JP4183127B2 - Sub-chamber internal combustion engine - Google Patents

Description

  The present invention relates to a sub-chamber internal combustion engine.

In the sub-chamber internal combustion engine, a lean air-fuel mixture is supplied to a main combustion chamber having a deep dish-type toroidal shape (cross section “ω” shape) or a bathtub-shaped cavity, and combustion of the air-fuel mixture is promoted.
For this purpose, a sub-combustion chamber (sub-chamber) communicating with the main combustion chamber is provided, and an air-fuel mixture having a relatively high fuel concentration is formed in the sub-combustion chamber, which is rapidly burned. The nozzle has a structure in which it is ejected as a flame jet through a nozzle (see, for example, Patent Document 1).

  However, as described above, in the combustion method in which the flame jet collides with the cavity of the main combustion chamber, the internal main chamber lean mixture rapidly burns due to turbulence and swirl in the cavity, and the combustion temperature rises too much, It becomes easy to generate NOx.

  On the other hand, since the flame of a flame jet or a lean mixture is difficult to propagate from the main chamber cavity to the top clearance part and clevis part (the gap formed on the inner wall of the cylinder and the outer periphery of the piston), the lean mixture However, the lean air-fuel mixture in such a region is a major cause of emission of unburned fuel and unburned hydrocarbons (UHC).

  In addition, in the direction of the nozzle hole where the sub-chamber flame jet is not injected into the center of the cavity, the flame propagation in the main chamber cavity area directly below the sub-chamber is delayed compared to other areas, so unburned fuel is likely to be generated. I have a problem.

In order to deal with such problems, the present applicant has proposed a sub-chamber internal combustion engine in which the piston top surface is a flat surface (Japanese Patent Application No. 2003-43023).
In the sub-chamber internal combustion engine having such a configuration, since the main combustion chamber has a uniform combustion chamber shape, the main combustion chamber has a deep dish type toroidal shape (cross section “ω” shape) or a bathtub shape. As in the case of the chamber, the local high temperature due to the biased combustion that burns locally at a stretch can be avoided, and thus uniform and stable combustion can be obtained. And generation | occurrence | production of NOx is suppressed by the high temperature of combustion temperature being avoided.

However, in the technology according to the prior application, the region between the flame jets is difficult to burn, and so-called “bulk quench” (a part of the combustion chamber or cavity remains as a mass of the air-fuel mixture without burning) Has a problem that occurs.
Japanese Patent Laid-Open No. 10-14164

  The present invention has been proposed in view of the above-mentioned problems of the prior art, and reduces bulk quenching while maintaining high combustion efficiency comparable to that of a sub-chamber internal combustion engine in which the piston top surface is a flat surface. An object of the present invention is to provide a sub-chamber internal combustion engine that can reduce the amount of unburned hydrocarbon (UHC) emissions.

  The sub-chamber internal combustion engine of the present invention has a radial concave groove (4a) on the top surface of the piston (4) and a convex portion (4t) other than the concave groove (4a). The position of 4a) is aligned with the position of the intake / exhaust valves (Vi, Vo) of the cylinder head (3), and the depth of the concave groove (4a) is determined by the intake / exhaust valves (Vi, Vo) and the sub chamber (5). ) The concave groove (4a) is set to have a constant width along its length direction and is opened to the outer periphery of the piston, and its bottom surface (4b) is flat. The convex portion (4t) is formed with a flat top surface, and its side surface is formed parallel to the longitudinal center line of the concave groove (4a) so that the planar shape is substantially triangular. The position of the peripheral edge of the convex part (4t) in contact with the piston outer peripheral part (4d) is a curved surface ( In the sub-chamber internal combustion engine formed in 1), the flame jet (J) ejected from the protruding portion of the sub-chamber (5) is ejected radially outward along the concave groove (4a). It is characterized by.

  In the present invention, the bottom surface (4b) of the concave groove (4a) is preferably flat along the radial direction (Claim 2).

  In the present invention, the bottom surface (4b) of the concave groove (4a) is preferably formed with an inclination so that the piston outer periphery (4d) side becomes higher.

  In the present invention, the bottom surface (4b) of the concave groove (4a) is preferably formed in an arc shape so that the outer peripheral side of the piston becomes higher.

The sub-chamber internal combustion engine of the present invention has a radial concave groove (4a) on the top surface of the piston (4) and a substantially triangular convex portion (4t) which is a portion other than the concave groove (4a). The concave groove (4a) is aligned with the intake / exhaust valve (Vi, Vo) of the cylinder head (3), and the depth of the concave groove (4a) is the intake / exhaust valve (Vi, Vo). And the sub-chamber (5) is set so as not to collide with the protruding portion, and the concave groove (4a) is formed to have a constant width along its length direction, and is opened to the outer periphery of the piston, and the bottom surface ( 4b) is formed in a plane, and the convex portion (4t) has a top surface formed in a plane, and its side surface is formed in parallel with the longitudinal center line of the concave groove (4a), so that the planar shape is substantially the same. It is formed in a triangle, and at the corner of the peripheral edge of the convex part (4t), the piston outer peripheral part (4d) In the sub-chamber internal combustion engine formed by the curved surface (R1), the flame jet (J) injected from the protruding portion of the sub-chamber (5) is projected between the concave grooves (4a) (4t ) In the direction of colliding with the radially inner part.

  According to the present invention having the above-described configuration (the sub-chamber internal combustion engine of claim 1), since the cavity (6) is constituted by the groove (4a) of the piston top surface, The shape is a substantially flat surface. Therefore, unlike conventional pistons that have a deep-plate toroidal shape (cross section “ω” shape) or a bathtub-shaped cavity, local high temperatures due to uneven combustion can be avoided, thus achieving uniform and stable combustion. It is done. And generation | occurrence | production of NOx is suppressed by the high temperature of combustion temperature being avoided.

Further, according to the present invention (the sub-chamber internal combustion engine of claim 1), the flame jet (J) can easily reach the top clearance portion (Ct) and the clevis portion (7), so that unburned carbonization at the location is not possible. Generation of hydrogen (UHC) can be suppressed.
In addition to this, the occurrence of bulk quench can be suppressed, and unburned hydrocarbons (UHC) can be further reduced.

  In the present invention, the position of the groove is aligned with the position of the intake / exhaust valve (Vi, Vo) of the cylinder head (3), and the depth of the groove (4a) is the intake / exhaust valve (Vi, Vo) and the sub chamber. Since it is set so as not to collide with the protruding portion (5), the piston top does not interfere with the intake / exhaust valves (Vi, Vo) and the sub chamber protruding portion (5) of the cylinder head (3).

  In addition to this, in the present invention, the number of flame jets (J) injected from the sub chamber protruding portion (5) is less than or equal to the number of intake and exhaust valves (Vi, Vo) provided in the cylinder head (3). (Claim 4), since the width dimension between the grooves (4a) can be secured to a certain value or more, even if the number of intake and exhaust valves (Vi, Vo) increases, the cylinder head (3) The shape is not complicated, and the possibility of breakage due to heat is reduced.

In the present invention, if the peripheral corners (the ridge line 4k of the corner of the top surface of the convex portion 4t and the corner 4m with the groove 4a) of the portion other than the groove (the convex portion 4t) on the piston top surface are formed as curved surfaces ( If R processing is performed), the heat concentration at the corner (4 m) can be alleviated and the durability of the component can be improved.
In addition, by performing such R processing (for example, R1), it is possible to obtain an effect that a jet or a propagation flame easily enters (Fr) into the piston outer peripheral portion (4d).

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, a first embodiment will be described with reference to FIGS.
In FIG. 1, a cylinder head 3 is fixed to a cylinder block (not shown) by a known means above a cylinder 1 via a gasket 2.
A piston 4 is slidably fitted in the cylinder 1. In the illustrated example, the engine has two intake valves Vi and two exhaust valves Vo per cylinder.

  Above the center point (C) of the piston 4, a holder 5 having a sub chamber 5 a for burning fuel in advance is mounted on the cylinder head 3 so as to protrude from the lower surface of the cylinder head 3.

As shown in FIG. 2, four grooves 4a, 4a having a concave section are formed radially (or two grooves intersecting in a cross shape) at the top of the piston 4, and the four radial grooves are formed. The concave groove 4a constitutes the cavity (6) of the main chamber.
In the projected portion on the plane of the four concave grooves 4a (in the state shown in FIG. 2), the intake valves Vi and the exhaust valves Vo are positioned in at least one adjacent groove 4a. Is arranged.

  The width of the groove 4a is wider than any of the diameters of the intake valve Vi and the exhaust valve Vo, and the convex portion 4t surrounded by the grooves 4a and 4a intersecting in a cross shape is formed when the valves Vi and Vo are opened and closed. It is configured not to interfere with Vo.

  Referring also to FIG. 1, in the vicinity of the lower end of the holder 5, in the illustrated example, there are formed injection holes 5b for injecting flame jets at four locations so as to divide the circumference of the holder 5 into four equal parts. In addition, the jet direction of the flame jet J is configured to be along the center line in the longitudinal direction of the groove 4 a formed at the top of the piston 4. On the elevational view including the axis of the flame jet J (the state shown in FIG. 1), the flame jet J collides with the bottom (concave groove bottom) 4b of the groove 4a with a gentle inclination. The distance L from the collision point on the concave groove 4a of the flame jet J, that is, the piston center point C to the collision point is formed so as to satisfy L> r / 2 when the radius of the piston is r.

  In the illustrated example, a four-valve engine is used, but the number of intake / exhaust valves may be larger. In that case, each valve is preferably plural. In the illustrated example, the number of the concave grooves 4a is four. However, for example, when the total number of intake / exhaust valves is six or more, the number may be smaller than the total number of intake / exhaust valves. That is, when the number of grooves is increased, the convex portion becomes too thin at the position near the jet outlet of the flame jet and may be melted by heat. Therefore, it is necessary to reduce the number of flame jets and increase the width dimension of the convex portion in the vicinity of the flame jet to some extent so as not to be melted by heat.

A cooling oil passage (cooling channel) 4f is formed below the flame jet collision point in order to alleviate heat concentration caused by the flame jet collision.
In forming the cooling channel 4f, the top ring groove 4a is made as close as possible to the concave groove bottom surface 4b while keeping the distance Lc between the piston outer peripheral portion 4d and the cooling channel 4f constant. The volume of the convex part 4t at the top of the piston is reduced as much as possible.

The corner 4m (the corner ridge 4k of the corner of the top surface of the convex 4t and the corner 4m with the groove 4a) at the peripheral edge of the convex 4t of the piston top is subjected to R machining. In particular, a large R process (R1) is applied to a position where the corner of the concave groove 4a is in contact with the piston outer peripheral portion 4d.
The R processing R1 is formed so that a jet or a propagation flame easily enters (Fr) into the piston outer peripheral portion 4d.

In the example of FIG. 1, the shape of the concave groove bottom surface 4b is flat as shown in FIG. 3 (the same shape as FIG. 2), but the concave groove bottom surface 4b does not collide with the holder 5. It is necessary to make it as narrow as possible within the avoidable range.
On the other hand, by doing so, the distance between the top ring groove 4e and the concave groove bottom surface 4ab may be too small to form the cooling channel 4f for cooling the piston.
In such a case, as shown in FIG. 4, the concave groove bottom surface 40b is formed with an inclination so that the piston outer periphery 4d side becomes higher, or as shown in FIG. 5, the concave groove bottom surface 45b is formed on the piston outer periphery side. It is also possible to form it in an arc shape so as to be higher.

In FIG. 6, it is preferable that the top clearance Ct between the convex part 4t of the piston top part and the lower surface of the cylinder head 3 is formed as narrow as possible.
By narrowing the top clearance Ct as much as possible, the intake air that has been compressed in the compression process and has entered the top clearance Ct has a narrow top clearance Ct, so the flow velocity is increased (with the squish flow Fs increased), The tumble flow Ft when escaped to the concave groove 4a beside the convex 4t is also enlarged.
The enlargement of the squish Fs and the tumble Ft improves the mixing of the flame jet J injected from the holder 5 and the intake air.

FIG. 10 is a graph showing experimental results obtained by measuring the ratio of unburned hydrocarbon “UHC” contained in the exhaust gas when the first embodiment is performed with respect to the advance angle with respect to the top dead center.
As a comparison (parameter), experimental results under the same conditions for a conventional piston having a “ω” -shaped cavity and a piston having a flat top surface are shown.
According to the experimental results of FIG. 10, when using the first embodiment, “line A” does not discharge unburned carbide with respect to the piston “line C” having a conventional section “ω” -shaped cavity. The result is extremely large at around 55%. Moreover, it has decreased also with respect to piston "B line" which comprised the top surface with the plane, and has become a favorable result.

According to 1st Embodiment of this invention which comprises the structure mentioned above, since the cavity 6 is comprised by the groove | channel 4a of the piston top surface, the whole shape of a piston top surface is a substantially flat surface shape. Therefore, unlike conventional pistons that have a deep-plate toroidal shape (cross section “ω” shape) or a bathtub-shaped cavity, local high temperatures due to uneven combustion can be avoided, thus achieving uniform and stable combustion. It is done.
And generation | occurrence | production of NOx is suppressed by the high temperature of combustion temperature being avoided.

  Moreover, since the flame jet J can easily reach the top clearance portion Ct and the clevis portion 7, the generation of unburned hydrocarbons (UHC) at the location can be suppressed.

  In addition to this, the occurrence of bulk quench can be suppressed, and unburned hydrocarbons (UHC) can be further reduced.

  In the first embodiment, the position of the groove 4a is aligned with the intake / exhaust valve position of the cylinder head, and the depth of the groove 4a is set so as not to collide with the tip of the holder 5. It does not interfere with the intake / exhaust valves Vi and Vo of the cylinder head 3 and the tip of the holder 5.

  In addition to this, in this embodiment, if the number of flame jets J injected from the tip of the holder 5 is less than or equal to the number of intake and exhaust valves Vi and Vo provided on the cylinder head 3, the width of the groove 4a is increased. Since the dimension can be secured above a certain value, the shape of the cylinder head 3 does not become complicated and the possibility of breakage due to heat is reduced even if the number of intake and exhaust valves Vi and Vo increases.

Next, a second embodiment will be described with reference to FIGS.
In the first embodiment of FIGS. 1 to 6, the jet direction of the flame jet J emitted from the holder 5 is configured to be along the longitudinal center line of the groove 4 a formed at the top of the piston 4. It was an embodiment. On the other hand, in the second embodiment shown in FIGS. 7 and 8, the injection direction of the flame jet J emitted from the injection hole 50b of the holder 50 is such that the protrusion 4t formed at the top of the piston is tip from the piston center. The difference is that the nozzle hole 50b of the holder 50 is formed so as to face 4c.

  The second embodiment of FIGS. 7 to 9 is substantially the same as the first embodiment of FIGS. 1 to 6 except that the injection direction of the flame jet J emitted from the holder 50 is different. It is the same as the form.

In the second embodiment, as shown in FIG. 8, after the flame jet J fired from the nozzle hole 50 b of the holder 50 collides with the tip 4 tc from the piston center of the convex portion 4 t formed at the top of the piston 4. A part Jb of the jet J reaches the outer peripheral part 4d of the piston along the side wall 4g of the concave groove 4a.
Then, as shown in FIG. 9, the remaining jet Jc once collides with the convex portion 4t, then rides on the upper surface of the convex portion 4t and proceeds on the upper surface of the convex portion 4t toward the piston outer periphery 4d.
1 to 6, the number of nozzle holes 50b can be reduced to the number of convex portions or less.

In the case of the second embodiment, the top clearance Ct is formed wider than the first embodiment so that the flame jet J easily flows on the upper surface of the convex portion 4t (so that combustion on the upper surface of the convex portion 4t is promoted), It is configured so that the flame jet can easily enter.
That is, if the top clearance Ct is increased, the squish Fs may surely be weakened. However, since the effect of the flame wrapping around the top clearance Ct can be obtained, the flame propagates well and uniformly when considering the combustion chamber as a whole. The unburned portion is eliminated, and the effect of improving the combustion efficiency is improved.

The illustrated embodiment is merely an example, and is not intended to limit the technical scope of the present invention.
For example, in the illustrated embodiment, a case in which two supply / exhaust valves have a total of four valves is shown, but the present invention is not limited thereto.

The fragmentary sectional view explaining the principal part composition of a 1st embodiment of the present invention. The top view which showed the piston top part of 1st Embodiment of this invention. The fragmentary sectional view which shows an example of the cross section of the piston top part of 1st Embodiment of this invention. The fragmentary sectional view which shows the other example of the cross section of the piston top part of 1st Embodiment of this invention. The fragmentary sectional view which shows another example of the cross section of the piston top part of 1st Embodiment of this invention. The fragmentary sectional view explaining the squish (flow) and the tumble (flow) in the first embodiment of the present invention. The fragmentary sectional view explaining the principal part structure of 2nd Embodiment of this invention. The top view which showed the piston top part of 2nd Embodiment of this invention. The perspective view which showed the locus | trajectory of the flame jet in 2nd Embodiment of this invention in three dimensions. The graph of the measurement result explaining the effect of this invention compared with a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylinder 3 ... Cylinder head 4 ... Piston 4a ... Groove / concave groove 4d ... Outer peripheral part 4c ... Tip part 4f ... Cooling channel 4t ... Convex part 5, 50 ... Holder 5a ... Sub chamber 5b, 50b ... Injection hole Ct ... Top clearance Vi ... Intake valve Vo ... Exhaust valve J ... Flame jet

Claims (5)

  The top surface of the piston (4) has a radial concave groove (4a) and a convex portion (4t) other than the concave groove (4a), and the concave groove (4a) is positioned at the cylinder head (3). The depth of the concave groove (4a) is set so as not to collide with the intake / exhaust valve (Vi, Vo) and the protruding portion of the sub chamber (5). The concave groove (4a) is formed to have a constant width along its length direction, and is open to the outer periphery of the piston, and its bottom surface (4b) is formed into a flat surface, and the convex portion (4t) is The top surface is formed in a flat surface, and the side surface is formed in parallel with the longitudinal center line of the concave groove (4a) so that the planar shape is substantially triangular, and the peripheral portion of the convex portion (4t) The sub-chamber formed by the curved surface (R1) at the corner portion is in contact with the piston outer peripheral portion (4d). In an internal combustion engine, said auxiliary chamber (5) pre-combustion chamber internal combustion engine, wherein a flame jet ejected from the protruding portion (J) is injected radially outwardly along the concave groove (4a).   The sub-chamber internal combustion engine according to claim 1, wherein a bottom surface (4b) of the concave groove (4a) is flat along a radial direction.   The sub-chamber internal combustion engine according to claim 1, wherein the bottom surface (40b) of the concave groove (4a) is formed with an inclination so that the piston outer periphery (4d) side becomes higher.   The sub-chamber internal combustion engine according to claim 1, wherein the bottom surface (45b) of the concave groove (4a) is formed in an arc shape so that the piston outer periphery (4d) side becomes higher.   The top surface of the piston (4) has a radial concave groove (4a) and a substantially triangular convex portion (4t) which is a portion other than the concave groove (4a), and the position of the concave groove (4a) is a cylinder. It is aligned with the position of the intake / exhaust valves (Vi, Vo) of the head (3), and the depth of the recessed groove (4a) does not collide with the intake / exhaust valves (Vi, Vo) and the protruding portion of the sub chamber (5). The concave groove (4a) is formed to have a constant width along its length direction, and is open to the outer periphery of the piston, and its bottom surface (4b) is formed in a plane, and the convex portion (4t) has a top surface formed in a plane, and a side surface formed in parallel with the longitudinal center line of the concave groove (4a) so that the planar shape is formed in a substantially triangular shape, and the projection (4t) The position in contact with the piston outer peripheral part (4d) at the corner of the peripheral part of the peripheral part is formed by the curved surface (R1) In the sub-chamber internal combustion engine, the flame jet (J) injected from the protruding portion of the sub-chamber (5) collides with the radially inner portion of the convex portion (4t) between the concave grooves (4a). A sub-chamber internal combustion engine characterized by being injected in a direction to perform.

Images