JPH09256879A - Spark ignition internal combustion engine - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] When the intake stroke and the exhaust stroke overlap, unburned fuel and oil from the combustion chamber and the exhaust pipe blow back to the intake valve side, and the inside of the intake port becomes oil or tar-like. Prevent the occurrence of malfunctions by preventing dirt from the deposits. SOLUTION: An intake pressure sensor 6 for detecting an engine load and an intake pressure determining means 1 for determining a low load.
0a and a movable valve control means 10b that variably controls the valve overlap and controls the valve overlap to a predetermined value or less when it is determined that the load is low.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for suppressing deposit accumulation in an intake port of a spark ignition type internal combustion engine in which fuel is directly injected into a cylinder.

[0002]

2. Description of the Related Art A conventional spark-ignition internal combustion engine for direct cylinder fuel injection is shown in FIG. 8 (FIG. 9 of JP-A-6-146886). According to this, the intake-exhaust overlap is set at a crank angle of 10 to 20 degrees.

[0003]

However, in such a conventional spark ignition type internal combustion engine, since the valve overlap is a value of zero or more in the entire operating range, the intake pipe inside is particularly low. Since negative pressure develops, unburned fuel or oil from the combustion chamber or exhaust pipe blows back to the intake valve side when the intake stroke and exhaust stroke overlap, and oil or tar-like deposits in the intake port. It becomes dirty, and in the worst case, the accumulation of deposit progresses, the deposit gets caught in the intake valve seat, and the compression pressure drops,
There is concern that the engine may start poorly or the engine output may drop.

The present invention has been made by paying attention to such a conventional problem, and in particular, at a low boost in which blowback to intake air becomes a problem, the valve overlap is set to a predetermined value or less, preferably to zero or less. By doing so, it is intended to solve the above problems.

[0005]

Means for Solving the Problems For this reason, the present invention provides
In a spark ignition type internal combustion engine that directly injects fuel into a cylinder, means for detecting an engine load, determining means for determining that the load is low, control means for variably controlling valve overlap, and low A control means for controlling the valve overlap to a predetermined value or less when it is determined to be a load is provided.

[0006]

Hereinafter, the present invention will be described with reference to the drawings. FIG. 2 is a diagram showing Embodiment 1 of the present invention. First, the structure will be described. The fuel injection valve 1 is provided below the intake port 3 to inject fuel directly into the combustion chamber. The intake valve 5 is variably controlled in its operating angle and lift amount by the variable valve mechanism 2. The details of the variable valve mechanism 2 are shown in FIG. 3, and the details are described in Japanese Patent Laid-Open No. 146830/1994.

The control system is shown in FIG. The intake pressure sensor 6 is provided in the collector and the intake pressure is sensed. The control unit 10 is provided with intake pressure determination means 10a for comparing the intake pressure signal with a predetermined value and variable valve control means 10b for controlling the overlap of the variable valve mechanism 2 based on the result of the intake pressure determination means 10a. To be

Next, the operation will be described. A description will be given according to the flowchart of FIG. When it is determined that the output signal of the intake pressure sensor 6 is lower than a predetermined pressure, a command signal is issued from the variable valve control means 10b so that the intake / exhaust exhaust overlap becomes zero or less. As a result, as shown in FIG. 5, the intake valve is switched to a cam having a small operating angle and a small lift amount, so that the overlap becomes zero or less from the next cycle of the command. This ensures that the overlap becomes zero or less at the time of low boost, and the unburned fuel and the oil content in the exhaust do not return to the intake side.
Therefore, it is possible to prevent the inside of the intake port 3 from being contaminated with an oily substance and depositing a carbonaceous substance or the like on it to form a deposit. Further, since the NOx component in the exhaust gas does not come into direct contact with the intake port 3, the generation of a muddy oil deposit due to the reaction between NOx and unburned hydrocarbons is suppressed.

Although there are similar concerns in a normal port injection type internal combustion engine, in fact, in port injection, the port is washed with gasoline fuel in each cycle, so the intake of oil and unburned fuel due to the port adhering mechanism. Dirt and deposits in the port are no longer an issue.

FIG. 6 shows a second embodiment. In the second embodiment, the valve overlap is set to zero or less at the time of fuel cut, and when the boost is extremely continued such as at the time of fuel cut, the blowback is suppressed and the intake port is suppressed from being contaminated. be able to.

FIG. 7 shows a third embodiment. This example shows a method of determining the development of boost when the intake pressure sensor 6 is not provided. As the boost develops when the throttle opening is small, the valve overlap is set to zero or less. By limiting the engine speed to a certain level or more, it is possible to specify the region where the boost has been developed and change the valve.

In addition, although not shown, a vehicle in which the valve overlap is zero or less when the load is low can be considered. However, for example, in the case of lean combustion at low load, boost does not necessarily develop, so there is the convenience of being able to control by the accelerator opening, but effective controllability is poor.

As described above, according to these embodiments, the configuration is such that the intake / exhaust valve overlap is set to zero or less in the operating range where the boost develops. Therefore, the oil in the intake port 3 is reduced. It is possible to obtain the effect that it is possible to suppress the stains caused by the components and the accumulation of deposits caused thereby. Further, each embodiment has the following effects in addition to the common effects described above. In the second embodiment shown in FIG. 6, when the high speed no-load condition where the boost is particularly developed is determined by the fuel cut, the overlap can be effectively reduced to zero or less at low cost without new sensing. In the third embodiment shown in FIG. 7, since the overlap is simply determined by the throttle opening, it is possible to reduce the cost and easily suppress the contamination in the intake port in a wide operating range.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention. Even if it is included in the present invention.

[0015]

As described above, according to the invention of claim 1, when the load of the engine is lower than a predetermined value, the valve overlap becomes a predetermined value or less, preferably zero or less. Due to the development of negative pressure in the intake pipe, exhaust gas in the exhaust pipe and blowback of burnt gas in the combustion chamber returning to the intake port are suppressed, and the intake port is covered with oil and tar-like deposits in the exhaust gas. It is possible to prevent the adhered parts from accumulating and biting into the valve seat to lower the compression pressure, resulting in poor starting and reduced output.

According to the second aspect of the present invention, when the negative pressure in the intake port is directly detected and the negative pressure in the intake develops and becomes smaller than the predetermined value, the valve overlap is equal to or less than the predetermined value.
Desirably, it is less than or equal to zero. Therefore, the exhaust gas in the exhaust pipe and the blowback of the burnt gas in the combustion chamber from returning to the intake port are suppressed, and the intake port is covered with oil in the exhaust gas and tar-like deposits. Is suppressed, the adhered matter is accumulated and bites into the valve seat to reduce the compression pressure,
It is possible to prevent a start-up failure and a decrease in output.

According to the third aspect of the present invention, when the fuel cut state is directly detected and the fuel is cut, the valve overlap becomes a predetermined value or less, preferably zero or less. Since the throttle valve is closed at the time, the negative pressure in the intake pipe develops, which suppresses exhaust gas in the exhaust pipe and blowback of burnt gas in the combustion chamber from returning to the intake port, and exhaust gas in the intake port. It is possible to prevent the oil from being covered with oil or tar-like deposits in the gas, and to prevent the deposits from accumulating and biting into the valve seat to reduce the compression pressure, resulting in poor starting or reduced output. Can be suppressed.

According to the fourth aspect of the present invention, when the throttle valve opening becomes smaller than a predetermined value, the valve overlap becomes a predetermined value or less, preferably zero or less. Therefore, since the throttle valve is closed, the intake pipe is closed. Due to the development of negative pressure, the exhaust gas in the exhaust pipe and the blowback of burnt gas in the combustion chamber from returning to the intake port are suppressed, and the inside of the intake port is filled with oil and tar-like deposits in the exhaust gas. It is possible to suppress the cover from being covered, and to prevent the adhered matter from being accumulated and caught in the valve seat to lower the compression pressure, resulting in a poor starting and a decrease in the output.

According to the invention of claim 5, when the throttle valve opening is smaller than a predetermined value and the engine speed is higher than the predetermined value, the valve overlap becomes a predetermined value or less, preferably zero or less. Because the engine speed is high and the throttle valve is closed, the negative pressure in the intake pipe is slightly developed, which suppresses the blowback of exhaust gas in the exhaust pipe and burned gas in the combustion chamber that returns to the intake port. The inside of the intake port is prevented from being covered with oil in the exhaust gas and tar-like deposits, and these deposits accumulate and bite into the valve seat, reducing the compression pressure, resulting in poor starting or output. Can be suppressed.

According to the sixth aspect of the invention, the valve overlap becomes zero or less, and therefore the negative pressure in the intake pipe develops, so that the exhaust gas in the exhaust pipe and the burnt gas in the combustion chamber enter the intake port. The reverse blowback is more completely suppressed, and the inside of the intake port is prevented from being covered with oil in the exhaust gas or tar-like deposits, and these deposits accumulate and bite into the valve seat to reduce the compression pressure. It is possible to more reliably suppress the decrease in the engine output and the decrease in the output.

[Brief description of drawings]

FIG. 1 is a control system diagram of a first embodiment.

FIG. 2 is an overall view of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the variable valve mechanism according to the first embodiment.

FIG. 4 is an operation explanatory diagram of the first embodiment.

FIG. 5 is an explanatory diagram of a valve operating angle and a lift according to the first embodiment.

FIG. 6 is an operation explanatory diagram of the second embodiment of the present invention.

FIG. 7 is an operation explanatory diagram of the third embodiment of the present invention.

FIG. 8 is a diagram showing an example of a conventional in-cylinder injection internal combustion engine.

[Explanation of symbols]

 1 Fuel Injection Valve 2 Variable Valve Mechanism 3 Intake Port 5 Intake Valve 6 Intake Pressure Sensor 10 Control Unit 10a Intake Pressure Judgment Means 10b Variable Valve Control Means

Claims (6)

[Claims] 1. In a spark ignition type internal combustion engine in which fuel is directly injected into a cylinder, a means for detecting an engine load, a determining means for determining that the load is low, and a valve overlap are variably controlled. A spark ignition type internal combustion engine having a control means and a control means for controlling the valve overlap to a predetermined value or less when it is determined that the load is low. 2. In a spark ignition type internal combustion engine for injecting fuel directly into a cylinder, a detecting means for detecting a pressure in an intake port, and a judging means for determining whether the pressure in the intake port is below a predetermined value. 2. A control means for variably controlling the valve overlap, and a control means for controlling the valve overlap below a predetermined value when it is determined that the pressure in the intake port is below a predetermined value. Spark ignition internal combustion engine. 3. A detection means for detecting a fuel cut state, a control means for variably controlling the valve overlap, and a control means for controlling the valve overlap below a predetermined value when the fuel cut state is determined. A spark ignition type internal combustion engine according to claim 1 or 2. 4. A spark ignition internal combustion engine for injecting fuel directly into a cylinder, detecting means for detecting a throttle opening, judging means for judging when the throttle opening is below a predetermined value, and valve overlap. 2. The spark ignition type internal combustion engine according to claim 1, further comprising: a control unit that variably controls the valve opening amount; and a control unit that controls the valve overlap to a predetermined value or less when the throttle opening is determined to be a predetermined value or less. 5. A spark ignition type internal combustion engine for injecting fuel directly into a cylinder, a detecting means for detecting a throttle opening, a determining means for judging that the throttle opening is below a predetermined value, and an engine speed. Detecting means for detecting the engine speed, determining means for determining that the engine speed is higher than a predetermined value, and determining means for determining that the throttle opening is smaller than the predetermined value and the engine speed is higher than the predetermined value. And a control means for variably controlling the valve overlap, and controlling the valve overlap below a predetermined value when it is determined that the throttle opening is smaller than a predetermined value and the engine speed is higher than the predetermined value. Spark ignition type internal combustion engine having a control means for controlling. 6. The spark ignition type internal combustion engine according to claim 1, wherein the predetermined value of the valve overlap is less than or equal to zero.