JP5454022B2 - Vehicle power supply - Google Patents

Description

  The present invention relates to a vehicle power supply device including an in-vehicle battery.

  A vehicle such as an automobile includes an alternator (on-vehicle generator, AC generator), a battery, and the like. The electric power generated by the alternator in conjunction with the engine is used for charging the battery and is supplied to an electric load mounted on the vehicle. Generally, the generated voltage of the alternator is about 14V and the voltage of the battery is about 12.8V, but the voltage of the battery varies depending on the usage state of the electric load. For this reason, even when the voltage of the battery fluctuates, the function of the electric load is designed to operate normally.

  On the other hand, when a large-capacity electric load such as an electric power steering apparatus is operated, the battery voltage may decrease, and a technique for maintaining the voltage applied to the electric power steering apparatus has been developed. For example, when switching means for electrical loads are installed in a concentrated manner and the power supply is abnormal, such as when the battery voltage drops significantly, the switching means is directly controlled to cut off the electrical load and maintain the battery voltage. A vehicle load control system is disclosed (see Patent Document 1).

JP 2008-87534 A

  However, the device of Patent Document 1 is configured such that when the battery voltage drops below a predetermined threshold voltage, the battery voltage applied to the electric power steering device is not reduced by cutting off the electrical load. However, there is a time (time lag) required for the control processing until it is detected that the battery voltage has dropped below the predetermined threshold voltage until the electrical load is actually turned off. On the other hand, when the degree of deterioration of the battery is different, the temporal change of the battery voltage is different, and the battery voltage that is lowered during the time lag is also different. For this reason, a situation occurs in which the voltage applied to a large-capacity electric load such as an electric power steering device differs depending on the degree of deterioration of the battery. In order to maintain a desired voltage regardless of the degree of deterioration of the battery, the threshold voltage may be set high. However, when the battery is normal (not deteriorated or the degree of deterioration is small). It becomes an excessive load limit.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicular power supply device that can maintain an optimal voltage of the in-vehicle battery regardless of the degree of deterioration of the in-vehicle battery.

  According to a first aspect of the present invention, there is provided a vehicular power supply device including a vehicle-mounted battery, a voltage detection unit that detects a voltage of the vehicle-mounted battery, a resistance calculation unit that calculates an internal resistance of the vehicle-mounted battery, and the resistance. A determination unit that determines a threshold voltage according to the internal resistance calculated by the calculation unit; a voltage determination unit that determines whether or not the voltage detected by the voltage detection unit is lower than the determined threshold voltage; and the voltage determination unit Control means for controlling energization to an electric load supplied with electric power from the in-vehicle battery according to the determined result.

  According to a second aspect of the present invention, there is provided a vehicular power supply apparatus according to the first aspect, further comprising: current detection means for detecting the current of the in-vehicle battery, wherein the resistance calculation means is the voltage detected by the voltage detection means and the current detection means. An internal resistance of the in-vehicle battery is calculated based on the detected current.

  According to a third aspect of the present invention, there is provided the vehicle power supply device according to the first or second aspect, wherein the initial internal resistance value of the in-vehicle battery, the load current value of a predetermined electric load supplied with power by the in-vehicle battery, and the load current Storage means for storing information relating to a rise time and a control delay time of the control means is provided, and the determination means is configured to determine a threshold voltage using the internal resistance calculated by the resistance calculation means and the stored information. It is characterized by being.

  According to a fourth aspect of the present invention, there is provided the vehicle power supply device according to the third aspect, wherein the predetermined electric load is an electric power steering.

  In the present invention, the internal resistance of the in-vehicle battery is calculated, and the threshold voltage is determined according to the calculated internal resistance. The internal resistance is related to the degree of deterioration of the in-vehicle battery. When the in-vehicle battery is normal (no deterioration or little deterioration), the internal resistance is small, and when the in-vehicle battery is deteriorated, the internal resistance Resistance increases. Further, the internal resistance can be calculated from, for example, a change in the voltage of the in-vehicle battery with time or a voltage / current of the in-vehicle battery. If the calculated internal resistance is large, a large threshold voltage is determined assuming that the in-vehicle battery has deteriorated, and if the calculated internal resistance is small, it is determined that the in-vehicle battery is normal and a small threshold voltage is set. decide.

  It is determined whether or not the voltage of the in-vehicle battery is lower than the determined threshold voltage, and the energization to the electric load supplied with the electric power from the in-vehicle battery is controlled according to the determination result. For example, when the voltage of the in-vehicle battery is lower than the determined threshold voltage, control is performed to cut off the power supply to the electric load. And when the vehicle battery is normal, after determining that the voltage of the vehicle battery is lower than the determined threshold voltage, during the time lag that is the time required for the control processing until the electrical load is actually cut off Since the voltage of the in-vehicle battery that decreases is also small, the threshold voltage is reduced to maintain the voltage of the in-vehicle battery at a desired value when the electric load is cut off. On the other hand, when the in-vehicle battery is deteriorated, the voltage of the in-vehicle battery that decreases during the time lag is large. Therefore, the threshold voltage is set larger than when the in-vehicle battery is normal, and the electric load is cut off. For example, the voltage of the in-vehicle battery is maintained at the same level as the voltage when the in-vehicle battery is normal. Thus, regardless of the degree of deterioration of the in-vehicle battery, it is possible to minimize the excessive load limit and to maintain the voltage of the in-vehicle battery at the same value when the electric load is interrupted.

  In the present invention, the internal resistance is calculated according to the voltage and current of the in-vehicle battery. Since the degree of deterioration of the in-vehicle battery can be obtained from the calculated internal resistance, the degree of deterioration of the in-vehicle battery can always be accurately grasped according to the voltage and current of the in-vehicle battery even if the degree of deterioration changes over time. .

  In the present invention, the threshold voltage is determined using the calculated internal resistance and the stored information. The stored information includes the initial internal resistance value r0 of the in-vehicle battery, the load current value Iw of the predetermined electric load, the rise time ΔT of the load current, and the control delay time Δt (after determining that the in-vehicle battery voltage is lower than the threshold voltage, This is information relating to the time lag that is the time required for control processing until the electrical load is actually cut off. For example, if the calculated internal resistance is r, the threshold voltage when the in-vehicle battery is normal is Vth, and the threshold voltage when the in-vehicle battery is deteriorated is Vth + α, α = (r−r0) · Δt · Iw / The threshold voltage can be calculated and determined by ΔT. Alternatively, the threshold voltage may be stored in advance in association with the internal resistance, and the threshold voltage corresponding to the calculated internal resistance may be selected and determined. Thereby, an optimal threshold voltage can be obtained according to the degree of deterioration of the in-vehicle battery.

  In the present invention, the predetermined electric load is an electric power steering. As a result, an optimum voltage can always be applied to the electric power steering regardless of the degree of deterioration of the in-vehicle battery even when the electric power steering consumes a large amount of power.

  ADVANTAGE OF THE INVENTION According to this invention, the optimal voltage of a vehicle-mounted battery can be maintained irrespective of the deterioration degree of a vehicle-mounted battery.

It is a block diagram which shows an example of a structure of the vehicle power supply device which concerns on this Embodiment. It is a time chart which shows the relationship between the load current waveform of an electric power steering, and the applied voltage. It is a time chart which shows the change of the battery voltage of the vehicle power supply device which concerns on this Embodiment. It is a flowchart which shows the process sequence of the vehicle power supply device which concerns on this Embodiment.

  Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments. FIG. 1 is a block diagram showing an example of a configuration of a vehicle power supply device according to the present embodiment. The vehicle power supply device includes a battery 1 as a vehicle-mounted battery, a current sensor 2 as current detection means for detecting a current of the battery 1, a power supply control unit 5, and the like. The power supply control unit 5 controls the entire control unit 51 as a determination unit that determines whether or not the voltage Vb of the battery 1 is lower than the threshold voltage Vth, and a detection unit that detects the voltage Vb of the battery 1 And an internal resistance calculation unit 52 as a resistance calculation unit that calculates the internal resistance of the battery 1, a storage unit 53 that stores predetermined information, a threshold voltage calculation unit 54 as a determination unit that determines the threshold voltage Vth, and the switching element ON The drive part 55 etc. are provided as a control means which controls energization to the electric load 4 by controlling / off.

  The electric power from the battery 1 is supplied to the electric load 4 through the plurality of branched electric paths 11, 12, 13, and is supplied to the electric power steering 6 as a predetermined electric load through the electric path 14. Each electric circuit 11-13 is provided with a switching element 3 such as an FET or a relay. Each electric circuit 11-14 is provided with a fuse at an appropriate location. In addition, in FIG. 1, although it is the structure provided with three electric loads 4, the number of the electric loads 4 is not limited to this.

  The internal resistance calculation unit 52 calculates the internal resistance of the battery 1 based on the voltage and current of the battery 1 under the control of the control unit 51. The internal resistance is related to the degree of deterioration of the battery 1, and when the battery 1 is normal (no deterioration or little deterioration), the internal resistance is small, and when the battery 1 is deteriorated, the internal resistance Resistance increases.

  Since the degree of deterioration of the battery 1 can be obtained using the calculated internal resistance, the degree of deterioration of the battery 1 can always be accurately grasped even if the degree of deterioration changes over time.

  The storage unit 53 includes, as predetermined information, for example, the initial internal resistance value r0 of the battery 1, the load current Iw of the electric power steering 6 as a predetermined electric load, and the load current from the time when the electric power steering 6 starts operating. Control process until the electric load 4 is actually cut off after the control unit 51 determines that the voltage Vb of the battery 1 is lower than the threshold voltage Vth, until the load current Iw reaches the load current Iw. Is related to the control delay time (time lag) Δt, which is the time required for. The rise time ΔT of the load current is not limited to the time from 0 to a constant current, and is defined as, for example, the time until the load current reaches 10% to 90% of the constant current value. May be.

  The storage unit 53 can also store a plurality of values of the threshold voltage Vth in association with the internal resistance of the battery 1.

  The threshold voltage calculation unit 54 calculates a threshold voltage Vth for determining whether to cut off the electrical load 4 using the information stored in the storage unit 53 and the internal resistance calculated by the internal resistance calculation unit 52. To do. For example, when the initial internal resistance value r0 of the battery 1, the load current value Iw of the electric power steering 6 and the load current rise time ΔT and the control delay time (time lag) Δt, the calculated internal resistance r, and the battery 1 is normal Is the threshold voltage Vth (Vn), and the threshold voltage Vth when the battery 1 is deteriorated is Vn + α (α is the correction amount), the correction amount α is α = (r−r0) · Δt · Iw. / ΔT, and the threshold voltage Vth can be calculated and determined regardless of the degree of deterioration of the battery 1.

  As numerical examples of the predetermined information described above, for example, the initial internal resistance value r0 of the battery 1 is 10 mΩ, the load current value Iw of the electric power steering 6 is 100 A, the rise time ΔT of the load current is 100 ms, and the control delay time (time lag) Δt can be 10 ms, the threshold voltage Vn can be 10 V, and the like. Note that the present invention is not limited to these numerical examples.

  Thereby, when the calculated internal resistance r is large, it is determined that the battery 1 is deteriorated, and a large threshold voltage Vth is determined. When the calculated internal resistance r is small, it is assumed that the battery 1 is normal. A small threshold voltage Vth is determined.

  The threshold voltage calculation unit 54 can also select and determine the threshold voltage Vth corresponding to the calculated internal resistance using the association between the internal resistance stored in the storage unit 53 and the threshold voltage Vth.

  The control unit 51 compares the voltage Vb of the battery 1 detected via the internal resistance calculation unit 52 with the threshold voltage Vth determined by the threshold voltage calculation unit 54, and determines whether or not the voltage Vb of the battery 1 is lower than the threshold voltage Vth. Determine whether. When the voltage Vb of the battery 1 is lower than the threshold voltage Vth, the control unit 51 outputs a control signal to the drive unit 55 so as to turn off the switching element 3. Further, when the voltage Vb of the battery 1 is not lower than the threshold voltage Vth, the control unit 51 outputs a control signal to the drive unit 55 in order to keep the switching element 3 in the on state. Further, when the voltage Vb of the battery 1 is higher than the ON threshold voltage, the control unit 51 outputs a control signal to the driving unit 55 so as to turn on the switching element 3 in the OFF state.

  The drive unit 55 turns on or off the switching element 3 based on the control signal output from the control unit 51.

  With the above-described configuration, for example, when the voltage Vb of the battery 1 is lower than the threshold voltage Vth, control is performed to cut off the energization of the electric load 4. Then, when the battery 1 is normal, after determining that the voltage Vb of the battery 1 is lower than the threshold voltage Vth, during the time lag that is the time required for the control processing until the electric load 4 is actually cut off. Since the voltage of the battery 1 that decreases to a small value is also small, the threshold voltage Vth is decreased to maintain the voltage of the battery 1 when the electric load 4 is turned off at a desired value. On the other hand, when the battery 1 is deteriorated, the voltage of the battery 1 that decreases during the time lag is large. Therefore, the threshold voltage Vth is set larger than when the battery 1 is normal, and the electric load 4 is energized. For example, the voltage Vb of the battery 1 at the time of being shut off is maintained at a voltage comparable to the voltage when the battery 1 is normal. Thereby, irrespective of the degree of deterioration of the battery 1, the voltage of the battery 1 when the electric load 4 is cut off can be maintained at an equivalent value, and the voltage applied to the electric power steering 6 can be set to a desired voltage. Value can be maintained.

  FIG. 2 is a time chart showing the relationship between the load current waveform of the electric power steering 6 and the applied voltage. 2A shows the transition of the load current waveform according to the operating state of the electric power steering 6, and FIG. 2B shows the transition of the voltage of the battery 1 applied according to the operating state of the electric power steering 6. Show. As shown in FIG. 2 (a), if the operation of the electric power steering 6 starts at time t1, the load current becomes Iw when the load current rise time ΔT has elapsed from time t1, and then a constant load Current flows. If the operation of the electric power steering 6 stops at time t2, the load current decreases.

  As shown in FIG. 2B, when the internal resistance of the battery 1 is small (when the battery 1 is normal or the degree of deterioration is small), the voltage Vb starts to decrease at time t1, and the voltage Vb becomes the threshold voltage Vth. When the control delay time (time lag) Δt elapses from the time when the electric load 4 is reached, the electric load 4 is deenergized, and the voltage Vb of the battery 1 is maintained in a state of Vb = V1. That is, the voltage V 1 of the battery 1 is applied to the electric power steering 6. That is, the load control is executed when the voltage of the battery 1 is V1.

  On the other hand, when the internal resistance of the battery 1 is large (when the battery 1 is deteriorated), the temporal change of the voltage drop is large compared to the normal case. Then, at time t1, the voltage Vb starts to drop, and when the control delay time (time lag) Δt has elapsed from the time when the voltage Vb reaches the threshold voltage Vth, the electric load 4 is deenergized, and the voltage Vb of the battery 1 is It is maintained in a state of Vb = V2 (V2 <V1). That is, the voltage V2 of the battery 1 is applied to the electric power steering 6. That is, the load control is executed when the voltage of the battery 1 is V2.

  That is, a difference between V1 and V2 is generated in the voltage applied to the electric power steering 6 according to the difference in the degree of deterioration of the battery 1. In the present embodiment, the voltage applied to the electric power steering 6 is, for example, V1 by maintaining the difference between the voltages V1 and V2 at the same (same level) voltage regardless of the deterioration degree of the battery 1. To.

  FIG. 3 is a time chart showing changes in the battery voltage of the vehicle power supply device according to the present embodiment. As in the case of FIG. 2, it is assumed that the operation of the electric power steering 6 starts at time t1, and the load current becomes Iw when the load current rise time ΔT has elapsed from time t1, and then a constant load current flows. And

  When the internal resistance of the battery 1 is small (when the battery 1 is normal or the degree of deterioration is small), the voltage Vb of the battery 1 starts to decrease at time t1, and the control delay time from the time when the voltage Vb reaches the threshold voltage Vth. (Time lag) At the time when Δt has elapsed, the energization of the electric load 4 is cut off, and the voltage Vb of the battery 1 is maintained in a state of Vb = V1. That is, the voltage V 1 of the battery 1 is applied to the electric power steering 6. That is, the load control is executed when the voltage of the battery 1 is V1. In this case, when the operation of the electric power steering 6 starts at time t1, the internal resistance of the battery 1 is calculated by detecting the voltage Vb, current, etc. of the battery 1, and the threshold voltage is set to Vth by the calculated internal resistance. Suppose that.

  On the other hand, when the internal resistance of the battery 1 is large (when the battery 1 is deteriorated), the temporal change of the voltage drop is large compared to the normal case. In this case, when the operation of the electric power steering 6 starts at time t1, the internal resistance of the battery 1 is calculated by detecting the voltage Vb, current, etc. of the battery 1, and the correction amount α is obtained from the calculated internal resistance. Assume that the threshold voltage is Vth + α. Then, at time t1, the voltage Vb starts to decrease, and when the control delay time (time lag) Δt has elapsed from the time when the voltage Vb reaches the threshold voltage Vth + α, the energization of the electric load 4 is cut off, and the voltage Vb of the battery 1 is The state of Vb = V1 is maintained. That is, the voltage V 1 of the battery 1 is applied to the electric power steering 6. Thus, the correction amount α is equal to the voltage of the battery 1 at the time when the control delay time (time lag) Δt has elapsed after the voltage of the battery 1 reaches the threshold voltage regardless of the degree of deterioration of the battery 1. Ask to be. Thereby, an optimum threshold voltage can be obtained according to the degree of deterioration of the battery 1. The voltage of the battery 1 when the electric load 4 is cut off can be maintained at an equivalent value regardless of the degree of deterioration of the battery 1.

  In FIG. 3, only two cases of the case where the internal resistance of the battery 1 is large and the case where the internal resistance is small are illustrated in a simplified manner, but actually, the internal resistance changes according to the degree of deterioration of the battery 1. .

  Next, the operation of the vehicle power supply device according to the present embodiment will be described. FIG. 4 is a flowchart showing a processing procedure of the vehicle power supply device according to the present embodiment. The control unit 51 determines whether or not the ignition switch is turned on (S11), and when the ignition switch is not turned on (NO in S11), the processing after step S11 is continued. When the ignition switch is turned on (YES in S11), the control unit 51 detects the voltage / current of the battery 1 (S12) and calculates the internal resistance of the battery 1 (S13).

  The control unit 51 calculates the threshold voltage Vth using the calculated internal resistance (S14). In this case, the threshold voltage Vth can be obtained by calculation, or can be obtained by referring to a table (LUT or the like) in which the internal resistance and the threshold voltage Vth are associated. Thereby, the threshold voltage Vth according to the deterioration degree of the battery 1 can be determined.

  The control unit 51 determines whether or not the voltage Vb of the battery 1 is lower than the threshold voltage Vth (S15). If the voltage Vb of the battery 1 is lower than the threshold voltage Vth (YES in S15), the electric load 4 is turned off ( It is determined whether or not the ignition switch has been turned off (S17). When the ignition switch is not turned off (NO in S17), the control unit 51 continues the processing from step S15. When the ignition switch is turned off (YES in S17), the control unit 51 ends the process.

  On the other hand, when the voltage Vb of the battery 1 is not lower than the threshold voltage Vth (NO in S15), the control unit 51 determines whether or not the voltage Vb of the battery 1 is higher than the on-threshold voltage (S18). When the voltage Vb of the battery 1 is higher than the ON threshold voltage (YES in S18), the control unit 51 turns on (energizes) the electrical load (S19), and performs the process of step S17. When the voltage Vb of the battery 1 is not higher than the ON threshold voltage (NO in S18), the control unit 51 performs the process of step S17 without performing the process of step S19.

  As described above, according to the present embodiment, when the battery is normal, after the battery voltage is determined to be lower than the threshold voltage, the control process is performed until the electrical load is actually cut off. Since the voltage of the battery that decreases during the time lag, which is the time required, is also small, the threshold voltage is reduced to maintain the battery voltage at a desired value when the electric load is cut off. On the other hand, when the battery is degraded, the voltage of the battery that decreases during the time lag is large, so the threshold voltage is set larger than when the battery is normal, and the electric load is turned off. For example, the voltage of the battery is maintained at a voltage comparable to that when the battery is normal. As a result, regardless of the degree of deterioration of the battery, the voltage of the battery when the electric load is cut off can be maintained at an equivalent value, which is excessive for large-capacity electric loads such as electric power steering. It is possible to minimize the load limitation and to always apply the same voltage.

DESCRIPTION OF SYMBOLS 1 Battery 2 Current sensor 3 Switching element 4 Electric load 5 Power supply control part 51 Control part 52 Internal resistance calculation part 53 Memory | storage part 54 Threshold voltage calculation part 55 Drive part 6 Electric power steering (predetermined electric load)

Claims (4)

In a vehicle power supply device including an in-vehicle battery,
Voltage detecting means for detecting the voltage of the vehicle battery;
Resistance calculation means for calculating the internal resistance of the in-vehicle battery;
Determining means for determining a threshold voltage according to the internal resistance calculated by the resistance calculating means;
Voltage determination means for determining whether or not the voltage detected by the voltage detection means is lower than the determined threshold voltage;
A vehicle power supply apparatus comprising: control means for controlling energization to an electric load supplied with electric power from the in-vehicle battery according to a result determined by the voltage determination means. Current detection means for detecting the current of the in-vehicle battery,
The resistance calculating means includes
2. The vehicle power supply according to claim 1, wherein an internal resistance of the in-vehicle battery is calculated based on a voltage detected by the voltage detection unit and a current detected by the current detection unit. apparatus. A storage means for storing information on an initial internal resistance value of the on-vehicle battery, a load current value of a predetermined electric load supplied with power by the on-vehicle battery, a rise time of the load current, and a control delay time of the control means;
The determining means includes
3. The vehicle power supply device according to claim 1, wherein a threshold voltage is determined using the internal resistance calculated by the resistance calculation means and the stored information. The predetermined electrical load is
The vehicle power supply device according to claim 3, wherein the power supply device is an electric power steering.

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