AC asynchronous motor speed measuring device and range hood

Abstract

The present invention discloses an AC asynchronous motor speed measurement device, comprising: a transmission mechanism, a DC motor, a detection circuit, and a first controller. The DC motor is connected to the AC asynchronous motor via the transmission mechanism, and the detection circuit is electrically connected to the DC motor and the first controller, respectively. When the AC asynchronous motor drives the DC motor to rotate via the transmission mechanism, the DC motor generates an induced current. The detection circuit detects the induced current and converts it into an induced voltage. The first controller determines the speed of the AC asynchronous motor based on the induced voltage and a predetermined relationship between the induced voltage and the speed. The present invention provides a device for determining the speed of an AC asynchronous motor, further enabling automatic cruise control of an AC range hood and adjusting the gear position, thereby controlling the range hood's air volume without requiring the user to manually adjust the gear position, thereby improving the user experience.

Description

Technical Field

[0001] The present invention relates to the field of AC asynchronous motor speed measurement, and in particular to an AC asynchronous motor speed measurement device and a range hood. Background Art

[0002] Currently, AC range hoods occupy a larger share on the market. The AC motor is used as a tap and a relay is used to control the conduction of different taps to achieve a fixed speed of the motor. It is difficult to control the motor speed and it is impossible to adjust the speed according to the flue resistance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defect in the prior art that it is difficult to control the motor speed of an AC motor, and to provide an AC asynchronous motor speed measuring device and a range hood.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] In a first aspect, an AC asynchronous motor speed measuring device is provided, the AC asynchronous motor speed measuring device comprising: a transmission mechanism, a DC motor, a detection circuit and a first controller;

[0006] The DC motor is transmission-connected to the AC asynchronous motor via the transmission mechanism, and the detection circuit is electrically connected to the DC motor and the first controller respectively;

[0007] In the process of the AC asynchronous motor driving the DC motor to rotate through the transmission mechanism, the DC motor is used to generate an induced current;

[0008] The detection circuit is used to detect the induced current and convert the induced current into an induced voltage;

[0009] The first controller is used to determine the rotational speed of the AC asynchronous motor according to the induced voltage and a predetermined corresponding relationship between the induced voltage and the rotational speed.

[0010] Optionally, the detection circuit includes a current sampling subcircuit and an operational amplifier;

[0011] The input end of the current sampling subcircuit is connected to the rotor of the DC motor, and the output end of the current sampling subcircuit is connected to the input end of the operational amplifier;

[0012] The output end of the operational amplifier is connected to the first controller.

[0013] Optionally, the current sampling sub-circuit further includes a current sensing resistor, and two ends of the current sensing resistor are respectively connected to two input ends of the current sampling sub-circuit.

[0014] Optionally, the detection circuit also includes a first current limiting resistor and a second current limiting resistor, one end of the current sensing resistor is connected to the first input end of the operational amplifier through the first current limiting resistor; the other end of the current sensing resistor is connected to the second input end of the operational amplifier through the second current limiting resistor.

[0015] Optionally, the detection circuit further includes a filter circuit, and the filter circuit includes a third resistor and a capacitor;

[0016] One end of the third resistor is connected to the operational amplifier, and the other end is connected to the first controller;

[0017] One end of the capacitor is connected to the first controller, and the other end is grounded.

[0018] In a second aspect, a range hood is provided, comprising a second controller, an AC asynchronous motor, and the AC asynchronous motor speed measuring device according to the first aspect; the second controller is electrically connected to the AC asynchronous motor and the first controller respectively;

[0019] The second controller is used to adjust the gear position of the range hood to a target gear position, and the target gear position matches the rotational speed of the AC asynchronous motor calculated based on the first controller.

[0020] Optionally, each gear corresponds to an induced current range; the first controller is further configured to determine whether the induced current falls within the induced current range corresponding to the current gear of the range hood;

[0021] If the judgment result is negative, the first controller sends an adjustment instruction to the second controller, and the second controller adjusts the gear position of the range hood to a gear position that matches the current induced current.

[0022] Optionally, each gear corresponds to an induced voltage range; the first controller is further configured to determine whether the induced voltage falls within the induced voltage range corresponding to the current gear of the range hood;

[0023] If the judgment result is negative, the first controller sends an adjustment instruction to the second controller, and the second controller adjusts the gear position of the range hood to a gear position that matches the current induced voltage.

[0024] The positive progress effect of the present invention is that: the present invention designs a speed measuring device for an AC asynchronous motor, which realizes the speed measurement of the AC asynchronous motor;

[0025] Furthermore, the gear position of the range hood can be adjusted according to different flue resistances, thereby realizing air volume control of the range hood and enabling the range hood to automatically cruise and adjust the gear position. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic structural diagram of an AC asynchronous motor speed measuring device provided by an exemplary embodiment of the present invention;

[0027] Figure 2 A schematic diagram of a detection circuit of an AC asynchronous motor speed measuring device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0029] Figure 1 A schematic diagram of the structure of an AC asynchronous motor speed measuring device provided by an embodiment of the present invention. Figure 2 A schematic diagram of a detection circuit for an AC asynchronous motor speed measuring device provided in an embodiment of the present invention is provided. The AC asynchronous motor speed measuring device includes a transmission mechanism 12, a DC motor 13, a detection circuit 24, and a first controller 14. The DC motor 13 is transmission-connected to the AC asynchronous motor 11 via the transmission mechanism 12. The detection circuit 24 is electrically connected to the DC motor 13 and the first controller 14, respectively. When the AC asynchronous motor 11 drives the DC motor 13 to rotate via the transmission mechanism 12, an induced current is generated in the rotor coil of the DC motor 13. The induced current generated by the DC motor 13 is proportional to the rotational speed of the DC motor 13. The detection circuit 24 detects the induced current generated in the DC motor 13, converts the induced current into an induced voltage, and transmits the voltage to the first controller 14. The first controller 14 determines the rotational speed of the AC asynchronous motor 11 based on the obtained induced voltage and a predetermined correspondence between the induced voltage and the rotational speed.

[0030] In one embodiment, a gear mechanism is fixed on the rotating shaft of the AC asynchronous motor 11, and the transmission mechanism 12 is engaged with the AC asynchronous motor 11 through gears. The transmission mechanism 12 is composed of a multi-stage gear reduction mechanism with a transmission ratio of a. The different sizes of gears are used to reduce the number of revolutions of the asynchronous AC motor 11 to the target number of revolutions, thereby realizing the transmission of power between different mechanisms.

[0031] The target number of revolutions can be set according to the actual situation.

[0032] In one embodiment, the detection circuit 24 includes a current sampling subcircuit 21 and an operational amplifier 22; the input end of the current sampling subcircuit 21 is connected to the rotor of the DC motor 13, and the output end of the current sampling subcircuit 21 is connected to the input end of the operational amplifier 22; the output end of the operational amplifier 22 is connected to the first controller 14, and the operational amplifier 22 is used to obtain and amplify the induced current, and convert the amplified induced current into an induced voltage and transmit it to the first controller 14, so that the first controller 14 can receive the induced voltage and perform subsequent signal processing, reduce the error of signal acquisition, and improve the acquisition accuracy.

[0033] In one embodiment, the current sampling subcircuit 21 further includes a current sensing resistor, the two ends of which are respectively connected to the two input ends of the current sampling subcircuit 21. The current sensing resistor is used to monitor the current flowing through the circuit and transmit it to the current sampling subcircuit 21 to ensure that the circuit can operate stably.

[0034] In one embodiment, the detection circuit 24 further includes a first current-limiting resistor R4 and a second current-limiting resistor R2. One end of the current sensing resistor is connected to the first input terminal of the operational amplifier 22 through the first current-limiting resistor R4, and the other end of the current sensing resistor is connected to the second input terminal of the operational amplifier 22 through the second current-limiting resistor R2. The first current-limiting resistor R4 and the second current-limiting resistor R2 are used to limit the magnitude of the current flowing through the detection circuit 24 to prevent excessive current and ensure the safety of the circuit operation.

[0035] The resistance values of the first current limiting resistor R4 and the second current limiting resistor R2 are set according to actual conditions.

[0036] In one embodiment, the detection circuit 24 also includes a filtering circuit 23, which includes a third resistor R3 and a capacitor C2. One end of the third resistor R3 is connected to the operational amplifier 22, and the other end is connected to the first controller 14. One end of the capacitor C2 is connected to the first controller 14, and the other end is grounded. The third resistor R3 and the capacitor C2 are used to filter out interference signals in the induced voltage output by the operational amplifier 22, reduce the deviation of signal acquisition, and improve the accuracy of acquisition.

[0037] An embodiment of the present invention further provides a range hood, comprising a second controller, an AC asynchronous motor 11, and the AC asynchronous motor speed measuring device described in any of the above embodiments, wherein the second controller is electrically connected to the AC asynchronous motor 11 and the first controller 14, respectively;

[0038] The second controller is used to adjust the gear of the range hood to a target gear, which matches the speed of the AC asynchronous motor 11 calculated by the first controller;

[0039] The speed of the AC asynchronous motor 11 is proportional to the flue resistance of the range hood. The gear of the range hood changes according to the speed of the AC asynchronous motor 11, so that the range hood can automatically adjust the gear and realize the air volume control of the range hood.

[0040] Among them, the target gear is set according to the actual situation.

[0041] In one embodiment, each gear corresponds to an induced current range, and the first controller 14 is also used to determine whether the induced current falls within the induced current range corresponding to the current gear of the range hood. If the judgment is not, the first controller 14 will send an adjustment instruction to the second controller, and the second controller will adjust the gear of the range hood to a gear that matches the current induced current to prevent frequent switching of gears from consuming electricity, thereby ensuring the oil absorption effect while reducing kitchen noise and improving the cooking experience.

[0042] In one embodiment, each gear corresponds to an induced voltage range, and the first controller 14 is also used to determine whether the induced voltage falls within the induced voltage range corresponding to the current gear of the range hood. If the judgment is not, the first controller 14 will send an adjustment instruction to the second controller, and the second controller will adjust the gear of the range hood to a gear that matches the current induced voltage to prevent frequent switching of gears from consuming electricity, ensuring the oil absorption effect while reducing kitchen noise and improving the cooking experience.

[0043] The following combination Figure 1 The working principle of the AC asynchronous motor speed measuring device is further explained:

[0044] The AC asynchronous motor 11 drives the DC motor 13 to rotate through the transmission mechanism 12. During the rotation of the DC motor 13, an induced current is generated. The induced current is converted into an induced voltage by the detection circuit 24 and transmitted to the first controller 14. The first controller 14 determines the speed of the AC asynchronous motor 11 based on the obtained induced voltage and a predetermined correspondence between the induced voltage and the speed.

[0045] Among them, the transmission ratio of the transmission mechanism is a, the speed of the AC asynchronous motor is ra, the speed of the DC motor is ra / a, and the induced current is Ia.

[0046] The following combination Figure 2 The following are the specific steps to determine the corresponding relationship between induced voltage and speed:

[0047] According to the virtual short and virtual disconnect principle of the operational amplifier, the formula can be obtained:

[0048]

[0049] Um=Im*RS1,

[0050] That is, the corresponding relationship between Vad and Im is:

[0051]

[0052] Where RS1 is the current sensing resistor, Im is the induced current, R2 is the second current limiting resistor, Vad is the induced voltage, Um is the total voltage in the detection circuit, and VCC is the voltage after being divided by R4 and R2;

[0053] At the same time, the resistance values of R1 and R2 are determined based on the DC motor Im value obtained when the AC asynchronous motor 11 is at its highest speed, ensuring that the following relationship is satisfied between VCC and Im at this time, ensuring that the op amp output will not be saturated at the highest speed:

[0054]

[0055] The first controller 14 obtains the change in the rotational speed of the AC asynchronous motor 11 according to the relationship between the detected Vad and Im.

[0056] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A range hood, characterized in that: The range hood includes a second controller, an AC asynchronous motor and an AC asynchronous motor speed measuring device; The AC asynchronous motor speed measuring device comprises: a transmission mechanism, a DC motor, a detection circuit and a first controller; The second controller is electrically connected to the AC asynchronous motor and the first controller respectively; The DC motor is transmission-connected to the AC asynchronous motor via the transmission mechanism, and the detection circuit is electrically connected to the DC motor and the first controller respectively; In the process of the AC asynchronous motor driving the DC motor to rotate through the transmission mechanism, the DC motor is used to generate an induced current; The detection circuit is used to detect the induced current and convert the induced current into an induced voltage; The first controller is used to determine the rotational speed of the AC asynchronous motor according to the induced voltage and a predetermined corresponding relationship between the induced voltage and the rotational speed; The second controller is used to adjust the gear position of the range hood to a target gear position, and the target gear position matches the rotational speed of the AC asynchronous motor calculated based on the first controller.

2. The range hood according to claim 1, wherein: The detection circuit includes a current sampling subcircuit and an operational amplifier; The input end of the current sampling subcircuit is connected to the rotor of the DC motor, and the output end of the current sampling subcircuit is connected to the input end of the operational amplifier; The output end of the operational amplifier is connected to the first controller.

3. The range hood according to claim 2, wherein: The current sampling subcircuit further includes a current sensing resistor, and two ends of the current sensing resistor are respectively connected to the two input ends of the current sampling subcircuit.

4. The range hood according to claim 3, wherein: The detection circuit also includes a first current limiting resistor and a second current limiting resistor. One end of the current sensing resistor is connected to the first input end of the operational amplifier through the first current limiting resistor; the other end of the current sensing resistor is connected to the second input end of the operational amplifier through the second current limiting resistor.

5. The range hood according to claim 4, wherein: The detection circuit further includes a filter circuit, and the filter circuit includes a third resistor and a capacitor; One end of the third resistor is connected to the operational amplifier, and the other end is connected to the first controller; One end of the capacitor is connected to the first controller, and the other end is grounded.

6. The range hood according to claim 1, wherein: Each gear corresponds to an induction current range; the first controller is further used to determine whether the induction current falls within the induction current range corresponding to the current gear of the range hood; If the judgment result is negative, the first controller sends an adjustment instruction to the second controller, and the second controller adjusts the gear position of the range hood to a gear position that matches the current induced current.

7. The range hood according to claim 1, wherein: Each gear position corresponds to an induced voltage range; the first controller is further configured to determine whether the induced voltage falls within the induced voltage range corresponding to the current gear position of the range hood; If the judgment result is negative, the first controller sends an adjustment instruction to the second controller, and the second controller adjusts the gear position of the range hood to a gear position that matches the current induced voltage.

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