JP2013207956A - Electric wire protection device and electric wire protection method - Google Patents

Abstract

An electric wire protection device capable of calculating the temperature of an electric wire with high accuracy and exhibiting the capability of the electric wire to the limit is provided.
A first control means 3 measures a voltage at one end of a protection target wire 14 and a second control means 22 through a communication means 12 to the other end of the protection target wire 14. The voltage is acquired, the potential difference between one end and the other end of the protection target wire 14 is calculated, the current flowing through the protection target wire 14 measured by the current measuring means (shunt resistor 5a, etc.), and the protection target The resistance value of the protection target wire 14 is calculated from the potential difference between one end and the other end of the wire 14, and the temperature of the protection target wire 14 is calculated from the resistance value of the protection target wire 14.
[Selection] Figure 1

Description

  The present invention relates to an electric wire protection device and an electric wire protection method, and more particularly, to an electric wire protection device and an electric wire protection method that can accurately calculate the temperature of an electric wire.

  2. Description of the Related Art Conventionally, in a circuit or the like mounted on an automobile, there is an apparatus that measures a current to be applied by installing a shunt resistor in series with an electric power supply wire and a load. In such a circuit, when an abnormal current flows, it is determined that the load is abnormal, and the load operation is stopped in order to protect the electric wire and avoid the fuse from being blown.

  For example, in Patent Document 1, a second shunt resistor having the same temperature coefficient is installed by branching from a shunt resistor installed in series with a load, and the two shunt resistors are arranged in the vicinity to be thermally coupled. It was. Then, by passing a small current through the second shunt resistor and comparing and adjusting the potential difference between the two shunt resistors, the temperature-corrected current is calculated and assumed without a temperature correction by a microcomputer or the like. When a current larger than the load current flows, the load is stopped as an abnormal current.

JP 2005-197104 A

  However, in the invention according to Patent Document 1, although the current flowing through the electric wire can be measured with high accuracy, there is a problem in that a breaking current for stopping the load must be set for each of a large number of loads mounted on the automobile. In addition, since only the current flowing through the electric wire is measured, there is a problem in that only a sufficient current is allowed to flow until the limit of the electric wire, and the capability of the electric wire cannot be fully exhibited.

  The present invention has been made in view of the above-described problems, and provides an electric wire protection device and an electric wire protection method capable of accurately calculating the temperature of an electric wire and exhibiting the capability of the electric wire to the limit. For the purpose.

  In order to achieve the above-described object, the first invention includes a protection target wire having a temperature-dependent resistance value, and first control means for measuring a voltage at one end of the protection target wire. Measuring the voltage at the other end of the wire to be protected, second control means connected by the first control means and communication means, and current measuring means for measuring the current flowing through the wire to be protected; The first control means obtains the voltage at the other end of the protection target wire from the second control means via the communication means, and one end of the protection target wire. A potential difference between the first end and the other end, and a current flowing through the protection target wire measured by the current measuring unit and a potential difference between one end and the other end of the protection target wire. The resistance value of the wire to be protected is calculated. A wire protection apparatus and calculates the temperature of the protected wire from the value.

  Moreover, you may make it comprise the electric current interruption means which interrupts | blocks the electric current which flows into the said protection object electric wire when the temperature of the said protection object electric wire becomes more than predetermined value.

  Moreover, you may make it comprise the voltage correction means which correct | amends the dispersion | variation in the voltage which the said 1st control means measures, and the voltage which the said 2nd control means measures.

  Further, a synchronization unit may be provided for correcting and synchronizing a time difference between the time when the first control unit measures the voltage and the time when the second control unit measures the voltage.

  Moreover, you may make it comprise the reference electric potential correction | amendment means which correct | amends the reference electric potential of the one edge part of the said protection object electric wire, and the other edge part. At this time, the reference potential correcting means includes a current flowing between a ground point that is a reference ground potential and a reference potential point at one end and the other end of the protection target wire, the ground point, and the ground point. Depending on the resistance value between the reference potential points at one end and the other end of the protection target wire, the potential difference between the ground point and the reference potential point at one end and the other end of the protection target wire is determined. It is desirable to calculate.

  Further, the current interrupting means interrupts the current flowing through the protection target wire when the potential difference between one end and the other end of the protection target wire becomes a predetermined value or more. Good.

  According to the first invention, the temperature of the protection target wire can be accurately calculated, and the capability of the protection target wire can be exhibited to the limit.

  In addition, when the temperature of the protection target wire exceeds a predetermined value, if the current blocking means for blocking the current flowing through the protection target wire is provided, the protection target wire may smoke or ignite. Can be reliably prevented.

  Further, if the voltage correction means for correcting the variation between the voltage measured by the first control means and the voltage measured by the second control means is provided, the temperature of the protection target electric wire can be calculated more accurately. it can.

  In addition, if the synchronizing means for correcting the shift between the time when the voltage is measured by the first control means and the time when the second control means is measuring the voltage is provided, The time lag of the current flowing through one end and the other end can be synchronized, and the temperature of the protection target wire can be calculated more accurately.

  Further, if the reference potential correcting means for correcting the reference potential of one end and the other end of the protection target electric wire is provided, the reference potentials of the one end and the other end of the protection target electric wire ( Even when the ground potential is deviated, the temperature of the wire to be protected can be calculated with high accuracy.

  Further, the reference potential correcting means is configured such that the current flowing between the ground point that is the reference ground potential and the reference potential point at one end and the other end of the protection target wire, and one of the ground point and the protection target wire. By calculating the potential difference between the ground potential and the reference potential point at one end of the protection target wire and the other end by the resistance value between the reference potential point at the other end and the other end, The deviation of the reference potential (ground potential) between the one end and the other end of the protection target wire can be calculated with higher accuracy.

  Further, if the current interrupting means interrupts the current flowing through the protection target wire when the potential difference between the one end and the other end of the protection target wire exceeds a predetermined value, the protection target wire It is possible to reliably prevent a dangerous state such as fire.

  According to a second aspect of the present invention, there is provided a protection target wire having a temperature-dependent resistance value, first control means for measuring a voltage at one end of the protection target wire, and the other end of the protection target wire. A wire protection device comprising: a second control means connected by the first control means and a communication means; and a current measurement means for measuring a current flowing through the protection target wire. In the electric wire protection method, the first control means acquires the voltage at the other end of the protection target wire from the second control means via the communication means, and A potential difference calculating step for calculating a potential difference between one end and the other end; a current flowing through the protection target wire measured by the current measuring means; and one end and the other end of the protection target wire Resistance of the wire to be protected The resistance value calculating step of calculating a value, and temperature calculation step of calculating the temperature of the protected wire from the resistance value of the protected wire, a wire protection method, which comprises a.

  According to the second invention, the temperature of the protection target wire can be accurately calculated, and the capability of the protection target wire can be exhibited to the limit.

  According to the present invention, it is possible to provide an electric wire protection device and an electric wire protection method capable of calculating the temperature of an electric wire to be protected with high accuracy and capable of exhibiting the capability of the electric wire to be protected to the limit.

It is a figure which shows the structural example of an electric wire protection apparatus. It is a flowchart which shows the flow in which a 1st control part calculates the temperature of a protection object electric wire. It is a functional block diagram which shows the function of a 1st control part. It is a figure which shows the method in which a reference electric potential correction | amendment part correct | amends the reference electric potential of one edge part and the other edge part of a protection object electric wire.

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

  FIG. 1 is a diagram illustrating a configuration example of an electric wire protection device 1 according to an embodiment of the present invention.

  1 includes a first control unit 3, a switching element 4a, 4b, a controller 2 having shunt resistors 5a, 5b, an ECU (Electronic Control Unit) 20 having a second control unit 22, ECU 21 having two control units 23, protection target wires 14 and 15, communication means 12 for connecting the first control unit 3 and the second control units 22 and 23, and the like. An electric wire protection device 1 shown in FIG. 1 is mounted on, for example, an automobile, and controls driving of a load such as an engine and functions as an electric wire protection device.

  The controller 2 and the ECU 20 are connected by a protection target wire 14, and the controller 2 and the ECU 21 are connected by a protection target wire 15. The controller 2 is supplied with a drive voltage Vb from a drive power supply (not shown in FIG. 1).

  The drive voltage Vb is supplied to the ECU 20 via the switching element 4a of the controller 2, the shunt resistor 5a, and the protection target wire 14. The drive voltage Vb is supplied to the ECU 21 via the switching element 4b, the shunt resistor 5b, and the protection target wire 15 of the controller 2.

The first control unit 3 is a CPU (Central
Processing Unit), ROM (Read Only
Memory), RAM (Random Access)
And a gate voltage of switching elements 4a and 4b such as MOS-FETs. Thereby, the voltage etc. supplied to ECU20, 21 from a drive power supply are controlled. Moreover, the 1st control part 3 calculates the temperature of the protection target electric wires 14 and 15 as mentioned later.

  The shunt resistor 5a is connected to an A / D converter 10a built in the first control unit 3, and the first control unit 3 generates a current I1 flowing through the protection target wire 14 by the A / D converter 10a. taking measurement. The shunt resistor 5b is connected to an A / D converter 10b built in the first control unit 3, and the first control unit 3 has a current flowing through the protection target wire 15 by the A / D converter 10b. I2 is measured. The currents I1 and I2 flowing through the protection target wires 14 and 15 are measured by using the ON resistance of the switching elements 4a and 4b (resistance when the switching element is ON) and the source of the switching element instead of the shunt resistors 5a and 5b. -You may measure from the voltage between drains.

  In addition, an A / D converter 11a built in the first control unit 3 is connected to an end portion where the protection target wire 14 is connected to the controller 2, and the first control unit 3 is connected to the A / D converter 11a. The voltage V at the end where the protection target wire 14 is connected to the controller 2 is measured by the D converter 11a. Further, an A / D converter 11b built in the first control unit 3 is connected to an end portion where the protection target electric wire 15 is connected to the controller 2, and the first control unit 3 is connected to the A / D converter 11b. The voltage V at the end where the protection target wire 15 is connected to the controller 2 is measured by the D converter 11b.

  Similarly to the first control unit 3, the second control units 22 and 23 are computer systems each including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. , 21 are controlled. The second control unit 22 includes an A / D converter 24a, and measures the voltage V1 at the end where the protection target wire 14 is connected to the ECU 20 by the A / D converter 24a. Moreover, the 2nd control part 23 incorporates the A / D converter 24b, and measures the voltage V2 of the edge part to which the protection target electric wire 15 is connected to ECU21 by the A / D converter 24b.

  FIG. 2 is a flowchart illustrating a flow in which the first control unit 3 calculates the temperature of the protection target wire 14. 2 shows a procedure in which the first control unit 3 calculates the temperature of the protection target wire 14, but the temperature of the protection target wire 15 is calculated in the same manner. Further, the number of ECUs, wires to be protected, etc. is arbitrary.

  First, the 1st control part 3 measures the voltage V of the edge part (henceforth one edge part) by which the protection object electric wire 14 is connected to the controller 2 by A / D converter 11a (S1).

  Next, the first control unit 3 uses the voltage V1 at the end (hereinafter referred to as the other end) where the protection target wire 14 measured by the second control unit 22 is connected to the ECU 20 as the communication unit 12. (S2). In addition, although the communication means 12 should just use the voltage of the other edge part of the protection object electric wire 14, it is desirable to acquire with a multiplex communication means. Examples of multiplex communication means include LIN, CAN, Flexray, UART and the like. Further, as will be described later, it is desirable to synchronize the voltage at one end of the protection target wire 14 and the voltage at the other end because a time lag occurs during measurement.

  Then, the first control unit 3 calculates a potential difference between one end and the other end of the protection target wire 14 (S3). Note that the potential difference between one end and the other end of the protection target wire 14 is represented by (V−V1).

Then, the first control unit 3 determines the protection target wire from the current I1 flowing through the protection target wire 14 measured by the A / D converter 10a and the potential difference between one end and the other end of the protection target wire 14. The resistance value R1 of 14 is calculated (S4). The resistance value R1 of the protection target wire 14 is given by the following formula (1).
R1 = (V−V1) / I1 (1)

  Then, the first control unit 3 calculates the temperature of the protection target wire 14 from the resistance value R1 of the protection target wire 14 calculated in S4 (S5). The protection target wire 14 of the present embodiment is made of copper, for example, and has a temperature-dependent resistance value. The conductor resistance value of copper has temperature dependency, and the temperature coefficient α is expressed as α = 0.4% / ° C. Further, assuming that the protection target wire 14 is made of copper of 0.5 sq (square millimeter), it has a resistance value of 37.1 mΩ / m at 20 ° C. and a resistance value of 15 ° C. at 35 ° C. Will be added.

Moreover, since the cross-sectional area and length of the protection target wire 14 are known, the temperature of the protection target wire 14 can be calculated from the resistance value R1 of the protection target wire 14 calculated in S4. In addition, resistance value Rt of the electric wire 14 to be protected at a temperature of t ° C. is expressed by the following formula (2).
Rt = R20 × (1 + α × (t−20)) (2)
In addition, in Formula (2), R20 is the resistance value of the electric wire 14 to be protected at 20 ° C. Using the above equation (2), the temperature of the protection target wire 14 can be obtained. Similarly, the temperature of the protection target wire 15 is calculated in the same manner. In this case, the voltage V ′ at the end (hereinafter referred to as one end) where the protection target wire 15 is connected to the controller 2 is measured, and the resistance value R2 of the protection target wire 15 is
R2 = (V′−V2) / I2 (1 ′)
As long as you ask.

  FIG. 3 is a functional block diagram showing functions of the first control unit 3. In FIG. 3, all the configuration requirements shown in FIG. 3 are provided in the first control unit 1. However, some configuration requirements may be provided in the second control unit 22 and the like. Good. Also in FIG. 3, the protection target wire 14 will be described as an example.

  As shown in FIG. 3, the first control unit 3 includes a temperature calculation unit 31, a current interrupting unit 32, a voltage correction unit 33, a synchronization unit 34, a reference potential correction unit 35, and the like.

  As shown in FIG. 2, the temperature calculation unit 31 calculates the temperature of the protection target wire 14.

  The current interrupting unit 32 interrupts the current flowing through the protection target wire 14 when the temperature of the protection target wire 14 calculated by the temperature calculation unit 31 exceeds a predetermined value. For example, when the clothing of the protection target wire 14 emits smoke at 80 ° C., the current flowing through the protection target wire 14 is interrupted immediately before the protection target wire 14 reaches 80 ° C.

  The current interrupting unit 32 also interrupts the current flowing through the protection target wire 14 even when the potential difference between the one end and the other end of the protection target wire 14 becomes a predetermined value or more. If there is a voltage drop more than expected at one end and the other end of the protection target wire 14, the current is cut off before calculating the temperature of the protection target wire 14. This is to prevent a dangerous state such as fire.

  The voltage correction unit 33 is configured to measure the voltage measured by the first control unit 3 (voltage at one end of the protection target wire 14) and the voltage measured by the second control unit 22 (the other end of the protection target wire 14). Variation in voltage) is corrected. For example, in order to correct variations in voltage due to the length, cross-sectional area, device, etc. of the protection target wire 14, a constant current is passed through the protection target wire 14 at a constant environmental temperature, and the first control means 3 measures at that time. The voltage correction unit 33 stores the measured voltage and the voltage measured by the second control unit 22. The voltage correction unit 33 corrects variations in the voltage measured by the first control unit 3 and the voltage measured by the second control unit 22 using the voltage at that time.

  The synchronization unit 34 corrects a difference between the time when the first control unit 3 measures the voltage and the time when the second control unit 22 measures the voltage, and synchronizes. This is to correct a time lag until the current flowing through the protection target wire 14 reaches from one end to the other end. For example, the synchronization unit 34 acquires the voltage measured by the second control unit 22 via the communication unit 12 when the first control unit 3 is delayed by a predetermined number of bits from the time when the voltage is measured, and performs synchronization. take. Then, the temperature calculation unit 33 calculates a potential difference between one end and the other end of the protection target wire 14 from the synchronized voltage.

  The reference potential correction unit 35 corrects the reference potential (ground potential) at one end and the other end of the protection target wire 14. This is because the reference ground potential may be shifted depending on the magnitude of the flowing current depending on the location of the ECU 20 or the like to which power is supplied.

  FIG. 4 is a diagram illustrating a method in which the reference potential correction unit 35 corrects the reference potential at one end and the other end of the protection target wire 15. In FIG. 5, the protection target wire 15 will be described as an example.

  The reference potential correction unit 35 includes the ground point 50 that is the reference ground potential Gs, the current Ia flowing through the reference potential point (ground) 51 at one end of the protection target wire 15, the ground point 50, and the protection target wire 15. A potential difference between the ground point 50 and the reference potential point 51 at one end of the protection target electric wire 15 is calculated from the resistance value Ra between the reference potential points 51 at one end of the wire. In FIG. 4, the potential at the reference potential point 51 is Ga. Further, the negative side of the drive power supply 40 is connected to the ground point 50.

  In addition, the reference potential correction unit 35 includes a ground point 50 that is the reference ground potential Gs, a current Ib that flows through the reference potential point (ground) 52 at the other end of the protection target wire 15, a ground point 50, and a protection target. A potential difference between the ground point 50 and the reference potential point 52 at the other end of the protection target wire 15 is calculated from the resistance value Rb between the reference potential points 52 at the other end of the wire 15. In FIG. 4, the potential of the reference potential point 52 is Gb.

  In the present embodiment, since the load operating by the first control unit 3 or the like is known, the location where the currents Ia and Ib flow can be specified. The current values of the currents Ia and Ib take known values for each operating load. Furthermore, since the resistance values Ra and Rb are also known, the potential difference between the reference ground potential Gs and the reference potentials Ga and Gb can be calculated. As a result, the difference between the reference potential Ga and the reference potential Gb can be understood, and the reference potential at one end and the other end of the protection target wire 15 can be corrected.

  As described above, according to the wire protection device 1 according to the embodiment of the present invention, the resistance value of the protection target wires 14 and 15 is calculated from the potential difference between one end of the protection target wires 14 and 15 and the other end, Since the temperature of the protection target wires 14 and 15 is calculated from the resistance value of the protection target wires 14 and 15, the temperature of the protection target wires 14 and 15 can be accurately calculated, and the capability of the protection target wires 14 and 15 is limited. Can be demonstrated. In addition, since the current can flow up to the limit of the protection target wires 14 and 15, the protection target wires 14 and 15 can be reduced in diameter. Furthermore, in the wire protection device 1 according to the embodiment of the present invention, since the actual temperatures of the protection target wires 14 and 15 are calculated, when the protection target wires 14 and 15 have an external thermal influence, It can be used up to a temperature closer to the limit of the wires to be protected 14 and 15 than the method in which the current is cut off only.

  While the preferred embodiments of the wire protection device and the wire protection method according to the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present invention. Understood.

DESCRIPTION OF SYMBOLS 1 ......... Wire protection device 2 ......... Controller 3 ......... 1st control part 4a, 4b ......... Switching element 5a, 5b ......... Shunt resistance 10a, 10b ......... A / D converter 11a, 11b ......... A / D converter 12 ......... Communication means 14, 15 ......... Protected wire 20, 21 ......... ECU
22, 23 ......... Second control unit 24a, 24b ......... A / D converter 31 ......... Temperature calculation unit 32 ......... Current cut-off unit 33 ......... Voltage correction unit 34 ......... Synchronization unit 35 ……… Reference potential correction unit

Claims (8)

A protected wire with a temperature-dependent resistance value;
First control means for measuring a voltage at one end of the protection target wire;
Measuring the voltage at the other end of the wire to be protected, second control means connected by the first control means and communication means;
Current measuring means for measuring a current flowing through the protection target wire;
Comprising
The first control means acquires the voltage at the other end of the protection target wire from the second control means via the communication means, and the one end and the other end of the protection target wire. And calculating the resistance value of the protection target wire from the current flowing through the protection target wire measured by the current measuring means and the potential difference between one end and the other end of the protection target wire. And the temperature of the said protection object electric wire is computed from the resistance value of the said protection object electric wire, The electric wire protection apparatus characterized by the above-mentioned.   The electric wire protection device according to claim 1, further comprising a current interrupting unit configured to interrupt a current flowing through the protection target electric wire when a temperature of the protection target electric wire becomes equal to or higher than a predetermined value.   The wire protection device according to claim 1 or 2, further comprising a voltage correction unit that corrects a variation between the voltage measured by the first control unit and the voltage measured by the second control unit. .   2. The apparatus according to claim 1, further comprising synchronization means for correcting and synchronizing a time difference between the time when the first control means measures the voltage and the time when the second control means measures the voltage. The electric wire protection device according to claim 3.   The electric wire protection apparatus according to any one of claims 1 to 4, further comprising a reference potential correcting unit that corrects a reference potential of one end and the other end of the electric wire to be protected.   The reference potential correcting means includes a current flowing between a ground point that is a reference ground potential and a reference potential point at one end and the other end of the wire to be protected, and the ground point and the wire to be protected. And calculating a potential difference between the grounding point and the reference potential point at one end and the other end of the protection target wire based on the resistance value between the reference potential point at one end and the other end of the wire. The electric wire protection device according to claim 5.   The current interrupting means interrupts a current flowing through the protection target electric wire when a potential difference between one end and the other end of the protection target electric wire becomes a predetermined value or more. Item 3. The wire protection device according to Item 2. A protected wire with a temperature-dependent resistance value;
First control means for measuring a voltage at one end of the protection target wire;
Measuring the voltage at the other end of the wire to be protected, second control means connected by the first control means and communication means;
Current measuring means for measuring a current flowing through the protection target wire;
An electric wire protection method performed by an electric wire protection device comprising:
The first control means acquires the voltage at the other end of the protection target wire from the second control means via the communication means, and the one end and the other end of the protection target wire. A potential difference calculating step for calculating a potential difference of the part;
A resistance value calculating step of calculating a resistance value of the protection target wire from a current flowing through the protection target wire measured by the current measuring unit and a potential difference between one end and the other end of the protection target wire;
A temperature calculating step for calculating the temperature of the protection target wire from the resistance value of the protection target wire;
An electric wire protection method comprising:

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