JPH06280581A - Controller of engine - Google Patents

Abstract

PURPOSE:To promote evaporation/atmization of fuel and decrease pumping loss, in a direct injection type engine. CONSTITUTION:A fuel injection valve 20 for directly injecting fuel is provided in a combustion chamber 14. The valve opening timing of one side exhaust valve 27 out of two exhaust valves 27, 28 is set so as to certainly open the exhaust valve 27 during an intake stroke, namely during the period when intake valve 25, 26 are opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a direct injection type engine which directly injects fuel into a combustion chamber.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection engine, in order to realize lean combustion by stratifying the inside of the combustion chamber and to reduce fuel consumption, fuel is directly injected into the combustion chamber. Something is known (for example, Shoukai 58-
154825).

[0003]

In the above-mentioned direct injection type engine, it is difficult to sufficiently vaporize and atomize the fuel in the combustion chamber when the temperature in the cylinder is low, especially when the load is low. Are easily disturbed. Therefore, promotion of fuel vaporization and atomization is desired.

Further, in this direct injection type engine, as with other engines, it is a major problem to reduce pumping loss as much as possible.

In view of such circumstances, it is an object of the present invention to provide an engine control device capable of simultaneously promoting vaporization and atomization of fuel and reducing pumping loss.

[0006]

As means for solving the above problems, the present invention provides a fuel injection means for directly injecting fuel into a combustion chamber, and an exhaust valve for opening and closing an exhaust port opening in the combustion chamber. In the engine having the above, the exhaust valve drive means for opening the exhaust valve over the entire intake stroke is provided (Claim 1).

This device is more effective when it is provided with a supercharger (claim 2).

A single exhaust port may be used, but a plurality of exhaust ports are opened for one combustion chamber, an exhaust valve is provided for each exhaust port, and some exhaust valves are opened over the entire intake stroke. It is more preferable that the exhaust valve driving means is configured so that the valve is operated (claim 3).

Further, it is more preferable that the fuel injection means is arranged such that the exhaust port opened during the intake stroke is located on the downstream side of the ignition source as viewed from the fuel injection means (claim 5).

Further, the load detecting means for detecting the engine load and the exhaust valve is opened over the entire intake stroke at least in a region where the detected load is equal to or less than a certain value, and the exhaust valve is closed when the detected load increases. The exhaust valve drive control means for controlling the exhaust valve drive means so as to accelerate the exhaust valve drive means (claim 4), or the exhaust valve drive control means is operated at a timing for performing two-cycle operation according to operating conditions. The exhaust valve drive control so as to switch the exhaust valve drive mode by the exhaust valve drive means between a two-cycle operation mode in which the valve is opened and closed and a four-cycle operation mode in which the exhaust valve is opened and closed at the timing for performing the four-cycle operation. By configuring the means (claim 6), more excellent effects as described later can be obtained.

[0011]

In the device according to the first aspect, since the exhaust valve is opened over the entire intake stroke, a large amount of dilution gas (burned gas) flows back into the combustion chamber from the exhaust port during the intake stroke. To do. As a result, the temperature in the combustion chamber is raised, and the vaporization and atomization thereof is promoted. In addition, the introduction of dilution gas reduces NOx in the exhaust gas,
Further, when the catalyst is provided on the exhaust side, the catalyst temperature is raised by the rise of the exhaust temperature and the purifying action thereof is promoted. Moreover, since the opening area of the combustion chamber during the intake stroke is increased by opening the exhaust valve, the pumping loss is reduced accordingly.

Since the fuel injection means injects the fuel directly into the combustion chamber, unlike the case of injecting the fuel into the intake passage, even if the exhaust valve is opened during the intake stroke, the fuel is injected from the exhaust port. Fuel rarely blows outside the combustion chamber.

In such an apparatus, if the supercharger is provided as in the second aspect, the intake air can be sufficiently sent into the combustion chamber even when the opening area of the exhaust port during the intake stroke is large.

Further, as described in claim 3, a plurality of exhaust ports are opened to one combustion chamber, an exhaust valve is provided for each exhaust port, and at least one exhaust valve is opened over the entire intake stroke. If the exhaust valve driving means is configured to perform the above, by appropriately adjusting the opening / closing timing of each exhaust valve, the exhaust amount in the regular exhaust stroke other than the intake stroke and the amount of dilution gas introduced during the intake stroke Both can be adjusted appropriately.

According to the fourth aspect of the present invention, in the low-load operation region, that is, in the region where the temperature in the combustion chamber is low, the fuel is particularly difficult to vaporize and atomize, and the intake amount is small and the pumping loss is likely to increase, the intake stroke is increased. The exhaust valve is opened in a wide range including the temperature range to introduce a sufficient amount of dilution gas into the combustion chamber, while the high load operation range, that is, the temperature in the combustion chamber is high and the fuel vaporizes relatively.
In a region where the amount of intake air is large and the amount of intake air is relatively small and pumping loss is relatively small, the closing timing of the exhaust valve is advanced, so that the efficiency of filling air into the combustion chamber in the intake stroke is increased.

Further, in the apparatus according to the fifth aspect, since the exhaust port opened during the intake stroke is located on the downstream side of the ignition source as seen from the fuel injection means, the fuel injected from the fuel injection means to the ignition source is High temperature dilution gas from the exhaust port is efficiently mixed near the ignition source,
This improves ignitability.

Further, in the apparatus according to the sixth aspect, the two-cycle operation and the four-cycle operation can be selectively used depending on the operating condition by changing the opening / closing timing of the exhaust valve while the engine structure is constant.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

The direct injection type four-cycle engine shown in FIGS. 1 and 2 comprises a cylinder block 10, and a piston 12 is inserted into the cylinder. A combustion chamber 14 is formed above the piston 12, and the piston 12 is connected to a crank pin 17 via a connecting rod 16.

A cylinder head 18 is mounted on the upper surface of the cylinder block 10. This cylinder head 18
A first intake port 21, a second intake port 22, a first exhaust port 23, and a second exhaust port 24, which are opened obliquely from the upper side with respect to the combustion chamber 14, are formed therein. The first intake port 21 and the second intake port 22 are arranged on one side (left side in FIGS. 1 and 2) of the engine, and the first exhaust port 23 and the second exhaust port 24 are arranged on the other side. . First intake port 21 and second intake port 22
Are opened and closed by the operation of the first intake valve 25 and the second intake valve 26, respectively, and the first exhaust port 23 and the second exhaust port 24 are respectively connected to the first exhaust valve 27 and the second exhaust valve 28.
It is designed to be opened and closed by the operation of. Each intake valve 2
5, 26 are well-known intake valve opening / closing mechanisms 19, and the respective exhaust valves 27, 28 are adapted to be opened / closed by well-known exhaust valve opening / closing mechanisms 29.
Exhaust valves 27, 2 by receiving a command signal from the outside
It is configured so that the opening / closing timing of 8 can be changed.

A spark plug 30 and a fuel injection valve 20 are attached to the cylinder head 18. As shown in FIG. 2, the spark plug 30 is disposed in a position facing the center of the combustion chamber 14 from above, and the fuel injection valve 20
Is disposed at a position where the first exhaust port 23 is located on the downstream side of the spark plug 30 when viewed from the fuel injection valve 20.

Each of the intake ports 21 and 22 is connected to a surge tank 34 via an intake pipe 32.
A throttle valve 36 is provided on the upstream side of the throttle valve 4. Further, an exhaust pipe 33 is connected to the exhaust ports 23 and 24, and a catalyst converter (not shown) for purifying exhaust gas is provided at a confluent portion of the exhaust pipe 33.

Various sensors including an in-cylinder pressure sensor 37, an engine load sensor (load detecting means) 38, an engine speed sensor 39, etc. are connected to the engine, and the ECU 40 is based on these detection signals. Is a fuel injection control by the fuel injection valve 20 and a spark plug 30.
Control of the ignition timing and control of the opening / closing timing of the exhaust valves 27, 28 by the exhaust valve opening / closing mechanism 29.

Specifically, in this engine, as shown in FIG. 3, the opening and closing timings of the intake valves 25 and 26 and the exhaust valves 27 and 28 are set as follows. Intake valves 25 and 26: The opening and closing timings of the intake valves 25 and 26 are
They are equal to each other and are fixed irrespective of the operating conditions, and as shown by the broken line 51 in FIG. 3, the pistons on the intake and exhaust stroke sides in the 4-cycle operation start to open before the top dead center of the piston, and this piston The valve is set to close after the piston bottom dead center closest to the top dead center has passed.

Second exhaust valve 28: The opening / closing timing of the second exhaust valve 28 is also fixed regardless of operating conditions.
As shown by the solid line 52 in the figure, the valve starts to open from a time point immediately before the piston bottom dead center immediately before the piston top dead center on the intake / exhaust stroke side, and closes after the piston bottom dead center has passed. It is configured.

First exhaust valve 27: The opening / closing timing of the first exhaust valve 27 is controlled by a command signal from the ECU 40 according to the engine load detected by the engine load sensor 38. Specifically, in a region where the engine load is equal to or less than a preset value (that is, a low load region), as shown by a solid line 53 in FIG. 3, the intake valves 25 and 26 start opening earlier than the opening timing. , The intake valves 25 and 26 are set to open at a time later than the closing time, and in a region where the engine load is equal to or higher than the set value (that is, a high load region), as shown by a two-dot chain line 54 in FIG. In addition, the first exhaust valve 27 is set to be closed earlier than the low load region, and the first exhaust valve 27 is closed earlier than the closing timing of the intake valves 25 and 26. That is, the opening / closing timing of the first exhaust valve 27 is set so that it is always opened at least in the intake stroke (the stroke in which the intake valves 25 and 26 are open) in the low load region.

Next, the operation of this engine will be described.

First, in the operating region where the engine load is below a predetermined value, stratification is performed by direct fuel injection into the combustion chamber 14 by the fuel injection valve 20, thereby realizing lean combustion. Here, in the conventional engine, since the fuel is lean, the temperature in the combustion chamber tends to be low, the fuel is less likely to be vaporized and atomized, and the pumping loss tends to be larger than that under high load operation.

However, in the engine shown in this embodiment, as shown by the solid line 53 in FIG. 3, the opening period of the first exhaust valve 27 completely includes the opening periods of the intake valves 25 and 26 in the low load operation region. Since the first exhaust port 23 is open at least during the intake stroke, this first exhaust port 2
3 increases the temperature in the combustion chamber 14 by the dilution gas introduced into the combustion chamber 14 to evaporate the fuel.
Atomization is accelerated. Further, since the first exhaust port 23 is located on the downstream side of the spark plug 30 as viewed from the fuel injection valve 20, the fuel injection valve 20 is not connected to the spark plug 30.
To the second exhaust port 2
The dilution gas introduced into the combustion chamber 14 from 3 is efficiently mixed in the vicinity of the ignition plug 30, and the ignitability is significantly improved.

Further, the opening area of the combustion chamber 14 is increased by the amount of the opening of the first exhaust port 23, and the pumping loss is also reduced. Further, since the exhaust temperature rises, the purifying action by the catalytic converter provided in the exhaust pipe 33 is promoted.

Further, in this embodiment, two exhaust ports 23, 24 and exhaust valves 27, 28 are provided, of which the first
Since only the exhaust port 23 and the first exhaust valve 27 are opened during the intake stroke, both exhaust ports 23, 24
It is possible to adjust both the exhaust amount outside the intake stroke and the introduction amount of the dilution gas during the intake stroke to appropriate amounts by appropriately determining the opening / closing timing of.

Here, if the engine is of a type that injects fuel into the intake pipe, the air-fuel mixture introduced from the first intake port 21 into the combustion chamber 14 remains as it is in the first exhaust port 23. From outside to the outside of the combustion chamber (Fig. 2
Although there is a possibility that the combustion chamber 14 will not be sufficiently filled with fuel by this (see the arrow), this engine is a direct injection type, so even if the first exhaust port 23 is opened during the intake stroke, the fuel cannot be reliably filled in the combustion chamber 14. Can be filled.

On the other hand, in a high load operation region where the engine load exceeds the above-mentioned predetermined value, the temperature in the combustion chamber is high and the fuel is relatively easily vaporized and atomized, and the pumping loss is lower than that under the low load, so that it is low. It is not necessary to introduce a large amount of dilution gas as in the load operation area. Therefore, in this high load operation region, as shown by the chain double-dashed line 54 in FIG. 3, by advancing the closing timing of the first exhaust valve 27, the air filling efficiency can be increased without any inconvenience.

In this embodiment, the engine load and the predetermined value are compared, and the closing timing of the first exhaust valve 27 is switched based on the magnitude of the engine load. The closing timing of the exhaust valve 27 may be advanced in multiple stages or continuously. However, even if the exhaust valve closing timing is controlled according to the engine load as described above, even if the exhaust valve closing timing is always fixed, a large amount of dilution gas is introduced. The above effects can be obtained.

Next, a second embodiment will be described with reference to FIGS.

In this embodiment, the intake ports 21 and 2 are
2 and the intake valves 25, 26, an intake port 42 is formed on the side wall of the cylinder and communicates with the inside of the cylinder through a large number of holes 43.
2 is connected. Therefore, as shown by the broken line 61 in FIG. 6, the intake port 42 is opened (that is, intake is performed) in the combustion chamber 14 at each time of the piston bottom dead center.
It is like this. In the intake pipe 32, the throttle valve 3
An intercooler 44 and a supercharger (supercharger) 46 are provided at a position upstream of 6, and these upstream side and downstream side are connected by a bypass passage 48, and a bypass valve is provided in the middle of the bypass passage 48. 49 are provided.

On the other hand, the ECU 40 controls the first exhaust valve 2 by the exhaust valve opening / closing mechanism 29 according to the operating conditions detected by the engine load sensor 38 and the engine speed sensor 39.
The open / close drive mode 7 is switched between the 4-cycle operation mode and the 2-cycle operation mode. More specifically, as shown in FIG. 5, in the high load operation region and the start operation region (low rotation operation region) where a relatively high output is required, the two-cycle operation mode is set, and the other regions (low load medium) The ECU 40 is configured to switch to the 4-cycle operation mode in the high-speed operation region). Here, the opening / closing timing of the first exhaust valve 27 set in each mode is as follows.

4-cycle operation mode: As shown by the solid line 62 in FIG. 6 (a), the first exhaust valve 27 is opened in the region between the piston bottom dead center immediately after the piston top dead center where combustion is performed. Moreover, the valve opening timing is set earlier than the opening timing of the intake port 42, and the valve closing timing is set later than the closing timing of the intake port 42. That is, in this mode, the first exhaust valve 27 is opened once every two reciprocations of the piston,
In addition, the valve opening period is set to a period that completely includes the opening period of the intake port 42.

Two-cycle operation mode: As shown by the solid line 63 in FIG. 6 (b), the first exhaust valve 27 is opened every time the piston bottom dead center is sandwiched, and the valve opening timing is the intake time. The valve closing timing is set earlier than the opening timing of the port 42, and is set to be substantially equal to the closing timing of the intake port 42. That is, in this mode, the first exhaust valve 2
7 is opened, and the valve opening period is set shorter than the valve opening period in the above-mentioned 4-cycle operation mode. Further, in the 4-cycle operation mode, fuel injection and ignition are performed once every two reciprocations of the piston.
In the cycle operation mode, the fuel injection valve 20 and the spark plug 30 are arranged so that fuel injection and ignition are performed for each reciprocation of the piston.
Is set, and therefore, in this 2-cycle operation mode, the 2-cycle operation is actually executed.

Even in such an engine, in the low load operation region, as shown in FIG. 6 (a), the first exhaust valve 27 is opened during a period including at least the intake stroke, so that a large amount of gas is introduced into the combustion chamber 14. In order to promote the vaporization and atomization of fuel by introducing the dilution gas and reduce the pumping loss, the first exhaust valve 27 is closed in the high load operation region where the introduction of the dilution gas is not required so much. By advancing the timing, it is possible to enhance the efficiency of air filling.

Moreover, according to this engine, by changing the opening / closing timing of the first exhaust valve 27, it is possible to switch between the 4-cycle operation mode and the 2-cycle operation mode with a single structure. The 2-cycle operation mode is switched in a region where relatively high output is required (starting operation region and high-load operation region in this embodiment), and 4-cycle operation mode is switched in other regions (low-load medium-high speed operation region in this embodiment). As a result, it is possible to perform an operation suitable for the operating condition.

Further, since the supercharger 46 is provided in this embodiment, even if the opening area of the first exhaust port 27 during the intake stroke is large, fresh air can be sufficiently sent into the combustion chamber 14. .

The present invention is not limited to such an embodiment, and the following modes can be adopted as an example.

(1) In the present invention, regardless of the number of exhaust ports and exhaust valves per cylinder, a single exhaust port and exhaust valve may be provided, or three or more exhaust ports and exhaust valves may be provided. An exhaust valve may be provided. When three or more exhaust ports are provided, by opening only some of these exhaust ports at least during the intake stroke, the same effect as in the above embodiment can be obtained.

(2) In the present invention, regardless of the type of supercharger,
In addition to the supercharger shown in FIG. 4, a turbocharger, a pressure wave, etc. can be applied.

(3) In the present invention, the specific heat ratio in the combustion chamber is measured by using the in-cylinder pressure sensor 37 and the like, and the exhaust gas content ratio determined based on the specific heat ratio is set to a preferable value. It is also possible to control the opening and closing timing.

(4) In the second embodiment described above, the switching between the 2-cycle operation and the 4-cycle operation is immediately performed at the time when the operation area is shifted, but such switching frequently occurs. In order to prevent this, for example, control may be performed such that the 4-cycle operation is switched to the 2-cycle operation only after a certain period of time has elapsed after the low-load operation area is changed to the high-load operation area.

[0048]

As described above, according to the present invention, the following effects can be obtained.

In the apparatus according to the first aspect, the exhaust valve is opened over the entire intake stroke, so a large amount of dilution gas (burnt gas) is burned from the exhaust port during the intake stroke. By introducing it in the room,
The temperature of the combustion chamber is raised to promote vaporization and atomization thereof, and at the same time, the opening area of the combustion chamber in the intake stroke due to the opening of the exhaust valve is increased, so that pumping loss can be reduced. Further, NOx can be reduced by introducing dilution gas, and when a catalyst for purifying exhaust gas is provided on the exhaust side, the temperature of the exhaust gas also rises to raise the catalyst temperature and improve its purifying action. The effect that can be produced also occurs.

Moreover, since the fuel is directly injected into the combustion chamber, even if the exhaust port is opened during the intake stroke, the fuel is injected from the exhaust port to the outside of the combustion chamber as in the case where the fuel is injected into the intake pipe. There is almost no blow-through, and fuel can be reliably supplied into the combustion chamber.

Further, according to the one provided with the supercharger as set forth in claim 2, there is an effect that the intake air can be sufficiently sent into the combustion chamber even when the opening area of the exhaust port in the intake stroke is large. is there.

If a plurality of exhaust ports and exhaust valves are provided, and some of the exhaust valves are opened over the entire intake stroke, the exhaust valves can be opened and closed. By appropriately adjusting the timing, there is an effect that both the exhaust amount in the regular exhaust stroke other than the intake stroke and the introduction amount of the dilution gas during the intake stroke can be appropriately adjusted.

According to the fourth aspect of the present invention, the intake stroke is reduced in the low load operation region where the temperature in the combustion chamber is low and the fuel is difficult to vaporize and atomize, and the intake amount is small and pumping loss is likely to increase. By opening the exhaust valve in a wide range including the above, a sufficient amount of dilution gas is introduced into the combustion chamber to obtain the above effect, while the temperature in the combustion chamber is high and fuel is relatively easily vaporized and atomized. In the high load operation region where the intake amount is large and the pumping loss is relatively small (that is, the region where dilution gas is not required to be introduced so much), the closing timing of the exhaust valve is advanced so that the combustion chamber in the intake stroke is increased. There is an effect that the efficiency of filling air into the air can be increased.

Further, in the apparatus according to the fifth aspect, the layout is such that the exhaust port opened during the intake stroke is located on the downstream side of the ignition source as seen from the fuel injection means. By efficiently mixing the fuel injected to the source with the dilution gas from the exhaust port in the vicinity of the ignition source, it is possible to more effectively use the high temperature dilution gas and improve the ignitability. There is an effect that can be done.

Further, in the engine according to the sixth aspect of the present invention, the two-cycle operation and the four-cycle operation can be selectively used according to the operating conditions by changing the opening / closing timing of the exhaust valve while the engine structure is constant. There is an effect that it is possible to always carry out the operation suitable for the operating condition.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of an engine according to a first embodiment of the present invention.

FIG. 2 is a schematic plan view showing a main part of the engine.

FIG. 3 is a graph showing opening and closing timings of intake and exhaust valves provided in the engine.

FIG. 4 is a sectional view showing a main part of an engine according to a second embodiment of the present invention.

FIG. 5 is a graph showing an operating region in which a 4-cycle operation is performed and an operating region in which a 2-cycle operation is performed in the engine.

FIG. 6A is a graph showing opening and closing timings of intake and exhaust valves in a high load operation region and a starting operation region of the engine,
(B) is a graph showing the opening / closing timing of the intake / exhaust valve in the low load operation region of the engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cylinder block 12 Piston 14 Combustion chamber 18 Cylinder head 20 Fuel injection valve (fuel injection means) 23 First exhaust port 24 Second exhaust port 27 First exhaust valve 28 Second exhaust valve 29 Exhaust valve drive mechanism (exhaust valve drive means) ) 30 spark plug 38 engine load sensor (load detection means) 40 ECU (exhaust valve drive control means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Sakurai 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (6)

[Claims] 1. An engine having a fuel injection means for injecting fuel directly into a combustion chamber and an exhaust valve for opening and closing an exhaust port opening in the combustion chamber, wherein exhaust gas is opened over the entire intake stroke. An engine control device comprising valve driving means. 2. The engine control device according to claim 1, further comprising a supercharger. 3. The engine control device according to claim 1 or 2, wherein a plurality of exhaust ports are opened for one combustion chamber, an exhaust valve is provided for each exhaust port, and a part of the exhaust valves is provided. An engine control device comprising the exhaust valve driving means configured to open the valve over the entire intake stroke. 4. The engine control device according to any one of claims 1 to 3, wherein a load detecting means for detecting an engine load, an exhaust valve is opened over the entire intake stroke in at least a region where the detected load is a fixed value or less, and An engine control device comprising: an exhaust valve drive control means for controlling the exhaust valve drive means so as to accelerate the closing timing of the exhaust valve as the detected load increases. 5. The engine control device according to claim 1, wherein the fuel is arranged such that an exhaust port opened during an intake stroke is located downstream of the ignition source as viewed from the fuel injection means. An engine control device having an injection means. 6. The engine control device according to claim 1, wherein the exhaust valve is opened / closed at a timing for performing a two-cycle operation according to operating conditions.
The exhaust valve drive control means is configured to switch the exhaust valve drive mode by the exhaust valve drive means between a cycle operation mode and a 4-cycle operation mode in which the exhaust valve is opened and closed at a timing for performing the 4-cycle operation. An engine control device characterized by: