JP2015077029A - Electric wire protection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric wire protection device capable of detecting an overload current with small throughput of a microprocessor to protect an electric wire even when a periodic overload current in synchronization with vibration of a vehicle is generated in a circuit with a short pulse width in the electric wire in the vehicle.SOLUTION: An electric wire protection device includes: a microprocessor 5 for setting an acquisition cycle for performing A/D conversion on a signal related to a current value flowing in an electric wire 15 measured by a current sensor 6b and acquiring the converted current value, on the basis of the oscillation cycle of a vehicle; and a switch 6a capable of switching on/off the current flowing through the electric wire 15 based on the acquired current value. A value based on the oscillation cycle which is the same as an engine rotational cycle acquired by an engine ECU13 is set as the acquisition cycle. All the phases in a cycle are scanned and the acquisition cycle is set to be the same as the oscillation cycle when an overload current is detected. In succession, when a continuous overload current is detected, the switch 6a is controlled to be off and the electric wire 15 is protected.

Description

  The present invention relates to an electric wire protection device that protects an electric wire by interrupting energization when an overcurrent flowing through the electric wire is detected.

  Joule heat is generated when power is supplied to the wire. If an overcurrent that generates Joule heat that exceeds the heat dissipation of the electric wire flows, the electric wire may overheat and the electric wire may burn out. In order to prevent this, it is necessary to cut off energization and protect the wire before the wire is overheated.

  In Patent Document 1, an energization current of a wire is sampled every predetermined time, a wire temperature is calculated using a value of the sampled energization current, and a switch is controlled to be turned on or off based on the calculated temperature. An electric wire protection method is disclosed. When the calculated wire temperature becomes equal to or higher than a predetermined upper limit temperature, the supply of power from the power source to the load is stopped, and the wire is protected.

JP 2009-130944 A

  By the way, in the electric wire in the vehicle, there is a possibility that the electric wire rubs against other electric wires due to the vibration of the vehicle, the coating is worn, the circuit is intermittently short-circuited, and a short-time overcurrent flows periodically and repeatedly in the electric wire. is there. However, in the method disclosed in Patent Document 1, since the current value is sampled at a predetermined time unrelated to the vibration period, if the overcurrent is generated at the same period as the vibration period of the vehicle, Current may not be detected. For this reason, there exists a possibility that protection of an electric wire may not be made appropriately.

  On the other hand, if the current value is sampled frequently by setting the time interval for sampling the current value to be very short regardless of the occurrence period of the overcurrent, It is possible to detect current. However, in such a case, the amount of calculation performed for each sampling increases, which may affect other calculation processing performed by the apparatus.

  The present invention has been made in view of such circumstances, and can detect periodic overcurrent caused by vibration of a vehicle without increasing the amount of calculation related to current value sampling, and can detect the overcurrent. It is an object of the present invention to provide an electric wire protection device capable of interrupting energization and protecting an electric wire in the case of failure.

  An electric wire protection device according to the present invention includes a current value acquisition unit that periodically acquires a current value flowing through an electric wire in a vehicle, and a determination that determines whether or not the current value acquired by the current value acquisition unit is greater than a threshold value. A vibration period measuring unit that measures a vibration period of a vehicle, and a current value, in the electric wire protection device including a switch and a switch that is interposed in the electric wire and is turned on or off based on a determination result of the determination unit An acquisition cycle setting unit that sets an acquisition cycle in which the acquisition unit acquires a current value to a value based on the vibration cycle measured by the vibration cycle measurement unit.

  In this electric wire protection device, the current value acquisition unit acquires the current value flowing through the electric wire in the vehicle for each acquisition cycle, and the determination unit determines whether the current value acquired by the current value acquisition unit is greater than a predetermined threshold value. Determine. Based on the determination by the determination unit, the switch interposed in the electric wire is turned on or off. The vibration cycle measuring unit measures the vibration cycle of the vehicle. The acquisition cycle setting unit sets the acquisition cycle based on the vibration cycle of the vehicle. Therefore, in order to detect an overcurrent caused by a short circuit caused by the vibration of the vehicle, the acquisition cycle can also be set to a value corresponding to the vibration cycle of the vehicle. Therefore, it is not necessary to fix the acquisition cycle too short and increase the number of times the current value is acquired and determined.

  In the wire protection device according to the present invention, when the determination unit determines that the current value acquired by the current value acquisition unit is greater than a threshold value, the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle. It is characterized by being set to.

  In this electric wire protection device, when the current value acquired by the current value acquisition unit is larger than the threshold value, the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle. Therefore, once an overcurrent is detected, the current can be acquired from the next current value acquisition in the same phase every cycle as the phase in which the occurrence of the overcurrent is detected on the vibration cycle. Therefore, when the overcurrent is generated in the same cycle as the vehicle vibration cycle, the overcurrent can be detected a plurality of times.

  In the electric wire protection device according to the present invention, after the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle, the current value acquisition unit exceeds a predetermined number of times within a predetermined current value acquisition count. When the determination unit determines that the current value acquired by is greater than the threshold, the switch is turned off.

  In this wire protection device, after the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle, the current value acquired by the current value acquisition unit exceeds the predetermined number of times within the predetermined number of current value acquisition times. If the determination unit determines that the value is greater than the value, the switch is turned off. Therefore, it is possible to estimate whether the overcurrent detected once is transient or generated at the same period as the vehicle vibration period according to the determination condition. It is possible to protect the wire properly.

  In the wire protection device according to the present invention, after the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle, the determination that the current value acquired by the current value acquisition unit is greater than the threshold value. When the number of times determined by the unit does not exceed the predetermined number of times within the predetermined number of current value acquisition times, the acquisition cycle setting unit is a value based on the vibration cycle measured by the vibration cycle measurement unit. It is characterized by being set to.

  In this wire protection device, after the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle, the number of times that the determination unit determines that the current value acquired by the current value acquisition unit is greater than the threshold is set. If the predetermined number of times is not exceeded within the predetermined number of subsequent current value acquisitions, the acquisition cycle setting unit sets the acquisition cycle to a value based on the vibration cycle measured by the vibration cycle measurement unit. Therefore, when it is estimated that the overcurrent detected once is transient, it is not necessary to turn off the switch, and the state returns to the state of continuously monitoring the abnormality of the current value.

  According to the present invention, it is possible to detect an overcurrent caused by a short circuit of a wire that occurs at the same cycle as the vehicle vibration cycle, and when the overcurrent is detected, the power supply from the power source is cut off and the wire is protected. An electric wire protection device that can be used can be realized.

It is a block diagram showing a schematic structure of an embodiment of an electric wire protection device concerning the present invention. It is a flowchart which shows operation | movement of embodiment of the electric wire protection apparatus which concerns on this invention. It is a flowchart which shows operation | movement of embodiment of the electric wire protection apparatus which concerns on this invention. It is a timing chart showing the relation between the generation timing of pulsed overcurrent and the sampling timing. It is a timing chart showing the relation between the generation timing of pulsed overcurrent and the sampling timing. It is a timing chart showing the relation between the generation timing of pulsed overcurrent and the sampling timing. It is a timing chart showing the relation between the generation timing of pulsed overcurrent and the sampling timing.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an electric wire protection device according to the present invention.
This electric wire protection device is provided in the middle of an electric wire 15 that supplies electric power from a power source 1 such as an in-vehicle battery or an in-vehicle generator to a load 2 such as a vehicle air conditioner and a door power window.

  In FIG. 1, 3 is a body ECU (Electronic Control Unit) that controls the load 2. Reference numerals 4, 5, and 6 denote a power supply IC, a microcomputer, and an IPD (Intelligent Power Device) provided in the body ECU 3, respectively. An engine ECU 13 is connected to the microcomputer 5 via a CAN (Controller Area Network) bus 12. The environmental temperature sensor 14 is also connected to the microcomputer 5.

The power supply IC 4 steps down the voltage supplied from the power supply 1 to a control voltage value and supplies it to the body ECU 3.
The microcomputer 5 includes an A / D conversion unit 7, a CPU (Central Processing Unit) 8 having a cache memory, a storage unit 9, a timer 10, and an input interface (hereinafter referred to as input I / F) 11. As will be described in detail below, the microcomputer 5 calculates the temperature of the electric wire 15 and controls the energization of the electric wire 15.

  The IPD 6 is interposed in the electric wire 15 connecting the power source 1 and the load 2, and internally measures the switch 6 a that is controlled to be turned on or off by the microcomputer 5 and the current value flowing through the electric wire 15 to measure the A / D. A current sensor 6b that outputs to the converter 7 is provided.

  An engine rotation sensor (not shown) is connected to the engine ECU 13. The engine ECU 13 measures the rotation period of the engine based on a signal input from the engine rotation sensor. The engine ECU 13 outputs the measured engine rotation cycle to the input I / F 11 of the microcomputer 5 through the CAN bus 12. The environmental temperature sensor 14 measures the temperature near the electric wire 15 and outputs it to the A / D conversion unit 7.

  The A / D conversion unit 7 performs A / D conversion on the signal related to the current value input from the current sensor 6b and the signal related to the temperature value input from the environmental temperature sensor 14 based on the signal from the CPU 8, and the CPU 8 Obtains the converted current value and temperature value. In particular, A / D conversion of a signal related to a current value is performed at a sampling period (“acquisition period” described in claims) determined by a method described later. Therefore, the current sensor 6b, the A / D conversion unit 7 and the CPU 8 constitute a “current value acquisition unit” described in the claims.

  The storage unit 9 stores programs and data related to the operation of the CPU 8. The CPU 8 accesses the storage unit 9 as necessary, reads the program and data into the cache memory, or writes the data to the storage unit 9. The program is, for example, a calculation program for obtaining an estimated wire temperature, and the data is, for example, a wire temperature threshold value and a current threshold value.

The CPU 8 controls various in-vehicle devices including the IPD 6 according to instructions in the program read from the storage unit 9. Among the arithmetic processes performed by the CPU 8, there is a process for determining whether or not the acquired current value is larger than a predetermined threshold value. Therefore, the CPU 8 functions as a “determination unit” described in the claims.
The CPU 8 sets the engine rotation cycle input from the engine ECU 13 via the input I / F 11 as the vehicle vibration cycle. Therefore, the CPU 8, the engine ECU 13, and the engine rotation sensor connected to the engine ECU 13 constitute the “vibration period measuring unit” described in the claims.
Further, the CPU 8 performs A / D conversion of the signal related to the current value based on the result of determining whether or not the acquired current value is larger than the predetermined threshold and the calculated vibration cycle. Set the sampling period. Therefore, the CPU 8 also functions as an “acquisition period setting unit” described in the claims.

  The timer 10 measures time. The CPU 8 outputs a measurement time interval and a measurement start signal to the timer 10. The timer 10 determines whether or not the elapsed time from the start of measurement has reached the time interval transmitted from the CPU 8, and transmits an interrupt signal to the CPU 8 when determining that it has reached. The timer 10 has a plurality of channels for inputting / outputting signals related to the measurement time, and can independently input a measurement time interval and a measurement start signal, make a determination, and output an interrupt signal. In response to the interrupt signal, the CPU 8 outputs a signal instructing the A / D converter 7 to perform A / D conversion of the signal related to the current value output from the current sensor 6b. Alternatively, the engine rotation period is acquired from the engine ECU 13 via the input I / F 11 and set as the vibration period of the vehicle.

  The CPU 8 obtains the A / D converted current value and the environmental temperature value, substitutes them into a predetermined calculation formula read from the storage unit 9, and calculates the estimated electric wire temperature. Based on the calculation result, the CPU 8 determines whether or not to transmit a switch-off signal to the switch 6a. Details of the calculation formula are described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-133830, and thus description thereof is omitted.

  Each time the CPU 8 acquires the A / D converted current value, the CPU 8 compares the current value with a predetermined threshold value. When it is determined that the acquired current value is continuously larger than the threshold value by the process described later, a switch-off signal is transmitted to the switch 6a regardless of the estimated temperature value.

  FIG.2 and FIG.3 is a flowchart which shows operation | movement of embodiment of the electric wire protection apparatus based on this invention. Below, the example of operation | movement of this electric wire protection apparatus is demonstrated, referring FIG.2 and FIG.3.

  First, the CPU 8 acquires the engine rotation cycle output by the engine ECU 13 and sets the rotation cycle as the vehicle vibration cycle T (step S1). Next, the CPU 8 outputs a signal for resetting the first elapsed time t1 to the timer 10 (step S2). t1 is reset whenever the CPU 8 newly sets the vibration period T. t1 is the time measured by the timer 10 after the reset.

  Subsequently, the CPU 8 substitutes 0 for the count variable C (step S3). C is stored in, for example, a cache memory or the storage unit 9. Next, the CPU 8 substitutes a value T + ΔT obtained by adding ΔT to the vehicle vibration period T set in step S1 into the sampling period Ts (step S4). Here, ΔT is a time width equal to or smaller than the pulse width of the periodic overcurrent determined from the electrical characteristics of the in-vehicle device. The value of Ts is output from the CPU 8 to the timer 10 and written in, for example, a register of the timer 10.

4 and 5 are timing charts showing the relationship between the generation timing of the pulsed overcurrent and the sampling timing. The horizontal axis represents time, the vertical axis represents current, and the vertical arrow represents sampling timing.
As shown in FIG. 4, if a pulsed overcurrent is periodically generated in the same period as the vehicle vibration period T, if T is substituted for Ts in step S4, the excess current is detected for each vibration period. Since there is always a constant phase difference between the current generation timing and the sampling (A / D conversion) timing, an overcurrent cannot be detected. Therefore, as shown in FIG. 5, in the embodiment according to the present invention, by substituting T + ΔT for Ts in step S4, the phase difference between the overcurrent generation timing and the sampling timing is calculated every time one vibration period elapses. It changes by ΔT and overcurrent can be detected after several cycles. For example, when T is 10 ms and the pulse width of the overcurrent is 1 ms or more, ΔT is 1 ms, and the sampling period Ts is 11 ms of T + ΔT. In this case, an overcurrent can be detected once within at most 10 cycles.

  After step S4, the CPU 8 outputs a signal for resetting the second elapsed time t2 to the timer 10 (step S5). t2 is reset each time the A / D converter 7 performs A / D conversion on the signal related to the current value. t2 is the time measured by the timer 10 after the reset. The timer 10 counts up time (step S6). The timer 10 determines whether t2 is equal to or greater than Ts (step S7). When it is determined that it is not Ts or more (S7: NO), steps S6 and S7 are repeated until it is determined that Ts or more.

  When it is determined that the elapsed time t2 is equal to or greater than Ts (S7: YES), the timer 10 determines whether t1 is equal to or greater than Te (step S8). Here, Te is a period in which the CPU 8 acquires the engine rotation period from the engine ECU 13 and sets it as the vibration period T. Te is a value sufficiently larger than the range of values that the vibration period T can take.

  When the timer 10 determines that t1 is equal to or greater than Te (S8: YES), the process returns to step S1. When the timer 10 determines that t1 is not equal to or greater than Te (S8: NO), the CPU 8 transmits a signal to the A / D conversion unit 7, and the A / D conversion unit 7 sets the current value measured by the current sensor 6b. The signal is A / D converted. CPU8 acquires electric current value I from A / D conversion part 7 (Step S9).

  The CPU 8 determines whether or not the acquired current value I is greater than a predetermined threshold It (step S10). If the CPU 8 determines that I is not greater than It (S10: NO), the process returns to step S3.

FIG. 6 is a timing chart showing the relationship between the generation timing of the pulsed overcurrent and the sampling timing. The horizontal axis represents time, the vertical axis represents current, and the vertical arrow represents sampling timing.
As shown in FIG. 6, when the CPU 8 determines that I is greater than It (S10: YES), it substitutes T for the sampling period Ts (step S11). Here, when an overcurrent is detected even once, the next sampling is performed every T seconds by substituting T for Ts. Therefore, when the overcurrent is periodically generated in the oscillation period T, Overcurrent can be detected at every sampling. In other words, if an overcurrent is detected continuously after substituting T for Ts in step S11, it can be estimated that the overcurrent is generated in the vibration period T.

  After step S11, the CPU 8 increments C (step S12). Subsequently, the CPU 8 determines whether or not C is larger than a predetermined threshold value Ct (step S13). If the CPU 8 determines that C is not greater than Ct (S13: NO), the process returns to step S5.

  If the CPU 8 determines that C is greater than Ct (S13: YES), it can be estimated that an overcurrent has occurred in the same cycle as the vibration cycle T, and therefore the CPU 8 transmits a switch-off signal to the switch 6a. 6a interrupts energization of electric wire 15 (Step S14), and finishes all the processes.

FIG. 7 is a timing chart showing the relationship between the generation timing of the pulsed overcurrent and the sampling timing. The horizontal axis represents time, the vertical axis represents current, and the vertical arrow represents sampling timing.
After detecting an overcurrent once and substituting T for Ts in step S11, the process is returned from step S13, and step S13 is repeated several times until it is determined that C is greater than Ct. If it is determined in S10 that I is not greater than It, the overcurrent has not been detected continuously for a predetermined number of times or more, so the first overcurrent detected is a transient one that is unrelated to the vibration of the vehicle. Can be estimated. Therefore, as shown in FIG. 7, by returning the processing to step S3, T + ΔT is substituted for Ts, and the state where the occurrence of overcurrent can be monitored again is returned.

  In parallel with performing the above processing, the CPU 8 calculates the estimated wire temperature based on the measured current value and the environmental temperature every time the current value is measured, and based on the calculation result, the switch 6a. Whether or not to send a switch-off signal is determined.

  Even if a periodic overcurrent synchronized with the vibration of the vehicle is generated in the electric wire 15 by the above configuration and processing, the overcurrent is detected without imposing an excessive load on the microcomputer 5, and the electric wire 15 appropriately. Can be cut off and the electric wire 15 can be protected.

  Further, with the above configuration and processing, when a pulsed overcurrent is generated at the same cycle as the vibration of the vehicle, the overcurrent can be detected continuously every sampling.

  Furthermore, when an overcurrent is detected continuously, a switch-off signal can be transmitted to the switch 6a to appropriately protect the electric wire 15. In addition, when no overcurrent is detected continuously, overcurrent monitoring can be continued again.

  In the above-described embodiment, the engine rotation period output from the engine ECU 13 is set as the vehicle vibration period, but the present invention is not limited to this. For example, a vibration sensor that directly measures the vibration period of the vehicle may be provided. In this case, it is possible to detect a short circuit caused by vibrations caused by causes other than engine driving.

  In the above-described embodiment, the IPD 6 includes both the switch 6a and the current sensor 6b inside, but the present invention is not limited to this. For example, the switch and the current sensor may be provided separately.

  Furthermore, in the above-described embodiment, in step S3, the value of T + ΔT is substituted for the sampling period Ts. However, the present invention is not limited to this. For example, T−ΔT may be substituted for Ts. Even in this case, the same effect as that obtained when T + ΔT is substituted for Ts can be obtained.

  In addition, in the above-described embodiment, the CPU 8 instructs the A / D conversion unit 7 at the sampling timing, but the present invention is not limited to this. For example, the CPU 8 may give the sampling period Ts to the A / D conversion unit 7 and the A / D conversion unit 7 may autonomously sample based on this.

  In the above-described embodiment, the condition for turning off the switch is that once the sampling period Ts is changed from T + ΔT to T, the measured current value I is continuously greater than a predetermined number of times after a predetermined number of times. However, the present invention is not limited to this. For example, the switch may be turned off when it is determined that I is greater than It within a predetermined number of determinations, exceeding the predetermined number.

  Further, in the above-described embodiment, once the sampling period Ts is changed from T + ΔT to T, the number of times that the measured current value I is continuously determined to be greater than the predetermined threshold It has not reached the predetermined number. In this case, Ts is reset to T + ΔT, but the present invention is not limited to this. For example, Ts may be reset to T + ΔT when the number of times that I is determined to be greater than It does not exceed the predetermined number of times within a predetermined number of current value acquisitions.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Power supply 2 Load 3 Body ECU
4 Power supply IC
5 Microcomputer 6 IPD
6a switch 6b current sensor 7 A / D converter 8 CPU
9 Storage unit 10 Timer 11 Input I / F
12 CAN bus 13 Engine ECU
14 Environmental temperature sensor 15 Electric wire

Claims (4)

A current value acquisition unit that periodically acquires a current value flowing through the electric wire in the vehicle, a determination unit that determines whether the current value acquired by the current value acquisition unit is greater than a threshold value, and the electric wire. In the wire protection device comprising a switch that is turned on or off based on the determination result of the determination unit,
A vibration period measuring unit for measuring the vibration period of the vehicle;
An electric wire protection device comprising: an acquisition cycle setting unit that sets an acquisition cycle in which the current value acquisition unit acquires a current value to a value based on a vibration cycle measured by the vibration cycle measurement unit. When the determination unit determines that the current value acquired by the current value acquisition unit is greater than a threshold value,
The wire protection device according to claim 1, wherein the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle. After the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle, the current value acquired by the current value acquisition unit exceeds the predetermined value within a predetermined number of current value acquisition times. The wire protection device according to claim 2, wherein the switch is turned off when the determination unit determines that the value is large. The number of times the determination unit determines that the current value acquired by the current value acquisition unit is greater than the threshold after the acquisition cycle setting unit sets the acquisition cycle to the same value as the vibration cycle. If the predetermined number of times is not exceeded within the current value acquisition count, the acquisition cycle setting unit sets the acquisition cycle to a value based on the vibration cycle measured by the vibration cycle measurement unit. The electric wire protection device according to claim 3, wherein

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