JP6530443B2 - Low voltage battery deterioration detection system and vehicle equipped with the system - Google Patents

Description

  The present invention relates to an apparatus for detecting deterioration of a low voltage battery and a vehicle equipped with the system, which detects deterioration of the low voltage battery, in an apparatus including a high voltage battery and a low voltage battery whose voltage is lower than the high voltage of the high voltage battery.

  Conventionally, for example, in Patent Document 1, a buck-boost converter is controlled to charge a high voltage battery from a low voltage battery at the start of an internal combustion engine, and the current-voltage characteristic of the low voltage battery is analyzed at the time of control. A control device for a vehicle which determines a deterioration state of a low voltage battery is disclosed ([0025], [0028], [0033] of Patent Document 1).

JP, 2006-211859, A

  By the way, in the control device of the vehicle according to the above-mentioned prior art, it is judged that the low voltage battery is deteriorated when the constant current value is flowing and the voltage value is largely dropped within the predetermined time. ([0033] of Patent Document 1).

  However, since the current-voltage characteristics obtained by flowing a constant current value are pinpoint characteristics and not current-voltage characteristics of the entire low-voltage battery usage area, detection of deterioration of the low-voltage battery is limited. It becomes a range.

  The present invention has been made in consideration of such problems, and is a system for detecting deterioration of a low voltage battery which can obtain the electric characteristics (a wide range of electric characteristics) of the low voltage battery including the entire use area. An object is to provide a vehicle equipped with the system.

The low voltage battery deterioration detection system according to the present invention is
High voltage battery which applies high voltage to high voltage load,
A low voltage battery that applies a low voltage to a low voltage load;
A buck-boost converter, provided between the high voltage battery and the low voltage battery, which boosts the low voltage to the high voltage or reduces the high voltage to the low voltage.
Buck-boost control means for controlling the buck-boost of the buck-boost converter;
Electrical characteristic acquisition means for acquiring the electrical characteristics of the low voltage battery;
Deterioration degree acquiring means for acquiring the deterioration degree of the low voltage battery;
Equipped with
The step-up / step-down control means performs step-up control of the step-up / step-down converter to supply current from the low voltage battery to the high voltage battery.
The electrical characteristic acquiring unit acquires the electrical characteristic of the low voltage battery when the current is supplied.
The deterioration degree acquiring means acquires the deterioration degree of the low voltage battery based on the electrical characteristic,
The step-up / step-down control means is configured to vary the step-up ratio of the step-up / step-down converter when supplying the current.

  According to the present invention, when obtaining the degree of deterioration of the low voltage battery, the current supplied from the low voltage battery to the high voltage battery is varied by performing boost control to change the boost ratio of the buck-boost converter. Since the degree of deterioration of the low voltage battery is acquired based on the electrical characteristics of the low voltage battery acquired when the variable current is supplied, the electrical characteristics in a wide range of the use area of the low voltage battery are acquired It is possible to improve the acquisition accuracy of the degree of deterioration (electrical characteristics).

In this case, the buck-boost control means
When changing the boost ratio of the buck-boost converter,
The current supplied from the low voltage battery to the high voltage battery may be set to a gradually smaller value.

  According to this invention, the electrical characteristics in the wide range can be reliably obtained.

Further, the buck-boost control means
The step-up ratio may be set to change the current from a large value to a small value in a damped oscillation manner.

  As described above, by damping and oscillating the current value supplied from the low voltage battery to the high voltage battery, for example, the low voltage load of the low voltage battery appropriately acquires the electrical characteristics corresponding to the situation where the magnitude changes during actual traveling of the vehicle. can do. Also, after the current supplied from the low voltage battery to the high voltage battery is initially set to a large value in the discharging direction, the charging direction, the discharging direction, the charging direction,. Since the current value is attenuated from the high voltage battery side to the low voltage battery side in the charge direction, the decrease of the remaining capacity of the low voltage battery can be suppressed.

  The deterioration detection system for a low voltage battery according to the invention described above may be mounted on a vehicle.

In this case, the vehicle
An internal combustion engine,
An electric rotating machine which is supplied with electric power from the high-voltage battery at the start of the internal combustion engine to rotationally drive a crankshaft;
At the start-up, when the internal combustion engine is started by rotationally driving the rotary electric machine by the power of the high-voltage battery, the step-up / step-down control means changes the step-up ratio of the step-up / step-down converter to perform the step-up control. By supplying a current from the low voltage battery to the high voltage battery, the high voltage battery is charged, and the electrical characteristic acquiring means acquires the electrical characteristic of the low voltage battery being supplied with the current, and the deterioration is caused The degree acquisition means is configured to acquire the degree of deterioration of the low voltage battery based on the electrical characteristic.

  According to the vehicle of the present invention, since the charging power of the high voltage battery for acquiring the electrical characteristics of the low voltage battery can be used for starting the internal combustion engine, the power for starting the internal combustion engine is secured in the high voltage battery. There is no need to keep

Also, in this vehicle,
The low pressure load is
A traveling system load directly connected to the low voltage battery;
The low-voltage battery is connected to the non-traveling system load connected via the blocking means and connected to the low-pressure side of the buck-boost converter,
The buck-boost control means
When the step-up ratio is set so as to change the current value from a large value to a small value in a damped oscillation manner, the damped vibration may be performed based on the amount of fluctuation during the actual running of the current value of the traveling system load.

  According to the present invention, the current value supplied from the low voltage battery to the high voltage battery is attenuated and oscillated based on the amount of fluctuation during the actual traveling of the current value of the traveling system load, so the traveling system load changes in size Electrical characteristics (deterioration degree) corresponding to the above can be acquired.

  According to the present invention, the electrical characteristics can be acquired in a wide range including the entire use area of the low voltage battery, and the acquisition accuracy of the degree of deterioration (electrical characteristics) can be improved.

It is a schematic block diagram of the vehicle concerning this embodiment by which the degradation detection system of the low voltage battery concerning this embodiment was carried. 5 is a time chart provided to explain the operation of the first embodiment. It is explanatory drawing of the electrical property estimated in 1st and 2nd Example. FIG. 7 is a block diagram provided to explain the operation of the main part of the first embodiment. It is a time chart provided for operation explanation of the 2nd example. It is a time chart provided for operation explanation of comparative example 1 (conventional engine vehicle). It is explanatory drawing of the electrical property estimated by the comparative example 1 (conventional engine vehicle). FIG. 10 is a time chart provided to explain the operation of Comparative Example 2 (hybrid vehicle). It is explanatory drawing of the electrical property estimated by the comparative example 2 (hybrid vehicle).

  Hereinafter, a system for detecting deterioration of a low voltage battery and a vehicle equipped with the system according to the present invention will be exemplified and described in detail with reference to the accompanying drawings.

[Constitution]
FIG. 1 is a schematic configuration diagram of a vehicle 10 according to this embodiment on which the deterioration detection system for a low voltage battery according to this embodiment is mounted.

  Vehicle 10 shows a series parallel type hybrid vehicle. However, the vehicle 10 to which the deterioration detection system for a low voltage battery according to the present invention is applied is not limited to a hybrid vehicle, and may be an electric vehicle (EV), a fuel cell vehicle, or the like.

  Vehicle 10 basically includes an internal combustion engine (ENG) 12, a motor generator internal transmission 14, a high voltage battery 16, a low voltage battery 18, a buck-boost converter (first buck-boost converter SUDC1) 21, and ascent and descent Pressure converter (second step-up / down converter SUDC2) 22, inverter (first inverter INV1) 31, inverter (second inverter INV2) 32, and ECU (Electronic Control Unit) 20 as control means (control unit); Equipped with

  In this embodiment, as is known, the ECU 20 has a CPU and a memory, and the CPU reads and executes the program stored in the memory to thereby realize the first and second buck-boost converters 21 and 22. It functions as a step-up / step-down control unit that controls step-up / step-down, an electrical characteristic acquisition unit that acquires electrical characteristics (such as current and voltage characteristics) of low voltage battery 18, and a deterioration degree acquisition unit that acquires the deterioration degree of low voltage battery 18 . These means may be provided separately for the ECU 20.

  The motor generator internal transmission 14 includes a motor generator (first motor generator MG1) 41, a motor generator (second motor generator MG2) 42, a drive system 44, and a reduction gear 46. A wheel (drive wheel) 48 is connected to the reduction gear 46.

  The drive system 44 includes a clutch that directly connects the internal combustion engine (engine: ENG) 12 to the reduction gear 46, and a transmission or fixed gear interposed between the clutch and the reduction gear 46.

  One step-up / down converter 21 boosts the primary voltage V1 of the high voltage Vh of the high voltage battery 16 to the secondary voltage V2 during powering of the motor generator 42 and causes the motor generator 42 for traveling through the inverter 32 to operate. Supply power. On the other hand, at the time of regeneration of motor generator 42, secondary voltage V2 generated in inverter 32 is stepped down to high voltage Vh which is primary voltage V1, and high voltage battery 16 is charged.

  The other buck-boost converter 22 basically converts the power of high voltage Vh of high voltage battery 16 into the stepped-down power of low voltage Vb, and generates a low voltage (low voltage battery voltage or battery voltage) through fuse 50. Also supplied to the low voltage battery 18 which generates Vb, the low voltage battery 18 is charged.

  The ECU 20 performs boost control to control the magnitude of the current Isudc2 that passes the buck-boost converter 22 from the low voltage battery 18 side to the high voltage battery 16 side when acquiring the electrical characteristics of the low voltage battery 18, for example current-voltage characteristics. Set the boost ratio as you do. When the step-up ratio is increased, the current Isudc2 passing from the low voltage battery 18 to the high voltage battery 16 is increased. Therefore, the ECU 20 controls the step-up ratio so that the waveform of the current Isudc2 or the waveform of the battery current Ib becomes a desired waveform. Do.

  The low voltage battery 18 directly supplies the power of the low voltage Vb to the traveling system load 51 and supplies the power of the low voltage Vb to the comfort equipment system load 52 via the fuse 50.

  The traveling system load 51 driven by the low voltage Vb is, for example, an essential load for traveling of the vehicle 10, such as a motor of an electric power steering apparatus, a wiper motor, etc. Be done.

  The comfort equipment system load 52 is, for example, a non-traveling system load including an AV apparatus such as a radio and an audio apparatus and an air conditioner, and a comfort equipment system load current Ic is supplied from the low voltage battery 18.

  The low voltage battery 18 is provided with a voltage sensor 53 and a current sensor 54 for detecting the battery voltage Vb and the battery current Ib. The battery voltage Vb and the battery current Ib are acquired by the ECU 20.

  In FIG. 1, thick solid lines indicate mechanical connection, double solid lines indicate power wiring, and thin solid lines indicate control lines.

[Overall Operation of Vehicle 10 and Starting Operation of Internal Combustion Engine 12]
Here, a known operation of the vehicle 10 which is a series parallel hybrid vehicle will be briefly described. The vehicle 10 can travel in (a) EV drive mode, (b) engine drive mode, and (c) hybrid drive mode.

  (A) In the EV drive mode, the drive system 44 is opened by the ECU 20, and the internal combustion engine 12 and the motor generator 41 are stopped.

  On the other hand, the motor generator 42 is driven as a motor (powering operation) by the power of the high voltage battery 16 through the buck-boost converter 21 (boost control) and the inverter 32. When the vehicle 10 is braked, the regenerative power of the motor generator 42 charges the high voltage battery 16 through the inverter 32 and the buck-boost converter 21 (step-down control).

  (B) In the engine drive mode, the drive system 44 is engaged by the ECU 20, basically the motor generators 41 and 42 are stopped, and the wheels 48 are driven by the internal combustion engine 12, but the motor generator 42 is Drive of the wheel 48 by the above-mentioned, or the generation of electricity by the motor generator 41.

  Here, starting of the internal combustion engine 12 of the vehicle 10 will be described. Under the control of the ECU 20, when the ignition is turned on, DC power of the high voltage battery 16 is converted into AC power through the buck-boost converter 21 and the inverter 31, and the motor generator 41 is rotated (as a motor).

  The rotation of the motor generator 41 rotationally drives (cranks) the crankshaft of the internal combustion engine 12 to start the internal combustion engine 12 (start).

  That is, the internal combustion engine 12 is started by operating the motor generator 41 as a so-called starter motor by the power of the high voltage battery 16.

  As will be described later as Comparative Example 1, in a conventional internal combustion engine vehicle in which the wheels are driven only by the internal combustion engine, the starter motor is rotated by the power of the low voltage battery 18 at the time of start (ignition ON). Since the operation is performed, the electrical characteristics of the low voltage battery 18 can be obtained by monitoring the current carried out from the low voltage battery 18 at the start. However, in a hybrid vehicle in which the internal combustion engine 12 is started by the motor generator 41 to which the high voltage Vh is applied at the start, the electrical characteristics of the low voltage battery 18 can not be acquired at the start.

  (C) In the hybrid drive mode, the drive system 44 is opened by the ECU 20 and functions as a series hybrid. That is, basically, the internal combustion engine 12 is started under the control of the ECU 20. In this case, the motor generator 41 is driven as a generator by the rotational power of the internal combustion engine 12, and the generated power of the motor generator 41 drives the motor generator 42 through the inverter 31 and the inverter 32.

  Of the generated power generated by the motor generator 41, surplus generated power is charged to the high voltage battery 16 via the inverter 31 and the buck-boost converter 21 (step-down control). Conversely, when the output required for driving is large and the efficiency is degraded only by engine driving, the electric power of high-voltage battery 16 is also used to drive motor generator 42 via buck-boost converter 21 (boost control) and inverter 32. To drive.

[Deterioration degree acquisition operation of low voltage battery 18]
[First embodiment]
The first embodiment will be described with reference to the time chart of FIG.

  In a period from time point t0 to time point t1, it is a period of so-called ignition off (IGOFF) in which the internal combustion engine 12 is stopped.

  In order to avoid complexity, it is assumed that there is no outflow (discharge) and inflow (charge) of the battery current Ib from the low voltage battery 18 in this IGOFF period. Therefore, the battery voltage Vb is an open circuit voltage Vocv (OCV: Open Circuit Voltage).

  It is assumed that an ignition ON request occurs between time t1 and time t2. In this ignition ON (IGON) request period, it is assumed that a battery current Ib = Ibc corresponding to the comfort equipment system load current Ic flows from the low voltage battery 18. Due to the supply of the battery current Ibc, the low-voltage battery voltage Vb becomes the battery voltage Vb = Vbc = Vocv−Vc which is reduced by the drop voltage Vc from the open circuit voltage Vocv.

Here, assuming that the internal resistance of the low voltage battery 18 is rb, the drop voltage Vc is Vc = Ibc × rb.
A period from time t2 to time t4 is a start (START) period of the internal combustion engine 12.

  At this time, the ECU 20 performs boost control to change the boost ratio of the buck-boost converter 22 between time t2 and time t4 (active deterioration degree acquisition period Ti), thereby the high voltage battery 16 side from the low voltage battery 18 side. After setting the current Isudc2 flowing into the current to a large current Isudc2m, it is varied so that the value gradually decreases to the zero value.

  Accordingly, battery current Ib, which is a discharge current flowing from low voltage battery 18, is set to discharge current Ib2 and discharge current Ib3 whose values gradually decrease from a large discharge current Ib1 (Ib1 = Isudc2m) to a zero value.

  For example, the discharge current Ib1, Ib2 and Ib3 at three points are acquired by the ECU 20 through the current sensor 54, and the battery voltage Vb at the three points is acquired as battery voltages Vb1, Vb2 and Vb3 by the ECU 20 via the voltage sensor 53. .

  On the other hand, between time t3 and time t4 after delay time Td from time t2, the start current Istart is supplied to the motor generator 41 by the power of the high voltage battery 16, and the internal combustion engine 12 is started. , Ready (READY) state.

  After time t4, the buck-boost converter 22 supplies the current Isudc2 from the high voltage battery 16 to the low voltage battery 18 side, the battery voltage Vb rises via the open circuit voltage Vocv at time t5, and then, in this example, It reaches a constant voltage.

  FIG. 3 shows a current-voltage characteristic for estimating the electrical characteristic (battery characteristic) of the low voltage battery 18 in the ECU 20.

  In addition to the open circuit voltage Vocv (0, Vocv) and the comfort equipment system current voltage (Ibc, Vbc) on the current voltage coordinate (Ib, Vb), the active deterioration degree acquisition period Ti at time t2 to time t4 (see FIG. Current voltages (Ib1, Vb1), (Ib2, Vb2), and (Ib3, Vb3) in 2) are plotted, and battery characteristics shown by solid lines are estimated. The dashed line is the actual battery characteristic.

  As shown in FIG. 4, according to the first embodiment, when the ignition is ON, buck-boost converter 22 is controlled in the reverse direction, that is, current Isudc2 is reversely flowed from low voltage battery 18 to high voltage battery 16 and Discharge current of battery current Ib is gradually decreased from discharge current Ib1 to zero value as current Ib2, current Ib3, etc., and discharge current Ib1, Ib2, Ib3 detected by current sensor 54, and battery voltage Vb1 at the discharge current, By detecting Vb2 and Vb3 with the voltage sensor 53, it is possible to estimate the battery characteristic (the battery characteristic of the solid line in FIG. 3) with high accuracy.

  From the battery characteristics (estimated) shown by the solid line, the deterioration of the low voltage battery 18, in particular, the increase of the internal resistance can be accurately estimated. The normal value and the change with time of the internal resistance are stored in the ECU 20. As the internal resistance increases, the slope (ΔVb / ΔIb) of the battery characteristics becomes steeper. In other words, the voltage drop of the battery voltage Vb becomes large even with the same battery current (discharge current) Ib.

  As shown in FIG. 3, according to the first embodiment, it is possible to improve the estimation accuracy in the high current area of the use area Ad of the low voltage battery 18, which is a normal area when using the traveling system load 51. it can.

  Moreover, since the energy used to start the internal combustion engine 12 can be supplied as the discharge current Ib from the low voltage battery 18, it is not necessary to reserve the energy of the high pressure battery 16 for starting the internal combustion engine 12.

  The use area Ad is also an area for determining whether or not the idle stop of the vehicle 10 is permitted (if the characteristics are degraded, the idle stop is prohibited), and whether or not the automatic driving is permitted is determined (use area Ad In the case where the characteristics of the vehicle are deteriorated, automatic operation is not permitted.

Second Embodiment
The second embodiment will be described with reference to the time chart of FIG.

  With respect to the reference numerals used on the time chart of FIG. 5, the same reference numerals are attached to the same or corresponding parts as those used on the time chart of FIG.

  According to the second embodiment, when the ignition is ON, switching control is performed alternately between the buck-boost converter 22 in the reverse direction and the normal direction, that is, the current Isudc2 is damped and oscillated between the low voltage battery 18 side and the high voltage battery 16 side. By varying the voltage, it is possible to estimate the battery characteristics (see FIG. 3) under conditions approximate to the actual use conditions (during actual travel) of the traveling system load 51.

  More specifically, after the current Isudc2 (= Ib) supplied from the low voltage battery 18 to the high voltage battery 16 is initially set to a large value (discharge current Ib1) in the discharge direction, the charge direction, discharge The direction (discharge current Ib2), the charge direction, the discharge direction (discharge current Ib3), ... while changing the flow direction and damping to a small value (discharge current Ib3), in the charge direction, from the high voltage battery 16 side Since the current is returned to the low voltage battery 18, the reduction of the remaining capacity of the low voltage battery 18 can be suppressed.

[Summary and comparative example]
As described above, the deterioration detection system for the low voltage battery 18 according to the embodiment described above includes the high voltage battery 16 of high voltage Vh connected to the motor generator 42 or the like which is the high voltage load, the traveling system load 51 which is the low voltage load, It is provided between the low voltage battery 18 of low voltage Vb connected to the comfort equipment system load 52, the high voltage battery 16 and the low voltage battery 18, and boosts the low voltage Vb to the high voltage Vh or low voltage of the high voltage Vh. A step-up / step-down converter 22 that steps down to Vb, a step-up / step-down control unit that controls the step-up / step-down of the step-up / step-down converter 22, an electrical characteristic acquisition unit that acquires the electrical characteristics of the low voltage battery 18, and a deterioration degree of the low voltage battery 18 And an ECU 20 functioning as acquisition means for acquiring the degree of deterioration.

  The ECU 20 performs boost control of the buck-boost converter 22 to supply the discharge current Isudc2 from the low voltage battery 18 to the high voltage battery 16, acquires the electrical characteristics of the low voltage battery 18 supplying the discharge current Isudc2, When acquiring the deterioration degree of the low voltage battery 18 based on the electrical characteristics, the boost ratio of the buck-boost converter 22 is varied.

  As described above, when determining the degree of deterioration of the low voltage battery 18, boost control is performed to change the boost ratio of the step-up / down converter 22 to supply the current Isudc2 from the low voltage battery 18 to the high voltage battery 16. Since the degree of deterioration of the low voltage battery 18 is acquired based on the electrical characteristics of the low voltage battery 18 being supplied, the low voltage battery 18 receives a low voltage as a low voltage load (comfortable equipment load 52 and traveling load 51). Electrical characteristics can be acquired in a wide range including the use area Ad of the low-voltage battery 18 despite the fact that the battery voltage Vb is applied, and the accuracy of acquiring the degree of deterioration (electrical characteristics) is improved. it can.

  The ECU 20 sets the current Isudc2 supplied from the low voltage battery 18 to the high voltage battery 16 first to a large value (Isudc2m) when varying the boost ratio of the buck-boost converter 22, and then gradually reduces the value. By setting as such, it is possible to surely obtain the electrical characteristics in a wide range including the use area Ad (FIG. 2).

Alternatively, the ECU 20 sets the boost ratio to change the current Isudc2 from the large value to the small value in a damping oscillation manner, whereby the low-voltage load, in particular, the traveling system load 51 changes in magnitude during actual traveling of the vehicle 10. You can acquire the electrical characteristics that correspond precisely to the situation (Figure 3).
In this case, after the current Isudc2 supplied from the low voltage battery 18 to the high voltage battery 16 is initially set to have a large discharge current Ib1 in the discharge direction, the charge direction, discharge direction (discharge current Ib2), charge Since the current and the discharge direction (discharge current Ib3) are attenuated to a small value while changing the flow direction, the current Isudc2 is returned from the high voltage battery 16 side to the low voltage battery 18 side in the charge direction. The reduction of the remaining capacity of 18 can be suppressed.

[vehicle]
As shown in FIG. 1, the vehicle 10 on which the low voltage battery deterioration detection system described above is mounted is supplied with power from the high voltage battery 16 at the start of the internal combustion engine 12 and the internal combustion engine 12 to rotate the crankshaft. The ECU 20 as a step-up / step-down control means is provided with a motor generator 41 as a rotating electric machine to be driven to vary the step-up ratio (Vh / Vb) of the step-up / step-down converter 22 when the motor generator 41 of the internal combustion engine 12 starts. The high voltage battery 16 is charged by supplying the current Isud2 (battery current Ib, see FIG. 2 etc.) from the low voltage battery 18 to the high voltage battery 16 by performing the step-up control and charging the high voltage battery 16 as an electrical characteristic acquiring means. The ECU 20 acquires the electrical characteristics of the low voltage battery 18 being supplied with the current Isud2 (battery current Ib), ECU20 as reduction degree obtaining means obtains the deterioration degree of the low voltage battery 18 based on the electrical characteristics.

  Vehicle 10 sets the start current Istart by the power of high-voltage battery 16 charged by battery current Ib between time t2 and time t3 and the power of battery current Ib between time t3 and time t4 The voltage is supplied to the first motor generator (MG1) 41 through the step-up / step-down converter 21 and the first inverter (INV1) 31 to rotationally drive the first motor generator 41 (MG1). The rotation of the first motor generator (MG1) 41 starts the internal combustion engine 12.

  Thus, at start-up, the charging power to the high voltage battery 16 for acquiring the electrical characteristics of the low voltage battery 18 (charging power from time t2 to time t3, t4 from the low voltage battery 18 to the high voltage battery 16) Since it can be used for starting the internal combustion engine 12 {FIG. 2, start current Istart (high voltage battery 16) in FIG. 5}, it is not necessary to secure power for starting the high voltage battery 16.

  Here, the low voltage load is connected to a traveling system load 51 directly connected to the low voltage battery 18 and a low voltage battery 18 via a shutoff means, for example, a fuse 50, and connected to the low voltage side of the buck-boost converter 22. It is divided into a comfortable equipment system load 52 as a non-driving system load.

  In this case, when setting the boost ratio so as to change the current value from a large value to a small value in a damping oscillation manner, the ECU 20 sets the fluctuation amount of the current Ir of the traveling system load 51 of the vehicle 10 during actual traveling. Damping vibration based on.

  As described above, since the current Isudc2 supplied from the low voltage battery 18 to the high voltage battery 16 is damped and vibrated based on the fluctuation amount of the current Ir of the traveling system load 51 during actual traveling, the traveling system load 51 changes in size. It is possible to acquire electrical characteristics that correspond precisely to the situation.

  Even if the fuse 50 is cut off, the traveling system load 51 can be operated by the low voltage battery 18. In this case, the internal combustion engine 12 can be started by the power of the high voltage battery 16.

Comparative Example 1
FIG. 6 is a time chart for explaining the starting state of the conventional internal combustion engine automobile (engine vehicle) according to Comparative Example 1 by the starter motor. At time t2, the starting current Istart (discharge current Ibs) is applied to the starter motor from the low voltage battery. It shows the state of supply. FIG. 6 also depicts the alternator current Iacg from time t4 after engine start.

  In this first comparative example, when the starting current Istart is supplied, the battery current Ib causes a large voltage drop because the large discharge current Ibs corresponding to the starting current Istart flows. It drops to Vbs.

  FIG. 7 shows the current-voltage characteristics according to Comparative Example 1 for estimating the electrical characteristics (battery characteristics) of the low voltage battery 18.

  In this example shown in FIGS. 6 and 7, the time that the starting current Istart flows is an instant, and the plot on the large current side in the positive deterioration degree acquisition period Tj is one point, which is smaller than the first embodiment and the first embodiment. The measurement accuracy of the current-voltage characteristics is not good as compared with the two embodiments.

Comparative Example 2
FIG. 8 is a time chart for explaining the engine start state of the hybrid vehicle according to Comparative Example 2, and shows a state in which the engine start current Istart is supplied from the high voltage battery 16 at time t2.

  In the hybrid vehicle according to the second comparative example, the current from time t2 to time t3 of the engine start does not flow from the low voltage battery, and the starting current Istart is supplied from the high voltage battery. It is approximately the same value as the current Ibc at the time of ON (comfortable equipment system load current), and as shown in FIG. 9, it can be seen that the estimation accuracy in the high current region of the use region Ad of the low voltage battery 18 is poor.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various configurations can be adopted based on the contents described in this specification.

10 Vehicle 12 internal combustion engine (engine)
16 ... high voltage battery 18 ... low voltage battery 20 ... ECU 22 ... buck-boost converter 42 ... motor generator 51 ... traveling system load 52 ... comfortable equipment system load

Claims (4)

A high voltage battery for applying a high voltage to a rotating electrical machine for starting an internal combustion engine ;
In a use area of the internal combustion engine after start-up , a low-voltage battery which applies a low voltage to a low-voltage load which consumes a large current compared to the current value in the use area immediately before start-up ;
A buck-boost converter, provided between the high voltage battery and the low voltage battery, which boosts the low voltage to the high voltage or reduces the high voltage to the low voltage.
Buck-boost control means for controlling the buck-boost of the buck-boost converter;
Electrical characteristic acquisition means for acquiring the electrical characteristics of the low voltage battery;
Deterioration degree acquiring means for acquiring the deterioration degree of the low voltage battery;
Equipped with
When starting the internal combustion engine through the rotary electric machine with the power of the high voltage battery, the buck-boost control means performs boost control of the buck-boost converter from immediately before to immediately after the start to start the low voltage battery from the low voltage battery Supply current to the battery,
The electrical characteristic acquiring unit acquires the electrical characteristic of the low voltage battery when the current is supplied.
The deterioration degree acquiring means acquires the deterioration degree of the low voltage battery based on the electrical characteristic,
The step-up / step-down control means supplies the current from the low voltage battery to the high voltage battery immediately before the start when the low voltage battery supplies the current to the high voltage battery from immediately before the start of the internal combustion engine to immediately after the start. The step-up ratio of the buck-boost converter is varied so that the current to be used becomes the large value equivalent to the use area after the start-up, and then gradually becomes a small value until immediately after the start-up. Battery degradation detection system. In the low voltage battery deterioration detection system according to claim 1 ,
The buck-boost control means
A system for detecting deterioration of a low voltage battery, wherein the step-up ratio is set so that the current is attenuated and changed from a large value to the small value. It is a vehicle by which the degradation detection system of the low voltage battery according to claim 1 or 2 is mounted,
The vehicle is
The internal combustion engine;
At the start of the internal combustion engine, and a said rotary electric machine for rotating the crankshaft power is supplied from the high-voltage battery,
At the start-up, when the internal combustion engine is started by rotationally driving the rotary electric machine by the power of the high-voltage battery, the step-up / step-down control means changes the step-up ratio of the step-up / step-down converter to perform the step-up control. By supplying a current from the low voltage battery to the high voltage battery, the high voltage battery is charged, and the electrical characteristic acquiring means acquires the electrical characteristic of the low voltage battery being supplied with the current, and the deterioration is caused A vehicle characterized in that the degree acquisition means acquires the degree of deterioration of the low voltage battery based on the electrical characteristic. In the vehicle according to claim 3 ,
The low pressure load is
A traveling system load directly connected to the low voltage battery;
The low-voltage battery is connected to the non-traveling system load connected via the blocking means and connected to the low-pressure side of the buck-boost converter,
The buck-boost control means
When setting the boost ratio so as to change the current value from a large value to a small value in a damping oscillation, the damping vibration is performed based on the amount of fluctuation during the actual traveling of the current value of the traveling system load. The vehicle to be

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