WO2019201300A1

WO2019201300A1 - Power tool and control method

Info

Publication number: WO2019201300A1
Application number: PCT/CN2019/083240
Authority: WO
Inventors: 张传兵; 陆骏; 钟红风
Original assignee: 苏州宝时得电动工具有限公司
Priority date: 2018-04-18
Filing date: 2019-04-18
Publication date: 2019-10-24
Also published as: CN111919378B; CN110401385B; CN110401385A; CN111919378A

Abstract

The present invention relates to a power tool and a control method. The power tool comprises: a battery connecting part, wherein the battery connecting part is used for connecting a first battery pack and a second battery pack in a detachable manner, and a rated output voltage of the first battery pack is greater than a rated output voltage of the second battery pack; an electric motor serving as a power source; a driving unit located between the battery connecting part and the electric motor, and comprising a power switch tube for driving the operation of the electric motor; and a control unit for outputting a control signal to a control end of the power switch tube, and enabling the electric motor to be adapted to the rated output voltage of the first battery pack or the second battery pack by adjusting a duty cycle of the control signal so that a rotational speed of the electric motor is equal to a pre-set rotational speed, wherein a rated voltage of the electric motor is lower than at least one of the rated output voltage of the first battery pack and the second battery pack.

Description

Power tool and control method

Cross reference related reference

The present application claims priority to Chinese Patent Application No. 20181, 034, 967, filed on Apr. 18, s., the entire disclosure of which is incorporated herein by reference.

Technical field

The present invention relates to the field of electric power, and in particular to a power tool capable of adapting a battery pack that is lower than a rated voltage of a power tool and a battery pack that is higher than a rated voltage of the tool.

Background technique

A cordless tool or a cordless power tool uses a battery pack that is pluggably mounted on a tool as a power supply unit. Since it uses a battery pack to supply direct current (DC) power, it is not used. AC (AC) powered power cord (rope), so called cordless power tools.

Like most electromechanical products, cordless power tools are mainly composed of energy unit (battery pack), power head (motor), transmission system (gearbox), control unit (switch, control board), and execution unit (work head). At present, when designing and producing a power tool, the rated voltage of the tool is matched with the voltage of the energy unit (battery pack), that is, the rated voltage of the corresponding tool of the battery pack with a rated voltage of 18V must also be 18V. If the battery voltage is too high, the motor will be overloaded, easy to burn out or cause the motor to run at a speed. If the battery voltage is too low, the motor will run under load, making the output of the motor smaller or even unable to work.

Since most companies' current battery pack interfaces of different voltages are incompatible, that is, battery packs of different voltages have corresponding product platforms. Battery packs with different voltages cannot be plugged into other voltage platforms, which inevitably produces battery packs with a wide range of specifications, is not suitable for mass production, and has high logistics management costs for production, sales, and maintenance.

In order to solve the above problems, B&D Company has introduced the FLEX20V~60V general-purpose battery pack, which realizes the change of the battery output voltage by mechanical switch to control the change of the battery core string and the parallel connection mode, and can be plugged in at the same time at 20V and 60V. Product line. However, the battery pack has a complicated structure, high process requirements, high cost, low reliability, and it can only achieve compatibility between two (20V/60V) voltage product lines and batteries.

Summary of the invention

In order to overcome the deficiencies of the prior art, the problem to be solved by the present invention is to provide a more compatible power tool that can adapt a battery pack having a voltage lower than or higher than a certain range of the rated voltage of the motor.

The technical solution adopted by the present invention to solve the prior art problem is:

A power tool includes a battery connecting portion for detachably connecting a first battery pack and a second battery pack, wherein a rated output voltage of the first battery pack is greater than a rated output voltage of the second battery pack ;

Motor as a power source;

a driving unit, located between the battery connecting portion and the motor, including a power switch tube for driving the motor to operate;

a control unit, configured to output a control signal to the control end of the power switch tube, and adjust a duty ratio of the control signal to make the speed of the motor equal to a preset speed, so that the motor can adapt to the first battery pack or The rated output voltage of the second battery pack, the rated voltage of the motor being lower than at least one of the rated output voltages of the first battery pack and the second battery pack.

Preferably, the rated voltage of the motor is between the rated output voltage of the first battery pack and the rated output voltage of the second battery pack.

Preferably, the rated output voltage of the first battery pack is at least 20% higher than the rated voltage of the motor, and the rated output voltage of the second battery pack is not lower than 40% of the rated voltage of the motor.

Preferably, the power tool further includes a rotation speed detecting module, configured to acquire a rotation speed of the motor, and the control unit adjusts a duty ratio of the control signal to cause the motor to run at a preset speed at a steady speed, the pre-predetermined Set the speed to be less than or equal to the rated speed of the motor.

Preferably, the power tool is started, the control unit gradually increases the duty ratio of the control signal, and if the speed obtained by the speed detecting module is equal to the first preset speed, the control unit controls the motor to be the first The preset speed is running at a steady speed, otherwise the control unit controls the motor to run at a third preset speed, and the first preset speed is less than or equal to the rated speed of the motor, the third preset The rotation speed is less than or equal to the second preset rotation speed, and the second preset rotation speed is the maximum rotation speed of the electric power tool when the second battery pack is powered.

Preferably, the power tool further includes a first speed control device and a second speed control device, wherein the first speed control device corresponds to a first preset speed, and the second speed control device corresponds to a third preset speed. The first preset speed is greater than the third preset speed, and the third preset speed is less than the second preset speed.

Preferably, when the first speed regulating device is operated, and the power tool is started, the control unit gradually increases the duty ratio of the control signal, if the speed obtained by the speed detecting module is equal to the first preset When the rotational speed is set, the control unit controls the motor to run at a steady speed at the first preset rotational speed. Otherwise, the control unit controls the motor to operate at a steady speed at the second preset rotational speed.

Preferably, the second speed regulating device is operated, and after the power tool is started, the control unit gradually increases the duty ratio of the control signal until the speed obtained by the speed detecting module is equal to the third preset. At the time of the rotational speed, the control unit controls the motor to maintain the third predetermined rotational speed operation.

Preferably, the power tool further includes a power tool housing, the power connector is disposed on the power tool housing, and the second battery pack includes a first battery pack and a second battery pack, the first battery The package and the second battery pack are connected in series to provide electrical power to the power tool.

Preferably, the power interface includes a first power interface for electrically connecting an adapter, and the adapter is detachably connected to a casing of the power tool, and the adapter is disposed on the adapter There are a plurality of battery pack connectors, and the plurality of battery packs are connected in series or in parallel to form a first battery pack. The adapter is provided with a voltage output port electrically connected to a power input port of the power tool to supply power to the power tool.

Preferably, the adapter is detachably mounted in a housing of the backpack assembly, and the backpack assembly is connected to the power tool through the connection assembly to provide power to the power tool.

Preferably, the adapter is provided with four battery pack connectors, and the output voltage of the four battery pack connectors in series is greater than the rated voltage of the motor.

Preferably, the connection assembly comprises a cable.

Preferably, the power tool further includes a voltage detecting module for detecting a terminal voltage of the motor, and the control unit adjusts a duty ratio of the control signal to make a terminal voltage of the motor less than or equal to the The rated voltage of the power tool.

Preferably, the first battery pack includes a first battery pack and a second battery pack, and the power tool further includes a first switch and a second switch, one end of the first switch and the start and stop switch of the power tool Connected to one end and form a first node, wherein the other end of the start-stop switch is connected to the motor; one end of the second switch is connected to the other end of the first switch, and forms a second node, The other end of the second switch is connected to the input end of the driving unit, and forms a third node; wherein a positive pole of the first battery pack is connected to the first node, and a negative pole of the first battery pack is connected The second node, the positive pole of the second battery pack is connected to the second node, the negative pole of the second battery pack is connected to the third node, and when the first battery pack is not connected, the The first switch is in a closed state, the first switch is in an open state when the first battery pack is accessed, and the second switch is in a closed state when the second battery pack is not connected, the first When the second battery pack is accessed, the second switch is broken. State.

Preferably, the first battery pack includes a first battery pack and a second battery pack, and the power tool further includes:

a first diode, a cathode of the first diode is connected to one end of the start-stop switch of the power tool, wherein the other end of the start-stop switch is connected to the motor;

a second diode, a cathode of the second diode being respectively connected to a cathode of the first diode and one end of the start-stop switch;

a third diode, a cathode of the third diode is connected to an anode of the second diode, an anode of the third diode is connected to an input end of the driving unit, and forms a fourth node;

a third switch, one end of the third switch is connected to an anode of the first diode, and the other end of the third switch is respectively connected to an anode of the second diode and the third diode The cathodes are connected and form a fifth node;

a fourth switch, one end of the fourth switch is connected to the fifth node, and the other end of the fourth switch is connected to the fourth node;

a first selection switch, wherein the first moving end of the first selection switch is respectively connected to one end of the third switch and an anode of the first diode, and the second moving end of the first selection switch is connected ;

a second selection switch, the first moving end of the second selection switch is connected to the fifth node, and the second moving end of the second selection switch is connected to the air;

The anode of the first battery pack is connected to the fixed end of the first selection switch, the cathode of the first battery pack is connected to the fifth node, and the anode of the second battery pack is connected to the second selection. a fixed end of the switch, a negative pole of the second battery pack is connected to the fourth node, and when the first battery pack is not connected, the third switch is in a closed state, and when the first battery pack is connected The third switch is in an off state, the fourth switch is in a closed state when the second battery pack is not connected, and the fourth switch is in an off state when the second battery pack is accessed. .

Preferably, the method further includes:

a storage module, wherein the storage module prestores a working condition database, wherein the working condition database includes a correspondence between a load and a duty ratio of the electric tool under various working conditions;

Wherein, the control unit further adjusts the duty ratio of the control signal according to the load size, so that the terminal voltage of the motor is equal to the rated voltage of the power tool.

Preferably, the method further includes:

a wireless communication module, wherein the control unit communicates with the server through the wireless communication module to acquire a control parameter corresponding to the power tool from the server to operate according to the control parameter, and/or The operating parameters of the power tool are sent to the server to store the working parameters in a history database of the server, so that the server corresponds to the power tool according to working parameters in the historical database. Control the parameter database for optimization.

Preferably, the switching frequency of the power switch tube ranges from 4 to 20 Khz.

Preferably, the motor adopts one of a brush motor, a brushless motor, a switched reluctance motor or a high frequency AC induction motor.

Preferably, the battery pack comprises: a single battery pack, the battery pack having a rated voltage greater than or equal to a rated voltage of the power tool.

Preferably, the battery pack includes: a battery pack composed of a plurality of battery packs, a battery pack composed of the plurality of battery packs has a rated voltage greater than or equal to a rated voltage of the power tool; a voltage regulating unit, the voltage adjustment The unit is used to select a battery pack that operates according to the rated voltage of the power tool.

Preferably, when the battery pack is composed of two battery packs, the two battery packs are respectively recorded as a first battery pack and a second battery pack, and the voltage adjustment unit includes: a first switch, the first switch One end is connected to one end of the start-stop switch of the power tool, and forms a first node, wherein the other end of the start-stop switch is connected to the motor; the second switch, one end of the second switch is The other end of the first switch is connected to form a second node, and the other end of the second switch is connected to the input end of the driving module, and forms a third node; wherein the positive pole of the first battery pack a first node, a cathode of the first battery pack is connected to the second node, a cathode of the second battery pack is connected to the second node, and a cathode of the second battery pack is connected to the third node. When the first battery pack is not connected, the first switch is in a closed state, when the first battery pack is accessed, the first switch is in an off state, and the second battery pack is not connected. The second switch is in a closed state, Second access to the battery pack, the second switch is in the off state.

Preferably, when the battery pack is composed of two battery packs, the two battery packs are respectively recorded as a first battery pack and a second battery pack, and the voltage adjustment unit includes: a first diode, the first a cathode of the diode is connected to one end of the start-stop switch of the power tool, wherein the other end of the start-stop switch is connected to the motor; the second diode, the cathode of the second diode respectively Connected to a cathode of the first diode and one end of the start-stop switch; a third diode, a cathode of the third diode is connected to an anode of the second diode, the An anode of the three diode is connected to an input end of the driving module, and forms a fourth node; a third switch, one end of the third switch is connected to an anode of the first diode, and the third switch The other end is connected to the anode of the second diode and the cathode of the third diode, respectively, and forms a fifth node; the fourth switch, one end of the fourth switch is connected to the fifth node The other end of the fourth switch is connected to the fourth node; The first moving end of the first selection switch is respectively connected to one end of the third switch and the anode of the first diode, and the second moving end of the first selection switch is connected; the second selection a switch, a first moving end of the second selection switch is connected to the fifth node, and a second moving end of the second selection switch is vacant; wherein a positive pole of the first battery pack is connected to the first Selecting a fixed end of the switch, a negative pole of the first battery pack is connected to the fifth node, a positive pole of the second battery pack is connected to a fixed end of the second selection switch, and a negative pole of the second battery pack is connected When the fourth node is not connected, the third switch is in a closed state, and when the first battery pack is accessed, the third switch is in an off state, the second When the battery pack is not connected, the fourth switch is in a closed state, and when the second battery pack is accessed, the fourth switch is in an open state.

Preferably, the power tool further includes: a battery management unit, wherein the battery management unit is configured to perform equalization processing on the battery pack according to a voltage of each battery pack in an operating state when the plurality of battery packs are in an operating state.

Preferably, the undervoltage protection voltage of the battery pack is greater than or equal to a rated voltage of the power tool.

Preferably, the battery pack of the plurality of battery packs has an undervoltage protection voltage greater than or equal to a rated voltage of the power tool.

Preferably, the operating parameter of the motor satisfies the preset condition that the terminal voltage of the motor is equal to the rated voltage of the power tool, or the rotational speed of the motor is equal to the rated rotational speed of the motor.

Preferably, the power tool further includes: a motor detecting module, wherein the motor detecting module is respectively connected to the motor and the control module, wherein the motor detecting module is configured to detect a terminal voltage of the motor or the motor The rotation speed of the control module is further configured to adjust a relationship between a terminal voltage of the motor and a rated voltage of the power tool or a relationship between a rotational speed of the motor and a rated rotational speed of the motor. The duty cycle of the control signal.

Preferably, the power tool further includes: a first battery detecting module, wherein the first battery detecting module is configured to detect a voltage or an internal resistance of the battery pack in an operating state when the power tool starts to work; The control module is further configured to determine a rated voltage provided by the battery pack according to a voltage or an internal resistance of the battery pack in an operating state, and call a corresponding subroutine to control the motor according to the rated voltage.

Preferably, the power tool further includes: a storage module, wherein the storage module prestores a working condition database, wherein the working condition database includes a load and a duty ratio of the power tool under various working conditions. Corresponding relationship; wherein, after determining the rated voltage currently provided by the battery pack, the control module further adjusts a duty ratio of the control signal according to a load magnitude of the motor.

Preferably, the power tool further includes: a wireless communication module, wherein the control module communicates with the server through the wireless communication module to acquire a control parameter corresponding to the power tool from the server, according to the Controlling parameters to operate, and/or transmitting operational parameters of the power tool to the server to store the operational parameters in a history database of the server such that the server is in accordance with the historical database The operating parameters are optimized for a database of control parameters corresponding to the power tool.

Preferably, the control module is further configured to acquire a voltage change amount of the battery pack, and when a voltage change amount of the power supply module is greater than or equal to a preset voltage value, if a terminal voltage of the motor is smaller than the electric power The rated voltage of the tool, the control module increases the duty ratio of the control signal such that the terminal voltage of the motor reaches the rated voltage of the power tool again, or if the rotational speed of the motor is less than the The rated speed of the motor, the control module increases the duty ratio of the control signal to cause the speed of the motor to reach the rated speed of the motor again.

In order to achieve the above object, a power tool system according to a second aspect of the present invention includes: the power tool of the above embodiment; a server, wireless communication between the server and the power tool; wherein the power tool is used Obtaining a control parameter corresponding to the power tool from the server to operate according to the control parameter, and/or transmitting an operating parameter of the power tool to the server to store the working parameter In a history database of the server, the server is optimized to control a database of control parameters corresponding to the power tool according to working parameters in the history database.

According to the electric power tool system of the embodiment of the present invention, by the wireless power communication between the power tool and the server of the above embodiment, the power tool can acquire the control parameter of the corresponding power tool from the server to operate according to the control parameter, and/or The working parameters of the power tool are sent to the server to store the working parameters in the historical database of the server, so that the server optimizes the control parameter database corresponding to the power tool according to the working parameters in the historical database, thereby effectively solving the electric problem The limited storage space of the tool and the limited processing speed of the control module are beneficial to improve the use efficiency of the power tool.

The present invention also provides a power tool control method, the power tool including a first voltage interface and a second voltage interface for respectively connecting battery packs of different output voltages, the power tool further comprising a motor and a control unit, The rated voltage of the motor is between the voltages output by the first voltage interface and the second voltage interface, and the method includes:

Step S1, after the power tool is started, gradually increasing the duty ratio of the control signal;

In step S2, it is determined whether the rotational speed of the motor is equal to the preset rotational speed, wherein the preset rotational speed is less than or equal to the rated rotational speed of the motor, and if so, step S3 is performed, otherwise step S4 is performed;

Step S3, controlling the motor to maintain the preset speed operation;

Step S4, it is determined whether the duty ratio is equal to the preset duty cycle, and if so, step S5 is performed, otherwise, step S1 is performed;

In step S5, the control motor maintains the second preset speed operation, wherein the second preset speed is less than or equal to the speed corresponding to the preset duty ratio.

Compared with the prior art, the beneficial effects of the present invention are:

The power tool of the present invention comprises a first battery interface connected to the first battery pack, a second battery connection interface for connecting the second battery pack, the rated output voltage of the first battery pack being greater than the second battery The rated output voltage of the group, the rated voltage of the motor is between the rated output voltage of the first battery pack and the rated output voltage of the second battery pack, and the control unit does not need to identify the type of the battery pack, but the control of the power tool after starting. The unit gradually increases the duty ratio so that the speed of the tool satisfies the preset condition. Thus, when the power tool requires a large output power, the first battery pack connected to the high voltage is used, and when the power tool does not require a large output power, Connecting the low-voltage second battery pack expands the range of battery packs that the power tool can adapt, while increasing the efficiency of the battery pack by limiting the duty cycle to the speed.

DRAWINGS

The objects, technical solutions, and advantageous effects of the present invention described above can be achieved by the following figures:

1 is a schematic structural view of a power tool according to an embodiment of the present invention;

2 is a schematic flow chart of internal control of a power tool according to an embodiment of the present invention;

3 is a schematic structural view of a carrier according to an embodiment of the present invention;

4 is a graph showing a relationship between a battery pack voltage and a duty ratio according to an embodiment of the present invention;

Figure 5 is a schematic structural view of a power tool according to an embodiment of the present invention;

6 is a schematic structural view of a power tool according to another embodiment of the present invention;

7 is a schematic structural view of a power tool according to another embodiment of the present invention;

Figure 8 is a flowchart showing the operation of the electric power tool according to the first specific example of the present invention;

Figure 9 is a flowchart showing the operation of a power tool according to a second specific example of the present invention;

Figure 10 is a flow chart of an undervoltage protection subroutine in accordance with one example of the present invention;

Figure 11 is a flowchart showing the operation of a power tool according to a third specific example of the present invention;

Figure 12 is a flowchart showing the operation of a power tool according to a fourth specific example of the present invention;

Figure 13 is a flow chart of an undervoltage protection subroutine in accordance with another example of the present invention;

Figure 14 is a circuit diagram of a power tool in accordance with one specific example of the present invention;

Figure 15 is a circuit diagram of a power tool according to another specific example of the present invention;

Figure 16 is a schematic illustration of a switching frequency in accordance with one example of the present invention.

detailed description

The embodiments of the present invention are described in detail below, and the examples of the embodiments are illustrated in the drawings, wherein the same or similar reference numerals are used to refer to the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are intended to be illustrative of the invention and are not to be construed as limiting.

A power tool according to an embodiment of the present invention will be described below with reference to Figs.

As shown in FIG. 1, the electric power tool 100 includes a motor 10, a battery connecting portion 20, a driving unit 30, and a control unit 40. The battery connecting portion 20 is configured to detachably connect the first battery pack and the second battery pack, the rated output voltage of the first battery pack is greater than the rated output voltage of the second battery pack, and the input end of the driving unit 30 and the battery The output end of the connecting portion 20 is connected, and the output end of the driving unit 30 is connected to the motor 10. The driving unit 30 includes a power switch tube 31 for outputting a control signal to the control end of the power switch tube 31, and Adjusting the duty ratio of the control signal to make the rotational speed of the motor 10 equal to the preset rotational speed, so that the motor 10 can adapt to the rated output voltage of the first battery pack or the second battery pack, and the rated voltage of the motor 10 is lower than At least one of the rated output voltages of the first battery pack and the second battery pack.

The power tool of the invention can adapt to the battery pack with the rated voltage greater than or equal to the rated voltage of the motor, or the battery pack with the rated voltage less than the rated voltage of the motor. When the battery pack is installed on the power tool, it is not necessary to identify the type of the battery pack. Only by adjusting the speed, the battery packs with different output voltages can be adapted to the power tool so that the voltage across the motor does not exceed its rated output voltage.

The power switch tube 31 can be a bridge circuit composed of MOSFET tubes.

Specifically, the drive unit 30 is configured to drive the motor 10 to operate in accordance with the electrical energy provided by the battery connection 20. The control unit 40 is configured to output a control signal to the control end of the power switch tube 31. When the battery connection portion 20 is connected to the first battery pack or the second battery pack, and after the power tool 100 is activated, the control unit 40 gradually increases the duty ratio of the control signal. The operating parameters of the motor 10 are modulated until the operating parameters of the motor 10 meet the preset conditions.

Taking a 60V power tool as an example, as shown in FIG. 16, the voltage supplied from the battery connecting portion 20 is adjusted to 60V (effective value) by PWM to be applied to a brush motor having a rated voltage of 60V, assuming that the duty ratio is It is 50%. If the PWM frequency is 4kHz, the period T=0.25ms, and the on-on time in T in a single period is 0.125ms. During this time, the carbon brush is enough to generate a large spark, making two carbons The spark of the brush is connected to the arc. At this time, even if it is turned to the off state, the spark has not yet been extinguished, and it is in the on state, so there will be a continuous arc phenomenon. If the PWM frequency is reduced, the on time is longer, the spark is larger, and the arc is more inevitable.

Further, if the PWM frequency is increased, such as reaching f=8 kHz, the period T=0.125 ms, the on time is only 0.0625 ms, such a short time carbon brush is not enough to generate a large spark, and even if there is a certain normal The spark is then in the off state, enough to extinguish. Therefore, increasing the frequency can avoid the occurrence of carbon brush sparks.

Secondly, the PWM frequency can't be too high: It is well known that the DC power supply PWM voltage regulation is realized by a power switch tube such as Mosfet. The Mosfet power switch tube has on-state loss and switching loss. The switching loss is proportional to the PWM frequency, so increasing the frequency is bound to be Increase switching losses, which increase device temperature rise and reduce reliability.

The control unit 40 of the present invention controls the turning on or off of the power switching transistor 31 in the driving unit 30 by transmitting a PWM (Pulse Width Modulation) signal. The PWM signal is a pulse signal with adjustable duty ratio, and includes a high level portion and a low level portion. The high level portion causes the power switch tube 31 to be in an on state, and the battery connection portion 20 supplies power to the motor 10 when the motor After the start-up operation, the low-level portion of the pulse signal causes the power switch tube 31 to be in an off state, and the power supply circuit of the battery connection portion 20 to the motor 10 is disconnected. The control unit 40 can control the magnitude of the electric energy supplied to the motor 10 by the battery connecting portion 20 by controlling the ratio of the high level portion and the low level portion of the PWM signal. Wherein, the duty ratio is high, that is, the high-level portion is high, the power-on time of the power switch tube 31 is long, the power supplied from the battery connecting portion 20 to the motor 10 is high, and the terminal voltage of the motor 10 and the rotational speed of the motor 10 are high; The duty ratio is low, that is, the ratio of the high level portion is low, the conduction time of the power switch tube 31 is short, the power supplied from the battery connection portion 20 to the motor 10 is low, and the terminal voltage of the motor 10 and the rotation speed of the motor 10 are low. Thereby, the fitting range of the voltage of the electric power tool 100 is improved, and the efficiency of the battery connecting portion 20 is improved.

In this embodiment, the motor 10 may be one of a brush motor, a brushless motor, or a switched reluctance motor to facilitate the control unit 40 to control the rotational speed of the motor 10.

Alternatively, the power tool 100 can be, but is not limited to, a cordless hand-held power tool, a cordless garden tool, a cordless wheeled moving tool, and the like.

In the embodiment of the present invention, the switching frequency of the power switch tube 31 may range from 4 to 20 Khz, preferably from 6 to 12 Khz, and most preferably from 7 to 9 Khz.

In the embodiment of the present invention, the battery connecting portion 20 is detachably connected to the battery pack, and the battery pack may be a single battery pack or a battery pack composed of a plurality of batteries. In order to facilitate the replacement of the battery pack, the battery pack may be designed to be detachably mounted in the power tool 100. For example, a battery slot for installing the battery pack may be disposed in the housing, or a battery compartment may be disposed separately from the housing. The piggyback assembly 90 (shown in Figure 3) is used to mount the battery pack.

Alternatively, the type of the battery pack may be a lithium battery, a nickel cadmium battery, a lead acid battery, or a super capacitor.

In one embodiment of the present invention, the rated output voltage of the motor is between the rated output voltages of the first battery pack and the second battery pack, and the control unit stabilizes the rotational speed by a predetermined duty value by controlling the duty ratio. The set value is less than or equal to the rated speed of the motor, so that the terminal voltage of the motor is less than or equal to the rated voltage of the motor. The control unit of the invention adjusts the rotational speed by adjusting the duty ratio of the control signal, and does not need to identify the type of the battery pack, and the power tool can be adapted to the battery pack larger than the rated voltage of the power tool and less than the rated voltage of the power tool by only one set of procedures. Battery pack.

For details, please refer to FIG. 2, which is a schematic flowchart of a method for controlling a power tool according to the present invention. Control methods include:

In step S1, after the power tool is started, the duty ratio of the control signal is gradually increased. The power tool of the present invention gradually increases the duty ratio by a soft start mode until the duty ratio reaches a predetermined value.

In step S2, it is judged whether the rotation speed of the motor is equal to the preset rotation speed, and if so, step S3 is performed, otherwise step S4 is performed. After the duty ratio reaches a preset value, the control unit determines whether the motor speed obtained by the rotation speed detecting unit is equal to the preset speed, and the preset speed is less than or equal to the rated speed of the motor. In one embodiment, the preset speed may be It is the speed set by the operator through the speed control device, or it can be a preset speed value stored in the system.

In step S3, the control motor maintains the preset speed operation. In the above steps, if it is determined that the rotational speed of the motor is equal to the preset rotational speed, the controller controls the motor to operate at a steady speed at a preset rotational speed.

In step S4, it is determined whether the duty ratio is equal to the preset duty ratio, and if so, step S5 is performed; otherwise, step S1 is performed. In a preferred embodiment of the present invention, the preset duty ratio is 100%. As is known to those skilled in the art, the preset duty ratio may also be slightly less than 100%.

In step S5, the control motor maintains the second preset speed operation, wherein the second preset speed is less than or equal to the speed corresponding to the 100% duty ratio. In the above preferred embodiment, when it is determined that the duty ratio is equal to the preset duty ratio, the control unit controls the motor to operate at a duty ratio of 100%, which corresponds to the second preset speed.

After the motor is started in the above step, the duty ratio is gradually increased, and the control unit determines whether the motor speed obtained by the rotation speed detecting unit is equal to the preset speed. If not, the duty ratio is continuously increased, and it is determined whether the increased duty ratio is equal to 100. %, if yes, maintain the 100% duty cycle control motor or the corresponding second preset speed when the 100% duty cycle is pre-stored in the system. When the duty ratio is equal to 100%, the control device controls the motor to maintain the second. The preset speed runs at a steady speed. Otherwise, if the duty cycle is not equal to 100%, continue to increase the duty cycle until the motor speed is equal to the preset speed.

The power tool of the present invention can be adapted to a battery pack higher than the rated voltage of the power tool, or can be adapted to a battery pack lower than the rated voltage of the power tool, and can control the high voltage battery pack without identifying the type of the battery pack by the identification module. Instead, by gradually increasing the duty cycle, the low-voltage battery pack maintains a 100% duty cycle operation, and the high-voltage battery pack maintains the preset speed operation, which saves cost, simplifies the control procedure, and is recognized by The module can only recognize a limited number of battery packs, and the versatility of the battery pack is limited. The present invention eliminates the need for an identification module and improves the compatibility of the power tool with the battery pack.

In one of the embodiments of the present invention, the rated output voltage of the first battery pack is at least 20% higher than the rated voltage of the motor, and the rated output voltage of the second battery pack is not less than 40% of the rated voltage of the motor. In another embodiment of the invention, the undervoltage of the first battery pack, ie, the lowest discharge voltage, is greater than the rated output voltage of the second battery pack. When the second battery pack is connected to the power tool, the control device controls the motor to operate at a 100% duty cycle, or pre-stores the maximum speed when the second battery pack is connected to the power tool, ie, the second speed, when the tool is started After that, the duty ratio is gradually increased. When the duty ratio is increased to 100% and the rotational speed is still less than the target rotational speed, the control device controls the motor to maintain the second preset rotational speed to operate at a steady speed.

In one embodiment of the present invention, the power tool further includes a speed control device, and the speed control device may be a knob for multi-speed speed regulation, or a plurality of buttons or buttons for gear speed regulation. Specifically, the two-speed speed adjustment is taken as an example. The power tool includes a first speed control device and a second speed control device. The first speed control device may be a first button, corresponding to the high speed gear, corresponding to the first preset speed, The second speed regulating device may be a second button, corresponding to the low speed gear, corresponding to the third preset speed. The first preset speed is less than or equal to the rated speed of the motor, and the third preset speed is less than or equal to the speed when the second battery pack is adapted to the power tool and the power tool is operated at 100% duty cycle.

When the first button is triggered, after the power tool is started, the control unit gradually increases the duty ratio of the control signal, and the control unit determines whether the motor speed obtained by the rotation speed detecting unit is equal to the first preset speed, and if not equal, continues to increase Empty ratio, and determine whether the duty ratio at this time is equal to 100%. If the duty ratio at this time is equal to 100%, the control unit maintains the 100% duty cycle control motor. If it is not equal to 100%, continue to increase the duty. Comparing, and determining whether the rotation speed at this time is equal to the first preset rotation speed. If equal, the control unit controls the motor to run at a steady speed at the first preset rotation speed. If not, it determines whether the duty ratio at this time is equal to 100%. If not equal to continue to increase the duty cycle until the motor speed is equal to the first preset speed, if equal, the control unit maintains the 100% duty cycle control motor.

When the second button is triggered, after the power tool is started, the control unit gradually increases the duty ratio of the control signal, and the control unit determines whether the motor speed obtained by the rotation speed detecting unit is equal to the third preset speed, and if not equal to the third preset speed, Then continue to increase the duty cycle until the motor speed is equal to the third preset speed.

The electric tool of the present invention includes a power tool such as a grass cutter, a pruning machine, a hair dryer, a chain saw, a high pressure cleaner, and the like. The power tool includes a battery connecting portion 20, and the battery connecting portion 20 includes a first power port and a second power port. The first power port has a detachable connection voltage that is greater than a rated battery voltage of the first battery pack, and the second power port has a detachable connection voltage. A second battery pack that is less than the rated voltage of the motor. Taking a 60V power tool as an example, the power tool can supply power from a 40V battery pack through the second power interface, or from the 80V battery pack through the first power interface. When the power tool requires a small power output or there is no battery pack of 60V or 80V around, the power tool can be fitted with a 40V battery pack. When the power tool requires a large output power, the power tool is adapted to the 80V battery pack. The 40V battery pack may be a single 40V battery pack, or may be composed of two 20V battery packs in series. In the present invention, two 20V battery packs are preferably connected in series to form a 40V output voltage. Specifically, the second The power interface includes a first battery slot and a second battery slot. The first battery slot and the second battery slot are electrically connected to respectively connect the first battery pack and the second battery pack, and the first battery pack and the second battery pack are respectively 20V battery pack. When the power tool requires a higher output power, in one embodiment, the first battery pack can be composed of four 20V battery packs in series to form an output voltage of 80V. The 80V first battery pack can be located on the power tool housing or outside the housing of the power tool.

The invention further includes an adapter, the adapter is provided with a plurality of battery holders for mounting a plurality of battery packs, the plurality of battery packs are connected in series or in parallel, the adapter has a voltage output port, and the voltage input port of the power tool is connected through the connection component, Provide power to power tools. In one embodiment, four battery slots are provided on the adapter, four 20V battery packs can be installed, and four 20V battery packs are connected in series or in parallel. The adapter is provided with a first voltage output port, a second voltage output port and The third voltage output ports are 20V, 40V and 80V respectively. At the same time, the adapter also has a power input port, and the external AC power source charges the battery pack on the battery slot through the power input port. The adapter is further provided with a first connecting portion for detachably connecting the first power interface of the power tool.

Taking a 60V lawn mower as an example, the second power port in the tool housing of the lawn mower is provided with a first battery slot and a second battery slot, and the first battery slot and the second battery slot are electrically connected to accommodate 2 A 20V battery pack, two battery packs in series. At the same time, the lawn mower housing is also provided with a first power connector for the detachable connection adapter. The operator can select two 20V battery packs to supply power to the lawn mower in series or select the four 20V battery packs in series, that is, the 80v voltage output port to supply power to the lawn mower.

For handheld tools such as lawn mowers and hair dryers, the adapter is mounted on the tool housing to increase the weight of the tool, and the operator's hand operation is inconvenient. As shown in FIG. 3, the power tool of the present invention further includes a piggyback component, which is convenient for the user to carry. Similar to the backpack style, the backpack assembly includes a housing in which a housing is disposed for receiving the adapter, and the backpack assembly further includes a cable a for electrically connecting the power tool, and the electrical energy output by the adapter is transmitted to the power tool through the cable. The carrying component reduces the force on the operator's hand and is more convenient to operate.

In an embodiment of the present invention, the adapter has only one voltage output port, and the adapter is provided with a knob switch, and the serial-parallel structure of the plurality of battery packs is changed by rotating the knob switch, thereby changing the voltage of the output port. The output port is connected to the power tool through a connection assembly to supply power to the power tool. As shown in FIG. 3, the battery pack 21 is composed of four 20V battery packs in series. The user can select the target rated voltage through the knob A according to the rated voltage of the power tool. For example, the rated voltage of the tool is 60V, and the black on the knob A can be selected. The arrow is aligned to the 4*20V position.

In another embodiment of the present invention, a voltage detecting module is further included for detecting a terminal voltage of the motor, and adjusting a duty ratio of the control signal such that a terminal voltage of the motor is equal to a rated voltage of the power tool.

In the following, the 80V battery pack is reduced to 60V, and the brushed motor with rated voltage of 60V is used as an example. The selection of the switching frequency is specifically described:

First of all, the PWM frequency can not be too low: after debugging, if the frequency below 4 kHz is used, there will be a carbon brush fire and arc phenomenon, that is, a continuous bright spark will appear, the motor 10 will be burnt in a short time, and there is a fire hazard. .

For a motor 10 with a rated voltage of 60V, if a voltage of 60V is applied, the current is large at the initial stage of the motor 10, and when the carbon brush and the commutator realize current commutation, a large peak back electromotive force is generated between the carbon brush and the commutator. Thereby, a certain intensity arc discharge is generated; when the motor is started, the current is reduced, and when the carbon brush and the commutator realize current commutation, the peak back electromotive force generated between the carbon brush and the commutator becomes small, and substantially no spark is seen.

However, if the voltage supplied from the battery connecting portion 20 is increased to 60V, a larger peak counter electromotive force is generated between the carbon brush and the commutator, resulting in a large spark, so that the sparks of the two carbon brushes are connected together. Ablation of carbon brushes and commutators occurs.

In order to avoid the phenomenon of spark arcing, it is necessary to control the energy of the carbon brush spark so that it is not enough to cause arcing.

When the battery connection portion 20 includes a single battery pack and the rated voltage of the battery pack is equal to the rated voltage of the power tool 100, the control unit 40 controls the duty ratio to be 100% in order to maintain higher efficiency. During the use of the power tool 100, the voltage will gradually decrease and the efficiency of the battery pack will decrease.

Further, the use efficiency of the battery pack is increased. When the under-voltage protection voltage of the battery pack should be greater than or equal to the rated voltage of the power tool such that the terminal voltage of the motor 10 is equal to the rated voltage of the power tool 100, the power tool 100 is at the rated voltage. Continue to work efficiently. For example, a 20V battery pack provides a rated voltage of 18V and an undervoltage protection voltage of 12.5V. The rated voltage of the power tool 100 using the battery pack must be less than or equal to 12.5V; the 40V battery pack provides the rated voltage. For 36V, the undervoltage protection voltage is 25V, the rated voltage of the power tool 100 using the battery pack should be less than or equal to 25V; the 60V battery pack provides a rated voltage of 48V, and its undervoltage protection voltage is 37.5V. Then, the rated voltage of the power tool 100 using the battery pack needs to be less than or equal to 37.5V.

Specifically, as shown in FIG. 4, the minimum duty ratio during operation = the rated voltage of the motor / the rated voltage supplied by the battery connection, the maximum duty ratio during operation = the rated voltage of the motor / the undervoltage of the battery connection. Since the duty cycle ranges from 0 to 100%, the minimum duty cycle during operation = motor rated voltage / rated voltage provided by the battery connection ≤ 100%, maximum duty cycle during operation = motor rated voltage / battery The undervoltage of the connection is ≤100%, that is, the rated voltage of the motor is ≤ the undervoltage of the battery connection.

When the battery connecting portion 20 includes the battery pack 21 composed of a plurality of batteries and the voltage adjusting unit 22, the rated voltage of the battery pack 21 composed of the plurality of batteries is greater than or equal to the rated voltage of the electric power tool 100. The voltage adjusting unit 22 is configured to select a battery pack that operates according to the rated voltage or the target rated voltage of the power tool, so that the battery connecting portion 40 provides the target rated voltage when the selected battery pack operates.

In this example, the number and connection relationship of the plurality of battery packs constituting the battery pack 21 can be set as needed (such as the type of the power tool 100, etc.), for example, the battery pack 21 is composed of three 20V battery packs connected in series; 21 consists of three 20V batteries, and two are connected in parallel and the other in series.

It should be understood that the target rated voltage is the voltage input by the user according to the needs of the power tool. For example, as shown in FIG. 3, the battery pack 21 is composed of four 20V battery packs connected in series, and the user can pass the knob A according to the rated voltage of the power tool. By selecting the target rated voltage, such as 36V, the black arrow on the knob A can be aligned to the 2*20V position, and the voltage adjusting unit 22 can select the battery packs in series to operate. Of course, the voltage regulating unit 22 can also select four 20V battery packs to work, and the two in parallel are connected in series.

In other words, the number of battery packs selected for operation by the voltage adjustment unit 22 can be determined according to the connection relationship between the battery packs set in advance, for example, four 20V battery packs (number: 1#, 2#, 3#, 4) #) After the series connection is made to form the battery pack 21, when 2*20V is selected, the voltage adjustment unit 22 can select 1# and 2# or 2# and 3# or 3# and 4# to operate.

Similarly, in order to improve the use efficiency of the battery pack, the under-voltage protection voltage of the battery pack 21 composed of a plurality of batteries should be greater than or equal to the rated voltage of the power tool.

It should be noted that, in the PWM adaptive voltage regulation, the output voltage of the battery connecting portion 20 corresponding to the large load is appropriately increased, that is, the duty ratio is increased; and the output voltage of the battery connecting portion 20 corresponding to the small load is appropriately lowered, that is, The duty ratio is reduced, thereby achieving an effect of high efficiency and single package capability in all working conditions.

Further, when the number of battery packs in the working state is at least two, in order to ensure the working performance of the battery pack, the power tool 100 may further be provided with a battery management module, and the battery management module is used to work in multiple battery packs. In the state, the battery pack is equalized according to the voltage of each battery pack in the working state, for example, the battery pack with higher control voltage is preferentially discharged, and when all the voltages of the battery packs in the working state are the same, all the control can be controlled. The battery pack in operation is discharged at the same time.

In some embodiments of the present invention, the operating parameters of the motor 10 satisfy the preset conditions including: the terminal voltage of the motor 10 is equal to the rated voltage of the power tool 100, or the rotational speed of the motor 10 is equal to the rated speed of the motor 10.

As shown in FIG. 5, the power tool 100 further includes a motor detecting module 50 connected to the motor 10 and the control unit 40, respectively, and the motor detecting module 50 is configured to detect the terminal voltage of the motor 10 or the rotational speed of the motor 10. The control unit 40 is further configured to adjust the duty ratio of the control signal according to the relationship between the terminal voltage of the motor 10 and the rated voltage of the power tool 100 or the relationship between the rotational speed of the motor 10 and the rated rotational speed of the motor 10.

Specifically, when the terminal voltage of the motor 10 is less than the rated voltage of the power tool 100, the control unit 40 increases the duty ratio of the control signal to increase the terminal voltage of the motor 10 until the terminal voltage of the motor 10 is equal to the rated value of the power tool 100. Voltage; When the rotational speed of the motor 10 is less than the rated rotational speed of the motor 10, the control unit 40 increases the duty ratio of the control signal to increase the rotational speed of the motor 10, and the rotational speed of the motor 10 is equal to the rated rotational speed of the motor 10. It can be understood that the driving unit 30 and the motor detecting module 50 constitute a feedback circuit, and the control unit 40 can implement closed-loop control of the terminal voltage of the motor 10 according to the feedback circuit.

In this embodiment, the control unit 40 can adjust the duty ratio of the control signal when the power tool 100 is turned on from a preset initial safety duty cycle to gradually increase in a preset step until the terminal voltage of the motor 10 is equal to the power tool. The rated voltage of 100 or the rotational speed of the motor 10 is equal to the rated rotational speed of the motor 10, and the current duty ratio of the control signal is acquired, and the rated voltage currently supplied by the battery connecting portion 20 is determined based on the current duty ratio.

Wherein, the preset initial safety duty ratio may be set according to the maximum value of the rated voltage that the battery connecting portion 20 can provide and the rated voltage of the power tool 100, for example, the maximum rated voltage that the battery connecting portion 20 can provide. For Umax, the rated voltage of the power tool 100 is U0, then the preset initial safety duty ratio may be any value less than U0/Umax to prevent the battery connector 20 from burning the motor 10 or the power tool when the battery is connected at a high voltage. Other electronic devices in 100.

Further, as shown in FIG. 6, the power tool 100 further includes a first battery detecting module 60 for detecting the voltage or internal resistance of the battery pack in an operating state when the power tool 100 starts operating. The control unit 40 is further configured to determine the rated voltage provided by the battery connecting portion 20 according to the voltage or internal resistance of the battery pack in the working state, and call the corresponding subroutine to control the motor according to the rated voltage.

The subroutine includes a duty cycle subroutine, that is, a duty ratio adjustment subroutine corresponding to the rated voltage provided by the battery connecting portion 20.

Optionally, the subroutine may further include a battery protection subroutine, such as an overcurrent protection subroutine, an overtemperature protection subroutine, an undervoltage protection subroutine, and the like.

Further, the power tool 100 may further include a second battery detecting module for detecting the voltage and/or operating current of the battery pack in the working state of the battery connecting portion 20 in real time during the operation of the power tool 100. The control unit 40 is further configured to: when the voltage of the battery pack in the working state is less than the corresponding undervoltage voltage, and/or, when the operating current of the battery pack in the working state is greater than the corresponding current threshold and continue for a preset time The power supply circuit is disconnected by controlling the battery connection portion 20 to stop the motor 10 from operating. Thereby, undervoltage protection and/or overcurrent protection of the power tool can be achieved, and damage of the motor can be reduced. Wherein, the current threshold and the preset time can be calibrated according to the actual working circuit of the battery connecting portion 20.

For example, during the operation of the power tool 100, the second battery detecting module detects the voltage of the battery connecting portion 20 in real time, and sends the voltage detecting result to the control unit 40. The control unit 40 determines the battery pack in the battery connecting portion 20 according to the voltage detecting result. (such as 20V battery pack) whether the voltage is less than the preset undervoltage voltage (such as 12.5V), if so, the control unit 40 determines the battery undervoltage, and controls the power switch tube in the drive unit 30 to disconnect, to cut off the battery The power supply circuit of the connecting portion 20 stops the operation of the motor 10, thereby achieving undervoltage protection of the battery connecting portion 20.

During the operation of the power tool 100, the second battery detecting module can detect the operating current of the battery connecting portion 20 in real time, and send the current detecting result to the control unit 40. The control unit 40 determines the working of the battery connecting portion 20 according to the current detecting result. Whether the current is greater than a current threshold (eg, 25A), and if so, the motor detection module 50 further records the duration of the operating current being greater than the preset current threshold. If the duration is longer than the preset time (eg, 2 s), the control unit 40 determines that the battery connecting portion 20 is overcurrent, and controls the power switch tube in the driving unit 30 to be disconnected to cut off the power supply circuit of the battery connecting portion 20, so that the motor 10 is turned off. The operation is stopped, thereby achieving overcurrent protection of the battery connecting portion 20.

In this example, the control unit 40 is further configured to acquire the voltage change amount of the battery connection portion 20 (such as the voltage change amount of each battery pack in the working state, or the total voltage of all the battery packs in the working state). The amount of change), and when the amount of voltage change of the battery pack (such as the voltage change amount of the at least one battery pack or the total voltage change amount) is greater than or equal to the corresponding preset voltage value, if the terminal voltage of the motor 10 is smaller than that of the power tool 100 The rated voltage, the control unit 40 increases the duty ratio of the control signal so that the terminal voltage of the motor 10 reaches the rated voltage of the power tool 100 again, or if the rotational speed of the motor 10 is less than the rated speed of the motor 10, the control unit 40 By increasing the duty cycle of the control signal, the rotational speed of the motor 10 again reaches the rated rotational speed of the motor 10. Alternatively, the amount of voltage change of the battery connection portion 20 may also be the total voltage variation amount of all the battery packs in an operating state.

It should be noted that, if the rated voltage provided by the battery connecting portion 20 is large, for example, the rated voltage of the battery connecting portion 20 is provided by two battery packs with a rated voltage of 18V, which is 36V, and the rated voltage of the power tool 100 is 18V. There may be a case where the amount of voltage change is large, which affects the terminal voltage of the motor 10 or the rotational speed of the motor 10, that is, the terminal voltage of the motor 10 or the rotational speed of the motor 10 is abrupt. At this time, the control unit 40 acquires the voltage change amount of each battery pack in real time, and adjusts when the difference between the voltage values of the at least one battery pack acquired twice consecutively is greater than or equal to a preset voltage value such as 0.5V. The duty cycle of the control signal is such that the terminal voltage of the motor 10 is equal to the rated voltage of the power tool 100, or the rotational speed of the motor 10 is equal to the rated speed of the motor 10.

In some embodiments of the present invention, the power tool 100 further includes a storage module in which the operating condition database is pre-stored, wherein the operating condition database includes the power tool 100 in various operating conditions (such as different ratings provided by the battery connecting portion 20). Correspondence between load and duty ratio under no-load, small load, large load, full load, etc. under voltage, the correspondence may be stored in the form of a table or a curve. In this example, control unit 40 also adjusts the duty cycle of the control signal based on the magnitude of the load of motor 10.

It should be understood that when the rated voltage is constant, the load is positively correlated with the operating current of the motor 10, that is, the larger the load, the larger the operating current of the motor 10, so the corresponding relationship between the load and the duty ratio under various operating conditions can be replaced with The corresponding relationship between the operating current and the duty ratio under various operating conditions, the motor detecting module 50 is further configured to detect the operating current of the motor, and the control unit 40 can adjust the duty ratio of the control signal according to the operating current of the motor 10.

Optionally, in order to improve the working efficiency of the control unit 40, a main program, a subroutine, and the like required for the control unit may be pre-stored in the storage module.

As shown in FIG. 7, the power tool 100 further includes a wireless communication module 70. The control unit 40 communicates with the server 200 through the wireless communication module 70 to acquire control parameters of the corresponding power tool 100 from the server 200 to operate according to the control parameters. And/or, transmitting the operating parameters of the power tool 100 to the server 200 to store the operating parameters in the history database of the server 200, so that the server 200 compares the control parameters corresponding to the power tool 100 according to the operating parameters in the historical database. The database is optimized (such as using big data processing methods, etc.). Thus, through the self-learning and remote learning functions of the power tool 100, when the power tool 100 encounters the same working condition again, the previous duty cycle data can be automatically invoked, thereby improving the control efficiency of the power tool and increasing the power tool. Scope of application.

The working principle of the power tool according to the embodiment of the present invention will be described below with reference to FIG. 5, FIG. 6, and FIG. 8 to FIG. 13, respectively.

Embodiment 1:

In this embodiment, as shown in FIG. 8, the CPU determines the rated voltage supplied from the battery connecting portion 20 based on the voltage of the motor 10 terminal, and adjusts the duty ratio and performs undervoltage protection according to the voltage of the motor 10 terminal.

Specifically, as shown in FIG. 5 and FIG. 8 , the main switch of the power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the CPU adjusts the duty ratio of the MOSFET from a preset initial safety duty ratio of 0 to a preset step. The distance X% (such as 1%, 3%, 5%, etc.) is gradually increased until the terminal voltage of the motor 10 is equal to the rated voltage of the power tool 18V, and the current duty ratio of the MOSFET is obtained. If the current duty ratio is 100%, it can be determined that the battery connection portion 20 is a 20V battery pack. If the terminal voltage of the motor 10 is detected to be less than 12.5V during the operation of the motor, that is, the undervoltage voltage of the 20V battery pack is reached. The CPU gives an alarm prompt or directly shuts down the motor 10. Wherein, when the voltage of the motor 10 terminal is greater than or equal to 12.5 V and less than or equal to 18 V, the duty ratio is maintained at 100%.

If the duty ratio of the MOSFET is less than 100% when the voltage at the motor terminal 10 is equal to 18 V, it is judged that the battery connection portion 20 is another voltage battery pack. When the voltage of the motor 10 terminal is equal to 18 V and the current duty ratio is 33% or less, it is judged that the battery connecting portion 20 is a 60 V battery pack. During the operation of the motor 10, the voltage of the motor 10 terminal is detected in real time, and when the terminal voltage is less than 18V, the duty ratio is increased by a preset step X% to maintain the terminal voltage at 18V. When the motor terminal voltage is less than or equal to 18V and the corresponding duty ratio reaches 48%, it is judged that the 60V battery pack is under voltage, then the CPU gives an alarm prompt or directly shuts down the motor 10.

If the duty ratio of the MOSFET is less than 100% when the voltage at the motor terminal 10 is equal to 18 V, it is judged that the battery connection portion 20 is another voltage battery pack. When the voltage of the motor 10 terminal is equal to 18 V and the current duty ratio is greater than 33% and less than or equal to 50%, it is judged that the battery connecting portion 20 is a 40V battery pack. During the operation of the motor 10, the voltage of the motor 10 terminal is detected in real time, and when the terminal voltage is less than 18V, the duty ratio is increased by a preset step X% to maintain the terminal voltage at 18V. When the motor terminal voltage is less than or equal to 18V and the corresponding duty ratio reaches 72%, it is judged that the 40V battery pack is under voltage, and the CPU gives an alarm prompt or directly shuts down the motor 10.

Embodiment 2:

In this embodiment, the rated voltage supplied from the battery connecting portion 20 is determined in accordance with the output voltage or resistance of the battery connecting portion 20, and the duty ratio of the control signal is adjusted in accordance with the voltage of the motor terminal 10 and undervoltage protection is performed.

Specifically, as shown in FIG. 6 and FIG. 9, the main switch of the power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the main program is controlled. The CPU acquires the output voltage U of the battery connecting portion 20, determines the rated voltage provided by the battery connecting portion 20 according to U, and calls a corresponding protection subroutine according to the rated voltage (such as an overtemperature protection subroutine, an overcurrent protection subroutine, and undervoltage protection). Subprograms, etc.). For example, as shown in FIG. 10, when the undervoltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the voltage of the motor 10 terminal, and determines the undervoltage of the battery pack when the duty ratio is equal to 72%. , CPU alarm or shutdown protection of motor 10.

Similarly, as shown in FIG. 6 and FIG. 11, the main switch of the power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the main program is controlled. The CPU acquires the resistance R of the battery connection portion 20, determines the rated voltage provided by the battery connection portion 20 according to R, and calls a corresponding protection subroutine according to the rated voltage (eg, an overtemperature protection subroutine, an overcurrent protection subroutine, an undervoltage protection subroutine). Program, etc.). For example, as shown in FIG. 10, when the undervoltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the voltage of the motor 10 terminal, and determines the undervoltage of the battery pack when the duty ratio is equal to 72%. , CPU alarm or shutdown protection of motor 10.

Embodiment 3:

In this embodiment, as shown in FIG. 12, the CPU determines the rated voltage supplied from the battery connecting portion 20 based on the rotational speed of the motor 10, and adjusts the duty ratio and performs undervoltage protection according to the rotational speed of the motor 10.

Specifically, as shown in FIG. 5 and FIG. 12, the main switch of the power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the CPU adjusts the duty ratio of the MOSFET from a preset initial safety duty ratio of 0 to a preset step. The distance X% (such as 1%, 3%, 5%, etc.) is gradually increased until the speed of the motor 10 is equal to the rated speed of the motor 10, and the current duty ratio of the MOSFET is obtained. If the current duty ratio is 100%, it can be determined that the battery connection portion 20 is a 20V battery pack. If the terminal voltage of the motor 10 is detected to be less than 12.5V during the operation of the motor, that is, the undervoltage voltage of the 20V battery pack is reached. The CPU gives an alarm prompt or directly shuts down the motor 10. Wherein, when the voltage of the motor 10 terminal is greater than or equal to 12.5 V and less than or equal to 18 V, the duty ratio is maintained at 100%.

If the rotational speed of the motor 10 is equal to the rated rotational speed of the motor and the duty ratio of the MOSFET is less than 100%, it is judged that the battery connecting portion 20 is another voltage battery pack. When the rotational speed of the motor 10 is equal to the rated rotational speed and the current duty ratio is 33% or less, it is judged that the battery connecting portion 20 is a 60V battery pack. During the operation of the motor 10, the rotational speed of the motor 10 is detected in real time, and when the rotational speed is less than the rated rotational speed, the duty ratio is increased by a preset step X% so that the rotational speed maintains the rated rotational speed. When the motor speed is less than or equal to the rated speed and the corresponding duty ratio reaches 48%, it is judged that the 60V battery pack is under voltage, then the CPU gives an alarm prompt or directly shuts down the motor 10.

If the rotational speed of the motor 10 is equal to the rated rotational speed of the motor, and the duty ratio of the MOSFET is less than 100%, it is judged that the battery connecting portion 20 is another voltage battery pack. When the rotational speed of the motor 10 is equal to the rated rotational speed and the current duty ratio is greater than 33% and less than or equal to 50%, it is determined that the battery connecting portion 20 is a 40V battery pack. During the operation of the motor 10, the rotational speed of the motor 10 is detected in real time, and when the rotational speed is less than the rated rotational speed, the duty ratio is increased by a preset step X% so that the rotational speed maintains the rated rotational speed. When the motor speed is less than or equal to the rated speed and the corresponding duty ratio reaches 72%, it is judged that the 40V battery pack is under voltage, then the CPU gives an alarm prompt or directly shuts down the motor 10.

It should be noted that when the power tool 100 adopts the 20V motor 10, and the battery connecting portion 20 only includes a single 20V battery pack, the CPU needs to control the motor 10 with a 100% duty ratio, and the motor 10 terminal voltage or battery pack can be detected at this time. Voltage to determine if the battery pack is under voltage. In other words, when the rated voltage of the motor 10 is greater than the undervoltage of the battery connecting portion 20, it is necessary to determine whether the battery connecting portion 20 is undervoltage by detecting the voltage at the motor terminal 10 or the voltage of the battery connecting portion 20. To this end, it is preferable that the battery connecting portion 20 whose undervoltage is equal to or higher than the rated voltage of the motor 10 supplies power to the electric power tool 100.

Embodiment 4:

In this embodiment, the rated voltage supplied from the battery connecting portion 20 is determined in accordance with the output voltage or resistance of the battery connecting portion 20, and the duty ratio of the control signal and the undervoltage protection are adjusted in accordance with the rotational speed of the motor 10.

Specifically, as shown in FIG. 6 and FIG. 9, the main switch of the power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the main program is controlled. The CPU acquires the output voltage U of the battery connecting portion 20, determines the rated voltage provided by the battery connecting portion 20 according to U, and calls a corresponding protection subroutine according to the rated voltage (such as an overtemperature protection subroutine, an overcurrent protection subroutine, and undervoltage protection). Subprograms, etc.). For example, as shown in FIG. 13, when the undervoltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the rotational speed of the motor 10, and determines the undervoltage of the battery pack when the duty ratio is equal to 72%. , CPU alarm or shutdown protection of motor 10.

Similarly, as shown in FIG. 6 and FIG. 11, the main switch of the power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the main program is controlled. The CPU acquires the resistance R of the battery connection portion 20, determines the rated voltage provided by the battery connection portion 20 according to R, and calls a corresponding protection subroutine according to the rated voltage (eg, an overtemperature protection subroutine, an overcurrent protection subroutine, an undervoltage protection subroutine). Program, etc.). For example, as shown in FIG. 13, when the undervoltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the rotational speed of the motor 10, and determines the undervoltage of the battery pack when the duty ratio is equal to 72%. , CPU alarm or shutdown protection of motor 10.

In addition, when the battery connecting portion 20 includes a battery pack composed of a plurality of batteries, in order to facilitate understanding of the operation principle of the battery connecting portion 20, description will be made below with reference to FIGS. 14 and 15:

As shown in FIG. 14 and FIG. 15, the battery pack 21 is composed of two battery packs (a first battery pack Pack1 and a second battery pack Pack2), and the rated voltages U1 and U2 of each battery pack are equal to or greater than the rated value of the motor 10. Voltage U0.

In the embodiment shown in FIG. 14, the voltage adjusting unit 22 includes a first switch S2 and a second switch S3, wherein one end of the S2 is connected to one end of the start-stop switch S1 of the power tool, and forms a first node a. The other end of the stop switch S1 is connected to the motor 10; one end of the S3 is connected to the other end of the S2, and a second node b is formed, and the other end of the S3 is connected to the input end of the drive unit 30, and forms a third node c; The positive pole is connected to the first node a, the negative pole of Pack1 is connected to the second node b, the positive pole of Pack2 is connected to the second node b, and the negative pole of Pack2 is connected to the third node c.

When both Pack1 and Pack2 are plugged in, S2 and S3 are disconnected, S1 is closed, and Pack1 and Pack2 are connected in series. The rated voltage provided by battery connection unit 20 is U1+U2, which is greater than U0 and PWM step-down output. When Pack1 is removed, S2 is closed, S3 is disconnected, S1 is closed, Pack2 is the working battery pack, and the rated voltage provided by the battery connecting portion 20 is U2, greater than or equal to U0. If U2 is greater than U0, the PWM step-down output, if U2 is equal to U0, then the duty cycle is adjusted to 100%. When Pack2 is removed, S2 is disconnected, S3 is closed, S1 is closed, Pack1 is the working battery pack, and the rated voltage provided by the battery connecting portion 20 is U1, greater than or equal to U0. If U1 is greater than U0, the PWM step-down output, if U1 is equal to U0, and the duty ratio is adjusted to 100%.

In this embodiment, when both battery packs are inserted, the two battery packs are connected in series. If one battery pack is previously de-energized, the package is only removed, and the power tool 100 is still operating normally, and the cost is low.

In the embodiment shown in FIG. 15, the voltage adjusting unit 22 includes: a first diode D1, a second diode D2, a third diode D3, a third switch S4, a fourth switch S5, and a first selection. Switch Relay1 and second selection switch Relay2. Wherein, the cathode of D1 is connected to one end of the start-stop switch S1 of the power tool, the other end of S1 is connected to the motor 10; the cathode of D2 is respectively connected to the cathode of D1 and one end of S1, and the cathode of D3 is connected to the anode of D2, D3 The anode is connected to the input end of the driving unit 30 and forms a fourth node d; one end of S4 is connected to the anode of D1, and the other end of S4 is respectively connected to the anode of D2 and the cathode of D3, and forms a fifth node e; S5 One end of the connection is connected to the fifth node e, and the other end of the S5 is connected to the fourth node d; the first mobile end of the Relay1 is connected to one end of the S4 and the anode of the D1, and the second mobile end of the Relay1 is connected; the first of the Relay2 The mobile end is connected to the fifth node e, and the second mobile end of the Relay 2 is vacant; the positive end of the Pack1 is connected to the fixed end of the Relay1, the negative end of the Pack1 is connected to the fifth node e, the positive end of the Pack2 is connected to the fixed end of the Relay2, and the negative end of the Pack2 is connected. Four nodes d.

When both Pack1 and Pack2 are plugged in, S4 and S5 are disconnected, and S1 is closed. If the port 1 (ie, the fixed end) of Relay1 is connected to port 3 (ie, the first mobile end), the port 1 of Relay 2 (ie, the fixed end) is When port 3 (ie, the first mobile end) is connected, Pack1 and Pack2 are connected in series, and the rated voltage provided by the battery connecting portion 20 is U1+U2, which is greater than U0, and the PWM step-down output. When Pack1 is removed, S4 is closed, S5 is disconnected, S1 is closed, port 1 of Relay1 is connected to port 3, port 1 of Relay 2 is connected to port 3, and Pack 2 is a working battery pack, and the rated voltage provided by the battery connecting portion 20 is U2 is greater than or equal to U0. If U2 is greater than U0, the PWM step-down output. If U2 is equal to U0, the duty cycle is adjusted to 100%. When Pack2 is removed, S4 is disconnected, S5 is closed, S1 is closed, and Pack1 is the working battery pack. The rated voltage provided by battery connection unit 20 is U1, greater than or equal to U0. If U1 is greater than U0, PWM step-down output, if U1 is equal to U0, and the duty ratio is adjusted to 100%. When Pack1 is first discharged to the protection point, port 1 of Relay1 is switched to be connected to port 2 (ie, the second mobile end), and Pack1 is disconnected. Only Pack2 is discharged, and the discharge circuit is: Pack2+→Relay2(1-3)→S1→ M→Mosfet→Pack2-. When Pack2 is first discharged to the protection point, port 1 of Relay2 is switched to be connected to port 2 (ie, the second mobile end), and Pack2 is disconnected. Only Pack1 is discharged, and the discharge circuit is: Pack1+→Relay1(1-3)→D1→ S1→M→Mosfet→D3→Pack1-.

In this embodiment, when two battery packs are inserted, the series connection of the two battery packs can be realized, and if one battery pack is first dead, there is no need to manually remove the under-pressure pack, which is convenient to use.

In summary, the power tool according to the embodiment of the present invention adjusts the duty ratio of the control signal by the control unit when the battery pack of different rated voltages greater than its own rated voltage is supplied with power, so that the terminal voltage of the motor is equal to the rated value of the power tool. The voltage or the speed of the motor is equal to the rated speed of the motor. Therefore, the power tool can be adapted to the battery pack of different rated voltages, the adaptation range of the power tool voltage is improved, and the efficiency of the battery pack is improved.

Based on the power tool of the above embodiment, the present invention proposes a power tool system.

Referring to Fig. 7, the power tool system includes the power tool 100 and the server 200 of the above embodiment, wherein the server 200 and the power tool 100 perform wireless communication.

In this embodiment, the power tool 100 is configured to acquire control parameters of the corresponding power tool 100 from the server 200 to operate according to the control parameters, and/or send the operating parameters of the power tool 100 to the server 200 to work. The parameters are stored in the history database of the server 200 to cause the server 200 to optimize the control parameter database corresponding to the power tool 100 based on the operating parameters in the history database.

It should be noted that other specific embodiments of the power tool system of the embodiment of the present invention can refer to the specific embodiment of the power tool of the above embodiment of the present invention.

According to the electric power tool system of the embodiment of the present invention, by the wireless power communication between the power tool and the server of the above embodiment, the power tool can acquire the control parameter of the corresponding power tool from the server to operate according to the control parameter, and/or The working parameters of the power tool are sent to the server to store the working parameters in the historical database of the server, so that the server optimizes the control parameter database corresponding to the power tool according to the working parameters in the historical database, thereby effectively solving the electric problem The limited storage space of the tool and the limited processing speed of the control unit are beneficial to improve the efficiency of use of the power tool.

In the description of the present specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means a specific feature described in connection with the embodiment or example. A structure, material or feature is included in at least one embodiment or example of the invention. In the present specification, the schematic representation of the above terms is not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, various embodiments or examples described in the specification, as well as features of various embodiments or examples, may be combined and combined.

It should be understood that portions of the invention may be implemented in hardware, software, firmware or a combination thereof. In the above-described embodiments, multiple steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware and in another embodiment, it can be implemented by any one or combination of the following techniques well known in the art: discrete with logic gates for implementing logic functions on data signals Logic circuits, application specific integrated circuits with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), and the like.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules. The integrated modules, if implemented in the form of software functional modules and sold or used as stand-alone products, may also be stored in a computer readable storage medium.

The above mentioned storage medium may be a read only memory, a magnetic disk or an optical disk or the like. Although the embodiments of the present invention have been shown and described, it is understood that the above-described embodiments are illustrative and are not to be construed as limiting the scope of the invention. The embodiments are subject to variations, modifications, substitutions and variations.

Claims

A power tool characterized by comprising a battery connecting portion for detachably connecting a first battery pack and a second battery pack, the first battery pack having a rated output voltage greater than the second battery pack Rated output voltage;

Motor as a power source;

a driving unit, located between the battery connecting portion and the motor, including a power switch tube for driving the motor to operate;

a control unit, configured to output a control signal to the control end of the power switch tube, and adjust a duty ratio of the control signal to make the speed of the motor equal to a preset speed, so that the motor can adapt to the first battery pack or The rated output voltage of the second battery pack, the rated voltage of the motor being lower than at least one of the rated output voltages of the first battery pack and the second battery pack.
The power tool according to claim 1, wherein said motor has a rated voltage between a rated output voltage of said first battery pack and a rated output voltage of said second battery pack.
The electric power tool according to claim 1, wherein the rated output voltage of the first battery pack is at least 20% higher than the rated voltage of the motor, and the rated output voltage of the second battery pack is not lower than the rated voltage of the motor. 40%.
The electric power tool according to claim 2, wherein said electric power tool further comprises a rotation speed detecting module for acquiring a rotation speed of said motor, and said control unit adjusts said duty ratio of said control signal to cause said motor Running at a preset speed at a preset speed that is less than or equal to the rated speed of the motor.
The power tool according to claim 4, wherein said power tool is activated, said control unit gradually increasing a duty ratio of said control signal, if said speed detected by said speed detecting module is equal to a first predetermined speed And the control unit controls the motor to run at a steady speed at a first preset speed; otherwise, the control unit controls the motor to run at a third preset speed, and the first preset speed is less than or equal to the The rated speed of the motor, the third preset speed is less than or equal to a second preset speed, and the second preset speed is a maximum speed of the power tool when the second battery pack is powered.
The power tool according to claim 5, wherein the power tool further comprises a first speed control device and a second speed control device, wherein the first speed control device corresponds to a first preset speed, the second The speed regulating device corresponds to the third preset speed, the first preset speed is greater than the third preset speed, and the third preset speed is less than the second preset speed.
The electric power tool according to claim 6, wherein said control unit gradually increases a duty ratio of said control signal when said first speed regulating device is operated and said power tool is activated, The control unit controls the motor to run at a steady speed at the first preset speed, and the control unit controls the motor to control the second preset. The speed runs at a steady speed.
The electric power tool according to claim 6, wherein said second speed regulating device is operated, and said control unit gradually increases a duty ratio of said control signal after said power tool is activated until said When the speed obtained by the rotation speed detecting module is equal to the third preset speed, the control unit controls the motor to maintain the third preset speed running.
The electric power tool according to claim 1, wherein said electric power tool further comprises a power tool housing, said battery connecting portion is disposed on said power tool housing, and said second battery pack includes a first battery The package and the second battery pack, the first battery pack and the second battery pack are connected in series to provide electrical power to the power tool.
The power tool according to claim 1, wherein said battery connecting portion comprises a first power port and a second power port, said first power port being for electrically connecting an adapter, said adapter being detachably connected to On the housing of the power tool, the adapter is provided with a plurality of battery pack connecting seats, and the plurality of battery packs are connected in series or in parallel to form a first battery pack, and the adapter is provided with a voltage output port electrically connected to the power input port of the power tool. Provide power to power tools.
The power tool according to claim 10, wherein said adapter is detachably mounted in a housing of the backpack assembly, and said backpack assembly is coupled to the power tool via the connector assembly to provide electrical power to the power tool.
The power tool according to claim 10 or 11, wherein the adapter is provided with four battery pack connectors, and the output voltage of the four battery pack connectors in series is greater than the rated voltage of the motor.
The power tool of claim 11 wherein said connecting assembly comprises a cable.
A power tool according to claim 1, wherein said power tool further comprises a voltage detecting module for detecting a terminal voltage of said motor, said control unit adjusting said duty ratio of said control signal to The terminal voltage of the motor is less than or equal to the rated voltage of the power tool.
The power tool according to claim 14, wherein said first battery pack includes a first battery pack and a second battery pack, and said power tool further includes a first switch and a second switch, said first switch One end of the power tool is connected to one end of the start-stop switch of the power tool, and forms a first node, wherein the other end of the start-stop switch is connected to the motor; one end of the second switch and the first switch The other end of the second battery is connected to the input end of the driving unit and forms a third node; wherein the positive pole of the first battery pack is connected to the first node a node, a cathode of the first battery pack is connected to the second node, a cathode of the second battery pack is connected to the second node, a cathode of the second battery pack is connected to the third node, and When the first battery pack is not connected, the first switch is in a closed state, when the first battery pack is accessed, the first switch is in an off state, and when the second battery pack is not connected, The second switch is in a closed state, the second When the packet access pool, the second switch is in the off state.
The power tool according to claim 14, wherein the first battery pack comprises a first battery pack and a second battery pack, and the power tool further comprises:

a first diode, a cathode of the first diode is connected to one end of the start-stop switch of the power tool, wherein the other end of the start-stop switch is connected to the motor;

a second diode, a cathode of the second diode is respectively connected to a cathode of the first diode and one end of the start-stop switch;

a third diode, a cathode of the third diode is connected to an anode of the second diode, an anode of the third diode is connected to an input end of the driving unit, and forms a fourth node;

a third switch, one end of the third switch is connected to an anode of the first diode, and the other end of the third switch is respectively connected to an anode of the second diode and the third diode The cathodes are connected and form a fifth node;

a fourth switch, one end of the fourth switch is connected to the fifth node, and the other end of the fourth switch is connected to the fourth node;

a first selection switch, wherein the first moving end of the first selection switch is respectively connected to one end of the third switch and an anode of the first diode, and the second moving end of the first selection switch is connected ;

a second selection switch, the first moving end of the second selection switch is connected to the fifth node, and the second moving end of the second selection switch is connected to the air;

The anode of the first battery pack is connected to the fixed end of the first selection switch, the cathode of the first battery pack is connected to the fifth node, and the anode of the second battery pack is connected to the second selection. a fixed end of the switch, a negative pole of the second battery pack is connected to the fourth node, and when the first battery pack is not connected, the third switch is in a closed state, and when the first battery pack is connected The third switch is in an off state, the fourth switch is in a closed state when the second battery pack is not connected, and the fourth switch is in an off state when the second battery pack is accessed. .
The power tool according to claim 14, further comprising:

a storage module, wherein the storage module prestores a working condition database, wherein the working condition database includes a correspondence between a load and a duty ratio of the electric tool under various working conditions;

Wherein, the control unit further adjusts the duty ratio of the control signal according to the load size, so that the terminal voltage of the motor is equal to the rated voltage of the power tool.
The power tool according to claim 14, further comprising:

a wireless communication module, wherein the control unit communicates with the server through the wireless communication module to acquire a control parameter corresponding to the power tool from the server to operate according to the control parameter, and/or The operating parameters of the power tool are sent to the server to store the working parameters in a history database of the server, so that the server corresponds to the power tool according to working parameters in the historical database. Control the parameter database for optimization.
The power tool according to claim 1, wherein the switching frequency of the power switch tube ranges from 4 to 20 Khz.
The electric power tool according to claim 1, wherein said motor is one of a brush motor, a brushless motor, a switched reluctance motor, or a high frequency AC induction motor.
A power tool control method, the power tool including a battery connecting portion for detachably connecting a first battery pack and a second battery pack, wherein the rated output voltage of the first battery pack is greater than a rated output voltage of the second battery pack, the rated voltage of the motor being lower than at least one of the rated output voltages of the first battery pack and the second battery pack, wherein the method comprises:

Step S1, after the power tool is started, gradually increasing the duty ratio of the control signal;

In step S2, it is determined whether the rotational speed of the motor is equal to the preset rotational speed, wherein the preset rotational speed is less than or equal to the rated rotational speed of the motor, and if so, step S3 is performed, otherwise step S4 is performed;

Step S3, controlling the motor to maintain the first preset speed operation;

Step S4, it is determined whether the duty ratio is equal to the preset duty cycle, and if so, step S5 is performed, otherwise, step S1 is performed;

In step S5, the control motor maintains the second preset speed operation, wherein the second preset speed is less than or equal to the speed corresponding to the preset duty ratio.