CN111384884A

CN111384884A - Electric tool, and control unit and control method for bidirectional rotating motor of electric tool

Info

Publication number: CN111384884A
Application number: CN201811605970.9A
Authority: CN
Inventors: 嵇万里; 余芳; 林小霞
Original assignee: Bosch Power Tools China Co Ltd
Current assignee: Bosch Power Tools China Co Ltd
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2020-07-07
Also published as: DE112019006491T5; BR112021012203A2; WO2020134159A1

Abstract

A control unit (40) and a determination method for determining a rotational direction of a motor (10) of an electric tool, and an electric tool comprising such a control unit (40) are provided. Wherein the motor (10) is a bidirectional rotary motor and the power tool alternately performs an active operation stroke and an idle stroke during operation, the control unit (40) comprising a current sensor (42) and a controller (48), the controller (48) being configured for: judging whether the decision parameter satisfies a corresponding reversal condition when the electric tool starts a new operation process; and, when satisfied, instructing the motor (10) to start reversing the direction of the rotary motion it outputs with respect to the direction of the rotary motion during the last operation, wherein the decision parameter and the corresponding reversal condition are related to the effective operating stroke performed by the electric tool since the last reversal of the rotary motion output by the motor (10). The decision method of the present application is essentially related only to the active operating stroke and not to the idle stroke performed by the power tool.

Description

Electric tool, and control unit and control method for bidirectional rotating motor of electric tool

Technical Field

The present invention relates to an electric power tool including a bidirectional rotary motor, and particularly also relates to a control unit and a control method that control a reverse operation of a rotation direction of the bidirectional rotary motor of the electric power tool.

Background

Many hand-held power tools, such as reciprocating saws, hammer drills, electric picks, and the like, utilize a motor to drive the tool head of the power tool to perform a desired action, the motor of the tool typically outputting a unidirectional rotational motion. A motion transmission mechanism is arranged between the motor and the tool head, and the gear transmission mechanism is widely applied to the application due to the advantages of compact structure, high transmission precision, wide application range, large transmission ratio and the like. In applications utilizing gear trains as the transmission, the teeth of the meshing gears are typically formed with a hardened layer to resist wear during meshing and to extend the useful life of the gears.

Even so, with the use of the electric power tool, after the gear is engaged for a long time, the hardened layer on the surface of the gear teeth is gradually worn out, or even falls off, which greatly accelerates the wear of the gear, thus shortening the service life of the electric power tool. In this case, the use of a motor capable of providing bi-directional rotation allows the wear on the gear teeth to be shared between the opposite flanks of the gear teeth to alleviate the problem to some extent.

However, due to the limited control technology for the direction of rotation of the motor, the wear of the teeth on the two opposite flanks is not even and as a result unsatisfactory. At present, the reverse control of the rotation direction of the motor is performed either manually or automatically in accordance with a specific time interval or a specific motor accumulated power consumption, but all of them do not consider actual operating factors such as the performance or load of a specific power tool. For example, in the case of electric tools such as drills, reciprocating saws and the like, the action performed by the tool head includes both an active operating stroke or tool machining stroke in which active machining is performed and an idle stroke or tool return stroke in which active machining is not performed, while the loads, power consumption, time and wear on the teeth are different, the above control obviously does not take these factors into account, so that the wear on the opposite flanks of the teeth of the wheel is not balanced.

It is desirable to solve the above technical problems.

Disclosure of Invention

An object of the present application is to optimize reverse control of the rotational direction of the output of a bidirectional rotary motor of an electric tool, and to provide a control unit and a control method for achieving this optimized control.

To this end, the present application provides a control unit for determining a direction of a rotational motion output from a motor of a power tool, the motor being a bidirectional rotary motor and an actuator of the power tool alternately performing an active operation stroke and an idle stroke during operation, the control unit comprising a current sensor for measuring a current of the motor in real time and a controller communicatively connected to the current sensor and the motor, the controller being configured to:

determining whether a decision parameter satisfies a corresponding reversal condition when the power tool begins a new operational process; and the number of the first and second electrodes,

in the case where it is determined that the determination parameter satisfies the respective reversal condition, instructing the motor to start causing the direction of the rotational motion output by the motor to be reversed with respect to the direction of the rotational motion output by the motor during the last operation of the electric power tool, otherwise, in the case where it is determined that the determination parameter does not satisfy the respective reversal condition, instructing the motor to start causing the direction of the rotational motion output by the motor to be the same as the direction of the rotational motion output by the motor during the last operation of the electric power tool,

wherein the decision parameter and the corresponding reversal condition relate to an effective operating stroke that the power tool has performed since a last reversal of the rotary motion output by the motor. The application has the advantages that: the present determination method is substantially only related to the active operating stroke of the power tool, irrespective of the idle stroke performed by said power tool, and is more precise and targeted, so that the wear of the transmission components, in particular the gears, within the power tool is more even.

In particular, the decision parameter and the corresponding reversal condition may be based on both the measured current of the electric machine and the specific current related to the active operating stroke.

The determination parameter may be an accumulated time during which the current of the motor measured from the last reversal of the rotational motion output by the motor exceeds the specific current, and/or a number of effective current cycles during which the current of the motor measured from the last reversal of the rotational motion output by the motor passes; accordingly, the reversal condition may be that the accumulated time reaches or exceeds the specific critical duration of the power tool, and/or that the number equals or exceeds a specific number of current cycles of the power tool.

The present application also provides an electric tool including: a motor; a transmission mechanism coupled to and driven by an output shaft of the motor; an actuator driven by the transmission mechanism; and a control unit according to the above. The actuator may perform a reciprocating linear motion or a reciprocating oscillating motion, or output a unidirectional rotary motion.

The present application is particularly advantageous, in particular, in the case where the transmission is a gear transmission. The motor reverse direction is accurately judged and controlled on the basis of the effective operation stroke actually bearing the workpiece machining load, so that the abrasion of two meshing surfaces of each gear tooth of the gear transmission mechanism is balanced to the maximum extent, and the service life of the gear and the whole electric tool is prolonged to the maximum extent.

The present application also provides a method of determining a direction of a rotational movement output from a motor of a power tool using the above control unit, the method comprising, when the power tool starts a new operational process: judging whether the judgment parameters meet corresponding reverse conditions; a step of actuating the motor, wherein the direction of the rotational motion output by the motor is reversed with respect to the direction of the rotational motion output by the motor during the last operation of the electric tool when the above-described determination result determines that the determination parameter satisfies the corresponding reversal condition, and otherwise, the direction of the rotational motion output by the motor is made the same as the direction of the rotational motion output by the motor during the last operation of the electric tool in a case where the above-described determination result determines that the determination parameter does not satisfy the corresponding reversal condition, wherein the determination parameter and the corresponding reversal condition are related to an effective operation stroke that has been performed by the electric tool since the last reversal of the rotational motion output by the motor, regardless of an idle stroke that is performed by the electric tool.

According to the application, after the electric tool executes a certain number of effective operation strokes or effective current cycles, the rotary motion output by the motor in the next operation process of the electric tool is reversed, and the reverse control method excludes the idle strokes executed by the electric tool, so that the control is more accurate, the abrasion of the electric tool is minimized, and the service life is longest. This is particularly true for power tools that include a gear train, where the exact reversal of the motor is controlled based on the number of times or the time that the power tool or its gear train is subjected to a payload so that the wear on both meshing surfaces of each gear tooth is substantially equal, and balanced to the greatest extent, thereby extending the useful life of the gear train, as well as the entire power tool.

Drawings

The above-mentioned and other features and advantages of this application will be better understood by those skilled in the art from the following description of a preferred embodiment taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a simplified functional block diagram of a power tool according to the principles of the present application;

FIG. 2 depicts a view of a portion of a pair of meshing gears of an exemplary power tool according to the present application;

FIG. 3 is a flow chart of a method for determining a rotational direction of a bi-directional rotating motor of a power tool according to the principles of the present application; and

fig. 4 is a schematic diagram of the meaning of the active current period of the power tool.

Detailed Description

The present application is directed to an electric power tool that includes a bidirectional rotary electric machine as a power source and alternately performs operations of an active operation stroke and an idle stroke. Herein, the term "effective operation stroke" refers to a stroke period during which an effective operation is performed on a workpiece or object of a power tool and thus the load and power consumption are large, and "idle stroke" or "tool return stroke" refers to a stroke period during which an effective operation is not performed on a workpiece or object and thus the load and power consumption are small. From another perspective, the power tool output may be a reciprocating motion, a reciprocating oscillating motion, or a unidirectional rotary motion, and these output motions of the power tool are composed of alternating active and idle strokes.

The basic principle of the application is as follows: whether the output rotation direction of the bidirectional rotating motor of the electric tool should be reversed at the beginning of the next operation process is judged based on detecting the real-time current of the bidirectional rotating motor of the electric tool in the operation process and judging whether the judgment parameter related to the real-time current meets the corresponding reversing condition. In this context, the term "next operation" refers to an operation performed when the electric power tool is restarted after the end of the present operation, that is, the electric power tool undergoes one power-off and one power-on action between the present "operation process" and the "next operation process" when the real-time current is measured.

According to the present application, the "determination parameter related to the real-time current" includes at least one of a first determination parameter and a second determination parameter, wherein the first determination parameter is the number of effective current cycles that the current of the motor passes, which is measured from the last reversal of the rotational motion of the motor output, and the corresponding reversal condition is that the number equals or exceeds the number N of specific current cycles of the present electric power tool₀. Herein, the term "active current period" is defined as: the real-time current of the bidirectional rotating motor of the electric tool is lower than the specific current I₀Across the specific current I₀To above the specific current I₀So far, the real-time current is higher than the specific current I₀Across the specific current I₀To below the specific current I₀End of time (1); the second determination parameter is the cumulative time that the current of the motor exceeds the specific current of the electric tool measured from the last reversal of the rotary motion output by the motor, and the corresponding reversal condition is that the cumulative time reaches or exceeds the specific critical duration T of the electric tool₀。

How to follow is described in detailBefore at least one of the two determination parameters is used to determine whether the electric power tool should reverse the output rotation direction of the bidirectional rotary motor at the start of the next operation process, three inherent features of the electric power tool related to the present application are explained: specific current I₀Specific number of current cycles N₀And a critical duration of specificity T₀。

For a specific type, a specific model or a specific application of an electric tool, in particular to an electric tool comprising a gear transmission mechanism, in the design stage of the electric tool, a designer collects and analyzes relevant data such as the use condition of the electric tool, the load data to be born, the failure condition of the electric tool, historical test data and the like to obtain the causal relationship between the current of a motor of the electric tool and the abrasion of gears in the electric tool, so as to obtain the specific current I for the type, the model and the application of the electric tool in advance₀Specific number of current cycles N₀And a critical duration of specificity T₀. Specific current I₀Substantially corresponding to the current value at which the electric tool performs an active operating stroke, not an idle stroke, and to which the above-mentioned decision parameter according to the present application is both associated₀And (4) associating.

These parameters are stored in the power tool in advance. As will be described in detail below in particular, the power tool comprises a control unit, and the above-mentioned parameters may be stored in a memory of the control unit or in any other memory means of the power tool. It should be noted herein that the term "specific" parameter or characteristic refers to a parameter or characteristic that is specific or specific to the particular type, model, or application of power tool, and that parameters or characteristics may be different for different types or models or applications of power tools.

The following first describes an example of determining whether the output rotation direction of the bidirectional rotary motor during the next operation of the electric power tool is the same as or opposite to the rotation direction during the previous operation, based on the first determination parameter. A control unit is provided for performing this decision process.

Fig. 1 is a simplified functional block diagram of an electric power tool including a bidirectional rotary motor and a control unit as described above. As shown in fig. 1, the electric power tool generally includes, from the functional viewpoint, a bidirectional rotary motor 10, a transmission mechanism 20, an actuator 30, and a control unit 40 for controlling the reverse operation of the rotational direction of the output of the motor 10. The bidirectional rotary electric machine 10 transmits a rotary motion to the transmission mechanism 20 through the output shaft 12. The transmission mechanism 20 is connected between the motor 10 and the actuator 30, and converts the rotary motion of the motor 10 into the appropriate motion form of the actuator 30 to be transmitted to the actuator 30. The actuator 30 may be a tool head of a power tool, or an action bar attached to and driving a tool head or a cutter of a power tool to perform a desired action on an execution object or a workpiece.

The control unit 40 comprises a current sensor 42, a memory 44, a counter 46, and a controller 48 communicatively connected to the current sensor 42, the memory 44, the counter 46 and the motor 10, wherein the communicatively connection is represented in the block diagram of fig. 1 by a connection line with arrows. The counter 46 is arranged to count the number of active current cycles that the current (I) of the motor (10) has passed since the last reversal of the rotational movement output by the motor (10). 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 relevant parameters and calculations or logic algorithms including those listed above, for example, at least the specific current I mentioned above₀Specific number of current cycles N₀And a critical duration of specificity T₀. According to the application, the current I from the motor 10 is from below the specific current I₀Across the specific current I₀To above the specific current I₀To a current I from above said specific current I₀Across the specific current I₀To below the specific current I₀End of time, and is recorded as an active current period. The meaning of the active current period is shown in fig. 4, P1, P2 in fig. 4 indicating the active current period.

When the power tool is started and a new operational process is to begin, the controller 48 first retrieves the costs from the memory 42Specific current cycle number N of electric tool₀And determines whether the present count N of the counter 46 is greater than or equal to the number N of specific current cycles₀. The current count N is greater than or equal to the specific current period number N₀In the case where 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 electric power tool, and the counter 46 is cleared; otherwise the direction of rotation of the output shaft 12 is the same as during the last operation and the counter 46 is not cleared. The count N in the counter 46 is set to 0 when the new power tool is delivered for use, and the motor 10 has a preset initial rotational direction when the new power tool is delivered for use.

After determining the direction of rotation of the output shaft 12 of the electric reversible machine 10, the controller 48 instructs the electric machine 10 to start starting, and the current sensor 42 of the control unit 40 starts monitoring or measuring the current I of the electric machine 10 in real time 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 I of the present power tool from the memory 42₀And specific number of current cycles N₀. The controller 48 determines whether the real-time current I meets the above definition of "active current period" and, when met, determines that the current I of the motor 10 has experienced an active current period, at which time the controller 48 instructs the counter 46 to increment the count N by 1. This is repeated until the end of the operation, after which the electric tool is stopped by de-energizing the motor 10.

When the electric power tool is used next time or when the electric power tool is used for the next operation process, it is first determined whether the count N in the counter 46 at the end of the current operation process matches N or not, as described above₀In order to determine the direction of rotation of the motor 10 next.

In the present determination method, the count N of the counter 46 at the end of the previous operation of the electric power tool is the only criterion for determining whether the direction of rotation of the output shaft of the motor of the electric power tool is to be reversed during the next operation, and this count N is the number of active current cycles that have elapsed since the last reversal of the motor of the electric power tool, that is, the number of active operation strokes that the electric power tool has performed. It follows that the control unit according to the present application controls the motor reversal on the basis of the number of active operating strokes performed by the power tool, irrespective of the idle stroke. Compared with a judging method which does not exclude idle travel in the prior art, the judging method is more accurate.

Now, description will be made of an example of determining whether the output rotation direction of the bidirectional rotary motor during the next operation of the electric power tool is the same as or opposite to the rotation direction during the previous operation, based on the second determination parameter.

As mentioned above, the second decision parameter is that the measured real-time current I exceeds the specific current I of the power tool₀The elapsed cumulative time T. Accordingly, the control unit 40 comprises a timer 52 for accumulating the real-time current I of the motor 10 over the specific current I₀And the memory 42 of the control unit 40 stores the specific critical time T for the present electric tool₀。

When the electric tool is started, the controller 48 first extracts the accumulated time T of the electric tool at the end of the last operation process from the timer 52, and extracts the specific critical time T of the electric tool from the memory 42₀Judging whether the cumulative time T reaches or exceeds the specific critical time T₀. Reaching or exceeding a specificity critical time T at a cumulative time T₀In this case, 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 electric power tool, and the timer 52 is cleared; otherwise the direction of rotation of the output shaft 12 is the same as during the last operation and the timer 52 is not cleared. When a new electric power tool is delivered for use, the cumulative time T in the timer 52 is set to 0.

After determining the direction of rotation of the output shaft 12 of the electric reversible machine 10, the electric machine 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 electric machine 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, fromThe memory 42 extracts the specific current I of the electric tool₀And when the real-time current I is greater than the specific current I₀The time indication counter 52 starts accumulating time. When the real-time current I is reduced to be lower than the specific current I₀The timer controller 48 notifies the counter 52 to count down until the end of the present operation process, and then stops the present electric power tool by powering down the motor 10.

When the electric power tool is used next time or when the electric power tool is used to start the next operation process, as described above, it is first determined whether the time period T in the timer 52 at the end of the previous operation process reaches or exceeds the specific threshold time T₀Thereby determining the next rotation direction of the motor 10 and determining whether the counter 52 is cleared.

Referring again to FIG. 4, due to the specific current I₀Corresponding to the effective operating stroke of the power tool, so that the real-time current I, which requires the counter 52 to accumulate for a long time, is greater than the specific current I₀Also substantially corresponds to the active operating stroke of the power tool and likewise to the active current period described in relation to the first decision parameter. Therefore, the present second determination method is substantially the same as the above-described first determination method, and has the same advantages over the prior art.

Preferably, the controller of the control unit 40 according to the present application may determine both determination parameters simultaneously. That is, when the power tool begins to initiate a new operational process, the controller 28 determines whether the count N in the counter 46 exceeds the specific number N of current cycles₀And determines whether the time period T in the counter 52 exceeds the specificity threshold time T₀And in the event that at least one of these two reversal conditions is met, indicates that the motor 10 is outputting a rotational movement that is opposite to the last operational procedure, while the

counters

46 and 52 are both cleared. Conversely, in the event that neither of the above conditions is met, the motor 10 is instructed not to change the reverse direction of the output rotary motion and neither the counter 46 nor the counter 52 is cleared.

The principle of the present application as described above is advantageous for most electric tools that include a bidirectional rotary motor and alternately output an active stroke and an idle stroke. The power tool according to the present application may be any suitable type of power tool including the bi-directional rotary drive motor 10 as described above, such as a hand-held power tool, which may be a power tool for operating on hard objects such as concrete or masonry, and may be a power tool for operating on objects such as metal, plastic or wood, such as a pick, drill, hammer drill. The power tool according to the present application may also be a power saw for cutting a workpiece, such as a reciprocating saw.

The present application is particularly advantageous for power tools that include gears, such as power tools that include gear trains. As an illustrative example, fig. 2 shows a pair of intermeshing gears 5 and 7 included in a certain power tool.

In fig. 2, the gear 5 may be used as a pinion on the output shaft 12 of the motor 10. In the case where the output shaft 12 of the motor 10, i.e., the gear 5, rotates clockwise, the

flanks

5a and 7a of the pair of gears 5 and 7 mesh with each other and transmit power torque. In the electric tool execute N₀One effective current period or N₀After a less effective operating stroke or while the power tool is experiencing a specific critical duration T₀Thereafter, the

flanks

5a and 7a of the gears 5 and 7 are subjected to N₀Sub-effective heavy loads and corresponding heavy wear. In accordance with the principles of the subject application, the controller 48 now instructs the output shaft 12 of the motor 10 to reverse direction of rotation, i.e., begin outputting counterclockwise rotation. At this time, the

flanks

5b and 7b of the pair of gears 5 and 7 mesh with each other and transmit power torque, and the electric tool again performs N₀One effective current period or N₀Less efficient operation stroke or specific critical duration T₀The

flanks

5a and 7a of the gears 5 and 7 are likewise subjected to N₀The next significant heavy load and corresponding heavy wear, the output shaft 12 of the motor 10 is again instructed to reverse direction, turning back to clockwise rotation. At this time, it is apparent that by controlling the direction of the output rotation of the motor 10 in this manner, the load and wear on each flank of the teeth of the gear are substantially balanced, which is an optimal solution for the whole gear and the whole power tool. Especially for efficient operation of strokes and spacesThis control scheme is most reasonable and optimal for power tools where the load and duration of the stroke is uncertain or unbalanced.

Fig. 3 illustrates a flow chart of a method for determining a direction of rotational motion output from the motor 10 of a power tool according to the principles of the present application. The method comprises the following steps:

s1) the electric tool is started, namely the electric tool is about to start a new operation process;

s2) the controller 28 of the control unit 40 judges whether the determination parameter satisfies the respective reversal condition, and when the determination parameter satisfies the respective reversal condition, determines that the direction of the rotational motion output by the motor 10 is reversed with respect to the direction of the rotational motion output by the motor 10 during the last operation of the electric power tool, and otherwise determines that the motor 10 will rotate in the same rotational direction;

s3) actuates the motor 10 to rotate its output shaft 12 in the rotational direction determined in the previous step. Preferably, in this step 3), the controller 28 instructs the counter 46 and the timer 52 to be cleared.

The method only uses the effective operation stroke experienced by the electric tool as a basis to judge whether the rotary motion output by the motor needs to be reversed or not in the next operation process of the electric tool, and the reverse control method excludes the idle stroke executed by the electric tool, so that the control is more accurate, the abrasion in the electric tool is minimum, and the service life is longest. This is particularly true for power tools that include a gear train, where the exact reversal of the motor is controlled based on the number of times or the time that the power tool or its gear train is subjected to a payload so that the wear on both meshing surfaces of each gear tooth is substantially equal, and balanced to the greatest extent, thereby extending the useful life of the gear train, as well as the entire power tool.

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

Claims

1. A control unit (40) for determining a direction of a rotational movement output from a motor (10) of a power tool, the motor (10) being a bi-directional rotating motor and an actuator (30) of the power tool alternately performing an active operating 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 with the current sensor (42) and the motor (10), the controller (48) being configured for:

in the event that it is determined that the determination parameter satisfies the respective reversal condition, instructing the motor (10) to start causing the direction of the rotational motion output by it to be reversed with respect to the direction of the rotational motion output by the motor (10) during the last operation of the power tool, otherwise, in the event that it is determined that the determination parameter does not satisfy the respective reversal condition, instructing the motor (10) to start causing the direction of the rotational motion output by it to be the same as the direction of the rotational motion output by the motor (10) during the last operation of the power tool,

wherein the decision parameter and the corresponding reversal condition are related to an effective operating stroke performed by the power tool since a last reversal of the rotary motion output by the motor (10).

2. The control unit (40) according to claim 1, wherein the decision parameter and the corresponding reversal condition are both based on the measured current (I) of the electric machine (10) and on a specific current (I) related to the active operating stroke₀) And both.

3. The control unit (40) according to claim 2, wherein the decision parameter is that the current (I) of the motor (10) measured since the last reversal of the rotational movement output by the motor (10) exceeds the specific current (I)₀) The respective reversal condition being that the accumulated time reaches or exceeds the electricityThe specificity critical duration of the mover (T0).

4. A control unit (40) according to claim 2, wherein the decision parameter is the number of active current cycles that the current (I) of the motor (10) has passed since the last reversal of the rotational movement output by the motor (10), the respective reversal condition being that the number equals or exceeds a specific number of current cycles (N) of the power tool₀)。

5. The control unit (40) according to claim 2, wherein the decision parameter is the number of active current cycles that the current (I) of the motor (10) has passed since the last reversal of the rotational movement output by the motor (10) and the current (I) of the motor (10) measured since the last reversal of the rotational movement output by the motor (10) exceeds the specific current (I)₀) The respective reversal condition being that the accumulated time reaches or exceeds the specific critical duration (T0) of the power tool or the number equals or exceeds a specific number of current cycles (N) of the power tool₀)。

6. The control unit (40) according to claim 3 or 5, wherein the control unit (40) comprises a timer (52) for accumulating the accumulated time, wherein the controller (48) instructs the counter (52) to be cleared when it is determined that the accumulated time reaches or exceeds the specificity threshold duration (T0) and thus instructs the motor (10) to output a reverse rotational movement.

7. The control unit (40) according to claim 4 or 5, wherein the active current period is a self current (I) from below the specific current (I)₀) Across the specific current (I)₀) To above the specific current (I)₀) To a current (I) from above the specific current (I)₀) Across the specific current (I)₀) To below the specific current (I)₀) Time knot ofAnd (4) bundling.

8. The control unit (40) according to claim 7, wherein the control unit (40) comprises a counter (46) for counting the number of times, wherein the controller (48) determines that the number of times equals or exceeds the specific number of current cycles (N)₀) And thus the counter (46) is instructed to clear when the motor (10) is instructed to output a reverse rotational motion.

9. The control unit (40) according to any one of claims 1-8, wherein the control unit (40) further comprises a memory (42) for storing at least the specific current (I) of the power tool₀) The number of the specific current cycles (N)₀) And the critical duration of specificity (T)₀) The controller (48) is communicatively connected with the memory (44).

10. A power tool, comprising:

a 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

the control unit (40) according to any one of claims 1-9.

11. The power tool according to claim 10, wherein the actuator (30) performs a reciprocating linear motion or a reciprocating oscillating motion, or outputs a unidirectional rotary motion.

12. The power tool according to claim 10 or 11, wherein the transmission mechanism (20) is a gear transmission mechanism, e.g. the transmission mechanism (20) comprises a gear wheel which meshes with a pinion provided on the output shaft (12).

13. The power tool of any one of claims 10-12, wherein the power tool is a hand-held power tool.

14. The power tool according to any one of claims 10-13, wherein the power tool is a pick, a reciprocating saw, or an output reciprocating power tool.

15. Method for determining the direction of a rotational movement output from a motor (10) of a power tool with a control unit (40) according to any of claims 1-9, the method comprising, when the power tool starts a new operational process:

judging whether the judgment parameters meet corresponding reverse conditions;

a step of actuating the motor (10), wherein the direction of the rotational motion output by the motor (10) is reversed with respect to the direction of the rotational motion output by the motor (10) during the last operation of the electric tool when the above-mentioned judgment result determines that the judgment parameter satisfies the corresponding reversal condition, otherwise, the direction of the rotational motion output by the motor (10) is made the same as the direction of the rotational motion output by the motor (10) during the last operation of the electric tool in the case where the above-mentioned judgment result determines that the judgment parameter does not satisfy the corresponding reversal condition,

wherein the decision parameter and the corresponding reversal condition are related to an effective operating stroke performed by the power tool since the last reversal of the rotary motion output by the motor (10), irrespective of an idle stroke performed by the power tool.

16. The method of claim 15, further comprising determining the specific current (I) of the power tool based on the operating conditions of the power tool, load data to be experienced, failure conditions of the power tool, historical test data₀) Specific number of current cycles (N)₀) And specificity critical duration (T)₀) The step (2).