CN108326802B - Electric tool - Google Patents
Electric tool Download PDFInfo
- Publication number
- CN108326802B CN108326802B CN201810303236.0A CN201810303236A CN108326802B CN 108326802 B CN108326802 B CN 108326802B CN 201810303236 A CN201810303236 A CN 201810303236A CN 108326802 B CN108326802 B CN 108326802B
- Authority
- CN
- China
- Prior art keywords
- motor
- current value
- max
- control unit
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D17/00—Details of, or accessories for, portable power-driven percussive tools
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D11/00—Portable percussive tools with electromotor or other motor drive
- B25D11/06—Means for driving the impulse member
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D16/00—Portable percussive machines with superimposed rotation, the rotational movement of the output shaft of a motor being modified to generate axial impacts on the tool bit
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
- Details Of Spanners, Wrenches, And Screw Drivers And Accessories (AREA)
Abstract
The invention discloses an electric tool, which comprises a shell, a motor, a transmission device, an output shaft, a control unit and a switch, wherein the motor, the transmission device, the output shaft, the control unit and the switch are positioned in the shell, the motor drives the output shaft to rotate through the transmission device, the control unit controls the motor to operate according to the switch state, the control unit comprises a current detection unit, a storage unit and a judgment unit, the current detection unit is used for detecting the current value I of a real-time motor, and the storage unit is used for storing the maximum current value I max; when the judging unit judges that the current value I of the current motor is smaller than or equal to K times of the stored maximum current value I max during the reverse rotation of the motor, the control unit cuts off the current of the motor, and the value range of K is 0.3 to 0.7. The technical scheme provided by the invention can realize the reversing automatic stop function of the tool and prevent the risk of falling off due to complete separation of the bolt and the nut.
Description
[ Technical field ]
The present invention relates to an electric tool, and more particularly, to an electric tool capable of automatically stopping.
[ Background Art ]
Currently, common electric tools, such as screw driver, impact wrench, etc., are used to tighten or remove fasteners, such as screws, bolts, etc., by driving an output shaft to rotate by a motor. When the fastening piece is removed, the fastening piece can be removed in a short time due to the high rotating speed of the electric tool, so that the problem that the fastening piece is easy to fall off after the fastening piece is removed is solved, and in order to solve the problem, a technical scheme is provided in Chinese patent publication No. CN104656549B, the rotating speed of the motor is changed or the machine is stopped if the rotating speed of the motor is smaller than or equal to a preset threshold value by detecting the current value of the motor and comparing the current value of the motor with the preset threshold value. However, in actual situations, as the service time of the electric tool is prolonged, the permanent magnet of the motor is degraded to different degrees, so that under the same current driving, the output torque of the motor is reduced, and if a fixed preset current threshold is adopted as a standard for stopping judgment, the phenomenon that the screw is excessively loosened after the electric tool is used for a long time can occur.
[ Summary of the invention ]
Aiming at the defects of the prior art, the invention aims to provide an electric tool capable of realizing automatic stop under the condition of changing working parameters of a motor. In order to achieve the above purpose, the invention adopts the following technical scheme: a power tool, comprising: the motor drives the transmission device to drive the output shaft to do forward and reverse rotation motions, the control unit controls the motor to run according to the switching state, and the control unit comprises a detection unit, a storage unit and a judgment unit, wherein the detection unit is used for detecting a real-time current value I of the motor and storing a maximum current value I max through the storage unit; when the motor rotates reversely, the control unit cuts off the motor current when the judging unit judges that the current motor current value I is smaller than or equal to K times of the stored maximum current value I max, and the value range of K is 0.3 to 0.7.
Further, the current detecting unit acquires the motor current value I through a current detecting circuit composed of a resistive element and a filter circuit.
Further, when the judging unit judges that the current value I of the current motor is smaller than or equal to K times of the stored maximum current value I max, and after the preset duration T passes, the control unit cuts off the current motor, and the value range of the preset duration T is 30ms to 300ms.
Further, the detection unit acquires a motor current value I through periodic sampling, and the sampling period is smaller than a preset duration T.
Further, the filter circuit is a first-order lag filter circuit.
Further, the method for obtaining the maximum current value I max is as follows: after the motor reverse start is completed, the storage unit stores the first current value detected by the detection unit as a maximum current value I max.
Further, the method for obtaining the maximum current value I max further includes: the control unit periodically compares the maximum current value I max stored in the storage unit with the current value I detected in real time, if the maximum current value I max stored in the storage unit is greater than or equal to the current value I detected in real time, the maximum current value I max is unchanged, otherwise, the newly detected current value I of the motor is set as the maximum current value I max.
Further, the motor reverse rotation start time is a preset fixed value.
Further, the power tool is a brushless impact wrench.
Compared with the prior art, the invention has the following beneficial effects: when the battery voltage is reduced or the working performance of the motor is reduced due to the degradation of the permanent magnet, accurate reverse automatic stop can still be realized, and the fastener is prevented from falling off.
[ Description of the drawings ]
The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings:
FIG. 1 is a schematic view of a power tool of the present invention;
FIG. 2 is a logic diagram of a power tool circuit of the present invention;
FIG. 3 is a schematic view of the current flow of the power tool of the present invention when reversing the direction of removal of the fastener;
FIG. 4 is a schematic diagram of the current curve of the power tool of the present invention in the idle state during the reverse rotation;
FIG. 5 is a schematic circuit diagram of the power tool of the present invention;
FIG. 6-1 is a graph of the current carrying on the power tool of the present invention at K of 0.3;
FIG. 6-2 is a graph of the current load of the power tool of the present invention when K is 0.3;
FIGS. 6-3 are graphs of the current carried by the power tool of the present invention at K of 0.5;
FIGS. 6-4 are graphs of current loading for a power tool of the present invention at K of 0.5;
FIGS. 6-5 are graphs of the current carried by the power tool of the present invention at K of 0.7;
FIGS. 6-6 are graphs of current loading for a power tool of the present invention at K of 0.7;
Detailed description of the preferred embodiments
Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.
Referring to the electric power tool and the circuit logic diagram shown in fig. 1 and 2, the electric power tool, for example, an impact wrench, mainly includes a housing 1, a motor (not shown in the drawings) located in the housing, the motor drives an output shaft 2 to rotate through a transmission device, the motor used in the present embodiment is a brushless motor, a battery pack 3 connected to a tool main body as a power source, a main switch SW1 for controlling the start/stop of the motor, and a control unit MCU4, the control unit MCU4 includes: the control unit MCU4 receives input signals of the main switch SW1, the reversing switch SW2 and the current detection circuit 5, and controls the motor to perform corresponding actions accordingly.
Referring to the current graph shown in fig. 3, when the user operates the reversing switch SW2 to switch the impact wrench to the reverse mode, the working head at the end of the output shaft 2 collides with the fastener, the main switch SW1 is pressed, the motor is started, the motor starting time is a preset fixed value, and the starting time is set to 100ms in this embodiment. In the start-up phase, the motor current I rapidly increases, and reaches a maximum value when the start-up phase is completed. When the start-up phase is completed, i.e. after the main switch SW1 is triggered for 100ms, the control unit MCU4 starts to collect the current value I through the current detection circuit 5, and the storage unit of the control unit MCU4 stores the current value I collected for the first time as the maximum current value I max. The detection unit of the control unit MCU4 obtains the current value I of the motor from the current detection circuit 5 in real time, the judgment unit of the control unit MCU4 compares the current value I detected in real time with the maximum current value I max in the storage unit, if the current value I detected in real time is smaller than K times of the maximum current value I max, i.e. if the shutdown judgment condition is I < K x I max, The control unit MCU4 sends a signal for cutting off the power supply of the motor, the motor driving current I becomes zero, and the reverse automatic stop of the impact wrench is realized. If the stop judgment condition is less than 0.1 times the maximum current value I max, the current value is close to the idle current value of the impact wrench, and the purpose of preventing the fastener from loosening cannot be achieved, but if the stop judgment condition is too large, the fastener cannot be smoothly separated. Fig. 6-1 is a graph of current when the electric tool is loaded with K being 0.3, current begins to increase after the motor is turned on in reverse, periodic impact on the fastener causes periodic change of current waveform, current drops after the fastener is released, and current interruption becomes zero and stops when the real-time current value I reaches 0.3 times of the maximum current value. Fig. 6-2 is a graph of current at 0.3 for K at no load and motor reversal, and also for shutdown when the real-time current value I reaches 0.3 times the maximum current value. Fig. 6-3 are graphs of current when the power tool is loaded with K at 0.5, which are substantially the same as K at 0.3, and when the real-time current value I reaches 0.5 times the maximum current value, the current interruption becomes zero, and the power tool is stopped. Fig. 6-4 are graphs of current when the motor is reversed at 0.5 for K, no load, and likewise shut down when the real-time current value I reaches 0.5 times the maximum current value. Fig. 6-5 are graphs of current when the power tool is loaded with K at 0.7, which are substantially the same as K at 0.3, and when the real-time current value I reaches 0.7 times the maximum current value, the current interruption becomes zero, and the power tool is stopped. Fig. 6-6 are graphs of current when the motor is reversed at 0.7 for K, no load, and likewise shut down when the real-time current value I reaches 0.7 times the maximum current value. It is considered that the shutdown judgment condition is set to be 0.3 to 0.7 times of the maximum current value I max through a plurality of experiments.
In order to prevent erroneous stop caused by too small real-time current value I detected by the detection unit due to motor current jitter or the like, in another embodiment: the stopping judgment condition is that the real-time current value I is continuously smaller than 0.4 times of the maximum current value I max, the duration is not smaller than 30ms, the duration is not too short or too long, erroneous judgment cannot be prevented, the stopping time is easily delayed when the duration is too short, the fastener is loosened and falls off, the duration is preferably 30ms to 300ms, the control unit MCU4 sends out a signal for cutting off the power supply of the motor, and the tool is stopped.
In addition, since the starting time is a preset fixed value, but the actual working condition is complicated, after the starting phase is finished, the motor current value I may not reach the maximum value, or a situation that the motor current value exceeds the current value at the end of the starting phase may occur in the impact phase, in another embodiment, the detecting unit periodically, that is, every 50ms, collects the motor current value I from the current detecting circuit 5 at the end of the starting phase, compares the collected current value I with the maximum current value I max stored in the storage unit, and if the maximum current value I max stored in the storage unit is smaller than the current value I collected last, replaces the current value originally stored in the storage unit with the current value I collected last as the maximum current value I max.
The motor output torque t=k t ×i, where K t is a torque coefficient, related to motor characteristics, I is a motor current value, generally considered as K t is a constant, and after the motor model is fixed, the output torque can be calculated through the current value I. However, the permanent magnet magnetism of the brushless motor is weakened due to the physical environment, the natural loss of the machine, and the like, so that the motor characteristics are lowered, the torque coefficient K t is reduced, and therefore, after the torque coefficient K t is reduced, the motor output current I is increased in response to the same load. If the fixed current threshold judgment mode in the prior art is adopted, the actual shutdown time is delayed, so that the risk of excessive loosening and falling of the fastener exists, by adopting the technical scheme in the embodiment, after the torque coefficient K t is reduced, the maximum current value I max stored in the storage unit can be increased under the condition of unchanged load, the actual shutdown judgment condition is K times of the maximum current value I max, the value range of K is 0.3 to 0.7, the proportional increase is also caused, and the actual shutdown time is the same as that before the motor characteristic is reduced. That is, by adopting the technical scheme in the embodiment, the change condition of the actual load can be monitored more accurately, and the adverse effect of the change of the motor characteristic on the tool is eliminated.
Referring to the current diagram of fig. 4, the main switch SW1 is triggered to be actuated in the reverse mode in the idle state, i.e., when the working head at the end of the output shaft 2 is not in contact with a fastener. The starting time of the motor is still 100ms, the motor current value I is rapidly increased in the starting stage, the motor current value I reaches the maximum value after the starting stage is finished, but the motor current I starts to gradually decrease because no actual load exists at the working end, and finally the current value I can be stabilized at a lower level value, namely the motor no-load current, and the motor no-load current value is usually 0.1 to 0.3 times of the maximum current value of the motor. In the idle state, the detection unit of the control unit MCU4 starts to acquire the current value I after the start-up phase is finished, the storage unit stores the motor current value I acquired for the first time as the maximum current value I max, when the judgment unit judges that the motor driving current value I is reduced to 0.4 times of the maximum current value I max, the control unit MCU4 sends a signal for cutting off the motor power supply, namely the control logic of the control unit MCU4 in the idle state is the same as that in the reverse screw loosening mode, and the impact wrench also automatically stops when in idle reverse.
Referring to the schematic circuit diagram shown in fig. 5, since the motor driving current has many burrs and shakes in the actual working condition, in order to better collect the current value I of the motor, the current detection circuit 5 is composed of a first-order hysteresis filter circuit composed of a resistor 6 and a capacitor 7 and a resistor R1, and the burrs and partial shakes of the motor driving current can be eliminated through the first-order hysteresis filter circuit, so that the current signal obtained by the detection unit is smoother. In other embodiments, other circuits may be used to sample and filter the motor current value I, such as an average circuit, a sliding window filter circuit, a linear regression circuit, and the like.
The above embodiments do not limit the present invention in any way, and all the technical solutions obtained by adopting equivalent substitution or equivalent transformation fall within the protection scope of the present invention.
Claims (7)
1. The utility model provides an electric tool, includes the casing, is located motor, transmission, output shaft, control unit and switch in the casing, and motor drive transmission drives the output shaft and does forward and reverse rotary motion, and control unit is according to the operation of switch state control motor, its characterized in that:
The control unit comprises a detection unit, a storage unit and a judging unit, wherein the detection unit is used for detecting a real-time current value I of the motor and storing a maximum current value I max through the storage unit;
When the motor rotates in the no-load reverse direction, the maximum current value I max is obtained by the following steps: after the motor is reversely started, the storage unit stores the first current value detected by the detection unit as a maximum current value I max; when the judging unit judges that the current value of the current motor is smaller than or equal to 0.4 times of the maximum current value I max in the storage unit I, the control unit cuts off the current motor;
When the motor rotates reversely under load, the method for acquiring the maximum current value I max comprises the following steps: the control unit periodically compares the maximum current value I max stored in the storage unit with the current value I detected in real time, if the maximum current value I max stored in the storage unit is greater than or equal to the current value I detected in real time, the maximum current value I max is unchanged, otherwise, the newly detected current value I of the motor is set as the maximum current value I max;
When the judging unit judges that the current value I of the current motor is smaller than or equal to K times of the maximum current value I max in the storage unit, the control unit cuts off the current motor, and the value range of K is 0.3 to 0.7.
2. The power tool of claim 1, wherein: the detection unit acquires a motor current value I through a current detection circuit consisting of a resistance element and a filter circuit.
3. The power tool of claim 2, wherein: when the judging unit judges that the current value I of the current motor is smaller than or equal to K times of the stored maximum current value I max, and the preset duration T is over, the control unit cuts off the current motor, and the value range of the preset duration T is 30ms to 300ms.
4. A power tool according to claim 3, wherein: the detection unit acquires a motor current value I through periodic sampling, and the sampling period of the detection unit is smaller than the preset duration T.
5. The power tool of claim 4, wherein: the filter circuit is a first-order lag filter circuit.
6. The power tool of claim 1, wherein: the motor reverse rotation starting time is a preset fixed value.
7. The power tool of claim 6, wherein: the electric tool is a brushless impact wrench.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810303236.0A CN108326802B (en) | 2018-04-07 | 2018-04-07 | Electric tool |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810303236.0A CN108326802B (en) | 2018-04-07 | 2018-04-07 | Electric tool |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108326802A CN108326802A (en) | 2018-07-27 |
| CN108326802B true CN108326802B (en) | 2024-07-23 |
Family
ID=62932802
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810303236.0A Active CN108326802B (en) | 2018-04-07 | 2018-04-07 | Electric tool |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108326802B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110208688A (en) * | 2019-05-09 | 2019-09-06 | 石家庄科林电气股份有限公司 | A kind of failure pre-judging method of breaker energy storage motor |
| CN114453620B (en) * | 2020-11-09 | 2024-01-05 | 南京泉峰科技有限公司 | Intelligent electric tool and control method thereof |
| EP4205906B1 (en) | 2020-11-09 | 2024-12-04 | Nanjing Chervon Industry Co., Ltd. | Smart electric power tool and control method thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN204651901U (en) * | 2015-04-08 | 2015-09-16 | 江苏东成机电工具有限公司 | A kind of electric tool |
| CN208697343U (en) * | 2018-04-07 | 2019-04-05 | 江苏东成机电工具有限公司 | A kind of electric tool |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3690091B2 (en) * | 1997-11-05 | 2005-08-31 | 日産自動車株式会社 | Impact type screw tightening method and equipment |
| DE102009001132B4 (en) * | 2009-02-25 | 2022-04-28 | Robert Bosch Gmbh | power tool |
| JP2013188812A (en) * | 2012-03-13 | 2013-09-26 | Hitachi Koki Co Ltd | Impact tool |
| CN104656551B (en) * | 2014-09-02 | 2016-09-14 | 苏州宝时得电动工具有限公司 | The control method of electric tool and system, electric tool |
| US10322498B2 (en) * | 2014-10-20 | 2019-06-18 | Makita Corporation | Electric power tool |
| JP6709129B2 (en) * | 2016-08-05 | 2020-06-10 | 株式会社マキタ | Electric tool |
-
2018
- 2018-04-07 CN CN201810303236.0A patent/CN108326802B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN204651901U (en) * | 2015-04-08 | 2015-09-16 | 江苏东成机电工具有限公司 | A kind of electric tool |
| CN208697343U (en) * | 2018-04-07 | 2019-04-05 | 江苏东成机电工具有限公司 | A kind of electric tool |
Also Published As
| Publication number | Publication date |
|---|---|
| CN108326802A (en) | 2018-07-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US11975427B2 (en) | Method for controlling an electric motor of a power tool | |
| CN108326802B (en) | Electric tool | |
| JP5622354B2 (en) | Power tool with signal generator | |
| TWI492824B (en) | Kraftschrauber | |
| JP5780896B2 (en) | Electric tool | |
| US9073186B2 (en) | Electric power tool | |
| US9936634B2 (en) | Power tool and control method thereof | |
| CN107701782B (en) | A Valve Controller Using Hall Signals of Brushless Motors | |
| AU6486298A (en) | Controller for variable speed motor | |
| US9555525B2 (en) | Rotation speed control method for impact type fastening tools | |
| EP2764956A1 (en) | Motor-driven appliance and battery pack | |
| JP2017517407A5 (en) | ||
| DE102006016441A1 (en) | Electric machine tool operating method, involves driving electric machine tool by electric motor, where connection of battery unit is made to energize motor that is interrupted upon identification of blocking case | |
| US7750587B2 (en) | Method of controlling a motor of a battery-operated power tool | |
| CN110572089A (en) | Electric tool and control method thereof | |
| CN103358289A (en) | Handheld electric tool and control method thereof | |
| JP2002224972A (en) | Power rotary tool having internal heat/temperature rise detective function | |
| JP2005001039A (en) | Electric tool switch and electric tool using the switch | |
| CN208697343U (en) | A kind of electric tool | |
| JP2006288053A (en) | Electrical equipment | |
| WO2012079936A2 (en) | Method and device for operating an electric hand tool driven by an electric motor | |
| CN113497573A (en) | Electric tool rotation speed control method and electric tool | |
| US5083068A (en) | Method and device for enlarging a stoppage safety function for electric motors | |
| CN113411034B (en) | Non-inductive brushless permanent magnet motor locked-rotor control method and variable frequency controller | |
| CN108459519B (en) | Electric wrench control method and device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |