JP2018200283A - Gas sensor, gas alarm, control device, control method, and heater driving method - Google Patents

Abstract

To shorten time to be spent on applying a voltage to a heater by shortening time until a heater reaches a target temperature in a gas sensor.SOLUTION: A gas sensor having a gas detection part 12 and a heater 14 for heating the gas detection part for detecting object gas on the basis of an electric signal of the gas detection part heated to a target temperature by the heater comprises a heating control part 30 for applying an initial drive voltage larger than a set voltage corresponding to the target temperature to the heater, and for changing the voltage to be applied to the heater from the initial drive voltage to the set voltage in a state that the temperature of the heater rises.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas sensor, a gas alarm device, a control device, a control method, and a heater driving method.

Conventionally, a gas sensor realizing power saving has been known (see, for example, Patent Document 1). The gas sensor includes a heater that heats the gas detection unit. For example, the gas sensor heats the gas detection unit to a target temperature by applying a pulsed voltage to the heater. The gas sensor determines the presence or absence of the detection gas by measuring the electrical resistance of the gas detection unit heated to the target temperature. As a related technique, a technique is known in which the application time of a pulse voltage applied to the heater is adjusted based on the measurement result of the ambient temperature of the gas sensor (see, for example, Patent Document 2). A technique for adjusting the value of a pulsed voltage applied to a heater according to gas sensitivity characteristics is known (see, for example, Patent Document 3).
[Patent Literature]
[Patent Document 1] Japanese Patent No. 5946004 [Patent Document 2] Japanese Patent Application Laid-Open No. 11-248659 [Patent Document 3] Japanese Patent Application Laid-Open No. 11-248661

  In the gas sensor, it is desirable from the viewpoint of power saving to shorten the time for applying the voltage to the heater by shortening the time until the heater reaches the target temperature.

  In a first aspect of the present invention, a gas sensor is provided. The gas sensor may include a gas detection unit and a heater. The heater may heat the gas detector. The gas sensor may detect the target gas based on an electric signal of a gas detection unit heated to a target temperature by a heater. The gas sensor may include a heating control unit. The heating control unit applies an initial drive voltage larger than a set voltage corresponding to the target temperature to the heater, and changes the voltage applied to the heater from the initial drive voltage to the set voltage while the heater temperature is rising. You may change it.

  The heating control unit may change the voltage applied to the heater from the initial driving voltage to the set voltage in a state where the heater temperature T1 (° C.) is in a range satisfying the following mathematical formula 1. Formula 1 is 0.8T2 <= T1 <= 1.2T2. However, T2 is a target temperature (° C.).

  The heating control unit may change the voltage applied to the heater from the initial driving voltage to the set voltage when the heater temperature is lower than the target temperature.

  The gas sensor may further include a storage unit. The storage unit may store information about a period during which the initial drive voltage is applied. The heating control unit may change the voltage applied to the heater from the initial drive voltage to the set voltage when the period has elapsed.

  The gas sensor may further include a temperature measurement unit and a period setting unit. The temperature measuring unit may measure the temperature of the heater. The period setting unit may set the period based on a temperature rise characteristic of the heater according to a measurement result by the temperature measurement unit when a predetermined voltage is applied to the heater. The storage unit may store information about the period set by the period setting unit.

  The gas sensor may further include a temperature measurement unit. The temperature measuring unit may measure the temperature of the heater. The heating control unit may change the voltage applied to the heater from the initial drive voltage to the set voltage when the temperature of the heater measured by the temperature measurement unit reaches a predetermined value.

  The heating control unit applies a second initial drive voltage that is greater than the first initial drive voltage and greater than the set voltage after the first initial drive voltage is applied to the heater, and the heater is in a state where the heater temperature is increased. The voltage applied to may be changed from the second initial drive voltage to the set voltage. The first initial drive voltage may be greater than the set voltage.

  The heating control unit applies a second initial drive voltage that is smaller than the first initial drive voltage and greater than the set voltage after applying a first initial drive voltage that is greater than the set voltage to the heater, so that the heater temperature rises. In this state, the voltage applied to the heater may be changed from the second initial drive voltage to the set voltage.

  The gas sensor may include a temperature measurement unit and a heating condition setting unit. The temperature measuring unit may measure the temperature of the heater. The heating condition setting unit is a first period in which the first initial drive voltage is applied based on a temperature rise characteristic of the heater according to a measurement result by the temperature measurement unit when a predetermined voltage is applied to the heater, The magnitude of the second initial drive voltage may be set.

  The gas sensor may include an ambient temperature measurement unit and a correction unit. The ambient temperature measurement unit may measure the ambient temperature of the gas sensor. The correction unit may correct at least one of the first period in which the first initial drive voltage is applied and the second period in which the second initial drive voltage is applied based on the ambient temperature. The correction unit may correct at least one value of the first initial drive voltage and the second initial drive voltage based on the ambient temperature.

  The heating control unit may periodically pulse the heater. In each pulse drive, the heating control unit may change the voltage applied to the heater from the initial drive voltage to the set voltage in a state where the initial drive voltage is applied to the heater and the temperature of the heater is rising. The gas alarm may include a gas sensor. The gas alarm device may further include an alarm generation unit. The alarm generation unit may issue an alarm when the target gas is detected based on the electric signal of the gas detection unit.

  In a second aspect of the present invention, a control device is provided. The control device may control the gas sensor. The gas sensor may include a gas detection unit and a heater. The heater may heat the gas detector. The gas sensor may detect the target gas based on an electric signal of a gas detection unit heated to a target temperature by a heater. The control device may include a heating control unit. The heating control unit applies an initial driving voltage larger than the set voltage corresponding to the target temperature to the heater, and sets the voltage applied to the heater from the initial driving voltage while the heater temperature is rising. You may change to voltage.

  In the third aspect of the present invention, a control method is provided. The control method may be a gas sensor control method. The gas sensor may include a gas detection unit and a heater. The heater may heat the gas detector. The gas sensor may detect the target gas based on an electric signal of a gas detection unit heated to a target temperature by a heater. The control method may include a step of applying to the heater an initial drive voltage that is higher than a set voltage corresponding to the target temperature. The control method may include a step of changing a voltage applied to the heater from an initial drive voltage to a set voltage in a state where the temperature of the heater is rising.

  In a fourth aspect of the present invention, a heater driving method is provided. The heater may include a semiconductor substrate, a thermally insulating support layer, and a heater layer. A space having an opening may be formed in the semiconductor substrate. The heat insulating support layer may be provided on the space. The heater layer may be supported on the heat insulating support layer. The heater driving method may include a step of applying to the heater layer an initial driving voltage that is higher than a set voltage corresponding to the target temperature. The heater driving method may include a step of changing a voltage applied to the heater layer from an initial driving voltage to a set voltage while the temperature of the heater layer is rising.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is the schematic of the gas sensor 100 of 1st Embodiment of this invention. 2 is a cross-sectional view illustrating an example of a schematic configuration of a detection unit 10. FIG. 4 is a plan view illustrating another example of the schematic configuration of the detection unit 10. FIG. It is sectional drawing along the AA 'line of the detection part 10 of FIG. It is a figure which shows an example of the intermittent drive of the heater. It is a figure which shows the heater drive voltage pattern in the gas sensor 100 of 1st Embodiment of this invention. It is a figure which shows the change of the heater temperature in the gas sensor 100 of 1st Embodiment of this invention. It is a figure which shows the heater drive voltage pattern in the gas sensor of a comparative example. It is a figure which shows the change of the heater temperature in the gas sensor of a comparative example. It is a figure explaining other examples of heater drive in gas sensor 100 of a 1st embodiment of the present invention. It is a figure explaining other examples of heater drive in gas sensor 100 of a 1st embodiment of the present invention. It is a flowchart which shows an example of the processing content by the gas sensor 100 of 1st Embodiment of this invention. It is a flowchart which shows an example of the setting process of an initial drive period. It is a flowchart which shows an example of the processing content by the gas sensor 100 of 2nd Embodiment of this invention. It is a figure which shows the heater drive voltage pattern in the gas sensor 100 of 3rd Embodiment of this invention. It is a figure which shows the change of the heater temperature in the gas sensor 100 of 3rd Embodiment of this invention. It is a flowchart which shows an example of the processing content by the gas sensor 100 of 3rd Embodiment of this invention. It is a figure which shows the heater drive voltage pattern in the gas sensor 100 of 4th Embodiment of this invention. It is a flowchart which shows an example of the processing content by the gas sensor 100 in the gas sensor 100 of 4th Embodiment of this invention. It is a flowchart which shows an example of the setting process of heating conditions.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a schematic diagram of a gas sensor 100 according to a first embodiment of the present invention. The gas sensor 100 of this example detects a target gas. The target gas may be a combustible gas. The target gas may be city gas mainly containing methane, or LP gas mainly containing propane and butane. Further, the target gas may be CO (carbon monoxide) or VOC (volatile organic compound).

  The gas sensor 100 includes a detection unit 10 and a control device 200. The detection unit 10 includes a gas detection unit 12 and a heater 14. The detection unit 10 of this example includes a temperature measurement unit 16 that measures the temperature of the heater 14. Unlike this example, the detection unit 10 may not include the temperature measurement unit 16.

  The electrical signal of the gas detector 12 varies depending on the type and concentration of the existing gas. For example, the gas detection unit 12 includes a sensor resistance whose resistance value varies depending on the type and concentration of gas. The heater 14 heats the gas detection unit 12. The gas sensor 100 detects the target gas based on the electrical signal of the gas detector 12 heated to the target temperature by the heater 14. The target temperature is the temperature of the heater when the set voltage is applied to the heater 14 and the heater temperature is stabilized. The target temperature may be a gas detection processing temperature. The target temperature may be 350 ° C. or higher and 450 ° C. or lower, and particularly about 400 ° C.

  The control device 200 controls the gas sensor 100. In this example, both the detection unit 10 and the control device 200 are built in the gas sensor 100. However, the control device 200 may be a control device externally attached to the gas sensor 100. The control device 200 includes a measurement unit 20 and a heating control unit 30. The measurement unit 20 acquires an electrical signal from the gas detection unit 12. For example, the measurement unit 20 measures the resistance value of the sensor resistance in the gas detection unit 12. Specifically, the measurement unit 20 may measure the voltage across the sensor resistance by passing a current through the sensor resistance in the gas detection unit 12. Thus, the electric signal of the gas detection unit 12 may be a voltage or a current associated with the electric resistance value of the sensor resistance.

  The heating control unit 30 controls the voltage applied to the heater 14. In particular, the heating controller 30 applies an initial drive voltage to the heater 14 that is larger than the set voltage corresponding to the target temperature. Then, the heating control unit 30 changes the voltage applied to the heater 14 from the initial driving voltage to the set voltage in a state where the temperature of the heater 14 is increased by applying the initial driving voltage. For example, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage when a predetermined period has elapsed.

  After the voltage applied to the heater 14 is switched from the initial drive voltage to the set voltage, the temperature of the heater 14 converges to the target temperature. The heating control unit 30 shortens the heating period compared to the case where the set voltage is applied from the beginning. Thereby, power saving is realized. The heating control unit 30 may be configured by a microcomputer.

  The gas sensor 100 may be a gas alarm device that issues an alarm when a target gas is detected. When the gas sensor 100 is a gas alarm device, the control device 200 may include an alarm generation unit. The alarm generation unit issues an alarm when the target gas is detected based on the measurement by the detection unit 10. The alarm generation unit may include an alarm sound output unit that emits a sound such as an alarm sound. The alarm sound output unit may include a speaker, a buzzer, and the like. The alarm generation unit may include an alarm display unit that displays an alarm state by blinking or lighting an LED (light emitting diode) or the like. However, the alarm generation unit is not an essential component.

  The control device 200 of this example includes a setting unit 50, a storage unit 60, a correction unit 70, and an ambient temperature measurement unit 80. The setting unit 50 sets information or parameters necessary for the heating control unit 30 to control the heater 14. For example, the setting unit 50 sets the heating condition by the heating control unit 30. The setting unit 50 of this example sets the timing for switching the voltage applied to the heater 14 from the initial drive voltage to the set voltage. In one example, the setting unit 50 functions as a period setting unit that sets a period during which the initial drive voltage is applied to the heater 14 based on the temperature rise characteristics of the heater 14. The temperature rise characteristic of the heater 14 may be acquired according to a measurement result by the temperature measurement unit 16 when a predetermined test voltage is applied to the heater 14.

  The storage unit 60 stores information or parameters necessary for the heating control unit 30 to control the heater 14. For example, the storage unit 60 stores information on the initial drive period t1, which is a period during which the initial drive voltage is applied to the heater 14. Information about the initial drive period t1 may be stored in the storage unit 60 in advance at the time of factory shipment. As described above, when the setting unit 50 automatically sets the initial drive period t1, the storage unit 60 may store information on the initial drive period t1 set by the setting unit 50.

  The ambient temperature measurement unit 80 measures the ambient temperature of the gas sensor 100. The ambient temperature may be a temperature in an environment where the gas sensor 100 is disposed. The above-described temperature measurement unit 16 may also be used as the ambient temperature measurement unit 80. The correction unit 70 may correct at least one of the period and voltage value of the initial drive voltage applied to the heater 14 based on the measured ambient temperature. The correction unit 70 may increase the period of the initial drive voltage applied to the heater 14 and increase the voltage value of the initial drive voltage as the ambient temperature decreases.

  In addition, although the case where the control apparatus 200 of this example includes the setting unit 50, the storage unit 60, the correction unit 70, and the ambient temperature measurement unit 80 has been described, the control apparatus 200 is not limited to this case. Unlike the present example, the control device 200 does not necessarily include each unit. For example, when the period during which the initial drive voltage is applied is not automatically set, the setting unit 50 is omitted. Further, when the correction of the initial drive voltage is not performed according to the ambient temperature, the correction unit 70 and the ambient temperature measurement unit 80 may be omitted. Further, as described above, an alarm generation unit may be provided so as to issue an alarm when the target gas is detected based on the measurement by the detection unit.

FIG. 2 is a cross-sectional view illustrating an example of a schematic configuration of the detection unit 10. The detection unit 10 of this example is a thin film semiconductor sensor. The detection unit 10 of this example includes a silicon substrate 2, a thermal insulation support layer 3, a heater layer that functions as a heater 14, an electrical insulation layer 4, and a gas detection unit 12. A through hole 6 is provided in the silicon substrate 2. The through-hole 6 constitutes a diaphragm structure. The gas detection unit 12 includes a bonding layer 7, a gas detection layer electrode 8, a gas detection layer 5, and a catalyst layer 9. The gas sensing layer 5 may be a sensor resistance. The gas sensing layer 5 is formed as a sensing layer mainly composed of a metal oxide such as SnO ₂ , In ₂ O ₃ , WO ₃ , ZnO, and TiO ₂ .

The catalyst layer 9 is a sintered body supporting at least one type of catalyst such as Pd, PdO, and Pt. In one example, the catalyst layer 9 is a catalyst-supported Al ₂ O ₃ sintered body and is mainly composed of a metal oxide such as Cr ₂ O ₃ , Fe ₂ O ₃ , Ni ₂ O ₃ , ZrO ₂ , SiO ₂ , or zeolite. May be formed. The silicon substrate 2 is an example of a semiconductor substrate. The silicon substrate 2 is composed of a silicon wafer. The heater 14 heats the gas detection unit 12. The detection unit 10 detects the target gas based on the electrical signal of the gas detection unit 12 when the gas detection unit 12 is heated by the heater 14. For example, the detection unit 10 detects the target gas based on the resistance value of the gas sensing layer 5.

  In the detection unit 10 of this example, a heater structure using MEMS technology is employed. The heater structure of this example includes a silicon substrate 2 in which a space having an opening is formed. In this example, a through hole 6 is formed in the silicon substrate 2 as a space having an opening. A heat insulating support layer 3 is provided on the space having the opening. In this example, the heat insulating support layer 3 may be stretched over the entire opening of the through hole 6 of the silicon substrate 2 to form a diaphragm structure. The heater 14 which is a heater layer is supported by the heat insulating support layer 3.

  The gas sensor 100 using the heater 14 realizing low power consumption is realized by the heater structure using the MEMS technology. The thermal responsiveness of the heater 14 is improved by downsizing the heater 14 and reducing the heat capacity. Further, by providing the through hole 6 in the silicon substrate 2, heat transfer from the heater 14 to the surrounding environment can be reduced. However, the structure of the detection unit 10 is not limited to that having a diaphragm structure.

  FIG. 3 is a plan view illustrating another example of the schematic configuration of the detection unit 10. FIG. 4 is a cross-sectional view taken along the line AA ′ of the detection unit 10 of FIG. 3 and 4 also employs a heater structure using MEMS technology. In the heater structure shown in FIGS. 3 and 4, a cavity 18 is formed in the silicon substrate 2 as a space having an opening. The cavity 18 has an opening on the upper surface of the silicon substrate 2, but the lower surface side of the silicon substrate 2 is not open. The cavity 18 may have a quadrangular pyramid shape or a truncated pyramid shape.

  A thermally insulating support layer 3 is provided on the cavity 18. The heat insulating support layer 3 may include a central portion located at the center on the cavity 18 and a plurality of bridge portions connecting the central portion and the peripheral portion. The heat insulating support layer 3 is partially provided with holes 17. A heater 14 is provided at the center of the heat insulating support layer 3. Also in the detection unit 10 shown in FIGS. 3 and 4, heat transfer from the heater 14 to the surrounding environment can be reduced.

  Moreover, the detection part 10 is not necessarily restricted to a thin film semiconductor type sensor like this example. The detection unit 10 may be a hot-wire semiconductor sensor or a contact combustion sensor. The hot-wire semiconductor sensor includes a gas detection unit made of a metal oxide semiconductor electrically connected in parallel to a heater. The contact combustion type sensor includes a gas detection element including a catalyst layer having oxidation activity on a heater, and a gas detection unit including a compensation element having a catalyst layer inactive to gas on the heater. In the case of a hot-wire semiconductor sensor and a catalytic combustion sensor, a heater that constitutes a part of the gas detection unit is also used as a heater for heating the gas detection unit. Therefore, the gas detection unit and the heater may be combined without being provided separately.

  Next, driving of the heater 14 by the heating control unit 30 will be described. FIG. 5 is a diagram illustrating an example of intermittent driving of the heater 14. The heating control unit 30 periodically drives the heater 14 in pulses. That is, the heating control unit 30 periodically applies a pulsed voltage as a heater driving voltage to the heater 14. The heating control unit 30 may apply a pulsed voltage to the heater 14 with a period P of 30 seconds or more and 60 seconds or less. The heater 14 is intermittently driven between room temperature and a target temperature of 400 ° C. The period P may be a repetition period of adjacent pulsed voltages.

  The gas detector 12 is heated to a target temperature by the heater 14. The heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage in a state where the initial drive voltage is applied to the heater 14 and the temperature of the heater 14 is rising in each pulse drive. .

  FIG. 6 is a diagram illustrating a heater driving voltage pattern in the gas sensor 100 according to the first embodiment of the present invention. FIG. 6 shows a voltage waveform obtained by enlarging one pulse-like voltage portion shown in FIG. The vertical axis represents the ratio of the heater drive voltage to the set voltage. The ratio is 1 when the heater driving voltage is a set voltage value. The ratio is greater than 1 when the heater drive voltage is greater than the set voltage. The horizontal axis indicates time.

  As shown in FIG. 6, the heating control unit 30 applies an initial drive voltage, which is larger than the set voltage corresponding to the target temperature, to the heater 14. Next, when the initial drive period t1 has elapsed, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage. The heating control unit 30 applies a set voltage to the heater 14 over a period t2. A period obtained by adding the period t1 and the period t2 corresponds to the heating period. In the gas sensor 100 of the first embodiment, the target temperature may be 400 ° C. The power consumption of the heater may be several tens of mW. The heater driving voltage may be several volts.

  FIG. 7 is a diagram illustrating changes in the heater temperature in the gas sensor 100 according to the first embodiment of the present invention. FIG. 7 shows the transition of the heater temperature when the heater 14 is driven with the heater drive voltage pattern shown in FIG. The vertical axis in FIG. 7 indicates the ratio of the heater temperature to the target temperature. The horizontal axis in FIG. 7 indicates time.

  As shown in FIG. 7, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage while the temperature of the heater 14 is rising. Specifically, the initial voltage is applied so that the voltage applied to the heater 14 is changed from the initial drive voltage to the set voltage while the temperature of the heater 14 is rising when the initial drive voltage is applied to the heater 14. A driving period t1 may be set.

  The heating control unit 30 may read information on the initial drive period t1 stored in the storage unit 60. The heating control unit 30 may change the voltage applied to the heater 14 from the initial driving voltage to the set voltage with reference to the read information of the initial driving period t1. When the voltage applied to the heater 14 is changed from the initial drive voltage to the set voltage, the temperature of the heater 14 may stop rising and converge to the target temperature. Thereafter, when the heating period ends and the heater 14 is turned off, the temperature of the heater 14 decreases.

  FIG. 8 is a diagram showing a heater driving voltage pattern in the gas sensor of the comparative example. The vertical axis represents the ratio of the heater drive voltage to the set voltage. The ratio is 1 when the heater driving voltage is a set voltage value. As shown in FIG. 8, the gas sensor of the comparative example applies a set voltage corresponding to the target temperature to the heater as a heater drive voltage from the beginning of applying the voltage. In the comparative example, the set voltage is applied to the heater 14 over a period in which the pulse width is 0.1 seconds. Except for this point, the structure of the gas sensor of the comparative example may be the same as the structure of the gas sensor 100 of the first embodiment shown in FIGS. 1 and 2. Therefore, repeated description is omitted.

  FIG. 9 is a diagram illustrating changes in the heater temperature in the gas sensor of the comparative example. FIG. 9 shows changes in the heater temperature when the heater is driven with the heater drive voltage pattern shown in FIG. When the heater is driven, the shortest pulse width applied to the heater is the time t1 ′ required for the temperature rise to a predetermined target temperature, and the electric signal of the gas detection unit 12 while being heated to the target temperature. Etc., and may be defined as the total time with the processing time t2 ′ of the device. In the gas sensor of the comparative example, for example, the time t1 ′ is 0.05 seconds, the processing time t2 ′ is 0.05 seconds, and the total time of the time t1 ′ and the time t2 ′ is 0.1 seconds. .

  In the gas sensor of the comparative example, for example, when the target temperature is 400 ° C., the power consumption of the heater is several tens of mW, and the heater driving voltage is several volts, the heater of the gas sensor of the comparative example The time t1 ′ required for the temperature rise may be about 0.05 seconds. In addition, time t1 'has shown the response time in the state in which the gas detection part 12 which is a heating target exists. If only the heater 14 is present without the gas detector 12, the time required for the temperature rise to the target temperature of 400 ° C. may be about 1/10 of about 0.005 seconds.

  The gas sensor as in the comparative example has a time t1 ′ of about 0.05 seconds and good thermal response. Therefore, it is difficult to keep the temperature of the heater constant by general PWM control. Therefore, fluctuations in the pulse voltage applied to the heater during intermittent driving can be suppressed over the entire pulse application time (heating period) as shown in FIG. That is, a constant set voltage for keeping the heater temperature at the target temperature may be applied to the heater over a period of about 0.1 seconds.

  As shown in FIG. 2, the gas sensor of the comparative example reduces power consumption by increasing the diameter of the through-holes constituting the diaphragm structure or by thinning the heat insulating support layer 3 constituting the diaphragm. Can do. However, even if a heater with reduced power consumption is used, t1 ′ required for temperature rise to the target temperature is not shortened.

  For example, even if a heater with half power consumption compared to the conventional case is applied to a gas sensor with a time t1 ′ of about 0.05 seconds, the time t1 ′ is the same as long as the heater and the heating object have the same heat capacity. Is about double. The processing time t2 ′ does not change because it is irrelevant to the power consumption. Therefore, the entire heating period is t1 + t2 = 0.15 seconds. As a result, even if the heater power consumption Ph is halved, the heating period is increased by a factor of 1.5, so the average power consumption of the heater is not halved but 3/4.

  Further, the power consumed in the control circuit part other than the heater becomes smaller as the pulse output time becomes shorter. Therefore, it is desirable from the viewpoint of power saving to shorten the time for applying the voltage to the heater. According to the gas sensor 100 of the first embodiment, as shown in FIG. 6, by applying an initial drive voltage higher than the set voltage to the heater 14 in the initial drive period t1, the time required for the temperature rise to the target temperature is reduced. This can be made shorter than the time t1 ′ required for the temperature rise in the comparative example.

  The initial drive period t1 may be shorter than the time t1 ′ required for the temperature rise in the comparative example. According to a specific experiment, by setting the initial drive voltage to 1.44 times the set voltage and setting the initial drive period t1 to 0.01 seconds, the temperature of the heater 14 reaches the target temperature of 400 ° C. in 0.01 seconds. I was able to reach. After the temperature of the heater 14 reached the target temperature, a set voltage was applied to the heater 14 over a period t2 so as to keep the temperature of the heater 14 at the target temperature.

As described above, according to the gas sensor 100 of the present embodiment, the entire heating period can be shortened from 0.1 seconds in the comparative example to 0.06 seconds. If the power consumption in the heater 14 is given by V ² / R (where V is the heater drive voltage and R is the resistance of the heater), in the comparative example, the power consumption per pulse (W (Second) is (V ₁ ² /R)·(0.05+0.05)=0.1 (V ₁ ² / R).

On the other hand, in the case of the gas sensor 100 of the present embodiment, the power consumption (W · second) per pulse is ((1.44 · V ₁ ) ² /R)·0.01+(V ₁ ² / R) · (0.05) ≈0.07 (V ₁ ² / R). Therefore, according to this example, the power consumption amount is reduced by about 30% compared to the comparative example. Furthermore, the heating period during which pulses are output is shortened from 0.1 seconds to 0.06 seconds in the comparative example. Therefore, the power consumption in the control circuit portion other than the heater 14 is also reduced.

  In the example shown in FIGS. 6 and 7, the time when the temperature T1 of the heater 14 becomes the target temperature T2, that is, the time when the ratio shown on the vertical axis in FIG. 7 becomes 1, coincides with the initial drive period t1. Yes. However, the gas sensor 100 of this embodiment is not limited to this case.

  FIG. 10 is a diagram illustrating another example of heater driving in the gas sensor 100 according to the first embodiment of the present invention. In FIG. 10, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage when the heater temperature is lower than the target temperature. Depending on the heat capacities of the heater 14 and the gas detection unit 12 that is the object to be heated, if the voltage applied to the heater 14 is changed after the heater temperature reaches the target temperature, the heater temperature exceeds the target temperature and overshoots. There is a case.

  As shown in FIG. 10, when the heater temperature is lower than the target temperature, the voltage applied to the heater 14 is changed from the initial drive voltage to the set voltage, thereby preventing overshoot and reducing power consumption. Can do. In FIG. 10, when the heater temperature T1 reaches 0.8T2 or 0.9T2 (where T2 is the target temperature), the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage. The initial drive period t1 is set so as to change to the set voltage.

  FIG. 11 is a diagram illustrating another example of heater driving in the gas sensor 100 according to the first embodiment of the present invention. In FIG. 11, when the heater temperature T1 is higher than the target temperature, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage. When the voltage applied to the heater 14 is changed to the set voltage and the temperature of the heater 14 is stabilized, the temperature of the heater 14 converges to the target temperature.

As described above, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage in a state where the temperature T1 (° C.) of the heater 14 is in a range satisfying the following Equation 1. You can do it.
[Formula 1]
0.8T2 ≦ T1 ≦ 1.2T2 where T2 is the target temperature (° C.).

  If the voltage applied to the heater 14 is switched to the set voltage in a state where the temperature T1 (° C.) of the heater 14 is lower than 0.8T2, the time until the target temperature is reached becomes longer. On the other hand, if the voltage applied to the heater 14 is switched to the set voltage while the temperature T1 (° C.) of the heater 14 is higher than 1.2T2, the heater temperature overshoots and power consumption increases. Therefore, it is desirable to switch the voltage applied to the heater 14 to the set voltage in a state where the temperature T1 (° C.) of the heater 14 is in a range satisfying the following mathematical formula 1.

  FIG. 12 is a flowchart illustrating an example of processing contents performed by the gas sensor 100 according to the first embodiment of the present invention. FIG. 12 shows a control method of the gas sensor 100. The heating control unit 30 applies an initial drive voltage higher than the set voltage to the heater 14 (step S101). Waiting for the initial drive period t1 to elapse (step S102: YES), the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage (step S103).

  In step S103, the voltage change timing is set so that the voltage applied to the heater is changed from the initial drive voltage to the set voltage while the temperature of the heater 14 is rising. Specifically, the voltage change timing may be set in advance by the initial drive period t1. Step S103 corresponds to a voltage change stage in which the voltage applied to the heater 14 is changed from the initial drive voltage to the set voltage while the temperature of the heater 14 is rising.

  When the set voltage is applied to the heater 14 and the temperature of the heater 14 is stabilized, the temperature of the heater 14 becomes the target temperature. The gas detector 12 heated by the heater 14 also reaches the target temperature with a slight delay. The measurement unit 20 acquires an electrical signal from the gas detection unit 12 (step S104). For example, the measurement unit 20 measures the voltage across the gas sensing layer 5 by passing a current through the gas sensing layer 5 in the gas sensing unit 12. Thereby, the measurement unit 20 may acquire an electric resistance value of the gas sensing layer 5 or a voltage corresponding to the electric resistance value as an electric signal of the gas detection unit 12.

  The gas sensor 100 detects the target gas based on the electric signal from the gas detector 12 (step S105). Specifically, as the concentration of the target gas present increases, the electrical resistance value of the gas sensing layer 5 in the gas sensing unit 12 decreases. Therefore, the gas sensor 100 may determine that the target gas exists if the electrical resistance value of the gas sensing layer 5 is less than a predetermined threshold value. The determination may be performed by the measurement unit 20 or may be performed by another configuration.

  When the target gas is detected (step S105: YES), the control device 200 generates a signal indicating the detection of the target gas (step S106). For example, the alarm generation unit of the control device 200 issues a gas leak alarm. If the electric resistance value of the gas sensing layer 5 is equal to or greater than the threshold value, the target gas is not detected (step S105: NO), and the process proceeds to step S107.

  When the entire heating period in which the period t1 and the period t2 are added has elapsed (step S107: YES), the heating control unit 30 stops energizing the heater 14 (step S108). The heating control unit 30 may pulse-drive the heater 14 periodically. Accordingly, the heating control unit 30 waits for the heater driving period P of 30 seconds to 60 seconds to elapse (step S109: YES), and then applies the initial drive voltage to the heater 14 again (step S101). .

  FIG. 13 is a flowchart illustrating an example of an initial drive period setting process. The heating control unit 30 applies a predetermined voltage to the heater 14 (step S201). With the voltage applied to the heater 14, the temperature measurement unit 16 measures the heater temperature at a plurality of times (step S202). The temperature rise characteristic of the heater 14 according to the measurement result by the temperature measurement unit 16 is acquired. The acquired temperature rise characteristic may be stored in the storage unit 60 or the like. The acquired temperature rise characteristic reflects the heat capacities of the heater 14 and the gas detector 12. When the same voltage is applied to the heater 14, the smaller the heat capacity, the shorter the time for raising the temperature to a predetermined temperature.

  The setting unit 50 sets a period during which an initial drive voltage is applied to the heater 14, that is, an initial drive period t1 based on the temperature rise characteristics of the heater 14 (step S203). Specifically, the setting unit 50 may set the initial drive period t1 to be longer as the heat capacities of the heater 14 and the gas detection unit 12 calculated based on the acquired temperature rise characteristics are larger. This is because the larger the heat capacities of the heater 14 and the gas detector 12, the longer it takes to reach the target temperature. Information on the set initial drive period t1 is stored in the storage unit 60 (step S204).

  The initial drive period setting process shown in FIG. 13 may be executed when the product of the gas sensor 100 is shipped. The setting unit 50 may periodically execute the initial drive period setting process. For example, the setting unit 50 may execute the initial drive period setting process at a predetermined time once a day. However, the frequency of executing the initial drive period setting process is not limited to this case. The initial drive period t1 can be appropriately set by the initial drive period setting process. Therefore, even when the heat capacities of the heater 14 and the gas detection unit 12 vary, the heating control unit 30 can change the initial drive voltage to the set voltage at an appropriate timing.

  The processing of the gas sensor 100 of the present embodiment is not limited to the case shown in FIG. The setting unit 50 may set the initial drive voltage of the heater 14 based on the temperature rise characteristics of the heater 14 with the initial drive period t1 as a fixed period. When the initial value of the initial drive voltage is applied to the heater 14 and the time until the heater temperature reaches the target temperature is shorter than the expected time, the setting unit 50 sets the initial drive voltage to be smaller than the initial value. To do. When the time until the heater temperature reaches the target temperature is longer than the assumed time, the setting unit 50 may set the initial drive voltage larger than the initial value. The assumed time may be the initial driving period t1.

  Thereby, the setting part 50 may set the magnitude | size of an initial stage drive voltage so that heater temperature may reach target temperature in the assumed time. Information about the set initial drive voltage may be stored in the storage unit 60. Alternatively, the setting unit 50 may determine the magnitude of the initial drive voltage and the initial drive period t1 while calculating the temperature by measuring the heater resistance value.

  As described above, according to the gas sensor 100 of the first embodiment, an initial driving voltage larger than the set voltage corresponding to the target temperature is applied to the heater 14. Then, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage while the temperature of the heater 14 is rising. Therefore, the time until the temperature of the heater 14 reaches the target temperature can be shortened. By shortening the heating time, the power consumption in the heater 14 can be reduced. Further, since the time for outputting the pulsed voltage to the heater 14 is shortened, the amount of power consumed in the control circuit portion other than the heater 14 is also reduced.

  According to the gas sensor 100 of the first embodiment, information on the initial drive period t1 is stored in the storage unit 60. When the initial drive period t1 has elapsed, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage. Therefore, since the voltage applied to the heater 14 can be switched over time, the voltage applied to the heater 14 can be switched quickly without depending on the thermal responsiveness of the temperature measuring unit 16.

  FIG. 14 is a flowchart showing an example of processing contents performed by the gas sensor 100 according to the second embodiment of the present invention. The gas sensor 100 according to the second embodiment includes a temperature measuring unit 16 that measures the temperature of the heater 14. Then, the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage when the temperature of the heater 14 measured by the temperature measurement unit 16 reaches a predetermined value. The heating control unit 30 controls the voltage according to the measurement result of the heater temperature. Therefore, the setting unit 50 does not have to set the initial drive period t1. Except for switching the voltage applied to the heater 14 in accordance with the heater temperature, the structure of the gas sensor 100 of the second embodiment is the same as the structure of the gas sensor 100 of the first embodiment, so that repeated description is omitted. Is done.

  Also in the gas sensor 100 of the present embodiment, the heating control unit 30 applies an initial drive voltage higher than the set voltage to the heater 14 (step S301). The temperature measurement unit 16 measures the heater temperature (step S302). Waiting for the heater temperature to reach a predetermined value (step S302: YES), the heating control unit 30 changes the voltage applied to the heater 14 from the initial drive voltage to the set voltage (step S304). While the temperature of the heater 14 is rising, the voltage applied to the heater is changed from the initial drive voltage to the set voltage. In one example, the predetermined value may be set in advance within a range from 0.8T2 to 1.2T2. However, T2 is a target temperature (° C.).

  The following processing from step S305 to step S310 is the same as the processing from step S104 to step S309 in FIG. Therefore, repeated description is omitted. Also in the gas sensor 100 of the second embodiment, the heating control unit 30 applies an initial drive voltage to the heater 14 that is larger than the set voltage corresponding to the target temperature. Then, the voltage applied to the heater 14 is changed from the initial drive voltage to the set voltage while the temperature of the heater 14 is rising. Therefore, the time until the temperature of the heater 14 reaches the target temperature can be shortened, and the heating period can be shortened.

  FIG. 15 is a diagram illustrating a heater driving voltage pattern in the gas sensor 100 according to the third embodiment of the present invention. The vertical axis represents the ratio of the heater drive voltage to the set voltage. The ratio is 1 when the heater driving voltage is a set voltage value. The ratio is greater than 1 when the heater drive voltage is greater than the set voltage. The horizontal axis indicates time.

  In the gas sensor 100 of the third embodiment, the heating control unit 30 applies a second initial drive voltage that is greater than the first initial drive voltage and greater than the set voltage after applying the first initial drive voltage to the heater 14. Then, the heating control unit 30 changes the voltage applied to the heater 14 from the second initial drive voltage to the set voltage while the temperature of the heater 14 is rising. In particular, the first initial drive voltage may be greater than the set voltage. Except for these points, the structure of the gas sensor 100 of the third embodiment is the same as the structure of the gas sensor 100 of the first and second embodiments. Therefore, repeated description is omitted.

  In the gas sensor 100 of this example, the total time t1 of the first initial driving period (first period) t11 and the second initial driving period (second period) t12 is the time required for the temperature rise to the target temperature in the comparative example. It may be shorter than t1 ′. The first initial drive period t11 is a period during which the first initial drive voltage is applied to the heater 14. The second initial drive period t12 is a period during which the second initial drive voltage is applied to the heater 14.

  In this example, both the first initial drive period t11 and the second initial drive period t12 are 0.005 seconds. In this example, by setting the first initial drive voltage to 1.25 times the set voltage and the second initial drive voltage to 1.55 times the set voltage, the temperature of the heater 14 becomes the target temperature of 400 ° C. in 0.01 seconds. Was able to reach. The entire heating period is 0.06 seconds, which is a total of the period t1 that is 0.01 seconds and the period t2 that is 0.05 seconds. Also in the present embodiment, the heating period can be shortened from 0.1 seconds to 0.06 seconds as compared with the comparative example shown in FIGS. However, the heating conditions are not limited to these cases.

  According to the gas sensor 100 of the present embodiment, since the first initial drive voltage is smaller than the second initial drive voltage, the inrush current of the heater 14 can be limited. The inrush current means a large current that temporarily flows when a voltage is applied to the heater 14. Immediately after the voltage is applied to the heater, the heater 14 is still at a temperature lower than the target temperature, so the electrical resistance of the heater 14 is small, and therefore a large current flows. When the heater 14 generates heat and warms up, the electric resistance of the heater 14 increases and the flowing current decreases. According to the gas sensor 100 of this example, the inrush current can be limited and the heater 14 can be protected by making the first initial drive voltage first applied to the heater 14 lower than the second initial drive voltage. Can do.

  In the gas sensor 100 of the present embodiment, the case where the two stages of the initial driving voltage, that is, the first initial driving voltage and the second initial driving voltage are applied, has been described. It may be. In order to limit the inrush current, the first initial drive voltage may be lower than the set voltage. However, from the viewpoint of shortening the heating period while limiting the inrush current to some extent, it is desirable that the heating control unit 30 applies a first initial drive voltage higher than the set voltage to the heater.

  FIG. 16 is a diagram illustrating changes in the heater temperature in the gas sensor 100 according to the third embodiment of the present invention. FIG. 16 shows changes in the heater temperature when the heater 14 is driven with the heater drive voltage pattern shown in FIG. The vertical axis in FIG. 16 indicates the ratio of the heater temperature to the target temperature. The horizontal axis in FIG. 16 indicates time. As shown in FIG. 16, the time when the temperature T1 of the heater 14 becomes the target temperature T2, that is, the time when the ratio shown on the vertical axis of FIG. 16 becomes 1, coincides with the total time t1. However, the gas sensor 100 of this embodiment is not limited to this case.

  The heating control unit 30 may change the voltage applied to the heater 14 from the second initial drive voltage to the set voltage when the heater temperature is lower than the target temperature. Alternatively, the heating control unit 30 may change the voltage applied to the heater 14 from the second initial drive voltage to the set voltage when the heater temperature is higher than the target temperature.

The heating control unit 30 may change the voltage applied to the heater 14 from the second initial drive voltage to the set voltage in a state where the temperature T1 (° C.) of the heater 14 is in a range satisfying the following mathematical formula 1. .
[Formula 1]
0.8T2 ≦ T1 ≦ 1.2T2 where T2 is the target temperature (° C.).

  FIG. 17 is a flowchart illustrating an example of processing contents performed by the gas sensor 100 according to the third embodiment of the present invention. The heating control unit 30 applies a first initial drive voltage higher than the set voltage to the heater 14 (step S401). However, unlike the present example, the first initial drive voltage does not necessarily have to be greater than the set voltage. Next, after waiting for the first initial drive period t11 to elapse (step S402: YES), the heating control unit 30 applies a second initial drive voltage higher than the first initial drive voltage to the heater 14 (step S403). . The second initial drive voltage is greater than the set voltage.

  Next, after the second initial drive period t12 has elapsed (step S404: YES), the heating control unit 30 changes the voltage applied to the heater 14 from the second initial drive voltage to the set voltage (step S405). ). The voltage change timing is set so that the voltage applied to the heater is changed from the second initial drive voltage to the set voltage while the temperature of the heater 14 is rising. Specifically, the voltage change timing may be set in advance by the first initial drive time t11 and the second initial drive period t12. When a set voltage is applied to the heater 14 and the temperature of the heater 14 is stabilized, the temperature of the heater 14 becomes the target temperature.

  The processing from step S406 to step S411 is the same as the processing from step S104 to step S109 in FIG. Therefore, repeated description is omitted. According to the gas sensor 100 of the third embodiment, the time until the temperature of the heater 14 reaches the target temperature can be shortened, and the heating period can be shortened. Further, the heater 14 can be protected by limiting the inrush current.

  FIG. 18 is a diagram illustrating a heater driving voltage pattern in the gas sensor 100 according to the fourth embodiment of the present invention. The vertical axis represents the ratio of the heater drive voltage to the set voltage. The ratio is 1 when the heater driving voltage is a set voltage value. The ratio is greater than 1 when the heater drive voltage is greater than the set voltage. The horizontal axis indicates time.

  In the gas sensor 100 of the fourth embodiment, the heating control unit 30 applies a second initial drive voltage that is smaller than the first initial drive voltage and greater than the set voltage after applying a first initial drive voltage greater than the set voltage to the heater 14. Apply. Then, the heating control unit 30 changes the voltage applied to the heater 14 from the second initial drive voltage to the set voltage while the temperature of the heater 14 is rising.

  The setting unit 50 sets the first initial drive period (first period) t11 in which the first initial drive voltage is applied and the magnitude of the second initial drive voltage based on the temperature rise characteristics of the heater 14. It may function as a condition setting unit. The correction unit 70 may correct at least one of the first initial drive period t11 and the second initial drive period (second period) t12 based on the ambient temperature. The correction unit 70 may correct at least one of the first initial drive voltage value and the second initial drive voltage value based on the ambient temperature. Except for the configuration of the heating control unit 30 and the setting unit 50 as described above, the structure of the gas sensor 100 of the fourth embodiment is the same as the structure of the gas sensor 100 of the first to third embodiments. Therefore, repeated description is omitted. Also in the case of the third embodiment, the setting unit 50 performs the first initial drive period (first period) t11 in which the first initial drive voltage is applied based on the temperature rise characteristics of the heater 14, and the second initial stage. The magnitude of the driving voltage may be set.

  Depending on the heat capacities of the heater 14 and the gas detector 12, if the initial drive voltage applied to the heater 14 is too high or the initial drive period is too long, the heater temperature will overshoot beyond the target temperature, There are cases where the power consumption cannot be reduced. On the other hand, if the initial drive voltage is too low, the time required for the heater temperature to reach the target temperature becomes long.

  According to this example, after the first initial drive voltage higher than the set voltage is applied to the heater 14, the heating control unit 30 performs the process of applying the second initial drive voltage that is smaller than the first initial drive voltage and larger than the set voltage. By doing so, it is possible to prevent the heating period from becoming unnecessarily long while preventing the heater temperature from exceeding the target temperature and overshooting. In addition, the heater temperature can be prevented from dropping below the target temperature. In the gas sensor 100 of the present embodiment, the case where the two initial drive voltages of the first initial drive voltage and the second initial drive voltage are applied has been described. However, the number of stages for applying different drive voltages is three or more. May be.

  FIG. 19 is a flowchart illustrating an example of processing contents performed by the gas sensor 100 in the gas sensor 100 according to the fourth embodiment of the present invention. The heating control unit 30 applies a first initial drive voltage higher than the set voltage to the heater 14 (step S501). Next, after the first initial drive period t11 has elapsed (step S502: YES), the heating control unit 30 applies a second initial drive voltage that is smaller than the first initial drive voltage and greater than the set voltage to the heater 14. (Step S503).

  Next, after the second initial drive period t12 has elapsed (step S504: YES), the heating control unit 30 changes the voltage applied to the heater 14 from the second initial drive voltage to the set voltage (step S505). ). The voltage change timing is set so that the voltage applied to the heater 14 is changed from the second initial drive voltage to the set voltage while the temperature of the heater 14 is rising. Specifically, the voltage change timing may be set in advance by the first initial drive time t11 and the second initial drive period t12. When the set voltage is applied to the heater 14 and is stabilized, the temperature of the heater 14 becomes the target temperature.

  The processing from step S506 to step S511 is the same as the processing from step S104 to step S109 in FIG. Therefore, repeated description is omitted.

  FIG. 20 is a flowchart illustrating an example of a heating condition setting process. The heating control unit 30 applies a predetermined voltage to the heater 14 (step S601). With the voltage applied to the heater 14, the temperature measurement unit 16 measures the heater temperature at a plurality of points in time (step S602). The temperature rise characteristic of the heater 14 according to the measurement result by the temperature measurement unit 16 is acquired. The acquired temperature rise characteristic may be stored in the storage unit 60 or the like. The acquired temperature rise characteristic reflects the heat capacities of the heater 14 and the gas detector 12. When the same voltage is applied to the heater 14, it can be determined that the shorter the time for raising the temperature to the predetermined temperature, the smaller the heat capacity.

  The setting unit 50 sets the first period t11 during which the first initial drive voltage is applied and the magnitude of the second initial drive voltage based on the temperature rise characteristics of the heater 14 (step S603). Specifically, the setting unit 50 may set the first initial drive period t11 longer as the heat capacities of the heater 14 and the gas detection unit 12 are larger. This is because it takes longer to reach the target temperature as the heat capacities of the heater 14 and the gas detector 12 are larger. The heat capacity may be calculated from the acquired temperature rise characteristic.

  Further, as the heat capacity of the heater 14 and the gas detection unit 12 is increased, the temperature of the heated heater 14 is less likely to decrease. Therefore, the setting unit 50 may decrease the magnitude of the second initial drive voltage as the heat capacities of the heater 14 and the gas detection unit 12 are increased. Information on the set initial drive period t1 and information on the magnitude of the second initial drive voltage are stored in the storage unit 60 (step S604).

  The heating condition setting process shown in FIG. 20 may be executed when the gas sensor 100 product is shipped. The setting unit 50 may periodically execute the initial drive period setting process. For example, the setting unit 50 may execute the initial drive period setting process at a predetermined time once a day. However, the frequency of executing the initial drive period setting process is not limited to this case.

  The first initial driving period t11 and the second initial driving voltage can be appropriately set by the heating condition setting process. Therefore, even when the heat capacities and the like of the heater 14 and the gas detection unit 12 vary, the heating control unit 30 can realize appropriate heater temperature characteristics.

  As described above, according to the gas sensor 100 of the fourth embodiment, it is smaller than the first initial drive voltage and larger than the set voltage in the period between the state where the first initial drive voltage is applied and the state where the set voltage is applied. A second initial drive voltage that is an intermediate voltage is applied to the heater 14. Therefore, the gas sensor 100 can prevent occurrence of a situation where the heater temperature exceeds the target temperature, as compared with the case where the first initial drive voltage is applied for a long period of time. Moreover, it can prevent that heater temperature falls below target temperature.

  In the first to fourth embodiments, the case where the heater of the gas sensor 100 is driven has been described. However, the heater driving method described in the first to fourth embodiments can be applied to heaters other than the gas sensor 100. 2, 3, and 4, the heater structure to which the heater driving method is applied includes the silicon substrate 2 in which a space having an opening is formed, and the heat provided on the space having the opening. The insulating support layer 3 and a heater layer supported by the heat insulating support layer 3 may be provided. A heater having such a heater structure is referred to as a MEMS heater. In the heater structure, another semiconductor substrate may be used instead of the silicon substrate 2. The heat insulating support layer 3 may be formed of various materials. For example, the thermal insulating support layer 3 is a silicon oxide film, a silicon nitride film, or a silicon oxynitride film. The thermal insulating support layer 3 may be a laminated film in which silicon oxide films and silicon nitride films are alternately laminated.

  The MEMS heater configured as described above can be used not only for a gas sensor but also for various devices such as a humidity sensor, a flow sensor, and a heat distribution detection type acceleration sensor. In the humidity sensor, the moisture sensitive film to which water molecules are adsorbed may be a heating object. The flow sensor and the thermal acceleration sensor detect the movement of a fluid such as a gas heated by a heater with a temperature sensor. Therefore, in the flow sensor and the thermal acceleration sensor, the fluid (gas) in the space may be an object to be heated. These various apparatuses are the same as the configurations described in the first to fourth embodiments except that the heating object is different from the configurations shown in FIGS. 2, 3, and 4. Therefore, the heater driving technique described in the first to fourth embodiments can be used for various apparatuses.

  As described above, the present invention has been described using the embodiment, but each embodiment in the present specification can be appropriately combined. The technical scope of the present invention is not limited to the scope described in the above embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Even if the operation flow in the claims, the description, and the drawings is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

2 .... Silicon substrate, 3 .... Thermal insulation support layer, 4 .... Electrical insulation layer, 5 .... Gas sensing layer, 6 .... Through hole, 7 .... Junction layer, 8 .... Gas sensing layer electrode, 9 ....・ Catalyst layer, 10 ・ ・ Detection unit, 12 ・ ・ Gas detection unit, 14 ・ ・ Heater, 16 ・ ・ Temperature measurement unit, 17 ・ ・ Hole, 18 ・ ・ Cavity, 20 50, Setting unit 60, Storage unit 70, Correction unit 80, Ambient temperature measurement unit 100, Gas sensor 200, Control device

Claims (16)

A gas sensor having a gas detector and a heater for heating the gas detector, and detecting a target gas based on an electric signal of the gas detector heated to a target temperature by the heater;
An initial driving voltage larger than a set voltage corresponding to the target temperature is applied to the heater, and the voltage applied to the heater is changed from the initial driving voltage to the heater while the temperature of the heater is rising. A gas sensor with a heating control unit that changes to a set voltage. The heating control unit changes a voltage applied to the heater from the initial driving voltage to the set voltage in a state where the temperature T1 (° C.) of the heater is in a range satisfying the following mathematical formula 1. Item 1. Gas sensor according to item 1 [Formula 1]
0.8T2 ≦ T1 ≦ 1.2T2 where T2 is the target temperature (° C.). The gas sensor according to claim 1, wherein the heating control unit changes a voltage applied to the heater from the initial driving voltage to the set voltage when a temperature of the heater is lower than the target temperature. A storage unit for storing information about a period for applying the initial drive voltage;
The gas sensor according to claim 1, wherein the heating control unit changes the voltage applied to the heater from the initial drive voltage to the set voltage when the period has elapsed. A temperature measuring unit for measuring the temperature of the heater;
A period setting unit for setting the period based on a temperature rise characteristic of the heater according to a measurement result by the temperature measurement unit when a predetermined voltage is applied to the heater;
The gas sensor according to claim 4, wherein the storage unit stores information about the period set by the period setting unit. A temperature measuring unit for measuring the temperature of the heater;
The heating control unit changes the voltage applied to the heater from the initial driving voltage to the set voltage when the temperature of the heater measured by the temperature measuring unit reaches a predetermined value. Item 2. The gas sensor according to Item 1. The heating control unit applies a second initial drive voltage that is greater than the first initial drive voltage and greater than the set voltage after the first initial drive voltage is applied to the heater, so that the temperature of the heater increases. 2. The gas sensor according to claim 1, wherein the voltage applied to the heater is changed from the second initial drive voltage to the set voltage in a state where the heater is on. The gas sensor according to claim 7, wherein the first initial drive voltage is greater than the set voltage. The heating control unit applies a second initial drive voltage smaller than the first initial drive voltage and larger than the set voltage after applying a first initial drive voltage larger than the set voltage to the heater, and the heater The gas sensor according to claim 1, wherein the voltage applied to the heater is changed from the second initial drive voltage to the set voltage in a state where the temperature of the heater is increased. A temperature measuring unit for measuring the temperature of the heater;
A first period in which the first initial driving voltage is applied based on a temperature rise characteristic of the heater according to a measurement result by the temperature measurement unit when a predetermined voltage is applied to the heater; and The gas sensor according to any one of claims 7 to 9, further comprising a heating condition setting unit that sets a magnitude of the second initial drive voltage. An ambient temperature measurement unit for measuring the ambient temperature of the gas sensor;
At least one of a first period in which the first initial drive voltage is applied and a second period in which the second initial drive voltage is applied, or at least one of the first initial drive voltage and the second initial drive voltage The gas sensor according to claim 9, further comprising: a correction unit that corrects the value of based on the ambient temperature. The heating control unit periodically pulse-drives the heater,
In each pulse drive, the heating control unit applies a voltage applied to the heater from the initial drive voltage to the set voltage in a state where the temperature of the heater is increased by applying the initial drive voltage to the heater. The gas sensor according to claim 1, wherein the gas sensor is changed to: A gas sensor according to any one of claims 1 to 12, comprising:
A gas alarm device further comprising an alarm generation unit that issues an alarm when a target gas is detected based on an electric signal of the gas detection unit. A control device that controls a gas sensor that detects a target gas based on an electric signal of the gas detection unit that has a gas detection unit and a heater that heats the gas detection unit and is heated to a target temperature by the heater. ,
An initial driving voltage larger than a set voltage corresponding to a target temperature is applied to the heater, and the voltage applied to the heater is set from the initial driving voltage in a state where the temperature of the heater is rising. A control device comprising a heating control unit for changing to a voltage. A gas sensor control method for detecting a target gas on the basis of an electric signal of the gas detection unit having a gas detection unit and a heater for heating the gas detection unit and heated to a target temperature by the heater;
Applying an initial driving voltage to the heater that is larger than a set voltage corresponding to the target temperature;
Changing the voltage applied to the heater from the initial drive voltage to the set voltage while the temperature of the heater is rising;
A control method comprising: A heater driving method for driving a heater comprising: a semiconductor substrate having a space having an opening; a heat insulating support layer provided on the space; and a heater layer supported by the heat insulating support layer. And
Applying a large initial driving voltage to the heater layer compared to a set voltage corresponding to a target temperature;
Changing the voltage applied to the heater layer from the initial drive voltage to the set voltage while the temperature of the heater layer is rising.

Images