JP2015206650A - Resistance detection signal generation circuit for variable resister - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance detection signal generation circuit capable of outputting a signal indicating occurrence of an anomaly from an output line when an anomaly occurs that blocks an output of an output terminal of a variable resistor from the output line.SOLUTION: A resistance detection signal generation circuit 10 includes a current path 12 that connects one power supply terminal 11b of a pair of power supply terminals 11a, 11b for applying a DC power supply voltage and an a-th terminal T1 of a variable resistor 1, a current path 13 that connects the other power supply terminal 11a and a b-th terminal T2 of the variable resistor, and an output line 16 electrically connected to the b-th terminal T2.

Description

  The present invention relates to a circuit that generates and outputs a signal corresponding to a resistance value of a variable resistor.

  It has three terminals (hereinafter, may be referred to as a-th terminal, b-th terminal, and c-th terminal), and the resistance value between each of the a-th terminal and the c-th terminal and the b-th terminal is 2. Description of the Related Art Conventionally, a variable resistor configured so as to be changeable by operating an operation element such as a knob within a range of a predetermined resistance value between the first terminal and the c-th terminal is generally known.

  In a device using this type of variable resistor, the resistance value of the variable resistor is detected in order to detect the resistance value of the variable resistor (or the operating position of the operation element for variably operating the resistance value). A resistance detection signal generation circuit that generates and outputs a corresponding signal (hereinafter sometimes referred to as a resistance detection signal) is provided.

  The resistance detection signal generation circuit is configured to output a signal having a voltage value corresponding to the resistance value of the variable resistor as a resistance detection signal from the b-th terminal of the variable resistor. For example, in FIG. 1 or FIG. 5 of Patent Document 1, a constant voltage is applied to a resistor (a resistor having a fixed resistance value) between the a terminal and the c terminal of the variable resistor. A circuit is described in which the voltage of the b-th terminal that is conducted to the movable contact that contacts the resistor is output from the b-terminal via an output line.

JP 58-678 A

  By the way, the output of the resistance detection signal from the b terminal to the output line is cut off due to poor connection between the b-th terminal which is the output terminal of the variable resistor and the output line conducted to the b terminal. May end up.

  In such a case, in the circuit configuration as shown in Patent Document 1, since the input terminal of the signal receiving circuit for inputting the resistance detection signal is an open end, the voltage applied to the input terminal of the signal receiving circuit Is undefined. As a result, the signal receiving circuit may malfunction. Further, when the signal receiving circuit is constituted by a microcomputer or the like that performs operation control of various devices, there is a possibility that malfunction of the operation control may occur.

  The present invention has been made in view of such a background, and when an abnormality occurs in which the output from the output terminal of the variable resistor to the output line is interrupted, a signal indicating the occurrence of the abnormality is output from the output line. An object of the present invention is to provide a resistance detection signal generation circuit capable of performing

  The first aspect of the resistance detection signal generating circuit of the variable resistor according to the present invention has three terminals of the a-th terminal, the b-th terminal, and the c-th terminal, and each of the a-th terminal, the c-th terminal, and the b-th terminal. This is a signal corresponding to the variable resistance value of the variable resistor configured to be able to change the resistance value between the terminal and the a-th terminal and the c-th terminal within a predetermined resistance value or less. A resistance detection signal generation circuit for outputting a resistance detection signal from the b-th terminal, wherein a pair of power supply terminals to which a DC power supply voltage of a predetermined value is applied and one power supply terminal of the pair of power supply terminals An a th current path connected to the a th terminal of the variable resistor; a b th current path connecting the other power terminal of the pair of power terminals to the b th terminal of the variable resistor; and the b th current. The b-th terminal via a portion of the path between the b-th resistance element and the b-th terminal And a voltage generated at the b-th terminal is output from the output line as the resistance detection signal in a state where the DC power supply voltage is applied to the pair of power supply terminals. It is configured (first invention).

  According to the first invention, in the normal state of the resistance detection signal generation circuit, when the DC power supply voltage is applied between the pair of power supply terminals, the ath current path, the ath terminal of the variable resistor, and the bth terminal A current flows through the resistance between the terminals and the b-th current path.

  For this reason, a voltage corresponding to the resistance value between the a-th terminal and the b-th terminal of the variable resistor is generated at the b-th terminal. Then, this voltage is output from the b-th terminal through the output line as the resistance detection signal.

  In this case, since the b-th resistance element is interposed in the b-th current path, a potential difference corresponding to the voltage drop in the b-th resistance element is generated between the b-th terminal and the other power supply terminal.

  On the other hand, the output from the b-th terminal to the output line may be interrupted due to poor connection between the b-th terminal and the b-th current path, which are output terminals of the variable resistor. In this case, the b-th current path is interrupted on the b-th terminal side, but the output line is connected to the other power supply terminal via the b-th resistance element. For this reason, the potential of the output line is substantially the same as that of the other power supply terminal.

  Accordingly, when an abnormality occurs in which the output from the b-th terminal to the output line is interrupted, a voltage different from that in the normal state of the resistance detection signal generation circuit, that is, a voltage indicating that an abnormality has occurred in the output line. Will be granted.

  Therefore, according to the first invention, when an abnormality occurs in which the output from the b-th terminal as the output terminal of the variable resistor is interrupted to the output line, a signal indicating the occurrence of the abnormality is output from the output line. Can do.

  In the first invention, a voltage limiting circuit connected to the output line is further provided to prevent the voltage of the output line from becoming higher than a predetermined allowable input voltage of the signal receiving circuit for inputting the resistance detection signal. Preferably, the DC power supply voltage of the predetermined value is set to a voltage value higher than the predetermined allowable input voltage (second invention).

  According to the second aspect of the invention, since the magnitude of the DC power supply voltage can be increased, the voltage of the resistance detection signal with respect to a change in resistance value between the a-th terminal and the b-th terminal of the variable resistor can be increased. The range of change can be increased. As a result, the sensitivity of the change in the voltage of the resistance detection signal with respect to the change in the resistance value can be increased.

  In addition, by having the voltage limiting circuit, for example, even if a situation occurs where both ends of the b-th resistance element are short-circuited by dust or the like, a voltage higher than the allowable input voltage is output to the signal receiving circuit. Can be prevented from being input.

  In the first or second invention, a configuration further including an a-th resistance element interposed in the a-th current path may be employed (third invention).

  According to the third aspect of the invention, in the normal state of the resistance detection signal generating circuit, at least the a-th current path is interposed between the b-th terminal of the variable resistor and the one power supply terminal. A potential difference corresponding to the voltage drop in the resistance element occurs.

  On the other hand, for example, when an abnormality occurs in which a short circuit occurs between the b-th terminal and the one power supply terminal due to dust or the like, the b-th terminal is at substantially the same potential as the one power supply terminal. Become. Therefore, when an abnormality occurs in which the b-th terminal and the one power supply terminal are short-circuited, a voltage different from the normal state of the resistance detection signal generation circuit, that is, an abnormality has occurred in the output line. A voltage indicating is applied.

  Therefore, according to the third aspect, a signal indicating that the abnormality has occurred can be output from the output line.

  In the first to third aspects of the invention, the resistance detection signal is input to a signal receiving circuit having a function of controlling the amount of fuel supplied to the burner, for example, according to the voltage value of the resistance detection signal. Can be used as

  In this case, when the DC power supply voltage is applied to the pair of power supply terminals in a state where the resistance value between the b-th terminal and the a-th terminal of the variable resistor is the minimum value of the variable width, When the voltage value generated at the b-th terminal is defined as V1, the signal receiving circuit decreases the amount of fuel supplied to the burner as the voltage value of the resistance detection signal input is closer to V1. (4th invention).

  According to the fourth aspect of the invention, for example, when an abnormality occurs in which the a-th terminal and the b-th terminal are short-circuited due to dust or the like, or the a-th terminal and the c-th terminal are due to dust or the like. Even when the actual resistance value between the a-th terminal and the b-th terminal is not zero when a short circuit abnormality occurs, the amount of fuel supplied to the burner, and hence the burner's thermal power, can be reduced. .

  In order to achieve the above object, a second aspect of the resistance detection signal generation circuit for a variable resistor of the present invention has three terminals, an a terminal, a b terminal, and a c terminal, and the a terminal The variable resistor can be changed in such a manner that the resistance value between each of the c-th terminal and the b-th terminal can be changed within a predetermined resistance value between the a-th terminal and the c-th terminal. A resistance detection signal generation circuit for outputting a resistance detection signal, which is a signal corresponding to a resistance value, from the b-th terminal, and a pair of power supply terminals to which a DC power supply voltage of a predetermined value is applied, and the pair of power supply terminals An a-th current path connecting one of the power terminals to the a-th terminal of the variable resistor, and a second current terminal connecting the other power terminal of the pair of power terminals to the c-th terminal of the variable resistor. c current path, a first resistance element interposed in the a-th current path, and the variable resistance An output line conducting to the b-th terminal, and a resistance element connecting a middle portion of the output line to the one power supply terminal, the resistance value of the first resistance element and the a-th terminal of the variable resistor And a second resistance element having a resistance value greater than the sum of the predetermined resistance value between the c-th terminal and the b-th power supply voltage when the DC power supply voltage is applied to the pair of power supply terminals. A voltage generated at a terminal is output from the output line as the resistance detection signal (fifth invention).

  According to the fifth aspect of the invention, the resistance value of the auxiliary resistance element is obtained by summing the resistance value of the a-th resistance element and the predetermined resistance value between the a-th terminal and the c-th terminal of the variable resistor. Can be set to a sufficiently large resistance value.

  Therefore, in a normal state of the resistance detection signal generation circuit, when the DC power supply voltage is applied between the pair of power supply terminals, most of the current flowing between the pair of power supply terminals is reduced to the a-th current path. And the resistance between the a-th terminal and the c-th terminal of the variable resistor and the c-th current path. In other words, the current flowing through the auxiliary resistance element can be made sufficiently smaller than the current flowing through the a-th current path.

  In this case, a voltage corresponding to the resistance value between the a-th terminal and the b-th terminal of the variable resistor (or the resistance value between the c-th terminal and the b-th terminal) is generated at the b-th terminal. Then, this voltage is output from the b-th terminal through the output line as the resistance detection signal.

  In this case, since the a-th resistance element is interposed in the a-th current path, a potential difference corresponding to at least a voltage drop in the a-th resistance element is generated between the b-th terminal and the one power supply terminal. .

  On the other hand, the output from the b-th terminal to the output line may be interrupted due to poor connection between the b-th terminal, which is the output terminal of the variable resistor, and the output line. In this case, the output line is connected to the one power supply terminal via the a-th resistance element. For this reason, the potential of the output line is substantially the same as that of the one power supply terminal.

  Accordingly, when an abnormality occurs in which the output from the b-th terminal to the output line is interrupted, a voltage different from that in the normal state of the resistance detection signal generation circuit, that is, a voltage indicating that an abnormality has occurred in the output line. Will be granted.

  Therefore, according to the fifth aspect, when an abnormality occurs in which the output from the b-th terminal as the output terminal of the variable resistor is interrupted to the output line, a signal indicating the occurrence of the abnormality is output from the output line. Can do.

  In the fifth aspect of the invention, a configuration further including a c-th resistance element interposed in the c-th current path may be employed (sixth aspect).

  According to the sixth aspect of the invention, in the normal state of the resistance detection signal generation circuit, at least the c-th current path interposed between the b-th terminal of the variable resistor and the other power supply terminal is provided in the c-th current path. A potential difference corresponding to the voltage drop in the resistance element occurs.

  On the other hand, for example, when an abnormality occurs in which the b-th terminal and the other power supply terminal are short-circuited due to dust or the like, the b-th terminal has substantially the same potential as the other power supply terminal. Become. Therefore, when an abnormality occurs in which the b-th terminal and the other power supply terminal are short-circuited, a voltage different from the normal state of the resistance detection signal generation circuit, that is, an abnormality has occurred in the output line. Will be given.

  Therefore, according to the sixth aspect, a signal indicating that the abnormality has occurred can be output from the output line.

  Supplementally, in the first to sixth inventions described above, the DC power supply voltage applied between the pair of power supply terminals is such that one power supply terminal of the pair of power supply terminals has a higher potential than the other power supply terminal. And a DC power supply voltage in which the one power supply terminal is at a lower potential than the other power supply terminal.

The figure which shows the resistance detection signal generation circuit in 1st Embodiment of this invention, and the structure of the system containing this. The graph which illustrates the relationship between the resistance value of the variable resistor shown in FIG. 1, and the voltage of a resistance detection signal. The figure which shows the resistance detection signal generation circuit in 2nd Embodiment of this invention, and the structure of the system containing this. The figure which shows the resistance detection signal generation circuit in 3rd Embodiment of this invention, and the structure of the system containing this. The figure which shows the resistance detection signal generation circuit in 4th Embodiment of this invention, and the structure of the system containing this. The figure which shows the resistance detection signal generation circuit in 5th Embodiment of this invention, and the structure of the system containing this.

[First Embodiment]
A first embodiment of the present invention (the first to fourth inventions) will be described with reference to FIGS.

  Referring to FIG. 1, reference numeral 1 denotes a variable resistor, 10 denotes a resistance detection signal generation circuit, 110 denotes a microcomputer as an example of a signal reception circuit that inputs a resistance detection signal output from the resistance detection signal generation circuit 10 (hereinafter referred to as a microcomputer). Is called a microcomputer).

  The variable resistor 1 has a known structure, and has three terminals, a first terminal T1, a second terminal T2, and a third terminal T3. The variable resistor 1 has a resistance value between each of the first terminal T1 and the third terminal T3 and the second terminal T2, which is equal to or less than a predetermined resistance value between the first terminal T1 and the third terminal T3. It can be changed within the range.

  More specifically, a resistor 1r having a predetermined resistance value R13 (fixed resistance value) is interposed between the first terminal T1 and the third terminal T3.

  The second terminal T2 is slidably contacted with the resistor 1r and is electrically connected to a movable contact 1s that is slidable along the resistor 1r. Then, by sliding the movable contact 1s between both ends of the resistor 1r, the resistance value R12 between T1 and T2 and the resistance value R32 between T3 and T2 become the resistance of the resistor 1r between T1 and T3. It can be changed within the range of the value R13 or less.

  In this case, the resistance value R12 between T1 and T2 and the resistance value R32 between T3 and T2 are kept at the same value as the resistance value R13 (constant value) of the resistor 1r as the sum (= R12 + R32) thereof. , R12, R32 increases as one increases.

  In this embodiment, the movable contact 1s of the variable resistor 1 is, for example, a resistor according to the operation of the operating device for adjusting the thermal power of the burner 100 of the combustion device such as a gas stove or by an actuator such as an electric motor. It slides with respect to 1r.

  A proportional valve 102 as a flow rate control valve for adjusting the amount of fuel supply is interposed in the fuel supply path 101 for supplying fuel to the burner 100. The proportional valve 102 is controlled by the microcomputer 110 via the proportional valve drive circuit 103.

  The resistance detection signal generation circuit 10 includes a pair of power supply terminals 11a and 11b to which a DC power supply voltage of a predetermined value is applied, and the power supply terminal 11b of the power supply terminals 11a and 11b is connected to the first terminal T1 of the variable resistor 1 and the first power supply terminal 11b. One of the three terminals T3, for example, a T1 current path 12 connected to the first terminal T1, a T2 current path 13 connecting the power supply terminal 11a to the second terminal T2, and a T1 current path 12 and a T2 current path 13, respectively. And the output line 16 connected to the second terminal T2 through a portion of the T2 current path 13 between the resistance element 15 and the second terminal T2. . More specifically, one end of the output line 16 is conducted to a portion of the T2 current path 13 between the resistance element 15 and the second terminal T2, and is led out from the portion.

  The T1 current path 12 and the T2 current path 13 are current paths through which current flows as indicated by broken arrows Y1 and Y2, respectively.

  Then, the resistance detection signal generation circuit 10 applies the voltage generated at the second terminal T2 in a state where the DC power supply voltage is applied between the power supply terminals 11a and 11b to the resistance value R12 (T12 between T1 and T2 of the variable resistor 1). Alternatively, a resistance detection signal corresponding to the resistance value R32 between T3 and T2) is output via the output line 16.

  In the present embodiment, the other end of the output line 16 (the end opposite to the second terminal T <b> 2) is connected to a predetermined input port of the microcomputer 110 via the resistance element 17. The applied voltage value Vx is input to the microcomputer 110 as indicating the voltage value of the resistance detection signal.

  Of the power supply terminals 11a and 11b of the resistance detection signal generation circuit 10, the power supply terminal 11b is a grounded power supply terminal (hereinafter sometimes referred to as a ground side power supply terminal 11b), and the power supply terminal 11a is a ground side power supply terminal. 11b is a power supply terminal to which a positive DC power supply voltage is applied (hereinafter, it may be referred to as a positive-side power supply terminal 11a).

  Therefore, in this embodiment, the DC power supply voltage applied between the power supply terminals 11a and 11b is a DC power supply voltage at which the positive power supply terminal 11a has a higher potential than the ground power supply terminal 11b.

  In the present embodiment, the resistance value R1 of the resistance element 14 in the T1 current path 12 is set to a resistance value sufficiently smaller than the resistance value R2 of the resistance element 15 in the T2 current path 13. Furthermore, the resistance value R2 of the resistance element 15 in the T2 current path 13 is in response to a change in the resistance value R12 between T1 and T2 of the variable resistor 1 (hereinafter, simply referred to as the resistance value R12 of the variable resistor 1). Thus, the voltage value of the resistance detection signal (the voltage value Vx of the output line 16) changes in a linear manner as much as possible (specifically, as the resistance value R12 increases, the voltage value Vx increases almost linearly). Is set to go.

  As an example, when the resistance value R13 (= maximum value of the resistance value R12) of the resistor 1r of the variable resistor 1 is 10 kΩ, R1 and R2 are set to 330Ω and 22 kΩ, respectively, for example.

  Further, in this embodiment, in order to make the change width of the voltage value of the resistance detection signal according to the change of the resistance value R12 of the variable resistor 1 equal to the power supply voltage of the microcomputer 110 (5 V in this embodiment), The voltage value of the DC power supply voltage applied between the power supply terminals 11a and 11b is set to a voltage higher than the power supply voltage of the microcomputer 110, for example, 13V.

  In this case, when the resistance values R1 and R2 are set as in the above example, the voltage value of the resistance detection signal (the voltage value Vx of the output line 16) is the resistance value of the variable resistor 1 as shown in FIG. In response to the change of R12 in the range from 0Ω to 10kΩ, it changes almost linearly in the range from about 0.2V to 4.2V. Note that the microcomputer 110 has a sufficiently large input impedance, and the current flowing from the T2 current path 13 to the microcomputer 110 can be considered to be negligible.

  By the way, since the voltage value of the DC power supply voltage applied between the power supply terminals 11a and 11b is higher than the power supply voltage of the microcomputer 110 as described above, for example, between both ends of the resistance element 15 of the T2 current path 13 is caused by dust or the like. When a short circuit occurs, the voltage value Vx input to the microcomputer 110 from the output line 16 may exceed the allowable input voltage of the microcomputer 110.

  Therefore, in the present embodiment, the resistance detection signal generation circuit 10 further includes a voltage limiting circuit 18 that prevents the voltage value Vx of the output line 16 from becoming higher than the allowable input voltage of the microcomputer 110.

  The voltage limiting circuit 18 is a circuit having a configuration in which a diode 19 and a resistance element 20 are connected in series, and an auxiliary voltage to which the same voltage as the power supply voltage (5 V) of the microcomputer 110 is applied between the ground side power supply terminal 11b. The power supply terminal 21 and the output line 16 are connected.

  In this case, the forward direction of the diode 19 is the direction from the output line 16 toward the auxiliary power supply terminal 21. For this reason, the diode 19 becomes conductive only when the voltage value Vx of the output line 16 exceeds the voltage (5 V) applied to the auxiliary power supply terminal 21.

  The resistance value R3 of the resistance element 20 of the voltage limiting circuit 18 is set to a resistance value sufficiently smaller than the resistance value R2 of the resistance element 15 of the T2 current path 13. For example, as in the above example, when R2 = 22 kΩ, R3 is set to a resistance value on the order of one hundred Ω (eg, 330Ω).

  The above is the detail of the resistance detection signal generation circuit 10 of this embodiment.

  Supplementally, in the present embodiment, the first terminal T1, the second terminal T2, and the third terminal T3 of the variable resistor 1 are respectively the a-th terminal, the b-th terminal, and the first terminal in the present invention (first to fourth inventions). It corresponds to the c terminal. The T1 current path 12 and the T2 current path 13 correspond to the a-th current path and the b-th current path in the present invention, respectively, and the resistance elements 14 and 15 correspond to the a-th resistance element and the b-th resistance element in the present invention, respectively. To do.

  In the resistance detection signal generation circuit 10 having such a configuration, when the resistance detection signal generation circuit 10 is in a normal state, the voltage value of the resistance detection signal output from the output line 16 with the DC power supply voltage applied between the power supply terminals 11a and 11b. Vx increases almost linearly within a predetermined voltage range below the power supply voltage of the microcomputer 110 as the resistance value R12 of the variable resistor 1 increases from zero to the maximum value (= resistance value R13 of the resistor 1r). To do.

  In this case, the voltage value Vx of the resistance detection signal becomes the minimum voltage value (hereinafter referred to as the normal minimum voltage value Vx_min) when the resistance value R12 is zero, and the resistance value R12 is the maximum value (resistance between T1 and T3). The maximum voltage value (hereinafter referred to as a normal maximum voltage value Vx_max). Vx_max is a voltage value smaller than the voltage value of the DC power supply voltage (potential of the power supply terminal 11a) by the voltage drop at the resistance element 15, and Vx_min is zero (potential of the power supply terminal 11b) by the voltage drop of the resistance element 14. ) Is a larger voltage value. Vx_min corresponds to the voltage value V1 in the present invention.

  On the other hand, when the output line 16 is electrically disconnected from the second terminal T2 due to, for example, a connection failure between the second terminal T2 of the variable resistor 1 and the T2 current path 13 (and thus the T2 current path 13 is second). Or when the T1 current path 12 is electrically disconnected from the first terminal T1 due to a poor connection between the first terminal T1 and the T1 current path 12 or the like. Although the current passing through the variable resistor 1 is cut off, the positive power supply terminal 11a of the power supply terminals 11a and 11b to the resistance element 15 of the T2 current path 13, the resistance element 20 of the voltage limiting circuit 18, and the diode 19 Current flows through the auxiliary power supply terminal 21 via the. Then, a voltage at the midpoint between the resistance element 15 and the resistance element 20 is applied to the output line 16.

  The voltage value Vx of the output line 16 in this case is a voltage value slightly larger than the power supply voltage (5 V) applied to the auxiliary power supply terminal 21 (> normal maximum voltage value Vx_max), but the allowable input voltage of the microcomputer 110 Fits below.

  Next, control processing of the microcomputer 110 will be described.

  In the present embodiment, the microcomputer 110 controls the proportional valve 102 according to the voltage value Vx of the resistance detection signal input from the resistance detection signal generation circuit 10 to the burner 100.

  Specifically, the microcomputer 110 acquires the voltage value Vx of the resistance detection signal input from the resistance detection signal generation circuit 10 as data indicating the resistance value R12 of the variable resistor 1 (and consequently the required thermal power of the burner 100). Then, the target combustion amount to the burner 100 is determined based on a data table created in advance from the voltage value Vx or an arithmetic expression. Then, the microcomputer 110 controls the energization current of the proportional valve 102 via the proportional valve drive circuit 103 in accordance with the target combustion amount so as to supply the burner 100 with an amount of fuel corresponding to the determined target combustion amount. .

  As a result, the burner 100 is burned with the heating power corresponding to the resistance value R12 of the variable resistor 1.

  In this case, in this embodiment, the movable contact 1s of the variable resistor 1 is slid with respect to the resistor 1r in the direction in which the resistance value R12 of the variable resistor 1 decreases when the heating power of the burner 100 is decreased. It comes to move.

  In the resistance detection signal generation circuit 10 of the present embodiment, as described above, the voltage value Vx of the resistance detection signal increases as the resistance value R12 of the variable resistor 1 increases. In other words, as the resistance value R12 of the variable resistor 1 decreases, the voltage value Vx of the resistance detection signal decreases.

  For this reason, the microcomputer 110 controls the proportional valve 102 so that the amount of fuel supplied to the burner 100 decreases as the voltage value Vx of the input resistance detection signal decreases.

  Further, in the present embodiment, the microcomputer 110, when the voltage value Vx input from the output line 16 exceeds a predetermined upper limit threshold value Vth1 that is greater than the normal maximum voltage value Vx_max, Alternatively, when a value lower than the normal minimum voltage value Vx_min falls below a predetermined lower limit side threshold value Vth2, it is detected that an abnormality such as a failure of the variable resistor 1 has occurred. The upper limit side threshold value Vth1 and the lower limit side threshold value Vth2 are set, for example, as shown in FIG.

  When the microcomputer 110 detects the occurrence of an abnormality as described above, the microcomputer 110 shuts off the fuel supply to the burner 100 by closing a solenoid valve (not shown) provided in the fuel supply path 101. A measure such as stopping combustion of the burner 100 is performed.

  Here, as described above, the output line 16 (and thus the T2 current path 13) is electrically disconnected from the second terminal T2 due to a poor connection between the second terminal T2 of the variable resistor 1 and the T2 current path 13. In this case, or when the T1 current path 12 is electrically disconnected from the first terminal T1 due to poor connection between the first terminal T1 and the T1 current path 12, the voltage value Vx of the output line 16 is The voltage value (> Vx_max) is slightly larger than the power supply voltage (5 V) applied to the power supply terminal 21.

  In such a case, the voltage value Vx of the output line 16 is higher than the upper threshold value Vth1.

  Therefore, when an abnormality occurs in which the output line 16 is electrically disconnected from the second terminal T2 as described above, or an abnormality occurs in which the T1 current path 12 is electrically disconnected from the first terminal T1. In addition, the microcomputer 110 can detect that an abnormality has occurred in the resistance detection signal generation circuit 10. As a result, the fuel supply to the burner 100 can be cut off.

  For example, even when an abnormality occurs such that the second terminal T2 of the variable resistor 1 and the power supply terminal 11a are short-circuited due to dust or the like, the voltage value Vx of the output line 16 is greater than the upper threshold value Vth1. Becomes a higher voltage value (a voltage value slightly higher than the power supply voltage (5 V) applied to the auxiliary power supply terminal 21). For this reason, even in this case, the microcomputer 110 can detect that an abnormality has occurred. As a result, the fuel supply to the burner 100 can be cut off.

  In this case, the voltage limiting circuit 18 prevents the voltage value Vx of the output line 16 from exceeding the allowable input voltage of the microcomputer 110.

  For example, when an abnormality occurs in which the second terminal T2 of the variable resistor 1 and the ground-side power supply terminal 11b are short-circuited due to dust or the like, the voltage value Vx of the output line 16 is almost equal. 0V, which is smaller than the lower limit side threshold value Vth2.

  For this reason, when a short circuit as described above occurs, the microcomputer 110 can detect that an abnormality has occurred. As a result, the fuel supply to the burner 100 can be cut off.

  According to the embodiment described above, when an abnormality occurs in which the output line 16 (and thus the T2 current path 13) is electrically disconnected from the second terminal T2, or the T1 current path 12 is electrically connected from the first terminal T1. When an abnormality that is interrupted automatically occurs, or when an abnormality that causes a short circuit between the second terminal T2 of the variable resistor 1 and the power supply terminal 11a or 11b occurs, resistance detection is performed from the output line 16. It is possible to output a voltage value Vx that is higher than the normal value of the signal generation circuit 10 or lower than the normal value.

  For this reason, it is possible to appropriately detect the occurrence of an abnormality in the resistance detection signal generation circuit 10 on the microcomputer 110 side that inputs the voltage value Vx of the output line 16. As a result, the microcomputer 110 can execute measures such as shutting off the supply of fuel to the burner 100.

  Further, in this embodiment, the microcomputer 110 has a low voltage value Vx of the output line 16 as a voltage value of the resistance detection signal within a range between the normal time minimum voltage value Vx_min and the normal time value maximum voltage value Vx_max. The proportional valve 102 is controlled so as to decrease the amount of fuel supplied to the burner 100 (the smaller the resistance value R12 of the variable resistor 1 is).

  Here, for example, when an abnormality occurs in which the first terminal T1 and the second terminal T2 of the variable resistor 1 are short-circuited due to dust or the like, or the first terminal T1 and the third terminal T3 of the variable resistor 1 are generated. When an abnormality occurs in which a short circuit is caused by dust or the like, the resistance value R12 between T1 and T2 becomes zero or a resistance value smaller than the resistance value before the occurrence of the abnormality.

  When an abnormality occurs in which the first terminal T1 and the third terminal T3 of the variable resistor 1 are short-circuited due to dust or the like, the resistance between T1 and T2 in the resistor 1r between T1 and T3. Since the resistance component between T3 and T2 is connected in parallel to the component, the resistance value R12 between T1 and T2 is the resistance of the resistance component between T1 and T2 in the resistor 1r between T1 and T3. Smaller than the value.

  For this reason, when these abnormalities occur, the microcomputer 110 automatically controls the proportional valve 102 in a direction to decrease the fuel supply amount to the burner 100.

  Supplementally, in the present embodiment, the resistance element 14 is provided in the T1 current path 12, but the resistance element 14 may be omitted. In other words, the resistance value of the T1 current path 12 may be zero (or almost zero).

  Even in this case, there is an abnormality such that the output line 16 (and thus the T2 current path 13) is electrically disconnected from the second terminal T2, or the T1 current path 12 is electrically disconnected from the first terminal T1. When this occurs, the occurrence of an abnormality can be detected on the microcomputer 110 side.

[Second Embodiment]
Next, a second embodiment of the present invention (the first to fourth inventions) will be described with reference to FIG. This embodiment is different from the first embodiment only in the configuration of a part of the resistance detection signal generation circuit. For this reason, the description of the present embodiment will be focused on the differences, and description of the same matters as in the first embodiment will be omitted.

  Referring to FIG. 3, in the resistance detection signal generation circuit 30 in the present embodiment, the third terminal T3 of the variable resistor 1 has a resistance at the end opposite to the power supply terminal 11a of the resistance element 15 of the T2 current path 13. It is connected via the element 31.

  In this case, the resistance value of the resistance element 31 is larger than the maximum value of the resistance value R12 of the variable resistor 1 (= the resistance value of the resistor 1r). For example, when the resistance value of the resistor 1r of the variable resistor 1 is 10 kΩ, the resistance value of the resistance element 31 is about 1 MΩ.

  For this reason, most of the current flowing from the power supply terminal 11a to the resistance element 15 flows through the T2 current path 13 to the second terminal T2 of the variable resistor 1. Therefore, the current flowing through the resistance element 31 is as small as negligible compared to the current flowing through the T2 current path 13.

  As described above, the external noise acts on the third terminal T3 by connecting the third terminal T3 of the variable resistor 1 to the end of the resistive element 15 of the T2 current path 13 via the resistive element 31. Can be prevented.

  In the present embodiment, a jumper wire 32 is interposed in the T2 current path 13 between the resistance element 15 and the second terminal T2 of the variable resistor 1. The T2 current path 13 can be interrupted by appropriately cutting the jumper wire 32.

  Except for the matters described above, the second embodiment is the same as the first embodiment. In this embodiment, the same operational effects as those of the first embodiment can be obtained. Further, in the present embodiment, the resistance detection signal generation circuit having a specification different from that of the resistance detection signal generation circuit 30 is configured by cutting the jumper wire 32 as necessary and further short-circuiting both ends of the resistance element 31. You can also. Therefore, the specifications of the resistance detection signal generation circuit 30 can be easily changed as necessary.

  Also in this embodiment, the resistance element 14 of the T1 current path 12 may be omitted.

[Third Embodiment]
Next, a third embodiment of the present invention (the first to fourth inventions) will be described with reference to FIG. This embodiment is different from the first embodiment only in the configuration of a part of the resistance detection signal generation circuit. For this reason, the description of the present embodiment will be focused on the differences, and description of the same matters as in the first embodiment will be omitted.

  Referring to FIG. 4, a resistance detection signal generation circuit 40 of the present embodiment includes a pair of power supply terminals 11a and 11b to which a predetermined value of DC power supply voltage is applied, and a power supply terminal of these power supply terminals 11a and 11b. 11a is connected to one of the first terminal T1 and the third terminal T3 of the variable resistor 1, for example, the T1 current path 41 connected to the first terminal T1, and the power supply terminal 11b is connected to the second terminal T2 of the variable resistor 1. Between the T2 current path 42 connected to the T1, the resistance elements 43 and 44 interposed in the T1 current path 41 and the T2 current path 42, respectively, and between the resistance element 44 of the T2 current path 42 and the second terminal T2. And an output line 16 connected to the second terminal T2 through the portion. More specifically, one end of the output line 16 is conducted to a portion between the resistance element 44 and the second terminal T2 in the T2 current path 42 and is led out from the portion.

  The T1 current path 41 and the T2 current path 42 are current paths through which current flows as indicated by broken arrows Y3 and Y4, respectively.

  The resistance detection signal generation circuit 40 applies the voltage generated at the second terminal T2 in a state where the DC power supply voltage is applied between the power supply terminals 11a and 11b to the resistance value R12 ( Alternatively, a resistance detection signal corresponding to the resistance value R32 between T3 and T2) is output via the output line 16.

  The DC power supply voltage applied between the power supply terminals 11a and 11b is the same as that in the first embodiment. The power supply terminal 11a is a positive power supply terminal and the power supply terminal 11b is a ground power supply terminal.

  In the present embodiment, the resistance value R4 of the resistance element 43 in the T1 current path 41 is set to a resistance value larger than the resistance value R5 of the resistance element 44 in the T2 current path 4. Further, the resistance value R5 of the resistance element 44 in the T2 current path 42 increases with the increase in the resistance value R12 of the variable resistor 1 (with the increase in the required heating power of the burner 100), and the voltage value (output line 16) of the resistance detection signal. Voltage value Vx) is set to decrease almost linearly.

  As an example, when a constant resistance value R13 (= maximum value of resistance value R12) between T1 and T3 of the variable resistor 1 is 10 kΩ, R4 and R5 are set to 22 kΩ and 470Ω, respectively, for example.

  In this case, since the DC power supply voltage applied between the power supply terminals 11a and 11b is 13V, which is the same as that in the first embodiment, when the resistance values R4 and R5 are set as in the above example, the resistance detection signal The voltage value (voltage value Vx of the output line 16) changes substantially linearly in response to the resistance value R12 of the variable resistor 1 changing in the range from 0Ω to 10kΩ.

  The resistance detection signal generation circuit 40 of the present embodiment is the same as that of the first embodiment except for the matters described above. Accordingly, the voltage limiting circuit 18 is connected to the output line 16 as in the first embodiment.

  Supplementally, in this embodiment, the first terminal T1, the second terminal T2, and the third terminal T3 of the variable resistor 1 are respectively the a-th terminal, the b-th terminal, and the first terminal in the present invention (first to fourth inventions). It corresponds to the c terminal. The T1 current path 41 and the T2 current path 42 correspond to the a-th current path and the b-th current path in the present invention, respectively, and the resistance elements 43 and 44 correspond to the a-th resistance element and the b-th resistance element in the present invention, respectively. To do.

  In the resistance detection signal generation circuit 40 having such a configuration, when the resistance detection signal generation circuit 10 is in a normal state, the voltage value of the resistance detection signal output from the output line 16 with the DC power supply voltage applied between the power supply terminals 11a and 11b. Vx decreases almost linearly within a predetermined voltage range below the power supply voltage of the microcomputer 110 as the resistance value R12 of the variable resistor 1 increases from zero to the maximum value (resistance value R13 between T1 and T3). To do.

  In this case, when the resistance value R12 is zero, the voltage value Vx of the resistance detection signal becomes the maximum voltage value (normal maximum voltage value Vx_max), and the resistance value R12 is the maximum value (resistance value R13 between T1 and T3). Is the minimum voltage value (normal minimum voltage value Vx_min).

  In this case, Vx_max is a voltage value smaller than the voltage value of the DC power supply voltage (potential of the power supply terminal 11a) by the voltage drop at the resistance element 43, and Vx_min is zero by the voltage drop of the resistance element 44 (power supply terminal 11b potential). In the present embodiment, Vx_max corresponds to the voltage value V1 in the present invention.

  On the other hand, for example, when the output line 16 is electrically disconnected from the second terminal T2 due to, for example, a poor connection between the second terminal T2 of the variable resistor 1 and the T2 current path 42 (as a result, the T2 current path 42 is second). Or when the T1 current path 41 is electrically disconnected from the first terminal T1 due to poor connection between the first terminal T1 and the T1 current path 41 or the like. Although the current passing through the variable resistor 1 is interrupted, the output line 16 is grounded via the resistance element 44 of the T2 current path 42. For this reason, the voltage value Vx of the output line 16 becomes zero or almost zero.

  Next, regarding the control processing of the microcomputer 110, in the present embodiment, as described above, as the resistance value R12 of the variable resistor 1 increases (as the required thermal power of the burner 100 increases), the output line 16 The voltage value Vx of the resistance detection signal input to the microcomputer 110 decreases.

  For this reason, in this embodiment, the microcomputer 110 controls the proportional valve 102 so that the amount of fuel supplied to the burner 100 is increased as the voltage value Vx of the input resistance detection signal is smaller.

  The control process of the microcomputer 110 in this embodiment is the same as that of the first embodiment except for the matters described above. Therefore, as in the first embodiment, the microcomputer 110 determines that the voltage value Vx input from the output line 16 exceeds the predetermined upper limit side threshold value Vth1 (> normal maximum voltage value Vx_max) or a predetermined value. When the value falls below the lower limit side threshold value Vth2 (<normal minimum voltage value Vx_min), it is detected that an abnormality such as a failure of the variable resistor 1 has occurred.

  According to the embodiment described above, when an abnormality occurs in which the output line 16 (and thus the T2 current path 42) is electrically disconnected from the second terminal T2, or the T1 current path 41 is disconnected from the first terminal T1. When an abnormality that is electrically interrupted occurs, or when an abnormality that causes a short circuit between the second terminal T2 of the variable resistor 1 and the power supply terminal 11a or 11b due to dust or the like occurs, From the output line 16, it is possible to output a voltage value Vx that is higher than the normal value of the resistance detection signal generation circuit 40 or lower than the normal value.

  For this reason, it is possible to appropriately detect the occurrence of abnormality on the microcomputer 110 side that inputs the voltage value Vx of the output line 16.

  In the present embodiment, the microcomputer 110 determines that the voltage value Vx of the output line 16 as the voltage value of the resistance detection signal is higher in a range between the normal minimum voltage value Vx_min and the normal maximum voltage value Vx_max. The proportional valve 102 is controlled so as to decrease the amount of fuel supplied to the burner 100 (the smaller the resistance value R12 of the variable resistor 1 is).

  Here, for example, when an abnormality occurs in which the first terminal T1 and the second terminal T2 of the variable resistor 1 are short-circuited due to dust or the like, or the first terminal T1 and the third terminal T3 of the variable resistor 1 are generated. When an abnormality occurs in which a short circuit is caused by dust or the like, the resistance value R12 between T1 and T2 becomes zero or a resistance value smaller than the resistance value before the occurrence of the abnormality.

  For this reason, when these abnormalities generate | occur | produce, the microcomputer 110 can control the proportional valve 102 in the direction which reduces the fuel supply amount to the burner 100 similarly to 1st Embodiment.

  Supplementally, in the present embodiment, the resistance element 43 is provided in the T1 current path 41, but the resistance element 43 may be omitted. In other words, the resistance value of the T1 current path 41 may be zero (or almost zero).

  Even if it does in this way, when the abnormality in which the output line 16 is electrically disconnected from the second terminal T2 occurs, or the abnormality in which the T1 current path 41 is electrically disconnected from the first terminal T1 has occurred. In this case, the occurrence of an abnormality can be detected on the microcomputer 110 side.

  Further, in this embodiment, in order to prevent a noise signal from being mixed into the third terminal T3, the third terminal T3 of the variable resistor 1 is connected to a resistance element (the same resistance as the resistance element 31 in the second embodiment). You may make it connect to the edge part (edge part on the opposite side to the power supply terminal 11b) of the resistive element 44 of the T2 current path 42 via an element.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention (the fifth invention or the sixth invention) will be described with reference to FIG. Note that this embodiment is different from the first embodiment only in the configuration of the resistance detection signal generation circuit. For this reason, the description of the present embodiment will be focused on the differences, and description of the same matters as in the first embodiment will be omitted.

  Referring to FIG. 5, the resistance detection signal generation circuit 50 of the present embodiment includes a pair of power supply terminals 11a and 11b to which a DC power supply voltage of a predetermined value is applied, and the positive side of these power supply terminals 11a and 11b. A T3 current path 51 that connects the power supply terminal 11a to the third terminal T3 of the variable resistor 1, a T1 current path 52 that connects the ground-side power supply terminal 11b to the first terminal T1 of the variable resistor 1, and a T3 current path 51. And the resistive elements 53 and 54 interposed in the T1 current path 52, the output line 16 conducting to the second terminal T2 of the variable resistor 1, and the middle part of the output line 16 of the power supply terminals 11a and 11b. On the other hand, for example, a resistance element 55 connected to the positive power supply terminal 11a is provided. More specifically, one end of the output line 16 is conducted to a portion between the output line 16 and the second terminal T2, and is led out from the second terminal T2.

  Then, the resistance detection signal generation circuit 10 applies the voltage generated at the second terminal T2 in a state where the DC power supply voltage is applied between the power supply terminals 11a and 11b to the resistance value R12 (T12 between T1 and T2 of the variable resistor 1). Alternatively, a resistance detection signal corresponding to the resistance value R32 between T3 and T2) is output via the output line 16.

  In the present embodiment, the voltage value of the DC power supply voltage is 5 V, which is the same as the power supply voltage of the microcomputer 110, for example.

  In this embodiment, the resistance value R7 of the resistance element 54 of the T1 current path 52 is a constant resistance value R13 between T1 and T3 of the variable resistor 1 (= maximum value of the resistance value R12 between T1 and T2). ) Is set to a sufficiently smaller resistance value.

  The resistance value R8 of the resistance element 55 is sufficiently larger than the sum of the resistance value R6 of the resistance element 53 of the T3 current path 51 and the resistance value R13 (constant value) between T1 and T3 of the variable resistor 1. The resistance value is set. More specifically, when a DC power supply voltage is applied between the power supply terminals 11a and 11b, most of the current flowing from the positive power supply terminal 11a to the ground power supply terminal 11b flows via the T3 current path 51. R8 is set to a sufficiently large resistance value so that the current flowing through the resistance element 55 becomes sufficiently small.

  As an example, when the resistance value R13 (= maximum value of the resistance value R12) of the resistor 1r of the variable resistor 1 is 10 kΩ, R6, R7, and R8 are set to, for example, 18 kΩ, 330Ω, and 560 kΩ, respectively.

  The present embodiment is the same as the first embodiment except for the matters described above. In the present embodiment, since the voltage value Vx of the output line 16 does not become higher than the allowable input voltage of the microcomputer 110, the voltage limiting circuit shown in the first embodiment is not provided.

  Supplementally, in this embodiment, the first terminal T1, the second terminal T2, and the third terminal T3 of the variable resistor 1 are respectively the c-th terminal, the b-th terminal, and the third terminal T3 in the present invention (the fifth or sixth invention). This corresponds to the a-th terminal. The T1 current path 52 and the T3 current path 51 correspond to the c-th current path and the a-th current path in the present invention, respectively, and the resistance elements 53, 54, and 55 respectively correspond to the a-th resistance element and the c-th resistance element in the present invention. Corresponds to an auxiliary resistance element.

  In the resistance detection signal generation circuit 50 having such a configuration, when the resistance detection signal generation circuit 10 is in a normal state, a predetermined value (5 V) of DC power supply voltage is applied between the power supply terminals 11a and 11b and output from the output line 16. The voltage value Vx of the resistance detection signal increases linearly as the resistance value R12 of the variable resistor 1 increases from zero to the maximum value (resistance value R13 between T1 and T3).

  In this case, the voltage value Vx of the resistance detection signal becomes the minimum voltage value (normal minimum voltage value Vx_min) when the resistance value R12 is zero, and the resistance value R12 is the maximum value (resistance value R13 between T1 and T3). In this case, the maximum voltage value (normal maximum voltage value Vx_max) is obtained.

  On the other hand, when the output line 16 is electrically disconnected from the second terminal T2 due to, for example, a poor connection between the second terminal T2 of the variable resistor 1 and the output line 16, the output line 16 is always positive. A voltage having the same magnitude as the DC power supply voltage (> maximum normal voltage value Vx_max) is applied through the resistance element 55 from the side power supply terminal 11a.

  As described above, according to the present embodiment, an abnormality occurs in which the output line 16 is electrically disconnected from the second terminal T2 due to poor connection between the output line 16 and the second terminal T2 of the variable resistor 1 or the like. In this case, a higher voltage value Vx (> normal maximum voltage value Vx_max) than normal can be output from the output line 16.

  In the present embodiment, for example, when an abnormality occurs in which the T1 current path 52 is electrically disconnected from the first terminal T1 due to, for example, a poor connection between the first terminal T1 of the variable resistor 1 and the T1 current path 52. Alternatively, when an abnormality occurs in which the both ends of the resistance element 55 are short-circuited due to dust or the like, the voltage value Vx of the output line 16 is almost the same as the DC power supply voltage between the power supply terminals 11a and 11b. Voltage. As a result, a voltage value Vx having a higher value than that in the normal state (> maximum normal voltage value Vx_max) can be output from the output line 16.

  Furthermore, for example, when an abnormality occurs in which the T3 current path 51 is electrically disconnected from the third terminal T3 due to a poor connection between the third terminal T3 and the T3 current path 51 of the variable resistor 1, or the variable resistor When an abnormality occurs in which a short circuit occurs between the second terminal T2 of the device 1 and the ground side power supply terminal 11b due to dust or the like, the voltage value Vx of the output line 16 becomes substantially zero. As a result, a voltage value Vx (<normal minimum voltage value Vx_min) having a lower value than normal can be output from the output line 16.

  Therefore, the occurrence of the abnormality as described above can be appropriately detected on the microcomputer 110 side that inputs the voltage value Vx of the output line 16.

  Supplementally, in the present embodiment, the resistance element 54 is provided in the T1 current path 52, but the resistance element 54 may be omitted. In other words, the resistance value of the T1 current path 52 may be zero (or almost zero).

  Even in this case, when an abnormality occurs in which the output line 16 is electrically disconnected from the second terminal T2, the occurrence of the abnormality can be detected on the microcomputer 110 side.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention (the fifth invention or the sixth invention) will be described with reference to FIG. This embodiment is different from the fourth embodiment only in the configuration of a part of the resistance detection signal generation circuit. For this reason, the description of the present embodiment will be focused on the differences, and the description of the same matters as in the fourth embodiment will be omitted.

  Referring to FIG. 6, the resistance detection signal generation circuit 60 of the present embodiment is configured such that the middle part of the output line 16 is connected to the ground side instead of the resistor element that connects the middle part of the output line 16 to the positive power supply terminal 11 a. A resistance element 65 connected to the power supply terminal 11b is provided.

  The resistance value R9 of the resistance element 65 is a total resistance of the resistance value R7 of the resistance element 54 of the T1 current path 52 and the resistance value R13 of the resistor 1r of the variable resistor 1 (= maximum value of the resistance value R12). The resistance value is set sufficiently larger than the value.

  As an example, when the resistance value R13 of the resistor 1r of the variable resistor 1 is 10 kΩ and the resistance value of the resistance element 54 is 330Ω, R9 is set to 1 MΩ.

  This embodiment is the same as the fourth embodiment except for the matters described above.

  Supplementally, in this embodiment, the first terminal T1, the second terminal T2, and the third terminal T3 of the variable resistor 1 are respectively the a-th terminal, the b-th terminal in the present invention (the fifth or sixth invention), This corresponds to the c-th terminal. The T1 current path 52 and the T3 current path 51 correspond to the a-th flow path and the c-th current path in the present invention, respectively, and the resistance elements 53, 54, and 65 respectively correspond to the c-th resistance element and the a-th resistance element in the present invention. Corresponds to an auxiliary resistance element.

  In the resistance detection signal generation circuit 60 of the present embodiment, when the resistance detection signal generation circuit 10 is in a normal state, the output is output from the output line 16 with a DC power supply voltage of a predetermined value (5 V) applied between the power supply terminals 11a and 11b. As in the fourth embodiment, the voltage value Vx of the resistance detection signal to be generated is normal when the resistance value R12 of the variable resistor 1 increases from zero to the maximum value (resistance value R13 between T1 and T3). It linearly increases from the minimum voltage value Vx_min to the normal maximum voltage value Vx_max.

  On the other hand, for example, when an abnormality occurs in which the output line 16 is electrically disconnected from the second terminal T2 due to, for example, a poor connection between the second terminal T2 of the variable resistor 1 and the output line 16, or the variable resistor 1 When an abnormality occurs in which the T3 current path 51 is electrically disconnected from the third terminal T3 due to a poor connection between the third terminal T3 and the T3 current path 51, or between both ends of the resistance element 65 becomes dust or the like. When an abnormality that causes a short circuit occurs, the voltage value Vx of the output line 16 becomes substantially the same potential as the ground-side power supply terminal 11b. For this reason, the voltage value Vx of the output line 16 becomes a voltage value (<normal value minimum voltage value Vx_min) lower than that in the normal state.

  Further, for example, when an abnormality occurs in which the T1 current path 51 is electrically disconnected from the first terminal T1 due to, for example, a poor connection between the first terminal T1 of the variable resistor 1 and the T1 current path 52, or the variable resistance When an abnormality occurs in which a short circuit occurs between the second terminal T2 of the device 1 and the positive power supply terminal 11a due to dust or the like, the voltage value Vx of the output line 16 becomes substantially equal to the DC power supply voltage. . As a result, a voltage value Vx having a higher value than that in the normal state (> maximum normal voltage value Vx_max) can be output from the output line 16.

  Therefore, the occurrence of the abnormality as described above can be appropriately detected on the microcomputer 110 side that inputs the voltage value Vx of the output line 16.

  In this embodiment, for example, due to dust or the like, the second terminal T2 of the variable resistor 1 and the positive power supply terminal 11a are short-circuited, or the resistance element 53 of the T3 current path 51 When an abnormality occurs such that both ends are short-circuited, a voltage value Vx (<normal maximum voltage value Vx_min) having a value higher than normal can be output from the output line 16.

  For example, when an abnormality occurs in which the T3 current path 51 is electrically disconnected from the third terminal T3 due to a connection failure between the third terminal T3 and the T3 current path 51 of the variable resistor 1, or the variable resistor 1 When an abnormality occurs in which a short circuit occurs between the second terminal T2 and the ground-side power supply terminal 11b due to dust or the like, the voltage value Vx of the output line 16 becomes substantially zero. As a result, a voltage value Vx (<normal minimum voltage value Vx_min) having a lower value than normal can be output from the output line 16.

  Supplementally, in the present embodiment, the resistance element 53 is provided in the T3 current path 51, but the resistance element 53 may be omitted. In other words, the resistance value of the T3 current path 51 may be zero (or almost zero).

  Even in this case, when an abnormality occurs in which the output line 16 is electrically disconnected from the second terminal T2, the occurrence of the abnormality can be detected on the microcomputer 110 side.

[Modification]
Next, some modifications of the embodiment described above will be described. In the first to third embodiments, the first terminal T1 and the third terminal T3 of the variable resistor 1 correspond to the a-th terminal and the b-th terminal in the present invention (first to fourth inventions), respectively. Although the resistance detection signal generation circuits 10, 30, and 40 are configured, the first terminal T1 and the third terminal T3 are respectively equivalent to the c-th terminal and the a-th terminal in the present invention (first to fourth inventions). A resistance detection signal generation circuit may be configured.

  In each of the above embodiments, the DC power supply voltage is applied between the power supply terminals 11a and 11b so that the power supply terminal 11a has a higher potential than the power supply terminal 11b. However, the power supply terminal 11a is connected to the power supply terminal 11b. It is also possible to configure the resistance detection signal generation circuit so as to have a lower potential.

  In each of the above embodiments, the resistance detection signal generation circuits 10, 30, 40, 50, and 60 have been described by way of example in the system for controlling the combustion of the burner 100. However, the resistance detection signal generation circuit according to the present invention is used. The circuit may be applied to systems or equipment other than the combustion system.

  Further, the signal receiving circuit for inputting the resistance detection signals of the resistance detection signal generation circuits 10, 30, 40, 50, 60 may be a circuit other than the microcomputer 110.

DESCRIPTION OF SYMBOLS 1 ... Variable resistor, T1 ... 1st terminal (a terminal or c terminal), T2 ... 2nd terminal (b terminal), T3 ... 3rd terminal (c terminal or a terminal) 10, 30 , 40, 50, 60 ... resistance detection signal generation circuit, 11a, 11b ... power supply terminal, 12, 41 ... T1 current path (a-th current path), 13, 42 ... T2 current path (b-th current path), 14, 43... Resistive element (a-th resistive element), 15 and 44... Resistive element (b-th resistive element), 16... Output line, 18 ... voltage limiting circuit, 51... T3 current path (a-th current path or c-th current path) ), 52... T1 current path (c-th current path or a-th current path), 53... Resistance element (a-th resistance element or c-th resistance element), 54. , 55, 65... Resistive element (auxiliary resistive element), 100... Burner, 110. Reception circuit).

Claims (6)

It has three terminals, the a-th terminal, the b-th terminal, and the c-th terminal, and the resistance value between each of the a-th terminal and the c-th terminal and the b-th terminal is determined between the a-th terminal and the c-th terminal. A resistance detection signal generation circuit that outputs a resistance detection signal, which is a signal corresponding to the variable resistance value of a variable resistor configured to be changeable within a range of a predetermined resistance value, from the b-th terminal. ,
A pair of power supply terminals to which a DC power supply voltage of a predetermined value is applied;
An a-th current path connecting one of the pair of power-supply terminals to the a-th terminal of the variable resistor;
A b-th current path connecting the other power terminal of the pair of power terminals to the b-th terminal of the variable resistor;
A b-th resistance element interposed in the b-th current path;
An output line connected to the b-th terminal through a portion between the b-th resistance element and the b-th terminal in the b-th current path;
A variable resistor configured to output a voltage generated at the b-th terminal from the output line as the resistance detection signal in a state where the DC power supply voltage is applied to the pair of power supply terminals. Resistance detection signal generator circuit. In the resistance detection signal generation circuit of the variable resistor according to claim 1,
A voltage limiting circuit connected to the output line to prevent a voltage of the output line from becoming higher than a predetermined allowable input voltage of a signal receiving circuit that inputs the resistance detection signal output from the output line; The resistance detection signal generation circuit of the variable resistor is further provided, wherein the DC power supply voltage having the predetermined value is set to a voltage value higher than the predetermined allowable input voltage. In the resistance detection signal generation circuit of the variable resistor according to claim 1 or 2,
A resistance detection signal generation circuit for a variable resistor, further comprising an a-th resistance element interposed in the a-th current path. In the resistance detection signal generation circuit of the variable resistor according to any one of claims 1 to 3,
The resistance detection signal is a signal input to a signal receiving circuit having a function of controlling the amount of fuel supplied to the burner according to the voltage value of the resistance detection signal.
The b-th terminal when the DC power supply voltage is applied to the pair of power supply terminals in a state where the resistance value between the b-th terminal and the a-th terminal of the variable resistor is the minimum value of the variable width. When the voltage value generated at V is defined as V1, the signal receiving circuit is configured to decrease the amount of fuel supplied to the burner as the voltage value of the input resistance detection signal is closer to V1. A resistance detection signal generation circuit for a variable resistor. It has three terminals, the a-th terminal, the b-th terminal, and the c-th terminal, and the resistance value between each of the a-th terminal and the c-th terminal and the b-th terminal is determined between the a-th terminal and the c-th terminal. A resistance detection signal generation circuit that outputs a resistance detection signal, which is a signal corresponding to the variable resistance value of a variable resistor configured to be changeable within a range of a predetermined resistance value, from the b-th terminal. ,
A pair of power supply terminals to which a DC power supply voltage of a predetermined value is applied;
An a-th current path connecting one of the pair of power-supply terminals to the a-th terminal of the variable resistor;
A c-th current path connecting the other power terminal of the pair of power terminals to the c-th terminal of the variable resistor;
An a-th resistance element interposed in the a-th current path;
An output line conducting to the b-th terminal of the variable resistor;
A resistance element for connecting a middle portion of the output line to the one power supply terminal, the resistance value of the a-th resistance element and the predetermined resistance value between the a-th terminal and the c-th terminal of the variable resistor An auxiliary resistance element having a resistance value greater than the sum of
A variable resistor configured to output a voltage generated at the b-th terminal from the output line as the resistance detection signal in a state where the DC power supply voltage is applied to the pair of power supply terminals. Resistance detection signal generator circuit. In the resistance detection signal generation circuit of the variable resistor according to claim 5,
A resistance detection signal generation circuit for a variable resistor, further comprising a c-th resistance element interposed in the c-th current path.