JP2006136131A - Controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid the occurrence of energy loss in the high-vehicle speed range of a vehicle mounted with a secondary battery having such a characteristic that the maximum value of input power is increased with reduction in SOC. <P>SOLUTION: A battery ECU executes a program including a step (S100) at which vehicle speed is detected; a step (S150) at which, when the vehicle speed is in the high-vehicle speed range (YES at S110) and a preset battery target SOC is not less than a control lower limit SOC (YES at S130), the battery target SOC is lowered; and a step at which the SOC of the battery for running is controlled so that it agrees with the battery target SOC. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle control device equipped with a secondary battery for driving a traveling motor, and more particularly to a vehicle control device that avoids energy loss at high vehicle speeds.

  A vehicle equipped with a power train called a hybrid system combining an engine (for example, a known engine such as a gasoline engine or a diesel engine) and an electric motor has been developed and put into practical use. In such a vehicle, regardless of the amount of accelerator operation by the driver, the operation by the engine and the operation by the electric motor are automatically switched and controlled so as to obtain the highest efficiency. For example, when the engine is operated in a steady state to operate a generator that charges a secondary battery (battery), or depending on the state of charge (SOC) of the secondary battery When the vehicle is intermittently operated during traveling, the engine is repeatedly operated and stopped regardless of the amount of accelerator operation by the driver. That is, by operating the engine and the electric motor individually or in cooperation, it is possible to improve fuel consumption and significantly reduce exhaust gas.

  For example, in low load areas where engine efficiency is poor (especially when starting or at very low speeds), the vehicle is driven only by an electric motor without starting the engine, and if the vehicle speed shifts to a speed area where engine efficiency improves, a large torque Starts the engine that can output and stops the electric motor. Further, when a larger output is required, such as during acceleration, the engine and the electric motor can be driven simultaneously, and torque assist by the electric motor can be performed to obtain a desired output.

  Thus, when using an electric motor, electric power is supplied from the battery mounted in the vehicle. Therefore, in such a vehicle, it is necessary to mount a large-capacity battery, and in order to use the good electric motor as described above, it is necessary to always manage the SOC of the battery.

  Normally, such a vehicle is equipped with a motor generator (MG) having an electric motor function and a power generation function, and this MG generates electric power so that the amount of charge converges to the target charge value (target SOC) of the battery. Controlled to do. The target SOC is a fixed value (for example, the total charge amount is large) with a margin at the upper and lower limits so that both a discharge request (electric motor drive request) and a charge request (regenerative power charge request) can be accepted. 60 [%]) is set.

  Japanese Patent Application Laid-Open No. 11-164402 (Patent Document 1) discloses a hybrid vehicle control device that makes the most effective use of the charging capacity of a power storage unit as a power source for a vehicle running motor. The hybrid vehicle control device includes a drive unit including an electric motor for driving the vehicle, a power generation unit that generates electrical energy based on a power generation command, and generates electric energy by the motor during regeneration, and a power generation unit Hybrid vehicle having a power storage unit that stores electrical energy from the battery and supplies it to the motor as needed, a charge state detection unit that detects a charge state of the power storage unit, and a control unit that outputs a power generation command to the power generation unit The control unit is a charging state management target that is variable depending on a charging state value detected from the charging state detection unit and a parameter indicating a state of the vehicle that can determine whether charging is possible. The power generation amount to be generated by the power generation unit is calculated from the value, and the power generation amount is output to the power generation unit as a power generation command. This parameter is the vehicle speed, and the charge state management target value is set high when the speed is low, and is set low when the speed is high.

  According to this hybrid vehicle control device, it is possible to easily predict the driver's acceleration / deceleration request by using the parameter representing the vehicle state as the vehicle speed. For example, when the vehicle is stopped or traveling at a low speed, the driver's intention to accelerate is likely to occur next. Therefore, in preparation for driving the motor for this acceleration, set the charging state management target value higher and reverse In addition, in high-speed cruise operation, the driver's intention to decelerate due to traffic jams in the front is likely to occur, so the management target value for the state of charge should be adjusted lower to recover energy by regenerative braking during deceleration. Can do. Therefore, it is possible to recover the energy of regenerative braking that occurs until a future stop by adjusting the charging state management target value to a lower value during high-speed traveling.

  Japanese Patent Laying-Open No. 2001-268719 (Patent Document 2) discloses a battery charge control device for a hybrid vehicle that can efficiently perform the required charge and discharge. This battery charge control device for a hybrid vehicle is a battery charge control device for a hybrid vehicle that includes an internal combustion engine, a motor generator capable of assisting vehicle travel, and a battery connected to the motor generator. Charge / discharge prediction means for predicting the charge / discharge state; and target value change means for changing the charge target value of the battery based on the charge / discharge prediction result of the battery. The charge / discharge prediction means predicts a future charge / discharge state of the battery based on the running state of the vehicle. The target value changing means increases the charging target value in the case of a vehicle running state in which the battery is predicted to be discharged by a predetermined amount or more in the future, and the vehicle running in which the battery is predicted to be charged by a predetermined amount or more in the future. In the state, the charging target value is decreased.

According to the battery charge control device of this hybrid vehicle, the charge / discharge prediction means performs charge / discharge prediction based on vehicle speed information, for example. For example, if the low vehicle speed continues for a predetermined time or more, the vehicle is expected to stop in the future or accelerate greatly. In this case, since large electric energy is consumed by the electric motor function of the motor generator, the target charge amount is increased to ensure a sufficient charge amount. Conversely, for example, when the high vehicle speed continues for a predetermined time or more, the vehicle is expected to decelerate in the future. In this case, since large regenerative energy can be obtained by the power generation function of the motor generator, the target charge amount is reduced, the regenerative energy recovery area is increased, and the regenerative energy is sufficiently recovered. Therefore, the required charge / discharge can be performed efficiently.
JP-A-11-164402 JP 2001-268719 A

  However, large electric power is generated during regenerative braking in the high vehicle speed region. That is, the regenerative power value increases as the vehicle speed increases. The battery has a maximum output power value (maximum output power value) and a maximum input power value (maximum input power value). The battery can be used to discharge more power than the maximum output power value or The regenerative power exceeding the input power value cannot be charged. In the above-mentioned patent document, the target value of the SOC of the battery is merely reduced so that the regenerative electric energy generated for the future deceleration or the deceleration until the future stop can be charged during high-speed traveling. In other words, focusing only on the amount of electric power, the target SOC is merely lowered during high-speed traveling, and is not focused on the battery accepting (capable of charging) a large regenerative power value generated during regenerative braking during high-speed traveling. . For this reason, when a large regenerative power value is generated, the regenerative power cannot be used for charging the battery, causing energy loss.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to generate a regenerative power having a large power value when a vehicle equipped with a secondary battery is regeneratively braked in a high vehicle speed range. It is possible to provide a vehicle control device that controls a secondary battery so as to avoid occurrence of energy loss in a high vehicle speed region.

  A vehicle control device according to a first aspect of the invention controls a vehicle equipped with a secondary battery that stores electric power for traveling. The secondary battery has a characteristic that the power value that can be input varies depending on the state of the secondary battery. The control device includes a means for controlling a recovery mechanism that recovers the kinetic energy of the vehicle as regenerative power as the vehicle decelerates, and a changing means for changing a target value for the state of the secondary battery, And a control means for controlling the secondary battery based on the target value. The recovery mechanism recovers larger regenerative power as the vehicle speed increases. The changing means includes means for changing the target value so as to cope with recovery of regenerative power in the high vehicle speed range.

  According to the first aspect of the present invention, when recovering the kinetic energy of the vehicle as regenerative power as the vehicle decelerates in the high vehicle speed region, the secondary battery can be input to the secondary battery even if recovered power with a large power value is generated. The target value for the battery state (eg, SOC) is changed. If it does in this way, a secondary battery can be charged using regenerative electric power of a big electric power at the time of vehicles with a rechargeable battery carrying out regenerative braking in the high vehicle speed field. As a result, it is possible to provide a vehicle control device that controls the secondary battery so as to avoid the occurrence of energy loss in the high vehicle speed region.

  In the vehicle control apparatus according to the second aspect of the invention, in addition to the configuration of the first aspect of the invention, the secondary battery has a characteristic that the input power value is large when the charge capacity is low. The changing means includes means for changing the target value of the charging capacity. The control means includes means for controlling charging / discharging of the secondary battery based on the target value. The changing means includes means for changing the target value of the charging capacity to be low.

  According to the second aspect of the invention, the target power can be collected so that the regenerative power having a large power value in the high vehicle speed range can be recovered by utilizing the characteristic that the input power value is large when the charge capacity (SOC) of the secondary battery is low. Lower the SOC. By changing the target SOC to a low value, the power value that can be input increases due to the characteristics of the secondary battery. For this reason, a secondary battery can be charged using regenerative electric power having a large electric power value generated when a vehicle equipped with a secondary battery is regeneratively braked in a high vehicle speed region, and energy loss can be avoided.

  In the vehicle control apparatus according to the third aspect of the invention, in addition to the configuration of the second aspect of the invention, the power value that can be input varies greatly with respect to the characteristic that the charge capacity decreases.

  According to the third aspect of the invention, when the charge capacity (SOC) of the secondary battery is low, the power value (WIN) that can be input becomes large. Therefore, in a high vehicle speed region where regenerative power with a high power value is generated, The target SOC is changed to be low so that input to the secondary battery is possible. The charging / discharging of the secondary battery is controlled by the control means so as to achieve the target SOC thus changed.

  In the vehicle control apparatus according to the fourth invention, in addition to the configuration of any one of the first to third inventions, the recovery mechanism is a motor generator.

  According to the fourth aspect of the invention, the regenerative power at the time of braking can be recovered and the secondary battery can be charged by using the motor generator that generates a large power value at the time of regenerative braking in the high vehicle speed region.

  In the vehicle control apparatus according to the fifth invention, in addition to the configuration of any one of the first to fourth inventions, the secondary battery is a lithium ion battery.

  According to the fifth aspect of the invention, the lithium ion battery is suitable for a vehicle running battery such as a higher battery operating voltage, higher charge / discharge efficiency, and no memory effect than other secondary batteries. . This lithium ion battery has a characteristic that when the SOC is low, the input power value is large. Therefore, in consideration of this characteristic, the lithium ion battery can be charged using regenerative power in the high vehicle speed region.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  A control block diagram of a hybrid vehicle according to an embodiment of the present invention will be described with reference to FIG. The present invention is not limited to the hybrid vehicle shown in FIG. It may be a hybrid vehicle having another aspect equipped with a secondary battery. Further, it may be an electric vehicle or a fuel cell vehicle. As will be described later, it is assumed that the secondary battery has a characteristic that the power value that can be input and output is large when the SOC is low. One such secondary battery is a lithium ion battery.

  The hybrid vehicle includes an internal combustion engine (hereinafter simply referred to as an engine) 120 such as a gasoline engine or a diesel engine, and a motor generator (MG) 140 as drive sources. In FIG. 1, for convenience of explanation, the motor generator 140 is expressed as a motor 140A and a generator 140B (or a motor generator 140B), but the motor 140A functions as a generator depending on the traveling state of the hybrid vehicle. The generator 140B functions as a motor. A recovery mechanism corresponds to this motor generator. As will be described later, this motor generator generates regenerative power having a higher power value at higher vehicle speeds.

In addition to this, the hybrid vehicle transmits a power generated by the engine 120 and the motor generator 140 to the drive wheels 160, and a reduction gear 180 that transmits the drive of the drive wheels 160 to the engine 120 and the motor generator 140, and the engine 120. Power split mechanism (for example, planetary gear mechanism) 200 that distributes the generated power to two paths of drive wheel 160 and generator 140B, travel battery 220 that charges power for driving motor generator 140, and travel Inverter 240 that performs current control while converting the direct current of battery 220 and the alternating current of motor 140A and generator 140B, and a battery control unit (hereinafter referred to as a battery ECU (Electronic Control Unit)) that manages and controls the charge / discharge state of traveling battery 220 260) and En Engine ECU controlling an operation state of the emission 120
280 and MG_ECU 300 that controls motor generator 140, battery ECU 260, inverter 240, etc., and battery ECU 260, engine ECU 280, MG_ECU 300, etc. according to the state of the hybrid vehicle are mutually managed and controlled so that the hybrid vehicle can operate most efficiently. HV_ECU 320 and the like for controlling the entire hybrid system.

  In the present embodiment, boost converter 242 is provided between battery for traveling 220 and inverter 240. This is because the rated voltage of the traveling battery 220 is lower than the rated voltage of the motor 140A or the motor generator 140B, and therefore when the power is supplied from the traveling battery 220 to the motor 140A or the motor generator 140B, the boost converter 242 supplies the power. Boost the pressure.

  In FIG. 1, each ECU is configured separately, but may be configured as an ECU in which two or more ECUs are integrated (for example, MG_ECU 300 and HV_ECU 320, as shown by a dotted line in FIG. 1). An example is an integrated ECU).

  The power split mechanism 200 uses a planetary gear mechanism (planetary gear) in order to distribute the power of the engine 120 to both the drive wheel 160 and the motor generator 140B. By controlling the rotation speed of motor generator 140B, power split device 200 also functions as a continuously variable transmission. The rotational force of the engine 120 is input to the planetary carrier (C), which is transmitted to the motor generator 140B by the sun gear (S) and to the motor and the output shaft (drive wheel 160 side) by the ring gear (R). When the rotating engine 120 is stopped, since the engine 120 is rotating, the kinetic energy of this rotation is converted into electric energy by the motor generator 140B, and the rotational speed of the engine 120 is reduced.

  In a hybrid vehicle equipped with a hybrid system as shown in FIG. 1, the hybrid vehicle travels only by the motor 140 </ b> A of the motor generator 140 when the engine 120 is inefficient, such as when starting or running at a low speed. During normal travel, for example, the power split mechanism 200 divides the power of the engine 120 into two paths, and on the other hand, the drive wheels 160 are directly driven, and on the other hand, the generator 140B is driven to generate power. At this time, the motor 140A is driven by the generated electric power to assist driving of the driving wheels 160. Further, at the time of high speed traveling, electric power from the traveling battery 220 is further supplied to the motor 140A to increase the output of the motor 140A and to add driving force to the driving wheels 160. On the other hand, at the time of deceleration, motor 140 </ b> A driven by drive wheel 160 functions as a generator to perform regenerative power generation, and the collected power is stored in traveling battery 220. When the amount of charge of traveling battery 220 decreases and charging is particularly necessary, the output of engine 120 is increased to increase the amount of power generated by generator 140B to increase the amount of charge for traveling battery 220. Of course, control is performed to increase the drive amount of the engine 120 as necessary even during low-speed traveling. For example, it is necessary to charge the traveling battery 220 as described above, to drive an auxiliary machine such as an air conditioner, or to raise the temperature of the cooling water of the engine 120 to a predetermined temperature.

  A technical feature of the control device according to the present embodiment for controlling such a control block will be described. During traveling of the vehicle, as shown in FIG. 2, the motor generator 140 generates regenerative electric power with a larger electric power as the vehicle speed increases. The lithium ion battery described as an example of the traveling battery 220 has input / output characteristics as shown in FIG. That is, the higher the SOC is, the larger the maximum input power value (WIN) is (exactly, since the input side is described as minus, the absolute value of the maximum input power value increases). The low SOC can input electric power having a larger electric power value than the high SOC, that is, can be charged.

  Therefore, in the control device in the present embodiment, as shown in FIG. 4, in the high vehicle speed region, the target SOC is set lower than in the low vehicle speed region, and the regenerative electric power having a large power value is set for the traveling battery. It is possible to input to a lithium ion battery 220. In FIG. 4, the control lower limit value (in this example, 30 [%]) is provided for the target SOC because, when an acceleration request is made during high-speed driving, power is supplied from the driving battery 220 to the motor generator 140. This is because the engine 120 can be torque-assisted. 2 to 4 are examples, and do not limit the present invention. Particularly, the vehicle speed value on the horizontal axis, the target SOC on the vertical axis, and the decreasing slope of the target SOC in FIG. 4 are examples. The decrease in the target SOC is not limited to a linear shape, and may be a decrease in a curve.

  With reference to FIG. 5, the control structure of the target SOC changing process executed by MG_ECU 300 will be described. In the following description, the battery ECU 260 is described as performing the target SOC changing process, but may be performed by another ECU.

  In step (hereinafter step is abbreviated as S) 100, battery ECU 260 detects the vehicle speed. At this time, battery ECU 260 detects the vehicle speed by receiving from HV_ECU 320 a vehicle speed signal detected by a vehicle speed sensor (not shown) and input to HV_ECU 320, for example.

  In S110, battery ECU 260 determines whether or not it is a high vehicle speed region. At this time, it is determined that the vehicle is in the high vehicle speed region unless the vehicle speed is extremely low. In addition, when the target SOC reduction of FIG. 4 does not start from 0 [km / h], for example, when it starts from 40 [km / h], it is in the high vehicle speed range unless it is 40 [km / h] or less. It is judged that there is. If it is determined that the vehicle is in the high vehicle speed region (YES in S110), the process proceeds to S120. Otherwise (NO in S110), this process ends.

  In S120, battery ECU 260 reads battery target SOC stored in the memory. In S130, battery ECU 260 determines whether or not read battery target SOC is equal to or higher than control lower limit SOC (here, 30 [%] as shown as an example in FIG. 4). If the read battery target SOC is equal to or greater than the control lower limit SOC (YES in S130), the process proceeds to S140. Otherwise (NO at S130), this process ends.

  In S140, battery ECU 260 calculates a battery target SOC. At this time, for example, based on FIG. 4 and the like, the battery target SOC is calculated to be lower as the vehicle speed is higher.

  In S150, battery ECU 260 lowers the target SOC to the calculated target SOC. The battery ECU 260 executes charge / discharge control of the traveling battery 220 so that the reduced battery target SOC is obtained. In S160, battery ECU 260 stores the reduced target SOC in the memory.

  An operation of the vehicle according to the present embodiment based on the above-described structure and flowchart will be described.

  When a vehicle equipped with a traveling battery 220 composed of a lithium ion battery enters a high vehicle speed range while traveling (YES in S110), battery target SOC is read from the memory. When the read battery target SOC is equal to or higher than the management lower limit SOC (YES in S130), the battery target SOC is lowered as the vehicle speed increases (S150).

  The higher the vehicle speed, the larger the regenerative power value generated by the motor generator 140, and the lower the SOC of the lithium ion battery, the higher the maximum input power value. For this reason, as the vehicle speed increases, the battery target SOC is reduced within a range that does not fall below the control lower limit value, the maximum input power value is increased, and the regeneration of a large power value that occurs when regenerative braking is performed in the high vehicle speed range. Electric power can be input to the traveling battery 220 to charge the traveling battery 220.

  As described above, according to the battery ECU that is the control device according to the present embodiment, the characteristic that the input power value is large when the SOC in the traveling battery such as a lithium ion battery mounted on the vehicle is low is used. Then, the target SOC is changed to be low so that regenerative power having a large power value in the high vehicle speed range can be effectively recovered. By changing the target SOC to a low value, the power value that can be input increases due to the characteristics of the battery for traveling. For this reason, the battery for traveling can be charged using the regenerative electric power having a large electric power value generated when the vehicle equipped with the battery for traveling is regeneratively braked in the high vehicle speed region, and the occurrence of energy loss that has conventionally occurred can be avoided. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a control block diagram of the hybrid vehicle which concerns on embodiment of this invention. It is a figure which shows the relationship between a vehicle speed and regenerative electric power. It is a figure which shows the relationship between a vehicle speed and target SOC. It is a figure which shows the relationship between SOC and the maximum input / output electric power value. It is a flowchart which shows the control structure of the engine stop process performed by MG_ECU.

Explanation of symbols

  120 Engine, 140 Motor Generator, 140A Motor, 140B Generator, 160 Drive Wheel, 180 Reducer, 200 Power Dividing Mechanism, 220 Traveling Battery, 240 Inverter, 242 Boost Converter, 260 Battery ECU, 280 Engine ECU, 300 MG_ECU, 320 HV_ECU.

Claims (5)

A vehicle control device equipped with a secondary battery that stores electric power for traveling,
The secondary battery has a characteristic that an input power value varies depending on a state of the secondary battery,
The controller is
Means for controlling a recovery mechanism that recovers the kinetic energy of the vehicle as regenerative electric power as the vehicle decelerates;
Change means for changing a target value for the state of the secondary battery;
Control means for controlling the secondary battery based on the target value,
The recovery mechanism recovers larger regenerative power as the vehicle speed is higher,
The control means for a vehicle includes a means for changing the target value so as to cope with recovery of regenerative power in a high vehicle speed range. The secondary battery has a characteristic that the input power value is large when the charging capacity is low,
The changing means includes means for changing a target value of the charging capacity,
The control means includes means for controlling charging / discharging of the secondary battery based on the target value,
The vehicle control device according to claim 1, wherein the changing unit includes a unit for changing the target value of the charging capacity to a low value.   The vehicle control device according to claim 2, wherein the characteristic is that a power value that can be input varies greatly with respect to a variation in which the charging capacity decreases.   The vehicle control device according to claim 1, wherein the recovery mechanism is a motor generator.   The vehicle control device according to claim 1, wherein the secondary battery is a lithium ion battery.

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