JP2009024637A - Inner cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always execute appropriate homogeneous combustion while a tumble flow is sufficiently reinforced and kept immediately before an ignition timing even when the tumble flow generated in an intake stroke is relatively weak. <P>SOLUTION: In the intake stroke, the tumble flow T turning upward at an intake port 15 side and downward at an exhaust port 16 side in a combustion chamber 10 is generated by air supplied from the intake port 15. Fuel is injected in the combustion chamber 10 in a latter half of the compression stroke by a fuel injection valve 21 provided near the intake port 15 of a cylinder head 14. This fuel spray collides with and reflects from a guide part formed at the intake port side of a piston top face 19 and deflects in a flowing direction of the tumble flow T. Thus, the tumble flow T is reinforced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an in-cylinder injection spark ignition internal combustion engine, and more particularly to a configuration for enhancing a tumble flow generated in a combustion chamber.

  In order to achieve homogeneous combustion of an air-fuel mixture in an in-cylinder injection spark ignition internal combustion engine, it is known to form a tumble flow by the intake air supplied into the combustion chamber. When the tumble flow is maintained until the end of the compression stroke, a homogeneous air-fuel mixture is generated by the turbulence generated by the collapse of the tumble flow at the ignition timing, and the combustion speed is increased to achieve good homogeneous combustion.

The tumble flow is a vortex that swirls so that it rises on the intake port side and descends on the exhaust port side, and this tumble vortex tends to collapse earlier than the ignition timing due to the rise of the piston. Patent Document 1 proposes that a squish flow is generated in the vicinity of the top dead center of the compression stroke by the piston top surface and the cylinder head wall surface to enhance the tumble flow.
JP 2006-322348 A

  The tumble flow is strengthened by the squish flow near the top dead center of the compression stroke, and it is effective if the tumble flow is maintained up to this point. However, in the case of operating conditions where it is difficult to maintain the tumble flow to near the top dead center, the tumble flow cannot be strengthened by the squish flow.

  According to the present invention, even when the tumble flow generated in the intake stroke is relatively weak, the tumble flow can be sufficiently strengthened and maintained until just before the ignition timing, and always good homogeneous combustion can be realized. An object of the present invention is to obtain an in-cylinder injection spark ignition internal combustion engine.

  An in-cylinder injection spark ignition internal combustion engine according to the present invention is provided in the vicinity of an intake port of a cylinder head, injects fuel directly into a combustion chamber, and rises on the intake port side in the combustion chamber, and an exhaust port On the side, a means for generating a tumble flow swirling so as to descend, and a fuel spray injected by the fuel injection valve when the piston is in the compression stroke are formed in a portion on the intake port side of the piston top surface. And a guide portion that deflects in the flow direction.

  The fuel spray injected by the fuel injection valve is deflected in the flow direction of the tumble flow by colliding with the guide portion. That is, the fuel spray tends to spread in the lateral direction, but by colliding with the guide portion, the fuel spray is formed into a fan shape having an angle corresponding to the range in which the tumble flow is generated, and effectively strengthens the tumble flow.

  The fuel injection is preferably performed in the latter half of the compression stroke. According to this, the fuel spray collides with the guide portion on the piston top surface and is deflected upward, and the component of the tumble flow from the intake port side toward the exhaust port side Strengthen enough.

  For example, the guide portion is provided with a partition wall extending from the fuel injection valve side toward the ignition plug. The partition wall separates the fuel spray into two parts and prevents the fuel spray from being directed to the spark plug, thereby preventing the spark plug from being wetted by the fuel.

  It is preferable that a warping portion for deflecting the fuel spray in a direction along the tumble flow is formed on the bottom surface of the cylinder head and in the vicinity of the exhaust port. According to this configuration, the fuel spray not only strengthens the component of the tumble flow from the intake port side toward the exhaust port side, but also collides with the warped part and deflects along the warped part, thereby causing the tumble on the exhaust port side. Also strengthens the downward flow component.

  According to the present invention, even when the tumble flow generated in the intake stroke is relatively weak, the tumble flow can be sufficiently strengthened and maintained until just before the ignition timing, and always good homogeneous combustion is achieved. Can be realized.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a first embodiment of a direct injection spark ignition internal combustion engine of the present invention.

  A piston 13 is slidably provided in a cylinder bore 12 formed in the cylinder block 11, and an intake port 15 and an exhaust port 16 are formed in a cylinder head 14 provided on the cylinder block 11. The intake port 15 is opened and closed by an intake valve 17, and the exhaust port 16 is opened and closed by an exhaust valve 18. A cavity 20 having a cross-sectional shape that is recessed in an arc shape is formed in the piston top surface 19. The combustion chamber 10 is defined by the wall surface of the cylinder bore 12, the bottom surface of the cylinder head 14, and the piston top surface 19.

  In the cylinder head 14, a fuel injection valve 21 is provided in the vicinity of the lower side of the intake port 15, and a spark plug 22 is provided at substantially the center. The fuel injection valve 21 faces obliquely downward, and is disposed so as to inject fuel to the peripheral portion of the piston top surface 19 when the piston 13 is in the latter half of the compression stroke. The fuel stored in a fuel tank (not shown) is pressurized and supplied to the fuel injection valve 21 by a fuel injection pump (not shown).

  The shape of the piston top surface 19 will be described in detail with reference to FIGS. The peripheral portion 25 of the piston top surface 19 is a conical inclined surface that is gently inclined so that the center side of the piston 13 becomes higher, and a guide portion 30 is formed on the portion of the peripheral portion 25 on the intake port 15 side. . The guide part 30 is recessed from the peripheral part 25, is a plane substantially parallel to the peripheral part 25, and is open to the cavity 20 side. The guide portion 30 has a sector shape when the piston top surface 19 is viewed from above, and the central angle of the sector shape, that is, the angle formed by the two side walls 31 and 32 of the guide portion 30 is, for example, 60 to 80 °.

  The fuel injection valve 21 is configured to inject fuel directly into the combustion chamber 10 so that the fuel diffuses in the lateral direction but hardly diffuses in the vertical direction. This fuel injection is performed in the latter half of the compression stroke (for example, a crank angle of 20 to 90 ° BTDC), and the fuel spray F collides with the guide portion 30 and is reflected, that is, deflected. At this time, the fuel spray F tends to spread in the lateral direction, but is guided by the side walls 31 and 32 of the guide portion 30 and formed into a sector shape having a central angle substantially the same as the angle formed by the side walls 31 and 32. This fan-shaped angle corresponds to the range in which the tumble flow is generated, and the fuel spray works effectively to strengthen the tumble flow.

  The operation of this embodiment will be described with reference to FIG. FIG. 4 shows a state in the latter half of the compression stroke, and both the intake valve 17 and the exhaust valve 18 are closed. In an intake stroke (not shown), the air supplied from the intake port 15 generates a tumble flow T that swirls in the combustion chamber 10 so as to rise on the intake port 15 side and descend on the exhaust port 16 side. Although the tumble flow T is weakened in the latter half of the compression stroke, the tumble flow T is strengthened by the fuel spray F in this embodiment. That is, in the latter half of the compression stroke, the fuel is injected by the fuel injection valve 21 and the fuel spray F is deflected by colliding with the guide portion 30 of the piston top surface 19, and obliquely upward, that is, along the bottom surface (pent roof) of the cylinder head 14. move on. The fuel spray F is formed in a fan shape with a relatively small central angle by the guide portion 30 and acts to urge a component of the tumble flow T that flows from the intake port 15 side to the exhaust port 16 side. . As a result, the tumble flow T is strengthened and maintained until just before the top dead center, so that the large vortex of the tumble flow collapses and changes to turbulence (small vortices) at the ignition timing, and the mixture becomes uniform and flame The propagation speed of the is increased, and good homogeneous combustion is realized.

  5 and 6 show a second embodiment of the present invention. These drawings show the guide portion 30 formed on the piston top surface 19, and other configurations are the same as those of the first embodiment.

  In the second embodiment, a partition wall 33 extending from the fuel injection valve side toward the spark plug 22 is provided on the cavity 20 side of the guide portion 30. The partition wall 33 is formed on the cavity 20 side of the guide portion 30 and has an isosceles triangle having two sides parallel to the side walls 31 and 32 when viewed from above. The upper surface of the partition wall 33 is the same height as the peripheral edge portion 25.

  Accordingly, the fuel spray F is prevented from being separated into two by the partition wall 33 and directed to the spark plug 22, so that the spark plug 22 is prevented from getting wet by the fuel and ignition is not hindered. Other operations are the same as those in the first embodiment.

  7 and 8 show a third embodiment of the present invention. FIG. 7 is a view of the cylinder head 14 as viewed from below. FIG. 8 shows fuel injection executed in the latter half of the compression stroke, and corresponds to FIG. 4 in the first embodiment. In the third embodiment, similarly to the second embodiment, the piston top surface 19 is provided with a partition wall (not shown).

  As shown in FIG. 7, the cylinder head 14 is formed with two intake ports 15 and two exhaust ports 16, and a spark plug 22 is disposed at the center. Further, warped portions 34 are respectively formed on the bottom surface of the cylinder head 14 and in the vicinity of the exhaust ports 16 and 16. As shown in FIG. 8, the warped portion 34 protrudes downward from the other portions of the bottom surface, and the lower end surface thereof is substantially at the same height as the boundary surface with the cylinder block 11. Further, the warped portion 34 has an arc shape along the contour of the exhaust port 16 in FIG. 7, and is located on the wall surface side of the cylinder bore 12 relative to the exhaust port 16.

  Accordingly, the fuel spray F is separated into two so as to avoid the spark plug 22 by a partition wall (not shown), and then flows along the exhaust valve 18 and is reflected or deflected at the warping portion 34 to flow the tumble flow T. It goes to the piston top surface 19 side along the direction. Thus, since the fuel spray F is deflected downward in the warping portion 34, not only the component of the tumble flow T from the intake port 15 side to the exhaust port 16 side is strengthened, but also collides with the warping portion 34 and the warping portion. By deflecting along 34, the downward component of the tumble flow T on the exhaust port 16 side is also strengthened. Furthermore, as compared with the first and second embodiments, the fuel injection pressure can be increased to the extent that the fuel injection pressure collides with the warped portion 34, so that the tumble flow T can be further strengthened. Further, similarly to the second embodiment, the spark plug 22 is prevented from getting wet by the fuel, and ignition is not hindered.

  In each of the above embodiments, the shape of the guide portion 30 has been described as a fan shape. However, any shape may be used as long as the fuel spray is directed to the region where the tumble flow exists.

1 is a longitudinal sectional view showing a first embodiment of a direct injection spark ignition internal combustion engine of the present invention. It is a cross-sectional view which shows the guide part formed in the piston top surface. It is a top view which shows the guide part formed in the piston top surface. It is a figure which shows the fuel spray in a compression process. It is a cross-sectional view which shows the guide part in the 2nd Embodiment of this invention. It is a cross-sectional view which shows the guide part in 2nd Embodiment. It is the figure which looked at the cylinder head in the 3rd Embodiment of this invention from the bottom. It is a figure which shows the fuel spray in the compression process of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Combustion chamber 13 Piston 15 Intake port 16 Exhaust port 21 Fuel injection valve 30 Guide part T Tumble flow

Claims (5)

A fuel injection valve provided near the intake port of the cylinder head and injecting fuel directly into the combustion chamber;
Means for generating a tumble flow that swirls so as to rise on the intake port side and descend on the exhaust port side in the combustion chamber;
In-cylinder injection comprising: a guide portion formed on a portion of the piston top surface on the intake port side and deflecting fuel spray injected by the fuel injection valve in the flow direction of the tumble flow when the piston is in a compression stroke Type spark ignition internal combustion engine.   The direct injection spark ignition internal combustion engine according to claim 1, wherein the fuel spray is deflected in a flow direction of the tumble flow by colliding with the guide portion.   2. The direct injection spark ignition internal combustion engine according to claim 1, wherein the fuel injection is performed in the second half of the compression stroke.   The in-cylinder injection spark ignition internal combustion engine according to claim 1, wherein a partition wall extending from the fuel injection valve side toward the ignition plug is provided in the guide portion.   The in-cylinder injection spark ignition internal combustion engine according to claim 1, wherein a warping portion for deflecting the fuel spray in a direction along the tumble flow is formed on a bottom surface of the cylinder head and in the vicinity of the exhaust port. .

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