JP2008075565A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely perform pre-assist until start by avoiding exhaustion of battery in relation to a control device for an internal combustion engine. <P>SOLUTION: Rotation speed of a supercharger 50 is kept being raised before start of a vehicle by driving the supercharger 50 by a generator 56 during idling operation. When voltage of a battery 44 is lower than charge reference voltage, idling speed is raised and electric power generated by a generator 40 is increased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine including a supercharger with an electric motor.

Conventionally, a turbocharger with an electric motor having an electric motor attached to a rotating shaft is known. According to the turbocharger with an electric motor, the rotational speed of the compressor can be arbitrarily controlled by operating the electric motor to drive the compressor, regardless of the magnitude of the exhaust energy supplied from the internal combustion engine. For example, Patent Document 1 discloses a technique in which a compressor is driven by an electric motor during idle operation before the vehicle starts to increase the rotational speed of the compressor in advance (hereinafter referred to as “this specification”). Technology is called pre-assist). According to this pre-assist, a high start acceleration performance can be obtained by eliminating the response delay of the supercharging pressure with respect to the depression of the accelerator at the start.
Japanese Patent No. 3038784 JP 2004-169673 A

  When performing pre-assist, the electric power required for the operation of the electric motor is supplied from the battery. Although the battery is charged by the alternator during idle operation, the generated power of the alternator at the idling speed is small, and the power required for operating the motor is likely to exceed the generated power of the alternator. For this reason, when idle operation continues for a long time, there is a possibility that pre-assist may not be continued until the start due to battery exhaustion.

  As a method for avoiding battery consumption during pre-assist, it is conceivable to limit the operating time and the rotational speed of the electric motor. However, if such a restriction is provided, the supercharging pressure does not increase sufficiently, and there is a high possibility that the intended start acceleration performance cannot be obtained.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a control device for an internal combustion engine that can reliably perform pre-assist until the start of the vehicle while avoiding battery consumption. To do.

In order to achieve the above object, a first invention provides a generator for generating electric power using the energy of an internal combustion engine, a battery for charging electric power generated by the generator, and supply of electric power from the battery. A control device for an internal combustion engine having an electric motor that receives and operates, and a supercharger that is driven by the electric motor,
Pre-assist means for driving the supercharger by the electric motor during idle operation and increasing the rotational speed of the supercharger prior to starting the vehicle;
Idle rotation speed increasing means for increasing the idle rotation speed of the internal combustion engine and increasing the generated power of the generator when the voltage of the battery is lower than a predetermined charging reference voltage;
It is characterized by having.

According to a second invention, in the first invention,
The apparatus further includes pre-assist start prohibiting means for prohibiting the start of pre-assist by the pre-assist means when the voltage of the battery is lower than a predetermined start voltage set below the charging reference voltage.

According to a third invention, in the second invention,
When the voltage of the battery falls below a stop voltage set lower than the start voltage during pre-assist, the pre-assist means is further provided to stop the pre-assist.

A fourth invention is any one of the first to third inventions,
The idling speed increasing means sets a target idling speed in accordance with the voltage of the battery.

A fifth invention is the fourth invention,
The idle speed increasing means increases the target idle speed as the voltage difference between the charging reference voltage and the battery voltage increases.

A sixth invention is any one of the first to fifth inventions,
The internal combustion engine has a first generator that is connected to a crankshaft as the generator and is driven, and a second generator that is driven by exhaust energy of the internal combustion engine, and the idle speed increasing means is the first generator. It is characterized by giving priority to the generator.

A seventh invention is the invention according to any one of the first to sixth inventions,
It is further characterized by further comprising split injection means for injecting a part of the fuel after compression top dead center when the idle speed is higher than a predetermined reference speed.

In an eighth aspect based on the seventh aspect,
The supercharger has an exhaust turbine disposed in an exhaust passage of an internal combustion engine, and is configured as a turbocharger that rotates using exhaust energy of the internal combustion engine received by the exhaust turbine.

  According to the first aspect of the invention, when the battery voltage is lower than the charging reference voltage, the idle rotation speed is increased to increase the generated power of the generator. Therefore, during pre-assist, the battery is consumed due to the supply of power to the motor. Can be avoided, and pre-assist can be reliably performed until the vehicle starts.

  According to the second invention, since the start of the pre-assist is prohibited when the battery voltage is lower than the start voltage, it is avoided that the operation of the internal combustion engine is hindered due to the rapid power consumption accompanying the start of the pre-assist. be able to.

  According to the third invention, since the pre-assist is stopped when the battery voltage falls below the stop voltage during the pre-assist, it is possible to prevent the battery from being consumed until the operation of the internal combustion engine is disturbed. it can.

  According to the fourth invention, by setting the target idle rotation speed according to the battery voltage, it is possible to charge the battery with the electric power according to the battery voltage, and it is possible to reliably avoid battery consumption.

  According to the fifth aspect of the invention, the larger the battery voltage drop, the larger the power charged in the battery, and the quicker charging can more reliably avoid battery consumption.

  According to the sixth aspect of the invention, the first generator driven by being connected to the crankshaft is preferentially used, so that emission characteristics are deteriorated due to a sudden change in exhaust pressure due to the use of the second generator. Can be prevented.

  According to the seventh invention, the combustion pressure can be lowered by injecting a part of the fuel after the compression top dead center, and the increase of the combustion noise accompanying the increase in the idle speed can be suppressed. Further, when the internal combustion engine is a diesel engine, the generation of smoke can be suppressed by the stirring effect caused by the combustion of fuel injected after the compression top dead center.

  According to the eighth invention, the exhaust energy increased by the combustion of the fuel injected after the compression top dead center can be recovered by the exhaust turbine, and the rotational speed of the supercharger can be increased using the recovered energy. .

Embodiment 1 FIG.
The first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an internal combustion engine as a first embodiment of the present invention. In the present embodiment, the present invention is applied to a diesel engine (hereinafter simply referred to as an engine) having a turbocharger with a motor (motor-assisted turbocharger, also referred to as MAT for short).

  As shown in FIG. 1, this engine has an engine body 2 having a plurality of cylinders (four cylinders in FIG. 1). The engine body 2 is provided with an in-cylinder injector 36 for directly injecting fuel into the combustion chamber. The in-cylinder injector 36 is provided for each cylinder and is connected to the common rail 38. That is, this engine is configured as a common rail type diesel engine. Fuel stored in a fuel tank (not shown) is compressed to a predetermined fuel pressure by a supply pump and supplied to the common rail 38.

  An exhaust manifold 6 that collects exhaust gas discharged from each cylinder is connected to the exhaust side of the engine body 2. An exhaust pipe 10 is connected to the outlet of the exhaust manifold 6. An exhaust purification device 32 such as a NOx catalyst, DPF, or DPNR is disposed in the middle of the exhaust pipe 10. Further, an exhaust throttle valve 30 is provided upstream of the exhaust purification device 32 in the exhaust pipe 10. The exhaust throttle valve 30 is normally fully opened.

  An intake manifold 4 for distributing intake air to each cylinder is connected to the intake side of the engine body 2. An intake pipe 8 is connected to the inlet of the intake manifold 4 for taking air from the atmosphere and guiding it to the intake manifold 4. An air cleaner 12 is attached to the inlet of the intake pipe 8. An intake throttle valve 20 is provided upstream of the intake manifold 4. The intake throttle valve 22 is normally opened fully.

  A compressor 52 of the MAT 50 is provided upstream of the intake throttle valve 20 in the intake pipe 8. The MAT 50 includes a compressor 52, a turbine 54, and an electric motor 56 disposed between the compressor 52 and the turbine 54. The turbine 54 is provided in the middle of the exhaust pipe 10 extending from the exhaust manifold 6 to the exhaust purification device 32. The compressor 52 and the turbine 54 are integrally connected by a connecting shaft, and the compressor 52 is rotationally driven by the exhaust energy received by the turbine 54 from the exhaust gas. Further, the connecting shaft is also a rotor of the electric motor 56, and the compressor 52 can be forcibly driven by operating the electric motor 56. An intercooler 18 that cools the air supercharged by the compressor 52 is provided downstream of the compressor 52 in the intake pipe 8.

  An EGR pipe 22 is connected in the middle of the intake pipe 8 from the intake throttle valve 20 to the intake manifold 4. The opposite end of the EGR pipe 22 is connected to the exhaust manifold 6, and a part of the exhaust gas (EGR gas) is introduced into the intake pipe 8 through the EGR pipe 22. By introducing EGR gas, which has a higher specific heat than that of air and a small amount of oxygen, into the intake pipe 8, the combustion temperature in the cylinder can be lowered and the amount of NOx produced can be reduced. An EGR valve 28 that opens and closes the EGR pipe 22 is provided in the middle of the EGR pipe 22. An EGR cooler 24 for cooling the EGR gas flowing inside is provided upstream (exhaust side) of the EGR valve 28 in the EGR pipe 22. Cooling increases the density of the EGR gas, and it is possible to improve the EGR rate while securing the intake air amount. Between the EGR cooler 24 and the EGR valve 28, a switching valve 26 for bypassing the EGR cooler 24 and flowing EGR gas is provided.

  The intake pipe 8 is connected to a bypass pipe 16 that bypasses the compressor 52 and connects the outlet side and the inlet side of the compressor 52. A bypass valve 14 for controlling the flow rate of air flowing through the bypass pipe 16 is disposed at a connection portion between the intake pipe 8 and the upstream side of the bypass pipe 16 (the outlet side of the compressor 52).

  The engine includes an alternator 40 that is driven by the engine body 2. The alternator 40 has its input shaft connected to the output shaft (crankshaft) of the engine body 2 via a power transmission member such as a belt 42. The electric power generated by the alternator 40 is charged in a battery 44 mounted on the vehicle. Various electric devices mounted on the vehicle operate by receiving power supplied from the battery 44. The electric motor 56 of the MAT 50 is one of such devices, and is supplied with power from the battery 44 via the motor controller 58.

  This engine has an ECU (Electronic Control Unit) 60 as a control device for comprehensively controlling the entire engine. In addition to the motor controller 58, various devices such as the injector 36 are connected to the output unit of the ECU 60. Various sensors such as an engine speed sensor 62, an accelerator opening sensor 64, and a vehicle speed sensor 66 are connected to the input section of the ECU 60. The engine speed NE (rpm), the accelerator opening ACCP (%), and the vehicle speed SPD (m / s) input from the sensors 62, 64, and 66 are all used as information related to engine control. Further, a battery 44 is connected to the input section of the ECU 60, and the battery voltage Vb (V) is also input as information related to engine control. The ECU 60 drives each device in accordance with a predetermined control program based on various input information.

  The ECU 60 performs pre-assist by the MAT 50 as one of engine controls. The pre-assist is engine control in which the compressor 52 is driven by the electric motor 56 during idle operation before the vehicle starts, and the rotation speed of the compressor 52 is increased in advance. By performing the pre-assist, it becomes possible to eliminate the delay in the response of the supercharging pressure to the depression of the accelerator at the time of starting and obtain a high starting acceleration performance.

  The flowchart of FIG. 2 shows a routine for engine control during idling that is executed by the ECU 60. In this engine control, the start / stop of pre-assist is determined based on the battery voltage Vb, and the idle speed is controlled based on the battery voltage Vb. Hereinafter, engine control during idling according to the present embodiment will be described with reference to FIG.

  In the first step S100 of the routine shown in FIG. 2, the engine speed NE, the accelerator opening ACCP, the vehicle speed SPD, and the battery voltage Vb are acquired. In the next step S102, it is determined whether or not the engine is in an idle state based on the accelerator opening ACCP and the vehicle speed SPD acquired in step S100. If accelerator opening ACCP is zero and vehicle speed SPD is zero, it is determined that the engine is in an idle state. The processes of steps S100 and S102 are repeatedly performed until the engine becomes idle.

  If the engine is idle, the determination in step S104 is performed. In step S104, it is determined whether or not the battery voltage Vb is higher than a predetermined charging reference voltage α. The charging reference voltage α is set to 12 to 14V, for example.

  If the battery voltage Vb is higher than the charging reference voltage α, the process proceeds to step S106, power is turned on to the MAT 50, and pre-assist is started. On the other hand, if the battery voltage Vb is equal to or lower than the charging reference voltage α, the process proceeds to step S112, and control for increasing the idle speed (engine speed NE during idling) is performed. By increasing the idle speed, the power generated by the alternator 40 is increased. In this engine, the idling speed can be increased by increasing the fuel injection amount.

  In the process in step S112, the engine speed is set according to the battery voltage Vb. FIG. 3 is a diagram showing the relationship between the battery voltage Vb and the set value of the engine speed NE. As shown in FIG. 3, when the battery voltage Vb is higher than the charging reference voltage α, the engine speed NE is set to a constant base idle speed NEia, and as the battery voltage Vb is lower than the charging reference voltage α, The engine speed NE is set to a higher value than the base idle speed NEia. According to such setting of the engine speed NE, the power charged to the battery 44 can be increased as the decrease in the battery voltage Vb is increased, and consumption of the battery 44 can be reliably avoided by quick charging. .

  After the process of step S112, the determination of step S114 is performed. In step S114, it is determined whether or not the battery voltage Vb is higher than a predetermined pre-assist start voltage β. The pre-assist start voltage β is set to a value equal to or lower than the charging reference voltage α. Steps S112 and S114 are repeated until the battery voltage Vb becomes higher than the pre-assist start voltage β.

  As a result of the determination in step S114, if the battery voltage Vb is higher than the pre-assist start voltage β, the process proceeds to step S116. In step S116, pre-assist is started by applying power to the MAT 50 while continuing the control for increasing the idle rotation speed in accordance with the battery voltage Vb. Note that the pre-assist start voltage β is set so as not to fall below a predetermined engine control stop voltage ε even if the battery voltage Vb suddenly decreases immediately after power is supplied to the MAT 50. The engine control stop voltage ε is a limit voltage at which energization from the battery 44 to the ECU 60 is stopped. If the battery voltage Vb falls below the engine control stop voltage ε, the engine operation is hindered.

  After the start of pre-assist by the process of step S106, the determination of step S108 is performed. Further, after the start of pre-assist by the process of step S116, the determination of step S118 is performed. In FIG. 2, an arrow between steps indicated by a solid line means that pre-assist is being performed, and an arrow between steps indicated by a broken line means that pre-assist is being stopped.

  In step S108 and step S118, it is determined whether or not the battery voltage Vb is higher than a predetermined pre-assist stop voltage γ. The pre-assist stop voltage γ is set to a value lower than the pre-assist start voltage β and higher than the engine control stop voltage ε. If the battery voltage Vb is equal to or lower than the pre-assist stop voltage γ as a result of the determination in steps S108 and S118, the process proceeds to step S120 in any case. In step S120, the power supply to the MAT 50 is interrupted and the pre-assist is stopped. After stopping the pre-assist, the process proceeds to step S112, and control for increasing the idle speed is performed.

  As a result of the determinations in steps S108 and S118, if the battery voltage Vb is higher than the pre-assist stop voltage γ, the process proceeds to step S110 while continuing the pre-assist in any case. In step S110, it is determined whether or not the engine is in an idle state. If the engine is still idle, this routine ends while continuing the pre-assist.

  On the other hand, when the engine is not in an idle state, for example, when the accelerator is stepped on or when the vehicle starts to travel, the process proceeds to step S122. In step S122, the power supply to the MAT 50 is interrupted and the pre-assist is stopped. After stopping the pre-assist, the process proceeds to step S124, and the control for increasing the idle speed is also stopped. After the process of step S122, the process is executed again from the first step S100.

  According to the routine described above, when the battery voltage Vb is lower than the charging reference voltage α during idling, the generated power of the alternator 40 is increased by the control for increasing the idle speed. Thereby, after the start of the pre-assist, it is possible to avoid the consumption of the battery 44 accompanying the supply of power to the MAT 50, and the pre-assist can be reliably performed until the vehicle starts.

  Further, since the start of the pre-assist is prohibited when the battery voltage Vb is lower than the pre-assist start voltage β, it is possible to avoid the trouble of the engine operation due to the rapid power consumption accompanying the start of the pre-assist. . Furthermore, since the pre-assist is stopped when the battery voltage Vb falls below the pre-assist stop voltage γ during the pre-assist, it is possible to prevent the battery 44 from being consumed until the engine operation is hindered.

  In the present embodiment, the “pre-assist means” according to the first aspect of the present invention is implemented by the ECU 60 executing the process of step S106 or step S116 of the routine shown in FIG. Further, the processing of step S104 and step S112 is executed by the ECU 60, thereby realizing the “idle speed increasing means” of the first, fourth and fifth inventions. Further, the “pre-assist start prohibiting means” of the second aspect of the present invention is realized by the ECU 60 executing the process of step S114. Further, the “pre-assist stopping means” according to the third aspect of the present invention is realized by the ECU 60 executing the processing of step S108 and step S120 or the processing of step S118 and step S120.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to the drawings. The internal combustion engine as the second embodiment of the present invention is realized by causing the ECU 60 to execute a routine shown in FIG. 4 described later in addition to the routine shown in FIG. 2 in the configuration of the first embodiment. .

  According to the routine shown in FIG. 2 described above, it is possible to avoid exhaustion of the battery 44 due to pre-assist by increasing the idle speed. However, an increase in the idling speed also causes an increase in combustion noise. Therefore, in the engine control according to the present embodiment, when the idle speed is increased during pre-assist, after-injection is performed in which part of the fuel is injected after compression top dead center. By dividing and injecting the fuel into main injection and after injection, rapid ignition can be avoided and the combustion pressure can be reduced, and an increase in combustion noise accompanying an increase in the idle speed can be suppressed. Hereinafter, the engine control during idling according to the present embodiment will be described with reference to FIG.

  In the first step S200 of the routine shown in FIG. 4, the engine speed NE, the accelerator opening ACCP, and the vehicle speed SPD are acquired. In the next step S202, it is determined whether or not pre-assist is currently being performed. If pre-assist is not being performed, this routine ends.

  If pre-assist is being performed, the determination in step S204 is performed. In step S204, it is determined whether or not the engine speed NE is higher than a predetermined reference speed NEib. This reference rotational speed NEib is set to a value equal to or higher than the above-described base idle rotational speed NEia. If the engine speed NE is equal to or lower than the reference speed NEib, this routine ends.

  If the engine speed NE is higher than the reference speed NEib, the processes of step S206 and step S208 are performed. First, in step S206, an after injection interval Aintplaf (° CA ATDC) and an after injection amount Qplaf (mm3 / st) are calculated from a map preset in the ECU 60 based on the engine speed NE and the accelerator opening ACCP. Is done. The after injection interval Aintplaf is a crank angle at which after injection is started, and the after injection amount Qplaf is a fuel amount injected by the after injection.

  In the next step S208, after injection is executed according to the after injection interval Aintplaf and the after injection amount Qplaf obtained in step S206. After the process of step S208, the process returns to step S202, and the processes of step S202 to step S208 are repeatedly performed until the pre-assist stops or until the engine speed NE becomes equal to or lower than the reference speed NEib.

  According to the routine described above, when the idle speed is increased during pre-assist, an increase in combustion noise accompanying an increase in the idle speed can be suppressed. In addition, the generation of smoke can be suppressed by the stirring effect generated by the combustion of the fuel after-injection. Furthermore, after-injection can increase the exhaust gas temperature by increasing the exhaust gas temperature. By recovering the increased exhaust energy by the turbine 54, the rotational speed of the compressor 52 can be increased and the start acceleration performance can be further enhanced.

  In the present embodiment, the “divided injection means” according to the seventh aspect of the present invention is implemented by the ECU 60 executing the routine shown in FIG.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  According to the configuration of FIG. 1, the motor 56 of the MAT 50 can be used as a generator (second generator) separately from the alternator (first generator) 40 that is connected to the crankshaft and driven. By using the electric motor 56 as a generator, the exhaust energy of the engine can be recovered as electric energy and the battery 44 can be charged. However, in the routine shown in FIG. 2, the alternator 40 is used in preference to the electric motor 56 as means for charging the battery 44 with electric power. This is because if the electric motor 56 is operated as a generator, the emission characteristics may be deteriorated due to a sudden change in exhaust pressure.

  In the configuration of FIG. 1, the present invention is applied to a diesel engine, but the present invention can also be applied to other internal combustion engines such as a gasoline engine. Moreover, although the turbocharger is used as the supercharger, in the present invention, the supercharger may be an electric compressor that drives the compressor only by the electric motor.

1 is a schematic configuration diagram of an internal combustion engine as Embodiment 1 of the present invention. It is a flowchart which shows the routine of the engine control at the time of idling implemented in Embodiment 1 of this invention. It is a figure which shows the relationship between a battery voltage and the setting value of an engine speed. It is a flowchart which shows the routine of the engine control at the time of idling implemented in Embodiment 2 of this invention.

Explanation of symbols

2 Engine body 4 Intake manifold 6 Exhaust manifold 8 Intake pipe 10 Exhaust pipe 36 Injector 38 Common rail 40 Alternator 44 Battery 50 MAT (turbocharger with electric motor)
52 Compressor 54 Turbine 56 Electric motor 58 Motor controller 60 ECU
62 Engine speed sensor 64 Accelerator opening sensor 66 Vehicle speed sensor

Claims (8)

A generator that generates electric power using the energy of the internal combustion engine, a battery that charges the electric power generated by the generator, an electric motor that operates by receiving electric power supplied from the battery, and an overdrive driven by the electric motor A control device for an internal combustion engine having a feeder,
Pre-assist means for driving the supercharger by the electric motor during idle operation and increasing the rotational speed of the supercharger prior to starting the vehicle;
Idle rotation speed increasing means for increasing the idle rotation speed of the internal combustion engine and increasing the generated power of the generator when the voltage of the battery is lower than a predetermined charging reference voltage;
A control device for an internal combustion engine, comprising:   2. The apparatus according to claim 1, further comprising pre-assist start prohibiting means for prohibiting the pre-assist start by the pre-assist means when the voltage of the battery is lower than a predetermined start voltage set to be equal to or lower than the charge reference voltage. The internal combustion engine control device described.   The pre-assist means for stopping the pre-assist in the pre-assist means when the voltage of the battery falls below a stop voltage set lower than the start voltage during pre-assist. 3. A control device for an internal combustion engine according to 2.   The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the idle speed increasing means sets a target idle speed in accordance with a voltage of the battery.   5. The control device for an internal combustion engine according to claim 4, wherein the idle speed increasing means increases the target idle speed as the voltage difference between the charging reference voltage and the battery voltage increases.   The internal combustion engine has a first generator connected to a crankshaft as the generator and driven, and a second generator driven by the exhaust energy of the internal combustion engine, and the idle speed increasing means is the first generator. The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the generator is used preferentially.   7. The split injection unit according to claim 1, further comprising a split injection unit that injects a part of the fuel after the compression top dead center when the idle rotation speed is higher than a predetermined reference rotation speed. Control device for internal combustion engine.   The turbocharger has an exhaust turbine disposed in an exhaust passage of an internal combustion engine, and is configured as a turbocharger that rotates using exhaust energy of the internal combustion engine received by the exhaust turbine. 8. A control device for an internal combustion engine according to claim 7.

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