JP4487580B2 - Battery system for hybrid vehicles - Google Patents

Description

  The present invention relates to a hybrid vehicle battery system, and more particularly to a hybrid vehicle including a secondary battery that repeats charging that is powered by braking energy during vehicle braking and discharging that is powered by driving energy to the motor of the vehicle. The present invention relates to a battery system.

  A hybrid vehicle (HV vehicle) that uses both a vehicle drive motor (electric motor) driven by electric power and an engine drive is known. Such an HV vehicle includes an assembled battery in which a plurality of secondary batteries are connected in series as unit batteries (for example, battery cells and battery blocks), and electric power is supplied to the motor by the assembled batteries. It is normal. The assembled battery drives the driving motor with the electric power at the time of discharging. The assembled battery is charged with electric power obtained by driving the engine or regenerating. Such an assembled battery is repeatedly charged and discharged, and the HV vehicle achieves an appropriate drivability.

  FIG. 2 shows a configuration example of a conventional assembled battery control system 300 for an HV vehicle. A voltage detector 14 for detecting the voltage of the battery cell 10 is connected to the assembled battery 400 of the secondary battery in which the plurality of battery cells 10 are connected in series. Based on the output of the voltage detector 14, the battery ECU 16 calculates a state of charge (SOC) of the battery cell 10. The voltage value detected by the voltage detector 14 may be the voltage value of each battery cell 10 as described above, but the assembled battery 400 is usually a battery block in which a plurality of battery cells 10 are connected in series. Furthermore, since it becomes the structure connected in series, the voltage value for every battery block may be sufficient. In this case, the SOC of each battery block is calculated by the battery ECU 16 from the voltage value for each battery block. Based on the calculated SOC, the HVECU 18 controls the load 20 including the drive motor, the generator drive engine, the generator, the inverter, and the like, and adjusts the charge / discharge amount of the assembled battery 400 to thereby adjust the assembled battery. Control is performed so that 400 SOCs are within a predetermined range. Such battery control is required because HV vehicles require battery control that matches the characteristics of HV vehicles, such as frequent charging and discharging. If rapid or frequent charging / discharging is repeated, the temperature of the battery may increase and the life of the secondary battery may be shortened. Preventing this problem is one of the main purposes of the battery control system.

  On the other hand, it has been reported that the battery for HV vehicles and other devices related to the battery itself are adapted to the HV vehicle and the life of the secondary battery is improved without using such systematic battery control. Patent Document 1 below discloses a battery system for an HV vehicle that takes into account sudden energy accumulation during braking of the HV vehicle and sudden energy release during acceleration. In this publication, power storage means by a flywheel device is used together with a secondary battery, energy generated at the time of braking is regenerated to the flywheel device as rotational energy, and driven by using rotational energy stored in the flywheel device at acceleration. Is disclosed. This publication suggests that the provision of such power storage means can reduce the number of times the secondary battery is charged / discharged, suppress the rise in battery temperature, extend the life, and reduce the size of the secondary battery. Has been.

  Patent Document 2 listed below discloses a secondary battery capacity detection device having a characteristic in which a charge capacity and a discharge capacity are substantially equal. It is disclosed that a chargeable capacity of a secondary battery is calculated from a charging current measured by a current detection unit, and the chargeable capacity is detected as a dischargeable capacity.

JP-A-10-295002 JP 7-270503 A

  However, in the said patent document 1, a flywheel apparatus must be used together as an electrical storage means besides a secondary battery, and the electrical storage means which requires big electric power other than a secondary battery is needed. When the power storage means having such a large power storage contribution power is provided, the power storage system as a whole including the secondary battery may be enlarged even if the secondary battery is downsized.

  Moreover, the said patent document 1 does not mean that the secondary battery itself was designed by considering the charging characteristics and discharging characteristics of the HV vehicle for the secondary battery, but uses a conventional secondary battery. In the case where the secondary battery considering the charge / discharge characteristics of the HV vehicle is not used, there may be a case where a secondary battery suitable for the characteristics of the HV vehicle cannot be provided. Thus, if the charge / discharge characteristics of the HV vehicle are not taken into consideration, the secondary battery may become larger than necessary.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a more improved HV vehicle battery system.

The battery system for a hybrid vehicle including a secondary battery that repeats charging that is supplied with electric power from braking energy at the time of vehicle braking according to the present invention and discharge that supplies electric power to the electric motor of the vehicle. dischargeable electric capacity per unit time than the chargeable electric capacity per unit much time about wherein the small.

  In the battery system for a hybrid vehicle, the chargeable electric capacity per unit time is equal to or greater than a required charge electric capacity per predetermined unit time required when receiving braking energy at the time of braking of the vehicle, The dischargeable electric capacity per unit time is preferably equal to or greater than the required discharge electric capacity per predetermined unit time required when driving the electric motor from a state where the vehicle is stopped.

  The present invention can provide an improved HV vehicle battery system.

  Hereinafter, embodiments of the present invention will be described based on the drawings. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

“Overall configuration of battery system for HV vehicles”
FIG. 1 shows an assembled battery control system 100 for an HV vehicle according to the present embodiment applied to an HV vehicle having a size of Prius (manufactured by Toyota Motor Corporation: HEV vehicle). The assembled battery 200 according to this embodiment includes a plurality of battery blocks 10 connected in series. The assembled battery 200 corresponds to the charging characteristics and discharging characteristics required for the assembled battery 200 of the HV vehicle, and the dischargeable electric capacity per unit time is designed to be smaller than the chargeable electric capacity per unit time. ing. Further, the chargeable electric capacity per unit time is equal to or greater than the required charge electric capacity per unit time supplied from the braking energy when the vehicle is braked. Further, the dischargeable electric capacity per unit time is not less than the required discharge electric capacity per unit time that is required to be supplied to the electric motor when the vehicle is driven from a stopped state. Specifically, the dischargeable electric capacity per unit time is 10 kw, while the chargeable electric capacity per unit time is 15 kw. A voltage detector 14 for detecting the voltage of the battery block 10 is connected to the assembled battery 200. The battery ECU 16 calculates the SOC of each battery block 10 constituting the assembled battery 200 based on the output of the voltage detector 14. The battery ECU 16 calculates the SOC sent from the SOC of each battery block 10 to the HVECU 18 by the charge / discharge control program. Based on the SOC calculated by the battery ECU 16, the SOC is determined, and the HVECU 18 controls the load 20 including a drive motor, a generator drive engine, a generator, an inverter, and the like. That is, the amount of charge / discharge of the assembled battery 200 is adjusted so that the entire SOC of the assembled battery 200 falls within a predetermined range. As the SOC control range, for example, a range of 20% to 80% is adopted. The battery control system 100 includes the battery ECU 16, the HVECU 18, the assembled battery 200, the load 20, the voltage detector 14, and the like.

  The battery block 10 that is a unit battery constituting the assembled battery 200 is an assembled battery in which a large number of battery cells are connected in series. It consists of battery cells. The SOC of each battery block 10 is preferably calculated in consideration of not only the voltage but also the temperature of the battery block and the measured current value.

  The above is a configuration in which the HVECU 18 and the battery ECU 16 are separated, but the HVECU 18 and the battery ECU 16 can be integrated into one device.

  Examples of the load 20 include an engine ECU (E / GECU), a motor ECU, an inverter, and a motor generator. The HVECU 18 issues an engine output command to the E / GECU that controls engine output and the like, and receives engine output control information from the E / GECU and the like. Further, the HVECU 18 outputs a torque command or the like to the motor and inputs motor control information from the motor ECU. The motor ECU performs switching control in the inverter. Thereby, the input to the motor generator is determined, and the drive wheels can be driven according to the output.

`` Charge / discharge characteristics ''
<Discharge characteristics> The assembled battery 200 incorporated in the HV vehicle battery system 100 has the following discharge characteristics. When the HV vehicle is driven by a motor from a stopped state, the vehicle is driven by discharging electric power stored in the assembled battery 200 from the internal combustion engine and driving the motor (EV traveling). At that time, the necessary dischargeable electric capacity per unit time that the driver satisfies as drivability is less than 10 kw, and is usually 6 kw to 7 kw. In order to start the engine, which is an internal combustion engine, from EV traveling, a dischargeable electric capacity per unit time is sufficient to be several kW, that is, 2 kW to 3 kW. Therefore, the larger 6 kw to 7 kw is the required discharge electric capacity per unit time. Thereafter, the required discharge electric capacity required to satisfy acceleration, horsepower, and the like is changed depending on the power sharing between the engine and the motor, but 10 kW per unit time of the assembled battery 200 is usually sufficient. Accordingly, it is preferable that the required discharge electric capacity is 10 kw. In this way, the predetermined required discharge electric capacity is determined in consideration of the discharge characteristics of the HV vehicle. After determining a predetermined required discharge electric capacity, a dischargeable electric capacity per unit time is designed.

<Charging Characteristics> The assembled battery 200 incorporated in the HV vehicle battery system 100 has the following charging characteristics. The regenerative energy at the time of braking is large, and the electric power supplied to the assembled battery 200 per unit time has a value larger than 10 kW which is the dischargeable electric capacity per unit time. However, it has been found that the chargeable electric capacity per unit time is 15 kw in the examination by the present inventors in the mode running. The larger the chargeable electric capacity, the more regenerative energy can be absorbed, but about 15% can be recovered even at 15 kW. It is sufficient that about 95% can be recovered, and it is not necessary to design a secondary battery having a chargeable electric capacity ( for example, 20 kw) per unit time. Therefore, it is preferable that the chargeable electric capacity per unit time is 15 kW. In this way, the predetermined required charging electric capacity is determined in consideration of the charging characteristics of the HV vehicle. After determining a predetermined required charging electric capacity, a more chargeable electric capacity per unit time is designed.

  <Design method> Rechargeable electric capacity per unit time and unit time by changing the material and thickness of the conductive wire connected to the battery electrode, the size of the battery electrode, the type of electrolyte, the type of electrode material, etc. It is generally possible to design the permissible discharge capacity (for example, JP-A-9-514133). By using this general method, for example, a person skilled in the art can sufficiently and clearly design a secondary battery having a dischargeable electric capacity per unit time of 10 kw and a chargeable electric capacity per unit time of 15 kw.

  Since the secondary battery is a device that stores (charges) or releases (discharges) energy by a chemical reaction, there is a limit to the rate of energy storage and release. If the battery is used at a rate exceeding this energy storage and release rate, that is, the chemical reaction rate, the temperature of the battery rises and energy is wasted, and the electrode is deteriorated to shorten the battery life. Therefore, in order to prevent battery deterioration, it is necessary to increase the capacity of the battery. However, when the battery capacity becomes larger than necessary, the battery is usually increased in size. On the other hand, the battery capacity is increased more than necessary by designing the battery for HV vehicles together with the charging characteristics and discharging characteristics of the HV cars as in the present embodiment, and the battery is prevented from becoming larger than necessary. it can. The chargeable capacity per unit time is made larger than the dischargeable capacity per unit time in accordance with the charging characteristics and discharging characteristics of the HV vehicle. That is, the dischargeable capacity per unit time is made smaller than the chargeable capacity per unit time in correspondence with the dischargeable characteristics. Since the chargeable capacity is reduced, the secondary battery can be made smaller than the secondary battery in which both the chargeable capacity per unit time and the dischargeable capacity per unit time are increased. The size of the secondary battery itself in the battery system for HV vehicles can be reduced, and the life of the secondary battery by charging and discharging can be maintained. Further, it is possible to reduce the power storage contribution by the power storage means other than the secondary battery and to reduce the size of the power storage means or to make it unnecessary, and to reduce the size of the entire power storage system including the secondary battery.

  The present invention can be applied as a battery system for HV vehicles in general for HV vehicles (including both FVEV vehicles and HEV vehicles). For example, the battery system for HV vehicles of the present invention can be applied to all HV vehicles such as light vehicles, passenger cars, large / small special vehicles, and large vehicles (buses, trucks).

It is a block diagram of the assembled battery control system for HV vehicles which concerns on this embodiment. It is a block diagram of the conventional assembled battery control system for HV vehicles.

Explanation of symbols

  10 unit battery (battery block), 14 voltage detector, 16 battery ECU, 18 HVECU, 20 load, 100,300 HV vehicle assembled battery control system, 200,400 assembled battery.

Claims (2)

A battery system for a hybrid vehicle including a secondary battery that repeats charging that is supplied with electric power from braking energy at the time of vehicle braking and electric discharge that supplies electric power to the electric motor of the vehicle,
The secondary battery may cell system for dischargeable electric capacity is small hybrid vehicles per unit time than the chargeable electric capacity per unit of time. The hybrid vehicle battery system according to claim 1,
The chargeable electric capacity per unit time is not less than a required charge electric capacity per predetermined unit time required when receiving braking energy at the time of braking of the vehicle,
The hybrid vehicle battery system wherein the dischargeable electric capacity per unit time is equal to or greater than a required discharge electric capacity per predetermined unit time required when driving the electric motor from a state where the vehicle is stopped.

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