CN103368480A - Handheld electric-driven tool and control method thereof - Google Patents
Handheld electric-driven tool and control method thereof Download PDFInfo
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Abstract
The invention discloses a control method of a handheld electric-driven tool, wherein a first current threshold value and a smaller second current threshold value are set; when the current of a motor achieves the second current threshold value, the rotary speed of the motor is maintained; and when the current of the motor achieves the first current threshold value, the motor is controlled to be stopped, thus improving the precision of torsion adjusting. The invention also provides a handheld electric-driven tool.
Description
Technical Field
The invention relates to a hand-held electric tool and a control method thereof.
Background
For hand-held power tools, such as drills or screwdrivers, it is often necessary to limit the torque that it outputs to prevent damage to the workpiece or burning of the motor.
A typical power drill or screwdriver has a mechanical overload clutch between the tool driver and the motor to limit the output torque. However, the mechanical overload clutch is bulky and the accuracy of torque regulation is low.
Still other drills or screwdrivers use electronic means to limit the output torque, and since the torque of a permanently excited dc motor is approximately proportional to the motor current, the corresponding torque can be substantially limited by limiting the motor current. Compared with a mechanical overload clutch, the mode has the advantages that the size is reduced, and the accuracy is improved. However, the torque of the dc motor is not only related to the motor current, but also limited by limiting the motor current, and the accuracy is still not high, so that there is a need for improvement of the existing hand-held power tool.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a control method of a handheld electric tool with high torque limitation precision.
The technical scheme of the invention is realized as follows: a method of controlling a hand-held power tool including a motor and a controller outputting a first drive signal to control the motor, the method comprising the steps of: setting a first current threshold; the controller controls the rotating speed of the motor to be maintained at a preset rotating speed value; and detecting the motor current, and controlling the motor to stop when the motor current reaches the first current threshold value by the controller.
Further, after setting the first current threshold, setting a second current threshold lower than the first current threshold, and when the motor current reaches the second current threshold, controlling the rotating speed of the motor to be kept at a predetermined rotating speed value by the controller.
Further, the first current threshold is equal to a sum of the second current threshold and a predetermined constant.
Further, the controller calculates a voltage required for maintaining a predetermined rotation speed value according to the detected motor current and the predetermined rotation speed value, and adjusts the actual voltage of the motor to the calculated voltage.
Furthermore, the controller uses the calculated voltage as a reference voltage, detects the actual voltage of the motor in real time, and adjusts the first driving signal output by the controller according to the difference between the actual voltage of the motor and the reference voltage.
The present invention also provides a hand-held power tool comprising a housing, a motor located within the housing, a transmission mechanism driven by the motor, and a control circuit for controlling the motor, the control circuit comprising: a first current threshold setting unit for setting a first current threshold; the controller is connected with the first current threshold setting unit; the storage unit is connected with the controller and used for storing the first current threshold value; the controller outputs a first driving signal to the electronic switch, and controls the rotating speed of the motor to be kept at a preset rotating speed value after the motor is started; the current detection unit is connected with the electronic switch and the controller and is used for detecting the current of the motor; the controller compares the motor current with the first current threshold, and stops outputting the first driving signal to the electronic switch when the motor current reaches the first current threshold so as to control the motor to stop.
Further, the control circuit further comprises a second current threshold setting unit for setting a second current threshold lower than the first current threshold, the controller compares the motor current with the second current threshold, and when the motor current reaches the second current threshold, the controller controls the rotation speed of the motor to be kept at a predetermined rotation speed value.
Further, the controller calculates a second current threshold lower than the first current threshold, compares the motor current with the second current threshold, and controls the rotation speed of the motor to be kept at a predetermined rotation speed value when the motor current reaches the second current threshold.
Further, a predetermined constant is stored in the storage unit, and the first current threshold is equal to the sum of the second current threshold and the predetermined constant.
Further, the controller calculates a voltage required for maintaining a predetermined rotation speed value according to the detected motor current and the predetermined rotation speed value, and adjusts the actual voltage of the motor to the calculated voltage.
Furthermore, the control circuit further comprises a voltage detection unit for detecting the actual voltage of the motor, and the controller uses the calculated voltage as a reference voltage and adjusts the first driving signal according to the difference between the detected actual voltage and the reference voltage.
According to the handheld electric tool and the control method thereof, the first current threshold and the second current threshold are set, the rotating speed of the motor is maintained when the current of the motor reaches the second current threshold, and the motor is controlled to stop when the current of the motor reaches the second current threshold, so that the accuracy of torque adjustment is improved.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a schematic view of a hand held power tool of the present invention.
Fig. 2 is a schematic circuit diagram of the hand held power tool of the present invention.
FIG. 3 is a graphical representation of torque, motor current, and motor speed for a hand held power tool.
FIG. 4 is a graph of motor current, motor voltage, and motor speed for a hand held power tool.
FIG. 5 is a circuit diagram of the first preferred embodiment of the manual mode of the hand-held power tool of the present invention.
FIG. 6 is a circuit diagram of a second preferred embodiment of the manual mode of the hand-held power tool of the present invention.
Fig. 7 is a circuit schematic of the automatic mode of the hand held power tool of the present invention.
FIG. 8 is a flow chart of the first preferred embodiment of the manual mode of the control method of the hand-held power tool of the present invention.
Fig. 9 is a graph illustrating a manual mode of the control method of the hand-held power tool according to the first preferred embodiment of the present invention.
FIG. 10 is a flow chart of a second preferred embodiment of the manual mode of the control method of the hand-held power tool of the present invention.
FIG. 11 is a graphical representation of a manual mode of the control method of the hand held power tool according to the second preferred embodiment of the present invention.
Fig. 12 is a graphical representation of a first stage of operation of the automatic mode of the hand held power tool of the present invention.
Fig. 13 is a graphical representation of a second stage of operation of the automatic mode of the hand held power tool of the present invention. Wherein,
100. a hand-held power tool; 10. A housing; 20. A motor;
30. a transmission device; 40. A clamp; 50. A power supply module;
60. a control circuit; s1, an electronic switch; s2, a motor switch;
s3, a mode selection switch; s4, a working phase change-over switch; r1, resistance;
61. a controller; 62. A switch detection unit; 63. A storage unit;
64. a first current threshold setting unit; 65. A second current threshold setting unit; 66. A current limiting unit;
67. a current detection unit; 68. A voltage detection unit;
Detailed Description
Referring to fig. 1, a hand-held power tool 100, such as a drill or screwdriver, has a housing 10, a motor 20 disposed within the housing 10, a transmission 30 connected to the motor 20, a chuck 40 driven by the transmission 30, a power supply module 50 for supplying power to the motor 20, and a control circuit 60 for controlling the motor 20.
Referring to fig. 2, the control circuit 60 includes a controller 61, an electronic switch S1, a motor switch S2, a mode selection switch S3, an operating phase switch S4, a resistor R1, a switch detection unit 62, a storage unit 63, a first current threshold setting unit 64, a second current threshold setting unit 65, a current limiting unit 66, a current detection unit 67, and a voltage detection unit 68.
The positive pole of the motor 20 is connected to the positive pole of the power supply module 50 through the motor switch S2, and the negative pole is connected to the first end of the electronic switch S1. The second terminal of the electronic switch S1 is connected to the first terminal of the controller 61, and the third terminal is connected to the negative terminal of the power supply module 50 through the resistor R1.
The second terminal of the controller 61 is connected to a node between the motor switch S2 and the motor 20, the third terminal is connected to the positive electrode of the motor 20 through the voltage detecting unit 68, the fourth terminal is connected to the second terminal of the electronic switch S1 through the current limiting unit 66, the fifth terminal is connected to the third terminal of the electronic switch S1 through the current detecting unit 67, the sixth terminal is connected to the first current threshold setting unit 64, the seventh terminal is connected to the second current threshold setting unit 65, the eighth terminal is connected to the mode selecting switch S3, the ninth terminal is connected to the operating phase switching switch S4, and the tenth terminal is connected to the storage unit 63. In the present embodiment, the controller 61 is an MCU, and outputs a first driving signal to the electronic switch S1.
The current limiting unit 66 is also connected to the current detecting unit 67. The switch detection unit 62 has a first end connected to the positive electrode of the power supply module 50 and a second end connected to the second end of the controller 61.
The hand held power tool 100 of the present invention can be selectively operated in either a manual mode or an automatic mode. In the manual mode, the user can obtain high accuracy by performing torque adjustment through the first current threshold setting unit 64; in the automatic mode, the handheld power tool 100 has a first working stage for automatically setting a current threshold and a second working stage for limiting the torque according to the set current threshold, so that a user with less experience can conveniently operate the handheld power tool 100 and the workpiece can reach a consistent depth.
The user can operate the mode selection switch S3 to switch to the manual mode or the automatic mode as desired. In the automatic mode, the operation phase changeover switch S4 is operable to switch to the first operation phase or the second operation phase of the automatic mode.
In this embodiment, the mode selection switch S3, the operation stage switch S4, and the first current threshold setting unit 64 can be triggered by the same trigger, which is a toggle switch. When the toggle switch is toggled to different positions, different working modes, working stages or different current thresholds are triggered.
The manual mode and the automatic mode of the hand-held power tool 100 according to the present invention will be described with reference to the drawings.
Referring to fig. 3, the relationship between the output torque T of the motor 20 and the motor current and the motor speed N is: when the motor current is a fixed value, the higher the motor rotating speed N is, the smaller the torque T is; when the motor rotating speed N is a fixed value, the larger the motor current is, the larger the torque T is; when the torque T is a constant value, the motor current is larger, and the motor rotation speed N is higher. Therefore, under the condition that the motor rotating speed N is determined, the torque T and the motor current have a corresponding relation, and the torque T of the motor 20 is limited by limiting the motor current, so that the accuracy of torque adjustment is greatly improved.
Referring to fig. 5, in the first preferred embodiment of the manual mode of the handheld electric tool 100 of the present invention, the control circuit 60 has a controller 61, an electronic switch S1, a motor switch S2, a resistor R1, a voltage detecting unit 68, a current detecting unit 67, a first current threshold setting unit 64, a second current threshold setting unit 65 and a storage unit 63. The motor 20 is controlled by the controller 61 and the electronic switch S1.
The user operates the first current threshold setting unit 64 to manually set the first current threshold I1.
The second current threshold setting unit 65 sets a second current threshold I2 lower than the first current threshold I1. In the present embodiment, the storage unit 63 stores a plurality of predetermined constants, each of which corresponds to a different first current threshold, the second current threshold setting unit 65 is a separate subtractor, and the second current threshold setting unit 65 subtracts a predetermined constant from the first current threshold I1 to obtain the second current threshold I2. The second current threshold I2 can also be calculated by software, that is, the controller 61 also functions as the second current threshold setting unit 65 to calculate the second current threshold I2. In other embodiments, the user may also directly operate the second current threshold setting unit 65 to manually set the second current threshold I2.
The memory cell 63 stores the first current threshold I1 and the second current threshold I2.
The motor switch S2 is a trigger that the user presses to activate the motor 20 of the hand held power tool 100.
The current detection unit 67 detects a motor current. The controller 61 compares the detected motor current with a second current threshold I2, and when the motor current reaches the second current threshold I2, the controller 61 controls the rotation speed of the motor 20 to be maintained at a predetermined rotation speed value N1. The predetermined rotation speed value N1 is lower than the motor rotation speed in the normal operation state, so that the motor can quickly react in the subsequent control.
Referring to fig. 4, since the motor speed N is related to the motor voltage and the motor current I, and when the load increases, the motor current I also increases correspondingly, if the motor speed N needs to be maintained, the corresponding motor voltage needs to be increased. Therefore, the voltage value required for maintaining the predetermined rotational speed N1 can be calculated according to the detected motor current I, and then the actual voltage of the motor 20 is adjusted to the calculated voltage value to maintain the rotational speed N of the motor as the predetermined rotational speed N1.
In the present embodiment, the storage unit 63 stores a predetermined speed value N1, the current detection unit 67 detects the motor current, and the controller 61 calculates a voltage value required to maintain the predetermined speed value N1 according to the predetermined speed value N1 and the detected motor current. The controller 61 uses the calculated voltage value as a reference voltage. The voltage detecting unit 68 detects the actual voltage of the motor 20 in real time, and the controller 61 adjusts the first driving signal output by the controller 61 according to the difference between the detected actual voltage and the reference voltage, so as to maintain the motor speed.
In the present embodiment, the first driving signal is a pulse width modulation signal, and if the actual voltage of the motor 20 exceeds the reference voltage, the controller 61 decreases the duty ratio of the first driving signal; if the actual voltage of the motor 20 is less than the reference voltage, the controller 61 increases the duty ratio of the first driving signal.
While maintaining the motor speed, the controller 61 continues to detect the motor current through the current detecting unit 67, and compares the detected motor current with the first current threshold I1, and when the motor current reaches the first current threshold I1, the controller 61 stops outputting the first driving signal to control the motor 20 to stop.
Referring to fig. 6, in the second preferred embodiment of the manual mode of the handheld electric tool 100 of the present invention, the control circuit 60 has a controller 61, an electronic switch S1, a motor switch S2, a resistor R1, a voltage detecting unit 68, a current detecting unit 67, a current limiting unit 66, a first current threshold setting unit 64, a second current threshold setting unit 65 and a storage unit 63.
The second current threshold setting unit 65 sets a second current threshold I2 lower than the first current threshold I1. In the present embodiment, the storage unit 63 stores a plurality of predetermined constants, each of which corresponds to a different first current threshold, the second current threshold setting unit 65 is a separate subtractor, and the second current threshold setting unit 65 subtracts a predetermined constant from the first current threshold I1 to obtain the second current threshold I2. The second current threshold I2 can also be calculated by software, that is, the controller 61 also functions as the second current threshold setting unit 65 to calculate the second current threshold I2. In other embodiments, the user may also directly operate the second current threshold setting unit 65 to manually set the second current threshold I2.
The memory cell 63 stores the first current threshold I1 and the second current threshold I2.
The motor switch S2 is a trigger that the user presses to activate the motor 20 of the hand held power tool 100.
The current detection unit 67 detects a motor current. The current limiting unit 66 compares the detected motor current with a second current threshold I2, and when the motor current reaches the second current threshold I2, the current limiting unit 66 controls the motor current to be kept at the second current threshold I2, and the rotation speed of the motor 20 is reduced accordingly.
Specifically, the current limiting unit 66 has a comparator, and the comparator outputs an on signal when the detected motor current is smaller than the second current threshold I2, and outputs an off signal when the detected motor current is greater than or equal to the second current threshold I2. The on/off signal is fed back to the first drive signal output by the controller 61, resulting in a second drive signal, thereby maintaining the motor current value at the second current threshold I2.
While maintaining the motor current, the controller 61 determines the rotation speed of the motor 20 and when the motor rotation speed falls to a rotation speed predetermined value N1, the controller 61 controls the rotation speed of the motor 20 to be maintained at a rotation speed predetermined value N1. The predetermined rotation speed value N1 is lower than the motor rotation speed in the normal operation state, so that the motor can quickly react in the subsequent control.
Referring to fig. 4 again, when the motor current is constant, the smaller the motor voltage is, the lower the motor speed is, and the controller 61 detects the actual voltage of the motor 20 through the voltage detecting unit 68, thereby determining the motor speed.
The storage unit 63 stores a predetermined speed value N1, the controller 61 calculates the motor voltage when the motor speed is N1 and the motor current is I2, the voltage detecting unit 68 detects the actual voltage of the motor 20, and the controller 61 controls the speed of the motor 20 to be maintained at the predetermined speed value N1 when the actual voltage of the motor 20 drops to the motor voltage value calculated by the controller 61.
The controller 61 calculates a voltage value required for maintaining the predetermined speed value N1 based on the predetermined speed value N1 and the detected motor current, and uses the voltage value required for maintaining the predetermined speed value N1 as a reference voltage. The controller 61 detects an actual voltage of the motor 20 through the voltage detecting unit 68, and adjusts the first driving signal output from the controller 61 according to a difference between the detected actual voltage and the reference voltage, thereby maintaining the motor rotation speed.
While maintaining the motor speed, the controller 61 continuously detects the motor current through the current detecting unit 67, compares the detected motor current with the first current threshold I1, and when the detected motor current reaches the first current threshold I1, the controller 61 stops outputting the first driving signal to control the motor 20 to stop.
In the automatic mode of the handheld power tool 100 of the present invention, the control circuit 60 has a controller 61, an electronic switch S1, a motor switch S2, a resistor R1, an operation stage switch S4, a voltage detecting unit 68, a current detecting unit 67, a memory unit 63, a current limiting unit 66, and a switch detecting unit 62. The motor 20 is controlled by the controller 61 and the electronic switch S1.
The operation stage switch S4 is operable to switch the hand-held power tool 100 to the first operation stage, in which the hand-held power tool 100 is operated by a user with a high experience, and the controller 61 controls the rotation speed of the motor 20 to be maintained at the predetermined rotation speed N1.
Specifically, the storage unit 63 stores a predetermined speed value N1, the current detection unit 67 detects the motor current, and the controller 61 calculates a voltage value required for maintaining the predetermined speed value N1 according to the predetermined speed value N1 and the detected motor current, and uses the voltage value required for maintaining the predetermined speed value N1 as a reference voltage. The controller 61 detects an actual voltage of the motor 20 through the voltage detecting unit 68, and adjusts the first driving signal output from the controller 61 according to a difference between the detected actual voltage and the reference voltage, thereby maintaining the motor rotation speed.
While maintaining the motor speed, the user turns off the motor switch S2 to control the motor 20 to stop depending on the operating conditions, such as the workpiece reaching a desired depth, position, etc. The switch detecting unit 62 detects the state of the motor switch S2 and sends a corresponding signal to the controller 61.
When the switch detection unit 62 detects that the motor switch S2 is turned off, the controller 61 records the current Ia of the motor at this time through the current detection unit 67, and automatically sets a current threshold Ib corresponding to the corresponding target torque according to the current Ia of the motor at the time of shutdown.
Specifically, the controller 61 calculates the torque T1 when the motor current is Ia and the motor speed is a predetermined speed value N1, calculates the motor current when the torque is T1 and the motor speed is 0, and determines the motor current as the current threshold Ib, based on the data relationship among the motor current, the torque T, and the motor speed N in fig. 2.
In a second operating phase of the automatic mode, the current detection unit 67 detects the motor current. The current limiting unit 66 compares the detected motor current with a current threshold Ib, and when the detected motor current reaches the current threshold Ib, the current limiting unit 66 controls the motor current to be kept at the current threshold Ib, so as to control the motor current not to be greater than the current threshold Ib, and at this time, the motor speed is reduced.
Specifically, the current limiting unit 66 has a comparator, and the comparator outputs an on signal when the detected motor current is smaller than the current threshold Ib, outputs an off signal when the detected motor current is greater than or equal to the current threshold Ib, and feeds back the on/off signal to the first driving signal to obtain the second driving signal, so as to maintain the motor current value as the current threshold Ib.
The controller 61 judges the rotation speed of the motor 20 while maintaining the motor current and when the motor rotation speed falls to a constant value, the controller 61 controls the motor 20 to stop. When the current of the motor is constant, the smaller the voltage of the motor is, the lower the rotating speed of the motor is, so that the rotating speed of the motor can be judged by detecting the voltage of the motor.
In this embodiment, the controller 61 detects the duty ratio of the second driving signal, and when the duty ratio of the second driving signal is lower than 0.1, it indicates that the voltage of the motor is lower than the predetermined value, and further indicates that the rotation speed of the motor is lower than the predetermined value, at this time, the controller 61 stops outputting the first driving signal, so as to control the motor 20 to stop.
The present invention also provides two control methods for the hand-held power tool 100: manual mode and automatic mode.
Referring to fig. 8, the first preferred embodiment of the manual mode includes the following steps:
step S1: the first current threshold I1 is manually set, and the user can set the current threshold corresponding to the target torque by operating the first current threshold setting unit 64 on the hand-held power tool 100.
Step S2: the second current threshold I2 is manually set or automatically calculated, and the second current threshold I2 is lower than the first current threshold I1, the first current threshold I1 is equal to the sum of the second current threshold I2 and a predetermined constant. In the present embodiment, the second current threshold I2 is calculated by the controller 61 in the hand-held power tool 100.
Step S3: the user depresses the trigger of the hand held power tool 100 to activate the motor 20.
Step S4: the motor current is detected in real time.
Step S5: and judging whether the motor current reaches a second current threshold I2, if so, entering the step S6, and if not, returning to the step S4.
Step S6: when the motor current reaches the second current threshold I2, the rotation speed of the motor 20 is controlled to be maintained at the predetermined rotation speed value N1. The predetermined rotational speed value N1 is lower than the motor rotational speed in the normal operating state.
Step S7: and judging whether the motor current reaches the first current threshold I1, if so, entering the step S8, and otherwise, returning to the step S6.
Step S8: when the motor current reaches the first current threshold I1, the motor 20 is controlled to stop.
As shown in fig. 9, at the instant of starting the motor 20 within the time t1, the motor speed N rapidly rises, and the motor current I steadily rises; during the time t1-t2, as the load increases, the motor current I continues to increase; controlling the rotating speed N of the motor to rapidly decrease to a rotating speed preset value N1 within the time t2-t 3; during the time t3-t4, the motor speed N is maintained at the preset speed value N1, and the motor current I continues to rise; at time t4, the motor current I reaches a first current threshold I1, which controls the motor 20 to stop. In the present embodiment, when the motor current I reaches the first current threshold I1, the controller 61 stops outputting the first drive signal, thereby controlling the motor 20 to stop.
Referring to fig. 4, since the motor speed N is related to the motor voltage and the motor current I, and when the load increases, the motor current I also increases correspondingly, if the motor speed N needs to be maintained, the corresponding motor voltage needs to be increased. Therefore, the voltage value required for maintaining the preset rotating speed value N1 can be calculated according to the detected motor current I, and the motor voltage is adjusted to maintain the motor rotating speed N as the preset rotating speed value N1.
In the present embodiment, the storage unit 63 stores a predetermined speed value N1, the current detection unit 67 detects the motor current, and the controller 61 calculates a voltage value required to maintain the predetermined speed value N1 according to the predetermined speed value N1 and the detected motor current. The controller 61 uses the voltage value required to maintain the rotation speed predetermined value N1 as a reference voltage. The controller 61 detects the actual voltage of the motor 20 in real time through the voltage detecting unit 68, and adjusts the first driving signal output by the controller 61 according to the difference between the detected actual voltage and the reference voltage, thereby maintaining the motor rotation speed.
Referring to fig. 10, in the second preferred embodiment of the manual mode, the second current threshold I2 is used as a reference threshold, and the current threshold is maintained for a period of time, and then the motor speed is maintained to complete the fastening of the workpiece. Thus, sudden changes of the motor current are prevented before the workpieces are fastened, and the motor 20 is effectively protected. Specifically, the second preferred embodiment of the manual mode comprises the following steps:
step S1: the first current threshold I1 is set manually.
Step S2: the second current threshold I2 is manually set or automatically calculated, and the second current threshold I2 is lower than the first current threshold I1, the first current threshold I1 is equal to the sum of the second current threshold I2 and a predetermined constant.
Step S3: the user depresses the trigger of the hand held power tool 100 to activate the motor 20.
Step S4: the motor current is detected in real time.
Step S5: and judging whether the motor current reaches a second current threshold I2, if so, entering the step S6, and if not, returning to the step S4.
Step S6: when the motor current reaches the second current threshold I2, the motor current is maintained at the second current threshold I2.
Step S7: and judging whether the motor speed is reduced to a preset speed value N1, if so, entering the step S8, and if not, returning to the step S6. The predetermined rotational speed value N1 is lower than the motor rotational speed in the normal operating state.
Step S8: the rotation speed of the control motor 20 is maintained at the predetermined rotation speed value N1.
Step S9: and judging whether the motor current reaches the first current threshold I1, if so, entering the step S10, and otherwise, returning to the step S8.
Step S10: when the motor current reaches the first current threshold I1, the motor 20 is controlled to stop.
As shown in fig. 11, at the instant of starting the motor 20 within the time t1, the motor speed N rapidly rises, and the motor current I steadily rises; during the time t1-t2, as the load increases, the motor current I continues to increase; in the time t2-t3, the motor current reaches a second current threshold I2, the motor is controlled to maintain the motor current at the second current threshold I2, and meanwhile the motor speed is reduced; during the time t3-t4, the motor speed N is maintained at the preset speed value N1, and the motor current I continues to rise; at time t4, the motor current I reaches a first current threshold I1, which controls the motor 20 to stop.
In the manual mode, when the motor current reaches the second current threshold I2, the motor speed N is controlled to be constant, and when the motor current reaches the first current threshold I1, the motor 20 is controlled to stop, so that the motor current I is limited, the output torque T of the motor 20 is further limited, and the accuracy of torque adjustment is greatly improved.
The automatic mode has a first working phase in which the handheld electric tool 100 automatically sets a parameter threshold value, and a second working phase in which the handheld electric tool 100 performs torque limitation according to the set parameter threshold value.
Referring to fig. 12, in the first working phase, the handheld power tool 100 is operated by a user with experience, and the user turns off the motor switch S2 to control the motor 20 to stop according to working conditions, such as the depth, position, etc. of the workpiece reaching a desired depth, position, etc., automatically detects at least one motor parameter at the time of the stop, and automatically sets a parameter threshold according to the motor parameter, wherein the parameter threshold corresponds to a corresponding target torque.
In the second working stage, the motor 20 is restarted, the handheld electric tool 100 is operated by a user with less experience, the corresponding motor parameter is detected in real time, the detected motor parameter is compared with the parameter threshold value, and when the motor parameter reaches the parameter threshold value, the motor parameter is controlled not to be larger than the parameter threshold value, so that the torque is not larger than the target torque, the workpiece reaches the depth consistent with that of the first working stage, and the operation of the user with less experience is facilitated.
In this embodiment, the motor parameter is a motor current, the motor current Ia during shutdown is recorded in the first working phase, and a current threshold Ib is set according to the motor current Ia. Referring to fig. 3 again, since the motor current is larger and the torque T is larger when the motor speed N is a fixed value, the motor speed is maintained in the first working phase, so that the parameter threshold set according to the motor current at the time of shutdown is more accurate. For design convenience, in the present embodiment, the motor rotation speed in the first operation phase is maintained at the predetermined rotation speed value N1.
In this embodiment, the motor voltage is adjusted to maintain the motor speed at the predetermined speed N1, which is the same as the step S6 in the first preferred embodiment of the manual mode.
According to the data relationship among the motor current, the torque T and the motor speed N in fig. 3, the controller 61 calculates the torque T1 when the motor current is Ia and the motor speed is a predetermined speed value N1, calculates the motor current when the torque T1 and the motor speed are 0, and determines the motor current as the current threshold Ib.
In the second working phase, when the motor current reaches the current threshold Ib, the current value of the motor 20 is maintained as the current threshold Ib, so that the motor current is controlled not to be greater than the current threshold Ib.
As shown in fig. 13, at the instant of starting the motor 20 at time t1, the motor speed rapidly rises, and the motor current steadily rises; during time t1-t2, as the load increases, the motor current continues to increase; and controlling the motor current to be maintained at the current threshold Ib and simultaneously reducing the motor speed after the motor current reaches the current threshold Ib in the time t2-t 3. At time t3, the motor 20 is controlled to stop when the motor speed drops to a certain value (e.g., zero).
In other embodiments, other torque limiting manners may be adopted in the second operation phase, as shown in fig. 9, where the first current threshold I1 is the current threshold Ib automatically set in the first operation phase.
The hand-held power tool 100 in this embodiment has a manual mode and an automatic mode. In the manual mode, the first and second current thresholds are manually set, the motor speed is maintained when the motor current reaches the second current threshold, and the motor 20 is controlled to stop when the motor current reaches the second current threshold, so that the accuracy of torque adjustment is improved. In the first working stage of the automatic mode, experienced users control the motor 20 to stop according to working conditions, parameter thresholds are set according to motor parameters during stopping, and when the motor parameters reach the parameter thresholds, the motor parameters are controlled not to be greater than the parameter thresholds, so that workpieces reach consistent depths, and the users with less experience can conveniently operate the handheld electric tool 100.
The person skilled in the art can appreciate that the specific structure of the mower and the docking charging system of the present invention can be varied in many ways, but the main technical features of the solution adopted are the same as or similar to those of the present invention, and all of them are covered by the scope of the present invention.
Claims (11)
1. A method of controlling a hand-held power tool including a motor and a controller outputting a first drive signal to control the motor, the method comprising the steps of: setting a first current threshold (I1);
the controller controls the motor speed to be maintained at a preset speed value (N1);
detecting a motor current, and controlling the motor to stop when the motor current reaches the first current threshold (I1).
2. The control method according to claim 1, characterized in that: after setting the first current threshold (I1), setting a second current threshold (I2) lower than the first current threshold (I1), when the motor current reaches the second current threshold (I2), the controller controls the rotation speed of the motor to be maintained at a predetermined rotation speed value (N1).
3. The control method according to claim 2, characterized in that: the first current threshold (I1) is equal to the sum of the second current threshold (I2) and a predetermined constant.
4. The control method according to claim 1, characterized in that: the controller calculates a voltage required to maintain a predetermined rotational speed value (N1) based on the detected motor current and the predetermined rotational speed value (N1), and adjusts the actual voltage of the motor to the calculated voltage.
5. The control method according to claim 4, characterized in that: the controller takes the calculated voltage as a reference voltage, detects the actual voltage of the motor in real time, and adjusts the first driving signal output by the controller according to the difference between the actual voltage of the motor and the reference voltage.
6. A hand held power tool comprising a housing, a motor located within the housing, a transmission driven by the motor, and a control circuit for controlling the motor, the control circuit comprising:
a first current threshold setting unit for setting a first current threshold (I1);
the controller is connected with the first current threshold setting unit;
-a memory unit connected to said controller for storing said first current threshold value (I1);
an electronic switch connected with the motor, the controller outputs a first driving signal to the electronic switch,
the controller controls the rotating speed of the motor to be kept at a rotating speed preset value (N1) after the motor is started;
the current detection unit is connected with the electronic switch and the controller and is used for detecting the current of the motor;
the controller compares the motor current with the first current threshold (I1), and stops outputting the first driving signal to the electronic switch when the motor current reaches the first current threshold (I1) so as to control the motor to stop.
7. The hand-held power tool of claim 6, wherein: the control circuit further includes a second current threshold setting unit for setting a second current threshold (I2) lower than the first current threshold (I1), the controller compares the motor current with the second current threshold (I2), and when the motor current reaches the second current threshold (I2), the controller controls the rotation speed of the motor to be maintained at a predetermined rotation speed value (N1).
8. The hand-held power tool of claim 6, wherein: the controller calculates a second current threshold (I2) lower than the first current threshold (I1), compares the motor current with the second current threshold (I2), and controls the rotation speed of the motor to be maintained at a predetermined rotation speed value (N1) when the motor current reaches the second current threshold (I2).
9. The hand-held power tool according to claim 7 or 8, wherein: the memory cell also has a predetermined constant stored therein, and the first current threshold (I1) is equal to the sum of the second current threshold (I2) and the predetermined constant.
10. The hand-held power tool of claim 6, wherein: the controller calculates a voltage required to maintain a predetermined rotational speed value (N1) based on the detected motor current and the predetermined rotational speed value (N1), and adjusts the actual voltage of the motor to the calculated voltage.
11. The hand-held power tool of claim 10, wherein: the control circuit further comprises a voltage detection unit for detecting the actual voltage of the motor, and the controller takes the calculated voltage as a reference voltage and adjusts the first driving signal according to the difference between the detected actual voltage and the reference voltage.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201210105436.8A CN103368480B (en) | 2012-03-31 | 2012-03-31 | Electric hand tool and control method thereof |
| PCT/CN2013/073449 WO2013143489A1 (en) | 2012-03-31 | 2013-03-29 | Hand-held electric tool and control method thereof |
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| CN201210105436.8A CN103368480B (en) | 2012-03-31 | 2012-03-31 | Electric hand tool and control method thereof |
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| CN103368480B CN103368480B (en) | 2016-11-16 |
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