Electric Tool Control Circuit
An electric tool control circuit includes a central control module, a motor drive module, a motor, and a working parameter detection module. The working parameter detection module can detect and communicate a parameter to the central control module related to a load on the motor detected during running of the motor. The motor drive module is separately electrically connected to the motor by using first and second switch modules, and the motor drive module controls the first and second modules to be discontinuously on and off to thereby reduce variation of a speed of the motor caused by a variation of the load on the motor. The status of the first and second switch modules being on and off are always contrary. A related method is disclosed.
This application is a continuation of U.S. application Ser. No. 15/531,043, filed May 26, 2017, which is a national stage of International Application No. PCT/CN2015/094867, filed Nov. 18, 2015, and claims benefit to Chinese Patent Application No. 201410695333.0 filed Nov. 27, 2014, all of which are incorporated by reference herein.
TECHNICAL FIELDThe present disclosure relates to an electric tool control circuit, especially to the control circuit of an electric reciprocating saw.
BACKGROUNDMotors of some electric tools need to have stable output during operation thereof, especially, it is important to keep the motor with a relatively stable rotating speed in the use of the electric tool that requires high power output. For example, in order to obtain a better cutting effect, the speed of the motor needs to be relatively stable when the reciprocating saw is started, if the motor in the process of rotation suddenly fasts or slows rotation speed, which is then easy to cause beating phenomenon of the reciprocating saw. Usually, the reciprocating saw uses a silicon controlled rectifier to achieve the motor's power on and off, rotation speed of the motor is controlled by adjusting the proportion of power on and off times, that is, via duty cycle to adjust the motor's rotation speed. However, the high-speed rotating motor produces an induced electromotive force in an opposite direction to an original direction of the induced electromotive force, the reversing electromotive force will generate an impedance to the power supply when it is turned on again, this impedance makes it impossible to convert electric energy into kinetic energy, and will increase heat generated by the motor. As the motor produces more heat, the electric energy can't be effectively converted into the kinetic energy, so when the motor is loaded, and required torque thereof becomes larger, the speed of the motor will drop rapidly, and when the load decreases, the speed of the motor will be rapidly increased, which will cause the motor output to be unstable, when the reciprocating saw began to cut, it is easy to cause beating phenomenon thereof, and adversely affecting the cutting effect.
Therefore, a new technical program needs to be proposed to solve the above problems.
SUMMARYIn order to solve the above problems, the present disclosure provides an electric tool control circuit comprises a central control module, a motor drive module, a motor, and a working parameter detection module; the central control module being electrically connected to the motor drive module, and the central control module controlling the turn on and off of the motor drive module; the control circuit comprising a protection module which can prevent a motor peripheral circuit from being damaged by the motor clutter produced during running of the motor; the working parameter detection module being electrically connected to the motor and the central control module respectively, and the working parameter detection module returning a parameter that is detected during running of the motor to the central control module. The motor drive module is electrically connected to the motor respectively by a first switch module and a second switch module, and the motor drive module controls the first and second modules to be discontinuously on and off, features of the first switch module and the second switch module being on and off are always contrary, that is, when the first switch is on, the second switch is off, and when the first switch is off, the second switch is on.
Preferably, the first and second switch modules, the motor drive module and the motor are electrically connected to form a half-bridge driving circuit.
Preferably, field effect transistors are used as the first and second switches.
Preferably, the working parameter detection module detects a current parameter of the motor during running of the motor and then return the current parameter to the central control module.
Preferably, the protection module has a spike absorption module and a follow current module, which respectively form a circuit loop with the motor.
Preferably, the spike absorption module includes a first spike absorption module and a second spike absorption module.
Preferably, a capacitor is used as the first spike absorption module, a schottky dode is used as the second spike absorption module, and a dode is used as the follow current module.
Preferably, the working parameter detection module has a current detection module which detection time is inversely proportional to magnitude of detected current value, when the motor is loaded to increase rotate speed.
Preferably, the working parameter detection module has a current detection module which detection time is proportional to magnitude of detected current value, when the motor idling at high speed and reducing its speed.
The protection module can eliminate the spikes generated by the motor when the motor is operating to protect the first and second switch modules.
The first switch module controls duty cycle of power supply when the motor is running, so that the motor reaches the proper speed. The first spike absorption module absorbs reverse electromotive force generated by both ends of the motor when the first switch module is turned off to protect the first and second switch modules, at the same time, the follow current module turns on, then the second switch module turns on, the second switch module opens to release the induced electrical energy generated by the motor, which reduces the impedance effect of the motor when the first switch module is turned on again, and reduce heat generated by the motor and the first switch module. The second spike absorption module absorbs spikes generated by the motor commutation during the motor operating to protect other electronic components. The turn-on of the first switch module and the turn-off of the second switch module are always carried out at the same time, but it takes a certain time to turn on due to the characteristics of the switch module itself, so that the first switch is always open slower than the follow current module and the first spike absorption module, the same as the follow current module is always open slower than the first spike absorption module. As heat generated by the motor and the first switch module are reduced, the electric tool control circuit can effectively convert the electric energy into kinetic energy relative to the traditional motor control mode. So the motor speed is more stable and affected by the load becomes smaller, and beating phenomenon of the electric chain saw is also greatly reduced when the motor is loaded and requirement of torque becomes larger.
The following is nonrestrictive detailed description of the technical proposal of the present disclosure in combination with drawings.
The present disclosure uses the reciprocating saw as an electric tool in the embodiment to illustrate the technical proposal. However, the technical proposal of the present invention can not only apply to reciprocating saws, but also apply to other electric tools, such as tree trimmer, hand-held brush cutter, etc. As shown in
A control circuit in the above-described control board is shown in
The protection module further shown in
Referring to
The working parameter detection module is also provided with a current sampling resistor R2, which is electrically connected to the motor. The resistor R2 can collect current from different working conditions of the reciprocating saw and return the current back to the central control module. The central control module will compare the feedback current with a preset current value and determine working state of the reciprocating saw. The motor stalls or excessive load acts on the reciprocating saw which will cause the current of the motor being too large, the central control module can be timely shut down power of reciprocating saw to make it stop working. The working parameter detection module can also provide a temperature detection module to detect the temperature of the motor, and a voltage detection module detecting the voltage of the battery pack, so that the motor can be shut down when the motor is overheated or under voltage.
According to
In order to make feedback of the reciprocating saw be more rapid and sensitive to the load, length of the current detection time T1 is inversely proportional to magnitude of the detected current value, that is, the greater the detected current is, the shorter the current detection time T1 is. When the user operates the reciprocating saw, the greater the force applied on the saw blade, the shorter the time of increasing speed of the reciprocating saw, so that the user has a good experience. The relationship between the detection time T1 and the current can be described by the function T1=f (i), which makes the detection time decrease as current I increases. f (I) can be a linear function or a non-Linear function, or discrete set of mapping relationships. Similarly, the current detection time T5 is proportional to the magnitude of the detected current, that is, the smaller the detected current, the shorter the current detected time T5, so that when the user makes the reciprocating saw convert suddenly from a cutting state to a non-cutting state, the motor speed will be quickly reduced to reduce high-speed idle time of the motor.
Claims
1. An electric tool control circuit comprising:
- a motor;
- a central control module, a motor drive module, a working parameter detection module, a first switch module, and a second switch module;
- the central control module being electrically connected to the motor drive module, and the central control module controlling turn on and off of the motor drive module; and
- the working parameter detection module being electrically connected to the motor and the central control module, the working parameter detection module detecting and communicating a parameter to the central control module, the parameter being related to a load on the motor detected during running of the motor, the motor drive module being electrically connected to the motor by a first switch module and a second switch module, the motor drive module controlling the first and second switch modules to be discontinuously on and off to thereby reduce variation of a speed of the motor caused by a variation of the load on the motor, the respective statuses of the first switch module and the second switch module being on and off are always contrary so that when the first switch module is on, the second switch module is off, and when the first switch module is off, the second switch module is on.
2. The electric tool control circuit according to claim 1, wherein the first and second switch modules, the motor drive module and the motor are electrically connected to form a half-bridge driving circuit.
3. The electric tool control circuit according to claim 2, wherein field effect transistors are used as the first and second switch modules.
4. The electric tool control circuit according to claim 1, wherein the parameter detected by the working parameter detection module is at least one of a current of the motor, a voltage of the motor, a speed of the motor, and a temperature of the motor.
5. The electric tool control circuit according to claim 1, wherein the protection module has a spike absorption module and a follow current module, which respectively form a circuit loop with the motor.
6. The electric tool control circuit according to claim 5, wherein the spike absorption module includes a first spike absorption module and a second spike absorption module.
7. The electric tool control circuit according to claim 6, wherein the first spike absorption module is a capacitor, the second spike absorption module is a schottky diode, and the follow current module is a diode.
8. The electric tool control circuit according to claim 1, wherein the working parameter detection module has a current detection module which has a detection time inversely proportional to a magnitude of current value detected when the motor is loaded to increase rotation speed.
9. The electric tool control circuit according to claim 1, wherein the working parameter detection module has a current detection module which has a detection time proportional to a magnitude of current value detected when the motor idling at high speed reduces speed.
10. The electric tool control circuit according to claim 1, further including a protection module which can prevent a motor peripheral circuit from being damaged by motor clutter produced during running of the motor.
11. A method of controlling a speed of a motor of a tool having a central control module, a motor drive module, a working parameter detection module, a first switch module, and a second switch module, the method including the steps of:
- controlling a turning on and a turning off of the motor drive module using the central control module;
- detecting a parameter related to a load on the motor during running of the motor using the working parameter detection module, communicating the parameter detected to the central control unit using the working parameter detection module, the motor drive module being electrically connected to the motor by a first switch module and a second switch module; and
- controlling the first and second switch modules using the motor drive module to be discontinuously on and off to thereby reduce variation of a speed of the motor caused by a variation of the load on the motor, the controlling step including setting respective on and off statuses of the first switch module and the second switch module to always be opposite so that when the first switch module is on, the second switch module is off, and when the first switch module is off, the second switch module is on.
12. The method according to claim 11, wherein the first and second switch modules, the motor drive module and the motor are electrically connected to form a half-bridge driving circuit.
13. The method according to claim 12, wherein field effect transistors are used as the first and second switch modules.
14. The method according to claim 11, wherein detecting step includes detecting at least one of a current of the motor, a voltage of the motor, a speed of the motor, and a temperature of the motor.
15. The method according to claim 11, wherein the protection module has a spike absorption module and a follow current module, which respectively form a circuit loop with the motor.
16. The method according to claim 15, wherein the spike absorption module includes a first spike absorption module and a second spike absorption module.
17. The method according to claim 16, wherein the first spike absorption module is a capacitor, the second spike absorption module is a schottky diode, and the follow current module is a diode.
18. The method according to claim 11, wherein the working parameter detection module has a current detection module which has a detection time inversely proportional to a magnitude of current value detected when the motor is loaded to increase rotation speed.
19. The method according to claim 11, wherein the working parameter detection module has a current detection module which has a detection time proportional to a magnitude of current value detected when the motor idling at high speed reduces speed.
20. The method according to claim 11, further including a protection module which can prevent a motor peripheral circuit from being damaged by motor clutter produced during running of the motor.
Type: Application
Filed: Sep 30, 2019
Publication Date: Jan 23, 2020
Inventor: Fufei Wu (Suzhou)
Application Number: 16/587,385