CN111919378B

CN111919378B - Electric tool and control method

Info

Publication number: CN111919378B
Application number: CN201980022875.2A
Authority: CN
Inventors: 张传兵; 陆骏; 钟红风
Original assignee: Positec Power Tools Suzhou Co Ltd
Current assignee: Positec Power Tools Suzhou Co Ltd
Priority date: 2018-04-18
Filing date: 2019-04-18
Publication date: 2022-07-12
Anticipated expiration: 2039-04-18
Also published as: CN110401385B; CN110401385A; CN111919378A; WO2019201300A1

Abstract

The invention relates to an electric tool and a control method, the electric tool comprises a battery connecting part, the battery connecting part is used for detachably connecting a first battery pack and a second battery pack, and the rated output voltage of the first battery pack is greater than that of the second battery pack; a motor as a power source; the driving unit is positioned between the battery connecting part and the motor, comprises a power switch tube and is used for driving the motor to operate; and the control unit is used for outputting a control signal to the control end of the power switch tube, and adjusting the duty ratio of the control signal to enable the rotating speed of the motor to be equal to a preset rotating speed so that the motor can adapt to the rated output voltage of the first battery pack or the second battery pack, and the rated voltage of the motor is lower than at least one of the rated output voltages of the first battery pack and the second battery pack.

Description

Electric tool and control method

Cross reference to related citations

The present application claims priority from chinese patent application No. 201810349671.7 entitled "power tool and power tool system," filed on 2018, 4, month 18, the entire contents of which are incorporated herein by reference.

Technical Field

The invention relates to the technical field of electromotion, in particular to an electric tool which can be adapted to a battery pack with a voltage lower than the rated voltage of the electric tool and can also be adapted to a battery pack with a voltage higher than the rated voltage of the tool.

Background

Cordless tools (cordless tools) or cordless power tools (cordless power tools) employ a battery pack that is removably mounted on the tool as an energy supply unit, and are called cordless power tools because the battery pack supplies Direct Current (DC) power and a power cord (cord) for Alternating Current (AC) power is not used.

Like most electromechanical products, a cordless electric tool mainly comprises an energy unit (a battery pack), a power head (a motor), a transmission system (a gear box), a control unit (a switch and a control panel), an execution unit (a working head) and the like. At present, when designing and producing electric tools, the rated voltage of the tools is matched with the voltage of an energy unit (battery pack), namely, the rated voltage of the corresponding tool of the battery pack with the rated voltage of 18V is also determined to be 18V. If the voltage of the battery is too high, the motor can run in an overload mode, and is easy to burn out or the motor runs in an overspeed mode to cause safety problems; if the battery voltage is too low, the motor runs under load, so that the output of the motor is reduced and even the motor cannot work.

Since the interfaces of the different voltage battery packs of most companies at present are incompatible, i.e. the different voltage battery packs have corresponding product platforms. The battery packs with different voltages cannot be inserted into other voltage platforms, so that the battery packs with various specifications are inevitably generated, the battery packs are not suitable for mass production, and the logistics management cost of production, sales and maintenance is high.

In order to solve the problems, B & D company has provided FLEX 20V-60V universal battery pack, which realizes the change of battery output voltage by controlling the change of the serial and parallel connection modes of the battery core body through a mechanical switch, and can be plugged in 20V and 60V product lines at the same time. However, the battery pack has the advantages of complex structure, high process requirement, high cost and low reliability, and can only realize the compatibility of two (20V/60V) voltage product lines and batteries.

Disclosure of Invention

To overcome the drawbacks of the prior art, the present invention provides a more compatible power tool that can accommodate a battery pack having a voltage that is lower or higher than the rated voltage of the motor by a certain range.

The technical scheme adopted by the invention for solving the problems in the prior art is as follows:

an electric tool includes a battery connecting portion for detachably connecting a first battery pack and a second battery pack, the rated output voltage of the first battery pack being greater than the rated output voltage of the second battery pack;

a motor as a power source;

the driving unit is positioned between the battery connecting part and the motor, comprises a power switch tube and is used for driving the motor to operate;

and the control unit is used for outputting a control signal to the control end of the power switch tube, and adjusting the duty ratio of the control signal to enable the rotating speed of the motor to be equal to a preset rotating speed so that the motor can adapt to the rated output voltage of the first battery pack or the second battery pack, and the rated voltage of the motor is 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 electric tool further comprises a rotation speed detection module for acquiring the rotation speed of the motor, and the control unit makes the motor operate at a preset speed and a stable speed by adjusting the duty ratio of the control signal, wherein the preset rotation speed is less than or equal to the rated rotation speed of the motor.

Preferably, the electric tool is started, the control unit gradually increases the duty ratio of the control signal, if the rotating speed obtained by the rotating speed detection module is equal to a first preset rotating speed, the control unit controls the motor to operate at the first preset rotating speed at a stable speed, otherwise, the control unit controls the motor to operate at the third preset rotating speed at a stable speed, the first preset rotating speed is less than or equal to the rated rotating speed of the motor, the third preset rotating speed is less than or equal to a second preset rotating speed, and the second preset rotating speed is the maximum rotating speed of the electric tool when the second battery pack supplies power.

Preferably, the electric tool further comprises a first speed regulating device and a second speed regulating device, the first speed regulating device corresponds to a first preset rotating speed, the second speed regulating device corresponds to a third preset rotating speed, the first preset rotating speed is greater than the third preset rotating speed, and the third preset rotating speed is less than the second preset rotating speed.

Preferably, when the first speed adjusting device is operated and the electric tool is started, the control unit gradually increases the duty ratio of the control signal, if the rotating speed acquired by the rotating speed detecting module is equal to a first preset rotating speed, the control unit controls the motor to operate at the first preset rotating speed at a stable speed, otherwise, the control unit controls the motor to operate at the second preset rotating speed at a stable speed.

Preferably, after the second speed regulating device is operated and the electric tool is started, the control unit gradually increases the duty ratio of the control signal until the rotation speed acquired by the rotation speed detection module is equal to a third preset rotation speed, and the control unit controls the motor to maintain the third preset rotation speed to operate.

Preferably, electric tool still includes the electric tool casing, power source sets up in on the electric tool casing, the second group battery includes first battery package and second battery package, first battery package and second battery package are established ties and are constituteed, do electric tool provides the electric energy.

Preferably, power source includes first power source and second power source, first power source is used for the electricity to connect the adapter, adapter detachable connects on electric tool's casing, be provided with a plurality of battery package connecting seats on the adapter, a plurality of battery package series connection or parallel connection form first group battery, are provided with voltage output port electricity on the adapter and connect electric tool's power input port, provide the electric energy for electric tool.

Preferably, the adapter is detachably mounted in a shell of the backpack assembly, and the backpack assembly is connected with the electric tool through the connecting assembly to provide electric energy for the electric tool.

Preferably, the adapter is provided with four battery pack connecting seats, and the output voltage of the four battery pack connecting seats after being connected in series is greater than the rated voltage of the motor.

Preferably, the connection assembly comprises a cable.

Preferably, the electric tool further comprises a voltage detection module for detecting a terminal voltage of the motor, and the control unit adjusts a duty ratio of the control signal so that the terminal voltage of the motor is smaller than or equal to a rated voltage of the electric tool.

Preferably, the first battery pack comprises a first battery pack and a second battery pack, the electric tool further comprises a first switch and a second switch, one end of the first switch is connected with one end of a start-stop switch of the electric tool and forms a first node, and the other end of the start-stop switch is connected with the motor; one end of the second switch is connected with the other end of the first switch to form a second node, and the other end of the second switch is connected with the input end of the driving unit to form a third node; the positive pole of the first battery pack is connected with the first node, the negative pole of the first battery pack is connected with the second node, the positive pole of the second battery pack is connected with the second node, the negative pole of the second battery pack is connected with 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 connected, the first switch is in an open state, when the second battery pack is not connected, the second switch is in a closed state, and when the second battery pack is connected, the second switch is in an open state.

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

the cathode of the first diode is connected with one end of a start-stop switch of the electric tool, and the other end of the start-stop switch is connected with the motor;

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

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

one end of the third switch is connected with the anode of the first diode, and the other end of the third switch is respectively connected with the anode of the second diode and the cathode of the third diode to form a fifth node;

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

a first moving end of the first selection switch is respectively connected with one end of the third switch and the anode of the first diode, and a second moving end of the first selection switch is in idle connection;

a first moving end of the second selector switch is connected with the fifth node, and a second moving end of the second selector switch is in idle connection;

wherein, the positive pole of first battery package connects first select switch's stiff end, the negative pole of first battery package connects the fifth node, the positive pole of second battery package connects the stiff end of second select switch, the negative pole of second battery package connects the fourth node, just when first battery package is not connected, the third switch is in the on-state, when first battery package connects, the third switch is in the off-state, when second battery package is not connected, the fourth switch is in the on-state, when second battery package connects, the fourth switch is in the off-state.

Preferably, the method further comprises the following steps:

the storage module is pre-stored with a working condition database, wherein the working condition database comprises the corresponding relation between the load and the duty ratio of the electric tool under various working conditions;

the control unit is used for adjusting 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 electric tool.

Preferably, the method further comprises the following steps:

the control unit is communicated with a server through the wireless communication module to acquire control parameters corresponding to the electric tool from the server to work according to the control parameters, and/or the working parameters of the electric tool are sent to the server to be stored in a historical database of the server, so that the server optimizes the control parameter database corresponding to the electric tool according to the working parameters in the historical database.

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

Preferably, the motor is one of a brush motor, a brushless motor, a switched reluctance motor or a high-frequency alternating current induction motor.

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

Preferably, the battery pack includes: the rated voltage of the battery pack consisting of a plurality of battery packs is greater than or equal to the rated voltage of the electric tool; and the voltage regulating unit is used for selecting the battery pack to work according to the rated voltage of the electric tool.

Preferably, when the battery pack is composed of two battery packs, the two battery packs are respectively denoted as a first battery pack and a second battery pack, and the voltage adjusting unit includes: one end of the first switch is connected with one end of a start-stop switch of the electric tool and forms a first node, and the other end of the start-stop switch is connected with the motor; one end of the second switch is connected with the other end of the first switch to form a second node, and the other end of the second switch is connected with the input end of the driving module to form a third node; the positive pole of the first battery pack is connected with the first node, the negative pole of the first battery pack is connected with the second node, the positive pole of the second battery pack is connected with the second node, the negative pole of the second battery pack is connected with 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 connected, the first switch is in an open state, when the second battery pack is not connected, the second switch is in a closed state, and when the second battery pack is connected, the second switch is in an open state.

Preferably, when the battery pack is composed of two battery packs, the two battery packs are respectively denoted as a first battery pack and a second battery pack, and the voltage adjusting unit includes: the cathode of the first diode is connected with one end of a start-stop switch of the electric tool, and the other end of the start-stop switch is connected with the motor; the cathode of the second diode is respectively connected with the cathode of the first diode and one end of the start-stop switch; a cathode of the third diode is connected with an anode of the second diode, and an anode of the third diode is connected with an input end of the driving module and forms a fourth node; one end of the third switch is connected with the anode of the first diode, and the other end of the third switch is respectively connected with the anode of the second diode and the cathode of the third diode to form a fifth node; one end of the fourth switch is connected with the fifth node, and the other end of the fourth switch is connected with the fourth node; a first moving end of the first selection switch is respectively connected with one end of the third switch and the anode of the first diode, and a second moving end of the first selection switch is in idle connection; a first moving end of the second selector switch is connected with the fifth node, and a second moving end of the second selector switch is in idle connection; wherein, the positive pole of first battery package connects first select switch's stiff end, the negative pole of first battery package connects the fifth node, the positive pole of second battery package connects the stiff end of second select switch, the negative pole of second battery package connects the fourth node, just when first battery package is not connected, the third switch is in the on-state, when first battery package connects, the third switch is in the off-state, when second battery package is not connected, the fourth switch is in the on-state, when second battery package connects, the fourth switch is in the off-state.

Preferably, the electric power tool further includes: and the battery management unit is used for carrying out equalization processing on the battery packs according to the voltage of each battery pack in the working state when the plurality of battery packs are in the working state.

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

Preferably, the undervoltage protection voltage of the battery pack composed of the plurality of battery packs is greater than or equal to the rated voltage of the electric tool.

Preferably, the step of enabling the working parameters of the motor to meet the preset conditions includes: the terminal voltage of the motor is equal to the rated voltage of the electric tool, or the rotating speed of the motor is equal to the rated rotating speed of the motor.

Preferably, the electric power tool further includes: the motor detection module is respectively connected with the motor and the control module, and is used for detecting the terminal voltage of the motor or the rotating speed of the motor, wherein the control module is also used for adjusting the duty ratio of the control signal according to the relation between the terminal voltage of the motor and the rated voltage of the electric tool or the relation between the rotating speed of the motor and the rated rotating speed of the motor.

Preferably, the electric power tool further includes: the first battery detection module is used for detecting the voltage or the internal resistance of the battery pack in a working state when the electric tool starts to work; the control module is further used for judging the rated voltage provided by the battery pack according to the voltage or the internal resistance of the battery pack in the working state and calling a corresponding sub program to control the motor according to the rated voltage.

Preferably, the electric power tool further includes: the storage module is pre-stored with a working condition database, wherein the working condition database comprises the corresponding relation between the load and the duty ratio of the electric tool under various working conditions; after the control module judges the rated voltage currently provided by the battery pack, the duty ratio of the control signal is adjusted according to the load of the motor.

Preferably, the electric power tool further includes: the control module is communicated with a server through the wireless communication module to acquire control parameters corresponding to the electric tool from the server to work according to the control parameters, and/or the working parameters of the electric tool are sent to the server to be stored in a historical database of the server, so that the server optimizes the control parameter database corresponding to the electric tool according to the working parameters in the historical database.

Preferably, the control module is further configured to obtain a voltage variation of the battery pack, and when the voltage variation of the power supply module is greater than or equal to a preset voltage value, if the terminal voltage of the motor is smaller than a rated voltage of the electric tool, the control module increases the duty ratio of the control signal to enable the terminal voltage of the motor to reach the rated voltage of the electric tool again, or if the rotation speed of the motor is smaller than the rated rotation speed of the motor, the control module increases the duty ratio of the control signal to enable the rotation speed of the motor to reach the rated rotation speed of the motor again.

In order to achieve the above object, an embodiment of a second aspect of the present invention provides a power tool system, including: the electric power tool of the above embodiment; a server in wireless communication with the power tool; the electric tool is used for acquiring control parameters corresponding to the electric tool from the server to work according to the control parameters, and/or sending the working parameters of the electric tool to the server to store the working parameters in a historical database of the server, so that the server optimizes the control parameter database corresponding to the electric tool according to the working parameters in the historical database.

According to the electric tool system provided by the embodiment of the invention, through the wireless communication between the electric tool and the server, the electric tool can acquire the control parameters corresponding to the electric tool from the server to work according to the control parameters, and/or the working parameters of the electric tool are sent to the server to store the working parameters in the historical database of the server, so that the server can optimize the control parameter database corresponding to the electric tool according to the working parameters in the historical database, therefore, the defects of limited storage space of the electric tool and limited processing speed of a control module can be effectively overcome, and the use efficiency of the electric tool is favorably improved.

The invention also provides a control method of an electric tool, the electric tool comprises a first voltage interface and a second voltage interface which are respectively used for connecting battery packs with different output voltages, the electric tool also comprises 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 comprises the following steps:

step S1, after the electric tool is started, the duty ratio of the control signal is gradually increased;

step S2, judging whether the rotating speed of the motor is equal to a preset rotating speed, wherein the preset rotating speed is less than or equal to the rated rotating speed of the motor, if so, executing step S3, otherwise, executing step S4;

step S3, controlling the motor to operate at a preset rotating speed;

step S4, judging whether the duty ratio is equal to the preset duty ratio, if so, executing step S5, otherwise, executing step S1;

and step S5, controlling the motor to operate at a second preset rotating speed, wherein the second preset rotating speed is less than or equal to the rotating speed corresponding to the preset duty ratio.

Compared with the prior art, the invention has the beneficial effects that:

the electric tool comprises a first battery interface and a second battery interface, wherein the first battery interface is connected with a first battery pack, the second battery interface is used for connecting a second battery pack, the rated output voltage of the first battery pack is greater than the rated output voltage of the second battery pack, the rated voltage of a motor is between the rated output voltage of the first battery pack and the rated output voltage of the second battery pack, a control unit does not need an identification module to identify the type of the battery pack, but the control unit gradually increases the duty ratio after the electric tool is started so that the rotating speed of the tool meets the preset condition, so that the high-voltage first battery pack is connected under the condition that the electric tool needs large output power, the low-voltage second battery pack is connected under the condition that the electric tool does not need large output power, the range of the battery pack which can be adapted to the electric tool is expanded, and the rotating speed is limited by adjusting the duty ratio, the efficiency of the battery pack is improved.

Drawings

The above objects, technical solutions and advantages of the present invention can be achieved by the following drawings:

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

FIG. 2 is a schematic diagram of the internal control flow of a power tool according to one embodiment of the present invention;

fig. 3 is a schematic structural diagram of a carrier according to an embodiment of the present invention;

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

FIG. 5 is a schematic diagram of a power tool according to an embodiment of the present invention;

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

fig. 7 is a schematic configuration diagram of a power tool according to another embodiment of the present invention;

fig. 8 is a flowchart of the operation of the electric power tool according to the first specific example of the invention;

fig. 9 is an operation flowchart of a power tool according to a second specific example of the invention;

FIG. 10 is a flow diagram of an under-voltage protection subroutine according to one example of the present invention;

fig. 11 is an operation flowchart of an electric power tool according to a third specific example of the invention;

fig. 12 is an operation flowchart of a power tool according to a fourth concrete example of the invention;

FIG. 13 is a flow diagram of an under-voltage protection subroutine according to another example of the present invention;

FIG. 14 is a schematic electrical circuit diagram of a power tool according to one particular example of the invention;

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

fig. 16 is a schematic diagram of a switching frequency according to one example of the invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

An electric power tool according to an embodiment of the present invention will be described with reference to fig. 1 to 16.

As shown in fig. 1, the electric power tool 100 includes: a motor 10, a battery connecting part 20, a driving unit 30, and a control unit 40. The battery connecting part 20 is used for detachably connecting a first battery pack and a second battery pack, the rated output voltage of the first battery pack is greater than the rated output voltage of the second battery pack, the input end of the driving unit 30 is connected with the output end of the battery connecting part 20, the output end of the driving unit 30 is connected with the motor 10, the driving unit 30 comprises a power switch tube 31, and a control unit 40 which is used for outputting a control signal to the control end of the power switch tube 31 and enabling the rotating speed of the motor 10 to be equal to a preset rotating speed by adjusting the duty ratio of the control signal, 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 electric tool can be adapted to the battery pack with the rated voltage more than or equal to the rated voltage of the motor and also can be adapted to the battery pack with the rated voltage less than the rated voltage of the motor, when the battery pack is arranged on the electric tool, the type of the battery pack does not need to be identified, and the battery packs with different output voltages can be adapted to the electric tool only by adjusting the rotating speed, so that the voltages at two ends of the motor do not exceed the rated output voltage of the motor.

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

Specifically, the driving unit 30 is used to drive the motor 10 to operate according to the power supplied from the battery connecting part 20. The control unit 40 is configured to output a control signal to the control end of the power switch tube 31, and when the battery connection portion 20 is connected to the first battery pack or the second battery pack and the electric tool 100 is started, the control unit 40 gradually increases the duty ratio of the control signal to modulate the operating parameter of the motor 10 until the operating parameter of the motor 10 meets a preset condition.

Taking a 60V electric tool as an example, as shown in fig. 16, the voltage supplied by the battery connection portion 20 is adjusted to 60V (effective value) by PWM and is applied to a brush motor with a rated voltage of 60V, assuming that the duty ratios are both 50%, if the PWM frequency is 4kHz, the period T is 0.25ms, and the on time in a single period T is 0.125ms, during which the carbon brushes are enough to generate a large spark, so that the sparks of the two carbon brushes are connected, and at this time, even if the brush is operated to an off state, the spark is not extinguished, and is in an on state, so that a continuous arc connection phenomenon occurs. If the PWM frequency is reduced, the on time is longer, the spark is larger, and arcing is less avoidable.

Further, if the PWM frequency is increased, e.g., to f 8kHz, the period T is 0.125ms, and the on time is only 0.0625ms, which is a short time when the carbon brush is not sufficiently sparking and even if there is some normal sparking, it is then in an off state, sufficiently extinguished. Increasing the frequency avoids the occurrence of carbon brush sparking.

Secondly, the PWM frequency cannot be too high: as is well known, the PWM voltage regulation of the dc power supply is realized by Mosfet power switching tubes, which have on-state loss and switching loss, and the switching loss is in direct proportion to the PWM frequency, so that increasing the frequency will increase the switching loss, increase the temperature rise of the device, and reduce the reliability.

The control unit 40 of the present invention controls the on/off of the power switch tube 31 in the driving unit 30 by sending a PWM (Pulse Width Modulation) signal. The PWM signal is a pulse signal with an adjustable duty ratio, and includes a high level part and a low level part, the high level part makes the power switch tube 31 in a conducting state, the battery connecting part 20 supplies power to the motor 10, when the motor 10 starts to work, the low level part of the pulse signal makes the power switch tube 31 in a disconnecting state, and a power supply loop from the battery connecting part 20 to the motor 10 is disconnected. The control unit 40 may control the amount of power supplied from the battery connecting part 20 to the motor 10 by controlling the ratio of the high level part and the low level part of the PWM signal. Wherein, the duty ratio is high, i.e. the high level part is high, the conducting time of the power switch tube 31 is long, the electric energy provided by the battery connecting part 20 to the motor 10 is high, the terminal voltage of the motor 10 and the rotating speed of the motor 10 are high; the duty ratio is low, i.e. the duty ratio of the high level part is low, the on time of the power switch tube 31 is short, the power supplied to the motor 10 by the battery connecting part 20 is low, and the terminal voltage of the motor 10 and the rotation speed of the motor 10 are low. Thus, the voltage adaptation range of the power tool 100 is increased, and the efficiency of the battery connection part 20 is improved.

In this embodiment, the motor 10 may be one of a brush motor, a brushless motor or a switched reluctance motor, so that the control unit 40 controls the rotation speed of the motor 10.

Alternatively, the power tool 100 may be, but is not limited to, a cordless hand-held power tool, a cordless garden tool, a cordless wheeled mobile tool, or the like.

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

In the embodiment of the present invention, the battery connecting portion 20 is detachably connected to a battery pack, and the battery pack may be a single battery pack or a battery pack formed by 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 jar for mounting the battery pack may be provided in the housing, or a backpack assembly 90 (shown in fig. 3) separate from the housing may be provided for mounting the battery pack.

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

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 rotation speed at a preset value by controlling the duty ratio, wherein the preset value is less than or equal to the rated rotation 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 adjusts the rotating speed by adjusting the duty ratio of the control signal, does not need to identify the type of the battery pack, and can realize that the electric tool is adaptive to the battery pack with the voltage larger than the rated voltage of the electric tool and the battery pack with the voltage smaller than the rated voltage of the electric tool only by one set of program.

Specifically, fig. 2 is a schematic flow chart illustrating a control method of an electric tool according to the present invention. The control method comprises the following steps:

in step S1, the duty ratio of the control signal is increased step by step after the power tool is started. The electric tool adopts a soft start mode to gradually increase the duty ratio until the duty ratio reaches a preset value.

And step S2, judging whether the rotating speed of the motor is equal to the preset rotating speed, if so, executing step S3, otherwise, executing step S4. When the duty ratio reaches a preset value, the control unit determines whether the rotating speed of the motor acquired by the rotating speed detecting unit is equal to a preset rotating speed, where the preset rotating speed is less than or equal to a rated rotating speed of the motor.

And step S3, controlling the motor to operate at a preset rotating speed. In the above steps, if the rotation speed of the motor is judged to be equal to the preset rotation speed, the controller controls the motor to operate at the preset rotation speed at a stable speed.

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

And step S5, controlling the motor to operate at a second preset rotating speed, wherein the second preset rotating speed is less than or equal to the rotating 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 rotation speed.

After the motor is started in the above steps, the duty ratio is gradually increased, the control unit judges whether the motor rotating speed acquired by the rotating speed detection unit is equal to the preset rotating speed, if not, the duty ratio is continuously increased, and whether the increased duty ratio is equal to 100% is judged, if yes, the corresponding second preset rotating speed is maintained when the motor is controlled by 100% duty ratio or the system stores 100% duty ratio in advance, and when the duty ratio is detected to be equal to 100%, the control device controls the motor to maintain the second preset rotating speed to operate at a stable speed. Otherwise, if the duty ratio is not equal to 100%, the duty ratio is continuously increased until the rotating speed of the motor is equal to the preset rotating speed.

The electric tool can be adapted to the battery pack with the voltage higher than the rated voltage of the electric tool and also can be adapted to the battery pack with the voltage lower than the rated voltage of the electric tool, and the identification module is not needed to identify the type of the battery pack to control the high-voltage battery pack, but the duty ratio is gradually increased to ensure that the low-voltage battery pack keeps 100 percent of the duty ratio to operate and the high-voltage battery pack keeps the preset rotating speed to operate, so that the cost is saved, the control program is simplified, meanwhile, the identification module can only identify limited battery packs, the universality of the battery packs is limited, the identification module is not needed, and the compatibility of the electric tool to the battery packs is improved.

In one embodiment of the 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 lower than 40% of the rated voltage of the motor. In another embodiment of the present invention, the undervoltage, i.e., the lowest discharge voltage, of the first battery pack is greater than the rated output voltage of the second battery pack. When the second battery pack is connected to the electric tool, the control device controls the motor to operate at a duty ratio of 100%, or the system stores the maximum rotating speed, namely the second rotating speed, of the second battery pack when the second battery pack is connected to the electric tool in advance, after the tool is started, the duty ratio is increased step by step, and when the duty ratio is increased to 100% and the rotating speed is still less than the target rotating speed, the control device controls the motor to maintain the second preset rotating speed for stable-speed operation.

In one embodiment of the present invention, the electric tool further includes a speed adjusting device, and the speed adjusting device may be a knob for performing multi-gear speed adjustment, or may be a plurality of buttons or keys for performing gear speed adjustment. Specifically, taking two-gear speed regulation as an example for illustration, the electric tool includes a first speed regulation device and a second speed regulation device, the first speed regulation device may be a first button corresponding to a high gear and corresponding to a first preset rotation speed, and the second speed regulation device may be a second button corresponding to a low gear and corresponding to a third preset rotation speed. The first preset rotating speed is less than or equal to the rated rotating speed of the motor, the third preset rotating speed is less than or equal to the rotating speed when the second battery pack is adapted to the electric tool and the electric tool runs at 100% duty ratio.

When the first key is triggered, after the electric tool is started, the control unit gradually increases the duty ratio of the control signal, the control unit judges whether the rotating speed of the motor acquired by the rotating speed detection unit is equal to a first preset rotating speed, if not, the duty ratio is continuously increased, and judges whether the current duty ratio is equal to 100%, if the current duty ratio is equal to 100%, the control unit maintains 100% of the duty ratio to control the motor, if not, the duty ratio is continuously increased, and judges whether the current rotating speed is equal to the first preset rotating speed, if so, the control unit controls the motor to stably operate at the first preset rotating speed, if not, the control unit judges whether the current duty ratio is equal to 100%, if not, the duty ratio is continuously increased, until the rotating speed of the motor is equal to the first preset rotating speed, and if so, the control unit maintains 100% of the duty ratio to control the motor.

When the second key is triggered and the electric tool is started, the control unit gradually increases the duty ratio of the control signal, judges whether the rotating speed of the motor acquired by the rotating speed detection unit is equal to a third preset rotating speed or not, and if not, continuously increases the duty ratio until the rotating speed of the motor is equal to the third preset rotating speed.

The electric tool of the invention comprises electric tools such as a grass trimmer, a pruner, a blower, a chain saw, a high-pressure cleaning machine and the like. The electric tool comprises a battery connecting part 20, wherein the battery connecting part 20 comprises a first power interface and a second power interface, the first power interface is detachably connected with a first battery pack of which the voltage is greater than the rated voltage of a motor, and the second power interface is detachably connected with a second battery pack of which the voltage is less than the rated voltage of the motor. Taking the 60V power tool as an example, the power tool can be powered by the 40V battery pack through the second power interface, and can also be powered by the 80V battery pack through the first power interface. The power tool may be adapted to a 40V battery pack when the power tool requires a smaller power output or no 60V or 80V battery pack is around, and to an 80V battery pack when the power tool requires a larger output power. The 40V battery pack may be a single 40V battery pack, or may be formed by connecting two 20V battery packs in series, in the present invention, preferably, 2 20V battery packs are connected in series to form a 40V output voltage, specifically, the second power interface includes a first battery slot and a second battery slot, the first battery slot and the second battery slot are electrically connected and are respectively used for connecting the first battery pack and the second battery pack, and both the first battery pack and the second battery pack are 20V battery packs. When the power tool needs higher output power, in one embodiment, the first battery pack may be composed of 4 20V battery packs connected in series to form an output voltage of 80V. The 80V first battery pack may be located on the power tool housing or outside the power tool housing.

The invention also comprises an adapter, wherein the adapter is provided with a plurality of battery seats for mounting a plurality of battery packs, the battery packs are connected in series or in parallel, and the adapter is provided with a voltage output port which is connected with a voltage input port of the electric tool through the connecting component to provide electric energy for the electric tool. In one embodiment, 4 battery slots are arranged on the adapter, 4 20V battery packs can be installed, the 4 20V battery packs are connected in series or in parallel, and a first voltage output port, a second voltage output port and a third voltage output port are arranged on the adapter and are respectively 20V, 40V and 80V. Meanwhile, the adapter is also provided with a power input port, and an external alternating current power supply charges the battery pack on the battery jar through the power input port. Still be provided with first connecting portion on the adapter for detachable connects electric tool's first power source.

Taking a 60V mower as an example, a first battery slot and a second battery slot are arranged on a second power interface in a tool housing of the mower, the first battery slot and the second battery slot are electrically connected, 2 20V battery packs can be accommodated, and the two battery packs are connected in series. Meanwhile, a first power interface is further arranged on the mower shell and used for detachably connecting the adapter. The operator can select 2 20V battery packs to be connected in series to supply power to the mower or select 4 20V battery packs to be connected in series in the adaptation, namely, a voltage output port of 80V to supply power to the mower according to requirements.

For handheld tools such as grass trimmers and hair dryers, the adapter is arranged on the tool shell, the weight of the tool can be increased, and the handheld operation of an operator is inconvenient.

In one embodiment of the invention, the adapter is provided with only one voltage output port, the knob switch is arranged on the adapter, the series-parallel connection structure of the plurality of battery packs is changed by rotating the knob switch, so that the voltage of the output port is changed, and the output port is connected with the electric tool through the connecting component to provide electric energy for the electric tool. As shown in fig. 3, the battery pack 21 is composed of 4 batteries connected in series by 20V, and the user can select a target rated voltage, such as 60V rated voltage of the tool, through the knob a according to the rated voltage of the power tool, i.e. the black arrow on the knob a can be aligned to the position of 4 × 20V.

In another embodiment of the invention, the electric tool further comprises a voltage detection module for detecting the terminal voltage of the motor, and the terminal voltage of the motor is made to be equal to the rated voltage of the electric tool by adjusting the duty ratio of the control signal.

The selection of the switching frequency is specifically described below by taking the example of reducing the 80V battery pack to 60V and supplying power to the brush motor with the rated voltage of 60V:

first, the PWM frequency cannot be too low: it is found through debugging that if the frequency below 4kHz is used, the phenomenon of carbon brush sparking and arc connecting, namely continuous bright sparks, can occur, the motor 10 can be burnt out in a short time, and fire hazard exists.

For the motor 10 with 60V rated voltage, if 60V voltage is applied, the current is large at the initial stage of starting the motor 10, and when the carbon brush and the commutator realize current commutation, a large peak counter electromotive force can be generated between the carbon brush and the commutator, so that arc discharge with certain intensity is generated; when the current is reduced after the motor is started and the current commutation is realized between the carbon brush and the commutator, the peak counter electromotive force generated between the carbon brush and the commutator becomes small, and basically no spark is observed.

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, thereby causing a large spark to occur, so that the sparks of the two carbon brushes are connected together and the carbon brush and the commutator are ablated.

In order to avoid the phenomenon of spark arcing, the energy of the carbon brush spark needs to be controlled so that the spark is not enough to generate the arcing.

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

Further, the efficiency of using the electric quantity of the battery pack is improved, and when the undervoltage protection voltage of the battery pack is greater than or equal to the rated voltage of the electric tool, so that the terminal voltage of the motor 10 is equal to the rated voltage of the electric tool 100, the electric tool 100 can work continuously and efficiently at the rated voltage. For example, a 20V battery pack provides a rated voltage of 18V and an undervoltage protection voltage of 12.5V, and the rated voltage of the electric power tool 100 using the battery pack needs to be less than or equal to 12.5V; a 40V battery pack, which provides a rated voltage of 36V and an undervoltage protection voltage of 25V, and the rated voltage of the electric tool 100 using the battery pack needs to be less than or equal to 25V; in a 60V battery pack, a rated voltage of 48V is provided, and an undervoltage protection voltage of 37.5V is provided, so that the rated voltage of the electric 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 is the rated voltage of the motor/the rated voltage supplied to the battery connection unit, and the maximum duty ratio during operation is the rated voltage of the motor/the undervoltage voltage of the battery connection unit. The duty ratio ranges from 0% to 100%, so that the minimum duty ratio is equal to or less than 100% of the rated voltage of the motor/the rated voltage provided by the battery connecting part in the work, and the maximum duty ratio is equal to or less than 100% of the rated voltage of the motor/the under-voltage of the battery connecting part in the work, namely, the rated voltage of the motor is equal to or less than the under-voltage of the battery connecting part.

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 a plurality of batteries is greater than or equal to the rated voltage of the electric power tool 100. The voltage regulation unit 22 is used to select the battery pack to be operated according to the rated voltage or the target rated voltage of the power tool, so that the battery connection unit 40 provides the target rated voltage when the selected battery pack is operated.

In this example, the number and connection relationship of the plurality of battery packs constituting the battery pack 21 may be set as needed (such as the type of the electric power tool 100, etc.), for example, the battery pack 21 is composed of 3 20V battery packs connected in series; the battery pack 21 is composed of 3 20V batteries, and two batteries are connected in parallel and then connected in series with one another, and so on.

It should be understood that the target rated voltage is the voltage that the user inputs according to the requirement of the power tool, for example, as shown in fig. 3, the battery pack 21 is composed of 4 battery packs connected in series, and the user can select the target rated voltage, for example, 36V, through the knob a according to the rated voltage of the power tool, i.e., the black arrow on the knob a can be aligned with the 2 × 20V position, and at the same time, the voltage regulating unit 22 can select the battery packs connected in series to operate. Of course, the voltage regulating unit 22 may also select 4 20V battery packs to operate, and two of the battery packs are connected in parallel and then connected in series.

In other words, the number of battery packs selected by the voltage adjusting unit 22 to be operated may be determined according to a preset connection relationship between the battery packs, for example, 4 battery packs of 20V (numbers: 1#, 2#, 3#, 4#) are connected in series in sequence to constitute the battery pack 21, and when 2 × 20V is selected, the voltage adjusting unit 22 may select 1# and 2# or 2# and 3# or 3# and 4# to be operated.

Similarly, to improve the efficiency of using the charge of the battery pack, the under-voltage protection voltage of the battery pack 21 consisting of a plurality of batteries should be greater than or equal to the rated voltage of the power tool.

It should be noted that, during PWM adaptive voltage regulation, the output voltage of the battery connection unit 20 corresponding to a large load is appropriately increased, that is, the duty ratio is increased; the output voltage of the battery connecting part 20 corresponding to the small load is appropriately reduced, that is, the duty ratio is reduced, so that the effects of high efficiency in all operating conditions and strong single-pack capacity can be realized.

Further, when the number of the battery packs in the working state is at least two, in order to ensure the working performance of the battery packs, the electric tool 100 may further include a battery management module, where the battery management module is configured to perform equalization processing on the battery packs according to the voltage of each battery pack in the working state when the plurality of battery packs are in the working state, and if the battery packs with higher control voltage preferentially discharge, when the voltages of all the battery packs in the working state are the same, it may be controlled that all the battery packs in the working state discharge simultaneously.

In some embodiments of the present invention, the satisfaction of the preset conditions of the operating parameters of the motor 10 comprises: the terminal voltage of the motor 10 is equal to the rated voltage of the electric power tool 100, or the rotation speed of the motor 10 is equal to the rated rotation speed of the motor 10.

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

Specifically, when the terminal voltage of the motor 10 is smaller than the rated voltage of the electric 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 voltage of the electric power tool 100; when the rotation speed of the motor 10 is less than the rated rotation speed of the motor 10, the control unit 40 increases the duty ratio of the control signal to increase the rotation speed of the motor 10, and the rotation speed of the motor 10 is equal to the rated rotation speed of the motor 10. It is understood that the driving unit 30 and the motor detection module 50 form a feedback circuit, and the control unit 40 can perform closed-loop control on the terminal voltage of the motor 10 according to the feedback circuit.

In this embodiment, the control unit 40 may adjust the duty ratio of the control signal to be gradually increased by a preset step from a preset initial safe duty ratio when the power tool 100 is turned on until 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 rotational speed of the motor 10, acquire the current duty ratio of the control signal, and determine the rated voltage currently provided by the battery connecting part 20 according to the current duty ratio.

The preset initial safety duty cycle may be set according to the maximum value of the rated voltage provided by the battery connection part 20 and the rated voltage of the electric power tool 100, for example, the maximum value of the rated voltage provided by the battery connection part 20 is Umax, and the rated voltage of the electric power tool 100 is U0, so that the preset initial safety duty cycle may be any value less than U0/Umax to prevent the motor 10 or other electronic devices in the electric power tool 100 from being burnt when the battery connection part 20 is connected at a high voltage.

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

The sub-routine includes a duty ratio sub-routine, i.e., a duty ratio adjustment sub-routine corresponding to the rated voltage supplied from the battery connecting part 20.

Optionally, the sub-routine may further include a sub-routine for battery protection, such as an overcurrent protection sub-routine, an over-temperature protection sub-routine, an under-voltage protection sub-routine, and the like.

Furthermore, the electric tool 100 may further include a second battery detection module, which is configured to detect a voltage and/or an operating current of the battery pack in the battery connection portion 20 in an operating state in real time during the operation of the electric tool 100, wherein the control unit 40 is further configured to disconnect the power supply loop by controlling the battery connection portion 20 to stop the operation of the motor 10 when the voltage of the battery pack in the operating state is less than a corresponding under-voltage and/or when the operating current of the battery pack in the operating state is greater than a corresponding current threshold and lasts for a preset time. Therefore, under-voltage protection and/or over-current protection of the electric tool can be realized, and damage to the motor is reduced. The current threshold and the preset time can be calibrated according to the actual working circuit of the battery connecting part 20.

For example, in the working process of the electric tool 100, the second battery detection module detects the voltage of the battery connection portion 20 in real time, and sends the voltage detection result to the control unit 40, the control unit 40 determines whether the voltage of a battery pack (such as a 20V battery pack) in the battery connection portion 20 is smaller than a preset undervoltage voltage (such as 12.5V) according to the voltage detection result, if so, the control unit 40 determines that the battery is undervoltage, and controls the power switch tube in the driving unit 30 to be turned off, so as to cut off the power supply loop of the battery connection portion 20, so that the motor 10 stops working, and thus, undervoltage protection of the battery connection portion 20 is realized.

In the working process of the electric tool 100, the second battery detection module can detect the working current of the battery connection part 20 in real time and send the current detection result to the control unit 40, the control unit 40 judges whether the working current of the battery connection part 20 is greater than the current threshold (for example, 25A) according to the current detection result, and if so, the motor detection module 50 further records the duration that the working current is greater than the preset current threshold. If the duration time is longer than the preset time (for example, 2s), the control unit 40 determines that the battery connecting part 20 is in overcurrent, and controls the power switch tube in the driving unit 30 to be turned off to cut off the power supply loop of the battery connecting part 20, so that the motor 10 stops working, thereby implementing overcurrent protection on the battery connecting part 20.

In this example, the control unit 40 is further configured to obtain a voltage variation of the battery connecting portion 20 (for example, a voltage variation of each battery pack in an operating state, or a total voltage variation of all battery packs in the operating state), and when the voltage variation of the battery pack (for example, a voltage variation or a total voltage variation of at least one battery pack) is greater than or equal to a corresponding preset voltage value, if the terminal voltage of the motor 10 is less than the rated voltage of the electric power tool 100, 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 electric power tool 100 again, or if the rotation speed of the motor 10 is less than the rated rotation speed of the motor 10, the control unit 40 increases the duty ratio of the control signal so that the rotation speed of the motor 10 reaches the rated rotation speed of the motor 10 again. Alternatively, the voltage variation amount of the battery connecting part 20 may also be the total voltage variation amount of all the battery packs in the 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 electric power tool 100 is 18V, there may be a case where the voltage variation is large, which affects the terminal voltage of the motor 10 or the rotation speed of the motor 10, that is, the terminal voltage of the motor 10 or the rotation speed of the motor 10 is abruptly changed. At this time, the control unit 40 acquires the voltage variation of each battery pack in real time, and adjusts the duty ratio of the control signal so that the terminal voltage of the motor 10 is equal to the rated voltage of the electric tool 100 or the rotation speed of the motor 10 is equal to the rated rotation speed of the motor 10 when the difference between the voltage values of at least one battery pack acquired twice in succession is greater than or equal to a preset voltage value, such as 0.5V.

In some embodiments of the present invention, the power tool 100 further includes a storage module, in which a working condition database is pre-stored, wherein the working condition database includes a corresponding relationship between the load and the duty ratio of the power tool 100 under various working conditions (such as no load, small load, large load, full load, etc. under different rated voltages provided by the battery connection portion 20), and the corresponding relationship may be stored in the form of a table, a curve, or the like. In this example, the control unit 40 also adjusts the duty cycle of the control signal according to the load size of the motor 10.

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

Alternatively, in order to improve the working efficiency of the control unit 40, a main program, a sub program, etc. required for the control thereof may be prestored in the storage module.

As shown in fig. 7, the electric power tool 100 further includes a wireless communication module 70, and the control unit 40 communicates with the server 200 through the wireless communication module 70 to obtain the control parameters corresponding to the electric power tool 100 from the server 200 to operate according to the control parameters, and/or transmits the operating parameters of the electric power tool 100 to the server 200 to store the operating parameters in a history database of the server 200, so that the server 200 optimizes the control parameter database corresponding to the electric power tool 100 according to the operating parameters in the history database (e.g., by using a big data processing method, etc.). Therefore, through the self-learning and remote-learning functions of the electric tool 100, when the electric tool 100 encounters the same working condition again, the previous duty ratio data can be automatically called, so that the control efficiency of the electric tool is improved, and the application range of the electric tool is enlarged.

The working principle of the electric tool of the embodiment of the present invention is described below with reference to fig. 5, 6, and 8 to 13, respectively:

the first embodiment is as follows:

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

Specifically, as shown in fig. 5 and 8, the main switch of the electric power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, the duty cycle of the CPU regulating MOSFET is increased step by a preset step X% (e.g., 1%, 3%, 5%, etc.) from the preset initial safe duty cycle 0 until the terminal voltage of the motor 10 is equal to the rated voltage 18V of the electric power tool, and the current duty cycle of the MOSFET is obtained. If the current duty ratio is 100%, the battery connecting part 20 can be judged to be a 20V battery pack, and if the terminal voltage of the motor 10 is detected to be less than 12.5V in the running process of the motor, namely the undervoltage voltage of the 20V battery pack is reached, the CPU gives an alarm or directly performs shutdown protection on the motor 10. When the terminal voltage of the motor 10 is greater than or equal to 12.5V and less than or equal to 18V, the duty ratio is maintained at 100%.

If the duty ratio of the MOSFET is less than 100% when the terminal voltage of the motor 10 is equal to 18V, the battery connecting portion 20 is determined as another voltage battery pack. When the terminal voltage of the motor 10 is equal to 18V and the current duty ratio is less than or equal to 33%, the battery connecting part 20 is determined to be a 60V battery pack. In the running process of the motor 10, the terminal voltage of the motor 10 is detected in real time, and when the terminal voltage is smaller than 18V, the duty ratio is increased by a preset step pitch X% so as to maintain the terminal voltage at 18V. When the voltage of the motor terminal is less than or equal to 18V and the corresponding duty ratio reaches 48%, the voltage of the 60V battery pack is judged to be undervoltage, and then the CPU gives an alarm or directly performs shutdown protection on the motor 10.

If the duty ratio of the MOSFET is less than 100% when the terminal voltage of the motor 10 is equal to 18V, the battery connecting portion 20 is determined as another voltage battery pack. When the terminal voltage of the motor 10 is equal to 18V and the current duty ratio is greater than 33% and less than or equal to 50%, the battery connecting portion 20 is determined to be a 40V battery pack. During the operation of the motor 10, the terminal voltage of the motor 10 is detected in real time, and when the terminal voltage is smaller than 18V, the duty ratio is increased by X% of a preset step pitch so as to maintain the terminal voltage at 18V. When the voltage of the motor terminal is less than or equal to 18V and the corresponding duty ratio reaches 72%, judging that the 40V battery pack is under-voltage, the CPU gives an alarm or directly performs shutdown protection on the motor 10.

The second embodiment:

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

Specifically, as shown in fig. 6 and 9, the main switch of the electric power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the control main program is invoked. The CPU obtains 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 (such as an over-temperature protection subroutine, an over-current protection subroutine, an under-voltage protection subroutine, etc.) according to the rated voltage. For example, as shown in fig. 10, when the under-voltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the terminal voltage of the motor 10, and when the duty ratio is equal to 72%, determines that the battery pack is under-voltage, the CPU gives an alarm or performs shutdown protection on the motor 10.

Similarly, as shown in fig. 6 and 11, the main switch of the electric power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the main control program is invoked. The CPU obtains the resistance R of the battery connection part 20, determines the rated voltage provided by the battery connection part 20 according to R, and calls a corresponding protection subroutine (such as an over-temperature protection subroutine, an over-current protection subroutine, an under-voltage protection subroutine, etc.) according to the rated voltage. For example, as shown in fig. 10, when the under-voltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the terminal voltage of the motor 10, and when the duty ratio is equal to 72%, determines that the battery pack is under-voltage, the CPU gives an alarm or performs shutdown protection on the motor 10.

Example three:

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

Specifically, as shown in fig. 5 and 12, the main switch of the electric tool 100 is turned on, the 5V module is powered on, the CPU is powered on, the duty ratio of the CPU regulating the MOSFET is gradually increased by a preset step distance X% (e.g., 1%, 3%, 5%, etc.) from a preset initial safe duty ratio 0 until the rotation speed of the motor 10 is equal to the rated rotation speed of the motor 10, and the current duty ratio of the MOSFET is obtained. If the current duty ratio is 100%, the battery connecting part 20 can be judged to be a 20V battery pack, and if the terminal voltage of the motor 10 is detected to be less than 12.5V in the running process of the motor, namely the undervoltage voltage of the 20V battery pack is reached, the CPU gives an alarm or directly performs shutdown protection on the motor 10. When the terminal voltage of the motor 10 is greater than or equal to 12.5V and less than or equal to 18V, the duty ratio is maintained at 100%.

If the duty ratio of the MOSFET is less than 100% when the rotation speed of the motor 10 is equal to the rated rotation speed of the motor, it is determined that the battery connecting part 20 is the other voltage battery pack. When the rotation speed of the motor 10 is equal to the rated rotation speed and the current duty ratio is less than or equal to 33%, the battery connecting part 20 is determined to be a 60V battery pack. In the running process of the motor 10, the rotating speed of the motor 10 is detected in real time, and when the rotating speed is smaller than the rated rotating speed, the duty ratio is increased by X% of the preset step pitch, so that the rotating speed is maintained at the rated rotating speed. When the rotating speed of the motor is less than or equal to the rated rotating speed and the corresponding duty ratio reaches 48%, judging that the 60V battery pack is under-voltage, and carrying out alarm prompt by the CPU or directly carrying out shutdown protection on the motor 10.

If the duty ratio of the MOSFET is less than 100% when the rotation speed of the motor 10 is equal to the rated rotation speed of the motor, it is determined that the battery connecting part 20 is the other voltage battery pack. When the rotation speed of the motor 10 is equal to the rated rotation speed and the current duty ratio is greater than 33% and less than or equal to 50%, it is determined that the battery connecting part 20 is a 40V battery pack. In the running process of the motor 10, the rotating speed of the motor 10 is detected in real time, and when the rotating speed is smaller than the rated rotating speed, the duty ratio is increased by X% of the preset step pitch, so that the rotating speed is maintained at the rated rotating speed. When the rotating speed of the motor is less than or equal to the rated rotating speed and the corresponding duty ratio reaches 72%, the 40V battery pack is judged to be under-voltage, and then the CPU gives an alarm or directly performs shutdown protection on the motor 10.

It should be noted that, when the electric tool 100 adopts the 20V motor 10 and the battery connection portion 20 only includes a single 20V battery pack, the CPU needs to control the motor 10 at a duty ratio of 100%, and at this time, the terminal voltage of the motor 10 or the battery pack voltage may be detected to determine whether the battery pack is under-voltage. In other words, when the rated voltage of the motor 10 is greater than the under-voltage of the battery connecting portion 20, it is necessary to detect the terminal voltage of the motor 10 or the voltage of the battery connecting portion 20 to determine whether the battery connecting portion 20 is under-voltage. For this reason, it is preferable that the battery connecting portion 20, which has an undervoltage equal to or higher than the rated voltage of the motor 10, supplies power to the electric power tool 100.

Example four:

in this embodiment, the rated voltage supplied from the battery connecting part 20 is determined according to the output voltage or resistance of the battery connecting part 20, and the duty ratio of the control signal is adjusted and the undervoltage protection is performed according to the rotation speed of the motor 10.

Specifically, as shown in fig. 6 and 9, the main switch of the electric power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the control main program is invoked. The CPU obtains the output voltage U of the battery connecting part 20, determines the rated voltage provided by the battery connecting part 20 according to U, and calls a corresponding protection subroutine (such as an over-temperature protection subroutine, an over-current protection subroutine, an under-voltage protection subroutine, etc.) according to the rated voltage. For example, as shown in fig. 13, when the under-voltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the rotation speed of the motor 10, and when the duty ratio is equal to 72%, it determines that the battery pack is under-voltage, and the CPU gives an alarm or performs shutdown protection on the motor 10.

Similarly, as shown in fig. 6 and 11, the main switch of the electric power tool 100 is turned on, the 5V module is powered on, the CPU is powered on, and the main control program is invoked. The CPU obtains the resistance R of the battery connection part 20, determines the rated voltage provided by the battery connection part 20 according to R, and calls a corresponding protection subroutine (such as an over-temperature protection subroutine, an over-current protection subroutine, an under-voltage protection subroutine, etc.) according to the rated voltage. For example, as shown in fig. 13, when the under-voltage protection subroutine of the 40V battery pack is called, the CPU adjusts the duty ratio of the control signal according to the rotation speed of the motor 10, and when the duty ratio is equal to 72%, it determines that the battery pack is under-voltage, and the CPU gives an alarm or performs shutdown protection on the motor 10.

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

as shown in fig. 14 and 15, the battery Pack 21 includes two battery packs (a first battery Pack1 and a second battery Pack2), and the rated voltage U1 and U2 of each battery Pack is equal to or higher than the rated voltage U0 of the motor 10.

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

When both Pack1 and Pack2 are plugged, S2 and S3 are disconnected, S1 is closed, Pack1 and Pack2 are connected in series, the rated voltage provided by the battery connecting part 20 is U1+ U2 and is greater than U0, and PWM voltage reduction output is achieved. When Pack1 is removed, S2 is closed, S3 is opened, S1 is closed, Pack2 is an operating battery Pack, the rated voltage provided by battery connecting part 20 is U2 and is greater than or equal to U0, PWM voltage reduction output is performed if U2 is greater than U0, and the duty ratio is adjusted to 100% if U2 is equal to U0. When Pack2 is removed, S2 is opened, S3 is closed, S1 is closed, Pack1 is an operating battery Pack, the rated voltage provided by battery connecting part 20 is U1 and is greater than or equal to U0, PWM voltage reduction output is performed if U1 is greater than U0, and the duty ratio is adjusted to 100% if U1 is equal to U0.

In this embodiment, when two battery packs are inserted, the two battery packs are connected in series, and if one battery pack is powered off first, the power tool 100 still works normally only by taking the battery pack down, 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, a first selection switch Relay1, and a second selection switch Relay 2. The cathode of the D1 is connected with one end of a start-stop switch S1 of the electric tool, and the other end of the S1 is connected with the motor 10; a cathode of D2 is connected to a cathode of D1 and one end of S1, respectively, a cathode of D3 is connected to an anode of D2, and an anode of D3 is connected to an input terminal of the driving unit 30, and forms a fourth node D; one end of S4 is connected with the anode of D1, the other end of S4 is respectively connected with the anode of D2 and the cathode of D3, and a fifth node e is formed; one end of the S5 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 Relay1 is respectively connected with one end of S4 and the anode of D1, and the second mobile end of Relay1 is connected in an air-connected mode; the first mobile terminal of the Relay2 is connected with the fifth node e, and the second mobile terminal of the Relay2 is in idle connection; the positive pole of Pack1 is connected with the fixed end of Relay1, the negative pole of Pack1 is connected with the fifth node e, the positive pole of Pack2 is connected with the fixed end of Relay2, and the negative pole of Pack2 is connected with the fourth node d.

When both Pack1 and Pack2 are plugged, S4 and S5 are opened, S1 is closed, if port 1 (i.e. fixed end) of Relay1 is connected with port 3 (i.e. first movable end) and port 1 (i.e. fixed end) of Relay2 is connected with port 3 (i.e. first movable end), Pack1 and Pack2 are connected in series, the rated voltage provided by battery connecting part 20 is U1+ U2 and is greater than U0, and PWM step-down output is achieved. When Pack1 is removed, S4 is closed, S5 is opened, S1 is closed, port 1 of Relay1 is connected with port 3, port 1 of Relay2 is connected with port 3, Pack2 is a working battery Pack, battery connecting part 20 provides rated voltage of U2 which is equal to or greater than U0, if U2 is greater than U0, PWM voltage reduction output is performed, and if U2 is equal to U0, the duty ratio is adjusted to 100%. When the Pack2 is removed, S4 is disconnected, S5 is closed, S1 is closed, the Pack1 is a working battery Pack, the rated voltage provided by the battery connecting part 20 is U1 and is greater than or equal to U0, if U1 is greater than U0, PWM voltage reduction output is performed, and if U1 is equal to U0, the duty ratio is adjusted to 100%. When Pack1 discharges to the protection point first, port 1 of Relay1 switches to connect with port 2 (i.e. the second mobile terminal), and Pack1 is disconnected, and only Pack2 discharges, and the discharge loop is: pack2+ → Relay2(1-3) → S1 → M → Mosfet → Pack 2-. When Pack2 discharges to the protection point first, port 1 of Relay2 switches to connect with port 2 (i.e. the second mobile terminal), and Pack2 is disconnected, only Pack1 discharges, and the discharge loop is: pack1+ → Relay1(1-3) → D1 → S1 → M → Mosfet → D3 → Pack 1-.

In this embodiment, when two battery wraps all inserted, can realize the series connection of two battery wraps, and if a battery package did not have the electricity earlier, then need not artificial under-voltage package of taking off convenient to use.

To sum up, when the electric tool of the embodiment of the present invention is connected to the battery pack with different rated voltages, which is greater than the rated voltage of the electric tool, to supply electric energy, the duty ratio of the control signal is adjusted by the control unit so that the terminal voltage of the motor is equal to the rated voltage of the electric tool or the rotational speed of the motor is equal to the rated rotational speed of the motor, thereby enabling the electric tool to adapt to the battery pack with different rated voltages, improving the adaptation range of the voltage of the electric tool, and improving the efficiency of the battery pack.

Based on the electric tool of the above embodiment, the invention provides an electric tool system.

Referring to fig. 7, the power tool system includes: the power tool 100 and the server 200 of the above embodiments, wherein the server 200 wirelessly communicates with the power tool 100.

In this embodiment, the power tool 100 is configured to obtain the control parameters corresponding to the 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 store the operating parameters in the historical database of the server 200, so that the server 200 optimizes the control parameter database corresponding to the power tool 100 according to the operating parameters in the historical database.

It should be noted that, for other specific embodiments of the power tool system according to the embodiment of the present invention, reference may be made to the specific embodiments of the power tool according to the above-mentioned embodiment of the present invention.

According to the electric tool system provided by the embodiment of the invention, through the wireless communication between the electric tool and the server, the electric tool can acquire the control parameters corresponding to the electric tool from the server to work according to the control parameters, and/or the working parameters of the electric tool are sent to the server to store the working parameters in the historical database of the server, so that the server can optimize the control parameter database corresponding to the electric tool according to the working parameters in the historical database, therefore, the defects of limited storage space of the electric tool and limited processing speed of a control unit can be effectively overcome, and the use efficiency of the electric tool is improved.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.

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

The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. An electric tool, characterized by comprising a battery connecting part 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 that of the second battery pack;

a motor as a power source;

the control unit is used for outputting a control signal to a control end of the power switch tube and enabling the rotating speed of the motor to be equal to a preset rotating speed by adjusting the duty ratio of the control signal so that the motor can adapt to the rated output voltage of the first battery pack or the second battery pack, and the rated voltage of the motor is located between the rated output voltage of the first battery pack and the rated output voltage of the second battery pack;

the electric tool also comprises a rotating speed detection module used for acquiring the rotating speed of the motor, and the control unit enables the motor to stably run at a preset speed by adjusting the duty ratio of the control signal, wherein the preset rotating speed is less than or equal to the rated rotating speed of the motor;

the electric tool starts, the control unit gradually increases the duty ratio of the control signal, if the rotating speed obtained by the rotating speed detection module is equal to a first preset rotating speed, the control unit controls the motor to operate at a first preset rotating speed and a stable speed, otherwise, the control unit controls the motor to operate at a third preset rotating speed and a stable speed, the first preset rotating speed is less than or equal to the rated rotating speed of the motor, the third preset rotating speed is less than or equal to a second preset rotating speed, and the second preset rotating speed is the maximum rotating speed of the electric tool when the second battery pack supplies power.

2. The power tool of 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 no lower than 40% of the rated voltage of the motor.

3. The power tool of claim 2, further comprising a first speed regulating device and a second speed regulating device, wherein the first speed regulating device corresponds to a first predetermined speed, the second speed regulating device corresponds to a third predetermined speed, the first predetermined speed is greater than the third predetermined speed, and the third predetermined speed is less than the second predetermined speed.

4. The electric tool according to claim 3, wherein when the first speed adjusting device is operated and the electric tool is started, the control unit gradually increases the duty ratio of the control signal, and if the rotation speed obtained by the rotation speed detecting module is equal to a first preset rotation speed, the control unit controls the motor to operate at the first preset rotation speed at a steady speed, otherwise, the control unit controls the motor to operate at the second preset rotation speed at a steady speed.

5. The power tool of claim 3, wherein 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 rotation speed obtained by the rotation speed detecting module is equal to a third preset rotation speed, and the control unit controls the motor to maintain the third preset rotation speed.

6. The power tool of claim 1, further comprising a power tool housing, wherein the battery connector is disposed on the power tool housing, and wherein the second battery pack comprises a first battery pack and a second battery pack, the first battery pack and the second battery pack being connected in series to provide power to the power tool.

7. The power tool of claim 1, wherein the battery connecting portion includes a first power interface and a second power interface, the first power interface is used for electrically connecting an adapter, the adapter is detachably connected to a housing of the power tool, the adapter is provided with a plurality of battery pack connecting seats, 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 a power input port of the power tool to provide power for the power tool.

8. The power tool of claim 7, wherein the adapter is removably mounted within a housing of a backpack assembly, the backpack assembly being connected to the power tool via a connection assembly to provide power to the power tool.

9. The power tool of claim 7 or 8, wherein the adapter is provided with four battery pack connecting seats, and the output voltage of the four battery pack connecting seats after being connected in series is greater than the rated voltage of the motor.

10. The power tool of claim 8, wherein the connection assembly includes a cable.

11. The power tool of claim 1, further comprising a voltage detection module for detecting a terminal voltage of the motor, wherein the control unit adjusts a duty cycle of the control signal such that the terminal voltage of the motor is less than or equal to a rated voltage of the power tool.

12. The power tool of claim 11, wherein the first battery pack comprises a first battery pack and a second battery pack, the power tool further comprising a first switch and a second switch, one end of the first switch being coupled to one end of a start/stop switch of the power tool and forming a first node, wherein the other end of the start/stop switch is coupled to the motor; one end of the second switch is connected with the other end of the first switch to form a second node, and the other end of the second switch is connected with the input end of the driving unit to form a third node; the positive pole of the first battery pack is connected with the first node, the negative pole of the first battery pack is connected with the second node, the positive pole of the second battery pack is connected with the second node, the negative pole of the second battery pack is connected with 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 connected, the first switch is in an open state, when the second battery pack is not connected, the second switch is in a closed state, and when the second battery pack is connected, the second switch is in an open state.

13. The power tool of claim 11, wherein the first battery pack includes a first battery pack and a second battery pack, the power tool further comprising:

14. The power tool of claim 11, further comprising:

15. The power tool of claim 11, further comprising:

the control unit is communicated with a server through the wireless communication module to acquire control parameters corresponding to the electric tool from the server to work according to the control parameters, and/or send the working parameters of the electric tool to the server to store the working parameters in a historical database of the server, so that the server optimizes a control parameter database corresponding to the electric tool according to the working parameters in the historical database.

16. The electric tool as claimed in claim 1, wherein the switching frequency of the power switch tube is in a range of 4-20 Khz.

17. The power tool of claim 1, wherein the motor is one of a brush motor, a brushless motor, a switched reluctance motor, or a high frequency ac induction motor.

18. 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, a rated output voltage of the first battery pack being larger than a rated output voltage of the second battery pack, and a motor having a rated voltage lower than at least one of the rated output voltages of the first battery pack and the second battery pack, the method comprising:

step S2, determining whether the rotation speed of the motor is equal to a first preset rotation speed, wherein the first preset rotation speed is less than or equal to the rated rotation speed of the motor, if so, executing step S3, otherwise, executing step S4;

step S3, controlling the motor to operate at a first preset rotating speed;

and step S5, controlling the motor to operate at a fourth preset rotating speed, wherein the fourth preset rotating speed is less than or equal to the rotating speed corresponding to the rated output voltage of the second battery pack at the preset duty ratio.