Internal combustion engine, and control apparatus and method thereof
The amount of air to be introduced is controlled for each cylinder, whereby it is intended to make it possible to control the torque generated in each cylinder, perform an ultra-lean burn operation, purify the exhaust gas, and increase the output of an engine. An air flow control valve adapted to be on-off controlled in accordance with an operated quantity of an accelerator pedal is disposed in each branch pipe or intake port. The air flow control valve may be a throttle valve disposed in each branch pipe or it may be a variable intake valve for opening and closing the intake port.
The present invention relates to an apparatus and method for controlling an internal combustion engine, capable of adjusting the amount of air to be fed to each cylinder in accordance with an operated quantity of an accelerator pedal.
The present invention is also concerned with an internal combustion engine itself.
BACKGROUND ARTIn a conventional internal combustion engine, an air flow control valve called a throttle valve is disposed in a main intake pipe, and this throttle valve is on-off controlled, for example, in accordance with a displacement of an accelerator pedal and is branched downstream into branch pipes connected to cylinders.
In a control apparatus for an internal combustion engine which is known in Japanese Patent Laid Open No. Hei 1-271634 for example, in addition to the above configuration, the fuel injection volume is adjusted so as to eliminate a difference in output torque for each cylinder detected by a crank angle sensor and it is compensated in response to a pressure variation detected by an internal cylinder pressure sensor.
In the above prior art, the air passage length from the throttle valve to each cylinder is too long and there occurs a delay in a change of air volume controlled by the throttle valve, thus giving rise to a problem that it is impossible to obtain an optimum air volume for each cylinder. There also has been a problem that the branch pipes connected to cylinders are different in length and shape, thus making it impossible to distribute air uniformly to the cylinders.
Thus, since the amount of air required for each cylinder cannot fed accurately, even if the amount of fuel is controlled for each cylinder, it has so far been impossible to accurately control the output torque for each cylinder.
Due to consequent unevenness in torque for each cylinder, the output of the entire internal combustion engine is lowered and a limit has so far encountered in fuel economy improving measures or emission improving measures, such as lean burn control, ultra-lean burn control, and cylinder-direct fuel injection control.
DISCLOSURE OF INVENTIONThe present invention has been accomplished for solving the above-mentioned problems and it is the first object of the invention to make it possible to control the amount of intake air for each cylinder in an internal combustion engine.
It is the second object of the present invention to make it possible to control the output torque for each cylinder in an internal combustion engine.
It is the third object of the present invention to diminish a pumping loss between an air flow control valve and each cylinder and/or eliminate unevenness in air distribution caused by the difference in shape of branch pipes.
It is the fourth object of the present invention to make it possible to control the amount of air to be fed to each cylinder more accurately in response to the amount of operation (say, displacement) of an accelerator pedal.
It is the fifth object of the present invention to make it possible to accurately control the amount of exhaust gas to be recirculated in an internal combustion engine provided with an exhaust gas recirculation system (EGR system).
The above first object is achieved by disposing an air flow control valve in each of branch pipes branched from a main intake pipe or in an intake port of each cylinder, the air volume control valve controlling the amount of intake air in response to an operated quantity of an accelerator pedal.
The second object is achieved by providing an air flow control valve for each cylinder to control the amount of intake air and by compensating the degree of opening of the air flow control valve in accordance with a required output torque for each cylinder.
The third object is achieved by controlling an opening/closing timing or stroke of an intake valve which is for opening and closing an intake port of each cylinder and thereby controlling the amount of intake air for each cylinder.
The fourth object is achieved by disposing a throttle valve in each branch pipe or intake port, the throttle valve being controlled its opening and closing motions in accordance with an operated quantity of an accelerator pedal.
The fifth object is achieved by providing a reverse flow detection type air flow sensor capable of detecting the amount of air flowing through each branch pipe, including the amount of air reverse-flowing through each branch pipe and by controlling an opening/closing timing of an intake valve disposed in an intake port of each cylinder.
BRIEF DESCRIPTION OF DRAWINGS
Embodiments of the present invention will be described below with reference to the drawings.
In an operational region wherein the engine speed is low and the engine torque is small, as shown in
In this embodiment, in the case where the throttle valve 10 as an air control valve for controlling the flow rate of air is provided in each branch pipe 11 and is controlled in accordance with an operated quantity (displacement) of the accelerator pedal, the intake valve 16 may be controlled by a mechanical cam mechanism.
Even where the intake valve 16 is actuated electromagnetically, the air flow control may be taken charge of by only the throttle valve 10 while controlling the intake valve 16 merely as an ON-OFF valve.
Conversely, in a low load, low speed operation region, the throttle valve 10 may be fully opened irrespective of an operated quantity of the accelerator pedal and the stroke and/or opening/closing timing of the intake valve 16 may be controlled as a function of the operated quantity of the accelerator pedal.
Further, where the stroke and/or opening/closing timing of the intake valve 16 are controlled over the whole operational region of the engine, the throttle valve 10 may be omitted as in the system shown in
In this case, the throttle valve 10 may also be used as a traction control valve. To be more specific, the control of air flow according to an operated quantity of the accelerator pedal is performed by the intake valve 16, while upon occurrence of skidding of a wheel, the throttle valve 10 is closed to suppress the engine output torque and prevent wheel skidding, irrespective of an operated quantity of the accelerator pedal, that is, irrespective of in what state the intake valve 16 is controlled. In this case, therefore, the throttle valve 10 assumes a fully open position in normal condition.
As shown in
When voltage is applied to the solenoid 19 as in
Reference is now made to
In the prior art, a throttle valve is disposed in a main intake pipe located upstream of a joining portion of branch pipes to control the amount of air to be introduced into the engine. However, if the size of each intake pipe is reduced for the reduction of weight, the shape of the intake pipe is restricted and this restriction, as well as the deterioration of engine, give rise to a problem that the amount of air required for each cylinder is different.
On the other hand, in this embodiment of the present invention, the amount of air to be introduced into each cylinder can be adjusted accurately by controlling the air flow control valve (one or both of the throttle valve 10 and the intake valve 16 provided in each intake port) in accordance with an operated quantity (say, displacement) of the accelerator pedal. Besides, since the distance between the air flow control valve and the cylinder can be made short, it is possible to diminish variations in the amount of air and pumping loss caused by the difference in shape of intake passages.
In the conventional torque control for each cylinder, the difference in output torque among cylinders is compensated by adjusting the amount of fuel to be injected, so there arise variations in the air/fuel ratio among cylinders. Consequently, the state of exhaust gas discharged from the engine becomes worse and the use at a low catalytic efficiency obstructs a satisfactory purification of exhaust gas. Therefore, for equalizing the cylinders in the amount of air introduced therein, there arise restrictions in the shape of intake pipes, which is an obstacle to the attainment of size reduction.
An ultra-lean burn operation by a cylinder-direct fuel injection engine is effective for the improvement of fuel economy. In such an engine, the throttle valve is opened as large as possible to decrease the pumping loss. In a lean burn operation, however, a three-way catalytic converter is not employable, so it becomes necessary to decrease the amount of NOx in lean operation. For the decrease of NOx, not only the development of an effective catalyst but also EGR is effective. Particularly, the addition of much EGR is possible in cylinder-direct fuel injection and, because of operation in an open condition of the throttle valve, the internal pressure of each intake pipe approaches the atmospheric pressure and the difference between the exhaust pressure and the intake pressure becomes small. For these reasons there arises a problem that a pipe for EGR which connects the exhaust pipe and the intake pipe, as well as an EGR control valve, become larger in size. To solve this problem, studies are being made about a method of adjusting the opening/closing timing of the intake/exhaust valves, thereby controlling the internal EGR and decreasing NOx. However, since the valve opening/timing is controlled using a map to control the internal EGR, it is difficult to effect a highly accurate internal EGR control.
According to this embodiment of the present invention, since the amount of fuel is controlled in an independent manner, it becomes possible to control the engine torque for each cylinder without deteriorating the emission of exhaust gas. Moreover, it is possible to improve the control accuracy for the internal EGR.
In this embodiment, there are used a torque detecting means for each cylinder in the engine and an air quantity/fuel quantity control means for controlling the torque for each cylinder, an air flow control valve for controlling for each cylinder the amount of air to be introduced into each cylinder is disposed upstream of each intake port, and the air flow control valve is varied according to the degree of opening of the accelerator pedal to control the amount of air, thereby controlling the engine output torque. Further, the amount of air introduced into each cylinder is detected by a reverse flow detection type air flow sensor, and in accordance with an output signal provided from the said sensor the on-off condition of the air flow control valve is feedback-controlled, whereby the accuracy of the air flow control made by the air flow control valve can be improved.
Further, a more accurate EGR control can be attained by controlling the intake valve opening/closing timing in accordance with signal provided from the reverse flow detection type air flow sensor which detects a reverse flow including internal EGR from the engine. One reason why the fuel economy is not improved in an internal combustion engine is that there still remains a pumping loss in a low and medium load region. Another reason is that in a high load condition the air/fuel ratio is set to an overrich value relative to the stoichiometric air/fuel ratio. In this embodiment, while the pumping loss in a low and medium load condition is diminished to a great extent, the occurrence knocking can be suppressed even if the air/fuel ratio is set lean in a high load condition.
According to this embodiment, as described above, since the amount of air can be controlled accurately for each cylinder, there is no fear of worsening of the exhaust emission even if there is made a lean burn control or an ultra-lean burn control.
Moreover, since the output torque for each cylinder can be controlled more accurately, the total engine output is improved.
Further, it is possible to decrease the pumping loss in the air passage between the air flow control valve and each cylinder.
Additionally, if there is used a reverse flow detection type air flow sensor which detects a reverse flow including internal EGR from the engine and the intake valve opening/closing timing is controlled in accordance with a signal provided from the said sensor, it is possible to control the internal EGR with a high accuracy.
Claims
1. An apparatus for controlling an internal combustion engine, comprising:
- means for determining a required amount of air for each cylinder in the engine;
- a control circuit which produces a control signal in accordance with an output of said determining means;
- an intake valve disposed in an intake port of each cylinder in the internal combustion engine;
- an actuator which controls at least one of an opening/closing timing and stroke of said intake valve in accordance with the control signal outputted from said control circuit; and
- an air flow control valve arranged in each branch passage of the internal combustion engine upstream of each intake port and is operable such that the required amount of intake air is controlled by said intake valve and said air flow control valve.
2. A method for controlling an internal combustion engine, comprising controlling at least one of opening/closing timing and stroke of at least one of intake and exhaust valves in an engine in accordance with a determined amount of air required for each cylinder of the internal combustion engine, and operating an air flow control valve arranged in each branch passage of the internal combustion engine upstream of each intake port of the internal combustion engine to control intake air with the respective intake valves and air flow control valve at each cylinder of the internal combustion engine.
3. An internal combustion engine provided with intake valves for controlling the opening and closing of intake ports formed in cylinders, wherein at least one of opening/closing timing and stroke of at least one of intake and exhaust valves in an engine is controllable in accordance with a determined amount of air required for each cylinder of the internal combustion engine, wherein the on-off condition of each said intake valve is defined as a function of an operated quantity of an accelerator pedal, and
- an air flow control valve arranged in each branch passage of the internal combustion engine upstream of each intake port and is operable such that the required amount of intake air is controlled by said intake valve and said air flow control valve.
4. A method for controlling an output torque of an internal combustion engine in accordance with the degree of opening of an accelerator pedal, comprising controlling at least one of opening/closing timing and stroke of at least one of intake and exhaust valves in an engine in accordance with a determined amount of air required for each cylinder of the internal combustion engine, controlling said output torque in accordance with the on-off condition of each intake valve provided in the engine, and operating an air flow control valve arranged in each branch passage of the internal combustion engine upstream of each intake port of the internal combustion engine to control intake air with the respective intake valves and air flow control valve at each cylinder of the internal combustion engine.
5. The method according to claim 5, wherein an intake quantity detecting sensor is provided and the on-off condition of the intake valve is feedback-controlled in accordance with an output signal provided from said intake quantity detecting sensor.
6. The method according to claim 5, wherein an internal cylinder pressure sensor for detecting an internal cylinder pressure is provided and the on-off condition of the intake valve is feedback-controlled in accordance with an output signal provided from said internal cylinder pressure sensor.
7. A method according to claim 5, wherein a torque sensor for detecting a rotational torque of the engine is provided and the on-off condition of an intake valve is controlled in accordance with an output signal provided from said torque sensor.
8. An internal combustion engine provided with intake valves for controlling opening and closing of intake ports formed in cylinders and an air flow sensor for detecting the amount of air introduced into the cylinders, wherein at least one of opening/closing timing and stroke of at least one of intake and exhaust valves in an engine is controllable in accordance with a determined amount of air required for each cylinder of the internal combustion engine, wherein the on-off condition of each said intake valve is defined as a function of both an operated quantity of an accelerator pedal and an output signal provided from said air flow sensor, and
- an air flow control valve arranged in each branch passage of the internal combustion engine upstream of each intake port and is operable such that the required amount of intake air is controlled by said intake valve and said air flow control valve.
9. An apparatus for controlling an internal combustion engine operated by introducing air from intake ports of cylinders, comprising a variable intake valve arrangement associated with each of the cylinders, and an air flow control valve is provided in each branch passage upstream of each intake port such that the required amount of air to be introduced into each of the cylinders is controllable by the respective intake valve arrangement and said air flow control valve at each cylinder.
10. A method according to claim 2, wherein the output torque of each cylinder is controlled by controlling the required amount of air to be introduced into each cylinder.
11. A variable intake valve mechanism in an internal combustion engine, comprising:
- an intake valve for opening and closing each intake port formed in each cylinder;
- a motor-driven actuator for actuating said intake valve electrically;
- a control circuit which produces a control signal for said motor-driven actuator,
- wherein said control circuit produces the control signal for said motor-driven actuator in accordance with an amount of air determined to be required for each cylinder so as to vary at least one of the opening/closing time and stroke of the intake valve of each cylinder, and
- an air flow control valve arranged in each branch passage of the internal combustion engine upstream of each intake port and is operable such that the required amount of intake air is controlled by said intake valve and said air flow control valve.
12. An apparatus for controlling the torque of an internal combustion engine, comprising:
- branch pipes connected respectively to intake ports in cylinders to feed air to the cylinders;
- a main intake pipe connected to an upstream side of said branch pipes to introduce air to the branch pipes;
- a reverse flow detection type air flow sensor disposed in said main intake pipe and capable of measuring an amount of air flow through each said branch pipe, including the amount of air reverse flowing through the branch pipe;
- a torque measuring means for measuring an output torque of the engine;
- an air flow control valve for controlling the amount of air flowing through each said branch pipe in accordance with an amount of air determined to be required for each of the cylinders so as to control at least one of opening/closing timing and stroke of the intake valve of each cylinder; and
- an air flow control valve opening compensating means for compensating the degree of opening of said air flow control valve in accordance with a variation in output of said torque measuring means to adjust the amount of air flowing through each said branch pipe.
Type: Application
Filed: Jun 9, 2006
Publication Date: Oct 12, 2006
Inventors: Toshiharu Nogi (Hitachinaka), Takuya Shiraishi (Hitachinaka), Minoru Ohsuga (Hitachinaka), Youko Nakayama (Hitachinaka), Noboru Tokuyasu (Hitachinaka)
Application Number: 11/449,846
International Classification: F02D 9/10 (20060101); F02D 13/00 (20060101);