JP5975068B2 - Vehicle power supply - Google Patents

Description

  The present invention relates to a vehicle power supply device.

  In order to collect energy at the time of deceleration of the vehicle (regenerative function), a power supply device having a capacitor in addition to a normal auxiliary battery has become widespread. In such a power supply device, a DC / DC converter is provided between an alternator, an auxiliary battery, or the like and a capacitor in order to adjust the voltage.

  In such a power supply device, when power is supplied to the starter for restarting the internal combustion engine stopped by idling stop, control using the power of the capacitor instead of the secondary battery may be performed. Here, when the capacitor is deteriorated, the voltage applied to the starter decreases, and the internal combustion engine may not be restarted. Patent Document 1 describes that the lower limit voltage of a capacitor is changed according to the internal resistance of the capacitor.

JP 2013-233011 A

However, the conventional technique has a problem that it is not possible to appropriately control the idling stop according to the degree of deterioration of the capacitor.
For example, Patent Document 1 evaluates the degree of deterioration based on the internal resistance of the capacitor, but does not describe other specific evaluation criteria.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a vehicle power supply device that can appropriately control an idling stop in accordance with the degree of deterioration of a capacitor.

A power supply device for a vehicle according to the present invention includes a secondary battery, an auxiliary device and a DC / DC converter connected in parallel to the secondary battery, and a DC / DC converter for the secondary battery and the auxiliary device. The DC / DC converter includes capacity estimating means for estimating the capacity of the capacitor, and the power supply apparatus is configured according to the estimated capacity of the capacitor. The voltage command value of the capacitor as the reference value for the idling stop of the internal combustion engine that is started using the starter is changed to increase the voltage command value of the capacitor when the capacity of the capacitor decreases , and the idling stop is being performed. When the voltage of the capacitor exceeds the voltage command value, the capacitor is discharged.

  According to such a configuration, the reference value for control related to idling stop is changed according to the capacitance of the capacitor.

Control of discharging the key Yapashita is
-Capacitor voltage exceeds voltage command value,
-Power can be supplied to the auxiliary machine from both the secondary battery and the capacitor; and-Power supply to the auxiliary machine from the secondary battery or capacitor is required. Control may be included.
When starting the internal combustion engine, if the voltage of the capacitor is less than the voltage command value, power may be supplied from the capacitor and the secondary battery to the starter.
The control related to idling stop may include control that does not supply power from the capacitor to the auxiliary machine when the voltage of the capacitor is equal to or lower than the voltage command value.
The control related to idling stop may include control for starting the internal combustion engine when the voltage of the capacitor becomes equal to or lower than the voltage command value during idling stop.

  According to the power supply device for a vehicle according to the present invention, since the reference value for the control related to idling stop is changed according to the capacity of the capacitor, it is possible to appropriately control the idling stop according to the degree of deterioration of the capacitor.

It is a figure which shows the structure containing the power supply device of the vehicle which concerns on Embodiment 1 of this invention. It is a figure explaining the determination method of the voltage command value based on the capacity | capacitance of the capacitor of FIG. 3 is a flowchart for explaining an example of the operation of the power supply device of FIG. 1.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration including a power supply device 1 according to Embodiment 1 of the present invention.
The power supply device 1 is a power supply device for a vehicle and supplies power to a load mounted on the vehicle. The load is, for example, the auxiliary machine 2.

  The power supply device 1 includes an alternator 3, an auxiliary battery 4, a capacitor 5, a DC / DC converter 6, and a starter 7. The alternator 3 functions as a motor or a generator. The auxiliary battery 4 is a secondary battery, for example, a lead battery. The capacitor 5 is, for example, a lithium ion capacitor (LiC) or an electric double layer capacitor.

  At least a part of the load (auxiliary machine 2 in the example of FIG. 1), the alternator 3, and the DC / DC converter 6 are connected in parallel to the auxiliary battery 4. Capacitor 5 is connected to auxiliary battery 4 and auxiliary machine 2 via DC / DC converter 6, and starter 7 is connected to capacitor 5 via starter activation switch 8. In particular, in this embodiment, the capacitor 5 and the starter 7 are connected in parallel to the auxiliary machine 2, the alternator 3 and the auxiliary battery 4 via the DC / DC converter 6.

  Although the internal configuration of the DC / DC converter 6 is not particularly described, the DC / DC converter 6 has a function of converting the voltage of power supplied from at least one of the alternator 3 and the auxiliary battery 4 and supplying the voltage to the capacitor 5. . Further, the DC / DC converter 6 has a function of converting the voltage of the electric power supplied from the capacitor 5 and supplying it to at least one of the auxiliary machine 2, the alternator 3 and the auxiliary battery 4.

  In other words, a part of the load (auxiliary machine 2) is directly connected to the auxiliary battery 4, and is connected to the capacitor 5 via the DC / DC converter 6. For this reason, when the auxiliary machine 2 is supplied with power from the auxiliary battery 4, the voltage of the auxiliary battery 4 is applied as it is. On the other hand, when the auxiliary machine 2 is supplied with electric power from the capacitor 5, the voltage can be controlled via the DC / DC converter 6.

  The starter 7 receives power supplied from the capacitor 5 and starts an internal combustion engine (not shown).

  Although not particularly illustrated, the power supply device 1 includes a control device that controls the operation of the power supply device 1. The control device is constituted by, for example, a computer (for example, a microprocessor or the like) that includes a calculation unit and a storage unit. Although not specified below, the control of the alternator 3, the auxiliary battery 4, the capacitor 5, the DC / DC converter 6 and the starter 7 is executed by this control device.

  Further, the DC / DC converter 6 includes a capacitance measuring unit for measuring the capacitance of the capacitor 5. The capacity measuring means can be configured using, for example, the voltage measuring means 9 and the current measuring means 10. Such a capacitance measuring unit measures the capacitance of the capacitor 5 based on, for example, a change in voltage during charging due to a constant current.

The capacity is estimated periodically, for example. A specific example of the estimation method is as follows.
It is assumed that the capacitor 5 is charged from time 0 to time T + ΔT. The current time is T, and an estimated value of T + ΔT is obtained. The charge of the capacitor 5 at the current time (T) is Q (T), and the charge of the capacitor 5 at the time T + ΔT is Q (T + ΔT). Further, the capacity of the capacitor 5 to be obtained is C (T + ΔT), and the current related to charging is I (T). Further, it is assumed that the voltage of the capacitor 5 can be regarded as constant during the time ΔT, and this is defined as V (T) (in the case where it cannot be regarded as constant, the voltage V (T) of the capacitor 5 at time T + ΔT is approximated). . When placed in this way, the following two expressions hold.
C (T + ΔT) = Q (T + ΔT) / V (T)
Q (T + ΔT) = I (T) * ΔT + Q (T)
In these two equations, if ΔT, I (T), V (T) and Q (T) are known, the capacitance C (T + ΔT) of the capacitor 5 can be obtained.

  The configuration of the capacity measuring means and the capacity measuring method can be realized using any other known technique. Further, information indicating the capacity (for example, a capacity value) may be notified to the control device or the like.

Next, the operation of the power supply device 1 according to Embodiment 1 will be described.
When the vehicle is decelerated, the power supply device 1 generates power with the alternator 3. At least a part of the generated electric power charges the capacitor 5 after adjusting the voltage and current by the DC / DC converter 6.

  When the power supply device 1 charges the capacitor 5, the capacity measurement unit measures the capacity of the capacitor 5. Then, the control reference value for idling stop of the internal combustion engine is changed according to the capacity of the capacitor 5.

  The reference value is, for example, a voltage command value Vc that is a target for voltage control of the capacitor 5 during idling stop. The control device of the power supply device 1 controls the voltage of the capacitor 5 during idling stop to approach the voltage command value Vc. Alternatively, the control device of the power supply device 1 performs control so that the voltage of the capacitor 5 during idling stop does not move away from the voltage command value Vc.

  Here, as the voltage command value Vc, for example, an internal combustion engine startable lower limit voltage value that represents the lower limit of the voltage value of the capacitor 5 that can start (or restart) the internal combustion engine via the starter 7 may be used. It is also possible to use a value with a certain margin for this lower limit voltage value. Further, “control to approach” means, for example, that the voltage is positively changed so that the difference from the voltage command value Vc is reduced. Further, “controlling so as not to move away” includes the above-mentioned “controlling so as to be close”, and further controlling so as not to increase the difference from the voltage command value Vc (for example, controlling so as not to change the voltage). Included).

  FIG. 2 shows a specific example of a method for determining the voltage command value Vc. When the value of the capacitance of the capacitor 5 is obtained, the value of the voltage command value Vc is determined according to the capacitance based on the illustrated map. In the example of FIG. 2, when the capacity decreases due to the deterioration of the capacitor 5 or the like, the voltage command value of the capacitor 5 increases accordingly. That is, even if the capacity decreases, the internal combustion engine can be started by increasing the voltage command value Vc. Further, when the capacity is large, the starter current is suppressed without forcibly increasing the voltage of the capacitor 5, thereby suppressing the deterioration of the components.

FIG. 3 is a flowchart for explaining an example of the operation of the power supply device 1 when the voltage command value Vc is used as a reference value in the control during idling stop.
First, the power supply device 1 acquires the voltage command value Vc (step S1). For example, a value determined based on the map of FIG. 2 is acquired. Next, the power supply device 1 compares the voltage of the capacitor 5 with the voltage command value Vc (step S2).

  When the voltage of the capacitor 5 exceeds the voltage command value Vc in step S2, the power supply device 1 discharges the capacitor 5 (step S3). On the other hand, when the voltage of the capacitor 5 is less than the voltage command value Vc (including the case where it is equal in the example of FIG. 3) in step S2, the power supply device 1 charges the capacitor 5 (step S4).

  As an operation for discharging the capacitor 5, for example, an operation in which the capacitor 5 supplies power to the auxiliary machine 2 in preference to the auxiliary battery 4 is possible. In other words, the voltage of the capacitor 5 exceeds Vc, power can be supplied from both the auxiliary battery 4 and the capacitor 5 to the auxiliary machine 2, and power is supplied from the auxiliary battery 4 or the capacitor 5 to the auxiliary machine 2. Is not supplied from the auxiliary battery 4 to the auxiliary machine 2, and the electric power is supplied to the auxiliary machine 2 from the capacitor 5. It is controlled as follows.

Further, as an operation of discharging the capacitor 5, for example, an operation of supplying electric power from the capacitor 5 to the auxiliary battery 4 via the DC / DC converter 6 is possible.
Further, the control for discharging the capacitor 5 may be control for prohibiting charging of the capacitor 5 or may include such control.

  On the other hand, as an operation of charging capacitor 5, for example, an operation of supplying power to capacitor 5 from auxiliary battery 4 via DC / DC converter 6 is possible.

  Further, the control for charging the capacitor 5 may be control for prohibiting discharging of the capacitor 5 or may include such control. For example, control for prohibiting the supply of power from the capacitor 5 to the auxiliary machine 2 may be performed.

  In this way, the power supply device 1 controls the voltage of the capacitor 5 during idling stop to approach the voltage command value Vc by the control of steps S1 to S4. Alternatively, control is performed so that the voltage of the capacitor 5 during idling stop is not far from the voltage command value Vc. As a result, the voltage of the capacitor 5 during idling stop is maintained around the voltage command value Vc.

  Next, the power supply device 1 determines whether or not it is instructed to start the internal combustion engine (step S5). If not instructed (for example, when idling stop is continued as it is), the process returns to step S1.

  On the other hand, when it is instructed to start the internal combustion engine (for example, when it is necessary to restart the internal combustion engine according to the driver's operation or the like during idling stop), the power supply device 1 Compares the voltage of the capacitor 5 with the voltage command value Vc (step S6).

When the voltage command value Vc and the lower limit voltage value at which the internal combustion engine can be started are the same or the margin is small, the voltage of the capacitor 5 may be lower than the voltage command value Vc when the internal combustion engine is actually restarted. . In this embodiment, it is possible to cope with such a situation. When the voltage of the capacitor 5 is less than the voltage command value Vc in step S6, the power supply device 1 calculates a shortage of starter current (step S7). The deficiency ΔI of the starter current is obtained based on the following formula, for example.
ΔI = ΔQ / Tst
However, Tst is the time during which current is supplied to the starter 7, and corresponds to, for example, the maximum time allowed until the start of the internal combustion engine is completed. In other words, the time is as long as possible without causing the driver to feel uncomfortable. ΔQ is a value obtained by subtracting the charge to be supplied to the starter 7 to start the internal combustion engine from the charge supplied to the starter 7 from the capacitor 5, and ΔQ = C * (V−Vc). . However, V represents the voltage of the capacitor 5 at that time. Since V <Vc in step S7, ΔT and ΔQ become negative when Tst is positive.

Next, the power supply device 1 supplies electric power to the starter 7 based on the shortage ΔI of the starter current to start the internal combustion engine (step S8). That is, a current is supplied from the capacitor 5 to the starter 7, and a current corresponding to the shortage ΔI is supplied from another power source (for example, the auxiliary battery 4) to the starter 7.
As described above, in the calculation of ΔI, when Tst is set to the maximum time allowed until the start of the internal combustion engine is completed, ΔI becomes the minimum allowable value. Current can be suppressed.

  When the voltage of the capacitor 5 exceeds the voltage command value Vc in step S6 (including the case where it is equal in the example of FIG. 3), the power supply device 1 supplies electric power from the capacitor 5 to the starter 7 to start the internal combustion engine. Start (step S9). In this case, power is not supplied from the auxiliary battery 4 to the starter 7.

  As described above, according to the power supply device 1 for a vehicle according to the first embodiment of the present invention, the idling stop can be appropriately controlled according to the degree of deterioration of the capacitor 5. Generally, when the capacitor 5 is deteriorated, the capacity is reduced. Accordingly, unless the capacitor 5 is charged to a high voltage, electric power necessary for starting the internal combustion engine is not supplied to the starter 7, and the internal combustion engine is There is a possibility that it cannot start normally. According to the present invention, as shown in FIG. 2, the voltage command value Vc increases as the capacity decreases, so that such a situation can be avoided and the internal combustion engine can be started reliably. Alternatively, the burden on the auxiliary battery 4 relating to the start of the internal combustion engine can be minimized.

  Further, when starting the internal combustion engine, the power supply device 1 supplies power from the capacitor 5 and the auxiliary battery 4 to the starter 7 when the voltage of the capacitor 5 is less than the voltage command value Vc. The internal combustion engine can be reliably started even if the voltage of V is lower than the voltage command value Vc.

  For this reason, the voltage command value Vc can be set to a necessary minimum value without having an excessive margin. If the voltage command value Vc is set to a large value including an excessive margin, excessive power may be supplied to the starter 7 when the internal combustion engine is started. This can cause the life of the capacitor 5 and the starter 7 to deteriorate. According to the present invention, such a situation can be avoided and the lifetime of the capacitor 5 and the starter 7 can be extended.

Embodiment 2. FIG.
The second embodiment changes the control when the voltage of the capacitor 5 is reduced in the first embodiment. Hereinafter, differences from the first embodiment will be described.
In the second embodiment, the control for starting the internal combustion engine when the voltage of the capacitor 5 becomes equal to or lower than the voltage command value Vc during idling stop is included as part of the control for idling stop.

This is realized, for example, by performing control for instructing start of the internal combustion engine in place of control for charging the capacitor 5 in step S4 of FIG. In this manner, during idling scan top-, Yuki decreases the voltage of the capacitor 5 gradually by the loop of steps S1~S3 and S5, step S4 is executed as it becomes lower than the voltage command value Vc Thus, the process branches from step S5 to step S6, and the internal combustion engine is started.

  According to the power supply device for a vehicle according to the second embodiment of the present invention, the idling stop can be appropriately controlled according to the degree of deterioration of the capacitor 5 as in the first embodiment.

  DESCRIPTION OF SYMBOLS 1 Power supply device, 2 Auxiliary machine, 4 Auxiliary battery (secondary battery), 5 Capacitor, 6 DC / DC converter, 7 Starter, 9 Voltage measurement means (capacity measurement means), 10 Current measurement means (capacity measurement means), Vc Voltage command value.

Claims (5)

A power supply device for a vehicle,
A secondary battery,
An auxiliary machine and a DC / DC converter connected in parallel to the secondary battery;
A capacitor connected to the secondary battery and the auxiliary machine via the DC / DC converter;
A starter connected to the capacitor,
The DC / DC converter includes capacity estimating means for estimating the capacity of the capacitor,
In accordance with the estimated capacity of the capacitor, the power supply device reduces the voltage command value of the capacitor as a reference value for control related to an idling stop of an internal combustion engine started using the starter, and the capacity of the capacitor decreases. Then, the voltage command value of the capacitor is changed to increase, and when the voltage of the capacitor during idling stop exceeds the voltage command value, the capacitor is discharged.
Vehicle power supply. The control for discharging the capacitor includes:
-The voltage of the capacitor exceeds the voltage command value;
-It is possible to supply power to the auxiliary machine from both the secondary battery and the capacitor; and-When it is necessary to supply power to the auxiliary machine from the secondary battery or the capacitor, from the capacitor The power supply device for a vehicle according to claim 1, comprising control for supplying electric power to the auxiliary machine.   3. The vehicle according to claim 1, wherein when starting the internal combustion engine, if the voltage of the capacitor is less than a voltage command value, electric power is supplied from the capacitor and the secondary battery to the starter. Power supply.   4. The control according to claim 1, wherein the control related to the idling stop includes control not to supply power from the capacitor to the auxiliary machine when the voltage of the capacitor is equal to or lower than the voltage command value. The power supply device for a vehicle according to one item.   The control relating to the idling stop includes a control for starting the internal combustion engine when the voltage of the capacitor becomes equal to or lower than the voltage command value during the idling stop. Vehicle power supply.

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