Electric tool and control unit and control method of bidirectional rotating motor thereof

Abstract

The present application provides a control unit (40) and a determination method for determining the rotation direction of a motor (10) of an electric tool, and an electric tool including the control unit (40). The motor (10) is a bidirectional rotating motor and the electric tool alternately performs an effective operation stroke and an idle stroke during operation. The control unit (40) includes a current sensor (42) and a controller (48). The controller (48) is configured to: determine whether a determination parameter satisfies a corresponding reverse condition when the electric tool starts a new operation process; and, if satisfied, instruct the motor (10) to start so that the direction of the rotational motion output by the motor (10) is reversed relative to the direction of the rotational motion in the last operation process, wherein the determination parameter and the corresponding reverse condition are related to the effective operation stroke performed by the electric tool since the last reverse rotation of the rotational motion output by the motor (10). The determination method of the present application is essentially only related to the effective operation stroke, and has nothing to do with the idle stroke performed by the electric tool.

Description

Technical Field

[0001] The present application relates to an electric tool including a bidirectional rotating motor, and in particular, to a control unit and a control method for controlling a reverse operation of the bidirectional rotating motor of the electric tool. Background Art

[0002] Many handheld power tools, such as reciprocating saws, hammer drills, electric picks, etc., use motors to drive the tool heads of power tools to perform the desired actions. The motors of these tools usually output unidirectional rotational motion. A motion transmission mechanism is provided between the motor and the tool head. The gear transmission mechanism is widely used in this application due to its compact structure, high transmission accuracy, wide application range, and large transmission ratio. In applications where the gear transmission mechanism is used as a transmission device, the teeth of the meshing gears are usually formed with a hardened layer to resist wear during the meshing process and extend the service life of the gears.

[0003] Even so, as the power tool is used, the hardened layer on the gear tooth surface will gradually wear away or even fall off after a long period of meshing, which will greatly accelerate the wear of the gear and thus shorten the service life of the power tool. In this case, using a motor that can provide bidirectional rotation to distribute the wear on the gear teeth on the two opposite tooth sides of the gear teeth can alleviate this problem to a certain extent.

[0004] However, due to the limited control technology of the motor rotation direction, the wear of the gear teeth on the two opposite tooth sides is not balanced, and the results are not satisfactory. At present, the reverse control of the motor rotation direction is either performed manually or automatically according to a specific time interval or a specific motor cumulative power consumption, but all of these do not take into account the actual working factors such as the performance or load of the specific power tool. For example, for power tools such as electric drills and reciprocating saws, the actions performed by the tool head include both the effective operating stroke or tool processing stroke for performing effective processing and the idle stroke or tool return stroke for not performing effective processing. The load, power consumption, time, and wear on the gear teeth of these two stroke segments are not the same. The above control method obviously does not take these factors into consideration, so that the wear on the two opposite tooth sides of the gear teeth is still uneven.

[0005] It is hoped that the above technical problems can be solved. Summary of the invention

[0006] The purpose of the present application is to optimize the reverse control of the rotation direction of the output of a bidirectional rotating motor of an electric tool, and to provide a control unit and a control method for realizing this optimized control.

[0007] To this end, the present application provides a control unit for determining the direction of a rotational motion output from a motor of an electric tool, wherein the motor is a bidirectional rotation motor and an actuator of the electric tool alternately performs an effective operation stroke and an idle stroke during operation, wherein the control unit includes a current sensor for measuring the current of the motor in real time and a controller in communication with the current sensor and the motor, wherein the controller is configured to:

[0008] When the electric tool starts a new operation process, it is determined whether the determination parameter meets the corresponding reverse condition; and

[0009] If it is determined that the determination parameter satisfies the corresponding reverse condition, the motor is instructed to start so that the direction of the rotational motion output by the motor is opposite to the direction of the rotational motion output by the motor during the last operation of the power tool; otherwise, if it is determined that the determination parameter does not satisfy the corresponding reverse condition, the motor is instructed to start so that the direction of the rotational motion output by the motor is the same as the direction of the rotational motion output by the motor during the last operation of the power tool.

[0010] The determination parameter and the corresponding reverse condition are related to the effective operation stroke performed by the electric tool since the last reverse rotation of the rotational motion output by the motor. The advantage of the present application is that the determination method is substantially only related to the effective operation stroke of the electric tool, and has nothing to do with the idle stroke performed by the electric tool. This determination method is more accurate and targeted, so that the wear of the transmission components in the electric tool, especially the gears, is more balanced.

[0011] Specifically, the determination parameter and the corresponding reverse condition may be based on both the measured current of the motor and a specific current associated with the effective operating stroke.

[0012] The judgment parameter may be the cumulative time during which the motor current measured since the last reverse rotation of the rotational movement output by the motor exceeds the specific current, and / or the number of effective current cycles passed by the motor current measured since the last reverse rotation of the rotational movement output by the motor; accordingly, the reverse condition may be that the cumulative time reaches or exceeds the specific critical duration of the power tool, and / or the number is equal to or exceeds the specific current cycle number of the power tool.

[0013] The present application also provides an electric tool, comprising: a motor; a transmission mechanism engaged with and driven by the output shaft of the motor; an actuator driven by the transmission mechanism; and a control unit according to the above. The actuator can perform reciprocating linear motion or reciprocating swing motion, or output unidirectional rotation motion.

[0014] In particular, when the transmission mechanism is a gear transmission mechanism, the present application is particularly advantageous. The present application accurately determines and controls the reverse rotation of the motor based on the effective operating stroke that actually bears the workpiece processing load, so that the wear of the two meshing surfaces of each gear tooth of the gear transmission mechanism is balanced to the greatest extent, and the service life of the gear and thus the entire power tool is extended to the greatest extent.

[0015] The present application also provides a method for determining the direction of the rotational motion output from the motor of an electric tool by using the above-mentioned control unit, the method comprising: when the electric tool starts a new operation process: a step of determining whether a judgment parameter satisfies a corresponding reverse condition; and a step of actuating the motor, wherein, when the above-mentioned judgment result determines that the judgment parameter satisfies the corresponding reverse condition, the direction of the rotational motion output by the motor is reversed relative to the direction of the rotational motion output by the motor during the last operation process of the electric tool; otherwise, when the above-mentioned judgment result determines that the judgment parameter does not satisfy the corresponding reverse condition, the direction of the rotational motion output by the motor is the same as the direction of the rotational motion output by the motor during the last operation process of the electric tool, wherein the judgment parameter and the corresponding reverse condition are related to the effective operation stroke performed by the electric tool since the last reverse direction of the rotational motion output by the motor, and have nothing to do with the idle stroke performed by the electric tool.

[0016] According to the present application, each time the electric tool performs a certain number of effective operation strokes or effective current cycles, the rotational motion output by the motor of the electric tool will be reversed in the next operation process. This reverse control method excludes the idle stroke performed by the electric tool, making the control more precise, minimizing the wear of the electric tool and maximizing the service life. This is especially true for electric tools including gear transmission mechanisms. The reverse rotation of the motor is precisely controlled according to the number or time of effective loads borne by the electric tool or its gear transmission mechanism so that the wear degree of the two meshing surfaces of each gear tooth is equal and balanced to the greatest extent, thereby extending the service life of the gear transmission mechanism and the entire electric tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Those skilled in the art will be able to better understand the above and other features and advantages of the present application from the preferred embodiments described below in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A simplified functional block diagram illustrating a power tool according to the principles of the present application;

[0019] Figure 2 A view depicting a portion of a pair of meshing gears of an exemplary power tool according to the present application;

[0020] Figure 3is a flow chart of a method for determining the rotation direction of a bidirectional rotating motor of a power tool according to the principles of the present application; and

[0021] Figure 4 This is a schematic diagram showing the meaning of the effective current cycle of a power tool. DETAILED DESCRIPTION

[0022] The present application is directed to an electric tool that includes a bidirectional rotating motor as a power source and alternately performs effective operating strokes and idle strokes. In this article, the term "effective operating stroke" refers to a stroke cycle in which an effective operation is performed on a workpiece or object of the electric tool, and thus the load and power consumption are large, and "idle stroke" or "tool return stroke" refers to a stroke cycle in which no effective operation is performed on the workpiece or object, and thus the load and power consumption are small. From another perspective, the output of the electric tool may be reciprocating motion, reciprocating swing motion or unidirectional rotation motion, and these output motions of the electric tool are composed of alternating effective operating strokes and idle strokes.

[0023] The basic principle of the present application is to determine whether the output rotation direction of the bidirectional rotating motor of the power tool should be reversed at the beginning of the next operation process based on the detection of the real-time current of the bidirectional rotating motor of the power tool during the operation process and whether the determination parameters related to the real-time current meet the corresponding reverse conditions. In this article, the term "next operation" refers to the operation performed by the power tool when it is restarted after the end of the current operation, that is, between the current "operation process" when measuring the real-time current and the "next operation process", the power tool undergoes a shutdown and a startup action.

[0024] According to the present application, "the judgment parameter related to this real-time current" includes at least one of the first judgment parameter and the second judgment parameter, wherein the first judgment parameter is the number of effective current cycles that the current of the motor measured since the last reverse rotation of the rotational motion output by the motor has passed, and the corresponding reverse condition is that the number is equal to or exceeds the specific current cycle number N0 of the present electric tool. Herein, the term "effective current cycle" is defined as: starting from the moment when the real-time current of the bidirectional rotating motor of the present electric tool crosses the specific current I0 from below the specific current I0 to above the specific current I0, and ending at the moment when the real-time current crosses the specific current I0 from above the specific current I0 to below the specific current I0; the second judgment parameter is the cumulative time that the current of the motor measured since the last reverse rotation of the rotational motion output by the motor exceeds the specific current of the present electric tool, and the corresponding reverse condition is that the cumulative time reaches or exceeds the specific critical time length T0 of the present electric tool.

[0025] Before describing in detail how to judge whether the power tool should reverse the output rotation direction of the bidirectional rotating motor at the beginning of the next operation process based on at least one of the above two judgment parameters, three inherent characteristics of the power tool related to the present application are explained: specific current I0, specific current cycle number N0 and specific critical time length T0.

[0026] For a power tool of a certain type, a certain model or a certain application, especially a power tool including a gear transmission mechanism, during the design stage of the power tool, the designer collects and analyzes the use conditions of the power tool, the load data to be borne, the failure conditions of the power tool, historical test data and other related data, and obtains the causal relationship between the current of the motor of the power tool and the wear of the gears in the power tool, so as to pre-derive the specific current I0, the specific current cycle number N0 and the specific critical time length T0 for the power tool of this type, this model and this application. The specific current I0 substantially corresponds to the current value when the power tool performs an effective operating stroke rather than an idle stroke, and the above-mentioned judgment parameters according to the present application are all associated with this specific current I0.

[0027] These parameters are pre-stored in the power tool. As described in detail below, the power tool includes a control unit, and the above parameters can be stored in a memory of the control unit or in any other storage device of the power tool. It should be noted here that the term "specific" parameter or feature refers to a parameter or feature that is specific or dedicated to this particular type, characteristic model or special application of the power tool, and the parameters or features of power tools of different types, models or applications may be different.

[0028] The following first describes an example of determining whether the output rotation direction of the bidirectional rotating motor of the electric tool during the next operation is the same as or opposite to the rotation direction during the previous operation based on the first determination parameter. The present application provides a control unit for executing this determination process.

[0029] exist Figure 1 The functional block diagram of the electric tool including the bidirectional rotating motor and the control unit as described above is simplified. Figure 1As shown, from a functional perspective, the power tool generally includes a bidirectional rotating motor 10, a transmission mechanism 20, an actuator 30, and a control unit 40 for controlling the reverse operation of the rotation direction output by the motor 10. The bidirectional rotating motor 10 transmits the rotational motion to the transmission mechanism 20 via the output shaft 12. The transmission mechanism 20 is connected between the motor 10 and the actuator 30, and converts the rotational motion of the motor 10 into a suitable motion form of the actuator 30 and transmits it to the actuator 30. The actuator 30 can be a tool head of the power tool, or an action rod attached to the tool head or tool of the power tool and drives the tool head or tool to perform a desired action on the execution object or workpiece.

[0030] The control unit 40 includes a current sensor 42, a memory 44, a counter 46, and a controller 48 connected to the current sensor 42, the memory 44, the counter 46 and the motor 10 in communication. Figure 1 In the block diagram, the communication connection is represented by a connecting line with an arrow. The counter 46 is used to count the number of effective current cycles that the current (I) of the motor (10) measured since the last reverse rotation of the rotational motion output by the motor (10) has passed. The current sensor 42 is configured to measure the real-time current I of the motor 10 in real time. The memory 44 is used to store all the relevant parameters listed above and the calculation or logic algorithms, for example, at least the above-mentioned specific current I0, the number of specific current cycles N0 and the specific critical time T0 are stored. According to the present application, from the moment when the current I of the motor 10 crosses the specific current I0 from lower than the specific current I0 to higher than the specific current I0, to the moment when the current I crosses the specific current I0 from higher than the specific current I0 to lower than the specific current I0, it is recorded as an effective current cycle. The meaning of the effective current cycle is as follows. Figure 4 It is shown in Figure 4 P1 and P2 in it represent the effective current cycle.

[0031] When the power tool is started and a new operation process is about to begin, the controller 48 first extracts the specific current cycle number N0 of the power tool from the memory 44 and determines whether the current count N of the counter 46 is greater than or equal to the specific current cycle number N0. When the current count N is greater than or equal to the specific current cycle number N0, the rotation direction of the output shaft 12 of the bidirectional motor 10 is determined to be opposite to the rotation direction of the output shaft 12 during the last operation of the power tool, and the counter 46 is cleared; otherwise, the rotation direction of the output shaft 12 is the same as the rotation direction during the last operation, and the counter 46 is not cleared. When a new power tool is delivered for use, the count N in the counter 46 is set to 0, and when the new power tool is delivered for use, the motor 10 has a preset initial rotation direction.

[0032] After determining the rotation direction of the output shaft 12 of the bidirectional rotating motor 10, the controller 48 instructs the motor 10 to start, and the current sensor 42 of the control unit 40 starts to monitor or measure the real-time current I of the motor 10, and transmits the measured current I to the controller 48. The controller 48 receives the measured current I from the current sensor 42, and extracts the specific current I0 and the specific current cycle number N0 of the power tool from the memory 44. The controller 48 determines whether the real-time current I meets the above definition of "valid current cycle", and if it does, it determines that the current I of the motor 10 has experienced a valid current cycle, at which time the controller 48 instructs the count N of the counter 46 to increase by 1. This cycle is repeated until the operation process ends, and then the power tool is stopped by powering off the motor 10.

[0033] When the power tool is used next time, or when the power tool is used for the next operation, as described above, it is first determined whether the count N in the counter 46 at the end of the current operation matches N0, so as to determine the next rotation direction of the motor 10.

[0034] In this determination method, the count N in the counter 46 at the end of the previous operation process of the electric tool is the only criterion for determining whether the rotation direction of the motor output shaft of the electric tool is to be reversed in the next operation process, and this count N is the number of effective current cycles that the current of the electric tool motor has passed since the last reverse rotation, that is, the number of effective operation strokes performed by the electric tool. It can be seen that the basis for the control unit of the present application to control the motor reverse is the number of effective operation strokes performed by the electric tool, and has nothing to do with the idle stroke. Compared with the determination method in the prior art that does not exclude the idle stroke, the determination method of the present application is more accurate.

[0035] An example of determining whether the output rotation direction of the bidirectional rotating motor of the electric tool during the next operation is the same as or opposite to that during the previous operation based on the second determination parameter will now be described.

[0036] As described above, the second judgment parameter is the cumulative time T that the measured real-time current I exceeds the specific current I0 of the power tool. Accordingly, the control unit 40 includes a timer 52 for accumulating the cumulative time that the real-time current I of the motor 10 exceeds the specific current I0, and the memory 44 of the control unit 40 stores the specific critical time T0 for the power tool.

[0037] When the power tool is started, the controller 48 first extracts the accumulated time T at the end of the last operation of the power tool from the timer 52, extracts the specific critical time T0 of the power tool from the memory 44, and determines whether the accumulated time T reaches or exceeds the specific critical time T0. When the accumulated time T reaches or exceeds the specific critical time T0, the controller 48 instructs the output shaft 12 of the bidirectional motor 10 to rotate in the opposite direction to the output shaft 12 during the last operation of the power tool, and the timer 52 is reset; otherwise, the output shaft 12 rotates in the same direction as in the last operation, and the timer 52 is not reset. When a new power tool is delivered for use, the accumulated time T in the timer 52 is set to 0.

[0038] After determining the rotation direction of the output shaft 12 of the bidirectional rotating motor 10, the motor 10 starts to start, and the current sensor 42 of the control unit 40 starts to monitor or measure the real-time current I of the motor 10, and transmits the measured current I to the controller 48 in real time. The controller 48 receives the measured current I from the current sensor 42, extracts the specific current I0 of the power tool from the memory 44, and instructs the timer 52 to start accumulating time when the real-time current I is greater than the specific current I0. When the real-time current I drops below the specific current I0, the controller 48 notifies the timer 52 to stop timing until the end of the operation process, and then stops the power tool by turning off the power to the motor 10.

[0039] The next time the power tool is used, or when the next operation process is started using the power tool, as described above, it is first determined whether the duration T in the timer 52 at the end of the previous operation process reaches or exceeds the specific critical time T0, so as to determine the next rotation direction of the motor 10 and determine whether the timer 52 is reset.

[0040] Reference again Figure 4 It can be seen that, since the specific current I0 corresponds to the effective operating stroke of the electric tool, the time period during which the real-time current I accumulated by the timer 52 is greater than the specific current I0 substantially corresponds to the effective operating stroke of the electric tool, and also corresponds to the effective current cycle described with respect to the first determination parameter. Therefore, the second determination method is substantially the same as the first determination method described above, and has the same advantages over the prior art.

[0041] Preferably, the controller of the control unit 40 according to the present application can determine these two determination parameters at the same time. That is, when the electric tool starts a new operation process, the controller 28 determines whether the count N in the counter 46 exceeds the specific current cycle number N0 and determines whether the duration T in the timer 52 exceeds the specific critical time T0, and when at least one of the two reverse conditions is met, the motor 10 is instructed to output a rotational motion opposite to the previous operation process, and the counter 46 and the timer 52 are both reset. On the contrary, when neither of the above conditions is met, the motor 10 is instructed not to change the reverse direction of the output rotational motion and the counter 46 and the timer 52 are not reset.

[0042] The principle of the present application as described above is advantageous for most electric tools that include a bidirectional rotating motor and alternately output an effective operating stroke and an idle stroke. The electric tool according to the present application can be any suitable type of electric tool including the bidirectional rotating drive motor 10 as described above, such as a handheld electric tool, which can be an electric tool for operating on hard objects such as concrete or masonry, and can be an electric tool for operating on objects such as metal, plastic or wood, such as an electric pick, an electric drill, and a hammer drill. The electric tool according to the present application can also be an electric saw for cutting a workpiece, such as a reciprocating saw.

[0043] The present application is particularly advantageous for power tools that include gears, such as power tools that include gear transmission mechanisms. As an illustrative example, Figure 2 A pair of mutually meshing gears 5 and 7 included in a certain electric tool is shown.

[0044] exist Figure 2In the embodiment, the gear 5 can be used as a pinion on the output shaft 12 of the motor 10. When the output shaft 12 of the motor 10, i.e., the gear 5, rotates clockwise, the tooth flanks 5a and 7a of the pair of gears 5 and 7 mesh with each other and transmit power torque. After the power tool performs N0 effective current cycles or N0 effective operation strokes or the power tool experiences a specific critical time length T0, the tooth flanks 5a and 7a of the gears 5 and 7 are subjected to N0 effective heavy loads and corresponding heavy wear. According to the principle of the present application, at this time, the controller 48 instructs the output shaft 12 of the motor 10 to reverse its rotation direction, i.e., start to output counterclockwise rotation. At this time, the tooth flanks 5b and 7b of the pair of gears 5 and 7 mesh with each other and transmit power torque, and the power tool performs N0 effective current cycles or N0 effective operation strokes or experiences a specific critical time length T0 again, and the tooth flanks 5a and 7a of the gears 5 and 7 are also subjected to N0 effective heavy loads and corresponding heavy wear, and the output shaft 12 of the motor 10 is instructed to reverse again and turn back to clockwise rotation. At this point, it is obvious that by controlling the direction of the output rotation of the motor 10 according to this rule, the load and wear on each tooth side of the gear teeth are basically balanced, which is the best solution for the gear as a whole and the power tool as a whole. In particular, for power tools with uncertain or unbalanced load and duration of effective operating stroke and idle stroke, this control solution is the most reasonable and optimized.

[0045] Figure 3 A flow chart of a method for determining the direction of rotational motion output from the motor 10 of a power tool according to the principles of the present application is shown. The method comprises the following steps:

[0046] S1) The power tool is turned on, i.e. the power tool is about to start a new operation process;

[0047] S2) the controller 28 of the control unit 40 determines whether the determination parameter satisfies the corresponding reverse condition, and when the determination parameter satisfies the corresponding reverse condition, determines that the direction of the rotational motion output by the motor 10 is reverse to the direction of the rotational motion output by the motor 10 during the last operation of the power tool, and vice versa, determines that the motor 10 will rotate in the same rotational direction;

[0048] S3) actuates the motor 10 to rotate its output shaft 12 in the rotation direction determined in the previous step. Preferably, in this step 3), the controller 28 instructs the counter 46 and the timer 52 to be reset.

[0049] The present application only uses the effective operation stroke experienced by the power tool as a basis to determine whether the rotational motion output by the motor of the power tool should be reversed during the next operation process. This reverse control method excludes the idle stroke performed by the power tool, making the control more precise, minimizing the wear inside the power tool, and maximizing the service life. This is especially true for power tools including gear transmission mechanisms. The reverse rotation of the motor is precisely controlled according to the number or time of effective loads borne by the power tool or its gear transmission mechanism so that the wear degree of the two meshing surfaces of each gear tooth is equal and balanced to the greatest extent, thereby extending the service life of the gear transmission mechanism and the entire power tool.

[0050] The present application has been shown and described based on preferred embodiments, but the present application is not limited to the details shown in the drawings and described above. Instead, various modifications or variations can be made without departing from the spirit and scope defined by the appended claims.

Claims

1. A control unit (40) for determining the direction of a rotational motion output from a motor (10) of an electric tool, wherein the motor (10) is a bidirectional rotation motor and an actuator (30) of the electric tool alternately performs an effective operation stroke and an idle stroke during operation, the control unit (40) comprising a current sensor (42) for measuring a current (I) of the motor (10) in real time and a controller (48) communicatively connected to the current sensor (42) and the motor (10), the controller (48) being configured to: When the electric tool starts a new operation process, it is determined whether the determination parameter meets the corresponding reverse condition; and If it is determined that the determination parameter satisfies the corresponding reverse condition, the motor (10) is instructed to start so that the direction of the rotational motion outputted by the motor (10) is opposite to the direction of the rotational motion outputted by the motor (10) during the last operation of the electric tool; otherwise, if it is determined that the determination parameter does not satisfy the corresponding reverse condition, the motor (10) is instructed to start so that the direction of the rotational motion outputted by the motor (10) is the same as the direction of the rotational motion outputted by the motor (10) during the last operation of the electric tool. in, The determination parameter and the corresponding reverse condition are related to the effective operation stroke performed by the electric tool since the last reverse rotation of the rotational motion output by the motor (10), and the determination parameter and the corresponding reverse condition are based on both the measured current (I) of the motor (10) and the specific current (I0) related to the effective operation stroke, wherein: The determination parameter is the number of effective current cycles of the current (I) of the motor (10) measured since the last reverse rotation of the rotational motion output by the motor (10), and the corresponding reverse condition is that the number is equal to or exceeds the specific current cycle number (N0) of the electric tool; or The judgment parameters are the number of effective current cycles that the current (I) of the motor (10) measured since the last reverse rotation of the rotational movement output by the motor (10) has passed and the cumulative time that the current (I) of the motor (10) measured since the last reverse rotation of the rotational movement output by the motor (10) exceeds the specific current (I0), and the corresponding reverse condition is that the cumulative time reaches or exceeds the specific critical time length (T0) of the power tool or the number is equal to or exceeds the specific current cycle number (N0) of the power tool.

2. The control unit (40) according to claim 1, wherein: In the case where the determination parameter is the accumulated time, the control unit (40) includes a timer (52) for accumulating the accumulated time, wherein the controller (48) instructs the timer (52) to be reset when determining that the accumulated time reaches or exceeds the specific critical time length (T0) and thus instructs the motor (10) to output reverse rotation motion.

3. The control unit (40) according to claim 1, wherein: The effective current cycle refers to the moment when the current (I) crosses the specific current (I0) from lower than the specific current (I0) to higher than the specific current (I0) and ends when the current (I) crosses the specific current (I0) from higher than the specific current (I0) to lower than the specific current (I0).

4. The control unit (40) according to claim 3, wherein: The control unit (40) includes a counter (46) for counting the number of times, wherein the controller (48) instructs the counter (46) to be cleared when determining that the number of times is equal to or exceeds the specific current cycle number (N0) and thus instructs the motor (10) to output reverse rotation movement.

5. The control unit (40) according to claim 1, wherein: The control unit (40) also includes a memory (44) for storing at least the specific current (I0) of the power tool, the specific current cycle number (N0), and the power tool specific critical time (T0), and the controller (48) is communicatively connected to the memory (44).

6. An electric tool comprising: Motor (10); a transmission mechanism (20) engaged with and driven by an output shaft (12) of the motor (10); an actuator (30) driven by the transmission mechanism (20); and A control unit (40) according to any one of claims 1-5.

7. The electric tool according to claim 6, wherein: The actuator (30) performs reciprocating linear motion or reciprocating swing motion, or outputs unidirectional rotation motion.

8. The electric tool according to claim 6, wherein: The transmission mechanism (20) is a gear transmission mechanism.

9. The electric tool according to claim 8, wherein: The transmission mechanism (20) comprises a gear meshing with a pinion gear arranged on the output shaft (12).

10. The electric tool according to any one of claims 6 to 9, wherein: The electric tool is a handheld electric tool.

11. The electric tool according to any one of claims 6 to 9, wherein: The electric tool is an electric pick, a reciprocating saw or an electric tool that outputs reciprocating swing.

12. A method for determining the direction of a rotational motion output from a motor (10) of a power tool using a control unit (40) according to any one of claims 1 to 5, the method comprising, when the power tool starts a new operation process: The step of judging whether the determination parameter satisfies the corresponding reverse condition; The step of actuating the motor (10), wherein: When the above judgment result determines that the judgment parameter satisfies the corresponding reverse condition, the direction of the rotational motion output by the motor (10) is reversed relative to the direction of the rotational motion output by the motor (10) during the last operation of the electric tool; otherwise, when the above judgment result determines that the judgment parameter does not satisfy the corresponding reverse condition, the direction of the rotational motion output by the motor (10) is the same as the direction of the rotational motion output by the motor (10) during the last operation of the electric tool. wherein the determination parameter and the corresponding reverse condition are related to the effective operation stroke performed by the electric tool since the last reverse rotation of the rotational motion output by the motor (10), and are irrelevant to the idle stroke performed by the electric tool, The determination parameter and the corresponding reverse condition are both based on the measured current (I) of the motor (10) and the specific current (I0) associated with the effective operating stroke, wherein: The determination parameter is the number of effective current cycles of the current (I) of the motor (10) measured since the last reverse rotation of the rotational motion output by the motor (10), and the corresponding reverse condition is that the number is equal to or exceeds the specific current cycle number (N0) of the electric tool; or The judgment parameters are the number of effective current cycles that the current (I) of the motor (10) measured since the last reverse rotation of the rotational movement output by the motor (10) has passed and the cumulative time that the current (I) of the motor (10) measured since the last reverse rotation of the rotational movement output by the motor (10) exceeds the specific current (I0), and the corresponding reverse condition is that the cumulative time reaches or exceeds the specific critical time length (T0) of the power tool or the number is equal to or exceeds the specific current cycle number (N0) of the power tool.

13. The method according to claim 12, wherein: It also includes the steps of determining the specific current (I0), specific current cycle number (N0) and specific critical time (T0) of the power tool based on the operating conditions of the power tool, the load data to be borne, the failure conditions of the power tool, and historical test data.

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