JP2006188130A - Battery state detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery state detector for accurately detecting the deterioration of a battery. <P>SOLUTION: A microcomputer of a battery controller (battery state detector) calculates a time constant τ<SP>(n+m)</SP>(step 114). A threshold value V<SB>st_th</SB><SP>(n+m-1)</SP>previously calculated based on the calculated time constant τ<SP>(n+m)</SP>is corrected so as to correspond to an increase of electric resistance on a vehicle side (step 116), and a lead battery life is determined based on the corrected threshold value V<SB>st_th</SB><SP>(n+m-1)</SP>(step 122). The deterioration of the lead battery can be detected, regardless of the electric resistance on the vehicle side which increases due to change with the lapse of time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery state detection device, and more particularly to a battery state detection device that detects a state of a battery for starting an engine of a vehicle.

  Conventionally, internal resistance, discharge voltage, open circuit voltage, remaining capacity, state of charge, and the like are used as parameters representing the battery state or measurement parameters for calculating the battery state. As the load on the batteries used for automobiles and portable devices increases, the importance of such battery state monitoring and battery state control is increasing. Yes. In order to cope with idle stop / start (ISS), regenerative charging, and the like performed for reducing exhaust gas, a vehicle battery is required to have a technology for keeping the battery in a battery state suitable for these applications. Lead batteries are one of the typical batteries that can be applied to these applications.

  In order to meet such demands, there has been proposed a battery remaining capacity detection device for a hybrid vehicle that calculates a battery state by comparing a voltage and DC internal resistance at the time of starting an engine with a data map measured in advance (for example, for vehicles) (for example, , See Patent Document 1). In general, when the battery state is calculated from the voltage at the time of starting the engine, the deterioration of the battery is determined according to how much the engine starting voltage has dropped from the new state.

  As a battery test method using a vehicle, a method for evaluating a voltage in a state where a starter motor is rotated is known. This method has been used for a long time as a battery check method for investigating whether a starter or a battery is the cause of a vehicle whose engine cannot be started. In this method, measurement with a simple voltmeter that does not use an oscilloscope and has a slow time response is common. For example, if the voltage is relatively stable after an inrush current, the voltage is determined to be normal if the voltage is about 9 V or higher. To do. If measures are taken not to supply fuel to the engine so that the engine does not actually start even if the starter motor rotates, a time-stable voltage can be obtained even in a normal vehicle, and battery check Can do.

JP-A-7-63830

  However, when the deterioration is determined based on how much the engine starting voltage has decreased from the new state, for example, a DC motor with a brush used for a starter motor of a vehicle increases the electric resistance on the vehicle side due to deterioration of the brush over time. Since this is an error factor in battery state detection due to the starting voltage, there is a problem that battery deterioration cannot be detected accurately.

  In view of the above case, an object of the present invention is to provide a battery state detection device capable of accurately detecting battery deterioration regardless of electric resistance on the vehicle side.

  In order to solve the above problems, the present invention provides a battery state detection device for detecting a state of a battery for starting an engine of a vehicle, and a voltage for detecting an open circuit voltage of the battery before starting the engine and a discharge voltage when starting the engine. A plurality of discharge voltage values detected by the voltage detection unit over a certain period of time at a certain time when the discharge voltage detected by the detection unit and the voltage detection unit is greater than a preset value; Storage means for storing, a specifying means for specifying the lowest voltage value among the plurality of discharge voltage values stored in the storage means, and a discharge voltage value among the plurality of discharge voltage values stored in the storage means. The time constant is calculated from the discharge voltage value at two times between the first measured time and the time at which the lowest voltage value is measured and the open circuit voltage value detected by the voltage detecting means. Threshold correction means for correcting a threshold value calculated in advance based on the calculated time constant so as to correspond to an increase in electric resistance on the vehicle side; and a minimum voltage value specified by the specifying means is Determination means for determining that the battery has a life when the threshold value corrected by the threshold value correction means is exceeded.

  In the present invention, the open circuit voltage before starting the engine of the battery and the discharge voltage at the start of the engine of the battery are detected by the voltage detecting means, and a voltage equal to or higher than a preset value set to the discharge voltage detected by the voltage detecting means by the storage means. When there is a decrease, a plurality of discharge voltage values detected by the voltage detection means over a certain time at a certain time are stored, and the lowest voltage value is selected from the plurality of discharge voltage values stored in the storage means by the specifying means. Two times between the time when the discharge voltage value is first measured and the time when the lowest voltage value is measured among the plurality of discharge voltage values specified and stored in the storage means by the threshold correction means. The time constant is calculated from the discharge voltage value of the current and the open circuit voltage value detected by the voltage detection means, and the threshold value calculated in advance based on the calculated time constant increases the electrical resistance on the vehicle side. It is corrected so as to respond, the lowest voltage value specified by the specifying means by determining means battery is determined to life when exceeds the corrected threshold by threshold correction means.

  In the present invention, the minimum voltage value specified by the specifying means may be used as one of the discharge voltage values at the two times. Further, in order to improve the calculation accuracy of the time constant, the threshold value correcting means is based on the open circuit voltage value of the battery before starting the engine in which at least one of the discharge voltage values at two times is detected by the voltage detecting means. It is preferable to correct the threshold value calculated in advance when the difference from the open circuit voltage value is 1 V or less. Furthermore, it is preferable to provide a nonvolatile memory for storing the threshold value corrected by the threshold value correction means in order to perform an appropriate life determination regardless of the power supply to the battery state detection device. It is more preferable to further include an output means for outputting a notification signal for notifying that the battery is at the end of its life when the determination means determines that the battery is at the end of its life.

  According to the present invention, the threshold value previously calculated based on the time constant by the threshold value correcting means is corrected so as to correspond to the increase in the electric resistance on the vehicle side, and corrected by the threshold value correcting means by the determining means. Since the battery life is determined based on the set threshold value, it is possible to obtain an effect that the deterioration of the battery can be accurately detected regardless of the electric resistance on the vehicle side.

  Hereinafter, an embodiment in which the present invention is applied to a battery controller that detects the state of a vehicle lead battery will be described with reference to the drawings.

(Constitution)
As shown in FIG. 1, the battery controller 10 (battery state detection device) of the present embodiment functions as a subordinate device of the vehicle controller 20 that controls the vehicle side such as the engine, and a CPU that functions as a central processing unit. , A ROM that stores a basic control program of the battery controller 10 and program data such as mathematical formulas to be described later, and a RAM that serves as a work area of the CPU and temporarily stores data, and a part of the voltage detection means, Microcomputer 2 as storage means, identification means, threshold correction means and determination means, EPROM 3 connected to the external bus of microcomputer 2 and functioning as a non-volatile memory, analog voltage from the external terminal of lead battery 1 is converted to digital voltage A / D converter (not shown) as a part of the voltage detection means to perform, and the vehicle controller 2 It is configured to include an interface for communicating with, and is connected to the vehicle controller 20 by a communication line.

  A positive external output terminal of the lead battery 1 is connected to a central terminal of an ignition switch (hereinafter abbreviated as IGN) 11. The IGN11 has an OFF terminal, an ON / ACC terminal, and a START terminal in addition to the central terminal. The central terminal and any of these OFF, ON / ACC, and START terminals can be switched in a rotary manner. is there. An MG 12 serving as a load of the lead battery 1 and representing a motor generator, a starter, a generator, and the like is connected to the ON / ACC terminal and the START terminal side of the IGN 11. On the other hand, the negative external output terminal of the lead battery 1 is connected to the ground. The vehicle controller 20 constantly monitors the connection state of the IGN.

  Here, the voltage change of the lead battery 1 at the time of engine start is demonstrated. FIG. 3 schematically shows the voltage waveform of the lead battery 1 when the engine is started. The voltage waveform of the lead battery 1 at the start of the engine is that after the start of energization when the IGN 11 is located at the START terminal, a rapid first-stage pulse discharge to the starter motor is performed, and the voltage waveform is abruptly falling. The minimum voltage value Vst at the start appears. After that, the engine start is completed after a few attenuations. The voltage waveform is influenced by the structure of the engine and the friction of the clutch connecting the engine and the starter motor, but is mainly influenced by the brush of the starter motor, and generally has a waveform as shown in FIG.

  FIG. 4 is a schematic view of the rapid first stage pulse discharge portion to the starter motor. In the present embodiment, as will be described later, when the microcomputer 2 of the battery controller 10 takes in the open circuit voltage OCV every predetermined time and the voltage of the lead battery 1 becomes equal to or lower than a preset value Vc, the D / A converter , And a plurality of discharge voltage values are measured over a certain period of time from the time t1 at the first discharge voltage value V (t1) that is equal to or lower than the set value Vc. In FIG. 4, in order to easily understand the present invention, the time t2 when the discharge voltage value is measured between the time t1 and the time when the lowest voltage value Vst is measured (discharge voltage value at that time: V (t2)) ).

(Operation)
Next, with reference to a flowchart, the operation of the battery controller 10 of the present embodiment will be described with the CPU of the microcomputer 2 as a main component. The CPU of the microcomputer 2 executes a battery state detection routine shown in FIG. 2 when the battery controller 10 is powered on.

  In the battery state detection routine, first, in step 102, it is determined whether or not there is a notification from the vehicle controller 20 that the IGN 11 is located at the ON terminal. If the determination is negative, the open circuit voltage of the lead battery 1 is determined in step 104. The value OCV is acquired (measured) via the A / D converter, and the process returns to step 102. Note that the measurement of the open circuit voltage of the lead battery 1 in step 104 is preferably performed when the sulfuric acid concentration of the lead battery 1 is stabilized, for example, with a long sampling period (interval) of about 6 hours.

  On the other hand, when an affirmative determination is made at step 102, the discharge voltage value of the lead battery 1 is captured (measured) at step 105. Note that the measurement of the discharge voltage value of the lead battery 1 in step 105 is performed with a sampling period of 10 ms or less because the voltage waveform is predicted to fall sharply as shown in FIG. Is preferred.

  Next, at step 106, it is determined whether or not the voltage drop of the discharge voltage value with respect to the OCV measured at step 104 is greater than or equal to a set value Vc (for example, 0.3V). In the next step 108, the lead battery 1 over a certain time (for example, 64 ms) at a certain time (for example, with a sampling period of 0.4 ms or less). The discharge voltage value is measured (see also FIG. 4) and stored in the RAM according to the measured time.

When the measurement of the discharge voltage for a fixed time and the storage in the RAM are completed in step 108, the next step 110 specifies the lowest voltage value Vst from the plurality of discharge voltage values stored in the RAM. Next, at step 112, the discharge voltage value V (t1) at time t1 when the discharge voltage is first measured at step 108 is greater than or equal to OCV-1V and less than OCV measured at step 104 (OCV−V (t1) ≦ 1V). If the determination is affirmative, in the next step 114, the electrical time constant τ ^{(n + m)} of the vehicle is calculated by the following equation (1).

  Here, OCV: open circuit voltage value, Vst: lowest voltage value at engine start, t1, t2: time when discharge voltage was measured between the voltage drop start at engine start and Vst measurement, t: at engine start The time when the discharge voltage is measured from the start of voltage drop to the Vst measurement and may be the same time as t1 or t2, V (t): between the voltage drop start at the time of engine start and the Vst measurement This is the discharge voltage value at time t.

In the next step 116, the electric time constant τ ^{(n) of} the vehicle calculated in advance by equation (1) from the discharge voltage value at the start of the engine with a new battery, the threshold value V _{st_th} ⁽ⁿ with the new battery ⁾ . ⁾ Is read from the EPROM 3 and the threshold value V _{st — th} ⁽ⁿ⁾ is corrected (updated) by the following equation (2). In the equation _{(2), OCV ful} is an open circuit voltage of the lead battery 1 in fully charged 25 ° C.

Next, at step 118, the threshold value V _{st — th} ^{(n + m)} calculated at step 116 is stored in the EPROM 3 for the time when the microcomputer is reset, and the routine proceeds to step 122. On the other hand, when a negative determination is made in step 112, the calculation accuracy of the electrical time constant τ of the vehicle, and hence the update accuracy of the threshold value V, cannot be achieved. _Therefore, the threshold value V _{st_th} ^{(n + m−)} previously calculated in step 120 is not achieved. ¹⁾ is read from EPROM 3 and the process proceeds to step 122.

In step 122, whether or not the minimum voltage value Vst specified in step 110 is larger _than the threshold value V _{st_th} ^{(n + m)} corrected in step 116 (or the threshold value V _{st_th} ^{(n + m−1)} read in step 120). If the determination is negative, the process returns to step 102. If the determination is affirmative, a notification signal indicating that the lead battery 1 is at the end of its life is output to the vehicle controller 20 in the next step 124, and the process returns to step 102. For example, the vehicle controller 20 displays that fact on the installation panel. Thereby, the driver can know that the lead battery 1 has reached the end of its life.

(Action etc.)
Next, the operation and the like of the battery controller 10 of the present embodiment will be described.

In the battery controller 10 of the present embodiment, the time constant τ ^{(n + m)} is calculated (step 114), and the threshold value V _{st — th} ⁽ⁿ⁾ calculated in advance based on the calculated time constant τ ^{(n + m)} is used on the vehicle side. (Step 116), and the life of the lead battery 1 is determined based on the corrected threshold value _{Vst_th} ^{(n + m)} (step 122). The deterioration of the lead battery 1 can be accurately detected regardless of the electric resistance on the vehicle side. Since the time constant τ ^{(n + m)} is calculated when the discharge voltage value V (t1) is greater than or equal to OCV−1V and less than OCV (steps 112 and 114), the calculation accuracy of the time constant τ ^{(n + m)} is improved. Improvements can be made. Further, since the threshold value V _{st — th} ^{(n + m)} is stored in the EPROM 3, when the operating power of the battery controller 10 is supplied from the lead battery 1, the power supply from the lead battery 1 is caused by discharge to the MG 12 or the like. Even if it _stops , V _st ^{— th (n + m−1)} calculated last time after the lead battery 1 is charged can be used.

  In the present embodiment, the example in which the discharge voltage value of the lead battery 1 is measured in step 108 with a sampling period of 0.4 ms or less is shown, but the discharge voltage value may be measured with a sampling period of about 1 ms. Good. Since the sampling period of about 1 ms is rough, there is a case where an affirmative determination is not made in step 112 (voltage data close to OCV cannot be obtained). In this case, the threshold value is not corrected (updated), and the OCV is changed to the OCV after the next time. You may make it update at the time of engine starting which the near voltage data was able to be measured. In such an aspect, a relatively low cost microcomputer 2 or A / D converter can be used. On the other hand, if the sampling period is 0.4 ms or less as in this embodiment, voltage data close to OCV can be sampled every time the engine is started.

  In this embodiment, the discharge voltage value V (t2) at the time t2 when the discharge voltage value is measured between the time t1 and the time when the minimum voltage value Vst is measured is described. However, the time t2 is the minimum voltage. The voltage V (t2) may be the same as the lowest voltage value Vst at the same time when the value Vst is measured. Further, the example in which the discharge voltage value V (t1) is the discharge voltage value of the lead battery 1 at the first time t1 when the discharge voltage value V (t1) becomes equal to or lower than the set value Vc has been described. May be the discharge voltage value of the lead battery 1 at an arbitrary time before time t2 after the value becomes equal to or lower than the set value Vc. In order to improve the accuracy of the electrical time constant τ of the vehicle, it is desirable that the time between the time t1 and the time t2 is a fixed time.

  Furthermore, in this embodiment, although the example which received the notification from the vehicle controller that the IGN11 was connected to the ON / ACC terminal, and measured the discharge voltage value of the lead battery 1 was shown, there is no notification from the vehicle controller 20. However, as indicated by a dotted line in FIG. 1, a current sensor 4 such as a Hall element may be inserted to grasp the engine start time. In this example, the battery controller 10 needs to have an A / D converter for current measurement connected to the current sensor 4. The microcomputer 2 takes in a current value (strictly, a value obtained by converting the current into a voltage value) from the A / D converter for current measurement, and when it is less than a predetermined value (for example, 0.1 A), the IGN 11 is set to the OFF terminal. Assuming that the battery is connected, the discharge voltage of the lead battery 1 may be measured every predetermined sampling time when the current value taken in is greater than or equal to a predetermined value.

Moreover, in this embodiment, although the example which outputs a notification signal to the vehicle controller 20 was shown, the battery controller 10 or the lead battery 1 has LED, a battery state detection apparatus, etc., and CPU of the microcomputer 2 is LED. The life of the lead battery 1 may be displayed on the liquid crystal display panel. Furthermore, in the present embodiment, an example is shown in which the threshold value V _{st_th} is calculated after calculating the vehicle time constant τ. However, by substituting the expression (1) into the expression (2), the calculation can be performed once. Needless to say, the threshold value can be calculated.

  Next, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1
A lead battery for an 80D26 type automobile that was deteriorated after being used for 4 years was adjusted to SOC 70% at room temperature (25 ° C.). A 2500cc gasoline engine passenger car was used as the vehicle. In this vehicle, the engine starting voltage Vst of the 80D26 type lead battery used for 5 years was 8.1 V at room temperature, so the threshold value was set to 8.1 V. First, the engine start waveform was measured at a sampling period of 1 ms. Next, the starter motor was disassembled and replaced with a deteriorated old vehicle that used a brush for 50,000 km for 5 years, and the engine start waveform was measured in the same manner. Table 1 below shows the parameters substituted into Equation (2) and the calculation results of the time constant τ.

Substituting this time constant τ into equation (1) to obtain the threshold value V _{st_th yielded 8.39V} . The Vst when using the deteriorated brush was determined based on this threshold value of 8.39V. The same determination result was obtained regardless of the deterioration of the starter motor brush (starter brush).

(Comparative Example 1)
In Comparative Example 1, as in the prior art, without correcting the threshold V _{St_th,} starter brushes also deteriorated, was determined using the threshold 8.1 V. The results are shown in Table 2.

  In Example 1 and Comparative Example 1, the same lead battery is used, but in the comparative example, the deterioration judgment result of the lead battery differs depending on the deterioration state of the starter brush. From the above results, it can be seen that the battery controller of Example 1 that corrects the threshold value is superior.

  Since the present invention provides a battery state detection device capable of accurately detecting battery deterioration regardless of the electric resistance on the vehicle side, it contributes to the manufacture and sale of the battery state detection device, so that it can be used industrially. Have sex.

It is a block circuit diagram of a battery controller of an embodiment to which the present invention is applicable. It is a flowchart of the battery state detection routine which CPU of the microcomputer of the battery controller of the embodiment executes. It is the graph which showed typically the voltage waveform of the lead battery at the time of engine starting. It is the graph which further modeled and showed the part of the rapid fall at the time of engine starting among the voltage waveforms shown in FIG.

Explanation of symbols

1 Lead battery (battery for engine start)
2 Microcomputer (part of voltage detection means, storage means, identification means, threshold value correction means and determination means)
3 EPROM (nonvolatile memory)
10 Battery controller (battery state detection device)

Claims (5)

In the battery state detection device for detecting the state of the battery for starting the engine of the vehicle,
Voltage detection means for detecting an open circuit voltage of the battery before starting the engine and a discharge voltage at the time of starting the engine;
A memory for storing a plurality of discharge voltage values detected by the voltage detection unit over a certain period of time at a certain time when the discharge voltage detected by the voltage detection unit has a voltage drop equal to or higher than a preset value. Means,
Specifying means for specifying a minimum voltage value from among a plurality of discharge voltage values stored in the storage means;
The discharge voltage value and the voltage detection at two times between the time when the discharge voltage value is first measured and the time when the lowest voltage value is measured among the plurality of discharge voltage values stored in the storage means. Threshold value for calculating a time constant from the open circuit voltage value detected by the means and correcting a threshold value calculated in advance based on the calculated time constant so as to correspond to an increase in electric resistance on the vehicle side Correction means;
Determining means for determining that the battery has a life when a minimum voltage value specified by the specifying means exceeds a threshold value corrected by the threshold value correcting means;
A battery state detection device comprising:   The battery state detection device according to claim 1, wherein one of the discharge voltage values at the two times is the lowest voltage value specified by the specifying means.   The threshold value correcting means is such that at least one of the discharge voltage values at the two times is lower than the open circuit voltage value of the battery before starting the engine detected by the voltage detecting means, and the difference from the open circuit voltage value is The battery state detection device according to claim 1 or 2, wherein the threshold value calculated in advance is corrected when the voltage is 1 V or less.   The battery state detection device according to any one of claims 1 to 3, further comprising a non-volatile memory that stores the threshold value corrected by the threshold value correction unit.   5. The apparatus according to claim 1, further comprising output means for outputting a notification signal for notifying that the battery is at the end of its life when the determination means determines that the battery is at the end of its life. The battery state detection device according to any one of the above.

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