JP2946712B2 - Power supply system for vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle power supply system.

[Prior Art] Conventionally, a vehicle power supply system that controls the amount of power generated by an alternator so that a battery voltage becomes a set value (for example, 14.5 V) is known.

[Problem to be Solved by the Invention] However, the power supply system for a vehicle has the following disadvantages.

(A) The battery discharge state cannot be accurately grasped, and the battery is likely to be overcharged or overdischarged.

(A) During acceleration, the alternator deprives the engine of energy for power generation, which deteriorates the acceleration.
For this reason, the driver tends to depress the accelerator greatly, forcibly accelerating, and the fuel efficiency deteriorates.

(C) At the time of deceleration, kinetic energy is wasted
Not helping battery charge.

(D) Efficient power generation is not performed during idling.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle power supply system that is excellent in battery charging performance and improves fuel efficiency.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configurations.

(1) A battery for supplying electric power to an electric load of a vehicle, an alternator driven by an engine to generate electric power and charge the battery, and a field current of the alternator is switched by a semiconductor element based on the detected battery voltage. A power supply system for a vehicle, comprising: a regulator that controls a power generation amount of the alternator so that a battery voltage becomes a target voltage, wherein the target voltage is a first set voltage slightly higher than an open-circuit voltage of the battery;
It has two types of second setting voltage higher than the first setting voltage,
The duty difference of the semiconductor element is measured by appropriately switching the target voltage, and when the duty difference is less than a predetermined value, the target voltage is set to the first set voltage, and when the duty difference is equal to or more than a predetermined value or detected. If the battery voltage falls below the overdischarge warning voltage set lower than the open voltage for more than a predetermined time, the target voltage is set to the second set voltage.

(2) In addition to the configuration of (1), the target voltage is set to be equal to or lower than the first set voltage while the vehicle is accelerating.

(3) In addition to the configuration of (1), while the vehicle is decelerating, the target voltage is set to be equal to or higher than the second set voltage.

(4) In addition to the configuration of (1), while the vehicle is in an idling state, the engine speed is controlled so that the duty of the semiconductor element falls within a set range.

[Functions and Effects of the Invention] (Claim 1) When the battery is fully charged or close to the full charge, the charging current to the battery is small, so that even if the target voltage is switched, the duty difference is small and becomes smaller than the predetermined value. In this case, the target voltage is set to the first set voltage in order to suppress the amount of power generation.

When the battery is over-discharged or close to it, the charging current to the battery at the second set voltage is large. Therefore, when the target voltage is switched, the duty difference becomes large and becomes a predetermined value or more. When the load current is larger than the output current of the alternator, the overdischarge warning voltage tends to be continuously reduced. In this case, the target voltage is set to the second set voltage in order to quickly recover the state of charge of the battery.

By the above operation, the discharge state of the battery can be accurately grasped, and overcharge and overdischarge of the battery can be prevented. Further, when the duty difference is less than the predetermined value, the amount of power generated by the alternator is suppressed to reduce the engine load, thereby improving fuel efficiency.

(Claim 2) During acceleration, power generation of the alternator is suppressed, and the load on the engine is reduced, so that acceleration is improved.

(About Claim 3) Since kinetic energy released at the time of deceleration is converted into electric energy for charging the battery and is effectively used, fuel efficiency is improved.

(About claim 4) The power generation efficiency of the alternator during idling is improved,
In addition, fuel efficiency is improved because the idle speed is kept at an appropriate level.

Embodiment Next, the present invention will be described based on an embodiment shown in FIGS. 1 and 2. FIG.

As shown in FIG. 1, a vehicle power supply system A includes a battery 1 for supplying power to a fluctuating electric load R of an automobile.
An alternator 2 driven by the engine E to generate electric power; a regulator 3 for controlling the amount of electric power generated by the alternator 2; a vehicle state detecting means 4;
And

In this embodiment, the battery 1 has an electromotive force of 12 V (open voltage 12.
8V) lead-acid battery.

The alternator 2 includes a three-phase AC generator having an armature coil, a field coil 21, a brush, and the like, and a rectifying diode, and is connected to a crankshaft of the engine by a belt.

The regulator 3 includes a transistor Tr for switching the field current If of the field coil 21 of the alternator 2, a duty detection unit for measuring the duty D of the transistor Tr, a battery voltage detection unit, an overdischarge monitoring unit, a vehicle state signal j to be described later, and the like. A target voltage switching unit that changes the target voltage according to the above, a power generation control unit that switches the transistor Tr so that the battery voltage Eb becomes the target voltage, and sets the idling speed within the set value when the duty D is not within the set value at the time of idling. And a microcomputer for controlling these.

The vehicle state detecting means 4 detects a vehicle state such as an engine speed, idling, acceleration, and deceleration, and sends the vehicle state signal j to the regulator 3. This detection is performed using the engine speed, the negative pressure in the in-tech manifold, the degree of depression of the accelerator or brake, the output signal of a vehicle speed sensor or an acceleration sensor, and the like.

The idle controller 5 adjusts the engine speed during idling based on the control signal k of the regulator 3.

Next, the algorithm of the microcomputer
A description will be given based on the drawings. The first set voltage was 13 V, the second set voltage was 14.5 V, the target voltage during deceleration was 15 V, the target voltage during acceleration was 12 V, and the overdischarge warning voltage was 12.5 V.

At the time of starting the engine, the target voltage is set to 14.5 V (step S1, hereinafter abbreviated as step).

In S2, it is determined whether or not the target voltage is 13V. If not, the process proceeds to S3, and if it is 13V, the process proceeds to S15.

In S3, the engine speed during idling is within the set value (for example,
500RPM), measure the duty D1 of the transistor Tr when the target voltage is 14.5V (S4), and set the target voltage to 13V.
And the duty D2 is measured (S5). If it exceeds the set value, the process proceeds to S8.

If (D1−D2) <α in S6, it is considered that the charging current to the battery 1 is small (that is, the battery 1 is sufficiently charged), the target voltage is reduced to 13 V (S7), and the process proceeds to S8. Note that α is, for example, 0.1. If (D1−D2) ≧ α in S6, it is considered that the charging current to the battery 1 is large (that is, the battery 1 is in the discharged state and needs to be charged), and the process proceeds to S8.
Proceed to.

In S8, if the vehicle state detecting means 4 detects deceleration, the target voltage is set to 15 V during that time (S9).

In S10, if the vehicle state detection means 4 sends out acceleration, the target voltage is set to 12 V during that time (S11). When the vehicle is not accelerating, the process proceeds to S12 without changing the target voltage.

If the vehicle state detecting means 4 detects the idling state in S12, the process proceeds to S13. If no idling is detected, the process returns to S2.

In step S13, the duty D of the transistor Tr is measured, and if the duty D is within a set value (for example, 0.8 to 0.95), S
Return to 2. Further, if the duty D is out of the above set value, the control signal k is sent to the idle controller 5 and corrected so that the duty D becomes 0.8 to 0.95 (S14).
Then, the process returns to step S2.

In S15, if the state where the battery voltage Eb is less than 12.5V continues for 20 seconds or more, the target voltage is changed to 14.5V (S16), and thereafter, the process proceeds to S8. Otherwise, the process proceeds directly to S8.

 Hereinafter, the operation and effect of the vehicle power supply system A will be described.

(A) If it is determined in S4 to S6 that the battery 1 is sufficiently charged, the target voltage is set to 13 V to prevent overcharging of the battery 1 and reduce the load on the engine. This can improve fuel efficiency.

(I) After the discharge state of the battery 1 is continued by S15 and S16, by setting the voltage (14.5V) having a high charge performance,
Battery running out can be prevented.

(C) Due to S10 and S11, the alternator 2 does not take energy for power generation from the engine during acceleration. That is, even if the driver does not step on the accelerator greatly, the vehicle accelerates smoothly, so that fuel efficiency is improved.

(E) By S8 and S9, the energy at the time of deceleration of the car is effectively used for charging the battery 1 (generation voltage is 13V, 14.5V
At both times). In addition, S10 and S11 reduce the load on the engine during acceleration. Therefore, fuel efficiency is improved.

(I) According to S13 and S14, when the electric load R is small or the battery 1 is sufficiently charged, the idle speed is reduced, so that the fuel efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a vehicle power supply system according to one embodiment of the present invention, and FIG. 2 is a flowchart for explaining the operation of the system. In the drawing, 1 ... battery, 2 ... alternator, 3 ... regulator, A ... vehicle power supply system, E ... engine, R ... electric load, Tr ... transistor (semiconductor element), If ... field current , Α …… Duty difference

Claims (4)

(57) [Claims] 1. A battery for supplying electric power to an electric load of a vehicle, an alternator driven by an engine to generate electric power and charge the battery, and a field current of the alternator based on a detected battery voltage by a semiconductor element. A power supply system for a vehicle, comprising: a regulator configured to perform switching and control a power generation amount of the alternator so that a battery voltage becomes a target voltage. A first set voltage slightly higher than an open voltage of a battery as the target voltage; A second set voltage higher than the first set voltage; and a target voltage is appropriately switched to measure a duty difference of the semiconductor element. If the duty difference is less than a predetermined value, the target voltage is set to the first set voltage. Set voltage, and when the duty difference is equal to or greater than a predetermined value or when the detected battery voltage is Vehicle power supply system for, characterized in that the target voltage and the second set voltage when the over-discharge warning voltage set from discharging voltage lower below exceeds a predetermined time. 2. The vehicle power supply system according to claim 1, wherein the target voltage is set to be equal to or lower than the first set voltage while the vehicle is accelerating. 3. The vehicle power supply system according to claim 1, wherein the target voltage is set to be equal to or higher than the second set voltage while the vehicle is decelerating. 4. The vehicle power supply system according to claim 1, wherein the engine speed is controlled such that the duty of the semiconductor element is within a set range while the vehicle is in an idling state.