JP6386759B2 - Temperature history storage device - Google Patents

Description

  The present invention relates to a temperature history storage device, and more particularly to a device for storing a temperature history for determining whether or not a temperature history exceeding a predetermined temperature has passed, for example, a temperature in a vehicle engine or a transmission in a transmission. The present invention relates to a technique for measuring temperature and the like and leaving the temperature history.

  In recent years, electronic control devices have been used to control vehicle engines and transmissions. However, depending on operating conditions and environmental temperature, there is a possibility that the operating limit temperature of the electronic control device may be exceeded. Failure 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 a temperature history can be kept whether or not the temperature has become equal to or higher than a predetermined temperature, it becomes easy to investigate the cause of the failure.

  One method for grasping the temperature history is to use a thermal fuse. If a thermal fuse is used, a metal having a predetermined melting point is used, and when the temperature reaches a predetermined temperature, the temperature fuse melts or breaks, resulting in an infinite resistance between the terminals, so that the temperature history can be grasped. Is possible. 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 Document 2 and Patent Document 3 describe a configuration in which a temperature history is stored by writing an output from a temperature sensor into a memory as temperature data.

  Patent Document 4 discloses a parallel circuit of a fuse element and a PTC thermistor. Patent Document 5 discloses a circuit in which a plurality of parallel circuits of antifuse elements and PTC thermistors are connected in series. When an unsteady high temperature is detected and the PTC thermistor becomes high resistance, the voltage applied to the antifuse elements connected in parallel exceeds the trigger voltage, so that the antifuse element transitions from the insulated state to the conductive state. Is described. Further, it is described that the detection is performed by taking a change in the output voltage of the voltage dividing circuit connected to the parallel circuit into a microcomputer.

  In Patent Document 6, a capacitor is charged by an off-leakage current of a transistor that changes with temperature, the potential is connected to an inverter input, and the output is connected to a counter to obtain temperature change information.

  FIG. 1 of Non-Patent Technology 1 describes a “frequency modulation output type thin film photosensor” circuit. The potential fluctuation of the capacitor due to the light leakage current of the transistor is used as the input of the ring oscillator (multi-stage inverter), and a part of the output is connected to the gate electrode of the reset transistor to control the charging of the capacitor. This circuit is characterized in that a change in light quantity (illuminance) can be obtained from the output terminal as a frequency modulation signal of a voltage pulse.

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" JP 2009-32696 JP "Integrated thermistor, metal element device and method" JP 2013-024718 A “Temperature Abnormality Detection Sensor” International Publication WO2009 / 084352 "Temperature Measuring Device and Method"

The 60th JSAP Spring Meeting (Spring 2013) 28a-G6-7 “Thin Film Photosensor with Frequency Modulation Output”

  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.

  The technique described in Patent Document 4 does not operate as a temperature history storage device but is a device that functions as a circuit protection device.

  Further, claim 1 of Patent Document 4 only describes that the fuse element has a lower resistance than the PTC thermistor.

Patent Documents 5 and 6 are not parallel circuits of a fuse element and a PTC thermistor.
The circuit of Non-Patent Technology 1 is characterized in that a light amount (illuminance) change is obtained from an output terminal as a frequency modulation signal of a voltage pulse, and there is no further disclosure. There is no disclosure of the relationship between the resistance value of the fuse or thermistor and the rated current of the fuse.

  An object of the present invention is to make it possible to easily determine whether or not a measurement target region 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.

  The present invention provides a temperature history storage device that can easily determine whether or not a measurement site has passed a temperature history exceeding a predetermined temperature in view of the problems of the prior art.

According to one aspect of the present invention, current fuse element (F ₁₎ and comprises a parallel circuit of a PTC thermistor element (PT _1), the voltage applied to the parallel circuit and is V, the PTC thermistor (PT ₁₎ is the resistance value R _ptl in the following low temperature the predetermined temperature T _c, the a predetermined temperature T _c resistance R _pth at higher temperatures, the internal resistance value R _f1 of the current fuse (F ₁₎ is R _ptl <a R _f1 <R _pth, rated current I _r of the current fuse element (F _{1) is, V * R ptl / {R} 0 (R f1 + R ptl) + R f1 R ptl} <I r <V There is provided a temperature history storage device characterized by having a relationship of * R _pth / {R ₀ (R _f1 + R _pth ) + R _f1 R _pth }.
However, R ₀ is the resistance value of the connection protection resistor R in series with the parallel circuit.

According to this temperature history storage device, it depends on the Curie temperature of the PTC thermistor element (PT ₁ ), which is a parameter independent of the fusing temperature of the current fuse element (F ₁ ), compared with the case where a thermal fuse is used. A temperature history can be obtained.

  The present invention is a temperature history storage device in which a plurality of the parallel circuits described above are connected in series, and the PTC thermistors of the respective parallel circuits have different Tc.

  For example, if the predetermined temperatures Tc of the plurality of parallel circuits are different, the presence / absence of a plurality of different temperature histories can be determined.

In the present invention, the current fuse element F _i (i = 1, 2,..., N) and the PTC thermistor element PT _i (i = 1, 2,..., N) are divided into two branches and connected. At that branch point, the voltage applied to the branch point is V, and the PTC thermistor element PT _i (i = 1, 2,..., N) is connected to the fuse element F _{i + 1} (i = 1, 2, ..., n) and a PTC thermistor element PT _{i + 1} are connected, and the current fuse element F _i (i = 1, 2, ..., n) is formed by repeating a grounded unit circuit. that a plurality of consists of a temperature detection unit, the PTC thermistor element from the first to the n has a resistance value R _ptl below the predetermined temperature T _c, if it has a resistance value R _pth at a temperature above the T _c The resistance value R _fm of the m-th current fuse element is a temperature history storage device having the following relationship.

R _ptl + R _{f (m + 1)} || {R _ptl + R _{f (m + 2)} || {R _ptl + R _{f (m + 3)} || ・ ・ ・ || {R _ptl + (R _fm || R _ptl )}}} <R _fm <R _pth + R _{f (m + 1)} || {R _pth + R _{f (m + 2)} || {R _pth + R _{f (m + 3)} || ... || {R _pth + (R _fm || R _pth )}}}
Here, m is 1 ≦ m ≦ n, and the symbol: || indicates the combined resistance of the parallel connection.

Either the first terminal, the second terminal, or both of the first to n-th current fuse elements are electrically disconnected from the temperature history storage device, and the first to m-th current fuses are electrically disconnected. By determining whether or not the resistance between the first terminal and the second terminal of each of the elements is greater than the initial value, the temperature history of the measurement site is higher than the predetermined temperature _Tc , It can be determined that at least t _f1 + t _f2 +... + T _fm , which is the total of the fusing time of each fuse element, has passed.

Different _Tc in the PTC thermistor may be obtained by substituting a part of Ba of barium titanate (BaTiO ₃ ) with strontium (Sr) or lead (Pb) and adjusting the concentration thereof. Thereby, it is possible to easily obtain thermistor elements having different Curie temperatures.

  You may make it have a measurement terminal for measuring the resistance between the both ends of the said current fuse.

  The temperature history storage device can reduce power consumption by providing 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 parallel circuit or the unit circuit. An inverter in which a capacitor C having a capacitance Cs is connected in parallel to the connected temperature history storage device, one electrode of the parallel circuit or the unit circuit is connected to a ground potential, and the other electrode is connected to a plurality of stages of inverter circuits When the inverter circuit has an odd number of stages, the output of the inverter circuit is connected to the gate of an n-type transistor provided between the other electrode and a power source, and the inverter circuit In the case of an even number of stages, the output of the inverter circuit is connected to the gate of a P-type transistor provided between the other electrode and the power source, and is connected to the n-type transistor. Alternatively, one of the source and drain electrodes of the P-type transistor may be connected to the power supply voltage, and the other one may be connected to the other electrode.

Instead of the PTC thermistor element, it may be used for a bimetal switch that conducts at a predetermined temperature _Tc or lower and becomes non-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.

  In addition, a reduction in power consumption during operation of the temperature history storage device can be realized.

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 the example of 1 structure of the current fuse and the PTC thermistor in the temperature history memory | storage device shown to FIG. 1A. It is a figure which shows the example of a manufacturing process of the temperature history memory | storage device of 3rd Embodiment. It is a figure which shows an example of the temperature-resistivity characteristic of a PTC thermistor. It is a figure which shows one structural example of the temperature history memory | storage device which has a socket. It is a figure which shows an example of the measuring method in the temperature history memory | storage device which has a socket. 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. It is a figure which shows the input-output characteristic of the inverter circuit shown in FIG. FIG. 7 is a diagram showing a configuration example of a temperature history device according to the third embodiment of the present invention. In obtaining materials having different T _c than to a part of Ba of barium titanate (BaTiO ₃₎ is replaced with strontium (Sr) and lead (Pb), etc., to adjust the concentration, T _c and resistivity It is a figure which shows the temperature dependence of. 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 perspective view which shows the structure of FIG.

  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 first embodiment of the present invention. As shown in FIG. 1A, the temperature history storage device 1 according to the present embodiment includes a parallel circuit of a current fuse element (F ₁ ) and a PTC thermistor element (PT ₁ ), and a resistance value as a protective resistance is included in this parallel circuit. A resistor (R) having R ₀ is connected in series.

The PTC thermistor (PT ₁ ) has a resistance value R _ptl at a temperature lower than a predetermined temperature T _c and has a resistance value R _pth at a temperature higher than T _c . The internal resistance value R _f1 of the current fuse (F ₁ ) is set to R _ptl <R _f1 <R _pth . In the temperature history storage device 1 shown in FIG. 1, at least a PTC thermistor (PT ₁ ) is installed in the vicinity of the measurement site, and a power supply voltage (V) is applied.

  The PCT thermistor has a temperature-resistivity characteristic as shown by the solid line in FIG. 2 (Source: “Temperature Sensor” Author: Hisao Futaki, Koichi Murakami Published by 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 suddenly increases as the temperature rises).

The thermistor can be formed of a material in which a part of Ba is replaced with strontium (Sr), calcium (Ca), or lead (Pd) based on barium titanate (BaTiO ₃ ). Further, yttrium (Y) may be added to adjust the resistivity. Further, in order to make the change in resistivity at a predetermined temperature Tc abrupt, manganese (Mn) may be added. Alternatively, an oxide containing Zn, Ti, Ni, an oxide containing Pb, Fe, or Nb, a polymer material such as polyethylene containing a conductive material such as polycrystalline Si, or graphite may be used.

  As shown in FIG. 2, the PTC thermistor is characterized in that the resistivity changes greatly at the Curie temperature. For example, in the low temperature range below the Curie temperature, the change in resistance value is about twice or less than the temperature change of 10 ° C. It shows a large change in resistance value by one digit or more.

For example, by previously adjusted to the same or near the Curie temperature of the predetermined temperature T _c and the PTC thermistor to be measured, the PTC thermistor element in a high temperature range than the T _c in comparison with the following temperature range T _c resistance changes significantly (increase from R _ptl to R _pth).

The operation of the temperature history storage device 1 will be described below. At a temperature equal to or lower than the predetermined temperature T _c , the current I _fl flowing through the current fuse (F ₁ ) and the current I _ptl flowing through the PTC thermistor (PT ₁ ) are respectively expressed as follows.

_{I fl = V * R ptl /} {R 0 (R f1 + R ptl) + R f1 R ptl} (1)
I _ptl = V * R _f1 / {R ₀ (R _f1 + R _ptl ) + R _f1 R _ptl } (2)

Here, since R _ptl <R _f1 , the current I _pt1 flowing through the PTC thermistor (PT ₁ ) is large, and the current I _fl flowing through the current fuse (F ₁ ) is small. I _fl is set to be smaller than the rated current I _r of the current fuse (F ₁ ). Thus, the current fuse (F ₁ ) is not blown in the temperature range below the predetermined temperature T _c .

A case will be described in which the temperature of the measurement site rises and becomes higher than the predetermined temperature _Tc .

The current I _fh flowing through the current fuse (F ₁ ) and the current I _pth flowing through the PTC thermistor (PT ₁ ) in the temperature region higher than T _c are respectively described as follows.

I _fh = V * R _pth / {R ₀ (R _f1 + R _pth ) + R _f1 R _pth } (3)
I _pth = V * R _f1 / {R ₀ (R _f1 + R _pth ) + R _f1 R _pth } (4)

Here, since R _f1 <R _pth , the current I _pth flowing through the PTC thermistor (PT ₁ ) is small, and the current I _fh flowing through the current fuse (F ₁ ) is large. And I _fh is designed to be larger than the rated current I _r of the current fuse (F ₁ ). As a result, the current fuse (F ₁ ) is blown. Thereafter, the current fuse (F ₁ ) is kept blown even if the measurement site becomes lower than the predetermined temperature T _C.

As described above, the internal resistance R _f1 of the current fuse (F ₁₎ is an _{R ptl <R f1 <R pth} , the rated current I _r of the current fuse element (F _1), (1) (4 ) From the following formula:

V * R _ptl / {R ₀ (R _f1 + R _ptl ) + R _f1 R _ptl } <I _r <V * R _pth / {R ₀ (R _f1 + R _pth ) + R _f1 R _pth } (5)
However, R ₀ is the resistance value of the protective resistor R connected in series to the parallel circuit.

Later, by measuring the resistance value between both ends of the current fuse (F ₁ ) with an ohmmeter (connection is indicated by a broken line), you can determine whether the current fuse (F ₁ ) is blown, Therefore, PTC thermistor (PT ₁₎ has, can easily be determined whether the received high temperature history than T _C.

Thus, for example, when investigating the temperature history of the measurement site due to a failure analysis in the measurement target site, such as engines, one of the first terminal T1 or the second terminal T2, the current fuse (F ₁₎ Alternatively, both T1 and T2 are electrically disconnected from the temperature history storage device 1, and the presence or absence of fusing is confirmed from the resistance value between the first terminal T1 and the second terminal T2 of the current fuse (F ₁ ). can do.

For example, as shown in FIG. 3A, it is desirable not to directly connect one terminal T2 of the current fuse (F ₁ ) and the PTC thermistor (PT ₁ ) but to connect through a component such as a socket 1b. Thereby, when investigating the temperature history, the resistance between the terminals T1 and T2 of the current fuse (F ₁ ) can be easily confirmed by removing the socket 1b from the main body 1a, and abnormal (current fuse (F _When the fusing ₁ ) is not detected, the main body 1a can be attached to the socket 1b again and used.

FIG. 3B is a diagram illustrating an example of another measurement method. As shown in FIG. 3B (a), the U-shaped region 11y is removed from the substrate 11 so that the substrate 11 is cut at both ends of the current fuse (F ₁ ) between the current fuses (F ₁ ). Alternatively, it may be (FIG. 3B (b)). As shown in FIG. 3B (c), 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 fuses (F ₁ ) is measured. It is convenient to do so. In this case, the resistance value can be measured by connecting the terminals of the ohmmeter to both ends of the current fuse (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 the present embodiment, a current fuse is used, and the temperature _{Tc at} which the resistance value of the PTC thermistor (PT ₁ ) changes and the current fuse is blown can be set to a temperature lower than the mounting temperature such as soldering. Thus, there is no restriction on the mounting temperature as in the case of using a conventional thermal fuse.

It is also possible to replace the PTC thermistor element in the present embodiment with a bimetal switch. That is, the same effect as that of a PTC thermistor element is obtained by connecting a bimetal that conducts at a predetermined temperature T _c or less and is in a non-conduction state at a temperature higher than T _{c in} parallel with the current fuse (F ₁ ). It is possible. In addition, it goes without saying that PTC thermistor elements and elements having the same characteristics as fuses can be used in any combination.

  FIG. 1B is a diagram illustrating an example of the structure of the temperature history storage device. 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 (F ₁ ), an insulating substrate or a substrate 11 on which an insulating film is deposited is formed. A fuse and wiring layer 51 is deposited. As shown in the plan view of FIG. 1B (c), the current fuse (F ₁ ) has, for example, a shape in which a Cu film is constricted in the middle.

As shown in the sectional structure (B)-(B ′) of FIG. 1B (d), the PT film 71 for the PTC thermistor (PT ₁ ) has a current in the film thickness direction by the lower electrode 81 and the upper electrode 91. The structure that flows. As a result, the resistance value of the PTC element generally having a high specific resistance can be set to about 0.1Ω to 10Ω with respect to the resistance value of the fuse (for example, about 1Ω). Here, the resistance element 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.

The PTC thermistor (PT ₁ ) is sandwiched between the upper and lower electrodes 81, 91, but the lower electrode 81 is connected to the current fuse (F ₁ ) side wiring through a socket or a part of the lower electrode 81 A wiring layer may be connected to each other. Note that an insulating film may be formed as a protective film on the whole or a part of the structure.

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

  As described above, according to the present embodiment, it can be easily determined whether or not the measurement target site has passed a temperature history exceeding a predetermined temperature.

(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 parallel circuit of the current fuse (F ₁ ) and the PTC thermistor (PT ₁ ) of the temperature history storage device 1 according to the first embodiment to consume the temperature history storage device. A drive circuit for reducing power is added.

As shown in FIG. 4, the temperature history storage device with a drive circuit according to the present embodiment includes a parallel circuit of a current fuse (F ₁ ) and a PTC thermistor (PT ₁ ), and a resistance value R as a protective resistance is included in this parallel circuit. A capacitor C having a capacitance Cs 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) having _0, and one electrode G of the parallel circuit is connected to the ground potential. 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 INV21 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.

Hereinafter, the operation of the circuit of FIG. 4 will be described with reference to FIG.
First, consider a case where the n-type transistor _Tr is in an on state (energized state). In this case, the temperature history storage device via the n-type transistor T _r (protective resistor (R), and the parallel circuit of the current fuse (F ₁₎ and the PTC thermistor (PT ₁₎₎ to 1 and a voltage is applied.

Here, if the temperature of the measurement site is lower than the predetermined temperature _Tc , the current flows through the protective resistance (R) and the PTC thermistor (PT ₁ ), and the current fuse (F) is not blown. 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 (P21).

The output of the inverter INVn 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 _Tc , the discharge current flows through the protective resistance (R) and the PTC thermistor (PT ₁ ), and the current fuse (F ₁ ) is not blown.

As shown in FIG. 5, the potential V _{n of the} electrode N can be calculated by using the protective resistance (R), the PTC thermistor (PT ₁ ), the resistance value of the current fuse (F ₁ ), and the capacitance C _{0 of the} capacitor C as shown in FIG. (-1 / {(R ₀ + R _f R _ptl / (R _f + R _ptl )) C ₀ }, and decreases from time t ₁ to t ₂ along L ₁ by discharging capacitor C. When the potential V _{n of} N falls below the logic inversion threshold V _th of the inverter INV1, 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 (P22). _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. 5: 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 potential fluctuation width (V _{thL to} V _thH ) of V _n is related to the width ΔV _th of the transition region in the input / output characteristics of the inverter INV1 shown in FIG. 6, and this is the n-type and p-type constituting the inverter INV. This is due to the characteristics of the transistor. 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 (INV1) and gradually increases toward the output stage side, and the nth final stage inverter (INVn) It is desirable that the output voltage has substantially the same amplitude as 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. As a result, the potential of the electrode N varies between V _thL and V _thH as shown in FIG.

State temperature history storage device 1 operating state, i.e. when the temperature of the measurement site is higher than the predetermined temperature T _c, the resistance value of the PTC thermistor (PT ₁₎ is to be blown next R _pth, the fuse (F ₁₎ to hold, it is sufficient with respect to the rated current I _r of the voltage V _thL and fuse so that the relationship of the following expression holds.

I _r ≤ I _fh = V _thL R _pth / {R ₀ (R _f + R _pth ) + R _f R _pth }

At the same time, the temperature of the measurement site holds the state of the fuse (F ₁₎ is not blown when the following lower predetermined temperature T _c is designed so that the following relationship is established with respect to the rated current I _r of the fuse .

I _r > I _fl = V _thL R _ptl / {R ₀ (R _f + R _ptl ) + R _f R _ptl }
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 1 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 _fh = V _thH R _pth / {R ₀ (R _f + R _pth ) + R _f R _pth }
I _r > I _fl = V _thH R _ptl / {R ₀ (R _f + R _ptl ) + R _f R _ptl }

  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.

Further, the drive circuit is, for example, if the temperature change of the temperature measurement site occurs at longer duration than the time t _r necessary for the blowing of the fuse, the voltage applied to the temperature history storage device 1, t _r more can be replaced with the time width (. to the sum of the time not applied to the time T _on which a voltage is applied T _off period) pulse waveform having a (time width is energized).

(Third embodiment)
FIG. 7 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 parallel circuit of a pair of current fuses and PTC thermistors has been described. In this embodiment, a plurality of parallel circuits in the first embodiment are connected in series. ing. The PTC thermistor of each parallel circuit may be configured with different temperatures at which resistance value changes occur. Then, it is possible to grasp the temperature history for a plurality of different predetermined temperatures by confirming whether or not the fuses are blown from both ends of each current fuse, for example, from a resistance value indicated by an ohmmeter. A temperature history storage device in which n stages of parallel circuits are connected in series will be described using FIG. 7 as an example. Note that the ohmmeter in the figure is used at the time of measurement, and in fact, the temperature history can be examined using one ohmmeter.

PTC thermistor element _{PT 1, PT 2, ...,} PT , each T _c1, T _c2, ..., at a temperature of T _ci, has a characteristic that the resistance value change occurs. For example, as shown in FIG. 8, a PTC thermistor element having different characteristics replaces a part of Ba of barium titanate (BaTiO ₃ ) with strontium (Sr), lead (Pb), etc., and adjusts its concentration. It can be formed by obtaining materials with different T _c (Source: “Temperature Sensor” Author: Hisao Futaki, Koichi Murakami Published by Nikkan Kogyo Shimbun). Further, the resistance value of each PTC thermistor element can be adjusted by the film thickness (the thickness of 71 in FIG. 1B (d)) and the area (the overlapping portion of 91 in FIG. 1B (d)).

FIG. 1C is a diagram illustrating a process example of forming the thermistor elements having different Tc on the substrate 11. First, as shown in FIG. 1C (a), for example, a BaTiO ₃ film 17 is formed on the substrate 11. Next, as shown in FIG. 1C (b), a mask 31a having a first opening in a partial region is formed on the substrate 11, and, for example, Sr33 is added. Thereby, a part of Ba of the BaTiO ₃ film 17 in the region corresponding to the first opening is partially replaced with Sr, and the Ba _1-y Sr _y TiO ₃ film 41 is obtained.

Next, as shown in FIG. 1C (c), a mask 31b or the like having a second opening in a partial region different from the first opening is formed on the substrate 11, and for example, Pb34 is added. As a result, part of Ba in the BaTiO ₃ film 17 in the region corresponding to the second opening is partially replaced with Pb, and the Ba _1-y Pb _y TiO ₃ film 43 is obtained.

In this way, the thermistor films having different _Tc as shown in FIG. 1C (d) can be formed in any region, and can be formed with a planar structure.

  These creation methods are examples, and are not construed as limiting. For example, a film having a different composition may be formed in each region using a photolithography technique.

PTC thermistor PT _m of the parallel circuit of the m-th (1 ≦ m ≦ n), in T _cm below low temperature, the resistance value R _Ptml, so that the resistance value R _Ptmh at temperatures above T _cm. The resistance of the current fuse F _m which are connected in parallel to each PTC thermistor element PT _m is R _fm. These have the relationship of R _ptml <R _fm <R _ptmh as in the first embodiment. In the present embodiment, in order to facilitate understanding of the explanation, and T _c1 <T _c2 <... <that there is a relation of T _cn.

When the temperature T of the measurement site is T <T _c1 , the current that flows in the parallel circuit when the voltage V is applied flows mainly on the PT _m side of each parallel circuit, so the current fuse F _m does not melt. .

When the temperature T of the measurement part rises to T _cm <T <T _{c (m + 1)} , R _fm <R _{ptmh in} the first to m-th parallel circuits, so that the current fuse F _m A lot of current flows. By keeping the above rated current of the current-current fuse F _m flowing when this in advance as fusing current fuse F _m is generated.

On the other hand, in the _{(m + 1)} th to nth parallel circuits, since R _{pt (m + 1)} <R _{f (m + 1)} , a large amount of current flows through the PTC thermistor element PT _{(m + 1).} . By keeping the amount of current flowing through the current fuse F _{(m + 1)} smaller than the rated current during this, fusing the current fuse F _{(m + 1)} does not occur.

When investigating the temperature history of the measurement site, as in the first embodiment of the present invention, the resistance value is measured by a tester, or the resistance value is measured for each temperature history memory element as shown in FIG. 3B. You may do it. As a result, it is possible to determine 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)} .

  Also, if all fuses have the same rated current, that is, if multiple fuses with the same rated current are used, the fuses are the same and the time to blow is the same for all fuses. When it is desired to grasp the time required for the fuse to blow, the length of the period exceeding the predetermined temperature can be known relatively easily by multiplying the fusing time by the number of fuse elements blown.

Here, similarly to the second embodiment, the drive circuit connected to the parallel circuit of the current fuse (F ₁ ) and the PTC thermistor (PT ₁ ) is also applied to the third embodiment, thereby realizing a reduction in power consumption. be able to.

(Fourth embodiment)
A fourth embodiment of the present invention will be described.

9 and 10 are diagrams showing a configuration example of the temperature history recording apparatus according to the present embodiment. In the temperature history recording apparatus according to the present embodiment, a first current fuse element F ₁ and a first PTC thermistor element PT ₁ having a positive temperature coefficient (PTC) are connected in parallel (bifurcated). A parallel circuit of the second current fuse element F ₂ and the second PTC thermistor element PT ₂ is connected in series to the PTC thermistor element PT ₁ , and these unit circuits are repeated in the same manner, and the (n -1) current fuse element _Fn-1 and (n-1) th PTC thermistor element PTn _-1 are connected in parallel, and the (n-1) th PTC thermistor element PTn _-1 is connected in series. to include a circuit parallel circuit of a PTC thermistor element PT _n current fuse element F _n and the n of the n are connected, PTC Sasuta element from the first to the n-th resistor below the predetermined temperature T _c has a value R _ptl, if having a resistance value R _pth at a temperature higher than the T _c, the resistance value R _fm of the current fuse element of the m, the temperature history SL having the following relationship It is a device.

R _ptl + R _{f (m + 1)} || {R _ptl + R _{f (m + 2)} || {R _ptl + R _{f (m + 3)} || ・ ・ ・ || {R _ptl + (R _fn || R _ptl )}}} <R _fm <R _pth + R _{f (m + 1)} || {R _pth + R _{f (m + 2)} || {R _pth + R _{f (m + 3)} || ... || {R _pth + (R _fn || R _pth )}}}
Here, m is 1 ≦ m ≦ n, and the symbol: || indicates the combined resistance of the parallel connection.

The above formula extends the circuit configuration of FIG. 9 to a configuration of n fuses and n PTC thermistors. In the first (uppermost stage), all circuit configurations except R and F ₁ contribute to the combined resistance, and in the second, the parts excluding R, F ₁ , F ₂ and PT ₁ contribute. Thus, it is sufficient to consider the internal resistance in consideration of only the lower circuit.

That is, the above formula relates to a case where a plurality of temperature history devices are connected in a bifurcated connection, and the m th PTC thermistor PT at a low temperature equal to or lower than T _c and the internal resistance value R _fm of the m th fuse. The combined resistance value from _m to the n th PTC thermistor PT _n , the combined resistance value from the m th PTC thermistor PT _m to the n th PTC thermistor PT _n at a temperature higher than T _c , and the above three resistance values Represents a magnitude relationship. Since the relationship of R _ptl <R _pth is _obtained from the characteristics of the PTC thermistor, it is expressed by the above inequality.

In the temperature history storage device having the above relationship, a part or all of the first to nth current fuse elements have the characteristics of a slow blow fuse, and the first to nth current fuse elements are: It is a current fuse having a rated current I _r1 = I _r2 =... = I _rn = I _r and having a relationship of _f1 < _tf2 <... < _tfn with respect to the fusing time.

In the temperature history storage device, the first terminal and / or the second terminal of each of the first to n-th current fuse elements is electrically disconnected from the temperature history storage device, and the first to nth current fuse elements are electrically disconnected. By determining whether or not the resistance between the first terminal and the second terminal of each of the current fuse elements up to the m-th is greater than the initial value, the temperature history of the measurement site is equal to the predetermined temperature T _c It is possible to provide a temperature history determination method for determining that a higher temperature has passed a period of t _f1 + t _f2 +... + T _fm , which is at least the total fusing time of each fuse element.

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.

With respect to the selection of the fuse element, designed according to the object to be temperature measurement, there are two ways in the way going longer toward the bottom as the fusing time _{t r1 <t r2 <t r3} <t r4. The first method is suitable for the case where it is desired to grasp the temperature history in fine steps by designing the fusing time, and a method in which a fusing time slightly deviated from the previous (upper) fuse is employed.

  In contrast to the first method, the second method is suitable when it is desired to grasp the temperature history in rough steps. A fuse that has a longer fusing time than the previous fuse is used, and You may make it grasp temperature.

  The use of the slow blow fuse has the following advantages.

By using a slow blow fuse that has a longer fusing time than a fast blow type fuse, it is possible to accurately grasp the temperature change of the object whose temperature is to be measured in accordance with the time scale, that is, the temperature history. For example, when a temperature history device is designed with the first fuse as a normal fast-breaking fuse and the second fuse as a slow blow fuse, it is determined whether or not the temperature history exceeds a predetermined temperature _Tc in a short time. the judged by fusing time of the fuse, beyond the T _c of the first fuse, and a total second time required until the blown beyond the T _c of the fuse (by fusing time of the second fuse), It is possible to grasp the time and temperature required to reach the predetermined temperature. That is, as described above, it is possible to select and design fuses with different fusing times (those with different rated currents) depending on how much temperature history you want to grasp. Can have a degree.

Here, similarly to the second embodiment, the drive circuit connected to the parallel circuit of the current fuse (F ₁ ) and the PTC thermistor (PT ₁ ) is also applied to the fourth embodiment, thereby realizing reduction in power consumption. be able to.

  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.

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

DESCRIPTION OF SYMBOLS 1 ... Temperature history storage device (parallel circuit), 1a ... Main body, 1b ... Socket, F (n) ... Fuse element, PT (n) ... PTC thermistor element, R ... Protection resistor, 21 ... Inverter device, Tr ... transistor.

Claims (7)

Including parallel circuit of current fuse element (F ₁ ) and PTC thermistor element (PT ₁ )
The voltage applied to the parallel circuit and is V, the PTC thermistor (PT ₁₎ has a resistance value R _ptl in the following low temperature the predetermined temperature T _c, the resistance R _pth at a temperature higher than the predetermined temperature T _c And the internal resistance value R _f1 of the current fuse (F ₁ ) is R _ptl <R _f1 <R _pth ,
The rated current I _r1 of the current fuse element (F ₁₎ is
V * R _ptl / {R ₀ (R _f1 + R _ptl ) + R _f1 R _ptl } <I _r <V * R _pth / {R ₀ (R _f1 + R _pth ) + R _f1 R _pth }
A temperature history storage device characterized by the following relationship:
However, R ₀ is the resistance value of the protective resistor R connected in series to the parallel circuit. 2. The temperature history storage device according to claim 1, wherein a plurality of the parallel circuits according to claim 1 are connected in series, and the PTC thermistors of the respective parallel circuits have different T _c . The current fuse element F _i (i = 1, 2,..., N) and the PTC thermistor element PT _i (i = 1, 2,..., N) are divided into two branches and connected at the branch point. , V is a voltage applied to the branch point, and the fuse element F _{i + 1} (i = 1, 2,..., To the PTC thermistor element PT _i (i = 1, 2,..., N). n) and a PTC thermistor element PT _{i + 1} are connected, and the current fuse element F _i (i = 1, 2,..., n) is a plurality of temperature detection units formed by repetition of a grounded unit circuit in the structure, the PTC thermistor element from the first to the n has a resistance value R _ptl below the predetermined temperature T _c, if it has a resistance value R _pth at a temperature higher than the T _c, current fuse of the m The resistance value R _{fm of the} element is a temperature history storage device having the following relationship.
R _ptl + R _{f (m + 1)} || {R _ptl + R _{f (m + 2)} || {R _ptl + R _{f (m + 3)} || ・ ・ ・ || {R _ptl + (R _fn || R _ptl )}}} <R _fm <R _pth + R _{f (m + 1)} || {R _pth + R _{f (m + 2)} || {R _pth + R _{f (m + 3)} || ... || {R _pth + (R _fn || R _pth )}}}
Here, m is 1 ≦ m ≦ n, and the symbol: || indicates the combined resistance of the parallel connection. The current fuse element _{F i (i = 1,2, ···} , n) is the temperature history storage device according to claim 3, characterized in that it consists of slow blow fuse. The temperature history storage device according to any one of claims 1 to 4, further comprising a measurement terminal for measuring a resistance between both ends of the current fuse element. The temperature history storage device
The temperature history storage device according to any one of claims 1 to 5 , further comprising a drive circuit that intermittently applies the voltage V during temperature history driving. 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 Cs is connected in parallel to a temperature history storage device connected in series with a resistor as a protective resistor to the parallel circuit or the unit circuit,
One electrode of the parallel circuit or the unit 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 inverter circuits are connected,
When the inverter circuit has an odd number of stages, the output of the inverter circuit is connected to the gate of an n-type transistor provided between the other electrode and a power source, and when the inverter circuit has an even number of stages, The output of the inverter circuit is connected to the gate of a P-type transistor provided between the other electrode and the power supply, and one of the source and drain electrodes of the n-type transistor or P-type transistor is connected to the power supply voltage. The temperature history storage device according to claim 6 , wherein the other one is connected to the other electrode.

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