JPH0974612A - Vehicle battery charge control device and charge control method - Google Patents

Abstract

(57) Abstract: In a system in which a motor / generator is connected to an engine output shaft, highly efficient power generation is performed during braking, and a battery is charged. A motor / generator M / G2 is connected when an engine E / G1 is output. The control circuit 5 includes an inverter, causes the M / G 2 to function as a motor or a generator, and charges and discharges the battery 6. Control circuit 5
Does not generate power until the voltage between the terminals of the battery 6 becomes smaller than a predetermined value, and when it becomes smaller than a predetermined value, generates and charges with high torque. Further, during power generation, the engine computer 4 increases the output of the engine and suppresses torque fluctuations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle battery charging control apparatus and charging control method, and more particularly to an apparatus and method for charging a battery with regenerative power from a motor / generator connected to an engine output shaft.

[0002]

2. Description of the Related Art Conventionally, an induction machine is connected to an engine output shaft, and electric power is supplied from a battery (including a capacitor) to function as a motor to perform torque assist during engine start and acceleration, and also during generator braking. A system for recovering electric power by functioning as is has been proposed. According to such a system, there is an advantage that the fuel efficiency can be improved by performing the torque assist, and the mechanical energy at the time of braking can be converted into the electric energy to improve the energy efficiency. It is important to manage the charge amount of the battery that supplies power or recovers power from the induction machine.

For example, in a battery charge amount management device disclosed in Japanese Patent Laid-Open No. 5-316658, a terminal current of a vehicle-mounted battery is detected, and a discharge mode / charge mode of the battery is determined according to a sum of current amounts within a predetermined time. However, a configuration for controlling the inverter is disclosed.

[0004]

However, when the induction machine is made to function as a generator, its power generation efficiency is determined by the rotation speed and torque of the induction machine, and is therefore as high as possible from the viewpoint of effectively utilizing the energy during regeneration. It is necessary to regenerate it under the condition that the power generation efficiency is obtained.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a vehicle battery charging control device and a charging control method capable of charging a battery with high power generation efficiency. is there.

[0006]

In order to achieve the above object, a first aspect of the invention is to connect a battery to a motor / generator connected to an engine output shaft, and to make the motor / generator function as a generator to generate energy. A charging control device for a vehicle battery that regenerates the battery and charges the battery, wherein voltage detecting means for detecting a terminal voltage of the battery, and only when the detected terminal voltage becomes smaller than a predetermined value, The motor / generator functions as a generator to generate power at a predetermined torque or more to charge the battery.

Power generation is not controlled so that the battery is always maintained at the target terminal voltage, but when the terminal voltage of the battery is above a predetermined value, power is not generated and high torque is generated when the voltage becomes lower than the predetermined value. By generating power with, the battery can be efficiently charged. Since the power generation is controlled when it becomes smaller than the predetermined value, the power generation operation of the motor / generator is performed in a short time and intermittently.

In order to achieve the above object, a second aspect of the present invention is the same as the first aspect, wherein the motor / generator functions as a generator, and at the same time, the engine output is increased to suppress fluctuations in output torque. The engine output control means is provided.

When power generation control is performed with a high torque, the output torque of the engine output shaft sharply decreases and torque fluctuations occur. However, by increasing the engine output in synchronization with the power generation operation in this way, torque fluctuations are reduced. It can be suppressed and drivability can be maintained almost constant.

In order to achieve the above object, a third aspect of the present invention is a vehicle battery charging control method for accumulating regenerative electric power from a motor / generator connected to an engine output shaft, the terminal of the battery. The battery is charged by causing the motor / generator to function as a generator with a torque equal to or more than a predetermined torque only when the inter-voltage becomes smaller than a predetermined value.

In order to achieve the above object, a fourth aspect of the invention is the third aspect of the invention, in which the engine output is increased by increasing the engine output while the motor / generator is functioning as a generator at a predetermined torque or more. It is characterized in that fluctuations in torque are suppressed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of the configuration of this embodiment. A motor / generator M / G2 such as an induction machine is connected to the output shaft of the engine E / G1, and a transmission T / M3 is further connected to transmit the driving force to the drive wheels. The state of the engine E / G1 is monitored by the engine computer 4, and the intake air temperature, the engine speed, the engine output value, etc. are monitored by the engine computer (engine EC
U) 4 is input. The vehicle speed and the opening signal of the accelerator pedal 9 are also input to the engine computer 4 to determine the running state of the vehicle. The control circuit 5 includes an inverter, and causes the M / G 2 to function as a motor or a generator based on a command from the engine computer 4. Specifically, when the engine is started or accelerated, the M / G 2 is supplied with electric power from the battery 6 so as to function as a motor, and during braking, it is operated as a generator and regenerated electric power is supplied to and stored in the battery 6. The electric energy stored in the battery 6 is used not only to supply electric power for M / G2 but also to electric power for auxiliary equipment such as an air conditioner via a DC-DC converter or the like. A capacitor may be used instead of the battery 6.

The characteristic feature of the present embodiment is that the control circuit 5 causes the M / G 2 to function as a generator under conditions of high power generation efficiency, even if the terminal voltage of the battery is the target terminal voltage. Even if the voltage is (for example, 200 V) or less, charging is not performed when the power generation efficiency is low.

FIG. 2 shows the relationship among the rotational speed N, the torque T, and the power generation efficiency when the induction machine functions as a generator. Generally, the higher the rotational speed and the larger the torque, the higher the power generation efficiency. Therefore, in order to increase power generation efficiency, it is sufficient to generate power at a high rotation speed or high torque.

Therefore, in the present embodiment, the terminal voltage of the battery 6 decreases (for example, 190 V with respect to the target 200 V).
V) does not generate power with low torque, but generates power with high torque when the inter-terminal voltage drops to a lower voltage (for example, 170 V), so that the battery 6 is charged all at once with high power generation efficiency. . As a result, regenerated energy can be effectively recovered and energy efficiency can be improved.

FIG. 3 shows a processing flowchart of the control circuit 5. First, the control circuit 5 detects the terminal voltage VB of the battery 6 and compares it with a predetermined value (S10).
1). The predetermined value is ΔV from the terminal voltage VB1 at full charge
Is a voltage decreased by only, for example, VB1 = 200V, Δ
V = 30V (therefore, the predetermined value is 170
V). When the voltage between the terminals of the battery 6 is equal to or higher than this predetermined value, the M / G 2 does not function as a generator and the battery 6 is not charged. The battery 6
If the voltage between the terminals is about 170 V, electric power can be supplied to M / G2 even if torque assist is required during vehicle acceleration. Then, when the voltage between the terminals decreases and becomes smaller than the predetermined value, a power generation start signal is transmitted to the engine ECU 4 (S102), and the M / G 2 functions as a generator to start power generation. The power transmission to the engine ECU 4 at the start of power generation is that the power generation in the present embodiment is performed with a higher output torque compared to the conventional one, so that the output torque is sharply reduced, and drivability deteriorates unless any measures are taken. This is because there is a risk that it will end up. The engine ECU 4 that has received this signal performs a process of increasing the engine output in order to suppress torque fluctuations, the details of which will be described later. Power generation is performed by instructing a high torque to gradually increase the generated power amount Pgen to the target generated power Pgen1 (S103, S104). This torque is a high torque of about 20 N when the conventional torque is about 5 N when the terminal voltage of the battery is 190 V, for example. Of course, the value of this torque changes according to the characteristics of the induction machine, and it is generally desirable to set a high torque that is the closest to the torque at which the maximum power generation efficiency of the induction machine is obtained at the number of rotations during power generation. . When the target generated power is reached, the control circuit 5 again detects the terminal voltage of the battery 6 and determines whether or not the target voltage VB1 has been reached (S105). When the battery 6 is charged to the target terminal voltage, the power generation end signal is transmitted to the engine ECU 4 (S106), the generated power Pgen is gradually reduced, and power generation is ended (S106, S108). As a result, the battery 6 can be charged with high efficiency, regenerative energy can be effectively accumulated, and torque assist during subsequent acceleration can be smoothly performed.

On the other hand, FIG. 4 shows a processing flowchart of the engine ECU 4. The engine ECU 4
As described above, in order to suppress the torque fluctuation during the power generation period, the process of increasing the engine output is performed. Specifically, first, it is determined whether or not the power generation start signal from the control circuit 5 is received (S201), and when the power generation signal is received, that is, when the M / G2 starts power generation, the engine EC
U4 gradually increases the engine output Pe / g to the target value Pe / g1 (S202, S203). When power is generated with high efficiency, torque fluctuations occur because high torque in the opposite direction is applied to the engine output shaft, but by increasing the engine output and compensating for the decrease in torque in this way, the torque is steep. Fluctuations can be suppressed. In addition, the increase amount of engine output,
That is, the target value Pe / g1 is preferably as close as possible to the torque at the time of power generation at Pgen1, but the upper limit will be determined in consideration of fuel consumption. Then, when the power generation end signal is received from the control circuit 5 (S204), the engine output Pe / g is also reduced accordingly, and is returned to the normal output value, that is, the output value Pe / g2 when power generation is not performed (S205). , S20
6).

As described above, in this embodiment, the battery is intermittently charged only when high power generation efficiency is obtained,
Moreover, during power generation, the engine ECU increases the engine output by a predetermined amount to compensate for the decrease in the torque of the engine output shaft, so that energy can be recovered very efficiently and drivability can be prevented from decreasing.

[0020]

As described above, according to the vehicle battery charging control apparatus and charging control method of the present invention, energy can be regenerated and the battery can be charged with high efficiency. Further, it is possible to prevent the fluctuation of the engine output torque during regeneration and maintain the drivability substantially constant.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is an efficiency explanatory diagram of the motor / generator according to the embodiment of the present invention during power generation.

FIG. 3 is a processing flowchart of a control circuit according to the embodiment of the present invention.

FIG. 4 is a processing flowchart of an engine computer (engine ECU) according to the embodiment of the present invention.

[Explanation of symbols]

1 engine E / G, 2 motor / generator M /
G, 3 transmission T / M, 4 engine computer (engine ECU), 5 control circuit, 6 battery.

Claims (4)

[Claims] 1. A charging control device for a vehicle battery, wherein a battery is connected to a motor / generator connected to an engine output shaft, and the motor / generator functions as a generator to regenerate energy and charge the battery. Voltage detecting means for detecting a voltage between terminals of the battery, and only when the detected voltage between the terminals becomes smaller than a predetermined value, the motor / generator is caused to function as a generator to generate power at a predetermined torque or more to generate the battery. A charging control device for a vehicle battery, comprising: 2. The vehicle battery charge control device according to claim 1, further comprising engine output control means for increasing the engine output and suppressing fluctuations in output torque, while the motor / generator functions as a generator. A vehicle battery charge control device characterized by the above. 3. A charging control method for a vehicle battery for accumulating regenerative electric power from a motor / generator connected to an engine output shaft, the method comprising the steps of: only when a voltage between terminals of the battery becomes smaller than a predetermined value. A method of charging control of a vehicle battery, comprising causing a motor / generator to function as a generator at a predetermined torque or more to charge the battery. 4. The vehicle battery charging control method according to claim 3, wherein engine output is increased to suppress fluctuations in output torque while the motor / generator is functioning as a generator at a predetermined torque or more. A method for controlling charging of a vehicle battery, comprising: