JP3900416B2 - Engine automatic stop / restart device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine stop / restart apparatus for an automobile equipped with an engine.
[0002]
[Prior art]
Conventionally, when an automobile stops at an intersection or the like, the engine is automatically stopped under a predetermined stop condition, and then the engine is restarted under a predetermined start condition, thereby saving fuel or improving exhaust emission. An engine automatic stop / start device (also referred to as an idle stop control device) is known. Also in a hybrid vehicle, the engine is automatically stopped or automatically restarted according to the vehicle running condition and the battery state.
[0003]
The automatic stop of the engine is usually performed by determining that the vehicle state satisfies a predetermined automatic stop condition such that the vehicle speed becomes a certain level or less.
[0004]
[Problems to be solved by the invention]
In the above-described automatic engine stop / restart device, reliable automatic engine restart is desired in spite of a decrease in the outside air temperature, a deterioration with time of the battery, and a decrease in the true SOC of the battery.
[0005]
In order to achieve this, as one of the automatic stop conditions described above, it may be possible to provide a determination condition that the state of charge of the battery is equal to or greater than a predetermined threshold value. However, if the determination threshold value in this case is set small (to the small SOC side), there is a possibility that the engine automatic restart may fail due to some change in the situation, and if this determination threshold value is set large (to the large SOC side). The target engine stop time is shortened and the original effect of the engine stop operation is reduced.
[0006]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an automatic engine stop / restart device that promotes automatic engine stop and reliably performs automatic engine restart.
[0007]
[Means for Solving the Problems]
The engine automatic stop / restart device according to the present invention automatically stops the engine when the detected vehicle state satisfies a predetermined automatic stop condition, and the engine stops when the detected vehicle state satisfies a predetermined automatic restart condition. In the engine automatic stop / restart apparatus for instructing automatic restart, the battery polarization improving means for forcibly executing charge enhancement or discharge reduction of the battery only for a predetermined period immediately before the automatic stop is characterized.
[0008]
That is, the present invention is characterized in that the battery is intentionally induced in a charging tendency in the period immediately before the engine automatic stop. As a result, charge polarization tends to occur inside the battery immediately before the engine is automatically stopped. Therefore, this charge polarization energy can be used for the next automatic engine restart, and reliable automatic engine restart can be realized. it can. Further, since the charge state of the battery as an engine automatic stop condition can be determined in consideration of this charge polarization energy, the battery's true (permanent charged amount (SOC) not taking charge polarization energy into consideration) Even if it is small due to deterioration, battery management mistakes, low temperature start environment, etc., it is possible to reliably perform the automatic engine restart after the automatic engine stop without causing any trouble in the next automatic engine restart, improving fuel consumption and reducing emissions. The original effects of automatic engine stop such as the above effects can be realized in a wider battery environment.
[0009]
This will be described in more detail below.
[0010]
The present invention is characterized by utilizing or taking into account fluctuations in the state of charge of the battery due to a polarization phenomenon, which is a phenomenon specific to a normal battery, in the determination of the engine automatic stop prohibition of the idle stop control device.
[0011]
As is well known, the state of charge of a normal battery can be estimated from its terminal voltage, current accumulated capacity, etc., and in order to estimate it more accurately, its voltage drop that estimates internal resistance is obtained, and this voltage is calculated from the terminal voltage. Many methods are known, such as a method of determining a charge state (capacity) from an open circuit voltage (battery electromotive force) obtained by subtracting a drop.
[0012]
However, in lead batteries and nickel metal hydride batteries, which are electrolyte-based secondary batteries that are normally used as automobile batteries, a charge polarization phenomenon occurs during charging, and a discharge electrode phenomenon occurs during discharge. This polarization cannot be eliminated in a short time. It is known. Note that the polarization elimination time of the lithium battery is faster than that of the lead battery or nickel metal hydride battery, but it has been found that polarization occurs. That is, immediately after the battery changes from the charged state to the discharged state, a voltage that is temporarily higher by the charge polarization voltage is output, and an excessive amount of discharge power is obtained accordingly. Conversely, immediately after the battery changes from the discharged state to the charged state, a voltage that is temporarily lower by the discharge polarization voltage is output, and only a discharge power smaller than the original discharge power can be obtained. Since the phenomenon caused by the discharge polarization can be considered to be the reverse of the phenomenon caused by the charge polarization, the charge polarization phenomenon and its usage in the present invention will be described below.
[0013]
The charge polarization phenomenon here is a phenomenon in which ions are excessively accumulated on the electrode surface due to a delay in electrochemical reaction on the electrode surface of the battery during charging, and a charging voltage higher than the open circuit voltage of the battery is required. .
[0014]
Note that the charging voltage of the battery also increases due to a voltage drop of the internal electrical resistance of the battery. Therefore, the difference between the charging voltage and the open circuit voltage (which has a more accurate correlation with the SOC than the charging voltage or discharging voltage) is roughly represented by the sum of the charging polarization voltage and the voltage drop of the internal electrical resistance. The magnitude of the charging polarization voltage is a parameter related to the magnitude of the charging current and the charging time. Within a certain range, the charging current becomes larger and the charging time becomes longer. It tends to saturate later.
[0015]
This polarization phenomenon can be roughly understood in terms of a circuit by an equivalent circuit in which a charging polarization capacitor is connected in series with an ideal battery indicated by an open circuit voltage. That is, the charge polarization can be roughly regarded as electric energy temporarily stored in the electric double layer capacitor inside the battery. This charge polarization is eliminated (discharged) over a long time when the battery is opened, but is eliminated in a relatively short time when the battery is changed from the charged state to the discharged state. This polarization elimination time when switching from the charged state to the discharged state is also correlated with the magnitude of the discharge current, and the polarization elimination time is shortened as the discharge current is increased.
[0016]
This can be interpreted as preferentially consuming excessively accumulated ions on the electrode surface without requiring ion transport between the electrodes. This means that if the battery has a large charge polarization immediately before the discharge, the stored energy is output from the battery to the external load due to the elimination of the charge polarization in a relatively short period immediately after the subsequent discharge. That is, immediately after the change from the charge state to the discharge state, a voltage that is higher by the charge polarization voltage is temporarily output, and an excess discharge power is obtained accordingly. There has never been a plan to actively use this charge polarization energy effectively. This is because this charge polarization is eliminated within a relatively short time.
[0017]
On the other hand, in the present invention, attention is paid to the fact that the start of the vehicle engine is a very short time, and this is a phenomenon that forces the battery to discharge a large current. In such a short-time high-current discharge, there is a problem that a deteriorated battery, a capacity-reduced battery, a low-temperature discharge battery, etc. have a large voltage drop due to a voltage drop of the battery internal resistance, and a sufficient engine starting power cannot be obtained. Therefore, if sufficient charge polarization is generated in the battery immediately before starting the engine, the battery voltage increases in a short period of time, so that the discharge power that can be extracted from the battery can be increased and a powerful engine starting torque can be obtained. It should be. Moreover, since the movement of ions in the electrolyte is unevenly distributed in the direction of suppressing the discharge polarization by the amount of charge polarization, the development of discharge polarization due to large current discharge at the start of the engine immediately after is suppressed, and the battery voltage is lowered by this discharge electrode. Can be suppressed, and the discharge voltage drop caused thereby can be suppressed, and the discharge power that can be extracted from the battery when the engine is started can be temporarily increased.
[0018]
However, the charge polarization energy can only be used for a short period of time immediately after the discharge, and after a few hours have elapsed from the end of the charge, it is a phenomenon that decays even if there is almost no discharge during that time. There is a problem that there are limitations. Therefore, the present invention solves this problem by using this charge polarization phenomenon for automatic restart after automatic stop of the engine. In other words, in an idle stop vehicle or a hybrid vehicle, the engine is automatically restarted within a relatively short time after the automatic stop, so that the charge polarization attenuation is small within this short time and the engine start is very Since the time is short, the above problem does not occur.
[0019]
In the present invention, the battery polarization improving means forcibly executes an increase in the charging current of the battery by commanding an increase in the generated current or a decrease in the load current during the predetermined period . In this way, the charge polarization of the battery can be easily promoted immediately before the engine is automatically stopped.
[0020]
In a preferred aspect, the battery polarization improving means commands an increase in the battery charge amount by a predetermined amount during the predetermined period. Thereby, it is possible to reliably realize the charge polarization immediately before the engine is automatically stopped. Note that a certain increase in the battery charge (SOC) can be realized by increasing the battery voltage (preferably an open-circuit voltage, but may be simply a terminal voltage) for a predetermined period. . Of course, if the current sensor is used, the charge amount can be accurately controlled. The battery voltage can be increased while keeping the battery voltage at or above a predetermined level. In other words, if the battery voltage is too small (SOC is too small), the engine automatic restart cannot be achieved by the charge polarization alone.
[0021]
In a preferred aspect, the battery polarization improving unit performs the forced execution when it is determined that the state of charge of the battery may be equal to or lower than a predetermined level.
[0022]
The predetermined level may be determined simply based on the terminal voltage or open circuit voltage of the battery as described above.
[0023]
In a preferred aspect, when the battery polarization improving means determines that the charge polarization of the battery is sufficiently performed based on the detected electric quantity related to the charge state of the battery, the forced execution is performed. Stop or suppress.
[0024]
For example, if the battery voltage is higher than a certain level immediately before the engine automatic stop, the SOC is sufficient for the engine automatic restart and the forced charge immediately before the engine automatic stop is not required, so that it is stopped. The automatic engine stop can be executed quickly. Also, if the battery voltage increases for a certain period of time just before the engine stops automatically, charge polarization has occurred sufficiently, and it is not necessary to forcibly charge immediately before the engine stops automatically. An automatic stop can be performed.
[0025]
In a preferred aspect, the battery charge state determining means for determining the state of charge of the battery based on the amount of electricity related to the detected SOC (storage capacity) of the battery, and the detected vehicle state satisfies a predetermined automatic stop condition The engine is automatically stopped, and when the detected vehicle condition satisfies a predetermined automatic restart condition, the engine is provided with stop / restart determination means for instructing automatic restart of the engine. look including the condition that the state of charge of the battery is the predetermined threshold value, the battery state of charge determination means, the charging of the battery based on an electric quantity related to the polarization of the battery with electrical quantity associated with the SOC It is characterized by determining the state.
[0026]
That is, according to this aspect , the engine automatic stop is permitted only after confirming that the dischargeable energy (power amount) or the discharge power of the battery taking into account the charge polarization amount or the charge polarization energy is secured.
[0027]
As a result, it is not necessary to set the battery SOC and discharge voltage threshold values for permitting automatic stop to be unnecessarily high, thereby further improving the effect of automatic engine stop without avoiding failure of automatic engine restart. be able to.
[0028]
In a preferred aspect, the battery charge state determination means determines an amount of electricity related to a polarization amount of the battery based on a charge / discharge state of the battery immediately before the engine is automatically stopped. Thereby, the amount of electricity related to this amount of polarization can be determined relatively. For example, if the battery voltage (preferably an open-circuit voltage but may be a terminal voltage) is increased immediately before the engine is automatically stopped, it can be considered to be in a charged state, and if the battery voltage is decreased It can be considered as a discharge state. Therefore, if the battery voltage has increased for a predetermined time in the period immediately before the engine automatic stop, it can be considered that the charge polarization has occurred, and the charge state of the battery that permits the engine automatic stop in consideration of this charge polarization A threshold value for determination (for example, a battery voltage threshold value) can be lowered. Conversely, if the battery voltage has dropped for a predetermined time in the period immediately before the engine automatic stop, it can be considered that discharge polarization has occurred. It is possible to raise the threshold for determining the state (for example, the threshold of the battery voltage). Thereby, the engine automatic stop can be performed early without waiting for the improvement (for example, voltage increase) of the charge state of the battery while preventing the engine automatic restart failure.
[0029]
Note that the charge polarization immediately before the engine is automatically stopped and the amount of the discharge electrode (polarization amount) can be obtained by current integration or the like, and the threshold value can be adjusted based on this. Further, simply, if the battery voltage increase period lasts for a predetermined time, it is determined that a predetermined charge polarization has occurred, and the threshold voltage as the minimum charge state of the battery that should be secured for permitting the automatic engine stop is set to a predetermined value. On the contrary, if the battery voltage regular price period lasts for a predetermined time, it is determined that a predetermined discharge polarization has occurred, and the threshold voltage as the minimum state of charge of the battery to be secured for automatic engine stop permission is set to a predetermined value. Can only be raised.
[0030]
In a preferred aspect, the battery is a battery that is provided separately from a battery that does not drive a starter motor for starting the engine and is mainly used for driving the starter motor. In this way, the battery polarization phenomenon can be more effectively used in the engine automatic stop and the subsequent automatic engine restart.
[0031]
That is, even if charging polarization occurs in the battery immediately before the engine automatic stop described above, if the driving of the vehicle auxiliary machine or the electric load for the vehicle continues for a long time until the engine automatic restart is started, this charging polarization is There is a problem of disappearing. However, this problem is greatly improved in a vehicle power supply system having a battery exclusively for engine start and a battery that drives all or most of the loads other than the engine start motor, and the above effect can be realized. .
[0032]
In a preferred aspect, there is provided means for instructing an operation for suppressing consumption of charge polarization of the battery during a period from the engine automatic stop to the engine automatic restart. Thereby, the disappearance of the charge polarization of the battery during the automatic engine stop can be suppressed.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the engine automatic stop / restart device of the present invention will be described in more detail below.
[0034]
Embodiment
The engine automatic stop / restart device of this embodiment will be described with reference to FIG.
[0035]
(overall structure)
FIG. 1 is a block circuit diagram showing the main part of the circuit system of the idle stop type automobile of this embodiment.
[0036]
DESCRIPTION OF SYMBOLS 1 is an engine, 2 is a high voltage battery, 3 is a low voltage battery, 4 is a generator, 5 is a regulator, 6 is a DC-DC converter, 7 is a power transmission controller, 8 and 9 are low voltage electric loads, 10 is an engine automatic stop and restart An engine control ECU 11 operating as a device is a starter motor.
[0037]
The high voltage battery 2 is fed with DC power from the generator 4 and also feeds the starter motor 4 and a high voltage electric load (not shown). The low voltage battery 3 is fed from the high voltage battery 2 through the DC-DC converter 6 and feeds the low voltage electric loads 8 and 9. The generator 4 is a normal rectifier built-in field winding type three-phase synchronous generator, and the field current is adjusted by a regulator 5. The regulator 5 normally adjusts the power generation amount of the generator 4 by feedback PWM control of the field current so that the terminal voltage of the high voltage battery 2 is maintained within a predetermined target range. The DC-DC converter 6 is a normal step-down DC-DC converter, and the power transmission controller 7 performs feedback PWM control of the field current so as to maintain the voltage of the low-voltage battery within a predetermined target range. The engine control ECU 10 controls the engine 1 based on signals from various vehicle sensors and engine control sensors (not shown) and the voltage of the high-voltage battery 2 or performs engine automatic stop / restart control that forms the gist of this embodiment. ing. The starter motor 11 is started based on a manual engine start command from an ignition switch (not shown) or an automatic restart command from the engine control ECU 10 to start the engine 1.
[0038]
Since each of the components described above is already known, further detailed description is omitted. Of course, a generator motor in which the starter motor 4 and the generator 4 are integrated may be used.
(Engine automatic stop control)
A specific example of the engine automatic stop control executed by the engine control ECU 10 will be described below with reference to the flowchart shown in FIG.
[0039]
First, based on signals from various vehicle sensors and engine control sensors (not shown) and the voltage of the high-voltage battery 2, it is determined whether or not a preset engine automatic stop condition is satisfied (S100). If it is satisfied, it is determined whether or not the charge polarization is currently sufficient (S102).
[0040]
In this embodiment, whether or not the charge polarization is sufficient is simply determined by whether or not the voltage of the high-voltage battery 2 has increased for a predetermined time immediately before by a step not shown in the figure. It is determined that sufficient charge polarization has occurred, and the process proceeds to step S104. Otherwise, the process returns to the main routine. Of course, the charge amount of the battery in the immediately preceding period may be grasped more precisely by integrating the current of the high voltage battery 2 or the like.
[0041]
In S104, it is determined whether the state of charge of the battery has sufficient capacity for the next automatic engine restart (S104). If so, the process proceeds to step S106, and if not, the process returns to the main routine.
[0042]
In this embodiment, whether or not the state of charge of the battery is sufficient is simply determined by whether or not the battery voltage is equal to or higher than a predetermined threshold level by steps not shown in the figure, but it is more accurate by current integration or the like. It is also possible to measure to
[0043]
In S106, the DC-DC converter 6 is stopped, the field current is increased by a predetermined amount, and a high voltage electric load (not shown) is cut off. Thereby, the high voltage battery 2 is forcibly charged. In this step, the field current may be increased only by a predetermined amount, and the DC-DC converter 6 may be shut off or the high voltage electric load (not shown) may be shut off when the engine is automatically stopped.
[0044]
Next, the system waits for a predetermined time required for sufficient charge polarization to occur (S108), and then instructs to stop the engine automatically (S110), and the field current is cut off (S112). The standby time and the field current increase amount can be adjusted based on the state of the high voltage battery 2 before step S106.
[0045]
Thereby, the battery after an engine automatic stop can be hold | maintained in a charge polarization state.
(Engine automatic restart control)
The engine automatic restart control of this embodiment will be described with reference to FIG.
[0046]
First, it is determined whether the engine is currently automatically stopped (S200). If the engine is not automatically stopped, the process returns to the main routine. If the engine is not automatically stopped, signals from various vehicle sensors and engine control sensors (not shown) Based on the voltage of the high-voltage battery 2, it is determined whether or not a preset engine automatic restart condition has been satisfied (S202). If not satisfied, the process returns to a main routine (not shown). A start is commanded (S204). This engine automatic restart control itself is the same as a normal one.
(Engine automatic stop condition change control)
The engine automatic stop condition change control of this embodiment will be described with reference to FIG.
[0047]
First, the current polarization amount of the high-voltage battery 2 is estimated (S300), and the threshold value for determining whether or not automatic stop is permitted based on the estimated polarization amount is changed (S304).
[0048]
In this embodiment, the amount of charge polarization is simply estimated from the degree and time of increase of the immediately preceding battery voltage, and the amount of discharge polarization is similarly estimated from the degree and time of decrease of the immediately preceding battery voltage. Then, the threshold voltage is changed based on the polarization state. More specifically, if the degree and time of the previous battery voltage increase are equal to or greater than a predetermined value, the threshold voltage is decreased by a predetermined value on the assumption that a predetermined amount of charge polarization has occurred. Conversely, if the degree or time of the previous battery voltage drop is equal to or greater than a predetermined value, it is considered that a predetermined amount of charge polarization has occurred and the threshold voltage is raised by a predetermined value. Of course, it is also possible to continuously change the threshold voltage based on the amount of change in the battery voltage and the relationship between the duration of the battery voltage and the threshold voltage. Then, in step S100 shown in FIG. 2, it is determined whether or not the battery voltage as a parameter indicating the state of charge of the battery exceeds the threshold voltage, and the automatic engine stop is permitted only when it exceeds the threshold voltage.
[0049]
As a result, the degree of polarization of the high voltage battery 2 immediately before the engine is automatically stopped can be reflected in the automatic stop condition.
(Modification)
In the above-described embodiment, the present invention is applied to an idle stop vehicle having a so-called two-battery vehicle power supply device. However, the present invention can also be applied to a one-battery type idle stop vehicle. In this case, it is preferable to equip means for suppressing battery discharge after the engine is automatically stopped.
[0050]
Further, the technical idea of this embodiment can be applied not only to an idle stop vehicle, but also to a hybrid vehicle that similarly performs engine automatic stop and engine automatic restart.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of an automatic engine stop / restart device of the present invention.
FIG. 2 is a flowchart showing engine automatic stop control of the apparatus of FIG. 1;
FIG. 3 is a flowchart showing engine automatic restart control of the apparatus of FIG. 1;
FIG. 4 is a flowchart showing engine automatic stop condition change control of the apparatus of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 2 High voltage battery 3 Low voltage battery 4 Generator 5 Regulator 6 DC-DC converter 9 Engine control ECU (Battery polarization improvement means, battery charge state determination means, stop / restart determination means)
11 Starter motor

Claims (8)

When the detected vehicle state satisfies a predetermined automatic stop condition, the engine is automatically stopped, and when the detected vehicle state satisfies a predetermined automatic restart condition, the engine automatic stop / restart command for instructing the automatic restart of the engine is performed. In the starting device,
Battery polarization improving means for forcibly executing an increase in the charging current of the battery by instructing an increase in generated current or a decrease in load current compared to immediately before the predetermined period only for a predetermined period immediately before the automatic stop. An automatic engine stop / restart device . The engine automatic stop / restart device according to claim 1,
The engine automatic stop / restart apparatus, wherein the battery polarization improving means commands an increase in the battery charge amount by a predetermined amount during the predetermined period. The engine automatic stop / restart device according to claim 1,
The engine automatic stop / restart device, wherein the battery polarization improving means performs the forced execution when it is determined that the state of charge of the battery may be a predetermined level or less. The engine automatic stop / restart device according to claim 1,
When the battery polarization improving unit determines that the charge polarization of the battery is sufficiently performed based on the detected amount of electricity related to the charge state of the battery, the battery polarization improvement unit stops or suppresses the forced execution. An automatic engine stop / restart device. The engine automatic stop / restart device according to claim 1,
The battery charge state determining means for determining the charge state of the battery based on the amount of electricity related to the detected SOC (storage capacity) of the battery;
Stop / restart determination that automatically stops the engine when the detected vehicle state satisfies a predetermined automatic stop condition, and commands the automatic restart of the engine when the detected vehicle state satisfies a predetermined automatic restart condition Means,
With
The automatic stop condition is seen including a condition that the state of charge of the battery is a predetermined threshold value,
The battery state of charge determining means, prior SL automatic engine stop and restart device, characterized in that on the basis of the amount of electricity to determine the state of charge of the battery associated with the polarization of the battery with the electrical quantity related to the SOC. In the automatic engine stop / restart device according to claim 5 ,
The battery charge state determination means includes:
An engine automatic stop / restart apparatus, wherein an electric quantity related to a polarization amount of the battery is determined based on a charge / discharge state of the battery immediately before the engine is automatically stopped. The engine automatic stop / restart device according to any one of claims 1 to 6 ,
The engine automatic stop / restart device, wherein the battery is a battery that is provided separately from a battery that does not drive a starter motor for starting the engine and is mainly used for driving the starter motor. The engine automatic stop / restart device according to any one of claims 1 to 7 ,
An automatic engine stop / restart apparatus comprising: means for instructing an operation for suppressing consumption of charge polarization of the battery in a period from the automatic engine stop to the automatic engine restart.

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