CN111245312A - Electric tool and control method of electric tool - Google Patents

Abstract

The invention discloses an electric tool, comprising a working part for realizing the function of the electric tool, a tool main body for installing the working part, a brushless motor for driving the working part, a driving circuit for driving the rotor of the brushless motor to run, and a driving circuit Including a switching element; a controller for controlling the switching element in a drive circuit; a braking signal generating device for generating a braking signal to cause the power tool to enter a braking process, the controller is configured to, during the braking process, according to The position of the rotor, control the switching elements of the driving circuit so that the current direction of the winding is opposite to the current direction during the driving process. The invention also discloses the control method of the above electric tool. The power tool of the present invention can realize quick braking more quickly.

Description

Electric tool and control method of electric tool

technical field

The invention relates to the field of electric tools, in particular to an electric tool capable of rapid braking and a control method thereof.

Background technique

At present, power tools are widely used in households, gardens and other fields, and brushless motors are more and more applied to power tools due to their large torque and high power to meet users' needs for energy-efficient power tools. .

In particular, electric garden tools, such as chainsaws, are garden tools that use a power device to drive the staggered L-shaped blades on the saw chain to move laterally to cut wood or branches. When the chain saw is in normal operation, when the sawtooth is stuck in the object being sawed, the continuous rotation of the motor will cause the chain saw to swing upward, causing the chain saw to reverse in the direction of the user's face, that is, recoil, causing an accident. Emergency braking to stop the chain from moving forward in a dangerous situation.

SUMMARY OF THE INVENTION

In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a safe electric tool capable of rapid braking.

In order to achieve above-mentioned goal, the present invention adopts following technical scheme:

An electric tool includes: a working part, including a guide plate and a saw chain; a tool body, the front end of the tool body is configured to be able to install the working part; a brushless motor, which outputs power to drive the working part to work; the The brushless motor includes a rotor, a motor shaft and windings, and the motor shaft is driven by the rotor of the brushless motor; a driving circuit is electrically connected to the brushless motor for driving the rotor of the brushless motor to rotate; The drive circuit includes a switch element; a controller is electrically connected to the drive circuit for controlling the switch element in the drive circuit; a braking signal generating device is associated and connected to the controller for generating a braking signal. a driving signal to make the power tool enter a braking process; the controller is configured to control the switching element of the driving circuit to make the current direction of the windings according to the position of the rotor during the braking process Opposite to the direction of current flow during driving.

Further, the controller is configured to control the switching element of the driving circuit to short-circuit the winding after the braking process reaches a prescribed time or after the rotor speed of the brushless motor drops to a prescribed value.

Further, the braking signal generating device includes a braking control member and a signal switch, the signal switch is triggered by the braking control member, and the signal switch is electrically connected to the controller for providing braking control. The controller is further configured to, when the state of the signal switch changes, according to the position of the rotor, control the switching element of the driving circuit so that the winding is in each sector The current direction of the zone is opposite to the current direction during the driving process.

Further, the braking signal generating device includes a motion detection device, the motion detection device is associated and connected with the tool body or the working part, and is connected with the controller for detecting the tool body or the working part. The movement of the working member in at least one direction varies; the controller is further configured to, when the amount of movement variation of the tool body or the working member in at least one direction exceeds a preset threshold value, according to the The position of the rotor, the switching element of the driving circuit is controlled so that the current direction of the winding in each sector is opposite to the current direction during the driving process.

An electric tool, comprising: a working part for realizing the function of the electric tool; a tool body, the front end of the tool body is configured to be able to install the working part; a brushless motor, which outputs power to drive the working part Action; the brushless motor includes a rotor, a motor shaft and a winding, the motor shaft is driven by the rotor of the brushless motor; a drive circuit is electrically connected to the brushless motor for driving the brushless motor the rotor rotates; the drive circuit includes a switch element; a controller is electrically connected to the drive circuit for controlling the switch element in the drive circuit; a braking signal generating device is associated and connected to the controller, for generating a braking signal to cause the power tool to enter a braking process; the controller is configured to, during the braking process, control a switching element of the drive circuit to cause the The current direction of the winding is opposite to the current direction during driving.

Further, the controller is configured to control the switching element of the driving circuit to short-circuit the winding after the braking process reaches a predetermined time or after the rotational speed of the rotor of the brushless motor drops to a predetermined value.

Further, the braking signal generating device includes a braking control member and a signal switch, the signal switch is triggered by the braking control member, and the signal switch is electrically connected to the controller for providing braking control. The controller is further configured to, when the state of the signal switch changes, according to the position of the rotor, control the switching element of the driving circuit so that the winding is in each sector The current direction of the zone is opposite to the current direction during the driving process.

Further, the braking signal generating device includes a motion detection device, the motion detection device is associated and connected with the tool body or the working part, and is connected with the controller for detecting the tool body or the working part. The movement of the working member in at least one direction varies; the controller is further configured to, when the amount of movement variation of the tool body or the working member in at least one direction exceeds a preset threshold value, according to the The position of the rotor, the switching element of the driving circuit is controlled so that the current direction of the winding in each sector is opposite to the current direction during the driving process.

A control method for the above-mentioned electric power tool includes: acquiring a braking signal of the braking signal generating device; when receiving the braking signal, causing the electric power tool to enter a braking process; during the braking process , controlling the switching element of the driving circuit according to the position of the rotor so that the current direction of the winding in each sector is opposite to the current direction during the driving process.

Further, after the braking process reaches a predetermined time or after the rotational speed of the rotor of the brushless motor drops to a predetermined value, the switching element of the driving circuit is controlled to short-circuit the winding.

The advantages of the present invention lie in that the braking time is short and the braking time is adjustable, which can meet the situation of emergency braking.

Description of drawings

1 is a perspective view of the overall structure of an electric power tool as an embodiment;

Fig. 2 is a partial cross-sectional view of the power tool shown in Fig. 1;

3 is a circuit diagram of a circuit system as an embodiment;

Fig. 4 is the relationship diagram of the Hall signal, the conduction switch, the conduction winding and the sector where the rotor is located in the driving state of the circuit system shown in Fig. 3;

Fig. 5 is the relationship diagram of the Hall signal, the conduction switch, the conduction winding and the sector where the rotor is located in the braking state of the circuit system of Fig. 3;

6 is a flowchart of a control method of an electric power tool during braking as an embodiment;

7 is a flowchart of a control method of an electric power tool during braking as another embodiment;

Fig. 8 is the schematic diagram of the electric tool shown in Fig. 1 when recoil occurs;

FIG. 9 is a flowchart of a control method of the electric power tool when detecting backlash according to an embodiment.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The power tool 10 of the present invention can be a hand-held power tool or a garden tool, which is not limited herein. The power tool 10 of the present invention includes, but is not limited to, the following: screwdrivers, electric drills, wrenches, angle grinders, etc., sanders, reciprocating saws, circular saws, jigsaws, electric hammers, pruning machines, chainsaws, and the like. As long as these power tools 10 can adopt the essential content of the technical solutions disclosed below, they can fall within the protection scope of the present invention.

The power tool 10 of the present invention includes but is not limited to: a working part for realizing the functions of the power tool; a tool body, the front end of the tool body is configured to be able to install the working part; a brushless motor, which outputs power to drive the working part moves; the brushless motor includes a stator, a rotor, a motor shaft and a winding, the motor shaft is driven by the rotor of the brushless motor; a drive circuit is electrically connected to the brushless motor for driving The rotor of the brushless motor operates; the drive circuit includes a switch element; a controller is electrically connected to the drive circuit for controlling the switch element in the drive circuit; a braking signal generating device is connected to the drive circuit. The controller is associated and connected for generating a braking signal and outputting it to the controller, so that the power tool enters a braking process; the controller is configured to, during the braking process, according to the rotor position, the switching element of the driving circuit is controlled so that the current direction of the winding is opposite to the current direction during the driving process.

As an embodiment, the power tool 10 takes a chain saw as an example. The power tool 10 includes a working part and a main body part, wherein the working part includes a guide plate 151 and a saw chain 152 , the main body part includes a casing, and the front end of the main body part is configured to be able to Install the working part.

1 and 2 , the power tool 10 includes a housing 11 , a front handle 12 and a main handle 13 arranged on the housing 11 , a switch trigger 14 arranged on the main handle 13 , and a working part 15 for implementing specific functions. and the power supply 16 .

The working part 15 of the power tool 10 includes a guide plate 151 and a saw chain 152 . The saw chain 152 surrounds the edge of the guide plate 151 and can be cyclically guided along the guide plate 151 under the drive of the driving mechanism (not shown). housing 11 .

A switch trigger 14 is operably triggered by a user, and the switch trigger 14 is associated with a main switch 18 which is electrically connected in the main circuit of the power tool 10 . When the switch trigger 14 is actuated, the main switch 18 associated with the switch trigger 14 is correspondingly actuated, enabling or disabling the electrical connection of the circuit components across the main switch 18 .

The power tool 10 also includes a power supply 16 for powering the power tool. In some embodiments, the power tool 10 is powered by a DC power source, and more specifically, the power tool 10 is powered by a battery pack, and the power supply device includes a battery pack. In other embodiments, the power tool 10 is powered by an AC power source, and the AC power source can be 120V or 220V AC mains power. The power supply device 16 includes a power conversion circuit, and the AC power source cooperates with some power conversion circuits connected to the AC power. (not shown), the alternating current is converted into electrical energy usable by the power tool 10 by rectifying, filtering, dividing, and reducing the alternating current signal output by the power supply through a hardware circuit. In this embodiment, the power tool 10 is powered by a battery pack, and the voltage output by the battery pack is changed by a specific power supply circuit (eg, a DC-DC conversion chip) to output a power supply voltage suitable for motors, control units, and the like. For the battery pack as a DC power supply, it is necessary to cooperate with the corresponding power supply circuit.

The housing 11 also includes an automatic lubrication system (not shown in the figure). For those of ordinary skill in the art, the specific structures of the front handle 12, the main handle 13, the working part 15, and the lubrication system are all common knowledge, and will not be detailed here. describe.

FIG. 2 is a cross-sectional view of the power tool 10 shown in FIG. 1 with the working part 15 and the battery pack removed. The housing 11 is provided with a brushless motor 17 for driving the movement of the saw chain 152, a main switch 18 controlled by the switch trigger 14, the main switch 18 is used to control the opening and closing of the power tool 10 during normal use, and the circuit board 19, Electronic components, circuit components, and the like are provided on the circuit board 19 .

The power tool 10 further includes a braking signal generating device (not shown), which is associated and connected with the controller 41 for generating a braking signal to output to the controller, so that the power tool enters a braking process. The braking signal generating device may be a device that generates a braking signal based on an action triggered or operated by a user. For example, the braking signal generating device is a combination of a trigger mechanism and a switch, and the trigger mechanism is triggered, so that the switch state associated with the trigger mechanism occurs. Change, so that the electrical parameters of the circuit where the switch is located (for example, current, voltage, etc.) changes, and the change in electrical parameters can determine whether braking is required, thereby generating a braking signal, and the controller controls the power tool according to the braking signal. 10 Braking; the braking signal generating device can also generate a braking signal not based on the trigger action of the user, but based on the internal changes of the power tool or external influences, for example, based on the change of the power tool posture, or based on a certain or multiple electrical signals to generate a braking signal, for example, for chainsaws and other power tools that are prone to recoil, when the power tool recoils, the braking signal generating device generates a braking signal, Or by detecting one or more other electrical parameters (eg, current, voltage, etc.), and after these electrical parameters satisfy preset conditions, a braking signal is generated.

As an embodiment, the braking signal generating device includes a braking control member 20 and a switch 21 , the switch 21 is triggered by the braking control member, and the switch 21 is electrically connected to the controller 41 . , for providing a braking signal to the controller; the controller 41 is further configured to control the switch element of the drive circuit 42 to make the switch 31 change according to the position of the rotor when the state of the switch 31 changes. The current direction of the windings in each sector is opposite to the current direction during driving. In some specific embodiments, the switch is a signal switch.

In some specific implementations, the brake control member 20 is a brake baffle plate, and can rotate relative to the housing 11 around the fulcrum O. It can be understood that the brake control member 20 can also be set according to actual design requirements. In the form of a button, you can press the button when you need to brake. One end of the brake control member 20 is formed with a brake operating portion 201 for the operator to perform a braking operation when encountering a dangerous situation, and the other end is formed with a cantilever arm 202 that can rotate relative to the housing 11 . The brake control member 20 is associated with a switch 21, the cantilever arm 202 is formed with a groove on the part that cooperates with the switch 21, and the brake switch 21 has a switch rocker installed in the groove. The lever 211 and the switch rocker 211 swing with the rotation of the cantilever arm 202 to control the state of the switch 21 . When the controller 41 detects that the state of the switch 21 changes, it controls the power tool 10 to enter the braking process. Of course, the different states of ON and OFF of the switch 21 correspond to different modes of the driving mode and the braking mode. Specifically, the switch 21 has two states, and different states can realize switching between the working mode and the braking mode. When in the first state (for example, the disconnected state), the power tool 10 can be turned on to enter the driving mode, and in the first state In two states (eg, the ON state), the braking mode is on, the braking routine is running, and the power tool 10 is braked. The switch 21 is electrically connected to the controller 41 for providing a braking signal to the controller 41. When the controller 41 receives the braking signal, it enters the braking mode and starts the braking procedure to The driving of the brushless motor 17 is stopped.

A limiting device (not shown), such as a V-shaped leaf spring element, is installed on the housing 11 of the power tool 10 and is matched with the brake control member 20 , and the brake control member 20 has a V-shaped leaf spring element. The cam surface corresponding to the V-shaped structure (not shown in the figure), so that when the power tool 10 is working normally, the cam surface on the brake control member 20 is located on one side of the V-shaped structure of the leaf spring element and is limited, and when the brake is activated When the control member 20 overcomes the elastic force of the leaf spring and compresses it to the other side of the V-shaped structure, it is limited again. achieved by intermeshing elements.

As another embodiment, the braking signal generating device includes a motion detection device 43 ( FIG. 3 ), and the motion detection device 43 is associated and connected with the tool body or the working part of the power tool 10 for detecting the tool body or the working part. The amount of movement and/or the speed of movement of the working part in at least one direction. The output end of the motion detection device 43 is connected to the controller 41, which sends the detected result to the controller 41, when the motion detection device 43 detects the movement of the tool body or the working part in at least one direction When the amount and/or the moving speed exceeds the preset threshold, the braking signal generating device generates a braking signal to the controller 41. After the controller receives the signal, it controls the switching element of the driving circuit 42 to make the brushless motor 17 Stop driving or enter the braking process, see below for details.

The operation of the above-mentioned power tool 10 also needs to rely on electronic components or circuit components provided on the circuit board 19 . 3 , the electronic components or circuit components of the power tool 10 may specifically include the following controller 41 , a drive circuit 42 , a motion detection device 43 , and a position detection device 44 . The above-mentioned controller 41 , the driving circuit 42 , the position detection device 44 , and the brushless motor 17 are all enclosed by the casing 11 . The above-mentioned controller 41 , driving circuit 42 , motion detection device 43 , position detection device 44 , brushless motor 17 , battery pack 16 , etc. are electrically connected to constitute the circuit system of the power tool 10 .

The brushless motor 17 outputs power to drive the working part 15 to work. The brushless motor 17 includes a stator, a rotor 171 , a motor shaft and windings, and the motor shaft is driven by the rotor 171 of the brushless motor 17 . The rotor 171 rotates relative to the stator, and the stator has an iron core and stator windings wound around the stator iron core. In this embodiment, the brushless motor 17 has three-phase windings, which are a first-phase winding A, a second-phase winding B, and a third-phase winding C, respectively.

The driving circuit 42 is electrically connected to the brushless motor 17 for driving the rotor 171 of the brushless motor 17 to rotate, and the driving circuit includes a switching element. The drive circuit 42 is specifically electrically connected to the three-phase windings of the brushless motor 17 to drive the brushless motor 17 to operate. The drive circuit 22 specifically includes a switch circuit, and the switch circuit is used to drive the rotor 171 of the brushless motor 17 to rotate according to the control signal of the controller 41 . The drive circuit 42 shown in FIG. 4 includes switching elements VT1, VT2, VT3, VT4, VT5, and VT6. The switching elements VT1, VT2, VT3, VT4, VT5, and VT6 form a three-phase bridge, wherein VT1, VT3, and VT5 are The upper bridge switch, VT2, VT4, VT6 are the lower bridge switches, the upper bridge switch and the lower bridge switch of each phase bridge circuit are connected to the same winding, for example, the switching element VT1 and the switching element VT4 are connected to the first phase winding A, the switching element The VT3 and the switching element VT6 are connected to the second phase winding B, and the switching element VT5 and the switching element VT2 are connected to the third phase winding C. The switching elements VT1-VT6 can be selected from field effect transistors, IGBT transistors, etc. The gate terminal of each switching element is electrically connected to the driving signal output terminal of the controller 41 respectively, and the drain or source of each switching element is electrically connected to the winding of the brushless motor 17 . The switching elements VT1-VT6 change the on state according to the driving signal output by the controller 41, so as to change the voltage state loaded by the battery pack 16 on the windings of the brushless motor 17, and drive the brushless motor 17 to run.

In order to make the brushless motor 17 rotate, the driving circuit 42 has a plurality of driving states. In one driving state, the stator winding of the motor will generate a magnetic field. The controller 41 is configured to output corresponding driving according to the rotational position of the rotor of the brushless motor 17 . The signal is sent to the drive circuit 42 to make the drive circuit 42 switch the drive state, thereby changing the state of the voltage loaded on the windings of the brushless motor 17 , generating an alternating magnetic field to drive the rotor to rotate, thereby realizing the driving of the brushless motor 17 .

The power tool 10 further includes a position detection device 44 for detecting the position of the rotor of the brushless motor. The position detection device 44 may be sensorless detection or sensor detection.

As an embodiment, the position detection device 44 includes a position sensor. The position sensors are three Hall sensors (not shown), which are arranged along the circumferential direction of the rotor 171 of the brushless motor 17. The rotor detected by the Hall sensors The position information of , is input to the position detection device 44 . The position detection device 44 converts the input position of the rotor through logical processing into rotor position information which can be communicated with the controller 41 and is input to the controller 41 . When the rotor rotates into and out of the preset range, the signal of the Hall sensor changes, and the output signal of the position detection device 44 also changes accordingly.

When the rotor rotates into the preset range, the output signal of the position detection device 44 is defined as 1, and when the rotor rotates out of the preset range, the output signal of the position detection device 44 is defined as 0. Place the three Hall sensors at a physical angle of 120° from each other.

Referring to FIG. 5 , when the rotor rotates, the three Hall sensors will generate a position signal including six signal combinations so that the position detection device 44 outputs a position signal including one of the six signal combinations. Six different signal combinations 100, 110, 010, 011, 001, 101 appear if arranged in the order in which the Hall sensors are placed. In this way, the position detection device 44 can output one of the above-mentioned six position signals, and the position of the rotor can be known according to the position detection signal output by the position detection device 44 . For a brushless motor with three-phase windings, it has six driving states in one power-on cycle corresponding to the output signal generated by the above scheme. Therefore, when the output signal of the position detection device 44 changes, the brushless motor will be A commutation can be performed. Obviously, the brushless motor 17 commutates once every time the rotor rotates through 60°, and the interval from one commutation to the next commutation of the brushless motor 17 is defined as one sector or one beat.

For the convenience of description, the drive state is represented by the connected terminal corresponding to the drive state in the following. For example, if the controller 41 controls the switching elements of the drive circuit 42 to connect the first phase winding A to the power supply positive pole 16a and the second phase winding B to the power supply negative pole 16b, the drive state is denoted by AB, if the controller 42 controls the drive The switching element of the circuit 42 connects the first phase winding A to the negative pole 16b of the power supply and the second phase winding B to the positive pole 16a of the power supply, then the driving state is represented by BA, and the driving method represented in this way is also applicable to the delta connection scheme of the windings . In addition, the switching of the drive state can also be simply referred to as the commutation operation of the brushless motor.

According to the above definition, referring to FIGS. 4 and 5 , when the rotor 171 of the brushless motor 17 rotates, the respective switching elements of the driving circuit 42, the signals of the Hall sensor and the sector position where the rotor is located correspond to the following table 1:

Table 1

In some other embodiments, the position detection device 44 does not include a position sensor, but indirectly obtains the rotor position by performing corresponding calculations on the back EMF signal or the bus current of the motor and/or the terminal voltage of the motor, which will not be repeated here. , those skilled in the art can easily know according to the professional knowledge in the field.

The controller 41 is electrically connected to the driving circuit 42 for outputting a driving signal to control the operation of the driving circuit 42 . In some embodiments, the controller 41 uses a dedicated control chip (eg, MCU, microcontroller unit, Microcontroller Unit). The control chip includes a storage unit for storing the braking program and the driver program. The controller 41 can control the circuit state of the entire machine and realize various electronic functions, such as motor soft start, electronic braking, battery protection to avoid over-temperature, over-current, etc. All switch actions are also performed by the controller. The brushless motor 17 is operated after the analysis of 41 .

For a chain saw with a three-phase motor, the short-circuit braking method is usually used for braking. When braking, the windings of the motor are short-circuited, that is, the controller 41 controls all the upper bridge switching elements or the lower bridge of the driving circuit 42. All the switching elements are turned on, so that the ends of the windings of each phase connected to the neutral point are connected to each other, so that the windings of each phase are short-circuited. In this way, the resistance of the winding itself is used to consume energy. Due to the small resistance of the winding, the energy consumption is very fast, and there is a certain risk that the motor may be burned. And as the speed of the chain saw line gets faster and faster, the time required for short-circuit braking will also become longer. When the electric tool 10 recoils, the short-circuit brake cannot achieve rapid braking, which does not meet the safety in the case of recoil. Require. To this end, the present invention provides an electric tool 10 through which the controller 41 controls the on or off of the switch element of the drive circuit 42 to realize braking, the braking time is short, and the braking time is adjustable.

As an embodiment, the control method of the power tool 10 includes:

obtaining the braking signal of the braking signal generating device;

When receiving the braking signal, make the power tool enter a braking process;

In the braking process, the switching element of the driving circuit is controlled according to the position of the rotor so that the current direction of the winding is opposite to the current direction in the driving process.

Preferably, in the braking process, the switching element of the driving circuit is controlled according to the position of the rotor so that the current direction of each sector of the winding is opposite to the current direction in the driving process, so as to quickly realize the braking process. verb: move.

Specifically, the power tool 10 includes a driving mode and a braking mode. In the drive mode, the controller 41 executes a drive program and controls the switching elements of the drive circuit 42 to operate the rotor of the brushless motor 17 . In the braking mode, the controller 41 executes the braking procedure, and controls the switching elements of the driving circuit 42 to make the brushless motor 17 enter the braking procedure.

As an embodiment, after the braking process reaches a predetermined time, the switching element of the driving circuit is controlled to short-circuit the winding.

As another embodiment, in the braking process, after the rotor speed of the brushless motor drops to a predetermined value, the switching element of the driving circuit is controlled to short-circuit the winding.

In this embodiment, the braking mode includes a first braking process and a second braking process. In the first braking process, the controller 41 controls the switching elements of the driving circuit 42 according to the position of the rotor, so that the current of each sector of each phase winding during braking is opposite to the current direction of the winding during driving, so as to generate The reverse torque of the brushless motor 17 is braked until the preset condition is satisfied, and the controller controls the power tool 10 to switch to the second braking process. In this embodiment, the second braking process brakes the brushless motor 17 in a short-circuit braking manner.

As an embodiment, after the braking process reaches a predetermined time, the switching element of the driving circuit is controlled to short-circuit the winding.

As another embodiment, in the braking process, after the rotor speed of the brushless motor drops to a predetermined value, the switching element of the driving circuit is controlled to short-circuit the winding.

Specifically, referring to FIG. 3 and FIG. 5 , in the first braking process, the Hall sensor detects the position of the rotor in real time. When the rotor rotates to sector 1, the position detection device 44 outputs 010. In the braking mode, this When the rotor turns to sector 2, the position detection device 44 outputs the signal 011, and the switch is switched on at this time. When CA is turned on, correspondingly, the controller 41 controls the switching elements VT4 and VT5 to be turned on, and the other switching elements are turned off, and so on, until the rotor speed drops to the specified value or the first braking process reaches the specified time. The second braking process. During the first braking process, the controller 41 controls the on-off state of the switching element of the driving circuit 42 to realize the motor braking. By changing the on-off switch, the current of the windings during the first braking process and the driving state are changed. The direction of the current is reversed, so that the motor runs in reverse phase sequence. The duration of the braking process can be realized by software. By outputting a certain or changing duty cycle, when the motor speed or rotor speed drops to the preset threshold or the first The braking process reaches the preset time and then switches to the second braking process, so that the braking time can be adjusted, and a shorter braking time can be set, and the braking effect is better.

During the first braking process, the relationship between the rotor sector position, the Hall signal, the on-off switching element, and the on-winding is shown in Table 2 below. The table can be stored in the memory, and the controller 41 can execute the first Braking process:

Table 2

In the second braking process, the controller 41 controls all the upper bridge switching elements VT1, VT2 and VT3 to be turned on or the lower bridge switching elements VT4, VT6 and VT2 are all turned on, so that the three-phase windings are short-circuited, and the brushless motor 17 The inertial rotation will generate an opposite torque, causing the brushless motor 17 to stop quickly.

Due to the short-circuit braking method of the second braking process, all the upper bridge switching elements or the lower bridge switching elements are turned on, all the windings of the motor are short-circuited, and the kinetic energy of the motor is consumed on the windings. If it is small, it will generate a large short-circuit current, and the kinetic energy of the motor is quickly released quickly, so that the motor generates a great braking torque instantaneously, which can achieve the effect of rapid braking. However, due to the small resistance of the winding, the energy consumption is very fast, and there is a certain danger, which may burn the motor.

In the above-mentioned braking method of the first braking process, the braking time can be adjusted, but after the braking process is over, it is impossible to judge when the motor stops rotating. The rotor of the brush motor continues to rotate in the opposite direction, so the first braking process can only last for a short time. In this embodiment, when the rotational speed of the motor drops to a predetermined value or a predetermined time is reached after the braking process is started, the short-circuit braking of the second braking process is switched to stop it. In this embodiment, switching between the above two braking modes can make the motor stop quickly, and the braking process is more safe and reliable.

6 , as an embodiment of the braking process or control method of the power tool 10, the controller 41 controls the power tool braking process as follows:

S60: start the braking process;

When the braking signal generating device sends a braking signal to the controller 41, the controller 41 starts the braking process. Make the power tool 10 start the braking process.

S61: start the first braking process;

In the braking mode, the controller 41 first starts the first braking process, and executes the first braking process;

S62: Obtain the real-time position of the rotor;

The position detection device 44 detects the position of the rotor in real time. As an embodiment, the position of the rotor is detected by a Hall sensor. When the rotor rotates to a preset range that can be used by the Hall sensor, the position sensor is in a signal state. The position sensor switches to another signal state when it is rotated out of the preset range. The signal of the Hall sensor is output to the position detection device 44, and the position detection device 44 converts the input rotor position through logical processing into rotor position information that can communicate with the controller 41 and is input to the controller 41. The controller 41 is based on the Hall sensor. The signal judges the current sector position of the rotor.

S63: control the switching element of the drive circuit according to the rotor position to reverse the current of the winding in each sector;

According to the current sector position of the rotor, the controller 41 controls the drive circuit 42 through the relationship table (Table 2) of the rotor sector position, the Hall signal, and the conduction switch element in the first braking process pre-stored in the memory. The corresponding switching elements of the switch are turned on or off, so that the current of the winding in each sector is reversed to the current when driving, thereby generating a reverse torque that brakes the brushless motor.

S64: Determine whether the start time of the first braking process reaches the specified time, if yes, go to step S85, if not, go to step S83;

The power tool 10 includes a timer. The timer may be built in the controller 41 or externally disposed in the controller 41 , and the timer is used to determine the start time of the first braking process. In some specific implementations, when the controller 41 starts the braking process, it sends a signal to the timer, the timer starts to count, and the controller 41 compares the acquired time of the timer with the preset time to determine the Whether the start-up time of the braking process reaches the specified time, if yes, go to step S84, if not, go to step S83 to continue the braking control.

S65: start the second process;

After judging that the start time of the first braking process reaches a predetermined time, the controller 41 starts the second braking process.

S66: control the switching element of the driving circuit to short-circuit the winding;

The controller 41 controls all the lower bridge switching elements or all the upper bridge switching elements of the driving circuit 42 to be turned on, so that the three-phase windings are short-circuited, and the kinetic energy of the motor is consumed on the windings. Short-circuit current, the kinetic energy of the motor is quickly released quickly, so that the motor generates a great braking torque instantaneously, which can achieve the effect of fast braking.

S67: End the braking process.

7, as another embodiment of the braking process or control method of the power tool 10, the controller 41 controls the braking process of the power tool 10 as follows:

S70: start the braking process;

When the braking signal generating device sends a braking signal to the controller 41, the controller 41 starts the braking process. Make the power tool 10 start the braking process.

S71: start the first braking process;

In the braking mode, the controller 41 first starts the first braking process, and executes the first braking process;

S72: Obtain the real-time position of the rotor;

The position detection device 44 detects the position of the rotor in real time. In this embodiment, the position of the rotor is detected by the Hall sensor. When the rotor rotates to the preset range that can be used by the Hall sensor, the position sensor is in a signal state. The position sensor switches to another signal state when it is rotated out of the preset range. The signal of the Hall sensor is output to the position detection device 44, and the position detection device 44 converts the input rotor position through logical processing into rotor position information that can communicate with the controller 41 and is input to the controller 41. The controller 41 is based on the Hall sensor. The signal judges the current sector position of the rotor.

S73: control the switching element of the drive circuit according to the rotor position to reverse the current of the winding in each sector;

According to the current sector position of the rotor, the controller 41 controls the drive circuit 42 through the relationship table (Table 2) of the rotor sector position, the Hall signal, and the conduction switch element in the first braking process pre-stored in the memory. The corresponding switching elements of the switch are turned on or off, so that the current of the windings in each sector is in the opposite direction to the current during driving, thereby generating a reverse torque that brakes the brushless motor 17 .

S74: Determine whether the motor speed has dropped to a predetermined value, if yes, go to step S75, if not, go to step S73;

The power tool 10 includes a speed detection device for detecting the rotational speed of the rotor or the rotational speed of the motor shaft, and sending the detected result to the controller 41 , and the timer can be built into the controller 41 or externally arranged in the controller 41 , The controller 41 compares the rotation speed detected by the speed detection device with the preset specified value to determine whether the motor rotation speed has dropped to the specified value. motion control.

S75: start the second process;

After it is judged that the motor speed drops to a predetermined value, the controller 41 starts the second braking process.

S76: control all the lower bridge switching elements of the driving circuit to be turned on to short-circuit the windings;

The controller 41 controls all the lower bridge switching elements or the upper bridge switching elements of the driving circuit 42 to be turned on, so that the three-phase windings are short-circuited, and the kinetic energy of the brushless motor 17 is consumed on the windings. With a large short-circuit current, the kinetic energy of the brushless motor 17 is quickly released quickly, so that the brushless motor instantly generates a great braking torque, which can achieve the effect of rapid braking.

S77: End the braking process.

After experiments, taking the chain saw as an example, when the linear speed of the saw chain is 18.973m/s, the braking time of the original short-circuit braking using the braking method of this scheme is 153.4ms, while the braking time of this scheme is 93.4ms, compared with the original braking method, the braking time of this solution is shorter than the braking time of the short-circuit braking method, which meets the safety requirements that the braking time is less than 0.12s, and can effectively avoid the safety caused by the recoil. ACCIDENT.

Referring to FIG. 8, for a chain saw, when the chain saw near the front end attachment of the guide plate 151 is in contact with, for example, a log or a branch, the chain saw may move rapidly upward or backward, which is often referred to as kickback or backlash. kick event. 3, when the chain saw kicks back, the main body or working part of the chain saw will rotate around the Z axis in the XY plane, and the guide plate 151 and the saw chain 152 will move toward the direction of the operator, which may cause the operator to Injuries may even cause serious injury or death to the operator. In order to prevent the occurrence of the recoil event, it is necessary to detect the recoil in time and accurately, and control the 41 to control the power tool 10 to enter the above braking process after the occurrence of the recoil is detected. Achieving quick braking can quickly brake to avoid the occurrence of safety accidents to the greatest extent.

Therefore, as another embodiment, the braking signal generating device of the power tool 10 includes a motion detection device 43 , and the motion detection device 43 is associated and connected with the tool body or the working part of the power tool 10 , and is connected with the controller 41 A connection for detecting the movement amount and/or movement speed of the tool body or the working part in at least one direction. The output end of the motion detection device 43 is connected to the controller 41, which sends the detected result to the controller 41, when the motion detection device 43 detects the movement of the tool body or the working part in at least one direction When the amount and/or the moving speed exceeds the preset threshold, the braking signal generating device generates a braking signal to the controller 41, and the controller controls the switching element of the driving circuit 42 to make the brushless motor 17 after receiving the signal. Stop driving or enter braking process. The above-mentioned braking signal generating device further includes related units such as a comparison unit, an arithmetic unit, and a judgment unit, which are used for comparing, calculating, and judging the detected signals. Of course, the above-mentioned comparison unit, arithmetic unit, judgment unit and other related units of the braking signal generating device can also use the related units of the controller 41 , and the motion detection device 43 sends the detection result to the controller 41 , and the related units in the controller 41 According to the detection result, it is determined whether the detection value exceeds the preset threshold. If the detection value exceeds the preset threshold, it is determined that the electric tool 10 has a backlash, and a signal indicating braking is generated inside the controller 41, so that the controller 41 controls the electric tool 10. Enter the braking process and perform emergency braking to avoid safety accidents. At the same time, the driving circuit 42 is controlled to make the motor enter the braking process.

The motion detection device 43 may specifically include a gyroscope sensor, and more specifically, the gyroscope sensor is a MEMS9 (Micro Electro Mechanical System) multi-axis gyroscope sensor, which is used to detect the tool body or the working part. Angular velocity and/or angular displacement in at least one direction. For example, the angular velocity and/or the angular displacement of the tool body or the working part being rotated about the Z axis is detected. MEMS gyroscope sensors are small and can be easily incorporated into existing circuits, and output voltages that the sensor can scale.

In some embodiments, a gyro sensor can be installed on the tool body of the power tool 10. For a chain saw, when recoil occurs, the front handle is close to the center of rotation. In order to measure a larger angular velocity or movement, the gyro sensor It can be installed at various positions away from the front handle, such as the front end of the guide plate 151 and the main handle 13 . The selection of the installation position of the gyro sensor should ensure that the rotational angular velocity or angular displacement of the tool body of the power tool 10 or the working part 15 can be accurately detected, which is not limited here. In some embodiments, the gyro sensor measures the angular velocity of the movement of the power tool 10, and the angular displacement is obtained by integrating the angular velocity. When the angular velocity and/or angular displacement detected by the gyro sensor exceeds a preset threshold, the controller 41 controls the switching element of the driving circuit 42 to make the brushless motor 17 enter the braking process.

In this embodiment, the controller 41 is configured to control the movement of the tool main body or the main body part or the working part in at least one direction when the movement detection device 43 detects that the movement variation in at least one direction exceeds a preset threshold value. The switching element of the drive circuit 42 causes the brushless motor 17 to enter a braking process.

In this embodiment, the control method of the above-mentioned electric power tool 10 includes the following contents:

acquiring the angular velocity and/or angular displacement of the tool body or the working part in at least one direction;

Determine whether the angular velocity and/or angular position of the tool body or the working part in at least one direction exceeds a preset threshold, and if so, enter the braking process; in the braking process, according to the rotor The position controls the switching elements of the drive circuit 42 to reverse the current flow of the windings.

As an embodiment, when the gyro sensor detects that the value of the rotation angular velocity W of the power tool 10 is greater than or equal to the first preset angular velocity threshold TW1 and less than or equal to the second preset angular velocity threshold TW2, and the rotation angle When the displacement θ is greater than or equal to the preset angular displacement threshold Tθ, the controller 41 controls the switching element of the driving circuit 42 to stop the driving of the brushless motor 17 or enter the braking process.

When the rotational angular velocity W of the electric tool 10 is large, for example, greater than the second preset angular velocity threshold TW2, it is not necessary to judge the angular displacement θ again, and it can be determined that backlash occurs. Therefore, as another embodiment, when the gyro sensor detects that the angular velocity W of the power tool 10 moving is greater than the second preset angular velocity TW2, the controller 41 controls the switching element of the driving circuit 42 to make the brushless The motor 17 stops driving or enters a braking process.

Referring to FIG. 9 , as an embodiment of the recoil detection method or control method of the power tool 10 , the process of the controller 41 for controlling the power tool 10 is as follows:

S90: start the power tool;

S91: Obtain the rotational angular velocity W collected by the gyro sensor;

S92: Integrate the rotational angular velocity W to obtain the angular displacement θ;

S93: Compare and judge whether the rotational angular velocity W is less than the first preset angular velocity threshold TW1, if so, go to step S91, if not, go to step S94;

S94: Compare and judge whether the rotational angular velocity W is less than the second preset angular velocity threshold TW2, if so, go to step S95, if not, go to step S96;

S95: Compare and judge whether the angular displacement θ is less than the preset angular displacement Tθ, if so, go to step S91; otherwise, go to step S96;

S96: Start the braking process.

In the above embodiment, the motion detection device 43 of the gyroscope sensor is used to detect the angular velocity or angular displacement of the tool body or the working part of the power tool 10 to detect whether the power tool has recoil, which avoids the traditional recoil detection that uses an accelerometer to measure acceleration. Since the method is sensitive to vibration, the implementation of the recoil detection in this embodiment and the later data processing are simpler, the vibration interference is small, and the recoil detection is more accurate.

After detecting the occurrence of backlash, the power tool 10 enters the above braking process, and after the first braking process and the second braking process, emergency braking is implemented to avoid the occurrence of safety accidents. The electric tool 10 of the present invention can realize motor braking more quickly, and the braking time is adjustable, which can meet the occasions with high braking time requirements.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above-mentioned embodiments do not limit the present invention in any form, and all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (10)

1. A power tool, comprising: Working parts, including guide bars and saw chains; a tool body, the front end of the tool body is configured to be capable of mounting the working part; a brushless motor, the output power drives the working part to work; the brushless motor includes a rotor, a motor shaft and a winding, and the motor shaft is driven by the rotor of the brushless motor; a drive circuit, electrically connected to the brushless motor, for driving the rotor of the brushless motor to rotate; the drive circuit includes a switch element; a controller, electrically connected to the drive circuit, for controlling the switch element in the drive circuit; a braking signal generating device, associated and connected with the controller, for generating a braking signal to make the power tool enter a braking process; The controller is configured to control the switching elements of the drive circuit to cause the current direction of the windings to be opposite to the current direction during the drive process according to the position of the rotor during the braking process. 2 . The power tool according to claim 1 , wherein the controller is configured to control the brushless motor after a braking process reaches a predetermined time or after the rotor speed of the brushless motor drops to a predetermined value. 3 . The switching element of the drive circuit shorts the windings. 3. The power tool according to claim 1, wherein the braking signal generating device comprises a braking control member and a switch, the switch is triggered by the braking control member, and the switch is connected with the braking control member. the controller is electrically connected for providing a braking signal to the controller; the controller is further configured to control the switch of the drive circuit according to the position of the rotor when the state of the switch changes The element causes the current to flow in the windings in each sector in the opposite direction of the current during driving. 4 . The power tool according to claim 1 , wherein the braking signal generating device comprises a motion detecting device, the motion detecting device is associated and connected with the tool body or the working part, and is connected with the the controller is connected for detecting a change in motion of the tool body or the working part in at least one direction; the controller is further configured to detect movement of the tool body or the working part in at least one direction When the movement variation of the winding exceeds a preset threshold value, according to the position of the rotor, the switching element of the driving circuit is controlled so that the current direction of the winding in each sector is opposite to the current direction during the driving process. 5. A power tool, comprising: a working part for realizing the function of the power tool; a tool body, the front end of the tool body is configured to be capable of mounting the working part; a brushless motor, the output power drives the action of the working part; the brushless motor includes a rotor, a motor shaft and a winding, and the motor shaft is driven by the rotor of the brushless motor; a drive circuit, electrically connected to the brushless motor, for driving the rotor of the brushless motor to rotate; the drive circuit includes a switch element; a controller, electrically connected to the drive circuit, for controlling the switch element in the drive circuit; a braking signal generating device, associated and connected with the controller, for generating a braking signal to make the power tool enter a braking process; The controller is configured to control the switching elements of the drive circuit to cause the current direction of the windings to be opposite to the current direction during the drive process according to the position of the rotor during the braking process. 6 . The power tool according to claim 5 , wherein the controller is configured to control the braking process after the braking process reaches a predetermined time or after the rotor speed of the brushless motor drops to a predetermined value. 7 . The switching element of the drive circuit shorts the windings. 7. The power tool according to claim 5, wherein the braking signal generating device comprises a braking control member and a switch, the switch is triggered by the braking control member, and the switch is connected with the braking control member. the controller is electrically connected for providing a braking signal to the controller; the controller is further configured to control the switch of the drive circuit according to the position of the rotor when the state of the switch changes The element causes the current to flow in the windings in each sector in the opposite direction of the current during driving. 8. The power tool according to claim 5, wherein the braking signal generating device comprises a motion detecting device, the motion detecting device is associated and connected with the tool body or the working part, and is connected with the the controller is connected for detecting a change in motion of the tool body or the working part in at least one direction; the controller is further configured to detect a movement change of the tool body or the working part in at least one direction When the movement variation of the winding exceeds a preset threshold value, according to the position of the rotor, the switching element of the driving circuit is controlled so that the current direction of the winding in each sector is opposite to the current direction during the driving process. 9. A control method for an electric power tool as claimed in any one of claims 1 to 8, comprising: obtaining the braking signal of the braking signal generating device; When receiving the braking signal, make the power tool enter a braking process; In the braking process, the switching element of the driving circuit is controlled according to the position of the rotor so that the current direction of the winding in each sector is opposite to the current direction in the driving process. 10 . The control method of an electric power tool according to claim 9 , wherein the driving circuit is controlled after the braking process reaches a predetermined time or after the rotor speed of the brushless motor drops to a predetermined value. 11 . The switching element shorts the windings.

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