WO2015186262A1

WO2015186262A1 - Spark ignition timing control device for internal combustion engine

Info

Publication number: WO2015186262A1
Application number: PCT/JP2014/065161
Authority: WO
Inventors: 松田　健
Original assignee: 日産自動車株式会社
Priority date: 2014-06-06
Filing date: 2014-06-06
Publication date: 2015-12-10

Abstract

An internal combustion engine is provided with a supercharging compressor that pressurizes intake air in an intake air passage, and an exhaust refluxing device that refluxes part of exhaust into a supply passage upstream of the compressor. An exhaust concentration sensor is disposed downstream of the compressor in the intake air passage, and a controller controls spark ignition timing on the basis of a detected exhaust concentration. By disposing the exhaust concentration sensor downstream of the compressor, it is possible to detect the exhaust concentration with the intake air and the exhaust sufficiently mixed together. Therefore, exhaust concentration detection accuracy is increased. Further, because the exhaust concentration is detected at a position close to the combustion chamber of the internal combustion engine, a time lag between a change in the exhaust concentration detected and a change in the actual exhaust concentration in the intake air in the combustion chamber is reduced, whereby the spark ignition timing can be controlled with high accuracy in accordance with the actual exhaust concentration in the intake air in the combustion chamber.

Description

Spark ignition timing control device for internal combustion engine

The present invention relates to ignition timing control in a spark ignition type internal combustion engine.

Exhaust gas recirculation control for recirculating a part of exhaust gas to the intake air of the internal combustion engine is known as a temperature control technique for the combustion chamber of the internal combustion engine. When the concentration of the exhaust gas in the intake air changes due to the exhaust gas recirculation control, the optimal ignition timing for the air-fuel mixture in the combustion chamber also changes.

In order to keep the ignition timing optimal at all times, JPS63-289266A issued by the Japan Patent Office in 1988 detects the oxygen concentration of the intake air of the internal combustion engine with an oxygen sensor, and determines the ignition timing based on the detected oxygen concentration. Propose to control. In this prior art, the oxygen concentration downstream of the throttle is detected by an oxygen sensor, and the ignition timing of the spark plug facing the combustion chamber is controlled to a timing suitable for the oxygen concentration.

On the other hand, in order to improve the output performance and fuel consumption of an internal combustion engine, it is known to supercharge intake air using a supercharger such as a turbocharger or a supercharger. The supercharger includes a compressor, and the intake air in the intake passage is supplied to the combustion chamber of the internal combustion engine while being compressed by the compressor. Even in such a supercharged internal combustion engine, the temperature of the combustion chamber can be controlled by performing the exhaust gas recirculation control. In that case, the exhaust gas recirculation passage is connected to the intake passage upstream of the turbocharger or supercharger compressor.

However, when the exhaust gas recirculation passage is connected to the intake passage upstream of the compressor and the ignition timing is controlled based on the oxygen concentration upstream of the compressor, the following problem occurs.

That is, since the control of the boost pressure and the exhaust gas recirculation control are different in responsiveness, if the ignition timing is controlled to the target timing set based on the target exhaust gas recirculation (EGR) rate, the target EGR rate of the actual EGR rate during the transient Due to delays in following, knocks and misfires may occur. Therefore, it is necessary to limit the target EGR rate, and as a result, it becomes difficult to perform optimal exhaust gas recirculation control. This becomes a problem in improving fuel consumption.

In the above prior art, the oxygen sensor arranged upstream of the compressor detects the oxygen concentration immediately downstream of the connection portion of the exhaust pipe flow passage to the intake passage. It will be. In general, the fresh air sucked in by the intake passage and the exhaust gas flowing in from the exhaust pipe flow passage are not immediately mixed, so there is a possibility that a considerable deviation has occurred in the exhaust concentration of the gas at the point where the oxygen sensor detects the oxygen concentration. is there. Therefore, it cannot be said that the accuracy of the actual EGR rate obtained from the detection value of the oxygen sensor is sufficient.

Therefore, an object of the present invention is to enable accurate detection of the EGR rate even when the internal combustion engine is in a transient state.

In order to achieve the above object, an embodiment of the present invention includes a supercharging compressor that pressurizes intake air in an intake passage, and an exhaust gas recirculation device that recirculates part of exhaust gas to a supply passage upstream of the compressor. The present invention is applied to a spark ignition timing control device for an internal combustion engine. The spark ignition timing control device includes an exhaust concentration sensor provided downstream of the compressor in the intake passage, and a controller that controls the spark ignition timing based on the exhaust concentration detected by the exhaust concentration sensor.

FIG. 1 is a schematic configuration diagram of a spark ignition timing control device according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between oxygen concentration and oxygen sensor output. FIG. 3 is a diagram showing the relationship between the EGR rate and the oxygen concentration. FIG. 4 is a flowchart showing an ignition timing control routine executed by the controller according to the embodiment of the present invention.

Fig. Of the drawing. Referring to FIG. 1, a spark ignition type multi-cylinder internal combustion engine 1 for a vehicle is rotated by injecting fuel into intake air sucked from an intake passage 2 and igniting and burning a mixture of intake air and fuel with a spark plug. To do. The combustion gas is discharged through the exhaust passage 3.

An exhaust gas recirculation (EGR) passage 4 for connecting a part of the exhaust gas to the intake air is connected to the intake passage 2. The EGR passage 4 is provided with an exhaust cooler 5 for cooling the exhaust and an EGR valve 6 for adjusting the exhaust flow rate.

The intake air mixed with a part of the exhaust is pressurized by the compressor 8 of the turbocharger 7 and cooled by the intercooler 9 provided in the intake passage 2. The intake passage 2 is provided with an intake bypass passage 10 and an intake bypass valve 11 that bypass the compressor 8. The intake air in the intake passage 2 cooled by the intercooler 9 is supplied to the combustion chambers 14 of the internal combustion engine 1 via the intake manifold 13 after the flow rate is adjusted by the throttle 12.

On the other hand, the combustion gas discharged from the combustion chamber 14 is collected into the exhaust passage 16 via the exhaust manifold 15. An exhaust turbine 17 of the turbocharger 7 is provided in the exhaust passage 3. After the exhaust turbine 17 is driven to rotate, the exhaust gas is purified by oxidizing or reducing the exhaust catalyst 18 and then released into the atmosphere. The exhaust turbine 17 is coupled to the compressor 8 with a common rotating shaft, and the compressor 8 operates according to the rotation of the exhaust turbine 17.

The exhaust passage 3 is provided with an exhaust bypass passage 19 that bypasses the exhaust turbine 17 and an exhaust bypass valve 20. Both the intake bypass valve 11 and the exhaust bypass valve 20 have a role of preventing the turbocharger 7 from surging.

In the internal combustion engine 1 configured as described above, the ignition timing control by the spark plug is performed by the spark ignition timing control device. The spark ignition timing control device includes a controller 21.

The controller 21 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller 21 with a plurality of microcomputers.

In order to control the ignition timing, an oxygen sensor 22 for detecting the oxygen concentration in the intake air is connected to the controller 21 as an exhaust concentration sensor through a signal circuit. The oxygen sensor 22 is provided in the middle of the intake manifold 13 located on the downstream side of the compressor 8 in the intake passage 2.

Also connected to the controller 21 via a signal circuit are a rotation speed sensor for detecting the rotation speed of the internal combustion engine 1 and an accelerator pedal depression amount sensor for detecting the depression amount of the accelerator pedal of the vehicle, for example. The In the ignition timing control of the internal combustion engine 1, these sensors are well known and are not shown.

FIG. The ignition timing control routine executed by the controller 21 will be described with reference to FIG. This routine is repeatedly executed at regular time intervals of, for example, 10 milliseconds during operation of the internal combustion engine 1.

In step S1, the controller 21 determines basic ignition timing based on the rotational speed and load of the internal combustion engine 1. This determination is made in advance with reference to a map that is predetermined according to the rotational speed and load of the internal combustion engine 1 and stored in the ROM.

In step S2, the controller 21 reads the output value of the oxygen sensor 22. The output of the oxygen sensor 22 is output as a current value Ip milliampere (mA).

In step S3, the controller 21 calculates the FIG. The current value Ip is converted into the oxygen concentration O ₂ (%) with reference to the map having the contents shown in FIG. Next, FIG. The EGR rate K (%) is calculated from the oxygen concentration O ₂ (%) with reference to the map shown in FIG. Here, the higher the oxygen concentration O ₂ (%), the lower the exhaust concentration in the intake air. In other words, the higher the oxygen concentration O ₂ (%), the lower the EGR rate K (%).

In step S4, the controller 21 corrects the basic ignition timing based on the EGR rate K and determines the final ignition timing. Specifically, correction is performed to advance the ignition timing as the EGR rate K increases. This is to promote ignition of the air-fuel mixture containing a large amount of exhaust gas, which is an inert gas. After the process of step S4, the controller 21 ends the routine.

The above control is performed in combination with the control of the EGR rate K by adjusting the opening degree of the EGR valve 6. In this spark ignition timing control device, an oxygen sensor 22 for obtaining the actual EGR rate K is provided in the middle of the intake manifold 13. This brings about the following preferable effect in controlling the ignition timing.

First, in the control of the EGR amount, it takes time until the exhaust gas concentration of the intake air supplied to the combustion chamber 14 changes after the opening degree of the EGR valve 6 is changed. On the other hand, since the ignition by the spark plug is performed in synchronization with the pulse signal from the controller 21, the responsiveness is extremely high. Therefore, for example, when the oxygen sensor 22 is provided between the connection portion of the EGR passage 4 of the intake passage 2 and the compressor 8, the intake air of the EGR rate K calculated based on the output signal of the oxygen sensor 22 is actually burned. There is a time delay before it is sucked into the chamber 14.

On the other hand, when the basic ignition timing is corrected to advance based on the output signal of the oxygen sensor 22, the ignition timing immediately changes to the corrected timing. As a result, when the internal combustion engine 1 is in a transient state, the period until the EGR rate of the air-fuel mixture in the combustion chamber 14 actually changes is changed to the air-fuel mixture at an ignition timing that does not correspond to the actual intake air EGR rate. Will be ignited. Such a deviation in the ignition timing causes misfire and knocking.

Further, when the oxygen sensor 22 is disposed between the connection portion of the EGR passage 4 of the intake passage 2 and the compressor 8, the oxygen sensor 22 detects the oxygen concentration of the intake air immediately after the exhaust gas flows into the intake passage 2 from the EGR passage 4. Will do. It takes time for the exhaust gas flowing into the intake passage 2 to mix with fresh air, and during this time, the distribution of the exhaust gas in the cross section of the intake passage 2 tends to be biased. Therefore, the accuracy of the oxygen concentration detected by the oxygen sensor 22 tends to vary. Such variations reduce the detection accuracy of the EGR rate K.

From the above situation, it is necessary to control the ignition timing of the internal combustion engine 1 with a sufficient safety factor. However, as a result, it is inevitable that it becomes difficult to perform a sufficient amount of EGR or that the ignition timing control accuracy is lowered.

Since this spark ignition timing control device is provided with the oxygen sensor 22 in the middle of the intake manifold 13, it is possible to solve the above-mentioned problems and perform highly accurate ignition timing control. That is, the detected oxygen concentration O ₂ (%) of the intake air is very close to the oxygen concentration of the intake air actually supplied to the combustion chamber 14. That is, the accuracy of detecting the oxygen concentration is improved. Further, since the time lag between the change in the EGR rate K obtained from the oxygen concentration O ₂ (%) and the change in the actual EGR rate of the intake air in the combustion chamber 14 is small, the change in the EGR rate of the intake air in the combustion chamber 14 The ignition timing can be corrected with high accuracy.

As described above, according to this spark ignition timing control device, the time lag between the change in the EGR rate K based on the output signal of the oxygen sensor 22 in the transient state and the actual EGR rate of the intake air in the combustion chamber 14 can be kept small. . Further, since the oxygen sensor 22 provided in the middle of the intake manifold 13 downstream of the compressor 8 detects the oxygen concentration in a state where the intake air and the exhaust gas are sufficiently mixed, the EGR rate based on the oxygen concentration O ₂ (%) is detected. The calculation accuracy of K (%) can be increased.

As mentioned above, although this invention has been described through specific embodiments, this invention is not limited to the above embodiments. Those skilled in the art can make various modifications or changes to these embodiments within the scope of the claims.

For example, in the above embodiment, the oxygen sensor 22 is used as the exhaust gas concentration sensor, but the exhaust gas concentration in the intake air is detected by a carbon dioxide sensor that detects the concentration of carbon dioxide (CO ₂ ), which is the main component of the combustion gas. Can be used as an exhaust concentration sensor instead of the oxygen sensor 22.

As described above, since the spark ignition timing control device according to the present invention has the exhaust gas concentration sensor provided downstream of the compressor, it can detect the change in the EGR rate of the intake air in the combustion chamber with high accuracy and high response. Therefore, an effect of improving the control accuracy of the ignition timing in the transient state of the vehicle internal combustion engine in which the operating conditions widely vary can be expected.

Claims

In a spark ignition timing control device for an internal combustion engine, comprising: a supercharging compressor that pressurizes intake air in an intake passage; and an exhaust gas recirculation device that recirculates part of exhaust gas to a supply passage upstream of the compressor.
An exhaust concentration sensor provided downstream of the compressor in the intake passage;
A spark ignition timing control device for an internal combustion engine, comprising: a programmable controller programmed to control spark ignition timing based on an exhaust concentration detected by an exhaust concentration sensor.
2. The spark ignition timing control device for an internal combustion engine according to claim 1, wherein the exhaust concentration sensor is provided downstream of the throttle.
The spark ignition timing control device for an internal combustion engine according to claim 2, wherein the exhaust concentration sensor is provided in the intake manifold.
The spark ignition timing control device for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust concentration sensor comprises an oxygen sensor that detects an oxygen concentration in the intake air.
The spark ignition timing control device for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust gas concentration sensor is a carbon dioxide sensor that detects a carbon dioxide concentration in the intake air.
The controller is further programmed to determine a final ignition timing by setting a basic ignition timing based on the rotational speed and load of the internal combustion engine and correcting the basic ignition timing based on exhaust concentration. A spark ignition timing control device for an internal combustion engine.