Control method of oxygen sensor, oxygen sensor, and cooking appliance

Abstract

The present application relates to the technical field of intelligent household appliances, and in particular to a control method of an oxygen sensor, an oxygen sensor and a cooking appliance, through the time sequence of starting the first heating assembly to preheat the metal shell to remove water and then starting the second heating assembly to heat the detection electrode, the condensed water on the surface of the detection electrode can be effectively evaporated, the ceramic matrix is prevented from being fractured due to water quenching caused by cold and hot impact during subsequent high-power heating, and the service life and reliability of the oxygen sensor are improved. Meanwhile, the scheme does not need to use traditional slow and gradual heating, the detection electrode can be directly and quickly heated to the working temperature, so that the preheating response time is greatly shortened, and the continuous cooking efficiency and user experience of the cooking appliance are improved.

Description

Technical Field

[0001] This invention relates to the field of smart home appliance technology, and in particular to a control method for an oxygen sensor, an oxygen sensor, and a cooking appliance. Background Technology

[0002] Oxygen sensors in steam ovens are primarily used to detect the steam content or oxygen concentration within the cavity, thereby enabling intelligent control of the cooking process. A typical oxygen sensor's core detection element (such as a zirconia ceramic substrate) requires high temperatures (usually above 300°C) to activate its ionic conductivity and generate an effective electrical signal.

[0003] In existing technology, after a steam oven completes its steaming function, the user opens the door to remove the food, and the cavity typically cools naturally. During this process, the residual hot and humid steam inside the cavity easily condenses on the relatively cool surface of the oxygen sensor (especially its ceramic detection electrode), forming condensate. When the user immediately proceeds with the next cooking cycle (such as baking or steaming again), the heating element operates rapidly, causing a sharp rise in the ambient temperature around the oxygen sensor. If the condensate on the sensor's detection electrode surface has not completely evaporated, the sudden high-power heating can subject the electrode ceramic material to severe localized thermal shock (i.e., the "water quenching" effect), easily leading to the ceramic material cracking due to thermal stress and causing permanent sensor failure. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a control method for an oxygen sensor, an oxygen sensor, and a cooking appliance.

[0005] In a first aspect, embodiments of the present invention provide a control method for an oxygen sensor, the oxygen sensor comprising a metal housing, a detection electrode disposed within the metal housing, a first heating component disposed on the inner surface of the metal housing, and a second heating component disposed on the surface of a ceramic substrate of the detection electrode; the method comprising: In response to the heating start signal, the first heating component is controlled to preheat the metal housing of the oxygen sensor in order to evaporate the condensate adhering to the surface of the detection electrode of the oxygen sensor. After the preheating lasts for a first duration, the second heating component is controlled to heat the detection electrode until the detection electrode reaches the preset operating temperature.

[0006] In conjunction with the first aspect, the first duration is 10 to 60 seconds.

[0007] In conjunction with the first aspect, the step of controlling the second heating component to heat the detection electrode further includes: The first heating element can be controlled to continue heating the metal casing of the oxygen sensor, or switched to an auxiliary heat preservation mode.

[0008] In conjunction with the first aspect, the method also includes: In response to the cooking end signal, the first heating component is controlled to heat the metal casing to a second preset temperature range; After the second duration, the second heating component is controlled to stop operating, so as to stop heating the detection electrode and allow the detection electrode to cool down slowly; After the third time interval, the first heating component is controlled to stop operating.

[0009] Secondly, this application also provides an oxygen sensor for implementing the above-mentioned control method, comprising: Detection electrode; The second heating component is disposed on the surface of the ceramic substrate of the detection electrode and is used to heat the detection electrode; A metal casing is fitted over the detection electrode; The first heating component is disposed on the inner surface of the metal casing and is used to heat the metal casing; The control unit is connected to the first heating component and the second heating component respectively; the control unit is configured to: in response to the heating start signal, first control the first heating component to preheat the metal shell, and then control the second heating component to heat the detection electrode.

[0010] In conjunction with the second aspect, the control unit includes a detection circuit, which is used to control the start / stop, power, and heating sequence of the first heating component and the second heating component.

[0011] In conjunction with the second aspect, the detection circuit includes a first heating circuit and a second heating circuit; the first heating circuit is used to drive the first heating component, and the second heating circuit is used to drive the second heating component.

[0012] In conjunction with the second aspect, the first heating component is disposed on the inner surface of the metal casing in the form of a surface-mount circuit; the second heating component is disposed on the ceramic substrate surface of the detection electrode, and a circuit pattern is formed by etching after metallization.

[0013] In conjunction with the second aspect, it also includes: A sealing ring is located in the middle section of the oxygen sensor. The signal lead of the detection electrode and the connection line of the second heating component pass through the sealing ring and are connected to the external circuit.

[0014] Thirdly, this application provides a cooking appliance, including a cooking cavity and a door, and also includes the aforementioned oxygen sensor, which is used to detect the oxygen level inside the cooking cavity.

[0015] The embodiments of this invention bring the following beneficial effects: The oxygen sensor control method, oxygen sensor, and cooking appliance provided in this application, by first activating the first heating component to preheat and remove moisture from the metal casing, and then activating the second heating component to heat the detection electrode, can effectively evaporate the condensate on the surface of the detection electrode, avoiding water quenching and cracking of the ceramic substrate due to thermal shock during subsequent high-power heating, thus improving the service life and reliability of the oxygen sensor. Simultaneously, after preheating, the detection electrode can directly and rapidly heat up to the operating temperature, thereby significantly shortening the response time and improving the continuous cooking efficiency and user experience of the cooking appliance.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a control method for an oxygen sensor provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of an oxygen sensor provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a cooking utensil provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the first heating circuit in the oxygen sensor provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the second heating circuit in the oxygen sensor provided in an embodiment of the present invention.

[0020] Figure label: 1-Metal casing, 2-Detection electrode, 3-Protective cover, 4-Sealing ring, 5-First heating component, 6-First heating electrode, 7-Contact snap ring, 8-Second heating electrode, 9-Sealing plug. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To facilitate understanding of this embodiment, the technical terms used in this application will be briefly introduced below.

[0023] Oxygen sensor: refers to a zirconium oxide (ZrO2) based oxygen sensor used in cooking appliances (such as steam ovens) to detect the oxygen concentration or steam content in the cooking cavity.

[0024] Detection electrode: The core detection element of the oxygen sensor, usually made of zirconium dioxide ceramic material. This material has ionic conductivity at high temperatures (>300℃) and can output an electrical signal related to the oxygen partial pressure; below this threshold, the conductivity is extremely weak, and it needs to be heated to the operating temperature (500℃~700℃) by a heating component.

[0025] Condensation: After the steaming function ends, the residual hot and humid steam in the cooking cavity will physically condense into liquid water droplets when it comes into contact with the surface of the oxygen sensor (especially the detection electrode) which has a lower temperature.

[0026] Water quenching refers to the phenomenon where ceramic materials are suddenly and rapidly heated in the presence of liquid water, resulting in cracking and fragmentation due to the enormous thermal stress generated by localized thermal shock. The technical problem this application aims to solve is to prevent the detection electrode from failing due to water quenching during high-power heating because the condensate has not evaporated in time.

[0027] After introducing the technical terms used in this application, the application scenarios and design concepts of the embodiments of this application will be briefly described below.

[0028] Existing steam oven oxygen sensors are prone to condensation after the steaming function ends. When cooking again, rapid heating can cause them to crack due to thermal shock. While existing slow heating solutions can prevent cracking, the excessive preheating time negatively impacts the user experience.

[0029] Based on this, embodiments of this application provide a control method for an oxygen sensor, an oxygen sensor, and a cooking appliance.

[0030] Example 1 This application provides a control method for an oxygen sensor. The oxygen sensor includes a metal housing 1, a detection electrode 2 disposed within the metal housing 1, a first heating component 5 disposed on the inner surface of the metal housing 1, and a second heating component disposed on the surface of a ceramic substrate of the detection electrode 2; combined with Figure 1As shown, the method includes: S110, in response to the heating start signal, controls the first heating component to preheat the metal housing of the oxygen sensor to evaporate the condensate adhering to the surface of the detection electrode of the oxygen sensor.

[0031] S120: After preheating for a first duration, the second heating component is controlled to heat the detection electrode so that the detection electrode reaches the preset working temperature.

[0032] The method provided in this application is used to control an oxygen sensor, such as... Figure 2 As shown, the oxygen sensor includes: a metal housing 1, a detection electrode 2, a first heating component 5 for heating the metal housing 1, and a second heating component for heating the detection electrode 2. The first heating component 5 is disposed on the inner surface of the metal housing 1, and the second heating component is disposed on the surface of the ceramic substrate of the detection electrode 2. The first heating component 5 and the second heating component are respectively connected to a control unit. The control unit is used to execute the above-described method.

[0033] In step S110, when the user selects the steaming function, baking function or continuous cooking mode through the interactive interface, the main control unit automatically generates a heating start signal; or when the sensor is woken up from the standby state, the main control unit generates a heating start signal and sends the signal to the oxygen sensor control unit.

[0034] In response to the signal, the control unit first activates the first heating component 5, which is disposed on the inner surface of the metal housing 1 of the oxygen sensor, to heat the metal housing 1.

[0035] It should be noted that the first heating component 5 is disposed on the inner surface of the metal casing 1, located at the front end of the metal casing 1. The two ends of the first heating component 5 are respectively connected to the first heating electrode 6 and the second heating electrode 8 in the heating circuit. The first heating electrode 6 and the second heating electrode 8 serve as lead-out terminals of the first heating component 5, used to introduce the heating current from the control unit into the first heating component 5. The first heating component 5 is a resistance heating element disposed on the inner surface of the metal casing 1, which generates Joule heat after being energized, directly heating the metal casing 1.

[0036] A metal casing 1 is fitted over the detection electrode 2, which is a zirconia ceramic substrate, at least partially located within the space enclosed by the metal casing 1. Heat from the metal casing 1 is gently transferred to the detection electrode 2 via thermal conduction and radiation, causing the condensate adhering to its surface to gradually evaporate. Throughout the preheating process, the second heating element (a heating element, such as a heating wire, not shown in the figure, disposed on the surface of the ceramic substrate of the detection electrode 2) is not activated; that is, the detection electrode 2 itself is not directly heated, thus avoiding thermal shock. Simultaneously, the preheating of the casing allows the internal temperature of the sensor to rise gradually, creating a dry and safe environment for the subsequent rapid heating of the detection electrode 2.

[0037] The above preheating treatment effectively prevents the detection electrode 2 from being directly heated at high power before the condensate evaporates, eliminating the risk of water quenching and cracking of the ceramic substrate due to thermal shock, thereby ensuring the service life and reliability of the oxygen sensor.

[0038] After the first heating component 5 has preheated the metal casing 1 for a preset first duration, the control unit determines that the condensate adhering to the surface of the detection electrode 2 has been fully evaporated, and the oxygen sensor is now in a dry and safe thermal environment. At this time, the control unit activates the second heating component (in this embodiment, specifically a heating wire disposed on the surface of the ceramic substrate of the detection electrode 2) to directly and efficiently heat the detection electrode 2.

[0039] Since the condensate is completely removed during the preheating stage, there is no liquid water on the surface of detection electrode 2. Therefore, the second heating component does not need to use low voltage for slow preheating as in existing technologies. Instead, it can directly heat the electrode at its normal operating power, rapidly raising the detection electrode 2 to its preset operating temperature (e.g., 500°C to 700°C). Within this temperature range, oxygen ions inside detection electrode 2 can move freely, enabling the oxygen sensor to generate stable ionic conductivity and thus output an accurate oxygen concentration or vapor content detection signal.

[0040] While the second heating component heats the detection electrode 2, the first heating component 5 can continue heating as needed (e.g., maintaining auxiliary heat preservation of the housing at a lower power) or switch to heat preservation mode to maintain the overall thermal balance of the sensor and avoid affecting the thermal stability of the detection electrode 2 due to a sudden drop in housing temperature. This transition control ensures a smooth switch from preheating to normal operation, further improving the reliability and response speed of the sensor.

[0041] Through the control described in step S120, since the condensate has been pre-removed, the detection electrode 2 can be directly and rapidly heated without undergoing a lengthy low-pressure preheating buffer stage. This significantly shortens the time required for the oxygen sensor to stabilize and output a valid detection signal, improving the continuous cooking efficiency of the cooking appliance and the user experience. Furthermore, the heating process of the detection electrode 2 is carried out in a dry and safe environment, completely eliminating the risk of water quenching and breakage of the detection electrode 2 due to thermal shock, effectively ensuring the long-term service life and detection reliability of the oxygen sensor.

[0042] In conjunction with the first aspect, the first duration is 10 to 60 seconds.

[0043] The first duration refers to the period from the start of the first heating component preheating the metal casing 1 to the start of the second heating component heating the detection electrode 2.

[0044] In this invention, the preferred range for the first duration is 10 to 60 seconds. Setting the lower limit of this duration to 10 seconds is to ensure that the metal casing 1 can transfer sufficient heat to the detection electrode 2 through thermal conduction and thermal radiation, allowing the condensate adhering to its surface to evaporate fully. If the preheating time is less than 10 seconds, there may be a risk that the condensate will not be completely removed, which could lead to the detection electrode 2 still facing the possibility of water quenching and breakage during subsequent heating.

[0045] Setting the maximum duration to 60 seconds is to avoid unnecessary energy waste and extended cooking time caused by excessive preheating, and to prevent the internal temperature of the sensor from becoming too high due to excessive preheating, which would affect the independent temperature control of the subsequent detection electrode 2.

[0046] By controlling the first duration within a reasonable window of 10 to 60 seconds, this invention minimizes the response time from sensor startup to readiness while ensuring that condensate is completely removed and eliminating the risk of thermal shock failure, thus achieving a balance between safety and high efficiency.

[0047] It is understandable that in practical applications, the above-mentioned parameters can be flexibly adjusted according to the actual heating power, ambient temperature and sensor heat capacity, etc., and are not limited here.

[0048] In conjunction with the first aspect, step S120, which involves controlling the second heating component to heat the detection electrode, further includes: S121, Simultaneously, control the first heating component to continue heating the metal casing of the oxygen sensor, or switch to auxiliary heat preservation mode.

[0049] After the first preheating period ends, the control unit activates the second heating component to directly heat the detection electrode 2, rapidly raising its temperature to the preset operating temperature (e.g., 500℃-700℃). Simultaneously, the control unit does not immediately shut down the first heating component 5, but instead selects one of the following two operating modes based on actual needs: Mode 1: Continue heating That is, the first heating component 5 continues to heat the metal casing 1 at its original power or a appropriately reduced power. This mode is suitable for scenarios with low ambient temperature, large overall heat capacity of the oxygen sensor, or where it is necessary to maintain the thermal stability of the detection electrode 2. By continuously heating the metal casing 1, the temperature difference between the detection electrode 2 and the metal casing 1 can be reduced, avoiding adverse thermal stress caused by the casing being too cold during rapid heating of the detection electrode 2. At the same time, it can also prevent the casing from absorbing heat from the detection electrode 2, thus preventing a decrease in heating efficiency.

[0050] Mode 2: Switch to auxiliary heat preservation mode This means reducing the heating power of the first heating component 5, so that it only maintains the metal outer shell 1 within a relatively low but above-room temperature range (e.g., 150℃-200℃). This mode is suitable for scenarios where the detection electrode 2 has sufficient heating power and the outer shell can maintain thermal balance without additional heating. The auxiliary heat preservation mode can save energy while preventing the outer shell temperature from being too high and causing adverse effects on surrounding electronic components or sealing structures, and also provides a temperature buffer for subsequent cooling control after cooking may be completed.

[0051] The switching between the two modes can be automatically executed by the control unit based on temperature sensor feedback, preset algorithms, or user-defined cooking modes. Regardless of the mode used, after the detection electrode 2 enters the rapid heating stage, step S121 avoids a sudden drop in the temperature of the metal casing 1, thereby maintaining a stable transition of the overall thermal environment of the oxygen sensor. This ensures that the detection electrode 2 can efficiently and stably reach the operating temperature, while creating favorable conditions for subsequent normal detection or cooling control. It also avoids temperature fluctuations caused by a sudden interruption of the heat source of the metal casing 1, further improving the thermal stability and response consistency of the oxygen sensor, while also taking into account energy consumption optimization and component protection.

[0052] In conjunction with the first aspect, the method also includes: S210, in response to the cooking end signal, control the first heating component to heat the metal shell 1 to the second preset temperature range.

[0053] S220, after the second duration, control the second heating component to stop operating, so as to stop heating the detection electrode and allow the detection electrode to cool down slowly.

[0054] S230, after a third duration, control the first heating component to stop operating.

[0055] When the cooking program ends (e.g., the user presses the stop button, the cooking countdown resets to zero, or the cooking process completes automatically), the main control unit of the cooking appliance sends a cooking end signal. In response to this signal, the control unit activates the first heating component 5 (located on the metal housing 1 of the oxygen sensor) to actively heat the metal housing 1, causing its temperature to rise and stabilize within a second preset temperature range. In this embodiment, the second preset temperature range is 150°C to 200°C. Thus, by actively heating the metal housing 1 before the detection electrode 2 stops working, a relatively high and stable thermal environment is maintained inside the oxygen sensor, preventing the detection electrode 2 from cooling down too quickly due to natural cooling after cooking. Simultaneously, this temperature range effectively prevents the re-condensation of hot, humid vapor on the surface of the detection electrode 2, creating a stable starting condition for subsequent segmented cooling.

[0056] After the first heating component 5 continuously heats the metal casing 1 for a second duration (this duration can be preset according to factors such as sensor heat capacity and casing heating power, for example, several seconds to tens of seconds, and in this embodiment, 5-30 seconds), the control unit first shuts down the second heating component (located on the ceramic substrate of the detection electrode 2), causing the detection electrode 2 to stop actively heating. Since the metal casing 1 is still maintained at a relatively high second preset temperature range (150℃-200℃) by the first heating component 5, the detection electrode 2 will not cool suddenly due to the cutoff of its own heating source, but will slowly cool down through the thermal radiation and conduction of the casing. This segmented control method, which first cuts off electrode heating and then relies on the metal casing 1 for heat preservation, effectively avoids excessive thermal stress in the zirconia ceramic substrate due to a rapid temperature drop, thereby reducing the risk of cracking or breakage during the cooling process.

[0057] After the second heating component stops operating and a third time period (also a preset time, such as several seconds to tens of seconds, 10-60 seconds in this embodiment) has elapsed, the control unit finally shuts off the first heating component 5, causing the metal casing 1 to stop actively heating, and the entire oxygen sensor to begin naturally cooling to room temperature. The third time period must be set to ensure that the temperature of the detection electrode 2 has dropped below a safe threshold.

[0058] Specifically, ordinary zirconia ceramic materials are not prone to water quenching and cracking even when exposed to condensation after the temperature drops below 250°C. Therefore, by delaying the shutdown for a third duration, the detection electrode 2 is further cooled to this safe range in the insulation environment. At this point, even if residual vapor in the cavity forms condensation on the sensor surface, it will not cause substantial damage.

[0059] Through the above three-step cooling control, this invention achieves stable, segmented cooling protection for the oxygen sensor. Compared to the prior art method of directly cutting off all power and allowing the sensor to cool naturally, in this embodiment, the first heating component 5 is used to heat the metal casing 1 to actively maintain heat in the early stage of cooling, slowing down the cooling rate of the detection electrode 2 and completely eliminating the risk of thermal shock caused by sudden temperature drops and secondary condensation of condensate. At the same time, the cooling control and preheating control (S110, S120) form a complete temperature management closed loop, ensuring that the oxygen sensor is always in a protected thermal environment throughout the entire working cycle (from start-up preheating, rapid activation to stable cooling), maximizing the sensor's service life and ensuring detection reliability.

[0060] Secondly, this application provides an oxygen sensor for implementing the above-mentioned control method, combined with Figure 2 As shown, the oxygen sensor mainly consists of a metal housing 1, a detection electrode 2, a protective cover 3, a sealing ring 4, a first heating component 5, a first heating electrode 6, a contact spring 7, a second heating electrode 8, and a sealing plug 9. The components are assembled as follows: The metal casing 1 is the external main structure of the sensor, cylindrical in shape, and is fitted over the detection electrode 2, serving to protect, support, and conduct heat. The detection electrode 2 is located inside the metal casing 1, and is usually made of zirconium dioxide (ZrO2) ceramic substrate. Its surface is integrated with a heating wire for heating the electrode, which is the second heating component (this heating wire is not separately labeled in this figure, but can be driven by the first heating electrode 6 and the second heating electrode 8).

[0061] In practical applications, the front end of the metal shell 1 (i.e. the end of the sensor facing the cooking cavity) is also provided with a protective cover 3. The protective cover 3 has a steam inlet hole, which allows steam in the cooking cavity to enter and contact the detection electrode 2, while preventing large particles such as food residue from directly hitting the electrode.

[0062] The first heating element 5 is disposed on the inner surface of the metal casing 1. When energized, it heats the metal casing 1, thereby evaporating the condensate on the surface of the detection electrode 2 using the heat of the casing. The first heating electrode 6 and the second heating electrode 8 are both lead-out electrodes, respectively connected to both ends of the first heating element 5, for introducing the heating current from the external control unit into the first heating element 5. The first heating electrode 6 is located near the front end of the metal casing 1, and the second heating electrode 8 is located near the rear end of the oxygen sensor. The heating current from the control unit is introduced into the first heating element 5 through the first heating electrode 6, flows through the first heating element 5, and then returns to the control unit through the second heating electrode 8, thus forming a complete heating circuit.

[0063] By combining the above components, the oxygen sensor not only possesses the basic function of detecting oxygen concentration as a traditional sensor, but also achieves independent heating control of the metal shell 1 by adding a first heating component 5 and matching first heating electrode 6 and second heating electrode 8, thus providing a hardware foundation for the safe control sequence of preheating to remove water and then heating the electrodes.

[0064] The control unit is connected to both the first heating component 5 and the second heating component. The control unit precisely manages the start / stop, power, and heating sequence of the two heating components according to the control method described in the first aspect. Specifically: upon receiving a heating start signal, the control unit first activates the first heating component 5 to preheat the metal casing 1. After preheating continues for a first duration (e.g., 10-60 seconds), the second heating component is then activated to heat the detection electrode 2. After cooking is complete, the control unit shuts down both heating components according to the set sequence to achieve stable cooling. The control unit may include a detection circuit, which simultaneously processes the electrical signal output from the detection electrode 2 and converts it into a detection value.

[0065] Through the above structural configuration, this oxygen sensor provides a physical basis for achieving a safe timing sequence of water removal followed by heating at the hardware level. The first heating component 5 and the second heating component are independent of each other and have a clear division of labor. With the timing management of the control unit, the problem of water quenching and cracking caused by condensation can be effectively solved, while shortening the sensor preheating response time.

[0066] In conjunction with the second aspect, the control unit includes a detection circuit, which is used to control the start / stop, power, and heating sequence of the first heating component 5 and the second heating component.

[0067] The control unit integrates a detection circuit to precisely drive and manage the first heating component 5 (heating of the metal casing 1) and the second heating component (heating of the detection electrode 2). In addition, it can also collect, convert and process the electrical signal output by the detection electrode 2 and output usable detection values.

[0068] The control unit integrates a detection circuit. The detection circuit includes a first heating circuit and a second heating circuit. The first heating circuit drives the first heating component 5 (heating the metal casing 1), and the second heating circuit drives the second heating component (heating the detection electrode 2), thus achieving precise driving and management of the two heating components. In addition, the detection circuit can also collect, convert, and process the electrical signal output by the detection electrode 2, and output usable detection values.

[0069] In terms of heating drive, the detection circuit controls the start / stop, power, and heating sequence of the first heating component 5 and the second heating component through its first heating circuit and second heating circuit, respectively. Specifically, the detection circuit outputs control signals from the microcontroller to the drive switches of each heating circuit to control the on / off state of the two heating circuits, and precisely controls the heating power of each heating component by adjusting the duty cycle of the PWM signal, thereby achieving precise management of the preheating temperature of the metal shell 1, the working temperature of the detection electrode 2, and the timing logic of "preheating to remove water first, then heating the electrode".

[0070] In terms of signal detection, the detection circuit is used to convert the electrical signal output by the detection electrode 2 into a detection value. Specifically, the electrical signal generated by the detection electrode 2 at high temperature has a definite functional relationship with the oxygen partial pressure of its environment. The detection circuit samples, filters, and performs analog-to-digital conversion on the electrical signal before sending it to the microcontroller. The microcontroller then converts it into an oxygen concentration value or a steam content value according to a preset algorithm, which is used by the main control unit of the cooking appliance for intelligent control.

[0071] The detection circuit integrates two major functions: heating drive and signal acquisition. This enables the control unit to independently complete the entire workflow from sensor preheating and heating control to signal output. The circuit is compact and has a rapid response.

[0072] In conjunction with the second aspect, the detection circuit includes a first heating circuit and a second heating circuit; the first heating circuit is used to drive the first heating component, and the second heating circuit is used to drive the second heating component.

[0073] In this embodiment, the detection circuit adopts an independent dual-channel drive architecture, including two channels: a first heating circuit and a second heating circuit, to achieve independent timing control of the first heating component 5 and the second heating component. The microcontroller serves as a shared control core, and the first and second heating circuits are each independently configured with a set of drive switches and freewheeling diodes to achieve their respective on / off control and protection functions.

[0074] The first heating circuit is used to drive the first heating component 5 (located on the inner surface of the metal casing 1), combined with Figure 4 As shown, it mainly consists of a driving power supply VCC, a microcontroller, a base limiting current resistor R90, a driving switch Q2, a freewheeling diode D5, and a first heating component 5. The first heating component 5 is connected as a load between VCC and the driving switch Q2, and is connected in series with Q2. The PWM control signal output from pin 1 of the microcontroller is sent to the base of Q2 through R90. The emitter of Q2 is grounded. The freewheeling diode D5 is connected in parallel with the first heating component 5.

[0075] During operation, the microcontroller outputs a PWM control signal from pin 1. When the output is high, Q2 is saturated and turned on, energizing the first heating component 5 and initiating heating of the metal casing 1. When the output is low, Q2 is turned off, de-energizing the first heating component 5 and stopping heating. The freewheeling diode D5 provides an energy discharge circuit for the inductor coil of the first heating component 5 at the moment Q2 is turned off, preventing the reverse induced electromotive force from breaking down Q2. By adjusting the duty cycle of the PWM signal, the heating power of the first heating component 5 can be precisely controlled. The microcontroller executes control according to a preset timing sequence: first, the first heating component 5 preheats the metal casing 1 at a set power for a first duration (10-60 seconds), and after the condensate has fully evaporated, the second heating circuit is activated to heat the detection electrode 2. This circuit structure is reliable and responds quickly, ensuring the safe startup strategy of "preheating the casing to remove water before heating the electrode" for the oxygen sensor from a hardware perspective.

[0076] The second heating circuit drives the second heating component (located on the surface of the ceramic substrate of the detection electrode 2). It also employs a single-tube drive circuit structure (the drive section is not shown in the figure), and its drive control principle is the same as that of the first heating circuit. In addition, the second heating circuit also includes a sampling feedback circuit to collect the working status signal of the heating loop in real time and feed it back to the microcontroller, thereby achieving closed-loop control of the heating power and output of the detection signal. Figure 5 As shown, the sampling feedback circuit mainly consists of a +5V driving power supply, a filter capacitor C40, voltage divider resistors R91 and R92, a filter capacitor C41, and a microcontroller (MCU). The +5V power supply provides the operating voltage for the second heating circuit; C40 is connected between +5V and ground to filter out power supply ripple and stabilize the supply voltage; R91 and R92 form a series voltage divider circuit, connected between +5V and ground, to sample the voltage signal of the heating circuit; C41 is connected between pin 1 of the MCU and ground to filter out high-frequency noise in the sampled signal; pin 1 of the MCU is the ADC input terminal, and pin 2 is the signal loop (ground).

[0077] During operation, R91 and R92 perform voltage division sampling on the heating circuit. The sampled signal is filtered by C41 and then sent to pin 1 of the microcontroller. The microcontroller converts the sampled voltage signal into the corresponding oxygen concentration or steam content value according to a preset algorithm. The electrical signal output by the detection electrode 2 at high temperature has a definite functional relationship with the oxygen partial pressure of its environment. Therefore, by accurately measuring this signal and performing calibration calculations, the oxygen value or steam content in the cooking cavity can be output in real time. Simultaneously, by sampling the operating current of the heating circuit in real time, the microcontroller can determine the current heating power. When the sampled value deviates from the preset target value, the microcontroller dynamically adjusts the duty cycle of the PWM signal to maintain the detection electrode stably within the operating temperature range of 500℃-700℃, achieving closed-loop power control.

[0078] Through the aforementioned sampling feedback circuit, the microcontroller can acquire the working current information of the detection electrode in real time. This information is used to convert the electrical signal into a detection value and to adjust the heating power in a closed loop, thereby ensuring the accuracy and reliability of the oxygen sensor's output signal.

[0079] The first and second heating circuits share the same microcontroller (MCU), which outputs control signals to the drive switches of each heating circuit. The two heating circuits work together to complete the entire workflow of the oxygen sensor. The first heating circuit provides the necessary conditions for the normal operation of the second heating circuit, while the second heating circuit outputs the final detection result for the entire sensor.

[0080] Start-up phase: The microcontroller first outputs a PWM signal to the first heating circuit to drive the first heating component 5 to preheat and remove water from the metal shell 1 at a set power; after the preheating lasts for a first duration (10-60 seconds), it outputs a PWM signal to the second heating circuit to drive the second heating component to heat the detection electrode 2.

[0081] Transition phase: After the second heating circuit is activated, the first heating circuit can continue to heat (maintaining the shell temperature at a lower power) or switch to auxiliary heat preservation mode to ensure a smooth transition of the overall thermal environment of the sensor.

[0082] Shutdown Phase: After cooking, the microcontroller first shuts down the second heating circuit (the detection electrode stops heating), and then shuts down the first heating circuit after a delay (the outer casing continues to keep warm, allowing the detection electrode to cool down slowly), avoiding thermal stress caused by a sudden temperature drop in the detection electrode. In conjunction with the first aspect, the second heating component is disposed on the surface of the ceramic substrate of the detection electrode 2, and a circuit pattern is formed by metallization followed by etching.

[0083] The main body of detection electrode 2 is a zirconium dioxide (ZrO2) ceramic substrate. This ceramic material exhibits ionic conductivity at high temperatures but is not conductive itself. The second heating component is formed through a surface metallization process on the ceramic substrate. This involves coating or depositing a thin metal film (such as platinum, gold, or other high-temperature conductive metals) on the surface of the ceramic substrate (usually the outer surface or a specific internal area). Then, using semiconductor processing techniques such as photolithography and etching, the desired circuit pattern (e.g., serpentine, spiral, or multi-segment series resistance traces) is precisely etched onto the metal film. This circuit pattern essentially constitutes a resistance heater, with electrodes leading out from its two ends to connect to the detection circuit.

[0084] When the control unit powers the second heating component according to the timing described in the first aspect (after a first preheating period), current flows through the etched metal resistance pattern, generating Joule heating due to the resistance heating effect, directly and uniformly heating the ceramic substrate. Because the circuit pattern is tightly bonded to the ceramic substrate, the high thermal conductivity allows the detection electrode 2 to rapidly heat to the operating temperature range of 500℃-700℃ within a short time, thereby activating the oxygen ion conductivity of zirconium dioxide and generating a stable detection electrical signal.

[0085] Compared to the traditional method of winding or attaching heating wires to the ceramic surface, etching circuit patterns after metallization has the following advantages: First, the pattern has high precision, allowing for the design of uniform heating areas and avoiding localized overheating or undercooling; second, the circuit pattern is firmly bonded to the ceramic substrate, exhibiting good high-temperature resistance and thermal shock resistance, and is not prone to detachment or breakage during long-term use; third, the process is mature, suitable for mass production, and the cost is controllable.

[0086] With the above structural design, the second heating component can reliably achieve the function of rapidly heating the detection electrode 2 after the condensate is removed, providing a stable and efficient heat source guarantee for the accurate detection of the oxygen sensor.

[0087] In conjunction with the first aspect, the first heating component is disposed on the inner surface of the metal housing 1 in the form of a surface-mount circuit.

[0088] The first heating component 5 is responsible for the initial task of preheating the metal casing 1 and evaporating the condensate on the surface of the detection electrode 2 after receiving the heating start signal. To achieve rapid, uniform and controllable heating of the metal casing 1, the first heating component 5 is disposed on the inner surface of the metal casing 1 using a surface-mount circuit.

[0089] Specifically, the metal casing 1 is typically made of a high-temperature resistant metal material (such as stainless steel). Its inner surface is insulated (e.g., coated with an insulating layer or fitted with an insulating gasket). A pre-fabricated heating circuit (e.g., a patterned metal resistance wire or a thick-film resistor circuit) is then attached to the inner wall of the casing using a surface mount technology (SMT) process. Electrodes from both ends of this heating circuit pass through the casing's insulating and sealed structure (e.g., a sealing ring 4) and connect to the control unit. When the control unit responds to the heating start signal and supplies power to the first heating component 5, current flows through the surface mount circuit, and the heat generated by the resistance is directly conducted to the metal casing 1, causing its temperature to rise rapidly.

[0090] The surface-mount circuit is tightly bonded to the inner surface of the metal casing 1, resulting in a short heat conduction path, low heat loss, and rapid heating of the casing, which can quickly reach the temperature required for evaporating condensate. Furthermore, the surface-mount circuit can be designed in a uniformly distributed pattern (such as a wraparound, serpentine, or grid pattern) to avoid localized overheating and ensure uniform overall casing temperature, thereby gently heating the internal detection electrode 2 through thermal radiation and heat conduction.

[0091] Understandably, surface mount technology is mature and highly reliable, making it suitable for implementation in compact sensor spaces without affecting the original mechanical strength and sealing performance of the housing.

[0092] With the above structural configuration, the first heating component 5 can efficiently and uniformly heat the metal shell 1 during the preheating stage (first duration 10-60 seconds), so that the heat of the shell can be fully transferred to the detection electrode 2, and the condensate adhering to the surface of the detection electrode 2 can be completely evaporated, creating a dry and stable thermal environment for the subsequent rapid and safe heating of the detection electrode 2 by the second heating component.

[0093] In conjunction with the second aspect, the oxygen sensor also includes a sealing ring 4, which is disposed in the middle section of the oxygen sensor. The signal lead of the detection electrode 2 and the connection line of the first heating component 5 pass through the sealing ring 4 and are connected to the external circuit.

[0094] The sealing ring 4 is usually made of materials that are resistant to high temperature and corrosion and have good electrical insulation properties (such as ceramics, rubber or special engineering plastics). Its core function is to achieve isolation and sealing between the inside and outside of the sensor.

[0095] Specifically, the signal lead-out wires of the detection electrode 2 and the connecting wires of the second heating component both need to extend from the sensor head through the middle section to the tail section in order to achieve electrical connection with external circuits (such as control units and detection circuits). When these connecting wires pass through the sealing ring 4, they are tightly wrapped and fixed by the sealing ring 4 to ensure that the gap between the sensor head and tail is completely sealed.

[0096] By incorporating a sealing ring 4, steam, water vapor, or condensation within the cooking cavity can be prevented from seeping into the sensor tail along the gaps in the connecting wire, thus avoiding corrosion or short circuits to the detection circuitry and connection terminals. Simultaneously, it maintains thermal isolation between the heating area at the sensor head and the room-temperature area at the tail, reducing heat conduction to the tail and protecting external circuit components from high-temperature damage. Furthermore, it provides mechanical support and stress buffering for the connecting wire, preventing breakage or poor contact due to pulling during assembly or use.

[0097] Therefore, although the sealing ring 4 is an auxiliary structure, it plays a crucial protective role in ensuring the long-term reliable operation of the oxygen sensor under high temperature and high humidity cooking environments. Together with the first heating component 5, the second heating component, and the control unit, it forms a complete, durable, and well-sealed overall structure for the oxygen sensor.

[0098] The oxygen sensor also includes a contact spring 7, located at the tail end of the sensor. This spring spring, typically a flexible metal sheet, allows for pluggable electrical connections to external circuitry (such as sockets or pads in the control unit), ensuring stable signal transmission. A sealing plug 9, located at the very end of the oxygen sensor, seals the tail opening and, together with the sealing ring 4, forms a double seal, further protecting the internal electrical connections from external moisture and oil contamination, ensuring the sensor's long-term reliability in high-humidity cooking environments.

[0099] Thirdly, embodiments of this application provide a cooking appliance, including a cooking cavity and a door, such as... Figure 3 It also includes the aforementioned oxygen sensor, which is used to detect the oxygen level inside the cooking cavity.

[0100] Combination Figure 3 As shown, the cooking appliance includes a cooking cavity and a door, and also includes the aforementioned oxygen sensor structure.

[0101] The cooking chamber is used to hold food and perform closed cooking, and the door works with the cooking chamber to form a relatively sealed cooking environment. The oxygen sensor structure is set inside the cooking chamber (for example, installed on the side wall, rear wall or top of the chamber), and its detection electrode 2 is exposed to the air inside the chamber to detect the oxygen level or vapor content inside the chamber in real time.

[0102] In practical operation, the main control unit of the cooking appliance is communicatively connected to the control unit of the oxygen sensor. When the user starts a cooking program (especially the "steam" function or a mode requiring steam control), the main control unit sends a heating start signal to the oxygen sensor. The oxygen sensor then sequentially activates the first heating element 5 (preheating the metal casing 1 to remove condensate) and the second heating element (heating the detection electrode 2 to the operating temperature) according to the control method described in the first aspect. After the oxygen sensor stably outputs a detection signal, the main control unit dynamically adjusts the power of the steam generator, the working status of the heating element, or the opening of the exhaust valve based on the changes in oxygen value or steam content fed back by the oxygen sensor, thereby achieving precise steam quantity control, food doneness judgment, or optimization of the cooking process.

[0103] By integrating the aforementioned oxygen sensor structure and control method into cooking appliances, firstly, condensation can be actively removed by preheating the outer shell before each start-up, eliminating the risk of sensor failure due to thermal shock and improving the reliability of the cooking appliance in scenarios involving continuous steaming or alternating steaming and baking. Secondly, the oxygen sensor's preheating response time is significantly shortened, allowing users to enter precise steam control mode without long waiting times, thus improving cooking efficiency and user experience. Finally, the oxygen or steam detection data output by the sensor can participate in intelligent closed-loop control, giving the cooking appliance more accurate environmental perception capabilities, which is conducive to achieving automated and programmed high-quality cooking results.

[0104] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0105] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0106] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0107] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0108] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A control method for an oxygen sensor, characterized in that, The oxygen sensor includes a metal housing, a detection electrode disposed within the metal housing, a first heating component disposed on the inner surface of the metal housing, and a second heating component disposed on the surface of the ceramic substrate of the detection electrode; the method includes: In response to the heating start signal, the first heating component is controlled to preheat the metal housing of the oxygen sensor in order to evaporate the condensate adhering to the surface of the detection electrode of the oxygen sensor. After the preheating lasts for a first duration, the second heating component is controlled to heat the detection electrode so that the detection electrode reaches the preset working temperature.

2. The control method for the oxygen sensor according to claim 1, characterized in that, The first duration is 10 to 60 seconds.

3. The control method for the oxygen sensor according to claim 1, characterized in that, The step of controlling the second heating component to heat the detection electrode further includes: The first heating component can be controlled to continue heating the metal casing of the oxygen sensor, or switched to an auxiliary heat preservation mode.

4. The control method for the oxygen sensor according to claim 1, characterized in that, The method further includes: In response to a cooking end signal, the first heating component is controlled to heat the metal casing to a second preset temperature range; After the second duration, the second heating component is controlled to stop operating, so as to stop heating the detection electrode and allow the detection electrode to cool down slowly; After a third time interval, the first heating component is controlled to stop operating.

5. An oxygen sensor for implementing the control method according to any one of claims 1 to 4, characterized in that, include: Detection electrode; The second heating component is disposed on the ceramic substrate surface of the detection electrode and is used to heat the detection electrode; A metal casing is fitted over the detection electrode; A first heating component is disposed on the inner surface of the metal casing and is used to heat the metal casing; The control unit is connected to the first heating component and the second heating component respectively; the control unit is configured to: in response to a heating start signal, first control the first heating component to preheat the metal shell, and then control the second heating component to heat the detection electrode.

6. The oxygen sensor according to claim 5, characterized in that, The control unit includes a detection circuit, which is used to control the start / stop, power, and heating sequence of the first heating component and the second heating component.

7. The oxygen sensor according to claim 6, characterized in that, The detection circuit includes a first heating circuit and a second heating circuit; the first heating circuit is used to drive the first heating component, and the second heating circuit is used to drive the second heating component.

8. The oxygen sensor according to claim 5, characterized in that, The first heating component is disposed on the inner surface of the metal casing in the form of a surface-mount circuit; the second heating component is disposed on the ceramic substrate surface of the detection electrode, and a circuit pattern is formed by etching after metallization.

9. The oxygen sensor according to claim 5, characterized in that, Also includes: A sealing ring is disposed in the middle section of the oxygen sensor. The signal lead of the detection electrode and the connection line of the second heating component pass through the sealing ring and are connected to the external circuit.

10. A cooking appliance, comprising a cooking cavity and a door, characterized in that, It also includes an oxygen sensor according to any one of claims 5 to 9, the oxygen sensor being used to detect the oxygen level inside the cooking cavity.

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