JP6587338B2 - Electric vehicle control device and vehicle battery control method - Google Patents

Description

  The present invention relates to a control device for an electric vehicle provided with a battery in which power generation elements are accommodated in a plurality of accommodating portions, and a method for controlling the vehicle battery.

  Conventionally, as an electric vehicle, a motor generator is connected to an output shaft of an engine via a clutch, and the rotational driving force of the motor generator is transmitted as a drive output to a transmission, and the drive output of the transmission is transmitted from a differential gear. Hybrid vehicles having a structure for transmitting to a drive axle are known. Such a hybrid vehicle travels by the rotational driving force of either one or both of the engine and the motor generator, and at the time of deceleration, the motor generator acts as a generator that recovers the kinetic energy of the vehicle as electric energy. is there.

  Since such a hybrid vehicle runs the vehicle not only in the engine but also in the motor generator, a relatively large capacity battery is mounted to drive the motor generator. Conventionally, nickel-metal hydride secondary batteries have been used for the batteries used in this hybrid vehicle, and this nickel-metal hydride secondary battery has a battery case provided with a plurality of accommodating portions, and each of the accommodating portions has a power generation element. (For example, refer to Patent Document 1).

  And, in the case of a battery used in a hybrid vehicle such as this nickel-metal hydride secondary battery, its temperature rises by repeated charging and discharging, and the electrical characteristics deteriorate when it deviates from a predetermined battery proper temperature range. There are many things to do. For this reason, in the control apparatus used for the conventional hybrid vehicle which is an electric vehicle, it controls so that charging / discharging of a battery may be performed within the range of permissible electric power of charging / discharging determined for every battery temperature. Yes.

  In addition, in the nickel metal hydride secondary battery in Patent Document 1, it is known that gas is generated from each of the power generation elements housed in the plurality of housing portions, and by providing a safety valve in the battery case, the gas is generated from the power generation element. Even when the internal pressure of the housing portion rises abnormally due to the occurrence of gas, gas is released through the safety valve to prevent deformation or breakage of the housing portion.

JP 2008-311015 A

  However, in nickel-metal hydride secondary batteries conventionally used as hybrid vehicle batteries, when oxygen gas is generated from each power generation element due to polarization of the power generation elements, the partial pressure of the generated oxygen is Cause different phenomena.

  That is, if the amount of oxygen gas generated from each power generation element is different, even if the internal pressure of each storage part is the same, the oxygen gas partial pressure in each storage part is kept constant. The oxygen gas moves from the part to the accommodating part having a low oxygen partial pressure. Then, in the power generation element of the housing part into which oxygen gas has been transferred from another housing part, the hydrogen gas provided as the discharge reserve is consumed by this oxygen gas (recombined into water), and this power generating element (negative electrode) The discharge reserve amount is reduced, and the discharge reserve variation that the discharge reserve amount is different for each power generation element divided into the respective accommodating portions is caused. And if this reserve dispersion | variation expands, the malfunction which a capacity | capacitance degradation will produce will be produced.

  In order to reduce such discharge reserve variation, in the nickel metal hydride secondary battery in Patent Document 1, communication holes are provided in the partition walls that partition the storage parts, and the size of the communication holes is made appropriate so that the space between the storage parts is reduced. The movement of oxygen gas is suppressed, and the discharge reserve variation between the power generation elements is reduced by taking structural measures.

  On the other hand, in recent years, battery performance has been improved, and it has been studied to increase the allowable power for charging / discharging determined for each battery temperature to improve the output of the battery. In order to achieve the recent demand for improving the output of such a battery, when the allowable power for charging determined for each battery temperature is increased, the amount of oxygen gas generated from each power generation element may also increase. is expected.

  Also, the cause of the progress of the reserve variation is not limited to this increase in charging power, but the reserve variation also progresses even when charging at low power for a long time, so depending on the state of charge, only measures from the structural aspect of the battery Then, the malfunction which becomes difficult to fully suppress discharge reserve dispersion | variation is produced.

  An object of the present invention is to provide a control device for an electric vehicle and a vehicle that can prevent variation in the amount of oxygen gas generated between the power generation elements housed in a plurality of housing portions in the battery from the point of control, and suppress variation in discharge reserve. A battery control method is provided.

  As a result of diligent research, the present inventor has found that the electromotive force in the battery is an important factor in the generation of oxygen gas, and has come to the present invention.

  That is, the present invention is an improvement of a control device for an electric vehicle provided with a battery in which power generation elements are housed in a plurality of housing portions.

  The characteristic configuration is that when the internal resistance of the battery is R, the terminal voltage of the battery is V, the current flowing through the battery is I, and the electromotive force of the battery calculated in V + (I × R) is E, The power is monitored and charging of the battery is controlled so that the electromotive force E does not exceed a predetermined upper limit value.

  Another aspect of the present invention is an improvement in a method for controlling an automotive battery in which power generation elements are housed in a plurality of housing portions.

  The characteristic point is that when the internal resistance of the battery is R, the terminal voltage of the battery is V, the current flowing through the battery is I, and the electromotive force of the battery calculated in V + (I × R) is E, The power is monitored and charging of the battery is controlled so that the electromotive force E does not exceed a predetermined upper limit value.

  Here, the predetermined upper limit value in these inventions is preferably determined by the temperature of the battery and the current flowing through the battery.

  In the electric vehicle control device and the vehicle battery control method of the present invention, the electromotive force of the battery, which is considered to be an important factor for the generation of oxygen gas, is monitored, and the electromotive force is a predetermined value that causes a variation in the amount of oxygen gas generation. Since the charging of the battery is controlled so as not to exceed the upper limit value, even if oxygen gas is generated from each of the power generation elements stored in the plurality of storage units, it is possible to prevent the amount of generated oxygen gas from varying. it can. As a result, it is possible to suppress variation in the discharge reserve from the viewpoint of control, and it is possible to make maximum use of the battery while suppressing capacity deterioration.

  If the predetermined upper limit value is determined by the battery temperature and the current flowing through the battery, it is possible to suppress the variation in oxygen gas generation for each battery temperature, and to reduce the allowable power for charging the battery. It becomes possible to expand sufficiently.

1 is a block configuration diagram of a hybrid vehicle according to an embodiment of the present invention. It is a figure which shows the predetermined | prescribed upper limit which controls charge of the battery. It is a figure which shows the relationship between the electromotive force and oxygen gas generation rate for every electric current. It is a figure which shows the procedure which derives | leads-out the predetermined | prescribed upper limit. It is a figure which shows the relationship between the electromotive force of a battery of a certain temperature, and oxygen gas generation speed. It is a schematic diagram which shows the structure of the battery.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating an example of a configuration of a hybrid vehicle 1 that is an electric vehicle. The hybrid vehicle 1 includes an engine 10 that generates power for running the hybrid vehicle 1, a motor generator 13 connected to the engine 10 via a clutch 12, and a transmission 16 connected to the motor generator 13.

  The engine 10 is an example of an internal combustion engine, and generates power to drive the hybrid vehicle 1 by internally burning gasoline, light oil, CNG (Compressed Natural Gas), LPG (Liquefied Petroleum Gas), or alternative fuel. Configured as follows. In the figure, the engine 10 is a diesel engine using light oil as a fuel, and reference numeral 10a indicates a fuel injection device 10a that injects light oil that is the fuel.

  The clutch 12 is exemplified as one that is mechanically controlled by the clutch booster 22 in accordance with the hydraulic pressure controlled by the clutch actuator 21. A motor generator 13 is connected to the engine 10 via the clutch 12, and the transmission 16 further connected to the motor generator 13 is a semi-automatic one. The clutch 12 is configured to transmit the shaft output from the engine 10 to the wheel 1 c via the transmission 16. That is, the clutch 12 is configured to connect the engine 10 and the transmission 16 to run the hybrid vehicle 1.

  The motor generator 13 is a so-called motor generator that generates power for rotating the shaft by the electric power supplied from the inverter 14 and supplies the shaft output to the transmission 16 to drive the hybrid vehicle 1. Alternatively, the power is generated by the power that rotates the shaft supplied from the transmission 16 due to the traveling of the hybrid vehicle 1 or the power that is directly supplied from the engine 10, and the power is supplied to the inverter 14.

  The hybrid vehicle 1 includes a battery 15, and the inverter 14 converts DC power from the battery 15 into AC power, or converts AC power generated by the motor generator 13 into DC power. When the motor generator 13 generates power, the inverter 14 converts the DC power of the battery 15 into AC power, supplies the motor generator 13 with power, and when the motor generator 13 generates power, the inverter 14 The AC power from the motor generator 13 is configured to be converted into DC power. That is, the inverter 14 serves as a rectifier and a voltage regulator for supplying DC power to the battery 15.

  The battery 15 is a chargeable / dischargeable secondary battery. When the motor generator 13 generates power, the battery 15 supplies power to the motor generator 13 via the inverter 14 or the motor generator 13 generates power. When the motor generator 13 is in operation, it is charged by the electric power generated by the motor generator 13. The battery in this embodiment is a nickel hydride secondary battery 15 conventionally provided. The nickel hydride secondary battery 15 is provided with a plurality of accommodating portions 15b partitioned by a partition wall 15c in a battery case 15a. Each of the accommodating portions 15b accommodates a power generation element 15d including a positive electrode 15e and a negative electrode 15f.

  The hybrid vehicle 1 is also provided with a cooling device (not shown) for cooling the battery 15 because the amount of power generated by the motor generator 13 is large.

  In addition, the hybrid vehicle 1 is provided with a control device 2 that controls the engine 10 and the clutch 12 to run the hybrid vehicle 1. The control device 2 in this embodiment includes an engine ECU 11 that controls the engine 10 in accordance with a driver request torque obtained from the depression amount of the accelerator pedal 3, a hybrid ECU 17 that controls the motor generator 13 via an inverter 14, and a battery ECU 23. And at least.

  Here, the engine ECU 11 that controls the engine 10 and the hybrid ECU 17 that controls the motor generator 13 cause the engine 10 and the motor generator 13 to output torque equal to the driver request torque obtained from the depression amount of the accelerator pedal 3. In that respect, the driving power control means 19 is configured.

  An engine ECU 11 that controls the engine 10 is a so-called computer configured by a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a microprocessor (microcomputer), a DSP (Digital Signal Processor), and the like. , An arithmetic unit, a memory, an I / O (Input / Output) port, and the like are provided.

  The engine ECU 11 is connected to a detection output of an accelerator sensor 4 that detects the amount of depression of the accelerator pedal 3, and the control output of the engine ECU 11 is connected to a fuel injection device 10 a of the engine 10. The engine ECU 11 is configured to control the engine 10 such as a fuel injection amount and a valve timing in accordance with a driver request torque required from a depression amount of the accelerator pedal 3.

  The hybrid ECU 17 that constitutes the traveling power control means 19 together with the engine ECU 11 is a computer that operates in cooperation with the engine ECU 11, and is configured to control the motor generator 13 by controlling the inverter 14. When the accelerator pedal 3 is not depressed, the motor generator 13 is driven by the power supplied from the transmission 16 due to the traveling of the hybrid vehicle 1 to generate power, and the electric power obtained by the power generation is The battery 15 is configured to be charged.

  The hybrid ECU 17 is an example of a computer, and includes a CPU, an ASIC, a microprocessor (microcomputer), a DSP, and the like, and includes an arithmetic unit, a memory, an I / O port, and the like.

  The battery ECU 23 is connected to the battery 15, and the battery 15 is connected to the hybrid ECU 17 via the battery ECU 23. The battery ECU 23 detects the temperature of the battery 15 and the current value at the time of charging / discharging and outputs the detected value to the hybrid ECU 17, and the battery 15 within the allowable charging / discharging power range determined for each temperature of the battery 15. The battery 15 is managed so as to be charged and discharged.

  The battery ECU 23, the engine ECU 11, and the hybrid ECU 17 are connected to each other by a bus that complies with a standard such as CAN (Control Area Network) together with other control devices (not shown). The program executed by the hybrid ECU 17 is stored in advance in a non-volatile memory inside the hybrid ECU 17 so that the program is installed in advance in the hybrid ECU 17 that is a computer.

  The hybrid ECU 17 acquires the accelerator opening information, the brake operation information, the vehicle speed information, the gear position information acquired from the transmission 16, the engine rotation speed information acquired from the engine ECU 11, and the acquired accelerator opening for the hybrid traveling. The inverter 14 is controlled based on the degree information and other information, and a control instruction for the engine 10 is given to the engine ECU 11. Accordingly, the hybrid vehicle 1 is configured to run or stop.

  In the electric vehicle control device and the vehicle battery control method of the present invention, the electromotive force E of the battery 15 is calculated and monitored from the current I of the battery 15 detected by the battery ECU 23, and the electromotive force E is calculated. The charging of the battery 15 is controlled so as not to exceed a predetermined upper limit value.

  That is, as shown in FIG. 6, since the battery 15 has the internal resistance R, the battery 15 can be divided into the internal resistance R and the power generator M. Here, considering the generation of oxygen gas from each of the power generation elements 15d (FIG. 1) accommodated in the plurality of accommodating portions 15b of the battery 15, since the generation of oxygen gas is caused by electrolysis, the internal resistance R It is considered that the electromotive force E in the power generator M affects the oxygen gas generation without affecting the oxygen gas generation.

  For this reason, assuming that the internal resistance of the battery 15 is R, the terminal voltage of the battery 15 is V, and the current flowing through the battery 15 during charging / discharging is I, the electromotive force E in the power generator M is obtained by V + (I × R). . When the electromotive force is E, the control device 2 of the electric vehicle monitors the electromotive force E of the battery 15 and generates oxygen gas generated from each power generation element 15d accommodated in the plurality of accommodating portions 15b. The charging of the battery 15 is controlled so that the electromotive force E does not exceed a predetermined upper limit value determined as the limit electromotive force E considered to vary in quantity.

  Accordingly, the predetermined upper limit value is determined as a limit electromotive force E that is considered to cause the amount of oxygen gas generated from each power generation element 15 d to vary when the upper limit value is exceeded, and is determined individually by the battery 15. An example of the predetermined upper limit value is shown in FIG. As described above, the predetermined upper limit value shown in FIG. 2 is determined as the limit electromotive force E that is considered to vary in the amount of oxygen gas generated from each power generation element 15d accommodated in the plurality of accommodating portions 15b. FIG. 2 shows that a predetermined upper limit value (electromotive force) determined by the current I flowing through the battery 15 is determined for each temperature of the battery 15.

  Then, by controlling so that the electromotive force E does not exceed such a predetermined upper limit value, it is possible to prevent the amount of oxygen gas generated from each of the power generation elements 15d accommodated in the plurality of accommodating portions 15b from varying. Thus, it becomes possible to suppress the discharge reserve variation for each power generating element 15d.

  Here, although the predetermined upper limit value is individually determined by the battery 15, an example of how to obtain the predetermined upper limit value shown in FIG. 2 will be described.

  That is, the generation of oxygen gas from each power generation element 15d is considered to be generated by electrolysis of water in the electrolytic solution, and it is known that the general redox potential of water is 1.229V. On the other hand, as shown in FIG. 5, oxygen gas is not generated immediately even if the electromotive force E of the battery 15 exceeds this oxidation-reduction potential due to an additive to the electrode or the like. However, it is known that the generation rate of the oxygen gas significantly increases after the electromotive force E of the battery 15 exceeds the oxidation-reduction potential.

  Here, considering the suppression of the discharge reserve variation in each power generation element 15d (FIG. 1) accommodated in the plurality of accommodation portions 15b, which is the object of the present invention, each power generation element separately accommodated in the plurality of accommodation portions 15b. Oxygen gas is generated separately from 15d, and if there is a variation in their amounts, the variation in discharge reserve will be significant. Therefore, in order to achieve this object, oxygen gas is not generated from each power generation element 15d accommodated in the plurality of accommodating portions 15b, or even if oxygen gas is generated, the amount of oxygen gas generated It is considered effective as a countermeasure to suppress the variation of the above.

  Considering the oxygen gas generation rate in the oxygen gas generation region shown in FIG. 5, as described above, the oxygen gas generation rate increases remarkably as the electromotive force E increases. For this reason, in the oxygen gas generation region, even if there is a variation ΔE1 in the electromotive force E of each power generation element 15d of the battery 15, at a low value of the electromotive force E, the oxygen gas generation rate is small. The difference ΔA generated in the amount of oxygen gas generated between the power generation elements 15d is small. However, when the electromotive force E of each power generation element 15d of the battery 15 is high, the oxygen gas generation speed is fast, and therefore, only a slight difference ΔE2 occurs in the electromotive force E, and the oxygen gas generated between the power generation elements 15d. The difference ΔB that occurs in the quantity increases.

  Then, the reserve variation proceeds in a region where the oxygen gas generation rate is high where the difference in the amount of oxygen gas generated between the power generation elements 15d becomes large, and a predetermined variation before reaching the region where the oxygen gas generation rate is high is reached. It is necessary not to exceed the value C. Thereby, even if oxygen gas is generated from each power generation element 15d accommodated in the plurality of accommodating portions 15b, variation in the amount of oxygen gas generated between the power generation elements 15d is suppressed, and as a result, discharge reserve variation is reduced. It is thought that it can be suppressed.

  Therefore, as shown in FIG. 3, the electromotive force E of the battery 15 is taken on the horizontal axis, the oxygen gas generation rate is taken on the vertical axis, and the electromotive force E and the oxygen gas generation rate at a plurality of current I values flowing through the battery 15 are The relationship is obtained for each temperature of the battery 15. FIG. 3 shows a case where the temperature of the battery 15 is a certain temperature and is drawn on the front surface. Then, from the obtained relationship diagram, a predetermined value C with a low oxygen gas generation amount that can suppress variation in the amount of oxygen gas generated between the respective power generation elements 15d is determined, and a predetermined upper limit value is obtained from this relationship diagram. .

  FIG. 4 shows a procedure for obtaining a predetermined upper limit value. Here, FIG. 4A shows the vicinity of the predetermined value C in the diagram showing the relationship between the electromotive force and the oxygen gas generation rate shown in FIG. 3, and the predetermined value C where the amount of generated oxygen gas is low. 4A is converted, and as shown in FIG. 4B, the electromotive force E of the battery 15 is taken on the horizontal axis, and the current I value flowing through the battery 15 is taken on the vertical axis. Then, the relationship between the electromotive force E and the current I for generating the oxygen gas generation rate having a predetermined value C is obtained. FIG. 4B shows a case where the temperature of the battery 15 is a certain temperature, and this is obtained for each temperature of the battery 15.

  FIG. 2 is a graph showing the relationship between the electromotive force E and the current I generated in the battery 15 at each temperature determined in this way. The electromotive force E in this graph is the temperature of the battery 15 and the battery 15. This represents a predetermined upper limit value of the electromotive force E obtained for each flowing current I.

  Then, the graph shown in FIG. 2 is stored in the memory of the control device 2, and the control device 2 compares the temperature of the battery 15 and the current I flowing through the battery 15 with this graph, and the electromotive force E with respect to the temperature and current I. Is determined, and charging of the battery 15 is controlled so that the electromotive force E of the battery 15 does not exceed the predetermined upper limit value.

  In this embodiment, the battery 15 is managed by the battery ECU 23 that constitutes the control device 2 according to the charge / discharge allowable power determined for each temperature, and the graph shown in FIG. The hybrid ECU 17 calculates and monitors the electromotive force E of the battery 15 from the temperature and current I of the battery 15 provided from the battery ECU 23 and is monitored so that the electromotive force E does not exceed a predetermined upper limit value. It is assumed that charging of the battery 15 is controlled.

  Therefore, the battery ECU 23 in this embodiment includes an electromotive force calculation means for calculating the electromotive force E of the battery 15 from the temperature and current I of the battery 15 provided from the battery ECU 23, and the electromotive force E obtained thereby is Control means for controlling charging of the battery 15 so as not to exceed a predetermined upper limit value that causes variation in the amount of oxygen gas generation in the power generation element 15d is configured.

  Thus, if the hybrid ECU 17 is controlled so that the electromotive force E of the battery 15 does not exceed a predetermined upper limit value, a control device for a conventional electric vehicle can be realized by simply correcting the control of the hybrid ECU 17. It becomes possible to change easily to the control apparatus 2 of invention.

  In the electric vehicle control device and the vehicle battery control method of the present invention, the battery 15 is charged so that the electromotive force E does not exceed a predetermined upper limit value that causes variation in the amount of oxygen gas generated in each power generation element 15d. Therefore, it is possible to prevent the amount of oxygen gas generated from each of the power generation elements 15d accommodated in the plurality of accommodation portions 15b from varying, and to suppress variation in discharge reserve for each power generation element 15d. It is.

  As described above, when the reserve variation is suppressed according to the present invention, the allowable charge / discharge power determined for each temperature can be increased, and the range in which the battery ECU 23 limits the charge by the power of the battery 15 can be expanded. Thus, the battery 15 can be utilized to the maximum while suppressing the capacity deterioration.

  In the above-described embodiment, the case where the hybrid ECU 17 performs control so that the electromotive force E of the battery 15 does not exceed a predetermined upper limit value has been described, but this control may be performed by another ECU. .

  In the above-described embodiment, the terminal voltage V and the electromotive force E are monitored and restricted in the entire battery 15, but the power generation element 15d including the positive electrode 15e and the negative electrode 15f accommodated in each of the accommodation portions 15b. In each unit, the terminal voltage V and the electromotive force E may be monitored and limited. Moreover, you may make it monitor and restrict | limit the terminal voltage V and the electromotive force E by another unit, such as a module, as needed.

  In the above-described embodiment, the case where the electric vehicle is the hybrid vehicle 1 including the engine 10 and the motor generator 13 has been described. However, the electric vehicle may be an electric vehicle that does not include an engine as long as it includes the battery 15 in which the power generation elements 15d are accommodated in the plurality of accommodating portions 15b.

  Even if the electric vehicle is the hybrid vehicle 1 including the engine 10 and the motor generator 13, the hybrid vehicle 1 in which the engine 10 is connected to the motor generator 13 via the clutch 12 in the above-described embodiment. Illustrated. However, the arrangement of the engine 10 and the motor generator 13 is not limited to this as long as the batteries 15 in which the power generation elements 15d are respectively housed in the plurality of housing portions 15b are provided. For example, a hybrid vehicle in which the clutch 12 is not provided between the engine 10 and the motor generator 13 may be used.

  Furthermore, in the above-described embodiment, the case where the battery is the nickel hydride secondary battery 15 provided conventionally has been described. However, as long as the reserve variation due to the generation of oxygen gas occurs, the battery is the nickel hydride secondary battery 15. The present invention is not limited to this, and other alkaline secondary batteries may be used.

DESCRIPTION OF SYMBOLS 1 Hybrid vehicle 2 Control apparatus 15 Battery 15b Housing | casing part 15d Power generation element

Claims (2)

In a control device for an electric vehicle including a battery (15) in which a power generation element (15d) is housed in a plurality of housing portions (15b),
The internal resistance of the battery (15) is R, the terminal voltage of the battery (15) is V, the current flowing through the battery (15) is I, and the start of the battery (15) determined by V + (I × R). When the power is E,
The so as not to exceed a predetermined upper limit value determined by the current (I) flowing through the temperature and the battery (15) of the electromotive force E of the above electromotive force E by monitoring a battery (15) of the battery (15) A control device for an electric vehicle, characterized by controlling charging of a battery (15). In the vehicle battery control method in which the power generation element (15d) is accommodated in each of the plurality of accommodating portions (15b),
The internal resistance of the battery (15) is R, the terminal voltage of the battery (15) is V, the current flowing through the battery (15) is I, and the electromotive force of the battery (15) obtained by V + (I × R) Is E,
The electromotive force E of the battery (15) is monitored so that the electromotive force E does not exceed a predetermined upper limit value determined by the temperature of the battery (15) and the current (I) flowing through the battery (15). A method for controlling an automotive battery, comprising: controlling charging of the battery (15).

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