JP3485017B2 - Charge control device - Google Patents

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 stable idling operation.

[0002]

In a hybrid vehicle (vehicle driven by an internal combustion engine and a vehicle drive motor) and the like, in addition to a power supply for driving the internal combustion engine and various auxiliary machines, a power supply for a vehicle drive motor is also provided. It also has a dual power supply system. Further, in recent years, various electric devices have been incorporated in a vehicle, and the amount of electric power required for an on-vehicle battery tends to increase. For this reason, the inventors of the present invention, in addition to a conventional battery (such as a 12V power source for passenger cars), install another battery of higher voltage (about 40V) onboard a dual power source system even if it is not a hybrid vehicle. Trying to build.

A hybrid vehicle is equipped with a generator, which is a generator, and drives the vehicle with electric power generated by the generator and also charges a battery. Even normal vehicles that are not hybrid vehicles have an alternator as a generator, and when the vehicle's electrical load exceeds the alternator's power output, the battery discharges to make up for the shortfall, and the alternator's power output exceeds the vehicle's electrical load. Sometimes the battery is charged.

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

However, when charging is performed via the DC-DC converter, the DC-DC converter tries to make its output voltage constant, so that the input voltage to the DC-DC converter and the generator current are as shown in FIG. The relationship is as shown in. That is,
As the input voltage to the DC-DC converter drops, the generator voltage is increased to keep the output voltage constant. Therefore, in the idling state where most of the load of the internal combustion engine is the load of the generator, the rotation of the internal combustion engine fluctuates and 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 the 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, which increases the generator current. Since the generator current and the load torque acting on the internal combustion engine due to power generation are substantially proportional to each other, 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 the idling state becomes unstable, and in the worst case, engine stall occurs. Therefore, when charging is performed via the DC-DC converter in the idling state, improvement that does not make the idling state unstable is desired.

Therefore, an object of the present invention is to provide a charge control device which can realize stable idling operation.

[0008]

SUMMARY OF THE INVENTION A charging control device according to the first aspect of the present invention comprises a generator for generating a direct current by generating electric power with a driving force of an internal combustion engine, and a DC-converter for converting the voltage of the direct current generated by the generator. A DC converter, a rechargeable battery charged by the output of the DC-DC converter, and an idling detection means for detecting an idling state of the internal combustion engine are provided.
DC-DC converter, when the idling state is detected by the idling detection means, DC-DC converter
The feature is that the output from the DC-DC converter is changed according to the input to the converter .

According to the charge control apparatus of the first aspect of the present invention, when the internal combustion engine is in the idling state, the output of the DC-DC converter is changed according to the input, so that the output of the generator is changed by the fluctuation of the internal combustion engine. Even if fluctuates, the generator does not promote the fluctuation in rotation of the internal combustion engine. As a result, stable idling operation is realized.

Here, if the DC-DC converter detects the idling state by the idling detecting means, if the output voltage is lowered when the input voltage to the DC-DC converter is lowered, the idling state The engine stall from can be reliably suppressed.

Further, the charging control device of the second invention converts a voltage of the direct current generated by the generator and a generator which generates power by the driving force of the internal combustion engine and outputs a direct current.
A DC-DC converter, a rechargeable battery charged by the output of the DC-DC converter, and a rotation speed detection unit that detects the rotation speed of the internal combustion engine are provided, and the DC-DC converter detects the rotation speed detection unit. The DC-DC controller
It is characterized by changing the output from the converter .

According to the charge 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, stable idling operation is realized.

Here, the DC-DC converter lowers the output voltage from the DC-DC converter when the number of revolutions detected by the number-of-revolutions detecting means becomes equal to or lower than a predetermined number of revolutions. Therefore, it is possible to reliably prevent the engine stall from occurring when the number of revolutions of the internal combustion engine is equal to or lower than the predetermined value.

Further, in the charging control device of the first invention and the second invention, a rechargeable battery which is directly charged by the output of the generator is provided between the generator and the DC-DC converter. It is possible to build a system power supply system, and to efficiently operate on-board electrical equipment. Further, charging can be performed for both of the two rechargeable batteries, and at this time, the fluctuation in the rotation of the internal combustion engine is not promoted.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION First, an embodiment of the charge control device of the first invention will be described. FIG. 1 shows the 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 on. Therefore, when the engine 1 is driven, the alternator pulley 6 of the alternator 5 is rotated, and the alternator 5 generates electric power. The belt 4 is also hung on other accessory pulleys (water pump pulley, air conditioner pulley, etc.), and these accessory machines are driven at the same time.

The alternator 5 uses the rotation of the engine 1 to generate an alternating current, rectifies and smoothes this alternating current to convert it into a direct current, and further converts the voltage of this direct current.
Output after stabilizing by IC regulator. Here, the alternator 5 outputs a direct current with a reference voltage of 42V. A high voltage side rechargeable battery (high voltage battery) 7 is connected to the alternator 5, and the high voltage battery 7 (reference voltage 42
V) is directly charged by the alternator 5. Also,
A low voltage side 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 12V) is charged via the DC-DC converter 8.

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

The electric power generated by the alternator 5 is
It is directly used for driving the high-voltage side auxiliary machines or charging the high-voltage battery 7, while it is used for driving the low-voltage side auxiliary machines or charging the low-voltage battery 9 after the voltage is converted by the DC-DC converter 8. When the electric load due to the driving of the auxiliary machinery exceeds the power generation amount of the alternator 5, the high-voltage battery 7 and / or the low-voltage battery 9 is discharged, and the power generation amount of the alternator 5 exceeds the electric load due to the driving of the respective auxiliary machinery. when,
The high voltage battery 7 and / or the low voltage battery 9 are charged.

The DC-DC converter 8 converts a direct current into a voltage by using a transformer and a diode bridge. The DC-DC converter 8 once converts the input DC current into AC, then converts the voltage, rectifies and smoothes again, and outputs the voltage-converted DC current. As described above, since the reference voltage of the alternator 5 is adjusted to the high voltage side power source (high voltage battery 7), when the low voltage side rechargeable battery 9 is to be charged by the output of the alternator 5, such a DC- 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 when the instruction from the engine ECU 10 is given, the output can be changed. The engine ECU 10 has an engine 1
Sensors that detect various state quantities necessary for driving are connected. Among these sensors, there are a crank position sensor 11 for detecting the rotational speed of the engine 1 and a throttle position sensor 14 for detecting the opening of a throttle valve 13 arranged on an intake passage 12 of the engine 1.
There is.

In the present embodiment, the engine ECU 10
Also, the throttle position sensor 14 functions as an 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 the idling state.

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

When the engine 1 is not idling, the DC-DC converter 8 operates as shown in FIG.
As shown in middle (a), the constant voltage V ₀ is output as usual. At this time, if there is a surplus in the electric power generated by the alternator 5, the DC-DC converter 8 charges the low-voltage battery 9. 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 by (a) 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 the idling state. When determining 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 has an idling signal.
When the input voltage is ₁In the above cases,
Constant output voltage V as usual₀To output. On the contrary,
When the idling signal is received, the input voltage is the specified value V₁
If less than, the DC-DC converter 8 is indicated by (b) in FIG.
Thus, its output voltage is lowered in proportion to the input voltage.
The input voltage to the DC-DC converter 8 is the engine 1
Will decrease as the number of rotations decreases.

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

From the viewpoint of improving fuel efficiency and reducing exhaust emission, it is desirable to keep the engine speed of the engine 1 in the idling state to the minimum necessary for keeping the engine 1 running. For this reason, if the load torque due to power generation increases and the rotation of the engine 1 decreases, the engine speed tends to fluctuate and the engine stalls easily. However, by performing the above-described control, the idling operation can be stabilized, and the fuel consumption can be improved and the exhaust emission can be effectively reduced.

In the idling state, the output voltage of the DC-DC converter 8 will drop to some extent.
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, and the rotation of the engine 1 is stable and DC-D
When the input voltage to the C converter 8 is restored, there is no problem because the state preferable for charging the low voltage battery 9 is restored.

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

Since the configuration of the charging device of this embodiment is the same as the configuration of the device of the first invention described above, a detailed description thereof will be omitted here, but in the present embodiment, the engine is used.
The ECU 10 and the crank position sensor 11 function as a rotation speed detection unit that detects the rotation speed of the engine 1.

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

When the rotation speed of the engine 1 obtained from the detection result of the crank position sensor 11 is equal to or higher than a predetermined value R ₀ , the DC-DC converter 8 normally operates as shown in FIG. 4 regardless of the input voltage. Output a constant voltage. If there is a surplus in the electric 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 by (a) in FIG.

On the other hand, when the rotation speed of the engine 1 obtained from the detection result of the crank position sensor 11 is less than the predetermined value R ₀ , the engine ECU 10 sends a rotation speed signal to the DC-DC converter 8. Here, the predetermined value R ₀ is defined as a rotation speed that becomes a boundary of whether the engine 1 is in the idling state, and is set to 600 rpm, for example.

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 a predetermined value R _{0, the} point X in FIG. 4 (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. 5 (b). 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.

As a result, when the engine 1 is operated at the rotational speed R ₁ , the DC-DC converter 8 always outputs the constant output voltage V
Output at ₂ (<V ₀ ). When the output voltage is lowered, the generator current is also lowered, the load torque acting on the engine 1 is reduced, and it is possible to prevent further reduction of the rotation of the engine 1. 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, it is possible to effectively improve the fuel consumption and reduce the exhaust emission by stabilizing the rotation speed of the engine 1.

The charging control device of the present invention is not limited to the above embodiment. For example, in the alternator (generator) 5 of the above-described embodiment, there are a portion that generates alternating current, a portion that rectifies and smoothes the alternating current to smooth the direct current, and a portion that stabilizes and outputs the converted direct current. It was made one. However, the generator may be configured such that each of the above-mentioned functions is not integrated but is divided, and may be one that generates power and outputs a direct current as a whole. Further, the generator may directly generate direct current.

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

Further, in the above-described first embodiment of the invention, the DC-DC converter 8 outputs the output voltage as a linear function with respect to the input voltage when the input voltage becomes less than the predetermined value V _{0 in the} idling state. I lowered it. However, the output voltage may be changed not only in a part of the region below the predetermined value V ₀ but also in the entire region of the input voltage, and the change may not be a linear change in a linear function. .

Further, particularly regarding the invention described in claim 1, it is sufficient that the output can be changed according to the input of the DC-DC converter in the idling state, and the state quantity other than the voltage is used as the reference of the input. Good.

Further, in the above-described second embodiment of the invention, the DC-DC converter 8 makes the output voltage a linear function with respect to the input voltage when the rotation speed of the engine 1 becomes less than the predetermined value R _0. Lowered to. However, the output voltage may be changed not only in such a partial region below the predetermined value R ₀ but also in the entire region of the rotational speed of the engine 1, and the change is not a linear function linear change. May be.

Alternatively, the predetermined value V _O of the input voltage of the DC-DC converter 8 in the above-described first embodiment of the invention or the rotational speed R ₀ of the engine 1 in the above-described second embodiment of the invention.
Are fixed values, but these numerical values may be variably controlled according to various vehicle state quantities such as various engine state quantities. When performing variable control, the engine ECU 10 described above is used.
It suffices to take various state quantities into and to perform the calculation based on the fetched various state quantities.

Further, in the above-described embodiment, the idling signal and the rotation speed signal are sent from the engine ECU 10 to the DC-DC converter 8. However, the output voltage of the DC-DC converter 8 is calculated in the engine ECU 10, The output voltage command signal may be directly sent from the ECU 10 to the DC-DC converter 8. Further, the embodiment described above was not applied to the hybrid vehicle, but may be applied to the hybrid vehicle.

[0044]

According to the charge control device of the first aspect of the present invention, when the idling state of the internal combustion engine is detected, the DC-DC converter changes its output according to its input, so that the generator fluctuates depending on the rotation fluctuation of the internal combustion engine. Even if the output of V fluctuates, it is possible to reliably prevent the rotation fluctuation of the internal combustion engine from being accelerated by the generator. In addition, the charge control device of the second invention,
Since the DC-DC converter changes its output according to the number of revolutions of the internal combustion engine, even if the output of the generator fluctuates due to fluctuations in the internal combustion engine, the fluctuations in the engine's rotation are promoted by the generator. Can be reliably suppressed.

[Brief description of drawings]

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

FIG. 2 shows an embodiment of the charge control device of the first invention.
It is a graph which shows the relationship between the input voltage and output voltage of a DC-DC converter.

FIG. 3 shows an embodiment of a charge control device of the first invention.
It is a graph which shows the relationship between the 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 of the second invention.
It is a graph which shows the relationship between the 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 (rotation speed detection means), 14 ... Throttle position sensor (idling detection means).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI H02J 7/14 (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 9/04 B60L 11/02 B60K 6/00 B60K 8/00 H02J 7/10 H02J 7/14

Claims (5)

(57) [Claims] 1. A generator that generates electric power by driving force of an internal combustion engine to output a direct current, a DC-DC converter that converts the voltage of the direct current generated by the generator, and the DC-DC converter.
A rechargeable battery charged by the output of the DC converter, and an 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. Is the DC-D
A charge control device characterized in that an output from the DC-DC converter is changed according to an input to the C converter . 2. The DC-DC converter, when the idling state is detected by the idling detection means, the output voltage from the DC-DC converter when the input voltage to the DC-DC converter drops. The charging control device according to claim 1, wherein the charging control device is lowered. 3. A generator that generates a direct current by generating power by the driving force of an internal combustion engine, a DC-DC converter that converts the voltage of the direct current generated by the generator, and the DC-DC converter.
The rechargeable battery charged by the output of the DC converter, and a rotation speed detection means for detecting the rotation speed of the internal combustion engine, the DC-DC converter, the rotation speed detected by the rotation speed detection means. According to the DC-DC converter
A charging control device characterized by changing the output from the battery. 4. The DC-DC converter lowers an output voltage from the DC-DC converter when the number of rotations detected by the number-of-rotations detecting means is equal to or lower than a predetermined number of rotations. The charge control device according to claim 3. 5. The rechargeable battery, which is directly charged by the output of the generator, is further provided between the generator and the DC-DC converter. The charging control device described.