JP2008189121A - Hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the life of, for example, a nickel-hydrogen battery loaded on a plug-in hybrid vehicle. <P>SOLUTION: The initial lower limit value of a charge level is set to higher than the upper limit value of discharge reserve, so that a fixed chargeable/dischargeable capacity can be secured between the upper limit value of the discharge reserve and the lower limit value of charge reserve, and that the margin of the discharge level can be set on the upper limit value of the discharge reserve. The charge reserve becomes smaller than the initial charge reserve by the deteriorated capacity. However, the charge reserve is largely set in an early stage, so that a time period to exhaust the charge reserve can be extended and decrease in electrolytic solution generated due to excess charging can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes, for example, a so-called plug-in that includes an engine that operates by burning fuel and another power source that operates by using electric power charged in the battery, and is configured to be able to charge the battery from an external power source. The present invention relates to the technical field of hybrid vehicles.

  This type of hybrid vehicle has an engine that operates by burning fuel such as gasoline, and a battery that charges electric power supplied from a power source such as a motor. The hybrid vehicle is configured to be able to use energy efficiently by being supplied with driving force from each of the engine and the motor in accordance with the traveling state of the hybrid vehicle. In such a hybrid vehicle, not only the electric power generated by driving the motor by regeneration or the like is stored in the battery, but also the so-called plug that can charge the battery from an external power source provided outside the vehicle. In-hybrid vehicles are known. As the battery, for example, a nickel hydride storage battery that is small in size and capable of high capacity is often used. The charge amount (SOC) of such a nickel metal hydride storage battery is controlled to about half of the capacity of the storage battery so that charging or discharging according to the running state of the hybrid vehicle is possible. Since it is important to accurately detect the storage amount (SOC) of the nickel-metal hydride storage battery in order to drive the hybrid vehicle with good fuel consumption, Patent Document 1 discloses a remaining capacity that can calculate the remaining capacity of the nickel-metal hydride storage battery. The calculation device of is proposed.

  On the other hand, the negative electrode of the nickel-metal hydride storage battery contains more active material than the positive electrode so that the battery characteristics are not deteriorated due to charging / discharging of the storage battery. More specifically, the nickel-metal hydride storage battery has a negative electrode capacity that exceeds that of the positive electrode so that the negative electrode absorbs oxygen at the negative electrode and hydrogen is not generated from the negative electrode itself when charged excessively with respect to the capacity of the storage battery. And a capacity (hereinafter referred to as a discharge reserve) provided in the negative electrode so that the capacity of the storage battery does not become a negative electrode regulation. Yes. According to each of such charge reserve and discharge reserve, even when excessive charge / discharge is performed on the nickel-metal hydride storage battery, the deterioration of the nickel-metal hydride storage battery can be suppressed, and the deterioration of the battery characteristics of the storage battery can be suppressed. . Patent Document 2 proposes a nickel-metal hydride storage battery that can suppress deterioration in battery characteristics by suppressing fluctuations in discharge reserve and charge reserve in the negative electrode of the nickel-metal hydride storage battery.

JP 2005-114648 A JP 2006-19171 A

  However, in the nickel metal hydride storage battery mounted on the vehicle as the battery of the hybrid vehicle, the hydrogen storage alloy of the negative electrode is oxidized by charging / discharging the storage battery, and the discharge reserve increases. In addition, the charge reserve decreases as the discharge reserve increases. According to such a decrease in the charge reserve and the increase in the discharge reserve, the electrolyte contained in the storage battery is consequently reduced, and it becomes difficult to extend the life of the nickel-metal hydride storage battery.

  There is also a demand for downsizing the storage battery while maintaining the battery characteristics of the nickel-metal hydride storage battery.

  Therefore, the present invention has been made in view of the above-mentioned problems and the like, for example, a hybrid vehicle that can extend the life of a nickel-metal hydride storage battery mounted as a battery, or a miniaturized nickel-metal hydride storage battery as a battery. It is an object of the present invention to provide a hybrid vehicle that can travel without hindrance.

  In order to solve the above problems, a hybrid vehicle according to the present invention uses an engine that operates by fuel combustion, a nickel-metal hydride battery that is a battery that can be charged from an external power source, and electric power that is charged in the nickel-metal hydride battery. The initial lower limit value of the charge amount of the nickel metal hydride battery is set to a value higher than the upper limit value of the discharge reserve of the nickel metal hydride storage battery and another power source that is operated and different from the engine, and the initial lower limit value is set. And setting means for setting the lower limit value of the charge amount so that the lower limit value of the charge amount is lower than the initial lower limit value as the use period during which the nickel-metal hydride storage battery has been used has elapsed.

  According to the hybrid vehicle of the present invention, for example, an engine such as a 2-cycle or 4-cycle reciprocating engine operates in accordance with the explosive force of fuel such as gasoline burned in the combustion chamber to generate power. Such power is output to an output shaft such as a crankshaft via a mechanical power transmission path such as a piston and a connecting rod.

  The nickel metal hydride storage battery is a battery mounted on the hybrid vehicle so that it can be charged from an external power source arranged in a chargeable place such as a house. That is, the hybrid vehicle according to the present invention is included in a type of hybrid vehicle called a plug-in hybrid vehicle that is distinguished from a hybrid vehicle that cannot be charged from an external power source. The nickel-metal hydride storage battery is configured so that the capacity of the negative electrode is larger than the capacity of the positive electrode, and the capacity of the nickel-metal hydride storage battery is limited by the capacity of the positive electrode (that is, positive electrode regulation).

  The other power source operates using electric power charged in the nickel metal hydride storage battery, and is provided as a power source different from the engine. The other power source is, for example, a generator such as a generator or a motor generator, which can operate using the power supplied from the nickel-metal hydride storage battery, and converts the power generated according to the traveling state of the hybrid vehicle to nickel. A hydrogen storage battery can be charged.

  The setting means is mounted on the hybrid vehicle as various processing units such as an ECU (Electronic Control Unit) or as a part of these processing units, and the nickel-metal hydride storage battery is not used, that is, the hybrid vehicle is At the stage of a new vehicle or when the nickel hydride storage battery is replaced with a new nickel hydride storage battery, the initial lower limit value of the charge amount of the nickel hydride storage battery is set to a value higher than the upper limit value of the discharge reserve of the nickel hydride storage battery. Here, the “discharge reserve” is an excessive negative electrode capacity that can be discharged out of the negative electrode capacity set larger than the positive electrode capacity. According to such a discharge reserve, when supplying electric power from the nickel hydride storage battery to another power source such as a motor generator, even if excessive discharge is performed from the nickel hydride storage battery, the internal pressure of the nickel hydride storage battery is reduced. It is possible to suppress the rise.

  On the other hand, in the nickel metal hydride storage battery, a charge reserve is set corresponding to the discharge reserve. “Charge reserve” is an excess negative electrode capacity that can be charged among negative electrode capacities set larger than the positive electrode capacity. According to such a charge reserve, when charging the nickel metal hydride storage battery from another power source such as a motor generator, even if the nickel hydride storage battery is excessively charged, the internal pressure of the nickel metal hydride storage battery is reduced. It is possible to suppress the rise.

  The amount of charge of the nickel metal hydride storage battery means the remaining amount of power charged in the nickel metal hydride storage battery. “Initial lower limit value” refers to the amount of charge of the nickel-metal hydride storage battery that can be changed by discharging or charging depending on the traveling state of the hybrid vehicle, that is, the remaining amount of power stored in the nickel-metal hydride storage battery, for example This is the lower limit value set in the unused state of the hybrid vehicle, that is, in the new vehicle stage or when the nickel hydride storage battery is replaced with a new nickel hydride storage battery. Therefore, “initial” means an initial period including a cumulative amount in which factors that cause deterioration of the nickel-metal hydride storage battery such as charge and discharge are accumulated or a starting point of the cumulative period.

  In a nickel-metal hydride storage battery mounted on a hybrid vehicle, discharge reserve is usually set according to the relative sizes of the negative and positive electrodes. Depending on the running state of the hybrid vehicle, i.e., the amount of power charged to the nickel metal hydride storage battery from another power source such as a motor generator, the lower limit value of the storage capacity of the nickel metal hydride storage battery is usually above the upper limit value of the discharge reserve. The amount of power storage is adjusted so that it can change. Therefore, the lower limit value of the amount of electricity stored in the nickel-metal hydride storage battery may be the upper limit value of the discharge reserve. According to such a nickel metal hydride storage battery, it becomes difficult to sufficiently secure a charge reserve that decreases as the storage battery deteriorates, and the electrolyte reserve is reduced by reducing the charge reserve according to the deterioration of the nickel metal hydride storage battery. Liquid leakage that leaks to the outside of the battery, or gas leakage in which oxygen gas or hydrogen gas generated from the electrolyte due to a chemical reaction leaks to the outside of the battery occurs, resulting in a decrease in the electrolyte. According to such a decrease in the electrolytic solution, the reliability of the nickel metal hydride storage battery is significantly impaired, and the life of the storage battery is also shortened.

  Therefore, according to the hybrid vehicle of the present invention, the setting means sets the initial lower limit value of the charge amount of the nickel metal hydride storage battery to a value higher than the upper limit value of the discharge reserve, whereby the upper limit value of the discharge reserve and the charge reserve value are set. The charge amount margin can be set on the upper limit value of the discharge reserve while ensuring a certain capacity between the lower limit values. In other words, it is possible to increase the charge reserve by reducing the discharge reserve, which increases with the deterioration of the nickel-metal hydride storage battery, in advance with respect to the lower limit value of the charged amount. By setting the initial lower limit value in this way, even if the charge reserve decreases as the use period of the nickel metal hydride storage battery elapses, the charge reserve is set to be large in the initial stage so as to meet the elapse of the use period. The period until the charge reserve disappears can be extended, and the life of the nickel-metal hydride storage battery can be extended.

  According to the hybrid vehicle of the present invention, the amount of electric power that can be substantially supplied from the nickel-metal hydride storage battery to another power source such as a motor generator is set when the initial lower limit value is not set, that is, the discharge set by the positive electrode regulation. Compared to the case where electric power is supplied from the nickel-metal hydride storage battery to another power source in the capacity range between the upper limit value of the reserve and the lower limit value of the charge reserve, the power becomes smaller. More specifically, for example, electric power is supplied to other power sources so that the hybrid vehicle can only travel 150 km in the place where the hybrid vehicle can originally travel 200 km only by the power supplied from the nickel-metal hydride storage battery charged by one charge. Will be limited.

  However, according to the hybrid vehicle of the present invention, the nickel metal hydride storage battery can be charged from an external power source. Therefore, even when the amount of charge of the nickel metal hydride storage battery decreases to the initial lower limit value, Charging is possible even if the nickel hydride storage battery is not charged by the source. Therefore, even if the initial lower limit value of the charged amount is set higher than the upper limit value of the discharge reserve, the nickel metal hydride storage battery can be charged without receiving power supply from the motor generator based on the power generated by the engine. The fuel consumption of the vehicle is not reduced.

  After setting the initial lower limit value, the setting means sets the lower limit value of the charge amount so that the lower limit value of the charge amount becomes lower than the initial lower limit value as the use period during which the nickel-metal hydride storage battery is used has elapsed. By setting the lower limit value of the charge amount to be lower than the initial lower limit value, it is possible to secure the capacity that can be stored in the nickel-metal hydride storage battery.

  Here, “use period” means a broad concept including a cumulative amount in which deterioration factors that deteriorate the nickel-metal hydride storage battery are accumulated. More specifically, the “use period” can be adopted as an index indicating the deterioration factor, for example, all the indexes of the travel distance of the hybrid vehicle, the travel period, the number of times of charge / discharge with respect to the nickel metal hydride storage battery, and the charge / discharge amount, or A cumulative amount of specific numerical values of at least one of these indicators, and a guideline for estimating the degree of deterioration of the storage battery that deteriorates more or less over time even if the storage battery is in a non-operating state; It is a concept including the elapsed time. Therefore, the lower limit value of the storage amount is not only the driving time when the hybrid vehicle is driven, but also, for example, the number of charge / discharge or the amount of charge / discharge that can directly display the usage frequency of the nickel hydride storage battery, or indirectly the nickel hydride storage battery It is set lower than the initial lower limit value according to the cumulative amount such as the travel distance of the hybrid vehicle that can display the usage frequency. In addition, the period of use does not mean the period when the life of the hybrid vehicle is exhausted, but the passage of time as the hybrid vehicle continues to be used, more specifically, the nickel metal hydride storage battery Note that this is an expression used to conveniently define a period.

  As described above, according to the hybrid vehicle according to the present invention, it is possible to extend the period until the charge reserve disappears while securing the storage amount of the nickel-metal hydride storage battery. Therefore, the nickel mounted on the hybrid vehicle as a battery. It is possible to extend the life of the hydrogen storage battery and improve the reliability.

  Further, according to the hybrid vehicle of the present invention, when the initial lower limit value of the charged amount is set to a value higher than the upper limit value of the discharge reserve and the charge reserve capacity is not set large, the charged amount of the nickel metal hydride storage battery is reduced. It is possible to reduce the amount of active material contained in the nickel-metal hydride storage battery while keeping it constant. Therefore, according to the hybrid vehicle of the present invention, the size of the nickel hydride storage battery mounted on the vehicle as a battery can be reduced while maintaining the capacity. In order to reduce the size of the nickel-metal hydride storage battery, it is difficult to make a large charge reserve. Therefore, in the hybrid vehicle according to the present invention, it is difficult to achieve the long life and the miniaturization of the nickel-metal hydride storage battery at the same time. There is a contradictory relationship. Therefore, according to the hybrid vehicle of the present invention, only one of the life extension and size reduction of the nickel-metal hydride storage battery is possible.

  In another aspect of the hybrid vehicle according to the present invention, the setting means may use a travel distance of the hybrid vehicle as an index indicating the passage of the usage period.

  According to this aspect, the driving force output from the other power source is the power output from the engine, or after the power is charged to the nickel-metal hydride storage battery as electric power through the other power source. Since it is generated by being supplied to another power source, it is possible to use the travel distance of the hybrid vehicle as one of indexes that specifically indicate the progress of the use period of the nickel-metal hydride storage battery. The setting unit may acquire a specific measurement value of the travel distance, and for example, when the travel distance of the hybrid vehicle reaches a predetermined value, that setting is transmitted to the setting unit. Also good. In addition, data indicating the travel distance may be transmitted to the setting unit at regular time intervals.

  According to this aspect, since the elapsed time of use of the nickel-metal hydride storage battery can be obtained from specific and quantitative data such as travel distance, the degree of deterioration of the nickel-metal hydride storage battery, that is, the shift amount of the upper limit value of the discharge reserve can be accurately determined. The lower limit value of the charged amount can be accurately set so as not to become smaller than the upper limit value of the discharge reserve according to the estimated value.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

  Hereinafter, embodiments of a hybrid vehicle according to the present invention will be described with reference to the drawings.

  First, the configuration of the hybrid vehicle according to the present embodiment will be described with reference to FIG. FIG. 1 is a conceptual diagram showing a configuration of a main part of the hybrid vehicle according to the present embodiment. The hybrid vehicle 1 is an engine 2 that is an internal combustion engine as one power source, a motor generator (MG) 3 that is an example of “another power source” of the present invention, and a nickel metal hydride storage battery (hereinafter referred to as a battery) that is used as a battery. ) 4, the external charging device 6, and the HVECU 10 which is an example of the “setting means” of the present invention.

  The engine 2 uses gasoline as fuel and is configured as a gasoline engine such as a 2-cycle or 4-cycle reciprocating engine that operates by combustion of gasoline. The engine 2 operates according to the explosive force of fuel such as gasoline burned in the combustion chamber, and generates power. The MG 3 is connected to the battery 4 via an inverter (not shown) and operates using the electric power charged in the battery 4, while the electric power generated according to the situation can be charged in the battery 4. The battery 4 is connected to an SOC sensor 5 for detecting the amount of stored electricity, in other words, the remaining amount of the battery.

  The external charging device 6 is connected to an external power source (not shown) by a user in a chargeable place such as a residential area where the hybrid vehicle 1 can be charged. The battery 4 is charged by receiving power from the external power supply in a state where the external charging device 6 is connected to the external power supply. Such a hybrid vehicle 1 is sometimes referred to as a so-called plug-in hybrid vehicle, as distinguished from a vehicle that cannot be charged by an external power source.

  The output shafts of the engine 2 and the MG 3 are connected to the power split mechanism 7. The outputs of the engines 2 and MG3 are transmitted to the drive wheels 9 via mechanical power transmission paths such as the power split mechanism 7 and the transaxle 8 and output shafts such as a crankshaft. In the hybrid vehicle 1, the driving power distribution of the engine 2 and the MG 3 is operated by the power split mechanism 7 to perform proper driving.

  The electronic control unit (HVECU) 10 is a computer that appropriately controls the operation of the hybrid vehicle 1, and controls the operations of the engine 2, the MG 3, and the power split mechanism 7.

  Next, an adjustment method in which the HVECU 10 adjusts the charge amount of the battery 4 will be described with reference to FIGS. 1 to 5. FIG. 2 is a flowchart showing a main processing routine of the adjustment method for adjusting the charge amount of the battery 4. FIG. 3 is a conceptual diagram schematically showing the capacity of the battery at the initial stage and after the lapse of the use period, and FIG. 4 schematically shows the capacity of the battery according to the comparative example of FIG. It is a conceptual diagram. FIG. 5 is a graph schematically showing changes in the amount of stored electricity with respect to the travel distance in the initial stage and after the lapse of the use period.

  1 and 2, the HVECU 10 includes a time point when the hybrid vehicle 1 is in a non-running state, more specifically, a use period of the nickel-metal hydride storage battery, and the travel distance of the hybrid vehicle 1 is zero. Initially, the initial lower limit value of the charge amount of the battery 4 is set to a value higher than the upper limit value of the discharge reserve of the battery 4 (step S10).

  Here, the relationship between the lower limit value of the charged amount and the upper limit value of the discharge reserve in the initial stage of the battery 4 will be described with reference to FIGS.

  In FIG. 3 (a), at the initial stage, the capacity of the battery 4 constituted by the nickel-metal hydride storage battery is limited (that is, positive electrode regulation) by the capacity of the positive electrode. The discharge reserve is an excessive negative electrode capacity that can be discharged among negative electrode capacities set larger than the positive electrode capacity. According to such a discharge reserve, the internal pressure of the battery 4 increases even when excessive discharge is performed from the battery 4 following the rapid power demand required by the MG 3 when the hybrid vehicle 1 starts suddenly. Can be suppressed.

  On the other hand, the battery 4 is set with a charge reserve corresponding to the discharge reserve. The charge reserve is an excessive negative electrode capacity that can be charged among negative electrode capacities set larger than the positive electrode capacity. According to such a charge reserve, even when the battery 4 is charged excessively when the MG 3 charges the battery 4, it is possible to suppress an increase in the internal pressure of the battery 4.

  The amount of electricity stored in the battery 4, that is, the initial lower limit value that is the lower limit of the chargeable range, is set to a value higher than the upper limit value of the discharge reserve in the battery 4 in which no deterioration has occurred. The capacity range is defined by the initial lower limit value and the lower limit value of the charge reserve. The initial lower limit value is determined based on the amount of charge of the battery 4 that can be changed by discharging or charging according to the traveling state of the hybrid vehicle 1, that is, the remaining amount of electric power stored in the battery 4. This is the lower limit set at the stage or when the replaced new nickel-metal hydride storage battery is mounted on the hybrid vehicle 1.

  Here, the relationship between the lower limit value of the storage amount and the upper limit value of the discharge reserve in the nickel metal hydride storage battery according to the comparative example of the battery 4 will be described with reference to FIG. As shown in FIG. 4, the chargeable / dischargeable capacity range, that is, each of the upper limit value and the lower limit value of the chargeable range is normally a discharge set according to the relative capacity of each of the negative electrode and the positive electrode. It is defined by the upper limit value of the reserve and the lower limit value of the charge reserve. Therefore, depending on the amount of discharge discharged from the nickel metal hydride storage battery, the amount of charge stored in the nickel metal hydride storage battery may coincide with the upper limit value of the discharge reserve.

  In the nickel metal hydride storage battery according to the comparative example, the margin of the amount of electricity stored is not set on the upper limit value of the discharge reserve, so that the charge reserve cannot be made larger than that of the battery 4, and the nickel hydride storage battery has a certain amount. It becomes difficult to extend the life of the nickel metal hydride storage battery in a state where a chargeable capacity is secured. More specifically, since a sufficient charge reserve cannot be secured, a liquid leak that the electrolyte solution leaks to the outside of the battery, or a gas leak that leaks oxygen gas or hydrogen gas generated from the electrolyte solution due to a chemical reaction to the outside of the battery occurs. As a result, the electrolyte solution is reduced. According to the decrease in the electrolytic solution, the reliability of the nickel metal hydride storage battery is significantly impaired, and the life of the storage battery is shortened.

  Therefore, as shown in FIG. 3A, the battery 4 is configured such that the HVECU 10 sets the initial lower limit value of the storage amount to a value higher than the upper limit value of the discharge reserve, whereby the upper limit value of the discharge reserve and the lower limit of the charge reserve. A margin of the charged amount is set on the upper limit value of the discharge reserve while ensuring a certain chargeable / dischargeable capacity between the values. In other words, by setting the upper limit value of the discharge reserve that increases with the deterioration of the battery 4 relatively lower than the lower limit value of the charged amount, it is possible to increase the charge reserve accordingly.

  As shown in FIGS. 3A and 4, the amount of power that can be substantially supplied from the battery 4 to the MG 3, that is, the chargeable range that can fluctuate due to charging / discharging is set when the initial lower limit value is not set, that is, the positive electrode Compared to the case where power is supplied from the battery to the MG 3 in the capacity range between the upper limit value of the discharge reserve and the lower limit value of the charge reserve set by the regulation, it becomes smaller. More specifically, in the hybrid vehicle 1, for example, the electric power to the MG 3 so that the hybrid vehicle 1 can only travel 150 km in the place where the hybrid vehicle 1 can originally travel 200 km only by the power supplied from the battery 4 charged by one charge. Supply will be limited.

  However, according to the hybrid vehicle 1, since the battery 4 can be charged from the external power source, the battery 4 can be charged from the external power source in a chargeable place even when the amount of power stored in the battery 4 decreases to the initial lower limit value. Therefore, even when the chargeable / dischargeable capacity range becomes smaller than when the initial lower limit value is not set, the battery 4 can be charged without receiving power supply based on the power generated in the engine 2.

  Next, the relationship between the lower limit value of the charged amount and the upper limit value of the discharge reserve in the battery 4 after the usage period has elapsed will be described with reference to FIG.

  In FIG. 3B, the discharge reserve increases with the passage of the use period of the hybrid vehicle 1, and the upper limit value shifts upward in the drawing. On the other hand, the charge reserve is reduced by a deteriorated capacity generated in accordance with the deterioration of the battery 4 compared to the initial charge reserve. However, as described with reference to FIG. 3A, according to the hybrid vehicle 1, since the charge reserve can be set large in advance in the initial stage, it is possible to extend the time until the charge reserve disappears. Yes, it is possible to reduce the decrease in the electrolyte caused by excessive charging.

  Again, in FIG. 2, the HVECU 10 determines the passage of the usage period of the hybrid vehicle 1 after the usage period in which the hybrid vehicle 1 has been used, in other words, after the hybrid vehicle 1 has passed an arbitrary running state or driving state. Acquire data about the indicated index. More specifically, the HVECU 10 acquires data including information on the travel distance of the hybrid vehicle 1 or the years of use from, for example, a sensor that detects the travel distance of the hybrid vehicle 1 or a counter that counts the years of use (step). S20).

  In the hybrid vehicle 1, the driving force output from the MG 3 is supplied to the battery 4 again after the power output from the engine 2 or the power is charged to the battery 4 as power via the MG 3. Therefore, the travel distance of the hybrid vehicle 1 can be used as one of the indexes that specifically indicate the passage of the usage period of the battery 4. The HVECU 10 can accurately set the lower limit value of the storage amount lower than the initial lower limit value based on the specific and quantitative data of the usage period of the battery 4 as the travel distance. Therefore, according to the hybrid vehicle 1, the degree of deterioration of the nickel-metal hydride storage battery constituting the battery 4 can be accurately estimated, and the lower limit value of the charged amount can be set according to the estimated value.

  When the travel distance of the hybrid vehicle 1 reaches a predetermined value, the HVECU 10 may acquire data including a fact that the travel distance has reached the predetermined value from a sensor that detects the travel distance of the hybrid vehicle 1. Data indicating the travel distance may be acquired from the sensor at the time intervals. In addition, as an index indicating the period of use, an index such as the number of times of charging / discharging the battery 4 or the amount of charging / discharging corresponding to the degree of deterioration of the battery 4 may be used.

  Next, in FIG. 2, the HVECU 10 sets the lower limit value of the charged amount of the battery 4 so that the lower limit value of the charged amount of the battery 4 becomes lower than the initial lower limit value as the usage period of the hybrid vehicle 1 elapses. (Step S30). Thus, by setting the lower limit value of the charge amount to be lower than the initial lower limit value, it is possible to secure a capacity that can be stored in the battery 4.

  Note that the HVECU 10 sets the lower limit value of the charged amount of the battery 4 to be lower than the initial lower limit value every time the period of use of the hybrid vehicle 1 elapses. More specifically, for example, in each travel distance or travel time corresponding to the travel distance or travel time of the hybrid vehicle, the lower limit value of the storage amount is set lower as the distance or time increases. Thus, by setting the lower limit value low, a constant charge amount can be secured even when the battery 4 is deteriorated.

  Next, an example of a change in the charge amount when the hybrid vehicle 1 is driven will be described with reference to FIGS. 1 and 5.

  In FIG. 5, in an initial stage, hybrid vehicle 1 travels with motive power transmitted from MG 3 that operates with electric power supplied from battery 4 to drive wheels 9 after charging battery 4 in a chargeable place. Therefore, the amount of charge of the battery 4 is reduced (Depleting region in the figure). Next, when the travel distance of the hybrid vehicle 1 reaches the point where the amount of power stored in the battery 4 has decreased to the initial lower limit value, that is, one charge travel distance capable of supplying power from the battery 4 to the MG 3 by one charge. 1 travels by power supplied from the engine 2. During the period in which the hybrid vehicle 1 is traveling by the power supplied from the engine 2, the amount of power stored in the battery 4 is maintained at the initial lower limit (SOC1) (the Sustaining region in the figure). Next, when the hybrid vehicle 1 reaches a chargeable place, the battery 4 is charged by the electric power supplied from the external power source.

  Next, in FIG. 5, after the usage period has elapsed, the hybrid vehicle 1 charges the battery 4 in the rechargeable place after the use period, and then operates from the MG 3 that is operated by the electric power supplied from the battery 4. Power is transmitted to 9 and the vehicle travels. Therefore, the charge amount of the battery 4 decreases. However, since the lower limit value of the charge amount of the battery 4 is set to a lower limit value (SOC2) lower than the initial lower limit value (SOC1), only the electric power supplied from the battery 4 is relatively compared to the initial stage. The distance that can be traveled is increasing. Next, when the travel distance of the hybrid vehicle 1 reaches the point where the amount of power stored in the battery 4 decreases to the lower limit (SOC2), that is, the travel distance in which electric power can be supplied from the battery 4 to the MG 3 by one charge. 1 travels by power supplied from the engine 2. During the period in which the hybrid vehicle 1 is traveling by the power supplied from the engine 2 (Sustaining region), the amount of power stored in the battery 4 is maintained at the lower limit (SOC2). Next, when the hybrid vehicle 1 reaches a chargeable place, the battery 4 is charged by the electric power supplied from the external power source. According to the hybrid vehicle 1, even if the charged amount of the battery 4 is reduced to the lower limit value (SOC 2), it can be charged from the external power source, so that the fuel efficiency can be improved as the entire hybrid vehicle 1.

  FIG. 5 shows an example of the change in the charge amount with respect to the travel distance after the use period has elapsed. More specifically, the longer the use period, the more specifically the travel distance and the number of times of charging / discharging the battery 4 As the cumulative value increases, the lower limit value of the charged amount is set lower.

  As described above, according to the hybrid vehicle according to the present embodiment, it is possible to extend the period until the charge reserve disappears while securing the capacity of the battery composed of the nickel hydride storage battery. It is possible to extend the life of a battery composed of a hydrogen storage battery and increase its reliability.

  Further, according to the hybrid vehicle according to the present embodiment, when the initial lower limit value of the charged amount is set to a value higher than the upper limit value of the discharge reserve and the capacity of the charge reserve is not taken large, the charged amount of the nickel metal hydride storage battery It is possible to reduce the amount of active material contained in the nickel-metal hydride storage battery while keeping the constant. Therefore, according to the hybrid vehicle which concerns on this embodiment, the size of the nickel hydride storage battery mounted in the said vehicle as a battery can be reduced in size. In order to reduce the size of the nickel-metal hydride storage battery, it is impossible to make a large charge reserve. Therefore, the extension of the life of the nickel-metal hydride storage battery and the downsizing of the nickel-metal hydride storage battery have a contradictory relationship that is difficult to achieve simultaneously. Therefore, according to the hybrid vehicle according to the present embodiment, only one of the life extension and size reduction of the nickel metal hydride storage battery is possible.

It is the conceptual diagram which showed the structure of the principal part of the hybrid vehicle which concerns on this embodiment. It is the flowchart which showed the main process routine of the adjustment method which adjusts the electrical storage amount in the battery with which the hybrid vehicle which concerns on this embodiment is provided. In the hybrid vehicle which concerns on this embodiment, it is the conceptual diagram which showed typically the structure of the capacity | capacitance of the battery in each after an initial stage and use period progress. It is the conceptual diagram which showed the capacity | capacitance of the battery which concerns on the comparative example of Fig.3 (a) graphically. It is the graph which showed typically the change of the electrical storage amount of the battery at the time of making the hybrid vehicle concerning this embodiment run.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Hybrid vehicle, 2 ... Engine, 3 ... Motor generator (MG), 10 ... Electronic control unit (HVECU)

Claims (2)

An engine that operates by burning fuel,
A nickel metal hydride storage battery that can be charged from an external power source;
It operates using electric power charged in the nickel metal hydride storage battery, and another power source different from the engine,
The initial lower limit value of the charge amount of the nickel metal hydride storage battery is set to a value higher than the upper limit value of the discharge reserve of the nickel metal hydride battery, and after the initial lower limit value is set, A hybrid vehicle comprising: setting means for setting the lower limit value of the charge amount so that the lower limit value of the charge amount becomes lower than the initial lower limit value as time elapses. The hybrid vehicle according to claim 1, wherein the setting unit uses a travel distance of the hybrid vehicle as an index indicating the passage of the use period.

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