JP2006329065A - Internal combustion engine for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate air quantity inside a cylinder at the time of return from fuel cut. <P>SOLUTION: Intake air quantity GAA measured by an air flow meter is read (Step S10), and remaining air quantity GAE is calculated (Step S20). Whether or not fuel cut is being performed is determined (Step S30). When it is determined that fuel cut is being performed, rotation quantity of a rotation quantity counter for counting rotation quantity after return from fuel cut is cleared (Step S40), and when it is determined that fuel cut is not being performed, such rotation quantity is not cleared. Then, it is determined whether or not the number of the rotation quantity after return from fuel cut exceeds two (Step S50). When it is determined that the number exceeds two, the intake air quantity GAA is regarded as air quantity GACY inside the cylinder without changing (Step S60). When it is determined that the number does not exceed two, air quantity obtained by adding the remaining air quantity GAE to the intake air quantity GAA is regarded as the air quantity GACY inside the cylinder (Step S70). Fuel injection quantity achieving a target air fuel ratio with respect to the air quantity GACY inside the cylinder is determined. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly to a vehicle internal combustion engine having a fuel cut mechanism.

The amount of intake air supplied to a combustion chamber in an internal combustion engine is also a basis for calculating the amount of fuel to be mixed, and is a very important parameter. This intake air amount is often measured by an air flow meter or a pressure sensor provided in the intake pipe.
By the way, in general, in an internal combustion engine, the valve opening period is set so that the intake valve and the exhaust valve have an overlap period. As a result, so-called internal EGR occurs in which the gas once exhausted is sucked again. The mixture of the air newly sucked through the air cleaner and the fuel injected from the fuel injection valve is further mixed with the exhaust gas from the internal EGR and burned in the combustion chamber.

  On the other hand, many internal combustion engines for vehicles include a so-called fuel cut that stops fuel supply between two predetermined speeds while the vehicle is coasting to reduce fuel consumption. At the time of recovery from the fuel cut, the internal EGR gas is not burned up to that point, so it is not exhaust gas but new air. Therefore, in such a case, a larger amount of air than the amount of intake air measured by the intake pipe is introduced into the combustion chamber. Therefore, if the fuel amount is determined in accordance with the intake air amount measured by the air flow meter, there is a possibility that the air-fuel mixture becomes leaner than planned and NOx increases. For this reason, it is required to accurately keep the amount of air when returning from the fuel cut.

The invention of Patent Document 1 relates to the relationship between the fuel cut and the internal EGR rate, but estimates the internal EGR amount during the fuel cut and when returning from the fuel cut, and the actual air amount introduced into the cylinder Is not exactly accurate.
The invention of Patent Document 2 tries to stop the internal EGR accurately. However, the actual amount of air introduced into the cylinder when returning from the fuel cut is not accurately determined.

JP 2002-227687 A JP 2001-221105 A

  In view of the above situation, an object of the present invention is to accurately determine the actual air amount in a cylinder when returning from a fuel cut in an internal combustion engine for a vehicle.

According to the invention of claim 1, in the internal combustion engine for a vehicle, the fuel cut is performed between two predetermined speeds when the vehicle coasts,
An intake air amount detecting means for detecting an intake air amount sucked into the cylinder through the intake pipe;
An overlap amount detecting means for detecting the valve overlap amount of the intake valve and the exhaust valve;
A residual air amount calculating means for calculating a residual air amount remaining in the cylinder based on a valve overlap amount;
During normal operation, the intake air amount detected by the intake air amount detection means is the total intake air amount,
When returning from the fuel cut, the total intake air amount is obtained by adding the residual air amount to the intake air amount detected by the intake air amount detection unit,
An internal combustion engine configured to determine a fuel injection amount based on a total intake air amount is provided.

  In the internal combustion engine configured as described above, when returning from the fuel cut, the fuel injection amount is determined with respect to the correct air amount obtained by adding the cylinder residual air amount to the air amount sucked through the intake pipe. A target air-fuel ratio can be obtained.

According to the second aspect of the present invention, in the first aspect of the invention, the internal combustion engine is a four-cycle engine, and the remaining air amount is detected by the intake air amount detected by the intake air amount detecting means for two rotations after the fuel cut is restored. An internal combustion engine is provided in which the residual air amount calculated by the calculating means is added to obtain a total air amount.
In a four-cycle engine, since the air discharged from the exhaust valve is rotated twice as residual air and combusted with the intake air, the total intake air is obtained by adding the residual air amount to the intake air amount for the two rotations after the fuel cut is restored. Quantities.

According to the invention of claim 3, in the invention of claim 1, the variable valve timing mechanism capable of changing the overlap amount of the intake valve and the exhaust valve is provided, and the residual air when the valve overlap is maximum in each operating condition. A maximum residual air amount that is an amount and an internal residual air amount ratio that is a ratio of the residual air amount to the maximum residual air amount in each valve overlap amount,
The maximum internal residual air amount determined according to the detected operating condition is multiplied by the internal residual air amount ratio in the detected valve overlap amount to obtain the residual air amount.

  According to the present invention, the intake air amount is accurately determined at the time of return from the fuel cut, and the fuel injection amount is determined for the intake air amount, so that the target air-fuel ratio can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing a hardware configuration common to the embodiments of the present invention.
Reference numeral 1 denotes a spark ignition internal combustion engine. The internal combustion engine 1 includes a cylinder head 1a and a cylinder block 1b. The cylinder head 1 a includes an intake port 5, an exhaust port 6, an intake valve 7, an exhaust valve 8, and an ignition plug 40, and a high voltage current is supplied to the ignition plug 40 from an ignition coil 41.

  The piston 2 connected to the crankshaft 3 reciprocates in the cylinder block 1b, and a combustion chamber 1c is formed between the piston 2 and the cylinder head 1a. A crank angle sensor 52 is attached to the cylinder block 1b, and the engine speed is calculated based on a signal from the crank angle sensor 52.

An intake valve timing adjustment device 70 that adjusts the phase of the valve opening period of the intake valve 7 in accordance with operating conditions is attached to the intake cam 7c.
FIG. 2 is a diagram for explaining the structure of the intake valve timing adjustment device 70.
The intake valve timing adjusting device 70 has a housing part 71 and a vane part 72. The housing part 71 is fixed to a gear 75 driven by the crankshaft 3 (see FIG. 1) via a chain (not shown). The vane portion 72 is fixed to the intake camshaft 7c.

  Three hydraulic chambers 73 are formed inside the housing portion 71, and three vanes 74 of the vane portion 72 are arranged in each hydraulic chamber 73. The angular width of the hydraulic chamber 73 is larger than the angular width of the vane 74, and the hydraulic chamber 73 is separated into an advance side hydraulic chamber 73a and a retard side hydraulic chamber 73r with the vane 74 interposed therebetween.

When the engine is stopped, the advance-side hydraulic chamber 73a is minimized and the retard-side hydraulic chamber 73r is maximized by an urging mechanism (not shown), and is set to the most retarded phase. During operation, the hydraulic pressure acting on the advance side hydraulic chamber 73a and the retard side hydraulic chamber 73r is adjusted via an oil control valve (not shown) so that an optimum phase is obtained for the operating conditions. Therefore, although not shown, a cam position sensor for detecting the cam position is attached.
In addition, what is necessary is just to attach the exhaust valve timing adjustment apparatus of the same structure to the exhaust cam 8c, when adjusting the phase of the valve opening period of the exhaust valve 8 according to an operating condition.

  In FIG. 1, a fuel injection valve 31 for injecting fuel into the intake port 5 is attached to the cylinder head 1a. Fuel is supplied to the fuel injection valve 31 from a fuel tank 30 by a fuel pump (not shown) via a fuel pipe (not shown).

  An intake pipe 10 is connected to the intake port 5, and an air cleaner 11 is attached to the upstream end of the intake pipe 10. An air flow meter 51 for detecting the intake air amount is disposed immediately downstream of the air cleaner 11. A throttle valve 12 is disposed downstream of the air flow meter 51. The throttle valve 12 is driven by a throttle motor 13. On the other hand, an accelerator pedal sensor 50 for detecting the depression amount of the accelerator pedal 14 is attached to the accelerator pedal 14, and the throttle valve 12 is operated by the throttle motor 13 in accordance with the depression amount of the accelerator pedal 14 detected by the accelerator pedal sensor 50. The degree of opening is changed.

  An exhaust pipe 20 is connected to the exhaust port 6, and a three-way catalyst 21 is disposed in the exhaust pipe 20. A first air-fuel ratio sensor 22 is disposed near the upstream side of the three-way catalyst 21, and a second air-fuel ratio sensor 23 is disposed near the downstream side of the three-way catalyst 21. The exhaust gas generated in the combustion chamber 1a is led to the exhaust pipe 20 through the exhaust port 6 whose flow path is opened and closed by the exhaust valve 8, and is purified by the three-way catalyst 21 before being discharged. The fuel injection amount injected from the port injection valve 31 and the in-cylinder injection valve 32 is feedback controlled so that a predetermined air-fuel ratio is obtained based on the outputs of the first air-fuel ratio sensor 22 and the second air-fuel ratio sensor 23.

  An electronic control unit (hereinafter referred to as ECU) 100 is formed by connecting an input port 101, an output port 102, a CPU 103, a ROM 104, a RAM 105, and the like with a common bus. A signal detected by each sensor is input to the ECU 100, and a control signal for performing control related to the present invention is sent to each actuator.

Hereinafter, the control of the embodiment of the present invention configured as described above will be described.
FIG. 3 is a flowchart of the control according to the embodiment of the present invention, and will be described below for each step. In step S10, the intake air amount GAA measured by the air flow meter 51 is read. In step S20, a residual air amount GAE is calculated. FIG. 4 is a subroutine for calculating the residual air amount GAE in step S20, the details of which will be described later.

  In step S30, it is determined whether or not the fuel cut is in progress. If the determination is affirmative, the rotation amount counter that counts the rotation amount after returning from the fuel cut is cleared in step S40, and then the process proceeds to step S50. If a negative determination is made, the process proceeds directly to step S50. The rotation amount counter is provided in a circuit in the ECU 100 and counts the rotation amount based on a signal from the crank angle sensor 52.

In step S50, it is determined whether or not the rotation amount after returning from the fuel cut is 2 or more. This is because in a four-cycle engine, it is necessary to make two revolutions in order for the air discharged from the exhaust valve to be burned as residual air together with the intake air. If an affirmative determination is made, the process proceeds to step S60, and the intake air amount GAA measured by the air flow meter 51 is directly used as the intake air amount GACY of the cylinder. The residual air amount GAE calculated in step S20 is added to the cylinder intake air amount GACY. In step S80, the rotation amount counter is incremented and the process ends.
Although not shown in the flowchart, the fuel injection amount is determined so as to obtain the required air-fuel ratio based on the intake air amount GACY of the cylinder stopped in steps S60 and S70.

Next, a subroutine for calculating the residual air amount GAE in step S20 of FIG. 3 will be described with reference to FIG.
In step S21, the overlap amount OL between the intake valve 7 and the exhaust valve 8 is read. In step S22, the rotational speed NE is read. In step S23, the intake pipe pressure PM is read. In step S24, the basic residual air amount GAEB is calculated based on the map shown in FIG. 5 from the rotational speed NE read in step S22 and the intake pipe pressure PM read in step S23. In step S25, the intake air read in step S21. Based on the overlap amount OL between the valve 7 and the exhaust valve 8, reading is performed based on the map shown in FIG. 6, and the correction coefficient KOL of the basic residual air amount GAEB corresponding to the overlap amount OL is calculated. In step S26, the residual air amount GAE is calculated by multiplying the basic residual air amount GAEB calculated in step S24 by the correction coefficient KOL calculated in step S26.

  As described above, the fuel injection amount is calculated based on the intake air amount GACY of the cylinder. If the intake air amount GACY of the cylinder has not completely returned from the fuel cut, the residual air amount is calculated as in step S70. Since the calculation is performed by adding the remaining fuel amount of the calculated fuel cut, the air amount is assumed to be highly accurate close to the actual state. Therefore, the amount of air that is the basis of the fuel injection amount is set to a value that is smaller than the actual value, and as a result, the air is prevented from becoming lean relative to the actual air amount and the air-fuel ratio becoming lean.

  The present invention can be applied to an internal combustion engine, and particularly when applied to an internal combustion engine for a vehicle having a fuel cut mechanism that stops fuel injection between two predetermined large and small speeds when the vehicle is coasting. Therefore, it is possible to accurately obtain the amount of intake air at the time of return from and to prevent the air-fuel ratio from deviating.

It is a figure which shows the hardware constitutions of embodiment of this invention. It is a figure which shows the structure of VVT for shifting the valve opening period of an intake valve. It is a flowchart of control of the present invention. It is a flowchart of the subroutine of step S20 of the flowchart of FIG. 5 is a map used for calculation in step S24 in the flowchart of FIG. 5 is a map used for calculation in step S25 of the flowchart of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 7 Intake valve 8 Exhaust valve 10 Intake manifold 12 Intake pipe 13 Air cleaner 30 Fuel injection valve 50 Crank angle sensor 51 Air flow meter 70 Intake valve timing adjustment apparatus 100 ECU (electronic control unit)

Claims (3)

An internal combustion engine for a vehicle that performs a fuel cut between two predetermined speeds when the vehicle coasts.
An intake air amount detecting means for detecting an intake air amount sucked into the cylinder through the intake pipe;
An overlap amount detecting means for detecting a valve overlap amount of the intake valve and the exhaust valve;
A residual air amount calculating means for calculating a residual air amount remaining in the cylinder based on a valve overlap amount;
During normal operation, the intake air amount detected by the intake air amount detection means is the total intake amount,
When returning from the fuel cut, the total intake air amount is obtained by adding the residual air amount to the intake air amount detected by the intake air amount detecting unit,
Determine the fuel injection amount based on the total intake amount,
An internal combustion engine characterized by that.   The internal combustion engine is a four-cycle engine, and for the two rotations after the fuel cut is restored, the residual air amount calculated by the residual air amount calculating means is added to the intake air amount detected by the intake air amount detecting means to obtain the total air amount The internal combustion engine according to claim 1, wherein: Equipped with a variable valve timing mechanism that can change the amount of overlap between the intake and exhaust valves,
The maximum residual air amount that is the residual air amount when the valve overlap is the maximum in each operating condition and the internal residual air amount ratio that is the ratio of the residual air amount to the maximum residual air amount in each valve overlap amount in advance Remember,
Multiply the maximum internal residual air amount determined according to the detected operating conditions by the internal residual air amount ratio in the detected valve overlap amount to obtain the residual air amount.
The internal combustion engine according to claim 1.

Images