JPH055476A - Ignition device for rotary piston engine - Google Patents

Abstract

PURPOSE:To reduce generation of NOx by ignition control in a rotary piston engine. CONSTITUTION:A rotor side spark plug 41 is provided in each surface appearing in an operating chamber 17 of a rotor 15, and an ignition control means 40, by which a plurality of times of continuous ignition can be performed during one combustion stroke, is connected to the concerned rotor side spark plug so as to perform the continuous ignition in the case where a flame speed is lower than a rotor rotational speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary piston engine ignition device for suppressing the amount of NOx produced.

[0002]

2. Description of the Related Art Conventionally, as an ignition device for a rotary piston engine, a plurality of ignition plugs are arranged at positions facing a combustion stroke of a rotor housing, as disclosed in Japanese Patent Laid-Open No. 64-36929. A technique is known in which a plurality of ignitions are performed for one combustion stroke to improve combustion efficiency and improve output performance and fuel efficiency performance.

[0003]

By the way, in a rotary piston engine, improvement of fuel efficiency is an important issue. For that purpose, the fuel is unevenly distributed in the vicinity of the spark plug to secure a good ignitability and the working chamber. Although the stratified charge combustion technology that makes the overall air-fuel ratio lean is effective, this stratified charge combustion technology has the following emission problems, making it difficult to obtain a significant improvement in fuel efficiency. ing.

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 response to the above-mentioned problems, the intake closing timing is delayed to lower the pressure and temperature of the working chamber at the compression top dead center to suppress combustion and reduce the amount of NOx produced. It is possible to raise the temperature of exhaust gas by promoting combustion, or to raise the temperature of exhaust gas by restricting intake air to suppress the amount of air filled in the working 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.

On the other hand, as in the above-mentioned prior art, a plurality of ignition plugs are arranged in the rotor housing along the direction of rotation of the rotor, that is, the shape of the working chamber, and multipoint ignition is carried out from the ignition point to the end of combustion. Shortening the distance to shorten the combustion time reduces adiabatic compression due to flame propagation and reduces the NOx generation amount as the combustion temperature decreases, but further reduces the NOx generation. Therefore, in order to increase the number of ignitions, it is necessary to increase the number of installed spark plugs, which is difficult from the viewpoint of the installation interval of the spark plugs and the strength of the rotor housing.

In view of the above circumstances, an object of the present invention is to provide an ignition device for a rotary piston engine, which can perform ignition control so as to further reduce the generation of NOx.

[0008]

In order to achieve the above object, the ignition device for a rotary piston engine according to the present invention is provided with a rotor-side ignition plug on each surface facing the working chamber of the rotor, and the rotor-side ignition plug is provided once. The ignition control means capable of performing continuous ignition a plurality of times during the combustion stroke is connected.

Further, the ignition control means performs continuous ignition by the rotor-side spark plug only when the flame speed is lower than the rotor rotation speed, and the flame speed is set to engine rotation, charging efficiency and charging efficiency in order to execute the continuous ignition. It is preferable to provide a fuel injection valve for injecting fuel directly into the working chamber, which is obtained from the air-fuel ratio.

[0010]

In the ignition device for a rotary piston engine as described above, the rotor-side spark plug capable of continuous ignition is provided on the rotor side, and the rotor-side spark plug ignites in response to the rotation of the rotor. The position moves, the rotor rotation speed is higher than the flame speed associated with the first ignition, and in the operating state where ignition can precede the flame, continuous ignition is performed by the spark plug on the rotor side and adiabatic compression is not received. A large number of flames are formed, the combustion temperature is suppressed and N
The generation of Ox can be effectively reduced without requiring spark plugs for the number of ignitions. In particular, by reducing the adiabatic compression combustion at the end of the working chamber, it is possible to effectively reduce the generation of NOx even in the light load region, and eventually it becomes possible to make lean by stratified combustion, while ensuring emission performance. It is possible to improve fuel efficiency.

That is, in general, the amount of NOx produced in combustion has a strong correlation with the combustion temperature, and further, the combustion temperature has a very strong correlation with the distance from the ignition point. That is,
Since the flame generated from the ignition point proceeds while adiabatically compressing the unburned air-fuel mixture portion which is the traveling direction, the temperature of the unburned air-fuel mixture is considerably increased at the combustion end, and as a result, the NOx generation amount at the end is maximized. .. If these relationships are shown by a formula, the amount of NOx generated per unit volume at the distance x from the ignition point is [dθ _NOx / dv] _x = f (ξ) · ^{xg (K)} where f (ξ): Form factor of working chamber g (K): Specific heat ratio x in the atmosphere of working chamber f (ξ)> 0, dg (K) / dK> 0. Therefore, it is understood that the NOx generation amount can be effectively suppressed even at the end of the working chamber by reducing the distance from the ignition point.

As in the present invention, continuous ignition is performed in a light load operation region in which the rotation speed of the rotor is faster than the flame speed, so that the ambient temperature is increased by the adiabatic compression by the first ignition flame. A new flame can be formed by the rotor-side spark plug before the flame reaches No. 2, and NOx can be effectively reduced by reducing the combustion temperature.

Furthermore, if a fuel injection valve for injecting fuel directly into the working chamber is installed, stratified charge combustion due to uneven distribution of fuel can be easily carried out, combustion efficiency is improved, and fuel consumption performance is improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall structure of a rotary piston engine equipped with an ignition device according to an embodiment.

The casing of the rotary piston engine E has a rotor housing 11 having an inner peripheral surface formed in a trochoid shape, and side housings 12 located on both sides of the rotor housing 11 (in the case of a plurality of cylinders, located between the cylinders). And an intermediate housing), which form a cylinder. A substantially triangular rotor 15 is housed in the space in the cylinder, and the rotor 15 is provided with an eccentric shaft 16
It is supported by and is designed to make a planetary rotational motion. With this rotor 15, the space inside the cylinder has three working chambers 17
In addition to being partitioned into
The compression, explosion and exhaust strokes are carried out.

Although not shown in detail, in order to seal the working chambers 17 of the rotor 15, there are apex seals slidably contacting 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 on both sides of each top, and a circular oil seal is attached on the inner side surface.

An intake port 21 opening to the working chamber 17 is formed in the side housing 12 at a position where an intake stroke should be performed, and an intake passage 22 connected to the intake port 21 has
A throttle valve 25 is installed on the upstream side of the surge tank 23,
An air flow sensor 26 for detecting the intake air amount is provided in the intake passage 22 further upstream, and a manifold injection valve is provided downstream.
27 are provided.

Further, the rotor housing 11 is formed with an exhaust port 31 opening to the working chamber 17 at a position where an exhaust stroke should be performed, and a housing side ignition plug 32 is arranged at a position where an explosion stroke should be performed. It is set up. Further, an in-cylinder high pressure injection valve 33 is installed adjacent to the ignition plug 32, and the in-cylinder high pressure injection valve 33 directly injects fuel into the working chamber 17. A catalyst device 36 is provided in the exhaust passage 35 connected to the exhaust port 31. Also,
A fuel passage from a high-pressure fuel injection pump 38 is connected to the in-cylinder high-pressure injection valve 33, and pressurized fuel is supplied.

On the other hand, in the recessed portion of the rotor 15, a rotor side ignition plug 41 is provided on each surface facing the respective working chambers 17, and an igniter is provided to the rotor side ignition plug 41 via ignition energy transmission means 42. An ignition control means 40 having a coil 43 is connected. The ignition control means 40 is partially configured by a controller 50 that controls the entire engine. Then, in accordance with the ignition control according to the operating state by the ignition control means 40, a signal for performing continuous ignition a plurality of times during one combustion stroke is input to the rotor-side ignition plug 41.

The ignition energy transmission means 42 is a known non-contact type or contact type energizing mechanism for energizing the rotor-side ignition plug 41 inside the rotor in response to the rotation of the rotor 15. It is composed of. An igniter coil (not shown) is also connected to the housing side ignition plug 32, and an ignition signal according to ignition control by the controller 50 is input.

Ignition by the rotor-side ignition plug 41 is
Discharge is performed so as to perform the continuous ignition in a predetermined region on the low load side (see FIG. 3 described later) where the flame speed is lower than the rotor rotation speed, and in other regions, one ignition is performed at a predetermined ignition timing. Controlled to do. Further, the flame speed is obtained by the engine rotation, the charging efficiency and the air-fuel ratio,
The control region is set by comparison with the rotation speed of the rotor, that is, the engine speed.

In the fuel injection control by the manifold injection valve 27 and the in-cylinder high pressure injection valve 33, the in-cylinder fuel injection is performed only by the in-cylinder high pressure injection valve 33 in the light load region where the engine load is below a predetermined value. The fuel injection by the manifold injection valve 27 is stopped to perform stratified charge combustion. The fuel injection control is performed by the control signals output from the controller 50 to the manifold injection valve 27 and the high-pressure fuel injection pump 38. In addition, the throttle valve 25
A throttle motor 51 is connected to and is opened / closed to a predetermined throttle opening by the operation of the throttle motor 51.

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. The reference signal from the reference sensor 56, the rotation signal from the phase sensor 57, and the like are input to detect the phase of each.

Ignition control by the controller 50 will be described with reference to the flowchart of FIG. After the control is started, it is determined in step S1 whether or not an ignition flag IF, which will be described later, is set to 1. In the initial stage, the ignition flag IF is 0 and N
When the O determination is made, the process proceeds to step S2, and it is determined based on the map of FIG. 4 whether the current operating state is the multiple ignition region (continuous ignition region). The map of FIG. 4 is set by the engine speed and the load (filling efficiency, fuel injection amount, etc.),
The region P on the low load side is a continuous ignition region, and the continuous ignition region P is set to have a characteristic that the load gradually decreases in the low rotation portion, and the other high load side is set to the single ignition region S.

If the determination in step S2 is YES and the ignition range is in the continuous ignition region P, the advance angle amount θig for performing the first ignition, the ignition interval Δt, the required number of times of ignition Nmax are set to the load and the engine speed in step S3. Calculate accordingly. Then, the ignition flag IF is set to 1 in step S4, and the timer is started in step S5.
In step S6, the first ignition is executed based on the advance angle amount θig, and in step S6, the ignition counter J is reset.

After the first ignition, the YES flag is set in step S1 in accordance with the setting of the ignition flag IF, and the process proceeds to step S8 so that the area determination is not performed again. If the determination in step S2 is NO and the ignition timing is in the single ignition region S, the process proceeds to step S14 to calculate the advance angle amount θig for single ignition, and based on this, step S14 is calculated.
Ignite at 15.

In step S8, it is determined whether or not the time corresponding to the ignition interval Δt before the next ignition in the continuous ignition has elapsed by comparing with the timer value t, and YES when the ignition interval Δt has elapsed. At the time of determination, step S9
In step S10, the ignition counter J is incremented, and the second ignition is performed. In the same process, continuous ignition is sequentially performed at every ignition interval Δt, and it is determined in step S11 whether the value of the ignition counter J has reached the required number of times of ignition Nmax.

When the determination in step S11 is YES and the required number of times Nmax of continuous ignition is completed, step S12
And the ignition flag IF is reset at step S13.
Reset the timer with and end the continuous ignition.

The 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 S21, and it is determined in step S22 whether or not the current operating state is in the light load region. This control map is set by, for example, the engine speed and the accelerator opening, the operating state of the low accelerator opening and the low rotation range is set to the light load region, and different injection control is performed in the other middle and high load regions. Is set to do.

If the determination in step S22 is YES and the engine is in the light load region, the process proceeds to step S23, the throttle valve 25 is opened to the fully open state, and the fuel injection by the manifold injection valve 27 is stopped in step S24. .. Then, in step S25, the basic injection amount based on the accelerator opening is variously corrected to calculate the fuel injection amount, and in step S26, a signal corresponding to this fuel injection amount is sent to the high-pressure fuel injection pump 38.
The fuel is injected into the working chamber 17 by the in-cylinder high-pressure injection valve 33, the load is controlled by this injection amount, and the stratified charge combustion is performed.

On the other hand, when the determination in step S22 is NO, that is, in the medium and high load range, the routine proceeds to step S27, where the opening of the throttle valve 25 based on the accelerator opening is calculated. Perform load control. Then, in step S28, a control signal corresponding to the throttle opening is output to the throttle motor 51 to drive the throttle valve 25.

Further, while the fuel injection by the in-cylinder high-pressure injection valve 33 is fixed to a predetermined value in step S29, step S29
In step 30, various corrections are made to the basic injection amount based on the intake air amount and the engine speed to calculate the fuel injection amount.
At 31, a signal corresponding to this fuel injection amount is output to the manifold injection valve 27, and fuel is supplied to the working chamber 17 from the intake passage 22.

Explaining the operation of the above-mentioned processing, in the light load region, the intake air passes through the fully open throttle valve 25, the intake passage 22 and the intake port 21, and the intake operation corresponding to the intake stroke. Before being sucked into the chamber 17 and compressed to be ignited by both spark plugs 32 and 41, fuel is injected and supplied by the in-cylinder high pressure injection valve 33 to perform stratified combustion. Further, when in the continuous ignition region P where the rotor rotation speed is faster than the flame speed, the rotor-side spark plug 41 performs multiple continuous ignitions during one combustion stroke according to the rotation of the rotor 15 to generate a flame. NOx is reached by igniting the parts that have not reached
Is effectively reduced.

That is, FIG. 5 shows the characteristic of calculating the NOx generation amount together with a comparative example, under the conditions that the engine speed is 1500 rpm and the average effective pressure is 3 kg / cm ² . The horizontal axis of this figure is the distance x from the ignition point, and the vertical axis shows the amount of NOx generated. Basically, as the distance from the ignition point increases, the adiabatic compression progresses and the combustion temperature increases. The amount of NOx generated tends to increase. The long dashed line is the characteristic in the case of premixed combustion (single ignition) in which fuel and intake air are mixed in advance by the manifold injection valve 27 and supplied to the working chamber, and stratified combustion is not performed. Since combustion is performed even in a portion where the distance is large, a large amount of NOx is generated by the combustion at this end. Further, the short broken line indicates the state where the in-cylinder high pressure injection valve 33 is performing stratified combustion (single ignition), the combustibility is good and the NOx generation amount is large at each distance, but the total fuel amount is small and the combustion completion distance is long. Is shortened, and the amount of NOx generated at the end portion is reduced.

On the other hand, in the case of the stratified combustion in which the continuous ignition is performed according to the present invention shown by the solid line, the combustion temperature is lowered by performing the combustion with a low temperature rise due to the adiabatic compression in the formation of a plurality of flames. The NOx generation amount is reduced as a whole, the combustion completion distance is shortened by the stratified combustion, and the NOx generation amount at the end portion is also reduced.

Further, the fuel supplied by the in-cylinder high pressure injection valve 33 at the time of the light load depending on the load is injected so as to be unevenly distributed in the vicinity of the ignition plug 32, and stratified charge combustion is performed. Fuel economy can be improved by making the fuel ratio lean. Moreover, in this state, since the throttle valve 25 is fully opened and the load control is performed by the injection amount of the in-cylinder high pressure injection valve 33, the pumping loss is reduced, and the fuel economy performance is further improved in addition to the lean combustion due to the stratified combustion.

On the other hand, in the operation on the high load side, the flame speed is faster than the rotor rotation speed, continuous ignition is stopped, and single ignition is performed by the housing side spark plug 32 and the rotor side spark plug 41 at a predetermined time. Fuel is mainly supplied by the manifold injection valve 27 to intake air that has flowed in through the throttle valve 25 that is open to a different opening, and is mixed with intake air in the intake passage 22 in advance to promote vaporization and atomization. The in-cylinder high-pressure injection valve 33 injects a predetermined amount of fuel, and the operation reliability is obtained by cooling the injection valve and preventing clogging.

According to the above-mentioned embodiment, the rotor 15 is provided with the rotor-side spark plug 41 capable of continuous ignition, and when the flame speed becomes lower than the rotor rotation speed, continuous ignition is performed to perform adiabatic compression. Combustion before the temperature rise due to becomes large makes it possible to form a flame that is less likely to undergo adiabatic compression, and lowering the combustion temperature effectively reduces the generation of NOx, especially in the light load region, and improves emission performance. While ensuring the fuel consumption, the in-cylinder high pressure injection valve 33 performs the stratified charge combustion to achieve both the improvement of the fuel efficiency due to the lean air-fuel ratio.

In the above embodiment, the spark plug 32 is arranged not only on the rotor side spark plug 41 but also on the housing side.
32 does not have to be installed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a rotary piston engine including an ignition device according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining ignition processing of a controller.

FIG. 3 is a flow chart for explaining a fuel injection process of a controller.

FIG. 4 is a map diagram showing an example of setting a continuous ignition region.

FIG. 5 is a characteristic diagram showing a relationship between continuous ignition and NOx generation amount together with a comparative example.

[Explanation of symbols]

 E Rotary piston engine 11 Rotor housing 15 Rotor 17 Working chamber 27 Manifold injection valve 32 Housing-side ignition plug 33 In-cylinder high-pressure injection valve 36 Catalyst device 40 Ignition control means 41 Rotor-side ignition plug 42 Ignition energy transmission means 43 Igniter coil 50 Controller

Claims (1)

Claim: What is claimed is: 1. In a rotary piston engine in which a rotor makes a planetary rotational movement in a casing to form a plurality of working chambers on the outer peripheral side of the rotor, the rotor side is provided on each surface facing the working chamber of the rotor. An ignition device for a rotary piston engine, wherein an ignition plug is provided, and an ignition control means capable of performing continuous ignition a plurality of times during one combustion stroke is connected to the rotor-side ignition plug. 2. The ignition device for a rotary piston engine according to claim 1, wherein the ignition control means performs continuous ignition by the rotor-side spark plug only when the flame speed is lower than the rotor rotation speed. 3. The ignition device for a rotary piston engine according to claim 2, wherein said ignition control means obtains the flame speed from engine rotation, charging efficiency and air-fuel ratio. 4. The ignition device for a rotary piston engine according to claim 1, wherein a fuel injection valve for directly injecting fuel into the working chamber is provided on the casing side.