Non-contact anti-overflow detection liquid heater

Abstract

The invention relates to kitchen appliances, in particular to a non-contact anti-overflow detection liquid heater which is characterized in that a PCB (printed circuit board) detection board for liquid level detection is mounted on the outer wall of a pulping container and comprises a substrate and capacitor pole pieces, and the capacitor pole pieces comprise a plurality of first capacitor pole pieces and a plurality of second capacitor pole pieces which are arranged at intervals; the first capacitor pole pieces form a water level detection area on the substrate, the second capacitor pole pieces form an anti-overflow detection area on the substrate, the anti-overflow detection area is located above the water level detection area, and the detection height of the single second capacitor pole piece is larger than that of the single first capacitor pole piece in the height direction of the substrate. According to the liquid heater, detection of water level signals of multiple different pulping capacities and detection of anti-overflow signals corresponding to the different pulping capacities can be achieved, detection of foam pulp overflow signals is more reliable, the anti-overflow signals can be more effectively recognized, and the safety risk of overflow of bubbles and foam pulp is not likely to exist.

Description

Technical Field

[0001] The invention relates to kitchen appliances, in particular to a non-contact anti-overflow detection liquid heater. Background Art

[0002] Prior art CN97225228.2 discloses a liquid level sensor that can detect the position of the milk liquid level without contacting the milk. The solution particularly emphasizes that the liquid level sensor is suitable for all other non-metallic containers that need to perform contactless liquid level control, because conductive metal containers will interfere with the induction of the liquid level sensor and affect the actual liquid level detection effect. At the same time, prior art CN200920291175.7 also discloses an easy-to-clean soybean milk machine, which is provided with a capacitor plate that can detect the change of liquid state, wherein the capacitor plate is a circular metal sheet, or a plurality of capacitor plates arranged around the machine head or cup body, and the capacitor induction effect is used to achieve overflow prevention, dry burning prevention and water level detection. Compared with previous soybean milk machines, since there is no need to drill holes on the lower cover of the machine head to install overflow prevention electrodes, it can not only reduce the hidden danger of water entering the machine head, but also improve the convenience of cleaning the soybean milk machine. However, the capacitor plates arranged on the soymilk machine need to be arranged around the machine head or the cup body, the capacitor plates occupy a large space, and the installation is relatively complicated.

[0003] In order to further simplify the non-contact capacitive liquid level detection device, the prior art discloses a capacitive water level stepless detection device, including a capacitive slider formed by a number of equidistantly arranged capacitive sensors, and the capacitive slider is connected to a chip through an induction line, and the chip is connected to a central processing unit through a signal line, and the central processing unit is connected to a water level display. When working, under the control of the chip, the data detected by the capacitive sensor is transmitted to the central processing unit, and the central processing unit processes the received data and transmits it to the water level display to display the current water level. The structure is simple, and the stepless detection of the water level can be realized. In addition, the detection method is not affected by the water temperature, and can effectively avoid the parasitic characteristics caused by the change of the detection environment and other factors such as the water temperature, which leads to the problem of inaccurate water level detection. The inventor has found that for this scheme, although the signal induction detection of water has a high accuracy, for the detection of water or other liquid substances in non-liquid shape, such as bubbles, foams, slurry substances such as slurry substances, on the one hand, due to the poor conductivity of the above substances, the capacitive sensor senses a small change in capacitance value, and the chip cannot distinguish whether it is a liquid level signal or a parasitic capacitance. On the other hand, when the liquid produces bubbles, foam, slurry, especially slurry foam, there will be a thicker slurry layer above the liquid surface. In addition, due to the presence of foam in the slurry layer, the slurry will be blocked from contacting the cup wall, resulting in a distance gap between the slurry and the cup wall, affecting the capacitance value sensed by the capacitive sensor. Moreover, the surface of the slurry layer is not flat. Generally, the slurry in the center of the cup body is higher, while the slurry in contact with the cup wall is lower, and even the height of the slurry in contact with different positions of the cup wall is different. The capacitive sensor may not be able to sense the specific capacitance value or the sensed capacitance value is small. Therefore, the chip cannot identify the specific position of the liquid level, which is prone to overflow safety risks. Therefore, this solution is generally suitable for water level signal detection of health pots, etc.

[0004] At the same time, the prior art CN201610753199.4 also discloses an anti-overflow method and a food processor, on which a signal PCB board is installed, and metal sheets of the same size are equidistantly arranged on the signal PCB board. When the volume of the liquid level in the cup body gradually increases, the capacitance formed by the metal sheet and the liquid in the cup body will increase, thereby realizing the detection of the water level signal and the anti-overflow signal by sensing the liquid level using the metal sheet. However, the anti-overflow detection position of this scheme is the highest fixed position located on the PCB board. In actual use, the metal sheet below the anti-overflow detection position can recognize the water level signal. However, based on the characteristics of slurry foam and slurry foam, the fixed anti-overflow detection position is greatly affected by external parasitic capacitance and cannot accurately identify the anti-overflow signal of the slurry. At the same time, since the surface of the slurry foam is not flat, the fixed anti-overflow detection position may cause the detected anti-overflow position to deviate greatly from the actual slurry foam position, and there is a safety risk of overflow.

[0005] In addition, the prior art CN201921962352.X also discloses a capacitive continuous liquid level detection structure and an electric kettle thereof, wherein the liquid level detection structure has two parallel-arranged sensing electrode sheets, and also discloses detecting the height of the water level by a duty cycle. In this scheme, the outer surface of the kettle body of the electric kettle is an arc-shaped structure, so it is necessary to use a soft PFB board to be installed on the outer wall of the kettle body by pasting. The inventors of the present invention have found that since two sensing electrode sheets are arranged on the PFB soft board, the sensing electrode sheets arranged in an arc shape on the outer wall of the kettle body will show a change in capacitance value when the water level rises, and the sensing part near the actual water level can also sense the change in capacitance value, while the water level calculated according to the duty cycle will deviate from the actual water level, and the accuracy of detection will be reduced. Fortunately, for the electric kettle, the detection deviation of the water level is not serious and will not cause safety risks. However, the inventors further discovered that this solution can only be used for water level detection in electric kettles, but cannot detect overflow prevention signals because the conductivity of bubbles and foams is reduced, and the sensitivity of the sensing electrode to bubbles and foams is reduced. Moreover, the unevenness of the surface of bubbles and foams will further increase the error of the arc-shaped PFB soft board detection. Based on this, this solution is less suitable for detecting overflow prevention signals and is prone to the safety risk of pulping overflow. Summary of the invention

[0006] The purpose to be achieved by the present invention is to provide a liquid heater with non-contact anti-overflow detection. The liquid heater can realize water level signal detection of multiple different pulping capacities and anti-overflow signal detection corresponding to different pulping capacities, thereby realizing intelligent production of slurry beverages with different pulping capacities. Moreover, the detection of foam-type slurry overflow signals generated in the pulping process is more reliable, and the anti-overflow signals can be more effectively identified, and there is no safety risk of overflow of bubbles and foam-type slurries.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a non-contact anti-overflow detection liquid heater, comprising a pulping container and a main control device, wherein a PCB detection board for liquid level detection is installed on the outer wall of the pulping container, and the PCB detection board is electrically connected to the main control device, characterized in that: the PCB detection board comprises a strip-shaped substrate, a capacitor electrode piece installed on the substrate, a control chip and an output terminal, the capacitor electrode piece is electrically connected to the control chip, and the control chip is connected to the main control device through the output terminal, the capacitor electrode piece comprises a plurality of first capacitor electrode pieces and a plurality of second capacitor electrode pieces arranged at intervals, the plurality of first capacitor electrode pieces form a water level detection area on the substrate, and the plurality of second capacitor electrode pieces form an anti-overflow detection area on the substrate, and the anti-overflow detection area is located above the water level detection area, wherein the plurality of first capacitor electrode pieces and the plurality of second capacitor electrode pieces are electrically connected to the control chip one by one through the printed circuits on the substrate, and along the height direction of the substrate, the detection height of a single second capacitor electrode piece is greater than the detection height of a single first capacitor electrode piece.

[0008] Furthermore, a dividing groove is provided on the anti-overflow detection area of ​​the substrate, and the dividing groove divides the anti-overflow detection area into a first sub-anti-overflow detection area and a second sub-anti-overflow detection area arranged side by side, and each second capacitor electrode is divided into two sub-electrode pieces respectively located in two columns of sub-anti-overflow detection areas, and each sub-electrode piece of the two columns of sub-anti-overflow detection areas is electrically connected to the control chip one by one through printed circuits, wherein, at the same liquid level height below the highest point of the anti-overflow detection area, the sensing area of ​​the first sub-anti-overflow detection area is not equal to the sensing area of ​​the second sub-anti-overflow detection area.

[0009] Furthermore, when the overflow prevention signal detection is performed at the same time, the capacitance value increment detected by each sub-electrode piece in the first sub-overflow prevention detection area is accumulated to ΔC tri1 The capacitance increment detected by each sub-electrode in the second sub-overflow detection area is accumulated to ΔC tri2 , wherein the control chip is based on ΔC tri1 With ΔC tri2 The ratio of determines the current overflow prevention detection position;

[0010] Alternatively, the capacitance value sensed by a single second capacitor electrode piece is formed by the accumulation of the capacitance values ​​detected by the sub-electrode piece corresponding to the first sub-overflow prevention detection area and the sub-electrode piece corresponding to the second sub-overflow prevention detection area, wherein, when performing overflow prevention signal detection at the same time, the control chip determines the current overflow prevention detection position according to the capacitance value difference between two adjacent second capacitor electrodes;

[0011] Alternatively, the dividing groove is a straight dividing groove arranged obliquely relative to the substrate;

[0012] Alternatively, the dividing groove is a curved dividing groove;

[0013] Alternatively, the total sensing area of ​​the first anti-overflow detection sub-zone is equal to the total sensing area of ​​the second anti-overflow detection sub-zone.

[0014] Furthermore, the first capacitor electrodes are arranged equidistantly in the water level detection area, and the detection height of a single first capacitor electrode is Among them, V L is the minimum pulping capacity of the pulping container, V H The pulping container has a maximum pulping capacity and is at least between the minimum pulping capacity and the maximum pulping capacity and has a cylindrical structure. r is the radius of the cylindrical pulping container. n is the number of first capacitor electrodes in the water level detection area, and the spacing between adjacent first capacitor electrodes is Δh.

[0015] Furthermore, the second capacitor electrodes are arranged equidistantly in the overflow prevention detection area, and the detection height of a single second capacitor electrode is The height from the bottom of the water level detection area on the substrate to the top of the overflow prevention detection area is Hm, N is the number of overflow prevention detection gears corresponding to different pulping capacities, and the spacing between adjacent second capacitor electrodes is Δh, wherein, N and n are integers.

[0016] Furthermore, the detection height of a single second capacitor electrode piece is not less than twice the detection height of a single first capacitor electrode piece;

[0017] Alternatively, the detection height of a single second capacitor electrode is 8 mm to 12 mm;

[0018] Alternatively, each first capacitor electrode is used to detect a different pulping capacity liquid level, and each second capacitor electrode is used to detect a different anti-overflow detection liquid level, wherein each pulping capacity liquid level on the water level detection area has a corresponding second capacitor electrode on the anti-overflow detection area for anti-overflow liquid level detection.

[0019] Furthermore, a mesh shielding layer is attached to the substrate, and the mesh shielding layer is grounded.

[0020] Furthermore, the capacitor electrode is attached to the front surface of the substrate facing the pulping container, the grid shielding layer includes a first shielding layer attached to the rear surface of the substrate and a second shielding layer attached to the front surface of the substrate, the second shielding layer is enclosed along the edge of the substrate outside the water level detection area and the anti-overflow detection area, and the lower side of the second shielding layer is open;

[0021] Alternatively, the mesh shielding layer is a copper-clad mesh.

[0022] Furthermore, the capacitor electrode is attached to the front surface of the substrate facing the pulping container, the control chip and the output terminal are arranged on the rear surface of the substrate, and the control chip and the output terminal are located below the water level detection area, wherein a grid shielding layer corresponding to the capacitor electrode is also arranged on the rear surface of the substrate, and the printed circuit is attached to the rear surface of the substrate and routed along the outer peripheral edge of the grid shielding layer.

[0023] Furthermore, a third capacitor electrode is disposed on the substrate above the anti-overflow detection area, and the third capacitor electrode is used to assist in the detection of dangerous overflow signals.

[0024] In the prior art, the capacitor electrode detects the water level and anti-overflow signal and also utilizes the principle of touch sensing. When the capacitor electrode is close to the liquid, it will sense the capacitance value, and the control chip will indirectly judge the water level signal and the anti-overflow signal according to the fluctuation of the capacitance value. The inventor has found through continuous research that the capacitance value of the capacitor electrode sensing the liquid signal has a large range of variation. When the capacitor electrode is close to the liquid, the capacitance value fluctuates greatly, and when it is far away, the capacitance value fluctuates less. At the same time, the capacitance value fluctuation generated by the capacitor electrode is also related to the liquid form and conductivity. When the liquid is pure liquid and has strong conductivity, the capacitance value fluctuates greatly, which can realize accurate detection of the liquid level. When the liquid is in the form of bubbles or foam, the capacitance value fluctuates relatively little due to the reduced conductivity. It is precisely because the capacitance value induced by the capacitor electrode fluctuates less when the liquid is in the form of bubbles or foam, and the control chip cannot determine whether it is a liquid level signal. Moreover, the capacitance change produced by the capacitor electrode will also be affected by environmental factors, which can easily form parasitic capacitance, and the parasitic capacitance will also cause the capacitor electrode to sense smaller capacitance fluctuations, and the control chip may also misjudge. For example, when a person's hand is close to the capacitor electrode, the capacitance value will also fluctuate. At this time, the control chip cannot distinguish whether it is an interference capacitance value or an actual liquid level capacitance value, or water droplets on the outer wall of the pulping container will also cause the capacitor electrode to sense the fluctuation of the capacitance value, and the control chip may misjudge. In addition, although the existing capacitor electrode can be used to detect both water level signals and overflow prevention signals, for slurries formed by bubbles, foams, etc., due to the uneven surface of the slurry, the existing fixed overflow prevention capacitor electrode cannot accurately identify the actual slurry height, and the slurry is more likely to overflow.

[0025] For the liquid heater of the present invention, a water level detection area and an anti-overflow detection area are arranged by a plurality of first capacitor electrodes and a plurality of second capacitor electrodes at intervals on the PCB detection board, which can realize water level detection of a variety of different pulping capacities, and can also realize detection of different anti-overflow signals corresponding to a variety of different pulping capacities. Compared with the existing anti-overflow detection position with only one fixed position, the liquid heater of the present invention can realize more intelligent production of slurry beverages, with higher pulping efficiency. While ensuring the production of one or more beverages, it can also solve the problems of only one fixed anti-overflow detection position in the prior art that is prone to failure, long anti-overflow time, and slurry foam sticking to the wall. In addition, the present invention adopts different anti-overflow detection positions corresponding to different pulping capacities, which not only ensures that the problem of slurry overflow does not occur, but also has a higher space utilization rate of the pulping container, can achieve the optimization of pulping efficiency, and avoid the problem of long pulping time or poor crushing.

[0026] Among them, the first capacitor electrode in the water level detection area is used to detect the pulping water level under the corresponding pulping capacity, and the second capacitor electrode in the anti-overflow detection area is used to detect the anti-overflow height reached by the slurry under the corresponding pulping capacity during the pulping process. When the second capacitor electrode detects that the slurry of the current pulping capacity has reached the preset anti-overflow detection position, the control chip will transmit the signal to the main control device, and the main control device will perform corresponding operations according to the program settings, such as stopping the motor and stopping the heating to wait for overflow. However, during the pulping process, when the slurry is whipped or heated, bubbles, foam and other substances will rise on the surface of the slurry, and the capacitance value of the capacitor electrode sensing bubbles and foam fluctuates slightly, and the control chip cannot accurately identify whether it is a parasitic capacitor or an actual anti-overflow signal. For the liquid heater of the present invention, since the detection height of a single second capacitor electrode is greater than the detection height of a single first capacitor electrode, the second capacitor electrode has a larger sensing area during actual detection, and can obtain a larger fluctuating capacitance value, thereby achieving more accurate anti-overflow signal detection. Compared with the prior art, it can detect rising bubbles, foams and other anti-overflow signals, effectively solving the problem that the existing single type of capacitor electrode can only detect the water level more accurately but cannot effectively detect the anti-overflow signal, and greatly reducing the safety risk of overflow of bubbles, foams and other slurries that are prone to occur during the application of the existing capacitive anti-overflow detection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings:

[0028] Figure 1 It is a structural schematic diagram of a first embodiment of a liquid heater of the present invention;

[0029] Figure 2 for Figure 1 Schematic diagram of the front surface structure of the PCB test board;

[0030] Figure 3 for Figure 1 Schematic diagram of the rear surface structure of the PCB inspection board;

[0031] Figure 4 for Figure 1 The topological circuit diagram of the PCB detection board;

[0032] Figure 5 This is a schematic diagram of the structure of the second embodiment of the PCB detection board of the present invention. DETAILED DESCRIPTION

[0033] Embodiment 1:

[0034] like Figure 1 , Figure 2 , Figure 3 , Figure 4 The figure shows a schematic diagram of the structure of a liquid heater of the present invention. The liquid heater is a food processing machine for making soy milk beverages, comprising a glass cup body 1 forming a pulping container 10 and a cup cover 2 mounted on the glass cup body 1, a heating device 4 for heating the pulping container 10 is arranged at the bottom of the glass cup body 1, and a motor 3 is arranged in the mounting cavity 20 below the glass cup body 1, a rotating shaft driven by the motor 3 passes through the bottom of the glass cup body 1 and extends into the pulping container 10, and a crushing device (not marked in the figure) is connected to the end of the rotating shaft, a PCB detection board 5 for liquid level detection is installed on the outer side of the side wall of the glass cup body 1, the PCB detection board 5 is installed between the glass cup body 1 and a handle (not marked in the figure), and a main control device (not drawn in the figure) is also arranged in the mounting cavity 20 below the glass cup body 1, and the main control device is electrically connected to the motor 3, the heating device 4 and the PCB detection board 5 respectively.

[0035] The PCB detection board 5 includes a strip-shaped substrate 51, a capacitor electrode installed on the substrate, a control chip 52 and an output terminal 53. The capacitor electrode is electrically connected to the control chip 52, and the control chip 52 is connected to the main control device through the output terminal 53. The capacitor electrode includes a plurality of first capacitor electrodes 54a and a plurality of second capacitor electrodes 54b arranged at intervals. The plurality of first capacitor electrodes 54a form a water level detection area 55a (a dotted box below the W plane) on the substrate 51, and the plurality of second capacitor electrodes 54b An anti-overflow detection area 55b (a dotted frame above the W plane) is formed on the substrate 51, and the anti-overflow detection area 55b is located above the water level detection area 55a, wherein different first capacitor electrodes 54a correspond to different pulping capacity liquid levels on the water level detection area 55a, and different second capacitor electrodes 54b correspond to different anti-overflow detection positions on the anti-overflow detection area 55b, and each pulping capacity liquid level on the water level detection area 55a has a corresponding second capacitor electrode 54b on the anti-overflow detection area 55b to realize detection of the anti-overflow detection position. In addition, the plurality of first capacitor electrodes 54a and the plurality of second capacitor electrodes 54b are electrically connected to the control chip 52 one by one through the printed circuits (not shown) on the substrate 51, and along the height direction of the substrate 51, the detection height of a single first capacitor electrode 54a is smaller than the detection height of a single second capacitor electrode 54b.

[0036] In this embodiment, the first capacitor electrode 54a and the second capacitor electrode 54b are both attached to the front surface of the substrate 51 facing the glass cup body 1, and the control chip 52 and the output terminal 53 are arranged on the rear surface of the substrate 51, and the control chip 52 and the output terminal 53 are both located below the water level detection area 55. At the same time, a mesh shielding layer is also attached to the substrate 51, and the mesh shielding layer is grounded. The mesh shielding layer includes a first shielding layer 57a attached to the rear surface of the substrate 51 and a second shielding layer 57b attached to the front surface of the substrate 51. The second shielding layer 57b is enclosed along the edge of the substrate 51 on the outside of the water level detection area 55a and the anti-overflow detection area 55b, and the lower side of the second shielding layer 57b is open 571. In this embodiment, the mesh shielding layer is a copper-clad mesh, which is used to shield the inductive interference of external parasitic capacitance on the capacitor electrode. In this embodiment, the printed circuit is attached to the rear surface of the substrate 51, and the input end passes through the substrate 51 and is electrically connected to each capacitor electrode, and the output end of the printed circuit is routed along the outer peripheral edge of the grid shielding layer, wherein the output end of the printed circuit can pass through the lower opening of the second shielding layer 57b and be electrically connected to the control chip 52.

[0037] Moreover, in the present embodiment, a dividing groove 58 is provided on the overflow prevention detection area 55b of the substrate 51, and the dividing groove 58 divides the overflow prevention detection area 55b into a first sub-overflow prevention detection area tri1 and a second sub-overflow prevention detection area tri2 arranged side by side, and each second capacitor electrode 54b is divided into two sub-electrode plates respectively located in two columns of sub-overflow prevention detection areas, and each sub-electrode plate of the two columns of sub-overflow prevention detection areas is electrically connected to the control chip 52 one by one through printed circuits, wherein, at the same liquid level height below the highest point of the overflow prevention detection area 55b, the sensing area of ​​the first sub-overflow prevention detection area tri1 is not equal to the sensing area of ​​the second sub-overflow prevention detection area tri2, and in the present embodiment, the dividing groove 58 is inclined along the diagonal of the overflow prevention detection area 55b to divide the overflow prevention detection area 55b into two triangular sub-overflow prevention detection areas of equal area.

[0038] In the prior art, the capacitor electrode detects the water level and anti-overflow signal and also utilizes the principle of touch sensing. When the capacitor electrode is close to the liquid, it will sense the capacitance value, and the control chip will indirectly judge the water level signal and the anti-overflow signal according to the fluctuation of the capacitance value. The inventor has found through continuous research that the capacitance value of the capacitor electrode sensing the liquid signal has a large range of variation. When the capacitor electrode is close to the liquid, the capacitance value fluctuates greatly, and when it is far away, the capacitance value fluctuates less. At the same time, the capacitance value fluctuation generated by the capacitor electrode is also related to the liquid form and conductivity. When the liquid is pure liquid and has strong conductivity, the capacitance value fluctuates greatly, which can realize accurate detection of the liquid level. When the liquid is in the form of bubbles or foam, the capacitance value fluctuates relatively little due to the reduced conductivity. It is precisely because the capacitance value induced by the capacitor electrode fluctuates less when the liquid is in the form of bubbles or foam, and the control chip cannot determine whether it is a liquid level signal. Moreover, the capacitance change produced by the capacitor electrode will also be affected by environmental factors, which can easily form parasitic capacitance, and the parasitic capacitance will also cause the capacitor electrode to sense smaller capacitance fluctuations, and the control chip may also misjudge. For example, when a person's hand is close to the capacitor electrode, the capacitance value will also fluctuate. At this time, the control chip cannot distinguish whether it is an interference capacitance value or an actual liquid level capacitance value, or water droplets on the outer wall of the pulping container will also cause the capacitor electrode to sense the fluctuation of the capacitance value, and the control chip may misjudge. In addition, although the existing capacitor electrode can be used to detect both water level signals and overflow prevention signals, for slurries formed by bubbles, foams, etc., due to the uneven surface of the slurry, the existing fixed overflow prevention capacitor electrode cannot accurately identify the actual slurry height, and the slurry is more likely to overflow.

[0039] For the food processing machine of this embodiment, the PCB detection board is provided with a water level detection area and an anti-overflow detection area respectively arranged by a plurality of first capacitor electrodes and a plurality of second capacitor electrodes, which can realize the water level detection of a variety of different pulping capacities, and can also realize the detection of different anti-overflow signals corresponding to a variety of different pulping capacities. Compared with the existing anti-overflow detection position with only one fixed position, the food processing machine of this embodiment can realize more intelligent production of slurry beverages, with higher pulping efficiency. While ensuring the production of one or more beverages, it can also solve the problems of only one fixed anti-overflow detection position in the prior art that is prone to failure, long anti-overflow time, and slurry foam hanging on the wall. In addition, the present invention adopts different anti-overflow detection positions corresponding to different pulping capacities, which not only ensures that the problem of slurry overflow does not occur, but also has a higher space utilization rate of the pulping container, can achieve the optimization of pulping efficiency, and avoid the problem of long pulping time or poor crushing.

[0040] Among them, the first capacitor electrode in the water level detection area is used to detect the pulping water level under the corresponding pulping capacity, and the second capacitor electrode in the anti-overflow detection area is used to detect the anti-overflow height reached by the slurry under the corresponding pulping capacity during the pulping process. When the second capacitor electrode detects that the slurry of the current pulping capacity has reached the preset anti-overflow detection position, the control chip will transmit the signal to the main control device, and the main control device will perform corresponding operations according to the program settings, such as stopping the motor and stopping the heating to wait for overflow. However, during the pulping process, when the slurry is whipped or heated, bubbles, foam and other substances will rise on the surface of the slurry, and the capacitance value of the capacitor electrode sensing bubbles and foam fluctuates slightly, and the control chip cannot accurately distinguish whether it is a parasitic capacitor or an actual anti-overflow signal. As for the food processing machine of the present invention, since the detection height of a single second capacitor electrode is greater than the detection height of a single first capacitor electrode, the second capacitor electrode has a larger sensing area during actual detection, and can obtain a larger fluctuating capacitance value, thereby achieving more accurate anti-overflow signal detection. Compared with the prior art, it can detect rising bubbles, foams and other anti-overflow signals, effectively solving the problem that the existing single type of capacitor electrode can only detect the water level more accurately but cannot effectively detect the anti-overflow signal, and greatly reducing the safety risk of overflow of bubbles, foams and other slurries that are prone to occur during the application of the existing capacitive anti-overflow detection technology.

[0041] Since the non-contact PCB detection board is bonded to the outside of the glass, and considering that the non-contact PCB detection board detects and judges the liquid level signal by detecting the change in capacitance value, the presence of water flow during the user's use, the user touching the installation structure position of the PCB detection board, etc., will cause the capacitance value of the capacitor electrode on the PCB detection board to change, resulting in abnormal liquid level detection, overflow during the pulping process, and other risks. In this embodiment, the three-sided copper shielding of the water level detection area and the anti-overflow detection area on the substrate of the PCB detection board and the grid copper shielding on the rear surface of the substrate can eliminate the inductive interference of the outside world on the capacitor electrode to the maximum extent, effectively solve the abnormal capacitance value fluctuation caused by the presence of condensed water on the side of the PCB detection board after assembly or the user's hand touching, resulting in abnormal detection results, and ensure detection reliability.

[0042] It should be noted that the pulping container in this embodiment is in the shape of a straight barrel, and the PCB detection board can be used for detecting both the water level signal and the anti-overflow signal, and the substrate of the PCB detection board is a hard board, and the PCB detection board is arranged vertically on the outer wall of the pulping container, which can effectively prevent the arc structure of the pulping container from causing the capacitor electrode to sense the non-demand capacitance value. In this embodiment, the minimum pulping capacity is not lower than the lower limit of the lowest first capacitor electrode, so as to ensure that at least one capacitor electrode detects the water level. The maximum pulping capacity is generally not higher than the lower limit of the lowest second capacitor electrode or is located between the highest first capacitor electrode and the lowest second capacitor electrode, so as to ensure that there is at least one inter-electrode capacitance difference detection judgment point. Similarly, the minimum anti-overflow detection position is generally not lower than the lowest second capacitor electrode, so that the second capacitor electrode can sense the anti-overflow signal, and the maximum anti-overflow detection position corresponding to the maximum pulping capacity should be lower than the lower limit of the highest second capacitor electrode, so that the highest second capacitor electrode can be used as the last auxiliary anti-overflow safety detection.

[0043] In this embodiment, the first capacitor electrodes on the water level detection area are arranged equidistantly, and the detection height h of the water level detection area is actually the maximum pulping capacity V H With minimum pulping capacity V L The height between them has the following relationship: Where r is the radius of the pulping container, n is the number of first capacitor electrodes, Δh is the spacing between adjacent first capacitor electrodes, and h n is the detection height of a single first capacitor electrode. It can be seen that for the first capacitor electrode of this embodiment, In this embodiment, n first capacitor electrodes are provided in the water level detection area, that is, the water level detection area has n different pulping capacities.

[0044] Moreover, in the present embodiment, the second capacitor electrodes on the anti-overflow detection zone are also arranged at an equal distance of Δh, wherein the distance between the highest first capacitor electrode and the lowest second capacitor electrode is also Δh. At the same time, in the present embodiment, for n different pulping capacities, the anti-overflow detection zone has corresponding anti-overflow detection gears, wherein the number of anti-overflow detection gears is set to N. At the same time, in order to increase the safety of anti-overflow detection, a second capacitor electrode needs to be added to the substrate to be used as an anti-overflow detection electrode. Based on this, the number of second capacitor electrodes in the anti-overflow detection zone is N+1, and the first N second capacitor electrodes correspond to N anti-overflow detection positions, and N anti-overflow detection positions correspond to n different pulping capacities. Set H m is the detection height of the PCB detection board, that is, the sum of the heights of the water level detection area and the overflow prevention detection area. Among them, the height of the overflow prevention detection area satisfies H=H m -h=(N+1)h N +NΔh,h N is the detection height of a single second capacitor electrode, that is, And N and n satisfy: Both N and n are integers.

[0045] Generally, the detection height h of a single first capacitor electrode is n The detection height h of a single second capacitor electrode is selected to be 3mm to 6mm. N Generally, it is not less than 2 times the detection height of a single first capacitor electrode, which is generally selected to be 8mm to 12mm. Among them, the first capacitor electrode in this embodiment is preferably selected to be 4mm to 5mm, and the second capacitor electrode is preferably selected to be 10mm.

[0046] It should be noted that the capacitor electrode at the highest point of the overflow prevention detection area is used to assist in the detection of dangerous overflow signals, which can effectively prevent the overflow safety risk caused by the failure of the maximum overflow prevention detection gear corresponding to the maximum pulping capacity, and is the last safety guarantee to prevent slurry overflow. Therefore, for this embodiment, a third capacitor electrode can be separately set on the substrate above the overflow prevention detection area to assist in the detection of dangerous overflow signals. At this time, the number of second capacitor electrodes corresponding to the water level detection area is the same as the number of overflow prevention gears, both of which are N, and the detection height of a single second capacitor electrode satisfies

[0047] like Figure 4As shown, it is the circuit layout topology diagram of the PCB test board of the present embodiment, the contactless PCB test board includes a control part and an electrode part (capacitor electrode piece), the electrode part is configured with a multi-section capacitor electrode piece and is connected one by one with the control MCU (control chip), the device of the control part is placed on the other side of the substrate relative to the capacitor electrode piece, the bottom of the control part is provided with an interface module (output terminal), the terminal of the interface module adopts a patch mode, the control MCU is arranged on the top of the interface part, and the reset circuit module, the power circuit module, the output circuit module and the burning port are respectively configured on both sides of the control MCU. Wherein, the control MCU has a rewritable storage module, and the control program can be repeatedly updated to the storage module through the burning port, and the update of the control program can be realized. For the present embodiment, the reliability of the control system is guaranteed by setting the PCB test board topology structure, and the setting of the interface position guarantees that the installation position is minimized, and the cost of the PCB test board is reduced while improving the reliability. In addition, the capacitor electrode piece and other device partitions are arranged, which is conducive to improving the anti-interference ability and ensuring the reliability.

[0048] For the PCB detection board of this embodiment, different detection and control methods are used in different pulping stages. In the process of making drinks, the food processing machine of this embodiment has a water level detection stage for detecting water added by the user or automatic water inflow and an anti-overflow detection stage for detecting the pulping process.

[0049] Water level detection stage: The control chip on the PCB detection board starts to detect the capacitance value on the first capacitor electrode in real time, and determines whether the user has placed the material to the preset water level. During the real-time detection process, at a certain moment, only one of the multiple first capacitor electrodes is in the induction state, and the other capacitor electrodes are grounded, so that it can be ensured that only one capacitor electrode can generate a capacitance value at each cycle, so as not to be affected by the induction of other capacitor electrodes. The PCB detection board detects the capacitance value change process of each capacitor electrode from bottom to top. When it is detected that the capacitance value of the segmented electrode is in an obvious change process in turn, it is judged as the material placement process. When the capacitance value of the upper capacitor electrode of a certain segmented electrode does not change, the control chip confirms that the current liquid level is at the water level position corresponding to this capacitor electrode. When it is detected that the capacitance value of the segmented electrode has not changed significantly, it is judged that the user has placed the material and then powered on, and then detects the change in the capacitance value difference between the segmented electrodes. When the capacitance value difference between two adjacent segmented electrodes has a significant change, the control chip determines that the current liquid level is at the position of this segmented electrode.

[0050] like Figure 2 In the PCB detection board shown, the control chip detects the capacitance value of the first capacitor electrode of each segment in turn at a set time frequency t0, and the control chip calculates the capacitance difference ΔC between the electrodes according to the capacitance value of each segment electrode.Ln-Ln-1 , confirm that the point with the maximum capacitance difference is the current water level.

[0051] For example, at time point T1-n*t0 (n is the number of first capacitor electrodes), the control chip detects that L1 has a significant change. As the detection time approaches T1, the capacitance difference between the segmented first capacitor electrode L2 and the segmented first capacitor electrode L1 continues to increase, while the capacitance difference of other segmented electrodes remains basically unchanged. Therefore, the control chip confirms that the capacitance difference ΔC between the segmented first capacitor electrode L2 and the segmented first capacitor electrode L1 is L2-L1 Maximum, the control chip confirms that the current water level is between L1 and L2.

[0052] For the existing non-contact water level detection, the water level detection is basically carried out by using the capacitance change of a single capacitor electrode. Since the capacitor electrode is non-continuous, the temperature difference between the electrodes is obvious, and the capacitance value of the capacitor electrode is greatly affected by the slurry temperature and the ambient temperature. Therefore, it is easy to cause misjudgment and increase the probability of water level detection failure. However, this embodiment controls the chip to dynamically track and detect the capacitance difference between the first capacitor electrodes of two adjacent segments, and determines that the maximum capacitance difference is the current water level position, which effectively solves the problem of water level misjudgment. Similarly, this water level detection method can also be applied to overflow prevention signal detection. However, due to the foam characteristics of the slurry, the detection method has a slightly poor detection effectiveness.

[0053] For this embodiment, the detection of water level signals also includes other detection methods, such as detection based on the capacitance fluctuation amount sensed by a single first capacitor electrode. The control chip still detects the capacitance value of each segmented first capacitor electrode in a cycle within the set time, and at any time, only one capacitor electrode is powered on for detection, and the other capacitor electrodes are in a grounded state. When the capacitance fluctuation amount sensed by a first capacitor electrode is greater than the fluctuation threshold value preset by the control chip, the control chip determines that the water level has reached the pulping water level corresponding to the first capacitor electrode, otherwise, each segmented capacitor electrode still detects in a cycle.

[0054] For the PCB detection board of this embodiment, the above two water level signal detection methods are compatible. When any of the above methods obtains the current water level signal, the control chip will feed back the signal to the main control device. The main control device determines the corresponding pulping program according to the corresponding water level signal to realize the subsequent slurry production. Of course, for the above methods, when one of the detection methods obtains the water level signal, the other detection method can also be re-checked. Through the double water level signal detection, the water level signal detection can be more accurate to prevent the influence of external parasitic capacitance.

[0055] After the water level detection stage, the slurry production process begins. At the same time, during the slurry production process, the PCB detection board also needs to perform overflow signal detection in the overflow detection stage.

[0056] Overflow prevention detection stage: For this embodiment, the overflow prevention detection area includes multiple second capacitor electrodes, and the overflow prevention detection area is provided with a dividing groove arranged along the diagonal of the rectangle. The dividing groove divides the overflow prevention detection area into two triangular sub-overflow detection areas. At the same time, at the same liquid level height, the sensing areas corresponding to the two sub-overflow detection areas are not equal.

[0057] like Figure 2 As shown in the figure, the overflow prevention detection area is divided into a first sub-overflow prevention detection area tri1 and a second sub-overflow prevention detection area tri2 in two columns of left and right triangles by a dividing groove, with the tip of tri1 facing upward and the tip of tri2 facing downward, and tri1 and tri2 are respectively configured as multiple segmented sub-pole pieces. Similarly, when the overflow prevention signal is detected at a certain moment, the control chip detects the capacitance value of each sub-pole piece in the left and right triangular areas in turn at a set time frequency t0, and accumulates the increments of the capacitance values ​​sensed by each sub-pole piece of tri1 and tri2, respectively, to obtain ΔC tri1 With ΔC tri2 The control chip then calculates the ratio of the accumulated value of the capacitance value increments on both sides. Determine the current overfill prevention signal height.

[0058] At the same time, during the pulping process, the foam height on the slurry surface is not flat, with some areas being higher and some areas being lower. Therefore, during the overflow prevention detection process, the capacitance values ​​sensed by the sub-electrodes of tri1 and tri2 will jump, and different liquid heating structures will cause differences in the installation of the PCB detection board relative to the pulping container. Based on this, the control chip will compare the values. Perform the corresponding correction calculation to obtain (η is the correction coefficient, and liquid heaters with different structural forms have corresponding correction coefficients).

[0059] At the same time, the control chip is also preset with K0, where the preset value K0 is the height ratio of the left and right sub-overflow detection areas at the same overflow prevention height. When K is close to or equal to K0, the control chip confirms the overflow prevention height reached by the current foam, and the control chip then feeds back the overflow prevention signal to the main control device to implement corresponding program operations, such as motor stop or heating stop, etc., thereby effectively preventing the safety risk of foam overflow. Of course, for this embodiment, the control chip can also preset the total height H of the overflow prevention detection area. During the overflow prevention detection process, the control chip calculates the incremental ratio of the capacitance value of the first sub-overflow prevention detection area to that of the second sub-overflow prevention detection area. The control chip determines the current anti-overflow height according to the ratio of K to H. Of course, different liquid heater control chips will also correct the K value with different correction coefficients η.

[0060] Since the existing non-contact liquid level detection basically uses the change in the capacitance value of a single electrode for overflow prevention liquid level detection, when pulping, there will be a thicker slurry foam layer above the liquid surface, and the presence of foam in the slurry foam layer will prevent the slurry foam from contacting the cup wall, resulting in a distance gap between the slurry foam and the cup wall, which will affect the capacitance value sensed by a single electrode. Moreover, the surface of the slurry foam layer is not flat, and the slurry foam in the center area of ​​the pulping container is not the same height as the slurry foam on the cup wall. Even the height of the slurry foam at different positions of the cup wall is different. A single electrode can only sense a certain value, and this certain value does not necessarily reflect the current slurry foam height. For example, when there are large bubbles in the middle layer of the slurry foam, the slurry foam in the lower layer of the bubbles and the slurry foam in the upper layer of the bubbles will be sensed by a single electrode. However, a single electrode can only sense a maximum capacitance value. Based on this, a single electrode cannot convey to the control chip the existence of slurry foam in the upper layer of the bubbles, causing the control chip to be unable to identify the slurry foam overflow prevention signal in the upper layer of the bubbles. At the same time, the capacitance value change sensed by a single electrode will also be affected by the slurry temperature, ambient temperature, etc., and it is impossible to accurately detect the overflow prevention position, and there is a problem of large detection deviation. Therefore, in the pulping process, it is easy to have overflow prevention misjudgment, resulting in overflow prevention failure and slurry overflow. The inventor has found through research that by using multiple capacitor pole pieces in a segmented setting, using each capacitor pole piece to sense the capacitance value of each segment respectively, and then using the capacitance value increment ratio of the two triangles to be basically equivalent to the area ratio of the two triangles covered by the slurry foam, according to this principle, the detected overflow prevention level can be closer to the set overflow prevention level, thereby greatly reducing the probability of slurry overflow and improving the safety risk of overflow prevention.

[0061] The above-mentioned anti-overflow detection method can make the anti-overflow detection position detected by the PCB detection board closer to the actual anti-overflow position, which can effectively prevent the occurrence of overflow. Of course, for this embodiment, a single second capacitor electrode is actually formed by a sub-electrode corresponding to the first sub-overflow detection area and a sub-electrode corresponding to the second anti-overflow detection area. Therefore, the water level detection method can also be used to determine the capacitance value of the corresponding second capacitor electrode by accumulating the capacitance values ​​sensed by the two sub-electrodes, and the control chip determines the current anti-overflow detection position based on whether the capacitance value difference between the two adjacent second capacitor electrodes is the largest. It should be noted that for these two anti-overflow signal detection methods, only one of them can be selected, and both cannot be applied to the detection of anti-overflow signals at the same time. Among them, for this embodiment, using the accumulated value of the capacitance values ​​sensed by the left and right triangles to compare and determine the anti-overflow detection position is more accurate and closer to the actual anti-overflow position reached by the slurry foam, and this scheme is also the preferred scheme of this embodiment.

[0062] In addition, it should be noted that, in the present embodiment, the dividing groove divides the overflow prevention detection area into triangles, so that the sensing areas of the two sub-overflow prevention detection areas at the same liquid level are unequal. It is based on the unequal sensing areas that different overflow prevention heights can be determined according to different ratios. Therefore, for the present embodiment, the dividing groove is not limited to dividing the overflow prevention detection area into two equal triangles, but can also be dividing the overflow prevention detection area into two equal trapezoids. Similarly, the dividing groove is not limited to a straight dividing groove that is inclined relative to the substrate, but can also be a curved dividing groove. For example, the overflow prevention detection area is divided according to the Tai Chi curve, and the overflow prevention detection area is divided into Tai Chi figures.

[0063] It should also be noted that, for this embodiment, the pulping container generally requires that at least the installation area where the PCB detection board is installed is made of non-conductive material, such as a pulping container surrounded by a full glass or full plastic cup body, a pulping container formed by a combination of a through glass cup and a heating plate, or a pulping container formed by a combination of a metal cup body and a non-metallic transparent window, and the PCB detection board is installed in the transparent window structure. In general, it is to avoid the conductive pulping container from causing detection interference to the capacitor electrode on the PCB detection board, affecting the actual detected capacitance value change. In addition, in this embodiment, the general water level detection area is configured to detect only the water level signal, but not the overflow prevention signal, and the overflow prevention detection area is generally configured to detect only the overflow prevention signal, but not the water level signal. Of course, for this embodiment, the several second capacitor electrodes at the bottom of the overflow prevention detection area can also be used to detect water level signals, while the several second capacitor electrodes at the top of the overflow prevention detection area are used to detect overflow prevention signals, that is, the maximum pulping capacity of the pulping container is higher than the several second capacitor electrodes at the bottom of the overflow prevention detection area, but will not exceed the highest second capacitor electrode, so as to achieve ultra-high water level pulping of the pulping container. Similarly, based on the same principle, the several first capacitor electrodes at the top of the water level detection area can also be used for ultra-low water level overflow prevention detection, which can be realized as long as the control chip is programmed accordingly.

[0064] It should be noted that the above-mentioned structural changes and parameter selections of this embodiment may also be applicable to other embodiments of the present invention.

[0065] Embodiment 2:

[0066] like Figure 5As shown, it is a schematic diagram of the structure of the PCB detection board of the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that: there is no dividing groove on the PCB detection board in this embodiment, and each second capacitor electrode 54b on the overflow prevention detection area 55b is a complete capacitor electrode. The same as the first embodiment, the water level detection area 55a in this embodiment is formed by a plurality of first capacitor electrodes 54a arranged at equal intervals, and the overflow prevention detection area 55b is formed by a plurality of second capacitor electrodes 54b arranged at equal intervals. In addition, the detection height of a single second capacitor electrode 54b is greater than the detection height of a single first capacitor electrode 54a.

[0067] For this embodiment, the pulping process of the food processor also includes a water level detection stage and an overflow prevention detection stage. In the water level detection stage, the control chip is still used to calculate the capacitance difference ΔC between the electrodes according to the capacitance values ​​of each segmented electrode. Ln-Ln-1 , confirm that the maximum position point of the capacitance difference is the position of the current water level, and the main control device determines the corresponding pulping program according to the water level signal fed back by the control chip, that is, different water levels correspond to different pulping processes, so that pulping at different water levels has different anti-overflow detection positions, and the slurry beverage is made fully and efficiently. At the same time, multiple different anti-overflow detection positions also ensure the safety of pulping and effectively prevent the slurry from overflowing. At the same time, during the pulping process, in the anti-overflow detection stage, the control chip will determine the current anti-overflow detection position according to the maximum difference in capacitance between two adjacent second capacitor electrodes, and then perform corresponding program operations according to the relationship between the current anti-overflow detection position and the anti-overflow detection position set by the program, on the one hand, ensuring the detection of the anti-overflow signal, and on the other hand, ensuring that there is no safety risk of overflow during the pulping process. This embodiment is the same as the first embodiment. Since the detection height of the second capacitor electrode is significantly greater than the detection height of the first capacitor electrode, a larger capacitance value can be sensed for slurry bubbles, foams, etc., thereby realizing more accurate detection of anti-overflow signals and preventing misjudgment or failure to identify anti-overflow signals, which may cause safety risks.

[0068] It should be noted that, for this embodiment, the water level detection stage and the overflow prevention detection stage can also be used as needed to use the control chip to determine the water level and / or overflow prevention signal according to the capacitance fluctuation of a single capacitor electrode.

[0069] In addition, it should be noted that the liquid heater of the present invention is not limited to the food processor with integrated motor and cup body disclosed in the embodiment of the present invention, but can also be a soymilk machine with motor mounted on top, a wall-breaking machine with cup body and base separated, and a food processor that can realize automatic pulp discharge and automatic cleaning without hand washing. Moreover, the liquid heater of the present invention can also be applied to heating appliances that can perform pulp boiling operations, rice paste making, etc., such as health pots, health cookers, etc.

[0070] Those skilled in the art should understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A non-contact anti-overflow detection liquid heater, comprising a pulping container and a main control device, wherein a PCB detection board for liquid level detection is installed on the outer wall of the pulping container, and the PCB detection board is electrically connected to the main control device, characterized in that: The PCB detection board includes a strip-shaped substrate, a capacitor electrode installed on the substrate, a control chip and an output terminal, the capacitor electrode is electrically connected to the control chip, and the control chip is connected to the main control device through the output terminal, the capacitor electrode includes a plurality of first capacitor electrodes and a plurality of second capacitor electrodes arranged at intervals, the plurality of first capacitor electrodes form a water level detection area on the substrate, and the plurality of second capacitor electrodes form an anti-overflow detection area on the substrate, and the anti-overflow detection area is located above the water level detection area, wherein the plurality of first capacitor electrodes and the plurality of second capacitor electrodes are electrically connected to the control chip one by one through the printed circuits on the substrate, and along the height direction of the substrate, the detection height of a single second capacitor electrode is greater than the detection height of a single first capacitor electrode.

2. The liquid heater with non-contact overflow prevention detection according to claim 1, characterized in that: A dividing groove is provided on the overflow prevention detection area of ​​the substrate, and the dividing groove divides the overflow prevention detection area into a first sub-overflow prevention detection area and a second sub-overflow prevention detection area arranged side by side, and each second capacitor electrode is divided into two sub-electrode pieces respectively located in two columns of sub-overflow prevention detection areas, and each sub-electrode piece of the two columns of sub-overflow prevention detection areas is electrically connected to the control chip one by one through printed circuits, wherein, at the same liquid level height below the highest point of the overflow prevention detection area, the sensing area of ​​the first sub-overflow prevention detection area is not equal to the sensing area of ​​the second sub-overflow prevention detection area.

3. The liquid heater with non-contact overflow prevention detection according to claim 2, characterized in that: When the overflow prevention signal detection is performed at the same time, the capacitance value increment detected by each sub-electrode in the first sub-overflow prevention detection area is accumulated to ΔC tri1 The capacitance increment detected by each sub-electrode in the second sub-overflow detection area is accumulated to ΔC tri2 , wherein the control chip is based on ΔC tri1 With ΔC tri2 The current overflow prevention detection position is determined by the ratio of the first and second overflow prevention detection areas; or, the capacitance value sensed by a single second capacitor electrode piece is formed by the accumulation of the capacitance values ​​detected by the sub-electrode piece corresponding to the first sub-overflow prevention detection area and the sub-electrode piece corresponding to the second sub-overflow prevention detection area, wherein, when the overflow prevention signal detection is performed at the same time, the control chip determines the current overflow prevention detection position according to the capacitance value difference between two adjacent second capacitor electrodes; Alternatively, the dividing groove is a straight dividing groove arranged obliquely relative to the substrate; Alternatively, the dividing groove is a curved dividing groove; Alternatively, the first anti-overflow detection sub-zone and the second anti-overflow detection sub-zone have the same area.

4. The liquid heater with non-contact overflow prevention detection according to claim 1, characterized in that: The first capacitor electrodes are arranged equidistantly in the water level detection area, and the detection height of a single first capacitor electrode is Among them, V L is the minimum pulping capacity of the pulping container, V H The pulping container has a maximum pulping capacity and is at least between the minimum pulping capacity and the maximum pulping capacity and has a cylindrical structure. r is the radius of the cylindrical pulping container. n is the number of first capacitor electrodes in the water level detection area, and the spacing between adjacent first capacitor electrodes is Δh.

5. The liquid heater with non-contact overflow prevention detection according to claim 4, characterized in that: The second capacitor electrodes are arranged equidistantly in the overflow prevention detection area, and the detection height of a single second capacitor electrode is The height from the bottom of the water level detection area on the substrate to the top of the overflow prevention detection area is H m , N is the number of anti-overflow detection gears corresponding to different pulping capacities, and the spacing between adjacent second capacitor electrodes is Δh, where, N and n are integers.

6. The liquid heater with non-contact overflow prevention detection according to claim 1, characterized in that: The detection height of a single second capacitor electrode piece is not less than twice the detection height of a single first capacitor electrode piece; Alternatively, the detection height of a single second capacitor electrode is 8 mm to 12 mm; Alternatively, each first capacitor electrode is used to detect a different pulping capacity liquid level, and each second capacitor electrode is used to detect a different anti-overflow detection liquid level, wherein each pulping capacity liquid level on the water level detection area has a corresponding second capacitor electrode on the anti-overflow detection area for anti-overflow liquid level detection.

7. The liquid heater with non-contact overflow prevention detection according to claim 1, characterized in that: A grid shielding layer is attached to the substrate, and the grid shielding layer is grounded.

8. The liquid heater with non-contact overflow prevention detection according to claim 7, characterized in that: The capacitor electrode is attached to the front surface of the substrate facing the pulping container, the grid shielding layer includes a first shielding layer attached to the rear surface of the substrate and a second shielding layer attached to the front surface of the substrate, the second shielding layer is enclosed along the edge of the substrate outside the water level detection area and the anti-overflow detection area, and the lower side of the second shielding layer is open; Alternatively, the mesh shielding layer is a copper-clad mesh.

9. The liquid heater with non-contact overflow prevention detection according to claim 1, characterized in that: The capacitor electrode is attached to the front surface of the substrate facing the pulping container, the control chip and the output terminal are arranged on the rear surface of the substrate, and the control chip and the output terminal are located below the water level detection area, wherein a grid shielding layer corresponding to the capacitor electrode is also arranged on the rear surface of the substrate, and the printed circuit is attached to the rear surface of the substrate and is routed along the outer peripheral edge of the grid shielding layer.

10. The liquid heater with non-contact overflow prevention detection according to claim 1, characterized in that: Located above the anti-overflow detection area, a third capacitor electrode is also arranged on the substrate, and the third capacitor electrode is used to assist in the detection of dangerous overflow signals.

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