JP2015057017A - Control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device that can suppress a degradation of a wire due to a temperature rise in the event of an overcurrent state.SOLUTION: A CPU 63 of a microcomputer 6 of a control device 1 controls on/off a FET 51 of an IPD 5 for providing connection/interruption between a battery 2 and a load 3 via a control section 53. A current detection section 52 of the IPD 5 detects a current through a wire 4. The CPU 63 calculates a temperature of the wire 4 on the basis of the detected current, and if determining that the calculated temperature is equal to or higher than a second threshold, controls on/off the FET 51 so as to supply a pulse voltage to the load 3. The CPU 63 controls off the FET 51 if determining that the calculated temperature is equal to or higher than a first threshold higher than the second threshold.

Description

  The present invention relates to a control device that calculates an electric wire temperature and interrupts an electric current flowing through the electric wire when the calculated electric wire temperature is equal to or higher than a threshold value.

  When a current flows through a wire of a harness that connects a large number of electric devices mounted on a vehicle, the wire generates Joule heat. Even if the current flowing through the electric wire is an overcurrent having a current value that does not need to be interrupted immediately, the Joule heat generated by the current flowing through the electric wire may exceed the heat radiation amount of the electric wire. When Joule heat generated from the electric wire exceeds the heat radiation amount of the electric wire, the electric wire temperature rises. When the wire temperature exceeds a certain temperature, the wire is ignited.

  Patent Document 1 discloses a control device that can prevent the ignition of such electric wires. This control device detects the current flowing through the electric wire, and repeatedly calculates the temperature difference (rising temperature) between the ambient temperature of the electric wire and the electric wire temperature over time. The control device described in Patent Document 1 calculates the rising temperature using the detected current value and the previously calculated rising temperature, and the temperature obtained by adding the calculated rising temperature to the ambient temperature, that is, the calculated wire temperature is predetermined. When the temperature is higher than the temperature, the current flowing in the wire is cut off. By interrupting the current flowing through the electric wire before the electric wire ignites as described above, the electric wire is prevented from igniting.

Japanese Patent No. 4624400

  In the control device described in Patent Document 1, when an overcurrent occurs, the overcurrent continues to flow until the current is interrupted, so that there is a problem that the temperature rises and the electric wire deteriorates.

FIG. 5A is a graph showing the relationship between the temperature of the electric wire and the elapsed time, and FIG. 5B is a graph showing the relationship between the energization current of the load and the elapsed time.
Assume that an overcurrent occurs at time t ₁ . Until time t ₁ , the energization current is I ₀ , the wire temperature is saturated at T ₀ , and no smoke is generated.
If overcurrent t ₁ occurs, energizing current increases from I ₀ to I _1. Accordingly, the electric wire temperature rises, when it reaches the threshold temperature T ₂ of the cut-off at time t _2, power supply to the load is interrupted. Since the calculated temperature energization of the load until it reaches T ₂ is continued, the actual electric wire temperature has risen up to T _2, so that the deterioration of the electric wire as described above.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a control device that can suppress deterioration of an electric wire due to a temperature rise when an overcurrent state occurs.

  The control device according to the first aspect of the invention controls on / off of a switch provided between a power source and a load, detects a current flowing from the power source to the load by a detecting unit, and calculates based on the detected current In the control device configured to calculate the temperature of the electric wire connecting the power source, the switch, and the load, and to turn off the switch when the calculated temperature exceeds a first threshold, the calculation Means for determining whether or not the temperature calculated by the means is equal to or higher than a second threshold lower than the first threshold; and when the means determines that the temperature is equal to or higher than the second threshold, the load is pulsed And a means for controlling on / off of the switch so that a voltage is supplied.

  In the present invention, when an overcurrent occurs and the wire temperature rises and reaches the second threshold value, the switch is on / off controlled so that the pulse voltage is supplied to the load. Since the wire temperature is calculated using the current value when the switch is turned on, the energization to the load is interrupted when the calculated wire temperature reaches the first threshold value. Although the timing at which the energization is interrupted is not different from the conventional one, the actual degree of increase in the wire temperature is kept small because the effective current is reduced by the on / off control. Therefore, the actual electric wire temperature at the time of interruption | blocking is lower than a 1st threshold value, and deterioration of the electric wire accompanying a temperature rise is suppressed.

  The control device according to a second aspect of the present invention is the control device according to the first aspect, wherein the switch is turned on / off, and the temperature of the electric wire calculated by the calculation means exceeds the first threshold value and the switch is turned off. A means for determining whether or not the temperature calculated by the calculating means is equal to or lower than a third threshold lower than the second threshold; and when the means determines that the temperature is equal to or lower than the third threshold, And a means for releasing the off control.

  In the present invention, when the calculated electric wire temperature exceeds the first threshold value and the energization is interrupted, the on-control is released when the calculated electric wire temperature decreases and becomes the third threshold value or less. That is, when energization is interrupted, monitoring is performed until the wire temperature is reliably reduced.

In the control device according to a third aspect of the present invention, in the first or second aspect, the calculating means calculates the temperature of the electric wire by adding the rising temperature of the electric wire to the ambient temperature of the electric wire, and the rising temperature is It is comprised so that it may calculate based on following formula (1), It is characterized by the above-mentioned.
ΔTw (n) = ΔTw (n−1) × exp (−Δt / τw)
+ Rthw * Rw (n-1) * I (n-1) ² * (1-exp (-[Delta] t / [tau] w)) (1)
However, I (n): detection n (an integer of 1 or more) detection energization current value (A)
ΔTw (n): Temperature rise of wire when detecting n times (℃)
Rw (n) = Rw (0) × (1 + κw × (Tw−To)): Wire resistance at detection n times (Ω)
Rw (0): Wire resistance (Ω) at a predetermined temperature To (° C)
Rthw: Electric wire thermal resistance (° C / W)
τw: Heat dissipation time constant (s)
κw: Wire resistance temperature coefficient (/ ° C)
Δt: Calculation interval (s) of the calculation means

  In the present invention, the temperature of the electric wire is calculated more accurately.

  According to the present invention, when an overcurrent occurs and the wire temperature rises and reaches a second threshold value that is lower than the first threshold value for interrupting energization, the switch is turned on so that a pulse voltage is supplied to the load. Control off / on. Therefore, when the calculated wire temperature reaches the first threshold and the energization to the load is interrupted, the actual temperature rise of the wire is kept low, and the thermal degradation of the wire due to the temperature rise is suppressed.

It is a block diagram which shows the structure of the control apparatus which concerns on embodiment of this invention. FIG. 2A is a graph showing the relationship between the temperature of the electric wire and the elapsed time, and FIG. It is a flowchart which shows the procedure of the process which CPU performs. It is a flowchart which shows the procedure of the process which CPU performs. FIG. 5A is a graph showing the relationship between the temperature of the electric wire and the elapsed time, and FIG. 5B is a graph showing the relationship between the energization current of the load and the elapsed time.

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 configuration of a control device 1 according to the embodiment of the present invention. The control device 1 is preferably mounted on a vehicle and connected by a wire 4 between the positive terminal of the battery 2 and one end of the load 3. Examples of the load 3 include a lamp and a wiper. The negative terminal of the battery 2 and the other end of the load 3 are grounded. The control device 1 detects the current value flowing through the electric wire 4 and the ambient temperature of the electric wire 4, and calculates the electric wire temperature of the electric wire 4 using the detected current value and the ambient temperature. Controller 1, when the calculated electric wire temperature is the first threshold value T ₂ or higher, interrupting the flow of current in the wire 4.

  The control device 1 includes an IPD (Intelligent Power Device) 5, a microcomputer 6, and a temperature detection unit 12. The IPD 5 is connected by a wire 4 between the positive terminal of the battery 2 and one end of the load 3, and further connected to the microcomputer 6. The temperature detection unit 12 is disposed in the vicinity of the electric wire 4 and is connected to the microcomputer 6. The microcomputer 6 is connected to the IPD 5 and the temperature detection unit 12.

The IPD 5 detects the current flowing through the electric wire 4 and outputs current information indicating the detected current value to the microcomputer 6 when receiving an instruction to output a current value from the microcomputer 6. A power supply instruction / interruption instruction (on instruction / off instruction) instructing power supply from the battery 2 to the load 3 or interruption of the power supply is input to the IPD 5 from the microcomputer 6. The IPD 5 performs power supply / cutoff from the battery 2 to the load 3 in accordance with the input ON instruction / OFF instruction.
The temperature detector 12 detects the ambient temperature of the electric wire 4 and outputs temperature information indicating the detected ambient temperature to the microcomputer 6.

  The microcomputer 6 obtains current information from the IPD 5 and outputs temperature information from the temperature detection unit 12 by outputting an output instruction to the IPD 5. The microcomputer 6 repeatedly calculates the wire temperature of the wire 4 over time using the current value and the temperature indicated by the current information and the temperature information acquired from the IPD 5 and the temperature detection unit 12, respectively.

The rising temperature of the electric wire 4 is calculated by the following formula (1).
ΔTw (n) = ΔTw (n−1) × exp (−Δt / τw)
+ Rthw * Rw (n-1) * I (n-1) ² * (1-exp (-[Delta] t / [tau] w)) (1)
However, I (n): detection n (an integer of 1 or more) detection energization current value (A)
ΔTw (n): Temperature rise of wire when detecting n times (℃)
Rw (n) = Rw (0) × (1 + κw × (Tw−To)): Wire resistance at detection n times (Ω)
Rw (0): Wire resistance (Ω) at a predetermined temperature To (° C)
Rthw: Electric wire thermal resistance (° C / W)
τw: Heat dissipation time constant (s)
κw: Wire resistance temperature coefficient (/ ° C)
Δt: Calculation interval (s) of the calculation means

The temperature of the electric wire 4 is calculated by the following formula (1).
Tw = ambient temperature + ΔTw (n) (2)

As will be described later, the microcomputer 6 outputs an on / off instruction to the IPD 5 to supply a pulse voltage to the load 3 when the calculated wire temperature exceeds the second threshold T ₃ , and calculates the calculated wire temperature. When the value exceeds the first threshold value T ₂ , an OFF instruction is output to interrupt the current flowing through the electric wire 4.

  The IPD 5 includes an N-channel FET (Field Effect Transistor) 51, a current detection unit 52, and a control circuit 53. Regarding the FET 51, the drain is connected to the positive terminal of the battery 2 by the electric wire 4, the source is connected to one end of the load 3 by the electric wire 4, and the gate is connected to the control circuit 53. The control circuit 53 is connected to the current detection unit 52 and the microcomputer 6 in addition to the gate of the FET 51.

The FET 51 functions as a switch. When a voltage higher than a predetermined voltage is applied to the gate, the current flows from the drain to the source and turns on. When the voltage applied to the gate is lower than the predetermined voltage, the current is drained. Turns off without flowing from source to source.
The current detection unit 52 detects the current value flowing through the electric wire 4 and outputs the detected current value to the control circuit 53. The current detection unit 52 functions as detection means.

  The control circuit 53 turns on / off the FET 51 by adjusting the voltage applied to the gate of the FET 51. Further, the control circuit 53 receives the output instruction or the on instruction / off instruction from the microcomputer 6. When receiving the output instruction, the control circuit 53 outputs current information indicating the current value detected by the current detection unit 52 to the microcomputer 6. When the control circuit 53 receives an on instruction / off instruction, the control circuit 53 turns on / off the FET 51 to supply / cut off the current flowing through the electric wire 4.

The microcomputer 6 includes an input unit 61, an output unit 62, a CPU 63, a storage unit 64, and a RAM 65, which are connected to a bus 66.
An operation instruction / stop instruction for instructing the operation or stop of the load 3 is input to the input unit 61 from the outside. Further, current information and temperature information are input to the input unit 61 from the control circuit 53 and the temperature detection unit 12 of the IPD 5, respectively. The input unit 61 sets the current value and ambient temperature indicated by the input current information and temperature information to the CPU 63. Notify The output unit 62 outputs the output instruction and the on instruction / off instruction to the control circuit 53 according to the instruction of the CPU 63.

  CPU63 loads the control program memorize | stored in the memory | storage part 64 to RAM65, and performs control of operation | movement of the output part 62, calculation of electric wire temperature, etc. by executing the loaded control program. The storage unit 64 is a nonvolatile memory, and the content stored in the storage unit 64 is read by the CPU 63. The RAM 65 is a memory that temporarily stores information, and the CPU 63 performs writing to the RAM 65 and reading from the RAM 65.

FIG. 2A is a graph showing the relationship between the temperature of the electric wire 4 and the elapsed time. The horizontal axis is the elapsed time (sec), and the vertical axis is the temperature (° C.). FIG. 2B is a graph showing the relationship between the energization current of the load 3 and the elapsed time, the horizontal axis is the elapsed time (sec), and the vertical axis is the current (A). In FIG. 2, t ₁ <t ₃ <t ₂ <t ₄ , T ₄ <T ₀ <T ₃ <T ₂ , and I ₀ <I ₁ .

Assume that an overcurrent occurs at time t ₁ when the CPU 63 turns on the FET 51 to supply power, the energizing current is I ₀ , and the wire temperature is also saturated at T ₀ . At this time, the energization current increases from I ₀ to I ₁ . Along with this, the wire temperature rises. If the temperature at time t ₃ has reached the second threshold value T _3, CPU 63 is turned on / off control of the FET 51. As shown in FIG. 2B, since the current value is detected by the current detection unit 52 at a timing when the current value is I ₁ , the temperature of the wire calculated by the CPU 63 is the same as that in FIG. 5 described above. To rise.

However, since the effective current is actually reduced by the on / off control, the temperature rise of the electric wire can be suppressed to a small level. Therefore, the electric wire temperature calculated at time t ₂ becomes the first threshold value T _2, when the CPU63 turns off the FET 51, the actual electric wire temperature is lower than the first threshold value T _2. Therefore, the deterioration of the electric wire is suppressed.

After the FET 51 is turned off, the CPU 63 continues to calculate the temperature of the electric wire, and when the time falls below the third threshold value T ₄ at time t ₄ , the on control is released.

Hereinafter, a detailed operation of the CPU 63 of the microcomputer 3 will be described. 3 and 4 are flowcharts showing a procedure of processing executed by the CPU 63.
First, the CPU 63 determines whether an operation instruction has been received from the outside via the input unit 34 (S1). When the CPU 63 determines that an operation instruction has not been received (S1: NO), that is, when it has been determined that a stop instruction has been received, the CPU 63 causes the control circuit 53 of the IPD 5 to output an off instruction via the output unit 62. Thereby, the control circuit 53 turns off the FET 51 (S2), and advances the process to step S4.

  If the CPU 63 determines that the operation instruction has been received (S1: YES), the CPU 63 causes the control circuit 53 of the IPD 5 to output an ON instruction via the output unit 62 (S3). As a result, the control circuit 53 turns on the FET 51 and supplies power from the battery 2 to the load 3.

Next, the CPU 63 outputs an output instruction to the control circuit 53, and obtains the current value indicated by the current information input from the control circuit 53 to the input unit 61 from the input unit 61 (S4).
The CPU 63 acquires the ambient temperature detected by the temperature detection unit 13 from the input unit 61 (S5), and reads the previously calculated rise temperature ΔTw (n−1) from the storage unit 63 (S6).

  Next, the CPU 63 substitutes the ambient temperature acquired in step S5 and the rising temperature ΔTw (n−1) read in step S6 into the above equation (1), whereby the temperature of the current wire 4 and the wire 4 The temperature difference (rise temperature) ΔTw (n) from the ambient temperature is calculated, and this ΔTw (n) is stored as the next ΔTw (n−1) (S7).

The CPU 63 calculates the wire temperature by substituting the ambient temperature and the rising temperature ΔTw (n) into the equation (2) (S8).
CPU63 determines whether the electric wire temperature is a second threshold value T ₃ or more (S9).
CPU63 If the electric wire temperature is determined not to be the second threshold value T ₃ or more (S9: NO), the process returns to step S1.

When determining that the electric wire temperature is equal to or higher than the second threshold T ₃ (S9: YES), the CPU 63 determines whether the electric wire temperature is equal to or higher than the first threshold T ₂ (S10).
When the CPU 63 determines that the wire temperature is equal to or higher than the first threshold T ₂ (S10: YES), the CPU 63 causes the control circuit 53 to output an off instruction via the output unit 62. Thereby, the control circuit 53 turns off the FET 51 (S11), and advances the process to step S15.

When determining that the electric wire temperature is not equal to or higher than the first threshold T ₂ (S10: NO), the CPU 63 determines whether a stop instruction has been received from the outside via the input unit 61 (S12).
When the CPU 63 determines that a stop instruction has been received (S12: YES), the CPU 63 causes the control circuit 53 to output an off instruction via the output unit 62. Thereby, the control circuit 53 turns off the FET 51 (S13) and ends the process.

  When the CPU 63 determines that a stop instruction has not been received (S12: NO), the control circuit 53 is caused to output an on / off control instruction via the output unit 62. Thereby, the control circuit 53 performs on / off control of the FET 51 (S14), and returns the process to step S4.

As described above, the current detector 52, when the control circuit 53 is on / off control of the FET51, the current value shown in FIG. 2 is configured to sample at the timing became I _1. Accordingly, the CPU 63 acquires the current value indicated by the current information input from the control circuit 53 to the input unit 61 from the input unit 61 at the above timing (step S4).
CPU63 performs the process of step S5-S8, and calculates electric wire temperature.

CPU63 determines that the electric wire temperature is a second threshold value T ₃ or more (S9: YES), if the electric wire temperature is determined to be the first threshold value T ₂ or higher (S10: YES), via the output unit 62, An off instruction is output to the control circuit 53. Thereby, the control circuit 53 turns off the FET 51 (S11).

As described above, the actual wire temperature when the FET 51 is turned off is lower than the first threshold value T ₂ , and thermal deterioration of the wire due to temperature rise is suppressed.

In step S15, the CPU 63 acquires the current value indicated by the current information input from the control circuit 53 to the input unit 61 from the input unit 61 (S15).
The CPU 63 acquires the ambient temperature detected by the temperature detection unit 13 from the input unit 61 (S16), and reads the previously calculated rise temperature ΔTw (n−1) from the storage unit 63 (S17).

  Next, the CPU 63 substitutes the ambient temperature acquired in step S16 and the rising temperature ΔTw (n−1) read in step S17 into the above-described equation (1), whereby the temperature of the current wire 4 and the wire 4 The temperature difference (rising temperature) ΔTw (n) from the ambient temperature is calculated, and this ΔTw (n) is stored as the next ΔTw (n−1) (S18).

The CPU 63 calculates the wire temperature by substituting the ambient temperature and the rising temperature ΔTw (n) into the equation (2) (S19).
CPU63 determines whether the electric wire temperature is a third threshold value T ₄ or less (S20).
CPU63 If the electric wire temperature is determined not to be the third threshold value T ₄ or less (S20: NO), the process returns to step S15.
When the CPU 63 determines that the electric wire temperature is equal to or lower than the third threshold T ₄ (S20: YES), the off control of the FET 51 is canceled and the process is terminated.

As described above, in the present embodiment, when the calculated electric wire temperature exceeds the first threshold value T ₂ and the energization is interrupted, the calculated electric wire temperature decreases and becomes the third threshold value T ₄ or less. Sometimes, the off control of the FET 51 is released. That is, when energization is interrupted, monitoring is performed until the wire temperature is reliably lowered to, for example, (ambient temperature + 5 ° C.).

Note that the equation by which the CPU 63 calculates the rising temperature of the electric wire temperature of the electric wire 4 is not limited to the equation (1). Any expression may be used as long as it is composed of the sum of the term of heat dissipation that depends on the previously calculated rise temperature ΔTw (n-1) and the term of heat generation that depends on the value I (n-1) of the current flowing through the wire 4. .
In the present embodiment, the rising temperature is calculated using the previously calculated rising temperature and the current value of the electric wire 4 detected by the current detection unit 52, but the electric current value of the electric wire 4 is not used. May be. The CPU 63 calculates the temperature difference between the ambient temperature and the wire temperature using the previously calculated rise temperature and a value related to the current flowing in the wire 4, for example, the voltage across the resistor provided in the wire 4. May be.

  Furthermore, the formula for calculating the wire temperature is not limited to the formula (2). Instead of using the ambient temperature detected by the temperature detector 12, a constant such as 60 ° C. or 80 ° C. may be used.

Since the FET 51 only needs to function as a switch, a switch such as a P-channel FET, a bipolar transistor, or a relay contact may be used instead of the FET 51. Furthermore, the configuration for interrupting the current flowing through the electric wire 4 is not limited to the configuration in which a switch is provided in the middle of the electric wire 4 and the switch is turned on / off.
When the FET 51 is on / off controlled, PWM control may be performed in which the duty ratio is adjusted to be large or small according to the magnitude of the current value detected by the current detection unit 52.

  The embodiment disclosed herein should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined not only by the above description but also by the scope of claims for patent, and is intended to include all modifications within the scope and meaning equivalent to the scope of claims for patent.

1 Control Device 2 Battery 3 Load 4 Electric Wire 5 IPD
51 FET
52 Current Detection Unit 53 Control Circuit 6 Microcomputer 61 Input Unit 62 Output Unit 63 CPU
64 storage unit 65 RAM

Claims (3)

A switch provided between a power source and a load is turned on / off, a current flowing from the power source to the load is detected by a detection unit, and the power source, the switch, and In the control device configured to calculate the temperature of the electric wire connecting the load, and to turn off the switch when the calculated temperature exceeds a first threshold,
Means for determining whether or not the temperature calculated by the calculating means is equal to or higher than a second threshold lower than the first threshold;
A control device comprising: means for controlling on / off of the switch so that a pulse voltage is supplied to the load when the means determines that the temperature is equal to or higher than the second threshold value. When the switch is turned on / off, and the temperature of the electric wire calculated by the calculating unit exceeds the first threshold value and the switch is turned off, the temperature calculated by the calculating unit is greater than the second threshold value. Means for determining whether or not it is equal to or lower than a low third threshold;
2. The control device according to claim 1, further comprising: a unit that cancels the off control when the unit determines that the temperature is equal to or lower than the third threshold value. 3. The calculating means is configured to calculate the temperature of the electric wire by adding the rising temperature of the electric wire to the ambient temperature of the electric wire, and the rising temperature is calculated based on the following formula (1). The control device according to claim 1, wherein:
ΔTw (n) = ΔTw (n−1) × exp (−Δt / τw)
+ Rthw * Rw (n-1) * I (n-1) ² * (1-exp (-[Delta] t / [tau] w)) (1)
However, I (n): detection n (an integer of 1 or more) detection energization current value (A)
ΔTw (n): Temperature rise of wire when detecting n times (℃)
Rw (n) = Rw (0) × (1 + κw × (Tw−To)): Wire resistance at detection n times (Ω)
Rw (0): Wire resistance (Ω) at a predetermined temperature To (° C)
Rthw: Electric wire thermal resistance (° C / W)
τw: Heat dissipation time constant (s)
κw: Wire resistance temperature coefficient (/ ° C)
Δt: Calculation interval (s) of the calculation means

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