JP2012010503A - Power supply system for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure charging of a secondary storage device during startup of a power supply system, while enhancing the energy efficiency of a vehicle in an electric vehicle mounting primary and secondary storage devices.SOLUTION: An auxiliary battery 210 is charged using output voltage from a DC-DC converter 200 that steps down output voltage from a main battery 150. An ECU 170 sets up a voltage command value Vdcr for the DC-DC converter 200 at a voltage for charging the auxiliary battery 210 during startup of a power supply system. The ECU 170 estimates a necessary charging time for the auxiliary battery 210 based on transition of charging current Ichg of the auxiliary battery 210, and lowers the voltage command value Vdcr after elapse of estimated necessary charging time.

Description

  The present invention relates to a power supply system for an electric vehicle, and more particularly to a power supply system for an electric vehicle equipped with a main power storage device for generating vehicle driving force and a sub power storage device for driving auxiliary equipment.

  In an electric vehicle such as an electric vehicle, a hybrid vehicle, and a fuel cell vehicle configured to be able to generate a vehicle driving force by an electric motor, a power storage device (for example, a main battery) that stores electric power for driving the electric motor, A configuration is employed in which two types of power storage devices are mounted, such as a power storage device for driving voltage auxiliary machinery (for example, an auxiliary battery). This is because the output voltage suitable for driving the electric motor for traveling and the rated voltage (for example, 12 V) of auxiliary equipment such as headlights and air conditioning equipment or control equipment such as an electronic control unit (ECU) are greatly different. In such a configuration, the auxiliary battery is generally charged by the output voltage of a voltage converter (DCDC converter) that steps down the output voltage of the main battery.

  Such charge control of the auxiliary battery is described in Japanese Patent Laid-Open No. 2003-37903 (Patent Document 1) and Japanese Patent Laid-Open No. 9-46921 (Patent Document 2). In particular, Patent Document 1 describes an appropriate setting of the charging voltage of an auxiliary battery that is charged in parallel with the charging of the main battery. Specifically, the charging of the auxiliary battery is started based on the start of charging of the main battery, and the charging is started from the charging start to the specified time at the first specified voltage (14.5 V) that can reliably charge the auxiliary battery. On the other hand, there is described control for charging the auxiliary battery with a second specified voltage (13.4 V) lower than the first specified voltage after the specified time has elapsed.

  Japanese Patent No. 3554057 (Patent Document 3) describes control using an estimated value of a required charging period when charging a storage battery for an electric vehicle. Japanese Patent Application Laid-Open No. 11-341696 (Patent Document 4) describes charge control of a plurality of rechargeable batteries having different battery types.

JP 2003-37903 A JP-A-9-46921 Japanese Patent No. 3554057 JP-A-11-341696

  In Patent Document 1, it is assumed that the auxiliary battery is charged in parallel when the main battery is charged. Then, during charging of the main battery, which takes a long time, the charging voltage of the auxiliary battery is lowered when the specified time elapses, thereby reliably charging while preventing overcharging of the auxiliary battery. is there.

  On the other hand, the charging of the auxiliary battery of the electric vehicle is preferably performed when the power supply system is started when the vehicle is started (for example, when the ignition switch is turned on). This is because the operation of the auxiliary machine including the control device can be ensured by ensuring the charging of the auxiliary battery when starting the vehicle. In particular, in a hybrid vehicle of a type that does not include a charging mechanism using an external power source, there is no opportunity for charging an auxiliary battery as in Patent Document 1, so charging at the time of starting the vehicle is required.

  When the charging control described in Patent Document 1 is applied to the charging of the auxiliary battery at the time of starting the power supply system, the time (specified time) until the charging voltage of the auxiliary battery is lowered is fixed. Therefore, there is a concern that the output voltage of the DCDC converter may remain high even when the auxiliary battery is completely charged. On the other hand, the power consumption of the voltage converter (DCDC converter) increases as the output voltage increases.

  For this reason, in the charge control described in Patent Document 1, even if the charging of the auxiliary battery is completed, there is a possibility that the efficiency is lowered because the charging voltage remains high. The charging of the auxiliary battery in Patent Document 1 is performed at the time of charging the main battery before the start of running of the electric vehicle. Therefore, even if such a reduction in efficiency occurs, the vehicle running efficiency (fuel consumption) itself does not drop. On the other hand, in charging at the time of starting the power supply system, unlike in Patent Document 1, if the charging efficiency is low, the fuel consumption of the vehicle may be deteriorated.

  The present invention is for solving such problems, and an object of the present invention is in an electric vehicle equipped with a main power storage device for generating vehicle driving force and a sub power storage device for driving auxiliary equipment. By appropriately setting the output voltage of the voltage converter that generates charging power for the sub power storage device, the sub power storage device is reliably charged when the power supply system is activated, and the energy efficiency of the vehicle is increased.

  In one aspect of the present invention, a power system for an electric vehicle equipped with an electric motor for generating vehicle driving force includes a main power storage device, a voltage converter, a sub power storage device, an auxiliary load, and a charging current detection unit. And a voltage detector and a voltage command setting unit. The main power storage device is configured to store electric power input / output to / from the electric motor. The voltage converter is configured to step down the output voltage of the main power storage device according to the voltage command value and output the voltage to the power supply wiring. The sub power storage device and the auxiliary load are electrically connected to the power supply wiring. The charging current detection unit is configured to detect a charging current of the sub power storage device. The voltage detector is configured to detect an output voltage of the sub power storage device. The voltage command setting unit sets the voltage command value to the first voltage for charging the sub power storage device when starting the voltage converter, and based on the transition of the charging current detected by the charging current detection unit. Then, the time required for charging the sub power storage device is estimated, and when the estimated time required for charging elapses, the voltage command value is set to a second voltage lower than the first voltage.

  Preferably, the voltage command setting unit estimates the required charging time based on the slope of the change in the charging current after starting the voltage converter and the charging current when starting the voltage converter.

  Preferably, the voltage converter is started at a second time delayed by a predetermined time from the first time when the power supply system is activated. The voltage command setting unit includes a slope of a change in the charging current after the voltage converter is started and an output of the sub power storage device between the first time and the second time with respect to the output voltage of the sub power storage device before the first time. The required charging time is estimated based on the voltage difference between the output voltages.

  More preferably, the voltage command setting unit estimates the discharge amount from the sub power storage device during the period in which the voltage command value is set to the second voltage, and sets the voltage command value based on the estimated discharge amount. Increase to 1 voltage.

  Alternatively, more preferably, the power supply system for the electric vehicle further includes a deterioration determination unit. The deterioration determining unit determines the degree of deterioration of the sub power storage device based on the required charging time estimated by the voltage command setting unit and the voltage drop of the sub power storage device before and after starting the power supply system.

  More preferably, the voltage command setting unit sets the voltage command value to a third voltage lower than the open voltage of the sub power storage device before setting the voltage command value to the first voltage when starting the voltage converter. It is comprised so that the predetermined period to set may be provided. The charging current detection unit includes an auxiliary current estimation value based on a detection value in a predetermined period of the current sensor for detecting an output current from the voltage converter to the power supply wiring, and a detection value of the current sensor when the sub power storage device is charged. The charging current is detected based on the difference between the two.

  More preferably, the electric vehicle is a hybrid vehicle equipped with an engine in addition to the electric motor, and electric power used for starting the engine is supplied from the main power storage device.

  According to the present invention, in an electric vehicle equipped with a main power storage device for generating vehicle driving force and a sub power storage device for driving auxiliary equipment, the output voltage of the voltage converter that generates charging power for the sub power storage device is appropriately set. By setting, the sub power storage device can be reliably charged when the power supply system is activated, and the energy efficiency of the vehicle can be increased.

1 is a schematic configuration diagram of a hybrid vehicle shown as a representative example of an electric vehicle according to an embodiment of the present invention. FIG. 2 is a collinear diagram showing a relationship between rotational speeds of an engine and a motor generator in the hybrid vehicle shown in FIG. 1. It is a block diagram which shows the structure of the power supply system of the electric vehicle by embodiment of this invention. It is a conceptual diagram explaining control of the DCDC converter at the time of starting of the power supply system shown in FIG. It is a wave form diagram explaining transition of the voltage and electric current of an auxiliary machine battery at the time of starting of the power supply system shown in FIG. It is a wave form diagram explaining transition of the charging current at the time of charge of an auxiliary machine battery. FIG. 4 is a functional block diagram illustrating charging control for an auxiliary battery according to Embodiment 1. It is a conceptual diagram explaining the correspondence of the output voltage and output current of a DCDC converter. 6 is a conceptual diagram illustrating setting of a voltage command value of a DCDC converter in charging control of an auxiliary battery according to Embodiment 1. FIG. 4 is a flowchart illustrating a processing procedure for auxiliary battery charging control according to the first embodiment. 6 is a flowchart illustrating a processing procedure of auxiliary battery charging control according to the second embodiment. FIG. 10 is a functional block diagram illustrating charging control for an auxiliary battery according to a third embodiment. It is a conceptual diagram explaining the deterioration determination of a general auxiliary machine battery. FIG. 10 is a conceptual diagram illustrating deterioration determination of an auxiliary battery according to a third embodiment. 10 is a flowchart illustrating a processing procedure for determining deterioration of an auxiliary battery according to a third embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a hybrid vehicle shown as a representative example of an electric vehicle according to an embodiment of the present invention.

  Referring to FIG. 1, hybrid vehicle 5 includes an engine 100, a first motor generator 110 (hereinafter also simply referred to as “MG1”), and a second motor generator 120 (hereinafter also simply referred to as “MG2”). A power split mechanism 130, a speed reducer 140, and a main battery 150 are provided.

  Hybrid vehicle 5 travels by driving force from at least one of engine 100 and MG2. Engine 100, MG1 and MG2 are connected via power split device 130. The power generated by the engine 100 is divided into two paths by the power split mechanism 130. One is a path for driving the front wheels 190 via the speed reducer 140. The other is a path for driving MG1 to generate power.

  Each of MG1 and MG2 is typically a three-phase AC rotating electric machine. MG1 generates power using the power of engine 100 divided by power split device 130. The electric power generated by MG1 is selectively used according to the traveling state of the vehicle and the SOC (State Of Charge) of main battery 150. For example, during normal travel, the electric power generated by MG1 becomes the electric power for driving MG2 as it is. On the other hand, when the SOC of main battery 150 is lower than a predetermined value, the electric power generated by MG1 is converted from alternating current to direct current by an inverter (not shown) and stored in main battery 150.

  When MG1 is acting as a generator, MG1 generates a negative torque. Here, the negative torque means a torque that becomes a load on engine 100. When MG1 receives power supply and acts as a motor, MG1 generates a positive torque. Here, the positive torque means a torque that does not become a load on the engine 100, that is, a torque that assists the rotation of the engine 100. The same applies to MG2.

  MG1 operates as a starter that motors engine 100 by generating positive torque when engine 100 is started. Therefore, in hybrid vehicle 5, electric power for starting engine 100 is output from main battery 150.

  MG2 is driven by at least one of the electric power stored in main battery 150 and the electric power generated by MG1. The driving force of MG2 is transmitted to the front wheels 190 via the speed reducer 140. Thereby, hybrid vehicle 5 travels only by the driving force from MG2 or by the driving force of both engine 100 and MG2. In the hybrid vehicle 5, the rear wheels may be driven instead of the front wheels 190, or both the front wheels and the rear wheels may be driven.

  At the time of regenerative braking of the hybrid vehicle 5, MG2 is driven by the front wheels 190 via the speed reducer 140, and MG2 operates as a generator. Thus, MG2 operates as a regenerative brake that converts braking energy into electric power. The electric power generated by MG2 is stored in main battery 150.

  Power split device 130 includes a planetary gear including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear so that it can rotate. The sun gear is connected to the rotation shaft of MG1. The carrier is connected to the crankshaft of engine 100. The ring gear is connected to the rotation shaft of MG 2 and the speed reducer 140.

  Engine 100, MG1 and MG2 are connected via power split mechanism 130 made of planetary gears, so that the rotational speeds of engine 100, MG1 and MG2 are connected in a straight line in the collinear diagram as shown in FIG. It becomes a relationship.

  Returning to FIG. 1, the main battery 150 is an assembled battery including a plurality of secondary battery cells. The voltage of the main battery 150 is about 200V, for example. Main battery 150 may be charged by electric power supplied from an external power supply of the vehicle in addition to electric power generated by MG1 and MG2. Main battery 150 corresponds to “main power storage device”. The “main power storage device” of the present invention may be configured by using another power storage device such as an electric double layer capacitor instead of the secondary battery, or by combining the secondary battery and another power storage device. Good.

  Engine 100, MG1 and MG2 are controlled by an ECU (Electronic Control Unit) 170. ECU 170 may be divided into a plurality of ECUs.

  ECU 170 is composed of a CPU (Central Processing Unit) (not shown) and an electronic control unit having a built-in memory, and performs arithmetic processing using detection values from each sensor based on a map and a program stored in the memory. Composed. Alternatively, at least a part of the ECU may be configured to execute predetermined numerical / logical operation processing by hardware such as an electronic circuit.

  Schematically, the hybrid vehicle 5 travels only by the driving force of the MG 2 with the engine 100 stopped when the efficiency of the engine 100 decreases, such as when the vehicle starts or travels at a low speed. The hybrid vehicle 5 starts the engine 100 according to the required vehicle driving force when the driving speed is increased due to the increase in vehicle speed or when the vehicle driving force is increased due to an acceleration request. Thus, the vehicle travels by the driving force of both engine 100 and MG2. In particular, the energy efficiency, that is, the fuel efficiency, is reduced by controlling the power distribution in the entire vehicle so that the engine 100 is operated in a limited manner at a highly efficient operating point and the MG2 generates a deficient vehicle driving force. Can be improved. In addition, even when it is not necessary to start engine 100 when the vehicle is running, engine 100 is started to generate charging power for main battery 150 when the SOC of main battery 150 decreases.

  FIG. 3 is a block diagram showing the configuration of the power supply system of the electric vehicle according to the embodiment of the present invention.

  Referring to FIG. 3, the power of main battery 150 is supplied to high voltage system circuit 155. High voltage system circuit 155 includes a power converter (an inverter, a converter, etc.) (not shown) for driving and controlling MG1, MG2 and MG1, MG2 shown in FIG.

  The power of the main battery 150 is also used for driving power of the auxiliary system. The DCDC converter 200 steps down the output voltage of the main battery 150 and outputs it to the power supply wiring 205.

  DCDC converter 200 is started in response to an operation instruction from ECU 170. In operation, DCDC converter 200 controls output voltage Vdc to power supply wiring 205 according to voltage command value Vdcr from ECU 170. The DCDC converter 200 is typically a switching regulator including a semiconductor switching element (not shown), and any known circuit configuration can be applied. The DCDC converter 200 supplies the output current Idc to the power supply wiring 205 within a range not exceeding the output current rating while controlling the output voltage Vdc.

  The auxiliary battery 210 is connected to the power supply wiring 205. Auxiliary battery 210 is formed of, for example, a lead storage battery. The voltage of auxiliary battery 210 is lower than the output voltage of main battery 150, for example, about 12V. Auxiliary battery 210 corresponds to a “sub power storage device”. Note that the “secondary battery” of the present invention is used by using a secondary battery other than the lead-acid battery, another power storage device such as an electric double layer capacitor other than the secondary battery, or a combination of the secondary battery and another power storage device. A “power storage device” may be configured.

  Auxiliary machine loads 221 to 224 are further connected to the power supply wiring 205. Auxiliary machine loads 221 to 224 operate in response to an operation instruction from the driver, and operate upon receiving supply of auxiliary system power (low voltage) from power supply wiring 205. The auxiliary machine loads 221 to 224 include various control devices including an electronic control unit (ECU), audio, headlights, and the like. A sum of current consumption by the auxiliary machine loads 221 to 224 is expressed as an auxiliary machine current Ild. The auxiliary machine current Ild is determined according to the operation / stop of each auxiliary machine load and the conditions at the time of operation.

  That is, when auxiliary machine current Ild is larger than output current Idc of DCDC converter 200, charging current Ichg <0, and the power stored in auxiliary battery 210 is consumed. On the other hand, when the voltage of power supply line 205 is higher than the output voltage (open circuit voltage) of auxiliary battery 210 and Idc> Ild, charging current Ichg> 0 and auxiliary battery 210 is charged.

  The power supply wiring 205 is provided with at least a current sensor 201 for detecting an output current Idc from the DCDC converter 200. Furthermore, a voltage sensor 202 is provided for detecting an output voltage Vbat of the auxiliary battery 210 (hereinafter referred to as a battery voltage Vbat).

  As will be apparent from the following description, in the power supply system according to the embodiment of the present invention, charging of auxiliary battery 210 is controlled based on charging current Ichg of auxiliary battery 210. For detection of the charging current Ichg, the auxiliary battery 210 may be provided with a current sensor 203 for detecting the charging current Ichg, and the charging current Ichg may be detected by calculation from the detection value of the current sensor 201. .

  ECU 170 controls the operation of each device of high-voltage circuit 155 and DCDC converter 200. In particular, as control of the auxiliary system, starting and stopping of the DCDC converter 200 are controlled, and a voltage command value Vdcr of the DCDC converter 200 is output.

  Further, ECU 170 receives a detected value by current sensor 201 of output current Idc of DCDC converter 200 and a detected value by voltage sensor 202 of battery voltage Vbat. ECU 170 further receives a detected value of charging current Ichg of auxiliary battery 210 when current sensor 203 is further provided. Alternatively, ECU 170 detects charging current Ichg by calculation based on detected output current Idc.

  Next, the DCDC converter control at the time of starting the power supply system will be described with reference to FIG.

  Referring to FIG. 4, the power supply system of hybrid vehicle 5 is activated in response to a user switch operation (for example, an ignition switch is turned on). When the power supply system is activated, DCDC converter 200 starts in response to an instruction from ECU 170.

  When the DCDC converter 200 is started, a constant voltage charging mode for charging the auxiliary battery 210 is set. In this constant voltage charging mode, voltage command value Vdcr is set to a voltage higher than open circuit voltage Voc of auxiliary battery 210. For example, Vdcr is set to about 13.5 to 15V. The voltage command value Vdcr at this time is preferably variably set according to the temperature of the auxiliary battery 210 in order to ensure a sufficient charging voltage corresponding to the change in internal resistance due to the battery temperature.

  In the constant voltage charging mode, the auxiliary machine current Ild and the charging current Ichg (Ichg> 0) are ensured by the output current Idc of the DCDC converter 200 (Idc = Ichg + Ild). That is, the charging current Ichg> 0 and the auxiliary battery 210 is charged. As the auxiliary battery 210 is charged in the constant voltage charging mode, the charging current Ichg gradually decreases.

  When charging of auxiliary battery 210 is completed, DCDC converter 200 transitions to the low voltage mode. Since the output voltage Vdc may be lower than the open circuit voltage Voc of the auxiliary battery 210 in the low voltage mode, the ECU 170 lowers the voltage command value Vdcr than in the constant voltage charging mode. For example, Vdcr is set to about 12V in accordance with the operating voltage of auxiliary machine loads 221 to 224. In the low voltage mode, basically, the auxiliary machine current Ild is secured by the output current Idc of the DCDC converter 200 (that is, Ichg = 0).

  When the auxiliary machine current Ild becomes large and cannot be covered by the output current Idc of the DCDC converter 200, the auxiliary machine current Ild is secured by the power of the auxiliary battery 210. That is, Ichg <0.

  When the output voltage Vdc of the DCDC converter 200 decreases, the power consumption in the DCDC converter 200 also decreases. For this reason, if the charging of the auxiliary battery 210 is accurately detected and the DCDC converter 200 is shifted from the constant voltage charging mode to the low voltage mode, the efficiency in the DCDC converter 200 is improved and the hybrid vehicle 5 as a whole is improved. It can be expected to improve the energy efficiency, that is, the fuel consumption.

  FIG. 5 shows changes in the voltage and current of the auxiliary battery when the power supply system is started.

  Referring to FIG. 5, when the power supply system is activated at time ta, auxiliary machine loads 221 to 224 are activated to consume power. Then, DCDC converter 200 starts at time td after time ta.

  Until the time ta when the power supply system is activated, the auxiliary battery 210 is not charged / discharged, and the battery voltage Vbat corresponds to the open circuit voltage Voc. On the other hand, during the period from time ta to tb, the auxiliary machine current Ild consumed by the auxiliary machine loads 221 to 224 is consumed by the discharge of the auxiliary battery 210 (Ichg <0). For this reason, the battery voltage Vbat during the period from time ta to td corresponds to the closed circuit voltage Vcc. That is, voltage drop ΔV (ΔV = Voc−Vcc) corresponding to auxiliary machine current Ild (that is, charging current Ichg) occurs in auxiliary battery 210 at time ta. Hereinafter, the closed circuit voltage Vcc when only the auxiliary machine current Ild at the time ta to td is consumed is referred to simply as the closed circuit voltage Vcc.

  At the time of starting DCDC converter 200 (time td), voltage command value Vdcr is set to V1 (for example, V1 = 13.5 to 15 (V)) in the constant voltage charging mode. Accordingly, since output voltage Vdc of DCDC converter 200 becomes V1, auxiliary battery 210 is charged. As a result, a charging current Ichg is generated as shown in FIG.

  FIG. 6 shows the transition of charging current Ichg during charging of auxiliary battery 210. The charging start time t0 that is the origin of the time axis that is the horizontal axis in FIG. 6 corresponds to the starting time td of the DCDC converter 200 shown in FIG.

  Referring to FIG. 6, ECU 170 estimates required charging time Tf of auxiliary battery 210 based on the transition of charging current Ichg after the start of charging. For example, the required charging time Tf can be estimated based on the slope of the charging current Ichg estimated from the charging current Ichg at times t1 and t2 when a predetermined time has elapsed from the charging start time t0.

  For example, the current value I1 at time t1 and the current value I2 at time t2 and the time t3 when Ichg = 0 with the slope of the charging current Ichg remains as a function of (I1 · t2−I2 · t1). Is understood.

  Therefore, the required charging time Tf up to the charging completion time tf of the auxiliary battery 210 can be obtained by the following equation (1), for example.

Tf = (I1 · t2−I2 · t1) · k (1)
In the equation (1), the coefficient k can be a value proportional to the charging current value I0 at the charging start time t0. When the charging current at the start of charging is large, the charge amount of the auxiliary battery 210 is reduced, and it is estimated that the charge amount until the auxiliary battery 210 is fully charged is large. If the coefficient k is set so as to be proportional to I0, the required charging time Tf can be estimated in accordance with this phenomenon.

  Alternatively, the coefficient k can be a value proportional to the voltage drop ΔV (ΔV = Voc−Vcc) detected when the auxiliary machine load is operated, which is detected before the DCDC converter 200 is started. When the voltage drop ΔV is large, it is estimated that the internal resistance of the auxiliary battery 210 is increasing, and therefore it is estimated that charging of the auxiliary battery 210 requires a relatively long time. If the coefficient k is set so as to be proportional to the voltage drop ΔV, the required charging time Tf can be estimated in accordance with this phenomenon.

  As described above, the hybrid vehicle 5 is basically driven by the driving force from the MG 2 using the power of the main battery 150 while the engine 100 is stopped when the vehicle starts. That is, engine 100 is started only under special conditions such as when the SOC of main battery 150 is lowered. In addition, even when engine 100 is started, the power (power consumption of MG1) for motoring engine 100 is supplied from main battery 150.

  As a result, in hybrid vehicle 5, engine 100 is not cranked using the power of auxiliary battery 210 when the power supply system corresponding to turning on the ignition switch is started. For this reason, since the power consumption in the auxiliary system does not include the power consumption of the engine starter, it changes relatively stably. As a result, the voltage behavior and current behavior at the time of starting the power supply system and starting the DCDC converter 200 shown in FIGS. 5 and 6 are also stable. Therefore, since the disturbance when estimating the required charging time Tf of the auxiliary battery 210 based on the transition of the charging current Ichg is small, the charging control of the auxiliary battery according to the present embodiment described below can be applied. .

  FIG. 7 is a functional block diagram for illustrating charging control of auxiliary battery 210 according to Embodiment 1 of the present invention. For each functional block shown in FIG. 7, a circuit (hardware) having a function corresponding to the block may be built in ECU 170, or ECU 170 executes software processing according to a program stored in advance. May be realized.

  Referring to FIG. 7, charging current detection unit 310 detects charging current Ichg based on the output of current sensor 201, or when current sensor 203 is provided, based on the output of current sensor 203. To do. Here, a method for detecting the charging current Ichg based on the detection value (Idc) of the current sensor 201 will be described with reference to FIGS. 8 and 9.

  FIG. 8 shows the correspondence between the output voltage and the output current of the DCDC converter. 8 represents the output voltage Vdc of the DCDC converter 200, and the vertical axis represents the output current Idc of the DCDC converter 200.

  When output voltage Vdc is set to voltage V0 lower than open circuit voltage Voc, auxiliary battery 210 is not charged (that is, Ichg = 0). Therefore, the output current Idc is determined by the auxiliary machine current Ild consumed by the auxiliary machine loads 221 to 224. That is, the output current Idc is determined according to the driving pattern of the auxiliary machine loads 221 to 224. The output current Idc (auxiliary device current Ild) at this time is substantially proportional to the output voltage Vdc.

  On the other hand, when output voltage Vdc rises to voltage V1 higher than open circuit voltage Voc, charging current Ichg of auxiliary battery 210 is generated. As a result, the output current Idc is the sum of the charging current Ichg and the auxiliary machine current Ild.

  Even in the region of Vdc> Voc, the auxiliary machine current Ild is substantially proportional to the output voltage Vdc, so that the compensation in Vdc> Voc (particularly Vdc = V1) is based on the detected value (Idc) in the region of Vdc <Voc. The machine current predicted value Ild # can be obtained by extrapolation.

  In the region of Vdc> Voc, the charging current Ichg is calculated by subtracting the auxiliary machine current predicted value Ild # from the output current Idc detected by the current sensor 201. This makes it possible to detect the charging current Ichg of the auxiliary battery 210 without providing the current sensor 203 (FIG. 1).

  As shown in FIG. 6 and equation (1), if the charge required time Tf is estimated based on the initial charge current Ichg (time t1, t2) after the start of charging, While the driving pattern of 224 does not change, the estimation of the required charging time Tf can be completed. That is, an error factor in detecting the charging current Ichg can be eliminated without providing the current sensor 203 (FIG. 1).

  Referring to FIG. 7 again, timer 330 outputs a count value CNT indicating an elapsed time from turning on the ignition switch (IGON) and starting DCDC converter 200 (DCON). Therefore, arrival at the times td, t0 to t2, tf, etc. in FIGS. 5 and 6 can be detected based on the count value CNT by the timer 330.

  Based on the battery voltage Vbat detected by the voltage sensor 202, the charging current Ichg detected by the charging current detection unit 310, and the count value CNT of the timer 330, the voltage command setting unit 350 performs DCDC as shown in FIG. Voltage command value Vdcr of converter 200 is set.

  Referring to FIG. 9, voltage command setting unit 350 sets voltage command value Vdcr = V0 (V0 <Voc) prior to constant voltage charging mode for a predetermined time T1 from start time td of DCDC converter 200. To do. Thereby, the current data for calculating the auxiliary machine current predicted value Ild # shown in FIG. 8 can be detected.

  From the time t0 (charge start time) when the predetermined time T1 has elapsed, the DCDC converter 200 shifts to the constant voltage charge mode. Thereby, the voltage command setting unit 350 sets the voltage command value Vdcr = V1 (V1> Voc). When the current sensor 203 capable of directly detecting the charging current Ichg is provided, the predetermined time T1 = 0 may be set to Vdcr = V1 immediately from the time td.

  By setting voltage command value Vdcr = V1, charging of auxiliary battery 210 is started. The voltage command setting unit 350 estimates the required charging time Tf according to the equation (1) based on the transition of the charging current Ichg after the start of charging. Then, at time tf when the required charging time Tf has elapsed from the charging start time t0, the voltage command setting unit 350 decreases the voltage command value Vdcr from V1 to V2. That is, the DCDC converter 200 shifts to the low voltage mode. As described above, voltage command value V2 in the low voltage mode can be a voltage at which auxiliary battery 210 cannot be charged. The voltage command value V0 until the charging start time t0 and the voltage command value V2 in the low voltage mode may be the same voltage.

  FIG. 10 shows a flowchart for explaining the processing procedure of the auxiliary battery charging control according to the first embodiment of the present invention. Each step of the flowchart described below including FIG. 10 is realized by software processing (execution by the CPU of the stored program) or hardware processing (operation of the dedicated electronic circuit) by the ECU 170.

  Referring to FIG. 10, in step S100, ECU 170 activates the power supply system of hybrid vehicle 5 in response to, for example, turning on the ignition switch (time ts). Then, ECU 170 measures open circuit voltage Voc of auxiliary battery 210 based on the output of voltage sensor 202 at the timing before starting the auxiliary load when the electric system is started (step S110).

  Then, ECU 120 starts operation of auxiliary machine loads 221 to 224 in step S120, and in step S130, ECU 120 starts the operation of auxiliary battery 210 when auxiliary machine current Ild is generated from the output voltage of voltage sensor 202 at that time. The closed circuit voltage Vcc is measured. Thereby, the voltage drop ΔV = Voc−Vcc can be calculated.

  Further, ECU 170 activates DCDC converter 200 in step S140 (time td). In step S150, ECU 170 is set to voltage command value Vdcr = V1 so as to enter the constant voltage charging mode.

  Note that if the current sensor 203 is not disposed, the ECU 170 executes the process of step S145 prior to step S150. In step S145, ECU 170 sets voltage command value Vdcr = V0. Further, ECU 170 obtains predicted auxiliary machine current value Ild # based on output current Idc of DCDC converter 200 at this time. As described above, the auxiliary machine current predicted value Ild # can be obtained by extrapolation from the output current Idc at this time (Vdc <Voc).

  In step S160, ECU 170 detects charging current Ichg in the initial stage (time t1, t2) after the start of charging, as described in FIG. In step S170, ECU 170 estimates charge required time Tf according to equation (1) based on the charging current value detected in step S160 (step S170).

  Then, when estimating the required charging time Tf, ECU 170 determines in step S180 whether or not the time tf at which the charging required time Tf has elapsed from the charging start time t0 has been reached based on the count value CNT by the timer. Until the time tf is reached (NO determination in S180), ECU 170 sequentially increments the count value CNT of the timer in step S190.

  When ECU 170 reaches time tf (when YES is determined in S180), ECU 170 causes DCDC converter 200 to transition from the constant voltage charging mode to the low voltage mode in step S195. That is, ECU 170 decreases voltage command value Vdcr from V1 to V2.

  Thus, in the charging control of the auxiliary battery in the power supply system for the electric vehicle according to the first embodiment, a constant voltage with a high voltage command value Vdcr for charging auxiliary battery 210 based on the transition of charging current Ichg. The charging mode period can be set without excess or deficiency. As a result, when the charging of the auxiliary battery 210 is completed, it is possible to quickly shift to the low voltage mode and lower the output voltage of the DCDC converter 200, so that the output voltage of the DCDC converter 200 is maintained unnecessarily high. Can be avoided. As a result, while the auxiliary battery 210 is reliably charged, the power consumption of the DCDC converter 200 can be reduced, and the energy efficiency of the hybrid vehicle 5, that is, the fuel efficiency can be improved.

[Embodiment 2]
In the second embodiment, the operation after the DCDC converter 200 shifts to the low voltage mode by the charge control of the auxiliary battery described in the first embodiment will be further described.

  FIG. 11 is a flowchart for explaining a processing procedure of auxiliary battery charging control according to the second embodiment.

  Referring to FIG. 11, ECU 170 executes charging control for auxiliary battery 210 when DCDC converter 200 is started, based on steps S100 to S195 (FIG. 10). That is, at the end of steps S100 to S195, the DCDC converter 200 has shifted to the low voltage mode.

  The ECU estimates the amount of discharge from auxiliary battery 210 in step S200 during the low voltage mode. The discharge amount corresponds to the integrated value of the charging current Ichg. Therefore, when the current sensor 203 (FIG. 1) is arranged, the discharge amount can be estimated based on the detection value of the current sensor 203.

  On the other hand, when current sensor 203 is not disposed, ECU 170 calculates estimated discharge amount Qch based on, for example, the following equation (2).

Qch = Tlim · Idchg (2)
In the equation (2), Tlim is obtained by counting the operating time of the overcurrent limiter that operates when the output current Idc of the DCDC converter 200 becomes equal to or greater than a predetermined current. When the overcurrent limiter is operated, the auxiliary machine current Ild cannot be covered only by the output current Idc of the DCDC converter 200, so that it is predicted that the auxiliary battery 210 is discharged. Idchg is an estimated value of the discharge current from auxiliary battery 210 when the overcurrent limiter is activated. Idchg can be determined from the rating of the DCDC converter 200 and the estimated current consumption of the auxiliary loads 221 to 224.

  In step S210, ECU 170 compares discharge amount estimated value Qch in step S200 with determination value Qth. Determination value Qth is preferably set corresponding to the charge amount of auxiliary battery 210 in steps S100 to S195. For example, determination value Qth can be set by the integrated value of charging current Ichg in the constant voltage charging mode. Alternatively, based on the transition of the charging current Ichg shown in FIG. 6, for example, the determination value Qth is simply set based on the product of the charging current value I0 at the start of charging and the required time at times t0 to t3. It is also possible to do.

  When discharge amount estimated value Qch does not reach determination value Qth (NO in S210), ECU 170 maintains the low voltage mode in step S220, and calculates discharge amount estimated value Qch in step S200. continue. Thereby, the estimated discharge amount Qch in step S200 is integrated throughout the period in which the low voltage mode is maintained.

  When the accumulated discharge amount estimated value exceeds the determination value (when YES is determined in S210), ECU 170 proceeds to step S230 and causes DCDC converter 200 to transition to the constant voltage charging mode again. Thereby, voltage command value Vdcr is set to V1 again, so that auxiliary battery 210 is charged by the output voltage of DCDC converter 200. At this time, the estimated discharge amount Qch in step S220 is once cleared.

  When the DCDC converter 200 shifts to the low voltage mode, the processes of steps S150 to S195 shown in FIG. 10 are executed. When the charging of the auxiliary battery is completed (YES in S180), the DCDC converter 200 shifts to the low voltage mode again (S195).

  And if it transfers to a low voltage mode, the process of step S200-S230 of the flowchart of FIG. 11 will be performed again. At this time, the determination value Qth used in step S210 is updated based on data at the time of charging the auxiliary battery 210 in the immediately preceding constant voltage charging mode. The processes in steps S200 to S230 are executed by the voltage command setting unit 350 in FIG.

  In the charge control of the auxiliary battery in the power supply system of the electric vehicle according to the second embodiment, in addition to the effect in the first embodiment, it is possible to prevent the auxiliary battery 210 from being overdischarged after shifting to the low voltage mode. . In particular, since it is determined whether or not the auxiliary battery 210 needs to be recharged based on the estimation of the discharge amount, it is possible to avoid unnecessary provision of an opportunity for recharging in which the output voltage of the DCDC converter 200 is increased. As a result, the efficiency of the DCDC converter 200 and, consequently, the fuel efficiency of the hybrid vehicle 5 can be improved.

[Embodiment 3]
In the third embodiment, a configuration will be described in which deterioration determination of auxiliary battery 210 is also executed based on data at the time of charging auxiliary battery 210 in the constant voltage charging mode.

  FIG. 12 is a functional block diagram illustrating charging control of the auxiliary battery according to the third embodiment.

  Referring to FIG. 12, the auxiliary battery charging control according to the third embodiment is different from the configuration according to the first embodiment shown in FIG. 7 in that a deterioration determination unit 360 is further provided. The other portions are the same as those in FIG. 7, and therefore description thereof will not be repeated.

  Degradation determination unit 360 determines the degree of deterioration of auxiliary battery 210 based on required charging time Tf estimated by voltage command setting unit 350 and voltage drop ΔV of auxiliary battery 210 when the power supply system is activated. Then, the deterioration determination unit 360 turns on the deterioration detection flag Fd when the deterioration degree exceeds a predetermined level. On the other hand, the deterioration detection flag Fd is turned off at the normal time when the deterioration of the auxiliary battery 210 is not detected.

FIG. 13 shows a general deterioration determination based on the output voltage of auxiliary battery 210.
Referring to FIG. 13, the closed circuit voltage Vcc of the auxiliary battery 210 decreases from the open voltage Voc by a voltage drop ΔV corresponding to the internal resistance. Therefore, when the voltage drop ΔV is larger than a predetermined value, an increase in internal resistance is detected, and deterioration of the auxiliary battery 210 is detected. Specifically, deterioration of auxiliary battery 210 is detected when battery voltage Vbat (that is, closed circuit voltage Vcc) at the time of startup of the power supply system (time ta to td in FIG. 5) is lower than determination voltage Vth. The The determination voltage Vth is lower than the open circuit voltage Voc by the reference value ΔVth. That is, when the voltage drop ΔV is larger than the reference value ΔVth, the deterioration of the auxiliary battery 210 is detected.

  In the deterioration determination in the charge control of the auxiliary battery according to the third embodiment, the deterioration of the auxiliary battery 210 is determined using the required charging time Tf described in the first embodiment in addition to the voltage drop ΔV.

  FIG. 14 is a conceptual diagram illustrating the deterioration determination of the auxiliary battery according to the third embodiment. The horizontal axis of FIG. 14 is the battery voltage Vbat (closed circuit voltage Vcc), and the vertical axis is the required charging time Tf estimated by the voltage command setting unit 350.

  As described above, when the closed circuit voltage Vcc is low, that is, when the voltage drop ΔV is large, the internal resistance of the auxiliary battery 210 is increased. On the other hand, when the required charging time Tf is long, the chargeable capacity is large, and conversely, when the required charging time Tf is short, the chargeable capacity is small.

  The degradation determination unit 360 detects degradation in a region 403 having a large internal resistance and a small chargeable capacity. On the other hand, even if the internal resistance is relatively large, deterioration determination unit 360 determines that auxiliary battery 210 is still usable in region 401 where charging time Tf is long and chargeable capacity is large. Do not detect. That is, auxiliary battery 210 is determined to be normal.

  In addition, deterioration determination unit 360 detects deterioration of auxiliary battery 210 according to the internal resistance in region 402 where charge required time Tf is short and chargeable capacity is small.

  In this way, it is possible to perform a more precise deterioration determination as compared with the case where the deterioration of the auxiliary battery 210 is determined based only on the battery voltage Vbat (voltage drop ΔV).

  In addition, it is possible to quantitatively evaluate the degree of deterioration using the parameter P defined by the following formula (3).

P = Tf / ΔV (3)
If the deterioration detection flag Fd is turned on when the parameter P is lower than a predetermined value, the deterioration determination shown in FIG. 14 can be realized.

  FIG. 15 is a flowchart illustrating a processing procedure for determining the deterioration of the auxiliary battery according to the third embodiment.

  Referring to FIG. 15, ECU 170 performs charging control of auxiliary battery 210 at the time of starting the power supply system in accordance with steps S100 to S195 (FIG. 10). Thereby, auxiliary battery 210 is charged, and DCDC converter 200 shifts from the constant voltage charging mode to the low voltage mode.

  Further, when charging of auxiliary battery 210 is completed and the ECU 170 shifts to the low voltage mode, ECU 170 executes deterioration determination of auxiliary battery 210 according to FIG. 14 based on the charging data at the time of startup in step S300. That is, the process in step S300 corresponds to the function of the deterioration determination unit 360 in FIG.

  In the auxiliary battery charging control in the power supply system of the electric vehicle according to the third embodiment, in addition to the effect of the first embodiment, the deterioration determination is further performed in accordance with the charging of the auxiliary battery 210 at the time of starting the power supply system. it can. In particular, not only the evaluation of the internal resistance by the voltage drop ΔV. Since the deterioration determination is performed by evaluating the chargeable capacity based on the estimated value of the required charging time Tf, it is possible to perform a more accurate deterioration determination.

  In this embodiment, a hybrid vehicle including an engine and an electric motor has been described as a representative example of an electric vehicle. However, an electric vehicle including a main power storage device (main battery) and a sub power storage device (auxiliary battery) The present invention can also be applied to the sub power storage device (auxiliary battery) at the time of starting the power supply system to other electric vehicles such as fuel cell vehicles. For electric vehicles other than hybrid vehicles that are not equipped with an engine, the current consumption of the auxiliary system at the time of starting the power supply system is stable, so that the same charge control can be applied without any problem. Conversely, as described above, the hybrid vehicle equipped with the engine also has a configuration in which power for starting the engine is not supplied from the auxiliary battery, so the current consumption of the auxiliary system at the time of starting the power supply system is stable. To do.

  Further, even when the electric vehicle includes a mechanism for charging the main power storage device (main battery) with a power supply external to the vehicle, the present invention can be applied to the sub power storage device (auxiliary battery) when the power supply system is activated.

  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.

  The present invention can be applied to an electric vehicle equipped with a power storage device for generating vehicle driving force (main battery) and a power storage device for driving auxiliary equipment (auxiliary battery).

  5 Hybrid Vehicle, 100 Engine, 110 First Motor Generator (MG1), 120 Second Motor Generator (MG2), 130 Power Dividing Mechanism, 140 Reducer, 150 Main Battery, 155 High Voltage System Circuit, 190 Front Wheel, 200 DCDC Converter, 201, 203 Current sensor, 202 Voltage sensor, 205 Power supply wiring, 210 Auxiliary battery, 221-224 Auxiliary load, 310 Charging current detection unit, 330 Timer, 350 Voltage command setting unit, 360 Degradation determination unit, 401, 402, 403 region, CNT count value, Fd deterioration detection flag, I0 to I2 charging current value, Ichg charging current, Idc output current (DCDC converter), Ild auxiliary machine current, Ild # auxiliary machine current prediction value, Qch discharge amount estimated value, Tf charging time , V0 voltage command value (before starting charging), V1 voltage command value (constant voltage charging mode), V2 voltage command value (low voltage mode), Vbat battery voltage, Vcc closed circuit voltage, Vdc output voltage (DCDC converter), Vdcr voltage Command value, Voc open voltage, Vth determination voltage, t0 charge start time, td converter start time, tf charge completion time.

Claims (7)

A power supply system for an electric vehicle equipped with an electric motor for generating vehicle driving force,
A main power storage device for storing electric power input / output to / from the electric motor;
A voltage converter for stepping down the output voltage of the main power storage device according to a voltage command value and outputting it to the power supply wiring;
A sub power storage device electrically connected to the power supply wiring;
An auxiliary load electrically connected to the power supply wiring;
A charging current detector for detecting a charging current of the sub power storage device;
A voltage detector for detecting an output voltage of the sub power storage device;
A voltage command setting unit for setting the voltage command value;
The voltage command setting unit sets the voltage command value to a first voltage for charging the sub power storage device when starting the voltage converter, and the charging detected by the charging current detection unit. Based on the transition of current, the required charging time of the sub power storage device is estimated, and when the estimated required charging time elapses, the voltage command value is set to a second voltage lower than the first voltage. Electric vehicle power system.   The voltage command setting unit estimates the required charging time based on a slope of a change in the charging current after starting the voltage converter and the charging current at the time of starting the voltage converter. The power supply system of the electric vehicle according to 1. The voltage converter is started at a second time delayed by a predetermined time from the first time when the power supply system is activated,
The voltage command setting unit includes the slope of the change in the charging current after the voltage converter is started and the second time from the first time with respect to the output voltage of the sub power storage device before the first time. The power supply system for an electric vehicle according to claim 1, wherein the required charging time is estimated based on a voltage difference between output voltages of the sub power storage devices between the two.   The voltage command setting unit estimates a discharge amount from the sub power storage device during a period in which the voltage command value is set to the second voltage, and sets the voltage command value based on the estimated discharge amount. The power supply system for an electric vehicle according to claim 1, wherein the power supply system is increased to the first voltage. 0
A deterioration determining unit that determines a degree of deterioration of the sub power storage device based on the required charging time estimated by the voltage command setting unit and a voltage drop of the sub power storage device before and after starting the power supply system; The power supply system of the electric vehicle of any one of Claims 1-4. The voltage command setting unit sets a third voltage lower than the open voltage of the sub power storage device before setting the voltage command value to the first voltage when starting the voltage converter. Configured to provide a predetermined period to be set,
The charging current detector is
An auxiliary current estimation value based on a detection value of the current sensor for detecting an output current from the voltage converter to the power supply wiring in the predetermined period, and a detection value of the current sensor at the time of charging the sub power storage device; The power supply system for an electric vehicle according to any one of claims 1 to 5, wherein the charging current is detected based on a difference between the two. The electric vehicle is a hybrid vehicle equipped with an engine in addition to the electric motor,
The electric power system for an electric vehicle according to claim 1, wherein electric power used for starting the engine is supplied from the main power storage device.

Images