Power Tools

Abstract

The present invention discloses an electric tool, a motor, comprising a stator and a rotor, the motor being a motor capable of generating a magnetic resistance torque; a power supply device, for providing electric energy to the motor; a drive circuit, electrically connected to the motor to drive the motor; a controller, for controlling the drive circuit, when the controller controls the drive circuit, the motor obtains a second constant speed torque interval; assuming that when the controller controls the drive circuit in a first control mode, the motor obtains a first constant speed torque interval; wherein the length of the second constant speed torque interval is greater than the length of the first constant speed torque interval. The electric tool motor of the present invention has a wider constant speed range.

Description

Technical Field

[0001] The invention relates to an electric tool, in particular to an electric tool with a wider constant speed range. Background Art

[0002] Existing electric tools usually use traditional square waves to drive their internal motors, and control the motor speed and torque by adjusting the duty cycle of the square wave signal.

[0003] For brushless DC motors, under the traditional square wave modulation control method, in one electrical cycle, the brushless motor has only six states, or the stator current has six states (the three-phase bridge arm has six switching states). Each current state can be regarded as a vector torque that synthesizes a direction. The six vectors are converted regularly and step by step, thereby driving the rotor to rotate, and the motor rotor will rotate synchronously. The traditional square wave control is simple to implement, but because it only has six discrete, non-continuous vector torques, this will make the motor efficiency low, the overall machine efficiency low, and under heavy load conditions, stalling may occur frequently.

[0004] In addition, the constant speed range of the motor under the traditional square wave control method is not enough, which cannot meet the working requirements of some electric tools that need to work in a constant speed range. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, an object of the present invention is to provide an electric tool with a wider constant speed range.

[0006] The present invention provides the following technical solution: an electric tool, comprising: a motor, comprising a stator and a rotor, the motor being a motor capable of generating a magnetic resistance torque; a power supply device, for providing electrical energy to the motor; a drive circuit, electrically connected to the motor to drive the motor; a controller, for controlling the drive circuit, when the controller controls the drive circuit, the motor obtains a second constant speed torque interval; assuming that when the controller controls the drive circuit in a first control mode, the motor obtains a first constant speed torque interval; wherein the length of the second constant speed torque interval is greater than the length of the first constant speed torque interval.

[0007] Optionally, when the controller controls the drive circuit so that the motor rotates in a preset torque range, the motor obtains a second speed; assuming that the controller controls the drive circuit in a first control manner so that the motor rotates in the preset torque range, the motor obtains a first speed; wherein the second speed is greater than the first speed.

[0008] Optionally, the controller outputs a PWM signal to the drive circuit, and a duty cycle of the PWM signal changes with a position of the rotor.

[0009] Optionally, the controller controls the drive circuit so that the input voltage of the motor changes approximately in a sinusoidal wave.

[0010] Optionally, the motor is a three-phase motor, and the three-phase input voltages of the motor have a phase angle of 120° with each other.

[0011] Optionally, the controller comprises: a first speed loop, configured to generate a target current of the motor according to a target speed of the motor and an actual speed of the motor.

[0012] Optionally, the controller also includes: a first current distribution unit, used to distribute the direct-axis target current and the quadrature-axis target current according to the target current of the motor generated by the first speed loop; a first current conversion unit, used to generate the direct-axis actual current and the quadrature-axis actual current according to the actual current of the motor and the position of the rotor of the motor; a first current loop, used to generate a first voltage regulation amount according to the direct-axis target current and the direct-axis actual current; a second current loop, used to generate a second voltage regulation amount according to the quadrature-axis target current and the quadrature-axis actual current; a first voltage conversion unit, used to generate a first voltage control amount and a second voltage control amount according to the first voltage regulation amount and the second voltage regulation amount; a first control signal generating unit, used to generate a control signal according to the first voltage control amount and the second voltage control amount, and the control signal is used to control the drive circuit.

[0013] Optionally, the controller includes: a second speed loop, configured to generate a target torque of the motor according to a target speed and an actual speed of the motor.

[0014] Optionally, the controller also includes: a torque loop, used to generate a third voltage regulation amount based on the target torque and actual torque of the motor; a flux loop, used to generate a fourth voltage regulation amount based on the target stator flux and actual stator flux of the motor; a second voltage conversion unit, used to generate a third voltage control amount and a fourth voltage control amount based on the third voltage regulation amount and the fourth voltage regulation amount; a second control signal generating unit, used to generate a control signal based on the third voltage control amount and the fourth voltage control amount, and the control signal is used to control the drive circuit.

[0015] Optionally, the electric tool further comprises: a speed regulating mechanism, at least for setting a target rotation speed of the motor.

[0016] The present invention is beneficial in that the electric tool of the present invention has a wider constant speed range of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the appearance structure diagram of the electric drill;

[0018] Figure 2 is a circuit system block diagram of an electric drill in one embodiment;

[0019] Figure 3 is a circuit system block diagram of an electric drill in another embodiment;

[0020] Figure 4 As a more specific exemplary circuit system of an electric drill;

[0021] Figure 5 A stator and a rotor of an electric machine in one embodiment;

[0022] Figure 6 It is the torque-angle characteristic curve of the motor's permanent magnet torque T1, reluctance torque T2, and electromagnetic torque Te;

[0023] Figure 7 It is the space vector diagram of the stator flux, rotor flux and current in the dq coordinate system of the motor;

[0024] Figure 8 This is the relationship curve between the motor bus current and motor torque of the electric drill;

[0025] Fig. 9 It is the relationship curve between the motor speed and motor torque of the electric drill;

[0026] Fig.10 This is the relationship curve between the motor efficiency and motor torque of the electric drill;

[0027] Fig.11 It is the relationship curve between the output power of the electric drill and the motor torque;

[0028] Fig.12 This is the appearance picture of the angle grinder;

[0029] Fig.13 yes Fig.12 A partial structural cross-sectional view of the angle grinder;

[0030] Fig.14 It is a circuit system as an exemplary angle grinder;

[0031] Fig.15 It is the space vector diagram of the stator flux, rotor flux and current in the dq coordinate system of the motor;

[0032] Fig.16 This is the relationship curve between the motor speed and motor torque of the angle grinder;

[0033] Fig.17 It is the torque-angle relationship curve of the motor's permanent magnet torque T1, reluctance torque T2, and electromagnetic torque Te;

[0034] Fig.18This is the relationship curve between the motor efficiency and motor torque of the angle grinder;

[0035] Fig.19 This is the relationship curve between the motor bus current and motor torque of the angle grinder;

[0036] Fig. 20 This is the relationship curve between the output power of the angle grinder and the motor torque. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The power tools of the present invention may be handheld power tools, garden tools, garden vehicles such as vehicle-type lawn mowers, and are not limited thereto. The power tools of the present invention include, but are not limited to, the following: power tools that require speed regulation, such as screwdrivers, electric drills, wrenches, angle grinders, etc., power tools that may be used to grind workpieces, such as sanders, reciprocating saws, circular saws, jigsaws, etc., that may be used to cut workpieces; and power tools such as electric hammers that may be used for impact. These tools may also be garden tools, such as pruning machines, chain saws, and vehicle-type lawn mowers; in addition, these tools may also be used for other purposes, such as blenders. As long as these power tools can adopt the substantive content of the technical solutions disclosed below, they can fall within the protection scope of the present invention.

[0039] Reference Figure 1 , exemplarily showing an electric tool 10, which is an electric drill. The electric tool 10 mainly includes: a housing 11, a functional part 12, a grip 13, a speed regulating mechanism 14, a motor 15, and a power supply device 16. Of course, the electric drill also includes a transmission mechanism, a drill bit, a circuit board, etc. (not exposed in the Figure 1 perspective).

[0040] The housing 11 is formed with a grip 13 for the user to grip. Of course, the grip 13 can be a separate part. The housing 11 constitutes the main body of the power tool 10 and is used to accommodate the motor 15, the transmission mechanism and other electronic components such as circuit boards. The front end of the housing 11 is used to install functional parts.

[0041] The functional part 12 is used to realize the function of the electric tool 10, and the functional part is driven by the motor 15. The functional elements are different for different electric tools. For an electric drill, the functional part 12 is a drill bit (not shown) for realizing the drilling function. The drill bit is operably connected to the motor 15, and specifically, the drill bit is electrically connected to the motor 15 through an output shaft and a transmission mechanism.

[0042] The power supply device 16 is used to provide power to the power tool 10. In this embodiment, the power tool 10, an electric drill, is powered by a battery pack 16. Optionally, the power tool 10 further includes a battery pack coupling portion 17 for connecting the battery pack 16 to the electric drill.

[0043] The speed regulating mechanism 14 is at least used to set the target speed of the motor 15, that is to say, the speed regulating mechanism 14 is used to achieve the speed regulation of the motor 15. The speed regulating mechanism 14 can be but not limited to a trigger, a knob, etc. In the present embodiment, the speed regulating mechanism 14 is configured as a trigger structure. The above is merely an exemplary description and does not constitute a limitation of the present invention. In other embodiments, the power supply device 16 can also be an AC power supply. In other embodiments, the power tool 10 is powered by an AC power supply, and the AC power supply can be 120V or 220V AC mains. The power supply device 16 includes a power conversion unit, which is connected to the AC power and is used to convert the AC power into electrical energy that can be used by the power tool 10.

[0044] In another embodiment of the present invention, a handheld power tool includes a motor having a stator and a rotor; a motor drive shaft or output shaft driven by the motor rotor; a tool accessory shaft for supporting a tool accessory; and a transmission device for connecting the motor output shaft to the tool accessory shaft to transmit the torque output by the motor to the tool accessory. The motor output shaft can be coaxial, substantially parallel, substantially perpendicular, or inclined with the tool accessory shaft, which is not limited here.

[0045] In another embodiment of the present invention, a garden tool, such as a vehicle-type lawn mower, includes a main body, at least one drive wheel or drive wheel group supported by the main body; a drive device, such as a motor, that provides torque to the at least one drive wheel or drive wheel group; and a circuit system that controls the motor drive operation, as will be described below.

[0046] Reference Figure 2 The circuit system 20 of one embodiment of the electric tool 10 shown includes a power supply device 21 , a power supply circuit 22 , a controller 23 , a drive circuit 24 , a parameter acquisition module 25 , a rotation speed detection module 26 , and a motor 27 .

[0047] The power supply device 21 is used to power the power tool 10. In some embodiments, the power supply device 21 outputs direct current. More specifically, the power supply device 21 includes a battery pack. In other embodiments, the power supply device 21 outputs alternating current. The alternating current power supply can be a 120V or 220V AC mains power supply. The alternating current is converted into electric energy that can be used by the power tool by rectifying, filtering, dividing, and reducing the voltage of the AC signal output by the AC power supply through a hardware circuit. As an optional solution, the power tool 10 is powered by a battery pack, and the power supply device 21 includes a battery pack.

[0048] The power supply circuit 22 is electrically connected to the power supply device 21 and is used for converting the electric energy from the power supply device 21 into electric energy suitable for the power tool. The power supply circuit 22 is electrically connected to the controller 23 and can at least supply power to the controller 23 .

[0049] The current detection module 25 is connected to the motor 27 and is used to collect the current of the motor 27. The current can be the bus current of the motor 27 or the phase current of the motor 27. As an embodiment, the current detection module 25 detects the current of each phase of the motor 27, and the bus current of the motor 27 can be directly calculated from the detected three-phase current.

[0050] In a preferred embodiment of the present invention, the parameter acquisition module 25 is used to acquire at least one of the current of the motor 27, the speed of the motor 27 and the position of the rotor. Figure 2 In the implementation manner, the parameter acquisition module 25 includes a current detection module 251 and a position and speed detection module 252, wherein the current detection module 251 is used to detect the current of the motor, the current including the phase current, and the current detection module 251 can also be used to detect the bus current of the motor 27; the speed and position detection module 252 includes a sensor, the sensor is associated with the motor 27, and directly detects the speed and position of the motor 27. The speed and position detection module 252 is, for example, a Hall sensor.

[0051] exist Figure 2 In one embodiment, the speed and position detection module 252 directly detects the speed and position of the motor 27. In another embodiment, referring to Figure 3 , the parameter detection module 36 uses the position and speed estimation module 362 to estimate the speed of the motor 37 and the position of the rotor of the motor by the detected current of the motor 37, such as the state observer detection method. In other embodiments of the present invention, the parameter acquisition module 25 is used to obtain the current of the motor and the speed of the motor; and the position of the motor rotor can be obtained by analyzing and estimating the current and / or voltage of the motor, or by parameter characteristics of other components associated with the motor. In some other embodiments of the present invention, the parameter acquisition module 25 can only obtain the current of the motor, and the speed of the motor can be indirectly obtained by the current and / or voltage of the motor; and the position of the motor rotor can be obtained by analyzing and estimating the current and / or voltage of the motor, or by parameter characteristics of other components associated with the motor, which is not limited here. That is, the parameter detection module 25 obtains at least one of the current of the motor 27, the speed of the motor 27 and the position of the rotor, and the other parameters can be obtained by calculation or estimation using the obtained parameters.

[0052] The controller 23 is electrically connected to the driving circuit 24 to control the operation of the driving circuit 24. In some embodiments, the controller 43 uses a dedicated control chip (eg, MCU, Microcontroller Unit).

[0053] The drive circuit 24 is electrically connected to the controller 23 and the motor 27, and can drive the motor 27 to operate according to the control signal of the controller 23. For a three-phase motor, the drive circuit 24 is specifically electrically connected to the three-phase winding of the motor 27. The drive circuit 24 specifically includes a switch circuit, and the switch circuit is used to drive the rotor of the motor 27 to operate according to the control signal of the controller 23. Of course, the number of phases of the motor 27 can also be other phases, which is not limited here.

[0054] In order to make the motor 27 rotate, the drive circuit 24 has multiple drive states. In one drive state, the stator winding of the motor 27 will generate a magnetic field. The controller 23 is configured to output a corresponding drive signal to the drive circuit 24 according to the rotor rotation position of the motor 27 so that the drive circuit 24 switches the drive state, thereby changing the state of the voltage and / or current loaded on the winding of the motor 27, generating an alternating magnetic field to drive the rotor to rotate, thereby realizing the operation of the motor 27.

[0055] Figure 2 As shown as an exemplary drive circuit 24, it includes switch elements Q1, Q, Q3, Q4, Q5, Q6, and the switch elements Q1, Q2, Q3, Q4, Q5, Q6 form a three-phase bridge, wherein Q1, Q3, Q5 are upper bridge switches, and Q2, Q4, Q6 are lower bridge switches. The switch elements Q1~Q6 can be selected from field effect tubes, IGBT transistors, etc. The control end of each switch element is electrically connected to the controller 23 respectively, and the switch elements Q1~Q6 change the connection state according to the drive signal output by the controller 23, thereby changing the voltage and / or current state of the power supply device 21 loaded on the winding of the motor 27, and driving the motor 27 to operate. Of course, the present invention is not limited to a drive circuit using any specific number of switches and a motor with any specific number of phases.

[0056] Reference Figure 4 , as an exemplary controller 43 , specifically includes: a first speed loop 431 , a first current distribution unit 432 , a first current loop 433 , a second current loop 434 , a first voltage conversion unit 435 , a current conversion unit 437 , and a first control signal generation unit 436 .

[0057] The speed regulating mechanism 48 may be Figure 1The speed regulating mechanism 14 shown is used for the user to set the target speed n0 of the motor 47. The first speed loop 431 is associated with the speed regulating mechanism 48 and the position and speed detection module 452, and the first speed loop 431 obtains the target speed n0 of the motor 47 set by the user from the speed regulating mechanism 48 and the actual speed n of the motor 47 detected by the position and speed detection module 452.

[0058] The first speed loop 431 is used to generate the target current is0 according to the target speed n0 and the actual speed n of the motor 47. Specifically, the first speed loop 431 can generate the target current is0 according to the target speed n0 and the actual speed n of the motor 47 by comparison and adjustment.

[0059] The first current distribution unit 432 is connected to the first speed loop 431, and is used to distribute the first target current id0 and the second target current iq0 according to the target current is0. The target current is0, the first target current id0 and the second target current iq0 are all vectors with direction and magnitude, wherein the directions of the first target current id0 and the second target current iq0 are perpendicular to each other, and the target current is0 is synthesized by the first target current id0 and the second target current iq0 vectors. Among them, the first target current id0 and the second target current iq0 can be obtained according to the following formula:

[0060]

[0061] in, Ψ f is the flux generated by the permanent magnets in the rotor, Lq and Ld are the inductances of the d-axis and q-axis of the stator winding respectively. Is is the target current is0 generated by the first speed loop 231 according to the target speed n0 and the actual speed n of the motor 27.

[0062] The current detection module 451 transmits the detected three-phase currents Iu, Iv, and Iw in the actual operation of the motor 47 to the current conversion unit 436 in the controller 43. The first current conversion unit 236 obtains the three-phase currents Iu, Iv, and Iw, and performs current conversion, and converts the three-phase currents Iu, Iv, and Iw into two-phase currents, namely the first actual current id and the second actual current iq.

[0063] The first current loop 433 is connected to the first current distribution unit 432 and the current conversion unit 437 , obtains the first target current id0 and the first actual current id, and generates a first voltage adjustment amount Ud according to the first target current id0 and the first actual current id.

[0064] The second current loop 434 is connected to the first current distribution unit 432 and the current conversion unit 437 to obtain the second target current iq0 and the first actual current iq, and to generate a second voltage adjustment amount Uq according to the second target current iq0 and the second actual current iq.

[0065] The first voltage conversion unit 435 is connected to the first current loop 433 and the second current loop 434, obtains the first voltage regulation amount Ud and the second voltage regulation amount Uq, and the position of the rotor of the motor 47 from the position and speed detection module 452, and can convert the first voltage regulation amount Ud and the second voltage regulation amount Uq into intermediate quantities Ua and Ub related to the three-phase voltages Uu, Uv, and Uw loaded on the motor 47 and output them to the first control signal generating unit 436. The first control signal generating unit 436 generates a PWM signal according to the intermediate quantities Ua and Ub for controlling the switching elements of the drive circuit 44, so that the power supply device 41 can output the three-phase voltages Uu, Uv, and Uw to be loaded on the windings of the motor 47, Uu, Uv, and Uw are three-phase symmetrical sinusoidal wave voltages or saddle wave voltages, and the three-phase voltages Uu, Uv, and Uw have a phase difference of 120°.

[0066] That is to say, in this embodiment, the first current distribution unit 432 is used to distribute the direct axis target current and the quadrature axis target current according to the target current of the motor 47 generated by the first speed loop 431; the current conversion unit 427 is used to generate the direct axis actual current and the quadrature axis actual current according to the actual current of the motor 47 and the position of the rotor of the motor; the first current loop 433 is used to generate the first voltage regulation amount Ud according to the direct axis target current and the direct axis actual current; the second current loop 434 is used to generate the second voltage regulation amount Uq according to the quadrature axis target current and the quadrature axis actual current; the first voltage conversion unit 435 is used to generate the first voltage control amount Ua and the second voltage control amount Ub according to the first voltage regulation amount Ud and the second voltage regulation amount Uq; the first control signal generation unit 436 generates a control signal according to the first voltage control amount Ua and the second voltage control amount Ub, and the control signal is used to control the drive circuit 44. The control signal is a PWM signal. The duty cycle of the PWM signal changes with the position of the rotor. The controller 43 controls the drive circuit 44 so that the input voltage of the motor 47 changes approximately in a sinusoidal wave. The motor 47 is a three-phase motor, and the three-phase input voltages of the motor 47 are at a phase angle of 120°.

[0067] The control method of this embodiment includes: the current conversion unit 437 obtains the three-phase currents Iu, Iv, Iw and the rotor position information detected by the current detection module 45, and performs current conversion to convert the three-phase currents Iu, Iv, Iw into two-phase currents, which are the first actual current id and the second actual current iq respectively.

[0068] The first current loop 433 obtains the first target current id0 and the first actual current id, and generates a first voltage adjustment amount Ud according to the first target current id0 and the first actual current id.

[0069] The second current loop 434 obtains the second target current iq0 and the first actual current iq, and generates a second voltage adjustment amount Uq according to the second target current iq0 and the second actual current iq.

[0070] The first voltage conversion unit 435 obtains the first voltage regulation quantity Ud, the second voltage regulation quantity Uq and the rotor position, and converts the first voltage regulation quantity Ud and the second voltage regulation quantity Uq into the first voltage control quantity Ua and the second voltage control quantity Ub related to the three-phase voltage Uu, Uv, Uw loaded to the motor 47, and outputs them to the first control signal generating unit 436. The first control signal generating unit 436 generates a PWM signal according to the first voltage control quantity Ua and the second voltage control quantity Ub for controlling the switching elements of the drive circuit 44, so that the power supply device 41 outputs the three-phase voltage Uu, Uv, Uw loaded to the winding of the motor 47, Uu, Uv, Uw are three-phase symmetrical sinusoidal wave voltages or saddle wave voltages, and Uu, Uv, Uw have a phase difference of 120°.

[0071] The motor 47 can be used as follows Figure 5 The motor 50 shown is a brushless permanent magnet motor. The motor 50 includes a stator 511, a rotor 52 and a rotor output shaft 573. The rotor 52 can be built into the stator 511 or externally placed on the stator 51, which is not limited here. In this embodiment, taking the inner rotor motor as an example, the rotor 52 is built into the stator 51, and the rotor output shaft 53 is fixedly connected to the rotor 52. When the rotor 52 rotates, the rotor output shaft 53 rotates to drive the functional part 12 to work. The stator 51 includes a stator winding (not shown), which is arranged in the stator 51. The present invention is not limited to the above-mentioned motor, and can also have motors with other numbers of phases, other numbers of slots, and other numbers of poles.

[0072] The rotor 52 includes a permanent magnet 521 and a rotor core 522. The rotor core 522 is provided with a slot for installing the permanent magnet 521, so that the inductance (i.e., Ld and Lq) of the rotor 52 in the direct axis (D axis) and the quadrature axis (Q axis) directions are not equal. The rotor 52 can generate two different types of torques, including a permanent magnet torque T1 generated by the permanent magnet 521 and a reluctance torque T2 generated by the rotor core 522. The permanent magnet torque T1 and the reluctance torque T2 vectorially synthesize a total electromagnetic torque Te, which drives the rotor 52 to rotate. The direct axis D axis and the quadrature axis Q axis correspond to Figure 7 and Fig.15 The electrical angle between the d-axis and the q-axis is 90°. The d-axis is the direct axis and the q-axis is the cross axis.

[0073] The relationship among permanent magnet torque T1, reluctance torque T2 and electromagnetic torque Te is as follows: Figure 6 As shown, the horizontal axis represents the electrical angle in degrees, the vertical axis represents the torque in Nm, and the permanent magnet torque T1 and the reluctance torque T2 vector synthesize the electromagnetic torque Te. For the convenience of explanation, the electrical angle here is defined as the torque angle of the motor 50. The relationship between the permanent magnet torque T1, the reluctance torque T2 and the electromagnetic torque Te is as follows:

[0074] Te = 1.5 P n [ Ψ f i q + ( L d - L q ) i d i q ],

[0075] The formula contains two items, the former 1.5 P n Ψ f i q is the permanent magnet torque T1, such as Figure 6 Middle curve T1; latter 1.5 P n ( L d - L q ) i d i q is the reluctance torque T2, such as Figure 6 The middle curve is T2; Te is the synthesis of curves T1 and T2, which is Figure 6 The Te curve, where Ψ f is the rotor flux, i q is the q-axis current, i d is the d-axis current, Ld is the d-axis inductance of the stator winding, and Lq is the q-axis inductance of the stator winding. Figure 6 It can be seen that the synthesized electromagnetic torque Te has an approximate maximum value Tmax or a maximum value Tmax when the corresponding torque angle is in the range of 90°~135°. In the embodiment of the present invention, in fact, when running, the motor stator current id<0 is loaded: In the above formula, assuming that id=0, T1= 1.5 Pn Ψ f i q , that is, the maximum value of T1 is 1.5 at this time P n Ψ f Is (when id=0, i q= Is), where Kt=1.5 P n y f , then the maximum value of T1 is KtIs, Is is the phase current input to the motor, P n is the number of pole pairs of the magnet. For example, 4 magnets have 2 pole pairs. y f is the flux linkage constant of a motor; when the power tool is actually running, the motor stator current id is loaded <0, and L d < L q , then the maximum value of Te Tmax>KtIs. In this formula, i q Corresponds to Figure 4 The first target current id0 in i d Corresponding to the second target current iq0. In some other embodiments of the present invention, according to the actual characteristics and actual current of different motors, the angle between the stator flux and the rotor flux can be varied within a value range of 90° to 135°.

[0076] As an implementation scheme, in this embodiment, the following is adopted: Figure 4The controller 43 shown is configured as follows: the current loaded to the stator is dynamically adjusted according to at least one of the current of the motor 47, the speed of the motor 47 and the position of the rotor so that the angle between the stator flux and the rotor flux is in the range of 90°~135°. That is to say, the controller 43 dynamically controls the current loaded to the stator to adjust the stator flux according to the speed, current and rotor position of the motor 47 directly obtained or detected, so that the angle between the stator flux and the rotor flux varies within the range of 90°~135°. Of course, according to the actual working conditions of the power tool, the current loaded to the stator can be dynamically controlled according to the speed and current of the motor to adjust the stator flux, so that the angle between the stator flux and the rotor flux is continuously maintained at the angle at which an approximate maximum value Tmax or a maximum value Tmax is obtained, that is, at this time Tmax is continuously maintained at a value greater than KtIs, which can greatly improve the output performance of the power tool. It should be noted that, in the present invention, "the controller is based on at least one of the motor speed, the motor current and the motor rotor position" means that the controller obtains at least one of the motor speed, the motor current and the motor rotor position, and the other parameters of these three parameters can be obtained by calculation or estimation based on the parameters that have been obtained. The controller ultimately obtains the motor speed, the motor current and the motor rotor position based on the direct or indirect acquisitions, which will not be elaborated below.

[0077] In other embodiments, the angle between the stator flux and the rotor flux can also range from 90° to 120°. In other embodiments, the angle between the stator flux and the rotor flux can also range from 110° to 120°. In other embodiments, the angle between the stator flux and the rotor flux can also range from 110° to 130°. In other embodiments, the angle between the stator flux and the rotor flux can also range from 105° to 115°. In other embodiments, the angle between the stator flux and the rotor flux can also range from 90° to 165°. In a preferred embodiment of the present invention, the angle between the stator flux and the rotor flux can be continuously maintained at approximately Tmax or Tmax by regulating the angle, so that the synthesized electromagnetic torque Te can reach the maximum value as much as possible, thereby greatly improving the output torque of the motor.

[0078] In a preferred embodiment of the present invention, the three-phase Uu, Uv, and Uw loaded on the motor 47 are controlled so that the angle between the stator flux and the rotor flux of the motor 27 is between 90° and 135°. The three-phase Uu, Uv, and Uw are three-phase symmetrical sinusoidal wave voltages or saddle-shaped waveforms, and the three-phase Uu, Uv, and Uw have a phase difference of 120°.

[0079] Figure 7The control method of the present invention is shown from the perspective of the space vector of the motor 47. In this embodiment, the following is adopted: Figure 4 The controller 43 shown in the figure controls the current loaded on the stator by controlling the three-phase voltages Uu, Uv, and Uw loaded on the motor 47, so that the stator winding generates a stator current space vector is0, and the stator current space vector is0 is in phase with the stator flux space vector Ψs, and the angle β between the stator flux Ψs and the rotor flux Ψf is, where the angle β is Figure 6 The torque angle represented by the horizontal axis in the curve shown. Specifically, the controller 43 controls the voltage loaded on the motor 47 to control the current loaded on the stator according to the speed, current and rotor position of the motor 47 directly or detected. The voltage loaded on the stator is a three-phase symmetrical sinusoidal voltage Uu, Uv, and Uw. The three-phase voltages Uu, Uv, and Uw are 120° out of phase with each other. The current loaded on the stator causes the stator to generate a stator flux. The controller 43 dynamically adjusts the current so that the angle β between the stator flux Ψs and the rotor flux Ψf is in the range of 90° to 135°.

[0080] Combination Figure 4 and Figure 7 The controller 47 obtains the target speed n0 of the motor 47 and the actual speed n of the motor 47 obtained by the position and speed detection module 452 according to the speed regulation mechanism 48, and obtains the target current is0 through the first speed loop according to the target speed n0 and the actual speed n, and then the first current distribution unit 432 distributes the first target current id0 and the second target current iq0 according to the target current is0. Figure 4 The target current is0 corresponds to Figure 7 The current space vector is0 in Figure 4 The first target current id0 corresponds to Figure 7 The d-axis component current id0 in the second target current iq0 corresponds to Figure 7 The q-axis component of the current iq0.

[0081] At the same time, the controller 43 obtains the first actual current id and the second actual current iq after conversion by the current conversion unit 437 according to the three-phase currents Iu, Iv, Iw detected by the current detection module 451 and the rotor position of the motor 47 detected by the position and speed detection module 452, and then uses the first current loop 433 to obtain the first voltage regulation amount Ud according to the first target current id0 and the first actual current id, and uses the second current loop 434 to obtain the second voltage regulation amount Uq according to the second target current iq0 and the second actual current iq, and obtains the first voltage regulation amount Ud and the second voltage regulation amount Uq after conversion by the first voltage conversion unit 435 and sends the result to the first control signal generating unit 4 36, the first control signal generating unit 436 generates a PWM signal according to the result transmitted by the first voltage conversion unit 435, and the PWM signal generated by the first control signal generating unit 436 controls the driving circuit 44 to control the three-phase voltages Uu, Vu, and Ww loaded by the power supply device 41 to the motor 47, and the three-phase voltages Uu, Vu, and Ww are three-phase symmetrical sinusoidal wave voltages or saddle wave voltages, and the three-phase voltages Uu, Vu, and Ww are 120° apart from each other, and the three-phase voltages Uu, Vu, and Ww loaded to the motor 47 can make the stator winding generate current, and the controller 43 controls the stator current to adjust the stator flux, so that the angle β between the stator flux Ψs and the rotor flux Ψf is in the range of 90°~165°.

[0082] Combination Figure 4 , Figure 6 and Figure 7 , Figure 4 The first current distribution unit 432 in the embodiment distributes the first target current id0 and the second target current iq0 according to the target current is0, which can make the rotor of the motor 47 generate permanent magnet torque T1 and reluctance torque T2. The electromagnetic torque Te obtained by the motor is the vector synthesis of T1 and T2, and Te=1.5 P n [Ψ f *iq0+ (L d -L q ) id0* iq0].

[0083] Figure 8 From the perspective of the relationship curve between the motor bus current and the motor torque Figure 1 The control method of the electric drill shown in the figure. The solid line is the control method of this embodiment, and the thick dotted line is the traditional square wave control method. The horizontal axis represents the motor output torque in Nm, and the vertical axis represents the motor bus current in A.

[0084] This embodiment adopts Figure 2 The circuit system shown and Figure 4The controller 43 shown controls the current of the motor 47 by controlling the voltage applied to the motor 47 by the power supply device 41. The voltage is a three-phase symmetrical sinusoidal voltage Uu, Uv, and Uw, and Uu, Uv, and Uw are 120° out of phase with each other.

[0085] Specifically, the controller 43 dynamically adjusts the current loaded on the stator according to at least one of the rotation speed of the motor 47, the current of the motor and the rotor position of the motor so that the bus current of the motor changes with the first current torque characteristic curve in the first torque interval (i.e., the torque interval of 0~Tm0), and changes with the second current torque characteristic curve in the second torque interval (i.e., the torque interval of Tm0~Tm1), wherein the slope of the first virtual straight line L1 where 0 and Tm0 are selected in the first current torque characteristic curve is defined as the first slope, and the slope of the second virtual straight line L2 where Tm0 and Tm1 are selected in the second current torque characteristic curve is defined as the second slope, wherein the first slope of the first virtual straight line L1 where the first current torque characteristic curve is located is greater than the second slope of the second virtual straight line L2 where the second current torque characteristic curve is located. Optionally, the first slope is the slope of any point of the first current torque characteristic curve in the first torque interval (i.e., the torque interval of 0~Tm0), and the second slope is the slope of any point of the second current torque characteristic curve in the second torque interval (i.e., the torque interval of Tm0~Tm1). That is to say, there is an inflection point R in the bus current of the motor 47, and the first slope before the inflection point R is greater than the second slope after the inflection point R. That is to say, before the inflection point, the bus current of the motor increases at a faster rate with the motor torque, and after the inflection point, the bus current of the motor increases at a slower rate with the motor torque. That is, the first current-torque characteristic curve and the second current-torque characteristic curve increase the bus current with the increase of torque, but the first current-torque characteristic curve increases the current faster with the increase of torque, while the second current-torque characteristic curve increases the current slower with the increase of torque. That is to say, in the control method of this embodiment, when the electric tool is lightly loaded, the current increases faster; when the electric tool is heavily loaded, the current increases slower.

[0086] See also Figure 8 , using the control method of the present invention, when the controller 43 controls the drive circuit 44 to make the motor 47 rotate at a preset torque, the output current of the power supply device 41 is the second output current; assuming that the controller 43 controls the drive circuit 44 in the first control method to make the motor 47 rotate at the preset torque, the output current of the power supply device 41 is the first output current; wherein, the second output current is less than the first output current. In this embodiment, the first control method is a traditional square wave control method.

[0087] It should be noted that the "assuming that the controller controls the drive circuit in the first control mode" or "assuming that the controller controls the drive circuit in the third control mode" in the present invention is only used to compare the control mode of the present invention with other control modes. Optionally, the first control mode and the third control mode are traditional square wave control modes. In other words, the controller 43 of the present invention is only used to implement the control mode of the present invention, and will not be used to implement the first control mode or the third control mode to control the drive circuit 44. The following "assuming that the controller controls the drive circuit in the first control mode" or "assuming that the controller controls the drive circuit in the third control mode" are all as described above and will not be repeated below.

[0088] As a specific embodiment, the preset torque is set to Tm2. At this time, the first output current output by the power supply device 41 is controlled by a conventional square wave method, corresponding to Figure 8 The motor bus current is I1, and the control method of this embodiment is used to make the second output current output by the power supply device 41 correspond to Figure 8 The motor bus current is I2, and the second output current I2 is less than the first output current I1.

[0089] Combination Figure 8 and Fig.11 Through such a control method, in the heavy load area, the control method of this embodiment is compared with the traditional square wave control method. Under the same output torque, the bus current of the motor 47 is smaller, the output current of the power supply device 41 is smaller, and the output power of the power tool 10 is higher. This can save energy. For a battery pack used as the power supply device 41, the battery pack's cruising capacity can be improved.

[0090] Fig. 9 To show the relationship between motor speed and motor torque Figure 1 The control method of the electric drill shown in FIG. Figure 2 The circuit system shown and Figure 4 The controller 43 shown controls the current of the motor 47 by controlling the voltage applied to the motor 47 by the power supply device 41. The voltage is a three-phase symmetrical sinusoidal voltage Uu, Uv, Uw, wherein Uu, Uv, Uw are 120° out of phase with each other.

[0091] Specifically, the controller 43 dynamically adjusts the current loaded on the stator according to at least one of the rotational speed of the motor 47, the current of the motor and the rotor position of the motor. The controller 43 controls the current loaded on the stator by controlling the voltage loaded on the motor 47. The voltage loaded on the stator is a three-phase symmetrical sinusoidal wave voltage Uu, Uv, and Uw. The three-line voltages Uu, Uv, and Uw have a phase difference of 120°. The current loaded on the stator causes the stator to generate a stator flux. The controller 43 dynamically adjusts the current on the stator so that the angle between the stator flux and the rotor flux is in the range of 90° to 135°.

[0092] When the controller 43 of this embodiment controls the drive circuit 44, the motor 47 obtains a second constant speed torque interval; assuming that the controller 43 controls the drive circuit 44 in a first control mode, the motor 47 obtains a first constant speed torque interval; wherein the length of the second constant speed torque interval is greater than the length of the first constant speed torque interval.

[0093] Fig. 9 In the figure, the horizontal axis represents the motor output torque in Nm, and the vertical axis represents the motor speed n in rpm. The solid line is the effect curve of the motor speed changing with the motor torque using the control method of this embodiment, and the thick dotted line is the effect curve of the motor speed changing with the motor torque using the traditional square wave control method. In this embodiment, when the torque is in the range of 0~Tm4, the motor speed is basically in a constant speed state, while the traditional square wave control method does not have such a long constant speed range.

[0094] from Fig. 9 It can be seen that compared with the traditional square wave control method, the control method of this embodiment has the advantage of a wide constant speed range. This is for some power tools working in a light to medium load range, such as electric drills, electric screwdrivers, etc., which have a wider constant speed characteristic and can obtain better and more consistent working results.

[0095] In this embodiment, the controller 43 controls the drive circuit 44 to make the motor 47 rotate in the preset torque range, and the motor 47 obtains the second speed; assuming that the controller 43 controls the drive circuit 44 in the first control mode to make the motor rotate in the preset torque range, the motor obtains the first speed; wherein the second speed is greater than the first speed. Fig. 9 As an option, the preset torque interval is set to a torque interval where the torque is greater than Tm4, i.e., greater than Tm4), for example, Fig. 9 In the torque range of Tm3~Tm2, when the motor outputs the same torque (for example, Tm2), the motor speed is higher than that of the motor in the traditional square wave control method. For electric tools such as electric drills, a higher motor speed means higher working efficiency. Figure 8 and Fig. 9 When the torque is preset (for example, Tm2), the control method of the present invention is adopted, and the motor speed is higher than the motor speed of the traditional square wave control method, but the required current is smaller than that of the traditional square wave control. That is to say, the control method of the present invention can obtain a higher speed with a smaller current. For the electric tool that uses a battery pack as the power supply device 41, the battery life of the battery pack can be improved.

[0096] Fig.10 The effect of the control method of this embodiment is compared with the effect of the traditional square wave control method from the perspective of the relationship curve between motor efficiency and motor torque. The horizontal axis represents the motor output torque in Nm, and the vertical axis represents the motor efficiency without unit. The solid line is the effect curve of the motor efficiency changing with the motor torque using the control method of this embodiment, and the thick dotted line is the effect curve of the motor efficiency changing with the motor torque using the traditional square wave control method. Fig.10 It can be seen that compared with the traditional square wave control method, the motor using the control method of the implementation method is more efficient.

[0097] Fig.11 From the perspective of the relationship curve between the power tool output power and the motor torque, it can be shown Figure 1 The control method of the electric drill shown in the figure. The horizontal axis represents the motor output torque, in Nm, and the vertical axis represents the power output of the electric tool, in W. The solid line represents the control method of this embodiment, and the thick dotted line represents the traditional square wave control method.

[0098] In this embodiment, when the controller 43 controls the drive circuit 44 to make the motor 47 rotate at a preset torque (e.g., Tm6) in a preset torque interval (e.g., greater than Tm5), the output power of the power tool 10 is the second output power w2; assuming that the controller 44 controls the drive circuit 44 in a first control mode to make the motor 47 rotate at the preset torque (e.g., Tm6) in the preset torque interval (e.g., greater than Tm5), the output power of the power tool 10 is the first output power w1; wherein the second output power w2 is greater than the first output power w1. In this embodiment, the first control mode is a traditional square wave control mode.

[0099] from Fig.11 It can be seen from the figure that compared with the traditional square wave control method, the control method of this embodiment can make the output power of the electric tool 10 higher when the output torque of the motor 47 is the same. Figure 8 and Fig.11When the motor rotates at a preset torque (for example, Tm2) within a preset torque range (for example, greater than Tm1), the control method of the present invention is compared with the traditional square wave control method. The current output by the power supply device 41 is smaller, and the output power of the power tool is higher, thereby enabling the battery pack serving as the power supply device 41 to have a longer battery life.

[0100] Combination Figure 8 , Fig. 9 and Fig.11 When the motor rotates at a preset torque (for example, Tm2) within a preset torque range (for example, greater than Tm1), the control method of the present invention is compared with the traditional square wave control method. The control method of the present invention makes the current output by the power supply device 41 smaller, and the output power of the power tool 10 is higher, and the speed of the motor 47 is higher, so that the battery pack serving as the power supply device 41 can have a higher battery life.

[0101] Of course, the above implementation is not limited to the above Figure 4 The controller 43 indirectly controls the stator flux by controlling the current or voltage vector to adjust the angle between the stator flux and the rotor flux. Fig.14 The controller 73 can also achieve the above effect by directly controlling the stator flux to adjust the angle between the stator flux and the rotor flux. Specifically, the controller 73 includes: a second speed loop 731, which is used to generate the target torque of the motor 77 according to the target speed and actual speed of the motor 77. The controller 73 also includes: a torque loop 733, which is used to generate a third voltage regulation amount v1 according to the target torque and actual torque of the motor 77; a flux loop 734, which is used to generate a fourth voltage regulation amount v2 according to the target stator flux and actual stator flux of the motor 77; a second voltage conversion unit 735, which is used to generate a third voltage control amount Uα and a fourth voltage control amount Uβ according to the third voltage regulation amount v1 and the fourth voltage regulation amount v2; a second control signal generation unit 736, which is used to generate a control signal according to the third voltage control amount Uα and the fourth voltage control amount Uβ, and the control signal is used to control the drive circuit.

[0102] Fig.12 and Fig.13 Another electric tool 60 is shown by way of example. The electric tool 60 is an angle grinder, which mainly includes a housing 61 , a functional part 62 , a grip 63 , a speed regulating mechanism 64 , a motor 65 , and a power supply device 66 .

[0103] The housing 61 is formed with a grip portion 63 for the user to grip. Of course, the grip portion 63 can be a separate part. The housing 61 constitutes the main body of the power tool 60, and is used to accommodate the motor 65, the transmission mechanism and other electronic components such as circuit boards. The front end of the housing 61 is used to install the functional part 62.

[0104] The functional part 62 is used to realize the function of the electric tool 60, and the functional part is driven by the motor 65. The functional elements are different for different electric tools 60. For an angle grinder, the functional part 62 is a grinding disc, which is used to realize the grinding or cutting function. The functional part 62 is operably connected to the motor 65, and specifically, the functional part 62 is electrically connected to the motor 65 through the output shaft 69 and the transmission mechanism 68.

[0105] The speed regulating mechanism 64 is at least used to set the target speed of the motor 65, that is, the speed regulating mechanism 64 is used to achieve speed regulation of the motor 65, and the speed regulating mechanism 65 can be but is not limited to a trigger, a knob, a sliding mechanism, etc. In this embodiment, the speed regulating mechanism 64 is configured as a sliding mechanism.

[0106] The power supply device 66 is used to provide electric energy to the electric tool 60. In this embodiment, the electric tool 60 is powered by a battery pack 66. Optionally, the electric tool 60 also includes a battery pack coupling portion 67 for connecting the battery pack 66 to the electric tool 60. In other embodiments, the power supply device 66 may also be an AC power supply, which may be a 60V or 220V AC mains power supply. The power supply device 66 includes a power conversion unit, which is connected to the AC power and is used to convert the AC power into electric energy that can be used by the electric tool.

[0107] The operation of the electric tool 60 also depends on the circuit system. Fig.14 As an exemplary circuit system, the controller 73 includes: a second speed loop 731, a second current distribution unit 732, a torque loop 733, a flux loop 734, a second voltage conversion unit 735, a second control signal generation unit 736, a second current conversion unit 737, a torque and flux calculation unit 738, a target flux calculation unit 739 and a feedback linearization control unit 730. The feedback linearization control unit 730 and the second voltage conversion unit 735 can be collectively referred to as a voltage change unit, both of which realize voltage conversion.

[0108] Reference Fig.15As shown in FIG. 17 , the controller 73 is configured to perform the following operations: in a first load interval (0 to Tn1), the drive circuit 74 is controlled in a first characteristic control mode so that the motor 77 rotates within a first speed range; in a second load interval (greater than Tn1), the drive circuit 74 is controlled in a second characteristic control mode so that the motor 77 rotates within a second speed range; the first characteristic control mode includes: dynamically adjusting the current loaded to the stator based on at least one of the current of the motor 47, the speed of the motor 47, and the position of the rotor of the motor 47 so that the angle β between the stator flux and the rotor flux is in the range of 135° to 180°; the second characteristic control mode includes: dynamically adjusting the current loaded to the stator based on at least one of the current of the motor 77, the speed of the motor 77, and the position of the rotor of the motor 77 so that the angle β between the stator flux and the rotor flux is in the range of 90° to 135°; wherein, when the controller 73 controls the drive circuit 74 in the second characteristic control mode, the output torque of the motor 77 is greater than the output torque of the motor 77 when the controller 73 controls the drive circuit 74 in the first characteristic control mode (see Fig.17 ). The output torque of the motor is positively correlated with the electromagnetic torque Te of the motor. The larger the electromagnetic torque Te of the motor, the larger the output torque of the motor.

[0109] That is, in the first load interval (0~Tn1 torque interval), the controller 77 controls by a first characteristic control method of regulating the angle between the stator flux and the rotor flux; and in the second load interval (greater than the Tn1 torque interval), the controller controls by a second characteristic control method of regulating the angle between the stator flux and the rotor flux and obtaining approximate Tmax or Tmax. Specifically, the first characteristic control method includes: dynamically adjusting the current loaded to the stator according to at least one of the current of the motor 77, the speed of the motor 77 and the position of the rotor so that the angle β between the stator flux and the rotor flux has a value range of 135°~180°, so that the torque of the motor 77 is not greater than or less than or equal to the preset threshold value KtIs, where Kt=1.5PnΨf, Pn is the number of pole pairs of the magnet, for example, 4 magnets have 2 pole pairs, Ψf is the flux constant of the motor; Is is the phase current of the motor. The second characteristic control method includes: dynamically adjusting the load to the stator flux according to at least one of the current of the motor 77, the speed of the motor 77 and the position of the rotor so that the angle β between the stator flux and the rotor flux is in the range of 90°~135°, so that the torque of the motor 77 runs continuously greater than the preset threshold value KtIs within the preset time range, wherein Kt=1.5PnΨf, Pn is the number of pole pairs of the magnet, for example, 4 magnets have 2 pole pairs, Ψf is the flux constant of the motor; Is is the phase current of the motor; wherein, when the controller 73 controls the drive circuit 74 in the second characteristic control method, the output torque of the motor 77 is greater than the output torque of the motor 77 when the controller 73 controls the drive circuit 74 in the first characteristic control method.

[0110] In some other embodiments of the present invention, in the first characteristic control mode, the angle between the stator flux and the rotor flux can also be adjusted to have a value in the range of 90°~120°, or 90°~135°, or 110°~120°, or 110°~130°, or 110°~140°, or 105°~135°, or 115°~145°, or 120°~160°, or 135°~165°, or 150°~18 0°, so that the torque of the motor 77 runs at no more than the preset threshold value KtIs; and in the second characteristic control mode, the angle between the stator flux and the rotor flux can also be adjusted to have a value range of 110°~120°, or 110°~130°, or 105°~115°, or 115°~135°, or 120°~145°, but the torque of the motor 77 runs at a value continuously greater than the preset threshold value KtIs within a preset time range. Specifically, the second speed loop 731 in the controller 73 obtains the actual speed n of the motor 77 from the position and speed detection module 752 and the target speed n0 of the motor set by the user through the speed control mechanism 78, and outputs the target electromagnetic torque Te0 according to the actual speed n of the motor and the target speed n0 of the motor. The speed control mechanism 78 can be used as follows Fig.12 The speed regulating mechanism 64 is shown.

[0111] The second current distribution unit 732 distributes the first target current id0 and the second target current iq0 according to the target torque Te0 output by the second speed loop 731. Fig.15 , the first target current id0 and the second target current iq0 are vectors with direction and magnitude, and the electrical angle between the first target id0 and the second target current iq0 is 90°, the first target id0 and the second target current iq0 are respectively located on the d-axis and the q-axis, and the first target id0 and the second target current iq0 can vector synthesize the target current is0. The target flux calculation unit 739 can calculate the target stator flux Ψs0 according to the first target id0 and the second target current iq0, and the target stator flux Ψs0 is in the same direction as the target current is0. In this way, the controller 73 directly and dynamically adjusts the stator flux to control the angle β between the stator flux Ψs and the rotor flux Ψf to be within the range of 90°~135° or 135°~180°, thereby improving the output performance of the power tool under different actual working conditions.

[0112] Next, it is necessary to compare and adjust the target stator flux Ψs0 and the target electromagnetic torque Te0 with the actual stator flux Ψs and the actual electromagnetic torque Te, and generate a control signal to adjust the actual stator flux Ψs and the actual electromagnetic torque Te, so that the actual stator flux Ψs and the actual electromagnetic torque Te can reach the target stator flux Ψs0 and the target electromagnetic torque Te0 as much as possible. The angle between the actual stator flux Ψs and the rotor flux Ψf is preferably in the range of 90°~135°, or 135°~180°. In other words, by establishing the function relationship Te=f(Ψs,Ψf, β), the stator flux is dynamically adjusted so that the angle between the actual stator flux Ψs and the actual rotor flux Ψf, is in the range of 90°~135°. In some other embodiments of the present invention, the stator flux can also be dynamically adjusted by establishing the function relationship Te=f(Ψs,Ψf, β), so that the angle between the stator flux and the rotor flux can also range from 90° to 120°, or 110° to 120°, or 110° to 130°, or 110° to 140°, or 105° to 115°, or 115° to 145°, or 120° to 160°, or 135° to 165°.

[0113] Specifically, the second current conversion unit 737 obtains the three-phase currents Iu, Iv, Iw detected by the current detection module 731 and the rotor position θ output by the position and speed detection module 732, and converts the three-phase currents Iu, Iv, Iw into two-phase actual currents id and iq, where id and iq are vectors with direction and magnitude, and the directions of id and iq are perpendicular to each other.

[0114] The torque and flux calculation unit 738 obtains the two-phase actual currents id and iq from the second current conversion unit 737 and generates the actual electromagnetic torque Te and the actual stator flux Ψs according to the two-phase actual currents id and iq. The actual electromagnetic torque Te is output to the torque loop 733, and the actual flux Ψs is output to the flux loop 734.

[0115] The torque loop 733 obtains the actual torque Te calculated by the torque and flux calculation unit 738 and the target electromagnetic torque Te0 output by the second speed loop 731, and generates a voltage adjustment amount v1 according to the actual electromagnetic torque Te and the target electromagnetic torque Te0.

[0116] The flux loop 734 obtains the actual stator flux Ψs calculated by the torque and flux calculation unit and the target stator flux Ψs0 generated by the target flux calculation unit 739, and generates a voltage adjustment amount v2 according to the actual stator flux Ψs and the target stator flux Ψs0.

[0117] The feedback linearization control unit 730 generates the voltage control quantity Uq and the voltage control quantity Ud in the dq coordinate system based on the voltage regulation quantity v1 generated by the torque loop 733, the voltage regulation quantity v2 generated by the flux loop 734, and the d-axis component Ψd and q-axis component Ψq of the actual stator flux Ψs generated by the torque and flux calculation unit 738, and based on v1, v2, Ψd, and Ψq.

[0118] The second voltage conversion unit 735 obtains the first voltage control amount Uq and the second voltage control amount Ud, and converts the voltage control amount Uq and the voltage control amount Ud into the voltage control amount Uα and the voltage control amount Uβ in the α-β coordinate system.

[0119] The second control signal generating unit 736 generates a PWM control signal for controlling the drive circuit 74 according to the voltage control quantity Uα and the voltage control quantity Uβ in the α-β coordinate system, so that the power supply device 71 outputs a three-phase voltage Uu, Uv, and Uw to be loaded on the winding of the motor 77, Uu, Uv, and Uw are three-phase symmetrical sinusoidal wave voltages or saddle wave voltages, Uu, Uv, and Uw are 120° phase difference, and the three-phase Uu, Uv, and Uw loaded on the motor 77 make the stator flux Ψs0 and the rotor flux Ψ f The included angle is in the range of 90°~135°, or 135°~180°.

[0120] That is to say, the second speed loop 731 is used to generate the target torque of the motor according to the target speed and actual speed of the motor 77. The torque loop 733 is used to generate the third voltage regulation amount v1 according to the target torque and actual torque of the motor 77; the flux loop 734 is used to generate the fourth voltage regulation amount v2 according to the target stator flux and actual stator flux of the motor 77; the second voltage conversion unit 735 is used to generate the third voltage control amount Uα and the fourth voltage control amount Uβ according to the third voltage regulation amount v1 and the fourth voltage regulation amount v2. Optionally, the controller 73 also includes a feedback linearization control unit 730, the input end of which is connected to the torque loop 733 and the flux loop 734, and the output end is connected to the second voltage conversion unit 735. The second control signal generating unit 736 is used to generate a control signal according to the third voltage control amount Uα and the fourth voltage control amount Uβ, and the control signal is used to control the drive circuit 74. The control signal is a PWM signal, and the duty cycle of the PWM signal changes with the position of the rotor. The controller 73 controls the driving circuit 74 so that the input voltage of the motor 77 changes approximately in a sinusoidal wave. The motor 77 is a three-phase motor, and the three-phase input voltages of the motor 77 have a phase angle of 120° with each other.

[0121] In this way, direct torque control is performed directly according to the actual feedback electromagnetic torque and stator flux, so that the rotor flux Ψs and stator flux Ψ f The included angle β is in the range of 90°~135°, or 135°~180°, thereby improving the driving performance of the motor 77.

[0122] Fig.16 From the perspective of motor speed and motor torque curve Fig.12 The control method of the angle grinder shown in the figure. The horizontal axis represents the motor output torque in Nm, and the vertical axis represents the motor speed in rpm. The solid line represents the control method of this embodiment, and the thick dotted line represents the traditional square wave control method.

[0123] like Fig.16 As shown, as the load of the motor increases, the motor output torque should also increase accordingly. In this embodiment, the first load interval corresponds to the torque interval from 0 to Tn1, and the second load interval corresponds to the torque interval greater than Tn1.

[0124] In the first load interval, the drive circuit 74 is controlled in a first characteristic control mode to make the motor 77 rotate within a first preset speed range. The first characteristic control mode can control the motor to reach a higher speed after the voltage loaded on the motor 77 reaches the maximum power supply voltage of the power supply device 71. In the first load interval, when the controller 73 controls the drive circuit 74 in the first characteristic control mode, the motor 77 outputs a first speed. In the second load interval, when the controller 73 controls the drive circuit 74 in the second characteristic control mode, the motor 77 outputs a second speed. Assuming that the controller 73 controls the drive circuit 74 in a third control mode, the motor 77 outputs a third speed, wherein the first speed is greater than the third speed, and the second speed is greater than the third speed. In this way, the control mode of this embodiment is compared with the traditional square wave control mode. Regardless of light or heavy load or medium and heavy load, under the same motor output torque, the control mode of this embodiment makes the motor speed higher than the traditional square wave control mode. As an option, the third control mode is a traditional square wave control mode.

[0125] Combination Fig.16 and Fig.17 , in the first load interval (i.e., within the torque interval of 0~Tm3), the drive circuit 74 is controlled in a first characteristic control mode so that the motor 77 is less than a preset threshold value, and the preset threshold value is set according to the characteristics of the motor and the current of the motor. In this embodiment, the size of the preset threshold value is KtIs, where Kt=1.5PnΨf, Pn is the number of pole pairs of the magnet, for example, 4 magnets have 2 pole pairs, and Ψf is the magnetic flux constant of the motor. Is is the current of the motor. In the second torque interval (i.e., within the interval greater than Tm3), the drive circuit 74 is controlled in a second characteristic control mode so that the torque of the motor 77 is continuously greater than the preset threshold value KtIs within at least a preset time range, and the preset threshold value KtIs is set according to the characteristics of the motor kt and the current Is of the motor. Among them, the motor load torque in the first load interval is less than the motor load torque in the second load interval.

[0126] Of course, this embodiment is not limited to the above Fig.14 The controller 73 can adjust the angle between the stator flux and the rotor flux by directly controlling the stator flux. Figure 4The controller 43 indirectly controls the stator flux by controlling the current or voltage vector to adjust the angle between the stator flux and the rotor flux. Similarly, regardless of light or heavy load or medium or heavy load, under the same motor output torque, the motor speed of this embodiment is higher than the traditional square wave control method. Specifically, the controller 73 includes a first current distribution unit 432 for distributing a direct-axis target current and a quadrature-axis target current according to the target current of the motor 47 generated by the first speed loop 431; a current conversion unit 427 for generating a direct-axis actual current and a quadrature-axis actual current according to the actual current of the motor 47 and the position of the rotor of the motor; a first current loop 433 for generating a first voltage regulation amount Ud according to the direct-axis target current and the direct-axis actual current; a second current loop 434 for generating a second voltage regulation amount Uq according to the quadrature-axis target current and the quadrature-axis actual current; a first voltage conversion unit 435 for generating a first voltage control amount Ua and a second voltage control amount Ub according to the first voltage regulation amount Ud and the second voltage regulation amount Uq; a first control signal generation unit 436 for generating a control signal according to the first voltage control amount Ua and the second voltage control amount Ub, and the control signal is used to control the drive circuit 44. The control signal is a PWM signal. The duty cycle of the PWM signal changes with the position of the rotor. The controller 43 controls the drive circuit 44 so that the input voltage of the motor 47 changes approximately in a sinusoidal wave. The motor 47 is a three-phase motor, and the three-phase input voltages of the motor 47 are at a phase angle of 120°.

[0127] Fig.18 The effect of the control method of this embodiment is compared with the effect of the traditional square wave control method from the perspective of the relationship curve between motor efficiency and motor torque, where the horizontal axis represents the motor output torque in Nm, and the vertical axis represents the motor efficiency without unit. The solid line is the effect curve of the motor efficiency changing with the motor torque under the control method of this embodiment, and the thick dotted line is the effect curve of the motor efficiency changing with the motor torque under the traditional square wave control method. It can be seen from the figure that compared with the traditional square wave control method, the motor using the control method of the embodiment has higher efficiency in the light and medium load range.

[0128] Reference Fig.19 , the effects of the control method of this embodiment and the traditional square wave control method are compared from the perspective of the relationship curve between the motor bus current and the motor torque, wherein the horizontal axis represents the motor output torque, in Nm, and the vertical axis represents the motor bus current, in A. The solid line is the effect curve of the motor efficiency changing with the motor torque under the control method of this embodiment, and the thick dotted line is the effect curve of the motor efficiency changing with the motor torque under the traditional square wave control method.

[0129] In this embodiment, the bus current of the motor 77 increases at a first slope within the first torque range (e.g., 0 to Tn2), and increases at a second slope within the second torque range (e.g., Tn2 to t4), where the first slope is greater than the second slope. Whether it is a certain torque range in the first load range or a certain torque range in the second load range, or a certain torque range spanning the first load range and the second load range, in short, in this embodiment, there is an inflection point S in the bus current of the motor 77, and the first slope before the inflection point is greater than the second slope after the inflection point S. That is to say, before the inflection point S, the bus current of the motor increases at a faster rate with the motor torque, and after the inflection point, the bus current of the motor increases at a slower rate with the motor torque. Optionally, the first slope can be the slope of the virtual straight line connecting the rotational speeds corresponding to the two endpoints 0 and Tn2 of the first torque range, the second slope is the slope of the virtual straight line L3 connecting the two endpoints of the second torque range, and the second is the slope of the virtual straight line L4 connecting the rotational speeds corresponding to the two endpoints Tn2 and Tn4 of the second torque range. Optionally, the first slope is the slope at any point on the curve of the motor bus current varying with torque in the first torque range, and the second slope is the slope at any point on the curve of the motor bus current varying with torque in the second torque range.

[0130] In this embodiment, when the controller 73 controls the drive circuit 74 in the second characteristic control mode to make the motor 77 rotate at a preset torque, the output current of the power supply device 71 is the second output current; assuming that the controller 74 controls the drive circuit 74 in the third control mode to make the motor 77 rotate at the preset torque, the output current of the power supply device 71 is the third output current; where the second output current is less than the third output current. Optionally, the third control mode is the traditional square wave control mode.

[0131] See Fig.19 , at the preset torque Tn4, the bus current of the motor under the second characteristic control mode of this embodiment is I3, and the bus current under the traditional square wave control is I4, and I3 < I4. Therefore, compared with the traditional square wave control mode, when using the second control mode of the control mode of the embodiment, the current output by the power supply device 71 is smaller under medium and heavy loads.

[0132] Refer to Fig. 20In this embodiment, when the controller 73 controls the driving circuit 74 in the first characteristic control mode, the output power of the electric tool 60 is the first output power; when the controller 73 controls the driving circuit 74 in the second characteristic control mode, the output power of the electric tool 60 is the second output power; assuming that the controller 73 controls the driving circuit 74 in the third control mode, the output power of the electric tool 60 is the third output power; wherein the first output power is greater than the third output power, and the second output power is greater than the third output power. Optionally, the third control mode is a traditional square wave control mode, that is, in this embodiment, whether it is the first characteristic control mode or the second characteristic control mode, the output power of the electric tool 60 is higher than the output power of the electric tool 60 under the traditional square wave control.

[0133] Fig. 20 The effect of the control method of this embodiment is compared with the traditional square wave control method from the perspective of the curve of the power tool output power changing with the motor torque, where the horizontal axis represents the motor torque in Nm and the vertical axis represents the power tool output power in W. Fig. 20 It can be seen that, compared with the traditional square wave control method, the control method of this embodiment has a higher output power of the electric tool 60 when the motor output torque is the same.

[0134] Combination Fig.19 and Fig. 20 According to the control method of the present invention, when the motor rotates at a preset torque (for example, Tn4) in a preset torque range (greater than Tn3), the motor bus current is smaller, the output current of the power supply device 71 is smaller, and the output power of the power tool 60 is higher, which can save energy. For the power tool using a battery pack as the power supply device 71, this makes the battery pack have a longer battery life.

[0135] Combination Fig.16 , Fig.19 and Fig. 20 According to the control method of the present invention, when the motor rotates at a preset torque (for example, Tn4) in a preset torque range (greater than Tn3), the motor bus current is smaller, the output current of the power supply device 71 is smaller, and at the same time, the output power of the power tool 60 is higher and the motor speed is higher, which can save energy. For the power tool using a battery pack as the power supply device 71, this makes the battery pack have a higher endurance.

[0136] In the above embodiment of the present invention, by establishing the functional relationship Te=f(Ψs,Ψf, β), the angle between the stator flux Ψs and the rotor flux Ψf, is dynamically adjusted to obtain the angle between the stator flux Ψs and the rotor flux Ψf, which is implemented on the power tool. Figure 8~Figure 11 characteristic curve, or implement it on the power tool Figure 16~Figure 20characteristic curve so that the output performance of the electric tool of the present invention is better.

[0137] In some other embodiments of the present invention, the controller used outputs a PWM signal that changes with the rotor position to control the drive circuit according to at least one of the motor current, the motor speed and the rotor position, so that the input voltage of the motor changes approximately in the form of a sine wave or a saddle wave, and the amplitude and / or phase of the input voltage and / or current are adjusted to adjust the angle between the stator flux and the rotor flux, so that the motor has a continuous, alternating current state on the three-phase stator winding within at least one electrical cycle or part of the electrical cycle, and the three-phase input voltages of the motor are at a phase angle of 120° to each other. The current state on the three-phase stator winding can synthesize vector torques, which move approximately continuously along the circumference, and the rotor of the motor rotates synchronously with the vector torque that moves approximately continuously along the circumference. Compared with the traditional square wave control method with only 6 discrete, non-continuous drive states, the present invention can improve the motor drive efficiency. Through the above control method, the electric tool of the present invention can obtain Figure 8~Figure 11 ,or Figure 16~Figure 20 Better output performance.

[0138] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. An electric tool comprising: A motor, comprising a stator and a rotor, wherein the motor is a motor capable of generating a reluctance torque; A power supply device, used for providing electrical energy to the motor; A driving circuit, electrically connected to the motor to drive the motor; A controller, used to control the drive circuit, when the controller controls the drive circuit, the motor obtains a second constant speed torque interval; assuming that when the controller controls the drive circuit in a first control mode, the motor obtains a first constant speed torque interval; wherein the first control mode is a traditional square wave control mode, and the length of the second constant speed torque interval is greater than the length of the first constant speed torque interval; The controller comprises: A second speed loop, used for generating a target torque of the motor according to the target speed and actual speed of the motor; A torque loop, used for generating a third voltage adjustment amount according to the target torque and actual torque of the motor; A flux link, used for generating a fourth voltage adjustment amount according to a target stator flux and an actual stator flux of the motor; A second voltage conversion unit, configured to generate a third voltage control amount and a fourth voltage control amount according to the third voltage adjustment amount and the fourth voltage adjustment amount; A second control signal generating unit, configured to generate a control signal according to the third voltage control amount and the fourth voltage control amount, wherein the control signal is used to control the driving circuit; The controller controls the included angle between the stator flux and the rotor flux to be between 105° and 135°.

2. The electric tool according to claim 1, characterized in that: When the controller controls the driving circuit to make the motor rotate in a preset torque range, the motor obtains a second speed; Assuming that the controller controls the driving circuit in a first control mode so that the motor rotates in the preset torque range, the motor obtains a first speed; Wherein, the second rotation speed is greater than the first rotation speed.

3. The electric tool according to claim 1, characterized in that: The controller outputs a PWM signal to the driving circuit, and a duty cycle of the PWM signal changes with a position of the rotor.

4. The electric tool according to claim 1, characterized in that: The controller controls the driving circuit so that the input voltage of the motor changes approximately in a sinusoidal manner.

5. The electric tool according to claim 4, characterized in that: The motor is a three-phase motor, and the three-phase input voltages of the motor are at a phase angle of 120° with each other.

6. The electric tool according to claim 1, characterized in that: The electric tool further comprises: The speed regulating mechanism is at least used to set the target speed of the motor.

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