Power tool and control method thereof

Abstract

The application discloses an electric tool and a control method thereof. The electric tool comprises a motor, an output shaft, a commutation detection unit electrically connected with the motor and used for detecting commutation information of each commutation of the motor, and a controller receiving the commutation information of the motor. When the commutation information does not match a preset commutation condition, the controller adjusts a control signal based on the commutation information so as to maintain a target rotating speed of the motor. Thus, the existing electric tool can be prevented from being difficult to complete a target work task due to small and unstable speed at low speed, and the electric tool can maintain the target rotating speed of the motor by receiving the commutation information of the motor and adjusting the control signal based on the commutation information when the commutation information does not match the preset commutation condition, so that the electric tool can complete the work task and low-speed constant-speed control of the electric tool can be realized.

Description

Technical Field

[0001] This invention relates to the field of power tool control technology, and more particularly to a power tool and its control method. Background Technology

[0002] With the development of power tools, intelligent control technology for power tools is being used more and more widely. For example, controllers are used to adjust the power supply voltage of the motor to achieve characteristics such as rapid start-up and smooth braking of power tools.

[0003] However, existing power tools, due to their low speed and low torque, are prone to stalling when performing impact actions at low speeds, making it difficult to complete tasks under special working conditions. These special working conditions include, for example, when impacting soft materials such as wood or other materials, or when the impact drill bit is small, requiring the tool to perform impact actions at a lower speed. Summary of the Invention

[0004] This invention provides an electric tool and its control method to achieve constant speed control of the electric tool.

[0005] In a first aspect, embodiments of the present invention provide an electric tool, the electric tool comprising:

[0006] Electric motor;

[0007] The output shaft is electrically connected to the motor.

[0008] A commutation detection unit, electrically connected to the motor, is used to detect and obtain commutation information for each commutation of the motor.

[0009] The controller is electrically connected to at least the motor and the commutation detection unit;

[0010] The controller is configured to:

[0011] Receive the commutation information of the motor;

[0012] When the commutation information does not match the preset commutation conditions, the control signal is adjusted based on the commutation information to maintain the target speed of the motor.

[0013] Optionally, adjusting the control signal based on the commutation information to maintain the target speed of the motor when the commutation information does not match the preset commutation conditions includes:

[0014] When the motor fails to complete the commutation in the current phase, the commutation information of the current phase is updated according to the commutation information of the previous phase, and the control signal is adjusted according to the updated commutation information of the current phase so that the motor speed is maintained at the target speed.

[0015] Optionally, adjusting the control signal based on the updated commutation information of the current commutation to maintain the target speed of the motor includes:

[0016] The motor speed is calculated based on the updated commutation information of the current commutation, and when the motor speed does not meet the target speed, the control signal is adjusted and output to maintain the motor speed at the target speed.

[0017] Optionally, the commutation information for each commutation of the motor includes at least: the commutation start point, the commutation end point, and the time required to complete each commutation.

[0018] Optionally, calculating the motor speed based on the updated commutation information of the current commutation includes:

[0019] The commutation duration of the current commutation is updated by taking the commutation end point of the previous commutation as the commutation start point of the current commutation, and the rotational speed of the motor is calculated based on the updated commutation duration of the current commutation.

[0020] Optionally, the failure of the motor to complete commutation in the current phase includes: the commutation time of the current phase is longer than the commutation time of the previous phase, or no commutation is performed within the current commutation time.

[0021] Optionally, the target rotational speed is greater than or equal to 100 RPM and less than or equal to 300 RPM.

[0022] Optionally, the commutation detection unit is a Hall sensor.

[0023] Secondly, embodiments of the present invention also provide a control method for an electric tool, the control method of which is executed by the electric tool, the electric tool comprising: a motor; an output shaft electrically connected to the motor; a commutation detection unit electrically connected to the motor for detecting and obtaining commutation information of each commutation of the motor; and a controller electrically connected to at least the motor and the commutation detection unit.

[0024] The control method includes:

[0025] Receive the commutation information of the motor;

[0026] When the commutation information does not match the preset commutation conditions, the control signal is adjusted based on the commutation information to maintain the target speed of the motor.

[0027] Optionally, the commutation information for each commutation of the motor includes at least: the commutation start point, the commutation end point, and the time required to complete each commutation.

[0028] This invention provides an electric tool and its control method. This electric tool solves the problem that existing electric tools struggle to complete tasks at low speeds due to low speed and low torque. During operation, the electric tool receives commutation information from the motor and adjusts the control signal based on this information when it does not match preset commutation conditions. This maintains the motor speed at the target speed, preventing the electric tool from failing to complete tasks due to low or unstable motor output speed. This invention achieves constant speed control at low speeds. Attached Figure Description

[0029] Figure 1 This is a circuit structure block diagram of an electric tool according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of an impact tool according to an embodiment of the present invention;

[0031] Figure 3 This is a flowchart of a power tool control method according to an embodiment of the present invention. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0033] Figure 1 This is a circuit structure block diagram of a power tool provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of an impact tool provided in an embodiment of the present invention. It should be noted that, except for... Figure 2 The control method described in this application can be used for any other impact power tool that uses a sensorless brushless motor or a sensored brushless motor and is capable of low-speed control.

[0034] refer to Figure 1 The power tool includes: a motor 10; an output shaft 20 electrically connected to the motor 10; a commutation detection unit 30 electrically connected to the motor 10 for detecting and obtaining commutation information of the motor 10 each time it commutates; and a controller 40 electrically connected to at least the motor 10 and the commutation detection unit 30. The controller 40 is configured to: receive commutation information of the motor 10; and adjust the control signal based on the commutation information when the commutation information does not match the preset commutation conditions, so that the speed of the motor 10 maintains the target speed.

[0035] The motor 10 can be a brushless DC motor, which performs multiple commutations within one electrical cycle. The output shaft 20 is connected to the motor 10 and rotates under its drive, thereby rotating the drill bit or other tool attachments mounted on the output shaft 20. The commutation detection unit 30 is electrically connected to both the motor 10 and the controller 40. It detects and obtains the commutation information of each commutation of the motor 10 and sends this information to the controller 40. The controller 40 receives the commutation information of each commutation of the motor 10 and adjusts the control signal based on the commutation information when it does not match the preset commutation conditions, so that the rotational speed of the motor 10 maintains the target speed. It is understood that the control information output by the controller 40 can control the switching elements in the drive circuit (not shown) of the tool to change the drive state, thereby driving the motor 10 to change its rotational state.

[0036] It should be noted that the preset commutation conditions can be: whether the motor completes the commutation action each time, whether the motor completes the commutation when the current commutation time reaches the previous commutation time, etc. The specific settings can be made according to the actual situation, and no specific limitations are made here.

[0037] In the technical solution of this embodiment, the power tool can be an impact tool, such as an impact wrench. For example, combined with... Figure 1 and Figure 2 Taking an impact wrench as an example, impact wrenches are typically used for impact work at low speeds, such as impacting very soft wooden boards or aligning small drill bits. However, impact wrenches are difficult to operate at low speeds and maintain a constant low-speed output, making it difficult to perform operations such as impacting wooden boards and aligning drill bits smoothly. To address this, the power tool provided by this invention enables the following: when a user needs to operate the power tool at a constant low speed for operations such as impacting wooden boards or aligning drill bits, the commutation detection unit 30 detects and obtains the commutation information of the motor 10 at each commutation and sends it to the controller 40. The controller 40 receives the commutation information of the motor 10 and compares it with preset commutation conditions. When a mismatch occurs, the controller adjusts the control signal based on the commutation information to maintain the speed of the motor 10 at the target speed, thereby ensuring that the output shaft 20 can also continuously and stably output the target speed. This allows the user to continuously impact wooden boards and align drill bits, among other operations.

[0038] For example, Figure 2 A schematic diagram of an impact tool is shown, for reference. Figure 2The impact tool includes a housing 50, a trigger 60, a grip 70, a battery pack 80, a motor, an output shaft 20, a commutation detection unit, and a controller. The housing 50 has the grip 70 formed for the user to hold; however, the grip 70 can also be a separate component. The housing 50 constitutes the main body of the impact tool, housing the motor, controller, transmission components, and other electronic components such as circuit boards. The output shaft 20 can be used to mount functional components, such as drill bits.

[0039] Optionally, the target speed can be greater than or equal to 100 RPM and less than or equal to 300 RPM, for example, 100 RPM, 150 RPM, 200 RPM, 250 RPM, 300 RPM, etc.

[0040] The technical solution of this embodiment provides an electric tool, which includes: a motor; an output shaft electrically connected to the motor; a commutation detection unit electrically connected to the motor for detecting and obtaining commutation information of the motor at each commutation; and a controller electrically connected to at least the motor and the commutation detection unit. The controller is configured to: receive the commutation information of the motor; and adjust the control signal based on the commutation information when the commutation information does not match the preset commutation conditions, so as to maintain the motor speed at a target speed. Therefore, this electric tool can solve the problem that existing electric tools are unable to complete target work tasks at low speeds due to low speed and low torque. During operation, the electric tool receives the commutation information of the motor and adjusts the control signal based on the commutation information when it does not match the preset commutation conditions, so as to maintain the motor speed at a target speed. This avoids situations where the electric tool cannot complete the work task due to low or unstable motor output speed, and achieves low-speed constant speed control of the electric tool.

[0041] Optionally, when the commutation information does not match the preset commutation conditions, the control signal is adjusted based on the commutation information to maintain the motor speed at the target speed, including:

[0042] If the motor fails to complete commutation in the current phase, the commutation information of the current phase is updated based on the commutation information of the previous phase, and the control signal is adjusted based on the updated commutation information of the current phase to keep the motor speed at the target speed.

[0043] The preset commutation condition can be set to whether the motor has completed commutation each time it commutates. Specifically, assuming the motor is currently in a commutation state, if the commutation detection unit detects that the motor has not completed commutation in this current commutation, the controller updates the commutation information of the current commutation based on the commutation information of the motor in the previous commutation, and uses the updated commutation information as the commutation information for the current commutation state to adjust the output of the control signal, so that the motor can maintain the target speed.

[0044] Optionally, the control signal is adjusted based on the updated commutation information for the current commutation to maintain the motor speed at the target speed, including:

[0045] The motor speed is calculated based on the updated commutation information for the current commutation, and the output control signal is adjusted to maintain the target speed when the motor speed does not meet the target speed.

[0046] The motor's speed is related to its commutation information. Therefore, to ensure the motor outputs a stable target speed, the controller calculates the motor speed based on the updated commutation information and compares the calculated speed with the target speed. If the target speed is not met, the controller adjusts the output control signal, for example, by increasing the duty cycle, to maintain the motor speed at the target speed. This allows the output shaft to output the target speed constantly, enabling users to impact very soft wood boards or align small drill bits.

[0047] The control signal can be a control signal with a certain duty cycle, used to drive the motor 10 to operate at a constant target speed. The control signal can be adjusted by increasing or decreasing the duty cycle. For example, taking a target speed of 100 RPM as an example, assuming the motor speed calculated based on the updated commutation information is less than 100 RPM, the controller outputs an adjustment signal by increasing the PWM duty cycle to maintain the motor speed at 100 RPM. It should be noted that this adjustment has a certain lag, but it will not affect the power tool's ability to carry a load at low speeds. For example, when the motor speed drops to 80 RPM, the power tool can still operate under load while adjusting the PWM duty cycle according to the updated commutation information to increase the target speed to 100 RPM.

[0048] Optionally, the commutation information for each commutation of the motor includes at least: the commutation start point, the commutation end point, and the time required to complete each commutation.

[0049] During operation, a motor performs multiple commutations according to a certain cycle, for example, six commutations within one cycle. Normally, the commutation time for each commutation within the same cycle is the same. However, due to factors such as motor stalling, the commutation time of a current commutation may be longer than the previous commutation, or no commutation may occur within the current commutation time. This results in variations in the commutation time for each commutation within the same cycle. Since the commutation time is related to the motor's speed, it is necessary to monitor the commutation time, commutation start point, and commutation end point for each commutation.

[0050] Optionally, the motor speed is calculated based on the updated commutation information for the current commutation, including:

[0051] The commutation duration of the current commutation is updated by taking the commutation end point of the previous commutation as the commutation start point of the current commutation, and the speed of the motor is calculated based on the updated commutation duration of the current commutation.

[0052] Specifically, when the commutation information of the motor in the current commutation does not meet the preset commutation conditions, the commutation end point of the previous commutation is used as the commutation start point of the current commutation for updating. Based on the actual commutation end point of the current commutation and the updated commutation start point of the current commutation, the commutation duration of the current commutation is calculated and updated. The motor speed is then recalculated using the updated commutation duration, and the calculated speed is compared with the target speed. If the target speed is not met, the output control signal is adjusted, for example, by increasing the duty cycle, so that the motor speed maintains the target speed. This allows the output shaft to output the target speed at a constant speed, enabling users to impact very soft wooden boards, align small drill bits, etc.

[0053] Optionally, the motor fails to complete commutation in the current commutation, including: the commutation time of the current commutation is longer than the commutation time of the previous commutation, or no commutation is performed within the current commutation time.

[0054] The motor's speed is related to the commutation time of each phase change. For example, taking a target speed of 100 RPM as an example, when the motor is not stalled, the speed is calculated based on the commutation time. However, when the motor stalls, the commutation time increases due to the stall, but if the speed is still calculated based on the previous commutation time, the calculated speed will be greater than the timed speed. Furthermore, the motor speed is already less than the target speed of 100 RPM, but because the calculated speed is still 100 RPM, the controller will not automatically increase the PWM duty cycle, and therefore the actual motor speed cannot reach the target speed. If the speed continues to drop, the power tool will be unable to achieve low-speed (e.g., 100 RPM) impact, thus failing to achieve low-speed load carrying. Therefore, when the commutation time of the current commutation is longer than the commutation time of the previous commutation, or when no commutation occurs within the current commutation time, the commutation end point of the previous commutation is used as the commutation start point of the current commutation for updating. Based on the actual commutation end point of the current commutation and the updated commutation start point of the current commutation, the commutation time of the current commutation is calculated and updated. The motor speed is then recalculated using the updated commutation time, and the calculated speed is compared with the target speed. If the target speed is not met, the output control signal is adjusted, for example, by increasing the duty cycle, so that the motor speed maintains the target speed. This allows the output shaft to output the target speed at a constant speed, enabling users to impact very soft wooden boards, align small drill bits, etc.

[0055] Optionally, the commutation detection unit is a Hall sensor.

[0056] Among them, the Hall sensor is used to detect the commutation start point, commutation end point, and the duration required for each commutation of the motor.

[0057] Figure 3 This is a flowchart of a control method for an electric tool provided in an embodiment of the present invention. This embodiment can be applied to the implementation process of the control method for an electric tool. The method can be executed by the electric tool provided in the embodiment of the present invention. The electric tool includes: a motor; an output shaft electrically connected to the motor; a commutation detection unit electrically connected to the motor for detecting and obtaining commutation information of each commutation of the motor; and a controller electrically connected to at least the motor and the commutation detection unit.

[0058] refer to Figure 3 The control method for this power tool includes the following steps:

[0059] Step 110: Receive the commutation information of the motor.

[0060] Specifically, the power tool includes a motor, an output shaft, a commutation detection unit, and a controller. The commutation detection unit is electrically connected to both the motor and the controller. Through the commutation detection unit, such as a Hall sensor, the commutation information of each motor commutation can be detected and sent to the controller.

[0061] Step 120: When the commutation information does not match the preset commutation conditions, adjust the control signal based on the commutation information to keep the motor speed at the target speed.

[0062] Specifically, the controller receives the commutation information of the motor and compares it with the preset commutation conditions. When the commutation information does not match the preset commutation conditions, the controller adjusts the control signal based on the commutation information to maintain the motor speed at the target speed. This allows the output shaft to output the target speed at a constant speed, enabling users to impact very soft wooden boards and align small drill bits.

[0063] This embodiment provides a power tool control method. The power tool control method is executed by the power tool, which includes: a motor; an output shaft electrically connected to the motor; a commutation detection unit electrically connected to the motor for detecting and obtaining commutation information for each commutation of the motor; and a controller electrically connected to at least the motor and the commutation detection unit. The power tool control method includes: receiving commutation information from the motor; and adjusting a control signal based on the commutation information when the commutation information does not match preset commutation conditions, so that the motor speed maintains a target speed. This power tool control method solves the problem that existing power tools struggle to complete target tasks at low speeds due to low speed and low torque. By receiving commutation information from the motor during operation and adjusting the control signal based on the commutation information when it does not match preset commutation conditions, the power tool can maintain a target speed, thus avoiding situations where the power tool cannot complete tasks due to low or unstable motor output speed. This achieves low-speed constant speed control of the power tool.

[0064] Optionally, the commutation information for each commutation of the motor includes at least: the commutation start point, the commutation end point, and the time required to complete each commutation.

[0065] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A power tool, characterized in that, include: Electric motor; The output shaft is connected to the motor; A commutation detection unit, electrically connected to the motor, is used to detect and obtain commutation information for each commutation of the motor. The controller is electrically connected to at least the motor and the commutation detection unit; The controller is configured to: Receive the commutation information of the motor; When the commutation information does not match the preset commutation conditions, the control signal is adjusted based on the commutation information to keep the motor speed at the target speed. When the commutation information does not match the preset commutation conditions, adjusting the control signal based on the commutation information to maintain the motor speed at the target speed includes: When the motor fails to complete commutation in the current phase, the commutation information of the current phase is updated according to the commutation information of the previous phase, and the control signal is adjusted according to the updated commutation information of the current phase so that the motor speed is maintained at the target speed. The step of adjusting the control signal based on the updated commutation information of the current commutation to maintain the target speed of the motor includes: The motor speed is calculated based on the updated commutation information of the current commutation, and when the motor speed does not meet the target speed, the control signal is adjusted and output to maintain the motor speed at the target speed, thereby achieving constant speed control of the power tool.

2. The power tool according to claim 1, characterized in that, The commutation information for each commutation of the motor includes at least: the commutation start point, the commutation end point, and the time required to complete each commutation.

3. The power tool according to claim 2, characterized in that, The step of calculating the motor speed based on the updated commutation information for the current commutation includes: The commutation duration of the current commutation is updated by taking the commutation end point of the previous commutation as the commutation start point of the current commutation, and the rotational speed of the motor is calculated based on the updated commutation duration of the current commutation.

4. The power tool according to claim 2, characterized in that, The failure of the motor to complete commutation in the current phase includes: the commutation time of the current phase is longer than the commutation time of the previous phase, or no commutation is performed within the current commutation time.

5. The power tool according to claim 1, characterized in that, The target rotational speed is greater than or equal to 100 RPM and less than or equal to 300 RPM.

6. The power tool according to claim 1, characterized in that, The commutation detection unit is a Hall sensor.

7. A control method for an electric tool, characterized in that, Performed by a power tool, the power tool comprising: a motor; an output shaft connected to the motor; a commutation detection unit electrically connected to the motor for detecting and obtaining commutation information for each commutation of the motor; and a controller electrically connected to at least the motor and the commutation detection unit. The control method includes: Receive the commutation information of the motor; When the commutation information does not match the preset commutation conditions, the control signal is adjusted based on the commutation information to keep the motor speed at the target speed. When the commutation information does not match the preset commutation conditions, adjusting the control signal based on the commutation information to maintain the motor speed at the target speed includes: When the motor fails to complete commutation in the current phase, the commutation information of the current phase is updated according to the commutation information of the previous phase, and the control signal is adjusted according to the updated commutation information of the current phase so that the motor speed is maintained at the target speed. The step of adjusting the control signal based on the updated commutation information of the current commutation to maintain the target speed of the motor includes: The motor speed is calculated based on the updated commutation information of the current commutation, and when the motor speed does not meet the target speed, the control signal is adjusted and output to maintain the motor speed at the target speed, thereby achieving constant speed control of the power tool.

8. The control method for power tools according to claim 7, characterized in that, The commutation information for each commutation of the motor includes at least: the commutation start point, the commutation end point, and the time required to complete each commutation.

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