JP2004245104A - Supercharging type engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercharging type engine capable of improving acceleration responsiveness by improving turbo lug in a simple constitution where opening and closing timing of an existing intake/exhaust valve is adjusted. <P>SOLUTION: The supercharging type engine comprises a supercharger 22 for supercharging intake air by driving a turbine 24 and a compressor 23 by exhaust stream of the engine 1, a variable valve timing mechanism 13 for changing valve overlap by altering opening/closing timing of at least one of an intake valve 7 and an exhaust valve 9 of the engine, and an electronic control unit 12 for controlling the variable valve timing mechanism 13 with an acceleration request detecting section for detecting an acceleration request of a driver. When the acceleration request detecting section detects the acceleration request of the driver, the electronic control unit 12 controls the variable valve timing mechanism 13 to enlarge the valve overlap. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a supercharged engine provided with a supercharger (turbocharger) that drives a turbine and a compressor by an exhaust flow of the engine to supercharge intake air.
[0002]
[Prior Art and Problems to be Solved by the Invention]
Since the supercharged engine drives the compressor (compressor) using the energy of the exhaust gas, the operating state (the number of revolutions) of the compressor is such that the occupant operates the accelerator (intake throttle valve) like the engine body. Can not be controlled directly. In addition, since the number of revolutions of the compressor greatly depends on the state of exhaust gas (the amount and pressure of exhaust gas), when the number of revolutions of the supercharged engine is low and the amount of exhaust gas and pressure are low, the occupant accelerates the vehicle. Even if the opening of the accelerator is increased as much as possible, the amount of exhaust and pressure will not rise immediately in conjunction with this, causing the phenomenon that the rotation speed of the compressor does not increase with the increase of the opening of the accelerator (Hereinafter, this phenomenon is called turbo lag.)
[0003]
In order to reduce the turbo lag, conventional improvements have been made to the turbocharger body, such as a reduction in inertia (inertia weight), or air (secondary air) is sent into the exhaust gas in the exhaust manifold during deceleration to reburn. In this way, the exhaust energy is increased so that the rotation of the turbocharger is not reduced, which leads to the next acceleration.
[0004]
However, although the above method can be expected to have some effect, further improvement is desired in the market. In the case of reducing inertia, the capacity of the turbocharger itself is reduced.On the other hand, in the case of supplying secondary air, it is necessary to provide secondary air piping. There was a problem of becoming.
[0005]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a supercharged engine capable of improving turbo lag and improving acceleration responsiveness with a simple configuration of adjusting the opening and closing timing of existing intake and exhaust valves.
[0006]
Incidentally, as the above-described reburning method, after the main injection of fuel into the combustion chamber by the fuel injection valve, additional fuel is injected from the fuel injection valve at a time when the fuel can be reburned in the combustion chamber or in the exhaust passage near the combustion chamber. Patent Document 1 discloses that the additional fuel is reburned upstream of the turbine to increase the exhaust pressure in the exhaust passage and increase the rotation speed of the turbine. The technical idea is different from that of adjusting the opening / closing timing of the exhaust valve.
[0007]
On the other hand, as a method of adjusting the opening / closing timing of the intake and exhaust valves, the auxiliary intake valve is opened earlier than the main intake valve to increase the valve overlap with the exhaust valve, and the air-fuel mixture is supplied from the main intake valve. Patent Literature 2 discloses a configuration in which air is passed through a combustion chamber and blows through an exhaust valve to cool the combustion chamber, the exhaust valve, and the like. The purpose and configuration are different from those in which the exhaust energy is increased by reburning unburned HC in the exhaust gas.
[0008]
[Patent Document 1]
JP 2000-345889 A [Patent Document 2]
Japanese Utility Model Publication No. 4-10335
[Means for Solving the Problems]
In order to achieve the above object, a supercharged engine according to claim 1 of the present invention drives a turbine and a compressor by an exhaust flow of the engine to supercharge intake air, and an intake valve or exhaust of the engine. A valve overlap changing device that changes a valve overlap by changing an opening / closing timing of at least one of the valves; an acceleration request detecting unit that detects a driver's acceleration request; and a control unit that controls the valve overlap changing device. Wherein the control means controls the valve overlap changing device to increase the valve overlap when the acceleration request detection unit detects a driver's acceleration request. Features.
[0010]
Thereby, at the time of acceleration, the valve overlap is increased, and the unburned HC in the exhaust gas is reburned using the blow-by of the air, so that the exhaust energy is increased. As a result, the rotation speed of the turbocharger is increased earlier than usual, the increase in the intake air amount is accelerated, the speed of the increase in the torque is increased, and the feeling of acceleration is improved.
[0011]
The supercharged engine according to claim 2, wherein the control unit has an air-fuel ratio control unit that controls an air-fuel ratio of the engine, and the air-fuel ratio control unit controls the air-fuel ratio of the engine when a valve overlap is enlarged. It is characterized by enrichment.
[0012]
Thereby, at the time of acceleration, the unburned HC increases, and the fuel is reliably reburned.
[0013]
4. The supercharged engine according to claim 3, wherein the control means has an output estimating unit for estimating an output equivalent value of the engine, and the output equivalent value estimated by the output estimating unit after the valve overlap is enlarged is a target output. The valve overlap is continuously expanded until the value reaches the equivalent value, and when the target output equivalent value is reached, the valve overlap changing device controls the valve overlap to return to the value before the enlargement.
[0014]
As a result, after reaching the predetermined output, the valve overlap is returned to a steady state, and the adverse effect of the enlarged valve overlap is avoided.
[0015]
The invention according to claim 4 is characterized in that the control means performs control such that the valve overlap changing device enlarges the valve overlap more when the rotation speed of the engine is low than when the rotation speed is not so. And
[0016]
Thereby, the feeling of acceleration in the low-speed operation range is further improved.
[0017]
According to a fifth aspect of the present invention, a valve overrun is performed by changing a timing of opening and closing at least one of an intake valve and an exhaust valve of the engine by driving a turbine and a compressor with an exhaust flow of the engine to supercharge intake air. A valve overlap changing device for changing the lap, an operation region determining unit for determining whether or not a specific operating region in which the supercharging capability of the supercharger is reduced, and a control for controlling the valve overlap changing device Means, the control means, when the operating region determination unit determines that the supercharging ability of the supercharger is a specific operating region is low, the valve overlap changing device Is controlled to enlarge the valve overlap.
[0018]
As a result, the feeling of acceleration in a specific operating region where the supercharging ability of the supercharger is low is further improved.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a supercharged engine according to the present invention will be described in detail with reference to the drawings using embodiments.
[0020]
[Example]
FIG. 1 is a schematic configuration diagram of a supercharged engine showing first and second embodiments of the present invention, FIG. 2 is a flowchart showing a valve overlap control routine of the first embodiment of the present invention, and FIG. 7 is a graph of a specific operation region of the second embodiment.
[0021]
First, a first embodiment will be described.
As shown in FIG. 1, a supercharged engine (hereinafter, referred to as an engine) 1 has a combustion chamber 5 defined by a cylinder head 2, a cylinder block 3, and a piston 4 housed in the cylinder block 3. .
[0022]
A spark plug 6 is mounted at the center of the combustion chamber 5, and an intake port 8 opened and closed by an intake valve 7 and an exhaust port 10 opened and closed by an exhaust valve 9 communicate with each other so as to face each other. The ignition plug 6 is connected to an electronic control unit (hereinafter, referred to as ECU) 12 as control means via an ignition coil 11, and its ignition timing and the like are controlled according to the operating state of the engine 1. I have. The ECU 12 includes a microcomputer including an input / output device, a storage device (ROM, RAM, and the like), a central processing unit (CPU), a timer counter, and the like.
[0023]
The intake valve 7 is provided with a variable valve timing mechanism (VVT) 13 as a valve overlap changing device. The variable valve timing mechanism 13 drives, for example, a helical geared piston with hydraulic pressure, changes the phase of the camshaft and the timing pulley to change the opening / closing timing of the intake valve 7, and thereby controls the intake and exhaust valves 7,9. It is well known to change valve overlap. The variable valve timing mechanism 13 is also controlled by the ECU 12 via the hydraulic switching valve (not shown) according to the operating state of the engine 1.
[0024]
An intake manifold 14 is communicatively connected to the intake port 8, and an intake pipe 15 is communicatively connected to the intake manifold 14, and an air cleaner 16 is attached to a tip of the intake pipe 15. On the other hand, an exhaust manifold 17 is connected to the exhaust port 10 and an exhaust pipe 18 is connected to the exhaust manifold 17. A muffler (not shown) is connected to the exhaust pipe 18 via a three-way catalyst 19. Is connected.
[0025]
An electromagnetic fuel injection valve 19 and a throttle valve 20 are attached to the intake manifold 14, and a Karman vortex airflow sensor 21 for measuring an intake air amount is attached to an intake pipe 15 near the air cleaner 16.
[0026]
Fuel injection (fuel injection amount, injection timing, etc.) of the fuel injection valve 19 is controlled in accordance with the operating state of the engine 1 by controlling ON / OFF of an electromagnetic valve (not shown) by the ECU 12. It has become. The throttle valve 20 is provided with a throttle sensor 20a for detecting a throttle opening θth, and a detection signal thereof is input to the ECU 12. Further, a detection signal of the air flow sensor 21 is also input to the ECU 12.
[0027]
The ECU 12 includes a crank angle sensor 26 for detecting an engine speed (speed), a water temperature sensor (not shown) for detecting an engine coolant temperature, an outside air temperature sensor for detecting an outside air temperature, and an accelerator opening for detecting an accelerator opening. Various detection signals from operating state detecting means such as sensors are input.
[0028]
A supercharger 22 is provided between the intake pipe 15 and the exhaust pipe 18. The supercharger 22 is configured such that a compressor (wheel) 23 provided on the intake pipe 15 side and a turbine (wheel) 24 provided on the exhaust pipe 18 side are connected by a shaft 25 so as to be synchronously rotatable. Thus, the turbine 24 and the compressor 23 are rotated at a high speed, and the intake air in the intake pipe 15 is compressed to increase the charging efficiency in the combustion chamber 5.
[0029]
In the first embodiment, when the ECU 12 detects that the driver has requested a certain level of acceleration (including deceleration) by an acceleration request detection unit provided therein, the ECU 12 controls the valve by the variable valve timing mechanism 13. The overlap (the period during which both the intake valve 7 and the exhaust valve 9 are open) is enlarged and controlled.
[0030]
In addition, as is understood from the valve overlap control routine shown in FIG. 2, a request for acceleration exceeding a certain value is obtained when the accelerator opening based on the signal from the accelerator opening sensor is equal to or greater than the predetermined opening and the signal from the water temperature sensor is used. The engine cooling water temperature is within a predetermined range (see step S2), the outside air temperature is within a predetermined range based on a signal from the outside air temperature sensor (see step S3), and the engine speed is determined based on a signal from the crank angle sensor 26. The determination is made when it is within the range (see step S4), and when the actual volume efficiency (Ev actual) based on the signal from the airflow sensor 21 has not reached the target volume efficiency (Ev target) (see step S5).
[0031]
When all the conditions of steps S1 to S5 are satisfied, the ECU 12 activates the variable valve timing mechanism 13 in step S6 to enlarge and control the valve overlap, while the conditions of steps S1 to S5 are one. If even one is missing, in step S7, the steady valve overlap is maintained.
[0032]
As described above, in the first embodiment, when the acceleration request detecting unit detects the driver's acceleration request, the ECU 12 expands and controls the valve overlap by the variable valve timing mechanism 13. The overlap is increased, and the unburned HC in the exhaust gas is reburned by using the air blow-by, so that the exhaust energy is increased. As a result, the rotation speed of the turbocharger is increased earlier than usual, the increase in the intake air amount is accelerated, the speed of the increase in the torque is increased, and the feeling of acceleration is improved.
[0033]
Also, at this time, the ECU 12 has an air-fuel ratio control unit that controls the air-fuel ratio of the engine 1. When the air-fuel ratio is enriched when the valve overlap is expanded by the air-fuel ratio control unit, the ECU 12 does not operate when the engine is accelerated. It is preferable that the fuel HC increases and the fuel is reliably reburned.
[0034]
Further, the ECU 12 has an output estimating unit for estimating the output equivalent value of the engine 1, and determines the valve overlap until the output equivalent value estimated by the output estimating unit reaches the target output equivalent value after the valve overlap expansion. When the valve overlap changing device controls the valve overlap to return to the value before the enlargement when the valve overlap changing device reaches the target output equivalent value, the valve overlap is returned to a steady state after reaching the predetermined output, This is advantageous because the adverse effect of the enlarged valve overlap is avoided.
[0035]
Further, in the present embodiment, the actual volume efficiency based on the signal from the airflow sensor 21 is controlled as the output equivalent value, and the target volume efficiency is controlled as the target output equivalent value as in step S5 in FIG. 2 described above. The target volume efficiency is stored in the ECU 12 in advance as a map based on the engine speed, the accelerator opening, and the like.
[0036]
When the variable valve timing mechanism 13 controls the variable valve timing mechanism 13 to increase the valve overlap more when the rotation speed of the engine 1 is low than when the rotation speed of the engine 1 is not high, the ECU 12 has a higher sense of acceleration in the low-speed operation range. It is further improved and preferable.
[0037]
Next, a second embodiment will be described. In the present embodiment, the description of the same parts as those of the first embodiment will be omitted, and only different parts will be described.
[0038]
In the present embodiment, the ECU 12 is operated by the operating region determination unit provided therein to determine a specific operating region in which the supercharging capacity of the supercharger 22 is low (for example, a low-medium speed / low-medium load region indicated by hatching in FIG. 3). Is determined (detected), the valve overlap is expanded and controlled by the variable valve timing mechanism 13. The specific operating range is determined based on the engine speed (speed) detected by the crank angle sensor 26 and the throttle opening θth (ie, engine load) detected by the throttle sensor 20a.
[0039]
As described above, in the second embodiment, the ECU 12 expands and controls the valve overlap in the operation region where the rotation speed of the supercharger 22 is originally low to increase the exhaust energy, so that the rotation speed of the supercharger 22 is relatively low. It is kept high, and the acceleration response when an acceleration request is made is improved.
[0040]
It should be noted that the present invention is not limited to the above embodiments, and various changes can be made without departing from the scope of the present invention. For example, although the opening and closing timing of the intake valve 7 is changed by the variable valve timing mechanism 13, the opening and closing timing of the exhaust valve 9 may be changed, or both the intake valve 7 and the exhaust valve 9 may be changed. good. Further, although an example in which the present invention is applied to a port injection type engine has been described, the present invention can also be applied to a direct injection type engine.
[0041]
【The invention's effect】
As described above, according to the first aspect of the present invention, in the supercharged engine including the supercharger, the valve overlap changing device, the acceleration request detecting unit, and the control unit, the control unit includes the acceleration request detection unit. When the unit detects a driver's acceleration request, the valve overlap changing device controls the valve overlap to be enlarged, so that at the time of acceleration, the valve overlap is increased, and the valve overlap is increased by utilizing air blow-through. The unburned HC is reburned, and the exhaust energy is increased. As a result, the rotation speed of the turbocharger is increased earlier than usual, the increase in the intake air amount is accelerated, the speed of the increase in the torque is increased, and the feeling of acceleration is improved.
[0042]
According to the invention of claim 2, the control means has an air-fuel ratio control unit for controlling an air-fuel ratio of the engine, and the air-fuel ratio control unit enriches the air-fuel ratio of the engine when a valve overlap is enlarged. Therefore, during acceleration, the unburned HC increases and the fuel is reliably reburned.
[0043]
According to the invention of claim 3, the control means has an output estimating unit for estimating the output equivalent value of the engine, and the output equivalent value estimated by the output estimating unit after the valve overlap is enlarged is the target output equivalent value. The valve overlap changing device controls the valve overlap changing device to return the valve overlap to the value before the enlargement when the output reaches the target output equivalent value. Is returned to the steady state, and the adverse effect of the enlarged valve overlap is avoided.
[0044]
According to the invention of claim 4, the control means controls the valve overlap changing device to increase the valve overlap more when the rotation speed of the engine is low than when it is not. The feeling of acceleration in the low-speed operation range is further improved.
[0045]
According to a fifth aspect of the present invention, in the supercharged engine including the supercharger, the valve overlap changing device, the operating region determining unit, and the control unit, the control unit includes a control unit that determines whether the operating region determining unit determines the supercharging. When it is determined that the operation is in the specific operation region in which the supercharging capacity of the turbocharger is low, the valve overlap changing device controls the valve overlap to be enlarged, so that the specific operation in which the supercharging capacity of the supercharger is low is performed. The feeling of acceleration in the region is further improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a supercharged engine showing first and second embodiments of the present invention.
FIG. 2 is a flowchart showing a control routine of valve overlap according to the first embodiment of the present invention.
FIG. 3 is a graph of a specific operating region according to a second embodiment of the present invention.
[Explanation of symbols]
1 supercharged engine, 2 cylinder head, 3 cylinder block, 4 piston, 5 combustion chamber, 6 spark plug, 7 intake valve, 8 intake port, 9 exhaust valve, 10 exhaust port, 11 ignition coil, 12 electronic control unit ( ECU), 13 variable valve timing mechanism (VVT), 14 intake manifold, 15 intake pipe, 16 air cleaner, 17 exhaust manifold, 18 exhaust pipe, 19 three-way catalyst, 20 throttle valve, 20a throttle sensor, 21 air flow sensor, 22 excess Feeder, 23 compressor, 24 turbine, 25 shaft, 26 crank angle sensor.

Claims (5)

A supercharger that drives a turbine and a compressor by an exhaust flow of the engine to supercharge intake air;
A valve overlap changing device that changes a valve overlap by changing an opening / closing timing of at least one of an intake valve and an exhaust valve of the engine,
An acceleration request detection unit that detects a driver's acceleration request,
Control means for controlling the valve overlap changing device,
In a supercharged engine with
The control means,
When the acceleration request detection unit detects the driver's acceleration request,
A supercharged engine wherein the valve overlap changing device controls the valve overlap to be enlarged. The control unit has an air-fuel ratio control unit that controls an air-fuel ratio of the engine,
The air-fuel ratio control unit,
The supercharged engine according to claim 1, wherein the air-fuel ratio of the engine is made rich when the valve overlap is enlarged. The control unit has an output estimating unit that estimates an output equivalent value of the engine,
After the valve overlap is expanded, the valve overlap is continuously expanded until the output equivalent value estimated by the output estimating unit reaches the target output equivalent value, and when the output equivalent value reaches the target output equivalent value, the valve overlap changing device enlarges the valve overlap. 3. The supercharged engine according to claim 1, wherein the supercharged engine is controlled to return to a previous value. The control means controls the valve overlap changing device to increase the valve overlap more when the rotation speed of the engine is low than when the rotation speed of the engine is not low. 3. The supercharged engine according to 3. A supercharger that drives a turbine and a compressor by an exhaust flow of the engine to supercharge intake air;
A valve overlap changing device that changes a valve overlap by changing an opening / closing timing of at least one of an intake valve and an exhaust valve of the engine,
An operation region determination unit that determines whether or not a specific operation region in which the supercharging capacity of the supercharger is low,
Control means for controlling the valve overlap changing device,
In a supercharged engine with
The control means,
When the operating region determination unit determines that the supercharging capability of the supercharger is a specific operating region where the supercharging ability is low,
A supercharged engine wherein the valve overlap changing device controls the valve overlap to be enlarged.

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