JP2009097470A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set fuel injection time of an intake process so as not to increase a pumping loss and the discharging amount of unburned fuel when intake-air temperature is set to be a set temperature or higher by an intake-air temperature changing means, in a cylinder injection type spark ignition internal combustion engine equipped with the intake-air temperature changing means for changing the intake-air temperature. <P>SOLUTION: When the intake-air temperature is changed to be the set temperature or higher by the intake-air temperature changing means, fuel injection starting timing is set on a delay angle side in the intake process more than a fuel injection starting timing range (a2 to a3) in which intake filling efficiency becomes not less than a set value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a direct injection spark ignition internal combustion engine.

  In an internal combustion engine equipped with an intercooler, when the engine is under a low load where knocking does not occur, the intake air temperature is raised without operating the intercooler, thereby increasing the upper limit of the air-fuel ratio at which combustion can occur and reducing fuel consumption It has been proposed (see, for example, Patent Document 1). Further, since the intake air density is decreased by increasing the intake air temperature and the intake charge efficiency is lowered, the throttle valve opening can be increased to supply the same intake air amount, and the pumping loss is reduced.

JP 2003-247422 A JP 10-339219 A

  However, in the case of an in-cylinder spark ignition internal combustion engine in which fuel is injected during the intake stroke to perform homogeneous combustion, depending on the fuel injection timing, the intake air temperature in the cylinder when the intake valve is closed may be excessive due to the latent heat of vaporization of the fuel. In this case, the intake charging efficiency is increased, thereby reducing the throttle valve opening to supply the required intake air amount, thereby increasing the pumping loss.

  In addition, if the fuel injection timing is advanced so that the intake charging efficiency does not become excessively high, the distance between the fuel injection valve and the piston top surface at the fuel injection timing becomes short, so that the injected fuel tends to collide and adhere to the piston top surface. As a result, the amount of unburned fuel is increased.

  Accordingly, an object of the present invention is to increase the pumping loss when the intake air temperature is set to be equal to or higher than the set temperature in the direct injection spark ignition internal combustion engine provided with the intake air temperature changing means for changing the intake air temperature. The fuel injection timing of the intake stroke is set so as not to increase the discharge amount of unburned fuel.

  The in-cylinder injection spark ignition internal combustion engine according to claim 1 of the present invention is an in-cylinder injection spark ignition internal combustion engine provided with an intake air temperature changing means for changing an intake air temperature. When the intake air temperature is equal to or higher than the set temperature, the fuel injection start timing is set to be retarded in the intake stroke from the fuel injection start timing range in which the intake charging efficiency is equal to or higher than the set value.

  The direct injection spark ignition internal combustion engine according to claim 2 of the present invention is the direct injection spark ignition internal combustion engine according to claim 1, wherein the intake temperature changing means is an intake air heating device. To do.

  The direct injection spark ignition internal combustion engine according to claim 3 of the present invention is the direct injection spark ignition internal combustion engine according to claim 1, wherein the intake air temperature changing means is an intake air cooling device. To do.

  According to a fourth aspect of the present invention, there is provided the direct injection spark ignition internal combustion engine according to the first aspect, wherein the fuel injection start timing range is 5 ms from the intake valve closing timing. It is a range that is 7 ms before.

  According to the in-cylinder injection spark ignition internal combustion engine of the first aspect of the present invention, when the intake air temperature is set to the set temperature or higher by the intake temperature changing means, the fuel injection start timing is set to the intake charge efficiency equal to or higher than the set value. The fuel injection start timing range is set to be retarded in the intake stroke. As a result, fuel injection is started within this fuel injection start timing range, the intake charge efficiency becomes equal to or higher than the set value, and the pumping loss increases because the throttle valve opening must be decreased to achieve the required intake amount. In addition, fuel injection is started on the advance side of the fuel injection start timing range in which the intake charging efficiency is equal to or higher than the set value, and the distance between the fuel injection valve and the piston top surface is short, so the injected fuel It is also possible to prevent the amount of unburned fuel from increasing due to collision and adhesion on the piston top surface.

  According to the in-cylinder injection spark ignition internal combustion engine according to claim 2 of the present invention, in the in-cylinder injection spark ignition internal combustion engine according to claim 1, the intake air temperature changing means is an intake air heating device.

  According to the in-cylinder injection spark ignition internal combustion engine of the third aspect of the present invention, in the in-cylinder injection spark ignition internal combustion engine of the first aspect, the intake air temperature changing means is an intake air cooling device.

  According to the direct injection spark ignition internal combustion engine according to claim 4 of the present invention, in the direct injection spark ignition internal combustion engine according to claim 1, the fuel injection start timing at which the intake charge efficiency is equal to or higher than a set value. The range is a range of 4 ms to 8 ms before the intake valve closing timing.

  FIG. 1 is a schematic diagram showing a first embodiment of a direct injection spark ignition internal combustion engine according to the present invention. In the figure, 1 is an engine body, 2 is an intake system, and 3 is an exhaust system. The intake system 2 has an air cleaner 4 at the most upstream part, and is connected to the engine body 1 through an intercooler 5 as a heat exchanger. A throttle valve 6 is provided on the downstream side of the intercooler 5 of the intake system 2.

  The intercooler 5 uses cooling water cooled by the radiator 7 for intake air cooling. A branch passage 8 connected to the intercooler 5 on the downstream side of the circulation pump P is connected to the inflow passage 7 a connecting the engine body 1 and the radiator 7, and the outflow connecting the engine body 1 and the radiator 7. A joining passage 9 from the intercooler 5 is connected to the passage 7b. A control valve 10 is disposed in the merge passage 9.

  In such a configuration, by opening the control valve 10, the cooling water is circulated to the intercooler 5, the intake air temperature supplied into the cylinder is lowered, and knocking is less likely to occur. The intake air charging efficiency can be increased. Further, by closing the control valve 10, the circulation of the cooling water to the intercooler 5 is stopped, and the temperature of the intake air supplied into the cylinder does not decrease. Thus, the intercooler 5 functions as intake air temperature changing means for changing the intake air temperature.

  FIG. 2 is a schematic view showing a second embodiment of a direct injection spark ignition internal combustion engine according to the present invention. In the figure, 1 is an engine body, 2 is an intake system, and 3 is an exhaust system. The intake system 2 has an air cleaner 4 at the most upstream part, and is connected to the engine body 1 through an interheater 50 as a heat exchanger. A throttle valve 6 is provided downstream of the interheater 50 of the intake system 2.

  The interheater 50 uses cooling water heated by cooling the engine body 1 for intake air heating. A circulation pump P is disposed in the inflow passage 7a ′ connecting the engine body 1 and the radiator 7, and a switching valve 100 is disposed in the outflow passage 7b ′ connecting the engine body 1 and the radiator 7. At the same time, a branch passage 80 is provided that branches at the switching valve 100 and passes through the interheater 50 and joins on the downstream side of the switching valve 100.

  In such a configuration, by switching the switching valve 100 so that the cooling water heated in the engine body 1 circulates through the interheater 50, the intake air temperature supplied into the cylinder is increased. Further, by switching the switching valve 100 so that the cooling water does not circulate through the interheater 50, the intake air temperature supplied into the cylinder is not increased, making it difficult for knocking to occur and increasing the intake charging efficiency. be able to. Thus, the interheater 50 functions as intake air temperature changing means for changing the intake air temperature.

  FIG. 3 is a schematic view showing a third embodiment of a direct injection spark ignition internal combustion engine according to the present invention. In the figure, 1 is an engine body, 2 'is an intake system, and 3' is an exhaust system. The intake system 2 ′ has an air cleaner 4 at the most upstream portion, and is connected to the engine body 1 through an upstream first interheater 51 and a downstream second interheater 52 as heat exchangers. A throttle valve 6 is provided on the downstream side of the second interheater 52 of the intake system 2 '.

  The first and second interheaters 51 and 52 use the heat of the exhaust gas for intake air heating, and the exhaust system 3 ′ passes through the second interheater 52 and the first interheater 51. The exhaust system 3 ′ can bypass the first interheater 51 by the first switching valve 101 and can bypass the second interheater 52 by the second switching valve 102. In the exhaust system 3 ′, the catalyst device 11 is disposed between the first interheater 51 and the second interheater 52.

  In such a configuration, the first switching valve 101 and the second switching valve 102 allow exhaust gas to pass through neither the first interheater 51 nor the second interheater 52 so that the exhaust gas is supplied into the cylinder. The intake air temperature is not increased, making it difficult for knocking to occur and increasing the intake charge efficiency.

  Further, the exhaust gas passes through at least one of the first interheater 51 and the second interheater 52 by at least one of the first switching valve 101 and the second switching valve 102, thereby entering the cylinder. The intake air temperature supplied is increased. In this case, when the catalyst device 11 is not sufficiently warmed up immediately after the engine is started, the exhaust gas bypasses the second interheater 52 and passes through the first interheater 51, whereby the catalyst Since the temperature of the exhaust gas flowing into the device 11 does not decrease, the warm air of the catalyst device 11 can be prevented from deteriorating. Further, when the temperature of the catalyst device 11 is excessively high due to continued high engine load operation, the exhaust gas flows into the catalyst device 11 by allowing the exhaust gas to pass through the second interheater 52. It is possible to reduce the temperature and prevent the temperature of the catalyst device 11 from excessively increasing. Thus, the first interheater 51 and the second interheater 52 function as intake air temperature changing means for changing the intake air temperature.

  FIG. 4 is a schematic view showing a fourth embodiment of the direct injection spark ignition internal combustion engine according to the present invention. In the figure, 1 is an engine body, 2 "is an intake system, and 3 is an exhaust system. The intake system 2" has an air cleaner 4 at the most upstream portion, and a switching valve 200 is disposed. The downstream side of the switching valve 200 is connected to the throttle valve 6 on the one hand through the intercooler 5 ′ and connected to the throttle valve 6 on the other hand through the interheater 50 ′. A downstream side of the throttle valve 6 is connected to the engine body 1.

  Reference numeral 7 denotes a radiator, which is connected to the engine body 1 by an inflow passage 7a and an outflow passage 7b, and a circulation pump P is disposed in the inflow passage 7a. As shown in FIG. 4, the intercooler 5 ′, the radiator 7, and the interheater 50 ′ are arranged in this order from the vehicle front side, and the traveling wind cools the intercooler 5 ′ and the radiator 7 as indicated by arrows. At the same time, the interheater 50 'is heated by the traveling wind heated by the cooling.

  In such a configuration, by allowing the intake air to pass through the intercooler 5 ′ by the switching valve 200, the temperature of the intake air supplied into the cylinder is lowered, making it difficult for knocking to occur and improving the intake charging efficiency. Can be increased.

  Further, by allowing the intake air to pass through the interheater 50 'by the switching valve 200, the temperature of the intake air supplied into the cylinder is increased. In the present embodiment, the intercooler 5 ′ and the interheater 50 ′ need not be heated and cooled by the cooling water, and the structure can be simplified.

  Further, as another embodiment, when a plurality of interheaters for heating intake air to different temperatures are provided in series, the intake air passes through the interheater having a lower temperature first, thereby efficiently The intake air temperature can be raised.

  As yet another embodiment, when a plurality of interheaters that heat intake air to different temperatures are provided in parallel, the intake air temperature that passes through each interheater is appropriately feedback controlled so that the intake air temperature Can be controlled to a desired temperature.

  FIG. 5 is a schematic longitudinal sectional view of the engine body 1. In the figure, reference numeral 60 denotes a fuel injection valve arranged substantially at the center of the cylinder upper portion, and 61 denotes an ignition plug arranged near the intake valve side of the fuel injection valve 60. An intake port 62 communicates with the cylinder via a pair of intake valves (not shown), and an exhaust port 63 communicates with the cylinder via a pair of exhaust valves (not shown). Reference numeral 64 denotes a piston.

  The fuel injection valve 60 has a substantially semicircular arc-shaped slit injection hole and has a hollow semiconical shape toward the exhaust port side lower part of the cylinder bore or the exhaust port side peripheral part of the piston top surface near the intake bottom dead center. It is to be jetted. Further, the fuel injection valve 60 has a plurality of round injection holes, and in the vicinity of the intake bottom dead center, a plurality of injection holes are provided from the injection holes toward the exhaust port side lower part of the cylinder bore or the exhaust port side peripheral part of the piston top surface. You may make it inject a fuel. The plurality of round nozzle holes may be arranged in a substantially semicircular arc shape.

  If such fuel f is injected in the vicinity of the intake bottom dead center, which is the injection timing of the fuel injection valve 60, it is difficult to collide and adhere to the piston top surface or the cylinder bore, and the tumble flow T can be enhanced well. If the tumble flow T is strengthened in this way, the tumble flow T is reliably maintained in the cylinder until it is crushed by the piston 64 in the latter half of the compression stroke, and a turbulence that is crushed by the piston 64 and continues until the ignition timing is generated. The combustion speed can be increased and good homogeneous combustion can be realized.

  In order to surely increase the tumble flow T, the penetration force of the fuel f injected by the fuel injection valve 60 is preferably strengthened so that, for example, the fuel tip after 1 ms from the start of injection reaches 60 mm or more.

  Further, the fuel injection valve 60 has a partial arc shape, a straight line shape, or a polygonal line slit injection hole, and injects fuel having a partial arc cross section, a linear cross section, or a polygonal line cross section. It may have a plurality of circular injection holes arranged in a shape and inject fuel into a plurality of columns. In such a case, the injected fuel is directed to at least one of the lower part on the exhaust port side of the cylinder bore (a belt-like part having a substantially semicircular cross section) and the peripheral part on the exhaust port side of the piston top surface (a belt-like part having a substantially semicircular arc). It should be done. Of course, in the vicinity of the intake bottom dead center, the fuel injection valve 60 has at least the exhaust port side lower part of the cylinder bore (a belt-like part having a substantially semicircular cross section) and the exhaust port side peripheral part (a belt part having a substantially semicircular arc) of the piston top surface. A fuel having a hollow or solid conical shape may be injected toward one side.

  By the way, at low engine loads where knocking is unlikely to occur, if the intake air temperature is set to a set temperature or higher by stopping the operation of the intercooler or operating the interheater, the air-fuel ratio at which combustion can occur In order to increase the upper limit value, the amount of fuel injected can be reduced to reduce fuel consumption. Further, when the intake air temperature is equal to or higher than the set temperature, the intake air density decreases, so that the throttle valve opening can be increased to supply the same intake air amount into the cylinder, and the pumping loss is reduced.

  However, in the case of an in-cylinder spark-ignition internal combustion engine with intake stroke fuel injection as in this embodiment, depending on the fuel injection timing, the intake air temperature in the cylinder when the intake valve closes due to fuel vaporization latent heat is excessive. Since the intake charge efficiency is lowered and the required intake air amount is supplied, the increased throttle valve opening may be excessively reduced to increase the pumping loss.

  FIG. 6 is a graph showing the lift of the intake valve with respect to the crank angle. The intake valve starts to open at a crank angle a0 prior to the intake top dead center (TDC) crank angle a1, and the intake valve closes at a crank angle a5 after the intake bottom dead center (BDC) crank angle a4. Exit. When fuel injection is started within the crank angle range a2 to a3 a predetermined time before the closing timing of the intake valve (hereinafter referred to as intake valve closing timing), most of the injected fuel is taken to the intake valve closing timing. In order to vaporize in the cylinder, the intake air temperature in the cylinder is excessively lowered.

  Thereby, since the intake charge efficiency becomes too high, the opening degree of the throttle valve 6 must be reduced in order to realize the required intake amount, and the pumping loss increases. Accordingly, it is conceivable that fuel injection is started before the crank angle range a2 to a3. However, in this case, since the distance between the fuel injection valve 60 and the piston 64 is shortened, the injected fuel is injected into the piston top surface. Since some of the adhering fuel is vaporized in the expansion stroke and discharged as unburned fuel, the amount of unburned fuel discharged is increased.

  Therefore, in this embodiment, when the intake air temperature is set to be equal to or higher than the set temperature by an intake air temperature changing means such as an intercooler or an interheater when the occurrence of knocking is not a concern, the fuel injection start timing is set as the intake charge efficiency. Is set to be retarded in the intake stroke from the fuel injection start timing range (range of crank angles a2 to a3) in which is greater than the set value. That is, the fuel injection start timing is set later than the crank angle a3 and before the intake valve closing timing a5.

  Accordingly, the injected fuel is not sufficiently vaporized at the intake valve closing timing a5, and the intake temperature in the cylinder does not excessively decrease due to the latent heat of vaporization, so that the intake charging efficiency does not become too high. Since it is not necessary to decrease the valve opening, the pumping loss does not increase. Further, since the fuel injection timing is still near the bottom dead center of the intake air, the tumble flow T can be strengthened by the injected fuel as described above. Further, the distance between the fuel injection valve 60 and the piston top surface becomes short during fuel injection, and the injected fuel does not collide and adhere to the piston top surface.

  The aforementioned fuel injection start timing range in which the intake charging efficiency is increased to a set value or more can be between 4 ms and 8 ms before the intake valve closing timing. This fuel injection start timing range is a fuel injection start timing range in which the intake charging efficiency is equal to or higher than a set value at a fuel injection amount within the fuel injection amount range of the engine low load at which the occurrence of knocking is not a concern. If fuel injection is started later than 4 ms before the intake valve closing timing at any fuel injection amount within the engine low load fuel injection range where generation is not a concern, the intake charge efficiency will not exceed the set value. Therefore, it is not necessary to reduce the increased throttle valve opening (throttle valve opening set as the intake charge efficiency does not exceed the set value), and the pumping loss does not increase.

1 is a schematic view showing a first embodiment of a direct injection spark ignition internal combustion engine according to the present invention. It is the schematic which shows 2nd embodiment of the cylinder injection type spark ignition internal combustion engine by this invention. It is the schematic which shows 3rd embodiment of the cylinder injection type spark ignition internal combustion engine by this invention. It is the schematic which shows 4th embodiment of the cylinder injection type spark ignition internal combustion engine by this invention. 1 is a schematic longitudinal sectional view of an engine body of a direct injection spark ignition internal combustion engine according to the present invention. It is a graph which shows the relationship between a crank angle and intake valve lift amount.

Explanation of symbols

1 Engine body 5, 5 'Intercooler 50, 50', 51, 52 Interheater 6 Throttle valve

Claims (4)

  An in-cylinder injection type spark ignition internal combustion engine having an intake air temperature changing means for changing an intake air temperature, and when the intake air temperature is set to be equal to or higher than a set temperature by the intake air temperature changing means, An in-cylinder injection type spark ignition internal combustion engine characterized in that it is on the retard side in the intake stroke from a fuel injection start timing range in which is equal to or greater than a set value.   The in-cylinder injection spark ignition internal combustion engine according to claim 1, wherein the intake air temperature changing means is an intake air heating device.   The in-cylinder injection spark ignition internal combustion engine according to claim 1, wherein the intake air temperature changing means is an intake air cooling device.   The in-cylinder injection spark ignition internal combustion engine according to claim 1, wherein the fuel injection start timing range is a range from 5 ms to 7 ms before the intake valve closing timing.

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