than or equal to 15,000 rpm and less than or equal to 60,000 rpm.

[0019] In one embodiment, the stator includes a stator core, the stator core includes teeth, every two teeth define a slot for accommodating a coil winding, and the slot fill rate of the motor is greater than or equal to 40%.

[0020] In one embodiment, the shape of the outer edge of the coil winding changes with the shape of the slot portion, so that the outer edge of the coil winding is substantially in contact with the side wall of the slot portion.

[0021] In one embodiment, each turn of the coil winding has the same cross-sectional area.

[0022] In one embodiment, the nominal voltage of the DC power supply is less than or equal to 48V.

[0023] In one embodiment, the gear ratio is greater than one.

[0024] In one embodiment, the maximum rotation speed of the motor is negatively correlated with the number of turns of the coil winding of the motor.

[0025] In one embodiment, at least one drive switch in the drive circuit comprises a gallium nitride transistor.

[0026] An electric tool comprises: a motor configured to rotatably drive an output part coupled to the motor; the motor is configured with a maximum speed; the maximum speed is a motor performance parameter; a drive circuit for driving the motor to output power; the drive circuit comprises one or more drive switches, and the power-on state of the coil winding is switched by turning the drive switch on and off; wherein at least one drive switch in the drive circuit comprises a wide bandgap semiconductor switch and the ratio of the maximum speed of the input end of the output part to the maximum speed of the motor is less than or equal to 0.9.

[0027] In one embodiment, the output portion is configured with an input end for receiving motor power and an output end for implementing the function of the power tool.

[0028] In one embodiment, an electric machine includes a stator, a rotor, and coil windings.

[0029] In one embodiment, a DC power supply provides electrical energy to the motor.

[0030] In one embodiment, the controller is connected to the driving circuit and is configured to output a control signal to control one or more driving switches of the driving circuit.

[0031] An electric tool comprises a motor, wherein the motor comprises a stator, a rotor and a coil winding arranged on the stator; the cross section of each coil winding is a non-circular cross section; the tool comprises a drive circuit for driving the motor to output power; the drive circuit comprises one or more drive switches, and the power-on state of the coil winding is switched by turning the drive switches on and off; at least one drive switch in the drive circuit comprises a gallium nitride transistor.

[0032] In one embodiment, a motor is configured to rotatably drive an output coupled to the motor.

[0033] In one embodiment, a DC power supply provides electrical energy to the motor.

[0034] In one embodiment, the controller is electrically connected to the driving circuit and is configured to output a control signal to control one or more driving switches of the driving circuit.

[0035] A walking device comprises: a walking component, comprising at least one walking wheel supporting a main machine; the walking component is configured with a maximum output speed; a walking motor, used to drive at least one walking wheel to rotate; a driving circuit, used to drive the walking motor to output power; the driving circuit comprises one or more driving switches, and the power-on state of a coil winding is switched by turning the driving switches on and off; at least one driving switch in the driving circuit comprises a wide bandgap semiconductor switch and the ratio of the required maximum speed of the walking motor to the maximum speed of the walking motor is less than or equal to 0.9.

[0036] In one embodiment, the product of the maximum output speed of the travel component and the transmission ratio is limited to the required maximum speed of the travel motor.

[0037] In one embodiment, it includes: a host; a DC power supply to provide power for the travel motor.

[0038] In one embodiment, the travel motor includes a stator, a rotor and a coil winding; the travel motor is configured with a maximum speed; and the maximum speed is a motor performance parameter.

[0039] In one embodiment, it includes: a transmission assembly mechanically connected to the travel motor and the travel assembly; the transmission assembly is configured with a transmission ratio.

[0040] In one embodiment, the invention comprises: a controller connected to a driving circuit; the controller is used to output a control signal to control one or more driving switches of the driving circuit.

[0041] A walking device comprises: a walking component, comprising at least one walking wheel supporting a main machine; the walking component is configured with a maximum output speed; a walking motor, used to directly drive at least one walking wheel to rotate; a driving circuit comprises one or more driving switches, and when the ratio of the maximum output speed of the walking component to the maximum speed of the walking motor is less than or equal to 0.9, at least one driving switch in the driving circuit comprises a wide bandgap semiconductor switch.

[0042] In one embodiment, it includes: a host; a DC power supply to provide power for the travel motor.

[0043] In one embodiment, the travel motor includes a stator, a rotor and a coil winding; the travel motor is configured with a maximum speed; and the maximum speed is a motor performance parameter.

[0044] In one embodiment, it includes: a driving circuit for driving a walking motor to output power; and switching the power-on state of the coil winding by turning the driving switch on and off.

[0045] In one embodiment, the method includes: a controller connected to the driving circuit, the controller being configured to output a control signal to control one or more driving switches of the driving circuit.

[0046] A walking device comprises: a walking component, comprising at least one walking wheel supporting a main machine; a walking motor, each coil winding having a non-circular cross section; and at least one driving switch in a driving circuit comprising a gallium nitride transistor.

[0047] In one embodiment, it includes: a host; a DC power supply to provide power to the travel motor.

[0048] In one embodiment, the travel motor is used to drive at least one travel wheel to rotate.

[0049] In one embodiment, the travel motor includes a stator, a rotor and a coil winding arranged on the stator.

[0050] In one embodiment, the driving circuit is used to drive the travel motor to output power; the driving circuit includes one or more driving switches, and the power-on state of the coil winding is switched by turning the driving switch on and off.

[0051] In one embodiment, the controller is electrically connected to the driving circuit and is configured to output a control signal to control one or more driving switches of the driving circuit.

[0052] The benefit of the present application lies in that when the gap between the maximum speed of the motor and the required maximum speed of the motor increases, and at the same time the maximum speed of the motor is further increased, a wide bandgap semiconductor switch is used to form a drive circuit to prevent the electronic device from heating up due to the increase in switching frequency, thereby affecting the service life of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a structural diagram of the first embodiment of the present application;

[0054] Figure 2 is an exploded schematic diagram of the motor in this application;

[0055] Figure 3 is a schematic diagram of a cross-section of the motor in this application;

[0056] Figure 4 It is the control principle diagram of the motor in this application;

[0057] Figure 5 is a schematic diagram of a cross-sectional view of a motor filled with a circular wire in the related art;

[0058] Figure 6 is a schematic diagram of a cross-sectional view of the motor of the present application filled with flat wire windings;

[0059] Figure 7 This is a comparison chart of the motor phase current ripple current waveforms using wide bandgap semiconductor switches and Si material MOSFETs in the drive circuit;

[0060] Figure 8 It is a schematic diagram of a cross-sectional view of a flat wire winding filling method of the motor of the present application filled with a flat wire winding;

[0061] Fig. 9 It is a schematic diagram of a cross-sectional view of another flat wire winding filling method of the motor of the present application filled with flat wire windings;

[0062] Fig.10 This is a torque-efficiency comparison diagram of the motor of the present application when it is filled with flat wire windings at different slot filling rates;

[0063] Fig.11This is a comparison chart of torque-motor speed at different slot filling rates when the motor of the present application is filled with flat wire windings;

[0064] Fig.12 is a three-dimensional structural diagram of a walking device as another embodiment of the present application;

[0065] Fig.13 yes Fig.12 Schematic diagram from another perspective. DETAILED DESCRIPTION

[0066] Before any embodiments of the application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the above drawings.

[0067] In this application, the terms "comprises", "includes", "has" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0068] In this application, the term "and / or" is a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects before and after are in an "and / or" relationship.

[0069] In the present application, the terms "connect", "combine", "couple", and "install" may refer to direct connection, combination, coupling, or installation, or indirect connection, combination, coupling, or installation. For example, direct connection refers to two parts or components being connected together without the need for an intermediate piece, and indirect connection refers to two parts or components being connected to at least one intermediate piece respectively, and the two parts or components being connected via the intermediate piece. In addition, "connect" and "couple" are not limited to physical or mechanical connections or couplings, and may include electrical connections or couplings.

[0070] In the present application, it will be understood by those of ordinary skill in the art that relative terms (e.g., "about," "approximately," "substantially," etc.) used in conjunction with quantities or conditions include the values ​​and have the meaning indicated by the context. For example, the relative terms include at least the degree of error associated with the measurement of a specific value, the tolerances caused by manufacturing, assembly, and use associated with a specific value, and the like. Such terms should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. Relative terms may refer to plus or minus a certain percentage (e.g., 1%, 5%, 10% or more) of the indicated value. Numerical values ​​that do not use relative terms should also be disclosed as specific values ​​with tolerances. In addition, "substantially" may refer to plus or minus a certain degree (e.g., 1 degree, 5 degrees, 10 degrees or more) on the basis of the indicated angle when expressing a relative angular position relationship (e.g., substantially parallel, substantially perpendicular).

[0071] In this application, it will be understood by those skilled in the art that the function performed by a component can be performed by one component, multiple components, one part, or multiple parts. Similarly, the function performed by a part can also be performed by one part, one component, or a combination of multiple parts.

[0072] In the present application, the terms "upper", "lower", "left", "right", "front", "back" and other directional words are described based on the orientation and positional relationship shown in the accompanying drawings, and should not be understood as limiting the embodiments of the present application. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element. It should also be understood that directional words such as upper side, lower side, left side, right side, front side, back side, etc. not only represent the positive orientation, but can also be understood as the lateral orientation. For example, the bottom can include directly below, lower left, lower right, lower front, and lower back, etc.

[0073] In this application, the terms "controller", "processor", "central processing unit", "CPU", and "MCU" are interchangeable. When a unit "controller", "processor", "central processing unit", "CPU", or "MCU" is used to perform a specific function, unless otherwise specified, these functions can be performed by a single unit or multiple units.

[0074] In the present application, the terms “device”, “module” or “unit” may be implemented in the form of hardware or software to achieve specific functions.

[0075] In this application, the terms "calculate", "judge", "control", "determine", "identify", etc. refer to the operations and processes of a computer system or similar electronic computing device (e.g., controller, processor, etc.).

[0076] In order to clearly illustrate the technical solution of the present application, an upper side, a lower side, a left side, a right side, a front side and a rear side are defined in the drawings of the specification.

[0077] like Figure 1 As shown, a power tool is provided. In this embodiment, the power tool is an electric circular saw 100. In some embodiments, the power tool can also be a garden tool, such as a pruning machine, a hair dryer, a lawn mower, a chain saw, a snow blower, a cleaning machine, etc. Alternatively, the power tool can also be a decoration tool, such as a screwdriver, a wrench, an electric hammer, a nail gun, a sander, etc. Alternatively, the power tool can also be a sawing tool, such as a reciprocating saw, a jigsaw, etc. Alternatively, the power tool can also be other bench-type tools, such as a bench saw, a metal cutting machine, a bakelite milling machine, etc. Alternatively, the power tool can also be a grinding tool, such as an angle grinder, a sander, etc. Alternatively, the power tool can also be other power tools, such as a lamp, a fan, etc.

[0078] It is understandable that any electric tool driven by a motor can adopt the technical solution disclosed in this embodiment, and any power equipment adopting the technical solution disclosed in this embodiment belongs to the scope of protection of this application. For example, the electric tool can also be a power head, which includes a motor. The power head is used to adapt some output components to realize the function of the tool.

[0079] In this embodiment, an electric circular saw 100 is taken as an example. The electric circular saw 100 includes: a housing 11, a working component 12, a motor 30, a DC power supply 20 and a bottom plate 15, wherein the working component 12 is a circular saw blade that can rotate about a first axis 101. In other alternative embodiments, the working component can be a grinding disc, a blade, etc.

[0080] The housing 11 includes a main body shell 111 and a grip portion 112. The main body shell 111 contains at least a motor 30 and a saw blade, etc. The main body shell 111 is formed with or connected to a grip portion 112 for user operation.

[0081] The bottom plate 15 includes a bottom plate plane 151 for contacting the workpiece to be cut, and the bottom plate plane 151 extends in the first plane. The bottom plate 15 is also connected to the housing 11 so as to be rotatable about the second axis 102, and the second axis 102 is parallel to the first axis 101 of the saw blade. Thus, when the bottom plate 15 rotates relative to the housing 11 about the second axis 102, the size of the cutting portion of the saw blade extending below the bottom plate plane 151 will also change, thereby adjusting the size of the workpiece to be cut.

[0082] The electric circular saw 100 also includes: a transmission assembly 16 and an output shaft (not shown in the figure). The transmission assembly 16 and the output shaft are arranged between the motor 30 and the working part 12, i.e., the saw blade. The transmission assembly 16 and the output shaft are used to transmit the power of the motor 30 to the saw blade so that the saw blade performs cutting work with a certain torque. In some embodiments, the motor 30 directly drives the output shaft. The above does not affect the substantive content of the present application. The overall structure of the electric circular saw 100 is substantially the same as that of a general electric circular saw, and will not be described in detail here.

[0083] In this embodiment, the DC power supply 20 includes a battery pack. The battery pack is detachably connected to the housing 11. The location of the battery pack is different for different types of power tools. The location of the battery pack does not affect the substantive content protected by this application. In this embodiment, the battery pack 20 is used as the energy source of the electric circular saw 100. It should be noted that the battery pack 20 will be used to replace the DC power supply below, but it cannot be used as a limitation of the present invention.

[0084] In the present application, the nominal voltage of the battery pack 20 is less than or equal to 48V. In some embodiments, the nominal voltage of the battery pack 20 is less than or equal to 36V. In some embodiments, the nominal voltage of the battery pack 20 is less than 24V. In this embodiment, the battery pack 20 adopts a nominal voltage of 18V. For walking equipment, the voltage of its walking motor will also be limited. The nominal voltage generally refers to the voltage specified by the manufacturer or seller on the label, packaging, user manual, instruction manual, advertisement, marketing or other supporting documents of these products so that users can understand which power tools and battery packs can operate with each other. Alternatively, the nominal voltage of the battery pack 30 can also be obtained by detection or calculation. The nominal voltage can be the voltage of the battery pack when its battery's state of charge (State of Charge, referred to as SOC) is fifty percent (50%).

[0085] like Figure 2-3 As shown, in this embodiment, the motor 30 is a brushless DC motor. The motor 30 includes a stator 31 and a rotor 32. The stator 31 includes a stator core 311 and. The coil winding 315 is arranged on the stator core 311. The rotor 32 includes a rotor core 321, and the rotor core 321 is provided with permanent magnets 322, which are arranged at intervals along the circumference of the rotor core 321, and the permanent magnets 322 are used to generate a magnetic field. The rotor core 321 is provided with permanent magnet slots 323 for placing the permanent magnets 322. A motor shaft 324 is formed or connected to the rotor 32 for outputting power. The coil winding 315 is a winding of conductive metal, such as a copper winding.

[0086] like Figure 4As shown, the electric circular saw 100 also includes a drive circuit 22 and a controller 21 for controlling and driving the motor to operate. The drive circuit 22 is used to drive the motor 30 to output power, and is electrically or signal-connected to the motor 30, including at least one of a digital signal connection, an analog signal connection, and a wireless signal connection. The drive circuit 22 is also electrically or signal-connected to the controller 21, and receives a drive signal from the controller 21, including at least one of a digital signal connection, an analog signal connection, and a wireless signal connection. Driven by the drive signal output by the controller 21, the drive circuit 22 distributes the voltage to each phase winding on the stator 31 of the brushless motor in a certain logical relationship, so that the brushless motor 30 starts and generates continuous torque.

[0087] Reference Figure 4 , the drive circuit 22 includes a plurality of drive switches Q1, Q2, Q3, Q4, Q5, and Q6. The drive circuit 22 is a circuit that drives the brushless motor to rotate by switching the power-on state of each phase winding of the brushless motor and controlling the power-on current of each phase winding. The conduction sequence and time of each phase winding depend on the position of the rotor 32 of the brushless motor. In order to rotate the brushless motor, the drive circuit 22 has multiple drive states. In one drive state, the stator winding of the brushless motor will generate a magnetic field. The controller 21 outputs a control signal based on different positions of the rotor 32 to control the drive circuit 22 to switch the drive state so that the magnetic field generated by the coil winding 315 rotates to drive the rotor 32 to rotate, thereby realizing the drive of the brushless motor. In this embodiment, taking the motor 30 as a three-phase motor as an example, the drive switch Q forms a bridge circuit. The drive switches Q1 to Q6 form a three-phase full-bridge circuit.

[0088] The controller 21 is arranged on a control circuit board, and the control circuit board includes: a printed circuit board (PCB) and a flexible printed circuit (FPC). The controller 21 adopts a dedicated control chip, for example, a single chip microcomputer, a microcontroller unit (MCU). The controller 21 specifically controls the on or off state of the switch element in the drive circuit 171 through the control chip. In some embodiments, the controller 21 controls the ratio between the on time and the off time of the drive switch based on a pulse width modulation (PWM) signal. It should be noted that the control chip can be integrated into the controller 21, or it can be set independently of the controller 21. As for the structural relationship between the drive chip and the controller 21, it can be set according to actual conditions.

[0089] like Figure 2-3As shown, in this embodiment, the motor 30 is an inner rotor brushless motor. In other alternative embodiments, the motor 30 is an outer rotor brushless motor. For the inner rotor motor, the stator 31 is sleeved on the outside of the rotor 32. For the outer rotor motor, the rotor 32 is sleeved on the outside of the stator 31. In this embodiment, the brushless motor is set as a three-phase brushless motor. It can be understood that the motor is not limited to a three-phase brushless motor, and can also be other types of DC motors, and the above does not affect the substantive content of this application.

[0090] In this embodiment, the coil windings 315 on the same phase are connected in series and parallel, and then the phases are connected in a triangle shape or a Y shape, etc., to form the input and output lines of the motor 30.

[0091] In this embodiment, the stator core 311 further includes a plurality of teeth 312 and an insulating member 313 extending inwardly along the circumference. The insulating member 313 is disposed on the plurality of teeth 312. The coil winding 315 is wound on the teeth 312 via the insulating member 313. Every two teeth 312 define a slot 314 for accommodating the coil winding 315. The insulating member 313 is disposed around the slot 314. The slot 314 includes a first side wall 3141 close to the yoke 316, a second side wall 3142 located on the teeth 312, and a third side wall 3143 close to the pole shoe 317.

[0092] like Figure 5 In the related art, the cross-sectional view of the motor with the coil winding using round wire 33. Among them, since the slot 314 and the insulating member 313 are both roughly trapezoidal, the round wire 33 is not easy to fill the edge of the slot 314. On the other hand, it is difficult to connect the round wires 33 tightly, and there will be an air gap in the tangential connection between two round wires 33. When using round wire 33, in order to improve the slot filling rate, one way is to use thin wire multi-strand wire to form a turn of coil winding. However, winding multiple strands of wire will increase the amount of paint and increase the internal resistance of the motor. And the improvement of the slot filling rate is also limited. Another way is to reduce the winding wire diameter and increase the number of winding turns. However, increasing the number of winding turns causes the voltage of the motor to change. It is known from the related art that when other electrical parameters remain unchanged, the more the number of winding turns is increased, the voltage also needs to increase accordingly. However, for example, for the convenience of user operation of handheld power tools, when the power tools are powered by DC, the weight of the battery pack needs to be controlled, and increasing the voltage requires increasing the weight of the battery pack. On the other hand, when performing work, high output speed and high output power are required. Increasing the number of winding turns will increase the internal resistance of the motor, resulting in low motor efficiency when the motor needs to output higher power. Increasing the number of coil turns will cause the motor output speed to decrease.

[0093] In this application, if Figure 6As shown, the cross section of the coil winding 315 of the motor 30 is a non-circular cross section. That is, the motor uses a flat wire winding 34. Since the flat wire winding 34 has a larger cross-sectional area, when the same slot filling rate as the round wire winding 33 is achieved, the number of turns used by the flat wire winding 34 can be less than the number of turns used by the round wire 33. Reducing the number of winding turns can reduce the internal resistance of the motor. That is, it reduces the copper loss of the motor, thereby improving the efficiency of the motor. The cross section of each turn of the flat wire winding 34 is the same. Alternatively, several flat wire windings 34 with fixed cross sections and the same cross-sectional area are set to reduce the difficulty of winding and the number of molds for the flat wire winding 34.

[0094] The motor 30 is configured with a maximum speed Vmax. The "maximum speed" is determined by the motor's own characteristics. It can be understood as the maximum speed reached by the motor when the motor does not consider the influence of the duty cycle or modulation ratio in the motor control system, or when the duty cycle or modulation ratio is 1. The "maximum speed" of the motor is determined by the number of coil turns of the motor, the motor structure and the electrical characteristics of the motor. The maximum speed Vmax of the motor 30 is negatively correlated with the number of turns of the coil winding of the motor 30. When the number of turns of the winding is reduced by using the flat wire winding 34, the maximum speed of the motor 30 is increased.

[0095] Under the premise of equal motor output power and equal output torque, in order to meet the working conditions, the output speed of the power tool is pre-set, that is, the output speed of the power tool is pre-set according to the use conditions or environment, and the motor matches the requirements of the power tool. The output speed of the power tool is the output speed of the working part 12. The output speed of the working part 12 is related to the speed output by the motor after adjustment by the controller. In order to match the working condition requirements of the power tool, the output speed of the motor after adjustment by the controller is limited to the required speed of the motor.

[0096] In some embodiments, the power tool includes an output portion, which is rotatably coupled to a motor, and the motor drives the output portion. In some embodiments, the motor shaft is connected to a transmission assembly, and the transmission assembly is connected to a working part 12, so that the working part 12 can realize the power tool function. In such a power tool, the output portion includes all components of the entire transmission path between the transmission assembly and the working part 12. Figure 1As shown, taking the electric circular saw 100 as an example, the transmission assembly 16 is mechanically connected to the motor 30 and the working part 12 (such as a saw blade), and the transmission assembly 16 transmits the rotation speed of the motor 30 to the working part 12 at a certain transmission ratio. The transmission ratio of the transmission assembly 16 is a value or several values ​​set according to the working conditions. Among them, the transmission ratio can be greater than 1 or less than 1. Optionally, the transmission ratio is equal to 1. Among them, the required rotation speed of the motor is limited to the product of the rotation speed of the working part 12 and the transmission ratio. Among them, the required maximum rotation speed Vr of the motor is the product of the maximum rotation speed of the working part 12 and the corresponding transmission ratio. It can be understood that the output part is driven by the motor shaft, and the input end of the output part is connected to the motor shaft. The rotation speed of the input end of the output part is basically the same as the output rotation speed of the motor. For example, the rotation speed of the input end of the output part is basically the same as the required rotation speed Vr of the motor. The rotation speed of the output end of the output part is basically the same as the rotation speed of the working part 12.

[0097] Take BLDC control, i.e. adjusting the duty cycle to adjust the motor speed, as an example. The required maximum speed Vr of the motor is basically the same as the product of the maximum speed Vmax*maximum duty cycle (P) of the motor, i.e. Vr=Vmax*P. The duty cycle is positively correlated with the required speed of the motor. The larger the duty cycle, the greater the required speed of the motor. The greater the output speed of the power tool. The output speed of the power tool is the output speed of the working part 12. In the related art, when the working part 12 of the power tool is at the highest output speed, the controller 21 controls the drive switch to turn on at the maximum duty cycle. In order to ensure the safety of the motor tool, in the related products, the maximum duty cycle of the control signal output by the controller 21 of the power tool is close to 100%, that is, the required maximum speed Vr of the motor is basically the same as the maximum speed Vmax of the motor. In some embodiments of the related art, the maximum duty cycle of the control signal output by the controller 21 of the power tool is greater than or equal to 95%.

[0098] In the present application, since the number of winding turns 315 is reduced after using the flat wire winding 34, the maximum speed of the motor 30 is increased, but the maximum output speed of the working component 12 does not change, and therefore the required maximum speed of the motor does not change. Therefore, the maximum duty cycle of the controller output control signal needs to be less than 95%, or even smaller, so that the maximum output speed of the working component 12 can meet the operating requirements.

[0099] The gap between the maximum speed Vmax of the motor and the required maximum speed Vr of the motor increases, and at the same time the maximum speed of the motor is further increased, resulting in the operating frequency of the drive switches Q1, Q2, Q3, Q4, Q5, and Q6 in the drive circuit 22 needing to be increased accordingly, which in turn will lead to an increase in the loss of the drive switch Q in the drive circuit 22.

[0100] In the present embodiment, the drive switches Q1, Q2, Q3, Q4, Q5, and Q6 include metal oxide semiconductor field effect transistors (MOSFETs). Among them, at least one drive switch includes a wide bandgap semiconductor switch. The maximum duty cycle of the control signal output by the controller 21 of the power tool 300 needs to be less than or equal to 90% in order to enable the maximum output speed of the working component 12 to meet the working condition requirements. Therefore, the ratio of the required maximum speed Vr of the motor to the maximum speed Vmax of the motor is less than or equal to 0.9. In some embodiments, the maximum duty cycle of the control signal output by the controller 21 of the power tool is less than or equal to 85% in order to enable the maximum output speed of the working component 12 to meet the working condition requirements. Therefore, the ratio of the required maximum speed Vr of the motor to the maximum speed Vmax of the motor is less than or equal to 0.85. In some embodiments, the maximum duty cycle of the control signal output by the controller 21 of the power tool is less than or equal to 80% in order to enable the maximum output speed of the working component 12 to meet the working condition requirements. Therefore, the ratio of the required maximum speed Vr of the motor to the maximum speed Vmax of the motor is less than or equal to less than or equal to 0.8.

[0101] Due to the increased loss of the driving switch in the driving circuit 22, in the specific device, the temperature of the mosfet transistor increases, thereby increasing the temperature of the controller 21. The present application uses a wide bandgap semiconductor switch tube as a driving switch. Compared with the traditional Si material driving switch, the wide bandgap semiconductor switch has excellent high-frequency performance. Wide bandgap semiconductor switches include gallium nitride transistors, silicon carbide transistors and gallium arsenide transistors. Among them, in this embodiment, gallium nitride transistors are taken as an example. Gallium nitride transistors have a large bandgap width and a higher critical field strength. At the same time, gallium nitride transistors have high breakdown voltage, high electron saturation mobility, small dielectric constant, strong radiation resistance and good chemical stability. Gallium nitride power devices can provide lower gate charge and fast switching speed. So that the components of the control module meet the requirements of high-speed motors and high-frequency switching.

[0102] In some embodiments, the power tool includes an output unit. The motor shaft is directly connected to the working component 12, that is, the working component 12 is directly connected to the motor shaft, for example, a fan product or a lawn mower. In such a power tool, the output unit is the working component 12. The required maximum speed Vr of the motor is substantially the same as the maximum speed of the working component 12 (there may be certain differences due to connection loss or tolerance). It can be understood that the output unit is driven by the motor shaft, the input end of the output unit is connected to the motor shaft, and the speed of the input end of the output unit is substantially the same as the required maximum speed Vr of the motor. The speed of the input end of the output unit is substantially the same as the output speed of the motor. In this embodiment, the speed of the input end of the output unit is substantially the same as the speed of the output end of the output unit. The speed of the output end of the output unit is substantially the same as the speed of the working component 12.

[0103] In some embodiments, the maximum duty cycle of the control signal output by the controller 21 of the power tool 300 needs to be less than or equal to 90% in order for the maximum output speed of the working component 12 to meet the working condition requirements. Therefore, the ratio of the required maximum speed Vr of the motor to the maximum speed Vmax of the motor is less than or equal to 0.9. The ratio of the speed of the input end of the output part to the maximum speed Vmax of the motor is less than or equal to 0.9. In some embodiments, the ratio of the speed of the input end of the output part to the maximum speed Vmax of the motor is less than or equal to 0.85. In some embodiments, the ratio of the speed of the input end of the output part to the maximum speed Vmax of the motor is less than or equal to 0.8.

[0104] Since the motor phase current ripple is inversely proportional to the PWM switching frequency, the motor phase current ripple is converted into torque pulsation in the machine, generating vibration and reducing the drive accuracy and efficiency. Figure 7 As shown in the figure, the i2(t) curve represents the motor phase current ripple using a GaN transistor in the drive circuit, and the i1(t) curve represents the motor phase current ripple using a Si material MOSFET in the drive circuit. Through experimental tests, the current ripple using a GaN transistor is smaller than the current ripple using a Si material semiconductor transistor. This reduces the heating of electronic devices caused by the increase in PWM switching frequency, thereby affecting the service life of electronic devices.

[0105] Current RMS refers to the effective value of current, which can more accurately reflect the current characteristics than the current value. The calculation formula of current RMS is as follows, where I 1rms is the RMS value of the current of the MOSFET using Si material. 2rms is the RMS value of the current using the GaN transistor.

[0106]

[0107] Where t0 is time; t0+T s The time elapsed is TS The time of the cycle; i1(t) is the motor phase current of the motor using Si material MOSFET in the driving circuit; i2(t) is the motor phase current of the motor using GaN transistor in the driving circuit.

[0108] According to the formula, the RMS value of the current using the GaN transistor is smaller than the RMS value of the current using the Si material MOSFET.

[0109] Therefore, based on the same PWM switching frequency, the motor phase current ripple of the GaN transistor and Si material MOSFET is greater than that of the GaN transistor. The modulated current RMS is the effective value of the current. The effective value of the motor current using the Si material MOSFET is greater than that of the motor current using the GaN transistor.

[0110] It is understandable that when the motor adopts FOC (weak magnetic field) control, the speed is adjusted by adjusting the modulation ratio. In the present application, due to the reduction in the number of winding turns, the maximum speed of the motor is increased, but the maximum output speed of the working part 12 does not change. Therefore, the maximum modulation ratio of the control signal output by the controller 21 of the power tool is less than or equal to 90%, so that the maximum output speed of the working part 12 can meet the working condition requirements. The ratio of the required maximum speed Vr of the motor to the maximum speed Vmax of the motor is less than or equal to 0.9. In some embodiments, the maximum modulation ratio of the control signal output by the controller 21 of the power tool is less than or equal to 85%, so that the maximum output speed of the working part 12 can meet the working condition requirements. The ratio of the required maximum speed Vr of the motor to the maximum speed Vmax of the motor is less than or equal to 0.85. In some embodiments, the maximum modulation ratio of the control signal output by the controller 21 of the power tool is less than or equal to 80%, so that the maximum output speed of the working part 12 can meet the working condition requirements. The ratio of the required maximum speed Vr of the motor to the maximum speed Vmax of the motor is less than or equal to 0.8.

[0111] In the present embodiment, the maximum speed Vmax of the motor 30 is greater than or equal to 15000rpm and less than or equal to 60000rpm. In some embodiments, the maximum speed Vmax of the motor 30 ranges from 20000rpm to 60000rpm. In some embodiments, the maximum speed Vmax of the motor 30 ranges from 25000rpm to 60000rpm. In some embodiments, the maximum speed Vmax of the motor 30 ranges from 30000rpm to 60000rpm. In some embodiments, the maximum speed Vmax of the motor 30 ranges from 35000rpm to 60000rpm. In some embodiments, the maximum speed Vmax of the motor 30 ranges from 40000rpm to 60000rpm.

[0112] In some embodiments, we define Q1, Q3, Q5 as the high-side drive switch of each phase bridge, and Q2, Q4, Q6 as the low-side drive switch of each phase bridge. The high-side drive switch and the low-side drive switch of each phase bridge circuit are connected to the same phase winding. The drive switches Q1 and Q2 are connected to the first phase winding W, the drive switches Q3 and Q4 are connected to the second phase winding V, and the drive switches Q5 and Q6 are connected to the third phase winding U. The three-phase windings W, V, and U of the brushless motor are connected to the DC power supply 20 through a bridge composed of six drive switches Q1 to Q6. The dead time between the high-side drive switches Q1, Q3, Q5 and the low-side drive switches Q2, Q4, and Q6 is less than or equal to 50ns, that is, the dead time between the high-side gallium nitride transistor and the low-side gallium nitride transistor is less than or equal to 50ns. In some embodiments, the dead time between the high-side gallium nitride transistor and the low-side gallium nitride transistor is less than or equal to 40ns, 30ns, 20ns, and 10ns. In this embodiment, the controller 21 controls the ratio between the on time and the off time of the driving switch Q based on the PWM signal, and the frequency of the PWM signal is greater than 12KHz. In some embodiments, the frequency of the PWM signal is greater than 20KHz. In some embodiments, the frequency of the PWM signal ranges from greater than or equal to 12KHz to less than or equal to 5GHz. This allows for smoother and quieter operation with higher system efficiency. Lower torque ripple can be obtained at high frequency and low loss.

[0113] In general, if the current flowing through the motor 30 is the same, the lower the nominal voltage of the battery pack 20, the higher the efficiency value of the motor 30. A portion of the power actually output by the motor 30 is mechanically lost in the transmission assembly 16, etc., and the remaining portion becomes the actual output applied to the workpiece from the working part 12 (a saw blade in this embodiment). Therefore, even if the capacity of the DC power supply 20 is the same, the actual output power of the working part 12 can be increased by improving the electrical comprehensive efficiency, thereby increasing the power density.

[0114] In order to improve the overall efficiency of the motor system and increase the power density, it is necessary to reduce the electrical losses generated from the DC power supply to the motor (including the motor). In this embodiment, the resistance of the coil winding 315 of the motor 30 is reduced to suppress the losses in the motor 30 (i.e., improve the efficiency of the motor system). In this embodiment, in order to reduce the resistance of the coil winding 315 of the motor 30, on the one hand, a non-circular cross-section is used to increase the cross-sectional area of ​​the wire of the winding and reduce the number of turns. On the other hand, by using a variety of coil windings 315 with non-circular cross-sectional shapes, the slot full rate of the motor 30 winding is improved.

[0115] like Figure 8-9As shown, the coil winding 315 wound on each tooth portion 312 is set as a winding whole 315a. The outer edge shape of the winding whole 315a changes with the shape of the groove portion 314, so that the outer edge of the winding whole 315a is basically in contact with at least two side walls of the groove portion 314. The winding fills the groove portion 314 as much as possible, thereby improving the slot fill rate. Among them, the outer edge of the winding whole 315a is composed of the outer edge of a single coil in the coil winding 315. In the related art, such as Figure 5 As shown, the outer edge of the winding 315a formed by the circular wire 33 is basically wavy, so the winding 315a formed by the circular wire 33 is in point contact with the side wall of the groove 314, and cannot form a fit, and there is an air gap between them. Figure 6 As shown, the outer edge of the winding body 315a of the conventional flat wire winding 34 is substantially step-shaped or similar to a step-shaped. Therefore, one side wall of the groove 314 of the conventional flat wire winding 34 can be fitted, but the other two side walls are also point-contacted and cannot be fitted, with an air gap between them.

[0116] In this embodiment, the first side wall 3141 of the groove portion 314 includes multiple curves. The cross section of each turn of the coil winding 315 includes at least one edge that fits the curve of the first side wall 3141. The air gap between the coil winding 315 and the first side portion of the groove portion 314 is reduced. In this embodiment, the cross section of each turn of the coil winding 315 includes at least one edge that fits the curve of the second side wall 3142. The air gap between the coil winding 315 and the first side portion of the groove portion 314 is reduced.

[0117] like Figure 8The above is an embodiment of the coil winding 315 and stator structure of the motor 30 of the present application. The cross section of each turn of the coil winding 315 includes: a first edge 3151 and a second edge 3152 adjacent to the first edge 3151. The ratio of the length of the first edge 3151 to the length of the second edge 3152 is greater than 1. In this embodiment, the first edge 3151 of the coil winding 315 matches the first side wall 3141, and the second edge 3152 matches the tooth portion 312, that is, the second side wall 3142. It can be understood that the flat wire winding 34 is wound in a vertical manner. In this embodiment, at least two shapes of coil windings 315 are wound on each tooth portion 312, and the cross-sectional areas of the coil windings of different shapes are the same. Specifically, the coil winding 315 close to the first side wall 3141 is set as the first layer winding 1A, and the coil winding 315 close to the third side wall is set as the last layer winding. According to the different number of winding turns, in this embodiment, the coil winding 315 close to the third side wall is the last layer winding 4A. The size of the first edge 3151 of the coil winding 315 decreases from the first layer winding 1A to the last layer winding 4A. The size of the second edge 3152 of the coil winding 315 increases from the first layer winding 1A to the last layer winding 4A. To ensure that the cross-sectional area from the first layer winding 1A to the last layer winding 4A is equal. The cross-sectional area of ​​the coil winding 315 is the same so that the current density flowing through the coil winding 315 is the same. In some alternative embodiments, the cross-sectional area of ​​the coil winding 315 may be different.

[0118] In this embodiment, in order to reduce the number of turns of the coil winding 315, when the coil winding 315 is wound in a vertical manner, the size of the first edge 3151 of the coil winding 315 is as large as possible while ensuring a safe gap between the windings. The specific size varies according to different stator designs of the motor 30.

[0119] In this embodiment, the cross-sectional shape of the coil winding 315 is not limited to a regular polygon. The cross-sectional shape of the coil winding 315 varies with the shape of the first side wall 3141 or the second side wall 3142 matched therewith. The coil winding 315 can substantially fill or completely fill the groove 314. In this embodiment, the coil winding 315 is wound around the tooth portion 312 in a turn-by-turn manner. In some embodiments, the coil winding 315 is implemented on the tooth portion 312 using a 3D printer.

[0120] In some embodiments, due to the different shapes of the slots 314 , the cross-sections of the coil windings 315 may have the same shape and area. The coil windings 315 may substantially fill or completely fill the slots 314 .

[0121] In this embodiment, each turn of the coil winding 315 is heat-melted by a laser welding machine. That is, the first layer winding 1A and the second layer winding 2A are heat-melted by a laser welding machine. The second layer winding 2A and the third layer winding 3A are heat-melted by a laser welding machine. And so on, until the last layer winding 4A is welded to the previous layer winding. The coil winding 315 belonging to each phase (U, V, W three phases) reserves a lead-out terminal and an introduction line segment to connect with other phases.

[0122] like Fig. 9 The above is another embodiment of the coil winding 315 and stator structure of the motor 30 of the present application. The cross section of each turn of the coil winding 315 includes: a first edge 3151 and a second edge 3152 adjacent to the first edge 3151, and the ratio of the length of the first edge 3151 to the length of the second edge 3152 is greater than 1. In this embodiment, the first edge 3151 of the coil winding 315 matches the second side wall 3142, and the second edge 3152 matches the tooth portion 312, that is, the first side wall 3141. It can be understood that the flat wire winding 34 is wound in a horizontal manner. In this embodiment, at least two types of coil windings 315 are wound on each tooth portion 312, and the cross-sectional areas of the coil windings 315 are the same. Specifically, the coil winding 315 close to the second side wall 3142 is set as the first layer winding 1B, and the coil winding 315 farthest from the second side wall 3142 is the last layer winding. According to the number of winding turns, in this embodiment, the coil winding 315 farthest from the second side wall 3142 is the last layer winding 3B. The size of the first edge 3151 of the coil winding 315 increases from the first layer winding 1B to the last layer winding 3B. The size of the second edge 3152 of the coil winding 315 decreases from the first layer winding 1B to the last layer winding 3B. To ensure that the cross-sectional area from the first layer winding 1B to the last layer winding 3B is equal. The cross-sectional area of ​​the coil winding 315 is the same so that the current density flowing through the coil winding 315 is the same. In some alternative embodiments, the cross-sectional area of ​​the coil winding 315 may be different. Among them, in this embodiment, the second edge 3152 matches the first side wall 3141, so the shape of the second edge 3152 changes with the shape of the first side wall 3141. The coil winding 315 can substantially fill or completely fill the groove 314.

[0123] In this embodiment, in order to reduce the number of turns of the coil winding 315, when the coil winding 315 is wound in a horizontal manner, the size of the first edge 3151 of the coil winding 315 is substantially the same as the distance from the first side wall 3141 to the third side wall. The specific size varies according to different stator designs of the motor 30.

[0124] Each turn of the winding is heat-melted by a laser welding machine. That is, the first layer winding 1B and the second layer winding 2B are heat-melted by a laser welding machine. The second layer winding 2B and the third layer winding 3B are heat-melted by a laser welding machine. The coil winding 315 belonging to each phase (U, V, W three phases) reserves a lead-out terminal and an introduction line segment to connect with other phases.

[0125] ◆In some embodiments, due to the different shapes of the slots 314, the cross-sections of the coil windings 315 may have the same shape. The coil windings 315 may substantially fill or completely fill the slots 314. In this embodiment, the coil windings 315 are wound around the teeth 312 in a turn-by-turn manner. In some embodiments, the coil windings 315 are implemented on the teeth 312 using a 3D printer.

[0126] A third embodiment of the coil winding 315 and stator structure of the motor 30. At least two types of coil windings 315 are wound on each tooth portion 312, and the cross-sections of adjacent coil windings are arranged to interlock with each other. It can be understood that the cross-sections of two adjacent turns of coil windings can match the concave-convex structure. Specifically, one side of the coil winding includes a triangular or trapezoidal tooth structure. So that adjacent coil windings are arranged closely. Further improve the slot fill rate. In this embodiment, the coil winding is wound on the tooth portion in a turn-by-turn manner. In some embodiments, the coil winding is implemented on the tooth portion using a 3D printer.

[0127] Each turn of the winding is heat-melted by a laser welding machine. That is, the first layer of winding and the second layer of winding are heat-melted by a laser welding machine. The second layer of winding and the third layer of winding are heat-melted by a laser welding machine. And so on, until the last layer of winding is welded to the previous layer of winding. The coil winding 315 belonging to each phase (U, V, W three phases) is electrically connected through the printed circuit board.

[0128] In this embodiment, the stator core 311 is assembled from a plurality of split cores along the circumferential direction. In some embodiments, the stator core 311 may be a monolithic structure. In this embodiment, the teeth 312 of the stator core 311 are of equal width, and the slots 314 are also of equal width. In some embodiments, the teeth 312 of the stator core 311 are of unequal width, and the slots 314 are also of unequal width. The above does not affect the substantive content of this application.

[0129] The structure and shape of the coil winding 315 reduce the gap between the coil windings 315 and increase the contact area, thereby improving the thermal conductivity between the coil windings 315 of the motor 30 and effectively suppressing the temperature rise of the motor 30.

[0130] On the other hand, it can be learned from the test results that compared with the round wire 33 motor of the same specification, since the motor slot fill rate of the flat wire winding 34 is significantly improved relative to the slot fill rate of the round wire 33 motor, the motor of the flat wire winding 34 of the present application has lower power consumption and higher working efficiency. In this embodiment, compared with the round wire 33 motor of the same specification, the slot fill rate of the motor of the flat wire winding 34 is greater than or equal to 40%. In some embodiments, the slot fill rate of the motor of the flat wire winding 34 is greater than or equal to 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%. Fig.10 As shown in the figure, based on different slot fill rates, under the condition of the same output torque, the higher the slot fill rate of the motor, the higher the efficiency of the motor. Fig.11 As shown, based on different slot fill rates, under the same output torque, the higher the slot fill rate of the motor 30, the higher the maximum speed of the motor, the higher the maximum speed of the motor, and the higher the power density of the motor. In this embodiment, by increasing the slot fill rate and reducing the number of turns of the winding coil, combined with the driving circuit of the driving switch Q of the gallium nitride transistor, the efficiency of the motor system is improved and the power density of the motor system is improved.

[0131] In some embodiments, the output power of a high-speed brushless motor using the above gallium nitride transistor drive circuit, a low number of motor coil winding turns, and a high slot fill rate ranges from 120W to 3000W. In some embodiments, the output power of the brushless motor ranges from 120W to 500W. In some embodiments, the output power of the brushless motor ranges from 500W to 1500W. In some embodiments, the output power of the brushless motor ranges from 1500W to 2000W. In some embodiments, the output power of the brushless motor ranges from 2000W to 2500W. In some embodiments, the output power of the brushless motor ranges from 2500W to 3000W.

[0132] In some embodiments, the output torque of the brushless motor using the above technical solution ranges from 0.1N·m to 8N·m. In some embodiments, the output torque of the brushless motor ranges from 0.1N·m to 3N·m. In some embodiments, the output torque of the brushless motor ranges from 3N·m to 5N·m. In some embodiments, the output torque of the brushless motor ranges from 5N·m to 8N·m.

[0133] As another embodiment of the present application, Figures 12 to 13As shown, the present application provides a walking device 400. The walking device 400 is specifically a riding lawn mower, which can walk outdoors and mow grass. It is understandable that the walking device 400 can also be other vehicles that only walk outdoors, such as a multi-purpose vehicle, and can also be a beach car, a farmer's car (Utility Vehicle, UTV), a golf cart, and an all-terrain vehicle (All Terrain Vehicle, ATV). The walking device 400 can also be a vehicle that can realize another function in addition to the walking function like the riding lawn mower shown in this embodiment, such as a snowplow, which can walk outdoors and also realize the function of snow removal. It can also be an agricultural machinery vehicle, such as a harvester, a sprayer, etc. Of course, it is understandable that for the walking device 400, it can also be a cleaning machine.

[0134] The walking device 400 includes a main unit 400a and a walking assembly 420. The walking assembly 420 is connected to the main unit 400a to support the main unit 400a. The walking assembly 420 can at least drive the walking device 400 to walk in the front-rear direction. The walking device 400 also includes a walking motor 430 for driving the walking assembly 420. The walking assembly 420 includes a rear walking wheel 431 and a front walking wheel 432, and the walking motor 430 drives the rear walking wheel 431 or the front walking wheel 432 to rotate, so as to enable the walking device 400 to walk on the ground. The number of the walking motors 430 can also be two, and the two walking motors 430 respectively drive the two rear walking wheels 431, so that the outdoor walking device 400 can turn in other directions that deviate from the front-rear direction.

[0135] The host 400a includes a working part for realizing the tool function and a driving motor for driving the working part. In the present embodiment, the working part is a mowing blade or a mowing disc. The driving motor is a motor arranged in the host and connected to the mowing blade or the mowing disc. It can be understood that the working part and the driving motor for driving the working part can refer to the working part 12 and the motor 30 of the electric tool 100 in the above embodiment, or the working part and the driving motor for driving the working part belong to the working part 12 and the motor 30 of the electric tool 100 in the above embodiment. Therefore, the motor drive circuit structure and principle of the above electric tool are also applicable. The structure and principle of the motor 30 of the above electric tool are also applicable.

[0136] In this embodiment, the travel motor 430 has a similar structure to the motor 30 of the electric tool. Figures 8 to 11 The motor structure and motor parameters shown are also applicable and will not be repeated here.

[0137] The travel motor 430 is configured with a maximum speed V'max. The "maximum speed" is determined by the characteristics of the motor itself. It can be understood that when the travel motor 430 does not consider the influence of the duty cycle or modulation ratio in the motor control system, or when the duty cycle or modulation ratio is 1, the travel motor 430 reaches the maximum speed. The "maximum speed" of the travel motor 430 is determined by the number of coil turns, the motor structure and the electrical characteristics of the motor. The maximum speed V'max of the travel motor 430 is negatively correlated with the number of turns of the coil winding of the travel motor 430. When the number of winding turns is reduced by using the flat wire winding 34, the maximum speed of the travel motor 430 is increased.

[0138] Under the premise of equal motor output power and equal output torque, in order to meet the working conditions, the output speed of the travel component 420 is preset, that is, the output speed of the travel component 420 is set according to the preset rules based on the user's input, and the travel motor 430 matches the user's input requirements. The output speed of the travel component 420 is related to the speed output by the travel motor 430 after being adjusted by the controller. In order to match the user's input requirements, the output speed of the travel motor 430 after being adjusted by the controller is limited to the required speed of the travel motor 430.

[0139] In some embodiments, the travel motor 430 is mechanically connected to the travel component 420 through a transmission assembly. The transmission assembly transmits the rotation speed of the travel motor 430 to the travel component 420 at a certain transmission ratio. The transmission ratio of the transmission assembly is a value or several values ​​set according to the working conditions. Among them, the transmission ratio can be greater than 1 or less than 1. Optionally, the transmission ratio is equal to 1. Among them, the required rotation speed of the travel motor is limited to the product of the rotation speed of the travel component 420 and the transmission ratio. Among them, the required maximum rotation speed V'r of the travel motor is the product of the maximum rotation speed of the travel component 420 and the corresponding transmission ratio.

[0140] Take BLDC control, i.e. adjusting the duty cycle to adjust the speed of the travel motor, as an example. The required maximum speed V'r of the travel motor is basically the same as the product of the maximum speed V'max*maximum duty cycle (P) of the travel motor, i.e. V'r=V'max*P. The duty cycle is positively correlated with the required speed of the travel motor. The larger the duty cycle, the greater the required speed of the travel motor. The output speed of the power tool is the output speed of the travel component 420. In the related art, when the travel component 420 of the power tool is at the highest output speed, the controller 21 controls the drive switch to turn on at the maximum duty cycle. In order to ensure the safety of the travel motor 430, in the related products, the maximum duty cycle of the control signal output by the controller 21 is close to 100%, that is, the required maximum speed V'r of the travel motor is basically the same as the maximum speed V'max of the travel motor. In some embodiments of the related art, the maximum duty cycle of the control signal output by the controller 21 of the power tool is greater than or equal to 95%.

[0141] In the present application, since the number of winding turns 315 is reduced after using the flat wire winding 34, the maximum speed of the walking motor 430 is increased, but the maximum output speed of the walking component 420 does not change, and therefore the required maximum speed of the walking motor does not change. Therefore, the maximum duty cycle of the controller output control signal needs to be less than 95%, or even smaller, so that the maximum output speed of the walking component 420 can meet the working condition requirements.

[0142] The difference between the maximum speed V'max of the walking motor and the required maximum speed V'r of the walking motor increases, and at the same time the maximum speed of the walking motor is further increased, resulting in the operating frequency of the driving switches Q1, Q2, Q3, Q4, Q5, and Q6 in the driving circuit 22 needing to be increased accordingly, which in turn will lead to an increase in the loss of the driving switch Q in the driving circuit 22.

[0143] In this embodiment, the drive switches Q1, Q2, Q3, Q4, Q5, and Q6 include metal-oxide-semiconductor field-effect transistors (MOSFETs), wherein at least one drive switch includes a wide-bandgap semiconductor switch.

[0144] In some embodiments, the maximum duty cycle of the control signal output by the controller 21 needs to be less than or equal to 90% so that the maximum output speed of the walking component 420 can meet the working condition requirements. Therefore, the ratio of the required maximum speed V'r of the walking motor to the maximum speed V'max of the walking motor is less than or equal to 0.9. In some embodiments, the maximum duty cycle of the control signal output by the controller 21 is less than or equal to 85% so that the maximum output speed of the walking component 420 can meet the working condition requirements. Therefore, the ratio of the required maximum speed V'r of the walking motor to the maximum speed V'max of the walking motor is less than or equal to 0.85. In some embodiments, the maximum duty cycle of the control signal output by the controller 21 is less than or equal to 80% so that the maximum output speed of the walking component 420 can meet the working condition requirements. Therefore, the ratio of the required maximum speed V'r of the walking motor to the maximum speed V'max of the walking motor is less than or equal to 0.8.

[0145] Due to the increased loss of the driving switch in the driving circuit 22, in the specific device, the temperature of the mosfet transistor increases, thereby increasing the temperature of the controller 21. The present application uses a wide bandgap semiconductor switch tube as a driving switch. Compared with the traditional Si material driving switch, the wide bandgap semiconductor switch has excellent high-frequency performance. Wide bandgap semiconductor switches include gallium nitride transistors, silicon carbide transistors and gallium arsenide transistors. Among them, in this embodiment, gallium nitride transistors are taken as an example. Gallium nitride transistors have a large bandgap width and a higher critical field strength. At the same time, gallium nitride transistors have high breakdown voltage, high electron saturation mobility, small dielectric constant, strong radiation resistance and good chemical stability. Gallium nitride power devices can provide lower gate charge and fast switching speed. So that the components of the control module meet the requirements of high-speed walking motors and high-frequency switching.

[0146] In some embodiments, the travel motor 430 is directly connected to the travel component 420, that is, the travel component 420 is directly connected to the travel motor 430. The required maximum speed V'r of the travel motor is substantially the same as the maximum output speed of the travel component 420 (there may be certain differences due to connection loss or tolerance). In some embodiments, the maximum duty cycle of the control signal output by the controller 21 needs to be less than or equal to 90% in order for the maximum output speed of the travel component 420 to meet the working condition requirements. Therefore, the ratio of the maximum output speed of the travel component 420 to the maximum speed V'max of the travel motor is less than or equal to 0.9. In some embodiments, the ratio of the maximum output speed of the travel component 420 to the maximum speed V'max of the travel motor is less than or equal to 0.85. In some embodiments, the ratio of the maximum output speed of the travel component 420 to the maximum speed V'max of the travel motor is less than or equal to 0.8.

[0147] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the above embodiments do not limit the present application in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. An electric tool, characterized in that: include: A working component, used to realize the function of the electric tool; the working component is configured with a maximum output speed; A motor, used to drive the working part; the motor comprises a stator, a rotor and a coil winding; the motor is configured with a maximum speed; the maximum speed is a motor performance parameter; a transmission assembly mechanically connected to the motor and the working member; the transmission assembly being configured with a transmission ratio; A DC power supply, providing electrical energy to the motor; A drive circuit, used to drive the motor to output power; the drive circuit includes one or more drive switches, and the power-on state of the coil winding is switched by turning the drive switch on and off; a controller connected to the driving circuit; The controller is used to output a control signal to control one or more drive switches of the drive circuit; The product of the maximum output speed of the working component and the transmission ratio is limited to the required maximum speed of the motor; wherein at least one of the drive switches in the drive circuit includes a wide bandgap semiconductor switch and the ratio of the required maximum speed of the motor to the maximum speed of the motor is less than or equal to 0.

9.

2. The electric tool according to claim 1, characterized in that: At least one of the drive switches in the drive circuit includes a wide bandgap semiconductor switch and a ratio of a required maximum speed of the motor to a maximum speed of the motor is less than or equal to 0.

85.

3. The electric tool according to claim 1, characterized in that: At least one of the drive switches in the drive circuit includes a wide bandgap semiconductor switch and a ratio of a required maximum speed of the motor to a maximum speed of the motor is less than or equal to 0.

8.

4. The electric tool according to claim 1, characterized in that: The cross section of each coil winding is a non-circular cross section.

5. The electric tool according to claim 1, characterized in that: The controller controls the ratio between the on-time and the off-time of the driving switch based on a pulse width modulation signal, and the frequency of the pulse width modulation signal is greater than 12 KHz.

6. The electric tool according to claim 1, characterized in that: The controller controls a ratio between an on-time and an off-time of the driving switch based on a pulse width modulation signal, and a dead time between the driving switches is less than or equal to 50 ns.

7. The electric tool according to claim 1, characterized in that: The nominal output power of the motor is greater than or equal to 120W and less than or equal to 5000W.

8. The electric tool according to claim 1, characterized in that: The maximum rotation speed of the motor is greater than or equal to 15000 rpm and less than or equal to 60000 rpm.

9. The electric tool according to claim 4, characterized in that: The stator includes a stator core, the stator core includes teeth, every two teeth define a slot for accommodating the coil winding, and a slot fill rate of the motor is greater than or equal to 40%.

10. The electric tool according to claim 9, characterized in that: The shape of the outer edge of the coil winding changes with the shape of the groove portion, so that the outer edge of the coil winding is substantially in contact with the side wall of the groove portion.

11. The electric tool according to claim 9, characterized in that: Each turn of the coil winding has the same cross-sectional area.

12. The electric tool according to claim 1, characterized in that: The nominal voltage of the DC power supply is less than or equal to 48V.

13. The electric tool according to claim 1, characterized in that: The transmission ratio is greater than 1.

14. The electric tool according to claim 1, characterized in that: The maximum rotation speed of the motor is negatively correlated with the number of turns of the coil winding of the motor.

15. The electric tool according to claim 1, characterized in that: At least one of the drive switches in the drive circuit comprises a gallium nitride transistor.

16. An electric tool, characterized in that: include: a motor configured to rotatably drive an output coupled to the motor; The output part is configured with an input end for receiving motor power and an output end for realizing the function of the electric tool; The motor comprises a stator, a rotor and a coil winding; the motor is configured with a maximum speed; the maximum speed is a motor performance parameter; A DC power supply, providing electrical energy to the motor; A drive circuit, used to drive the motor to output power; the drive circuit includes one or more drive switches, and the power-on state of the coil winding is switched by turning the drive switch on and off; a controller, connected to the drive circuit, for outputting a control signal to control one or more drive switches of the drive circuit; Wherein, at least one of the drive switches in the drive circuit includes a wide bandgap semiconductor switch and a ratio of a maximum rotational speed of an input end of the output unit to a maximum rotational speed of the motor is less than or equal to 0.

9.

17. An electric tool, characterized in that: include: a motor configured to rotatably drive an output coupled to the motor; The motor comprises a stator, a rotor and a coil winding arranged on the stator; the cross section of each coil winding is a non-circular cross section; A DC power supply, providing electrical energy to the motor; A drive circuit, used to drive the motor to output power; the drive circuit includes one or more drive switches, and the power-on state of the coil winding is switched by turning the drive switch on and off; A controller is electrically connected to the drive circuit and is used to output a control signal to control one or more drive switches of the drive circuit; wherein at least one of the drive switches in the drive circuit includes a gallium nitride transistor.

18. A walking device, characterized in that: include: Host; A walking assembly, comprising at least one walking wheel supporting the main machine; The travel assembly is configured with a maximum output speed; A travel motor, used to drive the at least one travel wheel to rotate; the travel motor comprises a stator, a rotor and a coil winding; The travel motor is configured with a maximum speed; the maximum speed is a motor performance parameter; A transmission assembly is mechanically connected to the travel motor and the travel assembly; the transmission assembly is configured with a transmission ratio; A DC power supply, providing electrical energy to the travel motor; A driving circuit, used for driving the travel motor to output power; the driving circuit includes one or more driving switches, and the power-on state of the coil winding is switched by turning the driving switches on and off; a controller connected to the driving circuit; The controller is used to output a control signal to control one or more drive switches of the drive circuit; The product of the maximum output speed of the walking component and the transmission ratio is limited to the required maximum speed of the walking motor, wherein at least one of the drive switches in the drive circuit includes a wide bandgap semiconductor switch and the ratio of the required maximum speed of the walking motor to the maximum speed of the walking motor is less than or equal to 0.

9.

19. A walking device, characterized in that: include: Host; A walking assembly, comprising at least one walking wheel supporting the main machine; The travel assembly is configured with a maximum output speed; A travel motor, used to directly drive the at least one travel wheel to rotate; the travel motor comprises a stator, a rotor and a coil winding; The travel motor is configured with a maximum speed; the maximum speed is a motor performance parameter; A DC power supply, providing electrical energy to the travel motor; A driving circuit, used for driving the travel motor to output power; the driving circuit includes one or more driving switches, and the power-on state of the coil winding is switched by turning the driving switches on and off; a controller connected to the drive circuit, the controller being configured to output a control signal to control one or more drive switches of the drive circuit; At least one of the drive switches in the drive circuit includes a wide bandgap semiconductor switch and a ratio of the maximum output speed of the travel component to the maximum speed of the travel motor is less than or equal to 0.

9.

20. A walking device, characterized in that: include: Host; A walking assembly, comprising at least one walking wheel supporting the main machine; A travel motor, used for driving the at least one travel wheel to rotate; The travel motor comprises a stator, a rotor and a coil winding arranged on the stator; the cross section of each coil winding is a non-circular cross section; A DC power supply, providing electrical energy to the travel motor; A driving circuit, used for driving the travel motor to output power; the driving circuit includes one or more driving switches, and the power-on state of the coil winding is switched by turning the driving switches on and off; A controller is electrically connected to the drive circuit and is used to output a control signal to control one or more drive switches of the drive circuit; wherein at least one of the drive switches in the drive circuit includes a gallium nitride transistor.

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