JP2005014637A - Device for monitoring state of on-vehicle battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate a SOC (state of charge: charging rate) by utilizing a correlation relation of pseudo OCV (Open Circuit Voltage: open terminal voltage) and the SOC by making an internal part state corresponding to open of an on-vehicle battery. <P>SOLUTION: A vehicle is provided with an on-vehicle generator 7 to be driven by an engine, a voltage control device 8 for adjusting power generation amount of the generator 7 and the on-vehicle battery 5 for accumulating power generated in the generator 7. The voltage control device 8 temporarily stops the power generation of the on-vehicle generator during working of the engine. When the power generation amount is gradually increased, battery voltage is detected when charging/discharging current of the battery is in a very small prescribed range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and a method for monitoring the internal state of an automobile battery.
[0002]
[Prior art]
In general, a charging rate (hereinafter referred to as SOC; state of charge [%]) indicating a state of charge of a lead storage battery is an electromotive voltage in a state where a battery terminal is opened, so-called open terminal voltage (hereinafter referred to as OCV; Open Circuit Voltage). It is known that there is a very strong correlation (FIG. 5). Therefore, it is common to measure the OCV as the battery SOC measuring means in the simplest manner (see, for example, Patent Documents 1 and 2).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-222668
[Patent Document 2]
JP 2002-250757 A
[Problems to be solved by the invention]
However, lead-acid batteries (hereinafter referred to as in-vehicle batteries) mounted on automobiles are not limited to whether the vehicle is operating or stopped, but are always connected to some electrical device, and their terminals are physically opened at any time. It is difficult. In other words, it is difficult to implement a means for calculating the SOC from the OCV measurement with the on-vehicle battery of the automobile.
[0006]
The present invention has been made in view of the above problems, and calculates the SOC using the correlation between the pseudo open terminal voltage and the SOC by creating an internal state equivalent to the open state without opening the terminal of the in-vehicle battery. .
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, an on-vehicle generator driven by an engine, a control device that adjusts the amount of power generated by the generator, and an on-vehicle vehicle that stores electric power generated by the generator. In a vehicle equipped with a battery, the control device temporarily stops power generation while the engine is running, and when the power generation amount is gradually increased, the charge / discharge current of the battery falls within a minute predetermined range. The battery voltage is detected. Preferably, the minute range of the current value is within ± 1A.
[0008]
By controlling the in-vehicle generator in this manner, the charging / discharging current of the in-vehicle battery within a very small range is almost in a state that is almost similar to a state in which the terminal of the battery is physically opened. It became clear by experiment. That is, it is possible to create a state in which the terminals are opened in a pseudo manner even in an automobile battery in which it is substantially difficult to open the terminals. The SOC of the in-vehicle battery can be obtained using the correlation between the pseudo OCV detected in this way and the actual SOC.
[0009]
According to claim 2, the battery monitoring device adjusts the power generation amount of the on-vehicle generator to create a state in which the polarization state inside the battery is within a predetermined range, and from this state, the power generation amount of the generator The battery voltage is detected when the charge / discharge current of the battery falls within a predetermined range.
[0010]
Since the actual SOC fluctuates greatly depending on the polarization state of the battery, it is generally known that an accurate SOC cannot be obtained unless the polarization state is well managed. This will be described with reference to FIG. The actual SOC for the pseudo OCV appears higher as shown by the broken line when it is in a charging state compared to the equilibrium state, while the actual SOC for the pseudo OCV appears lower as shown by a one-dot chain line when it is in a discharging state. . Further, when the process of charging → discharging is continuously repeated, the curve changes while exhibiting hysteresis as shown in FIG.
[0011]
Therefore, in order to accurately estimate the SOC, it is necessary to manage the polarization state.
[0012]
Thus, by detecting the pseudo OCV while the polarization state of the in-vehicle battery is maintained in a predetermined state, the correlation coefficient between the pseudo OCV and the real SOC is increased, and the SOC estimation accuracy can be remarkably improved. .
[0013]
According to a fourth aspect of the present invention, the control for creating the polarization state inside the battery within a predetermined range is executed after a predetermined time has elapsed after the engine is started. That is, when starting the engine, a very large current is consumed by the starter motor for starting, that is, the battery discharges a very large current. That is, the polarization state is remarkable immediately after the start, and the electrochemical reaction promotes the reaction to immediately eliminate the polarization state, so that the internal state is extremely unstable. This state is far from the ideal ideal terminal open state. Therefore, since it is necessary to eliminate the polarization due to the starting discharge, the control for creating the polarization state is prohibited for a predetermined time after the starting, and the control is performed after the elapse of the predetermined time.
[0014]
By controlling in this way, the SOC estimation accuracy is further improved.
[0015]
According to claim 5, the polarization state of the battery is defined as P _n-1 as the polarization index obtained at the previous charge / discharge current sample, Δt as the sample interval time of the charge / discharge current, and at the time of battery electrolyte diffusion. When the constant is τ, the polarization index P _n at the current charge / discharge current sample is defined by the following equation.
[0016]
P _n = P _n−1 + I · Δt−P _n−1 · Δt / τ
If defined quantitatively in this way, the polarization state can be managed with high accuracy.
[0017]
According to the sixth aspect of the present invention, the battery charging rate relative to the voltage when the charging / discharging current value of the battery falls within a predetermined range is calculated as the initial charging rate.
[0018]
Furthermore, according to claim 7, the charge and discharge current of the battery detected by the sample interval △ t, the value obtained by dividing the battery capacity value arithmetic product of the sample value I _n of the current and the sample interval Δt The sequential battery charge rate is calculated by adding to the initial charge rate value.
[0019]
By doing this, it is possible to obtain the actual SOC while traveling by adding the amount of change (integrated amount) of the charge / discharge current based on the SOC calculated at the time of detecting the OCV, thereby reducing the chance of opening the terminal. And the charge state is not deteriorated.
[0020]
According to the eighth aspect of the present invention, the battery monitoring device controls the engine so that the power generation amount is gradually increased and the charge / discharge current value of the battery is kept within a minute predetermined range after the on-vehicle generator is stopped. During the regular implementation.
[0021]
If the pseudo OCV is obtained periodically as described above, the error integration of the current sensor, which is a disadvantage of the charge / discharge current integration method, can be periodically reset and eliminated.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a diagram showing the overall configuration of the present embodiment. The on-vehicle battery state monitoring system shown in FIG. 1 includes a starter 1, a starter switch 2, an electric load 3, a current sensor 4, an on-vehicle battery 5, an on-vehicle battery monitoring device 6, an on-vehicle generator 7, a voltage control device 8, an ECU (engine). Control device) 9 and power cable 10. The on-vehicle generator 7 is rotationally driven by an engine (not shown) to generate charging power for the on-vehicle battery 5 and operating power for the electric load 3.
[0023]
The voltage control device 8 adjusts the output voltage of the in-vehicle generator 7 to a predetermined value by controlling the conduction state of the excitation current with respect to the field coil provided in the in-vehicle generator 7. In this voltage control device 8, a power supply circuit that generates an operating voltage of a component circuit, a power element such as a power transistor that controls conduction of excitation current, a logic circuit that performs this conduction control, and the like are realized by a CMOS-IC. Yes.
[0024]
The electric load 3 is an electric device such as an illumination or an air conditioner. Recently, these electric devices are often highly electronic devices including electronic components for control.
[0025]
A power cable 10 connects between the in-vehicle generator 7 and the in-vehicle battery 5 and between the in-vehicle battery 5 and the electric load 3. In addition, the voltage control device 8 is built in the in-vehicle generator 7, and necessary electrical connection is performed inside the in-vehicle generator 7.
[0026]
The ECU 9 is an external control device that performs engine rotation control and power generation control of the in-vehicle generator 7 based on the state of the engine, the vehicle speed, the rotational speed and the power generation state of the in-vehicle generator 7, and the like. For example, the power generation state information of the in-vehicle generator 7 is sent from the voltage control device 8 to the ECU 9, and conversely, the generated voltage command information for setting the output voltage of the in-vehicle generator 7 is sent from the ECU 9 to the voltage control device 8. Sent. This power generation command information also has a function as a power generation suppression signal. By sending power generation command information for setting the output voltage of the in-vehicle generator 7 low from the ECU 9 to the voltage control device 8, the in-vehicle generator 7 It becomes possible to suppress power generation.
[0027]
Further, a current sensor 4 as a current detection unit that detects a charging / discharging current of the in-vehicle battery 5 is provided in the vicinity of one terminal (for example, the positive terminal side) of the in-vehicle battery 5. The detection signal of the current sensor 4 and the terminal voltage of the in-vehicle battery 5 are input to the in-vehicle battery monitoring device 6. The in-vehicle battery monitoring device 6 stores OCV vs. SOC map data (FIG. 5) in a predetermined polarization state.
[0028]
The in-vehicle battery state monitoring system of the present embodiment has such a configuration, and the operation thereof will be described next.
[0029]
FIG. 2 is a flowchart showing an operation procedure for SOC detection of the automobile battery while the engine is operating, and will be described based on this figure.
[0030]
FIG. 3 is a characteristic diagram showing the characteristics of the power generation voltage Va, battery voltage Vb, battery current Ib, battery polarization index Pa, and starter signal ST with respect to the elapsed time.
[0031]
First, when the IG is ON in step 30, it is determined in step 40 that the starter signal has been switched from Hi to Lo. As a result, the engine is started, but immediately after the engine is started, a large amount of current is consumed by the starter motor for starting, that is, the battery is immediately after discharging the large current, so that the polarization state is extremely remarkably unstable. Therefore, control for creating the polarization state inside the battery within a predetermined range is prohibited for a predetermined time after the engine is started, and is performed after the predetermined time has elapsed. A timer for measuring the passage of a predetermined time is set in steps 50, 60, and 70. For example _{T 1} is set to 60 seconds. The discharge current I _n of the battery is sampled by the current sensor 4 in step 80, calculates the polarization index P _n at step 90. Here, the polarization index P _n is the polarization index obtained at the previous charge / discharge current sampling, P _n−1 , the charge / discharge current sampling interval time is Δt, and the battery electrolyte diffusion time constant is τ, The polarization index P _n at the current charge / discharge current sample is defined by the following equation.
[0032]
P _n = P _n−1 + I · Δt−P _n−1 · Δt / τ
When the time T in step 100 after a predetermined time T ₁ elapses, transmits a power generation stop signal from the voltage control device 8 in step 110, once the predetermined voltage for stopping the power generation of the vehicle generator 7 (e.g. 11.8 (V)) ((1) in FIG. 3). As a result, the battery is discharged, but in step 120, the polarization index _Pn is controlled to be within a predetermined range. If the polarization index Pn falls within a predetermined range, the map stored in the in-vehicle battery monitoring device 6 can be used. Next, in order to obtain the SOC, in a state where the internal state of the battery is stable, in step 130, the voltage control device 8 is caused to gradually increase the power generation voltage of the in-vehicle generator 7 from a predetermined voltage (for example, 11.8 (V)) (2 in FIG. 3).
[0033]
At this time, the gradually increasing the generated voltage of the vehicle generator 7 is to not abruptly change the discharge current I _n of the battery. Step 140 in the charge and discharge current I _n of the battery is to measure the battery terminal voltage when subsided small range (e.g., ± 1A) (the ▲ 3 ▼ Figure 3). To keep the discharge current I _n of the vehicle battery in the small range is to fabricate in a state very close to the state of being physically open almost terminal of the battery.
[0034]
Based on this, the terminal voltage of the battery measured in step 150 can be regarded as OCV.
[0035]
FIG. 5 is a characteristic diagram showing characteristics of the battery SOC with respect to the battery OCV.
[0036]
From this characteristic diagram, it becomes possible to calculate the SOC of the battery from the OCV of the battery at step 160.
[0037]
This invention, running in it without actually opening the terminal, which can be determined criteria SOC calculated during OCV detection, thereafter gradually adding the change amount of the charge and discharge current I _n (accumulated amount) It is possible to obtain the actual SOC.
[0038]
(Other embodiments)
In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. For example, in the above-described embodiment, the case where the predetermined time T _{1 has} elapsed after the engine start has been described. However, as shown in FIG. The charging / discharging current In may be controlled periodically (for example, T ₁ << T _{2 and} T ₂ for several hours) while the engine is operating. If the pseudo OCV is obtained periodically as described above, the error integration of the current sensor 4 which is a disadvantage of the charge / discharge current integration method can be periodically reset and eliminated.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an in-vehicle battery state monitoring system.
FIG. 2 is a flowchart showing an operation procedure for SOC detection of a vehicle battery while the engine is operating in the embodiment.
FIG. 3 is a characteristic diagram showing characteristics of a power generation voltage of an in-vehicle generator, a battery voltage, a battery current, a battery polarization index, and a starter signal with respect to elapsed time in the present embodiment.
FIG. 4 is a characteristic diagram showing characteristics of an on-vehicle generator power generation voltage, battery voltage, battery current, battery polarization index, and starter signal with respect to elapsed time, in a modified example in which SOC detection is periodically performed during engine operation; is there.
FIG. 5 is a characteristic diagram showing a correlation between a pseudo OCV and a real SOC.
FIG. 6 is a characteristic diagram showing a correlation between a pseudo OCV and a real SOC with respect to a polarization state.
FIG. 7 is a characteristic diagram showing a correlation between a pseudo OCV and a real SOC with respect to a charge / discharge process.
[Explanation of symbols]
1 ... starter, 2 ... starter switch, 3 ... electrical load, 4 ... current sensor,
5 ... In-vehicle battery, 6 ... In-vehicle battery monitoring device, 7 ... In-vehicle generator,
8 ... Voltage control device, 9 ... ECU (Engine control device), 10 ... Electric power cable.

Claims (8)

An in-vehicle generator driven by an engine;
A control device for adjusting the power generation amount of the generator;
In a vehicle equipped with an in-vehicle battery that stores electric power generated by the generator,
While the engine is running, the control device temporarily stops generating power and detects the battery voltage when the charge / discharge current of the battery falls within a minute predetermined range when the power generation amount is gradually increased. An in-vehicle battery monitoring device characterized by that. The battery monitoring device adjusts the power generation amount of the in-vehicle generator to create a state in which the polarization state inside the battery is within a predetermined range, and gradually increases the power generation amount of the generator from that state. The in-vehicle battery monitoring device according to claim 1, wherein the battery voltage when the charge / discharge current of the battery falls within a predetermined range is detected. The in-vehicle battery monitoring device according to claim 1 or 2, wherein the minute predetermined range is within ± 1A. The on-vehicle battery monitoring device according to claim 2 or 3, wherein the control for creating the polarization state inside the battery within a predetermined range is executed after a predetermined time has elapsed after the engine is started. The polarization state of the battery is as follows, _assuming that the polarization index obtained at the previous charge / discharge current sampling is P _n−1 , the charge / discharge current sampling interval time is Δt, and the battery electrolyte diffusion time constant is τ. The polarization index P _n at the charge / discharge current sample of
P _n = P _n−1 + I · Δt−P _n−1 · Δt / τ
The vehicle-mounted battery monitoring device according to claim 2, wherein the vehicle-mounted battery monitoring device is defined by: The in-vehicle apparatus according to any one of claims 1 to 5, wherein a charge rate of the battery with respect to a voltage when a charge / discharge current value of the battery is within a predetermined range is calculated to obtain an initial charge rate. Battery monitoring device. The charge and discharge current of the battery detected by the sample interval Delta] t, the value obtained by dividing the battery capacity value arithmetic product of the sample value I _n of the current and the sample interval Delta] t, is added to the charging rate initial value The in-vehicle battery monitoring device according to claim 6, wherein a sequential battery charging rate is calculated by moving. The battery monitoring device periodically performs control during engine operation to temporarily increase the power generation amount after stopping the on-vehicle generator, and to keep the charge / discharge current value of the battery within a minute predetermined range. The in-vehicle battery monitoring device according to any one of claims 1 to 7, wherein

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