JP2017147842A - Hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately protect a battery in a hybrid vehicle in which external charging can be performed.SOLUTION: A battery 100 includes a plurality of blocks 101 to 10n connected in series. Each of the plurality of blocks 101 to 10n has a plurality of cells 110 connected in parallel. A vehicle 1 has an ECU 300 that controls charging and discharging of the battery 100 so as to prevent power charged into the battery 100 from exceeding a charged-power upper limit value Win and also prevent power discharged from the battery 100 from exceeding a discharged-power upper limit value Wout. Using an elapsed time T after external charging and the probability that any of the plurality of cells 110 may fail per unit time (failure occurrence probability), the ECU 300 calculates the number of cells that have failed (the number N of open failures). The larger the number N of open failures is, the lower the charged-power upper limit value Win and the discharged-power upper limit value Wout are set.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a hybrid vehicle, and more particularly to a hybrid vehicle configured to be able to perform external charging in which a battery is charged with electric power supplied from an external power source.

  Hybrid vehicles (so-called plug-in hybrid vehicles) configured to be able to perform external charging have been put into practical use. A battery mounted on a plug-in hybrid vehicle may include a configuration including a plurality of blocks connected in series with each other and a plurality of cells each connected in parallel with each other.

  Various failures may occur in the battery having the above configuration. Specifically, an open failure such as a disconnection in the block or a bus bar provided in the block may be mentioned. Therefore, for example, Japanese Patent Laying-Open No. 2009-216448 (Patent Document 1) discloses an abnormality detection device that determines the presence or absence of an open failure based on the voltage fluctuation amount of a block.

JP 2009-216448 A JP 2000-340266 A

  In general, in a hybrid vehicle including a plug-in hybrid vehicle, a limit is imposed on the charge / discharge power of the battery in order to protect the battery. More specifically, the charging / discharging of the battery is controlled such that the charging power to the battery does not exceed the charging power upper limit value Win and the discharging power from the battery does not exceed the discharging power upper limit value Wout.

  When the open failure of the battery as described above occurs, the charge / discharge current does not flow through the location where the open failure occurs, and the charge / discharge current flowing through the normal location can increase accordingly. For example, when an open failure occurs in a certain cell, the charge / discharge current flowing through a normal cell connected in parallel to that cell increases, and as a result, normal cell deterioration (so-called high-rate deterioration) proceeds. there is a possibility. Therefore, in order to protect normal cells, when a battery open failure occurs, charging / discharging is performed by setting the charging power upper limit Win and the discharging power upper limit Wout lower than when the battery is normal. It is desirable to tighten power limits.

  The determination of the presence or absence of an open failure of the battery (and calculation of the number of locations where an open failure has occurred) may be performed based on the voltage fluctuation amount of the block as disclosed in, for example, Patent Document 1. In a plug-in hybrid vehicle, the voltage of the block rises with the recovery of the SOC (State Of Charge) of the battery during external charging, so that the failure determination can be performed accurately.

  However, depending on the use mode of the user, external charging may not be performed for a long time even in a plug-in hybrid vehicle. As a result, the above-described voltage rise does not occur, and an opportunity to make a failure determination cannot be obtained. Therefore, the charge power upper limit value Win and the discharge power upper limit value Wout cannot be set appropriately, and the battery may not be properly protected.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a technique for appropriately protecting a battery in a hybrid vehicle configured to be able to perform external charging.

  A hybrid vehicle according to an aspect of the present invention is configured to be able to perform external charging for charging a battery with electric power supplied from an external power source. The battery includes a plurality of battery blocks connected in series with each other. Each of the plurality of battery blocks has a plurality of cells connected in parallel to each other. The hybrid vehicle includes a control device that controls charging / discharging of the battery so that the charging power to the battery does not exceed the charging power upper limit value and the discharging power from the battery does not exceed the discharging power upper limit value. The control device uses the elapsed time after the external charging and the probability that a failure occurs in any one of the plurality of cells per unit time (failure occurrence probability). The number of cells) is calculated, and the charging power upper limit value and the discharging power upper limit value are set lower as the number of failed cells is larger.

  A battery failure (for example, an open failure) occurs with a certain statistical probability (failure occurrence probability). Therefore, it is possible to estimate the number of failed cells using the elapsed time after external charging and the failure occurrence probability. According to the above configuration, by estimating the number of failed cells in this way, the charge power upper limit value and the discharge power upper limit value are set to appropriate values even if the number of failed cells cannot be calculated based on the actual measurement value such as voltage fluctuation. Can be set to Thereby, a battery can be protected appropriately.

1 is a block diagram schematically showing an overall configuration of a hybrid vehicle according to an embodiment. It is a figure which shows the structure of a battery and a monitoring unit. It is a perspective view which shows the structure of each cell. It is an enlarged view of the cover part of a cell. It is a figure for demonstrating the open failure of a battery. It is a figure for demonstrating the estimation method of the number of open faults. It is a flowchart for demonstrating the setting process of the charging power upper limit Win of the battery and the discharge power upper limit Wout in this Embodiment. It is a figure for demonstrating the setting method of the charge power upper limit Win according to the number of open faults, and the discharge power upper limit Wout.

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

<Configuration of hybrid vehicle>
FIG. 1 is a block diagram schematically showing the overall configuration of the hybrid vehicle according to the present embodiment. The vehicle 1 is a hybrid vehicle (plug-in hybrid vehicle) configured to be capable of external charging in which an in-vehicle battery is charged with electric power supplied from an external power source.

  The vehicle 1 includes motor generators (MG) 10 and 20, a power split mechanism 30, an engine 40, a power control unit (PCU) 50, and a system main relay (SMR). 60, an inlet 70, an AC / DC converter 80, a charge relay (CHR) 90, a battery 100, a monitoring unit 200, and an electronic control unit (ECU) 300.

  Each of motor generators 10 and 20 is, for example, a three-phase AC rotating electric machine. Motor generator 10 is coupled to the crankshaft of engine 40 via power split mechanism 30. The motor generator 10 rotates the crankshaft of the engine 40 using the power of the battery 100 when starting the engine 40. The motor generator 10 can also generate power using the power of the engine 40. The AC power generated by the motor generator 10 is converted to DC power by the PCU 50 and the battery 100 is charged. Further, the AC power generated by the motor generator 10 may be supplied to the motor generator 20.

  Motor generator 20 rotates the drive shaft using at least one of the electric power stored in battery 100 and the electric power generated by motor generator 10. The motor generator 20 can also generate power by regenerative braking. The AC power generated by the motor generator 20 is converted into DC power by the PCU 50 and the battery 100 is charged.

  Power split device 30 mechanically connects the three elements of the crankshaft of engine 40, the rotation shaft of motor generator 10, and the drive shaft. The engine 40 is an internal combustion engine such as a gasoline engine or a diesel engine. Engine 40 generates a driving force for vehicle 1 to travel in response to a control signal from ECU 300.

  Although not shown, the PCU 50 includes an inverter and a converter. The inverter performs power conversion between battery 100 and motor generators 10 and 20. The converter boosts or steps down the DC voltage between the battery 100 and the inverter.

  SMR 60 is electrically connected to a power path connecting battery 100 and PCU 50. The conduction / non-conduction of the SMR 60 is controlled according to a control signal from the ECU 300. When SMR 60 is conductive, power can be exchanged between battery 100 and PCU 50.

  The inlet 70 is configured to be able to connect a charging cable 400 for external charging. Charging cable 400 includes a plug 410, a connector 420, and an electric wire 430. During external charging, the plug 410 is connected to an outlet 510 of an external power source (typically commercial AC power source) 500, and the connector 420 is connected to the inlet 70 of the vehicle 1. The electric wire 430 electrically connects the plug 410 and the connector 420.

  The AC / DC converter 80 converts AC power supplied from the external power source 500 via the charging cable 400 into DC power and supplies the DC power to the battery 100. The CHR 90 is electrically connected to a power path that connects the AC / DC converter 80 and the battery 100. The conduction / non-conduction of the CHR 90 is controlled according to a control signal from the ECU 300. During external charging, CHR 90 is turned on, and battery 100 is charged with power from AC / DC converter 80.

  The battery 100 is a direct current power source configured to be chargeable / dischargeable, and typically includes a secondary battery such as a lithium ion battery or a nickel metal hydride battery, or a capacitor such as an electric double layer capacitor. The battery 100 supplies electric power for generating the driving force of the vehicle 1 to the PCU 50 during operation of the vehicle 1, while storing electric power generated by the motor generators 10 and 20 during regenerative braking of the vehicle 1.

  The monitoring unit 200 includes a voltage sensor (see FIG. 2), a current sensor (not shown), and a temperature sensor (not shown). The voltage sensor detects the voltage VB of the battery 100. The current sensor detects a current IB that is input to and output from the battery 100. The temperature sensor detects the temperature TB of the battery 100. Each sensor outputs the detection result to ECU 300. ECU 300 calculates an SOC (State Of Charge) of battery 100 based on voltage VB, current IB and temperature TB of battery 100. The configurations of the battery 100 and the monitoring unit 200 will be described in detail with reference to FIGS.

  Although not shown, ECU 300 includes a CPU (Central Processing Unit), a memory, an input / output buffer, and the like. ECU 300 controls each device so that vehicle 1 is in a desired state based on a signal received from each sensor and a map and a program stored in the memory.

  FIG. 2 is a diagram illustrating the configuration of the battery 100 and the monitoring unit 200. The battery 100 includes a plurality (n) of blocks 101 to 10n connected in series with each other. Each of the plurality of blocks 101 to 10n includes a plurality (m) of cells 110 connected in parallel to each other, and a plurality of (m) fuses 120 connected in series to the plurality of cells 110, respectively. Note that n and m are natural numbers of 2 or more.

  The monitoring unit 200 includes a plurality (n) of voltage sensors 201 to 20n connected between the plurality of blocks 101 to 10n. Each of the plurality of voltage sensors 201 to 20n detects a voltage of a corresponding block (indicated by block voltages V1 to Vn), and outputs the detection result to the ECU 300.

  In the battery 100, as will be described later (see FIG. 5), an open failure due to various factors may occur. The ECU 300 determines the presence or absence of an open failure in any of the plurality of blocks 101 to 10n based on the fluctuations in the block voltages V1 to Vn, and calculates the “open failure number” N that is the number of locations where the open failure has occurred. . Since this determination method is known, detailed description will not be repeated (see, for example, Patent Document 1), but the block including the failed cell is specified by comparing the fluctuations of the block voltages V1 to Vn with each other during external charging. Is possible.

  FIG. 3 is a perspective view showing the configuration of each cell 110. The cell 110 is a hermetically sealed cell in which the case 111 is sealed by the lid portion 112.

  FIG. 4 is an enlarged view of the lid portion 112 of the cell 110. The lid portion 112 is provided with a positive terminal 113 and a negative terminal 114. The positive terminal 113 includes a terminal plate 113A and a bolt 113B. Although not shown, a pressure type current interrupt device (CID: Current Interrupt Device) is provided below the positive electrode terminal 113, and the terminal plate 113A serves as a lid disposed on the top of the CID. The configuration of the negative electrode terminal 114 is different from the configuration of the positive electrode terminal 113 in that no CID is provided, but the other configuration is the same as the configuration of the positive electrode terminal 113, and thus detailed description will not be repeated.

  Although not shown in the figure, an electrode body in which a positive electrode and a negative electrode are wound through a separator is accommodated in the case 111 together with an electrolytic solution. When the electrolyte is decomposed and the gas is generated with the increase in the number of charge / discharge cycles or the passage of time, the gas is accumulated in the case 11. The lid portion 112 is further provided with a discharge valve 115 for discharging excess gas accumulated in the case 111.

<Battery charge / discharge control>
As the main control executed by the ECU 300, charge / discharge control of the battery 100 is exemplified. Based on temperature TB and SOC of battery 100, ECU 300 calculates charging power upper limit value Win indicating a limit value of charging power to battery 100 and discharging power upper limit value Wout indicating a limiting value of discharging power from battery 100. Set. ECU 300 controls charging / discharging of battery 100 such that charging power to battery 100 does not exceed charging power upper limit Win and discharging power from battery 100 does not exceed discharging power upper limit Wout.

<Battery open failure>
FIG. 5 is a diagram for explaining an open failure of the battery 100. For example, as shown in a block 101, the electrolyte in the case 111 of the cell 110 or an additive contained in the electrolyte is decomposed to increase the pressure in the case 111, and the CID built in the lid 112 is activated. There is a case.

  For example, as shown in a block 102, the fuse 120 connected in series to the cell 110 may be broken. Specifically, the fuse 120 expands by being heated by Joule heat when energized, and contracts by being cooled by the atmosphere when de-energized (or at a low current). This cooling / heating cycle may cause the fuse 120 to break due to fatigue failure.

  Alternatively, for example, as shown in a block 103, a disconnection (for example, a bus bar not shown) may occur in the block 103.

  When such an open failure occurs, the charging / discharging current of the battery 100 does not flow through the location where the open failure occurs. However, since a plurality of cells 110 are connected in parallel in each of the blocks 101 to 10n, even if an open failure occurs, a charge / discharge current can flow to other normal cells 110 in the block. In this case, the charge / discharge current flowing through the other normal cells 110 can be increased by the amount that the charge / discharge current does not flow through the open failure location. As a result, normal cell 110 deterioration (high-rate deterioration) may progress. Therefore, in order to protect the normal cell 110, when an open failure of the battery 100 occurs, the charging power upper limit value Win and the discharging power upper limit value Wout are set lower than when the battery 100 is normal. Thus, it is desirable to reinforce restrictions on charging and discharging.

  The presence / absence of an open failure (and the number N of open failures) of the battery 100 may be determined based on the fluctuation amount of the block voltages V1 to Vn as disclosed in, for example, Patent Document 1. In vehicle 1 that is a plug-in hybrid vehicle, each block voltage V <b> 1 to Vn increases with the recovery of the SOC of battery 100 during external charging, and therefore it is possible to accurately determine an open failure.

  However, depending on the use mode of the user, external charging may not be performed for a long time even in a plug-in hybrid vehicle. As a result, the block voltages V1 to Vn do not increase, so that an opportunity to determine an open failure cannot be obtained. Therefore, charging power upper limit value Win and discharging power upper limit value Wout cannot be set appropriately, and battery 100 may not be protected properly.

  Therefore, in the present embodiment, the “elapsed time” T after the external charging is performed is acquired, and there is an open failure in the acquired elapsed time T and any one of the plurality of cells 110 per unit time. A configuration is adopted in which the number N of open faults is estimated using the “failure occurrence probability” that is the probability of occurrence. An open failure occurs with a statistical probability, and the statistical probability (failure occurrence probability) can be obtained in advance by experiment or simulation. Therefore, it is possible to estimate the number N of open failures by multiplying the elapsed time T after the external charging is performed and the failure occurrence probability. Hereinafter, this estimation method will be described in more detail.

  FIG. 6 is a diagram for explaining a method for estimating the number N of open faults. In FIG. 6A, the horizontal axis represents elapsed time. The vertical axis represents a “failure index” F, which is an index for the cell 110 to reach an open failure with time. In the failure index F, a determination value Sk (k: natural number) for comparing the magnitude relationship is determined in advance.

  Ease of occurrence of an open failure in battery 100 is affected by current IB, temperature TB, or SOC of battery 100. Specifically, as the current IB is relatively large, the Joule heat in the cooling / heating cycle increases, so that the fuse 120 is easily broken. In addition, the higher the temperature TB or SOC, the easier the decomposition of the electrolytic solution and additive, and the CID becomes easier to operate.

  The slope of the straight line L1 represents a failure occurrence probability under a certain use condition of the battery 100 (a condition relating to the current IB, temperature TB, or SOC of the battery 100). The greater the slope of the straight line L1, that is, the higher the failure occurrence probability, the faster the failure index F increases. The straight line L2 represents a state in which the failure index F increases with the passage of time under a condition different from the condition of the straight line L1 (a condition in which an open failure is unlikely to occur compared to the straight line L1).

  As indicated by the straight line L1, when the external charging ends at time t0, the failure index F increases with the passage of time thereafter (with the increase of the elapsed time T). When the failure index F reaches the determination value S1, it is determined (estimated) that the number of open failures N = 1. When the failure index F further increases with time and reaches the determination value S2, it is determined that the number of open failures N = 2. In FIG. 6A, only S1 and S2 are shown as determination values, but the determination values are also determined after S3. When the failure index F reaches the determination value Sk, it is determined that the number of open failures N = k.

  For example, since the fuse 120 rupture and the CID operation are basically independent events, it is desirable to separately calculate the number of open failures due to the fuse 120 rupture and the number of open failures due to the CID operation. . The number of open failures is calculated for each cause of the open failure, and the sum is used as the number N (total number) of open failures that have occurred in the battery 100.

  In addition to the straight lines L1 and L2 shown in FIG. 6A, various straight lines can be adopted depending on the failure occurrence probability. Further, as indicated by L3, the failure occurrence probability (that is, the slope) may be changed every predetermined time according to the use condition of the battery 100. The failure index F (integrated value) can be calculated by integrating the failure index calculated every predetermined time.

<Setting judgment value>
Each determination value Sk is determined in advance based on experiments or simulations. Hereinafter, an example of a method for setting the determination value S1 will be described as a representative example, but other determination value setting methods are also the same.

  FIG. 6B is a diagram for explaining an example of a method for setting the determination value S1. FIG. 6B shows a probability density function with the failure index F as a random variable. The probability density function is approximated by a normal distribution. For example, as shown in FIG. 6 (B), when an open fault occurs almost certainly in at least one cell (for example, when the standard deviation is σ and the fault index F = average value + 3σ), the fault index F increases. A value can be set as the determination value S1. As described with reference to FIG. 5B, since there are a plurality of factors in the open failure, the determination value Sk is preferably set according to the magnitude of the risk of each factor.

<Setting of charge power upper limit Win and discharge power upper limit Wout>
FIG. 7 is a flowchart for illustrating processing for setting charging power upper limit value Win and discharging power upper limit value Wout of battery 100 in the present embodiment. This flowchart is called from the main routine and executed when a predetermined condition is satisfied or every predetermined time interval. Each step included in this flowchart is basically realized by software processing by ECU 300, but may be realized by dedicated hardware (electric circuit) produced in ECU 300.

  In S10, the ECU 300 acquires an elapsed time T from the time of external charging. During external charging, it is possible to calculate the number N of open failures based on the block voltages V1 to Vn. Therefore, the elapsed time T after the end of external charging, at which the number N of open failures cannot be calculated by such a method, is acquired.

  In S20, the ECU 300 calculates the failure index F from the elapsed time T acquired in S10 and the use condition of the battery 100. As described with reference to FIG. 6A, the failure index F can be calculated by multiplying the elapsed time T by the failure occurrence probability.

  In S30, the ECU 300 determines whether or not the failure index F calculated in S20 is equal to or greater than a predetermined determination value Sk. Note that the initial value of the determination value Sk is set to S1 (that is, k = 1).

  When failure index F is equal to or greater than determination value Sk (YES in S30), ECU 300 increments open failure number N by 1 (S40). Note that the initial value of the number N of open failures is set to a value calculated based on the fluctuation amount of the block voltages V1 to Vn during external charging. That is, the number of open failures estimated after external charging is added to the number of open failures calculated based on the fluctuation amount of the block voltages V1 to Vn during external charging.

  In S50, ECU 300 increments determination value Sk (subscript k) by one. Thereafter, ECU 300 advances the process to S60.

  After execution of the process of S50 or when the failure index F is less than the determination value Sk (NO in S30), the ECU 300 sets the charge power upper limit Win and the discharge power upper limit Wout according to the open failure number N (S60). .

  FIG. 8 is a diagram for explaining a method for setting the charging power upper limit value Win and the discharging power upper limit value Wout according to the number N of open failures. In FIG. 8, the horizontal axis represents the number N of open failures. The vertical axis represents the charge / discharge power of the battery 100. As shown in FIG. 8, the charging power upper limit Win (absolute value) is set lower as the open failure number N is larger. Further, the discharge power upper limit Wout (absolute value) is set lower as the open failure number N is larger.

  Returning to FIG. 7, in S70, the ECU 300 determines whether or not the number N of open failures is equal to or greater than a predetermined reference value. When open failure number N is equal to or greater than the reference value (YES in S70), ECU 300 notifies the user of abnormality of battery 100 (S80). The notification method is not particularly limited. For example, a warning light (not shown) can be turned on, or a message indicating an abnormality can be displayed on the display (not shown) of the car navigation system. The user who has received the notification can bring the vehicle 1 into the dealer and request repair or replacement of the battery 100. Thereafter, the ECU 300 returns the process to the main routine.

  When open failure number N is less than the reference value (NO in S70), ECU 300 returns the process to the main routine without notifying the user of abnormality of battery 100. Thereafter, the flowchart shown in FIG. 7 is called from the main routine and repeatedly executed when a predetermined condition is satisfied or at predetermined time intervals, whereby the number N of open faults and the determination value Sk gradually increase as time passes.

  As described above, according to the present embodiment, the number N of open failures is estimated by using the elapsed time T after the external charging is performed and the failure occurrence probability. Thereby, even if the open failure number N cannot be calculated based on the actual measurement values such as fluctuations in the block voltages V1 to Vn, the charging power upper limit value Win and the discharging power upper limit value Wout can be set to appropriate values. The battery 100 can be appropriately protected.

  More specifically, in order to protect the battery 100 despite the unknown open failure number N, the charging power upper limit value Win and the discharging power upper limit value Wout (the absolute values thereof) are set to the lowest possible values. It is required to do. However, in that case, charging / discharging of the battery 100 is excessively limited, and the battery 100 cannot be fully utilized, and the fuel consumption of the vehicle 1 may be deteriorated.

  On the other hand, according to the present embodiment, the charging power upper limit value Win and the discharging power upper limit value Wout can be set according to the estimated value of the number N of open failures, and therefore the charging power upper limit value Win and the discharging power upper limit value Wout are set. Setting it to an excessively low value can be avoided. Thereby, since the battery 100 can be fully utilized, the fuel consumption of the vehicle 1 can be improved.

  In addition, it is desirable to inform the user that the charge power upper limit value Win and the discharge power upper limit value Wout can be set to appropriate values by performing external charging, for example, in the owner's manual of the vehicle 1. Since the user who has obtained such knowledge can expect to actively carry out external charging, the frequency of EV traveling (running without using the engine) of the vehicle 1 increases, and the fuel efficiency of the vehicle 1 is improved. be able to.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  1 vehicle, 10, 20 motor generator, 101 to 10n block, 30 power split mechanism, 40 engine, 50 PCU, 60 SMR, 70 inlet, 80 AC / DC converter, 90 CHR, 100 battery, 110 cell, 111 case, 112 Lid part, 113 positive terminal, 113A, 114A terminal plate, 113B, 114B bolt, 114 negative terminal, 115 discharge valve, 120 fuse, 200 monitoring unit, 201-20n voltage sensor, 300 ECU, 400 charging cable, 410 plug, 420 Connector, 430 electric wire, 500 external power supply, 510 outlet.

Claims (1)

A hybrid vehicle configured to be able to perform external charging for charging a battery with electric power supplied from an external power source,
The battery includes a plurality of battery blocks connected in series with each other,
Each of the plurality of battery blocks has a plurality of cells connected in parallel to each other,
The hybrid vehicle further includes a control device that controls charging / discharging of the battery so that charging power to the battery does not exceed a charging power upper limit value and discharging power from the battery does not exceed a discharging power upper limit value. Prepared,
The control device calculates the number of failed cells by using an elapsed time after the external charging is performed and a probability that a failure occurs in any one of the plurality of cells per unit time, The hybrid vehicle that sets the charge power upper limit value and the discharge power upper limit value lower as the number of the failed cells is larger.

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