JP2015215214A - Temperature history storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily determine whether or not a temperature history in which a measuring object portion goes over a prescribed temperature is experienced.SOLUTION: A temperature history storage device includes a series circuit with an electric current fuse element (F) and an NTC thermistor element (NT) having a negative temperature coefficient (NTC). A voltage applied to the series circuit is denoted by V. The NTC thermistor element (NT) has a resistance value Rin the temperature lower than a prescribed temperature T, and a resistance value Rin the temperature higher than the prescribed temperature T. When the internal resistance value of the electric current fuse element (F) is denoted by R, a rating electric current Iof the electric current fuse element (F) is expressed by V/(R+R)<I<V/(R+ R).

Description

  The present invention relates to a temperature history storage device, and more specifically, determines whether or not a temperature history exceeding a predetermined temperature has been obtained, and further stores a temperature history for grasping the number of times or the duration time exceeding the predetermined temperature. For example, the temperature in the engine of the vehicle or the temperature in the transmission is measured and the temperature history is recorded.

  In recent years, electronic control devices are used to control vehicle engines and transmissions. However, the operating limit temperature of electronic control devices may be exceeded depending on operating conditions and environmental temperatures, and malfunctions and failures of electronic control devices may occur. May occur. This causes the engine and transmission itself to exceed the design temperature and cause a failure. For this reason, if the temperature of these parts is measured and it is possible to leave a temperature history such as whether or not the temperature has exceeded the predetermined temperature, and how long the period of time when the temperature has exceeded the predetermined temperature can be maintained, the cause of the failure Makes it easier to investigate.

  One method for grasping the temperature history is to use a thermal fuse. When using a thermal fuse, a metal with a predetermined melting point is used, and when the temperature reaches that temperature, the thermal fuse melts and breaks, making the resistance value between the terminals infinite and grasping the temperature history It is. However, when a thermal fuse is mounted on a printed circuit board or the like by soldering, the heat may cause the metal to melt and break. That is, it is difficult to stably grasp the temperature history with a thermal fuse for a temperature lower than about 230 ° C. to 280 ° C. used for soldering.

As related technologies, there are Patent Documents 1 to 3. These will be described below.
Patent Document 1 describes that when a certain temperature is reached, the color changes, and thereafter a warmth level that maintains the color is pasted to the measurement site.
Patent Documents 2 and 3 describe a configuration in which an output from a temperature sensor is written as temperature data in a memory and a temperature history is stored. Patent Document 4 discloses a series circuit of a current fuse and an NTC thermistor element.

Japanese Patent Application Laid-Open No. 2002-294123 “Temperature Sensitive Ink and Temperature History Indicator Using It” Japanese Patent Laid-Open No. 2003-140979 “Recording Method to EEPROM” JP 2007-199014 A "Temperature History Measuring Method and Apparatus" Japanese Patent Laid-Open No. 2005-251702 “Fuse with Inrush Current Suppression Function and Current Distribution Device Using the Fuse”

  In Patent Document 1, in the environment of a vehicle used outdoors, dirt or the like adheres over a long period of time, so it is difficult to maintain the color holding function, and it was difficult to actually use it in a vehicle or the like.

  In Patent Document 2 and Patent Document 3, detailed temperature history data can be acquired. However, the system is complicated and expensive, and uses and installation locations are limited. In order to determine the temperature history as to whether or not the part to be measured has reached a predetermined temperature or higher as an investigation of the cause of failure, a simpler method has been desired.

  In Patent Document 4, since the current fuse element is intended to protect the load device, the rated current depends on the load device, and the relationship with the resistance value of the NTC thermistor element described in the present application is not disclosed. .

  An object of the present invention is to make it possible to easily determine whether or not a measurement target portion has passed a temperature history exceeding a predetermined temperature. It is another object of the present invention to reduce power consumption during operation of the temperature history storage device.

According to one aspect of the present invention, a series circuit of a current fuse element (F ₁ ) and an NTC thermistor element (NT ₁ ) having a negative temperature coefficient (NTC) is included, and the voltage applied to the series circuit is expressed as V and, the NTC thermistor element (NT ₁₎ is the resistance value R _ntl in the following low temperature the predetermined temperature T _c, has a resistance value R _nth at a temperature higher than the predetermined temperature T _c, current fuse element (F ₁ when the internal resistance value was R _f1) of the rated current I _r of the current fuse element (F ₁₎ I am in _{V / (R f1 + R ntl} ) <I r <V / (R f1 + R nth) A temperature history storage device is provided.

In this temperature history storage device, since the resistance between the first terminal or the second terminal of the current fuse element is larger than the initial value, the temperature history of the measurement site is higher than the predetermined temperature _Tc. It is judged that it passed.

The present invention is a temperature history storage device in which a plurality of the series circuits described above are connected in parallel, and the NTC thermistor elements of the respective series circuits have different T _c .

V / (R _fm + R _ntml ) <I _rm <V / (R _fm + R _ntmh )
m is a positive integer.

Then, in the temperature history storage device, by measuring the resistance value between the terminals of the current fuse elements included in the n series circuits, the temperature history of the measurement site is higher than the predetermined temperature T _cm , and T _c It is determined that the temperature is lower than _{(m + 1)} .

Further, the present invention provides a temperature history storage device, wherein a plurality of the series circuits described above are connected in parallel, and the current fuse elements of each series circuit have different fusing times _trm. is there.

V / (R _fm + R _ntml ) <I _rm <V / (R _fm + R _ntmh )
m is a positive integer.

Then, in the temperature history storage device, by measuring the resistance value between the terminals of the current fuse elements included in the n series circuits, the temperature history of the measurement site is longer than the fusing time _trm and _{tr (m + 1)} It is determined that a temperature higher than the predetermined temperature T _cm has been passed for a shorter period of time.

Further, according to the present invention, a first NTC thermistor element having a negative temperature coefficient (NTC) and a first current fuse element are connected in series, branching from the node, and the second NTC thermistor element and the second current fuse element. A series circuit of current fuse elements is connected, and the same is repeated thereafter, and the (n-1) th NTC thermistor element and the (n-1) current fuse element are connected in series and branch from the node. A circuit in which a series circuit of an nth NTC thermistor element and an nth current fuse element is connected, and the voltage applied to the whole is V, and the NTC thermistor element has a low temperature of a predetermined temperature T _cm or less. has a resistance value R _NTML, if having a resistance value of the resistance value R _Ntmh at a temperature above the T _cm, the resistance value R _fm of the current fuse element of the _{m-th, R fm <R nt (m} + 1) h + R _{f (m + 1)} || {R _{nt (m + 2) h} + R _{f (m + 2)} || {R _{nt (m + 3) h} + R _{f (m + 3)} ||… || {R _ntnh + R _fn }…}} <R _{nt (m + 1) l} + R _{f (m + 1)} || {R _{nt (m + 2) l} + R _{f (m + 2)} || {R _{nt (m + 3) l} + R _{f (m + 3)} || ... || {R _ntnl + R _fn } ...}} is a temperature history storage device.

Here, m is 1 ≦ m ≦ n, and the symbol: || indicates the combined resistance of the parallel connection. In this temperature history storage device, some or all of the first to n-th current fuse elements have the characteristics of a slow blow fuse, and the first to n-th current fuse elements have a rated current I _r1 = I _r2 =. = in I _rn = I _r, a current fuse element having a fusing time _{t r1 <t r2 <... <} t rm.

In this temperature history storage device, either or both of the first terminal and the second terminal of each of the first to m-th current fuse elements are electrically disconnected from the temperature history storage device, and the first to Since the resistance between the first terminal and the second terminal of each of the m-th current fuse elements is larger than the initial value, the temperature history of the measurement site is higher than the predetermined temperature T _cm . less is also temperature history determination method for determining that passing through the period of _{t r1 <t r2 <... <} t rm. This NTC thermistor element is a thermistor element having a CTR (Critical Temperature Resistor) characteristic in which the resistance value changes sharply at a predetermined temperature T _cm .

This temperature history device is a temperature history storage device characterized in that the NTC thermistor elements have different T _c . For example, when T _cm <T _c <T _{c (m + 1)} , the resistance between the first terminal and the second terminal of each of the first to m-th current fuse elements is higher than the initial value. By increasing the temperature, it is determined that the temperature history of the measurement site has passed a temperature higher than the predetermined temperature T _cm and lower than T _{c (m + 1)} .

The NTC thermistor element is formed using vanadium oxide as a main component.
For example, depending on the degree of reduction of V ₂ O ₅ , the characteristics can be adjusted as shown in FIG. Alternatively, when sputtering film formation is performed using vanadium or vanadium oxide as a target, a thin film with adjusted characteristics can be obtained even if the oxygen concentration in the atmospheric gas is adjusted.

A voltage measuring terminal for measuring a voltage between both ends of the current fuse element is provided.
The temperature history storage device includes a drive circuit that intermittently applies the voltage V during temperature history driving.

The temperature history storage device has a drive circuit that intermittently applies the voltage V during temperature history drive, and the drive circuit is connected in series with a resistor as a protective resistor to the series circuit. A capacitor C having a capacitance C _s is connected in parallel, one electrode of the series circuit is connected to a ground potential, and the other electrode is connected to an input of an inverter circuit in which a plurality of inverters are connected, and the inverter circuit Is connected to the gate of a transistor provided between the one electrode and a power supply, one of the source and drain electrodes of the transistor is connected to the power supply voltage, and the other is connected to the other electrode. It is connected. Here, when the inverter circuit has an odd number of stages, the transistor is n-type, and when the inverter circuit has an even number of stages, the transistor is p-type.

Instead of the NTC thermistor element, it is characterized in that it is used for a bimetal switch that is non-conductive at a temperature equal to or lower than a predetermined temperature _Tc and that is conductive at a temperature higher than _Tc .

According to the present invention, it can be easily determined whether or not the measurement target site has passed a temperature history exceeding a predetermined temperature.
Further, it is possible to reduce power consumption during operation of the temperature history storage device.

It is a circuit diagram showing an example of 1 composition of a temperature history storage device in a 1st embodiment of the present invention. It is a figure which shows one structural example of the current fuse element and the NTC thermistor element in the temperature history storage device shown in FIG. 1A. It is a figure which shows an example of the temperature-resistivity characteristic of an NTC thermistor element. It is a figure which shows an example of the measuring method in a temperature history memory | storage device. It is a circuit diagram which shows the example of 1 structure of the temperature history memory | storage device with a drive circuit by the 2nd Embodiment of this invention. It is a diagram showing a time variation of the potential V _n of electrode N of the driver circuit shown in FIG. 4A. It is a figure which shows the input-output characteristic of the inverter circuit shown to FIG. 4A. It is a figure which shows the structural example of the temperature history apparatus by the 3rd Embodiment of this invention. It is a figure which shows the temperature dependence of _Tc and a resistivity, when obtaining the material which has different _Tc by substituting and adjusting the density | concentration. It is a circuit diagram which shows the example of 1 structure of the temperature history recording device by the 4th Embodiment of this invention. It is a circuit diagram which shows the example of 1 structure of the temperature history recording device by the 5th Embodiment of this invention.

  Hereinafter, a temperature history storage device according to an embodiment of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1A is a circuit diagram showing a configuration example of a temperature history storage device according to the present embodiment. As shown in FIG. 1A, the temperature history storage device 1 according to the present embodiment includes a series circuit of a current fuse element (F ₁ ) and an NTC thermistor element (NT ₁ ) having a negative temperature coefficient, and includes at least an NTC thermistor. An element (NT ₁ ) is installed near the measurement site. If necessary, a protective resistor R ₀ having a resistance value R may be connected in series to the series circuit. The operation of the temperature history storage device 1 will be described with reference to FIG. 1A.

The current fuse element (F ₁ ) has a rated current I _r and a resistance value R _f1 . The NTC thermistor element (NT ₁ ) has a resistance value R _{ntl at} a temperature lower than a predetermined temperature T _c and a resistance value R _{nth at} a temperature higher than T _c . When the voltage V to the series circuit of the current fuse element (F ₁₎ and NTC thermistor element (NT ₁₎ is applied, the current I ₁ flowing through the series circuit, in the following lower temperature _{T c I 1 = V / (} R + R _f1 + R _ntl ). This value by setting such that the value smaller than the rated current I _r of the current fuse element (F _1), the fusing current fuse element (F ₁₎ is not generated.

When the temperature of the measurement site rises and becomes higher than T _c , the current I ₂ flowing through the series resistance is I ₂ = V / (R + R _f1 + R _nth ). Since the resistance value in the NTC thermistor element (NT ₁ ) has a relationship of R _ntl > R _nth , I ₁ <I ₂ is satisfied. By setting I ₂ to be larger than the rated current I _r of the current fuse element (F ₁ ), the current fuse (F ₁ ) element is blown. Thereafter, the current fuse element (F ₁ ) is held in a blown (cut) state even when the measurement site is lower than the predetermined temperature T _c .

That is, in the temperature history storage device of the present embodiment, the following formula (1) is _{satisfied with} respect to the rated current Ir.

V / (R + R _f + R _ntl ) <I _r <V / (R + R _f + R _nth ) (1)
Here, when the protective resistance R ₀ is not necessary, R = 0 may be set in the above equation (1).

When investigating the temperature history of the measurement site by failure analysis or the like, the presence or absence of fusing is confirmed from the resistance value between the first terminal and the second terminal at both ends of the current fuse element (F ₁ ). be able to.

In the case of this embodiment, it is not necessary to remove the first terminal and the second terminal at both ends of the current fuse element (F ₁ ) from the temperature history device, and whether or not the current fuse element (F ₁ ) is blown out easily. Can be confirmed. With the above method, it is possible to determine whether or not the temperature history of the measurement site has exceeded a predetermined temperature _Tc .

In the present embodiment, the temperature _{Tc at} which the resistance value of the NTC thermistor element (NT ₁ ) changes can be set to a temperature lower than the mounting temperature such as soldering, and a conventional temperature fuse element is used. As in the case of technology, it is not limited by the mounting temperature.

The NTC thermistor element (NT ₁ ) is more preferably an NTC thermistor element having a CTR (Critical Temperature Resistor) characteristic in which the resistance value changes sharply at a predetermined temperature T _c .

FIG. 2 is a diagram showing the relationship between temperature and electrical resistance, and is a diagram showing an example of the characteristics of an NTC thermistor element having CTR characteristics. The characteristics ( _Tc and resistance value) of the characteristics as shown in FIG. 2 can be adjusted by, for example, the degree of reduction of V ₂ O ₅ . Alternatively, when sputter deposition is performed using vanadium or vanadium oxide as a target, a thin film with adjusted characteristics can be obtained by adjusting the oxygen concentration in the atmospheric gas.

When the temperature T of the measurement site is equal to or lower than the predetermined temperature _Tc, the resistance value of the NTC thermistor element is high, so that the current flowing through the series circuit of the temperature history storage device 1 is small, while T is higher than _Tc. In this case, since the resistance value of the CTR thermistor element becomes small, the amount of current flowing through the series circuit of the temperature history storage device 1 increases and the current fuse element (F ₁ ) is blown. Thereafter, even if the measurement site becomes lower than the predetermined temperature T _C , the current fuse element (F ₁ ) is held in a blown state.

FIG. 1B is a diagram showing an example of the structure of the temperature history storage device shown in FIG. 1A.
As shown in FIG. 1B (a), the temperature history storage device is formed on an insulating substrate 11 or a substrate 11 on which an insulating film is deposited on at least one surface of a conductive substrate.

As shown in the sectional structure (A)-(A ′) of FIG. 1B (b), in order to form the current fuse element (F ₁ ), an insulating substrate or a substrate 11 on which an insulating film is deposited is formed. A fuse and wiring layer 51 are deposited on the substrate. As shown in the plan view of FIG. 1B (c), the current fuse element (F ₁ ) has, for example, a shape in which a Cu film pattern is constricted in the middle.

As shown in the sectional structure (B)-(B ′) of FIG. 1B (d), the NT film 71 for the NTC thermistor element (NT ₁ ) is formed in the film thickness direction by the lower electrode 81 and the upper electrode 91. A structure that allows current to flow. As a result, the resistance value of the NTC element generally having a high specific resistance can be set to about 0.1Ω to 10Ω relative to the resistance value of the fuse (for example, about 1Ω). Here, the protective resistance element R ₀ using the resistance film 61 is also formed on the same substrate 11. As shown in the (B)-(B ′) cross-sectional structure of FIG. 1B (e), the wiring layer 51 may be formed on a part of the lower electrode 81.

  In this manner, the temperature history storage device shown in FIG. 1A can be easily integrated on the substrate 11.

The NCT thermistor element has a temperature-resistivity characteristic as shown by a solid line in FIG. 2 (Source: “Temperature Sensor” Hisao Futaki, Koichi Murakami, Nikkan Kogyo Shimbun). That is, it has a CTR (Critical Temperature Resistor) characteristic in which the resistance value changes greatly at a predetermined temperature _Tc (the resistance value rapidly decreases as the temperature rises).

  In the example of FIG. 2, the electric resistance value at a temperature of 60 ° C. or lower has a characteristic that the electric resistance value is reduced by two digits or more at 70 ° C. or higher. That is, the current flowing in FIG. 1A changes by two digits or more, and by appropriately setting the rated current of the current fuse element, it can be easily blown in a temperature range higher than a predetermined temperature. A thermistor element having CTR characteristics undergoes a sharp change in resistance value with respect to temperature, so that the temperature history of the measurement site can be recorded with high accuracy.

1A, the current resistance value across the resistance thermometer of the fuse element (F ₁₎ (showing the connection by a broken line.) By measuring the like later, whether current fuse element (F ₁₎ is off Therefore, it can be easily determined whether the NTC thermistor element (NT ₁ ) has received a temperature history higher than T _C.

FIG. 3 is a diagram illustrating an example of another measurement method. As shown in FIG. 3A, the U-shaped region 11y is separated from the substrate 11 so that the substrate 11 is cut at both ends of the current fuse element (F ₁ ) between the current fuse elements (F ₁ ). You may make it come off (FIG.3 (b)). As shown in FIG. 3C, the measurement substrate 11z having the same shape as the U-shaped region 11y is inserted into the remaining substrate 11x, and the resistance value between the current fuse elements (F ₁ ) is set. It is convenient to measure. In this case, the resistance value can be measured by connecting the terminals of the ohmmeter to both ends of the current fuse element (F ₁ ) on the measurement substrate 11z.

When the temperature history storage device according to the present embodiment is used by the above method, it is possible to determine whether or not the temperature history of the measurement site has exceeded the predetermined temperature _Tc with a device having a simple configuration.

According to this embodiment, it is possible to set the temperature _{Tc at} which the resistance value of the NTC thermistor element (NT ₁ ) changes to a temperature setting lower than the mounting temperature such as soldering, and a conventional temperature fuse is used. There are no restrictions on the mounting temperature.

Further, the NTC thermistor element in the present embodiment can be replaced with a bimetal switch. That is, the same effect as that of the NTC thermistor element is obtained by connecting a bimetal that is non-conductive at a predetermined temperature _Tc or less and that is conductive at a temperature higher than _{Tc in} parallel with the current fuse element (F ₁ ). It is possible to obtain. In addition, it goes without saying that NTC thermistor elements and elements having the same characteristics as fuses can be used in any combination.

(Second Embodiment)
Next, a temperature history storage device according to the second embodiment of the present invention will be described. The temperature history storage device according to the present embodiment is connected to the series circuit of the current fuse element (F ₁ ) and the NTC thermistor element (NT ₁ ) of the temperature history storage device 1 according to the first embodiment to connect the temperature history storage device. The details of the driving circuit are described below.

As shown in FIG. 4A, the temperature history storage device with a drive circuit according to the present embodiment includes a series circuit of a current fuse element (F ₁ ) and an NTC thermistor element (NT ₁ ). A capacitor C having a capacitance C _s is connected in parallel to a temperature history storage device (for example, the circuit shown in FIG. 1A) connected in series with a resistor (R ₀ ) having a resistance value R as a protective resistor. One electrode G is connected to the ground potential, and the other electrode N is connected to the input of an inverter circuit INV21 in which inverters are connected in odd stages (n is an odd number). The output of the inverter circuit 21 is connected to the gate of the provided with an electrode (N) between the power supply (V) n-type transistor T _r, connected to one of a source and a drain electrode of the n-type transistor T _r is the power supply voltage V The other one is connected to the electrode N.

The operation of the circuit of FIG. 4A will be described below.
First, consider a case where the n-type transistor _Tr is in an on state (energized state). In this case, a voltage is applied to the 1 (series circuit of the protective resistor R _0, and a current fuse (F ₁₎ and the NTC thermistor element (NT ₁₎₎ Temperature history storage device via the n-type transistor T _r.

Here, if the temperature of the measurement site is lower than the predetermined temperature T _c , the NTC thermistor element (NT ₁ ) is in a high resistance state, so that the protective resistance (R ₀ ), the NTC thermistor element (NT ₁ ), and the current The current flowing through the fuse element (F ₁ ) is small, and the current fuse element (F ₁ ) is not melted. At the same time, a voltage is applied to the capacitor C connected in parallel to the temperature history storage device 1 to charge the capacitor C. When the potential V _n of electrodes N by charging of the capacitor C exceeds the logic inversion threshold V _th of the inverter INV1, the input of the inverter INV1 is recognized as High state. Then, the logic is inverted by the inverter, and the output of the inverter INVn after n stages (n is an odd number) becomes the Low state.

The output of the inverter INV _n is because it is connected to the gate of the n-type transistor T _r, T _r is the off state (substantially non-energized), and a substantially blocked state and the power supply V and the electrode N. Here, when _Tr is turned off, the charge charged in the capacitor C is discharged through the temperature history storage device 1. Also at this time, if the temperature of the measurement site is lower than the predetermined temperature T _c , the discharge current is small and the current fuse element (F ₁ ) is not blown.

As shown in FIG. 4B, the potential V _{n of the} electrode N is obtained by using the protection resistance R ₀ , the NTC thermistor element (NT ₁ ), the resistance value of the current fuse element (F ₁ ), and the capacitance C _{s of the} capacitor C, as shown in FIG. proportional to exp {-1 / ((R + R f + R ntl) * C s)}, along with L1, it decreases from the time t ₁ to t _2. When the potential V _n of the electrode N falls below the logic inversion threshold V _th of the inverter INV1 due to the discharge of the capacitor C, the input of the inverter INV1 is recognized as the low state, and the output of the inverter INV _n after the odd-numbered stage becomes the high state . As a result, _Tr is turned on, and the power supply V and the electrode N are in a substantially conductive state.
Thereafter, this operation is repeated.

By this operation, the potential V _n of the electrode N fluctuates along the time axis with the charge / discharge of the capacitor C in the vicinity of the logic inversion threshold V _th of the inverter INV1 (FIG. 4B: V _{thL to} V _thH ). As a result, only the electric charge accompanying charging / discharging of the capacitor C needs to be intermittently supplied from the power source V, and the operation can be performed with lower power consumption than in the prior art.

The width of the potential fluctuation of V _n (V _{thL to} V _thH ) is related to the width ΔV _th of the transition region of the inverter INV1 shown in FIG. 4C, and this is the characteristic of the n-type and p-type transistors constituting the inverter INV. Due to If the rise characteristic of the transistor from the off state to the on state is steep, that is, if the threshold swing (S value) under the threshold voltage is small, ΔV _th is small, and if the S value is large, ΔV _th is large.

The channel width of the n-type and p-type transistors constituting the inverter INV is small in the input stage side inverter (INV ₁ ) and gradually increases toward the output stage side, and the nth final stage inverter (INV _n It is desirable that the output voltage of) has an amplitude substantially equal to the power supply voltages V _dd and V _{ss of} the inverter. More specifically, the channel width of the transistor is preferably increased by about 2 to 3 times. In practice, the number of inverter stages is three or more, and in particular, n = 5 or n = 7 is preferable. The potential of the electrode N varies between V _thL and V _thH as shown in FIG. 4B.

When the temperature history storage device 1 is in an operating state, that is, when the temperature of the measurement site becomes higher than the predetermined temperature _Tc , the resistance of the NTC thermistor element (NT ₁ ) becomes R _nth and the current fuse element (F ₁ ) is blown. to hold the state to be, it is sufficient so that the relationship of the following expression holds with respect to the rated current I _r of the voltage V _thL and current fuse element.
I _r ≤ I _f2 = V _thL / {R + R _f + R _nth } (2)

At the same time, the temperature of the measurement site holds the state of current fuse element is lower than the predetermined temperature T _c (F ₁₎ is not blown, the following relationship holds with respect to the rated current I _r of the current fuse element Design as follows.
I _r > I _f1 = V _thL / {R + R _f + R _ntl } (3)
Thereby, if the voltage of the electrode N is V _thL or more, the temperature of the measurement site is always monitored.

Note that the temperature history storage device can be put into an operating state only when the potential of the electrode N becomes V _thH . In this case, the design may be made so that the following two expressions hold.
I _r ≤ I _f2 = V _thH / {R + R _f + R _nth } (4)
I _r > I _f1 = V _thH / {R + R _f + R _ntl } (5)
When the period of potential fluctuation is T, the temperature of the measurement site is intermittently monitored only 1 / T times per second, and the power consumption can be further reduced.

As these applications, it is also possible to set a threshold value for operating the temperature history storage device 1 between V _thL and V _thH .

As described above, the temperature history of the measurement site can be monitored continuously or intermittently to determine whether or not the predetermined temperature _Tc has been exceeded. According to this embodiment, there is no need for an external control signal or the like, and the previous history storage device is operated continuously or intermittently by a simple drive circuit, so that the power consumption of driving the device can be kept low. it can.

In this embodiment, _Tr is an n-type transistor and inverter INV is configured from an odd number of stages. However, _Tr is a p-type transistor and inverter INV is configured from an even number of stages. The same operation is possible.
This drive circuit can also be used in the following third and fourth embodiments.

(Third embodiment)
FIG. 5 is a diagram showing a configuration example of a temperature history device according to the third embodiment of the present invention. In the first embodiment, the temperature history storage circuit using a series circuit of a set of current fuse elements and NTC thermistor elements has been described. In this embodiment, a plurality of series circuits in the first embodiment are provided in parallel. Connected. The NTC thermistor elements of each series circuit may be configured by different temperatures at which resistance value changes occur. Then, after receiving the temperature history, either or both of the first terminal and the second terminal of each current fuse element are electrically disconnected from the temperature history storage device, and the first terminal of each current fuse element is connected to the first terminal of each current fuse element. By measuring the resistance value between the second terminals, it is possible to grasp the temperature history for a plurality of predetermined temperatures. A temperature history storage device in which series circuits are connected in parallel in n stages will be described with reference to FIG.

NTC thermistor element _{NT 1, NT 2, ... NT} n are each T _c1, T _c2, in ... T _cn of temperature, has a characteristic that the resistance value change occurs. As shown in FIG. 6, NTC thermistor elements having different characteristics can be realized by adding metals such as Ge, Si, Ni, Ag, W, and Mo to a VO ₂ material, for example (Source: "Temperature sensor" Hisao Futaki, Koichi Murakami, Nikkan Kogyo Shimbun).

  Further, the resistance value at this time can be adjusted by the film thickness of the NT film 71 shown in FIGS. 1B and 1E and the overlapping area of the upper electrode 91 and the lower electrode 81 in the planar view.

NTC thermistor NT _m of the series circuit of the m-th (1 ≦ m ≦ n) is the resistance value R _NTML in T _cm below low temperature, the resistance value R _Ntmh at temperatures above T _cm. The rated current of the current fuse element F _m connected in series to each NTC thermistor element NT _m is I _rm , and the resistance value is R _fm .

These have a relationship of V / (R _fm + R _ntml ) <I _rm <V / (R _fm + R _ntmh ), as in the fourth embodiment described later. In the present embodiment, in order to simplify the description, it is assumed that there is relationship between _{T c1 <T c2 <... <} T cn.

When the temperature T of the measurement site is T <T _c1 , the resistance value of NT _{m in} each series circuit is as large as R _{ntml. Therefore} , the current that flows in each series circuit when voltage V is applied is less than I _rm , and the current fuse The element F _m is not melted.

When the temperature T of the measurement part rises to T _cm <T <T _{c (m + 1)} , the resistance value of NT _m of the 1st to m-th series circuits decreases to R _ntmh. A lot of current flows through. By previously designing a current amount at this time than the rated current I _rm current fuse element F _m, fusing current fuse element F _m is generated.

On the other hand, in the _{(m + 1)} th to nth series circuits, the resistance value of NT _{(m + 1)} remains large as R _{nt (m + 1) l} , and the amount of current flowing through the series circuit is determined as the current fuse element F. _{Since it} is smaller than the rated current I _{r (m + 1) of (m + 1)} , the current fuse element F _{(m + 1)} is not blown.

When investigating the temperature history of the measurement site may be examined whether the measured fusing the resistance between terminals of the current fuse element F _m included in the temperature history storage device. As a result, it is possible to determine that the temperature history of the measurement site has passed the temperature higher than the predetermined temperature T _cm and lower than T _{c (m + 1)} .

  Further, in the present embodiment, the current fuse elements of each series circuit may be configured with different melting times. Then, after receiving the temperature history, either or both of the first terminal and the second terminal of each current fuse element are electrically disconnected from the temperature history storage device, and the first terminal of each current fuse element is connected to the first terminal of each current fuse element. By measuring the resistance value between the second terminals, it is possible to grasp the length of time during which the measurement site is held at a temperature higher than the predetermined temperature.

For example, the fusing time t _rm current fuse element F _m, when the relationship of easy for _{t r1 <t r2 <... <} t rn, current fuse element F _m to m-th being in the non-conducting state, m By confirming that the current fuse elements F _{m + 1} up to the (+1) th are in the conductive state, the time during which the current fuse element F _{m + 1} is in the temperature state higher than the predetermined temperature T _{cm is not} less than _trm and _{tr (m +} You can see that it was shorter than ₁₎ .

As in the second embodiment, the drive circuit connected to the series circuit of the current fuse element (F ₁ ) and the NTC thermistor element (NT ₁ ) is also applied to the third embodiment, thereby reducing power consumption. It can also be made.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
FIG. 7 is a diagram illustrating a configuration example of the temperature history recording apparatus according to the present embodiment.

In the temperature history storage device according to the present embodiment, the first NTC thermistor element (NT ₁ ) and the first current fuse element (F ₁ ) having a negative temperature coefficient (NTC) as in the first embodiment. Are connected in series, branching from the node, and a series circuit of a second NTC thermistor element and a second current fuse element is connected. The voltage applied to the entire circuit is V. First and second NTC Sasuta elements each have a resistance value R _Nt1l and R _Nt2l the following low temperature the predetermined temperature T _c, has a resistance value of each resistance value R _Nt1h and R _Nt2h at a temperature above the T _c If the resistance value R _f2 of the resistance value R _f1, and a second current fuse element (F ₂₎ of the first current fuse element (F ₁₎ has the following relation.
R _f1 <R _nt2h + R _f2 <R _nt2l + R _f2 (6)

In this temperature history storage device, at least the first NTC thermistor element (NT ₁ ) and the second NTC thermistor element (NT ₂ ) are installed in the vicinity of the measurement site, and the voltage of the constant voltage source (V) is applied.
The operation of the temperature history storage device according to this embodiment will be described below.

In the following low temperature the predetermined temperature T _c, the first NTC thermistor device current flowing through the current flow through _{(NT 1)} I nt1l and the first current fuse element _{(F 1)} I f1l, second NTC thermistor ( NT ₂ ) current I _nt2l and second current fuse element (F ₂ ) current If _2l are respectively expressed as follows:

When the rated current of the first current fuse element (F ₁₎ and I _r1, by the I _f1L is set so as to be smaller than I _r1, the first current fuse element (F ₁₎ No fusing occurs. Qualitatively, the resistance value R _{nt1l of} the first NTC thermistor element (NT ₁ ) may be a sufficiently large value.

If the rated current of the second current fuse element (F ₂ ) is I _r2 , the relation of I _f2l <I _f1l is _obtained from the relationship of the above formula (6), so if I _r1 = I _r2 The second current fuse element (F ₂ ) does not melt.

Next, the case where the temperature of the measurement part rises and becomes higher than _Tc will be described. First NTC thermistor device current flowing through the current flow through _{(NT 1)} I nt1h and the first current fuse element (F ₁₎ I _f1h, the current flowing through the second NTC thermistor element _{(NT 2)} I nt2h and second Each current I _f2h flowing through the current fuse element (F ₂ ) is expressed as follows.

The rated current I _r1 of the first current fuse element (F _1), said by I _F1h is set so as to be a large value, fusing time t _f1 of the first current fuse element (F ₁₎ Later, the first current fuse element (F ₁ ) is blown. Qualitatively, the resistance value R _{nt1h of} the first NTC thermistor element (NT ₁ ) may be a sufficiently small value. Also, before the first current fuse element (F ₁₎ is blown, a current I _F2H flowing through the second current fuse element (F ₂₎ from the relationship of Equation (6), the relationship of _I f2h <I f1h If I _r1 = I _r2 , the second current fuse element (F2) is not melted at this time.

After that, when the measurement site becomes lower than the predetermined temperature _Tc, only the first current fuse element (F ₁ ) is held while being blown (cut).

Also, once again after becoming less temperature condition T _c, it will be described when it becomes a temperature higher than the T _c. Since the first current fuse (F ₁ ) is blown, the current passes through the first NTC thermistor element (NT ₁ ) and the second NTC thermistor element (NT ₂ ) and the second current fuse element (F ₂ ) Flowing. _Assuming that the currents at this time are _Int2h and _If2h , respectively,

Here I _F2H is set to be larger than the rated current I _r2 of the second current fuse element (F _2). Qualitatively, it may be a resistance value R _Nt2h is sufficiently small values of the resistance value R _Nt1h and second NTC thermistor element (NT ₂₎ of the first NTC thermistor element (NT _1). As a result, after a fusing time t _f2 having the second current fuse element (F ₂₎ is a second current fuse element (F ₂₎ is blown (cut). That is, in the circuit shown in FIG. 7, by confirming that the first current fuse element (F ₁ ) and the second current fuse element (F ₂ ) are in a non-conductive state, the temperature higher than the predetermined temperature T _c. It can be seen that the time in the state was t _f1 + t _f2 or more.

On the other hand, the second current fuse element (F ₂ ) is not blown when the temperature becomes equal to or lower than the predetermined temperature T _c before t _f2 elapses. That is, by confirming that the first current fuse element (F ₁ ) is in a non-conductive state and the second current fuse element (F ₂ ) is in a conductive state, in a temperature state higher than a predetermined temperature T _c. It can be seen that the time was greater than t _f1 and shorter than t _f1 + t _f2 .

In the above description, the case where the temperature once decreased to T _c or less after t _{f1 has} elapsed and again became higher than T _c has been described, but the case where the temperature continuously exceeds T _c after t _{f1 has} elapsed is also described. It is the same.

When investigating the temperature history of the measurement site by failure analysis or the like, the first terminal of each of the first current fuse element (F ₁ ) and the second current fuse element (F ₂ ), or the second Either or both of the terminals can be electrically disconnected from the temperature history storage device, and the presence or absence of fusing can be confirmed from the resistance value between the first terminal and the second terminal of each current fuse element.

  In the present embodiment, any or all of the current fuse elements are desirably slow blow fuses having a relatively long fusing time. By using a slow blow fuse having a fusing time that matches the time scale of the temperature change of the measurement target, it is possible to accurately grasp the temperature history.

Further, for example, the first current fuse element may be a normal (rapid cut) current fuse, and a slow blow fuse may be used for the second current fuse element. In this case, whether or not there has been a temperature history exceeding the predetermined temperature _Tc even in a short time is judged from the blown state of the first current fuse element, and if it exceeds _Tc , the second current fuse for the duration is exceeded. Judgment can be made by the fusing state of the element.

In the present embodiment, the NTC thermistor element may have a different _Tc . For example, when _Tc of NT ₁ is T _c1 and T _{C of} NT ₂ is T _c2 and T _C1 <TC ₂ , the first terminal and the second terminal of each of the first to second current fuse elements It is possible to determine that the temperature history of the measurement region has passed the temperature higher than the predetermined temperature T _c1 and lower than T _c2 .

(Fifth embodiment)
In the fourth embodiment, the connection between the first and second current fuse elements and the NTC thermistor element has been described. In the fifth embodiment, as shown in FIG. It is possible to connect the current fuse element and the NTC thermistor element in the same manner. That is, the configuration of FIG. 7 is repeated in the same manner, and the (n−1) th NTC thermistor element and the (n−1) th current fuse element are connected in series, branching from the node, and the nth A circuit in which a series circuit of an NTC thermistor element and an nth current fuse element is connected is included.

When 1 ≦ m ≦ n, the resistance value R _fm of the m-th current fuse element has the following relationship. This is obtained by extending equation (6).

R _fm <R _{nt (m + 1) h} + R _{f (m + 1)} || {R _{nt (m + 2) h} + R _{f (m + 2)} || {R _{nt (m + 3) h} + R _{f (m + 3)} ||… || {R _ntnh + R _fn }…}}
<R _{nt (m + 1) l} + R _{f (m + 1)} || {R _{nt (m + 2) l} + R _{f (m + 2)} || {R _{nt (m + 3) l} + R _{f (m + 3)} ||… || {R _ntnl + R _fn }…}} (14)
Here, the symbol: || indicates the combined resistance of the parallel connection.

As a result, the length of time exceeding the predetermined temperature _Tc can be grasped in detail over a wide range. For example, when the fusing time of the first current fuse element (F ₁ ) is t _f1 and the fusing time of the nth current fuse element (F _n ) is t _fn ,
t _f1 <t _f2 <… <t _fn (15)
Further, by setting an appropriate magnification relationship, it is possible to design such that the time is fine in the short time region and roughly grasps the time in the long time region. In particular, the NTC thermistor element (NT) is more preferably a thermistor element having a CTR (Critical Temperature Resistor) characteristic in which the resistance value changes sharply at a predetermined temperature _Tc .

Further, by using a plurality of the circuits shown in FIG. 7 using a thermistor element (see FIG. 6) having CTR characteristics at different temperatures, it is possible to grasp temperature histories related to a plurality of predetermined temperatures T _cm .

Above the temperature history of the measurement site by the method, it is possible to determine whether more than a predetermined temperature T _c, it becomes possible to grasp more the length of time that exceeds the predetermined temperature T _c.

Also in this embodiment, it is possible to set the temperature _{Tc at} which the resistance value of the NTC thermistor element (NT) changes to a temperature lower than the mounting temperature such as soldering, and when a conventional temperature fuse is used There is an advantage that it is not restricted by the mounting temperature.

  In the above-described embodiment, the configuration and the like illustrated in the accompanying drawings are not limited to these, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  Each component of the present invention can be arbitrarily selected, and an invention having a selected configuration is also included in the present invention.

According to the present invention, it can be easily determined whether or not the measurement target site has passed a temperature history exceeding a predetermined temperature.
In addition, a reduction in power consumption during operation of the temperature history storage device can be realized.

  The present invention can be used as a temperature history storage device.

DESCRIPTION OF SYMBOLS 1 ... Temperature history memory | storage device (series circuit), F (n) ... Fuse element, NT (n) ... NTC thermistor element, _R0 ... Resistor of protection resistance, INV21 ... Inverter apparatus, _Tr ... Transistor.

Claims (9)

Including a series circuit of a current fuse element (F ₁ ) and an NTC thermistor element (NT ₁ ) having a negative temperature coefficient (NTC), the voltage applied to the series circuit is V,
The NTC thermistor element (NT ₁ ) has a resistance value R _ntl at a temperature lower than a predetermined temperature T _c , and has a resistance value R _nth at a temperature higher than the predetermined temperature T _c ,
When the internal resistance of the current fuse element (F ₁ ) is R _f1
Rated current I _r of the current fuse element (F ₁₎ is
V / (R _f1 + R _ntl ) <I _r <V / (R _f1 + R _nth )
A temperature history storage device.   A temperature history storage device, wherein a plurality of series circuits according to claim 1 are connected in parallel, and the NTC thermistor elements of each series circuit have different Tc. A temperature history storage device, wherein a plurality of series circuits according to claim 1 are connected in parallel, and the current fuse elements of each series circuit have different fusing times _Tr . The first NTC thermistor element having a negative temperature coefficient (NTC) and the first current fuse element are connected in series, branching from the node, and the second NTC thermistor element and the second current fuse element A series circuit is connected, and thereafter the same is repeated, and the (n-1) th NTC thermistor element and the (n-1) current fuse element are connected in series, branching from the node, and the nth NTC Including a circuit in which a series circuit of a thermistor element and an nth current fuse element is connected, the voltage applied to the whole is V,
When the m-th NTC thirster element has a resistance value R _ntml at a temperature lower than a predetermined temperature T _cm and has a resistance value R _{ntmh at} a temperature higher than T _cm , the resistance value of the m-th current fuse element R _fm
R _fm <R _{nt (m + 1) h} + R _{f (m + 1)} || {R _{nt (m + 2) h} + R _{f (m + 2)} || {R _{nt (m + 3) h} + R _{f (m + 3)} ||… || {R _ntnh + R _fn }…}}
<R _{nt (m + 1) l} + R _{f (m + 1)} || {R _{nt (m + 2) l} + R _{f (m + 2)} || {R _{nt (m + 3) l} + R _{f (m + 3)} ||… || {R _ntnl + R _fn }…}}
The temperature history storage device having the relationship
Here, m is 1 ≦ m ≦ n, and the symbol: || indicates the combined resistance of the parallel connection. In this temperature history storage device, some or all of the first to n-th current fuse elements have the characteristics of slow blow fuse elements, and the first to n-th current fuse elements have a rated current I _r1 = I _r2 = ... = in I _rn = I _r, a current fuse element having a fusing time _{t r1 <t r2 <... <} t rm.   The temperature history storage device according to any one of claims 1 to 4, wherein the NTC thermistor element is formed using vanadium oxide as a main component.   5. The temperature history storage device according to claim 1, further comprising a voltage measurement terminal for measuring a voltage between both ends of the current fuse element. 6. The temperature history storage device
The temperature history storage device according to any one of claims 1 to 6, further comprising a drive circuit that intermittently applies the voltage V during temperature history drive. The temperature history storage device
A drive circuit that intermittently applies the voltage V during temperature history driving;
The drive circuit is
A capacitor C having a capacitance C _s is connected in parallel to the series circuit,
One electrode of the series circuit is connected to a ground potential, and the other electrode is connected to an input of an inverter circuit in which a plurality of inverters are connected,
The output of the inverter circuit is connected to the gate of a transistor provided between the one electrode and a power source, one of the source and drain electrodes of the transistor is connected to the voltage, and the other is connected to the other The temperature history storage device according to claim 7, wherein the temperature history storage device is connected to an electrode. 9. Instead of the NTC thermistor element, it is used for a bimetal switch which is non-conductive at a temperature lower than a predetermined temperature _Tc and is conductive at a temperature higher than _Tc . The temperature history storage device according to any one of the above.

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