JP2000270407A - Charging control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging control device capable of realizing a stable idling operation. SOLUTION: This charging control device is equipped with an alternator, which generates electric power from the driving force of an internal combustion engine 1 and outputs a direct current, a DC/DC converter 8 for converting a voltage of the direct current generated by the alternator, a battery 9 which is charged by the output of the DC/DC converter 8, and idling detection means 10, 14 detecting the idling state of the internal combustion engine 1. When the idling state is detected by the idling detection means 10, 14, the DC/DC converter 8 changes the output according to the input.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control device capable of realizing a stable idling operation.

[0002]

In a hybrid vehicle (a vehicle driven by an internal combustion engine and a vehicle drive motor) and the like, a power supply for the vehicle drive motor is provided in addition to a power supply for driving the internal combustion engine and various accessories. And a dual power supply system has been constructed. In recent years, various electric devices have been incorporated in vehicles, and the amount of required power for on-vehicle batteries tends to increase. For this reason, even if it is not a hybrid vehicle, the inventors have installed another battery with a higher voltage (about 40 V) in addition to the conventional battery (such as a 12 V power supply for a passenger car), and mounted the dual power system. Trying to build.

[0003] A hybrid vehicle includes a generator as a generator, and drives the vehicle with the electric power generated by the generator and also charges a battery. Even ordinary vehicles that are not hybrid vehicles are equipped with an alternator as a generator, and when the electric load of the vehicle exceeds the amount of power generated by the alternator, the battery discharges to compensate for the shortage, and the amount of power generated by the alternator exceeds the electric load of the vehicle Sometimes the battery is charged.

As described above, in a vehicle having a two-system power supply system, two power supply voltages are different, so that charging of one power supply can be directly performed by the output of the generator, while charging of the other power supply is performed by the generator. A DC-DC converter is arranged between the power supply and the other power supply, and performs voltage conversion before charging. As an example of such a DC-DC converter, the one described in Japanese Patent Application Laid-Open No. 5-260731 is known.

However, when charging via a DC-DC converter, the input voltage to the DC-DC converter and the generator current are different from those shown in FIG. The relationship is as shown in FIG. That is,
When the input voltage to the DC-DC converter decreases, the generator voltage is increased to keep the output voltage constant. For this reason, in an idling state in which most of the load of the internal combustion engine is the load of the generator, the rotation of the internal combustion engine fluctuates and the DC-D
When the input to the C converter fluctuates, the DC-DC converter acts to promote the fluctuation.

For example, when the rotation of an internal combustion engine is reduced, DC-DC
When the input voltage to the converter drops, the DC-DC converter tries to keep the output voltage constant, so that the generator current increases. Since the generator current and the load torque acting on the internal combustion engine by power generation are substantially proportional, the load torque acting on the internal combustion engine increases as the generator current increases. When the load torque increases, the rotation of the internal combustion engine further decreases, so that the idling state becomes unstable and in the worst case, the engine stalls. For this reason, when charging via a DC-DC converter in an idling state, an improvement that does not make the idling state unstable is desired.

Accordingly, an object of the present invention is to provide a charge control device capable of realizing a stable idling operation.

[0008]

According to a first aspect of the present invention, there is provided a charge control device that generates a DC current by generating a driving force of an internal combustion engine and outputs a DC current, and a DC-DC converter that converts a voltage of the DC current generated by the generator. A DC converter, a rechargeable battery charged by the output of the DC-DC converter, and idling detection means for detecting an idling state of the internal combustion engine,
When the idling state is detected by the idling detection means, the DC-DC converter changes its output according to the input.

According to the charge control device of the first invention, when the internal combustion engine is in an idling state, the output of the DC-DC converter is changed in accordance with the input, so that the output of the generator is changed by the rotation fluctuation of the internal combustion engine. Does not fluctuate the rotation of the internal combustion engine by the generator. As a result, a stable idling operation is realized.

Here, if the DC-DC converter detects the idling state by the idling detecting means, the output voltage is lowered when the input voltage is lowered, and the engine stall from the idling state is performed. Deterrence can be surely suppressed.

A charge control device according to a second aspect of the present invention generates a DC current by generating power by a driving force of an internal combustion engine, and converts a DC current voltage generated by the generator.
A DC-DC converter, a rechargeable battery charged by an output of the DC-DC converter, and a rotation speed detection unit for detecting a rotation speed of the internal combustion engine, wherein the DC-DC converter is detected by the rotation speed detection unit. The output is changed in accordance with the number of rotations performed.

According to the charging control device of the second invention, the DC-DC
Since the output of the converter is changed according to the rotation speed of the internal combustion engine, even if the output of the generator fluctuates due to the fluctuation of the rotation of the internal combustion engine, the fluctuation of the engine rotation is not promoted by the generator. As a result, a stable idling operation is realized.

Here, if the DC-DC converter is configured to reduce its output voltage when the rotation speed detected by the rotation speed detecting means falls below a predetermined rotation speed, the rotation speed of the internal combustion engine is reduced. The engine stall from the state where the number becomes equal to or less than the predetermined value can be reliably suppressed.

Furthermore, in the charge control devices of the first and second inventions, if a rechargeable battery directly charged by the output of the generator is further provided between the generator and the DC-DC converter, The system power supply system can be constructed, and the onboard electrical equipment can be operated efficiently. In addition, any of the two rechargeable batteries can be charged, and at this time, fluctuations in the rotation of the internal combustion engine are not promoted.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of a charge control device according to the first invention will be described. FIG. 1 shows a configuration of the charge control device of the present embodiment.

A crankshaft pulley 3 is attached to one end of a crankshaft 2 of an engine 1 which is an internal combustion engine, and the crankshaft pulley 3 rotates with the operation of the engine 1. A belt 4 is hung on the crankshaft pulley 3, and the belt 4
Is the alternator pulley 6 of the generator (alternator) 5
Is also hung. For this reason, when the engine 1 is driven, the alternator pulley 6 of the alternator 5 is rotated, and the alternator 5 generates power. The belt 4 is also hung on other accessory pulleys (a water pump pulley, an air conditioner pulley, etc.), and these accessories are driven at the same time.

The alternator 5 generates an alternating current using the rotation of the engine 1, rectifies and smoothes the alternating current, converts it into a direct current, and further converts the voltage of the direct current.
Output after being stabilized by IC regulator. Here, the alternator 5 outputs a DC current having a reference voltage of 42V. A high-voltage rechargeable battery (high-voltage battery) 7 is connected to the alternator 5, and the high-voltage battery 7 (reference voltage 42
V) is charged directly by the alternator 5. Also,
A low-voltage rechargeable battery (low-voltage battery) 9 is also connected to the alternator 5 via a DC-DC converter 8. The low-voltage battery 9 (reference voltage 12 V) is charged via the DC-DC converter 8.

That is, in the vehicle equipped with the charging control device of the present embodiment, a two-system power supply system composed of a high-voltage power supply having a reference voltage of 42 V and a low-voltage power supply having a reference voltage of 12 V is constructed.
The high-voltage power supply drives accessories that consume a large amount of power, such as electric power steering, and the low-voltage power supply drives accessories that do not consume much power. Since the two-system power supply system is constructed in this way, the electrical equipment of the entire vehicle can be operated efficiently.

The power generated by the alternator 5 is
While it is used directly for driving high-voltage accessories and charging the high-voltage battery 7, it is used for driving low-voltage accessories and charging the low-voltage battery 9 after voltage conversion by the DC-DC converter 8. When the electric load due to the driving of the auxiliary devices exceeds the amount of power generated by the alternator 5, the high-voltage battery 7 and / or the low-voltage battery 9 discharges, and the amount of power generated by the alternator 5 exceeds the electric load generated by driving each of the auxiliary devices. when,
The high voltage battery 7 and / or the low voltage battery 9 are charged.

The DC-DC converter 8 converts a DC current into a voltage using a transformer and a diode bridge. The DC-DC converter 8 converts the input DC current into AC once, converts the voltage again, and rectifies and smoothes again to output the DC current after voltage conversion. As described above, the alternator 5 has its reference voltage adjusted to the high-voltage power supply (high-voltage battery 7). Therefore, when the low-voltage rechargeable battery 9 is charged by the output of the alternator 5, such a DC-power supply is used. It is necessary to convert the voltage using the DC converter 8.

The DC-DC converter 8 is also connected to the engine ECU 10. The DC-DC converter 8 normally outputs a constant voltage, but is configured to be able to change the output particularly when a command is issued from the engine ECU 10. The engine ECU 10 has the engine 1
Sensors for detecting various state quantities necessary for the operation of the vehicle are connected. These sensors include a crank position sensor 11 for detecting the number of revolutions of the engine 1 and a throttle position sensor 14 for detecting the opening of a throttle valve 13 disposed on an intake passage 12 of the engine 1.
There is.

In the present embodiment, the engine ECU 10
The throttle position sensor 14 functions as idle detection means for detecting the idling state of the engine 1. When the throttle position sensor 14 detects that the throttle valve 13 is closed, the engine ECU 10 determines that the engine 1 is in an idling state.

A case where the low voltage battery 9 is charged by the charge control device of the present embodiment will be described.

When the engine 1 is not idling, the DC-DC converter 8 operates as shown in FIG.
As shown in (a), to output a constant voltage V ₀ as normal. At this time, if there is a surplus in the power generated by the alternator 5, the low-voltage battery 9 is charged by the DC-DC converter 8. That is, the relationship between the input voltage to the DC-DC converter 8 and the current generated by the alternator 5 (generator current) is as shown in FIG.

On the other hand, when the throttle position sensor 14 detects that the throttle valve 13 is closed, the engine ECU 10 determines that the engine 1 is in an idling state. When the engine ECU 10 determines that the engine 1 is in the idling state, the engine ECU 10 sends an idling signal indicating that the engine 1 is in the idling state to the DC-DC converter 8.

The DC-DC converter 8 outputs an idling signal
When the input voltage is ₁In the case above,
Constant output voltage V as usual₀Output. On the contrary,
When an idling signal is received, the input voltage₁
If less than, the DC-DC converter 8 is indicated by (b) in FIG.
Thus, the output voltage is reduced in proportion to the input voltage.
Note that the input voltage to the DC-DC converter 8 is
Decreases as the rotational speed of the motor decreases.

In the region where the output voltage is lowered, FIG.
As shown in (b), the generator current is accordingly reduced. Since the generator current is reduced, the load torque acting on the engine 1 by the power generation is reduced, and it is possible to prevent the rotation of the engine 1 from further lowering. As a result, fluctuations in the rotation speed of the engine 1 can be suppressed, and stable idling operation can be performed.

It is desirable that the number of revolutions of the engine 1 in the idling state be kept to a minimum necessary for keeping the engine 1 rotating from the viewpoint of improving fuel efficiency and reducing exhaust emissions. For this reason, if the load torque generated by the power generation increases and the rotation of the engine 1 decreases, the rotation speed fluctuates easily and the engine stalls easily. However, by performing the above-described control, the idling operation can be stabilized, and the fuel efficiency can be improved and the exhaust emission can be effectively reduced.

In the idling state, the output voltage of the DC-DC converter 8 slightly decreases.
From the viewpoint of charging the low-voltage battery 9, the output of the DC-DC converter 8 is not optimal. However, it is more important to stabilize the rotation of the engine 1 than to charge the low-voltage battery 9.
If the input voltage to the C converter 8 recovers, there is no problem because the state suitable for charging the low-voltage battery 9 recovers.

Next, an embodiment of the charge control device of the second invention will be described.

The configuration of the charging device of the present embodiment is the same as the configuration of the above-described device of the first invention, and therefore detailed description is omitted here.
The ECU 10 and the crank position sensor 11 function as rotation speed detecting means for detecting the rotation speed of the engine 1.

The case where the low voltage battery 9 is charged by the charge control device of the present embodiment will be described.

When the rotational speed of the engine 1 obtained from the detection result of the crank position sensor 11 is equal to or more than a predetermined value R ₀ , the DC-DC converter 8 operates normally as shown in FIG. Outputs a constant voltage. If there is a surplus in the power generated by the alternator 5, the low-voltage battery 9 is charged with a constant output voltage from the DC-DC converter 8. That is, DC-DC at this time
The relationship between the input voltage to the converter 8 and the generator current is as shown in FIG.

On the other hand, when the rotation speed of engine 1 obtained from the result of detection by crank position sensor 11 is less than predetermined value R ₀ , engine ECU 10 sends a rotation speed signal to DC-DC converter 8. Here, the predetermined value R ₀ is determined as a rotation speed that is a boundary of whether or not the engine 1 is in an idling state, and is set to, for example, 600 rpm.

Upon receiving the rotation speed signal, the DC-DC converter 8 lowers its output voltage in proportion to the rotation speed of the engine 1 as shown in FIG. As an example of the case where the rotation speed of the engine 1 becomes less than the predetermined value R _{0, a} point X (the rotation speed R _{1 of} the engine 1, the output voltage of the DC-DC converter 8)
The relationship between the output voltage at V ₂ ) and the generator current is shown in FIG. That is, when the rotation speed of the engine 1 becomes less than the predetermined value R ₀ , the output voltage-generator current curve moves downward in proportion to the decrease in the rotation speed.

[0036] As a result, when the engine 1 is operated at a rotational speed R _1, DC-DC converter 8 is always constant output voltage V
Output at ₂ (<V ₀ ). When the output voltage is reduced, the generator current is also reduced, the load torque acting on the engine 1 is reduced, and it is possible to prevent the rotation of the engine 1 from further lowering. As a result, fluctuations in the rotation speed of the engine 1 can be suppressed, and stable idling operation can be performed. As described above, by stabilizing the rotation speed of the engine 1, it is possible to effectively improve fuel efficiency and reduce exhaust emissions.

The charging control device according to the present invention is not limited to the above embodiment. For example, the alternator (generator) 5 of the above-described embodiment includes a portion that generates an AC current, a portion that rectifies and smoothes the AC current to smooth a DC current, and a portion that stabilizes and outputs the converted DC current. It was integrated. However, the generator may be configured such that each of the above-described functions is divided without being integrated, and may be a unit that performs power generation and direct current output as a whole. Further, the generator may directly generate DC current.

In the above-described first embodiment, the engine ECU 10 and the throttle position sensor 14 function as idle detecting means. However, the idling state of the engine 1 may be detected by another mechanism. For example, the idling state of the engine 1 may be detected using an accelerator position sensor that detects an accelerator opening, a wheel speed sensor that detects a wheel speed, or the like.

In the first embodiment of the present invention, when the input voltage becomes less than the predetermined value V _{0 in the} idling state, the DC-DC converter 8 changes the output voltage with respect to the input voltage by a linear function. Lowered. However, not only a partial region of such a less than the predetermined value V _0, the entire region of the input voltage may be varied output voltage may be the change not a linear function of linear change .

In particular, with regard to the first aspect of the present invention, it is sufficient that the output can be changed according to the input of the DC-DC converter under an idling state, and a state quantity other than voltage is used as a reference of the input. Is also good.

In the above-described embodiment of the second invention, when the rotation speed of the engine 1 becomes less than the predetermined value R ₀ , the DC-DC converter 8 converts the output voltage into a linear function with respect to the input voltage. Lowered to However, the output voltage may be changed not only in a part of the region below the predetermined value R ₀ but also in the whole region of the rotation speed of the engine 1, and the change is not a linear change in a linear function. You may.

Alternatively, the predetermined value V _O of the input voltage of the DC-DC converter 8 in the first embodiment of the present invention and the rotation speed R ₀ of the engine 1 in the second embodiment of the present invention described above.
Are fixed values, but these values may be variably controlled according to various vehicle state quantities such as various engine state quantities. In the case of variable control, the above-described engine ECU 10
In this case, various state quantities may be fetched, and calculations may be performed based on the fetched various state quantities.

In the above embodiment, the engine ECU 10 sends an idling signal and a rotation speed signal to the DC-DC converter 8, but the engine ECU 10 calculates the output voltage of the DC-DC converter 8, An output voltage command signal may be directly sent from the ECU 10 to the DC-DC converter 8. Further, the above-described embodiment is not applied to a hybrid vehicle, but may be applied to a hybrid vehicle.

[0044]

According to the charging control device of the first invention, when the idling state of the internal combustion engine is detected, the output of the DC-DC converter is changed according to the input. Even if the output of the internal combustion engine fluctuates, it is possible to surely prevent the rotation of the internal combustion engine from being promoted by the generator. In addition, the charge control device of the second invention,
Because the DC-DC converter changes its output according to the internal combustion engine speed, even if the output of the generator fluctuates due to the fluctuation of the internal combustion engine speed, the generator will foster the engine speed fluctuation. Can be reliably suppressed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of an embodiment of a charge control device of the present invention.

FIG. 2 shows an embodiment of a charge control device according to the first invention;
3 is a graph showing a relationship between an input voltage and an output voltage of a DC-DC converter.

FIG. 3 shows an embodiment of a charge control device according to the first invention;
4 is a graph showing a relationship between an input voltage of a DC-DC converter and a generator current.

FIG. 4 is a graph showing a relationship between an engine speed and an output voltage of a DC-DC converter in one embodiment of the charge control device of the second invention.

FIG. 5 shows an embodiment of the charge control device according to the second invention;
4 is a graph showing a relationship between an input voltage of a DC-DC converter and a generator current.

FIG. 6 is a graph showing a relationship between an input voltage and a generator current in a conventional DC-DC converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 5 ... Generator, 7 ... High voltage side rechargeable battery (high voltage battery), 8 ... DC-DC converter, 9 ... Low voltage side rechargeable battery (low voltage battery), 10 ... Engine ECU (rotation speed detection means, idling detection) Means), 11 ... Crank position sensor (rotational speed detecting means), 14 ... Throttle position sensor (Idling detecting means).

Continued on front page F-term (reference) 5G003 AA07 BA02 CA12 CB09 DA06 FA06 GB03 GC05 5G060 AA04 BA08 CA04 DB07 DB08 5H115 PC06 PG04 PI16 PI24 PI30 PO01 PO09 PU08 PV02 QA01 QA10 QE20 QN03 RB21 TB03 TE02 TE03 TO21

Claims (5)

[Claims] A generator for generating a DC current by driving the internal combustion engine to output a DC current; a DC-DC converter for converting a voltage of the DC current generated by the generator;
A rechargeable battery charged by the output of the DC converter, and idling detection means for detecting an idling state of the internal combustion engine, the DC-DC converter, when the idling state is detected by the idling detection means A charge control device, wherein the output is changed according to the input. 2. The DC-DC converter according to claim 1, wherein, when the idling state is detected by the idling detection means, the output voltage is reduced when the input voltage is reduced. Charge control device A generator for generating a DC current by driving the internal combustion engine to output a DC current; a DC-DC converter for converting a voltage of the DC current generated by the generator;
A rechargeable battery charged by an output of a DC converter, and a rotation speed detection unit that detects a rotation speed of the internal combustion engine, wherein the DC-DC converter has a rotation speed detected by the rotation speed detection unit. A charge control device, wherein the output is changed according to the output. 4. The DC-DC converter according to claim 3, wherein the output voltage of the DC-DC converter is reduced when the rotation speed detected by the rotation speed detection means is lower than a predetermined rotation speed. Charge control device 5. The battery according to claim 1, further comprising a rechargeable battery directly charged by an output of the generator, between the generator and the DC-DC converter. Charge control device described