JP3959815B2 - Battery charge detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery charge amount detection device that detects a charge amount of a secondary battery.
[0002]
[Prior art]
An electric vehicle (including a hybrid vehicle) that obtains all or part of the vehicle driving force by an electric motor is equipped with a secondary battery (hereinafter simply referred to as a battery), and the electric motor stores the electric motor using electric power stored in the battery. Is driving. A function unique to such an electric vehicle is regenerative braking. In regenerative braking, when the vehicle is braked, the motor is functioned as a generator to convert the kinetic energy of the vehicle into electrical energy and perform braking. In addition, the obtained electric energy is stored in the battery and reused when accelerating. Therefore, according to regenerative braking, it is possible to reuse the energy that has been dissipated in the atmosphere as thermal energy in a vehicle that runs only with a conventional internal combustion engine, which can greatly improve energy efficiency. it can.
[0003]
Here, in order to store the electric power generated during the regenerative braking effectively in the battery, the battery needs to have enough margin. Moreover, in a hybrid vehicle of a type that can generate electric power by driving a generator with an on-board heat engine and charge the battery, the electric power stored in the battery, that is, the amount of electricity stored can be freely controlled. . Therefore, in the hybrid vehicle as described above, the amount of electricity stored is in a fully charged state (100 so that the amount of electricity stored in the battery can be received regenerative power, and power can be supplied to the motor as soon as required. %) And a state in which no power is stored (0%), it is desirable to control the vicinity of approximately the middle, for example, 50 to 60%. Therefore, it is necessary to accurately detect the charged amount of the battery.
[0004]
The relationship between the storage amount (SOC) of such a battery, for example, a nickel metal hydride battery, and the terminal voltage has characteristics as shown in FIG. In FIG. 6, in the region where the SOC is slightly higher than 20% to slightly lower than 80%, the terminal voltage hardly changes, and this change cannot be detected from the outside. On the other hand, when the SOC is lower than this including about 20% or higher than this including about 80%, if the SOC changes, this change appears as a change in the terminal voltage. This change can be detected from the outside of the battery. Therefore, when the SOC is about 20% or less and about 80% or more, the SOC can be calculated based on the terminal voltage and the current flowing through the battery. A method for calculating the SOC based on the terminal voltage and current is hereinafter referred to as IV determination, and this region is referred to as an IV determination region. On the other hand, in the region where the SOC is between about 20% and about 80%, the change in the terminal voltage cannot be detected from the outside, so it is necessary to estimate the SOC by integrating the current flowing through the battery.
[0005]
In a hybrid vehicle, charging / discharging of the battery is repeated, and the SOC of the battery changes every moment. Normally, the SOC is sequentially accumulated with respect to the initial value, and is estimated as the SOC at that time. In this integration, calculation is performed with the current during charging as positive and the current during discharge as negative. This estimated value deviates from the actual SOC due to the fact that the charging efficiency changes due to environmental conditions such as temperature, and self-discharge such as when left for a long time.
[0006]
In order to correct this deviation, the SOC is calculated based on the terminal voltage and the current flowing through the battery, and if it is estimated that the calculated SOC has entered the IV determination region, the estimated value of the SOC is corrected. In this correction, when the SOC decreases and reaches 20%, the estimated value of SOC is set to 20%, and when the SOC increases and reaches 80%, the estimated value of SOC is set to 80%.
[0007]
The SOC detection method as described above is disclosed in, for example, Japanese Patent Laid-Open No. 6-59003.
[0008]
[Problems to be solved by the invention]
However, in the conventional SOC detection method, the estimated SOC value is corrected at predetermined time intervals while the SOC is in the IV determination region. As described above, this correction is fixed at 20% or 80% even when the actual SOC is 20% or less or 80% or more due to charging / discharging of the battery. Therefore, there is a problem that the actual SOC and the estimated value are shifted by the correction.
[0009]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a battery storage amount detection device with high detection accuracy of a battery storage amount.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problem, a battery storage amount detection device according to the present invention includes a storage amount detection unit that detects a storage amount of a secondary battery based on a voltage and a current that can be detected from the outside, and a storage amount detection unit. Detection is performed , the amount of charge of the secondary battery is calculated based on the voltage and current, and the voltage of the secondary battery is compared with the region where the voltage of the secondary battery does not change due to the change in the amount of charge of the secondary battery. A battery storage amount detection device including a region definition means for defining a region having a large change , and when the detection by the storage amount detection means is performed, the secondary battery of the secondary battery defined by the region definition means Confirmation that a sufficient amount of charge or discharge has been performed to escape from the region where the secondary battery voltage change is large compared to the region where the secondary battery voltage does not change due to the change in the storage amount Means and confirmation by confirmation means It is characterized by and a prohibiting means for prohibiting the detecting operation by the charged amount detection means.
[0012]
Further, in the battery storage amount detection device, the storage amount detection means further dT / dt characteristics (T is the battery temperature, t is time) characterized by utilizing.
[0013]
Further, in the battery storage amount detection device, the confirmation unit confirms a predetermined amount of charge or discharge by current integration.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. FIG. 1 shows a schematic diagram of a power plant of a vehicle on which the charge control device of the present invention is mounted. A planetary carrier 20 that supports a planetary gear 18 of the planetary gear mechanism 16 is connected to the output shaft 12 of the engine 10 via a torsion damper 14. The sun gear 22 and the ring gear 24 of the planetary gear mechanism 16 are connected to the rotors 30 and 32 of the first motor generator 26 and the second motor generator 28, respectively. The first and second motor generators 26 and 28 function as a three-phase AC generator or a three-phase AC motor. A power take-out gear 34 is further connected to the ring gear 24. The power take-out gear 34 is connected to a differential gear 40 via a chain 36 and a gear train 38. Connected to the output side of the differential gear 40 is a drive shaft 42 to which a driving wheel (not shown) is coupled at the tip. With the above structure, the output of the engine 10 or the first and second motor generators 26 and 28 is transmitted to the drive wheels to drive the vehicle.
[0015]
The engine 10 has its output, rotational speed, and the like controlled by the engine ECU 46 based on the operation amount of the accelerator pedal 44, environmental conditions such as cooling water temperature and intake pipe negative pressure, and the operating states of the first and second motor generators 26 and 28. Be controlled. The first and second motor generators 26 and 28 are controlled by the control device 48. The control device 48 includes a battery (secondary battery) 50 that supplies electric power to the two motor generators 26 and 28 and receives electric power therefrom. In the present embodiment, the battery 50 is a nickel metal hydride battery. Power exchange between battery 50 and first and second motor generators 26 and 28 is performed via first and second inverters 52 and 54, respectively. The control of the two inverters 52 and 54 is performed by the control CPU 56, and this control is determined by the information on the operating state of the engine 10 from the engine ECU 46, the operation amount of the accelerator pedal 44, the operation amount of the brake pedal 58, and the shift lever 60. Shift range, battery storage state, planetary gear mechanism 16 sun gear rotation angle θs, planetary carrier rotation angle θc, ring gear rotation angle θr, and the like. The rotation angles of the three elements of the planetary gear mechanism 16 are detected by a planetary carrier resolver 62, a sun gear resolver 64, and a ring gear resolver 66, respectively. The battery ECU 68 calculates the electric power stored in the battery, that is, the charged amount. The control CPU 56 supplies or supplies the above-mentioned conditions, the u-phase and v-phase currents Iu1, Iv1, Iu2, and Iv2 of the first and second motor generators 26 and 28, and the battery or the other inverter. Based on L1, L2, etc., the transistors Tr1 to Tr6 and Tr11 to Tr16 of the first and second inverters 52 and 54 are controlled.
[0016]
The planetary gear mechanism 16 has a sun gear rotation speed Ns, a planetary carrier rotation speed Nc, and a ring gear rotation speed Nr as the gear ratio ρ of the sun gear and the ring gear.
[Expression 1]
Ns = Nr− (Nr−Nc) (1 + ρ) / ρ (1)
There is a relationship indicated by. That is, if two of the three rotation speeds Ns, Nc, and Nr are determined, another rotation speed is determined. Since the rotation speed Nr of the ring gear is determined by the speed of the vehicle, one of the rotation speed Nc of the planetary carrier, that is, the engine rotation speed, and the rotation speed Ns of the sun gear, that is, the first motor generator rotation speed is determined. The other is determined. Then, the field currents of the first and second motor generators 26 and 28 are controlled in accordance with the number of rotations at that time, and it is determined whether these motor generators are to act as a generator or as an electric motor. When the two motor generators 26 and 28 consume electric power as a whole, electric power is taken out from the battery 50, and when the electric power is generated as a whole, the battery 50 is charged. For example, when the battery ECU 68 detects that the storage amount of the battery 50 is low, the battery 50 generates power by one or both of the two motor generators 26 and 28 using a part of the torque generated by the engine 10. To charge. Further, when the storage amount of the battery 50 increases, the output of the engine is suppressed and the second motor generator 28 is operated as an electric motor, and the torque generated thereby is controlled to be used for vehicle travel. Further, at the time of braking, one or both of the two motor generators 26 and 28 are operated as a generator, and the generated electric power is charged in the battery 50.
[0017]
Since it is difficult to predict when the automobile will be braked, it is desirable that the battery 50 be in a state that can sufficiently accept the electric power generated by the regenerative braking. On the other hand, when the acceleration desired by the driver cannot be obtained only by the output of the engine 10, the battery 50 must secure a certain amount of charge in order to operate the second motor generator 28 as an electric motor. Therefore, the amount of electricity stored in the battery 50 is normally controlled to be about half the battery capacity, that is, the maximum power stored in the battery.
[0018]
In particular, in the case of a hybrid vehicle that can charge the battery by generating power by the output of the engine, by appropriately managing the amount of electricity stored in the battery, the regenerative power at the time of braking can be sufficiently recovered to increase the energy efficiency, Further, the acceleration desired by the driver can be achieved during acceleration. In other words, in the case of the hybrid vehicle as described above, it is necessary to accurately detect and appropriately control the amount of charge (SOC) of the battery in order to increase energy efficiency and obtain desired acceleration.
[0019]
FIG. 2 shows a schematic configuration of the present embodiment. In FIG. 2, the same reference numerals are given to components common to FIG. 1. The battery 50 is an assembled battery in which a plurality of cells are connected in series as shown in the figure, and is connected to the motor generators 26 and 28 via inverters 52 and 54. The two motor generators 26 and 28 are connected to the engine 10 via a transmission mechanism including a planetary gear mechanism. In addition, a voltage sensor 70 as voltage detecting means for detecting a terminal voltage of the battery 50 and a current sensor 72 as current detecting means for detecting a current flowing through the battery 50 are provided. Furthermore, temperature sensors 74 as temperature detecting means for detecting the battery temperature are provided at a plurality of locations of the battery 50. The reason why the temperature sensors 74 are provided at a plurality of locations is that the temperature of the battery 50 varies depending on the location. Outputs of the voltage sensor 70, the current sensor 72, and the temperature sensor 74 are sent to the battery ECU 68. The battery ECU 68 calculates the SOC of the battery based on the obtained voltage and current, and sends information related to the temperature to the control CPU 56. The control CPU 56 determines the operating state of the motor generators 26 and 28 by combining the data sent from the battery ECU 68 and various data such as the engine ECU 46, and controls the inverters 52 and 54 accordingly. As described above, in the hybrid vehicle of this embodiment, the motor generators 26 and 28 consume the electric power stored in the battery 50. Further, regenerative electric power from the motor generators 26 and 28 and electric power from the motor generators 26 and 28 as generators driven by the engine are supplied to the battery 50. Therefore, motor generators 26 and 28 and engine 10 function as charging / discharging means for supplying power to battery 50 or consuming the power of the battery. The control CPU 56 and the engine CPU 46 that control the motor generators 26 and 28 via the inverters 52 and 54 function as charge / discharge control means for controlling the charge / discharge means.
[0020]
In the present embodiment, the SOC of the battery 50 is estimated by integrating the current flowing through the battery by the battery ECU 68 based on the output of the current sensor 72. This is because the estimated value of the SOC deviates from the actual value due to a change in charging efficiency or self-discharge while charging and discharging are repeated, so that calibration is also performed in this embodiment.
[0021]
When the battery is discharged, as shown in FIG. 6, when the SOC decreases to around 20%, a change in the terminal voltage can be detected by the voltage sensor 70. Therefore, based on the outputs of the voltage sensor 70 and the current sensor 72, when the SOC calculated by the battery ECU 68 is below the IV determination region, that is, when the SOC reaches 20% or less, the estimated SOC value is rewritten to 20%. In addition, if the SOC is increased to about 80% during charging, the voltage sensor 70 can also detect a change in the terminal voltage. Therefore, the estimated value is rewritten to 80% when the calculated value of SOC becomes 80% or more. In this way, the estimated SOC value is calibrated. Therefore, in this calibration control, the battery ECU 68 functions as a storage amount detection unit. Further, the IV determination area in which such calibration control is executed is also defined by the battery ECU 68, and constitutes an area defining means.
[0022]
A characteristic point of the present invention is that once the calculated value of the SOC by the battery ECU 68 reaches the IV determination region and the estimated value of the SOC is calibrated once, the estimated value of the SOC does not leave the IV determination region again. The point is that no calibration is performed.
[0023]
3 and 4 show the flow of the calibration operation of the battery charged amount detection device according to the present invention. FIG. 3 shows an operation when the calculated SOC value reaches the lower limit side (20% or less) of the IV determination region, and FIG. 4 shows an operation when the calculated SOC value is the upper limit side (80% or more) of the IV determination region. Each of the actions taken when reaching is shown.
[0024]
In FIG. 3, when the IV lower limit determination process is started, it is determined whether the calculated value of the SOC by the battery ECU 68 has reached the lower limit (20%) of the IV determination region (S10). Here, until it is determined that the lower limit has been reached, the battery ECU 68 performs an SOC estimation calculation based on current integration (S12).
[0025]
On the other hand, if it is determined in S10 that the lower limit has been reached, a calibration operation for correcting the estimated SOC value to 20% is executed (S14).
[0026]
When the estimated SOC value is corrected once, the battery ECU 68 again performs an SOC estimation calculation based on current integration (S16).
[0027]
Next, after the lower limit is determined in S10, the battery 50 is charged by a predetermined amount, and it is confirmed whether the estimated SOC calculation value in S16 has left the IV determination region, that is, has exceeded 20% (S18). This confirmation is also executed by the battery ECU 68. Therefore, the battery ECU 68 also serves as a confirmation unit. Here, the SOC estimation calculation is continued until the IV determination area is exited (S16).
[0028]
On the other hand, if the estimated SOC value exceeds 20% and the IV determination region is left, the IV lower limit determination process is repeated from the beginning.
[0029]
Also in FIG. 4, basically the same operation as the flow of FIG. 3 is executed. 4, when the IV upper limit determination process is started, it is determined whether the calculated value of the SOC has reached the upper limit (80%) of the IV determination area (S20). Here, until it is determined that the upper limit has been reached, the battery ECU 68 performs an SOC estimation calculation based on current integration (S22).
[0030]
On the other hand, if it is determined in S20 that the upper limit has been reached, a calibration operation for correcting the estimated SOC value to 80% is executed (S24).
[0031]
When the estimated SOC value is corrected once, the battery ECU 68 again performs an SOC estimation calculation based on current integration (S26).
[0032]
Next, after the lower limit is determined in S20, the battery 50 is discharged by a predetermined amount, and it is determined by the battery ECU 68 whether the estimated SOC value in S26 has left the IV determination region, that is, less than 80% (S28). Here, the SOC estimation calculation is continued until the IV determination area is exited (S26).
[0033]
On the other hand, if the estimated value of SOC falls below 80% and the IV determination area is left, the IV upper limit determination process is repeated from the beginning.
[0034]
FIG. 5 shows the change in SOC over time when the IV upper limit determination process shown in FIG. 4 is executed. In FIG. 5, when the battery 50 is charged and the SOC increases and reaches the upper limit of the IV determination region, the estimated value of SOC is corrected to 80%. Thereafter, the IV upper limit determination process is prohibited until the battery 50 is discharged by a predetermined amount. This prohibition is also performed by the battery ECU 68.
[0035]
Accordingly, only the SOC estimation calculation by the battery ECU 68 is executed during this period. When the battery ECU 68 as the confirmation means confirms that a predetermined amount has been discharged, the IV upper limit determination process is permitted again.
[0036]
In addition, since the temperature sensor 74 is provided in the battery 50, SOC can also be estimated from the temperature change of a battery. That is, when the SOC of the battery 50 reaches 100%, the value of dT / dt increases rapidly. Therefore, if the value of dT / dt is calculated by the battery ECU 68 from the temperature detection result of the temperature sensor 74 input to the battery ECU 68, it can be detected that the SOC has reached 100%. Can be corrected.
[0037]
As described above, according to the present invention, the SOC of the battery can be detected with high accuracy. In the present embodiment, a battery mounted on a hybrid vehicle has been described as an example. However, the present invention can be applied to any battery. Further, the present invention is not limited to the nickel metal hydride battery of the present embodiment, and can be applied to a lithium ion battery, a nickel cadmium battery, a lead battery, and the like.
[0038]
【The invention's effect】
As described above, according to the present invention, after the SOC estimation value is corrected once at the upper limit or lower limit of the IV determination region, a sufficient amount of charging or discharging is performed to exit the IV determination region. Since the correction is not performed again, it is possible to prevent an error in the estimated SOC value.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a drive system of a hybrid vehicle.
FIG. 2 is a diagram showing a schematic configuration of an embodiment of a battery charged amount detection device according to the present invention.
FIG. 3 is a flowchart of the operation of IV lower limit determination processing of the embodiment shown in FIG. 2;
FIG. 4 is a flowchart of the operation of the IV upper limit determination process of the embodiment shown in FIG. 2;
FIG. 5 is a diagram showing a change with time of SOC during the IV upper limit determination process shown in FIG. 4;
FIG. 6 is a graph showing terminal voltage characteristics with respect to a charge amount of a nickel metal hydride battery.
[Explanation of symbols]
10 engine, 26 first motor generator, 28 second motor generator, 46 engine ECU, 50 battery, 52 first inverter, 54 second inverter, 56 control CPU, 68 battery ECU, 70 voltage sensor, 72 current sensor, 74 temperature Sensor.

Claims (3)

A storage amount detecting means for detecting a storage amount of the secondary battery based on a voltage and current detectable from the outside, and detection by the storage amount detection means is executed , and a storage amount of the secondary battery is calculated based on the voltage and current. A battery charge amount detection comprising: a region defining means for defining a region where a change in the voltage of the secondary battery is large compared to a region where the voltage of the secondary battery does not change due to a change in the charge amount of the secondary battery. A device,
When the detection by the storage amount detection means is performed , the secondary battery is compared with a region where the voltage of the secondary battery does not change due to a change in the storage amount of the secondary battery specified by the region definition means. A confirmation means for confirming that a sufficient amount of charging or discharging has been performed to escape the region where the voltage change of
A battery storage amount detection device comprising: prohibiting means for prohibiting detection operation by the storage amount detection means until confirmation by the confirmation means. In the battery storage amount detecting apparatus according to claim 1, wherein the charged amount detection means further dT / dt characteristics (T is the battery temperature, t is time) battery storage amount detecting apparatus characterized by utilizing.   2. The battery storage amount detection device according to claim 1, wherein the confirmation unit confirms a predetermined amount of charge or discharge by current integration.

Images