JP3097509B2 - Vehicle battery charge control device and charge control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for charging a vehicle battery, 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 motor is connected to an output shaft of an engine, and electric power is supplied from a battery (including a capacitor) to function as a motor to provide torque assist at the time of engine start or acceleration and a generator at the time of braking. There has been proposed a system that functions as a power recovery device. According to such a system, it is possible to improve fuel efficiency by performing torque assist, and it is possible to convert mechanical energy at the time of braking into electric energy to increase energy efficiency. It is important to manage the charge amount of a battery that supplies power or recovers power from an induction machine.

[0003] For example, a battery charge management device disclosed in Japanese Patent Laid-Open No. 5-316658 detects a terminal current of a vehicle-mounted battery and determines a discharge mode and a charge mode of the battery according to the sum of the current amounts within a predetermined time. 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. Therefore, from the viewpoint of effectively utilizing the energy during regeneration, it is as high as possible. It is necessary to regenerate under conditions where power generation efficiency can be obtained.

The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention 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]

According to the present invention, 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. A vehicle battery charging control device for charging the battery, comprising: a voltage detecting means for detecting a voltage between terminals of the battery; and a motor / charger only when the detected terminal voltage becomes smaller than a predetermined value. Control means for causing the generator to function as a generator, generating power at a torque close to the torque at which the maximum power generation efficiency can be obtained at that speed, and charging the battery; and increasing the engine output while the motor / generator functions as the generator. Engine output control means for suppressing fluctuations in output torque by causing To.

The power generation is not controlled so that the battery is always maintained at the target terminal voltage. If the battery terminal voltage is equal to or higher than a predetermined value, the battery is not generated. , The battery can be charged efficiently. Since the power generation is controlled when the value becomes smaller than the predetermined value, the power generation operation of the motor / generator is performed intermittently in a short time.

[0008]

When the power generation is controlled at a high torque, the output torque of the engine output shaft rapidly decreases, causing a torque fluctuation. In this way, the torque fluctuation is reduced by increasing the engine output in synchronization with the power generation operation. Suppression and drivability can be maintained almost constant.

According to another aspect of the present invention, there is provided a charge control method for a vehicle battery for storing regenerative power from a motor / generator connected to an engine output shaft. Only when is smaller than a predetermined value, the motor / generator is caused to function as a generator to generate power at a torque close to the torque at which the maximum power generation efficiency is obtained at the rotation speed at that time, and to charge the battery. While the generator is functioning as the generator, the engine output is increased to suppress the fluctuation of the output torque.

[0011]

[0012]

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

FIG. 1 is a block diagram showing the configuration of this embodiment. A motor / generator M / G2 such as an induction machine is connected to an output shaft of the engine E / G1, and a transmission T / M3 is connected to transmit driving force to driving 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 and the like 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, at the time of engine start or acceleration, power is supplied from the battery 6 so that the M / G 2 functions as a motor, and at the time of braking, it functions as a generator, and regenerative power is supplied to the battery 6 and stored. The electric energy stored in the battery 6 is used not only for supplying power for the M / G 2 but also for powering auxiliary equipment such as an air conditioner via a DC-DC converter or the like. Further, a capacitor can be used instead of the battery 6.

A characteristic 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. (For example, 200 V) or less, charging is not performed when 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 rotation speed and the larger the torque, the higher the power generation efficiency. Therefore, in order to increase the power generation efficiency, power generation should be performed at a high rotation speed or a high torque.

Therefore, in the present embodiment, the voltage between the terminals of the battery 6 decreases (for example, 190 V with respect to the target 200 V).
V), the battery 6 is not generated at a low torque, but is generated at a high torque when the inter-terminal voltage is reduced to a lower voltage (for example, 170 V), thereby charging the battery 6 at a stretch with high power generation efficiency. . Thereby, the regenerative energy can be effectively recovered, and the energy efficiency can be improved.

FIG. 3 shows a processing flowchart of the control circuit 5. First, the control circuit 5 detects the inter-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 when fully charged.
, For example, VB1 = 200V, Δ
V = 30 V (the predetermined value is therefore 170
V). When the voltage between terminals of the battery 6 is equal to or higher than the predetermined value, the M / G 2 does not function as a generator, and the battery 6 is not charged. The battery 6
Is approximately 170 V, power can be supplied to the M / G 2 even when torque assist is required during vehicle acceleration. Then, when the inter-terminal voltage becomes lower than the predetermined value, a power generation start signal is transmitted to the engine ECU 4 (S102), and the power generation is started by causing the M / G 2 to function as a generator. The transmission to the engine ECU 4 at the start of the power generation is because the power generation in the present embodiment is performed with a higher output torque than in the related art, so that the output torque is sharply reduced, and if no measures are taken, the drivability deteriorates. This is because there is a danger that they will be lost. In response to this signal, the engine ECU 4 performs a process of increasing the engine output in order to suppress the torque fluctuation, 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 as high as about 20 Nm, for example, when the conventional torque when the voltage between the terminals of the battery is 190 V is about 5 Nm. 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 closest to the torque at which the maximum power generation efficiency of the induction machine is obtained at the number of revolutions during power generation. . When the power reaches the target generated power, the control circuit 5 again detects the voltage between the terminals of the battery 6 and determines whether or not the voltage reaches the target voltage VB1 (S105). When the battery 6 has been charged to the target inter-terminal voltage, a power generation termination signal is transmitted to the engine ECU 4 (S106), and the power generation Pgen is gradually reduced to terminate power generation (S106, S108). As a result, the battery 6 can be charged with high efficiency, regenerative energy can be effectively stored, 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, the processing for increasing the engine output is performed to suppress the torque fluctuation during the power generation period. Specifically, first, it is determined whether or not the power generation start signal from the control circuit 5 has been received (S201). When the power generation signal has been received, that is, when the M / G2 has started 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, a high torque in the opposite direction is applied to the engine output shaft, causing torque fluctuations.However, by increasing the engine output and compensating for the decrease in torque, the sharp torque increases. Fluctuations can be suppressed. Note that the amount of increase in engine output,
That is, the target value Pe / g1 is desirably closer to the torque at the time of power generation by Pgen1, but the upper limit will be determined in consideration of fuel efficiency. When the power generation end signal is received from the control circuit 5 (S204), the engine output Pe / g is also reduced accordingly, and returns to the normal output value, that is, the output value Pe / g2 when power is not generated (S205). , S20
6).

As described above, in this embodiment, the battery is charged intermittently only when high power generation efficiency is obtained.
Further, 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 extremely efficiently and drivability can be prevented from lowering.

[0020]

As described above, according to the vehicle battery charging control device and charging control method of the present invention, energy can be regenerated with high efficiency and the battery can be charged. Further, fluctuation of the engine output torque during regeneration can be prevented, and drivability can be maintained substantially constant.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of efficiency 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.

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60L 11/02-11/14 B60K 6/02 B60L 7/00-7/28 H02J 7/00

Claims (2)

(57) [Claims] 1. A vehicle battery charging control device, 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 detection means for detecting a voltage between terminals of the battery, and a motor / generator functioning as a generator only when the detected voltage between terminals becomes smaller than a predetermined value, and a maximum power generation efficiency at a rotation speed at that time Control means for generating electricity with a torque close to the torque obtained to charge the battery, and engine output control means for increasing the engine output and suppressing fluctuations in the output torque while the motor / generator functions as a generator. A charge control device for a vehicle battery, comprising: 2. A method for controlling charging of a vehicle battery for storing regenerative power from a motor / generator connected to an engine output shaft, the method comprising: controlling the battery only when a terminal voltage of the battery becomes lower than a predetermined value. While the motor / generator is functioning as a generator and generating power at a torque close to the torque at which the maximum power generation efficiency is obtained at the rotation speed at that time to charge the battery, the engine output is output while the motor / generator is functioning as the generator. A vehicle battery charging control method characterized by increasing fluctuations in output torque and suppressing fluctuations in output torque.