Oil cup liquid level detection device, method and range hood

Abstract

The present invention discloses an oil cup liquid level detection device, method, and range hood, wherein the oil cup liquid level detection device includes a first electrode plate, a second electrode plate, a control unit, a power supply, and a reference capacitor; the first electrode plate and the second electrode plate are disposed in the oil cup, and the first electrode plate and the second electrode plate constitute a first capacitor; wherein the capacitance of the first capacitor increases as the liquid level in the oil cup increases; the control unit is configured to control the power supply to charge the first capacitor based on a first control signal, and to control the first capacitor to charge the reference capacitor based on a second control signal, and to determine the liquid level in the oil cup based on a first charging time taken for the first capacitor to charge the reference capacitor to a preset reference voltage. This method solves the technical problem in the prior art that liquid level detection devices are susceptible to interference, resulting in inaccurate detection, and can automatically and accurately detect the liquid level of the oil cup, and promptly alert the user when the liquid level reaches a set condition.

Description

Technical Field

[0001] The present invention relates to the technical field of kitchen appliances, and in particular to a device and method for detecting the liquid level of an oil cup, and a range hood. Background Art

[0002] The grease generated during the use of the range hood will be discharged into the oil cup. Usually, the oil level in the oil cup needs to be manually observed and detected. When the oil accumulates to a certain level, it is necessary to pour out the oil in time to prevent overflow. However, with the accelerated pace of life, people often forget to clean the oil cup, which can easily cause the oil in the oil cup to seep out, causing secondary pollution to the kitchen environment and increasing the difficulty of cleaning the kitchen grease. Therefore, only by accurately detecting the oil level in the oil cup can we ensure that the user can disassemble and clean the oil cup in time to ensure the range hood's extraction effect.

[0003] Current liquid level detection methods typically use an infrared pair of tubes. That is, when the liquid level in the oil cup reaches the position of the infrared transceiver tube, it causes obstruction and changes in the infrared transceiver tube signal. The control circuit converts the received signal change into a prompt signal to inform the user that the oil cup should be cleaned in time. The use of infrared pair of tubes requires oil-proof protection, so its structural design and installation are relatively complex and easily contaminated by oil, which affects the detection accuracy. Alternatively, an ultrasonic probe is used for detection. That is, an ultrasonic probe is used to transmit ultrasonic waves into the oil cup and then receive an echo signal reflected by the waste oil surface in the oil cup. The time difference between the two signals is then calculated to obtain the corresponding distance difference. Finally, the distance difference is subtracted from the oil cup height to detect the oil level in the oil cup. Since there must be a sufficient distance between the ultrasonic probe and the oil cup to ensure that the signal can be detected, a too small installation distance will result in poor detection accuracy. At the same time, the ultrasonic probe is difficult to install on the range hood and is expensive. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defect in the prior art that the liquid level detection device is easily disturbed and causes inaccurate detection, and to provide an oil cup liquid level detection device, method and range hood.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] The present invention provides a device for detecting the liquid level of an oil cup, the device comprising a first electrode plate, a second electrode plate, a control unit, a power supply and a reference capacitor;

[0007] The first electrode plate and the second electrode plate are disposed in the oil cup, and the first electrode plate and the second electrode plate constitute a first capacitor; wherein the capacitance of the first capacitor increases as the liquid level in the oil cup increases;

[0008] The control unit is configured to control the power supply to charge the first capacitor based on a first control signal, and to control the first capacitor to charge the reference capacitor based on a second control signal, and to determine the height of the liquid level in the oil cup according to a first charging time taken for the first capacitor to charge the reference capacitor to a preset reference voltage;

[0009] The second control signal is an inverted signal of the first control signal.

[0010] Preferably, the detection device further comprises a switching unit and a comparing unit;

[0011] The first electrode plate is connected to the power supply or one end of the reference capacitor through the switching unit, one end of the reference capacitor is connected to the first input end of the comparison unit, the output end of the comparison unit is connected to the control unit, the second input end of the comparison unit is connected to the reference power supply, the voltage of the reference power supply is a preset reference voltage, the control unit is further connected to the switching unit, and the other end of the second electrode plate and the reference capacitor is grounded;

[0012] The control unit is further configured to send the first control signal to the switching unit to connect the first plate to the power supply; and send the second control signal to the switching unit to connect the first plate to the reference capacitor.

[0013] Preferably, the detection device further comprises a third electrode plate;

[0014] The third electrode plate is disposed in the oil cup, and the second electrode plate and the third electrode plate constitute a second capacitor. The first electrode plate, the second electrode plate, and the third electrode plate are sequentially disposed along the length of the oil cup; wherein the capacitance of the second capacitor increases as the liquid level in the oil cup increases;

[0015] The control unit is further configured to control the reference capacitor to discharge based on a third control signal when the voltage across the reference capacitor reaches the preset reference voltage;

[0016] and when the reference capacitor has completed discharging, controlling the power supply to charge the second capacitor based on a fourth control signal, and controlling the second capacitor to charge the reference capacitor based on a fifth control signal, and determining the height of the liquid level in the oil cup according to a second charging time for the second capacitor to charge the reference capacitor to a preset reference voltage;

[0017] The fifth control signal is an inverted signal of the fourth control signal.

[0018] Preferably, the distance between the first electrode plate and the second electrode plate is smaller than the distance between the third electrode plate and the second electrode plate.

[0019] Preferably, the switching unit includes a first switch, a second switch, a third switch, a fourth switch and an inverter;

[0020] One end of the inverter is connected to the control end of the control unit and the control end of the second switch respectively, and the other end is connected to the control end of the first switch;

[0021] One end of the first switch is connected to the power supply, and the other end is connected to one end of the second switch, one end of the third switch, and one end of the fourth switch respectively;

[0022] The other end of the second switch is connected to the first input end of the comparison unit;

[0023] A control end of the third switch is connected to the control unit, and the other end of the third switch is connected to the first electrode plate;

[0024] A control end of the fourth switch is connected to the control unit, and the other end of the fourth switch is connected to the third electrode plate.

[0025] Preferably, the detection device further comprises a discharge unit;

[0026] The discharge unit includes a fifth switch and a resistor;

[0027] One end of the reference capacitor is connected to one end of the resistor via the fifth switch, a control end of the fifth switch is connected to the control unit, and the other end of the resistor is grounded;

[0028] The control unit is further configured to send the third control signal to the control terminal of the fifth switch;

[0029] The fifth switch connects the reference capacitor to the resistor based on the third control signal.

[0030] Preferably, if the first charging time reaches a preset charging time and / or the second charging time reaches a preset charging time, the control unit determines that the liquid level of the oil cup is full.

[0031] Preferably, the control unit is further configured to output a full cup prompt signal when the oil cup is full.

[0032] The present invention further provides a method for detecting the oil cup liquid level, which is implemented using the oil cup liquid level detection device described above. The method includes:

[0033] controlling the power supply to charge the first capacitor based on a first control signal;

[0034] Controlling the first capacitor to charge the reference capacitor based on a second control signal; wherein the second control signal is an inverted signal of the first control signal;

[0035] The liquid level height of the oil cup is determined according to a first charging time taken for the first capacitor to charge the reference capacitor to a preset reference voltage.

[0036] The present invention further provides a range hood comprising an oil cup and the above-mentioned device for detecting the liquid level of the oil cup.

[0037] The positive progress of the present invention lies in the following: the oil cup liquid level detection device of the present invention includes a first electrode plate, a second electrode plate, a control unit, a power supply, and a reference capacitor; the first electrode plate and the second electrode plate are disposed in the oil cup, and the first electrode plate and the second electrode plate constitute a first capacitor; wherein the capacitance of the first capacitor increases as the liquid level in the oil cup increases; the control unit is used to control the power supply to charge the first capacitor based on a first control signal, and to control the first capacitor to charge the reference capacitor based on a second control signal, and to determine the height of the liquid level in the oil cup based on a first charging time for the first capacitor to charge the reference capacitor to a preset reference voltage. This solves the technical problem in the prior art that liquid level detection devices are easily affected by interference, resulting in inaccurate detection, and can automatically and accurately detect the liquid level of the oil cup and promptly alert the user when the liquid level reaches the set condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the circuit structure of the oil cup liquid level detection device of Example 1 of the present invention.

[0039] Figure 2 This is a schematic diagram of the circuit structure of the oil cup liquid level detection device of Example 2 of the present invention.

[0040] Figure 3 This is a schematic diagram of the electrode plate installation of the oil cup liquid level detection device of Example 2 of the present invention.

[0041] Figure 4 This is another circuit structure diagram of the oil cup liquid level detection device according to Example 2 of the present invention.

[0042] Figure 5 This is a flow chart of a method for detecting the oil cup liquid level according to Example 3 of the present invention.

[0043] Figure 6 Schematic diagram of the flow of the oil cup liquid level detection method of Example 4 of the present invention. DETAILED DESCRIPTION

[0044] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0045] Example 1

[0046] This embodiment provides a device for detecting the level of the oil cup. Figure 1 As shown, the detection device 1 of this embodiment includes a first electrode plate 101 , a second electrode plate 102 , a control unit 2 , a power supply 3 and a reference capacitor 4 .

[0047] In this embodiment, the first electrode plate 101 and the second electrode plate 102 are disposed in the oil cup, and the first electrode plate 101 and the second electrode plate 102 constitute a first capacitor. The capacitance of the first capacitor increases as the liquid level in the oil cup increases. This capacitance change can be demonstrated by the capacitance calculation formula of a parallel plate capacitor. Specifically, the calculation formula for the parallel plate capacitance is:

[0048]

[0049] In the above formula, C is the capacitance of the capacitor, ε is the dielectric constant of the medium between the plates, and ε r is the relative dielectric constant of the medium between the plates, ε0 is the dielectric constant of vacuum, ε0=8.85×10 -12 F / m, S is the effective relative area between the plates, and d is the relative distance between the plates; therefore, the change in capacitance is related to the change in the three parameters of dielectric constant ε, relative area S, and plate distance d. Since the vacuum dielectric constant ε0 is a constant, when S and d remain unchanged, the capacitance C is directly related to the relative dielectric constant ε. r The capacitance is directly proportional to the capacitance of the liquid. Therefore, by changing the dielectric material between the plates (i.e., the liquid whose liquid level needs to be detected), the relative dielectric constants of different dielectric materials are different, causing a change in capacitance. After the corresponding parameter adjustments, using the above principles, those skilled in the art should know that the detection device of this embodiment can be used not only to detect the liquid level of oil, but also for the level detection of other liquids.

[0050] In this embodiment, the control unit 2 is used to control the power supply 3 to charge the first capacitor based on a first control signal, and to control the first capacitor to charge the reference capacitor 4 based on a second control signal, and to determine the height of the liquid level in the oil cup according to the first charging time for the first capacitor to charge the reference capacitor 4 to a preset reference voltage Vref, wherein the second control signal is an inverted signal of the first control signal.

[0051] In a specific example, the first control signal is a high-level signal, and the second control signal is a low-level signal. The control unit 2 continuously controls the power supply 3 to charge the first capacitor based on the high-level signal. When the first capacitor reaches a certain voltage (which can be 3.3V), the control unit 2 sends a low-level signal. The control unit 2 controls the first capacitor to charge the reference capacitor 4 based on the low-level signal.

[0052] In another specific example, the first control signal and the second control signal are periodic signals, such as pulse signals, emitted by the control unit 2. Therefore, those skilled in the art can flexibly set the first control signal and the second control signal according to the application scenario.

[0053] In an alternative embodiment, Figure 1 As shown, the detection device 1 further includes a switching unit 5 and a comparison unit 6 .

[0054] Specifically, the first electrode 101 is connected to the power supply 3 or one end of the reference capacitor 4 through the switching unit 5, one end of the reference capacitor 4 is connected to the first input end of the comparison unit 6, the output end of the comparison unit 6 is connected to the control unit 2, the second input end of the comparison unit 6 is connected to the reference power supply, the voltage of the reference power supply is a preset reference voltage Vref, the control unit 2 is also connected to the switching unit 5, and the other end of the second electrode 102 and the reference capacitor 4 are grounded.

[0055] In this embodiment, the control unit 2 is further configured to send a first control signal to the switching unit 5 to connect the first plate 101 to the power supply 3 , and to send a second control signal to the switching unit 5 to connect the first plate 101 to the reference capacitor 4 .

[0056] In a specific implementation process, when the liquid level height in the oil cup is detected, the control unit 2 starts timing and sends a first control signal and a second control signal at a fixed frequency. The control unit 2 controls the power supply 3 to charge the first capacitor based on the first control signal, and controls the first capacitor to charge the reference capacitor 4 based on the second control signal. The above charging process is always switched alternately to realize the transfer of the charge on the first capacitor to the reference capacitor 4. After a certain period of time, when the voltage on the reference capacitor 4 reaches the preset reference voltage Vref, the comparison unit 6 outputs a rising edge signal or a falling edge signal to the control unit 2. At this time, the control unit 2 stops timing after receiving the flip signal, thereby obtaining the first charging time t2 of the entire process. Therefore, the detection device of this embodiment can determine the height of the liquid level in the oil cup based on the first charging time t2.

[0057] In another specific implementation, the control unit 2 also records the charging time t1 for the first capacitor to charge the reference capacitor 4 to a preset reference voltage Vref when the oil cup is empty, as a comparison benchmark, and stores the time t1 when the control unit 2 loses power. At the same time, the control unit also pre-records the charging time change Δc1 of the first capacitor. The charging time change Δc1 can be set according to any height of the liquid level in the oil cup, that is, one charging time change Δc1 corresponds to one liquid level height. For example, when the oil cup is full, the charging time change Δc1 is 10 seconds. When the oil cup is half full, the charging time change Δc1 is 5 seconds. A person skilled in the art can set the charging time variation Δc1 based on the capacitance of the first capacitor and the liquid to be detected. The following example uses a full oil cup as an example. The control unit 2 always monitors the charging time of the reference capacitor 4. As the amount of oil in the oil cup increases, the charging time of the reference capacitor 4 gradually increases. When t2-t1=Δc1, the control unit 2 issues a prompt indicating that the oil cup is full, prompting the user that the oil cup needs to be cleaned. Thus, the oil cup liquid level detection device of this embodiment can automatically and accurately detect the liquid level of the oil cup and promptly remind the user to clean it when the liquid level reaches the set condition, thereby avoiding overflow of liquid and contamination of the kitchen environment.

[0058] Example 2

[0059] This embodiment provides a device for detecting the level of the oil cup. Figure 2 As shown, the detection device of this embodiment is a further improvement of the embodiment. Specifically, the detection device 1 also includes a third electrode plate 103, which is arranged in the oil cup. The second electrode plate 102 and the third electrode plate 103 constitute a second capacitor, and the capacitance of the second capacitor increases with the increase of the liquid level in the oil cup; the first electrode plate 101, the second electrode plate 102 and the third electrode plate 103 are arranged in sequence along the length direction of the oil cup. In order to reduce errors and ensure accurate liquid level detection, it is also necessary to set the three electrode plates at the same horizontal height.

[0060] In a preferred embodiment, Figure 3 As shown, the distance between the first electrode plate 101 and the second electrode plate 102 is smaller than the distance between the third electrode plate 103 and the second electrode plate 102. Therefore, according to the above-mentioned parallel plate capacitance calculation formula, the capacitance of the first capacitor formed by the first electrode plate 101 and the second electrode plate 102 is greater than the capacitance of the second capacitor formed by the third electrode plate 103 and the second electrode plate 102. Therefore, liquid level detection can be performed separately according to two capacitors with different capacitances to improve the accuracy of liquid level detection.

[0061] Optionally, the three plates of this embodiment are fixed in the oil cup by silicone, and a certain gap is left around the oil cup. The plates are made of conductive material that is corrosion-resistant and wear-resistant, and the plates are electrically connected to the detection device 1 through contact springs.

[0062] In this embodiment, the control unit 2 is also used to control the reference capacitor 4 to discharge based on the third control signal when the voltage across the reference capacitor 4 reaches a preset reference voltage Vref, and to control the power supply 3 to charge the second capacitor based on the fourth control signal when the reference capacitor 4 completes discharging, and to control the second capacitor to charge the reference capacitor 4 based on the fifth control signal, and to determine the height of the liquid level in the oil cup according to the second charging time for the second capacitor to charge the reference capacitor 4 to the preset reference voltage Vref; wherein the fifth control signal is an inverted signal of the fourth control signal.

[0063] In a specific example, the fourth control signal is a high-level signal, the fifth control signal is a low-level signal, and the control unit 2 continuously controls the power supply 3 to charge the first capacitor based on the high-level signal. When the first capacitor reaches a certain voltage (which can be 3.3V), the control unit 2 sends a low-level signal, and the control unit 2 controls the first capacitor to charge the reference capacitor 4 based on the low-level signal.

[0064] In another specific example, the fourth control signal and the fifth control signal are periodic signals, such as pulse signals, emitted by the control unit 2. Therefore, those skilled in the art can flexibly set the fourth control signal and the fifth control signal according to the application scenario.

[0065] Preferably, if the first charging time reaches the preset charging time and / or the second charging time reaches the preset charging time, the control unit 2 determines that the liquid level of the oil cup is full and outputs a full cup prompt signal when the oil cup liquid level is full. That is, in this embodiment, the control unit 2 can separately determine whether the first charging time for the first capacitor to charge the reference capacitor 4 to the preset reference voltage Vref reaches the preset charging time, or separately determine whether the second charging time for the second capacitor to charge the reference capacitor 4 to the preset reference voltage Vref reaches the preset charging time, or after the first charging time for the first capacitor to charge the reference capacitor 4 to the preset reference voltage Vref reaches the preset charging time, continue to determine whether the second charging time for the second capacitor to charge the reference capacitor 4 to the preset reference voltage Vref reaches the preset charging time. Therefore, the detection device of this embodiment can use the capacitor formed by the two plates to detect the liquid level height, and can also use the two capacitors formed by the three plates to detect the liquid level height in sequence, so that the accuracy of the detection can be effectively improved through two detections.

[0066] In an optional embodiment, as Figure 4As shown, the switching unit 5 includes a first switch 501 , a second switch 502 , a third switch 503 , a fourth switch 504 and an inverter 505 .

[0067] Specifically, one end of the inverter 505 is connected to the control unit 2 and the control end of the second switch 502 respectively, and the other end is connected to the control end of the first switch 501. One end of the first switch 501 is connected to the power supply 3, and the other end is connected to one end of the second switch 502, one end of the third switch 503 and one end of the fourth switch 504 respectively. The other end of the second switch 502 is connected to the first input end of the comparison unit 6, the control end of the third switch 503 is connected to the control unit 2, the other end of the third switch 503 is connected to the first electrode plate 101, the control end of the fourth switch 504 is connected to the control unit 2, and the other end of the fourth switch 504 is connected to the third electrode plate 103.

[0068] In another optional embodiment, as Figure 4 As shown, the detection device 1 of this embodiment further includes a discharge unit 7 .

[0069] Specifically, the discharge unit 7 includes a fifth switch 701 and a resistor 702. One end of the reference capacitor 4 is connected to one end of the resistor 702 through the fifth switch 701. The control end of the fifth switch 701 is connected to the control unit. The other end of the resistor 702 is grounded. The control unit 2 is also used to send a third control signal to the control end of the fifth switch 701. The fifth switch 701 connects the reference capacitor 4 to the resistor based on the third control signal. Through the discharge unit 7, it can be ensured that each capacitor is in an initial state each time a liquid level detection is performed, thereby further reducing the detection error.

[0070] In one embodiment, the control unit 2 pre-records the charging time variation Δc1 of the first capacitor and the charging time variation Δc2 of the second capacitor. The configuration of the charging time variation Δc1 of the first capacitor and the charging time variation Δc2 of the second capacitor in this embodiment is the same as the configuration of the charging time variation Δc1 of the first capacitor in Example 1, and is not described in detail here. After the control unit 2 completes the first capacitance detection, i.e., when the charging of the first capacitor to the reference capacitor satisfies t2-t1=Δc1, the control module 2 controls the discharge unit 7 based on the third control signal to discharge each capacitor to an initial state, and then performs detection on the second capacitor. The detection process is the same as that for the first capacitor, and is not described in detail here. It should be noted that, in this embodiment, the control unit 2 outputs the full cup prompt signal only when the charging of the first capacitor to the reference capacitor satisfies t2-t1=Δc1 and the charging of the second capacitor to the reference capacitor satisfies t2-t1=Δc2.

[0071] The detection device of this embodiment outputs a full cup prompt signal after two tests, ensuring that the detection device will not give false alarms or missed alarms, thereby improving the user experience.

[0072] Example 3

[0073] This embodiment provides a method for detecting the oil cup liquid level. Figure 5 As shown, the oil cup liquid level detection method of this embodiment is implemented by using the oil cup liquid level detection device of Example 1. Specifically, the detection method of this embodiment includes:

[0074] S1. Control a power supply to charge a first capacitor based on a first control signal.

[0075] S2. Control the first capacitor to charge the reference capacitor based on a second control signal; wherein the second control signal is an inverted signal of the first control signal.

[0076] S3. Determine the liquid level of the oil cup according to a first charging time during which the first capacitor charges the reference capacitor to a preset reference voltage.

[0077] In this embodiment, a power supply is controlled by a first control signal to charge a first capacitor, and a second control signal is used to control the first capacitor to charge a reference capacitor. Thus, the liquid level in the oil cup is determined based on a first charging time taken for the first capacitor to charge the reference capacitor to a preset reference voltage. This enables automatic and accurate detection of the liquid level in the oil cup, and promptly reminds the user to clean the oil cup when the liquid level reaches a set condition, thereby preventing overflow and contamination of the kitchen environment due to liquid accumulation.

[0078] Example 4

[0079] This embodiment provides a method for detecting the oil cup liquid level. Figure 6 As shown, the oil cup liquid level detection method of this embodiment is implemented by using the oil cup liquid level detection device of Example 2. Specifically, the detection method of this embodiment includes:

[0080] S1. Control a power supply to charge a first capacitor based on a first control signal.

[0081] S2. Control the first capacitor to charge the reference capacitor based on a second control signal; wherein the second control signal is an inverted signal of the first control signal.

[0082] S3. When the voltage across the reference capacitor reaches a preset reference voltage, control the reference capacitor to discharge based on a third control signal.

[0083] S4. When the reference capacitor finishes discharging, control the power supply to charge the second capacitor based on the fourth control signal.

[0084] S5. Control the second capacitor to charge the reference capacitor based on a fifth control signal; wherein the fifth control signal is an inverted signal of the fourth control signal.

[0085] S6. Determine the height of the liquid level in the oil cup according to a first charging time for the first capacitor to charge the reference capacitor to a preset reference voltage and a second charging time for the second capacitor to charge the reference capacitor to the preset reference voltage.

[0086] This embodiment uses two capacitors formed by three plates to detect the liquid level in sequence, and confirms the liquid level after two detections, which can effectively improve the accuracy of the detection.

[0087] Example 5

[0088] This embodiment provides a range hood, which includes an oil cup and the oil cup liquid level detection device of embodiment 1 or embodiment 2.

[0089] Since the range hood of this embodiment adopts the oil cup liquid level detection device of embodiment 1 or embodiment 2, the range hood of this embodiment can also achieve the effects of embodiment 1 or embodiment 2, which will not be described in detail here.

[0090] 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 device for detecting the liquid level of an oil cup, characterized in that: The detection device includes a first electrode plate, a second electrode plate, a control unit, a power supply and a reference capacitor; The first electrode plate and the second electrode plate are disposed in the oil cup, and the first electrode plate and the second electrode plate constitute a first capacitor; wherein the capacitance of the first capacitor increases as the liquid level in the oil cup increases; The control unit is configured to control the power supply to charge the first capacitor based on a first control signal, and to control the first capacitor to charge the reference capacitor based on a second control signal, and to determine the height of the liquid level in the oil cup according to a first charging time taken for the first capacitor to charge the reference capacitor to a preset reference voltage; Wherein, the second control signal is an inverted signal of the first control signal; The detection device further includes a third electrode plate; The third electrode plate is disposed in the oil cup, and the second electrode plate and the third electrode plate constitute a second capacitor. The first electrode plate, the second electrode plate, and the third electrode plate are sequentially disposed along the length of the oil cup; wherein the capacitance of the second capacitor increases as the liquid level in the oil cup increases; The control unit is further configured to control the reference capacitor to discharge based on a third control signal when the voltage across the reference capacitor reaches the preset reference voltage; and when the reference capacitor has completed discharging, controlling the power supply to charge the second capacitor based on a fourth control signal, and controlling the second capacitor to charge the reference capacitor based on a fifth control signal, and determining the height of the liquid level in the oil cup according to a second charging time for the second capacitor to charge the reference capacitor to a preset reference voltage; Wherein, the fifth control signal is an inverted signal of the fourth control signal; The first electrode plate, the second electrode plate, and the third electrode plate are fixed in the oil cup via silica gel, and a gap is left around the plate and the oil cup.

2. The oil cup liquid level detection device according to claim 1, characterized in that: The detection device further includes a switching unit and a comparison unit; The first electrode plate is connected to the power supply or one end of the reference capacitor through the switching unit, one end of the reference capacitor is connected to the first input end of the comparison unit, the output end of the comparison unit is connected to the control unit, the second input end of the comparison unit is connected to the reference power supply, the voltage of the reference power supply is a preset reference voltage, the control unit is further connected to the switching unit, and the other end of the second electrode plate and the reference capacitor is grounded; The control unit is further configured to send the first control signal to the switching unit so as to connect the first electrode plate to the power supply; and sending the second control signal to the switching unit to connect the first plate to the reference capacitor.

3. The oil cup liquid level detection device according to claim 1, characterized in that: The distance between the first electrode plate and the second electrode plate is smaller than the distance between the third electrode plate and the second electrode plate.

4. The oil cup liquid level detection device according to claim 2, characterized in that: The switching unit includes a first switch, a second switch, a third switch, a fourth switch and an inverter; One end of the inverter is connected to the control end of the control unit and the control end of the second switch respectively, and the other end is connected to the control end of the first switch; One end of the first switch is connected to the power supply, and the other end is connected to one end of the second switch, one end of the third switch, and one end of the fourth switch respectively; The other end of the second switch is connected to the first input end of the comparison unit; A control end of the third switch is connected to the control unit, and the other end of the third switch is connected to the first electrode plate; A control end of the fourth switch is connected to the control unit, and the other end of the fourth switch is connected to the third electrode plate.

5. The oil cup liquid level detection device according to claim 1, characterized in that: The detection device further includes a discharge unit; The discharge unit includes a fifth switch and a resistor; One end of the reference capacitor is connected to one end of the resistor via the fifth switch, a control end of the fifth switch is connected to the control unit, and the other end of the resistor is grounded; The control unit is further configured to send the third control signal to the control terminal of the fifth switch; The fifth switch connects the reference capacitor to the resistor based on the third control signal.

6. The oil cup liquid level detection device according to claim 1, characterized in that: If the first charging time reaches the preset charging time and / or the second charging time reaches the preset charging time, the control unit determines that the liquid level of the oil cup is full.

7. The oil cup liquid level detection device according to claim 6, characterized in that: The control unit is further configured to output a full cup prompt signal when the oil cup is full.

8. A method for detecting the liquid level of an oil cup, characterized in that: The detection method is implemented using the oil cup liquid level detection device according to claim 1, and the detection method includes: controlling the power supply to charge the first capacitor based on a first control signal; Controlling the first capacitor to charge the reference capacitor based on a second control signal; wherein the second control signal is an inverted signal of the first control signal; The liquid level height of the oil cup is determined according to a first charging time taken for the first capacitor to charge the reference capacitor to a preset reference voltage.

9. A range hood, characterized in that: The range hood comprises an oil cup and an oil cup liquid level detection device according to any one of claims 1 to 7.

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