Electrothermal cooker

Abstract

The invention discloses an electrothermal cooker, which comprises a body, a temperature change detection element and a temperature control circuit, wherein the body is provided with a cooking cavity; the temperature change detection element is a positive temperature coefficient (PTC) thermal resistor; and the PTC thermal resistor is printed on the surface of a substrate in a printing way. Compared with an electrothermal cooker in the prior art, the electrothermal cooker has the advantages that: temperature is controlled by using the PTC thermal resistor, and the resistance value of the PTC thermal resistor increases along the rise of the temperature and changes linearly, so that high linearity, high reaction speed, high sensitivity and accurate pressure control are realized, the reaction speed is still within two seconds after an insulating layer is printed, and real accurate temperature control can be realized; a printing mode is adopted, so that the overall cost of the PTC thermal resistor can be reduced greatly, the process is simplified, and manufacturing is available by adopting a simple screen printing process; and meanwhile, insulation can be realized without influencing the temperature measuring accuracy by printing a very thin insulating layer, so that large-scale production is facilitated.

Description

technical field [0001] The invention belongs to the temperature control technology of an electric heating cooker. Background technique [0002] The temperature measurement and control of the electric cooker in the prior art is mainly carried out by setting an NTC thermistor on the cover to control the temperature, and its realization form is shown in the attached figure 1 As shown, the NTC thermistor is generally encapsulated by glass 2', covered with an insulating sleeve 3', leading wires 4' at both ends, and packaged as a whole in a metal sleeve 5' with one end closed, and the closed end of the metal sleeve extends into the pot. The cover and the metal sleeve transmit the temperature of the steam in the pot to the NTC thermistor, and the resistance of the thermistor changes, which is then controlled by a single-chip microcomputer. For uniform heat transfer, the NTC thermistor often needs to be packaged in the metal sleeve Inject heat-conducting silicone grease 6' to achie...

AI Technical Summary

Problems solved by technology

[0004]1. NTC thermistor has a negative temperature coefficient, its resistance value decreases with the increase of temperature, its change is non-linear, difficult to control, and the accuracy is not high

[0005]2. The response speed of NTC thermistor is slow, and its response lag has reached more than 5 seconds when it is not packaged in a metal sleeve, while the existing electric cooker Generally, it is a liquid heater, and the NTC thermistor cannot be completely insulated. It needs to be covered with an insulating sleeve outside the glass package, and then inserted into a metal sleeve with one end closed, in order to directly detect the steam temperature in the pot. Due to the insulating sleeve The thermal conductivity is poor, and its heat conduction is still transmitted to the metal sleeve through the steam temperature in the pot and then passed to the NTC thermistor for control, resulting in a serious lag in the response speed in actual use, reaching more than 15 seconds, and it is impossible to realize the true temperature of the steam in the pot. precise control

[0006]3. The NTC thermistor currently used is generally glass packaged, which is prone to damage during installation, use or transportation. If it is damaged during installation, the product Without full inspection, it will lead to control problems after the product leaves the factory, which will affect the use of consumers, especially if it is damaged during use, the resistance value will change greatly and cannot be controlled, which may also pose a threat to consumer safety.

[0007]4. The components of existing NTC thermistors are generally mixed and sintered metal oxides. Because different electric cooker products require different control temperatures, the accuracy is different (including Stage control accuracy, for example, electric pressure cooker products require a more accurate resistance value at about 100 degrees, while rice cooker products require a more accurate resistance value at about 90 degrees), and for non-linear NTC thermistors, its manufacturers must Samples are produced according to the control requirements of different products, and its versatility is not wide. At the same time, the control requirements of stage precision lead to a relatively low pass rate of NTC thermistors when manufacturing products, usually about 80%.

[0008]5. Electric cooking utensils use NTC thermistor components, and the manufacturing process is relatively complicated. The metal sleeve is generally turned, with many processes and high cost. The middle of the metal sleeve is A closed deep hole for the insertion of the NTC thermistor. In order to ensure good contact and heat transfer, the aperture can only be slightly larger than the size of the NTC thermistor, which makes it difficult to insert, and the depth of the hole is relatively deep. When inserting the thermistor, it is often only Confirm whether the NTC thermistor is in place by feeling, causing many finished products to actually have the NTC thermistor not installed in place, and control problems

PTC thermistor is the abbreviation of Positive Temperature Coefficient, which means a positive temperature coefficient. Usually, PTC refers to a positive temperature coefficient thermistor, which is a typical semiconductor resistor with temperature sensitivity. When it exceeds a certain temperature, its resistance value increases with the temperature. The increase is a step performance increase. In the prior art, PTC is mostly used in the body tube temperature compensation circuit, temperature measurement and temperature control circuit, and overheating protection circuit. However, the PTC thermistor in the prior art is also packaged in the tube, which has the same complicated process. , the defect of large temperature measurement error

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