JP2009138568A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of improving anti-knocking performance of an engine while maintaining an output torque of the engine. <P>SOLUTION: The internal combustion engine 1 has a port fuel injection valve 65 for injecting the fuel at an intake port 4, and a cylinder fuel injection valve 66 for injecting the fuel in a cylinder 2. In the internal combustion engine 1, an octane number of the fuel injected from the port fuel injection valve 65 is set to be higher than the octane number of the fuel injected from the cylinder fuel injection valve 66. When a volumetric efficiency is decreased in a high load operation of the engine, a fuel injection amount of the port fuel injection valve 65 is decreased and the octane number of the fuel injected from the cylinder fuel injection valve 66 is increased. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly, to an internal combustion engine that can improve engine knock resistance while maintaining the output torque of the engine.

  In recent internal combustion engines, a configuration in which low-octane fuel is injected into a cylinder and high-octane fuel is port-injected is employed. In such a configuration, the ignition timing can be easily adjusted and the engine anti-knock performance is improved as compared with a configuration in which only in-cylinder injection is performed.

  As an internal combustion engine that employs such a configuration, a technique described in Patent Document 1 is known. A conventional internal combustion engine (a fuel injection control device for an internal combustion engine) includes an intake passage fuel injection valve that injects fuel into an intake passage of the engine as fuel supply means to the internal combustion engine, and a fuel in a combustion chamber of the engine. A fuel injection control device for an internal combustion engine that controls the fuel injection mode of each fuel injection valve in accordance with the operating state of the engine. And a ratio changing means for changing a ratio between the fuel injection amount from the in-cylinder fuel injection valve and the fuel injection amount from the intake passage fuel injection valve.

JP 2005-127192 A

  An object of the present invention is to provide an internal combustion engine that can improve the engine knock resistance while maintaining the output torque of the engine.

  In order to achieve the above object, an internal combustion engine according to the present invention includes a port fuel injection valve that injects fuel at an intake port and an in-cylinder fuel injection valve that injects fuel within a cylinder. An internal combustion engine in which the octane number of the fuel injected from the injection valve is set higher than the octane number of the fuel injected from the in-cylinder fuel injection valve, and when the volumetric efficiency decreases during high load operation of the engine, The fuel injection amount of the port fuel injection valve is reduced, and the octane number of the fuel injected from the in-cylinder fuel injection valve is increased.

  In this internal combustion engine, when the volumetric efficiency decreases during high-load operation of the engine, (a) the fuel injection amount of the port fuel injection valve is reduced, and (b) the fuel injected from the in-cylinder fuel injection valve. The octane number of is increased. As a result, (a) the volumetric efficiency of the engine is increased and the output torque of the engine is improved, and (b) the trace knock point D is shifted to the retard side to improve the knock resistance performance of the engine. There are advantages.

  In the internal combustion engine according to the present invention, a first fuel passage for supplying fuel to the port fuel injection valve, a second fuel passage for supplying fuel to the in-cylinder fuel injection valve, the first fuel passage, A communication passage connecting the second fuel passages, and the fuel in the first fuel passage is introduced into the second fuel passage through the communication passage, whereby the octane number of the fuel in the second fuel passage is Is changed.

  In this internal combustion engine, the octane number of the fuel (low octane number fuel) supplied to the in-cylinder fuel injection valve is changed by diverting the fuel (high octane number fuel) supplied to the port fuel injection valve. Thereby, there exists an advantage by which the means (octane number change means) which increases the octane number of the fuel injected from a cylinder fuel injection valve is comprised simply.

  In the internal combustion engine according to the present invention, a flow control valve is disposed in the communication passage, the fuel in the first fuel passage is set at a higher pressure than the fuel in the second fuel passage, and the flow control valve By controlling the opening degree, the octane number of the fuel in the second fuel passage is adjusted.

  This internal combustion engine has an advantage that the means for adjusting the octane number of the fuel injected from the in-cylinder fuel injection valve (octane number changing means) is simply configured.

  In the internal combustion engine according to the present invention, (a) the fuel injection amount of the port fuel injection valve is reduced and (b) the injection from the in-cylinder fuel injection valve when the volumetric efficiency decreases during high-load operation of the engine. The octane number of the generated fuel is increased. As a result, (a) there is an advantage that the volume efficiency of the engine is increased and the output torque of the engine is improved, and (b) the trace knock point D is shifted to the retarded side, and the knock resistance performance of the engine is improved. There are advantages.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a block diagram showing an internal combustion engine according to an embodiment of the present invention. 2 to 7 are a flowchart (FIG. 2) and an explanatory diagram (FIGS. 3 to 7) showing the operation of the internal combustion engine shown in FIG.

[Internal combustion engine]
The internal combustion engine 1 is applied to, for example, a four-cycle gasoline engine. The internal combustion engine 1 includes a cylinder (cylinder bore) 2, a piston 3 reciprocally accommodated in the cylinder 2, an intake port 4 and an exhaust port 5 connected to the cylinder 2, and an intake valve 41 that opens and closes the intake port 4. In addition, an exhaust valve 51 that opens and closes the exhaust port 5, a fuel supply system 6 that supplies fuel, and an ignition plug 7 that ignites the fuel in the cylinder 2 (see FIG. 1).

  When the engine is operating, first, the piston 3 is lowered and the intake valve 41 is opened, and intake air is drawn into the cylinder 2 (combustion chamber) from the intake port 4 (intake stroke). At this time, fuel is injected into the intake air by the fuel supply system 6 to form an air-fuel mixture. Next, the piston 3 rises and the intake air in the cylinder 2 is compressed (compression stroke). Next, the air-fuel mixture is ignited by the spark plug 7 and burned in the cylinder 2 (combustion stroke), and the piston 3 is driven by the combustion energy to reciprocate in the cylinder 2. The reciprocating motion of the piston 3 is converted into the rotational motion of a crankshaft (not shown) to generate power. Thereafter, the piston 3 rises and the exhaust valve 51 is opened, so that the combustion gas in the cylinder 2 is discharged to the outside from the exhaust port 5 (exhaust stroke).

[Fuel supply system]
In the internal combustion engine 1, the fuel supply system 6 includes a first fuel tank 61 and a second fuel tank 62, a first feed pump 63 and a second feed pump 64, a port fuel injection valve 65 and an in-cylinder fuel injection. It has a valve 66, a fuel passage 67, and a high-pressure pump 68 (see FIG. 1).

  The first fuel tank 61 and the second fuel tank 62 are tanks for storing fuel. The first fuel tank 61 and the second fuel tank 62 store fuels having different octane numbers (high octane fuel and low octane fuel), respectively. Specifically, high octane fuel is stored in the first fuel tank 61, and low octane fuel is stored in the second fuel tank 62. The first feed pump 63 is a pump that pumps up the fuel in the first fuel tank 61, and the second feed pump 64 is a pump that pumps up the fuel in the first fuel tank 61. The outlet pressure of the first feed pump 63 is set higher than the outlet pressure of the second feed pump 64. The port fuel injection valve 65 and the in-cylinder fuel injection valve 66 are injectors for injecting fuel. Specifically, the port fuel injection valve 65 injects fuel in the intake port 4 (intake port injector). In-cylinder fuel injection valve 66 injects fuel in cylinder 2 (in-cylinder injector).

  The fuel passage 67 includes a first fuel passage 671 and a second fuel passage 672. In the fuel passage 67, the first fuel passage 671 connects the first feed pump 63 and the port fuel injection valve 65, and the second fuel passage 672 connects the second feed pump 64 and the in-cylinder fuel injection valve 66. Further, the first fuel passage 671 and the second fuel passage 672 communicate with each other through the communication passage 673. A flow rate control valve 674 is disposed in the communication path 673. The flow control valve 674 adjusts the flow rate of fuel in the communication passage 673. The high pressure pump 68 is disposed on the second fuel passage 672 and boosts the fuel supplied to the in-cylinder fuel injection valve 66.

  In this fuel supply system 6, (1) when the flow control valve 674 is in the closed state, fuel does not flow through the communication passage 673, so the first fuel passage 671 and the second fuel passage 672 are independent of each other. (See FIG. 6). Therefore, only the high octane number fuel in the first fuel tank 61 is supplied to the port fuel injection valve 65, and only the low octane number fuel in the second fuel tank 62 is supplied to the in-cylinder fuel injection valve 66. Specifically, first, the high octane fuel in the first fuel tank 61 is pumped up by the first feed pump 63 and supplied to the port fuel injection valve 65 through the first fuel passage 671. Then, this high octane fuel is injected from the port fuel injection valve 65 into the intake port 4. The low-octane fuel in the second fuel tank 62 is pumped up by the second feed pump 64 and supplied to the in-cylinder fuel injection valve 66 through the second fuel passage 672. At this time, the low-octane fuel is boosted by the high-pressure pump 68 and supplied to the in-cylinder fuel injection valve 66. This is because the outlet pressure of the second feed pump 64 is set low. The low octane fuel is injected into the cylinder 2 from the in-cylinder fuel injection valve 66. As a result, high octane fuel is injected into the intake port 4 and low octane fuel is injected into the cylinder 2.

  Also, (2) when the flow control valve 674 is in the open state, the outlet pressure of the first feed pump 63 is higher than the outlet pressure of the second feed pump 64, so that the high-octane fuel in the first fuel passage 671 is high. It flows into the second fuel passage 672 through the communication passage 673 (see FIG. 7). Accordingly, the in-cylinder fuel injection valve 66 is supplied with a mixed fuel of the high octane fuel in the first fuel passage 671 and the low octane fuel in the second fuel passage 672. At this time, the opening ratio of the flow rate control valve 674 adjusts the mixing ratio of the high-octane fuel and the low-octane fuel. Thereby, the octane number of the fuel supplied to the in-cylinder fuel injection valve 66 is controlled. Note that only high octane fuel is supplied to the port fuel injection valve 65 via the first fuel passage 671.

[Relationship between fuel injection mode and engine characteristics]
Generally, in an internal combustion engine, engine characteristics (ignition timing and output torque) change as follows according to the mode of fuel injection (see FIG. 3). In FIG. 3, points A to D indicate trace knock points.

  (1) Graph a shows engine characteristics when only in-cylinder injection (fuel injection in the cylinder) is performed and port injection (fuel injection at the intake port) is not performed. In the configuration of the graph a (trace knock point A), a fuel having a predetermined octane number (for example, a low octane number fuel) is injected into the cylinder. In such a configuration, the volumetric efficiency of the engine is improved because the air in the cylinder is cooled by the latent heat of vaporization of the fuel, compared to a configuration in which only port injection is performed.

  (2) The graph b shows engine characteristics when both in-cylinder injection and port injection are performed. In the configuration of the graph b (trace knock point B), low-octane fuel is injected into the cylinder and high-octane fuel is port-injected. In such a configuration, the trace knock point B shifts to the advance side as compared with the configuration in which only in-cylinder injection is performed (trace knock point A). Therefore, the ignition timing can be easily adjusted, and the engine knock resistance is improved. However, in such a configuration, the fuel injection amount for in-cylinder injection decreases, so that the volumetric efficiency decreases and the output torque of the engine decreases.

  (3) Graph c shows the engine characteristics when both in-cylinder injection and port injection are performed. In the configuration of the graph c (trace knock point C), low-octane fuel is injected into the cylinder and high-octane fuel is port-injected. Further, the fuel injection amount for the port injection is reduced as compared with the configuration of the graph b (trace knock point B). As a result, the volumetric efficiency of the engine is increased and the output torque of the engine is improved. However, in such a configuration, since the trace knock point C shifts to the retard side, the knock resistance performance of the engine decreases.

[Fuel injection control]
Therefore, in the internal combustion engine 1, the following fuel injection control is performed in order to improve the knocking resistance performance of the engine while maintaining the output torque of the engine. That is, (4) a configuration is employed in which both in-cylinder injection and port injection are performed, and low-octane fuel is injected into the cylinder and high-octane fuel is port-injected (see FIG. 1). Further, when the volumetric efficiency of the engine is reduced during high load operation, (a) the fuel injection amount of the port fuel injection valve 65 is reduced, and (b) the amount of fuel injected from the in-cylinder fuel injection valve 66 is reduced. Octane number is increased. Then, (a) increases the volumetric efficiency of the engine and improves the output torque of the engine, and (b) shifts the trace knock point D to the retarded angle side and improves the engine anti-knock performance ( (See FIG. 3).

  For example, in this embodiment, fuel injection control is performed as follows. First, the internal combustion engine 1 has a control system 8 for fuel injection control (see FIG. 1). The control system 8 is provided with an ECU (Engine Control Unit) 81 and various sensors 82 and 83 (see FIG. 1). The various sensors 81 and 82 include, for example, a rotational speed sensor 82 that detects the engine rotational speed, an intake air amount sensor 83 that detects the intake air amount, and the like. In this control system 8, the ECU 81 determines the fuel injection amount of the port fuel injection valve 65 and the in-cylinder fuel injection valve based on the output signals from the sensors 81 and 82 and a predetermined control map (see FIGS. 4 and 5). The fuel injection ratio with respect to the fuel injection amount, the opening degree of the flow control valve 674 and the like are controlled.

  In the fuel injection control, first, the engine speed and the intake air amount are read (ST1) (see FIG. 2). Next, a fuel injection ratio between the fuel injection amount of the port fuel injection valve 65 and the fuel injection amount of the in-cylinder fuel injection valve 66 is set based on the engine speed and the intake air amount (ST2) (see FIG. 3). ). The fuel injection ratio is determined based on a predetermined control map (see FIG. 4). For example, in this embodiment, the volumetric efficiency of the engine decreases when the intake air amount changes to a decreasing side with reference to a predetermined threshold (graph d) in a region where the engine speed is high (high load operation region). It is judged that Therefore, in this case, the port injection ratio is set small, and the fuel injection amount of the port fuel injection valve 65 is reduced. Thereby, the volumetric efficiency of the engine is increased and the output torque of the engine is improved.

  Next, the opening degree of the flow control valve 674 is set based on the engine speed and the intake air amount (ST3). The opening degree of the flow control valve 674 is determined based on a predetermined control map (see FIG. 5). For example, in this embodiment, the flow control valve 674 is opened in a region where the engine speed is high and the intake air amount is larger than a predetermined threshold (graph e). Then, the high octane fuel in the first fuel passage 671 flows into the second fuel passage 672 through the communication passage 673 and is mixed with the low octane fuel in the second fuel passage 672. Thereby, the octane number of the fuel supplied to the in-cylinder fuel injection valve 66 is increased, and the engine anti-knock performance is improved. In this region, the opening degree of the flow control valve 674 is controlled according to the intake air amount. Specifically, the opening degree of the flow control valve 674 is set larger as the intake air amount increases. As a result, the octane number of the fuel supplied to the in-cylinder fuel injection valve 66 is optimized, and the engine anti-knock performance is efficiently improved. These improve the combustibility and operability of the engine.

[effect]
As described above, in the internal combustion engine 1, when the volumetric efficiency is reduced during high-load operation of the engine, (a) the fuel injection amount of the port fuel injection valve 65 is reduced, and (b) in-cylinder The octane number of the fuel injected from the fuel injection valve 66 is increased. As a result, (a) there is an advantage that the volume efficiency of the engine is increased and the output torque of the engine is improved, and (b) the trace knock point D is shifted to the retarded side, and the knock resistance performance of the engine is improved. There are advantages (see FIG. 3).

[Additional matters]
In the internal combustion engine 1, the first fuel passage 671 that supplies fuel to the port fuel injection valve 65, the second fuel passage 672 that supplies fuel to the in-cylinder fuel injection valve 66, the first fuel passage 671, A communication passage 673 connecting the two fuel passages 672 is provided (see FIG. 1). The fuel in the first fuel passage 671 (high-octane fuel) is introduced into the second fuel passage 672 via the communication passage 673, whereby the octane number of the fuel (low-octane fuel) in the second fuel passage 672 is changed. (See FIG. 7). That is, by diverting the fuel (high octane number fuel) supplied to the port fuel injection valve 65, the octane number of the fuel (low octane number fuel) supplied to the in-cylinder fuel injection valve 66 is changed. Thus, there is an advantage that the means for increasing the octane number of the fuel injected from the in-cylinder fuel injection valve 66 (octane number changing means) is simply configured.

  In the above configuration, the flow rate control valve 674 is disposed in the communication passage 673, and the fuel in the first fuel passage 671 is set at a higher pressure than the fuel in the second fuel passage 672 (see FIG. 7). Then, the octane number of the fuel in the second fuel passage 672 is adjusted by controlling the opening degree of the flow control valve 674. Thereby, there exists an advantage by which the means (octane number change means) which adjusts the octane number of the fuel injected from the cylinder fuel injection valve 66 is comprised simply.

  In this embodiment, high-octane fuel is stored in the first fuel tank 61, and low-octane fuel is stored in the second fuel tank 62 (see FIG. 1). The high-octane fuel is supplied from the first fuel tank 61 to the first fuel passage 671, and the low-octane fuel is supplied from the second fuel tank 62 to the second fuel passage 672. In such a configuration, the first fuel tank 61 and the second fuel tank 62 may be replenished with fuel, respectively, and a fractionator (not shown) that fractionates gasoline into high-octane fuel and low-octane fuel. The fuel tanks 61 and 62 may be replenished with fuel.

  As described above, the internal combustion engine according to the present invention is useful in that it can improve the knock resistance of the engine while maintaining the output torque of the engine.

1 is a configuration diagram illustrating an internal combustion engine according to an embodiment of the present invention. It is a flowchart which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG.

Explanation of symbols

Reference Signs List 1 internal combustion engine 2 cylinder 3 piston 4 intake port 41 intake valve 5 exhaust port 51 exhaust valve 6 fuel supply system 61 first fuel tank 62 second fuel tank 63 first feed pump 64 second feed pump 65 port fuel injection valve 66 cylinder Inner fuel injection valve 67 Fuel passage 671 First fuel passage 672 Second fuel passage 673 Communication passage 674 Flow control valve 68 High-pressure pump 7 Spark plug 8 Control system 81 ECU
82 Rotational speed sensor 83 Intake air amount sensor

Claims (3)

The fuel injection valve has a port fuel injection valve that injects fuel at the intake port, and an in-cylinder fuel injection valve that injects fuel in the cylinder. An internal combustion engine set higher than the octane number of fuel injected from a valve,
When the volumetric efficiency decreases during high-load operation of the engine, the fuel injection amount of the port fuel injection valve is reduced and the octane number of the fuel injected from the in-cylinder fuel injection valve is increased. An internal combustion engine.   A first fuel passage for supplying fuel to the port fuel injection valve; a second fuel passage for supplying fuel to the in-cylinder fuel injection valve; and a communication passage connecting the first fuel passage and the second fuel passage. And the fuel in the first fuel passage is introduced into the second fuel passage through the communication passage, whereby the octane number of the fuel in the second fuel passage is changed. Internal combustion engine.   A flow control valve is disposed in the communication passage, the fuel in the first fuel passage is set at a higher pressure than the fuel in the second fuel passage, and the second fuel is controlled by opening control of the flow control valve. The internal combustion engine according to claim 2, wherein the octane number of the fuel in the passage is adjusted.

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