JP2010180724A - Control device of cylinder direct injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the deterioration in exhaust performance caused by interference between injection fuel and intake valves, while restraining an output shortage of an internal combustion engine in a cylinder direct injection internal combustion engine. <P>SOLUTION: This control device includes a fuel injection valve for directly injecting the fuel into a cylinder, the two intake valves and a variable valve train capable of changing a lift characteristic of the intake valves. When a request load of the internal combustion engine becomes a higher load than a predetermined reference in cold time of the internal combustion engine, a low lift characteristic capable of securing the suction air volume of not lacking in the request load, is calculated when setting only one intake valve to the low lift characteristic, and the timing in the latter period of a valve opening period of the intake valve set to the low lift characteristic, that is, timing when a lift quantity of the intake valve becomes a lift quantity of non-interfering between the intake valve and the injection fuel, is calculated, and the variable valve train is controlled for setting the one intake valve to the low lift characteristic, and the fuel injection valve is controlled so as to start fuel injection on and after the calculated timing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for a direct injection internal combustion engine.

  In an internal combustion engine that directly injects fuel into a cylinder, when fuel injection is performed in an intake stroke, the injected fuel may collide with the intake valve that is being opened, and a part of the fuel may adhere to the intake valve. In a cold state where the temperature of the intake valve is low, the fuel adhering to the intake valve does not evaporate well, which may increase the amount of PM and unburned fuel components in the exhaust. As countermeasures, for example, the following techniques have been proposed.

  Patent Document 1 describes that when the fuel injection is performed in the intake stroke, the lift amount of the intake valve is reduced.

  Patent Document 2 describes that when fuel injection is performed in the intake stroke, the valve opening operation of one of the two intake valves is stopped.

  Patent Document 3 describes that when fuel injection is performed in the intake stroke, fuel injection is performed within at least one of the above-mentioned and later periods of the intake valve opening period.

  An internal combustion engine that uses an alcohol-containing fuel as a fuel has a problem that startability is not good because the alcohol-containing fuel is less likely to vaporize than gasoline. For example, the following techniques have been proposed as countermeasures.

  In Patent Document 4, when starting an internal combustion engine using an alcohol-containing fuel, if the alcohol concentration of the fuel is a predetermined value or more, the fuel injection is stopped and the lift amount of the intake valve or the exhaust valve is minimized for a predetermined period. It is described to do.

  Patent Document 5 describes that when the internal combustion engine using an alcohol-containing fuel is started, the lift amount of the intake valve is decreased as the alcohol concentration of the fuel is higher.

  As techniques related to an internal combustion engine having two intake valves, for example, the following techniques have been proposed.

  In Patent Document 6, in an internal combustion engine in which both of the two intake valves are opened in the high rotation operation region and one of the two intake valves is stopped in the low rotation operation region, It is described that the operating range for opening both intake valves is expanded.

JP 2004-218603 A JP 2004-257352 A JP 2007-177740 A JP 2008-215143 A JP 2007-315355 A JP-A-7-097938

  If the lift amount of the intake valve is lowered or the opening operation of one of the two intake valves is stopped as in the above technique, the intake air amount is limited, so the required load is high. If this happens, the output of the internal combustion engine may be insufficient.

  In addition, in an internal combustion engine that uses alcohol-containing fuel, it is necessary to ensure a longer fuel injection period than in an internal combustion engine that uses normal fuel, so the fuel injection period tends to overlap with the valve opening period of the intake valve. Therefore, depending on the technique described above, it may be difficult to suitably avoid the interference between the in-cylinder injected fuel and the opened intake valve.

  The present invention has been made in view of these problems, and in a direct injection internal combustion engine, the interference between the in-cylinder injected fuel and the open intake valve is suppressed while suppressing the shortage of the output of the internal combustion engine. It aims at suppressing the deterioration of the exhaust performance resulting from this. It is another object of the present invention to suppress deterioration in exhaust performance caused by interference between an in-cylinder direct injection fuel and an open intake valve in an in-cylinder direct injection internal combustion engine that uses alcohol-containing fuel.

In order to achieve the above object, a control device for a direct injection internal combustion engine of the present invention is as follows.
A fuel injection valve for directly injecting fuel into the cylinder of the internal combustion engine;
Two intake valves provided in the cylinder;
A variable valve mechanism capable of changing a lift characteristic of at least one of the two intake valves;
When the internal combustion engine is cold, the variable valve mechanism is controlled so that the lift characteristic of at least one of the two intake valves is set to a low lift characteristic having a lift amount lower than that during warm-up. Control means;
With
When the control load of the internal combustion engine is higher than a predetermined reference when the internal combustion engine is cold,
The low lift characteristic so that the intake air amount of the internal combustion engine when the lift characteristic of one of the two intake valves is a low lift characteristic is an intake air amount that is not insufficient with respect to the required load. To calculate
The intake valve is opened in accordance with the calculated low lift characteristic at a later stage of the valve opening period, and the lift amount of the intake valve is determined so that the fuel injected from the fuel injection valve does not collide with the intake valve. Calculate the time when
Controlling the variable valve mechanism so as to set the lift characteristic of one of the two intake valves to the calculated low lift characteristic;
The fuel injection valve is controlled to start fuel injection after the calculated time.

  In the above configuration of the present invention, when the internal combustion engine is cold, when the fuel injected from the fuel injection valve collides with and adheres to the open intake valve, the attached fuel is less likely to evaporate well. Therefore, it refers to a temperature state that may cause the exhaust performance to deteriorate. When warming up, the temperature is higher than when cold, that is, even if the injected fuel collides with the intake valve and adheres, the adhered fuel evaporates well, so it is unlikely to deteriorate exhaust performance. It refers to such a temperature state.

The “predetermined standard” for the required load is whether or not a sufficient intake air amount can be secured when the lift characteristics of both of the two intake valves are set to low lift characteristics. Is the reference value of the required load for determining When the required load is higher than the reference, it can be determined that it is difficult to secure a sufficient intake air amount if both of the two intake valves have low lift characteristics.

  According to the present invention, when the required load is higher than the reference when the internal combustion engine is cold, one of the two intake valves is set to have a low lift characteristic. This low lift characteristic is calculated so as to ensure an intake air amount that is sufficient for the required load even when one of the two intake valves is set to the low lift characteristic. The Since the other of the two intake valves is set to a normal lift characteristic, it is possible to suitably secure an intake air amount that is not insufficient with respect to the required load.

  Further, based on the low lift characteristic calculated in this way, a time in the latter period of the valve opening period in which the lift amount is set so that the injected fuel does not collide with the intake valve set to the low lift characteristic is calculated. The fuel injection start time is set at. Here, “the latter period of the valve opening period” means that, during the valve opening period from when the intake valve starts to open until the valve is closed, the lift amount toward the valve closing after the lift amount peaks Refers to the period of decrease. Thereby, it is possible to avoid collision of fuel injected from the fuel injection valve with the intake valve set to the low lift characteristic. Therefore, even when the internal combustion engine is cold, it is possible to suppress the deterioration of the exhaust performance caused by the injected fuel colliding with the opened intake valve.

  According to the present invention, one of the two intake valves is set to the low lift characteristic, and fuel injection is started after the time when the injected fuel does not collide with the intake valve set to the low lift characteristic. Therefore, the interference between the intake valve set to the low lift characteristic and the fuel injection is avoided. Therefore, even when the internal combustion engine is cold, it is possible to suitably suppress the deterioration of the exhaust performance caused by the injected fuel colliding with the intake valve. In addition, one of the two intake valves is set to a normal lift characteristic, and when only one of the two intake valves is set to a low lift characteristic, a low intake air amount that is sufficient for the required load can be secured. Since the lift characteristics are calculated, it is possible to suppress the output of the internal combustion engine from being insufficient with respect to the required load even under high load conditions.

  The fuel injection start timing can be set to any timing as long as it is a late timing of the valve opening period in which the lift amount is such that the injected fuel does not collide with the intake valve set to the low lift characteristic.

  If the required load is not higher than the reference load when the internal combustion engine is cold, both the two intake valves are set to low lift characteristics to further prevent interference between the injected fuel and the opened intake valve. You may make it avoid reliably.

In a direct injection internal combustion engine using an alcohol-containing fuel, in order to suppress deterioration in exhaust performance due to interference between the direct injection fuel in the cylinder and the intake valve being opened, the present invention provides:
A fuel injection valve for directly injecting alcohol-containing fuel into the cylinder of the internal combustion engine;
Two intake valves provided in the cylinder;
A variable valve mechanism capable of changing a lift characteristic of at least one of the two intake valves;
When the internal combustion engine is cold, the variable valve mechanism is controlled so that the lift characteristic of at least one of the two intake valves is set to a low lift characteristic having a lift amount lower than that during warm-up. Control means;
Alcohol concentration acquisition means for acquiring the alcohol concentration of the alcohol-containing fuel;
With
When the alcohol concentration acquired by the alcohol concentration acquisition unit is higher than a predetermined reference when the internal combustion engine is cold,
A fuel injection start timing is calculated so that fuel injection from the fuel injection valve ends by a predetermined injection end limit timing;
The low lift characteristic is calculated as a lift characteristic in which the lift amount after the calculated fuel injection start timing is a lift amount at which the fuel injected from the fuel injection valve does not collide with the intake valve,
Controlling the variable valve mechanism so as to set the lift characteristic of one of the two intake valves to the calculated low lift characteristic;
The fuel injection valve is controlled to start fuel injection at the calculated fuel injection start timing.

  In the configuration of the second invention, when the internal combustion engine is cold and warm, it can be defined by replacing "fuel" in the first invention with "alcohol-containing fuel". That is, when the internal combustion engine is cold, when the alcohol-containing fuel injected from the fuel injection valve collides with and adheres to the open intake valve, the attached alcohol-containing fuel does not easily evaporate. It refers to a temperature state that may cause the exhaust performance to deteriorate. When warming up, the temperature is higher than when cold, that is, even if the injected fuel collides with the intake valve and adheres, the adhering alcohol-containing fuel evaporates well, causing the exhaust performance to deteriorate. It refers to a temperature state that is difficult to become.

  Alcohol-containing fuels have a smaller theoretical air-fuel ratio than ordinary fuels and are less likely to vaporize when cold, so it is necessary to ensure a longer fuel injection period than internal combustion engines that use ordinary fuels. If the fuel injection end time becomes excessively late due to the long fuel injection period, the exhaust performance deteriorates. The “injection end limit time” in the second aspect of the invention is a limit value of the fuel injection end time that does not cause deterioration of exhaust performance, and can be determined in advance. In the second aspect of the invention, it is assumed that the fuel injection is performed so that the fuel injection end timing is not later than the injection end limit timing.

  The higher the alcohol concentration of the alcohol-containing fuel, the longer the required fuel injection period. Therefore, depending on the alcohol concentration of the alcohol-containing fuel, the required fuel injection period is the fuel injection start timing calculated according to the first invention described above (that is, when one of the two intake valves is set to the low lift characteristic) Furthermore, in the low lift characteristics calculated so as to ensure a sufficient intake air amount with respect to the required load, the fuel is generated at a later time when the lift amount is such that the fuel injection and the intake valve do not interfere with each other. When the injection is started, there is a possibility that the fuel injection cannot be completed by the injection end limit timing.

  The “predetermined standard” regarding the alcohol concentration in the configuration of the second aspect of the invention is that when fuel injection is started at the fuel injection start time calculated according to the first aspect described above, fuel injection is performed before the injection end limit time. This is a reference value of the alcohol concentration for determining whether or not it can be terminated. When the alcohol concentration is higher than the reference, it can be determined that it is difficult to end the fuel injection by the injection end limit time when the fuel injection is started at the fuel injection start time calculated according to the first invention.

  In such a case, according to the second aspect of the invention, based on the required fuel injection period, a fuel injection start timing is calculated so that the fuel injection ends before the injection end limit timing, and the calculated fuel injection start timing is calculated. The injection of the alcohol-containing fuel is started.

  As a result, it is possible to suppress the fuel injection end timing from being delayed beyond the injection end limit timing, and thus it is possible to suppress the deterioration of the exhaust performance due to the delay of the fuel injection end timing.

Similarly to the first invention described above, the second invention also suppresses the interference between the injected fuel and the intake valve by setting the lift characteristic of one of the two intake valves to a low lift characteristic. However, in the second invention, the low lift characteristic is calculated based on the fuel injection start timing calculated as described above.

  Specifically, the lift characteristic that the lift amount of the intake valve set to the low lift characteristic after the fuel injection start time calculated as described above is a lift amount that does not interfere with the intake valve and the injected fuel. Is set as one of the intake valves as a low lift characteristic. In other words, a lift characteristic is calculated such that the lift amount at the fuel injection start timing calculated as described above is equal to or less than the upper limit value of the lift amount at which the intake valve and the injected fuel do not interfere with each other, and this is used as a low lift characteristic. Set to the intake valve.

  Thereby, it is possible to avoid collision between the intake valve set to the low lift characteristic and the fuel injected from the fuel injection valve. Accordingly, it is possible to suppress the deterioration of the exhaust performance due to the injected fuel colliding with the intake valve even under the cold condition of the internal combustion engine.

  According to the second aspect of the present invention, in-cylinder injected fuel and intake air during valve opening are suppressed while suppressing deterioration in exhaust performance due to excessively late fuel injection end timing in an internal combustion engine using alcohol-containing fuel. It is possible to suppress the deterioration of the exhaust performance due to the interference with the valve.

  Note that even in an internal combustion engine using an alcohol-containing fuel, the low-lift characteristic calculated so that the alcohol concentration is below the standard and a sufficient intake air amount can be secured for the required load as in the first invention. If it is determined that the fuel injection end timing does not exceed the injection end limit timing even if the fuel injection start timing is set based on the above, the low lift characteristic calculated according to the first invention is set for one intake valve. You may do it.

  As described above, in both the first invention and the second invention, it is avoided that the fuel injected from the fuel injection valve collides with the intake valve set to the low lift characteristic. Even under the cold machine conditions, it is possible to suitably suppress the deterioration of the exhaust performance due to the injected fuel colliding with the intake valve.

  Further, in the first invention, even when the required load is high, it is possible to secure a sufficient intake air amount with respect to the required load, so that it is possible to prevent the output of the internal combustion engine from being insufficient.

  In the second aspect of the invention, even when the alcohol concentration is high, it is avoided that the fuel injection end timing is excessively delayed, so that deterioration of exhaust performance due to the fuel injection end timing being delayed is also suppressed. can do.

  In the second aspect of the invention, the intake air amount can be supplemented by the effect of latent heat when alcohol evaporates in the cylinder, so that the output shortage of the internal combustion engine due to the insufficient intake air amount is suppressed.

  According to the present invention, in an in-cylinder direct injection internal combustion engine, it is possible to suppress deterioration of exhaust performance due to interference between in-cylinder injected fuel and an open intake valve while suppressing the output of the internal combustion engine from being insufficient. Can do. Further, in a direct injection internal combustion engine that uses an alcohol-containing fuel, it is possible to suppress deterioration in exhaust performance caused by interference between the in-cylinder injected fuel and the intake valve that is being opened.

1 is a diagram schematically illustrating a schematic configuration of an internal combustion engine according to a first embodiment. It is a figure which shows the lift characteristic of the intake valve of the internal combustion engine which concerns on Example 1 and 2. FIG. 4 is a flowchart showing the processing contents of fuel injection control and variable valve control according to the first embodiment. It is a figure for demonstrating the calculation method of the lift characteristic of the intake valve which concerns on Example 1, and fuel injection start time. FIG. 3 is a diagram schematically illustrating a schematic configuration of an internal combustion engine according to a second embodiment. It is a figure for comparing the fuel injection period of a gasoline engine with the fuel injection period of the engine which uses ethanol content fuel. It is a flowchart showing the processing content of the fuel-injection control which concerns on Example 2, and variable valve control. It is a figure for demonstrating the calculation method of the lift characteristic of the intake valve which concerns on Example 2, and fuel injection start time.

  DETAILED DESCRIPTION Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment are not intended to limit the technical scope of the invention only to those unless otherwise specified.

  FIG. 1 is a diagram schematically illustrating a schematic configuration of an internal combustion engine according to the present embodiment.

  An internal combustion engine 1 shown in FIG. 1 is an in-cylinder direct-injection spark ignition gasoline engine having four cylinders 2. A piston 3 is slidably inserted into the cylinder 2. A combustion chamber 12 is formed between the upper part of the cylinder 2 and the top part of the piston 3. The cylinder 2 is connected to an intake port 4 for communicating a combustion chamber 12 with an intake passage (not shown). The intake port 4 is provided with an intake air temperature sensor 13 that measures the temperature of air taken into the combustion chamber 12 via the intake port 4. The cylinder 2 is connected to an exhaust port 5 for communicating the combustion chamber 12 with an exhaust passage (not shown). A fuel injection valve 6 that directly injects fuel into the cylinder 2 is provided in the vicinity of the connection portion of the intake port 4 in the cylinder 2. Reference numeral 11 denotes fuel injected from the fuel injection valve 6 into the combustion chamber 12. A spark plug 7 for igniting an air-fuel mixture formed by the fuel injected from the fuel injection valve 6 and the air sucked into the combustion chamber 12 from the intake port 4 is provided at the top of the cylinder 2. .

  The internal combustion engine 1 includes two intake valves 8A and 8B that open and close the intake port 4. Although an exhaust valve for opening and closing the exhaust port 5 is also provided, it is not shown in FIG. 1 in order to avoid complexity of the drawing. The internal combustion engine 1 is provided with a variable valve mechanism 9 that makes the lift characteristics of the intake valves 8A and 8B variable.

  The internal combustion engine 1 is provided with an ECU 10 that is a processing unit that controls the operation of the internal combustion engine 1 by controlling the operations of the fuel injection valve 6, the spark plug 7, and the variable valve mechanism 9 described above. Operation command signals from the ECU 10 to the fuel injection valve 6, the spark plug 7, and the variable valve mechanism 9 are transmitted via electrical wiring that connects the ECU 10 to these various devices. Further, the ECU 10 acquires measurement data obtained by the intake air temperature sensor 13 via an electrical wiring that connects the ECU 10 and the intake air temperature sensor 13.

The internal combustion engine 1 forms a combustible air-fuel mixture in the combustion chamber 12 by performing fuel injection from the fuel injection valve 6 in the intake stroke. Accordingly, there may be an overlap between the period during which the intake valves 8A and 8B are open and the period during which fuel injection is performed from the fuel injection valve 6. Therefore, depending on the lift amount of the intake valves 8A and 8B when the fuel injection from the fuel injection valve 6 is performed, the fuel 11 injected from the fuel injection valve 6 and the intake valves 8A and 8B interfere with each other, and one of the injected fuels Part is intake valve 8
A or 8B may collide.

  When the injected fuel 11 from the fuel injection valve 6 collides with the intake valves 8A and 8B, a part of the injected fuel adheres to the intake valves 8A and 8B. Under the cold condition where the temperature of the intake valves 8A and 8B is low, the fuel adhering to the intake valves 8A and 8B does not evaporate well, so the injected fuel 11 from the fuel injection valve 6 interferes with the intake valves 8A and 8B. In some cases, the amount of unburned fuel components and PM in the exhaust gas may increase.

  Therefore, in the internal combustion engine 1 of the present embodiment, when the internal combustion engine 1 is cold, the variable valve mechanism 9 sets the lift characteristic of the intake valve 8B to a low lift characteristic with a low lift amount. FIG. 2 is a diagram showing lift characteristics of the intake valves 8A and 8B when the lift characteristic of the intake valve 8B is set to a low lift characteristic by the variable valve mechanism 9. As shown in FIG. The horizontal axis in FIG. 2 represents the crank angle, and the vertical axis represents the lift amount of the intake valves 8A and 8B. A graph A in FIG. 2 represents the lift characteristic of the intake valve 8A, and a graph B represents the lift characteristic of the intake valve 8B. By the variable valve mechanism 9, the lift characteristic of the intake valve 8B is set to various low lift characteristics having a lift amount lower than the normal lift characteristic in addition to the normal lift characteristic as shown in the graph A of FIG. Is possible. Graph B shows an example of a low lift characteristic that can be set in the intake valve 8B.

  Even when the period during which the fuel injection from the fuel injection valve 6 is performed and the period during which the intake valves 8A and 8B are opened overlaps by setting the intake valve 8B to the low lift characteristic in this way, FIG. As shown in FIG. 5, it is possible to suppress at least the intake valve 8B from colliding with the injected fuel 11 from the fuel injection valve 6. Thereby, since the amount of fuel adhering to the intake valve can be reduced, it is possible to suitably suppress deterioration of exhaust performance even under cold machine conditions. At this time, since the intake valve 8A opens and closes with a normal lift characteristic as shown in FIG. 2, it is possible to prevent the intake air amount from being excessively limited and the output of the internal combustion engine 1 from being insufficient.

  Details of the fuel injection control and variable valve control in the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing the processing contents of the fuel injection control and the variable valve control according to this embodiment. The processing represented by the flowchart of FIG. 3 is repeatedly executed by the ECU 10 during the operation of the internal combustion engine 1.

  When the process of the flowchart of FIG. 3 is started, first in step S101, the ECU 10 determines whether or not the intake air temperature Ta acquired by the intake air temperature sensor 13 is lower than a predetermined threshold value Ta0. This step is a step for determining whether or not the fuel can be vaporized well when the injected fuel adheres to the intake valves 8A and 8B. This intake air temperature threshold Ta0 is a reference value determined based on the lower limit value of the intake air temperature at which the temperature condition that allows the fuel adhering to the intake valves 8A and 8B to evaporate well can appear in the combustion chamber 12. Yes, obtained in advance by experiment or calculation.

  If the intake air temperature Ta is not lower than the threshold Ta0 (Ta ≧ Ta0, step S101: No), even if the injected fuel collides with the intake valves 8A and 8B and some of them adhere to the intake valves 8A and 8B, the attachment Therefore, the interference between the injected fuel and the intake valves 8A and 8B is unlikely to cause the deterioration of the exhaust performance. Therefore, in this case, the ECU 10 performs a process of controlling the variable valve mechanism 9 so as to set both the intake valves 8A and 8B to the normal lift characteristics as shown by the graph A in FIG. 2 (step S106).

On the other hand, when the intake air temperature Ta is lower than the threshold Ta0 (Ta <Ta0, step S101: Yes), the injected fuel collides with the intake valves 8A and 8B and a part thereof adheres to the intake valves 8A and 8B as described above. There is a possibility that it may cause deterioration of exhaust performance. Therefore, in this case, the ECU 10 performs a process of setting the intake valve to the low lift characteristic and avoiding the interference between the injected fuel and the intake valve (step S102 and subsequent steps).

  In step S102, the ECU 10 determines whether the required load L of the internal combustion engine 1 is higher than a predetermined threshold L0. This step is a step for determining whether or not both of the intake valves 8A and 8B can be set to the low lift characteristic. The threshold L0 for the required load is an upper limit of the required load that can ensure a sufficient intake air amount with respect to the required load even when both intake valves 8A and 8B are set to low lift characteristics. This is a reference value determined based on the value, and is obtained in advance by experiment, calculation or the like.

  When the required load L is higher than the threshold value L0 (L> L0, step S102: Yes), setting both intake valves 8A and 8B to low lift characteristics may ensure a sufficient intake air amount for the required load. Since it can be determined that it is difficult, a process for controlling the variable valve mechanism 9 is performed to set only the intake valve 8B to the low lift characteristic (step S103).

  In step S103, when the intake valve 8A is set to a normal lift characteristic and the intake valve 8B is set to a low lift characteristic, the ECU 10 can ensure a sufficient intake air amount with respect to the required load. Calculate low lift characteristics. Then, the variable valve mechanism 9 is controlled to set the lift characteristic of the intake valve 8B to the calculated low lift characteristic.

  Further, in the subsequent step S104, the ECU 10 calculates a fuel injection start timing at which fuel injection can be executed without interference between the intake valve 8B set to the low lift characteristic and the injected fuel. Calculation of the fuel injection start timing in step S104 will be described with reference to FIG.

  FIG. 4 is a graph showing the lift characteristics of the intake valves 8A and 8B. Graph A represents a normal lift characteristic set for the intake valve 8A, and graph B represents a low lift characteristic set for the intake valve 8B in step S103. A broken straight line indicates the upper limit h0 of the lift amount at which the injected fuel and the intake valves 8A and 8B do not interfere with each other. When the lift amount of the intake valves 8A and 8B is less than or equal to the upper limit value h0, the injected fuel does not collide with the intake valves 8A and 8B.

  In step S104, based on the low lift characteristic B calculated in step S103, the intake valve is set to the low lift characteristic B at the time of the late valve opening period ΔTB of the intake valve set to the low lift characteristic B. The time after the time when the valve lift amount becomes equal to or less than the upper limit value h0 is set as the fuel injection start time θFS. The “late period of the valve opening period” of the intake valve refers to the lift toward the valve closing after the lift amount reaches a peak during the valve opening period from when the intake valve starts to open until it closes. It refers to the period during which the amount decreases. FIG. 4 shows an example in which the fuel injection start timing θFS is set to the time when the lift amount of the intake valve set to the low lift characteristic B becomes equal to the upper limit value h0.

  By starting the fuel injection at the fuel injection start timing θFS set in this way, the intake valve 8B set to the low lift characteristic B over the entire fuel injection period ΔTF as shown in FIG. This lift amount is a lift amount that does not interfere with the injected fuel. Therefore, it is possible to suppress the injected fuel from colliding with the intake valve 8B set to the low lift characteristic B. As a result, even under the cold condition of the internal combustion engine 1, it is possible to suitably suppress the deterioration of the exhaust performance due to the interference between the injected fuel and the intake valve 8B.

In addition, since one of the two intake valves 8A and 8B is set to a normal lift characteristic, the internal combustion engine with respect to the required load even when the high load operation condition of the internal combustion engine 1 is satisfied. It is also possible to suppress the shortage of the output of 1. Therefore, by executing steps S103 and S104, it is possible to suppress the deterioration of the exhaust performance due to the interference between the injected fuel and the intake valve while suppressing the output of the internal combustion engine 1 from being insufficient.

  When the required load L is not higher than the threshold value L0 (L ≦ L0, step S102: No), a sufficient intake air amount is ensured with respect to the required load even if both intake valves 8A and 8B are set to low lift characteristics. Since it can be determined that the intake valve 8A and 8B can be set to low lift characteristics, a process for controlling the variable valve mechanism 9 is performed (step S105). Note that the low lift characteristic at this time is that the lift amount of the intake valves 8A and 8B after the fuel injection start timing is based on the fuel injection amount calculated based on the required load and the fuel injection start timing. It can be calculated as a lift characteristic that is not more than the upper limit h0 of the lift amount that does not interfere with the intake valve. Alternatively, similarly to step S104 executed when the required load L is higher than the threshold value L0, first, the intake air amount that is not insufficient with respect to the required load when both the intake valves 8A and 8B are set to the low lift characteristic is set. A low lift characteristic that can be ensured is calculated, and based on the calculated low lift characteristic, the latter period of the valve opening period in the low lift characteristic, and after the period when the lift amount is equal to or less than the upper limit value h0 This time may be set as the fuel injection start time.

  Since both the intake valves 8A and 8B are set to have a low lift characteristic, interference with the injected fuel can be avoided for both the intake valves 8A and 8B. Therefore, even under cold conditions, the injected fuel and the intake valves 8A and 8B can be avoided. It is possible to suitably suppress the deterioration of the exhaust performance due to the interference.

  In the present embodiment, the ECU 10 that executes the processes of steps S101 to S104 corresponds to the control means in the present invention.

  Next, an embodiment in which the present invention is applied to an in-cylinder direct-injection spark-ignition internal combustion engine that uses ethanol-containing fuel as the fuel will be described.

  FIG. 5 is a diagram schematically illustrating a schematic configuration of the internal combustion engine according to the present embodiment.

  The internal combustion engine 1 ′ shown in FIG. 5 is substantially the same as the direct injection spark ignition gasoline engine described in the first embodiment except that ethanol-containing fuel is used as the fuel. Detailed description will be omitted using the same reference numerals and names. As a difference from the internal combustion engine 1 described in the first embodiment, the internal combustion engine 1 ′ of the present embodiment further includes a concentration sensor 14 that measures the ethanol concentration of the ethanol-containing fuel. Data measured by the concentration sensor 14 is provided to the ECU 10 via electrical wiring.

  An engine using an ethanol-containing fuel has a smaller stoichiometric air-fuel ratio than a normal gasoline engine and is difficult to vaporize. Therefore, it is necessary to ensure a longer fuel injection period than a gasoline engine. FIG. 6 is a diagram illustrating, for comparison, a fuel injection period of an engine using an ethanol-containing fuel corresponding to an equal required load and a fuel injection period of a gasoline engine. As shown in FIG. 6, the ethanol-containing fuel injection period ΔTFA is longer than the gasoline injection period ΔTFG. The “injection end limit time θFE0” shown in FIG. 6 is a limit value of the fuel injection end time that does not cause deterioration in exhaust performance. In this embodiment, the fuel injection start timing θFS is set so that the fuel injection end timing θFE is not later than the injection end limit timing θFE0. It is assumed that it is set.

In order to satisfy the constraint condition regarding the fuel injection end timing θFE and to ensure a long fuel injection period of the ethanol-containing fuel in this way, as shown in FIG. 6, the fuel injection start timing θFSA of the ethanol-containing fuel is set to the intake stroke. It needs to be set at a fairly early time. And
The higher the ethanol concentration of the ethanol-containing fuel, the longer the required fuel injection period. Therefore, as described in the first embodiment, a low lift characteristic that can secure an intake air amount that is not insufficient with respect to the required load is calculated, and at the fuel injection start timing calculated based on the low lift characteristic, the ethanol concentration depends on the ethanol concentration. In some cases, it is difficult to end the fuel injection by the injection end limit timing θFE0.

  Therefore, in this embodiment, when the internal combustion engine 1 ′ is cold, only one of the two intake valves 8A and 8B is set to have a low lift characteristic, thereby avoiding interference between the injected fuel and the intake valve 8B. The point is the same as in the first embodiment, but in this embodiment, the fuel injection of the ethanol-containing fuel can be ended by the injection end limit time θFE0 in the calculation of the low lift characteristic set in the intake valve 8B in that case. The fuel injection start timing is calculated as described above.

  Thereby, in the internal combustion engine 1 ′ using the ethanol-containing fuel, the exhaust performance due to the interference between the injected fuel and the intake valve while satisfying the precondition of the fuel injection control of ending the fuel injection by the injection end limit timing. It becomes possible to suppress the deterioration of.

  Details of the fuel injection control and variable valve control in the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing the processing contents of the fuel injection control and the variable valve control according to this embodiment. 7 is repeatedly executed by the ECU 10 during the operation of the internal combustion engine 1 '.

  When the processing of the flowchart of FIG. 7 is started, first in step S201, the ECU 10 determines whether or not the intake air temperature Ta acquired by the intake air temperature sensor 13 is lower than a predetermined threshold value Ta0 '. This step is a step for determining whether or not the ethanol-containing fuel can be favorably evaporated when the ethanol-containing fuel adheres to the intake valves 8A and 8B. The intake air temperature threshold Ta0 ′ is determined based on the lower limit value of the intake air temperature at which the temperature condition that allows the ethanol-containing fuel adhering to the intake valves 8A and 8B to evaporate well can appear in the combustion chamber 12. It is a reference value, and is obtained in advance through experiments and calculations. The process in step S201 corresponds to the process in step S101 of the flowchart in the case of the gasoline engine shown in FIG.

  When the intake air temperature Ta is not lower than the threshold Ta0 ′ (Ta ≧ Ta0 ′, Step S201: No), the injected ethanol-containing fuel collides with the intake valves 8A and 8B, and a part of them adheres to the intake valves 8A and 8B. Even so, the adhering ethanol-containing fuel evaporates satisfactorily and participates in combustion. Therefore, the interference between the injection of the ethanol-containing fuel and the intake valves 8A and 8B may cause the exhaust performance to deteriorate. Is low. Therefore, in this case, the ECU 10 performs a process of controlling the variable valve mechanism 9 so as to set both the intake valves 8A and 8B to the normal lift characteristics as shown by the graph A in FIG. 2 (step S207). The process of step S207 corresponds to the process of step S106 in the flowchart in the case of the gasoline engine shown in FIG.

  On the other hand, when the intake air temperature Ta is lower than the threshold Ta0 ′ (Ta <Ta0 ′, Step S201: Yes), the injected ethanol-containing fuel collides with the intake valves 8A and 8B, and a part of the fuel enters the intake valves 8A and 8B. If it adheres, it may cause the deterioration of the exhaust performance as described above. Therefore, in this case, the ECU 10 performs a process of setting the intake valve to the low lift characteristic to avoid interference between the injected fuel and the intake valve (step S202 and subsequent steps).

In step S202, the ECU 10 determines whether the ethanol concentration D of the ethanol-containing fuel acquired by the concentration sensor 14 is higher than a predetermined threshold value D0. This step determines whether or not the fuel injection can be completed by the above-mentioned injection end limit timing θFE0 when the injection of the ethanol-containing fuel is started at the fuel injection start timing calculated by the method described in the first embodiment. It is a step for judging. The ethanol concentration threshold value D0 is set to the fuel injection start timing before the latest fuel injection start timing at which the injection of the ethanol-containing fuel can be ended by the injection end limit timing θFE0 by the method described in the first embodiment. Is a reference value determined on the basis of the upper limit value of the ethanol concentration that can be set, and is obtained in advance through experiments, calculations, or the like.

  When the ethanol concentration D is higher than the threshold D0 (D> D0, Step S202: Yes), even if the fuel injection is started at the earliest fuel injection start time that can be set by the method described in the first embodiment, the injection end limit timing Since it can be determined that it is difficult to finish the injection of the ethanol-containing fuel by the time, the fuel injection start timing and the low lift characteristic are calculated by the method described in this embodiment (steps S203 to 205).

  Calculation of fuel injection start timing and low lift characteristics in steps S203 to 205 will be described with reference to FIG.

  FIG. 8 is a diagram showing the lift characteristics of the intake valves 8A and 8B. Graph A represents a normal lift characteristic set for the intake valve 8A, and graph B represents a low lift characteristic set for the intake valve 8B in step S205 described later. A broken straight line indicates the upper limit h0 of the lift amount at which the injected fuel and the intake valves 8A and 8B do not interfere with each other. When the lift amount of the intake valves 8A and 8B is less than or equal to the upper limit value h0, the injected fuel does not collide with the intake valves 8A and 8B.

  In step S203, the ECU 10 calculates a fuel injection period ΔTFA for the ethanol-containing fuel. This is calculated based on the required load and the ethanol concentration acquired by the concentration sensor 14.

  In subsequent step S204, the ECU 10 calculates the fuel injection start timing θFSA of the ethanol-containing fuel. Here, the latest fuel injection start timing that satisfies the condition that the fuel injection end timing is not later than the injection end limit timing θFE0 is calculated as the fuel injection start timing θFSA of the ethanol-containing fuel. In other words, the fuel injection start timing θFSA is set to a time that goes back from the injection end limit timing θFE0 by the fuel injection period ΔTFA calculated in step S203.

  In subsequent step S205, the ECU 10 calculates a lift characteristic such that the lift amount at the fuel injection start timing θFSA calculated in step S204 becomes the upper limit value h0, and avoids interference between the intake valve 8B and the injected fuel. Therefore, a low lift characteristic for setting the intake valve 8B is used. Then, the variable valve mechanism 9 is controlled to set the intake valve 8B to the calculated low lift characteristic. As shown in FIG. 8, the low lift characteristic is set such that the fuel injection start timing θFSA is set when the lift amount reaches the upper limit value h0 in the latter half of the valve opening period.

  When the intake valve 8B performs the opening / closing operation with the low lift characteristic set in this way, the intake valve 8B set to the low lift characteristic B over the entire fuel injection period ΔTFA as shown in FIG. This lift amount is a lift amount that does not interfere with the injected fuel. Therefore, it is possible to suppress the injected fuel from colliding with the intake valve 8B set to the low lift characteristic B. As a result, even when the cold condition of the internal combustion engine 1 ′ is satisfied, it is possible to suitably suppress the deterioration of the exhaust performance due to the interference between the injected fuel and the intake valve 8 </ b> B.

In addition, since the injection of the ethanol-containing fuel is started at the fuel injection start timing θFSA, the injection of the ethanol-containing fuel can be ended by the injection end limit timing θFE0, so that the fuel injection end timing is excessively delayed. It is also possible to suppress the deterioration of the exhaust performance caused by.

  The low lift characteristic calculated as described above may be a lift characteristic having a lower lift amount than the low lift characteristic calculated by the method of the first embodiment, but ethanol evaporates in the combustion chamber 12. Since the intake air amount can be supplemented by the effect of the latent heat at the time, it is possible to suppress the output of the internal combustion engine 1 'from being insufficient due to the shortage of the intake air amount.

  When the ethanol concentration D is not higher than the threshold value D0 (D ≦ D0, step S202: No), the fuel injection start timing at which the injection of the ethanol-containing fuel can be ended by the injection end limit timing θFE0 is described in the first embodiment. Since it can be determined that it can be calculated by the described method, the ECU 10 calculates the low lift characteristic and the fuel injection start timing by the method described in the first embodiment (step S206). That is, even in an internal combustion engine that uses ethanol-containing fuel, if the ethanol concentration is not so high, an intake air amount that is not insufficient for the required load is ensured when only the intake valve 8B is set to a low lift characteristic. The fuel injection start timing is calculated at a later stage of the valve opening period of the low lift characteristics, and after the period when the lift amount becomes the upper limit value h0 or less. Set. As a result, as described in the first embodiment, it is possible to obtain the effect of suppressing the deterioration of the exhaust performance.

  In the present embodiment, the ECU 10 that executes the processes of steps S201 to S205 corresponds to the control means in the present invention.

  The above-described embodiment is an example for explaining the present invention, and various modifications can be made to the above-described embodiment without departing from the gist of the present invention. For example, in the first embodiment, the variable valve mechanism 9 can change the lift characteristics of both the intake valves 8A and 8B. If the required load is not higher than the threshold value, both the intake valves 8A and 8B are low lifted. Although it has been described that the characteristic is set, a variable valve mechanism capable of setting only the lift characteristic of at least one intake valve to the low lift characteristic is sufficient to implement the present invention. In the configuration including such a variable valve mechanism, even if a negative determination is made in step S102 of FIG. 3, the same processing as in steps S103 and 104 may be performed.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 1 'Internal combustion engine 2 Cylinder 3 Piston 4 Intake port 5 Exhaust port 6 Fuel injection valve 7 Spark plug 8A Intake valve 8B Intake valve 9 Variable valve mechanism 10 ECU
11 Injected fuel 12 Combustion chamber 13 Intake air temperature sensor 14 Concentration sensor

Claims (2)

A fuel injection valve for directly injecting fuel into the cylinder of the internal combustion engine;
Two intake valves provided in the cylinder;
A variable valve mechanism capable of changing a lift characteristic of at least one of the two intake valves;
When the internal combustion engine is cold, the variable valve mechanism is controlled so that the lift characteristic of at least one of the two intake valves is set to a low lift characteristic having a lift amount lower than that during warm-up. Control means;
With
When the control load of the internal combustion engine is higher than a predetermined reference when the internal combustion engine is cold,
The low lift characteristic so that the intake air amount of the internal combustion engine when the lift characteristic of one of the two intake valves is a low lift characteristic is an intake air amount that is not insufficient with respect to the required load. To calculate
The intake valve is opened in accordance with the calculated low lift characteristic at a later stage of the valve opening period, and the lift amount of the intake valve is such that the fuel injected from the fuel injection valve does not collide with the intake valve. Calculate the time when
Controlling the variable valve mechanism so as to set the lift characteristic of one of the two intake valves to the calculated low lift characteristic;
A control apparatus for an in-cylinder direct injection internal combustion engine, wherein the fuel injection valve is controlled to start fuel injection after the calculated time. A fuel injection valve for directly injecting alcohol-containing fuel into the cylinder of the internal combustion engine;
Two intake valves provided in the cylinder;
A variable valve mechanism capable of changing a lift characteristic of at least one of the two intake valves;
When the internal combustion engine is cold, the variable valve mechanism is controlled so that the lift characteristic of at least one of the two intake valves is set to a low lift characteristic having a lift amount lower than that during warm-up. Control means;
Alcohol concentration acquisition means for acquiring the alcohol concentration of the alcohol-containing fuel;
With
When the alcohol concentration acquired by the alcohol concentration acquisition unit is higher than a predetermined reference when the internal combustion engine is cold,
A fuel injection start timing is calculated so that fuel injection from the fuel injection valve ends by a predetermined injection end limit timing;
The low lift characteristic is calculated as a lift characteristic in which the lift amount after the calculated fuel injection start timing is a lift amount at which the fuel injected from the fuel injection valve does not collide with the intake valve,
Controlling the variable valve mechanism so as to set the lift characteristic of one of the two intake valves to the calculated low lift characteristic;
A control apparatus for a direct injection internal combustion engine, wherein the fuel injection valve is controlled to start fuel injection at the calculated fuel injection start timing.

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