JP2012181184A - Arithmetical controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arithmetical controlling device comprising a Wheatstone bridge circuit and a microcomputer, having improved reliability as a whole device.SOLUTION: An arithmetical controlling device includes a microcomputer, and an energization control circuit having a bridge circuit. When turning on a start-up switch allows a DC power source to supply a current to the microcomputer and the energization controlling circuit (S210), a CPU of the microcomputer initializes respective sections therein to start up (S220), and then outputs a change-over signal to change-over switches to turn on one of the change-over switches and turn off the other thereof (S230), and thereby switches one of fixed resistors in a change-over resistance part to a conductive state and the other thereof to a non-conductive state (S240), and then outputs an operation permission signal to a switching circuit to permit operation of the energization control circuit (consequently, operation of the bridge circuit) (S250). Accordingly, the device can securely prevent the energization control circuit from starting the operation during start-up of the microcomputer.

Description

  The present invention relates to a calculation control device that calculates a scale representing an environment in a detected atmosphere.

  In recent years, research on fuel cells has been actively conducted as a high-efficiency, clean energy source due to social demands such as environmental protection and nature conservation. Among them, solid polymer fuel cells (PEFCs) and hydrogen internal combustion engines are expected as energy sources for home use and on-vehicle use due to advantages such as low temperature operation and high output density.

In these systems, for example, hydrogen, which is a flammable gas, is used as a fuel, so detection of gas leakage is cited as one of important issues.
In this type of combustible gas detection device as a calculation control device that calculates (detects) the gas concentration of the combustible gas present in the detected atmosphere, it is arranged in the detected atmosphere and depends on the concentration of the combustible gas. It is known to use a heating resistor whose resistance value changes or a resistance temperature detector whose resistance value changes according to the environmental temperature.

  Specifically, in this combustible gas detection device, the resistance value of the heating resistor becomes a resistance value corresponding to a plurality of predetermined set temperatures (for example, two of the first set temperature and the second set temperature). , Controlled by the Wheatstone bridge circuit, and input detection signals based on the voltage across the heating resistor and resistance temperature detector at that time, and the temperature (environment temperature), humidity, and combustible gas concentration in the atmosphere to be detected Calculation is performed by a microcomputer.

  Note that the gas concentration of the combustible gas in the atmosphere to be detected is obtained from, for example, the signal level (voltage level) of the detection signal corresponding to the heating resistor at the first or second set temperature. Correction is made using the humidity corresponding to the ratio between the environmental temperature corresponding to the voltage level of the resistor and the voltage level at the first and second set temperatures in the heating resistor.

  In addition, a plurality of set temperatures (first set temperature, second set temperature, etc.) are selectively switched by a microcomputer between the conduction states of a plurality of fixed resistors having different resistance values installed in the Wheatstone bridge circuit. (See, for example, Patent Document 1).

Japanese Patent No. 4302611

  However, in the conventional combustible gas detection device, power is supplied in a state where none of the plurality of fixed resistors operates effectively (that is, all of the plurality of fixed resistors remain in a non-conductive state). Then, the Wheatstone bridge circuit may not operate properly, and the voltage level corresponding to the heating resistor may not reflect the gas concentration (and thus does not reflect the set temperature). In addition, a detection signal may be input while the microcomputer is starting up, which may cause the microcomputer operation to become unstable, and the gas concentration may be calculated in an unstable state. It was.

  In order to solve the above problems, an object of the present invention is to improve the reliability of the entire apparatus in an arithmetic and control apparatus including a Wheatstone bridge circuit and a microcomputer.

  The arithmetic and control device according to claim 1, which is an invention made to achieve the above object, is a device comprising a Wheatstone bridge circuit and a microcomputer. However, the Wheatstone bridge circuit is exposed to the atmosphere to be detected and has a resistance value that changes due to its own temperature change, a first fixed resistance unit, a second fixed resistance unit, and a command from the outside. A third resistor unit capable of switching itself to a conductive state or a non-conductive state, the first fixed resistor unit and the detection resistor unit, the second fixed resistor unit and the third resistor unit connected in series, Of each series circuit (two series circuits connected in series), the detection resistor unit and the third resistor unit side are connected to the reference potential, and the first and second fixed resistor unit sides are connected to the power source. Has been.

  On the other hand, the microcomputer outputs a command to switch the third resistance portion to a conductive state or a non-conductive state, inputs a detection signal based on a voltage across the detection resistance portion, and detects the detection based on the detection signal. A scale representing the environment in the detected atmosphere to which the resistance portion is exposed is calculated.

  In the present invention, the arithmetic and control unit configured as described above includes a power supply control circuit that controls power supply from the power supply to the Wheatstone bridge circuit, and the microcomputer operates the Wheatstone bridge circuit via the power supply control circuit. The operation permission means is permitted, and the operation permission means is configured to output a command to switch the third resistance portion from the non-conductive state to the conductive state before or simultaneously with the permission of the operation of the Wheatstone bridge circuit.

  In other words, in the arithmetic and control unit of the present invention, the Wheatstone bridge circuit does not operate unless permitted by the operation permission means of the microcomputer, and before the operation permission means permits the operation of the Wheatstone bridge circuit or simultaneously with the permission. Since the third resistance unit is switched from the non-conducting state to the conducting state, the control voltage (the detection signal based on the voltage across the detection resistor unit) does not have to be input during startup of the microcomputer. In other words, the microcomputer can input a detection signal based on the voltage across the detection resistor section while the Wheatstone bridge circuit is operating properly.

  Therefore, according to the present invention, the microcomputer operation does not become unstable, or the microcomputer does not have to calculate a scale representing the environment in the detected atmosphere in an unstable state. The reliability of the control device can be increased, and the detection accuracy of the scale representing the environment can be increased.

  In the arithmetic and control unit of the present invention, for example, a heating resistor whose resistance value changes according to the concentration of the combustible gas may be used as the detection resistance unit, or a temperature measurement whose resistance value changes depending on the environmental temperature. A resistor may be used. In addition, the first fixed resistor portion or the second fixed resistor portion may be configured by one fixed resistor or a plurality of fixed resistors. Furthermore, the third resistor portion may be configured with one fixed resistor or may be configured with a plurality of fixed resistors.

  For example, as described in claim 2, the third resistor unit effectively operates a plurality of fixed resistors that are connected in parallel and have different resistance values, and any one of these fixed resistors (details). Includes at least one switching unit connected to each fixed resistor and capable of switching each fixed resistor to a conductive state or a non-conductive state. In this case, the microcomputer outputs a command for switching each fixed resistor to the conductive state or the non-conductive state so as to selectively change the resistance value of the third resistor unit, thereby the third resistor unit. The arithmetic and control unit of the present invention is configured so as to selectively change the temperature of the detection resistor unit from among a plurality of preset temperatures preset in accordance with the resistance value.

  That is, in the arithmetic and control unit configured as described above, the Wheatstone bridge circuit can be appropriately operated even when the set temperature of the detection resistor unit is selectively switched. Therefore, a scale that represents the environment in the atmosphere to be measured can be obtained with high accuracy based on the output from the detection resistor unit under the configuration of selectively switching the set temperature of the detection resistor unit.

  The detection resistor unit generates heat when one of the fixed resistors constituting the third resistor unit is energized via the switching unit, and is set according to the fixed resistor in the conductive state (energized state). The temperature of the detection resistor portion rises to the temperature. For this reason, when each of the fixed resistors constituting the third resistance portion is in a non-conduction state (non-energization state), the temperature of the detection resistance portion converges to the temperature of the external environment.

  Here, in general, the plurality of set temperatures are temperatures at which the operation of the Wheatstone bridge circuit is stabilized when obtaining a scale representing the environment in the atmosphere to be measured, which is much higher than the temperature of the external environment. Become. Therefore, immediately after the third resistor portion switches from the non-energized state to the energized state and the detection resistor portion starts to generate heat, the above operation becomes a slight but unstable state, which is a scale representing the environment in the measured atmosphere. The detection accuracy may be reduced.

  To this end, as described in claim 3, the command output from the microcomputer before or simultaneously with the permission of the operation of the Wheatstone bridge circuit by the operation permission means is defined as the first switching command. The switching command may be a command for changing the resistance value of the third resistance unit so that the temperature of the detection resistor unit becomes a value corresponding to the highest set temperature among a plurality of set temperatures.

In this case, since the temperature of the detection resistor portion can reach the stable temperature at the time of energization relatively quickly, the detection accuracy of the scale representing the environment in the measured atmosphere can be further improved.
Further, as described in claim 4, the detected atmosphere is a gas atmosphere containing a combustible gas, and the microcomputer calculates the concentration of the combustible gas as a scale representing the environment in the detected atmosphere. In addition, the arithmetic and control unit of the present invention can be configured.

  When the atmosphere to be detected to which the detection resistance unit is exposed is a gas atmosphere containing a flammable gas, power may be supplied to the Wheatstone bridge circuit while the third resistance unit is in a non-conductive state. There is a risk that the resistance value of the detection resistor portion will increase greatly, leading to an excessive temperature rise in the detection resistor portion, and ignition of the combustible gas may occur. However, if the arithmetic and control unit of the present invention is applied, since the power is not supplied to the Wheatstone bridge circuit while the third resistance portion remains in a non-conductive state, the detection resistance portion includes a gas atmosphere containing flammable gas. The risk of ignition can be avoided even when exposed to.

It is a whole block diagram of a combustible gas detection apparatus. It is explanatory drawing which shows the structure of the gas detection element used as the principal part of a combustible gas detection apparatus. It is a flowchart which shows the content of the gas concentration calculation process. It is the 1st explanatory view showing the timing which changes the temperature setting, and detects the voltage at the time of high temperature, the voltage at the time of low temperature, and the temperature voltage, when obtaining gas concentration. It is explanatory drawing which shows possibility that the temperature of a heating resistor will overshoot, when an electricity supply control circuit act | operates before starting a microcomputer. It is a flowchart which shows the content of the operation start process. It is the 2nd explanatory view showing the timing which changes the temperature setting, and detects the voltage at the time of high temperature, the voltage at the time of low temperature, and the temperature voltage when obtaining gas concentration. It is the 1st schematic which illustrates arrangement of each part of a gas detection element. It is the 2nd schematic which illustrates arrangement of each part of a gas detection element.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall configuration diagram of a combustible gas detection device 1 to which the present invention is applied. 2A and 2B are explanatory views showing the configuration of the gas detection element 3 which is a main part of the combustible gas detection device 1. FIG. 2A is a plan view (however, the internal configuration is also partially shown), and FIG. It is AA sectional drawing in a).

[overall structure]
The combustible gas detection device 1 detects the concentration of combustible gas using a heat-conducting gas detection element 3, and is installed in a passenger room of a fuel cell vehicle, for example, to detect hydrogen leakage. Used for purposes.

  As shown in FIG. 1, the combustible gas detection device 1 includes a control circuit 5 that drives and controls the gas detection element 3 (see FIG. 2), an energization signal (operation permission signal S <b> 1) that controls the operation of the control circuit 5, Various processes such as a process (gas concentration calculation process) for generating the switching signal CG1 and the like and calculating the gas concentration of the combustible gas contained in the detected gas based on the detection signals V1 and VT obtained from the control circuit 5 A microcomputer (hereinafter referred to as “microcomputer”) 7 that executes processing, and a control circuit 5 and a microcomputer 7 that start and stop by connecting and disconnecting the power supply path from the DC power source Vcc to the combustible gas detector 1 And a switch 9.

The control circuit 5, the microcomputer 7, and the start switch 9 are configured on a single circuit board, and the gas detection element 3 is configured separately from the circuit board.
[Gas detection element]
Next, the gas detection element 3 will be described.

  As shown in FIG. 2, the gas detection element 3 includes a base 30 having a flat plate shape (square shape in plan view), and a plurality of electrodes 31 are formed on one surface (hereinafter referred to as “surface”) of the base 30. On the other surface (hereinafter referred to as “rear surface”), one recess 301 is formed in the vicinity of the center of the base 30 along one direction of the base 30.

The gas detection element 3 has a size of about several mm (for example, 3 mm × 3 mm) in both vertical and horizontal directions, and is manufactured using, for example, a micromachining technique.
The electrode 31 includes two electrodes 311 and 312 (hereinafter also referred to as “first electrode group”) arranged along one side of the base 30 (the lower side in FIG. 2A) and the other side. It consists of two electrodes 314 and 315 (hereinafter also referred to as “second electrode group”) arranged along the upper side in FIG. Among these, the electrodes 312 and 315 are also referred to as ground electrodes below. Moreover, as a material which comprises the electrode 31, aluminum (Al) or gold | metal | money (Au) is used, for example.

  The base 30 includes a silicon substrate 32 and an insulating layer 33 formed on one surface of the substrate 32, and a part of the substrate 32 so that the insulating layer 33 is partially exposed (here, approximately square). The diaphragm structure in which the recessed part 301 was formed is comprised by removing. That is, in the base portion 30, the insulating layer 33 side (the side where the substrate 32 is not removed) is the surface of the base portion 30, and the substrate 32 side (including the side where a part of the substrate 32 is removed) is the back surface of the base portion 30. It becomes.

  In the insulating layer 33, a linear heating resistor 34 wired in a spiral shape is embedded in a portion exposed on the back surface of the base 30 by the recess 301, and the side on which the second electrode groups 314 and 315 are formed. A resistance temperature detector 35 used for temperature measurement is embedded along one side of the base 30. In other words, the heating resistor 34 is arranged in a region closer to the center than the resistance temperature detector 35 in the insulating layer 33, and the resistance temperature detector 35 extends along one of the four sides forming the edge of the insulating layer 33. Is located in the area.

  Note that the insulating layer 33 may be formed of a single material, or may be formed of a plurality of layers using different materials. As the insulating material constituting the insulating layer 33, for example, silicon oxide (SiO2) or silicon nitride (Si3N4) is used.

  The heating resistor 34 is made of a conductive material whose resistance value changes according to its own temperature change, and the temperature measuring resistor 35 changes its electrical resistance in proportion to the temperature (in this embodiment, the temperature rises). It is made of a conductive material whose resistance value increases accordingly. However, the heating resistor 34 and the temperature measuring resistor 35 are both made of the same resistance material, platinum (Pt) in this embodiment.

  The heating resistor 34 is connected to the first electrode group 311, 312 via a wiring 36 and a wiring film 37 embedded in the same plane as the heating resistor 34 is formed, and the resistance thermometer 35. Are connected to the second electrode groups 314 and 315 via a wiring film (not shown) embedded in the same plane as that on which the resistance temperature detector 35 is formed.

  In addition, as a material constituting the wiring 36 and the wiring film 37, the same resistance material as that of the heating resistor 34 and the temperature measuring resistor 35 is used. Further, the electrode 31 formed on the surface of the base 30 and the wiring film 37 formed inside the base 30 (insulating layer 33) are connected by a contact hole (connection conductor).

  That is, one end of the heating resistor 34 is connected to the electrode 311 and the other end is connected to the ground electrode 312, and the resistance temperature detector 35 is connected so that one end is connected to the electrode 314 and the other end is connected to the ground electrode 315. .

The gas detection element 3 configured as described above is used in a state where it is exposed to the atmosphere to be detected (in this embodiment, a gas atmosphere containing a flammable gas).
[Control circuit]
Next, the configuration of the control circuit 5 will be described.

  As shown in FIG. 1, the control circuit 5 controls the energization of the heating resistor 34 and outputs a detection signal V 1 corresponding to the voltage across the heating resistor 34, and the resistance temperature detector 35. And a temperature adjustment circuit 80 that outputs a temperature detection signal VT representing the temperature of the atmosphere to be detected.

[Energization control circuit]
The energization control circuit 50 includes a bridge circuit (Wheatstone bridge circuit) 51 configured to include the heating resistor 34, an amplifier circuit 53 that amplifies the potential difference detected by the bridge circuit 51, and an output of the amplifier circuit 53. A current adjustment circuit 55 that increases and decreases the current flowing through the circuit 51 and a switching circuit 57 that controls power supply to the bridge circuit 51 are provided.

  The switching circuit 57 is connected to the power supply line that supplies the DC power supply Vcc to the bridge circuit 51 and the control line CL1 that changes the energization state of the current adjustment circuit 55, and is turned on and off in accordance with the operation permission signal S1 from the microcomputer 7. It is composed of a transistor, and is configured to output an activation signal S11 to the control line CL1 for a predetermined period during which the transistor is on. Note that a predetermined period during which the transistor is turned on (hereinafter also referred to as “start-up period”) is set in advance so as not to prevent the output of the adjustment signal C described later.

  The current adjustment circuit 55 includes a transistor that is connected to the power supply line and the bridge circuit 51 and whose energization state (ON resistance) changes according to a signal flowing through the control line CL1. Specifically, current supply to the bridge circuit 51 is started in accordance with the activation signal S11 that is the output of the switching circuit 57. When the current supply to the bridge circuit 51 is started, the ON resistance increases as the adjustment signal C increases in accordance with the adjustment signal C output from the amplifier circuit 53, and the current flowing through the bridge circuit 51 decreases. Conversely, the smaller the adjustment signal is, the smaller the on-resistance is, and the current flowing through the bridge circuit 51 is increased.

  The amplifier circuit 53 includes an operational amplifier 531, fixed resistors 532 and 533 connected to the inverting input terminal and the non-inverting input terminal of the operational amplifier 531, and the inverting input terminal and output terminal of the operational amplifier 531. It consists of a well-known differential amplifier circuit composed of a fixed resistor 534 and a capacitor 535 connected in parallel.

  That is, when the input voltage of the non-inverting input terminal is larger than the input voltage of the inverting input terminal, the adjustment signal C that is the output of the amplifier circuit 53 increases (and the current flowing through the bridge circuit 51 decreases), and conversely. When the input voltage at the non-inverting input terminal is smaller than the input voltage at the inverting input terminal, the adjustment signal C is reduced (and the current flowing through the bridge circuit 51 is increased).

  The bridge circuit 51 includes a heating resistor 34, two fixed resistors 511, 512, and a switching resistor 52 that can switch a resistance value. The fixed resistor 511, the heating resistor 34, the fixed resistor 512, and the switching resistor The units 52 are connected in series, and the end portions PG on the heating resistor 34 side and the switching resistor unit 52 side of each series circuit are grounded (that is, connected to the ground potential as the reference potential), and the fixed resistors 511, Each end on the 512 side is connected to the power supply side (current adjustment circuit 55).

  The connection point P + between the fixed resistor 511 and the heating resistor 34 is connected to the non-inverting input terminal of the operational amplifier 531 via the fixed resistor 532, and the connection point between the fixed resistor 512 and the switching resistor unit 52. P− is connected to the inverting input terminal of the operational amplifier 531 through the fixed resistor 533. Further, the potential at the connection point P + is supplied to the microcomputer 7 as the detection signal V1.

  In addition, the switching resistance unit 52 is configured to effectively operate either one of the fixed resistors 521 and 522 in accordance with the two fixed resistors 521 and 522 having different resistance values and the switching signal CG1 from the microcomputer 7. Thus, the balance of the bridge circuit 51 can be changed by switching the resistance value of the switching resistor 52 by the changeover switch 523.

  However, the changeover switch 523 is composed of two switches 524 and 525 for connecting the fixed resistor 512 and the fixed resistors 521 and 522, respectively, and turns on one of the switches 524 and 525. And the other is turned off, and when the on / off operation is switched alternately, the structure is switched after passing through a non-energized state in which neither of the solid resistors 521 and 522 is energized. I have it.

  The fixed resistor 521 has a resistance value at which the heating resistor 34 becomes the first set temperature CH (for example, 400 ° C.), and the fixed resistor 522 has the heating resistor 34 set lower than the first set temperature CH. The resistance value becomes the second set temperature CL (for example, 300 ° C.).

  In the energization control circuit 50 configured as described above, when the switching circuit 57 is turned on only during the start-up period and energization of the bridge circuit 51 is started, the amplifier circuit 53 and the current adjustment circuit 55 are connected between the connection points P + and P−. The current flowing in the bridge circuit 51 is adjusted so that the potential difference generated in the circuit becomes zero. As a result, the resistance value (and thus the temperature) of the heating resistor 34 is controlled to a constant value (and thus the first set temperature CH or the second set temperature CL) determined by the switching resistance unit 52.

  Specifically, when the content of the combustible gas in the atmosphere to be detected changes and the amount of heat taken away by the combustible gas becomes larger than the amount of heat generated by the heat generating resistor 34, As the temperature decreases, the resistance value of the heating resistor 34 decreases. Conversely, when the amount of heat taken away by the combustible gas is smaller than the amount of heat generated by the heating resistor, the temperature of the heating resistor 34 rises, and the resistance value of the heating resistor 34 increases.

  On the other hand, when the resistance value of the heat generating resistor 34 decreases, the amplifier circuit 53 and the current adjusting circuit 55 increase the current flowing through the bridge circuit 51 and thus the amount of heat generated by the heat generating resistor 34. When the resistance value of the resistor 34 increases, the current flowing through the bridge circuit 51, and hence the amount of heat generated by the heating resistor 34, is reduced, so that the resistance value (and thus the temperature) of the heating resistor 34 is kept constant. .

  In other words, from the detection signal V1 representing the potential at the connection point P +, the magnitude of the current flowing through the heating resistor 34, that is, the amount of heat necessary for keeping the temperature (resistance value) of the heating resistor 34 constant (and further, , The amount of heat taken away by the combustible gas), and the amount of heat has a magnitude corresponding to the gas concentration, so that the gas concentration of the combustible gas can be determined from the detection signal V1. Specifically, when calculating the gas concentration, correction is performed using the humidity H in the atmosphere to be detected. This will be described in “gas concentration calculation processing” described later.

[Temperature measurement circuit]
Next, the temperature adjustment circuit 80 includes a bridge circuit (Wheatstone bridge) 81 that includes the resistance temperature detector 35 and an amplifier circuit 83 that amplifies the potential difference obtained from the bridge circuit 81.

  The amplifier circuit 83 includes an operational amplifier 831, fixed resistors 832 and 833 connected to the inverting input terminal and the non-inverting input terminal of the operational amplifier 831, and the inverting input terminal and the output terminal of the operational amplifier 831. It consists of a well-known differential amplifier circuit composed of a fixed resistor 834 and a capacitor 835 connected in parallel.

  The bridge circuit 81 includes a resistance temperature detector 35 and three fixed resistance bodies 811, 812, and 813, and the fixed resistance body 811 and the resistance temperature detector 35, and the fixed resistance body 812 and the fixed resistance body 813 are connected in series. In each series circuit, each end on the resistance temperature detector 35 and the fixed resistor 813 side is grounded, and each end on the fixed resistor 811, 812 side is connected to a power source.

  The connection point P− between the fixed resistor 811 and the resistance temperature detector 35 is connected to the inverting input terminal of the operational amplifier 531 via the fixed resistor 833, and the connection point between the fixed resistor 812 and the fixed resistor 813. P + is connected to the non-inverting input terminal of the operational amplifier 831 via the fixed resistor 832. The output of the operational amplifier 831 is supplied to the microcomputer 7 as the temperature detection signal VT.

The resistance temperature detector 35 is set such that the temperature detection signal VT becomes a reference value when the temperature of the detected atmosphere (gas atmosphere) to which the gas detection element 3 is exposed is a preset reference temperature.
The resistance value of the resistance temperature detector 35 changes as the temperature of the atmosphere to be detected changes. As a result, a potential difference corresponding to the difference from the reference temperature is generated. An amplified version of this potential difference is used as the temperature detection signal VT. Is output.

  In connection between the gas detection element 3 and the control circuit 5, the electrode 31 (311, 312, 314, 315) of the gas detection element 3 is connected to the connection point P + of the energization control circuit 50 and the electrode 314 is connected to the electrode 311. The ground electrodes 312 and 315 are connected to the common ground line of the control circuit 5 at the connection point P− of the temperature adjustment circuit 80.

[Microcomputer]
The microcomputer 7 is a storage device (ROM, RAM, etc.) that stores various programs and data for executing gas concentration calculation processing, a CPU that executes programs stored in the storage device, and inputs and outputs various signals. For example, a well-known device including an IO port, a timer for timekeeping, and the like.

  Here, the signal level of the detection signal V1 detected at the first set temperature (400 ° C.) is the high temperature voltage VH1, and the signal level of the detection signal V1 detected at the second set temperature (300 ° C.) is the low temperature voltage. The signal level of the temperature detection signal VT read from VL1 and the temperature adjustment circuit 80 is referred to as a temperature voltage VL.

  In the storage device, temperature conversion data representing the correlation between the environmental temperature T and the temperature voltage VT in the detected atmosphere, the humidity H and the high temperature voltage VH1, the low temperature voltage VL1, and the temperature voltage VT in the detected atmosphere. The humidity conversion data representing the correlation between the high temperature voltage VH1 or the low temperature voltage VL1 and the concentration conversion data representing the correlation between the gas concentration X of the combustible gas are stored. Each conversion data specifically includes conversion map data, a conversion calculation formula, and the like, and is created in advance based on data obtained through experiments or the like.

The humidity conversion data includes the environmental temperature T (and thus the temperature voltage VT) and a voltage ratio V described later.
Voltage ratio conversion map data representing a correlation with C (0) and humidity conversion map data representing a correlation between a voltage ratio difference ΔVC and humidity H described later are included. Further, the concentration conversion data includes high temperature voltage conversion map data representing a correlation between the temperature voltage VT and a high temperature voltage VH1 (0) described later, a high temperature voltage VH1 and a humidity H, and a high temperature voltage change ΔVH1 described below. (H) includes humidity voltage change conversion map data, temperature voltage VT and high temperature voltage VH1, and gas sensitivity conversion map data indicating a correlation between gas sensitivity G (VT) described later. Yes.

[Gas concentration calculation processing]
Here, the gas concentration calculation process executed by the CPU of the microcomputer 7 will be described with reference to the flowchart shown in FIG.

The CPU of the microcomputer 7 executes an operation permission process (described later) for permitting the operation of the control circuit 5, and starts the gas concentration calculation process after the completion of the process.
When this process (gas concentration calculation process) is executed, first, in S110, the low temperature voltage VL1 and the high temperature voltage VH1 are acquired from the energization control circuit 50, and the temperature voltage VT is acquired from the temperature adjustment circuit 80.

  Specifically, the resistance value of the bridge circuit 51, that is, the set temperature of the heating resistor 34 is held at the second set temperature CL for a certain time TW (hereinafter referred to as “low temperature measurement period”) by the switching signal CG1. Thereafter, the setting is switched, and control is performed to maintain the first set temperature CH for a certain time TW again (hereinafter referred to as “high temperature measurement period”) (see FIG. 4).

  That is, by performing on / off control for alternately switching the on / off operations of the switches 524 and 525 of the changeover switch 523 every predetermined time TW, the set temperature of the heating resistor 34 is set to the first set temperature CH and the second set temperature CH. The temperature is alternately switched to the set temperature CL.

  In parallel with this, the low-temperature voltage VL1 is detected during the low-temperature measurement period, the high-temperature voltage VH1 is detected during the high-temperature measurement period, and the temperature voltage VT is detected at any timing in both periods. The fixed time TW may be, for example, a time required for the output of the detection signal V1 to be sufficiently stabilized after switching the temperature setting, and is set to 10 ms to several hundred ms (for example, 200 ms).

In S120, the voltage ratio VC is calculated using the low temperature voltage VL1 and the high temperature voltage VH1 acquired in S110 as input values of the following equation (1).
VC = VH1 / VL1 (1)
In parallel with this, in S130, based on the temperature voltage VT acquired in S110 and the map data for voltage ratio conversion, the gas concentration X and the humidity H at the environmental temperature T (and thus the temperature voltage VT) are obtained. The voltage ratio VC (0) when is zero is calculated.

  In S140, the voltage ratio difference VC in the ambient temperature T (and thus the temperature voltage VT) is obtained by using the voltage ratio VC calculated in S120 and the VC (0) calculated in S130 as input values of the following equation (2). Is calculated.

ΔVC = VC−VC (0) (2)
Next, in S150, the humidity H at the voltage ratio difference ΔVC is calculated based on the voltage ratio difference ΔVC calculated in S140 and the humidity conversion map data.

In parallel with this, in S160, based on the high temperature voltage VH1, the temperature voltage VT acquired in S110, and the high temperature voltage conversion map data, the gas concentration at the ambient temperature T (and thus the temperature voltage VT). A high-temperature voltage VH1 (0) when X and humidity H are zero is calculated.

  Subsequently, in S170, the high temperature voltage VH1 obtained in S110, the humidity H calculated in S150, and the humidity voltage change conversion map data are provided by the humidity H of the high temperature voltage VH1. A high-temperature voltage change ΔVH1 (H) that represents the voltage change is calculated.

  In S180, the high-temperature voltage VH1 acquired in S110, the high-temperature voltage VH1 (0) calculated in S160, and the high-temperature voltage change ΔVH1 (H) calculated in S170 are expressed by the following equation (3). As an input value, a high-temperature voltage change ΔVH1 (G) representing a voltage change caused by the combustible gas in the high-temperature voltage VH1 is calculated.

ΔVH1 (G) = VH1−VH1 (0) −ΔVH1 (H) (3)
In parallel with this, in S190, based on the high temperature voltage VH1, the temperature voltage VT acquired in S110, and the gas sensitivity conversion map data, the environmental temperature T (and thus the temperature voltage VT) is determined for the high temperature voltage VH1. ) Gas sensitivity G (VT) representing the sensitivity (in units of the reciprocal of the gas concentration X) for the combustible gas set in advance.

  Finally, in S200, the gas concentration of the combustible gas is obtained by using the high-temperature voltage change ΔVH1 (G) calculated in S180 and the gas sensitivity G (VT) calculated in S190 as input values of the following equation (4). X is calculated, and the process returns to S110.

X = ΔVH1 (G) / G (VT) (4)
As described above, in the present process, the on / off control for alternately switching the on / off operations of the switches 524 and 525 of the changeover switch 523 every predetermined time TW is performed, whereby the fixed resistor 512 and the switching resistor unit 52 are The energization path (the energization path in the switching resistor 52) from the connection point P- to the end PG (the end on the ground side in the switching resistor 52) is changed from one of the fixed resistors 521 and 522 to the other. By switching, the low temperature voltage VL1 and the high temperature voltage VH1 are acquired. Then, the humidity H and the gas concentration X of the combustible gas in the detected atmosphere are calculated using the low temperature voltage VL1 and the high temperature voltage VH1 acquired by switching the energization path in the switching resistance unit 52. .

  However, since the changeover switch 523 has a structure in which the on / off operation of the two switches 524 and 525 can be alternately switched as described above, the energization path in the changeover resistor 52 is changed from one side to the other. When switching to the side, a non-energized period (time lag period) in which neither path is energized is generated. Since this time lag period is a minute time with respect to the fixed time TW, a large current flows to the connection point P + side between the fixed resistor 511 and the heating resistor 34, so that the temperature of the heating resistor 34 overshoots. You do n’t have to. However, if this process ends by chance during the time lag period, the time lag period will increase if the energization control circuit 50 is activated before the microcomputer 7 is started after the DC power supply Vcc is turned on next time. As a result, the temperature of the heating resistor 34 (and consequently the signal level of the detection signal V1) may overshoot (see FIG. 5), and the operation of the combustible gas detection device 1 may become unstable.

In order to prevent this, when the DC power supply Vcc is turned on, the CPU of the microcomputer 7 performs the following operation permission process before starting the gas concentration calculation process.
[Operation permission processing]
That is, as shown in FIG. 6, when the CPU of the microcomputer 7 is supplied with power from the DC power source Vcc to the microcomputer 7 (and the control circuit 5) by turning on the start switch 9 (S210), each part in the microcomputer 7 Is started (S220), and the operation permission process is started.

  Subsequent to the process of S220, by outputting the change signal CG1 to the changeover switch 523, among the switches 524 and 525 of the changeover switch 523 that are both in the non-energized state (off state), the switches 524 of the changeover switch 523 are both. One of 525 is operated to be turned on and the other is operated to be turned off (S230), whereby one of the fixed resistors 521 and 522 in the switching resistor unit 52 (one set in advance to be selected) is conducted. While switching to a state, the other is switched to a non-conducting state (S240). That is, the fixed resistor which is set to be selected in advance in the switching resistor 52 is switched from the non-conductive state to the conductive state, so that the fixed resistor is effectively operated. Note that the switching signal CG1 output to the selector switch 523 at this time corresponds to the first switching command.

  Then, by outputting the operation permission signal S1 to the switching circuit 57, the operation of the energization control circuit 50 (and hence the operation of the bridge circuit 51) is permitted (S250), this process is terminated, and the above-described gas concentration calculation process is performed. Start. Note that energization of the heating resistor 34 is started by permitting the operation of the energization control circuit 50 in S260.

[effect]
As described above, in the combustible gas detection device 1 of the present embodiment, when the DC power supply Vcc is turned on, the microcomputer 7 is activated to execute the operation permission process, whereby the energization control circuit 50 (and the temperature). The operation of the adjusting circuit 80) is permitted.

  Therefore, according to the combustible gas detection device 1 of the present embodiment, the energization control circuit 50 is activated when the microcomputer 7 is activated or when both the fixed resistors 521 and 522 of the switching resistor 52 are in the non-conduction state. It is possible to prevent the operation from starting, thereby preventing the temperature of the heating resistor 34 from overshooting.

  In the combustible gas detection device 1, since the microcomputer 7 performs the gas concentration calculation process after the operation permission process is performed, any one of the fixed resistors 521 and 522 of the switching resistor unit 52 after the microcomputer 7 is started up. Various control voltages (high temperature voltage VH1, low temperature voltage VL1, temperature voltage VT) can be detected in the conductive state, thereby preventing the microcomputer 7 from outputting an erroneous calculation value. it can.

  Further, the combustible gas detection device 1 calculates the humidity H from the high temperature voltage VH1, the low temperature voltage VL1, and the environmental temperature T from the temperature voltage VT in the gas concentration calculation process. Is used to calculate (correct) the gas concentration X in the atmosphere to be detected, so that the gas concentration X can be obtained with high accuracy.

[Correspondence with Claims]
In the present embodiment, the heating resistor 34 is the detection resistor, the fixed resistor 511 is the first fixed resistor, the fixed resistor 512 is the second fixed resistor, and the fixed resistors 521 and 522 are the third resistor. The fixed resistor, the switching circuit 57 corresponds to the power supply control circuit, the operation permission processing S250 corresponds to the operation permission means, and the switches 524 and 525 of the changeover switch 523 correspond to the switching unit.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, the combustible gas detection device 1 of the above embodiment is merely an example of the calculation control device of the present invention, and does not necessarily include the temperature adjustment circuit 80 as a component, and calculates the gas concentration in the detected atmosphere. be able to.

  In addition, the combustible gas detection device 1 of the above-described embodiment has the switching resistor 52 having two fixed resistors 521 and 522 in order to calculate the humidity (in other words, to increase the gas concentration detection accuracy). Although any one of them is configured to operate effectively, the switching resistor 52 includes only one of the fixed resistors 521 and 522, and the state of the fixed resistor is in a conductive state or a non-conductive state. It may be configured to switch to

  Furthermore, the arithmetic and control unit of the present invention may be applied to a humidity detection device that detects only the humidity H in the detected atmosphere instead of the gas concentration. In addition, when applying to a humidity detection apparatus, the temperature adjustment circuit 80 becomes unnecessary.

  In the operation permission process of the above embodiment, after outputting the switching signal CG1 to the changeover switch 523 (S230), the operation permission signal S1 for permitting the operation of the bridge circuit 51 is output (S250). However, the switching signal CG1 and the operation permission signal S1 may be output simultaneously. In this case, the operation permission process can be shortened, and the gas concentration calculation process can be started immediately.

  In the operation permission process of the above embodiment, one of the fixed resistors 521 and 522 in the switching resistor 52 is switched to the conductive state and the other is switched to the non-conductive state. Of the fixed resistors 521 and 522, the one to be switched to the conductive state first may be determined in advance.

  For example, the heating resistor 34 generates heat when one of the fixed resistors 521 and 522 in the switching resistor 52 is energized via the switches 524 and 525 of the changeover switch 523, and the fixed resistor is in an energized state. Therefore, the temperature of the heating resistor 34 rises to a set temperature corresponding to the above. For this reason, when all of the fixed resistors 521 and 522 in the switching resistor unit 52 are in a non-conduction state (non-energization state), the temperature of the heating resistor 34 converges to the environmental temperature T.

  Here, the first set temperature (400 ° C.) and the second set temperature (300 ° C.) are temperatures at which the operation of the energization control circuit 50 is stabilized when the gas concentration X of the flammable gas is obtained. The temperature is much higher than that. Therefore, immediately after any one of the fixed resistors 521 and 522 in the switching resistor unit 52 is switched from the non-energized state to the energized state and the heating resistor 34 starts to generate heat, the operation is unstable to a slight extent. Thus, the detection accuracy of the gas concentration X of the combustible gas may be lowered.

  On the other hand, in the operation permission process, as shown in FIG. 7, among the fixed resistors 521 and 522 in the switching resistor 52, the heating resistor 34 is the first set temperature (400) that is the set temperature on the high temperature side. It is preferable that the fixed resistor 521 having a temperature of [° C.] is switched to the conductive state and the other fixed resistor 522 is switched to the non-conductive state in advance.

  In this case, since the temperature of the heating resistor 34 can reach the stable temperature at the time of energization relatively quickly, the detection accuracy of the gas concentration X of the combustible gas immediately after the start of the combustible gas detection device 1 is further improved. Can be made.

  By the way, in the combustible gas detection apparatus 1 of the said embodiment, in the gas detection element 3, the resistance temperature sensor 35 is arrange | positioned in the area | region along one side of the four sides which form the edge of the insulating layer 33, For example, as shown in FIG. 8, the resistance temperature detector 35 is a region (heating resistance) along the three sides of the edge of the insulating layer 33 in a state where the gas detection element 3 is viewed in plan. The region surrounding the body 34) may be arranged.

  Further, in the combustible gas detection device 1 of the above embodiment, the first electrode group 311, 312 and the second electrode group 314, 315 are arranged along the sides facing each other on the surface of the base 30. For example, as shown in FIG. 8, the first electrode group 311, 312 and the second electrode group 314, 315 are arranged in a region along the same side of the edge of the surface of the base 30. May be.

  That is, in the arrangement configuration of each part in the gas detection element 3 shown in FIG. 8, it is possible to secure a wider arrangement region of the resistance temperature detector 35 as compared with the above embodiment. It is easy to design the length so as to obtain a resistance value in a desired range, the degree of design freedom can be further improved, and the temperature detection accuracy can be increased.

  Further, in the arrangement configuration of each part in the gas detection element 3 shown in FIG. 8, an input / output circuit (for example, a circuit) provided outside the gas detection element 3 and the first electrode groups 311 and 312 and the second electrode groups 314 and 315. As a result, the wiring structure can be simplified, and as a result, the entire combustible gas detection device 1 can be reduced in size.

  In addition, the arrangement configuration of each part in the gas detection element 3 is not limited to the configuration illustrated in FIG. 8. For example, as illustrated in FIG. 9A, the first electrode groups 311 and 312 and the second electrode groups 314 and 315 include A region (a region surrounding the heating resistor 34 and the first electrode groups 311, 312) arranged along the sides facing each other on the base 30 and the resistance temperature detector 35 along the three sides at the edge on the base 30. ).

  Further, for example, as shown in FIG. 9B, the arrangement configuration of each part in the gas detection element 3 is a region along the two sides where the resistance thermometer 35 is connected at the edge on the base 30 (the heating resistor 34 and (A region surrounding the first electrode group 311, 312).

  DESCRIPTION OF SYMBOLS 1 ... Combustible gas detection apparatus, 3 ... Gas detection element, 5 ... Control circuit, 7 ... Microcomputer, 9 ... Starting switch, 34 ... Heating resistor, 35 ... Resistance temperature detector, 50 ... Current supply control circuit, 51 ... Bridge Circuit 52, switching resistor 55 55 current adjustment circuit 57 switching circuit 80 temperature adjustment circuit 81 bridge circuit 87 switching circuit 511 512 521 522 fixed resistor 523 switching switch.

Claims (4)

A detection resistor part that is exposed to the atmosphere to be detected and whose resistance value changes due to its own temperature change, a first fixed resistor part, a second fixed resistor part, and a third resistor part including at least one fixed resistor And comprising a third resistance unit capable of switching itself to a conductive state or a non-conductive state based on a command from the outside, the first fixed resistance unit, the detection resistance unit, and the second fixed resistance unit, Each of the third resistor units is connected in series, and of the two series circuits connected in series, the detection resistor unit and the third resistor unit side are connected to a reference potential, and the first and second fixed resistors are connected. Wheatstone bridge circuit configured by connecting the part side to the power supply,
The command to switch the third resistance portion to a conductive state or a non-conductive state is output, and a detection signal based on a voltage across the detection resistor portion is input, and based on the detection signal, the environment in the detected atmosphere A microcomputer for calculating a scale representing
An arithmetic and control unit comprising:
A power control circuit for controlling power supply from the power source to the Wheatstone bridge circuit;
The microcomputer has an operation permission means for permitting the operation of the Wheatstone bridge circuit via the power supply control circuit, and before or simultaneously with the permission of permitting the operation of the Wheatstone bridge circuit by the operation permission means. The calculation control device characterized in that the command for switching the third resistance unit from a non-conducting state to a conducting state is output. The third resistor unit includes a plurality of fixed resistors having different resistance values connected in parallel and at least one of the fixed resistors connected to the fixed resistors and capable of switching the fixed resistors to a conductive state or a non-conductive state. Including the above switching unit,
The microcomputer outputs the command to switch the fixed resistor to a conductive state or a non-conductive state so as to selectively change the resistance value of the third resistor unit, thereby outputting the command to the switching unit. The arithmetic control device according to claim 1, wherein the temperature of the detection resistor unit is selectively changed from among a plurality of preset temperatures preset according to the resistance value of the three resistor units. The command output by the microcomputer before or simultaneously with the permission of the operation of the Wheatstone bridge circuit by the operation permission means is a first switching command,
The first switching command is a command for changing the resistance value of the third resistor unit so that the temperature of the detection resistor unit becomes a value corresponding to the highest set temperature among the plurality of set temperatures. The arithmetic and control unit according to claim 2 characterized by things. The detected atmosphere is a gas atmosphere containing a flammable gas,
4. The calculation control device according to claim 1, wherein the microcomputer calculates a concentration of the combustible gas as a scale representing an environment in the detected atmosphere. 5.

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