KR100739606B1 - Method for Sensing Badness of Sensor in The Cook Machine Using Capacity Type Humidity Sensor - Google Patents

Abstract

The present invention relates to a sensor failure detection method for more accurately sensing the fastening and sensitivity failure of the sensor in the cooking appliance to which the capacitive humidity sensor is applied, the heater to remove the humidity in the sensor and the impedance according to the detected humidity A cooking apparatus using a capacitive humidity sensor comprising a variable capacitor, the cooking apparatus comprising: starting driving of the heater according to an external command and periodically reading an output value of the humidity sensor while the heater is being heated; The method may include determining whether the sensor is defective by using an output value of the humidity sensor and an output level change amount of the humidity sensor at a preset sensor diagnosis time.

Therefore, the present invention can improve the quality of the shipped product by providing inspection criteria for checking the fastening state and sensitivity of the sensor in the manufacturing process. In addition, the service quality can be improved by providing a sensor diagnostic function that allows the engineer to check the sensor for defects at any time after the user's A / S request after the product is shipped.

Humidity / Capacitive Sensor

Description

Method for Sensing Badness of Sensor in The Cook Machine Using Capacity Type Humidity Sensor}

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1 shows an equivalent circuit of a relative humidity sensor according to the prior art.

2 is a circuit diagram showing the configuration of a microwave oven to which a capacitive humidity sensor according to the present invention is applied.

3 shows an equivalent circuit of FIG.

4 is a flow chart showing a cooking control method of the microwave oven to which the capacitive humidity sensor according to the present invention is applied.

5 is a flow chart showing a sensor failure detection method of the microwave oven according to the present invention.

6 illustrates an input / output signal of a controller

* Explanation of symbols for main parts of the drawings

10: capacitive sensor 11: heater

20: Micom

Q1, Q2, Q3: first, second, third transistor

R1, R2, and R3: first, second and third resistors

C1, C2: first and second capacitors

The present invention relates to a cooking appliance, and more particularly, to a sensor failure detection method for more accurately sensing the fastening and sensitivity failure of the sensor in the cooking appliance to which the capacitive humidity sensor is applied.

In general, a microwave oven is a device that performs cooking by heating a cooking object in a cavity using a microwave generated from a built-in magnetron (MGT) as a main heating source.

Recently, the microwave oven calculates the final cooking time in consideration of the humidity in the cooking chamber after sensing the humidity in the cooking chamber.

The microwave oven to which the relative humidity sensor of the prior art is applied includes a relative humidity sensor for detecting humidity in a cooking chamber according to a change in internal resistance, an amplifier for amplifying an output value of the relative humidity sensor, and a default value of the relative humidity sensor. (Default) Zero balancing unit for adjusting the output level (Zero Balancing) and comprises a microcomputer to calculate the cooking time in consideration of the output value of the relative humidity sensor input after the zero balancing process is completed.

Looking at the operation of the microwave oven to which the relative humidity sensor according to the prior art configured as described above, first, the variable resistance value inside the sensor is changed according to the humidity in the relative humidity sensor.

In this case, the relative humidity sensor may be represented by an equivalent circuit as shown in FIG. 1.

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로서, 습도에 따라 상기

의 값이 변하게 된다.As shown, the relative humidity sensor is

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=

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As above, depending on the humidity

The value of is changed.

The amplifying unit amplifies the output value of the relative humidity sensor according to a set amplification factor and outputs the amplified output to the microcomputer.

On the other hand, when the user inputs a cooking start command, the microcomputer first blows air by operating a fan motor to remove moisture inside the relative humidity sensor.

At this time, when the air blowing is completed, the microcomputer controls the zero balancing unit to set a default output level of the relative humidity sensor.

For example, internal resistances R1 to R5 of the zero balancing part are set such that the output value of the relative humidity sensor input to the sensor input port P0 is output at a level of 2.5V when the air blowing is completed.

The microcomputer sets the output value of the relative humidity sensor input to the sensor input port P0 as an initial value when the zero balancing process is completed.

Subsequently, the microcomputer reads the predetermined humidity level according to the cooking information set by the user, and controls the entire system such as the magnetron such that cooking is performed until the humidity in the cooking chamber reaches the set humidity level.

The preset humidity level is based on a look up table stored in the microcomputer by setting each humidity level according to the type of cooking through simulation.

That is, the microcomputer reads the preset humidity level corresponding to the cooking type selected by the user, counts the time T1 at which the output of the relative humidity sensor reaches the preset humidity level, and then counts the counted time T1. The cooking time (T2) is calculated by applying to the following equation (1).

T2 = T1 * к

(Where к is a variable constant according to the set cooking conditions)

Subsequently, cooking is performed by driving the magnetron for the calculated cooking time T2.

However, the microwave oven to which the relative humidity sensor according to the related art described above has the following problems.

First, in the case of the conventional humidity sensor that outputs the value of the variable resistance changes according to the change in humidity, the output is a few kW, there was a problem that the sensitivity to the change in humidity falls.

Second, since a separate amplification unit for amplifying the low output of the humidity sensor tens or hundreds of times has to be configured separately, the manufacturing cost is increased and the circuit diagram configuration is complicated.

Third, the driving of the fan motor during the blowing may be effective to remove moisture in the cooking chamber, but the moisture inside the humidity sensor cannot be directly removed. Therefore, accurate cooking time calculation was difficult due to the remaining moisture inside the humidity sensor.

Accordingly, the present invention has been made to solve the above problems, an object of the present invention is to apply a high-capacity capacitive humidity sensor to a cooking appliance requiring humidity sensing.

Another object of the present invention is to check the defect of the capacitive sensor applied to the cooking appliance in the manufacturing process to improve the quality of the shipped product.

Still another object of the present invention is to provide a sensor diagnostic function for checking a sensor defect to improve A / S quality after shipment of the product.

Sensor failure detection method of a cooking appliance to which the capacitive sensor according to the present invention for achieving the above object is achieved using a capacitive humidity sensor consisting of a heater for removing humidity inside the sensor and a capacitor whose impedance is changed according to the humidity. In the cooking apparatus, starting the heater in accordance with an external command, and periodically reading the output value of the humidity sensor while the heater is heating, and obtaining the highest value and the lowest value of the output value of the read humidity sensor And the present output value of the humidity sensor is greater than the first set voltage V1 at the time when the first set time elapses after the start of the heater starts, and the difference between the maximum value and the present output value is the first set value DELTA V1. If it is smaller than the step of recognizing the failure of the sensor to display a sensor failure message, and the second set time after the start of the operation of the heater If the current output value of the humidity sensor is greater than the second set voltage (V2) at one point and the difference between the highest value and the lowest value is less than the second set value (ΔV2), it is recognized as a sensitivity of the sensor and a sensor bad message is displayed. It is characterized by consisting of steps.

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Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments with reference to the accompanying drawings.

A preferred embodiment of a sensor failure detection method of a cooking appliance according to the present invention will be described with reference to the accompanying drawings.

In the cooking appliance according to the present invention, as shown in FIG. 2, a capacitance type humidity sensor 10 including a heater 11 for removing moisture inside the sensor and a capacitor C1 whose impedance changes according to a sensed humidity change is included. ) To detect the change in humidity inside the cooking chamber.

Since the capacitive humidity sensor 10 outputs a voltage of several V levels according to the detected humidity, the output value of the capacitive humidity sensor 10 may be directly recognized by the controller 20 without a separate amplification means.

Referring to the operation of the humidity sensing circuit of the cooking appliance according to the present invention, the control unit 20 outputs a heater driving signal through the first port P1 as the user inputs a cooking start command.

In this case, the heater driving signal is a signal for continuously driving the heater 11 for a predetermined time (about 15 seconds).

According to the heater driving signal output from the controller 20, the first and second transistors Q1 and Q2 are sequentially turned on to supply a driving voltage to the heater 11.

Here, the heater 11 receives the driving voltage to generate heat while removing the internal moisture of the capacitive humidity sensor 10.

In addition, the capacitor C1 of the capacitive humidity sensor 10, the third transistor Q3 and the resistor R2 connected thereto may be illustrated in an equivalent circuit as shown in FIG. 3.

The control unit 20 outputs a sensor signal having a 200 V waveform of 5 V every 100 ms period through the second port P2 in order to read the output value of the capacitive humidity sensor 10.

In this case, the third transistor Q3 connected to the second port P2 is turned on in response to a sensor signal, and the output voltage of the third transistor Q3 is divided by the divided voltage of the resistor R2 and the capacitor C1. It is output to the third port P3 of the control unit 20.

The voltage level input through the third port P3 represents the current humidity in the cooking chamber.

In addition, another resistor R3 and capacitor C2 connected to the third port P3 of the controller 20 serve as a noise filter.

Referring to the cooking control method of the microwave oven to which the capacitive humidity sensor of the present invention operating as described above are as follows.

As shown in FIG. 4, when the user selects a cooking type and inputs a cooking start command (S10), the heater 11 is driven for a preset time to remove the internal humidity of the capacitive humidity sensor 10. (S11).

At the time when the driving of the heater 100 is stopped, the current humidity level is read from the capacitive humidity sensor 10 and set as an initial value (S12 and S13).

The magnetron is driven at the same time as reading the preset humidity level according to the cooking type input by the user (S14).

In this case, the set humidity level is set to a humidity level corresponding to the type of cooking through a pre-stored lookup table.

Subsequently, the controller 20 periodically reads the output value of the capacitive humidity sensor 10 and checks the current humidity level, and the time required for the current humidity level to reach the preset humidity level (T1). To calculate (S15).

Then, the final cooking time (T2, T2 = T1 * к) is calculated on the basis of the calculated time (T1) (S16) and then the magnetron is driven during the calculated final cooking time (T2) to perform cooking ( S17).

The present invention detects the humidity inside the cooking chamber using the capacitive humidity sensor 10, and an inspection standard for checking a fastening defect and a poor sensitivity of the sensor during a product manufacturing process is required.

According to the present invention, since the capacitive humidity sensor 10 is charged / discharged in a very short time, it detects a defect of the sensor by considering the output value of the sensor and the output change of the sensor according to time at the same time. There is this.

After the product manufacturing process or after the product is shipped, the software will configure the 'Sensor Diagnosis' which allows the engineer to check the sensor for defects at any time.

For example, when the 'cancel' key and the 'start cooking' key of the microwave oven are simultaneously input for about 1 second, the sensor function is configured as a hidden function so that the sensor diagnostic function can be started.

The sensor failure detection method of the cooking appliance according to the present invention will be described in detail as follows.

As shown in FIG. 5, when a command for executing a 'sensor diagnosis function' is input from the outside, the diagnostic mode for checking a failure of the capacitive humidity sensor 10 is entered (S21).

First, the controller 20 outputs the heater driving signal A as shown in FIG. 6 to drive the internal heater 11 of the capacitive humidity sensor 10 for a predetermined driving time (15 seconds), and the heater 11. While the driving is periodically read the output value of the capacitive humidity sensor 10 (S23).

At this time, the controller 20 outputs a sensor signal having a 200V waveform of 5V every 100ms period as shown in FIG. 6B to read the output value of the capacitive humidity sensor 10.

The signal of the capacitive humidity sensor 10 input by the sensor signal B has a waveform as shown in (C) of FIG. 6 and extracts a voltage of a portion where a more stable signal is formed in the charging process and detects it as a humidity level. .

In general, the capacitive humidity sensor 10 has a humidity level detected by the sensor when the heating of the heater 11 starts to fall from 5V to less than 3.5V. When the driving of the heater 11 is stopped, the 5V voltage is again. Demonstrates return to level.

Therefore, the sensor diagnosis function is performed to determine whether the sensor is fastened or the sensor has a poor sensitivity within 15 seconds of driving the heater 11 of the capacitive humidity sensor 10.

First, the output value of the capacitive humidity sensor 10 is periodically input and the highest value H having the largest signal level and the lowest value L having the smallest signal level are stored (S25).

For 7 seconds immediately after the heater 11 is driven, the current output value C is greater than the maximum value H by comparing the current output value C of the capacitive humidity sensor 10 with the stored maximum value H. In this case, the current output value C is updated to the highest value H (S31, S33, S35).

On the other hand, when the first set time (7 seconds) has elapsed immediately after the driving of the heater 11, the 'clamping state of the sensor' is inspected, and the current output value C of the capacitive humidity sensor 10 is read. In operation S41, it is determined whether the current output value C is greater than the first set voltage (4.61V).

In general, the capacitive humidity sensor 10 has a level of approximately 4.7 V regardless of whether the sensor is fastened, so the first set voltage for determining the fastening state is set to 4.61 V.

The determination result (S41), if the current output value (C) of the capacitive humidity sensor 10 is greater than the first set voltage (4.61V) subtracts the current output value (C) from the stored maximum value (H) and the result It is determined whether the value HC is smaller than the preset first change amount 0.02V (S43).

As a result of the determination (S43), when the difference value HC between the maximum value H and the current output value C is smaller than the first change amount (0.02V), the capacitive humidity sensor 10 is not normally fastened. Alternatively, the controller detects an internal disconnection and displays an error message corresponding to 'sensor fastening' (S45).

On the other hand, the determination result (S41, S43), the current output value (C) of the capacitive humidity sensor 10 is the first set voltage when the first set time (7 seconds) has elapsed immediately after the heater 11 is driven. Less than or equal to (4.61V), or when the difference value HC between the highest value H and the current output value C is greater than or equal to the first variation amount (0.02V) Check it.

Subsequently, after the first set time (7 seconds) has elapsed immediately after the heater 11 is driven, the current output value C of the capacitive humidity sensor 10 is compared with the stored minimum value L for another 7 seconds. When the current output value C is smaller than the minimum value L, the current output value C is updated to the minimum value L (S51, S53, S55).

When the second set time (14 seconds) has elapsed immediately after driving of the heater 11, the sensor 's sensitivity is not checked', and the current output value C of the capacitive humidity sensor 10 is read. In operation S61, it is determined whether the current output value C is greater than the second set voltage (4.49V).

As a result of the determination (S61), if the current output value (C) of the capacitive humidity sensor (10) is greater than the second set voltage (4.49V), the lowest value (L) is subtracted from the stored maximum value (H) and the result value. It is determined whether (HL) is smaller than the preset second change amount (0.06V) (S63).

If the difference (HL) between the highest value (H) and the lowest value (L) is smaller than the second change amount (0.06V), the determination result (S63) determines that the sensor is more than the sensitivity and corresponds to the 'sensor sensitivity poor'. An error message is displayed (S65).

On the other hand, the determination result (S61, S63), the current output value (C) of the capacitance-type humidity sensor 10 is the second set voltage when the second set time (14 seconds) immediately after the drive of the heater 11 has passed. If less than or equal to (4.49V), or the difference value (HL) between the highest value (H) and the lowest value (L) is greater than or equal to the second change amount (0.06V), it is determined as a normal sensor and all the sensor diagnostic functions are Quit.

Accordingly, the present invention provides a sensor diagnostic function that can determine whether the sensor is defective by checking the fastening state and sensitivity of the capacitive sensor in the product applying the capacitance-type humidity sensor that changes the impedance according to the humidity change.

Sensor failure detection method of the cooking appliance to which the capacitive humidity sensor according to the present invention as described above has the following effects.

First, it is possible to improve the quality of the shipped product by providing an inspection standard for checking the fastening state and sensitivity of the sensor in the manufacturing process.

Second, the quality of service can be improved by providing a sensor diagnostic function that allows an engineer to check the defect of the sensor at any time when the user requires A / S after shipping.

Third, more accurate inspection is performed by comparing (maximum value-present value) or (maximum value-minimum value) with the sensor output value detected at the time of judging sensor failure, not based only on the absolute value of the sensor that is detected momentarily. can do.                     

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (4)

In a cooking appliance using a capacitive humidity sensor composed of a heater for removing humidity inside the sensor and a capacitor whose impedance changes according to the humidity, Starting driving of the heater according to an external command and periodically reading an output value of the humidity sensor while the heater is being heated; Obtaining the highest value and the lowest value among the output values of the read humidity sensor; If the current output value of the humidity sensor is greater than the first set voltage V1 and the difference value between the highest value and the current output value is smaller than the first set value ΔV1 at the time when the first set time elapses after the start of the heater starts. Recognizing the sensor as a fastening failure and displaying a sensor bad message; If the current output value of the humidity sensor is greater than the second set voltage V2 and the difference between the highest value and the lowest value is smaller than the second set value ΔV2 at the time when the second set time elapses after the start of the heating of the heater, The sensor failure detection method of the cooking appliance to which the capacitive sensor is applied, characterized in that it comprises the step of displaying a sensor failure message by recognizing the sensitivity failure. delete The method of claim 1, Updating the maximum value to the current output value when the current output value of the humidity sensor is greater than the maximum value while the heater is driven; And updating a minimum value to a current output value when the current output value of the humidity sensor is smaller than the minimum value. The method of claim 1, The current output value of the humidity sensor is less than or equal to the first set voltage V1 at the time when the first set time elapses after the driving of the heater is started, or the current output value of the humidity sensor is greater than the first set voltage V1. If the difference between the highest value and the current output value is greater than or equal to the first set value ΔV1, determining that the sensor is a normal sensor; When the second preset time elapses after the start of the heater, the current output value of the humidity sensor is less than or equal to the second set voltage V2, or the current output value of the humidity sensor is greater than the second set voltage V2. If the difference between the highest value and the lowest value is greater than or equal to the second set value (ΔV2) further comprising the step of determining the normal sensor sensor failure detection method of a cooking appliance to which the capacitive sensor is applied.

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