JP2007318913A - State-of-charge controller of battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a state-of-charge controller of battery in which fuel consumption reduction effect can be ensured through regenerative power generation by controlling the state of charge (SOC) of a battery to an always chargeable state. <P>SOLUTION: Battery voltage C at a discharge start point after regenerative power generation is compared with upper and lower limit values D1 and D2 of a predetermined threshold range and a threshold D3 for judging overdischarge (S2-S4). If C>D1, the state of charge (SOC) of a battery is estimated to be large and the state of discharge is increased more than the state of charge obtained by regenerative power generation (S5). If D2>C>D3, the state of charge (SOC) of a battery is estimated to be small and the state of discharge is made fewer than the state of charge obtained by regenerative power generation (S6). If C<D3, transition is made to charge mode by estimating overdischarge state and forced charging is performed (S11). Regenerative control is forbidden if overdischarge state is judged even after repeating forced charging (S12). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a state-of-charge control device for a battery, and more particularly to a technique for controlling a state of charge (SOC) of a battery to a set value that can be charged by regenerative power generation control by an alternator.

  In recent years, when the vehicle is decelerating, the generator voltage is increased and regenerative power generation is performed to charge the battery, and then the power stored in the battery by regenerative power generation is used to cover the power consumption of the in-vehicle electric load, thereby driving the alternator. Energy is reduced and fuel consumption is improved. In order to keep constant the fuel consumption reduction effect and the deceleration acceleration performance by the deceleration regeneration control of the alternator, it is necessary to control the state of charge (SOC) of the battery to a predetermined set value that can be charged.

Thus, as a method for detecting the state of charge (SOC) of the battery, a method of integrating the charge / discharge current value of the battery is generally known (see, for example, Patent Document 1), and the charge current during regenerative power generation is integrated. Then, the amount of charge stored in the battery by regenerative power generation is detected and stored, and then the state of charge (SOC) of the battery is controlled to a set value by discharging the amount of charge stored by regenerative power generation. Can be considered.
JP 2003-52131 A

  However, as described above, in the control that discharges the rechargeable power generation and keeps the battery charge state (SOC) at a chargeable setting value, for example, the battery charge state (due to battery deterioration or current sensor error) ( If the SOC is deviated from a predetermined chargeable setting value, the deviation in the state of charge (SOC) is not eliminated, and the target charge amount cannot be secured during regenerative power generation, which may reduce the fuel consumption reduction effect. There is. Further, if this deviation in the state of charge (SOC) is left unattended, there is a risk that the battery will run out due to overdischarge. Furthermore, when the battery has deteriorated or has been replaced with a low-performance battery (a battery other than a reinforced battery for regenerative control), the battery may be further deteriorated by forcibly performing regenerative control. is there.

  The present invention has been made paying attention to the above-mentioned problems, and corrects the state of charge (SOC) of the battery during regenerative control so that the battery can be controlled to be constantly charged by regenerative power generation. An object is to provide an apparatus.

  Therefore, according to the present invention, when the vehicle is decelerated, the power generation voltage of the alternator driven by the engine is increased to perform regenerative power generation to charge the battery, and then the power generation voltage of the alternator is decreased to discharge the battery to A battery charge state control device for controlling a state (SOC) to a predetermined chargeable set value, wherein the state of charge (SOC) of the battery is estimated based on a battery voltage at the time of discharging after the regenerative power generation. The battery discharge amount is variably controlled based on the estimation result, and the state of charge (SOC) of the battery is controlled to be the set value.

  According to the present invention, the battery charge state (SOC) is estimated based on the battery voltage at the time of discharge after regenerative power generation, and the subsequent discharge amount is suppressed when the charge state (SOC) is estimated to be smaller than the set value. When the state of charge (SOC) is estimated to be larger than the set value, the subsequent discharge amount is increased, so that the battery can be kept in a constant state that can be always charged by regenerative power generation. Therefore, a desired charge amount can be obtained during regenerative power generation, and a desired fuel consumption reduction effect and deceleration performance can be ensured. Further, since the battery charge state can be estimated and corrected each time regenerative control is performed, there is an advantage that the battery charge state (SOC) can be prevented from changing greatly, and the fuel consumption reduction effect and the deceleration performance can be obtained stably.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system configuration diagram showing an embodiment of a battery charge state control apparatus according to the present invention.
In FIG. 1, an alternator 2 that is driven by an engine 1 through a fan belt to generate electric power receives a generated voltage command from an ECM (engine control module) 7 having a microcomputer to be described later, and the generated voltage is controlled by a regulator 3. Is done. The battery 4 is connected to the alternator 2 so as to be chargeable / dischargeable according to the generated voltage of the alternator 2. The current sensor 5 detects the charge / discharge current of the battery 4 and inputs the detection output to the ECM 7. Reference numeral 6 denotes a temperature sensor for detecting the battery temperature.

  The ECM 7 includes, for example, a computer and is driven by power supply from the battery 4. The ECM 7 controls the engine operating state by signals from various sensors (not shown) and performs regenerative control during deceleration. Further, the state of charge (SOC) of the battery 4 after the regenerative control is controlled to a preset value (for example, 90% of the rated capacity) so that the battery 4 can be charged during regenerative power generation. The ECM 7 performs fuel cut control to stop fuel injection when the engine speed is decelerated more than a predetermined value in the idle state where the throttle valve is substantially fully closed, based on signals from the throttle sensor and the engine speed sensor. In addition, a high power generation voltage command value (for example, 14.5V) is output to the regulator 3 of the alternator 2 to generate regenerative power to charge the battery 4, and after this regenerative power generation, from the battery voltage (for example, about 12.8V) A low power generation voltage command value (for example, 12.5 V) is output to discharge the battery 4. In this regenerative control, the state of charge (SOC) of the battery 4 is estimated from the battery voltage value at the time of discharge after regenerative power generation, and the discharge amount of the battery 4 is variably controlled based on the estimation result. 4 is controlled so that the state of charge (SOC) 4 becomes the set value that can be always charged. Further, the ECM 7 stores in memory a charge current value when the battery 4 is charged to the set value in advance in order to forcibly charge the battery 4 to the set value when the charging mode is shifted.

Next, the charge state control operation of the battery 4 by the ECM 7 of this embodiment will be described with reference to the flowchart of FIG.
In step 1 (indicated by S1 in the figure, the same shall apply hereinafter), it is determined whether or not the discharge is started. As shown in FIG. 3, during the deceleration fuel cut, a high power generation voltage command value (for example, 14.5 V) is output from the ECM 7 to the alternator 2 and regenerative power generation is started. 5V) is output, it is determined that the discharge is started, the determination is YES, and the process proceeds to step 2.

In steps 2 to 4, the battery voltage when the start of discharging of the battery 4 is confirmed from the output state of the current sensor 5 is the battery voltage C at the time of discharging (indicated by a black circle in FIG. 4). As shown in FIG. 4, the upper and lower limit values D1 and D2 of the preset threshold range and the overdischarge determination threshold value D3 are compared for determination of the state of charge (SOC).
In step 2, the battery voltage C at the time of discharging is compared with the upper limit value D1 of the threshold range, and it is determined whether C> D1. If the determination is NO, the process proceeds to step 3. In step 3, it is determined whether D2>C> D3 by comparing the battery voltage C with the lower limit value D2 of the threshold value range and the overdischarge determination threshold value D3. If the determination is NO, the process proceeds to step 4. In step 4, the battery voltage C is compared with the overdischarge determination threshold D3 to determine whether C <D3.

  When all the determinations in steps 2 to 4 are NO, that is, when the battery voltage C at the time of discharging is within the threshold range (D2 ≦ C ≦ D1) as shown by the solid line in FIG. It is estimated that the state of charge (SOC) is a preset value (for example, 90%) that can be charged at any time. In this case, at the time of subsequent discharge, the discharge time is set so as to discharge the charge amount SOC (charge current integrated value) stored in the regenerative power generation, and during that time, the power generation voltage command value of the alternator 2 is set to 12.5V. 4 is discharged.

On the other hand, in step 2, when the battery voltage C is larger than the upper limit value D1 (C> D1) and the determination is YES as shown by the dotted line in FIG. 4, the state of charge (SOC) of the battery before regenerative power generation is determined in advance. It is estimated that the set value is larger than the settable chargeable value (for example, 90%), and the process proceeds to Step 5.
In step 5, a predetermined amount (for example, 1% of the rated SOC of the battery 4) is added to the charge current integrated value (corresponding to the charge amount SOC) during regenerative power generation, so that the discharge amount is larger than the charge amount due to regenerative power generation. It is set and corrected so as to decrease the state of charge (SOC) of the battery 4. In this case, at the time of subsequent discharge, the discharge time is lengthened so that the discharge amount is larger than the charge amount SOC (charge current integrated value) stored in the regenerative power generation.

In step 3, when the battery voltage C is between the lower limit value D2 and the overdischarge determination threshold D3 (D2>C> D3) as shown by the one-dot chain line in FIG. 4, the determination becomes YES. The state of charge (SOC) of the battery is estimated to be smaller than a predetermined chargeable setting value (for example, 90%), and the process proceeds to step 6.
In step 6, a predetermined amount (for example, 1% of the rated SOC of the battery 4) is subtracted from the charging current integrated value (corresponding to the charging amount SOC) during the regenerative power generation, so that the discharge amount is smaller than the charge amount due to the regenerative power generation. It is set and corrected so as to increase the state of charge (SOC) of the battery 4. In this case, at the time of subsequent discharge, the discharge time is shortened so that the discharge amount is smaller than the charge amount SOC (charge current integrated value) stored in the regenerative power generation.

  Until the correction in step 6 is performed n times in succession, the determination in step 7 is NO, and the process proceeds to step 8 where the battery 4 is forcibly charged. When the mode is changed to the charging mode, the power generation voltage of the alternator 2 is forcibly increased so that the charging current value stored in advance when the battery charging state (SOC) corresponds to the set value (90%) is obtained. 4 is forcibly charged to a set value (SOC 90%) to prevent the battery from running out. If YES in step 3 is performed n times in spite of the forced charging, the process proceeds from step 7 to step 9 and the overdischarge state of the battery 4 is not cleared despite the forced charging. Therefore, it is determined that the battery 4 has deteriorated, and the regeneration control is prohibited to suppress the progress of deterioration of the battery 4.

In step 4, when the battery voltage C is smaller than the overdischarge determination threshold D3 (C <D3) and the determination is YES as shown by a two-dot chain line in FIG. 4, the state of charge of the battery (SOC) before regenerative power generation is determined. ) Is assumed to be an overdischarged state. Then, in step 10, it is determined whether or not the YES determination in step 4 is continued n times. If it is less than n times, the process proceeds to step 11.
In step 11, the battery charging mode is entered and the battery 4 is forcibly charged in the same manner as in step 8 to prevent the battery from running out.

If the determination of step 10 becomes YES after the overdischarge determination is continued n times, the process proceeds to step 12 and the battery 4 is determined to be deteriorated because the overdischarge state is not resolved despite the forced charging. Regenerative control is prohibited, and the progress of deterioration of the battery 4 is suppressed.
If the battery voltage C does not decrease even if the discharge amount increase control in step 5 is repeated, it is considered that the system is abnormal. Therefore, it is desirable to determine that the apparatus is abnormal and perform appropriate abnormality processing.

  According to the battery state of charge control device of this embodiment, the battery state of charge (SOC) before regenerative control is estimated based on the battery voltage at the start of discharge after regenerative power generation, and the state of charge (SOC) is a set value. If it is estimated to be smaller, the subsequent discharge amount is made smaller than the charge amount obtained by regenerative power generation. If the state of charge (SOC) is estimated to be larger than the set value, the subsequent discharge amount is regenerated. Since the discharge amount is variably controlled so as to be larger than the charge amount obtained in the above, the battery 4 can be kept in a constant state that can be always charged by regenerative power generation. Therefore, a desired fuel consumption reduction effect and deceleration performance can be ensured.

  In addition, when it is determined that the battery voltage is greatly reduced at the start of discharging and is in an overdischarged state, the battery can be prevented from being discharged by forcibly charging. Further, if it is determined that the battery is over-discharged even after repeated forced charging, or if the battery voltage does not rise even after repeated discharge amount reduction control, it is determined that the battery 4 has deteriorated and regenerative control is prohibited. Progress of deterioration can be suppressed.

Further, since the battery charge state can be estimated and corrected every time regenerative control is performed, it is possible to prevent the battery charge state (SOC) from changing greatly, and the fuel consumption reduction effect and the deceleration performance can be stably obtained.
Since the battery voltage at the time of discharge depends on the temperature and discharge current of the battery 4, the battery voltage C at the time of discharge is corrected based on the discharge current and the battery temperature, and the corrected battery voltage C and the upper and lower limit values D1 are corrected. , D2 and the overdischarge determination threshold value D3, the estimation accuracy of the state of charge (SOC) of the battery 4 is improved. The battery temperature may be estimated from the intake air temperature, the engine water temperature, and the like.

The system block diagram of one Embodiment of the charge condition control apparatus of the battery which concerns on this invention Flowchart for explaining the charge state control operation of the embodiment Timing chart for explaining the charge state control operation of the embodiment The figure which shows the relationship between the battery voltage at the time of discharge, the upper and lower limit value, and the threshold value for discharge determination

Explanation of symbols

1 Engine 2 Alternator 3 Regulator 4 Battery 5 Current sensor 6 Temperature sensor 7 ECM

Claims (8)

When the vehicle decelerates, the power generation voltage of the alternator driven by the engine is increased and regenerative power generation is performed to charge the battery. Then, the power generation voltage of the alternator is decreased to discharge the battery, and the state of charge (SOC) of the battery is determined in advance. A battery charge state control device that controls the set value to be rechargeable,
The state of charge (SOC) of the battery is estimated based on the battery voltage at the time of discharging after the regenerative power generation, the amount of discharge of the battery is variably controlled based on the estimation result, and the state of charge (SOC) of the battery is set to the set value. The battery state-of-charge control device is configured to control so that   When the battery voltage at the time of discharging is larger than an upper limit value of a preset threshold range, it is estimated that the state of charge (SOC) of the battery is larger than the set value, and the amount of discharge is obtained by the regenerative power generation. The battery charge state control device according to claim 1, wherein the battery charge state control device is further increased.   When the battery voltage at the time of discharging is smaller than a lower limit value of a preset threshold range, it is estimated that the state of charge (SOC) of the battery is smaller than the set value, and the amount of discharge is obtained by the regenerative power generation. The battery state-of-charge control device according to claim 1, wherein the battery charge state control device is further reduced.   An overdischarge determination threshold value smaller than the lower limit value of the threshold range is set, and when the battery voltage at the time of discharge is smaller than the overdischarge determination threshold value, the battery is determined to be in an overdischarge state and the battery is forced to the set value. The charging state control device for a battery according to any one of claims 2 and 3, wherein the charging state control device is configured to be charged.   The battery state-of-charge control device according to claim 4, wherein regenerative control is prohibited when the battery overdischarge determination is continued a predetermined number of times.   6. The battery charge state control device according to claim 2, wherein the discharge amount is increased or decreased by a predetermined amount.   The battery charge state control device according to any one of claims 1 to 6, wherein a value of a discharge start point of the battery is used as the battery voltage at the time of discharging.   The battery state-of-charge control device according to claim 1, wherein the battery voltage at the time of discharging is corrected according to a temperature and a discharging current of the battery.

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