JP2010185428A - Combustion chamber structure of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion chamber structure of an engine preventing a fault caused by the difference in the coefficients of thermal expansion of a cylinder member and an annular body member. <P>SOLUTION: The combustion chamber structure of the engine includes an annular groove 40 formed at a mating surface portion of a cylinder head (41) and a cylinder block (42) so as to be opened to a combustion chamber (10), and having a tapered surface at one surface out of a head surface (40h), a block surface (40b) and a sidewall surface (40s), and an annular ignition plug (20) arranged in the annular groove (40) and having the same cross-sectional shape as an annular groove cross section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a combustion chamber structure of an engine.

  Conventionally, a combustion chamber structure of a multi-point ignition engine in which a plurality of ignition plugs are provided in a combustion chamber in order to increase combustion efficiency is known. Further, in Patent Document 1, an annular spark plug having an annular body formed in an annular shape along a combustion chamber wall surface and made of an insulating member, and a plurality of ignition portions made of a conductive portion and a discharge gap facing the inner peripheral surface of the annular body. A combustion chamber structure is shown in which is fitted into the wall of the combustion chamber.

  Normally, in combustion with an engine having an ignition plug in the center of the combustion chamber, the gas at the outer periphery of the combustion chamber is compressed by a flame spreading from the center of the combustion chamber, so that the compressed gas becomes high temperature and knocking is likely to occur. However, as described above, the knocking is prevented by igniting a plurality of locations on the outer peripheral edge of the combustion chamber where knocking is likely to occur by discharge ignition from one central electrode located on the inner peripheral surface of the annular body. It is possible.

Japanese Patent Application No. 2007-213242

  However, in the conventional engine combustion chamber structure described above, since the material of the annular body and the cylinder are different, if the operating temperature range changes, the annular body may be deteriorated due to the influence of stress due to the difference in thermal expansion coefficient. there were.

  The cross-sectional shape of the annular body is rectangular. A similar rectangular cross-section groove is also provided on the cylinder side, and an annular body is fitted into the groove and assembled. When the annular body is assembled to the cylinder based on the dimensions of the annular body and the cylinder when it is cold, the cylinder that is a metal member expands when it is warm, but the annular body that is an insulating member such as a ceramic expands more than the cylinder. Is small and does not substantially deform, so a gap is formed between the annular body and the cylinder. A gap between the annular body and the cylinder is generated in both the diameter direction and the vertical direction of the combustion chamber. If there is such a gap, the annular body may collide with the cylinder due to the vibration of the engine and promote deterioration. Further, if the ignition position of the ignition part provided in the annular body is shifted, there is a possibility that the center of combustion is shifted from the center of the cylinder. As a result, combustion may vary and combustion efficiency may be reduced.

  As a measure for preventing the generation of the gap, it is conceivable to assemble the annular body into the cylinder by press-fitting or tightening in consideration of the gap generated between the annular body and the cylinder when warm. However, since the annular body has a length corresponding to the inner circumference of the combustion chamber with respect to the size of the cross section, it has an elongated shape. Therefore, buckling may occur depending on the crushing strength. On the other hand, it can be considered that the annular body is assembled to the cylinder based on the dimensions of the annular body and the cylinder when warm. In this case, the cylinder contracts when it is cold, but the annular body is not substantially deformed, so the annular body is pressed against the cylinder. If there is such pressure, there is a risk of promoting the deterioration of the annular body.

  The present invention has been made paying attention to such conventional problems, and an object of the present invention is to provide a combustion chamber structure for an engine that prevents problems due to a difference in thermal expansion coefficient between a cylinder member and an annular body member. And

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  According to the present invention, the cylinder head (41) and the cylinder block (42) are formed at the mating surface portion with an opening to the combustion chamber (10). An annular groove (40) having a tapered surface on any one of them, and an annular spark plug (20) disposed in the annular groove (40) and having the same cross-sectional shape as the annular groove cross section, To do.

  According to the present invention, the annular groove in which the annular spark plug is arranged is constituted by the head surface, the block surface and the side wall surface, and any one of the constituent surfaces has a tapered surface. Thereby, the distance between the head surface and the block surface or the distance between the side wall surface and the inner peripheral surface of the combustion chamber is not constant but gradually changes. Therefore, even if thermal expansion occurs after assembly, the annular groove of the cylinder moves along the tapered surface of the annular spark plug. Therefore, a gap is not easily generated between the surface of the annular groove facing the tapered surface and the annular spark plug. And since an annular spark plug becomes easy to be hold | maintained in a fixed position, degradation of an annular spark plug is prevented.

It is a figure which shows the combustion chamber structure of the engine of 1st Embodiment. It is a structural diagram of the annular spark plug of the first embodiment. It is a figure explaining the effect | action of the annular spark plug and annular groove of 1st Embodiment. It is a figure explaining the effect | action of the annular spark plug and annular groove of 2nd Embodiment. It is a block diagram of the annular spark plug of 3rd Embodiment. It is a figure explaining the effect | action of the annular spark plug and annular groove of 3rd Embodiment.

  Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a view showing a combustion chamber structure of an engine according to the first embodiment. FIG. 1A is a structural diagram of the engine, and FIG. 1B is an enlarged view of a portion including the annular groove of FIG.

  The combustion chamber 10 is formed by a cylinder head 41, a cylinder block 42, and a piston 33. The combustion chamber 10 is provided with an annular spark plug 20 on the outer periphery in addition to the center spark plug 30.

  The combustion chamber 10 is exemplified by a so-called pent roof type in this embodiment. A central spark plug 30 is provided on the pent roof ridgeline. An intake valve 31 is provided on one roof (the right roof in FIG. 1) across the pent roof ridgeline. An exhaust valve 32 is provided on the other roof (the left roof in FIG. 1) across the pent roof ridge line. Those skilled in the art of engine use the expression top dead center / bottom dead center separately from the direction of gravity. In a horizontally opposed engine, etc., the top dead center is not necessarily above the gravity direction and the bottom dead center is not below the gravity direction. If the engine is inverted, the top dead center is below the gravity direction. The bottom dead center is above the gravity direction. In the present specification, according to the custom, the top dead center side is up, the bottom dead center side is down, and the upper side of the combustion chamber 10 is expressed as a roof (ceiling).

  The piston 33 reciprocates up and down in the combustion chamber 10 along the cylinder wall surface 10a. The above-described top dead center is a position where the piston 33 is at the uppermost end, and the bottom dead center is a position where the piston 33 is at the lowermost end.

  The cylinder head 41 constitutes a cylinder ceiling surface of the combustion chamber 10. An annular groove 40 that opens to the combustion chamber 10 is provided annularly on the inner peripheral side of the mating portion of the cylinder head 41 and the cylinder block 42. A gasket 43 is provided between the surface 41 a on the cylinder head side 41 and the surface 42 a on the cylinder block side 42 on the outer peripheral side of the mating portion of the cylinder head 41 and the cylinder block 42.

  The cylinder block 42 constitutes a cylinder wall surface 10 a of the combustion chamber 10. The cylinder block 42 forms an annular groove 40 together with the cylinder head 41. An annular spark plug 20 is disposed in the annular groove 40.

  As shown in FIG. 1B, the annular groove 40 opens to the combustion chamber 10 along the cylinder wall surface 10a, and is formed by a head surface 40h, a block surface 40b, and a side wall surface 40s.

  The head surface 40 h is provided on the cylinder head 41 and is on the inner peripheral side of the mating surface 41 a with the cylinder block 42. The block surface 40b is provided on the cylinder block 42 so as to face the head surface 40h, and is a tapered surface having an inclination angle θ. The inclination of the block surface 40b is provided so that the distance between the head surface 40h and the block surface 40b becomes smaller toward the inner peripheral side. The inclination angle θ is calculated from the ratio of expansion amounts at which the material of the cylinder head 41 and the cylinder block 42 expands in the diameter direction and the vertical direction of the combustion chamber 10 due to thermal expansion. If the expansion amounts in the diameter direction and the vertical direction of the combustion chamber 10 are ΔD and Δh, respectively, the annular groove 40 expands by ΔD / 2 in the diameter direction of the combustion chamber 10 and Δh in the vertical direction. The inclination angle θ of the block surface 40b is obtained by the following equation.

  The side wall surface 40s is provided on the side opposite to the opening side of the annular groove 40 and is orthogonal to the head surface 40h. The head surface 40h, the block surface 40b, and the side wall surface 40s that form the annular groove 40 are in close contact with the upper surface 21b, the lower surface 21c, and the outer peripheral surface 21d of the annular body 21 of the annular spark plug 20, respectively. At this time, the block surface 40b of the annular groove 40 is provided so as to have a protruding portion at a distance d1 in the diameter direction of the combustion chamber 10 on the inner peripheral side with respect to the mating surface with the lower surface 21c of the annular body 21. The distance d1 is a movement amount (expansion amount) by which the cylinder wall surface 10a moves to the outer peripheral side of the combustion chamber 10 due to thermal expansion, and is represented by the following expression.

  The gasket 43 is interposed between the cylinder head 41 and the cylinder block 42 and seals between the two. The gasket 43 is an elastic member.

  The annular spark plug 20 is placed in the annular groove 40. As shown in FIG. 2, the annular spark plug 20 includes an annular body 21, a center electrode 22, a conductive portion 23, and a ground 24. The annular spark plug 20 has four ignition portions 25a to 25d.

  The annular body 21 is made of an insulating material such as ceramic. The height h2 of the outer peripheral surface 21d of the annular body 21 is greater than the height h1 of the inner peripheral surface 21a. The lower surface 21 c of the annular body 21 is a tapered surface having an inclination angle θ, similarly to the block surface 40 b of the annular groove 40.

  The center electrode 22 is an elongated rod-like electrode made of a heat-resistant and conductive material such as platinum (Pt) or iridium (Ir). The tip of the center electrode 22 is located on the inner peripheral surface 21 a of the annular body 21. Although not shown, the center electrode 22 is connected to the ignition coil.

  The conductive portion 23 is formed in a rectangular shape by depositing a heat-resistant and conductive material such as platinum (Pt) or iridium (Ir) on the inner peripheral surface 21 a of the annular body 21. In the present embodiment, four conductive portions 23a to 23d are provided. The four conductive portions 23 a to 23 d are provided in a row at a predetermined interval on the inner peripheral surface 21 a of the annular body 21 with the tip of the center electrode 22 as the head. Of the conductive portions 23 a and 23 d located on both sides of the center electrode 22, one conductive portion 23 a is adjacent to the center electrode 22 to form a discharge gap 25 a. The other conductive portion 23d is sufficiently separated from the center electrode 22 than the one conductive portion 23a. For this reason, even if a voltage is applied to the center electrode 22, no discharge occurs between the center electrode 22 and the conductive portion 23d. The distance between the tip 22a of the center electrode 22 and the upper surface 21b and the lower surface 21c of the annular body 21 is sufficiently larger than the distance between the tip 22a of the center electrode 22 and the conductive portion 23a. Three discharge gaps 25b to 25d are formed between the conductive portions 23 adjacent to each other. The gap amounts of the three discharge gaps 25b to 25d are all equal. Further, the discharge gap 25a is formed so as to be substantially equal to the gap amount. In the annular spark plug 20, the energy amount is determined by the sum of the gap amounts of the discharge gaps 25a to 25d, that is, the sum of the gap amounts.

  The ground 24 allows the voltage applied to the center electrode 22 to escape to the cylinder head 41. The ground 24 is formed so as to be continuous with the conductive portion 23 d spaced from the center electrode 22 among the conductive portions 23 a and 23 d located on both sides of the center electrode 22. Similarly to the conductive portion 23, the ground 24 is formed from the inner peripheral surface 21a to the upper surface 21b of the annular body 21 by vapor-depositing a heat-resistant and conductive material such as platinum (Pt) or iridium (Ir). It is formed. The portion applied to the upper surface 21 b of the annular body 21 comes into contact with the cylinder head 41, so that the voltage applied to the center electrode 22 is released to the cylinder head 41.

  The ignition part 25 is discharge gaps 25a to 25d formed in the annular spark plug 20.

  When the annular spark plug 20 having such a structure is used, the ignition coil energy is received and the sparks are ignited in the respective discharge gaps 25a to 25d, so that multipoint ignition can be performed.

  Next, the operation of this embodiment will be described with reference to FIG. FIG. 3 (A) shows the positional relationship between the annular body 21 and the annular groove 40 before thermal expansion, and FIG. 3 (B) shows the relationship after thermal expansion.

  When assembled in the cold state, the annular body 21 of the annular spark plug 20 is disposed so as to contact the side wall surface 40s of the annular groove 40 as shown in FIG. At this time, the cylinder wall surface 10 a is located on the inner peripheral side by a distance d <b> 1 from the inner peripheral surface 21 a of the annular body 21 in the diameter direction of the combustion chamber 10. And when it is warm, thermal expansion occurs. The cylinder members 41 and 42 have a large coefficient of thermal expansion, and the annular body 21 has a small coefficient of thermal expansion. Since the annular body 21 is not substantially deformed, the positional relationship between the annular body 21 and the annular groove 40 by relative displacement with respect to the annular body 21 is as shown in FIG. As shown in FIG. 3B, the cylinder head 41 and the cylinder block 42 move to the outer peripheral side by a distance ΔD / 2 in the diameter direction of the combustion chamber 10 due to thermal expansion. The cylinder wall surface 10 a becomes the same surface as the inner peripheral surface 21 a of the annular body 21, and the side wall surface 40 s of the annular groove 40 creates a gap ΔD / 2 between the outer peripheral surface 21 d of the annular body 21. Further, the cylinder block 42 is lowered by a distance Δh in the vertical direction of the combustion chamber 10. Since the inclination angle θ of the block surface 40b of the annular groove 40 is determined in consideration of these displacements due to thermal expansion, the cylinder block 42 slides in the direction of the thick arrow parallel to the block surface 40b of the annular groove 40. The block surface 40b and the head surface 40h of the annular groove 40 are always in contact with the lower surface 21c and the upper surface 21a of the annular body 21, respectively.

  Moreover, when assembling at the time of warm, it arrange | positions like FIG. 3 (B) first. Then, it heat-shrinks at the time of cold, and becomes an arrangement | positioning relationship as shown to FIG.

  According to the present embodiment, the block surface 40b of the annular groove 40 is a tapered surface, and the inclination angle is set in consideration of the expansion amount due to thermal expansion. As a result, the taper surface of the block surface 40b of the annular groove 40 slides along the taper surface of the lower surface 21c of the annular body 21 even if the temperature changes from the time of assembly and thermal expansion occurs. Further, the head surface 40 h of the annular groove 40 slides along the upper surface 21 b of the annular body 21. Therefore, there is no gap in the vertical direction between the annular groove 40 and the annular body 21. At this time, even if a gap occurs in the diameter direction of the combustion chamber 10, the annular body 21 is positioned and held by the block surface 40 b that is a tapered surface, so that there is no fear that the annular body 21 is displaced. Further, since the annular body 21 is held without applying an extra load, the annular body is not deteriorated.

  And if the annular body 21 is hold | maintained in a fixed position, the position of the ignition part 25 of the annular spark plug 20 will be stabilized. Therefore, stable combustion can be supplied.

  The annular groove 40 includes a cylinder head 41 and a cylinder block 42. Thus, the annular spark plug 20 may be disposed in the groove of the cylinder block 42 so as to cover the cylinder head 41. Therefore, the cylinder head 41 and the cylinder block 42 can be easily arranged in the process of assembling.

(Second Embodiment)
FIG. 4 is a diagram for explaining the operation of the annular spark plug and the annular groove according to the second embodiment. 4A shows the positional relationship between the annular body 21 and the annular groove 40 before thermal expansion, and FIG. 4B shows the relationship after thermal expansion. In the following description, the same functions as those described above are denoted by the same reference numerals, and redundant description will be omitted as appropriate.

  As shown in FIG. 4A, the head surface 40h of the head surface 40h, the block surface 40b, and the side wall surface 40s forming the annular groove 40 is a tapered surface having an inclination angle θ. The inclination of the head surface 40h is provided so that the distance between the head surface 40h and the block surface 40b becomes smaller toward the inner peripheral side. The side wall surface 40 s is composed of a cylinder head 41 and a cylinder block 42.

  The operation of this embodiment will be described. As shown in FIG. 4B, the cylinder head 41 and the cylinder block 42 move to the outer peripheral side by a distance ΔD / 2 in the diameter direction of the combustion chamber 10 due to thermal expansion. Further, the cylinder head 41 is raised by a distance Δh in the vertical direction of the combustion chamber 10. The cylinder head 41 slides in the direction of the thick arrow parallel to the head surface 40 h of the annular groove 40 with the annular body 21 as a reference.

  According to this embodiment, while the block surface 40b of the annular groove 40 is a tapered surface in the first embodiment, the opposing head surface 40h is a tapered surface. Therefore, as in the first embodiment, the block surface 40b and the head surface 40h of the annular groove 40 are always in contact with the lower surface 21c and the upper surface 21a of the annular body 21, respectively. Therefore, even if thermal expansion occurs, the position of the annular body 21 is maintained and does not shift.

(Third embodiment)
FIG. 5 is a structural diagram of the annular spark plug of the third embodiment. FIG. 5A is a plan view of the annular spark plug 20. FIG. 5B is a diagram illustrating the elastic structure portion 26, and FIG. 5C is a cross-sectional view taken along the line CC in FIG. 5B. FIG. 6 is a diagram for explaining the operation of the annular spark plug and the annular groove according to the third embodiment. 6A shows the arrangement relationship between the annular body 21 and the annular groove 40 before thermal expansion, and FIG. 6B shows the relationship after thermal expansion.

  As shown in FIG. 5A, elastic structure portions 26a, 26b, and 26c are provided at positions that divide the circumference of the annular spark plug 20 into three equal parts. The elastic structure portion 26 includes an elastic member 260, an annular body side caulking portion 261, and a cover 262. The elastic member 260 is a conductive leaf spring. The annular body side caulking portion 261 is also conductive. As shown in FIG. 5B, one end of the annular body side caulking portion 261 is continuous with the conductive portion 23 of the annular spark plug 20, and the other end is caulked with the elastic member 260. And the cover 262 is provided in the outer periphery of the elastic member 260 as shown in FIG.5 (C). The outer side of the elastic member 260 or the inner side of the cover 262 is subjected to insulation treatment. The cover 262 has a tapered surface on the outer peripheral side of the annular spark plug 20. The elastic member 260 and the body side caulking portion 261 housed in the cover 262 also have a tapered surface along the shape of the cover 262.

  As shown in FIG. 6A, the side wall surface 40s of the annular groove 40 is provided on the cylinder head 41 side. The side wall surface 40s is a tapered surface having an inclination angle θ. The inclination of the side wall surface 40s is provided such that the distance between the extended surface of the cylinder wall surface 10a and the side wall surface 40s increases toward the upper side. The inclination angle θ is set in consideration of the elastic characteristics of the elastic member 260 in addition to the expansion amount (ΔD / 2, Δh) of the combustion chamber 10 in the diameter direction and the vertical direction. The inner peripheral surface 21a of the annular body 21 is disposed on the same plane as the cylinder wall surface 10a.

  The operation of this embodiment will be described. As shown in FIG. 5A, when thermal expansion occurs, the elastic structure 26 extends in the direction of arrow A along the circumference of the annular spark plug 20. Since the annular body 21 receiving the force indicated by the arrow A is not substantially deformed by an insulating member such as ceramic, the force indicated by the arrow A is converted into a force indicated by the arrow B that expands the annular body 21 in the outer circumferential direction.

  Next, a description will be given with reference to FIG. When assembled in the cold state, the annular spark plug 20 is disposed in the annular groove 40 without a gap as shown in FIG. When thermal expansion occurs during the warm period, a gap is generated between the cylinder members 41 and 42 and the annular spark plug 20 due to the difference in the coefficient of thermal expansion of the material. At this time, the elastic structure 26 of the annular spark plug 20 expands, and the force indicated by the arrow B is generated in the annular spark plug 20 as described above. The annular spark plug 20 expands toward the outer periphery. Since the inclination angle θ of the side wall surface 40s of the annular groove 40 is set in consideration of the displacement of each member due to the thermal expansion, the annular spark plug 20 is parallel to the side wall surface 40s as shown in FIG. It slides in the direction of a certain thick arrow to follow the expansion of the annular groove 40.

  According to the present embodiment, when the annular groove 40 is expanded by thermal expansion, the annular spark plug 20 is such that the elastic structure portion 26 tends to extend in the circumferential direction, and this force becomes a force that expands the annular body 21 in the outer circumferential direction. As a result, the annular spark plug 20 is always applied with a force that presses the head surface 40h and the side wall surface 40s of the annular groove 40 uniformly. Therefore, since the annular spark plug 20 is held on the outer peripheral side of the annular groove 40 even if thermal expansion occurs, stable combustion can be supplied without deviation.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention. For example, it is effective to provide a tapered surface not only in the arrangement structure of the annular spark plug with respect to the cylinder member but also in the arrangement between a plurality of members having different thermal expansion coefficients. In the first and second embodiments, the gasket interposed between the mating surfaces of the cylinder head and the cylinder block does not extend to the annular spark plug, but there is no problem if the gasket is extended to the annular spark plug as in the third embodiment. Moreover, although the leaf | plate spring of the elastic member shown in Embodiment 3 made the shape of a mountain between crimping parts, it is not restricted to this, You may change the direction of a mountain, even if it is a lid mountain.

10 Combustion chamber 20 Annular spark plug 40 Annular groove 40h Head surface 40b Block surface 40s Side wall surface 41 Cylinder head 42 Cylinder block

Claims (4)

An annular groove formed in an opening of the combustion chamber at a mating surface portion of the cylinder head and the cylinder block, and having a tapered surface on any one of the head surface, the block surface and the side wall surface;
An annular spark plug disposed in the annular groove and having the same cross-sectional shape as the annular groove cross-section;
An engine combustion chamber structure comprising: The tapered surface is formed on the block surface, and the distance between the head surface and the block surface becomes smaller toward the inner peripheral side.
The combustion chamber structure for an engine according to claim 1. The tapered surface is formed on the head surface, and the distance between the head surface and the block surface becomes smaller toward the inner peripheral side.
The combustion chamber structure for an engine according to claim 1. The inclination angle of the tapered surface is calculated from a ratio of expansion amounts at which the material of the cylinder head and the cylinder block expands in the diameter direction and the vertical direction of the combustion chamber.
The combustion chamber structure for an engine according to claim 2 or 3, wherein

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