JP5082368B2 - Battery status detection system - Google Patents

Description

  The present invention relates to a battery state detection system, and more particularly to a battery state detection system provided with a computer that uses a battery that supplies power to an engine starter starter via an ignition switch as an operating power source and calculates the battery state of the battery.

  In recent years, an idling stop start (hereinafter abbreviated as ISS) has been performed in order to cope with the reduction of exhaust gas by an engine vehicle, and a technique for keeping the engine vehicle in an idling stopable state is desired. The engine automobile includes a battery that supplies electric power to an engine starter at the time of ISS. When the engine is started, electric power is supplied from the battery to the starter via the ignition switch. Lead batteries are typical batteries that can be used for this type of application. At idle stop, electric loads such as air conditioners and audio equipment are provided by batteries. The battery state is estimated (detected) from the state of charge (SOC) and the degree of deterioration (SOH) by the battery state detection system in order to keep the state where idling can be stopped.

  Methods for estimating (calculating) the state of charge of the battery include a method for obtaining from the differential internal resistance (the slope of the voltage / current line), a method for integrating the charge / discharge current, and a method for obtaining from the open circuit voltage of the battery (for example, Patent Document 1). See). On the other hand, as a method for estimating the deterioration state of the battery, there is a method in which the internal resistance is calculated from the voltage-current (V-I) characteristics at the time of discharging such as when the engine is started, and is estimated from a comparison with the initial internal resistance. .

  A battery state detection system generally includes a computer that calculates a battery state. This computer normally uses a battery as an operating power source. The presence or absence of an output necessary for starting the engine is monitored from the battery state of the battery calculated by the computer.

JP-A-6-242193

  However, in the above-described battery state detection system, when the battery state is actually detected, a voltage drop occurs in the battery due to an electrical load when the ignition switch is turned on or power supply when starting the engine with the starter. For this reason, there is a problem that detection of a battery state becomes impossible or inaccurate because a computer using a battery as an operating power supply stops operating or malfunctions.

  An object of the present invention is to provide a battery state detection system capable of appropriately detecting the battery state of a battery regardless of the state of the vehicle.

In order to solve the above-described problems, the present invention provides a battery state detection system including a computer that calculates the battery state of the battery, using a battery that supplies power to an engine starter starter via an ignition switch as an operating power source. The battery is connected in parallel with the battery and has a capacitor for ensuring a normal operation of computation by the computer when power is supplied from the battery to the starter, an A / D converter and a reference power supply unit, and detects the voltage of the battery The capacitor is connected in parallel to the reference power supply unit .

In the present invention, a capacitor is connected in parallel with the battery, and the capacitor is connected in parallel with the reference power supply unit of the voltage detection unit, and the capacitor is charged by the battery. Even if a battery voltage drop occurs when power is supplied to the starter, the power stored in the capacitor is supplied to the computer, so the battery voltage drop is alleviated. In addition, since the power stored in the capacitor is supplied to the reference power supply unit and the A / D converter functions normally, the battery voltage detection accuracy by the voltage detection unit can be ensured.

In this case, if a diode or a coil is inserted between the battery and the capacitor, supply of electric power stored in the capacitor to the starter is prevented by the diode or coil when power is supplied from the battery to the starter .

According to the present invention, since the capacitor is connected in parallel with the battery and the capacitor is connected in parallel to the reference power supply unit of the voltage detection unit, even if the battery voltage drop occurs when power is supplied to the starter. Since the power stored in the capacitor is supplied to the computer, the voltage drop of the battery is alleviated, so that normal operation of the calculation by the computer can be ensured and the power stored in the capacitor is supplied to the reference power supply unit. Since the supplied A / D converter functions normally, it is possible to obtain an effect that the battery voltage detection accuracy by the voltage detection unit can be ensured .

  Embodiments of a battery state detection system according to the present invention will be described below with reference to the drawings.

<Configuration>
As shown in FIG. 1, the battery state detection system 20 of the present embodiment is fixed to the battery case side away from the vent plug of the lead battery 1 mounted on a vehicle (automobile). Voltage detection that detects the open circuit (open circuit) voltage (OCV) and detects the voltage across the microcomputer 10 (hereinafter abbreviated as microcomputer) 10 and the lead battery 1 as a computer that calculates (estimates) the state of charge (SOC). Part 13 is provided. As the lead battery 1, for example, one cell is composed of, for example, six positive electrodes and seven negative electrodes, and a lead battery for a vehicle having a nominal 12V in series of six cells can be used.

  The microcomputer 10 includes a CPU that functions as a central processing unit, a ROM that stores program data such as a basic control program for the battery state detection system 20 and a map that indicates the relationship between OCV and SOC, a RAM that functions as a work area for the CPU, A A / D converter, a D / A converter, a non-volatile EEPROM, an interface for communicating with the host vehicle control system 11, and the like are included.

  A positive terminal of the lead battery 1 is connected to a central terminal of an ignition switch (hereinafter referred to as IGN switch) 5 via a current sensor 4 constituted by a Hall element or the like. The IGN switch 5 has an OFF terminal, an ON / ACC terminal, and a START terminal in addition to the center terminal, and can be switched and connected in a rotary manner.

  One end of a capacitor 14 is connected to the positive terminal of the lead battery 1 in parallel with the lead battery 1. A diode 15 is connected between the positive terminal of the lead battery 1 connected in parallel and one end of the capacitor 14. That is, the diode 15 is inserted (connected in series) between the lead battery 1 and the capacitor 14. The diode 15 has an anode side connected to the positive electrode terminal side of the lead battery 1 and a cathode side connected to the capacitor 14 side.

  The voltage detection unit 13 includes an A / D converter and a reference power supply unit B. The A / D converter is connected to the bipolar terminals of the lead battery 1. The A / D converter is supplied with a reference voltage (for example, 5 V) for detecting the voltage across the lead battery 1 from the reference power supply unit B. One end of the reference power supply unit B is connected to the cathode side of the diode 15, and the other end is connected to the negative terminal of the lead battery 1. That is, the reference power supply unit B and the capacitor 14 are connected in parallel. The output terminal of the voltage detector 13 is connected to the microcomputer 10, and the microcomputer 10 can take in the voltage across the lead battery 1 as a digital value. Further, the output terminal of the current sensor 4 is connected to an A / D converter built in the microcomputer 10, and the microcomputer 10 can take in the charge / discharge current flowing through the lead battery 1 as a digital value. Note that the battery state detection system 20 is configured to include such wiring.

  On the other hand, a starter (cell motor) 9 for starting the engine 8 by transmitting the rotational driving force to the rotating shaft of the engine 8 via a clutch mechanism (not shown) is disposed on the vehicle side. The rotation shaft of the engine 8 can transmit power to the generator 7 via a clutch mechanism (not shown). When the engine 8 is in a rotating state, the generator 7 is operated via this clutch mechanism. The power from the generator 7 is supplied to an auxiliary device 6 such as an air conditioner or an audio device, a lead battery 1, a reference power source B, and a capacitor 14 through a regulator (represented by a rectifying element symbol in FIG. 1). At the same time, it is supplied as an operating power source for the microcomputer 10. Such engine control and the like are executed by the vehicle control system 11.

  The ON / ACC terminal of the IGN switch 5 is connected to one end of the generator 7 via the auxiliary machine 6 and the regulator. The START terminal is connected to one end of the starter 9. Furthermore, the other end of the generator 7, the starter 9, and the auxiliary machine 6, the negative terminal of the lead battery 1, the other end of the capacitor 14, and the microcomputer 10 are connected to the ground.

  In addition, the lead battery 1 supplies an operating power source for the microcomputer 10 through a switch 2 including a current sensor 4 and an FET. When a high / low binary voltage is applied to the gate of the FET of the switch 2 from the output port of the vehicle control system 11 via the D / A converter, the switch 2 is turned on and off.

<Operation>
Next, with reference to a flowchart, the operation of the battery state detection system 20 of the present embodiment will be described with a CPU (hereinafter referred to as a CPU) of the microcomputer 10 as a subject.

  When the IGN switch 5 is connected to the ON / ACC terminal (M contact point ON), the power of the lead battery 1 is supplied to the auxiliary device 6, the reference power supply unit B, and the capacitor 14. After a certain time has elapsed, the switch 2 is turned on by applying a voltage from the vehicle control system 11. Thereby, electric power is supplied from the lead battery 1 to the microcomputer 10, and the CPU of the microcomputer 10 executes a charge state calculation routine for calculating the charge state (SOC) of the lead battery 1.

  As shown in FIG. 2, in the charging state calculation routine, first, in step 102, an initial setting process for expanding a program and program data stored in the ROM into the RAM is performed. Note that the CPU fetches the data of the current sensor 4 every predetermined time (for example, 1 ms) by the interrupt process after the initial setting process, and integrates the captured current. In FIG. The calculation step is discarded.

  When the IGN switch 5 is connected to the START terminal, the power of the lead battery 1 is supplied to the starter 9 via the IGN switch 5. Since the diode 15 is inserted between the lead battery 1 and the capacitor 14, the electric power stored in the capacitor 14 is not supplied to the starter 9 but is supplied to the microcomputer 10 and the reference power supply unit B. When the rotational driving force of the starter 9 is transmitted to the engine 8 and the engine 8 is started, the power of the engine 8 is transmitted to the generator 7. After the engine 8 is started, the IGN switch 5 is connected to the ON / ACC terminal. The electric power generated by the generator 7 is supplied to the auxiliary machine 6, the lead battery 1, the reference power supply B, and the capacitor 14, and is also supplied as an operating power supply for the microcomputer 10 via the switch 2 (see also FIG. 1). . Thereby, the lead battery 1 is charged and the capacitor 14 is charged. Here, the voltage change of the lead battery 1 when the engine 8 is started will be described. Immediately after the start of current flow in the starter 9, a sharp peak-shaped large current is discharged from the lead battery 1, and at the same time, the voltage across the lead battery 1 shows a sharp valley-shaped voltage drop, as shown in FIG. After the engine 8 is started, power is supplied from the generator 7 so that the voltage across the lead battery 1 is restored. Since the lead battery 1 of this example is nominally 12V, if the voltage across the lead battery 1 is approximately 10V or more, there is no hindrance to normal operation, and it takes a very short time to fall below 10V before and after reaching the minimum voltage. It is.

  Next, in step 104, the SOC of the lead battery 1 (when the engine 8 starts) is calculated (details will be described later). For example, the relationship between the OCV and the SOC is preliminarily mapped or mathematically expressed as program data, and the read OCV is assigned to the map or mathematical formula, and the SOC is obtained by dividing. The calculated SOC of the lead battery 1 is stored in the RAM.

  In the next step 106, the current SOC of the lead battery 1 is calculated from the SOC of the lead battery 1 that is the reference calculated in step 104 and the integrated current value integrated every predetermined time described above (the lead battery of the reference). 1), the calculated current SOC of the lead battery 1 is stored in the RAM, and is notified to the vehicle control system 11 via the interface. Thereby, the vehicle control system 11 can grasp | ascertain SOC of the lead battery 1, For example, it becomes possible to judge whether the engine 8 is stopped at the time of idle stop. In addition, the technique of calculating the present SOC of the lead battery from the SOC of the lead battery serving as a reference and the accumulated current value accumulated every predetermined time is known.

  Next, in step 108, it is determined whether or not the IGN switch 5 is connected to the OFF terminal (M contact point OFF), that is, whether or not the engine 8 has stopped. Such a determination may be received from the vehicle control system 11 side, or may be inserted between the generator 7 and the IGN switch 5 or may be inserted between the generator 7 and the IGN switch 5 with a current sensor built in the microcomputer 10. You may make it judge by monitoring the electric current between. If the determination is negative, the process returns to step 106 in order to continue the calculation of the current SOC of the lead battery 1. Therefore, in the charge state calculation routine, while the power is supplied from the generator 7 to the microcomputer 10, the CPU mainly calculates the SOC of the lead battery 1 and notifies the vehicle control system 11 of the calculation result. During this time, the IGN switch 5 is connected to the ON / ACC terminal, and the power from the generator 7 is supplied to the lead battery 1 and the capacitor 14 so that the lead battery 1 is charged and the capacitor 14 also receives power. Accumulated.

  On the other hand, if the determination in step 108 is affirmative, the CPU starts a timer. For such a timer, a dedicated timer IC different from the CPU may be used. However, in order to reduce power consumption, the timer may be clocked by an internal clock of the CPU. At this time, the operating power is supplied from the lead battery 1 to the microcomputer 10 via the switch 2 in the ON state, and the operation clock frequency of the CPU is lowered to shift to the low power consumption sleep mode. In the sleep mode, the SOC of the lead battery 1 is not calculated. When the voltage of the capacitor 14 is lowered, the capacitor 14 is charged with the lead battery 1.

  Next, in step 112, it is determined whether or not a predetermined time (for example, 6 hours) has elapsed until the voltage of the lead battery 1 is considered stable. When a negative determination is made in step 112, in the next step 114, data on the voltage across the lead battery 1 is taken in from the voltage detector 13 every predetermined time (for example, 1 ms). Thereby, the microcomputer 10 can grasp the voltage of the lead battery 1 and can determine whether or not the voltage of the lead battery 1 is stable. This may be determined to be stable when, for example, the voltage data for three times are compared and fluctuated within a certain range without continuously increasing or decreasing. Further, when the voltage is not stable before the predetermined time has elapsed, for example, the predetermined time may be extended. In the next step 116, it is determined whether or not the IGN switch 5 is connected to the ON / ACC terminal. If a negative determination is made, the process returns to step 112. If an affirmative determination is made, a flag indicating that the predetermined time has not elapsed in the next step 118 is set, and the process returns to step 104.

  On the other hand, when an affirmative determination is made at step 112, that is, when the voltage of the lead battery 1 is considered to be stable, the OCV of the lead battery 1 is measured (captured) at step 120, and the next step 122 stores the EEPROM into The OCV of the lead battery 1 measured in step 1 is written (the OCV of the lead battery 1 recorded previously is rewritten to the OCV newly measured in step 120). In the next step 124, the vehicle control system 11 is notified of the end of rewriting of the OCV, and the charging state calculation routine is terminated. The switch 2 is turned off by applying a voltage from the vehicle control system 11 that receives the notification from the CPU of the microcomputer 10. As a result, the switch 2 is opened (shut off), the power supply to the microcomputer 10 is shut down, and the microcomputer 10 does not become a load of the lead battery 1 (aside from the dark current).

  Here, the calculation of the SOC of the lead battery 1 serving as the reference in step 104 will be described in detail. If the flag is not set in step 118, that is, if a predetermined time has elapsed in step 112 (when the voltage of the lead battery 1 is considered stable), the OCV of the lead battery 1 written in the EEPROM in step 122 is set. Read and calculate the SOC of the lead battery 1 from the OCV-SOC map.

  On the other hand, when the flag is set in step 118, that is, when the predetermined time has not elapsed (when the voltage of the lead battery 1 is not considered stable), the exact OCV of the lead battery 1 is unknown, The SOC cannot be obtained by the same process as when the flag is not set. However, since the microcomputer 10 is not shut down, the last SOC data of the lead battery 1 calculated in step 106 and the current integrated value so far exist in the RAM. In step 116, the IGN switch 5 is connected to the ON / ACC terminal via the START terminal, and a large current is supplied from the lead battery 1 to the starter 9. Further, when the time from the timer start in step 110 to the time when the IGN switch 5 in step 116 is connected to the ON / ACC terminal (hereinafter referred to as elapsed time) is, for example, less than 10 minutes. There is a high possibility that the vehicle is in an idle stop state and is supplying electric power from the lead battery 1 to the auxiliary machine 6. The discharge current integrated value supplied from the lead battery 1 to the starter 9 and the discharge current integrated value supplied to the auxiliary machine 6 in the idle stop state can be calculated empirically, and by adding a margin with safety added thereto, A total discharge current integrated value discharged from the lead battery 1 can be obtained. For this reason, in step 104, the SOC of the lead battery 1 serving as a reference is the SOC of the last lead battery 1 calculated in step 106, and the current integrated value obtained by subtracting the total discharge current integrated value from the current integrated value so far. And calculate.

<Action etc.>
Next, the operation and effect of the battery state detection system 20 of the present embodiment will be described.

  In the battery state detection system 20 of the present embodiment, a capacitor 14 is connected in parallel with the lead battery 1, and a diode 15 is inserted between the lead battery 1 and the capacitor 14. For this reason, when the IGN switch 5 is connected to the ON / ACC terminal via the START terminal, the power generated by the generator 7 as the engine 8 is started is supplied to the lead battery 1 and the capacitor 14. The battery 1 can be charged and the capacitor 14 can be charged. When the IGN switch 5 is connected to the ON / ACC terminal before the engine 8 is started and power is consumed by the auxiliary machine 6, or when the IGN switch 5 is connected to the START terminal and supplies a large current to the starter 9. A voltage drop occurs in the lead battery 1 (see also FIG. 3). At this time, the diode 15 prevents the power stored in the capacitor 14 from being supplied to the auxiliary machine 6 and the starter 9. Thereby, since the microcomputer 10 can ensure the operating power supply from the capacitor | condenser 14, the influence of the voltage drop of the lead battery 1 can be relieve | moderated and an operation stop can be prevented. Therefore, according to the battery state detection system 20, since the power is reliably supplied to the microcomputer 10 from the capacitor 14, normal operation can be ensured when the IGN switch 5 is connected to the ON / ACC terminal. The battery state of the lead battery 1 can be detected appropriately.

  Moreover, in the battery state detection system 20 of this embodiment, the voltage detection part 13 is comprised by the A / D converter and the reference | standard power supply part B. FIG. The reference power supply unit B supplies a reference voltage for detecting the voltage across the lead battery 1 to the A / D converter. As described above, when the voltage of the lead battery 1 fluctuates when power is supplied to the starter 9 or the like. The reference voltage supplied by the reference power supply unit B also varies. In the present embodiment, since the capacitor 14 is connected in parallel to the reference power supply unit B, the power is supplied from the capacitor 14 to the reference power supply unit B even if the voltage of the lead battery 1 decreases, so that the reference voltage is accurate. Since the A / D converter functions normally, the detection accuracy of the voltage across the lead battery 1 by the voltage detector 13 can be ensured. Therefore, since the correct voltage across the lead battery 1 is detected, malfunction of the SOC calculation by the microcomputer 10 can be prevented.

  Furthermore, in the battery state detection system 20 of the present embodiment, since the OCV of the battery is captured when the voltage of the lead battery 1 can be considered stable in the sleep mode (step 120), the accurate OCV of the lead battery 1 is obtained. And the SOC of the lead battery 1 can be calculated with high accuracy (step 104).

In the present embodiment, although no mention is made of the capacity of the capacitor 14, the present invention is not limited in particular. For example, considering the fact that the voltage drop of the lead battery 1 due to the power supply to the starter 9 is extremely short as described above, it may be determined appropriately so that the operation of the microcomputer 10 and the reference power supply unit B can be secured. .

  Moreover, although the example which connects the one capacitor | condenser 14 in parallel with the lead battery 1 was shown in this embodiment, this invention is not limited to this, For example, it connects so that a some capacitor | condenser may be connected. It may be. Furthermore, in this embodiment, although the example which connects the diode 15 in series between the lead battery 1 and the capacitor | condenser 14 was shown, this invention is not limited to this, The voltage drop (electric power consumption) of the capacitor | condenser 14 is carried out. A preventable coil may be connected.

  Further, in the present embodiment, the rated voltage of 12V currently used as a standard for the lead battery 1 is shown. However, the rated voltage of 36V used in Europe and the like for ISS and other rated voltages is used. Needless to say, the present invention is applicable. Moreover, although the example which calculates the SOC of the lead battery 1 with the microcomputer 10 was shown in this embodiment, you may make it calculate on the vehicle control system 11 side with high calculation capability. In such a form, the vehicle control system 11 constitutes a part of the battery state detection system of the present invention. Furthermore, in this embodiment, although the example which performs on / off control of the switch 2 by the vehicle control system 11 was shown, you may make it carry out by the microcomputer 10. FIG.

  Furthermore, in the present embodiment, an example in which the current integrated value is used for the calculation of the SOC of the lead battery 1 is shown, but the present invention is not limited to the calculation method of the SOC, for example, a method of obtaining from the differential internal resistance. Etc. can be used. Furthermore, in this embodiment, for the sake of simplicity, an example in which the SOC of the lead battery 1 is calculated has been shown. However, the present invention is not limited to this, and for example, a health condition (SOH) is calculated. You may make it do.

  Furthermore, in the present embodiment, an example in which the voltage detection unit 13 is arranged outside the microcomputer 10 has been shown, but the voltage detection unit 13 may be built in the microcomputer 10. In addition, although the Hall element is exemplified in the current sensor 4, it may be replaced with a current detection unit having an A / D converter and a reference power supply unit. Furthermore, this current detection unit can be incorporated in the microcomputer 10. In this case, if the current detection unit and the voltage detection unit 13 share the reference power supply unit, the accurate reference voltage is supplied as described above, thereby ensuring both current and voltage detection accuracy. be able to.

  In the present embodiment, an example is shown in which it is determined in step 108 whether or not the engine 8 has been stopped based on whether or not the IGN switch 5 is connected to the OFF terminal. However, as described above, the vehicle control system 11 determines whether or not to stop the engine 8 during idling stop. If it is determined that idling stop is impossible, the IGN switch 5 may be connected to the OFF terminal. The charging of the lead battery 1 is continued with the electric power from the generator 7 without stopping the engine 8. For this reason, the stop of the engine 8 may be determined by, for example, monitoring the current between the generator 7 and the IGN switch 5 with a current sensor or the like, and the IGN switch 5 is connected to the OFF terminal. It may be determined that the engine 8 has been stopped when it is determined that the vehicle control system 11 has received a notification that idling can be stopped.

  Furthermore, in the present embodiment, for the sake of simplicity of explanation, when calculating the SOC of the lead battery 1, the temperature of the lead battery 1 is not mentioned, but the SOC of the lead battery 1 also depends on the temperature. Therefore, for example, a sensor insertion hole is formed in the partition wall at the center of the battery case of the lead battery 1, a temperature sensor such as a thermistor is inserted into the sensor insertion hole and fixed with an adhesive, and the microcomputer 10 is an A / D converter. If the temperature data of the temperature sensor is taken in every predetermined time (for example, 1 minute) and the SOC of the lead battery 1 is corrected with the fetched temperature data, the SOC of the lead battery 1 can be accurately grasped. .

  Since the present invention provides a battery state detection system capable of properly detecting the battery state of a battery regardless of the state of the vehicle, the present invention contributes to the manufacture and sale of the battery state detection system. Have

1 is a block wiring diagram of a battery state detection system and a vehicle according to an embodiment to which the present invention is applicable. It is a flowchart of the charge condition calculation routine which CPU of the microcomputer of the battery condition detection system of embodiment performs. It is a graph which shows typically the both-ends voltage of a lead battery at the time of engine starting.

Explanation of symbols

B reference power supply 1 Lead battery (battery)
5 Ignition switch 7 Generator 9 Starter (starter for engine start)
10 Microcomputer (computer)
13 voltage detector 14 capacitor 15 diode 20 battery state detection system

Claims (2)

In a battery state detection system comprising a computer that supplies power to an engine starter starter via an ignition switch as an operating power source and calculates a battery state of the battery, the battery state detection system is connected in parallel with the battery, and the battery A capacitor for ensuring a normal operation of computation by the computer when power is supplied to the starter, and a voltage detector having an A / D converter and a reference power supply unit for detecting the voltage of the battery , A battery state detection system connected in parallel to the reference power source .   The battery state detection system according to claim 1, wherein a diode or a coil is inserted between the battery and the capacitor.

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