JP5983910B2 - Fuel injection device for in-cylinder internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection device for a direct injection internal combustion engine, and more particularly to fuel injection control for an internal combustion engine that improves combustion during high load operation.

Conventionally, it is known that an improvement in thermal efficiency is required to improve the output and fuel consumption of an internal combustion engine. One technique for improving thermal efficiency is to increase the compression ratio.
However, at the exhaust top dead center of the internal combustion engine, the high-temperature residual gas after combustion remains in the combustion chamber formed by the cylinder head and the piston during the exhaust stroke and remains in the combustion chamber and burns in the intake stroke. There is a problem that the compression ratio cannot be increased because the fresh air introduced into the chamber and the residual gas are mixed in the combustion chamber and the temperature of the fresh air becomes high and knocks occur.

  For this reason, in Patent Document 1, for example, a bypass passage that bypasses the turbocharger and a control valve that adjusts the flow rate of exhaust gas flowing into the bypass passage are provided in the exhaust passage, and the control valve is controlled to flow into the bypass passage. By adjusting the flow rate of exhaust gas, the pressure in the exhaust passage is made lower than the pressure in the intake passage, or the air assist type fuel injection valve is used to inject air from the air assist type fuel injection valve and burn Higher compression ratio by increasing the pressure inside the exhaust passage and increasing the scavenging of residual gas in the combustion chamber to the exhaust passage, suppressing the temperature rise of fresh air and suppressing knocking Is possible.

JP 2007-146854 A

  However, in the technique of Patent Document 1, control for adjusting the flow rate of the exhaust gas flowing to the bypass passage for bypassing the exhaust gas in order to make the pressure in the exhaust passage lower than the pressure in the intake passage for scavenging the residual gas in the combustion chamber. It is necessary to provide a valve, or to provide an air assist type injection valve for supplying air into the combustion chamber in order to make the pressure in the combustion chamber higher than the pressure in the exhaust passage, which is not preferable because it leads to an increase in cost.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a fuel for a direct injection internal combustion engine that can suppress the occurrence of knock while suppressing an increase in cost. It is in providing an injection device.

In order to achieve the above-mentioned target, the fuel injection device for a direct injection internal combustion engine according to claim 1 comprises an intake valve, an exhaust valve, and fuel injection means arranged to face a combustion chamber, and the fuel A fuel injection device for a direct injection internal combustion engine that directly injects fuel from an injection means into the combustion chamber,
The exhaust valve comprises a plurality of the exhaust valves having a phase difference at the closing timing,
The fuel injection means is the other exhaust having a phase difference with respect to the exhaust valve at a later stage of the exhaust stroke of the direct injection internal combustion engine, wherein at least one of the plurality of exhaust valves is opened. During the period when the valve is closed, fuel is injected toward the intake valve which is closed in the latter stage of the exhaust stroke .

According to a second aspect of the present invention, there is provided a fuel injection device for an in-cylinder injection internal combustion engine comprising an intake valve, an exhaust valve, and fuel injection means disposed so as to face a combustion chamber, and fuel is burned from the fuel injection means. A fuel injection device for a direct injection internal combustion engine that directly injects into a room,
The exhaust valve comprises a plurality of the exhaust valves having a phase difference at the closing timing,
The fuel injection means is the other exhaust having a phase difference with respect to the exhaust valve at a later stage of the exhaust stroke of the direct injection internal combustion engine, wherein at least one of the plurality of exhaust valves is opened. During the period when the valve is closed, fuel is injected toward the exhaust valve that is closed in the latter stage of the exhaust stroke .
Further, in the fuel injection system for a cylinder injection internal combustion engine according to claim 3, in claim 1 or claim 2, wherein the fuel injection means is characterized by injecting fuel prior to the opening of the intake valve .

According to the present invention, at least one of a exhaust stroke late plurality of exhaust valves is opened, and the other exhaust valve having a phase difference with respect to the exhaust valve is closed By injecting fuel into the combustion chamber during the period, the fuel evaporates and expands in the high temperature combustion chamber. The expanded fuel can be scavenged so that residual gas remaining without being discharged in the combustion chamber is pushed out from the opened exhaust valve to the exhaust passage, and fresh air sucked in the intake stroke Temperature rise can be suppressed. Therefore, it is possible to increase the compression ratio by suppressing the occurrence of knocking, thereby improving the thermal efficiency of the internal combustion engine, reducing the fuel consumption and improving the output. Further, since the remaining gas in the combustion chamber can be scavenged only by changing the fuel injection timing of the existing fuel injection means without adding a new device or the like, an increase in cost can be suppressed.

In addition , it is possible to suppress the fuel injected and expanded for scavenging the residual gas in the combustion chamber from being directly discharged into the exhaust passage, and to reliably burn the injected fuel in the combustion chamber. The deterioration of the fuel consumption can be suppressed while the deterioration of the exhaust due to the outflow of the fuel is prevented.

According to the second aspect of the present invention, the exhaust valve becomes hot as exhaust gas passes through, and fuel is vaporized by injecting fuel toward the exhaust valve that is closed. As a result, the time for scavenging the residual gas in the combustion chamber can be shortened.

According to the invention of claim 3 , it is possible to prevent the vaporized fuel from being blown into the intake passage and the residual gas scavenged by the fuel from being blown back to the intake passage. It can be carried out.

1 is a schematic configuration diagram of an engine to which a fuel injection device for a direct injection internal combustion engine according to the present invention is applied. It is sectional drawing in the AA of FIG. It is a figure which shows the operation | movement of the engine at the time of the high load driving | running with the engine to which the fuel-injection apparatus of the cylinder injection type internal combustion engine which concerns on this invention is applied, operation | movement of a fuel injection valve, an intake valve, and an exhaust valve in time series. 3 is a flowchart for determining whether or not scavenging injection is performed in the fuel injection device for a direct injection internal combustion engine according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a cylinder fuel injection engine to which a fuel injection device for a cylinder injection internal combustion engine is applied. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a diagram showing the operation of the engine, the operation of the fuel injection valve, the intake valve, and the exhaust valve during the high load operation of the engine in time series. A hatched portion in FIG. 2 indicates an approximate fuel injection direction from the fuel injection valve. Also, the thick solid line in FIG. 3 indicates the fuel injection timing for the fuel injection valve, and the valve opening timing for each valve for the intake valve and the exhaust valve.

As shown in FIG. 1, an engine (in-cylinder injection internal combustion engine) 1 is a fuel injection valve (fuel) disposed in a cylinder head 3 so as to face a combustion chamber 10 formed by a cylinder head 3 and a piston 6. This is an in-cylinder injection type 4-cycle in-line four-cylinder gasoline engine in which fuel is directly injected into the combustion chamber 10 from the injection means) 23.
FIG. 1 shows a longitudinal section of one cylinder of the engine 1. In addition, illustration and description are abbreviate | omitted as what has the same structure also about another cylinder.

As shown in FIG. 1, the engine 1 is configured by mounting a cylinder head 3 on a cylinder block 2.
The cylinder block 2 is provided with a water temperature sensor 4 that detects the temperature of cooling water that cools the engine 1. A piston 6 is provided in the cylinder 5 formed in the cylinder block 2 so as to be slidable up and down. The piston 6 is connected to a crankshaft 8 via a connecting rod 7. The cylinder block 2 is provided with a crank angle sensor 9 that detects the rotational speed of the engine 1 and the phase of the crankshaft 8. A combustion chamber 10 is formed by the cylinder head 3, the cylinder 5, and the piston 6.

  The cylinder head 3 is provided with a spark plug 11 so as to face the combustion chamber 10. Further, an intake port 12 is formed in the cylinder head 3 from the combustion chamber 10 toward one side surface of the cylinder head 3, and an exhaust port 13 is formed from the combustion chamber 10 toward the other side surface of the cylinder head 3. Yes. The cylinder head 3 includes an intake valve 14 that communicates and shuts off the combustion chamber 10 and the intake port 12, and a first exhaust valve 15a that communicates and shuts off the combustion chamber 10 and the exhaust port 13, and a second exhaust. Each valve 15b is provided. An intake camshaft 18 having an intake cam 16 for driving the intake valve 14 and an exhaust camshaft 19 having an exhaust cam 17 for driving the first exhaust valve 15a and the second exhaust valve 15b are provided above the cylinder head 3. And are provided respectively. A cam angle sensor 20 that detects the phase of the intake camshaft 18 and a cam angle sensor 21 that detects the phase of the exhaust camshaft 19 are provided on the upper portion of the cylinder head 3. An intake manifold 22 is connected to one side surface of the cylinder head 3 so as to communicate with the intake port 12. Further, a fuel injection valve 23 is provided on the side surface of the cylinder head 3 to which the intake manifold 22 is connected so as to face the combustion chamber 10. On the other hand, an exhaust manifold 24 is connected to the side surface of the cylinder head 3 opposite to the side surface to which the intake manifold 22 is connected so as to communicate with the exhaust port 13.

  As shown in FIG. 3, each exhaust cam 17 of the exhaust camshaft 19 opens the second exhaust valve 15 b at a valve opening timing that is a period during which the valve is opened rather than the valve opening timing of the first exhaust valve 15 a. The phase of the exhaust cam 17 is set so that the timing is delayed. Here, the phase of each exhaust cam 17 is fixed so that the opening timing of the first exhaust valve 15a is earlier than the opening timing of the second exhaust valve 15b, but a variable valve mechanism is used. The phase of each exhaust cam 17 can be made variable, and the phase of the exhaust cam 17 is set by a variable valve mechanism so that the opening timing of the first exhaust valve 15a is earlier than the opening timing of the second exhaust valve 15b. You may make it do.

  As shown in FIG. 2, the fuel injection valve 23 is arranged so that the fuel injection port is arranged toward the first exhaust valve 15a whose valve opening timing is early, and the injected fuel reaches the vicinity of the first exhaust valve 15a. Has been. The fuel injection valve 23 is connected to a high-pressure pump (not shown) that supplies high-pressure fuel to the fuel injection valve 23 via a fuel pipe (not shown) and a feed pump that supplies fuel in a fuel tank (not shown) to the high-pressure pump. ing.

  An intake pipe (not shown) and an electronic control throttle valve (not shown) for adjusting the intake air flow rate are provided at the intake upstream end of the intake manifold 22. The electronically controlled throttle valve is provided with a throttle position sensor (not shown) that detects the opening degree of the throttle valve. An air flow sensor (not shown) for detecting the intake air flow rate is provided in the intake pipe upstream of the electronic control throttle valve, and an air cleaner (not shown) is provided at the intake upstream end of the intake pipe.

Further, an exhaust purification catalyst such as a three-way catalyst is provided at the exhaust downstream end of the exhaust manifold 24 via an exhaust pipe (not shown).
Various sensors such as the water temperature sensor 4, the crank angle sensor 9, the cam angle sensors 20 and 21, the intake pressure sensor, the throttle position sensor, the air flow sensor, and a vehicle speed sensor (not shown) that detect the vehicle speed of the vehicle are mounted on the vehicle. The electronic control unit (ECU) 30 is electrically connected to the input side, and detection information from these sensors is input to the ECU 30.

On the other hand, various devices such as the spark plug 11, the fuel injection valve 23, and the electronically controlled throttle valve are electrically connected to the output side of the ECU 30, and these various devices are based on detection information from various sensors. The calculated ignition timing, fuel injection amount, fuel injection timing, throttle opening, etc. are output.
Further, as shown in FIG. 3, the ECU 30 determines the operating state of the engine 1 based on detection information from various sensors before performing the main injection in the intake stroke, and determines the engine according to the operating state. The residual gas, which is a mixture after combustion remaining in the combustion chamber 10 in the latter stage of the exhaust stroke of 1, is injected from the fuel injection valve 23 toward the first exhaust valve 15a in the combustion chamber 10 which is closed. Thus, it is determined whether or not scavenging injection for scavenging the exhaust gas to the exhaust port 13 from the second exhaust valve 15b that opens the residual gas by the fuel vaporized and expanded by the temperature of the combustion chamber 10 is determined. When the scavenging injection is performed, the ECU 30 is a period in which the first exhaust valve 15a in the late stage of the exhaust stroke of the engine 1 is closed, the second exhaust valve 15b is opened, and the intake valve 14 is further closed. The fuel injection valve 23 is controlled so as to inject fuel.

Next, a method for determining whether or not scavenging injection is performed in the ECU 30 will be described.
FIG. 4 is a flowchart for determining whether or not scavenging injection is performed in the fuel injection device for a direct injection internal combustion engine according to the present invention.
The routine shown in FIG. 4 is repeated during engine operation.
First, in step S10, the volume efficiency of the engine 1 is calculated from the engine rotational speed that is detection information of the crank angle sensor 9, the intake air flow rate that is detection information of the airflow sensor, and the like. Then, the process proceeds to step S12.

  In step S12, it is determined whether or not the volume efficiency calculated in step S10 is a predetermined value or more. That is, it is determined whether or not the current volume efficiency is equal to or greater than a predetermined value and the operating state of the engine 1 is a high-load operating state. If the determination result is true (Yes), and the current volumetric efficiency is equal to or greater than a predetermined value, the process proceeds to step S14. On the other hand, if the determination result is NO (No) and the current volumetric efficiency is less than the predetermined value and not in the high load operation state, the process proceeds to step S22.

In step S14, it is determined whether or not the stroke of the engine 1 is an exhaust stroke. If the determination result is true (Yes) and the engine 1 is in the exhaust stroke, the process proceeds to step S16. If the determination result is NO (No) and the stroke of the engine 1 is not the exhaust stroke, the process proceeds to step S22.
In step S16, it is determined whether or not the first exhaust valve 15a is closed. If the determination result is true (Yes) and the first exhaust valve 15a is closed, the process proceeds to step S18. If the determination result is negative (No) and the first exhaust valve 15a is not closed, the process proceeds to step S22.

In step S18, it is determined whether or not the intake valve 14 is open. If the determination result is true (Yes) and before the intake valve 14 is opened, the process proceeds to step S20. If the determination result is negative (No) and the intake valve 14 is not open, the process proceeds to step S22.
In step S <b> 20, scavenging injection is performed from the fuel injection valve 22. Then, this routine is returned.

In step S22, the routine is returned without performing the scavenging injection from the fuel injection valve 22.
As described above, in the fuel injection device for a direct injection internal combustion engine according to the present invention, the phase of the exhaust cam 17 of the exhaust camshaft 19 of the engine 1 is set to be higher than that of the first exhaust valve 15a. The intake valve 14 is set so that the valve opening timing is delayed, the volume efficiency of the engine 1 is equal to or higher than a predetermined value, that is, in a high load operation state, the engine 1 is in the exhaust stroke, and the first exhaust valve 15a is closed. Is before the valve opening, scavenging injection is performed to inject fuel from the fuel injection valve 23 toward the first exhaust valve 15a.

  Therefore, the fuel injected toward the first exhaust valve 15a is vaporized at the temperature in the combustion chamber 10 and expands. Then, the expanded fuel can be scavenged from the second exhaust valve 15b to the exhaust port 13 so as to push out the residual gas remaining in the combustion chamber 10, and the residual gas in the combustion chamber 10 is reduced, so that the next intake air It becomes possible to suppress the temperature rise of fresh air sucked in the process. Therefore, the occurrence of knocking in the high-load operation state of the engine 1 can be suppressed, the compression ratio can be increased, the thermal efficiency of the engine 1 can be improved, the fuel consumption can be reduced, and the output can be improved. Moreover, since the remaining gas in the combustion chamber 10 can be scavenged only by changing the fuel injection timing of the existing fuel injection valve 23, an increase in cost can be suppressed.

  Further, since the fuel from the fuel injection valve 23 is injected toward the first exhaust valve 15a that is closed in the late stage of the exhaust stroke, the injected fuel is prevented from being directly discharged to the exhaust port 13. Therefore, it is possible to reliably burn the injected fuel while suppressing the deterioration of the exhaust due to the fuel discharge, and the deterioration of the fuel consumption can also be suppressed. Further, since the first exhaust valve 15a becomes high temperature as exhaust gas passes through, the fuel vaporization is accelerated by injecting the fuel toward the first exhaust valve 15a, and the expansion of the fuel is accelerated. The time for scavenging the residual gas in 10 can be shortened.

  Further, since the scavenging injection is performed before the intake valve 14 is opened, it is possible to prevent the vaporized fuel from being blown out to the intake port 12 and the residual gas scavenged by the fuel from being blown back to the intake port 12. The residual gas can be surely scavenged.

1 engine (cylinder injection internal combustion engine)
10 Combustion chamber 14 Intake valve (intake valve)
15a First exhaust valve (exhaust valve)
15b Second exhaust valve (exhaust valve)
23 Combustion injection valve (fuel injection means)
30 ECU

Claims (3)

A fuel injection device for a direct injection internal combustion engine, comprising an intake valve, an exhaust valve, and fuel injection means disposed so as to face a combustion chamber, and directly injecting fuel from the fuel injection means into the combustion chamber. ,
The exhaust valve comprises a plurality of the exhaust valves having a phase difference at the closing timing,
The fuel injection means is the other exhaust having a phase difference with respect to the exhaust valve at a later stage of the exhaust stroke of the direct injection internal combustion engine, wherein at least one of the plurality of exhaust valves is opened. A fuel injection device for a direct injection internal combustion engine, wherein fuel is injected toward the intake valve that is closed in a later stage of the exhaust stroke during a period in which the valve is closed. A fuel injection device for a direct injection internal combustion engine, comprising an intake valve, an exhaust valve, and fuel injection means disposed so as to face a combustion chamber, and directly injecting fuel from the fuel injection means into the combustion chamber. ,
The exhaust valve comprises a plurality of the exhaust valves having a phase difference at the closing timing,
The fuel injection means is the other exhaust having a phase difference with respect to the exhaust valve at a later stage of the exhaust stroke of the direct injection internal combustion engine, wherein at least one of the plurality of exhaust valves is opened. A fuel injection device for a direct injection internal combustion engine, wherein fuel is injected toward the exhaust valve that is closed in a later stage of the exhaust stroke during a period in which the valve is closed . The fuel injection device for a direct injection internal combustion engine according to claim 1 or 2 , wherein the fuel injection means injects fuel before the intake valve is opened.

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