JPH11148441A - Fuel supply device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the fuel consumption and the exhaust emission control improving effect, by expanding the stratified charge combustion operation area of an internal combustion engine. SOLUTION: The current is carried to a heater for fuel heating at the current carrying amount depending on an operating state, in the operating condition in which the fuel is difficult to be vaporized depending on the fuel temperature, the water temperature, and the carbon fouling condition of an ignition plug (S1 to S4). During the time to the warming-up where the water temperature Tw reaches a setting temperature Two or more, and when it is decided to be carbon fouling, the current carrying to the heater is continued to maintain the fuel temperature near its setting temperature Tso (S5 to S12).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for enabling a stratified combustion in a cold state in a spark ignition type direct injection internal combustion engine which performs a stratified combustion.

[0002]

2. Description of the Related Art In recent years, even in a spark ignition type engine such as a gasoline engine, an injection hole of a fuel injection valve is installed so as to face a combustion chamber, and fuel is directly injected into the combustion chamber by the fuel injection valve to perform partial load. Some are trying to perform stratified combustion in the area. According to the spark ignition type direct injection engine, compared to a premixed type spark ignition engine having a fuel injection valve at an intake port, fuel efficiency can be improved, transient operation characteristics are deteriorated due to fuel transport delay, and exhaust composition is reduced. There is an advantage that the deterioration of can be suppressed.

[0003] In this type of direct injection engine, as a method of increasing the fuel injection pressure in order to enhance the atomization effect of the fuel, a high pressure fuel pump is provided in the middle of a fuel supply passage, and the fuel pump is connected to the fuel injection valve. A fuel pressure sensor is provided in the fuel system, and the discharge pressure of the fuel pump is feedback-controlled so that the fuel pressure becomes an optimum target fuel pressure in accordance with the operation state (see Japanese Patent Application Laid-Open No. Hei 5-321784).

In addition, since fuel pressure cannot be expected to be increased by the high-pressure fuel pump at the time of start-up or immediately after start-up, there is a fuel supply system in which the fuel stored at a high pressure by an accumulator is supplied (see Japanese Utility Model Laid-Open No. 5-1854). ).

[0005]

However, the promotion of atomization of fuel by increasing the fuel pressure and improving the structure of the fuel injection valve as described above involves a great increase in costs such as development costs and piping strength. It also takes. Moreover, even in this case, there is a limit to atomization, and the fuel is not vaporized satisfactorily immediately after the start or in the cold period before the completion of warm-up, so that it is difficult to ignite even if stratified combustion is performed, and The liquid phase fuel adheres to the spark plug and causes smoldering, causing misfiring and generating a large amount of soot.

For example, it is possible to perform stratified combustion while suppressing the smoldering of the spark plug in the cold state by setting the shape of the piston crown so as to reduce the mixing ratio around the spark plug. However, such a fundamental system design change is substantially difficult, for example, stratified combustion after warm-up cannot be performed satisfactorily. Under these circumstances, a conventional spark ignition type direct injection engine that performs stratified combustion can perform stratified combustion only after warm-up, so that the effect of improving fuel efficiency and exhaust gas purification performance by stratified combustion is fully exhibited. Had not been.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem. In a spark ignition type direct injection engine which performs stratified charge combustion, fuel supply for an internal combustion engine capable of performing stratified charge combustion even at a cold time is provided. It is intended to provide a device.

[0008]

According to a first aspect of the present invention, there is provided an internal combustion engine having a fuel injection valve for injecting fuel into a combustion chamber and an ignition plug, and performing stratified combustion at least under predetermined operating conditions. In the fuel supply device, fuel supply means for heating the fuel supplied to the fuel injection valve at a cold time is provided.

According to the first aspect of the present invention, when the fuel is cold, the fuel is heated immediately after the start, thereby promoting the vaporization of the fuel spray and suppressing the smoldering of the spark plug. The stratified combustion can be performed as a ratio, so that the effect of improving the fuel efficiency and the exhaust gas purification performance by the stratified combustion can be maximized.

The invention according to claim 2 is characterized in that the fuel heating means is a ceramic heater.
According to the second aspect of the present invention, the use of the ceramic heater as the fuel heating means makes it possible to quickly increase the fuel temperature with good responsiveness.

The invention according to claim 3 is characterized in that the fuel heating means is provided at a connection between a fuel inlet of a fuel injection valve and a fuel supply pipe. According to the third aspect of the present invention, since the fuel heating means is disposed at a position closest to the fuel injection valve, it is possible to suppress a decrease in temperature from the time when the fuel is heated to the time when the fuel is injected, and the required amount of heating of the fuel is minimized. Limit.

Further, the invention according to claim 4 is characterized in that the fuel temperature,
At least one of the cooling water temperatures is detected, and the heating by the heating means is controlled according to the detected temperature value. According to the invention according to claim 4, the fuel temperature can be controlled to be heated to an appropriate temperature in accordance with the detected values of the fuel temperature and the cooling water temperature.

The invention according to claim 5 is characterized in that a smoldering state of the spark plug is detected and heating of the heating means is controlled according to the smoldering state of the spark plug. According to the fifth aspect of the invention, it is possible to control the heating amount of the fuel so as to suppress the smoldering according to the smoldering state of the ignition plug.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall system configuration of an embodiment of the present invention, and FIG. 2 shows the configuration around a fuel injection valve provided with fuel heating means according to the present invention. In FIG. 1, an engine 1 includes an electromagnetic fuel injection valve 2 and an injection hole thereof in a combustion chamber 3.
Inside the combustion chamber 3 through the intake port 4 and the intake valve 5, and the fuel injection valve 2
This is a spark-ignition direct-injection engine in which a fuel-air mixture is formed by injecting fuel from the fuel injector to ignite the fuel-air mixture by spark ignition using an ignition plug 6. It should be noted that stratified combustion performed by injecting fuel in the compression stroke to form a dense stratified mixture around the ignition plug 6 and homogeneous combustion performed by injecting fuel in the intake stroke to form a homogeneous mixture are: Switching is performed according to the operating state.

The exhaust gas of the engine 1 is discharged from the fuel chamber 3 through an exhaust valve 7 and an exhaust port 8, and is discharged to the atmosphere through an exhaust purification catalyst and a muffler (not shown). The fuel in the fuel tank 9 is discharged at a relatively low pressure by the first fuel pump 10 and filtered by a filter 12 interposed in a low-pressure fuel passage 11A. The fuel adjusted to a constant low pressure by the low-pressure regulator 13 provided by-passing the fuel passage 11B is sent to the high-pressure second fuel pump 14.

The high-pressure second fuel pump 14 is driven directly by a crankshaft or a camshaft of the engine 1 or indirectly via a gear or a belt, and pressurizes and discharges the low-pressure fuel to a high pressure. . From the second pump 14 to the high pressure side fuel passage 15
Is adjusted to a variable set fuel pressure by a high pressure regulator 16 as a fuel pressure control system provided integrally with the second fuel pump 14. The high-pressure regulator 16 is provided with a duty solenoid, and is capable of adjusting a set pressure by controlling a duty ratio.

The fuel injection valve 2 is controlled to open in response to a pulse signal of a predetermined width corresponding to the engine operating state sent from the control unit 17 containing a microcomputer at a predetermined injection timing to adjust the fuel pressure to the predetermined fuel pressure. The fuel thus injected is injected into the combustion chamber 3. The control unit 17 is provided for detecting the engine speed for the fuel injection control, and for controlling the second fuel pump 14.
A crank angle sensor 18 also for detecting the rotational speed of the air, an air flow meter 19 for detecting the intake air flow rate, a fuel pressure sensor 20 for detecting the fuel pressure in the high-pressure side fuel passage 15, and oxygen in the exhaust gas provided downstream of the exhaust manifold. Detection signals from various sensors such as an air-fuel ratio sensor (oxygen sensor) 21 for detecting the air-fuel ratio based on the detection of the air-fuel ratio are input.

Here, the control unit 17 controls the pulse width of the injection pulse signal, and starts the output of the injection pulse signal, that is, the fuel injection valve 2.
Controls the fuel injection period. FIG.
As shown, an annular ceramic heater 31 as a fuel heating means is fitted and attached to a connection portion between the fuel inlet of the fuel injection valve 2 and the common rail portion of the high-pressure side fuel passage 15. The energization of the ceramic heater 31 is controlled by a signal from the control unit 17.

Further, a fuel temperature sensor 32 for detecting a fuel temperature is provided in a fuel passage between the mounting portion of the ceramic heater 31 and the fuel injection valve 2, and a smoldering state of the ignition plug 6 is detected. A smoldering sensor 33 is provided. The smoldering sensor 32 detects that smoldering has occurred when the inter-electrode resistance during discharge of the spark plug 6 is less than a set resistance Os (for example, 2 MΩ) which does not reach the breakdown voltage.

In addition, a water temperature sensor for detecting the temperature of cooling water
A signal from the fuel temperature sensor 32, the water temperature sensor 34, and the smoldering sensor 32 is input to the control unit 17, and the control unit 17 detects the signal of the ceramic heater 31 based on the detected values. Control energization. FIG. 3 shows a flowchart of a power supply control routine for the ceramic heater 31. This routine is started after the start of the engine.

In step 1, the fuel temperature detected by the fuel temperature sensor 32, the water temperature detected by the water temperature sensor 34, and the smoldering state of the ignition plug 6 detected by the smoldering sensor 33 are read. In step 2, on / off determination of the ceramic heater 31 is performed based on the detection result read in step 1. Specifically, if at least one of the fuel temperature and the water temperature is equal to or lower than the set temperature or if the ignition plug 6 is smoldering, the process proceeds to step 3 and thereafter to turn on the heater 31 to heat the fuel. Start.

In step 3, based on the engine speed N and the load (such as the basic fuel injection amount Tp), the amount of power to the heater 31 is set according to the fuel flow rate. In step 4, the heater
31 is turned on, and control is performed so as to reach the set energization amount. In step 5, the detection result of the fuel temperature Ts is read. In step 6, it is determined whether the fuel temperature Ts has reached or exceeded the set temperature Tso.

If it is determined in step 6 that Ts ≧ Tso, the routine proceeds to step 7, in which the heater 31 is turned off to stop heating the fuel, and then the routine proceeds to step 8. Also, Ts <
If Tso is determined, the process returns to step 3 and the heater
Continue the energization heating of 31. In step 8, the detection result of the water temperature Tw is read. In step 9, it is determined whether the water temperature Tw has reached or exceeded the set temperature Two.

If it is determined in Step 9 that Tw <Two, the process returns to Step 3, and if it is determined that Tw ≧ Two, the process proceeds to Step 10. In step 10, the detection result of the smoldering state of the ignition plug 6 is read. In step 11,
It is determined whether or not smoldering has occurred. If it is determined that smoldering has occurred, the process returns to step 3, and if it is determined that smoldering has not occurred, the process proceeds to step 12, where the heater 31 is kept off and control is terminated. I do.

That is, it is necessary to avoid that the fuel temperature continues to rise excessively due to the energized heating of the heater 31, so that the heater 31 is turned off once when the set temperature Tso is reached, but before the warm-up, the heater 31 is turned off. When the fuel is turned off, the fuel temperature drops below an appropriate temperature, and the fuel vaporization decreases, and good stratified combustion cannot be continued. Therefore, the heater is energized and heated to maintain the fuel temperature near the set temperature Tso, and the fuel temperature is reduced. To prevent Also, when smoldering occurs, turning off the heater 31 and lowering the fuel temperature will further increase the smoldering.
Also, electric heating is performed so as to maintain the fuel temperature near the set temperature Tso, so that smoldering is quickly avoided.

Then, after the water temperature Tw reaches the set temperature Two and the warm-up is completed, the fuel temperature is maintained at a sufficiently high level even when the heater 31 is turned off, and smoldering does not occur. And the flow ends.
In this way, when the engine is cold, the heater 31 is energized immediately after the start to heat the fuel, thereby promoting the vaporization of the fuel spray and suppressing the smoldering of the ignition plug 6. The stratified combustion can be performed with a mixture ratio of, so that the effect of improving the fuel efficiency and the exhaust gas purification performance by the stratified combustion can be maximized.

In particular, in the present embodiment, since the ceramic heater is used as the fuel heating means, the fuel temperature can be raised quickly with good responsiveness. Further, since the energization of the heater is controlled while monitoring the fuel temperature, the water temperature, and the smoldering state, the fuel temperature can be maintained at an appropriate temperature. In addition,
Correcting the fuel injection pulse width Tp in the separately executed fuel injection amount control based on the detected value of the heated fuel temperature,
Further, the ignition timing is corrected and set based on the fuel temperature in the ignition timing control.

In the present embodiment, the ceramic heater 31 is mounted outside the fuel pipe and heated from the outside. However, as shown in FIG.
The heat wire 31 'may be provided through the inside of the fuel pipe at the same location as in FIG. 2. Since the fuel is directly heated, the thermal efficiency can be improved. Further, in the above-described embodiment, the fuel is heated after the start. However, also at the time of cranking, the heater is turned on at the time of cold when the fuel is hardly vaporized based on the detection results of the fuel temperature, the water temperature, and the smoldering state. A configuration may be adopted in which energization is performed and, if possible, stratified combustion is performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of a fuel supply device for an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is an enlarged view of a part around the fuel injection valve according to the embodiment;

FIG. 3 is a flowchart of a fuel heating control routine according to the embodiment.

FIG. 4 is a diagram showing a mounting structure of a ceramic heater according to another embodiment.

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 2 fuel injection valve 3 combustion chamber 17 control unit 18 crank angle sensor 31, 31 'ceramic heater 32 fuel temperature sensor 33 smoldering sensor 34 water temperature sensor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 69/00 310 F02M 31/12 321A 321G 321K 321H 321H

Claims (5)

[Claims] A fuel supply device for an internal combustion engine, comprising a fuel injection valve for injecting fuel into a combustion chamber and an ignition plug, and performing stratified combustion at least under predetermined operating conditions, wherein fuel supplied to the fuel injection valve is supplied. A fuel supply device for an internal combustion engine, comprising fuel heating means for heating when cold. 2. The fuel supply device for an internal combustion engine according to claim 1, wherein said fuel heating means is a ceramic heater. 3. The fuel supply for an internal combustion engine according to claim 1, wherein said fuel heating means is provided at a connection portion between a fuel inlet of a fuel injection valve and a fuel supply pipe. apparatus. 4. The apparatus according to claim 1, wherein at least one of a fuel temperature and a cooling water temperature is detected, and heating by said heating means is controlled in accordance with the detected temperature value. 3. A fuel supply device for an internal combustion engine according to claim 1. 5. The method according to claim 1, wherein a smoldering state of the ignition plug is detected, and heating of the heating means is controlled according to the smoldering state of the ignition plug. Fuel supply device for an internal combustion engine.