JP2021193643A - Heating element device and control device - Google Patents

Abstract

To provide a heating element device which uses two resistors, namely a heating resistor and a temperature measuring resistor, so as to enable size reduction as well as appropriate temperature control of the heating resistor, and also to provide a control device for controlling a heating part which uses both of the heating resistor and the temperature measuring resistor.SOLUTION: A heating element device 10 comprises a heating part and a control part. The heating part has: a heating resistor 22; a temperature measuring resistor 23 which measures the temperature of the heating resistor; a heating element terminal 24 which is brought into conduction with one end of the heating resistor; a temperature measuring element terminal 25 which is brought into conduction with one end of the temperature measuring resistor; and a common terminal 26 which is brought into conduction with the other end of the heating resistor and with the other end of the temperature measuring resistor. The control part has: a resistance detecting part which detects a resistance value of the temperature measuring resistor; a heating element control part 50 which controls electric power to be applied to the heating resistor, in accordance with the resistance value of the temperature measuring resistor thus detected; and a detection timing control part 80 which causes the resistance detecting part to detect the resistance value of the temperature measuring resistor during a period when the electric power is not applied to the heating resistor.SELECTED DRAWING: Figure 1

Description

INDUSTRIAL APPLICABILITY The present invention controls a heat generating element device having a heat generating resistor and a resistance temperature measuring resistor for measuring the temperature of the heat generating resistor, and a heating element having a heat generating resistor and a resistance temperature measuring resistor. Regarding the control device.

Conventionally, when energizing a heat-generating resistor to generate heat, a resistance temperature detector is placed in the vicinity of the resistance thermometer, and the resistance value of this resistance thermometer is detected to detect the temperature of the resistance thermometer. A heating element device that controls energization of a heat generating resistor is known.

On the other hand, as shown in Patent Documents 1 and 2, instead of using both the heat generation resistor and the resistance temperature detector, a temperature-dependent resistance heater having a characteristic that the resistance value changes depending on the temperature is used. Things are also known.

Japanese Unexamined Patent Publication No. 2008-234413 Japanese Unexamined Patent Publication No. 2009-86963

In a heating element device that uses both a heating element and a resistance temperature detector as described above, in order to energize the heating element, two terminals that conduct to one end and the other end of this heating element and two that are connected to this terminal. In order to energize the resistance temperature detector, a total of 4 terminals and 4 wires, 2 terminals conducting to one end and the other end of the resistance temperature detector and 2 wires connected to the terminal, are provided. Since it is used, it can be a circuit independent of each other. Therefore, regardless of the energization control of the heat generation resistor, the resistance value of the resistance temperature detector can be detected at an appropriate timing and used for the energization control of the heat generation resistor.

However, in order to use two of the heat generation resistor and the resistance temperature detector, four terminals and four wirings are required, and a heat generation part having the heat generation resistor and the resistance temperature detector and four wirings are provided. Space is required, and it is difficult to reduce the size.

On the other hand, when a temperature-dependent resistance heater is used as in Patent Documents 1 and 2 described above, two terminals conducting on one end and the other end of the temperature-dependent resistance heater and two wirings connected to the terminal are connected to the terminal. Is enough. Therefore, the space for providing the heat generating portion having the temperature-dependent resistance heater and the two wirings is small, which is advantageous for miniaturization. In addition to applying electric power to the temperature-dependent resistance heater using these two wires, a small current for measuring the resistance value is passed through the temperature-dependent resistance heater to detect the resistance value of the temperature-dependent resistance heater. Therefore, it is used for energization control of the temperature-dependent resistance heater.

However, if you want to generate heat by applying a large amount of power to this temperature-dependent resistance heater, especially if you want to drive the temperature-dependent resistance heater using a power supply with a low power supply voltage, the resistance of the temperature-dependent resistance heater There is no choice but to set the value low. However, when the resistance value of the temperature-dependent resistance heater is lowered, the voltage drop generated when a small current for measuring the resistance value is passed becomes small, and the resistance value of the temperature-dependent resistance heater is appropriately detected. hard. Further, the resistance generated in the wiring connecting the heater and the power supply cannot be ignored, and from this point as well, it becomes difficult to appropriately detect the resistance value of the temperature-dependent resistance heater. Therefore, when the current for measuring the resistance value is increased, the current for measuring the resistance value itself affects the temperature of the temperature-dependent resistance heater, and the influence of the resistance generated in the wiring also increases. Therefore, precise energization control using the resistance value of this temperature-dependent resistance heater becomes difficult.

The present invention has been made in view of the above problems, and by using two heating elements, a heating element and a resistance temperature detector, the temperature of the heating element can be appropriately controlled and the heat generation can be reduced. Provide body equipment. Further, a control device for controlling a heat generating portion using both a heat generating resistor and a resistance temperature detector is also provided.

One embodiment is a resistance thermometer that generates heat when energized, a resistance temperature detector that measures the temperature of the resistance thermometer, a resistance thermometer terminal that conducts to one end of the resistance thermometer, and a resistance thermometer that conducts to one end of the resistance temperature detector. A heat generating portion having a resistance thermometer terminal, a common terminal conducting to the other end of the resistance thermometer and the other end of the resistance temperature detector, a heating element wiring conducting to the heating element terminal, and the measurement. A resistance detector that detects the resistance value of the resistance temperature detector through the resistance thermometer wiring that conducts to the temperature measuring body terminal, the common wiring that conducts to the common terminal, the temperature measuring body wiring, and the common wiring, and the heating element. Power applied to the heat generating resistor through the wiring and the common wiring to control the power applied to the resistance temperature detector according to the resistance value of the resistance temperature detector detected by the resistance detector, and to the heat generating resistor. This is a heating element device including a control unit having a detection timing control unit that causes the resistance detection unit to detect the resistance value of the resistance temperature detector during a period in which the resistance temperature detector is not applied.

In this heating element device, although two heating elements and resistance temperature detectors are used, in the heating element, instead of four independent terminals, a heating element terminal, a resistance temperature detector terminal, and a heating element are measured. It has a total of three terminals, which are common terminals shared by the temperature resistor. The heating element and the control unit are usually connected by four wirings, but are connected by three wirings, a heating element wiring, a resistance temperature measuring element wiring, and a common wiring. Therefore, in this heating element device, the space for the heating element and wiring can be reduced.

On the other hand, since two types of heat-generating resistor and resistance temperature detector are used, the resistance value can be appropriately detected by the resistance detection unit regardless of the magnitude of the resistance of the heating resistor and the magnitude of the applied voltage, and the heating element can be controlled. The power applied to the heat generation resistor can be appropriately controlled by the unit.

Since a large current flows through the common wiring during the period when the power is applied to the heating element by the heating element control unit, the voltage drop generated by the resistance of the common wiring also becomes large. Therefore, when a current is passed through the resistance temperature detector wiring and the common wiring in order to detect the resistance value of the resistance temperature detector during the period when power is applied to the resistance temperature detector, the current is passed through the resistance temperature detector. Since the influence of the voltage drop that occurs in the common wiring due to the current is added to the resistance value of the resistance temperature detector, the detection accuracy of the resistance value is lowered.

On the other hand, in the above-mentioned heating element device, the resistance value of the resistance temperature detector is detected by the resistance detection unit during the period when the electric power is not applied to the heating element. Therefore, the influence caused by passing a large current through the heating element can be eliminated, the resistance value of the resistance temperature detector can be detected appropriately, and the temperature of the resistance temperature detector can be measured appropriately. Can be controlled appropriately.

The heating element terminal, resistance temperature detector terminal, and common terminal are, for example, installed on a heater substrate forming a heating element (heating element) provided with a heating element and a resistance temperature detector, and are used for cables, lead wires, and bonding wires. Examples include terminals to which connection wiring such as is connected.
Further, as the heating element wiring, the temperature measuring body wiring, and the common wiring, for example, a cable or a lead directly or indirectly connected to a terminal installed on a heater board forming a heat generating element provided with a heating element or a temperature measuring resistor. It is also possible to use connection wiring such as wires and bonding wires, external connection terminals such as lead pins provided in the package containing the heater substrate, and conductor wiring formed in the wiring board.

Further, the control method in the heating element control unit is not limited, and a pulse such as pulse width modulation (PWM) or pulse amplitude modulation (PAM) is used to control the voltage or current in order to change the power applied to the heating element. A modulation method can be adopted. Further, it is also possible to adopt an analog method in which a continuous voltage and current are applied to the heat generation resistor and the magnitude thereof is appropriately changed.

Further, the detection timing control unit detects the resistance value during the period when the electric power is not applied to the heat generation resistor. Specifically, for example, in the case of applying electric power by a pulse modulation method, the heating element control unit selects a period in which electric power is not applied to the heating element, such as a period in which the application of electric power is turned off, and the resistance detection unit. There is a method of detecting the resistance value. In addition, for example, a period during which power is not applied may be provided for a period including the detection period according to the period for detecting the resistance value by the resistance detection unit, such as the period of the first 100 ms of the period every 10 seconds. can.

Further, in the above-mentioned heating element device, the heating element control unit applies the electric power applied to the heating element to a predetermined frequency and an on-duty ratio within a range of an upper limit value of less than 100%. It is a heating element pulse control unit that controls pulse modulation, and the detection timing control unit is a period in which the power is not applied even when the power is applied to the heating element with the on-duty ratio of the upper limit. It is preferable to use a heating element device that causes the resistance detection unit to detect the resistance value.

In this heating element device, in the heating element pulse control unit, the power applied to the heating element is on-duty at a predetermined frequency and within an upper limit value of less than 100% (for example, an upper limit value of 90%). Pulse modulation control is performed by the ratio. Then, even when power is applied to the heat generation resistor at the on-duty ratio of the upper limit value (for example, 90%), the detection timing control unit does not apply power (for example, the remaining 10% off period). That is, the resistance value is detected by the resistance detection unit during the period when the power application is always turned off. Therefore, the resistance value of the resistance temperature detector can be appropriately detected by the resistance detection unit without being affected by the power applied to the heating element by the heating element pulse control unit, and the power control by the heating element pulse control unit is appropriate. Can be done.

As a method of pulse modulation control performed by the heating element pulse control unit, in addition to pulse width modulation (PWM) and pulse amplitude modulation (PAM), a method of changing both the pulse width and the amplitude can be mentioned.

Further, in the above-mentioned heating element device, it is preferable that the heating element pulse control unit is a heating element device that controls the electric power applied to the heating element by pulse width modulation.
When controlling the power applied to the heat-generating resistor by pulse width modulation control, the control can be easily performed by turning the output of the constant voltage power supply on and off with a switch element (MOSFET, transistor, thyristor, etc.). , Has the advantage of simplifying the control circuit.

Further, it is preferable that the heating element device according to any one of the above is a heating element device having a heating element that produces a function given in advance by a temperature rise due to heating from the heat generation resistor. ..

In this heating element device, the heating element also has a functional body to be heated. Therefore, since the functional body to be heated can be heated to an appropriate temperature by the heat generation resistor, the function given in advance to the functional body to be heated can be appropriately generated.

As the functional body to be heated, a sensor body or a sensor body that exhibits a detection function given in advance (for example, a flow velocity detection function for air flow, a gas detection function for reducing gas, methane, etc.) by heating to a predetermined temperature range. , An active functional body that exerts an active function given in advance (for example, a far-infrared radiation function).
Further, as the heat generating portion, in addition to the heat generating resistor and the resistance temperature detector, those having the above-mentioned sensor body and active functional body on the same substrate or in the package can be mentioned.

Further, in the above-mentioned heating element device, the heating element may be a heating element device which is a sensor body that produces a detection function given in advance by a temperature rise due to heating from the heating resistor.

In this heating element device, the functional body to be heated is a sensor body. In this heating element device, the sensor body can be heated to an appropriate temperature by the heating element, so that the function given in advance to the sensor body can be appropriately generated.

The sensor body is predetermined by heating to a predetermined temperature range (for example, a temperature range exceeding the activation temperature) and by changing the environment (environmental air flow velocity, gas concentration change of the measured gas) to be detected. Examples thereof include those that perform a detection function given in advance (for example, a flow velocity detection function for air flow, a gas detection function for methane, etc.), such as generating an electromotive force or changing a resistance value.

Further, the control unit includes a unit having a sensor body control unit that controls the sensor body and a control unit having no sensor body control unit. Here, in the above-mentioned heating element device, it is preferable that the control unit is a heating element device having a sensor body control unit that controls the detection function in the sensor body. This heating element device has a sensor body control unit in the control unit, and can control not only the heating element but also the sensor body, which facilitates handling.

Alternatively, other embodiments include a resistance thermometer that generates heat when energized, a resistance temperature detector that measures the temperature of the resistance thermometer, a resistance thermometer terminal that conducts to one end of the resistance thermometer, and one end of the resistance temperature detector. A heating element wiring that conducts to the heating element terminal in a heat generating portion having a conducting temperature measuring body terminal and a common terminal that conducts to the other end of the heat generating resistor and the other end of the temperature measuring resistor, the measuring element. It is a control device connected by a temperature measuring body wiring conducting to the temperature measuring body terminal and a common wiring conducting to the common terminal, and detects the resistance value of the resistance temperature detector through the temperature measuring body wiring and the common wiring. A heating element control unit that controls the power applied to the heat generating resistor through the heating element wiring and the common wiring according to the resistance value of the resistance temperature detector detected by the resistance detecting unit. Further, the control device includes a detection timing control unit that detects the resistance value of the resistance temperature detector during the period when power is not applied to the resistance temperature detector.

This control device is connected to a heating element having a heating element and a resistance temperature detector by three wirings: a heating element wiring, a resistance temperature measuring element wiring, and a common wiring. Then, the resistance detection unit detects the resistance value of the resistance temperature detector, and the heating element control unit controls the applied power to the resistance temperature detector according to the resistance value of the resistance temperature detector. , The resistance value of the resistance temperature detector is detected during the period when no power is applied to the resistance temperature detector. For this reason, the control device eliminates the effect of applying a large current to the resistance temperature detector, appropriately detects the resistance value of the resistance temperature detector, and measures the temperature of the resistance temperature detector appropriately. It can be appropriately controlled by the heating element control unit.

It is explanatory drawing which shows the whole structure of the heating element apparatus which concerns on Embodiment 1. FIG. It is explanatory drawing which shows the schematic structure of the substrate type heating element among the heating element apparatus which concerns on Embodiment 1. FIG. It is a graph which shows the relationship between the change of the voltage applied to a heating element and the measurement timing of the resistance value of a resistance temperature detector in the heating element apparatus which concerns on Embodiment 1. FIG. It is explanatory drawing which shows the whole structure of the sensor device which concerns on Embodiment 2. It is explanatory drawing which shows the schematic structure of the metal package type sensor unit among the sensor apparatus which concerns on Embodiment 2, (a) is a perspective view, (b) is a partial fracture sectional view. It is explanatory drawing which shows the schematic structure of the sensor element accommodated in the sensor unit among the sensor apparatus which concerns on Embodiment 2, (a) is the 1st main surface side, (b) is the outline of the 2nd main surface side. The configuration is shown. It is a graph which shows the relationship between the change of the voltage applied to the heat generation resistor and the measurement timing of the resistance value in a resistance temperature detector in the sensor apparatus which concerns on Embodiment 2. FIG.

(Embodiment 1)
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing an overall configuration of a heating element device 10 according to the first embodiment. FIG. 2 is a diagram showing a schematic configuration of a substrate-type heating element 20 forming a heating unit in the heating element device 10. Further, FIG. 3 is a graph showing the relationship between the change in the heating element voltage Vp applied to the heating element 22 and the measurement timing of the resistance value Rs of the resistance temperature detector 23 in the heating element device 10. The heating element device 10 includes a substrate-type heating element 20, a heating element control device 50 for controlling the heating element control device 50, and three wirings 41, 42, 43 connecting the heating element control device 50. This is a device that heats the heating element 20 to a predetermined temperature.

First, the heat generating element 20 will be described with reference to FIG. The substrate-type heating element 20 has a heating resistor 22 and a resistance temperature detector 23 formed on the first main surface 21A of the rectangular heater substrate 21. Of these, the heater substrate 21 is a plate-shaped body made of alumina. The heat generation resistor 22 is made of platinum and extends in a meandering shape so as to cover most of the first main surface 21A of the heater substrate 21. On the other hand, the resistance temperature detector 23 is made of platinum and extends in a meandering shape along the heat generation resistor 22 while maintaining a predetermined distance from the heat generation resistor 22.

The heating element 22 is wider than the heating element 22 at one end 22A (upper left in FIG. 2) and conducts to a substantially semicircular heating element terminal 24. Further, the resistance temperature detector 23 is wider than the resistance temperature detector 23 at one end 23A (upper right in FIG. 2) and conducts to a substantially semicircular resistance temperature detector terminal 25. Further, the other end 22B of the heat generation resistor 22 and the other end 23B of the resistance temperature detector 23 (lower right in FIG. 2) are both wider than the heat generation resistor 22 and the resistance temperature detector 23, and are approximately semi-circular. It is conductive to the common terminal 26.
These heat generation resistors 22, resistance temperature detectors 23, and the three terminals 24 to 26 are formed by screen-printing a material paste on a heater substrate 21 and firing it.

The three terminals 24 to 26 of the heating element 20 are connected to the terminals 51, 52, 53 of the heating element control device 50 described below by wirings 41, 42, 43, respectively (see FIG. 1). Specifically, the heating element terminal 24 is electrically connected to the terminal 51 of the heating element control device 50 via the heating element wiring 41. The resistance temperature detector terminal 25 is electrically connected to the terminal 52 of the heating element control device 50 via the resistance temperature detector wiring 42. Further, the common terminal 26 is electrically connected to the terminal 53 of the heating element control device 50 via the common wiring 43. The terminal 53 is grounded in the heating element control device 50.

The heating element control device 50 controls the heating element 20, and is roughly divided into a resistance detection circuit 60, a heating element control circuit 70, and a detection timing control unit 80. Of these, the resistance detection circuit 60 is connected to the terminal 52 and the terminal 53, and as shown in FIG. 1, is connected to the resistance temperature detector 23 of the heat generating element 20 through the resistance temperature detector wiring 42 and the common wiring 43. ing. The resistance detection circuit 60 includes a constant current source 61 through which a resistance detection current Is, which is a constant current, flows, and a voltage detection unit 62 that detects the voltage Vs generated in the constant current source 61. The voltage Vs detected by the voltage detection unit 62 is the resistance temperature detector voltage Vs generated by passing the resistance detection current Is through the resistance temperature detector 23. Therefore, the resistance value Rs of the resistance temperature detector 23 can be obtained by Rs = Vs / Is. The resistance value Rs of the resistance temperature detector 23 calculated in this way or the corresponding resistance temperature voltage Vs is input to the PWM control unit 73 of the heating element control circuit 70 described below, and the resistance temperature detector 22 Used for control of.

On the other hand, the heating element control circuit 70 is connected to the terminal 53 via the terminal 51 and the changeover switch 81, and as shown in FIG. 1, heat is generated to the heating element 22 through the heating element wiring 41 and the common wiring 43. A body voltage Vp is applied. As a result, the heating element current Ih flows through the heating element 22 and the heating element power PW is applied to the heating element 22. The heating element control circuit 70 is turned on by turning on / off the constant voltage power supply 71 that generates a predetermined on-voltage Vpon, the switch element 72 that interrupts the application of the on-voltage Vpon to the heating resistor 22, and the switch element 72. It has a PWM control unit 73 that performs PWM (pulse width modulation) control that controls the application period of the voltage Vpon. The switch element 72 is composed of, for example, a MOSFET, a thyristor, or the like. As described above, in the first embodiment, since the heating element power PW applied to the heating element 22 is controlled by the pulse width modulation control, the output of the constant voltage power supply 71 that generates a predetermined on-voltage Vpon is output by the switch element 72. Since control can be easily performed by turning it on and off, the control circuit becomes simple.

As shown in FIG. 3, the PWM control unit 73 has a predetermined frequency fp (for example, fp = 1 Hz), that is, a predetermined period Tp (= 1 / fp, for example, Tp = 1 / fp = 1 sec). When the voltage pulse Ep is repeatedly applied to the heat generation resistor 22, the length of the period during which the switch element 72 is turned on within the range of the predetermined upper limit on period Ponm (for example, Ponm = 900 msec out of Tp = 1 sec). Is PWM (Pulse Width Modulation) control. That is, the switch element 72 is turned on for a desired on-period Pon within this period, with the length of the upper limit on period Ponm as the upper limit. As a result, assuming that the maximum length of the on-period Ponm is 100%, the length of the on-period Pon can be changed in the range of 0 to 100%, and PWM control can be realized.

In the first embodiment, in the PWM control unit 73, the resistance value Rs (or the resistance thermometer) of the resistance temperature detector 23 obtained by the resistance detection circuit 60 as described above is used to determine the length of the on-period Pon. Voltage Vs) is used. For example, the currently obtained resistance value Rs is significantly larger than the resistance value Rs of the resistance temperature detector 23 corresponding to the target temperature of the heat generation resistor 22, and the temperature of the heat generation resistor 22 is significantly larger than the target temperature. If it is too low, the PWM control unit 73 controls to lengthen the length of the on-period Pon. As a result, more heating element power PW is applied to the heating element 22 to raise the temperature of the heating element 22 or accelerate the temperature rise. On the other hand, when the currently obtained resistance value Rs is close to the resistance value Rs of the resistance temperature detector 23 corresponding to the target temperature of the heat generation resistor 22, that is, the temperature of the heat generation resistor 22 is close to the target temperature. If this happens, the PWM control unit 73 controls to shorten the length of the on-period Pon. As a result, less heating element power PW is applied to the heating element 22 so that the temperature rise of the heating element 22 can be slowed down or lowered. The PWM control unit 73 may use a known control method, not limited to the above method, as a specific control method using the resistance value Rs or the resistance temperature detector voltage Vs, and detailed description thereof will be omitted. ..

By the way, the heating element voltage Vp is applied to the heating element 22 by the heating element control circuit 70, and the resistance value Rs of the resistance temperature detector 23 is measured by the resistance detection circuit 60 while the heating element current Ih is flowing. In some cases, the resistance value Rs to be measured contains an error, which is not preferable. In the heating element device 10 of the first embodiment, the heating element wiring 41 and the common wiring 43 are used to pass the heating element current Ih that drives the heating element 22, while the resistance value Rs of the temperature measuring resistor 23 is set. The resistance detection current Is for detection uses the heating element wiring 42 and the common wiring 43, and the common wiring 43 is shared. In FIG. 1, as symbolically shown by a broken line, the common wiring 43 includes a common wiring resistance 43R. Therefore, when a heating element current Ih is passed through the heating element 22, a voltage drop Vc of Vc = Rc · Ih is generated in the common wiring 43 due to the common wiring resistance 43R (the resistance value is Rc). appear.

Here, the magnitude of the heating element current Ih that drives the heating element 22 depends on the resistance value of the heating element 22, the required calorific value, and the magnitude of the on-voltage Vpon of the constant voltage power supply 71, and is, for example, Ih. In many cases, it is a large value such as = 10A. In particular, when a battery or the like is used as the constant voltage power supply 71, it is difficult to increase the on-voltage Vpon. Therefore, in order to apply the desired power to the heating element 22, the resistance value of the heating element 22 is lowered to generate a heating element. The current Ih tends to be large. On the other hand, the resistance detection current Is is far more than the heating element current Ih, such as Is = 10 mA, although it depends on the resistance value Rs of the resistance temperature detector 23 and the allowable voltage range of the voltage detection unit 62. There are many cases of making it smaller (Is << Ih).

Therefore, when the heating element current Ih is passed through the heat generating resistor 22, if the resistance detection current Is is also passed in order to measure the resistance value Rs of the resistance temperature detector 23, the measurement obtained by the voltage detection unit 62 is obtained. The warm body voltage Vs is Vs = Rs · Is + Rc (Ih + Is). When the heating element current Ih is much larger than the resistance detection current Is (Ih >> Is), Vs≈Rs · Is + Rc · Ih. In this case, even if the resistance value Rc of the common wiring resistance 43R is small, the heating element current Ih is much larger than the resistance detection current Is, so that the voltage drop Vc (= Rc · Ih) due to the heating element current Ih is , The voltage drop due to the resistance detection current Is in the temperature measuring resistor 23 is not negligible, and the resistance value Rs of the temperature measuring resistor 23 may not be appropriately obtained from the temperature measuring body voltage Vs. There is.

Therefore, as shown in FIG. 3, the resistance value Rs of the resistance temperature detector 23 is detected by the resistance detector 60 during the off-period Poff in which the power PW is not applied to the heat-generating resistor 22, which is the opposite of the on-period Pon. Let me. In the heating element device 10 of the first embodiment, the voltage pulse Ep is turned off during the absolute off period Poffa period (for example, Tp = 1 sec, Poffa = 100 msec) in the period Tp, and heat is generated in the common wiring 43. It is a period in which the body current Ih does not flow. Then, the resistance value Rs (resistance temperature detector voltage Vs) of the resistance temperature detector 23 is acquired within this absolute off period Poffa, that is, during the period when the heating element power PW is not applied to the heating element 22. Specifically, the detection timing control unit 80 includes a changeover switch 81 and a switch control unit 82 that controls the on / off of the changeover switch 81, and the switch control unit 82 synchronizes with the PWM control unit 73. Operate. Then, the switch control unit 82 turns off the changeover switch 81 during the absolute off period Poffa and turns on the changeover switch 81 during the upper limit on period Ponm in the cycle Tp. Thereby, during the period of the upper limit on period Ponm, the length of the on period Pon can be changed by the PWM control unit 73.

In the first embodiment, the on-duty ratio Don of this voltage pulse Ep is given by Don = Pon / Tp × 100 (%), and the upper limit value Donm of the on-duty ratio Don is Donm = Ponm / Tp × 100 (%). ). This upper limit value Donm has a size of less than 100% (for example, Donm = 900/1000 × 100 = 90%) because the absolute off period Poffa exists.

Thus, in the first embodiment, in synchronization with the switch control unit 82, in the resistance detection circuit 60, the heating element current Ih does not flow in the common wiring 43, and the resistance measurement period Pr in the absolute off period Poffa (for example, Poffa =). The resistance value Rs of the resistance temperature detector 23 is detected in (Pr = 30 msec) out of 100 msec. Specifically, during the resistance measurement period Pr, the resistance temperature detector voltage Vs is detected by the voltage detection unit 62 as described above, or the resistance value Rs of the resistance temperature detector 23 is further obtained by using this, and PWM control is performed. Input to the unit 73.

Thus, in the heating element device 10 of the first embodiment, although the heating element 22 and the resistance temperature detector 23 are used, these are the heating element terminal 24, the resistance temperature detector terminal 25, and the resistance temperature detector 23. It conducts to a total of three terminals, a common terminal 26 shared by 22 and the resistance temperature detector 23. Further, the heating element control device 50 is connected to the heating element control device 50 by three wirings of a heating element wiring 41, a temperature measuring element wiring 42, and a common wiring 43. Therefore, in the heating element device 10, the heater substrate 21 forming the heating element 20 may be provided with three terminals 24 to 26, and the heating element 20 (heater substrate 21) can be miniaturized. Further, in the heating element device 10, since it is sufficient to provide three wirings 41 to 43, the space for the wirings 41 to 43 can be reduced. On the other hand, since the heat generation resistor 22 and the resistance temperature detector 23 are used, the resistance detection circuit 60 can appropriately use the resistance detection circuit 60 regardless of the resistance of the heat generation resistor 22 and the on-voltage Vpon (applied voltage). The resistance value Rs can be detected, and the heating element power PW applied to the heating element 22 can be appropriately controlled by the heating element control circuit 70. Moreover, the influence caused by passing a large heating element current Ih through the heating element 22 can be eliminated, the resistance value Rs of the resistance temperature measuring resistor 23 can be appropriately detected, and the temperature of the heating element 22 can be appropriately measured. , The power can be appropriately controlled by the heating element control circuit 70.

While ensuring the length of the resistance measurement period Pr and the absolute off period Poffa that can appropriately measure the resistance value Rs (resistance voltage Vs), the upper limit value Donm, and therefore the upper limit on period Ponm, should be as large as possible. It is preferable to set it. This is because the allowable range of the on-period Pon can be increased and the range of the heating element power PW applied to the heating element 22 can be widened.

(Embodiment 2)
Next, the second embodiment will be described with reference to FIGS. 4 to 7. FIG. 4 is a diagram showing an overall configuration of the sensor device 110 according to the present embodiment. FIG. 5 is a diagram showing a schematic configuration of a package-type sensor unit 130 among the sensor devices 110. FIG. 6 is a diagram showing a schematic configuration of a sensor element 120 housed in a package type sensor unit 130. Further, FIG. 7 is a graph showing the relationship between the change in the heating element voltage Vp applied to the heating element 22 and the measurement timing of the resistance value Rs of the resistance temperature detector 23 in the sensor device 110. The sensor device 110 includes a package-type sensor unit 130 having a sensor element 120, a sensor control device 150 for controlling the sensor element 120, and three wirings 141B, 142B, 143B connecting between them. In this sensor device 110, the sensor body 127 provided in the sensor element 120 in the sensor unit 130 is heated to a predetermined temperature by the heat generated by the heat generation resistor 22 also provided in the sensor element 120 by the sensor control device 150. , The device to be used. The same part of the above-mentioned first embodiment will be omitted or simplified.

First, the schematic configuration of the sensor unit 130 will be described with reference to FIGS. 5A and 5B. This package-type sensor unit 130 has the sensor element 120 mounted on the package main body 132 among the known metal can packages (TO package, CAN package) 131, and is provided on the sensor substrate 121 of the sensor element 120 as described below. The terminals 124 to 126, 128, 129 and the upper end surface of each pin 133 fixed to the package body 132 are connected by a bonding wire 135. Therefore, in this sensor unit 130, the terminals 124 to 126, 128, 129 described below provided in the sensor element 120 are drawn out of the metal can package 131 by the bonding wires 135 and the pins 133.

Further, an opening 134O is provided in the center of the cap 134 covered with the package main body 132, and a mesh 136 is stretched so that air can flow inside and outside the cap 134. Therefore, the outside air can reach the sensor body 127 described below of the sensor element 120 mounted on the package main body 132 through the opening 134O.

Next, among the sensor units 130, the sensor element 120 mounted on the package main body 132 will be described (see FIG. 6). Like the heater substrate 21 of the first embodiment, the sensor element 120 is made of a rectangular plate-shaped sensor substrate 121 made of alumina, and is made of the same material as that of the first embodiment on the first main surface 121A of the sensor substrate 121. The heat generation resistor 22 and the resistance temperature detector 23 having the same meander shape are formed (see FIG. 6A).

However, in addition to this, the sensor element 120 is provided with a sensor body 127 (in the second embodiment, a gas sensor for reducing gas) on the second main surface 121B opposite to the first main surface 121A of the sensor substrate 121. (See FIG. 6 (b)). In this sensor body 127, the comb-shaped first sensor electrode 127A and the comb-shaped second sensor electrode 127B are arranged in combination so as to be engaged with each other while being separated from each other. An oxide semiconductor film 127C made of a metal oxide semiconductor is adhered on the second main surface 121B so as to cover them. Examples of the material of this metal oxide semiconductor include tin oxide, zinc oxide, tungsten oxide and the like. The first sensor electrode 127A is connected to the first sensor terminal 128 provided on the second main surface 121B, and the second sensor electrode 127B is connected to the second sensor terminal 129 also provided on the second main surface 121B. ing. When the oxide semiconductor film 127C is heated to a predetermined temperature, the sensor body 127 is activated and functions as a gas sensor. That is, the resistance value corresponding to the concentration of the reducing gas is shown. Therefore, by passing a constant current between the first sensor terminal 128 and the second sensor terminal 129, a voltage corresponding to the resistance of the oxide semiconductor film 127C, that is, a voltage corresponding to the concentration of the reducing gas is obtained. Can be done.

Further, in the heat generating element 20 of the first embodiment described above, the terminals 24 to 26 of the heat generating resistor 22 and the resistance temperature detector 23 are formed only on the first main surface 21A of the heater substrate 21. On the other hand, in the sensor element 120 of the second embodiment, the heating element terminal 124 and the resistance temperature measuring element terminal 125 connected to the heating element 22 and the resistance temperature measuring element 23 provided on the first main surface 121A of the sensor substrate 121. The common terminals 126 extend onto the second main surface 121B through the semi-cylindrical recesses 121D1 to 121D3 provided on the side surface 121C of the sensor substrate 121, respectively. Therefore, in this sensor element 120, the terminals 124 to 126, 128, 129 provided on the second main surface 121B of the sensor substrate 121 and the pins 133 of the metal can package 131 are connected by the bonding wire 135. be able to. Also in the second embodiment, the heat generating resistor 22, the resistance temperature detector 23, the sensor electrodes 127A, 127B, and the terminals 124 to 126, 128, 129 of the sensor element 120 are screen-printed with the material paste on the sensor substrate 121. It is formed by firing. The oxide semiconductor film 127C is also formed by screen-printing a material paste on the sensor substrate 121 and firing it.

As described above, the five terminals 124 to 126, 128, 129 of the sensor element 120 are connected to the five terminals 151 to 155 of the sensor control device 150 described below by wirings 141 to 145, respectively. See FIG. 4). Specifically, the heating element terminal 124 is conductive with the terminal 151 of the sensor control device 150 via the heating element wiring 141. The resistance temperature detector terminal 125 is conducting with the terminal 152 via the resistance temperature detector wiring 142. Further, the common terminal 126 is electrically connected to the terminal 153 via the common wiring 143. The terminal 153 is grounded in the sensor control device 150. Further, the first sensor terminal 128 is electrically connected to the terminal 154 of the sensor control device 150 via the first sensor wiring 144. The second sensor terminal 129 is electrically connected to the terminal 155 via the second sensor wiring 145.

However, the heating element wiring 141 is from the heating element wiring 141A in the unit belonging to the sensor unit 130, which is composed of the bonding wire 135 and the pin 133 from the heating element terminal 124 to the pin terminal 130A, and the pin terminal 130A of the sensor unit 130. It consists of an external heating element wiring 141B leading to the terminal 151. Similarly, the resistance temperature detector wiring 142 includes the resistance temperature detector wiring 142A in the unit consisting of the bonding wire 135 and the pin 133 from the resistance temperature detector terminal 125 to the pin terminal 130B, and the external temperature measurement from the pin terminal 130B to the terminal 152. It consists of body wiring 142B. The common wiring 143 includes an internal common wiring 143A including a bonding wire 135 and a pin 133 from the common terminal 126 to the pin terminal 130C, and an external common wiring 143B from the pin terminal 130C to the terminal 153. Further, the first sensor wiring 144 includes a first sensor wiring 144A in the unit composed of a bonding wire 135 and a pin 133 from the first sensor terminal 128 to the pin terminal 130D, and an external first sensor extending from the pin terminal 130D to the terminal 154. It consists of wiring 144B. The second sensor wiring 145 includes the second sensor wiring 145A in the unit consisting of the bonding wire 135 and the pin 133 from the second sensor terminal 129 to the pin terminal 130E, and the external second sensor wiring 145B from the pin terminal 130E to the terminal 155. It consists of.

The sensor control device 150 controls the sensor element 120 housed in the sensor unit 130, and includes a sensor detection unit 190, a resistance detection circuit 60 which is substantially the same as the heating element control device 50 of the first embodiment, and a resistance detection circuit 60. A heating element control circuit 170 and a detection timing control unit 80 are provided. Of these, the sensor detection unit 190 passes a constant current through a path arranged in the order of the first sensor wiring 144, the first sensor terminal 128, the sensor body 127, the second sensor terminal 129, and the second sensor wiring 145, and the sensor body 127 ( The resistance value of the oxide semiconductor film 127C) is detected to detect the concentration of the reducing gas. Then, a signal indicating the concentration of the detected reducing gas is output from the sensor output terminal 156 to the outside of the sensor control device 150 via the sensor output wiring 191.

On the other hand, the resistance detection circuit 60 is the same as that of the first embodiment, and is connected to the terminal 152 and the terminal 153. As shown in FIG. 4, the resistance detection circuit 60 measures the sensor element 120 through the temperature measuring body wiring 142 and the common wiring 143. It is connected to the temperature resistor 23. The description of the detection method in the resistance detection circuit 60 will be omitted. The resistance value Rs of the resistance temperature detector 23 calculated by the resistance detection circuit 60 or the corresponding resistance temperature voltage Vs is input to the PAM control unit 173 of the heating element control circuit 170 described below, and the resistance temperature detector is heated. 22 is used for control.

Next, the heating element control circuit 170 will be described. In the above-described first embodiment, the heating element control circuit 70 controls the energization of the heating element 22 by PWM control. On the other hand, the heating element control circuit 170 of the second embodiment is different in that the energization control of the heating element 22 is performed by PAM (pulse amplitude modulation) control, but the other points are the same. Therefore, the differences will be mainly explained.

The heating element control circuit 170 is connected to the terminal 153 via the terminal 151 of the heating element 22 and the changeover switch 81, and as shown in FIG. 4, the heating element 22 is connected through the heating element wiring 141 and the common wiring 143. The heating element voltage Vp is applied to. As a result, the heating element current Ih flows through the heating element 22 and the heating element power PW is applied to the heating element 22. The heating element control circuit 170 changes the magnitude of the on-voltage Vpx applied to the heating element 22 and the variable constant voltage power supply 171 that generates the on-voltage Vpx having a variable output voltage every predetermined period Tp. It has a PAM control unit 173 that performs PAM (pulse amplitude modulation) control.

As shown in FIG. 7, the PAM control unit 173 generates a voltage pulse Ep at a predetermined frequency fp (for example, fp = 1 Hz), that is, at a predetermined period Tp (= 1 / fp, for example, Tp = 1 sec). When repeatedly applied to the heat generation resistor 22, the on-voltage Vpx is applied over a predetermined on-period Pon (for example, Pon = 900 msec out of Tp = 1 sec). Unlike the PWM control of the first embodiment, in the PAM control in the PAM control unit 173, the on-period Pon is constant, so that the on-period Pon corresponds to the length of the upper limit on-period Ponm. However, the on-voltage Vpx is variable within the range of the upper limit on-voltage Vpxm or less. As a result, if the magnitude of the upper limit on-voltage Vpxm is set to 100% at the maximum, the magnitude of the on-voltage Vpx can be changed in the range of 0 to 100%, and PAM control can be realized.

In the second embodiment, in the PAM control unit 173, the resistance value Rs (or the resistance temperature Vs) of the resistance temperature detector 23 obtained by the resistance detection circuit 60 is used to determine the magnitude of the on-voltage Vpx. .. For example, the currently obtained resistance value Rs is significantly larger than the resistance value Rs of the resistance temperature detector 23 corresponding to the target temperature of the heat generation resistor 22, and the temperature of the heat generation resistor 22 is significantly larger than the target temperature. If it is too low, the PAM control unit 173 controls to increase the magnitude of the on-voltage Vpx. As a result, more heating element power PW is applied to the heating element 22 and the temperature rise of the heating element 22 can be accelerated. On the other hand, when the currently obtained resistance value Rs is close to the resistance value Rs of the resistance temperature detector 23 corresponding to the target temperature of the heat generation resistor 22, that is, the temperature of the heat generation resistor 22 is close to the target temperature. If this happens, the PAM control unit 173 controls to reduce the magnitude of the on-voltage Vpx. As a result, less heating element power PW is applied to the heating element 22 and the temperature rise of the heating element 22 can be slowed down. In the PAM control unit 173, the specific control method using the resistance value Rs or the resistance temperature detector voltage Vs is not limited to the above-mentioned method, but a known control method may be used, and detailed description thereof will be omitted. ..

By the way, also in the sensor device 110 of the second embodiment, the heating element wiring 141 and the common wiring 143 are used to pass the heating element current Ih that drives the heating element 22 while the resistance value Rs of the resistance temperature detector 23 is used. The resistance detection current Is for detecting is using the resistance temperature measuring element wiring 142 and the common wiring 143, and the common wiring 143 is shared, which is the same as the heating element device 10 of the first embodiment. That is, in FIG. 4, as symbolically shown by the broken line, the common wiring 143 includes the common wiring resistance 143R. Therefore, when a heating element current Ih is passed through the heating element 22, a voltage drop Vc of Vc = Rc · Ih is also generated in the common wiring 143 by the common wiring resistance 143R (the resistance value is Rc). appear. Therefore, as in the first embodiment, even if the resistance value Rc of the common wiring resistance 143R is small, when the heating element current Ih is much larger than the resistance detection current Is (Ih >> Is), the heating element current The voltage drop Vc (= Rc · Ih) due to Ih has a non-negligible magnitude compared to the voltage drop Rs · Is due to the resistance detection current Is in the temperature measuring resistor 23, and the temperature measuring resistor is derived from the temperature measuring body voltage Vs. There is a possibility that the resistance value Rs of 23 cannot be appropriately obtained.

Therefore, as shown in FIG. 7, similarly to the first embodiment, in the sensor device 110 of the second embodiment, the absolute off period Poffa period (for example, Tp = 1 sec, Poffa = 100 msec) in the period Tp is also used. ) Is a period in which the voltage pulse Ep is turned off and the heating element current Ih is not passed through the common wiring 43. Then, the resistance value Rs of the resistance temperature detector 23 is acquired within this absolute off period Pofa. Specifically, also in the sensor device 110 of the second embodiment, the detection timing control unit 80 includes a changeover switch 81 and a switch control unit 82 that controls on / off of the changeover switch 81, and is a switch control unit. 82 operates in synchronization with the PAM control unit 173. Then, the switch control unit 82 turns off the changeover switch 81 during the absolute off period Poffa and turns on the changeover switch 81 during the upper limit on period Ponm in the cycle Tp. As a result, during the upper limit on period Ponm in which the changeover switch 81 is turned on, the PAM control unit 173 can generate a voltage pulse in which the magnitude of the on voltage Vpx is changed.

In the second embodiment, the on-duty ratio Don of this voltage pulse Ep is constant (equal to the upper limit value Donm of the on-duty ratio), and is given by Don = Donm = Ponm / Tp × 100 (%). This upper limit value Donm has a size of less than 100% (for example, Donm = 900/1000 × 100 = 90%) because the absolute off period Poffa exists.

Thus, also in the second embodiment, in synchronization with the switch control unit 82, the heating element current Ih does not flow in the common wiring 143 in the resistance detection circuit 60, and the resistance measurement period Pr in the absolute off period Poffa (for example, Poffa =). The resistance value Rs of the resistance temperature detector 23 is detected in (Pr = 30 msec) out of 100 msec. Specifically, during the resistance measurement period Pr, the resistance temperature detector voltage Vs is detected by the voltage detection unit 62 as described above, or the resistance value Rs of the resistance temperature detector 23 is further obtained by using this, and PWM control is performed. Input to the unit 73.

Thus, even in the sensor device 110 of the second embodiment, although the heat generating resistor 22 and the resistance temperature detector 23 are used, they are conducted to the three terminals of the terminals 124 to 126, and the wirings 141 to 143 are connected. It is connected to the sensor control device 150 with three wires. Therefore, in the sensor device 110, in the sensor substrate 121 forming the sensor element 120, in addition to the terminals 128 and 129 for the sensor body 127, three terminals 124 to 126 may be provided, and the sensor element 120 ( The sensor board 121) can be miniaturized. Further, in the sensor device 110, in addition to the wirings 144 and 145 for the sensor body 127, three wirings 141 to 143 may be provided. Therefore, the sensor element 120 is mounted, and the space required for the wiring 141A to 143A in the unit provided by the bonding wire 135 and the pin 133 in the sensor unit 130 (metal can package 131) among the wirings 141 to 143 can be reduced. The sensor unit 130 (metal can package 131) can also be made smaller. Further, among the wirings 141 to 143, the space for the external wirings 141B to 143B can be reduced.

On the other hand, since the sensor device 110 of the second embodiment also uses the heating element 22 and the resistance temperature detector 23, the resistance detection circuit 60 can appropriately detect the resistance value Rs, and the heating element control unit 170 can detect the resistance value Rs appropriately. The heating element power PW applied to the heating element 22 can be appropriately controlled. Moreover, the influence caused by passing a large heating element current Ih through the heating element 22 can be eliminated, the resistance value Rs of the resistance temperature detector 23 can be appropriately detected, and the temperature of the resistance temperature detector 22 can be appropriately measured. , The power control by the heating element control unit 170 can be appropriately performed.

Moreover, in this sensor device 110, the sensor element 120 (heat generating portion) also has a sensor body 127 (heated functional body). Therefore, since the sensor body 127 can be heated to an appropriate temperature by the heat generation resistor 22, a predetermined function (in the second embodiment, a function of detecting the reducing gas) is appropriately generated in the sensor body 127. be able to.

Although the present invention has been described above with reference to the first and second embodiments, the present invention is not limited to the first and second embodiments, and can be appropriately modified and applied without departing from the gist thereof. Needless to say.
For example, in the first and second embodiments, in the heater substrate 21 and the sensor substrate 121, the heat generation resistor 22 and the resistance temperature detector 23 are formed in a meander shape, but the heat generation resistor is appropriately used depending on the member to be heated. You just have to choose the shape of. Further, the resistance temperature detector may be arranged in an appropriate shape at a position where the temperature of the heat generation resistor can be appropriately detected. Further, in the first and second embodiments, the heat generation resistor 22 and the resistance temperature detector 23 are integrally formed on the heater substrate 21 and the sensor substrate 121. However, the heat generation resistor and the resistance temperature detector can be separated from each other.

10 Heating element device 110 Sensor device (heating element device)
20 Heat generation element (heat generation part)
120 Sensor element (heat generation element, heat generation part, heated function part)
21 Heater board 21A (heater board) 1st main surface 121 Sensor board 121A (sensor board) 1st main surface 121B (sensor board) 2nd main surface 121C (sensor board) side surface 22 Heat generation resistor 22A (heat generation) One end 22B (of the resistance temperature) End 23 of the other end 23 of the resistance temperature detector 23A One end 23B of the resistance temperature detector 23B The other end 24,124 of the resistance temperature detector Terminal 25,125 Terminals 26,126 Common terminal 127 Sensor body (heated function body)
130 Sensor unit 131 Metal can package 41, 141 Heating element wiring 42, 142 Heating element wiring 43,143 Common wiring 43R, 143R Common wiring resistance 144 1st sensor wiring 145 2nd sensor wiring 50 Heating element Control device (control unit, control device)
150 Sensor control device (control unit, control device)
60 Resistance detection circuit (resistance detection unit)
70, 170 Heating element control circuit (heating element control unit, heating element pulse control unit)
73 PWM control unit 173 PAM control unit 80 Detection timing control unit 81 Changeover switch 82 Switch control unit 190 Sensor detection unit PW (applied to heating element) Heating element power (power)
Vp (applied to the heating resistor) Heat generator voltage Vpon (constant voltage power supply applied) On voltage Vpx (variable voltage power supply applied) On voltage Vpxm (variable voltage power supply can be applied) Upper limit on voltage Ih heating element Current Is (constant current power supply flows) Resistance detection current Rs (temperature measuring resistor) Resistance value Tp (pulse) period Pon on period Poff off period (period when power PW is not applied to the heating resistor)
Ponm upper limit on period Don on-duty ratio Donm (on-duty ratio) upper limit Poffa Absolute off period (period in which power is not applied even if the on-duty ratio is the upper limit)
Pr resistance measurement period

Claims (5)

A heat-generating resistor that generates heat when energized,
A resistance temperature detector that measures the temperature of the heat-generating resistor,
A heating element terminal that conducts to one end of the heating element
A resistance temperature detector terminal that conducts to one end of the resistance temperature detector, and
A heat generating portion having a common terminal that conducts to the other end of the heat generating resistor and the other end of the resistance temperature measuring resistor.
The heating element wiring that conducts to the heating element terminal and
The temperature measuring body wiring that conducts to the above temperature measuring body terminal,
Common wiring that conducts to the above common terminals and
A resistance detector that detects the resistance value of the resistance temperature detector through the resistance temperature detector wiring and the common wiring.
A heating element control unit that controls the power applied to the heating element through the heating element wiring and the common wiring according to the resistance value of the resistance temperature detector detected by the resistance detection unit, and
A heating element device including a control unit having a detection timing control unit that causes the resistance detection unit to detect the resistance value of the resistance temperature detector during a period in which electric power is not applied to the heat generation resistor. The heating element device according to claim 1.
The heating element control unit
A heating element pulse control unit that pulse-modulates and controls the electric power applied to the heating element at a predetermined frequency and at an on-duty ratio within the range of an upper limit value of less than 100%.
The detection time control unit
A heating element device that causes the resistance detection unit to detect the resistance value even when the electric power is applied to the heating element at the on-duty ratio of the upper limit value during the period when the electric power is not applied. The heating element device according to claim 1 or 2.
The heat generating part is
A heating element device having a functional body to be heated that produces a function given in advance by a temperature rise due to heating from the heat generation resistor. The heating element device according to claim 3.
The heated functional body is
A heating element device that is a sensor body that produces a detection function given in advance by a temperature rise due to heating from the heating element. A heat-generating resistor that generates heat when energized,
A resistance temperature detector that measures the temperature of the heat-generating resistor,
A heating element terminal that conducts to one end of the heating element
A resistance temperature detector terminal that conducts to one end of the resistance temperature detector, and
In the heat generating portion having a common terminal that conducts to the other end of the heat generating resistor and the other end of the resistance temperature measuring resistor,
A control device connected by a heating element wiring conducting to the heating element terminal, a resistance temperature measuring element wiring conducting to the resistance temperature measuring element terminal, and a common wiring conducting to the common terminal.
A resistance detector that detects the resistance value of the resistance temperature detector through the resistance temperature detector wiring and the common wiring.
A heating element control unit that controls the power applied to the heating element through the heating element wiring and the common wiring according to the resistance value of the resistance temperature detector detected by the resistance detection unit, and
A control device having a detection timing control unit that detects the resistance value of the resistance temperature detector during a period in which electric power is not applied to the heat generation resistor.

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