JPH04281338A - Battery charger for vehicle - Google Patents

Abstract

PURPOSE:To reduce fuel consumption and to increase the engine output by reducing a generator load to the engine. CONSTITUTION:A generator i.e., an alternator 2, is coupled with an engine 1 and the output voltage of the alternator 2 is controlled through a field current control circuit 8. When an engine brake decision unit 15 decides that engine brake is applied, the field current control circuit 8 increases the voltage generated by the alternator 2 forcibly regardless of the charge voltage of a battery 6 thus charging the battery 6.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a vehicle charging device.
Specifically, the invention relates to control of field current of an alternator or the like connected to the engine for driving.

0002

2. Description of the Related Art Conventionally, a vehicle charging device installed in an automobile or the like uses the output of an engine to rotate a rotor coil of an alternator, and charges a battery with the generated voltage. At this time, the charging voltage of the battery is compared with a preset reference voltage, and the field current of the alternator is controlled based on the deviation. That is, the smaller the battery charging voltage is than the reference voltage, the larger the field current is made to obtain a larger AC power supply voltage.

0003

[Problems to be Solved by the Invention] However, since the vehicle charging device described above utilizes the output of the engine, the engine is always under the load of the alternator. In particular, when increasing the field current and obtaining a large AC power supply voltage, the load on the alternator on the engine becomes large. Therefore, fuel consumption increases accordingly and engine output decreases.

The present invention has been made to solve the above problems, and its purpose is to provide a vehicle that can reduce the load on the engine caused by the generator, reduce fuel consumption, and increase engine output. The aim is to provide generators for

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention drives and connects an engine and a generator, charges a battery with power generated from the generator, and maintains a charging voltage of the battery at a predetermined level. In the vehicle charging device that controls the field current of the generator so that the charging voltage becomes a charging voltage of The gist of the present invention is to provide a vehicle charging device which is provided with field current control means for increasing the field current of the generator to increase the generated power when the generator is running.

[0006]

Therefore, according to the present invention, when an engine brake is applied to the engine, the field current of the alternator becomes large, and a large generated voltage can be obtained regardless of the charging voltage at that time. That is, in this state, a large generated voltage is obtained using the energy wasted due to engine braking, and the battery is charged. This charging increases the charging voltage of the battery. When the engine brake is released, the charging voltage of the battery has increased, so the field current can be controlled to be smaller by the increased voltage. As a result, the load on the engine becomes smaller as the field current becomes smaller.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an automobile equipped with a vehicle charging device will be described below with reference to FIGS. 1 to 3. FIG. 1 shows the drive system and electrical configuration of a vehicle charging device, and the output shaft of an engine 1 is connected to an alternator 2 via a ribbed belt (not shown). Same alternator 2
As shown in FIG. 2, there are a rotor coil 3 that rotates as the engine 1 is driven, a stator coil 4 that generates an alternating current voltage as the rotor coil 3 rotates, and a stator coil 4 that rectifies the alternating current voltage into a direct current voltage. The rectifier circuit 5 includes a rectifier circuit 5 made of diodes.

The DC voltage output from the rectifier circuit 5 is charged from the output terminal N1 to a battery 6 made of a lead-acid battery, and power from the battery 6 is supplied to each load 7. Further, as shown in FIG. 1, a field current control circuit 8 as a field current control means is connected to the alternator 2. As shown in FIG. 2, the field current control circuit 8 includes a MOS transistor 9 whose source terminal is connected to one end of the rotor coil 3, and a differential amplifier 1 to be described later.
0 and a reference voltage circuit 11.

The reference voltage circuit 11 includes voltage dividing resistors 12,1
M connected in parallel with a voltage dividing circuit consisting of 3 and a voltage dividing resistor 12
OS transistor 14, and its connection point N2
is connected to the non-inverting input terminal of the differential amplifier 10. Therefore, the divided potential of resistors 12 and 13 (output voltage value V
K (in this embodiment, VK is set to 13 volts)) will be applied to the non-inverting input terminal of the differential amplifier 10. On the other hand, a detection resistor 17 connected in parallel with the battery 6 is connected to the inverting input terminal of the differential amplifier 10. Therefore, the charging voltage value V of the battery 6 at that time is determined via the detection resistor 17 connected in parallel with the battery 6.
s will be applied to the inverting input terminal of the differential amplifier 10.

The differential amplifier 10 compares the charging voltage value VS from the battery 6 and the output voltage value VK from the reference voltage circuit 11, and applies a voltage VO proportional to the difference to the gate of the MOS transistor 9. . and,
The MOS transistor 9 is an electromagnetic control transistor, and is inputted to its gate terminal from the differential amplifier 10, so that the larger the voltage VO, the larger the current flows.

Therefore, the lower the charging voltage value VS is, the larger the difference from the output voltage value VK becomes, and the higher the voltage VO applied to the gate of the transistor 9 becomes, the larger the field current flowing through the rotor coil 3 becomes. Conversely, the higher the charging voltage value VS , the smaller the difference from the output voltage value VK, and the lower the voltage VO applied to the gate of the transistor 9, the smaller the field current flowing through the rotor coil 3.

The MOS transistor 14 of the reference voltage circuit 11 is a switching transistor, and an engine brake determination device 15 is connected to its gate terminal. An accelerator pedal 16 is connected to the engine brake determination device 15, and in this embodiment, when the accelerator pedal 16 is turned from on (depressed state) to off (separated state), engine brake is applied. The engine brake determination device 15 applies a voltage to the transistor 14 to turn it on. Further, when the accelerator pedal 16 is turned on from off, the engine brake determining device 15 turns off the transistor 14.

Therefore, when the accelerator pedal 16 is turned off from on and the transistor 14 is turned on by the engine brake determination device 15, the divided voltage potential output from the reference voltage circuit 11 to the non-inverting input terminal of the differential amplifier 10 will rise. That is, since the potential difference between the output voltage value VK compared in the differential amplifier 10 and the charging voltage value VS of the battery 6 becomes larger than when the transistor 14 is off, the voltage VO applied to the gate terminal of the transistor 9 increases. increases with the increased potential difference, and the field current flowing through the rotor coil 3 increases compared to when the transistor 14 is off. As the field current flowing through the rotor coil 3 increases, the voltage value generated from the stator coil 4 increases, and the battery 6 has at least 13
Volts or higher voltage will be supplied.

Next, the operation of the vehicle charging device constructed as described above will be explained with reference to FIG. First, the operation of the vehicle charging device during normal driving will be explained. For example, when a car runs while using the load 7, such as a car stereo or a rear defogger, the charging voltage value VS of the battery 6 decreases, and the remaining capacity also decreases. At this time, the output voltage value VK output from the reference voltage circuit 11 and the battery 6 are determined by the differential amplifier 10 of the field current control circuit 8.
The charging voltage value VS is compared with the charging voltage value VS from . When the charging voltage value VS is lower than the output voltage value VK, that is, when the charging voltage value VS of the battery 6 is less than 13 volts, the differential amplifier 10 applies a voltage proportional to the difference to the gate terminal of the transistor 9. Apply VO. Therefore, the transistor 9 causes a field current corresponding to the potential difference between the charging voltage value VS and the output voltage value VK to flow through the rotor coil 3. When a field current is passed through the rotor coil 3, an AC voltage corresponding to the difference is generated in the stator coil 4,
The DC voltage rectified by the rectifier circuit 5 is supplied to the battery 6.
Charging is controlled so that the charging voltage is 13 volts.

[0015] Then, the charging voltage value VS of the battery 6
When the voltage reaches the output voltage value VK, the differential amplifier 10 turns off the transistor 9 to prevent the field current from flowing through the rotor coil 3. Therefore, during normal driving, the above operation is repeated, and the charging voltage value VS of the battery 6
is always controlled at 13 volts. Next, the operation of the vehicle charging device when the engine brake is applied to decelerate during normal driving or when driving around a curve or stopping will be explained.

It is assumed that the charging voltage value VS of the battery 6 is 13 volts or less at this time. When the accelerator pedal 16 is turned from on to off in order to apply engine braking during normal driving, an on signal to an off signal from the accelerator pedal 16 is input to the engine brake determination device 15. When the off signal is input, the engine brake determination device 15 determines that the engine brake is applied, and applies a voltage to the gate terminal of the transistor 14 connected in parallel to the resistor 12 to turn on the transistor 14.

By turning on the transistor 14, the divided potential outputted from the reference voltage circuit 11 to the non-inverting input terminal of the differential amplifier 10 becomes larger than that during normal running. That is, the output voltage value V compared in the differential amplifier 10
The potential difference based on K and charging voltage value VS becomes much larger than during normal driving. Therefore, a voltage VO corresponding to the potential difference between the output voltage value VK and the charging voltage value VS is applied to the gate of the transistor 9, and a field current flows through the rotor coil 3. As a field current flows through the rotor coil 3, the stator coil 4 generates an alternating current voltage of 13 volts or more. The voltage is then rectified into a DC voltage by the rectifier circuit 5, and the battery 6 is charged. Therefore, the battery 6 at this time is charged with a voltage of at least 13 volts or more.

Then, when the accelerator pedal 16 is depressed again and an on signal is output to the engine brake determining device 15, the engine brake determining device 15 turns off the transistor 14 that was in the on state. Since the transistor 14 is turned off, the same output voltage value VK of 13 volts, which is the divided potential of the resistor 12 and the resistor 13 as during normal running, is again applied to the non-inverting input terminal of the differential amplifier 10. And this output voltage value VK
and the charging voltage value VS of the battery 6 are compared.

At this time, since the charging voltage value VS of the battery 6 was charged at a voltage of at least 13 volts or more during the previous engine braking state, the charging voltage value VS is the same as the output voltage value VK. Or it becomes a value very close to the output voltage value VK. As a result, the voltage VO of the differential amplifier 10 becomes 0 or becomes smaller by that amount. Therefore, the field current in the rotor coil 3 becomes small and no electromotive force is generated in the stator coil 4, so that a small alternating current voltage is generated from the stator coil 4. Therefore, the load on the alternator 2 that has been applied to the engine 1 is reduced by the amount that the field current is reduced, and the engine 1 rotates smoothly.

As described in detail above, since the conventional vehicle charging device uses engine output to drive the alternator 2, the load of the alternator is constantly placed on the engine 1, and fuel consumption is reduced accordingly. increased, and the engine output decreased. On the other hand, in the vehicle charging device of this embodiment, although the engine output is used to drive the alternator 2 as in the conventional case, the engine braking period used when driving around a curve or applying braking to the vehicle is To do this, a large field current was forced to flow through the rotor coil 3 to increase the voltage used to charge the battery 6.

At this time, since the charging voltage value VS is maintained higher than the output voltage value VK by utilizing the wasted output of the engine 1, when the engine braking period ends and normal driving is resumed, Since it is no longer necessary to apply a field current to the rotor coil 3 by that much, it is possible to reduce the load on the alternator 2 that has been applied to the engine 1 during that time and run the vehicle. Therefore, fuel consumption is reduced and, at the same time, a decrease in engine output after normal driving is resumed is prevented. Furthermore, since the field current is large when the engine brake is applied, the load on the engine 1 becomes large, and the braking force of the engine brake becomes better.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be configured as follows, for example, without departing from the spirit of the invention. (1) In the embodiments described above, the vehicle charging device was implemented as an automobile, but it may be constructed as a cargo handling vehicle or the like instead of the automobile. (2) In the embodiment described above, the engine brake determination device 15 determined the state of the engine brake based on the on/off signal of the accelerator pedal 16, but instead of the on/off signal of the accelerator pedal 16, the state of the engine brake is The state of engine braking may be determined based on the state or on/off signal of the brake pedal.

(3) In the above embodiment, the alternator 2 of an AC generator was used as the generator to configure the vehicle charging device, but the vehicle charging device could be constructed by replacing the alternator 2 with a dynamo of a DC generator. may be configured.

[0024]

As described in detail above, the present invention has the excellent effect of reducing the load on the engine caused by the generator, reducing fuel consumption, and increasing engine output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the drive system and electrical configuration of a vehicle charging device according to an embodiment of the present invention.

FIG. 2 is an electrical circuit diagram showing the electrical configuration of a vehicle charging device according to an embodiment of the present invention.

FIG. 3 is a graph showing the relationship between charging voltage values during normal running and during engine braking in an embodiment embodying the present invention.

[Explanation of symbols]

1 Engine 2 Alternator 6 as a generator Battery 8 Field current control circuit 15 as field current control means Engine brake determination device as engine brake detection means

Claims (1)

[Claims] Claim 1: An engine and a generator are drivingly connected, and a battery is charged with power generated from the generator, and the field current of the generator is controlled so that the charging voltage of the battery becomes a predetermined charging voltage. In a vehicle charging device that controls an engine brake state, the engine brake detection means detects an engine brake state of the engine, and when the engine brake detection means detects an engine brake state,
and field current control means for increasing the field current of the generator to increase the generated power.