Hybrid vehicle

Abstract

Hybrid vehicle (100) with a secondary battery (16), a drive mechanism (10) configured to generate a driving force by using electrical power from the secondary battery (16), an internal combustion engine (2), a power generation mechanism (6) configured to generate electrical power for charging the secondary battery (16) by using power output from the internal combustion engine (2), and an electronic control unit (25) which is configured, a) to calculate a control charge level based on an integrated current value, wherein the integrated current value is obtained by integrating an input current and an output current of the secondary battery (16), b) to control the operation of the power generation mechanism (6) such that the control charge state of the secondary battery (16) is kept close to a control setpoint (Sr) which is set as a predetermined control setpoint, c) to calculate an estimated actual state of charge of the secondary battery based on the integrated current value and a state of charge reduction magnitude due to self-discharge of the secondary battery (16), and, d) if the estimated actual state of charge has decreased to below a first lower limit state of charge, to raise the control setpoint.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The disclosure relates to a hybrid vehicle and more specifically to a charging and discharging control system on a secondary battery attached to a hybrid vehicle while the hybrid vehicle is in motion. 2. Description of the state of the art

[0002] A hybrid vehicle can charge a secondary battery mounted within the vehicle while driving by using power generation that accompanies the operation of a power engine. Therefore, as described in Japanese patent application publication JP 2011-225079A, the charging and discharging of a secondary battery are controlled by executing a forced discharge control or a forced charge control such that the state of charge (SOC) of the secondary battery is maintained within a predetermined range. Specifically, JP 2011-225079A describes a control for changing a control center's SOC in response to the number of times a forced charge control is executed and the number of times a forced discharge control is executed.

[0003] The Japanese patent application publication JP 2003 - 047 108 A) describes that when the charging memory effect of a secondary battery has been detected, the memory effect is eliminated while avoiding a reduction in vehicle performance and battery deterioration by increasing a target state of charge (SOC).

[0004] However, in the control system described in JP 2011-225079A, normal charge and discharge control is executed before a forced charge, triggered by the state of charge (SOC) approaching a lower control limit, is actually performed a certain number of times. For this reason, it is not possible to sufficiently prevent the occurrence of the memory effect, and there are concerns that the charge and discharge control at the secondary battery will be changed after the memory effect has occurred, as in the case of JP 2003-047108A.

[0005] German patent application DE 43 37 020 C1 discloses a method for monitoring the battery of a hybrid vehicle, wherein the state of charge of a battery is determined by balancing the amounts of charge supplied and withdrawn. The balancing process is restarted periodically from a reliable baseline value.

[0006] German patent application DE 10 2011 101 550 A1 discloses a method and a device for charging a vehicle battery. The method determines the frequency per unit of time with which the battery's state of charge falls below a lower threshold. Charging is then carried out based on this frequency.

[0007] Publication US 2013 / 0 124 029 A1 describes another method for controlling the state of charge of a vehicle battery, distinguishing between normal charging and extended charging when charging externally.

[0008] Publication JP 2002 - 171 609 A discloses a charging / unloading control method in which a forced charging mode is carried out depending on the vehicle's idle time.

[0009] German patent application DE 10 2005 058 469 B4 discloses a method for calculating the state of charge of a battery to prevent the memory effect. The calculation is performed using a reference capacity, which can be changed depending on the mode (normal state-of-charge maintenance mode, high state-of-charge range expansion mode, etc.). SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to provide a hybrid vehicle that controls the charging and discharging of a secondary battery in such a way as to prevent the occurrence of a memory effect.

[0011] This problem is solved according to an embodiment of the disclosure by a hybrid vehicle as specified in claim 1.

[0012] In the hybrid vehicle described above, if the estimated actual state of charge (SOC), which reflects the SOC reduction due to self-discharge of the secondary battery that cannot be replenished by integrating a current, has decreased, the SOC control setpoint is allowed to be raised using the power generation mechanism. Therefore, it is possible to prevent the occurrence of the charge memory effect of the secondary battery by preventing the actual SOC from remaining in a low SOC range due to the influence of self-discharge.

[0013] The electronic control unit can be configured to force the secondary battery to charge by operating the power generation mechanism when the control state of charge (SOC) drops to a second lower limit SOC, where the second lower limit SOC is higher than the first lower limit SOC. The electronic control unit can also be configured to prevent the control setpoint from rising even if the estimated actual SOC drops below the first lower limit SOC, but if the number of times the secondary battery has been forced to charge is less than a predetermined number.

[0014] With this configuration, before a forced charging cycle is activated to prevent the control SOC from dropping below the second lower limit SOC (S1), an increase in the control SOC setpoint is prevented for a predetermined number of times, even if the estimated actual SOC has decreased to the lower limit SOC (Sx). As a result, before the time spent in the low SOC range increases to a certain extent, a reduction in the amount of regenerated electrical power recovered can be prevented. Consequently, a decrease in the energy efficiency of the hybrid vehicle can be prevented or reduced.

[0015] The electronic control unit may still be configured to increase the control setpoint if the hybrid vehicle has been left in a parking area for longer than a predetermined time and the electrical power consumed by the auxiliary load is greater than or equal to a predetermined value.

[0016] This configuration makes it possible to temporarily raise the SOC control setpoint if the vehicle enters a state where there is a possibility of the SOC remaining in the low SOC range for an extended period. Therefore, it is possible to continue to reliably prevent the occurrence of the secondary battery's charge memory effect.

[0017] According to this disclosure, it is possible to control the charging and discharging of the secondary battery attached to the hybrid vehicle during driving in such a way as to prevent the occurrence of the memory effect of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and wherein: Fig. 1 a block diagram illustrating the overall configuration of a hybrid vehicle according to an embodiment of the disclosure shows, Fig. Figure 2 shows a concept graph illustrating the characteristics of a secondary battery attached to the hybrid vehicle according to the embodiment, Fig. 3. A flowchart illustrates the processing for calculating a control SOC. Fig. Figure 4 shows a concept diagram illustrating the SOC control at the secondary battery of the hybrid vehicle in broad outline, Fig. Figure 5 shows an example of an operating signal curve in the case where forced charging is repeatedly carried out in the hybrid vehicle according to the embodiment. Fig. Figure 6 shows a graph to illustrate changes in the actual state of charge (SOC) of the secondary battery. Fig. 7A and Fig. 7B Concept graphs illustrating a reduction in full charge capacity due to a charge memory effect of the secondary battery, Fig. Figure 8 shows a flowchart illustrating the processing for estimating the actual state of charge (SOC) of the secondary battery in the hybrid vehicle according to the embodiment. Fig. 9. A first flowchart illustrates the processing of the calculation of a SOC reduction due to self-discharge. Fig. 10. A second flowchart illustrates the processing for calculating a SOC reduction magnitude due to self-discharge. Fig. 11. A flowchart shows that the processing of the calculation of a SOC reduction quantity illustrates a charging efficiency, Fig. 12 shows a flowchart illustrating the processing of the execution of a SOC control in the hybrid vehicle according to the exemplary embodiment, Fig. 13 shows a flowchart to illustrate a first alternative embodiment for processing the implementation of the SOC control in the hybrid vehicle according to the embodiment, and Fig. Figure 14 shows a flowchart to illustrate a second alternative embodiment for processing the implementation of the SOC control in the hybrid vehicle according to the embodiment. DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0019] An embodiment of the disclosure is described in detail below with reference to the accompanying drawings. In the following description, the same reference numerals denote the same or corresponding sections in the drawings, therefore their description will not be repeated in principle.

[0020] Fig. Figure 1 shows a block diagram illustrating the overall configuration of a hybrid vehicle 100 according to the embodiment of the disclosure.

[0021] As it is in Fig. As shown in Figure 1, the hybrid vehicle 100 comprises a power unit 2, a power distribution device 4, motor generators 6, 10, a transmission gearbox 8, a drive shaft 12, and wheels 14. The hybrid vehicle 100 further comprises a secondary battery 16, electrical power converters 18, 19, an electronic control unit (ECU) 25, a vehicle speed sensor 29, an accelerator pedal 30, a parking switch 32, a gearshift lever 34, a shift position sensor 36, and an ignition switch (IG switch) 38.

[0022] The engine 2 is an internal combustion engine that delivers power by converting thermal energy, generated by burning fuel, into kinetic energy of moving components such as a piston and a rotor.

[0023] Each of the motor-generators 6, 10 is a rotating AC electric machine, and is, for example, a three-phase AC synchronous motor. The motor-generator 6 is not only used as a generator, driven by the power machine 2 via the power-sharing device 4, but is also used as an electric motor for starting the power machine 2.

[0024] The motor-generator 10 primarily functions as an electric motor and is used to drive the drive shaft 12 of the hybrid vehicle 100. Conversely, during deceleration of the hybrid vehicle 100, the motor-generator 10 operates as a generator to produce regenerative power.

[0025] The power distribution device 4, for example, comprises a planetary gear train with three rotating elements, namely a sun gear, a carrier gear, and a ring gear. The power distribution device 4 divides the driving force of the power machine 2 into power that is transmitted to the rotating shaft of the motor-generator 6 and power that is transmitted to the transmission gearbox 8. The transmission gearbox 8 is coupled to the drive shaft 12 for driving the wheels 14. The transmission gearbox 8 is also coupled to the rotating shaft of the motor-generator 10.

[0026] The secondary battery 16 is designed as a rechargeable DC power supply. According to the present embodiment, the secondary battery 16 is a nickel-metal hydride secondary battery. The secondary battery 16 is connected to the electrical power converters 18, 19 via a system main relay (SMR) 20.

[0027] A DC-DC converter 40 is arranged to generate a power supply voltage for an auxiliary load 45 by reducing the output voltage of the secondary battery 16. That is, when the DC-DC converter 40 is operating, the auxiliary load 45 can be operated using electrical power from the secondary battery 16.

[0028] The SMR 20 is switched on when the ignition switch 38 is turned on by a driver. Thus, the hybrid vehicle 100 enters a drivable state. Conversely, when the ignition switch 38 is turned off by the driver, the SMR 20 is switched off. When the SMR 20 is off, driving the vehicle using the electrical power of the secondary battery 16 is ineffective. The time when the SMR 20 is in the OFF state is also referred to below as the time when the secondary battery 16 is not in use (or when the secondary battery 16 is left standing). However, as can be seen from the configuration of Fig. 1 shows that even when the SMR 20 is in the OFF state, i.e., when the secondary battery 16 is not in use, the auxiliary load 45 can be operated by using the electrical power of the secondary battery 16.

[0029] When the SMR 20 is in the ON state, the electrical power converter 18 performs bidirectional DC / AC power conversion between the motor generator 6 and the secondary battery 16 based on a control signal received from the ECU 25. Likewise, when the SMR 20 is in the ON state, the electrical power converter 19 performs bidirectional DC / AC power conversion between the motor generator 10 and the secondary battery 16 based on a control signal received from the ECU 25.

[0030] Thus, each of the motor-generators 6, 10 is capable of delivering a positive torque for operation as an electric motor or a negative torque for operation as a generator as a result of exchanging electrical power with the secondary battery 15. A boost converter for DC voltage conversion can be arranged between the secondary battery 16 and each of the electrical power converters 18, 19.

[0031] The motor-generator 6 can form a power generation mechanism, since the motor-generator 6 has a generator operating mode for generating electrical power to charge the secondary battery 16 by using power supplied by the engine 2 and transmitted via the power distribution device 4. The motor-generator 10 can implement a drive mechanism for generating vehicle propulsion power by using electrical power from the secondary battery 16, if the motor-generator 10 operates as an electric motor using electrical power from the secondary battery 16.

[0032] A sensor unit 17 is located in the secondary battery 16. The sensor unit 17 is used to detect an output voltage Vb (hereinafter also referred to as battery voltage Vb), an input / output current Ib (hereinafter also referred to as battery current Ib), and a temperature Tb (hereinafter also referred to as battery temperature Tb). The battery voltage Vb, battery current Ib, and battery temperature Tb detected by the sensor unit 17 are sent to the ECU 25.

[0033] The ECU 25 includes a central processing unit (CPU), a memory device, an input / output buffer, and the like (all of which are not shown) and controls devices in the hybrid vehicle 100. These controls are not limited to software processing. These controls can be processed by dedicated hardware (electronic circuitry). The ECU 25 includes a timer 26 for measuring time.

[0034] Furthermore, an output signal from the shift position sensor 36 and an actuation signal from the park switch 32 are input into the ECU 25. The driver is enabled to select from any reverse position (R position), neutral position (N position), drive position (D position), and brake position (B position) by actuating the shift lever 34. The output signal from the shift position sensor 36 indicates the shift position currently selected by actuating the shift lever 34.

[0035] The driver can select a P position by pressing the parking switch 32 with a single touch. Depending on the driver's selection, the hybrid vehicle's shift range 100 is set to reverse (R range), neutral (N range), drive (D range), braking (B range), or park (P range). When P range is selected, the rotation of the drive shaft 12 is locked by activating a parking locking mechanism (not shown).

[0036] An accelerator pedal actuation value Acc, which is the actuation value of the accelerator pedal 30, and a vehicle speed V of the hybrid vehicle 100, measured by the vehicle speed sensor 29, are further supplied to the ECU 25. The ECU 25 controls the driving of the hybrid vehicle 100 in response to the selected shift range, the accelerator pedal actuation value Acc, and the actuation value of a brake pedal (not shown). For example, if the driving load is low and the efficiency of the power machine 2 is low, as in the case where the hybrid vehicle 100 is stopped or traveling at a low speed, the ECU 25 controls the electric power converter 19 such that the hybrid vehicle 100 stops the power machine 2 and drives solely using the motor generator 10 (EV mode (electric vehicle mode)).Conversely, if the driving load increases and the power machine 2 is operated efficiently, the ECU 25 controls the power machine 2 and the electrical power converters 18, 19 in such a way that the hybrid vehicle 100 starts the power machine 2 and drives using the power machine 2 and the motor generator 10 (HV mode (hybrid vehicle mode)).

[0037] When the hybrid vehicle 100 decelerates due to the application of the brake pedal, the ECU 25 controls the electric power converter 19 in such a way that regenerative braking is obtained by outputting a negative torque from the motor generator 10. Regenerated electrical power resulting from the generation of the negative torque can be converted into DC power by the electric power converter 19 and can then be used to charge the secondary battery 16.

[0038] In this way, the hybrid vehicle 100 drives while the secondary battery 16 is being charged or discharged. The state of charge of the secondary battery 16 is indicated by a SOC, which specifies the current amount of electrical charge relative to a full charge as a percentage. The SOC is calculated based on values ​​acquired by the sensor unit 17. Since the hybrid vehicle 100 has the power generation mechanism described above, the SOC of the secondary battery 16 can be controlled while driving (in HV mode). Control of the SOC of the secondary battery 16 in the hybrid vehicle 100 according to the present embodiment is described in detail below.

[0039] Fig. Figure 2 shows a concept diagram illustrating the characteristics (SOC voltage characteristics) of the secondary battery mounted on the hybrid vehicle 100 according to the present embodiment. Fig. Figure 2 shows a characteristic curve 201, which illustrates the relationship between the SOC and the voltage (open-circuit voltage (OCV)) of the secondary battery 16 according to Fig. 1 represents.

[0040] According to Fig. 2. The secondary battery 16 exhibits such a characteristic that the voltage variation relative to the state of charge (SOC) variation is large in a low-voltage range (AR2) and in a high-voltage range (AR3), whereas the voltage variation relative to the SOC variation is small in a medium-voltage range (AR1). Such battery characteristics are clearly evident, for example, in a nickel-metal hydride secondary battery.

[0041] The medium voltage range AR1, the low voltage range AR2, and the high voltage range AR3 are distinguished from one another based on the battery voltage (OCV). For example, secondary battery 16 falls within the high voltage range AR3 if OCV > V2, and secondary battery 16 falls into the low voltage range AR2 if OCV < V1. Conversely, if the OCV falls within the range of V1 to V2, secondary battery 16 falls into the intermediate voltage range AR1. The voltages V1 and V2 can be determined in advance according to the characteristics of each secondary battery.

[0042] Typically, the charging and discharging of the secondary battery 16, which is attached to the hybrid vehicle 100, are controlled such that the state of charge (SOC) is maintained within the range of approximately 50 to 60% to ensure the possibility of recovering renewable energy. Therefore, the secondary battery 16 is usually operated within the intermediate voltage range AR1. For this reason, it is difficult to calculate the SOC of the secondary battery 16 based on the battery voltage Vb. Therefore, during vehicle operation, the SOC of the secondary battery 16 is essentially calculated based on an integrated value of the battery current Ib.

[0043] Fig. Figure 3 shows a flowchart illustrating the processing of the calculation for a control SOC. According to Fig. In step S112, the ECU 25 calculates an integrated value of the battery current Ib in one period. In step S114, the ECU 25 updates the control SOC according to a SOC variation based on the integrated current value calculated in step S112. Specifically, a control SOC in the current control period is calculated from the sum of the control SOC in the last control period and the SOC variation.

[0044] In step S116, the ECU 25 determines, based on the battery voltage Vb, whether the OCV falls within the low-voltage range AR2 or the high-voltage range AR3. If the OCV falls within the low-voltage range AR2 or the high-voltage range AR3, the ECU 25 corrects the control SOC in step S118 based on the OCV according to characteristic curve 201 ( Fig. 2) That is, in a range where the OCV variation is large relative to the SOC variation, it is possible to improve the accuracy of the control SOC by correcting the calculated value of the control SOC based on the integrated current value based on the OCV.

[0045] If, on the other hand, the OCV does not fall within the low-voltage range AR2 or the high-voltage range AR3 (if a negative determination is made in step S116), the ECU 25 skips the processing of step S116. Thus, the calculated value based on the integrated current value calculated in step S114 is used directly as the control SOC.

[0046] As described above, the secondary battery 16 is typically used within the intermediate voltage range AR1, so that the hybrid vehicle 100 can calculate the control SOC based on the integrated value of the battery current Ib.

[0047] In contrast, with sufficient management, for example during maintenance work at a service center or similar, it is possible to calculate the SOC based on the battery voltage Vb by discharging or charging the secondary battery 16 until the SOC reaches the low-voltage range AR2 or the high-voltage range AR3. Therefore, if the OCV falls within the low-voltage range AR2 or the high-voltage range AR3 (if a positive determination is made in S116), the ECU 25 calculates the control SOC using the battery voltage Vb and the characteristic curve 201 in step S118. Thus, it is possible to correct the control SOC based on the integrated current value.

[0048] Fig. Figure 4 shows a concept diagram illustrating a SOC control of the secondary battery 16 in the hybrid vehicle.

[0049] According to Fig. 4. The state of charge (SOC) of the secondary battery 16 is controlled relative to the control SOC as a direct target (direct setpoint). For example, if a control target midpoint Sr is set as a control SOC target, the charging and discharging of the secondary battery 16 are controlled such that the control SOC is kept close to the control target midpoint Sr. For example, SOC control can be performed by adjusting the power of the power unit 2 such that, relative to the power required to propel the vehicle, electrical power is added to the SOC control or electrical power is reduced to the SOC control. In the following description, the control target midpoint Sr (for example, about 50%), which is a single SOC value, is set as the control target; instead, the control target can be set as a SOC range with a certain width.

[0050] To prevent under-discharging and overcharging of the secondary battery 16, the SOC control is implemented in such a way that the control SOC does not fall outside a predetermined control range (the range of a lower control limit S1 up to an upper control limit S3).

[0051] When the control SOC decreases to the lower control limit S1, forced charging is initiated by operating power unit 2. During forced charging, even if power unit 2 is not actually required—for example, if the required vehicle propulsion force is low or if the hybrid vehicle 100 is stopped—power unit 2 is forcibly operated to generate electrical power for charging the secondary battery 16. Forced charging continues until the control SOC reaches S2. Once the control SOC has increased to S2, forced charging is terminated.

[0052] Conversely, if the control state of charge (SOC) reaches the upper control limit S3, charging of the secondary battery 16 is prevented. In this case, not only is power generation by using the power generation mechanism—that is, power generation using the power of the motor 2—prevented, but also regenerative power generation. In this case, the vehicle's braking force is ensured by a disc brake mechanism (not shown).

[0053] SOC control is carried out by such an output control with a switching between operation and stop of the power machine 2, by controlling the electrical power generated by the power generation mechanism.

[0054] For example, if the auxiliary load 45 is operated in the case where the hybrid vehicle 100 is left in the P range as a result of prolonged parking, a forced charging is repeatedly carried out in the SOC range near the lower control limit S1, as described in Fig. 5 is shown.

[0055] Fig. Figure 5 shows an example of an operating signal curve in the case where forced charging is repeatedly performed in the hybrid vehicle according to the present embodiment.

[0056] According to Fig. 5. When the control state of charge (SOC) decreases to the lower control limit S1 at time t1 as a result of the electrical power consumption in the auxiliary load 45, the power machine 2 is operated, and a forced charge is initiated. Thus, the control state of charge increases and reaches S2 at time t2. Consequently, the forced charge ends at time t2, and the power machine 2 is stopped.

[0057] The control SOC decreases again after time t2, so another forced charge is performed from time t3 to time t4. In this way, if a similar vehicle condition continues, intermittent forced charging will be performed repeatedly. Thus, the SOC of secondary battery 16 remains within the range where the control SOC falls between S1 and S2.

[0058] Fig. Figure 6 shows a graph illustrating changes in the current or actual SOC (hereinafter also referred to as the actual SOC) of the secondary battery 16.

[0059] According to Fig. 6. It is known that in a nickel-metal hydride battery, the state of charge (SOC) actually decreases due to self-discharge during a period (time period) in which no battery current Ib is present. This means that a decrease in the SOC due to self-discharge does not appear in the control SOC, which is calculated based on the integrated value of the battery current Ib.

[0060] Therefore, there is at least a difference due to self-discharge (SOC reduction) between the control SOC and the actual SOC. Fig. 6. The control SOC (Sct) is indicated by the solid line, and the actual SOC (Sac) is indicated by the dashed line.

[0061] During the period of 110 in Fig. 6. A forced charge of the secondary battery 16 is repeatedly performed in a state where the difference between the control state of charge (SOC) and the actual state of charge (SOC) is relatively small. It is understood that by using the forced charge, which keeps the control state of charge above the lower control limit S1, the actual state of charge is controlled such that it does not remain in the low SOC range below the lower control limit S1.

[0062] In contrast, during time period 115, due to an increase in the SOC reduction magnitude caused by the influence of self-discharge, a forced charging of the secondary battery 16 is repeatedly carried out in a state where the difference between the actual SOC and the control SOC is large.

[0063] During the time period 115, even if the forced charging is carried out in such a way that the control SOC does not fall below the lower control limit S1, the actual SOC remains in the low SOC range below the lower control limit S1. If a phenomenon then occurs in which the secondary battery 16 is repeatedly charged and discharged in such a low SOC range, there are concerns that the full charge capacity of the secondary battery 16 will decrease due to a so-called charge memory effect.

[0064] The lower control limit S1 in the SOC control is set within a SOC range such that the charge memory effect (described later) does not occur, even with repeated charging and discharging cycles. Therefore, by forcing charging to prevent the actual SOC from remaining below the lower control limit S1, the memory effect can be prevented. Generally, the lower control limit S1 is located within the intermediate voltage range AR1 on a side close to the low voltage range AR2, according to... Fig. 2 is.

[0065] Fig. 7A and Fig. Figure 7B shows concept diagrams illustrating a reduction in full charge capacity due to the charge memory effect of the secondary battery. Fig. Figure 7A shows the characteristic curve 201 of secondary battery 16 when secondary battery 16 has not deteriorated (new). The characteristic curve 201 is similar to the one shown in Fig. Figure 2 shows that in a state where the battery voltage Vb has reached a voltage Vm, the secondary battery 16 assumes a full charge state.

[0066] Therefore, in parallel with the management of the control SOC based on the integrated value of the battery current Ib, which is related to Fig. As described in section 2, it is recognized that the secondary battery 16 is in an overcharge state when the battery voltage Vb (or the OCV based on the battery voltage Vb) increases to the voltage Vm (or a voltage close to the voltage Vm). In this case, as in the case where the control SOC increases to the upper control limit S3, as described in section 2, the system will be able to detect the problem. Fig. As described in section 4, further charging of the secondary battery 16 is prevented.

[0067] In contrast, it shows Fig. 7B the characteristic curve 202 at the time when the charge memory effect of the secondary battery 16 is present as a result of repeated charging and discharging in the low SOC range, compared to the characteristic curve 201 when the secondary battery 16 has not deteriorated.

[0068] According to Fig. 7B, if a charge memory effect occurs as a result of the SOC remaining in the low SOC range, the battery voltage (OCV) for the SOC is shifted from the low SOC range in characteristic curve 202 to a high voltage side compared to characteristic curve 201.

[0069] As a result, in a range where the SOC has not reached its original full charge (100%), the battery voltage Vb (or the OCV) increases to the voltage Vm, as described in Fig. 7A is shown. As a result, further charging of the secondary battery 16 is prevented, so it is understood that the equivalent full charge capacity is significantly reduced. Thus, there are concerns regarding a significant reduction in the operational efficiency of the secondary battery 16.

[0070] Therefore, in the hybrid vehicle according to the embodiment, a SOC control on the secondary battery 16 is implemented on the basis of a calculation of an estimated actual SOC, which at least reflects the SOC reduction due to self-discharge, in such a way that the occurrence of the charge memory effect is prevented.

[0071] Fig. Figure 8 shows a flowchart illustrating the processing of the estimation of the actual state of charge (SOC) of the secondary battery 16 in the hybrid vehicle according to the present embodiment. The in Fig. The control processing shown in Figure 8 is performed, for example, by the ECU 25 at predetermined intervals while the ignition switch 38 is in an ON state.

[0072] According to Fig. In step S110, ECU 25 reads the battery temperature Tb, the battery voltage Vb, and the battery current Ib based on the outputs (output signals) of the secondary battery 16's sensor unit 17. ECU 25 calculates the control state of charge (SOC) in step S110. In step S110, the control SOC for the current control period is determined by the processing operations of steps S112 to S118 according to... Fig. 3 calculated.

[0073] When the control SOC is calculated (S110), the ECU 25 obtains ΔSOC1, which is a SOC reduction value due to the self-discharge of the secondary battery 16, in step S120. The ECU 25 obtains ΔSOC2 in step S130, which is a SOC reduction value reflecting the charging efficiency.

[0074] In step S140, the ECU 25 calculates an estimated value Sac# of the actual SOC based on the control SOC calculated in step S110, the SOC reduction value ΔSOC1 read in step S120, and the SOC reduction value ΔSOC2 read in step S130. This means that the estimated value Sac# of the actual SOC is obtained using the mathematical equation Sac# = SCT - (ΔSOC1 + ΔSOC2).

[0075] According to the present embodiment, the actual state of charge (SOC) is estimated taking into account both the SOC reduction due to self-discharge (ΔSOC1) and the SOC reduction reflecting the charging efficiency (ΔSOC2). Alternatively, the actual SOC can be estimated taking into account only the SOC reduction due to self-discharge. That is, according to the present embodiment, the estimated value Sac# of the actual SOC is calculated based on the integrated current value of the secondary battery 16, which is reflected in the control SOC, and at least the SOC reduction due to self-discharge (ΔSOC1).

[0076] Below is a specific example of how to process the calculation of the SOC reduction quantities (ΔSOC1, ΔSOC2) in detail with reference to Fig. Described in sections 9 to 11.

[0077] Fig. 9 and Fig. Figure 10 shows flowcharts illustrating a control processing operation to calculate the SOC reduction magnitude due to self-discharge (ΔSOC1).

[0078] According to Fig. 9 is activated when the SMR 20 is in the OFF state (if a positive determination is made in step S121). The ECU 25 then activates the timer 26 in step S122 to measure the non-use time (i.e., standby time) of the secondary battery 16. In step S123, the ECU 25 stores the SOC (for example, the control SOC) and the battery temperature Tb at the time the SMR 20 is switched off.

[0079] In contrast, except when SMR 20 is in the off state (when a negative determination is made in S121), the processing operations of steps S122 and S123 are not executed. At this time, the time measured by timer 26 is deleted.

[0080] According to Fig. 10, when the SMR 20 is in the ON state (when a positive determination is made in S124), the ECU 25 in step S125 obtains a timer value Tx, which is measured by the timer 26. The timer value Tx is a value corresponding to a time compared to the time at which step S122 in Fig. 9 has been executed.

[0081] The self-discharge of the secondary battery 16 occurs during periods of non-use, i.e., the time during which the SMR 20 in the hybrid vehicle 100 is in the OFF state. The state of charge (SOC) reduction due to self-discharge varies depending on the battery temperature Tbx, the SOC level (SOCx), and the idle time. The timer value Tx, obtained in step S125, corresponds to the non-use time (idle time) of the secondary battery 16, which is the duration of the self-discharge.

[0082] Therefore, a characteristic map for calculating the SOC reduction magnitude due to self-discharge (ΔSOC1) based on the battery temperature Tbx, the SOC level (SOCx) and the standby time (Tx) can be generated in advance by a previous actual machine test or the like.

[0083] In step S126, the ECU 25 calculates the SOC reduction magnitude (ΔSOC1) during a standstill period based on the standstill time Tx of the secondary battery 16 and the battery temperature Tbx as well as the SOC level (SOCx) during standstill by using the pre-generated map described above.

[0084] Since the control SOC does not change while stationary, the step S123 ( Fig. 9) The stored control SOC can be used as SOCx. The one in step S123 ( Fig. 9) The stored battery temperature Tb can be used as the battery temperature Tbx. Alternatively, the battery temperature Tbx can be obtained from the average of the battery temperature Tb at the time of step S126 and the battery temperature Tb at the time of step S123.

[0085] In this way, the SOC reduction magnitude due to self-discharge (ΔSOC1) is preserved during a standby period from the time the SMR 20 is switched off until the time the SMR 20 is next switched on.

[0086] In step S127, the ECU 25 updates the SOC reduction value (ΔSOC1) by adding ΔSOC1, calculated in step S126, to the previously integrated value. ΔSOC1 may be adjusted in response to the fact that the battery voltage drops within the low-voltage range AR2 or the high-voltage range AR3 and the control SOC has been corrected (S118 in...). Fig. 3) are cleared (ΔSOC1 = 0). In contrast, before ΔSOC1 is cleared, ΔSOC1 is successively integrated each time the secondary battery 16 is charged. In step S120 of Fig. 8. The integrated value of ΔSOC1 is read at this time.

[0087] Fig. Figure 11 shows a flowchart illustrating the processing for calculating the SOC reduction magnitude, which reflects the charging efficiency.

[0088] According to Fig. In step S131, the ECU 25 determines whether the secondary battery 16 is being charged. If the secondary battery 16 is being charged (if a positive determination is made in S131), the processing proceeds to step S132. In step S132, the battery voltage Vb, battery current Ib, and battery temperature Tb of the secondary battery 16 during charging are obtained based on the outputs of the sensor unit 17.

[0089] The ECU 25 causes the processing to proceed to step S133 and calculates the SOC reduction quantity ΔSOC2, which corresponds to the loss of electrical charging power and reflects the charging efficiency, based on the battery voltage Vb, the battery current Ib and the battery temperature Tb.

[0090] Ideally, the charging efficiency is 1.0 when the entire charging current is used in the electrochemical reaction to store electrical power; however, in reality, some of the current is used in a side reaction, such as the generation of internal gas, resulting in a charging efficiency lower than 1.0. It is known that the charging efficiency changes in response to the battery temperature (Tb) and the state of charge (SOC). Therefore, a characteristic map of the charging efficiency for the battery temperature (Tb) and the SOC can be generated in advance through prior actual machine testing or similar methods.

[0091] If the charging efficiency decreases from 1.0, not all electrical power (Vb x Ib) supplied to the secondary battery 16 contributes to an increase in the actual state of charge (SOC). In contrast, an increase in the control SOC resulting from charging is calculated based on the battery voltage Vb and the battery current Ib. Therefore, a difference between the actual SOC and the control SOC occurs during charging in response to the magnitude of the electrical charging power loss. ΔSOC represents the difference described above, which occurs each time charging occurs.

[0092] For example, in step S133 ΔSOC2 can be calculated in each control period based on the control SOC and / or the charging efficiency obtained using the characteristic map based on the battery temperature Tb, and / or the electrical charging power (the battery voltage Vb and the battery current Ib).

[0093] In step S134, the ECU 25 updates the SOC reduction value (ΔSOC2) by adding ΔSOC2, calculated in step S133, to the last integrated value of ΔSOC2. ΔSOC2, as well as ΔSOC1, can be cleared (ΔSOC2 = 0) in response to the battery voltage dropping within the low-voltage range AR2 or the high-voltage range AR3, and the control SOC is being corrected (S118 in...). Fig. 3) As with ΔSOC1, before ΔSOC2 is cleared, ΔSOC2 is successively integrated each time the secondary battery 16 is charged. In step S130 of Fig. 8. The integrated value of ΔSOC2 is read at this time.

[0094] Fig. Figure 11 illustrates the processing for integrating ΔSOC2 in each control period during charging. Alternatively, the processing of calculating and integrating ΔSOC2 can be performed at the end of each charging operation by integrating the battery current Ib for each individual charging operation and using the integrated value of the battery current Ib, the battery voltage Vb, and the battery temperature Tb (charging efficiency) in that charging operation.

[0095] Fig. Figure 12 shows a flowchart illustrating the processing of the SOC control execution in the hybrid vehicle according to the present embodiment. The control processing according to Fig. For example, 12 is repeated by the ECU 25 at predetermined intervals together with the in Fig. The control processing shown in step 8 is executed while the ignition switch 38 is in the ON state.

[0096] According to Fig. In step S200, ECU 25 determines whether the estimated value Sac# of the actual SOC, which was determined in step S140, is correct. Fig. 8 is obtained, which has decreased to a lower limit SOC (Sx).

[0097] If Sac# has not decreased to the lower limit SOC (Sx) (if a negative determination is made in S200), the ECU 25 sets the control setpoint Sr in step S250 ( Fig. 4) set the SOC control to a default value Sr1.

[0098] If, on the other hand, the estimated value Sac# of the actual SOC has decreased below the lower limit SOC (Sx) (if a positive determination is made in S200), ECU 25 causes the processing to proceed to step S260 and raises the control setpoint Sr from the preset value (Sr = Sr1 + α). Thus, S1 and S2 increase ( Fig. 4), which are the thresholds for forced loading, also from the state where Sr = Sr1 (that is, a default state). Similarly, S3 increases ( Fig. 4), which is a threshold to prevent loading, preferably from the state to which Sr = Sr1 (that is, the default state).

[0099] In step S300, the ECU 25 executes the following with reference to Fig. The SOC control described in step 4 is configured such that the one described in step S120 ( Fig. 8) The calculated control SOC is maintained at the control setpoint (control setpoint midpoint Sr) determined in step S250 or step S260.

[0100] With renewed reference to Fig. 6 decreases during the time period 115, during which there is a large deviation between the actual SOC and the control SOC, even if the control SOC is controlled such that it does not fall below the lower control limit S1, the actual SOC (Sac) at time Tx reaches the lower limit SOC (Sx). As a result, at time Tx in step S200 ( Fig. 12) a positive determination is made so that the SOC control setpoint is raised by α (S260). For example, if α = S1 (default value) - Sx, the control SOC can be controlled such that the actual SOC does not decrease below the default value of the lower control limit S1 from time Tx onwards. That is, according to Fig. 6 the lower limit SOC (Sx) corresponds to a first lower limit SOC, and that the lower control limit S1 corresponds to a second lower limit SOC.

[0101] As a result, even if the decrease in the actual state of charge (SOC) relative to the control state (which is the target SOC for SOC control) increases, it is possible to prevent the actual SOC from remaining in the low SOC range. Thus, it is possible to prevent the charge memory effect of the secondary battery 16 from occurring.

[0102] Regarding the SOC reduction parameters (ΔSOC1, ΔSOC2), the accuracy of estimating a SOC variation decreases compared to the integrated current value. Therefore, a direct control value (control SOC) is obtained in the SOC control based on the integrated value, while the SOC reduction parameters are reflected in the control setpoint within the SOC control. This allows for continued stable control of the SOC within a suitable range.

[0103] As described above, the SOC reduction quantities ΔSOC1, ΔSOC2 are integrated sequentially before the SOC reduction quantities ΔSOC1, ΔSOC2 are deleted. Therefore, it is preferred essentially if the positive determination is made once in step S200 ( Fig. 12) has been made and the SOC control setpoint has been increased, retain the positive determination before the SOC reduction values ​​in step S118 ( Fig. 3) be deleted.

[0104] Alternatively, as a result of executing the SOC control, while the SOC control setpoint is being raised from the preset value to ensure the possibility of recovering renewable energy, if the estimated value Sac# of the actual SOC has increased by a certain amount, the SOC control setpoint can be reduced back to the preset value. For example, while the SOC control setpoint is being raised by setting the lower limit SOC (Sx) in step S200 to a value higher than that which would be the value if the SOC control setpoint were the preset value, it is possible to implement such control. Alternative example

[0105] An alternative implementation example for setting the SOC control range is described below.

[0106] Fig. Figure 13 shows a flowchart illustrating a first alternative embodiment for processing the execution of the SOC control in the hybrid vehicle according to the present embodiment.

[0107] From a comparison of Fig. 13 with Fig. 12 shows that if the estimated value Sac# of the actual SOC has decreased to the lower limit SOC (Sx) (if a positive determination is made in S200), the ECU continues to execute step S210.

[0108] In step S210, the ECU 25 determines whether the number Ncf, how often the forced charging control has been executed, exceeds a specified value Nt.

[0109] The number of forced Ncf loads is incremented by one each time the following occurs, referencing... Fig. 4 and Fig. The forced load described in section 5 is executed. The number of forced loads (Ncf) can, for example, be managed as a frequency in units of a set time duration (period) (a predetermined number of days or a predetermined number of months).

[0110] When Sac# decreases to the lower limit SOC (Sx) if the number of forced loads Ncf, corresponding to the number of repetitions of loading and unloading, exceeds the determination value Nt (if a positive determination is made in S210), the ECU 25 causes processing to proceed to step S260, as also in Fig. 12, and raises the SOC control setpoint (Sr, S1 to S3) from the default value.

[0111] Conversely, if the number of forced loads is small (or the frequency of forced loads is low) (if a negative determination is made in S210), even before Sac# decreases to the lower limit SOC (Sx) (if a negative determination is made in S200), or after Sac# has decreased to the lower limit SOC (Sx), the SOC control setpoint (Sr, S1 to S3) is maintained at the default value (S250).

[0112] Therefore, according to the in Fig. In the alternative embodiment shown in 13, if the number of repetitions of the loading and unloading by the forced loading is small, even if Sac# has decreased to the lower limit SOC (Sx), it is possible to prevent an increase in the SOC control setpoint.

[0113] As a result, the SOC control setpoint is not raised before the risk of the charge memory effect occurring as a result of actual repetitions of charging and discharging in the low-SOC range, thus making it possible to prevent or reduce a decrease in the energy efficiency of the hybrid vehicle 100 due to a reduction in the size of the recovered regenerated electrical power.

[0114] Fig. Figure 14 shows a flowchart illustrating a second alternative embodiment of the processing of the implementation of the SOC control in the hybrid vehicle according to the present embodiment.

[0115] From the comparison of Fig. 14 with Fig. 13 shows that the ECU 25 not only contains the Fig. 13 control processing shown, but also executes step S280 and step S285.

[0116] In step S230, the ECU 25 determines whether a predetermined time has elapsed (idle time) during which the hybrid vehicle 100 is in the P range. The idle time in the P range can be measured by activating the timer 26 of the ECU 25 in response to an output signal from the shift position sensor 36.

[0117] If the standby time in the P-area has exceeded the predetermined time (a positive determination is made in S280), the ECU 25 causes the processing to proceed to step S285 and determines whether the electrical power consumed by the auxiliary load 45 is greater than or equal to a predetermined electrical power. The determination in step S285 can be performed based on the operating state (ON / OFF state of each device) of the auxiliary load 45 or can be performed by actually measuring the consumed electrical power.

[0118] If the electrical power consumed by the auxiliary load 45 is greater than or equal to a predetermined value (if a positive determination is made in S285), the ECU 25 causes the processing to proceed to step S290 and raises the control setpoint Sr from the preset value (Sr = Sr1 + β). Thus, the range from S1 to S2, which is in Fig. 4 is shown, also from the state where Sr = Sr1 (that is, the default state).

[0119] If the idle time in the P range exceeds the predetermined time and the electrical power consumed by the auxiliary load 45 is greater than or equal to the predetermined value, the vehicle is placed in a state where forced charging will easily occur repeatedly. Therefore, in this vehicle state, even if the SOC control setpoint in step S260 ( Fig. 12, Fig. 13) If the SOC control setpoint is not raised, it is provisionally raised in step S290. The increase value β in S290 can be the same as the increase value in step S260.

[0120] If the standby time in the P area has not reached the predetermined time (if a negative determination is made in S280) or if the electrical power consumed by the auxiliary load 45 is less than the predetermined value (if a negative determination is made in S285), the ECU 25 executes the processing of step S200 according to Fig. 13. Alternatively, in the case where a negative determination is made in step S280 or step S285, the processing can be similar to that of Fig. 12 years old.

[0121] Therefore, according to the alternative embodiment, it is Fig. 14. If the vehicle is placed in a state where forced charging occurs repeatedly before the estimated value Sac# of the actual SOC decreases to the lower limit SOC (Sx), it is possible to temporarily raise the SOC control setpoint. This makes it possible to more reliably prevent the occurrence of the charge memory effect of the secondary battery 16 due to prolonged exposure to the low SOC range, which results from repeated charging and discharging.

[0122] The raising of the SOC control setpoint in step S290 is terminated when the vehicle condition described above disappears in response to the determination result of step S280 or step S285.

[0123] In contrast, if the SOC control setpoint has already been raised in step S260, step S290 for the preliminary raising of the SOC control setpoint is not required. Therefore, in such a case, step S280 or step S285 is preferably fixed to a negative value.

[0124] According to the present embodiment, the secondary battery 16 is a nickel-metal hydride battery. Alternatively, the disclosure is similarly applicable to a secondary battery that tends to exhibit a difference between a control state of charge (SOC) and an actual state of charge (SOC) due to battery characteristics that have a voltage range in which a voltage variation with respect to a state of charge (SOC) variation is small, as in the case of Fig. 2.

[0125] The configuration of the hybrid vehicle 100 according to Fig. 1 is merely illustrative. For example, the disclosure is applicable to various hybrid vehicles with a drive system configuration that differs from that described in Fig. Figure 1 illustrates how a series hybrid vehicle, in which the engine power is used exclusively to generate electrical power, and a parallel hybrid vehicle, as long as the hybrid vehicles have such a configuration that the SOC can be controlled by a mechanism (power generation mechanism) that generates electrical power to charge the secondary battery while driving.

[0126] The disclosure is also applicable to a so-called plug-in hybrid vehicle, in which the secondary battery 16 can be charged externally by charging from outside the vehicle. During external charging, the secondary battery 16 is generally charged to a fully charged state, so that opportunities to correct an error in the control state of charge (with respect to the actual state of charge) are relatively easily obtained.

[0127] The present embodiment is summarized below. The state of charge (SOC) of a secondary battery is controlled such that a control SOC (Sct) is maintained according to a setpoint. It is possible that the actual SOC of the secondary battery may decrease below the control SOC due to a SOC reduction caused by self-discharge or similar factors that cannot be determined from an integrated current value. If an estimated value (Sac) of the actual SOC, obtained by estimating the SOC reduction, decreases to a lower limit SOC (Sx), the system prevents the actual SOC from remaining in a low SOC range by shifting the control setpoint of the SOC controller towards a higher SOC.

[0128] The embodiment described above is for illustrative purposes only and is in no way limiting. The scope of disclosure is defined by the attached claims and not by the foregoing description. The scope of disclosure is intended to include all modifications within the scope of the attached claims and their equivalents.

[0129] As described above, a hybrid vehicle (100) has an electronic control unit (25). The electronic control unit (25) is configured to: a) control the operation of a power generation mechanism (6) such that the state of charge of a secondary battery (16) is maintained at a predetermined control setpoint; b) calculate an estimated actual state of charge of the secondary battery based on an integrated current value and a state-of-charge reduction magnitude due to self-discharge of the secondary battery (16), wherein the integrated current value is obtained by integrating an input current and an output current of the secondary battery (16); and c) if the estimated actual state of charge has decreased to below a first lower limit state of charge, raise the control setpoint.

Claims

Hybrid vehicle (100) comprising a secondary battery (16), a drive mechanism (10) configured to generate a tractive force by using electrical power from the secondary battery (16), an internal combustion engine (2), a power generation mechanism (6) configured to generate electrical power for charging the secondary battery (16) by using power output from the internal combustion engine (2), and an electronic control unit (25) configured to: a) calculate a control state of charge based on an integrated current value, the integrated current value being obtained by integrating an input current and an output current of the secondary battery (16); b) control the operation of the power generation mechanism (6) such that the control state of charge of the secondary battery (16) is maintained close to a control setpoint (Sr) set as a predetermined control setpoint.c) to calculate an estimated actual state of charge of the secondary battery based on the integrated current value and a state of charge reduction magnitude due to self-discharge of the secondary battery (16), and, d) if the estimated actual state of charge has decreased to below a first lower limit state of charge, to increase the control setpoint. Hybrid vehicle (100) according to claim 1, wherein the electronic control unit (25) is configured, e) when the control state of charge has decreased to a second lower limit state of charge, to force the charging of the secondary battery (16) by operating the power generation mechanism (6), wherein the second lower limit state of charge is higher than the first lower limit state of charge, and, f) when the estimated actual state of charge has decreased to below the first lower limit state of charge, and the number of times the secondary battery (16) has been forcibly charged is less than a predetermined number, to prevent an increase in the control setpoint. Hybrid vehicle (100) according to claim 1 or 2, further comprising an auxiliary load (45), wherein the electronic control unit (25) is configured, g) when the hybrid vehicle (100) has been left in a parking area for longer than a predetermined time and the electrical power consumed by the auxiliary load (45) is greater than or equal to a predetermined value, to increase the control setpoint.

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