JPH04140026A - Power supply system for vehicle - Google Patents

Abstract

PURPOSE:To improve charging performance and fuel consumption by an arrangement wherein a first set voltage slightly higher than the open voltage of a battery and a second set voltage slightly higher than the first set voltage are employed as the target voltages of the battery, differential duty of semiconductor elements is measured by switching the target voltages, and the first or the second set voltage is employed as a target voltage according to thus measured difference. CONSTITUTION:If the rotational speed of an engine is within a set value at the time of idling, duty D1 of a transistor Tr is measured at the time when a target voltage is 14.5V and a duty D2 is measured after the target voltage is switched to 13V. If (D1-D2)<alpha, it is decided that a battery 1 is fed with an insufficient current (i.e., insufficiently charged), and the target voltage is dropped to 13V alpha is 0.1 at that time. If (D1-D2)>=alpha, it is decided that the battery 1 is excessively charged (i.e., a discharged state requiring charging operation). When a vehicle state detecting means 4 detects deceleration, the target voltage is brought up to 15V. When acceleration is detected, the target voltage is brought down to 12V.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a vehicle power supply system.

[Prior art] Conventionally, the battery voltage has been set at a set value (for example, 14°5V).
A vehicle power supply system that controls the amount of power generated by an alternator is known.

[Problems to be Solved by the Invention] However, the above vehicle power supply system has the following drawbacks.

(a) It is not possible to accurately grasp the discharge state of the battery, which tends to lead to overcharging or overdischarging of the battery.

(a) During acceleration, the alternator steals energy for power generation from the engine, resulting in poor acceleration.

For this reason, the driver tends to press the accelerator hard to forcefully accelerate the vehicle, resulting in poor fuel efficiency.

(1) When decelerating, kinetic energy is wasted,
Not useful for battery charging.

(1) Efficient power generation is not occurring during idling.

An object of the present invention is to provide a vehicle power supply system that has excellent 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 configuration.

(1) A battery that supplies power to the electrical load of the vehicle, an alternator that is driven by the engine to generate electricity and charge the battery, and a semiconductor element that switches the field current of the alternator based on the detected battery voltage. and a regulator that controls the amount of power generated by the alternator so that the battery voltage becomes a target voltage, wherein the target voltage is a first set voltage slightly higher than the open circuit voltage of the battery; The target voltage is appropriately switched to measure the duty difference of the semiconductor element, and when the duty difference is less than a predetermined value, the target voltage is set to the first set voltage. set voltage, and if the duty difference is equal to or higher than a predetermined value, or if the detected battery voltage falls below an over-discharge warning voltage set lower than the open circuit voltage for more than a predetermined time, the target voltage is set to the second set voltage. do.

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

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

[Operations and Effects of the Invention] (Regarding Claim 1) When the battery is fully charged or close to it, the charging current to the battery is small, so even if the target voltage is changed, the duty is low.
The difference is small and less than a 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 over-discharge, the charging current to the battery at the second set voltage is large, so when the target voltage is switched, the duty difference is large and becomes more than a predetermined value. Further, when the load current is larger than the output current of the alternator, there is a tendency that the load current continues to fall below the overdischarge warning voltage.

In this case, the target voltage is set to the second set voltage in order to quickly restore the charging state of the battery.

Due to the above-mentioned action, the discharge state of the battery can be accurately grasped, and overcharging and overdischarging of the battery can be prevented. Further, when the duty difference is less than a predetermined value, the amount of power generated by the alternator is suppressed to reduce the engine load, thereby improving fuel efficiency.

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

(Regarding Claim 3) Since the kinetic energy released during deceleration is converted into electrical energy for charging the battery and used effectively, fuel efficiency is improved.

(Regarding Claim 4) The power generation efficiency of the alternator during idling is improved, and since the idling speed is maintained at an appropriate level, fuel efficiency is improved.

[Example] Next, the present invention will be explained based on an example shown in FIGS. 1 and 2.

As shown in FIG. 1, the vehicle power supply system A includes a battery 1 that supplies power to a fluctuating electrical load R of a vehicle;
Alternator 2 that is driven by engine E and generates electricity
, a regulator 3 that controls the amount of power generated by the alternator 2, a vehicle state detection means 4, and an idle controller 5.

In this embodiment, the battery l has an electromotive force of 12■ (open circuit voltage 1
2.8V) lead acid battery.

The alternator 2 includes an armature coil and a field coil 21. It consists of a three-phase alternating current generator with brushes, etc., and a rectifying diode, and is connected to the engine crankshaft with a belt.

The regulator 3 includes a transistor Tr that switches the field current If of the field coil 21 of the alternator 2, a duty detection section that measures the duty D of the transistor Tr, a battery voltage detection section, an overdischarge monitoring section, and a vehicle status signal described later. A target voltage switching unit that changes the target voltage by J, etc., a power generation control unit that switches the transistor Tr so that the battery voltage Eb becomes the target voltage, and a set value for the idling rotation speed when the duty-D is not within the set value during idling. The transmitter includes a transmitting section that transmits a control signal k for controlling the output voltage, and a microcomputer that controls these components.

The vehicle condition detection means 4 detects vehicle conditions such as engine speed, idling, acceleration, deceleration, etc., and outputs a vehicle condition signal j.
It is sent to regulator 3 as Note that this detection is performed using the engine speed, negative pressure in the inch manifold, the degree of depression of the accelerator or brake, the output signal of the vehicle speed sensor or 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 will be explained based on FIG. The first set voltage was 13V, the second set voltage was 14.5V, the target voltage during deceleration was 15V, the target voltage during acceleration was 12V, and the overdischarge warning voltage was 12.5V.

When starting the engine, set the target voltage to 14.5V (
Step S1 (hereinafter steps will be omitted).

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

If the engine speed at idle is within the set value (for example, 500 RPM) in S3, measure the duty -Dl of the transistor Tr when the target voltage is 14.5■ (S4)
, the target voltage is switched to 13V and the duty D2 is measured (S5). Note that if the set value is exceeded, the process proceeds to 88.

If (DI-D2)<α in S6, it is assumed that the charging current to the battery 1 is small (that is, it is sufficiently charged), and the target voltage is lowered to 13V.57) The process proceeds to 38. Note that α is, for example, 0.1. Also, in S6 <DI-
If D2>≧α, it is assumed that the charging current to the battery 1 was large (that is, it is in a discharged state and needs to be charged), and the process directly proceeds to S8.

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

In SIO, if the vehicle state detection means 4 sends acceleration, the target voltage is set to 12V (Sll) during that time, and if the vehicle is not accelerating, the process proceeds to 812 without changing the target voltage.

In S12, if the vehicle state detection means 4 detects an idling state, the process proceeds to 813. Further, if idling is not detected, the process returns to S2.

At 313, the duty D of the transistor Tr is measured,
If the duty-D is within the set value (for example, 08 to 0.95), the process returns to S2. Further, if the duty-D is out of the above set value, a control signal k is sent to the idle controller 5 to correct it so that the duty-D becomes 0.8 to 0.95 (514), and then step Return to S2.

In S15, if the battery voltage Eb remains below 12.57 for 20 seconds or more, the target voltage is set to 14.5V4. 516), and then proceeds to S8. Otherwise, the process directly proceeds to S8.

The effects of the vehicle power supply system A will be described below.

(A) If it is determined in steps 34 to S6 that the battery 1 is sufficiently charged, the target voltage is set to 13V to prevent overcharging of the battery 1 and to reduce the load on the engine. This can be expected to improve fuel efficiency.

(2) By S15.816, after the battery 1 continues to be discharged, the battery can be prevented from dying by setting the voltage to a voltage (14,5■) with high charging performance.

(c) Due to S10.11, the alternator 2 does not take energy for power generation from the engine during acceleration. In other words, the car accelerates smoothly without the driver having to press hard on the accelerator, improving fuel efficiency.

(E) With S8 and S9, the energy generated when the car decelerates is effectively used to charge one battery (the generated voltage is 13V).
, 14.5V). Also, S10
, Sll reduces the load on the engine during acceleration.

Therefore, fuel efficiency improves.

(O) 813, S14 determines whether the electrical load R is small or not.
When the battery l is sufficiently charged, the idle speed becomes low, which improves fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a vehicle power supply system according to an embodiment of the present invention, and FIG. 2 is a flowchart for explaining the operation of the system. In the diagram: 1...Battery 2...Alternator 3.
...Regulator A...Vehicle power system E.
...Engine R...Electrical load Tr...Transistor (semiconductor element) If...Field current α
...duty difference

Claims (1)

[Scope of Claims] 1) A battery that supplies power to an electrical load of a vehicle, an alternator that is driven by an engine to generate electricity and charge the battery, and a field current of the alternator based on the detected battery voltage. In a vehicle power supply system equipped with a regulator that switches using a semiconductor element and controls the amount of power generated by an alternator so that the battery voltage becomes a target voltage, the target voltage is a first set voltage that is slightly higher than the open circuit voltage of the battery. , and a second set voltage higher than the first set voltage, the target voltage is appropriately switched to measure the duty difference of the semiconductor element, and when the duty difference is less than a predetermined value, the target voltage is changed. Set the target voltage to the first set voltage, and set the target voltage to the second set if the duty difference is greater than or equal to a predetermined value or if the detected battery voltage falls below an overdischarge warning voltage set lower than the open circuit voltage for more than a predetermined time. A vehicle power supply system characterized by a voltage. 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 higher than the second set voltage while the vehicle is decelerating. 4) The vehicle power supply system according to claim 1, wherein the rotation speed of the engine is controlled so that the duty of the semiconductor element is within a set range while the vehicle is in an idling state.