TW202411026A - Power tools and power tool veneer stop control methods - Google Patents

Abstract

A power tool includes a trigger switch, a trigger detection circuit, a motor, a motor current detection circuit, and a control unit. The control unit sets a first current threshold and a second current threshold according to a pressing position of the trigger switch. The second current threshold is less than the first current threshold. The control unit, after determining that the current of the motor is greater than the first current threshold, determines whether the current of the motor continues to be greater than the second current threshold for more than a predetermined time. If yes, the control unit outputs a corresponding control signal to stop the motor. Thereby, the present invention can well determine whether a bolt has been locked to a surface of a flattened workpiece, and can improve the accuracy of the determination.

Description

Electric tool and electric tool veneer stop control method

The present invention relates to an electric tool and a control method, and in particular to an electric tool with an impact mechanism and a control method for stopping the electric tool from being lapped.

When using power tools to tighten bolts, if the user continues to press the trigger to allow the motor to continue to run after the bolt has been tightened to the surface of the workpiece, the power tool may over-hammer the bolt, causing the bolt to be tightened with excessive torque or even causing the workpiece to break.

In order to solve the above problem, as shown in U.S. Patent No. US6687567 "Power Tools", a sound receiver is installed on the power tool to determine whether the bolt is flush with the workpiece surface by detecting the impact sound made by the impact mechanism of the power tool when the bolt is locked and flush with the workpiece surface.

However, the disadvantage of the above method is that when the ambient sound is noisy, the sound receiver will receive a lot of noise, causing the power tool to easily misjudge. Therefore, it still cannot solve the problem that the bolt may be over-tightened.

Therefore, the object of the present invention is to provide an electric tool that can solve the above-mentioned problems.

Therefore, the electric tool of the present invention includes a trigger switch, a trigger detection circuit, a motor, a motor current detection circuit, and a control unit.

The trigger detection circuit detects the pressed position of the trigger switch.

The motor operates according to a control signal.

The motor current detection circuit is electrically connected to the motor to detect the current of the motor.

The control unit is electrically connected to the trigger detection circuit, the motor and the motor current detection circuit, receives the pressed position of the trigger switch and the current information of the motor, and sets a first current threshold and a second current threshold according to the pressed position of the trigger switch. The second current threshold is less than the first current threshold. After determining that the current of the motor is greater than the first current threshold, the control unit determines whether the current of the motor continues to be greater than the second current threshold for more than a predetermined time. If so, the control unit outputs the corresponding control signal to stop the motor from running.

Therefore, the purpose of the present invention is to provide a method for controlling the stopping of electric tool veneer application which can solve the above-mentioned problem.

Therefore, the present invention provides a method for controlling the stopping of the veneer operation of an electric tool. The electric tool includes a trigger switch, a motor, and a control unit. The method for controlling the stopping of the veneer operation of an electric tool includes the following steps:

(A) The control unit receives the pressed position of the trigger switch and sets a first current threshold and a second current threshold according to the pressed position of the trigger switch, wherein the second current threshold is smaller than the first current threshold.

(B) The control unit receives the current information of the motor and determines whether the current of the motor is greater than the first current threshold.

(C) When the determination in step (B) is yes, the control unit determines whether the current of the motor continues to be greater than the second current threshold for more than a predetermined time.

(D) When the answer in step (C) is yes, the control unit outputs a control signal to stop the motor from running.

The effect of the present invention is that by setting up the motor current detection circuit and matching the control unit to compare the motor current information with the first current threshold and the second current threshold, it is possible to well judge whether the bolt has been fastened to the surface of the workpiece, and the control unit also sets the first current threshold and the second current threshold according to the pressed position of the trigger switch, so that the accuracy of the judgment can be improved.

1 , 2 and 3 , an embodiment of the electric tool of the present invention comprises a housing 2, a trigger switch 3 disposed on the housing 2, a panel module 4 disposed on the housing 2, a power unit 5, a power unit 6, an impact unit 7, a detection unit 8, and a control unit 9.

The panel module 4 is electrically connected to the control unit 9 and can be implemented using a knob, a button or a touch panel. The panel module 4 is operated to input information of a predetermined time to the control unit 9.

The power unit 5 includes a battery 51 disposed in the housing 2, and a power circuit 52 electrically connected to the battery 51. The power circuit 52 provides the power provided by the battery 51 to the internal circuit after voltage regulation and voltage transformation. The power circuit 52 may include, for example, a low-dropout regulator (LDO) (not shown) to provide stable power.

The power unit 6 includes a motor 61 disposed in the housing 2, a drive circuit 62 electrically connected to the control unit 9, a switching circuit 63 electrically connecting the motor 61 and the drive circuit 62, and a spindle 64. The motor 61 has an output shaft 611 extending toward the front of the power tool and connected to the spindle 64. The motor 61 can be implemented, for example, using a brushless DC motor (BLDC). The drive circuit 62 receives a control signal in the form of a PWM signal output by the control unit 9, and controls the switching circuit 63 according to the duty ratio of the PWM signal to drive the motor 61 to rotate at a target speed. The switching circuit 63 can be implemented, for example, using a semiconductor (MOSFET) switch.

The impact unit 7 includes a hammer block 71 connected to the output shaft 611 via the main shaft 64, an anvil 72 detachably connected to the hammer block 71, a coil spring 73, and a tool holder 74 disposed on the anvil 72. The hammer block 71 is rotated in conjunction with the output shaft 611 via the main shaft 64, thereby rotating the anvil 72, and converting the rotational force of the output shaft 611 into a rotational impact force. The tool holder 74 is used for setting drill bits, screws or bolts.

The hammer block 71 has two hammer protrusions 711 protruding toward the tool seat 74 (hereinafter defined as toward the front) at intervals of approximately 180 degrees along the circumference of the main shaft 64, and the anvil 72 has two impact arms 721 extending toward the hammer block 71 (hereinafter defined as toward the rear) at intervals of approximately 180 degrees along the circumference of the main shaft 64. The coil spring 73 is connected to the hammer block 71 along the extension direction of the main shaft 64 to continuously provide stress to push the hammer block 71 forward. Thus, when the hammer block 71 is linked to the output shaft 611 via the main shaft 64, the anvil 72 is driven to rotate, and when the anvil 72 is applied with a torque exceeding a predetermined value, the hammer block 71 is pushed backward by the impact arms 721 to resist the thrust of the coil spring 73, and then when the hammer protrusions 711 cross the impact arms 721, the hammer block 71 is pushed toward the anvil 72 again by the coil spring 73. In this process, the hammer block 71 repeatedly strikes the anvil 72, and the rotational force of the hammer block 71 is converted into a rotational impact force intermittently applied to the anvil 72. Since a person skilled in the art can infer the expanded details based on the above description, no further explanation is given.

The detection unit 8 includes a battery detection circuit 81 , a trigger detection circuit 82 , a motor speed detection circuit 83 , and a motor current detection circuit 84 .

The battery detection circuit 81 is connected between the battery 51 and the control unit 9 to detect the voltage of the battery 51 so that the control unit 9 can adjust the duty cycle of the control signal output to the drive circuit 62 according to the voltage of the battery 51, so that the motor 61 can still operate at the target speed when the power tool is unloaded and the battery 51 is under different voltages.

The trigger detection circuit 82 is connected to the control unit 9 and is used to detect the pressed position of the trigger switch 3 and output the signal to the control unit 9 so that the control unit 9 can know the depth of the trigger switch 3 pressed by the user. The control unit 9 controls the motor 61 to operate according to the pressed position of the trigger switch 3, so that the rotation speed of the motor 61 is positively related to the pressed depth of the trigger switch 3.

The motor speed detection circuit 83 is provided corresponding to the motor 61, and is used to detect the rotor position of the motor 61 to obtain the speed of the motor 61, and output the speed of the motor 61 to the control unit 9. The motor speed detection circuit 83 can be implemented using a Hall sensor, for example.

The motor current detection circuit 84 is electrically connected to the motor 61 and can be matched with a detection resistor 85 to detect the current of the motor 61 and output it to the control unit 9 so that the control unit 9 can monitor the current of the motor 61. For example, when the current is too large, the driving circuit 62 can be controlled to stop the operation of the motor 61 to achieve an over-current protection effect.

Referring to Fig. 3, Fig. 4 and Fig. 5, curve 91 is a schematic diagram of the current change when the electric tool is locking a bolt, and curves 92 and 93 are schematic diagrams of the relationship between a first current threshold and a second current threshold and the pressed position of the trigger switch 3. Curves 92 and 93 are only for illustration, and they can be designed as straight lines or curves according to actual needs.

The control unit 9 is electrically connected to the panel module 4, the trigger detection circuit 82, the battery detection circuit 81, the power circuit 52, the drive circuit 62, the motor current detection circuit 84 and the motor speed detection circuit 83, and can be designed as a circuit with functions such as A/D conversion, I/O detection, PWM output, and speed calculation, and can be implemented using a microcontroller (MCU). The control unit 9 receives the predetermined time, the pressing position of the trigger switch 3 and the current information of the motor 61, and sets the first current threshold and the second current threshold according to the pressing position of the trigger switch 3, and the second current threshold is less than the first current threshold. After determining that the current of the motor 61 is greater than the first current threshold, the control unit 9 determines whether the current of the motor 61 continues to be greater than the second current threshold for more than the predetermined time. If so, the control unit 9 outputs the corresponding control signal to stop the motor 61 from running.

The predetermined time may be input by the user through the panel module 4, or may be pre-stored in the control unit 9. The control unit 9 may first store the data of the curves 92 and 93 in a table form, and then look up the table according to the depth of the pressed position of the trigger switch 3 to obtain the corresponding first current threshold and the second current threshold, or may pre-fit the data of the curves 92 and 93, and store the fitted curve formula in the control unit 9, and then substitute the pressed position of the trigger switch 3 into the curve formula to obtain the corresponding first current threshold and the second current threshold.

The method for setting the first current threshold and the second current threshold is, for example, to first find the maximum current value of the electric tool during a locking period, for example, to take a plurality of the electric tools for measurement, and take the average, median, mode, or theoretical value as a maximum current value, and take the first current threshold from 65% to 85% of the maximum current value (for example, 70%, 75%, or 80%), and take the second current threshold from 40% to 60% of the maximum current value (for example, 45%, 50%, or 55%). The locking period is the time of locking the bolts and hammering the bolts.

Referring to FIG. 3 , an embodiment of the electric tool veneer stop control method of the present invention is implemented by applying the above-mentioned electric tool and comprises the following steps:

Step A: The control unit 9 receives the pressed position of the trigger switch 3, and sets a first current threshold and a second current threshold according to the pressed position of the trigger switch 3, wherein the second current threshold is smaller than the first current threshold.

Among them, the first current threshold is between 65% and 85% of a maximum current value (for example, 70%, 75%, or 80%), the second current threshold is between 40% and 60% of the maximum current value (for example, 45%, 50%, or 55%), and the maximum current value is the maximum current value of the power tool during a locking period.

The first current threshold and the second current threshold are both positively correlated with the depth of the pressed position of the trigger switch 3.

Step B: The control unit 9 receives the current information of the motor 61 and determines whether the current of the motor 61 is greater than the first current threshold.

Step C: When the determination in step B is yes, the control unit 9 determines whether the current of the motor 61 is continuously greater than the second current threshold value for more than a predetermined time.

Step D: When the answer in step C is yes, the control unit 9 outputs a control signal to stop the motor 61 from running.

Below, refer to Figures 3, 4 and 6 to explain the actual usage process:

When the user uses the power tool, turns on the power, and presses the trigger switch 3, the process proceeds to step S01.

Step S01: The trigger detection circuit 82 detects the pressed position of the trigger switch 3 and outputs it to the control unit 9.

Step S02: The control unit 9 receives the pressed position of the trigger switch 3, outputs the control signal corresponding to the pressed position of the trigger switch 3, and drives the motor 61 to operate.

Step S03: The control unit 9 sets the first current threshold and the second current threshold according to the pressed position of the trigger switch 3.

Step S04: The control unit 9 receives the current information detected by the motor current detection circuit 84 and determines whether the current of the motor 61 is greater than the first current threshold. If yes, it indicates that the bolting stage has entered the bolt hammering stage from the bolt locking stage in FIG. 4, and then enters step S05. If no, it indicates that it is still in the bolt locking stage, and the current continues to be detected and the step S04 determination is performed again.

Step S05: The control unit 9 determines whether the current of the motor 61 continues to be greater than the second current threshold value for more than the predetermined time according to the current information detected by the motor current detection circuit 84. If yes, it means that the bolt hammering stage has been entered and has lasted for the predetermined time, and then enters step S06, if not, returns to step S04.

The predetermined time is related to the torque at which the bolt is locked. The longer the time is, the greater the torque is. The user can set the predetermined time according to actual needs so that the bolt can be locked at the expected torque.

Step S06: Stop the operation of the motor 61.

Through the above description, the effects of this embodiment are as follows:

By setting the motor current detection circuit 84 and collaborating with the control unit 9 to compare the current information of the motor 61 with the first current threshold and the second current threshold, it is possible to well judge whether the bolt has been fastened to the surface of the flat workpiece, and to avoid the situation where the bolt is fastened with excessive torque or even the workpiece is broken due to excessive hammering of the electric tool. In addition, by the control unit 9 also setting the first current threshold and the second current threshold according to the pressed position of the trigger switch 3, it is possible to further evaluate the current usage status, thereby improving the accuracy of the flatness judgment. Therefore, compared to the conventional method of using sound for judgment, this embodiment can avoid the influence of environmental noise and has better accuracy.

In summary, the electric tool and the electric tool veneer stopping control method of the present invention can indeed achieve the purpose of the present invention.

However, the above is only an example of the implementation of the present invention, and it cannot be used to limit the scope of the implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the patent of the present invention.

2: Housing 3: Trigger switch 4: Panel module 5: Power unit 51: Battery 52: Power circuit 6: Power unit 61: Motor 611: Output shaft 62: Drive circuit 63: Switch circuit 64: Spindle 7: Impact unit 71: Hammer block 711: Hammer protrusion 72: Anvil 721: Impact arm 73: Coil spring 74: Tool holder 8: Detection unit 81: Battery detection circuit 82: Trigger detection circuit 83: Motor speed detection circuit 84: Motor current detection circuit 85: Detection resistor 9: Control unit 91~93: Curve S01~S06: Steps

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG. 1 is a partial cross-sectional view of an embodiment of the electric tool of the present invention; FIG. 2 is another partial cross-sectional view of the embodiment; FIG. 3 is a block diagram of the embodiment; FIG. 4 is a waveform diagram illustrating the current change of the embodiment during operation; FIG. 5 is a waveform diagram illustrating the relationship between a first current threshold and a second current threshold of the embodiment and the pressing position of a trigger switch; and FIG. 6 is a flow chart of an embodiment of the electric tool veneer stop control method of the present invention.

3: Trigger switch

4: Panel module

5: Power unit

51:Battery

52: Power circuit

6: Power unit

61: Motor

62:Drive circuit

63: Switching circuit

8: Detection unit

81:Battery detection circuit

82: Trigger detection circuit

83: Motor speed detection circuit

84: Motor current detection circuit

85: Detecting resistance

9: Control unit

Claims (8)

An electric tool comprises: a trigger switch; a trigger detection circuit for detecting the pressed position of the trigger switch; a motor for operating according to a control signal; a motor current detection circuit for electrically connecting the motor and detecting the current of the motor; and A control unit is electrically connected to the trigger detection circuit, the motor and the motor current detection circuit, receives the pressed position of the trigger switch and the current information of the motor, and sets a first current threshold and a second current threshold according to the pressed position of the trigger switch. The second current threshold is less than the first current threshold. After determining that the current of the motor is greater than the first current threshold, the control unit determines whether the current of the motor continues to be greater than the second current threshold for more than a predetermined time. If so, the control unit outputs the corresponding control signal to stop the motor from running. The electric tool as described in claim 1 further includes a panel module, which is electrically connected to the control unit and is operated to input the information of the predetermined time into the control unit. An electric tool as described in claim 1, wherein the first current threshold and the second current threshold are both positively correlated with the depth of the pressed position of the trigger switch. An electric tool as described in claim 1, wherein the first current threshold is between 65% and 85% of a maximum current value, the second current threshold is between 40% and 60% of the maximum current value, and the maximum current value is the maximum current value of the electric tool during a locking period. A method for controlling the stopping of a power tool during the surfacing process, wherein the power tool comprises a trigger switch, a motor, and a control unit, and the method comprises the following steps: (A) the control unit receives the pressing position of the trigger switch, and sets a first current threshold and a second current threshold according to the pressing position of the trigger switch, wherein the second current threshold is less than the first current threshold; (B) the control unit receives the current information of the motor, and determines whether the current of the motor is greater than the first current threshold; (C) when the judgment in step (B) is yes, the control unit determines whether the current of the motor continues to be greater than the second current threshold for more than a predetermined time; and (D) When the judgment in step (C) is yes, the control unit outputs a control signal to stop the motor from running. As described in claim 5, the electric tool pasting stop control method, wherein the electric tool also includes a panel module, and the panel module is operated to input the information of the predetermined time to the control unit. As described in claim 5, the electric tool pasting stop control method, wherein the first current threshold value and the second current threshold value are both positively correlated with the depth of the pressing position of the trigger switch. An electric tool pasting stop control method as described in claim 5, wherein in step (A), the first current threshold is between 65% and 85% of a maximum current value, the second current threshold is between 40% and 60% of the maximum current value, and the maximum current value is the maximum current value of the electric tool during a locking period.