CN113941984B - Control method of impact type electric tool - Google Patents

Abstract

A method of controlling an impact power tool, comprising: controlling the motor to rotate; continuously obtaining a rotational speed signal from the detection result of a rotational speed detection device and obtaining a current signal from the detection result of a current detection device; obtaining a rotation time corresponding to each rotation angle of the motor according to the change of the pulse wave of the rotation speed signal, and obtaining a motor current from the current signal; judging the number of times of impact generated by the impact mechanism according to the change of the rotation time and the change of the motor current; and controlling the motor to stop rotating when the number of the impact reaches a preset number. Thus, the torque force output by the impact type electric tool can be accurately controlled.

Description

Control method of impact type electric tool

Technical Field

The present invention relates to a power tool; in particular to a control method of an impact type electric tool.

Background

The impact type electric tool comprises a motor and a punch mechanism, wherein the motor drives the impact mechanism to act so as to generate impact, and the more the number of times of impact is, the larger the torque value output by the workpiece is. The traditional impact type electric tool can only output fixed torsion, however, the fixed torsion cannot be applied to workpieces with various sizes, and when the torsion required for screwing the workpieces is larger than the torsion value output by the impact type electric tool, the workpieces cannot be screwed; when the torque force required to screw the workpiece is smaller than the torque force value output by the impact type electric tool, the workpiece is damaged.

Accordingly, an impact type power tool capable of adjusting the torque output is also generated, and the conventional impact type power tool capable of adjusting the torque output sets different impact time after the impact is generated as the adjustment of the torque output. The longer the impact time is set, the more the impact times are relatively increased, and the higher the generated torsion force is. However, the conventional impact type electric tool cannot know the number of impacts generated by the impact mechanism during the impact time, and thus the control of the torque force is not accurate enough.

Disclosure of Invention

Accordingly, the present invention is directed to a control method for an impact type electric tool, which can precisely control the torque output.

The present invention provides a control method of an impact type electric tool, wherein the impact type electric tool comprises a motor, an impact mechanism, a rotation speed detecting device and a current detecting device, the impact mechanism is connected with the motor and is driven by the motor to rotate, the rotation speed detecting device is used for detecting the rotation speed of the motor, and the current detecting device is used for detecting a motor current when the motor is operated; the control method comprises the following steps:

A. controlling the motor to rotate;

B. continuously obtaining a rotation speed signal from the detection result of the rotation speed detection device and obtaining a current signal from the detection result of the current detection device; the rotating speed signal is provided with a plurality of pulse waves corresponding to the rotating angles of the motor; obtaining a rotation time corresponding to each rotation angle of the motor according to the change of the pulse waves, and obtaining the motor current from the current signal;

C. judging the number of times of impact generated by the impact mechanism according to the change of the rotation time of the rotation speed signal and the change of the motor current of the current signal;

D. comparing whether the number of times of impact reaches a preset number of times, if not, enabling the motor to continue to rotate; if yes, the motor is controlled to stop rotating.

The invention has the advantages that the number of times of impact of the impact mechanism can be accurately judged through the motor current and the rotation time of the rotation speed signal, and the motor is controlled to stop rotating when the number of times of impact reaches the required preset number of times, thereby accurately controlling the torque force output by the impact type electric tool.

Drawings

Fig. 1 is a schematic view of an impact type power tool according to a first preferred embodiment of the present invention.

FIG. 2 is a system block diagram of the preferred embodiment.

FIG. 3 is a waveform diagram of the rotational speed signal of the preferred embodiment.

FIG. 4 is a flow chart of a control method of the impact type power tool according to the preferred embodiment.

Fig. 5 is a waveform diagram of the impact type power tool according to the preferred embodiment.

Fig. 6 is a waveform diagram of the impact type power tool according to the preferred embodiment.

Fig. 7 is a waveform diagram of the impact type power tool according to the preferred embodiment.

Fig. 8 is a waveform diagram of the impact type power tool according to the preferred embodiment.

Fig. 9 is a schematic view of an impact type power tool according to a second preferred embodiment of the present invention.

FIG. 10 is a flow chart of a control method of the impact type power tool according to the preferred embodiment.

FIG. 11 is a waveform diagram of the rotational speed signal of the preferred embodiment.

Detailed Description

In order to more clearly illustrate the present invention, preferred embodiments are described in detail below with reference to the accompanying drawings. Referring to fig. 1 and 2, an impact type electric tool 1 according to a first preferred embodiment of the present invention is exemplified by an electric impact wrench, which comprises a housing 10, a motor 12, an impact mechanism 14, a first circuit board 16 and a second circuit board 24 disposed in the housing 10, wherein:

the shaft 122 of the motor 12 is connected to the impact mechanism 14, and the motor 12 is controlled to rotate. The motor 12 is in this embodiment a three-phase dc brushless motor.

The impact mechanism 14 is driven by the motor 12 to rotate, the impact mechanism 14 is connected with an output shaft 142, and the output shaft 142 is connected with a workpiece to be driven. When the output shaft 142 receives a certain resistance during the rotation of the impact mechanism 14, the impact mechanism 14 will generate impact, and each impact will apply a predetermined torque to the workpiece.

The first circuit board 16 is provided with a first control device 18, a rotation speed detecting device 20 and a current detecting device 22, wherein,

the first control device 18 is electrically connected to the motor 12 for controlling the operation of the motor 12, in this embodiment, the first control device 18 includes a first controller 182 and a plurality of phase change switching elements 184, the first controller 182 may be a microcontroller, the first controller 182 is electrically connected to the plurality of phase change switching elements 184, and the plurality of phase change switching elements 184 are six MOSFETs in this embodiment and are electrically connected to the stator of the motor 12.

The rotation speed detecting device 20 is configured to detect the rotation speed of the motor 12 and output a rotation speed signal, in this embodiment, the rotation speed detecting device 20 includes a plurality of hall sensors 202 electrically connected to the first controller 182, the plurality of hall sensors 202 are three and are respectively configured to sense the position of the rotor of the motor 12, the output of each hall sensor 202 is changed between a first voltage level and a second voltage level, the plurality of hall sensors 202 respectively output pulse waves sequentially when the rotor rotates 120 degrees, in other words, the rotation speed signal includes the output of three hall sensors 202, and each pulse wave change represents the rotation of the motor by a rotation angle (for example, 120 degrees). In this embodiment, the first voltage level is exemplified by a low voltage level, and the second voltage level is exemplified by a high voltage level.

The second circuit board 24 is electrically connected to a battery 30 and an operation interface 32, and a second control device 26 and a display 28 are disposed on the second circuit board 24. The battery 30 provides power to the second circuit board 24, the operation interface 32 is electrically connected to the second control device 26 and includes a start switch 322 and a section selector 324, the start switch 322 is operated by a user to output a first start signal or a second start signal to the second control device 26, when the user lightly presses the start switch 322, the first start signal is output, and when the start switch 322 is re-pressed, the second start signal is output.

The segment selector 324 may be a switch and be operated by a user to output a segment selection signal to the second control device 26 to select one of a plurality of different torque segments.

The second control device 26 includes a second controller 262 and a storage unit 264, wherein the second controller 262 may be a microcontroller and is electrically connected to the display 28. In this embodiment, the storage unit 264 is a memory built in the second controller 262, and the storage unit 264 stores a plurality of predetermined times, where the plurality of predetermined times respectively correspond to the plurality of torsion segment bits, and the higher the torsion segment bit, the more the predetermined times. The second controller 262 may select a corresponding one of the predetermined times according to the segment selection signal.

The second circuit board 24 is electrically connected to the first circuit board 16 through a transmission line set 36, and the transmission lines of the transmission line set 36 include a power line 361, a ground line 362, a command transmission line 363, a brake signal line 364, a feedback signal line 365, a current signal line 366, and a rotational speed signal line 367. The power line 361 and the ground line 362 are used to transfer power from the second circuit board 24 to the first circuit board 16. The second control device 26 communicates with the first control device 18 via the command transmission line 363, the brake signal line 364, the feedback signal line 365, the current signal line 366, and the rotation speed signal line 367.

The second control device 26 transmits a pwm signal to the first control device 18 via the command transmission line 363 to control the rotation mode of the motor 12, wherein the pwm signal has a pulse frequency representing the rotation direction and a duty cycle representing the rotation speed, the first control device 18 analyzes the pulse frequency of the pwm signal to control the rotation direction of the motor 12, and the duty cycle to control the rotation speed of the motor 12. In one embodiment, two transmission lines may be used instead of the command transmission line 363, one of which transmits a rotation direction command and the other of which transmits a rotation speed command, and the first control device 18 controls the rotation direction of the motor 12 according to the rotation direction command and controls the rotation speed of the motor 12 according to the rotation speed command.

The second control device 26 transmits a braking command via the braking signal line 364, and the first control device 18 controls the motor 12 to stop rotating according to the braking command.

The first control device 18 transmits a corresponding impact signal via the feedback signal line 365, wherein the impact signal is generated according to the action state of the impact mechanism, and the method of generating the impact signal is described later.

The current detecting device detects a motor current when the motor 12 is running and outputs a current signal to the first control device, and the current signal can be transmitted to the second control device through the current signal line 366.

The feedback signal line 365 in the transmission line set 36 is a first transmission line defined in the present invention, and the brake signal line 364 is a second transmission line defined in the present invention.

Since the original rotation speed signal includes the outputs sensed by the three hall sensors 202, in order to facilitate the second control device to determine the rotation speed, in this embodiment, the first controller 182 converts the outputs sensed by the three hall sensors 202 into an integrated rotation speed signal, and the integrated rotation speed signal is transmitted to the second control device 26 through the rotation speed signal line 367 for the second control device 26 to determine the rotation speed of the motor 12. Referring to fig. 3, in the present embodiment, the first controller 182 changes the integrated rotation speed signal from a third voltage level V3 to a fourth voltage level V4 when the output of each hall sensor 202 is changed from the first voltage level V1 to the second voltage level V2, and the first controller 182 changes the integrated rotation speed signal from the fourth voltage level V4 to the third voltage level V3 when the output of each hall sensor 202 is changed from the second voltage level V2 to the first voltage level V1. In the present embodiment, the third voltage level V3 is exemplified by a low voltage level, and the fourth voltage level V4 is exemplified by a high voltage level. In other words, the integrated rotation speed signal has a pulse wave variation of one cycle every 120 degrees of rotation of the rotor, and has three pulse waves of three cycles every one rotation of the rotor, and the second control device 42 calculates the rotation speed of the rotor from the pulse wave cycle of the integrated rotation speed signal, so that the output of the three hall sensors 202 is integrated into one, and the number of transmission lines of the transmission line set 36 can be effectively reduced.

One pulse wave of the original rotational speed signal or one pulse wave of the integrated rotational speed signal corresponds to one rotation angle of the rotating shaft of the motor. The rotation angle corresponding to each pulse wave in this embodiment is 120 degrees.

In an embodiment, the output of one of the hall sensors 202 in the original rotation speed signal may also be transmitted by the first controller 182 to the second control device 26 through the rotation speed signal line 367, and the second control device 26 calculates the rotation speed of the rotor through the pulse wave period output by one of the hall sensors 202. In addition, if the second control device 26 does not need to acquire the rotation speed, the rotation speed signal line 367 may not be provided.

The first control device 18 and the second control device 26 may also be integrated into one control device and located on the same circuit board.

The control method shown in FIG. 4 can be performed by the structure of the impact type electric tool 1, which comprises the following steps:

step S11: the motor 12 is controlled to rotate.

In this embodiment, the user operates the operation interface 32 to select a desired torque segment by the segment selector 324, and the segment selector 324 outputs a corresponding segment selection signal to the second control device 26. The second controller 262 obtains the corresponding predetermined number of times from the storage unit 264 according to the required torque segment and displays the selected segment through the display 28.

After the user lightly depresses the start switch 322, the start switch 322 outputs a first start signal to the second controller 262, the second controller 262 outputs a corresponding pulse width modulation signal to the first control device 18 through the command transmission line 363, and the first controller 182 controls the plurality of phase change switch elements 184 according to the pulse frequency and the duty ratio of the pulse width modulation signal, so as to control the motor 12 to rotate. At this time, the rotation shaft 122 of the motor drives the impact mechanism 14 to rotate, and the output shaft 142 can drive the workpiece.

Referring to fig. 5, during the rotation of the motor 12, the motor can be divided into a first load region, a second load region and a third load region, and the motor current Im is smaller when the rotation resistance of the motor 12 is minimum in the first load region.

Step S12: the rotation speed signal is continuously obtained from the detection result of the rotation speed detection device 20 and the current signal is continuously obtained from the detection result of the current detection device 22.

In this embodiment, the first controller 182 continuously converts the original rotation speed signal detected by the rotation speed detecting device 20 into an integrated rotation speed signal.

With continued reference to fig. 5, as the workpiece is gradually locked, the rotation resistance of the motor 12 gradually increases, at this time, after the user re-presses the start switch 322, the start switch 322 outputs a second start signal to the second controller 262, and the second controller 262 outputs a corresponding pulse width modulation signal through the command transmission line 363, so that the first control device 18 controls the motor 12 to rotate at a fixed rotation speed, and the process of rotating the motor 12 enters the second load area. The fixed rotational speed is greater than the rotational speed in the first load zone. In the second load region, the motor current gradually increases as the workpiece is gradually locked, and the rotational speed gradually decreases.

As the workpiece is locked tighter, the rotational resistance of the motor 12 is greater, the process of rotating the motor 12 enters a third load zone in which the rotational speed of the motor 12 is lower, the motor current increases, and the impact mechanism 14 generates an impact in the third load zone. Next, a description will be given of how the first control device 18 determines that the impact mechanism 14 generates an impact, in which:

step S13: the first control device 18 obtains a rotation time T corresponding to each rotation angle of the motor 12 according to the change of the plurality of pulse waves of the rotation speed signal, and obtains the motor current from the current signal.

As shown in fig. 3, the time difference between the pulse wave generation change of the output sensed by one of the hall sensors 202 and the pulse wave generation change of the output sensed by the other hall sensor 202 in the rotation speed signal is the rotation time T, which is equivalent to the rotation time T obtained from the pulse wave change in the integrated rotation speed signal. The rotation time T is obtained by integrating the pulse wave changes in the rotation speed signal, but not limited thereto, and the rotation time T corresponding to each rotation angle of the motor 12 may be obtained according to the pulse wave changes of the output signals sensed by the three hall sensors 202 in the original rotation speed signal.

Referring to fig. 6, in the present embodiment, after the motor 12 rotates at the fixed rotation speed (i.e. in the second load zone), the first control device 18 uses the rotation time T of one of the pulse waves in the integrated rotation speed signal as a first reference time T1 (e.g. 520 μs between arrow a and arrow a'), and uses the motor current of the current signal as a first reference current I1 (e.g. 3A as indicated by arrow B). The rotation time T and the first reference time T1 may be, for example, the time of the high voltage level between the rising edge and the falling edge, but not limited thereto, and may be the time of the low voltage level between the falling edge and the rising edge.

In one embodiment, the first reference time T1 and the first reference current I1 may also be a time value and a current value preset by the first control device 18.

Step S14, the first control device 18 judges the number of times the impact mechanism 14 generates impact and the second control device 26 judges impact according to the change of the rotation time T and the change of the motor current Im of the current signal;

referring to fig. 6, when the first control device 18 determines that the change of the rotation time T and the change of the motor current Im meet a first condition, the first condition is that the obtained ratio of the rotation time T (e.g. 620 μs between arrow C and arrow C') to the first reference time T1 reaches a first ratio, and the obtained ratio of the motor current Im (e.g. 9A as indicated by arrow D) to the first reference current I1 reaches a second ratio.

In this embodiment, the first reference time T1 is exemplified by 520 μs, and the first ratio is exemplified by 1.19, i.e. when the obtained rotation time T is 618.8 μs or more, the first ratio is reached. Preferably, the first ratio is between 1.1 and 1.25. In one embodiment, the first ratio is between 1.15 and 1.2.

The first reference current I1 is exemplified by 3A, and the second ratio is exemplified by 3, i.e., when the obtained motor current Im is 9A or more, the second ratio is reached. Preferably, the second ratio is between 1.5 and 4.5. In one embodiment, the second ratio is between 2.5 and 3.5. In one embodiment, the second ratio is between 2.8 and 3.2.

When the first condition is met, the first control device 18 starts generating the impact signal and converts the impact signal from a first voltage level (for example, a low voltage level) to a second voltage level (for example, a high voltage level) to form a first pulse edge of the impact pulse wave of the impact signal.

Referring to fig. 7 and 8, fig. 7 is a waveform diagram after generating the second pulse edge, fig. 8 is a waveform diagram after generating the third pulse edge, and fig. 8 illustrates the third pulse edge, but the steps for generating the second pulse edge are the same, and the difference is only that the pulse edge is a rising edge or a falling edge. In this embodiment, after the impact mechanism 14 generates the first impact, the first control device 18 uses the rotation time of one of the pulse waves in the integrated rotation speed signal as a second reference time T2 (520 μs between arrow a and arrow a' in fig. 8), and uses the motor current of the current signal as a second reference current I2 (8A indicated by arrow B in fig. 8). Since the motor 12 is rotating in the third load region, the second reference current I2 is larger than the first reference current I1.

In an embodiment, the second reference time T2 may be the first reference time T1, and the second reference current I2 may be the first reference current I1, so that the step of obtaining the second reference time T2 and the second reference current I2 may be omitted. In one embodiment, the second reference time T2 and the second reference current I2 may also be a default time value and a default current value of the first control device 18.

After the first impact is generated by the impact mechanism 14, the first control device 18 switches the voltage level of the impact signal, that is, switches the impact signal from one of the first voltage level and the second voltage level to the other, each time when a second condition is met, to form the other pulse edges of the impact pulse wave of the impact signal, that is, the pulse edges after the second pulse edge.

The second condition is: the ratio of the obtained rotation time T (620 μs between the arrow C and the arrow C') to the second reference time T2 reaches a third ratio, and the ratio of the motor current Im (13A as indicated by the arrow D) to the second reference current I2 reaches a fourth ratio.

In this embodiment, the second reference time T2 is exemplified by 520 μs, and the third ratio is exemplified by 1.19, i.e. when the obtained rotation time T is 618.8 μs or more, the third ratio is reached. Preferably, the third ratio is between 1.1 and 1.25. In one embodiment, the third ratio is between 1.15 and 1.2.

The second reference current I2 is exemplified by 8A, and the fourth ratio is exemplified by 1.625, i.e., when the obtained motor current Im is 13A or more, i.e., the fourth ratio is reached. Preferably, the fourth ratio is between 1.5 and 4.5. In one embodiment, the fourth ratio is between 1.5 and 2. In one embodiment, if the second reference current I2 is the first reference current I1, the fourth ratio is 3-4.5, such as 4.33 (i.e., 13A/3A).

Thereby, the first control device 18 is able to generate a shock signal with a plurality of shock pulse waves, and one pulse wave edge (rising or falling edge) of each shock pulse wave generates one shock corresponding to the shock mechanism 14. The impact signal is transmitted to the second control device 26 via the feedback signal line 365. The second control device 26 can determine the number of impact times according to the number of pulse edges of the impact signal.

In step S15, the second control device 26 receives the impact signal via the feedback signal line 365 and determines the number of pulse edges of the impact signal, for example, to count the number of pulse edges as the number of impacts, and the second controller 262 of the second control device 26 compares whether the number of impacts reaches the predetermined number acquired in step S11,

if not, maintaining the motor 12 to continue rotating;

if so, a braking command is output, the braking command is transmitted to the first control device 18 through a braking signal wire 364, and the first control device 18 controls the motor 12 to stop rotating after receiving the braking command.

As can be seen from the above, the control method of the impact type electric tool 1 of the present embodiment can accurately determine the number of times the impact mechanism 14 impacts by the motor current and the rotation time of the rotation speed signal, and control the motor 12 to stop rotating when the number of times of impact reaches the required predetermined number of times, thereby accurately controlling the torque force output by the impact type electric tool 1.

In the following, another embodiment is provided, which can achieve the effect of precisely controlling the torque output by the impact type electric tool.

Fig. 9 shows an impact type electric tool 2 according to a second preferred embodiment of the present invention, which has a structure substantially identical to that of the first embodiment, except that the present embodiment includes a circuit board 40, and a control device 42, the rotation speed detecting device 20, and the current detecting device 22 are disposed on the circuit board, the control device 42 includes a controller 422 and the plurality of phase change switching elements 184, the controller 422 may be a microcontroller, and the controller 422 is electrically connected to the plurality of phase change switching elements 184.

The circuit board 40 is electrically connected to the battery 30 and the operation interface 32, and the display 28 is disposed on the circuit board 40. The operation interface 32 is electrically connected to the control device 42 and includes an activation switch 322 and a segment selector 324.

The control device 42 includes a storage unit 424, the storage unit 424 is a memory built in the controller 422, and the storage unit 424 stores a plurality of predetermined times, and the predetermined times respectively correspond to the plurality of torsion segments.

The control method shown in FIG. 10 can be performed by the structure of the impact type electric tool 2, which comprises the following steps:

step S21: the motor 12 is controlled to rotate. In this embodiment, the user operates the operation interface 32 to select a desired torque segment by the segment selector 324, and the segment selector 324 outputs a corresponding segment selection signal to the control device 42. The controller 422 obtains the corresponding predetermined number of times from the storage unit 424 according to the required torque segment bit.

After the user lightly depresses the start switch 322, the start switch 322 outputs a first start signal to the controller 422, and the controller 422 controls the plurality of phase change switch elements 184 to further control the motor 12 to rotate. At this time, the shaft 122 of the motor 12 drives the impact mechanism 14 to rotate, and the output shaft drives the workpiece.

Step S22: the control device 42 continuously obtains the rotation speed signal from the detection result of the rotation speed detection device 20 and obtains the current signal from the detection result of the current detection device 22.

Step S22 is substantially the same as step S12 of the first embodiment, except that the original rotational speed signal is not converted into an integrated rotational speed signal.

After the user re-presses the start switch 322, the start switch 322 outputs a second start signal to the controller 422, and the controller 422 controls the plurality of phase change switch elements to rotate the motor 12 at a fixed rotation speed.

Step S23: the control device 42 obtains a rotation time T corresponding to each rotation angle of the motor 12 according to the change of the plurality of pulse waves of the original rotation speed signal, and obtains the motor current from the current signal.

Referring to fig. 11, since the same control device 42 is used for controlling in the present embodiment, the difference from the first embodiment is that the rotation time T corresponding to each rotation angle of the motor is obtained according to the pulse wave variation of the output sensed by the three hall sensors 202 in the original rotation speed signal. The time difference between the change in the pulse wave of the output sensed by one of the hall sensors 202 and the change in the pulse wave of the output sensed by the other hall sensor 202 is the rotation time.

After the motor 12 rotates at the fixed rotation speed, the control device 42 takes one of the rotation times T in the rotation speed signal as a first reference time, and the motor current obtained from the current signal as a first reference current. The first reference time and the first reference current are obtained in the same manner as in the foregoing embodiment.

In step S24, the control device 42 determines the number of impacts and the number of times of impacts generated by the impact mechanism 14 according to the change of the rotation time T of the rotation speed signal and the change of the motor current of the current signal.

In this embodiment, the step S24 is substantially the same as the step S14 of the first embodiment, and the first impact generated by the impact mechanism 14 is determined when a first condition is met, where the first condition is: the ratio of the obtained rotation time T to the first reference time reaches a first ratio, and the ratio of the motor current to the first reference current reaches a second ratio.

In addition, step S24 differs from step S14 in this embodiment in that the control device 42 does not generate an impact signal.

And then, judging that the impact mechanism generates impact when judging that the impact after the second impact meets a second condition, wherein the second condition is that: the ratio of the obtained rotation time T to a second reference time reaches a third ratio, and the ratio of the motor current to a second reference current reaches a fourth ratio. The second reference time and the second reference current obtaining method are the same as the above embodiments.

In step S25, the controller 422 of the control device 42 counts the number of shocks and compares whether the number of shocks reaches a predetermined number:

if not, maintaining the motor 12 to continue rotating;

if so, the motor 12 is controlled to stop rotating.

Thus, the control method of the present embodiment can also control the motor 12 to stop rotating when the number of impacts reaches the required predetermined number, and accurately control the torque force output from the impact type electric tool 2.

The above description is only of a preferred embodiment of the invention, and all changes that come within the meaning and range of equivalency of the description and the claims are therefore intended to be embraced therein.

Description of the reference numerals

1: impact type electric tool

10: shell body

12: motor with a motor housing

122: rotating shaft

14: impact mechanism

142: output shaft

16: first circuit board

18: first control device

182: first controller

184: phase change switching element

20: rotation speed detecting device

202: hall sensor

22: current detecting device

24: second circuit board

26: second control device

262: second controller

264: storage unit

28: display device

30: battery cell

32: operation interface

322: start switch

324: segment selector

36: transmission line group

361: power line

362: grounding wire

363: command transmission line

364: brake signal line

365: feedback signal line

366: current signal line

367: rotational speed signal line

2: impact type electric tool

40: circuit board

42: control device

422: controller for controlling a power supply

424: storage unit

A. A ', B, C, C', D: arrows

I1: first reference current

I2: second reference current

Im: motor current

S11 to S15, S21 to S25: step (a)

T: time of rotation

T1: first reference time

T2: second reference time

V1: a first voltage level

V2: second voltage level

V3: third voltage level

V4: fourth voltage level

Claims (12)

1. The control method of the impact type electric tool comprises a motor, an impact mechanism, a rotation speed detection device and a current detection device, wherein the impact mechanism is connected with the motor and is driven by the motor to rotate, the rotation speed detection device is used for detecting the rotation speed of the motor, and the current detection device is used for detecting a motor current when the motor is operated; the control method comprises the following steps:

A. controlling the motor to rotate;

B. continuously obtaining a rotation speed signal from the detection result of the rotation speed detection device and obtaining a current signal from the detection result of the current detection device; the rotating speed signal is provided with a plurality of pulse waves corresponding to a plurality of rotating angles of the motor; obtaining a rotation time corresponding to each rotation angle of the motor according to the change of the pulse waves, and obtaining the motor current from the current signal;

C. judging the number of times of impact generated by the impact mechanism according to the change of the rotation time of the rotation speed signal and the change of the motor current of the current signal;

D. comparing whether the number of times of impact reaches a preset number of times, if not, enabling the motor to continue to rotate; if yes, controlling the motor to stop rotating;

wherein, the step C comprises the step of judging that the impact mechanism generates the first impact, which comprises the following steps:

when a first condition is met, judging that the striking mechanism generates first impact, wherein the first condition is as follows: the ratio of the obtained rotation time to a first reference time reaches a first ratio, and the ratio of the motor current to a first reference current reaches a second ratio.

2. The method of claim 1, wherein step C comprises generating a shock signal, wherein the shock signal comprises a plurality of shock pulse waves, and a pulse wave edge of each shock pulse wave generates a shock corresponding to the shock mechanism; in the step D, the number of pulse wave edges of the impact signal is used as the number of times of impact.

3. The method of claim 2, wherein in step C, the impact signal is generated by a first control device and transmitted to a second control device through a first transmission line; in step D, the second control device compares the number of pulse edges of the received impact signal with the predetermined number of times, and when the number of times of the compared impact reaches the predetermined number of times, a braking command is transmitted to the first control device through a second transmission line, and the first control device stops the rotation of the motor.

4. The method of claim 2, wherein the step C of determining that the impact mechanism is generating the first impact includes converting the impact signal from a first voltage level to a second voltage level to form a first pulse edge of the impact signal when the first condition is met.

5. The method for controlling an impact type electric tool according to claim 4, wherein in step C, after judging that the impact mechanism generates the first impact, further comprising:

converting the impulse signal from one of the first voltage level and the second voltage level to the other when a second condition is met, to form other pulse wave edges of the impulse signal, wherein the second condition is: the ratio of the obtained rotation time to a second reference time reaches a third ratio, and the ratio of the motor current to a second reference current reaches a fourth ratio.

6. The method of controlling an impact type electric tool according to claim 5, wherein in step C, after judging that the impact mechanism generates the first impact, further comprising:

the motor current of the current signal is taken as the second reference current.

7. The control method of an impact type electric tool according to claim 5, wherein the second reference current is larger than the first reference current.

8. The control method of an impact type electric tool according to claim 1, wherein in step C, after judging that the impact mechanism generates the first impact, further comprising:

when a second condition is met, judging that the striking mechanism generates impact, wherein the second condition is as follows: the ratio of the obtained rotation time to a second reference time reaches a third ratio, and the ratio of the motor current to a second reference current reaches a fourth ratio.

9. The control method of an impact type electric tool according to claim 8, wherein in step C, after judging that the impact mechanism generates the first impact, further comprising:

the motor current of the current signal is taken as the second reference current.

10. The control method of an impact type electric tool according to claim 8, wherein the second reference current is larger than the first reference current.

11. The method of claim 1, wherein in step a, the motor is controlled to rotate at a fixed rotational speed.

12. The control method of an impact type electric tool according to claim 11, wherein after the step B, the motor current of the current signal is taken as the first reference current with one of the rotation times of the rotation speed signal as the first reference time after the motor rotates at the fixed rotation speed.