JP7013987B2 - Hybrid car - Google Patents

Description

The present disclosure relates to a hybrid vehicle, and more specifically, to a technique for controlling charging of a nickel-metal hydride battery mounted on the hybrid vehicle.

The hybrid vehicle is configured to be able to run by using both the power output from the internal combustion engine and the power output from the motor that receives the electric power stored in the battery. Even when the hybrid vehicle is stopped (for example, parked), the internal combustion engine may be operated for the purpose of heating the vehicle interior or activating a catalyst (for example, a catalyst for exhaust gas purification). Japanese Unexamined Patent Publication No. 2010-36788 (Patent Document 1) discloses a technique of generating electricity by using power output from an internal combustion engine driven at the time of heating a vehicle interior to charge a battery. Hereinafter, power generation using the power output from the internal combustion engine may be referred to as "engine power generation". Further, the electric power generated by the engine power generation may be referred to as "engine generated electric power".

Japanese Unexamined Patent Publication No. 2010-36788

Nickel-metal hydride batteries are known as batteries installed in hybrid vehicles. And it is known that a memory effect occurs in a nickel-metal hydride battery. The memory effect is the initial state (that is, the memory effect) of the discharge voltage of the nickel-metal hydride battery when charging is repeated in a state where the power stored in the nickel-metal hydride battery is not completely consumed (so-called replenishment charging). It is a phenomenon that becomes lower than when (when) does not occur. The memory effect may also occur on the charging side of the nickel-metal hydride battery, and the charging voltage on the charging side is higher than in the initial state.

When a nickel-metal hydride battery (battery) is charged by engine power generation, the charging stop condition may be determined by SOC (State Of Charge). For example, it is conceivable that charging is performed until the SOC of the nickel-metal hydride battery reaches a predetermined SOC (hereinafter, referred to as “charging stop SOC”). When the hybrid vehicle is stopped or when the load is low, the nickel-metal hydride battery does not consume much power because the power of the nickel-metal hydride battery is hardly used for the hybrid vehicle. Therefore, the above charge control is executed when the hybrid vehicle is stopped or when the load is low, and once the nickel hydrogen battery is charged to the charge stop SOC by the engine power generation, the power of the nickel hydrogen battery is thereafter. Is mainly consumed by auxiliary load (lighting device, audio device, etc.), and the nickel hydrogen battery is charged by the power generated by the engine by the amount consumed. That is, after charging is stopped at the charging stop SOC, charging / discharging of the nickel-metal hydride battery is repeated in the vicinity of the charging stop SOC until the hybrid vehicle starts high-load running. If the charge stop SOC is maintained at the same value, the nickel-metal hydride battery will be repeatedly charged and discharged with the same SOC.

When the nickel-metal hydride battery is repeatedly charged and discharged at the same SOC, the memory effect is likely to occur in the nickel-metal hydride battery at that SOC. Hereinafter, the SOC in which the memory effect occurs may be referred to as "SOCm". In a nickel-metal hydride battery in which a memory effect is generated in SOCm, an SOC region lower than SOCm in a graph showing the relationship between SOC and OCV (Open Circuit Voltage) (hereinafter, may be referred to as “SOC-OCV curve”). The OCV of the SOC is lower than the initial state, and the OCV of the SOC region higher than the SOCm is higher than the initial state. When estimating the SOC from the OCV of a nickel-metal hydride battery using a map showing a predetermined SOC-OCV curve, the occurrence of the memory effect causes the actual SOC-OCV curve to be between the actual SOC-OCV curve and the SOC-OCV curve shown in the map. There may be a discrepancy in the SOC and the estimation accuracy of the SOC may decrease.

In order to improve the estimation accuracy of SOC, it is premised that the nickel-metal hydride battery has a memory effect at a predetermined SOC (hereinafter referred to as "correction standard SOC") (that is, the correction standard SOC matches SOCm). , Correction Criteria It is also conceivable to correct the above map with reference to the SOC. However, even if such correction is performed, if a memory effect occurs in the nickel-metal hydride battery with SOCm outside the prerequisites, the actual SOC-OCV curve and the SOC-OCV curve shown in the corrected map will be used. There will be a divergence between them. Therefore, depending on the SOCm, the above correction may not be effective.

Further, when the memory effect occurs in the nickel-metal hydride battery, the OCV in the SOC region higher than the SOCm rises, so that gas may be easily generated in the battery case depending on the SOCm. For example, when a nickel-metal hydride battery is overcharged, a side reaction occurs and oxygen gas is generated from the positive electrode. When gas is generated in the battery case, the internal pressure of the battery rises, and the SOC area (battery use area) in which the battery can be used tends to be narrowed.

The present disclosure has been made to solve the above-mentioned problems, and an object thereof is to suppress the memory effect of a nickel-metal hydride battery from being generated in SOC outside the preconditions.

The hybrid vehicle of the present disclosure includes an internal combustion engine, a nickel metal hydride battery, and a control device. The control device uses the power output from the internal combustion engine to generate electricity to charge the nickel-metal hydride battery, and if the SOC of the nickel-metal hydride battery becomes the charge stop SOC during the charging, the charge is stopped. It is composed. The frequency (hereinafter referred to as "target SOC frequency") in which the SOC of the nickel hydrogen battery is within the predetermined SOC region (hereinafter referred to as "target SOC region") is higher than the predetermined value (hereinafter referred to as "boundary value"). When it is low, the charge stop SOC is in the target SOC region, and when the target SOC frequency is higher than the boundary value, the charge stop SOC is changed to an SOC outside the target SOC region by the above control device. It is composed.

For example, by periodically counting (integrating) the frequency (frequency) for each SOC region, the frequency for each SOC region can be obtained. The target SOC frequency can be obtained from, for example, the SOC frequency distribution of a nickel-metal hydride battery. In a typical SOC frequency distribution, the horizontal axis is provided with a plurality of sections (that is, SOC regions) according to the size of the SOC, and the vertical axis is the SOC region (SOC numerical range) provided on the horizontal axis. Shows the frequency of each. Of the plurality of SOC regions provided on the horizontal axis of the SOC frequency distribution, the frequency of the target SOC region corresponds to the target SOC frequency.

The SOC of the nickel-metal hydride battery may be the SOC of one nickel-metal hydride battery (single battery) or the SOC of a battery module including a plurality of nickel-metal hydride batteries. The SOC indicates the remaining amount of electricity stored, and for example, the ratio of the current amount of electricity stored to the amount of electricity stored in a fully charged state is expressed by 0 to 100%.

In the above control device, the nickel-metal hydride battery is charged by the power generated by the engine, and if the SOC of the nickel-metal hydride battery becomes the charge stop SOC during the charging, the charge is stopped. Therefore, when the hybrid vehicle is stopped running or running at a low load, the nickel-metal hydride battery is repeatedly charged and discharged in the vicinity of the charging stop SOC. When the target SOC frequency is lower than the boundary value, since the charge stop SOC is in the target SOC region, the target SOC frequency increases when the nickel-metal hydride battery is repeatedly charged and discharged in the vicinity of the charge stop SOC.

The above control device changes the charge stop SOC to an SOC outside the target SOC region when the target SOC frequency becomes higher than the boundary value. As a result, the nickel-metal hydride battery is repeatedly charged and discharged outside the target SOC region, and the generation of the memory effect in the target SOC region is suppressed.

In the above control device, it is possible to suppress the occurrence of the memory effect in the target SOC area. That is, it is preferable to set the SOC area in which the memory effect is not desired to occur as the target SOC area. The number of target SOC regions is not limited to one, and may be arbitrary, and a plurality of target SOC regions may be set. Different boundary values may be provided for each target SOC region.

By suppressing the occurrence of the memory effect in the target SOC area, the possibility that the memory effect will occur in the SOC area outside the target SOC area becomes relatively high. Utilizing this, the SOCm can be controlled within the SOC region outside the target SOC region (hereinafter, may be referred to as a “target SOCm region”). More specifically, when the target SOC frequency becomes higher than the boundary value, the charge stop SOC is changed to the SOC in the target SOCm area, so that a memory effect can occur in the SOC in the target SOCm area. The sex becomes high.

Whether the target SOC frequency of the nickel-metal hydride battery is higher or lower than the boundary value may be determined at a predetermined cycle, or may be performed only when a predetermined memory effect generation condition is satisfied.

The above memory effect generation condition is set so as to be satisfied when the memory effect in the nickel-metal hydride battery is not saturated and the SOC-OCV curve of the nickel-metal hydride battery can be changed by the generation of a further memory effect. The above-mentioned memory effect generation conditions can be determined by the usage history of the nickel-metal hydride battery and the like. The memory effect generation condition is, for example, when the integrated mileage of the hybrid vehicle measured by the odometer is within a predetermined value and / or the elapsed time measured by the timer (for example, the usage time of the nickel hydrogen battery). It may be established when it is within a predetermined value.

The hybrid vehicle may be provided with a heating device that heats the inside of the vehicle (for example, the interior of the vehicle) using an internal combustion engine as a heat source. Then, the above-mentioned control device performs heating and generates electricity by using the power output from the internal combustion engine during the heating to charge the nickel-metal hydride battery, and during the charging, the nickel-metal hydride battery is charged. The charging may be stopped when the SOC becomes the charging stop SOC.

As the target SOC region, an SOC region defined within the range of SOC 65% to 100% (hereinafter, may be referred to as “high SOC region”) may be adopted. Then, when the target SOC frequency is higher than the boundary value, the charging stop SOC may be changed to an SOC lower than the target SOC region (high SOC region) by the above control device.

In addition, "defined within the range of SOC 65% to 100%" means that both the upper limit SOC and the lower limit SOC defining the SOC region are within the range of 65% to 100%. That is, the SOC region of 65% or more and 80% or less corresponds to the high SOC region. On the other hand, the SOC region of 30% or more and 65% or less does not correspond to the high SOC region.

According to the above configuration, when the target SOC frequency is lower than the boundary value, the nickel-metal hydride battery has a high SOC (charge stop SOC included in the range of SOC 65% to 100%) due to the engine power generated during heating or the like. By being charged to, energy efficiency can be improved. However, since the nickel-metal hydride battery is charged and discharged near the charge stop SOC when the hybrid vehicle is stopped or running at a low load, if the charge stop SOC as described above is adopted, the frequency of the high SOC region tends to increase. Therefore, in the control device of the hybrid vehicle, when the frequency of the high SOC region becomes high, the charge stop SOC is lowered so that the charge is not performed up to the high SOC. By doing so, it is possible to prevent the nickel-metal hydride battery from being repeatedly charged and discharged in the high SOC region. Then, it is possible to suppress the occurrence of the memory effect (and thus the increase in the charging voltage) in the high SOC region.

According to the present disclosure, it is possible to suppress the memory effect of the nickel-metal hydride battery from being generated in the SOC outside the preconditions.

It is a block diagram schematically showing the overall structure of the hybrid vehicle according to the embodiment of the present disclosure. It is a figure which shows the structure of one cell contained in the battery shown in FIG. It is a figure which shows the actual SOC-OCV curve when a battery is used in the 1st SOC frequency distribution. It is a figure which shows the actual SOC-OCV curve when a battery is used in the 2nd SOC frequency distribution. It is a flowchart which showed the processing procedure of the SOC frequency distribution creation which is executed by the control device of the hybrid vehicle according to the embodiment of this disclosure. It is a flowchart which showed the processing procedure of the charge control executed by the control device of the hybrid vehicle according to the embodiment of this disclosure. It is a flowchart which showed the processing procedure of the charge stop SOC setting executed by the control device of the hybrid vehicle according to the embodiment of this disclosure. It is a figure which shows the target SOC area which concerns on embodiment of this disclosure. It is a figure which shows an example of the SOC frequency distribution of a battery. It is a figure which shows an example of the change of the SOC frequency distribution by changing the charge stop SOC.

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

FIG. 1 is a block diagram schematically showing an overall configuration of a vehicle 1 equipped with a control device according to this embodiment.

With reference to FIG. 1, the vehicle 1 includes motor generators (hereinafter referred to as “MG (Motor Generator)”) 11 and 12, an engine 20, a drive wheel 30, a power dividing device 31, and a drive shaft 32. , A power control unit (hereinafter referred to as "PCU (Power Control Unit)") 40, a system main relay (hereinafter referred to as "SMR (System Main Relay)") 50, a battery system 2, and a heating device 3. To prepare for.

The battery system 2 includes a battery 100, a voltage sensor 210, a current sensor 220, a temperature sensor 230, and an electronic control unit (hereinafter referred to as "ECU (Electronic Control Unit)") 300. The ECU 300 corresponds to an example of the "control device" according to the present disclosure.

The heating device 3 is configured to heat the inside of the vehicle interior 500 (the space in the vehicle 1 on which the occupant is on board) using the engine 20 as a heat source. The heating device 3 includes a heat exchanger 401, a blower device 402, and a switching device 403.

The vehicle 1 is a hybrid vehicle configured to be able to travel by using both the power output from the engine 20 and the electric power stored in the battery 100.

The battery 100 is a DC power source configured to be rechargeable. The battery 100 includes an assembled battery composed of a plurality of secondary batteries. In this embodiment, the assembled battery included in the battery 100 is composed of a plurality of nickel-metal hydride batteries connected in series. The nickel-metal hydride battery is a secondary battery having a positive electrode, a negative electrode, and an aqueous electrolytic solution (for example, an alkaline aqueous solution) in a case. Hereinafter, the secondary battery (in this embodiment, the nickel hydrogen battery) constituting the assembled battery is referred to as a “cell”.

FIG. 2 is a diagram showing the configuration of the cell 101 included in the battery 100. Since the configuration of each cell 101 is common, only one cell 101 is typically shown in FIG. In FIG. 2, a part of the case 102 of the cell 101 is seen through to show the electrode body 104.

With reference to FIG. 2, cell 101 is a square sealed cell comprising, for example, a metal case 102. The case 102 contains an electrode body 104 and an electrolytic solution (not shown) constituting a nickel-metal hydride battery. A gas release valve 103 is provided on the upper part of the case 102.

The case 102 is a square case including a case body and a lid made of metal, and the lid is sealed by being welded all around the opening of the case body. The gas release valve 103 is opened when the pressure in the case 102 (cell internal pressure) exceeds a predetermined valve opening pressure, and a part of the gas (oxygen gas or the like) in the case 102 is discharged to the outside.

The electrode body 104 includes a positive electrode plate, a negative electrode plate, and an insulating separator. The positive electrode plate and the negative electrode plate are alternately laminated via a separator. That is, an insulating separator is sandwiched between the positive electrode plate and the negative electrode plate. The positive electrode plate and the negative electrode plate are electrically connected to the positive electrode terminal and the negative electrode terminal (not shown), respectively.

As the material of the electrode body 104 and the electrolytic solution constituting the nickel-metal hydride battery, a material arbitrarily selected from various materials known as materials of the nickel-metal hydride battery can be used. In this embodiment, the positive electrode plate includes a positive electrode active material layer containing a solid solution of nickel hydroxide (Ni (OH) ₂ or NiOOH) and a cobalt compound, and an active material support (foamed nickel or the like). An electrode plate is used. The positive electrode plate may be subjected to higher-order Na treatment. As the negative electrode plate, an electrode plate containing a hydrogen storage alloy is used. The hydrogen storage alloy is, for example, an alloy of a metal having an excellent hydrogen storage capacity (Ti, Zr, Pd, Mg, etc.) and a metal having an excellent hydrogen release capacity (Fe, Co, Ni, etc.). As the separator, a non-woven fabric made of a hydrophilized synthetic fiber is used. As the electrolytic solution, an alkaline aqueous solution containing potassium hydroxide (KOH) or sodium hydroxide (NaOH) is used.

With reference to FIG. 1 again, the PCU 40 performs bidirectional power conversion between the battery 100 and the MGs 11 and 12 according to the control signal from the ECU 300. The PCU 40 is configured so that the states of the MGs 11 and 12 can be controlled separately. For example, the MG12 can be put into a power running state while the MG11 is in a regenerative (power generation) state. The PCU 40 includes, for example, two inverters provided corresponding to MGs 11 and 12, and a converter that boosts the DC voltage supplied to each inverter to a voltage higher than the output voltage of the battery 100.

The MGs 11 and 12 are AC rotary electric machines, for example, three-phase AC synchronous motors in which a permanent magnet is embedded in a rotor. The MG 11 is mainly used as a generator driven by the engine 20 via the power splitting device 31. The electric power generated by the MG 11 is supplied to the MG 12 or the battery 100 via the PCU 40.

The MG 12 mainly operates as an electric motor and drives the drive wheels 30. The MG 12 is driven by receiving at least one of the electric power from the battery 100 and the electric power generated by the MG 11, and the driving force of the MG 12 is transmitted to the drive shaft 32. On the other hand, when the vehicle is braking or the acceleration is reduced on a downhill slope, the MG 12 operates as a generator to generate regenerative power generation. The electric power generated by the MG 12 is supplied to the battery 100 via the PCU 40.

The SMR 50 is electrically connected to a current path connecting the battery 100 and the PCU 40. When the SMR 50 is closed in response to a control signal from the ECU 300, electric power can be exchanged between the battery 100 and the PCU 40.

The voltage sensor 210 detects the voltage of the battery 100 (voltage between terminals). The current sensor 220 detects the current IB input / output to / from the battery 100. The current IB during charging is represented by a positive number, and the current IB during discharging is represented by a negative number. The temperature sensor 230 detects the temperature of the battery 100. Each sensor outputs the detection result to the ECU 300.

The engine 20 is an internal combustion engine that outputs power by converting the combustion energy generated when the air-fuel mixture is burned into the kinetic energy of movers such as pistons and rotors. The power splitting device 31 includes, for example, a planetary gear mechanism having three rotation axes of a sun gear, a carrier, and a ring gear. The power splitting device 31 divides the power output from the engine 20 into a power for driving the MG 11 and a power for driving the drive wheels 30.

Further, the cooling system of the engine 20 (not shown) is configured so that the engine 20 is cooled by circulating cooling water around the engine 20. The temperature of the cooling water of the engine 20 changes according to the temperature of the engine 20. The water temperature sensor 410 detects the temperature of the cooling water of the engine 20 (cooling water temperature TW), and outputs the detection result to the ECU 300.

The heat exchanger 401 is attached to the cooling system of the engine 20 and is configured to exchange heat between the air input from the switching device 403 and the cooling water of the engine 20. The blower 402 is configured to blow the air output from the heat exchanger 401 into the passenger compartment 500. As the blower 402, for example, a fan or a blower can be adopted. The switching device 403 is configured to switch whether the outside air (air outside the vehicle) or the air inside the vehicle interior 500 is sent to the heat exchanger 401. The outside air temperature sensor 420 detects the temperature of the outside air (outside air temperature TA1). Further, the vehicle interior sensor 430 detects the temperature inside the vehicle interior 500 (indoor temperature TA2). Each sensor outputs the detection result to the ECU 300. The blower 402 and the switching device 403 operate according to the control signal from the ECU 300.

The combustion energy generated by the engine 20 is converted not only into kinetic energy but also into thermal energy. The heating device 3 uses this heat energy to heat the inside of the vehicle interior 500. More specifically, when the engine 20 is stopped in a situation where the outside air temperature is low (for example, in winter), the temperature of the engine 20 (and thus the cooling water temperature TW) decreases. In such a case, when the user requests the execution of heating, the ECU 300 operates the engine 20 to raise the cooling water temperature TW to a temperature suitable for heating (for example, 50 ° C to 60 ° C). When the engine 20 is operated, the temperature of the engine 20 becomes high due to combustion, and the cooling water temperature TW rises. At this time, when the MG 11 is driven by the power output from the engine 20 to generate electricity and the battery 100 is charged using the generated electric power, the load on the engine 20 becomes large and the cooling water temperature TW rises. It will be faster. When the cooling water temperature TW rises to a temperature suitable for heating, the air input from the switching device 403 to the heat exchanger 401 is warmed by heat exchange with the cooling water of the engine 20. By blowing the air warmed in this way into the vehicle interior 500 by the blower 402, the temperature inside the vehicle interior 500 can be raised.

An input device 440 is provided in the vehicle interior 500. The input device 440 is a device that receives an instruction from the user. The input device 440 is operated by the user and outputs a signal corresponding to the user's operation to the ECU 300. The communication method between the ECU 300 and the input device 440 may be wired or wireless. The user can operate the input device 440 to request the ECU 300 to execute the heating or set the target temperature for the heating. The ECU 300 controls the engine 20 and the heating device 3 so that the target temperature for heating and the room temperature TA2 match, based on the cooling water temperature TW, the outside air temperature TA1, the room temperature TA2, and the like.

The ECU 300 includes a CPU (Central Processing Unit) 301, a memory 302, and an input / output buffer (not shown). The memory 302 includes a ROM (Read Only Memory), a RAM (Random Access Memory), and a rewritable non-volatile memory. Various controls are executed by the CPU 301 executing the program stored in the memory 302 (for example, ROM). The ECU 300 controls each device so that the vehicle 1 and the battery system 2 are in a desired state based on, for example, a signal received from each sensor and a map and a program stored in the memory 302. The ECU 300 executes running control of the vehicle 1 and charge / discharge control of the battery 100 by controlling the engine 20 and the PCU 40, for example. The various controls performed by the ECU 300 are not limited to software processing, but can also be processed by dedicated hardware (electronic circuits).

Further, the ECU 300 includes an odometer (not shown). The total mileage of the vehicle 1 is measured by this odometer. Further, the ECU 300 includes a timer (not shown) that cumulatively counts the elapsed time from the time when the battery 100 is attached (at the start of use). The usage time of the battery 100 is measured by this timer. Note that such a timer function can also be realized by software.

The ECU 300 outputs the acquired information (calculation result by the CPU 301, etc.) to the memory 302 (for example, a rewritable non-volatile memory) and stores it in the memory 302. Further, the memory 302 stores information used for controlling the vehicle 1 and detecting the battery state in advance.

Even when the vehicle 1 is stopped (a state in which the vehicle 1 is not traveling), the engine 20 may be operated for the purpose of heating the interior of the vehicle interior 500 or activating a catalyst (not shown). In this embodiment, the ECU 300 controls the heating device 3 to heat the inside of the vehicle interior 500 while the vehicle 1 is stopped (for example, when a shift lever (not shown) is in the parking range). The battery 100 is charged with the power generated by the engine during the heating, and the charging is stopped when the SOC of the battery 100 becomes the charging stop SOC during the charging. The engine power generation power is, for example, the power generated in the MG 11 by driving the MG 11 by the engine 20.

The above charge control is executed while the vehicle 1 is stopped, and once the battery 100 is charged to the charge stop SOC by the engine generated power, the power of the battery 100 is mainly used as an auxiliary load (not shown). It is consumed by the lighting device, wiper device, audio device, car navigation system, etc.) or the ECU 300, and the battery 100 is charged by the power generated by the engine by the amount consumed. That is, after charging is stopped at the charging stop SOC, charging / discharging of the battery 100 is repeated in the vicinity of the charging stop SOC until the vehicle 1 starts traveling. Therefore, if the charge stop SOC is maintained at the same value, the battery 100 is repeatedly charged and discharged with the same SOC. For example, if the vehicle 1 is left for a long time with the shift lever (not shown) of the vehicle 1 in the parking range, the battery 100 is repeatedly charged and discharged with the same SOC for a long time. When the nickel-metal hydride battery is repeatedly charged and discharged at the same SOC, the memory effect is likely to occur in the nickel-metal hydride battery at that SOC.

Therefore, in the vehicle 1 according to this embodiment, when the target SOC frequency is lower than the boundary value, the charge stop SOC is in the target SOC region, and when the target SOC frequency is higher than the boundary value, the ECU 300 The charging stop SOC is changed to an SOC outside the target SOC area. That is, when the target SOC frequency becomes higher than the boundary value, the charge stop SOC is set to the value before the target SOC frequency becomes higher than the boundary value (that is, when the target SOC frequency is lower than the boundary value). Is set to a different value so that the charge stop SOC is not included in the target SOC region. As a result, the charging / discharging of the nickel-metal hydride battery in the battery 100 is repeatedly executed outside the target SOC region, and the generation of the memory effect in the target SOC region of the nickel-metal hydride battery is suppressed.

In this embodiment, the target SOC region is a high SOC region defined within the range of SOC 65% to 100% (for example, the first to third SOC regions described later). Further, the charge stop SOC when the frequency of the target SOC region is lower than the boundary value is set to, for example, 70%. When the frequency of the target SOC region of the battery 100 is higher than the boundary value, the charging stop SOC is changed to an SOC lower than the target SOC region by the ECU 300.

According to the above configuration, when the frequency of the high SOC region is lower than the boundary value, the nickel-metal hydride battery has a high SOC (for example, 70%) due to the engine power generated during heating while the vehicle 1 is stopped. By being charged to, energy efficiency can be improved. However, since the battery 100 is charged and discharged near the charge stop SOC while the vehicle 1 is stopped, if the charge stop SOC as described above is adopted, the frequency of the high SOC region is high while the vehicle 1 is stopped. Become. Therefore, in this embodiment, when the frequency of the high SOC region becomes high, the ECU 300 lowers the charge stop SOC so that the charge is not performed up to the high SOC. By doing so, it is possible to prevent the nickel-metal hydride battery from being repeatedly charged and discharged in the high SOC region. Then, it is possible to suppress the occurrence of the memory effect (and thus the increase in the charging voltage) in the high SOC region.

In this embodiment, the ECU 300 is configured to estimate the SOC from the OCV of the battery 100 by using the SOC estimation information indicating the relationship between the SOC of the battery 100 and the OCV. The SOC estimation information is stored in the memory 302, and may be a map, a table, a mathematical formula, or a model. Specific examples of SOC estimation information will be described later (see FIG. 3).

Since the relationship between the SOC and the OCV in the battery 100 changes due to the memory effect occurring in the nickel-metal hydride battery in the battery 100, the SOC estimation information is sequentially corrected. More specifically, when the memory effect occurs in SOCm, the SOC-OCV curve of the nickel-metal hydride battery is higher than SOCm because the OCV in the SOC region lower than SOCm is lower than the OCV in the initial state by the amount of memory. The OCV in the SOC area is higher than the OCV in the initial state by the amount of memory. The amount of memory corresponds to the amount of voltage change due to the memory effect.

The SOC estimation information is corrected on the precondition that the nickel-metal hydride battery in the battery 100 has a memory effect according to the correction reference SOC. In this embodiment, the correction reference SOC is set to 50% or more and less than 65% in consideration of the fact that the traveling battery is generally charged and discharged at around 60% SOC while the hybrid vehicle is running. Let it be SOC.

The SOC estimation information is corrected by the following procedure, for example. The ECU 300 estimates the memory amount (voltage change amount for each SOC) based on the correction reference SOC using the usage time and usage history of the battery 100 (information indicating under what conditions the battery 100 was used). .. The amount of memory tends to increase as the usage time of the battery 100 increases. The amount of memory also changes depending on the usage conditions of the battery 100 (battery voltage, battery temperature, etc.). The ECU 300 corrects (updates) the SOC estimation information to the content corresponding to the memory amount estimated as described above.

A problem in estimating the SOC of the battery 100 using the SOC estimation information corrected as described above will be described with reference to FIGS. 3 and 4. Hereinafter, the actual SOC-OCV curve (more specifically, the SOC-OCV curve close to the true value measured precisely in an experiment or the like) is referred to as a predetermined SOC-OCV curve (map, etc.) used for SOC estimation. For the sake of distinction, it may be referred to as a "real SOC-OCV curve".

FIG. 3 is a diagram showing an actual SOC-OCV curve when the battery 100 is used in the first SOC frequency distribution. The first SOC frequency distribution is the SOC frequency distribution shown by the line k21. By charging the battery 100 only while the vehicle 1 is running without charging with the engine generated power while the vehicle 1 is stopped, the SOC frequency distribution of the battery 100 becomes the SOC frequency distribution as shown by the line k21. became.

In FIG. 3, line k11 shows the actual SOC-OCV curve of the battery 100 in the initial state (immediately after the start of use). Line k22 shows the actual SOC-OCV curve when the battery 100 is used in the SOC frequency distribution shown by line k21. The line k12 is the SOC estimation information corrected with the SOC 60% as the correction reference SOC when the battery 100 is used in the SOC frequency distribution shown by the line k21 (more specifically, the map corrected as shown below). ) Is shown.

With reference to FIG. 3, SOC estimation information (initial SOC estimation information) corresponding to the actual SOC-OCV curve shown by the line k11 is obtained and stored in the memory 302 in advance by an experiment or the like. Therefore, immediately after the start of use of the battery 100, the ECU 300 estimates the SOC from the OCV of the battery 100 using the SOC estimation information. After that, the ECU 300 estimates the amount of memory based on the SOC 60% (correction reference SOC) using the usage time and usage history of the battery 100, and corrects the initial SOC estimation information (line k11) based on the SOC 60%. .. More specifically, the OCV in the SOC region lower than 60% is lower by the memory amount (estimated value) than in the initial state (line k11), and the OCV in the SOC region higher than 60% is in the initial state (line k11). By making corrections so that the memory amount (estimated value) is higher than that of the line k12, SOC estimation information as shown by the line k12 can be obtained. The OCV of the correction reference SOC (SOC60%) has the same value (both voltage V1) in the SOC estimation information (line k11) before correction and the SOC estimation information (line k12) after correction.

When the battery 100 is used in the SOC frequency distribution shown by the line k21, the actual SOC-OCV curve (line k22) and the corrected SOC estimation information (line k12) substantially match. In the SOC frequency distribution shown by line k21, the frequency is highest at 60% and decreases as the distance from 60% increases. When the battery 100 is used in such an SOC frequency distribution, charging / discharging of the battery 100 is repeated at SOC 60% while the vehicle 1 is running, and a memory effect is likely to occur in the nickel-metal hydride battery in the battery 100 at SOC 60%. .. The SOC estimation information shown by the line k12 is corrected on the precondition that a memory effect occurs in the nickel-metal hydride battery in the battery 100 at SOC 60% (correction reference SOC), so that the actual SOC-OCV curve (line k22) And the corrected SOC estimation information (line k12) generally match.

FIG. 4 is a diagram showing an actual SOC-OCV curve when the battery 100 is used in the second SOC frequency distribution. The second SOC frequency distribution is the SOC frequency distribution shown by the line k31. In addition to charging while the vehicle 1 is running, the SOC frequency distribution of the battery 100 is increased by charging with the engine generated power so that the SOC of the battery 100 becomes 70% (fixed value) while the running of the vehicle 1 is stopped. The SOC frequency distribution was as shown by the line k31.

In FIG. 4, the lines k11, k12, and k21 are the same as the lines k11, k12, and k21 in FIG. 3, respectively. Line k32 shows the actual SOC-OCV curve when the battery 100 is used in the SOC frequency distribution shown by line k31.

With reference to FIG. 4, when the battery 100 is used in the SOC frequency distribution shown by the line k31, the actual SOC-OCV curve (line k32) and the corrected SOC estimation information (line k12) deviate from each other. In the SOC frequency distribution shown by line k31, the frequency is highest at SOCs higher than 60%. When the battery 100 is used in the SOC frequency distribution shown by the line k31, the memory effect is likely to occur in the nickel-metal hydride battery in the battery 100 at SOC 80%. The SOC estimation information shown by the line k12 is corrected on the precondition that a memory effect occurs in the nickel-metal hydride battery in the battery 100 at SOC 60% (correction reference SOC), so that the actual SOC-OCV curve (line k32). And the corrected SOC estimation information (line k12) become divergent. For example, the OCV of 80% SOC is the voltage V3 in the corrected SOC estimation information (line k12), and the voltage V2 is lower than the voltage V3 in the actual SOC-OCV curve (line k32).

As described above, when a memory effect occurs in a nickel-metal hydride battery with SOCm outside the prerequisites, the actual SOC-OCV curve and SOC estimation information (based on the usage time and usage history of the battery 100) due to the occurrence of the memory effect. There will be a discrepancy with the sequentially corrected map), and the SOC estimation accuracy will decrease.

Therefore, in this embodiment, the ECU 300 controls the SOCm of the nickel-metal hydride battery to suppress the occurrence of the memory effect in the SOC outside the precondition. More specifically, when the frequency with which the SOC of the battery 100 is within the target SOC region (for example, SOC 65% to 80%) becomes higher than the boundary value, the ECU 300 sets the charge stop SOC in the target SOCm region (for example). , SOC 60% to 65%), thereby controlling the SOCm of the nickel-metal hydride battery within the target SOCm region.

Hereinafter, the charge control performed by the ECU 300 will be described in detail with reference to FIGS. 5 to 10.
FIG. 5 is a flowchart showing a processing procedure for creating an SOC frequency distribution executed by the ECU 300. The process shown in this flowchart is called from the main routine every predetermined time, for example, and is repeatedly executed.

With reference to FIG. 5, the ECU 300 acquires the current SOC of the battery 100 (step S11). Then, the ECU 300 stores the acquired SOC in the memory 302. An example of the SOC acquisition method is shown below. However, the SOC acquisition method is not limited to the methods shown below and is arbitrary.

The ECU 300 detects the detection value of the voltage sensor 210 (voltage VB indicating the current voltage between terminals of the battery 100), the detection value of the current sensor 220 (current IB indicating the current current of the battery 100), and the temperature sensor 230. The value (temperature TB indicating the current temperature of the battery 100) and the value (temperature TB indicating the current temperature of the battery 100) can be acquired, and the OCV of the battery 100 can be calculated according to the following formula (1).

OCV = VB-IB × R ... (1)
In formula (1), R represents the internal resistance of the battery 100. The ECU 300 can obtain the internal resistance of the battery 100 from the temperature TB by referring to, for example, a map or the like (information indicating the relationship between the internal resistance of the battery 100 and the temperature TB) stored in the memory 302 in advance.

The ECU 300 can acquire the OCV of the battery 100 by the above method. Then, the ECU 300 can estimate the SOC from the OCV of the battery 100 by referring to the SOC estimation information in the memory 302. Although details are omitted, the SOC estimation information in the memory 302 is corrected with SOC 60% as the correction reference SOC. The estimation of the memory amount based on the usage time and usage history of the battery 100 and the correction of the SOC estimation information based on the estimated memory amount are called from the main routine and repeatedly executed every predetermined time.

Next, the ECU 300 updates the SOC frequency distribution in the memory 302 by the SOC acquired in step S11 (step S12). More specifically, on the horizontal axis of the SOC frequency distribution, a plurality of sections (that is, SOC regions) are provided according to the magnitude of the SOC. In step S12, the frequency of the section (SOC region) corresponding to the size of the SOC acquired in step S11 is incremented by 1 (count up). After that, the process is returned to the main routine.

By repeatedly executing the processes of steps S11 to S12, a frequency distribution indicating the occurrence frequency of each section of the SOC of the battery 100 is created. A specific example of the SOC frequency distribution created by the process of FIG. 5 will be described later (see FIG. 9).

FIG. 6 is a flowchart showing a processing procedure of charge control executed by the ECU 300. In the process shown in this flowchart, the engine 20 is driven to raise the water temperature of the cooling water temperature TW and the SOC of the battery 100 is executed when the heating device 3 is performing heating while the vehicle 1 is stopped. It is executed when it is lower than a predetermined value (hereinafter, referred to as "charging start SOC"). The charging start SOC is a lower value than the charging stop SOC.

With reference to FIG. 6, the ECU 300 executes charging of the battery 100 by the engine generated power (step S21). More specifically, by driving the MG 11 with the power output from the driving engine 20, power is generated in the MG 11, and the battery 100 is charged by the generated power.

The ECU 300 determines whether or not the SOC of the battery 100 has reached the charge stop SOC (step S22). More specifically, the ECU 300 reads, for example, the current SOC of the battery 100 acquired by the process of FIG. 5 (step S11) from the memory 302 and compares it with the charge stop SOC. In this embodiment, the initial value of the charge stop SOC is 70%. The charge stop SOC may be changed during charging by the process of FIG. 7 described later.

The ECU 300 continues charging the battery 100 with the engine generated power until it is determined in step S22 that the SOC of the battery 100 has reached the charge stop SOC (steps S21 to S22). That is, while it is determined in step S22 that the SOC of the battery 100 has not reached the charge stop SOC (NO in step S22), the battery 100 is charged by the engine generated power.

When it is determined in step S22 that the SOC of the battery 100 has reached the charge stop SOC (YES in step S22), the ECU 300 controls the PCU 40 and the SMR 50 to stop the charging of the battery 100 by the engine generated power. (Step S23). After that, the process is returned to the main routine.

Even after the charging of the battery 100 is stopped in step S23, the heating by the heating device 3 is continued, the electric power of the battery 100 is consumed by the auxiliary load or the ECU 300 during heating, and the SOC of the battery 100 becomes lower than the charging start SOC. If so, the process of FIG. 6 is executed again.

FIG. 7 is a flowchart showing a processing procedure of the charge stop SOC setting executed by the ECU 300. The process shown in this flowchart is called from the main routine every predetermined time, for example, and is repeatedly executed.

With reference to FIG. 7, in step S31, the ECU 300 determines whether or not charging in step S21 of FIG. 6 is being executed.

In step S32, the ECU 300 determines whether or not a predetermined memory effect generation condition is satisfied. The fact that the memory effect generation condition is satisfied means that the memory effect in the nickel-metal hydride battery in the battery 100 is not saturated. In this embodiment, the memory effect generation condition is satisfied when the integrated mileage of the vehicle 1 is within a predetermined value and the usage time of the battery 100 is within a predetermined value. However, the condition is not limited to this, and the memory effect generation condition can be set arbitrarily.

In step S33, the ECU 300 refers to the SOC frequency distribution in the memory 302 (the SOC frequency distribution created by the process of FIG. 5), and determines whether or not the frequency of the target SOC region is equal to or higher than a predetermined boundary value. FIG. 8 is a diagram showing a target SOC region according to this embodiment.

With reference to FIG. 8, an SOC region of 65% or more and less than 70% (hereinafter referred to as “first SOC region”) and an SOC region of 70% or more and less than 75% (hereinafter referred to as “second SOC region”). , 75% or more and less than 80% of the SOC region (hereinafter referred to as “third SOC region”) is set as the target SOC region. Each of the first to third SOC regions corresponds to a high SOC region.

In this embodiment, a plurality of target SOC regions (first to third SOC regions) are set as described above, and different boundary values are provided for each target SOC region. The boundary values of the first SOC region, the second SOC region, and the third SOC region are the boundary values X _A , X _B , and X _C , respectively.

The number of target SOC regions is not limited to three and can be set arbitrarily. Further, the boundary value of the target SOC region may be a fixed value or may be variable according to the integrated mileage of the hybrid vehicle, the usage time of the nickel hydrogen battery (elapsed time from the start of use), and the like. .. Further, the boundary value of the target SOC region may be set based on the frequency of the SOC region having the highest frequency in the current SOC frequency distribution (hereinafter, may be referred to as “most frequent SOC region”). For example, the boundary value may be set as a ratio to the frequency of the most frequent SOC region, such as 60% of the frequency of the most frequent SOC region.

The first to third SOC regions are set corresponding to the SOC frequency distribution created by the process of FIG. FIG. 9 is a diagram showing an example of the SOC frequency distribution created by the process of FIG.

With reference to FIG. 9, by repeatedly executing the processes of steps S11 to S12 of FIG. 5, for example, the SOC frequency distribution D1 (hereinafter, also simply referred to as “D1”) is created and stored in the memory 302. The SOC frequency distribution in the memory 302 is sequentially updated by the process of FIG. The size of the section of the SOC frequency distribution D1 (width of each SOC region) is 5%, which corresponds to the width of the first to third SOC regions. The width of each SOC region is not limited to 5% and can be set arbitrarily.

In step S33 described above, the ECU 300 determines whether or not the frequency of any of the first to third SOC regions is equal to or higher than the boundary value. For example, when the current SOC frequency distribution in the memory 302 is D1, the frequency of the second SOC region in D1 is higher than the boundary value XB of the second SOC region by the difference _Δd , so that the target SOC region is selected in step S33. It is judged that the frequency is equal to or higher than the boundary value.

With reference to FIG. 7 again, the memory effect generation condition is satisfied during the charging execution in step S21 of FIG. 6, and the frequency of the target SOC region (frequency of any of the first to third SOC regions) is equal to or higher than the boundary value. If it is determined that (YES in all of steps S31 to S33), the process is returned to the main routine after the ECU 300 changes the charge stop SOC in step S34. On the other hand, if NO is set in any of steps S31 to S33, the charge stop SOC is not changed and the process is returned to the main routine.

In step S34, the charging stop SOC is changed by the ECU 300. For example, if the charge stop SOC is 70% (initial value) and the current SOC frequency distribution in the memory 302 is D1 shown in FIG. 9, the charge stop SOC is changed from 70% to 60%. As a result, the frequency of the second SOC region is reduced, and the frequency of the SOC region of 60% or more and less than 65% (hereinafter referred to as “central SOC region”) is increased. In this embodiment, the central SOC region corresponds to the target SOCm region.

FIG. 10 is a diagram showing an example of a change in the SOC frequency distribution due to a change in the charge stop SOC. With reference to FIG. 10, the charge stop SOC is changed from 70% to 60%, the SOC frequency distribution in the memory 302 is reset (the frequency of all SOC regions is set to 0), and then the step of FIG. 5 is performed. By repeatedly executing the processes S11 to S12, for example, the SOC frequency distribution D2 is created. In the SOC frequency distribution D1 shown in FIG. 9, when the frequency of the second SOC region decreases by the difference Δd and the frequency of the central SOC region increases by the difference Δd, the SOC frequency distribution D2 is obtained.

By changing the charge stop SOC from 70% to 60% during charging in step S21 of FIG. 6, in the nickel-metal hydride battery in the battery 100, in the target SOC region (SOC region of 65% or more and less than 80%). The memory effect is less likely to occur, and the memory effect near SOC 60% is more likely to occur. That is, the SOCm can be controlled to around 60% by changing the charge stop SOC as described above. As a result, the discrepancy between the actual SOC-OCV curve of the battery 100 and the current SOC estimation information (sequentially corrected map) in the memory 302 is suppressed, and the SOC of the battery 100 can be measured with high accuracy using the SOC estimation information. It becomes possible to estimate.

As described above, according to the hybrid vehicle control device (ECU 300) according to this embodiment, for example, when the battery 100 is charged while the vehicle 1 is stopped, the target SOC in the nickel-metal hydride battery in the battery 100 is used. It is possible to suppress the occurrence of a memory effect in an area (for example, a high SOC area). Further, by performing the process shown in FIG. 7, the SOCm of the nickel-metal hydride battery in the battery 100 is controlled in the target SOCm region, and the memory effect is generated in the SOC outside the prerequisites in the nickel-metal hydride battery. It will be suppressed.

In the above embodiment, a high SOC region (first to third SOC regions) is adopted as the target SOC region. Then, the ECU 300 makes the charge stop SOC when the frequency of the target SOC region is higher than the boundary value lower than the charge stop SOC (70%) when the frequency of the target SOC region is lower than the boundary value (more specific). The target is changed to 60%). However, the present invention is not limited to this, and the target SOC region may be an SOC region other than a high SOC region.

Further, in a nickel-metal hydride battery in which gas is likely to be generated in the battery case due to the memory effect occurring at a specific SOCm, the specific SOC region may be adopted as the target SOC region. By doing so, the rise in the battery internal pressure is suppressed, and the battery usage range is expanded. In addition, the life of the battery can be extended by suppressing the increase in the internal pressure of the battery.

In the above embodiment, the frequency of each SOC region is constantly detected by the process of FIG. However, the present invention is not limited to this, and the period for detecting the frequency for each SOC region (hereinafter, may be referred to as “SOC frequency detection period”) can be arbitrarily set. For example, the SOC frequency detection period may be limited to the travel stop period of the vehicle 1 (the period from the stop of travel to the start of travel again).

The SOC frequency distribution in the memory 302 may be reset (initialized) at a predetermined timing. As an example of the timing to reset the SOC frequency distribution, when the SOC frequency detection period ends, refresh charge / discharge (refresh charge or refresh discharge to eliminate the memory effect generated in the nickel hydrogen battery) is executed in the nickel hydrogen battery. The timing was given. At the timing when the nickel-metal hydride battery is refreshed / charged / discharged, the SOC frequency distribution may be reset and the charge stop SOC may be returned to the initial value.

It is not essential to reset the SOC frequency distribution. For example, the frequency of each SOC area in the SOC frequency distribution is continuously counted without resetting the SOC frequency distribution in the memory 302, and as the number of data in the SOC frequency distribution increases (or the frequency of the most frequent SOC area increases). (As it becomes), the boundary value of the target SOC region may be increased. Further, the boundary value of the target SOC region may be determined by the ratio to the frequency of the most frequent SOC region. Further, a relative frequency (ratio to the total frequency) may be adopted as the frequency.

In the above embodiment, the engine power generation is performed when the heating is executed while the vehicle 1 is stopped, but the engine power generation may be performed while the vehicle 1 is running (including when the vehicle 1 is running with a low load). For example, while the vehicle 1 is running, the heating device 3 is controlled to perform heating in the vehicle interior 500, the battery 100 is charged by the engine generated power during the heating, and the SOC of the battery 100 is charged during the charging. May stop charging when the charging stop SOC is reached.

The configuration of the hybrid vehicle is not limited to the configuration shown in FIG. 1, and can be appropriately changed. Further, the target for detecting OCV and SOC can be arbitrarily changed as long as the nickel-metal hydride battery is included. For example, a predetermined cell (one or a plurality of cells 101) included in the assembled battery of the battery 100 may be targeted. Further, the voltage sensor 210 may be provided so as to detect the voltage of each cell 101 or the voltage of each of a plurality of cells 101 connected in series. Further, the temperature sensor 230 may be provided so as to detect the temperature of each cell 101 or the temperature of each of a plurality of adjacent cells 101. Further, the SOC estimation method is arbitrary, and a method based on current value integration (coulomb count) can also be adopted. Further, the nickel-metal hydride battery to be the target of charge control is not limited to the assembled battery, and may be a single battery.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the scope of claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 vehicle, 2 battery system, 3 heating device, 11, 12 MG, 20 engine, 30 drive wheel, 31 power splitting device, 32 drive shaft, 40 PCU, 50 SMR, 100 battery, 101 cell, 102 case, 103 gas discharge Valve, 104 electrode body, 210 voltage sensor, 220 current sensor, 230 temperature sensor, 300 ECU, 301 CPU, 302 memory, 401 heat exchanger, 402 blower, 403 switching device, 410 water temperature sensor, 420 outside temperature sensor, 430 Vehicle interior sensor, 440 input device, 500 vehicle interior.

Claims (1)

With an internal combustion engine
Nickel-metal hydride batteries and
A control device that uses the power output from the internal combustion engine to generate electricity to charge the nickel-metal hydride battery, and stops the charging when the SOC of the nickel-metal hydride battery becomes a charge stop SOC during the charging. When,
Equipped with
When the frequency with which the SOC of the nickel-metal hydride battery is within the predetermined SOC region is lower than the predetermined value, the charge stop SOC is within the predetermined SOC region.
A hybrid vehicle in which the control device changes the charge stop SOC to an SOC outside the predetermined SOC region when the frequency is higher than the predetermined value.

Images