JP5765028B2 - Control device and control method for hybrid vehicle - Google Patents

Description

  The present invention relates to a control device and a control method for a hybrid vehicle, and more specifically to charge / discharge control of a secondary battery mounted on the hybrid vehicle.

  A hybrid vehicle, a fuel cell vehicle, and an electric vehicle that travel with driving force from a traveling motor are known. These vehicles are equipped with a battery (secondary battery) that stores electric power input and output with respect to the electric motor for traveling. Such a secondary battery is known to deteriorate due to continuous charge and discharge.

  Japanese Patent Laying-Open No. 2010-60406 (Patent Document 1) describes a monitoring device that estimates the degree of increase in battery resistance that occurs in a large current region. Specifically, based on the correlation between the difference in electrolyte salt concentration between electrodes (typically, the lithium ion concentration in the electrolyte in a lithium ion secondary battery) and the rate of increase in resistance, the battery It is described that the degree of increase in resistance is estimated. Furthermore, it is described that the salt concentration change in the electrolyte solution in the electrode can be estimated based on the history of the battery current.

  Japanese Unexamined Patent Application Publication No. 2009-123435 (Patent Document 2) describes control for suppressing deterioration of the secondary battery due to discharge (high rate discharge) performed with a relatively large current with respect to the battery capacity. Specifically, it is described that the deterioration evaluation value of the secondary battery is calculated based on the history of the discharge current value of the secondary battery, and the discharge power is limited based on the calculated deterioration evaluation value.

  Similarly, Japanese Unexamined Patent Application Publication No. 2009-100533 (Patent Document 3) describes that the progress of deterioration of the secondary battery is detected based on the estimation of the electrolyte ion concentration between the electrodes. In Patent Document 3, charging / discharging of the secondary battery is controlled based on the estimated electrolyte ion concentration so as to maintain the electrolyte ion concentration in a normal range.

  Japanese Unexamined Patent Application Publication No. 2008-59910 (Patent Document 4) describes a configuration of a battery model for analyzing a lithium ion concentration distribution in an electrolytic solution by a diffusion equation. In particular, Patent Document 4 describes a method for appropriately setting boundary conditions at electrode interfaces in a battery model.

  Japanese Patent Laid-Open No. 2009-290951 (Patent Document 5) discloses charge / discharge control for bringing the estimated SOC of a secondary battery whose SOC (State Of Charge) information has been reset closer to a true SOC in a short time. Have been described.

JP 2010-60406 A JP 2009-123435 A JP 2009-1000051 A JP 2008-59910 A JP 2009-290951 A

  Patent Documents 2 to 4 describe that the discharge power of the secondary battery is limited according to the electrolyte salt concentration. In particular, Patent Document 2 discloses introducing an evaluation value for evaluating deterioration of a secondary battery due to high-rate discharge. When the deterioration evaluation value exceeds the target value, the deterioration of the secondary battery is suppressed by setting the output power upper limit value (WOUT) smaller than usual.

  However, when the discharge power of the in-vehicle secondary battery is limited, the output torque of the traveling motor is limited. For this reason, there is a possibility that the power performance of the vehicle may deteriorate in a scene where the vehicle driving force is required due to, for example, a decrease in responsiveness to the acceleration request by the user's accelerator operation. Further, since the deterioration evaluation value described in Patent Document 2 is calculated based on the history of current values, once the deterioration evaluation value rises to a level that requires output restriction, even if the discharge current is suppressed by output restriction. There is a concern that it takes time until the degradation evaluation value decreases. For this reason, the output restriction once started may continue for a certain period of time.

  The present invention has been made in order to solve such problems, and an object of the present invention is to suppress deterioration of the power performance of the vehicle while suppressing deterioration of the secondary battery due to high-rate discharge. And controlling charging / discharging of the in-vehicle secondary battery.

In one aspect of the present invention, there is provided a control device for a hybrid vehicle equipped with a secondary battery, a detector for detecting a battery current value for charging / discharging the secondary battery, a calculation means, and charging of the secondary battery. Charge / discharge control means for controlling the level; and charge / discharge restriction means for setting a discharge power upper limit value of the secondary battery according to the state of the secondary battery . The calculation means calculates a deterioration evaluation value that reflects an increase in the deviation of ion concentration in the electrolyte of the secondary battery due to continuous discharge, based on the history of the battery current value. When the charge / discharge control means controls the charge / discharge of the secondary battery in the first control mode for controlling the charge level to a predetermined target, the calculated deterioration evaluation value is more than the first predetermined value. When it rises, charging / discharging is controlled by applying a second control mode for controlling the battery current value in the charging direction rather than the first control mode. When the deterioration evaluation value calculated by the calculation means rises above the second predetermined value, the charge / discharge limiting means limits the discharge power upper limit value than when the deterioration evaluation value is lower than the second predetermined value.

More preferably, the hybrid vehicle includes an electric motor for generating a vehicle driving force by electric power from the secondary battery, and a power generation mechanism for generating charging power for the secondary battery while the vehicle is traveling. The charge / discharge control means sets the required charge power of the secondary battery according to the charge level of the secondary battery, and the required charge power is set to a negative value when the secondary battery needs to be discharged. The control device is a travel control means for controlling the electric motor and the power generation mechanism so that a total power corresponding to the sum of the required power for outputting the required driving force for the entire vehicle and the required charging power is output. Is further provided. The charge / discharge control means changes the required charge power in the positive direction in the second control mode with respect to the same charge level of the secondary battery as compared with the first control mode.

  More preferably, the hybrid vehicle further includes an internal combustion engine and a power split mechanism for splitting the output of the internal combustion engine into a drive shaft and a power generation mechanism that are mechanically coupled to the electric motor. The power generation mechanism is configured to generate electric power by the output of the internal combustion engine transmitted through the power split mechanism. The traveling control means controls the distribution of the output of the internal combustion engine and the output of the electric motor with respect to the total power.

  Preferably, the calculation means includes a deterioration calculation means for calculating a change amount of the deterioration evaluation value to the deterioration side in accordance with an increase in the ion concentration bias due to discharge, and a reduction in the ion concentration bias over time. Accordingly, in order to calculate the deterioration evaluation value based on the non-deterioration calculation means for calculating the change amount of the deterioration evaluation value to the non-deterioration side and the change amount to the deterioration side and the change amount to the non-deterioration side Deterioration evaluation value calculation means.

  More preferably, the deterioration calculating means moves to the deterioration side at the second timing based on the current value detected at the second timing when a predetermined period has elapsed from the first timing and the predetermined period. Means for calculating the amount of change. The non-deterioration calculation means includes means for calculating the amount of change to the non-deterioration side at the second timing based on the evaluation value at the first timing and a predetermined period. The deterioration evaluation value calculation means is based on the deterioration evaluation value at the first timing, the amount of change toward the deterioration side at the second timing, and the amount of change toward the non-deterioration side at the second timing. Means for calculating an evaluation value are included.

In another aspect of the present invention, there is provided a method for controlling a hybrid vehicle equipped with a secondary battery, the step of detecting a battery current value for charging / discharging the secondary battery, and continuously based on a history of the battery current value. Calculating a degradation evaluation value that reflects an increase in ion concentration bias in the electrolyte of the secondary battery due to a random discharge, controlling the charge level of the secondary battery, and depending on the state of the secondary battery Setting a discharge power upper limit value of the battery . In the controlling step, the calculated deterioration evaluation value is higher than the first predetermined value when charging / discharging of the secondary battery is controlled by the first control mode for controlling the charging level to a predetermined target. Then, a step of controlling charging / discharging by applying a second control mode for controlling the battery current value in the charging direction rather than the first control mode is included. The setting step includes a step of limiting the discharge power upper limit value when the calculated deterioration evaluation value is higher than the second predetermined value than when the deterioration evaluation value is lower than the second predetermined value.

More preferably, the hybrid vehicle includes an electric motor for generating a vehicle driving force by electric power from the secondary battery, and a power generation mechanism for generating charging power for the secondary battery while the vehicle is traveling. In the step of controlling the charge level, the required charge power of the secondary battery is set according to the charge level of the secondary battery, and the required charge power is set to a negative value when the secondary battery needs to be discharged. The control method further includes a step of controlling the electric motor and the power generation mechanism so that total power corresponding to the sum of the required power for outputting the required driving force for the entire vehicle and the required charging power is output. The step of controlling the charge level includes a step of changing the required charge power in the positive direction in the second control mode with respect to the same charge level of the secondary battery as compared with the first control mode.

  More preferably, the hybrid vehicle further includes an internal combustion engine and a power split mechanism for splitting the output of the internal combustion engine into a drive shaft and a power generation mechanism that are mechanically coupled to the electric motor. The power generation mechanism is configured to generate electric power by the output of the internal combustion engine transmitted through the power split mechanism. The step of controlling the motor and the power generation mechanism controls the distribution of the output of the internal combustion engine and the output of the motor with respect to the total power.

  According to the present invention, charging / discharging of the in-vehicle secondary battery can be controlled so as to suppress the deterioration of the power performance of the vehicle while suppressing the deterioration of the secondary battery due to the high rate discharge.

It is a block diagram explaining the structural example of the hybrid vehicle by which the control apparatus by embodiment of this invention is mounted. It is a block diagram which shows the structure of the electric system of the hybrid vehicle shown in FIG. It is a functional block diagram of a control device concerning an embodiment of the invention. It is a wave form diagram for demonstrating the behavior of charging / discharging control by embodiment of this invention. It is a flowchart explaining the control processing for implement | achieving charging / discharging control by embodiment of this invention. It is a flowchart explaining the detailed control processing of the step which calculates the degradation evaluation value shown in FIG. It is a characteristic view for demonstrating charge / discharge control in normal mode and charge promotion mode. It is a flowchart explaining the detailed control process of the step for the traveling control shown in FIG. It is a conceptual diagram for demonstrating the setting of an engine operating point.

  Hereinafter, embodiments of the present invention will be described 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.

  FIG. 1 is a block diagram illustrating a configuration example of a hybrid vehicle on which a control device according to an embodiment of the present invention is mounted.

  Referring to FIG. 1, the hybrid vehicle operates as an engine 100, a first MG (Motor Generator) 200 that mainly operates as a generator, a PCU (Power Control Unit) 300, a battery 400, and mainly as an electric motor. Second MG 500, ECU (Electronic Control Unit) 600, and power split mechanism 700 are included.

  The control device according to the embodiment of the present invention is realized by software processing and / or hardware processing executed by ECU 600. Although the present embodiment will be described using a hybrid vehicle equipped with engine 100, the present invention is not limited to a hybrid vehicle equipped with engine 100, but a hybrid vehicle equipped with a fuel cell instead of engine 100. You may apply to (fuel cell vehicle).

  The power generated by the engine 100 is divided into two paths by the power split mechanism 700. One is a path for driving the wheel 900 via the speed reducer 800. The other is a path for driving the first MG 200 to generate power.

  First MG 200 and second MG 500 are typically configured by a three-phase AC motor.

  First MG 200 generates power using the power of engine 100 distributed by power split device 700. The electric power generated by first MG 200 is selectively used according to the driving state of the vehicle and the charge level (SOC) of battery 400. For example, during normal traveling or sudden acceleration, the electric power generated by first MG 200 becomes electric power for driving second MG 500 as it is. On the other hand, when the SOC of battery 400 is lower than a predetermined value, the power generated by first MG 200 is converted from AC power to DC power by inverter 302 of PCU 300. This DC power is stored in the battery 400 after the voltage is adjusted by the converter 304. First MG 200 operates as an electric motor for motoring engine 100 when the engine is started.

  The battery 400 is typically composed of a lithium ion secondary battery. In general, the battery 400 is an assembled battery formed by connecting a plurality of modules each of which integrates a plurality of lithium ion battery cells in series.

  The positive electrode of the lithium ion battery cell is made of a material (for example, a lithium-containing oxide) capable of reversibly occluding / releasing lithium ions. The positive electrode releases lithium ions into the electrolyte during the charging process, and occludes lithium ions in the electrolyte released from the negative electrode during the discharging process. The negative electrode of the lithium ion battery cell is made of a material (for example, carbon) capable of reversibly occluding / releasing lithium ions. The negative electrode occludes lithium ions in the electrolytic solution released from the positive electrode during the charging process, and releases lithium ions into the electrolytic solution during the discharging process.

  Second MG 500 is driven by at least one of the electric power stored in battery 400 and the electric power generated by first MG 200. The driving force of second MG 500 is transmitted to wheel 900 via speed reducer 800. Thus, second MG 500 assists engine 100 to cause the vehicle to travel, or causes the vehicle to travel only by the driving force from second MG 500.

  On the other hand, at the time of regenerative braking of the hybrid vehicle, second MG 500 is driven by wheel 900 via speed reducer 800, and second MG 500 is operated as a generator. Thus, second MG 500 functions as a regenerative brake that converts braking energy into electric power. The electric power generated by second MG 500 is stored in battery 400 via inverter 302.

ECU 600 includes a CPU (Central Processing Unit) 602, a memory 604, and a counter 606. The CPU 602 operates the vehicle, the accelerator opening (ACC) detected by the accelerator opening sensor 1100, the rate of change of the accelerator opening, the vehicle speed (V) detected by a vehicle speed sensor (not shown), the shift position, and the battery 400. The calculation processing is performed based on the SOC, the map and the program stored in the memory 604. Thereby, ECU 600 controls the devices mounted on the vehicle so that the vehicle is in a desired driving state. Note that at least a part of the ECU 600 may be configured to execute predetermined numerical / logical operation processing by hardware such as an electronic circuit.

  FIG. 2 is a block diagram showing the configuration of the electric system of the hybrid vehicle shown in FIG.

  Referring to FIG. 2, ECU 600 detects a voltage sensor 610 that detects an output voltage value of battery 400 (hereinafter also referred to as battery voltage Vb), and a charge / discharge current value (hereinafter also referred to as battery current Ib). Current sensor 612 is connected to battery temperature sensor 614 that detects the temperature of battery 400 (hereinafter also referred to as battery temperature Tb). In the following description, it is assumed that the battery current has a positive value (Ib> 0) when the battery 400 is discharged and the battery current has a negative value (Ib <0) when charged.

  ECU 600 calculates the charge / discharge power value of battery 400 from battery voltage Vb detected by voltage sensor 610 and battery current Ib detected by current sensor 612. Further, ECU 600 can calculate the SOC of battery 400 by tracing the SOC change based on the integration of battery current Ib. It should be noted that other well-known techniques may be used for calculating the SOC, and detailed description thereof will not be repeated here. The history of the battery current Ib detected by the current sensor 612 can be stored in the memory 604.

  ECU 600 has a charge power upper limit value (hereinafter also referred to as WIN) indicating a limit value of power charged in battery 400, and a discharge power upper limit value (hereinafter also referred to as WOUT) indicating a limit value of power discharged from battery 400. Set. The charging power value for battery 400 and the discharging power value from battery 400 are limited so as not to exceed WIN and WOUT. Note that other well-known techniques may be used as a method of limiting the charging power and discharging power of battery 400, and detailed description thereof will not be repeated here.

  As described in Patent Document 2, when high-rate discharge from the battery 400 is continuously performed, the internal resistance increases, and a phenomenon occurs in which the output voltage from the battery 400 starts to rapidly decrease at a certain timing. There is. If this phenomenon continues further, the battery 400 may deteriorate. It is considered that one of the causes of the deterioration is a deviation in ion concentration in the electrolytic solution due to continuous high-rate discharge. When deterioration due to high-rate discharge occurs, the output voltage does not recover even if the discharge current value is lowered or charged thereafter. Therefore, it is necessary to suppress high-rate discharge before such deterioration occurs.

  For this reason, in Patent Document 2, a deterioration evaluation value D corresponding to a change in the deviation of the lithium ion concentration in the electrolytic solution is calculated based on the battery current history. Then, WOUT is set based on the calculated deterioration evaluation value D. If WOUT is restricted, the output torque of the electric motor for traveling (second MG 500 in the example of FIG. 1) is also restricted, which affects the power performance of the vehicle, such as a decrease in responsiveness to acceleration requests by the user's accelerator operation. There is a risk of affecting. In the control of Patent Document 2, by appropriately providing a period for limiting WOUT based on the deterioration evaluation value D, it is possible to suppress deterioration of the secondary battery due to high-rate discharge while suppressing a decrease in power performance of the vehicle. It is aimed.

  However, once the deterioration evaluation value D rises to a level that requires WOUT restriction, there is a concern that it takes time until the deterioration evaluation value D decreases even if the discharge current is suppressed by WOUT restriction. That is, in the control according to Patent Document 2, there is a concern that a decrease in power performance due to WOUT restriction may continue for a certain period of time once it occurs.

  Therefore, in the present embodiment, deterioration evaluation value D is calculated according to a change in the deviation of the lithium ion concentration in the electrolyte of battery 400, and charging / discharging is controlled according to deterioration evaluation value D.

FIG. 3 is a functional block diagram of the control device according to the embodiment of the present invention.
The processing by each functional block shown in FIG. 3 can be realized by hardware mainly composed of a digital circuit or an analog circuit or software mainly composed of a program read from the memory 604 and executed by the CPU 602. Is possible.

  Referring to FIG. 3, this control device includes an SOC calculation unit 605, a deterioration evaluation value calculation unit 620, a charge / discharge restriction unit 640, a charge / discharge control unit 630, and a travel control unit 650.

  As described above, SOC calculation unit 605 calculates the SOC of battery 400 based on the battery state data representing the state of battery 400. The battery state data includes a battery current Ib, a battery voltage Vb, and a battery current Ib.

  Based on the history of battery current Ib, deterioration evaluation value calculation unit 620 calculates deterioration evaluation value D (N) reflecting an increase in ion concentration bias in the electrolyte solution of battery 400 due to continuous discharge.

  The deterioration evaluation value D is a value indicating a deterioration state due to the above-described high rate discharge. That is, as the deterioration evaluation value D is larger, it indicates that the deterioration due to the high rate discharge of the battery 400 is progressing. The deterioration evaluation value D can be calculated by a method similar to that of Patent Document 2. Details of the calculation method will be described later.

  Charging / discharging limiting unit 640 calculates WIN and WOUT of battery 400. Typically, WIN and WOUT are set according to the SOC of battery 400. WIN and WOUT can be set based on any known method. Furthermore, the charge / discharge restriction unit 640 may further restrict WIN and WOUT according to the deterioration evaluation value D calculated by the deterioration evaluation value calculation unit 620, as in Patent Document 2.

  Charging / discharging control unit 630 controls charging / discharging of battery 400 such that the SOC of battery 400 is maintained at a predetermined control target. Although details will be described later, the charge / discharge control unit 630 changes the mode of charge / discharge control according to the calculated deterioration evaluation value D. Then, the charge / discharge control unit 630 sets the charge request power Pchg of the battery 400 in order to control the charge / discharge of the battery 400. The required charging power Pchg is set to a positive value (Pchg> 0) when the battery 400 is to be charged, and is set to a negative value (Pchg <0) when the battery 400 is to be discharged.

  Traveling control unit 650 calculates the required driving force for the entire vehicle based on the state of the vehicle (typically, accelerator opening ACC and vehicle speed V). Then, traveling control unit 650 outputs engine 100 so as to output a total power that is the sum of the calculated power for generating the required driving force and the required charging power Pchg calculated by charge / discharge control unit 630. The operation command values of the first MG 200 and the second MG 500 are generated. That is, the power distribution with respect to the total power is determined.

  This power distribution is determined so that the power input / output from / to the first MG 200 and the second MG 500 from the battery 400 (that is, the charge / discharge power of the battery 400) falls within the range of WIN to WOUT. Therefore, since it is difficult to secure the output of the second MG 500 in a situation where WOUT is restricted, there is a possibility that acceleration response will be affected when the user requests vehicle acceleration by an accelerator operation.

  FIG. 4 is a waveform diagram for explaining the behavior of charge / discharge control of the secondary battery according to the embodiment of the present invention.

  Referring to FIG. 4, deterioration evaluation value D gradually increases due to continuous discharge (high-rate discharge). As indicated by a dotted line in the figure, in the conventional control (control according to Patent Document 2), when the deterioration evaluation value D exceeds the threshold value D2 at time t1, restriction of WOUT is started. Thereby, from time t1, WOUT is set lower than the normal value (Wmax). As a result, the acceleration performance of the vehicle is relatively lowered.

  After time t1, the battery current Ib decreases due to WOUT being limited. As a result, the rate of increase in the degradation evaluation value D decreases. However, as long as the same vehicle state continues, the deterioration evaluation value D does not decrease. For this reason, once the WOUT restriction is started, the WOUT restriction continues unless the vehicle state changes and the charging opportunity by regenerative braking of the second MG 500 comes. For this reason, there is a possibility that the WOUT restriction may occur over a relatively long period of time.

  Therefore, in the charge / discharge control according to the embodiment of the present invention, when deterioration evaluation value D exceeds threshold value D1 (D1 <D2) at time t0, the charge / discharge control mode is changed from the normal mode to the normal mode. The mode is switched to the charging side mode for setting the battery current Ib to the charging side rather than the mode.

  In the normal mode, charging request power Pchg is set so as to maintain the SOC of battery 400 at a predetermined control target (for example, control center). On the other hand, in the charge side mode, the battery current Ib is forcibly decreased as compared with the normal SOC control. In the example of FIG. 4, the behavior when the battery current Ib changes to negative by switching to the charging side mode is shown. As a result, the deterioration evaluation value D decreases after time t1. For this reason, the start of WOUT restriction is avoided, and WOUT is maintained at the normal value (Wmax) even after time t1. That is, normal acceleration performance can be continuously secured.

  In the charge side mode, since the battery current Ib is forcibly changed to the charge side (that is, the SOC increasing side) as compared with the normal SOC control, there is a problem in continuing the charge side mode for a long time. Therefore, in the charging side mode, when deterioration evaluation value D falls below threshold value D1 # (D1 # <D1), the control mode is switched to the normal mode again. This can prevent the battery 400 from being overcharged.

  Below, the control process for implement | achieving charging / discharging control shown in FIG. 3 and FIG. 4 is demonstrated.

  FIG. 5 is a flowchart illustrating a control process of charge / discharge control of the secondary battery according to the embodiment of the present invention.

  The flowchart shown in FIG. 5 is repeatedly executed at a predetermined cycle time ΔT (for example, 0.1 second). The processing of each step in FIG. 5 is executed by hardware processing and / or software processing by ECU 600.

  Referring to FIG. 5, ECU 600 obtains battery state data in step S100. The battery state data is acquired based on the detection values of the sensors 610, 612, and 614 shown in FIG.

  In step S110, ECU 600 calculates the SOC of battery 400 based on the battery state data acquired in step S100. The processing in step S110 corresponds to the function of the SOC calculation unit 605 in FIG.

  ECU 600 further calculates deterioration evaluation value D in step S200. The control process in step S200 corresponds to the function of the deterioration evaluation value calculation unit 620 in FIG.

  FIG. 6 is a flowchart for explaining detailed control processing of the step of calculating the deterioration evaluation value shown in FIG.

  Referring to FIG. 6, in step S210, ECU 600 calculates forgetting factor A based on the SOC of battery 400 and battery temperature Tb. The forgetting factor A is a factor corresponding to the diffusion rate of lithium ions in the electrolyte of the battery 400. The forgetting factor A is set so that the product of the forgetting factor A and the cycle time ΔT is a value from 0 to 1. Forgetting factor A is preferably set to a relatively large value when the diffusion rate of lithium ions is estimated to be high.

  For example, ECU 600 calculates forgetting factor A based on a map using SOC and battery temperature Tb as parameters. Specifically, the forgetting factor A is calculated such that the higher the SOC is, the higher the battery temperature Tb is, and the higher the battery temperature Tb is, the higher the SOC is, the same. This forgetting factor map can be stored in the memory 604 in advance.

  In step S220, ECU 600 calculates a decrease amount D (−) in one cycle for deterioration evaluation value D. The decrease amount D (−) is a variable for representing a decrease in the deviation of the lithium ion concentration due to the diffusion of lithium ions accompanying the passage of one cycle time ΔT from the previous calculation of the deterioration evaluation value D.

  For example, ECU 600 calculates reduction amount D (−) according to the following equation (1). In equation (1), D (N−1) represents the degradation evaluation value D calculated at the previous cycle time. The initial value D (0) is, for example, 0. Further, 0 <A × ΔT <1.

D (−) = A × ΔT × D (N−1) (1)
As is clear from the equation (1), the reduction amount D (−) becomes a larger value as the forgetting factor A is larger (that is, the diffusion rate of lithium ions is faster) and as the cycle time ΔT is longer. Note that the calculation method of the decrease amount D (−) is not limited to this calculation method.

  In step S230, ECU 600 reads current coefficient B stored in memory 604 in advance. Then, ECU 600 calculates limit threshold C based on the SOC of battery 400 and battery temperature Tb in step S240.

  The limit threshold C is calculated to be larger as the SOC is higher if the battery temperature Tb is the same, and to be larger as the battery temperature Tb is higher if the SOC is the same. . For example, ECU 600 calculates limit threshold value C based on a map stored in advance in memory 604 and using SOC and battery temperature Tb as parameters.

  Further, ECU 600 calculates an increase amount D (+) per cycle for deterioration evaluation value D in step S250. The increase amount D (+) is a variable for representing an increase in the bias of the lithium ion concentration due to the discharge during the elapse of one cycle time ΔT from the time of the previous evaluation value calculation.

For example, ECU 600 calculates increase amount D (+) according to the following equation (2).
D (+) = (B / C) × Ib × ΔT (2)
As understood from the equation (2), the increase amount D (+) increases as the battery current Ib increases and the cycle time ΔT increases. Further, when Ib <0 (during charging), the increase amount D (+) <0. Note that the method of calculating the evaluation value increase amount D (+) is not limited to this calculation method.

  In step S260, ECU 600 calculates D (N), which is deterioration evaluation value D at the current cycle time. D (N) is calculated according to the following equation (3). As described above, the initial value D (0) is, for example, 0.

D (N) = D (N−1) −D (−) + D (+) (3)
Then, ECU 600 stores current D (N) in memory 604 in step S270. The stored value is used as D (N−1) in the control process (S220) at the next cycle time. Thus, D (N) is calculated based on the history of the battery current Ib so far.

  Referring to FIG. 5 again, in step S300, ECU 600 compares deterioration evaluation value D calculated in step S200 with threshold value D1 (FIG. 4). Thereby, the charge / discharge control mode is determined.

  Specifically, ECU 600 calculates required charging power Pchg according to the normal mode in step S310 until deterioration evaluation value D rises to D1 (NO determination in S300). On the other hand, when deterioration evaluation value D rises above D1 (when YES is determined in S300), ECU 600 calculates charging request power Pchg according to the charging side mode in step S320.

  As described with reference to FIG. 4, once charging mode is selected, ECU 600 changes the threshold value used for the determination in step S300 to D1 # (D1 # <D1). The process by step S300-S320 respond | corresponds to the function of the charging / discharging control part 630 of FIG.

The charge / discharge control in the normal mode and the charge promotion mode will be described with reference to FIG.
Referring to FIG. 7, ECU 600 sets charge request power Pchg according to the SOC of battery 400. In the normal mode, the required charging power Pchg is set in accordance with the characteristic line 631 so that the SOC is maintained at the control center S0.

  Specifically, in the region where the SOC is lower than the control center S0 (SOC <S0), the charging request power Pchg is set to a positive value (Pchg> 0) in order to charge the battery 400. On the other hand, in the region where the SOC is higher than the control center (SOC> S0), the charging request power Pchg is set to a negative value (Pchg <0) so as to request the battery 400 to be discharged.

  Further, when the SOC coincides with the control center, Pchg = 0 is set, so that neither charge nor discharge is required for charge / discharge control. In FIG. 7, the control center S0 is a single SOC value, but a certain SOC range may be the control center S0.

  On the other hand, in the charge promotion mode, the characteristic line 631 is changed to the characteristic line 632 obtained by shifting Pchg in the positive direction (charging side), or the control center is temporarily changed from S0 to S0 # (S0 #> S0). Based on the shifted characteristic line 633, the required charging power Pchg is set. Alternatively, by combining the characteristic lines 631 and 632, the required charging power Pchg may be set using a characteristic line to which both the shift of Pchg and the shift of the control center are applied to the characteristic line 631.

  As a result, in the charging side mode, when the state of charge (SOC) of the battery 400 is the same, the required charging power Pchg changes in the positive direction (charging side) as compared to the normal mode.

  Referring to FIG. 5 again, ECU 600 compares deterioration evaluation value D calculated in step S200 with threshold value D2 (FIG. 4) in step S400. Thereby, it is determined whether or not WOUT needs to be restricted. The threshold value D2 is set to a value smaller than the boundary value of the deteriorated region, corresponding to the deteriorated region due to the high rate discharge.

  When D> D2 is not satisfied (NO in S400), ECU 600 sets WOUT to a normal value in step S410. The normal value of WOUT is typically set based on SOC, or based on SOC and battery temperature Tb.

  When D> D2 (when YES is determined in S400), ECU 600 sets WOUT lower than the normal value (S410) in step S420. As a result, as in Patent Document 2, WOUT is limited.

  Further, in step S500, ECU 600 reflects the charge request power Pchg set in steps S300 to S320 and WOUT set in steps S400 to S420, and distributes power among engine 100, first MG 200, and second MG 500. The traveling control for determining the vehicle is executed.

  FIG. 8 is a flowchart for explaining detailed control processing in step S500 for travel control shown in FIG.

  Referring to FIG. 8, ECU 600 calculates required driving force Tr * for the entire vehicle based on the vehicle state detected based on the sensor output signal in step S510. For example, a map (not shown) in which the relationship between the accelerator opening ACC and the vehicle speed V and the required driving force Tr * is determined in advance is stored in the memory 604 in advance. When the accelerator opening degree ACC and the vehicle speed V are detected, ECU 600 can calculate required driving force Tr * by referring to the map.

  Further, in step S520, ECU 600 calculates required power Pe for engine 100 according to the following equation (4) based on required driving force Tr * and required charging power Pchg. In Expression (4), Nr indicates the rotational speed of the drive shaft, and Loss is a loss term.

Pe = Tr * · Nr + Pchg + Loss (4)
The drive shaft is mechanically connected to the wheel 900 and is also connected to the engine 100 and the second MG 500 via the power split mechanism 700.

  In step S530, ECU 600 determines an operating point of engine 100 based on engine required power Pe.

FIG. 9 is a conceptual diagram for explaining the setting of the engine operating point.
Referring to FIG. 9, the engine operating point is defined by a combination of engine speed Ne and engine torque Te. The product of the engine speed Ne and the engine torque Te corresponds to the engine output power.

  The operation line 110 is determined in advance as a set of engine operating points that can operate the engine 100 with high efficiency. The operation line 110 corresponds to an optimum fuel consumption line for suppressing fuel consumption at the same power output.

  In step S530, as shown in FIG. 9, ECU 600 determines the intersection of predetermined operation line 110 and equal power line 120 corresponding to engine required power Pe calculated in step S520 as the engine operation point (target rotation). Number Ne * and target torque Te *). Further, the output torque of first MG 200 is determined such that the engine speed is controlled to the target speed Ne * by the output torque of first MG 200 that is mechanically coupled to engine 100 by power split mechanism 700.

  Referring to FIG. 8 again, in step S540, ECU 600 calculates drive torque (direct torque) Tep mechanically transmitted to the drive shaft when engine 100 is operated according to the engine operating point determined in step S530. To do. For example, direct torque Tep is set in consideration of the gear ratio of power split device 700.

  Further, in step S550, ECU 600 calculates the output torque of second MG 500 so as to compensate for the excess or deficiency (Tr * -Tep) of direct torque Tep with respect to required driving force Tr *. That is, when the output torque of the second MG 500 is Tm2, the following equation (5) is established. Tm2 * is a torque acting on the drive shaft by the output of the second MG 500.

Tr * = Tep + Tm2 * (5)
ECU 600 then determines operation command values for engine 100, first MG 200, and second MG 500 based on the operating point of engine 100 and the output torques of first MG 200 and second MG 500 determined in steps S530 to S550 in step S560. Set. Engine 100, first MG 200, and second MG 500 are controlled in accordance with these operation command values.

  With such traveling control, in the hybrid vehicle, the engine 100, the first MG 200, and the second MG 500 are operated such that the required driving force Tr * acts on the drive shaft while the engine 100 is operated on the high-efficiency operation line 110. The power distribution with respect to the total power can be determined.

  Since the charge / discharge power of the battery 400 is determined by this power distribution, the charge / discharge current value (battery current Ib) of the battery 400 cannot be directly controlled by the charge request power Pchg. However, since the charge request power Pchg is reflected in the total power, in the charge side mode in which the charge request power Pchg is set on the charge side, the battery current Ib is on the charge side (negative direction) compared to the normal mode. Can be changed. That is, the discharge current value can be reduced, or the continuation of discharge can be terminated to generate the charge current. As a result, further increase in the degradation evaluation value D based on the history of the battery current Ib can be suppressed.

  As described above, according to the charge / discharge control according to the present embodiment, before the degradation evaluation value D for evaluating the degradation progression due to the high-rate discharge reaches a level (threshold value D2) that is a WOUT limit, By switching the control mode to the charging side mode, further increase in the degradation evaluation value D can be suppressed.

  Therefore, from the viewpoint of suppressing high-rate discharge, it is possible to prevent the start of output restriction (that is, WOUT restriction) from the battery 400, which leads to output torque restriction of the electric motor for traveling (second MG 500). As a result, it is possible to suppress a decrease in power performance (typically acceleration performance) of the vehicle while suppressing deterioration of the secondary battery due to high-rate discharge.

  In the present embodiment, deterioration evaluation value D calculated based on battery current Ib is stored for each cycle time, and current value D (N) is stored using stored previous value D (N−1). However, the method of calculating the degradation evaluation value D is not limited to the examples in this specification. That is, if it is possible to quantitatively evaluate the increase / decrease in the bias of the electrolyte salt concentration (typically, the lithium ion concentration in the electrolyte solution in the lithium ion secondary battery) based on the history of the battery current Ib, It is also possible to use a method different from the example in the specification. For example, the deterioration evaluation value D may be calculated by calculating a value corresponding to the previous value D (N−1) for each cycle time based on the history of the battery current Ib.

  In the present embodiment, the limitation on the discharge power that affects the acceleration performance has been mainly described. However, as understood from the equation (1), when charging with a large current is continued, the degradation evaluation value D has an absolute value in a negative region. That is, even in the region where the deterioration evaluation value D <0, if the absolute value of the deterioration evaluation value D exceeds a predetermined threshold value, it is necessary to limit the charging power of the battery 400, that is, WIN.

  Therefore, even when the degradation evaluation value D <0, a discharge side mode opposite to the above-described charge side mode may be applied in a region before WIN restriction is necessary. For example, in the discharge-side mode, charging is performed using a characteristic line in which a shift in the negative direction (discharge side) of Pchg and / or a shift in the decrease direction of the control center is applied to the characteristic line 631 in FIG. The required power Pchg may be set.

  Further, the present invention is suitable for a lithium ion secondary battery. However, the present invention is applicable to any secondary battery having such a characteristic that the deviation of the electrolyte salt concentration affects the deterioration by continuous discharge or charging. The fact that charge / discharge control can be applied in a similar manner is also described in a confirming manner.

  Further, the configuration of the hybrid vehicle shown in FIG. 1 is merely an example, and it is confirmed that the present invention is applicable to a secondary battery mounted on a hybrid vehicle having a configuration different from that shown in FIG. To do. That is, in a hybrid vehicle that executes charge / discharge control for controlling the SOC of the in-vehicle secondary battery to a predetermined target as normal control, charge / discharge control is performed on the charge side (in other words, discharge suppression side) rather than normal control. As long as it can be adjusted, the present invention can be similarly provided to a secondary battery mounted on a hybrid vehicle having an arbitrary configuration.

  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 charge / discharge control of a secondary battery mounted on a vehicle.

  100 engine, 110 operation line, 120 equal power line, 200 1st MG, 302 inverter, 304 converter, 400 battery, 500 2nd MG, 600 ECU, 602 CPU, 604 memory, 605 SOC calculation unit, 606 counter, 610 voltage sensor, 612 Current sensor, 614 Battery temperature sensor, 620 Degradation evaluation value calculation unit, 630 Charge / discharge control unit, 631, 632, 633 Characteristic line, 640 Charge / discharge limiting unit, 650 Travel control unit, 700 Power split mechanism, 800 Reducer, 900 wheel, 1100 accelerator opening sensor, A forgetting factor, ACC accelerator opening, D, D (N) deterioration evaluation value, D (N-1) deterioration evaluation value (previous value), D (-) decrease (deterioration) Evaluation value), D (+) Increase amount (degradation evaluation value), D1, D2 Threshold, Tep direct torque, Ib battery current, Ne engine speed, Te engine torque, Pchg charge required power, Pe engine required power, Tp * engine required power, S0 SOC control center, Tb battery temperature, Tr * required drive force , V Vehicle speed, Vb Battery voltage.

Claims (8)

A control device for a hybrid vehicle equipped with a secondary battery,
A detector for detecting a battery current value for charging and discharging the secondary battery;
Based on the history of the battery current value, a calculation means for calculating a degradation evaluation value that reflects an increase in ion concentration bias in the electrolyte of the secondary battery due to continuous discharge;
Charge / discharge control means for controlling the charge level of the secondary battery;
Charge / discharge limiting means for setting a discharge power upper limit value of the secondary battery according to the state of the secondary battery ,
When the charge / discharge control unit controls charge / discharge of the secondary battery in a first control mode for controlling the charge level to a predetermined target, the calculated deterioration evaluation value is a first value. When rising above a predetermined value, the charge / discharge is controlled by applying a second control mode for controlling the battery current value in the charging direction rather than the first control mode ,
When the deterioration evaluation value calculated by the calculation means rises above a second predetermined value, the charge / discharge limiting means causes the discharge power to be lower than when the deterioration evaluation value is lower than the second predetermined value. Limit the upper limit,
The control device , wherein the first predetermined value is lower than the second predetermined value . The hybrid vehicle
An electric motor for generating vehicle driving force by electric power from the secondary battery;
A power generation mechanism for generating charging power of the secondary battery during vehicle travel,
The charge / discharge control means sets the required charge power of the secondary battery according to the charge level of the secondary battery,
The required charging power is set to a negative value when the secondary battery needs to be discharged,
The controller is
Travel control means for controlling the electric motor and the power generation mechanism so that a total power corresponding to the sum of the required power for outputting the required driving force for the entire vehicle and the required charging power is output. In addition,
The charge / discharge control means changes the required charging power in the positive direction in the second control mode with respect to the same charge level of the secondary battery as compared with the first control mode. The control device according to 1. The hybrid vehicle
An internal combustion engine;
A power split mechanism for splitting the output of the internal combustion engine into a drive shaft mechanically connected to the electric motor and the power generation mechanism;
The power generation mechanism is configured to generate power by the output of the internal combustion engine transmitted through the power split mechanism,
The control device according to claim 2 , wherein the travel control unit controls distribution of the output of the internal combustion engine and the output of the electric motor with respect to the total power. The calculating means includes
Deterioration calculating means for calculating the amount of change of the deterioration evaluation value to the deterioration side according to an increase in the deviation of the ion concentration due to discharge;
Non-deterioration calculating means for calculating a change amount of the deterioration evaluation value to the non-deteriorating side according to a decrease in the deviation of the ion concentration over time,
Based on the amount of change in the change amount and the non-deterioration side to the deterioration side, and a deterioration evaluation value calculating means for calculating the deterioration evaluating value, according to any one of claims 1 to 3 Control device. The deterioration calculating means is configured to supply the deterioration side at the second timing to the deterioration side based on the current value detected at the second timing when a predetermined period has elapsed from the first timing and the predetermined period. Including means for calculating the amount of change;
The non-deterioration calculation means includes means for calculating a change amount to the non-deterioration side at the second timing based on the evaluation value at the first timing and the predetermined period.
The deterioration evaluation value calculation means is configured to determine the first value based on a deterioration evaluation value at the first timing, a change amount toward the deterioration side at the second timing, and a change amount toward the non-deterioration side at the second timing. The control device according to claim 4 , comprising means for calculating a deterioration evaluation value at a timing of 2. A control method for a hybrid vehicle equipped with a secondary battery,
Detecting a battery current value for charging and discharging the secondary battery;
Based on the history of the battery current value, calculating a deterioration evaluation value reflecting an increase in ion concentration bias in the electrolyte of the secondary battery due to continuous discharge;
Controlling a charge level of the secondary battery ;
Setting a discharge power upper limit value of the secondary battery according to the state of the secondary battery ,
In the controlling step, when the charge / discharge of the secondary battery is controlled by a first control mode for controlling the charge level to a predetermined target, the calculated deterioration evaluation value is a first predetermined value. When higher than the value, look including the step of controlling the charging and discharging by applying the second control mode for controlling the charging direction the battery current value than the first control mode,
The setting step includes:
The control method includes a step of limiting the discharge power upper limit value when the calculated deterioration evaluation value is higher than a second predetermined value than when the deterioration evaluation value is lower than the second predetermined value. . The hybrid vehicle
An electric motor for generating vehicle driving force by electric power from the secondary battery;
A power generation mechanism for generating charging power of the secondary battery during vehicle travel,
The step of controlling the charge level sets the required charge power of the secondary battery according to the charge level of the secondary battery,
The required charging power is set to a negative value when the secondary battery needs to be discharged,
The control method is:
Further comprising the step of controlling the electric motor and the power generation mechanism so that the total power corresponding to the sum of the required power for outputting the required driving force in the entire vehicle and the required charging power is output,
The step of controlling the charge level is a step of changing the required charge power in the positive direction in the second control mode relative to the same charge level of the secondary battery than in the first control mode. The control method according to claim 6 , comprising: The hybrid vehicle
An internal combustion engine;
A power split mechanism for splitting the output of the internal combustion engine into a drive shaft mechanically connected to the electric motor and the power generation mechanism;
The power generation mechanism is configured to generate power by the output of the internal combustion engine transmitted through the power split mechanism,
The control method according to claim 7 , wherein the step of controlling the electric motor and the power generation mechanism controls distribution of an output of the internal combustion engine and an output of the electric motor with respect to the total power.

Images