JPH055421A - Engine intake/exhaust mechanism - Google Patents

Abstract

PURPOSE:To eliminate deterioration in emission due to exhaust gas temperature drop accompanied by laminar combustion for improving fuel consumption and, at the same time, provide fuel consumption. CONSTITUTION:In an engine having plural cylinders, there is provided a communication path for communicating a combustion chamber 17 of a cylinder which is in a later expansion stroke stage and a combustion chamber 17 of a cylinder which is in exhaust stroke in the light load region below a specified load and a communication control means 44 for opening the communication path at the time of a light load below a specified load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake / exhaust structure for an engine, which improves fuel efficiency while ensuring exhaust purification performance.

[0002]

2. Description of the Related Art A lean air-fuel ratio is effective in improving the fuel efficiency of an engine. For this reason, uneven distribution of fuel in the combustion chamber to carry out stratified combustion has been described, for example, It is publicly known as seen in Japanese Laid-Open Patent Publication No. 56534. In the fuel stratification in this prior art example, a fuel injection valve for directly supplying the fuel to the compression combustion chamber is arranged, and the fuel is unevenly distributed in the vicinity of the spark plug to secure good ignitability while maintaining the air-fuel ratio as a whole. It aims to achieve leanness.

[0003]

However, the above-described stratified combustion technique has the following problem of emission characteristics, and it is difficult to obtain a significant improvement in fuel efficiency.

That is, first, since the air-fuel mixture goes out of the stoichiometric air-fuel ratio region as the air-fuel ratio becomes leaner, the conventional three-way catalyst cannot be used, and excellent NOx purification can be performed even under lean conditions. NOx unless a high-performance catalyst is put to practical use
However, the amount of NOx generated must be suppressed by engine combustion, because the purification is insufficient and the amount of emission increases. Secondly, in order to significantly improve the fuel efficiency, it is necessary to make it extremely lean, but with this leaning, the exhaust gas temperature drops extremely, and the catalyst reaches the activation temperature for carrying out the oxidation reaction. As a result, unburned components cannot be sufficiently purified.

In order to solve the above problems, the intake closing timing is delayed to lower the pressure and temperature of the combustion chamber at the compression top dead center to suppress combustion and reduce the amount of NOx produced. It is possible to raise the exhaust gas temperature by promoting combustion, or raise the exhaust gas temperature by restricting the intake air to suppress the air filling amount in the combustion chamber. However, with the improvement of the emission performance by these methods, the combustion deteriorates from the idle region to the light load region where the most improvement in fuel efficiency performance is expected, so it is necessary to increase the fuel amount to ensure smooth drivability. There is a problem that improvement in fuel efficiency is insufficient.

In view of the above circumstances, the present invention provides an intake / exhaust structure for an engine capable of improving the fuel efficiency while increasing the exhaust temperature and ensuring the purification performance of the catalyst without causing deterioration of combustion. The purpose is that.

[0007]

In order to achieve the above object, an intake and exhaust structure for an engine of the present invention is an engine having a plurality of cylinders, and combustion of a combustion chamber of a cylinder in the latter half of the expansion stroke and combustion of a cylinder in the exhaust stroke. A communication passage for communicating with the chamber is provided, and a communication control means for opening the communication passage at a light load below a predetermined load is provided.

It is preferable that the communication passage is provided in the intermediate housing of the multi-cylinder rotary piston engine.

[0009]

In the intake and exhaust structure of the engine as described above, in the light load region, the communication passage opened by the communication control means changes the combustion chamber of the cylinder in the latter half of the expansion stroke from the combustion chamber of the cylinder in the exhaust stroke. Part of the exhaust gas during combustion is released, and exhaust gas with a high temperature is introduced from the cylinder in this exhaust stroke to the catalyst device in the exhaust passage to raise the catalyst temperature and promote its activation to improve purification performance. In addition to ensuring the above, the exhaust gas whose pressure is released during the combustion has an unburned component in which the reaction has stopped, causes post-combustion in the exhaust passage, further raises the exhaust temperature and the catalyst temperature, and has good purification performance. Thus, it becomes possible to obtain lean by stratified combustion, and it is possible to improve the fuel efficiency while ensuring the emission property by the good purification of NOx, HC, CO and the like.

If the communicating passage is formed in the intermediate housing of the rotary piston engine, it can be constructed simply and compactly.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 show a structure including an intake / exhaust structure of an embodiment 2
Fig. 1 shows the overall structure of a cylinder rotary piston engine.
Then, the two cylinders are shown expanded to the left and right.

The casing of the rotary piston engine E includes rotor housings 11 and 11 whose inner peripheral surfaces are formed in a trochoid shape and arranged in parallel, and side housings 12 and 11 which are located on both sides of the rotor housings 11 and 11, respectively. 12 and an intermediate intermediate housing 13, which form a first cylinder A and a second cylinder B. Spaces in these cylinders A and B respectively accommodate substantially triangular rotors 15 and 15, and each rotor 15 has an eccentric shaft 16
It is supported by and is designed to make a planetary rotational motion. The rotors 15 divide the spaces in the cylinders A and B into three combustion chambers 17 (working chambers), and
With the rotation of the rotor 15, intake, compression, explosion and exhaust strokes are performed. In the rotor 15, an internal gear formed on the inner circumference of one side surface meshes with an external gear fixed to both end side housings 12 and a predetermined phase difference (18
It is linked to rotate the planet at 0 °).

Although not shown in detail, in order to seal between the combustion chambers 17, the rotor 15 has apex seals abutting against the inner peripheral surface of the rotor housing at the tops of the rotors 15 on both sides. Side seals are attached in an arc shape connecting the tops along the top, corner seals are attached to both sides of each top, and oil seals are attached to the inner peripheral side surface.

The side housing 12 or the intermediate housing 13 is formed with an intake port 21 which opens into the combustion chamber 17 at a position where an intake stroke is to be performed for each cylinder A, B. Independent intake passages 22a and 22b are respectively connected to the intake ports 21 of the cylinders A and B, the independent intake passages 22a and 22b on both sides are gathered in the surge tank 23, and the main throttle valve is provided in the upstream gathered intake passage 22.
An air flow sensor 26 for detecting the amount of intake air is provided in the intake passage 22 further upstream. Manifold injection valves 27a, 27b are provided in the independent intake passages 22a, 22b for the cylinders on both sides.

Also, the rotor housing 11 of each cylinder A, B
An exhaust port 31 that opens into the combustion chamber 17 is formed at a position where an exhaust stroke should be performed, and an ignition plug 32 is disposed at a position where an explosion stroke should be performed. Further, in-cylinder high-pressure injection valves 33a, 33b are installed adjacent to the respective spark plugs 32 of the first and second cylinders A, B, and fuel is directly supplied to the combustion chamber 17 by these in-cylinder high-pressure injection valves 33a, 33b. It is supplied by injection. An exhaust passage 35 is connected to the exhaust ports 31 of the cylinders A and B, respectively, and the exhaust passages 35 on both sides are gathered on the downstream side, and a catalyst device 36 is interposed in this gathered portion. In-cylinder high-pressure injection valve for each of the first and second cylinders A and B
Fuel passages from the high-pressure fuel injection pump 38 are connected to 33a and 33b, respectively, and pressurized fuel is supplied.

On the other hand, on the inner surface of the intermediate housing 13 on the side of the first cylinder A, an exhaust communication port 40 which communicates with the combustion chamber 17 in the exhaust stroke from the expansion to the exhaust port 31 side is opened. An exhaust communication port 41 that communicates with the combustion chamber 17 in the expansion stroke from the expansion in the same phase is also opened on the inner surface of the intermediate housing 13 on the two-cylinder B side. Then, the exhaust communication port 4 of both cylinders A and B
0, 41 are communicated with each other by a communication passage 42, and the communication passage 42
A cut valve 44 is provided as a communication control means for opening and closing the passage. The communication passage 42 is linearly formed in the intermediate housing 13 as shown in FIG.

The openings of the exhaust communication ports 40, 41 are opened / closed by their side seals in response to the rotation of the rotor. The opening / closing timing is, for example, 100 ° of BBDC before exhaust bottom dead center. , After exhaust bottom dead center ABDC 100
It is provided at a closed position and an opening shape. And
The first cylinder A and the second cylinder B are alternately opened and closed at a predetermined time according to the phase difference between the first cylinder A and the second cylinder B.

The fuel injection control by both the manifold injection valves 27a, 27b and the in-cylinder high pressure injection valves 33a, 33b is performed by only the in-cylinder high pressure injection valves 33a, 33b in the light load region where the engine load is below a predetermined value. In-cylinder fuel injection is performed, fuel injection by the manifold injection valves 27a, 27b is stopped, and stratified charge combustion is performed. The fuel injection control is performed by the manifold injection valve from the controller 50 that controls the entire engine.
This is performed by outputting control signals to 27a, 27b and the high-pressure fuel injection pump 38.

A throttle motor 51 is connected to the main throttle valve 25, and is opened / closed to a predetermined throttle opening by the operation of the throttle motor 51. An actuator 54 is installed on the cut valve 44, and the cut valve 44 is activated by the operation of the actuator 54.
The opening / closing operation of is performed. And the above throttle motor
A control signal is output from the controller 50 to the actuator 54 of the cut valve 44, and the operation thereof is controlled in accordance with the operating state.

The controller 50 has an intake air amount signal from the air flow sensor 26, an accelerator opening signal from an accelerator sensor 55 for detecting an accelerator operation amount (engine load), and an engine rotation speed in order to detect an operating state. A rotation speed signal or the like is input from a rotation sensor 56 that detects the number of rotations.

Intake and fuel control by the controller 50 will be described with reference to the flowchart of FIG. After the control is started, detection signals from various sensors are read in step S1, and it is determined in step S2 whether or not the current operating state is in the light load region. For example, as shown in FIG. 3, this control map is set by the engine speed and the accelerator opening degree, the operating state of the low accelerator opening degree and the low rotation speed area is set to the light load area L, and other than that is set. It is set to the medium / high load region H.

If the determination in step S2 is YES and the vehicle is in the light load region L, the process proceeds to step S3 to open the main throttle valve 25 to the fully open state and open the cut valve 44 in step S4. Also, step S
5, manifold injection valves 27a, 27b for both cylinders A, B
To stop fuel injection.

Then, in step S6, the basic injection amount based on the accelerator opening is variously corrected to calculate the fuel injection amount, and in step S7, a signal corresponding to this fuel injection amount is output to the high-pressure fuel injection pump 38. , The fuel injection by the in-cylinder high-pressure injection valves 33a, 33b to the cylinders A, B is executed, and the load control is performed by the injection amount.

On the other hand, if the determination in step S2 is NO and the vehicle is in the medium-high load region H, the process proceeds to step S8 to calculate the opening of the main throttle valve 25 based on the accelerator opening. The load is controlled in degrees. Then, in step S9, a control signal corresponding to the throttle opening is output to the throttle motor 51 to drive the main throttle valve 25. Further, in step S10, the cut valve 44 is closed to close the communication passage 42.

Regarding the fuel injection, in step S11, the fuel injection by the in-cylinder high pressure injection valves 33a and 33b for the cylinders A and B is fixed to a predetermined value, while in step S12 it is based on the intake air amount and the engine speed. Various corrections are made to the basic injection amount to calculate the fuel injection amount, and in step S13, a signal corresponding to this fuel injection amount is output to the manifold injection valves 27a, 27b for each cylinder A, B, and intake is performed for both cylinders. The fuel is supplied from the passages 22a and 22b.

Explaining the operation of the above-mentioned processing, in the light load region L, the intake air passes through the fully open main throttle valve 25 and the independent intake passages 22a, 22a
Fuel is injected and supplied by the in-cylinder high-pressure injection valves 33a, 33b before being sucked into the intake combustion chamber 17 corresponding to the intake stroke from 22b through the respective intake ports 21, compressed and ignited by the spark plug 32. Stratified combustion is performed. The exhaust communication port 40 or 41 opens before the exhaust port 31 opens in the latter half of the combustion chamber 17 in the explosive expansion stroke,
In this light load region L, since the cut valve 44 of the communication passage 42 is open, the combustion pressure in the combustion chamber 17 is released,
Falls sharply. When the exhaust communication port 40 or 41 of the one cylinder A or B is opened, the exhaust communication port 41 or 40 of the other cylinder B or A is already open to the exhaust working chamber 17 and passes through the communication passage 42. The combustion gas in the latter stage of the expansion stroke flows out from the working chamber 17 in the exhaust stroke to the exhaust passage 35 through the exhaust port 31. Further, since the rotor phases of both cylinders A and B are shifted by 180 °, the combustion gas alternately flows through the communication passage 42 in the opposite direction in the latter stage of each expansion stroke.

In the state during the combustion stroke as described above,
When the combustion chamber is opened to communicate with the exhaust combustion chamber of another cylinder,
The following phenomenon occurs due to substantial volume expansion. That is, since the pressure and temperature in the combustion gas instantly drop (the drop level is small but the speed is extremely high), the growth of the flame in the combustion chamber stops and the flame disappears. In this state, the combustion gas is distributed to its own cylinder or other cylinders,
It is discharged from the exhaust port 31 and reburns in the exhaust passage 35. As a result, in the light load state, the combustion in the latter stage of combustion hardly contributes to the output, and the combustion in the latter stage is stopped,
In the vicinity of the catalyst device 36, the exhaust gas temperature is effectively contributed to increase.

In the rotary piston engine, the exhaust release timing can be substantially advanced by connecting the exhaust communication port to the exhaust passage of the own cylinder. However, in this case, a high pressure wave due to combustion is transmitted from the exhaust passage to the own cylinder. Of the exhaust combustion chamber, and in this state, since the exhaust combustion chamber is opened to the exhaust port and the intake port is opened, a large amount of combustion gas flows into the exhaust combustion chamber, and as a result, the combustibility is significantly impaired, which is preferable. Absent.

Further, the in-cylinder high pressure injection valve 33a at the time of the light load,
The fuel supplied according to the load by 33b is injected so as to be unevenly distributed in the vicinity of the spark plug 32, and stratified charge combustion is performed, which improves the fuel efficiency by making the air-fuel ratio lean, and The exhaust gas temperature for the catalyst is high as shown in FIG.
Good purification of Ox, HC, CO, etc. can be performed.

Further, since the main throttle valve 25 is fully opened and the load control is performed by the injection amount of the in-cylinder high pressure injection valves 33a, 33b, the pumping loss is reduced and the fuel consumption performance is further enhanced in addition to the lean combustion by stratified combustion. Become.

On the other hand, in the medium to high load operation H, the communication passage 42 is closed to stop the early release of the combustion gas, and the required output is secured by sufficient combustion. That is, the fuel is supplied mainly by the manifold injection valves 27a and 27b to the intake air that has flowed in through the main throttle valve 25 that is opened to an opening degree according to the load, and is mixed with the intake air in the intake passage in advance. Vaporization and atomization are promoted to obtain good flammability,
A predetermined amount of fuel is injected from the in-cylinder high-pressure injection valves 33a and 33b, and operation reliability is obtained by cooling the injection valves and preventing clogging.

According to the embodiment as described above, in the light load region, the combustion gas during the reaction is discharged to the exhaust passage,
Afterburning, the exhaust gas temperature can be raised to maintain good purification performance of the catalyst device 36 to ensure emission performance, and at the same time, fuel efficiency can be achieved by performing stratified charge combustion.

Although the example of the rotary piston engine has been described in the above embodiment, the present invention can be applied to other multi-cylinder engines.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a two-cylinder rotary piston engine having an intake / exhaust structure according to an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional view of the engine.

FIG. 3 is a map diagram showing a setting example of a control area.

FIG. 4 is a flow chart diagram for explaining processing of a controller.

[Explanation of symbols]

 E engine A, B cylinder 17 combustion chamber (working chamber) 21 intake port 22 intake passage 27a, 27b manifold injection valve 33a, 33b cylinder high pressure injection valve 35 exhaust passage 36 catalyst device 40, 41 exhaust communication port 42 communication passage 44 cut Valve (communication control means) 50 Controller

Claims (1)

Claim: What is claimed is: 1. An engine having a plurality of cylinders,
A communication passage is provided for communicating the combustion chamber of the cylinder in the latter half of the expansion stroke with the combustion chamber of the cylinder in the exhaust stroke, and a communication control means for opening the communication passage at a light load below a predetermined load is provided. The engine intake and exhaust structure. 2. The intake / exhaust structure for an engine according to claim 1, wherein the communication passage is provided in an intermediate housing of a multi-cylinder rotary piston engine.