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JP2014027875A - Protector of load circuit - Google Patents

Protector of load circuit Download PDF

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JP2014027875A
JP2014027875A JP2013169733A JP2013169733A JP2014027875A JP 2014027875 A JP2014027875 A JP 2014027875A JP 2013169733 A JP2013169733 A JP 2013169733A JP 2013169733 A JP2013169733 A JP 2013169733A JP 2014027875 A JP2014027875 A JP 2014027875A
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temperature
current
conductor
load
electric wire
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JP5684871B2 (en
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Yoshihide Nakamura
吉秀 中村
Akiyoshi Kanazawa
昭義 金澤
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Yazaki Corp
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Yazaki Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a protector of a load circuit, which can detect a temperature rise of a wire and can surely block the load circuit when a rare short-circuit occurs.SOLUTION: When a current flowing in a load 4 rises, a rise temperature of a wire 7 is calculated on the basis of a thermal characteristic (thermal resistance and heat capacity) of the wire 7 or a contact conductor, and calculates a drop temperature of the wire 7 in response to the thermal characteristic of the wire 7 when the current flowing in the load 4 is zero or decreases. The rise temperature and the drop temperature, which are calculated for each sampling time, are successively integrated and an integrated result is stored in a memory 64a as an estimated temperature. When the estimated temperature exceeds a prescribed permissible temperature, the load circuit is blocked. Thus, the circuit can highly precisely be protected on the basis of the temperature rise of the wire 7.

Description

本発明は、電線の温度が上昇した際にこれを検出して負荷回路を保護する負荷回路の保護装置に関する。   The present invention relates to a load circuit protection device that detects a temperature of an electric wire when it rises and protects the load circuit.

例えば、車両に搭載されるランプやモータ等の負荷に電力を供給する負荷回路は、バッテリと、該バッテリと負荷との間に設けられる電子スイッチ(半導体スイッチ等)とが備えられており、バッテリ、電子スイッチ、及び負荷がそれぞれ電線を含む導体を介して接続されている。更に、電子スイッチをオン、オフ操作する制御回路が設けられており、該制御回路より出力される駆動、停止信号により、電子スイッチがオン、オフ動作して負荷の駆動、停止が切り換えられる。   For example, a load circuit that supplies electric power to a load such as a lamp or a motor mounted on a vehicle includes a battery and an electronic switch (such as a semiconductor switch) provided between the battery and the load. The electronic switch and the load are connected to each other through a conductor including an electric wire. Further, a control circuit for turning on and off the electronic switch is provided. The drive and stop signals output from the control circuit are used to turn on and off the electronic switch to switch between driving and stopping of the load.

このような負荷回路においては、負荷に過電流が流れた際に、いち早く回路を遮断して、負荷、電線、電子スイッチ等を保護するために、ヒューズ等の過電流保護機能が設けられており、一定の閾値電流を超える過電流が流れた際に、これを検出して電子スイッチをオフとし、回路を遮断する。   In such a load circuit, an overcurrent protection function such as a fuse is provided to quickly shut down the circuit when an overcurrent flows through the load and protect the load, electric wire, electronic switch, etc. When an overcurrent exceeding a certain threshold current flows, this is detected and the electronic switch is turned off to shut off the circuit.

ところが、このような負荷回路では、上記した閾値電流を超える程度の過電流が流れた場合、即ち、デッドショート発生時には即時にこれを検出して回路を保護できるが、通常電流よりも大きく且つ閾値電流を超えない程度の電流が流れた場合、即ち、レアショート発生時には、これを検出することができないことがある。   However, in such a load circuit, when an overcurrent exceeding the above-mentioned threshold current flows, that is, when a dead short occurs, this can be detected immediately and the circuit can be protected. When a current that does not exceed the current flows, that is, when a rare short occurs, this may not be detected.

このようなレアショート発生時には、電線に発生するジュール熱により電線の温度が上昇し、電線の発熱量が放熱量を上回ると、電線温度が徐々に上昇し、発煙、焼損等のトラブルが発生することがある。   When such a short-circuit occurs, the temperature of the wire rises due to the Joule heat generated in the wire, and if the amount of heat generated by the wire exceeds the amount of heat released, the wire temperature gradually increases, causing problems such as smoke generation and burning. Sometimes.

このような問題を解決するため、例えば、特開2002−84654号公報(特許文献1)に記載されたものが知られている。該特許文献1では、負荷に電流が流れているときには、このときの電流値を読み取ってジュール熱を算出し、負荷に電流が流れていないときには、電線からの放熱量を算出し、電源オフの直後には、電源のオフに伴って発生するアーク熱量を算出する。そして、これらの総和熱量を求め、求められた総和熱量が所定の閾値を超えたときに、回路を遮断して回路全体を保護することが開示されている。   In order to solve such a problem, for example, what is described in JP 2002-84654 A (Patent Document 1) is known. In Patent Document 1, when current flows through the load, the current value at this time is read to calculate Joule heat, and when current does not flow through the load, the amount of heat released from the wire is calculated, and the power is turned off. Immediately after that, the amount of arc heat generated as the power is turned off is calculated. Then, it is disclosed that these total heat amounts are obtained, and when the obtained total heat amount exceeds a predetermined threshold, the circuit is shut off to protect the entire circuit.

特開2002−84654号公報JP 2002-84654 A

しかしながら、上記した特許文献1に記載された負荷回路の保護装置では、発熱量、及び放熱量を積算し、この積算値に応じて回路を遮断するか否かを判定するものであり、実際の電線の温度上昇を考慮しているものではない。即ち、発熱量が大きい場合でも太い電線を使用している場合には、放熱量が発熱量を上回り、大きな温度上昇が発生しない。従って、このような場合には継続した通電が可能であるにも関わらず、回路が遮断されてしまうという問題が発生する。   However, the load circuit protection device described in Patent Document 1 described above integrates the heat generation amount and the heat dissipation amount, and determines whether or not to shut off the circuit according to the integrated value. It does not take into account the temperature rise of the wire. That is, even when the heat generation amount is large, when a thick wire is used, the heat dissipation amount exceeds the heat generation amount, and a large temperature rise does not occur. Therefore, in such a case, there is a problem that the circuit is interrupted although continuous energization is possible.

更に、これとは反対に、細い電線を使用している場合には、発熱量が小さくても大きな温度上昇が発生し、発煙、焼損に至る恐れがあるにも関わらず、円滑な回路の遮断が行われないという問題が発生する。   On the other hand, when a thin wire is used, even if the calorific value is small, a large temperature rise occurs, and although there is a risk of causing smoke or burnout, smooth circuit interruption The problem that is not done occurs.

本発明は、このような従来の課題を解決するためになされたものであり、その目的とするところは、レアショート発生時に、電線の温度上昇に基づいて回路を遮断するか否かを判断し得る負荷回路の保護装置を提供することにある。   The present invention has been made to solve such a conventional problem, and the object of the present invention is to determine whether or not to interrupt the circuit based on the temperature rise of the electric wire when a rare short occurs. It is an object of the present invention to provide a load circuit protection device.

上記目的を達成するため、本発明は、電源、スイッチ及び負荷を備えた負荷回路の、前記負荷に流れる電流を検出し、検出した電流値により前記負荷回路を遮断する負荷回路の保護装置において、前記負荷に流れる電流を検出する電流検出手段と、前記電流検出手段で電流が検出されているとき、検出された電流値と、前記負荷と電源とを結ぶ導体の熱特性とに基づいて、前記導体の上昇温度を算出する上昇温度算出手段と、前記電流検出手段で電流が検出されていないとき、或いは検出した電流が下降したときに、前記導体の熱特性に基づいて、前記導体の下降温度を算出する下降温度算出手段と、前記上昇温度算出手段で算出される所定のサンプリング時間毎の上昇温度、及び下降温度算出手段で算出される所定のサンプリング時間毎の下降温度を、前記所定のサンプリング時間毎に積算し、積算した結果である導体の推定温度を算出し、更にこの推定温度を記憶するメモリを有する推定温度算出手段と、前記推定温度算出手段により算出される前記導体の温度が所定の閾値温度を超えたか否かを判定する温度判定手段と、前記温度判定手段により、前記導体の温度が所定の閾値温度を超えたと判定された際に、前記負荷回路を遮断する遮断制御手段と、を備えたことを特徴とする。   In order to achieve the above object, the present invention provides a load circuit protection device for detecting a current flowing through the load of a load circuit including a power source, a switch, and a load, and cutting off the load circuit based on the detected current value. Current detection means for detecting a current flowing through the load, and when a current is detected by the current detection means, based on the detected current value and the thermal characteristics of the conductor connecting the load and the power source, A rising temperature calculating means for calculating a rising temperature of the conductor, and when the current is not detected by the current detecting means, or when the detected current drops, the falling temperature of the conductor based on the thermal characteristics of the conductor; Falling temperature calculating means for calculating the rising temperature, rising temperature for each predetermined sampling time calculated by the rising temperature calculating means, and for every predetermined sampling time calculated by the falling temperature calculating means The temperature drop is integrated at every predetermined sampling time, the estimated temperature of the conductor as a result of the integration is calculated, and further calculated by the estimated temperature calculating means having a memory for storing the estimated temperature, and the estimated temperature calculating means Temperature determining means for determining whether or not the temperature of the conductor to be exceeded exceeds a predetermined threshold temperature, and when the temperature determining means determines that the temperature of the conductor has exceeded a predetermined threshold temperature, the load And a shut-off control means for shutting off the circuit.

また、前記熱特性は、熱の伝わり易さを示す熱抵抗R、及び単位温度上昇させるために必要な熱容量Cであることを特徴とする。   The thermal characteristics are a thermal resistance R indicating the ease of heat transfer and a heat capacity C required to increase the unit temperature.

請求項1の発明では、電流検出手段にて電流が検出され、この電流値が上昇或いは定電流を維持しているときには、この電流値と、導体(電線と接触導体)の熱特性に応じた、電線の上昇温度が求められる。また、電流検出手段にて電流が検出されていないとき、或いは検出した電流が減少しているときには、導体の熱特性に応じた電線の下降温度が求められる。そして、所定のサンプリング時間毎に算出される電線の上昇温度、或いは下降温度を積算して導体の推定温度を算出し、メモリ内に記憶する。つまり、メモリ内に記憶される推定温度は、サンプリング時間毎に算出される上昇温度、或いは下降温度に基づいて逐次更新される。そして、導体の推定温度が所定の閾値を超えたときに、電線の発煙状態と判定して、負荷回路を遮断する。従って、電線の温度に基づいて回路を遮断するか否かが判定されるので、電線温度に応じた高精度な回路の遮断制御を行うことができる。   In the invention of claim 1, when the current is detected by the current detection means and the current value is increased or maintained at a constant current, the current value and the thermal characteristics of the conductor (the electric wire and the contact conductor) are determined. The rising temperature of the electric wire is required. Further, when no current is detected by the current detecting means, or when the detected current is decreasing, the descending temperature of the electric wire corresponding to the thermal characteristics of the conductor is obtained. Then, the estimated temperature of the conductor is calculated by integrating the rising temperature or the decreasing temperature of the electric wire calculated every predetermined sampling time, and is stored in the memory. That is, the estimated temperature stored in the memory is sequentially updated based on the rising temperature or the falling temperature calculated every sampling time. Then, when the estimated temperature of the conductor exceeds a predetermined threshold, it is determined that the electric wire is smoking, and the load circuit is shut off. Therefore, since it is determined whether or not to interrupt the circuit based on the temperature of the electric wire, it is possible to perform highly accurate circuit interruption control according to the electric wire temperature.

請求項2の発明では、熱特性として、電線の熱抵抗、及び熱容量を含めた導体の熱抵抗R、及び熱容量Cが用いられるので、電線固有の特性に応じた極めて高精度な温度検出が可能となり、ひいては高精度な回路の遮断制御が可能となる。   In the invention of claim 2, since the thermal resistance of the electric wire, the thermal resistance R of the conductor including the thermal capacity, and the thermal capacity C are used as the thermal characteristics, it is possible to detect the temperature with extremely high accuracy according to the specific characteristics of the electric wire. As a result, high-accuracy circuit interruption control becomes possible.

請求項3,4の発明では、電線の熱抵抗、及び熱容量を含めた導体の熱抵抗R、及び熱容量C用いた発熱特性、及び放熱特性を示す数式を用いて電線の上昇温度、或いは下降温度が求められるので、高精度な温度検出が可能となり、ひいては高精度な回路の遮断制御が可能となる。   According to the third and fourth aspects of the present invention, the rising temperature or the falling temperature of the electric wire using the mathematical expression indicating the heat resistance of the electric wire, the heat resistance R of the conductor including the heat capacity, the heat generation characteristic using the heat capacity C, and the heat dissipation characteristic. Therefore, it is possible to detect the temperature with high accuracy, and consequently, it is possible to control the interruption of the circuit with high accuracy.

本発明の一実施形態に係る負荷回路の保護装置が用いられた負荷回路の構成を示す回路図である。It is a circuit diagram which shows the structure of the load circuit where the protection apparatus of the load circuit which concerns on one Embodiment of this invention was used. 図1に示した制御回路の具体的な構成を示す機能ブロック図である。FIG. 2 is a functional block diagram showing a specific configuration of a control circuit shown in FIG. 1. 本発明の一実施形態に係る負荷回路の保護装置の処理動作を示すフローチャートである。It is a flowchart which shows the processing operation of the protection apparatus of the load circuit which concerns on one Embodiment of this invention. 時間経過に伴う電線温度の変化を示す特性図であり、(a)は電流上昇時、(b)は温度が飽和した後の電流ゼロ、或いは電流減少時を示す。It is a characteristic view which shows the change of the electric wire temperature with progress of time, (a) is the time of an electric current rise, (b) shows the electric current zero after temperature saturation, or the time of electric current decrease. 時間経過に伴う電線温度の変化を示す特性図であり、(a)は電流上昇時、(b)は温度が飽和する前に電流が減少した時の変化を示す。It is a characteristic view which shows the change of the electric wire temperature with progress of time, (a) is a time of an electric current rise, (b) shows a change when an electric current reduces before temperature is saturated. アーク上昇温度算出部に設定されているアーク対応マップを示す説明図である。It is explanatory drawing which shows the arc corresponding | compatible map set to the arc raise temperature calculation part.

以下、本発明の実施形態を図面に基づいて説明する。図1は、本発明の一実施形態に係る負荷回路の保護装置を含む負荷回路の構成を示す回路図であり、例えば、車両に搭載されるランプやモータ等の負荷に、車両に搭載されたバッテリよりの電力を供給して駆動するための回路である。   Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram illustrating a configuration of a load circuit including a load circuit protection device according to an embodiment of the present invention. For example, the load circuit is mounted on a vehicle such as a lamp or a motor mounted on the vehicle. It is a circuit for supplying power from a battery for driving.

同図に示すように、負荷回路1は、車両に搭載されるバッテリ(電源)2と、ランプやモータ等の負荷4と、バッテリ2と負荷4との間に設けられ、負荷4への電力の供給、停止を切り換えるMOSFET等の電子スイッチ(スイッチ)3とを備えている。   As shown in FIG. 1, a load circuit 1 is provided between a battery (power source) 2 mounted on a vehicle, a load 4 such as a lamp or a motor, and between the battery 2 and the load 4. And an electronic switch (switch) 3 such as a MOSFET for switching between supply and stop.

また、負荷4に流れる電流を検出する電流計(電流検出手段)5と、電子スイッチ3のオン、オフを制御する制御回路6を備えている。更に、バッテリ2と電子スイッチ3との間、及び電子スイッチ3と負荷4との間は、電線7にて接続されている。ここで、本実施形態に係る負荷回路の保護装置10は、電子スイッチ3と、電流計5と、制御回路6により構成される。   Further, an ammeter (current detection means) 5 for detecting a current flowing through the load 4 and a control circuit 6 for controlling on / off of the electronic switch 3 are provided. Furthermore, a wire 7 connects between the battery 2 and the electronic switch 3 and between the electronic switch 3 and the load 4. Here, the load circuit protection device 10 according to the present embodiment includes an electronic switch 3, an ammeter 5, and a control circuit 6.

図2は、制御回路6の詳細な構成を示す機能ブロック図であり、同図に示すように、制御回路6は、上昇温度算出部61と、下降温度算出部62と、アーク上昇温度算出部63と、推定温度算出部64と、温度判定部65と、スイッチ制御部(遮断制御手段)66を備えている。   FIG. 2 is a functional block diagram showing a detailed configuration of the control circuit 6. As shown in FIG. 2, the control circuit 6 includes a rising temperature calculation unit 61, a falling temperature calculation unit 62, and an arc rising temperature calculation unit. 63, the estimated temperature calculation part 64, the temperature determination part 65, and the switch control part (shut-off control means) 66 are provided.

上昇温度算出部(上昇温度算出手段)61は、電子スイッチ3がオンとされ、負荷4に電流が流れているときの電流計5により検出される負荷電流、及び予め設定されている電線7と接触導体からなる導体の熱特性(後述する熱抵抗R及び熱容量C)に基づいて、所定のサンプリング時間(例えば、5msec)毎の電線7の上昇温度を算出する。   The rise temperature calculation unit (rise temperature calculation means) 61 includes a load current detected by the ammeter 5 when the electronic switch 3 is turned on and a current is flowing through the load 4, and a preset electric wire 7 Based on the thermal characteristics (thermal resistance R and thermal capacity C described later) of the conductor made of the contact conductor, the rising temperature of the electric wire 7 is calculated every predetermined sampling time (for example, 5 msec).

下降温度算出部(下降温度算出手段)62は、回路中の接触導体と電線7とが離間する等の理由により、電流計5にて電流が検出されないとき、或いは電流計5で検出された電流が下降したときに、電流が検出されなくなったとき、或いは電流の下降が開始されたときの電線7の推定温度と、電線7を含む導体の熱特性に基づいて、所定のサンプリング時間毎の電線7の下降温度を算出する。   The descending temperature calculating section (decreasing temperature calculating means) 62 is configured to detect the current detected by the ammeter 5 when the current is not detected by the ammeter 5 due to the contact conductor in the circuit and the electric wire 7 being separated from each other. , When no current is detected, or when the current starts to drop, based on the estimated temperature of the wire 7 and the thermal characteristics of the conductor including the wire 7, the wire at a predetermined sampling time 7 descending temperature is calculated.

アーク上昇温度算出部63は、接触導体と電線とが離間し、電流値が負荷の通常動作電流に復帰した直後に発生するアークによる電線7の上昇温度を、電流値が負荷の通常動作電流に復帰する直前に流れていた電流値に基づき、所定のサンプリング時間毎に算出する。具体的には、図6に示す如くの、電流値iと上昇温度Q(i)との関係を示すアーク対応マップを備えており、負荷に流れる電流値が負荷の通常動作電流に復帰した際には、この直前の電流値をアーク対応マップに当てはめることにより、上昇温度を求める。   The arc rising temperature calculation unit 63 sets the rising temperature of the electric wire 7 due to the arc generated immediately after the contact conductor and the electric wire are separated and the current value returns to the normal operating current of the load, to the normal operating current of the load. Based on the current value flowing immediately before returning, the calculation is performed at predetermined sampling times. Specifically, as shown in FIG. 6, an arc correspondence map showing the relationship between the current value i and the rising temperature Q (i) is provided, and when the current value flowing through the load returns to the normal operating current of the load. In this case, the rising temperature is obtained by applying the current value immediately before this to the arc correspondence map.

推定温度算出部(推定温度算出手段)64は、メモリ64aを備えており、上述した上昇温度算出部61で算出された所定のサンプリング時間毎の上昇温度、下降温度算出部62で算出された所定のサンプリング時間毎の下降温度、及びアーク上昇温度算出部63で算出された所定のサンプリング時間毎の上昇温度を積算して、現在における電線7の推定温度を算出する。即ち、メモリ64aは、周囲温度を基準とし、この周囲温度に対してサンプリング時間毎の上昇温度、及び下降温度を積算(加算または減算)して記憶保存する。   The estimated temperature calculation unit (estimated temperature calculation means) 64 includes a memory 64a, and a predetermined temperature calculated by the rising temperature / lowering temperature calculation unit 62 calculated for each predetermined sampling time calculated by the rising temperature calculation unit 61 described above. The estimated temperature of the electric wire 7 at the present time is calculated by integrating the falling temperature for each sampling time and the rising temperature for each predetermined sampling time calculated by the arc rising temperature calculation unit 63. That is, the memory 64a uses the ambient temperature as a reference, and accumulates (adds or subtracts) the rising temperature and the falling temperature for each sampling time with respect to the ambient temperature and stores and saves them.

従って、メモリ64aには、現在における電線7の推定温度が記憶されることになる。このため、電線7が発熱から放熱に転じた場合、或いは放熱から発熱に転じた場合、或いは、発熱と放熱を短時間で繰り返す場合でも、その時点における電線7の推定温度がメモリ64内に記憶されることになり、ひいては、現在における電線7の推定温度を算出することができる。 Therefore, the current estimated temperature of the electric wire 7 is stored in the memory 64a. For this reason, even when the electric wire 7 changes from heat generation to heat dissipation, or from heat dissipation to heat generation, or when heat generation and heat dissipation are repeated in a short time, the estimated temperature of the electric wire 7 at that time is stored in the memory 64. As a result, the current estimated temperature of the electric wire 7 can be calculated.

温度判定部65は、上述した推定温度算出部64で算出された電線7の推定温度Tnowと、予め設定した許容温度(所定の閾値温度)Tthとを比較し、推定温度Tnowが許容温度Tthを超えた(Tnow>Tth)と判定した場合に、スイッチ制御部66に回路遮断指令信号を出力する。   The temperature determination unit 65 compares the estimated temperature Tnow of the electric wire 7 calculated by the estimated temperature calculation unit 64 described above with a preset allowable temperature (predetermined threshold temperature) Tth, and the estimated temperature Ton determines the allowable temperature Tth. When it is determined that it has exceeded (Tnow> Tth), a circuit cutoff command signal is output to the switch control unit 66.

スイッチ制御部(遮断制御手段)66は、温度判定部65より、上記の回路遮断指令信号が出力された際に、電子スイッチ3をオフとして通電を停止させ、回路を保護する。   The switch control unit (shut-off control means) 66 turns off the electronic switch 3 to stop the energization when the above-described circuit shut-off command signal is output from the temperature determination unit 65, thereby protecting the circuit.

なお、上記した制御回路6の機能構成は、負荷回路にレアショートが発生したときに対応するための回路構成のみを示したものであり、デッドショート発生時の遮断回路については省略している。   Note that the functional configuration of the control circuit 6 described above shows only a circuit configuration for dealing with a rare short circuit occurring in the load circuit, and a cut-off circuit when a dead short circuit occurs is omitted.

次に、上昇温度算出部61、下降温度算出部62、及びアーク上昇温度算出部63における上昇温度或いは下降温度の算出方法について説明する。   Next, a method for calculating the rising temperature or the falling temperature in the rising temperature calculation unit 61, the falling temperature calculation unit 62, and the arc rising temperature calculation unit 63 will be described.

(イ)上昇温度算出部61における上昇温度の算出
電線7に電流が流れることによる発熱に伴う電線7の温度T1は、次の(1)式で示される。

Figure 2014027875
(A) Calculation of rising temperature in rising temperature calculation part 61 Temperature T1 of the electric wire 7 accompanying the heat_generation | fever by an electric current flowing through the electric wire 7 is shown by following (1) Formula.
Figure 2014027875

ここで、各記号は以下の通りである。   Here, each symbol is as follows.

T1 : 電線の温度[℃]
T2 : 周囲温度[℃]
i : 電流[A]
r : 導体の抵抗[Ω]
R : 導体の熱抵抗[℃/W]
C : 導体の熱容量[J/℃]或いは[W・sec/℃]
t : 経過時間[sec]
(1)式において、周囲温度T2は、電子スイッチ3がオンとされたときの電線7の温度であり、初期状態では固定値として例えば、通常の環境下では25℃、エンジンルーム等の高温環境下では85℃等に設定される。電流iは電流計5により測定される値である。抵抗rは定数である。熱抵抗Rは、電線7を含む導体の熱の伝わり易さを示す値であり、電線7の材質、太さ、形状等に基づく固有の値を含む導体の値である。熱容量Cは、電線7を含む導体の温度を1℃高めるのに必要な熱量であり、電線の材質、太さ、形状等に基づく固有の値を含む導体の値である。
T1: Wire temperature [° C]
T2: Ambient temperature [℃]
i: Current [A]
r: Resistance of conductor [Ω]
R: Thermal resistance of conductor [° C / W]
C: Heat capacity of conductor [J / ° C] or [W · sec / ° C]
t: Elapsed time [sec]
In the equation (1), the ambient temperature T2 is the temperature of the electric wire 7 when the electronic switch 3 is turned on, and is a fixed value in the initial state, for example, 25 ° C. in a normal environment, and a high temperature environment such as an engine room. Below, it is set to 85 ° C. or the like. The current i is a value measured by the ammeter 5. The resistance r is a constant. The thermal resistance R is a value indicating the ease of heat transfer of the conductor including the electric wire 7 and is a value of the conductor including a specific value based on the material, thickness, shape, and the like of the electric wire 7. The heat capacity C is the amount of heat necessary to raise the temperature of the conductor including the electric wire 7 by 1 ° C., and is a value of the conductor including specific values based on the material, thickness, shape, etc. of the electric wire.

従って、電流iと時間tが決定されると、(1)式を用いることにより、電線7の現在の温度T1を求めることができる。   Therefore, when the current i and the time t are determined, the current temperature T1 of the electric wire 7 can be obtained by using the equation (1).

(ロ)下降温度算出部62における下降温度の算出
電流計5で電流が検出されないとき、或いは検出される電流値が下降したときの、放熱に伴う電線の温度T1は、次に(2)式で示される。

Figure 2014027875
(B) Calculation of descending temperature in descending temperature calculation unit 62 When the current is not detected by the ammeter 5 or when the detected current value decreases, the temperature T1 of the electric wire accompanying heat radiation is expressed by the following equation (2). Indicated by
Figure 2014027875

ここで、(2)式における各記号は以下の通りである。   Here, each symbol in the formula (2) is as follows.

T1 : 電線の温度[℃]
T2 : 周囲温度[℃]
r : 導体の抵抗[Ω]
R : 導体の熱抵抗[℃/W]
C : 導体の熱容量[J/℃]或いは[W・sec/℃]
t : 経過時間[sec]
(2)式において、周囲温度T2は、電流計5で電流が検出されないとき或いは検出される電流値が下降したときの、電線7の温度である。また、「i」は、電流計5で電流が検出されないとき或いは検出される電流値が下降したときの、電線7の温度(上記した(1)式で求められる温度T1)にて発熱が飽和する電流[A]であり、電線7の温度が飽和状態である場合には、電流計5で電流が検出されないとき或いは検出される電流値が下降する直前の電流[A]となる。詳細については後述する。従って、電流iと時間tが決定されると、(2)式を用いることにより、電線7の現在の温度T1を求めることができる。
T1: Wire temperature [° C]
T2: Ambient temperature [℃]
r: Resistance of conductor [Ω]
R: Thermal resistance of conductor [° C / W]
C: Heat capacity of conductor [J / ° C] or [W · sec / ° C]
t: Elapsed time [sec]
In the equation (2), the ambient temperature T2 is the temperature of the electric wire 7 when no current is detected by the ammeter 5 or when the detected current value decreases. “I” indicates that the heat generation is saturated at the temperature of the electric wire 7 when the current is not detected by the ammeter 5 or when the detected current value is lowered (the temperature T1 obtained by the above equation (1)). When the temperature of the electric wire 7 is saturated, the current [A] is detected when no current is detected by the ammeter 5 or immediately before the detected current value is lowered. Details will be described later. Therefore, when the current i and the time t are determined, the current temperature T1 of the electric wire 7 can be obtained by using the equation (2).

(ハ)アーク上昇温度算出部63における上昇温度の算出
接触導体と電線7が離間し、電流値が負荷の通常動作電流に復帰した直前の電流iと、上昇温度Q(i)との関係を示すアーク対応マップ(図6参照)を予め記憶しておき、接触導体と電線7とが離間し、電流値が負荷の通常動作電流に復帰したときには、この復帰する直前の電流iに基づき、アーク対応マップを参照して上昇温度Q(i)を求め、次の(3)式を用いて、電線7の温度T1を求める。
(C) Calculation of rising temperature in arc rising temperature calculation unit 63 The relationship between the rising temperature Q (i) and the current i immediately before the contact conductor and the electric wire 7 are separated and the current value returns to the normal operating current of the load. The arc correspondence map shown (see FIG. 6) is stored in advance, and when the contact conductor is separated from the electric wire 7 and the current value returns to the normal operating current of the load, the arc is determined based on the current i immediately before the return. The rising temperature Q (i) is obtained with reference to the correspondence map, and the temperature T1 of the electric wire 7 is obtained using the following equation (3).

T1=T2+Q(i) ・・・(3)
ここで、周囲温度T2は、接触導体と電線7が離間し、電流値が負荷の通常動作電流に復帰したときの電線7の温度である。
T1 = T2 + Q (i) (3)
Here, the ambient temperature T2 is the temperature of the electric wire 7 when the contact conductor is separated from the electric wire 7 and the current value returns to the normal operating current of the load.

次に、上述のように構成された本実施形態に係る負荷回路1の動作について、図3に示すフローチャートを参照しながら説明する。なお、本フローチャートに示す処理は、例えば、5[msec]のサンプリング時間で周期的に実行される。   Next, the operation of the load circuit 1 according to the present embodiment configured as described above will be described with reference to the flowchart shown in FIG. Note that the processing shown in this flowchart is periodically executed with a sampling time of, for example, 5 [msec].

まず、ステップS1において、電流計5により負荷電流が流れているか否かが判定される。即ち、電子スイッチ3がオンとされて、バッテリ2と負荷4が電気的に接続され、電線7に電流が流れているか否かが判定される。   First, in step S1, it is determined by the ammeter 5 whether a load current is flowing. That is, the electronic switch 3 is turned on, the battery 2 and the load 4 are electrically connected, and it is determined whether or not a current is flowing through the electric wire 7.

そして、電流が検出されたと判定された場合には(ステップS1でYES)、ステップS2において、今回のサンプリング時の検出電流と前回のサンプリング時の検出電流とを比較する。   If it is determined that a current is detected (YES in step S1), in step S2, the detected current at the current sampling is compared with the detected current at the previous sampling.

そして、今回の検出電流が前回の検出電流以上であると判定された場合(ステップS2でYES)、即ち、負荷4に流れる電流が上昇しているか、或いは定電流で安定していると判定された場合には、ステップS4において、上昇温度算出部61は、タイマを作動させて時間経過を計時すると共に、電流計5で検出された電流値iと、タイマにより計時される経過時間に基づき、上述した(1)式を用いて、電線7の温度T1を算出する。なお、(1)式における周囲温度T2は初期温度として、例えば、25℃等の値を設定する。   If it is determined that the current detection current is greater than or equal to the previous detection current (YES in step S2), that is, it is determined that the current flowing through the load 4 is rising or stable at a constant current. In step S4, the rising temperature calculation unit 61 operates the timer to measure the time elapsed, and based on the current value i detected by the ammeter 5 and the elapsed time measured by the timer, The temperature T1 of the electric wire 7 is calculated using the equation (1) described above. The ambient temperature T2 in the equation (1) is set to a value such as 25 ° C. as an initial temperature.

次いで、ステップS7において、推定温度算出部64は、ステップS4で算出された温度T1を現在の電線7の推定温度Tnowとしてメモリ64aに記憶保存する。   Next, in step S7, the estimated temperature calculation unit 64 stores and saves the temperature T1 calculated in step S4 in the memory 64a as the current estimated temperature Tnow of the electric wire 7.

ステップS8では、温度判定部65により、上記のメモリ64aに記憶されている電線7の推定温度Tnowと、電線7が発煙しない程度に設定された許容温度(所定の閾値温度)Tthとが比較判定され、推定温度Tnowが許容温度Tth以下である場合(推定温度Tnow≦許容温度Tth)には、処理を元に戻す(ステップS8でYES)。   In step S8, the temperature determination unit 65 compares the estimated temperature Tnow of the electric wire 7 stored in the memory 64a with the allowable temperature (predetermined threshold temperature) Tth set to such an extent that the electric wire 7 does not smoke. If the estimated temperature Tnow is equal to or lower than the allowable temperature Tth (estimated temperature Tnow ≦ allowable temperature Tth), the process is returned (YES in step S8).

そして、上記の負荷4に流れる電流が上昇或いは定電流で安定している場合には、ステップS1,S2,S4,S7の処理が繰り返され、電線7の温度は(1)式においてt=∞として、次の(4)式に示す温度T1に収束する。   And when the electric current which flows into said load 4 rises or is stabilized with a constant current, the process of step S1, S2, S4, S7 is repeated and the temperature of the electric wire 7 is t = infinity in (1) Formula. As a result, the temperature converges to the temperature T1 shown in the following equation (4).

T1=T2+i2・r・R ・・・(4)
ここで、負荷回路1にレアショートが発生し、負荷4に流れる電流iが増大した場合には、電線7の温度が上昇し、現在の電線7の推定温度Tnowが許容温度Tthを上回るので、ステップS8でNOとなり、ステップS9にてスイッチ制御部66が電子スイッチ3をオフとして回路を遮断し、負荷回路1を発熱から保護する。
T1 = T2 + i 2 · r · R (4)
Here, when a short circuit occurs in the load circuit 1 and the current i flowing through the load 4 increases, the temperature of the electric wire 7 rises, and the current estimated temperature Tnow of the electric wire 7 exceeds the allowable temperature Tth. In step S8, the result is NO, and in step S9, the switch control unit 66 turns off the electronic switch 3 to shut off the circuit and protect the load circuit 1 from heat generation.

また、今回のサンプリング時における検出電流が、前回のサンプリング時における検出電流未満となった場合には(ステップS2でNO)、ステップS3において、前回のサンプリング時に検出した電流が負荷の通常動作電流範囲外であり、今回のサンプリング時に検出した電流が負荷の通常動作範囲内であるか否かが判定される。この判定処理では、アーク電流発生時にYES判定となる。そして、ステップS3の判定がYESである場合には、ステップS5において、アーク上昇温度算出部63は、アーク対応マップに基づき、上述した(3)式を用いて電線7の上昇温度を算出する。即ち、図6に示す如くのアーク対応マップに、検出電流が負荷4の通常動作電流に復帰する直前の電流値iを当てはめることにより、上昇温度Q(i)を求める。   If the detected current at the current sampling is less than the detected current at the previous sampling (NO at step S2), the current detected at the previous sampling is the normal operating current range of the load at step S3. It is determined whether the current detected during the current sampling is within the normal operating range of the load. In this determination process, a YES determination is made when an arc current occurs. If the determination in step S3 is YES, in step S5, the arc rising temperature calculation unit 63 calculates the rising temperature of the electric wire 7 using the above-described equation (3) based on the arc correspondence map. That is, by applying the current value i immediately before the detected current returns to the normal operating current of the load 4 to the arc correspondence map as shown in FIG. 6, the rising temperature Q (i) is obtained.

そして、ステップS7において、推定温度算出部64は、上記の処理で求められた上昇温度Q(i)を、メモリ64aに記憶されている電線7の温度に加算し、電線7の温度を更新する。即ち、メモリに記憶されている1回前のサンプリング期間で求められた電線7の温度を周囲温度T2とし、この周囲温度T2に上記した上昇温度Q(i)を加算し(即ち、上述した(3)式により)現在の電線7の温度T1を求め、これを推定温度Tnowとしてメモリ64aに記憶する。   And in step S7, the estimated temperature calculation part 64 adds the temperature rise Q (i) calculated | required by said process to the temperature of the electric wire 7 memorize | stored in the memory 64a, and updates the temperature of the electric wire 7. FIG. . That is, the temperature of the electric wire 7 obtained in the previous sampling period stored in the memory is set as the ambient temperature T2, and the above-described increased temperature Q (i) is added to the ambient temperature T2 (that is, the above-described ( 3) The current temperature T1 of the electric wire 7 is obtained by the equation (3), and this is stored in the memory 64a as the estimated temperature Tnow.

次いで、この時点で電線7の推定温度Tnowが許容温度Tth以下である場合には(ステップS8でYES)、ステップS1の処理に戻り、ステップS8の処理でNOとなった場合には、ステップS9にてスイッチ制御部66が電子スイッチ3をオフとして回路を遮断し、負荷回路1を発熱から保護する。   Next, if the estimated temperature Tnow of the electric wire 7 is equal to or lower than the allowable temperature Tth at this time (YES in step S8), the process returns to step S1, and if NO in step S8, the process returns to step S9. The switch control unit 66 turns off the electronic switch 3 to cut off the circuit and protect the load circuit 1 from heat generation.

また、ステップS3の処理でNOの場合、即ち、「前回サンプリング時の検出電流が負荷の通常動作電流範囲外であり、今回サンプリング時の検出電流が負荷の通常動作範囲内である」という条件を満たさない場合、換言すれば、アーク等の突発的な電流に起因せず、単に電流値が減少している場合、及び、ステップS1でNOの場合、即ち、負荷4に流れる電流値がゼロである場合には、ステップS6の処理に移行する。   Further, in the case of NO in the process of step S3, that is, the condition that “the detected current at the previous sampling is out of the normal operating current range of the load and the detected current at the current sampling is within the normal operating range of the load” is satisfied. If not, in other words, it is not caused by a sudden current such as an arc, but the current value is simply decreasing, and if NO in step S1, that is, the current value flowing through the load 4 is zero. If there is, the process proceeds to step S6.

ステップS6では、下降温度算出部62は、初期的な処理として、タイマをリセットし、タイマの計時を開始する。更に、上述した(2)式に、タイマにより計時される経過時間t、電流i及び周囲温度T2を代入することにより、現在の電線7の温度T1を算出する。この際、上述したように、(2)式の電流「i」は、電流が検出されなくなったとき、或いは電流の下降が開始したときの温度T1にて発熱が飽和する電流[A]である。また、電線7の温度が既に飽和状態である場合には、電流「i」は電流が検出されなくなったとき、或いは電流の下降が開始する直前の電流[A]となる。   In step S6, the descending temperature calculation unit 62 resets the timer and starts counting the timer as an initial process. Further, the current temperature T1 of the electric wire 7 is calculated by substituting the elapsed time t, the current i, and the ambient temperature T2 measured by the timer into the above-described equation (2). At this time, as described above, the current “i” in the equation (2) is the current [A] at which the heat generation is saturated at the temperature T1 when the current is not detected or when the current starts to decrease. . When the temperature of the electric wire 7 is already saturated, the current “i” is the current [A] when no current is detected or immediately before the current starts to decrease.

以下、(2)式の電流「i」について詳細に説明する。いま、周囲温度(電線7の初期的な温度)がT21であるときに、電流I1が継続して上昇すると、上述した(1)式に示した特性で電線7の温度が上昇し、ある一定の温度T11で飽和する。これを特性図で示すと、図4(a)に示す曲線s1の如くとなり、温度T21から時間の経過と共に温度が徐々に上昇し、温度T11に収束する。つまり、温度T11で飽和する。   Hereinafter, the current “i” in the equation (2) will be described in detail. Now, when the ambient temperature (the initial temperature of the electric wire 7) is T21, if the current I1 continues to rise, the temperature of the electric wire 7 rises with the characteristic shown in the above-described equation (1), and is constant. Saturates at the temperature T11. If this is shown in a characteristic diagram, it becomes like a curve s1 shown in FIG. 4A, and the temperature gradually rises from the temperature T21 with time and converges to the temperature T11. That is, it is saturated at the temperature T11.

そして、電線7の温度が温度T11で飽和しているときに、電流計5にて電流が検出されなくなったか、或いは電流が下降し始めた場合には、(2)式では、温度T11で電線7の温度が飽和する電流、即ち、電流が検出されなくなったとき、或いは電流の下降が開始する直前の電流I1が「i」として設定される。従って、図4(b)の曲線s2に示すように、同図(a)の曲線s1を上下反対にした特性で、電線7の温度が下降し、最終的に周囲温度T21に収束するように変化する。   Then, when the temperature of the electric wire 7 is saturated at the temperature T11, if the current is not detected by the ammeter 5 or the current starts to decrease, the electric wire at the temperature T11 is expressed by the equation (2). The current at which the temperature of 7 is saturated, that is, the current I1 when the current is not detected or immediately before the current starts to drop is set as “i”. Therefore, as shown by a curve s2 in FIG. 4B, the temperature of the electric wire 7 decreases with the characteristic that the curve s1 in FIG. 4A is turned upside down, and finally converges to the ambient temperature T21. Change.

また、電線7の温度が飽和していないときに、電流計5にて電流が検出されなくなったか、或いは電流が下降し始めた場合、即ち、図5(a)に示すように、曲線s1が温度T11に収束する前の、例えば時刻t1で電流が検出されなくなったか、或いは電流が下降し始めた場合には、この時点の温度T12で電線7の温度が飽和する電流が、電流「i」として設定される。つまり、電線7の温度が温度T12で飽和する電流I2を求め(曲線s3参照)、この電流I2が(2)式の電流「i」となる。   Further, when the temperature of the electric wire 7 is not saturated, when the current is not detected by the ammeter 5 or the current starts to drop, that is, as shown in FIG. For example, when the current is not detected at the time t1 before the temperature T11 converges or the current starts to decrease, the current at which the temperature of the electric wire 7 is saturated at the temperature T12 at this time is the current “i”. Set as That is, the current I2 at which the temperature of the electric wire 7 is saturated at the temperature T12 is obtained (see the curve s3), and this current I2 becomes the current “i” in the equation (2).

従って、放熱特性は、曲線s3を上下反対にした特性を有することになり、図5(b)に示す曲線s4に示すように、電線7の温度が下降する特性曲線となる。   Therefore, the heat dissipation characteristic has a characteristic in which the curve s3 is turned upside down, and becomes a characteristic curve in which the temperature of the electric wire 7 decreases as shown by a curve s4 shown in FIG. 5B.

そして、図3のステップS6で、上述した(2)式により下降温度が算出されると、ステップS7において、推定温度算出部64のメモリ64aに記憶されている現在の電線7の推定温度Tnowが更新される。   Then, when the descending temperature is calculated by the above-described equation (2) in step S6 of FIG. 3, the current estimated temperature Tow of the electric wire 7 stored in the memory 64a of the estimated temperature calculation unit 64 is calculated in step S7. Updated.

つまり、メモリ64aには、負荷電流が上昇しているときの温度上昇、アーク発生時の温度上昇、及び負荷電流オフ或いは減少しているときの放熱を全て考慮して求められる、電線7の推定温度Tnowが記憶保存されることになる。そして、ステップS8では、この電線7の推定温度Tnowと許容温度Tthとが比較され、推定温度Tnowが許容温度Tth以上となった場合に、電子スイッチ3をオフとして回路を遮断する。こうして、レアショートが発生し、電線7の温度が上昇した場合には、即時に回路を遮断することができるのである。   That is, the estimation of the electric wire 7 is obtained in the memory 64a by considering all of the temperature rise when the load current is rising, the temperature rise when the arc is generated, and the heat radiation when the load current is off or decreasing. The temperature Tnow is stored and saved. In step S8, the estimated temperature Tnow of the electric wire 7 is compared with the allowable temperature Tth, and when the estimated temperature Tnow becomes equal to or higher than the allowable temperature Tth, the electronic switch 3 is turned off to cut off the circuit. Thus, when a short circuit occurs and the temperature of the electric wire 7 rises, the circuit can be shut off immediately.

このようにして、本実施形態に係る負荷回路の保護装置では、負荷4に流れる電流が上昇しているときには、上記した(1)式を用いて電線7の温度を検出し、また、電流がゼロ、或いは電流が減少しているときには、上記した(2)式を用いて電線7の温度を検出し、更に、アークが発生したときの温度上昇を(3)式により加算して、トータル的に現在の電線7の温度を推定している。   Thus, in the load circuit protection device according to the present embodiment, when the current flowing through the load 4 is rising, the temperature of the electric wire 7 is detected using the above-described equation (1), and the current is When zero or the current is decreasing, the temperature of the electric wire 7 is detected using the above equation (2), and the temperature rise when the arc is generated is added according to the equation (3) to obtain a total. The current temperature of the electric wire 7 is estimated.

そして、現在の電線7の推定温度Tnowが、発煙を生じる許容温度Tthに達した時点で電子スイッチ3をオフとし、回路を保護する。つまり、電線7の熱抵抗R、熱容量Cといった電線7の固有の特性を用いて電線7の実際の温度を推定し、回路を遮断するか否かを判定しているので、電線7が発煙する前の時点で確実に回路を遮断して、負荷回路及び電線7を保護することができる。また、継続的な通電が可能である、極めて少ない発熱でむやみに負荷回路1が遮断されるというトラブルの発生を回避することができる。   Then, when the estimated temperature Tnow of the current electric wire 7 reaches the allowable temperature Tth that generates smoke, the electronic switch 3 is turned off to protect the circuit. That is, since the actual temperature of the electric wire 7 is estimated using the characteristic of the electric wire 7 such as the thermal resistance R and the heat capacity C of the electric wire 7 and it is determined whether or not the circuit is interrupted, the electric wire 7 emits smoke. The load circuit and the electric wire 7 can be protected by reliably interrupting the circuit at the previous time. In addition, it is possible to avoid the occurrence of trouble that the load circuit 1 is interrupted unnecessarily with very little heat generation, which allows continuous energization.

更に、負荷4に流れる電流がゼロ、或いは減少を開始したときには、この条件となる直前の温度で飽和する電流値を、上述の(2)式に当てはめて放熱による下降温度を算出するので、極めて高精度に下降温度を求めることができ、電線7の温度を高精度に求めることができ、ひいてはレアショートが発生した場合であっても、電線7が発煙する前の時点で確実に回路を遮断することができる。   Furthermore, when the current flowing through the load 4 is zero or starts decreasing, the current value saturated at the temperature immediately before this condition is applied to the above equation (2) to calculate the temperature drop due to heat dissipation. The temperature can be calculated with high accuracy, and the temperature of the electric wire 7 can be obtained with high accuracy. As a result, even if a rare short circuit occurs, the circuit is reliably interrupted before the electric wire 7 smokes. can do.

以上、本発明の負荷回路の保護装置を図示の実施形態に基づいて説明したが、本発明はこれに限定されるものではなく、各部の構成は、同様の機能を有する任意の構成のものに置き換えることができる。   Although the load circuit protection device of the present invention has been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part is an arbitrary configuration having the same function. Can be replaced.

例えば、上述した実施形態では、負荷回路の保護装置が、車両に搭載されるランプ、モータ等の負荷を駆動する負荷回路1に用いられる場合を例に挙げて説明したが、本発明はこれに限定されるものではなく、その他の負荷回路についても適用することができる。   For example, in the above-described embodiment, the case where the load circuit protection device is used in the load circuit 1 that drives a load such as a lamp or a motor mounted on the vehicle has been described as an example. The present invention is not limited, and can be applied to other load circuits.

レアショートが発生した際に、これを確実に検出して回路を保護する上で極めて有用である。   When a rare short occurs, it is extremely useful for reliably detecting this and protecting the circuit.

1 負荷回路
2 バッテリ
3 電子スイッチ
4 負荷
5 電流計(電流検出手段)
6 制御回路
7 電線
10 負荷回路の保護装置
61 上昇温度算出部(上昇温度算出手段)
62 下降温度算出部(下降温度算出手段)
63 アーク上昇温度算出部
64 推定温度算出部(推定温度算出手段)
64a メモリ
65 温度判定部(温度判定手段)
66 スイッチ制御部(遮断制御手段)
DESCRIPTION OF SYMBOLS 1 Load circuit 2 Battery 3 Electronic switch 4 Load 5 Ammeter (Current detection means)
6 Control Circuit 7 Electric Wire 10 Protective Device for Load Circuit 61 Rise Temperature Calculation Unit (Rise Temperature Calculation Means)
62 Falling temperature calculation unit (falling temperature calculation means)
63 Arc rising temperature calculation unit 64 Estimated temperature calculation unit (estimated temperature calculation means)
64a memory 65 temperature determination unit (temperature determination means)
66 Switch control unit (cut-off control means)

Claims (4)

電源、スイッチ及び負荷を備えた負荷回路の、前記負荷に流れる電流を検出し、検出した電流値により前記負荷回路を遮断する負荷回路の保護装置において、
前記負荷に流れる電流を検出する電流検出手段と、
前記電流検出手段で電流が検出されているとき、検出された電流値と、前記負荷と電源とを結ぶ導体の熱特性とに基づいて、前記導体の上昇温度を算出する上昇温度算出手段と、
前記電流検出手段で電流が検出されていないとき、或いは検出した電流が下降したときに、前記導体の熱特性に基づいて、前記導体の下降温度を算出する下降温度算出手段と、
前記上昇温度算出手段で算出される所定のサンプリング時間毎の上昇温度、及び下降温度算出手段で算出される所定のサンプリング時間毎の下降温度を、前記所定のサンプリング時間毎に積算し、積算した結果である導体の推定温度を算出し、更にこの推定温度を記憶するメモリを有する推定温度算出手段と、
前記推定温度算出手段により算出される前記導体の温度が所定の閾値温度を超えたか否かを判定する温度判定手段と、
前記温度判定手段により、前記導体の温度が所定の閾値温度を超えたと判定された際に、前記負荷回路を遮断する遮断制御手段と、
を備えたことを特徴とする負荷回路の保護装置。
In a load circuit protection device for detecting a current flowing through the load of a load circuit including a power source, a switch, and a load, and cutting off the load circuit according to the detected current value.
Current detection means for detecting a current flowing through the load;
When a current is detected by the current detection means, the temperature rise means for calculating the temperature rise of the conductor based on the detected current value and the thermal characteristics of the conductor connecting the load and the power source;
A descending temperature calculating means for calculating a descending temperature of the conductor based on a thermal characteristic of the conductor when no current is detected by the current detecting means or when the detected current falls;
A result of accumulating the rising temperature for each predetermined sampling time calculated by the rising temperature calculating means and the falling temperature for each predetermined sampling time calculated by the falling temperature calculating means for each predetermined sampling time. An estimated temperature calculating means having a memory for calculating the estimated temperature of the conductor and storing the estimated temperature;
Temperature determination means for determining whether the temperature of the conductor calculated by the estimated temperature calculation means exceeds a predetermined threshold temperature;
An interruption control means for interrupting the load circuit when the temperature determination means determines that the temperature of the conductor exceeds a predetermined threshold temperature;
A load circuit protection device comprising:
前記熱特性は、熱の伝わり易さを示す熱抵抗R、及び単位温度上昇させるために必要な熱容量Cであることを特徴とする請求項1に記載の負荷回路の保護装置。   2. The load circuit protection device according to claim 1, wherein the thermal characteristics are a thermal resistance R indicating ease of heat transfer and a heat capacity C required to increase a unit temperature. 前記上昇温度算出手段は、前記熱抵抗R、熱容量Cを用いて、次式にて前記導体の温度を算出することを特徴とする請求項2に記載の負荷回路の保護装置。
Figure 2014027875
但し、各記号は以下の通り。
T1:電線の温度[℃]
T2 :周囲温度[℃]
i :電流[A]
r :導体の抵抗[Ω]
R :導体の熱抵抗[℃/W]
C :導体の熱容量[J/℃]或いは[W・sec/℃]
t :経過時間[sec]
3. The load circuit protection device according to claim 2, wherein the rising temperature calculation means calculates the temperature of the conductor by the following formula using the thermal resistance R and the thermal capacity C. 4.
Figure 2014027875
However, each symbol is as follows.
T1: Wire temperature [° C]
T2: Ambient temperature [° C]
i: Current [A]
r: Conductor resistance [Ω]
R: Thermal resistance of conductor [° C / W]
C: Heat capacity of conductor [J / ° C] or [W · sec / ° C]
t: Elapsed time [sec]
前記下降温度算出手段は、前記熱抵抗R、熱容量Cを用いて、次式にて前記導体の温度を算出することを特徴とする請求項2または請求項3のいずれかに記載の負荷回路の保護装置。
Figure 2014027875
但し、各記号は以下の通り。
T1:電線の温度[℃]
T2:周囲温度[℃]
i :電流検出無し或いは電流減少した時の温度T1にて発熱が飽和する電流[A]
r :導体の抵抗[Ω]
R :導体の熱抵抗[℃/W]
C :導体の熱容量[J/℃]或いは[W・sec/℃]
t :経過時間[sec]
4. The load circuit according to claim 2, wherein the descending temperature calculation means calculates the temperature of the conductor by the following formula using the thermal resistance R and the thermal capacity C. 5. Protective device.
Figure 2014027875
However, each symbol is as follows.
T1: Wire temperature [° C]
T2: Ambient temperature [° C]
i: Current at which heat generation is saturated at temperature T1 when no current is detected or when current decreases [A]
r: Conductor resistance [Ω]
R: Thermal resistance of conductor [° C / W]
C: Heat capacity of conductor [J / ° C] or [W · sec / ° C]
t: Elapsed time [sec]
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