JPH0326026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging control method for a vehicle battery, and more particularly to an improved charging control method for a vehicle battery that can always ensure a good state of charge.

Vehicle batteries are indispensable to supply the necessary power to each electrical device in a vehicle, and especially in vehicles that have become increasingly electronically controlled in recent years or are equipped with many air conditioners and other electrically powered devices. The demands placed on batteries for vehicles have significantly increased, and the amount of current that is constantly output has only continued to increase compared to before.In order to meet these demands, vehicle batteries must always be sufficiently charged. It is necessary to maintain the condition. However, conventional charging control simply starts the charging action using the current from the alternator when the terminal voltage of the battery drops below a predetermined value. It was impossible to secure such a supply, often resulting in a breakdown. The battery failure itself is a major problem when driving a vehicle, and even if it does not lead to a battery failure, various problems have occurred, such as malfunction of electrical equipment due to insufficient charging or a shortened lifespan of the battery itself.

Normally, the battery terminal voltage, which is the standard for controlling the charging of the battery, is set to a relatively low voltage value to prevent overcharging, and for this reason, in conventional devices, the battery is discharged to some extent from a fully charged state. Charging will not start unless this occurs and the battery terminal voltage has dropped, and a considerable amount of the charge will be consumed during the waiting time before charging starts until this terminal voltage drops, and this will prevent the use of electrical equipment. Depending on the state, the battery capacity may not be fully recovered by subsequent charging after the discharge has progressed to a certain extent as described above, resulting in the aforementioned insufficient charging or dead battery.

The above-mentioned drawbacks of the conventional method can be overcome by setting the battery terminal voltage reference value high when charging starts, but this will lead to overcharging as mentioned above, and especially depending on the temperature of the battery fluid. Therefore, the optimum reference value changes significantly, and when the reference value is set high, there is a problem that overcharging tends to occur during high temperature periods, such as summer, and battery wear and tear occurs due to gas generation.

The present invention was made in view of the above-mentioned conventional problems, and its purpose is to maintain a good state of charge at all times,
In particular, it is an object of the present invention to provide an improved charging control method for a vehicle battery that can maintain the battery in a nearly fully charged state at all times.

In order to achieve the above object, the present invention detects the specific gravity of battery liquid and compares the electromotive force corresponding to the liquid specific gravity with the actual battery terminal voltage to determine the charging or discharging state of the battery. It is characterized in that when it is in a discharging state, it is automatically put into a charging control state.

According to the present invention, unlike the conventional method of detecting the discharge state of a battery using terminal voltage,
When the battery is discharged, the charging action from the alternator is immediately started without any waiting time before the start of charging.If other conditions are met at this time, for example, if the engine speed and other conditions permit the charging action, the battery is immediately started charging. Charging is started, and the decrease in the amount of charge due to discharging can be replenished without delay to restore the performance to a fully charged state, and it is possible to reliably prevent the occurrence of insufficient charging or battery exhaustion as in the conventional case.

Preferred embodiments of the present invention will be described below based on the drawings.

Fig. 1 shows the relationship between battery liquid specific gravity and battery electromotive force in a general vehicle battery.
The figure shows the characteristics at a battery liquid temperature of 25°C.
As is clear from this characteristic, it is understood that the electromotive voltage increases as the specific gravity increases.

Conventionally, the characteristics shown in Figure 1 have been considered as the relationship between battery liquid specific gravity and battery capacity, and various devices and methods have been proposed and put into practical use for inspecting and determining the remaining battery capacity from liquid specific gravity using this characteristic. .

However, in the present invention, this characteristic is understood as the relationship between liquid specific gravity and electromotive voltage, and this electromotive voltage, that is, the electromotive force estimated from the measured specific gravity, is compared with the actual battery terminal voltage to determine whether the battery is discharged at that time. It is characterized by determining whether the battery is in a charging state or a charging state.

FIG. 2 shows the temporal change characteristics of the battery terminal voltage during charging and discharging, and in this characteristic, the electromotive force corresponding to the specific gravity at the start of charging and discharging is shown by a broken line.

As is clear from Figure 2, during charging, the terminal voltage increases sequentially in accordance with a predetermined characteristic over time, and the terminal voltage at the start of charging always shows a value larger than the electromotive force equivalent to specific gravity. That is understood. This only shows the static terminal voltage where the electromotive force equivalent to specific gravity is estimated from the specific gravity.
On the other hand, during actual charging, in addition to this static estimated electromotive force, electrochemical electromotive force based on the charging action is taken into account, so the charging terminal voltage always exceeds the electromotive force equivalent to specific gravity. .

On the other hand, it is understood that the terminal voltage during discharge shows a tendency to decrease gradually over time, and the voltage at the start of discharge always shows a value lower than the electromotive voltage equivalent to specific gravity. That is, it is easily understood that there are various electrical losses during discharge, and such a dynamic terminal voltage is always lower than the static electromotive force equivalent to the specific gravity mentioned above.

Conventionally, the general characteristics shown in FIG. 2 have been theoretically clarified, but no attempt has been made to utilize them for battery charging control.

The present invention correctly takes this point into consideration and skillfully utilizes the theoretical features shown in Figure 2 for charging control. That is, by directly comparing the electromotive voltage equivalent to specific gravity and the actual terminal voltage of the battery, The charging or discharging state can be determined very easily, and predetermined charging control can be started immediately in the discharging state, thereby reliably resolving insufficient charging.

In the present invention, charging or discharging is determined simply by direct comparison of the electromotive voltage equivalent to specific gravity and the actual terminal voltage, and there is no need to consider the specific gravity or the value of the electromotive voltage equivalent to this, the outside temperature, or other external factors. When the battery is discharged, it simply starts a charging action to compensate for it, and quickly recovers the amount of electricity before the battery's electricity drops significantly. This does not require complex control. Optimum control is possible with a simple and simple configuration without any additional effort.

A preferred embodiment for realizing the above-described control method of the present invention is shown in the flowchart of FIG. It belongs to a part of the routines of various vehicle running control, auxiliary equipment control, and diagnostic control.

When the charging control method shown in FIG. 3 is started,
First, various detection information is converted into digital signals.

In this embodiment, since the charging control of the battery after the discharge state is determined is controlled based on the final charge voltage determined from the battery liquid temperature, not only the battery liquid specific gravity, battery terminal voltage, and alternator generated voltage necessary for the present invention are also controlled. Battery liquid temperature information is also taken in.

After the AD conversion is completed, the specific gravity information of the battery liquid is first taken in, and furthermore, the electromotive voltage V _R corresponding to the specific gravity shown in FIG. 1 is converted from this specific gravity.

Next, we will take the battery liquid temperature for the actual charging control mentioned above and the related end-of-charging voltage V _E
Then, the end-of-charging detected value V _th during charging control is determined from the end-of-charging voltage _VE using a predetermined coefficient k (0>k>1).

Further, the alternator generated voltage V _A and the battery terminal voltage V _B are taken in.

A characteristic feature of the present invention is that after the input of each of the above-mentioned information is completed, a comparison is made between the electromotive voltage V _R corresponding to specific gravity and the battery terminal voltage V _B , and thereby the charging or discharging state of the battery can be determined. It is to be accomplished.

That is, when the battery terminal voltage V _B is larger than the electromotive voltage V _R corresponding to specific gravity, the battery is in a charging state as is clear from FIG. 2, and in this state, the process moves to the next charging control step.

On the other hand, the battery terminal voltage V _B is the electromotive force equivalent to the specific gravity.
If it is smaller than V _R , as is clear from FIG. 2, it is determined that the battery is in a discharging state and a desired charging action is started.

In the embodiment, this charging action is performed by increasing the idling speed of the engine in an idling state and/or by increasing the excitation current of the alternator.
This forces the alternator to charge the battery. Of course, even with such charging force action, charging may not start immediately depending on the condition of the alternator or battery, especially the alternator rotation speed, but in the present invention, if other conditions are met, charging may not start immediately. Charging starts immediately, and it becomes possible to quickly recover the amount of current due to discharging.

Therefore, according to the present invention, a quick recovery action can be achieved without waiting for the battery terminal voltage to drop as in the conventional case.

On the other hand, after it is determined that the battery terminal voltage V _B is larger than the electromotive voltage V _R equivalent to specific gravity and the charging state is determined, normal charging control can be performed in the present invention, but in this embodiment, Furthermore, this charging control is also performed to obtain as full a charge as possible.

In other words, the charging characteristics shown in Figure 2 converge to a predetermined value over time, and this can be understood as the final charge voltage.This final charge voltage indicates the battery terminal voltage in a fully charged state, and it It is understood that in order to fully charge the battery, this end-of-charge voltage must be applied to the battery from the alternator. However, on the other hand, if a voltage higher than this charging end voltage is applied to the battery, various problems such as gas generation occur, as is well known, and the life of the battery is significantly shortened. The voltage at the end of charging changes significantly depending on the battery fluid temperature, and this characteristic is illustrated in FIG. As is clear from Figure 4,
It is understood that in winter when the ambient temperature is low, a full charge cannot be obtained unless a high voltage is supplied to the battery, while in summer when the ambient temperature is high, gas generation can easily occur unless the supply voltage is lowered. is understood.

Therefore, in conventional devices, the charging start voltage is set to a relatively low constant value that does not cause gas generation. For example, in Figure 4, the voltage is set at 14.4 volts, and when the battery terminal voltage drops below this voltage value, Only the charging action was performed. According to this conventional method, even when the battery liquid is at a high temperature, relatively quiet and stable charging without gas generation is performed, making it possible to maintain a long battery life.

However, as is clear from FIG. 4, charging is conventionally performed only in the shaded terminal voltage region regardless of the battery fluid temperature;
It is understood that the battery is fully charged only at a fairly high battery temperature, for example, about 70 to 80° C., and that the lower the battery temperature is, the lower the charging rate of the battery is. This means that
During winter, batteries have the disadvantage that they are rarely fully charged and only a portion of their capacity can be used, which is a major cause of insufficient charging and dry batteries. Taking this into account, a problem arises in that a battery with an unnecessarily large capacity must be mounted on the vehicle.

In this embodiment, in view of the above-mentioned problem, by controlling the charging start voltage in accordance with the charging end voltage, it is possible to always obtain the optimal full charge or a charging effect close to this regardless of the battery liquid temperature. shall be.

FIG. 5 shows the charging action in this example, and the shaded area shows the charging start voltage at each battery liquid temperature, and as is clear from the figure,
The charging start voltage V _A is set equal to the charging end voltage V _E . Therefore, in this embodiment, the charging operation is always performed at the final charging voltage in accordance with the battery liquid temperature, and it is possible to always perform full charging or charging close to this regardless of seasonal fluctuations.

In the example, the battery terminal voltage in FIG.
A comparison is made between V _B and the end-of-charge voltage _VE , and a desired charging action is performed until the two match, that is, until full charge is achieved.

According to this embodiment, when gas is likely to be generated, such as in the summer, the final charge voltage V _E will be a low value, so this gas generation can be reliably prevented and a full charge or a charge close to this can be obtained. On the other hand, in winter, the final charge voltage V _E is set high, thereby achieving the desired full charge or a charge close to this.

In the embodiment shown in Fig. 3, when the charging of the battery progresses further and it approaches full charge, the alternator generated voltage increases.
The set value of V _A is further increased by a certain amount and a final push is performed to effectively enable full charging.

Generally, when the battery approaches full charge, if the alternator generated voltage V _A is set equal to the end-of-charge voltage V _E , it will take an extremely long time to reach 100% full charge. for 100
In order to effectively obtain 100% full charge, as shown by the broken line in Figure 5, the alternator generated voltage V _A is increased by a predetermined amount α above the end-of-charge voltage V _E to achieve 100% full charge in a short time. is achieved. This final push is not necessary until the battery terminal voltage approaches full charge, and of course it is also unnecessary after reaching full charge, so this last push is only required in a specific narrow battery voltage range near full charge. What is necessary is to set an additional α for pushing.

As is clear from Figure 3, the battery terminal voltage
When V _B becomes equal to the end-of-charge voltage V _E , it is determined that the charge is fully charged, and the alternator generated voltage V _A
is set to the final charge voltage V _E itself.

Before reaching full charge, the battery terminal voltage V _B is compared with the end-of-charging detection value V _th described above, and if the battery terminal voltage V _B is smaller than this, it means that the end-of-charging stage has not been reached. The alternator generated voltage V _A is the final charging voltage
_However , when the battery terminal voltage V _B reaches the end-of-charge detection value V _th , an additional α is added to the alternator generated voltage V _A in addition to the end-of-charge voltage V _E , and the battery is finally Charging is performed by pressing the button once, and full charge is easily reached in an extremely short period of time. Immediately thereafter, the alternator generated voltage V _A returns to the normal charging end voltage V _E.

As described above, according to this embodiment, the voltage generated by the alternator can be set to the final charge voltage determined from the battery liquid temperature, so that the battery can always be controlled to a fully charged state, and within the range permitted by other conditions. Optimum full charging is achieved in this manner, and full charging can be achieved efficiently in a short period of time by giving the final push at a specific end of charging.

Note that in the embodiments described above, the charging control is performed by full charge control, but any other charging control can be used for the charging control after the discharge state of the battery is detected in the present invention.

As explained above, according to the present invention, the charging or discharging state of the battery can be easily determined by comparing the electromotive force corresponding to the specific gravity of the battery liquid and the actual terminal voltage of the battery, and when discharging, charging is immediately controlled. Since this is performed, it is possible to obtain a good state of charge.

[Brief explanation of drawings]

Fig. 1 is a specific gravity versus electromotive voltage characteristic diagram of a vehicle battery, Fig. 2 is a charging and discharging characteristic diagram of a vehicle battery, and Fig. 3 is a flowchart showing a preferred embodiment of the charging control method according to the present invention. , Figure 4 is a characteristic diagram of the battery fluid temperature versus the voltage at the end of charging for a vehicle battery.
FIG. 5 is an explanatory diagram showing the charging control action of the embodiment shown in FIG. 3. V _R : Electromotive voltage equivalent to specific gravity, V _E : End-of-charge voltage,
V _th ...Detected value at the end of charging, V _A ...Alternator generated voltage, V _B ...Battery terminal voltage, α...Additional.

Claims (1)

[Claims] 1 Detect the specific gravity of the battery liquid and compare the electromotive force corresponding to the liquid specific gravity with the actual battery terminal voltage,
A charging control method for a battery for a vehicle, characterized by determining whether the battery is charged or discharged, and when the battery is in a discharged state, automatically puts the battery into a charging control state.