JPH10271695A - Battery remaining capacity detection device and power generation control device for hybrid electric vehicle - Google Patents

Abstract

(57) [PROBLEMS] To provide a battery remaining capacity detecting device capable of detecting a battery remaining capacity more accurately than a conventional remaining capacity meter, and to apply a battery remaining capacity detecting device to a motor. Provided is a power generation control device for a hybrid electric vehicle that can start power generation at an appropriate time without lowering power performance. A based on the minimum cell voltage V _n of the battery current I _n and the battery, determine the internal resistance R and open-circuit voltage V _o of the cell, based on the internal resistance R and open-circuit voltage V _o, Battery voltage V _max required at maximum motor output
And, based on this battery voltage V _max ,
When the motor maximum output is continuously output, the battery voltage V _max
There (This corresponds to a battery residual capacity) remaining time [Delta] T _a to decrease the voltage limit VL to estimate, configured to start power generation by driving the engine on the basis of the remaining time [Delta] T _a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery remaining capacity detection device and a power generation control device for a hybrid electric vehicle, and more particularly to a high performance battery having a relatively small internal resistance such as a lithium ion battery and having little change in internal resistance. It is useful when applied to accurately detect the capacity.

[0002]

2. Description of the Related Art A hybrid electric vehicle includes a motor for driving a vehicle, a battery for supplying power to the motor, and a generator for charging the battery when the remaining capacity of the battery decreases. And an engine for driving the generator. In various types of electric vehicles including such hybrid electric vehicles, it is important to detect how long the vehicle can continue to run before charging the battery. In an automobile, a battery is charged at a charging facility at an appropriate time, and in a hybrid electric vehicle, power generation is started at an appropriate time to charge a battery.

[0003] Conventionally, in a hybrid electric vehicle, the power generation start time is determined by two methods, a method based on monitoring of a battery remaining capacity by a battery remaining capacity meter and a method based on monitoring of a motor output. FIG. 3 is an explanatory diagram of a method of determining a power generation start time based on monitoring of a remaining battery capacity by a remaining capacity meter, and FIG. 4 is an explanatory diagram of a method of determining a power generation start time based on monitoring of a motor output.

[0004] The remaining capacity meter refers to a battery capacity at full charge by external charging being 100%, and subtracting the integrated value (Ah) of the battery current (discharge current) from the 100% capacity (ampere hour: Ah). The remaining capacity is determined. As shown in FIG. 3, the method for determining a power generation start time based on monitoring of the remaining capacity of the battery by the remaining capacity meter is as follows. Is reached, power generation is started to charge the battery, and then, when the remaining battery capacity increases and reaches a predetermined power generation stop capacity, power generation is stopped.

A method of determining the power generation start timing based on the motor output monitoring is to calculate the ratio between the instruction output to the motor and the actual output of the motor, and when the ratio falls below the set ratio, as shown in FIG. Next, a plurality of actual outputs of the motors used in the ratio calculation are plotted in time series (white dots in FIG. 4).
Then, these plot data are approximated by the least squares method (solid line in FIG. 4), and the time T _{4 at} the intersection of the approximated solid line and the output limit of the motor (dotted line in the figure).
From the time T when the latest actual output of the motor is plotted
₃ by subtracting the estimates the remaining time [Delta] T _b to the motor output reaches the output limit, a method of determining power generation start timing based on the remaining time [Delta] T _b.

[0006]

However, in the above-described method of determining the start of power generation based on the remaining capacity monitoring by the remaining capacity meter, the difference between the remaining battery capacity obtained by the remaining capacity meter and the actual remaining battery capacity is determined. Is likely to occur, the actual battery remaining capacity is significantly reduced before the battery remaining capacity obtained by the remaining capacity meter reaches the power generation starting capacity, and the instruction output to the motor cannot be sufficiently increased due to torque suppression described later. In some cases, it may be impossible to drive.

The difference between the remaining battery capacity obtained by the remaining capacity meter and the actual remaining battery capacity occurs because the battery generates an electromotive force due to a chemical reaction. It is considered that the remaining capacity does not always correspond to the integrated value of the battery current detected at the battery terminal. In particular, the occurrence of large current discharge, the operation of the generator, and the regenerative braking of the motor on a downhill (power generation of the motor) The charging and discharging of the battery is repeatedly performed by charging the battery due to the mechanical function, for example, so that a difference occurs between the remaining battery capacity obtained by the remaining capacity meter and the actual remaining battery capacity. Further, even when the remaining battery capacity decreases due to deterioration of the battery, a difference occurs between the remaining battery capacity obtained by the remaining capacity meter and the actual remaining battery capacity.

In the above-described method for determining the power generation start time based on the motor output monitoring, it is necessary to reduce the motor output by suppressing the motor torque in accordance with the battery voltage in order to prevent the battery from being over-discharged. As a result, the power performance of the motor is reduced.

That is, depending on the battery, the battery voltage may drop significantly before the motor output reaches the output limit, and the maximum output is generated without suppressing the torque in the state where the battery voltage has dropped as described above. If this is attempted, since the battery itself has the ability to supply the maximum power, the battery voltage may fall below the lower limit of use voltage, causing overdischarge and damaging the battery.

In order to prevent such a situation, the battery voltage is monitored in a region where the maximum output can be generated, and when the battery voltage falls below a predetermined limit voltage, the torque is suppressed in accordance with the battery voltage. The remaining time _Tf must be estimated after reducing the maximum value of the command output to the motor so that the motor output does not exceed the limited output even when the accelerator pedal 7 is fully depressed. Did not. Therefore, as described above, the power performance of the motor is reduced.

SUMMARY OF THE INVENTION Accordingly, it is a first object of the present invention to provide a battery state-of-charge detecting device capable of detecting the state of charge of a battery more accurately than a conventional state-of-charge meter. A second object is to provide a power generation control device for a hybrid electric vehicle that can start power generation at an appropriate time without deteriorating the power performance of a motor by applying a remaining capacity detection device.

Incidentally, Japanese Patent Laid-Open No. Hei 6-3472 previously published.
No. 7 discloses a "battery remaining capacity meter". The battery remaining capacity meter detects a discharge current of a battery (battery), and when it is determined that the condition that the discharge current is equal to or more than a predetermined value and increases is satisfied, the discharge at that time is determined. A battery remaining capacity is calculated based on a current and a discharge voltage and a map indicating a remaining capacity with respect to a discharge current and a discharge voltage provided in advance, and a relatively large internal resistance is increased by discharging like a lead battery. This is an effective means for such a device, but the present invention is considered to be effective for a device such as a lithium ion battery in which the battery voltage (open-circuit voltage) decreases relatively linearly by discharging.

[0013]

According to a first aspect of the present invention, there is provided a battery remaining capacity detecting apparatus for detecting a battery current, a voltage detecting means for detecting a battery voltage, and Means for estimating the internal resistance of the battery based on the battery current detected by the means and the battery voltage detected by the voltage detecting means; and the battery current detected by the current detecting means and the voltage detecting means. Open voltage calculation means for calculating the open circuit voltage of the battery based on the battery voltage detected by the internal resistance estimating means and the internal resistance estimated by the internal resistance estimating means. When supplying the maximum power to the load of the battery based on the open-circuit voltage calculated by the open-circuit voltage calculating means, A voltage calculating means for calculating a required battery voltage, and a remaining for estimating a remaining time until the battery voltage drops to a predetermined voltage when the maximum power supply is continued based on the battery voltage calculated by the voltage calculating means. Time estimating means.

According to another aspect of the present invention, there is provided a power generation control apparatus for a hybrid electric vehicle which solves the second problem, comprising: a motor for driving the vehicle; a battery for supplying power to the motor;
A power generation control device for a hybrid electric vehicle including a generator for charging the battery and an engine for driving the generator, the current detection unit detecting a battery current, and the voltage detection unit detecting a battery voltage. Internal resistance estimating means for estimating the internal resistance of the battery based on the battery current detected by the current detecting means and the battery voltage detected by the voltage detecting means; and a battery current detected by the current detecting means. An open voltage calculating means for calculating an open circuit voltage of the battery based on the battery voltage detected by the voltage detecting means and the internal resistance estimated by the internal resistance estimating means; and Based on the internal resistance and the open circuit voltage calculated by the open circuit voltage calculation means, the motor maximum output Voltage calculating means for calculating a required battery voltage at the time, and estimating a remaining time until the battery voltage drops to a predetermined voltage when the motor maximum output is continuously output based on the battery voltage calculated by the voltage calculating means. The remaining time estimated by the remaining time estimating means to drive the engine to start power generation.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a hybrid electric vehicle provided with a power generation control device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of the power generation control device.

As shown in FIG. 1, a battery 1 is mounted on a hybrid electric vehicle, and the battery 1 is electrically connected to a motor 3 via a motor controller 2. The motor 3 is connected to driving wheels of a vehicle (not shown). Accordingly, in this hybrid electric vehicle, electric power is supplied from the battery 1 to the motor 3 via the motor controller 2, whereby the motor 3 rotates and drives the drive wheels to travel. The motor controller 2 sets an instruction output to the motor 3 based on the accelerator opening output from the accelerator opening sensor 8 in accordance with the amount of depression of the accelerator pedal 7 by the driver. Control the output of

The hybrid electric vehicle further includes a generator 10 for supplying power to the battery 1 and the motor 3;
An engine 9 for driving the generator 10 is mounted. Accordingly, when the remaining capacity of the battery 1 decreases, the engine 9 is started at an appropriate time (details will be described later) to start the power generation of the generator 10, and the battery 1 is charged. The engine 9 is provided with a water jacket 13, and the exhaust system of the engine 9 includes a catalyst device 17 for purifying exhaust gas,
A heating device (electric heater or the like) 15 for heating the catalyst of the catalyst device 17 is provided.

Further, the hybrid electric vehicle is provided with a power generation control device according to the present embodiment including a current detector 11, a voltage detector 12, and a control device 6.

[0020] In the current detector 11 detects the I _n (the discharge current output from the battery 1 to the motor 3) the battery current, and outputs the detected battery current I _n to the controller 6.

[0021] In the voltage detector 12 detects a terminal voltage of each cell constituting the battery 1, select the minimum cell voltage V _n from among the detected plurality of cell voltages, the minimum cell voltage V _n Output to the control device 6. The battery 1 is composed of a plurality of modules, and each module is composed of a plurality of cells. The minimum unit constituting the battery 1 is a cell.

[0022] In the control unit 6, based on the battery current I _n inputted from the current detector 11, and the minimum cell voltage V _n input from the voltage detector 12, and various constants are set in advance, the generator 10 power generation start timings are determined. Hereinafter, the processing content of the control device 6 will be described in detail with reference to FIG.

As shown in FIG. 2, in the control device 6, first,
In the internal resistance estimating unit 21, the battery current I _n detected during traveling by the current detector 11 and the voltage detector 12
Based on the minimum cell voltage V _n and estimates the internal resistance R of the cell.

[0024] That is, sampled and n battery current I _n and the minimum cell voltage V _n in a predetermined sampling cycle, the n data representing the relationship between these battery current I _n and the minimum cell voltage V _n After plotting (white point in the figure), these plot data are approximated by the least squares method (solid line in the figure), and the slope of the approximated solid line is defined as the internal resistance R of the cell. In other words, battery current I _n increases the internal resistance R minimum cell voltage V _n voltage drop increased by
Order but decreases, the battery current I _n and the minimum cell voltage V _n
Has a downward-sloping characteristic as shown in the figure, and this slope represents the internal resistance R.

[0025] Then, the open circuit voltage calculating unit 22, from the internal resistance R estimated by the internal resistance estimating unit 21, and the n battery current I _n and the minimum cell voltage V _n, the by (1) The open voltage V _{on of the} cell is calculated. That is, the minimum cell voltage V _n, a voltage drop due to the internal resistance R (R × I
_n ) is added to determine open-circuit voltage V _on . The open-circuit voltage of the cell is the cell terminal voltage (corresponding to the electromotive force of the cell) when no load is applied to the cell (battery 1) (when the motor 3 is stopped) and the cell (battery 1). ) to be Kakare load (is rotated with the motor 3) the battery current (load current according to the motor output) to I _n flows, a voltage drop due to the internal resistance R (I _n × R), a cell terminal voltage It falls below the open circuit voltage. Therefore, (1)
The open circuit voltage V _on of the cell is obtained by the equation.

[0026]

(Equation 1)

However, the open-circuit voltage calculating section 22 calculates
Open voltage V_onIs the total voltage of n sampling data
Therefore, in the next averaging section 23, this open discharge
Pressure V _onDivided by n, the average open-circuit voltage V_oAsk for.

The maximum output cell voltage calculator 24 calculates the average
The open circuit voltage V calculated by the calculation unit 23 _oAnd internal resistance estimation
Internal resistance R estimated by unit 21 and maximum supply for each cell
Power W_maxFrom equation (2), at the time of motor maximum output
Battery current I_maxAnd calculate the battery current
I_maxAnd the internal resistance R from the equation (3).
Cell voltage V at maximum output_maxIs calculated. Each section
Power supply W per unit _maxIs the maximum supply of the entire battery 1.
Power supply W_maxn(KW) is converted to (W) and the cell
Divide by number. Also, the maximum supply power W_maxnIs the motor
The maximum output in the motor 3 and the motor controller 2
Considering efficiency (power loss)
I have.

[0029]

(Equation 2)

[0030] (2) substitutes W _max = a I _max × V _max (3) equation, which is a formula obtained by organizing the formula I _max. Then, this I _max determined by (2) (3) are substituted into equation by subtracting the voltage drop due to the internal resistance R from the open circuit voltage V _o (R × I _max), the cell voltage at the motor maximum output seeking V _max.

On the other hand, the gain calculator 25 calculates a gain _Gmax which is a ratio between a preset motor maximum output _Mmax and a motor output limit ML.

The cell voltage limit setting section 26 calculates a cell voltage corresponding to the gain G _max from table data indicating a relationship between a predetermined cell voltage and a gain based on the gain G _max calculated by the gain calculating section 25. Then, this cell voltage is set as the cell voltage limit VL.

Then, the remaining time estimating unit 27 first plots a plurality of cell voltages V _max at the maximum output of the motor sequentially calculated by the maximum output cell voltage calculating unit 24 in time series (white dots in the figure). . Cell voltage V _max at the maximum motor output, by open voltage V _o and the internal resistance R with decreasing battery (cell) remaining capacity changes over time as illustrated (reduction in the remaining capacity) descend. Therefore, these plot data are approximated by the least squares method (solid line in the figure), and the approximated solid line and the cell voltage limit VL set by the cell voltage limit setting unit 26 are used.
The time T ₁ when the latest motor maximum output cell voltage V _max is plotted is subtracted from the time T _{2 at} the intersection with the dotted line in the figure to obtain the cell voltage V at the maximum motor output.
Remaining time ΔT _a until _max reaches cell voltage limit VL
Is estimated.

That is, the remaining time ΔT _a is the remaining time until the cell voltage V _max reaches the cell voltage limit VL when the motor maximum output is continuously output.

The power generation start time determination unit 28 estimates the remaining time.
Remaining time ΔT estimated by constant unit 27 _aAnd preheat time
And the remaining time ΔT_aIs less than the preheat time
Output power generation start command to engine 9 and generator 10
I do. Preheating time means heating the catalyst of the catalyst device 17.
Time needed to warm up the engine 9
It is obtained by adding time.

The preheating time is ensured by heating the catalyst of the catalyst device 17 to a predetermined temperature by the heating device 15 before starting power generation,
This is because the exhaust gas performance of the engine 9 is kept good by performing the warm-up operation by driving the engine 9 at idle rotation for a predetermined time.

Although illustration is omitted, the maximum cell voltage is monitored after the start of power generation, and charging of the battery 1 is stopped when the maximum cell voltage becomes equal to or higher than a predetermined voltage.

As described above, the hive according to the present embodiment
In the power generation control device of the lid electric vehicle, the internal resistance estimator
21 and the open-circuit voltage calculator 22 and the average calculator 23.
And the lowest cell voltage V during running_nAnd battery current I_nWhen
From the internal resistance R and the open circuit voltage V _oAnd after asking these
Internal resistance R and open circuit voltage V_oBased on the maximum output cell
The cell voltage V at the time of the motor maximum output in the voltage calculation unit 24
_maxAsk for. And the cell power at the time of this motor maximum output
Pressure V_maxTime ΔT until the voltage reaches the cell voltage limit VL
_a(This is equivalent to the remaining battery charge)
The remaining time ΔT_aBased on
Power generation start time determination unit 28 determines the power generation start time.
Set. Note that the battery current I_nAnd the minimum cell voltage V_n
Sampling is performed at all times while driving, and the remaining
Time ΔT_aAre sequentially estimated and updated.

For this reason, according to the power generation control device for a hybrid electric vehicle according to the present embodiment, the battery remaining capacity (when the motor maximum output is continuously output, the motor maximum output is more accurate than the conventional remaining capacity meter). The remaining time ΔT _a ) until the cell voltage V _max reaches the cell voltage limit VL can be detected, and in order to determine the power generation start timing based on the remaining time ΔT _a , the motor continues to run at the maximum output of the motor. cell voltage V _max is able to reliably initiate a power generation before the cell voltage VL, thus without causing over-discharge of the battery 1, moreover it is not necessary to lower the power performance of the motor 3 also.

In particular, the hybrid electronic device according to the present embodiment
In the electric vehicle power generation control device, the minimum cell voltage V_nMonitor
And the minimum cell voltage V_nRemaining time estimated based on
ΔT _aThe power generation start time is determined by the
If there is a relatively large voltage variation between cells in
If, for example, only one cell degrades faster than the other cells
Only the voltage of that cell is relatively lower than the voltage of other cells.
In such cases, ensure that the cell is overdischarged
Can be prevented.

[0041] Therefore Conversely, the smaller the variation in voltage between the cells (typically the voltage across the cell variation is small) monitors the terminal voltage of the battery 1 in place of the minimum cell voltage V _n, the battery voltage The remaining time until the battery voltage reaches the battery voltage limit may be estimated based on the battery current and the battery current.

It should be noted, without asking the open-circuit voltage V _o, as described above, but appear to be also possible to use a cell voltage detected by the voltage detector 12 directly, open voltage V _o for the following reasons: Need to ask.

That is, the cell voltage detected by the voltage detector 12 changes according to the running state (motor output change) that changes every moment and is not constant. In contrast, the open-circuit voltage V _o is a constant static voltage depending on the battery remaining capacity. As described above, if the estimated remaining time [Delta] T _a from the cell voltage V _max at the maximum motor output, by determining the power generation start timing based on the remaining time [Delta] T _a, and continue to run at the maximum motor output Although even the cell voltage will be able to reliably initiate a power generation before the voltage limit, therefore the need to calculate the cell voltage V _max at the maximum motor output, open-circuit voltage V _o in this calculation Is necessary.

In the above description, the case where the present invention is applied to a power generation control device of a hybrid electric vehicle has been described. However, the present invention is not limited to this, and other devices using a battery, such as an electric vehicle other than the hybrid electric vehicle, may be used. Can also be applied. For example when applied to an electric vehicle, used as a remaining capacity detecting apparatus, as the remaining time [Delta] T _a estimated by the remaining time estimation unit 27, or by displaying in terms of travel distance, the battery in the charging facility This will give you an idea of how far you can drive before charging.

Further, the reliability can be improved by forming a double system by using the conventional remaining capacity meter together.

[0046]

As described above in detail with the embodiments of the present invention, according to the remaining capacity detecting device of the first invention, the internal resistance and open circuit of the battery are determined based on the battery current and the battery voltage. Voltage, and based on these internal resistances and the open-circuit voltage, the battery voltage required to supply the maximum power to the battery load is determined, and the maximum power supply is continued based on the battery voltage. Sometimes (when the load of the battery is a driving motor of an electric vehicle, when the motor maximum output is continuously output), the remaining time until the battery voltage drops to a predetermined voltage (this corresponds to the remaining battery capacity) , The remaining battery capacity can be detected more accurately than the conventional remaining capacity meter.

Further, according to the power generation control device for a hybrid electric vehicle of the second invention, the internal resistance and the open voltage of the battery are obtained based on the battery current and the battery voltage. The required battery voltage at the time of the motor maximum output is calculated based on the battery voltage. Based on this battery voltage, the remaining time until the battery voltage decreases to the predetermined voltage when the motor maximum output is continued (this is the remaining battery capacity) Equivalent), the battery remaining capacity can be detected more accurately than the conventional remaining capacity meter, and based on the detection result, the engine is driven to start power generation. Even if continued, power generation can be reliably started before the battery voltage reaches the predetermined voltage, so that overdischarging of the battery does not occur, and It is not necessary to lower the power performance of chromatography data.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a hybrid electric vehicle including a power generation control device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of the power generation control device.

FIG. 3 is an explanatory diagram of a conventional method of determining a power generation start time based on monitoring of a remaining battery capacity by a remaining capacity meter.

FIG. 4 is an explanatory diagram of a conventional method for determining a power generation start time based on motor output monitoring.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 battery 3 motor 6 control device 9 engine 10 generator 11 current detector 12 voltage detector 21 internal resistance estimator 22 open voltage calculator 23 average calculator 24 maximum output cell voltage calculator 25 gain calculator 26 cell voltage limit Setting unit 27 Remaining time estimation unit 28 Power generation start time determination unit G _max gain I _n Battery current ML Motor output limit M _max motor maximum output R Internal resistance V _n Minimum cell voltage V _o Open voltage V _max Cell voltage at _maximum motor output VL Voltage limit W _maxn Maximum supply power of battery W _max Maximum supply power of each cell ΔT _a Remaining time

Claims (2)

[Claims] 1. A current detecting means for detecting a battery current; a voltage detecting means for detecting a battery voltage; and a battery current detected by the current detecting means and a battery voltage detected by the voltage detecting means. An internal resistance estimating means for estimating the internal resistance of the battery; a battery current detected by the current detecting means, a battery voltage detected by the voltage detecting means, and the internal resistance estimated by the internal resistance estimating means. Open voltage calculating means for calculating the open voltage of the battery by using the internal resistance estimated by the internal resistance estimating means and the open voltage calculated by the open voltage calculating means. Voltage calculating means for calculating a battery voltage necessary for supplying the battery, and a voltage calculated by the voltage calculating means. Was based on the battery voltage, the battery residual capacity detection device battery voltage when continued maximum power supply is characterized in that a remaining time estimating means for estimating the remaining time until the drops to a predetermined voltage. 2. A power generation control device for a hybrid electric vehicle comprising a vehicle driving motor, a battery for supplying power to the motor, a generator for charging the battery, and an engine for driving the generator. Current detection means for detecting a battery current; voltage detection means for detecting a battery voltage; and battery detection based on the battery current detected by the current detection means and the battery voltage detected by the voltage detection means. Internal resistance estimating means for estimating the internal resistance; a battery based on the battery current detected by the current detecting means, the battery voltage detected by the voltage detecting means, and the internal resistance estimated by the internal resistance estimating means Open-circuit voltage calculating means for calculating the open-circuit voltage of the internal resistance, and the internal resistance estimated by the internal resistance estimating means Voltage calculating means for calculating a battery voltage required at the time of motor maximum output based on the open voltage calculated by the open voltage calculating means; and motor maximum output based on the battery voltage calculated by the voltage calculating means. Remaining time estimating means for estimating the remaining time until the battery voltage drops to the predetermined voltage when the output of the engine is continued, and driving the engine based on the remaining time estimated by the remaining time estimating means. A power generation control device for a hybrid electric vehicle, which starts power generation.