Electric tool and control method thereof

Abstract

The invention provides an electric tool and a control method thereof, and when a driving current is greater than a preset current value, a control circuit starts timing of a temperature protection timing value, and obtains a heat accumulation value. In the timing process, the control circuit updates the heat accumulated value according to the obtained driving current. And when the temperature protection timing value reaches the preset time length or the heat accumulation value reaches the heat threshold value, it shows that the temperature of the motor is too high, and the control circuit controls the motor to stop running. Therefore, the motor can be protected in time when the motor is overheated. And the control circuit determines whether the temperature of the motor is too high according to the driving current, so that the situation that the control circuit cannot respond to overheat of the motor in time for temperature protection due to the fact that the heat dissipation performance of the control circuit and the heat dissipation performance of the motor are different, and then the motor is damaged can be prevented, and effective temperature protection is achieved for the electric tool.

Description

Technical Field

[0001] The present application relates to the technical field of the electric tool industry, and in particular to an electric tool and a control method thereof. Background Art

[0002] Electric tools generally have a temperature protection function, which controls the electric tool to stop in time when the temperature is high to protect it. In existing electric tools, the temperature in the controller is detected by the thermistor in the controller to achieve temperature protection. However, when the heat dissipation performance of the controller is better than the heat dissipation performance of the motor, when the operating temperature of the motor exceeds the safe range, the controller has not triggered the temperature protection, which will cause damage to the motor. Summary of the invention

[0003] In view of this, the present application provides an electric tool and a control method thereof, which can effectively perform temperature protection.

[0004] The first aspect of the present application provides a control method for an electric tool, the electric tool includes a motor, and the control method includes: obtaining a driving current of the motor; wherein the driving current is used to drive the motor to operate; when the driving current is greater than a preset current value, obtaining a temperature protection timing value and a heat accumulation value; wherein the preset current value corresponds to the temperature protection threshold of the motor; starting timing with the temperature protection timing value; updating the heat accumulation value according to the driving current; when the temperature protection timing value reaches a preset time length, or the heat accumulation value reaches the heat threshold, controlling the motor to stop operating.

[0005] In one embodiment, updating the heat accumulation value according to the driving current includes: integrating the driving current and the duration that the driving current is greater than a preset current value to obtain a current heat value; and updating the heat accumulation value according to the current heat value.

[0006] In one embodiment, the preset current value includes at least two, and the at least two preset current values ​​correspond one-to-one to at least two temperature protection thresholds, at least two preset time lengths, at least two temperature protection timing values ​​and at least two heat accumulation values; the preset current value and the temperature protection threshold are positively correlated, and the preset current value and the preset time length are negatively correlated.

[0007] In one embodiment, when the temperature protection timing value reaches a preset time length, or the heat accumulation value reaches a heat threshold, the motor is controlled to stop running, including: when any temperature protection timing value reaches the corresponding preset time length, or any heat accumulation value reaches the heat threshold, the motor is controlled to stop running.

[0008] In one embodiment, at least two preset current values ​​include a first current value, a second current value and a third current value, the first current value corresponds to a first duration, a first timing value and a first accumulated value, the second current value corresponds to a second duration, a second timing value and a second accumulated value, and the second current value corresponds to a third duration, a third timing value and a third accumulated value; wherein the first current value is less than the second current value, the second current value is less than the third current value, the first duration is greater than the second duration, and the second duration is greater than the third duration; when the driving current is greater than the preset current value, obtaining the temperature protection timing value and the heat accumulated value includes: when the driving current is greater than the first current value When the driving current reaches a certain value, a first timing value and a first accumulated value are obtained; when the driving current is greater than the second current value, a second timing value and a second accumulated value are obtained; when the driving current is greater than the third current value, a third timing value and a third accumulated value are obtained; when the temperature protection timing value reaches a preset time, or the heat accumulated value reaches a heat threshold, the motor is controlled to stop running, including: when the first timing value reaches a first time, or the second timing value reaches a second time, or the third timing value reaches a third time, or the first accumulated value reaches a heat threshold, or the second accumulated value reaches a heat threshold, or the third accumulated value reaches a heat threshold, the motor is controlled to stop running.

[0009] In one embodiment, at least two preset current values ​​are respectively in different multiples of the rated current of the motor, and each preset current value is greater than or equal to the rated current; the thermal threshold is determined according to the multiple of the thermal upper limit value of the motor, and the thermal threshold is greater than the thermal upper limit value.

[0010] In one embodiment, the control method also includes: when the driving current is less than a preset current value, the corresponding temperature protection timing value has not reached a preset time length, and the corresponding heat accumulation value has not reached a heat threshold, the corresponding temperature protection timing value and the corresponding heat accumulation value are cleared.

[0011] In one embodiment, the control method further includes: when a power-on instruction is received, clearing the temperature protection timing value and the heat accumulation value.

[0012] The second aspect of the present application provides an electric tool, which includes a motor drive circuit, a motor, a current detection circuit and a control circuit, wherein the input end of the motor drive circuit is used to connect to a drive power supply, and the output end of the motor drive circuit is connected to the motor; the current detection circuit is connected to the input end of the motor drive circuit, and the control circuit is connected to the motor drive circuit and the current detection circuit; wherein the motor drive circuit is used to drive the motor to operate; the current detection circuit is used to detect the drive current provided by the drive power supply to the motor drive circuit, and send the drive current to the control circuit; the control circuit is used to: obtain the drive current; when the drive current is greater than a preset current value, obtain a temperature protection timing value and a heat accumulation value; wherein the preset current value corresponds to the temperature protection threshold of the motor; start timing with the temperature protection timing value; update the heat accumulation value according to the drive current; when the temperature protection timing value reaches a preset duration, or the heat accumulation value reaches the heat threshold, control the motor to stop running.

[0013] In one embodiment, the electric tool also includes a control switch, which is connected between the motor drive circuit and the drive power supply, and the control circuit is connected to the control switch; the control circuit is used to output a disconnect signal to the control switch when the temperature protection timing value reaches a preset time or the heat accumulation value reaches a heat threshold; the control switch is used to disconnect the connection between the motor drive circuit and the drive power supply according to the disconnect signal to stop the motor from running.

[0014] In the electric tool and control method thereof of the embodiment of the present application, when the driving current is greater than the preset current value, the control circuit starts timing the temperature protection timing value and obtains the heat accumulation value. During the timing process, the control circuit updates the heat accumulation value according to the obtained driving current. When the temperature protection timing value reaches the preset duration, or the heat accumulation value reaches the heat threshold, it means that the temperature of the motor is too high, and the control circuit controls the motor to stop running. In this way, the motor can be protected in time when the motor is overheated. Moreover, the control circuit determines whether the motor temperature is too high based on the driving current, which can prevent the control circuit from being unable to respond to the motor overheating for temperature protection in time due to the different heat dissipation performance of the control circuit and the motor, thereby causing the motor to be damaged, thereby achieving effective temperature protection for the electric tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic block diagram of the electric tool provided in an embodiment of the present application.

[0016] Figure 2 It is a schematic block diagram of an electric tool provided in another embodiment of the present application.

[0017] Figure 3 It is a schematic diagram of the circuit structure of the electric tool provided in an embodiment of the present application.

[0018] Figure 4It is a flow chart of the control method of the electric tool provided in the embodiment of the present application.

[0019] Figure 5 yes Figure 4 Detailed flowchart of step S400 in FIG.

[0020] Figure 6 yes Figure 4 Detailed flowchart of step S200 in FIG.

[0021] Figure 7 It is a schematic diagram of the timing process of the temperature protection timing values ​​corresponding to each temperature protection level provided in the embodiment of the present application.

[0022] Figure 8 It is a flowchart of a control method provided by a specific example of the present application.

[0023] Main component symbols Power tools 100

[0024] Motor drive circuit 110

[0025] The first switch Q1

[0026] The second switch tube Q2

[0027] The third switch tube Q3

[0028] The fourth switch tube Q4

[0029] The fifth switch tube Q5

[0030] The sixth switch tube Q6

[0031] Motor 120

[0032] Current detection circuit 130

[0033] Detection resistor R1

[0034] Voltage acquisition unit 131

[0035] Control circuit 140

[0036] Control switch 150 DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application. In the absence of conflict, the following different embodiments and features in the embodiments can be combined with each other.

[0038] It should be noted that when a device is referred to as being “connected to” another device, it may be directly connected to the other device or may be indirectly connected (with an intervening device).

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0040] In order to prevent power tools from being damaged due to overheating, temperature protection is required for power tools. At present, the temperature in the controller is generally detected by the thermistor in the controller of the power tool to achieve temperature protection. However, if the heat dissipation performance of the controller is better than that of the motor, when the operating temperature of the motor exceeds the safe range, the temperature in the controller will be lower than the operating temperature of the motor due to the better heat dissipation performance of the controller, so that the controller does not trigger the temperature protection, and the motor is damaged.

[0041] To this end, an embodiment of the present application provides an electric tool and a control method thereof, so as to effectively perform temperature protection on the motor.

[0042] See also Figure 1 , Figure 1 FIG. 1 is a schematic block diagram of an electric tool 100 provided in an embodiment of the present application. In the embodiment of the present application, the electric tool 100 may include, for example, a lawn mower, an electric drill, an electric saw, and the like.

[0043] The electric tool 100 includes a motor drive circuit 110, a motor 120, a current detection circuit 130 and a control circuit 140. The input end of the motor drive circuit 110 is used to connect to a drive power supply, and the output end of the motor drive circuit 110 is connected to the motor 120; the current detection circuit 130 is connected to the input end of the motor drive circuit 110, and the control circuit 140 is connected to the motor drive circuit 110 and the current detection circuit 130. The motor drive circuit 110 is used to drive the motor 120 to operate. The current detection circuit 130 is used to detect the drive current provided by the drive power supply to the motor drive circuit 110, and send the drive current to the control circuit 140. The drive current is used to drive the motor 120 to operate.

[0044] The control circuit 140 can control the motor drive circuit 110 to drive the operation of the motor 120. It can be understood that the control circuit 140 can also control the motor drive circuit 110 according to the drive current detected by the current detection circuit 130, thereby controlling the operation state of the motor 120. For example, the control circuit 140 can perform PID (Proportional Integral and Derivative Regulating) control on the motor drive circuit 110 according to the drive current to adjust the drive current to the target current.

[0045] It can be understood that the motor drive circuit 110, the current detection circuit 130 and the control circuit 140 can be integrated to form a controller of the power tool 100, and the controller may include a housing and a circuit board. The motor drive circuit 110, the current detection circuit 130 and the control circuit 140 are integrated on the circuit board, and the circuit board is arranged in the housing.

[0046] In the embodiment of the present application, the control circuit 140 can also be used to obtain the driving current. When the driving current is greater than the preset current value, the control circuit 140 obtains the temperature protection timing value and the heat accumulation value of the motor 120. The control circuit 140 starts timing with the obtained temperature protection timing value and updates the heat accumulation value according to the driving current. When the temperature protection timing value reaches the preset duration, or the heat accumulation value reaches the heat threshold, the control circuit 140 controls the motor 120 to stop running.

[0047] The operating temperature of the motor 120 is directly related to its driving current. The temperature rise formula of the motor 120 is: ΔT = (P*R th ) / (K*M), where ΔT is the temperature rise of the motor 120, that is, the difference between the temperature of the motor 120 in the heating state and the temperature of the motor 120 in the cooling state (ambient temperature), P is the operating power of the motor 120, and R th is the thermal resistance of the motor 120, K is the heat capacity of the motor 120, M is the mass of the motor 120, R th, K, and M are all fixed values, P=U*I, where U is the driving voltage of the motor 120, and I is the driving current of the motor 120. The driving voltage of the motor 120 is a stable value, and the factor affecting the temperature rise of the motor 120 is the driving current. According to the temperature rise formula, the greater the driving current, the greater the temperature rise of the motor 120, that is, the higher the temperature of the motor 120. Based on this, a preset current value corresponding to the temperature protection threshold of the motor 120 can be set. When the driving current of the control circuit 140 is greater than the preset current value, it means that the temperature of the motor 120 is greater than the temperature protection threshold. At this time, the temperature protection timing value starts to be timed. When the temperature protection timing value reaches the preset duration, the control circuit 140 controls the motor 120 to stop running to prevent the motor 120 from being damaged by excessive temperature. Among them, by triggering the timing of the temperature protection timing value when the driving current is greater than the preset current value, and then controlling the motor 120 to run when the temperature protection timing value reaches the preset duration, it can prevent the impact current generated when the motor 120 is running from triggering the temperature protection, thereby improving the stability of the operation of the motor 120.

[0048] In addition, the temperature formula of the motor 120 is T=Q / A, and Q=∫Idt, where T is the temperature of the motor 120, Q is the heat of the motor 120, and A is the heat dissipation coefficient of the motor 120. According to the above formula, the heat of the motor 120 is obtained by integrating the driving current I over time t. Based on this, the control circuit 140 can calculate the heat accumulation value of the motor 120 according to the driving current of the motor 120 when the driving current is greater than the preset current value. When the heat accumulation value reaches the heat threshold, it means that the temperature of the motor 120 is too high, and the control circuit 140 controls the motor 120 to stop running to prevent the motor 120 from being damaged by excessive temperature. Among them, the heat accumulation value refers to: from the initial sampling moment to the current sampling moment, the value obtained by adding the heat calculated according to the driving current obtained at each sampling moment.

[0049] In the embodiment of the present application, when the driving current is greater than the preset current value, the control circuit 140 starts the timing of the temperature protection timing value and obtains the heat accumulation value. During the timing process, the control circuit 140 simultaneously updates the heat accumulation value according to the obtained driving current. When the temperature protection timing value reaches the preset duration, or the heat accumulation value reaches the heat threshold, it indicates that the temperature of the motor 120 is too high, and the control circuit 140 controls the motor 120 to stop running. In this way, the motor 120 can be protected in time when the motor 120 is overheated. Moreover, the control circuit 140 determines whether the temperature of the motor 120 is too high based on the driving current, which can prevent the control circuit 140 from being unable to respond to the overheating of the motor 120 for temperature protection in time due to the different heat dissipation performance of the control circuit 140 and the motor 120, thereby causing the motor 120 to be damaged, and realizing effective temperature protection for the power tool 100.

[0050] The control circuit 140 can be a control chip including a central processing unit (CPU), other general processors, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices.

[0051] like Figure 2 As shown, in some embodiments, the electric tool 100 may further include a control switch 150, the control switch 150 is connected between the motor drive circuit 110 and the drive power supply (not shown), and the control circuit 140 is connected to the control switch 150. When the electric tool 100 needs to operate, the control circuit 140 can turn on the control switch 150 so that the drive power supply can provide a drive current to the motor drive circuit 110. When the electric tool 100 stops operating, the control circuit 140 turns off the control switch 150 to disconnect the drive power supply and the motor drive circuit 110, so as to ensure that the electric tool 100 stops operating.

[0052] In this embodiment, the control circuit 140 can also disconnect the control switch 150 to stop the motor 120 when the temperature protection timing value reaches a preset time or the heat accumulation value reaches a heat threshold.

[0053] Specifically, Figure 3As shown, the motor driving circuit 110 may include a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, and a sixth switch tube Q6. The first ends of the first switch tube Q1, the third switch tube Q3, and the fifth switch tube Q5 are all connected to the positive electrode of the driving power supply through the control switch 150, the second end of the first switch tube Q1 is connected to the second end of the second switch tube Q2 and the first phase line of the motor 120, the second end of the third switch tube Q3 is connected to the first end of the fourth switch tube Q4 and the second phase line of the motor 120, the second end of the fifth switch tube Q5 is connected to the first end of the sixth switch tube Q6 and the third phase line of the motor 120, and the second ends of the second switch tube Q2, the fourth switch tube Q4, and the sixth switch tube Q6 are all connected to the negative electrode of the driving power supply. The control ends of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5 and the sixth switch tube Q6 are respectively connected to the control circuit 140. The control circuit 140 can respectively control the on and off of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5 and the sixth switch tube Q6 to control the operation of the motor 120.

[0054] The control circuit 140 can send a driving signal to each switch tube, so that each switch tube can be turned on or off under the driving of the driving signal. The driving signal is a pulse width modulation (PWM) signal.

[0055] In the embodiment of the present application, the current detection circuit 130 may include a detection resistor R1 and a voltage acquisition unit 131, the detection resistor R1 may be connected between the negative electrode of the driving power supply and the second end of the second switch tube Q2, and the voltage acquisition unit 131 is connected to both ends of the detection resistor R1 to obtain the voltage across the detection resistor R1. The voltage acquisition unit 131 may send the detected voltage to the control circuit 140, and then the control circuit 140 calculates the driving current based on the obtained voltage and the resistance value of the detection resistor R1. Alternatively, the voltage acquisition unit 131 may calculate the driving current based on the detected voltage and the resistance value of the detection resistor R1, and then send the driving current to the control circuit 140.

[0056] Of course, the current detection circuit 130 of the embodiment of the present application is not limited thereto. For example, the current detection circuit 130 can also be implemented by any one of a Hall element or a current transformer.

[0057] In the embodiment of the present application, the control circuit 140 needs to drive the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5 and the sixth switch tube Q6 to be alternately turned on and off to achieve the driving of the motor 120. Therefore, when the temperature protection timing value reaches the preset time length, or the heat accumulation value reaches the heat threshold, the control circuit 140 can also stop driving the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5 and the sixth switch tube Q6 to be alternately turned on and off, that is, stop sending driving signals to the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5 and the sixth switch tube Q6 to stop the operation of the motor 120.

[0058] See also Figure 4 , Figure 4 The flowchart of the control method of the electric tool provided in the embodiment of the present application is shown. The control method is applied to the electric tool 100, and in at least one embodiment, the control method can be executed by the control circuit 140 mentioned above.

[0059] like Figure 4 As shown, the control method includes:

[0060] S100, obtaining the driving current of the motor.

[0061] The control circuit 140 obtains the driving current of the motor 120 through the current detection circuit 130 .

[0062] S200: When the driving current is greater than a preset current value, a temperature protection timing value and a heat accumulation value are obtained.

[0063] When the driving current is greater than the preset current value, the temperature protection of the motor 120 is triggered, and the control circuit 140 obtains the temperature protection timing value and the heat accumulation value. Among them, the temperature protection timing value is realized by pre-defined timing parameters and related software programs. The temperature protection timing value is the specific value of the timing parameter, and the timing process is realized by executing the timing-related software program. In the embodiment of the present application, when the driving current is greater than the preset current value, that is, when the temperature protection is triggered, the corresponding timing program of the temperature protection is entered, thereby generating a temperature protection timing value. The obtained temperature protection timing value is based on the value generated by executing the corresponding timing program after the temperature protection is triggered last time. The temperature protection timing value can be 0 or other values, which shall be subject to the actual value obtained.

[0064] The heat accumulation value is also obtained through pre-defined heat parameters and corresponding software programs. The heat accumulation value is the specific value of the heat parameter, and the accumulation of the heat accumulation value is achieved by executing the corresponding software program. It can be understood that when the temperature protection is triggered, the heat accumulation value obtained is based on the value generated by executing the corresponding heat accumulation program after the temperature protection is triggered last time. The heat accumulation value can be 0 or other values, whichever is the actual number obtained.

[0065] S300, start timing with the temperature protection timing value.

[0066] In the embodiment of the present application, the control circuit 140 starts the forward timing with the currently obtained temperature protection timing value, that is, the timing is performed in a timing manner in which the temperature protection timing value is gradually accumulated. In this way, the forward timing starts from the timing value when the temperature protection is triggered, and the new temperature protection timing value will be greater than the initial temperature protection timing value. For example, if the temperature protection timing value obtained is 5S, the temperature protection timing value after starting the timing 10S is 15S.

[0067] S400: Update the heat accumulation value according to the driving current.

[0068] The control circuit 140 starts to accumulate with the currently acquired heat accumulation value, that is, firstly calculates the current heat value of the motor 120 according to the driving current, and then adds the acquired heat accumulation value to the current heat value to obtain a new heat accumulation value.

[0069] S500: When the temperature protection timing value reaches a preset time, or the heat accumulation value reaches a heat threshold, the motor is controlled to stop running.

[0070] When the temperature protection timing value reaches the preset time or the heat accumulation value reaches the heat threshold, it means that the temperature of the motor 120 is greater than the temperature protection threshold, and the control circuit 140 controls the motor 120 to stop running, so as to protect the motor 120 in time when the motor 120 is overheated. In addition, the control circuit 140 determines whether the temperature of the motor 120 is too high based on the driving current, which can prevent the control circuit 140 from being unable to respond to the overheating of the motor 120 in time for temperature protection due to the different heat dissipation performance of the control circuit 140 and the motor 120, thereby causing the motor 120 to be damaged, and realize effective temperature protection for the power tool 100.

[0071] It can be understood that when the temperature protection timing value does not reach the preset time length and the heat accumulation value does not reach the heat threshold, step S100 to step S500 are re-executed.

[0072] See also Figure 5 , Figure 5 Shows Figure 4 The detailed flow chart of step S400 in FIG. Figure 5As shown, step S400 may include:

[0073] S410, integrating the driving current and the duration for which the driving current is greater than the preset current value to obtain a current heat value.

[0074] The control circuit 140 can calculate the current heat value according to the heat formula Q=∫Idt, wherein the time parameter of the integration is determined according to the duration of the driving current being greater than the preset current value, that is, the temperature protection timing value obtained after the temperature protection is triggered. In this way, the control circuit 140 can calculate the current heat value according to the driving current and the temperature protection timing value using the aforementioned heat formula.

[0075] S420: Update the calorie accumulation value according to the current calorie value.

[0076] The control circuit 140 may add the current calorie value to the acquired calorie accumulated value to obtain an updated calorie accumulated value.

[0077] The greater the driving current of the motor 120, the more heat the motor 120 generates, which in turn leads to a higher temperature of the motor 120. The higher the temperature of the motor 120, the greater the damage to the motor 120. The higher the temperature of the motor 120, the shorter the time for temperature protection of the motor 120, which can reduce the damage to the motor 120.

[0078] To this end, in some embodiments, the preset current value may include at least two, and the at least two preset current values ​​correspond to at least two temperature protection thresholds, at least two preset durations, at least two temperature protection timing values, and at least two heat accumulation values, respectively. The preset current value and the temperature protection threshold are positively correlated, and the preset current value and the preset duration are negatively correlated. In other words, the larger the preset current value, the larger the corresponding temperature protection threshold, and the smaller the corresponding preset duration. In this way, protection of the motor 120 at different temperature levels can be achieved.

[0079] Further, at least two preset current values ​​are different multiples of the rated current of the motor 120, and each preset current value is greater than or equal to the rated current. The heat threshold is determined according to the multiple of the heat upper limit value of the motor 120, and the heat threshold is greater than the heat upper limit value.

[0080] The rated current of the motor 120 refers to the maximum current at which the motor 120 can run continuously for a long time under rated working conditions. That is, when the driving current is less than or equal to the rated current of the motor 120, the motor 120 can run continuously for a long time without its temperature being too high to damage the motor 120. Therefore, the preset current value can be set according to the rated current of the motor 120, for example, one preset current value is the rated current, another preset current value is twice the rated current, and so on.

[0081] The upper limit of the heat of the motor 120 depends on the maximum allowable operating temperature of the motor 120, and the upper limit of the heat is determined according to various performance parameters of the motor 120. The heat threshold is slightly larger than the upper limit of the heat, and when the accumulated heat value is larger than the heat threshold, the motor 120 will definitely overheat, so the control circuit 140 controls the motor 120 to stop running to prevent damage to the motor 120.

[0082] In some embodiments, the control method may further include: when the driving current is less than a preset current value, the corresponding temperature protection timing value has not reached a preset time length, and the corresponding heat accumulation value has not reached a heat threshold, the corresponding temperature protection timing value and the corresponding heat accumulation value are cleared.

[0083] If after the temperature protection is triggered, the control circuit 140 is in the process of timing the temperature protection timing value and updating the heat accumulation value, and the temperature protection timing value has not reached the preset time length and the corresponding heat accumulation value has not reached the heat threshold, the driving current obtained by the control circuit 140 is less than the preset current value, then the control circuit 140 will clear the corresponding temperature protection timing value and the corresponding heat accumulation value. In this way, it can be prevented that the temperature protection is triggered when the motor 120 generates fluctuations in the driving current when it is turned on, and the temperature protection timing value continues to count and the heat accumulation value continues to update, causing the motor 120 to turn on and then shut down, making the power tool 100 unable to be used normally.

[0084] In some other embodiments, the control method may further include: when a power-on instruction is received, clearing the temperature protection timing value and the heat accumulation value.

[0085] Among them, the power-on instruction can be generated by user operation. For example, the power tool 100 can be provided with a power-on button electrically connected to the control circuit 140. When the user presses the power-on button, a power-on instruction is generated to the control circuit 140. For another example, the power tool 100 can also be provided with a remote controller connected to the remote controller. The user operates the remote controller to generate a power-on instruction and transmits it to the control circuit 140 of the power tool 100. When the control circuit 140 receives the power-on instruction, the control circuit 140 clears the temperature protection timing value and the heat accumulation value. In this way, if the power tool 100 is in a state of stopping due to triggering temperature protection during the previous operation, and the user operates the power tool 100 again to start the power tool 100, if the motor 120 triggers the temperature protection again, the control circuit 140 can restart the timing and heat update with the cleared temperature protection timing value and heat accumulation value, so as to prevent the temperature protection timing value that triggers the temperature protection again from reaching the preset time or the heat accumulation value reaching the heat threshold in the initial stage, and quickly controlling the motor 120 to stop running. The embodiment of the present application clears the temperature protection timing value and the heat accumulation value when receiving the power-on command, thereby ensuring that the timing for triggering the temperature protection of the power tool 100 after power-on can reach the actual preset duration, or the heat accumulation value can reach the actual heat threshold, and then controls the motor 120 to stop running, thereby improving the accuracy of the temperature protection of the power tool 100.

[0086] In some embodiments, step S500 may include: when any temperature protection timing value reaches a corresponding preset time length, or any heat accumulation value reaches a heat threshold, controlling the motor 120 to stop running.

[0087] In this way, the control circuit 140 can promptly control the motor 120 to stop running when any temperature protection timing value reaches the corresponding preset time length, or when any heat accumulation value reaches the heat threshold.

[0088] Specifically, at least two preset current values ​​include a first current value, a second current value, and a third current value, the first current value corresponds to a first duration, a first timing value, and a first cumulative value, the second current value corresponds to a second duration, a second timing value, and a second cumulative value, and the second current value corresponds to a third duration, a third timing value, and a third cumulative value. Among them, the first current value is less than the second current value, the second current value is less than the third current value, the first duration is greater than the second duration, and the second duration is greater than the third duration.

[0089] In this embodiment, the first current value, the second current value, and the third current value correspond to the first temperature threshold, the second temperature threshold, and the third temperature threshold, respectively, that is, the motor 120 is set with three temperature protection levels, the first current value and the first temperature threshold correspond to the first protection level, the second current value and the second temperature threshold correspond to the second protection level, and the third current value and the third temperature threshold correspond to the third protection level. The first current value, the second current value, and the third current value can be set according to the rated current of the motor 120, for example, the first current value is In, the second current value is 1.5*In, and the third current value is 2*In, where In is the rated current of the motor 120.

[0090] like Figure 6 As shown, step S200 may include:

[0091] S210: When the driving current is greater than the first current value, obtain a first timing value and a first accumulated value.

[0092] When the driving current is greater than the first current value, the first protection level is triggered, and the control circuit 140 correspondingly obtains the first timing value and the first accumulated value, starts timing with the first timing value, and updates the first accumulated value according to the driving current.

[0093] S220: When the driving current is greater than the second current value, obtain a second timing value and a second accumulated value.

[0094] When the driving current is greater than the second current value, the second protection level is triggered, and the control circuit 140 correspondingly obtains the second timing value and the second accumulated value, starts timing with the second timing value, and updates the second accumulated value according to the driving current.

[0095] In some embodiments, when the driving current is greater than the second current value, the driving current must be greater than the first current value, and the first protection level can be triggered at the same time. The control circuit 140 simultaneously times the first timing value and the second timing value, and updates the first accumulated value and the second accumulated value according to the driving current. Since the first duration is greater than the second duration, if the motor 120 triggers the first protection level and the second protection level at the same time, when the second timing value reaches the second duration, the first timing value has not yet reached the first duration, and the control circuit 140 controls the motor 120 to stop running.

[0096] If the motor 120 first triggers the first protection level and then triggers the second protection level, that is, the driving current gradually increases, the control circuit 140 will first start timing the first timing value, and update the first accumulated value according to the driving current. When the second protection level is triggered later, the control circuit 140 starts timing the second timing value again, and updates the second accumulated value according to the driving current. At this time, it is possible that the first timing value reaches the first duration first and the second timing value reaches the second duration later, or it is possible that the second timing value reaches the second duration first and the first timing value reaches the first duration later, or it is possible that when the first timing value reaches the first duration, the second timing value reaches the second duration at the same time. Therefore, the control circuit 140 can control the motor 120 to stop running when the first timing value reaches the first duration, or the second timing value reaches the second duration, or the first accumulated value or the second accumulated value reaches the heat threshold.

[0097] S230: When the driving current is greater than the third current value, obtain a third timing value and a third accumulated value.

[0098] When the driving current is greater than the third current value, the third protection level is triggered, and the control circuit 140 correspondingly obtains the third timing value and the third accumulated value, starts timing with the third timing value, and updates the third accumulated value according to the driving current.

[0099] In some embodiments, when the driving current is greater than the third current value, the driving current must be greater than the first current value and the second current value. At this time, the first protection level and the second protection level can also be triggered at the same time. The control circuit 140 simultaneously times the first timing value, the second timing value and the third timing value, and updates the first accumulated value, the second accumulated value and the third accumulated value according to the driving current.

[0100] If the motor 120 first triggers the first protection level, then the second protection level, and finally the third protection level, that is, the driving current gradually increases, the control circuit 140 will first start timing the first timing value, and update the first accumulated value according to the driving current. When the second protection level is triggered later, the control circuit 140 starts timing the second timing value again, and updates the second accumulated value according to the driving current. When the third protection level is triggered later, the control circuit 140 starts timing the third timing value again, and updates the third accumulated value according to the driving current. At this time, it is possible that the first timing value reaches the first duration first, the second timing value reaches the second duration later, and the third timing value reaches the third duration later; it is also possible that the second timing value reaches the second duration first, the first timing value reaches the first duration later, and the third timing value reaches the third duration later; it is also possible that when the first timing value reaches the first duration, the second timing value reaches the second duration at the same time, and the third timing value reaches the third duration at the same time; it is also possible that the third timing value reaches the third duration first, the second timing value reaches the second duration later, and the first timing value reaches the first duration later. Therefore, the control circuit 140 can control the motor 120 to stop running when the first timing value reaches the first duration, or the second timing value reaches the second duration, or the third timing value reaches the third duration, or the first cumulative value, the second cumulative value, or the third cumulative value reaches the heat threshold.

[0101] As shown above, step S500 may include: when the first timing value reaches the first duration, or the second timing value reaches the second duration, or the third timing value reaches the third duration, or the first accumulated value reaches the heat threshold, or the second accumulated value reaches the heat threshold, or the third accumulated value reaches the heat threshold, controlling the motor 120 to stop running.

[0102] It can be understood that when the control circuit 140 controls the motor 120 to stop running, the driving current quickly drops to zero, and the first timing value, the second timing value, the third timing value, the first accumulated value, the second accumulated value and the third accumulated value are all cleared.

[0103] For a better understanding, the following Figure 7 The timing process of the temperature protection timing value in different situations of the embodiment of the present application is explained (the figure does not show the updating process of the heat accumulation value). Figure 7 In the example, only the case where the control circuit 140 controls the motor 120 to stop running when the temperature protection timing value reaches the preset time is considered.

[0104] like Figure 7As shown, the motor 120 triggers the first protection level at time T1, that is, the driving current is greater than the first current value, and the control circuit 140 obtains the first timing value and the first accumulated value, and starts timing the first timing value. At time T2, the first timing value reaches the first duration, the control circuit 140 controls the motor 120 to stop running, and the first timing value is reset.

[0105] At time T3, the motor 120 triggers the first protection level and the second protection level at the same time, that is, the driving current is greater than the second current value, and the control circuit 140 obtains the first timing value, the second timing value, the first cumulative value, and the second cumulative value, and starts timing the first timing value and the second timing value. At time T4, the second timing value reaches the second duration, and the first timing value has not reached the first duration, the control circuit 140 controls the motor 120 to stop running, and the first timing value and the second timing value are both reset to zero.

[0106] At time T5, the motor 120 triggers the first protection level, the second protection level, and the third protection level at the same time, that is, the driving current is greater than the third current value, and the control circuit 140 obtains the first timing value, the second timing value, the third timing value, the first cumulative value, the second cumulative value, and the third cumulative value, and starts timing the first timing value, the second timing value, and the third timing value. At time T6, the third timing value reaches the third duration, the first timing value does not reach the first duration, and the second timing value does not reach the second duration, the control circuit 140 controls the motor 120 to stop running, and the first timing value, the second timing value, and the third timing value are all reset to zero.

[0107] The motor 120 triggers the first protection level at T7, that is, the driving current is greater than the first current value, and the control circuit 140 obtains the first timing value and the first accumulated value, and starts timing the first timing value. Then, the motor 120 triggers the second protection level at T8, that is, the driving current is greater than the second current value, and the control circuit 140 obtains the second timing value and the second accumulated value, and starts timing the second timing value. At this time, the first timing value continues to be timed. At T9, the second timing value reaches the second duration, and the first timing value has not yet reached the first duration. The control circuit 140 controls the motor 120 to stop running, and the first timing value and the second timing value are both reset to zero.

[0108] The motor 120 triggers the first protection level at T10, that is, the driving current is greater than the first current value, and the control circuit 140 obtains the first timing value and the first cumulative value, and starts timing the first timing value. Then, the motor 120 triggers the second protection level at T11, that is, the driving current is greater than the second current value, and the control circuit 140 obtains the second timing value and the second cumulative value, and starts timing the second timing value. At this time, the first timing value continues to be timed. Afterwards, the motor 120 triggers the third protection level at T12, that is, the driving current is greater than the third current value, and the control circuit 140 obtains the third timing value and the third cumulative value, and starts timing the third timing value. At this time, the first timing value and the second timing value continue to be timed. At T13, the third timing value reaches the third duration, the second timing value has not reached the second duration, and the first timing value has not reached the first duration, the control circuit 140 controls the motor 120 to stop running, and the first timing value, the second timing value, and the third timing value are all reset.

[0109] It is understandable that in the embodiment of the present application, the timing process of the control circuit 140 for the first timing value, the second timing value and the third timing value is not limited to Figure 7 The examples shown may be used in a variety of different situations, all of which may fall within the scope of protection of this application.

[0110] In some other embodiments, the control circuit 140 may also determine the triggered temperature protection level and the corresponding preset duration according to the current value interval in which the driving current is located. For example, when the driving current is greater than the first current value and less than the second current value, it is determined that the motor 120 triggers the first protection level. When the driving current is greater than the second current value and less than the third current value, it is determined that the motor 120 triggers the second protection level. When the driving current is greater than the third current value, it is determined that the motor 120 triggers the third protection level.

[0111] See also Figure 8 , Figure 8 FIG. 2 shows a flow chart of the control method in this embodiment. Figure 8 As shown, the control method specifically includes:

[0112] Step S810: Obtain the driving current of the motor.

[0113] Step S820: Determine whether the driving current is between the first current value and the second current value.

[0114] Step S830: when the driving current is between the first current value and the second current value, obtain a first timing value and a first accumulated value.

[0115] Step S831, start timing with a first timing value, and update a first accumulated value according to the driving current.

[0116] Step S832: determine whether the first timing value reaches the first duration, or whether the first accumulated value reaches the heat threshold.

[0117] Step S833: When the first timing value does not reach the first duration and the first accumulated value does not reach the heat threshold, re-execute step S820.

[0118] Step S840: When the driving current is not between the first current value and the second current value, determine whether the driving current is between the second current value and the third current value.

[0119] Step S850: when the driving current is between the second current value and the third current value, obtain a second timing value and a second accumulated value.

[0120] Step S851, start timing with a second timing value, and update a second accumulated value according to the driving current.

[0121] Step S852: determine whether the second timing value reaches the second duration, or whether the second accumulated value reaches the heat threshold.

[0122] When the second timing value does not reach the second time length and the second accumulated value does not reach the heat threshold, step S820 is executed again.

[0123] Step S860: When the driving current is not between the second current value and the third current value, determine whether the driving current is greater than the third current value.

[0124] Step S870: when the driving current is greater than the third current value, obtaining a third timing value and a third accumulated value.

[0125] Step S871, start timing with a third timing value, and update a third accumulated value according to the driving current.

[0126] Step S872: determine whether the third timing value reaches the third duration, or whether the third accumulated value reaches the heat threshold.

[0127] When the third timing value does not reach the third time length and the third accumulated value does not reach the heat threshold, step S820 is executed again.

[0128] Step S880: When the first timing value is greater than the first duration, or the second timing value is greater than the second duration, or the third timing value is greater than the third duration, or the first cumulative value is greater than the heat threshold, or the second cumulative value is greater than the heat threshold, or the third cumulative value is greater than the heat threshold, the motor is controlled to stop running.

[0129] Therefore, when the motor 120 triggers any protection level, the control circuit 140 can promptly control the motor 120 to stop running, so as to achieve temperature protection for the motor 120 and prevent the motor 120 from being damaged due to over-temperature.

[0130] It should be noted that in the embodiment of the present application, the temperature protection level of the motor 120 is not limited to three, and can be set according to actual application requirements. For example, it can also be set to two, four, five, etc. The preset duration of each protection level is set according to the performance parameters of the motor 120.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A method for controlling an electric tool, characterized in that: The electric tool comprises a motor, and the control method comprises: Acquiring a driving current of the motor; wherein the driving current is used to drive the motor to operate; When the driving current is greater than a preset current value, a temperature protection timing value and a heat accumulation value are obtained; wherein the preset current value corresponds to a temperature protection threshold value of the motor; Start timing with the temperature protection timing value; updating the heat accumulation value according to the driving current; When the temperature protection timing value reaches a preset time length, or the heat accumulation value reaches a heat threshold, the motor is controlled to stop running.

2. The method according to claim 1, characterized in that The updating of the heat accumulation value according to the driving current comprises: The current heat value is obtained by integrating the driving current and the duration for which the driving current is greater than the preset current value; The calorie accumulation value is updated according to the current calorie value.

3. The method according to claim 1, characterized in that The preset current values ​​include at least two, and at least two of the preset current values ​​correspond one-to-one to at least two of the temperature protection thresholds, at least two of the preset time lengths, at least two of the temperature protection timing values, and at least two of the heat accumulation values; the preset current value and the temperature protection threshold are positively correlated, and the preset current value and the preset time length are negatively correlated.

4. The method according to claim 3, characterized in that When the temperature protection timing value reaches a preset time length, or the heat accumulation value reaches a heat threshold, controlling the motor to stop running includes: When any of the temperature protection timing values ​​reaches the corresponding preset time length, or when any of the heat accumulation values ​​reaches the heat threshold, the motor is controlled to stop running.

5. The method according to claim 3, characterized in that At least two of the preset current values ​​include a first current value, a second current value, and a third current value, the first current value corresponds to a first duration, a first timing value, and a first accumulated value, the second current value corresponds to a second duration, a second timing value, and a second accumulated value, and the second current value corresponds to a third duration, a third timing value, and a third accumulated value; wherein the first current value is less than the second current value, the second current value is less than the third current value, the first duration is greater than the second duration, and the second duration is greater than the third duration; When the driving current is greater than the preset current value, obtaining the temperature protection timing value and the heat accumulation value includes: When the driving current is greater than the first current value, acquiring the first timing value and the first accumulated value; When the driving current is greater than the second current value, acquiring the second timing value and the second accumulated value; When the driving current is greater than the third current value, acquiring the third timing value and the third accumulated value; When the temperature protection timing value reaches a preset time length, or the heat accumulation value reaches a heat threshold, controlling the motor to stop running includes: When the first timing value reaches the first duration, or the second timing value reaches the second duration, or the third timing value reaches the third duration, or the first accumulated value reaches the heat threshold, or the second accumulated value reaches the heat threshold, or the third accumulated value reaches the heat threshold, the motor is controlled to stop running.

6. The method according to claim 3, characterized in that At least two of the preset current values ​​are respectively in different multiples of the rated current of the motor, and each of the preset current values ​​is greater than or equal to the rated current; the heat threshold is determined according to the multiple of the heat upper limit value of the motor, and the heat threshold is greater than the heat upper limit value.

7. The method according to claim 3, characterized in that The method further comprises: When the driving current is less than the preset current value, the corresponding temperature protection timing value has not reached the preset time length, and the corresponding heat accumulation value has not reached the heat threshold, the corresponding temperature protection timing value and the corresponding heat accumulation value are cleared.

8. The method according to any one of claims 1 to 7, characterized in that: The method further comprises: When a power-on instruction is received, the temperature protection timing value and the heat accumulation value are reset to zero.

9. An electric tool, characterized in that: The electric tool comprises a motor drive circuit, a motor, a current detection circuit and a control circuit, wherein the input end of the motor drive circuit is used to connect to a drive power source, and the output end of the motor drive circuit is connected to the motor; The current detection circuit is connected to the input end of the motor drive circuit, and the control circuit is connected to the motor drive circuit and the current detection circuit; Wherein, the motor driving circuit is used to drive the motor to operate; The current detection circuit is used to detect the driving current provided by the driving power supply to the motor driving circuit, and send the driving current to the control circuit; The control circuit is used for: Acquiring the driving current; When the driving current is greater than a preset current value, a temperature protection timing value and a heat accumulation value are obtained; wherein the preset current value corresponds to a temperature protection threshold value of the motor; Start timing with the temperature protection timing value; updating the heat accumulation value according to the driving current; When the temperature protection timing value reaches a preset time length, or the heat accumulation value reaches a heat threshold, the motor is controlled to stop running.

10. The electric tool according to claim 9, characterized in that: The electric tool further comprises a control switch, wherein the control switch is connected between the motor drive circuit and the drive power supply, and the control circuit is connected to the control switch; The control circuit is used to output a disconnect signal to the control switch when the temperature protection timing value reaches a preset time or the heat accumulation value reaches a heat threshold; The control switch is used to disconnect the motor drive circuit and the drive power supply according to the disconnection signal, so as to stop the motor from running.

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