JP2008056050A - Battery state determination method, battery state determination device, and computer program - Google Patents

Abstract

A battery state determination method, a battery state determination device, and a computer program capable of determining whether or not an engine can be started and the state of a battery with higher accuracy than before are provided.
A CPU calculates an internal resistance Rb of a battery based on a current value and a voltage value of the battery detected when the current value of the battery is equal to or greater than a current threshold value Ith, and the current value of the battery is The open circuit voltage Vo of the battery 1 is calculated based on the current value and voltage value of the battery 1 detected when it is smaller than the current threshold Ith. When starting the engine 3 next time based on the internal resistance Rb, the open circuit voltage Vo, the allowable minimum starting current Ismin, and the starting resistance Rs obtained when the cell motor 4 is started, the CPU 14 starts the starting characteristic equation Rb <Vo / Ismin−Rs. Whether or not the engine 3 can be started is determined depending on whether or not the above condition is satisfied. When the CPU 14 determines that starting is impossible, the CPU 14 controls the charging current or discharging current of the battery 1.
[Selection] Figure 1

Description

  The present invention relates to a state of a secondary battery, in particular, a battery state determination method for determining whether or not an engine can be started, a battery state determination device, and a computer program for realizing the battery state determination device.

  Vehicles such as passenger cars, buses, and trucks are equipped with a battery (secondary battery, for example, a lead storage battery) for starting an engine and supplying electric power to an electric device provided in the vehicle. A lead-acid battery uses lead dioxide as a positive electrode active material, lead as a negative electrode active material, and sulfuric acid as an electrolyte. During discharge operation, lead is oxidized at the negative electrode to change from cation to lead sulfate, and at the positive electrode, lead dioxide is reduced to sulfuric acid. It becomes lead. During the charging operation, lead ions are reduced from lead sulfate at the negative electrode to lead metal, and lead ions are oxidized at the positive electrode to lead dioxide.

  When sufficient charge is not performed in a state in which the lead storage battery is discharged, lead sulfate generated by the discharge operation is crystallized, and a charge operation called sulfation cannot be performed, and the lead storage battery may be deteriorated. For this reason, the lead-acid battery is charged by an alternator while the engine is operating, and is maintained in a substantially fully charged state.

  In addition, in order to start the engine, it is necessary to rotate the engine by applying a DC voltage from a battery (lead storage battery) to a cell motor attached to the engine. There is a need to be able to start.

Therefore, the internal resistance of the internal combustion engine and the relationship between the internal resistance and health of the battery are stored in advance, and the open circuit voltage near the full charge of the battery and the discharge at the maximum voltage drop of the battery at the start of the internal combustion engine are stored. By measuring the voltage and calculating the internal resistance of the battery and detecting the health of the battery from the relationship between the internal resistance and the health, it is possible to detect the state of the battery only by measuring the voltage without using a current sensor. A battery state detection device that can be used has been proposed (see Patent Document 1).
JP 2005-304173 A

 However, in the apparatus of Patent Document 1, the resistance inherent to the internal combustion engine (engine), that is, the starting resistance of the cell motor uses a predetermined value, and the engine is operated by the ambient temperature, aging, etc. It is not considered that the starting resistance becomes a different value every time the engine is started. The internal resistance of the battery (secondary battery) is detected only when the engine is started. However, since a large current flows when the engine is started, the detected internal resistance of the battery is smaller than the actual value. There is a possibility that the battery state cannot be accurately detected as to whether or not the engine can be started.

  The present invention has been made in view of such circumstances, and detects the starting resistance of the electric motor each time the internal combustion engine is started, and calculates the internal resistance and open circuit voltage of the secondary battery after the internal combustion engine is started. Based on the detected starting resistance and the calculated internal resistance and open circuit voltage of the secondary battery, it is determined whether or not the state of the secondary battery can be started next time, so that the electric motor (for example, a cell motor) A battery state determination method, a battery state determination device, and a battery state capable of determining whether or not an internal combustion engine (engine) can be started regardless of changes over time or ambient temperature, more accurately than in the past. It is an object of the present invention to provide a computer program for realizing a determination device.

  Another object of the present invention is to repeatedly detect the current and voltage of the secondary battery after the internal combustion engine is started, compare the detected current value with the current threshold value, and detect it according to the comparison result. The current value and voltage value are stored, and the internal resistance or open circuit voltage of the secondary battery is calculated using the plurality of stored current values and voltage values, thereby obtaining the current value of the secondary battery after starting the internal combustion engine. Accordingly, an object of the present invention is to provide a battery state determination method and a battery state determination device that can accurately calculate the internal resistance or open circuit voltage of a secondary battery.

  Another object of the present invention is to calculate the internal resistance of the secondary battery using the detected current value and voltage value when the detected current value is larger than the current threshold, thereby It is an object of the present invention to provide a battery state determination method and a battery state determination device that can accurately calculate the internal resistance of a secondary battery corresponding to the change with time.

  Another object of the present invention is to discharge the secondary battery by calculating the open voltage of the secondary battery using the detected current value and voltage value when the detected current value is smaller than the current threshold. An object of the present invention is to provide a battery state determination method and a battery state determination device that can accurately calculate the open circuit voltage of a secondary battery regardless of the state or the state of charge.

  Another object of the present invention is to calculate the internal resistance and open-circuit voltage of the secondary battery a plurality of times, calculate the calculated internal resistance and open-circuit voltage statistics, and calculate the calculated internal resistance and open-circuit voltage. A battery that can determine the state of the secondary battery with higher accuracy as to whether or not the internal combustion engine can be started by determining whether or not the state of the secondary battery can be started next time based on the statistical value of The object is to provide a state determination method and a battery state determination device.

  Another object of the present invention is to provide a control means for controlling the charging current or discharging current of the secondary battery when it is determined that starting is impossible, thereby preventing the starting failure of the internal combustion engine. The object is to provide a battery state determination device.

  A battery state determination method according to a first aspect of the present invention is a battery state determination method for determining a state of a secondary battery that supplies electric power to an electric motor for starting an internal combustion engine. After the internal combustion engine is started, the internal resistance and open voltage of the secondary battery are calculated, and the state of the secondary battery is started next time based on the detected start resistance and the calculated internal resistance and open voltage of the secondary battery. It is characterized by determining whether or not it is possible.

  The battery state determination method according to a second aspect of the present invention is the first aspect of the invention, wherein after the internal combustion engine is started, the current and voltage of the secondary battery are repeatedly detected, the detected current value is compared with the current threshold value, and the comparison result The detected current value and voltage value are stored, and the internal resistance or open circuit voltage of the secondary battery is calculated using the stored current value and voltage value.

  When the detected current value is larger than the current threshold in the second invention, the battery state determination method according to the third invention is used to calculate the internal resistance of the secondary battery when the detected current value and the voltage value are larger than the current threshold. It is characterized by.

  When the detected current value is smaller than the current threshold in the second invention, the battery state determination method according to the fourth invention is used to calculate the open voltage of the secondary battery when the detected current value and voltage value are smaller than the current threshold. It is characterized by.

  According to a fifth aspect of the present invention, there is provided the battery state determination method according to any one of the first to fourth aspects, wherein the internal resistance or open circuit voltage of the secondary battery is calculated a plurality of times, and the calculated internal resistance or open circuit voltage statistics are calculated. A value is calculated, and based on the calculated statistical value of the internal resistance or open circuit voltage, it is determined whether or not the state of the secondary battery can be started next time.

  A battery state determination device according to a sixth aspect of the present invention is a battery state determination device that determines the state of a secondary battery that supplies electric power to an electric motor for starting an internal combustion engine. Means for calculating the internal resistance and open circuit voltage of the secondary battery when the internal combustion engine is started, the starting resistance detected by the detecting means, the internal resistance of the secondary battery calculated by the calculating means, and And determining means for determining whether or not the state of the secondary battery can be started next time based on the open circuit voltage.

  According to a seventh aspect of the present invention, there is provided a battery state determination apparatus according to the sixth aspect, wherein the means for detecting the current and voltage of the secondary battery, the means for comparing the detected current value and the current threshold value, Storage means for storing the detected current value and voltage value, and the calculation means calculates the internal resistance or open circuit voltage of the secondary battery using the plurality of current values and voltage values stored in the storage means. It is comprised so that it may carry out.

  According to an eighth aspect of the present invention, in the seventh aspect, when the detected current value is greater than the current threshold, the calculating means uses the detected current value and voltage value to determine the internal resistance of the secondary battery. It is characterized by calculating.

  According to a ninth aspect of the present invention, in the seventh aspect, when the detected current value is smaller than the current threshold, the calculating means uses the detected current value and voltage value to detect the open voltage of the secondary battery. It is characterized by calculating.

  According to a tenth aspect of the present invention, there is provided a battery state determination apparatus according to any one of the sixth to ninth aspects, further comprising means for calculating statistical values of a plurality of internal resistances and open-circuit voltages calculated by the calculation means. Is configured to determine whether or not the state of the secondary battery can be started next time based on the statistical values of the internal resistance and the open circuit voltage calculated by the above means.

  A battery state determination apparatus according to an eleventh aspect of the invention is the battery apparatus according to any one of the sixth to tenth aspects, wherein, when the determination means determines that starting is impossible, a control means for controlling the charging current or discharging current of the secondary battery. It is characterized by providing.

  A computer program according to a twelfth aspect of the invention is a computer program for causing a computer to determine a state of a secondary battery that supplies electric power to an electric motor for starting an internal combustion engine. Means for comparing the current value of the battery with the current threshold; and means for calculating the internal resistance or open voltage of the secondary battery using the current value and voltage value of the secondary battery according to the comparison result; Based on the calculated internal resistance and open-circuit voltage and the starting resistance of the electric motor when starting the internal combustion engine, the computer is caused to function as a means for determining whether or not the state of the secondary battery can be started next time. Features.

  In the first invention, the sixth invention, and the twelfth invention, each time the internal combustion engine (engine) is started, the starting resistance of the electric motor (cell motor) is detected. Since the equivalent circuit at the time of starting the engine is represented by a configuration in which the starting resistor Rs of the motor is connected to the positive and negative terminals of the secondary battery, the starting resistor Rs is based on the voltage V and current I of the secondary battery. Rs = V / I can be detected. The equivalent circuit of the secondary battery has a configuration in which the internal resistance Rb of the secondary battery is connected in series to a DC power source having a voltage Vo (corresponding to the open voltage Vo of the secondary battery). Assuming that the minimum allowable starting current of the motor is Ismin and the current flowing through the starting resistor Rs at the time of starting is I, the condition that enables the starting of the motor is I> Ismin. Since I = Vo / (Rb + Rs), Rb <Vo / Ismin−Rs is a condition for determining whether to start.

  After the internal combustion engine is started (after the start is completed), the internal resistance Rb and the open voltage Vo of the secondary battery are calculated, and the state of the secondary battery is determined next time based on the start resistance Rs, the internal resistance Rb, and the open voltage Vo. Whether or not the engine can be started is determined by whether or not the condition of Rb <Vo / Ismin−Rs is satisfied. Since the starting resistance of the motor is detected each time the engine is started, the starting resistance can be obtained with high accuracy even when the starting resistance changes in accordance with the secular change of the motor or the ambient temperature change in use. . Further, by calculating the internal resistance and open circuit voltage of the secondary battery after the internal combustion engine is started, for example, even when the internal resistance of the secondary battery changes while the vehicle is running, the internal resistance is accurately acquired. be able to. Thereby, it is possible to determine the state of the battery with higher accuracy than in the past, whether or not the internal combustion engine (engine) can be started.

  In the second and seventh inventions, after the internal combustion engine is started, the current and voltage of the secondary battery are repeatedly detected, the detected current value is compared with the current threshold value, and the detection is performed according to the comparison result. The measured current value and voltage value are stored. For example, when the detected current value is larger than the current threshold, the detected current value and voltage value are stored for calculating the internal resistance of the secondary battery. When the detected current value is smaller than the current threshold, the detected current value and voltage value are stored for calculating the open-circuit voltage of the secondary battery. The internal resistance or open circuit voltage of the secondary battery is calculated using the plurality of stored current values and voltage values. Accordingly, the internal resistance of the secondary battery is calculated using the current value and voltage value when the secondary battery current is large, and the secondary battery is calculated using the current value and voltage value when the secondary battery current is small. Calculate the open circuit voltage.

  In the third invention and the eighth invention, when the detected current value is larger than the current threshold, the internal resistance of the secondary battery is calculated using the detected current value and voltage value. For example, the internal resistance of the secondary battery is obtained by plotting a plurality of stored current values and voltage values on voltage / current coordinates, and a battery characteristic equation (V = Vo) that is a primary approximation formula along each plotted point. -IRb), and Rb, which is the slope of the straight line represented by this approximate expression, can be calculated as the internal resistance. Further, since the internal resistance is calculated using the detected current value and voltage value when the current value (for example, the discharge current value) of the secondary battery is larger than the current threshold value, the internal resistance is obtained at the start. Compared to the case, the internal resistance can be calculated with higher accuracy. Thereby, the internal resistance of the secondary battery according to the change with time after the start of the internal combustion engine can be accurately calculated.

  In the fourth and ninth inventions, when the detected current value is smaller than the current threshold, the open-circuit voltage of the secondary battery is calculated using the detected current value and voltage value. For example, the open-circuit voltage of the secondary battery is obtained by plotting a plurality of stored current values and voltage values on voltage / current coordinates, and a primary approximation formula (for example, V = Vo-IRb) along each plotted point. Can be calculated as a value on the voltage axis of the straight line represented by this approximate expression. In addition, since the open circuit voltage is calculated using the current value and the voltage value detected when the current value (for example, the discharge current value) of the secondary battery is smaller than the current threshold, the discharge state of the secondary battery Alternatively, the value when the current value is small can be used regardless of the state of charge, and the open-circuit voltage of the secondary battery can be calculated with high accuracy.

  In the fifth invention and the tenth invention, the internal resistance and open circuit voltage of the secondary battery are calculated a plurality of times, and the calculated statistical values (for example, average value, standard deviation) of the internal resistance and open circuit voltage are calculated. calculate. The engine can be started by determining whether or not the state of the secondary battery can be started next time based on statistical values (for example, average value, standard deviation, multiple of standard deviation) of the internal resistance and the open circuit voltage. Whether or not the state of the battery can be determined with higher accuracy.

  In the eleventh aspect of the invention, when it is determined that starting is impossible, the charging current or discharging current of the secondary battery is controlled. For example, when it is determined that starting is impossible, the discharge current of the secondary battery is suppressed and the charging current is increased. As a result, the state of the secondary battery is maintained in a good state, and the starting failure of the internal combustion engine is prevented before the next start.

  In the first invention, the sixth invention and the twelfth invention, each time the internal combustion engine is started, the starting resistance of the electric motor is detected, and after the internal combustion engine is started, the internal resistance and the open voltage of the secondary battery are calculated. Based on the detected starting resistance and the calculated internal resistance and open circuit voltage of the secondary battery, it is determined whether or not the state of the secondary battery can be started next time, so that the electric motor (for example, a cell motor) Whether the internal combustion engine (engine) can be started or not can be determined more accurately than in the past regardless of changes over time or ambient temperature.

  In the second and seventh inventions, after the internal combustion engine is started, the current and voltage of the secondary battery are repeatedly detected, the detected current value is compared with the current threshold value, and the detection is performed according to the comparison result. The stored current value and voltage value are stored, and the internal resistance or open-circuit voltage of the secondary battery is calculated using the stored plurality of current values and voltage values. Depending on the value, the internal resistance or open circuit voltage of the secondary battery can be calculated with high accuracy.

  In the third and eighth inventions, when the detected current value is larger than the current threshold value, the internal resistance of the secondary battery is calculated by using the detected current value and voltage value to calculate the internal resistance of the internal combustion engine. It is possible to accurately calculate the internal resistance of the secondary battery according to the change with time after starting.

  In the fourth and ninth inventions, when the detected current value is smaller than the current threshold, the secondary battery is calculated by calculating the open voltage of the secondary battery using the detected current value and voltage value. Regardless of the discharged state or the charged state, the open-circuit voltage of the secondary battery can be calculated with high accuracy.

  In the fifth and tenth aspects of the invention, the internal resistance and open circuit voltage of the secondary battery are calculated a plurality of times, the calculated values of the internal resistance and open circuit voltage are calculated, the calculated internal resistance and By determining whether or not the state of the secondary battery can be started next time based on the statistical value of the open-circuit voltage, it is possible to more accurately determine whether or not the engine can be started or not.

  In the eleventh aspect of the invention, when it is determined that starting is impossible, it is possible to prevent engine starting failure by providing a control means for controlling the charging current or discharging current of the secondary battery.

  Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments. FIG. 1 is a block diagram showing a configuration of a battery ECU (Electric Control Unit) 10 which is a battery state determination device according to the present invention. For vehicles such as automobiles, in addition to the battery ECU 10, a battery (lead storage battery) 1 that is a secondary battery, an electric component 2 such as an air conditioner, a car stereo, and a car light, an engine 3, and a cell motor for starting the engine 3 (Motor, starter) 4, alternator (generator) 5 that supplies power to the battery 1, electrical component 2, etc. by rotation of the engine 3, a rectifier 6 that converts alternating current generated by the alternator 5 into direct current, an ignition key 7, an engine A vehicle controller 20 that controls the above, a display unit 30 that includes a liquid crystal display, an operation panel, and the like are disposed. The battery ECU 10 is connected to the vehicle controller 20 and the display unit 30 via signal lines.

  The battery 1 is a lead storage battery. For example, the voltage when fully charged is 12 V (more precisely, about 12.8 V), and the capacity is 24 Ah (5-hour rate). The battery 1 uses lead dioxide as a positive electrode active material, lead as a negative electrode active material, and sulfuric acid as an electrolyte. During discharge, lead is oxidized at the negative electrode to become cation to lead sulfate (anode reaction), and lead dioxide is reduced at the positive electrode. To lead sulfate (cathode reaction). On the other hand, at the time of charging, lead ions are reduced from lead sulfate to metal lead at the negative electrode (cathode reaction), and lead ions are oxidized to lead dioxide at the positive electrode (anode reaction).

  The ignition key 7 includes a common terminal, a START terminal, an ON / ACC terminal, and an OFF terminal, and the common terminal is connected to any one of the START terminal, the ON / ACC terminal, and the OFF terminal. The positive terminal of the battery 1 is connected to the common terminal, and one end of the cell motor 4 is connected to the START terminal. The ON / ACC terminal is connected to the positive terminal of the electrical component 2 driven by direct current and to the cathode of the rectifier 6. Nothing is connected to the OFF terminal. One end of the alternator 5 is connected to the anode of the rectifier 6.

  By operating the ignition key 7 toward the START terminal, the DC voltage of the battery 1 is applied to the cell motor 4, and the rotation shaft (not shown) of the cell motor 4 rotates to drive the piston (not shown) of the engine 3. Then, the engine 3 is started. After the engine 3 is started, the common terminal of the ignition key 7 is connected to the ON / ACC terminal.

  When the engine 3 rotates, the rotating shaft of the alternator 5 is rotated, and the alternating current generated by the alternator 5 is rectified to direct current by the rectifier 6 to supply direct current to the electrical component 2 and charge the battery 1.

  When the ignition key 7 is operated and the engine 3 is started or the engine 3 is stopped, the vehicle controller 20 outputs a signal indicating each state to the battery ECU 10. Further, the vehicle controller 20 controls the alternator 5, the electrical component 2, and the like based on the control signal input from the battery ECU 10, and controls the charging current and discharging current of the battery 1.

  The battery ECU 10 includes a voltage detection unit 11, a current detection unit 12, an interface unit 13, a CPU 14, a RAM 15, a storage unit 16, and the like. The battery ECU 10 can be configured by a dedicated ASIC (Application Specified IC), FPGA (Field Programmable Gate Arrays), or the like.

  The interface unit 13 transmits and receives data between the CPU 14, the vehicle controller 20, and the display unit 30. For example, when the ignition key is operated and the engine 3 is started, the interface unit 13 receives an engine start signal transmitted from the vehicle controller 20 and outputs the received engine start signal to the CPU 14. Further, when the ignition key is operated and the engine 3 is stopped, the interface unit 13 receives the engine stop signal transmitted from the vehicle controller 20 and outputs the received engine stop signal to the CPU 14.

  Further, the interface unit 13 receives a signal corresponding to an operation on the operation panel of the display unit 30, outputs the received signal to the CPU 14, and outputs a control signal (for example, a state of the battery 1 described later) from the CPU 14. A signal for displaying the determination result on the liquid crystal display of the display unit 30 is output to the display unit 30.

  The state determination result of the battery 1 can be displayed on the liquid crystal panel of the display unit 30 with characters, symbols, figures, or the like, or can be displayed with a display lamp. For example, when it is determined that the engine 3 cannot be started next time, the charging current or discharging current of the battery 1 is controlled to display “Battery load current is limited.” it can. In addition, it is possible to alert the driver by displaying a message such as “suppress current consumption of the battery” or “charge the battery as soon as possible”, so that the starting failure of the engine 3 can be prevented. Can be prevented.

  Further, the interface unit 13 determines the charging current of the battery 1 when, for example, it is determined that the state of the battery 1 is not sufficient to start the engine 3 next time according to the result of the determination of the state of the battery 1 in the CPU 14. The control signal for increasing the discharge current is acquired from the CPU 14 and the acquired control signal is output to the vehicle controller 20.

  The voltage detection unit 11 detects the voltage of the battery 1 under the control of the CPU 14 and outputs the detection result to the CPU 14. More specifically, when receiving an engine start signal through the interface unit 13, the CPU 14 outputs a voltage detection signal for detecting the voltage of the battery 1 at the time of starting the engine 3 to the voltage detection unit 11. 11 detects the voltage of the battery 1 by receiving the voltage detection signal.

  The voltage detection unit 11 detects the voltage of the battery 1 at a predetermined time interval (for example, 5 ms) under the control of the CPU 14 after the engine 3 is started, and outputs the detection result to the CPU 14. More specifically, when receiving an engine start completion signal from the vehicle controller 20 through the interface unit 13, the CPU 14 sends a voltage detection signal for detecting the voltage of the battery 1 after the completion of the engine 3 start to the voltage detection unit 11. The voltage detection unit 11 receives the voltage detection signal and repeatedly detects the voltage of the battery 1 at a predetermined interval.

  The current detection unit 12 detects the current (discharge current, charging current) of the battery 1 under the control of the CPU 14 and outputs the detection result to the CPU 14. In this case, current detection and voltage detection are performed in synchronization. More specifically, when receiving an engine start signal through the interface unit 13, the CPU 14 outputs a current detection signal for detecting the current of the battery 1 at the time of starting the engine 3 to the current detection unit 12. 12 detects a current of the battery 1 by receiving a current detection signal.

  Further, after the engine 3 is started, the current detector 12 detects the current of the battery 1 at a predetermined time interval (for example, 5 ms) under the control of the CPU 14 and outputs the detection result to the CPU 14. In this case, current detection and voltage detection are performed in synchronization. More specifically, when receiving an engine start completion signal from the vehicle controller 20 through the interface unit 13, the CPU 14 sends a current detection signal for detecting the current of the battery 1 after the start of the engine 3 to the current detection unit 12. The current detection unit 12 receives the current detection signal, and repeatedly detects the current of the battery 1 at a predetermined interval.

  The CPU 14 loads a predetermined control program stored in the storage unit 16 into the RAM 15 and controls the operation of the battery ECU 10 by causing the CPU 14 to execute the control program.

  The storage unit 16 is a recording medium in which information can be written, and stores various information in addition to the control program. For example, the storage unit 16 stores information such as the nominal capacity of the battery 1 mounted on the vehicle. In addition, the storage unit 16 stores an allowable minimum starting current Ismin that needs to flow through the cell motor 4 in order to start the engine 3. Further, the storage unit 16 stores a current threshold Ith for determining whether to calculate the internal resistance Rb or the open circuit voltage Vo of the battery 1 according to the magnitude of the current value of the battery 1.

  The storage unit 16 stores the voltage value and current value detection history of the battery 1 detected by the voltage detection unit 11 and the current detection unit 12, respectively. In addition, the storage unit 16 stores the starting resistance Rs of the cell motor 4, the internal resistance Rb of the battery 1, and the open voltage Vo calculated by the CPU 14 based on the stored voltage value and current value.

  The CPU 14 calculates (detects) the starting resistance Rs of the cell motor 4 each time the engine 3 is started by detecting the voltage and current of the battery 1 when the engine 3 is started. When the voltage and current of the battery 1 are V and I, respectively, the starting resistance Rs can be calculated by Rs = V / I. Note that the voltage detection unit 11 or the current detection unit 12 is configured to calculate the starting resistance Rs of the cell motor 4 based on the detected voltage value and current value, and to output the calculated starting resistance Rs to the CPU 14. You can also.

  The CPU 14 can also calculate the internal resistance Rb of the battery 1 each time the engine 3 is started by detecting the voltage and current of the battery 1 when the engine 3 is started. When the voltage and current of the battery 1 are V and I, respectively, the internal resistance Rb can be calculated by Rb = (Vo−V) / I. In this case, the open-circuit voltage Vo of the battery 1 can be a rated voltage or, if already calculated, for example, a value calculated most recently.

  Whenever the current and voltage of the battery 1 are detected at a predetermined time interval (for example, 5 ms) after the start of the engine 3 is completed, the CPU 14 sets the current value of the battery 1 to a current threshold Ith (for example, about 5 A to 10 A). ) Or more (or whether the current value of the battery 1 is greater than the current threshold Ith), and if the current value of the battery 1 is greater than or equal to the current threshold Ith (or the current value of the battery 1 is current) When the current value of the battery 1 is smaller than the current threshold value Ith, a process for calculating the open-circuit voltage Vo of the battery 1 is performed.

  The calculation process of the internal resistance Rb of the battery 1 stores a plurality of current values and voltage values of the battery 1 detected when the current value of the battery 1 is equal to or greater than the current threshold Ith, and the stored number of samples is predetermined. When the threshold value (for example, 20) is exceeded, the stored current value and voltage value are plotted on the voltage / current coordinates, and a linear approximation formula (for example, V = Vo-IRb) is plotted along each plotted point. ) And the slope of the straight line represented by this approximate expression can be calculated as the internal resistance Rb.

  The CPU 14 stores a plurality of internal resistances Rb of the battery 1 calculated as described above, and when the stored number of samples is equal to or greater than a predetermined threshold (for example, 20), the average value Rbav of the internal resistance Rb, the standard deviation σ is obtained, and the internal resistance Rb used for determining whether the engine 3 can be started is calculated as Rb = Rbav + σ. The internal resistance Rb may be calculated as Rb = Rbav + 2σ or Rbav + 3σ. Whether to use standard deviation σ, 2σ, or 3σ can be set as appropriate according to how much the internal resistance Rb is allowed.

  The calculation process of the open circuit voltage Vo of the battery 1 is performed by storing a plurality of current values and voltage values of the battery 1 detected when the current value of the battery 1 is smaller than the current threshold value Ith, and the stored number of samples is predetermined. When the threshold value (for example, 20) or more is reached, the stored current value and voltage value are plotted on the voltage / current coordinates, and a linear approximation formula (for example, V = Vo-IRb) along each plotted point. And the value on the voltage axis of the straight line represented by this approximate expression can be calculated as the open circuit voltage Vo.

  The CPU 14 stores a plurality of open circuit voltages Vo of the battery 1 calculated as described above, and when the stored number of samples becomes a predetermined threshold (for example, 20) or more, obtains an average value Voav of the open circuit voltage Vo, The average value Voav is defined as an open circuit voltage Vo used for determining whether or not the engine 3 can be started.

  The CPU 14 determines whether or not the engine 3 can be started the next time the engine 3 is started based on the internal resistance Rb and the open circuit voltage Vo of the battery 1 calculated as described above. This is determined by whether or not the condition of / Ismin-Rs is satisfied. When it is determined that starting is impossible, the CPU 14 outputs a control signal for increasing the charging current of the battery 1 and suppressing the discharging current to the vehicle controller 20.

  FIG. 2 is an explanatory diagram showing an equivalent circuit around the battery 1 when the engine is started. As shown in the figure, the battery 1 can be represented by a DC power supply (voltage Vo) and an internal resistance Rb, and the equivalent circuit around the battery 1 at the time of starting is the DC voltage Vo (corresponding to the open voltage of the battery 1). The internal resistance Rb of the battery 1 and the starting resistance Rs of the cell motor 4 are expressed in a state connected in series. By detecting the current I and voltage V of the battery 1 when the engine 3 is started, the starting resistance Rs can be obtained by Rs = V / I.

  FIG. 3 is an explanatory diagram showing an equivalent circuit around the battery 1 after completion of engine start. As shown in the figure, the battery 1 can be expressed by a DC power supply (voltage Vo) and an internal resistance Rb, and the equivalent circuit around the battery 1 after the start is completed corresponds to the DC voltage Vo (the open voltage of the battery 1). ) Is represented in a state in which the load resistance R including the internal resistance Rb of the battery 1, the electrical component 2, the alternator 5, and the like are connected in series. After the start of the engine 3 is completed (for example, when the vehicle is traveling), the current I and the voltage V of the battery 1 are expressed by a battery characteristic equation V = Vo-IRb. The slope of the straight line represented by the battery characteristic equation represents the internal resistance Rb of the battery 1, and the value on the voltage axis represents the open circuit voltage Vo.

  FIG. 4 is an explanatory diagram illustrating an example of a voltage change of the battery 1. In the figure, the vertical axis represents the voltage of the battery 1 and the horizontal axis represents time (seconds). As shown in the figure, the voltage of the battery 1 immediately after the start of the engine 3 causes a steep start current to flow to the cell motor 4, so that the voltage of the battery 1 rapidly decreases and then gradually increases, and then a few seconds after the start. After the lapse of time, the voltage of the battery 1 changes stably. In the state where the voltage of the battery 1 changes, the voltage and current of the battery 1 are repeatedly detected at predetermined time intervals.

  FIG. 5 is an explanatory diagram showing a calculation example of the internal resistance Rb of the battery 1. In the state where the voltage of the battery 1 changes, the current and voltage of the battery 1 are detected, and when the detected current value is equal to or greater than the current threshold Ith, a plurality of detected current values and voltage values of the battery 1 are stored. When the number of stored samples exceeds a predetermined threshold value (for example, 20), the stored current value and voltage value are plotted on the voltage / current coordinates, and a linear approximation formula along each plotted point. (For example, V = Vo−IRb) is obtained, and the slope of the straight line A represented by this approximate expression is calculated as the internal resistance Rb.

  FIG. 6 is an explanatory diagram showing a calculation example of the open circuit voltage Vo of the battery 1. In the state where the voltage of the battery 1 changes, the current and voltage of the battery 1 are detected, and when the detected current value is smaller than the current threshold Ith, a plurality of detected current values and voltage values of the battery 1 are stored. When the number of stored samples becomes a predetermined threshold value (for example, 20) or more, the stored current value and voltage value are plotted on the voltage / current coordinates, and a linear approximation formula ( For example, V = Vo−IRb) is obtained, and the value on the voltage axis of the straight line B represented by this approximate expression is calculated as the open circuit voltage Vo. In the case of obtaining the primary approximate expression in FIG. 6, the current value is smaller than the current threshold Ith, and therefore the current range of the primary approximate expression is smaller than that in the case of FIG.

  FIG. 7 is an explanatory diagram illustrating a calculation example of a statistical value of the internal resistance Rb of the battery 1. In the figure, the vertical axis indicates the frequency, and the horizontal axis indicates the resistance value (Ω). As shown in FIG. 6, by calculating one primary approximate expression, one internal resistance Rb can be calculated. This calculation of the primary approximate expression is repeated a predetermined number of times, and the internal resistance Rb calculated each time is calculated. Find the frequency distribution of the values of. As shown in the figure, the average value Rbav of the internal resistance Rb is about 0.00625Ω and the standard deviation σ is 0.00225Ω, and the internal resistance Rb used to determine whether or not to start is obtained by adding the average value Rbav and the standard deviation σ. By doing so, a margin can be added to the determination of whether or not the engine can be started. Note that the open circuit voltage Vo of the battery 1 can be similarly obtained by performing statistical processing.

  Next, the operation of the battery ECU 10 will be described. 8 and 9 are flowcharts showing the procedure of the battery 1 state determination process. CPU14 determines whether the ignition key 7 was turned on based on the signal which the vehicle controller 20 outputs (S11). When the ignition key 7 is not turned on (NO in S11), the CPU 14 determines that the engine 3 is not started, continues the process of step S11, and waits until the ignition key 7 is turned on.

  When the ignition key 7 is turned on (YES in S11), the CPU 14 calculates the starting resistance Rs of the cell motor 4 by detecting the current and voltage of the battery 1 immediately after starting (S12). After the start of the engine 3 is completed, the CPU 14 detects the current and voltage of the battery 1 (S13), and determines whether or not the detected current value is smaller than a predetermined current threshold Ith (S14).

  When the current value is smaller than the current threshold Ith (YES in S14), the CPU 14 stores the detected current value and voltage value (S15), and determines whether or not a predetermined number of samples (eg, “20”) is stored (S15). S16). When the predetermined number of samples is stored (YES in S16), the CPU 14 calculates the open circuit voltage Vo of the battery 1 based on the primary approximation formula (S17), and whether or not the predetermined number of samples (for example, “20”) is calculated. Determine (S18).

  When the predetermined number of samples is calculated (YES in S18), the CPU 14 calculates the average value Voav of the open circuit voltage Vo of the battery 1 (S19), and sets the calculated average value Voav as the open circuit voltage Vo of the battery 1 (S20). If the predetermined number of samples is not stored (NO in S16), the CPU 14 continues the processing from step S13. If the predetermined number of samples has not been calculated (NO in S18), the CPU 14 continues the processing from step S13.

  If the current value is not smaller than the current threshold Ith (NO in S14), the CPU 14 stores the detected current value and voltage value (S21), and determines whether or not a predetermined number of samples (eg, “20”) is stored. (S22). When the predetermined number of samples is stored (YES in S22), the CPU 14 calculates the characteristic formula of the battery 1 (S23), calculates the slope of the calculated characteristic formula as the internal resistance Rb of the battery 1 (S24), and the predetermined sample It is determined whether or not a number (for example, “20”) has been calculated (S25).

  When the predetermined number of samples is calculated (YES in S25), the CPU 14 calculates an average value Rbav of the internal resistance Rb of the battery 1 (S26), calculates a standard deviation σ of the internal resistance Rb (S27), and calculates the calculated average value. A value obtained by adding the standard deviation σ to Rbav is set as the internal resistance Rb of the battery 1 (S28). If the predetermined number of samples is not stored (NO in S22), the CPU 14 continues the processing from step S13. If the predetermined number of samples has not been calculated (NO in S25), the CPU 14 continues the processing from step S13.

  The CPU 14 determines whether or not the engine can be started based on the start characteristic equation (S29). When the start is impossible (NO in S29), the CPU 14 controls to increase the charging current of the battery 1 (S30) and suppresses the discharging current of the battery 1. It is controlled accordingly (S31), and it is determined whether or not the ignition key 7 is turned off (S32). If the engine can be started (YES in S29), the CPU 14 performs the process of step S32.

  If the ignition key 7 is not turned off (NO in S32), the CPU 14 continues the processing from step S13. If the ignition key 7 is turned off (YES in S32), the process is terminated.

  As described above, in the present invention, whether the engine 3 can be started regardless of the secular change of the cell motor 4 or the ambient temperature can be determined with higher accuracy than in the past. it can. Further, according to the current value of the battery 1 after the engine 3 is started, it is possible to select whether the detected current value and voltage value are used for calculation of the internal resistance or the open voltage of the battery 1. The internal resistance or open circuit voltage can be calculated with high accuracy. Further, the internal resistance Rb of the battery 1 can be accurately calculated according to the change with time after the start of the engine 3 is completed. In addition, the open circuit voltage Vo of the battery 1 can be accurately calculated regardless of whether the battery 1 is discharged or charged. Further, it is possible to prevent a start failure of the engine 3 in advance.

  In the above-described embodiment, the lead storage battery is used as the battery. However, the battery is not limited to the lead storage battery, and the present invention can be applied to other batteries.

  In the above-described embodiment, the battery current value and voltage value are stored for a predetermined number of samples, and based on the stored current value and voltage value, a primary approximation expression is obtained to calculate the open circuit voltage of the battery. However, the present invention is not limited to this, and when another current threshold Ith2 smaller than the current threshold Ith is used and the detected current value is equal to or smaller than the current threshold Ith2, the voltage value detected in synchronization is released. The structure calculated | required as a voltage may be sufficient. Thereby, the processing effort required for the calculation process of the open circuit voltage can be reduced.

  In the above-described embodiment, the battery current value and voltage value are stored for a predetermined number of samples, the battery characteristic equation is obtained based on the stored current value and voltage value, and the battery is determined by the slope of the straight line represented by the characteristic equation. However, the present invention is not limited to this. For example, a battery characteristic equation assumed in advance is stored, and the battery characteristic equation closest to the detected current value and voltage value is stored. The internal resistance of the battery may be calculated by specifying the above.

  In the above-described embodiment, the minimum allowable starting current Ismin required for starting the cell motor is stored. However, when the starting characteristic changes according to the ambient temperature of the cell motor, the ambient temperature of the cell motor is changed. While providing a temperature sensor to detect, a plurality of allowable minimum starting currents Ismin corresponding to the temperature may be stored, and the allowable minimum starting current Ismin corresponding to the detected temperature may be selected.

  In the above-described embodiment, the current value and voltage value of the battery detected repeatedly are stored, and the internal resistance and open circuit voltage of the battery are calculated and stored based on the stored current value and voltage value. However, when there is a limit to the storage capacity, it is possible to store the calculation data of the most recent predetermined capacity and delete the calculation data that has become old.

It is a block diagram which shows the structure of battery ECU which is a battery state determination apparatus which concerns on this invention. It is explanatory drawing which shows the equivalent circuit around a battery at the time of engine starting. It is explanatory drawing which shows the equivalent circuit around a battery after engine starting completion. It is explanatory drawing which shows an example of the voltage change of a battery. It is explanatory drawing which shows the example of calculation of the internal resistance of a battery. It is explanatory drawing which shows the example of calculation of the open circuit voltage of a battery. It is explanatory drawing which shows the example of calculation of the statistical value of the internal resistance of a battery. It is a flowchart which shows the procedure of a battery state determination process. It is a flowchart which shows the procedure of a battery state determination process.

Explanation of symbols

1 battery 4 cell motor 10 battery ECU
11 Voltage Detection Unit 12 Current Detection Unit 13 Interface Unit 14 CPU
15 RAM
16 storage unit 20 vehicle controller 30 display unit

Claims (12)

In a battery state determination method for determining a state of a secondary battery that supplies power to an electric motor for starting an internal combustion engine,
Detect the starting resistance of the motor every time it starts,
After the internal combustion engine starts, calculate the internal resistance and open circuit voltage of the secondary battery,
A battery state determination method comprising: determining whether or not the state of the secondary battery can be started next time based on the detected starting resistance and the calculated internal resistance and open circuit voltage of the secondary battery. After the internal combustion engine is started, the current and voltage of the secondary battery are repeatedly detected,
Compare the detected current value with the current threshold,
According to the comparison result, the detected current value and voltage value are stored,
The battery state determination method according to claim 1, wherein an internal resistance or an open circuit voltage of the secondary battery is calculated using a plurality of stored current values and voltage values.   3. The battery state determination method according to claim 2, wherein when the detected current value is larger than the current threshold, the detected current value and voltage value are used to calculate the internal resistance of the secondary battery.   3. The battery state determination method according to claim 2, wherein when the detected current value is smaller than the current threshold, the detected current value and voltage value are used to calculate an open circuit voltage of the secondary battery. Calculate the internal resistance or open circuit voltage of the secondary battery multiple times,
Calculate the calculated values of multiple internal resistances or open-circuit voltages,
5. The method according to claim 1, wherein it is determined whether or not the state of the secondary battery can be started next time based on the calculated statistical value of the internal resistance or the open-circuit voltage. Battery state determination method. In a battery state determination device for determining a state of a secondary battery that supplies power to an electric motor for starting an internal combustion engine,
Detecting means for detecting the starting resistance of the motor each time the engine is started;
When the internal combustion engine is started, calculating means for calculating the internal resistance and open circuit voltage of the secondary battery;
Determining means for determining whether or not the state of the secondary battery can be started next time based on the starting resistance detected by the detecting means and the internal resistance and open circuit voltage of the secondary battery calculated by the calculating means; A battery state determination device comprising: Means for detecting the current and voltage of the secondary battery;
Means for comparing the detected current value with a current threshold;
Storage means for storing the detected current value and voltage value according to the comparison result, and
The calculating means includes
The battery state determination device according to claim 6, wherein the battery state determination device is configured to calculate an internal resistance or an open-circuit voltage of the secondary battery using a plurality of current values and voltage values stored in the storage unit. . The calculating means includes
The battery according to claim 7, wherein when the detected current value is larger than the current threshold, the internal resistance of the secondary battery is calculated using the detected current value and voltage value. State determination device. The calculating means includes
8. The battery according to claim 7, wherein when the detected current value is smaller than the current threshold, the open voltage of the secondary battery is calculated using the detected current value and voltage value. State determination device. Means for calculating a plurality of internal resistance and open circuit voltage statistics calculated by the calculating means;
The determination means includes
7. The apparatus according to claim 6, wherein a determination is made as to whether or not the state of the secondary battery can be started next time based on the statistical values of the internal resistance and the open circuit voltage calculated by the means. The battery state determination apparatus according to claim 9.   11. The battery state determination device according to claim 6, further comprising a control unit that controls a charging current or a discharging current of the secondary battery when the determination unit determines that starting is impossible. . In a computer program for causing a computer to determine a state of a secondary battery that supplies electric power to an electric motor for starting an internal combustion engine,
Means for comparing the current value of the secondary battery with the current threshold after starting the internal combustion engine;
Means for calculating the internal resistance or open-circuit voltage of the secondary battery using the current value and voltage value of the secondary battery according to the comparison result;
Based on the calculated internal resistance and open-circuit voltage and the starting resistance of the motor when starting the internal combustion engine, the computer functions as a means for determining whether or not the state of the secondary battery can be started next time. A computer program characterized by the above.

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