Electric tool and starting method thereof
阅读说明:本技术 电动工具及其启动方法 (Electric tool and starting method thereof ) 是由 周懿 杨德中 徐天啸 杨玉伟 段俊雅 陆冰 杨鑫 于 2019-09-12 设计创作,主要内容包括:本发明公开了一种电动工具,使用电池包供电,电动工具包括:工具附件;电机,用于驱动工具附件;驱动电路,与电机电性连接,用于使所述电池包的电压加载至所述电机;控制模块,与驱动电路电性连接,控制模块被配置为:获取电池包的输出电压;根据电池包的输出电压动态调整输出至驱动电路的PWM信号的占空比以使电池包的输出电压大于第一欠压保护阈值。本发明还公开上述电动工具的启动方法。本发明的电动工具及其启动方法能够在低温下安全启动。(The invention discloses an electric tool, which is powered by a battery pack and comprises: a tool accessory; a motor for driving the tool attachment; the driving circuit is electrically connected with the motor and is used for loading the voltage of the battery pack to the motor; a control module electrically connected to the drive circuit, the control module configured to: acquiring the output voltage of the battery pack; and dynamically adjusting the duty ratio of the PWM signal output to the driving circuit according to the output voltage of the battery pack so as to enable the output voltage of the battery pack to be larger than a first undervoltage protection threshold value. The invention also discloses a starting method of the electric tool. The electric tool and the starting method thereof can be started safely at low temperature.)
1. A power tool powered using a battery pack, the power tool comprising:
a tool accessory;
a motor for driving the tool attachment;
a drive circuit for applying a voltage of the battery pack to the motor;
a control module electrically connected to the driving circuit and capable of obtaining an output voltage of the battery pack, the control module being configured to:
and dynamically adjusting the duty ratio of a PWM signal output to the driving circuit according to the output voltage of the battery pack so as to enable the output voltage of the battery pack to be larger than a first undervoltage protection threshold value.
2. The power tool of claim 1,
the output voltage of the battery pack fluctuates up and down around a preset voltage threshold within a preset time range.
3. The power tool of claim 2,
when the temperature of the electric tool is lower than a preset temperature threshold value, setting the first undervoltage protection threshold value;
when the temperature of the electric tool is higher than a preset temperature threshold value, setting a second undervoltage protection threshold value;
wherein the first undervoltage protection threshold is less than the second undervoltage protection threshold;
the preset voltage threshold is greater than the first undervoltage protection threshold and less than the second undervoltage protection threshold.
4. The power tool of claim 3,
the value range of the preset temperature threshold is-20 ℃ to 10 ℃.
5. The power tool of claim 3,
the value range of the ratio of the first under-voltage protection threshold value to the rated voltage of the battery pack is 0.25-0.75.
6. The power tool of claim 3,
the value range of the ratio of the second under-voltage protection threshold value to the rated voltage of the battery pack is 0.3-0.8.
7. The power tool of claim 1,
the control module is configured to:
and if the output voltage of the battery pack is smaller than a preset voltage threshold, reducing the duty ratio of the PWM signal output to the driving circuit so as to enable the output voltage of the battery pack to be larger than or equal to the preset voltage threshold.
8. A method of starting the power tool of claim 1, comprising:
acquiring the output voltage of the battery pack;
judging whether the output voltage of the battery pack is smaller than a preset voltage threshold value or not;
if the output voltage of the battery pack is smaller than a preset voltage threshold, reducing the duty ratio of a PWM signal output to a driving circuit to enable the output voltage of the battery pack to be larger than or equal to the preset voltage threshold;
if the output voltage of the battery pack is larger than or equal to a preset voltage threshold, judging whether the duty ratio of the current PWM signal is equal to the final duty ratio or not; and if the duty ratio of the current PWM signal is equal to the final duty ratio, outputting the PWM signal with the final duty ratio to the driving circuit so as to enable the motor to operate at the final rotating speed.
9. The method of starting a power tool according to claim 8,
the preset voltage threshold is greater than a first undervoltage protection threshold and less than a second undervoltage protection threshold;
the value range of the ratio of the first under-voltage protection threshold value to the rated voltage of the battery pack is 0.25-0.75;
the value range of the ratio of the second under-voltage protection threshold value to the rated voltage of the battery pack is 0.3-0.8.
10. The method of starting a power tool according to claim 8,
before judging whether the output voltage of the battery pack is smaller than a preset voltage threshold, the method comprises the following steps:
acquiring the current of the motor;
judging whether the current of the motor is smaller than a preset current threshold value or not;
when the current of the motor is smaller than a preset current threshold value, outputting a first PWM signal with a gradually increased duty ratio to the driving circuit so as to enable the rotating speed of the motor to gradually increase to a preset rotating speed at a first change rate;
when the current of the motor is smaller than a preset current threshold value, outputting a second PWM signal with a gradually increased duty ratio to the driving circuit so that the rotating speed of the motor is gradually increased to a preset rotating speed at a second change rate; the rate of increase of the duty cycle of the second PWM signal is less than the rate of increase of the duty cycle of the first PWM signal.
Technical Field
The invention relates to an electric tool and a starting method thereof.
Background
In the electric tool with the transmission device, especially when a worm gear mechanism meshed with each other is used, when the electric tool is started in a low-temperature environment, the starting torque of the electric tool is increased due to the solidification of lubricating oil, at the moment, if the electric tool is started forcibly according to a starting mode in a normal environment, a larger starting current is needed, and the excessive starting current easily damages an electronic switching element (such as a field effect transistor) in the electric tool or enters overcurrent protection, so that the starting of the electric tool is unsuccessful. Particularly, in the case of a battery pack-powered electric tool, the low-temperature start may cause the output voltage of the battery pack to be too low, which may result in the electric tool being unable to start successfully due to the under-voltage protection, and may also affect the life of the battery pack.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an electric tool capable of being started safely at low temperature and a starting method thereof.
In order to achieve the above object, the present invention adopts the following technical solutions:
a power tool powered using a battery pack, the power tool comprising: a tool accessory; a motor for driving the tool attachment; a drive circuit for applying a voltage of the battery pack to the motor; a control module electrically connected to the driving circuit and capable of obtaining an output voltage of the battery pack, the control module being configured to: and dynamically adjusting the duty ratio of a PWM signal output to the driving circuit according to the output voltage of the battery pack so as to enable the output voltage of the battery pack to be larger than a first undervoltage protection threshold value.
Optionally, the output voltage of the battery pack fluctuates around a preset voltage threshold within a preset time range.
Optionally, when the temperature of the electric tool is lower than a preset temperature threshold, setting the first undervoltage protection threshold; when the temperature of the electric tool is higher than a preset temperature threshold value, setting a second undervoltage protection threshold value; wherein the first undervoltage protection threshold is less than the second undervoltage protection threshold; the preset voltage threshold is greater than the first undervoltage protection threshold and less than the second undervoltage protection threshold.
Optionally, the preset temperature threshold value ranges from-20 ℃ to 10 ℃.
Optionally, a value range of a ratio of the first under-voltage protection threshold to a rated voltage of the battery pack is 0.25 to 0.75.
Optionally, a value range of a ratio of the second under-voltage protection threshold to a rated voltage of the battery pack is 0.3-0.8.
Optionally, the control module is configured to: and if the output voltage of the battery pack is smaller than a preset voltage threshold, reducing the duty ratio of the PWM signal output to the driving circuit so as to enable the output voltage of the battery pack to be larger than or equal to the preset voltage threshold.
A starting method of the electric tool comprises the following steps: acquiring the output voltage of the battery pack; judging whether the output voltage of the battery pack is smaller than a preset voltage threshold value or not; if the output voltage of the battery pack is smaller than a preset voltage threshold, reducing the duty ratio of a PWM signal output to a driving circuit to enable the output voltage of the battery pack to be larger than or equal to the preset voltage threshold; if the output voltage of the battery pack is larger than or equal to a preset voltage threshold, judging whether the duty ratio of the current PWM signal is equal to the final duty ratio or not; and if the duty ratio of the current PWM signal is equal to the final duty ratio, outputting the PWM signal with the final duty ratio to the driving circuit so as to enable the motor to operate at the final rotating speed.
Optionally, the preset voltage threshold is greater than a first undervoltage protection threshold and less than a second undervoltage protection threshold; the value range of the ratio of the first under-voltage protection threshold value to the rated voltage of the battery pack is 0.25-0.75; the value range of the ratio of the second under-voltage protection threshold value to the rated voltage of the battery pack is 0.3-0.8.
Optionally, before determining whether the output voltage of the battery pack is smaller than a preset voltage threshold, the method includes: acquiring the current of the motor; judging whether the current of the motor is smaller than a preset current threshold value or not; when the current of the motor is smaller than a preset current threshold value, outputting a first PWM signal with a gradually increased duty ratio to the driving circuit so as to enable the rotating speed of the motor to gradually increase to a preset rotating speed at a first change rate; when the current of the motor is smaller than a preset current threshold value, outputting a second PWM signal with a gradually increased duty ratio to the driving circuit so that the rotating speed of the motor is gradually increased to a preset rotating speed at a second change rate; the rate of increase of the duty cycle of the second PWM signal is less than the rate of increase of the duty cycle of the first PWM signal.
The electric tool of the invention can be started safely at low temperature.
Drawings
Fig. 1 is an external view of an electric power tool of an embodiment;
FIG. 2 is a schematic diagram of circuitry for one embodiment of the power tool shown in FIG. 1;
FIG. 3 is a flow chart of a method of starting the power tool of FIG. 2;
FIG. 4 is a circuit schematic of another embodiment of the power tool shown in FIG. 1;
FIG. 5 is a flow chart of a method of starting the power tool of FIG. 4;
FIG. 6 is a schematic diagram of the output voltage of the battery pack as a function of time during start-up of the power tool of the present invention;
FIG. 7 is a schematic representation of motor speed over time during start-up of the inventive power tool.
Detailed Description
The invention is described in detail below with reference to the figures and the embodiments.
The power tool of the present invention may be a hand-held power tool, a garden-type tool, and is not limited thereto. The power tool of the present invention includes, but is not limited to, the following: electric tools needing speed regulation, such as a screwdriver, an electric drill, a wrench, an angle grinder and the like, electric tools possibly used for grinding workpieces, such as a sander and the like, and a reciprocating saw, a circular saw, a curve saw and the like possibly used for cutting the workpieces; electric hammers and the like may be used as electric tools for impact use. These tools may also be garden type tools, such as pruners, chain saws; in addition, the tools may be used for other purposes, such as a blender. It is within the scope of the present invention for such power tools to be able to employ the teachings of the following disclosure. The invention is particularly suitable for electric tools which may be used in low temperature environments.
Referring to fig. 1, an electric power tool 10 as an embodiment, taking a handheld circular saw as an example, specifically includes a mechanical structure: housing 11,
In the case of a circular saw, the tool attachment is a saw blade (not shown) for performing the function of the power tool 10. And a
For a circular saw, the power tool 10 further includes: the saw blade shaft 12 is used for supporting the saw blade to rotate in the saw blade cover 19 so as to realize the cutting operation of the workpiece; an operation switch 16 for operation by a user, the operation switch 16 being provided at the handle 18 and being capable of being operated by the user; a base plate 17 for contacting a workpiece; a handle 18 capable of being held by a user, the handle 18 being formed by the housing 11, or formed separately or mounted, the operating switch 16 including a trigger mechanism 461, the trigger mechanism 461 being triggerable to activate the
In the present embodiment, the power tool 10 is powered using a
Referring to fig. 2, the electric power tool 10 according to one embodiment includes:
The
The
Optionally, the power tool 10 further includes a current switch SW (fig. 2 and 4) for turning on or off the electrical connection between the power tool 10 and the
The transmission 14 is provided with a lubricant which at least partially solidifies when the temperature of the power tool 10 is below a preset temperature threshold. Particularly, when the worm and gear mechanism is used as a transmission, the starting torque of the electric tool 10 is increased due to the solidification of the lubricating oil when the electric tool is started in a low temperature environment, and at this time, if the electric tool is started by force in a normal starting mode, a large starting current is needed, and the electronic switch element (for example, a field effect transistor) in the electric tool is easily damaged or overcurrent protection is performed by the excessive starting current, so that the electric tool 10 is not started successfully.
The
In the present embodiment, the
Optionally, when the temperature of the electric tool 10 is lower than a preset temperature threshold, setting the first undervoltage protection threshold; when the temperature of the electric tool 10 is higher than the preset temperature threshold, setting a second undervoltage protection threshold; and the first undervoltage protection threshold value is smaller than the second undervoltage protection threshold value. Optionally, the preset temperature threshold value ranges from-20 ℃ to 10 ℃.
In some embodiments, the ratio of the first under-voltage protection threshold to the rated voltage of the
That is, different undervoltage protection thresholds are set according to the temperature of the power tool 10. The undervoltage protection threshold at low temperature is less than the undervoltage protection threshold at normal temperature.
The
The way for the
Because the preset voltage threshold is set between the undervoltage protection threshold of the normal temperature and the undervoltage protection threshold of the low temperature, at the normal temperature, after the output voltage of the
In the low-temperature start, the
That is, when the voltage of the
At the initial stage of starting, the temperature of the electric tool 10 is low, the lubricating oil is in a solidification state, the starting torque of the
If the output voltage of the
and in the whole process, the output voltage of the
Referring to fig. 3, the method for starting the electric power tool 10 shown in fig. 2 includes:
step S11: the power tool 10 is powered up;
the power tool 10 is powered up, the
Step S12: controlling the driving
specifically, the control module 221 first outputs an initial duty cycle to the driving
Step S13: and judging whether the output voltage of the
Specifically, the
Step S14: the duty ratio is reduced so that the output voltage of the
Specifically, if the output voltage of the
Wherein, the first undervoltage protection threshold value and the second undervoltage protection threshold value are set as follows: if the temperature of the electric tool 10 is lower than the preset temperature threshold, the undervoltage protection threshold of the electric tool 10 is set as a first undervoltage protection threshold; if the temperature of the electric tool 10 is higher than the preset temperature threshold, the under-voltage protection threshold of the electric tool 10 is set to be a second under-voltage protection threshold; and the first undervoltage protection threshold value is smaller than the second undervoltage protection threshold value.
Optionally, the preset temperature threshold value ranges from-20 ℃ to 10 ℃.
Optionally, a value range of a ratio of the first under-voltage protection threshold to a rated voltage of the
Optionally, a value range of a ratio of the second under-voltage protection threshold to a rated voltage of the
That is, the predetermined voltage threshold is greater than the under-voltage protection threshold of the electric tool 10 at the low temperature and is less than the under-voltage protection threshold of the electric tool 10 at the normal temperature. For example, taking the
Step S15: and judging whether the duty ratio of the PWM signal reaches a preset final duty ratio, if so, turning to the step S16, otherwise, turning to the step S13.
The
Step S16: the
The power tool 10 ends the start-up process and enters the normal operation phase.
Referring to fig. 4, as another embodiment, a circuit system of the electric power tool 10 includes: a
The present embodiment differs from the above embodiments in that a
In this embodiment, compared to the previous embodiment, the duty ratio of the PWM signal output to the driving
That is to say, at the initial stage of the initial start of the
Optionally, the value range of the preset current threshold is 50-100A. A preset current threshold value is set to prevent the starting current from being too large and easily entering overcurrent protection to cause unsuccessful starting. The invention takes the preset current threshold as a reference, and starts to reduce the duty ratio after the current of the
Optionally, the second rate of increase of the duty cycle of the second PWM signal is inversely related to the current of the
Optionally, a duty ratio increase rate of at least one of the duty ratio of the first PWM signal and the duty ratio of the second PWM signal when being smaller than a preset duty ratio threshold is greater than an increase rate of the duty ratio of the PWM signal when being greater than or equal to the preset duty ratio threshold.
For example, if the preset current threshold is set to 80A, when the current of the
With the above configuration, the duty ratio of the PWM signal is adjusted according to the current of the
Referring to fig. 5, the method for starting the electric power tool 10 shown in fig. 4 includes:
step S21: the
the power tool 10 is powered up and the
Step S22: and judging whether the current of the
Specifically, the
Step S23: controlling the driving
specifically, when the current of the
Step S24: controlling the driving
specifically, when the current of the
That is, if the current of the
Optionally, the second rate of increase of the duty cycle of the second PWM signal is inversely related to the current of the
Optionally, a duty ratio increase rate of at least one of the duty ratio of the first PWM signal and the duty ratio of the second PWM signal when being smaller than a preset duty ratio threshold is greater than an increase rate of the duty ratio of the PWM signal when being greater than or equal to the preset duty ratio threshold.
For example, if the preset current threshold is set to 80A, when the current of the
Step S25: and judging whether the output voltage of the
Specifically, the
Step S26: and reducing the duty ratio to enable the output voltage of the battery pack to be larger than or equal to a preset voltage threshold value.
Specifically, if the output voltage of the
Wherein, the first undervoltage protection threshold value and the second undervoltage protection threshold value are set as follows: if the temperature of the electric tool 10 is higher than the preset temperature threshold, the under-voltage protection threshold of the electric tool 10 is set to be a second under-voltage protection threshold; if the temperature of the electric tool 10 is lower than the preset temperature threshold, the undervoltage protection threshold of the electric tool 10 is set as a first undervoltage protection threshold; and the first undervoltage protection threshold value is smaller than the second undervoltage protection threshold value.
Optionally, the preset temperature threshold value ranges from-20 ℃ to 10 ℃.
Optionally, a value range of a ratio of the first under-voltage protection threshold to a rated voltage of the
Optionally, a value range of a ratio of the second under-voltage protection threshold to a rated voltage of the
That is, the predetermined voltage threshold is greater than the under-voltage protection threshold of the electric tool 10 at the low temperature and is less than the under-voltage protection threshold of the electric tool 10 at the normal temperature. For example, taking the
Step S27: and judging whether the duty ratio reaches a preset final duty ratio, if so, turning to the step S67, and otherwise, turning to the step S62.
The
Step S28: and finishing the starting of the
The power tool 10 ends the start-up process and enters the normal operation phase.
Referring to fig. 6, in the above two embodiments, by dynamically adjusting the duty ratio output to the driving
More specifically, the low-temperature starting process of the
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It should be understood by those skilled in the art that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by using equivalent alternatives or equivalent variations fall within the scope of the present invention.
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