JP2010112924A - Temperature detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature detection device capable of detecting a failure easily when an ON-failure occurs in some semiconductor switch. <P>SOLUTION: The device is provided with: a switching control means provided with a plurality of thermistors 5a, 6a, and a plurality of semiconductor switches Tr1, Tr2 for sending a current into each thermistor by ON-operation by being connected respectively to each of the thermistors 5a, 6a, and having a function for sending the current to each thermistor 5a, 6a, while being switched by each semiconductor switch Tr1, Tr2; and a potential detection means having a function for detecting a potential on the high potential side of the thermistors 5a, 6a. The device is also provided with a failure detection means having a function for detecting a failure wherein the semiconductor switches Tr1, Tr2 are always put into the ON-operation state based on a detected potential, by putting all the semiconductor switches Tr1, Tr2 into the OFF-operation during the switching operation of the thermistors 5a, 6a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature detection device that detects the temperature of a cooker or the like heated by a burner of a gas stove using a thermistor, for example.

  For example, in a gas stove, a temperature detection device is provided for automatically adjusting the amount of heating of the burner by detecting the temperature of a cooking device such as a pan placed on the virtues. In this type of temperature detection device, generally, a resistor and a thermistor are connected in series between both poles of an operating power source, and the potential between the resistor and the thermistor is controlled by analog / digital of a microcomputer that controls the operation of the burner. The temperature is detected by inputting to a conversion port (hereinafter referred to as A / D conversion port) and calculating the resistance value of the thermistor based on this potential.

  By the way, in this type of temperature detection device, in a gas stove including a plurality of burners, it is necessary to provide a thermistor for each burner. At this time, if one A / D conversion port of the microcomputer is assigned to one thermistor, an A / D conversion port corresponding to each of the plurality of thermistors is required. There is an inconvenience incurring high cost and large size by adding / D conversion port.

  Therefore, as seen in the following Patent Document 1, the high potential side of a plurality of thermistors is connected to one A / D conversion port of the microcomputer, the thermistors are connected in parallel to each other, and each thermistor is connected to each other. What provided the some semiconductor switch made into an energized state separately is known.

According to this, the thermistors can be switched one by one at a predetermined time by the ON / OFF operation of each semiconductor switch, and the potentials of all thermistors can be sequentially taken in by one A / D conversion port. High cost and large size can be prevented.
JP 2003-121270 A

  In the above-mentioned Patent Document 1, as described above, the thermistors are selectively connected one by one via the semiconductor switch, and at that time, the temperature detection by the selected thermistor is performed. In this configuration, when a so-called OFF failure that is always in the OFF operation state occurs in the semiconductor switch of the selected thermistor, the thermistor is not energized, and the input potential from the A / D conversion port becomes extremely high. The failure can be easily detected.

  However, even if a so-called ON failure that is always ON is generated in the semiconductor switch of the selected thermistor, the thermistor is energized in the same way as in normal operation, so the input potential from the A / D conversion port It is extremely difficult to detect an ON failure of a semiconductor switch. Moreover, when another thermistor is selected, the resistance value of the thermistor that is energized by the semiconductor switch in which the ON failure has occurred affects the resistance value of the other selected thermistor, and A / D The input potential from the conversion port becomes inaccurate, and the temperature detection accuracy decreases.

  In view of the above points, the present invention includes a plurality of semiconductor switches for energizing each of a plurality of thermistors connected in parallel to each other, and the thermistors are switched by the semiconductor switches. It is an object of the present invention to provide a temperature detection device that can easily detect a failure when an ON failure has occurred.

  In order to solve this problem, the present invention provides a plurality of thermistors connected in parallel to each other, a plurality of semiconductor switches connected to each of the thermistors and energized by the thermistor by an ON operation, and the ON of each semiconductor switch. A switching control means for switching the thermistor to energize every predetermined time by controlling the / OFF operation, and a potential detection means for detecting the potential on the high potential side of each thermistor, and the potential detected by the potential detection means In the temperature detecting device for detecting the temperature based on the above, during the switching operation of the thermistor by the switching control means, all the semiconductor switches are turned off, and the semiconductor switches are always turned on based on the potential detected by the potential detecting means. A failure detection means for detecting a failure in an operating state is provided.

  According to the present invention, there is provided a period in which all the semiconductor switches are turned off while the thermistor is sequentially switched every predetermined time by the switching control means. During this time, the failure detecting means detects a failure in which the semiconductor switch is always in an ON operation state.

  That is, when all the semiconductor switches are turned off, if the off operation is normally performed in all the semiconductor switches, the potential detected by the potential detecting means becomes the highest, and this is the normal potential. On the other hand, when all semiconductor switches are turned off, if any of the semiconductor switches has a failure that is always in the ON operation state, the potential detected by the potential detecting means is higher than the normal potential. Lower. Accordingly, in the failure detection means, the semiconductor switch ON failure can be detected very easily by comparing the potential detected by the potential detection means with the normal potential when all the semiconductor switches are turned OFF. Can be detected.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram illustrating a schematic configuration of a gas stove that employs the temperature detection device of the present embodiment, FIG. 2 is an explanatory diagram illustrating a configuration of the temperature detection device of the present embodiment, and FIG. 3 is an illustration of the temperature detection device of the present embodiment. It is a figure which shows an action | operation.

  As shown in FIG. 1, the gas stove 1 is provided with two burners 2 and 3 having different heating amounts. Each of the burners 2 and 3 is supplied with a fuel gas via a gas supply pipe 4 and is provided with a plurality of valve devices for supplying the fuel gas to the gas supply pipe 4 and adjusting the gas amount (not shown). Yes. The user can manually ignite the burners 2 and 3 and adjust the heating power. In addition, the burners 2 and 3 can be automatically cooked by automatically adjusting the heating amount. In addition, temperature detection members 5 and 6 having a thermistor are attached.

  The temperature detection members 5 and 6 are urged upward so as to always come into contact with the bottom surfaces of the cookers 7 and 8 such as pans placed on the burners 2 and 3 via the five virtues. Is provided. Further, the gas stove 1 is provided with a control means 9 for controlling the operation thereof, and the control means 9 includes a microcomputer 10 (see FIG. 2) described later. And each thermistor (the 1st thermistor 5a and the 2nd thermistor 6a mentioned later) of both the temperature detection members 5 and 6 is a part of the temperature detection apparatus 11 of this embodiment with the microcomputer 10 with which the said control means 9 is equipped. It is composed.

  Next, the structure of the temperature detection apparatus 11 of this embodiment is demonstrated. Referring to FIG. 2, the temperature detection device 11 is configured by connecting a voltage dividing means 12 and first and second thermistors 5a and 6a in series. The voltage dividing means 12 is composed of three resistors R1, R2, and R3 connected in series with each other. The temperature detection device 11 is provided with first semiconductor switches Tr1 and Tr2 that selectively connect the first and second thermistors 5a and 6a to the voltage dividing means 12. The voltage dividing means 12 is provided with second semiconductor switches Tr3 and Tr4, and the resistance values can be switched by short-circuiting some of the resistors R1, R2 and R3 by the second semiconductor switches Tr3 and Tr4. It is like that.

  The microcomputer 10 functions to switch the energization to the first thermistor 5a and the second thermistor 6a by turning on / off the first semiconductor switches Tr1 and Tr2 in response to signals from the third and fourth ports P3 and P4. Control means). Further, the microcomputer 10 changes the resistance value of the voltage dividing means 12 by turning on / off the second semiconductor switches Tr3, Tr4 by signals from the first and second ports P1, P2. Then, the microcomputer 10 takes the potential between the voltage dividing means 12 and the first thermistor 5a or the second thermistor 6a into a single A / D conversion port (A / D in the figure) which is a potential detecting means. The resistance value is calculated, and the temperature is detected from the resistance value.

  Each of the first and second semiconductor switches Tr1, Tr2, Tr3, and Tr4 is a transistor (an FET may be adopted) that switches when a predetermined pulse signal is input from the microcomputer 10. The semiconductor switches Tr1, Tr2, Tr3, Tr4 are switched at predetermined time intervals (for example, every 6 to 24 ms), and the thermistors 5a, 6a detect the temperature alternately.

  Further, the microcomputer 10 simultaneously turns off both the first semiconductor switches Tr1 and Tr2 during the switching operation of the thermistors 5a and 6a, and the potential taken in from the A / D conversion port at this time and the potential stored in advance. And a function (failure detection means) for detecting a failure of the first semiconductor switches Tr1 and Tr2.

  In this embodiment, the voltage dividing means 12 is provided with three resistors R1, R2, and R3, so that the resistance is changed to a plurality of resistance values so that the temperature can be accurately detected. The quantity and the like can be selected as appropriate.

  Next, the operation of the temperature detection device 11 will be described. Referring to FIG. 3, the initial voltage Vcc is input to the temperature detecting device 11, and first, the first semiconductor switch Tr1 for energizing the first thermistor 5a is turned on by the signal from the microcomputer 10, and the second thermistor 6a is turned on. The first semiconductor switch Tr2 for energization is turned off. In this state, the resistance values of the voltage dividing means 12 are sequentially switched by controlling both the second semiconductor switches Tr3 and Tr4 by a signal from the microcomputer 10, and each time between the voltage dividing means 12 and the first thermistor 5a. The potential is taken into the A / D conversion port. Then, the resistance value of the first thermistor 5a is calculated, and the resistance value is converted into a temperature with reference to the temperature-resistance value characteristic of the first thermistor 5a stored in advance. The resistance value of the voltage dividing means 12 in this case is the sum of the resistance values of the resistors R1, R2, and R3 that turn off both the second semiconductor switches Tr3 and Tr4, and the resistance that turns on only one second semiconductor switch Tr4 The resistance value of R3 and the sum of the resistance values of resistances R2 and R3 in which only the other second semiconductor switch Tr3 is turned on are sequentially changed. Thereby, the temperature detection operation by the first thermistor 5a is performed.

  Next, the first semiconductor switch Tr2 for energizing the second thermistor 6a is turned on by a signal from the microcomputer 10, and the first semiconductor switch Tr1 for energizing the first thermistor 5a is turned off. In this state, the resistance values of the voltage dividing means 12 are sequentially switched by controlling both the second semiconductor switches Tr3 and Tr4 according to a signal from the microcomputer 10, and each time between the voltage dividing means 12 and the second thermistor 6a. The potential is taken into the A / D conversion port. Then, the resistance value of the second thermistor 6a is calculated, and the resistance value is converted into a temperature with reference to the temperature-resistance value characteristic of the second thermistor 6a stored in advance. In this case, the resistance value of the voltage dividing means 12 is changed as described above. Thereby, the temperature detection operation by the second thermistor 6a is performed.

  Next, both the first semiconductor switches Tr1 and Tr2 are turned off by a signal from the microcomputer 10 so that the first thermistor 5a and the second thermistor 6a are not energized. At the same time, both the second semiconductor switches Tr3 and Tr4 are turned off by a signal from the microcomputer 10 so that the resistance value of the voltage dividing means 12 is the sum of the resistance values of the resistors R1, R2 and R3. At this time, one of the second semiconductor switches Tr3 and Tr4 may be turned on to set the resistance value of the voltage dividing means 12. In this state, the potential taken into the A / D conversion port is detected. The potential detected at this time is the highest, and this is the normal potential. However, if any one of the first semiconductor switches Tr1 and Tr2 has a failure that is always in the ON operation state, the potential is lower than the normal potential. Become. Therefore, the microcomputer 10 compares the normal potential (or normal potential range) stored in advance with the detected potential by the function as the failure detection means, and the detected potential is different from the normal potential (or normal). If it is outside the potential range), it is detected that an ON failure has occurred in one of the first semiconductor switches Tr1 and Tr2. By this detection, for example, the microcomputer 10 can also warn through an alarm or the like.

  In the present embodiment, the temperature detection by the two thermistors 5a and 6a has been described. However, the present invention is not limited to this. If the resistance of the voltage dividing means 12 and the second semiconductor switch are increased, the present embodiment is not limited thereto. Temperature detection is possible with multiple thermistors.

Explanatory drawing which shows schematic structure of the gas stove which employ | adopts the temperature detection apparatus of this embodiment. Explanatory drawing which shows the structure of the temperature detection apparatus of this embodiment. The figure which shows the action | operation of the temperature detection apparatus of this embodiment.

Explanation of symbols

  5a ... first thermistor, 6a ... second thermistor, 10 ... microcomputer (switching control means, potential detection means, failure detection means), 11 ... temperature detection device, Tr1, Tr2 ... first semiconductor switch (semiconductor switch).

Claims (1)

A plurality of thermistors connected in parallel to each other, a plurality of semiconductor switches connected to each of the thermistors to energize the thermistor by an ON operation, and an ON / OFF operation of each semiconductor switch by controlling each ON / OFF operation at predetermined time intervals In a temperature detection device that includes a switching control unit that switches the thermistor to energize and a potential detection unit that detects a potential on the high potential side of each thermistor, and detects a temperature based on the potential detected by the potential detection unit.
Failure detection means for detecting a failure in which all the semiconductor switches are turned OFF during the switching operation of the thermistor by the switching control means and the semiconductor switch is always in an ON operation state based on the potential detected by the potential detection means. A temperature detection device provided.

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